# Presentation: 061335

## Flammability Assurance for Printed Wiring Boards Certification by Similarity Analysis Proposal 

- Flammability Assurance for Printed Wiring Boards Certification by Similarity Analysis Proposal

**Boeing Commercial Airplanes Group**

**PWB Material Working Group**
**June, 2003**

## Test Results Summary
Background on PWB Working Group Task
Working Group/Test Plan Objectives
Test Results
Data Interpretation
Proposed Certification by Similarity Process
Recommendations

- Background on PWB Working Group Task
- Working Group/Test Plan Objectives
- Test Results
- Data Interpretation
- Proposed Certification by Similarity Process
- Recommendations

- Agenda

## Test Results Summary

- Data shows certification of PWBs by similarity is a valid process
- Investigated IPC*-4101 /21 and /24 laminates, and  IPC-CC-830 conformal coatings meeting IPC-TM-650 or UL-94 V0 flammability requirements
- No factors showed significant effect on PWB FAR flammability
- Laminate materials not a significant factor for /21 and /24 bare PWBs
- Thickness, layer count, PWB fabricator (fabrication process), and laminate manufacturer had minimal effect
- Adding conformal coating not a significant factor for /21 and /24 laminates
- Acrylic, urethane, and silicone conformal coatings all showed minimal effect on extinguishing time and burn length
- All conformal coated PWBs met FAR 25 requirements by large margin
- * The Institute for Interconnecting and Packaging Electronic Circuits

## PWB Working Group – Project Background

- FAA IMFTWG Subgroup was established to evaluate flammability certification alternatives to FAR 12 second vertical flammability test for each PWB part number
- Testing by individual part number is inefficient and expensive
- Baseline testing and establishing acceptable PWB industry specifications and process control provides better assurance
- Showing compliance by material similarity is a significant need for aerospace electronics
- FAA Seattle Aircraft Certification Office is involved in process and test plan development

## Flammability Test Plan Objectives

- Develop baseline FAR 25 flammability certification data for PWBs from IPC-4101 /21 and /24 resin “families” laminates and conformal coatings from IPC-CC-830 acrylic, urethane, and silicone material “families”
- PWB laminates meet IPC-4101 flammability requirements
- IPC-TM-650 (flammability) test method 2.3.10, or UL-94 V0
- Conformal coatings meet IPC-CC-830 plus UL-94 V0
- Validate that PWBs show similarity to previously tested materials contingent on meeting above criteria

## Flammability Test Plan Objectives

- Classify and test PWBs according to IPC-4101 data sheets (resin types)
- Test Plan Variables
- Test various thicknesses of PWBs from each resin system
- Test PWBs from several different pwb fabricators
- Test PWBs fabricated from different laminate manufactures

## Flammability Test Plan Objectives

- Classify and test conformal coatings according to IPC-CC-830 material families
- Three types of conformal coatings were included
- AR = Acrylic – Humiseal 1H71
- UR = Urethane – Dymax 984 LVUF
- SR = Silicone – Humiseal 1C53
- All coatings carry a UL-94 V0 flame rating

## Test  Summary

- 82 Production PWB’s tested
- Full FAA Conformity appropriate for certification data
- PWBs fabricated from the two major IPC 4101 resin “families” used in PWB fabrication today
- Low temp epoxy /21, high temp epoxy /24
- PWBs manufactured by four different PWB fabricators
- Viasystems, Tyco, Holaday Circuits, Cosmotronics
- PWBs fabricated from IPC-4101 laminates from 4 different manufacturers
- Nelco, Double Treat, Polyclad, Isola
- Both bare and conformal coated PWBs were tested
- Acrylic, urethane, and silicone conformal coatings meeting IPC-CC-830 and UL-94 V0
- Acrylic, urethane, and silicone

## Background on the Resin Systems

## Background on the three conformal coatings

## Bare PWB Test Results

- *Testing Performed by FAA at FAA Tech Center

## Conformally Coated PWB Test Results

## Burn Length Examples

## Burn Length Examples

- 12 sec vertical
- Zero” burn length

- 12 sec vertical
- 0.1” burn length

- 60 sec vertical
- 1” burn length

## Test Results Summary

- Data shows certification of PWBs by similarity is a valid process
- Investigated IPC*-4101 /21 and /24 laminates, and  IPC-CC-830 conformal coatings meeting IPC-TM-650 or UL-94 V0 flammability requirements
- No factors showed significant effect on PWB FAR flammability
- Laminate materials not a significant factor for /21 and /24 bare PWBs
- Thickness, layer count, PWB fabricator (fabrication process), and laminate manufacturer had minimal effect
- Adding conformal coating not a significant factor for /21 and /24 laminates
- Acrylic, urethane, and silicone conformal coatings all showed minimal effect on extinguishing time and burn length
- All conformal coated PWBs met FAR 25 requirements by large margin
- * The Institute for Interconnecting and Packaging Electronic Circuits

## Proposed Criteria for Flammability Certification of PWBs by Similarity

- FAR 25 flammability certification of Printed Wiring Boards PWBs by similarity to previously tested materials would be acceptable based upon the following processes and criteria:
- Industry specifications are used to group the PWBs into “material families”.  Certification by similarity would be limited to materials with the following criteria;
- PWBs claiming similarity must be manufactured in compliance with the same IPC-4101 laminate specification sheets (i.e. from the same resin family) for which FAR 25 certification data exists.
- PWBs must be constructed only from laminates according to IPC-4101 specification sheets that either include a required IPC flammability test as a laminate test, or include the flammability test as a PWB drawing requirement test via UL 94 and carry a V0 flame rating.
- 3) 	Conformal coating used on the PWB must be IPC-CC-830 compliant and carry a UL-94 VO flame rating.
- PWB certification data is established per FAR (12-sec vertical).  Another PWB part number may claim similarity to the original certification test data if the PWB satisfies the above criteria.

##  Proposed Certification by Similarity  Process Flow

-  Proposed Certification by Similarity  Process Flow

- Conformalcoating registered & tested UL 94 V0 ?

- NO

- YES

- NO

- FAR 25Flame Test

- NO

- YES

- Flame Test Report

- Design for a PWB

- YES

- PWB Laminates registered & tested per IPC 4101* or UL 94- V0?

- Flammability Assured

- Similarity to
- Documented
- test results

- IsPWB registered & tested per UL 94- V0?
- **

- * Requirement 2.10.3.1   IPC Test Method TM 650 for flammability
- ** Far 25 Certification data must exist for     similar pwb constructed of similar  laminate

## Recommendations

- Short Term Recommendations
- Formal Memo of Agreement between Boeing and FAA to allow implementation of proposed PWB Certification by Similarity Process
- Based upon released requirements document
- Mid/Long Range Recommendations
- FAA IMFTWG PWB sub-group to document PWB certification by similarity process for inclusion in appropriate FAA documentation (Fire Test Handbook, AC, ?)