Ultrasonic welding (US welding) is a joining technique that is used, among other things, in power electronics for power semiconductors. Since solder joints with
soft solder cannot withstand the increased operating temperatures in power components and can dissolve, ultrasonic welding joints are used for these components. Ultrasonic welding is based on friction welding, whereby one of the parts to be joined is firmly clamped while the other part is vibrated by an ultrasonic resonator. The vibrated part is then pressed onto the fixed part with pressure. At the point of contact between the two parts, the molecular structure is vibrated, causing the materials of both parts
to bond ona molecular basis.
In power semiconductor devices, this technique is used for bonding the load terminals to the power semiconductor.