Comprehensive study of wire bond reliability impacts from wire, molding compound and bond pad contaminations

Wire bond is the most common inter-connection method used to connect microchips to the terminals of a chip package. Wire bond reliability is vital to the performance of packaging device. The understanding of contamination sources and their impacts on wire bond reliability is important to prevent the potential risks. In this study, gold (Au) and copper (Cu) wires were boned to aluminum (Al) bond pad. Chlorine (Cl) and sulfur (S) contaminations were purposely introduced to wire, epoxy molding compound (EMC) and bond pad. Reliability tests bHAST (biased highly accelerated stress test) and HTS (high temperature storage test) were conducted. The results showed that Cl played a significant role on wire bond reliability. Whilst, S did not impact much on wire bond reliability. Instead, it is found that S will hinder the ball-pad IMC (intermetallic compound) growth and deteriorate the bond strength. It was noted that contaminations from EMC showed more critical impact on wire bond reliability compared to those from wire and bond pad. It was found that Cl was not easy to attack Au-Al and Cu-Al under HTS. Whilst Cl easily attacked Cu-Al under bHAST compared to that of Au-Al. Several ppm content of Cl could attack Cu-Al.