Physical modeling of electrical conduction in printed circuit board insulation

Abstract

This thesis is concerned with understanding the degradation of electrical and electronic components in automobiles due to environmental effects. A special emphasis is placed on understanding the physical processes underlying the degradation, so that accelerated reliability tests can be specified with increased confidence of their validity. As a first case,printed circuit board (PCB) insulation was selected as a target for investigation. With an increase in the electronics and circuit miniaturization coupled with an increase in voltage in 42 volt as well as hybrid vehicles, PCB reliability has become an important issue. We first provide a broad presentation of insulation degradation theory as well as electrical conduction theory according to existing literature and then narrow our focus towards printed circuit board insulation. We develop a novel first-order mathematical model to describe electrical currents in printed circuit board insulation as a function of temperature, relative humidity, absorbed moisture content, voltage and geometrical characteristics. This model was developed from a series of experiments that were carefully performed under controlled laboratory conditions. In addition to describing the experimental procedure and results, we also explain the details of the experimental setup and measurement instrumentation. Furthermore, we present an intuitive physical explanations for some observations and model responses.