JP2647347B2 - Manufacturing method of aluminum nitride sintered body heat sink - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a manufacturing method of an aluminum nitride sintered body radiator plate, more particularly, a dense, yet a method for producing a thermally conductive aluminum good nitride sintered body radiator plate.

[0002]

2. Description of the Related Art Aluminum nitride (AlN) is used as a heat-resistant material because it has a small decrease in strength up to high temperatures and is excellent in chemical resistance. On the other hand, a semiconductor device utilizing its high-temperature conductivity and high electrical insulation is used. It is also promising as a heat sink material. Since such AlN does not usually have a melting point and decomposes at a high temperature of 2,200 ° C. or more, it is used as a sintered body except for applications such as thin films.

[0003] Such an AlN sintered body is usually obtained by molding and sintering an AlN powder. However, when AlN powder is used alone, sinterability is not good, and it is difficult to obtain a dense, that is, high-density sintered body except by the hot press method. Therefore, when sintering at normal pressure, it is common practice to add a rare earth oxide or an alkaline earth metal oxide as a sintering aid to AlN powder for the purpose of increasing the density of the sintered body. Have been done.

[0004] The addition of such a sintering aid did indeed considerably increase the density of the sintered body, but on the other hand, the thermal conductivity of such an AlN sintered body was reduced by oxygen and other impurities. At present , it is lower than expected due to the existence of grain boundaries and the like. That is, while the theoretical thermal conductivity of AlN is 320 W / m · K , that of the AlN sintered body is at most 40 W / m · K.

For this reason, various attempts have been made to improve the thermal conductivity of the AlN sintered body, but none of them have been sufficiently satisfactory.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the conventional problems and to provide an AlN sintered body heat radiation plate having high density and high thermal conductivity, and a method of manufacturing the same.

[0007]

Means for Solving the Problems In order to achieve the above object, the present inventors have developed a sintering additive added to AlN powder;
As a result of variously examining the relationship between the density and the thermal conductivity of the obtained sintered body, the following findings were obtained.

[0008] That is, together with an alkaline earth compound as a sintering aid, the periodic table Va , VIa, VIIa and VIII
Metal of transition element selected from the group or oxidation containing the element
If the material is added to the AlN powder and sintered, the sintering can be performed at a lower temperature as compared with the conventionally known single addition of an oxide of an alkaline earth or rare earth element. Is dense and has high thermal conductivity.

That is, the method of manufacturing the aluminum nitride sintered body radiator plate of the present invention comprises: (a) aluminum nitride; (b) a compound containing an alkaline earth element; and (c) Va and VIa of the periodic table . , selected from VIIa and VIII
Metal transition elements which barrel or After mixing the oxide containing the element, molding, characterized by sintering.

[0010] AlN obtained by the production method of the present invention
Sintered body radiator plate, when microscopically observed its constituent phases, A
At the grain boundaries of the 1N crystal grains, a compound such as an oxide of alkaline earth aluminum and / or an oxyfluoride thereof and a compound containing a transition element selected from Groups Va , VIa, VIIa and VIII of the periodic table are provided. Has been generated.

In this AlN sintered body heat sink, when the contained alkaline earth element is, for example, calcium (Ca), the oxide with aluminum is 6Al ₂ O.
_{3 · CaO, 2Al 2 O 3} · CaO, Al 2 O 3 · Ca
O and other compounds .

Furthermore, in such an AlN sintered body heat sink, the composition ratio of AlN crystal grains as a main component is 80 to 80% of the whole.
Preferably it is 99.98% by weight. If the composition ratio is less than 80% by weight, the characteristics of AlN itself cannot be sufficiently obtained, and if it exceeds 99.98% by weight, it is difficult to sufficiently exert the effect of the additive .

The method for manufacturing the heatsink of the AlN sintered body of the present invention will be described. The production method of the present invention is a method for producing Al
N and a compound containing an alkaline earth element as a first additive, and Va and VIa of the periodic table as a second additive.
A metal of a transition element selected from Group VIIa and VIII , or
The main point is to mix with an oxide containing an element and to mold and sinter.

First, as the main component AlN powder,
It is particularly useful to use one containing 0.001 to 7% by weight of oxygen in consideration of sinterability and thermal conductivity.

[0015] Examples of the alkaline earth element contained in the first additive include Be, Mg, Ca, Sr, and Ba. In particular, Ca, Sr, and Ba are preferable. One or more of these elements are selected from the group consisting of AlN.
Added to powder. As a compound of these elements, an oxide, a nitride, a fluoride, an oxyfluoride, an oxynitride, or a substance which becomes these compounds by firing is preferable.
Examples of the substance that becomes an oxide upon firing include carbonates, nitrates, oxalates, and hydroxides of these elements.

Next, the transition elements contained in the second additive include Group Va of the periodic table (V, Nb, Ta) and Group VI.
group a (Cr, Mo, W), group VIIa (Mn, Re),
Or Group VIII (Fe, Co, Ni, Ru, Rh, Pd,
Os, Ir, Pt) as long as they belong to one or more of these elements, similar to the first additive.
As a powder of an oxide containing a metal, or said element is the transition element, is added to the AlN powder. Of these transition elements, those belonging to the fourth period, that is , V 1 , Cr, M
When n, Fe, Co or Ni is used, there is an advantage that an AlN sintered body having a high density and a high thermal conductivity can be manufactured at a lower sintering temperature, for example, 1600 to 1650 ° C. than the conventional one. Have.

[0017] The first and second additives described above, from 0.01 to 18 wt%, respectively in terms of oxide of each element, 及
And 0.01 to 15% by weight. The total of both is preferably 0.02 to 20% by weight. The amount added is 0.01% by weight.
When the amount is less than the above, the effect of the additive is not sufficiently exerted. On the other hand, when the amount is excessively large, the heat resistance and the high strength are impaired, and the thermal conductivity is undesirably lowered. More preferably, the second additive is 0.01 to 10% by weight,
The preferred total amount of both is 0.02 to 18% by weight.
If the amount of the second additive is large, electrical insulation may be deteriorated.

The average particle diameter of the AlN powder and the first and second sintering additive powders to be used is 5 μm or less, preferably 4 μm or less.

Next, an example of the method of manufacturing the AlN sintered body heat sink of the present invention will be described below. First, the AlN powder was added to the above alkaline earth element compound as a sintering additive, and a transition element selected from the groups IVa to VIII of the periodic table.
Genus, or After the powder of oxide containing said elemental added a predetermined amount, mixed using a ball mill or the like. For sintering, a normal pressure sintering method, a hot press method, or the like can be used. In the case of the normal pressure sintering method, a binder is added to the mixed powder, and the mixture is kneaded, granulated and sized, and then molded. As a molding method, a mold press, an isostatic press, a sheet molding, or the like can be applied. Subsequently, the molded body is heated, for example, in a stream of N ₂ gas to remove the binder, and then sintered under normal pressure. The sintering temperature depends on the type of the additive used, but is usually set at 1,650 to 1,800 ° C. On the other hand, when the hot press sintering method is used, the raw materials mixed by the ball mill or the like may be directly hot pressed.

The lowering effect of improvement and sintering temperature of the thermal conductivity of the AlN sintered body radiator plate of the present invention are currently unknown, but according to studies by the present inventors, the thermal conductivity of This is estimated as follows. That is, one of the factors for increasing the thermal conductivity is that the AlN sintered body of the present invention
Oxynitride (AlON) and a polytype of AlN (27R type) are difficult to produce. According to the research results of the present inventors, it is known that the sintered bodies in which AlON and 27R type are formed have low thermal conductivity.
AlON, the generation of the 27R type, purity of AlN powder, but also affects the kind and the addition amount of the sintering furnace atmosphere and a sintering aid, using the same AlN powder, the same experimental conditions in comparing sintered body produced, or in comparison with the case of adding a conventional rare earth oxide or an alkaline earth oxide, in the sintered body radiator plate of the present invention, it is clearly less generation of AlON and 27R type Is not generated at all.

On the other hand, with respect to the decrease in sintering temperature, a liquid phase is generated at a lower temperature during sintering as compared with the conventional case where a rare earth oxide or an alkaline earth oxide is added alone, and sintering proceeds. It is presumed to be.

Further, the sintered body radiator plate of the present invention is colored by containing a transition element as a second additive, and its color tone varies depending on the type of the additive element and the amount and combination thereof. It is possible to change to In other words, in general, the Al / N molar ratio of the AlN raw material is not always 1, but is often Al-rich,
With such a raw material, the color of the sintered body is gray or black.
Further, as the raw material becomes richer in Al, the blackening proceeds, while the thermal conductivity generally decreases. Therefore, in the AlN raw material, as the Al / N molar ratio is as close to 1 as possible and the contained amount of impurities is smaller, the thermal conductivity is improved, and a white or translucent sintered body is obtained. In other words, conventionally, when trying to obtain a material having a high thermal conductivity, the color of the sintered body is inevitably white or translucent, while when trying to obtain a colored product, the thermal conductivity decreases. Resulting in. On the other hand, in the present invention, by simultaneously adding an alkaline earth element and a transition metal element, a high thermal conductivity is secured by using an AlN raw material having an Al / N molar ratio close to 1 and a small amount of impurities. In addition, it is possible to obtain various colored sintered bodies by appropriately selecting the type or combination of the additional elements. For example, Cr
_{When 2} O ₃ , Co ₃ O _4, etc. are added, the color becomes dark gray.
It is . On the other hand, when Eu ₂ O ₃ , Sm ₂ O ₃ or the like is added, a pale red color is obtained, and when TiO ₂ and Cr ₂ O ₃ are simultaneously added, a black color is obtained. Therefore, according to the present invention, it is possible to manufacture an AlN sintered body having a desired color tone. Since the AlN sintered body colored in this way has a high heat emissivity, the heat dissipation is further improved, and the coloring can prevent unevenness in sintering at the time of production and enhance the appearance of the product. This has the advantage that it can be performed.

[0023]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 First, an AlN powder containing 3.6% by weight of oxygen as an impurity and having an average particle size of 2.2 μm was mixed with CaO powder having an average particle size of 2.0 μm as a first additive. 1.5 wt% of NiO powder having an average particle diameter of 2.5 μm was added as a second additive, and the mixture was pulverized and mixed by a ball mill to prepare a raw material. Then add 7 pieces of paraffin to this raw material.
After adding the powder by weight and granulating, it was pressed at a pressure of 500 kg / cm ² to obtain a green compact of 30 × 30 × 8 mm. Subsequently, the green compact was heated to 700 ° C. in a nitrogen atmosphere to remove paraffin. Then, it was housed in a carbon container and sintered under normal pressure at 1,700 ° C. for 2 hours in a nitrogen gas atmosphere to produce an AlN sintered body heat sink. The obtained AlN
The density of the sintered body heat sink was measured. Also, the diameter from the sintered body
Grind a 10mm, 2.5mm thick disk and use it as a test piece.
The thermal conductivity was measured by the laser flash method. Ma
The obtained sintered body was 4mm wide, 3mm thick and 40mm long.
6 rods are ground and used as a test piece for bending strength measurement.
Distance between fulcrums, crosshead speed 0.5mm / min
The three-point bending strength was measured under the following conditions. Table 1 shows these results.
It was shown in .

[0025] Examples 2-8, instead of the various kinds of types, as well as sintering additives powder of Comparative Example 1 to 4 AlN powder, in the same manner as in Example 1 to produce an AlN powder, for each, as well The density and the thermal conductivity were measured. The results are shown in Table 1 together with the particle size of each AlN powder, the oxygen content, the type of sintering additive, the particle size, and the amount of addition.

[0026]

[Table 1]

Example 9 Using AlN powder and sintering additive powder shown in Table 2 ,
An AlN sintered body heat sink was manufactured in the same manner as in Example 1 and the density and the thermal conductivity were measured. The result is AlN
Table 2 shows the particle size of the powder, the oxygen content, the type of the sintering additive, and the amount added.

[0028]

[Table 2]

Example 10 Oxygen as an impurity was contained at 1.0% by weight, and the average particle size was
1.2 μm AlN powder, 2.0 μm average particle size Ca
O ₂ % by weight and Fe ₂ O _{3 having} an average particle size of 2.0 μm
Was added and the mixture was pulverized and mixed using a ball mill to prepare a raw material. Next, this raw material powder was
Press forming with pressure of kg / cm ² 12mm in diameter and 10mm in thickness
Of a green compact. Thereafter, the green compact was placed in a carbon mold and placed in a nitrogen gas atmosphere at a temperature of 1,700 ° C and 40 ° C.
Hot press sintering was performed under a pressure of 0 kg / cm ² for 1 hour. In the same manner as in Example 1, the density and the thermal conductivity of the obtained sintered body heat sink were measured . Table 3 shows the results.

Comparative Examples 5 to 8 The heat radiation plates of AlN sintered bodies were produced in the same manner as in Example 9 except that the type of AlN powder and the type of the sintering additive powder were variously changed. The thermal conductivity was measured. The results are shown in Table 3 together with the particle size of each AlN powder, the oxygen content, the type of the sintering additive, the particle size, and the amount added.

[0031]

[Table 3]

Example 11 AlN powder containing 1.4% by weight of oxygen as an impurity and having an average particle diameter of 1.2 μm was added.
CO ₃ mixed powder (weight ratio 1: NiO: CaO conversion: 1)
1) was added 4 wt%, grinding in a ball mill, a mixing line
Thus, the raw material was prepared. Subsequently, the raw material was granulated by adding 7% by weight of paraffin, and then press-molded at a pressure of 500 kg / cm ² to obtain a green compact of 30 × 30 × 8 mm. Subsequently, the green compact was heated to 700 ° C. in a nitrogen atmosphere to remove paraffin. Then, it is housed in a carbon container and placed in a nitrogen gas atmosphere at 1600 ° C. and 1,650 ° C.
C., 1,700.degree. C., 1,750.degree. C., and 1,800.degree. C. for 2 hours under normal pressure sintering to produce five types of AlN sintered body heat sinks.

Comparative Example 9 CaCO ₃ was added to the same AlN powder as in Example 11
Using a raw material added at 4% by weight in terms of aO, the following Examples
In the same manner as in Example 11 , five types of AlN sintered body heat sinks were manufactured.

[0034] Using the raw material obtained by adding NiO only 5 wt% to the same AlN powder as in Comparative Example 10 Example 11 above, below, were prepared 5 kinds of AlN sintered body radiator plate in the same manner as in Example 11 .

Thus, Example 11 and Comparative Examples 9 and 10
The relationship between the density and the thermal conductivity with respect to the sintering temperature of the AlN sintered body radiator plate was examined, and the characteristic diagrams shown in FIGS . 1 and 2 were obtained. Note that A in FIGS. 1 and 2 indicates the first embodiment.
1 is a characteristic line, B is a characteristic line in Comparative Example 9 , and C is a characteristic line.
14 is a characteristic line in Comparative Example 10 . As is clear from FIG . 1 and FIG. 2 , the AlN sintered body radiator plate of the present invention can achieve a high density and a high thermal conductivity at a low sintering temperature.
The manufacturing cost can be reduced as compared with the N sintered body.

Example 12 AlN powder containing 2.4% by weight of oxygen as an impurity and having an average particle diameter of 1.6 μm was mixed with a mixed powder of CaCO ₃ and Fe ₂ O ₃ (Fe ₂ O ₃ : CaO conversion). Weight ratio of 3: 7)
Was added in an amount of 4% by weight in terms of CaO + Fe ₂ O _3.
C., 1,700.degree. C., 1,750.degree. C., and 1,800.degree. C. for 2 hours, and the density and thermal conductivity of the obtained AlN sintered body heat radiation plate were measured . and shown by curve D in FIG. 4.

COMPARATIVE EXAMPLE 11 For comparison, the same AlN powder as in Example 12 was added to CaC
Sintering was performed at each temperature in the same manner as described above using a raw material powder to which 7.14% by weight of O ₃ (4.0% by weight in terms of CaO was added) and a raw material powder to which 4% by weight of Y ₂ O ₃ was added. FIG the resulting measured density and thermal conductivity of the sintered body radiator plate results 3, FIG.
4 shows a curve E and a curve F , respectively. FIG. 3 and FIG.
As is clear from FIG. 4, the radiator plate of the AlN sintered body of the present invention can significantly reduce the sintering temperature, and has a high density and high conductivity. Costs can be kept low.

[0038]

As apparent from the above description, the aluminum nitride sintered body radiator plate obtained by the production method of the present invention has excellent having high density and high thermal conductivity. And, the additive to be added, in particular, the second
Depending on the type of the transition element, which is an additive, properties such as extremely high strength and sintering at a low temperature can be imparted. Furthermore, since the transition elements can be colored in various colors depending on the types and combinations of the transition elements, the range of use can be widened, and a reduction in production yield due to unevenness in sintering or the like can be avoided.
Therefore, its industrial value is extremely high, and it is particularly useful as a heat sink for semiconductor devices and the like.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a relationship between sintering temperature and density for AlN sintered bodies obtained in Example 11, Comparative Examples 9 and 10 .

FIG. 2 is a characteristic diagram showing a relationship between a sintering temperature and a thermal conductivity for AlN sintered bodies obtained in Example 11, Comparative Examples 9 and 10 ;

FIG. 3 is a characteristic diagram showing the relationship between the sintering temperature and the density of the AlN sintered bodies obtained in Example 12 and Comparative Example 11 .

FIG. 4 is a characteristic diagram showing the relationship between the sintering temperature and the thermal conductivity of the AlN sintered bodies obtained in Example 12 and Comparative Example 10 .

[Reference Numerals] A ...... Example 11 characteristic line B ...... characteristic line C ...... Comparative Example 10 Comparative Example 9 characteristic line D ...... Example 12 the characteristic line E, the F ...... Comparative Example 11 Characteristic line

Continued on the front page (72) Inventor Fumio Ueno 1 Toshiba-cho, Komukai-ku, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Research Institute, Inc. Inside Toshiba Research Institute (72) Inventor Akihiko Tsuge 1 Kosuka Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba Research Institute (72) Inventor Hiroshi Imagawa 1 Kosuka-Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Co., Ltd. Inside Toshiba Research Institute (72) Inventor Takeshi Takano 1 Kosaka Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba Research Institute (72) Inventor Hiroshi Inoue 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Corporation In Toshiba Research Institute (56) References JP-A-58-55376 (JP, A) JP-A-59-229843 (JP, A) JP-A-61-270262 (JP, A)

Claims (8)

(57) [Claims] 1. A compound selected from the group consisting of (a) aluminum nitride, (b) a compound containing an alkaline earth element, and (c) groups Va , VIa, VIIa and VIII of the periodic table .
Metal transition elements which barrel or After mixing the oxide containing the element, the molding method for producing an aluminum nitride sintered body radiator plate, characterized in that the sintering. 2. The content of the compound containing an alkaline earth element is 0.01 to 1 in terms of an alkaline earth element oxide.
The production method according to claim 1, wherein the content is 8% by weight. 3. Periodic Tables Va, VIa, VIIa and VIII
Metal of transition element selected from the group or oxidation containing the element
Content of things, in terms of oxide of the element, 0.01
The production method according to claim 1, wherein the amount is from 15 to 15% by weight. 4. A compound containing an alkaline earth element, said original
Oxide containing element, nitride, fluoride, acid fluoride, a substance or a combination thereof, and these compounds by oxynitride or baking method according to claim 1 or 2. 5. The aluminum nitride contains oxygen from 0.001 to 7% by weight The process of claim 1. 6. used sintering material, an average particle diameter of 5μm or less of powder, method according to claim 1 or 2. 7. The method according to claim 1, wherein the alkaline earth elements are Ca, Sr and B.
2. The method according to claim 1, wherein at least one of a is used. 8. Periodic Tables Va, VIa, VIIa and VIII
The transition element selected from the group is Ni, Cr, Mn, Fe,
The production method according to claim 1 , wherein the production method is at least one of Co and V.