Motion tracking MEMs devices or microphones?

-----Original Message-----

Hi all, to elaborate a little further, 30 out of 30 1st-article pcbs with t=
he invensense MEMS were destroyed by ultrasonic cleaning of the pcb.  100% =
failure rate of a relatively small sample I suppose statistically but way l=
arger than one wants as an engineer trying to finish a project.  :)  The In=
vensense datasheet warns about this as I recall.

I have heard the ultrasonic welding of cases causing grief with MEMs and xt=
als, as people have discussed.  For this project, there are 4 very small se=
lf-tapping screws to close the case, no welding.

That said, pretty clearly other wearable bluetooth devices (requiring at mi=
nimum an xtal in the 16-32Mhz range, and often a 32.768Khz as well if it is=
 bluetooth low-energy) are welded shut.  What devices like the Fitbit and t=
he like (MEMs and xtals) do would be interesting to know.=20
Presumably they have reliably solved the ultrasonic damage issue.

J


--=20
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