Piezoresistive graphite/polyimide thin films for micromachining applications

Abstract

In this work, graphite/polyimide composite thin films are introduced and characterized for micromachining applications. The material consists of submicron-sized graphite particles suspended in a benzophenone tetracarboxylic dianhydride–oxydianiline/metaphenylene diamine polyimide matrix. The resultant material represents a low cost, plasma-definable polyimide material which has been found to have a large piezoresistive coefficient over a range of graphite loadings. Selected film properties: Young’s modulus, residual stress, and piezoresistivity are investigated for a graphite loading range of 15%–25% by weight using a slightly modified in situ load/deflection technique. Results of mechanical property characterization show that the residual stress is independent of graphite loading and the Young’s modulus increases with increasing graphite loading. The maximum piezoresistive coefficient (gage factor) is 16.8 and occurs at a graphite loading of 18%.