MOTM

>
> I'm stuffing compenents in all my boards for the first pass solder/wash.
I
> normally mount electrolytic capacitors firmly up against the PCB.  After
> reading about the problems of organic flux residue, I am wondering how I
am
> going to clean under under them.  Does it matter if I can't clean under
them?
>  Or do I need to keep a centimeter or so space, so I can clean

Actually, the hole spacing is about 0.025 *wider* then 'spec' to make the
caps "stand up"
off the pcb about 1/32" so the water will flow under there. Note the "yellow
box caps"
have small cutouts for this purpose.


> Is the only  reason we are not using good old rosin core 63/37 solder
because it leaves
> unsightly flux marks?

There are two reasons MOTM does not use rosin core solder (in fact, no one
has used rosin-core solder
*in mass production* since about 1990).

#1 - rosin is designed to *attract moisture* (think of the rosin bag in
baseball, and in gymnastics). Attracting
moisture in *NOT* what we want in synths! Especially VCOs.

#2 - in order to *remove* the rosin off the boards, you need *horribly
messy* chemicals. Freon was the older
choice. There are spray cans of non-CFC rosin flux remover, but my
experience is that this makes a huge
mess because all you do is dissolve the flux and coat the whole pcb with it!
In production lines in the '70s/'80s
there were massive, high-power water jets that 'scrubbed' the flux off with
150 psi water nozzels after a good old Freon
bath (the boards were actually immersed in liquid Freon).

Today, *all* soldering is using "No Clean" flux.

So, a fair question is :"Why not use No Clean everywhere?"

The answer is that I felt that No Clean is harder to solder, and that
organic *still* has the best overall
joint construction. The only reason No Clean replaced organic is that the
manufacturers saved millions
of dollars on water bills (and floor space!).

Paul S.