The idea behind this instructable is to outline a different way of transferring toner to the board aside from the methods we have available to us currently. Instead of transferring the toner using an iron transfer method, you use an electrostatic deposition mechanism (powder coating gun) to deposit the toner on the copper clad board, and then selectively melt the toner using a laser cutter (that has an engraving option as well).
1 powder coating gun
1 air compressor
1 air regulator
1 compressed air moisture trap
1 laser cutter w/engraving capability (Luckily, I have access to the one at the Arch Reactor, a hackerspace in St. Louis, MO)
1 paint booth
1 copper clad board
1 bottle of refill toner (I used Brother brand, but I suppose any type will do, the laser isn’t too
Hydrochloric Acid (Muriatic Acid)
Plastic watertight container
A respirator or dust mask (>N95 perferred)
And a design/circuit you wish to put onto the copper clad.
Once you have all these things, we can get started.
DISCLAIMER: If you follow this instructable, please take your safety into consideration. Note that I have set up environmental engineering controls that are adequate for my own use (paint booth) and that you are responsible for your own safety in your shop/workplace. If you do not have an environmental set up like mine, please consider getting a respirator! It is a good thing to have in your tool kit for all kinds of safety reasons!
Step 1: STEP 1: the Prep
The most important part.
First, we’ll set up our powder coat gun; I got mine from Amazon for a little over 100$. You’ll most likely get a spare empty bottle with your purchase (hopefully) so we’ll fill that with the toner refill that you have.
Consult your manual for the correct air pressure settings, but most likely it'll be around 20-30 psi.
(Please be sure that your powder coat gun does indeed have air-flow through capability; I had to disassemble mine to drill a hole in an internal mating piece after figuring out that mine didn't. That was an interesting story.)
After setting up and testing your powder coat gun, you’ll move onto the copper clad.
You’ll want to cut the design into a scrap piece of something you have lying around - preferably something that’ll show the burn-ins from the laser more readily - so that you can see both what you need to cut out so you can accommodate the design, and so you can confirm that the design works the way you want it as well.
Then after that’s set, you’ll scrub down your board (not too aggressively) with acetone, and leave it in the paint booth ready to spray the coating on.
Check your air filters and your ventilation, and then you’re ready to start spraying.
Step 2: STEP 2: the Spraying
Now that you have everything ready, you must apply the coating to the board.
A good way I've found to make sure you get a quality coating is to turn on the power supply and create a charge before spraying by charging the end of the gun near the work piece - it allows for the powder to stick more readily.
*Be sure to not stick the gun too closely to the piece, as it will both negate the charge difference and create sparks that could potentially ignite the clouds of powder (this is more of an issue for actual powder coating).*
Then go ahead and start spraying. You will hear a definite electrostatic sound as the powder starts to cling to the copper clad. Make sure you don’t leave any gaps, and that you also do a couple even coatings (a couple passes should do), since the laser cutter will burn it off easily - especially if you skimp.
Once you finish there, it’s time to head to the melting stage.
Step 3: STEP 3: the Melting
Everyone’s laser cutter will be set up differently than the one we have at the space, and you’ll have to consult with the person who’s most experienced with it to figure out at what power level, feed rate and engraving line spacing your laser cutter should use to best affect a properly melted toner layer.
I found personally that the best general rule to follow is low (power) and slow (feed rate). This kept the final copper traces smooth and even, and still allowed for an even coating melt.
Further Please Note:
You by no means need a full-blown laser cutter to melt toner effectively - in fact, I had more problems with it burning off rather than it simply melting. I could easily see a simple balloon-popping capable laser pointer mounted to a small CNC machine performing adequately for this task (you may want to look into additional cooling for it to run it for extended periods).
Once you have all your settings the way you want them for what you wish to do, line up your workpiece and run the cut. You should see the toner turn glossy where properly melted, and bare copper where it burned off. If it burned off a bit, no worries! Go blow off the excess, wipe off the rest with acetone, and try again.
Step 4: STEP 4: the Etching and the Waiting
Ahh the waiting part. Killer.
I use the cupric chloride etchant method (a quick Google search yields quite a good selection of mixture instructions).
Hopefully in the near future, I’ll have a suspended board sprayer and I’ll be able to go from design to board in fifteen minutes.
Once everything is etched, rinse thoroughly with water and wipe the toner off with a cloth and some acetone.
Step 5: STEP 5: the Ending
If everything has gone well you should have a nice, shiny circuit ready for drilling and/or populating with parts, as the case may be.
Most people I imagine will want to know where to get a laser cutter to use for doing this, and my first suggestion will probably be to try to find a local TechShop or hackerspace, or maybe a sign making place, but remember that you really don't need a full blown laser cutter, only something that will melt the toner effectively where you want it melted. I'd try out a handheld burning laser, but I don't have one handy myself.
If you have any further questions, leave me a comment and I’ll answer as best as I can.
Thanks for reading!