Study on shear strength and fracture behavior of Cu-Sn system low-temperature TLP bonded joint

In this paper, the effects of bonding time and temperatures on the microstructures and mechanical properties of Cu/Sn/Cu sandwich low-temperature TLP bonded joint were investigated. The shear strength of the 300 ℃ bonded sample was firstly increased and then kept around higher than 30 MPa with the increase of bonding time from 15 min to 150 min, namely, with the strength increased from 16.9 MPa of 15 min to 32.4 MPa of 120 min, and then being remained higher than 30 MPa of 150 min. The Cu3Sn-type joint possessed the highest mechanical properties, even a few Cu₆Sn₅ particles still remained between two different Cu₃Sn layers. With the TLP joint changing from the pure Sn type to the Cu₃Sn type, the fracture mode was gradually turned from ductile facture to brittle fracture. In addition, with the bonding temperature increasing from 260 ℃ to 350 ℃, the shear strength of Cu₃Sn-type joint was mildly affected, always keeping higher than 30 MPa. All Cu₃Sn-type joints obtained at different temperatures fractured with a mode of cleavage fracture.