Improvement of the solderability of aluminum alloy, nickel, stainless steel and copper by metallization of silver and nickel for power semiconductors

With the rapid development of electric vehicles and aerospace electronics, wide band gap (WBG) power devices' harsh working environments pose significant challenges to packaging materials. Therefore, there is an urgent need to investigate novel materials and connecting techniques in order to enhance die-attach strength. In this paper, the effects of various silver plating thicknesses and coating types on the mechanical properties of joints have been researched. The findings presented in this work indicate that pure silver plating on materials with low solderability has no appreciable impact on the bonding strength of their joints, which is attributed to the poor combination between the sheets and the silver layer, as confirmed by additional microscopic investigations. But the shear strength of aluminum alloy and stainless steel joints can be increased to more than four times the initial value with a mixed coating of 300 nm nickel and 2 μm silver. This study is anticipated to offer recommendations for coating materials to increase their solderability, despite the fact that there are numerous different coating types and thicknesses that need to be further investigated.