fjimenezg2003 wrote:
>
>>I get %100 consistancy from spray-on PRP (green).
>
> I'vw tried the electrolube PRP spray (green) without any luck.
> Minutes after I've applied the spray over the surface of the board,
> the coating starts to corrupt, first appearing bubbles on the
> surface. Could you explain what procedure do you use?.
>
> Thanks.
>
> P.D.: I've tried Seno photoresist with great results.
Scrub the pcb with any abrasive household bathroom/kitchen cleaner
(usually white creamy stuff), then rinse and observe if the surface
stays wet with a thin layer of water or whether it beads (has oil).
If it beads, you'll need to figure out where the oil comes from.
Some cleaning sponges release their own oil, so try cleaning using
a wet paper towel and kitchen cleaner.
Dry the pcb with one or two swipes against a roll of paper towel,
and blow with hot-air gun for 5-10 secs. Brush surface with clean
paint brush to remove any dust and lint.
Hold the pcb horizontal by a corner with some pliers, and spray with
side-to-side strokes with prp to give a smooth coating. The thinnest
coating that allows all the droplets to join and give a smooth surface
is adequate.
Hold for 10-15s to allow solvent to evaporate a bit. Always hold the
pcb horizontal.
Blow/heat with hot air gun for 30 secs to fully dry. This step can often
be from as little as 15 secs to as long as you want. I can tell by feel
that the pcb is around 50-70 deg C.
PCB is now ready. No need to bake for hours or overnight as the
instructions say.
You can do it in ambient (non-fluoro) room light or outdoors (not in
direct sunlight).
In a lightbox with four 8 Watt black-light (whitish tubes) fluros
at 7-8cm from the pcb, exposure of 5 mins is ideal with a decent
transparency printout.
Beware that if you put your pcb against the ink side of a fresh transparency
printout, the prp may peel/flake off during developing. The vapour from the
ink does this. You'll need to dry the printout in front of a fan heater for
10-15mins, or put the pcb against the non-ink side of the printout (can give
less sharp detail tho). Epson ink/transparency has this problem, but usually
has the sharpest detail printouts because epson transparency has a gelatine
coating that absorbs the ink quickly.