Among so many process routes for porous ceramics, which one is more suitable for making vacuum chuck?
The perforated ceramic vacuum chuck, also known as the perforated ceramic chuck, is mainly composed of a micro-perforated ceramic layer and a support frame. It is a vacuum clamping device that achieves uniform negative pressure adsorption through micrometer-level or sub-micrometer-level interconnected channels. Among various ceramic materials, alumina ceramics have gained popularity as one of the most commonly used materials for manufacturing porous ceramic vacuum chuck due to their excellent chemical stability, strong corrosion resistance, high temperature resistance, high mechanical strength, excellent wear resistance, good dimensional stability, and high cost-effectiveness.
The ceramic vacuum chuck achieves the adsorption and clamping of the workpiece through vacuum negative pressure. Therefore, the permeability of the material has a decisive influence on the working effect of the chuck, and the through-hole structure is the basis for the material to achieve stable permeability. At the same time, in practical applications, the vacuum chuck not only requires the material to have good permeability, but also needs to have high mechanical strength, excellent wear resistance, good dimensional stability and high surface processing accuracy. In addition, in some application scenarios, the material should also have appropriate static charge dissipation capability to effectively suppress static charge accumulation and reduce the adverse effects of static discharge on the surface quality, processing accuracy and device performance of the workpiece.
There are various methods for preparing through-hole breathable ceramics, such as extrusion molding, freeze-drying method, organic foam impregnation method, particle stacking method, adding pore-forming agent method, gel injection molding method, 3D printing, etc. Which ones are more suitable for application in vacuum chuck?
1, Pore-forming agent method
Alumina powder is mixed with organic or inorganic pore-forming agents to form a shape. During firing, the pore-forming agents decompose or burn away, leaving pores. Common pore-forming agents include: starch, cellulose, stone tar, sucrose, PS microspheres, organic fibers, PMMA microspheres, carbon powder, paraffin wax, etc.
Using alumina as the matrix, introducing silicon nitride or silicon carbide and sintering in an oxygen-rich atmosphere, in-situ pore-making is achieved through the oxidation and decomposition of silicides. At the same time, the generated silicon dioxide is used to enhance the strength of the hole wall and sintering neck, thereby improving the flatness of the chuck to 4.5μm or even 3μm under the condition of a porosity of no less than 40%.
2. Gel Injection Molding Method
The gel injection molding method is an important technique for forming porous ceramics, which was proposed by the Oak Ridge National Laboratory in the United States in the 1990s. This method involves adding organic monomers, crosslinking agents, catalysts, and initiators to the ceramic slurry, and through in-situ polymerization reactions, forming a three-dimensional polymer network. This process fixes the ceramic particles in the slurry, resulting in a nearly net-shaped ceramic blank. Depending on the type of solvent used, gel injection molding can be divided into water-based gel injection molding and non-water-based gel injection molding.
This method for preparing the black oxidized alumina porous ceramic used for vacuum chuck involves using water-based gel injection molding combined with the pore-forming agent method. A coarse white corundum powder is used to build the framework, and a Fe2O3–Cr2O3–Co2O3–NiO composite coloring system is employed to achieve a consistent black color both inside and outside. This method ensures the gas porosity and the connectivity of the open pores, while enhancing the material's bending strength and giving it excellent light-blocking properties. It is suitable for vacuum handling of high-precision and photo-sensitive semiconductor components.
3, 3D printing,
3D printing to the significance of preparation of porous ceramics, mainly reflected in the "passive into hole" to "active design pore structure. 3D printing can directly control the morphology, size, distribution and connection mode of pores through digital modeling and layer-by-layer stacking, thereby achieving the collaborative design of the macroscopic structure and microscopic channels of porous ceramics.
The freeze-drying method is a technique for preparing porous ceramics by utilizing the process of solvent freezing - sublimation to construct pore structures. Its essence is to use the frozen solvent crystals as a temporary template, and through particle repulsion and subsequent sublimation, a porous structure is formed.
It induces the formation of pore channels along the direction perpendicular to the adsorption surface through one-way freezing, and combines them with a grooved base for sealing, thereby obtaining a porous vacuum chuck with fine pore diameters, low flow loss, uniform adsorption, and suitability for working conditions where the adsorption area is not fully covered.
Fountyl Technologies Pte Ltd, focus on the local manufacturing services in Singapore for semiconductor industry, our team members have accumulated over 20 years of industry experience. focusing on serving the markets of Southeast Asia, North America and the European Union.
Main products: silicon carbide wafer PIN chuck, porous ceramic vacuum chuck, ring groove chuck, transparent vacuum chuck, ceramic end effector and various of precision fixtures, we can also provide precision machining and assembly services.
Main materials: silicon carbide, aluminum-based silicon carbide, silicon nitride, alumina, zirconia, aluminum nitride, porous ceramics, quartz glass...etc.
