Homebrew PCBs

Hello...

Does someone know what energy is nedded to develop photoresist?
I thinking to make an atacchment to CNC to make something like 
photoploter(imagesetter) to develop direct pcb not film. Ie some lamp 
and lenses to make beam paralel and adjustable apprture (iris).
And when 'drawing' line the aperture is oppened to make trace of light 
of just correct width.

Now I'm stuck as I can't find data of different photoresist. I know that 
near all of them need UV light of aprox 400nm wavelenght.

I know that few people try similar with laser. But near all fail in 
presision. With laser the photoresist make buble as in developing 
process the nitrogen gas is released from photoresist. So we need lower 
energy.

So does someone have data for photoresists? And maybe some idea how to 
realise optics?

Thanks

Slavko

Dne 12.1.2012 11:01, pi\ufffde DJ Delorie:
> Slavko Kocjancic<eslavko@...>  writes:
>> Does someone know what energy is nedded to develop photoresist?
> Here's an example:
> http://www.thinktink.com/stack/volumes/voli/store/specs/m115spec.htm
>
> The key parameter is "energy" in mJ/cm2 (millijoules per square centimeter)
>
> To truly calibrate a system, though, you need to do a test exposure
> through a transmission step wedge, like:
>
> http://www.stouffer.net/TransPage.htm
> http://www.thinktink.com/stack/volumes/volvi/filmimag.htm#Calibration
>
> The wedge allows you to do a range of "exposures" at one time, and since
> it's calibrated(ish) the results tell you what actual exposure to use.
>
> For example, if you do a test run at 10 cm/sec laser travel, and the
> results are "held at step 10" but the resist says it wants step 8, and
> you're using a 21-step wedge (1.414x per step), you need to double the
> laser speed to 20 cm/sec or cut the energy in half.
>
>

With data on this page and One I already have the exposure needed lies 
somewhere in 350 to 1000mJ/cm2.

So here is my asumption.
For worst film (1000mJ/cm2) = 10mJ/mm2
and UV LED (350 MCD, 12mW) focused on 1mm2
give me that spot must be exposed for 1 second, ie sped should be 1mm 
per second.
Is it that calculation correct?

Slavko.

Slavko Kocjancic <eslavko@...> writes:
> Does someone know what energy is nedded to develop photoresist?

Here's an example:
http://www.thinktink.com/stack/volumes/voli/store/specs/m115spec.htm

The key parameter is "energy" in mJ/cm2 (millijoules per square centimeter)

To truly calibrate a system, though, you need to do a test exposure
through a transmission step wedge, like:

http://www.stouffer.net/TransPage.htm
http://www.thinktink.com/stack/volumes/volvi/filmimag.htm#Calibration

The wedge allows you to do a range of "exposures" at one time, and since
it's calibrated(ish) the results tell you what actual exposure to use.

For example, if you do a test run at 10 cm/sec laser travel, and the
results are "held at step 10" but the resist says it wants step 8, and
you're using a 21-step wedge (1.414x per step), you need to double the
laser speed to 20 cm/sec or cut the energy in half.