This article was intended to be an update to the How to make a printed circuit board step by step article however with what I discovered I decided it would be better as a feature in its own right. While experimenting with the PCB toner transfer method, a few scraps of PCB and a couple of techniques I’d read and taken further I produced some rather surprising results.
It seems that everyone with a hobby electronics interest is looking for a reliable and cheap way to produce a PCB. There doesn’t seem to be a definitive way that doesn’t have problems of being too expensive too complicated or not being repeatable.
I’ve been flitting from one method to the next without ever being overly convinced that what I had done was either worth the effort or cheap enough to bother with again.
That was until yesterday when I put together a few tips and techniques and literally surprised myself with the quality of the results. Now maybe it was a total fluke as I haven’t tried it again but if it encourages someone else to have a go then it’s been worth it.
So what’s the big deal then? Well if you’ve read any of my other posts you’ll know that I’ve been experimenting with producing PCB’s. To be honest I’ve been experimenting ever since I finished working at the university where I was introduced to the art of producing them. The method there was photographic but at home it seemed a bit too much. The main stumbling block for me is the photo resist. From what I’ve read recently it seems difficult to coat a board yourself. The stuff seems hard to get, expensive, difficult to get an even layer and there are reports that it may be a cacogenic.
Buying pre-coated board seems the poplar route but the prices of pre-coated board put it on par with the cheaper oversea production companies. Plus there’s the problem that if you make a mistake you can’t just recoat it and use it again.
Given the fact that you’ve got to experiment with exposure and developing it seems you could end up with a lot of unused copper clad board. Not only unused but without much chance of every getting it used if you can’t recoat it yourself.
If you read my post on over sea manufactures here you’ll know that I’m pretty keen on this method.
No time for over sea manufacture?
You can produce the artwork and files on your PC using free and very useful feature packed software. You can use two layers and have plated through holes and a screen printed component overlay not to mention it’s drilled for you as well. It’s no cheaper to not have them. If you need a few of the same board then this is definitely the way I’m going to go. The price then becomes even lower per board. If you read my article it worked out at £2.27 per board.
The only problem is the time it takes. If you want to try an idea they seem to take a lifetime. Like when you were a kid and waiting for Xmas. If you just want one board surely there’s a better way?
So I’m back to the laser printer and hot iron technique.
Best paper for toner transfer
The first problem I had with this was that I used thin magazine paper . I had read that that was the best material to use. Problem for me was getting it to feed through the laser printer. It would get stuck causing the machine to jam. In the end I minimised the jamming by taping it to a normal sheet of paper and separated it when it came out.
This time I had no magazine paper so I just pulled out a sheet of photo paper that I had lying about from years ago when I bought an inkjet and printed photos.
The paper specifically was PC Line photo glossy paper. It is however from years ago and even it I could still find it there's no guarantee that they haven't changed it in some way.
The photo paper that I used to great success.
No problems printing on this. Just open my Kyocera FS680 laser sheet feed tray, press a button and it’s ready for jam free printing. I had previously printed the design out onto a normal A4 sheet to check the size and image were correct. Always a good idea before you waste a sheet of photo paper
Just set it to print dark and sheet feed it, so all pretty easy so far.
Next step was to clean up a small piece of copper clad board with jif in the sink and let it dry while I cut out the photo paper print and put on my old clothes iron that my other half gave me so I wouldn’t use the proper one.
Using a roller?
Here’s something I read about. Some PCB paper manufacturers are saying not to use the iron method as you can’t get enough heat or pressure and it’s not repeatable. So you need to get a laminator but it has to be a special one to take the thickness of the PCB or you have to modify one? I can’t be bothered to go to those lengths so I’m sticking with the iron, however I’m sure I read somewhere about the rollers on a laminator being able to exert more pressure because of the smaller space the pressure was being applied to. It seems to make sense as with a roller all the pressure is one line on the board at a time. So to replicate this you need something like a roller, a piece of dowel or a round pencil.
Put the print out face down on the copper side of the board and put the iron set to its hottest setting on the back of the photo paper. This makes it stick to the copper, then put the “roller” on a flat surface and put the board on it paper side facing up and put the iron on top and roll it backwards and forwards applying pressure.
The idea being that the roller means all the pressure is applied to a very small section of the board at any time and therefore is greater than without a roller.
I did this for a couple of minutes and let it cool and turned the clothes iron off. After about ten minute I thought I’d try and pull the paper off and then hopefully there would be enough toner left on the copper for me to be able to draw over the top with a pen.
Previously with the thin magazine paper the only way to remove it was to soak it in water until it disintegrated and rub it off, pretty time consuming and messy.
I was amazed that he photo paper came off in one piece. I was even more amazed to see that the toner had successfully stuck to the board better than anything I had ever done before. I was total amazed to see the photo paper was almost white and with hardly any remaining toner.
Photo paper after transfer.
Looking at the board there were a couple of areas where the toner had stayed on the paper. If you look at the pictures it’s on the edges. I’m pretty sure that if I used a slightly larger board and left more blank paper around the design it would all have transferred perfectly.
Board after transfer.
I really wasn’t expecting it to be as good as it was given the fact that a company that manufactures paper specifically for this claim it can’t be done with an iron and then you need to use another paper laminated over the top as the toner is to porous to stop etchant pitting the copper at best.
Board after etching.
As you can see from the picture the toner transfer didn't seem to be porous at all. The board was etched using the contact method which is covered here and that might have also helped in the final result.
I’m not sure if the paper I used was magic and that’s why the results are so good. It could also be that the use of a roller may have made a difference because of the extra pressure that it exerts onto the transfer. It certainly looks like that may have played a part as the ends of the print out are the parts that didn’t transfer perfectly and that’s the area that didn’t get the same sort of application because I was aware that I was about to runout of board. In hindsight the next time I’ll make the board a bit larger so the pressure can be exerted all the way along.
In this close up you can judge the quality by looking at the text. The 8 pin DIL gives an indication of scale.
Without wanting to get too carried away this is by far the best result I've had using the PCB photo transfer method. It has certainly given me enough encouragement for another go in the future.