A simplistic printed circuit board fabrication process for course projects

A low-cost method of fabricating a printed circuit board (PCB) is presented. The process is favorable over conventional PCB fabrication due to fewer processing steps and lower capital investment. A laser printer is used to print a circuit layout onto ink-jet paper or specialized transfer paper (i.e., PnP-Blue from Technics, Inc.). The image is then heat transferred to a copper clad board using a standard household clothes iron. The transferred toner acts as an etch resist in a ferric chloride (FeCl/sub 3/) or other etchant bath, such as ammonium persulfate. Using this method, it is possible to fabricate PCBs with state-of-the art feature sizes as small as 4 mils using a 300 DPI laser printer. A higher resolution printer is expected to give finer resolutions. Tradeoffs between the ink-jet paper and the PnP-Blue paper is analyzed and discussed. This approach has been used for graduate-level courses including a VHDL class project to implement an ALU using a 44-pin CPLD and a microwave class project to implement a microstrip matching network for a high-gain, 875 MHz transistor. Over 200 students have successfully processed PCBs using this technique.