So you have a picture of a circuit board, or maybe a Gerber file, but you need that hard PCB STAT (right now)! Pop-Quiz: what-do-you-do?, what-do-you-do? There are quite a few sites out there on how-to make PCBs with your laser printer, a clothing iron, and an old magazine; I found this one quite informative. Beware, some of the new laser-printers don’t use toner that transfers (and ink-jet printers are right-out).
Not to be outdone by the simple (or being subjected to untold rounds of trial and error), I found a couple of companies that offer enhanced transfer paper and systems. One is Techniks Press-N-Peel PCB film, and the other, PCB Fab-in-a-box. The Techniks site doesn’t have a lot of information about their products, but Frank Miller’s Fab-in-a-box site is chock-full of great information and tips. After making a call to Frank, and getting quite the “download” of information from him, I decided to try his products (also, Frank boasts 5-mil accuracy with his techniques).
You can use a clothing iron with the Fab-in-the-box process, and Frank has articles on how-to calibrate the iron, and how-to get the best transfer. However, Frank has done a lot of research on alternatives to the clothing iron, and has settled on the GBC H-220 as a good low-cost “Toner Image Applicator” (TIA). I found one at Office Depot for $95, and had a $20 off coupon, so here it is:
Frank emailed me with a reminder to perform a modification to the H-220 to “slow it down” for better transfer:
This probably voids your warranty, so be sure to try out your unit before digging in. It took about 4 and 1/2 minutes for the unit to warm up, after which, I ran the “roller cleaner” sheet through it. Be sure to use the 5-mil (hot) setting, and let it warm up for a good 1/2 hour before running a board through; this gives the rollers a chance to absorb heat and create a good “thermal mass” for the transfer. If you buy the PCB kit from Frank (instead of Digi-key, Mouser, etc) select the “Free PCB Samples” for an extra bonus. Here’s what came:
The kit comes with images that you can compare the output of your laser-printer with. They should be dark and contrasty. I had to scale-up the antenna image so, in Linux, I used the following commands:
mogrify -quality 100 -resize 3033×1656! Image136.jpg (the size determined experimentally)
Bump contrast by 50%:
Then, from within gimp, using the “advanced” printer settings, I set the “contrast” and “toner darkness” to maximum (after a few test pages were run on regular paper to verify this worked well), then printed the antenna image onto the toner transfer paper. Lining up the paper onto the cleaned, blank circuit board (I used the 1/2 oz “scrap” that Frank had sent with the kit), I ran the paper and board through the TIA (after letting it warm-up for 1/2 hour). The first pass through, the paper didn’t stick to the board, so I ran it through a couple of more times (see instructions). This worked very well:
The next step was a bit trickier for me, and I didn’t quite get it right. To make sure that the toner has no “small holes” that the etchant will get into, the green TRF foil is then applied via the TIA (laminator) to make a good seal:
I didn’t do it carefully enough, so there were lots of wrinkles, and the TRF didn’t stick very well to the toner. Since you can’t just do that step again, Frank suggested I scrub off the toner and start over, but I had a resist-pen, and went over the whole pattern by hand (not that critical):
Using the 1/2 oz .032 copper boards made a huge difference; the Ferric Chloride etched quickly, and the board can be cut with scissors (instead of a shear). Frank’s “Ancillary Items” page has some neat stuff; I bought some of the silver plating powder from cool-amp, and after scrubbing the resist off the circuit board with Acetone (Naphtha didn’t work very well), I rubbed on the silver plating powder:
Notice the raw copper on the left side of the board compared to the (now silver coated) patterns. Pretty neat stuff! Now, on to assembly!
Printing and transferring using the white TRF foil, component placement outlines can be created on the circuit board. Now that I have the TIA (laminator), I’m looking forward to trying the Decal-Pro system! Frank has been very helpful, and extremely responsive to email queries — overall I’ve had a great user experience.