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The materials used in the hydrogen/oxygen catalytic combustion heat exchanger are gradually developed to the high strength and high conductivity copper alloy, and the brazing of the fins and separators of the heat exchanger is important to the thermal efficiency, service safety and reliability of the heat exchanger.The brazing of Cu-3Ag-0.5Zr alloy fins and baffles is studied in this paper.A Cu-3Ag-0.5Zr alloy was brazed at 840 ℃-900 ℃ brazing temperature for 5 min-20 min using 37.5Ag-48.8Cu-5.5Zn-8.2Mn braze filler that hadbeen produced into differern thickness.Solid-liquid interface morphology of the brazing joint at the insulation stage quenched by water was studied,which pointed that brazing joint structure has experienced the dissolution of the base material into the brazing filler metal area, the isothermal solidification of the Cu-rich phase, and the cooling and solidificationthree stages.Structures of the joints and shear fracture of joints were studied by scanning electron microscope(SEM) and energy dispersive spectrometers(EDS),which proved three kind of microstructures exist in joints which included Ag-rich phase distributing in a network between the base metal and the Cu-rich phase, AgCu eutectic structure in joint gap, and the filler zone structure consisted of AgCu eutectic and copper-rich phase constitute.And integrating these kinds of microstructures with shear strength datas of joints showed that CuZr in the brazing joint structure relatively weakens the joint shear strength,meanwhile Mn element strengthens the joint shear performance.shear strength of joint was effected in the way that brazing temperature,holding time and filler thickness control CuZr forming and Mn concentration in filler area of joints.The maximum shear strength value,308.29 MPa, was got at 100μm filler thickness,840℃ brazing temperature and 5 min holding time condition.