In recent years, for devices such as smartphones, MEMS microphones in which MEMS (Micro Electro Mechanical System) technology is utilized have been increasingly adopted. Further downsizing and acoustic characteristics improvement of MEMS microphone is required in electrical devices with the features of sound event detection or recording such as wearable products, action cameras, digital cameras, as well as smartphones. Also, high-performance microphone is a must in utilizing speech recognition interfaces. To respond to these needs, TDK has successfully achieved further downsizing/low profiling/high performance, based on the CSMP (Chip Size MEMS Packaging) technology cultivated thorough the development of SAW device, etc.
MEMS microphone is a compact microphone package in which MEMS chip, an acoustic sensor (acoustic transducer), and IC chip for signal processing are assembled. The MEMS chip is formed into a chip by forming a microstructure on a silicon wafer using the techniques of photolithography, etching, etc., applying semiconductor manufacturing technology. It is only several millimeters in size, and about three pieces of MEMS microphones are mounted in one smartphone. MEMS microphones are also used for a microphone with earphones for hands-free calls, headphones with noise canceling functions, and so on.
For T4064 and T4070, the new products, a new packaging that belongs to the TDK's 2nd-generation MEMS microphone is adopted. Figure 2 shows the overview of the internal structure. The microphone element MEMS chip and the signal processing ASIC are mounted on a ceramic substrate, sealed with a polymer foil, and covered with a cap. In these new products, T4064 and T4070, a metal cap is employed instead of the conventional resin cap.