Manufacturing most products, even simple things like flashlights, incorporates at least one printed circuit board (PCB) in the product design. The boards must remain free of contamination during the fabrication process to operate with low incidence of failure. Before fabrication, cleaning the bare board substrate prevents problems from occurring during the generation of traces on the board. After the last process in PCB fabrication -- soldering the components to the PCB using solder flux -- cleaning is also required. Before releasing the PCB for use, you should thoroughly clean the board to remove oils and excess flux.
Instructions
Cleaning the Substrate
1 Put on a pair of latex or rubber gloves. One of the worst contaminants in the production of PCBs is oil, which comes from your hands and keeps the surface from accepting resist evenly.
2 Scrub each board with a plastic scrub pad to remove any oxide coating on the copper side of the board. You can acquire a plastic scrub pad at your local grocery store where dish washing products are sold. Do not use water when performing the scrubbing as this will promote a new oxide coating on the board during the process. Handle the board by the edges. The less contact with the copper cladding the less chance of fouling the surface. Many manufacturers use acid to remove the oxide coating, but physical scrubbing works just as well. When you have finished scrubbing it, the surface should appear shiny with no spots.
3 Mix a small amount of metal free soap in deionized water and place in a container large enough to hold the PCBs.
4 Rinse the board in the mild soap solution. This will remove most remaining oil and inorganic contaminants from the surface of the board.
5 Wash the board in an isopropyl alcohol bath to remove any other organic residues remaining.
6 Rinse the cleaned board with acetone. Isopropyl alcohol contains approximately 30% water and the acetone will remove any alcohol or water left adhering to the board. The acetone evaporates quickly and doesn't leave a residue.
Cleaning the Finished Board
7 Put on a pair of latex or rubber gloves to protect the board from the oil present on your skin.
8 Dip a cotton tipped swab into isopropyl alcohol and carefully scrub each solder connection on the PCB. Scrub both sides of the board where solder connections were made.
9 Dip a new cotton tipped swab in deionized water and repeat the process of cleaning each solder connection on both sides of the board. Depending on the type of flux used in the soldering of components on the boards, any residue will be soluble in either isopropyl alcohol or deionized water.
10 Rinse the cleaned board under cold deionized water. This will remove any remaining soap or isopropyl alcohol.
11 Place in an oven at 100 degrees C to dry for approximately five minutes. The heat will dry any remaining water and leave the finished product ready for testing.
