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Flammability Certification of Printed Wiring Boards

Flammability Certification of Printed Wiring Boards. James M. Peterson Boeing Commercial Airplanes Group International Materials Fire Test Working Group March 5, 2003. Discussion Points. Typical Electronic Equipment Background Plan Test Results Where We Go From Here.

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Flammability Certification of Printed Wiring Boards

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  1. Flammability Certification of Printed Wiring Boards James M. Peterson Boeing Commercial Airplanes Group International Materials Fire Test Working Group March 5, 2003 March 5, 2003

  2. Discussion Points • Typical Electronic Equipment • Background • Plan • Test Results • Where We Go From Here March 5, 2003

  3. Typical Electronic Equipment Cooling holes Circuit cards March 5, 2003

  4. Typical Printed Wiring Board March 5, 2003

  5. Typical Electronic Equipment • Electric Wire • Printed Wiring Boards (PWBs) • Cathode Ray Tubes • Liquid Crystal Displays • Transformers • Switches • Small Components (diodes, resistors, etc.) March 5, 2003

  6. BackgroundReasons for Electronic Redesign • Airline requests for increased functionality • More features and options • In-flight entertainment • Product improvements • Updates, problem resolution, production improvements • Component obsolescence • Cancellation of the military specifications • Commercial components have a shorter production life due to high volume users March 5, 2003

  7. BackgroundCertification Issues • Certification of PWBs requires FAA 25.853 12-sec vertical Bunsen burner test • All PWB parts must have certification data • Certification by “similarity to previously approved components” currently has limited FAA acceptance for new PWBs March 5, 2003

  8. BackgroundHistorical • In the 1960’s, there were only a few electronic components in the EE bay and flight deck. • Only self-extinguishing materials compliant to Military Standards were used • Today significantly more electrical/electronic components are used • Military production standards have been canceled and replaced by industry production standards • IPC 4101 has replaced MIL standards for Printed Wiring Boards (PWBs) March 5, 2003

  9. BackgroundCurrent Study • PWBs tested so far are production boards • Procured before components were installed • Full FAA conformity required • Test results are suitable for certification data • FAA Technical Center has conducted parallel tests to corroborate results • FAA Seattle Aircraft Certification Office is involved in process planning March 5, 2003

  10. Plan – Develop Process for Certification by Similarity • Testing of every PWB part number does not add value if similarity data can be demonstrated • Showing compliance by board material similarity is a significant need for PWBs • PWBs are in constant redesign • Most PWB redesign does not change materials • Software updates • Re-locating electronic components and microcircuits • Baseline testing of PWB and continuous process control of components provides assurance March 5, 2003

  11. Plan - Objectives • Classify and test PWBs according to IPC 4101 “slash sheet” classifications • Use “slash sheet”, a specification for laminates made of a particular reinforcing fiber and a particular resin system, e.g., “/24” refers to an E-glass reinforcing fiber and FR epoxy resin • Develop baseline flammability certification data for PWBs by reinforcing fiber and resin type • Validate a certification process using similarity of reinforcing fiber and resin type baseline data and industry standard specifications March 5, 2003

  12. Plan - Objectives Flammability test and report PWB design 12-sec vertical flammability test Flammabilitycertification established? NO PWB Laminates registered & tested per IPC 4101 flam* Reqmts. ? NO YES Similarity established to documented test results ? Conformalcoating registered & tested perUL 94-V0 ? YES NO YES * IPC 4101 paragraph 2.10.3.1 and tested per method IPC-TM-650 March 5, 2003

  13. Current Activity • Test matrix basis • Test PWBs from several manufactures • Test three PWB thicknesses from each slash sheet type • Test PWBs with and without conformal coating • Three predominant conformal coatings March 5, 2003

  14. Longer Range Activity • 13 IPC-4101 resin systems commonly used • 21, 24, 25, 26, 30, 40, 41, 42, 50, 53, 55, 60, & 71 • Use process to establish certification by similarity for the predominant resin systems -- 21 and 24 • 21 and 24 (epoxy/glass) have flammability requirements • 41 (polyimide/glass) has no flammability requirements Certification by similarity may not be possible. • Use certification by similarity process for other resin systems as appropriate • Work to have International Materials Fire Test Working Group agree with and endorse the process • Include in Fire Test Handbook? March 5, 2003

  15. Current Test Plan Matrix 3 Thicknesses 3 conformal coatings • 4 laminate • manufacturers • Isola, Double Treat, Nelco, & Polyclad resinsystem manuf. Layers Coating 3 samples each 21 21 21 … 24 24 24 … 41 41 41 …. I D N … N I P … P N I …. Thin Med Thick … Thin Med Thick … Thin Med Thick …. Acrylic none none … none Urethane none … none none Silicone …. 3 3 3 … 3 3 3 … 3 3 3 …. 45 PWBs tested 3 resin systems 21, 24, 41 51 PWBs yet to be tested 96 total March 5, 2003

  16. IPC 4101 Specification Sheet # Resin System ID Reference Glass Transition Range Industry Testing 21 Woven E-glass fabric Epoxy, Flame Resistant NEMA FR-4, MIL-S13949/04–GF, GFN, GFK 110°C Minimum IPC-TM-650 per IPC 4101. Monthly samples at the laminate level. 24 Woven E-glass fabric Majority Epoxy, Modified or Unmodified, Flame Resistant NEMA FR-4, MIL-S-13949/04 – GF, GFG 150°C - 200°C IPC-TM-650 per IPC 4101. Monthly samples at the laminate level. IPC 4101 Resin Systems Reinforcement March 5, 2003

  17. Conformal Coat Description Boeing Conformal Coat Flammability Requirements Type AR (Acrylic) per IPC-CC-830 UL 94 V0 Type UR (Urethane) per IPC-CC-830 UL 94 V0 Type SR (Silicone) per IPC-CC-830 UL 94 V0 IPC 4101 Conformal Coating March 5, 2003

  18. Test Results To-Date Conformed Testing at the Boeing Facility March 5, 2003

  19. FAA Tech Center /24 PWB 12 sec.burn test results (Nov. 2002) March 5, 2003

  20. Future Testing March 5, 2003

  21. To-Date Results Max Burn Length = 8 in. Inches Max Extinguishing Time = 15 Sec /24 /24 /24 /24 /21 Seconds March 5, 2003 /24 /24 /24 /24 /21

  22. Typical Burn Lengths 12 sec vertical Zero” burn length 60 sec vertical 1” burn length 12 sec vertical 0.1” burn length March 5, 2003

  23. Typical Burn Lengths March 5, 2003

  24. Existing Individual Board Certification Test Results March 5, 2003

  25. Existing Individual Board Certification Test Results March 5, 2003

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