Passive Wireless Instrumented Getter

Getters are materials that chemically bind selected gas molecules after their activation. They are useful in maintaining vacuum quality in hermetic packages and have, therefore, been used with electronic devices since the advent of vacuum tubes, to prolong the useful lifetime of the device. However, once a getter has saturated, it can no longer bind additional molecules, at which point the vacuum quality begins to degrade. This is an open-loop system where getter saturation may only be detected by the electronic component failing. To mitigate this issue, the STAYDRY HiCap2019 getter was integrated with a sense capacitor such that the resulting capacitance decreased as the getter bound water molecules. Connecting this capacitor with a planar inductor realized a passive wireless LC sensor tag that could be inductively coupled with an external feedback oscillator. A prototype system demonstrated a 22 kHz frequency change over the full moisture capturing range of the getter, yielding a linear model with a sensitivity of 220 Hz per percent getter usage. The resulting wireless instrumented getter tag is suitable for use in hermetically packaged electronics.