I try to stay out of discussions that although wrong, have little impact.
 However there are some myths being spread here that will come down to haunt
all of us, if we remember them, and need some comment.

Yes, Cascade is actually a not too bad cleaner for PCB's, however there are
components of it that do not rinse easily, and this is especially from PCB's,
and especially the Tin/Lead surfaces.

And these components are NOT the surfactants, which, by and large, tend to be
very rinsable, if they are rinsed in cold water.  But to back up a moment,
surfactants and wetting agents, come both charged (Negative charge = Anionic
Surfactant, Positive Charge = Cationic Surfactant) and uncharged (Nonionic
Surfactant).  All the surfactants, save the Cationic (positively charged)
ones rinse easily.  Nobody,. almost, uses cationic surfactants in cleaners.
 Their principal uses include anti-stats, hair conditioners, and fabric
softeners, where you do not want them rinse off fully.

Cascade has only nonionic surfactants, which are inverserly soluble with
temperature, 
meaning more soluble at low temperatures than high, thus are best rinsed in
cold water.
However, Cascade contains Silicates, which are real good corrosion
inhibitors, but which tend to lay down insoluble precipitates, and especially
at mild pH values, and especially when they react with metal salts.  Cascade
is inhibited with silicates, and buffered so that the pH it runs at is below
that which Silcates are fully soluble at.  (This is done to minize attact on
glass, and especially chrystal.)  Hence, SOB.  (S**t On Board)  

The Silicate residues are hydroscopic, and can cause problems down the road.
 Incidently, one of the reasons why there may be seriously conflicting
stories on the use of Cascade is that the longer it is used, the lower the pH
that the use solution drops to, and the more deposits that it puts down.

I know all this, because we looked at the really excellent results some folks
were achieving with Cascade, analyzed it, corrected the problems, and came
out with our own version, which works like a champ!

Rudy Sedlak
RD Chemical Company
Phone 415-962-8004
fax 415-962-0370


>You are correct.  The wetting agents and the surfactants are 
>non-ionic materials which are not detected by the Omegameter or 
>the Ionigraph which only measures the concentration of the ionic 
>materials which are soluble in the alcohol water solution.  
>However, these non-ionic residues have a tendency to attract and 
>absorb water onto the surface of the PWB.  As the water is 
>absorbed it is polarized.  When a voltage deferential is applied 
>across two adjacent traces the water ionizes forming a plating 
>situation and dendritic growth occurs and eventually a short will 
>develop.  So, even though your PWB appears clean according to the 
>Omegameter or the Ionigraph, it is actually a potential problem 
>when it gets to the field.  
>(The differences I saw between boards cleaned by cascade and 
>those cleaned by other methods ranged from 10 to the minus 11th 
>ohms for others to below 10 to the minus 7th ohms for the cascade 
>cleaned boards.  This was at 35 degrees C and 85% RH.)


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