A Cooperative Project
between the
U.S. Environmental
Protection Agency
and PWB
Manufacturers
Nationwide
FOR
THE
PRINTED WIRING BOARD CASE STUDY 2
EPA
PRINTED WIRING BOARD
CASE STUDY 2
On-Site Etchant
Regeneration
In business today, being responsive to the
environment means learning new proce-
dures and using new tools to do the same
job with less environmental impact. Decisions
about the purchase of equipment and prod-
ucts depend not only on cost, availability, and
performance, but also on whether your envi-
ronmental goals can be met. The manufacture
of printed wiring boards (PWBs), the building
blocks of the electronics industry, requires
using substantial amounts of water and ener-
gy, and some hazardous chemicals that pose
potential environmental and health risks. To
facilitate the evaluation of alternative manu-
facturing technologies that reduce both envi-
ronmental risks and production costs, EPA has
entered into a partnership with the PWB
industry through its Design for the Environ-
ment (DfE) Program. One of the goals of this
cooperative effort (involving EPA, industry,
trade associations, and public interest groups),
is to generate and disseminate information on
viable pollution prevention alternatives so that
the industry can further explore cleaner man-
ufacturing methods.
This is the second in a series of DfE
case studies that illustrate the benefits of pollu-
tion prevention for PWB manufacturers. Specif-
ically, this case study focuses on the benefits
of etchant regeneration systems, and how they
can reduce the impact of etching processes on
the environment while reducing costs.
Why Etchant
Regeneration?
In the process of making PWBs using
the "subtractive" process, the circuit pattern is
created by chemically etching copper from the
unprotected (non-circuit) areas of the copper-
coated panel, leaving circuit traces protected
with photoresist. Etching can be accomplished
with acids or bases, depending on the etch
rate and the line width required. The ammoni-
acal etchants, either ammonium chloride or
ammonium sulfate, are most commonly used.
Cupric chloride is also used, even though it
often requires chlorine gas, a significant health
and environmental concern.
Approximately 60% of the copper on
the board is removed in the typical etching
process. As the copper content of the etchant
increases, the etchant cannot effectively
remove the copper from the board, and it is
considered spent. The copper-saturated, spent
etchant is stored in drums or a tank, and is
ultimately shipped off-site for reclamation.
Even in situations where the copper is recov-
ered and the etchant is regenerated by the
waste hauler, this waste stream may be an
environmental hazard. Transportation of the
spent etchant and its ultimate disposition may
Is Your Facility Shipping Revenue Off-site?
July 1995
-------
A Cooperative Project
between the
U.S. Environmental
Protection Agency
and PWB
Manufacturers
Nationwide
EPA744-F-95-005
FOR
THE
PRINTED WIRING BOARD CASE STUDY2
EPA
PRINTED WIRING BOARD
CASE STUDY 2
On-Site Etchant
Regeneration
In business today, being responsive to the
environment means learning new proce-
dures and using new tools to do the same
job with less environmental impact. Decisions
about the purchase of equipment and prod-
ucts depend not only on cost, availability, and
performance, but also on whether your envi-
ronmental goals can be met. The manufacture
of printed wiring boards (PWBs), the building
blocks of the electronics industry, requires
using substantial amounts of water and ener-
gy, and some hazardous chemicals that pose
potential environmental and health risks. To
facilitate the evaluation of alternative manu-
facturing technologies that reduce both envi-
ronmental risks and production costs, EPA has
entered into a partnership with the PWB
industry through its Design for the Environ-
ment (DfE) Program. One of the goals of this
cooperative effort (involving EPA, industry,
trade associations, and public interest groups),
is to generate and disseminate information on
viable pollution prevention alternatives so that
the industry can further explore cleaner man-
ufacturing methods.
This is the second in a series of DfE
case studies that illustrate the benefits of pollu-
tion prevention for PWB manufacturers. Specif-
ically, this case study focuses on the benefits
of etchant regeneration systems, and how they
can reduce the impact of etching processes on
the environment while reducing costs.
Why Etchant
Regeneration?
In the process of making PWBs using
the "subtractive" process, the circuit pattern is
created by chemically etching copper from the
unprotected (non-circuit) areas of the copper-
coated panel, leaving circuit traces protected
with photoresist. Etching can be accomplished
with acids or bases, depending on the etch
rate and the line width required. The ammoni-
acal etchants, either ammonium chloride or
ammonium sulfate, are most commonly used.
Cupric chloride is also used, even though it
often requires chlorine gas, a significant health
and environmental concern.
Approximately 60% of the copper on
the board is removed in the typical etching
process. As the copper content of the etchant
increases, the etchant cannot effectively
remove the copper from the board, and it is
considered spent. The copper-saturated, spent
etchant is stored in drums or a tank, and is
ultimately shipped off-site for reclamation.
Even in situations where the copper is recov-
ered and the etchant is regenerated by the
waste hauler, this waste stream may be an
environmental hazard. Transportation of the
spent etchant and its ultimate disposition may
Is Your Facility Shipping Revenue Off-site?
July 1995
-------
pose environmental risks and result in increased liability for
the PWB facility. In many plants, the spent etchant is the
largest waste stream generated, making it a prime pollution
prevention candidate. The costs of managing spent etchants
and the danger they pose to the environment can be reduced
dramatically with an on-site regeneration system.
On-site Etchant Regeneration Systems Offer
Opportunities for Pollution Prevention through:
• Eliminating off-site shipments of spent
etchant
• Reducing chemical purchases of etchant
• Recovering copper
• Reducing water use
The environmental and cost advantages of etchant
regeneration and copper recovery can include:
• reducing the danger of polluting the environment by elimi-
nating off-site shipments of spent etchant
• avoiding spills that can occur when transferring and trans-
porting dangerous materials
• eliminating your company's liability associated with the
off-site shipments of the spent etchant
• reducing or eliminating safety concerns associated with
drum handling and storage for spent and fresh etchant
• saving labor hours spent on manifesting and regulatory
reporting requirements associated with spent etchant (e.g., for
some facilities, eliminating spent etchant can put them under
the regulatory reporting threshold, or help them to maintain
Small Quantity Generator status).
•reducing chemical purchases for fresh etchant
•generating revenue from the sale of recovered copper
•reducing the amount of water used and discharged
Although the technology may not be suitable for all
operations, on-site etchant regeneration systems have suc-
cessfully prevented pollution both in very small, prototype
board shops, and in some of the highest volume PWB manu-
facturers in the country.
This case study provides an overview of the different types
of systems currently in use in the U.S. and is based on product
literature, and on interviews with both equipment manufactur-
ers and PWB manufacturers using the systems. The information
is offered only as an introduction and has not been independent-
ly validated by EPA. For more information on any of these
systems, contact the manufacturers at the numbers listed
throughout the text.
Ammoniacal Etchant
Regeneration
Alkaline etchants (ammonium chloride or ammonium
sulfate) are the most commonly used types of etchants in
PWB manufacturing. Without an etchant regeneration system,
an optimal copper concentration is maintained by replacing
spent etchant with fresh etch solution and shipping of the
spent etchant off-site.
MECER System,
manufactured by COGNIS, Inc.,
707-576-6225
System description:
This system regenerates ammonium chloride, recycles
rinse water, and recovers copper using a process of solvent
extraction and electrowinning. The regeneration and recovery
occurs in several stages: 1) a portion of the copper is
removed from the spent etchant so that it can be used for fur-
ther etching; 2) copper is removed from the rinse water so
that it can also be reused; 3) copper is re-extracted and trans-
ferred to the electrolyte; and 4) in the electrowinning unit,
copper is recovered from the now copper-enriched elec-
trolyte to produce high quality, saleable copper metal.
1
•Eliminates spent etchant generation.
• Replenisher consumption is reduced by about 90%. After
the copper is extracted, the alkaline etching solution is recy-
cled and the only replenisher needed is to compensate for
drag-out and evaporation losses.
•Copper is recovered from the spent etchant (where it is
typically at a concentration of 16 to 21 ounces/gallon) and
sold for approximately $1.00/lb (or about 90% of the COMEX
copper price).
•Water consumption is greatly reduced (users estimate a 50
to 80% reduction in etching rinse water) and the copper con-
centration in the discharged rinse water is less than 5 ppm.
Most of the copper content in the rinse water is recovered
with a portion of the water being reused as rinse water in the
etching machine. In addition to savings in water and sewer
costs, savings are also realized in waste water treatment
because fewer chemicals are needed for pH adjustment and
metals recovery.
• Copper concentration in the etching solution can be main-
tained through the recovery system, and a precise pH is main-
tained using ammonia gas injection.
Arailtihilily.
Units are sized based on the total throughput of the
etching line, best estimated by your current consumption rate
of replenisher. Ten different size systems are available
depending on the facility's annual replenisher volume, rang-
ing from 14,300 gal/year to 380,000 gal/year.
July 1995
-------
EFtt
Costs 'Sarings:
Savings associated with the installation of this system
include: savings associated with the elimination of off-site
shipments of spent etchant, raw materials savings associated
with a 90% reduction in replenisher purchased, revenue from
sale of recovered copper, and savings associated with
reduced water and sewer costs. Costs include the annual
costs of copper starter sheets, replenisher makeup, solvent
extractant, liquid ammonia, electricity, changes of anodes,
spare parts, and other chemicals, and a one-time capital
equipment cost. Users expect a payback of 2 years or less,
but it depends on the specific costs and operating conditions
of each facility. The manufacturer also offers the option to
rent the equipment.
Elo-Cbem Sys tern,
distributed by Atotech, 814-234-6543
System description:
Atotech supplies the Klo-chem Alkaline Regeneration
Module and Copper Recovery System which regenerates
ammonium sulfate and recovers copper in a closed-loop sys-
tem. Although using ammonium sulfate allows direct electrol-
ysis of the etchant, it also has a slower etch rate than
ammonium chloride. The Elo-chem system consists of two
separate regeneration circuits: an etchant recycling module
and a copper recovery module. Etchant is regenerated utiliz-
ing atmospheric oxygen and ammonia to restore the copper
in the spent etchant to the ionic form needed for etching. A
portion of the solution is guided to the electrolytic cell, where
copper is deposited on the cathodes. After electrolytic deposi-
tion of the copper is completed, the copper can be pulled off
of the cathodes as a copper sheet.
Features:
Both large and small facilities have installed the Elo-
chem system for etchant regeneration and recovery. The aver-
age copper recovery capacity of the system is 5.5 Ib/hour,
with a maximum hourly capacity of 6.6 Ib. One customer
who runs a prototype board shop (using fewer than 10,000
gallons of etchant/year), describes this as the "ideal" system
for their operation. They expect the system can eliminate the
time and resources associated with shipping spent etchant
off-site, reduce the space required for storage of fresh and
spent etchant, decrease chemical purchase costs, eliminate
safety issues associated with handling drums, and improve
etching process control. Ammonia gas, a proprietary rate
accelerator (added at 0.25 liter/plating hour), and small quan-
tities of ammonium sulfate crystals (from an industrial chemi-
cal supplier) are needed to operate the system; actual
quantities required depend on the carry-over losses. This sys-
tem does not recycle or remove copper from rinse water.
Arailtibility:
The system works with a wide range of production
capacities. The same equipment is used for all size facilities,
and multiple plating cells are added to accommodate facilities
with larger production capacities.
Cos l s/Sa i' ing s:
Savings associated with the installation of this system
include: annual savings associated with a 99% reduction in
off-site shipments of spent etchant, savings associated with
the elimination of replenisher purchases, and revenue from
the sale of recovered copper. Costs include the annual costs
of ammonia, electricity, spare parts, and other chemicals, and
a one-time capital equipment cost. The manufacturer esti-
mates a payback of 2.5 years or less, but this depends on the
specific costs and operating conditions of each facility.
Cupric Chloride Regeneration
Many PWB manufacturers use a cupric chloride etchant
to achieve fine line width etching, although it typically has a
slower etch rate than ammonium chloride. Without an etchant
regeneration system, manufacturers would typically purchase
bulk chemicals to blend etchant and spent etchant would be
shipped off-site. With etchant regeneration and recovery sys-
tems, saleable copper is recovered from the spent etchant and
off-site shipments of spent etchant are eliminated. The types
of regeneration equipment available include the FSL system,
which recovers copper and regenerates etchant; and the
Chemcut system, which regenerates etchant but does not
recover copper.
FSL System.
distributed by Finishing Services Limited, 214-259-3326
System description:
The FSL Electrolytic Regeneration system is a closed-
loop system that regenerates etchant and plates out the
copper.
Features:
• Spent etchant is eliminated when the system is operated
correctly within its maximum capacity according to the manu-
facturer. Customers have noted that they have reduced their
volume of spent etchant by 95%.
•The pure copper byproduct that is electroplated out of the
spent etchant solution is sold as scrap for about $0.75-
$1.00/pound (a very high purity, but powdered-form copper
is generated).
•The need for bulk chemical oxidizer is eliminated and the
volume of hydrochloric acid needed is reduced by about 70
to 80%.
•Better control of the etching process (through maintaining
constant copper concentration, HCl concentration, tempera-
ture and oxidation-reduction potential) can be obtained.
Availability:
The smallest FSL Regeneration system available is a
module that removes 2.2 pounds of copper per hour; by join-
ing these modules together, FSL can supply a system large
enough to accommodate hundreds of pounds of copper per
hour. As system capacity increases, however, so does the size
of the system.
July 1995
------- |