Effects of etching process inaccuracy in the malfunctioning level of PCB circuits - a simulaton based analysis

Abstract

The PCB is a mechanical base used for interconnection of electronic components. In PCB manufacturing industry, the quality and reliability of circuits is highly dependent upon the accuracy of the manufacturing processes. Among the manufacturing processes, etching is the most sensitive process and needs more accuracy. The etching inaccuracies cause severe problems that may result in degradation of circuit performance and malfunctioning of circuits. In this research the levels of effects of etching manufacturing process inaccuracies on the malfunctioning of PCB circuits is investigated and analysed. The effects of the process inaccuracies on circuits as well as how the process is related with the affecting parameters are addressed. A four-layer multilayer board is considered for the study and the software selected to study the effects of manufacturing inaccuracies is OrCAD PCB designer. Schematic development, PSpice simulation and layout design are made for selected circuits to study the effects
of the etching inaccuracies.According to the results obtained; inaccurate etching results in either larger or smaller width of traces, leaves unwanted conductive materials, and creates unnecessary holes or open circuits and short circuits. In the over etching scenario, when the over etching effect is increased and results in 14.36-ohm resistance, output voltage drops from 48mV to 22mV. For the open circuit scenario, it results in zero output voltage. Similarly, for the short circuit case which is the case of under etching, the output result shows 1.8nV which is very small and it can be considered as zero output voltage. For capacitive effects, the output becomes very small (140uV), unstable and oscillating. For the combined resistive and capacitive effects, the output is nearest to zero (65uV) and oscillating.