How To Resist Etch The Circuit Boards:
You will need to etch four circuit boards:
- Some Muriatic Acid (a half gallon should be more than enough) you can find it at your local hardware store. It is usually used to clean cement or brick surfaces.
- A liter of Acetone (It’s about $1 at Wal-Mart in the fingernail polish remover aisle)
- Two liters of hydrogen peroxide.
- A Scotch Brite
- Copper Clad Circuit Boards single sided preferred (You can get them at radio shack or we bought them online from http://shop.willyselectronics.com/ )
- 2 plastic tubs, one for etching and one for rinsing.
- A 2lb box of baking soda.
- Some plastic silverware for agitation.
- Plastic Chemical Gloves.
- You need to get the design (flipped, do not flip only if you intend to UV etch)
- printed on glossy cardstock. We had success at Kinkos. Be sure to tell them to do it on the darkest setting with the waxiest toner they have. It must be done with toner. Inkjet ink will not transfer to the circuit boards.
Procedure:
1. Polish the circuit boards using the scratchy side of the scotch brite. Rub firmly for 2-3 minutes until the board is very shiny (ie all oxidation is removed).
2. Clean the polished circuit board with acetone will paper towel is picks up no more residue. This removes all copper pieces and oils from hands.
3. Using a very hot iron, iron glossy cardstock design and copper side of the circuit board together. You MUST use a very hot iron. We found that cheap ones worked better because they lacked safety features that kept more expensive irons cool. Suggestion: Don’t use a good iron, because this may leave a little residue on your iron, instead go buy a $10 one. This is the most important step. Push firmly on the iron (ie put your weight on it) and continue to iron it for 10 minutes. Do not cheat the time limit! If you do the etching will not work properly.
4. Once the paper has firmly adhered to the board place it in a plastic tub full of hot tap water. Let it sit for about 5 minutes in order to fully absorb the water. Carefully peel off the paper. Hint: It may work better to remove the paper by simply rolling your thumb over it repeatedly. A toothbrush can also be used.
5. Now carefully inspect the boards to insure that all of the paper has been removed between the traces. If paper / toner is left between the traces your circuit board will contain bridges. You may use a small metal PIC carefully clear any bridges. Pay particular attention to the Ethernet port and PIC socket areas. You may repair any areas that toner did not adhere to using a Sharpie.
6. Prepare the enchant solution. SUGGESTION: WEAR SAFETY GOGGLES, WEAR GLOVES, AND DO THIS IN A WELL VENTED AREA!!! Please don’t take this lightly, trust us it produces some nasty fumes that you don’t want to breathe in. The solution should be mixed in the following ratio: 2 parts of Hydrogen Peroxide for every one part Muriatic acid. It really doesn’t take much solution to etch a board. We made way too much solution the first time that we did it. Have patients and use your plastic utensils as agitating devices. With good agitation the board will be etched in 5-7 min. It also helps to heat the solution but I did it outside when it was snowing and it still worked so heat is obviously not critical.
7. After all uncovered copper has been removed via the etching solution pull the board of the plastic container and rinse it with acetone. Simply take a paper towel with some acetone on it and wipe away all of the toner covering your copper traces. It takes very little acetone to accomplish this task.
8. Use the 2lb box of baking soda to neutralize all excess enchant before disposing of the liquid according to all local laws and regulations.
9. Now all you have to do is drill out the holes (we recommend using a Dremel), and solder in the components!
As always, we take no responsibility for errors, omissions, or accidents that occur as a result of using this guide. It is simply here as a reference to others who would like to make a Christmas light display.