Soldering terminology

Also called solubility line. In an alloy of several substances, precipitation of solids takes place at a certain temperature below the solidus line. The solvus line or area represents the composition of these phases that are in equilibrium with each other as a function of temperature and pressure within the phase diagram. In a binary system, at constant pressure, a curve points on to a surface in a ternary system. If the solvus and solidus lines do not intersect, there is a temperature and pressure area where the system forms a stable, continuous solid solution. Otherwise only partially solid solutions arise. In the solder alloy (Sn-Pb system), tin is separated from the lead solution along the solvus line, below the eutectic temperature.