Aqueous and Semi-Aqueous Alternatives for
CFC-113 and Methyl Chloroform Cleaning of
Printed Circuit Board Assemblies
Final
May 1991
Revised October 1994
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Printed on Recycled Paper
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AQUEOUS AND SEMI-AQUEOUS ALTERNATIVES
FOR CFC-113 AND METHYL CHLOROFORM
CLEANING OF PRINTED CIRCUIT BOARD ASSEMBLIES
by
ICOLP Technical Committee*
Stephen Greene (Chairman)
Bill Dixon
Yu Shen Kuo
Larry Hagner
Ray Pickering
Tony Makovitch
Farzan Riza
Richard Szymanowski
Gregory Tashjian
George Wenger
Stephen O. Andersen
U.S. Environmental Protection Agency
Revised by
Stephen O. Andersen, U.S. Environmental Protection Agency
Nina Bonnelycke, U.S. Environmental Protection Agency
John Sparks, U.S. Environmental Protection Agency
Michael Zatz, ICF Incorporated
* ICOLP is the International Cooperative for Ozone Layer Protection. ICOLP corporate member companies include AT&T, Boeing Company, British
Aerospace, Compaq Computer Corporation, Digital Equipment Corporation, Ford Motor Company, General Electric, Hitachi Limited, Honeywell, IBM,
Matsushita Electric Industrial Company, Mitsubishi Electric Corporation, Motorola, Northern Telecom, Sundstrand, Texas Instruments and Toshiba
Corporation. Industry association affiliates include American Electronics Association, Electronic Industries Association, Japan Electrical Manufacturers
Association and Halogenated Solvents Industry Alliance (U.S.). Government organization affiliates include the City of Irvine, California, the State Institute
of Applied Chemistry (U.S.S.R.), the Swedish National Environmental Protection Agency, U.S. Air Force, and U.S. Environmental Protection Agency
(EPA).
Stephen Greene,** Bill Dixon, and Ray Pickering are employed by Digital Equipment Corporation; George Wenger, Gregory Tashjian, and Tony
Makovitch are employed by AT&T; Yu Shen Kuo is employed by Boeing; Farzan Riza is employed by ICF Incorporated; Larry Hagner is employed by
Motorola; and Richard Szymanowski is employed by Northern Telecom. We would like to thank the many individuals and companies that provided insight
and information that helped produce this manual. This manual was funded by the U.S. EPA and ICOLP.
** Can now be reached at Polaroid Corporation, Cambridge, Massachusetts.
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Disclaimer
The U.S. Environmental Protection Agency (EPA), the International Cooperative for Ozone Layer
Protection (ICOLP), the ICOLP committee members, and the companies that employ the ICOLP
committee members do not endorse the cleaning performance, worker safely, or environmental
acceptability of any of the technical options discussed. Every cleaning operation requires consideration
of worker safely and proper disposal of contaminants and waste products generated from the cleaning
processes. Moreover, as work continues, including additional toxicity testing and evaluation under
Section 612 (Safe Alternatives Policy) of the Clean Air Act Amendments of 1990 and elsewhere, more
information on the health, environmental, and safely effects of alternatives will become available for use
in selecting among the alternatives discussed in this document.
EPA and ICOLP, in furnishing or distributing this information, do not make any warranty or
representation, either express or implied, with respect to its accuracy, completeness, or utility; nor does
EPA and ICOLP assume any liability of any kind whatsoever resulting from the use of, or reliance upon,
any information, material, or procedure contained herein, including but not limited to any claims regarding
health, safety, environmental effects or fate, efficacy, or performance, made by the source of the
information.
Mention of any company or product in this document is for informational purposes only, and does not
constitute a recommendation of any such company or product, either express or implied by EPA, ICOLP,
ICOLP committee members, and the companies that employ the ICOLP committee members.
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IV
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Table of Contents
List of Exhibits vii
Foreword 1
The Montreal Protocol 1
International Phaseout Schedules 1
Excise Tax 5
Cooperative Efforts 6
Structure of the Manual 9
Methodology for Selecting a Cleaning Process 11
Technical 11
Economics 13
Summary Charts 15
Cleaning Options 15
Summary Matrix 15
Characteristics of the Cleaning Process 19
Aqueous Cleaning 19
Water-Based Cleaning 19
Alkaline Saponified Water Cleaning 20
Semi-Aqueous Cleaning 21
Process and Equipment Characteristics 25
Underbrush Cleaning 26
Hydrocarbon/Surfactant Spray Cleaning 31
Batch Hydrocarbon/Surfactant Cleaning 36
In-Line Aqueous Cleaning 37
Batch Aqueous Cleaning 40
Water and Waste Stream Handling 41
Pre-Treatment of Water 41
Post-Treatment of Wastewater 42
Metal Contamination Control 42
Organics 43
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VI
pH
43
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VII
Table of Contents (Continued)
Recycling Equipment 44
Contract Hauling 44
Recap on Manual 47
Case Studies of Industrial Practices 49
Case Study #1: Terpene Cleaning of Surface Mount Assemblies 51
Case Study #2: Terpene Cleaning of Printed Circuit Board Assemblies 61
Case Study #3: Micro-Droplet Aqueous Cleaning of Surface Mount
Technology 63
Case Study #4: Organic Acid Flux Qualification for Aqueous
Cleaning 67
Case Study #5: Heavy Metals Removal System 71
Case Study #6: Conversion from CFC-113/Methanol Cleaning to
Aqueous Cleaning for Medium-Sized Surface Mount Device Assembler 74
References 77
Glossary 79
Appendix A: International Cooperative for Ozone Layer Protection 83
Appendix B: List of Vendors for CFC-113 and Methyl Chloroform Solvent
Cleaning Substitutes 85
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VIM
List of Exhibits
Exhibit 1 Parties to the Montreal Protocol 2
Exhibit 2 Successful Corporate Ozone-Depleting Solvent Phaseouts 3
Exhibit 3 Cleaning Options to Replace CFC-113 and Methyl Chloroform 16
Exhibit 4 Summary Matrix Comparing Cleaning Processes 17
Exhibit 5 Tendency to Form White Residue 22
Exhibit 6 Ionic Contamination Removal 23
Exhibit 7 Underbrush Cleaning Mechanism 27
Exhibit 8 Underbrush Cleaning FacilityAqueous 28
Exhibit 9 Underbrush Cleaning FacilitySemi-Aqueous 29
Exhibit 10 CFC-113 Chemical Clean Manufacturing Process Flow &
Terpene/Water Clean Process Flow 32
Exhibit 11 Semi-Aqueous Cleaning ProcessImmiscible Hydrocarbon 33
Exhibit 12 Typical Aqueous Cleaning Configuration 38
Exhibit 13 "Zero Discharge" Water Recycling System Concept for the
Electronics Industry 45
Exhibit 14 Semi-Aqueous Process Immiscible Hydrocarbon Solvent 46
Exhibit 15 Schematic of Semi-Aqueous Machine Wash Module 52
Exhibit 16 Schematic of Semi-Aqueous Machine Rinse/Dry Module 53
Exhibit 17 SIR Versus EC-7 Rinse Temperature 56
Exhibit 18 SIR for Striped Coupons (Normal Process EC-7 Spray and
Rinse) 57
Exhibit 19 SIR for Striped Coupons (Exposed to EC-7 for 7 Days) 58
Exhibit 20 Summary of Spray Cleaning Cost Per Square Foot of Board
Cleaned for Various Processes 60
Exhibit 21 High Pressure Aqueous Cleaning Pump and Rotary Spray Bar
System 65
Exhibit 22 Heavy Metals Removal System 72
Exhibit 23 Operating Cost & Resin Lifetime for Ion Exchange System 73
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IX
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FOREWORD
This manual has been developed jointly by the
International Cooperative for Ozone Layer Protection
(ICOLP) and the U.S. Environmental Protection Agency
(EPA) to aid the phaseout of ozone-depleting substances
(ODSs) in printed circuit board (PCB) cleaning
applications. It will prove useful to manufacturers world-
wide because the procedures used to clean PCB
assemblies apply to all manufacturers, regardless of
location or size. The manual has been prepared by the
U.S. EPA and an international committee of experts from
the solvent cleaning industry. Committee members
represent both developed and developing countries.
The manual describes a step-by-step approach for
characterizing the use of ozone-depleting solvents and
identifying and evaluating alternatives. It is a "how-to"
document which describes all of the steps necessary to
successfully phase out the use of CFC-113 and methyl
chloroform (MCF) in PCB cleaning applications. Many
of the alternatives described are currently in use at major
companies around the world. The manual addresses
primary cleaning applications and gives brief descriptions
of the commercially available aqueous and semi-aqueous
alternatives to CFC-113 and MCF. The manual provides
sufficient technical information on the solvent alternatives
to enable users to gather more detailed information on
their alternatives of choice. A list of equipment and
materials vendors is provided to facilitate such further
research.
The Montreal Protocol
The 1987 Montreal Protocol on Substances that Deplete
the Ozone Layer and subsequent 1990 and 1992
amendments and adjustments control the production and
consumption of ODSs internationally. As a result of the
most recent meetings in Copenhagen in November 1992,
two chemicals commonly used as solvents are scheduled
to be phased out. The chlorofluorocarbon 1,1,2-
trichloro-l,2,2-trifluoroethane (commonly referred to as
CFC-113) and 1,1,1-trichloroethane (commonly referred
to as methyl chloroform or MCF), will be completely
phased out in developed countries by 1996, and in
developing countries between 2006 and 2015 depending
on decisions taken by the Parties to the Protocol in 1995.
In addition, the 1992 amendments include a developed
country production freeze and reduction schedule for
hydrochlorofluorocarbons (HCFCs), with a phaseout in
developed countries by the year 2030.
Exhibit 1 lists the countries that are Parties to the
Montreal Protocol as of February 1994. In addition,
many companies world-wide have corporate policies to
expedite the phaseout of ozone-depleting chemicals.
Exhibit 2 lists corporations around the world that have
successfully phased out their use of ODSs.
In addition to providing regulatory schedules for the
phaseout of ODSs, the Montreal Protocol established a
fund that will finance the agreed incremental costs of
phasing out ODSs by eligible developing countries that
are Party to the Protocol. Eligible countries are defined
as those developing countries having a total annual
consumption of CFCs of less than 0.3 kg per person, and
of MCF and carbon tetrachloride of 0.2 kg per person.
International Phaseout
Schedules
Several countries have passed legislation to phase out
CFC-113 and MCF earlier than target dates set by the
Montreal Protocol in an effort to slow ongoing depletion
of the stratospheric ozone layer. Their policies are
summarized below.
Canada
Environment Canada, the federal agency responsible for
environmental protection in Canada, enacted a CFC
phaseout program more stringent than the Montreal
Protocol. Environment Canada has also announced a
series of target dates for the phaseout of CFCs in specific
end uses. For solvent cleaning applications such as metal
and precision cleaning, it mandates a phaseout of CFC-
113 by the end of 1994. Production, imports, and exports
of CFCs are to be eliminated by January 1, 1996, with a
75 percent reduction by January 1, 1994. For carbon
tetrachloride, the phaseout date is January 1, 1995 one
year earlier than that mandated by the Montreal Protocol.
Halons were eliminated by January 1, 1994. Production,
imports, and exports of MCF will be halted by January 1,
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1996, with
interim reductions of 50 percent by January 1, 1994, and
85 percent by January 1, 1995.
European Community
Under the Single European Act of 1987, the twelve
members of the European Community (EC) are subject to
environmental directives issued by the EC Governing
Council. Members of the EC are Belgium, Denmark,
Germany, France, Greece, Great Britain, Ireland, Italy,
Luxembourg, the
Exhibit 1
Algeria
Antigua and Barbuda
Argentina
Australia
Austria
Bahamas
Bahrain
Bangladesh
Barbados
Belarus
Belgium
Benin
Bosnia/Herzegovina
Botswana
Brazil
Brunei Darussalam
Bulgaria
Burkina Faso
Cameroon
Canada
Central African
Republic
Chile
China
Colombia
Congo
Costa Rica
Cote dlvoire
Croatia
Cuba
Cyprus
Czech Republic
Denmark
Dominica
Date: February 1994
PARTIES TO THE
Ecuador
Egypt
El Salvador
EEC
Fiji
Finland
France
Gambia
Germany
Ghana
Greece
Grenada
Guatemala
Guinea
Guyana
Honduras
Hungary
Iceland
India
Indonesia
Iran
Ireland
Israel
Italy
Jamaica
Japan
Jordan
Kenya
Kiribati
Kuwait
Lebanon
Libyan Arab
Jamahiriya
Liechtenstein
MONTREAL PROTOCOL
Luxembourg
Malawi
Malaysia
Maldives
Malta
Marshall Islands
Mauritius
Mexico
Monaco
Morocco
Myanmar
Namibia
Netherlands
New Zealand
Nicaragua
Niger
Nigeria
Norway
Pakistan
Panama
Papua New Guinea
Paraguay
Peru
Philippines
Poland
Portugal
Romania
Republic of Korea
Russian Federation
St. Kitts and Nevis
St. Lucia
Samoa
Saudi Arabia
Senegal
Seychelles
Singapore
Slovakia
Slovenia
Solomon Islands
South Africa
Spain
Sri Lanka
Sudan
Swaziland
Sweden
Switzerland
Syrian Arab Republic
Fanzania
Fhailand
Logo
Frinidad & Fobago
Funisia
Furkey
Furkmenistan
Fuvalu
Uganda
Ukraine
United Arab
Emirates
United Kingdom
United States
Uruguay
Uzbekistan
Venezuela
Viet Nam
Yugoslavia
Zambia
Zimbabwe
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Exhibit 2
SUCCESSFUL CORPORATE OZONE-DEPLETING SOLVENT PHASEOUTS
A-dec
ADC Telecommunications
Advanced Micro Devices
Alcatel Network Systems
Apple Computer
Applied Magnetics
Aishin Seiki
Alps Electric
AT&T
Cadillac Gage
Cal sonic
Canon
Corbin Russwin Hardware
Casio Computer
Chip Supply
Citizen Watch
Clarion
Compaq Computers
Conner Peripherals
Commins Engine
Diatek
Fuji Photo Film
Fujitsu
Funac
Harris Semiconductors
Hewlett Packard
Hitachi
Hitachi Metals
IBM
Iki Electric
Isuzu Motors
ITT Cannon
Japan Aviation Electronics
Kilovac
Kohyo Seiko
Kyocera
Mabuchi Motor
Matsushita
MDM
Minebea
Minolta Camera
Mitsubishi Electric
Mitsubishi Heavy Industry
Mitsubishi Motors
Mitsui High-tech
Motorola
Murata Erie NA.
Murata Manufacturing
National Semiconductor
NEC
NHK Spring
Nihon Dempa Kogyo
Nissan
Nissan Diesel Motor
Northern Telecom
NRC
NSK
Olympus Optical
Omron
OTC/SPX
Pacific Scientific EKD
Ricoh
Rohm
Sanyo MEG
Sanyo Energy
Seagate Technology
Seiko Epson
Seiko-sha
Sharp
Shin-etsu Polymer
SMC
Sony
Stanley Electric
Sumitomo Electric
Sumitomo Special Metals
Sun Microsystems
Suzuki Motor
Symmons Industries
Taiyo Yuden
Talley Defense Systems
Thomson Consumer Electronics
3M
Toshiba
Toshiba Display Devices
Toyota Motor
Unisia JECCS
Victor Japan
Yamaha
Yokogawa Electric
Zexel
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Netherlands, Portugal, and Spain. Council Regulation
number 594/91 of March 4, 1991 includes regulatory
provisions for the production of substances that deplete
the ozone layer. The EC phaseout schedule for CFC-113
production is more exacting than the Montreal Protocol.
It called for an 85 percent reduction of CFC-113
production by January 1, 1994 and a complete phaseout
by January 1, 1995. For MCF, the schedule called for a
50 percent cut in production by January 1, 1994 and a
complete phaseout by January 1, 1996. While all
members must abide by these directives, Council
Regulation number 3 322/88 of October 31, 1988 states
that EC members may take even more extensive
unilateral measures to protect the ozone layer.
European Free Trade Agreement
Countries
The European Free Trade Agreement (EFTA) countries
of Austria, Finland, Iceland, Norway, Sweden, and
Switzerland, have each adopted measures to completely
phase out fully-halogenated ODSs. Austria, Finland,
Norway, and Sweden will completely phase out their use
of CFC-113 in all applications by January 1, 1995.
Sweden plans to phase out MCF by this date as well. In
addition, some EFTA countries have set sector-specific
interim phaseout dates for certain solvent uses. Austria
phased out CFC-113 in a number of solvent cleaning
applications by January 1, 1994. Norway and Sweden
eliminated their use of CFC-113 on July 1, 1991 and
January 1, 1991, respectively for all applications except
textile dry cleaning.
Japan
On May 13,1992, the Ministry of International Trade and
Industry (MITI) requested its 72 Industrial Associations
to phase out CFC and MCF usage by the end of 1995.
United States
The U.S. Clean Air Act (CAA), as amended in 1990,
contains several provisions pertaining to stratospheric
ozone protection. ODSs are categorized by the CAA as
either Class I or Class II substances. Class I substances
include MCF, three types of halons, carbon tetrachloride,
and all fully-halogenated CFCs, including CFC-113.
Class II substances include 33 types of
hydrochlorofluorocarbons (HCFCs). The sections of the
CAA important to users of this manual are discussed
below.
Section 112: National Emission Standards for
Hazardous Air Pollutants
This section of the CAA requires the EPA to develop
emissions standards for 189 chemical compounds
listed as hazardous air pollutants (HAPs). The list of
HAPs includes the chlorinated solvents as well as
many organic solvents likely to be used in cleaning
metal parts.
Section 604 and Section 605: Phaseout of
Production and Consumption of Class I and Class
II Substances.
These sections detail the phaseout schedule for both
Class I and Class II substances. EPA accelerated the
schedule in response to both former President George
Bush's call for a more rapid phaseout and the recent
amendments made to the Protocol in Copenhagen.
Section 610: Nonessential Products Containing
Chlorofluorocarbons
This provision directs EPA to promulgate regulations
that prohibit the sale or distribution of certain
"nonessential" products that release Class I and Class
II substances during their manufacture, use, storage,
or disposal.
Section 611: Labeling
This section directed EPA to issue regulations
requiring the labeling of products that contain or were
manufactured with Class I and Class II substances.
Containers in which Class I and Class II substances
are stored must also be labeled. The label will read
"Warning: Contains or manufactured with [insert
name of substance], a substance which harms public
health and environment by destroying ozone in the
upper atmosphere". The label must clearly identify
the ODS by chemical name for easy recognition by
average consumers, and must be placed so that it is
clearly legible and conspicuous.
Labeling regulations affecting Class I substances took
effect on May 15, 1993. Products containing or
manufactured with a Class II substance must be
labeled no later than January 1, 2015.
Section 612: Safe Alternatives Policy
Section 612 establishes a framework for evaluating
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the overall environmental and human health impact of
current and future alternatives to ozone-depleting
solvents. Such regulation ensures that ODSs will be
replaced by substitutes that reduce overall risks to human
health and the environment. As a result of provisions set
in Section 612, the Environmental Protection Agency:
Issued rules in November 1992 that make it
unlawful to replace any Class I and Class II
substance with a substitute that may present
adverse effects to human health and the
environment when the EPA has identified an
available or potentially available alternative that
can reduce the overall risk to human health and
the environment.
Has published a list of prohibited substitutes,
organized by use sector, and a list of the
corresponding alternatives;
Will accept petitions to add or delete a substance
previously listed as a prohibited substitute or an
acceptable alternative;
Requires any company that produces a chemical
substitute for a Class I substance to notify EPA
90 days before the new or existing chemical is
introduced into commerce as a significant new
use of that chemical. In addition, EPA must be
provided with the unpublished health and safety
studies/data on the substitute.
To implement Section 612 EPA has (1) conducted
environmental risk characterizations for substitutes in
each end use and (2) established the Significant New
Alternatives Program (SNAP) to evaluate the
substitutes for Class I substances. EPA also initiated
discussions with NIOSH, OSHA, and other
governmental and nongovernmental associations to
develop a consensus process for establishing
occupational exposure limits for the most significant
substitute chemicals.
categorized each substance as unacceptable,
acceptable with limitations on use or quantity,
acceptable without comment, or delayed pending
further study. Petitions are allowed to change a
substance's status with the burden of proof on the
petitioner.
In early 1994, the EPA issued a list of alternatives it
found to be acceptable and unacceptable according to
this framework in its Significant New Alternatives
Policy (SNAP) Program ruling. The list will be
updated regularly as new alternatives become
available.
Excise Tax
As an incentive to reduce the production and
consumption of ODSs in the U.S., Congress placed an
excise tax on ODSs manufactured or imported for use in
the U.S. Taxes do not apply to recycled chemicals. This
tax provides a further incentive to use alternatives and
substitutes to CFC-113 and MCF and to recycle used
chemicals. The tax amounts are based on each chemical's
ozone-depleting potential. These taxes have recently
been increased as a part of the U.S. Congress'
comprehensive energy bill of 1992.
Calendar Year
1991
1992
1993
1994
1995
Tax Amount
Per Pound
CFC-113 MCF
$1.096
$1.336
$2.68
$3.48
$4.28
$0.137
$0.167
$0.211
$0.435
$0.535
The environmental risk characterizations for the
substitutes involve a comprehensive analysis based on
the following criteria: ozone-depleting potential,
flammability, toxicity, exposure effects, energy
efficiency, degradation impacts, air, water, and solid
waste/hazardous waste pollution effects, and global
warming potential. Economic factors are also
considered. EPA has organized these assessments by
use sector (i.e. solvents, refrigeration, etc). The risk
characterizations result in risk-management strategies
for each sector and substitute. EPA has also
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Cooperative Efforts
Japan
The Japanese Ozone Layer Protection Act gives its
Ministry of International Trade and Industry (MITI) the
authorization to issue restrictions on ODSs. MITI and
the Environmental Agency have established the
"Guidelines for Discharge Reduction and Use
Rationalization." Based upon these guidelines, various
government agencies have provided administrative
guidance and advice to the industries under their
respective jurisdictions. Specifically, MITI worked with
the Japan Industrial Conference for Ozone Layer
Protection (JICOP) to prepare two manuals that provide
technical information on alternatives to CFC-113 and
MCF. The manuals are titled:
Manual for Phasing-Out 1,1,1 -Trichloroethane; and
Manual for Reduction in the Use of Ozone-Depleting
Substances.
MITI also encourages industry to reduce consumption of
ODSs through economic measures such as tax incentives
to promote the use of equipment to recover and reuse
solvents.
Sweden
The Government/Industry/Research Institution sectors are
conducting two major cooperative efforts targeting the
phaseout of ODSs and chlorinated solvents:
The TRE-project (Technology for Clean Electronics);
and
The AMY-project (Cleaning of Metallic surfaces).
In addition, direct support is being provided to industry
for industrial scale introduction of new technologies.
These are, to name a few, closed loop systems,
microbiological cleaning systems, ion exchange
technologies, electrochemical cleaning systems, vacuum
evaporation systems, reverse osmosis, and alternative
solvent-based systems.
United States
EPA has been working with industry to disseminate
information on technically-feasible, cost-effective, and
environmentally-sound alternatives to ODSs. As part of
this effort, the Agency, along with ICOLP, prepared a
series of manuals that provide technical information on
alternatives to CFC-113 and MCF. Additional
information about ICOLP can be found in Appendix A.
The manuals are based on actual industrial experiences
and serve as a guide to users of CFC-113 and MCF
worldwide. These manuals will be updated periodically
as technical developments occur.
The complete set of manuals produced includes:
Alternatives for CFC-113 and Methyl Chloroform in
Metal Cleaning.
Aqueous and Semi-Aqueous Alternatives to CFC-113
and Methyl Chloroform Cleaning of Printed Circuit
Board Assemblies.
Conservation and Recycling Practices for CFC-113
and Methyl Chloroform.
Eliminating CFC-113 and Methyl Chloroform in
Aircraft Maintenance Procedures.
Eliminating CFC-113 and Methyl Chloroform in
Precision Cleaning Operations.
No-Clean Soldering to Eliminate CFC-113 and
Methyl Chloroform Cleaning of Printed Circuit Board
Assemblies.
This particular manual provides those in an organization
currently cleaning with ODSs with a simply-structured
program to help eliminate their use of CFC-113 and/or
MCF. Moreover, it presents aqueous and semi-aqueous
processes that can be used in cleaning PCB assemblies.
Many of these processes are currently in use around the
world. The goal of the manual is to:
Warn users of CFC-113 and MCF of the impending
halt in production and the consequences to their
operations;
Identify the currently available and emerging
alternatives for CFC-113 and MCF;
Provide an overview of the tasks that are required to
successfully implement an alternative process or
chemical;
Provide an overview of the environmental, health,
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safety, and other factors associated with alternatives and
the benefits achievable from the phaseout of CFC-113
and MCF;
Present detailed case studies on the actual industrial
applications of these technologies to:
Identify unresolved problems in eliminating CFC-
113 and MCF; and
Describe the equipment configuration of a typical
facility after it has eliminated its use of CFC-113
and MCF.
This manual will benefit all users of CFC-113 and MCF
in the PCB manufacturing industry. Ultimately, however,
the success of a CFC-113 and MCF elimination strategy
will depend upon how effectively reduction and
elimination programs are organized. Experience has also
shown that a strong education and training program for
workers using new processes results in greater efficiency
and a smooth transition away from CFC-113 and MCF.
The development and implementation of alternatives to
CFC-113 and MCF for PCB cleaning present a challenge
for most organizations. The rewards for success are the
contribution to global environmental protection and an
increase in industrial efficiency.
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oo
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CD
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10
STRUCTURE OF THE MANUAL
This manual is divided into the following sections:
METHODOLOGY FOR SELECTING A CLEANING PROCESS
This section discusses technical and economic issues that should be considered when
selecting a cleaning process.
SUMMARY CHARTS
This section presents two summary charts that match cleaning processes with the
evaluation criteria presented in the methodology section. The first chart explains that all
process selection begins by matching assembly technology to a fluxing system and to
potential cleaning methods. The second chart presents an overview of process advantages
and constraints.
CHARACTERISTICS OF THE CLEANING PROCESS
This section presents three cleaning choices: water, water with the addition of a saponifier,
and hydrocarbon/surfactants.
PROCESS AND EQUIPMENT CHARACTERISTICS
This section describes the mechanical systems that are typically associated with aqueous
and semi-aqueous cleaning.
WATER AND WASTEWATER HANDLING
This section presents information on pre- and post-treatment of water.
CASE STUDIES OF INDUSTRIAL PRACTICES
This section provides specific examples of actual industrial applications of aqueous and
semi-aqueous cleaning processes.
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11
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12
METHODOLOGY FOR SELECTING A
CLEANING PROCESS
The methodology used to select a cleaning process for
printed circuit boards (PCBs) must take into account a
host of important considerations. These can be grouped
into two categories: technical and economic.
Technical
The factors that determine the technical feasibility
include:
Compliance with specifications
Defect rate
Customer return issues
Industry direction
Cosmetics of the PCBs cleaned
Process flexibility
Ability to clean surface mount
assemblies
Fallback position
Process control
Process throughput
Time scale
Health, safely, and environmental
concerns
Future costs
Availability of the process
Process installation
Process compatibility
Floor space requirements
Operating and maintenance
requirements
Other selection criteria related to the
specific application
Compliance to Specifications. Military or civilian
contracts or specifications may strictly define process
parameters and performance. For example, military
specifications very frequently require conformal
coatings. Poor cleaning causes a special category of
surface defect, vesication. A military contractor
would have to ensure that the chosen cleaning
process/system will decrease or eliminate this type of
defect, whereas this would not be a concern for
manufacturers of non-military products. Before you
select a new process you should consider existing and
possible future contracts/provisions.
Defect Rate. This is defined as the rate that parts fail
to meet inspection standards. If the soldering process
is totally unchanged and only the cleaning portion is
affected, defect rates will likely not increase. Do not
be short-sighted. Question the impact of a different
cleaning process on downstream processes such as
test and post-wave assembly. Consider the possibility
that a change in the cleaning process may affect the
cost of components that are compatible with the new
process.
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13
Customer Return Issues. The choice of cleaning
process can influence how easily a returned unit can
be repaired or how well repairs and modifications can
be done in the field.
Industry Direction. Investing in a process that is
counter to existing industry direction may be
necessary, but using standard equipment sold to many
customers costs less. Parts and service become costly;
resources to answer waste stream issues or reliability
issues are limited; and risks tend to be higher for
custom equipment.
Cosmetics of the PCBs Cleaned. Although visual
appearance is becoming less important, some
customers may still impose standards on visual
appearance of electronic components.
Process Flexibility. The number of different types of
technology that can be cleaned efficiently with the new
process is a consideration for some parties. One must
consider the compatibility of the process with typical
materials. What are the viable options if the process
fails? Production can recover if the process is
sufficiently flexible.
Ability to Clean Surface Mount Technology (SMT).
The ability to penetrate close tolerance spaces typical
to SMT applications is a major advantage. SMT
applications are rapidly expanding.
Process Control This issue refers to the degree of
difficulty of operating the entire process. Simple
processes are better from a process control stand-
point. A process that can be easily monitored and
controlled is desirable.
Process Throughput. Throughput is extremely
important to the economic feasibility of a system. The
level of emissions from solvent systems is directly
related to throughput. As workloads are processed
faster than intended in the original design of the
equipment, solvent emissions increase. This
consideration is important when selecting an
alternative system.
Time Scale. Converting an existing process to CFC-
free alternatives cannot be expected to be completed
overnight. Physically removing old equipment,
installing new equipment, connecting the services,
performing acceptation trials, establishing
manufacturing protocols and integrating the new
process into production all take time. Production
projections during the conversion should be estimated
realistically: zero production should be expected
initially; low- to mid-levels of production should be
expected during the adjustment period; and full
production after all parties are fully educated. This
schedule also should take into account possible
fallback positions.
Health, Safety, and Environmental Concerns.
While methyl chloroform and CFC-113 are being
phased out due to the concern over stratospheric
ozone depletion, these chemicals were initially chosen
over many other candidates because of their low
flammability properties and relatively benign
toxicological profiles. In order to move forward,
alternatives should offer similar or better performance,
safely, health, and environmental aspects. The U.S.
EPA has conducted an overall risk characterization for
many substitutes under Section 612: Safe Alternatives
Policy of the Clean Air Act of 1990. This assessment
has involved a comprehensive analysis based on
ozone-depletion potential, flammability, toxicity,
exposure effects, energy efficiency, degradation
impacts, air, water, solid waste/hazardous waste
pollution effects, environmental releases, and global
warming potential.
Future Costs. Factors such as escalating solvent
costs or anticipated major expenditures associated
with pending control legislation should be considered.
Availability of Process. "Availability" is not the same
as "industry direction." "Availability" concerns the
ease with which vendors can supply the process. For
example, some alternatives might be available only
from a few vendors.
Process Installation. This is the work that will be
required to put the system into production and
includes physical installation of the process, material
handling considerations, and employee training.
Process Compatibility. The fewer the number of
changes required by the proposed process, the more
likely that the changeover will be successful. Form,
fit, and function of the product should not change.
Upstream and downstream process adjustments
required for a changeover should be considered. For
example, the reliability of the pin test is an important
concern.
Floor Space Requirements. The total amount of
space available and its value have a significant impact
on process selection. Compact units are often
preferred. Allow extra space for related items such as
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water heaters, storage tanks, treatment facilities, and
added process control tools. In some instances permits
may be required before installing a new process.
Operating and Maintenance Requirements. Each
new process will require establishing unique
operating and maintenance procedures. In some
instances a new process could be significantly
different in operation and would require special
operator training.
Depending on the process chosen, maintaining
process equipment on a regular basis may be critical
to preventing product defects. For example, it is
necessary to clean spray nozzles to remove
contamination that would make spraying less effective.
Pumps and leaky valves should also be checked
regularly.
return and payback period are important, environmental
protection and solvent supply reliability can justify the
CFC-113 and MCF usage reduction program. An
important component of the analysis should be a
recognition that the price of CFC-113 and MCF will
increase rapidly as supplies are reduced and taxes are
increased. Economic analysis should also include the
cost savings resulting from savings in solvent
consumption; for example, some new alternative
processes have much lower operating costs than the
current CFC-113 and MCF processes.
Economics
Process economics is a key factor in the selection of
alternative processes. Analysis of initial costs associated
with the alternative process should include capital costs
of equipment, capital costs associated with installation
and waste treatment/handling equipment, and costs
associated with obtaining local permits. In addition,
ongoing operating costs should be projected and include
materials, labor, maintenance, and utilities, such as
energy and water. The cost estimates for the alternative
process can be developed during preliminary process
design.
One simple approach to compare processes is to calculate
net present value (NPV) based on the discount rate and
period of investment your company uses. The NPV is
calculated as follows, where (n) is the number of years,
(i) is the discount rate, and cosl^ represents the
investment that occurs each year over the life of the new
process.
NPV = Costa + Cost/O+i) +
Cost2/(l+i)2 + ... + Costn/(l+i)n
While traditional economic considerations such as rate of
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SUMMARY CHARTS
The charts on the following page highlight aspects of the
most promising new technologies for specific
applications and present an overview of the options
presented in this manual. The remainder of the manual
provides additional detail.
Cleaning Options
The cleaning options chart, Exhibit 3, presents the
fluxing and cleaning combinations that have been
demonstrated to be successful with different types of
product. Assessing these combinations is a first step in
process selection.
When rosin fluxes are used, cleaning with
hydrocarbon/surfactants or with saponifiers is an effective
choice. With water soluble flux/paste, plain water
cleaning is preferred although aqueous saponified or
semi-aqueous cleaning also are applicable.
Summary Matrix
The second chart, Exhibit 4, provides brief, relevant
comments on the costs, applicability, strengths, and
weaknesses associated with eight machine and solvent
combinations discussed in this manual.
A brief explanation of some of the criteria displayed in
Exhibit 4 follows:
Possible Military Specifications Approval While every
process listed in this text has exhibited a good level of
performance and control, some may not yet have been
approved by the military. Military specifications should
be considered when evaluating alternative cleaning
technologies.
Component Issues. Concerns include corrosion, failure
of seals, effects on plastics, effects on functional
performance, removal of markings, and the potential to
trap flux or detergent residues. Underbrush cleaning with
no topside exposure has a "low" concern rating. Plain
water systems have a "high" concern rating if organic
fluxes that are very active are used. Entrapment of flux
residue in components is a high risk for long-term
reliability unless resolved by proper component design/
selection. Second, immersion/spray cleaning systems,
typically using elevated temperatures, can stress poorly
sealed or designed components and lead to failure.
Defect Rate. This concern refers to the soldering defect
rate associated with a flux selection. Plain water cleaners
typically used with the stronger organic fluxes probably
would have better solder yields. It is conceivable that the
other systems do not change the solder process, hence,
the defect rate would be unchanged.
Waste Stream Issues. Process control, volume, local
water quality, local regulations, and management
decisions influence this locality-specific issue. Every
process in this text has an identified, effective control
mechanism applicable to the effluent. Waste stream
considerations must be an important part of process
implementation.
Health and Safety Issues. These issues include toxicity,
flammability, odor, VOC concerns, and occupational
long-term exposure of semi-aqueous and aqueous
cleaners.
Idle Time Cost. The cost to sustain heated baths,
ventilation, and operating pumps during idle time is
important for applications with part-time usage. In most
instances terpene units are effective without added heat,
but some large facilities include chiller or cold water
packages to reduce flammability. In-line water units must
be ready during the entire shift while batch units can be
shut down. Idle time can represent costs particularly to
low volume operations that might choose to use in-line
machines.
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exhibit 3
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exhibit 4
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Processing Cost This manual does not cover the
associated cost of cleaning per square foot of product
produced because this is determined by a number of
variables at the local level. The manual does present an
approximation of what the processing cost might be
compared to CFC-113 systems.
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CHARACTERISTICS OF THE CLEANING
PROCESS
The effectiveness of a cleaning system depends on the
cleaning chemistry and the cleaning mechanics. The
selection of cleaner depends on the contaminants being
removed, the material being cleaned, the level of
cleanliness required, and the method used to apply the
cleaners. Cleaners may be formulated and used for one
application or for several. This diversity accounts for the
many cleaner formulations that are commonly available
for use in the electronics industry.
In this text, the discussion of cleaning begins with
aqueous cleaning including sections on cleaning with
plain water and cleaning with alkaline saponified water.
It next considers the hydrocarbon/surfactants followed by
water rinse, commonly referred to as semi-aqueous
cleaning.
Aqueous Cleaning
Water is an excellent solvent for removing ionic
contaminants and water-soluble flux. In combination
with a saponifier, water can remove non-polar substances
such as oil and rosin flux. Aqueous cleaning systems
generally consist of washing, rinsing, and drying stages.
Although waste disposal is clearly an issue, local
conditions determine its impact.
Water-Based Cleaning
By itself, tap water would seem to be the perfect solvent.
This notion, however, is false for two basic reasons:
Untreated water carries a variety of trace elements and
particles. The use of untreated water to clean
electronic assemblies can result in inadequate
cleaning.
Most water-soluble fluxes are corrosive and
incomplete removal can lead to problems. Many
saponifiers applied to treat this problem also cause
concerns if they are not adequately removed.
Complete rinsing is more difficult with surface mount
technology.
In reviewing plain water cleaning, consider the following
points:
The method is not effective for water immersible
product designs.
Reverse osmosis is a pre-treatment step commonly-
used to prepare the water used in the washing and the
rinsing stages.
Plain water (tap and soft) does not effectively remove
fingerprint residues.
Plain deionized water has a high surface tension. A
surfactant (wetting agent) may need to be added to
improve close tolerance cleaning. Some water soluble
flux residues contain surfactants that may aid water
penetration under components and reduce the need for
additional surfactants.
Deionized water must be used, especially for final
rinse.
Drying using air knives or heated air is often
necessary to speed drying times.
Most applications require waste stream treatment,
reducing the cost-effectiveness of the project.
In specific installations, plain water cleaning may be
compatible with closed loop water recycling packages
discussed later in this document.
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Alkaline Saponified Water Cleaning
This method can be used in applications with almost any
flux, including water-soluble formulations. The removal
of rosin flux by aqueous cleaners always requires using a
strongly alkaline saponifying detergent. The
saponification process uses the alkaline chemical to
convert rosin into a water-soluble soap that rinses freely
with water. Alkaline cleaners formulated for use in the
electronics industry generally consist of alkanolamines
such as monoethanolamine. The amines saponify the
rosin acids.
Quality cleaners provide the following process
advantages:
Low surface and interfacial tension to aid
detergent action;
Alkalinity to neutralize acidic soils (or
flux);
Dispersion properties to assist in solid soil
removal and to prevent redeposition;
Emulsification properties to prevent
redeposition of oils;
Inhibitors to minimize attack on metals or
other surfaces while cleaning;
Post-cleaning minimization of corrosion.
Surfactants improve the cleaning solution's ability to
penetrate close tolerance spaces, and they prevent the
released contaminants from recontaminating the
cleaned surface.
Nonionic surfactants are used widely because they are
a widely-compatible, non-electrolyte-forming
chemical with a large variety of molecular structures.
Pitfalls to avoid when considering a saponified water-
based system include:
Inadequate control of detergent concentration and
operating temperatures can lead to uncontrolled
foaming which hinders cleaning.
Improper selection of detergent can result in poor
cleaning, unnecessary costs, or poor product quality.
Detergents can have a high pH, as well as a high
biological oxygen demand; therefore wash water with
concentrated detergent solution should be checked for
compliance with sewer discharge requirements.
Discharging into a sanitary drain without warning can
have a major impact on the microbacterial population
used in treatment facilities. The biodegradability of
surfactants should also be evaluated.
Some detergent formulations include builders that are
complexing agents for heavy metals. The complexing
property tends to make metal separation difficult.
If closed loop water supply packages are considered,
it should be noted that detergents significantly reduce
the efficiency of the carbon adsorption bed media and
ion exchange columns.
Electronic cleaners tend to be formulated with an
alkanolamine, combined with a builder such as ethyl
butyl glycol ether, and some amount of a nonionic
surfactant. Sodium hydroxide or potassium hydroxide
may be included to add alkalinity. These ingredients
perform the following functions:
Monoethanolamine minimizes the possibility of
creating electrolytes that can cause conductivity
problems on circuit boards. Monoethanolamine
generally comprises 30 to 90 percent of the cleaner
concentrate.
Builders improve the overall cleaning performance.
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Semi-Aqueous Cleaning
A semi-aqueous process uses a hydrocarbon solvent to
clean the product by dissolving the contaminants,
followed by a water rinse to remove the hydrocarbon
solvent residue. In addition, a surfactant component is
generally added to the hydrocarbon solvent to provide
wetting, emulsification, and rinsing properties.
The advantages of hydrocarbon/surfactant cleaners
include:
Excellent cleaning of surface mount technology;
Low viscosity, low foaming properties;
Some have low vapor pressure (thus, evaporative loss
is minimized);
Polar and nonpolar contaminant removal capabilities;
Excellent surface insulation resistance (SIR), solvent
extract conductivity, and cosmetic results, including a
low tendency to form white residue (see Exhibit 5);
Specific cleaning characteristics can be enhanced with
blending;
Effective at room temperature;
Effectively rinsed with room temperature water;
Solvent extract conductivity measurements, using the
standard Dl/alcohol mixture at room temperature
(MIL-P-28809), indicate ionic levels typically below
1.53 micro gram NaCl equivalent per square
centimeter. That level is also typical whenever a
water rinsing operation is used (see Exhibit 6);
Excellent rosin-loading capacity;
Typically no corrosion in copper mirror tests.
In considering the use of hydrocarbon/surfactants for
cleaning, note the following points:
While rinsing may cause corrosion of the assemblies,
not rinsing can lower SIR by two orders of magnitude;
Material compatibility with plastics and rubbers used
in equipment should guide equipment selection;
finely atomized droplets can increase hazard of
flammability or loss of the hydrocarbon to the exhaust.
This can result in a major source of loss of the
hydrocarbon. This selective loss of hydrocarbon can
increase the concentration of surfactant in the wash
tank;
Limonene-based terpenes have a strong citrus odor
that may be objectionable;
Concentrated rinse water should not be discharged
without prior treatment;
When mixed with water at concentrations of
approximately 75 to 97 percent, some limonene-based
terpene cleaners form a gel that is incompatible with
most cleaning processes;
Some hydrocarbons could be classified as volatile
organic compounds which contribute to the formation
of smog an air quality concern in some areas;
Current formulas that decant very easily from water
have significantly reduced earlier concerns regarding
water pollution and system control.
Use of spraying that results in the formation of mist or
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exhibit 5
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exhibit <
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PROCESS AND EQUIPMENT
CHARACTERISTICS
This section presents some key process and equipment issues that should be considered before
selecting an aqueous or semi-aqueous cleaning process.
The technologies are presented in the following order:
Underbrush Cleaning (Aqueous and Semi-Aqueous);
Hydrocarbon/Surfactant Spray Cleaning;
Batch Hydrocarbon/Surfactant Cleaning;
In-Line Aqueous Cleaning; and
Batch Aqueous Cleaning.
Provision of this material in no way constitutes EPA or ICOLP recommendation or approval of any
company or specific offering. These technologies require case-by-case evaluation. A list of vendors
and references that can be used as additional sources of information is provided in the back of this
manual.
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Underbrush Cleaning
Underbrush cleaning scrubs only one side of the printed
circuit board assembly, typically the fluxed solder side
(see Exhibit 7). Because any fluxing and soldering
technique will result in the presence of top-side flux, this
cleaning process has been used only in conjunction with
very mild fluxes leaving residues that need not be
completely removed. This cleaning process is not
designed or suited for either SMT or total cleaning of the
printed circuit assembly. Reflowed surface mount
residues have not been effectively removed by either
detergent or hydrocarbon/surfactant underbrush
equipment.
Key features of underbrush cleaning are:
Equipment costs range from $40,000 to
$70,000;
In-line or batch processes can be used;
Not recommended for SMT;
Solvent, detergent, and hydrocarbon/
surfactant can all use the same
equipment.
A typical underbrush cleaner has a conveyor carrying
product across the two separate stainless steel tanks (see
Exhibits 8 and 9). The washing section ranges in length
from 3 to 6 feet. Seals and gaskets use Teflonฎ and
Vitonฎ. Most plastics and silicone rubbers are avoided.
A pair of rotating brushes in the first tank pick up the
wash solution from the sump, and mechanically scrub the
flux-covered bottom of the printed circuit board. The
concentration of the wash solution can range from 2 to 8
percent detergent in the aqueous process and 35 to 50
percent hydrocarbon in the semi-aqueous process. The
cleaning section of the tank can be heated to enhance the
cleaning action. For example, the aqueous wash solution
can be heated to between approximately 140ฐ and 160ฐF
and the semi-aqueous solution can be heated to
approximately 105ฐF. The solution is added
automatically to maintain operating levels of the cleaning
tank.
the boards. The temperature of the rinse water may be
anywhere from 75ฐ to 160ฐF. Fresh tap or deionized
water is added constantly while the used rinse is
discharged.
The following are some important characteristics of
underbrush cleaning:
Wave-soldered assemblies can be processed at four to
eight feet per minute.
Terpene emulsions can last two months before
showing signs of deterioration when running 400 sq.
ft. of product per shift.
Monthly replacement of the aqueous solution in the
wash tank avoids saturation of the cleaning solution
with rosin and subsequent decrease in cleaning
efficiency.
This process usually applies only to noncorrosive
rosin fluxes.
The amount of terpene consumed is generally about
50 percent of the quantity of solvent used in
underbrush processing.
Monoethanolamine is a typical detergent used in
underbrushing. The detergent consumption rate is
approximately two drums a week when producing
about 1,000 sq. ft. of product per day.
The conveyor system must be designed to suit the
product.
Hydrocarbon/surfactant emulsion rinses well at a
variety of temperatures, but warm water enhances the
drying of the printed circuit board. This drying is an
advantage to downstream assembly and test functions.
Water quality will affect SIR results.
The rinsing section uses a continuous supply of 0.5 to
1.0 gallons of water per minute. The flow cascades
forward in the cleaning machine and excess rinse
overflows through a particle filter. Local regulations
should be consulted prior to discharge to the drain.
The choice of deionized
A second tank with rotating brushes rinses the bottom of
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exhibit 7
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exhibit 8
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exhibit 9
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water or tap water depends on the quality of the local
plant water supply.
Operation and Maintenance
In a manufacturing environment, the ability to continue
operations often depends on backup strategies and
options.
In general, the basic design and control of underbrush
systems is simple, clear-cut, and easily-managed. The
use of a noncorrosive flux simplifies process control.
Fire and odor are usually the main concerns when a
hydrocarbon cleaner is suggested. A 50-50
hydrocarbon-water emulsion used in the wash stage,
however, reduces any fire hazards. Applying standard
operational methods for ventilation control reduces
odor problems.
Important process factors to control are the selection
of brushes and the water supply.
Brush material, brush size, and level of cleanliness
required determine how aggressive the cleaning
should be.
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Hydrocarbon/Surfactant
Spray Cleaning
This type of cleaning process is analogous to grease-
removing hand cleaners commonly used in the home.
The cleaner dissolves the soil, even in difficult to clean
areas, but it is not volatile enough to evaporate. The
solvent contains a surfactant that allows the solvent/soil
mixture to be rinsed away with water.
Typically, these cleaning systems have the
following sections:
Wash section with hydrocarbon/
surfactant spray;
Water rinse section;
Drying section.
These units look much like any in-line, conveyorized
aqueous or solvent cleaner. The cabinets are made out of
stainless steel and are usually at least 15 feet long. The
first half of the system is the hydrocarbon/surfactant
solvent wash module, and the second half is the rinse and
dry section. The equipment can be configured as one
long cabinet or as two in-line modules. Services must
include fire control, ventilation, power, drain, and water.
The rinse module may utilize an additional cabinet to
recycle the water. If the cleaning facility uses a water-
immiscible hydrocarbon/surfactant solvent, a separation
chamber is added to allow the solvent to decant from the
water (see Exhibit 11). All hydrocarbon/surfactant spray
washing systems use a hydrocarbon solvent at full
strength.
Concentrated hydrocarbon/surfactants have been shown
to be more effective cleaners than either CFC-113 or
aqueous cleaners for cleaning printed circuit board
assemblies, especially those with SMT (see Exhibit 10).
The key points to note are:
Equipment costs range from $90,000 to
$225,000;
Applicable for in-line systems;
Excellent for SMT cleaning;
More than adequate for through-hole
cleaning;
Retrofit of aqueous systems to terpene
systems may be unsafe because of
flammable mist formation;
9 fpm run rate potential;
Flammability and waste stream issues are
manageable.
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Virtually all hydrocarbon/surfactant spray cleaning
machine manufacturers adequately manage the important
concerns listed below:
Flammability can be controlled in the cabinet by:
Avoiding heat input to the system from both the
solder process and from the spray pumps;
Avoiding formation of hydrocarbon aerosol
caused by a spray stream impinging on a surface.
Using under-surface spraying. This technique
avoids mist formation by spraying the circuit
while it is immersed in the liquid. In some cases,
it can be used without inert gas fire protection.
Because some of the hydrocarbons are considered
VOCs, adequate containment is necessary. In the case
of terpenes, odor also can be objectionable and may
need to be controlled.
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exhibit 10
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exhibit 11
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Segregation of hydrocarbon/surfactant concentrate
from water makes handling waste solvent and
wastewater more manageable.
Machines must be constructed with compatible
materials.
Hydrocarbon/Surfactant Wash Section
Because spray-under-immersion reduces emissions and
fire hazards, new in-line semi-aqueous facilities are
moving away from direct spray cleaning. The wash
module sprays concentrated hydrocarbon from a room
temperature recirculating sump. To avoid forming a
terpene gel, this section must be separated from the water
rinse module. This segregation is accomplished by using
separate conveyor sections for each module. Dragout of
nearly 9 grams of solvent per square foot of board area
has been reported. An air knife is one method used to
remove excess surface liquid from the wash module. It
should be noted that an air knife can produce a mist of the
hydrocarbon. The use of an air knife is not recommended
in spray machines as it can make it difficult to design a
nitrogen inerting system. In a nitrogen-type system, the
goal is to prevent air from getting into the spray zone so
that the oxygen stays at a safe level, usually 6-8 percent
compared to air which is 20 percent oxygen. An air knife
will inject air into the system and the oxygen
concentration will rise to unsafe levels.
The wash area, not the rinse section, will present the fire
hazard. An incoming burning printed circuit board could
be an ignition source. The atomized spray and the impact
of the solvent against the printed circuit boards create
flammable atmospheres even though the temperature of
the solvent is below its flash point. These hydrocarbon
materials are conductive enough that a static electric
charge is not a problem in properly bonded and grounded
systems.
Water Rinse Section
As in most water wash systems, the cleanest water enters
the system closest to the exit and cascades forward in the
machine. The first rinse is always done with the worst
quality water that often overflows from that point to a
drain. Air knives in the rinse module remove the bulk of
the rinsing water on the surface.
The rinse module often sprays deionized water from a
recirculating sump. The use of deionized water is an
internal decision, affected by local water quality and
product cleanliness requirements. Before exiting the
rinse module, assemblies are sprayed with a final rinse of
fresh deionized water at a flow rate of approximately 0.75
gpm. A flammable atmosphere is unlikely in the rinse
module.
The rinse step is a critical parameter in cleaning because
an improper rinse can result in SIR dropping by two
orders of magnitude when hydrocarbon/ surfactant
residues are left on the board.
Drying Section
Although the use of infrared heaters aid in drying the
printed circuit boards, the drying process in these systems
usually emphasizes blowing off residual water rather than
drying entrapped water and residue.
Operation and Maintenance
In cleaning SMT products, the wash sump should be
drained once or twice a year, and the spent
hydrocarbon/surfactant should be barrelled and disposed
of as fuel. The larger machines have a wash sump
capacity of 110 gallons; the hydrocarbon/surfactant cost
is about $40/gal, and the disposal cost will be nearly
$75/drum. The frequency of change will increase if more
than average amounts of soil must be removed.
The vent system and air knives used in the wash section
affect the amount of solvent consumed per board. Unless
exhaust ventilation is excessive, hydrocarbon/surfactant
loss is almost entirely a result of solvent dragout either by
entrapment around board-mounted devices or by surface
film residue. Evaporation usually accounts for only a
small portion of hydrocarbon/surfactant losses. Typical
dragout should be between 9 and 13 grams per square
foot of product.
Typical servicing procedures for cleaning equipment
include lubrication of drives and bearings, belt and
tensioner adjustment, tightening or replacement of seals
and gaskets, and replacement of filters.
These units should be no more difficult to operate than
any other in-line system. An enforced preventive
maintenance program and a spare parts program are
desirable.
Using an existing water cleaner for the rinsing and drying
portion of the operation would significantly reduce the
capital outlay.
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WARNING: THIS MANUAL DOES NOT
RECOMMEND THE USE OF ANY FLAMMABLE
SOLVENT IN EQUIPMENT THAT IS NOT
PROPERLY PROTECTED AGAINST FIRE. Using a
hydrocarbon/surfactant solvent in equipment not designed
for its use (e.g., putting the solvent in unmodified
aqueous cleaning equipment that generates mists in air
from the sprays) would represent an extreme fire hazard
and cause potential for personal injury. Equipment such
as an unmodified aqueous sprayer is commonly found in
printed circuit board assembly shops, and there is a
natural desire to utilize existing equipment before
deciding to purchase new equipment.
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Batch Hydrocarbon/
Surfactant Cleaning
The first cycle in a hydrocarbon/surfactant batch cleaning
machine is the wash step and the second cycle is a water
wash and rinse step. The units tend to be very simple and
durable. The capital cost is low but the operating costs
are relatively high. This combination makes the units
best suited for low volume cleaning.
The performance of these batch cleaners is similar to the
hydrocarbon/surfactant in-line machine, except for
throughput capacity.
The following points should be noted:
Average equipment costs range from $10,000
to $70,000;
Batch cleaning is applicable for SMT and
through-hole technology;
In most instances drying with air knives or
heated air is necessary. This requirement
increases the cycle time of the cleaning
process.
Overloading reduces the cleaning or rinsing
effectiveness of these units;
Capacity will vary by board size and racking
configuration. Maximum panel size is about
18"x20";
Unlike the in-line units, these small packages
can be quickly and conveniently brought on-
line as required;
Some units utilize nitrogen blankets over the
solvent as a fire control feature;
Transfer between machines can be manual or
automated;
Typical water usage is about 1-5 GPM at a
temperature between 90ฐ and 140ฐF.
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In-Line Aqueous Cleaning
Aqueous cleaning of printed circuit boards relies on the
spray cleaning process. Cleaning per-formance depends
on the quality of process water. Plain water is effective
for ionic cleaning and water-soluble fluxes. With the
addition of saponi-fiers, water can remove nonpolar
substances such as oil and rosin flux as well. Although
difficult, cleaning of surface mount assemblies is possible
with this method.
Virtually every available in-line system has the same
configuration (see Exhibit 12), and most systems are
designed to be used with saponifiers. Most of these
machines can be used as the rinse module for a
hydrocarbon/surfactant system. This flexibility reduces
the capital outlay for a process change to
hydrocarbon/surfactant systems. However, full
conversion of in-line aqueous machines would require
new wash sections.
Factors to consider in evaluating in-line aqueous
cleaning systems are listed below:
Expect average in-line aqueous system capital
costs ranging from $40,000 to $150,000;
Be aware of applicability for SMT processing
with limitations;
Because water treatment is expensive, first try
cleaning with tap water and then shift to purified
water if the boards are not sufficiently clean;
Prewash sections can remove 70 to 80 percent of
the soils on a recently soldered printed circuit
board, thereby extending the life of the wash tank
solution. However, the water stream from the
wash section must be filtered to remove heavy
metals that might result from overextending the
wash tank bath life;
Anticipate process water temperatures up to
160ฐF;
Match flux to saponifier using a chemical
analysis. Experiment only when adequate
support is provided;
Blowing off excess solution from the board is
effective as a first stage in the drying process,
especially when saponifier is used;
Construction materials can be either stainless
steel or plastic (usually polypropylene). Each has
advantages and disadvantages. When making a
selection, consider durability, resistance to heat,
fire resistance, heat retention, chemical
resistance, aging, and repair;
Build in access to frequently-maintained
components, such as sumps, filters, drains, and
float switches. Consider the quality of hardware
and seals;
Anticipate using mechanical and chemical
descalers. Use sheet tube heaters and easily
replaced spray assemblies;
Install a pressure piston head on the water supply
to reduce hammering in the line caused by fast
actuating water supply solenoids;
As a first choice, use stainless steel vents, and
verify that condensate leaks will not be a
problem;
Include filters on all water lines, especially the
drain line, and change the filters as
recommended. Protect all solenoids with filters;
Secure necessary permits before purchasing
systems. Maintain waste stream monitoring logs
after installation. Keep abreast of relevant
regulations;
Recirculate water to insulated tanks with low
gradient immersion heaters where possible, or
use closed loop water recycling;
Product sensing systems are recommended to
reduce operating costs by shutting down the
pump when no product is being cleaned;
Consider modular units that allow reconfiguration
as needs change;
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exhibit 12
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Separate baths with splash curtains, notched
conveyor rails, drain areas, and air knives to
maintain machine efficiency.
Aqueous cleaners rely on spray nozzles to clean printed
circuit board assemblies. Innovative nozzle schemes are
emerging to provide better cleaning performance. For
example, one available nozzle design uses high velocity,
high volume water curtain systems to direct water at a
90ฐ angle to the conveyor. In this system, water does not
bounce back or splash after impinging the conveyor.
Instead, the water is directed radially outward, thus
enabling flow directly under conventional PCB and SMT
devices.
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Batch Aqueous Cleaning
"Dishwasher"-type batch spray machines are similar in
appearance to household dishwashers. These machines
have several cleaning stages. Electronic assemblies are
loaded into the machine in racks, and the machine fills
with water to a designated level. The water then heats up
and sprays onto the electronics assemblies. These
machines are fairly effective but they tend to operate on
long cycles. A typical dishwasher batch machine has a
throughput of 10 square meters of boards per eight hour
shift. This throughput rate can be a disadvantage because
most soldering machines have at least twice this
throughput.
High throughput batch machines are two to three times
more expensive than conventional batch machines and
require more floor space. However, they also have the
following benefits compared to a dishwasher batch
machine:
A higher throughput and three to eight times more
thorough cleaning;
75 percent less water consumption;
20 percent lower electricity usage because the wash
water remains in the tank and is not drained each
cycle, thus saving in heating costs; and
The full output of most wave soldering and reflow
machines can be managed.
During the two to three minute wash cycle, 120ฐF water
is pumped to high pressure jet sprays that wash the
printed circuit board assemblies. The machine stops for
a 15 to 30-second period to drain the water and then fan
sprays rinse the boards with water for 20 to 40 seconds.
Batch machines are not equipped with a drying unit. A
dryer is generally installed in addition to the batch
machine to avoid having to dry the walls of the batch
machine itself, to allow better heat accumulation (saving
energy), and because the physical movement of the
electronic assemblies from the batch machine to the dryer
shakes off considerable quantities of water. Drying
machines generally consist of upper and lower rotary air
knives fed from a large centrifugal blower. When the
cycle is started, these air knives blow off 90-98 percent
of the residual water. Next, hot air blows across the parts
to remove the excess water by evaporation. After
cooling, the printed circuit boards are generally dry and
can be tested immediately.
The effectiveness of batch cleaning machines depends a
great deal on the operator. To improve process control
and reduce the chance of operator error, batch machines
are equipped with automated controls for temperature,
cleaning solution dispensation, wash and rinse cycle
times, and rinse water cleanliness. Proper dispensation
and temperature control of saponifiers is especially
important because this type of cleaner can leave flux
residue or attack the electronic assembly if used
incorrectly. Automated machinery also is available to
load and unload batch machines.
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WATER AND WASTE STREAM HANDLING
Pre-Treatment of Water
The quality of the water used in aqueous and semi-
aqueous processes is important to achieve high
cleanliness. Therefore, the requirements for water supply
and water quality must be understood. In some areas,
water is in short supply and in others areas, the quality of
water is not suitable for cleaning printed circuit boards.
Factors to consider for water supply, quality,
and pre-treatment are:
Water supply requirements vary between
machines and with various recycling
schemes;
Water supply requirements range from 0.5
gpm to 10 gpm with 3 to 5 gpm being most
common. Systems that recycle water
require water only to make up for
evaporation and dragout;
Pre-treatment of water may be required to
reduce hardness and suspended
p articulates, or to reduce machine
maintenance. Water softening can be done
with off-the-shelf water softening
packages;
Water with hardness greater than four
should not be used with saponifiers;
Tap water costs less and wets better than
purified deionized water, but can introduce
contaminants or interfere with the cleaning
chemistry;
Highly deionized water can cause
problems.
rinsed with water is largely determined by the quality of
the rinse water.
The following treatments can adjust water quality.
Mechanical filtration to remove suspended particles;
Sedimentation (to allow suspended particles to settle);
Coagulation (to remove fine particles in colloidal
suspension);
Carbon filtration (to adsorb gases, vapors, organic
substances, and colloidal solids);
Bacteria filtration (to remove bacteria and other
microorgani sms);
Irradiation with ultraviolet light (to destroy bacteria
and other microorganisms);
Water softening (to exchange calcium and
magnesium). Softened water must never be used for
final rinse, as the sodium ions are hygroscopic and
thus incompatible with electronic assemblies;
Reverse osmosis (to remove dissolved solids and
colloids).
Ion exchange (to remove ions of all types except
hydrogen and hydroxy ions). This type of water
treatment can be either mixed-bed or separate-bed,
and have on-site or off-site regeneration. Ion
exchange is ideal for polishing reverse osmosis water,
or for providing rinse water for small- to medium-size
installations.
Typically, aqueous and semi-aqueous cleaning will use
tap water and/or deionized water. If the tap or deionized
water is inadequate for the specific application, water
treatment may be required. The cleanliness of assemblies
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Depending on the water quality, different combinations of
the above units are used to achieve the desired water
quality.
Post-Treatment of
Waste water
Wastewater generated from aqueous and semi-aqueous
cleaning processes may require treatment before being
discharged to local sanitary drains or publicly owned
treatment works (POTWs).
Wastewater can contain: (1) organic matter such as flux
residue and chemicals used in cleaner formulations
(monoethanolamines, terpenes, and other
hydrocarbon/surfactants); and (2) metals present either as
dissolved metals or as suspended metal (dissolved metals
will be present in saponified aqueous cleaning processes
due to the alkalinity of the solution). The wastewater
generated from a saponified aqueous cleaning process
also can have a high pH.
Note the items below in determining the
disposition of wastewater:
Local, state, and federal regulations on
wastewater may require treatment prior to
discharge into sewer or septic systems.
Wastewater discharge standards are expected
to become more stringent. Systems should be
designed to minimize or eliminate water
discharge.
Most saponified aqueous wastewater contains
alkanolamines, raising the pH of the wash tank
to between 10.5 and 11.8.
Rinse water from saponified aqueous cleaners
and hydrocarbon/surfactant cleaners will have
a high biological oxygen demand, unless
cleaner dragout from the wash section is
minimized.
Process water temperatures range from 120ฐ
to 165ฐF.
Wastewater can be removed from the site by
a contract waste hauler.
Closed loop water packages are available for
many, but not all, applications.
Metal Contamination Control
Dissolved metals, primarily copper, tin, and lead, are
toxic to both people and to the microorganisms that are
part of wastewater treatment facilities. Metals appear in
wastewater as a result of dissolution of the metal oxides
on parts being soldered, the flux activators, and etching
by the alkaline cleaner. More metals will be dissolved
when metal particulates, or metal fines, are allowed to
soak in the cleaning solution. Solder balls, solder splash,
and component parts are common types of metal
particulate found in wash tank sumps.
Metal contamination can be controlled by the methods
listed below:
Ion exchange beds are the most commonly used
technology to reduce concentration of dissolved metals
in wastewater. This technology is well developed and
established. Resins are available for removing a wide
range of cation and anion types. Regeneration of the
bed results in the production of a salt solution which
must be disposed of properly. Eventually, resin beds
lose their efficiency and must be replaced, thereby
producing additional waste to be managed properly.
Relative energy costs for this system are low, but the
ion exchange process is fairly capital intensive.
However, it can handle a high volume stream and has
a long useful life.
Filters are an inexpensive and effective way to remove
metal fines. When filtration efficiency drops off, it is
necessary to backwash the filter bed to remove
accumulated solids. These solids must be disposed of
as a sludge or mud, and may present a disposal
problem. Relative energy costs and other
requirements are low.
Lime and caustic soda can precipitate metals out of
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solution.
The following suggestions also will help control metal
contamination:
Monitor the alkalinity of the saponified aqueous
solution to avoid increases in dragout of heavy metal
contaminants.
Limit the amount of saponifier in the wash system to
the minimum required for the process.
Minimize the period of time a product is in the wash
system.
Include particle filters on the wash tank.
Change the filters as required.
Organics
Organic materials found in process wastewater are
generated from hydrocarbon chemicals and from
surfactants found in the chemical cleaners and fluxes used
in soldering.
Carbon adsorption is commonly used to remove organics.
It is important to note the items listed below when
considering carbon adsorption:
Carbon adsorption is one of the most efficient organic
removal processes available;
Carbon adsorption is reversible and the carbon beds
can be regenerated;
Control of the effluent stream entering the carbon bed
is critical to both the cost of operation and the
resultant quality of treated water. A mixed, low
concentration waste stream is very difficult and
expensive to treat;
Some organics such as rosin can quickly exhaust the
carbon, thus reducing the effective life of the bed;
If the dragout of organics from the cleaning process is
minimized, carbon adsorption may not be required.
Ultrafiltration is another membrane filtration process that
is used to separate high molecular weight solutes or
colloids from a solution or suspension. Pressure is
applied to force the solvent through the membrane after
which the solute is collected upstream, and the solvent
(containing very small molecular weight solutes) is
collected on the downstream side of the membrane. The
process concentrate and filter media may require
treatment prior to disposal. Relative energy costs tend to
fall in the medium range, whereas relative capital costs
would be on the high side due to the custom-designing of
the filter media to a specific range of solutes to be
controlled.
Reverse osmosis is used to remove dissolved materials
from water by filtration through a thin membrane.
Pressure is applied to force pure water molecules through
the membrane, leaving the larger contaminant molecules
behind. Reverse osmosis has been used to purify
brackish/sea water for drinking water purposes. It has
also been used to separate and concentrate heavy metals,
cyanide, ammonia, nitrates, and a variety of organic
materials such as glycols, organic acids, higher molecular
weight alcohols and carbohydrates. A concentrated
liquid waste containing the removed contaminant must be
disposed of properly. Careful pilot testing is often
required to tailor the porosity of the membrane for each
specific application. Many solvents and oxidizing agents
may damage or destroy particular kinds of membranes.
Compatibility of the membranes and the proposed
solvents should be tested prior to implementing the
alternative technology. Relative energy costs are in the
medium range. Capital and operating costs vary
depending on the pre-treatment required, stream volume
and level and type of contaminant(s) to be removed. In
general, the relative costs are expected to be high. This
process requires sophisticated pre-treatment and
operating equipment as well as sophisticated control
devices.
pH
Saponified aqueous wastewater is alkaline, having pH
levels between 7 and 12, depending on the cleaning
process. The type and strength of the chemical cleaner
used also has a direct bearing on the alkalinity of the
wastewater. Since the effluent is alkaline, corrective
treatments include the addition of sulfuric or hydrochloric
acid. The neutralizing process can be carried out
continuously or in batches and is economical. The
primary expense is the cost of the mixing tank. The
operating cost is essentially the cost of the acid.
Recycling Equipment
Recycling equipment can be used to purify and
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recirculate the rinse water used in rosin flux cleaning
operations, to purify all the wash and rinse water used in
a water-soluble flux cleaning operation, and to purify the
rinse water generated from semi-aqueous cleaning
processes. Recycling reduces energy use and avoids
disposal treatment costs. Exhibit 13 shows the concept
of a recycling treatment scheme.
A recycling system consists of filtration media that
remove particles and suspended matter (such as solder
balls), an ion exchange bed that removes dissolved
metals, and carbon adsorption that removes organic
matter. The water regenerated from the recycling system
is used as process water. Recycling equipment can be
retrofitted to existing cleaning machines. Different
recycling equipment and chemistry are required for rosin
and water-soluble fluxes because ion exchange beds are
rapidly exhausted by saponifier residue.
Recycling systems for semi-aqueous cleaning processes
can be used with hydrocarbon/surfactant solvents that
easily phase separate from water (Exhibit 14). The
advantage of the hydrocarbon/surfactant system over an
aqueous cleaning process is that the contaminants (soils)
removed from the printed circuit board are present in the
solvent phase that can be separated from the water phase.
This separation reduces the soil content in the recycled
water. The hydrocarbon/surfactant phase is separated
from the water phase using a unit such as a decanter. The
water phase is then recycled in a unit such as the one
described in Exhibit 14.
Contract Hauling
In certain cases, especially for small users of aqueous and
hydrocarbon/surfactant cleaning processes, it might be
more economical and efficient to enlist contractors to haul
the waste instead of recycling or reusing the wash water.
In recent cleaning system designs, the volume of
wastewater discharged is relatively small compared to
continuous, once-through systems (no recycling). This is
particularly true of the hydrocarbon/ surfactant processes,
especially if the system uses a concentrated solution in the
wash cycle. Waste from the hydrocarbon/surfactant wash
stage is a fuel source for incinerators or kilns.
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exhibit 13
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exhibit 14
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RECAP ON MANUAL
This manual has identified a structured program that provides basic information and identifies key
items that must be considered when selecting an aqueous or semi-aqueous cleaning process. The
manual has provided:
Key technical and economic issues that must be considered while selecting an alternative
cleaning process;
Major characteristics of three types of cleaning processes: water, water with the addition
of a saponifier, and hydrocarbon/surfactants;
Detailed description of machines used with these types of cleaning processes; and
Information on pre- and post-cleaning treatment of water.
The next section builds on this basic understanding of aqueous and semi-aqueous cleaning processes
and presents detailed case studies of these cleaning applications being implemented in industry.
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CASE STUDIES OF INDUSTRIAL PRACTICES
The following section presents actual industrial experiences with some of the alternative technologies
discussed earlier in this manual.
Mention of any company or product in this document is for informational purposes only and does not
constitute a recommendation of any such company or product, either express or implied by EPA,
ICOLP, ICOLP committee members, and the companies that employ the ICOLP committee members.
Case Study #1: Terpene Cleaning of Surface Mount Assemblies;
Case Study #2: Terpene Cleaning of Printed Circuit Board Assemblies;
Case Study #3: Micro-Droplet Aqueous Cleaning of Surface Mount Technology;
Case Study #4: Organic Acid Flux Qualification for Aqueous Cleaning;
Case Study #5: Heavy Metals Removal System
Case Study #6: Conversion from CFC-113/Methanol Cleaning to Aqueous Cleaning for
Medium-Sized Surface Mount Device Assembler
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CASE STUDY #1:
TERRENE CLEANING OF
SURFACE MOUNT
ASSEMBLIES
Case study #1 describes AT&T's terpene process for total
immersion cleaning of surface mount assemblies.
Traditionally AT&T and most of the industry has relied
on CFC-113 solvents for removing residues from surface
mount components. For both performance and
environmental reasons, however, AT&T selected an in-
line terpene spray cleaner.
The formulation of the d-Limonene/surfactant material
known as Bioactฎ EC-7 and the associated development
of a cleaning process to effectively utilize this new semi-
aqueous material constitute a cleaning technology that
provides the benefits of both solvent and aqueous
cleaning. The process for using EC-7 in cleaning printed
circuit board assemblies involves spraying the assembly
with EC-7 concentrate. The EC-7 spray removes the
bulk of the flux residue by emulsifying or dissolving the
constituents of the flux residue. The remaining EC-7/flux
residue is rinsed from the assembly with water.
The unique properties of EC-7 determine its mode of use
and the design of the facility. The material has a strong
citrus odor, a boiling temperature of about 350ฐF, a
vapor pressure of 1.6 mm Hg and a closed cup flash point
of 117ฐF. Since EC-7 has a deteriorating effect on some
elastomers and plastics, construction materials and
component qualifications demand considerable attention.
These factors resulted in the need for a machine different
from any system used before at AT&T.
AT&T determined that commercially-available systems
were not adequate for cleaning surface mount
components with EC-7 based on results obtained from
material characterization process studies. Therefore,
equipment vendors were approached regarding their
willingness to undertake a customized project. Based on
discussions with the individual manufacturers on the
project and the quotes received on the proposed
equipment, it was decided that Detrex Corporation would
build, per AT&T specifications, the first production EC-7
spray cleaning machine.
Cleaning equipment must meet the following
requirements:
All construction materials including seals
and gaskets must be compatible with EC-7
( such as stainless steel, Vitonฎ, and
Teflonฎ);
Mechanisms to control dragout and contain
the spray aerosol are required to minimize
material loss and odor;
High pressure spray is needed to facilitate
cleaning under low stand-off components;
System throughput, in continuous operation,
should be suited to the soldering operation
used;
Product must be washed and rinsed with
maximum isolation between wash and rinse
sections;
Fire safely measures are required to maintain
EC-7 below its flash point. These measures
include an inerting system to prevent ignition
and an automatic system to shut down the
facility in case of a problem.
The spray machine was designed to function adequately
in a production environment, yet be flexible enough to
determine optimal cleaning parameters. The machine
incorporated a programmable logic controller, separate
controls for each individual component in the system, and
both high and low pressure spray sections. Two
conveyorized spray modules are arranged end-to-end in
the pass-through system. Schematics of the modules are
shown in Exhibit 15 and Exhibit 16. Each module has a
60 gpm low pressure (approximately 30 psi) and a 40
gpm high pressure (approximately 90 psi) spray section
followed by an air knife to remove excess surface liquid.
The low
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exhibit 15
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exhibit 16
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pressure spray zone is approximately three feet long and
has 27 individually adjustable nozzles in six spray
headers. The wash module sprays concentrated (100
percent) EC-7 from a 110-gallon recirculating sump
maintained below 77ฐF. The rinse module sprays
deionized (DI) water from all 0-gallon recirculating
sump. The rinse module differs from the wash module in
that the rinse module sump overflows to a sanitary drain.
Before exiting the rinse module, assemblies are sprayed
with a final rinse of fresh DI water at a flow rate of
approximately 0.75 gpm. The final rinse water cascades
forward into the rinse sump. The rinse module is also
equipped with air knives to remove the bulk of the
surface rinsing water. The dryer is made up of an air
knife section, a recirculated hot air section, a series of
infrared dryers with high air flow convection, and a series
of infrared dryers with low air flow convection.
Other features incorporated into the design focus on
issues involving EC-7 material compatibility. Although
EC-7 tends to swell certain plastics and elastomers.
Teflon and Viton have been found to be acceptable
materials.
Rinse Water: Deionized rinse water is
supplied at 0.75 gpm at 125ฐF from a
deionized water heater.
Electricity: This facility requires a 200 amp,
480 volt, 3-phase electrical service.
Exhaust: The exhaust was specified to be
2,800 cfm maximum so that all recirculating
air flow could be 100 percent exhausted if
required.
Drain: Disposal of the rinse water is to a
sanitary drain. The effluent flow is
approximately 0.75 gpm. Test ports are
provided to sample water quality.
Eye Wash Station: Because chemicals are
being used, an eye wash station in the area is
necessary.
Due to the relatively large size (approximately 32 ft. x 6
ft.) and number of features included in the new machine's
design, extensive preparation was needed to install the
machine in the factory.
The following services were required for this
customized machine:
Nitrogen Supply: The design specification
required a nitrogen supply of approximately
2,000 cfh. At present, consumption of
nitrogen is about 1,200 cfh and it is
anticipated that the consumption can be
reduced further.
Chilled Water: Chilled water
(approximately 50 ฐF) is supplied to the
machine at 5 gpm to maintain the 110-gallon
sump of EC-7 below 70 ฐF and the
recirculating air knife below 95ฐF.
When assessing the key items to implement a cleaning
technology, it is important to consider cleaning
effectiveness, qualification issues, material usage,
wastewater and disposal requirements and process
economics. These factors are discussed below.
Cleaning Effectiveness
The spray facility has been successfully used to clean
SMT printed circuit boards with up to 5,000 surface
mount reflowed interconnections. Omega-Meterฎ 600-
SMD testing of one production code with 1,350
interconnections indicated an average decrease in ionic
residue from 6.1 micrograms NaCl equivalent per square
inch of surface area before cleaning to 1.8 after cleaning.
This printed circuit board code contained a mix of 68 to
84 pin plastic leaded chip carriers, 8 to 28 pin small
outline integrated circuits, and 1205 to 1210 size ceramic
chip capacitors. Measurements show that not only are
terpenes effective cleaners but they also provide
improved ionic cleaning results when compared with
CFC solvent cleaning.
Qualification Issues
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During the trial of the EC-7 spray machine, interdigitated,
metallic-conductor comb-patterned test coupons were
processed through the cleaning system using various
rinse water temperatures. It should be noted that only the
rinse water temperature was varied since the EC-7 spray
is maintained below 77 ฐF. After processing, these
boards were maintained at 95ฐF, 90 percent relative
humidity and 50 volt DC bias for 24 days. Once each
day, the bias was removed and an opposite polarity of
100 volt DC potential was applied and the SIR measured.
The average log SIR for these FR4 test boards are shown
in Exhibit 17. The rinsing temperature was varied from
77ฐF to 105ฐF to 150ฐF. No degradation of SIR was
observed over this range of temperature. SIR values for
boards underbrushed with a 35 percent emulsion of EC-7
maintained at approximately 110ฐF are plotted as dashed
lines in Exhibit 17. These boards were underbrushed
with 35 percent concentration EC-7 at 135ฐ F and
underbrush rinsed with either 65 ฐF or 150ฐF water.
Neither the EC-7 emulsion, brushing action, nor the
rinsing temperature degraded the SIR.
Exhibit 17 also plots the SIR for boards sprayed with
concentrated EC-7 and not rinsed. These EC-7 sprayed
boards were processed through the infrared drying
section of the rinsing module. Exhibit 17 shows a
decrease in log SIR to about 8 for these boards. This
drop is most likely due to polymerized EC-7 and
surfactant remaining on the surface. Although the SIR is
"low" in value, the trajectory is positive, indicating that
there is no metal migration or corrosion taking place.
This test does indicate that the effective rinsing of EC-7
residues is necessary to maintain process control.
In order to test the effect EC-7 has on solder mask
material, boards fabricated with stripes of the various
solder masks, oriented perpendicular to the interdigitated
metallic conductors, were processed. The average log
SIR for the boards processed through the EC-7 spray
machine at the normal conveyor speed of 9 feet per
minute are shown in Exhibit 18. The log SIR for "bare"
FR4 boards is typically in the range of 11 to 12.
Whenever SIR measurements are used to show the effect
of a process or material, control boards must be
processed. The log SIR shown in Exhibit 18 indicates
that although using solder mask lowers the SIR from the
base value of the FR4 boards, the value does not fall
below the lower value of 9.5. The log SIR values for the
solder mask striped boards exposed to EC-7 are the same
or better than the value for their respective controls.
Rather than processing boards at various conveyor speeds
to investigate longer exposures to EC-7, it was decided to
soak boards in EC-7 for an extended period (24 hours)
and measure the change in SIR over maximum EC-7
exposure and minimum rinsing. If boards were
processed in the EC-7 spray machine using various
conveyor speeds, the rinse duration as well as the EC-7
spray duration would be varied. Because of unforeseen
experimental interruptions and scheduling, the test boards
soaked in EC-7 for 7 days. After this extremely long
soak, the boards were processed through the EC-7 spray
machine. The average log SIR for the boards is
presented in Exhibit 19. The SIR of the solder mask
striped boards was not degraded. The average values for
the log SIR were 10 to 11.5. The SIR for the bare FR4
boards decreased approximately two orders of magnitude.
This decrease may be due to the absorption of EC-7 into
the surface during the extremely long soak. Although the
SIR decreased, the trajectory is positive. It should be
noted that the 7-day soak in concentrated EC-7 followed
by spraying with 90 psi EC-7 and rinsing water did not
remove the striped solder mask material from the
compounds as judged by visual observations at 20X
magnification.
Material Usage
The consumption of EC-7 depends on the amount of EC-
7 dragout from the wash module to the rinse module
coupled with evaporative losses. Although EC-7 is
biodegradable, it has a high biochemical oxygen demand
value and could overload a waste treatment system if
disposed of in large quantities.
Initial evaluations during acceptance testing indicated that
the air knives, if positioned immediately above and below
the board surface, could reduce the EC-7 dragout to about
4 grams of EC-7 per square foot of projected board area.
Without an air knife, the maximum dragout of EC-7 was
measured to be about 29 grams per square foot. With
various height components, the air
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exhibit 17
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exhibit 18
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exhibit 19
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knives have been adjusted to accommodate the current
product code mix. This configuration results in a dragout
of approximately 9 to 12 grams per square foot of board
area.
Wastewater and Disposal
Issues
Because EC-7 residue is noncorrosive, rinsing of EC-7
from assemblies is not as important as the removal of
water soluble flux or detergents. Consequently, not only
is the rinsing temperature in EC-7 cleaning machines
reduced, but the flow rate of rinsing water can also be
reduced. Final rinse flow rates of 0.5 to 1.0 gpm are
typical in EC-7 cleaning facilities. With these rinsing
rates, the concentration of EC-7 in the rinsing sump is in
the order of hundreds of ppm. Concentrations of these
proportions have presented no biological treatability
problems.
The concentration of lead and copper in the rinse water
that has been filtered with in-line filters (e.g., 100 micron
paper filters) has been measured to be less than 20 ppb
and tin has been measured at less than 100 ppb. The
metals concentration in EC-7 rinse water continues to be
monitored to ensure that high concentrations of EC-7 are
not inadvertently delivered to a sanitary drain.
Although the number of reflowed interconnections on
boards can number in the thousands, the actual amount of
solder paste flux residue needed to be removed is small.
The typical volume of solder paste per interconnection is
less than one-thousandth of a cubic inch and the paste is
only 11 percent flux by weight. Considering the "small"
amount of flux and the "large" rosin loading capability of
EC-7, it is anticipated that the initial 110-gallon sump
charge of EC-7 will not become saturated with flux until
after an entire year of production operation. The
concentrated EC-7 disposal cost is approximately $50
per 55-gallon drum, and the effluent is recycled by a fuel
blender to fire a cement kiln.
Process Economics
The final and one of the most important considerations is
the cost of the cleaning technology. Exhibit 20 illustrates
the cost of various cleaning technologies based on square
foot of board processed. Although we have focused on
the elimination of CFC cleaning, we have included costs
for aqueous processes to allow the relative baseline costs
for cleaning to be determined.
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Exhibit 20
SUMMARY OF SPRAY CLEANING COST PER SQUARE FOOT
OF BOARD CLEANED FOR VARIOUS PROCESSES
Alkaline
Saponified
Water Terpene Water CFC-113
Chemical $0.000 $0.121 $0.041
Water $0.017 $0.002 $0.018
Disposal $0.003 $0.001 $0.067
Energy $0.049 $0.026 $0.045
Maintenance $0.008 $0.008 $0.008
Nitrogen $0.000 $0.007 $0.000
TOTAL $0.077 $0.165 $0.179
Source: AT&T.
$0.178
$0.000
$0.000
$0.042
$0.008
$0.000
$0.228
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CASE STUDY #2:
TERRENE CLEANING OF
PRINTED CIRCUIT
BOARD ASSEMBLIES
In mid-1989, one of Motorola plants began an active
program to reduce its use of CFC-113 to zero by August
1990. As of July 20, 1990, this plant had accomplished
this goal. In 1988, there were 29 active CFC-113
systems in operation using 250,000 pounds of CFC-113
annually (valued at $700,000 at 1990 prices). This
Motorola plant accomplished this reduction by taking the
following four major steps.
The first step was to repair/retrofit existing stills to
prevent excessive solvent loss. In conjunction with this
process, a number of CFC-113 stills were also removed
from production based on re-evaluation of production
needs. New machines and new CFC material
technologies were implemented where possible. A 50
percent reduction in the use of CFC-113 was
accomplished.
The second step was the implementation of a wave-solder
"no clean" system. This action was taken early in 1990,
and much work was completed to make the system run
cleanly. (The boards soldered are densely populated,
leaded top side and surface mount bottom side boards.)
The third step was to implement production of a "no
clean" surface mount technology screen paste system.
This measure was also completed early in 1990.
The fourth and final step needed to bring this location to
the facility-wide CFC-113 elimination goal was the
implementation of an in-line terpene cleaner. It was
found that some applications could not be replaced with
a "no-clean" technology. Certain products demanded a
high levels of cleanliness (e.g., products with elastomeric
connections, resin flux performance issues, or that needed
encapsulation).
The terpene cleaning option allowed
Motorola to clean all the remaining board
types, solder stencils, misprinted PCBs, etc.
The products cleaned in this system are
cleaner than their CFC-113 counterparts.
Motorola has experienced an 80 percent cost
savings by cleaning with the terpene system.
Terpene Cleaning System
The plant selected a Vitronics S-2150 semi-aqueous
cleaning system. This system consists of one terpene
cleaner wash section, followed by one water rinse system.
A transfer conveyor couples the two sections. The
system dimensions are 23 feet long by 3 feet wide by 4
feet high. The system can handle up to 18-inch wide
products, with cleaning speeds exceeding 5 feet per
minute. However, drying products with connectors and
shields requires the system to run at a slower speed of 1.5
feet per minute.
System Requirements
Motorola's terpene cleaning system requires the
following:
A ventilation system capable of 1,500 cubic feet per
minute (cfm) at a pressure of 4 inches of water
equivalent.
Electrical service of 208V at 80 amperes (240V,
380V, and 480V models are also available).
Chilled water flow of 4 gallons per minute at 65 ฐF or
less (for cooling the terpene wash stage). This is
necessary to remove heat generated by the terpene
pump. Hot boards are not allowed to enter the terpene
section since this will trip the unit for terpene
overheat.
Compressed air at 100 psi (20 cfm may be required,
according to your drying configuration and need).
Heated deionized water at 120ฐ and 3 gallons per
minute. This site uses water heated by a 54 KV
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commercial-grade 120-gallon water heater and purified
by the reverse osmosis method. The purity of water
required for specific applications varies widely, from city
water (this may be a high risk if circuits are high
impedance) to greater than 1 mega ohm heated deionized
water.
Terpene-compatible materials in construction.
Because terpene can dissolve PVCs, CPVCs, and
natural rubbers, only stainless steel, Viton, Teflon, and
polypropylene plastics come in contact with the
terpene. Motorola uses a polypropylene sump system
with a backup pump and sensors. The sump system is
an in-house design using a Teel 3/4 H.P. stainless
steel pump and a second backup pump as well. A
polypropylene water level sensor with alarm and
backup switching to the second pump is also used in
case of failure. The water container is made of
polypropylene plastic.
Operational Issues
Some operational issues that Motorola has experienced
are:
The new system's hourly cost has typically been $7.50
per running hour as compared to $38.50 per hour for
CFC-113. This cost is based on a recyclable terpene
cleaner (EC-7R).
Production downtime is near zero.
The parts are cleaner than their CFC-113
counterparts.
Flammability is a minor issue, and there are redundant
on-board fire detection and suppres-sion systems on
the Vitronics equipment.
The advantages of such a recycling system are:
Very low lead or any heavy metal discharge;
Very low discharge of organic matter
(terpene);
Savings in water and energy costs to heat the
water.
In addition, preliminary results have shown that cleaning
solder screens and misprinted PCBs in the in-line terpene
system unnecessarily and prematurely load the terpene
solvent with contaminants and severely shorten the bath
life. Therefore, this Motorola plant has decided to use
batch cleaning capability to clean both screens and
misprinted PCBs. An Electronic Control Design batch
terpene system has been chosen at this location.
Future Plans
This site of Motorola plans to install and run a complete
stand alone terpene/water recycling system. This requires
installing a water scrubber/separator system to capture
and recondition the wastewater effluent for reuse. These
engineers have chosen a water/terpene separator made by
Separation Technologists. This system is designed to
separate the terpene from water, clean and filter the
heated water to deionized purity, and recycle it for reuse
in the water rinse section.
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CASE STUDY #3:
MICRO-DROPLET
AQUEOUS CLEANING OF
SURFACE MOUNT
TECHNOLOGY
Since 1974 Digital Equipment Corporation has pioneered
aqueous-based cleaning processes for through-hole
component modules. However, as surface mount
techniques for components emerged, results from
traditional aqueous cleaning chemistries and equipment
fell short of the expected cleanliness criteria generally
accepted in the electronics industry. The failure
mechanisms were attributed to more densely packed
components and the general topography of surface
mounted solder joints as opposed to through-hole solder
joints.
Many vendors and users of surface mount processes have
been trying to devise methodologies to overcome
problems associated with surface mounted components
and to extend aqueous cleaning techniques into the
surface mount space. Marginal successes have been
limited to surface mount architectures with coarser
pitches.
Digital perfected and patented a new cleaning process
that controls water droplet size and angle of impingement
for effectively cleaning rigid leaded surface mount
components. The process referred to as "Micro-Droplet"
aqueous cleaning will be made available to users of CFCs
worldwide, without any charge as part of Digital's
corporate commitment to protect the ozone layer.
Micro-Droplet Process
Overview
Digital embarked on a program aimed at identify-ing the
critical process parameters that assure success for
aqueous cleaning of fine pitch surface mount modules.
They began with a rigorous engineering evaluation, based
on the latest design of experiments and technology, and
a strong understanding of the parameters of the printed
wiring circuit modules manufacturing process.
The process development program allowed the engineers
to identify (previously uninvestigated) key process
parameters that would allow fine pitch surface mount
modules to be cleaned efficiently without using CFC
solvents. While others in the industry had concentrated
on their complex chemistries and water pressure
variables, Digital engineers defined the angle of
impingement of the water and the water droplet size as
being the key parameters driving the effectiveness of the
aqueous cleaning process, specifically for finer pitch,
rigid leaded surface mount components.
Working under a well-defined intellectual property
protection agreement, Digital engineers and engineers
from Bete Fog Nozzle Company, Inc. of Greenfield, MA
(a nozzle design and manufactur-ing firm) collaborated
on a combination nozzle design and water delivery
system that successfully met or exceeded the cleanliness
criteria set for fine pitch surface mount modules cleaned
with CFC solvents.
The highlights of this system are:
The delivery system is designed to create specific
micro-sized water drop-lets and provide a
continuously vary-ing angle of attack for the water
spray.
The process has been characterized for all rigid leaded
surface mount modules currently manufactured for
Digital products.
Hardware to support this technology is available as a
"retrofit kit."
The retrofit kit is field installable on an off-the-shelf
aqueous cleaning system.
Other manufacturers of aqueous cleaning systems may
accommodate the retrofit kit at some time in the
future, but no effort has been exerted to assure this at
this time.
Having successfully met extensive manufacturing
qualification procedures and documentation activities, the
process has been implemented in Digital's Modules
Manufacturing Line. More information on this patented
public domain technology can be obtained from the
International Cooperative for Ozone Layer Protection
(ICOLP). ICOLP's address is provided at the end of this
manual in Appendix A.
Process Development
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The micro-droplet aqueous cleaning process consists of
a rotating arm (as shown in Exhibit 21) that allows the
spray to impinge equally on all four sides of the
component. This coverage is accomplished using only
two nozzles compared to the many nozzles that would be
required in a fixed manifold system. This design reduces
the total flow rate, thereby minimizing the size of the
pump (power outage) required. The need for a high flow
rate combined with the high pressure needed in this
system would have otherwise required a very large
electric motor to power the pump.
The rotation of the arm causes the saponified solution to
be delivered intermittently to a particular section on the
surface of the circuit board. This intermittence caused by
the rotating arm allows the solution that has been sprayed
on the particular section of the board to drain from the
board surface. Thus, when the spray pattern returns, it
will be in direct contact with the surface of the board, not
the barrier layer of water that has flooded the surface of
the board as in more conventional cleaning operations.
The system uses a helically vaned spiral hollow cone
nozzle with a spray pattern angle of 50 degrees. This
angle along with the droplet size and flow characteristics
causes the water to strike the surface of the circuit board
and be redirected under the SMT components without
giving up its velocity upon impact, thereby improving the
cleaning performance.
The combination of high pressure and low flow rate
yields a small droplet size that is needed to penetrate the
tight spaces that are a by-product of utilizing surface
mount technology. Digital has qualified the process on
component packages down to 25 mil lead spacing.
Process Parameters
Digital is now operating the process at the parameters
listed below. These parameters were arrived at using
experimental design techniques for parametric
optimization during nearly two and one-half years of
process development work.
Process parameters include:
Saponifier concentration: 7 percent (in both
pre-wash and wash sections).
Water temperature: 150ฐF.
Conveyor belt speed: 3 feet per minute.
Micro-droplet spray pressure: 400 psi. (All
other spray pressures were per equipment
vendor's recommendation.)
The new cleaning process uses a Stoelting cleaning
machine (model CBW 224) modified with a retrofit kit
supplied by Bete Fog Nozzle.
Process Qualification
Based on the optimum process parameters, Digital
conducted a number of tests to qualify the process. The
tests focused on three areas: cleanliness, joint integrity,
and component and module functional testing.
For the cleanliness portion of the qualification the boards
were tested for ionic contamination. The results were
favorable and the conclusion was that the micro-droplet
system removed more potassium while leaving sodium
levels only slightly higher. It was clear that the micro-
droplet system was removing more contamination than
the conventional aqueous cleaner.
The joint integrity testing was conducted by performing
pull and peel tests of the leads on 25 mil parts and
comparing this data to the empirical data from earlier
testing on solvent cleaned
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exhibit 21
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assemblies. There was no discemable difference in the
test data.
Several tests were performed to determine component
integrity. Results of the High Acceleration Stress
Testing, which is a functional test of the component after
accelerated thermal cycling, showed that there were no
failures on several different component types.
To check for delamination, an x-ray of the die attach was
performed. To further verify that no delamination had
occurred, C-Scan was also performed. All test results
were negative.
A gross leakage test for violation to hermetic seals was
conducted by placing the components in a fluoro-inert
solution at 125ฐC and observing the bubbles that would
indicate outgassing in the component. No bubbles were
observed during this testing.
Module functional testing at ambient temperature was
conducted for over 1 million component hours and nearly
200,000 module hours with no failures.
Waste Treatment Costs
The treatment costs for a system that accommodates four
aqueous cleaners are broken out in the following
categories:
Cost to neutralize wastewater: $18 per day.
Cost of wastewater discharge: $35 per day.
It is important to understand that there is a wide diversity
in the costs of dealing with a waste stream and the
amount and type of treatment that must be performed to
be in compliance with local ordinances. Before selecting
a non-CFC alternative, check with local and municipal
authorities on requirements.
Process Economics
Process economics includes the capital costs of acquiring
the process, the operating cost, and the cost of the
treatment of the waste stream that is a by-product of the
process. Costs of operating this system will vary widely.
Capital Costs
Capital costs are as little as $30,000 to retrofit an in-line
aqueous cleaner and $150,000 to purchase a new cleaner
with this modification installed.
Operating Costs
Operating costs are based on a 16 hr/day production of
500 to 700 square feet (which is well below maximum
production capacity). Operating costs for this system are
broken out in the following categories:
Cost of saponifier: $ 125 per day per machine.
Cost to supply softened water: $3 per day (based on
four aqueous cleaning machines).
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CASE STUDY #4:
ORGANIC ACID FLUX
QUALIFICATION FOR
AQUEOUS CLEANING
Overview
Case study #4 describes how Company A conducted a
program to develop process methods for organic acid
(OA) flux usage and to select OA flux candidates for
qualification testing. This case study shows how
Company A took steps to change from using a rosin flux
and solvent cleaning of printed wiring boards to the
proposed water soluble OA flux and water cleaning
process. Part of this test also required the successful
application of a polyurethane conformal coating.
Current processes in Company A utilize a rosin flux (RA
or RMA) at the machine soldering area, followed by
cleaning with methyl chloroform. A final process
requires coating the printed wiring assemblies with a
polyurethane. The study was limited to glass/epoxy
PWAs with and without permanent solder mask.
Five OA fluxes were tested and two of these were
selected for further qualification testing. OA fluxed
assemblies were be cleaned to the current cleanliness
levels of the rosin based fluxes used in the factory.
Solderability defects of OA fluxed assemblies were
significantly reduced.
Test Plan
The fluxes selected for testing were cleaned with a
saponifier and deionized water.
A mil-spec rosin flux was selected as the control to be
cleaned with methyl chloroform.
A data package will be developed in the qualification
phase of this test program to support specification
changes for the use of OA fluxes.
The criteria included:
Cleanability of post-solder residues
Visual inspection
Ionic contamination testing
Humidity/moisture resistance testing
Solder yield performance
Quality Assurance visual inspection per
MIL-P-28809A
Material hazards and safety
Shelf life
Equipment requirements
Compatibility to SMD adhesives, part
marking, and tapes
Scope
This case study describes the test program conducted to
evaluate OA fluxes for wave soldering. The test program
consisted of two subsets. The first flux evaluated was
Superior 30 by using a process similar to the existing
manufacturing method. The second test procedure
evaluated the characteristics of four other OA fluxes and
a rosin flux in regard to cleanability and solderability.
This program examined flux compatibility with current
assembly processes and equipment. Long-term corrosion
reliability tests will be performed by Company A during
additional flux qualification testing.
The following machine settings were the same for all
fluxes:
Conveyor speed of 3 fpm;
Solder pot temperature of 500ฐ F;
Topside board temperature of 190-200ฐ F;
Wave solder air knife.
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Aqueous cleaning was performed on an in-line
machine, at 2 fpm, using the following process
conditions:
Saponifier concentration (Wash 1 stage):
0.4 - 0.6 percent by volume
Conveyor speed: 2 fpm
Wash 1 solution temperature: 150+10ฐF
Wash 2 solution temperature: 170+10ฐF
Final rinse water temperature: 160+10ฐF
The recirculating tanks were drained,
cleaned, and refilled after the wash solution
had been in use 20 hours.
Solvent cleaning was performed using a methyl
chloroform in-line solvent machine with a conveyor
speed of 2 to 4 fpm and with the following temperature
requirements and recommended pressure settings:
Boil sump temperature: 167 + 10ฐF
Distillate sump temperature: 155 + 10ฐF
High pressure sump temperature: 165 + 10ฐF
Spray-over-immersion sump temperature: 164 +
10ฐF
Pre-clean upper spray pressure: 20 psi
Pre-clean lower spray pressure: 15 psi
High-pressure upper spray pressure: 30 psi
High-pressure lower spray pressure: 25 psi
Immersion spray pressure: 25 psi
Distillate upper spray pressure: 20 psi
Distillate lower spray pressure: 15 psi
With the exception of fluxing, which was hand dipped,
was applied to all samples, in a controlled manner, by
foaming, Superior 30.
All samples were 0.062 inch thick epoxy glass material.
All test samples underwent a solder pre-bake cycle of
200 ฐF for 16 hours. Each flux group consisted of eight
boards. Six of the boards were PTH, populated with
DIPs and axial parts, and having half of the board
covered by a permanent solder mask. Two boards were
cleanliness tested for ionic contamination, and four were
humidity/moisture resistance tested, with one of these
boards having three components removed to check for
cleanliness under parts. The remaining two boards were
SMT configurations populated with LCCs, SOICs, and
chip components. One of these boards was tested for
ionic contamination and one for humidity/moisture.
Test Procedure
The following steps constitute the test procedure:
Label PWAs.
Apply part marking/overcoating materials on DIPs
and cure in accordance with the appropriate
specifications. Label the parts accordingly. Apply
adhesive dots to boards. This test will be performed
to check material compatibility with OA flux. Test
boards used for this testing will be separated from the
ones outlined above.
Apply solder paste to PWB and place SMDs.
Vapor phase solder and clean PWAs.
Apply OA flux to SMD PWAs and process through
wave solder and clean.
Insert DIPs and axial on PTH PWB
Flux and wave solder PWA.
Clean PWAs per aqueous process.
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Quality assurance inspection of PWAs per MIL-P-
28809A (must wear gloves).
Omega meter test two PTH PWAs and one SMD
PWA per flux.
Remove three components from one PTH PWA
(schedule for humidity testing) per flux type and check
for contaminants underneath parts.
Conformally coat assemblies with polyurethane.
Submit all coated samples to quality assurance for
visual inspection. Inspection performed at 10X.
Record and photograph any anomaly.
Submit samples to 10-cycle Moisture Resistance
testing in accordance with MIL-STD-202, method
106. Measure insulation resistance before and after
the first, fourth, seventh, tenth, and post-conditioning
cycles of testing.
Submit all samples for visual inspection after
completion of testing. Document and photograph
coating anomalies, if necessary.
Analyze test results.
Ionic Contamination
Using the Omegameter 600, all samples passed with
readings well below the allowable limit.
Conformal Coat/Moisture
Resistance
Polyurethane conformal coating was applied by spray and
by dipping. Spray did not provide consistent results.
Tests applied were MIL-I-46058C, MIL-STD-202F, and
visual inspection.
While many of the initial readings were lower than
expected, these values recovered, and except for 4
specifically identified faults, the post conditioning results
were above the minimum requirement of 5.0XE9 ohms.
The visual inspection results revealed that the best OA
candidate had slight mealing on one sample, with the rest
being acceptable. Coating adhesion was acceptable. On
the rosin flux control, one sample had a high degree of
mealing and minor delamination on another coating
adhesion was acceptable.
Test Results and Discussion
Solder Joint Visual Inspection
Using MIL-P-20809A, the ranking of candidates,
beginning with the best, was as follows: Kester 2331-
ZX, LONCO 3355 NB, ROSIN, Gardiner 5735, Alpha
Metal 857, and Superior 30.
Kester 2331-ZX fluxed boards had the lowest solder
defect rate and showed a 60 percent improvement over
the rosin flux system used in the factory. All OA fluxes
were able to solder marginally solderable parts parts
which are defined as axial parts in storage over 3 years
without pre-tinning. Different fluxes exhibited different
types of problems, and those noted included solder balls
on permanent mask areas, voids, and insufficient fill.
DIP Removal/Flux Residue
Inspection
There was no evidence of flux residue remaining
underneath DIPs after cleaning for all tested fluxes.
Materials Evaluation
Materials used to test OA flux compatibility to completed
board assemblies were polyurethane adhesive, epoxy
adhesive, marking ink, overcoat materials, and solder
stop. No deleterious effects resulting from OA flux
interaction with process materials were observed.
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Material Hazards/Safety
The prime ingredient in the evaluated fluxes was
isopropyl alcohol. Various activators included mild
organic acids, hydrohalides, and amines.
Controls similar to those in effect presently would be
suitable for safe use of the OA products.
Some fluxes emitted strong odors when soldered. Other
samples did not.
Facility Requirements
The flux application equipment should be made of epoxy,
polyethylene, polypropylene, or Teflon.
Preliminary investigations indicated that the effluent from
cleaning OA fluxes was acceptable for discharge per
environmental control. Further analysis of effluent
disposal, tied to production levels, will be investigated.
Conclusions and
Recommendations
OA flux can be a viable alternative to the currently used
rosin-based fluxes for soldering high reliability, mixed
technology printed wiring boards.
Screening flux candidates is required to confirm that the
most appropriate product is selected, thereby increasing
the likelihood of successful process change.
A primary flux candidate and an alternate were presented
from this study. Further qualification, such as corrosion
testing, and the result of higher volumes of effluent on the
waste handling facility should be conducted.
All process materials used in assembling PWAs and all
conformal coating products should be evaluated for use
with OA fluxes.
Industrial Engineering should conduct a method and cost
study for the implementation of OA fluxes to the factory.
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CASE STUDY #5:
HEAVY METALS
REMOVAL SYSTEM
Filtration System
The filtration system is designed to remove soluble and
insoluble metals from the wastewater. It consists of a
series of filters of selected type and particle size retention.
In using the heavy metals removal system, Digital
Equipment Corporation's objectives were twofold: (1) to
reduce the level of heavy metals in wastewater from
several of its aqueous manufacturing processes and (2) to
reduce the costs of waste disposal. In addition to meeting
these objectives, Digital was required to comply with all
applicable federal, state and local regulations. This
required, for example, preventing the introduction of
pollutants into Publicly Owned Treatment Works
(POTWs), establishing point source controls within the
manufacturing processes, and designing systems for
controlling and monitoring pollutant discharges.
This process should not be confused with a closed loop
water supply package for aqueous or semi-aqueous
cleaners. No organic matter removal takes place in this
process and the wastewater exiting after metal removal
and pH balancing is discharged to a local municipal
waste treatment facility. The ion beds used in this facility
were designed to hold the strong positive metal ions of
copper, tin, and lead. These beds do not get saturated
with the saponifier. The heavy metal removal package
described here is not intended to be used as a closed loop
water supply system.
Overview of Removal
Process
The three key components of the process are:
neutralization, filtration and ion exchange (see Exhibit
22).
Ion Exchange Resin
The ion exchange resin system consists of two down flow
cartridges containing 2-4 cubic feet of a specially treated
ion exchange resin operating at a flow rate of 4 gallons
per minute per cubic feet of resin. The resin is especially
designed to remove heavy metals while resisting the
adverse effects of organics in the wastewater. The system
has demonstrated effective lead removal while process-
ing in excess of 200,000 gallons of aqueous waste
effluent from wave solder/surface mount processes.
Maintenance
The primary/final filters have a useful service life of
about two to three months. Changing filters takes
approximately 30 minutes. Analysis of depleted filters
indicate that they are hazardous waste. The service life of
ion exchange resin is estimated to be three to five years.
Economics
The annual cost of disposal before installation of the
heavy metal treatment system was approxi-mately
$36,500. This figure includes disposal costs for 75
drums of hazardous waste. This figure should be
compared to the post-installation annual cost of
approximately $2,750, a sizeable annual savings of
approximately $33,750. Exhibit 23 presents additional
information on process economics.
Neutralization
The waste effluent first discharges into a pH-waste
holding tank for neutralization. The tank control system
monitors and controls all process waste effluent within
the holding tank. Parameters that are controlled include
pH, liquid level, equipment power, and drainage. After
neutralization, the discharge effluent enters a second
stage heavy metal filtration system.
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exhibit 22
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exhibit 23
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CASE STUDY #6:
CONVERSION FROM
CFC-113/METHANOL
CLEANING TO AQUEOUS
CLEANING FOR MEDIUM-
SIZED SURFACE MOUNT
DEVICE ASSEMBLER
Company L in Geneva, Switzerland, is a manufacturer of
miniature industrial controls. The reliability of the
finished articles is an important feature, bearing in mind
that they may be used anywhere in the world and under
any conditions. The majority of the products are
manufactured on panels about 190 x 160 mm and then
cut out. Nearly all of them are surface mount assemblies,
using various passive components and SOT-23 and SOIC
outlines. Although these components are not the most
difficult type to clean under, they are sometimes placed
very close together (spacings occasionally less than 0.5
mm). A small number of power circuits are also hand-
soldered, using through-hole components.
The SMD circuits are manufactured using screened
solder-paste, automatic placement on one side and infra-
red reflow. Until recently, the process used an RMA
solder paste and a two tank vapor degreaser with a
stabilized CFC-113/MeOH azeotrope cleaned the
circuits. The hand-soldered circuits were cleaned in the
same manner after assembly using an RA flux-cored
solder wire. Cleanliness levels obtained were sometimes
considered as marginal for the application. After
cleaning out the machine and refilling it with fresh
solvent, Contaminometer levels obtained on the SM
circuits were typically about 0.3-0.4 ug/cm2 eq. NaCl as
general surface contamination and twice this figure for
under-component levels. This measurement was related
to the surface of the whole panel, including supporting
margins. The real circuit surface area was less than half
this total. After a few hours of solvent use, the residual
contamination levels started to rise rapidly, forcing
frequent changes. The throughput did not justify in-house
off-line redistillation of the solvent. This was a costly
process.
In 1988, Company L decided to examine other
possibilities to reduce the cost of the highly competitive
articles while equally bearing in mind environmental
factors. Initial studies encompassed three potential
techniques: no-clean soldering, alcohol cleaning and
water-cleaning.
No-Clean Soldering
No-Clean Soldering was examined carefully, but none of
the rosin based solder pastes were considered to be
satisfactory for SMT because the residues were found to
cause malfunctioning under hot, humid conditions. The
paste types examined were RMA and DIN 8511 F-SW32
(carboxylic acid activated), mainly with ponderal metal
contents in the range of 85-90 percent.
On the other hand, the through-hole hand-soldered
circuits were considered reliable when soldered with
carefully selected RMA fluxes. Special low-residue flux
wires were rejected as being too difficult to use.
Alcohol Cleaning
This process was only briefly examined because of the
flammability and toxicity problems associated with using
isopropanol. Experimental hand cleaning did seem to
produce good results. This study also tested
hydrocarbon/surfactant solvents as they became available,
but no serious work has been done on them. They were
retained as a possibility for future study if all else failed.
Water Cleaning
This part of the study was divided into two sections: (1)
using water soluble fluxes and plain water cleaning and
(2) using rosin fluxes and saponifier cleaning. The latter
process was examined first as experience had already
been gained with rosin flux pastes and this option offered
the possibility of maintaining status quo on this difficult
variable. Concern was expressed that the saponifiers
would present difficulties with waste water treatment and
with operator safely, due to their high pH odor was also
considered a difficulty.
Initial trials with water-soluble solder pastes were far
from convincing with respect to three criteria: tack,
soldering quality and cleanliness (with experimental
manual cleaning). In late 1989, a new solder paste was
proposed and that seemed to fulfill all the requirements.
This option was retained as a strong possibility.
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Practical Implementation
In Spring 1990, the Management of Company L decided
to take the next step. Various machine types were
examined for aqueous cleaning, keeping in mind the need
for flexibility with the possibility of adding saponifier and
hydrocarbon/surfactant methods if the process was not
initially successful. The machine types examined
included modified dishwasher, high throughput batch,
and smaller conveyorized types. This last type was the
most practical but least flexible and odd demonstration
trials did not produce entirely convincing results,
although some of the conditions of the trials were
questionable. The modified dishwasher type was rejected
although economically interesting, because two or three
machines would be required to handle the production
volume. This configuration would entail difficult
manipulation of heavy loaded baskets. The most
satisfactory system appeared to be the high-throughput
batch system. The manufacturer installed a line on loan
in late August 1990.
Numerous practical trials were done using this line, with
simple mixed-bed deionization as water purification. The
retained water-soluble solder paste demonstrated
excellent cleanliness with a six-minute cycle (4.7 minute
wash, 0.5 minute drain, 0.7 minute rinse). As the
estimated total production would initially entail less than
ten cycles per day, adequate spare capacity was provided
for planned tripling of the production over the following
two years. After the cleaning/rinsing cycle, rotary air-
knife drying was done in a basket. After cooling, the
dried circuits could be tested immediately. It was
estimated that eight baskets each containing 33 panels
160 x 190 mm could be practically cleaned and dried per
hour, allowing time for the necessary manipulation.
Contaminometer tests showed the worst achieved
cleanliness levels to be about 0.2 ug/cm2 eq. NaCl as
general surface contamination and 0.3 ug/cm2 under the
components. The best figures obtained were about half
these levels. This range was considered acceptable.
Hand soldered circuits, using a water-soluble flux cored
solder wire, demonstrated slightly higher contamination
levels, typically under 0.4 ug/cm2 both as general surface
and under-component contamination. This contamination
level also was considered acceptable. Other accelerated
reliability tests were also positive in all cases.
The decision was made in late November 1990 to
purchase this equipment on the basis of the practical
trials under real, on-site conditions. As full production
has not yet been implemented, it is premature to give too
many figures, but estimated water and electricity
consumptions are about 8 liters and 750 watt hour per
basket and it is expected that overall costs of
soldering/cleaning/ drying/maintenance will fall to about
60 percent of the CFC-113 reference production method.
Future plans include automating the cleaning line and
probably introducing wave soldering with water-soluble
flux, to replace the hand soldering.
Environmental Aspects
No wastewater treatment has been found to be necessary.
The wastewater has been tested by the Geneva authorities
and conforms entirely to the requirements of the severe
Swiss law. The authorities have indicated they will
tolerate monthly pH excursions outside the limits during
maintenance cleaning of the machine with a descaling
product.
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References
Alpha Metals, Inc. 1989. Data sheet, Bioact EC-7. Jersey City, NJ.
Anders, Raymond H. undated. The do's and donts of switching to aqueous cleaning.
Crystal Corporation. Huntsville, AL.
Andras, James J. 1991. PWA aqueous and Semi-aqueous cleaning system approaches and tradeoffs. NEPCON West.
Hollis Automation, Inc. Nashua, NH.
Attalla, Gary J. 1988 (December). Designing cleaning equipment for the terpene alternative. Surface Mount Technology:
43-44.
Attalla, Gary J. 1990. Semi-aqueous equipment for in-line use. Vitronics Corp. Newmarket, NH.
Blake, Owen W. 1990 (September). Semi aqueous cleaning technology: an effective, environmentally safe alternative to
CFCs. Proceedings of Singapore-U.S. seminar on CFCs. Singapore.
Burress, Robert V. and Carole K. Ellenberger. 1991. Choosing an alternative to CFC cleaning technology. NEPCON West.
Texas Instruments Incorporated. Dallas, TX.
Dickinson, David A., and George M. Wenger. 1986. Terpene cleaning applications and technology. AT&T Bell
Laboratories. Princeton, NJ.
Dishart, Dr. K.T., and M.C. Wolff. 1990. Advantages and process options of hydrocarbon based formulations in semi-
aqueous cleaning. NEPCON: 513-527. San Jose, CA.
DuPontDe Nemours and Company. 1989 (October). Data sheet KCF - 9438 cleaning agent. Wilmington, DE.
Elliott, Donald A. 1990. Is aqueous the answer? NEPCON. Anaheim, CA.
Ellis, Brian N, 1986. Cleaning and Contamination of Electronics Components of Assemblies. Electrochemical Publications
Limited, Scotland, United Kingdom.
Gilbert, Jack. 1991. In-line semi-aqueous cleaning: meeting regulatory requirements. NEPCON West. 3 Com
Corporation. Santa Clara, CA.
Grunwald, Fred, and John Lowell. 1989. Aqueous cleaning of reflowed surface mount assemblies. NEPCON. Anaheim,
CA.
Guth, Leslie A., D.A. Dickenson, and G.M. Wenger. 1989 (November). Advances in cleaning surface mount assemblies.
IMF PC Group Conference. Teddington, England.
Hamblett, George W., and Glenn A. Larsson. 1990. Terpene/aqueous cleaning. CalComp Corporation. Hudson, NH.
Hayes, Michael E. 1988 (December). Cleaning SMT assemblies without halogenated solvents. Surface Mount
Technology: 37-40.
Hayes, Michael E. 1988. High performance cleaning with non-halogenated solvents. Petroferm Inc. Fernandina Beach,
FL.
Lambert, Leo. 1990 (September). The effectiveness of aqueous cleaning in the electronic industry a historical
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perspective. Singapore-U.S. CFC Seminar. Singapore.
Loy, Terry D. 1986 (February). The unsung process. Circuits Manufacturing: 62-64.
Manko, Howard H., 1979. Solders and Soldering, Second, Edition, McGraw-Hill.
Milla, Juan G. 1991. Defluxing high reliability surface mount assemblies with terpene hydrocarbons. NEPCON West.
Medtronic/Micro-Rel. Tempe, AZ.
Russo, John F., and Martin S. Fischer, Martin S. 1989 (July). Recycling boosts aqueous cleaners. Circuits Manufacturing:
34-39.
Smiley, B. Carrol. 1989. Semi-aqueous cleaning of PWAS: a ready solution to CFCs." E.I. DuPont de Nemours and Co.
Wilmington, DE.
United Nations Environment Programme (UNEP). June 1989. Electronics, Degreasing, and Dry Cleaning Solvents
Technical Options Report.
U.S. Environmental Protection Agency. 1990 (March). Manual of practices to reduce and eliminate CFC-113 use in the
electronics industry. EPA 400/3-90-003. Office of Air and Radiation. Washington, D.C.
Watkins, Ronald L. 1991. Implementing in-line semi-aqueous cleaning in a contract electronics assembly environment.
NEPCON West. Dover Electronics Manufacturing West. Longmont, CO.
Wenger, George, and Gregory Munie. 1988 (November). Defluxing using terpene hydrocarbon solvents. IPC Technical
Review, Institute for Interconnecting and Packaging Electronics Circuits: 17-23. Evanston, IL. .
Wenger, George M. 1990. Technology developments for terpene cleaning of electronic assemblies. AT&T Bell
Laboratories. Princeton, NJ.
Wenger, George M., and Gregory P. Tashjian. 1990. Terpene cleaning of electronic assemblies. AT&T Bell Laboratories
and AT&T Network Systems. Princeton, NJ and North Andover, MA.
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GLOSSARY
Acute toxicity The short-term toxicity of a product in a single dose. Can be divided into oral, cutaneous and respiratory
toxi cities.
Adsorption Not to be confused with absorption. Adsorption is a surface phenomenon which some products can exhibit,
whereby they can form a physicochemical bond with many substances.
Alcohols A series of hydrocarbon derivatives with at least one hydrogen atom replaced by an -OH group. The simplest
alcohols (methanol, ethanol, n-propanol, and isopropanol) are good solvents for some organic soils, notably rosin, but are
flammable and can form explosive mixtures with air: their use requires caution and well-designed equipment.
Aqueous cleaning Cleaning parts with water to which may be added suitable detergents, saponifiers or other additives.
Biodegradable Products in wastewater are classed as biodegradable if they can be easily broken down or digested by,
for example, sewage treatment.
BOD An abbreviation for biochemical oxygen demand.
CFC An abbreviation for chlorofluorocarbon.
CFC-113 - A common designation for the most popular CFC solvent, 1,1,2-trichloro-1,2,2-trifluoroethane, with an ODP
of approximately 0.8.
Chelation is the solubilization of a metal salt by forming a chemical complex or sequestering. One way of doing this is
with ethylenediaminetetra-acetic acid (EDTA) salts which have a multi-dentate spiral ligand form that can surround metallic
and other ions.
Chlorofluorocarbon An organic chemical composed of chlorine, fluorine and carbon atoms, usually characterized by
high stability contributing to a high ODP.
Chronic toxicity - The long-term toxicity of a product in small, repeated doses. Chronic toxicity can often take many years
to determine.
COD An abbreviation for chemical oxygen demand.
Conformal coating A protective material applied in a thin, uniform layer to all surfaces of a printed wiring assembly
including components.
Defluxing - The removal of flux residues after a soldering operation. Defluxing is a part of most high-reliability electronics
production.
Detergent -- A product designed to render, for example, oils and greases soluble in water, usually made from synthetic
surfactants.
Fatty acids The principal part of many vegetable and animal oils and greases, also known as carboxylic acids which
embrace a wider definition. These are common contaminants for which solvents are used in their removal. They are also
used to activate fluxes.
Flux An essential chemical employed in the soldering process to facilitate the production of a solder joint. It is usually
a liquid or solid material, frequently based on rosin (colophony).
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Greenhouse effect A thermodynamic effect whereby energy absorbed at the earth's surface, which is normally able to
radiate back out to space in the form of long-wave infrared radiation, is retained by gases in the atmosphere, causing a rise
in temperature. The gases in question are partially natural, but man-made pollution is thought to increasingly contribute to
the effect. The same CFCs that cause ozone depletion are known to be "greenhouse gases", with a single CFC molecule
having the same estimated effect as 10,000 carbon dioxide molecules.
HCFC An abbreviation for hydrochlorofluorocarbon.
HFC An abbreviation for hydrofluorocarbon.
Hydrocarbon/surfactant blend A mixture of low-volatile hydrocarbon solvents with surfactants, allowing the use of a
two-phase cleaning process. The first phase is solvent cleaning in the blend and the second phase is water cleaning to
remove the residues of the blend and any other water-soluble soils. The surfactant ensures the water-solubility of the
otherwise insoluble hydrocarbon. Terpenes and other hydrocarbons are often used in this application.
Hydrochlorofluorocarbon An organic chemical composed of hydrogen, chlorine, fluorine and carbon atoms. These
chemicals are less stable than pure CFCs, thereby having generally lower ODPs.
Inert gas soldering A soldering process done in a relatively oxygen-free atmosphere. The process greatly reduces
oxidation of the solder, so that less flux is required, thereby easing or eliminating the need for cleaning.
Leaded surface mount component A surface mount component (SMC) whose external connection consists of formed
leads.
Leadless surface mount component A surface mount component (SMC) whose external connection consists of
metallized terminations that are an integral part of the component body.
Low-solids flux - A flux which contains little solid matter, thereby easing or eliminating the need for cleaning. See no-clean
flux.
MEA An abbreviation for monoethanolamine.
Methyl chloroform See 1,1,1-trichloroethane.
Monoethanolamine A saponifier capable of eliminating rosin fluxes and fatty acids. Also abbreviated to MEA.
No-clean flux A flux whose residues do not have to be removed from an electronics assembly, therefore, no cleaning is
necessary. This type of flux is usually characterized by low quantities of residues.
ODP An abbreviation for ozone depletion potential.
Organic acid (OA) flux See water-soluble flux.
Ozone A gas formed when oxygen is ionized by, for example, the action of ultraviolet light or a strong electric field. It
has the property of blocking the passage of dangerous wavelengths of ultraviolet light.
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Whereas it is a desirable gas in the stratosphere, it is toxic to living organisms at ground level (see volatile organic
compound).
Ozone depletion Accelerated chemical destruction of the stratospheric ozone layer by the presence of substances
produced, for the most part, by human activities. The most depleting species for the ozone layer are the chlorine and bromine
free radicals generated from relatively stable chlorinated, fluorinated, and brominated products by ultraviolet radiation.
Ozone depletion potential A relative index indicating the extent to which a chemical product may cause ozone depletion.
The reference level of 1 is the potential of CFC-11 and CFC-12 to cause ozone depletion. If a product has an ozone
depletion potential of 0.5, a given weight of the product in the atmosphere would, in time, deplete half the ozone that the
same weight of CFC-11 would deplete. The ozone depletion potentials are calculated from mathematical models which take
into account factors such as the stability of the product, the rate of diffusion, the quantity of depleting atoms per molecule,
and the effect of ultraviolet light and other radiation on the molecules.
Ozone layer A layer in the stratosphere, at an altitude of approximately 10-50 km, where a relatively strong concentration
of ozone shields the earth from excessive ultraviolet radiation.
PCB An abbreviation for printed circuit board.
Printed circuit A printed circuit is an electronic component designed for interconnecting the other components. It usually
consists of a metallic conductor pattern on an organic insulating substrate. After fabrication, it is known as a printed circuit
board (PCB); after assembly where components are added, it is known as a printed wiring assembly (PWA).
PWA An abbreviation for printed wiring assembly.
Reflow soldering A method of electronics soldering commonly used with surface mount technology, whereby a paste
formed of solder powder and flux suspended in an organic vehicle is melted by the application of external heat.
Rosin - A solid resin obtained from pine trees which, in a pure form and usually with additives, is frequently used as a flux.
Rosin flux A flux whose main constituent is rosin. There are several categories of rosin flux, often designated by the
codes R (pure rosin), RMA (rosin, mild activation), RA (rosin, activated usually with free chloride ions), RSA (rosin, super
activated), SA (synthetic resin, activated).
Saponifier - A chemical designed to react with organic fatty acids, such as rosin, some oils and greases etc., in order to form
a water-soluble soap. This is a solvent-free method of defluxing and degreasing many parts. Saponifiers are usually alkaline
and may be mineral (based on sodium hydroxide or potassium hydroxide) or organic (based on water solutions of
monoethanolamine).
SMC An abbreviation for surface mount component.
SMD An abbreviation for surface mount device.
Solvent -- Although not a strictly correct definition, in this context a product (aqueous or organic) designed to clean a
component or assembly by dissolving the contaminants present on its surface.
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Surface mount technology (SMT) A technique of assembling SMDs or SMCs on the surface of PCBs and PWAs, as
opposed to wiring them through holes. Surface mount technology offers a number of important advantages, but also some
disadvantages, such as difficulty in defluxing under certain types of SMD.
Surface mount component (device) A component capable of being attached to (device) a PCB by surface mount
technology. The device may be either leaded or leadless.
Surfactant A product designed to reduce the surface tension of water. Also referred to as tensio-active agents/tensides.
Detergents are made up principally from surfactants.
Terpene Any of many homocyclic hydrocarbons with the empirical formula C10H16, characteristic odor. Turpentine is
mainly a mixture of terpenes. See hydrocarbon/surfactant blends.
Volatile organic compound (VOC) These are constituents that will evaporate at their temperature of use and which, by
a photochemical reaction, will cause atmospheric oxygen to be converted into potential smog-promoting tropospheric ozone
under favorable climatic conditions.
Water-soluble flux A flux, which itself may be free from water, but whose residues after soldering may be entirely
eliminated by a water wash. Such fluxes are usually very active so adequate defluxing is an essential part of their use. They
are also known as Organic Acid (OA) fluxes or inorganic acid fluxes.
Wave soldering - Also known as flow soldering, a method of mass soldering electronics assemblies by passing them, after
fluxing, through a wave of molten solder.
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APPENDIX A
INTERNATIONAL COOPERATIVE
FOR OZONE LAYER PROTECTION
The International Cooperative for Ozone Layer Protection
(ICOLP) was formed by a group of industries to protect
the ozone layer. The primary role of ICOLP is to
coordinate the exchange of non-proprietary information
on alternative technologies, substances, and processes to
eliminate ozone-depleting solvents. By working closely
with solvent users, suppliers, and other interested
organizations worldwide, ICOLP seeks the widest and
most effective dissemination of information harnessed
through its member companies and other sources.
ICOLP corporate members include:
AT&T
British Aerospace Defense
Ford Motor Company
Hitachi
Honeywell
IBM Corporation
Mitsubishi Electric Corporation
Motorola Corporation
Ontario Hydro
Northern Telecom
Texas Instruments
Toshiba Corporation
In addition, ICOLP has a number of industry association
and government organization affiliates. Industry
association affiliates include American Electronics
Association, Association Pour la Research et
Development des Methodes et Processus Industriels,
CANACINTRA (Mexico), Center for Global Change,
Electronic Industries Association, Halogenated Solvents
Industry Alliance (U.S.), Industrial Technology Research
Institute of Taiwan, Japan Electrical Manufacturers
Association, Korea Anti-Pollution Movement, and Korea
Specially Chemical Industry Association. Government
and NGO affiliates include the City of Irvine (CA),
National Academy of Engineering, Research Triangle
Institute, Russian Institute of Applied Chemistry, Russian
Ministry of Environmental Protection and Natural
Resources, Swedish National Environmental Protection
Agency, Technology Development Foundation of Turkey,
Turkish Ministry of the Environment, United Nations
Environment Programme, U.S. Air Force, and U.S.
Environmental Protection Agency (EPA). The American
Electronics Association, Electronic Industries
Association, City of Irvine, California, Japan Electrical
Manufacturers Association, Swedish National
Environmental Protection Agency, U.S. EPA, U.S. Air
Force, and the Russian Institute of Applied Chemistry
have signed formal Memorandums of Understanding with
ICOLP. ICOLP will work with the U.S. EPA to
disseminate information on technically feasible, cost
effective, and environmentally sound alternatives for
ozone depleting solvents.
ICOLP is also working with the National Academy of
Engineering to hold a series of workshops to identify
promising research directions and to make most efficient
use of research funding.
The goals of ICOLP are to:
Encourage the prompt adoption of safe,
environmentally acceptable, nonproprietary alternative
substances, processes, and technologies to replace
current ozone-depleting solvents;
Act as an international clearinghouse for information
on alternatives;
Work with existing private, national, and international
trade groups, organizations, and government bodies to
develop the most efficient means of creating,
gathering, and distributing information on alternatives.
One example of ICOLP's activities is the development
and support of an alternative technologies electronic
database "OZONET." OZONET is accessible worldwide
and has relevant information on the alternatives to ozone-
depleting solvents. OZONET not only contains technical
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publications, conference papers, and reports on the most
recent developments of alternatives to the current uses of
ozone-depleting solvents, but it also contains:
Information on the health, safety and environmental
effects of alternative chemicals and processes;
Information supplied by companies developing
alternative chemicals and technologies;
Names, addresses, and telephone numbers for
technical experts, government contacts, institutions
and associations, and other key contributors to the
selection of alternatives;
Dates and places of forthcoming conferences,
seminars, and workshops;
Legislation that has been enacted or is in place
internationally, nationally, and locally.
Information about ICOLP can be obtained from:
Ms. Allison Morrill
Project Manager
ICOLP
2000 L Street, N.W.
Suite 710
Washington, D.C. 20036
Tel: (202)737-1419
Fax: (202)296-7472
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APPENDIX B
LIST OF VENDORS FOR CFC-113 AND METHYL CHLOROFORM
SOLVENT CLEANING SUBSTITUTES
This is not an exhaustive list of vendors. Vendors can be cited in any subsequent editions of this document by sending
information to ICOLP. ICOLP's address is provided in Appendix A. Listing is for information purposes only, and does not
constitute any vendor endorsement by EPA, ICOLP, or the committee members, either express or implied, of any product
or service offered by such entity.
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