Bismuth as an alloyed component of solder has a function similar to that of lead. It lowers the melting temperature of the alloy and improves the flow characteristics of the solder. The melting point of eutectic Nib alloy lies at 138°C. Lead contained in an alloy also containing bismuth will lead to the formation of a ternary eutectic with a melting point of 96°C. Bismuth has the rare characteristic that it expands during the phase transition from liquid to solid, i.e. during solidification. For this reason, soft solder alloys containing bismuth can cause a safety risk for solder crucibles. There is a risk of the crucible weld seams cracking due to the pressure of the solder expansion during cooling.