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.