KR20180013404A - Boron nitride complex and preparing method thereof - Google Patents

Abstract

A high strength boron nitride composite material excellent in thermal conductivity and a preparing method thereof are suggested. The boron nitride composite material according to the present invention includes a boron nitride aggregate in which two or more plate-shaped boron nitride are aggregated, and a glass particle melted and positioned inside the boron nitride aggregate.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a boron nitride complex,

The present invention relates to a boron nitride composite material and a manufacturing method thereof, and more particularly, to a high strength boron nitride composite material having excellent thermal conductivity and a manufacturing method thereof.

In recent years, electronic devices such as smart phones and computers have become smaller and lighter, requiring high-density packaging of semiconductor packages and high integration and speeding up of devices in integrated circuits. Accordingly, heat generated from various electronic components is discharged to the outside to prevent damage to the component due to heat, so that research on a heat radiating plate or a heat radiating sheet has been actively conducted.

As a conventional heat sink, a heat-radiating metal such as aluminum is used. However, when metal is used as a heat sink material, there are limitations on low formability, productivity and part design, and research is being conducted to replace this material.

Therefore, in place of a metal-based electronic material, a carbon-based material (graphene, carbon nanotube), oxide (Al ₂ O ₃ , SiO ₂ , ZnO), silicon carbide (SiC) (Filler) such as AlN, BN, SI ₃ N ₄ and the like have been studied. According to various thermal conductivity prediction models, the thermal conductivity depends on the thermal conductivity characteristics of the material itself and the amount of filler added. Therefore, it is better to select fillers and polymers with high thermal conductivity to produce materials with high thermal conductivity.

Aluminum nitride (AlN) is used as a very useful filler because it exhibits high thermal conductivity, high temperature resistance, electrical insulation ability and excellent mechanical stability. However, AlN is easily hydrolyzed to moisture in the air, resulting in aluminum hydroxide on the surface, which negatively affects electronic devices.

Boron isride (BN), another inorganic filler, is attracting attention as a problem of AlN. BN is a plate-like material having a crystallographically isotropic structure such as graphite, has a good barrier property on the surface, has excellent thermal and mechanical properties, and exhibits very strong hydrophobic properties. Also, because of this isotropic material, when BN is used as a filler, the heat flow inside the polymer matrix changes depending on the orientation direction of BN. BN powder is a crystallographic anisotropy with a thermal conductivity of 2 to 3 W / mK in the Z-axis direction, but a characteristic of 160 W / mK in the x- and y-axis directions.

A typical thermally conductive sheet is prepared by forming a composition containing a filler and a thermosetting polymer into a sheet shape by a method such as press molding, injection molding, extrusion, doctor blade molding and curing. However, when the composition containing BN is molded by the above-described method, the sheet-like BN is liable to be collapsed in the sheet depending on the pressure and the flow, that is, the BN is liable to be aligned horizontally with the ground inside the polymer matrix.

1 is a cross-sectional view of a thermally conductive sheet including BN. Referring to FIG. 1, even when the desired heat flow is in the vertical direction, the BN is positioned in the horizontal direction, and the heat flow progresses in the horizontal direction to lower the thermal conductivity. That is, the desired heat flow direction and the orientation of the BN are perpendicular to each other, and the thermal conductivity is insufficient, so that the excellent heat conduction characteristics of the BN can not be exhibited.

It is an object of the present invention to provide a high-strength boron nitride composite material having excellent thermal conductivity and a manufacturing method thereof.

According to an aspect of the present invention, there is provided a boron nitride composite material comprising: a boron nitride aggregate having two or more plate-shaped boron nitride aggregated; And glass particles melted and positioned within the boron nitride agglomerate.

The boron nitride composite material according to the present invention may further include a plate-shaped boron nitride.

The boron nitride agglomerates may exhibit isotropic thermal conductivity characteristics.

The glass particles may include at least one of B ₂ O ₃ , MgCO ₃ , ZnO, SiO ₂ and Al ₂ O ₃ .

The glass particles may have a melting point of 300 ° C to 1500 ° C or the glass particles may have a melting point lower than the sintering temperature of the plate-shaped boron nitride.

According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: mixing a plate-shaped boron nitride and glass particles with a solvent; Spray-drying the mixed solution to form a boron nitride agglomerate including glass particles; And heat treating the boron nitride agglomerate containing the glass particles to melt the glass particles in the boron nitride agglomerate. The heat treatment may be performed at 300 ° C to 1500 ° C.

According to the present invention, in order to realize excellent physical properties of boron nitride in a heat dissipation material, boron nitride is realized as spherical agglomerate, and glass particles are used together to melt the glass particles by heat treatment to form a boron nitride agglomerate It is possible to obtain a high-strength boron nitride composite material exhibiting properties such as excellent thermal conductivity and increased bonding strength.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a heat flow of a heat radiation sheet including a conventional plate-shaped boron nitride. FIG.
2 is an SEM image of the glass particles obtained in the examples.
Figure 3 is an SEM image of a boron nitride agglomerate comprising a tabular boron nitride and glass particles obtained in the examples.
FIGS. 4 and 5 are SEM images after mechanical annealing of the boron nitride composite material before heat treatment and the boron nitride composite material after heat treatment obtained in the examples, respectively.
6 is an SEM image of the thermally conductive film of Comparative Example 1. Fig.
7 is an SEM image of the thermally conductive film of Example 1. Fig.
8 is an SEM image of the thermally conductive film of Example 2. Fig.
9 is a graph showing thermal conductivities of the thermal conductive films of Examples 1 and 2, and Comparative Examples 1 and 2 according to the volume fraction of boron nitride according to the total film volume.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention. It should be understood that while the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, The present invention is not limited thereto.

According to an aspect of the present invention, there is provided a boron nitride composite material comprising: a boron nitride aggregate in which two or more plate-shaped boron nitride are aggregated; And glass particles melted and positioned within the boron nitride agglomerate.

In the present invention, the boron nitride aggregate means a state in which two or more plate-shaped boron nitride is aggregated. The boron nitride has a hexagonal crystal structure or a cubic crystal structure depending on the pressure and temperature. The boron nitride agglomerates in the present invention are plate-shaped boron nitrides and include hexagonal boron nitride.

Boron isride (BN) has high thermal conductivity, excellent heat dissipation and chemical stability, and is resistant to thermal shock and exhibits rigid physical properties. Boron nitride is a non-oxide ceramics which is a ceramic with an insulating property but also has a thermal conductivity similar to that of a metal. Accordingly, boron nitride can be dispersed in lubricating oil, grease, water, solvent or the like to be used as an additive for a lubricant, and can be used as a high temperature lubricant additive utilizing strong heat resistance. In addition, boron nitride has high dielectric breakdown strength and resistance, so it can be used as an electrical insulator. Semiconductor substrates, transparent glass windows for microwave ovens, electrical insulators for fuel cells, battery electrodes, catalysts, encapsulants and the like, and can be used as filling materials for insulation and heat dissipation.

Although boron nitride has a crystal structure similar to that of graphite, it is difficult to provide insulation when graphite is applied as a heat-dissipating sheet. In contrast to carbon dioxide emissions, boron nitride is an excellent electrically insulating material and is unique among new material ceramics It is a material with excellent machinability.

In addition, boron nitride is stable to a maximum of 3,000 DEG C in an inert atmosphere such as a gas vacuum and is not softened because it does not sublimate at this temperature. This has a high thermal conductivity as high as that of stainless steel, , It has thermal excellence to such an extent that cracking or breakage does not occur even if rapid heating and quenching of about 1,500 ° C are repeated. In addition, the boron nitride is excellent in corrosion resistance against an organic solvent and does not react with a melt such as metal, glass, and silicone rubber, so that there is no reaction problem due to melting of the glass particles as in the present invention.

When the heat dissipation material is manufactured using such a boron nitride, it is difficult to obtain the desired heat dissipation characteristics as compared with the boron nitride which exhibits excellent physical properties, thermal conductivity, and heat dissipation. This is due to the plate shape of boron nitride. The heat radiation sheet using boron nitride generally exhibits a thermal conductivity of about 120 W / mk in the horizontal direction and a low thermal conductivity of about 3 W / mk in the vertical direction . When the heat-radiating sheet using boron nitride is used for a product on which a heat-generating object is mounted on a substrate such as a PCB or an LED backlight, the heat-radiating property is determined depending on the thermal conductivity in the vertical direction . Therefore, the plate-like boron nitride can not exhibit thermal conductivity characteristics in a desired direction due to restriction of the shape.

In order to compensate for the anisotropic thermal conductivity of the boron nitride, the present invention uses a plate-like boron nitride as an aggregate and uses it as a heat radiator without using a plate-like boron nitride. That is, in the present invention, as a boron nitride composite material containing glass particles in a boron nitride agglomerate including two or more plate-like boron nitride, the glass particles are melted in the boron nitride agglomerate to increase the bonding strength of the boron nitride A boron nitride composite is proposed.

The boron nitride agglomerates are weak in bonding strength between the boron nitride particles and can be returned to the plate-like boron nitride particle state in the mixing process with the polymer resin for producing the heat-radiating sheet. Therefore, in order to prevent deterioration of durability due to weakening of the bonding force, glass particles are added to form boron nitride aggregates, and the glass particles are heat-treated to induce melting of the glass particles, thereby improving the durability of the boron nitride aggregates.

As the glass particles, B ₂ O ₃ , MgCO ₃ , ZnO, SiO ₂ , Al ₂ O ₃ , MgO, TiO ₂ , Na ₂ O, K ₂ O, CaO, SrO, BaO, V ₂ O ₅ , MoO ₃ , Cr ₂ O ₃ , WO ₃ , MnO, P ₂ O ₅ , CdO, Ag ₂ O, AgI, AgBr, or AgCl. The glass particles are preferably low melting glass. Further, the glass particles preferably have a melting point lower than the sintering temperature of the plate-shaped boron nitride. When the melting point of the glass particles is higher than the sintering temperature of the plate-like boron nitride, the plate-like boron nitride is sintered before the glass particles are melted, thereby increasing the risk of breakage. Since the sintering temperature of the boron nitride is higher than 3,000 ° C, The process cost may increase. The glass particles preferably have a melting point of 300 ° C to 1500 ° C.

As the glass particles which can be used in the present invention, two or more different glass particles may be mixed or used, or two or more different glass particles may be mixed and melted and pulverized. In the case of using one kind of glass particles by melting different glass particles, a desired melting temperature can be obtained by controlling the melting point and mixing ratio of each glass particle.

The boron nitride agglomerates of the present invention preferably exhibit an isotropic thermal conductivity characteristic unlike the plate-shaped boron nitride. Accordingly, the boron nitride agglomerates of the present invention are implemented so that their shapes can exhibit an isotropic thermal conductivity. For example, the boron nitride agglomerates can be realized in such a shape that the plate-shaped boron nitride is aggregated in a spherical shape and the glass particles are present in an empty space.

Since the boron nitride agglomerate exhibits isotropic thermal conductivity characteristics, when a boron nitride composite material containing the boron nitride composite material is subjected to heat treatment, unlike the high-plate-type boron nitride in the horizontal direction, it exhibits excellent thermal conductivity in both the horizontal direction and the vertical direction .

The boron nitride composite material according to the present invention may further include a plate-shaped boron nitride. In order to exhibit the isotropic thermal conductivity characteristics of the boron nitride agglomerate, it is more likely that void spaces are formed between the boron nitride agglomerates and the boron nitride agglomerates because the agglomerates exhibit spherical agglomerate shape rather than a plate-like shape. Therefore, since the heat dissipation characteristics may be deteriorated due to such empty space, the boron nitride composite material may further include a plate-shaped boron nitride in addition to the boron nitride aggregate to improve the heat radiation characteristics by filling void spaces between the boron nitride aggregates .

In addition, in the case where only a plate-shaped boron nitride is present, the horizontal heat conductivity characteristic is excellent due to the shape of the plate-shaped boron nitride. However, when the boron nitride is present together with the boron nitride aggregate, The possibility of being located is increased. Accordingly, when the boron nitride agglomerate and the plate-like boron nitride are combined together as the boron nitride composite material, the thermal conductivity characteristics in the horizontal direction and the vertical direction of the heat radiation sheet including the boron nitride composite material can be improved.

According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: mixing a plate-shaped boron nitride and glass particles with a solvent; Spray-drying the mixed solution to form a boron nitride agglomerate including glass particles; And heat treating the boron nitride agglomerate containing the glass particles to melt the glass particles in the boron nitride agglomerate. A spray dry method may be used to manufacture the boron nitride composite material according to the present invention.

The spray drying method is a process in which a liquid raw material is sprayed, atomized, and then the solvent is evaporated instantaneously at a high temperature and dried to obtain a separated phase. When the boron nitride particles and the glass particles are mixed with a solvent to obtain a solution and sprayed through the nozzle, the particles are atomized and dropped. When the particles are dropped and dried through hot air or the like, boron nitride and boron nitride aggregates containing glass particles are obtained . The resulting boron nitride and boron nitride agglomerates including glass particles exhibit a weak bonding force between boron nitride or between boron nitride and glass particles.

The boron nitride agglomerates comprising boron nitride and glass particles are then heat treated. Since the glass particles are contained in the boron nitride agglomerate, the heat treatment induces the melting of the glass particles, and the bonding strength between the plate-like boron nitride is increased to obtain a boron nitride composite material having excellent properties.

The heat treatment can be performed at a temperature higher than the melting point of the glass particles. For example, the heat treatment may be performed at 300 ° C to 1500 ° C.

Hereinafter, specific test examples of the present invention will be described. However, the following test examples do not limit the present invention.

In this test example, first, glass particles are prepared, and boron nitride and boron nitride agglomerates including glass particles are formed by a spray drying method. Then, the glass particles are heat-treated and then formed into a sheet form to test the characteristics.

[Raw materials] Configuration Raw material manufacturer shape size Polymer resin Epoxy resin Mitsubishi Chemical - - 4,4'-dihydroxybiphenyl Sigma-Aldrich - - Glass particles B ₂ O ₃ KOJUNDO KOREA - - MgCO ₃ KOJUNDO KOREA - - ZnO KOJUNDO KOREA - - SiO ₂ KOJUNDO KOREA - - Al ₂ O ₃ KOJUNDO KOREA - - Boron nitride Plate Type Boron Nitride I DENKA Plate type 8 μm Plate Type Boron Nitride II Saint Gobain Plate type 18 to 25 μm Polyethylene glycol SAMCHUN chemical - - Plate type
Boron nitride Plate Type Boron Nitride III DENKA flake 27 μm KBM-403 Shinetsu Chemical - -

[Production of glass particles]

The glass particles in Table 1 were placed in a crucible together with methyl ethyl ketone (MEK) and stirred for 1 hour. Then, the crucible in which the MEK is volatilized is put into a box furnace and melted at 1300 ° C., and the completely melted mixture is cooled with water to obtain a bulk type glass. The glass thus obtained is first pulverized using a mortar and then subjected to a second milling process through a ball-milling process to obtain a size of 1 to 2 탆.

2 is an SEM (SNE 1500M, SEC Co.) image of the obtained glass particles.

[Manufacture of a boron nitride agglomerate containing a plate-like boron nitride and a glass particle]

Add distilled water, adjusted to pH 9 with NaOH, in the order of polyethylene glycol and glass particles, and mix at room temperature. Then, the slurry to be spray-dried is prepared by slowly adding the plate-like boron nitride I and the plate-like boron nitride II of Table 1 to the mixed solution. The slurry was spray-dried in an air atmosphere at 160 캜 using a spray dryer to obtain a boron nitride agglomerate containing a plate-like boron nitride and glass particles. The obtained boron nitride agglomerates are shown in Fig. Referring to FIG. 3, it can be seen that the boron nitride agglomerates are sphered with the agglomeration of the plate-shaped boron nitride.

[Heat treatment]

The plate-like boron nitride before the heat treatment and the boron nitride agglomerate including the glass particles are attached only by the weak binding force of the polyethylene glycol. Therefore, the glass particles are heat-treated through the heat treatment to increase the bonding force. The plate-like boron nitride and the boron nitride agglomerates including the glass particles were heat-treated at the melting point of the glass particles at 1125 DEG C for 15 minutes. After the heat treatment, the size of the boron nitride composite material sieved by pulverization and sieving was 35 to 50 mu m.

[Production of thermally conductive film]

Each boron nitride powder surface-treated with epoxy and DHBP solution dissolved in MEK was added according to the volume percentage of the desired filler, and a slurry was prepared using a magnetic stirrer. Thereafter, the mixture solution is degassed for 1 minute and 30 seconds to form a tape, and then the PET film is coated on the PET film to a thickness of about 300 mu m to obtain a thermally conductive film. The prepared thermally conductive film was preliminarily dried in an oven at 60 ° C. for 1 hour and 30 minutes to peel off the coating layer from the PET film, and then the sheet was laminated with about 6 sheets and heated at 105 ° C. for 20 minutes and at 135 ° C. for 40 minutes under pressure of 3 Mpa A sample was prepared.

<Evaluation>

[Strength evaluation]

The plate-like boron nitride not subjected to the heat treatment, the boron nitride agglomerate including the glass particles, and the boron nitride agglomerate after the heat treatment were respectively put into distilled water and stirred at 300 rpm for 24 hours. FIG. 4 shows an SEM image of the boron nitride agglomerate before the heat treatment, and FIG. 5 shows an SEM image of the boron nitride agglomerate after the heat treatment. Since the boron nitride agglomerate which has not undergone the post-heat treatment after spray drying is only bound to the polymer binder, if the powder is introduced into water or another solvent, the binding force becomes weak and it is easy to return to the first plate-like boron nitride. Accordingly, it was confirmed in FIG. 4 that the boron nitride agglomerate returned to the plate-like boron nitride. In contrast, the boron nitride agglomerates of FIG. 5 are retained in the spherical particle shape, indicating that the strength is increased due to the heat treatment. This is presumably because the glass particles contained in the boron nitride agglomerate were dissolved after the heat treatment to increase the binding force of the plate-like boron nitride.

[Evaluation of thermal conductivity]

A thermally conductive film using a plate-like boron nitride (Comparative Example 1), a thermally conductive film using a surface-treated plate-shaped boron nitride (Comparative Example 2), a thermally conductive film using a boron nitride composite material produced according to the present invention (Example 1), and a thermal conductive film (Example 2) using a boron nitride composite material further comprising a plate-like boron nitride was used to evaluate thermal conductivity characteristics. In Comparative Example 2, the surface of the plate-like boron nitride of Comparative Example 1 was subjected to surface treatment, and then a thermally conductive film was produced. The surface treatment is for improving the interface with the polymer resin.

6 is an SEM image of a thermally conductive film (Comparative Example 1) comprising a plate-shaped boron nitride. In the SEM image consisting of the plate-shaped boron nitride, the boron nitride is laid horizontally on the two-dimensional xy-axis. Therefore, it is predicted that the thermal conductivity in the vertical direction will be poor.

7 is an SEM image of a thermally conductive film (Example 1) including a boron nitride composite material according to the present invention. It is considered to be spherical and exhibit an isotropic thermal conductivity unlike in the case of the plate-shaped boron nitride shown in Fig. In the film of Example 1, since the glass particles were added and heat-treated, the boron nitride powders could be formed into films while keeping their shapes without breaking. However, it can be seen that vacancies are formed between the boron nitride agglomerates in the boron nitride composite material. This empty space may remain without penetration of the polymeric resin, i.e. the epoxy resin. Thus, a decrease in thermal conductivity due to void spaces between aggregates may occur.

8 is an SEM image of a thermally conductive film (Example 2) in which the boron nitride composite material of Example 1 further comprises a plate-shaped boron nitride. That is, in the thermally conductive film of Example 2, spherical boron nitride agglomerates and plate-like boron nitride particles are included. The volume ratio of the boron nitride agglomerate to the plate-like boron nitride is 4: 6. Thus, referring to FIG. 8, the vacant space between the circularly indicated boron nitride agglomerates is filled with a plate-shaped boron nitride that is indicated by a straight line. That is, the plate-shaped boron nitride penetrates into the vacant space between the boron nitride agglomerates to make the structure of the filler in the polymer resin more dense and reduce the vacancy, while the plate-shaped boron nitride having a high thermal conductivity is expressed in the vertical direction Thereby improving the thermal conductivity.

 9 is a graph showing thermal conductivities of the thermal conductive films of Examples 1 and 2, and Comparative Examples 1 and 2 according to the volume fraction of boron nitride according to the total film volume. Thermal conductivity can be obtained by multiplying thermal diffusivity, density and specific heat capacity by using laser flash method (LFA; LFA 447, NETZSCH Co.), Gas Displacement Pycnometry System (AccuPyc 1330, Micromeritics Co.), differential scanning calorimetry (DSC; DSC 200 F3, NETZSCH Co.).

In the case of Comparative Example 1 and Comparative Example 2, the plate-like boron nitride exhibits a curved line similar to a solid line oriented in the horizontal direction, and when the plate-shaped boron nitride is actually applied to the thermally conductive film, it is aligned in the horizontal direction and exhibits low thermal conductivity And it was found. On the contrary, Example 1 using the boron nitride composite material according to the present invention exhibited thermal conductivity superior to Comparative Example 1 and Comparative Example 2, so that the plate-shaped boron nitride was aggregated according to the present invention, It was confirmed that the thermal conductivity can be improved by using the increased boron nitride composite material. That is, it is presumed that the bonding force is increased due to the melting of the glass particles, and the return to the plate-shaped boron nitride is prevented again in the production of the thermally conductive film in addition to the epoxy resin.

In the case of Example 2 in which a plate-shaped boron nitride was added to the boron nitride composite material, the highest thermal conductivity was exhibited. In the production of the thermally conductive film, the vacancy space between the boron nitride and the isotropic boron nitride aggregates It is possible to manufacture a thermally conductive film having excellent thermal conductivity characteristics by adding the thermal conductivity property of the plate-shaped boron nitride to the thermal conductivity of the thermally conductive film.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, many modifications and changes may be made by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims. The present invention can be variously modified and changed by those skilled in the art, and it is also within the scope of the present invention.

Claims (8)

A boron nitride agglomerate in which two or more plate-shaped boron nitride is aggregated; And
And glass particles melted and positioned inside the boron nitride agglomerate.
The method according to claim 1,
A boron nitride composite material further comprising a plate-shaped boron nitride.
The method according to claim 1,
Wherein said boron nitride agglomerates exhibit isotropic thermal conductivity characteristics.
The method according to claim 1,
Wherein the glass particles comprise at least one of B ₂ O ₃ , MgCO ₃ , ZnO, SiO ₂ and Al ₂ O ₃ .
The method according to claim 1,
Wherein the glass particles have a melting point of 300 ° C to 1500 ° C.
The method according to claim 1,
Wherein the glass particles have a melting point lower than the sintering temperature of the plate-like boron nitride.
Mixing the plate-shaped boron nitride and the glass particles with a solvent;
Spray-drying the mixed solution to form a boron nitride agglomerate including glass particles; And
And thermally treating the boron nitride agglomerate containing the glass particles to melt the glass particles in the boron nitride agglomerate.
The method of claim 7,
Wherein the heat treatment is performed at 300 ° C to 1500 ° C.

Images