Oxidation on copper lead frame surface which leads to package delamination

Based on several studies, package delamination caused by copper oxide is one of the most common IC packaging defects detected in backend assembly processes. The possible root causes for the copper oxide formation could be due to leadframe surface oxidation, incompatible process temperature and ineffectiveness of surface cleaning prior to molding. In order to effectively investigate the contribution of copper oxide formation to package delamination, this study have been initiated with the application of relevant reliability stress tests and surface interface analytical techniques. Reliability stress test of HTS was carried out to accelerate the copper oxide formation after molding and the delamination occurrence being monitored by SAM scanning after defined stress test intervals. To further on the study, a detailed elemental low KeV EDX analysis was performed to assess the delaminated interfaces after mechanical decapsulation of the failure units. In addition, AES analysis including depth profiling was also applied to determine the copper oxide layer. A good correlation of copper oxide formation to package delamination was demonstrated and inappropriate temperature used in wirebonding clamping was identified to be the most probable root cause of the package delamination.