Silver‐glass Die Attachment—Adhesion Mechanisms with Gold and Chromium/Gold Backed Die

Silver‐glass die attach materials represent a significant advance in silicon packaging technology and are expected to displace gold‐silicon eutectic bonding as the preferred method of die attachment for high reliability applications. In this paper the rle of the glass in the adhesion mechanism of silver‐glass to gold and chromium/gold backed die has been determined using thermal analysis and X‐ray diffraction in addition to scanning electron microscopy and electron probe microanalysis of the sintered film. An adhesion mechanism is proposed in which the glass of the silver‐glass system migrates to the die interface during the firing cycle and chemically bonds to the silicon which is present at the surface of the gold‐silicon eutectic. Adhesion between the die back and the silver of the die attach material is by means of a simple mechanical bond between ‘fingers’ of glass and the sintered silver matrix. Thermodynamic and kinetic considerations suggest that insufficient silicon dioxide may be formed using chromium/gold backed die for acceptable adhesion. Processing changes are proposed which resolve this adhesion problem.