Effect of thermal ageing on the property of Cu/SAC0307 powder/Cu joint under ultrasonic- assisted at low-temperature

A new method that 45um Zn-powder and SAC0307 No.4 solder powder was mixed to fill the joint and successfully achieved micro-joining of Cu/Cu under ultrasonic- assisted at low-temperature, and then effect of aging time on the property of Cu/Cu joint at 150°C was researched. The results showed that the interfacial IMC changed from typical scallop- type Cu 6 Sn 5 to Zn 8 Cu 5 after adding Zn particles. The thickness of interfacial IMC in Cu/SAC0307 power+10wt.%Zn/Cu joint were 2.76μm and 2.65μm, 4.75μm and 8.25μm at 150°C for 12h and 24h, 48h and 96h respectively. There was only 2.28μm in the absence of thermal ageing. The shear strength of Cu/SAC0307 power+10wt.%Zn/Cu joint reached 34.35MPa, but the shear strength of Cu/SAC0307 power/Cu joint was only 12.24MPa before thermal aging. The shear strength of Cu/SAC0307 power+10wt.%Zn/Cu joint reached 23.82 MPa at 150°C for 6h, and then drop down to 21~22 MPa for 12~48h, finally reduced to 16.58 MPa for 96h. Under the action of heat flow,the thickness of IMC in soldered seam would gather and grow up with the increase of aging time. Accelerated growth of IMC on the interface and in soldered seam was the reason that its breakage.