printed circuit board exposure

KA4HJH ka4hjh at gte.net
Sun Jan 2 05:13:44 CET 2000


The most convenient thing is an exposure frame. Check out

http://www.thinktink.com/index.htm

Here you will find the plans for a really snazzy one (using commonly 
available stuff), as well as just about everything else you might 
need for fabricating PCB's (tanks, aereators, etc.). This place is a 
goldmine of info.


>   Don't even bother with exposing to sunlight-the insolation of UV is too
>variable based on air density/water vapor.

I've had success using sun exposure with Kepro's laminated film 
system, but there are limits:

1. The sun has to be out

2. The amount of UV varies a lot. The peak is in the middle of the 
day. When the sun is lower in the sky (early/late in the day, or in 
the winter) the amount of UV-B drops off considerably. Fortunately, 
this system produces a latent image on the resist so you can tell if 
you got the exposure.

I got good exposures in October and early November in about 50 seconds.


>As for halogen lamps, in
>order to get UV out of them you have to remove the quartz glass (as on a
>halogen work light), and then the device becomes quite dangerous in terms
>of UV exposure.

Just like any old sunlamp (you don't see many of those for sale 
anymore). I don't know what that transparent material is, but it's 
not pure quartz, as that transmits UV. The "bulb" itself is quartz.

Terry Bowman, KA4HJH
"The Mac Doctor"

ICQ: 45652354



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