Excerpt – Direct Bonded Copper NE

1 2003, D. C. of Curamic ElectronicsExcerpt Direct Bonded CopperPresented byDouglas C. Hopkins, Bonner HallUniversity at BuffaloBuffalo, NY 14620-1900607-729-9949, fax: 607-729-7129 2003, D. C. of Curamic ElectronicsAuthors thankAuthors thankCuramik ElectronicsA member ofA member offor providing information and photosfor providing information and photos 2003, D. C. of Curamic ElectronicsDCB Process Oxygen reduces the melting point of Cu from 1083 C to 1065 C (Eutectic melting temperature). Oxidation of Copper foils or injection of oxygen during high temperature annealing (1065 C and 1080 C) forms thin layer of eutectic melt. Melt reacts with the Alumina by forming a very thin Copper -Aluminum-Spinellayer. Copper to Copper is fused the same way.

2 Copper -Aluminum-Nitride (AlN) DBC is possible. The AlN-Surface must be transformed to Alumina by high temperature oxidation. 2003, D. C. of Curamic ElectronicsDBC ProcessCopperCeramicCopperCeramicO2 CopperOxideCopperCeramicEutecticMeltHeat ingO2 DiffusionandCoolingCopperCeramicCopperCo pperCopperCopperCopperCopperCopperCopper 1080 -1070 -1060 -1050 -O2-Concentration in Atom-% 2003, D. C. of Curamic ElectronicsDBC -InterfacesAl2O3 CopperAl2O3 AlNCopperCopper 2003, D. C. of Curamic ElectronicsFlow Chart of DBC ProcessingSubstrate Ni + Au surfaceSubstrate Ni platedSubstrate blank Copper surfaceControlShipping to customeras mastercardsShipping to customeras single partsSeparating mastercardsby breakingDBC ProcessMaskingEtchingFinal CleaningElectroless NickelElectroless GoldLaser Scribing 2003, D.

3 C. of Curamic ElectronicsMasking High precision screen printers for high volume Semiautomatic and fully automatic with pattern recognition Redundant equipment Photomaskingfor high density circuits Air conditioned clean rooms 2003, D. C. of Curamic ElectronicsEtching Specially designed precision etchers for thick Copper layers Automatic chemistry control Mask stripping integrated 3 separate high volume lines in operation Controlled by SPC 2003, D. C. of Curamic ElectronicsPlating / Final Cleaning Fully automatic high volume plating line for electrolessNi + Au Controlled by SPC Final cleaning for Cu integrated Parallel backup lines Solderabilityand wire bond testing 2003, D. C. of Curamic ElectronicsLaser Machining Fully automatic high precision CO2lasers with pattern recognition Designed for high volume throughput Scribing and drilling Multiple equipment Controlled by SPC 2003, D.

4 C. of Curamic ElectronicsFeatures of DBC Substrates Low thermal coefficient of expansion despite relatively thick Copper layers(TCE = -10-6 at / 12mil Copper ) High current carrying capability with thick Copper ( Copper width 1mm / 40mil, height / 12mil, continuous flow 100amps = temp rise of 14 -17 C) High peel strength of Copper to Al2O3 60N/cm;AlN 45N/cm at 50mm/min peel speed High thermal conductivity(Al2O3 = 24W/mK; AlN =170 W/mK) Low capacitance between front-and backside Copper (Appr. 18pF/cm2 for ceramic thickness) 2003, D. C. of Curamic ElectronicsRelative Heat Flux(W/sqm) 100 10 100 1000 10000 Surface of Sun Saturn V Engine (Case) Power Semiconductor Chip Logic Chips Light Bulb (100 W) Hot-Plate Heat Loss from Human Body Chips need CoolingAbsolute temperature [K]Source: Semikron 2003, D.

5 C. of Curamic ElectronicsPrincipal Design of IGBT Power ModuleHard encapsulationSoft encapsulationSolder jointIGBT / DiodeAl thick wire bondThermal greaseHeat sinkCu baseplateDBC substrateCurrent contactPlastic casing 2003, D. C. of Curamic ElectronicsIGBTIGBTD iodeDiodeDBC substrateDBC substrateSingle Switch Module4 Substrates, 4 IGBT s and 4 Diodes 2003, D. C. of Curamic Electronics0,4 0,45 0,5 0,55 0,6 0,65 0,7 Thermal resistance [K/W]10 100 1000 10000 Thermal conductivity[W/mK]DiamondAl2O3 AlNPower Module Thermal ResistanceThermal Resistance as a function of Substrate Thermal ConductivityChip area = 100mm2; ceramic thickness; 0,635mm; Copper baseplate 3mm; power dissipation 100W; solder 0,070mm 2003, D. C. of Curamic ElectronicsThermal Mass0 20 40 60 80 100 120 140 160 Junction Temperature [ C]1E-21E-11E01E11E21E3ln time [sec]0,15 mm0,3 mm 0,6 mmInfluence of copperthicknessInfluenceofRth staticCu-thickness (3)Junction temperature as function of the dynamic thermal resistance 2003, D.

6 C. of Curamic ElectronicsFlexural Strength of DBCas a function of Copper thickness3004005006007008009001000 Alumina Standard DBC dCu=0,20mm DBC dCu=0,25mm DBC dCu=0,30mm99907563,325101 Probability of Failure F [%]Flexural Strength [MPa] 2003, D. C. of Curamic ElectronicsFlexural Strength of HPS DBCC ompared with Blank HPS (optimizedAlumina) Ceramic500550600650700750800850900950100 0500100015002000 DBC Optimized Alumina 75999063,325101 Probability of Failure F [%]Flexural Strength [MPa] 2003, D. C. of Curamic ElectronicsDimple DesignTop viewCross section 2003, D. C. of Curamic ElectronicsThermal Cycling ReliabilityStandard Alumina DBC with and w/o Dimples204060801002003004005006007008009 0010002000 Standard DBC Dimples DBC99907563,325101 Probability of Chonchoidal Fracture F [%]Number of Temperature Cycles 2003, D.

7 C. of Curamic ElectronicsAverage Life N0 (Weibull)0501001502002503003508001000120 014001600180020002200>2000>2000 Number of thermal cyclesCurStdAlNCurMilCurHP*CurHPIwith Dimples ( Copper pattern design for thermal stress relief)without Dimples*d(ceramic)= 25 mil, d(Cu)= 12 mil -55 C / 150 C / 15 (ceramic)= 15 mil, d(Cu)= 8 mil -55 C / 150 C / 15 min. 2003, D. C. of Curamic ElectronicsSpecial Substrates Active Metal Brazed (AMB) Refractory Metallization Substrates with vias Substrates with lead offs 3-Dimensional substrates DBC Packages Water cooled substrates 2003, D. C. of Curamic ElectronicsVia TechnologyBoth sides flat surface. Ceramic hole diameter min. R<100 One side flat surface. Ceramic hole diameter min. R<100 One side flat surface low cost.

8 Ceramic hole diameter ( Copper layer) R<100 2003, D. C. of Curamic ElectronicsViasin DBC Substrates High current front to back feed-through 100 A current 100 Ohm For backside ground-plane or shield Both hermetic Version 1 can be used as thermal path also 2003, D. C. of Curamic ElectronicsIntegral Terminals Terminals made of same Copper sheet as circuit High electrical conductivity due to solid metal without interface resistance Very high reliability 2003, D. C. of Curamic Electronics3-Dimensional DBC For very high density circuits Extremely reliable due to integral connectors Base for power Sidewalls for non-power components Assembled flat and bend up 2003, D. C. of Curamic ElectronicsPackage TypesTop LeadKovar Frame2 Kovar LidChipWirebondKovar FrameKovar LidSide LeadChipWirebond1 CeramicCopper1 Via2 Direct Bonded Pin 2003, D.

9 C. of Curamic ElectronicsPackage TypesChipWirebondKovar LidKovar FrameSurface Mount1 Kovar PinKovar LidDown LeadKovar FrameChipWirebondChipWirebondKovar LidKovar FrameGlass to Metal Seals1 GlassCeramicCopper1 Via2 Direct Bonded Pin 2003, D. C. of Curamic ElectronicsKovarFrame Brazed on DBC SubstrateGlass Sealed Feed-Through 2003, D. C. of Curamic ElectronicsFluid Cooled DBC Lowest thermal resistance of all available solutions for COB Rthranging from to K/W using Al2O3 or AlN Power dissipation up to 3 kW on 2 x 2 Extremely compact design Modular system assembly 2003, D. C. of Curamic ElectronicsLiquid flow-through micro channelsBasisElementLiquidCeramic Isolation LayerChip Mounting Layer 2003, D. C. of Curamic ElectronicsMicro ChannelsCut ACut B 2003, D.

10 C. of Curamic ElectronicsMicro Channel Water Cooled ModuleHalf bridgeHalf bridge6 IGBT6 IGBT12 Diodes12 Diodes62 mm Standard 62 mm Standard module sizemodule size450 A450 ACooling water Cooling water temperature up to 80 C temperature up to 80 C possiblepossible 2003, D. C. of Curamic ElectronicsRthjaas a Function of Water Flow25 30 35 40 45 50 55 60 65 70 RtHja [ mK/W ]0 1 2 3 4 5 6 7 Water Flow [ l/min. ]AlN substrateAlN substrate 2003, D. C. of Curamic ElectronicsModule comparisonConventional v. Integrated water cooling1 Standard module on closed cooling system (calculation)2 Module with integrated cooling system(measurement: soldered Al2O3ceramics)3 Module with integrated AlNsubstrate100 0 20 40 60 80 Rth[K/kW]Junction -CaseCase-HeatSinkJunction AmbientJunction AmbientAbout 60% reduction of RthJA( ) 2 112 Heat Sink AmbientAbout 60% reduction of RthJA( ) 3 13