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Electrode Composition

IP.com Disclosure Number: IPCOM000095405D
Original Publication Date: 1964-Jan-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

DePaolo, GJ: AUTHOR [+4]

Abstract

This electrode composition has low resistivity, good solderability and excellent adhesion to ceramic-like substrates.

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Electrode Composition

This electrode composition has low resistivity, good solderability and excellent adhesion to ceramic-like substrates.

A typical composition is prepared by mixing 20% by weight of bismuth oxide and 80% by weight of gold plated copper spheres finer than 400 mesh. The copper spheres are plated with gold in an immersion gold plating process. A paste is formed of 70% by weight of the powdered bismuth oxide and gold plated copper spheres and 30% by weight of an organic vehicle, i.e., B-terpineol and ethyl-cellulose. The paste is silk screened onto a ceramic or like substrate in any desired electrode configuration.

The screened substrate is air dried for twenty minutes at room temperature. The paste is fused by firing the substrate in a furnace at 800 degrees C for approximately fifteen minutes. The bismuth oxide provides excellent adhesion of the fused paste to the ceramic substrate. During firing, there is mutual diffusion of the gold and copper resulting in the fused conductor having a gold outer layer which graduates to a copper core. The copper has very little oxidation and thus relatively low resistivity by suitably controlling the firing conditions.

The solidified conductors may be dip-soldered with excellent results. Gold is very soluble in tin-lead solders. During the soldering operation, the gold outer layer goes into the solder solution until a composition is reached where the solder bonds to the copper without further solution. Some gol...