Homebrew PCBs

On Thu, 13 Jul 2006 03:13:43 +0200, warrenbrayshaw  
<warrenbrayshaw@paradise.net.nz> wrote:

>
> I have always used Shellac to protect the newly etched PCB. Shellac is
> made by dissolving commercial Shellac flakes in methylated spirits.
> French polish is the same thing. Also I have a tin of product from the
> hardware store and it is known as "Patent Knotting."
> The Shellac goes on the colour of varnish and prevents oxidation and
> can be soldered through. It appears to react like a flux when soldering
> through it.



I use colophony resin. Basically tree resin with the turpentine removed.  
It's the same flux as used in rosin core solder wire. If given enough time  
to dry a laquer made of this will be dry and hard to the touch, although  
it does stay sticky longer than normal laquer (i believe this may be  
caused by water in the impure alcohols). It protects against corrosion,  
and acts as a flux during soldering. While it may not be ideal for the  
highest impedance circuits i have not had any problems so far.
I used (and still use) a ready-made spray can version of it, but i spotted  
colophony chunks at the chemicals shop, very good almost transparent  
quality. The lighter in color it is the lighter the flux residue will be,  
the dark brown stuff looks awful after soldering. The chunks can be solved  
in alcohol just like shellac to make a laquer.
I've also molten colophony into the little compartments at the end of my  
solder spool (the compartments to keep the plastic stiff). It's great to  
help with tinning wires.

I always thought shellac is a tree resin, but now i looked and it is  
actually produced by a beetle. I had no idea..

ST