lead free reliability study by boeing
TRANSCRIPT
© The Boeing Company 2002
Boeing’s Lead-Free Solder Efforts
Dr. Richard E. PinckertDirector, Design Integration &
Environmental AssuranceBoeing Military Aircraft & Missile Systems Group
Saint Louis, MO
1st European Union/United States Lead-Free SolderInterface Meeting
London, W1A U.K.March 27, 2002
CC14060001.ppt
© The Boeing Company 2002
AgendaAgenda
• Historical Approach• JG-PP Concept• JG-PP/Boeing Nonchrome Primer
Program• Boeing Lead Free Solder Activities• Testing• Future Lead Free Solder Activities
© The Boeing Company 2002
DoD
Historical ApproachHistorical Approach
Support andProgrammatics
Support andProgrammatics
Technical TaskInitiation and
Execution
Technical TaskInitiation and
Execution
Support andBusiness
Requirements
Support andBusiness
Requirements
@@
@
@
@
@@
DoD/BoeingF-15 Team
DoD/BoeingF/A-18 Team
DoD/BoeingSLAM Team
DoD/BoeingT-45TS Team
DoD/BoeingC-17 Team
DoD/BoeingAV-8B Team
Boeing
© The Boeing Company 2002
JG-PP ConceptJG-PP ConceptDoDDoD BoeingBoeing
• F/A-18• Harpoon/
SLAM• T-45TS
• F/A-18• Harpoon/
SLAM• T-45TS JG-PPJG-PP
•AV-8B•AV-8B
• F-15• C-17• F-15• C-17
© The Boeing Company 2002
Selection FactorsSelection Factors Program Offices Selected
Elimination of ChromatedPrimer on Exterior Surfaces– Improve Working Environment– EPA Regulation– Pending OSHA Regulation– Material Change Requires
Program Approvals– Life Cycle Cost Benefits– Primers Available Commercially
Program Offices SelectedElimination of ChromatedPrimer on Exterior Surfaces– Improve Working Environment– EPA Regulation– Pending OSHA Regulation– Material Change Requires
Program Approvals– Life Cycle Cost Benefits– Primers Available Commercially
© The Boeing Company 2002
ChallengesChallenges• Replace Hexavalent
Chromium - theHistorical CorrosionInhibitor forMost AluminumAircraft
• Define AcceptableTesting - Lab Testsand StandardsEstablishedfor ChromatedPrimers
• Minimize Risk
• Replace HexavalentChromium - theHistorical CorrosionInhibitor forMost AluminumAircraft
• Define AcceptableTesting - Lab Testsand StandardsEstablishedfor ChromatedPrimers
• Minimize Risk
© The Boeing Company 2002
Joint Test ProtocolJoint Test ProtocolLaboratory Testing Operational Testing++
© The Boeing Company 2002
Test Units Fielded Completed Inspections
Activity '96
Laboratory Testing(2) F-15 Aircraft + (2 in 2000)(7) F/A-18 Aircraft(4) T-45 Aircraft (2) Harpoon Canisters
‘97 ‘98 ‘99 ‘00 ‘01
(1) AV-8B Aircraft
Implementation Decision
(1) C-130 Aircraft (1) C-17 Aircraft
Project MilestonesProject Milestones
© The Boeing Company 2002
Operational Testing SummaryOperational Testing Summary
• Trend of operational performance validatedlaboratory test results
• Overall performance differences were notperceptible to field personnel
• Operational testing built confidence innonchrome primers for exterior moldlineapplications but not sufficient forimplementation
© The Boeing Company 2002
2001 Lead Free SolderActivities at Boeing
© The Boeing Company 2002
Lead-EliminationLead-Elimination• Boeing conducted a test program in 2001 to
determine:– Do lead-free solder joints have long-term reliability
equivalent to tin/lead?– Do lead-free solders leach toxic metals?
• Materials that were tested:– Lead-free solder for reflow soldering:
Tin/3.8%Silver/0.7%Copper– Lead-free solder for wave soldering:
Tin/0.7%Copper– Lead-free board finishes: Immersion silver, OSP
and electrolytic gold– Lead-free component finish: Tin/0.7%Copper
© The Boeing Company 2002
Soldering OperationsSoldering Operations• Reflow Soldering: solder paste is melted in an oven
• Wave Soldering: components are attached toboards using a wave of molten solder
HEAT
SOLDER WAVE
© The Boeing Company 2002
Test VehicleTest Vehicle• Components: 1206 ceramic chip resistors
were chosen because they– are inexpensive– can be obtained with lead-free finishes– have a high failure rate during thermal cycling
• 40 resistors were reflow soldered on the topof each test board
© The Boeing Company 2002
Test Vehicle continuedTest Vehicle continued
• 40 resistors were wave soldered on thebottom of each test board
• The test boards were thermally cycled.Continuous electrical monitoring of the solderjoints was done to detect failures.
• 4380 thermal cycles were accumulated;thermal cycle was -55°C to +125°C with 15minute dwells
© The Boeing Company 2002
Solder/Finish Combinations TestedSolder/Finish Combinations Tested
Board Finish Silver OSP GoldSolder Paste Tin/Silver/Copper Tin/Silver/Copper Tin/Silver/CopperComponent
Finish Tin/Copper Tin/Copper Tin/Copper
Wave Solder Tin/Copper Tin/Copper Tin/Copper
Lead-Free Specimens
Control SpecimensTin/Lead
Tin/Lead Tin/Lead Tin/Lead Tin/Lead
Tin/Lead Tin/Lead Tin/Lead Tin/Lead
Tin/Lead Tin/Lead Tin/Lead Tin/Lead
Board Finish Silver OSP GoldSolder PasteComponent
FinishWave Solder
© The Boeing Company 2002
Tin/Lead Tin/CopperSolder Joint AppearanceSolder Joint Appearance
Tin/Silver/CopperLead-free solder jointsare typically striated andrough. This means thatinspection criteria mustbe changed.
© The Boeing Company 2002
Reliability Test ResultsReliability Test ResultsReflowed Tin/Silver/CopperSolder(Tin/Copper Component Finish)
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
0 1000 2000 3000 4000 5000Cycles
Failu
res
(%) Tin/Lead Solder Control
Immersion Silver Finish
OSP Finish
Nickel/Electrolytic GoldFinish
© The Boeing Company 2002
Reliability Test ResultsReliability Test Results
Tin/Copper Wave Solder(Tin/Copper Component Finish)
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
0 1000 2000 3000 4000 5000Cycles
Failu
res
(%) Tin/Lead Solder Control
Immersion Silver Finish
OSP Finish
Nickel/Electrolytic GoldFinish
© The Boeing Company 2002
Reliability Test ResultsReliability Test Results• Reflowed tin/silver/copper is less reliable than
tin/lead.– Reduced reliability is seen with ceramic
components (e.g., chip resistors) that stress thesolder joints due to a large CTE mismatch with theboard.
– Other studies have seen similar results.– Other studies have shown that tin/silver/copper
performs as well as tin/lead when used with morecompliant components.
– Ceramic components are the “weakest link” wheretin/silver/copper is concerned.
• Tin/copper (wave soldered) is as reliable astin/lead.
© The Boeing Company 2002
Leachate TestingLeachate Testing• Leachate testing was conducted on the
solder joints to verify that the tin/silver/coppersolder would not be a bigger environmentalproblem than tin/lead solder.– Leachate Tests
> USEPA TCLP Test> State of Texas Seven-Day Distilled Water
Leachate Test– Elements looked for
> Pb (a neurotoxin and a haematotoxin)> Ag (very toxic to marine life)
© The Boeing Company 2002
Leachate Testing continuedLeachate Testing continued
• No silver was detected in leachates from thelead-free boards (detection limit was 0.01mg/l). Lead was leached from the controlboards in amounts above USEPA limits (5.0mg/l).
© The Boeing Company 2002
ConclusionsConclusions• Reflowed tin/silver/copper is less reliable than
tin/lead when used with ceramic components.
• Tin/silver/copper has little potential for leachingtoxic silver.
• Tin/copper (wave soldered) is as reliable astin/lead.
• Further work is needed to find a highly reliablesolder for reflow operations.
© The Boeing Company 2002
2002 Lead-EliminationActivities at Boeing
2002 Lead-EliminationActivities at Boeing
• The reliability of six lead-free solders for reflowoperations will be determined.
• The solders will also be contaminated with lead todetermine the effect of the lead upon reliability.This simulates the condition where lead-containingboards are reworked with lead-free solders.
• Boeing will support the activities of the No-LeadSolder JG-PP.