The Effect of Dust Covering Density on Electrochemical Migration Failure of Circuit Board

Under certain temperature, relative humidity and potential difference, the electrochemical migration (ECM) between adjacent wires and solder joints is prone to cause insulation failure in the high-density electrical packaging. In the case of serious dust pollution, the deposition of dust particles inside the electronic equipment changes the critical humidity of the circuit board surface, thereby changing the failure mechanism of ECM and time to failure (TTF). This paper studied the effects of the dust particle coverage density of 13-18μm diameter on the TTF of ECM of circuit board under the interaction of environmental temperature, relative humidity and electric field intensity by temperature and humidity bias (THB) experiments. It was found that the TTF of ECM caused by particle covering density was nonmonotonic. When the particle coverage density was lower than 350μg/cm2, the TTF and particle coverage density presented a negative exponential function; when the particle coverage density was higher than 350μg/cm2, it had a positive exponential function. The failure mechanism of ECM in high- and low-density zones was analyzed from the aspects of moisture adsorption and dendritic growth path change. It lays a foundation for establishing the reliability detection method of high-density circuit board in dusty environment. © 2020, Electrical Technology Press Co. Ltd. All right reserved.