High-purity quartz sand is widely used in electric light sources, optical fiber communications, solar cells, semiconductor integrated circuits, precision optical instruments, medical utensils, aerospace and other high-tech industries. It plays an important role in the development of a country’s science and technology and is of strategic significance. resource. However, subject to high-quality mineral sources, the domestic high-purity quartz sand market is in a situation of insufficiency driven by downstream industries, and the market has been monopolized by foreign countries for a long time. Especially in recent years, the development of semiconductor and photovoltaic industries has highlighted the contradiction between supply and demand of high-purity quartz sand, which has become a hot topic in the industry. The high-purity quartz sand industry chain is highly sought after in the industry. So, how is high-purity quartz sand defined?
Hunan Province once announced the local standard DB43/T1167-2016 high-purity (SiO2≥99.997%) quartz sand in 2016. The standard is applicable to natural quartz minerals as raw materials, after acid leaching, calcination, water quenching, drying, crushing, sieving Quartz sand processed by separation, purification, color separation, magnetic separation and other processes.
The national standard GB/T32649-2016 high-purity quartz sand for photovoltaics was implemented on November 1, 2016. The standard applies to high-purity quartz sand for photovoltaics, and the products are used for diffusion tubes and carriers for polysilicon and monocrystalline silicon photovoltaic production. And quartz products such as arc crucible. The standard makes the following technical requirements in terms of appearance, particle size, silica content, and impurity element content.
In addition, the industry standard SJ/T3328-2016 High-purity quartz sand for electronic products specifies the technical conditions, general rules of analysis methods, determination of burning vector, determination of silica, determination of iron, determination of copper, Determination of Chromium, Determination of Aluminum and Determination of Lead.
Among them, SJ/T3328.1-2016 High-purity quartz sand for electronic products Part 1 technical conditions is suitable for high-purity quartz sand for electronic products, which can be used to manufacture tubes, rods, blocks, plates, sheets and crucibles of semiconductor quartz devices. device. The technical requirements are as follows:
Appearance: High-purity quartz sand for electronic products is white particles with a certain degree of transparency, and there should be no heterochromatic and visible impurities.
Policy perspective
In view of the status of silicon materials in the modern electronic information industry and energy industry, and the irreplaceable role played in the development and progress of national strategic industries and pillar industries, the state has issued a series of policies to support the development of the quartz sand industry, especially High-purity quartz sand with high added value and development prospects.
The Ministry of Industry and Information Technology’s “Guidelines for the Development of Key Common Technologies in the Industry (2017)” put forward the main technical contents of sustainable quartz glass preparation technology including: high-quality quartz mineral development technology; high-purity quartz raw material purification technology; high-purity quartz raw material particle size distribution and morphology And so on and the melting process (electric melting and gas melting, etc.) adaptive technology and so on.
“Industrial Structure Adjustment Guidance Catalogue (2019 Edition)” encourages the technological development of high-quality artificial crystal materials, products and devices, and functional artificial diamond material production equipment in information, new energy, national defense, aerospace and other fields; high-purity quartz raw materials ( Development and production of manufacturing technologies such as high-end quartz crucibles for semiconductors and chemical vapor-phase synthetic quartz glass with a purity greater than or equal to 99.999%); development and production of special glass manufacturing technologies required in aerospace and other fields; The production and application of industrial silicon and the development and application of its technical equipment.
“Key New Materials First Batch Application Demonstration Guide Catalogue (2018 Edition)” proposes high-purity quartz sand, performance requirements: Fe, Mn, Cr, Ni, Cu, Mg, Ca, Al, Na, Li, K, B, a total of 12 The total content of various elements is less than 6ppm. Application areas: high-quality quartz products.
Large-scale high-purity quartz diffusion tube for semiconductors, specifications: outer diameter 300-400mm, partial wall thickness ≤0.6mm, metal impurity content <13ppm, long-term use temperature: 1150℃. Application field: semiconductor field, integrated circuit.
Semiconductor grade arc quartz crucible, specification: 14~24 inches; inner layer purity: all metal impurity content <12ppm; strength: 1500 degree high temperature deformation rate <2%; life span can reach 200 hours. Application areas: integrated circuits.
The “Key New Materials First Batch Application Demonstration Guidance Catalogue (2019 Edition)” has the same performance requirements for high-purity quartz sand and large-scale high-purity quartz diffusion tubes for semiconductors as the 2018 edition. Quartz furnace tube for optical fiber preform sintering, performance requirements: outer diameter > 200mm, length > 2000mm, wall thickness deviation in high temperature area ± 0.5mm, hydroxyl content < 20ppm, metal impurity content < 20ppm, the part in high temperature area should be able to withstand 2000 ℃ high temperature. Application field: optical fiber preform manufacturing.
“Key New Materials First Batch Application Demonstration Guidance Catalog (2021 Edition)” does not list high-purity quartz sand, but the performance requirements for high-purity quartz glass products for semiconductors are:
(1) Quartz diffusion tube: the outer diameter is 300-400mm, the partial wall thickness is ≤0.6mm, and the metal impurity content is less than 13ppm;
(2) Quartz outer tube, inner tube, process tube and quartz boat: hydroxyl content <30ppm, verticality <1mm, nozzle flatness <0.1mm, wall thickness deviation <0.5mm.
An industry expert’s perspective
Foreign scholars mainly classify high-purity quartz according to the content of harmful elements in quartz. Some domestic scholars classify high-purity quartz only based on the purity of SiO2; some scholars classify high-purity quartz based on the purity of SiO2 and the upper limit of the content of harmful impurity elements.
In 2017, Professor Chen Peirong proposed in the report “Production Status and Prospects of High-Purity Quartz Sand” that high-purity quartz sand refers to high-purity quartz sand produced from natural quartz minerals through a series of physical-chemical purification techniques with a particle size of 0.1~0.45mm. Quartz glass raw material. The internationally recognized high-purity quartz sand is equal to or higher than UNIMIN’s IOTA-CG standard, that is, 12 element impurities (Fe, Mn, Cr, Ni, Cu, Mg, Ca, Al, Na, Li, K, B) The total content is less than 20ppm, of which alkali metals (K, Na, Li) are less than 1ppm respectively.
Professor Wang Ling et al. proposed that high-purity quartz is a general term for quartz products with a purity of SiO2 greater than 99.9%. Its product grade can be divided according to the purity of SiO2, that is, low-end w (SiO2) ≥ 99.9% (3N), mid-end w (SiO2) ≥ 99.99% (4N), high-end w (SiO2) ≥ 99.998% (4N8); It can be divided according to the total amount of impurity elements such as Fe, Mn, Cr, Ni, Cu, Mg, Ca, Al, Na, Li, K, B, Ti in the product, that is, the low end ≤ 1000×10-6, the middle end ≤ 100×10-6, high-end≤20×10-6. Each grade of high-purity quartz can be divided into 40-80 mesh, 80-140 mesh, 80-200 mesh, 80-300 mesh and other varieties according to the particle size.
Professor Hou Qinglin and others believe that quartz sand is a translucent silicate mineral whose main component is SiO2. When the content of SiO2 is higher than 99.99%, it is called high-purity quartz sand.
Throughout the domestic research on high-purity quartz sand, there are still differences in the industry on the determination of the lower limit of SiO2 purity, the category of harmful elements and the upper limit of content of ordinary quartz sand and high-purity quartz sand. Especially in recent years, the emerging new glass industries such as photovoltaic glass, Low-E glass, ultra-white float glass, etc., have lowered the purity requirements for SiO2. Moreover, different impurity elements have different effects on the performance of quartz. For example, Al affects the light transmission rate in quartz, and metal elements such as Fe and Mn reduce the light transmittance of quartz. Quartz with excessive P and B content cannot be used in the photovoltaic industry. Since different industries require different qualities of quartz, there is no uniform standard for the quality of high-purity quartz sand.
Combining different perspectives, the editor believes that in a narrow sense (aside from chemical synthesis), high-purity quartz sand is made of natural quartz minerals through grinding, grading, gravity separation, magnetic separation, flotation, acid leaching, high-temperature chlorination roasting, etc. Processed quartz sand.
In appearance, it should be white particles with a certain degree of transparency and no discoloration. From the particle size, 40-160 mesh. In terms of purity, the SiO2 content is higher than 99.99%. The total content of Fe, Mn, Cr, Ni, Cu, Mg, Ca, Al, Na, Li, K, B, Ti impurity elements is less than 22ppm, of which alkali metals (K, Na, Li) are less than 1ppm respectively.