We have just had a delivery (from a pick/place subcontractor) of a few thousand populated circuits.
Each one has a 22uF 50N Nichicon aluminium electrolytic cap on it, SMT type.
I immediately noticed that all the caps have their top slightly bowed outwards.
So I applied a 370degC temperature controlled soldering iron to the case of a fresh one of these. After a long time, after the cap was smoking away quite a bit, the top of it did indeed come up. Eventually it came up a lot more than those on the PCBs... yet, it still measured
22uF-23uF with a capacitance meter.
I am going to visit the contractor on Monday to see if we can work out what they did with their reflow oven to cause this.
What concerns me is whether I should scrap all the circuits as a precaution. If I did that, what legal basis would I have for doing that? It would be hugely expensive, about US$20k.
The rest of the components are some SO-14/16 chips, HP optoisolators, loads of ceramic caps, 0805 mostly but some bigger, melf (glass) diodes, plastic power diodes, etc.