Lon

I think, in my book, I identified over 20 causes of what are commonly called "white
residues" but this list is certainly not exhaustive. From your description, it is
therefore impossible to put a finger on 'the' cause, in your case. One possibilty is
that you are seeing metal salts produced by the component manufacturer using a
water-soluble flux for tinning and then inadequately removing the residues (quite
common). Corrosion continues, to form a film of residues over the component leads. The
thermal shock of soldering could conceivably break the adhesion of the film. This is
not the only possibility, but is amongst the most plausible. This could be a
reliability problem, so I suggest you have the residues analysed, to make sure what is
happening. Ionic contamination tests on incoming components is a must.

Brian

Lon Weffers wrote:

> Hello technetters
>
> We have a small problem concerning white residue on the componentside of
> the boards.
> After soldering the boards on certain points we detect a small amount of
> white residue around the tin-leaded joints of an IC. First we thought it
> was flux, bud it seems to be something else. We detect it only around
> certain joints of that particullar IC. Is it possible that it has something
> to do with the leads of the IC?
>
> Thanks in advance
>
> Lon Weffers
> Matas Electronics bv
> De Dieze 16
> 5684PT Best
> Http://www.matas.nl
>
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