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Weld/ Braze Circuit Path Encapsulation and Corrosion/ Migration Barrier

IP.com Disclosure Number: IPCOM000050634D
Original Publication Date: 1982-Nov-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Phelps, DW: AUTHOR [+3]

Abstract

In certain types of ceramic substrates for mounting integrated circuit chips, it is necessary to join copper pins to refractory metal pads on the substrate. One desirable technique is by the use of copper/silver brazing alloy to form the connection. However, silver and silver alloys are very prone to corrosion and migration if exposed to the atmosphere.

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Weld/ Braze Circuit Path Encapsulation and Corrosion/ Migration Barrier

In certain types of ceramic substrates for mounting integrated circuit chips, it is necessary to join copper pins to refractory metal pads on the substrate. One desirable technique is by the use of copper/silver brazing alloy to form the connection. However, silver and silver alloys are very prone to corrosion and migration if exposed to the atmosphere.

The present technique allows the use of a desirable copper/silver alloy for brazing but minimizes or eliminates the corrosion and migration problems normally associated therewith.

Fig. 1 is a sectional view of a copper pin ready to be braze/welded to a metallized substrate according to this technique. In this technique a ceramic substrate 10 is provided having a plurality of tungsten- or molybdenum-filled vias, one of which is shown at 12. The vias terminate at enlarged head portions 14 at the surface of the ceramic.

A pad of copper/silver alloy 16 is applied to the head portion 14. Disposed over the layer of alloy 16 are successive layers of chromium 18 and copper 20 which are formed thereon as a protective barrier.

Over the layer 20 of copper are successive layers of chromium 22 and copper 24 which are used in a conventional manner overlying the entire substrate to allow electrical contact with all of the vias simultaneously. A copper alloy pin 26 is shown in position to be braze/welded to the via.

In performing the brazing/welding, a percus...