Material characterization of substrates for power modules

Lifetime predictions of mounted components and solder joints are established. Usually the effect of solder degeneration is described. However, in power modules solder junctions are not the only locations where damage occurs. In particular, ceramic substrates can also develop fractures and connections to heat sinks can be destroyed. In an attempt to consider this effect for lifetime predictions on complete power modules, it is necessary to characterize the strength of and loads on these substrates. In this article, methods are introduced regarding how these characteristics can be measured. The examined system is a direct copper bonding (DCB) substrate. For other power module substrates, e.g. active metal brazed substrates (AMB), characterization methods are similar. In general, it is introduced how a thin ceramic sheet with modified surfaces can be characterized in order to determine its state of stress and failure criteria.