Sn基软钎料合金的晶须快速生长行为和抑制方法研究

发布时间：2018-01-03 06:24

本文关键词：Sn基软钎料合金的晶须快速生长行为和抑制方法研究　出处：《哈尔滨工业大学》2017年博士论文　论文类型：学位论文

【摘要】：Sn基软钎料的晶须生长问题对电子封装互连可靠性的威胁由来已久。随着封装密度不断提高、互连点间距不断减小,数微米的Sn晶须就可能引发互连点的短路,因此探索可以有效减缓或抑制Sn晶须生长的方法成为了学术界的重要研究内容之一。然而Sn晶须生长的长期性和偶然性的特点对其研究工作造成很大困扰,所以加速晶须的形核和长大成为研究其形成机制和抑制机理的首要条件。目前,加速Sn晶须生长的方法主要有施加压力、电迁移诱导、等温时效和热循环等。不过上述方法均存在孕育期长、晶须密度低等缺点;此外,试样制备工艺同样会对Sn晶须的生长行为产生影响,进而干扰实验结果。基于上述原因,本研究创造性地开发了一种行之有效的Sn晶须加速生长方法,深入分析了钎料晶粒尺寸和弹性模量对Sn晶须生长的影响,并且提出了两种Sn晶须生长的抑制方法。该研究对明晰Sn基钎料晶须生长行为以及降低钎料晶须生长风险有重要的指导意义。本研究通过自主开发的超声辅助钎焊设备制造了Mg/Sn/Mg焊接接头,发现了该接头经过短时间室温等温时效之后焊缝表面有高密度的Sn晶须形成,确定了Sn晶须生长所需的驱动力主要来源于固溶在焊缝钎料基体内的间隙Mg原子原子转化为Mg2Sn过程中所引起的体积膨胀,提出了超声辅助钎焊制备Mg/Sn/Mg焊接接头的工艺可作为一种Sn晶须的快速生长方法并用于Sn晶须相关领域的研究。其次,本研究通过机械压合和超声振动相结合的方式制备了Sn-Si C复合钎料,利用超声辅助钎焊工艺与纳米Si C颗粒的异质形核作用制备了具有不同Sn晶粒尺寸的Mg/Sn-x Si C/Mg焊接接头,分析了提高Sn晶界数量对Sn晶须形核与生长的促进作用;通过对比Mg/Sn-x Pb/Mg接头焊缝表面Sn晶须生长特征分析了钎料基体的弹性模量和组织结构对Sn晶须生长的影响规律。再次,本研究观察了Sn-9Zn钎料中Zn原子在Sn晶界的偏聚行为,发现了Zn原子的晶界偏聚形成的位阻效应将严重阻碍Sn原子的晶界扩散,同时片层状富Zn相结构将破坏Sn原子的长程扩散,最终确认了Zn原子对Sn晶须生长的抑制作用。最后,本研究利用冷压焊工艺制备了具有良好接合界面的Sn/Cu/Sn钎料预制片,通过短时间加热获得了Cu焊盘/IMC/Cu/IMC/Cu焊盘结构的焊点,该合金化焊点不但可以完全避免Sn晶须生长风险,而且还具有耐高温能力,可用于大功率高温半导体器件的互连封装。
[Abstract]:The problem of whisker growth of Sn-base solder has long been a threat to the interconnection reliability of electronic packaging. A few microns of Sn whiskers may cause short circuit of interconnect points. Therefore, exploring methods that can effectively slow down or inhibit the growth of Sn whiskers has become one of the important research contents in academic circles. However, the long-term and accidental characteristics of Sn whiskers growth have caused great problems to its research work. Therefore, accelerating the nucleation and growth of whiskers has become the most important condition to study the mechanism of formation and inhibition. At present, the main methods to accelerate the growth of Sn whiskers are to apply pressure and induce electromigration. The isothermal aging and thermal cycling, however, have the disadvantages of long incubation period and low whisker density. In addition, the sample preparation process will also affect the growth behavior of Sn whisker, and then interfere with the experimental results. In this study, an effective method of Sn whisker growth was developed creatively, and the effects of grain size and elastic modulus of solder on the growth of Sn whisker were analyzed. Two methods of inhibiting the growth of Sn whiskers are proposed. This study is of great significance in clarifying the growth behavior of Sn based brazing whiskers and reducing the growth risk of Sn whiskers. Mg/Sn/Mg welding joint is manufactured by brazing equipment. High density Sn whiskers were found on the weld surface after a short time isothermal aging at room temperature. It is determined that the main driving force for Sn whisker growth is the volume expansion caused by the transformation of the interstitial mg atoms in the solder base into Mg2Sn. It is suggested that ultrasonic assisted brazing can be used as a rapid growth method of Sn whiskers and can be used in the research of Sn whiskers. In this study, Sn-Si C composite solder was prepared by mechanical compression and ultrasonic vibration. Mg/Sn-x sic / mg welded joints with different Sn grain sizes were prepared by ultrasonic assisted brazing process and heterogeneous nucleation of nano sic particles. The effect of increasing the amount of Sn grain boundary on the nucleation and growth of Sn whisker was analyzed. By comparing the growth characteristics of Sn whiskers on the weld surface of Mg/Sn-x Pb/Mg joints, the effects of elastic modulus and microstructure of solder matrix on the growth of Sn whiskers were analyzed. In this study, the segregation behavior of Zn atoms at Sn grain boundaries in Sn-9Zn solders was observed. It was found that the steric resistance of Zn atoms formed by grain boundary segregation would seriously hinder the grain boundary diffusion of Sn atoms. At the same time, the Zn-rich phase structure of lamellar layer will destroy the long-range diffusion of Sn atom, and finally confirm the inhibitory effect of Zn atom on the growth of Sn whisker. In this study, Sn/Cu/Sn solder prefabricated with good interface was prepared by cold pressing welding process. The solder joints of Cu / IMC / Cu / IMC / Cu / Cu pad structure were obtained by short time heating. The alloyed solder joints not only completely avoid the risk of Sn whisker growth, but also have high temperature resistance. It can be used in interconnection packaging of high-power high-temperature semiconductor devices.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TG425.1

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