Modification method of silicon powder
Ultrafine silicon powder is an important inorganic filler in copper clad laminates. It can improve the thermal expansion coefficient, bending strength, dimensional stability, etc. Performance requirements such as reduced electrical constant and reduced dielectric loss, so there are higher requirements for silicon micropowder, such as finer particle size, can improve the bonding force of the resin, low expansion rate, low dielectric constant, low dielectric loss, etc.
However, the finer the particle size and the larger the specific surface area, the more agglomerated silicon powder is, the higher the oil absorption, the greater the difference with the resin polarity, the greater the viscosity, and the worse the binding force. Therefore, it is necessary to use a suitable powder to modify The surface modification of the ultra-fine silicon powder (by combining with the functional groups on the surface of the ultra-fine silicon powder to form a stable covalent bond, so that the performance of the ultra-fine silicon powder is more stable and effectively combined with the resin), then the How to modify the surface of ultra-fine silicon powder, and how to modify it to be uniform?
- Dry modification of ultrafine silicon powder:
The dry modification method is relatively straightforward and has the lowest cost. It is mainly through modification equipment (high-speed mixer, continuous modifier) with powder modifier, synchronized stirring and spraying additives to achieve the modification effect, but If it is nano-level silicon powder, the molecular force is very large, and the purely applied mechanical force cannot open the agglomerates and cannot achieve the purpose of uniform modification. Therefore, the particle size of the ultra-fine silicon powder targeted by the dry modification method is basically all In the micron level.
- Wet modification of ultrafine silicon powder:
The method of wet modification of ultrafine silicon powder is mainly carried out under liquid phase conditions. By using a powder modifier containing amphiphilic groups or a powder modifier that can increase activity, let the solvent react to the ultrafine powder. The surface of the silicon powder is wetted to reduce the surface energy, and then the powder modifier can be effectively adsorbed to the surface of the ultrafine silicon powder to achieve a very high modification uniformity. However, after the wet modification, drying and drying are required. The filter cake is broken up, and the cost and operation process are relatively troublesome. At present, there are also companies that modify the surface of silicon powder through the chemical method of gas phase synthesis to reach the nanometer level.
To sum up, to meet the needs of surface modification of ultra-fine silicon powder used on different copper clad laminates, the modification method mainly selects suitable powder modifiers for dry modification, wet modification, and chemical modification. Modification, while in the modification process, the more uniform the modification, the better the effect.