Cu/SiC heterogeneous interconnection with high-frequency ultrasound at low-temperature

In this study, 1-μm Sn-3.5Ag-2Ti(0.5La) alloy powder was used as a solder for Cu/SiC heterogeneous interconnects at three different temperature gradients assisted by high-frequency ultrasound at 35 KHz in ambient atmosphere. The results showed that more stable Cu/SiC solder joints were formed at 230 ℃, 240 ℃ and 250 ℃. The Cu/solder side was observed to generate the interface IMC (Cu
6
Sn
5
), with its thickness increasing as the temperature increased. The connection to the SiC side occurred through diffusion of Ti atoms from the SiC/solder side. The study found that the shear strength increases continuously with an increase in temperature. At 230 ℃, the shear strength was measured to be 20.43 MPa, which slightly increased to 24.29 MPa when the temperature rose to 240 ℃, representing an 18.9% rise from 230 ℃. As the temperature was raised to 250 ℃, the strength experienced a further increase to 33.29 MPa, exhibiting a remarkable rise of 62.9% from the previous value recorded at 230 ℃. Meanwhile, the fracture morphology indicated that an increase in temperature led to higher amounts of solder residue on the surface of SiC joints, resulting in a more reactive environment. Additionally, the fracture location progressively shifted from the SiC side to the middle of the solder during this process.