Soldering Lead

The words eutectic solder describe a solder alloy that melts and freezes at one single temperature.  A good example of this is Tin 63% / Lead 37% solder which melts and freezes at 183 °C.  This melting point is much lower than the melting points of either pure metal which are 232 °C (tin) and 327 °C (lead).  If the concentration of tin and lead is shifted away from Sn63/Pb37 then the melting point becomes a melting range.For example, Sn 60% / Pb 40% melts in the range of 90 to 120 °C.  As this alloy is heated it starts to melt at 90 °C, is slushy between 90 °C and 120 °C, and becomes fully liquid at 120 °C. Eutectic solders tend to have a bright, shiny appearance while non-eutectic solders tend to have a dull, grainy appearance.