DOI QR코드

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전해Ni, 무전해 Ni pad에서의 Cu 함량에 따른 접합 신뢰성에 관한 연구

A Study of Joint Reliability According to Various Cu Contents between Electrolytic Ni and Electroless Ni Pad Finish

  • 이현규 (덕산하이메탈(주) R&D 센터) ;
  • 천명호 (덕산하이메탈(주) R&D 센터) ;
  • 추용철 (덕산하이메탈(주) R&D 센터) ;
  • 오금술 (덕산하이메탈(주) R&D 센터)
  • 투고 : 2015.08.24
  • 심사 : 2015.09.25
  • 발행 : 2015.09.30

초록

솔더 조인트의 신뢰성 강화를 위해서 다양한 pad finish material이 사용되고 있으며, 최근에는 Electroless Ni Electroless Pd Immersion Gold (이하 ENEPIG) pad가 많이 사용되고 있다. 따라서, 본 연구는 상용화 되어 사용중인 Electrolytic Ni (soft Ni) pad와 최근 이슈가 되고 있는 ENEPIG pad에 대한 신뢰성 평가에 관한 것으로, 다양한 Cu 함량에 따른 거동을 관찰 하였다. Reflow 후 솔더와 pad간의 접합층은 $Cu_6Sn_5$에 Ni이 치환된 형태의 금속간 화합물로 구성되어 있었으며, ENEPIG pad의 경우, 접합층과 Ni layer 사이에 $Ni_3P$ (dark layer) layer가 관찰 되었다. 또한, Cu 함량에 따라 Dark layer의 두께를 제어할 수 있었다. 충격 낙하 시험 후, 파괴모드를 관찰한 결과 soft Ni pad와 ENEPIG pad에서 서로 다른 파괴모드가 관찰 되었으며, soft Ni의 경우, 1차 IMC와 2차 IMC 경계에서 파괴가 관찰 되었고, ENEPIG pad의 경우, dark layer에서 파괴가 관찰 되었다. IMC와 pad material, bulk 솔더와의 lattice mismatch에 의해 불안정한 계면이 존재하며, 이는 연속적인 외부 충격에 의해 가해진 열적, 물리적 스트레스를 IMC 계면으로 전송하기 때문에, 솔더의 신뢰성 향상을 위해서는 솔더 벌크의 제어와 IMC의 두께 및 형상의 제어는 필요하다.

It has been used various pad finish materials to enhance the reliability of solder joint and recently Electroless Ni Electroless Pd Immersion Gold (the following : ENEPIG) pad has been used more than others. This study is about reliability according to being used in commercial Electrolytic Ni pad and ENEPIG pad, and was observed behavior of various Cu contents. After reflow, the inter-metallic compound (IMC) between solder and pad is composed of $Cu_6Sn_5$ (Ni substituted) by using EDS, and in case of ENEPIG, between IMC and Ni layer was observed the dark layer ($Ni_3P$ layer). Additional, it could be controlled the thickness of dark layer according to Cu contents. Investigated the different fracture mode between electrolytic Ni and ENEPIG pad after drop shock test, in case of soft Ni, accelerated stress propagated along the interface between $1^{st}$ IMC and $2^{nd}$ IMC, and in case of ENEPIG pad, accelerated stress propagated along the weaken surface such as dark layer. The unstable interface exists through IMC, pad material and solder bulk by the lattice mismatch, so that the thermal and physical stress due to the continuous exterior impact is transferred to the IMC interface. Therefore, it is strongly requested to control solder morphology, IMC shape and thickness to improve the solder reliability.

키워드

참고문헌

  1. Jack Josefowicz, Ph.D., Surface Finishes: 21st Century Challenge, Director of Technology, Tyco Printed Circuit Group
  2. A. Nadai, "Theory of flow and Fracture of solids", 2,535, McGraw-Hill, NY (1967).
  3. W. M. Chen, M. McCloskey and S. C. O, "Isothermal aging effects on the microstructure and solder bump shear strength of eutectic Sn37Pb and Sn3.5Ag solder", Microelectron. Reliab., 46, 896 (2006). https://doi.org/10.1016/j.microrel.2005.06.006
  4. Glenn O. Mallory and Juan B. Hadju, Electroless plating : fundamentals and applications, American electroplater and surface finishers society, Ch.4. (1990).
  5. R. Achenbrenner, A. Ostmann, U. Beutler, J. Simon and H.Reichl, "Electroless nickel/copper plating as a new bump metallization", IEEE Trans. CPMT, Part B 18(2), 334 (1995).
  6. T. I. Eijim, D. B. Hollesen, A. Holiday, S. A. Gahr and R. J. Coyle, "Assembly and reliability of thermally enhanced high I/O BGA packages", Proc 21st IEEE International Electronics manufacturing Symposium 25 (1997).
  7. Z.Mei, M. Kauffmann, A. Eslambolchi and P. Johnson, "Brittle interfacial fracture of PBGA packages on electroless Ni/ immersion Au", Proc 48th Electronic Component and Technology Conference 952 (1998).
  8. N. Biunno, "A root cause failure mechanism for solder joint integrity of electroless Ni/immersion gold surfaces", Proc IPC Printed Circuits Expo 1999 s15-5 (1999).
  9. G. M. Wenger, R. J. Coyle, P. P. Solan, J. K. Dorey, C. V. Dodd, R. Erich and A. Primavera, "Case sudies of brittle interfacial fractures in area array solder interconnects", Proc 26th International Symposium for testing and failure analysis 355 (2000).
  10. D. Cullen, E. Huenger, M. Toben, B. Houghton and K. Johal, "A study on interfacial fracture phenomenon of solder joints formed using the electroless nickel/immersion gold surface finish", Proc IPC works 2000 s03-2 (2000).
  11. C. H. Zhong and S. Yi, "Solder joint reliability of plastic ball grid array", Soldering and Surface Mount Technology, 11(1), 44 (1999). https://doi.org/10.1108/09540919910254930
  12. D. Goyal, T. Lane, P. Kinzie, C. Panichas, K. M. Chong and O. Villalobos, "Failure mechanism of brittle solder joint fracture in the presence of electroless Ni immersion gold (ENIG) interface", Proc 52nd Electronic Component and Technology Conference 732 (2002).
  13. S. Wiegele, P. Thompson, R. Lee and E. Ramsland, "Reliability and process characterization of electroless nickel-gold/ solder flip chip interconnect technology", Proc 48th Electronic Component and Technology Conference 861 (1998).
  14. K. Johal, H. Robertss, S. Lamprecht and H. J. Schreirer, "Impacts of Bulk Phosphorous Content of Electroless Ni layers to solder joint integrity and their use as gold and aluminum wire bond surfaces", J. SMT, 17, 18 (2002).
  15. Martin Goosey, "Factors influencing the formation of 'black pad' in electroless nickel-immersion gold solderable finishesa processing perspective", Circuit World, 28, 36 (2002). https://doi.org/10.1108/03056120310418475
  16. K. Yokomine, N. Shimizu, Y. Miyamoto, Y. Iwata, D. Love and K. Newman, "Development of electroless Ni/Au plated build-up flip chip package with highly reliable solder joints", Proc. Elec. Comp. Tech. Conf., 1384 (2001).
  17. D. Goyal, T. Lane, P. Kinzie, C. Panichas, K. M. Chong and O. Villalobos, "Failure mechanism of brittle solder joint fracture in the presence of electroless nickel immersion gold (ENIG) interface", Proc. Elec. Comp. and Technol. Conf., 732 (2002).
  18. M. Zequn, P. Johnson, M. Kaufmann and A. Eslambolchi, "Effect of electroless Ni/immersion Au plating parameters on PBGA solder joint attachment reliability", Proc. Elec. Comp. and Technol. Conf., 125 (1999).
  19. A. Bai, P. Y. Chuang and C. C. Hu, "The corrosion behavior of Ni-P deposits with high phosphorous contents in brine media", J. Mater. Chem. Phys., 82, 93 (2003). https://doi.org/10.1016/S0254-0584(03)00193-7
  20. M. O. Alam, Y. C. Chan and K. N. Tu, "Effect of 0.5 wt% Cu in Sn-3.5Ag solder on the interfacial reaction with Au/Ni metallization", Chem. Mater., 49, 813 (2003).
  21. Y. D. Jeon, K. W. Paik, K. S. Bok, W. S. Choi and C. L. Cho, "Study on the electroless nickel UBM-solder interfacial reaction and their effects on flip chip solder joint reliability", J. Electron Mater., 31(5), 520-528 (2002). https://doi.org/10.1007/s11664-002-0109-4
  22. Chen Xu, G. T. Galyon, S. Lai, B. Notohardjoni, and Asa Frye, "tin whisker modeling committee", INEMI (2005).
  23. J. W. Yoon, W. C. Moon and S. B. Jung, "Interfacial Reaction of ENIG/Sn-Ag-Cu/ENIG Sandwich Solder Joint during Isothermal Aging", Micro. Eng., 83, 2329 (2006). https://doi.org/10.1016/j.mee.2006.10.027