Boundary Element Heat Conduction and Thermoelastic Analyses of Interface Crack in LSI Package in Consideration of Contact Between Crack Surfaces.

The interface crack initiated between the die pad (lead frame) and the resin encapsulant in the LSI package sometimes leads to package cracking and becomes critical to package fracture design. On the other hand, the property of thermal diffusion has become a main concern for recent package design of power semiconductor devices. To simulate these problems, we developed the boundary element heat conduction and thermoelastic analysis code, which can deal with thermoelastic contact of the interface crack. The stress intensity factors for an interface crack are calculated by the extrapolation method which is proposed by one of the authors. Using the above technique, the interface crack initiated in a plastic-molded LSI package is analyzed under conditions of uniform temperature loading and heat generation in the Si-chip. Calculated interfacial stress intensity factor Ki shows a decreasing trend against the interface crack length in all the above cases. Taking into account the contact of the crack surface, the results of the disturbance in temperature distribution are outstanding. However, the normalized stress intensity factor Ki/|ΔTmax| Shows almost identical behavior against with the crack length and is less dependent on the contact region length and the amount of heat generation.