Analysis of Degradation Effects for Different Epoxy-Based Molding Compounds (EMC) Under High Temperature Aging

Electronic devices are commonly encapsulated with epoxy-based molding compounds (EMC) to protect them for environmental influences. However, EMCs are susceptible to changes in material properties (e.g. due to oxidation or embrittlement) when exposed to high temperatures and harsh conditions. This can result in affected reliability of the electronic components caused by modified mechanical, thermal, or hydroscopic properties as shown in previous investigations on bulk material. In our study, local analysis by fluorescence microscopy and nanoindentation mapping of mechanical properties was combined to determine potential local degradation mechanisms. First, the aging process induced by temperature treatment was visualized through fluorescence optical microscopy, revealing the affected areas of the EMC. In a second step, the local mechanical material properties, such as indentation hardness and modulus, of the epoxy matrix and glass filler components were determined at several locations and different conditions of thermal treatment. These areas could be correlated to significant changes in local material properties. In total, two types of mold compounds were analyzed for a deeper understanding of the aging and degradation behavior after thermal exposure up to T=175°C for a maximum time of t=2000 hours and thermal cycle testing with 3000 cycles at T=-50 /+150°C. As a result, this paper offers a comparative analysis of different EMCs regarding their local thermal aging effects. The study provides insights into the evolution and spread of material degradation within EMCs which has significance for the selection of EMCs for electronic packaging. In summary, the local characterization complements already known effects on bulk samples for a comprehensive understanding of material degradation of EMCs.