(bingo!) Resolved: Apple iPhone Failures

Following up on my rant of a few weeks ago regarding unexplained and sudden correlated iPhone "bricking", the answer turns out to be more interesting than I would have thought possible!

It turns out that Apple iPhones 6 and later and Watches use an ultra low po wer 32kHz MEMS oscillator. Further, it turns out that helium in the atmosph ere can diffuse INTO the oscillator and cause the device to quit, at least temporarily.

It so happens that in this particular workplace, there are quantities of he lium vented periodically when the instrument on which we are working is coo led to from 77K to 4.2K (some leaks off during operation but it's relativel y slow). O2 levels are monitored for worker safety (and additional ventilat ion is employed when there is a lot boiling off) but helium levels are not monitored.

Further reading: ?Output Drifting of Vacuum Packaged MEMS Sensors D ue to Room Temperature Helium Exposure?

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iPhone specific blog entry:

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The part in question:

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Reply to
speff
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Weird. I wonder why a tiny bit of helium inside the can will change a mems device.

I've seen an NMR magnet quench. It's pretty impressive.

--
John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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John Larkin

en correlated iPhone "bricking", the answer turns out to be more interestin g than I would have thought possible!

power 32kHz MEMS oscillator. Further, it turns out that helium in the atmos phere can diffuse INTO the oscillator and cause the device to quit, at leas t temporarily.

helium vented periodically when the instrument on which we are working is c ooled to from 77K to 4.2K (some leaks off during operation but it's relativ ely slow). O2 levels are monitored for worker safety (and additional ventil ation is employed when there is a lot boiling off) but helium levels are no t monitored.

Due to Room Temperature Helium Exposure?

Fascinating, thanks. Helium is sneaky stuff.

George H.

Reply to
George Herold

I can see that being a highly unusual problem with your workplace. I will warn my wife who has a couple of big NMR systems in her lab. It can't be a common mode of failure except in big science labs with superconducting kit (or party balloon businesses).

How weird. Still at least now you know! How did you find this out?

--
Regards, 
Martin Brown
Reply to
Martin Brown

I have a couple of doctor friends who also should know this because they work around MRIs.

Oh, I like to dig. Failure analysis must be fascinating for those who do it as a career. See the comments at the bottom of page 11 here, for example, for issues with the SR-71

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Tightening Ti bolts with the usual cad-plated tools left enough cadmium that the bolt heads would drop off at operating temperature. Inconvenient. Also, wing panels made in summer failing, but not those made in winter. ;-)

--Spehro Pefhany

Reply to
speff

Bruker? Or the departed Varian systems, which Agilent acquired and killed?

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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John Larkin

onsdag den 28. november 2018 kl. 17.15.43 UTC+1 skrev John Larkin:

den correlated iPhone "bricking", the answer turns out to be more interesti ng than I would have thought possible!

power 32kHz MEMS oscillator. Further, it turns out that helium in the atmo sphere can diffuse INTO the oscillator and cause the device to quit, at lea st temporarily.

helium vented periodically when the instrument on which we are working is cooled to from 77K to 4.2K (some leaks off during operation but it's relati vely slow). O2 levels are monitored for worker safety (and additional venti lation is employed when there is a lot boiling off) but helium levels are n ot monitored.

s Due to Room Temperature Helium Exposure?

it's basically a tuning fork

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30minutes in 2% helium and it stop oscillatin g

Reply to
Lasse Langwadt Christensen

Very interesting - thanks!

I recall reading in John Clark's "Ignition!" that the quirks of titanium caused quite some problems for the rocketry folks. They were trying to find metals which could be used to store red fuming nitric acid without corroding and ruining the acid... aluminum wouldn't work, stainless steel wouldn't work, so they tried some titanium.

Then, tragedy struck: a set of titanium-alloy samples immersed in RFNA exploded violently in the lab, killing the technician who was working with them.

It turned out that the acid triggered an intergranular corrosion process in the titanium, creating a "fine black powder" of mostly metallic titanium. When wetted with nitric acid this could oxidize explosively, and it was about as sensitive to shock as nitroglycerine or mercury fulmanate.

Not the best material to use to hold your rocket-fuel oxidizer in a missile, obviously. :-(

One wonders how the Fuzzies were able to use it to build starships... their technology was obviously ahead of ours.

Reply to
Dave Platt

Both Bruker - the newer one does magic angle as well.

--
Regards, 
Martin Brown
Reply to
Martin Brown

en correlated iPhone "bricking", the answer turns out to be more interestin g than I would have thought possible!

power 32kHz MEMS oscillator. Further, it turns out that helium in the atmos phere can diffuse INTO the oscillator and cause the device to quit, at leas t temporarily.

helium vented periodically when the instrument on which we are working is c ooled to from 77K to 4.2K (some leaks off during operation but it's relativ ely slow). O2 levels are monitored for worker safety (and additional ventil ation is employed when there is a lot boiling off) but helium levels are no t monitored.

Due to Room Temperature Helium Exposure?

They claim to have developed immune parts:

"How effective is the hermetic seal of MEMS oscillators?? One of the key elements enabling extremely stable MEMS resonators is SiTime ?s EpiSeal? process which hermetically seals the resonators during wafer processing, eliminating any need for hermetically sealed cera mic packaging. SiTime?s EpiSeal resonator is impervious to the high est concentration elements in the atmosphere, nitrogen and oxygen, and ther efore acts as a perfect seal. Previous generations of EpiSeal resonators ma y have been impacted by large concentrations of small-molecule gas. Newer E piSeal resonators are impervious to all small-molecule gases. Please contac t SiTime in case you are planning to use a SiTime device in large concentra tions of small-molecule gas, so that we can recommend an appropriate, immun e part."

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This small molecule stuff has been around a while:

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bloggs.fredbloggs.fred

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