Cu Pillar Bump Oxidation Control in Flip Chip Package

Flip Chip is one of the advanced semiconductor packages which is growing in recent years for various application. Key challenge is solder bump non-wetting which is contributed by several key factors such as bump oxidation, reflow temperature, substrate warpage and foreign material. As bump oxidation is one of the key factors contributing to non-wetting, therefore bump oxidation control is crucial in Flip Chip bumping and assembly processes. This paper focuses on the study of the key factors that significantly control Cu Pillar bump oxidation. Factor 1 refers to staging time control from bumping-out to assembly-FCbond-start. Factor 2 is found to be related to die attach flux dipping time. The result of this study shows that a proper staging time control and a well characterized die attach flux dipping time are able to control bump oxidation.