Powder, method for manufacturing the same, and resin composition

Abstract

To provide a powder capable of reducing dielectric constant and dielectric loss tangent of an insulating material, and yielding stably desired dielectric constant and dielectric loss tangent when mixed with a resin material serving as the main component of the insulating material, and a method for manufacturing the same.SOLUTION: The powder contains silica-based hollow particles, satisfies predetermined requirements, and is manufactured by the method of the present invention.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a powder containing silica-based hollow particles that is useful as a filler for insulating materials, a method for producing the same, and a resin composition. [Background technology]

[0002] In recent years, the volume of data transmitted in information and communications has increased, necessitating faster processing speeds in communications equipment. To achieve high-speed communications, insulating materials for printed wiring boards for semiconductors used in such communications equipment are required to have low dielectric constants (low Dk) and low dielectric loss tangents (low Df). A high dielectric constant of an insulating material leads to dielectric loss, while a high dielectric loss tangent of an insulating material not only leads to dielectric loss but can also cause problems such as increased heat generation.

[0003] In order to realize low dielectric constants and low dielectric loss tangents for insulating materials in printed wiring boards for semiconductors, resin materials that serve as the main insulating material have been developed. Furthermore, fillers are blended into such resin materials for durability (rigidity), heat resistance, etc. Powders of metal oxide particles such as silica are used as fillers (see, for example, Patent Document 1).

[0004] Furthermore, as a powder of such metal oxide particles, the present inventors have proposed a powder containing silica-based hollow particles that can realize a low dielectric constant and a low dielectric loss tangent for an insulating material and that does not interfere with the filterability and injectability of an insulating material-forming liquid in the manufacturing process (see Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-136363 [Patent Document 2] Japanese Patent Publication No. 2022-103683 Summary of the Invention [Problem to be solved by the invention]

[0006] The powder containing silica-based hollow particles proposed by the present inventors achieves low dielectric constant and low dielectric loss tangent and is highly practical. However, the inventors have newly discovered a problem that, when mixed with a resin material that is the main component of an insulating material, in some cases the desired dielectric constant and dielectric loss tangent that were initially expected may not be obtained.

[0007] An object of the present invention is to provide a powder that enables the dielectric constant and dielectric dissipation factor of an insulating material to be reduced, and that, when mixed with a resin material that is the main component of the insulating material, can stably provide a desired dielectric constant and dielectric dissipation factor, and a method for producing the powder. [Means for solving the problem]

[0008] In their research into solving the above problems, the inventors first discovered that cracks occur in the hollow particles when they are mixed with the resin material that is the main component of the insulating material, which changes the porosity (hollowness), and this is the reason why the originally expected desired dielectric constant and dielectric loss tangent cannot be obtained. As a result of further investigations aimed at improving this causative phenomenon, the inventors discovered that silica-based hollow particles that satisfy certain conditions can improve this phenomenon, leading to the completion of the present invention.

[0009] That is, the present invention relates to a powder containing silica-based hollow particles, which is characterized by satisfying the following requirements (i) to (vii): (i) The average particle size (D50) of the powder is 0.1 to 5.0 μm (ii) the maximum particle size (D100) of the powder is 20.0 μm or less (iii) The volume ratio of particles in the range of the peak particle diameter (Ps) × 0.75 to (Ps) × 1.25 μm in the particle size distribution of the powder is 50% or less of the total particles. (iv) the porosity of the powder is 10 to 50% (v) The powder has a cracked particle rate of 10% or less. (vi) When the powder is suspended in water, the floating particles are 7.0 to 25.0 mass%, the suspended particles are 0 to 4.0 mass%, and the settling particles are 71.0 to 93.0 mass%. (vii) The difference in porosity before and after pulverization of the powder under the following pulverization conditions is within 3% (Pulverization conditions) 20 g of the powder and 50 g of zirconia balls with a diameter of 10 mm were placed in a 500 ml zirconia container and pulverized for 10 minutes in a planetary ball mill at an orbital speed of 300 rpm and a rotation speed of 546 rpm.

[0010] The present invention also relates to a method for producing a powder containing silica-based hollow particles, comprising: a first step of spraying an aqueous alkali silicate solution in a hot air stream and drying to prepare hollow particles; a second step of neutralizing the alkali contained in the hollow particles with an acid and then washing to remove it; and a third step of firing the neutralized and washed hollow particles, wherein a crushing step of crushing fragile hollow particles is provided after the second step and before the third step, or after the third step. [Effects of the Invention]

[0011] The powder of the present invention can realize a low dielectric constant and a low dielectric loss tangent for an insulating material. Furthermore, the particles are less likely to crack when mixed with a resin material, and the desired dielectric constant and dielectric loss tangent can be stably obtained. DETAILED DESCRIPTION OF THE INVENTION

[0012] [powder] The powder of the present invention contains silica-based hollow particles and satisfies the following requirements. (i) The average particle size (D50) of the powder is 0.1 to 5.0 μm (ii) The maximum particle size (D100) of the powder is 20.0 μm or less (iii) The volume ratio of particles in the range of the peak particle diameter (Ps) × 0.75 to (Ps) × 1.25 μm in the particle size distribution of the powder is 50% or less of the total particles. (iv) Porosity of powder is 10 to 50% (v) The percentage of broken particles in the powder is 10% or less. (vi) When the powder is suspended in water, the floating particles are 7.0 to 25.0 mass%, the suspended particles are 0 to 4.0 mass%, and the settling particles are 71.0 to 93.0 mass%. (vii) The difference in porosity before and after pulverization under specified powder conditions is within 3%

[0013] The term "silica-based" in the silica-based hollow particles contained in the powder of the present invention means that the main component is silica, and in addition to silica, the particles may contain inorganic oxides such as alumina, zirconia, titania, etc. The silica content in the particles is preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, and it is particularly preferable that the particles consist essentially of silica alone.

[0014] The powder of the present invention can realize a low dielectric constant and a low dielectric loss tangent for insulating materials, thereby enabling an increase in the transmission speed of semiconductors and a reduction in transmission loss. Furthermore, the powder of the present invention is less likely to crack during the manufacturing process of the insulating material (when mixed with a resin material), making it possible to stably obtain the desired dielectric constant and dielectric loss tangent. In other words, while achieving a low dielectric constant and a low dielectric loss tangent for insulating materials is also a very important issue, even if this were achieved with brittle particles, they would be difficult to use in actual fields, and even if they were used, problems such as a decrease in manufacturing efficiency would arise. Therefore, a powder that can realize a strong low dielectric constant and a low dielectric loss tangent, as in the present invention, is very useful in actual fields.

[0015] The silica-based hollow particles of the present invention preferably have a dielectric constant of 2.8 or less, more preferably 2.5 or less, and a dielectric loss tangent of preferably less than 0.0010, more preferably less than 0.0005.

[0016] Hereinafter, each requirement of the powder of the present invention will be explained. (i) Average particle size (D50) is 0.1 to 5.0 μm Powders with an average particle size of less than 0.1 μm contain many fine particles, resulting in a high specific surface area (high SiOH group content), and therefore fail to achieve excellent dielectric properties. Powders with an average particle size of more than 5.0 μm are difficult to fill highly into thin-film insulating materials (resins) for semiconductors. Considering that the powders are intended for use in thin-film semiconductors, the average particle size is preferably 0.3 to 4.5 μm, and more preferably 0.5 to 4.0 μm.

[0017] (ii) Maximum particle size (D100) is 20.0 μm or less If the maximum particle size (D100) exceeds 20.0 μm, it becomes difficult to fill a thin resin. The maximum particle size (D100) is preferably 15.0 μm or less, more preferably 10.0 μm or less, and even more preferably 8.0 μm or less.

[0018] (iii) The volume ratio of particles in the range of the peak particle diameter (Ps) × 0.75 to (Ps) × 1.25 μm in the particle size distribution is 50% or less of the total particles. If the volume ratio of particles in the range of (Ps) x 0.75 to (Ps) x 1.25 μm exceeds 50% of the total particles, the particles will have a uniform diameter, making it difficult to highly fill them into a thin resin film and preventing excellent dielectric properties from being obtained. The volume ratio of particles in the range of (Ps) x 0.75 to (Ps) x 1.25 μm is preferably 45% or less, and more preferably 40% or less.

[0019] (iv) Porosity is 10 to 50% If the porosity of the powder is less than 10%, the effect of lowering the dielectric constant and dielectric loss tangent is insufficient, and the desired dielectric constant and dielectric loss tangent cannot be obtained. If the porosity exceeds 50%, the strength of the particles decreases, and the particles are prone to cracking. The porosity is preferably 15 to 45%, more preferably 20 to 40%.

[0020] (v) Cracked particle rate is 10% or less If the cracked particles exceed 10%, they do not contribute to lowering the dielectric constant and dielectric loss tangent (they reduce the overall porosity), making it impossible to obtain excellent dielectric properties and hindering high filling rates. The cracked particle ratio is preferably 8% or less, and more preferably 6% or less. Note that cracked particles refer to particles that retain their original shape, such as C-shaped particles, and do not include particles that have been broken into pieces.

[0021] (vi) When suspended in water, the floating particles are 7.0 to 25.0 mass%, the suspended particles are 0 to 4.0 mass%, and the settling particles are 71.0 to 93.0 mass%. The present invention contains a large amount of ideal floating particles with high porosity and strength, which contribute to a low dielectric constant and a low dielectric loss tangent. The content of the floating particles is preferably 8.0 to 20.0 mass%, more preferably 10.0 to 20.0 mass%. The content of the settling particles is preferably 76.0 to 90.0 mass%, more preferably 80.0 to 90.0 mass%.

[0022] (vii) The difference in porosity before and after grinding is within 3% Powders with a porosity difference of more than 3% before and after grinding are prone to cracking when mixed with resin materials during the manufacturing process, causing changes in the dielectric constant and dielectric dissipation factor of the insulating material. Therefore, the dielectric constant and dielectric dissipation factor of the insulating material cannot be obtained as originally intended. The powder of the present invention exhibits only a small change in porosity before and after grinding, allowing the originally intended dielectric constant and dielectric dissipation factor to be obtained. The difference in porosity before and after grinding is preferably within 2%, more preferably within 1%. The grinding conditions take into account impacts that may occur during resin mixing. Specifically, as shown in the examples, 20 g of powder and 50 g of 10 mm diameter zirconia balls are placed in a 500 ml zirconia container and milled in a planetary ball mill at an orbital speed of 300 rpm and a rotation speed of 546 rpm for 10 minutes.

[0023] Furthermore, the powder of the present invention preferably satisfies any one of the requirements (viii) to (xii), and more preferably satisfies all of the requirements (viii) to (xii).

[0024] (viii) The ratio (h / R) of the shell thickness (h) to the particle radius (R) of the extracted particles is 0.21 to 0.54. Hollow particles with a shell thickness (h) to particle radius (R) ratio (h / R) of 0.21 to 0.54 are less likely to break when mixed with a resin material, and can effectively suppress changes in the dielectric constant and dielectric loss tangent during the manufacturing process (when mixed with a resin). The ratio (h / R) is more preferably 0.40 to 0.54. Specifically, as shown in the examples, the ratio (h / R) is calculated by measuring the outer and inner diameters of 12 particles, calculating the ratio (h / R) from the measurement results, and then averaging the values ​​for 10 particles by discarding the maximum and minimum values.

[0025] (ix) The content of particles with a particle diameter of less than 2 μm is 20% by volume or more The powder of the present invention is usually produced through a pulverization process, and in this case, it contains a larger number of fine particles than conventional powders that have not been subjected to a pulverization process. Furthermore, since a classification process for fine particles is not usually performed, it contains a larger number of fine particles. The powder of the present invention usually contains 20% by volume or more, and may contain 25% by volume or more, of particles smaller than 2 μm.

[0026] (x) The content of particles with a particle diameter of less than 1 μm is 10% by volume or more As with the above requirement (viii), the powder of the present invention contains a large amount of fine particles. The powder of the present invention usually contains 10% by volume or more, and may contain 15% by volume or more, of particles smaller than 1 μm.

[0027] (xi) Alkali content is 100 ppm or less This allows for a low dielectric constant and a low dielectric loss tangent, making it suitable for semiconductor packaging. It also prevents particles from coalescing in subsequent processes, preventing the generation of sintered particles during the firing process. The alkali content is preferably 90 ppm or less, and more preferably 80 ppm or less.

[0028] (xii) Oil absorption per particle volume is 0.60 ml / cm 3 below The oil absorption per particle volume is 1cm 3This indicates the amount of oil required to make particles of 1 cm into a fluid paste. Therefore, the smaller the value, the higher the loading capacity of the resin. For example, 3 When it can be fluidized with 0.60 ml of oil, the particle packing rate in the paste is 62.5 vol%. The oil absorption per particle volume is 0.60 ml / cm 3 By ensuring that the oil absorption per particle volume is 0.50 ml / cm or less, high loading can be achieved when dispersed in resin. 3 Preferably less than 0.40 ml / cm 3 The following is more preferred:

[0029] The powder of the present invention is mostly spherical hollow particles, but may also contain solid particles. Hollow particles preferably account for 80% or more by number of the total, more preferably 90% or more by number. The percentage of hollow particles can be calculated, for example, from cross-sectional SEM images of any 100 particles.

[0030] The powder of the present invention is suitable for use as a filler for insulating materials for electronic materials such as semiconductors. Specifically, it can be blended into copper-clad laminates, prepregs, build-up films, etc. for forming printed wiring boards (including rigid and flexible boards). It can also be blended into semiconductor package-related materials such as mold resins, mold underfills, and underfills, as well as adhesives for flexible boards.

[0031] [Resin composition] The resin composition of the present invention contains the powder of the present invention as described above. Such a resin composition can be used for the above-mentioned applications, such as insulating materials for electronic materials such as semiconductors.

[0032] The resin contained in the resin composition (resin composition-forming liquid) of the present invention can be a curable resin generally used in electronic materials such as semiconductors. A photocurable resin may be used, but a thermosetting resin is preferred. Examples of such curable resins include epoxy resins, polyphenylene ether resins, fluorine-based resins, polyimide resins, bismaleimide resins, acrylic resins, methacrylic resins, silicone resins, BT resins, and cyanate resins. Specific examples of epoxy resins include bisphenol-type epoxy resins, novolac-type epoxy resins, triphenolalkane-type epoxy resins, epoxy resins having a biphenyl skeleton, epoxy resins having a naphthalene skeleton, dicyclopentadienephenol novolac resins, phenol aralkyl-type epoxy resins, glycidyl ester-type epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, and halogenated epoxy resins. These resins may be used alone or in combination.

[0033] The content of the powder in the resin composition (resin composition-forming liquid) of the present invention is preferably a mass ratio (A / B) of powder A to curable resin B of 10 / 100 to 95 / 100, more preferably 30 / 100 to 80 / 100. Such a mass ratio allows the resin composition-forming liquid to fully function as a filler while maintaining its properties such as fluidity.

[0034] The resin composition (liquid for forming a resin composition) of the present invention preferably contains a curing agent such as a phenol compound, an amine compound, an acid anhydride, etc. When an epoxy resin is used as the curable resin, examples of the curing agent include phenolic resins having two or more phenolic hydroxyl groups per molecule, such as bisphenol-type resins, novolac resins, triphenolalkane-type resins, resol-type phenolic resins, phenol aralkyl resins, biphenyl-type phenolic resins, naphthalene-type phenolic resins, and cyclopentadiene-type phenolic resins, and acid anhydrides such as methylhexahydrophthalic acid, methyltetrahydrophthalic acid, and methylnadic anhydride.

[0035] Various additives such as colorants, stress relaxation agents, antifoaming agents, leveling agents, coupling agents, flame retardants, and curing accelerators may be added to the resin composition (resin composition-forming liquid) as needed.

[0036] The resin composition of the present invention can be obtained by a conventionally known method, for example, by mixing a thermosetting resin, silica-based hollow particles, a curing agent, additives, etc., and kneading the mixture with a roll mill or the like to prepare a coating liquid (a liquid for forming a resin composition), applying the coating liquid to a substrate, and then curing the coating liquid with heat, ultraviolet light, or the like.

[0037] [Powder manufacturing method] The method for producing powder of the present invention comprises a first step of spraying an aqueous alkali silicate solution into a hot air stream and drying to prepare hollow particles, a second step of neutralizing the alkali contained in the hollow particles with an acid and then washing to remove it, and a third step of firing the neutralized and washed hollow particles, with a crushing step of crushing the fragile hollow particles after the second step and before the third step or after the third step. Note that other steps such as a drying step may be included between the respective steps.

[0038] The production method of the present invention can produce, for example, the powder of the present invention as described above. That is, the production method of the present invention can realize a low dielectric constant and low dielectric loss tangent for an insulating material, and can produce a powder that is less likely to crack when mixed with a resin material and can stably achieve a desired dielectric constant and dielectric loss tangent.

[0039] The powder manufacturing method of the present invention includes a crushing step in which the crushing strength is appropriately adjusted to actively crush (break) fragile hollow particles. Generally, large-diameter hollow particles have thin, fragile walls, and therefore, in the crushing step, these large, fragile hollow particles are primarily crushed and removed. Furthermore, compared to the method of removing large particles by classification, as in Patent Document 2, this method allows for the accurate removal of only fragile particles, thereby leaving behind ideal particles that are relatively large in diameter but not fragile (particles that are effective for achieving a low dielectric constant and a low dielectric tangent).

[0040] (First step: Hollow particle preparation step) In the first step, hollow particles are prepared by spray-drying an aqueous solution of alkali silicate in a hot air stream.

[0041] In this process, it is preferable to prepare hollow particles by adjusting the spray droplet diameter to be smaller and to exclude large droplets. For example, it is preferable to form droplets with an average particle diameter of 10.0 μm or less using an alkali silicate aqueous solution, spray them into a hot air stream, and dry them to prepare spherical hollow particles. The average particle diameter of the formed droplets is preferably 9.0 μm or less, more preferably 8.0 μm or less, with the lower limit being 5.0 μm. The average particle diameter of the droplets is measured by the liquid immersion method (Sauter average particle diameter).

[0042] As a spray drying method, conventionally known methods such as the rotating disk method, the pressurized nozzle method, and the two-fluid nozzle method can be used. However, as described above, a spray drying method that stably forms small-diameter droplets is preferably a method using an impingement-type two-fluid nozzle having a structure that further homogenizes and refines droplets emitted from a two-fluid nozzle that atomizes a liquid using compressed air, a nozzle that pulverizes a liquid by the collision of two opposing air streams, or a four-fluid nozzle. Specific examples include methods that use an impingement-type two-fluid nozzle manufactured by Kiri no Ikeuchi Co., Ltd., a nozzle (MicroFog) manufactured by Nozzle Network Co., Ltd., and a four-fluid nozzle manufactured by GF Co., Ltd. Smaller droplets can be obtained by increasing the volume ratio (gas / liquid volume ratio) of the gas supply rate to the raw liquid supply rate in the nozzle spray.

[0043] In spray drying, the inlet temperature of the spray dryer is preferably 300 to 600° C., more preferably 350 to 550° C. The outlet temperature is preferably 120 to 350° C., more preferably 200 to 300° C. By setting the inlet and outlet temperatures to relatively high temperatures, the drying speed can be improved, and a high porosity can be achieved.

[0044] The SiO2 concentration of the alkali silicate aqueous solution is preferably 1 to 30 mass%, more preferably 5 to 28 mass%, and even more preferably 10 to 25 mass%. By making the concentration of the alkali silicate aqueous solution relatively low, it is possible to reduce the viscosity and thereby form small droplets. As the alkali silicate, sodium silicate or potassium silicate, which are soluble in water, can be used, but sodium silicate is preferred.

[0045] The molar ratio (SiO2 / MO) of SiO2 to MO (M is an alkali metal) in the alkali silicate is preferably 1 to 5, more preferably 2 to 4. If this molar ratio is less than 1, not only will the amount of alkali be too large, making it difficult to remove the alkali with acid washing, but the deliquescence of the spray-dried product will be so great that it will be difficult to obtain the desired silica-based hollow particles. If this molar ratio exceeds 5, the solubility of the alkali silicate will decrease, making it difficult to prepare an aqueous solution. Even if an aqueous solution can be prepared, the desired silica-based hollow particles may not be formed by spray drying.

[0046] (Second step: alkali removal step) In this step, the alkali contained in the prepared hollow particles is neutralized with an acid and then removed by washing. Neutralization is preferably performed at a low pH. The pH is preferably 2.0 or less. For example, the alkali contained in the hollow particles is preferably neutralized by immersing the hollow particles in an acid solution.

[0047] In the second step, the silica-based hollow particles prepared in the first step are rapidly neutralized (dealkalized) with a large amount of acid, thereby suppressing dissolution of the silica in the outer shell and preventing the formation of large pores. This allows the pores to be sized (structured) to be easily closed by the subsequent calcination process, ultimately resulting in particles with a low SiOH group content, thereby achieving a low dielectric constant and low dielectric loss tangent for the insulating material. Furthermore, this favorable pore formation also suppresses changes in the dielectric loss tangent due to moisture absorption over time, allowing the low dielectric loss tangent to be maintained over the long term. Furthermore, particle adhesion is suppressed, improving particle dispersibility. Furthermore, the absence of large pores within the pores also improves particle strength.

[0048] In this step, it is more preferable to add the hollow particles to the acid solution rather than to add the acid solution to the hollow particles. This prevents the pH from becoming such that the particles dissolve near the particles, thereby preventing the particles from dissolving. In the column flow method, the H + If the concentration of the surfactant decreases (pH increases), it may come into contact with the particles at an insufficiently low pH, causing the particles to dissolve, which may result in the formation of large pores and the desired effect not being achieved.

[0049] In this step, the mole number of hydrogen ions of the acid (Msp) is calculated based on the value obtained by multiplying the mole number of alkali metal ions in the hollow particles by the valence (Msp). H+ ) ratio (M H+ It is preferable to use an acid solution with a pH of 1.5 or more (H / Msp) exceeding 4.7. By carrying out the neutralization treatment under such conditions, it is possible to remove alkali ions (H + and ion exchange), large pores are not formed in the hollow particles (outer shells), and good pore formation is achieved. This ratio (M H+ / Msp) is preferably 5.0 or more, more preferably 5.2 or more, and even more preferably 5.5 or more. There is no upper limit, but it is, for example, 7.0 or less.

[0050] In this process, the alkali content in the particles (outer shell) is removed, reducing the mass, but the change in particle shape and hollow structure (volume) is extremely small, so when comparing before and after this process, the particle density decreases according to the amount of alkali removed. Particle density can be measured using the gas pycnometer method (JIS Z 8837). Particles before this process (products after the first process) are measured as is, and particles after this process are measured after being dried at 120°C for 24 hours (after washing).

[0051] Pores are formed in the particles (outer shell) by the alkali removal in this process. Therefore, the particle density measurement results will vary depending on whether the gas used for density measurement passes through the pores or not. When helium is used, the helium penetrates the pores and fills the cavities inside the particles, so the measured particle density is the density of silica (approximately 2.2 g / cm3). 3 ) and almost the same value (2.1 to 2.3 g / cm 3 )

[0052] On the other hand, when nitrogen is used, it does not penetrate the pores of the outer shell, and the particle density can be measured, which reflects the presence of internal cavities. In this step, if no pores into which nitrogen can penetrate are formed in the particles (outer shells) and all alkali is removed, the particle density after this step (theoretical value: ρ 2T ) can be calculated using the following formula (X):

[0053] ρ 2T =ρ1×(1-W a )...Equation (X) ρ1: Particle density after the first step ρ 2T : Theoretical value of particle density after the second process W a : Mass ratio of alkali content in raw material solids

[0054] The more pores that nitrogen can penetrate are formed in the second step, the greater the difference between the actually measured particle density (ρ2) (after the second step) and the theoretical value (ρ 2T ) becomes larger. The pores formed in this process can be made smaller by subsequent heat treatments, etc., but if the size is too large or the amount is too large, they cannot be fully blocked and will ultimately remain in the particles (outer shells), causing increased hygroscopicity. Therefore, it is preferable that the pore size is small and the amount is small, and the particle density (ρ2) measured with nitrogen is less than the theoretical value (ρ 2T ) is preferable. Specifically, ρ2 / ρ 2THowever, the particle density (ρ2) after the second step is preferably 1.0 to 1.4, more preferably 1.0 to 1.3, and even more preferably 1.0 to 1.2. As described above, the particle density (ρ2) after the second step was obtained by measuring the particles that had been washed and then dried at 120°C for 24 hours.

[0055] In addition, even if cracks occur in the hollow particles between the end of the first process and the end of the second process, the density of the particles (ρ2) will not exceed the theoretical value (ρ 2T In the present invention, small-diameter hollow particles that are less likely to break are granulated in the first step, so the deviation from the theoretical value is smaller than in conventional methods in which large-diameter hollow particles that are more likely to break are granulated.

[0056] Furthermore, it is preferable to immerse the hollow particles in an acid solution so that the concentration of SiO2 is 1 to 30% by mass. If the concentration is less than 1% by mass, there will be no problems with alkali removal or cleaning, but production efficiency will decrease. If the concentration exceeds 30% by mass, the concentration will be too high and alkali removal and cleaning efficiency may decrease. Furthermore, problems such as particle cracking due to contact and friction between particles may occur. A concentration of 5 to 25% by mass is more preferable. The immersion treatment may be carried out multiple times.

[0057] The temperature condition for the immersion treatment is usually 5°C or higher and the boiling point of the solution or lower. From the viewpoint of forming better pores and more reliably realizing a low dielectric constant and low dielectric loss tangent of the insulating material, the temperature is preferably 50°C or higher, and more preferably 55°C or higher. The treatment time is, for example, 0.5 to 24 hours.

[0058] After the immersion treatment, the hollow particles are thoroughly washed by a conventionally known method, for example, by filtration and washing with pure water.

[0059] The amount (mass percentage) of alkali (M) remaining after alkali removal is preferably 100 ppm or less, more preferably 90 ppm or less, and even more preferably 80 ppm or less. By sufficiently removing the alkali in this step, the desired effects of the present invention can be achieved. In addition, particle coalescence in subsequent steps can be prevented, and the generation of sintered particles in the firing step can be prevented.

[0060] To determine the amount of residual alkali, particles are dissolved in acid and used as a sample, and Na or K is measured using an atomic absorption photometer. When sodium silicate is used, Na is measured, and when potassium silicate is used, K is measured.

[0061] The alkali content of the final product (silica-based hollow particles) is also preferably within the above range, and is usually the same as the alkali content after the alkali removal step.

[0062] Examples of the acid used in this step include mineral acids such as hydrochloric acid, nitric acid, and sulfuric acid, and organic acids such as acetic acid, tartaric acid, and malic acid. Mineral acids are preferably used, and sulfuric acid is particularly preferred in terms of valence. The acid solution is usually an aqueous solution, but may be mixed with an alcohol or the like.

[0063] (Third step: firing step) In this step, the neutralized and washed hollow particles are fired. The firing temperature is preferably 900°C or higher, and even more preferably 1000°C or higher. There is no upper limit, but it can be, for example, 1200°C. The second step sufficiently removes the alkali, preventing particle coalescence and preventing the generation of sintered particles even when fired at high temperatures. High-temperature firing closes the pores formed during alkali removal, rendering the outer shell nonporous. This reduces the SiOH group content and allows the production of particles with low dielectric constants and dielectric dissipation factors. For example, the invention of JP 2013-103850 A cannot produce particles with a dielectric dissipation factor of less than 0.0010, but the present invention can produce particles with a dielectric dissipation factor of less than 0.0010. Furthermore, high-strength particles can be obtained.

[0064] (Crushing process) The manufacturing method of the present invention includes a crushing step for crushing fragile hollow particles after the second step and before the third step, or after the third step. The crushing step is preferably performed after the third step, since it allows for more reliable selective crushing of fragile particles as the final product. In this crushing step, fragile hollow particles are actively crushed. This allows for accurate removal of only fragile particles, regardless of size, leaving behind ideal particles with a relatively large particle size and that are not fragile (particles effective for achieving a low dielectric constant and a low dielectric tangent), which would be removed by classification.

[0065] The strength of the pulverization is determined appropriately taking into consideration the pulverization that occurs when the insulating material is mixed with the resin in the manufacturing process. For example, it is preferable to adjust the pulverization strength so that a powder that satisfies the above condition (vii) is produced.

[0066] The pulverization treatment in this step may be wet pulverization or dry pulverization, but dry pulverization is preferred. For example, a ball mill, hammer mill, pin mill, etc. can be used, and a planetary ball mill is preferred. Specific examples include a planetary ball mill manufactured by Fritsch.

[0067] (drying process) The production method of the present invention may include a drying step. Examples of drying methods include heat drying. The drying temperature is preferably 50 to 400°C, more preferably 50 to 200°C. Specific examples include a method of drying at a low temperature of about 50 to 200°C over a long period of time, a method of drying by gradually increasing the temperature, and a method of drying by changing the temperature in several stages. The drying treatment can be carried out after the second step and before the third step, for example. It may be carried out multiple times as needed.

[0068] (Sieving process) Furthermore, it is preferable to carry out a sieving process to remove particle agglomerates at least one time after the drying process or after the third process. Here, particle agglomerates refer to, for example, foreign matter with a particle size exceeding 150 μm. The sieving process is carried out using a sieve with an opening size (mesh number) that can remove such particle agglomerates. [Example]

[0069] Examples of the present invention will be specifically described below.

[0070] [Example 1] Using 30,000 g of a water glass solution (SiO2 / Na2O molar ratio 3.2, SiO2 concentration 20% by mass), hot air with an inlet temperature of 450°C was sprayed into one of the four-fluid nozzles at a flow rate of 0.29 L / hr and air at a flow rate of 2,040 L / hr (air / liquid volume ratio 7,034) into the other nozzle to obtain hollow silica particles. The outlet temperature was 250°C (first step: hollow particle preparation step).

[0071] Next, 5,000 g of hollow silica particles were immersed in 40,000 g of a 25% by mass aqueous sulfuric acid solution and stirred for 15 hours. At this time, the solid content (SiO2) concentration was 8.4% by mass, the temperature of the dispersion was 35°C, and the pH was less than 1.0. The molar ratio (Ma) / (Msp) of the acid (Ma) was 5.2. After the immersion treatment, the particles were filtered and washed with pure water (second step: alkali removal step).

[0072] Next, the mixture was dried in a dryer at 120° C. for 24 hours (drying step). After drying, the mixture was crushed and passed through a sieve with 75 μm openings to remove coarse particles.

[0073] Next, the particles were heat-treated at 1000° C. for 10 hours (third step: firing step). Finally, the calcined particles were pulverized to obtain powder (A1) containing silica-based hollow particles according to the present invention (pulverization step). The pulverization was performed dry using a planetary ball mill (Fritsch P6 Classic Line). Specifically, 50 g of balls (zirconia, 10 mm diameter) and 20 g of the produced silica-based hollow particles (A1) were weighed into a container (zirconia, 500 ml capacity), which was then placed in the planetary ball mill (Fritsch P6 Classic Line). After processing for 30 minutes at an orbital speed of 300 rpm and a rotation speed of 546 rpm, the balls and powder (A1) were separated. Particle agglomerates (foreign matter) were removed using a sieve with 150 μm openings to obtain powder (A1-1).

[0074] [Example 2] Silica-based hollow particles (A1-2) were obtained in the same manner as in Example 1, except that the pulverization step was carried out before the firing step.

[0075] [Example 3] The process up to the firing step was the same as in Example 1. In the pulverization step, the silica-based hollow particles were suspended in water to obtain a water suspension with a solid content of 30%, which was then treated at 10,000 rpm for 30 minutes using a high-shear mixer (IKA (registered trademark) T50 ULTRA-TURRAX (registered trademark) Basic Homogenizer), followed by solid-liquid separation, drying in a dryer at 120°C for 24 hours, and then pulverization. Particle agglomerates (foreign matter) were removed using a sieve with 150 μm openings to obtain silica-based hollow particles (A1-3).

[0076] [Comparative Example 1] Using 30,000 g of a water glass solution (SiO2 / Na2O molar ratio 3.2, SiO2 concentration 24 mass%), hot air with an inlet temperature of 400°C was sprayed into one of the two-fluid nozzles at a flow rate of 0.62 kg / hr and air at a flow rate of 31,800 L / hr (air / liquid volume ratio 63,600) into the other nozzle to obtain hollow silica particles. The outlet temperature was 150°C (first step: hollow particle preparation step).

[0077] Next, 5,000 g of hollow silica particles were immersed in 40,000 g of a 25% by mass aqueous sulfuric acid solution and stirred for 15 hours. At this time, the solid content (SiO2) concentration was 8.4% by mass, the temperature of the dispersion was 35°C, and the pH was less than 1.0. The molar ratio (Ma) / (Msp) of the acid (Ma) was 5.2. After the immersion treatment, the particles were filtered and washed with pure water (second step: alkali removal step).

[0078] Next, the mixture was dried in a dryer at 120° C. for 24 hours (drying step). After drying, the mixture was crushed and passed through a sieve with 75 μm openings to remove coarse particles.

[0079] Next, dry centrifugal classification was performed using a cyclone manufactured by our company, with the flow rate of the powder transport line set to 5 m / s (classification step). The particles captured by the cyclone were recovered.

[0080] The particles were then heat-treated at 1000° C. for 10 hours (third step: firing step). After firing, particle agglomerates (foreign matter) were removed using a sieve with 150 μm openings (powder B1).

[0081] Comparative Example 2 Using 30,000 g of a water glass solution (SiO2 / Na2O molar ratio 3.2, SiO2 concentration 24 mass%), hot air with an inlet temperature of 450°C was sprayed into one of the four-fluid nozzles at a flow rate of 0.40 L / hr and air at a flow rate of 2,040 L / hr (air / liquid volume ratio 5,010) into the other nozzle to obtain hollow silica particles. The outlet temperature was 250°C (first step: hollow particle preparation step).

[0082] Next, 5,000 g of hollow silica particles were immersed in 32,000 g of a 25% by mass aqueous sulfuric acid solution and stirred for 15 hours. At this time, the solid content (SiO2) concentration was 10.2% by mass, the temperature of the dispersion was 35°C, and the pH was less than 1.0. The molar ratio (Ma) / (Msp) of the acid (Ma) was 4.1. After the immersion treatment, the particles were filtered and washed with pure water (second step: alkali removal step).

[0083] Next, the mixture was dried in a dryer at 120° C. for 24 hours (drying step). After drying, the mixture was crushed and passed through a sieve with 75 μm openings to remove coarse particles.

[0084] Next, dry inertial classification was carried out using an Elbow Jet (EJ-15) manufactured by Nittetsu Mining Co., Ltd. This equipment can separate the powder into three types: F powder (fine powder), M powder (fine powder), and G powder (coarse powder). Of these, the F edge distance was adjusted so that particles over 10 μm contained in the F powder (fine powder) were 5% by volume or less, and the powder was collected in a bag filter and used in the subsequent process (classification process).

[0085] Next, the mixture was heat-treated at 1000°C for 10 hours to obtain a powder containing the desired silica-based hollow particles (third step: firing step). After firing, particle agglomerates (foreign matter) were removed using a sieve with 150µm openings (powder C1).

[0086] <Production of Resin Composition> The produced powders (A1-1 to 3, B1, C1) were blended with the liquid epoxy resin "ZX-1059" manufactured by Nippon Steel Chemical & Material Co., Ltd., together with the liquid acid anhydride "Rikacid MH700" manufactured by New Japan Chemical Co., Ltd., and the imidazole epoxy resin curing agent "2PHZ-PW" manufactured by Shikoku Chemicals Co., Ltd., and the mixture was pre-mixed in a planetary mill, and then kneaded in a three-roll mill with the gap between the feed roll and the intermediate roll adjusted to 100 μm and the gap between the intermediate roll and the finishing roll adjusted to 40 μm, to prepare a liquid for forming a resin composition. The blend ratios were 100 parts by mass of "ZX-1059," 86 parts by mass of "Rikacid MH700," and 1 part by mass of "2PHZ-PW." The powders (A1-1 to 3, B1, C1) were blended so that their proportion in the resin composition was 35% by volume. The prepared resin composition-forming liquid was heated at 170°C for 2 hours to harden, and plate-shaped resin compositions (A1R to 3R, B1R, C1R) according to the example measuring 50 mm x 50 mm x 1 mm were obtained.

[0087] The properties of the powders and resin compositions according to the examples and comparative examples produced above were evaluated. Each evaluation was carried out as follows. The results are shown in Table 1 together with the preparation conditions.

[0088] (i) average particle size (D50), (ii) maximum particle size (D100), (iii) volume ratio of particles in the range near the peak value in the particle size distribution, (ix) content of particles smaller than 2 μm, (x) amount of particles smaller than 1 μm and coarse particles Measurement was performed using the laser diffraction / scattering method. Specifically, the measurement was carried out in a dry state using a laser micron sizer (LMS-3000) manufactured by Seishin Enterprise Co., Ltd. The particle volume fraction in the range near the peak value in the particle size distribution was calculated using the following formula [particle diameter of the peak in the particle size distribution (Ps) × volume of particles in the range of 0.75 to (Ps) × 1.25 μm]. The amount of coarse particles was calculated as the volume ratio of particles exceeding 8.0 μm.

[0089] (iv) Porosity The particle density was measured by the gas pycnometer method using Ultrapyc5000 manufactured by Quantachrome Instruments. From this particle density, the following equation is obtained: [2.2-(particle density)] / 2.2×100 The porosity (%) was calculated using the following formula: In this formula, the density of silica was set to 2.2 g / cm 3 It was decided.

[0090] (v) Crack particle rate The dispersion was diluted to 0.05% with pure water containing a dispersant and irradiated with ultrasound, and then observed under a microscope. Approximately 50,000 particles were observed, and the proportion of broken particles was calculated using image analysis (particles with an area solidity of less than 0.75 were considered broken particles).

[0091] (vi) The proportion of floating, suspended, and settling particles when suspended in water. Each particle was collected from the suspension and weighed, and the ratio was calculated. Specifically, silica-based hollow particles were mixed with water to a concentration of 0.5% by mass, and then ultrasonically treated for 10 minutes to prepare a dispersion. This dispersion was allowed to stand at 25°C for 24 hours, after which the floating particles, suspended particles, and settled particles were collected. Each particle was then dried at 105°C for 24 hours, weighed, and their proportions calculated.

[0092] (vii) Porosity before and after ball milling 50 g of balls (zirconia, 10 mm diameter) and 20 g of powder were weighed into a container (zirconia, 500 ml capacity), which was then placed in a planetary ball mill (Fritsch P6 Classic Line) and processed for 10 minutes at an orbital rotation speed of 300 rpm and a rotation speed of 546 rpm, after which the balls and powder were separated. The particle density was measured in the same manner as in (iv) above, and the porosity was calculated.

[0093] The difference in porosity of the particles before and after the treatment was compared and evaluated according to the following criteria. ○: Porosity difference is 0% or more and less than 3% △: Porosity difference is 3% or more and less than 10% ×: Porosity difference 10% or more

[0094] (viii) The ratio of the shell thickness (h) of a hollow particle to the particle radius (R) (h / R) The powder was mixed with Nissin EM Co., Ltd.'s low-viscosity, water-soluble epoxy resin "Quetol-651 Set," then placed in a gelatin capsule and heated at 60°C for 24 hours to cure. The resulting plate-shaped resin composition (A2S) was cut with an argon ion beam, and the particle cross-sections were observed using a FE-SEM (JSM-7600F, JEOL Ltd.) to measure the outer and inner diameters of 12 particles. From the measurement results, the ratio (h / R) of the particle shell thickness (h) to the particle radius (R) was calculated using the following formula, and the average value of 10 particles was calculated, discarding the maximum and minimum values. h / R=(particle outer diameter - particle inner diameter) / (particle outer diameter / 2)

[0095] (xi) Residual alkali amount (alkali content) The powder was pretreated with sulfuric acid and hydrofluoric acid, then dissolved in hydrochloric acid, and the amount of residual alkali was measured using an atomic absorption spectrophotometer (Hitachi Z-2310). In this example, the amount of Na was measured.

[0096] (xii) Oil absorption per particle volume The sample was weighed by mass, and the oil absorption was measured using boiled linseed oil according to JIS K 5421. The particle density obtained separately was used to convert the oil absorption per volume.

[0097] Dielectric constant (Dk) and dielectric loss tangent (Df) of powder The dielectric constant (Dk) and dielectric loss tangent (Df) of the powder were measured using a network analyzer (Anritsu MS46122B) and a cavity resonator (1 GHz) in accordance with ASTM D2520 (JIS C2565).

[0098] Dielectric constant (Dk) and dielectric loss tangent (Df) of the resin composition The dielectric constant (Dk) and dielectric loss tangent (Df) of a 50 mm × 50 mm × 1 mm plate-shaped molded body (resin composition) were measured at 9.4 GHz using a network analyzer (Anritsu MS46122B) and a coaxial resonator. The results were compared with a resin composition containing no silica-based hollow particles (filler) and evaluated according to the following criteria.

[0099] Dielectric constant (Dk) reduction rate (%) = (Dielectric constant without filler added - Dielectric constant with filler added) / Dielectric constant without filler added) × 100

[0100] 〇: Reduction rate is over 0% △: Reduction rate is 0% (no change) ×: Reduction rate is less than 0%

[0101] Reduction rate (%) of dielectric loss tangent (Df) = (Dielectric loss tangent without filler added - Dielectric loss tangent with filler added) / Dielectric loss tangent without filler added) x 100

[0102] 〇: Reduction rate 30% or more △: Reduction rate is 20% or more but less than 30% ×: Reduction rate less than 20%

[0103] Increase rate (%) from assumed dielectric constant (Dk) = (Dielectric constant with added filler - Estimated dielectric constant with added filler) / Estimated dielectric constant with added filler) × 100

[0104] ○: Increase rate less than 5% ×: Increase rate of 5% or more

[0105] Filterability of the resin composition-forming liquid Using a filter manufactured by ROKI TECHNO (SHP type: 30 μm), the amount of liquid passing through per unit area until the filter became clogged was evaluated.

[0106] The evaluation criteria are as follows: ◎: 1g / cm2 End 〇:0.5g / cm 2 More than 1.0g / cm 2 less than △: 0.3g / cm 2 More than 0.5g / cm 2 less than ×:0.3g / cm 2 less than

[0107] Injectability of the resin composition-forming liquid The injection was carried out between glass plates with a gap of 20 μm, and the evaluation was based on the time required to fill 25 mm.

[0108] The evaluation criteria are as follows: ◎: Within 200 seconds 〇: More than 200 seconds but less than 400 seconds △: More than 400 seconds and less than 600 seconds ×: Over 600 seconds

[0109] [Table 1] [Industrial Applicability]

[0110] The powder of the present invention can be used as a filler for insulating materials for semiconductors, and is therefore industrially useful.

Claims

1. A powder containing silica-based hollow particles, characterized in that it satisfies the following requirements (i) to (vii): (i) The average particle size (D50) of the powder is 0.1 to 5.0 μm (ii) the maximum particle size (D100) of the powder is 20.0 μm or less (iii) the volume ratio of particles in the range of the peak particle diameter (Ps) x 0.75 to (Ps) x 1.25 μm in the particle size distribution of the powder is 50% or less of the total particles (iv) the porosity of the powder is 10 to 50% (v) The powder has a cracked particle rate of 10% or less. (vi) When the powder is suspended in water, the floating particles are 7.0 to 25.0% by mass, the suspended particles are 0 to 4.0% by mass, and the settling particles are 71.0 to 93.0% by mass. (vii) The difference in porosity before and after pulverization of the powder under the following pulverization conditions is within 3% (Pulverizing conditions) 20 g of the powder and 50 g of zirconia balls with a diameter of 10 mm were placed in a 500 ml zirconia container and pulverized in a planetary ball mill at a revolution speed of 300 rpm and a rotation speed of 546 rpm for 10 minutes.

2. The powder according to claim 1, further satisfying the following requirement (viii): (viii) The ratio (h / R) of the shell thickness (h) to the particle radius (R) of the particles extracted from the powder is 0.21 to 0.54

3. The powder according to claim 1, further satisfying the following requirement (ix): (ix) The powder has a particle content of less than 2 μm in particle diameter of 20% by volume or more.

4. The powder according to claim 1, further satisfying the following requirement (x): (x) The powder contains particles with a particle diameter of less than 1 μm at a content of 10% by volume or more.

5. The powder according to claim 1, further satisfying the following requirement (xi): (xi) the alkali content of the powder is 100 ppm or less

6. The powder according to claim 1, further satisfying the following requirement (xii): (xii) the oil absorption per volume of the powder is 0.60 ml / cm ３ below

7. 2. The powder according to claim 1, wherein the powder has a dielectric constant of 2.8 or less and a dielectric loss tangent of less than 0.0010.

8. A resin composition comprising the powder according to any one of claims 1 to 7 in a dispersed state.

9. a first step of spraying an alkali silicate aqueous solution in a hot air stream and drying the sprayed solution to prepare hollow particles; a second step of neutralizing the alkali contained in the hollow particles with an acid and then removing the alkali by washing; a third step of firing the neutralized and washed hollow particles; and A method for producing a powder containing silica-based hollow particles, characterized in that a crushing step of crushing fragile hollow particles is provided after the second step and before the third step, or after the third step.

10. 10. The method for producing powder according to claim 9, wherein in the first step, droplets having an average particle diameter of 10.0 μm or less are formed using an alkali silicate aqueous solution, and in the second step, the alkali contained in the hollow particles is neutralized in an acid solution.

11. 10. The method for producing powder according to claim 9, wherein in the second step, the alkali content in the hollow particles is reduced to 100 ppm or less.

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