Interfacial delamination and delamination mechanism maps for 3D printed flexible electrical interconnects
Interfacial delamination and delamination mechanism maps for 3D printed flexible electrical interconnects
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DOI：
10.1016/j.eml.2021.101199
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发表时间：
2021-02-15
影响因子：
4.7
通讯作者：
Panat, Rahul
中科院分区：
文献类型：
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作者：
Brenneman, Jacob;Tansel, Derya Z.;Panat, Rahul
柔性电子系统集成了陶瓷、金属和弹性体等异质材料，导致界面在应力作用下容易分层。在这项研究中，我们证明了在直接印刷在聚二甲基硅氧烷衬底上的基于聚酰亚胺的柔性互连系统中可以引发分层，其中金属互连作为裂纹的起始点。对这一问题进行了实验和分析评估，以确定控制参数并提出防止分层的途径。分层的驱动力是聚合物中吸附的水分的蒸汽压。根据我们系统中裂纹的尺寸(20-60微米)和分层聚合物薄膜的厚度(2-6微米)，利用非线性von-Karman板理论来描述聚合物薄膜中的薄膜拉伸和薄板弯曲行为。该模型给出了将能量释放率与柔性互连/电路的几何尺寸联系起来的“分层机制图”。对于聚合物薄膜，出现了“蒸汽匮乏”状态，水分不足降低了分层的驱动力。对于较厚的薄膜，由于聚合物层的刚性增加，可以观察到更高的抗断裂性能，这是因为聚合物层起到了‘板’而不是‘膜’的作用。然而，在这些条件下，较厚薄膜中较高的滞留水分维持了能够达到临界能量释放率的断裂驱动力。机制图还揭示了金属导体的宽度(即初始裂纹尺寸)是控制断裂的重要因素。例如，当导体宽度从50微米减小到30微米时，当聚合物膜厚度为6微米时，断裂能量释放率从20.5降到4.6J/m(2)，这些预测与我们的实验观察结果是合理一致的。建立了有限元模型，并用来进一步验证分析模型。本文的工作为提高柔性电子系统的可靠性提供了非常重要和实用的设计指南。(C)2021年提交人。由爱思唯尔有限公司出版。这是CC BY-NC-ND许可证(http://creativecommons.org/licenses/by-nc-nd/4.0/).下的一篇开放获取文章
Flexible electronic systems integrate heterogeneous materials such as ceramics, metals, and elastomers, which results in interfaces prone to delamination under stress. In this research, we show that delamination can be initiated in a polyimide-based flexible interconnect system directly printed on a polydimethylsiloxane substrate where the metallic interconnect acts as the crack initiation site. This problem is experimentally and analytically evaluated to identify the controlling parameters and propose pathways to prevent delamination. The driving force for delamination is shown to be the vapor pressure of the absorbed moisture in the polymer. Based on the dimensions of the cracks in our system (20-60 mu m) and the thickness of the delaminated polymer films (2-6 mu m), nonlinear von-Karman plate theory is utilized to capture both membrane stretching and thin plate bending behavior in the polymer films. The model yields `delamination mechanism maps' that relate the energy release rate to the geometric dimensions of the flexible interconnects/circuits. For thin polymer films, a 'vapor starved' regime is shown where insufficient moisture reduces the driving force for delamination. For thicker films, a higher resistance to fracture is observed due to an increased rigidity of the polymer layer which behaves as a 'plate' rather than a 'membrane'. Under these conditions, however, the higher retained moisture in the thicker films sustains the driving force for fracture capable of reaching the critical energy release rate. The mechanism maps also reveal the width of the metallic conductor (i.e., the initial crack size) as an important factor controlling fracture. For example, it is shown that the energy release rate for fracture is reduced from 20.5 to 4.6 J/m(2) when the conductor width is reduced from 50 mu m to 30 mu m for a polymer film thickness of 6 mu m. These predictions are shown to be in reasonable agreement with our experimental observations. A finite element model is also developed and used to further validate the analytical model. The work presented in this paper provides highly important and practical design guidelines for improved reliability of flexible electronic systems. (c) 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).