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I'd like to get advice for failure analysis of IIS3DWB attached near motor shaft to measure vibration of the motor.


I made a sensor module with IIS3DWB to measure vibration of motors in temperature test machine.

The operational temperature was -20~ 100 ℃.

But some sensor modules went dead in less than three month continuously. The module had no response in SPI. I suspected the disconnection of wires at first. When I measured resistance values between wires, nothing unusual was detected.

So I did CT scan, but I haven't found any defects in terms of wiring and soldering. (I compared with a good module.) I strongly doubt damages inside the MEMS circuit. but checking by myself looks impossible

I really want to know the reason why the problem happened and get some advices on the failure analysis.

Or it might be wrong the way that I made the module. I put sensor PCB inside aluminum housing and filled epoxy resin (Araldite).

Is there anyone who has experience in similar situation here?0693W00000QMgXFQA1.png

ST Employee

Hi @SPyo.2​ ,

this is a peculiar application.

I saw you already tried with X-ray scanning (no issue with the aluminum housing?), so you might share these picture, so that we can submit them to our experts and expect a comment from them.

My question is: which kind of failure are you experiencing, exactly? For example, you might have experienced just a loss in SPI communication, or an overcurrent, or something else. Consider that the IIS3DWB module is composed by two parts inside the package: the MEMS (i.e. the mechanical structure) and the ASIC (i.e. the IC for the data acquisition). If the MEMS were damaged, the SPI communication should be there as well, while for a missing SPI the issue could be related to the chain cable - soldering - wire bonding between the chip and the substrate.