Aluminum nitride sintered body, its manufacturing method, and electronic component

Abstract

This aluminum nitride sintered body includes aluminum nitride particles and a sintering aid phase. This aluminum nitride sintered body is characterized by having a thermal conductivity of 240 W / mK or more when converted to a body having a thickness of 2.5 mm. In addition, this aluminum nitride sintered body has an insulation breakdown voltage of 20 kV / mm or more, a volume resistivity of 5.0 × 1013 Ω∙cm or more, and / or a lightness L* value of 57 or more.

Description

[Technical Field]

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

[0002] Aluminum nitride sintered body products are made of insulating materials with high thermal conductivity and have attracted 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 high temperatures can cause unstable operation. In recent years, aluminum nitride sintered body substrates have been widely used in electronic substrates for mobile applications, and higher heat dissipation capabilities are required. Therefore, various attempts have been 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 producing the same. The aluminum nitride sintered body in Patent Document 1 has a high thermal conductivity of 260 W / m K or more by specifying the constituent components and content ratios of the grain boundary phase and the microstructure, specifically the average diameter, minimum diameter, maximum diameter, and number of aluminum nitride crystal grains. This method for producing an aluminum nitride sintered body includes the following steps: a molding step of mixing aluminum nitride powder having an average particle size of 1.5 μm or less with a sintering aid containing at least a Y compound powder and molding the mixture to obtain a green body; a degreasing step of degreasing the green body; a deoxidizing step of heat-treating the deoxidized green 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 green body in a non-oxidizing atmosphere at 1800°C to 1950°C to obtain a primary sintered body having a thermal conductivity of 230 W / m·K or more; and a reducing 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 having a thermal conductivity of 260 W / m·K or more. In particular, in the sintering step, the deoxidized green body is heat-treated in a non-oxidizing atmosphere at 1800°C to 1950°C to obtain a primary sintered body having a thermal conductivity of 230 W / m·K or more. In the subsequent reduction process, the primary sintered body is heat-treated in a weakly reducing atmosphere at 1750°C to 1900°C to obtain an aluminum nitride sintered body with a thermal conductivity of 260 W / m·K or more (high thermal conductive aluminum nitride sintered body). In this reduction process, the grain boundary phase, which is a factor that inhibits thermal conductivity, is precipitated on the surface and removed, resulting in a final aluminum nitride sintered body with a thermal conductivity of 260 W / m·K or more. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-37691 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 provides an aluminum nitride sintered body having high thermal conductivity. Meanwhile, in recent years, with the further miniaturization of electronic circuits, the distance between conductors in circuit patterns on aluminum nitride sintered body substrates has become even smaller, making the electrical properties of aluminum nitride sintered bodies as insulators important. Therefore, the inventors set out to improve the insulating performance of aluminum nitride sintered bodies while maintaining their high thermal conductivity.

[0006] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an aluminum nitride sintered body having both high thermal conductivity and high insulating performance, and a method for producing 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 containing aluminum nitride particles and a sintering aid phase, The thermal conductivity is 240 W / mK or more and the dielectric strength is 20 kV / mm or more when converted to a thickness of 2.5 mm. The thermal conductivity is more preferably 260 W / mK or more. The dielectric strength is more preferably 23 kV / mm or more, and even more preferably 29 kV / mm or more.

[0008] The aluminum nitride sintered body of a further embodiment of the present invention more preferably has a volume resistivity of 5.0×10 13 It is characterized by a resistance of Ω·cm or more.

[0009] An aluminum nitride sintered body according to a further embodiment of the present invention is more preferably 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.

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

[0011] In a further embodiment of the present invention, the aluminum nitride sintered body is more preferably a substrate of the aluminum nitride sintered body, and the substrate .... * It is characterized by a value of 57 or greater.

[0012] An aluminum nitride sintered body according to a further embodiment of the present invention is more preferably characterized by being obtained 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 one 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 x 10 13 It is characterized in that the thermal conductivity is 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 one 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 L value indicates the average value of the brightness measured at one point in the center and four points on the corners of the aluminum nitride sintered body substrate. * The thermal conductivity is preferably 260 W / mK or more.

[0015] An aluminum nitride sintered body according to one embodiment of the present invention is an aluminum nitride sintered body containing aluminum nitride particles and a sintering aid phase, The dielectric strength is 20 kV / mm or more, and the L indicates the average value of the brightness measured at one point in the center and four points on the corners of the aluminum nitride sintered body substrate. * The dielectric strength is preferably 23 kV / mm or more, and more preferably 29 kV / mm or more.

[0016] An aluminum nitride sintered body according to one embodiment of the present invention is an aluminum nitride sintered body containing aluminum nitride particles and a sintering aid phase, Volume resistivity is 5.0 x 10 13 Ω·cm or more, and the average value of the brightness measured at one point in the center and four points on the corners of the aluminum nitride sintered body substrate is L * It is characterized by a value of 57 or greater.

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

[0018] A method for producing an aluminum nitride sintered body according to a further embodiment 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 method for producing an aluminum nitride sintered body of the present invention is more preferably characterized in that the reduction firing step includes placing the aluminum nitride precursor sintered body in a graphite container, or a BN container or an AlN container in which carbon black or a carbon sheet has been placed, and embedding the aluminum nitride precursor sintered body in aluminum nitride powder until it can no longer be seen.

[0020] An electronic component according to one embodiment of the present invention comprises the aluminum nitride sintered body described above, 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 more and improved insulating properties. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 2 is a schematic diagram showing an example of a reduction firing step in one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing an example of a reduction firing step in conventional examples (Comparative Examples 1 and 2). [Figure 3] 1 is a graph showing the relationship between the lightness L* value and the dielectric strength voltage of aluminum nitride sintered bodies (Examples 1 to 20 and Comparative Examples 1 to 6). [Figure 4] 1 is a schematic diagram showing an electronic component according to an embodiment of the present invention; DETAILED DESCRIPTION OF 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 formed by sintering 90 to 99.5% by weight of aluminum nitride as the main raw material and 0.5 to 10% by weight of a sintering aid. The aluminum nitride sintered body is composed of a crystalline phase of aluminum nitride particles and a liquid phase of the sintering aid.

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

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

[0026] The aluminum nitride sintered body of this embodiment has thermal conductivity characteristics 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 also has the following electrical properties as an insulator. Preferably, the aluminum nitride sintered body is characterized by a dielectric strength voltage of 20 kV / mm or more. More preferably, the dielectric strength voltage is 23 kV / mm or more, and even more preferably, 29 kV / mm or more. The dielectric strength voltage indicates the upper limit of voltage that can be applied to an insulator without causing dielectric breakdown, and is an index of the insulating performance of the sintered body. Furthermore, preferably, the aluminum nitride sintered body has a volume resistivity of 5.0 × 10 13 Ω·cm or more, preferably 7.1×10 13 The aluminum nitride sintered body is characterized by having a dielectric constant of 8.5 or less, preferably 8.3 or less, and a dielectric loss tangent of 0.001 or less, preferably 0.00086 or less. In other words, the aluminum nitride sintered body of this embodiment has both high thermal conductivity and high insulating performance.

[0027] In addition, aluminum nitride sintered bodies have a lightness L * The value is 57 or more. * The value indicates the average value of the lightness measured at one point in the center and four points at the corners of the aluminum nitride sintered body substrate. The aluminum nitride sintered body of this embodiment has higher lightness than aluminum nitride sintered bodies manufactured by conventional methods. Figure 3 shows the lightness L obtained from the experimental results. * As shown in Figure 3, the correlation between the lightness L * The value and the dielectric strength are directly proportional to each other. *If the value is 20kV / mm or more, the dielectric strength voltage is 20kV / mm or more. Conventionally, the characteristic inspection of aluminum nitride sintered products has been carried out by destructive evaluation through sampling. In contrast, by utilizing this correlation, it is possible to * By measuring the value, it became possible to sort all products non-destructively.

[0028] Next, a method for producing an aluminum nitride sintered body according to this embodiment will be described. The method for producing an aluminum nitride sintered body mainly includes a mixing step of mixing an aluminum nitride raw material powder, a sintering aid, and an organic solvent to produce a slurry of the 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 a dry air inflow or in a nitrogen atmosphere to degrease the molded body; a deoxidizing step of heating the deoxidized molded body in a deoxidizing temperature range in a nitrogen atmosphere to deoxidize the molded body; a sintering step of sintering the deoxidized molded body in a 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 in aluminum nitride powder to produce an embedded structure, and then 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 reduced-fired embedded structure to obtain an aluminum nitride sintered body. Each step will be described in detail below. In this specification, "embedded" does not only mean that the aluminum nitride precursor sintered body is completely covered with aluminum nitride powder (the outer peripheral surface of the aluminum nitride precursor sintered body is completely surrounded by aluminum nitride powder), but also that the aluminum nitride precursor sintered body is mostly covered with aluminum nitride powder to the extent that part of the outer peripheral surface is visible.

[0029] In the mixing process, an appropriate amount of aluminum nitride raw material powder and an appropriate amount of sintering aid powder are prepared. The aluminum nitride raw material powder, which is the main raw material, 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 is preferably Y2O3. In the manufacturing method of this embodiment, 90 to 99.5 wt% of aluminum nitride raw material powder and 0.5 to 10 wt% of Y2O3 are blended. The prepared raw materials (aluminum nitride and sintering aid) are charged into a grinding mixer such as a ball mill, and an organic solvent, dispersant, organic binder, and / or plasticizer are added. 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 a predetermined ratio. The amount of organic solvent is approximately 30 to 70 parts by weight per 100 parts by weight of the aluminum nitride raw material powder. The dispersant is, for example, a polycarboxylic acid surfactant. However, these organic solvents and dispersants can be selected arbitrarily. The organic binder is, 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. The plasticizer is, 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 the raw materials are sufficiently dispersed and mixed is obtained. Note that additional additives may be added to the mixture of aluminum nitride raw material powder and sintering aid powder.

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

[0031] In the debinding step, the compact is placed in a debinding oven and heated for at least about one hour in a debinding temperature range under a dry air inflow or a nitrogen atmosphere (although this is not a limitation), thereby removing organic components such as the added organic binder. The debinding temperature range is preferably about 400 to 600°C (so as not to sinter the compact). More preferably, the compact is placed in a BN (boron nitride) case and heated for four hours under a dry air inflow at about 500°C or in a nitrogen atmosphere at about 600°C, thereby properly debinding the organic components.

[0032] In the deoxidation step, the degreased compact is placed in a sintering furnace and heated in a nitrogen atmosphere within a deoxidation temperature range for 10 to 20 hours to deoxidize the compact. The deoxidation temperature range is preferably 1500 to 1650°C. More preferably, the degreased compact is placed inside a sealed BN case, and the case is placed in a sintering furnace for heat treatment.

[0033] In the sintering step, the deoxidized compact is heated and sintered in a sintering furnace in a nitrogen atmosphere within 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 step is carried out continuously without removing the deoxidized compact from the sintering furnace. The produced aluminum nitride precursor sintered body is then removed from the sintering furnace.

[0034] In the reduction-sintering process, as shown in FIG. 1, the aluminum nitride precursor sintered body is placed in a graphite (C) container, or a BN or AlN container containing carbon black or a carbon sheet. The aluminum nitride precursor sintered body is completely embedded in aluminum nitride powder until the sintered body is no longer visible, thereby producing an embedded structure made of aluminum nitride powder. At this time, it is preferable that all outer surfaces of the aluminum nitride precursor sintered body are surrounded by aluminum nitride powder. The container containing the embedded structure is then sealed and placed in a sintering furnace. The aluminum nitride powder used for embedding is preferably a powder with an oxygen content of 1% by weight or less. The resulting mixture is then heated at 1850 to 1950°C for 10 to 100 hours for reduction-sintering. The graphite (carbon) or carbon black functions as a weakly reducing atmosphere source, thereby creating a weakly reducing atmosphere inside the sintering furnace. Nitrogen gas may be introduced during this reduction-sintering process. Alternatively, instead of introducing graphite (carbon) or carbon black, CO gas, a reducing gas, may be introduced to create a weakly reducing atmosphere.

[0035] FIG. 2 is a schematic diagram showing a conventional reduction-sintering process. In this process, an aluminum nitride precursor is placed in a graphite container and sintered in a weakly reducing atmosphere, resulting in reduction of the aluminum nitride precursor. As a result, the sintering aid components are precipitated on the substrate surface and removed from the aluminum nitride precursor. However, in the conventional reduction-sintering process, the removal of the aid components is achieved solely through the atmosphere, resulting in inefficiency. Furthermore, it has been pointed out that the carbon component from the graphite container easily flows into the aluminum nitride precursor. In contrast, in the present invention, as shown in FIG. 1, the aluminum nitride precursor is embedded in aluminum nitride powder during the reduction-sintering process. This effectively controls the amount of removal of the aid components and the amount of inflow of the carbon component, resulting in both high thermal conductivity and excellent electrical properties. In particular, in addition to the removal of the aid components through atmospheric control, the adsorption of the aid components in the aluminum nitride precursor by the aluminum nitride powder further accelerates the removal of the aid components. Furthermore, because the aluminum nitride precursor sintered body does not come into direct contact with the graphite container, contamination with 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 the extent that the inflow of carbon (C) components is suppressed, 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, thereby obtaining the aluminum nitride sintered body of the present invention.

[0037] Furthermore, when the aluminum nitride sintered body manufactured by the manufacturing method of this embodiment is identified by crystalline phase X-ray diffraction, it may have diffraction peaks of the AlN crystalline phase as well as diffraction peaks of rare earth compounds (e.g., Y2O3, YAM, etc.) used as sintering aids.

[0038] The aluminum nitride sintered body of the above embodiment can be used to form 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 includes the aluminum nitride sintered body of the above embodiment and a laser diode mounted on the surface of the aluminum nitride sintered body. FIG. 4 is a schematic diagram of an electronic component 10 as an example of an electronic component. As shown in FIG. 4, the electronic component 10 includes 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 also includes a heat sink 15 bonded to the other surface of the aluminum nitride sintered body substrate 11 via the conductive film 17. The conductive film 17 is, 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 high thermal conductivity of the aluminum nitride sintered body substrate 11 allows the heat generated by the laser diode 13 to be efficiently conducted to the heat sink 15. The heat generated by the aluminum nitride sintered substrate 11 is dissipated by the heat sink 15, thereby effectively suppressing temperature rise in the electronic component 10 or the laser diode 13. Furthermore, the electrical characteristics of the aluminum nitride sintered substrate 11 in the electronic component 10 effectively prevent insulation breakdown between circuits and damage to the electronic component 10 when a high voltage is applied to the laser diode 13. [Example]

[0039] The present invention will be described in more detail below based on examples and comparative examples, but the present invention should not be construed as being limited by the following examples.

[0040] The aluminum nitride sintered bodies of Examples 1 to 20 and Comparative Examples 1 to 6 were produced under the following conditions and procedures. Predetermined amounts of aluminum nitride raw material powder and sintering aid powder were prepared. The aluminum nitride raw material powder used was produced by a reduction-nitridation method and had an average particle size (D50) of approximately 1.0 μm and an oxygen content of 1 wt % or less. Y2O3 powder with an average particle size (D50) of approximately 1.2 μm was used as the sintering aid.

[0041] For Examples 1-7, 9-20, and Comparative Examples 1-6, a predetermined amount of Y2O3 powder, approximately 0.5 parts by weight of a dispersant, and approximately 60 parts by weight of a toluene-ethanol mixed solvent were added to 100 parts by weight of aluminum nitride powder, and the mixture was ground and mixed using a ball mill equipped with a resin container and alumina balls. 3.5 parts by weight of an acrylic binder was further added to the ground mixture, and the mixture was stirred and mixed using a ball mill until the dissolved binder solution and the ground mixture were completely mixed, after which a slurry was produced. The raw material mixture was then 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-like molded body having a predetermined size and thickness.

[0042] On the other hand, Example 8 differs from the above in the process from mixing to molding, since it uses a sheet molding method. A predetermined amount of Y2O3 powder, approximately 0.8 parts by weight of a surfactant dispersant, and approximately 25 parts by weight of a toluene-ethanol mixed solvent were added to 100 parts by weight of aluminum nitride powder, and the mixture was ground and mixed using a ball mill equipped with a resin container and alumina balls. A dissolved binder solution consisting of approximately 8 parts by weight of polyvinyl butyral as a binder, approximately 3.5 parts by weight of dibutyl phthalate as a plasticizer, and approximately 25 parts by weight of a toluene-ethanol mixed solvent was then added to the ground mixture. The dissolved binder solution and the ground mixture were then mixed using a ball mill until completely mixed, after which a slurry was prepared. The slurry was then heated and left in a vacuum to degas and volatilize the solvent, adjusting the viscosity at 25°C to 20,000 cps. A plate-shaped green sheet was then obtained from the prepared slurry using a doctor blade method. The final drying temperature in the doctor blade molding device was 120° C. The obtained green sheet was cut into a predetermined size by die pressing to obtain a substrate-like molded product having a predetermined size and thickness.

[0043] Next, the prepared compact was placed in a BN housing and heated in a nitrogen atmosphere at approximately 600°C for 4 hours to perform a degreasing treatment to remove organic components such as binders. The degreasing compact was placed on a BN bottom plate, and BN side and top plates were attached to the bottom plate to assemble a closed housing. The housing containing the compact was then placed in a sintering furnace and heated in a nitrogen atmosphere at 1500-1650°C for 10-20 hours to perform a deoxidation treatment on the compact. For Examples 1-20 and Comparative Examples 1-4 and 6, the deoxidized compact was sintered by heating in a nitrogen atmosphere at 1750-1900°C for 2-20 hours without removing it from the sintering furnace to obtain an aluminum nitride precursor sintered body. For Comparative Example 5, the sintering step was not performed, and the sample was removed from the sintering furnace and proceeded to the subsequent reduction sintering step. For Comparative Example 6, the preparation of the sample for Comparative Example 6 was completed without proceeding to the subsequent reduction sintering step.

[0044] For Examples 1 to 20 and Comparative Examples 3 to 5, the obtained aluminum nitride precursor sintered body was placed in a graphite container, or a BN or AlN container containing carbon black or a carbon sheet. As shown in FIG. 1, the aluminum nitride precursor sintered body was embedded in AlN powder until it was no longer visible, and then sealed in the BN or AlN container. Aluminum nitride powder containing 1 wt. % or less of oxygen was used as the embedding AlN powder in each example. The resulting mixture was then heated at 1850 to 1950°C for 5 to 100 hours for reduction and sintering. In this manner, samples for Examples 1 to 20 and Comparative Examples 3 to 5 were prepared. For Comparative Examples 1 and 2, the obtained aluminum nitride precursor sintered body was placed in a graphite container or a BN container containing carbon black, and then sealed in the container. The resulting mixture was then heated at 1950°C for 70 hours for reduction and sintering. In this manner, samples for Comparative Examples 1 and 2 were prepared.

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

[0046] The samples prepared in Examples 1 to 20 and Comparative Examples 1 to 6 were subjected to the following evaluations of various characteristics.

[0047] (i) Thermal conductivity The aluminum nitride sintered body was cut into pieces measuring 10 mm x 10 mm x 0.5 mm thick, and a gold sputtering film of approximately 100 nm was formed on both sides of each piece. Then, graphene was sprayed onto both sides of each piece, with the graphene coating amount being approximately 0.1 mg / mm. 2 The samples were subjected to a uniform blackening treatment to achieve a uniform blackening temperature. Using a thermal diffusivity measurement device (Model LFA467) manufactured by Netsch Japan Co., Ltd., measurements were taken three times at a voltage of 250 V and a pulse width of 30 μs. The average value was used as the thermal diffusivity. The measured thermal diffusivity was multiplied by the density and specific heat of the sintered body, measured using the Archimedes method, to determine the thermal conductivity of the 0.5 mm thick sample. Furthermore, aluminum nitride sintered bodies exhibit a tendency for their thermal conductivity to decrease with increasing temperature. The laser flash method calculates thermal diffusivity from the time it takes for the sample to heat up, resulting in a measurement that includes a decrease in thermal diffusivity due to the increase in sample temperature. For example, a thinner sample will experience a greater temperature increase than a thicker sample, resulting in a lower measured thermal diffusivity. Therefore, the table below shows the thermal diffusivity data for the same sample measured at a thickness of 2.5 mm, followed by measurements after polishing to thicknesses of 1.5, 1.0, 0.75, and 0.5 mm. Table 1 clearly shows that the thermal conductivity is lower for thinner samples. The obtained thermal conductivity was used to calculate the multiplication factor for each thickness to convert it to a thickness of 2.5 mmT. Specifically, the thermal conductivity value of the 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 The aluminum nitride sintered body was cut into 20mm x 20mm pieces, and a 16mm diameter main electrode and a 19mm diameter guard electrode were printed on one side using Tanaka Kikinzoku Kogyo Co., Ltd.'s Ag paste, model TR-302XG. A 19mm diameter electrode was then printed on the other side. The pieces were then baked in dry air at 850°C for 10 minutes to prepare the measurement samples. The capacitance was measured at room temperature at a frequency of 1MHz using a Keysight Technologies International model 4990A impedance analyzer, and the relative permittivity was calculated from the plate thickness and electrode diameter.

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

[0050] (iv) Volume resistivity The individual pieces used in the dielectric loss tangent measurement were used as the measurement sample. A digital ultra-high resistance / microcurrent meter, model "5450," manufactured by ADCMT Co., Ltd., was used. A voltage of 1000 V 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, the plate thickness, and the electrode diameter.

[0051] (v) Dielectric strength The aluminum nitride sintered body was cut into 20mm x 20mm pieces to be used as measurement samples. A Fujikura Dia Cable Co., Ltd. partial discharge measurement device, model "A006," was used, with measurement electrodes of φ11mm on both the top and bottom 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 ramp rate was 500V / s. The measured breakdown voltage was divided by the sample thickness to determine the dielectric strength voltage.

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

[0053] (vii) Carbon content The produced aluminum nitride sintered body was cut into a piece of 50.8 mm x 50.8 mm, and a total of five points, the center and four corners of the substrate, were measured using a high-frequency heating combustion-infrared absorption method in an oxygen atmosphere using an EMIA-Pro manufactured by Horiba, Ltd., and the average value was taken as the carbon content.

[0054] (viii) Lightness L * value The aluminum nitride sintered body was cut into a piece of 50.8 mm x 50.8 mm, and the lightness of five points, the center and four corners of the substrate, was measured using a Konica Minolta color difference meter, model CR-400, using a diffused lighting and vertical light receiving method. The average value of these was calculated as the lightness L * The values ​​were taken as the values. To avoid the influence of reflected light from a desk or the like, the substrate was not placed on the desk or the like during measurement. Specifically, the color difference meter was held facing upward or sideways, and the substrate was placed against the measuring part. The light source during measurement was C.

[0055] Table 2 shows the conditions for each sample of Examples 1 to 20 and Reference Examples 1 to 6 and the results of various measurements on the properties of the sintered bodies.

[0056] [Table 2]

[0057] According to Table 2, the Y2O3 content in the sintered compacts of Examples 1 to 20 and Comparative Examples 1 and 2 was 0.10 wt% or less, while it was 1.5 wt% or more in Comparative Examples 3 to 6. In particular, the Y2O3 content in the sintered compacts of Examples 1 to 13 and 15 to 20 was 0.03 wt% or less, while the Y2O3 content in the sintered compact of Example 14 was 0.09 wt% and the Y2O3 content in the sintered compacts of Comparative Examples 1 and 2 was 0.04 wt% or more. The Y2O3 content in Example 14 was higher than in the other Examples because the treatment time (10 hours) of the reduction-sintering step was shorter than in the other Examples. The Y2O3 content in Examples 1 to 13 and 15 to 20, which underwent reduction-sintering for 30 hours or more, was lower than the Y2O3 content in Comparative Examples 1 and 2, which underwent reduction-sintering for 70 hours without embedding. This indicates that embedding with aluminum nitride powder and reduction firing for 30 hours or more effectively expels auxiliary components from the sintered body compared to reduction firing without embedding. Furthermore, in Examples 1 to 20 and Comparative Examples 3 to 6, the carbon content in the sintered body was 0.05 wt% or less, whereas in Comparative Examples 1 and 2, the carbon content in the sintered body was 0.08 wt% or more. In particular, in Examples 1 to 20, the carbon content in the sintered body was 0.03 wt% or less. This indicates that embedding with aluminum nitride powder and reduction firing the precursor sintered body can prevent carbon from entering the sintered body. That is, in Examples 1 to 20, the Y2O3 content in the sintered body was controlled to 0.10 wt% or less, and the carbon content in the sintered body was controlled to 0.05 wt% or less.

[0058] In Examples 1 to 20 and Comparative Examples 1 to 3, the thermal conductivity (2.5T equivalent) is high, at 240 W / mK or more, whereas in Comparative Examples 4 to 6, the thermal conductivity (2.5T equivalent) is 231 W / mK or less. This is because Comparative Examples 4 and 6 did not undergo an appropriate reduction firing process, and therefore auxiliary components were not sufficiently discharged. In Comparative Example 5, this is because the sintering process was not performed.

[0059] In Examples 1 to 20, L * In Comparative Examples 1 to 6, the L *In particular, in Comparative Examples 1 and 2 without embedding, the L * The value is 51 or less. This indicates that the appearance of the aluminum nitride sintered body substrate differs depending on whether or not it is embedded in the reduction firing step.

[0060] Next, Table 3 shows the conditions for each sample of Examples 1 to 20 and Comparative Examples 1 to 6 and the results of various measurements on the electrical properties of the sintered bodies.

[0061] [Table 3]

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

[0063] In Examples 1 to 20, the volume resistivity was 5.0 × 10 13 Ω·cm or more, whereas in Comparative Examples 1 to 6, the volume resistivity was 3.6×10 13 Ω·cm or less. That is, Examples 1 to 20 have higher electrical insulation properties as an insulating material than Comparative Examples 1 to 6. Furthermore, Examples 1 to 20 have a dielectric strength voltage of 20 kV / mm or more, whereas Comparative Examples 1 to 6 have a dielectric strength voltage of 17 kV / mm or less. In particular, Examples 1 to 20 have a dielectric strength voltage of 23 kV / mm or more. In contrast, Comparative Examples 1 to 3, which have a high thermal conductivity (2.5T equivalent) of 240 W / mK or more, have a dielectric strength voltage of 11 kV / mm or less. That is, Examples 1 to 20 have a thermal conductivity (2.5T equivalent) of 240 W / mK or more and a dielectric strength voltage of 20 kV / mm or more, and therefore achieve both high thermal conductivity and high insulating performance.

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

[0065] That is, by introducing an aluminum nitride powder embedding process into the reduction firing step, the aluminum nitride sintered body of the present invention has a Y2O3 content controlled to 0.10 wt% or less and a carbon content controlled to 0.05 wt% 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 (2.5 T equivalent) and high electrical properties (a dielectric strength of 20 kV / mm or more, and / or a dielectric strength of 5.0 × 10 13 It has a volume resistivity of Ω·cm or more.

[0066] The present invention is not limited to the above-described embodiments, and can be implemented in various forms 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 having a substrate shape with a predetermined thickness, comprising aluminum nitride particles and a sintering aid phase containing Y 2 O 3 , The thermal conductivity when converted to a thickness of 2.5 mm is 240 W / mK or more, and the dielectric strength voltage is 20 kV / mm or more, The dielectric constant is 8.5 or less and the dielectric loss tangent is 0.001 or less, An aluminum nitride sintered body, characterized in that the Y 2 O 3 content in the sintered body is 0.1 wt % or less.

2. Volume resistivity is 5.0 x 10 １３ 2. The aluminum nitride sintered body according to claim 1, wherein the resistance is Ω·cm or more.

3. An aluminum nitride sintered body having a substrate shape with a predetermined thickness, comprising aluminum nitride particles and a sintering aid phase containing Y 2 O 3 , 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, The dielectric constant is 8.5 or less and the dielectric loss tangent is 0.001 or less, An aluminum nitride sintered body, characterized in that the Y 2 O 3 content in the sintered body is 0.1 wt % or less.

4. An aluminum nitride sintered body described in any one of claims 1 to 3, characterized in that the carbon content in the sintered body is 0.05 wt% or less.

5. In the substrate of the aluminum nitride sintered body, the average value of the brightness measured at one point in the center and four points at the corners is L ＊ 4. The aluminum nitride sintered body according to claim 1, wherein the value of the sintered body is 57 or more.

6. 4. The aluminum nitride sintered body according to claim 1, which is obtained by sintering 90 to 99.5% by weight of aluminum nitride and 0.5 to 10% by weight of yttrium oxide.

7. 4. An electronic component comprising: the aluminum nitride sintered body according to claim 1; and a laser diode mounted on a surface of the aluminum nitride sintered body.

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