Think & Tinker, Ltd.
P.O. Box 1606, Palmer Lake, CO 80133
Tel: (719) 488-9640, Fax: (866) 453-8473
Sales: Sales@thinktink.com, Support: Support@thinktink.com
||Carbon Treating Acid
Copper Plating Baths
Periodically, it becomes necessary to remove organic contaminants from virtually every
commercial electroplating bath. The sources of these "pollutants" can include:
In the case of a relatively small plating bath (100 liters or less), removing these
contaminants is fairly straightforward. The easiest systems to purify are those that are
equipped with a recirculation pump (min. 30 lpm into 1 meter of head) and an in-line
filter housing that will accommodate commercially available activated carbon packs, . Such
an in-line filter is assumed in the following.
- leaching from tanks, filters, and tank plumbing
- leaching from dry-film and liquid plating resists, and
- poorly cleaned copperclad substrate.
- 19% to 50% hydrogen peroxide ( H2O2)
- activated carbon pack
- 5 micron polypropylene filter cartridge (leached)
- Remove all racks and anode banks from the plating bath.
- Thoroughly clean the surfaces of the anodes with a wire brush and set aside completely
immersed in a 10% solution of sulfuric acid.
- Put a 5 micron pre-leached wound polypropylene filter cartridge into the in-line
filter housing. If a pre-leached cartridge is not available. soak a food grade
polypropylene filter in a 10% solution of sulfuric acid for 5 to 8 hours before inserting
into the housing.
- To the bath, add 8 mL of 19% H2O2 (3 mL of 50% H2O2) for
every liter of electrolyte, and allow to circulate overnight (min. 8 hours). Circulating
the bath overnight will consume virtually all of the peroxide and prevent a harmful
interaction with the acitvated carbon pack.
- The next morning, replace the 5 micron filter element with an activated carbon pack
(same size and form factor as the wound filter) and circultate for another 8 hours.
- Run a Hull Cell test to make certain that all organics have been removed. The test plate
will be completely matte from the high current density area nearest the anode to the low
current density area. If a bright plated stripe is seen anywhere on the plate, organic
components remain and must be removed by adding more H2O2 (about 50% of the original addition) and circulating for
another 4 hours. Carbon treat for another 4 hours.
- Remove the filter pack (it can be reused at least one more time) and insert a 1 to 5
micron pre-leached wound polypropylene filter cartridge into the housing.
- Analyze the copper, sulfuric acid, and chloride ion content of the electrolyte and make
additions as necessary. Allow the bath to circulate at least 10 minutes after any addition
- Return the anodes to the bath and electrolyze by dummy plating at 5 ASF for 2 hours, at
12 ASF for 2 hours and finally at your normal operating ASF (typically 20 ASF) for 2
- Using a Hull Cell, determine the amount of carrier and additive needed to bring the
electrolyte up to specifications. Add the indicated volumes to the tank and allow to
circulate for at least 10 minutes.
- Run another Hull cell test and make additions as necessary.
- Record the additions in your equipment log to insure that a comprehensive record is kept
of everything that is added to the plating tank.
- Your plater is now ready to put back into service.
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