United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-93/201
December 1993
\yEPA Project Summary
Carbon-Black Dispersion
Preplating Technology for Printed
Wire Board Manufacturing
Dale W. Folsom, Arun R. Gavaskar, Jody A. Jones, and Robert F. Olfenbuttel
This project compared chemical use,
waste generation, costs, and product
quality between electroless copper and
carbon-black-based preplating tech-
nologies at the printed wire board
(PWB) manufacturing facility of
McCurdy Circuits in Orange, CA. The
carbon-black-based preplating technol-
ogy evaluated is used as an alternative
process for electroless copper (EC)
plating of through-holes before elec-
trolytic copper plating. The specific pro-
cess used at McCurdy Circuits is the
BLACKHOLE™1 (BH) technology pro-
cess, which uses a dispersion of car-
bon black in an aqueous solution to
provide a conductive surface for sub-
sequent electrolytic copper plating. The
carbon-black dispersion technology
provided effective waste reduction and
long-term cost savings. The economic
analysis determined that the new pro-
cess was cost efficient because chemi-
cal use was reduced and the process
proved more efficient; the payback pe-
riod was less than 4 yr. McCurdy Cir-
cuits found that the product quality
achieved was equal to that achieved
with EC plating. Thus, the new carbon
black dispersion process was found to
be a viable alternative to EC.
This Project Summary was developed
by EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to announce
key findings of the research project
that Is fully documented In a separate
1 Mention of trade names or commercial products does
not constitute endorsement or recommendation for
use.
report of the same title (see Project
Report ordering Information at back).
Introduction
This study, performed under the U.S.
Environmental Protection Agency's (EPA)
Waste Reduction and Innovative Technol-
ogy Evaluation (WRITE) Program, was a
cooperative effort between EPA's Risk
Reduction Engineering Laboratory (RREL)
and McCurdy Circuits. The goal of the
WRITE Program is to evaluate, in a typi-
cal workplace environment, examples of
prototype or innovative commercial tech-
nologies that have potential for reducing
wastes and to provide this information to
potential users. The objectives of the car-
bon-black dispersion technology study
were to evaluate (a) the waste reduction
potential of the technology, (b) the eco-
nomic feasibility of the technology, and (c)
the product quality of the PWBs.
McCurdy operates two process lines for
the through-hole plating of PWBs: one
uses EC and the other uses the carbon-
black dispersion process. The EC pro-
cess at McCurdy Circuits consists of the
following 18 operational steps:
1. Acid cleaner
2. Rinse (to discharge line)
3. Microetch (sodium persulfate
solution)
4. Rinse (to ion exchange line)
5. Activator-pre-dip
6. Catalyst
7. Rinse (to discharge line)
8. Rinse (to discharge line)
9. Accelerator
10. Rinse (to discharge line)
11. EC
Printed on Recycled Paper
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12. Rinse (to separate ion
exchange system)
13. Sulfuric acid 10%
14. Rinse (to ion exchange
system)
15. Anti-ox
16. Rinse (to discharge line)
17. Deionized (D.I.) water rinse (to
discharge line)
18. Forced air dry
In the first 17 steps, racks of PWBs are
moved from tank to tank with an auto-
mated hoist. All the rinses are single flow
through, which generates more wastewa-
ter than does cascading or multiple-use
rinses. Because of dragout, the rinse fol-
lowing the EC bath (Step 11) receives
complexed copper from the bath. This
complexed copper, which is discharged
with the rinse water, is hard to treat by
typical metal hydroxide precipitation. Rinse
water from the EC process is collected in
one of three drain lines: one to a dis-
charge line, another to the first ion-ex-
change collection system, and the third to
an ion-exchange system for the EC rinse.
Whereas the EC process is essentially
a batch process, the carbon-black pro-
cess is a continuous system in which parts
are placed on a roller conveyor. This car-
bon-black dispersion technology, termed
BLACKHOLE™ technology by the vendor/
inventor, consists of fewer baths and a
simplified process. It has only the follow-
ing 11 process steps:
1. BH™ cleaner
2. Rinse (water from step 4, to
discharge line)
3. BH™ conditioner
4. Rinse (fresh tap water, to
rinse #2)
5. BH™bath
6. Dryer
7. Microetch
8. Rinse (water from step 10, to ion
exchange system)
9. Anti-tarnish
10. Rinse (fresh tap water)
11. Dry
The BH™ bath (Step 5) is an aqueous,
carbon-black dispersion, which eliminates
the need for electroless copper metalliza-
tion before electrolytic plating. The steps
before and following Step 5 are similar to
those used in the EC copper process.
Unlike the EC process, with BH™ tech-
nology the rinse after the microetch pro-
cess step is the only rinse water stream
that goes to the ion-exchange system,
which is shared with the first ion-exchange
system for the EC process. The rest goes
to the discharge line. The carbon-black
dispersion process uses only two rinse
water flows, and the process solutions
contain nonhazardous materials.
Waste Reduction Evaluation
The amount of waste resulting from the
EC operation, run at full production, was
evaluated to represent baseline data. The
amount of waste from the carbon-black
dispersion process using BH™ technol-
ogy, run at full capacity, was then com-
pared with this baseline. The wastestreams
from both processes consisted of the bath
solutions (discarded periodically) and the
rinse water. The volumes of these
wastestreams were obtained from plant
records (bath volumes) and field measure-
ments (rinse-water flow). The pollutant con-
tent of the bath solutions was estimated
from plant records of the chemical makeup
of the baths. The pollutant content of the
rinse water was obtained by analyzing
samples collected during field testing. Mea-
surable factors in analyses to character-
ize the rinse water included copper, pH,
and total solids content.
Samples from both processes were ob-
tained to analyze the pollutants in the
rinse water. Six sample sets for the elec-
troless copper line and 11 sample sets for
the carbon-black dispersion process line
were taken over 4 days of operations.
Composite samples were required to al-
low for the cyclic concentration swings of
the rinse water caused by the batch rins-
ing operations of the racks used in the
electroless copper line. In contrast, the
carbon-black process was continuous and
reached steady state rather quickly, al-
lowing for shorter composite sampling
times.
The copper content in rinse water was
measured with the use of inductively
coupled plasma spectrometry by employ-
ing EPA Method 6010. Total solids were
measured by EPA Method 160.3. Only pH
measurements were taken in the field;
these were taken with a pH meter.
Rinse tanks were used as receiving ves-
sels to determine the rinse-water flow rates
of the two processes. After the rinse-tank
outlet had been plugged, a stopwatch mea-
sured the time required to raise the water
level by 2 in. The flow to each rinse tank
in the process was totaled for all rinse-
water flows listed in Table 1. This total
flow and the material concentrations were
used to determine the quantity of waste
discharged in the rinse water from each
process.
The production rate on the carbon-black
dispersion process line using BH™ tech-
nology (i.e., 3.3 ft2/min) was found to be
2.1 times as fast as the production rate on
the electroless copper (EC) process line
(i.e., 1.6 ft2/min). Production rates were
timed during field testing and compared
with production schedules maintained by
McCurdy Circuits. The production rate of
8 hr/day, 5 day/wk, for 50 wk/yr assumed
for this study is the approximate rate at
McCurdy Circuits. McCurdy Circuits oper-
ates the electroless copper process at ap-
proximately the full capacity of 1.6 ft2/min,
which yields 200,000 ft2/yr. The carbon-
black process line, installed in response
to increased demand, is currently oper-
ated at only about 11% of its capacity.
Equivalent productions must be used to
compare the waste types and quantities
generated by both processes. In this study,
because we assumed that the carbon-
black process could completely replace
the electroless copper process, the waste
reduction estimates reflect the potential
production of the carbon-black process at
McCurdy Circuits, not the actual produc-
tion. Tables 2, 3, and 4 generally show
the chemicals used, costs incurred, and
wastes generated as if each process were
operated at capacity for 1 yr; the figures
given for the carbon-black process are,
therefore, adjusted to account for the fact
that the carbon-black process would have
processed twice the number of PWBs as
the electroless copper process. In this way,
wastes generated can be compared for
equivalent annual productions.
As seen in Table 1, the BH process
uses much less water than does the EC
process. These water volume figures indi-
cate that a smaller quantity of wastewater
treatment chemicals would be needed be-
cause less wastewater would be gener-
ated.
Waste averages and standard devia-
tions for copper and total solids were cal-
culated, and a t-test was performed with a
95% level of confidence. The test statistic,
which takes into account the standard de-
viations, indicated that the levels of both
copper and total solids discharged by the
BH process are significantly lower than
those for the EC process. The average
reduction in copper is 76 mg/ft2, a reduc-
tion of 23%. The average reduction in
total solids is 19,300 mg/ft2, a reduction
of 81%.
The BH process thus releases signifi-
cantly less copper into the wastestream. If
approximately 200,000 ft2 of PWB (the
operating capacity of the EC process) were
run on both processes, the difference in
copper waste would average 15.2 kg (33.4
lb)/yr.
The total solids discharge is reduced
when the BH process is used. Although
the higher solids composition of the BH
baths would lead one to expect that this
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Table 1. Rinse Water Flow Rates
Process
Electro/ess copper
Blackhole™
Operation
Step
2
4
7
8
10
12
14
16
Total
2
8
Total
Flow Rate
(gpm)
2.5
0.9
1.4
6.0
4.6
1.6
1.5
3.8
22.3
2.9
2.6
5.5
Destination
To discharge line
To ion exchange
To discharge line
To discharge line
To discharge line
To complexed ion
exchange
To ion exchange
To discharge line
To discharge line
To ion exchange
process would discharge more solids, the
faster production rate and fewer process
baths containing chemicals apparently off-
set this effect when the data are normal-
ized.
Formaldehyde (a suspected human car-
cinogen that poses a significant health
hazard when inhaled or ingested or
through direct physical contact) is com-
pletely eliminated in the BH process,
whereas approximately 200 gal/yr are used
in the EC bath. Palladium and trace
amounts of cyanide, also used in the EC
process, are not present in the carbon-
black dispersion process.
EEconomic Evaluation
The economic evaluation was based on
data obtained from McCurdy Circuits, in-
cluding the unit costs and amounts used
of chemicals and water, and from suppli-
ers. The current capital cost of carbon-
black dispersion equipment was obtained
from an equipment vendor. The calcula-
tions are based on the production rate of
200,000 ft2 of PWB per year, approxi-
mately the rate of the current EC system.
The BH process cost basis is half a year,
running at capacity, i.e., the time it would
take to process approximately 200,000 ft2
of PWB.
Annual chemical usage and cost for
both processes are shown in Table 2. As
seen in Table 3, the summary of major
operating costs, BH has lower operating
costs than does EC in all cost categories
that could be obtained from company data.
The major savings accrued through lower
chemical and labor (time) costs, and the
total savings added up to more than 50%.
BH equipment having the capacity of
the system tested at McCurdy Circuits cur-
rently costs $212,000 (in 1992 dollars),
with an estimated installation cost of
$9,000. The payback period is less than 4
yr, with an assumed cost of capital of
15%.
Product Quality
The ability of the carbon-black disper-
sion process using BH technology to meet
product quality and performance require-
ments was evaluated based on results of
previous tests done in accordance with
the Military Standard MIL-P-55110D re-
quirements for through-hole plating and
internal testing done by McCurdy Circuits.
No additional testing was conducted dur-
ing this evaluation because the tests in-
volve destructive testing of a number of
PWBs and are time consuming.
McCurdy Circuits routinely conducts in-
ternal quality checks of 10% of the PWBs.
During these checks, small coupons are
punched from selected PWBs, cast in
resin, and polished to allow visual inspec-
tion of through-hole plating and layer bond-
ing. Also, the PWBs are placed on a test
grid that checks continuity of the circuits.
These quality checks made by McCurdy
Circuits and inspections by their clients
verify product quality.
Discussion
In this study of waste-reduction poten-
tial of the carbon-black dispersion pro-
cess using the BH technology, the pro-
cess was found to reduce waste by re-
ducing the number of process steps and
the number of hazardous chemicals used
in and wasted from the process as com-
pared to the EC process. Table 4 summa-
rizes the waste reduction achieved.
Rinse water use was reduced by a fac-
tor of eight. Chemical usage dropped con-
siderably, and copper waste in the rinse
water was reduced 23%. The only copper
found in the carbon-black dispersion rinse
water was that removed from the PWBs
during microetching. No additional copper
was introduced in the carbon-black dis-
persion baths during processing. This does
not take into account the copper lost due
to replacement of the electroless copper
solution. Each day, 20% of the 100-gal
electroless copper bath is replaced. A cop-
per solution concentration of 2 g/L re-
moved from the bath results in a loss of
83.4 Ib copper/yr, based on a 50-wk yr.
The quantity of total solids leaving with
the rinse water was reduced by a factor of
five because of the reduced use of rinse
water and the fewer number of process
baths. The reduced solids indicate that
fewer bath chemicals are lost and that
fewer chemicals are discharged to the
wastewater treatment system.
The carbon-black dispersion process
uses five chemical process baths and four
rinse baths that do not introduce the haz-
ardous metals and materials found in the
EC process baths (formaldehyde, cyanide,
palladium, and complexed copper). In ad-
dition to the positive long-term environ-
mental aspects of carbon-black dispersion,
eliminating the use of formaldehyde di-
minishes health risks to personnel and
reduces industry's potential environmen-
tal liabilities. Reducing the number of pro-
cess steps and quantities of chemicals
reduces storage and transportation require-
ments, minimizes the possibility of leaks
and accidental spills during storage and
transportation, and results in economic
savings too varied and intangible to be
included in the analysis of economic fac-
tors.
The BH technology proved to be cost
effective with the annual operating cost
determined to be less than half that of the
EC process and a payback period of less
than 4 yr. Further, the option of converting
electroless copper equipment to the car-
bon-black dispersion process would re-
duce the capital cost and result in an
even faster payback period.
The energy costs were assumed to be
almost equal for the two process lines.
The actual waste treatment costs at the
test site were unavailable. In both pro-
cesses, copper-containing wastewater is
passed through an ion-exchange resin to
remove the copper before entering the
discharge line. The copper is eluted from
the resin, recovered by electrowinning, and
given away as scrap. A plant that oper-
ates a conventional wastewater treatment
system consisting of pH adjustment and
precipitation should realize a significant
savings in treatment costs with the car-
bon-black process because of the reduced
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Table 2. Annual Chemical Use and Costs
Description
Chemical
Usage
(gal/yr)
Unit
Cost
Cost
Adjusted
Cost
Electroless Copper
Acid cleaner
Microetch:
Sulfuric acid
Sodium persulfate
Activator
Catalyst:
Predip
Catalyst
Accelerator
Electroless Copper:
Copper
Sodium hydroxide
Formaldehyde
Sulfuric Acid
Anti-Ox
Blackhole™
Cleaner
Conditioner
Blackhole™
Microetch
Sodium persulfate
Sulfuric acid
Copper sulfate
Anti-Tarnish
CTCS 501
Sulfuric acid
145
195
1,800 Ib
2,500
15.9
21.8
393
3,950
2,250
199
308
1,250
41.2
41.4
68.0
1,130lb
13.2
50.0 Ib
6.60
3.30
21.70
0.08
LOOIb
3.35
3.35
280
18.65
10.35
2.50
6.20
0.08
11.95
400
400
595
1.00
0.08
6.62
12.00
0.08
3,150
15.26
1,880
8,380
53.3
6,100
7,330
40,900
5,630
1,230
24.6
14,900
Total:
16,500
16,600
40,500
1,130
1.06
331
79.2
0.26
Total:
3,150
15.6
1,880
8,380
53.3
6,100
7,330
40,900
5,630
1,230
24.6
14,900
$89,600
8,250
8,280
20,250
565
0.53
166
39.6
0.13
$37,500
* Because the BLACKHOLE™ process has a production rate approximately twice that of the electroless copper process, costs were adjusted to compare
a half year of processing for BLACKHOLE™ to a full year for electroless copper.
Table 3. Comparison of Annual Adjusted Major Operating Costs*
Description
Electroless
Copper
Blackhole™
Blackhole™
Savings, %
Chemicals
Tap water
D.I. water
Energy &
Labor
Waste disposal
Waste treatment labor
Totals
$89,600
3,200
503
N/A
50,000
N/A
10,000
$153,000
$37,500
403
38.3
N/A
25,000
N/A
3,330
$66,300
58
87
92
0
50
0
67
57
' Because the BLA CKHOLE™ production rate is approximately twice as fast as that of the electroless copper process, the costs are adjusted to take this into
account. The BLACKHOLE™ costs reflect a half year of processing, whereas the electroless copper costs represent a full year.
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Table 4. Summary of Waste Reduction
Waste Types
Rinse water
Chemical use
Copper waste
(in rinse water)
Total solids
Electroless
Copper Process
13.8 gal/ff
11,755 gal + 38 Ib
324 mg/ff
23,800 mg/ff
Blackhole™
Process
1.7galrff
90 gal + 611 Ib
248 mg/ff
4,510 mg/ff
Net Change
in Waste
12.2 gal/ff
not calculable
76 mg/ff
19,300 mg/ff
amount of copper waste. This option was
not included in our evaluation.
In tests conducted by McCurdy Circuits,
product quality of the carbon dispersion
processed boards was similar to that of
the electroless copper processed boards—
boards from both processes were of ac-
ceptable product quality. In addition, PWBs
using the BH carbon dispersion technol-
ogy have passed MIL-P-55110D qualifica-
tion and performance standards for plated
through-holes.
Conclusions
Because the carbon-black dispersion
process reduces wastes, avoids many haz-
ardous chemicals and metals, is cost ef-
fective, and yields an acceptable product,
it should be considered a viable alterna-
tive to the EC process. If the shop in-
volved is a job shop, client input and re-
quirements would be important in deter-
mining the feasibility of incorporating the
carbon-black dispersion process. Although
this study provides generalizations for com-
panies considering carbon-black disper-
sion, it is recommended that each com-
pany examine its specific requirements to
determine the suitability of this alternative
technology for specific applications.
The full report was submitted in fulfill-
ment of Contract No. 68-CO-0003 by
Battelle under the sponsorship of the U.S.
Environmental Protection Agency.
•&U.S. GOVERNMENT PRINTING OFFICE: 1994 - 550-067/80139
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D.W. Folsom, A.R. Gavaskar, J.A. Jones, andR.F. Olfenbuttelare with
Battelle, Columbus, OH 43201-2693
Teresa Marten is the EPA Project Officer (see below).
The complete report, entitled "Carbon-Black Dispersion Preplating Technology
for Printed Wire Board Manufacturing," (Order No. PB94-114 790/AS;
Cost: $17.50, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
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