Preparation And Properties Of Silver@Tin Core-shell Structure Powder For Power Device

With the development of electronic products towards high-integration and miniaturization,the current density of the chips in electronic produ cts is getting higher and higher.As a result,the heat generated during the operation of the chip is also growing,and the service temperature of the chip increased significantly.A chip made of a conventional semiconductor material Si can not stably oper ate at temperatures higher than 150 ?.However,the Si C material can overcome the disadvantage of low service temperature,and can be stably operate at temperatures up to 600 ?.Therefore,Si C has attracted increased attention as the next generation of semiconductor materials.Unfortunately there are few bond material that can be used to connect chips which are made from this semiconductor material.The goal of this project is to study and develop a new connecting material for connecting the Si C chip and the substrate,so that the Si C chip can give full play to its ability to operate stably at high temperature.The Ag@Sn core-shell structure was used as the material for the interconnection of high-power device chips,and the Ag@Sn core-shell structure was obtained by electroless plating method.The influence of Sn2+ concentration,complexing agent concentration,reaction temperature,p H value and plating times on the thickness of silver coating was studied.It was found that the reaction temperature and p H had the greatest influence on the deposition of Sn layer on the surface of silver spheres,and the electroless tin plating process on the surface of silver spheres was also determined.Ag@Sn bimetallic powders which were obtained by optimized electroless tinning process can meet subsequent welding requirements.It was found that Ag reacts with Sn to form Ag3 Sn,its volume shrinks.Ag@Sn bimetallic powders which was obtained by electroless tinning was pressed into preform and reflowed.The reflow process parameters were determined and the influence of the thickness of the coating on the surface of silver ball was studied.The results show that the thermal conductivity of the preform is 5.84 ??·cm,and the thermal conductivity of the preform at 30 ?,150 ? and 300 ? are 228.7 W/m·k-1,221.8 W/m·k-1 and 186.9 W/m·k-1,respectively.The coefficient of the preform is 18.47 ppm/?.The shear strength of the weld seam at 400 ? is 27.8 MPa which is higher than Ag-Sn-Ag TLP at 400 ?.The fracture of the weld seam mainly occurs at the interface of Ag3 Sn grains,and some tear along the inside of the silver ball.