09 Feb 2024 Metallic sintering
Refers to the joining of materials using metal powders below their melting temperature. The process can be carried out with pressure support up to 50 MPa or without pressure. Typical joining temperatures for copper or silver powder are 200…300°C. The sintering time is usually 2-5 minutes. The actual joint is formed by diffusion processes. The metal powders have a particle size distribution either in the nano range or are microscale. The smaller the particles are, the more reactive they are. As the metal grains strive for surface miniaturization, they bond to each other and to the interfaces of the joining partners. This is why joints with identical elements work best – especially silver to silver. The surfaces must be free of oxides or impurities so as not to disrupt the diffusion process.
In recent years, metallic sintering has established itself as a high-performance alternative to soft soldering in power electronics. After the joining process at 200..300°C, the joint only melts again at the melting point of copper (1082°C) or silver (962°C). Both copper and silver have an order of magnitude higher thermal conductivity and strength than soft solders. Metallic sintering therefore results in a thermally and mechanically high-performance joint.
Metallic sintering has already established itself for bonding semiconductors to circuit carriers. Industrial developments are now moving strongly towards large-area sintering of substrates or printed circuit boards on heat sinks or base plates. Other connections include the application of terminal connections to substrates or the joining of busbars. Special high-temperature industries are also currently discovering metallic sintering for themselves, such as sensors or laser applications.