1. Print the circuit diagram of the circuit board to the smooth surface of the heat transfer paper with a laser printer.
2. Set the heat transfer paper to 150-180 degrees Celsius, apply one side of the circuit diagram printed on the copper-coated sheet for transfer printing, or replace the plate-making machine with an electric iron to transfer by hand.
3. Remove the transfer paper after printing and put the copper clad sheet into the solution of ferric chloride for corrosion.
4. Wash the carbon powder on the circuit board with gasoline, or rinse the carbon powder in water with abrasive paper.