Semiconductor ceramic parts preparation technology
The preparation process of semiconductor ceramic parts mainly includes powder preparation, powder molding, high temperature sintering, precision machining, quality inspection, surface treatment and so on.
1. Powder preparation
Raw materials usually need to be reprocessed, add various ingredients, dry spray after mechanical ball milling, to get the original powder that meets the requirements.
(3) The ceramic fine powder or powder precipitates, colloids, etc. prepared by spray drying often need to be washed, filtered, dried and calcined, and these processes generally affect the uniformity of the powder composition, the size and shape of the particles. The spray method can be used to disperse the solution into small droplets, spray into hot air, and make the solvent quickly steam, so that you can get a uniform size and shape of the powder. The powder after spray drying has finer grain after preparation of sintered body.
2, powder molding
Ceramic raw billet is prepared by the powder prepared by the corresponding formula. The forming methods of ceramic products usually include dry pressing, isostatic pressing, casting, injection molding, gel injection molding and so on. The corresponding ceramic blank can be obtained by these methods.
(1) Dry press molding The process is mainly through the granulation of the powder suitable for particle gradation, poured into the metal mold cavity, the pressure is applied to it with the indenter, the indenter is shifted in the mold cavity, and the pressure is transferred to the powder particles in the mold, so that it is compacted, and finally formed with a certain shape and strength of ceramic blank products.
(2) isostatic molding The process is to press the semiconductor ceramic parts into the isostatic press, the use of liquid incompressible and uniform transfer of pressure properties from all directions to the sample for uniform pressure, when the liquid medium through the pressure pump into the pressure vessel, the size of the pressure unchanged and uniform transfer to all directions, so that, The ceramic parts are subjected to uniform pressure of the same size in all directions, which makes the ceramic parts more dense.
(3) Casting casting is a more complex process, it is able to form a thickness of tens of microns to millimeters of ceramic blank wet forming technology, will have a certain viscosity and good dispersion of ceramic slurry, from the casting machine slurry groove knife edge flow to the base band, the slurry spread, under the action of surface tension, The billet film with smooth upper surface is generated, and the billet film together with the base strip is sent to the drying room. After the solvent is volatilized, the organic binder generates a network between the ceramic particles, thus generating the billet with certain strength and flexibility. After the dry billet is stripped from the base strip, the scroll is reserved. According to the needs of the product cutting, stamping, perforating and other processes, and then firing, that is, the processing of the product can be completed.
(4) Injection molding Injection molding is the thermoplastic material and ceramic powder mixed into a hot soluble body, and then injected into a relatively cold mold, after cooling, the molding of the good billet can be lifted out of the mold, the process can quickly and automatically carry out batch production, and its process can be accurately controlled, the process can be used to form complex shape ceramic products. Widely used. 3.2.5 Gel injection molding Gel injection molding is to add low concentration organic monomer into ceramic slurry with high solid content and low viscosity, then add initiator and pour, and then make the organic monomer in the slurry undergo in-situ polymerization reaction under certain conditions to form a solid cross-networking structure. After the slurry solidifies, the required ceramic parts are obtained by demudding, drying, stripping and sintering.
3, high temperature sintering
Some of the ceramic parts are drained and then sintered, and some are drained and sintered together. Usually the glue discharge temperature is lower than the sintering temperature, not more than 1000℃. High temperature sintering methods mainly include atmospheric pressure sintering, vacuum sintering, gas sintering. Through sintering, the ceramic can be transformed from green billet to ripe billet and become dense structure.
(1) atmospheric pressure sintering: atmospheric pressure sintering is the material is not pressurized and sintering under atmospheric pressure, is the most commonly used sintering method, this method is generally sintering under oxygen gas atmosphere or some special gas atmosphere conditions. In the process of atmospheric pressure sintering, the formed billet is not affected by external pressure, but the aggregate of powder particles is heated under normal pressure to transform into a grain combination.
(2) Vacuum sintering: vacuum sintering refers to the transformation of a specific form of ceramic billet into a dense and hard sintered body under vacuum condition through physical and chemical action under vacuum environment [12]. The pores in the oxide ceramic body are mainly composed of water, hydrogen and oxygen, which will escape through the pores during sintering. However, carbon monoxide, carbon dioxide, and especially nitrogen are difficult to escape through stomata, resulting in reduced product densification. Through vacuum sintering, all gases can be discharged, so that the density of the product is improved.
(3) Atmosphere sintering: For ceramics that are difficult to sintering in atmospheric pressure sintering, atmosphere sintering is commonly used. This method is to pass a certain gas into the furnace to form the required gas atmosphere, so that the ceramic parts are sintered in a specific atmosphere. Depending on the material, oxygen, hydrogen, nitrogen, argon and other different atmospheres can generally be used.
(4) Precision processing: the size of the ceramic parts after the green sintering has not reached the required size, and the sintered ceramic and ceramic products need to be further refined, usually using CNC lathes, grinding machines, etc. to cut, turn, grind, mill, cut, drill, etc., and process into the required ceramic products. Ceramic CNC machining refers to the reduction manufacturing process that uses computer control to operate and manipulate machines and cutting tools to shape ceramic parts. Ceramic materials due to high hardness, high strength, fragile and other characteristics, in its processing should pay special attention to, and many ceramic parts require high precision, processing difficulty. The precision can be well controlled by CNC machining to ensure the consistency of multiple zero parts.
(5) Product inspection Ceramic parts processed by the above steps need to be inspected by artificial products to check whether their appearance, size, porosity, roughness and other properties meet the requirements, and some products with high quality requirements need testing equipment to test to ensure the quality of semiconductor ceramic parts. The products that pass the inspection are then carried out the next step, and the unqualified ones are reworked or scrapped.
(6) Surface treatment; Semiconductor equipment cleanliness requirements are very high, qualified semiconducting ceramic parts also need to be further cleaned on the surface, usually pickling, alkali washing, organic solvent cleaning and other methods, after cleaning the product dry, check its quality again, qualified products to clean room packaging can be. Some special requirements of ceramic parts, but also need to arc fusion, plasma spraying, electrostatic spraying, vapor deposition, ultra-clean cleaning, anodizing, metallization and other further surface treatment to meet the requirements of use.
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