Interfacial microstructure of Al/Al and Cu/Al thin tubes by high frequency induction soldering

The interfacial microstructure of the solder joints between Al /Al and Cu /Al thin tubes were studied by high frequency induction soldering.Three kinds of Zn-Al system flux-cored wire,E02NC,SUPER5A,and E22NC were used in this research.The results showed that the microstructure of the three kinds of soldering interface was mainly composed of Zn(Al) solid solution in Al / Al solder joint.Defects such as air holes were investigated at the interface of the solder joints soldered by E02NC and E22NC solder wires.In Cu / Al solder joints,however,the compositions of the interfacial microstructures were Zn(Al) solid solution,Zn-Cu intermetallic compound,and Cu-Zn-Al intermetallic compound when the solder wire used was E02NC.There were air holes and a lot of intermetallic compounds at the interface in this kind of solder joint.Meanwhile,the compositions of the interfacial microstructures were Zn(Al) solid solution and Cu-Al intermetallic compound using SUPER5A solder wire.In this kind of solder joint,less intermetallic compounds and soldering defects were observed at the soldering interface than the solder joints using E02NC solder wire.The wettability of E22NC solder wire was poor on Cu and was not suggested in the high frequency induction soldering between Cu / Al thin tubes.