It seems that MEMS is very sensitive to helium, but only helium. This Link stated that hydrogen does not affect MEMS, which surprised me. Does anybody know why it's just helium, or what's really going on?
According to the link, an iPhone 8 will stop working after just a few minutes to hours of helium exposure, and will take days to recover, even using a vacuum.
According to this table from the linked article, a hydrogen molecule (120 pm radius) is actually smaller than a helium atom (140 pm radius), which is confusing as to why it is not more effusive. Is this correct?
An important "find" buried in the article was one solder bonding method that did keep out the Helium:
While the majority of the CSP (Chips Scale Packages) parts did show ingress of helium at varying rates, one type of metal solder seal did not show any indication of helium ingress. Unlike prior work, this study found a wafer-to-wafer bonding method that enabled diced, vacuum-bonded chip-scaled packages to pass 1000 hour, high-pressure helium testing with no change in sensor output due to helium ingress...