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IPC-9204

2017-February

GuidelineonFlexibilityandStretchabilityTestingforPrinted

Electronics

AninternationalstandarddevelopedbyIPC

AssociationConnectingElectronicsIndustries

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ThePrinciplesofStandardization

InMay1995theIPC’sTechnicalActivitiesExecutiveCommittee(TAEC)adoptedPrinciplesofStandardizationasaguidingprincipleofIPC’sstandardizationefforts.

StandardsShould:

ShowrelationshiptoDesignforManufacturability(DFM)andDesignfortheEnvironment(DFE)

Minimizetimetomarket

Containsimple(simplified)language

Justincludespecinformation

Focusonendproductperformance

Includeafeedbacksystemonuseandproblemsforfutureimprovement

StandardsShouldNot:

Inhibitinnovation

Increasetime-to-market

Keeppeopleout

Increasecycletime

Tellyouhowtomakesomething

Containanythingthatcannotbedefendedwithdata

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Notice IPCStandardsandPublicationsaredesignedtoservethepublicinterestthrougheliminatingmis-understandingsbetweenmanufacturersandpurchasers,facilitatinginterchangeabilityandimprove-mentofproducts,andassistingthepurchaserinselectingandobtainingwithminimumdelaytheproperproductforhisparticularneed.ExistenceofsuchStandardsandPublicationsshallnotinanyrespectprecludeanymemberornonmemberofIPCfrommanufacturingorsellingproductsnotconformingtosuchStandardsandPublication,norshalltheexistenceofsuchStandardsandPublicationsprecludetheirvoluntaryusebythoseotherthanIPCmembers,whetherthestandardistobeusedeitherdomesticallyorinternationally.

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IPC-9204

GuidelineonFlexibilityandStretchabilityTestingforPrintedElectronics

DevelopedbythePrintedElectronicsTestMethodDevelopmentandValidationSubcommittee(D-65)ofthePrintedElectroncsCommittee(D-60)ofIPC

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Usersofthispublicationareencouragedtoparticipateinthedevelopmentoffuturerevisions.

Contact:

IPC

3000LakesideDrive,Suite105NBannockburn,Illinois

60015-1249

Tel847615.7100

Fax847615.7105

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February2017 IPC-9204

Acknowledgment

Anydocumentinvolvingacomplextechnologydrawsmaterialfromavastnumberofsourcesacrossmanycontinents.WhiletheprincipalmembersofthePrintedElectronicsTestMethodDevelopmentandValidationSubcommitte(D-65)ofthePrintedElectronicsCommittee(D-60)areshownbelow,itisnotpossibletoincludeallofthosewhoassistedintheevolu-tionofthisstandard.Toeachofthem,themembersofIPCextendtheirgratitude.

PrintedElectronicsCommittee PrintedElectronicTestMethod

DevelopmentandValidationSubcommittee

TechnicalLiaisonoftheIPCBoardofDirectors

Co-ChairsNeilBolding

MacDermidEnthoneElectronicsSolutions

DanielGamota

PrintovateTechnologies,Inc.

Co-ChairsWeifengLiu

FlextronicsInternational

NeilBoldingMacDermidEnthoneElectronicsSolutions

BobNeves

Microtek(Changzhou)Laboratories

PrintedElectronicTestMethodDevelopmentandValidationSubcommittee

LeonardB.Allison,EngineeredMaterialsSystems,Inc.

SaiAvuthu,JabilCircuit,Inc.LanceAuer,RaytheonCompanyAnirbanBasu

AndyBehr,PanasonicIndustrialDevicesSalesCompanyofAmerica(PIDSA)

NeilBolding,MacDermidEnthoneElectronicsSolutions

AlanM.Burk,ALMAXMarcCarter,SAIC

DonDupriest,LockheedMartinMissiles&FireControl

MahendraS.Gandhi,NorthropGrummanAerospaceSystems

KenGann,LabTech

MaryAliceGill,JabilCircuit,Inc.JoshGoldberg,TaiyoAmericaInc.

ScottE.Gordon,DuPontTeijinFilmsMaryK.Herndon,Raytheon

Company

MichaelJ.Jawitz,OrbitalATKKellyKovalovsky,i3ElectronicsMuradKurwa,GEHealthcareJeffreyLee,ISTGroup

JieLian,Flextronics

WeifengLiu,FlextronicsInternational

KarenMcConnell,NorthropGrummanCorporation

DeboraL.Obitz,NTS-BaltimoreJanObrzut,NIST

JeffreyParker,Insulectro

RavindranPeriasamy,SandiaNationalLabsAlbuquerque

BenjaminPiepgrass,SouthwestResearchInstitute

CassandraRocha,BoeingCompanyHaridossSarma,GO2Scout4R&TPaulShaw,In2Tec

RussellS.Shepherd,.NationalTechnicalSystemsAnaheim

JeffShubrooks,RaytheonCompanyRichardC.Snogren,BristleconeLLCBrianJ.Toleno,Microsoft

Corporation

LouisY.Ungar,AdvancedTestEngineeringSolutions,Inc.

SteveJ.Vetter,NSWCCraneMichaelJ.Watson,BluestarSiliconesDianeH.Williams,Corning

Incorporated

MobinYahyazadehfar,DuPontEngineeringPolymers

SpecialAcknowledgment

LeonardB.Allison,EngineeredMaterialsSystems,Inc.

NeilBolding,MacDermidEnthoneElectronicsSolutions

AlanM.Burk,ALMAX

DonDupriest,LockheedMartinMissiles&FireControl

KenGann,LabTech

MaryAliceGill,JabilCircuit,Inc.WeifengLiu,Flextronics

International

KarenMcConnell,NorthropGrummanCorporation

MobinYahyazadehfar,DuPontEngineeringPolymers

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iii

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AssociationCoivnnectingElectronicsIndustries

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February2017 IPC-9204

TableofContents

SCOPE 1

Purpose 1

APPLICABLEDOCUMENTS 1

IPC 1

ASTM 1

InternationalElectrotechnical

Commission(IEC) 2

InternationalOrganizationforStandardization(ISO) 2

TERMSANDDEFINITIONS 2

Bending 2

Crease 2

Crumple 2

Curing 2

Flexibility 2

FlexographyPrinting 2

GravurePrinting 2

InkJetPrinting 2

MinimumBendingRadius 2

Preconditioning 2

PrintedElectronics 2

PrintedElectronicsProcess 2

ScreenPrinting 3

Stretchability 3

StretchablePrintedElectronics 3

Torsion 3

WearablePrintedElectronics 3

WearableSmartDevices 3

TESTPREPARATIONANDSETUP 3

TestSpecimenPreparationandStorage 3

SpecimenPreconditioning 3

StandardTestConditions 3

TestEquipment 3

TestSetupandParameters 3

Monitoring 3

Inspection 4

SUMMARYOFPRINTEDELECTRONICSFLEXIBILITYANDSTRETCHABILITYTESTS 4

STRETCHABILITYTESTINGPRINCIPLES 5

StretchabilityLimitTest 5

CyclicStretchabilityTest 5

StretchabilityUnderConstantElongationConditions 6

StretchabilityUnderConstantTorsion

Conditions 6

StretchabilityUnderCyclicTorsionConditions 7

BENDINGTESTPRINCIPLES 7

VariableRadiusBendingTest 7

VariableAngleBendingTest 8

FreeArcBendingTest 9

DeMattiaFlexibilityTest 9

LoopBendingTest 10

FoldingEnduranceTest 10

TORSIONTESTPRINCIPLES 11

ROLLINGTESTPRINCIPLES 12

RollingFlexTest 12

CoilingFlexTest 13

SlidingPlateTest 13

CRUMPLINGTESTPRINCIPLES 14

CreaseTest 14

SchildknechtFlexTest 15

CrumpleFlexTest 16

VampFlexTest 17

BallyFlexTest 17

APPENDIXATESTREPORT

RECOMMENDATIONS 18

APPENDIXBSTANDARDREFERENCES 19

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IPC-9204 February2017

Figures

Figure6-1 StretchabilityTestingofPrintedInk 5

Figure7-1 VariableRadiusBendingTestSetup 7

Figure7-2 VariableAngleBendingTestSetup 8

Figure7-3 FreeArcBendingTestSetup. 9

Figure7-4 DeMattiaFlexTestSetup 9

Figure7-5 LoopBendingTestSetup 10

Figure7-6 TestSetupUsingMITFoldingEndurance

TestInstrument 10

Figure8-1 TorsionTestSetup 11

Figure9-1 RollingFlexTestSetup 12

Figure9-2 CoilingFlexTestSetup 13

Figure9-3 SlidingPlateTestSetup. 13

Figure10-1 CreaseFlexTestSetup 14

Figure10-2 SchildknechtFlexTestSetup 15

Figure10-3 CrumpleFlexTestSetup 16

Figure10-4 BallyFlexTestSetup 17

Tables

Table5-1 PrintedElectronicsFlexibilityand

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StretchabilityTests 4

TableA-1 TestReportRecommendations 18

AssociationvCionnectingElectronicsIndustries

February2017 IPC-9204

GuidelineonFlexibilityandStretchabilityTestingforPrintedElectronics

SCOPE

Thisguidelinedescribesflexibilityandstretchabilityteststhatmaybeusedtoevaluateprintedelectronicsforflexible,stretchableandwearableapplications.

PurposeThisguidelinedescribestestswhichtheIPCD-65PrintedElectronicsTestMethodsandValidationSubcom-mitteedeemedappropriateforconsiderationforflexibilityandstretchabilitytestingofprintableelectronics.ThedescriptionsofthesetestswereprovidedbymembersoftheD-65Subcommittee.

Thisguidelinedoesnotrepresentanendorsementofanyofthedescribedtests.Itisintendedonlyasaneducationalresource,especiallyforthesmarttextilesandwearableprintedelectronicsmarkets,untilstandardizedtestmethodsaredevelopedandapproved.

TheD-65Subcommitteeinvitesusers,suppliers,testlaboratoriesandotherinterestedpartiestosubmitadditionaltestsormodificationstothoseexplainedhereinfornextrevisionsofthisguideline.

Thisguidelinealsoincludesreferencestoindustry-approvedtestmethodswhichcanbeusedoradaptedforflexibilityandstretchabilitytestingforprintedelectronics(seeSection5andAppendixB).

APPLICABLEDOCUMENTS

Thedocumentslistedinthissectionarethosewhicharereferencedinthebodyofthisguideline.AppendixBalsoprovidesacompendiumofindustry-approvedtestmethodswhichmaybeadaptedforflexibilityandstretchabilitytestingofprintedelectronics.

IPC1

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IPC-T-50TermsandDefinitionsforInterconnectingandPackagingElectronicCircuits

IPC-TM-650TestMethodsManual

IPC-6903TermsandDefinitionsfortheDesignandManufactureofPrintedElectronics

ASTM2

ASTMF392StandardPracticeforConditioningFlexibleBarrierMaterialsforFlexDurability

ASTMD430StandardTestMethodsforRubberDeterioration—DynamicFatigue

ASTMD813StandardTestMethodforRubberDeterioration—CrackGrowth

ASTMF2749StandardTestMethodforDeterminingtheEffectsofCreasingaMembraneSwitchorPrintedElectronicDevice

ASTMF2750StandardTestMethodforDeterminingtheEffectsofBendingaMembraneSwitchorPrintedElectronicDevice

ASTMD6182StandardTestMethodforFlexibilityandAdhesionofFinishonLeather

AssociationConnectingElectronicsIndustries 1

IPC-9204 February2017

InternationalElectrotechnicalCommission(IEC)3

IEC62715-6-1Flexibledisplaydevices-Part6-1:Mechanicalstresstestmethods

IEC62899-201Printedelectronics-Part201:Materials-Substrates

InternationalOrganizationforStandardization(ISO)4

ISO5402-2Leather—Determinationofflexresistance—Part2:Vampflexmethod

ISO5626Paper—Determinationoffoldingendurance

ISO7854Rubber-orplastics-coatedfabrics—Determinationofresistancetodamagebyflexing

TERMSANDDEFINITIONS

Inadditiontothetermsanddefinitionslistedhere,thereaderisreferredtoIPC-6903foradditionaltermsonflexiblehybridprintedelectronicsandprintedelectronicsandtoIPC-T-50fortermsonPCBsandPCBassemblies.

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BendingDeformationofprintedelectronicscausedbyexternalstressperpendiculartotheflatplaneofspecimen.

CreaseTomakealine,ridgeorgrooveonaprintedelectronicdevicewhichusesasubstratesuchasclothorpaperbyaddingpressuretofoldthesubstrateordevice.

CrumpleTocrushaprintedelectronicdevicewhichusesasubstratesuchasclothorpapersothatitformsnonuni-formfolds.

CuringAprocessduringwhichvolatilecomponents,ifpresent,evaporateandmaterialsundergochemicalreactionstoformacontinuousbulkmaterial.

FlexibilityThepropensityofaprintedelectronicdevicetobebent,creasedorstretched.

FlexographyPrintingAprintingprocesswhichusesaflexiblepositivemaster(flexoplate)totransferamediumfromasourcetoatargetsubstrateviapressureusingananiloxroller.

GravurePrintingPrintingmethodinwhichanimageisappliedtoaprintingsubstratebyuseofamasterimagecar-rierandthenthereverseoftheimagetobetransferredisengravedandetched.

InkJetPrintingAtypeofnoncontactprintingmethodthatrecreatesadigitalimagebypropellingdropletsofinkontopaper,plasticorothersubstrates.

MinimumBendingRadiusThesmallestbendingradiusatwhichaspecimendoesnotbreakordoesnotshowperma-nentdamage.

PreconditioningAsetofconditionsexposedonthetestspecimenpriortoactualtestingthateithersimulatetherealuseconditionsorbringthetestspecimentotherequiredstate.

PrintedElectronicsDevicesmanufacturedusingprintedelectronicsprocesses.

PrintedElectronicsProcessAdditiveprintingmethodsusedtogenerateelectricalandelectroniccircuitryordevicesonavarietyofsubstrates.

www.iec.ch

AssociationCo2nnectingElectronicsIndustries

February2017 IPC-9204

ScreenPrintingMethodofforcingmaterials(inkorpaste)throughapreparedscreen(eitherpolyesterorstainlesssteel)tocreateadesignpattern.

StretchabilityMechanicalpropertyofasubjecttorestoretoitsoriginalstateafterreleaseofatensionstresswhichpullsthesubjecttoacertainelongation.

StretchablePrintedElectronicsAprintedelectronicspartorproductthat,duetothedesignandtheintrinsicprop-ertiesofthematerialsandelementsusedtoconstructit,canbesubjectedtostaticanddynamicstrainwithoutanobserva-tioninperformancedegradation.Thesupplieroftheprintedelectronicprovidesguidanceastothepredefinedstrainlevelwherebytheassemblywillmaintainatleastaminimumlevelofperformance.

TorsionTheactionoftwistingasubjectbytheexertionofforces,tendingtoturnoneendorpartaboutalongitudi-nalaxiswhiletheotherisheldfastorturnedintheoppositedirection.

WearablePrintedElectronicsAprintedelectronicpartorproductthatcanbeattachedtoaperson’sbody(e.g.,arms,wrists,legs,waist,head,ear,etc.).Avarietyofstructuralelementsmaybeusedtoattachtheseproducts,suchasbutnotlimitedtoanelastomericmaterial(band),whichisamechanismthatintegratesadevicetoconstraintheassemblytoanarm,wristorleg(e.g.,Velcro,buckle,compressionfitting).Additionally,theycanbeaffixedtoaperson’sbodyviabiocom-patibleadhesivematerials.

WearableSmartDevicesWearableprintedelectronicswithafunctionalitytoconnectandinteractwithotherdevices,networks,theinternet,etc.

TESTPREPARATIONANDSETUP

TestSpecimenPreparationandStorageClearlydescribethetestspecimeninthetestreport.Thedescriptionshouldincludesamplesize,shapeanddimensions,materialsandstack-up,specialtreatmentpriortotesting,applicablestandardforspecimenpreparationand/orotherrelevantinformation.

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Specifythespecimenstorageconditionspriortotesting.Itisrecommendedtostorespecimensatatemperatureof20°Cto25°Candhumidityof30%to60%foratleast48hoursafterfabricationpriortotesting.Thiscanbedoneinacontrolledenvironment.Iftherearespecialrequirements,storageconditionsmaybedeterminedbetweenuserandsupplier.

SpecimenPreconditioningThespecimenmaybesubjectedtopreconditioningpriortostretchabilityandflexibilitytests,suchastemperatureaging,temperaturecycling,hightemperaturewithhumidity,durability,etc.,asagreeduponbetweenuserandsupplier.

StandardTestConditionsSpecifythetestconditionsintermsofatmosphere,temperatureandhumidity.Itisrecom-mendedtotestthespecimensat23°C±1°Cwitharelativehumidity(RH)50%±5%atambientatmosphereunlessotherwisespecified.Thespecimenmaybetestedatelevatedtemperatureorhumidityconditionsasagreeduponbetweenuserandsupplier.

TestEquipmentStatetheequipmenttobeusedinthetest,themakerofthemachineanditscapability.Gaugerepro-ducibilityandrepeatability(gaugeR&R)maybeperformedtoqualifytheequipmentandtestprocesspriortostretch-abilityandflexibilitytesting.AtestreportongaugeR&Rmaybeattachedtothefinaltestreport.

TestSetupandParametersClearlydescribethetestsetupinthetestreport(e.g.,fixturedesign,howthespecimenistobemountedonthefixture,etc.).Clearlydescribethetestparametersinthetestreport,suchassequence,strainrate,frequency,speed,lowerandupperlimitsofdisplacement,numberofcycles,etc.

MonitoringDescribehowthefunctionalityorelectricalresistanceoftestspecimensismonitoredduringthestretch-abilityandflexibilitytesting.Monitoringmaybedoneinsituorperiodicallyduring,priortoandaftertesting.Clearlystatedatatype,collectionfrequencyandacceptanceorrejectioncriteria.

AssociationConnectingElectronicsIndustries 3

IPC-9204 February2017

InspectionInspectthespecimensbeforeandafterstretchabilityandflexibilitytests.Thismaybedonebyvisualinspection,opticalmicroscope,scanningelectronmicroscope(SEM)orotherinspectionequipment.Recordanyqualityabnormality,damages,failuresymptomsandlocations.Ifafailureoccurs,failureanalysismaybedonetoidentifytherootcausesofthefailure.

SUMMARYOFPRINTEDELECTRONICSFLEXIBILITYANDSTRETCHABILITYTESTS

Printedelectronicswillexperienceavarietyofflexibilitystressesintheirapplications.Accordingly,differenttestproceduresarebeingdevelopedtoevaluatethesestresses.Ingeneral,thetestscanbeclassifiedintofivebasiccategories:

Stretchability

Bending

Torsion

Rolling

Crumpling

Acombinationofthesetestswillgiverisetomoretestoptions.Thedeterminationofthetesttobeused,sequencesandtestparametersarebetweenuserandsupplier.

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Table5-1PrintedElectronicsFlexibilityandStretchabilityTests

Category

TestItems

ExemplaryApplications

ApplicableStandard

Stretchabilitytesting

Stretchabilitylimittest

Stretchableprintedink

Noknownindustrystandard

Cyclicstretchabilitytest

Stretchableprintedink

Noknownindustrystandard

Stretchabilityunderconstantelongationcondition

Stretchableprintedink

Noknownindustrystandard

Stretchabilityunderconstanttorsioncondition

Stretchableprintedink

Noknownindustrystandard

Stretchabilityundercyclictorsioncondition

Stretchableprintedink

Noknownindustrystandard

Bendingtest

Variableradiusbendingtest

Flexibledisplay

IEC62715-6-1

Variableanglebendingtest

Flexiblebattery

Noknownindustrystandard

Freearcbendingtest

Flexibledisplay,flexibleOLEDlighting

Noknownindustrystandard

DeMattiaflexibilitytest

Wearableelectroluminescentlighting

ASTMD813,ASTMD430,ISO7854

Loopbendingtest

Wearablekeyboard

Noknownindustrystandard

Foldingendurancetest

Wearablewristband

ISO5626,IEC62899-201

Torsiontest

Torsiontest

Flexibleelectroluminescentdisplay

Noknownindustrystandard

Rollingtest

Rollingflextest

Rolltorollprinting,e-paper

ASTMF2750

Coilingflextest

Rolltorollprinting,e-paper

Noknownindustrystandard

Slidingplatetest

Flexibledisplay,flexiblebattery

Noknownindustrystandard

Crumplingtest

Creasetest

Printedinkcircuit

ASTMF2749

Schildknechtflextest

Wearablegarment

ISO7854

Crumpleflextest

Wearablegarment

ISO7854,ASTMF392

Vampflextest

Wearablegarmentandfootwear

ISO5402-2

Ballyflextest

Wearablegarmentandfootwear

ASTMD6182

AssociationCo4nnectingElectronicsIndustries

February2017 IPC-9204

STRETCHABILITYTESTINGPRINCIPLES

A

B

C

D

E

A IPC-9204-6-1

Thetestsin6.1through6.5areexamplesofthosewhichcanbeusedtoevaluatethefunc-tionalityofprintedelectronicdevicesunderrepeatedorconstantuniaxialstretchconditions.Theprinciplesdescribedinthissectioncanbeapplicabletobiaxialstretchabilitytestingaswell.

StretchabilityLimitTestThistestmethodcanbeusedtodeterminetheelongationlimit,inpercentage,ofprintedelectronicsbyuniaxialtensiletesting.Samplesmaybepre-paredintheoriginalproductformorusingtestcouponsuchasstraightedgestripsor‘‘dogbone’’stripsasdescribedinASTME-345,orotherformsagreeduponbetweenuserandsupplier.AschematictestsetupforevaluatingstretchabilityofprintedinkisshowninFig-ure6-1.

Thestretchablecircuitisheldfirmlybetweentwofixtures.Cushionsmaybeaddedattheinterfacebetweenthesamplegripsandconductiveinktopreventstressconcentrationandabnormalresistancereadings.Inthistest,thebottomfixturecanremainstationarywhilethetopfixtureismovable.Bymovingthefixture(s),thespecimenisstretchedtoacertainper-centageuntilthecircuitphysicallyorelectricallyfailsduringthestretchabilitytest.Itisimportanttocontinuouslymonitorthefunctionalityorresistanceofthecircuit.Intheothertestoptionbothfixturesaremovableandthespecimenisstretchedwhenthetwofixturesmoveinoppositedirections.

Note:

Stretchability%FinalinklengthInitialinklength

Initialinklength

TheinklengthmaybeobtainedbymeasuringthedistancebetweenthetwosamplegripsasshowninFigure6-1.Finalinklengthmaybedeterminedbypreviouslyestablishedfailurecriterionintermsofresistanceincreaseoftheprintedink,suchasmaximumvalueofresis-tance,resistanceincreasepercentage,etc.

Includethefollowinginthetestreport:

Descriptionofthespecimen

Samplesize

Environmentaltestconditions

Strainrate

Initiallength,displacementandforce

Stretchabilitylimit(inpercentage)

Failurecriteria

Continuouselectricaltestresults

Inspectionbeforeandaftertest

Plottheelectricaltestdataversusthestretchpercentage.

Figure6-1StretchabilityTestingofPrintedInk

A–Linktoresistancemeasurementprobe

B–Movingsampleholder

C–Stretchableink

D–Stretchablesubstrate

E–Stationarysampleholder

CyclicStretchabilityTestThistestmethodcanbeusedtoverifyifastretchable/wearableprintedelectronicdevicecanwithstandrepeatedelongationcyclesunderatensileload.SetupthetestasshowninFigure6-1,withthestretchablecircuitheldfirmlybetweentwofixtures.Inthistest,thebottomfixturecanremainstationary,whilethetopfixtureismov-ableorbothfixturescanmove.Bymovingthefixture(s)upanddown,thespecimenisstretchedtoacertainpercentageandthen,afteracertainholdingtime,returnstoitsinitialstatewhenloadisreleased.Thespecimenisstretchedagaintorepeatforsecondcycle.Continuouslymonitorthefunctionalityorresistanceofthecircuit.

Includethefollowinginthetestreport:

Descriptionofthespecimen

Samplesize

Environmentaltestconditions

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IPC-9204 February2017

Cyclicloadingprofileandfrequency

Strainrate

Initiallength,displacementandforce

Stretchpercentage

Holdingtime

Failurecriteria

Numberofcyclesperspecimen

Continuouselectricaltestresults

Inspectionbeforeandaftercycling

Plotelectricaltestdataversusthestretchpercentageandnumberofcycles.

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StretchabilityUnderConstantElongationConditionsThistestcanbeusedtoevaluatethefunctionalityoftheprintedelectronicdevicesunderconstantelongationconditions.AsshowninFigure6-1,thestretchablecircuitisheldfirmlybetweentwofixtures.Thebottomfixtureremainsstationary,whilethetopfixtureismovable.Bymovingthetopfixtureup,thespecimenisstretchedtoacertainpercentageandthenmaintainedatthesameelongationpercentageforaprolongedduration.Continuouslyorperiodicallymonitorthefunctionalityorresistanceofthecircuit.Includethefollowinginthetestreport:

Descriptionofthespecimen

Samplesize

Environmentaltestconditions

Strainrate

Initiallength,displacementandforce

S