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Selective Polymer Coating of Dissimilar Metals

IP.com Disclosure Number: IPCOM000074117D
Original Publication Date: 1971-Mar-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Pallady, PH: AUTHOR [+2]

Abstract

This is a process for coating a protective polymer on corrosive metal by an electrophoretic process by utilizing the electromotive force generated at the junction of dissimilar metals. Most systems used in the manufacture of printed circuit cards, boards or flexible laminates require a commoning bus bar to supply the required voltage for electroplating the contacts. This commoning bar is usually built into the circuit and sheared away after the plating process has been completed. The sheared edge which is devoid of plating and open to attack by corrosive agents. A solution to this problem requires the application of a conformal protective coating to the metal surfaces remaining after the shearing operation. Dip coating processes are inadequate to provide suitable protective coating at the sharp corners.

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Selective Polymer Coating of Dissimilar Metals

This is a process for coating a protective polymer on corrosive metal by an electrophoretic process by utilizing the electromotive force generated at the junction of dissimilar metals. Most systems used in the manufacture of printed circuit cards, boards or flexible laminates require a commoning bus bar to supply the required voltage for electroplating the contacts. This commoning bar is usually built into the circuit and sheared away after the plating process has been completed. The sheared edge which is devoid of plating and open to attack by corrosive agents. A solution to this problem requires the application of a conformal protective coating to the metal surfaces remaining after the shearing operation. Dip coating processes are inadequate to provide suitable protective coating at the sharp corners.

This process takes advantage of differences in potential that result when two dissimilar metals are in contact with each other. If the potential is sufficient, the more positive metal will be coated electrophoretically. Consequently, an array of springs or contact edges may be selectively coated by dipping them in an electrophoretic solution.

Tests indicate that a system utilizing a polyvinylidene chloride-epoxy ester in an approximate 6-to-4 ratio has proven satisfactory. The immersion time required is approximately 2 hours.

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