Design And Fabrication Research Of Contact Enhanced MEMS Inertia Switch

MEMS inertia switch also is called vibration threshold sensor,accelerator switch and so on.With the rapid development of wireless sensor network in recent years,the MEMS inertia switch as a passive components with ultra-low power consumption is widely used in the vibration monitoring in the internet of things(IOT).Now,many one-directional and multi-directional sensitive MEMS inertia switches are reported,but the rigid contacts(“Si-Si” or “Metal-Metal”)between fixed and movable electrode always lead to short contact time(less than 10?s)and bouncing phenomenon,which is much difficult for the signal extracting and processing in the related application system.And the rebound of the movable electrode will result in the instability of the signal,which is not convenient for the integration applications and signal processing in the IOT systems.With regards to this,in the present work two kinds of new MEMS inertia switch designs with contact-enhanced function between electrodes are proposed.One is realized by introducing the flexible CNTs/Cu composite layer between the movable electrode and the fixed electrode to prolong the contact time.The another one is realized by electrostatic locking to keep the switch be stable switched-on.The basic physical model and theoretical analysis in two kinds of novel designs are carried out.Then,the dynamic responses of the designed inertia switch and the contact impact between single CNT and fixed electrode/another CNT have been both simulated by ANSYS software.The dynamic response of the movable pull-in unit of the electrostatic locking inertia switch has been also simulated by Comsol software.The manufacturing process route of the contact-enhanced MEMS inertia switch was designed based on the research of sputtering,lithography,composite electroplating,spinning insulating film and release technology.By optimizing the production process,the MEMS inertia switch with flexible CNTs/Cu composite layer and the movable pull-in unit of the electrostatic locking MEMS inertia switch were fabricated.Finally,the dynamic response of the MEMS inertia switch with flexible CNTs/Cu composite layer was tested by drop hammer experiment,and electrostatic pull-in effect of the movable pull-in unit of the electrostatic locking inertia switch was tested by probe meter.The results show that the contact time of the designed inertia switch with flexible CNTs/Cu composite layer is about 112?s,which is in accordance with the simulation results(100?s),and the contact time is obviously prolonged comparing with the traditional rigid contact inertia switch.The movable pull-in unit of the electrostatic locking inertia switch in the current can realize a basic pull-in behavior,and it needs to be further optimized in the next research.