The feasibility of using ink-jet technology to write circuits on PC board material and TAB substrate has been demonstrated. Several systems were evaluated and the most successful system used paraffin as a resist material on a copper substrate. The copper was etched and the paraffin subsequently removed to form the conductive paths of the circuit. Line widths down to 100μm were achieved, and line widths of 50μm were shown feasible. The generation of the print pattern from a computer file illustrated the potential of coupling a circuit writing system to an electrical CAD system to provide rapid turnaround prototype circuits.