Most microphones used in practice are ECM (Electret Capacitor) microphones, which have a history of several decades. The working principle of ECM is to use a polymer material vibrating film with permanent charges.
Compared with the polymer vibration film of ECM, the performance
of MEMS microphones is very stable at different temperatures,
and their sensitivity is not affected by temperature, vibration,
humidity, and time. Due to its strong heat resistance, MEMS
microphones can withstand high temperature reflow soldering at
260 ℃ without any changes in performance. Due to minimal
sensitivity changes before and after assembly, it can also save
audio debugging costs during the manufacturing process.
MEMS microphones require external bias provided by ASICs, while
ECM does not have this bias. Effective bias will enable MEMS
microphones to maintain stable acoustic and electrical
parameters throughout the entire operating temperature range,
and also support microphone designs with different
sensitivities.
Traditional ECM sizes are usually larger than MEMS microphones
and cannot perform SMT (Surface Mount Technology) operations. In
the manufacturing process of MEMS microphones, SMT reflow
soldering simplifies the manufacturing process and eliminates a
manufacturing step that is usually done manually.
Electronic components for signal processing must be added to the
ECM microphone; In MEMS microphones, additional specialized
functions only need to be added on top. Compared to ECM, the
advantage of this additional feature is that it gives the
microphone a high power suppression ratio, which can effectively
suppress fluctuations in power supply voltage.
Another advantage is the broadband RF suppression function
integrated into the chip, which is particularly important not
only for RF applications such as mobile phones, but also for all
devices that operate similarly to mobile phones, such as hearing
aids.
The small vibrating film of MEMS microphones has another
advantage, as small films with a diameter of less than 1mm are
also lightweight. This means that compared to ECM, MEMS
microphones generate lower vibration coupling to PCB noise
caused by speakers installed on the same PCB.
