Homebrew PCBs

----- Original Message ----- 
From: scratch_6057
To: Homebrew_PCBs@yahoogroups.com
Sent: Saturday, January 06, 2007 3:34 PM
Subject: [Homebrew_PCBs] Re: My UV exposure unit


--- In Homebrew_PCBs@yahoogroups.com, "leon_heller" <leon355@...>
wrote:
>
> I've uploaded a photo of my simple UV exposure unit:
>
> Photos>Leon's>UV unit
>
> The black-light UV tubes are mounted in ordinary 8W fluorescent
light
> fittings. The box is made from MDF and wood, screwed and glued
> together. A sheet of ordinary window glass that I had cut to size
sits
> on the wood strips at the top of the side pieces. Exposure time is
13
> minutes.
>
> Leon
>

Nice job Leon! A lot less complicated that the one that Think N Tinker
describes. Lots of Questions; Did you consider white paint inside?
Diffuser plate (milk white translucent acrylic) between lamps and the
glass plate? Not getting any exposure variations from the areas
directly above the lamps and the area between them? I see a number of
people referring to various things as Black Light, `GROW'
lights, `Aquarium' fish tank lamps, Bug Zapper lamps and I remember
the `Black Light' lamps that had a dark blue or purple glass, (still
see them every so often,especially around Halloween) what exactly was
the INTENDED purpose of the lamps you are using?
How about telling us the physical size (dimensions) of that exposure
unit, PLEASE.

----------------------------------------

White paint or crumpled Al foil lining would probably help. I managed to get 
the PCB and artwork at just the right distance to get even illumination, and 
the distance helps with the collimation. Knowing the tube diameter it should 
be possible to calculate the optimum distance but I just guessed it, and 
checked that it looked OK with some paper on the glass.

The UV tubes I bought were sold specifically for PCB exposure (I got them 
from Service Trading Co. in Bridgman Road, West London). They are made by 
Sylvania but I don't know their intended purpose. Similar tubes are 
available from Farnell and RS here in the UK.

The tubes are about 4" apart and 6" from the upper glass surface. I left 
enough room for a third tube between the existing two tubes. That would 
considerably reduce the exposure time.

A timer would be a useful addition, but I just use a timer application 
running on my Palm PDA to remind me when the exposure is complete.

Leon
--
Leon Heller
Amateur radio call-sign G1HSM
Suzuki SV1000S motorcycle
leon355@...
http://www.geocities.com/leon_heller