Spherical Silica Powder Production

Spherical silicon powder has relatively high purity, very fine particles, good dielectric properties and thermal conductivity, and has the advantages of low expansion coefficient. It is widely used in large-scale integrated circuit packaging, aerospace, coatings, medicine and daily cosmetics, and is an irreplaceable important filler.

There are two methods for preparing spherical silicon micropowder: physical and chemical method and chemical method. The physical and chemical methods mainly include flame method, deflagration method, high temperature melt spray method, plasma method and self-propagating low temperature combustion method. The chemical method mainly includes gas phase method, liquid phase method (sol-gel method, precipitation method, microemulsion method), chemical synthesis method, etc.

In the production process of spherical silicon micropowder, strict control of each production link is the key to ensure that the product quality meets the standards.

The main raw material of spherical silicon micropowder is angular molten or crystalline silicon micropowder.

Stability of raw materials

The raw materials used to produce spherical silicon micropowder are preferably angular silicon micropowder processed from the same ore vein and the same production process, so as to maximize the uniformity of the raw materials and ensure that the products with high spheroidization rate are produced under the condition that the spheroidization temperature, gas supply, feed amount, pressure, flow rate and other factors remain unchanged.

The physical and chemical indicators of the raw materials should be controlled within a certain range

The physical and chemical indicators of the raw materials fluctuate too much, which will not only affect the spheroidization temperature, but also affect the dispersion of the spheres.

Raw material particle size and particle size distribution

Different particle sizes have different heating areas, and their passivation temperature points after heating are also different.

Raw material particle dispersibility

During the processing of angular silicon micropowder, especially ultrafine angular silicon micropowder, secondary agglomeration of powder often occurs due to the increase of surface energy.

Moisture content of raw materials

If the angular silicon micropowder used as the raw material of spherical silicon micropowder is affected by factors such as improper protection, too long storage time, and excessive environmental humidity, it will cause the powder to absorb moisture, have high moisture content, and agglomerate, which will also affect the spheroidization effect of spherical silicon micropowder.

Radioactive elements in raw materials should be low

For the raw materials for producing low-radiation spherical silicon micropowder, only when the radiation elements themselves (such as uranium U, thorium Th, etc.) are very low can the products produced meet the requirements of low-radiation spherical silicon micropowder.

There are two links in the surface modification of spherical silicon micropowder. One is to disperse the secondary agglomerated particles of spherical silicon micropowder raw materials – angular silicon micropowder, especially ultrafine angular silicon micropowder, and first perform surface activation treatment to disperse the particles before sphericalization. This requires that the surface dispersant used must be completely volatilized at high temperature, otherwise it will cause carbon deposits in the spherical silicon micropowder, affecting product quality.

The second is the late modification of spherical silicon micropowder. When silicon micropowder is used as an inorganic filler and mixed with organic resin, there are problems of poor compatibility and difficulty in dispersion, which leads to poor heat resistance and moisture resistance of materials such as integrated circuit packaging and substrates, thereby affecting the reliability and stability of the product. In order to improve the problem of interface bonding between silicon micropowder and organic polymer materials and improve its application performance, it is generally necessary to modify the surface of silicon micropowder.