本文針對電子遷移現象對覆晶錫球陣列封裝體中，錫球接點同時承受1*104 A/cm2電流密度及150℃環境溫度之孔洞生成模式及失效機制進行研究。測試對象包含4組錫球與2組基板，總共有8種錫球/基板的測試組合，以確認失效模式的一致性。並以保守型失效判定標準來定義及預測試片的失效電阻值，電子顯微鏡則用以進行接點微結構的即時（in situ）觀察與紀錄，以了解介金屬化合物（IMC）的生成與失效模式的種類。
結果顯示，所有試片的失效都發生於電子流由晶片端向下往基板端流動的接點之內，發生的原因都是沿著陰極晶片端錫球下層金屬（UBM）與錫球界面間的孔洞聚集，電子流由導線流入接點的轉角處皆為孔洞優先生成的位置，電流擁擠是造成此孔洞優先發生的原因。孔洞的詳細位置發生於2處，一為IMC/錫球界面，另一為UBM/IMC界面，此2種孔洞模式會同時出現在同一顆試片的不同錫球接點之內，混合型孔洞模式在此研究中並未被發現。由於錫球與IMC層內的原子擴散速率差異性，孔洞易生成於其接觸面間，1*104 A/cm2電流密度被發現可主導IMC/錫球界面間的孔洞生成模式；然而，位於UBM/IMC界面間的孔洞生成是起因於UBM層的消耗殆盡，因此，150℃環境溫度則被判定為主導UBM/IMC界面間的孔洞生成模式。錫球成分間的差異性對孔洞的生成模式及機制並無影響力。基於以上實驗結果的基礎數學模型則也被提及，以描述及了解孔洞的生成原因，但此模型則有需未來更多的實驗結果以提供參數來使計算結果更趨近於實際情況。
由其他結果亦觀察到，當錫球接點的電阻值達到初始阻值的120％之後，在電子流僅流經晶片端導線而未直接流入錫球接點時，錫球內原子可能會因晶片與基板間之溫度梯度而移動堆積於基板端以及隨電子流影響而移動堆積於電子流流出導線的另一端點。
由基板的差異性結果得知，搭配Cu/Ni/Au基板的錫球接點在受電子遷移測試之後，比搭配Cu-OSP基板的錫球接點更易於錫球/基板界面間生成孔洞。此結果顯示基板的搭配，可能使錫球/基板界面成為下一個承受電子遷移作用下導致失效的位置。

The effect of electromigration on void formation and the failure mechanism of FCBGA packages under a current density of 1*104 A/cm2 and an environmental temperature of 150℃ was investigated. Eight solder/substrate combinations of four lead-free solder systems with two substrates were examined to verify the failure modes. A conservative failure criterion was adopted to define and predict the failure of the package. SEM was employed to observe in situ microstructural changes, IMC growth, and failure modes.
All samples exhibited a similar failure, attributed mainly to void occupation along UBM/solder interfaces at the cathode chip side of the bumps with downward electron flow. Voids were initiated at the corner due to current crowding. Two specific void locations were identified at the IMC/solder and UBM/IMC interfaces, and they co-existed in the same specimen but in different bumps. No void coupling mode was found. Since the atom diffusion rate in the solder differs from that in the IMC layer, the voids can be formed between them. A current density of 1*104 A/cm2 was sufficiently high to form a void pattern at the IMC/solder interface. However, the formation of voids at the UBM/IMC interface is generally induced by the consumption of UBM, since the high temperature of 150℃ crucially dominates the void morphology at the UBM/IMC interface. The difference among solder systems did not affect the failure modes nor dominate mechanisms. Two theoretical models based on the experimental results were applied to describe the void formations. They will be more accurate and useful in understanding void formations by further experimental data provided.
According to the results of solder bumps with electrons only flowed through Al trace line at die side, it suggested that atoms transport toward the bottom substrate along with the temperature gradient and toward the right corners along with electron flow when electrons flowed through the trace after the resistances of solder joints reaching 120％ of their initial values.
With respect to the differences of substrate surface finishes, more voids appeared at the cathode substrate side of the solders combined with Cu/Ni/Au pad than those combined with Cu-OSP after long-term upward electron stressing. It suggested another possible failure at the substrate side when failure did not occur at the chip side in an EM test.

Table of Contents ……………………………………………………………………I
List of Tables ………………………………………………………………………IV
List of Figures ……………………………………………………………………...V
Abstract …………………………………………………………….………………X
摘要 ………………………………………………………………………….…...XII
Chapter 1 Introduction ……………………………………………………………...1
1.1 Prolog ………………………………………………………………………...1
1.2 Introduction of IC Packaging ………………………………………………...2
1.2.1 Introduction of Flip Chip Packaging Technology ……………………….4
1.3 The development in lead-free solder …………………………………………6
1.4 Reliability Test ……………………………………………………………….8
1.4.1 Introduction of Reliability ……………………………………………….8
1.4.2 Test Items of Reliability …………………………………………………9
1.5 Introduction of Electromigration ……………………………………………11
1.5.1 Acquirement of Effective charge ……………………………………….14
1.5.2 Current Crowding Effect ……………………………………………….15
1.5.3 Joule Heating Effect ……………………………………………………17
1.5.4 Back stress in electromigration ………………………………………...19
1.6 Electromigration in Flip Chip Solder Joints ………………………………...21
1.6.1 Current Density Threshold and Focus of Electromigration for the Flip Chip Solder Joint ……………………………………………………………..21
1.6.2 Current Crowding Effect in the Flip Chip Solder Joint ………………...22
1.6.3 Joule Heating Effect in the Flip Chip Solder Joint ……………………..23
1.6.4 Failure Modes and Mechanisms in the Flip Chip Solder Joint under EM Stressing ………………………………………………………………..25
1.7 Motivation and Briefly Related References Classification …………………27
1.8 Aim of this work ……………………………………………………………30
1.9 Organization and Content Index ……………………………………………30
Chapter 2 Experimental Setup ……………………………………………………..52
2.1 Sample ………………………………………………………………………52
2.2 Reflow and Cross-section …………………………………………………..52
2.3 Electromigration Test ……………………………………………………….53
2.4 Scanning Electron Microscope Observation ………………………………..54
2.5 Failure Definition …………………………………………………………...54
Chapter 3 Results ………………………………………………………………….60
3.1 Overview of Microstructural Change under EM Test ………………………60
3.2 Initiation and Formation of Voids …………………………………………..61
3.3 Specific Void Locations and the Failure Modes ……………………………61
3.4 Effect of Substrate Surface Finish Metallization on IMC Composition and Void Formation …………………………………………………………………...63
Chapter 4 Discussion ………………………………………………………………88
4.1 Effect of EM on Migration of Atoms and Current Crowding on Initiation and Formation of Voids …………………………………………………………88
4.2 Failure Modes and Mechanisms Induced by Current Density and Temperature ……………………………………………………………….89
4.3 Influence of the Ag-Cu Containing Ratio of Solder Systems upon Failure Modes ……………………………………………………………………….92
4.4 Introduction and Examination of Theoretical Models for Void Formations ..93
4.4.1 Model of Void Propagation along the IMC/solder Interface …………...93
4.4.2 Model of Void Propagation along the UBM/IMC Interface ……………96
4.4.3 Verification and Modification of Models for void formations …………98
4.5 Local Melting of Solder Joints before the Melting Failure Stage …………101
4.6 Effect of Substrate Surface Finish Metallization on Void Formation ……..102
4.7 Effect of EM and TM on atom migration in joints of current only flow through the trace line ……………………………………………………………….102
Chapter 5 Conclusion …………………………………………………………….113
Chapter 6 Future Work …………………………………………………………...116
References ………………………………………………………………………..117
Appendix A List of symbols and units …………………………………………128
Appendix B Nomenclature ……………………………………………………..129

[1] European Union Waste in Electrical and Electronic Equipment（WEEE）Directive, 3rd Draft, May 2000.
[2] Japanese Ministry of Health and Welfare Waste Regulation on Un-Reusable Pb, June 1998.
[3] K. S. Kim, S. H. Hun, and K. Suganuma, ” Effects of intermetallic compounds on properties of Sn-Ag-Cu lead-free solderd joints,” Journal of Alloys and Compounds, Vol. 352, pp. 226-236, March, 2003.
[4] S. Ou and K. N. Tu, “ A Study of Electromigration in Sn3.5Ag and Sn3.8Ag0.7Cu Solder Lines,” Proceedings of the 55th Electronic Components and Technology Conference, Vol. 2, pp. 1445-1450, June, 2005.
[5] Electronic packaging program, http://elearning.stut.edu.tw/teach/electron/
[6] 蘇宗麟, “Sn-3.5Ag/Ag厚膜銲錫球格陣列構裝界面反應研究” , 國立台灣大學材料科學與工程學研究所博士論文,(2002).
[7] 羅金龍, “58Bi-42Sn無鉛銲料與球矩陣封裝鐘Au/Ni/Cu墊層界面反應之研究” , 國立中央大學化學工程與材料工程研究所碩士論文,(2001).
[8] P. V. Zant, “ Microchip Fabrication,” 4th edition, The McGraw-Hill Companies, Inc., 2000.
[9] 侯振棋, “Si/Ta/TaCu/Cu/Ni-P/Sn-Pb銲錫隆點之製作與可靠度研究” , 國立成功大學材料科學及工程學系研究所碩士論文,(2001).
[10] 王祥文, “電遷移效應對錫微結構影響之探討” , 國立中央大學化學工程與材料工程研究所碩士論文,(2002).
[11] 劉益銘, “電子構裝銦基無鉛銲錫與金厚膜及銀基板之界面反應研究” , 國立台灣大學材料科學與工程學研究所博士論文,(2001).
[12] National Electronics Manufacturing Initiative (NEMI). http://www.inemi.org/ cms/projects/ese/lf_hottopics.html
[13] 郭世明, “錫銀銅覆晶銲錫隆點之熱/電遷移研究” , 國立成功大學材料科學及工程學系研究所碩士論文,(2005).
[14] 許穎超, “錫銀銅無鉛銲錫電遷移之研究” , 國立交通大學材料科學及工程學研究所博士論文,(2005).
[15] 黃雄年, “覆晶銲料的電子遷移研究” , 國立中山大學機械與機電工程研究所碩士論文,(2004).
[16] H. B. Huntington, “ Diffusion in Solids: Recent Developments,” edited by A. S. Nowick and J. J. Burton, Academic Press, New York, pp. 303-352, 1975.
[17] T. Kwok, T. Nguyen, P. Ho, and S. Yip, Proceedings of the 25th IEEE International Reliability Physics Symposium, San Diego, California, April 7-9, p. 130, 1987.
[18] T. Kwok, T. Nguyen, P. Ho, and S. Yip, Proceedings of the 5th IEEE International VLSI Multilevel Interconnection Conference, Santa Clara, California, June 13-14, p. 252, 1988.
[19] K. N. Tu and K. Zeng, “ Reliability Issues of Pb-free Solder Joints in Electronic Packaging Technology,” Proceedings of the 52nd Electronic Components and Technology Conference, pp. 1194-1200, 2002.
[20] R. Yongsunthon, A. Stanishevsky, J. McCoy, and E. D. Williams, “Observation of current crowding near fabricated voids in gold lines,” Applied Physics Letters, Vol. 78, pp. 2661-2663, April, 2001.
[21] 林彥良, “覆晶接點於承載電子流下之失效機制之研究” , 國立中央大學化學工程與材料工程研究所博士論文,(2007).
[22] 蔡家銘, “覆晶接點於電子流作用下電遷移及熱遷移之研究” , 國立中央大學化學工程與材料工程研究所博士論文,(2006).
[23] B. Y. Wu and Y. C. Chan, “ Electric current effect on microstructure of ball grid array solder joint,” Journal of Alloys and Compounds, Vol. 392, pp. 237-246, 2005.
[24] J. S. Zhang, Y. C. Chan, Y. P. Wu, H. J. Xi, and F. S. Wu, “ Electromigration of Pb-free solder under a low level of current density,” Journal of Alloys and Compounds, Vol. 458, Issues 1-2, pp. 492-499, June, 2008.
[25] J. He and Z. Suo, “ Statistics of Electromigration Lifetime Analyzed Using a Deterministic Transient Model,” Stress-Induced Phenomena in Metallization:7th International Workshop, pp. 15-26, 2004.
[26] S. H. Chiu, S. W. Liang, C. Chen, D.J. Yao, Y.C. Liu, K.H. Chen, and S.H. Lin, “ Joule Heating Effect under Accelerated Electromigration in Flip-chip Solder Joints,” Proceedings of the 56th Electronic Components and Technology Conference, pp. 663-666, June, 2006.
[27] S. W. Liang, Y. W. Chang, T. L. Shao, Chih Chen, and K. N. Tu, “ Effect of three-dimensional current and temperature distributions on void formation and propagation in flip-chip solder joints during electromigration,” Applied Physics Letters, Vol. 89, pp. 0221171-0221173, July, 2006.
[28] M. O. Alam, Chris Bailey, B. Y. Wu, Dan Yang, and Y. C. Chan, “ High Current Density induced Damage Mechanisms in Electronic Solder Joints: A State-of-the-Art Review,” International Symposium on High Density packaging and Microsystem Integration, Shanghai, pp. 1-7, June, 2007.
[29] Y-S. Lai, C-W. Lee, Y-T. Chiu, and Y-H. Shao, “ Electromigration of 96.5Sn-3Ag-0.5Cu Flip-chip Solder Bumps Bonded on Substrate Pads of Au/Ni/Cu or Cu Metallization,” Proceedings of the 56th Electronic Components and Technology Conference, pp. 641-645, June, 2006.
[30] J. D. Wu, C. W. Lee, P. J. Zheng, and S. Li, “ Effects of Substrate Metallization on the Degradation of Flip Chip Interconnects under Electromigration,” Proceedings of the 9th Int’l Symposium on Advanced Packaging Materials: Processes, Properties and Interfaces, pp. 25-30, 2004.
[31] J. D. Wu, C. W. Lee, P. J. Zheng, J. C. B. Lee, and S. Li, “ Electromigration Reliability of SnAgxCuy Flip Chip Interconnects,” Proceedings of the 54th Electronic Components and Technology Conference, Vol. 1, pp. 961-967, June, 2004.
[32] J. D. Wu, P. J. Zheng, Kelly Lee, C. T. Chiu, and J. J. Lee, “ Electromigration Failures of UBM/Bump Systems of Flip-Chip Packages,” Proceedings of the 52nd Electronic Components and Technology Conference, pp. 452-457, May, 2002 .
[33] H. Balkan, D. Patterson, G. Burgess, C. Carlson, P. Elenius, M. Johnson, B. Rooney, J. Sanchez, D. Stepniak, and J. Wood, “ Flip-Chip Reliability: Comparative Characterization of Lead Free (Sn/Ag/Cu) and 63Sn/Pb Eutectic Solder,” Proceedings of the 52nd Electronic Components and Technology Conference, pp. 1263-1269, May, 2002.
[34] Y-S. Lai and Y-T. Chiu, ” Failure Mechanism of Sn-Ag-Cu Flip-chip Solder Joints with Different Cu Weight Contents Under Comparatively Low Current Stressing,” Proceedings of the 57th Electronic Components and Technology Conference, pp. 1462-1466, June, 2007.
[35] J. W. Nah, K. W. Paik, J. O. Suh, and K. N. Tu, “ Mechanism of electromigration-induced failure in the 97Pb-3Sn and 37Pb-63Sn composite solder joints,” Journal of Applied Physics, Vol. 94, pp. 7560-7566, December, 2003.
[36] K. Yamanaka, Y. Tsukada, and K. Suganuma, “ Electromigration effect on solder bump in Cu/Sn-3Ag-0.5Cu/Cu system,” Scripta Materialia, Vol. 55, pp. 867-870, November, 2006.
[37] Y. W. Chang, S. W. Liang, and C. Chen, “ Study of void formation due to electromigration in flip-chip solder joints using Kelvin bump probes,” Applied Physics Letters, Vol. 89, pp. 0321031-0321033, July, 2006.
[38] C. C. Lee, C. C. Lee, C. C. Chiu, K. M. Chen, F. Kuo, and K. N. Chiang, “ Electromigration Characteristic of SnAg3.0Cu0.5 Flip Chip Interconnection,“ Proceedings of the 56th Electronic Components and Technology Conference, pp. 1164-1169, June, 2006.
[39] T. Miyazaki and T. Omata, “ Electromigration degradation mechanism for Pb-free flip-chip micro solder bumps,” Microelectronics Reliability, Vol. 46, pp. 1898-1903, September-November, 2006.
[40] J-H. Lee, Y-D. Lee, Y-B. Park, S-T. Yang, M-S. Suh, Q-H. Chung, and K-Y. Byun, “ Joule Heating Effect on the Electromigration Lifetimes and Failure Mechanisms of Sn-3.5Ag Solder Bump,” Proceedings of the 57th Electronic Components and Technology Conference, pp. 1436-1441, June, 2007.
[41] S-H. Chae, X. Zhang, H-L. Chao, K-H. Lu, P. S. Ho, M. Ding, P. Su, T. Uehling, and L. N. Ramanathan, “ Electromigration Lifetime Statistics for Pb-Free Solder Joints with Cu and Ni UBM in Plastic Flip-Chip Packages,“ Proceedings of the 56th Electronic Components and Technology Conference, pp. 650-656, June, 2006.
[42] P. Su, M. Ding, T. Uehling, D. Wontor, and P. S. Ho, “ An Evaluation of Electromigration Performance of SnPb and Pb-free Flip Chip Solder Joints,” Proceedings of the 55th Electronic Components and Technology Conference, Vol. 2, pp. 1431-1436, June, 2005.
[43] T. Y. Lee, K. N. Tu, S. M. Kuo, and D. R. Frear, “ Electromigration of eutectic SnPb solder interconnects for flip chip technology,” Journal of Applied Physics, Vol. 89, pp. 3189-3194, March, 2001.
[44] T. Y. Lee, K. N. Tu, and D. R. Frear, “ Electromigration of eutectic SnPb and SnAg3.8Cu0.7 flip chip solder bumps and under-bump metallization,” Journal of Applied Physics, Vol. 90, pp. 4502-4508, November, 2001.
[45] Y. H. Lin, Y. C. Hu, C. M. Tsai, C. R. Kao, and K. N. Tu, “ In situ observation of the void formation-and-propagation mechanism in solder joints under current-stressing,” Acta Materialia, Vol. 53, pp. 2029-2035, April, 2005.
[46] K-L. Lin and S-M. Kuo, “ The Electromigration and Thermomigration Behaviors of Pb-free Flip Chip Sn-3Ag-0.5Cu Solder Bumps,” Proceedings of the 56th Electronic Components and Technology Conference, pp. 667-672, June, 2006.
[47] M-H. R. Jen, L-C. Liu, and J. D. Wu, “ Flip-Chip Ball Grid Array Lead-Free Solder Joint Under Reliability Test,” Journal of Electronic Package, Vol. 127, pp. 446-451, December, 2005.
[48] D. Li, C. Liu, and P. P. Conway, “ Characteristics of intermetallics and micromechanical properties during thermal ageing of Sn-Ag-Cu flip-chip solder interconnects,” Materials Science and Engineering A, Vol. 391, pp. 95-103, January, 2005.
[49] J-W. Nah and K-W. Paik, “ Investigation of Low Cost Flip Chip Under Bump Metallization(UBM) Systems on Cu Pads,” Proceedings of the 51st Electronic Components and Technology Conference, pp. 790-795, June, 2001.
[50] G. A. Rinne, “ Emerging Issues in the Physics and Control of Electromigration in SnPb and Pb-Free Solder Bumps,” Proceedings of the 53rd Electronic Components and Technology Conference, pp. 72-76, December, 2003.
[51] A. Kumar, M. He, Z. Chen, and P. S. Teo, “ Effect of electromigration on interfacial reactions between electroless Ni-P and Sn-3.5％ Ag solder,” Thin Solid Films, Vol. 462-463, pp. 413-418, September, 2004.
[52] W. Lei, W. Fengshun, Z. Jinsong, A. Bing, and W. Yiping, “ Effects of electromigration on IMC evolution in Pb-free solder joints,” International Conference on the Business of Electronic Product Reliability and Liability, pp. 47-49, April, 2004.
[53] Y-C Hsu, T-L Shao, and C. Chen, “ Electromigration induced failure in SnAg3.8Cu0.7 Solder Joints for Flip Chip Technology,” Proceedings of the 4th Int’l Symposium on Electronic Materials and Packaging, pp. 287-290, December, 2002.
[54] W. Yiping, Z. Jinsong, W. Fengshun, A. Bing, W. Boyi, and W. Lei, “ Effects of UBM Thickness on Electromigration in Pb-free Solder Joints.” Proceedings of the 54th Electronic Components and Technology Conference, Vol. 1, pp. 998-1002, June, 2004.
[55] W. J. Choi, E. C. C. Yeh, K. N. Tu, P. Elenius, and H. Balkan, “ Electromigration of Flip Chip Solder Bump on Cu/Ni(V)/Al Thin Film Under Bump Metallization,” Proceedings of the 52nd Electronic Components and Technology Conference, pp. 1201-1205, May, 2002.
[56] Y-S. Lai, K-M. Chen, C-W. Lee, C-L. Kao, and Y-H. Shao, “ Electromigration Reliability of Sn-37Pb and Sn-3Ag-1.5Cu/Sn-3Ag-0.5Cu Composite Flip-chip Solder Bumps with Ti/Ni(V)/Cu Under Bump Metallurgy,” Proceedings of the 7th Electronics Packaging Technology Conference, Vol. 2, pp. 786-791, December, 2005.
[57] K. N. Tu, “ Recent advances on electromigration in very-large-scale-integration of interconnects,” Journal of Applied Physics, Vol. 94, pp. 5451-5473, November, 2003.
[58] T. L. Shao, I. H. Chen, and C. Chen, “ Electromigration Failure Mechanism of Sn96.5Ag3.5 Flip-Chip Solder Bumps,” Proceedings of the 54th Electronic Components and Technology Conference, Vol. 1, pp. 979-982, June, 2004.
[59] B. Ebersberger, R. Bauer, and L. Alexa, “ Reliability of Lead-Free SnAg Solder Bumps: Influence of Electromigration and Temperature,” Proceedings of the 55th Electronic Components and Technology Conference, Vol. 2, pp. 1407-1415, June, 2005.
[60] H. Balkan, “ Flip Chip Electromigration: Impact of Test Conditions in Product Life Predictions,” Proceedings of the 54th Electronic Components and Technology Conference, Vol. 1, pp. 983-987, June, 2004.
[61] R. N. Master, R. C. Blish, D. Morken, and E. Adem, “ Kinetics of C4 Bump Degradation in Overly Aggressive HTOL,“ Proceedings of the 50th Electronic Components and Technology Conference, pp. 60-63, May, 2000.
[62] H. Gan and K. N. Tu, “ Effect of Electromigration on Intermetallic Compound Formation in Pb-free Solder-Cu Interfaces,” Proceedings of the 52nd Electronic Components and Technology Conference, pp. 1206-1212, May, 2002.
[63] Y. C. Hu, S. W. Wan, and C. R. Kao, “ Electromigration in Tin Thin Film, “ Proceedings of the 4th International Symposium on Electronic Materials and Packaging, pp. 463-467, December, 2002.
[64] Y-M. Kwon and K-W. Paik, “ Electromigration of Pb-Free Solder Flip Chip Using Electroless Ni-P/Au UBM,” Proceedings of the 57th Electronic Components and Technology Conference, pp. 1472-1477, June, 2007.
[65] M. Amagai, M. Watanabe, M. Omiya, K. Kishimoto, and T. Shibuya, “ Mechanical characterization of Sn–Ag-based lead-free solders,” Microelectronics Reliability, Vol. 42, pp. 951-966, June, 2002.
[66] K-S. Kim and K. Suganuma,” Development of new Sn-Ag-Cu lead-free solders containing fourth elements,” Proceedings of the 3rd International Symposium on Environmentally Conscious Design and Inverse Manufacturing, pp. 414-415, December, 2003.
[67] A. Sharif, M.N. Islam, and Y.C. Chan, “ Interfacial reactions of BGA Sn–3.5%Ag–0.5%Cu and Sn–3.5%Ag solders during high-temperature aging with Ni/Au metallization,” Materials Science and Engineering B, Vol. 113, pp. 184-189, November, 2004.
[68] R. N. Master, A. Marathe, V. Pham, and D. Morken, “ Electromigration of C4 bumps in Ceramic and Organic Flip-Chip Packages,” Proceedings of the 56th Electronic Components and Technology Conference, pp. 646-649, June, 2006.
[69] C-L. Kao and Y-S. Lai, “ Electrothermal Coupling Analysis of Current Crowding and Joule Heating in Flip-chip Package Assembly,” Proceedings of the 54th Electronics Packaging Technology Conference, pp. 254-258, December, 2004.
[70] J. W. Nah, J. O. Suh, K. W. Paik, and K. N. Tu, “ Effects of current density on electromigration-induced failure in flip chip composite solder joints at room temperature,” Proceedings of the 10th International Symposium on Advanced Packaging Materials: Processes, Properties and Interfaces, pp. 50-53, March, 2005.
[71] W. Lei, W. Fengshun, W. Yiping, and Z. Jinsong, “ The Effect of Current Crowding on Electromigration in Lead-free Flip Chip Bump Interconnect,” Proceeding of the 6th IEEE CPMT Conference on High Density Microsystem Design and Packaging and Component Failure Analysis, pp. 224-226, July, 2004.
[72] Z. Jinsong, W. Fengshun, W. Lei, and W. Yiping, “ Effect of current density and geometry structure on Pb-free solder joints electromigration,” Proceedings of International IEEE Conference on Asian Green Electronics, pp. 77-80, 2004.
[73] G. A. Rinne, “ Electromigration in SnPb and Pb-Free Solder Bumps,” Proceedings of the 54th Electronic Components and Technology Conference, Vol. 1, pp. 974-978, June, 2004.
[74] K. N. Tu and K. Zeng, “ Reliability Issues of Pb-free Solder Joints in Electronic Packaging Technology,” Proceedings of the 52nd Electronic Components and Technology Conference, pp. 1194-1200, May, 2002.
[75] Lingyun Zhang, Shengquan Ou, Joanne Huang, K.N. Tu, Stephen Gee, and Luu Nguyen, “ Effect of current crowding on void propagation at the interface between intermetallic compound and solder in flip chip solder joints,” Applied Physics Letters, Vol. 88, pp. 0121061-0121063, 2006.
[76] F. M. d’Heurle, A. Gangulee, C. F. Aliotta, and V. A. Ranieri, “ Electromigration of Ni in Al thin-film conductors,” Journal of Applied Physics, Vol. 46, pp. 4845-4846, November, 1975.
[77] Luhua Xu, John H. L. Pang, and K. N. Tu, “ Effect of electromigration-induced back stress gradient on nanoindentation marker movement in SnAgCu solder joints,” Applied Physics Letters, Vol. 89, pp. 2219091-2219093, 2006.
[78] Seung-Hyun Chae, Brook Chao, Xuefeng Zhang, Jay Im, and Paul S. Ho, “ Investigation of Intermetallic Compound Growth Enhanced by Electromigration in Pb-Free Solder Joints,” Proceedings of the 57th Electronic Components and Technology Conference, Reno, NV, pp. 1442-1449, 2007.
[79] Kimihiro Yamanaka, Yutaka Tsukada, Katsuaki Suganuma, “ Studies on solder bump electromigration in Cu/Sn–3Ag–0.5Cu/Cu system,” Microelectronics Reliability, Vol. 47, pp. 1280-1287, 2007.
[80] D. Yang, Y. C. Chan, and K. N. Tu, “ The time-dependent melting failure in flip chip lead-free solder interconnects under current stressing,” Applied Physics Letters, Vol. 93, pp. 0419071-0419073, 2008.
[81] Jae-Woong Nah, J. O. Suh, K. N. Tu, Seung Wook Yoon, Chai Tai Chong, V. Kripesh, B. R. Su, and Chih Chen, “ Electromigration in Pb-free Solder Bumps with Cu Column as Flip-Chip Joints,” Proceedings of the 56th Electronic Components and Technology Conference, pp. 657-662, 2006.
[82] Hsiang-Yao Hsiao and Chih Chen, “ Thermomigration in flip-chip SnPb solder joints under alternating current stressing,” Applied Physics Letters, Vol. 90, pp. 1521051-1521053, 2007.
[83] Yi-Shao Lai, Kuo-Ming Chen, Chin-Li Kao, Chiu-Wen Lee, and Ying-Ta Chiu, “ Electromigration of Sn-37Pb and Sn-3Ag-1.5Cu/Sn-3Ag-0.5Cu composite flip-chip solder bumps with Ti/Ni(V)/Cu under bump metallurgy,” Microelectronics Reliability, Vol. 47, Issue 8, pp. 1273-1279, August, 2007.
[84] Yi-Shao Lai and Ying-Ta Chiu,” Failure Mechanism of Sn-Ag-Cu Flip-chip Solder Joints with Different Cu Weight Contents Under Comparatively Low Current Stressing,” Proceedings of the 57th Electronic Components and Technology Conference, Reno, NV, pp. 1462-1466, 2007.