Electromigration in flip chip with Cu pillar having a shallow Sn-3.5Ag solder interconnect

Abstract

Electromigration phenomena in Sn-3.5Ag solders with Cu pillar in the flip chip joints was investigated. The silicon die was mounting on a silicon substrate via thermal-compression bonding process. The diameter of the Cu pillar of flip chip is 40um, meanwhile the thickness of solder bump is 3um. Finite element modeling and analysis were established to understand the influences of Cu pillar structure on the electromigration reliability. The reliability of electromigration in shallow solder bump with Cu pillar was explored for various amounts of time under a high current density of 1×104A/cm2 at 100 °C. After the Sn-3.5Ag solder cap all forms Cu6Sn5 intermetallic compounds with the Cu pillars, the condition of the solder accelerates deterioration to generate many micro voids under the current stressing. However, the resistance of the daisy chain has hardly changed during this period.