Chlorine and Sulfur Effects on Gold-Aluminum Wire Bond Reliability

Abstract

Currently, wire bonding is still the dominant interconnection mode in microelectronic packaging, and epoxy molding compound (EMC) is the major encapsulant material. Normally EMC contains chlorine (Cl) and sulfur (S) ions. It is important to understand the control limit of Cl and S in the EMC to ensure good Au wire bond reliability. This paper discussed the influences of Cl and S on the Au wire bond. Different contents of Cl and S were purposely added into the EMC. Accelerated reliability tests were performed to understand the effects of Cl, S and their contents on the Au wire bond reliability. Failure analysis has been conducted to study the failure mechanism. It is found that Cl reacted with IMCs under humid environment. Cl also caused wire bond failure in HTS test without moisture. On the other hand, the results showed that S was not a corrosive ion. It was also not a catalyst to the Au bond corrosion. Whilst, high content of S remain on the bond pad hindered the IMCs formation and caused earlier failure of the wire bond.