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I've been working on a side project that has me experimenting with methods of creating printed circuit boards. Both of the geeklets have expressed an interest so I tried to come up with an idea they would find interesting.
The three of us discussed it for a while, and LEDs appear to be the coolest component I have in my junk box. We will be making small night lights using copper traces in the shape of their names. I considered a number of power methods, but settled on a single AA battery holder with a joule thief to extract every bit of energy from all the half dead AAs we seem to accumulate.
To get things started we'll need to gather some materials:
- Copper Clad Circuit Board
- Etching Fluid (Ferric Chloride)
- Glossy Photo Paper
- Laser Printer
- Iron (HOT)
- Plastic Containers
I bought some cheap copper clad boards from the Electronic Goldmine. The thinner boards cut easily with a sturdy pair of scissors and the traces don't lift as easily as on the thicker boards I tried from Radio Shack.
Etching fluid, aka Ferric Chloride, is a little harder to obtain. Radio Shack carries a bottle for $10 or a complete kit for $15. Phone ahead as not all stores appear to carry these items. If you order any online expect to wait for ground shipping.
To get the toner on the PCB we will need to transfer it to something the printer can handle. Glossy photo paper designed for Ink Jets works well since it won't absorb the toner when it passes through the fuser. I'm using a stack of glossy Epson photo paper that I picked up on a discount rack years ago and it works well. The purpose of the glossy paper is to keep the toner from soaking into the paper. This will let us transfer almost all of it to the circuit board, which brings us to the next item.
Yes, you have to use a laser printer, an ink-jet will not work with this method. The toner is a plastic powder, placed on the paper with an electrostatic charge, and fused in place with a heating element. Fortunately for us the toner also resists the acid that we will use for etching the boards. I am using a Brother 2070N network printer at home and it is my favorite small printer. I've also tried a Dell and HP printer at work with similar results.
When the design is printed we'll need a way to transfer it to the copper on the board. A heat laminater works very well, but a regular clothes iron will also work. Look for a very hot iron. Our good one goes up to linen, if it tops out at cotton then it might not get hot enough. My wife wasn't happy when I used her favorite clothes iron, so for the sake of marital harmony I suggest you get a used one from a garage sale or thrift store.
We will also need a plastic, not glass or metal, container with somewhat tall sides, a tight lid or both. The circuit board will be covered with a quarter to half inch of liquid that will be agitated gently.
And last, we should gather up some safety equipment. Chemical resistant gloves, safety glasses, an apron, and plenty of water. The etching solution is an acid and will eat holes in clothing and corrode most metals. It isn't a very nasty acid, and brief exposure to your skin won't cause any real damage, prolonged exposure could could cause chemical burns. If you spill any, clean up with paper towels and lots of water.
Next week I will talk about designing the circuit and getting the design onto the copper plate. Until then, have a safe and happy Fourth of July! If you need something to keep you busy, check out Eagle CAD by CadSoft. We'll be using it to design the circuit.
