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An innovative process to fabricate interphase-free
copper / diamond composite films
Thomas Guillemet 1, 2 *, Jean-Marc Heintz 1, Namas Chandra 3,
Yongfeng Lu 2 and Jean François Silvain 1Yongfeng Lu 2 and Jean-François Silvain 1
1 Institute of Condensed Matter Chemistry of Bordeaux, CNRS, Pessac, France2 Department of Electrical Engineering, 3 Department of Mechanical and Materials
Engineering, University of Nebraska-Lincoln, Lincoln, NE, USA
www.icmcb-bordeaux.cnrs.fr / * thomas.guillemet@gmail.com 1
Contents
1. Background & Motivations
2. Processing
3. Characterization and Results
4. Conclusions and Prospective
5. Acknowledgements
2
Contents
1. Background & Motivations
2. Processing
3. Characterization and Results
4. Conclusions and Prospective
5. Acknowledgements
3
1. Background – Copper / diamond composites
Diamond: high thermal conductivity, low thermal expansion
Copper: high thermal conductivity, ductility
Thermal management applications
Raw diamond particleRaw diamond particle
Various processes:
High Pressure / High Temperature
Infiltration Cr-coated diamond particleCr-coated diamond particle
Permanent issue: low Cu C chemical affinity
Spark Plasma Sintering
Permanent issue: low Cu-C chemical affinity
Current solution: carbide forming additives: B, Cr
HHowever:
K. Chu et al., Journal of Alloys and Compounds 490 (2010), 453-458
Carbide interphases degrade the thermal performances
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1. Motivations
What? Diamond dispersed copper matrix composite films
with high thermal performances
and no carbide interphaseRaw diamond particleRaw diamond particle
How? Tape casting of Cu/D filmsHow? Tape casting of Cu/D films
Cu coated diamond particleCu coated diamond particleCopper coating of diamond particles Cu-coated diamond particleCu-coated diamond particle
Vacuum hot pressing
5
1. Motivations
Why? Thermal management of power electronic modules
Silicon chips SnAgCu Solder joints
Copper films
Small CTESmall CTE
Large CTELarge CTE
Copper heat-sink Alumina substrate
Large CTELarge CTE
Trends: Packing density
Power / Heat flux density
Demand for efficient cooling materials at minimum cost
6Copper-Diamond films as heat-spreading layers in electronic packages
Contents
1. Background & Motivations
2. Processing
3. Characterization and Results
4. Conclusions and Prospective
5. Acknowledgements
7
2. Processing – Flowchart
Formulation Tape casting and drying Shaping
Hot pressing
DebindingReduction
400°C, 2h, under air400°C, 2h, under air400°C, 1h, under Ar/H2400°C, 1h, under Ar/H2650°C, 50 MPa, 30 min650°C, 50 MPa, 30 min8
2. Processing – Formulation
Chemical Role
MatrixMatrixDendritic copper powderDendritic copper powder
ReinforcementsReinforcementsMBD6 50 µm diamond powder
MBD6 50 µm diamond powder
SolventSolvent
pp
Ethanol / 2-butanone (60/40)
Ethanol / 2-butanone (60/40)
Dispersant + Functionalization agent
Dispersant + Functionalization agentPhosphate EsterPhosphate Ester
(60/40)(60/40)
PMMAPMMA
DiButyl PhtalateDiButyl Phtalate
BinderBinder
PlasticizerPlasticizerDiButyl PhtalateDiButyl Phtalate PlasticizerPlasticizer
Mixing 15h at 20 rpm9
2. Processing – Tape casting
Doctor blade
Motorized guide rail
Doctor blade Slurry
Silicon film SupportTape casting direction
Silicon film Support
Viscosity: 1 Pa sViscosity: 1 Pa.s
Doctor blade speed: 2 cm.s-1
G t thi k [300 1 5 ]Green tape thickness: [300 µm – 1.5 mm]
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2. Processing – Tape casting
Organics Diamond
Thickness controlGood surface finishL t
Net shapingEasy handlingL l bilit
Copper matrix
Low cost Large scale capability
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2. Processing – Debinding
2 hours / 400°C / under air: organics burnout
CuO nanowires growthCopper matrix oxidation
12
2. Processing – Reduction
1 hour / 400°C / under Ar/H2: copper matrix reduction
Cu particlesCopper particles deposition onto diamond powders through phosphorus chemical bonds: C-O-P-O-Cu
13
2. Processing – Copper / Carbon interface
Reduction step Hot pressing stepOxidation step
CuCuO
CuCuCuCuOCuO
Carbon
CarbonCarbon
Cu|
Cu|
CuP |P|O|
Cu|
P-O|C
P|O|C C CC
14
2. Processing – Vacuum hot pressing
30 minutes / 650°C / 50 MPa30 minutes / 650 C / 50 MPaFast and low-cost sintering techniqueMultilayered Cu/D samples for thermal measurements purposes (4 mm thick)
2 cm
Cu / 20 vol.% DCu / 20 vol.% D
15
Contents
1. Background & Motivations
2. Processing
3. Characterization and Results
4. Conclusions and Prospective
5. Acknowledgements
16
3. Characterization and Results – Relative density
The Cu coating effectively actsas interfacial chemical bonding agent
17
3. Characterization and Results – Thermal conductivity
The Cu coating enablesefficient interfacial heat transfer
λ = 470 W.m-1.K-1 with 40 vol.% diamondHigher conductivity is expected from single tape samplesHigher conductivity is expected from single tape samples
λ = 600 W.m-1.K-1 with 40 vol.% diamond using direct PM processing
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3. Characterization and Results – Thermal expansion coefficient
The Cu coating enablesefficient thermal expansion load transfer
12 × 10 6 °C 1 ith 40 l % di dα = 12 × 10-6 °C-1 with 40 vol.% diamond
19
Contents
1. Background & Motivations
2. Processing
3. Characterization and Results
4. Conclusions and Prospective
5. Acknowledgements
20
4. Conclusions
Advantageous tape casting process
Innovative and low-cost Cu coating process of diamond particlesof diamond particles
Dense Cu/D composite films with high thermal performances and no interphase
21
4. Conclusions – Integration to power modules
As single thin filmAs single thin film
As multilayered system
As complementAs complement to Cu and/or Cu/CF for composite heat sink
Cu/DCu/D Cu/CFCu/CF
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4. Prospectives Influence of…
Diamond particles size? 40 µm40 µm 80 µm80 µm
Cu particles size/coverage?Copper coating tunability
(t, T)1(t, T)1 (t, T)2(t, T)2
Single tape systems?Single tape systems?
23
Contents
1. Background & Motivations
2. Processing
3. Characterization and Results
4. Conclusions and Prospective
5. Acknowledgements
24
5. Aknowledgements
The authors are grateful to the Région Aquitaine (France) and the
Office of Naval Research (USA) for their financial support.
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