本研究目的在探討冷卻速率差異對不同Ag含量(Ag=0, 1.5, 2.0, 3.0)之Sn-xAg-0.7Cu無鉛銲料組織形貌之影響，不同冷卻速率造成其金屬間化合物Ag3Sn與Cu6Sn5形貌產生變化，利用拉伸試驗及硬度測試與標準商用試件SAC305進行比較與分析，最後利用150℃x225h高溫時效後之變化來評估不同冷卻速率下，降低Ag含量並提高冷卻速率取代原本業界常用SAC305無鉛銲料之可行性。

研究結果顯示，冷卻速率對Cu6Sn5凝固成長時間有顯著的影響，快速冷卻條件下，Ag3Sn與Cu6Sn5皆為1μm以下之細小顆粒狀，隨著冷卻速率降低，Cu6Sn5開始呈現粗大化，經高溫時效後因Ag3Sn較Cu6Sn5穩定，Ag3Sn顆粒沒有明顯變化，大小皆小於2μm，而Cu6Sn5則會聚集成大顆團塊狀，大至20μm以上皆可發現，使得原本細緻的網狀共晶組織形貌瓦解。拉伸強度因散布強化及細晶強化的效果，隨著Ag含量增加以及冷卻速率的提升而上升，強度及韌性值明顯優於SAC305，但經高溫時效後，團塊狀之Cu6Sn5析出物易造成組織上的不連續，成為缺陷所在，裂紋可能由此產生開裂，導致拉伸強度下降20-30MPa左右，表現皆不如SAC305銲料。

綜合本研究結果，冷卻速率及Ag含量對化合物形貌及拉伸強度皆有顯著的影響，快速冷卻條件下，SAC207具有優異的強度及韌性，在高溫時效後其表現亦可與SAC305比擬，故判定其有取代SAC305之潛力。

The effect of the different cooling rates on morphological evolution of the Ag3Sn and Cu6Sn5 formed during the solidification of SAC307、SAC207、SAC157 and SC07 solder was investigated. The tensile tests and hardness tests were used to compare with SAC305. Finally, the high temperature storage at 150℃ until 225hours was used to evaluate the feasibility of low Ag contained SAC solders to replace the SAC305 solder with the aid of raising cooling rate.

Experimental result showed that cooling rate has a significant effect on the solidification time, and therefore influences the size and the morphology of the eutectic Cu6Sn5. The Ag3Sn and Cu6Sn5 were fine particle-like at rapid cooling rate. As cooling rate was reduced, Cu6Sn5 ware coarsened. The Ag3Sn ware more stable than the Cu6Sn5 during high temperature storage. So the Ag3Sn particles were smaller than 2μm and the Cu6Sn5 particles were coarsened to more than 20μm. Consequently, cracking were easy to form and propagate. The tensile strength was reduced as well by fast cooling. The tensile strength and the toughness of low Ag contained SAC solders were higher than SAC305 solder by fast cooling. However, the tensile strength decrease 20-30MPa and the compound coarsened apparently after the high temperature storage. As the result, such the large and brittle primary compounds are harmful to the strength and toughness of the solders.

In the summary, Ag content and cooling rate have influences on morphological evolution and tensile strength. SAC207 solder with rapid cooling has excellent strength and toughness and comparable to SAC305 solder even after high temperature storage.

[1] R.R. Tummala, "Fundamentals of microsystems packaging," McGraw-Hill International Edition, Ch. 7, pp. 266-294, 2001.
[2] 陳怡靜, "脈衝式YAG雷射應用於共晶錫球無助銲劑迴銲接合之研究," 國立交通大學材料研究所, 碩士論文, 2005.
[3] 金拓(Kitco)貴重金屬交易網站(http://www.kitco.com).
[4] Y. Tsai, and W. Hwang, "Solidification behavior of Sn-9Zn-xAg lead-free solder alloys," Materials Science and Engineering: A, Vol. 413, pp. 312-316, 2005.
[5] T. Chang, M. Wang, and Min-Hsiung Hon, "Effect of Ag addition on the structures of intermetallic compounds and the adhesion strength of the Sn-9Zn-xAg/Cu interface," Journal of Crystal Growth, Vol. 252, pp. 391-400, 2003.
[6] NC254 SAC 305, Manufacturing and Distribution Worldwide.
[7] X. Deng, N. Chawla, K.K. Chawla, and M. Koopman, "Deformation behavior of (Cu,Ag)-Sn intermetallics by nanoindentation," Acta Materialia, Vol. 52, pp. 4291-4303, 2004.
[8] A. Molnar, D. Janovszky, I. Kardos, I. Molnar, and Z. Gacsi, "Effect of Ag and Pb Addition on Microstructural and Mechanical Properties of SAC 105 Solders," Journal of Electronic Materials, 2015.
[9] R.R. Chromik, R.P. Vinci, S.L. Allen, and M.R. Notis, "Measuring the Mechanical Properties of Pb-Free Solder and Sn-Based Intermetallics by Nanoindentation," JOM, pp. 66-69, 2003.
[10] A.A. El-Daly, Farid El-Tantawy, A.E. Hammad, M.S. Gaafar, E.H. El-Mossalamy, and A.A. Al-Ghamdi, "Structural and elastic properties of eutectic Sn-Cu lead-free solder alloy containing small amount of Ag and In," Journal of Alloys and Compounds, Vol. 509, pp. 7238-7246, 2011.
[11] 陳曉薇, "溫度與應變速率對Sn-Ag基底銲點結合強度影響之研究," 國立成功大學機械研究所, 碩士論文, 2009.
[12] 胡順源, "Sn-Ag-xSb無鉛銲錫接點與Au/Ni-P/Cu金屬層之界面微結構與剪切強度研究," 國立成功大學機械研究所, 碩士論文, 2003.
[13] F. Ochoa, X. Deng, and N. Chawla, "Effects of cooling rate on creep behavior of a Sn-3.5 Ag alloy," Journal of Electronic Materials, Vol. 33 (12), pp. 1596-1607, 2004.
[14] F. Ochoa, J. Williams, and N. Chawla, "Effects of cooling rate on the microstructure and tensile behavior of a Sn-3.5 wt.% Ag solder," Journal of Electronic Materials, Vol. 32(12), pp. 1414-1420, 2003.
[15] Y.F. Chen, "Evolution of Ag3Sn intermetallic compounds during solidification of eutectic Sn-3.5Ag solder," Journal of Alloys and Compounds, Vol. 509, pp. 2510-2521, 2011.
[16] 林冠宇, "冷卻速率對Sn-Ag-Cu無鉛銲料Ag3Sn形貌及拉伸強度之研究," 國立成功大學機械研究所, 碩士論文, 2010.
[17] 張銘峰, "冷卻速率對Sn-Ag-Cu無鉛銲料之組織微結構變化之研究, " 國立成功大學機械研究所, 碩士論文, 2011.
[18] K.N. Subramanian, "Lead-free solders: materials reliability for electronics," John Wiley & Sons, Ch. 5, pp. 122-134, 2012.
[19] H. Baker, and H. Okamoto, "Alloy phase diagrams," ASM International, ASM Handbook, Vol. 3, pp. 501-502, 1992.
[20] K. Suganuma, S.H. Huh, K. Kim, H. Nakase, and Y. Nakamura, "Effect of Ag content on properties of Sn-Ag binary alloy solder," Materials Transactions-JIM, Vol. 42(2), pp. 286-291, 2001.
[21] K. Kim, S. Huh, and K. Suganuma, "Effects of cooling speed on microstructure and tensile properties of Sn-Ag-Cu alloys," Materials Science and Engineering: A, Vol. 333(1-2), pp. 106-114, 2002.
[22] K.S. Kim, S.H. Huh, and K. Suganuma, "Effects of Intermetallic Compounds on Properties of Sn-Ag-Cu Lead-free Soldered Joints," Journal of Alloys and Compounds, vol. 325, pp. 226-236, 2003.
[23] D. Frear, D. Grivas, and J.W.M. Jr., "The Effect of Cu6Sn5 Whisker Precipitates in Bulk 60Sn-40Pb Solder," Journal of Electronic Materials, Vol. 16, pp. 181-186, 1987.
[24] J.C. Foley, A. Gickler, F.H. Leprovost, and D. Brown, "Analysis of Ring and Plug Shear Strengths for Comparison of Lead-Free Solders," Journal of Electronic Materials, Vol. 29, pp. 1258-1263, 2000.
[25] 陳明宏, "添加Sb對Sn-Ag無鉛銲料銲點冶金性質與機械性質之研究," 國立成功大學機械研究所, 博士論文, 2003.
[26] M. Abtew and G. Selvaduray, "Lead-free Solders in Microelectronics," Materials Science and Engineering: R: Reports, Vol. 27(5-6), pp. 95-141, 2000.
[27] W. Zhai, W.L. Wang, D.L. Geng, and B. Wei, "A DSC analysis of thermodynamic properties and solidification characteristics for binary Cu-Sn alloys," Acta Materialia, Vol. 60, pp. 6518-6527, 2012.
[28] J. Shen, Y. Liu, and H. Gao, "Formation of bulk Cu6Sn5 intermetallic compounds in Sn-Cu lead-free solders during solidification," Journal of Materials Science, Vol. 42, pp. 5375-5380, 2007.
[29] M. Reid, J. Punch, M. Collins, and C. Ryan, "Effect of Ag content on the microstructure of Sn-Ag-Cu based solder alloys," Soldering & Surface Mount Technology, Vol. 20, pp. 3-8, 2008.
[30] D. Swenson, "The effects of suppressed beta tin nucleation on the microstructural evolution of lead-free solder joints," Journal of Alloys and Compounds, Vol. 509, pp. 6276-6279, 2006.
[31] S.K. Kang, W.K. Choi, D.Y. Shih, D.W. Henderson, T. Gosselin, A. Sarkhel, C. Goldsmith, and K.J. Puttlitz, "Ag3Sn Plate Formation in the Solidification of Near-Ternary Eutectic Sn-Ag-Cu," Journal of the Minerals, Metals and Materials Society, Vol. 55, pp. 61-65, 2003.
[32] A.A. El-Daly, A.E. Hammada, A. Fawzy, and D.A. Nasrallh, "Microstructure, mechanical properties, and deformation behavior of Sn-1.0Ag-0.5Cu solder after Ni and Sb additions," Materials and Design, Vol. 43, pp. 40-49, 2012.
[33] L. Wang, F. Sun, Y. Liu, and L. Wang, "Effect of Ni addition on the Sn-0.3Ag-0.7Cu solder joints," ICEPT-HDP, pp. 830-833, 2009.
[34] L. Yang, S. Fenglian, and L. Xiaojing, "Improving Sn-0.3Ag-0.7Cu Low-Ag Lead-free Solder Performance by Adding Bi Element," IFOST Proceseeding, pp. 1-4, 2010.
[35] K. Kanlayasiri, and T. Ariga, "Influence of thermal aging on microhardness and microstructure of Sn-0.3Ag-0.7Cu-xIn lead-free solders," Journal of Alloys and Compounds, Vol. 504, pp. 15-19, 2010.
[36] K. Lu and M.L. Sui, "An Explanation To The Abnormal Hall-Petch Relation In Nanocrystalline Materials," Scripta Metallurgica et Materialia, Vol. 28, pp. 1465-1470, 1993.
[37] R.S. Mishra, Z.Y. Ma, I. Charit, "Friction stir processing: a novel technique for fabrication of surface composite," Materials Science and Engineering: A, Vol. 341, pp. 307-310, 2003.
[38] R.Z. Valiev, R.K. Islamgaliev, and I.V. Alexandrov, "Bulk nanostructured materials from severe plastic deformation," Progress in materials science 45, pp. 103-104, 2000.
[39] Kurz, W. Fisher, and D.J., "Fundamentals of Solidification," 4th rev. ed., 1998.
[40] K. Jackson and J. Hunt, "Lamellar and rod eutectic growth," AIME Met. Soc. Trans., Vol. 236, pp. 1129-1142, 1966.
[41] K.W. Moon, W.J. Boettinger, U.R. Kattner, F.S. Biancaniello, and C.A. Handwerker, "Experimental and Thermodynamic Assessment of Sn-Ag-Cu Solder Alloys," Published in J. Electron. Mater. 29, pp. 1122-1236, 2000.
[42] L. Snugovsky, P. Snugovsky, D.D. Perovic, and J.W. Rutter, "Effect of Cooling Rate on Microstructure of Ag-Cu-Sn Solder Alloys," Materials Science and Technology, Vol. 21(1), pp. 61-68, 2005.
[43] http://www.jedec.org/, Joint Electron Device Engineering Council(JEDEC).
[44] Weipeng Zhang, Bingge Zhao, Changdong Zou, Qijie Zhai, Yulai Gao, and Steve F. A. Acquah, "Investigating the Formation Process of Sn-Based Lead-Free Nanoparticles with a Chemical Reduction Method," Journal of Nanomaterials, No. 6, 2013.
[45] Changdong Zou, Yulai Gao, Bin Yang, and Qijie Zhai, "Nanoparticles of Sn3.0Ag0.5Cu alloy synthesized at room temperature with large melting temperature depression," Journal of Materials Science: Materials in Electronics, Vol. 23, pp. 2-7, 2012.
[46] A.A. El-Daly, T.A. Elmosalami, W.M. Desoky, M.G. El-Shaarawyb, and A.M. Abdraboh, "Tensile deformation behavior and melting property of nano-sized ZnO particles reinforced Sn-3.0Ag-0.5Cu lead-free solder," Materials Science and Engineering: A, Vol. 618, pp. 389-397, 2014.
[47] M.H. Mahdavifard, M.F.M. Sabri, D.A. Shnawaha, S.M. Saidb, I.A. Badruddina, and S. Rozali, "The effect of iron and bismuth addition on the microstructural, mechanical, and thermal properties of Sn-1Ag-0.5Cu solder alloy," Microelectronics Reliability, 2015.
[48] Xiao Yu, Xiaowu Hu, Yulong Li, and Ruhua Zhang, "Effect of alloying Cu substrate on microstructure and coarsening behavior of Cu6Sn5 grains of soldered joints," Journal of Materials Science: Materials in Electronics, 2015.
[49] N.C. Lee, "Reflow Soldering Processes," Newnws, Ch. 9, pp. 189-213, 2009.