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MEMS(Micro Electromechanical System) microphone is a microphone based on MEMS IC substrate technology. Simply put, a capacitor is integrated on a micro silicon chip, which is mounted on a IC substrate with a suitable ASIC by means of surface-attaching process. Finally, it is encapsulated by covering the shell. The following picture shows a typical MEMS microphone package structure. Compared with traditional ECM microphones, MEMS microphones have the following advantages: A. Surface mount, fully automated production, high production efficiency and good consistency of product performance; B. Can withstand reflow temperature above 250 degree Celsius, operating humidity and operating temperature range are greater than ECM microphone; C. It also has improved noise elimination performance and good RF and EMI suppression.
MEMS microphone packaging materials mainly include MEMS chip, ASIC chip, PCB IC substrate, metal shell, MEMS chip paste and ASIC-coated silica gel, ASIC chip paste, circuit connecting general gold wire, solder paste for metal shell and PCB substrate welding. The following is the picture of MEMS microphone packaging materials. It should be noted that due to the special structure of MEMS chips, special attention should be paid to the selection of adhesive glue, that is, to pay attention to the hardness and Young's modulus of watering, to ensure that MEMS chips have a low stress, to avoid the impact of stress brought by packaging MEMS microphone sensitivity.
The structure of MEMS chip determines that MEMS chip IC substratepackaging will be differentiated packaging, and one product will correspond to one type of packaging, so no one company can fully cover all MEMS sensor I C substratepackaging. The packaging process of MEMS microphone mainly includes: Chip pasting, gold wire welding line, point gluing protection chip, shell welding, laser marking, scribing, packaging and other processes. The encapsulation process is shown in the figure below. In the need of special note is due to membrane structure of the MEMS microphones unique environment influence on foreign bodies on the performance of the products, and packaging process, including the human body, is dust or foreign carriers, chip is very easy to pollution, complete packaging shall be carried out in the thousand grade purification workshop, workshop homework personnel the number of strict regulations.
