# Presentation: 499859

## 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

## Typical Electronic Equipment 
Background
Plan
Test Results
Where We Go From Here

**Background**
**Plan**
**Test Results**
**Where We Go From Here**

**Discussion Points**

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## Typical Electronic Equipment 

**Typical Electronic Equipment **

- Cooling holes

- Circuit cards

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## Typical Printed Wiring Board

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## 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  

- 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

## 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

- All PWB parts must have certification data
- Certification by “similarity to previously approved components” currently has limited FAA acceptance for new PWBs

**Background****Certification Issues**

- March 5, 2003

## 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) 

- 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)

**Background****Historical**

- March 5, 2003

## BackgroundCurrent 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

- 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

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## 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 - Objectives

**Plan - Objectives**

- Conformalcoating registered & tested perUL 94-V0
- ?

- NO

- 12-sec vertical flammability test

- NO

- YES

- Flammability test and report

- PWB design

- YES

- PWB Laminates registered & tested per IPC 4101 flam* Reqmts.
- ?

- Flammabilitycertification established?

- Similarity
- established
-  to documented
- test
- results
- ?

- YES

- NO

- * IPC 4101 paragraph 2.10.3.1 and tested per method IPC-TM-650

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## 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

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## 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

- 3 resin
- systems
- 21, 24, 41

- resinsystem

- 21
- 21
- 21
-  ...
- 24
- 24
- 24
- ...
- 41
- 41
- 41
- ....

- 4 laminate
- manufacturers
- Isola, Double Treat, Nelco, & Polyclad

- I
- D
- N
-  ...
- N
- I
- P
- ...
- P
- N
- I
- ....

- manuf.

- 3 Thicknesses

- Layers

- Thin
- Med
- Thick
-  ...
- Thin
- Med
- Thick
- ...
- Thin
- Med
- Thick
- ....

- Coating

- 3 conformal coatings

- Acrylic
- none
- none
-  ...
- none
- Urethane
- none
- ...
- none
- none
- Silicone
- ....

- 3 samples
- each

- 3
- 3
- 3
-  ...
- 3
- 3
- 3
- ...
- 3
- 3
- 3
- ....

- 45 PWBs tested

- 96 total

- 51 PWBs yet to be tested

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## IPC 4101 Resin Systems

- Reinforcement

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## IPC 4101 Conformal Coating

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## Test Results To-Date Conformed Testing at the Boeing Facility

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## FAA Tech Center /24 PWB 12 sec.burn test results (Nov. 2002)

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## Future Testing

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## To-Date Results 

- Inches

- Seconds

- Max Extinguishing Time = 15 Sec

- Max Burn Length = 8 in.

- /24

- /24

- /24

- /24

- /21

- /24

- /24

- /24

- /24

- /21

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## Typical Burn Lengths

**Typical Burn Lengths**

- 12 sec vertical
- Zero” burn length

- 12 sec vertical
- 0.1” burn length

- 60 sec vertical
- 1” burn length

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## Typical Burn Lengths

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## Existing Individual Board Certification Test Results

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## Existing Individual Board Certification Test Results

**Existing Individual Board ****Certification Test Results**

- March 5, 2003