2. Isostatic Pressing Isostatic pressing is an improved method of traditional dry pressing method. The AlN powder is placed in a high-pressure container, and the powder is placed in an elastic material using the incompressibility of the liquid and the characteristics of liquid to pressure transmission. In the manufactured molding die, the method is to uniformly press the powder to be pressed from different directions, and pressurize the die with a liquid to form the green body. Advantages: The compact has high density, uniform density distribution, and can be molded near the net size. Disadvantages: The molding equipment is expensive and there are mold release problems, which limits its application to large-scale industrial production.
3. Casting molding Casting molding is a very important ceramic substrate molding process. The AlN powder and the composite binder (dispersant, solvent, binder and plasticizer) are mixed evenly to obtain the AlN casting slurry. The slurry after degassing and other processes is poured into the hopper and passed through the blade After that, a thin layer with a uniform thickness and a smooth surface attached to the smooth belt is formed, and then dried to prepare a green body with good toughness; after debinding and sintering, an AlN substrate material is obtained. Advantages: simple equipment, continuous operation, high productivity, high degree of automation, etc. Disadvantages: strict requirements, the slurry is very sensitive to changes in process parameters, the surface of the shaped blank is rough and insufficiently combined, the strength is low, and it is easy to dry during the drying process Foaming, cracking, bending deformation and other phenomena occur; at the same time, casting molding can only be used for the production of sheet materials.
4. Injection molding AlN ceramic injection molding is a method of powder injection molding applied to ceramic powder molding. It is a molding technology based on plastic injection molding technology and technical improvement. The basic process is to add a binder to the AlN powder and mix it evenly to form a viscoplastic feed. Under heating, use an injection molding machine to inject the feed into the mold cavity to condense and form, and remove it after heating. After the binder, it can be used for sintering, as shown in Figure 3. The rheology of the feed is an important factor that affects the quality of the injection molded products. Generally, we hope that the feed viscosity is low, which requires that the raw material powder and the binder have good compatibility and are evenly mixed. Advantages: high density, uniform density distribution, can be used for complex morphology green body molding, and the molding accuracy is high, no post-machining is required; Disadvantages: defects such as under-injection, flashing, welding marks, air cavities and other defects are easy to affect AlN ceramic sintering.