Residual stress and thermal properties of rubber-modified epoxy systems for semiconductor package

The thermal and mechanical breakage of epoxy coating due to easy cracking, poor toughness, and large residual stress, occurring during curing and thermal aging process, is the key factor responsible for damage of silicon device on semiconductor elements. In this study, modified epoxy resins containing an imide ring and polybutadiene rubber-modified epoxy resin used as the toughening agents were prepared to investigate the residual stress generated during the curing and thermal aging process. The curing process and the thermal properties of the modified epoxy systems were assessed by differential scanning calorimetry and rotational rheometry, dynamic thermomechanical analysis, thermomechanical analysis, and thermogravimetric analysis. A thin film stress analyzer was used to analyze the changes in thermal stress of the modified epoxy systems during curing and cyclic stress and compared with the data from theoretical calculation. The results show that, with the increase in content of the toughening agent, the toughness of the modified epoxy systems was significantly improved, and the curing and thermal cycle stresses could be simultaneously reduced. Besides, we also envision the extension of the comprehensive evaluation method for residual stress described in this study to enable the modification of epoxy coatings prepared using a toughening agent, in the near future.