Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

----- Original Message -----
From: "Alan King" <alan@...>


>
>>Electroplating is still the best way to tin. I don't think anyone here is
>>doing it. Read up on it at www.thinktink.com. I think I'll try it after
>>using up the rest of the transfer paper. The workflow is a better fit with
>>negative photo resist.
>>
> Which trace are you going to tin with electroplating? Most want the
> whole board tinned, without having to connect each trace seperately. It
> can be done, it's how they do gold plating for LCD boards etc, but it is
> 10x the PITA you're giving it credit for.. There are some good reasons
> board houses do this step chemically, and cold plating solutions like
> tinnit exist.. By all means try it out though, electroplating is
> interesting and fun for other things anyway..

I'm really more interested in plating the holes, not just plating for
plating's sake. Plating tin or solder in addition to plating copper wouldn't
be much more complicated than just a setup for copper alone.

All the traces, Alan. Drill the board. Plate with copper, including and
especially the holes. Laminate with negative resist. Print the positive
image onto the resist. Develop. Since the image is reversed, this exposes
what will become the traces and leaves the etch area still covered. Plate
with tin or solder. The cladding underneath the resist is still intact and
conducts plating current to all areas, including and especially the holes.
The resist prevents the etch areas from plating. Strip the resist. The tin
plating is now the etch resist. Etch. The unplated areas are removed. In my
mind's eye of an idyllic world, this leaves bright tin traces and conductive
plated through holes, gleaming in the ethereal glare of an ideally lit
workroom. (I work by the single bare bulb of the dismally painted darkroom.)

The idea isn't so much that I like plating for plating's sake. I am so
completely tired of laying out around and probing and fixing the iffy top
connections hidden underneath components. Reflow isn't completely effective
with unconductive holes. I spent an hour yesterday reworking a single pin on
a shrouded header. I reflowed it a few times with as much paste as I could
shove under the header, before finally giving up and jumpering it with Kynar
wire.

BTW, kudos to whoever mentioned the Weller Portasol recently. I dug mine out
of semi retirement to reflow a few other incompletely reflowed parts.
Slightly over cooked is vastly better than even a little under cooked. It
(the Portasol) works great, and heats things up in a big hurry.