Electro-mechanical reliability of flexible electronics: an overview of testing and characterization techniques

Dr. Oleksandr Glushko | June 1, 2017 | 10.00 a.m. | V.1.34

Abstract

Fabrication of electronic devices on flexible polymer substrates is a new and constantly growing branch in microelectronics industry. The main advantages of flexible electronics are light-weight and ultra-thin design, possibility of large area roll-to-roll production as well as outstanding mechanical properties such as stretchability or bendability. For realization of these advantages within a final device not only development of novel appropriate materials and fabrication methods but also understanding of reliability issues and failure mechanisms are required.

In this presentation an overview of main mechanical test concepts along with the description of important reliability parameters which can be gained from these tests will be given. The cornerstone of materials testing – the monotonic tensile test – is used to characterize the general structural integrity of a film, to determine the crack onset strain and ductility but also to estimate the film-substrate adhesion. Cyclic tensile (fatigue) test is a well-established method to examine the stability of thin film components when small amounts of mechanical strain are repeatedly applied. Examples of different types of damage which develops with the increasing cycle number as well as the methods for fatigue life estimation will be shown. Finally, bending tests are required to prove the mechanical performance under conditions which closely simulate the real usage conditions of a flexible electronic device. The stability and fracture of different metallization lines during repeated bending will be systematically overviewed.

A special emphasize on the correlation between mechanical damage and the degradation of electrical conductivity will be made throughout the talk. In particular, it will be shown that formation and propagation of cracks in the film does not always lead to the electrical failure. At the end of the talk several suggestions for failure-free design of flexible electronics from the perspective of a mechanical engineer will be given.

Bio

photo_meOleksandr Glushko had received his PhD degree at the Montanuniversität Leoben in the area of photonic metamaterials in 2011. Afterwards he entered the Erich Schmid Institute of Materials Science where he started implementation of coupled electro-mechanical testing methods for reliability characterization of thin conductive films on polymer substrates. Currently he is a project leader at the Erich Schmid Institute investigating different fundamental and applied problems of thin film reliability. The fundamental research areas cover the mechanisms of microplasticity, room-temperature grain coarsening and strain-induced grain boundary migration. The applied scientific areas of interest are the correlation between mechanical damage and electrical degradation of polymer metallization, optimization of microstructure and geometry of conductive lines as well as development of new reliability test concepts for flexible electronics applications.

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