glass–silicon micropackage is to be tested inside an animal host,
body temperature (37 C) is being used in almost all the measurements.
The humidity response was typically measured from
30% RH to 70% RH with increments of 10% RH. Since it normally
takes 20–30 min for the humidity chamber to reach
equilibrium, all the readings are taken 30 min after a humidity
setting has been changed. Since polyimide humidity sensors
The sensor is wire bonded to a printed circuit board (PCB),
and tested inside an environmental chamber (ESPEC). Since the typically have a relatively fast response, 30 min is more than
sufficient for the device to reach equilibrium; the response time
of the sensor would be detailed in a following section. Almost
all capacitance measurements are performed at 1 MHz using a
HP 4280A Capacitance Meter with a resolution of 0.1 pF. Sensors
with 300-, 660-, and 1200-Å-thick polyimide are fabricated
and tested inside the humidity chamber, and test results are presented
below.