The two main challenges in electrothermal MEMS design are their slow response and inherently low efficiency. Therefore, thermal modeling is essential for design and optimization. A compact parametric model is desirable as it computationally efficient and can be used for optimization. Analogy between heat flow and electrical signal flow in a transmission line is used to develop a general procedure for parametric dynamic thermal modeling. The procedure is demonstrated by using an electrothermal micromirror that is actuated by thermal bimorphs. An embedded Pt resistor is used for heating. Silicon dioxide thermal isolation reduces heat leakage to substrate and mirror plate. First, finite element simulations are used to show that the heat flow in the micromirror is predominantly one dimensional. Then, a generic transmission line model is developed for a 1-D geometry in which voltage represents temperature rise above ambient and current represents heat flow. Simplification of the transmission line model results in a lumped element model with few circuit elements. Conditions under which lumped element approximation holds are identified. Thereafter, the networks representing the thermal isolation regions, bimorphs and mirror-plate are cascaded to build the complete thermal model. Validation against experimental results is provided for static and dynamic case.
Journal: TechConnect Briefs
Volume: 2, Nanotechnology 2010: Electronics, Devices, Fabrication, MEMS, Fluidics and Computational
Published: June 21, 2010
Pages: 589 - 592
Industry sectors: Advanced Materials & Manufacturing | Sensors, MEMS, Electronics
Topic: Informatics, Modeling & Simulation