Preforms are available in all silver solders as washers, pressed blanks or more commonly rings. They offer distinct advantages over manual brazing with rod.
Rings can often increase production rates as once the components have been assembled heating can be carried out using a variety of brazing machines. Production rate is governed purely by the assembly time.
A preform allows the brazing alloy to be fitted internally within a joint. The alloy melts and is drawn to the outside. The presence of a visual ''witness'' is a quick and easy guide to ensuring that a sound brazed joint has been made.
A ring is a very convenient method to meter the amount of brazing material used in a joint. Cost control is simplified.