Research And Design Of Packaging Structure Of High Temperature Pressure Sensor

The oil-filled diaphragm isolation package structure is often adopted for most of the pressure sensors to transmit the measured pressure and protect the sensitive resistance circuit with oil.However,this oily medium has poor resistance to high temperatures and takes up a lot of space when packaged,which greatly reduces the practicality of future development.The core problem of high-temperature pressure sensors is the packaging problem.Improving the packaging structure of the sensor has become a major problem to be solved urgently.Aiming at the lack of existing domestic technology and drawing on foreign excellent products,two new high-temperature pressure sensor packaging structures,leadless packaging structure and all-solid-state packaging structure,were designed.The reverse pressure flip-chip structure is adopted for the leadless packaging structure,and the electrostatic sealing technology is used to bond the front of the sensitive chip with the glass protective cover to form a vacuum cavity to isolate the sensitive resistance circuit.The glass is preset with a through hole at the metal electrode of the sensitive chip,and the isolation base is made by high temperature matching sintering process.The conductive pin is directly connected to the metal electrode of the sensitive chip with low resistance by high temperature conductive melting process to complete leadless packaging.The all-solid-state packaging structure adopts the form of reverse pressure and adopts static electricity.The sealing technology bonds the bottom of the sensitive chip with the glass base and the pressure tube of Kovar alloy material in sequence.The pressure port is reserved at the corresponding position of the glass and Kovar alloy.Wire bonding technology through soft wire to press the sensitive chips metal electrodes and guide tube connected,complete all-solid-state packaging.The two structures not only protect the sensitive resistance circuit,but also solve the problem that the traditional packaging structure fails at high temperature.Analyze the key processes involved in the packaging of the two structures,select materials with appropriate parameters,and use finite element analysis to optimize the design of the two structural parameters.Due to the different coefficients of thermal expansion between different materials,residual stress and deformation will be generated during high-temperature operation.The results of finite element analysis show that the thermal stress and thermal deformation increase with the increase of temperature,and at the same temperature,the height of the glass has the greatest influence on the thermal stress.The thickness of the glass can be adjusted to achieve a zero stress state or low stress state on the surface of the sensitive chip.The thickness of the glass is designed to be 1.7 ? 2.3 times of the sensitive chip thickness.Based on the Sensor National Engineering Research Center of Shenyang Instrument Research Institute,high-temperature testing of pressure sensors with all-solid-state packaging structure was carried out.The experimental results show that at a high temperature of 300? and a pressure range of 0 ? 0.6MPa,the sensor sensitivity is 200 m V/(m A·MPa),the nonlinearity is less than 0.59‰F·S,the repeatability is better than 0.04‰F·S,and the hysteresis is 0.03‰F·S.When the temperature is between-45 and 400?,the sensitivity temperature drift is less than-0.133 m V/(MPa·?).The experimental results are basically the same as the simulation results.The all-solid-state packaged pressure sensor can work reliably at a high temperature of 0 ? 300?,and its sensitivity remains stable in a wide temperature range.