A novel approach to modeling the transfer functions of four-terminal-transducer pressure sensors within a single simulation tool

Anisotropic electrical conductivity is rarely encountered in materials of t echnological importance. Not surprisingly, the simulation tools required fo r the modeling of anisotropic conduction phenomena (such as those observed in piezoresistive transducers) are less than sophisticated. Finite Element Analysis (FEA) software packages are often limited to dement types that pos sess orthotropic conductivity properties. We have developed a general metho d for the FEA of anisotropic conductivity materials that is based on the di agonalization of the conductivity matrix using main axis transformation. Th e new method was successfully applied to simulate piezoresistive pressure s ensors with Four-Terminal-Transducers (FTTs) within a single simulation too l. The principal advantages of the new method are the fact that it does not require the user to make simplifying assumptions concerning the boundary c onditions, and that it does not neglect parts of the mechanical stress tens ors. In this paper, simulation results obtained using our new method are co mpared against simulation data from other authors and with the experimental data obtained from Motorola series MPX10 pressure sensors. Diagonalization was found to be a powerful tool for solving problems related to anisotropi c conductivity in Finite Element simulation tools. (C) 2000 Elsevier Scienc e S.A. All rights reserved.