NASA/TM—2008–215577

Long-Term Effects of Soldering By-Products on Nickel-Coated Copper WireT.D. Rolin and R.E. HodgeMarshall Space Flight Center, Marshall Space Flight Center, Alabama

October 2008

National Aeronautics andSpace AdministrationIS20George C. Marshall Space Flight CenterMarshall Space Flight Center, Alabama35812

https://ntrs.nasa.gov/search.jsp?R=20080048252 2018-05-10T21:52:38+00:00Z

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�

NASA/TM—2008–215577

Long-Term Effects of Soldering By-Products on Nickel-Coated Copper WireT.D. Rolin and R.E. HodgeMarshall Space Flight Center, Marshall Space Flight Center, Alabama

October 2008

Nat�onal Aeronaut�cs andSpace Adm�n�strat�on

Marshall Space Fl�ght Center • MSFC, Alabama 35812

��

Ava�lable from:

NASA Center for AeroSpace Informat�on7115 Standard Dr�ve

Hanover, MD 21076 –1320301– 621– 0390

Th�s report �s also ava�lable �n electron�c form at<https://www2.st�.nasa.gov>

���

TABLE OF CONTENTS

1. INTRODUCTION ......................................................................................................................... 1

2. ANALYSIS .................................................................................................................................... 4

3. CONCLUSIONS ............................................................................................................................ 9

BIBLIOGRAPHY ............................................................................................................................... 11

�v

v

LIST OF FIGURES

1. Reactionofcopperoxidewithabieticacidproducesawater-insolublecopper soapcalledcopperabietate.................................................................................................. 1

2. Photographofwiresprovidedforanalysisofcorrosion.Thesmallestboxesthat makeupthegridinthisphotomeasure1×1cm................................................................ 2

3. Opticalphotographsof(a)Cleanwireand(b)Wirecoveredingreenmaterial................. 3

4. FTIRspectraof(a)Wireinsulationand(b)Greenmaterial............................................... 5

5. High-magnificationimageofwireshowingthepresenceofcontaminationthatislow molecularweightandinsulatingasindicatedbythelargeamountofcharging................. 6

6. High-magnificationimageofthecontaminationfromwhichanEDAXspectrum wastaken............................................................................................................................. 6

7. EDSspectrumindicatinganorganicmaterialandnochlorinecontamination. Thelocationofchlorine,hadtherebeenapeak,ismarkedwithitssymbol,Cl................. 7

8. Polarizedmicroscopicimageofcontaminatedareashowinganintactnickelcoating (blackarrows)andnocopperdegradation(×500magnification)....................................... 7

9. Polarizedmicroscopicimageofcontaminatedareashowinganintactnickelcoating andnocopperdegradation(×1000magnification)............................................................. 8

10. Polarizedmicroscopeimageofcontaminatedwireshowingminimumnickel thicknessismetbycalibratedmeasurement(numbersreportedinmicrons)..................... 8

v�

LIST OF ACRONYMS

EDS energydispersivespectroscopy

FTIR FourierTransformInfrared

v��

NOMENCLATURE

C-H carbon-hydrogenbond

C–O carbon-oxygenbond

O–H oxygen-hydrogenbond

R genericorganic

R–COO–Cu–OOC–R copperabietate

R–COOH carboxylicacid

v���

1

TECHNICALMEMORANDUM

LONG-TERM EFFECTS OF SOLDERING BY-PRODUCTS ON NICKEL-COATED COPPER WIRE

1. INTRODUCTION

Rosin,amaterialobtainedfromconifertrees,isafluxmaterialtypicallyincorporatedintothecoresofsolderwire.Thismaterialhasbeenusedforyearstoaidinthesolderwettingprocessbyremov-ingsurfaceoxidesfromthematerialstobesoldered.Theprimaryconstituentofcommercialrosinisacarboxylicacidknownasabieticacid.1Theremovalofsurfaceoxidesoccurswhenthiscarboxylicacidisconvertedtoametalestercalledabietate.Thereactionthatleadstotheabietateformisillustratedinfigure1.2Althoughsolderingrequirementsusuallystatethattherosinresidueshouldberemovedfromsolderedareas,usuallycleanedusingisopropylalcohol,itispossiblethatthematerialcanbewickedundertheinsulationofwiresbycapillaryaction.Thealcoholitselfcanassistwiththewickingandsubsequentdepositionoffluxresidueundertheinsulation.Excessivewickingisprohibitedbysolderingrequirements,butmanytimesthewickedmaterialisnotdetectedduetotheopaquenessoftheinsula-tion.Whencopperwireispartofthesolderingprocessthereactionproductiscopperabietate,whichisgreenincolor.However,copper(II)chlorideisalsogreenincolorandisanunwanted,corrosivecontaminate.Thepurposeofthisstudyistodeterminethecompositionofthegreenmaterialfoundonthirty-year-old,downgradedflightcablesandtoestablishthelong-termcorrosiveeffectsofthismaterialonnickel-platedcopperwire.

CH3

CH(CH3)2

CH3COOH

2(R–COOH) + CuO

X(R–COOH) + PbOSnOSnO2PbO2

(R–COO)xSn(R–COO)xPb

R–COO–Cu–OOC–R

Abietic Acid d - Pimaric Acid

R Grade (Rosin Flux)

H

H

CH3

CH2

CH3COOH

H

H

OCH3

F�gure 1. React�on of copper ox�de w�th ab�et�c ac�d produces a water-�nsoluble copper soapcalledcopperabietate.

2

Twowireassemblieswereanalyzedduringthisstudy.Photographsofbothwiresweretakenandtheimagesareshowninfigure2.Theshrink-wraptubingthatprotectsthesolderedareawasremovedalongwiththewireinsulationtoascertainthelocationandlengthofgreendiscoloration.Theshrink-wraptubingandinsulationwereremovedfromthewireandahighmagnificationimageofcleanandcontaminatedwireisshowninfigure3.Thelocationofthecontaminationshowsthatasignificantamountofwickinghadoccurred.Theshorterwirehasserialnumber009andwasdesignatedwithtwootheridentifiers:5104123-5andP48-55.Thenickel-coatedcopperoverallshieldportionofthisassem-blywasapproximately2.5incheslongandeachofthewirelead-outswasapproximately2.5incheslongmakingatotallengthof5inches.Thecontaminationonthiswirewasfoundtoextendfromthesolderedendto0.75inchesdownthelengthofthewire.TheotherwirehasadesignatorofBTB6andismuchlonger.Thedesignationidentifiesthelocationwherethecableisterminatedintheboxandwasusedtodifferentiatethetwowires.ThetotallengthoftheshieldedportionofBTB6isapproximately24inchesandeachofthewirelead-outswasapproximately3.5incheslongmakingthetotallength27.5incheslong.Thecontaminationonthiswirewasfoundtoextendfromthesolderedendtoapproximately1inchdownthelengthofthewire.FourierTransformInfrared(FTIR)spectrawereacquiredfromtheinsula-tionandfromthemetalitself,bothofwhichwerecoatedwithagreenmaterial.AnFTIRspectrumofuncontaminatedinsulationwasalsotakenforcomparison.Thebarewirewasalsoplacedinascanningelectronmicroscopetoconductanenergydispersivespectroscopic(EDS)analysis.

F�gure 2. Photograph of w�res prov�ded for analys�s of corros�on. The smallest boxes that makeupthegridinthisphotomeasure1×1cm.

3

F�gure 3. Opt�cal photographs of (a) Clean w�re and (b) W�re covered �n green mater�al.

Acrosssectionofeachsectionofcontaminatedwirewasperformedalongwithanuncontami-natedportionofthesamewire.Thewiresweremountedsuchthattheaxialsurfacewasexposedformetallographicpreparation.Thispositionwasnecessaryinordertodetermineifanycorrosionwaspresentbymeasuringthenickelcoatingthicknessinareasexposedtothegreenmaterial.Thewireswerepottedinatwo-partepoxy(Epo-Resin®andEpo-Hardener®,bothbyBuehler)andallowedtocureovernightwithoutheatorpressure.Astandardgritregimenwasusedtogrindthepottedsamples,namely240-grit,400-grit,800-grit,and1,200-grit.Grindingwasfollowedbypolishingwith6-microndiamondand0.05-micronalumina.

4

2. ANALYSIS

FourierTransformInfraredspectraofthewireinsulationandtheunderlyinggreenmaterialareshowninfigure4.Thetopspectrumisfromanareaofinsulationwherethegreenmaterialwassandwichedbetweentheinsulationandthenickel-coatedcopperwire.Thespectrumrevealsdistinctpolytetrafluoroethylene(PTFE),whichistheinsulation,fingerprintsat1,147and1,201cm–1.Thebot-tomspectrumisrepresentativeofgreenmaterialfromboththeinsulationandthenickel-coatedwire.Thegreenmaterialexhibitedcharacteristicpeaksat1,398cm–1and1,606cm–1thatpointtoanionizedcarboxylatestretchingmode.3,4Thesmallpeakat1,249cm–1resultsfromaC–Ostretchthatisalsoassociatedwiththecarboxylatestructure.4Thesepeakpositionsareclearevidencethatthebulkofthegreenmaterialistheabietateform.Thepeakat1,703cm–1indicatesthatunreactedabieticacidmayalsobepresentbecausethispositionistypicalforthecarbonylstretchofafreecarboxylicacid.5ThetypicalO–Hstretchbandforfreecarboxylicacidsisinthe2,700-3,300cm–1area,butthesizeandshapeofthesignaturefromthegreenmaterialisnotindicativeofastrongO–Hstretchmodeinthisband.TheO–HstretchpeakoffreecarboxylicacidisgenerallyverystrongandbroadandinmostcasesovershadowstheC–Hstretchingpeaks,whichinthiscaseisat2,867and2,925cm–1.3,4ThelackofastrongO–Hstretchpeakiscompellingevidencethatonlysmallamountsofcarboxylicacidarepresent.Inaddition,theweakerO–Hstretchappearstobeshiftedupwardtobetween3,100and3,600cm–1,whichisassoci-atedwithchanginghydrogenbondingowingtoadecreaseoffreecarboxylicacidmoietiesinthegreenmaterial.5

Scanningelectronmicroscopeimagesofthematerialareshowninfigures5and6.Thematerialisclearlyinsulatingduetotheamountofcharging.Energydispersivespectroscopywasusedtoana-lyzetheelementalmakeupofthegreenmaterial,asshowninfigure7.Theenergydispersivespectrumclearlyshowsthatnochloridesexist.ThisevidencecoupledwiththeFTIRdatastronglyindicatesthatthegreenmaterialiscopperabietatewithsomesmall,unreactedabieticacidandnotcopper(II)chlo-ride.

Crosssectionsofthewireswereobtainedsothatnickelthicknessescouldbemeasured,asdem-onstratedinfigures8–10.Typicalnickelthicknessmeasurements,acquiredusingaNationalInstituteofStandardsandTechnologytraceablecalibratedopticalsystem,areshowninfigure10.Theminimumnickelthicknessof50microinches(1.27microns)ascalledoutbythedrawingstowhichtheseassem-blieswerebuilt(40M39526,Sheet5,Section3.3.2.1)andAmericanSocietyforTestingandMaterialsSpecificationB355isclearlymet.Areaswherethecontaminationwasprevalentshowednosignsofgrossdegradationorcorrosionevenafteralmost30yearsofresidingonthewiresurface.

5

0.950.900.850.800.750.700.650.600.550.500.450.400.350.300.250.200.150.100.05

0

1.2

1.1

1

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

4,000 3,500 3,000 2,500 2,000 1,500 1,000 500

4,000 3,500 3,000 2,500 2,000 1,500 1,000 500

Wavenumbers (cm–1)(a)

(b) Wavenumbers (cm–1)

Abso

rban

ceAb

sorb

ance

671.8

672

2.75

766.8

683

7.631,0

38.79

1,196

.641,2

49.20

1,362

.161,4

59.32

1,702

.711,6

06.49

1,978

.492,0

34.792,1

60.62

2,866

.802,9

24.95

1,397

.69

993.8

8 638.3

3

1,146

.581,2

01.03

F�gure 4. FTIR spectra of (a) W�re �nsulat�on and (b) Green mater�al.

6

Figure 5. High-magnification image of wire showing the presence of contamination that is low molecularweightandinsulatingasindicatedbythelargeamountofcharging.

Figure 6. High-magnification image of the contamination from which an EDAX spectrum was taken.

7

0 5 10 15Cursor=2335keW 10cnt ID=Nb lb3 Pt mgl Pb ma2 Pt mg2 Pb mal Y lg2 Thmz2 Nb lb4 Wind Pt.m2nVert=254 Window0.005 - 40.955= 11420 cnt

contaminationshortwire v4

C

Cl Cu Cu

O

Ni

Ni

Figure 7. EDS spectrum indicating an organic material and no chlorine contamination. The location ofchlorine,hadtherebeenapeak,ismarkedwithitssymbol,Cl.

Figure 8. Polarized microscopic image of contaminated area showing an intact nickel coating (blackarrows)andnocopperdegradation(×500magnification).

8

Figure 9. Polarized microscopic image of contaminated area showing an intact nickel coating andnocopperdegradation(×1000 magnification).

Figure 10. Polarized microscope image of contaminated wire showing minimum nickel thicknessismetbycalibratedmeasurement(numbersreportedinmicrons).

9

3. CONCLUSIONS

Thegreenmaterialonthesurfaceofthenickel-coatedcopperwirehasbeenconfirmedwithEDSandFTIRtobecopperabietate.Furtheranalysisusingscanningelectronmicroscopyandhighmagni-ficationopticalmicroscopyconfirmthatnogrossdegradationorcorrosionofthenickel-coatedcopperwirehasoccurred.Thethicknessofthenickelplatingunderareasofcopperabietatestillmeetsthemini-mumthicknessrequirementsevenafterdecadesofexposuretothecopperabietateandsmallamountsofabieticacid.Itshouldbenoted,however,thattheseparticularwireshavebeenundercontrolledenvi-ronments.Duringflight,theirtimeisspentinasealedboxthatisback-filledwithdrynitrogenandisexposedtoambientconditionsduringlidremovalinacleanroom.Thesetestresultsandobservationsreflectcopperabietatebehaviourinthoseenvironments.

10

11

BIBLIOGRAPHY

1. Privatecommunications.KesterIncorporated.2006.

2. J.C.Ivankovits,B.M.Adams,andY.W.Loo:“ControlledAtmospheresforSoldering Processes.”PresentedatNEPCON-Malaysia,<http://www.airproducts.com/NR/rdonlyres/ trcntatms3d40ondvhtduxkueowvo.pdf>.1994,pp.1–12.

3. Lide,David,ed.CRC Handbook of Chemistry and Physics:67thed.,p.F-190,CRCPressInc., BocaRaton,FL,1986.

4. J.Coates:“InterpretationofInfraredSpectra,aPracticalApproach,”Encyclopedia of Analytical Chemistry,p.21,<http://infrared.als.lbl.gov/BLManual/IR_Interpretation.pdf>,JohnWileyand Sons,Ltd.,Hoboken,NJ,2000.

5. K.Tellefsen:“GreenResiduesandElectricalReliability”,Proceedings of the International Confer- ence on Electronic Assembly: Materials and Process Challenges.Atlanta,GA.June1998.

12

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Long-Term Effects of Soldering By-Products on Nickel-Coated Copper W�re

R.E. Hodge and T.D. Rolin

George C. Marshall Space Fl�ght CenterMarshall Space Fl�ght Center, AL 35812

Nat�onal Aeronaut�cs and Space Adm�n�strat�onWash�ngton, DC 20546–0001

Prepared by ES43 EEE Parts Engineering and Analysis Team, ES43 Parts, Packaging, and Fabrication Branch, and ES 40 Electrical Integration and Fabrication Division, Space Systems Department

Unclassified-UnlimitedSubject Category 12Ava�lab�l�ty: NASA CASI 301–621–0390

Ananalysisofthirty-year-old,downgradedflightcableswasconductedtodeterminethemakeupofagreenmaterialonthesurfaceoftheshieldedwirenearsolderedareasandtoascertainifthegreenmaterialhadcorrodedthenickel-coatedcopperwire.Twolikelycandidateswerepossibleduetothehandlingandenvironmentstowhichthesecableswereexposed.Thefluxusedtosolderthecablesisknowntocontainabieticacid,acarboxylicacidfoundinmanypinerosinsusedforthesolderingprocess.Theresultingmaterial,copperabietate,isgreenincolorandisformeddur-ingtheapplicationofheatduringsolderingoperations.Copper(II)chloride,whichisalsogreenincolor,isknowntocontaminateflightpartsandiscorrosive.Dataispresentedthatshowsthematerialiscopperabietate,notcopper(II)chloride,andmoreimportantlythattheabietatedoesnotaggressivelyattacknickel-platedcopperwire.

20

M–1242

Techn�cal MemorandumOctober 2008

NASA/TM—2008–215577

soldering, flux, rosin, nickel plated copper wire, corrosion

The NASA STI Program…in Profile

Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) Program Office plays a key part in helping NASA maintain this important role.

The NASA STI program operates under the auspices of the Agency Chief Information Officer. It collects, organizes, provides for archiving, and disseminates NASA’s STI. The NASA STI program provides access to the NASA Aeronautics and Space Database and its public interface, the NASA Technical Report Server, thus providing one of the largest collections of aeronautical and space science STI in the world. Results are published in both non-NASA channels and by NASA in the NASA STI Report Series, which includes the following report types:

• TECHNICAL PUBLICATION. Reports of completed research or a major significant phase of research that present the results of NASA programs and include extensive data or theoretical analysis. Includes compilations of significant scientific and technical data and information deemed to be of continuing reference value. NASA’s counterpart of peer-reviewed formal professional papers but has less stringent limitations on manuscript length and extent of graphic presentations.

• TECHNICAL MEMORANDUM. Scientific and technical findings that are preliminary or of specialized interest, e.g., quick release reports, working papers, and bibliographies that contain minimal annotation. Does not contain extensive analysis.

• CONTRACTOR REPORT. Scientific and technical findings by NASA-sponsored contractors and grantees.

• CONFERENCE PUBLICATION. Collected papers from scientific and technical conferences, symposia, seminars, or other meetings sponsored or cosponsored by NASA.

• SPECIAL PUBLICATION. Scientific, technical, or historical information from NASA programs, projects, and missions, often concerned with subjects having substantial public interest.

• TECHNICAL TRANSLATION. English-language translations of foreign scientific and technical material pertinent to NASA’s mission.

Specialized services also include creating custom thesauri, building customized databases, and organizing and publishing research results.

For more information about the NASA STI program, see the following:

• Access the NASA STI program home page at <http://www.sti.nasa.gov>

• E-mail your question via the Internet to <help@sti.nasa.gov>

• Fax your question to the NASA STI Help Desk at 301– 621–0134

• Phone the NASA STI Help Desk at 301– 621–0390

• Write to: NASA STI Help Desk NASA Center for AeroSpace Information 7115 Standard Drive Hanover, MD 21076–1320

NASA/TM—2008–215577

Long-Term Effects of Soldering By-Products on Nickel-Coated Copper WireT.D. Rolin and R.E. HodgeMarshall Space Flight Center, Marshall Space Flight Center, Alabama

October 2008

National Aeronautics andSpace AdministrationIS20George C. Marshall Space Flight CenterMarshall Space Flight Center, Alabama35812