Analysis of a Silver Substrate, Gold-Silicon Preform, Die Attach System

Using silver substrates, a gold-silicon preform die attach system requires tighter process controls than the use of the more conventional gold substrates. This paper explains the mechanism for die attach failures and presents methods of avoidance. The primary observation is that silver raises the minimum melt temperature when it alloys with the preform. Cross sections of four types of samples were prepared at temperatures ranging from 400 - 480°C. These were analyzed by means of metallographic, scanning electron microscopy and energy dispersive xray techniques. A ternary phase system is proposed which explains the observed metallographic structures.