軟銲是電子構裝中最主要之連接技術。銲點會因化學勢差異，引起銲料與基材原子間的相互擴散，於界面上生成介金屬化合物。無鉛銲料是電子構裝產業中最熱門的課題，以純Sn、Sn-3.0wt.%Ag-0.5wt.%Cu與Sn-9wt.%Zn為主之無鉛銲料，工業界應用上也越來越廣泛。近年來，覆晶技術受到極大的重視，而Ni-Mo基材也可被用來作為UBM阻障層，以避免銲料直接與線路發生反應。雖然不同銲料和Ni基材的反應之前就已被研究過，但是文獻中還是缺乏加入不同Mo含量的研究。然而，由於金屬Mo本身具有極高的熔點，熱穩定性佳，在UBM材料選擇上應為一不錯阻障層金屬或合金材料。故本研究將著重在探討純Sn、Sn-3.0wt.%Ag-0.5wt.%Cu、Sn-9wt.%Zn三種無鉛銲料分別與5種不同濃度組成之Ni-Mo基材，反應溫度240、255與270℃下，以反應偶形式在反應時間1、2、3、4小時，探討其界面反應後之IMC種類與形態、反應機制、動力學、成長速率常數與反應活化能。以期能對以Ni-Mo合金作為阻障層之銲接應用，提供業界重要的參考資料。
純Sn銲料系統生成Ni3Sn4介金屬化合物。SAC銲料系統在240℃時，生成Cu6Sn5與Ni3Sn4兩介金屬化合物；但在255與270℃時，就只生成Ni3Sn4介金屬化合物。Sn-9Zn銲料系統生成Ni5Zn21介金屬化合物。各組IMC厚度大小依序是：Sn-3.0Ag-0.5Cu>Sn>Sn-9Zn。IMC厚度會隨著反應時間平方根的增加呈現線性關係，符合動力學上的拋物線定律，溫度越高IMC厚度也越厚。成長速率常數k，隨著Mo含量的增加與反應溫度的上升而變大，依序是：Sn-3.0Ag-0.5Cu>Sn>Sn-9Zn。反應活化能Q，則隨著Mo含量的增加而減少，大小依序是：Sn>Sn-3.0Ag-0.5Cu >Sn-9Zn。

Soldering is the best most dominant technology used in the electronic packaging. Interdiffusion of atoms of solder and substrates occurs at the joints to the chemical potential gradient. Most often intermetallic compounds form as well. Lead-free solders as Sn, SAC and Sn-9Zn have attracted extensive studies recently. In recent years, the flip-chip technique plays an important role. Ni-Mo can be used as the barrier layer material in the under bump metallurgy in the microelectronic industry in order to avoid the reactions of solders and circuits. Although interfacial reactions between various solders with the nickel substrate have been investigated intensively, the effects of molybdenum addition upon the solder/(Ni, Mo) interfacial reactions have not been studies. It seems that molybdenum are high melting point, thermal stability well and good barrier in UBM structure. The interfacial reactions of Sn/Ni-Mo, SAC/Ni-Mo and Sn-9Zn/Ni-Mo at different 240, 255, and 270℃ were investigated in the study using the reaction couple technique. The molybdenum contents of the Ni-Mo substrates examined in the study are 0.5, 0.7, 1.0, 2.0 and 2.5wt% and the reaction time is 1, 2, 3 and 4 hours.
For the Sn/Ni-Mo system, Ni3Sn4 layer forms at the interface. For the SAC/Ni-Mo system, Ni3Sn4 and Cu6Sn5 layers form at 240℃. However, Ni3Sn4 layer only forms at different 255 and 270℃. For the Sn-9Zn/Ni-Mo system, Ni5Zn21 layer forms at the interface. The intermetallic compounds of both Ni and Mo in molten solders is Sn-3.0Ag-0.5Cu > Sn > Sn-9Zn. The intermetallic compounds of metallic substrates increases with increasing temperature, and it exhibits approximately linear increasing with increasing longer reaction time to fit in with kinetics of interfacial reaction. The growth rate constant k increases with the more content of molybdenum and higher temperature, and the growth of intermetallic compounds is also described by using the parabolic law. The growth rate constant of both Ni and Mo in molten solders is Sn-3.0Ag-0.5Cu > Sn> Sn-9Zn. On the contrary, reaction energy Q decreases with the addition of molybdenum and its value is Sn > Sn-3.0Ag-0.5Cu > Sn-9Zn.

1.D. R. Frear and P. T. Vianco, “Intermetallic growth and mechanical behavior of low and high melting temperature solder alloys”, Metallurgical Transactions A, Vol. 25A, pp. 1509 (1994).
2.B. Trumble, J. Brydges, “Technical progress on printed wired assembly using Nortel's no-lead solder assembly process”, IEEE International Symposium on Electronics & the Environment, pp. 112-116 (1998).
3.D. R. Frear, J. W. Jang, J. K. Lin, C. Zhang, P. T. Vianco, and D. R. Frear, ”Pb-free solders for flip-chip interconnects”, Journal of Materials, Vol. 53, pp. 28-38 (2001).
4.D. R. Frear, J. W. Jang, J. K. Lin, and C. Zhan, “Solders for flip-chip interconnects”, Journal of Materials, Vol. 53, pp. 28-38 (2001).
5.L. Hymes, Electronic Materials Handbook, Vol. 1 Packaging, ASM International, Materials Park, Ohio (1989).
6.D. R. Smith and A. R. Flegal, AMBIO (1995).
7.C. C. Chen, S. W. Chen and C. Y. Kao, “Interfacial reactions in the Sn-(Ag)/(Ni,V) couples and phase equilibria of the Sn-Ni-V system at the Sn-rich corner”, Journal of Electronic Materials, Vol. 35, pp. 922-928 (2006).
8.M. Li, F. Zhang, W. T. Chen, K. Zeng, K. N. Tu, H. Balkan and P. Elenius, “Interfacial microstructure evolution between eutectic SnAgCu solder and Al/Ni(V)/Cu thin films”, Journal of Materials Research, Vol. 17, pp. 1612-1621 (2002).
9.T. Laurila, V. Vuorinen and J. K. Kivilahti, “Interfacial reactions between lead-free solders and common base materials”, Materials Science and Engineering, Vol. 49, pp. 1-60 (2005).
10.J. D. Plummer, M. D. Deal, and P. B. Griffin, Silicon VLSI Technology : Fundamentals, Practice and Modeling, Prentice Hall, Inc., New Jersey, Chap. 2. (2001).
11.M. Abtew and G. Selvaduray, “Lead-free solders in microelectronics”, Materials Science and Engineering. R, Vol. 27, No. 5-6, pp. 95-141. (2000).
12.M. R. Pinnel and W. H. Knausenberger, “Interconnection system requirements and modeling”, AT&T Technical Journal, Vol. 66, No. 4, pp. 45-56 (1987).
13.D. P. Seraphim, R. C. Lasky, and C. Y. Li, Principles of Electronic Packaging, McGraw-Hill, Inc., pp. 3 (1989).
14.R. R. Tummala, E. J. Rymaszewaki and A. G. Klopfenstein, “Microelectronics Packaging Handbook”, Chapman & Hall, New York (1997).
15.田民波著、顏怡文修訂，半導體電子元件構裝技術，五南圖書出版社，台北 (2005)。
16.K. Yokomine, N. Shimizu, Y. Miyamoto, Y. Iwata, D. Love and K. Newman, “Development of electronics Ni/Au plated build-up flip chip package with highly reliable solder joints”, Proceedings-Electronic Components & Technology Conference, pp. 1384-1392 (2001).
17.Y. D. Jeon, S. Nieland, A. Ostmann, H. Reichl and K. W. Paik, “A study on interfacial reactions between electroless Ni-P under bump metallization and 95.5Sn-4.0Ag-0.5Cu alloy”, Journal of Electronic Materials, Vol. 32, pp. 548-557 (2003).
18.M. Li, F. Zhang, W. T. Chen, K. Zeng, K. N. Tu, H. Balkan and P. Elenius, “Interfacial microstructure evolution between eutectic SnAgCu solder and Al/Ni(V)/Cu thin films”, Journal of Materials Research, Vol. 17, pp. 1612-1621 (2002).
19.T. Laurila, V. Vuorinen and J. K. Kivilahti, “Interfacial reactions between lead-free solders and common base materials”, Materials Science and Engineering, Vol. 49, pp. 1-60 (2005).
20.T. B. Massalski, Binary Alloy Phase Diagrams, William W. Scott, Vol. 2, pp. 1848 (1986).
21.H. H. Manko, Solders and Soldering, 2nd Edn., McGraw-Hill, New York, Chap. 3, pp. 55-153 (1979)
22.J. S. Hwang, Solder Paste in Electronics Packaging, Van Nostrand Reinhold, New York, Chap. 4, pp. 71-121 (1992)
23.B. Trumble, “Get the Lead Out!”, IEEE Spectrum, Vol. 35, No. 5, pp. 55-60 (1998).
24.D. R. Frear, J. W. Jang, J. K. Lin, and C. Zhang, JOM, “Pb-free solders for flip-chip interconnects”, Journal of Materials, Vol. 53(6), pp. 28-32 (2001).
25.S. K. Kang and A. K. Sarkhel, “Lead (Pb)-free solders for electronic packaging”, Journal of Electronic Materials, Vol. 23(8), pp. 701-701 (1994).
26.W. J. Plumbridge, “Solders in electronics”, Journal of Materials Science, Vol. 31, pp. 2501-2514 (1996).
27.F. W. Gayle, G. Becka, J. Badgett, G. Whitten, T. Y. Pan, A. Grused, B. Bauer, R. Lathrop, J. Slattery, I. Anderson, J. Foley, A. Gickler, D. Napp, J. Mather, and C. Olson, “High temperature lead-free solder for microelectronics”, Journal of Materials, Vol. 53(6) pp. 17-21 (2001).
28.N. C. Lee, “Getting reading for lead-free solder”, Soldering ＆Surface Mount Technology, Vol. 9, pp. 65-69 (1997).
29.J. Glazer, “Metallurgy of low temperature Pb-free solders for electronic assembly”, International Materials Reviews, Vol. 40, No.2, pp. 65-93 (1995).
30.United States Environmental Protection Agency, “Emergency laning and Community Right-to-Know Act-Section 313: Guidance for Reporting Releases and Other Waste Management Quantities of Toxic Chemicals: Lead and Lead Compounds”, USEPA 260-B-01-027 (2001).
31.T. B. Massalski, Binary Alloy Phase Diagrams, William W. Scott, Vol. 1, pp. 71 (1986).
32.C. Lea. A, Scientific Guide to Surface Mount Technology, Electrochemical Publication Ltd., GB-Port Erin, British Isles, pp. 378-379 (1989).
33.S. Choi, J. G. Lee, F. Guo, T. R. Bieler, K. N. Subramanian, and J. P. Lucas, “Creep properties of Sn-Ag solder joints containing intermetallic particles”, Journal of Materials, Vol. 53(6), pp. 22-26 (2001).
34.K. N. Tu, J. C. M. Li, “Spontaneous whisker growth on lead-free solder finishes”,Materials Chemistry and Physics, Vol. 409, pp. 131-139 (2005).
35.G. T. T. Sheng, W. J. Choi, T. Y. Lee, K. N. Tu, N. Tamura, R.S. Celestre, A. A. MacDowell, Y. Y, Bong. L. Nguyen, Proceedings-Electronic Components and Technology Conference, pp. 628-633 (2002).
36.T. B. Massalski, Binary Alloy Phase Diagrams, William W. Scott, Vol. 1, pp. 965 (1986).
37.A. G. Robert. and E.F. Morris, “Growth of η-phase scallops and whisker in liquid tin-solid copper reaction couples”, Journal of Materials, Vol. 53, No. 6, pp. 33-38 (2001).
38.K. N. Tu, “Cu/Sn interfacial reactions: thin-film case versus bulk case”, Materials Chemistry and Physics, Vol. 46, No. 2-3, pp. 217-223 (1998).
39.K. S. Kim, S. H. Huh and K. Suganuma, “Effects of fourth alloying additive on microstructures and tensile properties of Sn-Ag-Cu alloy and joints with Cu”, Microelectronics Reliability, Vol. 43, No. 2, pp. 259-267 (2003).
40.M. O. Alam, Y. C. Chan, K. N. Tu, “Effect of 0.5wt.% Cu addition in Sn-3.5Ag% solder on the dissolution rate of Cu metallization”, Journal of Applied Physics, Vol. 94, No. 12, pp. 7904-7909 (2003).
41.M. Nishiura, A. Nakayama, S. Sakatani, Y. Kohara, K. Uenishi, and K. F. Kobayashi, “Mechanical strength and microstructure of BGA joints using lead-free solders”, Mat. Trans., Vol. 43, No. 8, pp. 1802-1807 (2002).
42.T. B. Massalski, Binary Alloy Phase Diagrams, William W. Scott, Vol. 2, pp. 2086 (1986).
43.De Kluizenaar, and E. E., “Surface oxidation of molten soft solder: an auger study”, Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, Vol. 1, No. 3, pp. 1480-1485 (1983).
44.M. McCormack, and S. Jin, “Progress in the design of new lead-free solders”, Journal of Materials, Vol. 45, No. 7, pp. 36-40 (1993).
45.S. Vaynman and M. E. Fine, “Development of flux for lead-free solders contain zinc”, Scripta Materialia, Vol. 41, No. 12, pp. 1269–1271 (1999).
46.B. K. Prasad, “Microstructure and tensile property characterization of a nickel-containing zinc-based alloy: effects of heat treatment and test conditions”, Materials Science and Engineering, Vol. 277, pp. 95-101 (2000).
47.L. H. Su, Y. W. Yen, C. C. Lin, and S. W. Chen,” Interfacial reactions in molten Sn/Cu and molten In/Cu couples”, Matallurgical and Materials Transactions B, Vol. 28B, pp. 927-934 (1997).
48.Kodentsov AA, Bastin GF, van Loo FJJ, “The diffusion couple technique in phase diagram determination”, Journal of alloys and compounds, Vol. 320(2), pp. 207-217 (2001).
49.顏怡文, “銀-錫/銅與銀-錫/金系統之相平衡與界面反應的研究”, 國立清華大學化學工程學系博士論文 (2002).
50.K. N. Tu, “Cu/Sn Interfacial Reactions: Thin-film case versus bulk case”,Mat. Chem. and Phys., Vol. 46, pp. 217-223 (1996).
51.S. Bader, W. Gust, and H. Hieber, “Rapid formation of intermetallic compounds by interdiffusion in the Cu-Sn and Ni-Sn systems”, Acta Metall. Mater., Vol. 43, pp. 329-337 (1995).
52.A. Hayashi , C. R. kao, and Y. A. Chang, ”Reactions of solid copper with pure liquid tin and liquid tin saturated with copper”, Scripta Materialia, Vol.37, No.4, pp. 393-398 (1997).
53.S. K. Kang and V. Ramachandran, “Growth kinetics of intermetallic phases at the liquid Sn and solid Ni interface” Scripta Metallurgica, Vol.14, pp. 421- 424 (1980).
54.K. Suganuma, “Advances in lead-free electronics soldering”, Current Opinion in Solid State and Materials Science, Vol. 5, No. 1, pp. 55-64 (2001).
55.S. K. Kang, W. K. Choi, M. J. Yim and D. Y. Shih, “Studies of the mechanical and electrical properties of lead-free solder joints”, Journal of Electronic Materials, Vol. 31, No. 11, pp. 1292-1303 (2002).
56.A. Hirose, T. Fujii, T. Imamura and K. F. Kobayashi, “Influence of interfacial reaction on reliability of QFP joints with Sn-Ag based Pb free solders”, Materials Transactions (JIM), Vol. 42, No. 5, pp. 794-802 (2001).
57.C. E. Ho, R. Y. Tsai, Y. L. Lin and C. R. Kao, “Effect of Cu concentration on the reactions between Sn-Ag-Cu solders and Ni”, Journal of Electronic Materials, Vol. 31, No. 6, pp. 584-590 (2002).
58.Y. D. Jeon, S. Nieland, A. Ostmann, H. Reichl and K. W. Paik, “Studies on the interfacial reactions between electroless Ni UBM and 95.5Sn-4.0Ag-0.5Cu alloy”, Proceedings-Electronic Components and Technology Conference, pp. 740-746 (2002).
59.A. Zribi, A. Clark, L. Zavalij, P. Borgesen and E. J. Cotts, “The growth of intermetallics compounds at Sn-Ag-Cu solder /Cu and Sn-Ag-Cu solder /Ni interfaces and the associated evolution of the solder microstructure”, Journal of Electronic Materials, Vol. 30, No. 6, pp. 1157-1164 (2001).
60.A. D. Roming Jr., F. G. Yost and P. F. Hlava, “Intermetallic layer growth in Cu /Sn-In solder joints”, Proceedings-Annual Conference Microbeam Analysis Society, Bethlehem, USA, pp. 87-92 (1984).
61.R. A. Islam, B. Y. Wu, M. O. Alam, Y. C. Chan and W. Jillek, “Investigations on microhardness of Sn-Zn based lead-free solder alloys as replacement of Sn-Pb solder”, Journal of Alloys and Compounds, Vol. 392, No. 1-2, pp. 149-158 (2005).
62.K. Suganuma, T. Murata, H. Noguchi and Y. Toyoda, “Heat resistance of Sn-9Zn solder /Cu interface with or without coating”, Journal of Materials Research, Vol. 15, No. 4, pp. 884-891 (2000).
63.M. Date, T. Shoji, M. Fujiyoshi, K. Sato and K. N. Tu, “Ductile-to-brittle transition in Sn-Zn solder joints measured by impact test”, Scripta Materialia, Vol. 51, No. 7, pp. 641-645 (2004).
64.Y. Chonan, T. Komiyama, J. Onuki, R. Urao, T. Kimura and T. Nagano, “Influence of P content in electroless plated Ni-P alloy film on interfacial structures and strength between Sn-Zn solder and plated Au/Ni-P alloy film”, Materials Transactions (JIM), Vol. 43, No. 8, pp. 1887-1890 (2002).
65.C. W. Huang and K. L. Lin, “Interfacial reactions of lead-free Sn-Zn based solders on Cu and Cu plated electroless Ni-P /Au layer under aging at 150°C”, Journal of Materials Research, Vol. 19, No. 12, pp. 3560-3568 (2004).
66.S. P. Yu, M. C. Wang and M. H. Hon, “Formation of intermetallic compounds at eutectic Sn-Zn-Al solder /Cu interface”, Journal of Materials Research, Vol. 16, No. 1, pp. 76-82 (2001).
67.C. H. Yu, K. S. Kim, H. I. Kim and H. J. Jeon, “Influence of interfacial reaction layer on reliability of chip-scale package joint from using Sn-37Pb and Sn-8Zn-3Bi solder”, Journal of Electronic Materials, Vol. 34, No. 2, pp. 161-167 (2005).
68.P. Nash and A.Nash, in ”Binary Alloy Phase Diagrams”ed. By T. B.Massalski, ASM international, Materials Park, Ohio (1990).
69.J. Haimovich, “Intermetallic compound growth in tin and tin-lead platings over nickel and its effects on solderability”, Welding Research Supplement, Vol. 68(3), pp. 102-111 (1989).
70.W. J. Tomlinson and H. G. Rhodes, “Kinnetics of intermetallic compound growth between nickel, electroless Ni-P, electroless Ni-B and tin at 453 to 493 K”, Journal of Materials Science, Vol.22(5), pp. 1769-1772 (1987).
71.S. W. Chen, C. M. Chen and W. C. Liu, “The electric current effects upon the Sn/Cu and Sn/Ni interfacial reactions”, Journal of Electronic Materials, Vol. 27(11), pp. 1193-1198 (1998).
72.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(9), pp. 4502-4508 (2001).
73.K. N. Tu and R. D. Thompson, “Kinetics of interfacial reaction in bimetallic Cu-Sn thin films”, Acta Metallurgica, Vol. 30(5), pp. 947-952 (1982).
74.S. K. Kang and V. Simic, “Room temperature interactions in Ni/metal thin film couples”, Thin Solid Films, Vol. 98(2), pp. 95-100 (1982).
75.J. A. Van Beek, S. A. Stolk, and F. J. Jvan Loo, Zeitschrift Fur Meatalkunde, Vol. 73(7), pp. 439-444 (1982).
76.C. E. Ho, Y. W. Lin, S. C. Yang, C. R. Kao and D. S. Jlang, “Effects of limited Cu supply on soldering reactions between SnAgCu and Ni”, Journal of Electronic Materials, Vol. 35, pp. 1017-1024 (2006).
77.S. Ishikawa, E. Hashino, T. Kono and K. Tatsumi, “IMC growth of solid state reaction between Ni UBM and Sn-3Ag-0.5Cu and Sn-3.5Ag solder bump using ball place bumping method during aging”, Materials Transactions, Vol. 46, pp. 2351-2358 (2005).
78.L. Y. Hsiao, S. T. Kao and J. G. Duh, “Characterizing metallurgical reaction of Sn3.0Ag0.5Cu composite solder by mechanical alloying with electroless Ni-P/Cu under-bump metallization after various reflow cycles”, Journal of Electronic Materials, Vol. 35, pp. 81-88 (2006).
79.C. Y. Chou and S.W. Chen, “Phase equilibria of the Sn-Zn-Cu ternary system”, Acta Materialia, Vol. 54, pp. 2393-2400 (2006).
80.R. A. Islam, B. Y. Wu, M. O. Alam, Y. C. Chan and W. Jillek, “Investigations on microhardness of Sn-Zn based lead-free solder alloys as replacement of Sn-Pb solder”, Journal of Alloys and Compounds, Vol. 392, pp. 149-158 (2005).
81.T. Shimozaki and M. Onishi, “Frame of reference and intrinsic diffusion coefficients for binary interdiffusion”, Journal of the Japan Institute of Metals, Vol. 45, pp. 1221-1222 (1981).