Research On The Key Techniques Of Passive MEMS Pressure Switch

Small,lightweight,low-power MEMS pressure switches offer a good development prospect for small,ultra-long,simple atmosphere environments.In order to realize MEMS pressure switch,it is necessary to solve a series of key technologies such as switch structure design,thermal robust optimization and composite substrate packaging.The main work of this paper is as follows:(1)Combined with the contact pressure sensor and the characteristics of physical switches,the design scheme of silicon micro-film pressure switch is put forward.Based on the theory of electrical contact and the theory of diaphragm deformation,the material/size of metal electrode and the thickness/area of diaphragm are analyzed.The finite element simulation software is used to simulate the switch.The influence of the length and height of the silicon island,also the length of the silicon film on the deflection of the silicon film are studied,and the size parameters of the pressure sensitive structure and the encapsulated bonding structure are optimized.Design the switch size 8mm×1Omm,diaphragm thickness 50?m,pressure threshold 90kPa,Electrode thickness of 1?m,the theoretical total resistance of 1OOm?.(2)The finite element simulation software is used to analyze the thermal behavior of the pressure switch,and the deformation law of the pressure switch diaphragm under different temperature is analyzed.The thermal stress release effect is studied from the stress release tank,the structure of fixed form and the thickness of the substrate,respectively.Finally,the design of the glass substrate thickness of 2.5mm is used to ensure that the structure is in extreme usage temperature(80?),the maximum equivalent stress value is reduced to a quarter of the original stress,only 154.13MPa.(3)In view of the requirement of metal/glass/silicon multi-substrate sealing in silicon micro-film pressure switch,this paper proposes a MEMS pressure switch packaged with glass frit bonding technology,which has good interface compatibility.Based on the structural features and glass frit bonding technology,the MEMS switch structure is designed and fabricated,placing emphasis on the high precision pressure film wet etching process,large thickness patterned metal electrode deposition process and composite base glass frit bonding process.Finally,pressure switches with the film thickness of 50.1?m,the package strength of 12.52MPa are prepared.The electronic parameters of the pressure switch prepared includes threshold pressure of 125kPa,operating voltage of 3.5V and operating current of 446mA.