Aluminum nitride sintered body

Abstract

To provide an aluminum nitride sintered body capable of suppressing variations in dielectric breakdown voltage and three-point bending strength, and responding to applications requiring a high dielectric breakdown voltage when actually formed to a thickness of about 100 μm.SOLUTION: A sintered aluminum nitride body contains aluminum nitride particles and particles of a sintering aid phase. Regarding a plate-shaped sintered aluminum nitride body having a thickness of 100 μm, the average value of dielectric breakdown voltage is 61 kV / mm or more with a standard deviation of 5.5 kV / mm or less when an AC voltage is applied, and the average value of 3-point bending strength is 485 MPa or more with a standard deviation of 30 MPa or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an aluminum nitride sintered body. [Background technology]

[0002] The applicant of the present application previously disclosed in Patent Document 1 a composite substrate comprising a semiconductor crystal layer connected onto a support layer, and a composite substrate comprising a semiconductor crystal layer connected onto a metal coating film covering the upper surface of the support layer.

[0003] They also clarified that by using sintered aluminum nitride, which has excellent thermal conductivity and three-point bending strength, as the support layer, the composite substrate can exhibit high heat dissipation performance and structural strength. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-195036 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the aluminum nitride sintered body disclosed in Patent Document 1 had a problem in that the dielectric breakdown voltage and three-point bending strength varied among the produced samples, and the average values ​​also decreased due to the variation, particularly on the lower side.

[0006] Aluminum nitride sintered bodies are also used as circuit boards, heat dissipation members, etc. in various products such as electronic devices, semiconductor devices, and automotive components. In recent years, as products have become smaller and lighter, there is a possibility that plate-shaped aluminum nitride sintered bodies with a thickness of about 100 μm are required. For this reason, a high breakdown voltage is required when actually measuring a plate-shaped aluminum nitride sintered body with a thickness of 100 μm. However, in the past, the breakdown voltage was often measured on a sintered body with a thickness of several hundred μm, and the value obtained by converting the measurement results per 100 μm is merely a theoretical value, and it is not possible to guarantee the breakdown voltage when actually formed to a thickness of about 100 μm.

[0007] Therefore, an object of the present invention is to provide an aluminum nitride sintered body in which variations in dielectric breakdown voltage and three-point bending strength are suppressed and which can be used for applications requiring a high dielectric breakdown voltage when actually formed to a thickness of about 100 μm. [Means for solving the problem]

[0008] The inventors of the present invention have thoroughly investigated the above problems and considered the influence of foreign matter (fibrous waste, slurry aggregates, etc.) mixed into the raw material. However, it is difficult to quantify the foreign matter, and it is difficult to see it even under a microscope, so it is difficult to suppress the mixing. Therefore, when the raw material is filtered at the time of making it into a slurry, it was found that the above problems were improved, and further investigation led to the present invention.

[0009] [1] An aluminum nitride sintered body comprising aluminum nitride particles and sintering aid phase particles, An aluminum nitride sintered body in the form of a plate having a thickness of 100 μm, when an AC voltage is applied, has an average dielectric breakdown voltage of 61 kV / mm or more with a standard deviation of 5.5 kV / mm or less, and an average three-point bending strength of 485 MPa or more with a standard deviation of 30 MPa or less.

[0010] [2] An aluminum nitride sintered body containing aluminum nitride particles and sintering aid phase particles, An aluminum nitride sintered body in the form of a plate having a thickness of 100 μm, the value of the dielectric breakdown voltage obtained by subtracting the standard deviation from the average value when an AC voltage is applied is 56 kV / mm or more, and the value of the three-point bending strength obtained by subtracting the standard deviation from the average value is 460 MPa or more.

[0011] [3] A circuit board using the aluminum nitride sintered body according to [1] or [2] above.

[0012] [4] A heat dissipation member using the aluminum nitride sintered body according to [1] or [2] above.

[0013] [5] An insulating member using the aluminum nitride sintered body according to [1] or [2] above.

[0014] In the present invention, the "thickness of 100 μm" is defined only as a condition for measuring the dielectric breakdown voltage and the three-point bending strength, and does not define the thickness of the aluminum nitride sintered body product. In other words, the aluminum nitride sintered body product may have any thickness, as long as the dielectric breakdown voltage and the three-point bending strength measured after processing the product to a thickness of 100 μm are within the ranges specified in the present invention.

[0015] The number of samples (n) for the average value and standard deviation of the breakdown voltage is not particularly limited, but is preferably 10 or more. The number of samples (n) for the average value and standard deviation of the three-point bending strength is not particularly limited, but is preferably 10 or more. Effect of the Invention

[0016] According to the present invention, it is possible to provide an aluminum nitride sintered body in which variations in dielectric breakdown voltage and three-point bending strength are suppressed, and which can be used for applications requiring a high dielectric breakdown voltage when actually formed to a thickness of about 100 μm. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] <1> Aluminum nitride powder raw material The raw material aluminum nitride powder is preferably one that has a high purity of 97% by weight or more, and more preferably 99% by weight or more, with an oxygen concentration suppressed to 1% by weight or less, and preferably 0.8% by weight or less, and an average particle size of about 0.5 to 2.0 μm, and preferably 1 μm or less.

[0018] <2> Raw material sintering aid powder The raw material sintering aid powder may be a rare earth metal compound, such as an oxide of a metal such as Y, La, Ce, Nd, Er, or Yb, with yttrium oxide being preferred. The amount of the sintering aid added is not limited in any way, but from the viewpoint of increasing thermal conductivity and strength, the amount is preferably 0.1 to 10 parts by weight, more preferably 2 to 6 parts by weight, per 100 parts by weight of the aluminum nitride powder.

[0019] <3> Sintering aid phase The sintering aid phase is preferably composed of YAL (Al2O3-Y2O3) and / or YAM (Al2O3-2Y2O3) and does not contain YAG (5Al2O3-3Y2O3). EXAMPLES

[0020] Next, examples embodying the present invention will be described with reference to the drawings, while comparing them with comparative examples. Note that the materials, quantities and conditions of each part in the examples are merely examples, and can be appropriately changed without departing from the gist of the invention.

[0021] [Table 1]

[0022] Aluminum nitride sintered bodies were produced according to the comparative example and examples 1 and 2 shown in Table 1. The details are as follows. The comparative example is Comparative Example 1 of Patent Document 1.

[0023] [1] Material The aluminum nitride powder used in each example was the main raw material, aluminum nitride, which had an average particle size (D50) of about 1.0 μm and an oxygen content of 1% by weight or less and was produced by the reduction nitridation method.Y2O3 powder with an average particle size (D50) of about 1.2 μm was used as the sintering aid in each example.

[0024] [2] Manufacturing method (i) Mixing process of materials For each example, 100 parts by weight of aluminum nitride powder was mixed with 5 parts by weight of Y2O3 powder, 0.8 parts by weight of a surfactant dispersant, and approximately 25 parts by weight of a mixed solvent of toluene and ethanol, and the mixture was ground and mixed in a ball mill using a resin container and alumina balls.

[0025] To this ground mixture, a dissolved binder solution consisting of 8 parts by weight of polyvinyl butyral as a binder, 3.5 parts by weight of dibutyl phthalate as a plasticizer, and about 25 parts by weight of a mixed solvent of toluene and ethanol was added, and the dissolved binder solution and the ground mixture were stirred and mixed by a ball mill until they were completely mixed, and then a slurry was prepared.Then, the slurry was heated and left in a vacuum to degas and volatilize the solvent, and the viscosity at 25°C was adjusted to 20,000 cps.

[0026] The viscosity-adjusted slurry was not filtered in the Comparative Example, whereas it was filtered using a CP filter manufactured by JNC Filter Co., Ltd. in Examples 1 and 2. The grade of the CP filter used in Example 1 was "CP-75" (absolute filtration accuracy 90 μm), and in Example 2 was "CP-10" (absolute filtration accuracy 35 μm).

[0027] (ii) Green sheet manufacturing process Next, a plate-shaped green sheet having a thickness of 450 μm was obtained from each of the slurries prepared by the doctor blade method. The final drying temperature in the doctor blade molding device was set to 120° C. The obtained green sheet was punched out to a predetermined size by die pressing.

[0028] A boron nitride (BN) powder slurry was sprayed onto the surface of the die-cut green sheet as a release agent, and the green sheet laminate made by stacking multiple green sheets was placed in a BN case and heated to 500°C in a dry air flow for approximately 4 hours to perform a degreasing process to remove organic components such as binders.

[0029] (iii) Green sheet sintering process The green sheet laminate was placed on a bottom plate made of BN, a setter made of BN was placed on top of it, a tungsten block was placed on the setter as a load, and a plate-shaped dummy aluminum nitride sintered body was placed on the load. Next, a side plate and a top plate made of BN were placed on the bottom plate to assemble a closed case. The case containing the green sheets and the like was placed in a sintering furnace and heated in a nitrogen atmosphere at 1800°C for 5 hours to sinter the green sheet laminate.

[0030] The sintered laminate was separated into individual aluminum nitride sintered bodies, and the BN release agent was removed from each of the separated aluminum nitride sintered bodies by honing. Thereafter, both surfaces were lapped and polished to obtain a plate-shaped aluminum nitride sintered body having a thickness of 100 μm.

[0031] [3] Characteristics As the properties of the aluminum nitride sintered body of each example, the dielectric breakdown voltage and three-point bending strength were measured for 10 samples (n), and the average value and standard deviation were calculated (the results are shown in Table 1).

[0032] (i) Breakdown 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 the measurement electrodes on both the top and bottom were set to φ11 mm, 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 rate was set to 500 V / s. The measured breakdown voltage was divided by the thickness of the sample to obtain the breakdown voltage.

[0033] (ii) Three-point bending strength The aluminum nitride sintered body was cut into individual pieces of 40 mm x 20 mm to be used as measurement samples. Using a universal testing machine (model "AG-IS") manufactured by Shimadzu Corporation, measurements were performed at a crosshead speed of 0.5 mm / min, a support distance of 30 mm, and room temperature (23±2°C).

[0034] [4] Consideration In the comparative example, the average dielectric breakdown voltage was low at 59.4 kV / mm, and the standard deviation was large at 6.5 kV / mm. The average three-point bending strength was low at 474 MPa, and the standard deviation was large at 37.3 MPa. This is thought to be due to the influence of foreign matter (fibrous waste, slurry aggregates, etc.) mixed in the raw material.

[0035] In contrast, in both Examples 1 and 2, the average value of the breakdown voltage was high at 61 kV / mm or more, and the standard deviation was small at 5.5 kV / mm or less. The average value of the three-point bending strength was high at 485 MPa or more, and the standard deviation was small at 30 MPa or less. The value obtained by subtracting the standard deviation from the average value of the breakdown voltage was 56 kV / mm or more, and the value obtained by subtracting the standard deviation from the average value of the three-point bending strength was 460 MPa or more, which was a more significant difference from the comparative example. This is believed to be the result of foreign matter mixed into the raw material being removed to a certain extent by filtration.

[0036] The present invention is not limited to the above-described embodiment, and can be embodied by making appropriate modifications without departing from the gist of the invention.

Claims

1. An aluminum nitride sintered body comprising aluminum nitride particles and sintering aid phase particles, An aluminum nitride sintered body in the form of a plate having a thickness of 100 μm, wherein when an AC voltage is applied, the average dielectric breakdown voltage is 61 kV / mm or more and the standard deviation is 5.5 kV / mm or less, and the average three-point bending strength is 485 MPa or more and the standard deviation is 30 MPa or less.

2. An aluminum nitride sintered body comprising aluminum nitride particles and sintering aid phase particles, A plate-shaped aluminum nitride sintered body having a thickness of 100 μm has a dielectric breakdown voltage obtained by subtracting the standard deviation from the average value when an AC voltage is applied thereto of 56 kV / mm or more and the standard deviation is 5.5 kV / mm or less, and a three-point bending strength obtained by subtracting the standard deviation from the average value of 460 MPa or more and the standard deviation is 30 MPa or less.

3. A circuit board using the aluminum nitride sintered body according to claim 1 or 2.

4. A heat dissipating member using the aluminum nitride sintered body according to claim 1 or 2.

5. An insulating member using the aluminum nitride sintered body according to claim 1 or 2.

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