摘要(英) |
Since 2010 the European RoHS 2.0 regulations come into effective and restricted to selling electronic products with limited lead content. The vast printed circuit boards and electronic assembly manufacturers, In order to meet product specifications of RoHS lead-free regulations, they have to upgrade own equipment and process capabilities to comply the requirements of the laws & the market.
In the exposed lead-free process relevant issues, the selection of lead-free solder has a very significant influence, which is not only related to the equipments of thermal assembly process and the choice of component materials. It is related to the product′s reliability and life cycle also. As the Sn-3.0wt%Ag-0.5wt% Cu solder alloy with excellent wetting and mechanical properties, Which as the best choice for lead-free process of recommendation by major research institutions and associations, and widely used in the industry in printed circuit board assembly process, that become the mainstream lead- free solder alloy of the industry.
Furthermore, due to the lead content as the strictly limited element of RoHS compliance, the traditional tin-lead HASL board has been restricted too. PCB industry needs to find another solutions to instead tin-lead HASL board . The organic surface protective (OSP) board has become the mainstream product due to low production equipment investment and manufacturing costs, good process yield rate and higher reliability of solder joints. But it is unlike gold plate (ENIG) or lead-free HASL (LF HASL) board, which with nickel protect copper surface to prevent Cu dissolute into solder and less copper dissolution affect in PCBA process.
In the search of copper dissolution studies, we found the most studies are for experimental purposes, or just focus on Surface Mount Technology (SMT) relevant issues, under limited solder alloy conditions. The dissolution rate will decrease as the copper solute into solder and increasing the concentration of copper, even to stop the dissolution reaction of the equilibrium point.
Due to the PCB copper is contacting to mass liquid solder directly, and caused the copper pad dissolution of through-hole components area during the wave solder process, That is the major concern of the current PCBA industry. In order to provide and stabilize the power to drive those attached devices, the amount of through hole components are necessary for high end Enterprise products. During the soldering process of through hole components, the huge melting solder alloy will contact with copper foil directly, and dissolve it into the solder. This study will based on selected solder alloy Sn-0.3Ag-0.5Cu, and using copper foils as the test vehicle, varying the solder’s temperature、immersion time and solder flow rate, to simulate actual production condition and calculate the copper dissolution, to carry out the relationship of copper dissolution v.s process parameter and further discussion.
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參考文獻 |
1. 謝清河, “壓接式連接器之針眼端子之分析與最佳化”, Jun 2009.
2. 謝東穎, “Cu原子濃度對Sn-Ag-Cu-Sb無鉛銲料微結構與機械性質之研 究”, Jun 2006.
3. X. Ma, F. Wang, Y. Qian, F. Yoshida, “Development of Cu-Sn intermetallic compound at Pb-free solder/Cu joint interface”, Materials Letters 57 (2003) 3361-3365.
4. “NEMI Group Recommends LF Alloys”, January 24, 2000.
5. 張書豪, “錫-銀-銅合金與金基材界面反應之研究”, Jul 2005.
6. K. Suganuma, “Advances in lead-free electronics soldering”, Current Opinion in Solid State and Materials Science, 5 (2001) 55-64.
7. J. Nguyen, “Assembly process feasibility of Low/No Silver alloy solder paste materials”. IPC APEX EXPO Conference. 2013.
8. W. Chao, E. Benedetto, “Thermal Fatigue Result for Low and No-Ag Alloys”, iNEMI Session, IMPACT, October 26, 2012.
9. L. Snugovsky, M. A. Ruggiero, D. D. Perovic and J. W. Rutter, “Experiments on interaction of liquid tin with solid copper”, Materials Science and Technology, (01 July 2003), pp. 866-874.
10. S. Mannan, M. P. Clode, “Dissolution of Solids in Contact with Liquid Solder”, Solder & Surface Mount Technology. 16/3 (2004) 31-33
11. S. Bader, W. Gust and H. Hieber, “Repid formation of intermetallic compounds by interdiffusion in the Cu-Sn and Ni-Sn system”. Acta Metallurgica et Materialia. Vol. 43, No. 1, pp. 329-337, (1995)
12. 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
13. C. W. Hwang, J. G. Lee, K. Suganuma, and H. Mori, “Interfacial microstructure between Sn-3Ag-xBi alloy and Cu substrate with or without electrolytic Ni plating”. Journal of Electronic Materials, Vol. 32, No, 2, 2003.
14. M. O. Alam, Y. C. Chan, And K. N. Tu, “Effect of 0.5wt% Cu addition in Sn-3.5%Ag solder on the dissolution rate of Cu metallization”, Journal of Applied Physics, 2003, Vol. 94, No. 12, 2003.
15. A. SHARIF and Y.C. CHAN, “Comparative Study of Interfacial Reactions of Sn-Ag-Cu and Sn-Ag Solders on Cu Pads during Reflow Soldering”, Journal of Electronic Materials, Vol. 34, No. 1, 2005.
16. G. Izuta, T. Tanabe, K. Suganuma, “Dissolution of copper on Sn-Ag-Cu system lead free solder”, Soldering & Surface Mount Technology, 19/2 (2007) 4-11
17. M. L. Huang, T. Loeher, A. Ostmann, and H. Reichi, “Role of Cu in dissolution kinetics of Cu metallization in molten Sn-based solders”. Applied Physics Letters. 86, 181908 (2005)
18. 張智強,”Cu濃度對銲接時墊層消耗速率及界面反應的影響”, 2007.
19. N. Mookam, K. Kanlayasiri, “Effect of soldering condition on formation of intermetallic phases developed between Sn-0.3Ag-0.7Cu low-silver lead-free solder and Cu substrate”, Journal of Alloys and Compounds, 509 (2011) 6276-6279.
20. Fangjie Cheng, Feng Gao, Jianyou Zhang, Wenshan Jin, Xin Xiao, “Tensile properties and wettability of SAC0307 and SAC105 low Ag lead-free solder alloys”. J Mater Sci (2011) 46: 3424 3429.
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