Evaluation of Cu-Sb Transient Liquid Phase Bonding Characteristics with Lotus-Type Porous Copper Interlayer for Power Module Applications

초록

With the increasing power density and miniaturization of power modules, the demand for bonding technologies capable of ensuring high-temperature reliability has grown. Transient liquid phase (TLP) bonding, which produces thermally stable joints through the formation of high-melting-point intermetallic compounds (IMCs), has emerged as a promising solution. However, conventional TLP bonding often requires prolonged processing times and can result in void formation. To address these challenges, the use of unidirectional porous metals, known as lotus-type porous metals, has been proposed. These materials exhibit anisotropic mechanical properties due to their aligned pore structure. This study investigates the microstructure and mechanical properties of TLP-bonded joints incorporating lotus-type porous copper (Lotus Cu) as an interlayer, compared to conventional TLP joints without it. Bonding was performed under vacuum at 300?°C for 60, 120, 180, and 240 minutes using Sn-3.0Ag-0.5Cu (SAC305) solder. Crosssectional and fracture surface analyses were conducted, and shear strength was evaluated. The results showed that Lotus Cu TLP joints bonded for 60 and 120 minutes achieved superior shear strengths exceeding 30?MPa, attributed to the suppression of crack propagation along the porous structure. Fracture path analysis revealed that Lotus Cu effectively altered crack growth directions, enhancing joint reliability. Additionally, the evolution of IMC thickness and void formation behavior was analyzed to explain the mechanical performance trends with bonding time.