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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 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:."?/-:
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-------
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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