gmc_za wrote:
>
> I've read a million post on the net about how to create a pcb with
> photosensative spray, and UV light and after about 30 failed attempts
> I'm almost ready to give up.
>
> If someone could please check my method and advise me where I'm going
> wrong:
>
> 1) Clean pcb - this is not a problem as its really shiny afterwards
> with no oil on etc
Make sure there is no oil by seeing if a coating of water "beads" on it,
or stays flat.
> 2) Spray with photoresist. I've tried various thicknesses from almost
> see through to a nice clear purple film on the board. Left it to dry
> for 24 hrs.
Only enough to give a "sealed" smooth surface is needed.
> 3) Created a artwork on tracing paper (90 gsm) with a deskjet
> printer.
Do tests without the tracing paper and using a strip of cardboard
to make the shadow pattern on the pcb.
> 4) expose using uv lamps - ive tried various exposure times. 4 mins
> seems to give the best results.
> 5) My caustic soda solution is 3 teaspoons to 1.5L water. Again this
> is from trial and error and sometimes seems to give the best results.
Buy the developer to eliminate a variable from your tests. Then ditch
the spoon and buy scales.
>>From the 30 attempts I've had - one board was almost usable. The
> problem is that nothing seems consistent. One day I'll create a pcb
> and all of the photo resist gets removed in the CS, the next day with
> the same quantities, the outsides of the board gets removed - the
> purple photo resist film toward the middle of the board refuses to
> get
> removed. I've even tried rotating the board under the UV light.
>
> Help!! Does everyone else have hassles like this? Is there any method
> I can use to produce good pcb's every time.
Usually it's problems with cleaning all the oil off or incorrect
developer.
I get %100 consistancy from spray-on PRP (green).