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Institute
MEMS microphones must be further miniaturized for use in mobile devices. So we developed packaging technologies for MEMS microphones using flip chip technology instead of wire bonding. The first two generations have the sound hole in a ceramic interposer at the bottom side of the package. Now a new flip chip microphone package with the sound hole on the top side has been developed. The new package technology combines a large acoustic reference volume for good signal to noise ratio with small size. Compared to other microphone packages the sensitivity is improved by 3 dB. The front volume is small to avoid resonances in the acoustic frequency range.
Fabrication and characterization of a piezoresistive humidity sensor with a stress-free package
(2014)
A highly miniturized piezoresistive humidity sensor has been developed. The starting point of the developement was a 1x1 mm2 piezsoresistive pressure sensor chip. As sensing material, a polyimide was used that swells with increasing adsorption of water molecules. To convert the swelling into an electrical signal, a thin layer of the polimide was deposited onto the bending plate of the pressure sensor. The humidity sensor was characterized in a climate chamber. The measurements show a sensittivity of 0.25 mV per percent relative humidity (%RH) and a non-linearity of 3.1 % full scale (FS) in the range of 30-80%RH. A high cross-sensitivity to temperature of around 0.5 mV°C was measured, so temperature compensation is necessary. For stress-free packaging of the sensor chip, a novel packaging technology was developed.