Research on the encapsulation method of the sound pressure channel of MEMS vector hydrophone

In order to obtain more comprehensive underwater sound field information, Micro-Electro-Mechanical System (MEMS) vector hydrophones often need to integrate sound pressure sensitive channels to improve the performance of a single transducer. The sensitive chip of MEMS vector hydrophone is prepared by MEMS technology, and its encapsulation must be water proofed. Traditional rubber potting method will destroy the electromechanical performance of MEMS sensitive chip. Therefore, MEMS sensitive chip is often sealed with oil, such as silicone oil/castor oil. In contrast, the encapsulation technology for the MEMS vector hydrophone sound pressure channel is not the same. In this paper, a given sized piezoelectric ceramic ring with radial-polarization is selected as the sound pressure channel, and the receiving sensitivities of the sound pressure channel with two different encapsulation forms, polyurethane seal and polyurethane sealant with silicone oil, are compared in the low frequency band of 5 2000 Hz. Firstly, four simulation encapsulation models for the ceramic ring are established to analyze the variation of receiving sensitivity with different models. Then, two kinds of encapsulation structures, polyurethane potting and silicone oil coupling polyurethane sealing, are designed and prepared. Finally, the receiving sensitivity calibration is carried out for the piezoelectric ceramic ring with the two packaging methods in the standing wave tube. The results show that polyurethane potting and silicone oil-coupled polyurethane sealing have little effect on the receiving sensitivity of the sound pressure channel, and in the actual operation process, it is necessary to pay attention to the difference in technical complexity between the two methods.