This instructable is part two in my circuit board manufacturing series. This part can be used as a stand alone instructable about etching circuit boards. After the traces on the board are drawn with a permanent marker, all the copper around the traces can be removed by a process called ferric chloride etching. This instructable will show you how to take a marked piece of copper clad board, and remove the copper around the traces. I will also give tips on how to do this in the most efficient way. The video below will compliment this instructable.
Step 1: How It Works
Ferric Chloride etching removes the copper through chemical reactions. When copper is introduced to the ferric chloride solution, it dissolves the copper. The way this happens is long and complicated, so I will not write it here. Precipitate will also form as a result of these reactions, it contains iron and copper.
Step 2: Preparing the Ferric Chloride Solution
To prepare the ferric chloride solution, take a small container, and fill it with about 3 centimeters of ferric chloride. If you already have a container with ferric chloride, pour off the liquid, dump the precipitate in the trash, and refill the container with the old liquid plus some new ferric chloride.
Step 3: Preparing the Hot Water Bath
To prepare the hot water bath, you need to find a container that is slightly larger than the container containing ferric chloride. You then need to fill this container with 3 centimeters of water. After that, heat the container of water for 1.5 minutes until the water is almost boiling. Finally, put the ferric chloride container inside the hot water bath.
Step 4: Agitating the Solution
To speed up the etching process, the ferric chloride can also be agitated. In a previous instructable, I showed how to build an agitator for ferric chloride. If you have not built a ferric chloride agitator, you can just leave the ferric chloride in its hot water bath to etch, but it will take longer.
Step 5: The Etching Process
To etch the circuit board, you just add the circuit board to the ferric chloride, copper side up, seal up the container, and fire up the agitator. It is best to check the board every ten minutes to check the progress of the etching. At these ten minute intervals, it is also good to re-warm up the hot water bath to keep the ferric chloride warm. The etching process can take anywhere from 15 minutes to 2 hours depending on the amount of times the ferric chloride has been used, the heat of the water, and if it is being agitated.
Step 6: Cleaning the Board
After the board is etched, remove the board from the ferric chloride using pliers(Ferric Chloride is corrosive!). Then, rinse it off in the sink. Finally, wash the permanent marker off using acetone on a cotton ball. You should have a board with clean copper traces on it. In part 3, you will learn how to solder the parts onto the board using the surface mount technique.
Step 7: Disposing of the Ferric Chloride
First of all, you should never dispose of ferric chloride after one use. It can be used for many uses. If you notice that it is taking too long to etch your circuit board (over 2 hours), then it is time to dispose of the ferric chloride. You will need to neutralize the liquid with baking soda, then dump the liquid down the sink. You then dispose of the precipitate according to local law.