Aluminum nitride sintered bodies and electronic components

Abstract

To provide an aluminum nitride sintered body having high thermal conductivity and high insulation performance, and an electronic component comprising the sintered body.SOLUTION: An aluminum nitride sintered body includes aluminum nitride particles and a sintering aid phase. In the aluminum nitride sintered body, the thermal conductivity, in terms of a thickness of 2.5 mm, is 240 W / mK or more; the content of Y2O3 in the sintered body is 0.1 wt.% or less; and the carbon content in the sintered body is 0.05 wt.% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to an aluminum nitride sintered body, a method for producing the same, and an electronic component. [Background technology]

[0002] Aluminum nitride sintered bodies are made of insulating materials with high thermal conductivity and are attracting attention as materials for high thermal conductivity substrates. Due to their excellent thermal conductivity, aluminum nitride sintered bodies are widely used as heat dissipation substrates for electronic components such as power transistor module substrates, light-emitting diodes, IC packages, and laser diodes in semiconductors and electronic devices where operation becomes unstable at high temperatures. In recent years, aluminum nitride sintered body substrates have been widely used in electronic circuit boards for mobile applications, and even higher heat dissipation is required. Therefore, various attempts are being made to improve the thermal conductivity of aluminum nitride sintered bodies.

[0003] For example, Patent Document 1 discloses an aluminum nitride sintered body and a method for manufacturing the same. The aluminum nitride sintered body of Patent Document 1 has a high thermal conductivity of 260 W / m·K or more by specifying the constituent components and content ratio of the grain boundary phase, as well as the microstructure, specifically the average diameter, minimum diameter, maximum diameter, and number of aluminum nitride crystal particles. The method for producing this aluminum nitride sintered body is characterized by comprising: a molding step of mixing aluminum nitride powder with an average particle size of 1.5 μm or less with a sintering aid containing at least Y compound powder and molding to obtain a molded body; a degreasing step of degreasing the molded body; a deoxidation step of heat-treating the degreasing molded body in a non-oxidizing atmosphere or a reduced-pressure atmosphere at 1300°C to 1550°C to deoxidize it; a sintering step of heat-treating the deoxidized molded body in a non-oxidizing atmosphere at 1800°C to 1950°C to obtain a primary sintered body with a thermal conductivity of 230 W / m·K or more; and a reduction step of heat-treating the primary sintered body in a weakly reducing atmosphere at 1750°C to 1900°C to obtain a high thermal conductivity aluminum nitride sintered body with a thermal conductivity of 260 W / m·K or more. In particular, in the sintering step, a primary sintered body with a thermal conductivity of 230 W / m·K or more is obtained by heat-treating the deoxidized molded body in a non-oxidizing atmosphere at 1800°C to 1950°C. In the subsequent reduction process, the primary sintered body is heat-treated in a weakly reducing atmosphere at a temperature between 1750°C and 1900°C to obtain an aluminum nitride sintered body with a thermal conductivity of 260 W / m·K or higher (high thermal conductivity aluminum nitride sintered body). In this reduction process, the grain boundary phase, which is an inhibitory factor in thermal conductivity, is precipitated and removed from the surface, ultimately resulting in an aluminum nitride sintered body with a thermal conductivity of 260 W / m·K or higher. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2011-37691 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Patent Document 1 provides an aluminum nitride sintered body having high thermal conductivity. On the other hand, in recent years, with the further miniaturization of electronic circuits, the distance between conductors in circuit patterns on an aluminum nitride sintered body substrate has become even smaller, and the electrical properties of the aluminum nitride sintered body as an insulator have also become important. Therefore, the inventors aimed to improve the insulating performance of the aluminum nitride sintered body while maintaining its high thermal conductivity.

[0006] The present invention was made to solve the above problems, and its objective is to provide an aluminum nitride sintered body having both high thermal conductivity and high insulation performance, and a method for manufacturing the same. [Means for solving the problem]

[0007] An aluminum nitride sintered body according to one embodiment of the present invention is an aluminum nitride sintered body comprising aluminum nitride particles and a sintering aid phase, The material is characterized by having a thermal conductivity of 240 W / mK or higher when converted to a thickness of 2.5 mm, and an dielectric strength of 20 kV / mm or higher. It is more preferable that the thermal conductivity is 260 W / mK or higher. It is more preferable that the dielectric strength is 23 kV / mm or higher, and even more preferable that it is 29 kV / mm or higher.

[0008] A further embodiment of the present invention is an aluminum nitride sintered body having a volume resistivity of 5.0 × 10⁻⁶ 13 It is characterized by being Ω·cm or larger.

[0009] A further embodiment of the present invention is characterized in that the aluminum nitride sintered body has a Y2O3 content of 0.1% by weight or less and a carbon content of 0.05% by weight or less.

[0010] A further embodiment of the present invention is an aluminum nitride sintered body, more preferably characterized by having a relative permittivity of 8.5 or less and a dielectric loss tangent of 0.001 or less.

[0011] In a further form of the aluminum nitride sintered body of the present invention, more preferably, in the substrate of the aluminum nitride sintered body, L represents the average value of the brightness measured at one central point and four corner points. * It is characterized in that the value is 57 or more.

[0012] A further form of the aluminum nitride sintered body of the present invention is more preferably characterized by sintering 90 to 99.5% by weight of aluminum nitride and 0.5 to 10% by weight of yttrium oxide.

[0013] An aluminum nitride sintered body according to an embodiment of the present invention is an aluminum nitride sintered body containing aluminum nitride particles and a sintering aid phase, The thermal conductivity when converted to a thickness of 2.5 mm is 240 W / mK or more, and the volume resistivity is 5.0×10 13 Ω·cm or more. It is more preferable that the thermal conductivity is 260 W / mK or more.

[0014] An aluminum nitride sintered body according to an embodiment of the present invention is an aluminum nitride sintered body containing aluminum nitride particles and a sintering aid phase, The thermal conductivity when converted to a thickness of 2.5 mm is 240 W / mK or more, and in the substrate of the aluminum nitride sintered body, L represents the average value of the brightness measured at one central point and four corner points. * It is characterized in that the value is 57 or more. It is more preferable that the thermal conductivity is 260 W / mK or more.

[0015] An aluminum nitride sintered body according to an embodiment of the present invention is an aluminum nitride sintered body containing aluminum nitride particles and a sintering aid phase, The breakdown voltage is 20 kV / mm or more, and in the substrate of the aluminum nitride sintered body, L represents the average value of the brightness measured at one central point and four corner points. * It is characterized in that the value is 57 or more. It is more preferable that the breakdown voltage is 23 kV / mm or more, and even more preferable that it is 29 kV / mm or more.

[0016] The aluminum nitride sintered body according to an embodiment of the present invention is an aluminum nitride sintered body including aluminum nitride particles and a sintering aid phase, having a volume resistivity of 5.0×10 13 Ω·cm or more, and in the substrate of the aluminum nitride sintered body, the average value of the brightness measured at one central point and four corner points is L * value being 57 or more.

[0017] A method for manufacturing an aluminum nitride sintered body according to an embodiment of the present invention is a mixing step of mixing an aluminum nitride raw material powder, a sintering aid, and an organic solvent to prepare a slurry of a raw material mixture, a molding step of molding the raw material mixture to obtain a molded body, a degreasing step of heating the molded body in a degreasing temperature range under an inflow of dry air or in a nitrogen atmosphere to perform degreasing treatment, a deoxidation step of heating the molded body after degreasing in a deoxidation temperature range in a nitrogen atmosphere to perform deoxidation treatment, a sintering step of sintering the molded body after deoxidation in a sintering temperature range in a nitrogen atmosphere to produce an aluminum nitride precursor sintered body, a reduction firing step of producing an embedded structure by embedding at least a part of the aluminum nitride precursor sintered body with aluminum nitride powder and heat-treating the embedded structure at 1850 to 1950°C in a weakly reducing atmosphere, a removal step of removing the aluminum nitride powder from the reduction-fired embedded structure to obtain an aluminum nitride sintered body, characterized by including

[0018] The method for manufacturing an aluminum nitride sintered body according to a further aspect of the present invention is more preferably characterized in that the sintering aid is 0.5 to 10% by weight of Y2O3.

[0019] A further embodiment of the present invention, more preferably, is a method for producing an aluminum nitride sintered body, characterized in that the reduction firing step includes placing the aluminum nitride precursor sintered body in a graphite container, or a BN container or AlN container containing carbon black or a carbon sheet, and embedding the aluminum nitride precursor sintered body with aluminum nitride powder until it is no longer visible.

[0020] An electronic component according to one embodiment of the present invention is characterized by comprising the aluminum nitride sintered body and a laser diode mounted on the surface of the aluminum nitride sintered body. [Effects of the Invention]

[0021] The present invention provides an aluminum nitride sintered body having a high thermal conductivity of 240 W / mK or higher, as well as improved insulating performance. [Brief explanation of the drawing]

[0022] [Figure 1] A schematic diagram showing an example of the reduction firing process in one embodiment of the present invention. [Figure 2] A schematic diagram showing an example of the reduction firing process in conventional examples (Comparative Examples 1 and 2). [Figure 3] A graph showing the relationship between the brightness L* value and dielectric strength of aluminum nitride sintered bodies (Examples 1-20, Comparative Examples 1-6). [Figure 4] A schematic diagram showing electronic components of one embodiment of the present invention. [Modes for carrying out the invention]

[0023] An aluminum nitride sintered body according to one embodiment of the present invention has a substrate shape of a predetermined thickness and can be used as a circuit board for mounting electronic components. The aluminum nitride sintered body is made by sintering 90 to 99.5% by weight of aluminum nitride and 0.5 to 10% by weight of a sintering aid as the main raw material. The aluminum nitride sintered body is composed of a crystalline phase of aluminum nitride particles and a liquid phase consisting of a sintering aid phase.

[0024] The sintering aid can be selected from the group of oxides of rare earth elements Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, and Yb. In this embodiment, yttrium oxide (Y2O3) was used as the sintering aid. It is known that adding rare earth oxides as sintering aids lowers the liquid phase formation temperature during sintering, densifies the crystal structure, and as a result, can achieve both relatively high thermal conductivity and mechanical strength.

[0025] The aluminum nitride sintered body of this embodiment is characterized in that the Y2O3 content remaining in the sintered body is 0.1% by weight or less, and the carbon (element C) content remaining in the sintered body is 0.05% by weight or less. It is more preferable that the Y2O3 content is 0.03% by weight or less. It is also more preferable that the carbon content is 0.03% by weight or less. The aluminum nitride sintered body of the present invention achieves both high thermal conductivity and high electrical properties as an insulator by controlling both the Y2O3 content and carbon content remaining in the sintered body.

[0026] The aluminum nitride sintered body of this embodiment has a thermal conductivity characteristic of 240 W / mK or more when converted to a thickness of 2.5 mm. The thermal conductivity is preferably 260 W / mK or more, and more preferably 265 W / mK or more. In addition to high thermal conductivity, the aluminum nitride sintered body has the following electrical characteristics as an insulator. Preferably, the aluminum nitride sintered body is characterized in that the withstand voltage is 20 kV / mm or more. More preferably, the withstand voltage is 23 kV / mm or more, and still more preferably 29 kV / mm or more. The withstand voltage indicates the upper limit of the voltage that can be applied to the insulator without causing dielectric breakdown, and is an index of the insulation performance of the sintered body. Also preferably, the aluminum nitride sintered body has a volume resistivity of 5.0×10 13 Ω·cm or more, preferably 7.1×10 13 Ω·cm or more. The volume resistivity is a physical property value indicating the electrical insulation as an insulating material. More preferably, the aluminum nitride sintered body is characterized in that the relative permittivity is 8.5 or less, preferably 8.3 or less, and the dielectric loss tangent is 0.001 or less, preferably 0.00086 or less. That is, the aluminum nitride sintered body of this embodiment has both high thermal conductivity characteristics and high insulation performance.

[0027] In addition, the aluminum nitride sintered body is characterized in that the lightness L * value is 57 or more. The lightness L * value indicates the average value of the lightness measured at one center point and four corner points on the substrate of the aluminum nitride sintered body. The aluminum nitride sintered body of this embodiment has a higher lightness than the aluminum nitride sintered body produced by the conventional manufacturing method. FIG. 3 shows the correlation between the lightness L * value obtained from the experimental results and the withstand voltage. As shown in FIG. 3, the lightness L * value and the withstand voltage are directly proportional to each other. The substrate of the aluminum nitride sintered body has a lightness L *If it has a value, it has an dielectric strength of 20kV / mm or more. Conventionally, the characteristic inspection of aluminum nitride sintered body products was performed by destructive evaluation by sampling. In contrast, by utilizing this correlation, the lightness L measured by a colorimeter can be used. * By measuring the values, it became possible to sort all products non-destructively.

[0028] Next, the method for manufacturing the aluminum nitride sintered body of this embodiment will be described. The method for manufacturing the aluminum nitride sintered body mainly includes a mixing step of mixing aluminum nitride raw material powder, a sintering aid, and an organic solvent to produce a slurry of raw material mixtures; a molding step of molding the raw material mixture to obtain a molded body; a degreasing step of heating the molded body in the degreasing temperature range under the inflow of dry air or in a nitrogen atmosphere to degrease it; a deoxidation step of heating the degreased molded body in the deoxidation temperature range in a nitrogen atmosphere to deoxidize it; a sintering step of sintering the deoxidized molded body in the sintering temperature range in a nitrogen atmosphere to produce an aluminum nitride precursor sintered body; a reduction firing step of embedding the aluminum nitride precursor sintered body with aluminum nitride powder to produce an embedded structure and heat-treating the embedded structure at 1850 to 1950°C in a weakly reducing atmosphere; and a removal step of removing the aluminum nitride powder from the reduction-fired embedded structure to obtain an aluminum nitride sintered body. Each step will be described in detail below. In this specification, "embedding" includes not only completely covering the aluminum nitride precursor sintered body with aluminum nitride powder (where the outer surface of the aluminum nitride precursor sintered body is completely surrounded by aluminum nitride powder), but also covering most of the aluminum nitride powder so that a portion of the outer surface of the aluminum nitride precursor sintered body is visible.

[0029] In the mixing step, an appropriate amount of aluminum nitride raw material powder and an appropriate amount of sintering aid powder are prepared. The main raw material, aluminum nitride raw material powder, is preferably a high-purity fine powder with few metal impurities and a low oxygen content. The sintering aid can be selected from the group of oxides of rare earth elements Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, and Yb, but Y2O3 is preferred. In the manufacturing method of this embodiment, 90 to 99.5% by weight of aluminum nitride raw material powder and 0.5 to 10% by weight of Y2O3 are blended. The prepared raw materials (aluminum nitride and sintering aid) are put into a grinding mixer such as a ball mill, and an organic solvent, dispersant, organic binder and / or plasticizer are added, and the mixed materials are thoroughly ground and mixed for a predetermined time. The organic solvent is, for example, a solvent prepared by blending toluene and ethanol in predetermined proportions. The amount of organic solvent is about 30 to 70 parts by weight, based on 100 parts by weight of aluminum nitride raw material powder. Furthermore, the dispersant is, for example, a polycarboxylic acid-based surfactant. However, these organic solvents and dispersants can be selected arbitrarily. In addition, an organic binder is used, for example, polyvinyl butyral resin or acrylic resin. The amount added is about 3 to 10 parts by weight per 100 parts by weight of the raw material powder. A plasticizer is used, for example, dibutyl phthalate (DBP). The amount added is about 1 to 5 parts by weight per 100 parts by weight of the raw material powder. Then, a slurry-like raw material mixture in which each raw material is sufficiently dispersed and mixed is obtained. Additional additives may be added to the mixture of aluminum nitride raw material powder and sintering aid powder.

[0030] In the molding process, the resulting slurry-like raw material mixture is molded into a shape having a predetermined size and thickness by any means such as press molding, casting, or doctor blade molding to produce a molded body.

[0031] In the degreasing process, the molded body described above is placed in a degreasing oven and heated for about 1 hour or more in the degreasing temperature range under the inflow of dry air or in a nitrogen atmosphere (but not limited to this range) to remove added organic components such as organic binders. The degreasing temperature range is preferably about 400 to 600°C (to avoid sintering the molded body). More preferably, the molded body is placed in a BN (boron nitride) enclosure and heated at about 500°C for 4 hours under the inflow of dry air, or at about 600°C for 4 hours in a nitrogen atmosphere to properly degrease the organic components.

[0032] In the deoxidation process, the degreased molded body is placed in a firing furnace and heated in a nitrogen atmosphere at a deoxidation temperature range for 10 to 20 hours to deoxidize the molded body. The deoxidation temperature range is preferably 1500 to 1650°C. More preferably, the degreased molded body is placed inside a sealed BN housing, and the housing is placed in the firing furnace and heat-treated.

[0033] In the sintering process, the deoxidized molded body is heated in a kiln in a nitrogen atmosphere at a sintering temperature range for 2 to 20 hours to produce an aluminum nitride precursor sintered body. The sintering temperature range is preferably 1750 to 1900°C. More preferably, the sintering process is carried out continuously without removing the deoxidized molded body from the kiln. The produced aluminum nitride precursor sintered body is then removed from the kiln.

[0034] In the reduction firing process, as shown in Figure 1, the prepared aluminum nitride precursor sintered body is placed in a graphite (C) container, or a BN or AlN container with carbon black or carbon sheets, and completely embedded with aluminum nitride powder until the precursor sintered body is no longer visible, thereby creating an embedded structure with aluminum nitride powder. At this time, it is preferable that the entire outer surface of the aluminum nitride precursor sintered body is surrounded by aluminum nitride powder. Then, the container containing the embedded structure is sealed and placed in the firing furnace. The aluminum nitride powder used for embedding is preferably a powder with an oxygen content of 1% by weight or less. After that, reduction firing is performed by heating at 1850 to 1950°C for 10 to 100 hours. At this time, graphite (carbon) or carbon black functions as a weak reducing atmosphere source, making the inside of the firing furnace a weak reducing atmosphere. Nitrogen gas may be introduced in this reduction firing process. Alternatively, instead of introducing graphite (carbon) or carbon black, CO gas, which is a reducing gas, may be introduced to create a weak reducing atmosphere.

[0035] Figure 2 is a schematic diagram showing a conventional reduction firing process. In the conventional reduction firing process, an aluminum nitride precursor sintered body is placed in a graphite container and fired in a weakly reducing atmosphere, thereby reducing the aluminum nitride precursor sintered body. As a result, the auxiliary components of the sintering aid precipitate on the substrate surface and are removed from the aluminum nitride precursor sintered body. However, in the conventional reduction firing process, the removal of auxiliary components is inefficient because it relies solely on the atmosphere, and it has been pointed out that the carbon component from the graphite container easily flows into the aluminum nitride precursor sintered body, which has been identified as a problem. In contrast, as shown in Figure 1, the present invention reduces the aluminum nitride precursor sintered body while it is embedded in aluminum nitride powder during the reduction firing process, thereby more effectively controlling the amount of auxiliary components removed and the amount of carbon component that flows in, and as a result, achieving both high thermal conductivity and high electrical properties. In particular, in addition to the removal of auxiliary components by atmosphere control, the removal of auxiliary components in the aluminum nitride precursor sintered body is further promoted by the adsorption of auxiliary components by the aluminum nitride powder. Furthermore, since the aluminum nitride precursor sintered body does not come into direct contact with the graphite container, the incorporation of carbon (C) components from the graphite container is suppressed. Therefore, although the aluminum nitride precursor sintered body is completely covered with aluminum nitride powder in Figure 1, by covering the aluminum nitride precursor sintered body with aluminum nitride powder to an extent that suppresses the inflow of carbon (C) components, it is possible to achieve both high thermal conductivity and high electrical properties.

[0036] Finally, in the removal step, the aluminum nitride powder is removed from the reduction-fired embedded structure to obtain the aluminum nitride sintered body of the present invention.

[0037] Furthermore, in X-ray diffraction identification of the crystalline phase of an aluminum nitride sintered body produced by the manufacturing method of this embodiment, the crystalline phase may have diffraction peaks of rare earth compounds (e.g., Y2O3, YAM, etc.) used as sintering aids, in addition to the diffraction peak of the AlN crystalline phase.

[0038] The aluminum nitride sintered body of the above embodiment can be used to construct an electronic component by mounting a semiconductor element such as a laser diode on its surface. That is, the electronic component of the present invention comprises the aluminum nitride sintered body of the above embodiment and a laser diode mounted on the surface of the aluminum nitride sintered body. Figure 4 is a schematic diagram of an electronic component 10 as an example of an electronic component. As shown in Figure 4, the electronic component 10 comprises an aluminum nitride sintered body substrate 11 and a laser diode (semiconductor element) 13 bonded to one surface of the aluminum nitride sintered body substrate 11 via a conductive film 17. The electronic component 10 further comprises a heat sink 15 bonded to the other surface of the aluminum nitride sintered body substrate 11 via a conductive film 17. The conductive film 17 is made of, for example, an Au film and is a thin film circuit formed on the substrate surface by etching. That is, in the electronic component 10, the heat generated by the laser diode 13 is efficiently conducted to the heat sink 15 due to the high thermal conductivity of the aluminum nitride sintered body substrate 11. Furthermore, the heat from the aluminum nitride sintered substrate 11 is dissipated by the heat sink 15, effectively suppressing the temperature rise of the electronic component 10 or the laser diode 13. In addition, the electrical properties of the aluminum nitride sintered substrate 11 effectively suppress dielectric breakdown between circuits and damage to the electronic component 10 when a high voltage is applied to the laser diode 13. [Examples]

[0039] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0040] The aluminum nitride sintered bodies in Examples 1-20 and Comparative Examples 1-6 were prepared under the following conditions and procedures. A predetermined amount of aluminum nitride raw material powder and sintering aid powder was prepared. The aluminum nitride raw material powder used was produced by the reductive nitriding method and had an average particle size (D50) of approximately 1.0 μm and an oxygen content of 1% by weight or less. As a sintering aid, Y2O3 powder with an average particle size (D50) of approximately 1.2 μm was used.

[0041] For Examples 1-7, 9-20, and Comparative Examples 1-6, 100 parts by weight of aluminum nitride powder was mixed with a predetermined amount of Y2O3 powder, approximately 0.5 parts by weight of a dispersant, and approximately 60 parts by weight of a mixed solvent of toluene and ethanol. The mixture was then ground and mixed using a ball mill with a resin container and alumina pebbles. To this ground mixture, 3.5 parts by weight of acrylic binder was added as a binder, and the mixture was stirred and mixed using a ball mill until the dissolved binder solution and the ground mixture were completely mixed to produce a slurry. Subsequently, the raw material mixture was molded to a predetermined size and thickness using a press molding method. Specifically, in the press molding method, the mixed and ground slurry was dried and granulated using a spray dryer to obtain AlN granules. The AlN granules were then press-molded to obtain a substrate-shaped molded body having a predetermined size and thickness.

[0042] On the other hand, in Example 8, the process from the mixing step to the molding step differs from the above because the sheet molding method is used for molding. To 100 parts by weight of aluminum nitride powder, a predetermined amount of Y2O3 powder, about 0.8 parts by weight of a surfactant dispersant, and about 25 parts by weight of a mixed solvent of toluene and ethanol were added, and the mixture was crushed and mixed using a ball mill with a resin container and alumina pebbles. To this crushed mixture, a dissolved binder solution consisting of about 8 parts by weight of polyvinyl butyral as a binder, about 3.5 parts by weight of dibutyl phthalate as a plasticizer, and about 25 parts by weight of a mixed solvent of toluene and ethanol was added. The dissolved binder solution and the crushed mixture were then stirred and mixed using a ball mill until completely mixed, and a slurry was prepared. The slurry was then heated and left in a vacuum to degas and evaporate the solvent, adjusting the viscosity at 25°C to 20,000 cps. Next, a plate-shaped green sheet was obtained from the prepared slurry by the doctor blade method. The final drying temperature in the doctor blade molding apparatus was set to 120°C. The obtained green sheet was die-cut to a predetermined size by die press processing to obtain a substrate-shaped molded body having a predetermined size and thickness.

[0043] Next, the fabricated molded body was placed in a BN housing and heated in a nitrogen atmosphere at approximately 600°C for 4 hours to degrease it and remove organic components such as binders. The degreased molded body was placed on a BN bottom plate, and BN side plates and a top plate were placed on the bottom plate to assemble a closed housing. The housing containing the molded body was then placed in a firing furnace and heated in a nitrogen atmosphere at 1500-1650°C for 10-20 hours to deoxidize the molded body. For Examples 1-20 and Comparative Examples 1-4 and 6, the deoxidized molded body was not removed from the firing furnace but heated in a nitrogen atmosphere at 1750-1900°C for 2-20 hours to sinter the molded body and obtain an aluminum nitride precursor sintered body. For Comparative Example 5, the sintering process was not performed, and the molded body was removed from the firing furnace and the process proceeded to the next reduction firing process. For Comparative Example 6, the process did not proceed to the next reduction firing process, and the preparation of the Comparative Example 6 sample was completed.

[0044] For Examples 1-20 and Comparative Examples 3-5, the obtained aluminum nitride precursor sintered bodies were placed in graphite containers, or in BN or AlN containers containing carbon black or carbon sheets. As shown in Figure 1, the aluminum nitride precursor sintered bodies were embedded with embedding AlN powder until they were no longer visible, and then sealed inside the BN or AlN container. For each example, aluminum nitride powder with an oxygen content of 1% by weight or less was used as the embedding AlN powder. Subsequently, the mixture was heated at 1850-1950°C for 5-100 hours to perform reduction firing. In this way, samples for Examples 1-20 and Comparative Examples 3-5 were prepared. For Comparative Examples 1 and 2, as shown in Figure 2, the obtained aluminum nitride precursor sintered bodies were placed in graphite containers, or in BN containers containing carbon black, and sealed inside the containers. Subsequently, the mixture was heated at 1950°C for 70 hours to perform reduction firing. In this way, samples for Comparative Examples 1 and 2 were prepared.

[0045] For each of the samples prepared in Examples 1-20 and Comparative Examples 1-6, the diffraction patterns obtained by X-ray diffraction measurements were identified with the diffraction peaks of the AlN crystal phase, confirming that aluminum nitride sintered bodies were obtained.

[0046] The following various characteristic evaluations were performed on each of the prepared samples from Examples 1-20 and Comparative Examples 1-6.

[0047] (i) Thermal conductivity Aluminum nitride sintered body is cut into 10mm x 10mm x 0.5mm thick pieces, a gold sputtered film of approximately 100nm is formed on both sides of the piece, and then graphene spray is applied to both sides of the piece, with a graphene coating amount of approximately 0.1mg / mm². 2 A sample was prepared by uniformly blackening it to achieve a uniform blackened appearance. A thermal diffusivity measuring device, model "LFA467," manufactured by Netch Japan Co., Ltd., was used. Three measurements were taken at a voltage of 250V and a pulse width of 30μs, and the average value was taken as the thermal diffusivity. The measured thermal diffusivity was multiplied by the density and specific heat of the sintered body, measured by the Archimedes method, to obtain the thermal conductivity of a 0.5mm thick sample. Furthermore, aluminum nitride sintered bodies have the property that their thermal conductivity decreases at higher temperatures. The laser flash method is a measurement method that calculates thermal diffusivity from the time it takes for the temperature of the sample to rise, and the measured value includes the decrease in thermal diffusivity due to the temperature rise of the sample. If measured with the same laser intensity, a thinner sample will have a greater temperature rise than a thicker sample, and the measured thermal diffusivity will be lower. Therefore, the table below shows the data for the same sample, measured for thermal diffusivity of a 2.5mm thick sample, and then measured after polishing to thicknesses of 1.5, 1.0, 0.75, and 0.5mm. According to Table 1, the thermal conductivity is clearly lower for thinner samples. Using the obtained thermal conductivity values, the multipliers for each thickness to convert to a thickness of 2.5 mmT were calculated. Specifically, the thermal conductivity value for a 0.5 mmT sample was multiplied by 1.10 to calculate the thermal conductivity value converted to a thickness of 2.5 mmT. [Table 1]

[0048] (ii) relative permittivity Aluminum nitride sintered bodies were cut into 20mm x 20mm pieces. Using Ag paste (model "TR-302XG") manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., electrodes with a main electrode of φ16mm and a guard electrode of φ19mm were printed on one side, and a φ19mm electrode was printed on the opposite side. The pieces were then heated in dry air at 850°C for 10 minutes to set them as measurement samples. Capacitance was measured at a frequency of 1MHz at room temperature using an impedance analyzer (model "4990A") manufactured by Keysight Technologies International, and the relative permittivity was calculated from the plate thickness and electrode diameter.

[0049] (iii) Dielectric loss tangent The individual samples used for relative permittivity measurement were used as the measurement samples, and the dielectric loss tangent was measured at a frequency of 1 MHz at room temperature using an impedance analyzer (model "4990A") manufactured by Keysight Technologies International.

[0050] (iv) Volume resistivity The individual samples used for dielectric loss tangent measurement were used as the measurement samples. A digital ultra-high resistance / micro-current meter, model "5450," manufactured by ADCMT Corporation, was used. A voltage of 1000V was applied at room temperature, and the volume resistance value was obtained after 1 minute of application. The volume resistivity was calculated from the obtained volume resistance value, plate thickness, and electrode diameter.

[0051] (v) Dielectric strength Aluminum nitride sintered bodies were cut into 20mm x 20mm pieces to be used as measurement samples. A partial discharge measurement device (model "A006") manufactured by Fujikura Dia Cable Ltd. was used, with measurement electrodes of φ11mm on both the upper and lower surfaces. An AC voltage (sine wave) was applied in a fluorine-based inert liquid (Fluorinert FC-43, manufactured by 3M Japan Ltd.). The AC voltage boosting rate was set to 500 V / s. The dielectric breakdown voltage was calculated by dividing the measured dielectric breakdown voltage by the thickness of the sample plate.

[0052] (vi) Y2O3 content A scanning X-ray fluorescence analyzer, model "Primus iv," manufactured by Rigaku Corporation, was used. The fabricated aluminum nitride sintered body was cut to 50.8 mm x 50.8 mm, and the Al and Y content was measured at a total of five points: the center and four corners of the substrate. The Y2O3 content was calculated using a calibration curve, and the average value was defined as the Y2O3 content.

[0053] (vii) Carbon content The fabricated aluminum nitride sintered body was cut to 50.8 mm x 50.8 mm, and the carbon content was measured at five points (center and four corners) using the EMIA-Pro manufactured by Horiba, Ltd., under high-frequency heating combustion-infrared absorption spectroscopy in an oxygen stream. The average value was defined as the carbon content.

[0054] (viii) Lightness L * value The fabricated aluminum nitride sintered body was cut to 50.8 mm x 50.8 mm, and the brightness of five points (center and four corners) was measured using a Konica Minolta colorimeter (model "CR-400") with diffuse illumination and vertical light reception. The average value of these measurements was used to determine the brightness L. * The value was determined as follows. To avoid the influence of reflected light from desks, etc., the circuit board was not placed on a desk or similar surface during measurement. Specifically, the circuit board was placed against the measurement area with the colorimeter facing upwards or sideways. The light source during measurement was defined as C.

[0055] Table 2 shows the conditions and various measurement results regarding the characteristics of the sintered bodies for each sample in Examples 1-20 and Reference Examples 1-6.

[0056] [Table 2]

[0057] According to Table 2, the Y2O3 content in the sintered bodies of Examples 1-20 and Comparative Examples 1 and 2 is 0.10% by weight or less, while that of Comparative Examples 3-6 is 1.5% by weight or more. In particular, the Y2O3 content in the sintered bodies of Examples 1-13 and 15-20 is 0.03% by weight or less, while that of Example 14 is 0.09% by weight, and that of Comparative Examples 1 and 2 is 0.04% by weight or more. The reason why the Y2O3 content in Example 14 is higher than that of the other examples is that the processing time (10 hours) of the reduction firing process is shorter compared to the other examples. The Y2O3 content of Examples 1-13 and 15-20, which underwent reduction firing for 30 hours or more, is lower than that of Comparative Examples 1 and 2, which underwent reduction firing for 70 hours without embedding. This indicates that the additive components in the sintered body are effectively discharged compared to reduction firing without embedding, through embedding with aluminum nitride powder and reduction firing for 30 hours or more. Furthermore, in Examples 1-20 and Comparative Examples 3-6, the carbon content in the sintered body is 0.05% by weight or less, while in Comparative Examples 1 and 2, the carbon content in the sintered body is 0.08% by weight or more. In particular, in Examples 1-20, the carbon content in the sintered body is 0.03% by weight or less. This indicates that the inflow of carbon into the sintered body is suppressed by reduction firing of the precursor sintered body along with embedding with aluminum nitride powder. That is, in Examples 1-20, the Y2O3 content in the sintered body was controlled to 0.10% by weight or less, and the carbon content in the sintered body was controlled to 0.05% by weight or less.

[0058] Examples 1-20 and Comparative Examples 1-3 show high thermal conductivity (calculated at 2.5T) of 240 W / mK or higher, whereas Comparative Examples 4-6 show thermal conductivity (calculated at 2.5T) of 231 W / mK or lower. This is because Comparative Examples 4 and 6 did not undergo a proper reduction firing process, resulting in insufficient removal of auxiliary components. Comparative Example 5 also did not undergo a sintering process.

[0059] In Examples 1-20, L * While the value is 57 or higher, in comparative examples 1-6, L *The value is 56 or less. In particular, in comparative examples 1 and 2 without embedding, L * The value is 51 or less. This indicates that differences in the appearance of the aluminum nitride sintered substrate occur depending on whether or not embedding is performed during the reduction firing process.

[0060] Next, Table 3 shows the conditions and various measurement results regarding the electrical properties of the sintered bodies for each sample in Examples 1-20 and Comparative Examples 1-6.

[0061] [Table 3]

[0062] According to Table 3, in Examples 1-20 and Comparative Examples 1, 2, and 6, the relative permittivity is 8.5 or less and the dielectric loss tangent is 0.001 or less, whereas in Comparative Examples 3-5, the relative permittivity is greater than 8.5 and the dielectric loss tangent is greater than 0.001.

[0063] In Examples 1-20, the volume resistivity was 5.0 × 10⁻⁶. 13 While the volume resistivity is Ω·cm or higher, in Comparative Examples 1-6, the volume resistivity is 3.6 × 10⁻⁶. 13 The dielectric strength is Ω·cm or less. In other words, Examples 1 to 20 have higher electrical insulation properties as insulating materials compared to Comparative Examples 1 to 6. Furthermore, while Examples 1 to 20 have a dielectric strength of 20kV / mm or more, Comparative Examples 1 to 6 have a dielectric strength of 17kV or less. In particular, Examples 1 to 20 have a dielectric strength of 23kV / mm or more. In contrast, Comparative Examples 1 to 3, which have a high thermal conductivity of 240W / mK or more (2.5T equivalent), have a dielectric strength of 11kV / mm or less. In other words, Examples 1 to 20 have a thermal conductivity of 240W / mK or more (2.5T equivalent) and a dielectric strength of 20kV / mm or more, thus achieving both high thermal conductivity and high insulation performance.

[0064] Dielectric strength and L * When the values ​​were plotted on a graph, a correlation was obtained between them as shown in Figure 3. Dielectric breakdown voltage and L * The value is linearly proportional. And L* It was found that a value of 57 or higher satisfies the requirement of at least 20kV / mm of dielectric strength.

[0065] In other words, the aluminum nitride sintered body of the present invention, by introducing an embedding process with aluminum nitride powder into the reduction firing process, controls the Y2O3 content in the sintered body to 0.10% by weight or less, and controls the carbon content in the sintered body to 0.05% by weight or less. As a result, the aluminum nitride sintered body of the present invention has a high thermal conductivity of 240 W / mK or more (calculated at 2.5T) and high electrical properties (dielectric withstand voltage of 20 kV / mm or more, and / or 5.0 × 10⁻¹⁰ 13 This achieves both a volume resistivity of Ω·cm or more and a constant resistivity of Ω·cm or more.

[0066] The present invention is not limited to the embodiments described above, and can be implemented in various forms as long as they fall within the technical scope of the present invention. [Explanation of Symbols]

[0067] 10 Electronic Components 11. Aluminum nitride sintered substrate 13 Laser Diode 15 Heatsink 17 Conductive film

Claims

1. An aluminum nitride sintered body comprising aluminum nitride particles and a sintering aid phase, and having a substrate shape of a predetermined thickness, The thermal conductivity, when converted to a thickness of 2.5 mm, is 240 W / mK or higher, and the dielectric strength is 20 kV / mm or higher. Y in the sintered body ２ O ３ An aluminum nitride sintered body characterized by having a content of 0.1% by weight or less, and a carbon content of 0.05% by weight or less in the sintered body.

2. A sintered aluminum nitride body comprising aluminum nitride particles and a sintering aid phase, and having a substrate shape of a predetermined thickness, The thermal conductivity, when converted to a thickness of 2.5 mm, is 240 W / mK or higher, and the volume resistivity is 5.0 × 10¹³ Ω·cm or higher. An aluminum nitride sintered body characterized in that the Y₂O₃ content in the sintered body is 0.1% by weight or less, and the carbon content in the sintered body is 0.05% by weight or less.

3. The aluminum nitride sintered body according to claim 1 or 2, characterized in that the carbon content in the sintered body is 0.03% by weight or less.

4. The aluminum nitride sintered body according to claim 1 or 2, characterized in that the relative permittivity is 8.5 or less and the dielectric loss tangent is 0.001 or less.

5. In the aluminum nitride sintered substrate, L represents the average value of the brightness measured at one point in the center and four points at the corners. ＊ The aluminum nitride sintered body according to claim 1 or 2, characterized in that the value is 57 or greater.

6. An electronic component comprising an aluminum nitride sintered body according to claim 1 or 2, and a laser diode mounted on the surface of the aluminum nitride sintered body.

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