EPA 742/F-99/021
PRINTED WIRING BOARD PROJECT
By Ksthy Hart,
Oipti Singh,
Lori Kmcsid,
Jack Geibig,
and Mery Sujsnson
trend in environmental protection toward increased cooperation
collaboration between government and "regulated entities " the U S
Environmental Protection Agency (EPA) Design for the Environment (DfE)
program has been working closely with the IPC and its member companies
the University of Tennessee's Center for Clean Products and Clean
Technologies, and other partners (academic, research, and public interest
representatives) since 1994 on the DfE 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 technologies, processes, and products
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Project partners have already completed and
published a major comparative study of tech-.
nologies used when making holes conductive
(MHC) in PWB manufacturing (i.e., alterna-
tives to the electroless copper process), and are
now conducting a similar evaluation of tech-
nologies that may be used in the surface finish-
ing step in place of hot air solder leveling.
Results of the surface finishes study are expect-
ed to be published in a draft report later this
year. A surface finishes project meeting will be
held at IPC Printed Circuits Expo '99 (Long
Beach, CA). The meeting is open to anyone
who would like to learn more about, or partici-
pate in, the surface finishes project.
In addition to the MHC study, the Dffi PWB
project has produced several technical reports,
including two on pollution prevention and
control technologies used in the PWB industry,
and produced and disseminated eight pollu-
tion prevention case studies.
Making Holes Conductive Study
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, required for electrolytic copper plating.
Although the electroless copper process for
making holes conductive is a mature technolo-
gy that produces reliable interconnects, the
typical process line is long (seventeen or more
process tanks, depending on rinse configura-
tions) and may have eight or more process
baths. It is also a source of formaldehyde emis-
sions and a major source of wastewater contain-
ing chelated, complex copper.
In the MHC study, project partners devel-
oped and analyzed technical information
regarding the potential human health and
environmental risks, performance, costs, and
chemical and natural resource use of the elec-
troless copper process and six "direct metaliza-
tion" technologies (Table 1). These analyses
were conducted by the University of
Tennessee, and the results were compiled into
a Cleaner Technologies Substitutes Assessment
(CTSA) and CTSA summary document. A
detailed description of the CTSA methodology
may be found in Section 1.3 of the CTSA docu-
ment. We believe that the CTSA results
described below demonstrate that the direct
metalization technologies make good econom-
ic and environmental sense for PWB manufac-
turers.
Table 2 lists the suppliers who participated ..
in the MHC CTSA, and the technologies they
submitted for evaluation. The suppliers provid-
ed publicly available chemistry data for their ,;
MHC chemical products, and were asked to
provide the identities and concentrations of
proprietary chemical ingredients.
Suppliers also completed a supplier data
sheet describing their products, and nominat-
ed test sites for a performance demonstration.
PWB manufacturers completed a workplace
practices survey, which requested detailed
information on their MHC processes as well as
worker activities related to chemical exposure.
The data collected from the suppliers and
through the workplace practices survey were
aggregated to develop generic process steps
and typical bath sequences for each technology
category, while acknowledging that the types
and sequence of baths in actual lines may vary,
depending on facility-specific operating condi-
tions.
There were a number of limitations to the
study, due to the predefined scope of the pro-
ject, the limit of the project's resources, and
uncertainties inherent to risk characterization
techniques. Those limitations are discussed in
detail in the MHC CTSA.
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The cost, energy, and resource use analyses
determined the comparative costs and con-
sumption rates of using an MHG techncjofy in
a model facility to produce 350,000 surface'
square'feet (ssf) of PWBs. As with the risk char-
acterization, this approach resulted in a com-
parative evaluation of cost or energy and natur-
al resource consumption, not an absolute eval-
uation or determination.
Risk Characterization of MKC Technologies
Risk results suggest that alternatives to the
nonconveyorized electroless copper process
pose lower overall occupational risks. This is
due to the reduced number of chemicals of
concern in the alternative technologies for
both inhalation and skin exposure, and to the
level of cancer risk from inhalation exposure to
formaldehyde in nonconveyorized electroless
copper processes. Detailed information 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 releas-
es, indicated low concern from all MHC
technologies.
Performance Demonstration Results
,..; In order to evaluate the relative performance
of each technology category, a comparative per-
formance 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 electrically pre-
screened, Mowed by electrical stress (1ST) test-
ing and mechanical (microsection) testing, in
order to distinguish variability in the perfor-
mance of the MHC interconnect The test meth-
ods used to evaluate performance were intend-
ed to indicate characteristics of a technology's
performance, not to define parameters of per-
formance or to substitute for thorough on-site
testing; rather, the study was intended to be a •
"snapshot" of the
technologies.
The microsection and 1ST tests were run
independently, and had extremely good corre-
lation of results. In terms of 1ST results, prod-
uct performance was divided into two func-
tions: plated through-hole (PTH) cycles-to-fail-
, ure and the integrity of the bond between the
internal lands (post) and PTH (referred to as
"post separation"). The PTH cycles-to-failure
observed in the study is a function of both elec-
trolytic plating and the MHC process. !
The mechanical testing and 1ST results indi-
cate that each MHC technology has the capabil-
ity to achieve comparable (or superior) levels-
of performance to electroless copper, if operat-
ed properly. Post separation results indicated
percentages of post separation that were unex-
pected 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
paper may be obtained by contacting Star
Summer-field at IPC (847-790-5347).
Cos't Rnslysis Results
The results of the cost analysis indicated that
all of the MHC alternatives are more economical
than the nonconveyorized electroless copper
process. The average cost for most MHC tech-
nologies ranged from 57-82 percent less than
the baseline technology (the cost for non-
formaldehyde electroless copper, nonconvey-
orized, was 22 percent less). Chemical cost was
.the single largest component cost for nine of the
ten technologies and equipment configurations
evaluated. Equipment cost was the largest cost
for the nonconveyorized electroless copper
process. Three separate sensitivity analyses of the
results indicated that chemical cost, production
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labor cost, and equipment costs have the great-
est effect on the overall cost results.
Energy and Resource USB Results
The-energy and water consumption rates of
MHC technologies were estimated, based on
data supplied by PWB manufacturers and their
suppliers, and through direct observation dur-
ing performance demonstration site visits. All
of the technologies consumed significantly less
water and energy than the baseline, nonconvey-
orized electroless copper technology. The
water use savings for most technologies ranged
from 85-96 percent on a ssf basis, and energy
savings ranged from 63-99 percent
Nonformaldehyde electroless, nonconvey-
orized, used 68 percent less water and 53 per-
cent less energy per ssf.
Surface Finishes Study
DfE PWB project partners are now evaluating
lead-free alternatives to the hot air solder level-
ing (HASL) process in order to identify those
surface finish technology alternatives that per-
form competitively, are cost-effective, and pose
fewer potential environmental and health risks.
The most commonly used PWB finishing tech-
nologies are HASL and electroplated tin-lead.
These technologies may pose potential health
and environmental risks due to their use of
228 • CIICtlUEt • KHtl • 1!»
lead, and the HASL process also generates sig-
nificant quantities of excess solder that must be
recycled. In addition to the HASL process,
which will be tested as the Baseline technology,
the alternatives being evaluated include: thick
organic solder protectorate, immersion tin,
immersion silver, electroless nickel/immersion
gold, and electroless nicki;l/electroless palladi-
um/immersion silver. The alternative tech-
nologies are expected to generate substantially
less hazardous waste and may be more cost
effective than the baseline technology.
Performance data for some of the technolo-
gies have been developed by the Circuit Card
Assembly and Materials Task Force (CCAMTF)
and die National Center for Manufacturing
Sciences (NCMS). However, performance data
for other technologies, and information on the
relative health and environmental risks and
costs of all technologies, have not been gener-
ated. The DfE PWB Surface Finishes Project
will supplement the work done by the : , -•
CCAMTF, and is expected to provide valuable
information to both die PWB manufacturing
and assembly industries.
To evaluate die performance of each surface
finish technology, a number of functional test
boards were fabricated (a modified version of
the IPC-B-24 board). The test boards contain a
variety of circuitry (including high voltage/low
current, high current/low voltage, high fre- -
quenq', and high-speed digital), and 'can be «;.
subjected to multiple processing steps (wave,
reflow, and hand soldering). The boards were r'
fabricated at one facility and then shipped to
the volunteer demonstration sites, where the
surface finishes were applied.
The boards were shipped to a common loca-
tion for assembly, including both through-hole
and surface mount components. Assembly was
completed 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
performance will be assessed under applicable
environmental stresses, with the HASL
process serving as a baseline. The functional
boards will be evaluated through a series of
reliability tests, including thermal shock and
mechanical shock. ©
Kathy Hart is an environmental protection spe-
cialist and Dipti Singh is a chemical engineer with
U.S. EPA's Design for the Environment program.
Lori Kincaidjack Geibig, and Mary Swanson are
with the University of Tennessee Center for Clean
Products and Clean Technologies. Kincaid js associ-
ate director of the center, Swanson is ajesearch scien-
tist, and, Geibig is a senior research associate. .
' Reprinted with permission from the January 1999 issue of Plating and
Surface Finishing, the journal of the American Electroplaters and
Surface Finishers Society, Orlando, FL.
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