Failure Studies of Au-Sn and Au-Au Inner Lead Bonds

摘要

Criteria for determining the quality of inner lead bonds were developed from pull test failure studies. Two thickness types of gold plated copper lead-gold bump samples and one type of tin plated copper lead-gold bump sample were evaluated. Bonding conditions and bond quality were related. Pull testing was performed on bonded samples which had been subjected to elevated temperatures. The types of bond and lead failure modes are described. Pull test results include the percentage of each failure type, average pull strengths in grams and kg/sq mm, and standard deviations. The thicker type of gold plated lead-gold bump system was superior in quality to the other two metallurgical systems. No pull test (destructive) failures occurred at the bump-lead interface for the thicker gold plated lead system. An average pull force value of 48 grams was determined for that system. Minimum values obtained in this study were approximately 1 order of magnitude in excess of bond strengths associated with wire bonds. It was determined that 20 grams force would be a reasonable limit value for non-destructive pull testing of inner lead bonds. (Author)