Investigation of Mechanical and Electrical Characteristics for Cracked Conductive Particle in Anisotropic Conductive Adhesive (ACA) Assembly
Investigation of Mechanical and Electrical Characteristics for Cracked Conductive Particle in Anisotropic Conductive Adhesive (ACA) Assembly
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DOI：
10.1109/tcapt.2008.916802
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发表时间：
2008-05
影响因子：
--
通讯作者：
B. Xie;Xunqing Shi;H. Ding
中科院分区：
文献类型：
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作者：
B. Xie;Xunqing Shi;H. Ding
在各向异性导电粘合剂（ACA）组件中，通常利用集成电路（IC）的凸块与玻璃基板上的相应导电迹线之间的导电颗粒来实现导电。充分了解ACA颗粒的力学和电学特性有助于优化组装工艺，提高ACA互连的可靠性。ACA组件中使用的大多数导电颗粒在ACA结合之后在颗粒的金属涂层中具有裂纹。在镍包覆聚合物颗粒的数值模型中引入内聚单元进行断裂分析，进一步模拟了ACA键合过程中镍包覆层中裂纹的萌生和扩展。仿真结果表明，含裂纹的镍包颗粒上的应力分布与无裂纹的镍包颗粒上的应力分布有显著差异，表明考虑裂纹的应力分析对ACA互连的可靠性评估具有重要意义。粘结单元的应力分析表明，裂纹起源于镍镀层的中心区域，并向极区扩展。通过引入虚拟电阻这一新参数，建立了描述含裂纹镍包覆颗粒电特性的数学模型。在优化的粘结压力范围内，有裂纹的镍包覆颗粒的颗粒电阻远高于无裂纹的颗粒，表明在颗粒导电分析中也有必要考虑裂纹的影响。因此，考虑裂纹的导电颗粒的断裂分析可以准确地评估ACA互连的可靠性，避免严重的可靠性问题。
In an anisotropic conductive adhesive (ACA) assembly, the electrical conduction is usually achieved with the conductive particles between the bumps of integrated circuit (IC) and corresponding conductive tracks on the glass substrate. Fully understanding of the mechanical and electrical characteristics of ACA particles can help to optimize the assembly process and improve the reliability of ACA interconnection. Most conductive particles used in the ACA assembly are with cracks in the metal coating of the particles after the ACA bonding. This paper introduced the fracture analysis by applying the cohesive elements in the numerical model of the nickel-coated polymer particle and further simulating the cracks initiation and propagation in the nickel coating during the ACA bonding. The simulation results showed that the stress distribution on the nickel-coated particle with cracks was significantly different from that on the nickel-coated particle without crack, indicating that the stress analysis by taking the crack into consideration is very important for the reliability assessment of the ACA interconnection. The stress analysis of cohesive elements indicated that the cracks initiated at the central area of the nickel coating and propagated to the polar area. Furthermore, by the introduction of a new parameter of the virtual resistance, a mathematical model was established to describe the electrical characteristics of the nickel-coated particle with cracks. The particle resistance of the nickel-coated particle with cracks was found to be much higher than that of the particle without crack in the optimized bonding pressure range, indicating that it is necessary to take the crack into consideration for the particle conduction analysis as well. Therefore, the fracture analysis on the conductive particle by taking the crack into consideration could accurately evaluate the reliability of ACA interconnection and avoid serious reliability issues.