Homebrew PCBs

Hi Robin,

Thanks for the comprehensive info.

Do you think a car quartz halogen headlamp would have sufficient UV output ? 
I have a new 12V dual filament 50W + 65W which I could parallel to give 115W

Alternatively, I have a new 12W T5 circular (11cm     41/2")  Fly Zapper tube.

My PC is only 8cm  x  3cm.

The sensitised PCB needs energy around 360nm. 

Thanks,
John  



--- In Homebrew_PCBs@yahoogroups.com, Robin Whittle <rw@...> wrote:
>
> Hi John,
> 
> Generally, gas discharge tubes cannot be operated in parallel.  They
> need a high voltage to start, but settle down to a low voltage ca. 90
> volts (I guess) once they are conducting.   With ordinary inductor
> ballasts I have seen two 20W short tubes, each with their own starter,
> wired in series with a 40W ballast.  This is for 240V.  Maybe that would
> work with a high frequency electronic ballast.
> 
> I chose to use a 500 watt floodlamp from the hardware store.  The short
> linear quartz halogen lamps give off a lot of near UV, which is what I
> want for exposing Riston negative photoresist.
> 
> At a distance of about 45cm I have exposure times of 2 to 3 minutes.
> 
> This is a much narrower angle source of light than having a bunch of
> fluorescent tubes only 10cm away, so for a given phototool and possible
> distance from the phototool to the top and bottom of the Riston, I get a
> much sharper image (shadow).
> 
> The only potential concern I can think of is heating of the phototool,
> PCB and whatever means is used to hold them together.  I have a fan
> blowing on them to keep them cool.
> 
> There's no warm-up time for a QI light.  Tubular fluorescent lamps are
> likely to have some kind of warm-up time, making it difficult to predict
> their light output unless they have just been running and are fully
> warmed up.  High pressure mercury vapor lamps have much longer warm-up
> times, and so do the compact fluorescent lamps which are now widely
> used.  All these fluorescent lamps - tubular, 400W (or other wattage)
> high pressure mercury vapor lamps, and compact fluorescent lamps - come
> in "black light" versions which I think put out the ideal wavelength for
> exposing Riston.
> 
> 
> http://www2.dupont.com/Imaging_Materials/en_US/tech_info/datasheets/index.html
> 
> I haven't looked at all the types, but the types I have looked at are
> specified to respond best to 350 to 380nm light.  This datasheet for a
> 400W high pressure mercury vapour fluorescent H500-BL:
> 
>   http://www.eyelighting.com/tb/Mercury/MVR/EQS-N-52-78-69917.pdf
> 
> shows most of the output at about 370nm.
> 
> However, I think their warm-up times are a problem.
> 
> QI lamps will vary their near UV output somewhat according to their
> operating voltage, but unless the mains voltage varies widely, I would
> be surprised if this variation was enough to cause trouble with Riston.
> 
> 
>  - Robin             http://www.firstpr.com.au/pcb-diy/
>