CN118929674A

CN118929674A - Black silicon dioxide filler and preparation method and application thereof

Info

Publication number: CN118929674A
Application number: CN202411246980.3A
Authority: CN
Inventors: 王珂; 沈海斌; 丁烈平; 史新阳; 李文; 杨原武
Original assignee: Zhejiang Sanshi New Material Technology Co ltd
Current assignee: Zhejiang Sanshi New Material Technology Co ltd
Priority date: 2024-03-22
Filing date: 2024-09-06
Publication date: 2024-11-12

Abstract

The invention relates to the technical field of fillers, and discloses a black silicon dioxide filler and a preparation method and application thereof. According to the invention, polysiloxane containing T units is taken as a starting material particle, then heating treatment is carried out under the condition of inert gas atmosphere, the upper limit of the moisture content in the gas atmosphere is 3500ppm when the temperature is higher than 650 ℃ in the heating process, organic groups in the particle are thermally decomposed into carbon, and then carbon on the surface of the particle is removed under the condition of oxygen-containing gas atmosphere, so that black silicon dioxide filler with the average particle size of 0.1-1 mu m can be obtained, and the black silicon dioxide filler with the small particle size has the excellent performances of few surface defects and small water absorption after being placed.

Description

Black silicon dioxide filler and preparation method and application thereof

Technical Field

The invention relates to the technical field of fillers, in particular to a black silicon dioxide filler and a preparation method and application thereof.

Background

In the semiconductor field, when passive elements, semiconductor elements, electroacoustic devices, display devices, optical devices, radio frequency devices, and the like are assembled into devices, circuit board substrate materials such as high-density interconnection boards, high-frequency high-speed boards, and mother boards are required. These substrate materials are generally mainly composed of an organic polymer such as a filler and an epoxy resin, and the filler has a main function of reducing the thermal expansion coefficient of the organic polymer, and is mainly angular or spherical silica. To facilitate laser printing, or to reduce photo-aging, pigments are typically added to the substrate material to dye it to grey or black, a common pigment being acetylene black. Acetylene black is an electronic conductor, however, which as a pigment of the substrate material has a risk of short circuits. Therefore, the black silicon dioxide is prepared, and the dyeing effect is simultaneously achieved in the process of filling the substrate material, so that the method has important significance.

In the prior art, as disclosed in patent application publication No. CN102924869A, black modified silicon dioxide is obtained by using white silicon dioxide as a raw material, carbonizing organic matters at high temperature and adsorbing the organic matters in the silicon dioxide. But it has the following disadvantages: ① The carbon of the black silicon dioxide is adsorbed on the surface, the carbon content of the outer surface is high, the carbon content of the inner part is low, and the carbon on the surface is concentrated and is easy to conduct; ② In order to reduce the dielectric properties of black silicon dioxide, it avoids carbon aggregation by reducing the carbon content, but with a consequent reduction in the blackness of the silicon dioxide.

As another patent with publication number CN113603103a, a semiconductor packaging material and a method for preparing the same are provided, wherein the patent uses polysiloxane including T units as a starting material particle, then the inside of the polysiloxane particle is carbonized by heat treatment under non-oxidizing gas or vacuum at 600-800 ℃ and the silicon hydroxyl groups on the surface are condensed, and then the remaining silicon hydroxyl groups are calcined and condensed at 800-1100 ℃ to obtain a semiconductor packaging material, namely black silicon dioxide powder. The black silica powder provided by the patent has a particle diameter of 0.8-4.5 μm, but the preparation method has the following problems: the carbon is remained in the powder, so that more pores are easily formed in silicon hydroxyl groups, the porosity is high, the powder is easy to absorb moisture in air, and the powder is applied to the filler of the substrate material, so that the substrate material has larger dielectric loss.

With the rapid development of microelectronics and communication technologies, semiconductor chips are continuously developed towards high integration, miniaturization, high frequency, high power and the like, so that higher requirements are also put forward on the dielectric performance requirements of electronic packaging materials of the semiconductor chips. The dielectric properties of the existing black silicon dioxide cannot meet the filler requirements of the current semiconductor field. Therefore, a new preparation method of black silicon dioxide is needed to solve the dielectric loss problem of black silicon dioxide.

Disclosure of Invention

In order to solve the dielectric loss problem of black silicon dioxide, the invention provides a black silicon dioxide filler, and a preparation method and application thereof. The invention prepares the black silicon dioxide powder with the average grain diameter of 0.1-1 mu m by controlling water treatment to the gas atmosphere in the preparation process of the black silicon dioxide filler.

The specific technical scheme of the invention is as follows:

In a first aspect, the present invention provides a black silica filler.

The carbon mass content of the black silica filler particles provided by the invention gradually increases from the surface to the inside; the average grain diameter is 0.1-1 mu m, and the mass content of carbon is 0.3-9%.

Preferably, the black silica filler particles of the present invention have a carbon content of 6 to 9% by mass.

Preferably, the black silica filler particles of the present invention are prepared by placing them at 25℃under 50% RH for 48 hours with a water content of less than 591ppm/m ².

Further, from the preparation, the water content is less than 245ppm/m ² when the mixture is left for 48 hours under the environmental conditions of 25 ℃ and 50% RH.

In the semiconductor field, the substrate material is filled with silica filler with small particle size of 0.5-2 μm as main material, and small particle size below 0.5 μm can be used for the grading filling. In order to simultaneously perform dyeing in the process of filling the substrate material, the invention provides a black silicon dioxide filler which has a single-layer structure, has an average particle diameter of 0.1-1 mu m and has a carbon mass content of 0.3-9%. The filler particles also have other excellent properties such as: the water content of the material is less than 591ppm/m ² after 48 hours under the environmental conditions of 25 ℃ and 50% RH, and the material has smaller water absorption capacity, and can lead the substrate material to have less dielectric loss when being used as the filler for filling the substrate material.

In the practical application process of the silica filler, the silica filler is generally not directly used after preparation, and has shelf life, so that the silica filler absorbs water in the placing process. The black silicon dioxide provided by the invention has little water absorption after being placed, and has great advantages for reducing dielectric loss caused by water absorption.

In a second aspect, the present invention provides a method for preparing a black silica filler, specifically:

Providing spherical polysiloxane particles comprising T units, performing the following steps of:

step S1: heating in inert gas atmosphere to decompose organic radical into carbon;

step S2: calcining in an oxygen-containing gas atmosphere to remove carbon on the surfaces of the particles;

Wherein the water content of the inert gas atmosphere is controlled to be not higher than 3500ppm when the temperature of the heating treatment process is higher than 650 ℃; the particle size of the black silicon dioxide filler is 0.1-1 mu m;

Wherein T unit = R ₁SiO₃-,R₁ is a hydrogen atom or an independently selectable hydrocarbyl group of carbon atoms 1 to 16.

The invention obtains black powder, namely the black silicon dioxide filler, by taking polysiloxane containing T units as initial raw material particles, then performing heating treatment under inert gas atmosphere conditions by controlling the upper limit of moisture content in the gas atmosphere to be 3500ppm when the temperature is higher than 650 ℃, thermally decomposing organic radicals in the particles into carbon, and then removing carbon on the surfaces of the particles under oxygen-containing gas atmosphere conditions, wherein the average particle size of the black silicon dioxide filler particles is 0.1-1 mu m. The preparation method provided by the invention has the advantages that the black silicon dioxide filler with small particle size and excellent dielectric property can be prepared.

The greatest reason for this is: the method of the invention carries out the water control treatment of the gas atmosphere in the particle heating treatment process, so that the water content of the gas atmosphere is controlled to be 3500ppm or less when the temperature is higher than 650 ℃.

The inventor found in experiments that during the heat treatment process of polysiloxane raw material particles, along with condensation of silicon hydroxyl groups, more moisture is generated in the particles, including adsorbed water, surface hydroxyl groups, internal hydroxyl groups and the like, so that the gas atmosphere contains a certain concentration of moisture, and at the temperature of the heat treatment, the water reacts with carbon to take away the carbon in the particles. When polysiloxane feedstock particles of small particle size are subjected to heat treatment, the presence of this reaction is a major factor in limiting the retention of carbon in the particles. In the case of heat treatment of polysiloxane raw material particles having a small particle diameter, black silica cannot be produced without controlling the moisture concentration of the gas atmosphere during heat treatment. Therefore, the invention is further researched, and the lowest temperature of the reaction of water and carbon is about 700 ℃, and when the temperature is higher than 650 ℃, the water content of the gas atmosphere of the polysiloxane is controlled to be 3500ppm or less, so that the water can be effectively prevented from taking away carbon decomposed from organic radicals of the polysiloxane raw material with small particle size.

In the polysiloxane raw material particles with large particle diameter, the amount of carbon in the particles is large, and after water takes part of carbon in the particles, more carbon can still remain in the particles, so that the polysiloxane raw material particles with large particle diameter can decompose organic groups under the condition that the moisture content of the heat treatment gas atmosphere is not controlled, and then the polysiloxane raw material particles with large particle diameter are calcined under the condition of oxygen content, but if the moisture concentration of the gas atmosphere is not controlled during the heat treatment, only the black silicon dioxide with large particle diameter of more than 5 mu m can be prepared, and the black silicon dioxide with small particle diameter cannot be prepared.

In order to prepare the black silicon dioxide with small particle size, the invention reduces the contact of carbon in the silicon dioxide balls with water by keeping the water content in the gas atmosphere at the temperature of not higher than 3500ppm when the temperature is higher than 650 ℃ during heat treatment of polysiloxane, avoids the carbon in the silicon dioxide balls with small particle size from being carried away by water, then takes away the carbon on the surfaces of the silicon dioxide balls by calcining under the condition of oxygen, and enables silicon hydroxyl groups to condense and repair the defects on the surfaces of the silicon dioxide balls, a compact layer is formed on the surfaces of the silicon dioxide balls, thus improving the compactness of products, reducing the problem that the carbon on the surfaces of the products falls off to form pores to cause easy water absorption, and finally preparing the black silicon dioxide filler particles with average particle size of 0.1-1 mu m.

In addition, the black silicon dioxide filler prepared by the method provided by the invention has the advantages of less surface defects, less water absorption and low dielectric loss.

In step S1, the final temperature of the heating treatment is preferably 850 to 1100 ℃.

As a preferable mode of the above preparation method of the present invention, the temperature is raised slowly or/and inert gas with a large flow rate is introduced during the heating.

The control of the moisture content of the gas atmosphere during the heat treatment is the key point of the preparation of the black silicon dioxide with small particle size. In the heating process, the moisture content of the gas atmosphere in the heating furnace can be controlled within a lower range by slowly heating and introducing inert gas with high flow rate.

In order to ensure that the prepared black silicon dioxide has higher density and smaller water absorption, the invention preferably controls the moisture in the heating furnace in a lower range by introducing high-flow nitrogen in the process of condensing the silicon hydroxyl. The reason is that in the heating treatment process of the step S1 under the inert gas atmosphere, the high-flow nitrogen rapidly brings out silicon hydroxyl in the polysiloxane raw material to condense to generate moisture, so that the arrangement of R1 groups of a T unit can be influenced, and further the overall structure arrangement of the polysiloxane is influenced, so that the density of the surface compact layer formed by the silicon hydroxyl condensation is higher in the later-stage calcination process. The silicon dioxide with higher density has smaller porosity, namely smaller specific surface area under the condition of the same particle size, and has less water absorption capacity when being placed in the air for a long time in the later period. Therefore, the invention more preferably controls the moisture in the heating furnace in a lower range by introducing a large flow of nitrogen in the silicon hydroxyl group condensation process.

By decreasing the rate of temperature increase, the rate of condensation of the silicon hydroxyl groups in the polysiloxane raw material is decreased, and further, the rate of formation of moisture is decreased, and also, the water content in the heat treatment gas atmosphere can be controlled to be not higher than 3500ppm, but in this manner, the water content is controlled to be easily burned white in the subsequent calcination step, or black silica can be obtained by adjusting the calcination treatment process, but the water absorption amount of the obtained black silica is large after a period of time of standing.

Further preferably, in step S1, the flow rate of the inert gas is 100 to 1000mL/min.

The flow rate of the inert gas during the heat treatment can be specifically adjusted and set according to the specific model of the heat treatment device, the amount of the heat treatment raw materials and the like, and the water content in the heat treatment gas atmosphere is preferably controlled to be not higher than 3500ppm when the temperature is higher than 650 ℃.

Further preferably, in step S1, the temperature increase rate of the slow temperature increase is 0.1 to 1 ℃/min.

As a preferable mode of the above production method of the present invention, in the step S2, the oxygen volume concentration in the oxygen-containing gas is 0.3% to 30%.

Further preferably, in step S2, the oxygen volume concentration in the oxygen-containing gas is 3% to 21%.

In the step S2, the volume concentration of oxygen in the oxygen-containing gas atmosphere is 3-21%, so that the surface densification of the particles has a better effect. In the radial direction of the silica particles, carbon on the surface side is more likely to contact oxygen in the gas atmosphere and thus more likely to react with the oxygen, and therefore, it is presumed that the black silica produced by the present invention has a structure in which the carbon content gradually increases from the surface to the inside and gradually increases from the surface to the inside with a uniform gradient.

As a preferable mode of the above preparation method of the present invention, in the step S2, the temperature of the calcination treatment is 850 to 1200 ℃.

Further preferably, in step S2, the calcination treatment is performed for 0.5 to 72 hours.

As a preferred embodiment of the above-described preparation process of the present invention, the polysiloxane further comprises Q units, D units and/or M units; wherein Q unit=sio ₄ -, D unit=r ₂R₃SiO₂ -, and M unit=r ₄R₅R₆SiO-;R₂、R₃、R₄、R₅、R₆ are each a hydrogen atom or a hydrocarbon group of carbon atoms 1 to 18 which can be independently selected.

Further preferably, the T unit raw material of the polysiloxane is a hydrocarbyl trialkoxysilane or a hydrocarbyl trichlorosilane, the Q unit raw material is at least one selected from the group consisting of tetraalkoxysilane, silicon tetrachloride and silicon dioxide, the D unit raw material is at least one selected from the group consisting of dialkyldialkoxysilane and dialkyldichlorosilane, and the M unit raw material is at least one selected from the group consisting of trialkylalkoxysilane, trialkylchlorosilane and hexahydrocarbyl disilazane.

In a third aspect, the invention provides application of the black silica filler in preparing semiconductor packaging materials and substrate materials.

In the semiconductor field, the packaging technology of the semiconductor chip needs to use plastic packaging materials, adhesive, underfill materials, chip carrier boards and other semiconductor packaging materials to package the semiconductor chip to protect the chip and provide mechanical support for the chip. When passive elements, semiconductor elements, electroacoustic devices, display devices, optical devices, radio frequency devices, and the like are assembled into devices, circuit board substrate materials such as high-density interconnection boards, high-frequency high-speed boards, and mother boards are required. For these semiconductor packaging materials and substrate materials, they are often colored gray or black for ease of laser printing on the component or ease of laser drilling, or for reduced photo-aging to improve durability, or for reduced light reflection, or reduced lot-to-lot color variation, etc. In contrast, in the industry, acetylene black containing no conductive ions is generally used as a dye to dye a semiconductor packaging material and a substrate material, but acetylene black is an electronic conductor, and therefore it is necessary to highly disperse acetylene black so that the size thereof is smaller than the metal spacing of a semiconductor element to prevent short-circuiting. However, as the packing density of semiconductor elements becomes higher, the risk of short circuit caused by acetylene black becomes larger. Based on the preparation method and the silicon oxide filler, the silicon oxide filler can replace acetylene black to be used as a substitute pigment for dyeing semiconductor packaging materials and substrate materials into black, so as to solve the problem of short circuit caused by acetylene black. The black spherical or amorphous silicon oxide filler provided by the invention can be used for replacing acetylene black pigment to be tightly filled in resin to form semiconductor packaging materials and substrate materials without any creative labor by a person skilled in the art, and therefore, the semiconductor packaging materials and the substrate materials are also included in the protection scope of the invention.

Preferably, the semiconductor packaging material and the substrate material can be used for plastic packaging materials, surface mount adhesives, underfills, chip carrier boards, circuit boards or intermediate semi-finished products thereof. The plastic package material is a DIP package type plastic package material, an SMT package type plastic package material, MUF, FO-WLP and FCBGA plastic package material. Preferably, the circuit board is an HDI, high frequency high speed board, or motherboard.

Compared with the prior art, the invention has the following technical effects:

(1) The invention provides a black silicon dioxide filler with a single-layer structure, an average particle diameter of 0.1-1 mu m and a carbon mass content of 0.3-9%, which can be used for tightly filling the gradation of a substrate material and can play a role in dyeing.

(2) The black silicon dioxide filler provided by the invention is prepared from the preparation, and the black silicon dioxide filler particles are placed for 48 hours under the environmental conditions of 25 ℃ and 50% RH, the water content is less than 245ppm/m ², and the black silicon dioxide filler has small water absorption capacity, so that the dielectric loss of a substrate material can be reduced when the black silicon dioxide filler is used as the filler for filling the substrate material.

(3) The invention also provides a preparation method of the black silicon dioxide filler, which takes polysiloxane containing T units as initial raw material particles, then controls the heat treatment under the condition that the water content of the gas atmosphere is not higher than 3500ppm when the temperature is higher than 650 ℃ so as to lead the organic radicals in the particles to be thermally decomposed into carbon, and then calcines under the condition of the oxygen-containing gas atmosphere to remove the carbon on the surfaces of the particles, so as to lead the surfaces of the particles to densify, thereby obtaining the black silicon dioxide filler with small particle size of 0.1-1 mu m.

Detailed Description

The invention is further described below with reference to examples. Those of ordinary skill in the art will be able to implement the invention based on these descriptions. In addition, the embodiments of the present invention referred to in the following description are typically only some, but not all, embodiments of the present invention. Therefore, all other embodiments, which can be made by one of ordinary skill in the art without undue burden, are intended to be within the scope of the present invention, based on the embodiments of the present invention.

In the radial direction of the silica particles, carbon on the surface side is more likely to contact oxygen in the gas atmosphere and thus more likely to react with the oxygen, and therefore, it is presumed that the black silica produced by the present invention has a structure in which the carbon content gradually increases from the surface to the inside and gradually increases from the surface to the inside with a uniform gradient.

In the semiconductor field, the substrate material is filled with silica filler with small particle size of 0.5-2 μm as main material, and small particle size below 0.5 μm can be used for the grading filling. In order to simultaneously perform dyeing in the process of filling the substrate material, the invention provides a black silicon dioxide filler which has a single-layer structure, has an average particle diameter of 0.1-1 mu m and has a carbon mass content of 0.3-9%. The filler particles also have other excellent properties such as: the particles were just prepared to have a water content of substantially 0 at 25 ℃ and 50% rh, and were left to stand for 48 hours from the start of the preparation to have a water content of less than 591ppm/m ², and it was found that the filler particles provided by the present invention have a smaller water absorption capacity, and when used as filler for filling a substrate material, can provide a substrate material with less dielectric loss.

The following embodiments provide specific implementation of the method according to the present invention, and the detection method includes:

the moisture content of the particles was 200 degrees celsius karl moisture and tested with a karl fischer moisture meter.

The average particle size is determined by means of a laser particle size distribution instrument LA-700 of HORIBA, which in this context refers to the volume average diameter of the particles.

The specific surface area was determined with FlowSorbIII of Shimadzu 2305.

The true specific gravity was determined with BELPycno of MicrotracBEL.

Uranium and thorium contents were measured by Agilent model 7700X ICP-MS, and the sample preparation method was 800 degrees f burned and then completely dissolved in hydrofluoric acid.

The carbon content of the silica particles was measured by a CS-8810C carbon-sulfur analyzer of Sichuan Saensi.

The carbon content of the silica particles surface was measured by X-ray photoelectron spectroscopy.

The water content of the gas atmosphere in the muffle furnace is characterized by the water content at the gas outlet of the furnace. In the invention, the water content of the gas atmosphere in the heat treatment process in the muffle furnace can be replaced by the water content at the gas outlet of the monitored heat treatment furnace. In the invention, the heating rate or the gas inlet flow or the gas inlet rate is regulated to ensure that the maximum value of the water content at the outlet is 3500ppm when the temperature is higher than 650 ℃, namely the water concentration in the muffle furnace is not more than 3500ppm when the temperature is higher than 650 ℃ in the whole heat treatment process.

The water content at the gas outlet of the heat treatment furnace is tested by a hygrothermograph, and the manufacturer of the hygrothermograph is Shenzhen Hua Hanwei hygrothermograph, and the model is TH11R-EX-H.

Example 1

Starting with a polysiloxane comprising T units, black silica was prepared as follows:

S1, placing 1300 parts by weight of deionized water into a reaction kettle with a stirrer at room temperature, starting stirring, and adding 200 parts by weight of methyltrimethoxysilane and a small amount of acetic acid to adjust the pH to about 5. After methyltrimethoxysilane was dissolved, 30 parts by weight of 5% strength by volume aqueous ammonia was added and stirred for 10 seconds, and then the stirring was stopped. After standing for 1 hour, filtering and drying to obtain spherical polysiloxane powder with average particle diameter of 1.31 μm.

S2, placing spherical polysiloxane powder into a muffle furnace, setting the nitrogen inlet flow to be larger flow and 300mL/min, so that the maximum value of water content at an outlet when the temperature in the muffle furnace is higher than 650 ℃ is 1800ppm, namely the water content in the muffle furnace when the temperature in the muffle furnace is higher than 650 ℃ is not more than 1800ppm. And (3) under the nitrogen atmosphere, heating the temperature in the furnace to 850 ℃ at a speed of 5 ℃/min, and preserving the temperature for 10 hours, and performing heat treatment on the particles so as to thermally decompose organic groups in the particles into carbon elements. In the heating process, the water concentration at the gas outlet of the muffle furnace is continuously monitored, and when the water concentration is increased to be more than 1800ppm when the temperature in the furnace is higher than 650 ℃, the inlet flow of nitrogen is increased appropriately. In this example, the moisture content at the gas outlet of the muffle furnace was continuously monitored, and the maximum moisture content was 1800ppm at a temperature above 650 ℃.

S3, switching the gas in the muffle furnace into air, adjusting the temperature to 850 ℃ and calcining for 3 hours, removing carbon on the surfaces of the particles, and densifying the surfaces of the particles to obtain the black silicon dioxide with the mass content of carbon uniformly increasing from the surfaces to the inside.

The process parameters of the heat treatment and calcination are shown in Table 1.

Example 2

The main difference between this embodiment and embodiment 1 is that: the moisture concentration in the muffle furnace is not more than 2500ppm when the temperature in the muffle furnace is higher than 650 ℃. Otherwise, the same as in example 1 was used.

This example starts with a polysiloxane comprising T units and produces black silica as follows:

S2, placing spherical polysiloxane powder into a muffle furnace, setting the nitrogen inlet flow to be larger flow and 250mL/min, so that the maximum value of the water content at the outlet of the muffle furnace at the temperature higher than 650 ℃ is 2500ppm, namely the water content in the muffle furnace at the temperature higher than 650 ℃ is not more than 2500ppm. And (3) under the nitrogen atmosphere, heating the temperature in the furnace to 850 ℃ at a speed of 5 ℃/min, and preserving the temperature for 10 hours, and performing heat treatment on the particles so as to thermally decompose organic groups in the particles into carbon elements. In the heating process, the water concentration at the gas outlet of the muffle furnace is continuously monitored, and when the water concentration is increased to more than 2500ppm when the temperature in the furnace is higher than 650 ℃, the inlet flow of nitrogen is increased appropriately. In this example, the moisture content at the gas outlet of the muffle furnace was continuously monitored, and the maximum moisture content was 2500ppm at a temperature above 650 ℃.

S3, switching the gas in the muffle furnace into air, adjusting the temperature to 850 ℃ and calcining for 3 hours to densify the particle surfaces, thereby obtaining the black silicon dioxide with the carbon mass content evenly increased from the surfaces to the inside.

Example 3

The main difference between this embodiment and embodiment 1 is that: the moisture concentration in the muffle furnace is not more than 3500ppm when the temperature in the muffle furnace is higher than 650 ℃. Otherwise, the same as in example 1 was used.

S2, placing spherical polysiloxane powder into a muffle furnace, setting the nitrogen inlet flow to be larger flow and 200mL/min, so that the maximum value of water content at an outlet when the temperature in the muffle furnace is higher than 650 ℃ is 3500ppm, namely the water content in the muffle furnace when the temperature in the muffle furnace is higher than 650 ℃ is not more than 3500ppm. And (3) under the nitrogen atmosphere, heating the temperature in the furnace to 850 ℃ at a speed of 5 ℃/min, and preserving the temperature for 10 hours, and performing heat treatment on the particles so as to thermally decompose organic groups in the particles into carbon elements. In the heating process, the moisture concentration at the gas outlet of the muffle furnace is continuously monitored, and when the moisture concentration is increased to be more than 3500ppm, the inlet flow of nitrogen is increased appropriately. In this embodiment, the moisture content at the gas outlet of the muffle furnace is continuously monitored, and the maximum moisture content value is 3500ppm when the temperature in the muffle furnace is higher than 650 ℃.

Example 4

The main difference between this embodiment and embodiment 1 is that: the particle size of the polysiloxane starting material in T units was 0.73. Mu.m. Otherwise, the same as in example 1 was used.

S1, placing 1300 parts by weight of deionized water into a reaction kettle with a stirrer at room temperature, starting stirring, and adding 200 parts by weight of methyltrimethoxysilane and a small amount of acetic acid to adjust the pH to about 5. After methyltrimethoxysilane was dissolved, 60 parts by weight of 5% strength by volume aqueous ammonia was added and stirred for 10 seconds, and then the stirring was stopped. After standing for 1 hour, filtering and drying to obtain spherical polysiloxane powder with average particle diameter of 0.73 μm.

Example 5

The main difference between this embodiment and embodiment 1 is that: the particle size of the polysiloxane starting material in T units was 0.35. Mu.m. Otherwise, the same as in example 1 was used.

S1, placing 1300 parts by weight of deionized water into a reaction kettle with a stirrer at room temperature, starting stirring, and adding 200 parts by weight of methyltrimethoxysilane and a small amount of acetic acid to adjust the pH to about 5. After methyltrimethoxysilane was dissolved, 100 parts by weight of 5% ammonia water was added and stirred for 10 seconds, and then the stirring was stopped. After standing for 1 hour, filtering and drying to obtain spherical polysiloxane powder with average particle diameter of 0.35 μm.

Example 6

The main difference between this embodiment and embodiment 1 is that: the particle size of the polysiloxane starting material in T units was 0.18. Mu.m. Otherwise, the same as in example 1 was used.

S1, placing 1300 parts by weight of deionized water into a reaction kettle with a stirrer at room temperature, starting stirring, and adding 200 parts by weight of methyltrimethoxysilane and a small amount of acetic acid to adjust the pH to about 5. After methyltrimethoxysilane was dissolved, 160 parts by weight of ammonia water having a volume concentration of 5% was added thereto and stirred for 10 seconds, and then the stirring was stopped. After standing for 1 hour, filtering and drying to obtain spherical polysiloxane powder with average particle diameter of 0.18 μm.

Example 7

The main difference between this embodiment and embodiment 1 is that: the particle size of the polysiloxane starting material in T units was 0.11. Mu.m. Otherwise, the same as in example 1 was used.

S1, placing 1300 parts by weight of deionized water into a reaction kettle with a stirrer at room temperature, starting stirring, and adding 200 parts by weight of methyltrimethoxysilane and a small amount of acetic acid to adjust the pH to about 5. After methyltrimethoxysilane was dissolved, 160 parts by weight of ammonia water having a volume concentration of 5% was added thereto and stirred for 10 seconds, and then the stirring was stopped. After standing for 1 hour, filtering and drying to obtain spherical polysiloxane powder with average particle diameter of 0.11 μm.

Example 8

The main difference between this embodiment and embodiment 1 is that: the means for controlling the moisture content of the gas atmosphere in the heat treatment process is to raise the temperature at a low speed. Otherwise, the same as in example 1 was used.

S2, placing the spherical polysiloxane powder into a muffle furnace, setting the nitrogen inlet flow to be 50mL/min, heating the temperature in the furnace to 850 ℃ at a speed of 1 ℃/min under the nitrogen atmosphere, and preserving the heat for 10 hours, and performing heat treatment on the particles so as to thermally decompose organic groups in the particles into carbon elements. The temperature is raised at a rate of 1 ℃/min to ensure that the maximum value of the water content at the outlet is 1800ppm when the temperature in the furnace is higher than 650 ℃, the water concentration at the gas outlet of the muffle furnace is continuously monitored in the heating process, and when the water concentration is increased to be more than 1800ppm when the temperature in the furnace is higher than 650 ℃, the inlet flow of nitrogen is properly increased. In the embodiment, the highest value of the moisture concentration at the gas outlet of the muffle furnace is 1800ppm, and the maximum nitrogen inlet flow is not more than 100mL/min during the period, namely, the moisture content in the muffle furnace is not more than 1800ppm when the temperature in the muffle furnace is higher than 650 ℃.

Example 9

The main difference between this embodiment and embodiment 1 is that: the means for controlling the moisture content of the gas atmosphere in the heat treatment process is to raise the temperature at a low speed, and the calcination treatment time is 0.5 hour. Otherwise, the same as in example 1 was used.

S3, switching the gas in the muffle furnace into air, adjusting the temperature to 850 ℃ and calcining for 0.5 hour, removing carbon on the surfaces of the particles, and densifying the surfaces of the particles to obtain the black silicon dioxide with the mass content of carbon uniformly increasing from the surface to the inside.

Example 10

S2, placing spherical polysiloxane powder into a muffle furnace, setting the nitrogen inlet flow to be larger flow and 300mL/min, so that the maximum value of water content at an outlet when the temperature in the muffle furnace is higher than 650 ℃ is 1800ppm, namely the water content in the muffle furnace when the temperature in the muffle furnace is higher than 650 ℃ is not more than 1800ppm. And heating the temperature in the furnace to 850 ℃ in a nitrogen atmosphere, and preserving the temperature for 10 hours, and performing heat treatment on the particles so as to thermally decompose organic groups in the particles into carbon elements. In the heating process, the water concentration at the gas outlet of the muffle furnace is continuously monitored, and when the water concentration is increased to be more than 1800ppm when the temperature in the furnace is higher than 650 ℃, the inlet flow of nitrogen is increased appropriately. In this example, the moisture content at the gas outlet of the muffle furnace was continuously monitored, and the maximum moisture content was 1800ppm at a temperature above 650 ℃.

Example 11

S2, placing spherical polysiloxane powder into a muffle furnace, setting the nitrogen inlet flow to be larger flow and 100mL/min, so that the maximum value of water content at an outlet when the temperature in the muffle furnace is higher than 650 ℃ is 3000ppm, namely the water content in the muffle furnace when the temperature in the muffle furnace is higher than 650 ℃ is not more than 3000ppm. And (3) under the nitrogen atmosphere, heating the temperature in the furnace to 850 ℃ at a speed of 5 ℃/min, and preserving the temperature for 10 hours, and performing heat treatment on the particles so as to thermally decompose organic groups in the particles into carbon elements. In the heating process, the water concentration at the gas outlet of the muffle furnace is continuously monitored, and when the water concentration is increased to more than 3000ppm when the temperature in the furnace is higher than 650 ℃, the inlet flow of nitrogen is increased appropriately. In this example, the moisture content at the gas outlet of the muffle furnace was continuously monitored, and the maximum moisture content was 3000ppm at a temperature above 650 ℃.

Example 12

S2, placing spherical polysiloxane powder into a muffle furnace, setting the nitrogen inlet flow to be larger flow and 1000mL/min, so that the maximum value of water content at an outlet when the temperature in the muffle furnace is higher than 650 ℃ is 1400ppm, namely the water content in the muffle furnace is not more than 1400ppm when the temperature in the muffle furnace is higher than 650 ℃. And (3) under the nitrogen atmosphere, heating the temperature in the furnace to 850 ℃ at a speed of 5 ℃/min, and preserving the temperature for 10 hours, and performing heat treatment on the particles so as to thermally decompose organic groups in the particles into carbon elements. In the heating process, the water concentration at the gas outlet of the muffle furnace is continuously monitored, and when the water concentration is increased to be more than 1400ppm when the temperature in the furnace is higher than 650 ℃, the inlet flow of nitrogen is increased appropriately. In this example, the moisture content at the gas outlet of the muffle furnace was continuously monitored, and the maximum moisture content was 1400ppm at a temperature above 650 ℃.

Example 13

S2, placing spherical polysiloxane powder into a muffle furnace, setting the nitrogen inlet flow to be larger flow and 100mL/min, so that the maximum value of water content at an outlet when the temperature in the muffle furnace is higher than 650 ℃ is 2000ppm, namely the water content in the muffle furnace is not more than 2000ppm when the temperature in the muffle furnace is higher than 650 ℃. And (3) heating the temperature in the furnace to 1000 ℃ at a speed of 10 ℃/min under the nitrogen atmosphere, and preserving the temperature for 10 hours, so that the organic radicals in the particles are thermally decomposed into carbon elements. In the heating process, the water concentration at the gas outlet of the muffle furnace is continuously monitored, and when the water concentration is increased to be more than 2000ppm when the temperature in the furnace is higher than 650 ℃, the inlet flow of nitrogen is increased appropriately. In this example, the moisture content at the gas outlet of the muffle furnace was continuously monitored, and the maximum moisture content was 2000ppm at a temperature above 650 ℃.

S3, switching the gas in the muffle furnace into air, adjusting the temperature to 1200 ℃ and calcining for 10 hours, removing carbon on the surfaces of the particles, and densifying the surfaces of the particles to obtain the black silicon dioxide with the mass content of carbon uniformly increasing from the surfaces to the inside.

Comparative example 1

The main difference from example 1 is that: in the heat treatment process of the step S2, the nitrogen gas inlet flow is 50mL/min, so that the water content in the furnace is in the range of 3500 ppm-4200 ppm. Otherwise, the same as in example 1 was used.

The silica particles of this comparative example were prepared as follows:

S2, placing the spherical polysiloxane powder into a muffle furnace, setting the nitrogen inlet flow to be 50mL/min, heating the temperature in the furnace to 850 ℃ under the nitrogen atmosphere, and preserving the heat for 10 hours, and performing heat treatment on the particles to ensure that organic radicals in the particles are thermally decomposed into carbon elements. During the temperature rise, the moisture concentration at the gas outlet of the muffle furnace was continuously monitored. In this example, the moisture concentration at the gas outlet of the muffle furnace was continuously monitored to be in the range of 2000ppm to 4200ppm, and after the temperature in the furnace reached 650 ℃ or higher, the moisture concentration was maintained in the range of 3500ppm to 4200ppm for a total of 5.3 hours.

S3, switching the gas in the muffle furnace into air, adjusting the temperature to 850 ℃ and calcining for 3 hours to obtain the silica particles.

Comparative example 2

The main difference from example 1 is that: in step S3, the gas is not switched to air. Otherwise, the same as in example 1 was used.

The silica particles of this comparative example were prepared as follows:

S2, placing spherical polysiloxane powder into a muffle furnace, setting the nitrogen inlet flow to be larger flow and 300mL/min, so that the maximum water content at an outlet is 1800ppm, namely when the temperature in the muffle furnace is higher than 650 ℃ in the heat treatment process, and the water content in the furnace is not more than 1800ppm. The temperature in the furnace is raised to 850 ℃ at a rate of 5 ℃/min under the nitrogen atmosphere, and the particles are subjected to heat treatment so that the organic radicals in the particles are thermally decomposed into carbon elements. In the heating process, the water concentration at the gas outlet of the muffle furnace is continuously monitored, and when the water concentration is increased to be more than 1800ppm at the temperature higher than 650 ℃, the inlet flow of nitrogen is increased appropriately. In this example, the moisture content at the gas outlet of the muffle furnace was continuously monitored, and the maximum moisture content was 1800ppm at a temperature above 650 ℃.

And S3, continuously calcining for 3 hours to obtain black silicon dioxide.

Comparative example 3

The main difference from example 1 is that: in the heat treatment process of the step S2, the nitrogen gas inlet flow is 50mL/min, so that the water content is lower than 4200ppm when the temperature in the furnace is higher than 650 ℃; in step S3, the gas is not switched to air. Otherwise, the same as in example 1 was used.

The silica particles of this comparative example were prepared as follows:

And S3, continuously calcining for 3 hours to obtain the silica particles.

Table 1 process parameters of examples and comparative examples

Characterization of Performance

The silica particles prepared in examples 1 to 13 and comparative examples 1 to 3 were subjected to tests of particle diameter, carbon content, and water content, and the analysis results are shown in Table 2. Wherein the 48-hour water content is a water content test performed by leaving the mixture open for 48 hours at 25 ℃ under 50% RH environmental conditions from the start of the preparation. The 100 day moisture content is a moisture content test performed by leaving the particles open for 100 days at 25 ℃ under 50% rh ambient conditions.

Table 2 results of characterization of properties of example and comparative articles

Data analysis:

① From the data of examples 1 to 13, the present invention can obtain a black silica filler having an average particle diameter of 0.1 to 1 μm, which has excellent properties of less surface defects and less water absorption after leaving it stand, by taking polysiloxane including T units as a starting material particle, then thermally decomposing organic groups in the particle into carbon elements under an inert gas atmosphere at a temperature of more than 650 ℃ and heat-treating the carbon elements under conditions where the water content is less than 3500ppm, and then calcining the surface of the particle under an oxygen-containing gas atmosphere to densify the surface of the particle.

② From comparative analysis of comparative example 1 with example 1, the main difference between comparative example 1 and example 1 is that the water content is not higher than 4200ppm at a temperature higher than 650 ℃ in an inert gas atmosphere, and the carbon content of the obtained silica particles is greatly reduced, thereby indicating that the water content of the production environment needs to be controlled during the heat treatment of small-sized carbon-containing particles, otherwise the carbon content of the product is reduced. Further analysis is made because, during the heat treatment of the polysiloxane raw material particles, water is generated in the particles in a large amount, including adsorbed water, surface hydroxyl groups, internal hydroxyl groups, and the like, and therefore the gas atmosphere contains a certain concentration of water, and at the heat treatment temperature, water reacts with carbon to carry away carbon in the particles, and during the heat treatment of the polysiloxane raw material particles having a small particle diameter, the presence of this reaction is a major factor that limits carbon to remain in the particles, and it has been found that the temperature at which water reacts with carbon is around 700 ℃ during the heat treatment to thermally decompose organic radicals into carbon, and that the concentration of water can be controlled at a temperature higher than 650 ℃ to prevent the water from carrying away carbon in the particles.

③ Meanwhile, as is clear from the comparative analysis of comparative example 1 and examples 1 to 3, the main difference between comparative example 1 and examples 1 to 3 is the amount of water content at a temperature higher than 650 ℃ in the inert gas atmosphere at the time of heat treatment, the black silica obtained in example 1 having the lowest water content during heat treatment has the smallest water content after being left to stand, and the black silica obtained in comparative example 1 having the highest water content has the largest water content after being left to stand. Therefore, the control of the water content in the environment is performed in the heat treatment process, which is beneficial to the improvement of the density of the prepared silicon dioxide. The reason for this is that defect sites are formed after the organic group becomes carbon, the defect sites are strong in water absorption, and after the defect sites absorb water, the defect sites on the surface are increased, and further the surface density of the particles is reduced, which is shown by the increase in water content after the particles obtained in comparative example 1 are placed as compared with those obtained in examples 1 to 3.

④ From comparative analysis of comparative example 2 with example 1, the main difference between comparative example 2 and example 1 is that comparative example 2 is calcined in an inert gas atmosphere. The silica particles obtained in comparative example 2 had a greatly increased water content after being left to stand, and thus, it was revealed that the surface of the particles could not be densified without calcining the particles in an oxygen-containing atmosphere, resulting in an increase in the water absorption after the product was left to stand. The reason for the further analysis is that carbon on the surface of the silicon dioxide ball can be taken away by calcining under the condition of oxygen, and the defect on the surface of the silicon dioxide ball is repaired by condensing silicon hydroxyl groups, so that a compact layer is formed on the surface of the silicon dioxide ball, the density of the product is improved, and the problem that the product is easy to absorb water due to the fact that carbon on the surface falls off to form pores during the shelf life or the service period of the product is avoided.

⑤ From comparative analysis of comparative example 1, comparative example 3 and example 1, it can be seen that: the main difference between comparative example 3 and example 1 is that the water content in the inert gas atmosphere at the time of heat treatment reached 4200ppm, the water content was large, and calcination was performed in the inert gas atmosphere; comparative example 3 the main difference from comparative example 1 is that comparative example 3 was calcined in an inert gas atmosphere; comparative example 1 differs from example 1 mainly in that the water content in the inert gas atmosphere at the time of heat treatment of comparative example 1 reached 4200ppm, and the water content was large. As can be seen from the performance characterization results of the three products, the comparative example 1 has small carbon content, but the water content is not obviously increased compared with the example 1, which indicates that the water content of the gas atmosphere is controlled during heat treatment, and the carbon content of the products is mainly influenced; comparative example 3 has significantly smaller carbon content than example 1, and the water content after placement is also significantly increased, i.e., the density of the product is decreased, thereby indicating that the density of the product surface is affected by the calcination atmosphere.

⑥ From comparative analyses of example 8, example 9 and example 1, the main difference between example 8 and example 1 is that the means for controlling the moisture concentration of the heat treatment gas atmosphere is a slow temperature rise, and the product characterization result of example 8 shows that the carbon content is reduced to some extent and the water absorption is greatly increased after the product is placed, thereby explaining the advantage of realizing the low moisture concentration of the gas atmosphere by rapid purge of nitrogen with a large flow rate. Example 9 by shortening the calcination time in an oxygen atmosphere, the carbon content of the product can be increased somewhat compared to example 8, but the water absorption after placement is still greatly increased.

The analysis realizes the low moisture concentration of gas atmosphere through the quick purge of high-flow nitrogen and has the advantages that in the heating treatment process under the inert gas atmosphere, the high-flow nitrogen rapidly brings out the silicon hydroxyl condensation in the polysiloxane raw material to generate moisture, the arrangement of R1 groups of T units can be influenced, and further the overall structural arrangement of the polysiloxane is influenced, so that in the later calcination process, the density of the surface compact layer formed by the silicon hydroxyl condensation is higher. The silicon dioxide with higher density has smaller porosity, namely smaller specific surface area under the condition of the same particle size, and has less water absorption capacity when being placed in the air for a long time in the later period.

The uranium, thorium content of all example samples of examples 1 to 13 was less than 1ppb. The example samples obtained in examples 1 to 13 above may be subjected to surface treatment. Specifically, a vinyl silane coupling agent, an epoxy silane coupling agent, a disilazane, and the like may be used for the treatment as needed. More than one type of treatment may be performed as needed.

The "main powder" referred to in the present invention refers to a powder of large particle segments of the total filler filled in the resin.

The raw materials and equipment used in the invention are common raw materials and equipment in the field unless specified otherwise; the methods used in the present invention are conventional in the art unless otherwise specified.

The foregoing description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and any simple modification, variation and equivalent transformation of the above embodiment according to the technical substance of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A black silica filler characterized by:

the mass content of carbon of the black silica filler particles gradually increases from the surface to the inside;

the average particle diameter of the black silicon dioxide filler particles is 0.1-1 mu m, and the mass content of carbon is 0.3-9%.

2. The black silica filler of claim 1 wherein: from the start of the preparation, the black silica filler particles were left to stand for 48 hours at 25 ℃ under 50% rh ambient conditions with a water content of less than 591ppm/m ².

3. The black silica filler of claim 1 wherein: from the start of the preparation, the black silica filler particles were left to stand for 48 hours at 25 ℃ under 50% rh ambient conditions with a water content of less than 245ppm/m ².

4. A preparation method of black silicon dioxide filler is characterized in that: providing spherical polysiloxane particles comprising T units, performing the following steps of:

5. The method for preparing a black silica filler according to claim 4, wherein: in step S1, the end temperature of the heating treatment is 850-1100 ℃.

6. A method of preparing a black silica filler according to claim 5, wherein: and (3) slowly heating or/and introducing inert gas with high flow rate in the heating process.

7. A method of preparing a black silica filler according to claim 6, wherein: the temperature rising rate of the slow temperature rising is 0.1-1 ℃/min.

8. A method of preparing a black silica filler according to claim 6, wherein: the flow rate of the inert gas is 100-1000 mL/min.

9. The method for preparing a black silica filler according to claim 4, wherein: in the step S2, the volume concentration of oxygen in the oxygen-containing gas is 0.3-30%.

10. A method of preparing a black silica filler according to claim 9, wherein: in the step S2, the volume concentration of oxygen in the oxygen-containing gas is 3-21%.

11. The method for preparing a black silica filler according to claim 4, wherein: in the step S2, the temperature of the calcination treatment is 850-1200 ℃.

12. The method for preparing a black silica filler according to claim 4, wherein: the polysiloxane further comprises Q units, D units and/or M units; wherein Q unit=sio ₄ -, D unit=r ₂R₃SiO₂ -, M unit=r ₄R₅R₆ SiO-;

R ₂、R₃、R₄、R₅、R₆ is a hydrogen atom or a hydrocarbon group of 1 to 18 carbon atoms which can be independently selected.

13. A method of preparing a black silica filler according to claim 12, wherein: the polysiloxane has a T unit material selected from at least one of the group consisting of tetraalkoxysilane, silicon tetrachloride and silicon dioxide, a D unit material selected from at least one of the group consisting of dialkyldialkoxysilane and dialkyldichlorosilane, and a M unit material selected from at least one of the group consisting of trialkylalkoxysilane, trialkylchlorosilane and hexahydrocarbyldisilazane.

14. Use of a black silica filler according to any one of claims 1 to 3, or a black silica filler prepared by the preparation method according to any one of claims 4 to 13, for preparing a semiconductor encapsulation material or a substrate material.