On Sat, 23 Feb 2013 15:21:55 +0000, you wrote:
>So germicidal works on negative photoresist and won't work on positiv 20 nor dry film. "need near UV and longwave UV (IIRC)." If I'm understanding this correctly this is mean "near visible light wavelength" right?
As I understand it, you're right.
I used the germicidal lamps with the KPR chemistry (negative resist
and relatively nasty stuff) many years ago.
I needed (and got) 6500 degree K lamps for the MG chemicals
presensitized positive resist boards.
I've used blacklight fluorescents (mine had the filter) with the same
MG chemicals/injectorall precoated boards.
As always, you need to make a test exposure strip or expose through a
stepped density filter used to make enlargers work.
Not sure that an enlarger timer would work all that well (the ones
with photocells), but I use an enlarger timer to control the exposure.
Rather convenient.
Harvey
>
>Thanks
>
>Hari
>
>-------Original Message-------
>From: Harvey White [madyn@...]
>Date: Sat, Feb 23, 2013
>To: [Homebrew_PCBs@yahoogroups.com]
>Reply To: [Homebrew_PCBs@yahoogroups.com]
>Subject: Re: [Homebrew_PCBs] Re: DIY pcb exposure box UV tl
>
> On Sat, 23 Feb 2013 10:41:43 -0000, you wrote:
>
>>I don't think so, I think the wavelength is wrong, exposure won't work or won't work properly.
>
>You used Germicidal (bare) lamps with the old Kodak KPR chemistry, a
>negative resist.
>
>Current positive films need near UV and longwave UV (IIRC).
>
>NEVER LOOK AT A GERMICIDAL LAMP DIRECTLY
>
>Never look at it except through a red filter that does not pass UV at
>all. The wavelength breaks apart proteins in your eyes (and germs)
>and can severely damage or destroy your sight.
>
>You can find the specs on what your resist needs, and find UV or the
>like fluorescents to do the same. The UV leds are still a bit
>dangerous, so do not look at them directly, but they are not as nasty.
>
>Harvey
>>
>>Never mind that they are much more dangerous for your eyes etc!!
>>
>>I've been using UV LEDs. Seem to work just fine...
>>
>
>
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