边缘电场传感器测量金属衬底绝缘层厚度

Measurement of Insulation Thickness on Metal Substrate Employing Fringing Field Capacitance Sensor

针对金属衬底上的绝缘层厚度测量的需求,研究了一种基于边缘电场传感器测量方法。位于同一平面的传感电极形成边缘场电容,边缘电场穿透绝缘层后在衬底表面发生突变。用三电容模型分析了传感器的测量原理,衬底作为一个浮动电极分别与两个传感器电极构成平行极板电容,与边缘场电容共同构成传感电容。通过Ansoft Maxwell软件进行二维有限元仿真,讨论了电容结构参数对传感电容的影响。实验结果表明,当边缘场电容传感器应用于金属衬底上的绝缘层测量时,表现出边缘场电容与平行板电容复合的特性,而且传感器灵敏度高。当绝缘层厚度相比电极长度较小时,电极的间距对传感器电容输出影响小。

Aiming at the requirement of insulation thickness measurement on metal substrates,a measurement method based on edge electric field sensors is investigated. When the substrate of insulation layer is a metal or other conductive material,the fringing field produces mutation for penetrating the insulation layer,which results in the distortion of fringing field capacitance. A capacitance model is presented to analyze the sensing capacitance. The substrate is described as a floating electrode and the sensing capacitor is divided to two parallel plate capacitors and a fringing field capacitor. Two-dimensional finite element simulations were performed using Ansoft Maxwell software to discuss the effects of capacitive structure parameters on the sensing capacitance. Experimental results show that when the fringe field capacitance sensor is applied to the measurement of the insulating layer on the metal substrate,the characteristics of the fringe field capacitance and the parallel plate capacitance are exhibited,meanwhile it has high sensor sensitivity. When the insulating layer thickness is smaller than the electrode length,the electrode spacing has little effect on the sensor capacitance output.