Cheap & Cheerful DIY UV PCB Exposure Unit

[Wendymott]

Hi Guys.... Hot off the press.... literally. I just tried this method using a "glossy magazine" page which had little on it...In most...it was ok....I did not apply the heat at the edges properly, thus some bits of track was missing.....I was not too happy with some of the edges which, on the artwork are straight, but when transferred to the copper were a bit un even. But as a "get out of jail free" method, for un important pcb's its great, and I will give it another go............well... as the iron is out.. I may as well do the domestic stuff.

[Bazz4CQJ]

Thinking of 'glossy paper'.... casting my mind back to the far-off days of making business presentations using overhead projectors / transparencies, I recall that those acetate (?) sheets had a matt side which was the side that had to be printed on, and a gloss side which must be avoided. I wonder whether printing on to the glossy side of those sheets would be a viable approach for making PCBs?

B

[Ti Pwun]

Originally Posted by Wendymott

.....I was not too happy with some of the edges which, on the artwork are straight, but when transferred to the copper were a bit un even....

That sounds like you were moving the iron in circles as I've seen on some of those videos on YouTube. I imagine that if the paper you're using is thin, it would be easy to distort the traces while moving the iron. Maybe just downward pressure would be better.

[Ti Pwun]

Originally Posted by Bazz4CQJ

Thinking of 'glossy paper'.... casting my mind back to the far-off days of making business presentations using overhead projectors / transparencies, I recall that those acetate (?) sheets had a matt side which was the side that had to be printed on, and a gloss side which must be avoided. I wonder whether printing on to the glossy side of those sheets would be a viable approach for making PCBs?

I think the iron might not like that idea too much!, It would probably make it necessary for you to sleep in the bath until you buy the wife a new iron!

[Bazz4CQJ]

What setting do you need to use on the iron? The overhead sheets survive the laser printer - don't know the max temperature they will actually survive. I have a pile of them which never got used and have been collecting dust for some time now.

B

[Oldcodger]

Thinking along the lines of those who use a light box. Instead of printing to a clear sheet, would it be possible to laser print to a sheet of suitable printer paper and feed paper plus sheet of laminator material through a laminator, transferring the image to the clear laminate material.

[Wendymott]

In my experience of clear acetate (Nobo). The toner does not adhere to the shiny surface and it is "thin". Thus to get a decent contrast ratio I make two copies and increase the density that way. If you use semi opaque material you get the density, but the overall contrast ratio is severely depleted, thus more exposure time, thus more chance of loosing the wanted tracks. Up to the latest method discussed, I think I have experimented with all options. In the old days it was a Roland pen plotter onto semi clear acetate, but even that was intermittent quality, if the pen ran out or blocked, start again. Ok TiPwun, I did rotate the iron. Next time I will keep stationary and use the main part of the iron plate, "no domestic situations here" haa haa.

[Ti Pwun]

I wouldn't have thought so, but there is a product called 'Press-n-Peel Blue' you might like to try - just print on the dull side (in reverse), iron it on (without rotating the iron) and then peel the film off. It will leave your artwork on the board and is ready for etching.

I like to use acetate because I use photo-sensitive board and a UV exposure unit but Press-n-Peel Blue is worth experimenting with if you can get hold of some for a decent price. It tends to be expensive here, even on eBay, but if you look at somewhere like Maplin, you definitely won't like the price! :/

[Wendymott]

Hi Ti.... This press and peel is the problem for me... too expensive...mostly I will continue with UV sensitive material.
Regards

[David G4EBT]

The reason I initiated the thread was to try to illustrate how you can make PCBs 'on a shoestring' (as implied in the title - 'Cheap & Cheerful PCB exposure Unit') because that's the major hurdle for anyone wishing to make their own PCBs using UV techniques. I mentioned the iron-on laser technique as a zero cost option for anyone who has a laser printer.

Neither technique is without its problems, but when things don't go to plan, the cheaper the approach, the less is the exenditure for any failures. If you use the iron-on laser technique using scrap glossy magazine paper and it doesn't turn out right, nothing is lost but a bit of time. However, if 'press 'n peel doesn't turn out right, the paper is quite expensive.

Same with spraying ones own PCBs with UV lacqer. Pre-sensitised boards aren't cheap and are fixed sizes, so you can end up with useless shaped offcuts, and if the PCB exposure and develpment isn't just right, you end up with a piece of copper clad board. However, when you spray your own, you can cut the laminate to size, and spray a good layer of lacquer on. I find that an exposure time of 4 - 5 minutes (not critical) usually produces a good outcome, but if not, all I've wasted is a couple of bursts of spray laquer. I just clean off the board and re-spray it. Most of the laminate I use, which I self spray, is acquired cheaply.

I use cheap 0.8mm and 1mm HSS drill bits from China and at only 5p each I can afford to discard them after one board has been drilled so as to avoid the risk of the drill bit 'skidding' or throwing up burrs. Not worth fiddling about trying to sharpen them at that price.

My overall aim is to try to be economical on tools and materials, while at the same time, acheiving a decent standard of workmanship. If prospective PCB home-brewers think it's expensive to set up and produce PCBs it can be off putting, so I hope that anyone who might be contemplating doing so will consider the cheap and cheerful approach. Certainly to anyone with a laser printer, even the paper comes free!

In looking at the youtube videos, I'd agree with other comments - seems to me to be asking for truoble to attempt to iron the paper on the PCB as though one was ironing a shirt - moving the iron back and forth. Makes more sense to hold the iron firmly down onto the paper for a few minutes to ensure that the toner firmly bonds onto the board, and that the risk of distorting the pattern is minimised, if not obviated.

No good attempting this - or any other task for that matter - if it's seen as a chore rather than a pleasure.

[Ti Pwun]

Hi David,

Oh, I agree! Press 'n Peel is just an option. You're right, though; it is drifting away from the intent of the thread - I only mention it because if just tearing out a magazine page and giving it a go brings up more questions and concerns then to prevent it becoming a chore/unenjoyable, it might be worth looking at.

But yes, if acetate and an exposure unit doesn't appeal, I would encourage people to try glossy magazine pages. Can't beat free unless that route isn't any fun.

Speaking of spraying ones own PCBs with UV lacquer - I really ought to revisit that, despite being happy with my current setup. I don't have waste with pre-prepared boards because I make specific items where two boards are made from one exactly and I use a wet tile cutter to cut the board in half, but it would be useful to cut several small boards from one large sheet...