A modified diamond powder, its preparation method and application

Abstract

This invention relates to the field of filler technology, and discloses a modified diamond powder, its preparation method, and its applications. The invention uses T-unit siloxane as a raw material to form a polysiloxane layer on the surface of diamond micropowder; 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; finally, through calcination, the organic groups of the T-unit siloxane are removed, transforming the uniform polysiloxane layer into a dense silica layer. The resulting modified diamond has a low porosity.

Description

Technical Field

[0001] This invention relates to the field of filler technology, and in particular to a modified diamond powder, its preparation method, and its application. Background Technology

[0002] With the rapid development of microelectronics and communication technologies, semiconductor chips are constantly evolving towards higher integration, miniaturization, higher frequency, and higher power. The power density of core devices is increasing dramatically, and the heat generated during operation is also increasing significantly. Heat dissipation has become an urgent problem to be solved in the field of microelectronics.

[0003] Uneven surfaces between heat-generating devices and heat sinks result in a small effective contact area, making it difficult for heat to dissipate. This leads to low heat sink efficiency and shortens the power consumption and lifespan of electronic components. Filling the gaps between the heat-generating device and heat sink surfaces with thermal interface materials eliminates air and establishes an effective heat conduction channel between the electronic component and the heat sink, allowing the heat sink to function optimally and significantly improving heat dissipation. Therefore, this field places higher demands on electronic packaging and heat dissipation materials.

[0004] Diamond has a thermal conductivity of approximately 1000-2000 W / m·K, making it one of the most thermally conductive substances in nature. It also possesses excellent properties such as high hardness, good chemical stability, and a low coefficient of thermal expansion, making it a suitable interface material. However, due to its extremely strong chemical inertness—becoming inert to acids, alkalis, and salts at room temperature—it is difficult to form chemical bonds with the binder matrix. Furthermore, diamond's tight covalent structure results in a high surface energy, leading to poor wettability with the binder. Therefore, diamond is difficult to directly use as a filler material in the gaps between the heat-generating device and the heat sink surface.

[0005] To enhance the bonding performance of diamond with other materials, existing technologies, such as Chinese patent application publication number CN114477167A, disclose a modified diamond composite functional material and its preparation method. This patent proposes to tightly coat the surface of diamond micropowder with a layer of nano-amorphous SiO2 film that can improve the surface reactivity of diamond micropowder. The active oxygen groups in the film can form a good cross-linking reaction with the -OH groups in the resin, thereby improving the adhesion between diamond and the resin binder. However, the diamond micropowder in this patent has a rough surface, resulting in a SiO2 film with numerous pores. Since the SiO2 film coating used in this patent to obtain reactive diamond micropowder is intended for use in diamond abrasives, the modified diamond micropowder only needs to have active oxygen groups grafted onto its surface; the porosity of the diamond micropowder is not a concern. However, in the semiconductor field, increased filler porosity means increased specific surface area. The functional relationship between particle specific surface area and diameter is: specific surface area = constant / particle diameter. This reciprocal relationship shows that a decrease in diameter leads to a sharp increase in specific surface area. This increase in specific surface area leads to increased water adsorption, ultimately affecting the performance of semiconductor devices.

[0006] Therefore, in the semiconductor field, modifying diamond requires not only improving the bonding ability between diamond and resin, but also reducing the water content of the modified diamond. Based on the above, this application presents a series of improvements and studies on modified diamond. Summary of the Invention

[0007] In the semiconductor field, materials with high thermal conductivity are needed as fillers between electronic components and heat sinks. To solve this problem, this invention provides a modified diamond powder, its preparation method, and its application.

[0008] First, this invention provides a modified diamond powder having a core-shell structure with diamond as the core and siloxane compounds as the shell, exhibiting good surface wettability; and making it suitable for solid... 29 The ratio of peak integral areas in the -80ppm to -120ppm range to the +20ppm to -120ppm range in the Si-NMR nuclear magnetic resonance spectrum is 50 to 99.5:100. When used in the field of semiconductor fillers, it can have low water absorption and excellent dielectric properties after long-term storage.

[0009] Secondly, the present invention provides a method for preparing modified diamond powder, which makes the siloxane compounds on the surface of the diamond powder more dense and has a low water content after being left for a long time by selecting the best raw materials and optimizing the preparation process.

[0010] Furthermore, this invention provides the application of modified diamond powder as a filler in the preparation of packaging materials or substrate materials in the semiconductor field.

[0011] The specific technical solution of this invention is as follows: In a first aspect, the present invention provides a modified diamond powder. The modified diamond is characterized by: It has a core-shell structure with a diamond core and a siloxane compound shell; in solid... 29 In the Si-NMR nuclear magnetic resonance spectrum, the ratio of the peak integral area of ​​the modified diamond in the range of -80ppm to -120ppm to the range of +20ppm to -120ppm is 50 to 99.5:100.

[0012] In the semiconductor field, to ensure the heat sink functions optimally, an effective heat conduction path needs to be established between the electronic components and the heat sink. Therefore, materials with high thermal conductivity are required as fillers to fill the gaps between the heat-generating components and the heat sink surface. Diamond, as one of the most thermally conductive substances in nature, has great potential as a filler in the semiconductor field. However, due to its poor wettability, diamond is not suitable for direct application as a semiconductor filler.

[0013] Therefore, based on the above problems, this invention provides a modified diamond powder with a core-shell structure consisting of a diamond core and a siloxane compound shell. The siloxane compound enhances the activity of the diamond in tightly bonding with other substances, and when used as a filler, it allows the inherent high thermal conductivity of diamond to be utilized, thus bridging the gap between heat-generating devices and heat sinks. This invention's modified diamond 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.

[0014] In the semiconductor field, fillers are generally not used directly after preparation; they have a shelf life and therefore absorb moisture during storage. The modified diamond powder provided by this invention absorbs less water after storage, which has a significant advantage in reducing dielectric loss caused by water absorption.

[0015] In the modified diamond powder of this invention, to ensure that the siloxane compound is uniformly coated on the diamond surface, the amount of the siloxane compound needs to be within a certain range. If the amount of siloxane compound is too small, it cannot completely coat the diamond surface. When mixed with resin and filled between electronic devices and heat sinks, the unmodified parts of the diamond are difficult to wet with the resin, resulting in many small pores in the diamond-resin mixture. This not only reduces heat dissipation but also causes water absorption problems later, affecting the operation of electronic devices. If the amount of siloxane compound is too large, the modified diamond will agglomerate, making it difficult to mix evenly with the resin. The mixture formed by the product and the resin will peel off, similarly increasing the pores in the diamond-resin mixture, affecting heat dissipation and causing water absorption problems. Therefore, this invention provides a modified diamond, which in solid form... 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.

[0016] Preferably, 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, which can be independently selected.

[0017] The modified diamond powder siloxane compound film provided by this invention has high density and continuity. The siloxane compound film prepared using polysiloxane containing more than 90% wt T units as raw material has high density. To coat diamond micropowder, the silanol groups of the siloxane need to be condensed to form a polysiloxane film layer on the surface of the diamond micropowder. Then, the siloxane compound is obtained through heat treatment. During the formation of the polysiloxane film layer, since T-unit molecules rotate more freely than Q-unit molecules, to form a uniform and dense film layer, the modified diamond film of 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.

[0018] Further preferred, the T-unit siloxane is selected from hydrocarbon-trialkoxysilane and hydrocarbon-trichlorosilane.

[0019] Preferably, the modified diamond provided by the present invention, after being placed in an environment of 25°C and 50% RH for 48 hours, has a Karl Fischer moisture content at 200°C not exceeding 150 ppm / m. 2 .

[0020] Because the modified diamond provided by this invention has a dense and continuous shell of siloxane compounds, it has the excellent property of low water absorption after storage, which can reduce the water absorption of modified diamond powder during the shelf life. As a filler for electronic devices, it can make the device have less dielectric loss during operation.

[0021] Secondly, the present invention provides a method for preparing the above-mentioned modified diamond powder, comprising the following steps: Step S1: Add T units of siloxane to diamond micro powder and react to form polysiloxane on the surface of diamond micro powder to obtain 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 modified diamond powder. Wherein, T unit = R1SiO3-, R1 is a hydrogen atom or a hydrocarbon group of 1 to 16 independently selectable carbon atoms, and the modified diamond powder has a dense siloxane compound shell.

[0022] To effectively utilize diamond as a filler between electronic components and heat sinks, it is necessary to improve the wettability of the diamond surface. Existing technologies enhance diamond surface activity by coating it with an active film. For example, patent application CN114477167A describes a method of tightly coating diamond micropowder with a nano-amorphous SiO2 film using tetraethyl orthosilicate to improve the surface reactivity of the diamond micropowder. However, the SiO2 film in this patent has a rough surface with numerous pores, leading to significant water adsorption after placement. While the diamond micropowder is used in diamond abrasives, where water absorption is not a concern, in the semiconductor field, increased water adsorption by the filler can cause dielectric loss in electronic devices, affecting their operation.

[0023] To improve the density of the siloxane compound film on diamond and reduce the water absorption of the finished product after placement, this invention provides a method for preparing the modified diamond powder described above, which forms a uniform, continuous, and dense siloxane compound film on the diamond surface. First, this invention uses T-unit siloxane raw materials to form a polysiloxane layer on the surface of diamond micropowder. Then, through drying, the polysiloxane layer is brought to a low moisture content state, promoting the condensation of silanol groups and allowing 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.

[0024] The conditions for the formation of a dense siloxane compound shell on the diamond surface according to the present invention include the following three aspects: ① Because T-unit siloxanes are polar, they can be rapidly adsorbed onto the diamond surface when mixed with diamond micropowder to form a polysiloxane film. Therefore, the first condition of the preparation method of this invention is to use T-unit siloxanes as raw materials. Since the molecules of T-units can rotate freely relatively easily, the first condition of using T-unit siloxanes as raw materials is a prerequisite for step S2 of this invention, which promotes the rotation and optimizes the arrangement of the organic groups of siloxanes by keeping the polysiloxane film in a low moisture content state.

[0025] ② The second condition in the preparation method of this invention is drying to bring the polysiloxane layer to a low moisture content state, which promotes the rotation and orderly arrangement of the organic groups of the T-unit siloxane, resulting in a uniform polysiloxane layer. A uniform polysiloxane layer is beneficial for the formation of a uniform and dense siloxane compound layer. ③ The third condition is to densify the polysiloxane layer by removing the organic groups through calcination. Under this condition, the uniform polysiloxane layer is transformed into a uniform and dense siloxane compound shell.

[0026] As a preferred embodiment of the above preparation method, in step S1, the particle size of the diamond micro powder is 0.05–40 μm.

[0027] To form a uniform siloxane compound shell on the surface of diamond micropowder, the particle size of the diamond micropowder needs to be within the range of 0.05–40 μm. If the particle size of the diamond micropowder is too small, the micropowder is prone to agglomeration, and it is difficult for T-unit siloxane to be uniformly adsorbed on the surface of the diamond micropowder. Therefore, it is difficult to form a uniform polysiloxane film, resulting in discontinuous 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 particle size of the diamond micropowder is too large, the siloxane will also have the problem of being difficult to uniformly adsorb on the surface of the diamond micropowder, resulting in uneven coating and high porosity. In this case, if the coating thickness and the amount of added siloxane raw material are increased to promote uniform coating, the resulting diamond micropowder will exhibit agglomeration.

[0028] Preferably, in step S1, the mass ratio of diamond micro powder to the added T-unit siloxane is 100:0.2-10.

[0029] As a preferred embodiment of the above preparation method, in step S1, an alkaline aqueous solution is added to carry out the reaction.

[0030] Step S1 involves the adsorption of T-unit siloxane onto the diamond surface 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.

[0031] Further optimization involves adding silica powder in step S1 to carry out the reaction.

[0032] Further preferred, the particle size of the silica powder is 10–100 nm.

[0033] 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 diamond micropowder 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 the porosity of the siloxane compound shell coated on the diamond 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.

[0034] As a preferred embodiment of the above preparation method, in step S2, the drying treatment reduces the water content of the precursor to 0.1-1%.

[0035] Maintaining a low moisture content in the polysiloxane layer promotes the rotation and orderly arrangement of the organic groups in the T-unit siloxane, resulting in a uniform polysiloxane layer and a denser, more uniform siloxane compound shell. The highest density of the siloxane compound shell formed on the diamond surface is achieved when the precursor's water content is 0.1–1%.

[0036] As a preferred method of the above preparation method, the drying treatment method is: heating to 50-200℃ and drying for 6-24 hours.

[0037] As a preferred embodiment of the above preparation method, in step S3, the calcination treatment is carried out under an inert gas atmosphere.

[0038] As a preferred embodiment of the above preparation method, in step S3, the calcination temperature is 600–1500°C and the time is 6–72 hours.

[0039] 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 600–1500℃, and the preferred treatment time is 6–72 hours.

[0040] As a preferred embodiment of the above preparation method, before step S1, the diamond micro powder is pretreated to make the conductivity ≤20μs / cm.

[0041] Excessively high electrical conductivity increases the electrostatic effect between powder particles, making it difficult to mix uniformly with T-unit siloxane. This ultimately results in an uneven shell of the siloxane compound and a high water absorption rate after storage. Therefore, in the method of this invention, the electrical conductivity of the diamond micron powder raw material needs to be reduced to 20 μS / cm or below.

[0042] Specifically, the pretreatment method can be as follows: soak diamond micro powder in ultrapure water and isopropanol in sequence, centrifuge at 1500-2000 rpm for 10-15 min in sequence, repeat the above steps several times until the conductivity is ≤20μs / cm, and then vacuum dry to obtain pretreated diamond micro powder.

[0043] Thirdly, the present invention also provides the application of the above-mentioned modified diamond powder in the preparation of semiconductor packaging materials or substrate materials.

[0044] In the semiconductor field, assembling passive components, semiconductor components, electroacoustic devices, display devices, optical devices, and radio frequency devices into equipment requires circuit board substrate materials such as high-density interconnect boards, high-frequency and high-speed boards, and motherboards. These substrate materials are generally composed mainly of fillers and organic polymers such as resins. Applying the modified diamond powder provided above in the present invention to the preparation of semiconductor packaging materials or substrate materials can effectively meet the heat dissipation requirements of semiconductor packaging materials or substrate materials.

[0045] Compared with the prior art, the present invention has the following technical effects: (1) This invention provides a modified diamond powder with a core-shell structure consisting of a diamond core and a siloxane compound shell, which is used in solid... 29 In the Si-NMR nuclear magnetic resonance spectrum, the ratio of the peak integral area of ​​the modified diamond of this invention in the -80ppm to -120ppm range to the +20ppm to -120ppm range is 50–99.5:100. The modified diamond powder of this invention can enhance the activity of diamond in tightly bonding with other substances through siloxane compounds. Using it as a filler allows the inherent excellent characteristic of diamond's high thermal conductivity to be utilized, achieving a bridging effect for efficient heat conduction from heat-generating devices to heat sinks. Furthermore, the modified diamond powder of this invention also has the excellent characteristic of low water absorption after storage, which can reduce the water absorption of diamond powder during its shelf life. As a filler in electronic devices, it can result in lower dielectric loss.

[0046] (2) This invention uses T-unit siloxane raw materials to form a polysiloxane layer on the surface of diamond micropowder; then, through drying treatment, 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; finally, through calcination treatment, some of the organic groups of the T-unit siloxane are removed and converted into Q units, transforming the uniform polysiloxane layer into a dense siloxane compound shell. Therefore, this invention provides a diamond powder with a dense siloxane compound shell, which has low water absorption after being placed. Detailed Implementation

[0047] 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.

[0048] The particle moisture content was measured at 200 degrees Celsius using a Karl Fischer moisture analyzer (Mitsubishi Chemical CA-310) and the coulometric method. The unit for moisture content in the performance testing was ppm / m³. 2 The 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).

[0049] 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.

[0050] 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 integral area in the range of +20ppm to -120ppm, and the content of Q units is represented by the peak integral area in the range of -80ppm to -120ppm. The modified diamond particles provided by this invention have a peak integral area ratio of 50 to 99.5:100 in the range of -80ppm to -120ppm to +20ppm.

[0051] The thickness of the modified diamond powder coating with siloxane compounds, i.e. the thickness of the modified diamond powder shell, was obtained by high-resolution transmission electron microscopy.

[0052] Example 1 A modified diamond powder with a dense, continuous siloxane compound shell is provided, which is prepared by the following method: Step S1: Immerse diamond micro powder with an average particle size of 0.5 μm in ultrapure water and centrifuge at 2000 rpm for 10 min. Then immerse it in isopropanol and centrifuge at 2000 rpm for 10 min. Repeat the above steps twice. Vacuum dry to obtain pretreated diamond micro powder. Its conductivity was measured to be 9.8 μs / cm.

[0053] Step S2: Add methyltrimethoxysilane (MTMS) to the pretreated diamond micro powder, mix thoroughly, then add 5% ammonia water (by volume), and react at 25°C to form polysiloxane on the surface of the diamond micro powder, thus obtaining the precursor. The mass ratio of diamond micro powder, MTMS, and 5% ammonia water is 100:1.7:1.7.

[0054] Step S3: Place the precursor obtained in step S2 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%.

[0055] Step S4: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 750°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The precursor is then cooled to room temperature in the furnace to obtain modified diamond powder with a dense, continuous siloxane compound coating. The coating thickness of the siloxane compound is 1.2 nm.

[0056] Example 2 A modified diamond powder with a dense, continuous siloxane compound shell is provided, which is prepared by the following method: Step S1: Immerse diamond micro powder with an average particle size of 0.5 μm in ultrapure water and centrifuge at 2000 rpm for 10 min. Then immerse it in isopropanol and centrifuge at 2000 rpm for 10 min. Repeat the above steps twice. Vacuum dry to obtain pretreated diamond micro powder. Its conductivity was measured to be 9.8 μs / cm.

[0057] Step S2: Add methyltrimethoxysilane (MTMS) to the pretreated diamond micro powder, mix thoroughly, then add 5% ammonia water (by volume), and react at 25°C to form polysiloxane on the surface of the diamond micro powder, thus obtaining the precursor. The mass ratio of diamond micro powder, MTMS, and 5% ammonia water is 100:1.7:1.7.

[0058] Step S3: Place the precursor obtained in step S2 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 0.2%.

[0059] Step S4: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 750°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The precursor is then cooled to room temperature in the furnace to obtain modified diamond powder with a dense, continuous siloxane compound coating. The coating thickness of the siloxane compound is 1.0 nm.

[0060] Example 3 A modified diamond powder with a dense, continuous siloxane compound shell is provided, which is prepared by the following method: Step S1: Immerse diamond micro powder with an average particle size of 0.5 μm in ultrapure water and centrifuge at 2000 rpm for 10 min. Then immerse it in isopropanol and centrifuge at 2000 rpm for 10 min. Repeat the above steps twice. Vacuum dry to obtain pretreated diamond micro powder. Its conductivity was measured to be 9.8 μs / cm.

[0061] Step S2: Add methyltrimethoxysilane (MTMS) to the pretreated diamond micro powder, mix thoroughly, then add 5% ammonia water (by volume), and react at 25°C to form polysiloxane on the surface of the diamond micro powder, thus obtaining the precursor. The mass ratio of diamond micro powder, MTMS, and 5% ammonia water is 100:1.7:1.7.

[0062] Step S3: Place the precursor obtained in step S2 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%.

[0063] Step S4: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 750°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The precursor is then cooled to room temperature in the furnace to obtain modified diamond powder with a dense, continuous siloxane compound coating. The coating thickness of the siloxane compound is 1.8 nm.

[0064] Example 4 A modified diamond powder with a dense, continuous siloxane compound shell is provided, which is prepared by the following method: Step S1: Immerse diamond micro powder with an average particle size of 1 μm in ultrapure water and centrifuge at 2000 rpm for 10 min. Then immerse it in isopropanol and centrifuge at 2000 rpm for 10 min. Repeat the above steps twice. Vacuum dry to obtain pretreated diamond micro powder. Its conductivity was measured to be 9.8 μs / cm.

[0065] Step S2: Add methyltrimethoxysilane (MTMS) to the pretreated diamond micro powder, mix thoroughly, then add 5% ammonia water (by volume), and react at 25°C to form polysiloxane on the surface of the diamond micro powder, thus obtaining the precursor. The mass ratio of diamond micro powder, MTMS, and 5% ammonia water is 100:1.7:1.7.

[0066] Step S3: Place the precursor obtained in step S2 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%.

[0067] Step S4: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 750°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The precursor is then cooled to room temperature in the furnace to obtain modified diamond powder with a dense, continuous siloxane compound coating. The coating thickness of the siloxane compound is 11.0 nm.

[0068] Example 5 A modified diamond powder with a dense, continuous siloxane compound shell is provided, which is prepared by the following method: Step S1: Immerse diamond micro powder with an average particle size of 10 μm in ultrapure water and centrifuge at 2000 rpm for 10 min. Then immerse it in isopropanol and centrifuge at 2000 rpm for 10 min. Repeat the above steps twice. Vacuum dry to obtain pretreated diamond micro powder. Its conductivity was measured to be 9.8 μs / cm.

[0069] Step S2: Add methyltrimethoxysilane (MTMS) to the pretreated diamond micro powder, mix thoroughly, then add 5% ammonia water (by volume), and react at 25°C to form polysiloxane on the surface of the diamond micro powder, thus obtaining the precursor. The mass ratio of diamond micro powder, MTMS, and 5% ammonia water is 100:1.7:1.7.

[0070] Step S3: Place the precursor obtained in step S2 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%.

[0071] Step S4: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 750°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The precursor is then cooled to room temperature in the furnace to obtain modified diamond powder with a dense, continuous siloxane compound coating. The coating thickness of the siloxane compound is 123.0 nm.

[0072] Example 6 A modified diamond powder with a dense, continuous siloxane compound shell is provided, which is prepared by the following method: Step S1: Immerse diamond micro powder with an average particle size of 0.05 μm in ultrapure water and centrifuge at 2000 rpm for 10 min. Then immerse it in isopropanol and centrifuge at 2000 rpm for 10 min. Repeat the above steps twice. Vacuum dry to obtain pretreated diamond micro powder. Its conductivity was measured to be 9.8 μs / cm.

[0073] Step S2: Add methyltrimethoxysilane (MTMS) to the pretreated diamond micro powder, mix thoroughly, then add 5% ammonia water (by volume), and react at 25°C to form polysiloxane on the surface of the diamond micro powder, thus obtaining the precursor. The mass ratio of diamond micro powder, MTMS, and 5% ammonia water is 100:1.7:1.7.

[0074] Step S3: Place the precursor obtained in step S2 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%.

[0075] Step S4: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 750°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The precursor is then cooled to room temperature in the furnace to obtain modified diamond powder with a dense, continuous siloxane compound coating. The coating thickness of the siloxane compound is 0.5 nm.

[0076] Example 7 A modified diamond powder with a dense, continuous siloxane compound shell is provided, which is prepared by the following method: Step S1: Immerse diamond micro powder with an average particle size of 40 μm in ultrapure water and centrifuge at 2000 rpm for 10 min. Then immerse it in isopropanol and centrifuge at 2000 rpm for 10 min. Repeat the above steps twice. Vacuum dry to obtain pretreated diamond micro powder. Its conductivity was measured to be 9.8 μs / cm.

[0077] Step S2: Add methyltrimethoxysilane (MTMS) to the pretreated diamond micro powder, mix thoroughly, then add 5% ammonia water (by volume), and react at 25°C to form polysiloxane on the surface of the diamond micro powder, thus obtaining the precursor. The mass ratio of diamond micro powder, MTMS, and 5% ammonia water is 100:1.7:1.7.

[0078] Step S3: Place the precursor obtained in step S2 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%.

[0079] Step S4: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 750°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The precursor is then cooled to room temperature in the furnace to obtain modified diamond powder with a dense, continuous siloxane compound coating. The coating thickness of the siloxane compound is 175.0 nm.

[0080] Example 8 A modified diamond powder with a dense, continuous siloxane compound shell is provided, which is prepared by the following method: Step S1: Immerse diamond micro powder with an average particle size of 40 μm in ultrapure water and centrifuge at 2000 rpm for 10 min. Then immerse it in isopropanol and centrifuge at 2000 rpm for 10 min. Repeat the above steps twice. Vacuum dry to obtain pretreated diamond micro powder. Its conductivity was measured to be 9.8 μs / cm.

[0081] Step S2: Add methyltrimethoxysilane (MTMS) to the pretreated diamond micro powder, mix thoroughly, then add 5% ammonia water (by volume), and react at 25°C to form polysiloxane on the surface of the diamond micro powder, thus obtaining the precursor. The mass ratio of diamond micro powder, MTMS, and 5% ammonia water is 40:1:1.

[0082] Step S3: Place the precursor obtained in step S2 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%.

[0083] Step S4: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 750°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The precursor is then cooled to room temperature in the furnace to obtain modified diamond powder with a dense, continuous siloxane compound coating. The coating thickness of the siloxane compound is 300.0 nm.

[0084] Example 9 A modified diamond powder with a dense, continuous siloxane compound shell is provided, which is prepared by the following method: Step S1: Immerse diamond micro powder with an average particle size of 10 μm in ultrapure water and centrifuge at 2000 rpm for 10 min. Then immerse it in isopropanol and centrifuge at 2000 rpm for 10 min. Repeat the above steps twice. Vacuum dry to obtain pretreated diamond micro powder. Its conductivity was measured to be 9.8 μs / cm.

[0085] Step S2: Methyltrimethoxysilane (MTMS) is added to the pretreated diamond micropowder. After mixing evenly, 5% (v / v) ammonia water and nano-silica powder are added. The mixture is reacted at 25°C to form polysiloxane on the surface of the diamond micropowder, thus obtaining the precursor. The mass ratio of diamond micropowder, MTMS, 5% (v / v) ammonia water, and nano-silica powder is 100:3:3:0.017. The average particle size of the nano-silica powder is 30 nm.

[0086] Step S3: Place the precursor obtained in step S2 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%.

[0087] Step S4: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 650°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The precursor is then cooled to room temperature in the furnace to obtain modified diamond powder with a dense, continuous siloxane compound coating. The coating thickness of the siloxane compound is 126.1 nm.

[0088] Example 10 A modified diamond powder with a dense, continuous siloxane compound shell is provided, which is prepared by the following method: Step S1: Immerse diamond micro powder with an average particle size of 10 μm in ultrapure water and centrifuge at 2000 rpm for 10 min. Then immerse it in isopropanol and centrifuge at 2000 rpm for 10 min. Repeat the above steps twice. Vacuum dry to obtain pretreated diamond micro powder. Its conductivity was measured to be 9.8 μs / cm.

[0089] Step S2: Methyltrimethoxysilane (MTMS) is added to the pretreated diamond micropowder. After mixing evenly, 5% (v / v) ammonia water and nano-silica powder are added. The mixture is reacted at 25°C to form polysiloxane on the surface of the diamond micropowder, thus obtaining the precursor. The mass ratio of diamond micropowder, MTMS, 5% (v / v) ammonia water, and nano-silica powder is 100:3:3:0.017. The average particle size of the nano-silica powder is 10 nm.

[0090] Step S3: Place the precursor obtained in step S2 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%.

[0091] Step S4: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 650°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The precursor is then cooled to room temperature in the furnace to obtain modified diamond powder with a dense, continuous siloxane compound coating. The coating thickness of the siloxane compound is 117.3 nm.

[0092] Example 11 A modified diamond powder with a dense, continuous siloxane compound shell is provided, which is prepared by the following method: Step S1: Immerse diamond micro powder with an average particle size of 10 μm in ultrapure water and centrifuge at 2000 rpm for 10 min. Then immerse it in isopropanol and centrifuge at 2000 rpm for 10 min. Repeat the above steps twice. Vacuum dry to obtain pretreated diamond micro powder. Its conductivity was measured to be 9.8 μs / cm.

[0093] Step S2: Add methyltrimethoxysilane (MTMS) to the pretreated diamond micropowder, mix thoroughly, then add 5% (v / v) ammonia water and nano-silica powder. React at 25°C to form polysiloxane on the surface of the diamond micropowder, obtaining the precursor. The mass ratio of diamond micropowder, MTMS, 5% (v / v) ammonia water, and nano-silica powder is 100:3:3:0.017. The average particle size of the nano-silica powder is 100 nm.

[0094] Step S3: Place the precursor obtained in step S2 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%.

[0095] Step S4: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 650°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The precursor is then cooled to room temperature in the furnace to obtain modified diamond powder with a dense, continuous siloxane compound coating. The coating thickness of the siloxane compound is 132.4 nm.

[0096] Example 12 A modified diamond powder with a dense, continuous siloxane compound shell is provided, which is prepared by the following method: Step S1: Immerse diamond micro powder with an average particle size of 10 μm in ultrapure water and centrifuge at 2000 rpm for 10 min. Then immerse it in isopropanol and centrifuge at 2000 rpm for 10 min. Repeat the above steps twice. Vacuum dry to obtain pretreated diamond micro powder. Its conductivity was measured to be 9.8 μs / cm.

[0097] Step S2: Methyltrimethoxysilane (MTMS) is added to the pretreated diamond micropowder. After mixing evenly, 5% (v / v) ammonia water and nano-silica powder are added. The mixture is reacted at 25°C to form polysiloxane on the surface of the diamond micropowder, thus obtaining the precursor. The mass ratio of diamond micropowder, MTMS, 5% (v / v) ammonia water, and nano-silica powder is 100:3:3:0.017. The average particle size of the nano-silica powder is 7 nm.

[0098] Step S3: Place the precursor obtained in step S2 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%.

[0099] Step S4: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 650°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The precursor is then cooled to room temperature in the furnace to obtain modified diamond powder with a dense, continuous siloxane compound coating. The coating thickness of the siloxane compound is 107.3 nm.

[0100] Example 13 A modified diamond powder with a dense, continuous siloxane compound shell is provided, which is prepared by the following method: Step S1: Immerse diamond micro powder with an average particle size of 10 μm in ultrapure water and centrifuge at 2000 rpm for 10 min. Then immerse it in isopropanol and centrifuge at 2000 rpm for 10 min. Repeat the above steps twice. Vacuum dry to obtain pretreated diamond micro powder. Its conductivity was measured to be 9.8 μs / cm.

[0101] Step S2: Methyltrimethoxysilane (MTMS) is added to the pretreated diamond micropowder. After mixing evenly, 5% (v / v) ammonia water and nano-silica powder are added. The reaction is carried out at 25°C to form polysiloxane on the surface of the diamond micropowder, thus obtaining the precursor. The mass ratio of diamond micropowder, MTMS, 5% (v / v) ammonia water, and nano-silica powder is 100:3:3:0.017. The average particle size of the nano-silica powder is 130 nm.

[0102] Step S3: Place the precursor obtained in step S2 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%.

[0103] Step S4: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 650°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The precursor is then cooled to room temperature in the furnace to obtain modified diamond powder with a dense, continuous siloxane compound coating. The coating thickness of the siloxane compound is 135.6 nm.

[0104] Example 14 A modified diamond powder with a dense, continuous siloxane compound shell is provided, which is prepared by the following method: Step S1: Immerse diamond micro powder with an average particle size of 10 μm in ultrapure water and centrifuge at 2000 rpm for 10 min. Then immerse it in isopropanol and centrifuge at 2000 rpm for 10 min. Repeat the above steps twice. Vacuum dry to obtain pretreated diamond micro powder. Its conductivity was measured to be 9.8 μs / cm.

[0105] Step S2: Methyltrimethoxysilane (MTMS) is added to the pretreated diamond micropowder. After mixing evenly, 5% (v / v) ammonia water and nano-silica powder are added. The reaction is carried out at 25°C to form polysiloxane on the surface of the diamond micropowder, thus obtaining the precursor. The mass ratio of diamond micropowder, MTMS, 5% (v / v) ammonia water, and nano-silica powder is 100:3:3:0.034. The average particle size of the nano-silica powder is 30 nm.

[0106] Step S3: Place the precursor obtained in step S2 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 0.8%.

[0107] Step S4: 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 precursor is then cooled to room temperature in the furnace to obtain modified diamond powder with a dense, continuous siloxane compound coating. The coating thickness of the siloxane compound is 109.7 nm.

[0108] Example 15 A modified diamond powder with a dense, continuous siloxane compound shell is provided, which is prepared by the following method: Step S1: Immerse diamond micro powder with an average particle size of 10 μm in ultrapure water and centrifuge at 2000 rpm for 10 min. Then immerse it in isopropanol and centrifuge at 2000 rpm for 10 min. Repeat the above steps twice. Vacuum dry to obtain pretreated diamond micro powder. Its conductivity was measured to be 9.8 μs / cm.

[0109] Step S2: Methyltrimethoxysilane (MTMS) is added to the pretreated diamond micropowder. After mixing evenly, 5% (v / v) ammonia water and nano-silica powder are added. The reaction is carried out at 25°C to form polysiloxane on the surface of the diamond micropowder, thus obtaining the precursor. The mass ratio of diamond micropowder, MTMS, 5% (v / v) ammonia water, and nano-silica powder is 100:3:3:0.01. The average particle size of the nano-silica powder is 30 nm.

[0110] Step S3: Place the precursor obtained in step S2 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 0.8%.

[0111] Step S4: 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 treatment to densify the precursor surface. The precursor is then cooled to room temperature in the furnace to obtain modified diamond powder with a dense, continuous siloxane compound coating. The coating thickness of the siloxane compound is 112.3 nm.

[0112] Example 16 A modified diamond powder with a dense, continuous siloxane compound shell is provided, which is prepared by the following method: Step S1: Immerse diamond micro powder with an average particle size of 0.5 μm in ultrapure water and centrifuge at 2000 rpm for 10 min. Then immerse it in isopropanol and centrifuge at 2000 rpm for 10 min. Repeat the above steps twice. Vacuum dry to obtain pretreated diamond micro powder. Its conductivity was measured to be 12.4 μs / cm.

[0113] Step S2: Add methyltrimethoxysilane (MTMS) to the pretreated diamond micro powder, mix thoroughly, then add 5% ammonia water (by volume), and react at 25°C to form polysiloxane on the surface of the diamond micro powder, thus obtaining the precursor. The mass ratio of diamond micro powder, MTMS, and 5% ammonia water is 100:1.7:1.7.

[0114] Step S3: Place the precursor obtained in step S2 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%.

[0115] Step S4: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 750°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The precursor is then cooled to room temperature in the furnace to obtain modified diamond powder with a dense, continuous siloxane compound coating. The coating thickness of the siloxane compound is 0.7 nm.

[0116] Example 17 A modified diamond powder with a dense, continuous siloxane compound shell is provided, which is prepared by the following method: Step S1: Immerse diamond micro powder with an average particle size of 0.5 μm in ultrapure water and centrifuge at 2000 rpm for 10 min. Then immerse it in isopropanol and centrifuge at 2000 rpm for 10 min. Repeat the above steps twice. Vacuum dry to obtain pretreated diamond micro powder. Its conductivity was measured to be 19.7 μs / cm.

[0117] Step S2: Add methyltrimethoxysilane (MTMS) to the pretreated diamond micro powder, mix thoroughly, then add 5% ammonia water (by volume), and react at 25°C to form polysiloxane on the surface of the diamond micro powder, thus obtaining the precursor. The mass ratio of diamond micro powder, MTMS, and 5% ammonia water is 100:1.7:1.7.

[0118] Step S3: Place the precursor obtained in step S2 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%.

[0119] Step S4: Nitrogen gas is introduced into the muffle furnace to create a nitrogen atmosphere. The furnace is then heated to 750°C at a rate of 5°C / min and held for 6 hours for calcination to densify the precursor surface. The precursor is then cooled to room temperature in the furnace to obtain modified diamond powder with a dense, continuous siloxane compound coating. The coating thickness of the siloxane compound is 0.9 nm.

[0120] Comparative Example 1 The main difference from Example 1 is that the average particle size of the diamond powder in step S1 is 0.02 μm. Everything else is the same as in Example 1.

[0121] The coating thickness of the siloxane compound obtained in this comparative example is 0.3 nm.

[0122] Comparative Example 2 The main difference from Example 1 is that the average particle size of the diamond powder in step S1 is 45 μm. Everything else is the same as in Example 1.

[0123] The coating thickness of the siloxane compound obtained in this comparative example was 102.9 nm.

[0124] Comparative Example 3 The main difference from Example 1 is that the average particle size of the diamond powder in step S1 is 45 μm; and the mass ratio of diamond powder, MTMS, and 5% ammonia in step S2 is 40:1:1. Everything else is the same as in Example 1.

[0125] The coating thickness of the siloxane compound obtained in this comparative example was 501.4 nm.

[0126] Comparative Example 4 The main difference from Example 1 is that the water content of the precursor in step S3 is 0.01%. Everything else is the same as in Example 1.

[0127] The coating thickness of the siloxane compound obtained in this comparative example is 1.0 nm.

[0128] Comparative Example 5 The main difference from Example 1 is that the water content of the precursor in step S3 is 1.2%. Everything else is the same as in Example 1.

[0129] The coating thickness of the siloxane compound obtained in this comparative example was 0.9 nm.

[0130] Comparative Example 6 The main difference from Example 1 is that the gas atmosphere for calcination in step S4 is air. Everything else is the same as in Example 1.

[0131] During the implementation of this comparative example, it was found that diamond reacts with air, making it impossible to obtain modified diamond products.

[0132] Comparative Example 7 The main difference from Example 1 is that the calcination temperature in step S4 is 600°C, and the holding time is 5 hours. Everything else is the same as in Example 1.

[0133] The coating thickness of the siloxane compound obtained in this comparative example is 1.1 nm.

[0134] Comparative Example 8 The main difference from Example 1 is that the calcination temperature in step S4 is 550°C, and the holding time is 6 hours. Everything else is the same as in Example 1.

[0135] The coating thickness of the siloxane compound obtained in this comparative example is 1.2 nm.

[0136] Performance Characterization The modified diamond powders prepared in Examples 1-17 and Comparative Examples 1-8 were tested for particle size, Q unit content, shell thickness, and moisture content after storage. The results are shown in Table 1. The moisture content after storage was determined by placing the powder in an open environment at 25°C and 50% RH for 48 hours from the point of preparation. Q unit content refers to the solid content of the modified diamond powder. 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.

[0137] Table 1 As shown in Table 1: (1) As shown in Examples 1-17, this invention uses T-unit siloxane raw materials to form a polysiloxane layer on the surface of diamond micropowder; then, through drying treatment, 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 to the formation of dense siloxane compounds; finally, through calcination treatment, some of the organic groups of the T-unit siloxane are removed and converted into Q units, transforming the uniform polysiloxane layer into a dense siloxane compound layer. The modified diamond obtained in this way has the excellent characteristic of low water content after storage. Since this modified diamond powder is used in semiconductor fillers, the dense siloxane compound shell can reduce the water absorption of diamond powder during shelf life, resulting in less dielectric loss during the operation of electronic devices.

[0138] (2) Analysis of the selection conditions for particle size in the preparation method of the modified diamond of the present invention: Comparative analysis of Comparative Examples 1 and 2 with Example 1 shows that the particle sizes of the diamond micropowder in Comparative Examples 1 and 2 are 0.02 μm and 45 μm, respectively, and their water content is significantly higher than that in Example 1. The reason for this is that if the diamond micropowder particle size is too small, the micropowder is prone to agglomeration, and the T-unit siloxane is difficult to be uniformly adsorbed on the surface of the diamond micropowder, thus making it 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 diamond micropowder particle size is too large, the siloxane will also have the problem of being difficult to be uniformly adsorbed on the surface of the diamond micropowder, resulting in uneven coating. Uneven coating will lead to increased water absorption after the product is placed. Therefore, the particle size of the diamond micropowder needs to be controlled within a suitable range when preparing modified diamond powder by the method of the present invention.

[0139] Comparative analysis of the characterization data of Examples 1, 6-7, and Comparative Examples 1-2 shows that the preferred particle size of the diamond micron powder of the present invention is 0.05-40 μm.

[0140] A comparative analysis of Example 8 with Examples 7 and 1 shows that the particle size of the diamond micropowder 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 film, the amount of added T-unit siloxane can be increased. For example, Example 8 increased the amount of added siloxane, and its coating uniformity was better than that of Example 7 (reflected in the lower water absorption of Example 8). However, comparing Comparative Example 3 with Comparative Example 2, when the particle size of the diamond micropowder 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 diamond micropowder was observed during the preparation process. It is speculated that excessive addition of T-unit siloxane will increase the viscosity of the diamond, preventing the siloxane from being uniformly adsorbed on the surface of the diamond micropowder to form a polysiloxane film, ultimately leading to a decrease in the density of the calcined siloxane compound film.

[0141] (3) Analysis of the conditions for the water content of the precursor in the preparation method of the modified diamond of the present invention: Comparative analysis of Comparative Examples 4-5 and Example 1 shows that the moisture content of the precursors in Comparative Examples 4 and 5 after drying was 0.01% and 1.2%, respectively. The moisture content of their products after storage was significantly higher than that of Example 1. This indicates that maintaining 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 maintaining the polysiloxane layer at a low moisture content of 0.1% to 1% promotes the rotation and orderly arrangement of the organic groups in the T-unit siloxane, resulting in a uniform polysiloxane layer. This leads to a denser siloxane compound shell with lower porosity.

[0142] (4) Analysis of the conditions of the precursor calcination gas atmosphere in the preparation method of the modified diamond of the present invention: Comparative analysis of Comparative Example 6 and Example 1 shows that the gas atmosphere of the calcination treatment in step S4 of Comparative Example 6 is air. Comparative Example 6 cannot obtain modified diamond products because diamond reacts with air at a certain temperature.

[0143] (5) Analysis of the conditions for the Q unit content of the product in the preparation method of the modified diamond of the present invention: Comparative analysis of Comparative Examples 7-8 and Example 1 shows that by adjusting the temperature and time of the calcination step, Comparative Examples 7 and 8 reduced the conversion of T units to Q units, resulting in Q unit contents of 45.1% and 36.7% for the products of Comparative Examples 7 and 8, respectively. The modified diamonds obtained from these examples had a water content of 202.4 ppm / m³ after storage. 2 281.3ppm / m 2 The water content increased significantly. Therefore, the modified diamond powder provided by this invention needs to control the Q unit content within a certain range.

[0144] (6) Analysis of the conditions for adding nano-silica during the preparation process of the modified diamond of the present invention: A comparative analysis of Examples 9-11 and Example 1 shows that nano-silica with different particle sizes and contents was added during the preparation process of Examples 9-11. After placement, the water content decreased to varying degrees, indicating that the addition of nano-silica can improve the density of the prepared siloxane compound film. The reason for this is that when siloxanes condense to form polysiloxanes, the polysiloxane is not dense. During the reaction, a small amount of silica powder is added and dispersed in the polysiloxane framework. When the polysiloxane organic groups are removed by calcination in step S4, this silica powder can effectively fill the positions of the organic groups, improving the density of the siloxane compound shell coating on the diamond surface. Furthermore, comparing Examples 9-11 with Examples 12-13, it can be seen that the particle size of the nano-silica powder needs to be 10-100 nm; otherwise, it cannot fill the polysiloxane skeleton. For example, Example 12 cannot function, and its water content is not significantly reduced compared to Example 1. The silica particles added in Example 13 are too large, which will destroy the continuity of the shell and ultimately result in a large water content.

[0145] The diamond micro powder used in the embodiments of this invention was purchased from Henan Hengwei Superhard Materials Co., Ltd.

[0146] 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.

[0147] 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 method for preparing modified diamond powder, characterized in that: Includes the following steps: Step S1: Add T units of siloxane to diamond micro powder and react to form polysiloxane on the surface of diamond micro powder to obtain the precursor. Step S2: Perform a drying process to bring the precursor to a low moisture content state, wherein the moisture content of the precursor in the low moisture content state is 0.1% to 1%; Step S3: Calcination treatment is performed to obtain modified diamond powder; wherein, the calcination temperature is 750~1500℃; the modified diamond has a core-shell structure with diamond as the core and siloxane compound as the shell; in solid... 29 In the Si-NMR nuclear magnetic resonance spectrum, the ratio of the peak integral area of ​​the modified diamond in the range of -80ppm to -120ppm to the range of +20ppm to -120ppm is 50~99.5:

100. Wherein, the T unit siloxane is selected from hydrocarbon-trialkoxysilane, wherein the hydrocarbon group of the hydrocarbon-trialkoxysilane is selected from hydrocarbon groups with carbon atoms 1 to 16, and the modified diamond powder has a dense siloxane compound shell.

2. The method for preparing modified diamond powder as described in claim 1, characterized in that: After being placed in an environment of 25℃ and 50%RH for 48 hours, the Karl Fischer moisture content of the modified diamond at 200℃ is no higher than 150 ppm / m. 2 .

3. The method for preparing modified diamond powder as described in claim 1, characterized in that: The thickness of the shell ranges from 0.5 nm to 300 nm.

4. The method for preparing modified diamond powder as described in claim 1, characterized in that: In step S1, an alkaline aqueous solution is added to carry out the reaction.

5. The method for preparing modified diamond powder as described in claim 1, characterized in that: Silica powder was also added to the reaction.

6. The method for preparing modified diamond powder as described in claim 5, characterized in that: The particle size of the silica powder is 10~100nm.

7. The method for preparing modified diamond powder as described in claim 1, characterized in that: In step S1, the particle size of the diamond powder is 0.05~40μm.

8. The method for preparing modified diamond powder as described in claim 1, characterized in that: In step S1, the electrical conductivity of the diamond micropowder is ≤20µs / cm.

9. The method for preparing modified diamond powder as described in claim 1, characterized in that: The drying process involves heating to 50-200℃ and drying for 6-24 hours.

10. The method for preparing modified diamond powder as described in claim 1, characterized in that: In step S3, the calcination process is carried out in an inert gas atmosphere.

11. The method for preparing modified diamond powder as described in claim 10, characterized in that: In step S3, the calcination treatment time is 6 to 72 hours.

12. The application of the modified diamond powder prepared by the preparation method according to any one of claims 1 to 11 in the preparation of semiconductor packaging materials or substrate materials.

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