Research On Piezoelectric Energy Harvester Based On Eutectic Bonding Technology

In recent years, as the rapid development of IC technology, MEMS technology and wireless sensing technology, many electronic products, such as the embedded system, the RF recognition system, wireless sensors as well as other implanted micro-sensors, have entered a new era which is characterized as integration,miniaturization and low power consumption. Therefore, the traditional immovable transmission line and chemical batteries with limited lifespan cannot meet the energy requirements of these electronic micro-devices. The vibration energy harvester based on MEMS technology, which can be well integrated with many micro-electronic chips, micro-sensors and micro-actuators, can convert the omnipresent vibration energy into electric energy by means of piezoelectric effect of piezoelectric materials, thus supply the electronic micro-devices with lasting, stable and clean electric energy. At present, the MEMS piezoelectric energy harvester which is of great scientific significance and has broad application areas has become the research hotspot of many research groups at home and abroad.In this thesis, MEMS piezoelectric energy harvester based on eutectic bonding technology is studied; the present status and trend of development is illustrated. Through analysis and comparison of different types of energy harvester, MEMS piezoelectric energy harvester based on eutectic bonding of bulk PZT with high piezoelectric properties to Si wafer is proposed. It is a beneficial explorer of design and fabrication of micro energy resources and makes a good theoretical and experimental basis of further improvement of micro piezoelectric energy harvester.The main contents of the thesis are: firstly, the research background and significance of energy harvesting technology is investigated on the basis of reading many Chinese and English papers and information, and the domestic and abroad research development of MEMS piezoelectric energy harvester is listed systemically. Then the principle of piezoelectric effect and classification of piezoelectric materials is introduced. Deeply analyze the theory related to micro piezoelectric energy harvester and derivate the expressions of resonant frequency, output voltage and power of piezoelectric cantilever. The relationship between output and structural parameters and applied acceleration is also discussed. The resonant frequency, output of voltage and power of the piezoelectric cantilever theoretically are analyzed. Given the situation that the frequency of common vibration resources in the operating environment is always below 1000Hz, static analysis, model analysis and harmonic analysis of the piezoelectric cantilever is performed using the finite element software—ANSYS to determine the optimal structure size. The technology of eutectic bonding of bulk PZT to Si is investigated, and the sample of MEMS piezoelectric energy harvester is fabricated using other standard MEMS technologies. The performance is tested with a test system containing a waveform generator, an amplifier, a vibrator, an oscilloscope and an acceleration monitor. The test result is close to the calculation. Other feasible suggestions of advancing the performance of the device are also discussed at the end of the paper.Eutectic bonding of bulk PZT ceramics to Si wafers using Au thin film as an intermediate layer was investigated. A bond strength of more than 13MPa was attained at bonding temperature of 500℃and the bonding time is about 1h. Testing of the samples demonstrate that the resonant frequency is 815 Hz and the AC output voltage is around 632 mV at the acceleration of 0.5g.