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Producing Directly Solderable, Brazeable, and Wire Bondable Surfaces on Ceramic Substrates

IP.com Disclosure Number: IPCOM000084222D
Original Publication Date: 1975-Oct-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Gniewek, JJ: AUTHOR [+4]

Abstract

It is known in top and bottom side metallurgy for semiconductor package substrates, to use an electroless nickel to plate the Mo or Mo-Ru alloy prior to gold plating. However, the nickel is highly susceptible to corrosion in a hostile atmosphere, causing module fails.

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Producing Directly Solderable, Brazeable, and Wire Bondable Surfaces on Ceramic Substrates

It is known in top and bottom side metallurgy for semiconductor package substrates, to use an electroless nickel to plate the Mo or Mo-Ru alloy prior to gold plating. However, the nickel is highly susceptible to corrosion in a hostile atmosphere, causing module fails.

One way to overcome the nickel corrosion problem is to eliminate the nickel and gold plating process, thus permitting direct soldering or brazing to the alloy metallurgy.

In this method, a two-component alloy metallurgy system is used on the top and/or bottom surfaces of the module substrate to form the contact and pin joining surfaces. One component of the system is a refractory metal, such as Mo, W and Re, whose oxide is volatile but whose solder wettability is poor. The second component is a noble metal, such as Pt, Pd, Rh and Au, with desirable wetting properties.

When the alloy composition on the module is fired in an oxidizing atmosphere, volatile oxides of the refractory metal are formed and leave the alloy. The wettable noble metal is surface enriched, which is wetted by Pb-In solder in the same manner as Pt surfaces.

A preferred embodiment of this method is a 55 Pt:45 Mo alloy deposited and subsequently oxidized in a 0.5% oxygen in nitrogen at 1000 degrees C for a total time of six minutes. This results in excellent braze wetting and solder wetting.

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