Abstract
This paper presents strain measurements using digital image correlation of common microelectronic metal nanofilms deposited onto a polymer substrate (SU-8), which has applications in flexible electronics and nano/microsystems reliability analysis. The novel experimental method is based on digital image correlation coupled with microtensile test apparatus for the in situ investigation of the deformation behaviour of the deposited thin films under uniaxial tensile loading. One of the key features of the method is the real-time two-dimensional strain field measurements on a bare thin film surface, during the deformation process, without any initial speckle or grid deposition. The outstanding performances of the method, having a spatial resolution of 0.7 µm, allow one to envisage further studies related to the understanding of the mechanical behaviour of such thin films and, in particular, the damage localization process.
Highlights
It is becoming clear that flexible electronics [1,2,3] will have a major impact in applications ranging from flexible screens and touch pads to nano/microelectromechanical systems such as strain gauges
Using a mesh size of 32 pixels, as the subdivision of the digital images (ZOI, see figure 2), performances of the displacement and strain field calculation in terms of accuracy and resolution were evaluated for the Au and Pt thin films
In subset-based digital image correlation (DIC), the users must manually select a subset (ZOI) size varying from several pixels to even more than 100 pixels
Summary
It is becoming clear that flexible electronics [1,2,3] will have a major impact in applications ranging from flexible screens and touch pads to nano/microelectromechanical systems such as strain gauges. Such systems, despite the possibility of hybrid manufacturing technologies, will still require conductive thin interconnections for devices that will be subjected to large mechanical strains (up to several tens of percent). Plastic deformation mechanisms (for bulk metals) are well understood and are known to be predominant due to the motion of lattice dislocations (glide). Size effects are important in terms of materials’ physical properties, e.g., giant piezoresistance [12, 13]
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