Re: gEDA-user: Isopropyl alcohol vs. ethanol

[Marvin Dickens <marvindickens@xxxxxxxxxxxxx>]

John Doty wrote:
> On Apr 23, 2006, at 10:43 PM, Dave McGuire wrote:
>
> >   Do you have any opinion on washing boards with something like  
> > Alconox (a trisodium phosphate-based cleaner)?
>
> I wouldn't want a cleaner containing sodium. Sodium ions have high  
> mobility in epoxy, especially in the presence of moisture. Sodium is  
> soluble in SiO2, so it can shift transistor gate thresholds. It is  
> common to passivate chips with a glass designed to getter sodium, but  
> that's not a perfect barrier.
>
> John Doty              Noqsi Aerospace, Ltd.
> jpd@xxxxxxxxxxxxx
The way the question was posed, I think he was asking about using 
alconox on bare, unpopulated boards - As a way of removing
photo resist after etching. In this scenario, sodium should not be an 
issue if the boards were properly washed and dried. Factoid:, sodium
is one the most common elements, if not the most common element here on 
earth (As well as other places in the universe). Its the reason
most flames burn with a yellow color - Sodium is in everything. This is 
an old problem - one that plastic packaging has for the most part solved.

Even so, if I were in your industry: Aerospace -  I'd worry about it too.


Best


Marvin