Session: 10-01 Interactive Presentations

Paper Number: 99237

99237 - Evolution of Interfacial Mechanics Due to Isothermal Exposure at the Substrate-Potting Compound Interfaces Under Monotonic and Fatigue Loading 

Electronics in harsh environment are frequently subjected to significant shock loads of up to 50,000Gs, dampness, and high temperatures. PCB potting is frequently used to defend against high mechanical shock loads, vibration loads, and thermo-mechanical stresses. Under dynamic stress loading, the cured potting materials are prone to interfacial delamination, which might lead to failures in the package interconnects. The literature on potting compounds focuses mostly on end-use dependability or the investigation of bulk material qualities. In this poster, a four-point bend specimen was utilized to investigate the Substrate/Epoxy system and analyze the fracture characteristics of the bi-material strips in order to determine the processes of interface delamination. The bi-material strips of Substrate/Epoxy were kept at elevated temperatures of 100°C for aging and then the sample specimens were subjected to quasi-static monotonic and cyclic loading to observe the critical stress intensity factors, fatigue slope parameters, and degradation interfaces bond adhesion of bi-material strips.  Potting compound, Epoxy-A is a stiff material with 12,260 psi of tensile strength before failure. The monotonic critical stress intensity factors and fatigue crack growth of the interfacial delamination for the epoxy systems were characterized using strain energy release rate. The mode-I stress intensity factor, mode-II stress intensity factors, and slope of degradation parameter were extracted to showcase the evolution of failure at the interface. These factors were used in a cohesive zone model to validate the results and developed the evolution damage properties of potting compounds. A prediction of several cycles to failure and the performance of different epoxy system resistance was evaluated during cyclic bending loading using the Paris Power Law.

Keywords: Paris Power-law, Four Point Loading, Stress Intensity Factor, number of cycles to failure, Fatigue constants.

Presenting Author: Padmanava Choudhury Auburn University