表面卤化降低导电银胶接触电阻的机理研究

Electrically conductive adhesives (ECAs) are a kind of important printed interconnect material in electronic packaging industry. We have first demonstrated that via a proper surface iodination process, the electrical resistivity of the ECA samples can be reduced significantly, and the percolation threshold can be reduced from over 70% to less than 30% by weight of silver filler. Preliminary studies suggested that some nonstoichiometric Ag/AgI nanoislands formed at the surface of the silver microflake fillers. As time passes by, the nanoislands go through an evolution process, which finally results in the Ohmic conductance property at the silver surface. However, the underlying mechanism is still unknown. This proposal is aimed to understand the evolution process and the mechanism of the free electron conductance through using the surface chemistry analytical method and solid state physics method. We are also aimed to understand the influence of the environmental oxygen. Meanwhile, we would investigate and compare the effectiveness of other halogens towards the improvement of electron conductance. Through this study, we are able to obtain better and novel electrical interconnecting materials with lower cost.

导电银胶是电子封装技术领域一种重要的导电印刷连接材料。我们已经首次证明了对市售微米银粉表面进行适当的碘化处理，可提高导电银胶的电导率上千倍甚至更高，且使导电渗流阈值从含银质量70%以上降低到30%以下。为什么金属填料表面发生了轻度碘化反而能大幅度提高导电复合材料的欧姆导电性呢？通过初步研究，我们发现碘处理过的银表面形成独特的非化学计量比的银/碘化银纳米岛状化合物；随着时间推移，这些纳米岛状化合物发生形态和结构演化，最终可在样品表面探测到欧姆导电。然而其欧姆导电的机制仍不清楚。本项目旨在通过表面化学测试方法和固体物理研究手段揭示这一演化过程的和填料间自由电子导电机制，以及氧气对于碘化过程的影响；同时，我们还将比较其他卤素对导电银胶接触电阻的影响。通过本项目的研究，将有利于得到成本更低，导电性能更好的新型导电连接材料。

导电银胶是电子封装技术领域一种重要的导电印刷连接材料。我们已经首次证明了对市售微米银粉表面进行适当的碘化处理，可提高导电银胶的电导率上千倍甚至更高，且使导电渗流阈值从含银质量70%以上降低到30%以下。为什么金属填料表面发生了轻度碘化反而能大幅度提高导电复合材料的欧姆导电性呢？通过初步研究，我们发现碘处理过的银表面形成独特的非化学计量比的银/碘化银纳米岛状化合物；随着时间推移，这些纳米岛状化合物发生形态和结构演化，最终可在样品表面探测到欧姆导电。然而其欧姆导电的机制也不清楚。本项目旨在通过表面化学测试方法和固体物理研究手段揭示这一演化过程的和填料间自由电子导电机制，以及氧气对于碘化过程的影响；同时，我们还将比较其他卤素对导电银胶接触电阻的影响。通过本项目的研究，将有利于得到成本更低，导电性能更好的新型导电连接材料。