Copper Phosphorus Brazing Filler Alloys with Low Melting Temperature (Report I) : Effect of Tin Addition

概要

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A new copper phosphorus self-fluxing filler alloy applicable to brazing at 650℃ has been developed by the addition of tin to Cu-Ag-P alloy. The influence of tin, phosphorus and silver content on the brazability at 650℃ has been investigated by evaluating the penetration length of filler alloy between two copper plates of 0.1mm lap joint clearance. Differential thermal analysis and metallographic observation were also carried out to define the temperature ranges of melting and the phase changes. Whthin the range of this investigation, the availabe filler alloy composition was found to be Ag/Cu (15/65)-15%Sn-(3〜3.5)%P. The solidus and liquidus temperatures of the alloys were about 475℃ and 620〜650℃, respectively. The alloys of more than 3.5%P content having primary Cu_3P phase showed poor penetration length because phosphorus content in coexisting liquid decreased due to the formation of Cu_3P. On the other hand, the alloys of less than 3.5%P content crystallized primary α-Cu phase, and then the coexisting liquid contained more phosphorus than the nominal concentration. Accordingly, the alloys exhibited excellent fluxing action.
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