Mechanisms of Mo–Mn–Ti Metallizing and Cu Brazing in Metal-to-Ceramic Seals

Abstract

In recent years, with the increasing emphasis on reliability of metal-to-ceramic seals, greater attention is being paid to Mo–Mn–Ti metallizing and Cu brazing. In response to these recent trends, the bonding mechanisms of Mo–Mn–Ti metallizing and Cu brazing were studied by means of the seal strength test, the heat cycle test, optical and electron microscopic observations, and electron probe microanalysis. The results obtained are as follows: The bonding of the Mo–Mn–Ti metallizing can be considered to consist of three different mechanisms; the primary bonding due to the formation of the reaction product layer, the secondary bonding due to the migration of the glassy phase, and the tertiary bonding due to the sintering of the metallized layer itself with a reactive liquid. The complete bonding is accomplished by the tertiary bonding. Various theories proposed hitherto are thought to be an interpretation only for the primary or secondary bonding. Also, the Cu brazing contains a phenomenon associated inevitably with its high temperature processing. This is the reason for the rapid decrease in both seal strength and vacuum tightness in the Cu brazed metal-to-ceramic seals by the heat cycling.