M. S. Hsu, TSMC (Taiwan Semiconductor Manufacturing Company), Hsinchu, Taiwan

Summary: For the purpose of saving our environment and adhering to the RoHS (Restriction of Hazardous Substances) guidelines, LF (Lead Free) bump is now frequently used in the semiconductor industry. Due to the brittle material characteristic of SnAg LF bump, cracking on SnAg LF bumps occurred easily during the TC (Thermal Cycle) test. Different LF bump crack behaviors, such as bump crack location and propagated path or direction, may indicate different fracture modes. The micro-crack and its propagation path are difficult to observe by the standard sample preparation method. Therefore, a new skill for sample preparation is required and essential. In this paper, a low angle ion-milling based technique is proposed to advance the LF bump sample preparation method that provides an excellent and clear image of micro-cracks as well as the grain boundary of LF bumps for the reliability test fracture failure study.