Cu@Sn Core–Shell Structure Powder Preform for High-Temperature Applications Based on Transient Liquid Phase Bonding

Abstract

This paper presents a novel die-attach material for high-temperature applications based on transient liquid phase (TLP) bonding. Cu particles are electroless plated with Sn to achieve Cu@Sn structure, and the fabricated Cu@Sn particles are compressed into preforms for die attachment. This material can be reflowed at a low temperature (<260 °C) due to the low melting temperature of the outer Sn layer. However, after reflow soldering, the resulting interconnections can withstand a high temperature of at least 415 °C, with the entire outer Sn layer transforming into Cu−Sn intermetallic compounds (IMCs) with high remelting temperatures. The formed bondlines exhibit good electrical and thermal conductivity due to the low porosity and the embedded Cu particles in the interconnections. A large shear strength at 400 °C can be achieved with the high-remelting Cu−Sn IMCs in the interconnections. Furthermore, the interconnections also exhibit excellent reliability under thermal shock cycling from −55 to 200 °C. The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> – <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> curve and breakdown voltages of the novel preform-bonded IGBTs are measured to examine the interconnection quality compared with those of Cu−Sn TLP-bonded IGBTs. This die-attach material is suitable for power devices operating under high temperatures or other harsh environments.