Making Home-Made PCBs

Tue Nov 20 2001 18:00:00 GMT-0600 (Central Standard Time)

A PCB is much more desirable than just a mess of wires, or even the little breadboards you can get @ Radio Shack. They’re not always the best way to do it, might not be worth the effort, but when you have a fairly complex wiring project, a PCB is VERY HANDY.

So, what do we need to make a PCB? Well, it’s not TOO much stuff… This method is the Iron Transfer method of making a home made PCB or PC Board.

Supplies

• Some way to draw the board. I use Eagle from CadSoft. It has a great free version available for download at their site.
• Copper-clad board (we’re doing single-sided, 1oz.) these run around $5 @ Radio Shack or online for a single/double sided, 6″x6″ board
• Glossy Ink Jet paper (I use JetPrint Photo, HP Glossy does ”’NOT”’ work)
• Laser Printer or Photocopier (need the toner to transfer)
• Iron (normal, household iron) & Ironing board
• PCB Etchant Solution (there are several)
  • Ferric Chloride
  • Ammonium Persulphate
• A ”’PLASTIC”’ tray (metal is a BAD IDEA)
• A drill of some kind (Dremel Tools work great)
• Some little tiny drill bits (hobby stores have ’em for like $5)

Process

Design and print the PCB Layout

First you draw your board, with whatever software you want. If you are using a PCB layout software package, then you already know what to do.  You can also just use any old drawing program, but I’d stick to 1 layer for that.  If simply drawing it, keep in mind you are drawing the BOTTOM of the PCB, so all pinouts, and arrangements are REVERSED (Unless you are making stuff for SMT parts, in which case, you probably don’t need this tutorial!). It’ll take practice and patience… Measure, draw, print on plain paper and see how your parts fit… Check, check, check, and check again to make sure all the lines you have drawn will mimic your wiring, you can’t change it without being sloppy once it’s etched…

Tip: Make sure your components have holes for each pad, once etched, it’ll make drilling much easier.

After we have that done, we’re ready to print it on our glossy paper. One thing you must remember to do, is to print this image flipped. You will be printing it to the page, then ironing it on, so to get it the right way, you must mirror it.

My laser printer doesn’t like the glossy paper, so I print it on a plain sheet of paper, then run it through a photocopier… Same result. You just need a flipped image of your board in toner on the glossy paper. The glossy paper lets the toner come off easier when you iron it.

Transfer the Image

Cut the paper to size to make it easier to handle and position on the copper-clad. You may also want to cut the copper-clad if don’t plan on using all of it for this board.

Really quick we need to prep the copper-clad to take the transfer. You simply scratch it up a bit, not gouge, just scratch. I usually wet-sand it with super-uber-fine grit sandpaper, or an abrasive sponge pad. It should be nice and shiny and dry when you are done.

Now we break out the Iron.

Turn it up to a medium temperature. I only put mine up about 1/3 of the way, too hot and it’ll smear the toner and burn the paper, no need for that.

Place the image on the copper-clad and line it up. Rub the iron across it holding firmly down til it starts to stick, once you have good contact you don’t need to worry about it moving around.

I usually put a piece of paper or two in between the iron and the transfer paper, so I can run the iron over easier. It helps diffuse both the heat and the pressure more evenly, but will slow the process down a bit.  Check every so often to see if it is transferring. Some areas like the edges might need special attention with the tip of the iron. I usually push down real hard to ensure good contact, and leave it on, moving around for a few minutes. Whatever feels right. If you mess up you can just scrape it off (re-sand as per the prep instructions), so experiment and find what works for you.

Once you think you’re done, remove the iron. Take the board (using hot pads or something so you don’t singe your fingers) and put it in your sink. I use it to cover the drain hole, then turn on a light stream of water.  This will make the sink fill, and let the board soak.

Stuck on

Soakin' it...

Transferred

After a while, the glossy material gets goopy and slimy and starts to come off, it can be a bit messy but it’s tolerable.

Once it’s pretty loose you can peel off a layer of paper… Some might stay on, it’s fine, just leave it in running water. Eventually it will lose it’s grip and just come right off, leaving (ideally) a perfect image of your PCB layout on the copper-clad.

Etch

Now that the image is transferred on, we can start to etch. The etchant solution eats away all the copper it can react with, but the toner on there stops it from getting our pattern, the result? An etched PCB.

You want to use a plastic tray of some kind, something you won’t be putting food in or anything. Rinse it out and dry it, then set the PCB in there. Pour in some solution and watch it work. 

Tip: The hotter the solution, the faster it works… Outside in the summer sun really makes it go fast.

Warning: Don’t do this in a closed area, breathing this is bad… Also try not to touch it, it stains quite effectively.

Agitate the solution as much as you can tolerate. It gets kinda boring so do it off and on. Just simply lift and set down one end to slosh the solution around so fresh solution can get at the board and continue the reaction.

Keep an eye on the board, I use plastic tongs to take it out every so often and check it, rubber gloves also work well.  Eventually you’ll be able to see how it’s eating away the copper and your board is appearing.

Once you feel it’s done, flood the tray with water, be careful not to spill it, you’ll be quite unhappy if you do. I usually fill it up w/water, then pour it into a bucket. This stuff is hazardous waste, so you might want to find out where to dispose of it with whatever local agency deals w/that in your area. Once you rinse a few times to dilute the solution, take the pcb out, and run that under water for a minute or so to make absolutely sure the  chemical reaction is neutralized.

Once you have that out of the way, you should have something that looks like this:

Etched PCB, bottom

Etched PCB, top

Drill

Ok lets drill. I have a little set of bits I found at Hobby Lobby. They’re for crafts or something, anyway they work really well and were cheap. You can also get a Dremel bit set from hardware stores.

Using these with a Dremel makes this process super easy, as the Dremel is easy to handle and nimble. But a normal hand drill should work fine too. Some people even go so far as to use a Dremel with a drill press, I’ve tried it, it’s neat, but no easier than by hand.

Just find the bit that fits your parts, and drill away, using the holes you left in your PCB layout to guide the bit. The material making up most of the board is super soft and cuts like butter w/the drill bits. 

Warning: Hazardous Materials! Be careful not to breathe the dust, it’s fibreglass and some of its other nasty friends, not something you want in your lungs.  Use appropriate masks/ventilation.

After you’re done drilling, I like to wet-sand again with super-fine sandpaper… The toner is VERY hard to get off with a simple scotch pad or other abrasive… But wet-sanding takes it right off and you have nice shiny copper underneath… Acetone (the nail polish remover kind, no need to go industrial here) will also work to remove the toner but some PCB materials may not particularly care for Acetone.

That’s all!  An optional final step is tinning the PCB.  Tinning puts a very thin layer of tin over the remaining copper, reducing oxidization problems you’ll get with exposed copper, and it also helps soldering a bit. You can find tinning solution from electronics shops online or in reality.