Solder Dewetting and Reliability Challenges in Microbumps Due to NCF Entrapment

The reliability of solder joints in Cu pillar microbumps is critical for advanced packaging technologies such as 2.5D and 3D integration. As thermocompression (TC) bonding with non-conductive film (NCF) becomes widely adopted, solder dewetting caused by NCF entrapment has emerged as one of major reliability concerns. In this study, we fabricated test vehicles with controlled NCF thickness and viscosity to intentionally induce solder dewetting. These test vehicles underwent multiple reflow cycles or high-temperature storage (HTS) to examine the evolution of dewetting behavior and assess the impact of thermal budget on solder wettability. Through microstructural analysis and dewetting rate measurements, we found that intermetallic compound (IMC) growth played a key role in recurrent dewetting during successive reflows. A modeling approach was proposed to describe how the dewetting rate decreases with increasing reflow cycles due to IMC growth and the size distribution of NCF entrapment. These findings provide insight into failure mechanisms related to solder dewetting and a tool for predicting the reliability of microbump interconnects after multiple reflow cycles during advanced packaging.