1PACKAGINGEEC116,Winter2010,B.Baas2IC Packaging•Purposes1) Electricalconnections• Signals•Powerandground2) Aidsheatdissipation• Increaseeffectivesurfaceareaforincreasedconvection•HeatconductionintoPCboard3) PhysicalprotectionforIC• e.g.,againstbreakage4) Environmentalprotection•Hermetic(airtight)seal• e.g.,againstcorrosionormoisture2EEC116,Winter2010,B.Baas3Rent’s Rule• Empiricalformula• P=KGβ•P=numberofinput/outputconnections(pins)K=averagenumberofI/Osper“gate”G=numberof“gates”β =empirically‐foundparameterthatvariesaccordingtoapplication;generallybetween0.1and0.760.12Staticmemory820.25Computer(board)1.40.63Computer(chip)KβEEC116,Winter2010,B.Baas4Package Metrics• Electrical•Lowcapacitance•Lowinductance•Lowresistance•Mechanical• Reliableacrosstemperaturevariations(thermalexpansionmatching)• Thermal•Lowthermalresistancetogettheheatout• Economical(cost)• Purchaseofpackage• Assembly(chipandboardassembly)•System(heatremovalequipmentincluded)3EEC116,Winter2010,B.Baas5Package Materials• Plastic–Lowcost– Typicallyrequiresacustom‐designedpackage• Ceramic– Betterheattransfercharacteristics– Generallymorereliable–Morelikelyanoff‐the‐shelfpartcanbeused• GoodforresearchandprototypingEEC116,Winter2010,B.Baas6Interconnection Levels•Multiplelevelsofpackaging–Easeofhandling–Reuseofintermediate‐sizedmodules(e.g.,DRAMmemorystick)•Useinmultipleproducts•Upgradeableinfield• Repairableinfieldsystemprinted circuit board(PCB)packagechip4EEC116,Winter2010,B.Baas7Solder•Solderistheuniversalelectrical“glue”–tinandleadalloy:50/50%,63/37%Sn/Pb eutecticmixture–lowmeltingtemperature:183°Cor361.4°Fforeutectic– goodelectricalconductivity• Largeeffortsnowunderwaytoeliminateorreducetheuseoflead–RoHS‐ RestrictionofHazardousSubstancesDirective–Manyreplacementsavailable•TypicalonesuseTin,Silver,Copper;maybeBismuth,Indium,Zinc,AntimonyEEC116,Winter2010,B.Baas8PC BoardSource: J-Machine, Dally5PC BoardiPhone 3GS, AppleInsider, June 19, 2009 EEC116,Winter2010,B.Baas10PC Board Stack With Host ComputerSource: J-Machine, Dally6EEC116,Winter2010,B.Baas11System•J‐Machine• BuiltatMITandStanfordintheearly1990’s• 1024processorsSource: J-Machine, Dally EEC116,Winter2010,B.Baas12IBM Blue Gene/L•Thefastestsupercomputerintheworldisa131,072‐processorBlueGenemachine7EEC116,Winter2010,B.Baas13IBM Blue Gene/L•Thefastestsupercomputerintheworldisa131,072‐processorBlueGenemachineEEC116,Winter2010,B.Baas14Chip to Package Connections1) Wirebonding–dieattached–goldoraluminumwires–oneatatime–notentirelyrepeatable– Electricalcharacteristics:•R:low•C:low•L:~1nH/mm8EEC116,Winter2010,B.Baas15Bonding TechniquesLead FrameSubstrateDiePadWire BondingSource: Digital Integrated Circuits, 2nd ©EEC116,Winter2010,B.Baas16Wire Bonds• Opticalmicroscopeviewofbondwiresforatwo‐padpackageSource: Assurance Technology9EEC116,Winter2010,B.Baas17Wire Bonds•SEMviewofbondwiresforatwo‐padpackageSource: Assurance Technology EEC116,Winter2010,B.Baas18Wire Bonds•SEMviewofasinglebondwireattachmentSource: Assurance Technology10EEC116,Winter2010,B.Baas19Wire Bonds•GoldwirebondonaluminumdiepadSource: SEM Lab, Inc. EEC116,Winter2010,B.Baas20Wire Bonding Machine•WirebondingmachineSource: TWI, Ltd.11EEC116,Winter2010,B.Baas21Chip to Package Connections2) Tapeautomatedbonding(TAB)–Dieattachedtometalleadframeprintedonpolymerfilmusingsolderbumps–Tapethenconnectedtopackage–Fastandparalleloperation–Lowerelectricalparasitics (R,L,C)EEC116,Winter2010,B.Baas22Tape-Automated Bonding (TAB)(a) Polymer Tape with imprinted (b) Die attachment using solder bumps.wiring pattern.SubstrateDieSolder BumpFilm + PatternSprocketholePolymer filmLeadframeTestpadsSource: Digital Integrated Circuits, 2nd ©12EEC116,Winter2010,B.Baas23Tape-Automated Bonding (TAB)Source: Computer Desktop EncyclopediaEEC116,Winter2010,B.Baas24Chip to Package Connections3) Flipchipsolderbump–chipplacedfacedowninpackage– connectedwithsolderbumps– verylowparasitics– allows“areapads”• padscancoverchipareaandarenotlimitedtochipperiphery13EEC116,Winter2010,B.Baas25Flip-Chip BondingSolder bumpsSubstrateDieInterconnectlayersSource: Digital Integrated Circuits, 2nd ©EEC116,Winter2010,B.Baas26Package to Board Connections 1) Through Hole• Classicapproach•Holesdrilledandplatedwithcopper•Soldering–Chipsplacedinsideholes– Bottomofboardpassedthroughamoltensolder“wave”14EEC116,Winter2010,B.Baas27Package to Board Connections 2) Surface Mount Technology (SMT)•MorewiringroominsidePCboard• Reducedspacebetweenpackageleads•Chipsonbothsidesofboard• StrongerPCboard•Soldering–Solderpasteapplied– Heatsuppliedbyintenseinfraredlight,heatedair,…EEC116,Winter2010,B.Baas28Package-to-Board Interconnect(a) Through-Hole Mounting(b) Surface MountSource: Digital Integrated Circuits, 2nd ©15EEC116,Winter2010,B.Baas29SMT Leadsa) Gull‐wing