I waited to see if you got any replies on this before adding my twopenneth as
I can really only offer anecdotal advice.
It is theoretically possible for acid [flux residues] to "attack" welds in
otherwise uneffected metals. The discontinuities in the metal structure at the
weld can be sufficient to cause reactions similar to the effect when an acid
is in contact with two different metals at the same time. This is particularly
the case if you have welded an alloy as opposed to a pure metal, and if the
flux is a powerful one.

However I would think the probability of this happening is slight with
electronic - ie weak- grade fluxes . Certainly it can be a problem with
brazing fluxes (which are hundreds of times more active).

How to find out more and what to do?

I suggest you ask these people for documentary evidence or references to
support their contention. That will give you a start point on finding the
answer to your posting.
In the short term tcan you use a spot mask, [peelable or washable] to avoid
flux contact, this will either give you a fix  and time to think for a long
term answer.  (eg have the assemblies plated). Or it will show the problem is
elsewhere.
If it looks as though there is any substance in this, to actually determine if
this is a problem you will need to do some proper metallurgical investigations
and maybe even some ageing trials. Here you enter the realms of theology as
the accelleration needed in the ageing may  kick off events that would not
actually happen in real life. I guess what I am saying is you would need
specialist advise,  somone like the International TIn Research Institute, TWI
etc.
....................................
In a message dated 11/01/99  09:06:48PM, you write:

>  am attempting to find some info or a standard that deals specifically with
> the soldering of purely mechanical parts,  ( a tube used to transfer
> hydraulic fluids in an electro-mechanical assembly soldered to another
> transfer tube) , the company thinks that the small amount of acid from the
> flux core solder is over a period of time weakening the "weld" and resulting
> in cracks or fractures.  Can anyone help me with this one?   Thanks in
> advance.
>
>  [log in to unmask]

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