Electronics > Projects, Designs, and Technical Stuff

Is "integrated circuit burn-in" a thing?

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amyk:

--- Quote from: IDEngineer on April 24, 2019, 01:49:10 am ---These chips are used in millions of cellphones and tablets. I find it hard to believe they're being power-cycled all the time. The chips have very aggressive power-saving modes that are openly and specifically intended for phones and tablets, to save power. Heck, this LSM6DS3 brags about "Compliant with Android K and L" as the fourth bullet item on the front page of its spec sheet. There's no mystery what market they're targeting. Do I think they added an FET to each cellphone to cycle power on these devices? No, I don't. Their internal power saving modes can drop their consumption to almost nothing... a quick glance shows the LSM goes to 6uA in "power down" mode.
--- End quote ---
I suspect this could be a case of "popular part with little-used feature has a bug" --- it might be worth finding some Android source code from some device that uses this IC to see if it uses the same options (filters, etc.) that you're using.

IDEngineer:

--- Quote from: AndyC_772 on April 24, 2019, 08:01:27 am ---I know that, with some of these parts, the board layout is critical to avoid asymmetric forces being applied to the device at the point the solder solidifies during reflow. What does your layout look like? Is there anything strongly asymmetrical around the device and the traces immediately leading to it? Maybe there's some residual thermal stress 'baked' into the device after reflow, which reduces over time as the PCB pads are able to move slightly?
--- End quote ---
You're absolutely correct about mechanical stress affecting such parts, and in the case of the ST LSM6DS3 the spec sheet does explicitly discuss that. But they say, and we've confirmed, that the effect is to impart a bias to measurements in one or more axes. It's interesting to watch the baseline values change as you twist the PCB. I've already written calibration routines into the firmware for exactly this reason. Soldering the parts to the board definitely "locks in" some stress, but twisting the PCB even slightly has a much greater effect. (Note this means the device will need calibration AFTER installation in its final location since mechanical mounting will likely impose some degree of stress on the board.) My calibration routines can be remotely accessed via a software command to make that easier.

No, there's nothing inherently asymmetrical about the layout. But it IS an interesting thought that, with time and power applied, the board might warm enough to allow solder migration. However, as I said, the effects stated by ST and seen by us seem to be limited to a measurement bias, not to (firmware?) lockups.

IDEngineer:

--- Quote from: SparkyFX on April 24, 2019, 05:45:07 am ---That question reminds me of something: Have the parts been passing an X-Ray while crossing a border or such?
--- End quote ---
I have no way to know what they might have encountered along the way, but neither we nor our assembly house x-rayed them!

IDEngineer:

--- Quote from: Whales on April 24, 2019, 11:01:52 am ---Customers not good enough to help directly?    Then you're not good enough for customers.
--- End quote ---
In fairness, their technical staff is supposed to be monitoring and responding on the forums. They didn't just abandon technical support, they got rid of the "private trouble ticket" system. I understand the advantages of that, including 1) someone else might answer faster, and 2) the answers become accessible to others with the same question. However, it's the abysmal quality of the "answers" that I'm getting that's so discouraging. As I illustrated above, it's like they don't even comprehend my question. Maybe they just don't believe their part could have such a problem, or that this particular customer is an idiot. The latter may be true, but I guarantee the former is too!

IDEngineer:

--- Quote from: amyk on April 24, 2019, 11:35:25 am ---I suspect this could be a case of "popular part with little-used feature has a bug" --- it might be worth finding some Android source code from some device that uses this IC to see if it uses the same options (filters, etc.) that you're using.
--- End quote ---
That's just it - this bug isn't in some little-used feature, or even an optional feature like the internal filters. This bug shuts down the SPI interface, the only way to interact with the device! To be clear, I have managed to eliminate several other bugs by disabling every filter and feature over which you have any sort of control, which I now presume lessens the processing burden on the internal firmware. But this one appears to correct itself with enough power-on time. I suppose I can just insist that Production build a burn-in rack with the appropriate connectors and give them 24? hours, but I'd sure like some sort of confirmation that we're treating the actual disease and not just a symptom.

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