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62 SMT007 MAGAZINE I APRIL 2023 process steps were checked for their impact on the electrolytic tin deposit of the QFN bottom pad; no negative impact could be detected. To prevent the formation of whiskers, which are a known risk for immersion tin deposits, an anti-whisker additive is introduced which deposits at the grain boundaries of the tin deposit and inhibits the formation of tin whiskers. SMT007 References 1. "Side Wettable Flanks for Leadless Automotive Packaging," by M.A. Mangrum, Semiconductor Engineering Whitepaper, Oct. 10, 2020. Figure 5: The results of the IMC and free tin thickness (stated in µm.)