Transient solid-liquid interfacial reaction between Al wire and Au/Cu pad during parallel gap micro-resistance welding

摘要

Reliable bonding of thick Al wires and plated Au pad is important for the packaging of power modules. The interfacial phases of the Al/Au/Cu joint after parallel gap micro-resistance welding were observed by transmission electron microscopy (TEM). Obvious Al, Au and Cu elemental interdiffusion can be observed by energy dispersive spectrometer (EDS) mapping, indicating the occurring of sufficient interfacial reaction. Under the effect of current and heat, the core temperature is higher than the melting point of Al. Liquid Al will react with Au and (Au, Cu) Al-2 intermetallic compound (IMC) phase was formed rapidly within 20 ms. Besides, excessive Al atoms rapidly diffuse through the Cu-based solid solution, and react with Cu forming (Cu, Au) Al-4 IMC phase. (C) 2021 Elsevier B.V. All rights reserved.