Film over wire (FOW) selection for copper wire application

High functionality integration, thinning and miniaturization of IC package dimensions, and cost benefit are the main stream in IC package development, especially in mobile application market. Stacked dies and copper wire technology are utilized to fulfill these demands. FOW (Film over wire) is an alternative material for interposer solution in stacked die package. A reliability test was performed on HAST (110°C/85). The lift ball failure was happened at 288 hours, the failure mechanism was confirmed due to bond pad corrosion that IMC (intermetallic compound) was corroded by chloride under high humidity with bias. The concentration of chloride ion in FOW material is a main factor of failing to pass the IC reliability test. The extracted ions were analyzed by ion chromatography and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) when temperature above 120 deg C chloride ion was leached. That contributed to reliability risk on Cu wire package under humidity environment. In summary, this study discloses how chloride ion attached and corroded bond pad at high temperature 110 deg C as result of ball lift. So, the way of work of FOW selection for copper wire bonding in stacked die package is the purpose of this paper.