A theoretical analysis of initially buckled, and thermally actuated bimorph micro bridge is presented in this paper. The micro bridge is to be buckled by compressive residual stress developed in the beam during fabrication. An analytical model that characterizes the buckling shape is proposed, and used in the analysis. This model considers symmetrical rotational stiffness, and infinite axial stiffness at both ends of the bridge. Deflections versus temperature characteristics for a bimorph micro-bridge of length, 1000µm, thickness, 4µm, with various initial deflections ranging from 5µm to 20µm are obtained, and plotted. The results show that a pin-pin micro bridge (rotational stiffness of zero) exhibits bi-stability at lower snapping temperatures when negative thermal expansion material is used as one of the layers. A snapping temperature of less than 100°C is possible. It is also shown that clamped-clamped (rotational stiffness of infinite) micro bridge does not snap at all, and there is maximum allowable rotational stiffness below which snapping is possible.

Date Published: 2 April 2004
PDF: 8 pages
Proc. SPIE 5276, Device and Process Technologies for MEMS, Microelectronics, and Photonics III, (2 April 2004); doi: 10.1117/12.522893

Published in SPIE Proceedings Vol. 5276:
Device and Process Technologies for MEMS, Microelectronics, and Photonics III
Jung-Chih Chiao; Alex J. Hariz; David N. Jamieson; Giacinta Parish; Vijay K. Varadan, Editor(s)