| As thin-film elements and devices are widely applied to kinds of engineering systems, investigation of thin film buckling is important to optimize the design and to improve the life and reliability of MEMS devices.A lot of achievements has been made in the study of thin film buckling under static load in theories and experiments, however, when actually used thin film devices with film-substrate structures mostly work under dynamic loading circumstance, theories of buckling under static load show the limitation when there is dynamic load working. With the increase of case that thin film devices are used under repetitive dynamic load and fatigue load, film-substrate structures'fatigue life become an important index to be concerned, it is particularly important to study the thin film bucking under fatigue load.In this paper, an experiment focus on thin film buckling under fatigue load has been completed and the straight-side buckling propagation process is investigated by using an optical microscope. A fatigue-loading device based on piezoelectric ceramic which also integrate the force-displacement measure module, has been designed to offer the fatigue loading and load the metal films deposited on PMMA substrate. The loading cycles is controlled to about 10 5～10 6. The cumulative buckling and propagation process of thin films are recorded and investigated by a CCD camera. By using a digital image correlation measurement, thin film buckling propagation rate da/dN are calculated by comparison of different images. By several groups of controlled trials, we analysis the relationship between parameters such as the film thickness, cycle times,film's material and the buckling. This work shows some preliminary research deal with thin film buckling propagation under fatigue load, with more and better experiment the study for thin film fatigue buckling may go further. |
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