chapter 7.2 tape casting
Post on 26-Aug-2014
133 views
TRANSCRIPT
VII. Colloidal Processes
7.2 Tape Castingp g
Professor W. J. WeiDept. Mat. Sci. Eng.National Taiwan University
Ref.1 J R Reed Chapter 25 and 261. J. R. Reed, Chapter 25 and 262. 陶瓷技術手冊, 第 13 章
http://www.mse.nthu.edu.tw/~jhjean/http://www.mse.nthu.edu.tw/ jhjean/resource.htm
What is “Tape Casing”?What is “Tape Casing”?What is Tape Casing ?What is Tape Casing ?
The tape casting (doctor blade process) is p g ( p )-a shape forming technique, which produces thin flat sheets.-a doctor blade to conrol a moving ceramic slurry.
bi d t ff h ' t th' t th'-a binder system offer enough 'green strength'green strength'Punching and Printing on TapesLaminationLaminationBinder-burn-out (BBO) stepsSintered.
Tape Casting Equipment
http://drm.kist.re.kr/cerapedia/ process/jgl003.html
Multi-layer Assembly of MLCC(passive chips) or ceramic/metal module
Formulation of Tape Casting
Powder + solution (water or organic solvent) +bi d + di t + d f + l ti i +h ibinder + dispersant + de-foamer + plasticizer +homogenizer
Binder and Plasticizer for Tape CastingBinder and Plasticizer for Tape Casting
Effect of Binder Content
Effect of Binder: ζ-potentialEffect of Binder: ζ-potential
B. Bitterlich and J. G. Heinrich, J. Euro. Ceram. Soc. 22(2002) 2427~2434 C.A. Gutierrez and R. Moreno, J. Euro. Ceram. Soc. 20(2000) 1527~1537
Ad ti I th f P l i AdditiAdsorption Isotherms of Polymeric Additives
0,2 μm Alumna powder0,2 μm Alumna powder with BET area: 11.2 m2/gm, in MEK/toluene
Plateau coverage:
PVB = 3.46 2mmg
MFO = 2.31 2mmg
Binders: PVB(B79 and B76) M W B79 = 65000 B76 = 105000Binders: PVB(B79 and B76) M.W B79 = 65000, B76 = 105000
Dispersants: Mahatan Fish Oil (MFO) M.W=2000-3000
Tape Forming FundamentalsTape Forming Fundamentals
a combination of pressure driven flow and shear driven flowa combination of pressure-driven flow and shear-driven flow
Y. T. Chou, Fluid flow model for ceramic tape casting, J. Am. Ceram.
Soc., 70 [10] C-280-C-282 (1987)
Effect of Casting Variables (the forces)Effect of Casting Variables (the forces)
the ratio of pressure force to viscous force, Π,
Thickness vs Tape Casting VelocityThickness vs. Tape Casting Velocity
At various viscosity!
High viscosity is in-sensitive to elocity!
Critical Tape Casting Factors: CCR & Gap
• critical casting rate is 5mm/s • the thickness and density• critical casting rate is 5mm/s• below C.C.R. the shearing is very low, and the viscosity of slurry is
• the thickness and density didn’t change at constant casting speed, y y
high.
Gap Size in Tape Castingp p g
s (m
m)
Blade Gap 1.2 mmBlade Gap 0.4 mmBl d G 0 2
hick
ness Blade Gap 0.25 mm
Tape
Th
Casting Speed (mm/s)
Fig. Plot of the green tape thickness obtained at different casting speeds for three different blade gaps.
Ref: A.I.Y. Tok et al., Tape casting of high dielectric ceramic composite substrates for microelectronics application”, Journal of Materials Processing Technology 89-90 (1999) 508-512
Thickness vs. Gap and Speedp p
s (m
m) Blade Speed 5 mm/s
Blade Speed 10 mm/sBlade Speed 20 mm/s
hick
ness
Tape
Th
Blade Gap (mm)Blade Gap (mm)
Fig. Plot of the green tape thickness obtained at different blade gaps for three different casting speeds.g p
Defects in Tape: cavity on surface
Green tape
Binder burn-out
SinteredSintered tape
Defects in Tape: Non-uniform Shrinkage5 cm
(0,Y)
(X,0)
Casting Direction
• Four main stabilization treatment– Bake: 2 h at 120oC in flowing air. – Thermal cycling: -5oC for 30 min, then 120oC for 30 min, 4 times.
S l t t t d t l f 1 h t– Solvent exposure: saturated toluene vapor for 1 h at room temperature, then simple bake.
– Humidity: 24 h at 100% RH, 80oC, then 24 h at 80oC in flowing air.• Aging : 23oC, 50% RH
Directional Linear Aging Shrinkage of Green Tapes
Treatment Shrinkage %
Solvent-based Aqueous-based
Untreated X : 0.92 Y : 0.71 X : 0.40 Y : 0.31
Bake 0 30 0 27 0 28 0 32Bake 0.30 0.27 0.28 0.32
Thermal cycle
0.25 0.27 0.40 0.36y
Solvent 0.25 0.27 0.40 0.44
Humidity 0 15 0 14 0 17 0 21Humidity 0.15 0.14 0.17 0.21
*After 35 days of agingte 35 days o ag g
Organic: bottom Microstructure of
AqueousAqueoussurface vs. bottom
AqueousqBottom Surface
3 μmsurface
10 μm
Cross-Sectional MicrostructuresCross-Sectional Microstructures
Laminated Sintered
1mm
• Laminated by compression at room temperaturey p p• Green tape sintered at 1800°C/60min• No single layer can be distinguished after laminated• No single layer can be distinguished after laminated and sintered
MLCC: Engineering of Ceramic TapeMLCC: Engineering of Ceramic Tape
Ref: http://www.tactilecomponents.com/ ceramicacapacitor.htm
Properties of Cofired multilayer Ceramic Capacitor (MLCC)
Important Properties Important Properties
1. Slip viscosity (mPa·s)2. Green density (g/cm3)3. States (thickness, etc.) of the tape 4. Microstructure of green tapes4. Microstructure of green tapes5. Tensile strength (kPa), for example6 Sintered density (g/cm3)6. Sintered density (g/cm3)7. Microstructure of sintered tapes8 Di l t i ititi it d di i ti f t (%)8. Dielectric permititivity and dissipation factor (%)
Tensile Strength and Strain-to-Failure of TapeTensile Strength and Strain-to-Failure of Tape
*Effect of plasticizerfor tape properties
Summary
• Multi-layer structure and tape process are most l d i f l ipopular and important process for electronic
components (e.g. L-C-R);• Processing parameters are extremely complex;• The manufacturing has faced the competition from g p
the field of silicon industry (system on chip, SOC). • Adapt several technologies from thin filmAdapt several technologies from thin film
processes and inject-printing.