Glass Sealing And Electrode Preparation Process Of Ceramic Capacitive Pressure Sensor Chip

In recent years,with the rapid development of the automotive and microelectronics industries,the application of pressure sensors in the automotive and microelectronics fields has attracted widespread attention.Ceramic capacitive pressure sensors are widely used due to their high accuracy,small temperature drift,strong anti-interference ability,and strong measurement repeatability,especially the advantages of strong impact resistance,overload resistance.The core technology of ceramic capacitive pressure sensors is high-quality sealing of ceramic chips and electrode preparation.In this study,Al₂O₃ ceramic is used as the substrate,borosilicate glass paste is used as solder,and gold is used as electrode preparation material.Wetting research,bonding layer preparation process research and electrode preparation process research have achieved bonding and electrode preparation of ceramic capacitive pressure sensor chips.The wetting interface,glass solder thickness and phase composition were systematically studied by scanning electron microscope?SEM?,energy dispersive spectroscopy?EDS?,laser confocal microscopy?LSCM?,atomic force microscopy?AFM?.Additionally,the microstructure of the gold electrode,the shear strength and fracture behavior of the ceramic glass sealing structure were investigated,and their wetting mechanism was analyzed.The organic solvent and surfactant are added into borate glass powder that is used as the main raw material to form high-performance green adhesive glass paste,which are used as solder.Based on the thermodynamic characterization and particle size analysis,the result shows that the melting temperature of the glass solder is between 500°C and 600°C;the average particle size of the glass powder after ball milling is 1064 nm,which is normally distributed.Wetting experiments were carried out to study the wetting of glass frit with Al₂O₃ ceramic substrate under two atmospheres and multiple temperatures using a high-temperature contact angle measuring instrument.The study found that the contact angle between the glass frit and the ceramic substrate is 15.54°at 580°C under vacuum,which exhibits good wetting properties,and,the contact angle increases with decreasing temperature.The glass powders with different compositions were selected as glass pastes for comparative test.Through the screen printing process,the bonding process of glass pastes on Al₂O₃ ceramic substrate was systematically studied.By adjusting the screen printing process and designing the bonding pattern,the effect of different printing times on the paste forming thickness was investigated.After printing 6 times,the paste forming thickness can reach 21?m.The paste can shrink by nearly 20%due to the long time standing.The bonding properties,thickness of glass bonding layer and interface bonding of glass paste and Al₂O₃ ceramic substrate at different loading pressures and sintering temperatures were tested.The thickness of the glass bonding layer can be controlled at 20±1?m to meet the design requirements.The bonding performance was tested by a shear test.The highest bonding strength can reach 36.38MPa when sintered at 580°C.The electrode design with double capacitor structure can effectively solve the edge effect of capacitor.Au film electrodes with different thicknesses were prepared by two processes of magnetron sputtering and screen printing,and the performance of the electrodes was tested by electrical performance testing and microstructure analysis.For the preparation process of preparing gold electrodes by magnetron sputtering,with the increase of sputtering power and sputtering time,the thickness of the gold conductive film layer increases,and when the film thickness is greater than 30 nm,it can conduct electricity.Under this process condition,the surface roughness of the film layer is inversely proportional to the thickness,and the electrical properties of the Au thin film fail after heat treatment at 600°C.The surface roughness of the Au film prepared by the screen printing process is proportional to the thickness.The Au film printed by 40%gold paste and 200#screen has thin thickness of 1.91?m,and low unit resistance of 1.18?·cm^-1 which cause the good electrical conductivity.A signal detection platform for ceramic capacitive pressure sensors was built,and a simulated gas pressure chamber and a detachable packaging shell for testing were designed.The main body of the package shell is made of metal materials,which has good mechanical strength;the sealing parts use insulating nylon materials to ensure internal sealing and electrical insulation.Combined with the signal conversion circuit board and the signal amplification integrated circuit,the sensor signal acquisition and processing functions are initially realized.