At the heart of most electronics devices lies a printed circuit board (PCB). The PCB holds the components and the connections between them, negating the need for large amounts of wires in modern electrical devices. One commonly used method of making a PCB is that of photo etching. Through photo etching, you can create a complicated circuit for an electrical device by exposing a laminate copper board to UV light and transferring the circuit design directly onto the board, much like exposing an image to film. It's a quick way to create a PCB for use in your DIY electric projects, providing you with crisp, clean circuit designs, at little expense.
Instructions
1 Design the circuit to be placed onto the board using PCB design software. You can purchase a design suite that handles everything from circuit layout to routing components on Mac, Linux or Windows platforms.
2 Print the circuit design onto two sheets of transparent ink-jet compatible paper. Set your printer for transparency printing, using the highest quality print settings. For monochrome printers, set the intensity and contrast settings as high as possible, in order to use as much black ink as the printer will allow during printing. Make sure that you print the design onto the slightly sticky side of the transparencies.
3 Trim the transparencies around the printed design and tape the transparencies to a thin glass panel like that found in a photo frame, using transparent tape.
4 Remove the protective paper cover from the photo PCB and place the PCB with the photo-resistant layer side to the transparency. The setup should be the glass piece, followed by the transparency, then PCB board, with the design centered on the board.
5 Place the PCB into the UV exposure unit, with the copper side of the board facing the UV bulbs. Turn on the unit and expose the PCB to the UV light, according to the time suggested by the UV exposure unit's manufacturer. The exposure will transfer the circuit design to the copper surface, hardening the photo-resist layer in the needed design on the board. The UV exposure unit can be purchased from most scientific supply stores, or be built using a UV lamp and an enclosed space. If using a DIY exposure method, you will have to experiment with exposure tiles to determine the best results.
6 Prepare the developer solution in a bowl large enough to hold the PCB board, following the solution manufacturer's instructions on mixing.
7 Remove the PCB board from the exposure unit and remove the glass and transparencies. Place the board into the developer and use a foam brush to remove the green photo resist layer from the board. The unhardened resist should come off quickly in one to two minutes. Be careful not to remove the hardened resist. Place the board in water to neutralize the developer.
8 Mix the ferric chloride with water, according to the instructions, and submerge the PCB board into ferric chloride solution, etching the circuit design into the board by removing all of the copper from the board, except that of your design. Remove the board from the solution and wash away the solution using running water.
9 Wet the cotton balls in acetone and clean the remaining photo-resist from the copper lines of your circuit design on the PCB board. This will brighten the copper lines wherever you've removed the resist. Wash the board again beneath running water and then drill holes into the PCB boards where needed, according to the circuit design, with a drill press.
