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Conductive filament formation in printed circuit boards: effects of reflow conditions and flame retardants

  • Bhanu Sood
  • Michael Pecht
Article

Abstract

Conductive filament formation, a major cause of failures in printed circuit boards, is an electrochemical process that involves the transport of a metal through or across a nonmetallic medium under the influence of an applied electric field. With an increasing potential to market “green” electronics, environmental and health legislations, and the advent of lead-free and halogen-free initiatives, newer types of printed circuit board materials are being exposed to ever higher temperatures during solder assembly. The higher temperatures can weaken the glass-fiber bonding, thus enhancing conductive filament formation. The effects of the inclusion of halogen-free flame retardants on conductive filament formation in printed circuit boards are not completely understood. Previous studies, along with analysis and examinations conducted on printed circuit boards with failure sites that were due to conductive filament formation, have shown that the conductive path is typically formed along the delaminated fiber glass and epoxy resin interfaces. This paper is a result of a year-long study on the effects of reflow temperatures, halogen-free flame retardants, glass reinforcement weave style, and conductor spacing on times to failure due to conductive filament formation.

Keywords

PCBs Print Circuit Board Hollow Fiber Conductive Filament Path Formation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgement

The authors would like to thank the more than 100 companies and organizations that support research activities at the Center for Advanced Life Cycle Engineering at the University of Maryland annually.

References

  1. 1.
    IPC. International Technology Roadmap for Electronic Interconnections at IPC APEX Expo, March 31April 2. (Las Vegas, NV, 2009)Google Scholar
  2. 2.
    J.N. Lathi, R.H. Delaney, J.N. Hines, The Characteristic Wear-Out Process In Epoxy Glass Printed Circuits for High Density Electronic Packaging. Reliability Physics, 17th Annual Proceeding, pp. 39–43 (1979)Google Scholar
  3. 3.
    D.J. Lando, J.P. Mitchell, T.L. Welsher, Conductive Anodic Filaments in Reinforced Polymeric Dielectrics: Formation and Prevention. Reliability Physics, 17th Annual Proceeding, pp. 51–63 (1979)Google Scholar
  4. 4.
    G.T. Kohman, H.W. Hermance, G.H. Downes, Silver migration in electrical insulation. Bell. Tech. J. 1115 (1955)Google Scholar
  5. 5.
    T.L. Welsher, J.P. Mitchell, D.J. Lando, CAF in Composite Printed-Circuit Substrates: Characterization, Modeling, and A Resistant Material. Reliability Physics, 18th Annual Proceeding, pp. 235–237 (1980)Google Scholar
  6. 6.
    J.P. Mitchell, T.L. Welsher, Conductive Anodic Filament Growth in Printed Circuit Materials. Proceedings of the Printed Circuit World Convention II, pp. 80–93 (1981)Google Scholar
  7. 7.
    J.A. Augis, D.G. DeNure, M.J. LuValle, J.P. Mitchell, M.R. Pinnel, T.L. Welsher, A Humidity Threshold for Conductive Anodic Filaments in Epoxy Glass Printed Wiring Boards. 3rd International SAMPE Electronics Conference, pp. 1023–1030 (1989)Google Scholar
  8. 8.
    B.S. Rudra, M.G. Pecht, Assessing time-to-failure due to conductive filament formation in multi-layer organic laminates. Packag. Manuf. Tech. Part B 17(3), 269–276 (1994)CrossRefGoogle Scholar
  9. 9.
    W.J. Ready, L.J. Turbini, S.R. Stock, B.A. Smith, Conductive Anodic Filament Enhancement in the Presence of a Polyglycol-Containing Flux. IEEE International Reliability Physics Proceedings, pp 267–273 (1996)Google Scholar
  10. 10.
    L.J. Turbini, W.R. Bent, W.J. Ready, Impact of higher melting lead-free solders on the reliability of printed wiring assemblies. J. Surf. Mount Tech. 10–14 (2000)Google Scholar
  11. 11.
    K. Sauter, Electrochemical migration testing results: evaluating PCB design, manufacturing process, and laminate material impacts on CFF resistance. CircuiTree (2002)Google Scholar
  12. 12.
    K. Rogers, P.V.D. Driessche, C. Hillman, M. Pecht, Do you know that your laminates may contain hollow fibers. Print. Circuit. Fabr. 22(4), (1999)Google Scholar
  13. 13.
    K. Rogers, C. Hillman, M. Pecht, S. Nachbor, Conductive filament formation failure in a printed circuit board. Circuit. World. 25(3) (1999)Google Scholar
  14. 14.
    H. Lee, K. Neville, Handbook of Epoxy Resins (McGraw Hill Book Company, New York, 1967), pp. 13-7–13-8Google Scholar
  15. 15.
    M. Li, K. Gohari, M. Pecht, Effect of Temperature and Humidity Cycling on FR-4, Bismaleide Triazine and Cyanate Ester Printed Wiring Boards. 7th International SAMPE Electronics Conference—Critical Materials Processing in a Changing World, pp. 446–457 (1994)Google Scholar
  16. 16.
    M. Pecht, A. Haleh, A. Shukla, J. Hagge, D. Jennings, Moisture ingress into organic laminates. IEEE Trans. Comp. Packag. Tech 22(1), 104–110 (1999)CrossRefGoogle Scholar
  17. 17.
    V. William, et al. Conductive Anodic Filament Resistant Resins. Proceedings of the IPC Printed Circuits Expo, (2002)Google Scholar
  18. 18.
    L. Domeier, J. Davignon, T. Newton, A Survey of Moisture Absorption and Defects in PWB Materials. Proceedings of the 1993 Fall IPC Meeting, pp. 3–5 (1993)Google Scholar
  19. 19.
    K. Rogers, P.V.D. Driessche, C. Hillman, M. Pecht, Do you know that your laminates may contain hollow fibers. Print. Cir. Fabr. 22(4), (1999)Google Scholar
  20. 20.
    K. Rogers, C. Hillman, M. Pecht, S. Nachbor, Conductive filament formation failure in a printed circuit board. Circuit World. 25(3), (1999)Google Scholar
  21. 21.
    M. Pecht, C. Hillman, K. Rogers, D. Jennings, Conductive filament formation: a potential reliability issue in laminated printed circuit cards with hollow fibers. IEEE/CPMT 22(1), 60–67 (1999)Google Scholar
  22. 22.
    M. Pecht, K. Rogers, C. Hillman, Hollow fibers can accelerate conductive filament formation. ASM. Int. Pract. Fail. Anal 1(4), 57–60 (2001)Google Scholar
  23. 23.
    S. O’Connell, A. Whitley, J. Burkitt, S. Ching, A. Fong, T. Brady, S. Tasa, Environmental assessment of halogen-free printed circuit boards, DfE phase II (HDP User Group International, Inc, Scottsdale, AZ, 2004), pp. 1–17Google Scholar
  24. 24.
    IPC Association Connecting Electronics Industries (2003) IPC white paper on halogen-free materials used for printed circuit boards and assemblies. IPC-WP/TR-584, available at: www.ipc.org/TOC/IPC-WP-TR-584.pdf. Accessed 30 June 2009
  25. 25.
    E. Kelley, An Assessment of the Impact of Lead-Free Assembly Processes on Base Material and PCB reliability. Proceedings of IPC APEX Conference pp. S16-2-1 (2004)Google Scholar
  26. 26.
    L. Turbini, Green alternatives to lead-free soldering. Elect. Packag. Prod. Suppl 40(6), 19–20 (2000)Google Scholar
  27. 27.
    S. Ganesan, M. Pecht, Lead-free Electronics (Wiley, Hoboken, NJ, 2006)CrossRefGoogle Scholar
  28. 28.
    M. Pecht, A. Govind, In situ measurements of surface mount IC package deformations during reflow soldering. IEEE Trans. Compon. Packag. Manuf. Techn. Part C 20(3), 207–212 (1999)CrossRefGoogle Scholar
  29. 29.
    IPC-TM-650 2.6.25, Conductive Anodic Filament (CAF) Resistant Test: X-Y axis, The Institute for Interconnecting and Packaging Electronic Circuits. IPC, Northbrook, IL (2003)Google Scholar
  30. 30.
    M. Li, M. Pecht, L. Wang, The Physics of Conductive Filament Formation in MCM-L Substrates. Proceedings of INTERpack, Maui, HI, pp. 517–527 (1995)Google Scholar
  31. 31.
    K. Rogers, M. Pecht, A variant of conductive filament formation failures in PWBs with 3 and 4 mil spacings. Circuit. World 32(3), 11–18 (2006)CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2011

Authors and Affiliations

  1. 1.Center for Advanced Life Cycle Engineering (CALCE)University of MarylandCollege ParkUSA
  2. 2.Center for Advanced Life Cycle Engineering (CALCE)University of MarylandCollege ParkUSA

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