Preparation, properties, and reliability of Cu/Sn composite joints with porous Cu as interlayer for high-temperature resistant packaging

In recent years, porous metals have been used for transient liquid phase bonding because of their high specific surface areas. However, current studies have mainly focused on the preparation of porous metal joints and lack awareness of their reliability issues. Therefore, we prepared a porous Cu joint for high-temperature-resistant packaging and investigated its aging and thermal shock resistance. Porous Cu joints were prepared using commercial porous Cu and pure Sn foils. After soldering at 250 °C for 10 min, the shear strength of the porous Cu joints was 83 MPa and 61 MPa at 25 and 300 °C of shear temperatures, respectively. The electrical resistivity and thermal conductivity of the porous Cu joints were 8.65 µΩ·cm and 58.9 W/(m·K), respectively. The room-temperature shear strength of the joints aged at 300 °C for 1000 h could still reach 60 MPa. Reticular Cu₂O/Cu₃Sn was discovered for the first time in aged porous Cu joints. After 1000 cycles, the room-temperature shear strength of the joints could still reach 73 MPa, which was only 14.5% lower than that of the joints without the thermal shock test. In conclusion, porous Cu joints exhibited good aging resistance and excellent thermal shock resistance.