Non-destructive identification of open circuit in wiring on organic substrate with high wiring density covered with solder resist

As the printed wiring density on organic substrate is increasing, the line width and spacing are reducing toward 25 μm and below. Present method of fault isolation will no longer be adequate, and capacitive voltage contrast method is proposed. The feasibility of the voltage contrast method is demonstrated, and the various key parameters for better contrast are identified and determined. Circuit model is developed to explain the experimental results and the significance of the various key parameters.