錫-銀-銅系統合金(SAC)為現今電子構裝產業當中最被廣泛使用的低溫無鉛銲料。在銲接的製程當中由於各組成間化學位勢的差異以及熱力學上區域平衡的存在，將造成銲接面生成介金屬相(intermetallic compound, IMC)；IMC的生成為不同物質接合的必要的條件，但其硬、脆的性質及隨反應時間增加的厚度也對電子產品可靠度造成困擾，但在傳統軟銲的製程當中此實為無法避免的因素。為研究減少界面生成相厚度及發展新式迴銲技術，本研究係以高功率之二氧化碳雷射機取代傳統熱風迴銲的方式，將工業界常用之Sn-4.0Ag-0.5Cu (SAC405)及Sn-4.0Ag-0.5Cu-0.05Ni-0.01Ge (SACNG)無鉛銲料分別與Au/Ni(P)/Cu/FR-4多層BGA基材進行快速迴銲接合，隨後於150℃下進行固態熱處理以模擬電子元件運作接點老化情形，藉觀察其與傳統熱風迴銲後界面IMC之種類、厚度以及晶粒形態之差異，並對接點強度抗剪變強度進行測試以評估接點可靠度。
實驗結果顯示，雷射迴銲後反應偶之界面生成相厚度遠低於傳統熱風迴銲，以35W及45W功率之CO2雷射迴銲接合後之SACNG及SAC405銲料與Au/Ni(P)/Cu反應偶界面均生成(Cu,Ni)6Sn5及(Ni,Cu)3Sn4混合相及Ni、Sn、Cu之金屬固溶體組成之連續層，在經長時間固態時效處理後界面則僅呈現(Cu,Ni)6Sn5與(Ni,Cu)3Sn4混合相。而對照之熱風迴銲反應偶在迴銲後則生成(Cu,Ni)6Sn5相，若延長反應時間則為 (Cu,Ni)6Sn5相與(Ni,Cu)3Sn4相共存，經固態時效處理後(Cu,Ni)6Sn5相與(Ni,Cu)3Sn4相則均存在於界面。並發現含Ni、Ge之銲料其界面IMC隨反應時間逐漸剝離界面。
在IMC晶粒形態方面，熱風迴銲呈現完整且稜面分明之晶粒，雷射迴銲則因IMC以固化析出生成，晶粒形態較無規則；而共通點在於經時效處理後各晶粒均因參與反應原子數增加而成長、熟化。
在接點可靠度的試驗中則發現銲接點之抗剪變強度與固態時效處理之時間並與顯著的關聯性，且在比較兩種方法之接點強度後可發現以CO2雷射迴銲亦可提供相當於傳統熱風迴銲後之接點抗剪變強度。

The BGA package is an important electronic connecting technology in electronic packaging industry. Due to the hurt of lead (Pb), the lead-free solders have become an important issue now. Sn-Ag-Cu (SAC) alloys are popular lead-free solders and widely use in electronic packaging industry, then Ni and Ge have been added into SAC solders in order to improve its wettability and oxidation resistivity. In the soldering process, because of the chemical potential gradient and the local equilibrium between solders and substrates, intermetallic compounds (IMCs) were formed at the interface. IMC formation can enhance bonding between the electronic device and substrate, but excessive growth of IMC can have detrimental effects on the long-term reliability of soldered points.
However, the microelectronic industry is moving toward small size which requires local heating reflow methods like laser reflow. This study investigate the interfacial reactions and mechanical property between Sn-4.0Ag-0.5Cu (wt%) and Sn-4.0Ag-0.5Cu-0.05Ni-0.01Ge (wt%) lead free solders with Au/Ni(P)/Cu substrate by CO2 laser reflow. These results would compare with the same systems under a conventional hot-air reflowing method in the oven. After reflow, the samples were aged at 150℃ for up to 1000 hours.
Under CO2 laser reflowing, mixtures of the (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4 phases and (Ni, P, Cu) solid solution were formed at the interface. After taking a long period of heat-treatment, the (Cu,Ni)6Sn5 + (Ni,Cu)3Sn4 were still observed at the interface. But, the (Ni, P, Cu) solid solution disappeared as increasing reaction times. The experimental results compared with the same couples by conventional hot-air reflowing at 240℃, two layer structures, the (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4 phases, were formed at the interface. The IMCs spalling off the interface could be observed in SACNG/Au/Ni/Cu reaction couple.
In addition, the grain morphology of the IMC reaction couples by hot-air reflowing was a polyhedron-type structure. This is due to long solidification process providing the enough time to make the IMC grain grow and ripen. Because of rapidly solidification of alloys in the reaction couples by CO2 laser, elements did not have enough time to diffuse then to form distinct IMC grain. Thus, the indistinct IMC grains formed at the interface. The result indicated their grain morphology were strongly dependent on the reflowing methods.
The mechanical property test indicated that the shear strength is independent to annealing time. The mechanical strength of solder joints by the laser reflowing technique is very similar to that by the hot-air reflowing method.

[1] 劉雨雯，RoHS綠色指令：全球環境規範&無鉛銲接技術，龍璟文化事業股份有限公司，台北 (2005).
[2] J.W. Yoon, S.W. Kim and S.B. Jung, “IMC morphology, interfacial reaction and joint reliability of Pb-free Sn-Ag-Cu solder on electrolytic Ni BGA substrate” , Journal of Alloys and Compounds, Vol. 392, pp.247-252 (2005).
[3] S.W. Cho, K. Han, Y. Yi, S.J. Kang, K.H. Yoo, K. Jeong and C.N. Whang, “Thermal oxidation study on lead-free solders of Sn-Ag-Cu and Sn-Ag-Cu-Ge” , Advanced Engineering Materials, Vol. 8, pp. 111-114 (2006).
[4] David R. Gaskell, Introduction to the thermodynamics of materials, Taylor & Francis, NY (2003).
[5] M. Datta, T. Osaka and J.W. Schultze, Microelectronic Packaging, CRE Press, USA (2005).
[6] 陳信文、陳立軒、林永森、陳志銘，電子構裝技術與材料，高立出版集團，台北 (2005).
[7] 田民波著、顏怡文修訂，半導體元件構裝技術，五南圖書出版有限公司，台北 (2007).
[8] 黃育智、楊青峰、陳信文，「軟銲」，科學發展期刊，Vol.416, pp. 58-63 (2007).
[9] N.C. Lee, “Getting ready for lead-free solders” , Solder & Surface Mount Technology, Vol.9, pp.65-69 (1997).
[10] M. Abtew and G. Selvaduray, “Lead-free solders in microelectronics” , Materials Science and engineering: R, Vol.27, pp. 95-141 (2000)
[11] T. B. Massalski, Binary Alloy Phase Diagram, William W.Scott, Vol.1, pp. 71 (1986).
[12] K.N. Tu, and J.C.M. Li, “spontaneous whisker growth on lead-free solder finishes” , Materials Chemistry and Physics, Vol.409, pp. 131-139 (2005).

[13] I. Karakaya and W.T. Thompson, ASM Hand book, Vol.3 Alloy Phase Diagrams, edited by H. Baker, ASM International, Materials Park, Ohio (1992).
[14] W.K. Choi and H.M. Lee, Journal of Materials Research, Vol.17, pp. 43-51 (2002).
[15] X. Demg, N. Chawla, K.K. Chawla and M. Koopman, Vol.52, pp. 4291-4303 (2004).
[16] S.L. Allen, M.R. Notis, R.R. Chromik and R.P. Vinci, Journal of Materials Research, Vol.19, pp. 1417-1424 (2004).
[17] N. Saunders and P. Miodwnik, ASM Hand book Vol.3 Alloy Phase Diagrams, edited by H. Baker, ASM International, Materials Park, Ohio (1992).
[18] C.E. Ho, R.Y. Tsai, Y.L. Lin and C.R. Kao, “Effect of Cu concentractiom on the reactions between Sn-Ag-Cu solders and Ni” , Journal of Electronic Materials, Vol.31, pp. 584-590 (2002).
[19] H. Okamoto, ASM Hand book Vol.3 Alloy Phase Diagrams, edited by H. Baker, ASM International, Materials Park, Ohio (1990).
[20] Z. Moser, J. Dutkiewicz, W. Gasior and J. Salawa, ASM Hand book Vol.3 Alloy Phase Diagrams, edited by H. Baker, ASM International, Materials Park, Ohio (1985).
[21] H. Okamoto, ASM Hand book Vol.3 Alloy Phase Diagrams, edited by H. Baker, ASM International, Materials Park, Ohio (1992).
[22] 閻吉祥著、鄭壽昌修訂，雷射原理與技術，新文京出版機構，台北 (2007).
[23] T.L. James and E.P. David, “Industrial Laser and their application” , Prentice Hall, New York, pp.153-156 (1992).
[24] J.D. Majumdar and I. Manna, “Laser processing of materials” , Sadhana, Vol.28, pp.495-562 (2003).
[25] C.E. Ho, W.T. Chen and C.R. Kao, “Interaction between solder and metallization during long-term aging of advanced microelectronic packages” , Journal of Electronic Materials, Vol.30, pp.389-387 (2001).

[26] C.E. Ho, R. Zheng, G.L. Luo, A.H. Lin and C.R. Kao, “Formation and resettlement of (AuxNi1-x)Sn4 in solder joint of ball-grid-array packages with the Au/Ni surface finish” , Journal of Electronic Materials, Vol.29, pp.1175-1181 (2000).
[27] 何政恩、蕭麗娟、高振宏，「先進封裝技術中金脆效應對銲點影響之探討」電子與材料雜誌，Vol.13, pp.73-78 (2002).
[28] J. Wang, L.G. Zhang, H.S. Liu, L.B. Liu and Z.P. Jin, “Interfacial reaction between Sn-Ag alloys and Ni substrate” , Journal of Alloys and Compounds, Vol.455, pp. 159-163 (2008).
[29] 顏怡文、方揚凱、江昱成、陳昭銘、李嘉平、黃孟槺，電子構裝中銅基材與無鉛銲料界面反應之文獻回顧，化工技術，Vol.176, pp. 211-223 (2007).
[30] 顏怡文、劉為開、郭孟翰、陳昆達，電子構裝之鎳基材與無鉛銲料界面反應之文獻回顧，化工技術，Vol.184, pp.224-236 (2008).
[31] J.W. Yoon, S.W. Kim and S.B. Jung, “Effects of reflow and cooling conditions on interfacial reaction and IMC morphology of Sn-Cu/Ni solder joint” , Journal of Alloys and Compounds, Vol.415, pp.56-61 (2006).
[32] J.W. Yoon and S.B. Jung, “Interfacial reactions between Sn-0.4Cu solder and Cu substrate with or without ENIG plating layer during reflow reaction” , Journal of Alloys and Compounds, Vol.396, pp.122-127 (2005).
[33] J.W. Yoon and S.B. Jung, “High temperature reliability and interfacial reaction of eutectic Sn-0.7Cu/Ni solder joints during isothermal aging” , Microelectronics Reliability Vol.46, pp.905-914 (2006).
[34] 陳文泰，「錫銅無鉛銲料與Ni基材界面反應之研究」，碩士論文，國立中央大學，桃園 (2002).
[35] W.C. Luo, C.E. Ho, J.Y. Tsai, Y.L. Lin and C.R. Kao, “Solid-state reactions between Ni and Sn-Ag-Cu solders with different Cu concentrations” , Materials Science and Engineering A, Vol.396, pp.385-391 (2005).
[36] C.H. Lin, S.W. Chen and C.H. Wang, “Phase equilibria and solidification properties of Sn-Cu-Ni alloys” , Journal of Electronic Materials, Vol.31, pp. 907-915 (2002).

[37] J.W. Yoon, S.W. Kim and S.B. Jung, “IMC morphology, Interfacial reaction and joint reliability of Pb-free Sn-Ag-Cu solder on electrolytic Ni BGA substrate” , Journal of Alloys and Compounds, Vol.392, pp. 247-252 (2005).
[38] C.E. Ho, Y.W. Lin, S.C.Yang, and C.R. Kao, “volume effect on the soldering reaction between SnAgCu solders and Ni” , Proceedings of the International Symposium and Exhibition on Advanced Packaging Materials Processes, Properties and Interfaces, pp.39-44 (2005).
[39] S.C. Yang, C.E. Ho, C.W. Chang and C.R. Kao, “Massive spalling of intermetallic compounds in solder-substrate reactions due to limited supply of the active element” , Journal of Applied Physics, Vol.101, pp.084911.1-084911.6 (2007).
[40] 楊素純、王儀雯、張智強、高振宏，「SnAgCu銲點中介金屬發生『大規模剝離』(Massive spalling)之探討」，化工，Vol.55, pp.27-35 (2008).
[41] Ahmed Sharif and Y.C. Chan, “Liquid and solid state interfacial reactions of Sn-Ag-Cu and Sn-In-Ag-Cu solders with Ni-P under bump metallization” , Thin Solid and Films, Vol.504, pp. 431-435 (2006).
[42] W.K. Liou, C.C. Jao, Y.W. Yen and C.H. Hsu,”Interfacial reactions and Sn whisker growth mechanism in Sn/NiP/Ni/Cu and Sn/Ni/Cu multu-layers” submit to Suface and Coatings Technology. (2009).
[43] 林詠淇、杜正恭，「在SAC/Ni-P銲接點中Ni-Sn-P相生成機制與抑制其生成方法之探討」，化工，Vol.55, pp.17-26 (2008).
[44] K.J. Lee and P. Nash, ASM Hand book Vol.3 Alloy Phase Diagrams, edited by H. Baker, ASM International, Materials Park, Ohio (1991).
[45] 江昱成，「BGA構裝中SAC與SACNG無鉛銲料與Au/Ni/Cu多層結構之界面反應與銲點破壞性質」，碩士論文，國立台灣科技大學，台北 (2008).
[46] T.H. Chuang, S.F. Yen and M.D. Cheng, “Intermetallic reactions in Sn3Ag0.5Cu and An3Ag0.5Cu0.06Ni0.01Ge solder BGA packages with Au/Ni surface finishes” , Journal of Electronic Materials, Vol.35, pp. 302-309 (2006).

[47] K.L. Lin and P.C. Shih, “IMC formation on BGA package with Sn-Ag-Cu and Sn-Ag-Cu-Ni-Ge solder balls” , Journal of Alloys and Compounds, Vol.452, pp.291-297 (2008).
[48] 施伯錚，「錫銀銅系無鉛銲錫與Cu/Ni-P/Au基板之界面接合行為」，碩士論文，國立成功大學，台南 (2003).
[49] J.H. Lee, Y.H. Lee and Y.S. Kim, “FLuxless Laser reflow bumping of Sn-Pb eutectic solder” , Scripta materialia, Vol.42, pp.789-793 (2000).
[50] Y. Tian, Chunqing. W, X. Ge, P. Liu and D. Liu, “Intermetallic compounds formation at interface between PBGA solder ball and Au/Ni/Cu/BT PCB substrate after laser reflow processes” , Materials Science and Engineerimg, Vol.95, pp.254-262 (2002).
[51] Y. Tian, C. Wang, X. Zhang and D. Liu, “Interaction kinetics between PBGA solder balls and Au/Ni/Cu metallization during laser reflow bumping” , Soldering and Surface Mount Technology, Vol.15, pp.17-21 (2003).
[52] Y. Tian, C. Wang and Y.Chen, “Characteristics of laser reflow bumping of Sn3.5Ag and Sn3.5Ag0.5Cu lead-free solder balls” , Journal of Materials Science and Technology, Vol.24, pp. 220-226 (2008).
[53] 魏洪堯，「在BGA製程中以銦作為UBM層對接點界面形態與機械性質之探討」’ 碩士論文，國立台灣科技大學，台北 (2006).
[54] W. Hume-Rothery, J.W. Christian and W.B. Pearson, “Metallurgical Equilibrium Diagrams” , The Institute of physics, London (1952).
[55] P. Nash and A.Nash, ASM Hand book Vol.3 Alloy Phase Diagrams, edited by H. Baker, ASM International, Materials Park, Ohio (1991).
[56] D.J. Chakrabarti, D.E. Laughlin, S.W. Chen and Y.A. Chan, ASM Hand book Vol.3 Alloy Phase Diagrams, edited by H. Baker, ASM International, Materials Park, Ohio (1991).
[57] R.W. Olesinski and G.J. Abbaschian, ASM Hand book Vol.3 Alloy Phase Diagrams, edited by H. Baker, ASM International, Materials Park, Ohio (1984).

[58] Y.K. Wu, K.L. Lin and B. Salam, “Specific heat capacities of Sn-Zn-based solders and Sn-Ag-Cu solders measured using differential scanning calorimetry” , Journal of electronic materials, Vol.38, pp.227-230 (2009).
[59] 鄭明達，「Sn-Ag-Cu銲錫球格陣列式構裝界面反應之研究」，博士論文，國立台灣大學，台北 (2004).