The Effects Of Dust Pollution On Temperature Performance Of Electrochemical Migration

The printed circuit board plays an important role of electronic circuits. With the internal size and the line spacing of electronic components getting smaller and smaller, the failure phenomenon of electrochemical migration (ECM) on printed circuit board (PCB) is more and more severe. Meanwhile, the air pollution is serious and the dust weather occurs frequently in China, which makes the dust and other contaminants to get into the interior of electronic equipment. The dust deposited on the surface of PCB causes the temperature of PCB to increase fast, and the temperature is an important factor to generate the(ECM). This paper focuses on the influence of dust on the PCB surface temperature and on the ECM failure of PCB.In this paper, by the establishment of dust thermal conductivity model, the theoretical calculation model of heat transfer on PCB, and the finite element simulation, the influence of the dust pollution on the temperature distribution of PCB surface was studied firstly, and then, the experiments were designed to validate the finite element simulation results. Secondly, the temperature humidity bias(THB)experiments were carried out to research the effects of different temperatures on ECM. Finally, quartz particles were sprayed on the PCB to investigate the effects of insoluble dust particles on the temperature characteristics of the (ECM) by THB tests.Research results showed that, there was an approximately linear increased relationship between the temperature on the PCB surface and the distribution density of dust particles, corresponding to outdoor deposition of dust for6-8months. Under the same dust density, the rising of temperature of high power electronic components was higher than that of the small power components. The time to failure (TTF) of ECM on PCB varied with the temperature as a negative exponential relationship. The TTF showed that a linear relationship between the line distance and TTF of ECM. The PCB covered with dust was more susceptible to ECM failure than the clean one.With the growth dust density on PCB surface, the temperature of the PCB surface also increased. The TTF of ECM showed a decrease firstly and then an increase trend. Finally, through the range analysis for orthogonal experiment, the significant ranking among the three effects of temperature, dust distribution density, relative humidity on the ECM failure were: relative humidity>dust distribution density>temperature.