Study On Brazing Process And Mechanism Of High Silicon Aluminum And Kovar Alloy

As a new type of electronic packaging material,high-silicon aluminum alloy has the advantages of low density,good thermal stability,high specific strength and high specific stiffness,etc.It is expected to replace traditional electronic packaging materials such as Kovar,it has broad application prospects in aerospace,electronic packaging and other fields.In this paper,high-silicon aluminum alloy(CE11)and Kovar alloy(4J29)are used as research objects to develop a new type of solder to achieve the connection between dissimilar materials.Using Al-Si-Cu solder,changing the mix ratio of Si and Cu,analyzing and testing the solder and solder joint,the optimal mix ratio of intermediate solder was Al-7.5Si-23Cu.Add Ni to Al-7.5Si-23Cu intermediate solder,change the Ni content and repeat the above test,and select Al-7.5Si-23Cu-2Ni as the optimal intermediate solder,finally,the element Ti is added to the solder,and the effect of the content of Ti in the solder on the performance of the solder and the soldered joint is explored.It is used for vacuum brazing tests of unnickeled high-silicon aluminum and kovar alloy and nickel-plated high-silicon aluminum and kovar alloy,respectively,to determine the optimal solder and the optimal brazing process.DSC,XRD,SEM,EDS,metallographic microscope,universal testing machine and helium mass leak detector were used to test and analyze the solder,joints and shear fractures.The findings are as follows:Vacuum brazing of unnickeled high-silicon aluminum and Kovar alloys using foil solders with different Ti contents,both the shear strength and airtightness of the joint showed a trend of first increase and then decrease with the increase of Ti content in the solder.When the content of Ti in the solder is 1.0wt%,that is,a solder with a composition of Al-7.5Si-23Cu-2Ni-1Ti is used.Under the optimal soldering process conditions:The brazing temperature is 580°C and the holding time is 30 minutes.The maximum shear strength of the brazed joint obtained is 96.62 MPa,and the leakage rate is the lowest,which is10^-10Pa·m³/s.The shear fracture is located at the high-silicon-aluminum base material,and the fracture form is brittle-tough mixed fracture.The electroless plating process is used to nickel-plat the high-silicon aluminum alloy,and the coating structure is dense and uniform.The thickness of the coating is 8-12?m,which is closely combined with the high-silicon aluminum base material.Vacuum brazing of nickel-plated high-silicon aluminum and kovar alloys using foil solders with different Ti contents,both the shear strength and airtightness of the joint showed a trend of first increase and then decrease with the increase of Ti content in the solder,When the Ti content is 1.5wt%,the joint shear strength and air tightness reach the maximum.At this time,the optimal solder composition is Al-7.5Si-23Cu-2Ni-1.5Ti.Vacuum soldering test of high-silicon aluminum and Kovar alloy using this solder,The best brazing process is:the brazing temperature is 590°C and the holding time is 45 minutes.At this time,the shear strength of the brazed joint obtained is up to 83.54MPa,and the leak rate is the lowest,which is 10^-9Pa·m³/s.At this time,the shear fracture position is at the solder layer,and the fracture form is brittle-ductile mixed fracture.The analysis of the test results found that using the optimal solder,under the best soldering process,the joints obtained by unnickeled high silicon aluminum and kovar alloy and nickel plated high silicon aluminum and kovar alloy can meet the requirements of electronic packaging.This research topic solves the problem of connection between high-silicon aluminum and Kovar alloy dissimilar materials,and can replace high-density Kovar alloy with high density as electronic packaging material,it can greatly reduce the weight of packaging materials and increase the operating radius of aircraft and other devices,which is of great significance to China's national defense.