Research On Eddy Current Sensor Probe Based On MEMS Technology

Eddy current testing technology is one of the important nondestructive testing technologies.The probe is the key element of the eddy current sensor.The planar spiral coil has the advantages of good consistency,high detection accuracy,and good environmental applicability.It has been widely used in eddy current sensor probes.With the increase in testing requirements,the miniaturization,precision,array and flexibility of detection coils have become the development direction of eddy current sensor probes.Based on MEMS technology,this article provides a new method for the design and production of eddy current probes.The main research contents of this paper are as follows:(1)Analyze the relationship between the impedance change of the detection coil and the coupling coefficient in eddy current testing,and study the direct influence of electrical parameters on the performance of the sensor.First,the measurement principle of eddy current detection is explained,and the method of coil impedance analysis is studied.According to the equivalent eddy current loop theory,the change of the equivalent inductance is used to respond to the change of the coupling coefficient,and the factors that affect the detection performance of the detection coil are analyzed.Through the finite element analysis method,the relationship between the structural parameters,electrical parameters and sensor performance of the probe is studied,and it is found that the greater the inductance of the induction coil per unit area,the better the sensor's sensitivity and measurement range performance.(2)Establish a physical model of the probe to realize rapid extraction of electrical parameters,and study the influence of probe structure parameters on electrical parameters.Using the equivalent circuit of the eddy current sensor probe,the calculation method of the electrical parameters of the probe detection coil is studied,and the detection coil is modeled and designed by Matlab software to realize the rapid extraction of the electrical parameters of the probe,which plays a guiding role in the preliminary design of the probe.The calculated electrical parameters obtained by the Matlab model are consistent with the simulation results.The model is used to analyze the influence of the probe structure parameters on the inductance,resistance,quality factor Q value and self-resonant frequency.In the design of the eddy current sensor,according to the actual performance requirements of the probe,according to this model,the preliminary determination of the structural parameters in the probe design can be realized,the design efficiency can be improved,and a new idea for the design of the probe can be provided.(3)Use MEMS technology to complete the production of rigid probes and flexible probes and conduct impedance testing.The thick glue process,electroforming process and seed layer process are analyzed,and a manufacturing method of eddy current sensor probe based on MEMS technology is proposed.Research on the dimensional accuracy of AZ50 XT photoresist,improve the uniformity of the film by optimizing the homogenization process and polishing process,and use multiple exposure and development processes to produce a positive film with a thickness of more than 50 ?m,and the structure is in the channel There is no residual glue,and the side wall has good steepness.Research on the micro-electroforming process,optimize the process parameters,configure the required electroforming liquid,and reduce the open circuit phenomenon.The base seed layer chooses Cr/Cu as the sputtering layer,the thickness is 20 nm and 50 nm,respectively,which has good bonding force and is easy to remove.On the basis of the research of the preparation process,a reasonable process flow is designed to produce a rigid probe and a flexible probe with a multilayer structure.Using impedance analyzer to test the probe,the inductance value reached 14 ?H,and the resistance value was only 14 ? and 17 ?.