Degradation mechanisms in electronic mold compounds subjected to high temperature in neighborhood of 200°C

Plastic encapsulated microelectronics (PEMs) has found wide spread applications in automotive environments for varied roles. Transition to hybrid electric vehicles and fully electric vehicles has increased the trend towards greater integration of electronics in automotive under hood environments. Electronics in such applications may be mounted directly on engine and on transmission. Electronics under hood may be subjected to temperatures in neighborhood of 200°C. Commercially available PEMs are able to operate in the neighborhood of 175°C. However, sustained operation at temperatures of 200°C or higher is beyond the state of art. Materials and processing techniques needed for sustained high temperature operation for 10 years and 100,000 miles of vehicle operation are yet unknown. There is need for studies for understanding the failure mechanisms of PEMs at sustained high temperature. In this paper, new approach is discussed to study physical and chemical stability of molding compound when it is subjected to very high temperature for prolonged duration. Four mold compound candidates were selected for test purpose. They were subjected to thermal aging at 200°C and 250°C, for 5000 hours. For degradation study, bulk mold compound specimens as well as 20 pin SOIC devices, encapsulated with MC candidates were used. Test vehicle was bonded with gold wires, and Pd coated Al pad. For bulk mold compound samples, weight loss test, DMA, FTIR, XPS tests were performed at fixed time intervals. To study integrity of SOIC devices, resistance spectroscopy, x-ray inspection and current leakage tests were selected. Another set was subjected to 120 hours of aging at 130°C/100%RH condition to check leakage current. Performance of MC candidates at high temperature was evaluated using all these tests. Sensitivity of each test towards detecting degradation of EMC´s is also discussed and most effective tests are suggested.