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DIY Laser Circuit Board

You should now have a sheet of blank circuit board in front of you, and your board design all printed out nice and dark on the optimum paper for this process.

We need to get that toner on the copper! To do so, go ahead and cut your print to size and if necessary cut your circuit board to size as well. For normal FR4 board, I've found a dremel with a 'roto-zip' style bit works well. It can also be done with a very fine tooth metal-cutting saw blade(ie. hack saw). If you are using a very thin board stock, you might also find that tin-snip cutters designed for cutting sheet metal work well.

Prepare the copper

First, clean your circuit board well. Soap and water with a 'scratchy type' sponge works well. I find that doing so leaves a slight scratch in the surface that helps to toner stick to the metal. Be careful though, we don't want the board to have deep scratches in it; nor do you want to thin the copper plating out. Follow that with a good wipe down with alcohol. Be careful not to get any contaminants on the copper after this wipe down; we don't want any kind of oils (ie. fingerprints) or foreign objects (ie. dust particles) to interfere with our toner sticking.

Getting the resist(toner) on the copper

Lay your clean, dry circuit board on a flat, clean, heat-resistant work surface. Then, lay your printed design face down on copper; and get it in the desired position.

Most articles on the internet will say to use a standard clothes iron at this point, so I assume that will work. What I like to use is something called a 'mono-kote sealing iron'. Nope, that doesn't come from working in a print shop - it comes from another hobby of mine - that being model aircraft. This iron is used for applying plastic heat shrink coverings to models; and can be found in most any hobby shop in several sizes and shapes. I find it much more practical for this purpose mainly because it is much smaller.

Regardless of what you decide to use for an iron, I have found a temperature of about 260 degrees F. works well. For my monokote iron, that is a setting of about 70% power. For other irons, you'll need to check the controls, use a thermometer, or just experiment a little bit. To little heat, and you will have difficulty get the artwork to stick. Too much can cause the toner to actually liquefy; which will result in your traces spreading. This spreading can be critical with tightly spaced traces (ie. surface mount components). With the optimum temperature found, you should be able to get a good adhesion without the toner spreading.

Photo of PCB after ironingHolding the artwork in place, apply your iron near the center and slowly work outwards with moderate pressure. Remember, copper is also a great conductor of heat; so it will pull away the heat at first. You'll need to work slowly enough to get the copper warmed up. You may start to see the traces thru the paper(this may or may not happen with paper types other than what I use), and that is a reasonable indication of when you have it adequately ironed down. Be sure to go over any small, tightly spaced artwork carefully - as its very difficult to fix those areas later.

Once you are confident you have it adequately ironed down, the resist should be stuck quite well to the board. Let it cool enough to handle.

Removing the Paper

This is the easy part, but you can ruin your project if you rush it. Simply put the board and its attached artwork in a container of cool water. Go have a cup of coffee with your XYL(ham speak for spouse), cut the grass, etc. It needs to soak for a bit. Rushing at this stage will leave traces with missing parts. What you want to happen is for the paper to degrade to the point where it falls off the board on its own. If you pull it off, you will pull both the paper and the toner - ruining your board.

That said, there will probably be a few stubborn spots. Lightly (ok very lightly) rub the remaining paper with your finger under running water. You will find that the remaining paper will roll up under this light rubbing pressure - leaving the toner layer undamaged.

Note that it is not necessary to remove any or all of the paper from the desired trace areas - it will only help to protect the copper. You do want to remove it from the areas where you don't want the copper though. The etching process will not work well thru the paper.

Once you have gotten most or all of the paper off the board, pat it dry with a paper towel and return it to your work bench. Carefully compare the newly 'printed' copper circuit with another copy of your artwork. This is your chance to touch up any imperfections in the thermal transfer process.

Image showing imperfections to look forIf you have missing resist (broken traces - blue circles), you can fill them in with a specialty resist pen - or I've found a good sharpie marker works just as well and is a lot less expensive! Either way, make sure you have a good coating of the ink on the copper by dabbing rather than simply writing.

You will also likely see small areas of paper left in between tightly spaced traces and contact pads, as well as most thru hole circles(circled in red). Carefully scratch this paper residue off with an Exacto knife blade. Be sure to look closely; its much easier to remove the paper residue now than it will be to remove copper later!

If you happen to be making a double sided-board, flip the board over and repeat the above process. Be careful not to damage the first side. Work on a clean surface, any contaminates on your work surface will stick to the board as its heated!

Second side artwork pinned in placeYou'll need the two sides to align with each other. I do that by selecting two thru holes that have contacts on both sides, and drilling them. Then, I insert a pin thru the 2nd side artwork in the appropriate place. Leaving the pins in the artwork, push the pins into the drilled holes. They will nicely hold the art in exactly the right place for ironing.

In the next section, I'll talk briefly about etching and getting rid of the resist after its done its job.