Deformation Behavior of Transient Liquid-Phase Sintered Cu-Solder-Resin Microstructure for Die-Attach

We have proposed a low-temperature bonding technology utilizing the sintering of Cu particles with transient liquid-phase of Sn-based solder, called transient liquid-phase sintering (TLPS), as a die-attach solution for high-temperature power modules. A copper-intermetallic compound-resin (Cu-IMC-resin) microstructure, which consists of Cu particles connected with Cu–Sn intermetallic compounds (IMCs) partially filled with polyimide resin, is obtained by the pressureless TLPS process at 250 °C for 1 min using a novel Cu-solder-resin composite as the bonding material in a nitrogen atmosphere. Macro- and micro-deformation properties of the unique microstructure of the TLPS Cu-IMC-resin are evaluated by finite element analysis using a three-dimensional image reconstruction model. The macroscopic computational uniaxial tensile tests of the Cu-IMC-resin model reveal that the utilization of the IMCs and the addition of the easily-deformable resin facilitates the temperature-stability and low-stiffness of the mechanical properties. The microstructure exhibits a significantly low homogenized Young’s modulus (11 GPa). Microscopic investigations show that the local stresses are broadly distributed on the IMC regions under uniaxial macroscopic tensile displacement, indicating highly reliable performance of the joint within a specific macroscopic strain condition. Numerical and experimental investigations demonstrate the excellent thermal cyclic reliability of die-attached joints between silicon carbide chips and directly bonded copper substrate.