Polar Organic Sensitive Film With Hydrophilic In QCM Humidity Sensor System

QCM humidity sensor uses moisture-sensitive film on quartz crystal surface as sensitive element to detect humidity.QCM sensor is a new type of measurement technology as a research hotspot in the field of sensor.It has fast response and high sensitivity.So it is widely used in the field of Aerospace and medical.The research group has long been engaged in electronic packaging materials.They have well hydrophilic properties when the quality of the two composite films were 4: 1 and 7: 2 about the polyimide(PI)and epoxy resin(EP)or phenolic resin(PF)and epoxy resin.This research uses PI / EP and PF / EP composite film as a sensitive film,combined QCM technology,FPGA platform,designs and develops a humidity sensor detection system that can quickly and stably measure environment humidity.First,builds the QCM oscillation circuit.The oscillation circuit is determined by ordinary oscillation.Using a comparator chip(MAX913)for output stage circuit design to achieve a stable square-wave signal within ± 2Hz of Frequency change.Secondly,designs hardware and software of FPGA platform.Builds the whole circuit FPGA platform(including frequency detection module,data communication module and a digital display module)by EP2C5T144 chip.Achieves and test function of each module by Verilog,modelsim and serial debugging tools.Infrared spectroscopy showed,PI / EP composite film hydroxyl(-OH)peak ratio PF / EP is strong,so PI / EP composite membrane is preferably hydrophilic by wetting angle experiments further prove this point.Therefore,the experiment mainly use PI / EP composite film as sensitive material.And studies the production process of sensitive probes.Identifies the dispensing method combined with rejection device.Finally,tests the developed humidity sensor detection system performance.Experiments using five kinds of saturated salt solution(LiCl-11%RH,MgCl-34% RH,K2CO3-43%RH,NaCl-76%RH,KCl-87%RH)as the humidity generating devices.The results shows that the sensitivity of the humidity detection system is 23Hz/RH%,adsorption time is 20 s,desorption time is about 25 s,and meets the expectations of humidity sensor test system.