Solder paste is a mix pulverized soldering metals, flux and pasty elements. Solder paste is used in surface mount processes to join in the reflow process SMT components to an assembly. Solder paste is printed onto the pads with a stencil printer, after which the components are placed into the solder paste deposit. In the following reflow process, the board assembly is heated up until the solder paste melts and forms the solder joint. In electronic manufacturing pastes with a metal content of 80-90 weight% are used. Aside from the composition of the solder, its grain size is an important factor. The grain size is determined by the size of the geometries to be printed.