Excerpt Direct Bonded Copper

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1 xcerpt irect Bonded Copper Presented by ouglas C. Hopkins, Ph Bonner Hall University at Buffalo Buffalo, Y , fax:

2 Authors thank Curamik lectronics A member of for providing information and photos

3 CB Process Oxygen reduces the melting point of Cu from 1083 C to 1065 C (utectic 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-Spinel layer. Copper to copper is fused the same way. Copper-Aluminum-itride (Al) BC is possible. The Al-Surface must be transformed to Alumina by high temperature oxidation.

of eutectic melt. Melt reacts with the Alumina by forming a very thin Copper-Aluminum-Spinel layer.

4 BC Process Copper Copper Ceramic Copper O 2 Copper Ceramic Copper Oxide Copper Copper Heating O 2 iffusion and Cooling Copper Ceramic Copper Ceramic utectic Melt Copper Copper Copper Copper utectic O 2 -Concentration in Atom-%

Copper Ceramic Copper Ceramic utectic Melt Copper Copper Copper

5 BC - Interfaces Copper Al 2 O 3 Al 2 O 3 Al Copper Copper

6 Flow Chart of BC Processing BC Process Masking tching Laser Scribing Final Cleaning lectroless ickel lectroless Gold Substrate blank copper surface Substrate i plated Substrate i + Au surface Control Separating mastercards by breaking Shipping to customer as single parts Shipping to customer as mastercards

Substrate i plated Substrate i + Au surface Control Separating mastercards

7 Masking High precision screen printers for high volume Semiautomatic and fully automatic with pattern recognition Redundant equipment Photomasking for high density circuits Air conditioned clean rooms

8 tching Specially designed precision etchers for thick copper layers Automatic chemistry control Mask stripping integrated 3 separate high volume lines in operation Controlled by SPC

9 Plating / Final Cleaning Fully automatic high volume plating line for electroless i + Au Controlled by SPC Final cleaning for Cu integrated Parallel backup lines Solderability and wire bond testing

10 Laser Machining Fully automatic high precision CO 2 lasers with pattern recognition esigned for high volume throughput Scribing and drilling Multiple equipment Controlled by SPC

11 Features of BC Substrates Low thermal coefficient of expansion despite relatively thick copper layers (TC = at 0.3mm / 12mil copper) High current carrying capability with thick copper (Copper width 1mm / 40mil, height 0.3mm / 12mil, continuous flow 100amps = temp rise of C) High peel strength of copper to Al2O3 60/cm; Al 45/cm at 50mm/min peel speed High thermal conductivity (Al2O3 = 24W/mK; Al =170 W/mK) Low capacitance between front- and backside copper (Appr. 18pF/cm2 for 0.63mm ceramic thickness)

3mm / 12mil, continuous flow 100amps = temp rise of 14-17 C) High peel strength of copper to Al2O3 60/cm; Al 45/cm at 50mm/min

12 Relative Heat Flux (W/sqm) Chips need Cooling Surface of Sun Power Semiconductor Chip Saturn V ngine (Case) Hot-Plate Logic Chips Light Bulb (100 W) Heat Loss from Human Body Absolute temperature [K] Source: Semikron

000.000 Saturn V ngine (Case) 100.000 Hot-Plate Logic Chips 10.

13 Principal esign of IGBT Power Module Current contact Plastic casing Hard encapsulation Al thick wire bond Soft encapsulation IGBT / iode BC substrate Cu baseplate Heat sink Solder joint Thermal grease

14 Single Switch Module 4 Substrates, 4 IGBT s and 4 iodes BC substrate iode IGBT

15 Power Module Thermal Resistance Thermal Resistance as a function of Substrate Thermal Conductivity 0,7 Thermal resistance [K/W] 0,65 0,6 0,55 0,5 0,45 Al2O3 Al 0,4 iamond Thermal conductivity[w/mk] Chip area = 100mm 2 ; ceramic thickness; 0,635mm; copper baseplate 3mm; power dissipation 100W; solder 0,070mm

0,4 iamond 10 100 1000 10000 Thermal conductivity[w/mk] Chip area = 100mm 2 ;

16 Thermal Mass Junction Temperature [ C] Influence of copper thickness Cu-thickness (3) Influence of Rth static ln time [sec] 0,15 mm 0,3 mm 0,6 mm Junction temperature as function of the dynamic thermal resistance

Rth static 1-2 1-1 10 11 12 13 ln time [sec] 0,15 mm 0,3 mm 0,6

17 Flexural Strength of BC as a function of copper thickness 99 Probability of Failure F [%] , Alumina Standard BC d Cu =0,20mm BC d Cu =0,25mm BC d Cu =0,30mm Flexural Strength [MPa]

18 Flexural Strength of HPS BC Compared with Blank HPS (optimized Alumina) Ceramic , BC Optimized Alumina Probability of Failure F [%] Flexural Strength [MPa]

Optimized Alumina 500 550 600 650 700 750 800 850 900 950

19 imple esign Top view Cross section

20 Thermal Cycling Reliability Standard Alumina BC with and w/o imples Probability of Chonchoidal Fracture F [%] , Standard BC imples BC umber of Temperature Cycles

75 63,3 25 10 1 Standard BC imples BC 20 40 60 80 100 200

21 Average Life 0 (Weibull) umber of thermal cycles >2000 >2000 without imples with imples (Copper pattern design for thermal stress relief) CurStd CurHPI CurHP* CurMil Al *d (ceramic) = 25 mil, d (Cu) = 12 mil -55 C / 150 C / 15 min. d (ceramic) = 15 mil, d (Cu) = 8 mil -55 C / 150 C / 15 min.

22 Special Substrates Active Metal Brazed (AMB) Refractory Metallization Substrates with vias Substrates with lead offs 3-imensional substrates BC Packages Water cooled substrates

23 Via Technology Both sides flat surface. Ceramic hole diameter min. 1.0mm R<100µΩ One side flat surface. Ceramic hole diameter min. 1.0mm R<100µΩ One side flat surface low cost. Ceramic hole diameter 2.5mm (0.3mm copper layer) R<100µΩ

24 Vias in BC Substrates High current front to back feed-through 100 A current 100 µohm For backside groundplane or shield Both hermetic Version 1 can be used as thermal path also

25 Integral Terminals Terminals made of same copper sheet as circuit High electrical conductivity due to solid metal without interface resistance Very high reliability

26 3-imensional BC For very high density circuits xtremely reliable due to integral connectors Base for power Sidewalls for non-power components Assembled flat and bend up

27 Package Types Kovar Lid Side Lead Kovar Frame Wirebond Chip 1 Kovar Lid Top Lead Kovar Frame Wirebond Chip 2 Ceramic Copper 1 Via 2 irect Bonded Pin

28 Package Types Kovar Lid own Lead Kovar Frame Wirebond Chip Kovar Lid Glass to Metal Seals Wirebond Chip Kovar Frame Glass Kovar Pin 1 Kovar Lid Surface Mount Kovar Frame Wirebond Chip 1 Ceramic Copper 1 Via 2 irect Bonded Pin

29 Kovar Frame Brazed on BC Substrate Glass Sealed Feed-Through

30 Fluid Cooled BC Lowest thermal resistance of all available solutions for COB Rth ranging from 0.08 to 0.02 K/W using Al2O3 or Al Power dissipation up to 3 kw on 2 x 2 xtremely compact design Modular system assembly

31 Liquid flow-through micro channels Liquid Ceramic Isolation Layer Basis lement Chip Mounting Layer

32 Micro Channels Cut A Cut B

33 Micro Channel Water Cooled Module Half bridge 6 IGBT 12 iodes 62 mm Standard module size 450 A Cooling water temperature up to 80 C possible

34 R thja as a Function of Water Flow RtHja [ mk/w ] Al integ. Al2O3 integ. Al2O3 substrate Al substrate Water Flow [ l/min. ]

35 Module comparison Conventional v. Integrated water cooling R th [K/kW] Heat Sink Ambient Case-Heat Sink Junction - Case Junction Ambient 1 2 About 60% reduction of R thja (flowrate 2.5l/min.) 2 1 About 60% reduction of R thja (flowrate 2.5l/min.) 3 1 Junction Ambient 3 1 Standard module on closed cooling system (calculation) 2 Module with integrated cooling system (measurement: soldered Al 2 O 3 ceramics) 3 Module with integrated Al substrate

Mounting Instructions for SP4 Power Modules

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