Method for preparing spherical silica powder with ultra-low cut-off point for hdi

Abstract

A method for preparing spherical silica powder with an ultra-low cut-off point for HDI, comprising the following steps: (1) selecting flame method based spherical silica powder with D50 equal to 1-15 μm and D100 equal to 10-50 μm as a raw material; (2) mixing water with the flame method based spherical silica powder according to a ratio, and carrying out high-speed stirring and ultrasonic treatment to obtain slurry A; (3) allowing the slurry A to settle, and extracting the upper-layer slurry by suction to obtain product B; (4) carrying out centrifugation on the product B, and dehydrating an upper-layer paste obtained after centrifugation to obtain product C; and (5) depolymerizing the product C to obtain spherical silica powder with D100 less than or equal to 6 μm. The method is simple and easy to implement, and common flame method based micron-sized spherical silica is used as a raw material, and steps of pulping, settling, centrifugation, and depolymerization are carried out in sequence to obtain spherical silica powder with D100 less than or equal to 6 μm, high purity and high sphericity, thereby meeting the requirement for the maximum size of a filler in the high-end HDI application field.

Description

Preparation method of ultra-low cut-off point spherical silicon powder for HDI

[0001] This application claims priority to a Chinese patent application filed with the Patent Office of China on December 21, 2023, with application number CN202311767719.3 and invention name “Method for preparing spherical silicon micropowder with ultra-low cut-off point for HDI”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application belongs to the technical field of inorganic fillers and relates to a method for preparing spherical silicon micropowder with an ultra-low cut-off point for HDI. Background Art

[0003] With the advent of the 5G era, high-end electronic devices are continuously developing towards higher frequencies, higher speeds, higher integration, and thinner profiles. The copper-clad laminate (CCL) industry, a crucial raw material for these electronic devices, has also responded with space-saving designs featuring ever-smaller apertures, higher wiring density, and inter-drilled trace routing. These increasing miniaturization requirements not only place demands on ultra-thin substrate materials, polypropylene (PP), and copper foil, but also place stricter limits on the maximum particle size of fillers, the most upstream component of HDI boards. High-end HDI products require a filler particle size of ≤6μm.

[0004] As the most widely used filler in copper-clad laminates, silica has long garnered widespread attention for its excellent chemical stability, moderate hardness, easy processing, and superior electrical properties. Traditional angular silica powders suffer from excessively high viscosity during use, limiting the filler ratio and failing to meet the performance requirements of the HDI industry. The large particles of common spherical silica powders are difficult to completely remove, and D100 does not meet the size restrictions imposed by the HDI industry. Other types of spherical silica powders, such as liquid-phase synthesis and combustion synthesis, remain expensive, hindering the HDI industry's cost control requirements. Therefore, to adapt to the continuous evolution of electronic products and advance communications technology, it is necessary to develop products with a D100 ≤ 6μm based on the common flame synthesis spherical silica. Furthermore, to meet the requirements of electronic-grade materials, the filler must also possess high purity.

[0005] Currently, there are two commonly used methods for removing large particles from powders: ball milling and graded cutting. Chinese patent CN113462196A uses a ball mill to grind raw materials such as quartz sand and glass flakes, while adding a dispersing agent to reduce agglomeration. While this method produces a product with a narrow distribution, a low cutoff point, and a low SSA, it also destroys the morphology of spherical particles, eliminating the flowability advantage of spherical powders. Chinese patent CN106335905B uses a precision grading process to classify powders within the D100 range of 5 to 55 μm, resulting in a cost-effective product. However, even increasing the classifier speed to 4000 rpm only reduces the D100 to 8.1 μm. This shows that reducing the D100 to 6 μm or even lower requires extremely high hardware requirements for the grading equipment, including speed, strength, and wear resistance, and the supporting equipment is difficult to purchase.

[0006] Therefore, developing a method for preparing spherical silicon micropowder with ultra-low cut-off point that has low equipment requirements and is easy to operate, as well as preparing spherical silicon micropowder products with ultra-low cut-off point, low viscosity, and high purity, are of great significance for meeting the miniaturization and thinning development of communication equipment in the 5G era.

[0007] Summary of the Invention

[0008] The purpose of this application is to provide a method for preparing spherical silicon powder with ultra-low cut-off point for HDI.

[0009] The technical solutions for achieving the purpose of this application are as follows:

[0010] The method for preparing ultra-low cut-off point spherical silicon powder for HDI comprises the following steps:

[0011] (1) Raw material selection: flame-processed spherical silicon powder with D50 = 1-15 μm and D100 = 10-50 μm is selected as the raw material;

[0012] (2) slurrying: mixing water and the raw materials of step (1) at a mass ratio of 0.5 to 5:1, stirring at a high speed of 1500 to 3000 r / min, and ultrasonically treating at 18000 to 20000 Hz to obtain slurry A;

[0013] (3) Sedimentation: The slurry A is allowed to settle for 5 to 20 hours, and after settling, the upper slurry is sucked out to obtain product B;

[0014] (4) Centrifugation: The product B is centrifuged at a speed of 3000 to 5000 r / min to perform solid-liquid separation, and the upper layer of the paste obtained by solid-liquid separation is dehydrated to obtain product C;

[0015] (5) Depolymerization: The product C is depolymerized to obtain ultra-low cut-off point spherical silica powder for HDI with D100≤6 μm.

[0016] In step (1), the flame-processed spherical silicon powder refers to spherical silicon powder prepared by a flame process. Further, the flame-processed spherical silicon powder has a D50 of 3 to 9 μm and a D100 of 10 to 30 μm.

[0017] Furthermore, in step (2), the mass ratio of water to flame-processed spherical silicon powder is 0.8 to 2:1, the processing time of the high-speed stirring and ultrasonic treatment is 10 to 30 minutes; and the stirring equipment used for the high-speed stirring is an electric stirrer or a high-speed stirrer.

[0018] Furthermore, in step (3), the sedimentation equipment used for the sedimentation is a sedimentation barrel or a sedimentation kettle.

[0019] Furthermore, in step (4), the centrifugal speed is 3750-4100 r / min, and the dehydration method is high-temperature blast oven drying or natural air drying, preferably high-temperature blast oven drying, the high-temperature blast oven drying temperature is 100-110° C., and the drying time is 4-20 h.

[0020] Furthermore, in step (5), the depolymerization equipment used for the depolymerization is one or more of a ball mill, a high-speed mixer and a jet mill, preferably a jet mill, which can maintain the original spherical morphology while avoiding the introduction of other impurities.

[0021] The ultra-low cut-off point spherical silicon micropowder for HDI prepared by the preparation method described in the above technical solution has a D100 of ≤6 μm.

[0022] Compared with the prior art, this application has the following advantages:

[0023] (1) The present application uses water as a solvent, which is low in price, has good compatibility with silicon micropowder and is environmentally friendly, controls the ratio of water to spherical silicon micropowder, and makes a slurry with flame-processed spherical silicon micropowder. The slurry is then stirred at high speed and ultrasonic treatment is performed simultaneously. The ultrasonic wave can fully break up the agglomerates of fine powder present in the slurry due to high-speed stirring, so that the powder is more evenly dispersed in the water, thereby avoiding the situation where particles below 6 μm are screened out because they agglomerated into large particles.

[0024] (2) This application prepares flame-processed spherical silicon powder into a slurry and then directly settles it. Under the combined effects of gravity, buoyancy, collision force between single crystals, intermolecular attraction, and repulsion, larger single crystal particles will fall before smaller particles. Within a specific period of time, all large particles larger than 6 μm will fall to the bottom of the container to form a sedimentation layer. The moisture content in this sedimentation layer is extremely low, and due to the super-hydrophilic properties of the silicon powder, this sedimentation layer has a certain strength and is not easily destroyed. After the sedimentation step, the removal and separation of large particles larger than 6 μm can be achieved. In addition, when large particles settle, a certain number of small particles will fall into the sedimentation layer with them, so the D50 of the product will also be reduced.

[0025] (3) This application uses common flame-processed micron-sized spherical silicon as raw material, controls the D50 and D100 of the raw material, mixes the spherical silicon powder with water to form a slurry, and then performs sedimentation, centrifugation, and deagglomeration steps in sequence to obtain spherical silicon powder with D100 ≤ 6 μm, high purity, and high sphericity, which meets the requirements of high-end HDI application fields for the maximum size of fillers. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG1 is a SEM image of the spherical silicon powder product prepared in Example 2;

[0027] FIG2 is a SEM image of the raw material of Example 2;

[0028] FIG3 is a SEM image of the spherical silicon micropowder product prepared in Comparative Example 3. DETAILED DESCRIPTION

[0029] The present application will be further described below in conjunction with specific embodiments and drawings.

[0030] Example 1

[0031] Flame-cured spherical silica powder with a D50 of 5 μm and a D100 of 15 μm was used as the raw material, and deionized water was used as the solvent. The deionized water and raw materials were placed in a high-speed blender at a mass ratio of 1:1 and stirred for 15 minutes at a speed of 3000 r / min. Ultrasonic waves were added at a frequency of 18000 Hz to obtain slurry A1. Slurry A1 was placed in a settling kettle for 7 hours. After settling, the upper layer of slurry was aspirated using a liquid aspirator to obtain product B1.

[0032] Product B1 was centrifuged at 4000 rpm. The supernatant was placed in a high-temperature forced air oven and dried at 100°C for 12 hours to obtain Product C1. Product C1 was depolymerized using a jet mill to obtain the final product D1. As shown in Table 1, the preparation process of Example 1 produced a spherical silicon micropowder product with a D100 reduced to 5.5 μm.

[0033] Example 2

[0034] This example is substantially the same as Example 1, except that the raw material is flame-processed spherical silicon powder with a D50 of 3 μm and a D100 of 10 μm, the mass ratio of deionized water to the raw material is 2:1, an electric stirrer is used for stirring for 20 minutes, the stirrer speed is 1500 r / min, the ultrasonic frequency is 20,000 Hz, the sedimentation time is 5 hours, the centrifuge speed is 3750 r / min, the drying temperature is 110°C, and the drying time is 14 hours to obtain the final product D2. As shown in Table 1, by following the preparation process of Example 2, a spherical silicon powder product with a D100 reduced to 5.2 μm can be obtained.

[0035] Figure 1 is a SEM image of the spherical silicon powder product prepared in Example 2, and Figure 2 is a SEM image of the raw material in Example 2. It can be seen from the figure that after the preparation process of Example 2, the sphericity of the product has not changed significantly and still maintains a high level.

[0036] Example 3

[0037] This example is substantially the same as Example 1, except that the raw material is flame-processed spherical silicon powder with a D50 of 9 μm and a D100 of 30 μm, the mass ratio of deionized water to the raw material is 0.8:1, an electric stirrer is used for stirring for 30 minutes, the stirrer speed is 2000 r / min, the ultrasonic frequency is 20,000 Hz, the sedimentation time is 20 hours, the centrifuge speed is 4100 r / min, the drying temperature is 105°C, and the drying time is 20 hours, to obtain the final product D3. As shown in Table 1, by following the preparation process of Example 3, a spherical silicon powder product with a D100 reduced to 5.9 μm can be obtained.

[0038] Comparative Example 1

[0039] This embodiment is substantially the same as embodiment 1, except that the mass ratio of deionized water to raw materials is adjusted from 1:1 to 0.3:1.

[0040] Comparative Example 2

[0041] This embodiment is substantially the same as embodiment 1, except that the settling time is adjusted from 5 hours to 3 hours.

[0042] Comparative Example 3

[0043] This comparative example uses the same raw materials as Example 1, except that the process route is adjusted from pulping, sedimentation, centrifugation, and deagglomeration to grinding, pulping, centrifugation, and deagglomeration, that is, the sedimentation step is not performed, and a grinding step is added before pulping. The grinding equipment used is a ball mill, the grinding time is 6 hours, and the subsequent pulping, centrifugation, and deagglomeration parameters are the same as in Example 1.

[0044] Comparative Example 4

[0045] This comparative example uses the same raw materials as Example 1, except that the process route is adjusted from pulping, sedimentation, centrifugation, and deagglomeration to classification, pulping, centrifugation, and deagglomeration, that is, the sedimentation step is not performed, and a classification step is added before pulping. The classification equipment used is a commonly used classifier, and the classifier speed is 3000-4000 r / min. The subsequent pulping, centrifugation, and deagglomeration parameters are the same as those in Example 1.

[0046] Comparative Example 5

[0047] Comparative Example 5 is a flame-processed spherical silicon micropowder product purchased on the market. This product is used in the high-end field of the HDI industry, and the product is currently highly recognized in the market.

[0048] Table 1 Particle size distribution of the final products of each embodiment and comparative example

[0049] Table 2 Particle size distribution and number of non-metallic foreign matter in the final products of Example 2 and Comparative Example 5

[0050] As can be seen from Table 1, the D100 of the spherical silicon micropowder products prepared by the preparation processes of Examples 1 to 3 is ≤6μm, and the original sphericity can be maintained, indicating that the spherical silicon micropowder products prepared by the method of the present application can meet the low cut-off point and high sphericity requirements of the HDI industry. Comparing the examples and comparative example 3, it can be seen that although the traditional method of controlling silica particles - the grinding method can reduce D100, due to the large number of collisions between particles and particles, and between particles and grinding media during grinding, the original spherical powder cannot maintain a spherical morphology, and becomes an irregular morphology, and D100 is not reduced to below 6μm, as shown in Figure 3. Comparing the examples and comparative example 4, it can be seen that even if the classification efficiency is opened to the limit of common machines, the classification method cannot completely remove the large particles present in the powder. Both methods cannot achieve the purpose of obtaining spherical silicon micropowder with D100 ≤ 6μm in the present application.

[0051] As can be seen from Table 2, the D100 of the product prepared in Example 2 is smaller than that of the spherical silicon micropowder for HDI (Comparative Example 5) which is highly recognized in the market, indicating that the spherical silicon micropowder product prepared in this application can be applied to higher-end fields in the HDI industry, and the number of non-metallic foreign matter in the product prepared in Example 2 is smaller than that in Comparative Example 5, indicating that the spherical silicon micropowder product prepared in this application has the characteristics of high purity.

[0052] In summary, the ultra-low cut-off point spherical silicon micropowder for HDI prepared in this application has the characteristics of low cut-off point, high sphericity, and high purity, which meets the requirements of fillers for the miniaturization and thinning development of communication equipment in the 5G era.

[0053] Although the above embodiment provides a detailed description of the present application, it is only a part of the embodiments of the present application rather than all the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present application.

Claims

1. A method for preparing spherical silicon powder with ultra-low cut-off point for HDI, characterized in that: The following steps are involved: (1) Raw material selection: flame-processed spherical silicon powder with D50 = 1-15 μm and D100 = 10-50 μm is selected as the raw material; (2) slurrying: mixing water and the raw material of step (1) at a mass ratio of 0.5 to 5:1, stirring at a high speed of 1500 to 3000 r / min, and ultrasonically treating at 18000 to 20000 Hz to obtain slurry A; (3) Sedimentation: Sediment the slurry A for 5 to 20 hours, and after sedimentation, suck out the upper slurry to obtain product B; (4) Centrifugation: centrifuging the product B at a speed of 3000 to 5000 r / min to separate the solid from the liquid, and dehydrating the upper paste obtained by the solid-liquid separation to obtain the product C; (5) Depolymerization: The product C is depolymerized to obtain ultra-low cut-off point spherical silica powder for HDI with D100≤6 μm.

2. The preparation method according to claim 1, characterized in that: In step (1), the flame-processed spherical silicon powder has a D50 of 3 to 9 μm and a D100 of 10 to 30 μm.

3. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of water to flame spherical silicon powder is 0.8 to 2:1, and the treatment time of high-speed stirring and ultrasonic treatment is 10 to 30 minutes.

4. The preparation method according to claim 1, characterized in that: In step (2), the stirring equipment used for high-speed stirring is an electric stirrer or a high-speed stirrer.

5. The preparation method according to claim 1, characterized in that: In step (3), the sedimentation equipment used for the sedimentation is a sedimentation barrel or a sedimentation kettle.

6. The preparation method according to claim 1, characterized in that: In step (4), the centrifugal rotation speed is 3750-4100 r / min.

7. The preparation method according to claim 1, characterized in that: In step (4), the dehydration method is high-temperature forced air oven drying or natural air drying.

8. The preparation method according to claim 7, characterized in that: In step (4), the dehydration method is high-temperature blast oven drying, the temperature of the high-temperature blast oven drying is 100-110° C., and the drying time is 4-20 hours.

9. The preparation method according to claim 1, characterized in that: In step (5), the depolymerization equipment used for the depolymerization is one or more of a ball mill, a high-speed mixer and a jet mill.

10. The ultra-low cut-off point spherical silicon powder for HDI prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The ultra-low cut-off point spherical silica powder for HDI has a D100 of ≤6 μm.

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