Capability of high-speed and low-cost manufacturing makes the printing techniques a very promising approach for large-area flexible electronics mass manufacturing. Due to fast and intensive technology development, the lack of knowledge about the reliability and lifetime of printed electronics is obvious, requiring further investigation. Especially, the effect of torsional bending on lifetime is a mostly unexplored field of reliability testing. In this article, a torsional bending test of parallel printed silver conductors (0.3-, 0.5-mm pitch) on polymer substrate (polyethylene terephthalate, 125- $\mu \text{m}$ thickness) was conducted and analyzed. According to the experimental results, torsional bending causes wear-out type failures in conductors and the length-to-width (LTW) ratio of the sample’s substrate was observed to have a significant impact on reliability. If the LTW ratio is smaller than 3, the lifetime of printed conductor seems to collapse and samples lasted for approximately only 17 bending cycles on average. Lifetime was improved by increasing the LTW ratio and samples withstood over hundreds of cycles with LTW ratio of higher than 15. However, the distance of a conductor from the edge of the substrate was not observed to have any significant influence on the reliability under torsional bending.

中文翻译：

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扭转弯曲对印刷银导体可靠性和寿命的影响

高速和低成本制造的能力使印刷技术成为大面积柔性电子大规模制造的一种非常有前途的方法。由于快速和密集的技术发展，显然缺乏对印刷电子产品的可靠性和寿命的了解，需要进一步研究。特别是，扭转弯曲对寿命的影响是可靠性测试的一个尚未探索的领域。在本文中，对聚合物基板（聚对苯二甲酸乙二醇酯，125-$\mu\text{m}$ 厚度）上的平行印刷银导体（0.3-、0.5-mm 间距）进行了扭转弯曲试验并进行了分析。根据实验结果，扭转弯曲会导致导体出现磨损型故障，并且观察到样品基板的长宽比 (LTW) 对可靠性有显着影响。如果 LTW 比小于 3，印刷导体的寿命似乎会缩短，并且样品平均仅持续大约 17 个弯曲循环。通过增加 LTW 比提高了寿命，并且样品经受住了数百次循环，LTW 比高于 15。然而，没有观察到导体与基板边缘的距离对扭转弯曲下的可靠性有任何显着影响.