Design for Manufacturability Assembly Guide line.docx
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Design for Manufacturability Assembly Guide line.docx
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DesignforManufacturabilityAssemblyGuideline
DocumentNumber:
702193-0000
Revision:
B0
Originator:
ChristineNolan-Brady
Dept:
RIBU-Mech.NPI
DesignforManufacturability/AssemblyGuideline–Mechanical
RevisionBupdatesandreviewsprovidedbytheMechanicalGuidelinesTeamwhichconsistsofthefollowingmembers:
▪DanBishop
▪
▪MichaelBrooks
▪
▪SamGupta
▪
▪BrianHill
▪
▪KevinMcKinsey
▪
▪SyedMohsin
▪
▪ChristineNolan-Brady
▪
▪RajanSohal
▪
▪ChyeTan
▪
▪CarlWoodward
▪
Approvals
Department
Name
ApprovalDate
MFG
LouBellardo(Director-Mfg)
3/25/03
MFG
BrianE.Jackson(NPIEMgr-Access)
3/25/03
MFG
AlbertLouie(NPIEMgr-GSR)
3/25/03
MFG
ToddTsudama(NPIEMgr-MRRBU)
3/25/03
MFG
BennyYap(NPIE-MSSBU)
3/25/03
MFG
AllistairLyall(NPIE-DSBU))
3/25/03
ModificationHistory
Rev
RCN#
Date
Originator
Comments
A0
R98-2501
11/10/98
C.Nolan-Brady
InitialRelease
B0
03-25-03
C.Nolan-Brady
MechanicalGuidelinesTeamUpdatestoprocedure
PURPOSE:
ToprovideaMechanicalGuidelineforreviewingproductsinboththedesignphaseandtheoveralllifecycleofproductsto:
∙IncreaseManufacturabilityofindividualcomponentsatvendors.
∙
∙IncreaseeaseofAssembly.
∙
∙Reducecost.
∙
∙Buildqualityandconsistencyintoproducts.
∙
SCOPE:
ThisprocedurewillcoverthebasicguidelinesusedinDesignforManufacturabilityandDesignforAssemblyandwillbeutilizedbeforeandduringthenewproduct’sdesignreviewprocessbytheNewProductIntroductionEngineers-Mechanical.Examplesincludebutarenotlimitedtomechanicalcomponentsandelectro-mechanicalassemblies.
DEFINITIONS:
Thefollowingaretermsusedinthisprocedure:
EMI:
ElectromagneticInterference
ESD:
ElectroStaticDischarge
DFA:
DesignforAssembly
DFM:
DesignforManufacturability
DVT:
DesignValidationandTest
PCA:
PrintedCircuitAssembly
SMT:
SurfaceMountTechnology
POLICIES:
ThisistoserveasaMechanicalguidelineduringthedesignreviewprocessaswellasthroughoutthelifecycleofaproduct.However,thisguidelinewillbemosteffectiveiftheseprinciplesareimplementedbeforeaproductisreleasedtomanufacturing.
PROCEDURE:
I.DesignforManufacturability:
A.StandardizationGuidelines:
B.
1.Usestandardizedpartswheneverpossiblei.e.useofftheshelfparts.
2.
3.Standardizedesignfeatures.i.e.utilizeexistingdesignswhenpossible.
4.
5.Minimizethenumberofdifferentparttypes.
6.
7.Minimizethetotalnumberofparts.
8.
9.Considerpre-finishedmaterialwheneverpossible.
10.
11.Minimizeoreliminate2ndoperationsorprocessesforplasticpartssuchaspainting,colormatchingorportidentification.
12.
7.Maketoleranceslarge,yetconsistentwithfunctional,quality,andsafetyrequirements.TolerancesshouldbeagreeduponbytheDesignEngineer,NPIE,SBEandthesupplierandshouldadhereto95-035-XXtoallowflexibilityinpartdesign,partmanufacturingandassembly.
C.PartShapeGuidelines:
D.
1.Avoidleft/righthandparts.
2.
3.Designpartswithsymmetry.
4.
5.Ifpartsymmetryisnotpossible,makepartsasasymmetricalaspossibleusing“poka-yoke”principlesorotherwiseknownasmakingthedesignfoolproof.
6.
7.Usechamfersandtaperstohelppartsengage.
8.
9.Provideregistrationandfixturinglocations.
10.
11.Providedrainageforpartsthatareeitherplatedorwashed.
12.
E.CombinationofPartsareapplicablewhen:
F.
1.Partsdonotmove(fixed)relativetooneanotherintheassembly.
2.
3.Donothavetobemadefromadifferentmaterial.
4.
5.Theircombinationwouldnotaffecttheassemblyofotherparts.
6.
7.Fieldservicedoesnotrequiretheirdisassembly.
8.
9.SampleMethodsforcombiningparts:
10.
a)incorporatehinges
b)
c)useintegralsprings
d)
e)usesnapfits
f)
g)
incorporateelementssuchasguides,bearingsandcovers.
h)
G.Designguidelines:
H.
1.Canthispartbepurchasedofftheshelf?
(refertoDFM-sectionI)
2.
3.Ensurethatthepartisfunctionallycriticaltotheproductandifabsenttheassemblycannotbecomplete.
4.
5.Determineifandwhenthepartisgoingtobesoftorhardtooled.
6.
7.Designpartssotheyareeasytohandle.Partsforassemblyshouldbefreeofsharpedgesandburrs.Specifythepunchdirectionappropriatelytominimizeissueswithburrsonproducts.Rolledgeswhennecessary.RefertospecificationP/N95-0699-XXforfurtherinformation.
8.
9.Avoiddesignsthataddandalignseveralpartsatonetimeforoneassembly.Forexample,adesignthatrequiresa“sandwich”ofseveralparts.
10.
11.Chassisassemblyshouldbeeasyforpartalignmentwithouttakingtimeforadditionaladjustmentsorreassembly.
12.
13.Usefunnelshapedopeningsandtaperedendswhenapplicabletoprovideleadinformatingpartsinassembly.
14.
15.Whenmatingparts,ensurethereisaccessibilityfortoolstoinstallfasteners.
16.
17.Overallassemblyshouldhavetheleaststepsformanufacturing.ConsiderusingBDI(BoothroydDewhurstInc.)AssemblyEfficiencyratingorothersimilarmethodologytobenchmark.
18.
19.Avoiduseofpartsthatmustbeheldinplacemanually.
20.
21.Limitsecondaryoperations,i.e.insertingPEMnutsonmetalchassis,weldingsheetmetalchassis,orinsertingpostmoldinsertintoplastics,etc.Insteadoftheseoperations“staking”(akaextrudeandswage)and“anthill”featuresshouldbeconsideredinsteadofrivetsandpressinstandoffsrespectively.
22.
23.Uselockingfeaturestoavoidsecondaryoperationofweldinginsheetmetalchassis.Avoidweldingofpre-platedmaterialsduetoenvironmentalconcerns.
24.
25.Avoidgluedonortapedonitemswheneverpossible.Ensureappropriatematerialpropertiesforeithertheglueortapeandthecomponentsbeingattached.Ensuretherearenodamagingmaterialinteractions.
26.
27.Providelocationorregistrationmarkstoguidepartplacement/orientation(ie,labels).Beawarethatthispracticedoeshavetoolingimplications.
28.
29.Considersilk-screeningorpad-printingforsinglecolorinformation.Ifinformationisinmorethanonecolorexaminethevolume,complexity,andcolorpatterntodetermineiflabelsmightbeamoreeconomicalmethod.
30.
31.Minimizenumberoflabelsbycombiningintoonesetwheneverpossible.Considerprintondemandlabelsforcomplianceorsafetyinformationtypelabelsusedonproducts.
32.
33.Reviewthetolerancestackupanalysis.Besuretheanalysisincludesofftheshelfparts(ie,hardware,largePCBAcomponents,etc.)aswellasCiscodesignedparts.
34.
35.Ifleveragingrackmountbrackets,doublecheckthatthemountingholesalignandthemountingbracketcansupporttheweightofafullyloadedunitwithcabling.
36.
37.Trytominimizepaintmasking,asthisisanexpensivehandoperation.Ifmaskingisneeded,trytoincludeagenerousoversprayallowance.Ifpossible,designpaintschemesothatwhencoverandbasearemated,thechassisisselfmasking.
38.
39.EnsureanyspecialMDVTconsiderationsaredocumentedintheMDVTTestPlan.
40.
41.Chassisshouldberobustenoughafterassemblytowithstandtheshippingprocesstothecustomerasindicatedbyacceptablepackagedtestresults.
42.
I.EMIShieldingConsiderations
J.
1.Understandthereasonashieldisrequiredanddesigntotheintent.
2.
3.ForEMIShieldingusedinplasticenclosures-securebypreferablyheatstakeorsnapfit.Avoidweldingoperationifpossible.
4.
5.Limituseofnon-integratedEMIfingercontactsinassemblybecauseofadditionalassemblytimeandcost.(RefertosectionI.)
6.
7.UseclosedendEMIspringshieldsforedgeswhenpossibletoavoidopenspringscatchingedges.
8.
9.ShortingofbottomsidecomponentstoEMIshieldcancauseintermittentfailuresorpotentiallycatastrophicfailureofthePCA.Ensurethatadequateminimumclearanceismaintainedoraninsulatingprotectorisused.Note:
Donotrelyontheinsulatinglayertopreventshortingtocomponentswithsharpedges,astheycanpunctureorwearthroughinsulatorsovertime.
10.
11.Checktoensurematerialsselectedwillberesistanttocorrosion,oxidationorothertypesofweatherdegradationintheregiontheproductisdeployed.
12.
13.Checktoensurematingpartswillnotbesusceptibletogalvanicreactions.
14.
15.Quantifygroundingcontactresistancei.e.“preload”valueforEMIcontacts.
16.
17.TrytoutilizespecificcomponentEMIshieldsor“cans”thatcanbeusedintheSMTpickandplaceprocess.
18.
19.FormoreinforegardingEMI/ESDshieldingpleaserefertoProducibilityGuidelineP/N700290-0000.
20.
K.Connectors/Switches/Fans/Misc.Hardware:
L.
1.Plasticthreadformingscrewsaregenerallygoodfor5orfewercycles.Ifitisanticipatedthatthiscyclecountwillbeexceededthenaninsertshouldbeconsidered.
2.
3.Forsteelthreadformingscrewsusethreadforminginsteadofthreadcuttingscrewstoavoidmetalshavingsthatcanshortcomponents.
4.
5.Integrated,square-conewasherswithscrewsshouldbeusedwithPCAapplications.
6.
7.PreferSMTconnectors,switches,etc.forPCAhardwarewhenpossible.
8.
9.Ensurethatinternalexpansionconnectorsorsockets,suchasRAM,canbeplacedsquarelyontheboard.
10.
11.Connectorshellswhichareallorpartplasticshouldbetestedtoensurethattheydonotdeformorundergohydrolysis(i.e.becomebrittle)inaconvectionovenorIRoven.
12.
13.ChecktoensurethatconnectorsandswitchescanwithstandthePCBAcleaningprocess(i.e.washing).
14.
15.Usekeyedconnectorswheneverpossible.
16.
9.Ensurethereisproperairflowandpropercoolingofcomponents.Wherepossibleusesnapinfanfeaturesforthesystem.Ensu
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