Abstract
When thick gold and tin come into contact the intermetallic formed is not one for long term reliability. AuSn intermetallics can lead to void formation, increased resistance and a very brittle joint that will fail in time. Such intermetallic formations occur when gold stud bumps are brought into contact with Sn based allows. Fine pitched devices, such as optical, typically use gold studs due to the tight pitch and small pad sizes. By transforming the gold to a less benign state the gold stud bumps allow assembly using standard Sn based solders. Such a process is beneficial when cheapers solders can be used as well as standard flip chip assembly equipment. This paper will provide cross sections of gold stud bumps with SAC305 solder after 3X reflow. The 3X reflow is required to demonstrate the capability and reliability of the modified solder joint. Rozalia/Ron ok move from 2.5/3D to FC/WLP 12-21-11.
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