Tin whisker-free printed circuit board
AssigneeAtotech Deutschland GmbH
InventorsGeorge S. Bokisa, Craig V. Bishop, John R. Kochilla
Life of this patent
Estimating the term…
Abstract
A printed circuit board including electrical circuitry formed on an outer surface of the printed circuit board, the circuitry comprising copper or a copper alloy; a final finish on the circuitry, the final finish including a coating of tin on the copper or copper alloy circuitry; and an alloy cap layer on the tin coating, the alloy cap layer comprising at least two immersion-platable metals. The immersion platable metals in the alloy cap layer may be at least two metals selected from tin, silver, bismuth, copper, nickel, lead, zinc, indium, palladium, platinum, gold, cadmium, ruthenium and cobalt. The circuitry remains whisker free and solderable.
Claims29
A printed circuit board comprising
- electrical circuitry formed on an outer surface of the printed circuit board, the circuitry comprising copper or a copper alloy;
- a final finish on the circuitry, the final finish comprising
- a coating of immersion-plated tin on the copper or copper alloy circuitry;
- and
- an alloy cap layer on the tin coating, the alloy cap layer comprising at least two immersion-plated metals.
A printed circuit board comprising
- electrical circuitry formed on an outer surface of the printed circuit board, the circuitry comprising copper or a copper alloy;
- a final finish on the circuitry, the final finish comprising
- a coating of immersion-plated tin on the copper or copper alloy circuitry;
- and
- an alloy cap layer on the tin coating, the alloy cap layer comprising tin and at least one immersion-plated metal other than tin.
A printed circuit board comprising
- electrical circuitry formed on an outer surface of the printed circuit board, the circuitry comprising copper or a copper alloy;
- a final finish on the circuitry, the final finish comprising
- a coating of tin on the copper or copper alloy circuitry;
- and
- an alloy cap layer on the tin coating,
- wherein the final finish is formed by a process comprising the steps of:
- (A) preparing an immersion tin plating solution;
- (B) applying the immersion tin plating solution to the circuitry to form the coating of tin;
- (C) preparing an immersion alloy plating solution containing at least two immersion-platable metals;
- (D) applying the immersion alloy plating solution to the circuitry to form the alloy cap layer on the coating of tin.
Dependencies are inferred from the claim text.