Research On Hot Indium Sealing Equipment And Process For Metal Shell Of Precision Device

Metal shells are often used in the packaging of precision devices to provide support and protection for devices.Because of its low melting point,great ductility and wettability,stable performance,indium materials are widely used in vacuum gas sealing between non-matched or non-high temperature resistant materials.Leakage at the indium seal of metal shell is one of the direct reasons for the failure of precision devices.Therefore,it is very important to study the indium seal technology for improving the sealing performance and sealing strength of the cavity.To ensure the airtightness and reliability of the metal seals for precision devices package and realize the non-destructive repairing of the sealing parts,this paper optimizes the sealing process of the shell for precision devices package and develops the automatic shell sealing equipment and the disassembly experimental device for the indium sealing parts.Based on the theory of atomic diffusion,the relationship between the sealing effect and sealing temperature,sealing pressure and holding time is analyzed.Software ANSYS Workbench is used to simulate the changing trend of dynamic temperature field of different devices inside the cavity and the deformation of indium ring during the sealing process.The influence of sealing temperature and pressure on sealing quality is obtained,so that the quality of sealing joint can be improved by optimizing the sealing process parameters.The simulation results show that the shell seals with better airtightness and reliability can be obtained by properly increasing the applied temperature of the upper heating device,decreasing the applied temperature of the lower heating device and increasing the sealing pressure.An automatic shell sealing equipment with temperature and pressure control system is developed.Based on the idea of modular design,shell sealing equipment can be divided into hot pressing device,positioning device,leveling device,control system and other parts.In addition to the closed frame for pressure and displacement control and guide structure,the hot pressing device also includes upper and lower heating devices to realize closed-loop control of sealing temperature and pressure.The positioning device and leveling device are used to ensure the assembly accuracy of the shell.The equipment automatically controls the pressing process by industrial computer,and collects the data of temperature,pressure and displacement during the pressing process to realize the precise control.According to the simulation results and practical experience,a group of sealing parameters are set up to seal the shell.The results show that the sealability and strength of shell seals are excellent and they can meet the sealing requirements.An experimental device for shell disassembly which can automatically separate the shell is developed.The shell disassembly device uses induction heating method to melt the sealing indium,mainly composed of linear guide rail,pneumatic gripper,Z-direction displacement platform and tension spring.The experimental results of shell disassembly show that the device can separate the upper shell and base plate without affecting the precision devices in the cavity,and realize the non-destructive repairing or maintenance of the shell for precision devices package.At present,the metal shell sealing equipment developed in this paper has been put into practical production.Using the optimized process curve to package the precision devices,the assembly precision of metal seals is higher,the air tightness,strength and consistency are great.Therefore,the production efficiency and product quality of the indium seals can be improved.The experimental device for shell disassembly can separate the shell stably and quickly,which lays a foundation for the realization of automatic shell disassembly.