自修复型导电胶的制备和自修复效率表征研究

Conductive adhesives have been widely used as a replacement for Sn-Pb solder in electrics packaging industries for many years. However, low conductivity and poor reliability have become the most important factors to restrict the development of conductive adhesives. In this project, we will try to solve these two shortages existed in actual applications by using a special method. On the one hand, one-dimensional silver nanowires are used as conductive filler in conductive adhesives which were prepared by redox method. The special fiber morphology will make these fillers more easy to contact each other to form a conductive network in resin,it will clearly improve the conductivity of the adhesive. On the other hand,microsized Polystyrene(PS)-Ag nanowires/Dimethylbenzylamine(DMBA)/Polythiol core-shell capsules were prepared by an emulsion polymerization method. A novel kind of self-healing conductive adhesive was developed by using these microcapsules as healing agents. When microcracks produced by outside force reached to these healing agents, the shell layer would be destroyed automatically and the healing agents in the core would release and react with access epoxy groups in resin substrates immediately, a new network would be formed again in bulk conductive adhesive, which has a healing effect for mechanical strength of conductive adhesive. Detail studies on self-healing mechanism, healing efficiency on conductivity and mechanical properties as well as the healing process of such self-healing system will be excuted. These researches will provide a theoretical guidance for preparations and applications of self-healing conductive adhesives as well as other self-healing composites.

导电胶已经作为Sn-Pb焊料的替代品在微电子封装行业沿用多年。目前电导率偏低以及可靠性差成为制约导电胶的重要因素。本项目研究从目前导电胶中存在的主要问题出发，一方面通过采用自制的一维银纳米线作为导电胶的导电填料，发挥一维纳米线的纤维状结构优势，使得填料在树脂基体中更容易形成导电网络来提高导电胶的电导率。另一方面采用乳液聚合法制备了壳为聚苯乙烯，核为分散有银纳米棒的聚硫醇与二甲基苯胺（DMBA）的混合物的核壳结构纳米粒子，利用这些纳米核壳结构粒子在外界作用力下，自动破裂，聚硫醇与DMBA的混合物与胶体中过量的环氧基团快速反应，自动快速修复受外力破坏产生的胶体微裂纹来提高导电胶的可靠性。通过系统研究自修复型导电胶的自修复体系对导电胶的电学及力学修复效率，修复机理以及修复过程动力学，用以指导自修复型导电胶的制备及产业化，同时为其他自修复复合材料的制备及应用提供可靠的理论依据。

锡铅焊料作为电子元器件的主要连接材料，其焊接温度高、对环境危害大，无法满足节距很小的工作环境等缺点，近年来逐渐显现出来。导电胶作为Sn-Pb电子封装材料的替代品，使用越来越广泛。随着导电胶在微电子封装行业中的广泛使用，其使用寿命及安全性，稳定性逐渐成为研究者们关注的焦点，采用导电胶粘结的微电子器件在受到外部冲击力的情况下，在导电胶的内部会产生微裂纹，而裂纹的扩展又会造成胶体的整体失效，如力学性能、电学性能产生突变，从而带来安全隐患问题。微胶囊自修复技术是今年来发展起来应用于复合材料内部裂纹修复的一种手段。其主要机理就是通过在复合材料制备过程中将微胶囊埋入复合材料中实现的，当材料在使用过程中产生微裂纹后，裂纹的扩展撕裂预埋入的胶囊，释放出胶囊核中的自修复剂，自修复剂在裂纹表面与促进剂发生聚合反应，粘结裂纹阻止裂纹进一步扩展而实现自修复。本项目针对导电胶及导电油墨在使用过程中经常发生的力学失效问题进行深入研究，研究了失效的机理，失效的表征以及失效部位的修复。研究中发现采用包覆型核壳微胶囊粒子填充的导电胶或是导电油墨具有很高的修复效率，修复后的电学力学强度达到未修复前的80%甚至更高。结合导电胶及导电油墨的电导率与失效裂纹之间的特殊及敏感的关系，采用了一种结合电导率表征的全新表征方法来实时高效地对微胶囊的修复效率进行表征，并取得了很好的效果。这一表征技术同样也适合于其他的微胶囊修复体系，可以为同行或是工业生产厂家提供参考。