Homebrew PCBs

----- Original Message ----- 
From: "Brian Clancy" <bclancy1@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Monday, January 24, 2005 5:26 AM
Subject: Re: [Homebrew_PCBs] UV lamps?


>
>
> G'day Jason,
> My understanding of it is that you need to have collimated light, i.e. all
> light rays are coming vertical to the artwork so that it does not go under
> the edges of the artwork.
> This is the reason that a negative should be placed with the emulsion on 
> the
> PCB to reduce any chances of the light going under the edges.
>
> I saw somewhere where they used an egg-crate diffuser (from a flourescent
> light fitting) painted matt black, to collimate the light. This meant a
> reduction in effective light output but a cleaner image.

For home use, collimated light isn't really necessary, as most of us can't 
create high-resolution artwork that can make use of it. In fact, none of the 
low-cost UV exposure boxes that one can buy use it, they just have two or 
four tubes quite close to the PCB/artwork. I get quite good results with a 
couple of tubes about 15 cm from the PCB. Exposure is quite long at 13 
minutes, I keep meaning to add another two tubes.

Leon
--
Leon Heller, G1HSM
http://www.geocities.com/leon_heller 



-- 
No virus found in this outgoing message.
Checked by AVG Anti-Virus.
Version: 7.0.300 / Virus Database: 265.7.1 - Release Date: 19/01/2005