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1、BGA(BallGridArray)NationalSemiconductorBGA(BallGridArray)ApplicationNote1126September1999PrintedCircuitBoard(PCB)LayoutNSMDdefinedpadsenhancevisionregistrationofcopperfi-ducialscomparedtotheSMDdefinedpad.ForSMDdefinedGuidelinespads,anymisregistrationofthe
2、soldermaskwillcontributetofurtherMoreover,SMDpaddefinitioncanintroducestressSOLDERBALLANDPBGABALLPADSIZESconcentrationpointsnearthesoldermaskonthePCBsideAs-receivedPBGAsolderballdiametersarelistedinTable1.thatmayresultinsolderjointcrackingunderextremefati
3、gueRecommendedsolderballdiametersasdescribedinJEDECconditions.Standard95-1Section14arelistedinTable2.Thediameteristhemaximumdiameteroftheballmeasuredparalleltothesubstratesurface.Theballsizesarefor2lowmelt2solder,whichisdefinedintheJEDECStandardasasolderm
4、etal-lurgythatwillgointotheliquidusstatewhensubjectedtostandardindustrymountreflowtemperaturesof220?C.Typi-calPBGApadopeningsizesasafunctionofpitcharelistedinTable3.TABLE1.As-ReceivedPbgaSolderBallDiametersPitch(mm)BallDiameter(mm)1.27(Note1)0.76AN101094-
5、11.0(Note1)0.5FIGURE1.NSMDandSMDPadDesignsA1:1ratiobetweenthepackagepadandPCBpadisdesir-TABLE2.PBGASolderBallDiameters(AttachedToabletobalancethestressduringtemperaturecycling,Substrate)thoughaslightlysmallerratio(0.8)canbeusedfortheBallDiameter(mm)PBGAto
6、facilitateroutingbetweenpadsintheareaarrayPitch(mm)MinNomMaxpackage.ForNSMDpadsitisnecessarytohaveaclear-ancearoundthecopperpadandthesoldermasktoaccount1.27(Note0.600.750.90formaskregistrationtolerances(typically±0.075mmor31)mils)andtovoidanyoverlapbetwee
7、nsolderjointandthe1.0(Note1)0.500.600.70soldermask.Table4listrecommendedguidelinesforPCB0.8(Note2)0.45-0.5paddesignsasafunctionofPBGAballpitch.TABLE3.PBGAPadOpeningSizeTABLE4.GuidelinesForPadDesignsPitchPadOpeningSizeNSMDSMDmm(mils)mm(mils)mm(mils)mm(mils
8、)1.27(50)0.63(25)PBGABallPitch=1.27mm1.0(40)0.45(18)BallSize0.75(30)0.75(30)0.8(31)0.35-0.45(14-18)PCBPadDiameter0.63(25)0.71(28)SolderMaskOpening0.78(31)0.63(25)Note1:JEDECSpecificationDiameterNote2:AvailablePBGABa
