Re: Dark deposit on pins near leaking SMD electrolytic caps


 

On Wed, Feb 10, 2021 at 01:13 AM, Ozan wrote:


Does anyone know the chemical composition of the dark deposits on IC pins that
are close to leaking SMD caps? What is the best way to clean them? Litmus
paper shows base (hard to tell because it gets stained by the deposit). I
couldn't find a good solvent for it.

Here is a picture from a TDS520A
https://groups.io/g/TekScopes/photo/260554/0?p=Name ,,,20,1,0,0

Interestingly sometimes one or two pins are covered but neighboring pins are
OK (maybe voltage at the pin making a difference?). I have seen this in CPU
card of 2467B, both acquisition and CPU cards of TDS520 and TDS520A.
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.

Raymond

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