Just something else that occured to me in regards to MV bulbs put to use for photoresist.
If you want to find them cheap/free make friends with some local reptile owners. Many of us
use them for the UVB that they emitt for a number of reptiles that require UVB for Vit D3
systhesis. The kicker is that UVB levels drop off to a point of being of no use for us
and as a result have to be replaced. However, they should still emitt plenty of UVA which would
longer wavelength UV.
Also beware of the self ballasting MV bulbs. I know of several people
that have had issues with them since the filaments tend to be quite fragile, especially when hot.
I have yet to hear of someone experiencing a failure with an externally ballasted bulb though.
----- Original Message -----
From: Leon Heller
To: Homebrew_PCBs@yahoogroups.com
Sent: Monday, September 25, 2006 2:26 AM
Subject: Re: [Homebrew_PCBs] UV Light Sources
----- 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
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