Filler induced metal crush failure mechanism in plastic encapsulated devices

Filler particles from the mold compound can give rise to local stress on the integrated circuit die surface, cracking the passivation, resulting in a metal to polysilicon short or a metal to metal short. The metal damage under the passivation is termed as metal crush. This study shows that metal crush takes place only in plastic encapsulated devices and is predominant in plastic packages with silicone gel die overcoat. Experiments and finite element simulations have shown that the use of ultra low stress molding compound without silicone gel die overcoat eliminates metal crush failures. This study also presents the minimum silicone gel die overcoat thickness that prevents metal crush failures in plastic encapsulated devices with low stress molding compound and silicone gel die overcoat