Aluminum nitride sintered body, method for producing same, 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

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

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

[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, followed by molding 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 step, 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 (high thermal conductive aluminum nitride sintered body) with a thermal conductivity of 260 W / m K or more. In this reduction step, the grain boundary phase, which is a factor inhibiting thermal conductivity, is precipitated on the surface and removed, thereby finally obtaining an aluminum nitride sintered body with a thermal conductivity of 260 W / m K or more.

[0004] JP 2011-37691 A

[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, and the electrical properties of aluminum nitride sintered bodies as insulators have also become 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.

[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, and is characterized in that the thermal conductivity when converted into a thickness of 2.5 mm is 240 W / mK or more and the dielectric strength voltage is 20 kV / mm or more. The thermal conductivity is more preferably 260 W / mK or more. The dielectric strength voltage 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 being Ω·cm or more.

[0009] In a further embodiment of the aluminum nitride sintered body of the present invention, more preferably, Y in the sintered body ２ O ３ The content 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 in that it has 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, the substrate being provided with an L which indicates an average value of lightness measured at one point in the center and four points at the corners.＊ It is characterized by a value of 57 or more.

[0012] The aluminum nitride sintered body according to a further embodiment of the present invention is more preferably characterized by being formed 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, and has a thermal conductivity of 240 W / mK or more when converted into a body having a thickness of 2.5 mm, and a volume resistivity of 5.0×10 １３ The thermal conductivity is preferably 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, and has a thermal conductivity of 240 W / mK or more when converted into a thickness of 2.5 mm, and an L value representing the average value of lightness measured at one point in the center and four points at the corners of a substrate of the aluminum nitride sintered body. ＊ 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, and has a dielectric strength of 20 kV / mm or more, and an L value representing the average value of brightness measured at one point in the center and four points at the corners of a substrate of the aluminum nitride sintered body. ＊ 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, and having a volume resistivity of 5.0×10 １３ Ω cm or more, and the L value indicates the average value of the brightness measured at one point in the center and four points at the corners of the aluminum nitride sintered body substrate. ＊It is characterized by a value of 57 or more.

[0017] A method for producing an aluminum nitride sintered body according to one embodiment of the present invention comprises: a mixing step of mixing 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 a dry air inflow or in a nitrogen atmosphere to perform a degreasing treatment; a deoxidizing step of heating the degreased molded body in a deoxidizing temperature range in a nitrogen atmosphere to perform a deoxidizing treatment; 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 reducing and firing step of embedding at least a portion of the aluminum nitride precursor sintered body with aluminum nitride powder to form an embedded structure, and heat-treating the embedded structure at 1850 to 1950°C in a weakly reducing atmosphere; and a removing step of removing the aluminum nitride powder from the reducing and fired embedded structure to obtain an aluminum nitride sintered body.

[0018] In a further embodiment of the present invention, the sintering aid is more preferably 0.5 to 10 wt % of Y. ２ O ３ It is characterized in that:

[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.

[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.

[0022] Schematic diagram showing an example of a reduction firing process in one embodiment of the present invention. Schematic diagram showing an example of a reduction firing process in conventional examples (Comparative Examples 1 and 2). Lightness L of aluminum nitride sintered bodies (Examples 1 to 20, Comparative Examples 1 to 6) ＊ 1 is a graph showing the relationship between the dielectric strength and the dielectric strength value;

[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, the sintering aid is yttrium oxide (Y ２ O ３ 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 a material that has both relatively high thermal conductivity and mechanical strength.

[0025] The aluminum nitride sintered body of this embodiment has residual Y in the sintered body. ２ O ３ The content is 0.1% by weight or less, and the carbon (C element) content remaining in the sintered body is 0.05% by weight or less. ２ O ３ The aluminum nitride sintered body of the present invention has a Y content of 0.03% by weight or less. The carbon content is more preferably 0.03% by weight or less. ２ O ３ By controlling both the content of iron and the carbon, it is possible to achieve both high thermal conductivity and excellent electrical properties as an insulator.

[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. Preferably, the aluminum nitride sintered body has a volume resistivity of 5.0 x 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] Furthermore, the aluminum nitride sintered body has a lightness L ＊ The lightness L 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 FIG. 3, the correlation between the lightness L ＊ The value and the dielectric strength are directly proportional to each other. ＊ When the value is 20 kV / mm or more, the dielectric strength voltage is 20 kV / mm or more. Conventionally, destructive evaluation was performed by sampling to inspect the characteristics of sintered aluminum nitride products. 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 degreased 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 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 step, 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 consisting of oxides of rare earth elements Y, La, Ce, Pr, Nd, Sm, Gd, Dy, Ho, Er, and Yb. ２ O ３ 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 Y ２ O ３The prepared raw materials (aluminum nitride and sintering aid) are placed in 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 over a predetermined period of time. The organic solvent is, for example, a solvent prepared by mixing 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 approximately 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 approximately 1 to 5 parts by weight per 100 parts by weight of the raw material powder. A slurry-like raw material mixture in which the raw materials are thoroughly dispersed and mixed is then obtained. An additional additive 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 process, 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 for four hours 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 housing, which is then placed in a sintering furnace and heat-treated.

[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 prepared 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 precursor sintered body is completely embedded in aluminum nitride powder until it 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, 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 this conventional reduction-sintering process, the removal of the auxiliary 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 auxiliary components removed and the amount of carbon component inflow, resulting in both high thermal conductivity and excellent electrical properties. In particular, in addition to the removal of the auxiliary components through atmospheric control, the auxiliary components in the aluminum nitride precursor are adsorbed by the aluminum nitride powder, further facilitating the removal of the auxiliary components. Furthermore, since 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 an extent that prevents 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, thereby obtaining the aluminum nitride sintered body of the present invention.

[0037] In the crystalline phase identification of the aluminum nitride sintered body manufactured by the manufacturing method of this embodiment, in addition to the diffraction peak of the crystalline phase of AlN, a rare earth compound (for example, Y ２ O ３ , YAM, etc.).

[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 heat generated by the laser diode 13 to be efficiently conducted to the heat sink 15. The heat generated by the sintered aluminum nitride 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 sintered aluminum nitride 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.

[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 according to 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. Y sintering aid powder with an average particle size (D50) of approximately 1.2 μm was used. ２ O ３ Powder was used.

[0041] In Examples 1 to 7, 9 to 20 and Comparative Examples 1 to 6, a predetermined amount of Y was added to 100 parts by weight of aluminum nitride powder. ２ O ３ The powder, approximately 0.5 parts by weight of a dispersant, and approximately 60 parts by weight of a mixed solvent of toluene and ethanol were added, and the mixture was ground and mixed in a ball mill using 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 in 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, in Example 8, the process from the mixing step to the molding step was different from the above because the molding was performed using a sheet molding method. ２ O ３ The powder, approximately 0.8 parts by weight of a surfactant dispersant, and approximately 25 parts by weight of a mixed solvent of toluene and ethanol were added and milled 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 mixed solvent of toluene and ethanol was then added to the milled mixture. The dissolved binder solution and the milled mixture were then mixed and stirred in a ball mill until completely mixed, after which a slurry was produced. 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. The resulting slurry was then doctor-bladed to obtain a plate-shaped green sheet. The final drying temperature in the doctor-blading machine was 120°C. The resulting green sheet was then die-cut to a predetermined size to obtain a substrate-shaped molded product of a predetermined size and thickness.

[0043] The prepared compact was then placed in a BN housing and heated in a nitrogen atmosphere at approximately 600°C for 4 hours to perform a degreasing process to remove organic components such as binders. The degreased 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 deoxidize the compact. For Examples 1-20 and Comparative Examples 1-4 and 6, the deoxidized compact was heated in a nitrogen atmosphere at 1750-1900°C for 2-20 hours without being removed from the sintering furnace to sinter the compact, obtaining an aluminum nitride precursor sintered body. For Comparative Example 5, the sintering process was not performed, and the sample was removed from the sintering furnace and proceeded to the next reduction sintering process. For Comparative Example 6, the preparation of the sample for Comparative Example 6 was completed without proceeding to the next reduction sintering process.

[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 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 samples prepared in Examples 1 to 20 and Comparative Examples 1 to 6, the diffraction patterns obtained by X-ray diffraction measurement were identified along with the diffraction peaks of the AlN crystalline phase, thereby confirming that an aluminum nitride sintered body had been 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 An aluminum nitride sintered body was cut into pieces measuring 10 mm × 10 mm × 0.5 mm thick, and a gold sputtering film of about 100 nm was formed on both sides of the pieces. Then, graphene was sprayed onto both sides of the pieces to form a graphene coating of about 0.1 mg / mm. ２ The measurement samples were subjected to a uniform blackening treatment to achieve a uniform blackening temperature. Using a thermal diffusivity measuring 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, and 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 a 0.5 mm thick sample. Furthermore, aluminum nitride sintered bodies have the property of decreasing in thermal conductivity at high temperatures. The laser flash method calculates thermal diffusivity from the time required for the sample to increase in temperature, resulting in a measurement value that includes the decrease in thermal diffusivity due to the increase in sample temperature. If measurements are taken with the same laser intensity, 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 mmT, and then polished to thicknesses of 1.5, 1.0, 0.75, and 0.5 mmT. According to Table 1, the thermal conductivity is clearly lower for thinner samples. Using the obtained thermal conductivity, the multiplication factor for each thickness was calculated to convert 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.

[0048] (ii) Relative permittivity The aluminum nitride sintered body was cut into individual pieces of 20 mm x 20 mm, and a main electrode of 16 mm diameter and a guard electrode of 19 mm diameter were printed on one side using Ag paste (Model TR-302XG) manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., and a φ19 mm electrode was printed on the other side. The pieces were then baked at 850°C for 10 minutes in dry air to prepare measurement samples. Using an impedance analyzer (Model 4990A) manufactured by Keysight Technologies International, Inc., the capacitance was measured at a frequency of 1 MHz at room temperature, and the relative permittivity was calculated from the plate thickness and electrode diameter.

[0049] (iii) Dielectric Loss Tangent The individual pieces used in the relative dielectric constant measurement were used as measurement samples, and the dielectric loss tangent was measured at room temperature and 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 measurement samples. 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 voltage The aluminum nitride sintered body was cut into individual pieces of 20 mm x 20 mm to be used as measurement samples. A partial discharge measurement device, model "A006" manufactured by Fujikura Dia Cable Ltd., was used, and measurement electrodes were set to φ11 mm on both the top and bottom surfaces, and 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-up rate was 500 V / s. The measured dielectric breakdown voltage was divided by the plate thickness of the sample to determine the dielectric strength voltage.

[0052] (vi) Y ２ O ３ A scanning X-ray fluorescence analyzer, model "Primus IV" manufactured by Rigaku Corporation, was used. The aluminum nitride sintered body prepared was cut into a size of 50.8 mm x 50.8 mm, and the Al and Y contents were measured at five points, namely the center and four corners of the substrate. The Y content was calculated using a calibration curve. ２ O ３ The content is calculated and the average value is Y ２ O ３ The content was determined as follows.

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

[0054] (viii) Lightness L ＊The aluminum nitride sintered body thus produced was cut into a piece of 50.8 mm x 50.8 mm, and the lightness of five points, namely 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 taken as the lightness L ＊ The values ​​were measured without placing the substrate on a desk or the like to avoid the influence of reflected light from the desk or the like. Specifically, the color difference meter was held facing upward or sideways, and the substrate was placed against the measuring part. The light source used during the 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]

[0057] According to Table 2, in Examples 1 to 20 and Comparative Examples 1 and 2, the Y content in the sintered body was ２ O ３ The content of Y in the sintered body is 0.10% by weight or less, whereas it is 1.5% by weight or more in Comparative Examples 3 to 6. In particular, in Examples 1 to 13 and 15 to 20, the content of Y in the sintered body is ２ O ３ In Example 14, the content of Y in the sintered body was 0.03 wt % or less. ２ O ３ In Comparative Examples 1 and 2, the content of Y in the sintered body was 0.09% by weight. ２ O ３ The content of Y in Example 14 is 0.04% by weight or more. ２ O ３ The reason why the content of Y is larger than that of other Examples is that the treatment time (10 hours) of the reduction firing step is shorter than that of other Examples. ２ O ３ The content of Y in Comparative Examples 1 and 2 was determined by performing reduction firing for 70 hours without embedding. ２ O ３This indicates that the embedding treatment with aluminum nitride powder and reduction firing for 30 hours or more effectively expels auxiliary components in the sintered body to the outside, 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 is 0.05 wt % or less, whereas in Comparative Examples 1 and 2, the carbon content in the sintered body is 0.08 wt % or more. In particular, in Examples 1 to 20, the carbon content in the sintered body is 0.03 wt % or less. This indicates that the embedding treatment with aluminum nitride powder and reduction firing of the precursor sintered body can prevent carbon from flowing into the sintered body. That is, in Examples 1 to 20, the Y content in the sintered body is 0.05 wt % or less. ２ O ３ The content of 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] 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 addition, Comparative Example 5 did not undergo a sintering process.

[0059] In Examples 1 to 20, L ＊ In contrast, 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]

[0062] According to Table 3, in Examples 1 to 20 and Comparative Examples 1, 2, and 6, the relative dielectric constant was 8.5 or less and the dielectric dissipation factor was 0.001 or less, whereas in Comparative Examples 3 to 5, the relative dielectric constant was greater than 8.5 and the dielectric dissipation factor was 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 insulating materials than Comparative Examples 1 to 6. Furthermore, while Examples 1 to 20 have a dielectric strength voltage of 20 kV / mm or more, 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 of 240 W / mK or more (2.5T equivalent), have a dielectric strength voltage of 11 kV / mm or less. That is, Examples 1 to 20 have a thermal conductivity of 240 W / mK or more (2.5T equivalent) 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, the correlation between the two was obtained 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 that the dielectric strength voltage is at least 20 kV / mm or more.

[0065] That is, the aluminum nitride sintered body of the present invention has an aluminum nitride powder embedding process introduced into the reduction firing step, and thus the Y in the sintered body is ２ O ３ 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 is a material that satisfies both the above requirements and 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.

[0067] REFERENCE SIGNS LIST 10 Electronic component 11 Aluminum nitride sintered substrate 13 Laser diode 15 Heat sink 17 Conductive film

Claims

1. An aluminum nitride sintered body containing aluminum nitride particles and a sintering aid phase, characterized in that 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.

2. Volume resistivity is 5.0 x 10 １３ 2. The aluminum nitride sintered body according to claim 1, characterized in that it has a resistivity of Ω·cm or more.

3. An aluminum nitride sintered body containing aluminum nitride particles and a sintering aid phase, the thermal conductivity of which, 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 An aluminum nitride sintered body having a resistivity of Ω·cm or more.

4. Y in the sintered body ２ O ３ 4. The aluminum nitride sintered body according to claim 1, wherein the content is 0.1% by weight or less, and the carbon content in the sintered body is 0.05% by weight or less.

5. An aluminum nitride sintered body according to any one of claims 1 to 4, characterized in that the relative dielectric constant is 8.5 or less and the dielectric tangent is 0.001 or less.

6. The L value indicates the average value of the brightness measured at one point in the center and four points at the corners of the aluminum nitride sintered body substrate. ＊ 6. The aluminum nitride sintered body according to claim 1, wherein the value is 57 or more.

7. An aluminum nitride sintered body containing aluminum nitride particles and a sintering aid phase, having a thermal conductivity of 240 W / mK or more when converted to a thickness of 2.5 mm, and an L value indicating the average value of the brightness measured at one point in the center and four points on the corners of the substrate of the aluminum nitride sintered body. ＊ An aluminum nitride sintered body having a value of 57 or more.

8. An aluminum nitride sintered body containing aluminum nitride particles and a sintering aid phase, having a dielectric strength of 20 kV / mm or more, and a L value that indicates the average value of the brightness measured at one point in the center and four points on the corners of the substrate of the aluminum nitride sintered body. ＊ An aluminum nitride sintered body having a value of 57 or more.

9. An aluminum nitride sintered body containing aluminum nitride particles and a sintering aid phase, having a volume resistivity of 5.0×10 １３ Ω·cm or more, and the average value of the brightness measured at one point in the center and four points at the corners of the aluminum nitride sintered body substrate is L ＊ An aluminum nitride sintered body having a value of 57 or more.

10. An aluminum nitride sintered body according to any one of claims 1 to 9, characterized in that it is produced by sintering 90 to 99.5% by weight of aluminum nitride and 0.5 to 10% by weight of yttrium oxide.

11. A method for producing an aluminum nitride sintered body, comprising: a mixing step of mixing 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 a flow of dry air or in a nitrogen atmosphere to perform a degreasing treatment; a deoxidizing step of heating the deoxidized molded body in a deoxidizing temperature range in a nitrogen atmosphere to perform a deoxidizing treatment; 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 reducing and firing step of embedding at least a part 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; and a removing step of removing the aluminum nitride powder from the reducing and firing embedded structure to obtain an aluminum nitride sintered body.

12. The sintering aid contains 0.5 to 10% by weight of Y. ２ O ３ 12. The method according to claim 11, wherein 13. A method according to claim 11 or 12, characterized in that the reduction and 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.

14. An electronic component comprising the aluminum nitride sintered body according to any one of claims 1 to 10, and a laser diode mounted on the surface of the aluminum nitride sintered body.

Images