Homebrew PCBs

----- Original Message ----- 
From: "John Craddock" <John.Craddock@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Monday, September 25, 2006 3:35 AM
Subject: RE: [Homebrew_PCBs] UV Light Sources


>I read somewhere on the web that a mercury vapour lamp with the outer uv 
>blocking envelope removed gives a very good source of uv light for 
>photo-pcb resist curing. Obviously removing the outer envelope would 
>require that the uv exposure box be totally enclosed when the system is 
>operating. Can any one confirm that this is comparable or better than the 
>black-light fluorescent approach?

It's a lot better (much shorter expoosure), but needs to be a long way from 
the PCB/artwork for good collimation (something like 1 m, IIRC). I've got 
some similar sodium lamps that can have the outer envelope removed. The 
ballasts can be difficult to find. For accurate exposure I think you need 
some sort of shutter arrangement as they take some time to warm up.

Leon