Low-moisture-content shell layer, coating method therefor, and use thereof

Abstract

The present invention relates to the technical field of semiconductors. Disclosed are a low-moisture-content shell layer, a coating method therefor, and a use thereof. In the present invention, T-unit siloxane is used as a raw material to form a polysiloxane layer on the surface of filler powder; then a drying treatment is carried out, so that the polysiloxane layer is in a low-moisture-content state, promoting condensation of silicon hydroxyl, and organic groups of the T-unit siloxane are orderly arranged to form a uniform polysiloxane layer; and finally, a calcination treatment is carried out to remove some of the organic groups of the T-unit siloxane to make the T unit converted into Q unit, so that the uniform polysiloxane layer is converted into a dense siloxane compound shell layer. By means of a preferred raw material and an optimized preparation process, the siloxane compound of the shell layer is more dense and more continuous, so that the resulting shell layer has low moisture content after being placed for a long time, and thus, the filler powder having the shell layer has the advantage of low moisture content.

Description

Low water content shell and its coating method and application TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a low water content shell and its coating method and application. BACKGROUND

[0002] With the rapid development of microelectronics and communication technology, semiconductor chips are constantly developing towards high integration, miniaturization, high frequency, high power and other directions, so higher requirements are put forward for the performance of electronic core devices. In the field of semiconductors, when passive components, semiconductor components, electroacoustic devices, display devices, optical devices and radio frequency devices are assembled into equipment, high-density interconnection boards, high-frequency high-speed boards and motherboard materials are needed.

[0003] The substrate material and packaging material of electronic devices need to have low water content performance to make the electronic devices have smaller dielectric loss in the running process, and at the same time, reduce the risk of the electronic devices being conducted due to the presence of water. Therefore, in order to meet the filler demand in the field of semiconductors, it is necessary to reduce the water absorption and water content of the filler of the substrate material and packaging material of electronic devices.

[0004] The existing semiconductor filler mainly includes two categories of heat-conducting materials and flame-retardant materials. The main function of the former is heat conduction to improve the heat dissipation effect of the heating elements in the electronic device, and the main function of the latter is flame retardation to avoid direct combustion of the electronic device after overheating. In order to improve the filling effect of the filler, the above filler needs to be mixed and filled with resin material. Generally, in order to improve the mixing effect of the filler and the resin material, the above filler is often surface modified.

[0005] For example, in order to increase the bonding performance of diamond heat-conducting material with other materials, a modified diamond composite functional material and a preparation method are disclosed in a Chinese patent with the application publication number CN114477167A. The patent proposes that a layer of nano-amorphous SiO2 film capable of improving the surface reaction activity of diamond micro powder is tightly coated on the surface of the diamond micro powder, and through the active oxygen groups in the film, a good cross-linking reaction can be formed with the -OH groups in the resin, thereby improving the bonding effect between the diamond and the resin binder. However, the surface of the diamond micro powder in the patent is rough, and the SiO2 film formed has many voids. Since the diamond micro powder with a surface having reaction activity obtained by coating with the SiO2 film in the patent is applied in diamond abrasive tools, as long as the active oxygen groups are grafted on the surface of the modified diamond micro powder, the porosity and water absorption problems of the diamond micro powder do not need to be considered. However, in the semiconductor field, the increase in the porosity of the filler means the increase in the specific surface area. The functional relationship between the specific surface area and the diameter of the particles is: specific surface area = constant / particle diameter. As can be seen from the inverse function relationship, the decrease in the diameter leads to a sharp increase in the specific surface area. The increase in the specific surface area leads to an increase in the adsorbed water, which in turn increases the dielectric loss of the semiconductor device, and finally affects the performance of the semiconductor device.

[0006] Therefore, in the semiconductor field, the modification of the filler powder not only needs to improve the good bonding ability between the filler powder and the resin as the target to be solved, but also needs to reduce the water content of the modified filler powder as the target to be solved. SUMMARY

[0007] The surface modification of the existing semiconductor filler leads to a high water content of the modified product. In order to solve the above technical problems, the present application provides a low-water-content shell layer and a coating method and application thereof.

[0008] Firstly, the present application provides a low-water-content shell layer, which is applied to a solid 29 The ratio of the peak integral areas in the range of -80 ppm to -120 ppm and the range of +20 ppm to -120 ppm in the Si-NMR nuclear magnetic resonance spectrum is 50-99.5:100. The application in the semiconductor filler field for a long time can have a low water absorption and excellent dielectric performance.

[0009] Secondly, the present application provides a coating method of a low-water-content shell layer. By optimizing the raw materials and the preparation process, the siloxane compound of the shell layer is more dense, and the water content is low after a long time.

[0010] Thirdly, the present application provides a filler powder, which contains a low-water-content shell layer, thereby making the powder have good affinity with the resin material and low dielectric loss in the operation of electronic devices.

[0011] Furthermore, this invention provides the application of filler powder containing a water-containing shell in the preparation of packaging materials or substrate materials in the semiconductor field.

[0012] The specific technical solution of the present invention is as follows: Firstly, the present invention provides a low-water-content shell. The shell has the following distinctive features: the shell comprises a siloxane compound; the siloxane compound is in the range of +20ppm to -120ppm... 29 The response in the Si-NMR nuclear magnetic resonance spectrum.

[0013] In solid 29 In the Si-NMR nuclear magnetic resonance spectrum, the ratio of the peak integrated area of ​​the shell in the range of -80ppm to -120ppm to the range of +20ppm to -120ppm is 50 to 99.5:100.

[0014] In the semiconductor field, in order to improve the filling effect of fillers, it is necessary to mix fillers with resin materials for filling. Furthermore, in order to better mix fillers with resin materials, it is necessary to modify the surface of the fillers to improve their affinity with the resin.

[0015] Therefore, based on the above problems, the present invention provides a siloxane compound shell layer, wherein the siloxane compound is in the range of +20ppm to -120ppm. 29 The response in the Si-NMR nuclear magnetic resonance spectrum shows that the shell provided by the present invention is set on the surface of the filler powder, which can improve the activity of the filler in tightly connecting with other substances, so that the filler can better combine with the resin material and improve the mixing effect.

[0016] The shell of this invention is in solid 29 In the Si-NMR nuclear magnetic resonance spectrum, the ratio of the peak integrated area in the range of -80ppm to -120ppm to the range of +20ppm to -120ppm is 50 to 99.5:100.

[0017] In the semiconductor field, fillers are generally not used directly after preparation; they have a shelf life and therefore absorb moisture during storage. The shell layer provided by this invention, disposed on the surface of the filler powder, reduces the amount of moisture absorbed by the filler powder after storage, thereby avoiding dielectric loss problems caused by high moisture content.

[0018] In the siloxane compound shell layer provided by this invention, to ensure that the siloxane compound shell layer uniformly coats the surface of the filler powder, the amount of a specific siloxane compound needs to be within a certain range. If the amount of the siloxane compound is too small, it cannot completely coat the surface of the filler powder, resulting in a discontinuous shell layer with high porosity, which can lead to water absorption problems later on. Excessive water content in the filler powder increases the risk of electronic devices being switched on, affecting their operation. Furthermore, high water content leads to significant dielectric loss. If the amount of siloxane compound is too large, the filler powder will agglomerate, making it difficult to mix evenly with the resin. The resulting mixture of filler and resin will peel off, increasing pore formation in the filler powder and resin mixture and causing water absorption problems. Therefore, this invention provides a shell layer that, in solid... 29 In the Si-NMR nuclear magnetic resonance spectrum, the ratio of the peak integrated area in the range of -80ppm to -120ppm to the range of +20ppm to -120ppm is 50 to 99.5:100.

[0019] In the siloxane compound shell layer provided by this invention, the choice of core material may affect the water content of the product containing the shell after placement. When the core material is a filler material with high surface energy, such as boron nitride, diamond, or aluminum nitride, the water content of the product after placement is generally higher than that of core materials with relatively low surface energy, such as boron nitride, diamond, and aluminum nitride. The reason is that core materials with high surface energy may form tiny gaps between themselves and the shell layer after coating, resulting in relatively high porosity and water absorption. Ultimately, core materials with high surface energy generally exhibit higher water content than core materials with low surface energy.

[0020] As a preferred embodiment of the shell of the present invention, the siloxane compound is prepared from a siloxane containing more than 90% wt T units; wherein, T units = R1SiO3-, and R1 is a hydrogen atom or a hydrocarbon group of 1 to 16 carbon atoms that can be selected independently.

[0021] The siloxane compound shell provided by this invention has high density and good continuity. The siloxane compound film prepared using polysiloxane containing more than 90% wt T units as raw material has high density and good continuity. To coat the filler powder, the silanol groups of the siloxane need to be condensed to form a polysiloxane film on the surface of the filler powder. Then, the siloxane compound is obtained through heat treatment. During the formation of the polysiloxane film, since T-unit molecules rotate more freely than Q-unit molecules, to form a uniform, continuous, and dense film, the shell provided by this invention needs to be prepared using polysiloxane containing more than 90% wt T units as raw material to achieve the advantage of low water absorption after placement.

[0022] Further preferred, the T-unit siloxane is selected from hydrocarbon-trialkoxysilane and hydrocarbon-trichlorosilane.

[0023] As a preferred embodiment of the shell layer of the present invention, the thickness of the shell layer is 0.5 nm to 300 nm.

[0024] As a preferred embodiment of the shell layer of the present invention, after being placed at 25°C and 50% RH for 48 hours, the Karl Fischer moisture content of the product containing the shell layer at 200°C is not higher than 160 ppm / m³. 2 .

[0025] Because the siloxane compound shell provided by this invention has good density and continuity, the filler powder with this shell has the excellent characteristic of low water absorption after placement, which can reduce the water absorption of the filler powder during the shelf life, and make the electronic device have a lower conduction risk and lower dielectric loss during operation.

[0026] Secondly, the present invention provides a method for coating a low-moisture shell, comprising the following steps: Step S1, adding T units of siloxane to the filler powder to be coated, reacting to form polysiloxane on the surface of the powder to be coated, thereby obtaining a precursor; Step S2, performing a drying treatment to bring the precursor to a low-moisture content state; Step S3, performing a calcination treatment to densify the surface of the precursor, thereby obtaining a shell on the surface of the filler powder; wherein, T units = R1SiO3-, and R1 is a hydrogen atom or a hydrocarbon group of 1 to 16 carbon atoms that can be independently selected.

[0027] In the prior art, in order to improve the bonding between filler powder and resin material, the focus is usually on improving the affinity of the filler powder surface. However, while improving the affinity of the filler powder surface, it is more important to ensure that the product has low moisture content. This is because the presence of moisture in the filler not only leads to dielectric loss problems, but also poses a risk of conduction to electronic devices.

[0028] To improve the density of the siloxane compound shell layer of the filler powder and reduce the water absorption of the finished product after placement, this invention provides a method for preparing the shell layer as described above, forming a uniform and dense siloxane compound film layer on the surface of the filler powder. First, this invention uses T-unit siloxane raw materials to form a polysiloxane layer on the surface of the filler powder; then, through drying, the polysiloxane layer is brought to a low moisture content state, promoting the condensation of silanol groups and causing the organic groups of the T-unit siloxane to arrange in an orderly manner, forming a uniform polysiloxane layer, which is beneficial for the formation of a dense siloxane compound; finally, through calcination, some of the organic groups of the T-unit siloxane are removed, transforming the uniform polysiloxane layer into a dense siloxane compound shell layer.

[0029] The conditions for forming a dense siloxane compound shell on the surface of the filler powder of this invention include the following three aspects: ① Because T-unit siloxanes are polar, they can be quickly adsorbed onto the surface of the filler powder when mixed with it, forming a polysiloxane film. Therefore, the first condition of the preparation method of this invention is to use T-unit siloxane as a raw material. Since the free rotation of T-unit molecules is relatively easy, the first condition of using T-unit siloxane as a raw material is a prerequisite for step S2 of this invention to promote the rotation and optimize the arrangement of the organic groups of siloxane by keeping the polysiloxane film in a low moisture content state.

[0030] ② The second condition of the preparation method of this invention is drying to bring the polysiloxane film to a low moisture content state, which promotes the rotation and orderly arrangement of the organic groups of the T-unit siloxane, thus forming a uniform polysiloxane layer. A uniform polysiloxane layer is beneficial for the formation of a uniform and dense siloxane compound shell. ③ The third condition is calcination to remove some of the organic groups from the polysiloxane shell, making it denser. Under these conditions, the uniform polysiloxane layer transforms into a uniform and dense siloxane compound shell.

[0031] As a preferred embodiment of the coating method of the present invention, in step S1, the mass ratio of the filler powder to the added T units of siloxane is 100:0.2 to 10.

[0032] As a preferred embodiment of the coating method of the present invention, in step S1, an alkaline aqueous solution is added to carry out the reaction.

[0033] Step S1 involves the adsorption of T-unit siloxane onto the surface of the filler powder to form a polysiloxane film. Adding an alkaline aqueous solution promotes the condensation of silanol groups. The alkaline aqueous solution can be one or more of the following: ammonia, tetramethylammonium hydroxide, choline, ethylenediamine, isopropylamine, and ethanolamine.

[0034] As a preferred embodiment of the coating method of the present invention, silica powder is also added for reaction.

[0035] Further preferred, the particle size of the silica powder is 10–100 nm.

[0036] To further improve the density of the siloxane compound shell, this invention also adds nano-silica powder during the formation of the polysiloxane shell in step S1. The siloxane compound coated on the surface of the filler powder in this invention can be primarily derived from T-unit siloxane raw materials, with a small portion being directly added nano-silica powder. During the condensation of siloxanes to form polysiloxanes, the mixture is not dense. During the reaction, a small amount of silica powder is added and dispersed within the polysiloxane framework. In step S3, when the organic groups of the polysiloxane are removed by calcination, this silica powder can fill the positions of the organic groups, reducing defects in the siloxane compound shell coating on the filler powder surface. The preferred particle size of the silica powder is 10–100 nm, and the preferred amount added is 0.5%–1.2% of the mass of T-unit siloxane raw materials.

[0037] As a preferred embodiment of the coating method of the present invention, in step S1, the particle size of the filler powder is 0.05 to 40 μm.

[0038] To form a uniform siloxane compound shell on the surface of the filler powder, the particle size of the filler powder needs to be within the range of 0.05–40 μm. If the filler powder particle size is too small, it is prone to agglomeration, making it difficult for T-unit siloxane to be uniformly adsorbed onto the filler powder surface. Therefore, it is difficult to form a uniform polysiloxane film, resulting in incomplete coating and poor coating effect. Since the thickness of the siloxane compound to be coated is small, less T-unit siloxane raw material is added. If the filler powder particle size is too large, the siloxane will also have the problem of being difficult to uniformly adsorb onto the filler powder surface, leading to uneven coating and high porosity. If the coating thickness and the amount of added siloxane raw material are increased to promote uniform coating, the resulting filler powder will agglomerate. Agglomeration will make it difficult for the coated filler powder to mix evenly with the resin, and the mixed filler formed by the product and resin will peel off. This will also increase the formation of pores in the filler powder and resin mixture, causing water absorption problems.

[0039] As a preferred embodiment of the coating method of the present invention, in step S2, the drying process reduces the moisture content of the precursor to 0.1-1%.

[0040] Maintaining a low moisture content in the polysiloxane layer promotes the rotation and orderly arrangement of the organic groups within the T-unit siloxane, resulting in a uniform polysiloxane layer. This leads to a denser and more uniform siloxane compound shell, ultimately resulting in lower water absorption and moisture content in the product after storage. The highest density of the siloxane compound shell formed on the surface of the filler powder is achieved when the precursor moisture content is 0.1–1%.

[0041] Further preferred, the drying method is: heating to 50-200℃ and drying for 6-24 hours.

[0042] As a preferred embodiment of the coating method of the present invention, in step S3, the calcination treatment is carried out in an inert gas atmosphere.

[0043] As a preferred embodiment of the coating method of the present invention, in step S3, the calcination temperature is 600–1200°C.

[0044] The purpose of calcination is to remove the organic groups of the T-unit siloxane, transforming the uniform polysiloxane layer into a dense siloxane compound layer. Calcination is carried out in an inert gas atmosphere, which provides superior densification. The preferred treatment temperature is 600–1200℃, and the preferred treatment time is 6–72 hours.

[0045] As a preferred embodiment of the coating method of the present invention, the calcination treatment time in step S3 is 6 to 72 hours.

[0046] Thirdly, the present invention provides a filler powder comprising the aforementioned low-moisture shell layer. The filler powder may be selected from one or more of thermally conductive materials commonly used as fillers in the semiconductor field and organophosphorus flame retardants. For example, the filler powder may be selected from one or more of boron nitride, PQ60, alumina, and aluminum nitride.

[0047] Fourthly, this invention provides the application of filler powder in the preparation of semiconductor packaging materials or substrate materials. In the semiconductor field, when assembling passive components, semiconductor components, electroacoustic devices, display devices, optical devices, and radio frequency devices into devices, circuit board substrate materials such as high-density interconnect boards, high-frequency and high-speed boards, and motherboards are required. These substrate materials are generally mainly composed of fillers and organic polymers such as resins. The application of the filler powder provided by this invention in the preparation of semiconductor packaging materials or substrate materials can effectively meet the requirements of high affinity for resin materials in semiconductor packaging materials or substrate materials, as well as their requirements of low water content and water absorption.

[0048] Compared with the prior art, the present invention has the following technical effects: (1) In the prior art, the coating modification of filler powder usually does not consider the water absorption and moisture content. However, in the semiconductor field, whether it is filler or inductor material, it is generally not used directly after preparation and there will be a shelf life. Therefore, it is necessary to pay attention to the water absorption during storage and the moisture content after storage. The present invention provides a siloxane compound shell (the siloxane compound is in the range of +20ppm to -120ppm) 29The shell layer exhibits a response in the Si-NMR nuclear magnetic resonance spectrum, and its peak integral area ratio in the solid-state 29Si-NMR nuclear magnetic resonance spectrum is 50–99.5:100 in the range of -80ppm to -120ppm to +20ppm. This results in a shell layer with excellent low water absorption after storage. Applying this shell layer to the surface of the filler powder not only enhances the activity of the filler in tightly bonding with other substances and allows the filler to better combine with the resin material, but also reduces the water absorption of the filler powder during the shelf life. This avoids the dielectric loss problem caused by high water content and reduces the conduction risk of electronic devices operating at high frequencies.

[0049] (2) This invention also provides a method for coating a low-moisture shell layer. Using T-unit siloxane raw materials, a polysiloxane layer is formed on the surface of the filler powder. Then, through drying, the polysiloxane layer is brought to a low-moisture state, promoting the condensation of silanol groups and causing the organic groups of the T-unit siloxane to arrange in an orderly manner, forming a uniform polysiloxane layer. Finally, through calcination, some of the organic groups of the T-unit siloxane are removed and converted to Q-units, transforming the uniform polysiloxane layer into a dense siloxane compound shell layer. This invention, through optimized raw materials and preparation process, results in a denser and more continuous siloxane compound shell layer, leading to a low moisture content even after prolonged storage.

[0050] (3) In the siloxane compound shell layer provided by the present invention, the selection of the core material may affect the water content of the product containing the shell layer after placement. For example, when the core material is a filler material with high surface energy such as boron nitride, diamond, or aluminum nitride, the water content of the product after placement is generally higher than that of a core material with relatively low surface energy, such as boron nitride, diamond, or aluminum nitride. The siloxane compound shell layer provided by the present invention can provide a filler material with lower water content by selecting a core material that is optimized. Detailed Implementation

[0051] The present invention will be further described below with reference to embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0052] The powder particles had a moisture content of 200 degrees Celsius, which was tested using a Karl Fischer moisture analyzer (Mitsubishi Chemical CA-310) and the coulometric method. In the performance testing, the unit for moisture content was ppm / m³. 2The calculation is to divide the measured moisture content by the geometric external surface area of ​​the test sample particles (calculated based on the measured average particle size).

[0053] The average particle size was measured using a Beckman Coulter LS-13320 laser particle size analyzer with deionized water as the solvent. In this paper, the average particle size refers to the volume average diameter of the particles.

[0054] In siloxane compounds 29 In the Si-NMR nuclear magnetic resonance spectrum, the total content of groups bonded to Si is represented by the peak integrated area in the range of +20 ppm to -120 ppm, and the content of Q units is represented by the peak integrated area in the range of -80 ppm to -120 ppm. The shell provided by this invention has a peak integrated area ratio of 50 to 99.5:100 in the range of -80 ppm to -120 ppm to +20 ppm.

[0055] The coating thickness of the siloxane compound, i.e. the shell thickness, was obtained by high-resolution transmission electron microscopy.

[0056] Example 1 provides a continuous and dense siloxane compound shell, prepared by the following method: Step S1: Methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 1.0 μm, and after uniform mixing, 5% ammonia water (by volume) is added, and the reaction is carried out at 25°C to form polysiloxane on the surface of the boron nitride powder, thus obtaining the precursor. The mass ratio of boron nitride powder, MTMS, and 5% ammonia water (by volume) is 50:1:1.

[0057] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 70°C for 24 hours for drying, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0058] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 800°C at a rate of 5°C / min and held for 7 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 1.0 nm.

[0059] Example 2 provides a continuous and dense siloxane compound shell, prepared by the following method: Step S1: Methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 1.0 μm, and after uniform mixing, 5% ammonia water (by volume) is added, and the reaction is carried out at 25°C to form polysiloxane on the surface of the boron nitride powder, thus obtaining the precursor. The mass ratio of boron nitride powder, MTMS, and 5% ammonia water (by volume) is 50:1:1.

[0060] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 70°C for 24 hours for drying, so that the precursor is in a low moisture content state with a water content of 0.1%.

[0061] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 800°C at a rate of 5°C / min and held for 7 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 1.0 nm.

[0062] Example 3 provides a continuous and dense siloxane compound shell, prepared by the following method: Step S1: Methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 1.0 μm, and after uniform mixing, 5% ammonia water (by volume) is added, and the reaction is carried out at 25°C to form polysiloxane on the surface of the boron nitride powder, thus obtaining the precursor. The mass ratio of boron nitride powder, MTMS, and 5% ammonia water (by volume) is 50:1:1.

[0063] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 70°C for 24 hours for drying, so that the precursor is in a low moisture content state with a water content of 1%.

[0064] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 800°C at a rate of 5°C / min and held for 7 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 1.0 nm.

[0065] Example 4 provides a continuous and dense siloxane compound shell, prepared by the following method: Step S1: Methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 0.5 μm. After mixing evenly, 5% ammonia water (by volume) is added, and the reaction is carried out at 25°C to form polysiloxane on the surface of the boron nitride powder, thus obtaining the precursor. The mass ratio of boron nitride powder, MTMS, and 5% ammonia water (by volume) is 50:1:1.

[0066] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 70°C for 24 hours for drying, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0067] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 800°C at a rate of 5°C / min and held for 7 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 12.9 nm.

[0068] Example 5 provides a continuous and dense siloxane compound shell, prepared by the following method: Step S1: Methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 6.0 μm. After mixing evenly, 5% ammonia water (by volume) is added, and the reaction is carried out at 25°C to form polysiloxane on the surface of the boron nitride powder, thus obtaining the precursor. The mass ratio of boron nitride powder, MTMS, and 5% ammonia water (by volume) is 50:1:1.

[0069] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 70°C for 24 hours for drying, so that the precursor is in a low moisture content state with a water content of 0.8%.

[0070] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 800°C at a rate of 5°C / min and held for 7 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 125.1 nm.

[0071] Example 6 provides a continuous and dense siloxane compound shell, prepared by the following method: Step S1: Methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 0.05 μm, and after uniform mixing, 5% ammonia water (by volume) is added, and the reaction is carried out at 25°C to form polysiloxane on the surface of the boron nitride powder, thus obtaining the precursor. The mass ratio of boron nitride powder, MTMS, and 5% ammonia water (by volume) is 50:1:1.

[0072] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 70°C for 24 hours for drying, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0073] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 800°C at a rate of 5°C / min and held for 7 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 0.5 nm.

[0074] Example 7 provides a continuous and dense siloxane compound shell, prepared as follows: Step S1: Methyltrimethoxysilane (MTMS) is added to a 40 μm layer and mixed thoroughly. Then, 5% ammonia solution is added, and the mixture is reacted at 25°C to form a polysiloxane on the surface of the boron nitride powder, thus obtaining the precursor. The mass ratio of boron nitride powder, MTMS, and 5% ammonia solution is 50:1:1.

[0075] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 70°C for 24 hours for drying, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0076] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 800°C at a rate of 5°C / min and held for 7 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 191.8 nm.

[0077] Example 8 provides a continuous and dense siloxane compound shell, prepared by the following method: Step S1: Methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 40 μm, and after uniform mixing, 5% ammonia water is added, and the reaction is carried out at 25°C to form polysiloxane on the surface of the boron nitride powder, thus obtaining the precursor. The mass ratio of boron nitride powder, MTMS, and 5% ammonia water is 42:1:1.

[0078] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 70°C for 24 hours for drying, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0079] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 800°C at a rate of 5°C / min and held for 7 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 298.9 nm.

[0080] Example 9 provides a continuous and dense siloxane compound shell, prepared by the following method: Step S1: Methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 12 μm. After mixing evenly, ammonia water with a volume concentration of 5% and nano-silica powder are added. The reaction is carried out at 25°C to form polysiloxane on the surface of the boron nitride powder, thus obtaining the precursor. The mass ratio of boron nitride powder, MTMS, ammonia water with a volume concentration of 5% and nano-silica powder is 50:4:4:0.01. The average particle size of the nano-silica powder is 30 nm.

[0081] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 70°C for 24 hours for drying, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0082] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 800°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 121.1 nm.

[0083] Example 10 provides a continuous and dense siloxane compound shell, prepared by the following method: Step S1: Methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 12 μm. After mixing evenly, ammonia water with a volume concentration of 5% and nano-silica powder are added. The reaction is carried out at 25°C to form polysiloxane on the surface of the boron nitride powder, thus obtaining the precursor. The mass ratio of boron nitride powder, MTMS, ammonia water with a volume concentration of 5% and nano-silica powder is 50:4:4:0.01. The average particle size of the nano-silica powder is 10 nm.

[0084] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 70°C for 24 hours for drying, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0085] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 800°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 119.3 nm.

[0086] Example 11 provides a continuous and dense siloxane compound shell, prepared by the following method: Step S1: Methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 12 μm. After mixing evenly, ammonia water with a volume concentration of 5% and nano-silica powder are added. The reaction is carried out at 25°C to form polysiloxane on the surface of the boron nitride powder, thus obtaining the precursor. The mass ratio of boron nitride powder, MTMS, ammonia water with a volume concentration of 5% and nano-silica powder is 50:4:4:0.01. The average particle size of the nano-silica powder is 100 nm.

[0087] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 70°C for 24 hours for drying, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0088] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 800°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 134.4 nm.

[0089] Example 12 provides a continuous and dense siloxane compound shell, prepared by the following method: Step S1: Methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 12 μm. After mixing evenly, ammonia water with a volume concentration of 5% and nano-silica powder are added. The reaction is carried out at 25°C to form polysiloxane on the surface of the boron nitride powder, thus obtaining the precursor. The mass ratio of boron nitride powder, MTMS, ammonia water with a volume concentration of 5% and nano-silica powder is 50:4:4:0.01. The average particle size of the nano-silica powder is 7 nm.

[0090] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 70°C for 24 hours for drying, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0091] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 800°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 112.0 nm.

[0092] Example 13 provides a continuous and dense siloxane compound shell, prepared by the following method: Step S1: Methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 12 μm. After mixing evenly, ammonia water with a volume concentration of 5% and nano-silica powder are added. The reaction is carried out at 25°C to form polysiloxane on the surface of the boron nitride powder, thus obtaining the precursor. The mass ratio of boron nitride powder, MTMS, ammonia water with a volume concentration of 5% and nano-silica powder is 50:4:4:0.01. The average particle size of the nano-silica powder is 120 nm.

[0093] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 70°C for 24 hours for drying, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0094] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 800°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 134.5 nm.

[0095] Example 14 provides a continuous and dense siloxane compound shell, prepared as follows: Step S1: Methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 12 μm. After mixing evenly, 5% ammonia water and nano-silica powder are added. The reaction is carried out at 25°C to form polysiloxane on the surface of the boron nitride powder, thus obtaining the precursor. The mass ratio of boron nitride powder, MTMS, 5% ammonia water, and nano-silica powder is 50:4:4:0.019. The average particle size of the nano-silica powder is 30 nm.

[0096] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 50°C for 10 hours to dry it, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0097] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 1000℃ at a rate of 5℃ / min and held for 10 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 126.4 nm.

[0098] Example 15 provides a continuous and dense siloxane compound shell, prepared by the following method: Step S1: Methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 12 μm. After mixing evenly, ammonia water with a volume concentration of 5% and nano-silica powder are added. The reaction is carried out at 25°C to form polysiloxane on the surface of the boron nitride powder, thus obtaining the precursor. The mass ratio of boron nitride powder, MTMS, ammonia water with a volume concentration of 5%, and nano-silica powder is 100:8:8:0.01. The average particle size of the nano-silica powder is 30 nm.

[0099] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 200°C for 6 hours to dry it, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0100] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 1200℃ at a rate of 5℃ / min and held for 24 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 115.6 nm.

[0101] Example 16 provides a continuous and dense siloxane compound shell, prepared by the following method: Step S1: Methyltrimethoxysilane (MTMS) is added to diamond micron powder with an average particle size of 1.0 μm, and after uniform mixing, 5% ammonia water (by volume) is added, and the reaction is carried out at 25°C to form polysiloxane on the surface of the organophosphorus flame retardant powder particles, thus obtaining the precursor. The mass ratio of organophosphorus flame retardant powder, MTMS, and 5% ammonia water (by volume) is 50:1:1.

[0102] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 70°C for 24 hours for drying, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0103] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 600°C at a rate of 5°C / min and held for 8 hours for calcination treatment to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the organophosphorus flame retardant powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 0.9 nm.

[0104] Example 17 provides a continuous and dense siloxane compound shell, prepared by the following method: Step S1: Methyltrimethoxysilane (MTMS) is added to aluminum nitride powder with an average particle size of 1.0 μm, and after uniform mixing, 5% ammonia water (by volume) is added, and the reaction is carried out at 25°C to form polysiloxane on the surface of the alumina powder particles, thus obtaining the precursor. The mass ratio of alumina powder, MTMS, and 5% ammonia water (by volume) is 50:1:1.

[0105] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 70°C for 24 hours for drying, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0106] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 900°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the alumina powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 1.5 nm.

[0107] Example 18 provides a continuous, dense siloxane compound shell, prepared as follows: Step S1: Methyltrimethoxysilane (MTMS) is added to an organophosphorus flame retardant powder with an average particle size of 1.0 μm. After mixing evenly, 5% ammonia water (by volume) is added, and the reaction is carried out at 25°C to form polysiloxane on the surface of aluminum nitride powder particles, thus obtaining the precursor. The mass ratio of aluminum nitride powder, MTMS, and 5% ammonia water (by volume) is 50:1:1.

[0108] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 70°C for 24 hours for drying, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0109] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 800°C at a rate of 5°C / min and held for 7 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the aluminum nitride powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 1.2 nm.

[0110] Example 19 provides a continuous and dense siloxane compound shell, prepared by the following method: Step S1: Methyltrimethoxysilane (MTMS) is added to metal magnetic powder with an average particle size of 1.0 μm, and after uniform mixing, 5% ammonia water is added, and the reaction is carried out at 25°C to form polysiloxane on the surface of aluminum nitride powder particles, thus obtaining the precursor. The mass ratio of aluminum nitride powder, MTMS, and 5% ammonia water is 50:1:1.

[0111] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 70°C for 24 hours for drying, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0112] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 800°C at a rate of 5°C / min and held for 7 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the aluminum nitride powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 1.2 nm.

[0113] Example 20 provides a continuous and dense siloxane compound shell, prepared by the following method: Step S1: Methyltrimethoxysilane (MTMS) is added to alumina powder with an average particle size of 1.0 μm, and after uniform mixing, 5% ammonia water (by volume) is added. The reaction is carried out at 25°C to form polysiloxane on the surface of the aluminum nitride powder particles, thus obtaining the precursor. The mass ratio of aluminum nitride powder, MTMS, and 5% ammonia water (by volume) is 50:1:1.

[0114] Step S2: Place the precursor obtained in step S1 into a muffle furnace and heat it to 70°C for 24 hours for drying, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0115] Step S3: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 800°C at a rate of 5°C / min and held for 7 hours for calcination to densify the precursor surface. The furnace is then cooled to room temperature, resulting in a continuous and dense siloxane compound shell on the surface of the aluminum nitride powder particles. The coating thickness of the siloxane compound, i.e., the shell thickness, is 1.2 nm.

[0116] The main difference between Comparative Example 1 and Example 1 is that the average particle size of the boron nitride powder in step S1 is 0.02 μm. Everything else is the same as in Example 1.

[0117] The coating thickness of the siloxane compound obtained in this comparative example is 0.1 nm.

[0118] The main difference between Comparative Example 2 and Example 1 is that the average particle size of the boron nitride powder in step S1 is 45 μm. Everything else is the same as in Example 1.

[0119] The coating thickness of the siloxane compound obtained in this comparative example was 103.2 nm.

[0120] The main difference between Comparative Example 3 and Example 1 is that the average particle size of the boron nitride powder in step S1 is 45 μm; and the mass ratio of boron nitride powder, MTMS, and ammonia water with a volume concentration of 5% in step S1 is 40:1:1. Everything else is the same as in Example 1.

[0121] The coating thickness of the siloxane compound obtained in this comparative example was 509.2 nm.

[0122] The main difference between Comparative Example 4 and Example 1 is that the water content of the precursor in step S2 is 0.03%. Everything else is the same as in Example 1.

[0123] The coating thickness of the siloxane compound obtained in this comparative example is 1.0 nm.

[0124] The main difference between Comparative Example 5 and Example 1 is that the water content of the precursor in step S2 is 1.5%. Everything else is the same as in Example 1.

[0125] The coating thickness of the siloxane compound obtained in this comparative example is 1.1 nm.

[0126] The main difference between Comparative Example 6 and Example 1 is that the gas atmosphere used for calcination in step S3 is air. Everything else is the same as in Example 1.

[0127] The coating thickness of the siloxane compound obtained in this comparative example was 0.9 nm.

[0128] The main difference between Comparative Example 7 and Example 1 is that the calcination temperature in step S3 is 600°C, and the holding time is 4 hours. Everything else is the same as in Example 1.

[0129] The coating thickness of the siloxane compound obtained in this comparative example is 1.1 nm.

[0130] The main difference between Comparative Example 8 and Example 1 is that the calcination temperature in step S3 is 550°C, and the holding time is 5 hours. Everything else is the same as in Example 1.

[0131] The coating thickness of the siloxane compound obtained in this comparative example is 1.2 nm.

[0132] Performance characterization was performed on the filler particles with siloxane compound shells prepared in Examples 1-18 and Comparative Examples 1-8. The particle size, Q unit content, shell thickness, and moisture content after standing were tested. The results are shown in Table 1. The moisture content after standing was determined by testing the moisture content after 48 hours of open storage at 25°C and 50% RH, starting from the initial preparation stage. Q unit content refers to the content of the prepared solid... 29 The ratio of the peak integral area in the Si-NMR nuclear magnetic resonance spectrum in the range of -80ppm to -120ppm to the peak integral area in the range of +20ppm to -120ppm.

[0133] Table 1 As shown in Table 1: (1) As shown in Examples 1-18, the present invention uses T-unit siloxane raw materials to form a polysiloxane layer on the surface of filler powder particles; then, through drying treatment, the polysiloxane layer is in a low moisture content state, which promotes the condensation of silanol groups and makes the organic groups of T-unit siloxane arranged in an orderly manner to form a uniform polysiloxane layer, which is conducive to the formation of dense siloxane compounds; finally, through calcination treatment, some of the organic groups of T-unit siloxane are removed and converted into Q units, so that the uniform polysiloxane layer is transformed into a dense siloxane compound layer. The filler particles with a siloxane compound shell obtained thereby have the excellent characteristic of low moisture content after placement. Since the powder with the siloxane compound shell is used in semiconductor fillers, such as boron nitride powder, PQ60 powder, alumina powder, and aluminum nitride powder coated with siloxane compound shells, it has a dense siloxane compound shell, which can reduce the water absorption of the filler powder during the shelf life, thereby reducing the dielectric loss during the operation of electronic devices and reducing the conduction risk caused by high water content.

[0134] (2) Regarding the method of coating the surface of filler powder with a low-moisture shell layer in this invention, the selection conditions for the particle size of the core filler powder are analyzed as follows: A comparison between Comparative Examples 1 and 2 and Example 1 shows that the particle sizes of the boron nitride powder in Comparative Examples 1 and 2 are 0.02 μm and 45 μm, respectively. The water content of the product is significantly higher than that of Example 1. The reason for this is that if the boron nitride powder particle size is too small, it is easy to agglomerate, and the T-unit siloxane is difficult to be uniformly adsorbed on the surface of the boron nitride powder. Therefore, it is difficult to form a uniform polysiloxane film layer, resulting in poor coating effect. Since the thickness of the siloxane compound to be coated is small, the amount of T-unit siloxane raw material added is small. If the boron nitride powder particle size is too large, the siloxane will also have the problem of being difficult to be uniformly adsorbed on the surface of the boron nitride powder, resulting in uneven coating. Uneven coating will lead to increased water absorption after the product is placed. Therefore, in order to coat the surface of the boron nitride powder with a low water content shell using the method of the present invention, the particle size of the boron nitride powder needs to be controlled within a suitable range.

[0135] Comparative analysis of the characterization data from Examples 1, 6-7, and Comparative Examples 1-2 shows that the preferred particle size of the boron nitride powder of the present invention is 0.05-40 μm. Furthermore, comparative analysis of Example 8 with Examples 7 and 1 shows that the particle size of the boron nitride powder in Example 7 is larger than that in Example 1. To increase the coating amount in Example 7 and thus improve the uniformity and density of the coating layer, this can be achieved by increasing the amount of added T-unit siloxane. For example, Example 8 increased the amount of added siloxane, resulting in a better coating uniformity than Example 7 (reflected in the lower water absorption of Example 8). However, comparing Comparative Example 3 and Comparative Example 2, when the particle size of the boron nitride powder in Comparative Example 2 increased to 45 μm, despite the addition of siloxane in Comparative Example 3, the water absorption of Comparative Example 3 was greater than that of Comparative Example 2. Furthermore, agglomeration of the boron nitride powder was observed during the preparation process. This suggests that excessive addition of siloxane per unit (T) increases the viscosity of the boron nitride powder, preventing the siloxane from uniformly adsorbing onto the surface to form a polysiloxane film, ultimately leading to a decrease in the density of the calcined siloxane compound film. Therefore, it is further speculated that to achieve a uniform and dense siloxane compound shell with low water content in the product, this method requires controlling the particle size of the boron nitride powder within a certain range.

[0136] (3) Analysis of the precursor moisture content conditions in the method of coating a low-moisture shell layer on the surface of filler powder according to the present invention: A comparison of Comparative Examples 4-5 with Example 1 shows that the moisture content of the precursors in Comparative Examples 4 and 5 after drying is 0.03% and 1.5%, respectively. The moisture content of the products after storage is significantly higher than that in Example 1. Therefore, keeping the moisture content of the precursor within a certain range is beneficial for the formation of dense siloxane compounds. The preferred moisture content of the precursor is a low moisture content of 0.1% to 1%. The reason for this is that keeping the polysiloxane layer in a low moisture content state of 0.1% to 1% promotes the rotation and orderly arrangement of the organic groups of the T-unit siloxane, resulting in a uniform polysiloxane layer. This leads to a denser siloxane compound shell layer with lower porosity.

[0137] (4) Analysis of the precursor calcination gas atmosphere conditions in the method of coating a low-moisture shell layer on the surface of filler powder according to the present invention: A comparison between Comparative Example 6 and Example 1 shows that the gas atmosphere for the calcination treatment in step S3 of Comparative Example 6 was air, and the moisture content of Comparative Example 6 increased significantly after placement. The reason for this is that air contains the active gas oxygen, which reacts with the carbon formed by the decomposition of organic groups. After carrying away the carbon, defects are formed at the carbon sites, resulting in high porosity, a non-dense shell layer, and high water absorption in the product. When calcination is carried out in an inert atmosphere, although the moisture released by the condensation of silanol groups also reacts with carbon and carries away the carbon, the moisture content is low, so the rate of carbon removal is slow. The continuous condensation of silanol groups in the film layer can repair the defect sites, thus resulting in low porosity.

[0138] (5) Regarding the method of coating a low-moisture shell layer on the surface of filler powder according to the present invention, the conditional analysis of the Q unit content of the shell layer is as follows: Comparative analysis of Comparative Examples 7-8 and Example 1 shows that Comparative Examples 7 and 8, by adjusting the temperature and time of the calcination step, reduced the conversion of T units to Q units, resulting in Q unit contents of 48.0% and 37.2% for the products of Comparative Examples 7 and 8, respectively. The resulting boron nitride powder with the shell layer had a moisture content of 216.7 ppm / m³ after standing. 2 284.5ppm / m 2 The moisture content increased significantly. Therefore, it can be concluded that the Q unit content needs to be controlled within a certain range when coating the surface of boron nitride powder with a low-moisture shell, as required by this invention.

[0139] (6) Analysis of the selection of core material in the method of coating a low-moisture shell layer on the surface of filler powder in this invention: A comparative analysis of Examples 1 and 16-20 shows that the selection of core material may affect the moisture content after placement. The core materials of Examples 1, 16, and 17 are boron nitride, diamond, and aluminum nitride, respectively, which are filler materials with high surface energy. The overall moisture content of their products after placement is higher than that of the products of Examples 18, 19, and 20. In contrast, the core materials of Examples 18, 19, and 20 are organic phosphorus flame retardant powder, magnetic metal powder, and alumina powder, which have relatively lower surface energies than boron nitride, diamond, and aluminum nitride. It is speculated that core materials with high surface energy, after being coated with a shell layer, may form tiny voids between themselves and the shell layer, resulting in relatively high porosity and water absorption. Ultimately, core materials with high surface energy generally exhibit a higher moisture content than core materials with low surface energy. Furthermore, it can be understood that the final water content of the preparation containing the shell provided by the present invention may be related to the core material.

[0140] The organophosphorus flame retardant powder used in the embodiments of the present invention was purchased from Daiichi Kogyo Pharmaceutical Co., Ltd., product model PQ-60; the raw materials boron nitride, alumina, and aluminum nitride used in the embodiments of the present invention were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.

[0141] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0142] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A low-water-content shell, characterized in that: The shell layer comprises siloxane compounds; The siloxane compound is in the range of +20ppm to -120ppm. 29 Response in the Si-NMR nuclear magnetic resonance spectrum; In solid 29 In the Si-NMR nuclear magnetic resonance spectrum, the ratio of the peak integrated area of ​​the shell in the range of -80ppm to -120ppm to the range of +20ppm to -120ppm is 50 to 99.5:

100.

2. The low water content shell as described in claim 1, characterized in that: After being placed at 25°C and 50% RH for 48 hours, the Karl Fischer moisture content of the product containing this shell at 200°C is no higher than 160 ppm / m³. 2 .

3. A low-water-content shell as described in claim 1, characterized in that: The siloxane compound is prepared from siloxanes containing more than 90% wt T units; Wherein, T unit = R1SiO3-, R1 is a hydrogen atom or a hydrocarbon group of 1 to 16 carbon atoms that can be chosen independently.

4. A low-water-content shell as described in claim 3, characterized in that: The T unit siloxane is selected from hydrocarbon-trialkoxysilane and hydrocarbon-trichlorosilane.

5. A low-water-content shell as described in claim 1, characterized in that: The thickness of the shell ranges from 0.5 nm to 300 nm.

6. A method for coating a low-water-content shell as described in any one of claims 1 to 5, characterized in that: Includes the following steps: Step S1: Add T units of siloxane to the filler powder to be coated, and react to form polysiloxane on the surface of the powder to be coated, thus obtaining the precursor. Step S2: Perform drying treatment to bring the precursor to a low moisture content state; Step S3: Calcination treatment is performed to densify the surface of the precursor and obtain a shell layer on the surface of the filler powder. Wherein, T unit = R1SiO3-, R1 is a hydrogen atom or a hydrocarbon group of 1 to 16 carbon atoms that can be chosen independently.

7. The coating method as described in claim 6, characterized in that: In step S1, an alkaline aqueous solution is added to carry out the reaction.

8. The coating method as described in claim 7, characterized in that: Silica powder was also added to the reaction.

9. The coating method as described in claim 8, characterized in that: The particle size of the silica powder is 10–100 nm.

10. The coating method as described in claim 6, characterized in that: In step S1, the particle size of the filler powder is 0.05–40 μm.

11. The coating method as described in claim 6, characterized in that: In step S2, the drying process reduces the moisture content of the precursor to 0.1-1%.

12. The coating method as described in claim 6 or 11, characterized in that: The drying process involves heating to 50–200°C and drying for 6–24 hours.

13. The coating method as described in claim 6, characterized in that: In step S3, the calcination process is carried out in an inert gas atmosphere.

14. The coating method as described in claim 6, characterized in that: In step S3, the calcination temperature is 600–1200℃.

15. The coating method as described in claim 14, characterized in that: In step S3, the calcination treatment time is 6 to 72 hours.

16. A filler powder, characterized in that: Includes the shell as described in any one of claims 1 to 5, or includes the shell obtained by the encapsulation method as described in any one of claims 6 to 15.

17. The filler powder according to claim 16, characterized in that: The filler powder is selected from one or more of thermally conductive materials and organophosphorus flame retardants.

18. The filler powder according to claim 17, characterized in that: The filler powder is selected from one or more of boron nitride, PQ60, alumina, and aluminum nitride.

19. The use of the filler powder as described in any one of claims 16 to 18 in the preparation of semiconductor packaging materials or substrate materials.

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