Building a UV PCB exposure box?

Hello,

Ideas please?

A small professional UV box with two 8W tubes will cost about £100, and is, professionally made and neat and tidy. I'm wondering if for sake of ease it would be easier to just go out and buy one?

I've seen the UV "fly killer," tubes on eBay for say £10, which are mentioned in a few of the tutorials online. Ballasts I have at home somewhere. Would need a neat little case, cut glass, switches, bits bobs, and time.

This is all purely for making the odd PCB so nothing commercial. There's also those little UV nail boxes for curing the plastic, they're only about £20 although I wonder about even coverage with those, and if indeed it is the right type of UV?

Circular tubes? U-shaped tubes? Straight tubes? Little 9W dual parallel tubes?

I'm just wondering in the end if it would be easier to just buy one, although that's not really in keeping with the spirit of diy.

Many thanks for any input, I'm just looking for ideas and opinons really. I'd also be half tempted to put in regular tubes too so that it can be used as a light box.

Friendly regards,

Alison

ps. There's this one at Rapid for £110 in a little kit;

Reply to
Aly
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"Aly" schreef in bericht news: snipped-for-privacy@bt.com...

The DIY spirit found a real cheap method some years ago. Use an obsolete face tanner and an old scanner. An example can be found on

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Although the text is Dutch, the pictures tell the story. I build one this way. Bought scanner and tanner for less then $15,-- on a flee market. The only extras were some pieces of scrapwood, some wire, two screws and piece of hot melt glue. Works like a charm. Two minutes exposure is enough to get perfect PCBs.

You only must make sure that your positives are pitchblack. My printer, although perfect in normal printing, does not make the artwork black enough. I have to stack two sheets to block the UV.

petrus bitbyter

Reply to
petrus bitbyter

You need _quartz_ glass to pass all UV. Apart from this issue, all the mechanical needs are satisfied by taking an old scanner and removing the innards; put the UV tubes and reflector inside where the scan mechanism used to go, and put your PCB on the glass, then close the lid.

Not advisable. If you're building a UV box, you should interlock it so that the tubes cannot come on while the lid is open. There are fun ways of going blind, and dumb ways... stick to the fun ways.

Reply to
larwe

_Quartz_ glass? I was told so very often. But the glas of scanner is apparently good enough.

Face tanners have no lid. So the need for an interlock will not be that strong. Nevertheless you should not look into the light. If you want to tan your face with it, you need to keep your eyes closed. The light can do serious damage to your eyes.

petrus bitbyter

Reply to
petrus bitbyter

Are scanner glasses usually quartz glass? I have an old scanner here now....

Reply to
Coyoteboy

Thank you to those who are replying. I'm following with interest.

At the moment I'm swaying towards the £100 for sake of ease. Oh, printer, photo inkjet, transparances, Brother DCP-340CW apparently 1200x6000dpi... we'll see about that.

:-) Aly

Aly :-)

Reply to
Aly

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I built one using two UV tubes in standard 12" fluorescent fittings, with a box made from MDF and a sheet of glass. It cost me about 20 GBP.

Leon

Reply to
Leon

You don't need quartz, ordinary window glass is transparent to the long-wave UV used for PCB exposure. The light isn't particularly hazardous.

Leon

Reply to
Leon

er,

I use an HP 5940 printer with JetStar premium film, results are excellent.

Leon

Reply to
Leon

I don't use the photo method much anymore, but for many years I did it wifh a UV tanning floodlamp in one of those clamp-on utility lights with a spun aluminum reflector. I'd lay the PCB on a piece of plywood on the floor, with the artwork taped over it and a sheet of ordinary window glass on top to make sure everything was flat. The tanning light was clamped to the back of a chair so it was 2-3 feet from the work, and pointing straight down at the center of the board.

True, that plain glass probably blocked some UV, but so what? The tanning flood puts out a ton of it, and you don't really want a super-short exposure here. Several minutes is fine, since it gives you some room to adjust exposure times.

Best regards,

Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis

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Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!

Reply to
Bob Masta

There was this idea in Elektor magazine last year.

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Pete

Reply to
Pete

It depends on the UV wavelength required for this application, I assumed it was rather short-wave. Below 170nm or so quartz glass is really necessary. Germicidal lamps have a quartz envelope.

Reply to
larwe

What nM are we talking about for photoresist exposure?

I'm looking at UV LEDs on eBay at the moment. 150mcd, about 400nM.

Search for inside the brackets. ( UV "LEDs" ) to weed out the other stuff.

Reply to
Aly

Not sure they have the intensity needed for etching, youd probably need hundreds of them lol. That said they're fairly cheap.

Reply to
Coyoteboy

UV LEDs can work, Elektor mag. had a design a few months ago.

Leon

Reply to
Leon

Thanks Pete, looking into this now :-)

Lots of info going on here, certainly enough to give someone pointers on Google Groups in the future. :-)

Aly

Reply to
Aly

I would think that used ones would be plentiful. I probably haven't erased a UV chip in 10 years, and would sell you mine if I could find it.

Hershel

Reply to
Hershel

For the occasional home made PCB, I find that the sun works much better than any UV tube. Depending on the time of day, I normally expose pre-coated PCB material for 20 to 80 seconds. This works quite well and it is fairly easy to produce boards with 12thou tracks with 12thou clearance. With a bit more care, one can do 10 thou. I have used a UV box bought from RS Components in the past, but I found the sun to give better results.

Regards Anton Erasmus

Reply to
Anton Erasmus

A light box is about the worst possible way to expose pcb's. To get good resolution, you need sharp shadows hence collimated light. The typical light box is a maze of position-dependent blurs. The light source should be far away from the film and the board, not close.

Get a bright light with decent UV concentration. A 175 watt warehouse-type mercury vapor lamp is ideal, and perfectly safe. Mount it about 3 feet above a table and add a bit of foil on top if it deosn't already have a reflector. Place the pcb, film, and a top piece of glass or plexiglass, on the table. Try 10 minutes to start. This will cast much sharper shadows than any light box can.

A tanning lamp isn't bad, and they're cheap.

The sun is pretty far away, too.

John

Reply to
John Larkin

Hi John,

Noted. Tell you what I do have.. A full size sunbed in the bathroom, hold on.. Eight 100W 6' tubes.

I've just been playing with the idea of fitting one of those small 25W 9" U-shaped tubes in a 12"x10"x5" flight case, or an 22W 8" circular tube.

But with what you've said here it's made me wonder..

Thanks again (and to everyone)

Aly :-)

Reply to
Aly

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