SnBi釬料電遷移機理及抑制的研究
發(fā)布時間：2018-07-24 11:22
【摘要】：隨著電子產(chǎn)品向著微型化、多功能化方向發(fā)展,焊點電流密度急劇增大,電遷移現(xiàn)象已成為影響焊點可靠性的重要問題。Sn Bi釬料由于熔點低、低膨脹系數(shù)、性能高及環(huán)境協(xié)調(diào)性良好等優(yōu)點而被廣泛應(yīng)用。但電遷移易導(dǎo)致Sn Bi釬料組織及性能發(fā)生惡化,嚴(yán)重影響焊點可靠性,故研究Sn Bi釬料電遷移行為在電子封裝領(lǐng)域具有重要的意義。本文以Sn Bi釬焊接頭作為研究對象,探究了電遷移對Sn Bi釬焊接頭微觀組織形貌、界面IMC及力學(xué)性能的影響。并進一步討論Al2O3和Ce顆粒對Sn Bi釬料電遷移性能的影響。Sn Bi釬焊接頭通電240h后,陰極界面產(chǎn)生了裂紋,焊縫組織中形成一條粗大的富Bi帶。Bi原子在電子風(fēng)力作用下不斷從陰極向陽極遷移,陰極界面附近由于大量Bi原子離開產(chǎn)生空位并逐步演化為空洞和裂紋。當(dāng)大量的Bi原子遷移到陽極界面附近時,持續(xù)通電導(dǎo)致接頭溫度上升,Bi相發(fā)生長大并形成富Bi帶。此外,Sn Bi釬焊接頭陽極界面IMC厚度隨著通電時間的延長不斷增加,當(dāng)通電時間超過240h后,陽極IMC厚度的增加的速度不斷加快,這可能是由于接頭界面產(chǎn)生部分?jǐn)嗔?界面面積減小,電流密度增大,加速Bi原子的遷移。Al2O3顆粒有效地提升了Sn Bi釬料的電遷移抗性,Sn Bi-0.5%Al2O3釬焊接頭隨通電時間的加長,顯微組織變化不大,IMC厚度變化程度也較小。這是由于Al2O3顆粒阻擋原子遷移的通道,使得原子遷移受阻,從而有效抑制了Sn Bi釬料的電遷移。Ce顆粒細化了Sn Bi釬料顯微組織,改善釬料的力學(xué)性能。隨通電時間延長,Sn Bi-0.5%Ce接頭較穩(wěn)定,當(dāng)通電330h后發(fā)生斷裂失效。接頭陽極界面IMC形貌由扇貝狀逐漸轉(zhuǎn)變?yōu)閷訝?相比于Sn Bi釬料界面IMC厚度,Sn Bi-0.5%Ce釬料陰極和陽極界面IMC厚度變化程度較低。隨著通電時間的增長,Sn Bi,Sn Bi-0.5%Al2O3和Sn Bi-0.5%Ce接頭陰極側(cè)顯微硬度均逐漸降低,而陽極側(cè)顯微組織的顯微硬度則逐漸增加。這是由于大量Bi原子從陰極向陽極遷移,陰極側(cè)組織產(chǎn)生空洞和富Sn相,導(dǎo)致陰極側(cè)硬度不斷降低;而陽極側(cè)形成大塊的Bi相,由于Bi相為硬脆相,最終導(dǎo)致陽極側(cè)組織的硬度不斷上升。其中Sn Bi-0.5%Al2O3釬焊接頭陰極和陽極側(cè)顯微硬度變化程度最低,這是由于Al2O3顆粒增強了釬料在電遷移過程的組織穩(wěn)定性。通電200h后,Sn Bi,Sn Bi-0.5%Al2O3和Sn Bi-0.5%Ce釬焊接頭抗拉強度分別為12MPa,33MPa和19 MPa。同時,Sn Bi-0.5%Al2O3和Sn Bi-0.5%Ce釬焊接頭的延伸長度也相比于Sn Bi接頭有明顯的增加,且Sn Bi-0.5%Al2O3和Sn Bi-0.5%Ce釬焊接頭拉伸斷口中分布著撕裂痕,具有部分韌性斷裂的特征,而Sn Bi接頭的斷口分布著大量解理臺階,為典型的脆性斷裂形式,其中Sn Bi-0.5%Al2O3和Sn Bi-0.5%Ce釬焊接頭呈現(xiàn)出比Sn Bi釬焊接頭更優(yōu)的力學(xué)性能。說明Al2O3和Ce顆粒都起到了抑制Sn Bi釬料電遷移的效果,且Al2O3顆粒的抑制效果更佳。
[Abstract]:With the development of electronic products towards miniaturization and multifunction, the current density of solder joint increases rapidly. The phenomenon of electromigration has become an important problem affecting the reliability of solder joint. Because of the low melting point, the expansion coefficient of Sn-Bi solder is low. High performance and good environmental coordination and other advantages are widely used. However, electromigration can lead to the deterioration of microstructure and properties of Sn-Bi solder, which seriously affects the reliability of solder joint. Therefore, it is of great significance to study the electromigration behavior of Sn-Bi solder in electronic packaging field. In this paper, the effect of electromigration on microstructure, interface IMC and mechanical properties of Sn-Bi brazed joints was investigated. The effect of Al2O3 and ce particles on the electromigration properties of Sn-Bi solder was further discussed. After the Sn-Bi brazing joint was electrified for 240 h, cracks occurred at the cathode interface. A coarse Bi-rich band. Bi atom in the weld microstructure is continuously migrated from cathode to anode under the action of electron wind. Due to a large number of Bi atoms leaving the cathode interface, a large number of Bi atoms leave to produce vacancies and gradually evolve into voids and cracks. When a large number of Bi atoms migrate to the anode interface, the continuous electrification leads to the increase of the junction temperature and the growth of the Bi phase and the formation of Bi-rich bands. In addition, the thickness of IMC at the anode interface of Sn-Bi brazed joint increases with the prolongation of the electrification time, and the increasing speed of the thickness of the anode IMC increases continuously when the electrification time exceeds 240 h, which may be due to the partial fracture of the interface of the joint. With the decrease of interface area and the increase of current density, accelerating the migration of Bi atoms. Al _ 2O _ 3 particles can effectively enhance the electromigration resistance of Sn Bi solder and the microstructure of Sn-Bi brazed joints increases with the time of electrification, and the change of microstructure is not so great as to change the thickness of Sn-Bi solders. This is due to the blocking of atom migration by Al2O3 particles, which effectively inhibits the electromigration of Sn Bi solder. Ce particles refine the microstructure of Sn-Bi solder and improve the mechanical properties of the filler metal. The Sn-Sn Bi-0.5 joint is stable with the prolongation of the power on time, and fracture failure occurs after 330 hours of electrification. The IMC morphology of the anode interface of the joint changed from scalloped to layered, and the thickness of Sn Bi-0.5 solder cathode and anode interface IMC changed less than that of Sn-Bi brazing metal interface. The microhardness of the cathode side of the Sn Bi-Sn Bi-0.5%Al2O3 and Sn Bi-0.5 joints decreases gradually with the increase of the electrification time, while the microhardness of the anode side increases gradually. This is due to the migration of a large number of Bi atoms from the cathode to the anode, and the formation of voids and Sn rich phases in the cathode side, which leads to the decrease of the hardness of the cathode side, while the formation of bulk Bi phase on the anode side, because the Bi phase is hard and brittle. Finally, the hardness of the anodic side structure increases continuously. The microhardness of Sn Bi-0.5%Al2O3 brazing joint is the lowest, which is due to the enhancement of the microstructure stability of the solder during electromigration by Al2O3 particles. The tensile strength of Sn-Bi-Sn Bi-0.5%Al2O3 and Sn Bi-0.5 brazed joints is 12 MPA and 19 MPA, respectively. At the same time, the elongation length of Sn Bi-0.5%Al2O3 and Sn Bi-0.5 brazed joints is also significantly longer than that of Sn Bi joints, and the tensile fracture of Sn Bi-0.5%Al2O3 and Sn Bi-0.5 brazing joints is characterized by partial ductile fracture. However, there are a lot of cleavage steps on the fracture surface of Sn-Bi joints, which are typical brittle fracture modes. The mechanical properties of Sn Bi-0.5%Al2O3 and Sn Bi-0.5 brazed joints are better than that of Sn-Bi brazed joints. The results show that both Al2O3 and ce particles can inhibit the electromigration of Sn-Bi solder, and Al2O3 particles have better inhibition effect.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG425
本文編號：2141220
[Abstract]:With the development of electronic products towards miniaturization and multifunction, the current density of solder joint increases rapidly. The phenomenon of electromigration has become an important problem affecting the reliability of solder joint. Because of the low melting point, the expansion coefficient of Sn-Bi solder is low. High performance and good environmental coordination and other advantages are widely used. However, electromigration can lead to the deterioration of microstructure and properties of Sn-Bi solder, which seriously affects the reliability of solder joint. Therefore, it is of great significance to study the electromigration behavior of Sn-Bi solder in electronic packaging field. In this paper, the effect of electromigration on microstructure, interface IMC and mechanical properties of Sn-Bi brazed joints was investigated. The effect of Al2O3 and ce particles on the electromigration properties of Sn-Bi solder was further discussed. After the Sn-Bi brazing joint was electrified for 240 h, cracks occurred at the cathode interface. A coarse Bi-rich band. Bi atom in the weld microstructure is continuously migrated from cathode to anode under the action of electron wind. Due to a large number of Bi atoms leaving the cathode interface, a large number of Bi atoms leave to produce vacancies and gradually evolve into voids and cracks. When a large number of Bi atoms migrate to the anode interface, the continuous electrification leads to the increase of the junction temperature and the growth of the Bi phase and the formation of Bi-rich bands. In addition, the thickness of IMC at the anode interface of Sn-Bi brazed joint increases with the prolongation of the electrification time, and the increasing speed of the thickness of the anode IMC increases continuously when the electrification time exceeds 240 h, which may be due to the partial fracture of the interface of the joint. With the decrease of interface area and the increase of current density, accelerating the migration of Bi atoms. Al _ 2O _ 3 particles can effectively enhance the electromigration resistance of Sn Bi solder and the microstructure of Sn-Bi brazed joints increases with the time of electrification, and the change of microstructure is not so great as to change the thickness of Sn-Bi solders. This is due to the blocking of atom migration by Al2O3 particles, which effectively inhibits the electromigration of Sn Bi solder. Ce particles refine the microstructure of Sn-Bi solder and improve the mechanical properties of the filler metal. The Sn-Sn Bi-0.5 joint is stable with the prolongation of the power on time, and fracture failure occurs after 330 hours of electrification. The IMC morphology of the anode interface of the joint changed from scalloped to layered, and the thickness of Sn Bi-0.5 solder cathode and anode interface IMC changed less than that of Sn-Bi brazing metal interface. The microhardness of the cathode side of the Sn Bi-Sn Bi-0.5%Al2O3 and Sn Bi-0.5 joints decreases gradually with the increase of the electrification time, while the microhardness of the anode side increases gradually. This is due to the migration of a large number of Bi atoms from the cathode to the anode, and the formation of voids and Sn rich phases in the cathode side, which leads to the decrease of the hardness of the cathode side, while the formation of bulk Bi phase on the anode side, because the Bi phase is hard and brittle. Finally, the hardness of the anodic side structure increases continuously. The microhardness of Sn Bi-0.5%Al2O3 brazing joint is the lowest, which is due to the enhancement of the microstructure stability of the solder during electromigration by Al2O3 particles. The tensile strength of Sn-Bi-Sn Bi-0.5%Al2O3 and Sn Bi-0.5 brazed joints is 12 MPA and 19 MPA, respectively. At the same time, the elongation length of Sn Bi-0.5%Al2O3 and Sn Bi-0.5 brazed joints is also significantly longer than that of Sn Bi joints, and the tensile fracture of Sn Bi-0.5%Al2O3 and Sn Bi-0.5 brazing joints is characterized by partial ductile fracture. However, there are a lot of cleavage steps on the fracture surface of Sn-Bi joints, which are typical brittle fracture modes. The mechanical properties of Sn Bi-0.5%Al2O3 and Sn Bi-0.5 brazed joints are better than that of Sn-Bi brazed joints. The results show that both Al2O3 and ce particles can inhibit the electromigration of Sn-Bi solder, and Al2O3 particles have better inhibition effect.
【學(xué)位授予單位】：中國礦業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TG425
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