Young-Wook Kim Functional Ceramics Laboratory, Department of Materials Science & Engineering, The University of Seoul, Seoul 130-743, Korea Processing of Polymer-Derived Porous SiC Ceramics Porous Ceramics for CSP Applications June 26, 2013
Young-Wook Kim
Functional Ceramics Laboratory, Department of Materials Science & Engineering, The University of Seoul, Seoul 130-743, Korea
Processing of Polymer-Derived
Porous SiC Ceramics
Porous Ceramics for CSP Applications
June 26, 2013
Motivation
Processing Strategies
Direct Foaming
Extrusion
Steam Chest Molding
Injection Molding
Powder Processing
Critical Issues
Outline
Functional Ceramics Laboratory The University of Seoul
Motivation
Porosity Morphology
Property
New Processing
Techniques
→ Possibility of
Porosity and
Microstructure
Control
Properties =
f (microstructure, porosity)
Microstructure and porosity are strongly dependent on the processing method.
Better understanding on the processing methods is essential.
Functional Ceramics Laboratory The University of Seoul
Low processing temperature
Additive-free densification
Low-cost polymer processes
Extrusion without organic binders
Compression molding, Injection molding
Steam chest molding
Utilization of unique polymer properties that can not be found in
ceramic powders
Appreciable plasticity
In situ gas evolution ability
Appreciable CO2 solubility
Appreciable preceramic polymer solubility in solvents
Why PS-Derived SiC?
Energy Level
Reaction State
Sintering Polysiloxane
Amorphous state
Powder
Nano
crystalline state
Ceramic
Direct foaming of polysiloxane /polyurethane solutions
Self-blowing of a polysiloxane melt
Direct foaming of preceramic polymers using CO2
Functional Ceramics Laboratory The University of Seoul
Motivation
Processing Strategies
Direct Foaming
Extrusion
Steam Chest Molding
Injection Molding
Powder processing
Critical Issues
Outline
Functional Ceramics Laboratory The University of Seoul
Direct Foaming Method
+
CO2
Preceramic
polymer
blends
Gas injection Diffusion
Cell growth Nucleation
1. Saturating preceramic polymers using gaseous, liquid, or supercritical CO2.
2. Nucleating and growing a large number of bubbles using a thermodynamic instability.
3. Transforming the microcellular preceramics into microcellular ceramics by pyrolysis.
Parameters
Blends Composition
Nucleation Agent
Cross-linking Degree
Temperature
Pressure
Pressure Drop Rate
Blowing Agent Type
U.S. Patent 7,008,576(2006) Kim et al., J. Am. Ceram. Soc. (2003)
Typical Microstructure
US Patent (2006)
• Cell size ∼50 m
• Cell density ∼107 cells/cm3
• Cell size ∼20 m
• Cell density ∼1010 cells/cm3
Closed Cell
50 µ m 100 µ m
Open Cell
Manoj and Kim, Sci. Tech. Adv. Mater. (2010)
Potential Applications/Motivation
Processing Strategies
Direct Foaming
Extrusion
Steam Chest Molding
Injection Molding
Powder processing
Critical Issues
Outline
Functional Ceramics Laboratory The University of Seoul
Expandable Microspheres
10 m
40 m
Heat
100-180ºC
Liquid
hydrocarbon
Copolymer of
vinylidene chloride,
acrylonitrile and
methylmethacrylate
Gaseous
isobutane or
isopentane
7/24
Functional Ceramics Laboratory The University of Seoul
Processing
Foamed Compact Cross-linked Compact
Macroporous
SiOC + C
Extrusion
& in situ foaming
Macroporous
SiC
Cross-linking Pyrolysis
Carbothermal Reduction & Sintering
Compounded polysiloxane/carbon/
additives/microsphere blends
130o
C 200o
C
1200o
C
1450o
C 1750-
1950oC
Polysiloxane + C(Filler) → SiOC + C
SiOC + C → SiC + CO
Extrusion
Reaction
Functional Ceramics Laboratory The University of Seoul
Kim et al., J. Am. Ceram. Soc. (2008)
Motor
Motor Die Second Extruder
First Extruder
Hopper
Batch Composition
As-extruded
10 20 30 40 50 60 70 80 90
Inte
nsity
2
SiC
Functional Ceramics Laboratory The University of Seoul
Sample Batch Composition (wt%)
Polysiloxane Carbon Black SiC Expandable
Microsphere Sintering Additive
PS5 79.2 11.1 0 5
1.9% Al2O3 + 2.8% Y2O3
PS10 74.8 10.5 0 10
PS15 70.4 9.9 0 15
PS10F10 66.0 9.3 10 10
PS10F20 57.3 8.0 20 10
Polysiloxane + C(Filler) → SiOC + C
SiOC + C → SiC + CO
Compounding: 115oC
Extrusion: 130oC/40 rpm
Pyrolysis: 1200oC/1 h
Processing
LDPE Template
Motor
Motor Die Second Extruder
First Extruder
Hopper Cross Section
Flow Direction
Functional Ceramics Laboratory The University of Seoul
50LDPE/50PS
0 500 1000 1500 2000 2500 3000 3500 400010
1
102
103
YR3370
LDPE
Co
mp
lex V
isco
sity
* (P
a.s
)
Time (s)
130oC
Porosity:78%
LC0520,
Nova
Chemical,
Canada
LDPE
Extrusion: Conclusions
Porous SiC ceramics were fabricated from extruded blends of carbon-filled polysiloxane using expandable microspheres as sacrificial templates.
Open cells were obtained by (i) in situ foaming of expandable microspheres during extrusion, (ii) pyrolysis of polysiloxane from the extruded blends, and (iii) carbothermal reduction of polysiloxane-derived SiOC by carbon.
The porosity could be controlled from 60% to 85% by adjusting the microsphere content, the sintering temperature, and the filler content.
Functional Ceramics Laboratory The University of Seoul
Motivation
Processing Strategies
Direct Foaming
Extrusion
Steam Chest Molding
Injection Molding
Powder processing
Critical Issues
Outline
Functional Ceramics Laboratory The University of Seoul
Functional Ceramics Laboratory The University of Seoul
• Principle
Steam Chest Molding
Steam Closed Cell
Permeable to Steam Steam Filled Cell
Pressurization
Expanded Cell
T
Low-melting-crystals melt and
contribute to good adhesion
High Tm crystals
maintain overall foam
structure
• Condition
Double peak is
required
for good sintering
(EPP/EPE)
Depressurization
Cooling
Closed cell Steam-permeable shell Bonding mechanism
SCM Temperature
Merits of SCM
Homogeneous temperature distribution
→ Easy to scale-up
Near-net shaping of the 3D morphology
Functional Ceramics Laboratory The University of Seoul
http://ciamp.mie.utoronto.ca/BeadFoamingSteamChestMolding.html
Experimental
Batch Composition (wt%) 74.6% Polysiloxane + 10.4% Carbon + 10% Microspheres + 3% Y2O3 + 2% AlN
Sample Packing Density (g/cm3)
SiC1 24/54 =0.4444
SiC2 32/54=0.5926
SiC3 40/54=0.7407
Polysiloxane
Blending Steam Chest
Molding
4.7 bar
(149.7oC)
45 seconds
Hollow Microsphere
Carbon
Source
Sintering Additives
Functional Ceramics Laboratory The University of Seoul
Experimental
Cross-linking
at 200℃ for 2h
Pyrolysis
SiC Foams
Carbothermal
Reduction
Sintering
Process Conditions
Pyrolysis 1100oC / 1 h / N2
Carbothermal Reduction 1450oC / 1 h / N2
Sintering 1750oC / 2 h / N2
Polysiloxane + C(Filler) → SiOC + C
SiOC + C → SiC + CO
Functional Ceramics Laboratory The University of Seoul
Kim et al., J. Am. Ceram. Soc. (2011)
Microstructure
59%
62% 60%
Cell size and Porosity
decreased with increasing
the initial loading because of
constrained expansion.
1750oC/2 h/N2
Functional Ceramics Laboratory The University of Seoul
Kim et al., J. Am. Ceram. Soc. (2011)
0.4 0.5 0.6 0.7 0.81.20
1.25
1.30
1.35
1.40
Density
Porosity
Packing Density (g/cm3)
De
nsity (
g/c
m3)
55
60
65 P
oro
sity
(%)
Density/Porosity
62%
59%
1.34 g/cm3
1.25 g/cm3
Functional Ceramics Laboratory The University of Seoul
Kim et al., J. Am. Ceram. Soc. (2011)
Cell Opening
0.4 0.5 0.6 0.7 0.82.0x10
8
4.0x108
6.0x108
8.0x108
1.0x109
Packing Density (g/cm3)
Win
do
w D
en
sity (
win
do
ws/c
m3)
Cell opening increased with increasing initial packing density.
Free expansion was limited by the fixed mold volume, leading
to less expansion and more contact between the microspheres.
12 m
16 m
Functional Ceramics Laboratory The University of Seoul
Microstructure
0.444 g/cm3 / 62% 0.741 g/cm3 / 59%
More porous struts were obtained at a lower packing density
because of the greater expansion of the specimen.
1750oC/2 h/N2
Functional Ceramics Laboratory The University of Seoul
56 58 60 62 640
20
40
60
80
100
120
Packing Density
0.444 g/cm3
0.593 g/cm3
0.741 g/cm3
Co
mpre
ssiv
e S
treng
th (
MP
a)
Porosity (%)
SCM: Compressive Strength
1750oC / 2 h
77 MPa
Functional Ceramics Laboratory The University of Seoul
Kim et al., J. Am. Ceram. Soc. (2011)
Expansion Method
1. Blending of ceramic precursor and expandable microspheres 2. In situ foaming 3. Cross-linking the foamed body 4. Transforming the foamed body into ceramic foams by pyrolysis and sintering.
Parameters
Content of Expandable
Microspheres
Foaming temperature
Foaming time
Cross-linking
conditions
Pyrolysis Temperature
Extrusion speed
Extrusion pressure
Heating rate Crosslinked
Preceramic Foam
+
Ceramic
precursor
Forming
Pyrolysis
Foaming
Green Compact
Preceramic Foam
Closed-Cell Ceramic Foam
Crosslinking Expandable
Microspheres
Kim et al. U.S. Patent 7,033,527(2006)
Cellular SiOC Ceamics
Closed Cell
T70 T40
Functional Ceramics Laboratory The University of Seoul
Characteristic Steam Chest Molding Expansion
Heating Medium Steam Air
Blowing Agent Steam Hydrocarbon
Temperature
Uniformity Highly Uniform Uniform (ΔT)
Maximum Size Large (~m) Small (~cm)
Mold Fixed Volume Fixed Volume
Shape Versatility 3D/Complex Shape 3D/Complex Shape
Cell Type Open/Closed Closed
Steam Chest Molding vs Expansion
Functional Ceramics Laboratory The University of Seoul
Merits of SCM for Porous SiC
Homogeneous temperature distribution
→ Easy to scale-up
Controllable openness of cells
Near-net shaping of the 3D morphology
Functional Ceramics Laboratory The University of Seoul
SCM: Conclusions
Open-cell SiC foams with a homogeneous microstructure
were fabricated from a mixture of polysiloxane, carbon black,
sintering additives (Y2O3-AlN), and microspheres using a
newly developed process based on a steam chest molding
and carbothermal reduction process.
The typical compressive strength of the open-cell SiC foam
was 77 MPa at 60% porosity.
Functional Ceramics Laboratory The University of Seoul
Motivation
Processing Strategies
Direct Foaming
Extrusion
Steam Chest Molding
Injection Molding
Powder processing
Critical Issues
Outline
Functional Ceramics Laboratory The University of Seoul
Injection Molding
Functional Ceramics Laboratory The University of Seoul
Injection: 120oC/70 mL/s
Pyrolysis: 1200oC/1 h
Carbothermal Reduction: 1450oC/1 h
Sintering: 1650oC~1750oC/1 h
Processing
Batch composition (wt%)
74.8% PS + 10.5% C + 10% Microsphere
+ 1.9% Al2O3 + 2.8% Y2O3
Polysiloxane + C(Filler) → SiOC + C
SiOC + C → SiC + CO
Reaction
As-injection molded
Injection molded samples
1650oC/78%
Porous SiC by Injection Molding
Functional Ceramics Laboratory The University of Seoul
1750oC/65%
55 60 65 70 75 80 85 900
20
40
60
80
100
120
Compression Molding
Injection Molding
Extrusion
Steam Chest Molding
Co
mp
ressiv
e S
tre
ng
th (
MP
a)
Porosity (%)
Injection molding process leads
to an enhanced expansion of
microspheres and results in the
formation of large pores.
Eom et al., J. Ceram. Soc. Jpn. (2012)
Compression Molding: Flexural Strength
74 76 78 80 82 84 861
2
3
4
5
6
7
8
9
10
11
12
13
Jin & Kim (2010)
Mouazer (2004)
Colombo (2008)
Mouazer (2005)
7 % hollow microspheres
10 % hollow microspheres
15 % hollow microspheres
Fle
xu
ral
Str
en
gth
(M
Pa)
Porosity (%)
1750oC / 2 h
8.3 MPa
Processing Flexural strength / Porosity Reference
Replica 0.5-2.0 MPa at 80% porosity Zhu et al. Mater Sci Eng A (2002)
Template 6 MPa at 80% porosity Jin & Kim, J Mater Sci (2010)
Foaming 2.9 MPa at 72-88% porosity Colombo, J Eur Ceram Soc (2008)
Gel Casting 5.1 MPa at 80% porosity Mouazer et al. Adv Eng Mater (2004)
The homogeneous
microstructure
The lack of continuous
pore channel inside of
the strut
Superior strength
Functional Ceramics Laboratory The University of Seoul
IM: Conclusions
Open-cell silicon carbide foams were fabricated from a blend of carbon-filled polysiloxane using injection molding.
Injection molding process led to an enhanced expansion of microspheres and resulted in moderate compressive strength (~9 MPa at 74% porosity).
Functional Ceramics Laboratory The University of Seoul
Motivation
Processing Strategies
Direct Foaming
Extrusion
Steam Chest Molding
Injection Molding
Powder processing
Critical Issues
Outline
Functional Ceramics Laboratory The University of Seoul
Experimental
Functional Ceramics Laboratory The University of Seoul
Sample
designation
Composition (wt%)
-SiC -SiC Al2O3 Y2O3 Microsphere
0A5AY 60 0 3 2 35
1A5AY 59.4 0.6 3 2 35
3A5AY 58.2 1.8 3 2 35
10A5AY 54 6 3 2 35
50A5AY 30 30 3 2 35
100A5AY 0 60 3 2 35
0A7AY 58 0 4.2 2.8 35
1A7AY 57.4 0.6 4.2 2.8 35
Raw Materials
Mixing
Template Removal
Sintering
1000oC/ 1h
1950oC/4h /Ar
Microstructure
Functional Ceramics Laboratory The University of Seoul
100β 100α
0 20 40 60 80 1000
10
20
30
40
Flexural Strength
Fracture Toughness
Content of -SiC (%)
Fle
xu
ral S
treng
th (
MP
a)
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Fra
ctu
re T
ou
gh
ne
ss (M
Pam
1/2)
0 5 10 15
0
5
10
15
20
25
Pressure (PSI)
Spe
cific
Flo
w R
ate
(Liters
/min
/cm
2)
0A5AY
1A5AY
100A5AY
0A7AY
1A7AY
99β/1α
Powder Processing: Conclusions
By adjusting the initial -SiC content in the processing of macroporous SiC
ceramics, the SiC grain morphology can be controlled from equiaxed to
large platelet grains. Large platelet -SiC grains were obtained from
powder or a mixture of / powders containing small (≤10%) amounts of
powders by sintering at 1950oC for 4 h.
Functional Ceramics Laboratory The University of Seoul
The flexural strength increased with increasing -phase content and
showed a maximum strength of 26 MPa at a porosity of 56% when the
starting material contained 100% -SiC particles.
The permeability of macroporous SiC ceramics is dependent on both the
porosity and microstructural characteristics. However, the development of
large platelet SiC grains was very effective in increasing the permeability of
the macroporous SiC ceramics at an equivalent porosity. The specific flow
rate at a Δp of 15 psi and the permeability of macroporous SiC ceramics
fabricated from β-SiC ceramics (porosity ~58%) were 23.3 L/min/cm2 and
1.9 X 10-12 m2, respectively.
Critical Issues
Functional Ceramics Laboratory The University of Seoul
Cost-effectiveness
Scale-up
Improved Properties
- Mechanical Properties
- Permeability
- Thermal Conductivity
Polymer Processing Techniques
- Steam Chest Molding
- Compression Molding
- Extrusion
Flexural Strength and Porosity
30 35 40 45 50 55 60 65 70 75 80 85 90
0
25
50
75
100
125
150
Chi et al.
Ceram. Int.
(2004)
Ding et al.
Mater. Charac.
(2008)
She et al.
J. Eur. Ceram. Soc.
(2003)
Eom et al.
Mater. Sci. Engg. A
(2007)
Colombo et al.
J. Am. Ceram. Soc.
(2001)
Jin and Kim
J. Mater. Sci.
(2010)
Chae et al.
J. Eur. Ceram. Soc.
(2009)
Fle
xu
ral S
tre
ng
th (
MP
a)
Porosity (%)
Sacrificial Template
Direct Foaming
Reaction Technique
Powder-Processing
Manoj & Kim, Sci. Tech. Adv. Mater. (2010)
Functional Ceramics Laboratory The University of Seoul
Acknowledgement
Functional Ceramics Laboratory The University of Seoul
Jung-Hye Eom, Sue-Ho Chae, and Shin-Han Kim Functional Ceramics Laboratory, Department of Materials Science &
Engineering, University of Seoul, Korea
Masaki Narisawa Osaka Prefecture University, Japan
Chul B. Park and Wentao Zhai Department of Industrial and Mechanical Engineering, University of Toronto,
Canada
Chunmin Wang
General Electric Global Research Centre, China
This study was supported by a grant from the National Research
Foundation of Korea (NRF).
Functional Ceramics Laboratory The University of Seoul
Many Thanks for your kind attention!