Effect of the Formation of CuO Flowers and SnO₂ on the Growth of Tin Whiskers on Immersion Tin Surface Finish

Abstract:

The effect of the formation of CuO flowers and SnO₂ on tin whiskers formation and growth in 30°C/60%RH environmental condition for tin surface finish had been studied. Immersion plating method was used to coat a layer of tin onto a copper, Cu substrates. The coated surface was subjected to external stress by micro hardness indenter with 2N load in order to simulate an external stress in coating layer and to promote the formation of tin whiskers. FESEM and EDX was used to study the type and chemical composition of whiskers and oxides formed. Image analyser was used to measure the whiskers length using JEDEC Standard No 22-A121A. After 1 week of the exposure under 30°C/60%RH environmental condition, kinked-type whiskers were formed and the whiskers growth were discontinued at week 4 due to the distruction at the end-tip of kinked-type tin whisker to grow further when it touched the coating surface. An obervation until 52 weeks of exposure time found that the formation and growth of CuO flowers and the oxidation of non-kinked-type of tin whiskers to form SnO₂ promoted by external stress also contributed to the discontinuity of whiskers growth.

• Periodical: Applied Mechanics and Materials (Volume 695)
• Pages: 301-305
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.695.301
• Online since: November 2014
• Authors: Nor Akmal Fadil*, Siti Zahira Yusof, Ali Ourdjini, Tuty Asma Abu Bakar
• Keywords: CuO Flowers, Immersion Tin Surface Finish, JEDEC Standard No. 22-A121A, SnO₂, Tin Whiskers

References

[1] K. J., Puttlitz and G. T., Galyon, Impact of the ROHS Directive on high-performance electronic systems. J Mater Sci: Mater Electron, 18 (2007) 347-365.

DOI: 10.1007/s10854-006-9024-4

[2] A., Vicenzo, Tin Whiskers. In: C. Z.G. GROSSMANN, (ed. ) The ELFNET Book on Failure Mechanisms, Testing Methods, and Quality Issues of Lead-Free Solder Interconnects. Springer-Verlag London, (2011).

DOI: 10.1007/978-0-85729-236-0_6

[3] A., Baated, K. S., Kim, and K., Suganuma, Effect of Intermetallic Growth Rate on Spontaneous Whisker Growth from a Tin Coating on Copper. J Mater Sci: Mater Electron, 22, (2011) 1685-1693.

DOI: 10.1007/s10854-011-0346-5

[4] S. M., Miller, U., Sahaym, and M. G., Norton, Effect of Substrate Composition on Sn Whisker Growth in Pure Sn Films. Metallurgical and Materials Transactions A, 41 A (2010) 3386-3395.

DOI: 10.1007/s11661-010-0431-z

[5] A., Dimitrovska and R., Kovacevic, Mitigation of Sn Whisker Growth by Composite Ni/Sn Plating. Journal of Electronic Materials, vol. 38 (2009) 2516-2524.

DOI: 10.1007/s11664-009-0930-0

[6] B., Illes, B., Horvath, and G., Harsanyi, Effect Of Strongly Oxidizing Environment on Whisker Growth form Tin Coating. Suface & Coating Technology, 205 (2010) 2262-2266.

DOI: 10.1016/j.surfcoat.2010.09.012

[7] B., Horvath, B., Illes, T., Shinohara, and G., Harsanyi, Copper-oxide Whisker Growth on Tin–Copper Alloy Coatings Caused by the corrosion of Cu6Sn5 Intermetallics. J Mater Sci: Mater Electron, 48 (2013) 8052-8059.

DOI: 10.1007/s10853-013-7619-8

[8] J. L., Jo, K. et. al, Least Lead Addition To Mitigate Tin Whisker For Ambient Storage. J Mater Sci: Mater Electron, 24 (2013) 3108-3115.

DOI: 10.1007/s10854-013-1218-y

[9] Y.H., Chen, Y. Y., Wang, and C. C., Wan, Microstructural Characteristics of Immersion tin Coatings on Copper Circuitries in Circuit Boards. Surface and Coatings Technology, 202 (2007) 417 – 424.

DOI: 10.1016/j.surfcoat.2007.06.004

[10] R., Gedney, J., Smetana, N., Vo, and G., Galyon, NEMI Tin Whisker Projects. (2004).

[11] M.A., Dudek, and N., Chawla, Mechanisms for Sn Whisker Growth in Rare Earth-Containing Pb-free Solders. Acta Materialia, 57 (2009) 4588 - 4599.

DOI: 10.1016/j.actamat.2009.06.031

[12] S.M., Miller, U., Sahaym, and M. G., Norton, Effect of Substrate Composition on Sn Whisker Growth in Pure Sn Films. Metallurgical and Materials Transactions A, 41A (2010) 3386 - 3395.

DOI: 10.1007/s11661-010-0431-z

[13] D., Susan, J., et. al, Morphology and Growth Kinetics of Straight and Kinked Tin Whiskers. Metallurgical and Materials Transactions A, vol. 44A (2013) 1485-1496.

DOI: 10.1007/s11661-012-1488-7

[14] J., Liang, Z. H., Xu, and X., Li, Whisker Nucleation in Indentation Residual Stress Field on Tin Plated Component Leads. J Mater Sci: Mater Electron, 18 (2007) 599-604.

DOI: 10.1007/s10854-007-9153-4

[15] J., Cheng, et. al., Optimum Thickness of Sn Film for Whisker Growth. Journal of Electronic Materials, 40 (2011) 2069-(2075).

[16] N.A., Fadil, S.Z., Yusof, T.A., Abu Bakar, A. Ourdjini,  Effect of Externally Applied Stress on Tin Whiskers Formation and Growth for Immersion Tin Surface Finish.  Proceeding of 9th International Materials Technology Conference & Exhibition (IMTCE2014), Kuala Lumpur, Malaysia (13-14 May 2014).

DOI: 10.4028/www.scientific.net/amm.695.301

[17] S.Z., Yusof, N.A., Fadil,  T.A., Abu Bakar, A. Ourdjini, Effect of Thin Coating Thickness on Tin Whiskers Formation and Growth. Proceeding of 8th SEATUC Symposium, Johor Bahru, Malaysia (4-5 March 2014).