Enhancement of Vacuum Reflow Process for CCPAK - A Solution to Oxidized Lead Frame

Abstract

With the development of high-power packages as a solution to customer needs and requirements, the CCPAK was introduced to fill the performance gap. A GaN (Gallium Nitride) is packaged with a silicon FET (Field Effect Transistor) and integrated with copper clip technology. This complex technology required process development, especially for the die attach clip attach process. In the initial CCPAK DACA characterization, visible evidence of lead frame oxidation was noted at the vacuum reflow process. As excessive lead frame oxidation is detrimental to package integrity and unlikely to occur in a vacuum state, the team decided to employ the DMAIC approach in systematically resolving this issue. Process elimination was conducted to pin down the problematic process from through the SIPOC diagram to understand, identify, and describe the failure. Monthly occurrence of oxidized lead frame was examined. Simulations were executed to validate the most possible cause of oxidation, which was the displacement of carrier on the heater block during the reflow process. Characterization was conducted, focusing on control of carrier movement during process. Initial results and prolonged performance were monitored. With the appropriate solution in placed, full elimination of lead frame oxidation was achieved resulting to yield improvement. Furthermore, the importance of proper process development prior production release was given emphasis.