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Circuit Training: a Brief Overview of Making PCB’s

As much as possible, the parts used in technologies made in AIDG-sponsored workshops are available in country. In cases when the components are not available, we’ve been able to find innovative solutions thanks to our staff, volunteers and the infinite bounty of the web.

My favorite example is the ballast load controllers we are using for the micro-hydroelectric project at the Comunidad Nueva Alianza. For those of you who do not know, a ballast load controller essentially acts as an electric brake by keeping a generator from over spinning and burning out. It does so by imposing a constant load on it. If we were to buy one in the States, we would have to pay between $3000-$4000. We made ours for roughly $400.

The controller requires some complex circuitry, which the XelaTeco team has been able to make on site. When Pete first told me how, I think my jaw dropped at the coolness of it all. It was all very MacGyvery. I’ll post pictures of some of the finished circuits in the gallery within the next few days.

Printing circuit boards using the Laser Printer Toner Transfer method.

Developed by Tom Gootee
(Go to the above link for the full methods. They are really quite detailed. It’s extraordinary).

Materials

• Laser Printer (if you are especially crafty, you will get it off craigslist. NOT inkjet)
• Paper (Staples “Photo Basic Paper” comes highly recommended: SKU 471861 or 471865 ; the type of paper used is crucial)
• Clothes Iron
• Copper plated blank printed circuit board
• Toothbrush, other soft brush, wet “Crinolin” material
• Rubber Gloves
• Desired circuit pattern
• Hot water bath (140 degrees F)
• Tupperware or similar plastic container
• Etchant: 1 part Muriatic Acid to 2 parts Hydrogen Peroxide (some nasty stuff)

Here are the basic steps. Click here for the detailed method.

1. Print circuit pattern using the darkest laser printer settings.
2. Prep the board by scrubbing it with a Scotchbrite or “artificial steel wool” pad. Clean with paper towel soaked in acetone until there is no more discoloration.
3. Lay the paper pattern face down on the copper.
4. Using an iron set as hot as it can go (usually Linen setting), place the iron on the back of the pattern for 30 seconds or more to preheat.
5. Iron the board systematically for about 2-3 minutes.
6. Soak board (pretty much immediately) in hot water for 2 minutes. Carefully peel off as many layers of paper as you can. Repeat this step until you get most of the paper off.
7. Remove remaining paper with a toothbrush.
8. Wash board with warm soapy water, rinse and dry.
9. Etch board in a clean plastic container using agitation for about 5 minutes. Do not use metal containers or utensils.
10. Rinse board under running tap water.
11. Wipe the board with a towel soaked with acetone to remove toner.
12. Drill the holes (if your PCB is for through-hole components, as opposed to the newer surface-mount).

Tada! A new and very nice circuit board.

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