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Mechanical and Piezoresistive Properties of Graphite-Filled Polyimide Thin Films

Published online by Cambridge University Press:  15 February 2011

A. Bruno Frazier ,
M. R. Khan  and
Mark G. Allen
A. Bruno Frazier
Affiliation:
Georgia Institute of Technology, School of Electrical Engineering, Atlanta, Georgia 30332-0250
M. R. Khan
Affiliation:
Georgia Institute of Technology, School of Electrical Engineering, Atlanta, Georgia 30332-0250
Mark G. Allen
Affiliation:
Georgia Institute of Technology, School of Electrical Engineering, Atlanta, Georgia 30332-0250
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Abstract

The piezoresistive effect of materials is used as the basis for many types of microsensors. Polyimide, a material widely used in microelectronic fabrication, may be made to exhibit this effect by addition of small graphite particles to form a composite material. Polyimide / graphite based piezoresistive films have the advantage of being spin-castable, plasma-processable, highly chemically resistant, and thermally stable up to 400 °C in nitrogen atmospheres. In this work, piezoresistive polyimide films are formed by addition of various amounts (loadings) of graphite particles one micron in diameter or less to DuPont PI-2555 polyimide. Thin films of these materials are spin-cast on silicon wafers, and an in-situ load-deflection measurement technique is used to evaluate the following film properties: piezoresistive coefficient as a function of both strain and graphite loading; Young's modulus as a function of graphite loading; and residual film stress as a function of graphite loading. The observed piezoresistive coefficient is a strong function of graphite loading, with good piezoresistive properties exhibited in the loading range of 15–25 wt% graphite.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 276: Symposia U/Y – Smart Materials Fabrication and Materials for Micro-Electro-Mechanical Systems , 1992 , 295
Copyright
Copyright © Materials Research Society 1992

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References

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