The effect of stress intensity on package cracking in lead-on-chip (LOC) packages

The effect of stress intensity factors on package cracking failure was studied based on fracture mechanics. The mechanical stress has made the stability of novel lead-on-chip (LOC) packaging technologies a grave concern. The dominant issue is device failure related to package cracking caused by a severe thermal stress concentration due to mismatch of dissimilar materials. The stress singularity appears at an interfacial edge and also the tip of interfacial delamination. To investigate package cracking, the stress singularity fields and the stress intensity factors at the interfacial edge and the tip of delamination were analyzed and the primary factors affecting the criterion of package cracking were subsequently defined. The criterion obtained from the experiment and the simulated results was verified by experiments on different types of the epoxy molding compounds. The results of these characterizations and an explanation of the primary factors affecting package cracking are presented in this paper.