PCB production

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tegwin

New Member
I do realise this is slightly off toppic...But

Im trying to produce some PCBs for my picaxe project using photo-etch style board...I can get hold of the chemicals required and the board nice and cheap, but a proper UV box is the best part of £100....

Could I use something like a 75W blacklight filament bulb to expose the UV reactant board? Like this? http://www.rapidonline.com/productinfo.aspx?&tier1=Electrical+&+Power&tier2=PA+&+Audio+/+Video&tier3=Lighting&tier4=75W+Blacklight+UV+bulb&moduleno=77725&catref=35-6044
 
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Rickharris

Senior Member
Sunlight - takes longer but it's free! Just leave it on the window sill in daylight - You can see the image when it is cooked!
 
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kevrus

New Member
You may need to check the UV wavelength of the blacklight lamp. When I once tried black UV tubes I found that the wavelength was incorrect (350 to 370 nm i believe) and no amount of exposure would develop the board.
I now use UV tubes for insect killers (quite cheap) and get good results with a homemade light box. It all comes down to the wavelength, it is possible to develop boards in sunlight as that has all wavelengths. I believe a wavelength of around 450nm is equired but it may depend on the pcb coating.
 
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profmason

Member
UV source

I use a pair of 9W UV fluorescent tubes in a box. These bulbs peak at 450 nm. Some ballast, a transformer and some aluminum foil and you are good to go. You want something that is reasonably bright and has the right frequency response. I suppose an array of bulbs like you listed would work, but those bulbs are using a filament and the coating and have a pretty wide spectrum. (Not that it matters that much, you are just trying to cook off coating.) If you are going to use those bulbs you might as well just leave it out in the sun.

Here is a link to project on building a giant UV box (This would cost more then $100 to build!)
http://www.scienceprog.com/ultraviolet-light-source-uv-80-for-pcb-exposure/

You can also build a box using UV leds.
http://www.scienceprog.com/pcb-exposure-using-uv-light-led-box/

have fun!
 

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moxhamj

New Member
A hundred pounds for a light box is expensive. The only reason it is in a box is to stop the light getting out and erasing your eyes, but a quick and simple box made out of MDF would work.

Then again, I have looked at the cost of blank board, drill bits, the hassle of aligning double sided boards, the difficulty doing home plate-through holes and concluded it is easier to get someone else to do it http://www.instructables.com/id/Professional-PCBs-almost-cheaper-than-making-them-/

Then again, aren't ferric chloride stains on one's underwear a true sign of being a nerd?
 
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100317

New Member
Some years ago I used the Face tanner of my wife to expose photo-coated prints. It has functioned very well. At the beginning always use small pieces to find out the exposure time.
 
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Michael 2727

Senior Member
I think the term Black Light came from the late 60s early 70s
when Poster Globes were popular. They were either an
incandescent globe or fluoro tube which had very dark
purple glass. They looked like black glass when turned OFF.
These were used to illuminate fluoro coloured velvet on a
black velvet background where posters of rock stars had
highlighted features, outlines in fluoro coluors.
( Jimi Hendrix in a full Afro was very popular )

These dark glass tubes/globes will not expose PCB material
as their wavelength is too long.
The term black light has stuck to everything UV since.

The original germicidal or antibacterial UV tubes used
various phosphors and exotic gas mixes to produce
the UV light, they use clear glass.
Most of these types will expose PCBs.
To look at, they produce purple or blue purple light and
look like a normal white fluoro tube when OFF.

Some of the newer UV LEDs are suitable for PCB making
but some of the earlier types may not be so good.
LED UV wavelengths are getting shorter every day and
the pricing is getting better also. 405nm to 375nm.
( check data sheets if available when buying them )

Many Mercury Vapor lamps also emit suitable UV light.

Last months Silicon Chip had a UV light box project, not
much use in the UK unless you go online & buy the article.

Dr Ac, use Ammonium Persulfate to etch your boards,
it leaves ferric chloride for dead.

And 1 teaspoon of Caustic Soda in 1 Litre of water
will develope +POS resist PC board as well as the
commercial stuff, and it's available in most supermarkets
in the washing powder or cleaning products section, cheap.


(brown stains, I ain't even going there)
 
K

kevrus

New Member
What a superb idea, I never even considered using my old scanner and built mine from MDF. I especially like the LED approach using the scanner carriage. I wonder how long the exposure time is?
I'm making a picaxe 'second' countdown timer for mine so I will be experimenting on the minimum exposure times required (4 x 15w 12" UV tubes).
 
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