The most likely cause of the problem you describe is overexposure.
For fix problem one you need to determine minimum exposure time. You
do this by taking a blank board with photoresist and expose it for
different lengths of time using a sliding cover. You must let the
light pass through the transparency material to compensate for any
absorption of light energy. Expose the blank board in steps of say 30
seconds for total of 5 minutes, and leave one section completely
unexposed. I use a piece of black plastic and slide it across.
Prepare your developer and develop the board. You then get a good idea
on how long the resist must be exposed for the developer to dissolve
away the resist. If the section exposed for 30 second completely
dissolves in the developer (assuming positive resist) then your
exposure times are obviously much shorter than a few minutes. Exposure
time measurement is essential for anyone first starting out with a
particular photoresist and exposure unit.
ghidera2000 wrote:
> Just attempted my first photofabrication and it failed at the
> developing stage. Within 30 seconds of immersion the board was
> completely devoid of resist...
>
> Here's what I did (all M.G. Chemicals supplies)
>
> -Printed out my circuit onto a transparency (IBM Laser
> Transparencies, 24L5041) using a Samsung ML-1210 laser printer.
> -Poured two litres of hot tap water into a tray.
> -Poured 200ml of Developer into the tray of water (10:1 as per
> instructions).
> -Set up the UV light using the supplied stands (about 5-6" high).
> -Placed the sensitized board blue side up. Positioned my
> transparency (ink side toward the board) and placed the plexi weight
> on top.
> - Waited 5 minutes then turned out the light (actually probably more
> like 5.5 minutes).
> - Immediately put the board into the developer solution. I used the
> supplies foam brush to agitate the water (didn't come within 1/2" of
> the board itself, just slowly waved it back and forth at the
> surface). Solution was about 95-100F by this time.
> - About 5 seconds in I could see my traces through the clouds of
> black ink. As the black ink cleared I could see traces starting to
> fade out too. This is about 15 seconds into the process. I realized
> the board was already toast so I waited to see how long it would
> take to completely erase the resist - was about 30 seconds.
>
> The instructions say it should take about 2 minutes to develop the
> board. This was a LOT faster... I'm thinking perhaps the developer
> was too strong? What about temperature? Should I just use developer
> at room temperature instead - give myself more "OOOOP" time?
>
> I guess its also possible that this laser's toner isn't UV opaque
> but, the speed at which the board completely blanked and the fact
> that I saw traces - even for a short time, makes me think its a
> developer problem.
>
> What do you guru's think?
>
>
>
> Be sure to visit the group home and check for new Bookmarks and files:
> http://groups.yahoo.com/group/Homebrew_PCBs
>
> To unsubscribe from this group, send an email to:
> Homebrew_PCBs-unsubscribe@yahoogroups.com
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>