JPS61275168A - High heat conductivity sintered body and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a highly thermally conductive sintered body made of cubic boron nitride, which has characteristics effective as a heat dissipation substrate material, for example, and a method for manufacturing the same.

[Prior Art] Cubic boron nitride (hereinafter abbreviated as CBN) has a hardness second only to diamond and is extremely stable thermally and chemically, so it is attracting attention as a material for tools. Furthermore, since cBN is second only to diamond not only in hardness but also in thermal conductivity, it is expected to be used in applications such as heat dissipation substrate materials.

By the way, as a heat dissipation board material, conventionally.

Various materials have been used that have the properties shown in Table 1.

From Table 1, it can be seen that diamond exhibits a much higher thermal conductivity than other materials.

On the other hand, Slack (5lack) is a journal of
Physical Chemistry Solutions (J.

Phys. This suggests its potential as a substrate material.

However, up to now, large cBN single crystals have not been obtained.1. Therefore 13W/Cff1・℃
The thermal conductivity of is not confirmed.

In addition, the thermal conductivity of the CBN sintered body containing the binder phase is as follows:
Only 2 W/cm·°C has been reported. this is,
This is presumed to be because the bonded phase becomes a large phonon scattering source and extremely reduces thermal conductivity.

In addition, as a method for producing an entire cBN sintered body with high thermal conductivity that does not contain a binder phase, for example, Japanese Patent Application Laid-Open No. 54-33510 uses pyrolytic boron nitride (pBN) as a starting material and uses a direct conversion method. A method for constructing a dense, highly thermally conductive cBN sintered body is disclosed.

[Problems to be solved by the invention] However, in the method of JP-A-54-33510,
To produce a sintered body with a thermal conductivity of 4 W/cm・℃ or higher,
Strict conditions such as a pressure cuff GPa of 8 degrees or more than 2000 degrees Celsius were required, and there were also problems in terms of reproducibility. moreover,
EIBN is also extremely expensive.

On the other hand, a method for manufacturing a CBN sintered body without a binder phase under relatively mild conditions and at low cost is disclosed, for example, by Materials Research Bulletin (Mat.

Res, 3u11): Volume 7 (1972) No. 999
As shown in the paper by Wakatsuki et al. Here, low-crystalline hexagonal boron nitride (hBN) is used as a starting material,
An OBN sintered body is obtained by the direct conversion method.

However, the low crystallinity hBN used as a starting material is chemically unstable and easily reacts with oxygen in the air, making it difficult to obtain uniform and sufficient sintering throughout the sintered body. .

Therefore, an object of the present invention is to provide an inexpensive cBN sintered body with excellent thermal conductivity.

[Means for Solving the Problems] The inventors of the present invention repeatedly conducted synthesis experiments using various methods in order to produce a highly thermally conductive sintered body at low cost and with good reproducibility. As a result, the method disclosed in JP-A-58-176179 and JP-A-59-57967 was adopted, namely, by mixing or diffusing an alkaline earth metal or an alkali metal boronitride into hBN. Maintained at a high temperature of 1350°C or higher under thermodynamically stable conditions for cBN,
It has been found that the method of forming the entire cBN sintered body is most suitable. These prior arts were not made to provide a sintered body with excellent thermal conductivity, but were mainly made to provide a sintered body with excellent translucency, but here, Part or all of the added boronitride is diffused out of the system during sintering under high pressure, and as a result, a sintered body consisting of substantially 100% cBN can be easily obtained.

When the thermal conductivity of the sintered body obtained as described above was measured, it was found that the average value was 2 to 3W10111°C, which is a relatively high value compared to sintered bodies using other binders. Ta. However, in some cases, 1.7W/cm・℃
There were also large variations, with some showing low values.

Therefore, the inventors of the present application repeated a large number of experiments under various conditions, and found that the thermal conductivity of the sintered body was determined by the raw material composition before sintering, that is, hB, rather than by the conditions during sintering.
It has been found that the amount of alkaline earth metal or alkali metal boronitride added to N is largely controlled. Furthermore, in order to obtain a highly thermally conductive sintered body, the amount of alkaline earth metal or alkali metal boronitride added must be controlled within the range of 0.6 mol% or more and 1.2 mol% or less. I found it necessary.

A hot-pressed h8N molded body of the above contents was used as a raw material, and magnesium boronitride (MOa B) was added as an additive.
2N4) will be specifically explained.

First, we changed the temperature conditions when adding M(J a B2 N4 into hBN), and the treatment temperature and the added MQ・82
N-! The results shown in Figure M7 were obtained.

Next, several raw material compositions with different amounts of MOs 82 N4 added were prepared using the results shown in FIG. 1, and each was treated under constant temperature and pressure conditions to obtain a sintered body. The thermal conductivity of the obtained sintered body was measured, and the M added to the raw material was measured.
When looking for the relationship with Q s 82 N4 Ilk,
The results shown in FIG. 2 were obtained.

In Figure 2, the amount of MO*BzN+ added is approximately 0.8
It can be seen that below mol %, the thermal conductivity shows a higher value as the amount of MQ s B2N4 added increases. this is,
The more Mga 82 N4 is added, the larger the unit grain size of cBN becomes, and the phonon scattering at grain boundaries decreases.
It is assumed that this is because the thermal conductivity increases as a result. Figure 3 shows the relationship between the amount of MgsB2N4 added and the average unit grain size of the obtained sintered body.
It can be seen that the larger the amount of N4 added, the larger the particle size.

However, in FIG. 2, M(II s 82
When the amount of N4 added is approximately 0.9 mol%, the thermal conductivity reaches a maximum value of 6°2.
W/cra·°C, and it can be seen that when the content exceeds 0.9 mol %, the thermal conductivity tends to decrease.

When 0.9 mol% or more of MO382N4 is added, the resulting sintered body will contain 0.5% by weight or more of Mg. It is thought that this residual Ma becomes a phonon scattering source and causes a decrease in thermal conductivity.

FIG. 4 shows the relationship between the thermal conductivity and Vickers hardness of each sintered body synthesized with varying amounts of Mga B2 N4 added.

Those with a thermal conductivity of 2 to 3 W/cm·°C show that the hardness is partially low and the sintered state is uneven. Areas where the sintering condition is not good, that is, areas with low hardness, are
It is thought that due to insufficient bonding between particles, there is a lot of phonon scattering at the grain boundaries, and as a result, the sintered body as a whole exhibits a relatively low thermal conductivity. On the other hand, a sintered body with uniform hardness of 5000 kg/mm2 or more has a hardness of 4W/mm2 or more.
[Has a thermal conductivity of 1°C or higher.]

Based on the relationship between the amount of MQs, B2 N4 added and the thermal conductivity shown in Figure 2, the amount of Mga B2 N4 added was set to 0.6 mol%.
Above, by setting it to 1.2 mol% or less, 4W/cn
It can be seen that a sintered body with high thermal conductivity of +°C or higher can be stably obtained.

Therefore, in this invention, 0.6
Boron nitride of an alkaline earth metal or an alkali metal of mol% or more and 1.2 mol% or less is uniformly diffused and supported under high pressure at a temperature of 1350°C or more under thermodynamically stable conditions of cubic boron nitride. Obtained by sintering, substantially 1
This is a highly thermally conductive sintered body made of 00% cubic boron nitride, and is a manufacturing method for obtaining a highly thermally conductive sintered body as described above.

The highly thermally conductive sintered body has a thermal conductivity of 4 W/am・℃ or more, a particle size of 5 μm or more, and a microknoop hardness of 5000 ka/
nun' or more, and the Mg content is 0.5% by weight or less.

From this, conversely, it is also possible to know the thermal conductivity of the sintered body from the particle size, hardness, and amount of impurities of the sintered body.

[Example] Example 1 MQsNt was diffused and impregnated into an hBN compact at various temperatures in the range of 1160 to 1175°C in a nitrogen atmosphere under normal pressure. MOa
Eight types were obtained in which the BzN weight ranged from 0.4 to 1.3 mol %. Each of these was filled into a container and held at a temperature of 5.5 GPa and 1450° C. for 30 minutes using a belt type device.

The obtained sintered body has a diameter of 3011I11 and a thickness of about 1.51
It was a single-phase dense sintered body. In the sintered body of sample number 1, some unconverted hBN remained, but the other sintered bodies were sintered uniformly and firmly over the entire surface in appearance.

From this result, 100%c3=B2N4 addition amount is approximately 0.
It can be seen that 45 mol% or more is required.

From the sintered bodies of sample numbers 2 to 8, 2.5x2.5x1.5
Cut out sample pieces of 1 InS for each sample piece.
b Thermal conductivity at room temperature was measured by direct temperature measurement using an infrared emission microscope. The results obtained are shown in Table 2 below.

When the amount of MO82N4 added to the raw material hBN compact is 0.6 mol% or more and 1.2 mol% or less, the obtained sintered body has a thermal conductivity of about 4 W/CI・℃ or more. I understand that.

Example 2 In order to investigate the necessary characteristics to become a highly thermally conductive sintered body,
The grain size, hardness, and amount of impurities of the sintered bodies of sample numbers 2 to 8 obtained in Example 1 were examined.

The grain size was measured by SEM after etching the surface of the sintered body with KOH to clarify the grain boundaries.

The hardness was determined using a Vickers indenter and a load of 10.

The press-fitting was performed for 15 seconds.

The impurity, ie, MO content, was measured using an ion microanalyzer.

The results are shown in Table 3 below.

When each sample was analyzed for impurities other than Mg using an ion microanalyzer, it was found that C, A1
1. C, a and Si were detected, all at 200
It was less than ppm.

From the results of Example 1 and the results shown in Table 3, a highly thermally conductive sintered body with a thermal conductivity of 4W10N・℃ or more has a unit particle size of 5 μm or more and a Vickers hardness of 5000 kg/mm.
It can be seen that the MO content is 2 or more, and furthermore, 0.5% by weight or less.

1i1 and MOs82N* in Example 1, 1-is B
A sintered body was obtained in the same manner as in Example 1 except that N2, Ca s B2 N4, and 5rsBzN4 were each diffused and supported in hBN in an amount of 0.6 to 1.2 mol %. The thermal conductivity was all 4 W/Cm·° C. or more, and the particle size, hardness, and amount of impurities were almost the same as the results of Example 2.

[Effects of the Invention] According to the present invention, 0.6 mol% or more and 1.2 mol% or less of alkaline earth metal or alkali metal boronitride is uniformly supported in hexagonal boron nitride. Since the sintering is carried out at
It becomes possible to obtain a sintered body with significantly higher thermal conductivity than other sintered body materials such as tC, AQN, and A120. Therefore, if used as a heat dissipation substrate material, for example, it can significantly improve the electrical characteristics and lifespan of semiconductor laser devices, microwave devices, etc., and at the same time stabilize the electrical characteristics and achieve Nagano differentiation in ICs and memories. becomes possible.

Further, according to the manufacturing method of the present invention, it is possible to stably and inexpensively supply the above-mentioned highly thermally conductive sintered body.

[Brief explanation of the drawing]

Figure 1 shows the treatment temperature in the MQa 82 N4 diffusion support treatment into the hBN molded body and the added MOs BZ.
It is a figure showing the relationship with the amount of N4. Figure 2 shows the thermal conductivity of the sintered body of the present invention and the Mgs 8 in the raw material hBN.
2 is a diagram showing the relationship with the amount of N4 added. Figure 3 shows the unit particle size of the sintered body of the present invention and the M!
1IsBzN* is a diagram showing the relationship with the addition amount. FIG. 4 is a diagram showing the relationship between Vickers hardness and thermal conductivity of the sintered body of the present invention. Figure 2 7 Amount of M9382/1114 added to raw material ILBN (one cup) Figure 3, Mg38zN + pulsation force υ cover (table-color) to raw material BN February lz, 1985 1, Indication of incident 1985 Patent Application No. 117179 2, Name of the invention Highly thermally conductive sintered body and its manufacturing method 3, Interaction with the case of the person making the amendment Patent applicant address 5-15 Kitahama, Zen-ku, Osaka City Name
(213) Sumitomo Electric Industries Co., Ltd. Representative Tetsube Kawakami 4, Agent address 5-1 Yachiyo Pill, Hirano-cho, Zen-ku, Osaka City, Yachiyo Pill 5, Date of amendment order Voluntary amendment 6, Specification subject to amendment Claims column and Detailed Description of the Invention column 7, Contents of amendment (1) The claims of the specification are amended as shown in the attached sheet. (2) “Micronoop” on page 10, line 12 of the specification
Correct that to "Vickers". Above 2, Claims (1) Cubic nitridation by uniformly diffusing and supporting an alkaline earth metal or alkali metal boronitride in an amount of 0.6 mol% or more and 1.2 mol% or less in hexagonal boron nitride. Obtained by high-pressure sintering of boron at temperatures above 1350°C under thermodynamically stable conditions, it consists essentially of 100% cubic boron nitride and has a thermal conductivity of at least 4W at room temperature. /
High thermal conductivity sintered body with CI・℃. (2) The highly thermally conductive sintered body according to claim 1, wherein the average unit grain size of the sintered body is 5 μm or more. (3) The Vickers hardness of the sintered body is 5000 k.
The highly thermally conductive sintered body according to claim 1, which has a molecular weight of M-12 or more. (4) The impurity content in the sintered body is 0.5% by weight.
A highly thermally conductive sintered body according to claim 1, which is as follows. (5) 0.6 mol% or more 1.2 in hexagonal boron nitride
To uniformly diffuse and support boronitride of an alkaline earth metal or alkali metal in an amount of mol% or less, and to sinter this at high pressure at a temperature of 1350'C or higher under thermodynamically stable conditions for cubic boron nitride. A method for producing a highly thermally conductive sintered body, characterized by:

Claims (5)

[Claims] (1) 0.6 mol% to 1.2 mol% of alkaline earth metal or alkali metal boronitride is uniformly diffused and supported in hexagonal boron nitride, and cubic boron nitride is thermodynamically stabilized. A highly thermally conductive sintered body made of substantially 100% cubic boron nitride, obtained by high-pressure sintering at a temperature of 1350° C. or higher under the following conditions. (2) The highly thermally conductive sintered body according to claim 1, wherein the average unit grain size of the sintered body is 5 μm or more. (3) Microknoop hardness of the sintered body is 5000k
The highly thermally conductive sintered body according to claim 1, which has a high thermal conductivity of at least g/mm^2. (4) The highly thermally conductive sintered body according to claim 1, wherein the content of impurities in the sintered body is 0.5% by weight or less. (5) 0.6 mol% to 1.2 mol% of alkaline earth metal or alkali metal boronitride is uniformly diffused and supported in hexagonal boron nitride, and the thermodynamics of cubic boron nitride is A method for producing a highly thermally conductive sintered body, the method comprising high-pressure sintering at a temperature of 1350° C. or higher under physically stable conditions.