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Use of Ternary and Quaternary Pastes in Chip Joining

IP.com Disclosure Number: IPCOM000089758D
Original Publication Date: 1977-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

DiGiacomo, G: AUTHOR [+2]

Abstract

In a chip joining process, a metallic paste may be placed at the top of a via hole that is filled with molybdenum. The assembly is then fired. Ternary and quaternary pastes may be used to advantage.

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Use of Ternary and Quaternary Pastes in Chip Joining

In a chip joining process, a metallic paste may be placed at the top of a via hole that is filled with molybdenum. The assembly is then fired. Ternary and quaternary pastes may be used to advantage.

A ternary paste that may be used has a composition of Ag-20 Au-20 Pd. The ternary paste may be screened in the vias of the top green sheet before substrate firing at about 1600 Degrees C. During substrate firing, the ternary alloy melts and, to same extent, penetrates the underlying porous Mo paste, thus resulting in a loss of height. If the loss is so great that chip joining cannot be performed directly on it, an additional ternary paste screening will be required after the substrate firing. If required, the second screening will be fired at 680 Degrees to 800 Degrees C. At this stage the paste is ready for chip joining with Pb-In, Pb-Sn, or Pb-Sn-In solders, which are all suitable and compatible with the ternary system. In all cases, the joint will be strong and ductile.

The ternary paste can also be screened directly on the molybdenum paste after substrate firing at about 1600 Degrees C, as Mo has about 30% solubility in Pd and also significant solubility in Ag. Addition of 20 to 40% Cr or Pt to the ternary paste, by suitable mixing with an adequate binder, would improve bonding with the Mo paste, as both Cr and Pt form a series of solid solutions with Mo.

Another alternative is "pretinning" the ternary after sub...