Pcb etching ??? exposing with sunlight

ward · Jul 20, 2005

I have some photosensitive board lying around and would like to give it a use.
But I'd rather not spend time/money makin/buying an UV box?

I read that exposing trough sunlight should be possible.
Is there anyone here that tried it ?

How do you decide what exposuretime to use ?
Is the exposuretime very important, I mean will a bit of overexposure give unusable results ?

btw: the pcb's I'd like to try are not complicated, thick lines, lots of space ...

thanks

gyraf · Jul 20, 2005

You find exposure times by doing a test strip under controlled circumstances - meaning that sunlight won't be a predictable light source.

You can use a 500W halogene work-light in something like a meter distance, and depending on actual photo-pcb type exposure time will be 2-10 min. Distance is as important as actual time! But don't get too close, as heat will make the photoresist sticky and wierd.

Bear in mind that photoresist has limited shelf-life - old stuff (more than a year or two) will give unpredictable results.

Once you've found an exposure time that works, stick to the same type photo-pcb - or you'll have to test to find new timing.

Jakob E.

Steffen · Jul 20, 2005

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http://cgi.ebay.de/ws/eBayISAPI.dll?ViewItem&category=50103&item=7530949315&rd=1

http://cgi.ebay.de/ws/eBayISAPI.dll?ViewItem&category=50103&item=7531869086&rd=1

http://cgi.ebay.de/ws/eBayISAPI.dll?ViewItem&category=50103&item=7530988973&rd=1

works perfect for me.

steff

asm · Jul 20, 2005

just like jakob said, the sunlight exposure time will be inconsistent.
also, it would take a bit longer. a good halogen or black light (not traditional Black light bulbs, those are called BLB bulbs, you want BL bulbs that are white like normal flourescent bulbs).

i bought the wrong ones and the exposure time was like:
sunlight=20-30min
BLB (wrong ones)=10min
BL (correct version of black light bulb)=4min
halogen or the expensive bulbs=15sec-2min

one adavantage, besides time to expose, is that there is less room for error when using a faster exposure time. you'll get more consitent (if workable at all) results and your lines will be alot crisper and fewer errors.

taylor