Think & Tinker Instrument Prototyping

Think & Tinker, Ltd.
P.O. Box 1606, Palmer Lake, CO 80133
Tel: (719) 488-9640, Fax: (866) 453-8473
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Acid-Copper Electroplating Module Model 1000 Manual
Electroplating - Pattern plating I

Pattern plating:

Calculate the total plating time.
An acid copper plating bath based on the PCM+ additive system deposits 0.0011" (1.10 mils, 28 microns, 0.81 oz) of high ductility copper in 1 hour at 20 ASF(Amps per Square Foot). Plating up "one ounce" of copper (i.e. plating 1 oz. of copper onto 1 square foot of board) is equivalent to plating a thickness of 0.0013" (1.3 mils or 34 microns).

Example: If you are starting with "half ounce" copperclad and want to plate up to a finished thickness of "one ounce", you will need to add .65 mils (0.00065"). The total plating time at 20 ASF will be:

[0.65 mils / (1.1 mils/hr.)] x 60 min./hr. = 35.5 minutes = T_C
Calculate the required plating current.
Convert the total area of the pattern being plated into square feet (remember both sides!) and multiply the result by 20. Some CAM packages output the area of the pattern as a percentage of the total board area (area enclosed by the board outline defined in the ECAD or CAM software), while others can calculate the total pattern area in any unit specified by the user. To normalize the plating field, it is often beneficial to add an exposed ¾" boundary around the board to increase to total plating area and suppress the formation of high potential areas at the edges of the pattern. These are referred to as "robber bars" or "thieving bars" since they "steal" some of the electric field from the circuit pattern.

Example: If you are plating a double-sided board with a total circuit area equal to 25 sqin. (robber bars included) you will need:

[25/144] x 20 = 3.5 Amps = C
Carefully inspect the substrate for deep scratches and nicks that might impair the quality of the finished circuit.
Format the drilling stack (assemble with entry foil and backing material) to minimize burr formation during drilling.
Drill the through-holes and mounting holes, and mill/router any slot or cavity that is to be plated.
Activate the hole-walls using conductive ink.
While the ink is curing, take a few minutes to analyze the electrolyte. If you have a hull cell, this is a good time to run a test to insure that the organic components of the bath (which are very difficult to test directly) are in balance and present in the proper concentrations.
After activation and curing, both sides of the substrate should be thoroughly cleaned to remove any trace of conductive ink from both surfaces. Any ink that is not removed will almost certainly show up in the worst possible place so take your time cleaning the board and make a good job of it!
An abrasive pad (e.g. Scotchbrite® pad) can be used to remove ink that proves to be too stubborn for conventional cleaning, but be careful. You must be certain that you do not break the electrical contact between the conductive ink on the inside of the holes and the copper foil on the surface of the board or the holes in question will not plate properly.
Rinse the board thoroughly in deionized water before proceeding
Dip the board into a 10% solution of sulfuric acid (if available) to minimize the introduction of contaminants into the copper plating tank.

Established 1990

On the web since 1994