Abstract: The three types of Cu-P based brazing alloys with macrosegregation, fusion impurities or imperfect microstructures were prepared by controlling processing parameters, to research the influence of microstructure defects of on the characters of solders and welding quality, research influence of microstructure defects of Cu-P based brazing alloys to characters and enrich the assessment methods of material factors affecting welding quality. Optical microscope (OM), different scanning calorimetry (DSC), microhardness tests were used to study the influence of different defect levels on properties of brazing filler metals. The liquidus temperature and the crystallization temperature range of samples reduce with the reduction of defect level under the same defect type. The microhardness of copper-rich location is lower than normal location in macrosegregation samples of extrusion condition. The size of the microstructure has no effect on the porosity, but slag inclusion and segregation cause the bigger porosity, and the porosity decreases with the decrease of the defect degree of the solder sample.

Key words: Cu-P based brazing alloy, Microstructure defects, Macrosegregation, Fusion impurity, Imperfect microstrueture, Fusing temperature, Hardness, Weld porosity/slag inclusion