JPH0774100B2 - Manufacturing method of high-purity aluminum nitride plate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a high-purity aluminum nitride (hereinafter referred to as AlN) plate material having a theoretical density ratio of 100% by a simple operation at a low cost. Is.

[Conventional technology]

In general, AlN sheet material has excellent heat resistance, corrosion resistance, and wear resistance, as well as excellent high temperature strength and high temperature thermal shock resistance, as well as high thermal conductivity and insulation, and low dielectric constant and thermal expansion coefficient. Since it is a material with outstanding characteristics among other ceramics, it is also used as a structural material for various devices, LSIs that require high heat dissipation recently, and functional ceramic board materials such as substrates for hybrid IC packages. It is getting attention.

Conventionally, this kind of AlN plate material has been manufactured by a powder metallurgy method which comprises using AlN powder as a raw material powder and compressing and sintering the powder into a plate material.

[Problems to be solved by the invention]

However, in order to manufacture a high-density AlN plate material by the above-mentioned conventional powder metallurgy method, (1) extremely fine AlN powder is used.

(2) Raise the sintering temperature to a high temperature of 1800 ° C or higher.

(3) Add an auxiliary agent that promotes the sinterability of AlN.

(4) Perform pressure sintering.

In addition, impurities in the raw material powder and oxides on the powder surface are segregated at crystal grain boundaries during sintering, or are solid-dissolved in the crystal grains, and the thermal and Since it deteriorates the electrical characteristics and strength, it is necessary to use AlN powder with the highest possible purity as the raw material powder and take care to minimize impurity contamination in the manufacturing process.
When using an AlN plate material as a substrate for an IC package, for example, a trace amount of oxygen and carbon, and further Si, F
If metal impurities such as e and Mg are contained, the thermal conductivity will be significantly reduced and it will be unusable for practical use.In this way, high density and high purity AlN plate material can be processed by ordinary powder metallurgy method. Therefore, in the manufacturing process, not only a complicated process is required, but also it is inevitable that the cost is high because it is indispensable to use finely powdered AlN powder as a raw material powder.

[Means for solving problems]

Therefore, from the above-mentioned viewpoints, the inventors of the present invention have sufficiently satisfactory thermal and electrical characteristics and strength if the AlN sheet material is manufactured by the ordinary powder metallurgy method.
Recognizing that it is extremely difficult to manufacture AlN sheet material at low cost, we conducted research to produce AlN sheet material with high density and high purity at low cost without using the powder metallurgy method. A heat-resistant plate that does not react with molten metal, a high-purity Al plate material, and a breathable porous ceramic plate are alternately stacked in this order from the bottom to the top, and one set or two or more sets are stacked. After removing the surface oxide film of the high-purity Al plate material by a means such as temporarily exposing it to a gas atmosphere containing hydrochloric acid in a heating furnace in a fixed state, the melting point of Al in a nitrogen-containing atmosphere. The above predetermined temperature, preferably 800 ° C. or higher temperature for a predetermined period of time, the nitrogen in the atmosphere through the air-permeable porous ceramic plate, a simple operation of reacting with the high-purity Al plate material in the molten state It is possible to form an AlN plate material using a heating furnace that can be controlled in a normal atmosphere, and the resulting AlN plate material has a high purity as the above AlN plate material, for example, a purity of 99.99% or more. If pure Al is used, it will have high purity in proportion to this,
And this high-purity Al plate material is not only much cheaper than fine high-purity Al powder, but also combined with the low reaction temperature, it is possible to manufacture at low cost, and further As described above, since it is formed by the reaction of molten Al with nitrogen in the atmosphere, it was found that the density as a melting material, that is, the theoretical density ratio: 100% is obtained.

This invention was made on the basis of the above findings, in which a heat-resistant plate that does not react with molten Al, a high-purity Al plate material, and a breathable porous ceramic plate were superposed in this order from bottom to top. One set or two or more sets are stacked and fixed in a heating furnace in a heating furnace to remove the surface oxide film of the high-purity Al plate material in a gas atmosphere, and then to remove Al in a nitrogen-containing atmosphere. A high-purity Al plate material is produced by heating and holding at a predetermined temperature equal to or higher than the melting point for a predetermined time, and passing nitrogen in the atmosphere through the air-permeable porous ceramic plate and reacting with the high-purity Al plate material in a molten state. The method has a feature.

In the method of the present invention, the breathable porous ceramic plate is used in addition to reacting nitrogen gas in the atmosphere with a high-purity Al plate material in a molten state (hereinafter referred to as an Al melt). This is because it effectively prevents aggregation of the melt.

That is, if the thickness of the Al plate material is as thin as 1 mm or less, for example, if it is heated above the melting point of Al in a state of being superposed with a plate having poor wettability, a plurality of Al melts may have surface tension. It tends to agglomerate into island pools, and is formed when the Al melt agglomerates into islands before the nitriding reaction.
Similarly, AlN also becomes an aggregated island shape, and it is not possible to manufacture an AlN plate material having a constant thickness.

However, even if the wettability with the Al melt is poor, this laminated plate has small pores, and the number of cells (holes per 1 inch length) is about 20 to 50. When a high quality ceramic plate is used, the surface tension of the Al melt prevents the Al melt from spreading into the narrow gaps between the plates, and as a result, the agglomeration of the Al melt is prevented and the flat shape is maintained. The nitriding reaction proceeds rapidly until AlN plate material with almost the same shape as the Al plate material is formed, and the material is Al ₂ O ₃
Single material such as or ZrO _2, and further _{Al 2 O 3 -ZrO 2, Al} 2 O 3 and Zr
It is preferable to use a composite material in which ceramic fibers such as O ₂ are hardened with an inorganic binder to form a sheet.

Further, as the heat-resistant plate on which the Al plate material is placed, the flat surface is smooth, there is no reaction with the Al melt, and there is no penetration of the Al melt. There is no particular limitation as long as it does not contain a solid solution as, for example, a crystalline or vitreous graphite plate, further preferably ZrO ₂ , Si ₃ N ₄ , or a ceramic plate composed of BN or the like, in this case The ceramic plate may have fine open pores that do not allow the Al melt to permeate.

Furthermore, in carrying out the method of the present invention, a fixing jig, such as a scissors jig, is used for integrally fixing the heat-resistant plate, the high-purity Al plate material, and the air-permeable porous ceramic plate. However, by using this fixing jig, the agglomeration phenomenon of the Al melt caused by the lifting of the breathable porous ceramic plate due to the surface tension of the Al melt can be prevented.

〔Example〕

Next, the method of the present invention will be specifically described by way of examples with reference to the drawings.

Example 1 As shown in the schematic sectional view of FIG. 1, 50 mm × 100 mm × 1
Purity with mm dimension: 99.99% high-purity Al plate material 1,
Place it on a heat-resistant plate 2 consisting of a crystalline graphite plate with dimensions of 60 mm × 110 mm × 1.5 mm, and place 50 mm × 100 mm × 5 mm dimensions, 75% porosity, and 30 cells on it. The air-permeable porous ceramic plates 3 made of alumina-cordierite ceramics are superposed, and the four side surface central portions of the set of the superposed bodies are attached to each other by a pad plate 4 made of the same material as the air-permeable porous ceramic plate. Are fixed with graphite fixing jigs 5 in contact with the respective side surfaces, and in this state, they are placed on the base plate 7 in the alumina furnace core tube 6 of the heating furnace and heated by the heater 8. First, the ratio of nitrogen gas and hydrochloric acid gas is 10: 1
Of the mixed gas of about 30 during the temperature rising process of 500-800 ℃ in the core tube.
Flow for a minute, and then at a temperature of 800 ° C., with the ratio of hydrochloric acid gas being zero, flow nitrogen at a ratio of 500 C.C./mim,
The method of the present invention was carried out by raising the temperature while forming a nitrogen atmosphere and maintaining the temperature at 1000 ° C. for 30 minutes to produce an AlN plate material (hereinafter referred to as AlN plate material 1 of the present invention).

Example 2 As shown in the schematic sectional view of FIG.
While using a plate material 1 with a purity of 99.99%,
In Example 1 except that the high-purity Al plate material 1, the heat-resistant plate 2 and the breathable porous ceramic plate 3 are alternately laminated four by four to form a four-layer superposed body. The method of the present invention was carried out under the same conditions as above to produce an AlN sheet material (hereinafter referred to as the present invention AlN sheet material 2).

In this case, if a heat-resistant plate 2 having a figure (pattern) drawn on the surface by engraving or the like is used, a high-purity AlN plate material having a surface figure can be manufactured.

Next, the purity, thermal conductivity, thermal expansion coefficient, dielectric constant, and bending strength of the AlN plate materials 1 and 2 of the present invention obtained as a result were measured. The results of these measurements are shown in Table 1.
Table 1 also shows characteristic values of commercially available sintered AlN sheet materials manufactured by the powder metallurgy method for the purpose of comparison.

[Effects of the Invention] From the results shown in Table 1, the AlN plate materials 1 and 2 of the present invention are
It is clear that it has excellent thermal and electrical properties and high strength because it has high purity and high density as compared with commercially available sintered AlN sheet material.

As mentioned above, according to the method of the present invention, the theoretical density ratio: 1
00%, that is, a high-purity AlN plate material as a melting material can be manufactured at a low cost by a simple operation, and the resulting AlN plate material has excellent thermal and electrical characteristics and high strength. Since it has, for example, the substrate of the IC package and the excellent translucency of AlN are used,
When it is used as a so-called functional ceramics member, it exhibits industrially useful effects such as excellent performance.

[Brief description of drawings]

1 and 2 are schematic sectional views showing an embodiment of the method of the present invention. 1 ... High-purity Al plate material, 2 ... Heat-resistant plate, 3 ... Breathable porous ceramic plate, 4 ... Paddle plate, 5 ... Fixing jig, 6 ... Reactor tube, 7 ... Base plate, 8 ... heater.

Claims (2)

[Claims] 1. A heat-resistant plate that does not react with molten Al and high-purity Al
A plate material and an air-permeable porous ceramic plate are superposed and fixed in this order from bottom to top, and in this state in a heating furnace, after removing the surface oxide film of the high-purity Al plate material in a gas atmosphere, In a nitrogen-containing atmosphere, by heating and holding at a predetermined temperature higher than the melting point of Al for a predetermined time, the nitrogen in the atmosphere is passed through the air-permeable porous ceramic plate, and the high purity in a molten state is obtained.
A method for producing a high-purity aluminum nitride plate material characterized by reacting with an Al plate material. 2. A heat-resistant plate that does not react with molten Al, and high-purity Al
The plate material and the breathable porous ceramic plate are superposed in this order from bottom to top to form one set, and two or more sets of these are stacked and fixed in a heating furnace in a gas atmosphere to produce the high-purity Al. After removing the surface oxide film of the plate material, in a nitrogen-containing atmosphere, by heating and holding at a predetermined temperature above the melting point of Al for a predetermined time, nitrogen in the atmosphere is passed through the air-permeable porous ceramic plate, A method for producing a high-purity aluminum nitride plate material characterized by reacting with a high-purity aluminum plate material.