Thin layer Ag-Sn transient liquid phase bonding using magnetron sputtering for chip to baseplate bonding

Abstract

The formation of a high temperature die attach based on transient liquid phase (TLP) bonding is demonstrated using the binary system Ag-Sn in a sputtered thin layer approach. The microstructure and shear strength are compared to a foil based approach and show the successful replacement of the Sn foil and thus a simplification of the stack assembly. The diffusion of the Ag-Sn system is investigated in a long-term experiment at room temperature as well as in short-term experiments in the temperature range of the tin melting point. The results show the bondability of long-term stored samples and the possibility for decreased layer thickness while still enabling formation of the liquid phase to create the bond. TLP joints with a tin thickness of 2 μm are manufactured successfully and show comparable microstructures to thick layer joints. This approach offers an improved manufacturability of power modules.