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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

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

discussion points
Discussion Points
  • Typical Electronic Equipment
  • Background
  • Plan
  • Test Results
  • Where We Go From Here

March 5, 2003

slide3

Typical Electronic Equipment

Cooling holes

Circuit cards

March 5, 2003

typical electronic equipment
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

background reasons for electronic redesign
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

background certification issues
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

background historical
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

background current study
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

plan develop process for certification by similarity
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

plan objectives
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

plan objectives1
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

current activity
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

longer range activity
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

current test plan matrix
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

ipc 4101 resin systems

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

ipc 4101 conformal coating

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

future testing
Future Testing

March 5, 2003

to date results
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

typical burn lengths
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