Thermal-Mechanical Evaluation of Plated Electro-Magnetic NiFe for MEMS Generators
- PDF / 180,039 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 16 Downloads / 178 Views
U11.35.1
Thermal-Mechanical Evaluation of Plated Electro-Magnetic NiFe for MEMS Generators Yibin Xue, Keithan Hillman, and David Veazie Department of Engineering, Clark Atlanta University PO Box 156, 223 James P. Brawley Dr. SW Atlanta, GA 30314 ABSTRACT In micro-electro-mechanical system (MEMS) devices that contain multi-layers of metallic, ceramic, and polymeric materials, acquiring a complete understanding of the mechanical properties and interfacial strength are critical in designing the devices. In general, these layered materials are specially fabricated with thickness of each layer on submicron and/or micron scale. Particularly, the properties of these layered materials strongly depend on the fabrication processes and subsequent treatments. In this paper, we study the magnetic metallic films, NiFe (80/20 in weight), for MEMS generator/motor applications. A set of tensile tests was conducted on the plated nickel-iron metallic films of various thicknesses and subjected to various annealing conditions. Distinctive differences in mechanical behaviors between the electroplated films and the corresponding bulk alloys were observed. Furthermore, the NiFe film as-deposited exhibits almost pure elastic deformation and brittle fracture at room temperature; whereas the NiFe film subjected to annealing exhibits strain hardening and ductile fracture when tested at room temperature. X-ray diffraction was used to capture the variation of crystalline structure and the residual stresses in the electroplated films as deposited and after annealing. An atomic force microscope was used to obtain the surface morphology of the films as deposited and after annealing. INTRODUCTION The Army concept, the Objective Force Warrior, requires compact energy sources that provide energy and power density at least ten times higher than what today’s best batteries can offer. A power microelectronic mechanical system is being developed to meet this challenge. This power MEMS device is intended to be a combination of a micro turbine engine powered by the combustion of hydrocarbon fuel and a coupled micro magnetic generator. This conceptual MEMS generator is to be compact, light in weight, and generate high-density power, which would constitute a good portable power unit for soldiers. Substantial high power handling potential of the MEMS generator is accompanied by significant challenges in its development. High power also implies high levels of other characteristics, such as voltages, currents, temperatures (over 300°C), and/or rotational speeds (over 1 Mrpm). The proposed MEMS device comprises a stack of at least five layers of silicon wafers, thus it requires stringent geometric confinement and operating accuracy under the specified operation conditions. Therefore, an accurate thermal-mechanical evaluation of the electroplated magnetic film, NiFe (80/20), is vital for the reliability of this MEMS generator/motor. Metallic thick Ni film was tested at Johns Hopkins University with strain measured using an interferometric strain/displacement gage
Data Loading...
