Re: Dark deposit on pins near leaking SMD electrolytic caps

Harvey White

Most people seem not to like 409 because of its effects on plastic.  I've heard several people suggest that simple green should be used for cleaning off PC boards (and rinsed thoroughly afterwards!).  Another option might just be dawn dish soap, which seems to be lacking in some of the chemicals in the (above two?) products that tend to eat plastic.  Certainly, there are stories about 409 being very nasty on plastic.

If you wanted  to be quite safe, I'd use whatever Tektronix used on their scopes, realizing that most scopes of that era did not use PC boards.


On 2/9/2021 7:43 PM, Ozan wrote:
Hi Raymond,
I know SMD caps are the reason and I know it needs to be cleaned as soon as possible. I am looking for chemistry gurus in the group to understand more about its composition, why it happens on some pins. Could it be left over flux interacting with the electrolyte? What will dissolve it? I usually do DeOxit (hoping to stop oxidation - probably unnecessary), isopropyl alcohol, 409, distilled water in sequence but I am still concerned about under the ICs.

I might have missed it but I couldn't find any posts talking about the chemistry of it. It gas from the cap (I don't see a liquid trail) somehow reacting around certain pins.


That's the result of electrolyte leakage from defective SMD ElCaps. It damages
PCB's, vias and traces below a PCB's surface.

It's a classic with 'scope models that you mention. If you want to prevent
future failure of the 'scope, it's important to thoroughly clean the PCB's.
This forum is full of references to what's happening, what to do about it and
what happens if it isn't dealt with in time.


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