Authors: Keith Sweatman, Takatoshi Nishimura and Takuro Fukami Company: Nihon Superior Co., Ltd Date Published: 9/27/2015
Abstract: Phosphorus has long been a "secret ingredient" in tin-lead solder, particularly solder made with recycled metal, as it is a powerful deoxidant that removes dross and brings a sparkle to the surface of the molten solder. With the change to high-silver lead-free solders, which have a strong tendency to oxidize and generate large volumes of dross, phosphorus became a widely used but seldom mentioned ingredient. The solder pot erosion that forced manufacturers to upgrade the materials used in the construction of wave soldering machines is primarily the result of the 100ppm phosphorus commonly included in the formulation of SAC alloys. Now, as solder manufacturers try to distinguish their low- and no-Ag solders from those of those offered by other suppliers, the presence or absence of phosphorus, with or without other antioxidants that have less detrimental side effects, has become a controversial issue. In this paper the authors will report a series of experiments that have been undertaken to determine the effects of phosphorus additions on the behaviour and properties of a widely used lead-free solder.