MicroElectroMechanical System (MEMS) assemblies include microphones and speakers to mention two examples. These MEMS devices may be used in diverse applications such as within hearing aids and cellular phones.
In the case of a MEMS microphone, acoustic energy typically enters through a sound port in the assembly, vibrates a diaphragm and this action creates a corresponding change in electrical potential (voltage) between the diaphragm and a back plate disposed near the diaphragm. This voltage represents the acoustic energy that has been received. Typically, the voltage signal is then transmitted to an electric circuit (e.g., an integrated circuit such as an application specific integrated circuit (ASIC)). Further processing of the signal may be performed on the electrical circuit. For instance, amplification or filtering functions may be performed on the voltage signal by the integrated circuit.
As mentioned, sound typically enters the assembly through an opening or port. When a port is used, this opening also allows other unwanted or undesirable items to enter the port. For example, various types of contaminants (e.g., solder, flux, dust, and spit, to mention a few possible examples) may enter through the port. Once these items enter the assembly, they may damage the internal components of the assembly such as the MEMS device and the integrated circuit.
Previous systems have sometimes deployed particulate filters that prevent some types of debris from entering an assembly. Unfortunately, these filters tend to adversely impact the operation of the microphone. For instance, the performance of the microphone sometimes becomes significantly degraded when using these previous approaches. Microphone customers often elect to not use such microphones in their applications because of the degraded performance.
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