Homebrew PCBs

On 19/03/12 22:14, John Anhalt wrote:
> That is negative acting film.  I meant the positive acting stuff.  I believe the positive acting resists have simpler developer systems.

To be honest, I don't mind :)
(the Mega stuff is negative-acting too)

I've tried spray-on photoresists -- the "new formula" Electrolube PRP is
a complete joke, and damn close to impossible to use reliably. I've got
a Seno SN100 roll-on photoresist dispenser on my Mega order, so I'll see
if that's up to much (a message posted here by Leon Heller back in 2004
suggests that it's far better than Electrolube's laughable attempt at a
photoresist coating).

I'm willing to wager that applying it fairly evenly then putting it in
my homebrew spin-coater (read: a PC fan mated to a programmable speed
controller) will produce a nice, even photoresist layer.

What I'd really like is a can of Kontakt-Chemie POSITIV-20, which can
apparently be used as a paint for front panels. You spray it on, expose
to UV as normal, then develop and dry. Heat it to a hundred degrees or
so, and leave it until the resist changes colour (it'll go from blue to
dark brown). Overcoat with clear lacquer.

Comments on Rapid's website seem to suggest this works with SN100 (aka
POSITIV-100) too... I might have to try it, though I doubt a brown
component print on green soldermask would look very nice.

Thanks,
-- 
Phil.
ygroups@...
http://www.philpem.me.uk/