Liquid gallium (Ga) enables low-temperature transient liquid phase bonding (TLPB), but optimizing microstructure and joint performance remains challenging. Here, we developed a copper (Cu)-powder/liquid-Ga composite paste for Cu/Cu interconnects and systematically studied the effects on the interconnect joint performance of Cu powder particle size (CuPS, 10–20, 20–30 and 30–40 μm) and Cu mass fraction (CuMF, 10–30 wt%). The microstructure, electrical conductivity, and shear strength of the joint were evaluated, followed by an assessment of bonding temperature, pressure, and time. Under bonding conditions of 220 °C, 5 MPa and 720 min, a dense intermetallic compound (IMC) microstructure predominantly composed of Cu9Ga4 and CuGa2 was formed, yielding an electrical conductivity of approximately 1.1 × 107 S·m−1 and a shear strength of 52.2 MPa, thereby achieving a synergistic optimization of electrical and mechanical properties; even under rapid bonding conditions of 220 °C, 5 MPa and 1 min, the joint still attained a shear strength of 39.2 MPa, demonstrating the potential of this process for high-efficiency, short-time interconnection applications. These results show that adjusting the composite paste formulation and dosage enables Cu–Ga TLPB joints that combine high conductivity with robust mechanical integrity for advanced packaging.
Wang et al. (Tue,) studied this question.