Homebrew PCBs

Hi Folks,
I'm mostly a learning lurker on these tech exchange lists, but the 
recent UV source discussion has stimulated a question I've been 
wondering about. I need a really compact UV source for a very portable 
exposure unit. Anyone know of any success using an array of UV LEDs 
as a UV light source for exposures? LEDs are pretty directional, so 
are fairly well collimated as is. And in their visible light forms, 
bright enough to use in traffic lights. But can these UV LEDs put out 
enough light energy to react the photoresist? Anybody have experience 
or know?

-Karl in Kalifornia

> Hi Folks,
> I'm mostly a learning lurker on these tech exchange lists, 
> but the recent UV source discussion has stimulated a question 
> I've been wondering about. I need a really compact UV source 
> for a very portable exposure unit. Anyone know of any success 
> using an array of UV LEDs as a UV light source for exposures? 
> LEDs are pretty directional, so are fairly well collimated as 
> is. And in their visible light forms, bright enough to use in 
> traffic lights. But can these UV LEDs put out enough light 
> energy to react the photoresist? Anybody have experience or know?
> 
> -Karl in Kalifornia


They're the wrong wavelength, so they don't work anyway.

Tony

----- Original Message ----- 

From: "yllawk" <hkwally@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Saturday, September 30, 2006 3:53 PM
Subject: [Homebrew_PCBs] UV LED arrays?


> Hi Folks,
> I'm mostly a learning lurker on these tech exchange lists, but the
> recent UV source discussion has stimulated a question I've been
> wondering about. I need a really compact UV source for a very portable
> exposure unit. Anyone know of any success using an array of UV LEDs
> as a UV light source for exposures? LEDs are pretty directional, so
> are fairly well collimated as is. And in their visible light forms,
> bright enough to use in traffic lights. But can these UV LEDs put out
> enough light energy to react the photoresist? Anybody have experience
> or know?

Elektor had an article on a unit like that, for PCBs up to single Eurocard 
size.

Leon

Yep, the LED's they used where: Kingbright L-7113UVC.
That particular LED has a 20 degree "beam", they put 24 of them in a grid 
~32mm appart. The distance from the LED to the PCB where 80mm and exposure 
time around 6min. Or so the claim...

    /Henrik Olsson.

----- Original Message ----- 

From: "Leon Heller" <leon.heller@...>
> Elektor had an article on a unit like that, for PCBs up to single Eurocard
> size.
>
> Leon

Some of y'all may be interested in this page that concerns using
UV LEDs to expose PC boards:

http://radikaldesig.blogspot.com/2006/10/insoladora-uv-leds.html

Dave

Nice, I love projects like that. Much more attainable than multi mega 
Watt UV lamps :) I've always exposed my photo sensitive board with a 
fluorescent desk lamp. 20 Years ago I used a home sun-tan lamp.

    Sander

D wrote:

>
> Some of y'all may be interested in this page that concerns using
> UV LEDs to expose PC boards:
>
> http://radikaldesig.blogspot.com/2006/10/insoladora-uv-leds.html 
> <http://radikaldesig.blogspot.com/2006/10/insoladora-uv-leds.html>
>
> Dave
>
>

--- In Homebrew_PCBs@yahoogroups.com, "Henrik Olsson" <henrik-
olsson@...> wrote:
>
> Yep, the LED's they used where: Kingbright L-7113UVC.
> That particular LED has a 20 degree "beam", they put 24 of them in 
a grid 
> ~32mm appart. The distance from the LED to the PCB where 80mm and 
exposure 
> time around 6min. Or so the claim...
> 
>     /Henrik Olsson.
> 
> ----- Original Message ----- 
> From: "Leon Heller" <leon.heller@...>
> > Elektor had an article on a unit like that, for PCBs up to single 
Eurocard
> > size.
> >

Just thought You would like to know. I bought one of these UV LEDs 
out of curiosity, along with many other non-curious stuff, and it 
does perform as stated on that magazine. 
In my case I made just a small 2cm x 2cm exposure and it turn out 
great. If I ever consider building an UV exposure unit, it will be 
with UV LEDs.
Make sure their wavelength falls in your photo resistivity product.

Nuno T.