Abstract: For Ni/(20 μm)The microstructure evolution of interfacial intermetallic compound(IMC)Ni3Sn4 and its effect on the mechanical properties of Sn/Ni micro solder joints were studied, and the tensile fracture was analyzed.The results showed that with the increase of reflux time, the thickness of Ni3Sn4 IMC increased rapidly, and its morphology also changed significantly, from short rod to long rod, and finally to block.The tensile strength of micro solder joints showed an abnormal trend of decreasing first and then increasing continuously.The micro morphology of interface Ni3Sn4 had evolved into the dominant factor.The transformation of long rod Ni3Sn4 caused stress concentration and reduced the strength of micro solder joints.The continuous transformation of massive Ni3Sn4 increased the crack resistance and improved the tensile strength.The fracture morphology of micro solder joints further confirmed the influence of Ni3Sn4 micro morphology evolution on the mechanical properties of micro solder joints.Highlights: Taking Ni/Sn/Ni micro solder joints with 20 μm interconnection height as the research object, a method was developed to achieve micro solder joints’ growth with Ni3Sn4 IMC as the only variable by controlling and extending the reflow time.The influence of microstructure evolution of Ni3Sn4 IMC on tensile strength of micro solder joints was studied.