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Substrate Solderability Enhancement

IP.com Disclosure Number: IPCOM000084412D
Original Publication Date: 1975-Nov-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Ward, WC: AUTHOR

Abstract

Described is a solder which is particularly adapted for tinning nickel or nickel-plated materials and which has a very low-melt temperature so that excess material can be readily removed.

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Substrate Solderability Enhancement

Described is a solder which is particularly adapted for tinning nickel or nickel- plated materials and which has a very low-melt temperature so that excess material can be readily removed.

A solder alloy combined of tin, lead, indium and bismuth in eutectic composition has a melting point of 58 Degrees C. This solder is highly reactive with nickel and nickel-plated surfaces, such that the nickel oxide coating thereon will be dissolved so that solder will bond to it.

The indium serves, as a flux, to clean the nickel oxide off the surface to permit the tin to bond thereto, while the lead and the bismuth act as carriers for the more reactive materials; and also serve to lower the solder melt point. Thus, the alloying can be accomplished at very low temperatures, which would not be detrimental to ceramic or organic resist coatings applied to such materials, especially in semiconductor manufacturing processing.

Furthermore, because of the low-melt temperature of the solder, if there is an excess of solder on the nickel surfaces it can be readily removed, leaving only a clean tinned surface by washing off the excess solder with very hot water, steam, hot gas, or a hot organic mix; leaving a thin coating of tin and indium alloyed with the nickel in a continuous and nonporous layer.

Because only a thin residual layer of solder will remain on the nickel surface, sufficient volume to significantly alter final desired solder composition i...