Etching Your Own Printed Circuit Board

The process of making your own printed circuit boards is not complex or even difficult, but it is time consuming, and it does involve using some nasty chemicals that cause stains on clothing and burns on skin. With the advent of low-cost PCB service bureaus, making your own circuit boards is something of a dying artform.

And more, it involves the use of a highly toxic and dangerous chemical, ferric chloride. This stuff eats through metal, stains clothes, and poisons people and animals. It damages plumbing. It can burn (at least irritate) skin, and it can seriously harm your eyes if it splashes your face.

So you get the idea that etching your own PC is not for the casual experimenter. Still, you may want to do it someday, so here are the basic steps.

  1. Prepare the layout for the board. You can use the free or paid version of CadSoft Eagle or any of a number of other design programs for circuit layout. If you’re making a board for use with the Arduino, you can use Fritzing, as described in the preceding section.
  2. If you have a laser printer: Use a sheet of transfer film, such as Press-n-Peel PCB from www.techniks.com. When printed, the black toner from your laser printer bonds with the film. You then use the film to transfer the design to the circuit board material.

If you don’t have a laser printer, print your design on white paper, then take it to a copy shop and ask them to run the Press-n-Peel transfer film through their copier.

RoboTip!
As you might guess, there are other ways to create patterns for use on printed circuit boards. More elaborate techniques include creating a film negative of the layout, then exposing specially treated light-sensitive PCB material to ultraviolet light. For more information on these techniques, look for books at your local library or authoritative Web sites.

  1. Obtain a blank printed circuit board sheet. These are made of a thin sheet of copper laminated to a plastic, epoxy, or phenolic base. Unless you’re making a double-sided board (not recommended for first timers), be sure the sheet has copper on one side only.
  2. Clean the copper using warm water and kitchen cleansing powder. Rinse thoroughly, then pat dry with a paper towel. Let air-dry for an additional 5 to 10 minutes.
  3. Using an ordinary household clothes iron, set the temperature to low or polyester (about 275°F to 375°F). Cut out the film and place it so the toner faces the copper of the PCB sheet. Apply the iron to the film side; this transfers the pattern on the other side of the film to the copper of the PCB sheet.
  4. Carefully peel the film away, (hopefully) leaving the pattern on the copper metal. Inspect the pattern for places where the toner didn’t stick well. Use a fine-tipped black marker (such as a Sharpie) to fill in any voids. The pattern forms what’s called a resist.
  5. The next step is to immerse the PCB sheet into a plastic tray filled with prepared ferric chloride. This chemical is available in several forms: premixed liquid (the highest cost, but readily available, including at RadioShack), liquid concentrate, or powder. Stay away from the powder! It can be downright dangerous if you’re not experienced at using it.
  6. For a period of 5 to 15 minutes (possibly longer), gently rock the tray back and forth, causing the ferric chloride to repeatedly wash over the copper surface. Over time, the chemical will eat away at any copper not covered with the resist.

Warning!
Avoid getting ferric chloride on your skin, but if you do, wash it off with water and soap immediately. Remove all metal jewelry. Wear protective goggles to protect your eyes in case the chemical splashes onto your face. Wear old clothing. You might want to use disposable latex gloves. Use plastic or bamboo tongs to manipulate the board when it’s in the tray.

Use the tray only on a wood, plastic, or ceramic table or sink. Keep away from metal. Work only in a well ventilated place. If you start feeling sick, stop immediately and seek medical help.

KEEP ETCHANT AND ALL CHEMICALS AWAY FROM CHILDREN.

  1. When all of the excess copper is removed, take the board out of the ferric chloride solution and rinse it off to stop further etching.
  2. Remove the resist using cleansing powder and a nonmetallic scouring pad. A properly etched board will show the full pads and traces of your layout. Any thin spots or voids mean that area was overetched. Only experience will help you avoid this in the future.
  3. Using a small bit (#60 to #53; 1mm to 1.5mm), drill holes for the components. This works best when you have a small portable drill press; a drill press attachment for a Dremel or other hobby tool will do.

Only now are you ready to solder components and wires to your homebrew PCB. And while you’re at it, you’ll need to either rebottle the ferric chloride etchant for later (use a plastic bottle) or dispose of it. You cannot just dump it down the drain. For one thing, it’s illegal in most places. And second, if you have metal plumbing, it can harm the pipes.