Ceramic forming is an important part of the ceramic preparation process, the forming technology to a large extent determines the uniformity of the body and the ability to prepare complex shaped parts, and directly affects the reliability of the material and the cost of the final ceramic parts.

1. Dry press molding
Dry press molding, also known as die molding, is one of the most commonly used molding methods. Dry press molding is to load the powder with good fluidity and suitable particle gradation into the metal mold cavity after granulation. By applying pressure to the indenter, the indenter is displaced in the mold cavity and the pressure is transferred, so that the powder particles in the mold cavity are rearranged and compacted to form a ceramic blank with certain strength and shape.

Main factors affecting dry press forming:
① Powder properties: particle size, particle size distribution, fluidity, moisture content, etc.
② Selection of binders and lubricants;
③ Mold design;
④Pressing force, pressure mode, pressure speed and pressure holding time in the pressing process.

Advantages of dry pressing:

① Simple process, convenient operation, short cycle, high efficiency, easy to implement automated production.

② High density, accurate size, shrinkage, high mechanical strength, good electrical properties.

Disadvantages of dry pressing:
① It is difficult to produce large billets, and the mold wear is large, the processing is complicated and the cost is high.
② Pressure can only be pressurized up and down, the pressure distribution is not uniform, the density is not uniform, the contraction is not uniform, will produce cracking, delamination and other phenomena. However, with the development of modern molding methods, these shortcomings have gradually been overcome by isostatic pressing.

Application: It is especially suitable for the preparation of various ceramic products with small section thickness, such as ceramic sealing ring, ceramic valve core for valves, ceramic liner, ceramic lining, etc.

2. Casting molding
Its basic principle is: the proportioned ceramic slurry flows out of the casting machine, flows to the transmission base band, and then the relative movement of the base band and the scraper, the ceramic slurry is assisted to unfold, and the thickness of the ceramic is mainly controlled by the gap between the scraper and the base band. Then it follows the baseband into the drying chamber, and the solvent evaporates the organic binder to form a network structure between the ceramic particles, forming a blank with a certain strength and flexibility.It can then be cut to the desired shape, punched or punched, and finally sintered to obtain the finished product.

The casting process can be divided into non-water based casting, water based casting, gel casting and so on.

The process of ceramic substrate preparation by casting process includes slurry preparation, casting process, drying, degreasing and sintering, among which the most critical process is slurry preparation and casting process control.

Advantages: The casting molding can prepare several microns to 1000μm smooth ceramic sheet material, and the equipment is simple, the process is stable, can be continuously operated, easy to automation, high production efficiency, product performance is consistent, so it is the most important and effective process for the preparation of single or multi-layer sheet material.

Disadvantages: The binder content is high, so the shrinkage rate can reach 20% to 21%.

Application: monolithic capacitor ceramic, back film and film circuit AL2O3 substrate, piezoelectric ceramic diaphragm, structural ceramic sheet, capacitor, thermistor, ferrite and piezoelectric ceramic body, hybrid integrated circuit substrate, etc.

See the next article for the remaining several structural ceramic molding processes.