Interfacial Fracture Toughness of EMC/Substrate Interface Under Mode–I Dynamic Loading with Long-Term High Temperature Aging

FCBGAs are widely used in automotive electronics to enable several advanced drive and assist functions. Delamination at epoxy molding compound (EMC) and substrate interface has been one of the important concerns in packages. The plastic integrated circuit packages can fail due to delamination at the interfaces of the different materials. The integrity of the interface is one of the major concerns for reliability. Though many interfacial layers in a package have been studied, EMC/Substrate interfaces and their failure modes have not been widely studied yet. The components are typically subjected to very high thermomechanical loads during operation. The underhood environments can easily expose the components to extreme temperatures in the range of 125°C-200°C. Delamination at the EMC/Substrate interfaces is accelerated with high-temperature long-term exposure. The properties of the interface change with high-temperature exposure over a period. Interfacial crack propagates along the interface and finally resulting extending into the solder-interconnect to cause the failure of the system. Delamination at the interface directly depends on the fracture resistance at the EMC/Substrate interface. Interfacial properties at EMC/Substrate interfaces for under extreme thermal and bending loads in underhood electronics have not been studied widely. Two EMC materials are examined in this study. Bimaterial beam specimens of EMC/Substrate are created. The samples are subjected to long-term isothermal aging at 100°C for 30 days, 60 days, 90 days, and 120 days. The samples are tested under pure mode I, four-point bend dynamic loading. The interfacial crack initiation, propagation, and failure modes are recorded. The Strain-energy release rate and fracture toughness for the interfaces are calculated. The change in interface properties is examined with respect to the number of days of aging.