Multichip package delamination and die fracture analysis

Multichip mechatronic power packages have been developed in Motorola for automotive applications. Copper heat sink based metal substrates were used to improve thermal and electrical performance. In the early stage of development, mold delamination and die cracking have been observed after assembly. With some mold compound materials, die backside have large delaminated areas, while with other mold compound, delamination stops early but die cracks. Finite element analysis, incorporated with interface fracture mechanics method, has been conducted to understand these phenomena. Impact of mold material properties and package geometry on post-assembly delamination has been evaluated. Good agreements have been obtained between experimental data and the simulation results. The phenomenon of crack branching into the die was also studied. Finite element simulation can be used to predict whether and when the crack at the interface will turn and crack the die. With a thorough understanding of the failure mechanism, both mold delamination and die cracks have been eliminated in the final package development.