On the determination of Young's modulus of film by nanoindentation

With the development of miniaturization of electronic chips and their packaging structures, electronic devices are becoming highly integrated. The thickness or area of packaging materials required for device packaging structures is significantly reduced, so that the properties of those small-sized packaging materials cannot be measured using the conventional testing methods. However, for the measurement of Young's modulus of thin film by nanoindentation technology, with the increase of indentation depth, the elastic-plastic deformation of the film and the substrate will change constantly. Therefore, the mechanical property evaluation of the composite is a complex function of the film and substrate's mechanical properties. Based on finite element simulations, the influence of Young's modulus of film and substrate on the mechanical properties of composite materials is studied. The accuracy of Young's modulus calculation of film is verified and summarized by four different weight functions which are used to simulate a variety of film/substrate combinations. At the same time, for the cases with Young's modulus of the film larger or smaller than that of the substrate, the stress distribution and indentation morphology of the film/substrate composite are also discussed. Generally, the substrate modulus is taken as a known parameter in the fitting process. The weight function is applied to a variety of real composite materials to verify the effectiveness of the conclusions drawn by unknow materials.