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金属学报  2017, Vol. 53 Issue (2): 227-232    DOI: 10.11900/0412.1961.2016.00232
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1哈尔滨工业大学先进焊接与连接国家重点实验室 哈尔滨 150001
2哈尔滨工业大学(威海)山东省特种焊接技术重点实验室 威海 264209
Microstructures and Mechanical Properties of Cu/Sn/Cu Structure Ultrasonic-TLP Joint
Jihou LIU1,2,Hongyun ZHAO1,2,Zhuolin LI2(),Xiaoguo SONG1,2,Hongjie DONG1,2,Yixuan ZHAO1,2,Jicai FENG1,2
1 State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China2 Shandong Provincial Key Lab of Special Welding Technology, Harbin Institute of Technology at Weihai, Weihai 264209, China
2 Shandong Provincial Key Lab of Special Welding Technology, Harbin Institute of Technology at Weihai, Weihai 264209, China
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利用超声波辅助过渡液相(超声-TLP)软钎焊工艺方法对Cu/Sn/Cu结构进行了钎焊实验,在极短的时间内获得了全Cu-Sn金属间化合物接头,并研究了接头的显微组织和力学性能。结果表明,超声-TLP接头由15 μm厚的Cu6Sn5中间层和1 μm厚的Cu3Sn边界层构成。在超声波作用下,Cu6Sn5晶粒呈现小尺寸等轴状,80%的Cu6Sn5晶粒直径在5 μm以下。由细化的Cu6Sn5晶粒构成的接头表现出较均匀的力学性能,具有较稳定的弹性模量和硬度,分别为123 GPa和6.0 GPa;同时具有较高的互连强度,达到了60 MPa。

关键词 过渡液相软钎焊,超声波,金属间化合物,纳米压痕,剪切强度    

The energy density of chip is becoming increasingly higher with the power electronic devices developing toward miniaturization, high power and integration, which will lead a higher operating temperature. However, the traditional Sn-based soldering process fails to meet the elevated temperature. Transient liquid phase (TLP) soldering, which can form high-melting-point joints at relatively low temperatures, has been proven to be a promising bonding method for solving this technological challenge. Nevertheless, a common drawback for TLP soldering is that it will consume a very long time for the complete formation of intermetallic joints, up to tens of minutes, which will lead extra thermal stress and seriously negative effects on the reliability of packaging systems. Recently, this technological puzzle has been proven to be solved by a novel ultrasonic-assisted TLP soldering process, in which the ultrarapid formation of complete intermetallic joints was achieved due to the accelerated diffusion of Cu from the substrates into the molten Sn interlayer under the complex sonochemical effects of acoustic field on the interfacial reaction. In this study, the microstructure and mechanical properties of complete Cu-Sn intermetallic joints ultrarapidly formed by ultrasonic-assisted TLP soldering process were investigated. The sandwich Cu/Sn/Cu system was placed on the heating platform, and then the ultrasonic vibrations and the bonding force were applied on it. The horizontal ultrasonic frequency, pressure, power, bonding temperature and time were fixed as 20 kHz, 0.5 MPa, 300 W, 250 ℃ and 5 s. In summary, the complete intermetallic joints composed of Cu6Sn5 interlayer with a thickness about 15 μm and Cu3Sn boundary layers with a thickness about 1 μm were ultrarapidly formed by ultrasonic-assisted TLP soldering process. The formed Cu6Sn5 grains were remarkably refined to be with an average grain size less than 5 μm. Compared with the intermatllic joints formed by traditional TLP soldering process, the resulted intermetallic joints performed more uniform mechanical properties with elastic modulus and hardness of about 123 GPa and 6.0 GPa respectively, as well as a higher reliability with a shear strength of 60 MPa.

Key wordstransient    liquid    phase    soldering,    ultrasonic,    intermetallics,    nanoindentation,    shear    strength
收稿日期: 2016-06-14      出版日期: 2016-11-23


刘积厚,赵洪运,李卓霖,宋晓国,董红杰,赵一璇,冯吉才. Cu/Sn/Cu超声-TLP接头的显微组织与力学性能[J]. 金属学报, 2017, 53(2): 227-232.
Jihou LIU,Hongyun ZHAO,Zhuolin LI,Xiaoguo SONG,Hongjie DONG,Yixuan ZHAO,Jicai FENG. Microstructures and Mechanical Properties of Cu/Sn/Cu Structure Ultrasonic-TLP Joint. Acta Metall Sin, 2017, 53(2): 227-232.

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图1  Cu/Sn/Cu结构的超声波辅助过渡液相(超声-TLP)软钎焊工艺过程示意图和钎焊过程温度曲线
图2  超声-TLP接头组织形貌的SEM像及Cu和Sn元素的面扫描图
图3  超声-TLP接头中金属间化合物的晶粒形貌图、相分布图、Cu6Sn5极图和Cu6Sn5晶粒尺寸分布图
图4  超声-TLP接头的纳米压痕测试位置、纳米压痕的载荷-位移曲线、压痕形貌AFM像及压痕的位置-高度分析图
Impression Elastic modulus Hardness
1 123.03 5.97
2 123.02 5.99
3 123.04 5.98
4 123.03 6.01
5 123.04 5.99
表1  图4a中不同位置的弹性模量和硬度
图5  超声-TLP接头断口形貌SEM像及XRD谱
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