A low water content shell and its coating method and application

Abstract

The application relates to the field of semiconductor technology and discloses a low-water-content shell layer and a coating method and application thereof. By using T unit siloxane raw materials, a polysiloxane layer is formed on the surface of filler powder; then through drying treatment, the polysiloxane layer is in a low-water-content state, the condensation of silicon hydroxyl groups is promoted, the organic groups of the T unit siloxane are orderly arranged, and a uniform polysiloxane layer is formed; finally, through calcination treatment, part of the organic groups of the T unit siloxane is removed to be converted into Q units, and the uniform polysiloxane layer is converted into a dense siloxane compound shell layer. By optimizing the raw materials and the preparation process, the siloxane compound of the shell layer is more dense and continuous, the water content of the obtained shell layer is low after long-time placement, and the filler powder with the shell layer has the advantage of low water content.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor technology, and 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, and therefore higher requirements are put forward for the performance of electronic core devices. In the field of semiconductors, when passive elements, semiconductor elements, 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 circuit board substrates are required.

[0003] The substrate material and packaging material of electronic devices need to have a low water content performance so that the electronic devices have a small dielectric loss during operation, and at the same time, reduce the risk of the electronic devices being turned on due to the presence of water. Therefore, in order to meet the filler requirements 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] Existing semiconductor fillers mainly include two categories of heat-conducting materials and flame-retardant materials. The former mainly functions as heat conduction to improve the heat dissipation effect of the heating elements in electronic devices, and the latter mainly functions as flame retardation to avoid direct combustion of electronic devices when overheated. In order to improve the filling effect of the filler, the above-mentioned 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-mentioned 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. The active oxygen groups in the film can form good cross-linking reaction 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, it is only necessary to graft active oxygen groups on the surface of the modified diamond micro powder, without considering the porosity and water absorption problems of the diamond micro powder. 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 and a coating method and application thereof.

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

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

[0010] Thirdly, the present application provides a filler powder containing the low-water-content shell, so that the powder has good affinity with the resin material and low dielectric loss in the operation of electronic devices.

[0011] Further, the application provides application of the filler powder with the shell layer with low water content in preparation of packaging materials or substrate materials in the semiconductor field.

[0012] The specific technical scheme of the application is:

[0013] In the first aspect, the application provides a shell layer with low water content.

[0014] The shell layer comprises a siloxane compound; the siloxane compound responds in the range of +20ppm to-120ppm 29 Si-NMR nuclear magnetic resonance spectrum.

[0015] In the solid 29 In the Si-NMR nuclear magnetic resonance spectrum, the ratio of the peak integral area in the range of-80ppm to-120ppm to the peak integral area in the range of +20ppm to-120ppm of the shell layer is 50-99.5:100.

[0016] In the semiconductor field, in order to improve the filling effect of the filler, the filler needs to be mixed with the resin material, and further, in order to better mix the filler with the resin material, the surface of the filler needs to be modified to improve the affinity of the filler with the resin.

[0017] Therefore, based on the above problems, the application provides a shell layer of a siloxane compound, wherein the siloxane compound responds in the range of +20ppm to-120ppm 29 Si-NMR nuclear magnetic resonance spectrum, the shell layer provided by the application is arranged on the surface of the filler powder, can improve the activity of the close connection of the filler with other substances, make the filler better combined with the resin material, and improve the mixing effect.

[0018] The shell layer of the application is in the solid 29 In the Si-NMR nuclear magnetic resonance spectrum, the ratio of the peak integral area in the range of-80ppm to-120ppm to the peak integral area in the range of +20ppm to-120ppm of the shell layer is 50-99.5:100.

[0019] In the semiconductor field, in the actual application process of the filler, the filler is generally not prepared directly for use, but will exist in the shelf life, and therefore will absorb water during storage. The shell layer provided by the application is arranged on the surface of the filler powder, can make the filler powder absorb less water after storage, and further avoid the dielectric loss problem caused by high water content.

[0020] The amount of the specific siloxane compound needs to be within a certain range in order to uniformly coat the siloxane compound shell layer on the surface of the filler powder. If the amount of the siloxane compound is too small, the siloxane compound cannot completely coat the surface of the filler powder, the shell layer is discontinuous and has high porosity, and there may be a problem of water absorption later, the water content of the filler powder is too large, the risk of the electronic device being turned on increases, which affects the operation of the electronic device, and a large dielectric loss may be caused by a large water content; if the amount of the siloxane compound is too large, the filler powder may agglomerate, and it is difficult to uniformly mix the filler powder with the resin, and the mixed filler formed by the product and the resin may be peeled off, which may increase the formation of pores in the mixed filler of the filler powder and the resin, and cause the problem of water absorption. Therefore, the present application provides a shell layer which, in the solid state 29 In the Si-NMR nuclear magnetic resonance spectrum, the ratio of the peak integral area in the range of -80ppm to -120ppm to the peak integral area in the range of +20ppm to -120ppm is 50-99.5:100.

[0021] In the siloxane compound shell layer provided by the present application, the selection of the core material may affect the water content of the product containing the shell layer after placement. When the core material is a filler material with high surface energy such as boron nitride, diamond, aluminum nitride, the water content of the product after placement is generally higher than that of the core material with relatively low surface energy such as boron nitride, diamond, aluminum nitride, etc. The reason is that the core material with high surface energy may form a small gap between the shell layer after being coated with the shell layer, so the porosity is relatively high, which may cause the problem of water absorption, and finally the core material with high surface energy generally has a higher water content than the core material with low surface energy.

[0022] As a preferred shell layer of the present application, the siloxane compound is prepared using a siloxane containing 90wt% or more T units as a raw material; wherein T unit = R1SiO3-, R1 is a hydrogen atom or a hydrocarbon group with 1 to 16 carbon atoms which can be independently selected.

[0023] The siloxane compound shell layer provided by the present application has high density and good continuity. The siloxane compound film prepared using a polysiloxane containing 90wt% or more T units as a raw material has high density and good continuity. In order to coat the filler powder, the silanol groups of the siloxane need to be condensed to form a polysiloxane film layer on the surface of the filler powder, and then the siloxane compound is obtained by heat treatment. During the formation of the polysiloxane film layer, the T unit has more freedom of rotation than the Q unit. Therefore, in order to form a uniform and continuous dense film layer, the shell layer provided by the present application needs to be prepared using a polysiloxane containing 90wt% or more T units as a raw material, so as to have the advantage of less water absorption after placement.

[0024] It is further preferred that the T-unit siloxane is selected from the group consisting of hydrocarbyl trialkoxysilane, hydrocarbyl trichlorosilane.

[0025] As a preferred embodiment of the shell layer of the present application, the thickness of the shell layer is 0.5 nm to 300 nm.

[0026] As a preferred embodiment of the shell layer of the present application, the moisture of the product containing the shell layer is not higher than 160 ppm / m2 at 200℃ under Karl Fischer moisture test under the environmental condition of 25℃, 50% RH for 48 hours. 2 .

[0027] Due to the good compactness and continuity of the siloxane compound shell layer provided by the present application, the filler powder provided with the shell layer has the excellent feature of low water absorption after storage, which can reduce the water absorption of the filler powder during the shelf life, and can make the electronic device have a lower risk of conduction and a lower dielectric loss during operation.

[0028] In a second aspect, the present application provides a coating method of a low-moisture shell layer, comprising the following steps:

[0029] Step S1, adding T-unit siloxane to the filler powder to be coated with the shell layer, and reacting to form polysiloxane on the surface of the filler powder to be coated with the shell layer, to obtain a precursor;

[0030] Step S2, drying treatment to make the precursor in a low-moisture state;

[0031] Step S3, calcination treatment to densify the surface of the precursor, and obtain a shell layer on the surface of the filler powder;

[0032] Wherein, T-unit = R1SiO3-, R1 is a hydrogen atom or a carbon atom 1 to 16 independently selected hydrocarbon group.

[0033] In the prior art, in order to improve the combination of the filler powder and the resin material, the focus is usually placed on improving the wettability of the surface of the filler powder. However, it is also the focus of the field to make the product have low moisture content while improving the wettability of the surface of the filler powder, because the presence of moisture in the filler not only causes dielectric loss problems, but also causes the electronic device to have a risk of conduction.

[0034] To improve the density of the siloxane compound shell layer of the filler powder and reduce the water absorption of the product after being placed, the present application provides a method for preparing the shell layer as described above to form a uniform and dense siloxane compound film layer on the surface of the filler powder. First, the present application forms a polysiloxane layer on the surface of the filler powder by using T-unit siloxane raw material; then, through drying treatment, the polysiloxane layer is in a low moisture content state, promoting the condensation of silanol groups, and the organic groups of T-unit siloxane are arranged in order to form a uniform polysiloxane layer, which is conducive to the formation of a dense siloxane compound; finally, through calcination treatment, part of the organic groups of T-unit siloxane are removed, and the uniform polysiloxane layer is converted into a dense siloxane compound shell layer.

[0035] The conditions for forming the dense siloxane compound shell layer on the surface of the filler powder of the present application include the following three aspects:

[0036] ① Since T-unit siloxane has polarity, it can be quickly adsorbed on the surface of the filler powder when mixed with the filler powder to form a polysiloxane film layer. Therefore, the first condition of the preparation method of the present application is to use T-unit siloxane raw material. Since the molecular free rotation of T-unit is relatively easy, the first condition uses T-unit siloxane as raw material, which is a prerequisite condition for the present application to promote the rotation of the organic groups of siloxane and optimize their arrangement by making the polysiloxane film layer in a low moisture content state in step S2.

[0037] ② The second condition of the preparation method of the present application is to dry the polysiloxane film layer to make it in a low moisture content state, promote the rotation of the organic groups of T-unit siloxane, and arrange them in order to form a uniform polysiloxane layer. The uniform polysiloxane layer is conducive to the formation of a uniform and dense siloxane compound shell layer.

[0038] ③ The third condition is to remove part of the organic groups of the polysiloxane shell layer by calcination to make it dense, and the uniform polysiloxane layer is converted into a uniform and dense siloxane compound shell layer under this condition.

[0039] As a preferred embodiment of the coating method of the present application, in step S1, the mass ratio of the filler powder to the added T-unit siloxane is 100:0.2-10.

[0040] As a preferred embodiment of the coating method of the present application, in step S1, an alkaline aqueous solution is added for reaction.

[0041] Step S1 is the reaction of T-unit siloxane adsorbed on the surface of the filler powder to form a polysiloxane film layer, and the addition of an alkaline aqueous solution for reaction can promote 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.

[0042] As a preferred embodiment of the coating method of the present application, the silica powder is also added to the reaction.

[0043] Further preferably, the particle size of the silica powder is 10-100 nm.

[0044] In order to further improve the density of the siloxane compound shell, the present application also adds nano-silica powder when forming the polysiloxane shell in step S1. The siloxane compound coated on the surface of the filler powder can be mostly prepared from T-unit siloxane raw material, and a small amount of nano-silica powder is directly added. When the siloxane is condensed to form polysiloxane, it is not dense, and a small amount of silica powder is added during the reaction and dispersed in the polysiloxane skeleton. When the organic group of the polysiloxane is removed by calcination in step S3, these silica powders can fill the positions of the organic groups, reducing the defects of the siloxane compound shell coated on the surface of the filler powder. Preferably, the particle size of the silica powder is 10-100 nm, and the amount added is preferably 0.5%-1.2% of the mass of the T-unit siloxane raw material.

[0045] As a preferred embodiment of the coating method of the present application, the particle size of the filler powder in step S1 is 0.05-40 μm.

[0046] In order to form a uniform siloxane compound shell on the surface of the filler powder, the particle size of the filler powder needs to be in the range of 0.05-40 μm. If the particle size of the filler powder is too small, it is easy to agglomerate, and the T-unit siloxane is difficult to uniformly adsorb on the surface of the filler powder, so it is difficult to form a uniform polysiloxane film layer, and the coating is incomplete and the coating effect is poor. Since the thickness of the siloxane compound to be coated is small, the amount of T-unit siloxane raw material added is small, and if the particle size of the filler powder is too large, the siloxane will also have the problem of being difficult to uniformly adsorb on the surface of the filler powder, resulting in uneven coating and high porosity. At this time, if the uniform coating is promoted by increasing the coating thickness and increasing the amount of siloxane raw material added, the filler powder obtained will have agglomeration phenomenon, which will make it difficult for the filler powder after coating to mix uniformly with the resin, and the mixed filler formed by the product and the resin will have peeling phenomenon, which will also increase the formation of pores in the mixed filler of the filler powder and the resin, causing water absorption problems.

[0047] As a preferred embodiment of the coating method of the present application, the drying treatment in step S2 makes the water content of the precursor 0.1-1%.

[0048] The polysiloxane layer is in a low moisture content state, the organic group of the T unit siloxane is rotated and arranged in order, a uniform polysiloxane layer is formed, the obtained siloxane compound shell layer is more dense and uniform, and finally the product has a small water absorption amount after storage and a low water content after storage. When the water content of the precursor is 0.1-1%, the density of the siloxane compound shell layer formed on the surface of the filler powder is the highest.

[0049] Further preferably, the drying treatment method is heating to 50-200°C and drying for 6-24 hours.

[0050] As a preferred coating method of the present application, in step S3, the calcination treatment is performed in an inert gas atmosphere.

[0051] As a preferred coating method of the present application, in step S3, the calcination treatment is performed in an inert gas atmosphere.

[0052] The calcination treatment removes the organic group of the T unit siloxane and converts the uniform polysiloxane layer into a dense siloxane compound layer. The calcination treatment is performed in an inert gas atmosphere, has a relatively good densification effect, and the treatment temperature is preferably 600-1200°C and the time is preferably 6-72 hours.

[0053] As a preferred coating method of the present application, in step S3, the calcination treatment is performed in an inert gas atmosphere.

[0054] In a third aspect, the present application provides a filler powder comprising the above-mentioned low water content shell layer. The filler powder can be selected from one or more of the heat-conducting materials commonly used as fillers in the semiconductor field and the organic phosphorus-based flame retardants. For example, the filler powder can be selected from one or more of boron nitride, PQ60, aluminum oxide, and aluminum nitride.

[0055] In a fourth aspect, the present application provides the use of the filler powder in the preparation of semiconductor packaging materials or substrate materials. In the field of semiconductors, when passive elements, semiconductor elements, electroacoustic devices, display devices, optical devices, and radio frequency devices are assembled into equipment, high-density interconnection boards, high-frequency high-speed boards, and motherboards and other circuit board substrate materials are required. These substrate materials are generally mainly composed of fillers and organic polymers such as resins. The use of the above-mentioned filler powder provided by the present application in the preparation of semiconductor packaging materials or substrate materials can effectively meet the high affinity requirement of the resin material in the semiconductor packaging material or substrate material and meet the low water content and water absorption requirements.

[0056] Compared with the prior art, the present application has the following technical effects:

[0057] (1) The prior art generally does not consider the water absorption and water content when coating and modifying the filler powder, but in the field of semiconductors, whether it is a filler or an inductor material, it is generally not directly used after preparation, and there is a shelf life, so it is necessary to pay attention to the water absorption during storage and the water content after storage. The present application provides a siloxane compound shell layer (the siloxane compound has a response in the range of +20ppm to-120ppm 29 The ratio of the peak integral area of the shell layer in the range of-80ppm to-120ppm to the peak integral area in the range of +20ppm to-120ppm in the solid 29Si-NMR nuclear magnetic resonance spectrum is 50-99.5:100, so that the shell layer has the excellent characteristic of low water absorption after storage. By arranging the above shell layer on the surface of the filler powder, not only the activity of the filler closely connected with other substances is improved, but also the filler is better combined with the resin material, and the water absorption of the filler powder during the shelf life is reduced, thereby avoiding the problem of dielectric loss caused by high water content, and reducing the risk of conduction of electronic devices operating at high frequency.

[0058] (2) The present application also provides a coating method of a low water content shell layer. By using T unit siloxane raw material, a polysiloxane layer is formed on the surface of the filler powder. Then, through drying treatment, the polysiloxane layer is in a low moisture content state, promoting the condensation of silicon hydroxyl groups, and the organic groups of T unit siloxane are arranged in order to form a uniform polysiloxane layer. Finally, through calcination treatment, part of the organic groups of T unit siloxane are removed to convert them to Q units, and the uniform polysiloxane layer is converted into a dense siloxane compound shell layer. By optimizing the raw materials and the preparation process, the siloxane compound of the shell layer is more dense and continuous, and the water content of the obtained shell layer is low after long-term storage.

[0059] (3) In the siloxane compound shell layer provided by the present application, the selection of the core material may affect the water content of the product containing the shell layer after storage. For example, when the core material is boron nitride, diamond, aluminum nitride and other filler materials with high surface energy, the water content of the product after storage is generally higher than that of the core material with relatively low surface energy, such as boron nitride, diamond, aluminum nitride, etc. The siloxane compound shell layer provided by the present application can provide a filler material with lower water content by optimizing the core material. DETAILED DESCRIPTION

[0060] The application will be further described in conjunction with the following examples. Those skilled in the art will be able to implement the application based on these descriptions. In addition, the examples of the application described in the following description are generally only examples of part of the application, rather than all examples. Therefore, all other examples obtained by those skilled in the art based on the examples in the application without creative work shall fall within the scope of protection of the application.

[0061] The water content of the powder particles is the moisture content at 200 degrees Celsius, which is tested by a Karl Fischer moisture meter, the instrument being a CA-310 of Mitsubishi Chemical, and the determination method being the Coulomb method. In the performance test, the unit of the water content is ppm / m 2 which is calculated as the measured water content divided by the geometric outer surface area of the particles of the test product (calculated based on the measured average particle size).

[0062] The average particle size is determined by a Beckman Coulter laser particle size distribution instrument LS-13320, and the solvent is deionized water. In this document, the average particle size refers to the volume average diameter of the particles.

[0063] In the 29 In the Si-NMR nuclear magnetic resonance spectrum, the total content of the groups connected to Si is shown as the peak integral area in the range of +20 ppm to -120 ppm, and the content of the Q unit is shown as the peak integral area in the range of -80 ppm to -120 ppm. The shell provided by the application has a ratio of the peak integral area in the range of -80 ppm to -120 ppm to the peak integral area in the range of +20 ppm to -120 ppm of 50-99.5:100.

[0064] The coating thickness of the siloxane compound, i.e. the shell thickness, is obtained by high-resolution transmission electron microscopy testing.

[0065] Example 1

[0066] A continuous and dense siloxane compound shell is provided, which is prepared as follows:

[0067] 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 to obtain a precursor. The mass ratio of the boron nitride powder, MTMS and 5% ammonia water by volume is 50:1:1.

[0068] Step S2, the precursor obtained in step S1 is placed in a muffle furnace and heated to 70°C for constant temperature drying treatment for 24 hours to make the precursor in a low moisture content state with a water content of 0.6%.

[0069] Step S3, nitrogen is introduced into the muffle furnace to make the furnace have a nitrogen atmosphere, and then the temperature is raised to 800°C at a temperature raising rate of 5°C / min, and the precursor is calcined for 7h to densify the surface of the precursor, and then the furnace is cooled to room temperature, and a continuous and dense shell layer of siloxane compound is obtained on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e. the shell layer thickness, is 1.0 nm.

[0070] Example 2

[0071] A continuous and dense shell layer of siloxane compound is provided and is prepared by the following method:

[0072] Step S1, methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 1.0 μm, and then 5% ammonia water by volume is added, and the mixture is uniformly mixed and reacted at 25°C to form polysiloxane on the surface of the boron nitride powder to obtain a precursor. The mass ratio of the boron nitride powder, the MTMS, and the 5% ammonia water by volume is 50:1:1.

[0073] Step S2, the precursor obtained in step S1 is placed in a muffle furnace, heated to 70°C, and kept at this temperature for 24h for drying treatment, so that the precursor is in a low moisture content state with a water content of 0.1%.

[0074] Step S3, nitrogen is introduced into the muffle furnace to make the furnace have a nitrogen atmosphere, and then the temperature is raised to 800°C at a temperature raising rate of 5°C / min, and the precursor is calcined for 7h to densify the surface of the precursor, and then the furnace is cooled to room temperature, and a continuous and dense shell layer of siloxane compound is obtained on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e. the shell layer thickness, is 1.0 nm.

[0075] Example 3

[0076] A continuous and dense shell layer of siloxane compound is provided and is prepared by the following method:

[0077] Step S1, methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 1.0 μm, and then 5% ammonia water by volume is added, and the mixture is uniformly mixed and reacted at 25°C to form polysiloxane on the surface of the boron nitride powder to obtain a precursor. The mass ratio of the boron nitride powder, the MTMS, and the 5% ammonia water by volume is 50:1:1.

[0078] Step S2, the precursor obtained in step S1 is placed in a muffle furnace, heated to 70°C, and kept at this temperature for 24h for drying treatment, so that the precursor is in a low moisture content state with a water content of 1%.

[0079] Step S3, nitrogen is introduced into the muffle furnace to make the furnace have a nitrogen atmosphere, and then the temperature is raised to 800°C at a temperature raising rate of 5°C / min, and the precursor is calcined for 7h to make the surface of the precursor densified, and then the furnace is cooled to room temperature, and a continuous and dense shell layer of siloxane compound is obtained on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e. the shell layer thickness, is 1.0 nm.

[0080] Example 4

[0081] A continuous and dense shell layer of siloxane compound is provided and is prepared by the following method:

[0082] Step S1, methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 0.5 μm, and then 5% ammonia water by volume is added, and the mixture is uniformly mixed and reacted at 25°C to form polysiloxane on the surface of the boron nitride powder to obtain a precursor. The mass ratio of the boron nitride powder, the MTMS and the 5% ammonia water by volume is 50:1:1.

[0083] Step S2, the precursor obtained in step S1 is placed into a muffle furnace and heated to 70°C for 24h for drying treatment to make the precursor have a low moisture content of 0.6%.

[0084] Step S3, nitrogen is introduced into the muffle furnace to make the furnace have a nitrogen atmosphere, and then the temperature is raised to 800°C at a temperature raising rate of 5°C / min, and the precursor is calcined for 7h to make the surface of the precursor densified, and then the furnace is cooled to room temperature, and a continuous and dense shell layer of siloxane compound is obtained on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e. the shell layer thickness, is 1.0 nm.

[0085] Example 5

[0086] A continuous and dense shell layer of siloxane compound is provided and is prepared by the following method:

[0087] Step S1, methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 0.5 μm, and then 5% ammonia water by volume is added, and the mixture is uniformly mixed and reacted at 25°C to form polysiloxane on the surface of the boron nitride powder to obtain a precursor. The mass ratio of the boron nitride powder, the MTMS and the 5% ammonia water by volume is 50:1:1.

[0088] Step S2, the precursor obtained in step S1 is placed into a muffle furnace and heated to 70°C for 24h for drying treatment to make the precursor have a low moisture content of 0.6%.

[0089] Step S3, nitrogen is introduced into the muffle furnace to make the furnace have a nitrogen atmosphere, then the temperature is raised to 800°C at a temperature raising rate of 5°C / min, calcination treatment is carried out for 7h, the surface of the precursor is densified, then the furnace is cooled to room temperature, and a continuous and dense shell layer of siloxane compound is obtained on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e. the shell layer thickness, is 125.1 nm.

[0090] Example 6

[0091] A continuous and dense shell layer of siloxane compound is provided and is prepared by the following method:

[0092] Step S1, methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 0.05μm, then ammonia water with a volume concentration of 5% is added, and the mixture is reacted at 25°C to form polysiloxane on the surface of the boron nitride powder to obtain a precursor. The mass ratio of the boron nitride powder, the MTMS and the ammonia water with a volume concentration of 5% is 50:1:1.

[0093] Step S2, the precursor obtained in step S1 is placed into a muffle furnace, heated to 70°C and kept constant for 24h to carry out drying treatment, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0094] Step S3, nitrogen is introduced into the muffle furnace to make the furnace have a nitrogen atmosphere, then the temperature is raised to 800°C at a temperature raising rate of 5°C / min, calcination treatment is carried out for 7h, the surface of the precursor is densified, then the furnace is cooled to room temperature, and a continuous and dense shell layer of siloxane compound is obtained on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e. the shell layer thickness, is 125.1 nm.

[0095] Example 7

[0096] A continuous and dense shell layer of siloxane compound is provided and is prepared by the following method:

[0097] Step S1, methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 0.05μm, then ammonia water with a volume concentration of 5% is added, and the mixture is reacted at 25°C to form polysiloxane on the surface of the boron nitride powder to obtain a precursor. The mass ratio of the boron nitride powder, the MTMS and the ammonia water with a volume concentration of 5% is 50:1:1.

[0098] Step S2, the precursor obtained in step S1 is placed into a muffle furnace, heated to 70°C and kept constant for 24h to carry out drying treatment, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0099] Step S3, nitrogen is introduced into the muffle furnace to make the furnace have a nitrogen atmosphere, then the temperature is raised to 800℃ at a rate of 5℃ / min and kept for 7h to perform calcination treatment, so as to densify the surface of the precursor, then the furnace is cooled to room temperature, and a continuous and dense siloxane compound shell layer is obtained on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e. the shell layer thickness, is 191.8nm.

[0100] Example 8

[0101] A continuous and dense siloxane compound shell layer is provided, which is prepared by the following method:

[0102] Step S1, methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 40μm, then 5% ammonia water by volume is added, and the mixture is uniformly mixed and reacted at 25℃ to form polysiloxane on the surface of the boron nitride powder to obtain a precursor. The mass ratio of the boron nitride powder, the MTMS, and the 5% ammonia water by volume is 42:1:1.

[0103] Step S2, the precursor obtained in step S1 is placed in a muffle furnace and heated to 70℃ for 24h to perform drying treatment, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0104] Step S3, nitrogen is introduced into the muffle furnace to make the furnace have a nitrogen atmosphere, then the temperature is raised to 800℃ at a rate of 5℃ / min and kept for 7h to perform calcination treatment, so as to densify the surface of the precursor, then the furnace is cooled to room temperature, and a continuous and dense siloxane compound shell layer is obtained on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e. the shell layer thickness, is 191.8nm.

[0105] Example 9

[0106] A continuous and dense siloxane compound shell layer is provided, which is prepared by the following method:

[0107] Step S1, methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 40μm, then 5% ammonia water by volume is added, and the mixture is uniformly mixed and reacted at 25℃ to form polysiloxane on the surface of the boron nitride powder to obtain a precursor. The mass ratio of the boron nitride powder, the MTMS, and the 5% ammonia water by volume is 42:1:1.

[0108] Step S2, the precursor obtained in step S1 is placed in a muffle furnace and heated to 70℃ for 24h to perform drying treatment, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0109] Step S3, nitrogen was introduced into the muffle furnace to make the furnace have a nitrogen atmosphere, then the temperature was raised to 800°C at a rate of 5°C / min and kept for 6h to perform calcination treatment to make the surface of the precursor densified, then the furnace was cooled to room temperature, and a continuous and dense shell layer of siloxane compound was obtained on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e. the shell thickness, was 121.1 nm.

[0110] Example 10

[0111] A continuous and dense shell layer of siloxane compound was provided and prepared by the following method:

[0112] Step S1, methyltrimethoxysilane (MTMS) was added to boron nitride powder with an average particle size of 12 μm, then 5% ammonia water and nano-silicon dioxide powder were added and mixed uniformly, and the mixture was reacted at 25°C to form polysiloxane on the surface of the boron nitride powder to obtain a precursor. The mass ratio of the boron nitride powder, MTMS, 5% ammonia water and nano-silicon dioxide powder was 50:4:4:0.01. The average particle size of the nano-silicon dioxide powder was 10 nm.

[0113] Step S2, the precursor obtained in step S1 was placed in a muffle furnace and heated to 70°C for constant temperature drying treatment for 24h to make the precursor have a low moisture content of 0.6%.

[0114] Step S3, nitrogen was introduced into the muffle furnace to make the furnace have a nitrogen atmosphere, then the temperature was raised to 800°C at a rate of 5°C / min and kept for 6h to perform calcination treatment to make the surface of the precursor densified, then the furnace was cooled to room temperature, and a continuous and dense shell layer of siloxane compound was obtained on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e. the shell thickness, was 121.1 nm.

[0115] Example 11

[0116] A continuous and dense shell layer of siloxane compound was provided and prepared by the following method:

[0117] Step S1, methyltrimethoxysilane (MTMS) was added to boron nitride powder with an average particle size of 12 μm, then 5% ammonia water and nano-silicon dioxide powder were added and mixed uniformly, and the mixture was reacted at 25°C to form polysiloxane on the surface of the boron nitride powder to obtain a precursor. The mass ratio of the boron nitride powder, MTMS, 5% ammonia water and nano-silicon dioxide powder was 50:4:4:0.01. The average particle size of the nano-silicon dioxide powder was 10 nm.

[0118] Step S2, the precursor obtained in step S1 is put into a muffle furnace and heated to 70°C for constant temperature of 24 hours for drying treatment, so that the precursor is in a low moisture content state with water content of 0.6%.

[0119] Step S3, nitrogen is introduced into the muffle furnace to make the furnace in a nitrogen atmosphere, then heated to 800°C at a heating rate of 5°C / min for 6h for calcination treatment, so that the surface of the precursor is densified, and then the furnace is cooled to room temperature, to obtain a continuous and dense siloxane compound shell layer on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e. the shell layer thickness, is 134.4nm.

[0120] Example 12

[0121] A continuous and dense siloxane compound shell layer is provided, which is prepared by the following method:

[0122] Step S1, methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 12μm, and then mixed uniformly, and then 5% ammonia water and nano-silicon dioxide powder are added, and the reaction is carried out at 25°C, so that polysiloxane is formed on the surface of the boron nitride powder to obtain a precursor. The mass ratio of the boron nitride powder, the MTMS, the 5% ammonia water and the nano-silicon dioxide powder is 50:4:4:0.01. The average particle size of the nano-silicon dioxide powder is 7nm.

[0123] Step S2, the precursor obtained in step S1 is put into a muffle furnace and heated to 70°C for constant temperature of 24 hours for drying treatment, so that the precursor is in a low moisture content state with water content of 0.6%.

[0124] Step S3, nitrogen is introduced into the muffle furnace to make the furnace in a nitrogen atmosphere, then heated to 800°C at a heating rate of 5°C / min for 6h for calcination treatment, so that the surface of the precursor is densified, and then the furnace is cooled to room temperature, to obtain a continuous and dense siloxane compound shell layer on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e. the shell layer thickness, is 134.4nm.

[0125] Example 13

[0126] A continuous and dense siloxane compound shell layer is provided, which is prepared by the following method:

[0127] Step S1, add methyltrimethoxysilane (MTMS) into boron nitride powder with an average particle size of 12 μm, mix uniformly, then add ammonia water with a volume concentration of 5% and nano-silica powder, and react at 25°C to form polysiloxane on the surface of the boron nitride powder to obtain a precursor. The mass ratio of the 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.

[0128] Step S2, place the precursor obtained in step S1 into a muffle furnace, heat to 70°C, and keep constant for 24 hours for drying treatment, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0129] Step S3, introduce nitrogen into the muffle furnace to make the furnace in a nitrogen atmosphere, then heat to 800°C at a heating rate of 5°C / min, keep constant for 6 hours for calcination treatment, so that the surface of the precursor is densified, then cool to room temperature with the furnace, and a continuous and dense shell layer of siloxane compound is obtained on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e. the shell layer thickness, is 134.5 nm.

[0130] Example 14

[0131] A continuous and dense shell layer of siloxane compound is provided and prepared by the following method:

[0132] Step S1, add methyltrimethoxysilane (MTMS) into boron nitride powder with an average particle size of 12 μm, mix uniformly, then add ammonia water with a volume concentration of 5% and nano-silica powder, and react at 25°C to form polysiloxane on the surface of the boron nitride powder to obtain a precursor. The mass ratio of the boron nitride powder, MTMS, ammonia water with a volume concentration of 5%, and nano-silica powder is 50:4:4:0.019. The average particle size of the nano-silica powder is 30 nm.

[0133] Step S2, place the precursor obtained in step S1 into a muffle furnace, heat to 50°C, and keep constant for 10 hours for drying treatment, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0134] Step S3, introduce nitrogen into the muffle furnace to make the furnace in a nitrogen atmosphere, then heat to 1000°C at a heating rate of 5°C / min, keep constant for 10 hours for calcination treatment, so that the surface of the precursor is densified, then cool to room temperature with the furnace, and a continuous and dense shell layer of siloxane compound is obtained on the surface of the boron nitride powder particles. The coating thickness of the siloxane compound, i.e. the shell layer thickness, is 126.4 nm.

[0135] Example 15

[0136] A continuous and dense shell of siloxane compound is provided and is prepared by the following method:

[0137] Step S1, methyltrimethoxysilane (MTMS) is added to boron nitride powder with an average particle size of 12 μm, and then ammonia water with a volume concentration of 5% and nano-silicon dioxide powder are added and mixed uniformly, and the surface of the boron nitride powder is formed with polysiloxane by reaction at 25°C to obtain a precursor. The mass ratio of the boron nitride powder, MTMS, ammonia water with a volume concentration of 5%, and nano-silicon dioxide powder is 100:8:8:0.01. The average particle size of the nano-silicon dioxide powder is 30 nm.

[0138] Step S2, the precursor obtained in step S1 is placed in a muffle furnace and heated to 200°C for 6 hours for drying treatment, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0139] Step S3, nitrogen is introduced into the muffle furnace to make the furnace in a nitrogen atmosphere, and then the temperature is raised to 1200°C at a temperature raising rate of 5°C / min for 24 hours for calcination treatment, so that the surface of the precursor is densified, and then the furnace is cooled to room temperature, and a continuous and dense shell of siloxane compound is obtained 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.

[0140] Example 16

[0141] A continuous and dense shell of siloxane compound is provided and is prepared by the following method:

[0142] Step S1, methyltrimethoxysilane (MTMS) is added to diamond micro-powder with an average particle size of 1.0 μm, and then ammonia water with a volume concentration of 5% is added and mixed uniformly, and the surface of the organic phosphorus flame retardant powder particles is formed with polysiloxane by reaction at 25°C to obtain a precursor. The mass ratio of the organic phosphorus flame retardant powder, MTMS, and ammonia water with a volume concentration of 5% is 50:1:1.

[0143] Step S2, the precursor obtained in step S1 is placed in a muffle furnace and heated to 70°C for 24 hours for drying treatment, so that the precursor is in a low moisture content state with a water content of 0.6%.

[0144] Step S3, nitrogen is introduced into the muffle furnace to make the furnace in a nitrogen atmosphere, and then the temperature is raised to 600°C at a temperature raising rate of 5°C / min for 8 hours for calcination treatment, so that the surface of the precursor is densified, and then the furnace is cooled to room temperature, and a continuous and dense shell of siloxane compound is obtained on the surface of the organic phosphorus flame retardant powder particles. The coating thickness of the siloxane compound, i.e. the shell thickness, is 0.9 nm.

[0145] Example 17

[0146] A continuous and dense shell layer of siloxane compound is provided and prepared by the following method:

[0147] Step S1, methyltrimethoxysilane (MTMS) is added to aluminum nitride powder with an average particle size of 1.0 μm, and then 5% ammonia water by volume is added after uniform mixing. The reaction is carried out at 25°C to form polysiloxane on the surface of the aluminum nitride powder particles to obtain a precursor. The mass ratio of the aluminum nitride powder, MTMS, and 5% ammonia water by volume is 50:1:1.

[0148] Step S2, the precursor obtained in Step S1 is placed in a muffle furnace and dried at 70°C for 24 hours to make the precursor in a low moisture content state with a water content of 0.6%.

[0149] Step S3, nitrogen gas is introduced into the muffle furnace to make the furnace in a nitrogen atmosphere, and then the temperature is raised to 900°C at a rate of 5°C / min and held for 6 hours for calcination treatment to densify the surface of the precursor. Then the furnace is cooled to room temperature to obtain a continuous and dense shell layer of siloxane compound on the surface of the aluminum nitride powder particles. The coating thickness of the siloxane compound, i.e. the shell layer thickness, is 1.5 nm.

[0150] Example 18

[0151] A continuous and dense shell layer of siloxane compound is provided and prepared by the following method:

[0152] Step S1, methyltrimethoxysilane (MTMS) is added to aluminum nitride powder with an average particle size of 1.0 μm, and then 5% ammonia water by volume is added after uniform mixing. The reaction is carried out at 25°C to form polysiloxane on the surface of the aluminum nitride powder particles to obtain a precursor. The mass ratio of the aluminum nitride powder, MTMS, and 5% ammonia water by volume is 50:1:1.

[0153] Step S2, the precursor obtained in Step S1 is placed in a muffle furnace and dried at 70°C for 24 hours to make the precursor in a low moisture content state with a water content of 0.6%.

[0154] Step S3, nitrogen gas is introduced into the muffle furnace to make the furnace in a nitrogen atmosphere, and then the temperature is raised to 800°C at a rate of 5°C / min and held for 7 hours for calcination treatment to densify the surface of the precursor. Then the furnace is cooled to room temperature to obtain a continuous and dense shell layer of siloxane compound on the surface of the aluminum nitride powder particles. The coating thickness of the siloxane compound, i.e. the shell layer thickness, is 1.2 nm.

[0155] Example 19

[0156] A continuous and dense shell layer of siloxane compound is provided and prepared by the following method:

[0157] Step S1, methyltrimethoxysilane (MTMS) is added to metal magnetic powder with an average particle size of 1.0 μm, and then 5% ammonia water by volume is added after uniform mixing. The surface of the aluminum nitride powder particles is formed with polysiloxane by reaction at 25°C to obtain a precursor. The mass ratio of aluminum nitride powder, MTMS and 5% ammonia water by volume is 50:1:1.

[0158] Step S2, the precursor obtained in step S1 is placed in a muffle furnace and dried at a constant temperature of 70°C for 24 hours to make the precursor in a low moisture content state with a water content of 0.6%.

[0159] Step S3, nitrogen is introduced into the muffle furnace to make the furnace in a nitrogen atmosphere, and then the temperature is raised to 800°C at a rate of 5°C / min and held for 7 hours for calcination treatment to densify the surface of the precursor. Then the furnace is cooled to room temperature to obtain a continuous and dense shell layer of siloxane compound 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.

[0160] Example 20

[0161] A continuous and dense shell layer of siloxane compound is provided and prepared by the following method:

[0162] Step S1, methyltrimethoxysilane (MTMS) is added to aluminum oxide powder with an average particle size of 1.0 μm, and then 5% ammonia water by volume is added after uniform mixing. The surface of the aluminum nitride powder particles is formed with polysiloxane by reaction at 25°C to obtain a precursor. The mass ratio of aluminum nitride powder, MTMS and 5% ammonia water by volume is 50:1:1.

[0163] Step S2, the precursor obtained in step S1 is placed in a muffle furnace and dried at a constant temperature of 70°C for 24 hours to make the precursor in a low moisture content state with a water content of 0.6%.

[0164] Step S3, nitrogen is introduced into the muffle furnace to make the furnace in a nitrogen atmosphere, and then the temperature is raised to 800°C at a rate of 5°C / min and held for 7 hours for calcination treatment to densify the surface of the precursor. Then the furnace is cooled to room temperature to obtain a continuous and dense shell layer of siloxane compound 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.

[0165] Comparative Example 1

[0166] The main difference from Example 1 is that the average particle size of the boron nitride powder in Step S1 is 0.02 μm. Other than that, it is the same as Example 1.

[0167] The coating thickness of the siloxane compound obtained in this comparative example is 0.1 nm.

[0168] Comparative Example 2

[0169] The main difference from Example 1 is that the average particle size of the boron nitride powder in Step S1 is 45 μm. Other than that, it is the same as Example 1.

[0170] The coating thickness of the siloxane compound obtained in this comparative example is 103.2 nm.

[0171] Comparative Example 3

[0172] The main difference from Example 1 is that the average particle size of the boron nitride powder in Step S1 is 45 μm; and in Step S1, the mass ratio of the boron nitride powder, MTMS, and ammonia water having a volume concentration of 5% is 40:1:1. Other than that, it is the same as Example 1.

[0173] The coating thickness of the siloxane compound obtained in this comparative example is 509.2 nm.

[0174] Comparative Example 4

[0175] The main difference from Example 1 is that the water content of the precursor in Step S2 is 0.03%. Other than that, it is the same as Example 1.

[0176] The coating thickness of the siloxane compound obtained in this comparative example is 1.0 nm.

[0177] Comparative Example 5

[0178] The main difference from Example 1 is that the water content of the precursor in Step S2 is 1.5%. Other than that, it is the same as Example 1.

[0179] The coating thickness of the siloxane compound obtained in this comparative example is 1.1 nm.

[0180] Comparative Example 6

[0181] The main difference from Example 1 is that the gas atmosphere for calcination in Step S3 is air. Other than that, it is the same as Example 1.

[0182] The coating thickness of the siloxane compound obtained in this comparative example is 0.9 nm.

[0183] Comparative Example 7

[0184] The main difference from Example 1 is that the temperature for calcination in Step S3 is 600°C, and the holding time is 4 h. Other than that, it is the same as Example 1.

[0185] The coating thickness of the siloxane compound obtained in this comparative example was 1.1 nm.

[0186] Comparative Example 8

[0187] The main difference from Example 1 is that the calcination temperature in step S3 is 550℃, and the holding time is 5h. The others are the same as Example 1.

[0188] The coating thickness of the siloxane compound obtained in this comparative example was 1.2 nm.

[0189] Performance characterization

[0190] The filler particles with siloxane compound shell layer prepared in Examples 1-18 and Comparative Examples 1-8 were tested for particle size, Q unit content, shell layer thickness, and water content after storage. The analysis results are shown in Table 1. The water content after storage is the water content test performed at 25℃, 50% RH environment conditions, and open storage for 48 hours since preparation. The Q unit content is the solid content of the prepared filler particles, which is calculated by the following formula: Q unit content (%) = (Q unit peak area / Si-NMR peak area) x 100%. The coating thickness is the thickness of the siloxane compound shell layer on the surface of the filler particles, which is calculated by the following formula: coating thickness (nm) = (Q unit peak area / Si-NMR peak area) x 100. 29 The ratio of the peak integral area in the range of -80ppm to -120ppm to the peak integral area in the range of +20ppm to -120ppm in the Si-NMR nuclear magnetic resonance spectrum.

[0191] Table 1

[0192]

[0193] From Table 1, it can be seen that:

[0194] (1) From Examples 1-18, it can be seen that by using T unit siloxane raw material, a polysiloxane layer is formed on the surface of the filler powder particles; then through drying treatment, the polysiloxane layer is in a low moisture content state, promoting the condensation of silanol groups, and the organic groups of T unit siloxane are arranged in order, forming a uniform polysiloxane layer, which is conducive to the formation of dense siloxane compounds; finally, through calcination treatment, part of the organic groups of T unit siloxane are removed and converted into Q units, and the uniform polysiloxane layer is converted into a dense siloxane compound layer. The filler particles with siloxane compound shell layer obtained have the excellent characteristic of low water content after storage. Since the powder with siloxane compound shell layer is applied in semiconductor fillers, such as siloxane compound coated boron nitride powder, PQ60 powder, alumina powder, and aluminum nitride powder, it has a dense siloxane compound shell layer, which can reduce the water absorption of the filler powder during the shelf life, thereby reducing the dielectric loss of electronic devices during operation and reducing the risk of conduction caused by high water content.

[0195] (2) For the method of coating a low water content shell layer on the surface of the filler powder according to the present application, the selection conditions for the particle size of the core filler powder are as follows:

[0196] From the comparative analysis of Comparative Examples 1-2 and Example 1, it can be seen that the particle sizes of the boron nitride powders of Comparative Examples 1-2 are 0.02 μm and 45 μm respectively, and the water contents thereof are greatly increased compared with Example 1. The reason is that if the particle size of the boron nitride powder is too small, the boron nitride powder is easy to agglomerate, and the T unit siloxane is difficult to be uniformly adsorbed on the surface of the boron nitride powder, so it is difficult to form a uniform polysiloxane film layer, thereby resulting in poor coating effect. Since the thickness of the siloxane compound to be coated is small, the amount of the T unit siloxane added is small, and if the particle size of the boron nitride powder is too large, the siloxane is also difficult to be uniformly adsorbed on the surface of the boron nitride powder, thereby resulting in uneven coating. The uneven coating will result in increased water absorption of the product after storage. Therefore, in the method of the present application, the particle size of the boron nitride powder needs to be controlled within a suitable range to coat a low-water-content shell layer on the surface of the boron nitride powder.

[0197] From the comparison of the characterization data of Example 1, Examples 6-7 and Comparative Examples 1-2, it can be seen that the particle size of the boron nitride powder of the present application is preferably 0.05-40 μm. From the comparison of Example 8 with Examples 7 and 1, it can be seen that the particle size of the boron nitride powder of Example 7 is larger than that of Example 1. In order to improve the coating amount of Example 7 to improve the uniformity of the coating film layer and to improve the density of the film layer, the amount of the T unit siloxane added can be increased, for example, the amount of the siloxane added in Example 8 is increased, and the uniformity of the coating of Example 8 is better than that of Example 7 (reflected in the lower water absorption of Example 8). However, from the comparison of Comparative Example 3 with Comparative Example 2, when the particle size of the boron nitride powder of Comparative Example 2 is increased to 45 μm, although the amount of the siloxane added in Comparative Example 3 is increased, the water absorption of Comparative Example 3 is more than that of Comparative Example 2, and agglomeration of the boron nitride powder is found during the preparation process. It is thus speculated that if the amount of the T unit siloxane added is too much, the viscosity of the boron nitride powder will be increased, the siloxane cannot be uniformly adsorbed on the surface of the boron nitride powder to form a polysiloxane film layer, and finally the density of the siloxane compound film layer obtained by calcination will be decreased. Therefore, it is further speculated that in order to form a uniform and dense siloxane compound shell layer and to reduce the water content of the product, the particle size of the boron nitride powder needs to be controlled within a certain range in the method of the present application.

[0198] (3) Analysis of the water content of the precursor in the method of the present application for coating a low-water-content shell layer on the surface of a filler powder:

[0199] From the comparative analysis of Comparative Examples 4-5 and Example 1, it can be seen that the water content of the precursor after drying of Comparative Examples 4 and 5 is 0.03% and 1.5%, respectively, and the water content of the product after storage is greatly increased compared with Example 1. Therefore, it can be seen that the water content of the precursor is within a certain range, which is beneficial to the formation of the dense siloxane compound, and the water content of the precursor is preferably in a low water content state of 0.1%-1%. The reason is that the polysiloxane layer is in a state of 0.1%-1% low water content, which can promote the rotation of the organic group of the T unit siloxane and orderly arrange, form a uniform polysiloxane layer, and further make the obtained siloxane compound shell layer more dense and have lower porosity.

[0200] (4) For the method of the present application for coating a low water content shell layer on the surface of filler powder, the condition analysis of the precursor calcination gas atmosphere:

[0201] From the comparative analysis of Comparative Example 6 and Example 1, it can be seen that the gas atmosphere of the calcination treatment of step S3 of Comparative Example 6 is air, and the water content of the product after storage of Comparative Example 6 is greatly increased. The reason is that in air, it contains active gas oxygen, which will react with carbon formed by the decomposition of organic groups, and after taking away the carbon, defects will be formed at the carbon sites, so the porosity is higher, the shell layer is not dense, and the product has a large water absorption. When calcination is carried out in an inert atmosphere, although the water content of the water discharged by the condensation of silicon hydroxyl groups will also react with carbon to take away carbon, the water content is low, so the rate of taking away carbon is slow, and the continuous condensation of silicon hydroxyl groups in the film layer can repair the defect sites, so the porosity is lower.

[0202] (5) For the method of the present application for coating a low water content shell layer on the surface of filler powder, the condition analysis of the content of Q unit in the shell layer:

[0203] From the comparative analysis of Comparative Examples 7-8 and Example 1, it can be seen that by adjusting the temperature and time of the calcination step, Comparative Examples 7 and 8 reduce the conversion of T unit to Q unit, so that the Q unit content of the products of Comparative Examples 7 and 8 is 48.0% and 37.2%, respectively, and the water content of the coated boron nitride powder after storage is 216.7 ppm / m 2 , 284.5 ppm / m 2 , respectively, and the water content is greatly increased. Therefore, it can be seen that the content of Q unit in the coating of a low water content shell layer on the surface of boron nitride powder needs to be controlled within a certain range.

[0204] (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.

[0205] 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.

[0206] 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.

[0207] 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 layer, characterized in that: the shell layer comprises a siloxane compound; The siloxane compound has a response in the range of +20 ppm to -120 ppm in a Si-NMR nuclear magnetic resonance spectrum 29 Si-NMR nuclear magnetic resonance spectrum In the solid state 29 In the Si-NMR nuclear magnetic resonance spectrum, the ratio of the peak integral area of the shell layer in the range of -80 ppm to -120 ppm to the peak integral area in the range of +20 ppm to -120 ppm is 50-99.5:

100. the siloxane compound is obtained by calcination treatment using a siloxane containing 90%wt or more T units as raw material, the calcination treatment being carried out in an inert gas atmosphere; wherein T unit = R1SiO3-, R1 is a hydrogen atom or an independently selected hydrocarbon group of 1 to 16 carbon atoms.

2. The low water content shell layer according to claim 1, characterized in that: The article containing the shell layer has a Karl Fischer moisture at 200°C of no more than 160 ppm / m 2 .

3. A low water content shell according to claim 1, wherein: the T unit siloxane is selected from a hydrocarbyl trialkoxysilane, a hydrocarbyl trichlorosilane.

4. A low water content shell according to claim 1, wherein: the thickness of the shell layer is 0.5 nm to 300 nm.

5. A method of coating a core with a low water content shell according to any one of claims 1 to 4, wherein: comprising the following steps: Step S1, adding a T unit siloxane to a filler powder to be coated with a shell layer, and reacting to form a polysiloxane on the surface of the filler powder to be coated with a shell layer, to obtain a precursor; Step S2, drying treatment to bring the precursor to a low moisture content state; Step S3, calcination treatment to densify the surface of the precursor, to obtain a shell layer on the surface of the filler powder; wherein T unit = R1SiO3-, R1 is a hydrogen atom or an independently selected hydrocarbon group of 1 to 16 carbon atoms. In step S2, the drying treatment brings the water content of the precursor to 0.1 to 1%.

6. The coating method of claim 5, wherein: In step S1, an aqueous alkaline solution is added to react.

7. The coating method of claim 6, wherein: Silicon dioxide powder is also added to react.

8. The coating method of claim 7, wherein: The particle size of the silicon dioxide powder is 10 to 100 nm.

9. The coating method of claim 5, wherein: In step S1, the particle size of the filler powder is 0.05 to 40 μm.

10. The coating method of claim 5, wherein: The drying treatment method is to heat to 50 to 200°C, and dry for 6 to 24 hours.

11. The coating method of claim 5, wherein: In step S3, the calcination treatment is carried out in an inert gas atmosphere.

12. The coating method of claim 5, wherein: In step S3, the calcination treatment temperature is 600 to 1200°C.

13. The coating method of claim 12, wherein: In step S3, the calcination treatment time is 6 to 72 hours.

14. A filler powder, characterized by: comprising the shell layer according to any one of claims 1 to 4, or the shell layer obtained by the coating method according to any one of claims 5 to 13.

15. The filler powder of claim 14, wherein: The filler powder is selected from one or more of a thermally conductive material, an organic phosphorus-based flame retardant.

16. The filler powder of claim 15, wherein: The filler powder is selected from one or more of boron nitride, PQ60, alumina, aluminum nitride.

17. Use of the filler powder according to any one of claims 14 to 16 in the preparation of a semiconductor packaging material or a substrate material.

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