Experimental Study on Mechanical Reliability of Flexible Silver Wire Based on Extrusion Bending
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摘要: 柔性电子产品在使用过程中不可避免地会受到拉伸、弯曲等多种形式的复杂变形，在长时间工作中疲劳成为产品失效的重要模式之一。针对柔性电子导线可靠性问题，通过原位疲劳测试平台对导线弯曲疲劳损伤行为进行研究。在弯曲测试过程中，通过理论分析定量确定薄膜最小曲率半径与挤压位移的关系，并利用有限元仿真及实验验证了推论的正确性，然后对试样分别进行单次和疲劳弯曲试验研究。结果表明，墨水浓度越低，制备出的银薄膜孔隙率越高，初始电阻越大，同时孔隙作为缺陷使薄膜抗弯曲性能变差，但是增大的孔隙率能够有效地抑制薄膜疲劳损伤演化，使其弯曲疲劳稳定性提高。Abstract: Under stretching, bending and many other mechanical loading forms, flexible electronics products would inevitably be subjected to complex deformation during working, and fatigue has become one of the most important failure modes during long-time working. In order to solve the reliability problem of flexible electronics, an in-situ fatigue testing platform is developed to study bending fatigue damage behavior of flexible electronic. In the process of bending, the relationship between the minimum radius of curvature and extrusion displacement is determined quantitatively by theoretical analysis, the correctness of the conclusion is verified by finite element simulation and experimental data, and the single and fatigue bending experiments are carried out on the samples of flexible electronics. The experimental results show that the lower concentration of silver nanoparticle ink results in silver film with higher porosity and initial electrical resistance. At the same time, the porosity as a defect makes the bending resistance worse. However, the free surface increases as the pore increases, making the vacancies formed during the deformation more easily annihilated. As a result, the fatigue damage evolution of silver thin films is effectively inhibited, which makes the bending fatigue stability higher.
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Key words:
- flexible electronics /
- radius of curvature /
- testing machine /
- bending fatigue /
- porosity
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图 2 理想压杆大变形示意图
Figure 2. Large deformation of the ideal pressure bar schematic diagram
图 3 试样曲率半径与轴向位移关系
Figure 3. Relationship between radius of curvature and axial displacement of the sample
图 4 挤压位移为25 mm时的ABAQUS仿真结果
Figure 4. ABAQUS Simulation result of extrusion displacement of 25 mm
图 8 试样扫描电镜表面形貌
Figure 8. SEM observations of the surface morphology of prepared samples
图 9 不同质量分数墨水制备样品与初始电阻之间关系
Figure 9. Relationship between prepared samples of different mass fractions of ink and initial electrical resistance
图 10 电阻变化率与单次弯曲关系
Figure 10. Relationship between change rate of the electrical resistance and single bending
图 11 电阻变化率与弯曲疲劳循环次数关系
Figure 11. Relationship between change rate of the electrical resistance and the number of bending fatigue cycles
图 12 弯曲疲劳循环后薄膜断裂裂纹形貌
Figure 12. Morphology of the fracture crack of thin film after bending fatigue cycles
表 1 轴向位移、转角、曲率半径的对应关系
Table 1. Corresponding relationships of axial displacement, angle and radius of curvature
x/mm α/（°） ρ/mm 0 0 ∞ 3 26.96 18.52 6 38.30 12.97 9 47.20 10.47 12 54.82 8.97 15 61.68 7.92 18 68.00 7.14 21 73.95 6.53 24 79.58 6.02 27 85.00 5.60 30 90.24 5.23 33 95.33 4.91 36 100.33 4.62 39 105.27 4.36 42 110.07 4.12 45 114.87 3.90 
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