Casram uses different joining techniques: brazing, welding, electron beam welding and back-casting. The back-casting is a technique to create a composite from two metals with very different melting points. The metal with the highest melting point (tungsten) is pressed to create a sponge which is then impregnated with liquid copper. An excess quantity of copper then allows the creation of a composite material W-Cu / Cu. This technique allows the creation of a perfectly homogeneous and solid bond between the two materials