Hello, new member here.
I joined because I think this should be the best place to solve a
problem I'm having with a dry film I'm testing (never used this method
before).
The stuff I'm testing is this:
http://www.es.co.th/Detail_eng.asp?Prod=WARA%2DDRYFILMI get it locally (I live in Bangkok), and unfortunately the
instructions are in Thai... my girlfriend helped me out with it but I
still think there may be something wrong with them...
But first let me lay out the scene.
Of course first I prepare the board, just before applying the film
sand it over with 600 grit sandpaper, buff it up with Brasso polisher,
rinse and clean with water and then final wiping with alcohol. I get a
very pleasing mirror finish! =)
No fingerprints, lint or dust on the PCB before applying the film.
I cut a piece of film slightly larger than the PCB area, remove the
backing layer and stick it to the PCB starting by and edge and using a
cloth to easily slide my fingers around the sticking edge as I lay it
down. No bubbles or anything, it adheres very well on its own.
I place a cloth over the PCB and film and use an iron on Silk setting
to fuse the film to the board, if I use a higher temperature the film
seems to liquefy under the backing film and make nasty spots... not
good. With some practice I've managed to do it right most of the time.
After ironing I place the negative mask over the board and expose it
with an incandescent light bulb for an hour until the exposed film
turns a darker blue. So far so good, the traces look perfect and the
backing film peels off easily.
Everything goes wrong when I try to wash away the unexposed film. Per
the instructions I used all the developer powder provided (about 50
grams of calcium carbonate) on 200cc of water. The instructions simply
say to use a sponge to wipe out the unexposed film, at first seems to
work but then the finer traces (0.3mm) start to break and by the time
the unexposed film is gone all looks mangy and frankly quite FUBARed.
I suspect the developing solutions is not correct, but having no
experience with this method I couldn't tell.
The bulk of my ignorance is the developing process, what is the
standard way of developing and cleaning the excess dry film?
-Should I do it right after exposing it, or should I leave the board
in a dark place for some time?
-Should I go at it with the sponge right away or first leave the PCB
submerged on the developing solution for some time?
I would appreciate very much some insight from the people in this group.
Cheers,
Ale