The process in which a filler material or metal is dispersed/spread by the capillary action between the metal surfaces in order to join them together is called brazing. In this process, the base metal never melts, only the filler metals are melted.
In this process, the filler metal that is used (also known as brazing metal) has a melting point in excess of 450 C but it is below the melting point of the base metal. The tensile strength of the joint thus formed is around 40000 psi.
Please note that brazing is different from welding. It has many significant advantages over welding. In case of brazing, any types of metals can be joined. Even the dissimilar ones. This cannot be done with welding. It is typically a faster process than welding hence it is more efficient.
It allows for joining of multiple joints. Which cannot be done in case of welding easily. The best application of brazing comes when joining thinly walled metals. This is just impossible to achieve from welding. Also, this process requires less energy to be performed. In this, the filler metal never penetrates the base metal whereas in welding the base metal is always penetrated.