Paddle tilt towards Paddle Flash performance on small outline package

Small outline package with exposed heatsink design provides better heat dissipation for power devices. This exposed heatsink package to have a flash free surface before plated is challenging in semiconductor assembly process. The small outline package had small heatsink area with thin leadframe thickness even had elevated risk in paddle flash creating on heatsink area. As result of this thin heatsink, the die paddle easily tilted after clamping, so the compound resin easily bleeds into heatsink area during encapsulation process. The solderability and heat dissipation property of the unit will reduce as the paddle flash inhibits the maximum contact area between the unit and the PCB board or external heatsink. In this paper, a few factors were assessed to understand more on the paddle tilted causes. Firstly, the paddle tilted performance had been studied through steps-by-steps process from incoming material till mid-end process to have better understanding on the paddle tilted performance impacting by assembly process. Other than this, different mold cavity designs with various antiflash profile gap (AFP) found to be significantly affect the paddle flash severity. Thus, the deep dive on the cavity design had been studied. The chamber design at side wall of the cavity called lead slot found impactful to paddle tilted performance during clamping process. Measurement on this lead slot through various versions of cavity fabrication had been conducted. Thus, the result proven different paddle flash performance was found at different cavity due to lead slot design. Another way CAE software simulation was also conducted to check on effect cavity design leadslot towards the paddle tilted. In this CAE study, various leadframe and cavity designs were also included to check on the paddle tilted effect. The result will help on the next improvement study. Conclusion, combination on leadslot design in cavity and different leadframe design can give the better paddle tilted deformation that help on paddle flash performance.