US 5,514,838 A · Circuit structure with non-migrating silver contacts

Abstract

An integrated circuit assembly that prevents silver migration by providing conductive rims around oxidizable silver contacts that contact a substrate. Typically the silver contacts are supported by respective metal pads on the substrate with a contact potential existing at each contact-pad junction. In many applications an electrical circuit transmits electrical signals via the contacts to produce potential differences between the contacts and create electrical fields at their surfaces. The conductive rims have a work function that is sufficiently small to reduce the electric fields and contact potentials so as to inhibit the ionization of the oxidized contacts' surfaces and prevent silver migration across the metal pads and the substrate.

Claims15

Dependent claims

A non-migrating silver contact structure, comprising:

a substrate;
a plurality of silver contacts that are spaced apart on said substrate and oxidize when exposed to the atmosphere;
a circuit for transmitting signals by means of said contacts wherein said signals produce difference potentials between said contacts and create electric fields at the contacts' surfaces of sufficient strength to ionize the oxidized contacts;
and
a plurality of conductive rims in contact with said substrate and around the periphery of said respective contacts wherein said conductive rims are formed of a material other than silver, whereby the silver in said contacts is prevented from migrating.

2 more elements

Dependencies are inferred from the claim text.

Circuit structure with non-migrating silver contacts

Life of this patent

Circuit structure with non-migrating silver contacts

Life of this patent

Abstract

Claims15