纳米活化表面与纳米金属材料连接尺度兼容性及其连接机理

A new method was introduced to prepare a novel nano-activated surface film with nano-metal array on the traditional pad in order to increase the dimensional compatibility with the nano-metal materials during the interconnection process. The joining mechanism between the nano-array film and the nano-metal jointing material was analyzed. The Ni/Au nano-array on the metal film surface was fabricated by direct electrodeposition method, which can achieve the dimensional compatibility between the traditional pad surface and the nano-metal jointing materials. The efficient and reliable interconnection between the nano-array and the nano-metal jointing materials can be fulfilled at low temperature, and the working temperature can be much higher. This interconnection can provide a potential novel interconnection method in the high density and high temperature packaging. Therefore, the addition agent effects on the array nanoscale can be characterized by model analysis. The Au self-catalysis replacement reaction on different nano-array structure should be studied. The method and mechanism in the specific surface energy control on nano-activated surface could be confirmed. The basic scientific problems about the interconnection mechanism between the nano-activated surface and the nano-metal jointing materials should be settled, the competitive relation between nano-metal particle self-coalescent and the joint of nano-array and the nano-metal jointing material can be discussed. The high temperature performances of the joints between the nano-array and the nano-metal jointing materials ought to be observed. The surface nano-array dimensional compatibility with the nano-metal jointing materials should be determined. The joint between the nano-activated surface and the nano-metal jointing materials can decrease the jointing temperature and increase the jointing efficiency.

提出通过制备新型表面活化纳米金属阵列薄膜，实现传统焊盘与纳米金属材料连接尺寸兼容性，并分析纳米阵列与纳米金属连接材料的连接原理。在传统焊盘表面通过直接电沉积的方法制备Ni/Au纳米阵列，实现传统焊盘表面与纳米金属连接材料的尺度兼容，得到高效可靠的低温连接/高温服役的新方法，为高密度高温封装制造提供新的互连技术。为此，对添加剂影响纳米阵列微观尺度进行模型分析，研究纳米结构对自催化置换金反应的影响机制，确定调控纳米活化表面比表面能的方法和机理；研究纳米活化表面与纳米金属连接材料连接过程的基本科学问题，分析连接过程中纳米金属颗粒自融合与纳米阵列与纳米金属连接材料连接的竞争关系；研究纳米阵列与纳米金属连接材料形成接头的高温服役性能，确定纳米阵列对纳米金属连接材料的尺度兼容性，达到降低连接温度，提高连接速度的目的。

纳米连接材料以其低温烧结后获得高导电率、高导热率以及良好耐高温性能的接头而在功率封装、高温封装领域受到极大关注。纳米连接材料在与基板或芯片实际连接时，纳米连接材料与基板的烧结速率比纳米连接材料之间的自烧结速率慢几个数量级，因此纳米银颗粒率先融合为块体材料再通过低温固相扩散反应实现焊膏与基板的连接，最终导致连接时间长、连接强度较低或需要更多的连接能量。针对以上问题，本研究提出了被连接材料表面结构纳米化，实现基板表面能与纳米颗粒表面能相匹配，使纳米颗粒与基板之间的烧结和纳米颗粒自烧结同时进行。.设计并采用电沉积方法在基板上制备Ni纳米阵列，研究了不同参数对Ni纳米阵列的粒径和形貌的影响以及添加剂在电沉积过程中的电化学行为。结果表明：通过控制添加剂的浓度、电流密度和电镀时间可以控制Ni纳米阵列的形貌和粒径大小。添加剂可以促进Ni的定向生长，降低电沉积的阻值。采用化学浸镀方法在镍薄膜表面覆盖金层，得到Cu/Ni/Au结构的焊盘，用以研究纳米连接材料与基板互连过程中的界面行为。.在无任何保护气体和外部压力的条件下将纳米结构阵列薄膜(Ni/Au nanomace (Ni/Au NM))与纳米银焊膏在不同温度下(150 ℃、200 ℃和250 ℃)进行烧结，在6MPa的压力下将表面平整的Ni/Au薄膜(flat Ni/Au)和纳米银焊膏烧结。烧结后分别采用SEM、TEM、EDS、剪切强度、断口分析和化学势分析纳米银焊膏与flat Ni/Au薄膜和Ni/Au NM薄膜烧结的界面行为。结果显示，Ni/Au NM薄膜与纳米银焊膏烧结后的连接强度是同等温度下flat Ni/Au薄膜与纳米银焊膏连接强度的6倍。分析得出，连接强度的提升一方面是纳米阵列与Ag层的机械互锁，更重要的是纳米阵列与纳米银焊膏的兼容性烧结促使Au元素加速扩散进入Ag层从而获得微纳尺度扩散连接，Au元素的扩散距离达到800 nm并与Ag形成合金化的冶金连接。通过纳米银和Cu/Ni/Au结构纳米阵列薄膜的制备以及它们之间烧结行为的研究证实了改善纳米连接材料烧结兼容性有利于获得高性能的连接接头。