A Drop-In High-Temperature Lead-Free Solder Paste that Outperforms High-Pb Pastes in Power Discrete Applications

Abstract

Indium Corporation has designed two Sn-based high-temperature lead-free (HTLF) solder pastes, which combine the merits of two constituent powders, to be used as drop-in solutions to replace high-Pb solder pastes in power discrete applications. Solder paste HTLF-1 maintained bond shear strength up to 15MPa, even around 290°C. Another solder paste, HTLF-2, had a similar bond shear strength as Pb92.5/Sn5/Ag2.5 around 290°C, but exceeded substantially below 250°C. The encapsulated components were built with both HTLF solder pastes through the traditional high-Pb process, demonstrating the drop-in processing compatibility. Those components have passed both moisture sensitivity level 1 (MSL-1) and TCT (-55/175°C). Both HTLF solder pastes outperformed Pb92.5/Sn5/Ag2.5 in RDS(on) before and after 1000cycles TCT (-55/175°C), which is attributed to the intrinsic lower electrical resistivity of Sn.