Re: Dark deposit on pins near leaking SMD electrolytic caps


Chris Wilkson
 

The classic recipe for battery leakage on PCBs is a toothbrush scrub (actually short bristled hogs hair) in a white vinegar rinse. Follow that with a scrub in a baking soda rinse to neutralize the acid. Followed by a "clean water" rinse: de-ionized water if you have it or can afford it, but distilled water is plenty good enough. There's no reason to use tap water...distilled is cheap enough. Last step is a compressed air dying and an oven bake at maybe 110-120C for a "long enough time".

With SMT devices a warm soak is probably better at each stage. To give the cleaning chemicals a chance to get in under the parts.

I was given a 7104 whose filter caps leaked and destroyed the power supply boards. I don't know the chemistry of the leaked electrolyte, but that was some *nasty* stuff! It ate the metal and the substrate of the PCBs. Of course it had been sitting undisturbed on a shelf for probably 20 years, eating away. Having nothing to lose I tried the battery cleanup process and it worked great. The vinegar fizzed up pretty nicely too.

About 7-8 years later I peeked inside again and there was no obvious sign of further damage.

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