EPA 742/F-99/022
By Kathy Hart,' Dipti Singh. Holly Evans/.Lori Kincaid.
Jack Geibig & Mary Swanson ;
frSeflecting a trend in envkonmental
!\.protection toward increased coop-
eration and collaboration between
government and "regulated entities,"
the U.S. Environmental Protection
Agency (EPA) Design for the Envi-
ronment (DfE) Program has been
working closely with the Institute for
Interconnecting and Packaging Elec-
tronic Circuits (IPC) and its member
companies, the University of
Tennessee's Center for Clean Prod-
ucts and Clean Technologies, and
other partners (academic, research and
public interest representatives) since
1994 on the Printed Wiring Board
(PWB) Project. The primary goal of
the DfE PWB Project is to encourage
PWB manufacturers to implement
cleaner technologies that will improve
the environmental performance and
competitiveness of the PWB industry.
The overall goal of the DfE program
is to encourage businesses to incorpo-
rate environmental, as well as cost
and performance, considerations into
the design and redesign of technolo-
gies, processes and products (Fig. 1).
Comparative Studies
Project partners have already com-
pleted a major comparative study of
technologies used in the "making
holes conductive" (MHC) step of
PWB manufacturing (i.e., alternatives
to the electroless copper process), and
are now conducting a similar evalua-
tion of technologies that may be used
in the surface finishing step, in place
of hot-air solder leveling. Results of
the surface finishes study are expected
to be published in a draft report in late
1999. A surface finishes project meet-
ing will be held at the 1999 Confer-
ence for Envkonmental Excellence,
sponsored by the AESF and EPA. The
meeting is open to anyone who would
like to learn more about or participate
in the surface finishes project.
In addition to the MHC study, the
DfE PWB Project has produced sev-
eral technical reports, including two
on pollution prevention and control
technologies used in the PWB indus-
try,1-2 and produced and disseminated
10 pollution prevention case studies.
Study on Making Holes
Conductive
The electroless copper plating process
has long been the standard method of
creating a conductive surface on the
drilled through-hole walls of rigid,
double-sided or multilayer PWBs
requked for electrolytic copper plat-
ing. Although the electroless copper
process for making holes conductive
is a mature technology that produces
reliable interconnects, the typical
process line is long (17 or moire proc-
ess tanks, depending on rinse configu-
rations) and may have eight or more
process baths. It is also a source of
formaldehyde emissions and a major
source of wastewater containing che-
lated, complexed copper.
In the MHC study, project partners
developed and analyzed technical
information regarding the potential
human health and envkonmental
risks, performance, costs and chemi-
cal and natural resource use of the
electroless copper process and six
"dkect metallization" technologies
(Table 1). These analyses were con-
ducted by the University of Tennes-
see, and the results were compiled
into a Cleaner Technologies Substi-
tutes Assessment (CTSA)3 and a
CTSA summary document.4 A de-
tailed description of the CTSA meth-
odology may be found in Section 1.3
of the CTSA document. We believe
that the CTSA results described below
demonstrate that the dkect metalliza-
tion technologies make good eco-
nomic and envkonmental sense for
PWB manufacturers.
Table 2 lists the suppliers who
participated in the MHC CTSA and
the technologies they submitted for
evaluation. The suppliers provided
publicly available chemistry data for
thek MHC chemical products, and
were asked to provide the identities
and concentrations of proprietary
chemical ingredients.
Suppliers also completed a Supplier
Data Sheet describing thek products,
and nominated test sites for a perfor-
mance demonstration. PWB manufac-
turers completed a Workplace Prac-
tices Survey, which requested detailed
information on thek MHC processes,
as well as worker activities related to
chemical exposure.
The data collected from the suppli-
ers and through the Workplace Prac-
tices Survey were aggregated to de-
velop generic process steps and typi-
cal bath sequences for each technol-
ogy category, while acknowledging
that the types and sequence of baths in
actual lines may vary, depending on
facility-specific operating conditions.
There were a number of Limitations
to the study, because of the predefined
scope of the project, the limit of the
project's resources and uncertainties
inherent to risk characterization tech-
niques. Those limitations are dis-
cussed in detail in the MHC CTSA.
The cost, energy and resource use
analyses determined the comparative
costs and consumption rates of using
an MHC technology in a model facil-
ity to produce 350,000 surface square
feet (ssf) of PWBs. As with the risk
characterization, this approach re-
sulted in a comparative evaluation of
Fig. 1—EPA's Design for the Environment Pro-
gram encourages businesses to consider envi-
ronmental factors, as well as performance and
cost, when making decisions.
46
PLATING & SURFACE FINISHING
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cost or energy and natural resource
consumption, not an absolute evalua-
tion or determination.
Risk Characterization
Of MHC Technologies
Risk results suggest that alternatives
to the non-conveyorized electroless
copper process pose lower overall
occupational risks. This is a result of
the reduced number of chemicals of
concern in the alternative technolo-
gies for both inhalation and dermal
exposure, and the level of cancer risk
from inhalation exposure to formalde-
hyde in non-conveyorized electroless
copper processes. Detailed informa-
tion on potential occupational risk
from inhalation and dermal contact for
each technology may be found in the
MHC CTSA. The indicators for public
health risk (risk to residents near a
facility), although limited to airborne
releases, indicated low concern from
all MHC technologies.
Performance Demonstration
Results
In order to evaluate the relative per-
formance of each technology cat-
egory, a comparative performance
demonstration was conducted. PWB
panels designed to represent industry
"middle-of-the-road" technology were
manufactured at one facility, run
through individual MHC lines at 25
facilities, and then electroplated at
one facility. The panels were electri-
cally pre-screened, followed by elec-
trical stress (1ST) testing and me-
Conductive
Graphite
Non-Formaldehyde Electroless Copper
Organic Palladium ----------------------------------- V
Tin-Palladium
'Cleaner Technologies Substitutes Assessment
SSSSSHK.
chanical (microsection) testing, in
order to distinguish variability in the
performance of the MHC intercon-
nect. The test methods used to evalu-
ate performance were intended to
indicate characteristics of a
technology's performance, not to
define parameters of performance or
to substitute for thorough on-site
testing; the study was intended to be a
"snapshot" of the technologies.
The microsection and 1ST tests •
were run independently, and had
extremely good correlation of results.
In terms of 1ST results, product per-
formance was divided into two func-
tions: Plated through-hole (PTH)
cycles to failure and the integrity of
the bond between the internal lands
(post) and PTH (referred to as "post
separation"). The PTH cycles to fail-
ure observed in the study is a function
of both electrolytic plating and the
MHC process.
The mechanical testing and 1ST
results indicated that each MHC tech-
nology has the capability to achieve
comparable (or superior) levels of
performance to electroless copper, if
operated properly. Post separation
results indicated percentages that
were unexpected by many members
of the industry. It was apparent that
all MHC technologies,-including
electroless copper, are susceptible to
this type of failure. A copy of the
complete technical papei~may be
obtained by contacting Sjiar
Summerfield at the Institute for
Interconnecting and Packaging Elec-
tronic Circuits, Northbrook, Illinois
(847/790-5347).
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47
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Cost Anaiysis Resuits
The results of the cost analysis indi-
cated that all of the MHC alternatives
are more economical than the non-
conveyorized electroless copper proc-
ess. The average cost for most MHC
technologies ranged from 57 to 82
percent less than the baseline technol-
ogy (the cost for non-formaldehyde
electroless copper, non-conveyorized,
was 22 percent less). Chemical cost
'• was the single largest component cost
i for nine of the 10 technologies and
j equipment configuratiorxs evaluated.
i Equipment cost'was the jargest cost
• for the non-cojiveyorized ejectroless'
; copper process. Three separate sensi-
j tivity analyses of the results indicated
that chemical cost, production labor
! cost and equipment costs had the '
j greatest effect on the overall cost
! results.
,.^WJE^Y- THE GROWTH IN:."?/-:
''"• • Ask.fit® coatings expertsjtt .
8* ItlBSFStf S@S. Ekctrocoaong is on the rise throughout
industry —from appliances to automotive, frames! 'furniture to
electronics, industrial, pans of every description And the reasons
are many
results in:
* Controlled^ uniform film thickness
• Superior corrosion resistance ^ -
* Improved color contro^ film hardness, and durability
The etsdrosoaitng precess rests!?s in:
• Lowest operating co
-------
lion to both the PWB manufacturing
and assembly industries.
To evaluate the performance of
each surface finish technology, a
number of functional test boards were
fabricated (a modified version of the
1PC-B-24 board). The test boards
contain a variety of circuitry (includ-
ing high voltage/low current, high
current/low voltage, high frequency
and high speed digital), and can be
subjected to multiple processing steps
(wave, reflow and hand soldering).
The boards were fabricated at one
facility and then shipped to the volun-
leer demonstration sites, where the
surface finishes were applied.
The boards were shipped to a com-
mon location for assembly, including
both through-hole and surface mount
components. Assembly was com-
pleted in November 1998. Half of the
boards for each surface finish are
being processed using a halide-free
low-residue flux; a halide-containing
water-soluble flux is being used on
the other half. The circuit perfor-
mance will be assessed under appli-
cable environmental stresses, with the
HASL process serving as a baseline.
The functional boards will be evalu-
ated through a series of reliability
tests, including thermal and mechani-
cal shock.
For More Information
For more information about the DfE
Program or the DfE PWB Project, or
to obtain copies of the CTSA or other
documents produced by the Project,
contact the Pollution Prevention
Information Clearinghouse, U.S.
Environmental Protection Agency,
401 M St., S.W. (7409), Washing-
ton, DC, 20460; phone: 202/260-
1023; FAX: 202/260-4659; e-mail:
PPIC@epa.gov. You may also view
or order the project documents,
including the CTSA, and obtain
additional project information by
visiting the DfE Program Website
(%vww.epa.gov/dfe) or the IPC
Website (www.ipc.org/hlml/
ehsiypes.htm#design). P*SF
References
1, Primed Wiring Board Pollution Prevention
and Control Technology: Analysis of Up-
dated Survey Results (EPA 744-R-98-003):
August 1998.
2. Printed Wiring Board Pollution Prevention
and Control Technology: Analysis of Survey
Results (EPA 744-R-95-006): September
1995.
3, Printed Wiring Board Cleaner Technologies
Substitutes Assessment: Making Holes
January 1999
Conductive. Volumes 1 and 2 (EPA 744-R-
98-004a and 004b): August 1998. •
4. Alternative Technologies for Making Holes
Conductive: Cleaner Technologies for
Printed Wiring Board Manufacturers (EPA
744-R-9S-002); September 1998.
About the Authors
Kathy Han is an environmental protec-
tion specialist and associate director for
U.S. EPA's Design for the Environment
Program Center.
Dipti Singh is a chemical engineer with
U.S. EPA 's Design for the Environment
Program.
Holly Evans is the director of Environ-
mental and Safety Programs for the Insti-
tute for Interconnecting and Packaging
Electronic Circuits, Northbrook, IL.
Lori Kincaid, Jack Ceibig, and Mary
Swanson are with the University of Ten-
nessee Center for Clean Products and
Clean Technologies, Knoxville, TN.
Ceibig is a senior research associate and
Swanson is a research scientist.
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49
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