 The composition of the solder paste varies, depending upon its intended use.For example, when soldering plastic component packages to an FR-4 glass epoxy circuit board, the solder compositions used are eutectic Sn-Pb (63 percent tin, 37 percent lead) or SAC alloys (tin/silver/copper, named for the elemental symbols Sn/Ag/Cu).If one needs high tensile and shear strength, tin-antimony (Sn/Sb) alloys might be used with such a board.