镓-钕协同效应对锡银、锡铜及锡银铜无铅钎料锡须生长抑制机制研究

The spontaneous growth of Sn whiskers in lead-free solder has been proved to be responsible for catastrophic losses in satellites, missiles, radars and other equipment, but the mechanism of tin whisker growth remain unclear. Considering about the increasing requirements of reliability in electronic industry, this research project provid an novel approach on tin whisker growth inhibition in Sn-Ag, Sn-Cu and Sn-Ag-Cu lead-free soldered joint and established an evaluation model for tin whisker growth through investigation on the combined action of Nd and Ga.. Through the researches on the oxidation of RE-phase which may induced the tin whisker growth at the nanoscale, the results can reveal the process of tin whisker growth sprout, growth, inhibition and the metallurgical mechanism of tin whisker growth under various conditions. . The mechanism of void and crack formation, initiation and propagation behavior in the interface of soldered joint will be investigated based on the thermodynamics and the primary model. The results will indicate the effect of alloy element and various temperature and aging time on the mechanical properties soldered joint and the relationship between the transformation of interface intermetallic and tin whisker growth.. The final results of this research project will clarify the mechanism of Ga/Nd combined action on tin whisker growth inhibition, and provide an novel method of tin whisker growth evaluation and prediction for lead-free soldered joint.

本项目针对电子工业中导致焊点失效从而引发灾难性事故的锡须生长现象进行深入研究，通过对不同环境下分别添加Ga、Nd和复合添加Ga、Nd元素的Sn-Ag、Sn-Cu、Sn-Ag-Cu等无铅钎料基体及焊点界面附近的锡须生长情况进行长期（3600h以上）时效观测，研究Ga、Nd的协同作用机制，提出抑制无铅钎料焊点锡须生长的新思路。拟重点开展以下研究：(1) 在微纳尺度研究Nd稀土相的氧化破裂行为，通过原位SEM技术获得锡须生长的物理机制; (2)研究不同环境载荷条件下锡须的生长行为与氧化产物之间的内在联系，获得锡须生长的驱动力；(3)研究锡须生长的不同形态，建立无铅焊点锡须生长的评估与预测模型；(4)采用热力学生成自由能及第一性原理模型，阐明Ga、Nd的协同抑制焊点锡须生长的作用机制。研究结果可以为“抑制锡须生长”机制与无铅焊点锡须抑制生长的研究提供理论基础。

针对电子工业中导致焊点失效从而引发灾难性事故的锡须生长现象，通过向Sn-Ag、Sn-Cu、Sn-Ag-Cu等无铅钎料中添加Ga/Nd元素进行改性，研究了不同条件下Ga/Nd元素对钎料组织及性能的影响以及Ga/Nd复合添加对无铅钎料基体及焊点界面附近锡须生长的抑制作用，揭示了Ga、Nd的协同作用机制，提出了抑制无铅钎料焊点锡须生长的新思路。.主要创新成果如下： .1）阐明了Ga、Nd元素在钎料中的存在形式，揭示了长期时效过程中焊点界面层的演化规律，研发了具有优良综合性能及焊点可靠性的新型无铅钎料。.2）揭示了Ga/Nd元素比例、冶炼条件、钎焊温度等因素对无铅钎料焊点界面组织中Ga-Nd相生成的影响规律，阐明了Ga-Nd相取代Sn-Nd相控制锡土相尺寸、数量，抑制稀土相生成，进而抑制锡须生长现象的作用机制。.3）阐明了纳米级Ga-Cu相控制焊点界面附近硬脆相金属间化合物尺寸和数量的作用机制，揭示了纳米级Ga-Cu相、Ga-Nd相协同作用对焊点可靠性的强化规律。.4）阐明了Ga/Nd复合添加对无铅钎料焊点界面附近金属间化合物的影响机制，揭示了时效过程中金属间化合物对焊点界面层演化的作用规律，提出了无铅焊点锡须生长抑制作用的综合评价机制。.5）发表学术论文5篇，其中SCI收录3篇，EI收录2篇；申请发明专利5件，获得授权3件；获2017年度河南省科技进步二等奖1项，获2019年度河南省科技进步二等奖1项，获2019中国腐蚀与防护学会科学技术奖一等奖1项。