A MEMS ceramic vertical leaf spring actuator

Low-temperature co-fired ceramics (LTCC) have been demonstrated as an excellent choice for the fabrication of MEMS sensors. The LTCC has similar mechanical properties to silicon and may be used to create a wide range of potentially useful three-dimensional structures, such as cantilevers, membranes, and other MEMS mechanical elements. Ceramic (LTCC) MEMS devices have the added benefit of being partially or completely self-packaged, which often precludes the need for complex packaging methodologies. Furthermore, LTCC can be exposed to higher temperatures and corrosive environments without special packaging, which increases the range of applications where ceramic MEMS may be employed. These features of LTCC have been combined to create a micromachined ceramic leaf spring device that offers vertical, electrostatic actuation. With submicron displacement control in any orientation, this ceramic vertical leaf spring actuator introduces ceramics to the MEMS actuator arena and addresses some of the issues that challenge MEMS vertical actuation. The micromachined ceramic vertical actuator presented is based on a multi-fold leaf-spring design appearing like a series of cantilevers oriented in opposite directions. The device employs electrostatic actuation to compress and release the structure resulting in vertical motion. The simplicity of the basic design made it possible to extend existing electrostatic cantilever models to develop a dual deflection model to characterize the device and to aid in the design process. This expanded model accounts for the effects of two electrostatically actuated cantilever beams bending towards each other without adding complexity to the established cantilever model. Techniques for the creation of the leaf spring structure were developed and actuators were fabricated. Mechanical testing revealed that single sheets of the chosen LTCC do not have uniform intrinsic mechanical properties. While this resulted in tremendous and unpredictable variations in device performance, advances in ceramic material should help to alleviate these problems.