Designing With High-Density BGA Packages for Altera Devices.pdf

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1、DesigningWithHigh-DensityBGAPackagesforAlteraDevicesDecember2007,ver.5.1ApplicationNote114IntroductionAsprogrammablelogicdevices(PLDs)increaseindensityandI/Opins,thedemandforsmallpackagesanddiversepackagingoptionscontinuestogrow.Ball-gridarray(BGA)packagesareanidealsolutionbecausetheI/Oconne

2、ctionsareontheinteriorofthedevice,improvingtheratiobetweenpincountandboardarea.TypicalBGApackagescontainuptotwiceasmanyconnectionsasquadflatpack(QFP)packagesforthesamearea.Further,BGAsolderballsareconsiderablystrongerthanQFPleads,resultinginrobustpackagesthatcantolerateroughhandling.Alteraha

3、sdevelopedhigh-densityBGAsolutionsforusersofhigh-densityPLDs.ThesenewformatsrequirelessthanhalftheboardspaceofstandardBGApackages.Thisapplicationnoteprovidesguidelinesfordesigningyourprintedcircuitboard(PCB)forAltera’shigh-densityBGApackagesanddiscusses:■OverviewofBGAPackages■PCBLayoutTermin

4、ology■PCBLayoutforHigh-DensityBGAPackagesOverviewofBGAInBGApackages,theI/Oconnectionsarelocatedontheinteriorofthedevice.LeadsnormallyplacedalongtheperipheryofthepackagearePackagesreplacedwithsolderballsarrangedinamatrixacrossthebottomofthesubstrate.ThefinaldeviceissoldereddirectlytothePCBusi

5、ngassemblyprocessesthatarevirtuallyidenticaltothestandardsurfacemounttechnologypreferredbysystemdesigners.Additionally,BGApackagesprovidethefollowingadvantages:■Fewerdamagedleads—BGAleadsconsistofsolidsolderballs,whicharelesslikelytosufferdamageduringhandling.■Moreleadsperunitarea—Leadcounts

6、areincreasedbymovingthesolderballsclosertotheedgesofpackageandbydecreasingpitchto1.0mmforflip-chipBGAsand0.8mmformicro-BGAs.AlteraCorporation1AN-114-5.1DesigningWithHigh-DensityBGAPackagesforAlteraDevices■Lessexpensivesurfacemountequipment—BGApackagescantolerateslightlyimperfectplacementduri

7、ngmounting,requiringlessexpensivesurfacemountequipment.TheplacementcanbeimperfectbecausetheBGApackagesself-alignduringsolderreflow.■Smallerfootprints—BGApackagesareusually20%to50%smallerthanQFPpackages,makingBGApackagesmoreattractiveforapplications