Carbon nanotube (CNT) filled adhesives for microelectronic packaging

M. Wirts-Rutters, M. Heimann, J. Kolbe, K. Wolter
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引用次数: 8

Abstract

This project evaluated the use of carbon nanotubes as a filler in electrically conducting adhesives in order to enhance the electrical, mechanical and thermal performance. As the carbon nanotubes caused a marked increase in the viscosity of the adhesive, a low viscosity polymer matrix (< 100 mPas) was chosen. This allowed a high CNT content. Multi-wall carbon nanotubes (MWNTs) were chosen for the experiments because these are available in favorable quantities and at reasonable prices. In order to enhance the dispersion properties, the MWNTs were also treated chemically via ozone/UV and low pressure plasma. For mixing the MWNTs into the polymer matrix different methodologies were tested. Ultrasound was found to be a very effective method, but the dispersion energy drops dramatically when viscosities above 10,000 mPas are reached. Hence high viscosity adhesives were treated using a calander as described in [1]. In general, good dispersion could be achieved by applying combinations of these two dispersion techniques. Adhesives were produced with varying CNT content, different CNT types and using different dispersion techniques. The influence of these parameters on the electrical resistance, thermal conductivity, impedance behavior and mechanical strength was investigated. In parallel, many samples were analyzed by TEM in order to get detailed knowledge of the adhesive nanostructure and learn how this structure is influenced by the above- mentioned parameters. Furthermore, the absorption of microwave radiation by the samples was investigated in order to further our understanding of microwave absorption by CNT-filled composites. Based on these results, the two standard formulations showing the best performance were chosen for bonding SMD components on a test assembly. For the curing of the adhesives two methods were used: Curing by microwave radiation and curing in a conventional oven at 130degC. Whilst the conventional curing took 30 minutes, it was possible to completely cure the adhesives using microwave radiation in only 3 minutes. Finally, the bonded assemblies were subjected to a system integrity test. The mechanical stability of the adhesive bonds showed very high resistance to ageing after exposure to humidity and after 1000 thermal cycles.
微电子封装用碳纳米管填充胶黏剂
本项目评估了碳纳米管作为导电胶粘剂填料的使用,以提高导电胶粘剂的电气、机械和热性能。由于碳纳米管导致黏合剂的粘度明显增加,因此选择了低粘度聚合物基质(< 100 mPas)。这使得碳纳米管含量高。之所以选择多壁碳纳米管(MWNTs)进行实验,是因为这些材料的数量和价格都很合理。为了提高MWNTs的分散性能,还对其进行了臭氧/紫外和低压等离子体的化学处理。为了将纳米碳管混合到聚合物基体中,测试了不同的方法。超声波是一种非常有效的方法,但当粘度超过10,000 mpa时,色散能量急剧下降。因此,采用[1]中所述的压延机处理高粘度粘合剂。一般来说,通过结合应用这两种色散技术可以获得良好的色散。用不同碳纳米管含量、不同碳纳米管类型和不同分散技术生产胶粘剂。研究了这些参数对电阻、导热系数、阻抗性能和机械强度的影响。同时,利用透射电镜对许多样品进行了分析,以详细了解胶粘剂的纳米结构,并了解上述参数对该结构的影响。此外,为了进一步了解碳纳米管填充复合材料对微波的吸收,研究了样品对微波辐射的吸收。基于这些结果,选择了两种表现出最佳性能的标准配方,用于在测试组装上粘合SMD组件。胶粘剂的固化采用两种方法:微波辐射固化和130℃常规烘箱固化。传统的固化需要30分钟,而使用微波辐射在3分钟内就可以完全固化粘合剂。最后,对粘接组件进行了系统完整性测试。在暴露于湿度和1000次热循环后,粘合剂的机械稳定性表现出非常高的耐老化性。
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