Electronics used in automotive underhood applications are subjected to extremely high operating temperatures ranging from 125 to 150°C for up to 10 years or longer over the vehicle’s use-life. Semiconductors in area-array packaging on laminate substrates are encapsulated in electronic mold compounds in microelectronic assemblies to meet unique functional needs. The robustness of the EMC-Substrate interface may also be influenced by the thermal mismatch stresses owing to the differences in the coefficients of thermal expansion between the glass-impregnated epoxy substrate and the silica-filled epoxy. This paper investigates the interface fracture toughness in bimaterial pre-cracked specimens made of PBGAs during thermal cycling exposure. Two EMC materials are subjected to 1000 automotive-grade thermal cycles. The samples are subjected to thermal cycling from −40°C to +125°C. Bi-material EMC-Substrate beam samples are created by polishing the solder balls from PBGA packages. Fracture toughness is measured under exposure to automotive-grade thermal cycling. Interfacial crack initiation, propagation, and failure mechanisms are investigated.

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