Kitchen Lighting System

RE: Kitchen Lighting System

ralphjy — Tue, 09 Nov 2021 06:35:29 GMT

I find it interesting that not many vendors talk about ESD damage to MLCCs. Most don't even have ESD ratings. Maybe because in general it is a low occurrence failure. We used to do extensive ESD testing of our high speed pin electronics because they were exposed to ESD at the test sockets. I got surprised when I was doing characterization to set the ESD spec for pins in a new design. We were getting some pins that started failing at relatively low voltage. I thought we were having clamp failures in our ASICs which were normally the weakest link, but it turned out that it was the broadband MLCC caps that we were using to AC couple the pins. Higher value MLCCs have very thin dielectric layers and we were getting variations in the ceramic particulate size in the slurry used to manufacture the parts. We were getting early punch through when the particulate was large enough to create gaps in the dielectric. Long story short - we started sample ESD testing and returned any lot that didn't meet our requirements. So there are other failure modes than mechanical damage and low voltage overstress.

RE: Kitchen Lighting System

Jan Cumps — Mon, 08 Nov 2021 17:46:06 GMT

The failure mode for (mechanical) defects on a ceramic SMD is often: Shortcut.

Both repair channels of Louis Rossmann and Paul Daniels spend a decent part of their time looking for broken SMD ceramic caps in MacBooks - except for laptops with liquid damage: there they look for corrosion.

Possible reasons:

already slight cracks before placed
damage during solder process
pcb bending
heat cycling causing stress.

(in some circuits, this is mitigated by putting 2 higher value caps in series, so that one cap can't cause havoc).

RE: Kitchen Lighting System

fmilburn — Mon, 08 Nov 2021 16:54:20 GMT

I need to go back and read your original articles as the counter tops in my new home are not well lit :-)