Thermomechanical failures in silicon electronic devices

In this paper we present the results related to thermomechanical failures (TMF) in silicon integrated circuits assembled in plastic packages. Damage to silicon was believed to be caused by the thermal mismatch stress due to large difference in coefficients of thermal expansion between silicon die and plastic assembly package. The damage was primarily concentrated at the comer of the unit and was considered as a high risk compromising reliability. In order to address the TMF damage to silicon, different structures such as metal locking structures, guard ring modification, slotting assembly fiducials and elimination of passivation at the scribe street were studied Silicon incorporating the structures was assembled in plastic packages and reliability tested. All the units were electrical tested. The results showed that the scribe street passivation and fab process alignment marks play a key role during assembly saw process and related TMF performance. Visual inspections were performed to understand the effect of nitride passivation thickness, package stiffness, and thermal cycling stresses on TMF damage induced on Si devices assembled in Organic Land Grid Array (OLGA) packages.