Yes, yet another toner transfer PCB etching tutorial - But wait! I've experimented a LOT and found the key to producing reliable results. The secret is in the execution, NOT the materials. I'm now producing 2 sided PCBs with perfect tracks on my 1st attempt. So, let's go....
Step 1: What You'll Need
- A cheapo laminator - these can be had form Lidl for under £8, or on ebay/Amazon.
- An iron
- A laser printer (Mine cost £45 and I buy no-name toner that seems to last forever - having a mono laser also saves you a fortune on ink as you can keep your colour inkjet just for printing, well, colour). Or, use the one at work :-)
- cheapo paper - the type that comes through the letterbox with supermarket offers on
- PCB etching kit - I'll leave that to you but you'll need an etchant basically
Step 2: The Cheap Paper
What you need is thin semi gloss paper. ALL the stuff that comes through UK letterboxes with supermarket promotions on is the stuff we need. Cheap, thin, translucent when held up to the light (this is very important), usually a bit rough. Like this Wilko's flyer...
Notice how it's semi transparent when held up to the light.
Step 3: Print Your PCB Layout/s
Now, using your PCB software, print out your component side and solder side. I print 1st onto plain paper so I can use them as references when I eventually get confused about the PCB orientation :-) Then Print each side onto your cheapo paper - My printer seems happy to feed the paper without fuss.
Step 4: Trim the Paper
Cut around the PCB prints leaving about 1cm around 3 edges and leave the last edge long - I leave it the length of the rest of the A4 - This long edge is important for feeding the PCB into the laminator later.
The border dimensions are not important - you can see mine are cut quite messily. You are just aiming to leave enough border for the Copper board to fit in with a little room to play.
It is worth mentioning here that it is important not to try to fit your PCB design right to the edges of the copper board. It makes aligning the board in a minute quite hard, and also toner right at the edges of the copper board can be harder to transfer.
Also, I'm guessing you already know, but your component side printout needs to be flipped horizontally (mirrored) in your software so it reverses when flipped over. This is standard in PCB printing.
Step 5: Making the Magic "Envelope" , Part 1
Now we need to marry the two prints together , aligned, in a nice pouch that we can slip the copper board into. It's actually really easy when you know how.
1st, hold op the "solder side" print, with the toner facing you, against a window - it's flat, and more importantly, light.
Now. flip over the "component side" print and place it on top, roughly aligning. You two pieces of paper should have the toner on the inside, toner - to- toner.
Now start by aligning a top corner. Gently slide the paper over each other until that corner looks perfect. The easiest way is to look at the holes in component pads, fine tuning until the holes are as large and clear as possible. Now put a small piece of masking tape over that corner, on the paper and the glass, holding it in place.
Repeat with the left top corner, taping in place.
Now you can to the bottom two corners. Just because the top is aligned, don't assume the bottom is perfect, it might need a tiny jiggle. Don't get too obsessed. Ultimately, a tiny amount of drift won't kill, as long as your holes go through close enough when you drill the board!
Step 6: Making the Magic "Envelope" , Part 2
Now, run a length of masking tape along the top three sides. I edge the tape along the very edge of the PCB design as you can still see it now on the window, but when we slip the copper board in later, you won't be able to see it so easily so the masking tape becomes a good guide as to the edges of the printed PCB.
Now gently peel off one side, I usually do the right side. Then fold the masking tape over and stick on the back. How much you fold it over is up to you but I tend to do it roughly evenly. You'll see in the photos. Again, this is not critical. We will be aligning the copper board by sight, not by "fit" later. Remember, this is a quick and simple method ! The whole point of this part is to secure everything in place so it doesn't move at all.
Now you have done one side you can peel off the whole thing from the window and do the same to the other 2 edges.
You will end up with an envelope with one open "long" end.
Step 7: PCB Copper Board Prep
If you've read other versions of this method, you'll know that it's important for the copper board to be clean of oxide and grease. I've actually found that though this is an important step, it's not nearly as important as people make out. After lots of failures I pointed the finger at board cleanliness / grease contamination. I was wrong. It turned out to be the heating / pressing method at fault - we'll cover that soon.
None the less, we need a clean board, but there is no need to obsess. A simple rub with a piece of fine grade wet and dry (emmery paper) until it is shiney all over, then a quick scrub with kitchen towel and alcohol cleaner or acetone (nail varnish remover) will suffice. I rub with isopropyl alcohol until the paper doesn't get dirty any more.
Keep your fingers off the copper from now on!
Step 8: Slipping the Board in the Envelope
So now, slip your copper board into our lovely envelope. Slide it in to that it goes nearly all the way, leaving a little more to go in.
You can fold back the excess paper flap and peer inside to see what's going on. This lets you see when the board is down far enough so that the printed design will land on target at the "long paper" end. Once this bit is on target, as long as your copper board is the right size (with a margin to spare) then the other end will be OK too.
You can also gently squeeze the board to be equal on the sides, though if you get the "long paper" "open" end lined up square, then the rest should be fine. If you have any doubts, hold the whole lot up to the glass window and check, you can still see a bit, and the masking tape edges will indicate the edge of the print out .
As long as you've left a bit of copper board margin spare, this bit is a non-event.
Now keep your little package secure somewhere and fire up your iron and laminator.......
Step 9: The Main Event - the Toner Transfer.
Now then. I've read so many ways of doing this. With an Iron / with a laminator / pressing the iron and wiggling it / pressing the iron tip all over the board, up and down / rubbing the iron all over the board / just passing it through the laminator. All of them failed in one of three ways.
You either end up with smudged toner (traces) from being over heavy handed with the iron tip, or pressing the whole iron down too hard. Or, you end up with toner not transferred in patches because you never got even pressure all over the board. Or, you don't end up with all the toner transferred because you used a laminator and it could not get hot enough for all of the copper board.
After loads of testing with the above methods, I got adequate results, occasionally. Not good enough.
Pressing the toner on with the iron alone is flawed. The Iron surface and your paper&copper surface are not flat enough to get even pressure. The gets worse as the board size grows. Using the tip of the iron makes things worse and much more prone to smudging.
Passing boards through a laminator works, but only with small boards. Once you go over 5 or 6 cm, unless you have some kind of super laminator, the machine can't keep the board (both sides) hot enough for the toner to transfer.
The iron gets the toner and board plenty hot enough, but is a coarse pressing tool. The laminator doesn't get hot enough, but is a great smooth pressing tool. See where we are going here? :-)
The secret is everything needs to be very hot, and the pressure has to be even. Good transfer, zero smudging.
So, wind your iron up to full, with no steam, and get your laminator preheated. I take my laminator apart - I do this because I can manage any jams easier, and more crucially, I can get my iron closer to the rollers.
Put the pouch in front of the laminator with the long leading edge pointing at it - that's the edge we will be feeding into the laminator.
Put your hot iron on the pouch/board and press with just a moderate pressure. We are trying to heat the board and toner here, not actually transfer the toner yet. You might have to heat the board in two areas to cover it all. Do this until the paper is too hot to touch. With my iron on full this takes less than a minute. Don't be tempted to "swish" the iron about here. If you need to move it to heat all of the board, lift the iron and place it down again.
Now put the iron aside (still on) and lift the packet by the edges and feed it into the laminator. It'll be very hot. Have a cloth handy.
Because we left a long leading edge on the paper, you will have some time to feed it in before the actual board goes between the rollers. If we didn't have that extra paper the rollers would probably not take the thickness of the board, and it would all happen too fast.
As the board approaches the rollers, place the iron over it, as close as you can to the rollers. So now we are super heating the board with the iron and then the rollers are doing the pressing. Keep the iron there until the board has gone through.
Now repeat with the other side. Exactly the same - although it will take less time to heat the board as it's already rather hot!
So one pass one side, and a second pass the other side.
If the laminator wont take the board - using a cloth (as it's too hot) - firmly hold the whole package and push / force it in. Once it "takes" it should go through. Another technique is to feed in the package at an angle.
Step 10: Paper Removal
Now we are done with the hot stuff it's time to clean off the paper. You can immediately put the super hot envelope under a cold tap. No need to wait. Within seconds the board will be cool enough to handle. Once it is, start peeling off the paper. You don't have to be delicate.
As the tap water runs over the paper it will quickly saturate it. Rub the board firmly with your thumbs - the paper will roll up and "melt" off. It only takes a minute. Be firm with your thumbs. Once you've done both sized you'll end up with a board looking like this. (The one in the photo is an experiment that went wrong, hence it's a little rough at the edges - I forgot to make the paper pouch long at one end so it got stuck entering the laminator).
All that's left to do now is etch it and clean off the toner...
Step 11: Etching & Cleaning
I won't go over old ground here. Etching is covered all over the web. Basically put your board in etching solution and when all the copper is gone, take it out!
Once done, you'll want to remove the toner. Acetone (nail polish remover) or lacquer remover do the job nicely. I put the board in a saucer and splurge nail varnish remover on, then scrub vigorously with an abrasive plastic dish scrubber. It comes off a treat.
If it doesn't seem to be coming off, be generous with the solvent, and firm with the scrubber. Gentle rubbing with a wire brush works instantly. If it's taking you more than 5 minutes you are being too gentle.
That's it! Job Done!
Remember, the key is heating with the iron AS it goes into the laminator.