United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-92/114 October 1992
EPA Project Summary
Modifications to Reduce Drag
Out at a Printed Circuit Board
Manufacturer
Teresa M. Harten and Paul E. Pagel
The waste reduction capabilities of
two simple, drag-out-reducing modifi-
cations were demonstrated at a Minne-
apolis-area, printed circuit board
manufacturer in an evaluation per-
formed under the Minnesota/U.S. Envi-
ronmental Protection Agency (EPA)
Waste Reduction Innovative Technol-
ogy Evaluation (WRITE) Program. The
low (or no) cost, low technology
changes made were (1) slowing the
withdrawal rate of racks containing the
printed circuit boards as they were
pulled from an etchant process tank
and an electroless copper process tank
and (2) combining an intermediate
withdrawal rate with a longer drain time
over the process tanks. Both modifica-
tions significantly reduced drag out of
concentrated, copper-containing bath
solutions into the rinse water systems.
The first modification reduced drag
out by 45% for the etchant bath and
50% for the electroless copper bath.
When compared with the baseline, the
second modification reduced drag out
by 41% for the etchant bath and 52%
for the electroless copper bath. By re-
ducing drag out in these amounts, 203
and 189 g of copper per day were not
discharged as waste in the rinse water
waste stream for modifications 1 and
2, respectively. Because copper con-
centration in rinse water was reduced,
the potential for conserving rinse wa-
ter flows was also shown, although this
was not directly tested.
The total potential annual savings
was calculated at $3350 for the first
modification and $3120 for the second
modification. For the first modification,
$2640 was saved in treatment and dis-
posal costs and the remainder, $710,
was the projected savings in water and
sewer charges because rinse water
could be reduced proportionate to drag
out reduction. The same figures for the
second modification were $2460 and
$660, respectively. Since no capital
costs were incurred in making the
changes, payback would be immediate.
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
report of the same title (see Project
Report ordering information at back).
Introduction
The program is one of seven WRITE
programs nationwide in which EPA and
cooperating states or local governments
evaluate and demonstrate the engineering
and economic feasibility of selected waste-
reducing technologies in a manufacturing
or fully operational setting. The program
in Minnesota, which began in mid-1989,
targets the metal finishing industry, spe-
cifically rinsing processes within metal fin-
ishing operations. The five technology
evaluations planned for the full life of the
Minnesota/EPA Program and subsequent
technology transfer activities are intended
to speed the early introduction of cleaner,
pollution-preventing technologies in the
metal finishing industry.
The report summarized here discusses
the results of the first project performed
under the Minnesota/EPA WRITE program.
The project evaluated modifications that
reduce drag out at a single plating line at
a printed circuit board manufacturer. It is
hoped that by demonstrating the success
of the modification in a fully operational
setting, the technology will be transferred
Printed on Recycled Paper
-------
to other plating/rinsing systems within the
company as well as to other companies in
the metal finishing Industry.
Two interrelated modifications that ef-
fectively help prevent wastes from entering
the rinsing processes are (1) reducing drag
out, which is the carryover of concentrated
solutions from plating baths and (2) re-
ducing rinse water flows. When drag out
is reduced, rinse water can be conserved
because less will be needed to achieve
effective rinsing. EPA previously discussed
these changes to reduce drag out and
rinse water use in the manual "Control
and Treatment Technology for the Metal
Finishing Industry - In-Plant Changes"
(EPA/625/8-82/008, 1982).
Procedure
Mfcom, Incorporated, is a medium-sized, ,
job-shop circuit board manufacturer em-
ploying approximately 240 people at its
plant in New Brighton, MN. Under a num-
ber of military and commercial contracts,
the company produces an average of 1000
to 1200 ft2 of double-sided multilayered
panels per day. In 1989, annual revenue
was $17 million.
The evaluation took place at the sensi-
tize line where a number of process baths
including etchant (micro-etch), activator,
accelerator, eloctroless copper, and rinse
tanks, first etch and then chemically de-
posit copper onto the insides of the circuit
board through holes. Drag out from two of
the line's process baths, the micro-etch
and the electroless copper, was a signifi-
cant source of waste copper discharged
into the rinse-water waste stream leaving
tha line. Figure 1 shows a schematic of
the micro-etch process, and Figure 2 pro-
vides the same for the etectroless copper
process. Rinse water from the two pro-
cesses had to be treated by an onsite, ion
exchange unit for copper removal before
it could be discharged to public sewer.
Treatment of spent micro-etch, and
electroless baths included copper recovery
in both cases and regeneration of etchant
in the case of the micro-etch solution.
When the micro-etch bath had to be re-
moved from the line and replaced with
fresh bath, it was company practice to
reclaim copper from the bath as copper
sulfate and reuse it in another copper
plating solution onsite. The etchant was
regenerated and also used onsite for less
critical operations such as stripping cop-
per from carrier racks. The company also
recovered copper from the spent electro-
less copper bath, although the copper was
sent offsite for reuse. Thus, copper-con-
taining bath solution retained in the process
baths after implementing drag out reduc-
tion changes would ultimately be subjected
to the company's recovery operations.
To determine baseline drag out, samples
were taken at the process tanks and at
the two rinse tanks following each process
tank — both before and after a rack of
circuit boards was moved through the
three-tank system. Over a 2-week period,
12 sample sets were taken to calculate 12
baseline drag out values. Additional mea-
surements taken to calculate drag out in-
cluded rinse-tank water volumes for each
of the rinses; these volumes were mea-
sured during each of the 12 sampling pe-
riods. The total surface area of the boards
plated for each rack was also tracked for
each sampling period. Samples were ana-
lyzed for total copper concentration. The
results of the copper analyses and the
other data collected for each sample set
were used to calculate drag out with the
following formula:
Drag out:
(ml/ft2)
change in rinse copper
concentration (mg/L)
rinse
volume (ml)
copper concentration in
process solution (mg/L)
board surface
area (ft2)
Softened Water
Micro-etch
A
Counter
Current
Rinse
A
ppqeea»a6p6£6£d£60Qd6d^£$£$p^6o66
ayssyxosaaaa^SK
\
Counter
Current
Rinse
A
A
Sampling
Location
2.6 gpm
to treatment (Ion Exchange)
Figure 1. Micro-etch process diagram.
Softened Water
Electroless
Copper
A
Counter
Current
Rinse
A
A
3.3 gpm
Sampling
Location
to treatment (Ion Exchange)
Figure 2. Electroless copper process diagram.
2
-------
To establish a baseline withdrawal rate
and drain times, both the withdrawal and
drain times were measured during each
sampling period.
Two modifications to reduce drag out
were made and independently tested af-
ter taking baseline samples. The first
modification was to slow the withdrawal
rate of the racks as they were pulled from
the process tanks. The withdrawal rate of
a programmable mechanical hoist system
was slowed from the baseline rate of 100
ft/min for the micro-etch line and 94 ft/min
for the electroless copper line to 11 ft/min
and 12 ft/min, respectively. Samples were
taken after the withdrawal rates were
slowed to determine the effect on drag
out.
A second modification was then made
and tested: using a withdrawal rate be-
tween the baseline and first modification
rates and increasing the drain time over
the process tank before transfer to the
rinse tank. The manually operated me-
chanical hoist had been taken out of ser-
vice because of persistent problems with
break downs that predated this study and
were unrelated to the evaluation; it was
replaced with an air-assisted manually op-
erated hoist that the company also used
to operate the line. With the use of this
hoist, the second modification withdrawal
rate was 40 ft/min for both the micro-etch
and the electroless copper baths. Drain
times were increased from baseline drain
times of 3.4 sec for the micro-etch bath
and 5.2 sec for the electroless bath to
12.1 sec and 11.9 sec, respectively.
Samples were again taken to determine
the effects of the intermediate withdrawal
rate and longer drain times on drag out.
Results and Discussion
The average drag out for 12 sampling
sets of the baseline evaluation was cal-
culated at 12.1 ml of bath solution per ft2
of circuit board processed from the micro-
etch bath and 6.0 ml/ft2 from the electro-
less copper bath. After the first modifica-
tion, slowing the withdrawal rate, the av-
erage drag out of 12 sampling sets was
calculated to be 6.7 ml/ft2 from the micro-
etch bath and 3.0 ml/ft2 from the electro-
less copper bath.
After the second modification, an inter-
mediate withdrawal rate and longer drain
time as compared with the baseline, the
average drag out of 12 sampling sets was
calculated to be 7.1 ml/ft2 from the micro-
etch bath and 2.9 ml/ft2 from the electro-
less copper bath.
Results for the micro-etch bath are sum-
marized in Table 1, and results for the
electroless copper bath are summarized
in Table 2. The reduction in drag out for
the micro-etch bath was 45% as a result
of the first modification and 41 % as a
result of the second modification. For the
electroless bath, drag out was reduced by
50% after the first modification and 52%
after the second modification.
For modification 1, the reduction in drag
out was calculated to prevent 194 g/day
of copper from the micro-etch bath and 9
g/day of copper from the electroless bath
from entering the rinse-water waste
stream. The figures for the second modifi-
cation were 180 and 9 g/day, respectively.
These figures assumed a copper concen-
tration of 30 g/L in the micro-etch bath;
2.4 g/L in the electroless bath; and a pro-
duction level of 1200 ft2 of printed circuit
board per day.
Economic calculations were based on
the cost of existing treatment and dis-
posal methods for the rinse-water waste
streams. Onsite ion-exchange canisters
with a capacity of 46 Ib copper treated the
rinse water. When capacity was reached,
canisters were regenerated offsite at $1096
per canister. The economic evaluation
showed that the company could save
$2640 per year in rinse water treatment
and disposal costs by implementing modi-
fication 1 or $2460 per year by imple-
menting modification 2. An additional sav-
Table 1. Summary of Micro-etch Results
ings of $710 per year for modification 1,
or $660 for modification 2, could be real-
ized in avoided water and sewer charges
if the company reduced rinse-water flow
rates in proportion to the reduced copper
contamination resulting from the modifica-
tions.
No savings in process bath chemicals
could be calculated since the company's
chemical supplier based its charges for
chemicals on square feet of boards pro-
duced, not on the actual quantity of
chemicals used. Thus the company did
not receive economic incentive from the
chemical supplier to conserve process
chemicals. If Micom could renegotiate the
cost of chemicals with the chemical sup-
plier based on reduced use, the econom-
ics of the waste reduction modifications
would be improved. -
implementation
For a number of site-specific reasons,
the company decided to implement a
longer drain time to reduce drag out in-
stead of altering the withdrawal rate. The
programmable mechanical hoist used for
modification 1 at Micom was unreliable,
often broke down, and was inflexible in its
programming. To slow the withdrawal rate
for modification 1, the vertical speed had
Baseline
Modification 1
Withdrawal Time of
Rate Withdrawal
(ft/min) (seconds)
100 1.7
11 14.9
Drain
Time
(seconds)
3.4
2.5
Total
Time
(seconds)
5.1
17.4
Drag Out
(ml/ft*)
12.1
6.7
slower rate of withdrawal
Modification 2
longer drain time with
intermediate withdrawal rate
40
4.3
12.1
16.4
7.1
Table 2. Summary of Electroless Copper Results
Baseline
Modification 1
Withdrawal
Rate
(ft/min)
94
12
Time of
Withdrawal
(seconds)
1.8
13.9
Drain
Time
(seconds)
5.2
3.2
Total
Time
(seconds)
7.0
17.1
Drag Out
(ml/ff)
6.0
3.0
slower rate of withdrawal
Modification 2
longer drain time with
intermediate withdrawal rate
40
4.3
11.9
16.3
2.9
•U.S. Government Printing Office: 1992— 648-080/60141
-------
to be adjusted. This adjustment slowed
not only the withdrawal rates for the micro-
etch and the electroless lines but also the
insertion rates. Further, these rates were
slowed for insertion and withdrawal into
all tanks on the sensitize line, not just the
micro-etch and the electroless tanks. To
maintain production rates at previous lev-
els, operators supplemented the me-
chanical hoist with an air-assisted hoist.
As a result of recurrent break downs of
the mechanical hoist and the inability to
specifically target and program slower
withdrawal rates for the two bath tanks,
the company took the mechanical hoist
out of service. Air-assisted hoists were
used as replacements. With this type op-
eration, it made more sense for the
company to implement a longer drain time
to achieve drag out reduction. The com-
pany believed that it would be easier to
train operators to increase the drain time
over the two tanks than to have them
stow withdrawal rates.
For modification 2, the additional time
added to the sensitize line to allow the
intermediate withdrawal rate and longer
drain time, when compared with the
baseline, was 21 sec. This amount was
negligible when compared with the total
production time through the sensitize line
of 60 min. Minor modifications to the op-
eration of the line could offset the added
time so that the baseline production rate
could be maintained. At Micom, filled racks
were often held beyond the necessary
times in rinse tanks while being processed
in the sensitize line or were placed at the
loading area before entering the line.
Changes such as shortening the timing
between rack starts and/or reducing hold-
ing times in rinse tanks—times that were
known to be more than adequate — could
makeup for the added 21 sec.
Conclusions
The waste reducing capabilities of two
simple, -drag-out-reducing modifications
were successfully demonstrated at a Min-
neapolis area printed circuit board manu-
facturer. Economics were favorable for
both modifications; savings were calcu-
lated at $3350 and $3120 per year for the
first and second modifications, respectively.
Since no capital costs were required to
make the changes, payback was immedi-
ate.
Although both modifications looked fa-
vorable from the standpoints of econom-
ics and waste reduction capability, the first
modification, slowing the withdrawal rate
of the circuit boards from process baths,
was not implemented by the company
because of reliability and programmability
limitations of the company's mechanical
hoist system. The company used the re-
sults from the second modification testing,
an intermediate withdrawal rate and a
longer drain time, in its decision to imple-
ment a longer drain time for drag out
reduction. The implementation of this
change was dependent on training opera-
tors to increase the drain time over tanks
and ensuring that this new operating pro-
cedure was maintained. The increase in
drain time did not slow production at the
company.
The full report was submitted in fulfill-
ment of Cooperative Agreement No. CR-
815821-01-0 by the University of Minne-
sota, Minnesota Technical Assistance Pro-
gram (MnTAP) under the sponsorship of
the U.S. Environmental Protection Agency.
The EPA author, Teresa M. Marten (also the EPA Project Officer, see below), is with the
Risk Reduction Engineering Laboratory, Cincinnati, OH 45268, and Paul E. Pagel is
with the Minnesota Technical Assistance Program, University of Minnesota, Minne-
apolis, MN 55414-4504.
The complete report, entitled "Modifications to Reduce Drag Out at a Printed Circuit
Board Manufacturer," (Order No. PB92-198 555/AS; Cost: $17.00, 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
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/SR-92/114
------- |