(中國(guó)科學(xué)院 金屬研究所，沈陽(yáng) 110016)
摘 要: 應(yīng)用第一原理方法研究通過(guò)元素?fù)诫s來(lái)抑制SnBi無(wú)鉛焊料中Bi的電遷移問(wèn)題。在SnBi體系中摻雜Zn和Sb元素，通過(guò)用近彈性帶方法計(jì)算摻雜體系中Bi元素的擴(kuò)散能壘。結(jié)果表明：加入Sb之后，Bi的擴(kuò)散能壘由原來(lái)的0.32 eV升高到0.46 eV，擴(kuò)散激活能由原來(lái)的1.14 eV升高到1.18 eV；加入Zn后，Bi的擴(kuò)散能壘由原來(lái)的0.32 eV升高到0.48 eV，擴(kuò)散激活能由原來(lái)的1.14 eV升高到1.22 eV。由此可得，Zn和Sb的加入都能夠提高Bi的擴(kuò)散激活能，起到抑制擴(kuò)散的作用。通過(guò)分析態(tài)密度可知：加入Zn和Sb后，體系中Sb與Bi的p態(tài)曲線幾乎完全重合，比Sn與Bi的p態(tài)曲線重合度高很多，說(shuō)明Sb和Bi的共價(jià)鍵作用很強(qiáng)，且比Sn-Bi的共價(jià)鍵作用強(qiáng)，從而增加Bi的擴(kuò)散能壘。同樣，Zn和Bi的p態(tài)曲線重合度也比Sn和Bi的曲線重合度高很多，表明Zn—Bi的共價(jià)鍵同樣比Sn—Bi的共價(jià)鍵強(qiáng)，所以Zn的加入同樣增加Bi的擴(kuò)散能壘。總結(jié)說(shuō)來(lái)，Sb和Zn的摻雜能夠抑制SnBi焊料中Bi的電遷移。
關(guān)鍵字: 第一原理計(jì)算；電遷移；SnBi無(wú)鉛焊料；元素?fù)诫s
electromigration of Bi
（Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China）
Abstract:The first-principles calculations on the elemental doping in SnBi lead-free solders were performed, aiming to inhabit electromigration of Bi element during microelectronic packaging. Zn and Sb elements were theoretically added into SnBi system, and the diffusion barrier energy of Bi was calculated with nudged elastic band (NEB) methods. The results show that, after Sb doping, the diffusion barrier energy of Bi increases from 0.32 eV to 0.46 eV, and the diffusion activation energy of Bi increases from 1.14 eV to 1.18 eV. On the other hand, after Zn doping, the diffusion barrier energy of Bi increases from 0.32 eV to 0.48 eV, and the diffusion activation energy of Bi increases from 1.14 eV to 1.22 eV. Zn and Sb can inhabit the diffusion of Bi during electromigration. The density of states (DOS) analyses show that p-state curves of Sb and Bi almost completely overlap, which indicates that Sb and Bi has stronger covalent bonding than Sn-Bi, thereby increases the diffusion barrier energy of Bi. The calculated DOS of Zn and Bi is the same as that of Sb and Bi, which indicates that Zn—Bi also has stronger covalent bonding than Sn—Bi, hence, the addition of Zn also increases the barrier energy of Bi. In conclusion, Sb and Zn doping can inhibit Bi electromigration in SnBi solder.
Key words: first-principles calculation; electromigration; SnBi lead-free solder; elemental doping
