[time-nuts] Helium and MEMS oscillators don;t mix well

[Wayne Holder]

The oscillator mentioned in the article is a SiT1532 made by SiTime
<http://SiT1532>.  It's sold in a chip scale package that's only 1.5mm x
.9mm, which means it'a no much more than a chip of silicon with some solder
balls attached.  The data sheet indicates there is a "polymer" coating on
the back side of the chip, but the working surface would be in the bottom
where the solder balls are.  There is a rectangular protrusion shown on the
"Dimensions and Patterns" section (page 12) that's right over where the
MEMS mechanism would sit that might be some type of seal, but there is no
descriptive text.

The curious thing to me is that some iPhones are said not to recover from
exposure to helium but, as an essentially mechanical device, I can think of
no reason that the SiT1532 would not recover from exposure to helium after
the gas had migrated out.  I wonder off the iPhone could be damaged by an
oscillator failure, o one that's running off frequency? The devices sell
for about $1.25 at Mouser and I have a tank of helium in the garage, so I'm
thinking about doing an experiment.  The only problems is finding a way to
solder wires to such a small part?  Might have to make a PCB, instead.

Wayne

On Wed, Oct 31, 2018 at 12:51 PM Mark Sims <holrum at hotmail.com> wrote:

> https://ifixit.org/blog/11986/iphones-are-allergic-to-helium/
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