Nickel-Tin Transient Liquid Phase Bonding Toward High-Temperature Operational Power Electronics in Electrified Vehicles

This paper presents the concept, fabrication, and evaluation for quality and reliability of nickel-tin transient liquid phase (Ni-Sn TLP) bonding that provides high reliability for high-temperature operational power electronics in electrified vehicles. The need for automotive power electronics to operate at high-temperature presents significant challenges in terms of packaging and bonding technology used. TLP bonding is one attachment approach that addresses these challenges and facilitates high remelting temperatures while allowing processing to occur at relatively low temperatures and pressures. In particular, the Ni-Sn TLP bonding process exhibits a number of desirable characteristics for power electronics, including popularity in conventional power electronics, low cost, and uniform and homogeneous alloy formation. The work herein presents Ni-Sn TLP bonding (ready for high-temperature operation) as applied to silicon power devices of relatively large size (12mm x 9 mm). The quality and reliability of the developed bonding process was characterized using material, optical, and electrical analysis. Analysis indicates that the resulting bondline is uniformly composed of Ni3Sn4 alloy throughout the bond area. This bonding approach has exhibited excellent reliability for bonded devices after thermal cycling from -40 degrees C to 200 degrees C. Electrical properties of the bonded insulated gate bipolar transistor power devices demonstrated that Ni-Sn TLP bonding exhibits electrical performance comparable with conventional solder and is reliable at high-temperature operation