A grading method for high-purity ultrafine spherical powder

Abstract

The present invention discloses a grading method for high-purity ultrafine spherical powder. By mixing raw powders and additive powders with different particle size distributions, a multi-peak distribution of the mixed powder in particles of each particle size level is formed. According to the classical continuous particle packing theory, the present invention rationally matches ultrafine spherical alumina powder and high-purity ultrafine spherical silica powder with different particle size distributions in a specific proportion. Through the ratio, close packing is achieved in a specific particle size region, achieving the effect of high filling rate during application, with the volume fraction being up to more than 90% at most. At the same time, the oil absorption values of the ultrafine spherical alumina powder and the high-purity ultrafine spherical silica powder are also reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrafine powder, and particularly to a grading method for high-purity ultrafine spherical powder. Background Art

[0002] In the 1980s of the 20th century, ultrafine powders gradually developed and increasingly became the focus of research in various countries, including particles of various materials such as metals, non-metals, organics, inorganics, and biomaterials.

[0003] High-purity ultrafine spherical silica powder has excellent properties such as low linear expansion coefficient, high chemical stability, high thermal stability, and high filling rate. Therefore, high-purity (SiO≥99.8%) and ultrafine (D50 = 2μm) spherical silica powder is required as the core filler for IC / EMC packaging in the semiconductor and microelectronics industries. Due to its unique morphology, high-thermal-conductivity spherical alumina has excellent properties such as corrosion resistance, high temperature resistance, high hardness, high strength, abrasion resistance, oxidation resistance, large fluidity, high thermal conductivity, and high insulation, which greatly improves the application performance of products and is widely used in high-tech fields such as electronics, chemical industry, national defense, and aerospace.

[0004] Both ultrafine spherical alumina powder and high-purity ultrafine spherical silica powder belong to micron-level ultrafine powders, but their particle sizes are close to the sub-micron level. For example, the D50 of high-purity ultrafine spherical silica powder is about 2μm. When used for integrated circuit packaging, it has high viscosity and low filling rate. The filling rate of ordinary ultrafine powders is generally about 70%, and the products produced will have defects such as flash, which limits its application in large-scale and very large-scale integrated circuits. Improving the filling rate not only requires spheroidization but also has requirements for grading. The ultrafine powder with a single-peak distribution still cannot achieve the closest packing and is difficult to meet the high filling requirements during customer use, and cannot maximize the excellent properties of ultrafine silica and ultrafine alumina.

[0005] In view of the above defects, the creator of the present invention finally obtained the present invention through long-term research and practice. Summary of the Invention

[0006] To solve the above technical defects, the technical solution adopted by the present invention is to provide a grading method for high-purity ultrafine spherical powder, which forms a multi-peak distribution of the powder after mixing in particles of each particle size range by mixing the original powder and the added powder with different particle size distributions, including the steps of:

[0007] S1, analyzing the particle sizes of the original powder and each of the added powders to obtain the percentage content of the original powder and each of the added powders in each particle size range;

[0008] S2, calculating the corresponding standard percentage content of the original powder in each particle size range using the closest packing equation;

[0009] S3, selecting the added powder according to the particle size range to be densely packed, and obtaining the ratio of the added powder to the original powder by calculation based on the percentage content of the added powder and the original powder in each particle size range.

[0010] S4, mixing the added powder and the original powder according to a proportion.

[0011] Preferably, in the step S1, the particle size intervals are distinguished based on the particle size of the raw powder, and the particle size intervals are set to 5, including a first particle size interval, a second particle size interval, a third particle size interval, a fourth particle size interval, and a fifth particle size interval, which are arranged in order from small to large, and the raw material has a proportion in the first particle size interval, the second particle size interval, the third particle size interval, the fourth particle size interval, and the fifth particle size interval.

[0012] Preferably, the first particle size interval a is set to 0<a≤3.72μm, the second particle size interval b is set to 3.72μm<b≤19.64μm, the third particle size interval c is set to 19.64μm<c≤46.21μm, the fourth particle size interval d is set to 46.21μm<d≤68.22μm, and the fifth particle size interval e is set to 68.22μm<e≤87.74μm.

[0013] Preferably, the added powder includes a first added powder, a second added powder and a third added powder, the first added powder only accounts for the first particle size range and the second particle size range, and the content of the first added powder in the first particle size range is greater than the content of the first added powder in the second particle size range; the second added powder only accounts for the first particle size range, the second particle size range and the third particle size range, and the content of the second added powder in the second particle size range is greater than the sum of the contents of the second added powder in the first particle size range and the third particle size range; the third added powder accounts for the first particle size range, the second particle size range, the third particle size range, the fourth particle size range and the fifth particle size range, and the sum of the contents of the third added powder in the third particle size range and the fourth particle size range is greater than the sum of the contents of the third added powder in the first particle size range, the second particle size range and the fifth particle size range.

[0014] Preferably, in step S2, the close packing equation is:

[0015] U(D)=100(D / D L )

[0016] Wherein, U(D) is the standard percentage content (wt%) of particles smaller than particle size D; D LD[[ID=]] is the particle size of the largest particles in the system; D is the particle size corresponding to U(D); n is the distribution modulus, and n = 1 / 3.

[0017] Preferably, in the step S3, the ratio of the added powder to the original powder satisfies the mixing formula:

[0018] Ax + B(1 - x) = C,

[0019] where A is the percentage content of the raw material in the particle size range to be closely packed in the step S1, B is the percentage content of the added powder in the particle size range to be closely packed in the step S1, C is the corresponding standard percentage content of the original powder in the particle size range to be closely packed in the step S2, and x is the content of the original powder in the ratio of the added powder to the original powder.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: According to the classical continuous particle packing theory, ultrafine spherical alumina powder and high-purity ultrafine spherical silica powder with different particle size distributions are reasonably matched in a specific ratio, and close packing is achieved in a specific particle size region through the ratio, achieving a high filling rate during application, with a maximum volume fraction of over 90%, and at the same time reducing the oil absorption value of the ultrafine spherical alumina powder and the high-purity ultrafine spherical silica powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a flowchart of the grading method of the high-purity ultrafine spherical powder. DETAILED DESCRIPTION OF THE INVENTION

[0022] The following further describes in detail the above and other technical features and advantages of the present invention with reference to the accompanying drawings.

[0023] The grading method of the high-purity ultrafine spherical powder of the present invention forms a multi-peak distribution of the mixed powder in particles of each particle size by mixing the original powder and the added powder with different particle size distributions, thereby achieving high filling, up to over 90%, and at the same time reducing the oil absorption value of the ultrafine powder, wherein both the original powder and the added powder are high-purity ultrafine spherical powders.

[0024] Specifically, according to the classical continuous particle packing theory, ultrafine spherical alumina powder and high-purity ultrafine spherical silica powder with different particle size distributions are reasonably matched in a specific ratio, and close packing is achieved in a specific particle size region through the ratio.

[0025] The close packing of classical continuous particles in powder science satisfies the close packing equation:

[0026] U(D) = 100(D / D L )n

[0027] where U(D) is the standard percentage content (wt%) of particles smaller than particle size D; D L is the particle size of the largest particles in the system; D is the particle size corresponding to U(D); n is the distribution modulus. The porosity of various distributions decreases as the value of the distribution modulus n in the equation decreases. When it decreases to n = 1 / 2 - 1 / 3, the porosity is the smallest, and when n is much less than 1 / 3, it is meaningless. Therefore, the general value is 1 / 3.

[0028] Using the above-mentioned close packing equation, the percentage content of particles smaller than the corresponding particle size in the close packing state can be calculated. Thus, the percentage content of each particle size of the target ultra-fine spherical alumina powder / high-purity ultra-fine spherical silica powder when reaching the close packing state can be obtained through calculation. By adding an appropriate proportion of additive powder, the close packing of the mixed powder in a specific particle size range can be achieved.

[0029] As Figure 1 shown Figure 1 is the flow chart of the grading method of the high-purity ultra-fine spherical powder. The specific operation steps include:

[0030] S1. Analyze the particle sizes of the original powder and each additive powder to obtain the percentage content of the original powder and each additive powder in each particle size range;

[0031] S2. Use the close packing equation to calculate the corresponding standard percentage content of the original powder in each particle size range;

[0032] S3. Select the additive powder according to the particle size range to be closely packed. Based on the percentage content of the additive powder and the original powder in each particle size range, calculate the ratio of the additive powder to the original powder.

[0033] S4. Mix and proportion the additive powder and the original powder according to the ratio.

[0034] Preferably, in step S1, the particle size range is distinguished based on the particle size of the original powder. The particle size range is set to 5, including a first particle size range, a second particle size range, a third particle size range, a fourth particle size range, and a fifth particle size range arranged in ascending order of particle size. The raw material has proportions in the first particle size range, the second particle size range, the third particle size range, the fourth particle size range, and the fifth particle size range. Dividing the particle size of the raw material into multiple ranges facilitates the calculation of the corresponding standard percentage content and also facilitates the determination of a specific range during close packing. At the same time, for the setting of multiple ranges, corresponding additive powders with different proportions in the particle size range are selected to perform mixed close packing for a specific range.

[0035] Preferably, the first particle size range a is set as 0 < a ≤ 3.72 μm, the second particle size range b is set as 3.72 μm < b ≤ 19.64 μm, the third particle size range c is set as 19.64 μm < c ≤ 46.21 μm, the fourth particle size range d is set as 46.21 μm < d ≤ 68.22 μm, and the fifth particle size range e is set as 68.22 μm < e ≤ 87.74 μm.

[0036] Preferably, the added powder includes a first added powder, a second added powder, and a third added powder. The first added powder only has a proportion in the first particle size range and the second particle size range, and the content of the first added powder in the first particle size range is greater than the content of the first added powder in the second particle size range; the second added powder only has a proportion in the first particle size range, the second particle size range, and the third particle size range, and the content of the second added powder in the second particle size range is greater than the sum of the content of the second added powder in the first particle size range and the third particle size range; the third added powder has a proportion in the first particle size range, the second particle size range, the third particle size range, the fourth particle size range, and the fifth particle size range, and the sum of the content of the third added powder in the third particle size range and the fourth particle size range is greater than the sum of the content of the third added powder in the first particle size range, the second particle size range, and the fifth particle size range. Through the setting of the content of the first added powder, the second added powder, and the third added powder, targeted close packing can be effectively carried out for each specific range. When carrying out close packing for the first particle size range, the first added powder is selected; when carrying out close packing for the second particle size range, the second added powder is selected; when carrying out close packing for the third particle size range or the fourth particle size range, the third added powder is selected. In actual preparation, it is difficult to screen and filter ultrafine powder, so it is difficult to obtain an added powder with a proportion only in a single range. Therefore, fine powders such as the first added powder and the second added powder are selected for close packing in relatively small particle size ranges, and coarse powders such as the third added powder are selected for close packing in relatively large particle size ranges to achieve grading in the actual production process.

[0037] Preferably, in step S3, the ratio of the added powder to the original powder satisfies the mixing formula:

[0038] Ax + B(1 - x) = C,

[0039] Among them, A is the percentage content of the raw materials in the particle size range to be closely packed in step S1, B is the percentage content of the added powder in the particle size range to be closely packed in step S1, C is the corresponding standard percentage content of the original powder in the particle size range to be closely packed in step S2, and x is the content of the original powder in the ratio of the added powder to the original powder. Through the mixing formula, it is ensured that the corresponding standard percentage content in the particle size range to be closely packed remains basically unchanged before and after mixing, thereby improving the close packing effect.

[0040] Example 1

[0041] As shown in Table 1 below, Table 1 is a parameter table of the original powder and each added powder. Among them, the proportion of the original powder and the added powder (fine powder 1, fine powder 2, and coarse powder 1) in each particle size range is analyzed using a laser particle size analyzer and obtained, and the standard content of the original powder at each corresponding particle size is calculated through an equation, where n takes 1 / 3, thereby obtaining each parameter in Table 1.

[0042] Table 1

[0043]

[0044] In this embodiment, for the close packing of the original powder in the range of 0 - 3.72 μm, fine powder 1 with a smaller particle size range is selected for addition and mixing. Let the content of the original powder be x, then the content of fine powder 1 is 1 - x. There is the following equation:

[0045] 10%x + 88.52%(1 - x) = 35.24%.

[0046] After calculation, the content of the original powder is 67.86%, and the addition amount of fine powder 1 is 32.14%. The mixed finished product can achieve close packing in this range.

[0047] As shown in Table 2 below, Table 2 is a parameter comparison table of the original powder and fine powder 1 before and after mixing.

[0048] Table 2

[0049]

[0050] Example 2

[0051] In this embodiment, for the close packing in the range of 19.64 - 46.21 μm, let the content of the original powder be x, then the content of fine powder 2 is 1 - x. There is the following equation:

[0052] 30%x + 9.17%(1 - x) = 19.91%.

[0053] After calculation, the content of the original powder is 51.56%, and the addition amount of fine powder 2 is 48.44%. The mixed finished product can achieve close packing in this range.

[0054] As shown in Table III below, Table III is a parameter comparison table before and after the mixing of the original powder and fine powder 2.

[0055] Table III

[0056]

[0057] Example 3

[0058] In this example, for the interval of 68.22 - 87.74 μm, close packing is carried out. Let the content of the original powder be x, then the content of coarse powder 1 is 1 - x, and there is the following equation:

[0059] 10%x + 2.15%(1 - x) = 7.97%.

[0060] After calculation, the content of the original powder is 84.96%, the addition amount of coarse powder 1 is 15.04%, and the mixed finished product can achieve close packing within this interval.

[0061] As shown in Table IV below, Table IV is a parameter comparison table before and after the mixing of the original powder and coarse powder 1.

[0062] Table IV

[0063]

[0064] The method for improving the filling rate of the present invention is to rationally mix ultrafine spherical alumina powder / high-purity ultrafine spherical silica powder with different particle size distributions in accordance with the classical continuous particle packing theory in a specific proportion, form a multi-peak distribution through the ratio, achieve high filling, and the volume fraction can reach more than 90% at most. At the same time, the oil absorption value of the ultrafine spherical alumina powder / high-purity ultrafine spherical silica powder is also reduced.

[0065] The above are only the preferred embodiments of the present invention, which are illustrative rather than restrictive to the present invention. Those skilled in the art understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, but all will fall within the protection scope of the present invention.

Claims

1. A grading method for high-purity ultrafine spherical powder, characterized in that The original powder and the added powder with different particle size distributions are mixed to form a multi-peak distribution of particles of various particle sizes of the mixed powder; the grading method of the high-purity ultrafine spherical powder comprises the steps of: S1, analyzing the particle sizes of the original powder and each of the added powders to obtain the percentage content of the original powder and each of the added powders in each particle size range; S2, using a close packing equation to calculate the corresponding standard percentage content of the original powder in each particle size range; S3, selecting the added powder according to the particle size range to be tightly packed, and obtaining the ratio of the added powder to the original powder by calculation based on the percentage content of the added powder and the original powder in each particle size range; S4, mixing the added powder and the original powder according to a proportion; In the step S1, the particle size intervals are distinguished based on the particle size of the original powder, and the particle size intervals are set to 5, including a first particle size interval, a second particle size interval, a third particle size interval, a fourth particle size interval, and a fifth particle size interval, which are arranged in order from small to large particle sizes, and the original powder has a proportion in the first particle size interval, the second particle size interval, the third particle size interval, the fourth particle size interval, and the fifth particle size interval; The first particle size interval a is set to 0<a≤3.72μm, the second particle size interval b is set to 3.72μm<b≤19.64μm, the third particle size interval c is set to 19.64μm<c≤46.21μm, the fourth particle size interval d is set to 46.21μm<d≤68.22μm, and the fifth particle size interval e is set to 68.22μm<e≤87.74μm; The added powder includes a first added powder, a second added powder, and a third added powder, wherein the first added powder only accounts for the first particle size range and the second particle size range, and the content of the first added powder in the first particle size range is greater than the content of the first added powder in the second particle size range; the second added powder only accounts for the first particle size range, the second particle size range, and the third particle size range, and the content of the second added powder in the second particle size range is greater than the sum of the contents of the second added powder in the first particle size range and the third particle size range; the third added powder accounts for the first particle size range, the second particle size range, the third particle size range, the fourth particle size range, and the fifth particle size range, and the sum of the contents of the third added powder in the third particle size range and the fourth particle size range is greater than the sum of the contents of the third added powder in the first particle size range, the second particle size range, and the fifth particle size range.

2. The grading method of the high-purity ultrafine spherical powder as described in claim 1, characterized in that, In step S2, the close packing equation is: U(D)=100(D / D L )n where U(D) is the standard percentage content of particles smaller than particle size D; D L is the particle size of the largest particles in the system; D is the particle size corresponding to U(D); n is the distribution modulus, and n = 1 / 3.

3. The grading method of the high-purity ultrafine spherical powder as described in claim 1, wherein, In step S3, the ratio of the added powder to the original powder satisfies the mixing formula: Ax+B(1-x)=C, Wherein, A is the percentage content of the original powder in the particle size range to be closely packed in the step S1, B is the percentage content of the added powder in the particle size range to be closely packed in the step S1, C is the corresponding standard percentage content of the original powder in the particle size range to be closely packed in the step S2, and x is the content of the original powder in the ratio of the added powder to the original powder.

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