The Effect of Strip Argon Plasma Cleaning onto the PPF and Ag-plated Cu Leadframe Surfaces

The effect of plasma power and plasma time parameters on the PPF and Ag-plated surfaces were successfully evaluated through surface characterization and leakage functional test. Surface characterization showed that the hydrophobic surface of PPF-plated and Ag-plated leadframes transformed into hydrophilic surface after application of different levels of plasma power and time which is an indication of improvement on wettability. Surface roughness showed that long exposure time can trigger further roughening of the PPF surface. Statistical analysis suggest that the plasma parameters should be kept at leg 6 (mid power, low time). Furthermore, leakage performance of the device showed that increasing the plasma time parameter affect the current leakage performance. Extreme conditions of plasma setting can result to re-deposition of unwanted elements on top of die due to over-etching. The recommended plasma parameter setting showed well-centered current distribution and zero occurrence of leakage failure.