I've done a couple different things as far as masking at home.
Acrylic floor polish works fairly well as long as you're using it to
protect the copper and not sending it through some type of oven/reflow
machine. Because the coating is pretty vulnerable to solder
temperatures it's a simple matter to first completely coat the board and
let it dry. Afterward a soldering iron will go right through the stuff
without interfering with the solder wicking and so forth. Makes for a
shiny, very nice looking board. I use liquid flux and so ideally you'd
be able to dissolve it without affecting the acrylic; I'm not sure this
would be possible, although you could simply strip the board and then
recoat the board.
I've also used dry-film resist as solder mask. Again, you end up with
remainders of whatever flux you use when soldering, but I expect the
resist would be tough enough to stand up to a mild solvent for a short
time. Gives the board a very "high-tech" look with a very high contrast
between the dark blue resist and the silver solder/copper pads. The
artwork for this is easy enough to make, as it's simply an inverted
version of the mask used to expose the board originally. Likewise, you
can use the dry-film resist as a poor-man's silk-screen for either side
of the board. Because it's so dark blue it looks wonderful, and is
pretty robust. I don't think I'll ever spring for real photo-resist; it
starts at $135 for a 40 foot roll and I only coat boards when I'm really
concerned about long-term performance.
In regards to dry-film resist, I really think people overestimate how
difficult it is to apply. There are definitely some important tricks
that you need when using it, but with those in hand you can do very
high-quality, cheap boards. The best part is, if you mess up
exposing/coating a board you can just strip it and start fresh. The
resist is sold from think-n-tinker
(
http://www.thinktink.com/stack/volumes/voli/store/specs/m115spec.htm)and for about $70 you can get enough resist (50 feet on a 12 inch roll)
to last for a LONG time. Theoretically the stuff goes bad over time,
but as long as you keep it cool (no temps above 80 degrees preferably)
it will be good for several years. I expect in a production environment
its characteristics change a bit over time which causes them problems
that a person using it on-and-off would never notice. I'm not
affiliated with TNT, just a happy customer. If anyone is interested, I
can share some of the things I've discovered over the years.
Larry
On Thu, 2003-05-22 at 13:43, Brian Schmalz wrote:
> I think this is also a great question - how to apply solder mask at
> home.
>
> For all you chemical gurus on this list, couldn't you mix up a
> solution of
> wet solder mask material, put it in a 'drafting pen' and then use an
> HP
> plotter to 'draw' the solder mask on the board? You would just have to
> create a file that draws everywhere you want the mask to be. That
> isn't
> hard. The hard part (to me) is to find the right stuff to put in the
> pen. I
> would assume that you'd then have to bake the board in an oven or
> something
> to get the liquid solder mask to dry.
>
> Can the same thing be done for do-it-yourself silk screen? I would
> guess so.
> We'd just need the right 'ink' to put in the pen and then draw on the
> silk
> screen layer. What type of ink could one use?
>
> ∗Brian
>