You can easily make your own high-quality PCBs (printed circuit boards), from a laser-printer or copier printout of the desired copper pattern, using an ordinary clothes iron, and the correct paper type. You can have finished boards in less than an hour, including printing, preparing the copper board, transferring the pattern, removing the paper, etching, and drilling. You can also use this method to print the component markings onto the non-copper side of a single-sided PCB.
There are many methods that can be used to make a PCB. Most of them involve applying a "mask" over the desired portions of the copper, and using an acid or etchant that can't easily penetrate the mask material to remove the unwanted copper from the remainder of the surface, although direct mechanical milling of the unwanted copper is also sometimes used. Most commercial boards seem to be made with a screen-printing process, for the mask. There are now available screen-printing materials that use a laser printout (or any black and white art), and a photo-sensitive screen material, that allow anyone to make a screen, at home (See http://www.cbridge.com, Circuit Bridge, San Jose, CA). Another popular method, which works with laser printouts, is photographic in nature: A transparent positive or negative image of the mask is created, and used to expose a PCB coated with a photo-sensitive etchant-resistant material. That seems to be the preferred method, for getting the best quality, finest traces, most repeatability, etc, at home, or in a low-volume, prototype-oriented situation. However, for many applications, and for the lowest budgets, the method described below can give results that are as good for certain applications, for less money, and maybe more quickly.
Very small trace-widths are said to be achievable with the photographic method mentioned above. I have not tried any traces that were less than 0.01-inches wide, with the toner-transfer method, described below. However, I have had absolutely no problem with the 0.01-inch traces. So, I assume that the achievable lower-limit is much less than 0.01-inches.
The type of paper used is the key. Almost all types will work, to some degree. But there are usually two problems: 1) Print quality; Some papers print with tiny pinholes in the toner, which greatly degrades the quality of the finished copper traces. 2) Removability; The paper has to be able to be removed relatively easily, and without causing any damage to the pattern on the copper. Glossy, coated paper has been found to work very well, since the coating on the paper will separate from the paper, when soaked in water.
I've recently tried many different paper types, and have finally found one or two that give excellent results for making PCBs (printed circuit boards) via a laser printer printout and the clothes iron toner transfer method.
I tried almost every glossy paper type that our local Staples office- supply store carries, plus the "house glossy" from our local printer. Most either had "pinholes" in the large black areas, or in the vertical (parallel to the print path) areas, or had removal problems after ironing. For example, the HP Premium Photo Paper had perfect printing, with no pinholes at ALL, ever. But, it was almost impossible to remove, even with long soaks in soapy hot water, or in alcohol, and sometimes pulled the traces off with it. Anyway, I finally found a good paper that's always free of pinholes and still removes fairly easily. It also leaves extremely strong toner/traces on the copper, which can be scrubbed fairly hard with a toothbrush, or rubbed very hard by fingers, without being damaged.
It is the JetPrint "Graphic Image Paper, Gloss Finish", Heavy Photo Paper (their product # 02735-0). They also make a product called JetPrint "Multi-Project Paper, Gloss Finish", Medium Weight (their product # 07033-0), which almost falls off the board by itself, after soaking for 10 minutes. Alas, it sometimes has pinholes. (I use an older HP LaserJet 4. Your mileage may vary...) However, the Multi-Project paper IS PERFECT for doing the component side markings of circuit boards, and anything else where etching isn't required, such as metal instrument panels.
Here's my procedure, for those of you who have never done this before:
- Print the pattern, using the darkest printer settings (On my LaserJet 4, I use: Dithering: None, Intensity: Darkest, "Raster Graphics", "Print Truetype as Graphics", and RET (Resolution Enhancement Technology): Dark). Never touch the pattern with fingers, or with anything else. Cut the pattern out, leaving AT LEAST 1/4-inch of extra paper, all the way around the pattern. Lay the pattern flat, face-up, until it's ready to be used.
- Scrub the board with a Scotchbrite or "artificial steel wool" pad, equivalent to '0' steel wool, usually in two orthogonal directions, with a lighter pass or '000' equivalent at the end, so it's not TOO rough. (I don't use real steel wool, since it may cause rust, after it's embedded in the copper.)
- Wash the board with liquid dish detergent, then with acetone, then with 70% or 90% isopropyl (rubbing) alcohol, drying with a new paper towel after each wash, and NEVER touching the board surface with fingers again, after the first wash.
- Lay the board on a paper towel that's on a rigid, flat, heat-resistant surface, such as a smooth piece of wood or plywood, copper side up. Blow any dust off of it, carefully, and off of the pattern paper, and lay the pattern face down on it, lining it up just right. (I experimented with pre-heating the board, before applying the pattern, but found no advantage to it.)
- I use a regular clothes iron, set as hot as it will go ("Linen", above "Cotton"), with no steam. (I have not measured the actual temperature of the iron. I will do so, at a later date, and update this page.)
- Place the iron on the back of the pattern, for about one minute, pressing very firmly (see addendum, below, for pounds force used). Pick up and rotate the iron by 180 degrees at the half-minute mark (just in case the holes on the bottom of the iron, or arm/holding-angle/torque, might cause a uniformity problem). (Note that if you try the HP paper, you better put a sheet of regular paper between it and your iron, because it will stick to the iron!). Note that as soon as the iron touches the pattern and presses it against the board, the pattern will no longer slip on the copper. So, sometimes I put the iron on a smaller portion of the pattern, at first, for just a few seconds, so I can hold the pattern in positon, with my other hand. This prevents the pattern from slipping, just as the iron is applied, especially if the pattern paper is slightly curled, or the iron is applied too slowly.
- After the board is heated (after the one minute), I place the rear of the iron along an edge of the board (with the rest of the iron on the board), and press hard near the rear of the iron's handle. I move the iron 1/4 to 1/2 inch away from the edge and press hard again, for about a half-second to a second, and continue that way until I'm near the other side of the board (with the rear of the iron), and it gets hard to keep the iron flat against the board. When I reach the other edge, I go back the other way, doing the same thing, over the same part of the board. If there are board-edges that are wider than the iron's rear edge, I make overlapping passes with the iron's side being along the outer edge of the board, on both sides of the wide edge. I usually do this whole procedure starting from each of the four edges of the board.
- Sometimes, at this point, I reheat the whole board for ten seconds or so, or more, with moderate to heavy pressure on the iron.
- I then usually go over the whole board with the tip of the iron, keeping it flat but torquing the iron forward as I go, moving either side to side, or by pulling the iron backwards, in lines about an inch or less apart, across the whole board. But I'm careful to never let the tip gouge, and never let any edge of the iron press against the board. I always try to keep the bottom of the iron flat against the board, whatever else I'm doing.
- At the end, I usually reheat the board (with pressure on the iron at the same time, again). I also usually just press the iron flat against the board, hanging almost halfway off one side, then in the middle, then off the other side (still always keeping it flat against the board), for good measure...
- The whole heating/ironing process takes between two and three minutes.
- Then, within five or ten seconds or so, I pick up the paper towel, with the board on it, and hold it under cold running tap water for 15 to 30 seconds, to stabilize the toner. I turn it over and cool both sides.
- Then I immediately place the board into a sinkful of hot water (about 130 deg F), for 10 to 20, or more, minutes. If the water is TOO hot, it might start to re-melt the toner. I THINK that most laser printer and copier toner startes to melt at about 160 degrees F (Fahrenheit).
- Peel off the paper, or at least the top layer. If the paper underneath is still a little dry-ish, put the board back into the water, for another ten minutes or so.
- Rub the remaining paper off with thumb pressure. It's OK to rub hard. But your thumbs' skin may get sore. Usually, almost all of the paper residue comes off, even off of the toner itself. So, you could SEE if there were any pinholes, etc, in the toner. (I have yet to see any, though, using this paper!)
At this point, if something has gone wrong, you can start over and not waste the board, by washing the board with laquer thinner (see below), to remove the toner. Then, begin again with the second (Scotchbrite) step, above.
- Use small circular motions with a toothbrush, to remove paper residue from small or tight areas, and from hole marks. This may be the hardest, or most tedious, part. I will soon try leaving the residue IN the holes, to see if the etchant can work through it. (Nope. Doesn't work very well. See addendum, below.)
- Rinse the board and wipe the board dry with a clean paper towel.
- Sometimes I wipe and rub the board with a paper towel and 70% alcohol, especially if it needs correction-pen marks.
- Make any necessary corrections, using a Sharpie or other etch- resistant marker. I sometimes have a couple of very small flakes of toner fall off, on about one out of three or four boards, at the most, especially if I scrub way too hard with the toothbrush.
- Etch. I use Ferric Chloride, in a tupperware plastic bread container, in a sink of hot water, agitated by an old metal record- player turntable turned on end, with a bolt an inch from the spindle attached to a small piece of wood that is also attached to a bolt that protrudes near the plastic container's top edge. I have a couple of bricks in the sink, to keep the container in line side-to-side as it's rocked front-to-back by the turntable-connected arm. I usually use either the 33 RPM or 45 RPM setting. Don't get the etchant on ANYTHING else, especially a good stainless-steel sink! I keep the lid loosely on the container, to catch any splashes. Don't use a metal container! And don't use any metal utensils, if you want to use them for anything else! Wipe and flush any accidental spills with lots of water.
Note that many people prefer Ammonium Persulfate as the etchant. One big advantage is that it is more or less transparent, allowing you to see the progress of the etching, without removing the board from the etchant. Note also that most people either agitate the etchant by hand, or use an air-bubbler tank. With an air-bubbler tank, etching times can be as low as 5 minutes, and etching is more-uniform. A bubbler-tank, with a heater, can easily be built, using plexiglas (or a Tupperware breakfast-cereal container), silicone sealer (caulk-type stuff), a fish-aquarium pump and tubing, and an aquarium-type water heater. I believe there are contruction plans on the Web. If anyone has a link, please let me know, so I can post it, here.
Thanks to Alain Parent, for this link to
If you use 1-ounce copper boards, instead of 2-ounce, etching is much faster, and, correction-pen marks will last long-enough to work well. Plus, over-etching isn't usually as much of a problem.
- When etching is almost complete, I usually remove the board, rinse it under running tap water, and put it in a small tub of half-strength etchant (diluted 1:1 with tap water), and lightly brush the areas that still have visible copper, until they have been removed. This seems to help prevent over-etching.
- Wash the board in laquer thinner, rubbing with a paper towel, to remove the toner instantly. But be careful! Laquer thinner is extremely volatile, flammable, explosive! I do it outside... I use small, disposable "crinkled"-aluminum pans, which are usually used for temporary food-storage. Mine are usually free, and filled with Chinese food, initially. I generally lay the board face-up in the pan, and then pour laquer thinner over it, to a depth of about about 1/4-inch (1/2 cm), or less. Then I wad a paper towel into a ball, and lightly rub the toner off. I then pick up the board and wipe off any remaining traces of toner. I suppose that I really wouldn't need to pour as much thinner into the pan. Possibly, it would even work as well with just a thinner-soaked paper towel.
- Drill. Some people have suggested drilling BEFORE you etch. OK. But I like the way the etched hole marks help guide my drill bit into themselves, especially on small pads and when holes are very close together, or when the drill/bit is a little wobbly. I use a regular floor-standing drill press, set at its highest RPM (revolutions per minute). I have tried the pure-carbide bits, about .035 inches, with the larger, 1/8-inch shanks. But they are so strong that they're too brittle, and they break too often, for me. (Even getting 50 of them for $5 at a hamfest doesn't seem like a good deal. That's how often I break them!) So, I usually just get the "wire-gauge" high-speed steel bits, from the local hardware store. I've been using the #60 (.04 inch), since they fit a large variety of component lead sizes (all but the largest). I got 15 bits for about $20. I change bits every few hundred holes, at least, or whenever I notice the edges of the holes are getting pulled away from the board too much. I guess the FR-4 board material doesn't transmit heat well at all, and the steel bits get hot quickly, and consequently dull very quickly. (It has been suggested that putting Carbosol on the bit occasionally may prevent it from dulling as quickly. I tried it, but didn't notice much difference.)
To hold the tiny bits in my large drill, I bought a small chuck that fits into my larger chuck.
Many people have had good success using a Dremel tool, with the Dremel drill-press/stand adapter. At least one person reported also using a large magnifier, at the same time. This would also help give eye-protection. Otherwise, safety glasses should be worn.
- If you're going to mark the component side of the board, scrub it with the Scothbrite pad, at this point, with the same method as used for the copper side. Then wash the board in soap and water, and then 70% (rubbing) alcohol, drying after each as above, and not touching the cleaned surface with fingers. Make sure the holes are all dried out. (Tapping each edge of the board sharply on a hard surface can help to dislodge any alcohol or water that's still in the holes. Then re-dry and allow to air dry for a few minutes.) Hold the board and pattern up to a bright light, to align then component markings with the holes' pattern. (If your boards aren't translucent, this may be a problem.) Then iron on the component- side pattern, but using the other, more-easily-removed "JetPrint Multi-Project" paper, mentioned above. Soak for five or ten minutes in warm water, then just peel it off. Rinse and lightly rub the very minimal residue away, dry the board, rub it with a paper towel with alcohol on it, dry it again, and it's ready!
If anyone's interested, I can try placing the board on a scale, and see how hard I'm actually pushing, with the iron (See addendum, below.).
The boards made this way come out nearly perfect, nearly every time.
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Well, I tried leaving the paper residue IN the holes and etching. But the result was less than satisfactory. So, in order to minimize the potential for damage to the traces from hard rubbing with the brush, I tried letting a board soak overnight in water. Voila! The drill holes were easily cleaned out with fairly light scrubbing with the toothbrush. Of course, I usually can't wait overnight. Adding some liquid dish detergent helps, if I'm in a hurry. Also, digging the bristles on the tip of the brush straight into the holes, while lightly making tight circular motions, gets the residue out with minimal brush pressure. It is still quite tedious, if there are lots of holes. Any suggestions?
Also, I DID put a bathroom scale under the iron, and simulated pressing on a board. I was using at least 25-30 LBS (pounds) of force. I don't always use the same PSI (pounds per square inch), apparently, because I use the same force on board sizes of 4x6 inches and 2.375x6 inches. Both seem to come out equally well. I have, several times, used a lot more force on the iron, and it IS possible to flatten out or blur pads or traces, if I press hard enough, or if I accidentally scrape with the edge or tip of the iron instead of keeping it flat.
Someone else suggested baking the boards in an oven, after the toner has been applied and before etching. With my current paper and method, I don't see why it would be necessary, since the toner seems so strongly bonded to the board. However, back when I was using paper that left pinholes in the toner, I wanted to try baking a board just to see if the pinholes would close up. At the time, it also seemed like heavier iron pressure might close them. But it never seemed to. Now that I'm using the JetPrint Graphic Image Paper, I don't need to worry about those things, any more.
Happy board-making, everyone!
Tom Gootee Gootee Systems tomg@fullnet.com
