Growth Rule Of Intermetallic Compound In Sn AgCu/Cu Brazed Joint Without Flux

With the rapid development of science and technology,the use of electronic products become more widely.People have a higher demand on the performance and service life of electronic products.And the packaging process have a direct impact on the life of electronic products.For most of the packaging process,flux is used to ensure that the solder is not oxidized during the package,thus ensuring the quality of the solder joint.However,there are a number of special optoelectronic devices,such as semiconductor lasers,residual flux have a serious impact on such optoelectronic devices,and even lead to device failure.In this paper,the microstructure and shear strength of the SnAgCu/Cu joints without the use of flux in aging state were studied.The results show that under vacuum / nitrogen / formic acid conditions without flux can prevent the generation of oxides and make the SnAgCu solder in good contact with the Cu substrate.With the extension of aging time,IMC layer gradually grow and thicken.It was observed that the growth rate of compound particles was faster at 150 ? for 72 h,but then the growth rate grew slowly,and the microstructure of the IMC layer gradually becomes flattened by the sharp,even into one.The shear strength of SnAgCu / Cu brazing joint without the use of flux under different conditions of time was studied.It was found that the shear strength of SnAgCu / Cu joint was slightly increased with the extension of aging time,and then began to have a sharp decline.Through the scanning electron microscopy of the cross section,it was found that there were many fine dimples and burrs in the shear section without aging after welding,showing typical ductile fracture.With the extension of the aging time,the smooth fracture surface gradually appears,and the area is getting bigger and bigger,indicating that the fracture properties gradually transition to the brittle fracture.The cracking location transits from the interior of the solder to the IMC layer.Compared with the micro-morphology and shear strength curves using flux under the same conditions,it was found that both IMC particles have an increasing trend.However,under the condition of no flux,compound particles are relatively flatand coarse at the beginning of formation,and the shear strength is also slightly smaller.In the aging process,the solder joint without the use of flux appeared earlier in the case of a decrease in shear strength.