Determining the Level of Dust on Printed Circuit Boards of Radio-Electronic Equipment by Optoelectronic Method

Abstract

An optoelectronic method for detecting dust deposition on printed circuit boards (PCB) of electronic equipment which can be used to inform about the critical thresholds of dust accumulation is developed with allowance for the humidity index. The proposed method in combination with the developed mathematical model, functioning diagrams, and light beam motion patterns is used to consider a possible construction and block diagram of the algorithm of the control program for the microcontroller of desired implementation of the experimental setup. The principle of operation of the optoelectronic method for detecting dust depositions on printed circuit boards of electronic equipment with allowance for the humidity is following. Light pulses are periodically emitted by two LEDs with a wavelength λ1 = 565 nm (to assess the level of dust deposition) and two LEDs with a wavelength λ2 = 930 nm (to take into account the level of humidity). The reflected signals from the three plates are taken by the photodiode. The first and second plates placed in a sealed enclosure have an artificially deposited maximum level of dust (humidity 10 and 90%, respectively). The third plate is the control. The plates and PCB are made of the same materials. The level of deposited dust (mass concentration per unit area) which triggers the leakage currents between the conductors of the printed circuit board is determined experimentally and depends on the minimum distance between the printed conductors through which the maximum current flows in the given electronic equipment and on the thickness of the dust layer deposited on the conductors at the maximum permissible humidity specified for the equipment.