热电耦合作用下功率器件引脚开裂的机理  

The open-pin failure of power device under the combined effect of thermo-migration and electro-migration

作　　者：高丽茵 李财富[2,3] 曹丽华 刘志权[1,2] Liyin Gao;Caifu Li;Lihua Cao;Zhiquan Liu(Shenzhen Institute of Advanced Electronic Materials,Shenzhen Institutes of Advanced Technology,Chinese Academy of Sciences,Shenzhen 518055,China;Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,China;School of Materials,Sun Yat-sen University,Guangzhou 510275,China)

机构地区：[1]中国科学院深圳先进技术研究院,深圳先进电子材料国际创新研究院,深圳518055 [2]中国科学院金属研究所,沈阳110016 [3]中山大学材料学院,广州510275

出　　处：《科学通报》2020年第20期2169-2177,共9页Chinese Science Bulletin

基　　金：国家重点研发计划重点专项(2017YFB0305700)资助。

摘　　要：在电子产品的小型化的趋势下,电力电子器件所承受的工作温度、电流密度越来越高,这给封装材料提出了严峻的挑战.一种引线框架材料为C194合金的MOSFET器件,在高电流密度的工作环境下服役3~4年后发生了引脚开裂的现象.针对该失效现象,使用扫描电子显微镜对界面金属间化合物和断口形貌进行了精细的微观表征,确定了电迁移和热迁移的耦合作用是导致引脚开裂的主要原因.具体地,对于器件源极来说,Cu原子的电迁移与热迁移方向相反,且热迁移扩散通量较大,抵消了电迁移的作用从而导致了阳极开裂的反常现象.对于器件漏极来说,Cu原子的热迁移方向与电迁移方向相同,热迁移加速了阴极界面裂纹的萌生与扩展,开裂情况最为严重.为了进一步揭示开裂机理,我们使用电子探针、透射电子显微镜分析发现,在C194合金与金属间化合物界面上,原本弥散分布于C194合金内部的铁晶粒发生了明显的晶粒长大,并富集形成连续层.由于细小铁晶粒组成的富铁层弱化原有的界面结合力,成为薄弱环节.因此,在外加热应力或机械应力下,裂纹总是沿着由铁晶粒形成的富铁层发生开裂.综上,该器件引脚开裂的失效模式为典型的多场耦合作用下的失效形式,相关机理将为产品工艺优化和提高使用寿命提供理论指导.With the miniaturization of electronic products,power devices sustain more and more operations under high power,high frequency,and high integration.Power electronic devices are subjected to high operating temperature and current density,which poses a serious challenge on the packaging materials.An open-pin failure was found on a metal-oxidesemiconductor field-effect transistor(MOSFE)device after operated for 3-4 a under high current density condition.The lead frame material is C194 alloy,belonging to Cu-Fe-P alloy,which is a copper base alloy strengthened by dispersion.The operating temperature of the MOSFET device is in the range of 88-120℃at the full working current of about 15A from the drain to the source,while the gate current is relatively small in a milliampere level.Failure analysis is conducted on the open-pin MOSFET device.According to the investigations by scanning electron microscopy(SEM)and energy dispersive spectrometer(EDS),two intermetallic compounds(IMCs),Cu3Sn and Cu6Sn5,were formed at both the C194 alloy/Sn-Pb and the Cu/Sn-Pb solder interfaces.However,the crack is always initiated at the C194 alloy/Sn-Pb solder interface,no matter for the source or the drain.Usually,the crack would initiate at the cathode side due to the sole effect of electromigration.In this work,the crack initiated at the cathode side for the drain,but at the anode side for the source.According to the working condition of the MOSFET device,this failure crack can be attributed to the combined effects of electromigration and thermo-migration on multi-element interfacial diffusion and vacancy migration.In detail,for the source of MOSFET device,the direction of Cu thermo-migration flux is opposite to the electro-migration flux,while the thermomigration flux is large so that it can compensate the effect of electro-migration flux,thus leading to the crack at the anode.For the drain of device,the direction of Cu thermo-migration flux is the same as that of electro-migration,which leads to a severe cracking at the cathode.Moreove

关 键 词：C194合金 引脚开裂 热迁移 电迁移 失效分析 

分 类 号：TN386[电子电信—物理电子学]