TMS320F28377S: [Agilent] FA request on damaged parts

Hi,

I have an engineer that is having a few failures on their TMS320F28377SPZPT where they get shorted on the boards (changing the part fixes it) - they are worried about what is happening and would like an FA, but these parts came from a convoluted path. Is there a way to get an FA done?

For more background:

Straight from their engineer:

We recently did a run of 6 proto boards, each one containing a single TMS320F28377SPZPT. Each board was powered up and tested successfully; the DSP was programmed, and everything looked fine. However, when I went to do some additional testing, I came across 2 of the boards that didn’t power up correctly, and I seem to have pinpointed the problem to the DSP chip – there are shorts to GND from both VDD (1.2V) and VDDIO (3.3V). I’m hoping you can help me figure out the root cause of this problem.

Here’s is part of our schematic. By removing E15 and E16, I found that the short to DCOM (GND) stayed with VDDIO and VDD. The outputs of the 3.3V and 1.2V supplies were no longer shorted to GND. There is the possibility that one of the 0.1uf the capacitors is shorted and one of the 2.2uF capacitors is shorted, but I am guessing that is less likely than there’s a problem with the DSP chip itself. We are going to change the DSP chip tomorrow to see if the shorts go away, and that will verify my guess.

I took a picture of our board’s power up (yellow=VDDIO, blue=VDD), and I’ve attached it. I think it looks fine – VDDIO is never less than VDD.

Power supply circuit.

Other info:

1. The DSP parts run cool – we really don’t tax them at all. In this case, none of them were hot or exposed to any temperatures other than normal room temp.
2. I purchased these parts in 2020, and until they were put onto these boards, they were in their original containers sitting in our R&D environment.

Questions:

1. Do the parts have a certain shelf-life?
2. The ground connection for the DSP chip is its thermal pad. If for some reason that was not properly heated during assembly, what happens if the pad is not connected to ground?