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Channel cracks in a hermetic coating consisting of organic and inorganic layers

Nicolas Cordero's picture

Abstract: Flexible electronic devices often require hermetic coatings that can withstand applied strains. This paper calculates the critical strains for various configurations of channel cracks in a coating consisting of organic and inorganic layers. We show that the coating can sustain the largest strain when the organic layer is of some intermediate thicknesses.

Flexible electronics are promising for diverse applications, such as rollable displays, conformal sensors, and printable solar cells. These systems are thin, rugged, and lightweight. They can be manufactured at low costs, for example, by roll-to-roll printing. The development of flexible electronics has raised many issues concerning the mechanical behavior of materials. This paper examines a particular issue: channel cracks in hermetic coatings.

Electronic devices (e.g., organic light-emitting devices, OLEDs) often degrade when exposed to air. Developing hermetic coatings has been a significant challenge. Organic films are permeable to gases, and inorganic films inevitably contain processing flaws, so that neither by themselves are effective gas barriers. These considerations have led to the development of multilayer coatings consisting of alternating organic and inorganic films. To be used in flexible electronics, these coatings must also withstand applied strains without forming channel cracks...

Nicolas Cordero, Juil Yoon and Zhigang Suo, Channel cracks in a hermetic coating consisting of organic and inorganic layers.  Applied Physics Letters 90, 111910 (2007).  



Jie-Hua Zhao's picture

The design window presented in Figure 5 of this paper is particularly helpful to the engineers. Zhigang and his group have been paying a lot of attention to explanation of the phenomena observed in industry, such as metal ratcheting in Al interconnects, electromigration failure, and providing simple solutions. This is another good example.

For practical purpose, if the function forms of fa, fb, fc and fd calculated by ABAQUS can be expressed as some kind of approximation, say polynomials, it will be more helpful to industry practitioners.


Juil Yoon's picture

Jie-Hua, thank you very much for your comment.

The comments from industry guys, like you, give me confidence and motivation to do more things. I know the industry people want simple solutions. Sure, we can approximate this function fa,fb,fc and fb. But we need more calculations for us to convince and may need to experimental data to compare.

Anyway, we'll keep going and hopefully want to report soon.

Thank you.

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