Homebrew PCBs

We had two DMVL-930 exposure units for dry film photoresist and they
used 1000 watt bulbs. When I closed the PWB plant I kept the best one
for my home shop and junked the other one since nobody wanted it at
the time. 

I think the bulb part number is R1000 if my memory is correct. It's
just a standard 1000 watt mecury vapor bulb with a reflector. There is
no need to worry about collimation of the beam unless you are exposing
very large panels. Don't break the outer glass from the lamp unless
you want ozone. 

Just the other day I saw a lamp assembly that would be perfect for a
homebrew exposure unit. It was a mercury vapor lamp with reflector in
a metal enclosure at the base of a flagpole. This lamp looked like a
400 watt bulb but that would work great for dry film resist. Just
build a box around the lamp assembly and leave a slot at the bottom
for your contact frame to slide in and out. The bulb could be about 12
inches from the contact frame. 

At 400 watts I'm guessing about 45 seconds for exposure at 12 inches.
My system uses the 1000 watt lamps. They idle at 1000 watts and during
exposure they are overdriven to 1500 watts. Exposure time for DuPont
1.5 mil photoresist is 17 seconds. I do 5 mil lines and spaces daily
with this system. My film work is photoplotted on 7 mil thick films. 
Dry film resist is negative acting and has a fast exposure time.
Positive resists are slower and will take longer to expose.

Tom


--- In Homebrew_PCBs@yahoogroups.com, "John Craddock"
<John.Craddock@...> wrote:
>
> 
> 
> > -----Original Message-----
> > From: Leon Heller [mailto:leon.heller@...]
> > Sent: 25 September 2006 16:27
> > To: Homebrew_PCBs@yahoogroups.com
> > Subject: Re: [Homebrew_PCBs] UV Light Sources
> > >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 
> Thanks Leon
> For the collimation I was going to use a parabolic reflector. With a
16" (400mm) dia., reflector it would seem to be feasible to have a
working exposure area of 12" to 18" (300 to 400mm) Instead of a
shutter I was thinking of using a slide-in frame holder. In OZ we can
get 250 watt self ballasting globes the run off our 240 volt mains
supply. This set-up would be far less expensive than say 4 or 5 fluro
tubes plus their associated ballasts, starters etc (at least in the
antipodes).
> Regards
> John C
>