United States
                           Environmental Protection
                           Agency
              Risk Reduction
              Engineering Laboratory
              Cincinnati, OH 45268
                           Research and Development
              EPA/600/M-91/022  July 1991
                           ENVIRONMENTAL
                           RESEARCH   BRIEF
              Waste Minimization Assessment for a  Manufacturer of
                                  Printed Circuit Boards

                                F. William Kirsch and Gwen P. Looby*
Abstract
    The U.S. Environmental Protection Agency (EPA) has
funded a pilot project to assist small- and medium- size manu-
facturers who want to minimize their generation of hazardous
waste but lack the expertise to do so. Waste Minimization
Assessment Centers (WMACs) were established at selected
universities and procedures were adapted from the EPA Waste
Minimization Opportunity Assessment Manual (EPA/625/7-
88/003, July 1988).  The WMAC team at Colorado State
University inspected a plant producing printed circuit boards —
a plant that already had taken steps to control its hazardous
wastes. Producing a circuit board involves many major pro-
cesses and subprocesses: preparing the board; depositing
copper en the board by electroless plating; applying dry film;
electrolytically plating copper; electrolytically plating tin; etch-
ing and stripping; applying solder; and, perhaps, plating gold on
connectors. Each of these steps produces hazardous wastes,
e.g., electrolytic copper plating  results in acid soap dumps,
copper and tin drag-out, and sulf uric acid. The main sources of
metallic contamination (copper [both dissolved and metallic],
tin, lead, gold) are the rinses after scrubbing, plating, and
etching. Although the greatest amount of waste can be reduced
by reusing effluent from the MEMTEK  f (with some further
treatment), the greatest dollar savings can be found by chang-
ing the dry film developer. The present brand adheres strongly
to the unexposed film and requires an aggressive acid soap; a
less aggressive, nonhazardous soap could be used with a less-
adhering dry film developer.
    This Research Brief was developed by the principal inves-
tigators and EPA's Risk Reduction Engineering Laboratory,
Cincinnati, OH, to announce key findings of an ongoing re-
search project that is fully documented in a separate report of
the same title available from the authors.

Introduction
    The amount of hazardous waste generated by industrial
plants has become an increasingly costly problem for manufac-
turers and an additional stress on the environment. One solu-
tion to the problem of hazardous waste is to reduce or eliminate
the waste at its source.

    University City Science Center (Philadelphia, PA) has
begun a pilot project to assist small- and medium- size manu-
facturers who want to minimize their formation  of hazardous
waste but  lack the inhouse expertise to do so.  Under agree-
ment with EPA's Risk Reduction Engineering Laboratory, the
Science Center has established three WMACs. This assess-
ment was done by engineering faculty and students at Colorado
State University's (Fort Collins) WMAC. The assessment teams
have considerable direct experience with process operations in
manufacturing plants and also have the knowledge and skills
needed to minimize hazardous waste generation.

    The waste minimization assessments are done for small-
and medium-size manufacturers at no out-of-pocket cost to the
client. To qualify for the assessment, each client must fall within
  University City Science Center, Philadelphia, PA 19104
  Mention of trade names or commercial products does not
  constitute endorsement or recommendation for use.
                                                                           Printed on Recycled Paper

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   persons, and lack mhouse expertise in waste minimization





   ment without more regulations and higher costs for manufactur-
   ers
   Methodology Of Assessments




  WMAC staff locates the sources of hazardous waste in the plant
  and identifies the current disposal or treatment methods and
  their associated costs. They then identify and analyze a variety
  of ways to reduce or eliminate the waste. Specific measures to
  achieve that goal are recommended and the essential support-
  ing technological and economic information is developed. Fi-
  nally, a confidential report that details the WMAC's findings and
  recommendations (including cost savings, implementation costs
  and payback times) is prepared for each client.             '
  _.  A _   ,
  Plant Background
      This plant  typically operates about 4,500 hr/yr to turn out
  printed circuit boards, which are distributed regionally Like the
  plants of some other small and medium-size manufacturers this
  one had taken several steps on its  own  initiative to control
  hazardous waste emissions.  It presented a challenge to the

                          in their 8fforts to idenwy addifonai
                                                            Manufacturing Operations

                                                                The lami'nated flat sheets of nonconducting material are





                                                                A thin layer of copper is deposited by electroless platinq on
                                                           boards that are first cleaned and rinsed and then coated wrth a
                                                           catalyst for the reduction of the copper To apply the circuit
                                                           pattern, a dry film process is used — laminating a photosensitive
                                                           polymer resist, covering parts of the board with the printed circuit
                                                           design mask before exposure to ultraviolet liqht develooina with
                                                           sod'um carbonate,  and eventually rinsing with' tap water
                                                               .-.
                                                               Electrolytic plating of copper occurs on the circuit design
                                                           developed in  the preceding series of operations  Then tin is
                                                           electronically plated on the^copper to protect the circuft deSgn
                                                           A    the alkahne etchant used to strip away the plating resist.
                                                           A"y.coPPe[ not Protected by  tin is also etched away by an
                                                           aiKalinฎ  solution. Finally,  an ammonium bifluoride-hydrogen
                                                           pero*lde sฐ'utl?n removes the tin to complete the electronic
                                                           circuitry on the board- whlch IS then water-rinsed and air-dried.
    The  plant had already taken these kinds of actions to
reduce hazardous waste:

        Using dry film photoresist to eliminate chlorinated
        solvents associated with silk screen application.
        Substituting tin for lead solder after electrolytic
                                                            areas, which are the portions of the boards not coated by an
                                                            epoxy solder mask, which also functions as an insulator Then
                                                            a eutectic solder is coated on the surface not covered by the
                                                            mask.                                              7

                                                                To meet certain customers' specifications, connectors are
                                                            sometimes gold plated before solder mask application.
         Combining  an automated electroless  plating
         machine with countercurrent rinsing to cut down
         drag-out of  plating  solution and to  reduce the
         quantity of rinse water.
         Agitating these rinse tanks with compressed air to
         get better rinsing in a given tank volume
                                                          .    Most of the hazardous waste generated in this plant occurs
                                                          m various liquid streams. These major waste streams, together
                                                          with their treatment, disposal, and recycling costs are given in
                                                          Table 1 •
                                                              Tnnirttha*!ซซ     *•   • .
                                                              iI5 E "V*u  lnformatlon Into Perspective, it is useful to keep
                  - .*•*  covered  racks tor those
         excess copper and tin deposits on the racks.
     •    Applying mechanical deburrers,  scrubbers, and
         hot-air dryers to eliminate some hazardous
         solvents.  (The dusts from these operations are
         collected and sold to a metal reclaimer )
                                           ''
     The basic  operation of the plant consists of  a complex
series of mechanical and chemical process steps to deposit
copper selectively on flat  sheets of  nonconducting materials
formed from resins and fiber glass. Of course, the copper must
                                                                lines- and in the alkaline "ch and
                                                              Metallic copper is generated by mechanical cleaning op-
                                                          orations, drilling and routing operations, and cutting operations

                                                          .   . ' In comes from electrolytic plating and stripping; lead from
                                                          rinsing and deburring.
                                                              D-
                                                                 .? streams discharged to the sewer because they are
                                                         IL  considlered hazardous are those from the dry film developer
                                                          ,8 P03^'830 rinse- the gold plating rinse, and the spent resist
                                                         sirippor.

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         Board Preparation

         •  Hydraulic shearing
         •  Drilling
         •  Debarring
Electroless Copper Plating

  Hot soap cleaner
  Rinses
  Preetch
  Miaoetch
  Catalyst predip
  Catalyst
  Rinses
  Accelerator
  Rinses
  Electroless copper plating
  Rinse
 Neutralizer
  Rinse
  Hot air dryer
Dry Film Application
• Photopolymer lamination
• Mask Application
• UV exposure
• Developer
• Rinse


Electrolytic Copper Plating
Acid soap
Cascade and bath rinse
Microetch
Spray and bath rinse
Sulfuric acid predip
Electrolytic copper plating
Spray Rinse
^-

Electrolytic Tin Plating
• Sulfuric acid predip
• Electrolytic tin plating

                                                         Etch & Strips

                                                           Resist stripper
                                                           Alkaline etch
                                                           Rinse
                                                           Tin stripper
                                                           Rinse
                                                           Hot air dryer
Gold Tab Plating
• Mask application
• Nickel plating
• Rinse
• Gold plating
• Rinse



Solder Application
Solder mask application
Thermocuring
Copper cleaner/rinse
Hot air leveling
Post clean
Fine scrubber
                                                                                                       Final Processes

                                                                                                       •  Inspection
                                                                                                       •  Labeling
                                                                                                       •  Routing
                                                                                                       •  Packaging
                                                                                                       •  Storage
Figure 1. Sequence of Manufacturing Operations.

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      The other rinses and dumps are directed into a large trench
  with a level controller (but without a sewer connection). The
  controller activates a pump to transport the liquids to a MEMTEK
  ultrafiltration system (to 0.1 u.) that uses chemical reactions,
  precipitation, and membrane filtration. Suspended solids in an
  associated concentration tank are removed by bleeding a "slip
  stream" to a settling tank,  from  which sludge is dewatered to
  about 60% solids before it  is hauled to a solid disposal site for
  hazardous wastes.

      As noted in Table 1, some  solutions are taken out of the
  plant for metal recovery and a credit.

  Summary of  Recommended Waste Minimization
      Eight waste minimization opportunities (WMOs) recom-
  mended by the WMAC team could cut the annual waste man-
  agement costs  at this plant from $86,850 to $42,225, about a
  51% reduction.  The largest waste volume is liquid (2.97 million
  gal/yr), but one  recommended WMO could reduce that by 62%
 through recycling effluent  from the MEMTEK filtration unit.
  Because of the relatively low cost of water supply and sewering,
  however, this large volumetric reduction will save only about
  $3,840/yr at the present time.

     A dry film  developer is applied to the  circuit boards to
 remove unexposed photopolymer (under the design mask) and
 reveal the circuit design. The largest cost saving for a particular
 WMO ($23,550/yr) is estimated to come from  substituting a
 different developer. The sodium carbonate developer being
 used requires a very aggressive  acid soap to remove it before
 copper is electrolytically deposited. When this soap is rinsed and
 the rinsings go to the ultrafiltration unit (MEMTEK), the relatively
                                    large soap molecules frequently plug the pores of the filtering
                                    membranes in the MEMTEK. With a less adhesive developer, a
                                    less aggressive soap solution can be applied, and then the
                                    washings can be adjusted for pH and sent directly to the sewer.
                                    In addition, the conditioner now used to treat the spent acid soap
                                    and rinsings before they go to the MEMTEK can be eliminated.
                                    The circuit board manufacturer knew of alternative developers,
                                    such as Morton Thiokol's Dynaclean, which reportedly can be
                                    cleaned by the MacDermid L5-B that forms a nonhazardous
                                    waste. Product names are given to illustrate that such products
                                    are commercially available.

                                       All eight WMOs are summarized in Table 2, together with
                                    their reductions in emissions and the associated savings and
                                    costs. The savings are calculated for each WMO independently,
                                    but it is obvious that some are related, so that the results from
                                    implementing one can affect the results  independently calcu-
                                    lated for another.

                                       This Research Brief summarizes a part of the work done
                                    under Cooperative Agreement No. CR-814903 by the University
                                    City Science Center under the sponsorship of the U.S. Environ-
                                    mental Protection Agency. The EPA Project Off icer was Brian A
                                   Westfall.
                                   at:
The EPA contact, Emma L. George, and can be reached


Pollution Prevention Research Branch
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
 Table 1. Summary of Current Waste Generation
 Waste Stream
 Hazardous Waste Generated
 Hazardous Liquid Waste
 A. Electroless copper:
   Waste rinses
   Catalyst predip
   Accelerator

 B. Electrolytic copper:
   Acid soap predean
   Water rinses
   Copper plating predip
   Tin plating predip

 C. Resist strip, copper
    etch, and tin strip:
   Water rinses
   Alkaline etch
   Tin strip
   Rack stripper

 D. Other processes:
   Deburrer #1
  Deburrer #2
  Scrubber
  Hot air leveling
Hazardous Solid Waste

A. MEMTEK unit
   Annual Quantity    Annual Waste Management Costs
     Generated     Treatment     Disposal    Recycling
 Copper plating and chemical drag-out           916,663 gal
 Table salt/water dumps                           530 gal
 Copper-laden, dilute hydrochloric acid               530 gal
Acid soap dumps                             10,189 gal
Soap, etch, copper and tin plating drag-out       366^665 gal
10% Sulfuric acid dumps                        3,266 gal
2% Sulfuric acid dumps                         3^266 gal
Etch, resist and tin strips drag-out               549,997 gal
Spent ammonium hydroxide                    13,950 gal
Spent ammonium bifluoride/peroxide              1,450 gal
Spent rack stripper                            1 [550 gal
Copper-laden rinse water                     366,665 gal
Copper-, tin/lead-, and gold-laden rinse water     366ie65 gal
Epoxy-, Copper-, and tin/tead-laden rinse water    183,332 gal
Copper-, ferric chloride-, hydrochloric
acid-laden rinse                             183,332 gal
                         Metal hydroxide sludge                         27,700 Ib
                                                         $10,488
                                                          $4,380
                                 $587
                                 $246
                                                          $6,285
                                 $352
$45.765
                                                                                 $12,570
                                                                        $704
                                                                      $5,471

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Table 1. Continued.
Waste Stream
Hazardous Waste Generated
B. Electroless copper:
   Microetch

C. Drilling and routing

D. Deburrer #1

E. Shearing

F. Filters:
   Electrolytic copper
   Post clean
   Auto tab plater
Copper sulfate crystals

Copper, aluminum, and gold dust

Metallic copper

 Copper/epoxy laminate dropoffs
Nonhazardous filter cake
Tin/lead-laden filters
Gold-laden resin filter cartridges
Annual Quantity     Annual Waste Management Costs
  Generated     Treatment      Disposal     Recycling
    2,800 Ib

      200 Ib

      200 Ib

    1,200lb
       25 Ib
       25 Ib
       25 Ib
Table 2.  Summary of Recommended Waste Minimization Opportunities
          Present Practice
                                Proposed Action
                           Waste Reduction and
                             Associated Savings
All but four rinse streams (dry film developer,
 post dean, gold plater, spent resist stripper)
and process bath dumps go to a common trench and
from there to the MEMTEK, in which they are
chemically reduced, precipitated, filtered, and settled.
The scrubber uses 183,300 gal/yr to rinse
particulates from circuit boards—metallic copper,
 lead, tin, and epoxy. The liquid containing
particulates goes to the MEMTEK.from which
effluent goes to the sewer.

Thorough rinsing is mandatory for many operations
in this plant. Observation of the plant revealed
operators set flow rates for water excessively
high.
The particular brand of dry film developer in use
adheres so strongly to the unexposed film that an
aggressive acid soap  is required for removal.
This soap presents problems in the MEMTEK and
necessitates prior treatment with conditioning
agents.

Tin is stripped away from the electrolytically
deposited copper sites that it protects. A
solution of ammonium bifluoride and hydrogen
peroxide is the stripping agent. The relatively
large quantity of washes is sent off-site for
treatment and recovery of tin.
Deionized water is used for rinsing on the
electrolytic copper and tin plating lines. Its
use should be extended to the electroless copper
plating line.
                      Reuse the MEMTEK effluent to reduce demand for
                      rinse water. To widen the range of possible uses,
                      some further treatment (e.g., ion exchange,
                      adsorption, and filtration) may be needed.
                      Additional storage tanks, pumps, and piping will
                      be required. Saving occurs in lower water demand
                      and sewer charges.

                      Filter (in a closed loop system) scrubber liquids
                      to remove hazardous particulates and recycle the
                      water for rinsing the scrubber. Dispose of filter
                      cartridge as solid hazardous waste.
                      Install flow reducers or flow meters on the water
                      supply to seven identified manufacturing
                      operations. Waste reduction and cost savings are
                      calculated only for reduced water usage, treatment
                      costs, and sewer costs.

                      Change to another dry film developer, use a less
                      aggressive soap (also nonhazardous), and
                      discharge the liquid to the sewer after pH
                      adjustment.
                      Concentrate the tin stripping solution to reduce
                      hauling and treatment costs. Partial freezing
                      will cost less than evaporation. The metal
                      reclaimer has said the concentrate is acceptable,
                      and there will be no increase in unit costs of
                      hauling and recycling. The separated solid can be
                      melted and sewered.

                      Use deionized water in five baths in the
                      electroless copper plating line, thereby reducing
                      sludge formation and extending the lifetime of the
                      bath. The savings will be achieved in lower cost
                      of treatment chemicals, as well as in lower water
                      and sewer costs. Use an ion-exchange regener-
                      ation  system.
                        Waste reduction = 1,833,325 gal/yr
                        Cost reduction = $3,840/yr (net)
                        Implementation cost = $22,000
                        Simple payback = 5.7 yr
                        Waste reducion = 183,300 gal/yr
                        Cost reduction  = $2,150/yr (net)
                        Implementation cost = $650
                        Simple payback = 4 mo


                        Waste reduction = 440,000 gal/yr
                        Cost reduction  = $5,840/yr
                        Implementation cost = $360
                        Simple payback = less than 1 mo
                        Waste reduction = 13,500 gal/yr
                        Cost reduction = $23,550/yr
                          (based on conditioner use alone)
                        Implementation cost = $0
                        Simple payback = immediate
                        Waste reduction = 1,650 gal/yr
                        Cost reduction = $4,030/yr (net)
                        Implementation cost = $10,000
                        Simple payback = 2.5 yr
                        Waste reduction = 1,015 gal/yr
                        Cost reduction = $1,840/yr
                        Ion-exchange saving = $6,500/yr
                        Implementation cost = $9,800
                        Simple payback = 1.2 yr

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Table 2. Continued.
          Present Practice                                  Prooosed Action                         Wa*Ste Reduction and
             		rroposea Acnon	               Associated Savings
                                                                                              Implementation cost = $0
                                                                                              Simple payback = immediate
                                                                                 reagents     implementation cost = $200
                                                copper nuggets, and tin anodes will result.          Simple payback = 9 mo
                                                                        &U.S. GOVERMMENT PRINTING OFFICE: 1991  548 028/40028

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Environmental Protection                 Information                               POSTAGE & FEES PAID
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Official Business
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EPA/600/M-91/022

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