Effect of leadframe design on aluminum wire bonding

Parameters such as Force, Power, Time, Clamping and Anvil block designs are important factors in obtaining a good aluminum wedge bond. Initially, the leadframe design has a fused lead connected to the die paddle. This connection of the lead to the die paddle causes ineffective clamping, resulting in lifted wedge bond after reliability stress. Moreover, the bonding is worsened by delamination at the leads, found after stress. In this study, investigations are done on the leadframe designs to determine the effectiveness of the clamping concept that lead to good bond integrity. Pull tests results showed that the wedge bonds bonded on Partial Cut leadframe (with narrow joint between the lead and die paddle) are slightly weaker as compared to those bonded on Full Cut leadframe (no joint between the lead and die paddle). Moreover, propagation of delamination is seen on the Partial Cut lead. This phenomenon is however, not observed on the Full Cut lead. Thus, further reliability stresses are performed on the Full Cut leadframe design to further check on the bond integrity. All units passed the reliability tests and the package is qualified as a Moisture Classification Level 3 package.