Failure analysis of IMC cracking and voiding induced by molding compound voids in advanced wire bonding packages

Cracking and voiding of the intermetallic compound (IMC) in bond balls are the leading causes of open failures in wire bonding packages. They are also the causes of functional failures in advanced wire bonding packages, such as SBGA, CSP, and HSBGA. It is well known that many factors, such as bonding parameters, contamination, stress, can induce IMC cracking and voiding of bond balls (V. Koeninger et al, IEEE Trans. Comp., Packaging, and Manuf., Part A, vol. 18. no. 4. pp. 835-841, 1995; G.E. Servais and S.D. Brandenburg, Proc. ISTFA´91, pp. 525-529, 1991; T. Koch et al, Proc. IEEE IRPS, pp. 55-60, 1996). However, a commonly used failure analysis (FA) procedure to analyze IMC problems tends to focus on integrated circuit processing issues while frequently overlooking packaging related problems. This procedure will damage possible evidence of IMC problems caused by packaging. We propose a modified FA procedure that takes care of this problem. Using this procedure, we found voids in molding compounds that induced high stress at high temperature testing resulting in IMC cracking.