Variable melting point solders and brazes

摘要

Variable melting point solders and brazes having compositions comprising a metal or metal alloy powder having a low melting point with a metal powder having a higher melting point. Upon heating, in-situ alloying occurs between the low and high melting point powders such that solidification occurs at the solder or braze temperature thus creating a new, higher solidus (or melting) temperature with little or no intermetallic formation. A solder comprising Sn powder mixed with a Sn-Bi eutectic powder having a composition of 63 wt % Sn, 57 wt % Bi such that the bulk composition of the mixture is 3 wt % BS has an initial melting point of 140° C. and a re-melt temperature of 220° C. after heating due to in-situ alloying. A composition of Pb powder mixed with a Pb-Sn eutectic powder having a composition of 62 wt % Sn:58 wt % Pb such that the bulk composition of the mixture is 15 wt % Sn has an initial melting point of 183° C. and a re-melt temperature of 250° C.