How to Etch With Hydrochloric Acid & Hydrogen Peroxide
A simple etchant can be made from common chemicals found at local hardware stores. Hydrochloric acid, also known as muriatic acid, is generally used to clean concrete foundations or patios. A pattern is either transferred or printed onto a 3 1/2-by-5 inch circuit board. The circuit board is made of copper that covers an insulator. Any indelible marker will work to trace a pattern onto the board, but some people prefer using a thin permanent marker to control the thickness of the lines drawn. The pattern could be transferred by ironing a copy of the pattern printed on photo paper. You would need to make a separate copy of the front and back of the pattern and iron the front to one side and the back on the flip side.
Things You'll Need
- Circuit board
- Indelible marker
- Vinyl gloves
- Glass or plastic bowl
- Hydrochloric acid: 38 percent by volume
- Hydrogen peroxide: 3 percent by volume
- Nonmetallic tongs
- Acetone or mineral spirits
Draw or iron a transfer of your pattern onto the circuit board. If you draw directly onto the circuit board, wipe off mistakes with a 1-to-1 mix of acetone and alcohol, then start over.
Put on the goggles and vinyl gloves before mixing the chemicals. In a large nonmetallic bowl or container, mix 1 part hydrochloric acid with 2 parts hydrogen peroxide. For example, you would use 1 cup of the acid to mix with 2 cups of the peroxide.
Slowly add the acid to the hydrogen peroxide. Never add the hydrogen peroxide to the hydrochloric acid, as it could cause a reaction that might splash the chemicals into your face.
Mix enough chemical solution to totally submerge the circuit board. Agitate the board in the solution for 10 to 15 minutes, using a pair of nonmetallic tongs.
Mix the acetone and rubbing alcohol together. Dip a paper towel into the solution and wipe both surfaces of the circuit board to stop the etching process and remove any remaining lines from the marker.
Dispose of the etchant properly or store the solution in a glass or plastic container with a lid. Mark the contents of the container and store it in a responsible place out of heat and excess light and out of reach of children.
Tips & Warnings
- Do not use metal of any kind while etching circuit boards. The metal will cause a chemical reaction that could burn whatever it comes into contact with.
- The solution will turn a green color during the etching process. This is normal.