Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer | 04.09.2007 | Page 1

Sven Knippscheer, Ravi Bollina, Tobias Mrotzek, Janet Landgraf

Workshop on Materials for Collimators and Beam Absorbers

CERN, 4. September 2007

Development and Manufacturing Status of Diamond-based Composites

Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer | 04.09.2007 | Page 2

Outline

• IntroductionMarkets, Applications, Thermal Materials

• Production Process of Diamond Composites

• Constitution and Microstructure

• Thermal Properties

• Thermal Cycling Tests

• Product Development

Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer | 04.09.2007 | Page 3

Optoelectronics

Diode laser for manufacturing, laser pumping and medical application

Higher power density and stability of

laser beam is limited by efficient heat transfer

Microelectronics

Server for large scale data processing

Higher clock rates and

miniaturization of transistors lead to higher power density in micro-

processors

Markets and Applications | Main Markets

Power-electronics

Power converters (IGBT) for energy conversion

Size reduction and higher currents in

power converters drive thermal conductivity of base plates

Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer | 04.09.2007 | Page 4

Technology | Heat flux challenge

Source: Honeywell

Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer | 04.09.2007 | Page 5

Materials | TC and CTE of Thermal Management Materials

0

50

100

150

200

250

300

350

400

450

0 3 6 9 12 15 18 21 24 27

Coefficient of thermal Expansion in ppm/K

Th

erm

al

Co

nd

uc

tivit

y i

n W

/mK

at

20

°° °° C

Be

CrCo

SiC (PC)

Fe Ni

Au

Cu

Ag

Al

Mg

Kovar3 Al2O3

BeO

AlN

Si N4

500

550

600

650

700

GaAs

Si

GaN

SiC (mc)

AlSi

AlSiCSilvar

CuCf

AlCf

Cu/MoCu/Cu-Laminate

Mo

W-15Cu

WMo-30Cu

AgCD

AlCD

CuCD

Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer | 04.09.2007 | Page 6P

ressu

rise

dg

as

Va

cu

um

Metal (solid)

Preform / Powder

Va

cu

um

Metal (liquid)

Pre

ssu

rise

dg

as

Composite

1 2

3 4

heating

heating

Pre

ssu

rise

dg

as

Va

cu

um

Metal (solid)

Preform / Powder

Va

cu

um

Metal (solid)

Preform / Powder

Va

cu

um

Metal (liquid)

Va

cu

um

Metal (liquid)

Pre

ssu

rise

dg

as

Pre

ssu

rise

dg

as

CompositeComposite

1 2

3 4

heating

heating

Diamond Composites | Gas Pressure Assisted Infiltration

Material income

Infiltration

Metallization

(“thick film”)

Machining

Inspection of diamond powder

Inspection of ingot material

Assembly and filling of molds

Gas pressure infiltration

Inspection of infiltrated parts

Cleaning / Surface preparation

Applying Ag or Cu layer

Final inspection

and shipping

Coating

(thin film)

Water jet cutting

Cleaning / Surface preparation

PVD Coating

Precision machining

Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer | 04.09.2007 | Page 7

Diamond Composites | Microstructure

FESEM images of ion beam etched copper diamond composite samples

• Homogeneous distribution of diamond particles

• low microporosity

• Carbide phase between metal and non-metal facilitates mechanical and thermal bond

Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer | 04.09.2007 | Page 8

Diamond Composites | Thermal Conductivity vs Diamond Grade

The properties of the composite are affected by the type and size

distribution of the diamond.

� Grade of diamond:

- synthetic (type I) vs. natural (type II)

- Content of Nitrogen and other impurities

- amount of metallic inclusions

� Size distribution of the diamond particles

� Shape and surface of the diamond particles

Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer | 04.09.2007 | Page 9

Composite Material with high thermal conductivity (up to 700 W/mK)

and tailored CTE (5 – 8 ppm / K)

� Diamond particles are implemented in a highly thermal

conductive metallic matrix (Ag, Cu, Al).

� The CTE can be tailored by the volume content of diamond.

� An estimation for the achievable thermal conductivity and CTE

can be given by the Hashin-Strikman bounds.

AgCD

Diamond Composites | Thermal Expansion vs Diamond Content

Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer | 04.09.2007 | Page 10

Diamond Composites | Coefficient of Thermal Expansion

Coefficient of Thermal Expansion

4

5

6

7

8

9

-100 -50 0 50 100 150 200 250 300

Temperature / °C

CT

E /

pp

m/K

AgCD | Dia QA ~ 60 vol%

Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer | 04.09.2007 | Page 11

200

250

300

350

400

450

500

550

600

650

700

-100 -50 0 50 100 150 200 250 300

Temperature / °C

TC

/

W/m

/K

Cu

AgCD | Dia QA ~ 60 vol%

Diamond Composites | Thermal Conductivity

α⋅⋅ρ=λ pc

Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer04.09.200712

Courtesy: Siemens AG

Thermal cycling tests were performed in a two chamber

cycling oven according to JESD-A104-C (temperature cycle

H and a soak mode 3 ):

Temperature: -55°C / +150°C, 1000 thermal cycles

20 min storage time in each chamber

Diamond Composites | Thermal Cycling Tests

Thermal cycling chamber

Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer04.09.200713

Thermal Diffusivity | Before and after thermal cycling

Silver-diamond composite

80

130

180

230

280

330

380

0 100 200 300 400 500

Temperature, °C

Th

erm

al

dif

fusiv

ity,

mm

²/s

A- before TC

B- before TC

A- after TC

B- after TC

Aluminum-diamond composite

60

100

140

180

220

0 100 200 300 400 500

Temperature,°CT

herm

al d

iffu

siv

ity, m

m²/

s

A- before TC

B- before TC

A- after TC

B- after TC

Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer04.09.200714

80

100

120

140

160

180

200

220

240

260

0 100 200 300 400 500

Temperature, °C

Th

erm

al d

iffu

siv

ity, m

m²/

s A- before TC

A- after TC

0

10

20

30

40

50

60

70

80

0 100 200 300 400 500

Temperature, °C

Th

erm

al

dif

fus

ivit

y,

mm

²/s

A- before TC

A- after TC

43%

37%

Copper-diamond composites

Cu-Cr

Cu-Si

Cu-B

Thermal Properties | Before and after thermal cycling (CuCD)

0

50

100

150

200

250

0 200 400 600

Temperature [°C]

Th

erm

al D

iffu

siv

ity [m

m2s

-1]

before

after

Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer04.09.200715

Fracture surface | After thermal cycling-AgCD

Intact Interfaces!

Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer | 04.09.2007 | Page 16

Silver diamond composite heat sinks can be provided with silver and copper metallization

on top, bottom and lateral faces. Metallization allows conventional finishing processes,

such as grinding, lapping, diamond milling, coating, etc..

Ag-diamond composite

Ag metallization

Diamond Composites | Surface Finish of AgCD Components

Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer | 04.09.2007 | Page 17

Diamond Composites | Product examples

Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer | 04.09.2007 | Page 18

Diamond Composites | Thermal and Physical Properties

AgCD AlCD CuCD

Thermal Management - Diamond Composites | Dr.-Ing. Sven Knippscheer | 04.09.2007 | Page 19

Stay cool!

� Questions??