In order to complete the creation of a PCB, one must etch the circuit on the copper board. One such method involves using UV light. This PCB fabrication method is good for making more complex circuit layouts.
First, one must prepare the UV light box or UV machine to be used. There are UV light boxes that can be purchased but if one wishes to make it instead, the materials needed are several LED lights, a box that is about one foot in height, a transparent plastic or glass to keep the transparency paper elevated, a material to hold the LED lights with, and its power supply. After the light box is done, it is now time to draw the schematic of the board.
There are several software packages available for use in drawing board schematics and can be used in different PCB fabrication methods.
Simply use any of them and once the schematic is done, print it using a laser printer on a transparent sheet. In order to avoid confusion, one may set the image to a mirrored one before printing it out. Once the schematic is printed, place it on the copper side of the board. Put the board in the light box with the printed side facing up and turn the lights on.
If one is using a custom made light box, take note of the distance of the lights from the PCB; otherwise, there’s no need to worry about it. If the lights are too close, the radiation may not distribute evenly throughout the PCB. Some UV machines have their own timer but if the UV machine being used doesn’t have one, then one can just manually time it at around fifteen to twenty minutes before turning it off.
When the UV exposure is finished, remove the PCB from the UV machine or UV light box then put the PCB in what is called a developer solution. It is a chemical solution often used in PCB fabrication; it will wash away the photo resist put in the PCB earlier. Still, be careful not to leave the PCB in the solution for too long because the solution can remove the photo resist completely, including the drawn schematic.
The advised time to put the PCB in the solution is about five to ten seconds only.
After that time, one must immediately put the PCB in cold water to stop the solution from removing the rest of the photo resist. Do note that the solution can still be used for multiple PCBs. Also, observe caution when using the solution; wear protective gloves and goggles during this process. This part, however, can be avoided if one is able to purchase what is called a photo revelator compatible with the photo resist used in the PCB.
One can use the photo revelator in place of the developer solution then rinse the PCB with distilled water. After this process is done, it is time to etch away the unwanted copper by using acid. Mix one part muriatic acid with two parts of hydrogen peroxide, put the PCB in the solution, and wait for the copper to be etched away. This usually takes around two minutes.
After the etching, it is time to remove the photo resist from the PCB. In order to do so, one must use a cotton swab dipped in acetone. With it, one has to carefully wipe off the photo resist from the PCB. When the photo resist is removed, the PCB can then be populated with its components. Take note that in using this PCB fabrication method, several attempts might be necessary before success is achieved.