Effect of Temperature and Humidity Conditioning on EMC-to-Substrate Interfacial Delamination Subjected to Monotonic and Fatigue Loading

Epoxy molding compounds (EMCs) are used in electronic packaging to protect semiconductor chips and other internal components against mechanical and chemical stress, as well as heat and moisture. However, challenges arise from material mismatch and stress concentrations caused by metal traces, impacting the interface between the Epoxy mold compounds (EMC) and the substrate solder mask, leading to shear stresses. Over the operational life of semiconductor packages, these shear stresses may result in progressive delamination at the interface. Consequently, significant attention has been directed toward studies on adhesion between EMC and different packaging materials. The research objectives of the study include the investigation of the effect of hygrothermal exposure on the EMC- substrate interface, weight gain measurement of bi-material samples after hygrothermal exposure, investigation of the effect of thermal cycling on the EMC-Substrate Interface, and study of the fracture toughness values, the amplitude of the stress intensity factor for both hygrothermal and thermal cycling conditions. The bi-material samples have been fabricated and stored in a Hygrothermal test chamber for moisture absorption at two conditions - 60°C/60% RH and 85°C/85% RH. In addition, a separate batch of samples has been kept in a thermal cycling chamber with a profile ranging from -40°C to 125°C for 50, 100, 200, 400, and 1000 automotive-grade thermal cycles. Both Monotonic and Fatigue testing are conducted on all bi-material samples to measure the mode-1 and mode-2 critical stress intensity factors. Moisture diffusivity, activation energy, and acceleration factors are investigated for hygrothermal exposure.