Journal of the Microelectronics and Packaging Society (마이크로전자및패키징학회지)

The Korean Microelectronics and Packaging Society (한국마이크로전자및패키징학회)
권호 표지

Effects of Heat Treatment on the Microstructure and Whisker Growth Propensity of Matte Tin Finish

  • Kim, K.S. (Department of Electronic Engineering, Yeoju Institute of Technology)
  • Received : 2010.03.03
  • Accepted : 2010.04.02
  • Published : 2010.06.30
Download PDF
⟨ Previous Next ⟩

Abstract

The effects of heat treatment on matte pure tin-plated Cu leadframes at high temperature and humidity conditions were investigated. After 1800 hrs of storage at $55^{\circ}C/85%$ RH, approximately 14.5 ${\mu}m$ long striation-shaped whiskers were observed on the surface of the without postbake treatment (WOPB) samples, while no whiskers were found in with postbake treatment (WPB) samples. The preferred orientations of Sn grains in WOPB and WPB sample did not change after the postbake treatment at $125^{\circ}C$ for 1 hr. However, both changed from (112) to (321) and (101), respectively, after 1800 hrs of storage at $55^{\circ}C/85%$ RH. The tensile stress of 8 MPa generated in as-plated sample was changed to a compression stress of 17 MPa after 2 days in room temperature storage. Due to the grain growth during postbake treatment, the WPB samples have more regular grains than the WOPB samples. In the as-plated sample, 0.32 ${\mu}m$ thickness of planar intermetallic compound (IMC) was observed. The IMCs in the WOPB and WPB samples had two distinct layers with large grains of $Cu_6Sn_5$ and with small grains of ${\eta}-Cu_{6.26}Sn_5$.

Keywords

References

  1. K. N. Subramanian, Lead-free electronic solders, pp.281, Springer, New York (2007).
  2. Y. U. Moon and J. H. Lee, "Fabrication of Sn-Cu bump using electroless plating method", J. Microelectron. Packag. Soc., 15(2), 17 (2008).
  3. U. Lindborg, "A model for the spontaneous growth of zinc, cadmium and tin whiskers", Acta Metall., 24(2), 181 (1976). https://doi.org/10.1016/0001-6160(76)90021-3
  4. C.H. Yu, "The observation of intermetallic compound microstructure under Sn whisker in lead-free finish", J. Microelectron. Packag. Soc., 16(2), 27 (2009).
  5. B. Z. Lee and D. N. Lee, "Spontaneous growth mechanism of tin whiskers", Acta Mater., 46(10), 3701 (1998). https://doi.org/10.1016/S1359-6454(98)00045-7
  6. I. Boguslavsky and P. Bush, "Recrystallization principles applied to whisker growth in tin", Proc. IPC/SMEMA Council APEX Conf., Anaheim, S12-4-1-10, (2003).
  7. W. J. Boettinger, C. E. Johnson, L. A. Bendersky, K. W. Moon, M. E. Williams and G. R. Stafford, "Whisker and hillock formation on Sn, Sn-Cu and Sn-Pb electrodeposits", Acta Mater., 53(11), 5033 (2005). https://doi.org/10.1016/j.actamat.2005.07.016
  8. K. N. Tu, C. Chen and A. T. Wu, "Stress analysis of spontaneous Sn whisker growth", J. Mater. Sci. Mater. Electron., 18(2), 269 (2007).
  9. C. Xu, Y. Zhang, C. Fan and J. Abys, "Driving force for the formation of Sn whiskers: Compressive stress-pathways for its generation and remedies for its elimination and minimization", IEEE Trans. Elect. Packag. Manuf., 28(1), 31 (2005). https://doi.org/10.1109/TEPM.2005.846461
  10. M. E. Williams, K. W. Moon, W. J. Boettinger, D. Josell and A. D. Deal, "Hillock and whisker growth on Sn and SnCu electrodeposits on a substrate not forming interfacial intermetallic compounds", J. Electron. Mater., 36(3), 214 (2007). https://doi.org/10.1007/s11664-006-0071-7
  11. W. Zang and F. Schwager, "Effects of lead on tin whisker elimination - efforts toward lead-free and whisker-free electrodeposition of tin", Electrochem. Soc., 153(5), C337 (2006). https://doi.org/10.1149/1.2186032
  12. P. Oberndorff, C. F. T. Philips and Eindhoven, "Root cause of tin whisker growth", EFSOT Europe, The Netherlands (2003).
  13. Y. Fukuda, M. Osterman and M. Pecht, "Length distribution analysis for tin whisker growth", IEEE Trans. Electron. Packag. Manuf.. 30(4), 36 (2007). https://doi.org/10.1109/TEPM.2006.890638
  14. P. Oberndorff, M. Dittes, P. Crema and S. Chopin, "Whisker formation on matte Sn influencing of high humidity", Proc. 55th Electron. Compon. Technol. Conf. (ECTC), Orlando, 429, (2005).
  15. Y. Fukuda, M. Osterman and M. Pecht, "The effect of annealing on tin whisker growth", IEEE Trans. Elect. Packag. Manuf., 29(4), 252 (2006). https://doi.org/10.1109/TEPM.2006.887390
  16. P. Oberndorff, M. Dittes, P. Crema, P. Su and E. Yu, "Humidity effects on Sn whisker formation", IEEE Trans. Elect. Packag. Manuf., 29(4), 239 (2006) https://doi.org/10.1109/TEPM.2006.887358
  17. J. H. Lau, S. H. Pan, C. Xu, "3D large deformation and nonlinear stress analyses of tin whisker initiation and growth on lead-free components", Proc. 52rd Electron. Compon. Technol. Conf. (ECTC), 692, New Orleans (2003).
  18. M. Sobiech and U. Welzel. et al, "The microstructure and state of stress of Sn thin films after post-plating annealing: An explanation for the suppression of whisker formation?", Proc. 57th Electron. Compon. Technol. Conf. (ECTC), 192, Reno (2007).
  19. S. Ganesan and M. Pecht, pp. 251, Lead-free electronics, CALCE EPSC Press, Maryland (2003).
  20. S. C. Britton, "Spontaneous growth of whiskers on tin coatings: 20 years of observation", Metal Finishing, 52, 95 (1974).
  21. D. Shangguan, Lead-free solder interconnect reliability, pp.161-162, ASM International, Ohio (2005).
  22. C.S. Barrett and T. B. Massalski, pp.204-206, Structure of metals, Pergamon, London (1966).
  23. J.M. Bennett and L. Mattsson, pp.28, Introduction to surface roughness and scattering, Optical Society of America, Washington (1989).
  24. C. E. Birchenall, Physical metallurgy, pp.216-217, McGraw-Hill, New York (1959).
  25. JEDEC,Current tin whiskers theory and mitigation practices guideline, JP002, J. S. S. T. Association, VA 22201-3834: Electronic Industries Association, Arlington (2006).
  26. K. N. Tu, Mater, "Cu/Sn interfacial reactions: thin-film case versus bulk case", Chem. Phys., 46(2-3), 217 (1996).
  27. K. N. Tu and R. Thompson, "Kinetics of interfacial reaction in bimetallic Cu-Sn thin films", Acta Metall., 30(10), 947 (1982). https://doi.org/10.1016/0001-6160(82)90201-2
  28. K. N. Tu, "Irreversible processes of spontaneous whisker growth in bimetallic Cu-Sn", Phys.Rev. B., 49(3), 2030 (1994). https://doi.org/10.1103/PhysRevB.49.2030
  29. Y. Fujiwara, "Sn deposition onto Cu and alloy layer growth by a contact immersion process", Thin Solid Films, 425(1-2), 121 (2003). https://doi.org/10.1016/S0040-6090(02)01136-7
  30. J. Y. Song, J. Yu and T. Y. Lee, "Effects of reactive diffusion on stress evolution in Cu-Sn films", Scripta. Mater., 51(2), 167 (2004). https://doi.org/10.1016/j.scriptamat.2004.03.032
  31. L. A. Clevenger, B. Arcot, W. Ziegler, E. G. Colgan, Q. Z. Hong, F. M. d'Heurle, C. Jr. Cabral, T. A. Gallo and J. M. E. Harper, "Interdiffusion and phase formation in Cu(Sn) alloy films", J. Appl. Phys., 83(1), 90 (1998). https://doi.org/10.1063/1.366728
  32. P. Vianco, J. Rejent and P. Hlava, "Solid-state intermetallic compound layer growth between copper and 95.5Sn-3.9Ag-0.6Cu solder", J. Electron Mater., 33(9), 991 (2004). https://doi.org/10.1007/s11664-004-0026-9
  33. JCPDS - International Centre for Diffraction Data, Newtown Square (2002).