Ceramic Processing for Ceramic Processing for Highly Integrated Highly Integrated Electronic Components Electronic Components FNML FNML http://fnml.korea.ac.kr/ http://fnml.korea.ac.kr/ Starting Point in Tape Casting: Surface D. J. Shanefield, Organic Additives & Ceramic Processing Green density Surface energy Fired density Homogeneous slurry formation using small amount of organic additive to the active(small) powder Ceramic Processing for Ceramic Processing for Highly Integrated Highly Integrated Electronic Components Electronic Components FNML FNML http://fnml.korea.ac.kr/ http://fnml.korea.ac.kr/ Tape Casting Ceramic Powder Binder Plasticizer Solvent Dispersent Ball milling in the jar Deairing Tape Casting Drying Cutting Electroding Lamination Co-firing Packaging
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Ceramic Processing for Ceramic Processing for Highly IntegratedHighly IntegratedElectronic ComponentsElectronic Components
♦ Designing the temperature-profile for drying (in order to keep thehomogeneity of the tape after sintering)
1. Thickness of the casting film2. The volatility and content of organic (especially solvent) in the slurry3. The total length of the drying line4. Feeding rate for casting
[Key items]1. Employ the Azeotropic Mixture, : solution that contains the same ratio of chemical constituents after itis distilled (see distillation). The most common example is a solutionof 4.43% water and 95.57% ethyl alcohol.
2. Controlling drying
Ceramic Processing for Ceramic Processing for Highly IntegratedHighly IntegratedElectronic ComponentsElectronic Components
First stage1. The solvent diffuse through the body to the surface, and then the
solvent waits for the right number of calories to diffuse to it via the random motion of warm molecules (fast)
2. It then evaporates (slowest)3. It swept away by moving air (slow)It is usually useful to nearly saturate the air with solvent vaporto prevent quick drying. Quick drying can promote skin formation or
cracking.
Second stageA. Ceramic green body becomes stiffB. 1 becomes much slower (it becomes controlling step)
- drying rate is dependent upon T and remaining solvent (that affect diffusion rate)
the temperature can be greatly increased without damage
Ceramic Processing for Ceramic Processing for Highly IntegratedHighly IntegratedElectronic ComponentsElectronic Components
D. J. Shanefield, Organic Additives & Ceramic Processing
Desirable properties of solvents1. Ability to dissolve other additives2. Low viscosity at high solid loading3. Low tendency to form bubbles during milling4. High evaporation rate5. Safe, including
(a) nonflammability(b) nontoxicity
6. Low cost7. Lack of chemical attack on the ceramic powder
Ceramic Processing for Ceramic Processing for Highly IntegratedHighly IntegratedElectronic ComponentsElectronic Components
D. J. Shanefield, Organic Additives & Ceramic Processing
m.w. of H2O ≅ m.w. of liquefied CH4
viscosity of H2O > viscosity of liquefied CH4
⇒ H-bonding
H-bonding between ceramic (covered with OH group adsorbed from air) and water molecule⇒ tends to raise the viscosity of slip
In order to achieve low porosity in the fired state⇒ solid loading as high as possible⇒ minimize the shrinkage during drying and firing to full density⇒ minimize the warpage and cracking
H-bonding is major cause for high viscosity ⇒ non-aqueous solvent such as toluene are used
Ceramic Processing for Ceramic Processing for Highly IntegratedHighly IntegratedElectronic ComponentsElectronic Components
- reaction can continue until all of the starting materials is used up- large molecule tends to be brittle solid- for desired(proper) molecule size, small amount of terminator is added- water ↑ ⇒ molecular weight↓- there is a variation in chain length (in molecular weight)- average molecular weight is usually used
B
D. J. Shanefield, Organic Additives & Ceramic Processing
Ceramic Processing for Ceramic Processing for Highly IntegratedHighly IntegratedElectronic ComponentsElectronic Components
GPC (Gel Permeation Chromatography)- a solution of the polymer diffuses through the inert gel- the smaller molecule (with low m.w.) diffuses fastest- get the m.w. distribution
relative amount median m.w.0.08 x 500 = 400.13 x 1500 = 1950.41 x 2500 = 10250.29 x 3500 = 10150.09 x 4500 = 405
total 1.00 2680/1 = 2680 # avg.m.w.
8% below 100013% between 1000 and 200041% between 2000 and 300029% between 3000 and 40009% between 4000 and 5000
D. J. Shanefield, Organic Additives & Ceramic Processing
Ceramic Processing for Ceramic Processing for Highly IntegratedHighly IntegratedElectronic ComponentsElectronic Components
Light scattering- larger molecule scatter more ultraviolet light than the smaller one- large ones actually scatter much more than the smaller one- yields weight average molecular weight- Because the larger molecules count much more than the smaller one,usually weight avg.m.w. > number avg.m.w. by GPC
Other methods- viscosity- osmosis- sedimentation- ultracentrifuge
D. J. Shanefield, Organic Additives & Ceramic Processing
Ceramic Processing for Ceramic Processing for Highly IntegratedHighly IntegratedElectronic ComponentsElectronic Components
D. J. Shanefield, Organic Additives & Ceramic Processing
Glass
RubberV
Tg
Temperature
TMA(Thermomehcanical analysis) : The height of polymer molecule is measured with a mechanical prove resting on its top surface during heating (similar with the dilatometery)