Quote:
Originally Posted by 60 oldjohn
Quote:
Originally Posted by knobtwiddler
Something also worth noting is that SMD ceramic caps can go short-circuit due to thermal stress. Annoyingly, this can happen a while down the line (typically when the unit is in service...). If you are soldering them, do everything you can to minimise heat stress - short circuited caps can do a lot of damage!
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I have had SMD caps go open circuit, actually breaking in two after a day or three, not sure if it is the capacitors, my soldering, or the thin PCB 0.7mm thick x 11m x11mm. The Ceramic caps can also be microphonic.
John. |
Consider yourself lucky! I have literally seen tens of them, from different brands, go short - when they've been hand soldered... On some occasions the PSU has soldiered on, without going into I-limiting, thus turning said cap / caps into charcoal. On other occasions the PSU's sensed the load and gone into protection. I've serviced items where the owner didn't think there was a fault, and I've seen blackened, crusty caps - looking like a dried insect.
I can't say 100% that the shorts weren't stress related. However, I find this implausible, considering how much abuse SMD caps get in modern gear such as phones and the like. Nor do I see how they'd get the physical abuse when soldered. My feeling is that they like a short, sharp soldering cycle - and beyond that can brew up trouble down the road.