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Flammability Assurance for Printed Wiring Boards Certification by Similarity Analysis Proposal. Boeing Commercial Airplanes Group. PWB Material Working Group June, 2003. Agenda. Test Results Summary Background on PWB Working Group Task Working Group/Test Plan Objectives Test Results

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flammability assurance for printed wiring boards certification by similarity analysis proposal

Flammability Assurance for Printed Wiring BoardsCertification by Similarity Analysis Proposal

Boeing Commercial Airplanes Group

PWB Material Working Group

June, 2003

agenda
Agenda
  • Test Results Summary
  • Background on PWB Working Group Task
  • Working Group/Test Plan Objectives
  • Test Results
  • Data Interpretation
  • Proposed Certification by Similarity Process
  • Recommendations
test results summary
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
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
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 objectives1
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 objectives2
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
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

PWB Speci-ficationSheet #

Re-inforcement

Resin System

ID Reference

Glass Transition Range

Industry Flammability Testing

IPC-4101 /21

WOVEN E-GLASS FABRIC

Epoxy, Flame Resistant

NEMA FR-4, MIL-S-13949/04–GF, GFN, GFK

110°C Minimum

IPC-TM-650 2.3.10 per IPC-4101---

Monthly samples at the laminate level

lPC-4101 /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 2.3.10 per IPC 4101 ---

Monthly samples at the laminate level

Background on the Resin Systems
background on the three conformal coatings

Conformal Coat Description/Classification

Flammability Rating

Type AR (Acrylic) per IPC-CC-830

Humiseal

UL-94 V0

Type UR (Urethane) per IPC-CC-830

Dymax 984 LVUF

UL-94 V0

Type SR (Silicone) per IPC-CC-830

Humiseal 1C53

UL-94 V0

Background on the three conformal coatings
bare pwb test results
Bare PWB Test Results

*Testing Performed by FAA at FAA Tech Center

burn length examples1
Burn Length Examples

12 sec vertical

Zero” burn length

60 sec vertical

1” burn length

12 sec vertical

0.1” burn length

test results summary1
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
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

Design for a PWB

Flame Test Report

FAR 25Flame Test

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

IsPWB registered & tested per UL 94- V0?

**

NO

NO

Flammability Assured

NO

YES

YES

Conformalcoating registered & tested UL 94 V0 ?

Similarity to

Documented

test results

YES

* 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
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, ?)