Non-metallic mineral powder materials in the copper clad plate industry is the main inorganic filler, copper clad plate production process mainly according to its performance to select the corresponding filler, commonly used inorganic filler talc powder, aluminum hydroxide, alumina, iron dioxide, silicon powder (silicon dioxide), etc., of which silicon powder (silicon dioxide) has been an important filler in all kinds of copper clad plate.
1, the performance characteristics of silicon powder
Silicon powder is a non-toxic, tasteless, non-polluting inorganic non-metallic material, from natural quartz (SiO2) or molten quartz (natural quartz after high temperature melting, cooling amorphous SiO2) by crushing, grinding (ball milling, vibration, air grinding), flotation, pickling purification and high purity water treatment and other processes.
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Silicon powder is a kind of functional filler, which can improve the insulation, thermal conductivity, thermal stability, acid and alkali resistance (except HF), wear resistance, flame retardant, bending strength and dimensional stability of the plate, reduce the thermal expansion rate of the plate and improve the dielectric constant of the copper clad plate. At the same time, due to the abundant raw materials and low price of silicon powder, it can reduce the cost of copper clad plate, so it is increasingly widely used in the copper clad plate industry.
2, the commonly used silicon powder filler for copper clad plate
In the production of copper clad plate, the feeding proportion of silicon powder mainly has two kinds of general proportion (15%-30%) and high filling proportion (40%-70%), of which high filling proportion technology is mostly used in the production of thin copper clad plate. The commonly used silica powder fillers for copper clad plates are ultrafine crystalline silica powder, fused silica powder, composite silica powder, spherical silica powder and active silica powder.
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(1) ultrafine crystalline silicon powder
Ultrafine crystalline silica powder is a kind of quartz powder which is processed by washing, crushing, magnetic separation, ultrafine crushing and grading. The application of crystalline silicon powder in the copper clad plate industry started earlier in foreign countries, and domestic silicon powder manufacturers have the production capacity of such powder around 2007, and soon won the recognition of users.
After the use of crystalline silicon powder, the stiffness, thermal stability and water absorption of copper-clad plate have been greatly improved, with the rapid development of the copper-clad plate market, the production and quality of crystalline silicon powder have been greatly improved.
Considering the dispersion of the filler in the resin and the requirements of the gluing process, the crystalline silica powder must be activated and then used with the spherical powder to avoid clumping when it is mixed with the epoxy resin, or the small particle size of the filler will lead to a sharp increase in the viscosity of the glue, resulting in the wetting of the glass fiber cloth during gluing.
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(2) Molten silicon powder
Molten silicon powder system selects natural quartz, amorphous silicon dioxide after high temperature melting and cooling as the main raw material, and then processed by a unique process, the molecular structure arrangement of the fine powder changes from orderly arrangement to disorderly arrangement. Due to its high purity, low linear expansion coefficient, good electromagnetic radiation, chemical corrosion resistance and other stable chemical characteristics, it is often used in the production of high frequency copper clad plate. With the development of high-frequency communication technology, the demand for high-frequency copper clad plate is increasing, and its market is growing at a rate of 15-20% every year, which will also drive the synchronous growth of the demand for molten silicon powder.
(3) compound silicon powder
Composite silica powder is a glassy silica powder material made from natural quartz and other inorganic non-metallic minerals (such as calcium oxide, boron oxide, magnesium oxide, etc.), which is processed by compounding, melting, cooling, crushing, grinding, grading and other processes.
The Mohs hardness of composite silicon powder is about 5, lower than that of pure silicon powder. During the processing of printed circuit board (PCB), it can not only reduce the bit wear, but also maintain the thermal expansion coefficient, bending strength, dimensional stability and other properties of copper clad plate. It is a kind of packing with excellent comprehensive performance. At present, many domestic copper-clad plate manufacturers have begun to use composite silicon powder to replace ordinary silicon powder.
(4) Spherical silicon powder
Spherical silicon powder is a kind of spherical silicon powder material with uniform particles, no acute Angle, small specific surface area, good fluidity, low stress and small bulk specific gravity obtained by high temperature near-melting and near-spherical processing of selected irregular angular silicon powder as raw materials. When added to the raw materials for copper clad plate production, it can greatly increase the filling amount and reduce the viscosity of the mixed material system. Improve the processing performance, improve the permeability of the coated glass fiber cloth, reduce the shrinkage of the epoxy resin curing process, reduce the thermal expansion difference to improve the warping of the sheet.
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The spherical silicon powder products with a purity of 99.8% and an average particle size of 0.5μm-1μm are mostly used by Japanese copper-clad plate manufacturers.
(5) Active silicon powder
The compatibility between silica powder and resin system can be improved by using active treated silica powder as filler, and the moisture and heat resistance and reliability of cop-clad plate can be further improved.
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At present, the domestic active silicon powder products because of its only silicon coupling agent simple mixing treatment, not ideal, powder and resin mixing is easy to unite, and many foreign patents have proposed the active treatment of silicon powder, such as the German patent proposed to use polysilane and silicon powder mixed, and stirred under ultraviolet irradiation, to obtain active silicon powder; Japanese experts proposed that silanediol derivatives treat silicon powder, and add catalysts in the mixing process, so that the coupling agent can evenly wrap the powder, so that the epoxy resin can achieve an ideal combination with silicon powder.
3, copper clad plate on the performance of silicon powder requirements
(1) Requirements for the particle size of silicon powder
In the copper clad plate using silicon powder filler, the particle size can not be too large or too small.
Matsushita Electric Company proposed: the use of average particle size of more than 10μm of silicon powder, made of copper clad plate in electrical insulation will be reduced. When the average particle size is lower than 0.05μm, the viscosity of the resin system will increase, and the manufacturability of the copper-clad plate will be affected.
Kyocera Chemical Company proposed that the average particle size of molten silicon powder should be within the range of 0.05-2μm, of which the particle size should be below 10μm, so as to ensure the good fluidity of the resin composition.
Hitachi Chemical Company proposed: in order to improve the heat resistance and copper foil bonding strength of the "mutually dual" relationship, the average particle size of the synthetic silicon powder is appropriate in the range of 1-5μm, and in the copper clad plate to pay special attention to the improvement of drilling processing "focus on consideration", then the average particle size of 0.4-0.7μm is more suitable.
(2) The selection of the morphology of silicon powder
In various forms of silica, compared with molten spherical silica, molten transparent silica and later nano silicon (resin), the effect of crystalline silica on the performance of the resin system is not the best, such as its dispersion, settlement resistance is not as good as molten spherical silica, heat shock resistance and thermal expansion coefficient is not as good as molten transparent silica; The overall performance is worse than nano silicon (resin), but from the cost and economic benefits, the industry is more inclined to use high purity crystalline silica.
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At present, most of the domestic copper-clad enterprises still use crystalline silicon powder. In addition to the relatively high price of molten silicon powder, its efficacy and characteristics are still in the stage of understanding and small batch application.
In the selection of silicon powder varieties in the copper clad plate, although the spherical silicon powder has many research results in the Japanese patent (mostly results in the laboratory range), and has a good effect in improving some properties of the copper clad plate, its price is high, and it is currently unable to be applied in large quantities in the conventional and medium grade copper clad plate.
Therefore, it is important to reduce the production cost of spherical silicon powder and do a good job in the development and application of cooperation with domestic copper-clad plate manufacturers.
In short, in the application of silicon powder, copper clad plate manufacturers need to consider comprehensively according to the main projects and indicators of the performance to be achieved, as well as the selection of other fillers, the application of filler surface treatment technology, cost and other aspects.
4, the development trend of silicon powder in the application of copper clad plate
(1) Promising ultrafine crystalline silicon powder
At present, the average particle size of the ultra-fine silicon powder applied to the copper-clad plate is 2-3 microns, and with the development of the substrate material to the ultra-thin direction, the filler will be required to have a smaller particle size and better heat dissipation. In the future, ultrafine fillers with an average particle size of 0.5-1 microns will be used for copper-clad plates. Crystalline silica powder will be widely used because of its good thermal conductivity. Considering the dispersion of the filler in the resin and the smooth development of the gluing process, crystalline silica powder is likely to be used in combination with spherical powder. Although there are many fillers with better thermal conductivity than crystalline silicon powder, such as alumina spherical powder, etc., they are high in price and difficult to be used on a large scale by copper clad plate manufacturers in the future.
(2) The rapid development of molten silicon powder market
With the development of various advanced communication technologies, a variety of high-frequency equipment has been widely used, and its market is growing at a rate of 15-20 every year, which will drive the rapid development of the fused silicon powder market to a certain extent.
(3) Stable composite silicon powder market
At present, most of the domestic copper clad plate manufacturers have begun to use composite silicon powder to replace crystalline silicon powder, and gradually increase the proportion of use, composite silicon powder market will reach saturation in the next two years. Silicon powder manufacturers are increasing production at the same time, but also continue to optimize product indicators, in order to further reduce drill wear, the development of lower hardness filler will be necessary.
(4) Optimistic high-end spherical powder market
PCB substrate materials are rapidly developing in the direction of thinning, especially the current thinning of HDI multilayer board substrate materials is more prominent. Many portable electronic products in the continuous promotion of its "thin, light, small" and multi-functional case, need more layers of PCB, thinner thickness. With the development of electronic products in the direction of miniaturization and integration, the proportion of HDI boards will increase in the future, and at the same time, domestic IC carrier board projects are also launched in many places in China. In a good market environment, it is required that domestic silicon powder manufacturers can launch high-end spherical silicon powder products with high purity, high fluidity, low expansion coefficient and good particle size distribution, so the application prospect of spherical silicon powder in the copper clad plate industry is worth looking forward to.
(5) The anticipated active silicon powder market
The use of active silicon powder as filler can improve some of the properties of copper clad plate, and there are already silicon powder manufacturers in the market to launch active silicon powder products. However, if you want to promote the use of active powder in the field of copper clad plate, silicon powder manufacturers have a long way to go, not only need the close cooperation of upstream coupling agent manufacturers, but also need the full cooperation of downstream copper clad plate manufacturers. As long as the technical problems of modification are solved, the market of activated silicon powder will be worth looking forward to.
