High Sensitivity Film Electrical Resistance Sensors For Atmospheric Corrosion Monitoring

As the industries of information, Internet and communication are developing rapidly computing center or cloud service system computer room, as the information hub, has be come the basis of today's social information exchange. With increasingly high intensity of the integrated circuits inside the precision electronic devices, traces of metal corrosion between the pins of the PCB boards or chips can cause short or broken circuit, resulting in data engine paralysis, and enormous economic losses. In order to guarantee high stability and high availability, in the long course of the operation and maintenance of the computer room, environmental parameters such as temperature, humidity, corrosive gas and PCB board and corrosion condition of Cu, Ag, Sn need to be monitored in a long term. In addition,to ensure the reliability of sealed electromechanical equipment or weapons during the process of stocking and transportation, an online monitoring equipment is urgently needed to detect or diagnose the corrosiveness of the metal inside the sealed box. To answer the demand for high-sensitivity corrosion monitoring on industrial equipment and computer rooms, this thesis is introducing an invented compact air corrosion monitoring device of high sensitivity, which is of great significance for improving the reliability of the operation and maintenance of the equipment.This thesis takes the typical metal vapor corrosion monitoring in the atmosphere as the background, uses the thin-film resistance probe as corrosion sensor to achieve the high-sensitivity atmospheric corrosion monitoring. In the thesis, the method of electrochemical deposition is applied to make PCB board being coated with a film of Fe, Cu or Sn of 5¹0mm in thickness. By measuring the resistance increase resulting from metal film's thinning, the corrosion amount and corrosion rate can be calculated. The method of micro resistance measuring based on alternating current is also applied to eliminate the contact potential and the Thomson potential between dissimilar metals such as Cu/Fe or Cu/Sn, thus improving the resistance measurement accuracy. In this thesis, a small-sized, cost-effective compact measuring system using ADu CM360 32-bit microprocessor is built to precisely measure the thinning rate of the thin film resistor, while achieving the monitoring of the environmental parameters which are taken into account for the analysis and calculation of metal vapor corrosion rate. Based on the threshold value of this rate, the audible and visual alarming is thus designed. Thi s method has the characteristics of high sensitivity, low power consumption and high reliability.In this thesis, we design a miniature corrosion sensor for vapor corrosion monit oring within the bore. This sensor supports Bluetooth module, and combining with wireless data collector it can make up a micro Internet of things system for rapid diagnose of corrosion condition inside the bore. The experimental results show that the metal thinning resolution of the sensor can as high as 1nm, with extremely high sensitivity. Through techniques such as reference resistance temperature compensation, alternating current excitation, the negative effects caused by temperature fluctuations can be further reduced, and the corrosion thinning resolution can be up to 1/5000 of the initial film thickness. This outcome can be used for fast reflection of the corrosion inside the bore owing to moisture or corrosive gas?such as H₂O, SO₂, NO₂, NaCl? permeation. The monitoring results can evaluation of vapor corrosion inhibitor filling.