we developed a product (a clock) based on Photon, we use its internal RTC for keeping the time. There are 600+ units deployed at customers.
We experienced strange failure in a recent batch (3 occurrences so far), the RTC stopped working and no longer increment time. It is not a software issue, same firmware and device OS runs at hundreds of clocks without issue. We haven’t seen such an issue before even in testing…
We tried to reproduce this problem, we took a healthy photon, removed the EMI shielding and shorted the 32kHz quartz oscillator used for the RTC. This way we achieved exactly the same behavior - all the functions of the Photon are working (Wifi etc…), but the RTC is not incrementing time.
So far we got one clock back from the customer, I removed carefully the EMI shielding (by soldering iron, not hot air), all looks good. It is interesting that after removing the shielding, the RTC started working as usual. The shielding was not damaged, it was perfectly straight, not touching the parts below.
crappy photo of that particular unit, the oscillator in right upper corner:
The Photons are soldered by reflow in assembly house (SnPb), we’ve done it this way for long time without a single issue. No parameters were changed for this particular batch. The clocks are tested and running for several days before shipping, so there might be something related to shipping/transportation.
Any ideas? Anyone else experienced such a failure?
All three clocks passed our QC, which is really frustrating…