Characterization of thermally conductive underfill materials for high performance flip-chip applications

In this paper, characterization of 3 types of underfill for high performance applications has been presented. Characterizations of underfill materials such as adhesion testing, contact angle measurement on different surfaces, filler size distribution were conducted to understand the underfill materials. The adhesion test results revealed that failure is mainly mixed mode, which is the failure between bulk underfill failure and interfacial failure. The thermal conductive underfill has a wider range of filler sizes and has the most hydrophilic behavior. From the glass chip flow test, the flow behavior of the underfill could be observed, with the most thermal conductive underfill having the slowest flow. Process optimization for thermal chip and daisy chain chip for void free underfill was also carried out based on dispensing temperature and patterns.