Cu-Cu joint with Sn-58Bi/Porous Cu/Sn-58Bi transient liquid phase bonding under formic acid atmosphere

Abstract

Purpose This paper aims to examine the effects of bonding temperature, bonding time, bonding pressure and the presence of a Pt catalyst on the bonding strength of Cu/SB/P-Cu/SB/Cu joints by transient liquid phase bonding (TLPB). Design/methodology/approach TLPB is promising to assemble die-attaching packaging for power devices. In this study, porous Cu (P-Cu) foil with a distinctive porous structure and Sn-58Bi solder (SB) serve as the bonding materials for TLPB under a formic acid atmosphere (FA). The high surface area of P-Cu enables efficient diffusion of the liquid phase of SB, stimulating the wetting, spreading and formation of intermetallic compounds (IMCs). Findings The higher bonding temperature decreased strength due to the coarsening of IMCs. The longer bonding time reduced the bonding strength owing to the coarsened Bi and thickened IMC. Applying optimal bonding pressure improved bonding strength, whereas excessive pressure caused damage. The presence of a Pt catalyst enhanced bonding efficiency and strength by facilitating reduction–oxidation reactions and oxide film removal. Originality/value Overall, this study demonstrates the feasibility of low-temperature TLPB for Cu/SB/P-Cu/SB/Cu joints and provides insights into optimizing bonding strength for the interconnecting materials in the applications of power devices.

Transparent Liquid Ag-Based Complex for the Facile Preparation of Robust Sintered Ag Joints in Power Devices

“…Various methods, including Pb–Sn alloy soldering, transient liquid phase (TLP) bonding, Cu sintering, and Ag sintering, − have been suggested for fabricating die attachments that can endure high temperatures. Among these methods, Ag sintering is particularly appealing because bulk Ag has a high melting point of 961.9 °C, which provides excellent high-temperature reliability. , During sintering, Ag nanoparticles (NPs) with high surface energies can be easily sintered into bulk Ag at temperatures far lower than its melting point .…”

Improvement of Solder Joint Shear Strength under Formic Acid Atmosphere at A Low Temperature

“…Thus, it is normally used for soldering below 200 °C to resist the destruction of thermal warpages [ 18 ]. Also, the Sn-58Bi can be a favorable candidate for low-temperature fluxless soldering, especially for FA soldering [ 19 ].…”