I have experienced a 500% increase in failures in the field over the last few months for one specific product. I've gotten some of the units back and it was just this week I was able to go through all the failed units, do a thorough post-mortem and tabulate the results.
It turns out a capacitor on the power input was failing as a dead short, causing the traces on the board leading to that cap to ultimately massively overheat and go up in smoke.
The capacitors are CL21A226MOCLRNC from Samsung. I went through our stack of boards that failed post-assembly testing and were awaiting rework, and found that most of the failures there are also due to this same capacitor. I then went through the drop-bin on the pick and place machine (where it drops parts it could not place for whatever reason), and pulled out all of the aforementioned caps and tested them... about 5% were bad - just a dead short. I looked under a microscope and there's nothing unusual to see, no cracks or problems with the solder points or anything else.
But the fact that I saw so many failed parts in the PnP reject bin tells me that it wasn't the reflow process, nor the testing process, nor the use in the field that was causing the issues... it was bad parts right off the reel.
I was wondering if anyone has seen anything like this before? Digikey has ~200,000 of these caps in stock, so it seems to be a pretty common usage part, and I am very surprised that a major manufacturer would be shipping parts with this problem. But maybe I have just been lucky in the past?