Mechanical and Chemical Treatment for Copper Burr Elimination in Wettable Flank QFN

The creation of a robust wettable flank architecture in quad-flat no-leads (QFN) packages is satisfied by the step-cut configuration, where the exposed sidewall is plated with Sn. The step-cut singulation process induces Cu burrs, which can lead to shorting via physical bridging between leads due to the burr, or the environmentally induced Cu migration during field application. Herein, we show that buffing and chemical deflash successfully eliminated the Cu burrs after step-cut singulation. The processes induce minimal effect of the plating quality thereby showcasing the a potential of buffing as one of the enablers for a robust wettable flank technology.