Think & Tinker, Ltd.
P.O. Box 1606, Palmer Lake, CO 80133
Tel: (719) 488-9640, Fax: (866) 453-8473
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Tin/Lead Electroplating Module
-Operation/Panel vs. Pattern II
Pattern plating copperclad substrates proceeds as follows:
The following process assumes that you are pattern plating both the bulk copper and tin/lead layers.
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 and plating current from the circuit pattern.
- Calculate the total plating time
A tin/lead (solder) plating bath based on the SolderPlate 60/40 additive system deposits 40 microinches (40e-6 in., 1 micron) of matte solder in 1 minute at 20 ASF (Amps per Square Foot). For effective resistance to peroxy-sulfuric etchants, 0.0002" to 0.0003" ( approx. 6 to 8 microns) of tin/lead should be deposited.
Example: To plate up 0.00025" (2.5 "tenths" or 6.4 microns) at 20 ASF, the total plating time (T) will be:
2.5x10-4 in./ (40x10-6 in./min.) = 6.25 min. = TL
- Calculate the required plating current
Example: If you are plating a double-sided board with a total circuit area equal to 25 sq.in. (robber bars included) you will need
[25/144] x 20 = 3.5 Amps = C
(during pattern plating, the total current is the same for both acid copper and tin/lead deposition)
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Updated 2/13/2014 8:36:58 AM