The Study On Structural Transition And Diffusing Behaviour Of Amorphous Cu-P Filler Metals

In this paper, the crystalline filler metal and the amorphous filler metal of Cu68.5Ni15.7P6.5Sn9.3(wt%) which have the same compositions are used, Many modern test aids such as X-ray diffraction,differential thermal analysis,electronic probe and so on were adopted to analysis the phase transition process during the different braze welding. Then the establishment mechanistic diffraction of the brazing copper joint with the brazing ribbons and the as-cast filler metal was discussed based on the element diffuse,liquid action and the changes of brazing seam thickness and diffusion layer thickness which caused by the brazing temperature. The influential factors to the brazing seam performance and the establishment of brazing welding remainder were analysised ,too.The research result indicated that the phases of both the brazing fillers were changed, during the process of temperature coming-up. At the process of pre-acting to the parent metal, the elements of Sn,P and Ni in the eutectic composition of both the brazing fillers were came into being segregation and gathering ,then the metastable phases of Cu₈₁Sn₂₂ and Ni₁₂P₅ was formed. In this action process, the amorphous fillers gave priority to bring new phases, while the crystalline filler gave priority to gather and grow on the old phases. After the reaction of the fillers and the parent metal, the metastable phase Cu₈₁Sn₂₂ began to resolve into the solid solution Cu_13.7Sn, while the metastable phase Ni₁₂P₅ transited to asleep phase Ni₂P. Ahead of reaching to the solidus curve, both of the fillers had occured obvious phenomenon of element diffusion, and the diffusion layers were formed. Under the same temperature, the element in the amorphous filler diffused faster than the crystalline filler, and the diffusion layers of the amorphous filler were more thick than the crystalline filler. With the hoist of temperature, both the fillers reached to the solidus curve and the liquid was brought in both the brazing seams. The soldering residue layers are composed of Cu₃P and Ni₂P. Increasing the brazing temperature and rosing the hoding time all will decrease amount of the soldering residue layers.Sn diffusion profile comparely accord with testing actually result of EPMA by constituting Sn diffusion model during temperature rise period ahead of reaching to the solidus curve and counting diffusion coefficient both two filler metals.