Building a UV PCB exposure box?

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

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

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 :-)

Yikes! Skin damage! Look good now, look like Brigitte Bardot later in life.

If you have proper emulsion-down film and good clamping to the board (say, felt below and flat glass above) a light box can be OK. Just keep in mind that the exposure will not be very uniform, and light will be coming in at all sorts of goofy angles.

John

If the artwork is in contact with the board ( ink-side up) this is really not a problem.

40-50 tracks/inch resolution is routinely do-able with a conventional light box.

I guess this idea is also not in the spirit of DIY, but getting PCBs made has gotten pretty inexpensive lately. I saw an ad the other day for a double sided board with plated through holes for $26 even at qty

1 for a first time customer. Olimex in Europe has some very low rates for small quantities, but I have not looked into them in detail.

Is this a cost thing or just a fun thing to make your own PCB lab?

UK prices are hideously expensive, like £200+ ($400) for 5 eurocards with a

2-week turnaround. Trouble with Olimex is that I'm not giving my credit card number to anyone in Bulgaria nor using Western Union.

The problem with the UK is that it's just such total rip off. I was charged £13 ($26) the other day for buying something in the States costing £22. This country is just a dump.

Looking at UV tubes right now.. £10 for single 12" UV tube. £10!! That's the cheapest round here where I can just walk in and buy. If I go to B&Q/Homebase they're about £20 and in fancy packaging with party goers all over them.

I dumped a load of laptop LCD screens at the rubbish tip the other day and had some jobsworth telling me I'd put them in the wrong bin, "they're LCD screens," I said pointing at the big plasma displays in there. He wanted me to put them in the metal bin as they were computers. Erm, no, they're all plastic you argumentative turd. "Do you want me to dump them in a lay by perhaps?" That's what all the sane people are doing. Go for a walk in the countryside, trip over a saucepan!

I HATE this bloody country. :-( Where I can't send my kids out to play football without some council official bringing them home saying they don't have insurance. Wot!! Insurance.

*rants*

:-) That was meant to be slightly humourous of course. But really, the UK has just gone mad. You can't do anything if it isn't approved, stamped and monitored.

"Really mad cow disease in England:

Cow: I say old chap, MOOOO!!! ;-)

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

I'm very interested in this angles scenario I must say. I can imagine that in alot of boxes the tubes are just too close. They're like 1-2cms from the board. That can't be good.

At a guess I'd say 5cm is better yet I don't know what I'm talking about admittedly. At 1-cm though, that's just too intense.

Yet the UK and Ireland are doing very well economically, much better than mainland Europe.

I took my kid to a baseball practice and asked the coach if she could try out for the team. He told her "go to left field" and that was it.

John

Most of the money coming here doesn't really exist, it's all offset by the amazing amounts of debt people are in.

House prices may be £250k for a modern terrace, yet most of the possessions owned, cars sofas kitchens this that, are all bought on credit. Thus making it look like there's more disposable income, when in reality there isn't. Also we have alot of foreign money coming into the country, again further stimulating the current debt culture in an effort to afford everyday living.

We're a bit like that bus at the end of The Italian Job with all of the gold balancing in it.

Pleased to hear your DD did ok. Quite inspiring that. :-)

Alison

Hi Leon,

Noted :-) I'm going through this right now planning for what happens next. JetStar film from Rapid is the likely candidate.

Thanks again, spotted your post here in a Google search.

Alison

is,

se it

bs,

A photo frame and a sunny day works for me. Just dont get caught taking her picture out of it.