Fast Two-Step Sintering Process with High Strength

Inhalt:
Sintering as a die-attach interconnect method in power electronics modules has advantages in reliability and aging phenomena over solder joints, especially at elevated temperatures. Some wide bandgap semiconductors, such as silicon carbide, can also be operated above the melting point of conventional solders. This necessitates alternative interconnection methods. However, the production of sintered interconnects requires more complex machinery compared to soldering because in addition to heat, mechanical pressure must be applied in the process to produce a satisfactory interconnect. The requirement for mechanical pressure requires the joint to be made in a press, and joint formation typically takes several minutes. This results in higher machine costs and reduced throughput compared to soldering. In this work, we therefore investigate a two-step manufacturing process of silver-sintered joints, where pressure is only required for a short time at the beginning of the joint formation, followed by a pressureless second step to complete the sintered joint. This second, non-pressure step can be performed in conventional soldering ovens in large batches, which can increase the overall throughput of the process. Shear strength tests showed bond strengths of up to 60 MPa, depending on the process parameters. The two-stage process can alleviate the problem of low throughput of pressure sintering without having to resort to more expensive and difficult-to-handle nano-sintering pastes for pressureless sintering.