Fabrication of Sn-plated Cu foam for high-efficiency transient-liquid-phase bonding

Abstract

To solve the problems of long reflowing time and poor high-temperature resistance of traditional transient-liquid-phase (TLP) bonding, a low cost Sn-plated Cu foam (CF@Sn) preform was developed and fabricated for low-temperature die attachment of high-temperature electronic devices. The preform is composed of a strip-shaped Cu skeleton coated with a uniform Sn layer, displaying a low-bonding-temperature and high re-melting temperature. The microstructure evolutions of interconnection layer and the mechanical properties of joints bonded at 280 °C under 2 MPa for different bonding time were investigated. After bonding for 40 min, the preform demonstrated excellent metallurgic bonding to the substrates, and the bond line with only Cu and Cu3Sn phase was obtained. Additionally, the average shear strength of bonded joints was improved to 28.1 MPa, the failures were occurred along the interface between the Cu skeleton and IMCs. The bonded joints presented good thermal reliability without micro-crack interfaces after the high temperature aging tests.