There are many kinds of inorganic fillers used in the copper clad laminate industry, such as talc, aluminum hydroxide, alumina, silica powder, etc. The copper clad laminate manufacturers mainly choose the corresponding fillers according to the performance of the copper clad laminate.
With the improvement of the surface treatment conditions of silicon micropowder, its compatibility with the resin system is improved. Therefore, the application of silicon micropowder as a filler to the copper clad laminate can not only reduce the cost, but also improve certain properties of the copper clad laminate (such as Thermal expansion coefficient, bending strength, dimensional stability, etc.) are truly functional fillers. Therefore, FR-4 copper clad laminates with the largest output on the market mainly use silicon micropowder as filler.
At present, silicon powder for copper clad laminates is mainly divided into the following categories:
1. Crystalline silica powder
That is, the quartz powder that is selected from high-quality quartz ore, processed by ore washing, crushing, magnetic separation, superfine crushing, and classification. After using crystalline silicon powder, the stiffness, thermal stability and water absorption of the copper clad laminate have been greatly improved. With the rapid development of the copper clad laminate market, the output and quality of crystalline silicon powder have been greatly improved. .
2. Fused silicon powder
That is, the fine silicon powder is refined by selecting quartz raw materials with high-quality crystal structure through acid leaching, water washing, air drying, high temperature melting, crushing, manual sorting, magnetic separation, superfine crushing, and classification.
Compared with crystalline silicon micro, it has a lower density (2.2g/cm3), a lower dielectric constant, and a lower coefficient of thermal expansion (0.5×10-6/K). This kind of powder is mainly used in high frequency Used as a filler in copper clad laminates.
With the continuous development of high-frequency technology today, from the traditional frequency below 1GHZ to 2G, 3G, 5G and even higher frequencies, the dielectric constant Dk and loss factor Df of the copper clad laminate have become particularly important indicators for applications in the high-frequency field. The high Dk of the copper clad laminate will slow down the signal in the transmission process, and the high Df will cause the signal loss in the transmission process. Therefore, how to reduce the Dk and Df of the copper clad laminate has become a hot issue in the copper clad laminate industry.
At present, the commonly used methods to reduce Dk and Df include: choosing low Dk and Df resin and choosing low Dk and Df glass fiber. Reducing the Dk and Df of the glass fiber is mainly achieved by changing the chemical composition of the glass fiber, that is, changing the glass melting formula to achieve this. It requires close cooperation with upstream manufacturers. It is also very difficult to select Low-Dk and Df resins. Because such resins are usually expensive and poor in processability. Therefore, under non-special circumstances, copper clad laminate manufacturers are more willing to modify the epoxy resin and add fillers to reduce the Dk and Df values of the sheet. Fused silica powder is a good choice as a filler.
3. Compound silicon powder
Compound silicon powder is also called low hardness silicon powder. Several kinds of inorganic minerals are melted into an amorphous glass body by precise proportioning, and then processed by crushing, magnetic separation, ultra-fine crushing, and grading.
The Mohs hardness of this kind of powder is about 5.5, and the composition of silicon dioxide is greatly reduced. The change of chemical composition can effectively reduce the hardness of silicon powder, reduce the wear of the drill bit in the drilling process, and reduce the drilling process. Dust pollution.
4. Spherical silicon powder
Refers to the individual particles are spherical, and the irregularly shaped quartz powder particles are instantly melted at high temperature to spheroidize under the action of surface tension, and then processed by cooling, grading, mixing and other processes. This kind of powder has good fluidity, high filling rate in resin, low internal stress, stable size, and low thermal expansion coefficient after being made into a sheet.
Spherical silicon powder technology is very mature in Japan. At present, several domestic manufacturers can mass produce spherical powder for epoxy molding compound. Due to the high price of spherical powder, it is currently not used on a large scale in the copper clad laminate industry. A small amount is used in IC substrates, HDI boards and other fields. I believe that with the development of copper clad laminates to high-end, the application of spherical powder will increase day by day.
5. Active silica powder
That is, the silicon powder is modified by adding an appropriate amount of coupling agent to the silicon powder and modifying it at an appropriate temperature. This kind of powder added to the resin has a very low viscosity and a strong bond with the resin. The resulting sheet has good peel strength, excellent high temperature resistance, and can also improve drilling performance.
However, the current resin systems used by copper clad laminate manufacturers are not the same. It is difficult for silicon powder manufacturers to make the same product suitable for all users’ resin systems, and copper clad laminate manufacturers are more willing to add modifiers by themselves due to their habit of use, so they are active The promotion and use of silicon powder in the copper clad laminate industry will take time.