Surface Characterization and Leadframe-to-Mold Adhesion Performance of Oxidation-Roughened Leadframes

Abstract

Leadframe surface roughening increases the leadframe-to-mold interfacial adhesion strength through mechanical locking and free-radical bonding mechanism. On this study, two different oxidation-roughened leadframes were successfully evaluated through leadframe surface characterization and leadframe-to-mold adhesion performance. Leadframe surface morphology characterization showed that both Leadframes have the same needle-like microstructure at zero-hour. After high temperature anneal, Leadframe A evolved into coarser structure while Leadframe B remains stable. Hypothesis tests confirmed that Leadframe B have higher surface stability than the Leadframe A upon exposure to high temperature annealing process. Leadframe-to-mold adhesion performance through Button Shear Test revealed that mold adhesion strength of Leadframe B is consistently higher than Leadframe A at Ag and Cu regions. Hypothesis tests also confirmed that Leadframe B have stable shear strength upon exposure to high temperature annealing process while Leadframe A showed a significant degradation of shear strength after annealing process. The leadframe-to-mold adhesion performance through SAM showed that the Leadframe B has better Leadframe-to-mold adhesion than the leadframe A. The mold adhesion improvements can be attributed to the microstructural and roughness stability of the surface. Leadframe B showed stable microstructure upon exposure to high temperature annealing process resulted to high and stable mold shear strength and leadframe-to-mold adhesion.