Study on the impact of primer process control and lead delamination towards cracked/broken wedge bond

This paper focuses on the study of the relationship between the preparation of primer and the lead top delamination and their impact on cracked/broken wedge bond. In a recent failure analysis, a plastic package that used 75 μm Aluminum wire and lead frame with primer was observed to have broken and cracked wedge bonds. Initial investigation attributed the defects to package delamination between the lead and the mold compound due to poor primer process control as all the electrical failures were observed to have lead top delamination. To further confirm this hypothesis, a design of experiment (DOE) with 13 runs were carried out to study how the primer staging time, primer stir time and primer preparation method could affect the adhesion between the lead and the mold compound. It was observed that the DOE run with staging time 1 day and stir time 1 hour produced the best package integrity where the samples showed the least lead top delamination. Internal visual inspection, however, revealed that cracked/broken wedge bonds were observed in samples with and without lead top delamination. These findings concluded that both the primer and the package integrity are not factors that contribute to the cracked/broken wedge bond. Investigation continued with experiments focused on package stress and wiring loop height. “p302.doc.”.