Enabling Low-Temperature Reworkability for Anisotropic Conductive Adhesives

Reworkable anisotropic conductive adhesives (ACAs) are of interest when the material is used for assembling electronic modules with high value, such as in medical devices. Adhesive matrices comprising a blend of a thermosetting epoxy and a thermoplastic polymer are selected because it has shown potential to ensure good electrical and mechanical integrity whilst still allowing reworkability for ACA assemblies. Our previous work demonstrated the feasibility of using blends of an epoxy and a thermoplastic polysulfone as an adhesive matrix for the reworkable ACAs. The rework temperature, however, is relatively high (190°C) which causes disadvantages for the rework process and safety of sensitive electronic components nearby. ACA material with lower rework temperature is thus of interest. This paper presents the findings of favorable mixing ratio between an epoxy compatible with ACA applications and a thermoplastic polymer that offers good mechanical strength combined with reworkability at a temperature as low as 100°C. The results show that the adhesive blends with a high concentration of thermoplastic polymer (35–65 wt%) exhibit satisfactory die shear strength at temperatures relevant for production/storage (23°C) and operation of medical devices (50°C). Furthermore, successful rework at temperature as low as 100°C is confirmed for such adhesive blends.