KR20190023485A - Aluminum nitride sintered body and method for manufacturing the same - Google Patents

Abstract

The present invention relates to an aluminum nitride sintered body with improved mechanical properties and a production method thereof. The aluminum nitride sintered body is obtained by sintering a composition comprising an aluminum nitride (AlN) powder and a sintering aid, wherein the sintering aid comprises zirconia stabilized with a metal oxide and an oxide of a composite metal containing an alkaline earth metal and zirconium.

Description

[0001] ALUMINUM NITRIDE SINTERED BODY AND METHOD FOR MANUFACTURING THE SAME [0002]

The present invention relates to an aluminum nitride sintered body capable of low temperature sintering and a method of manufacturing the same.

In recent years, there is an increasing demand for miniaturization, multi-functioning, and high-speed operation of electronic devices. In order to meet such demands, high-density packaging of semiconductor devices and high output are required. However, if the mounting density and output of the semiconductor device are increased, the amount of heat generated by the mounting substrate is increased, so that an insulating substrate having excellent heat dissipation characteristics is required. On the other hand, aluminum nitride (AlN) has attracted attention as one of recent fine ceramics as a material having high thermal conductivity and high insulation. Particularly, excellent thermal characteristics are attracting the most attention among the properties of aluminum nitride.

Since the aluminum nitride (AlN) is a sinter-resisting ceramic, rare-earth metal oxides such as yttrium oxide (Y ₂ O ₃ ) and calcium oxide (CaO), alkaline earth metals Etc. are used as sintering aids. However, in general, the sintering temperature of aluminum nitride (AlN) is higher than 1800 ° C., so that it is difficult to sinter compared with alumina, and accordingly, a large amount of sintering energy is required, thereby increasing manufacturing costs.

As a conventional art relating to the above aluminum nitride (AlN) sintered body, Korean Patent Registration No. 1996-0703766 discloses a sintering aid composed of a rare earth metal oxide, a glass frit and oxides such as B, Na, K, Ca, Discloses a method for producing a sintered body using an additive. In Korean Patent Laid-Open Publication No. 2010-0088479, a sintering aid for yttrium oxide and chromium oxide and an aluminum nitride (AlN) raw material powder are sintered at a sintering temperature of 1700 to 1800 ° C (AlN) sintered body exhibiting high thermal conductivity is obtained.

However, various methods of using a rare earth metal oxide or an alkaline earth metal oxide as a sintering assistant as a method for low temperature sintering in the process of manufacturing an aluminum nitride (AlN) sintered body including the above-described conventional techniques have been proposed to date, In order to satisfy the physical properties, the necessity of research for manufacturing aluminum nitride (AlN) sintered body capable of sintering at low temperature and having excellent mechanical strength is continuously increasing.

An object of the present invention is to provide an aluminum nitride sintered body capable of sintering at a low temperature and having improved mechanical properties such as bending strength and a method for manufacturing the same.

In order to achieve the above object, one aspect of the present invention is a sintered aluminum nitride obtained by sintering a composition comprising an aluminum nitride (AlN) powder and a sintering auxiliary agent, wherein the sintering auxiliary agent comprises zirconia and an alkaline earth metal stabilized with a metal oxide And an oxide of a composite metal containing zirconium.

In another aspect of the present invention, there is also provided a method for forming a slurry by mixing an aluminum nitride powder, an oxide of a composite metal containing an alkaline earth metal and zirconium, and zirconia stabilized with a metal oxide together with a solvent, Feeding the obtained powder into a sintering reactor, and sintering the sintered body by raising the temperature of the reactor.

Yet another aspect of the present invention is a method for forming a slurry by mixing an aluminum nitride powder, an oxide of a composite metal containing an alkaline earth metal and zirconium, and zirconia stabilized with a metal oxide together with a binder, casting the mixture to form a sheet, injecting the resulting molded body into a sintering reactor, and sintering the sintered body by raising the temperature of the reactor.

The aluminum nitride sintered body of the present invention is advantageous in that the secondary phase is formed at a lower temperature than in the prior art, so that the low-temperature sintering can be performed in comparison with the conventional aluminum nitride sintered body and the bending strength is excellent.

1 is a scanning electron microscope (SEM) image of an aluminum nitride sintered body according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.

1. Aluminum nitride sintered body

One aspect of the present invention provides an aluminum nitride sintered body (AlN)

The aluminum nitride sintered body can be obtained by sintering a composition including an aluminum nitride powder and a sintering auxiliary agent.

Aluminum nitride is an insulator having excellent thermal conductivity and has a thermal expansion coefficient close to that of silicon (Si). Therefore, aluminum nitride is widely used for substrates, heat sinks, and the like of highly integrated semiconductor devices.

The aluminum nitride is sinter-resisting ceramics, and a sintering aid is used to improve the density of ceramics. The sintering aid is solid-dissolving impurity oxygen contained in the aluminum nitride powder in the aluminum nitride crystal grains, Thereby suppressing an increase in thermal resistance of the ceramic.

The average particle diameter of the aluminum nitride powder is preferably 0.1 to 2 占 퐉. If the average particle diameter of the aluminum nitride powder is less than 0.1 탆, the thermal conductivity of the aluminum nitride sintered body is lowered, and if the average particle diameter of the aluminum nitride powder exceeds 2 탆, the strength of the aluminum nitride sintered body may be lowered.

The composition comprising the aluminum nitride (AlN) powder of the present invention and the sintering aid comprises 85 to 98 parts by weight of the aluminum nitride powder and 1 to 15 parts by weight of the sintering auxiliary. If the content of the aluminum nitride (AlN) powder is less than 85 parts by weight, thermal conductivity may be decreased due to the increase of impurities. If the content of the aluminum nitride powder exceeds 98 parts by weight, the content of the sintering auxiliary added is insufficient, It is difficult to achieve the sintering at a high temperature of 1800 DEG C or more. Also, excessive use of the sintering assistant agent may increase the thermal conductivity of the aluminum nitride crystal grains, but a large number of secondary phases having a low thermal conductivity may be formed, thereby increasing or decreasing the thermal conductivity depending on the content of the sintering auxiliary agent. Therefore, when the content of the sintering auxiliary agent is in the above range, the composition including the aluminum nitride (AlN) powder and the sintering aid may be excellent in sintering activity.

The sintering aid may comprise zirconia stabilized with a metal oxide, or an oxide of a composite metal containing an alkaline earth metal and zirconium, preferably zirconia stabilized with the metal oxide, a composite metal containing an alkaline earth metal and zirconium Can be used together.

The metal oxide stabilized zirconia means zirconia in which a crystal structure is partially stabilized by adding a metal oxide in order to prevent a rapid change in volume due to a change in a complex crystal structure accompanied by heating and cooling, may be a calcium (CaO), yttrium oxide (Y ₂ O _3), magnesium oxide (MgO), cerium oxide (CeO _2).

The metal oxide stabilized zirconia may be selected from the group consisting of calcia-stabilized zirconia (CaSZ), yttria-stabilized zirconia (YSZ), magnesia-stabilized zirconia (MSZ), ceria stabilized zirconia Ceria-stabilized zirconia, CSZ) and the like. Preferably, yttria-stabilized zirconia (YSZ) can be used. As described above, zirconia stabilized with a metal oxide maximizes strength and toughness, and the bending strength of the aluminum nitride sintered body using the zirconia can be improved.

The zirconia may be partially stabilized with 30 to 50 wt% of a metal oxide. The zirconia is partially stabilized with a metal oxide of 30 to 50 wt%, so that a toughening mechanism effect can be applied to the aluminum nitride (AlN) sintered body.

Meanwhile, the alkaline earth metal may be Be, Mg, Ca, Sr, Ba, Ra, or the like. As a possible example of a composite metal oxide of the alkaline earth metal and containing _{zirconium, BeZrO 3, MgZrO 3, CaZrO} 3, SrZrO 3, BaZrO 3, RaZrO 3 Or the like can be used, and CaZrO ₃ can be preferably used.

When such an oxide of a composite metal containing an alkaline earth metal and zirconium is used as a sintering aid, it is pinned to a grain boundary at the time of sintering to inhibit grain growth It is possible to produce an aluminum nitride sintered body which can have small crystal grains even after sintering and can have high mechanical strength.

Further, when zirconia (ZrO ₂ ) alone is added as a sintering aid in the composition containing the aluminum nitride powder and the sintering auxiliary agent, the aluminum nitride is thermally decomposed at the sintering temperature to deteriorate the properties as a sintered body. And CaZrO ₃ , which is a stable phase of zirconia (ZrO ₂ ).

In the sintering aid of the present invention, it is preferable that an oxide of a composite metal including an alkaline earth metal and zirconium, and zirconia stabilized with a metal oxide are mixed in a ratio of 5: 2 to 5: 5. If the content of the zirconia stabilized with the metal oxide is out of the above range, the bending strength and thermal conductivity of the aluminum nitride sintered body may be lowered.

Further, the sintering auxiliary agent of the present invention may further include a rare earth oxide to improve sinterability of the aluminum nitride sintered body. The rare earth oxides may be yttrium oxide, lanthanum oxide, cerium oxide, neodymium oxide, samarium oxide, gadolinium oxide, dysprosium oxide, erbium oxide, ytterbium oxide, and the like. Yttrium oxide is preferred. The content of the rare earth oxide may be 1 to 8 parts by weight based on 100 parts by weight of the composition. If the content of the rare earth oxide is less than 1 part by weight, the sinterability of the aluminum nitride sintered body is weakened and the relative density is lowered. When the content of the rare earth oxide exceeds 8 parts by weight, the rate of change of the volume resistivity of the aluminum nitride sintered body is relatively increased .

The composition comprising the aluminum nitride (AlN) powder of the present invention and the sintering aid may further comprise a solvent, a binder and the like.

The solvent may be distilled water, alcohols such as ethanol, methanol, isopropanol, ketones such as hydrocarbon, acetone, methyl ethyl ketone and the like. When distilled water is used, the characteristics of the sintered body are lowered and sintering property is also deteriorated. And the like. In some cases, it may be desirable to reduce the amount of water contained in the solvent used in the present invention.

The content of the solvent is not limited so far as it can prevent the (AlN) powder of aluminum nitride from being hydrated or oxidized, but it is preferably a mixture ratio of aluminum nitride powder: solvent = 3: 1 to 1: 3.

The binder may be a polyvinyl butyral resin, a cellulose resin, an acrylic resin, a vinyl acetate resin, a polyvinyl alcohol resin, or the like, but is not limited thereto.

The content of the binder may be 3 to 20 parts by weight, preferably 5 to 15 parts by weight, based on 100 parts by weight of the composition. If the binder content is out of the above range, a molded body crack may occur.

2. Manufacturing Method

Another aspect of the present invention provides a method of manufacturing an aluminum nitride sintered body.

Wherein the aluminum nitride sintered body is obtained by mixing aluminum nitride powder and the above-described sintering auxiliary agent together with a solvent to form a slurry, drying the slurry and injecting powder obtained by molding the slurry into a sintering reactor, Followed by sintering.

Specifically, 85 to 98 parts by weight of the aluminum nitride powder and 1 to 15 parts by weight of the sintering auxiliary are mixed with a solvent to prepare a mixture, and the mixture is pulverized through a ball mill to form a slurry.

The ball used for ball milling may be a ball made of ceramics such as alumina or zirconia, and the balls may be all the same size or may be used together with balls having two or more sizes. The size of the balls, the milling time, and the rotation speed per minute of the ball miller are adjusted so as to be crushed to the target particle size. The ball milling process is performed for 1 to 24 hours in consideration of the size of the target particles and the like. By means of ball milling, the blended raw materials are pulverized into fine-sized particles and have a uniform particle size distribution, so that a slurry having an average particle size of 0.6 mu m to 2.0 mu m, preferably 0.9 mu m to 1.2 mu m can be formed.

The slurry thus formed can be dried by stirring in a hot plate at 100 to 120 ° C for 40 minutes to 1 hour and 30 minutes so as not to precipitate using a stirrer, and this is dried in a 60 ° C vacuum oven for 30 minutes to 1 hour Dried to prepare a powder having homogeneity and then introduced into a sintering reactor.

In the drying process, the mixture may be stirred at a temperature of 80 to 90 ° C using a rotary evaporator, and dried in a vacuum atmosphere for 1 hour and 30 minutes to 2 hours. The present invention may include a step of forming a powder by a cold isostatic pressing (CIP) method before putting the dried powder into a sintering reactor to form a disk-shaped molded body having a diameter of 30 mm and a thickness of 2.5 mm. The pressure of the cold isostatic pressing method may be in the range of 100 to 1000 atm, preferably 100 to 500 MPa.

The cold isostatic pressing (CIP) is a method in which a material such as water is used as a pressure medium, a material is put into water, and a pressure is applied at a high isostatic pressure, so that the entire surface of the substrate having a thin film is pressed. To form a sintered body, which is put into a sintering reactor.

The temperature of the reactor may be raised to 1600 ° C or lower, the temperature may be increased from 20 ° C to 40 ° C per minute, preferably 10 ° C / minute, 10 hours, preferably 1 hour to 5 hours.

On the other hand, as another manufacturing method of the aluminum nitride sintered body of the present invention, a slurry is formed by mixing an aluminum nitride powder, an oxide of a composite metal containing an alkaline earth metal and zirconium, and zirconia stabilized with a metal oxide together with a binder, Slip casting the slurry to prepare a sheet, introducing the resulting molded body into a sintering reactor, and sintering the sintered body by raising the temperature of the reactor.

85 to 98 parts by weight of the aluminum nitride powder and 1 to 15 parts by weight of the sintering auxiliary are mixed with a binder to prepare a mixture, and the mixture is pulverized through a ball mill to form a slurry. At this time, the mixture may further contain a solvent.

Further, in order to form the slurry, the blending materials may be uniformly mixed and pulverized using a ball mill, and may be performed for about three to three days by primary ball milling. The binder may be further added after the ball milling process, in which case the ball milling may proceed with a second ball milling for 6 to 24 hours.

The thus formed slurry is subjected to slip casting to prepare a sheet, and the resulting molded body is put into a sintering reactor.

The slip casting can be performed by forming a slurry to be injected into a mold and pouring it into a mold having a predetermined shape in order to form a solid body in a mold. In the present invention, And then gradually raising the temperature from room temperature to 600 ° C for 12 to 48 hours, followed by sufficiently removing the binder while maintaining the temperature at 600 ° C for 2 hours to 8 hours, and then gradually lowering the temperature to room temperature for 4 to 24 hours To form a molded article from which the binder has been completely removed, and this is injected into the sintering reactor.

The temperature of the reactor is elevated to below 1600 ° C. The temperature of the reactor is preferably 1.0 ° C to 3.0 ° C per minute, and the sintering temperature is maintained for 1 hour to 10 hours, preferably 1 hour to 5 hours.

Hereinafter, the present invention will be described in detail with reference to examples.

However, the following examples illustrate the present invention in detail, and the present invention is not limited by the following examples.

[ Example ]

Example  1 to Example  6

The composition and the contents of the following Table 1 are prepared, and a binder and a plasticizer are mixed with 100 ml of isopropanol as a solvent to prepare a mixed solution. The slurry was prepared by dispersing the raw materials by ball milling at 400 rpm for 24 hours at room temperature using zirconia balls. The obtained slurry was poured into a mold having a predetermined shape, and the temperature was gradually raised from room temperature to 600 ° C for 12 hours and then maintained at 600 ° C for 6 hours to form a molded article from which an acrylic resin (binder) was removed. The shaped body was charged into a sintering reactor, and the temperature of the sintering reactor was gradually raised to 2 ° C per minute to reach a sintering temperature and sintering was carried out. During the sintering reaction, a nitrogen atmosphere was maintained to prevent oxidation during sintering. The sintered aluminum nitride sintered body was sintered at 1600 ° C, 1650 ° C, 1700 ° C and 1750 ° C in nitrogen atmosphere for 3 hours, respectively.

division Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Particle size D50 AlN 92 91 90 92 91 90 1 탆 Y ₂ O ₃ 5 5 5 5 5 5 1 to 2 탆 YSZ 2 2 2 One 2 3 0.04 m CaZrO ₃ One 2 3 2 2 2 1 to 1.5 탆

[ Comparative Example ]

Comparative Example  1 to Comparative Example  2

Aluminum nitride sintered bodies were prepared in the same manner as in the above examples, with the compositions and contents shown in Table 2 below.

division Comparative Example 1 Comparative Example 2 Particle size D50 AlN 94 85 1 탆 Y ₂ O ₃ 5 5 1 to 2 탆 YSZ - - 0.04 m CaZrO ₃ One 10 1 to 1.5 탆

[ Experimental Example ]

The aluminum nitride sintered bodies according to the above examples and comparative examples were evaluated by the following methods, respectively.

Relative density

The evaluation results are shown in Table 3 below.

division 1600 ° C 1650 ℃ 1700 ℃ 1750 ℃ Example 1 94% 96% 100% 100% Example 2 98% 100% 100% 100% Example 3 100% 100% 100% 100% Example 4 96% 99% 100% 100% Example 5 98% 100% 100% 100% Example 6 97% 99% 100% 100% Comparative Example 1 92% 94% 97% 100% Comparative Example 2 100% 100% 100% 100%

Microstructure

The aluminum nitride sintered body produced according to the above Examples 1 to 3 was confirmed by an electron microscope (SEM), which is shown in Fig.

Referring to FIG. 1, it can be seen that as the temperature increases, the size of the crystal grains increases.

Bending strength

The bending strength specimen is prepared by cutting the substrate into a rectangle of 4.0 mm × 0.63 mm × 50 mm using a laser. Three points were measured using UTM (universal test machine, Z020, Zwick / Roell AG, Germany). The measurement conditions were a cross-head speed of 0.2 mm / min.

The evaluation results are shown in Table 4 below.

division 1600 ° C 1650 ℃ 1700 ℃ 1750 ℃ Example 1 447 445 608 555 Example 2 492 514 592 555 Example 3 504 621 634 613 Example 4 482 508 615 540 Example 5 493 518 603 557 Example 6 490 510 618 570 Comparative Example 1 455 471 515 523 Comparative Example 2 535 527 488 465

Referring to Tables 3 and 4, it was confirmed that as the density of the aluminum nitride sintered body increases, the bending strength also increases. However, even when the density is increased, the sintering temperature (for example, 1750 ° C) is high and it is confirmed that the strength of the aluminum nitride sintered body is lowered when the crystal grain size exceeds 2 μm.

Claims (10)

1. An aluminum nitride sintered body obtained by sintering a composition comprising an aluminum nitride (AlN) powder and a sintering aid,
Wherein the sintering assistant comprises zirconia stabilized with a metal oxide, and an oxide of a composite metal containing an alkaline earth metal and zirconium. The method according to claim 1,
The metal oxide is calcium (CaO), yttrium oxide (Y ₂ O _3), magnesium oxide (MgO), and at least one member of aluminum nitride sintered body is selected from the group consisting of cerium oxide (CeO ₂₎ oxidation. The method according to claim 1,
Wherein the zirconia is partially stabilized with 30 to 50 wt% of a metal oxide. The method according to claim 1,
Wherein the alkaline earth metal is one selected from the group consisting of Be, Mg, Ca, Sr, Ba and Ra. The method according to claim 1,
And the oxide of the composite metal containing the alkaline earth metal and zirconium is CaZrO ₃ . The method according to claim 1,
Wherein the sintering aid further comprises a rare earth oxide. The method according to claim 1,
Wherein the sintering aid is a mixture of an oxide of a composite metal containing an alkaline earth metal and zirconium and zirconia stabilized by a metal oxide in a ratio of 5: 2 to 5: 5. The method according to claim 1,
Wherein the composition comprises 85 to 98 parts by weight of aluminum nitride powder and 1 to 15 parts by weight of a sintering aid. An aluminum oxide powder, an oxide of a composite metal including an alkaline earth metal and zirconium, and zirconia stabilized with a metal oxide together with a solvent to form a slurry,
Drying the slurry, molding the slurry, and introducing the obtained powder into a sintering reactor; and
Wherein the temperature of the reactor is raised to sinter the aluminum nitride sintered body. An aluminum oxide powder, an oxide of a composite metal including an alkaline earth metal and zirconium, and zirconia stabilized with a metal oxide together with a binder to form a slurry,
Slip casting the slurry to prepare a sheet, and introducing the resulting molded body into a sintering reactor; and
Wherein the temperature of the reactor is raised to sinter the aluminum nitride sintered body.

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