Analysis of production process of silicon powder

Silicon dioxide powder is a kind of silica powder material which is made from natural quartz ore and fused quartz. It is widely used in copper clad plate, epoxy plastic seal for chip packaging, electrical insulation material, adhesive, ceramics, coating, fine casting, daily chemical industry and other fields. At present, the production equipment of silicon powder mainly includes ball mill, vibration grinding, air flow mill, micro powder classifier and dryer, etc. the production process includes dry grinding and wet grinding. Dry grinding production process; put raw materials of silicon micro powder into ball mill or vibration grinding machine for grinding. The grinding process can feed and discharge materials continuously, or input several weight raw materials at a time, and then discharge after several times of continuous grinding; when discharging, the particle size shall be controlled by micro powder classifier, and coarse products shall be returned to mill for regrinding or as products, and the fine ones are products. Dry grinding should strictly control the moisture content of the grinding material, and the product will not be dried; wet grinding production process, put some weight of silicon micro powder raw materials into the ball mill once, add appropriate amount of water, and the working concentration shall be 65-80%. After continuous grinding for more than ten hours, the slurry shall be poured out, and the filter method or placed in the bucket shall be used to naturally precipitate and dehydrate to obtain the moisture content cake; the crusher shall be used to break the cake After dispersion, it is evenly and continuously put into the hollow shaft mixer, and the product is obtained after drying.

Whether dry or wet grinding, in order to avoid contamination of materials during grinding, the grinding medium used shall be non-metallic materials such as alumina ceramic balls or silica; the barrel of the mill is also lined with high-strength wear-resistant materials such as alumina ceramics, silica or polyurethane rubber. The quality control of the products is the key point of quality control. Ultrafine grinding is one of the core processes of the production of the micro silicon powder products, which directly affects the purity, particle size distribution and production cost. During the production of silicon micro powder, the key points of product quality control are as follows: mill control: grinding medium material can be selected reasonably, media ratio and filling rate can be controlled effectively, and the service life of equipment can be improved; according to the ratio of length to diameter of ball mill, lining plate structure and distribution, grinding granularity, etc., the rotation speed of ball mill can be adjusted reasonably to keep good movement of materials in grinding chamber State, thus improving grinding effect. Particle shaping: by optimizing the process conditions such as equipment running speed, pressure and temperature in the body, and material retention time, the surface regularity of silicon powder can be improved, the fluidity of products can be improved, and it is conducive to the high filling and high dispersion of silicon powder in the application of downstream resin system. Mixed compounding: the single peak distribution of silicon powder can not be packed tightly, it is difficult to meet the high filling requirements of customers, and the excellent performance of silicon micro powder cannot be greatly exerted. One of the ways to improve the filling rate is to mix the silicon powder products with different particle size distribution, and form multi peak distribution by mixing ratio to achieve high filling, and also reduce the oil absorption value of the silicon powder. Surface modification: as inorganic filler, silicon micro powder has poor compatibility and difficult dispersion when mixed with organic resin, which leads to poor heat resistance and moisture resistance of integrated circuit packaging and substrate, which affects the reliability and stability of products. In order to improve the interface bonding between silicon powder and organic polymer material and improve its application performance, surface modification of silicon micro powder is generally needed. Production condition control: the key to the production of electronic grade silicon powder is to remove the conductive impurities in quartz. Therefore, in addition to the selection of pure raw materials, the pollution of containers, environment and chemicals on the products should be minimized and strictly operated in every link of production.