Ag sinter joining and wiring for high power electronics

摘要

Sinter joining with Ag particle pastes has attracted much attention for wide band gap power assembly that requires high power and high temperature interconnection technology. The micron/submicron Ag particle hybrid paste, which is affordable with excellent performance, is one of the promising materials. Bonding conditions are very much mild such as 250°C, low pressure less than 1 MPa and air atmosphere. The metallization layer structure was evaluated by changing interlayer structures. The SiC die-attached on a DBC structure (Cu/Si_3N_4/Cu) with the Ag hybrid paste exhibits excellent stability at 250°C up to 1,000 hours in air, when a suitable layer structure was selected. Shear strength over 30 MPa was maintained. It was found that the interfaces both of a Ag layer and DBC and of SiC die and a Ag layer must be protected to prevent severe oxidation. A barrier layer of Ti was found to be effective to stop oxidation of the metallization such as Cu and Ni. Severe thermal cycling between -40°C and 250°C decreased strength while good strength beyond 10 MPa was maintained up to 1,000 cycles in air. The Ag hybrid paste can be also applied for wiring instead of Al or Cu wire-bonding. 3D printing of Ag hybrid paste provides heat-resistant wiring for SiC assembly. Microstructures and selected properties will be demonstrated.