Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" 
<stefan_trethan@...> wrote:
>
> On Thu, 13 Jul 2006 21:00:59 +0200, derekhawkins <eldata@...> wrote:
> 
> >
> > The point I'm trying to make is that cleanup with a solvent after
> > soldering is best avoided, even if desirable, with anything less 
than
> > real soldermask or a metal coating (Tin, solder paste etc.). This 
is
> > something to consider when choosing a protective coating. If you 
don't
> > really care how your solder joints look then it's a nonissue.
> 
> 
> Well, i guess the disputed point is that solder joints with any 
sort of  
> flux residue do not look good, which i don't agree with.
> 
> 
> ST
>
Using Shellac as a coating may not be good when SMD is involved but 
is fine for single sided through hole boards.

If your soldering produced unsightly flux residues then solder flux 
can be cleaned of with whatever you usually use. This will likely 
remove the shellac coating as well but is only a matter of applying a 
further flash coat as a final step. The advantage of the shellac 
solution being a mixture of beetle and methylated spirits (Meths) is 
its quick drying properties. It should be widely avaiable at 
woodworking outlets.

If you make a bad job of applying it, just brush meths over it until 
it looks good. As this suggests, it can forever be reactivated with 
the meths. This all works well with fibre glass PCB but the cheaper 
phenolic board goes soft with meths so applying a shellac coating is 
fine but keep large quantaities of meths away from it as the board 
will go sticky. 
     
In all, its a cheap way of preventing oxidation of your finished 
board. I have 20yr old boards that still look great. Well lets say as 
good as a copper track with solder pads at each end can look. This is 
where the aesthetics and performance of the tin or solder mask 
techniques take over.