Eutectic Solder

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).  

The phase diagram for tin and lead is shown below.

Eutectic Solder


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 183 to 191 °C.  As this alloy is heated it starts to melt at 183 °C, is slushy between 183 °C and 191 °C, and becomes fully liquid at 191 °C. 

There are a variety of common solder alloys used for electronics assembly, but only a few are eutectic solders as shown in the table below.

Eutectic Solder


Eutectic solders tend to have a bright and shiny appearance as compared to non-eutectic solders.  The physical and mechanical properties are also different for each solder alloy.

FCT Assembly sells a wide variety of solder products including eutectic solders in bar, wire and solder paste forms.  Please contact us for more information.