Preparation Of CuP Amorphous Solder And Investigation Of Its Brazing Performance

The CuP based filler metal is widely used in the connection of copper and copper alloys and its price is not high. Copper with phosphorus can greatly lower the melting point of copper and phosphorus plays the role of self-fluxing in brazing alloy as well as improves the wettability of solder on copper. Although processing forming is difficult for CuP based filler metals and the wettability of CuP based filler metals on ferrous metals is poor, which greatly limits the development of CuP based filler metals. Based on the optimization of alloy composition, six different composition of CuP based solder alloy were designed in this paper. Pure metals were melted into solders alloy in vacuum furnace and the solders were processed into amorphous strips solders by the sling with single roller to solve the problem of processing forming. Amorphous solders strip and as-cast solders as well as commercial solders were compared in the paper and the melting characteristics were tested by using DSC, to study the melting temperature and melting range, at the same time to analyze contrastively the influence of different elements on the formation of amorphous solders. Brazing and wetting experiments were made in the vacuum furnace to compare the wettability by using the spreading area after wetting. A variety of modern testing methods were used to compare the properties of based filler metals and brazing joints.The test results show that the amorphous strips made from the five kinds of Cu-P based solders with Cu70.6P14Ni11Sn4Si0.4, Cu72.6P14Ni9Sn4Si0.4, Cu_68.6P₁₄Ni₁₃Sn₄Si_0.4, Cu_71.6P₁4Ni₁₁Sn₃Si_0.4 and Cu69.6P14Ni11Sn5Si0.4 have smooth surface, uniform thickness, good flexibility. The melting temperature of Cu-P based amorphous solders are lower and the melting range is narrower than that of as-cast solders. Alloy elements like Ni and Sn can make solders obtain a narrower melting temperature range. Under the same condition of brazing technology, the wettability of amorphous solders are better than that of as-cast solders. The wettability of solders are greatly influenced by different brazing temperature and holding time. With the improving of brazing temperature and extension of brazing time, the wettability of Cu-P based solders appear a trend of decreasing after increasing.The joints of commercial solders have formed a good metallurgical combination and the base metal and the defect of brazing seam is less. Brazing seam is consisted of three regions that are diffusion zone, interfacial area and brazing seam center. The brazing seam center of the market solder HL201 is mainly composed of Cu-P compounds and ?-Cu solid solution,the brazing seam center of commercial solders HL205 and HL204 is mainly composed of ?-Cu solid solution,Cu-P compounds and a small mount of Ag. The good metallurgical combination that is formed of amorphous solders brazing joints, and can be divided into diffusion area, interfacial area and brazing seam center. The diffusion zone and interfacial area are made up of ?-Cu solid solution, while the compositions of the brazing seam center are ?-Cu solid solution, Cu3 P compounds and Ni3 P compounds. Hardness distribution of welded joint is a certain rule that the hardness of parent metal is minimum, the hardness of interfacial area is second, but the hardness of brazing seam center region is uneven distribution with solid solution hardness smaller and some phase hardness larger. Although the shear strength of the amorphous solder is weaker than that of commercial solders, it also can satisfy the ordinary use. With the extension of the holding time and the rising of brazing temperature, the shear strength of the amorphous brazing joints decrease after rising.