An estimation method on failure stress of micro thickness Cu film-substrate structure

Abstract

The failure of thin film-substrate structure occurs mainly at the thin film or the interface. However, the characterizing and estimating methods of failure stress in thin film are neither uniform nor effective because there are some complex effects of such as size, interface and stress state on the failure behavior of thin film-substrate structure. Based on the scanning electron microscope (SEM) in-situ investigation on the failure models of the Cu thin film-substrate structure and the nano scratched testing results, the failure stresses in different thicknesses of the Cu film-substrate were characterized, which were compared and confirmed by other methods, such as Stoney formula and other empiric equations. These results indicate that the novel estimating method of failure stress in thin film based on the critical wavelength of surface unstable analysis is better than other methods. The main reason is that the novel estimating method of failure stress in meso thickness film fully considered the effect factors of free surface unstable behavior and elastic anisotropy of thin film. Therefore, the novel estimating method of failure stress assists people to understand the critical interfacial strength and to set up the failure criterion of thin film-substrate structure.film-substrate structure, failure stress, interfacial strength, in-situ observation, nano scratch test

Investigations on the Mechanical Properties of Conducting Polymer Coating-Substrate Structures and Their Influencing Factors

“…In addition, Asaro [ 109 ] and Wang et al . [ 39 ] independently reported how to estimate failure stress in thin films. For example, it is shown that when the free surface of thin film is unstable or thin enough the following relationship exists: where the subscript c denotes the critical mean.…”

“…Wang et al . [ 25 , 35 , 39 , 78 , 92 , 93 ] used an electronic speckle pattern interferometry (ESPI) technology [ 94 , 95 ] and the digital image correlation (DIC) method [ 96 , 97 ], respectively, for measuring the deformation of highly flexible specimens of conducting polymer. Figure 7 shows a typical electronic speckle pattern interferometry system for measuring the in-plane displacement of a free surface by electronic speckle pattern interferometry (ESPI) technology.…”

“…[ 24 , 25 , 34 ] were concerned with the effects of thickness and microstructure on the mechanical properties of conducting polythiophene films, with special emphasis on failure behavior. In addition, they also demonstrated that the failure behaviors of film/coating-substrates under bending loadings or under thermal-mechanical loadings were dependent on complex factors, such as plane stress state or strain state, thickness of the layer of film and interface adhesion strength, which were in turn dependent on the synthesis processing technology used [ 35 – 39 ]. Baumert et al .…”

Evaluation of the critical stress of anodized coating-AZ91D substrate using SEM in-situ technology

“…In this study, the flexural stress was estimated using Eq. (7) from Wang et al (2009) and Eq. (8) from Yan and White (1999).…”

“…On the other hand, there are difficulties in mesh refinement using the FE method (Hutchinson and Suo, 1991;Fawcett, 1998;Yan and White, 1999;Michler and Blank, 2001;Zhao et al, 2002;Schwaiger and Kraft, 2003;Yang et al, 2014;Dean et al, 2015). Therefore, to investigate failure issues of thin coating layers/substrates, experimental study is the best and directly approach (Wang and Xu, 2003;2004;2009;Li et al, 2008a;2008b;Dean et al, 2015). In addition, it is necessary to estimate the delivery criterion of stress close to the interface of thin anodized coatings and thick substrates using SEM in-situ technology Wang and Fan, 2006;Jia et al, 2012;Ren et al, 2013;Ren and Wang, 2014).…”