JPH1095672A - Method of contacting aluminum nitride sintered body with water - Google Patents

Abstract

(57) [Summary] A novel aluminum nitride sintered body and water that can effectively suppress the hydrolysis of aluminum nitride in an environment where the aluminum nitride sintered body and water come into contact with each other. Provide a contact method. When an aluminum nitride sintered body is brought into contact with water, 10 to 100 parts by weight of an organic compound having an alcoholic hydroxyl group such as a polyhydric alcohol is added to 100 parts by weight of the water. And p depending on the buffer
The contact is made under the condition that H is 5 to 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing an aluminum nitride sintered body and water, which is capable of effectively suppressing the hydrolysis of aluminum nitride in an environment where the aluminum nitride sintered body comes into contact with water. It relates to a new contact method.

[0002]

2. Description of the Related Art Aluminum nitride has been spotlighted as a heat dissipating material by utilizing its property of having a high thermal conductivity with an increase in the amount of heat generated by increasing the output of semiconductor devices such as GTO thyristors and IGBTs. In such an application, the aluminum nitride sintered body has a cooling surface in contact with the semiconductor element, and is used by being formed into a cooler having a cavity therein. Then, the heat transfer medium is supplied to the cavity of the cooler to cool the cooling surface. As the heat transfer medium,
Conventionally, water is generally used in terms of safety and cost.

However, when an aluminum nitride sintered body is used as a material for such a cooler and water is used as a heat transfer medium, the surface of the aluminum nitride sintered body is hydrolyzed to form aluminum hydroxide or the like. It has a problem that it corrodes and its mechanical strength is significantly reduced.

In order to solve such problems, a method of forming a coating such as α-alumina on the surface of an aluminum nitride sintered body as a coating material from a material aspect, and a method of forming a coating such as glycerin into water from the aspect of a heat conductive medium. Is added to suppress the hydrolysis of aluminum nitride.

[0005]

However, when a film such as α-alumina is formed on the surface of the above aluminum nitride sintered body, water resistance is poor due to defects such as pores and micro cracks existing in the film. Enough or
In the case where glycerin or the like is added to water, if a small amount is added, the corrosion prevention effect cannot be obtained due to insufficient film formation on the aluminum nitride surface. When the ratio of water decreases, the thermal conductivity decreases, and the viscosity coefficient increases, the heat transfer capacity as a heat transfer medium decreases. There is a problem that a large heat exchanger having a large size is required.

[0006]

Means for Solving the Problems The present inventors have intensively studied to solve the above problems. As a result, when the aluminum nitride sintered body is brought into contact with water, without applying a coating material such as α-alumina on the surface thereof,
By containing a specific amount of an organic compound having an alcoholic hydroxyl group, and by contacting with water under conditions adjusted to a specific pH with a buffer, without remarkably exploiting the properties of water as a heat transfer medium The inventors have found that the above-mentioned object is achieved, and have come to propose the present invention.

That is, according to the present invention, when an aluminum nitride sintered body is brought into contact with water, an organic compound having an alcoholic hydroxyl group is added to 100 parts by weight of the water.
100 parts by weight, and the pH was adjusted to 5 to 5 with a buffer solution.
A method for contacting water with aluminum nitride sintered body, characterized by contacting under conditions adjusted to 10.

In the present invention, the aluminum nitride sintered body is not particularly limited, and can be applied to known aluminum nitride sintered bodies. Particularly effective aluminum nitride sintered bodies are: The aluminum nitride sintered body has a small amount of water entering from the surface to the inside and a relative density of 90% or more, preferably 95% or more.

The aluminum nitride has a heat conductivity of 100 W / m · K or more, particularly 180 W / K, in order to exhibit a sufficient cooling capacity in the above-mentioned applications such as a cooler.
It is preferably at least m · K.

[0010] The aluminum nitride sintered body is generally
It is composed of aluminum nitride alone or aluminum nitride and a sintering aid of 0.1 to 10% by weight. As the sintering aid, one or more selected from known sintering aids such as alkaline earth compounds and rare earth compounds are used.

In the present invention, although the surface treatment of the aluminum nitride sintered body is substantially unnecessary, grinding or polishing may be performed as necessary within a range that does not significantly impair the heat conductivity of the aluminum nitride sintered body. There is no problem if the surface is processed or the surface is coated with an inorganic or organic substance.

In the present invention, the amount of the organic compound having an alcoholic hydroxyl group to be added to water must be 10 to 100 parts by weight based on 100 parts by weight of water. If the addition amount of the organic compound is less than 10 parts by weight, corrosion due to hydrolysis of aluminum nitride proceeds and the water resistance effect of the present invention cannot be obtained, which is not preferable. On the other hand, if the amount of the organic compound exceeds 100 parts by weight, the specific heat of the aqueous solution becomes small, and the heat transfer ability is undesirably reduced. A more preferred range for the present invention is 15 to 90 parts by weight, especially 15 to 50 parts by weight.

The organic compound having an alcoholic hydroxyl group used in the present invention is not particularly limited, but polyhydric alcohols and saccharides are preferably used practically. Specific examples of the organic compound preferably used include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, monohydric alcohols such as butyl alcohol, ethylene glycol, propylene glycol, trimethylene glycol, butylene glycol and the like. Polyhydric alcohols such as glycols and glycol ethers, glycerin, erythritol, glucitol, mannitol, and aldoses such as glyceraldehyde, erythrose, ribose, arabinose, xylose, galactose, mannose, and glucose as sugars;
One or more of the organic compounds exemplified above, such as ketoses such as ribulose and fructose, and cyclic compounds and polysaccharides thereof, are used in combination. In the present invention, polyhydric alcohols are more preferably employed.

In the present invention, it is important to adjust the pH of the aqueous solution obtained by adding the organic compound to water to 5 to 10 with a buffer. When no buffer is added, the pH of the aqueous solution before contact with the aluminum nitride sintered body is 5 to 1
Even if it is 0, it is not preferable because after the contact with the aluminum nitride sintered body, the pH further increases due to the progress of hydrolysis of the aluminum nitride, and the corrosion of the aluminum nitride cannot be suppressed.

Further, even when a buffer is added, the above p
It is important to adjust to the range of H. When the pH is less than 5, the film quality is deteriorated due to the progress of corrosion due to the desorption of aluminum nitride particles and the like and the deterioration of the organic compound having an alcoholic hydroxyl group. It is not preferable because a decrease occurs. On the other hand, when the pH exceeds 10, the hydrolysis of aluminum nitride cannot be suppressed, corrosion proceeds, and the water resistance effect of the present invention cannot be obtained. Particularly, the pH is more preferably from 5.2 to 9.8.

Here, as a means for adjusting the pH of the aqueous solution to the above range, a known method using a buffer is used without any particular limitation. Such a buffer is soluble in water and has a pH of 5-1.
There is no particular limitation as long as the buffer can be adjusted to zero. Specific examples of suitably used buffers include potassium hydrogen phthalate and sodium hydroxide, potassium dihydrogen phosphate and sodium hydroxide, boric acid and potassium chloride and sodium hydroxide, glycine and sodium chloride and hydroxide. sodium,
Borax and hydrochloric acid, Borax and sodium hydroxide, sodium citrate and sodium hydroxide, potassium dihydrogen phosphate and disodium hydrogen phosphate, potassium hydrogen citrate and sodium hydroxide, succinic acid and borax, potassium hydrogen citrate and Borax, potassium dihydrogen phosphate and borax, borax and sodium carbonate, ammonium chloride and ammonia water, sodium diethylbarbitylate and sodium acetate and hydrochloric acid, sodium diethylbarbiturate and hydrochloric acid, boric acid and potassium chloride and sodium carbonate Boric acid and sodium chloride and borax, disodium hydrogen phosphate and citric acid, sodium carbonate and sodium bicarbonate, acetic acid and sodium acetate, acetic acid and potassium acetate, acetic acid and ammonium acetate, propionic acid and sodium propionate, and butyric acid Sodium butyrate, valery Sodium acid and valeric acid, sodium malonate and malonic acid, sodium succinate and succinic acid, sodium glutaric acid and glutaric acid, sodium adipate and adipic acid, sodium pimelic acid and pimelic acid and the like are preferably used. Particularly, on the acidic side, a buffer solution containing a carboxylic acid and a salt thereof or a dicarboxylic acid and a salt thereof is preferably used in order to suppress corrosion of a metal used as another material such as a pipe.

The concentration of the buffer solution is preferably 0.01 to 1 N, and more preferably 0.01 to 0.7 N, in order to suppress corrosion of other materials such as metal materials.

In the present invention, it is more effective to contain ammonium ions in the aqueous solution in terms of water resistance.
As a method of supplying ammonium ions, the above-mentioned method of adding acetic acid and ammonium acetate or ammonium chloride and ammonium hydroxide as a buffer solution or a method of separately adding other than a buffer solution is employed. The ammonium ion is preferably adjusted to a concentration of 5 × 10 ⁻³ to 2 parts by weight with respect to 100 parts by weight of water.

In the present invention, the method for preparing an aqueous solution in which the amount of the organic compound having an alcoholic hydroxyl group to be added is 10 to 100 parts by weight and the pH of the aqueous solution satisfies both 5 to 10 is not particularly limited. A method of adding an organic compound having an alcoholic hydroxyl group to a mixed solution of water and a buffer solution, or a method of mixing a water and an organic compound having an alcoholic hydroxyl group and then adding a buffer solution is suitably employed.

In the practice of the method of the present invention, the suitable contact conditions between the aluminum nitride sintered body and the above-mentioned aqueous solution vary depending on the application and are not necessarily limited, but generally, the temperature is from -50 to 150 ° C. It is desirable that the contact be made in static water and in running water having a flow rate of less than 5 m / sec.

The method of the present invention is suitably used for applications in which aluminum nitride sintered bodies such as heat sources such as the above-mentioned coolers, heat exchangers, heaters, heater covers, pipes, and heat radiating materials come into contact with water. Is done.

[0022]

The method for contacting aluminum nitride sintered body with water according to the present invention is extremely effective in terms of water resistance to a cooler or the like made of aluminum nitride sintered body using water as a heat transfer medium. It provides a simple method. Originally, aluminum nitride was hydrolyzed when it came into contact with water, so it was difficult to put it to practical use from the viewpoint of water resistance.However, according to the present invention, water is used as a heat transfer medium without deteriorating the performance of the heat transfer medium. This makes it possible to use aluminum nitride as a cooling material, thereby expanding the use of aluminum nitride as an industrial material.

[0023]

The present invention will be described more specifically with reference to the following Examples and Comparative Examples. However, the present invention is not limited to these Examples.

In the following examples and comparative examples, various physical properties were measured by the following methods.

1) Measurement of pH Using “Model pH81” manufactured by Yokogawa Electric Corporation,
A measurement was made. The measurement was performed three times, and the average value was taken as the measured value.

2) Change in Weight The change in weight obtained by subtracting the weight before the start of the test from the weight of the test sample of 3 × 4 × 40 mm after the test was divided by the surface area of the sample. The average value of the five samples was taken as the measured value.

3) Bending strength A three-point bending strength was measured in accordance with JIS R-1601. The average value of the five samples was taken as the measured value.

4) Appearance The surface of the sample after the test was visually observed and evaluated.

Example 1 As a buffer, an aqueous solution was prepared by mixing a 0.1N aqueous acetic acid solution and a 0.1N aqueous sodium acetate solution at a ratio of 1:16.
Next, 100 parts by weight of the aqueous solution in terms of water and 30 parts by weight of ethylene glycol were mixed to prepare a mixed aqueous solution. The pH of the mixed aqueous solution was 6.1. Distilled water was used as water.

This mixed aqueous solution is placed in a Teflon container for 100
cc, then a relative density of 99% and a thermal conductivity of 18
3 having ² W / m · K and bending strength of 375 N / mm ²
Five test pieces of a known aluminum nitride sintered body having a weight of × 4 × 40 mm were immersed and left at 90 ° C. for 10 days to perform a water resistance test. No abnormality was visually observed in appearance. Thereafter, the test piece was taken out, and the weight change, bending strength and pH of the mixed aqueous solution of the test piece were measured. The above conditions were set to No. 1 in Table 1. No. 1 in Table 2 shows the results. 1 is shown.

Examples 2 to 4 Same as Example 1 except that the mixing ratio of a 0.1N aqueous acetic acid solution and a 0.1N aqueous sodium acetate solution was changed to change the pH and the amount of ethylene glycol added was changed. And a water resistance test was performed. No abnormality was visually observed in appearance. The above conditions are shown in Table 1, and the results are shown in Table 2.

Examples 5 to 7 A water resistance test was performed in the same manner as in Example 1 except that ethylene glycol was changed to another organic compound having an alcoholic hydroxyl group. No abnormality was visually observed in appearance. The above conditions are shown in Table 1, and the results are shown in Table 2.

Examples 8 to 13 0.1 N acetic acid aqueous solution and 0.1 N acetic acid N
Example 1 except that the aqueous solution was changed to another buffer.
A water resistance test was performed in the same manner as described above. No abnormality was visually observed in appearance. The above conditions are shown in Table 1, and the results are shown in Table 2.

COMPARATIVE EXAMPLE 1 A buffer solution of 0.1N acetic acid aqueous solution and 0.1N acetic acid N
a The water resistance test was performed in the same manner as in Example 1 except that distilled water was used without using the aqueous solution. Whitening of the sample surface was visually observed. Table 1 shows the above conditions.
The results are shown in Table 2.

Comparative Example 2 0.1 N acetic acid aqueous solution and 0.1 N acetic acid N
A water resistance test was performed in the same manner as in Example 1 except that the aqueous solution a was mixed in a ratio of 4: 1. Whitening of the sample surface was visually observed. The above conditions are shown in Table 1, and the results are shown in Table 2.

Comparative Example 3 A water resistance test was conducted in the same manner as in Example 1 except that ethylene glycol was not added. Whitening of the sample surface was visually observed. Table 1 shows the above conditions.
Table 2 shows the results.

Comparative Example 4 A water resistance test was performed in the same manner as in Example 1 except that 5 parts by weight of ethylene glycol was added. Whitening of the sample surface was visually observed. Table 1 shows the above conditions.
Table 2 shows the results.

Comparative Example 5 A water resistance test was carried out in the same manner as in Example 1 except that a 0.05 M aqueous solution of sodium carbonate and a 0.1 N aqueous solution of sodium hydrogen carbonate were mixed at a ratio of 9: 1 as a buffer solution. . Whitening of the sample surface was visually observed.
The above conditions are shown in Table 1, and the results are shown in Table 2.

[0039]

[Table 1]

[0040]

[Table 2]

Examples 14 to 17 In Examples 1, 10, 11, and 12, a water resistance test was carried out in the same manner as in Examples 1, 10, 11, and 12, except that the samples were left for 30 days. In Examples 15 and 16, no abnormal appearance was observed visually, but in Examples 14 and 17,
Some whitening of the sample surface was observed. The above conditions are shown in Table 3, and the results are shown in Table 4.

[0042]

[Table 3]

[0043]

[Table 4]

Claims (2)

[Claims] When an aluminum nitride sintered body and water are brought into contact with each other, 10 to 100 parts by weight of an organic compound having an alcoholic hydroxyl group is added to 100 parts by weight of the water, and pH is adjusted with a buffer solution. A method of contacting aluminum sintered body with water, wherein the contact is carried out under conditions adjusted to 5 to 10. 2. The method for contacting aluminum nitride sintered body with water according to claim 1, wherein the aqueous solution contains ammonium ions.