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1©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialProcessCapability(Cp/Cpk/Pp/Ppk)Globa
lTrainingMaterialCreator:GlobalMechanicsProcessManagerFunction:MechanicsApprover:GaryBradley/GlobalProcessTeamDoc
umentID:DMT00018-ENVersion/Status:V.1.0/ApprovedLocation:Notes:\\…\NMP\DOCMANR4\PCP\PCProcessLibraryDocManChangeHistory:IssueDateHandl
edByComments1.021stDec’01JimChristy&SørenLundsfrydApprovedforGlobalUseNOTE–Allcommentsandimprovementsshouldbeaddressedtothecreatorofthisdocumen
t.2©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialContentsSectionHeading/DescriptionPage1Variation,TolerancesandDimensionalContro
l42Population,SampleandNormalDistribution153CpandCpkConcept284UseoftheNMPDataCollectionSpreadsheet445ConfidenceofCpk523©NO
KIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialProcessCapability-EvaluatingManufacturingVariationAcknowledgements•Benny
Matthiassen(NMPCMT,Copenhagen,Denmark)•FrankAdler(NMPAlliance,Dallas,USA)•JoniLaakso(NMPR&D,Salo,Finland)•JimChristy(NMPSRC,Southwood,UK)4©
NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialSection1Variation,TolerancesandDimensionalControl5©NOKIA2001T0001801.PP
T/21-Dec-2001/JimChristyCompanyConfidentialTwoTypesofProductCharacteristicsVariable:Acharacteristicmeasuredinphy
sicalunits,e.g.millimetres,volts,amps,decibelandseconds.ONOFFAttribute:Acharacteristicthatbycomparisontosomestandardisjudged“good”or“bad”,e.g.f
reefromscratches(visualquality).6©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialTheSourcesofProcess/SystemVariationMetho
dsOperatorsCustomerSatisfactionMaterialEnvironmentEquipmentProcess7©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialTwoTypesofProce
sses•Allprocesseshave:–Natural(random)variability=>duetocommoncauses•StableProcess:Aprocessinwhichvariationinoutcomesarisesonlyf
romcommoncauses•UnstableProcess:AprocessinwhichvariationisaresultofbothcommonandspecialcausesUSLLSLnominalvalueDefectUSLLSLnominalvalue
–Unnaturalvariability=>duetospecialcauses8©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialShewhart(1931)TheTw
oCausesofVariation•CommonCauses:–Causesthatareimplementedintheprocessduetothedesignoftheprocess,andaffectalloutcomesofthep
rocess–IdentifyingthesetypesofcausesrequiresmethodssuchasDesignofExperiment(DOE),etc.•SpecialCauses:–Causesthatarenotpresentintheprocessallth
etimeanddonotaffectalloutcomes,butarisebecauseofspecificcircumstances–SpecialcausescanbeidentifiedusingStat
isticalProcessControl(SPC)USLLSLNominalvalueDefectUSLLSLnominalvalue9©NOKIA2001T0001801.PPT/21-Dec-2001/JimChr
istyCompanyConfidentialTolerancesLSL(lowerspecificationlimit)10,7USL(upperspecificationlimit)10,9AcceptablepartRejectedPartRejectedProductNo
minal10,80,1RejectedPartAtoleranceisaallowedmaximumvariationofadimension.10©NOKIA2001T0001801.PPT/21-D
ec-2001/JimChristyCompanyConfidentialMeasurementReportInmostcaseswemeasureonlyonepartpercavityformeasurementreport11©NOKIA2001T000180
1.PPT/21-Dec-2001/JimChristyCompanyConfidentialExampleofCapabilityAnalysisData•Forsomecriticaldimensionsweneedtomeasuremorethan1part•F
orcapabilitydataweusuallymeasure5pcs2times/hour=100pcs(butsamplingplanneedstobemadeonthebasisofproductionquantity,rundurationandcycletime)1s
tSubgroup2ndSubgroup3rdSubgroup4thSubgroup118.53118.52118.54118.56118.54118.54118.52118.55118.51118.51118.50118.55118.53118.51118.52118.55118.51118.5
4118.54118.555thSubgroup6thSubgroup7thSubgroup8thSubgroup118.55118.54118.57118.60118.54118.56118.56118.57118.55118
.55118.57118.55118.54118.54118.55118.56118.56118.53118.54118.559thSubgroup10thSubgroup11thSubgroup12thSubgroup118.60118.6
1118.58118.60118.59118.60118.60118.63118.58118.61118.61118.63118.60118.59118.60118.61118.59118.59118.59118.6412©NOKIA2001T00018
01.PPT/21-Dec-2001/JimChristyCompanyConfidentialProcessCapability-Whatisit?•ProcessCapabilityisameasureoft
heinherentcapabilityofamanufacturingprocesstobeabletoconsistentlyproducecomponentsthatmeettherequireddesignspecificatio
ns•ProcessCapabilityisdesignatedbyCpandCpk•ProcessPerformanceisameasureoftheperformanceofaprocesstobeabletoconsistentlyproducecomponentsthatmeetthere
quireddesignspecifications.ProcessPerformanceincludesspecialcausesofvariationnotpresentinProcessCapability•ProcessPerfo
rmanceisdesignatedPpandPpk13©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialWhyMakeProcessCapabilityStudiesLSL(lower
specificationlimit)10,7USL(upperspecificationlimit)10,9Nominal10,80,1Thispartiswithinspec.Thetoolwouldbea
pprovedifonlythispartwasmeasuredThesepartsareoutofspecandcouldbeapprovedifonlyonegoodpartwasmeasuredAproc
esscapabilitystudywouldrevealthatthetoolshouldnotbeacceptedWhenadimensionneedstobekeptproperlywithinspec,wemuststu
dytheprocesscapability….butstillthisisnoguaranteefortheactualperformanceoftheprocessasitisonlyaninitialcapabil
itystudy14©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialE1.5E1E2E3E4E5TheNokiaProcessVerificationProcessBlackdiamonds
tobefixedbyE3(oftenachangeofawhitediamond)ProposalforblackdiamondstobediscussedwithSupplier.Max:105,85OngoingProcessControl(SPC)Tolerancesappliedtod
rawing-1part/cavitymeasuredformeasurementreportWhitediamonds(s)tobeagreedWhitediamonds(s)tobediscussedwithsupplier10parts/cavit
ymeasuredformeasurementreportCapabilitystudy:Requirement:CpandCpk>1.67byE3.Quantitiestobeagreedwithsuppli
er.Minimum5partspr1/2hourin10hoursmeasuredforeachcavity=100parts.Canvarydependingontoolcapacity,e.g.
stampedparts(seeDMY00019-EN)15©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialSection2.Population,SampleandNorm
alDistribution16©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialTheBellShaped(Normal)
Distribution•Symmetricalshapewithapeakinthemiddleoftherangeofthedata.•Indicatesthattheinputvariables(X's)totheprocessar
erandomlyinfluenced.17©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidential“PopulationParameters”=Populationmean=P
opulationstandarddeviationPopulationversusSamplePopulation•Anentiregroupofobjectsthathavebeenmadeorwillbemadecontainingach
aracteristicofinterestSample•Thegroupofobjectsactuallymeasuredinastatisticalstudy•Asampleisusuallyasubsetofthepopulationofinterest“SampleStatis
tics”x=Samplemeans=Samplestandarddeviation18©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialTheNormalDistribution19©NOKIA2001T00018
01.PPT/21-Dec-2001/JimChristyCompanyConfidentialWhatMeasurementsCanBeUsedtoDescribeaProcessorSystem?xxxxN
N12...Example:x1=5x2=7x3=4x4=2x5=68.4524562475x•mean(average)ordescribesthelocationofthedistributionx•µ(mü
),ameasureofcentraltendency,isthemeanoraverageofallvaluesinthepopulation.Whenonlyasampleofthepopulationisbeingdescribed,meanismoreproperlydenoteda
s(x-bar):x20©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidential),...,,min(),...,,max(2121NNxxxxxxRExa
mple:x1=5x2=7x3=4x4=2x5=6527)6,2,4,7,5min()6,2,4,7,5max(R•Themostsimplemeasureofvariabilityistherange.Therangeofasam
pleisdefinedbyasthedifferencebetweenthelargestandthesmallestobservationfromsamplesinasub-group,e.g.5consecutivepartsfromthemanufacturingproc
ess.WhatMeasurementsCanBeUsedtoDescribeProcessvariation?21©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidential•sST-oftennotatedaso
rsigma,isanothermeasureofdispersionorvariabilityandstandsfor“short-termstandarddeviation”,whichmeasuresthevariabilityofaprocessorsyst
emusing“rational”sub-grouping.sRNdRdSTjjN122**whereistherangeofsubgroupj,Nthenumberofsubg
roups,andd2*dependsonthenumberNofsubgroupsandthesizenofasubgroup(seenextslide)RXXjjjmaxminWhatMeasurementsCan
BeUsedtoDescribeProcessvariation?22©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentiald2*valuesforSSTWhere:N=no.ofsub-groups,n=no.ofsa
mplesineachsub-groupd2*d2Typical:N=20&n=523©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidential•••••••x3•x2•x1•x10x_t1)(...)()(2
22212NxxxxxxssNLTLT92.17.315)8.46()8.42()8.44()8.47()8.45(22222LTsExample:WhatMeasurementsCanBeUsedtoDescribe
Processvariation?24©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialTheDifferenceBetweenSSTa
ndsLT!!meanTimeDimensionShorttermStandardDeviationLongtermStandardDeviationSubgroupsizen=5NumberofsubgroupsN=7SubgroupNo.125©NOKIA2
001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialThedifferencebetweenthestandarddeviationssLTandsSTgivesanindicationofhowmuchbet
teronecandowhenusingappropriateproductioncontrol,likeStatisticalProcessControl(SPC).sxxxxxxNLTN()()...()
122221sRNdRdSTjjN122**Short-termstandarddeviation:Long-termstandarddeviation:ThedifferencebetweensSTandsLT26©NOKIA2001T0001801.PPT/21-De
c-2001/JimChristyCompanyConfidentialThedifferencebetweensSTandsLT•ThedifferencebetweensLTandsSTisonlyinthewaythatthestandarddeviati
oniscalculated•sLTisalwaysthesameorlargerthansST•IfsLTequalssST,thentheprocesscontroloverthelonger-termisth
esameastheshort-term,andtheprocesswouldnotbenefitfromSPC•IfsLTislargerthansST,thentheprocesshaslostcontroloverthelonger-term,andtheprocess
wouldbenefitfromSPC•ThereliabilityofsLTisimprovedifthedataistakenoveralongerperiodoftime.AlternativelysLTcanbecalculatedonseveraloccasio
nsseparatedbytimeandtheresultscomparedtoseewhethersLTisstable27©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialExer
cise1:SampleDistributions1.InExcelfile"Dataexercise1.xls"youfind100measurementsbeingtheresultofacapabilit
ystudy.Thespecificationforthedimensionis15,16,012.Howwelldoesthesamplepopulationfitthespecification,e.g.shouldweexpectanypartso
utsidespec?3.Mentionpossibleconsequencesofhavingapartoutsidespec.4.Mentionpossiblecausesofvariationforparts.5.Calcu
latethesamplemeanandsamplestandarddeviationforthe100measurements.UsetheaverageandstdevfunctionsExcel.28©NOKIA2001T0001801.PPT/21-Dec-200
1/JimChristyCompanyConfidentialSection3.CpandCpkConcept29©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialDefiningCpandPpSampleme
anProcessvariation6*sstpsLSLUSLC*6-USL-LSLLSLUSLNominaldimltpsLSLUSLP*6-Thetoleranceareadividedbythetotalprocessvariation,irrespectiveofpr
ocesscentring.30©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialDefiningCpkandPpkststpksmeanUSL
sLSLmeanC*3-,*3-minSamplemeanProcessvariation3sProcessvariation3sMean-LSLUSL-MeanLSLUSLNominaldimltltpksmeanUSLsLSLmeanP*3-,*3-minCpkandPpkI
ndexesaccountalsoforprocesscentring.31©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialWhatistheDifferenc
eBetweenCpandCpk?•TheCpindexonlyaccountsforprocessvariability•TheCpkIndexaccountsforprocessvariabilityandcenteri
ngoftheprocessmeantothedesignnominal•Therefore,CpCpk•NOTE:SameappliesalsoforPpandPpkCp=Cpk(bothlow)LSLUSLMean=NominalRejectpartsRejectpar
tsCphigh,CpklowProcessshouldbeoptimized!NominalLSLMeanUSLRejectparts32©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConf
identialWhatDoTheseIndexesTellUs??•Simplenumericalvaluestodescribethequalityoftheprocess>>Thehigherthenumberthebetter•RequirementforC
pandCpkis1.67min.•RecommendationforPpandPpkis1.33min.•Thisleavesussomespaceforthevariation,i.e.asafetymargin•Ar
eweabletoimproveourprocessbyusingSPC?•Ifindexislow,followingthingsshouldbegivenathought:•IstheproductdesignOK?
•Aretolerancelimitssetcorrectly?•Tootight?•Istheprocesscapableofproducinggoodqualityproducts?Processvariation?DOErequired?•Isthemeasuringsystemcapa
ble?(SeeGageR&R)33©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialCpk-Witha2-sigmasafetymargin-3sST+3sSTLCLUCLLS
LUSLMeanvalue=NominalvalueorTarget•RequirementforCpandCpkis1.67min.1.67isaratioof=5/3or10/6.6*standarddeviation10*standarddeviation2*standarddev
iation2*standarddeviation34©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidential•Cpk<1.67thepro
cessNOTCAPABLEAcceptabilityofCpkIndex•Cpk>=1.67theprocessisCAPABLE•Cpk>=2.0theprocesshasreachedSixSigmalevel
35©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialWhatDoTheseIndexesTellUs??•IfCp=Cpk,•IfP
p=Ppk,•IfCpk<Cp,•IfPpk<Pp,•IfCp=Pp,•IfCpk=Ppk,•IfPp<Cp,•IfPpk<Cpk,…thenprocessisaffectedbyspecialcauses.InvestigateX-bar
/R-chartforout-of-controlconditions.SPCmaybeeffective…thenprocessisnotaffectedbyspecialcausesduringthestudyrun.SPCwouldnotbeeffectiveinthisc
ase…thenprocessperfectlycentred…thenprocessnotcentred(checkprocessmeanagainstdesignnominal)36©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyC
onfidentialCpandCpkIndicesandDefects(bothtailsofthenormaldistribution)Cpk/PpkCp/Pp0.10.20.30.40.50.60.70.80.91.01.11.21.33
1.41.51.672.02.53.04.0%/PPM0.176.4256.6144.8940.0038.5638.2638.2138.2138.2138.2138.2138.2138.2138.2138.2138.2138.2138.2138.2138.21%0.254.8638.9331.
0228.2527.5627.4427.4327.4327.4327.4327.4327.4327.4327.4327.4327.4327.4327.4327.43%0.336.8125.0920.1918.7518.4518.4118.4118.4118.4118.411
8.4118.4118.4118.4118.4118.4118.4118.41%0.423.0115.1012.3311.6411.5211.5111.5111.5111.5111.5111.5111.5111.5111.5111.5111.5111.51%0.513.368
.477.036.736.696.686.686.686.686.686.686.686.686.686.686.68%0.67.194.413.733.613.593.593.593.593.593.593.593.593.593.
593.59%0.73.572.131.831.791.791.791.791.791.791.791.791.791.791.79%0.81.640.950.840.820.820.820.820.820.820.820.820.820.82%0.90.690.400.350
.350.350.350.350.350.350.350.350.35%1.027001509136313501350135013501350135013501350PPM1.1967532485484483483483483483483PPM1.231816
5160159159159159159159PPM1.336338333332323232PPM1.427141313131313PPM1.5733333PPM1.670.60.30.30.30.3PPM2.00.00
.00.00.0PPM2.50.00.00.0PPM3.00.00.0PPM4.00.0PPMPp=Ppk=1,3363ppmdefects=0,006%Cp=Cpk=1,670,6ppmdefects=0,00006%Note:Ppmrejectratesc
alculatedfromCp&Cpkarebasedontheshorttermvariationwhichmaynotrepresentthelongtermrejectrate37©NOKIA2001T0001801.PPT/21-Dec-2001/Ji
mChristyCompanyConfidentialTheEffectsofCpkandCponFFRCpkCpPpmdefectsTotalnumberofdefectsfor50,000,000parts
Totalnumberofdefectsifphonehas10oftheseparts0.81.338,200410,0004,100,00011.331,35067,500675,0001.331.33633,15031,5001.331.67331,65016
,5001.501.5073503,5001.671.671303002.002.0000138©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialExercise2:CpandCpk•Calcul
ateCpandCpkforthe100measurementsinthefile"Dataexercise1.xls"•DeterminetheapproximateCpandCpkforthe4samplepopula
tionsonthefollowingpage•Shouldactionsbemadetoimprovetheseprocesses.Ifyes,which?39©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompan
yConfidentialEstimateCpandCpk?Thewidthofthenormaldistributionsshowninclude±3*sLSLUSLA)LSLUSLB)LSLUSLC)USLLS
LD)40©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialEstimateCpandCpk?-A)LSLUSLA)Meanandnomi
nalUSL-LSL6*sUSL-MeanMean-LSL3*s41©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialEstimateCp
andCpk?-B)LSLUSLB)NominalMeanUSL-LSL6*sUSL-MeanMean-LSL3*s42©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialEst
imateCpandCpk?-C)LSLUSLC)NominalMeanUSL-LSL6*sUSL-MeanMean-LSL3*s43©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristy
CompanyConfidentialEstimateCpandCpk?-DUSLLSLD)NominalMeanUSL-LSL6*sUSL-MeanMean-LSL3*s44©NOKIA2001T0001801.
PPT/21-Dec-2001/JimChristyCompanyConfidentialSection4.UseoftheNMPDataCollectionSpreadsheet45©NOKIA2001T0001801.PPT/21-Dec-200
1/JimChristyCompanyConfidentialExampleofhowtoCollectData1.Runinandstabiliseprocess2.Notethemainparame
tersforreference3.Whentheprocessisstablerunthetoolfor10hours3.Take5partsoutfromeachcavityeveryhalfhourandmarkthemwithtime,dateandcavit
y.Total20setsof5partsfromeachcavitymustbemade,oraccordingtoagreement.4.Afterthelastsamplelotnotethemainprocessparametersforreference5.Measur
eandrecordthemainfunctionalcharacteristics(whitediamonds)6.FilldataintotheNMPdatacollectionspreadsheet7.Analyse!TimeDimensionSubgroupsizen=
5NumberofsubgroupsN=200,5hoursbetweensamplestakenNote:Forclarity,only6subgroupsareshown46©NOKIA2001T0001801.PP
T/21-Dec-2001/JimChristyCompanyConfidentialDataCollectionSheet(DMM00024-EN-5.0)47©NOKIA2001T0001801.PPT/21-Dec-
2001/JimChristyCompanyConfidentialDataCollectionSheet(DMM00024-EN-5.0)48©NOKIA2001T0001801.PPT/21-Dec-2001/JimCh
ristyCompanyConfidentialGraphicalPresentation:Histogram•Whatkindofdistribution?LocationversustoleranceareaWidth(deviation)•Example:Cp2.59Pp1.
86•Cpk0.88Ppk0.6349©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialGraphicalPresentation:X-barandR-Cha
rtX-BarChartR-Chart50©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialGraphicalPresentation-TimeS
eriesPlotSomethinghappenedhere!!!51©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialExercise3:CpkDataSpreadsh
eet•Openspreadsheet"Dataexercice3.xls".Dim13isidenticaltothedatafromthepreviousexercises.•Verifytheresultsfromthepreviousexercis
esfordimension13.•Analysetheremainingdatasetsancommenttheprocess,shouldanyactionsbemade?Remembertocreateandlookatthecharts.52©NOKI
A2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialSection5.ConfidenceofCpk53©NOKIA2001T0001801.PPT/21-Dec-2001/
JimChristyCompanyConfidentialConfidenceofCpk•Cpkvaluesarenotdefinitenumbersastheyarebasedonrelativelysmallsamplesofapopula
tion.•The95%confidenceintervaldeterminestheintervalwhichincludesthetrueCpkvaluewithaprobabilityof95%,
i.e."thereisaprobabilityof5%thatCpkiseitherlowerorhigher"thanthisconfidenceinterval.95%confidenceintervalActualcpkCpkupperconfidencelimitCpklowerc
onfidencelimit54©NOKIA2001T0001801.PPT/21-Dec-2001/JimChristyCompanyConfidentialConfidenceofCpk95%ConfidenceIntervalonaCpkof1.670.0000.5001.0001.
5002.0002.5003.0003.500050100150200250SampleSizeCpkCpk.LCpk.USmallsamplesizesgiveswideconfidenceintervals55©NOKIA2001T0001801.P
PT/21-Dec-2001/JimChristyCompanyConfidentialCpkConfidenceLimitswithasamplesizeof100andanominalCpkof1.67