An alloy used to join metal surfaces. A soft solder melts at a temperature in the range 200–300°C and consists of a tin-lead alloy. The tin content varies between 80% for the lower end of the melting range and 31% for the higher end. Hard solders contain substantial quantities of silver in the alloy. Brazing solders are usually alloys of copper and zinc, which melt at over 800°C.