树枝状银包铜形貌调控及其复合导电胶的导电机理研究

Nowadays, the poisonous tin lead solders are replaced by the electrically conductive adhesives, which is an important trend of development in the electronic packaging field. Dendritic silver-coated copper is one kind of ideal fillers for preparation of the electrically conductive adhesive. It is of great importance to explore low cost and structure controllable dendritic silver-coated copper for high-performance conductive adhesives. It is very promising to use the synthetic dendritic silver-coated copper as the conductive fillers to prepare new type electrically conductive adhesive from both the side view of fundamental research and practical applications. In this project, we propose to achieve the controllable synthesis of the dendritic copper by chemical reduction method. Then, the dendritic copper coated with silver by chemical plating. Therefore, the high-performance dendritic silver-coated copper with unique structure is obtained. On this basis, the influences of dendritic silver-coated copper on electrical, mechanic and thermal properties of conductive adhesives are investigated. Meanwhile, the percolation and sintering behaviors are also investigated. According to percolation theory, conductive network is constructed. This project will shed light on the preparation process and conductive mechanism of the dendritic silver-coated copper conductive adhesives, and will also explore a new approach for the preparation of high-performance and low cost electrically conductive adhesives.

目前，在电子封装领域，导电胶替代有毒锡铅焊料是一种重要的发展趋势。树枝状银包铜粉是制备导电胶的理想填料之一。探索并制备高性能、低成本树枝状银包铜材料是发展导电胶的重要环节。因此，以合成的树枝状银包铜粉为导电填料，制备新型聚合物基导电胶具有重要的基础研究价值和实际应用前景。本项目拟采用化学还原法实现树枝状铜的可控合成，并通过化学镀法实现银对树枝状铜的包覆，从而获得结构独特、性能优良的树枝状银包铜粉。在此基础上，探索树枝状银包铜对导电胶的电学、力学及热学性能的影响机理，并研究树枝状银包铜在导电胶中的渗流及烧结行为，通过渗流理论，构建导电网络。该项目的研究对深入认识树枝状银包铜导电胶的制备过程及导电机理具有重要意义，并将为高性能、低成本导电胶的制备开辟一条新途径。

目前，导电胶在电子封装领域替代有毒锡铅焊料是一种重要的发展趋势。三维树枝状银包铜粉、多维度银、不同分级纳米分支结构树枝状银是制备导电胶的理想填料。探索并制备高性能多形貌导电填料是发展导电胶的重要环节。因此，以合成的三维树枝状银包铜、多维度银和不同分级纳米分支结构树枝状银为导电填料，制备新型聚合物基导电胶具有重要的基础研究价值和实际应用前景。本项目采用化学还原法实现树枝状铜的可控合成，并通过化学镀法实现银对树枝状铜的包覆，从而获得结构独特、性能优良的树枝状银包铜粉。与此同时，我们又利用不同的化学法制备了多维度的银和不同分级结构树枝状银作为复合导电胶的导电填料。在此基础上，探索合成的导电填料对其复合导电胶的电学、力学及热学性能的影响机理，并研究其在导电胶中的渗流行为，通过渗流理论，构建导电网络，探索导电机理。我们制备的树枝状银包铜复合导电胶的渗流阈值低至25 wt%，其复合导电胶的电阻率低至1.2×10-4 Ω cm（60 wt%），完全可以满足当前市场需求。更为重要的是，我们制备的多维度银和不同纳米分支结构树枝状银复合导电胶的渗流阈值低至10 wt%，其电阻率最低可以达到4.06×10-5 Ω cm。这一电阻率数值已经远远低于之前报道的导电胶电阻率值，证明我们制备的多维度银复合导电胶具有一个非常优异的导电性能。该项目的研究对深入认识树枝状银包铜、多维度银和不同纳米分支结构树枝状银复合导电胶的制备过程及导电机理具有重要意义，并将为低成本、高性能复合导电胶的制备开辟一条新途径。