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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

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

Agenda

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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

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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

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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

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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

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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

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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

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Background on the Resin Systems

PWB Speci-fication Sheet #

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

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Background on the three conformal coatings

Conformal Coat Description/Classification

Flammability Rating

Type AR (Acrylic) per IPC-CC-830Humiseal

UL-94 V0

Type UR (Urethane) per IPC-CC-830Dymax 984 LVUF

UL-94 V0

Type SR (Silicone) per IPC-CC-830Humiseal 1C53

UL-94 V0

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Bare PWB Test ResultsBoeing Production P/N

PWB Fabricator IPC 4101 Data Sheet

Laminate Manufacturer

# of PWB Circuitry Layers

Thickness (inches)

Conformal Coating

Average Ext Time (seconds)

Average Burn Length (inches)

Meets Proposed Cert by Sim Criteria

906-30197 Viasystems 24 Isola 4 0.072 None 2.7 0.1 Yes906-71599 Viasystems 24 Isola 10 0.086 None 1.2 0.8 Yes906-40156 Viasystems 24 Isola 18 0.12 None 0 0 Yes

None 906-60424 Holaday 24 Double Treat 2 0.09 None 0 0.9 Yes906-30191 Holaday 24 Double Treat 6 0.09 None 0 0 Yes906-30193 Holaday 24 Double Treat 10 0.1 None 0 0.1 Yes

None 906-40055 Tyco 24 Nelco 12 0.062 None 0 0 Yes906-30263 Tyco 24 Nelco 14 0.079 None 2.4 0.1 Yes906-30264 Tyco 24 Nelco 14 0.091 None 0 0 Yes

None 906-40149 Cosmotronics 24 PolyClad 8 0.112 None 1.3 0.1 Yes906-60178 Cosmotronics 24 PolyClad 10 0.093 None 1.3 0.1 Yes906-71600 Cosmotronics 24 PolyClad 12 0.1 None 1.7 0.1 Yes

906-60242 Holaday 21 Double Treat 2 0.09 None 1.2 0.8 Yes906-30191 Holaday 21 Double Treat 6 0.09 None 0 0 Yes906-30193 Holaday 21 Double Treat 10 0.1 None 0 0.7 Yes

906-71600 * Cosmotronics 24 Polyclad 12 0.1 None 1 0.1 Yes

906-30193 * Holaday 24 Double Treat 10 0.1 None 0 0.05 Yes

906-40156 * Viasystems 24 Isola 18 0.12 None 0 0 Yes

*Testing Performed by FAA at FAA Tech Center

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Conformally Coated PWB Test Results

Boeing Production P/N

PWB Fabricator IPC 4101 Data Sheet

Laminate Manufacturer

# of PWB Circuitry Layers

Thickness (inches)

Conformal Coating

Average Ext Time (seconds)

Average Burn

Length (inches)

Meets Proposed

Cert by Sim Criteria

906-30197 Viasystems 24 Isola 4 0.09 Acrylic 7.5 0.7 Yes906-71599 Viasystems 24 Isola 10 0.09 Urethane 1.1 0.4 Yes906-40156 Viasystems 24 Isola 18 0.1 Silicone 0 0.1 Yes

906-60242 Holaday 24 Double Treat 2 0.1 Acrylic 0.4 0.5 Yes906-30191 Holaday 24 Double Treat 6 0.09 Urethane 0 0 Yes906-30193 Holaday 24 Double Treat 10 0.1 Silicone 0 0.5 Yes

906-40055 Tyco 24 Nelco 12 0.062 Acrylic 0 0.5 Yes906-30263 Tyco 24 Nelco 14 0.079 Urethane 0 0 Yes906-30264 Tyco 24 Nelco 14 0.091 Silicone 0 0.2 Yes

906-40149 Cosmotronics 24 PolyClad 8 0.112 Acrylic 0 0.3 Yes906-60178 Cosmotronics 24 PolyClad 10 0.093 Urethane 0 0 Yes906-71600 Cosmotronics 24 PolyClad 12 0.1 Silicone 1.9 0.1 Yes

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Burn Length Examples

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Burn Length Examples

12 sec verticalZero” burn

length

12 sec vertical0.1” burn

length

60 sec vertical1” burn length

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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

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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;

1) 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.

2) 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.

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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 Documentedtest 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

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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, ?)