FCCSP IMC Growth under Reliability Stress Following Automotive Standards

Abstract

The Kirkendall void (KV) has been a well-known issue for long term reliability of semiconductor interconnects. KVs exist at the interfaces of Cu and Sn and the growing intermetallic compound (IMC) Cu6Sn5 at the initial stage, and a part of the IMC is converted to Cu3Sn when the environmental stress added. In this article, all the assembled packages pass the condition of unbiased long-term reliability testing, especially for 2,000 cycles of temperature cycling test and 2,000 h of high-temperature storage. A large numbers of KVs was observed after 200 cycles of temperature cycling. Various assembly structures were monitored, and various IMC thicknesses were concluded to be functions of stress test. Cu3Sn, Ni3Sn4, and Cu6Sn5 are not significantly affected by heat, but Ni3Sn4 grows steadily.