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making a UV box: how many W/cm2 ?

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Thunderchild

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I'm thinking of making my own UV exsposure box for making PCB's. How many watts of bulb per square cm should i have ?
 

picbits

Well-Known Member
I'm building one with UV LEDs to compliment my other two lol.

I've got two identical scanners to fit them into so should be good for double sided work.

Not sure on the UV Tube type but I know my smaller unit uses 2 x 8W tubes for approx an A5 sized exposure unit.
 

Thunderchild

New Member
UV leds ? how much do these cost though ?

how much height will i need for the bulbs etc ? will any 2 X 8 W fluorescent light system work for UV bulbs ?
 

mneary

New Member
I've observed that all the "UV" LEDs that I buy glow what looks like purple to me. Is this me, or are they not actually UV? They don't actually confess what their wavelength is; what is the typical wavelength of LEDs that claim to be UV?

And the money question: Are they the ones you would use for PCB exposure? (e.g. GC Chemicals cat No 660 etc.)
 

jpanhalt

Well-Known Member
Most Helpful Member
I used one 15W UV lamp (type F15T8-BL) for years. Exposure distance was about 10 cm and time 15 minutes. Different brands of boards will vary. My current box has 3 tubes set a little higher, as I wanted a broader exposure area. Time is now about 10 minutes.

Re: testing UV output. Calciflor white is a very common whitener. If you have a white shirt done at a laundry, it probably has that whitener or something similar on it. Under near UV, it will look very bright white in a darkened room.

John
 
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Boncuk

New Member
75mW per square cm takes care of short exposure times.

Light sources should be distributed evenly for best exposure results.
 

Thunderchild

New Member
I've observed that all the "UV" LEDs that I buy glow what looks like purple to me. Is this me, or are they not actually UV? They don't actually confess what their wavelength is; what is the typical wavelength of LEDs that claim to be UV?

And the money question: Are they the ones you would use for PCB exposure? (e.g. GC Chemicals cat No 660 etc.)
I think it is normal for the light to be purple, I used to work for a printers as a press operator and often made my own plates (ie when I wanted them to be more accurate that the bosses so called accurate +-5mm :D) and the UV exsposure unit had a 2 KW uv lamp, this was actuaslly quite a visible purple light, while it was obviosly not 2 Kw worth of visible light, the visible component was perhaps equivalent to 60 W
 

Wp100

Well-Known Member
Hi,

You might find this proect an interesting alternative to the expensive uv tubes and chokes - the leds are available from a couple of uk web base suppliers Phenoptrix or GoodWillSales.
 

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Thunderchild

New Member
thanks thats a good pdf, to be honest i think that the cheapest are the ones on ebay from china, now yea i poo hoo chinese quality too (especially in my professional capacity of QC inspector) but where the hec do you think your uk suppliers get them RS included who then sell them for the bounty of £ 2+ each ? I have ordered 250 for a tenner. I'll give them a bash when they arrive and let the forum know if they are crap but the specs are better than motre exspensive ones detailed from the suppliers you mention. of course the final word is quality and price and quality do not always go hand in hand
 
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