<p>The effect of bonding time on the microstructure and shear property of Cu/InSnZnBi/Cu solder joints fabricated by transient liquid phase (TLP) bonding was investigated. The results showed that the microstructure of the in-situ reaction zone consisted of InBi, Zn-rich and Sn-rich phases. With increasing bonding time, the island-like InBi phase increased, while the Zn-rich and Sn-rich phases decreased. When bonded at 280&#xa0;℃ and 1&#xa0;MPa for 5&#xa0;min, the interfacial intermetallic compound (IMC) was Cu₅Zn₈, but transformed to Cu₆(Sn, In)₅ and Cu₅Zn₈ after 30&#xa0;min. The thickness of the interfacial IMCs increased with increasing bonding time, and Kirkendall voids formed at the interfacial IMCs after 120&#xa0;min. The growth kinetics index <i>n</i> of Cu₅Zn₈ and interfacial IMCs (Cu₅Zn₈ and Cu₆(Sn, In)₅) were 0.25 and 0.13, respectively, and the growth mechanism was controlled by grain boundary diffusion. With the increase of bonding time, the shear strength of the solder joint initially increased and then decreased, and the maximum value was 9.28&#xa0;MPa at 60&#xa0;min. After the bonding time was increased to 240&#xa0;min, micro-cracks occurred in the in-situ reaction zone caused by thermal expansion coefficient mismatch, resulting in the shear strength decreasing to the minimum 4.98&#xa0;MPa. The fracture position transited from the interface between the interface reaction zone and the in-situ reaction zone to the interior of the in-situ reaction zone with the increase of bonding time. The shear fracture mechanism was changed from brittle fracture to ductile–brittle mixed fracture, and then returned to the brittle fracture.</p>