Design and understanding of anisotropic conductive films (ACFs) for LCD packaging
Design and understanding of anisotropic conductive films (ACFs) for LCD packaging
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DOI：
10.1109/pep.1997.656495
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发表时间：
1997-10
期刊：
影响因子：
--
通讯作者：
M. Yim;K. Paik
中科院分区：
文献类型：
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作者：
M. Yim;K. Paik
各向异性导电膜（ACF）由粘合剂树脂和精细导电填料（例如金属颗粒或金属涂覆的聚合物球）组成，是用于精细间距膜上芯片（COF）和玻璃上芯片（COG）LCD封装的关键材料。为了理解和设计更好的ACF材料，模拟和实验证明了具有物理接触机制的导电模型。为了了解接触面积的变化，开发了两种压力相关模型-（1）弹性/塑性变形和（2）有限元模型-并通过测试各种ACF进行了验证。实验变量，如键合压力，和数量，尺寸，机械和电气性能的Ni粉和Au涂覆的聚合物导电颗粒被施加。模型与实验结果吻合良好，除了在较高的键合压力。在一般情况下，随着键合压力的增加，接触电阻急剧下降，然后是一个恒定的值后，观察到达到临界键合压力。然而，过大的键合压力反而增加了ACF连接电阻。如果添加更多的导电颗粒，则连接电阻迅速降低至恒定。这是两个相反因素的反作用：通过减少每个颗粒的接触面积来增加电阻，以及通过增加导电路径数量来降低电阻。此外，接触电阻和粘接强度的环境影响，如热老化，温度/湿度老化和温度循环也进行了研究。总体而言，通过了解ACF的导电机理，可以更好地设计ACF材料。
Anisotropic conductive films (ACF) composed of an adhesive resin and fine conductive fillers such as metallic particles or metal-coated polymer balls are key materials for fine pitch chip-on-film (COF) and chip-on-glass (COG) LCD packaging. To understand and design better quality ACF materials, a conduction model with a physical contact mechanism was simulated and experimentally proved. To understand the contact area changes, two pressure dependent models - (1) elastic/plastic deformation and (2) FEM - were developed and proved by testing various ACFs. Experimental variables such as bonding pressure, and the number, size, mechanical and electrical properties of Ni powders and Au-coated polymer conductive particles were applied. The models agreed well with experimental results, except at higher bonding pressures. In general, as bonding pressure increases, sharp decrease in contact resistance followed by a constant value is observed after reaching a critical bonding pressure. However, excessive bonding pressure inversely increased the ACF connection resistance. If more conductive particles were added, the connection resistance rapidly decreased to a constant. This is the counter-effect of two opposing factors: resistance increase by decrease in contact area per particle and resistance decrease by increased conduction path numbers. Also, environmental effects on contact resistance and adhesion strength such as thermal aging, temperature/humidity aging and temperature cycling were also investigated. As a whole, better design of ACF materials can be achieved by understanding the ACF conduction mechanism.