Design And Fabrication Of A Suspended Structure Nickel Chromium Alloy Thin Film Strain Sensor

Thin film sensors have been widely used in various intelligent manufacturing industries.In order to effectively monitor the processing status in the intelligent manufacturing process,high-precision and highly reliable strain thin film sensors are used to monitor the force conditions of cutting tools,providing data support for cutting fault prediction,tool life research,and cutting parameter optimization.The sensitivity and durability of strain thin film sensors are two important indicators for evaluating their performance.Aiming at the performance of strain thin film sensors used for cutting force measurement during machining,a novel suspension structure nickel chromium alloy thin film strain sensor is proposed in this paper.Through the combination of theoretical analysis,preparation,and characterization experimental research of nickel chromium alloy micro beams,relevant technologies have been thoroughly studied,Finding that suspension structures can effectively improve the performance of strain film sensors has very important theoretical significance and application value.In this paper,a nickel chromium alloy thin film strain sensor with suspension structure was designed based on improving the microstructure of the thin film.The advantages of suspension structure were explained at both macro and micro scales;Based on the modified couple stress theory,a theoretical model of a nickel chromium alloy micro beam was established,and the dynamic equations of the micro beam were obtained.The size effects of the deflection,stiffness,and electrical resistance change rate of the nickel chromium alloy micro beam were analyzed;Based on the variation of microstructure mechanical properties and characteristic dimensions,theoretical models and conclusions are applied to guide the structure and size design of suspended structure nickel chromium alloy thin film strain sensors.Based on the structure and size of the suspension cavity,a process flow for fabricating a suspension structure nickel chromium alloy thin film strain sensor was designed;To achieve layered nanostructures,the elastomer transition layer composite film was first prepared,and the micro morphology of the transition layer titanium nitride film was observed using atomic force microscopy(AFM)under selected parameters;Then,an insulating layer sacrificial layer composite film was prepared,in which the process of sacrificial layer tin film was explored and optimized.The microscopic morphology of tin film under different sputtering powers was observed using scanning electron microscopy(SEM),and the optimal sputtering rate of tin film was obtained when the sputtering power was 100 w and the argon flow rate was 70 sccm.The composite film layer was observed using confocal microscopy(LSCM)and analyzed by energy dispersive spectroscopy(EDS);Finally,using photolithography and IBE ion beam etching process to prepare Ni-Cr alloy thin film resistance gates,and observing them with a super depth of field microscope,it was found that the obtained resistance gates had regular boundaries and high etching accuracy.To solve the problem of sacrificial layer removal,a method of vacuum high-temperature removal using magnetron sputtering equipment was proposed to obtain a suspended structure nickel chromium alloy thin film strain sensor.Ultradepth of field,confocal microscopy(LSCM),and atomic force microscopy(AFM)were used to observe the microstructure after the removal of the sacrificial layer thin film.It was found that the surface color of each film layer changed,with different degrees of cracks appearing,and the film surface roughness was large;A semi quantitative analysis of the surface of a suspended structure nickel chromium alloy thin film strain sensor was conducted using X-ray photoelectron spectroscopy(XPS)testing to obtain seven elements and their contents on the surface.Finally,the electrical performance of the suspension structure nickel chromium alloy thin film strain sensor was tested and characterized.Using nanoindentation testing,the optimal elastic modulus of the sensor is(E)105.71 GPa,the nanohardness is(H)8.68 GPa,and the strength is(H ~3/E ~2)58.25 MPa.Analysis of the stiffness,nanohardness,and strength of the surface sensor is excellent;Establish a testing platform to preliminarily test the resistance strain coefficient of the suspended Ni-Cr alloy thin film strain sensor,and the linear error of the load voltage relationship curve obtained by fitting is very small;The results show that the electrical performance of the suspended structure nickel chromium alloy thin film strain sensor is consistent with the analysis of the theoretical model,and the preliminary research results of the suspended structure nickel chromium alloy thin film strain sensor have achieved the expected results.