Transient Liquid-Phase Bonding Using Sn/Ni/Sn Laminated Metal Preform for Power Device Packaging

Intermetallic compound (IMC) joints formed via transient liquid-phase (TLP) bonding offer excellent high-temperature durability. However, IMC formation at the joint requires long bonding times and high pressures. In this study, to reduce the bonding time and pressure required for IMC formation, a Sn/Ni/Sn laminated metal preform was fabricated by inserting Ni foil between Sn foils, and this material was used to bond a chip to a substrate. The microstructure of the joint cross-section was analyzed using field-emission scanning electron microscopy and energy-dispersive x-ray spectroscopy. The Sn foil was completely converted to 7 mu m Ni3Sn4 within 15 min, forming a stable TLP-bonded joint. After bonding, a shear test was conducted to evaluate the mechanical properties of the joints, which revealed high shear strength, exceeding 46 MPa.