Impact of Reflow on the Output Characteristics of Piezoelectric Microelectromechanical System Devices

Abstract

An animal health monitoring system and a wireless sensor node aimed at preventing the spread of animal-transmitted diseases and improving pastoral efficiency which are especially suitable for chickens, were developed. The sensor node uses a piezoelectric microelectromechanical system (MEMS) device and an event-driven system that is activated by the movements of a chicken. The piezoelectric MEMS device has two functions: a) it measures the activity of a chicken and b) switches the micro-control unit (MCU) of the wireless sensor node from the sleep mode. The piezoelectric MEMS device is required to produce high output voltages when the chicken moves. However, after the piezoelectric MEMS device was reflowed to the wireless sensor node, the output voltages of the piezoelectric MEMS device decreased. The main reason for this might be the loss of residual polarization, which is affected by the thermal load during the reflow process. After the reflow process, we were not able to apply a voltage to the piezoelectric MEMS device; thus, the piezoelectric output voltage was not increased by repoling the piezoelectric MEMS device. To address the thermal load of the reflow process, we established a thermal poling treatment, which achieves a higher temperature than the reflow process. We found that on increasing the thermal poling temperature, the piezoelectric output voltages did not decreased low significantly. Thus, we considered that a thermal poling temperature higher than that of the reflow process prevents the piezoelectric output voltage reduction caused by the thermal load.

Effects of Bipolar Pulse Poling on the Ferroelectric and Piezoelectric Properties of Tetragonal Composition Pb(Zr0.3,Ti0.7)O3 Thin Films on Microelectromechanical Systems Microcantilevers

“…Pb(Zr,Ti)O 3 (PZT) thin films are widely utilized to piezoelectric MEMS devices such as gyros, 1) inkjet heads, 2) RF-MEMS switches, 3) and ultrasonic transducers. 4) We have developed various kinds of piezoelectric devices including microscanners, 5,6) self-sensitive microcantilevers, 7,8) electrostatic field sensors, 9,10) accelerometers, 11,12) trigger switches for wireless sensor nodes, 13,14) and energy harvesters. 15,16) Moreover, we have utilized MEMS-based piezoelectric microcantilevers to investigate the crystal structure 17,18) and fatigue behavior 19) of PZT thin films.…”

Unique Activity-Meter with Piezoelectric Poly(vinylidene difluoride) Films and Self Weight of the Sensor Nodes

“…In our previous study, as proof of our successful measurement of the activity of chickens, the PZT output voltages were about 10 mV with frequencies below 15 Hz under 0.5 m/s 2 vibration. 25,26) Therefore, we expect that the PVDF film version sensor nodes can measure the activity of chickens.…”

“…Thus, we reported that the PZT MEMS devices poled under 250 C-18 V-5 min conditions had only slightly lower piezoelectric output voltages after the reflow process. 25) After the above thermal poling treatment, the PZT devices were reflowed to the wireless sensor nodes. We then attached the sensor nodes to more than one hundred chickens.…”

Pulse-Poled Porous BaTiO3 Ceramic for Piezocatalysis Applications

“…Furthermore, porous ceramic could be poled via pulse poling technique as traditional way of poling generally produce negligible enahcement in piezoelectric properties of porous ceramic pellets 22 . Generally, conventional dc poling is applied on piezoelectric material which takes several hours for their dipole orientation 23,24 . Such procedure of dipole alignment is not e cient in case of porous ceramics as applied electric eld concentrates in less permittivity phase 25 .…”