本文選題：Sn-Bi基焊料 + 界面反應��； 參考：《天津大學》2016年博士論文

【摘要】：在電子封裝領域中,低溫焊接可降低由于不同材料間熱膨脹失配性所引起的熱破壞性。于是,具有低熔點、潤濕性好的Sn-Bi基焊料成了低溫焊接所需無鉛焊料之一。本文系統(tǒng)、深入地研究了添加Zn元素的Sn-58Bi共晶焊料樣品相關性能,即對CuZn大規(guī)模剝離現象,經回流焊接和液態(tài)時效后焊點的拉伸、蠕變性能,以及經電流和熱應力共同作用后焊點機械性能等方面進行重點研究。CuZn的大規(guī)模剝離主要受Zn濃度的影響。在經過較長時間液態(tài)時效反應后,僅當焊料樣品中Zn濃度大小達到0.67 wt.%時,這種剝離行為才可能發(fā)生。和Sn-58Bi-0.7Zn塊狀焊料相比,大規(guī)模剝離現象更容易在小體積焊料球樣品中出現。焊料樣品的相關微結構演化機制可通過向Cu-Sn-Zn等溫相圖中引入Zn的擴散路徑進行分析和解釋。此外,當時效溫度大于Sn-58Bi-0.7Zn塊狀焊料液相線溫度時,Cu6(Sn,Zn)5和CuZn層間Sn的濃度會大幅度增加。這時,CuZn的大規(guī)模剝離行為就發(fā)生了。通過熱力學分析可以得出,這種大規(guī)模剝離行為的發(fā)生,在一定程度上歸結于Cu6(Sn,Zn)5/CuZn界面處自由能的減少,而Sn濃度是影響這個自由能減小的主要原因。另一方面,與Sn-58Bi共晶焊料樣品相比,Sn-58Bi-0.7Zn焊料樣品的極限拉伸強度在回流焊接和液態(tài)時效后都分別得到提升。其中,Sn-58Bi-0.7Zn焊條樣品分別提升6.05%和5.50%,而焊點樣品則分別提升21.51%和29.27%。Cu/Sn-58Bi-xZn焊點增強的主要原因是由于Zn的添加讓Bi晶粒得到細化,使斷裂面從基底和界面金屬間化合物之間轉移到了界面金屬間化合物和焊料之間。在經回流焊接和液態(tài)時效后的矩形焊料樣品中,Sn-58Bi-0.7Zn矩形焊料的抗蠕變能力也都分別明顯大于Sn-58Bi矩形焊料。此外,在拉伸試驗期間,陽極界面位置處界面金屬間化合物和富Bi層間連接性的大小會強烈影響電遷移和熱時效耦合Cu/Sn-58Bi-0.7Zn焊點的極限拉伸強度。由于富Bi層的持續(xù)生長加速了孔洞和裂紋形成,而裂紋在界面中進一步傳遞將導致焊點拉伸強度降低。對于未加載電流應力而僅進行固態(tài)時效的焊點,在Cu-Sn-Zn/Cu-Zn界面處由Bi偏析所形成的空位及應力集聚對其極限拉伸強度會產生極大影響。耦合應力期間電流應力能造成孔洞形核,所以耦合焊點的極限拉伸強度要小于時效焊點的極限拉伸強度。對于耦合樣品,通過有限元模型揭示了其陽極界面處生成的富Bi層可承擔部分載荷,從而使焊點界面處的壓入深度得到減小。因此,耦合樣品的抗蠕變性要高于時效樣品的抗蠕變性。
[Abstract]:In the field of electronic packaging, low temperature welding can reduce the thermal damage caused by thermal expansion mismatch between different materials.Therefore, Sn-Bi solder with low melting point and good wettability becomes one of the lead-free solders for low temperature welding.In this paper, the properties of Sn-58Bi eutectic solder samples with Zn addition have been studied systematically, that is, the tensile and creep properties of solder joints after reflux welding and liquid aging have been studied for CuZn stripping phenomenon, reflux welding and liquid aging.The mechanical properties of solder joints after the interaction of electric current and thermal stress were studied in detail. The effect of Zn concentration on the mass exfoliation of CuZn was studied.After a long time of liquid aging reaction, this kind of stripping behavior can occur only when the Zn concentration in the solder sample reaches 0.67 wt.%.Compared with Sn-58Bi-0.7Zn bulk solder, large scale peeling occurs more easily in small volume solder ball samples.The evolution mechanism of the microstructure of solder samples can be analyzed and explained by introducing Zn into the Cu-Sn-Zn isothermal phase diagram.In addition, when the aging temperature is higher than the liquid line temperature of Sn-58Bi-0.7Zn bulk solder, the concentration of Cu _ (6) O _ (2 +) Sn _ (5) and Sn between CuZn layers will increase greatly.In this case, the large-scale stripping of CuZn occurs.Through thermodynamic analysis, it can be concluded that the occurrence of this kind of large-scale stripping behavior is attributed to the decrease of free energy at the interface of Cu _ (6) O _ (6) SnN _ (5) Zn _ (5) / Cu _ (Zn), and the concentration of Sn is the main reason for the decrease of the free energy.On the other hand, compared with Sn-58Bi eutectic solder sample, the ultimate tensile strength of Sn-58Bi-0.7Zn solder sample is increased after reflux welding and liquid aging respectively.The main reason for the increase of Sn-58Bi-0.7Zn electrode sample was 6.05% and 5.50% respectively, while the solder joint sample increased 21.51% and 29.27%.Cu/Sn-58Bi-xZn solder joint enhancement was mainly due to the addition of Zn to refine the Bi grain.The fracture surface is transferred from substrate and interfacial intermetallic compound to interfacial intermetallic compound and solder.The creep resistance of Sn-58Bi-0.7Zn rectangular solder is obviously higher than that of Sn-58Bi rectangular solder after reflux welding and liquid aging.In addition, during tensile test, the intermetallic compounds and Bi-rich interlayer connectivity at the anode interface strongly affect the ultimate tensile strength of Cu/Sn-58Bi-0.7Zn solder joints coupled with electromigration and thermal aging.The continuous growth of Bi-rich layer accelerates the formation of pores and cracks, and the further propagation of cracks in the interface will result in the decrease of tensile strength of solder joints.For solder joints which are aged only by solid state without loading current stress, the vacancy formed by Bi segregation at the Cu-Sn-Zn/Cu-Zn interface and the stress concentration will have a great influence on the ultimate tensile strength of solder joints.During the coupling stress, the current stress can lead to the nucleation of holes, so the ultimate tensile strength of the coupling solder joint is smaller than the ultimate tensile strength of the aging solder joint.For the coupled samples, the Bi-rich layer formed at the anode interface is found to be partially loaded by the finite element model, thus reducing the depth of indentation at the interface of the solder joint.Therefore, the creep resistance of coupled samples is higher than that of aging samples.
【學位授予單位】：天津大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TG42

【參考文獻】

相關期刊論文 前4條

1 HE Peng;Lü Xiao-chun;LIN Tie-song;LI Hai-xin;AN Jing;MA Xin;FENG Ji-cai;ZHANG Yan;LI Qi;QIAN Yi-yu;;Improvement of mechanical properties of Sn-58Bi alloy with multi-walled carbon nanotubes[J];Transactions of Nonferrous Metals Society of China;2012年S3期

2 許磊;張宇鵬;張宇航;易江龍;楊凱珍;;時效處理對Sb改性的Sn-58Bi低溫無鉛釬料的影響[J];材料研究與應用;2010年04期

3 李群;黃繼華;張華;趙興科;齊麗華;;Al對Sn-58Bi無鉛釬料組織及性能的影響[J];電子工藝技術;2008年01期

4 ;Investigation on Aging-induced Softening of Eutectic Microstructure in SnBi/Cu Interconnect by Nanoindentation[J];Journal of Materials Science & Technology;2006年01期

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本文編號：1759833