JP2002173383A - Pore treatment method for ceramic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pore treatment method for ceramics which is hardly affected by a change in temperature and environment and can stably maintain hermeticity by embedding the microgaps existing within the ceramics by inorganic material. SOLUTION: After the ceramic is impregnated with an alcohol solution of methyl silicate of >=1 to <=15% in concentration, the excess methyl silicate is removed by cleaning the ceramic with alcohol before drying of the methyl silicate. The ceramic is subjected to alcohol removal in a vacuum state of >=10 to <=100 deg.C and is then heat treated at >=200 to <=800 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating pores in ceramics for improving airtightness by filling fine voids in the ceramics.

[0002]

2. Description of the Related Art Ceramics have microscopic voids inside due to their structure. In particular, in the case of ceramics for protecting electronic parts which dislike air and water vapor, air and water vapor entering from the microscopic voids are particularly harmful. There is a problem that the performance of the electronic component is reduced.

[0003] In order to solve these problems, conventionally, a surface treatment for coating an organic resin such as an epoxy resin on a ceramic surface is generally performed.

[0004]

However, in the above-mentioned conventional example, since only the surface treatment of coating the ceramic surface with an organic resin such as an epoxy resin is performed, the details are shown in FIG. When the airtightness is measured using an air permeability measuring device made by Sera, as shown in FIG. 5, the airtightness of the ceramic gradually decreases about 2 minutes after the start of the test, and the variation in each sample is large. found.

In FIG. 5, the horizontal axis represents elapsed time (minutes), and the vertical axis represents the degree of vacuum (× 10 ⁻⁴ Pa). Each of the ten samples was tested, and the decrease in the degree of vacuum with respect to the elapsed time (minutes) (pressure rise rate by passing air) was measured. The lower the pressure raising speed, the higher the sealing effect.

FIG. 6 is a diagram showing an example of pore distribution of untreated ceramics measured by a mercury intrusion porosimeter. In FIG. 6, the horizontal axis represents the pore diameter (μm),
The vertical axis indicates the volume (cc) of the pore. As shown in FIG. 6, it can be seen that there are large voids in the range A having a pore diameter of 10 μm to 20 μm, and further, there are voids in the range B of 0.05 μm or less.

[0007] The present invention is to solve the above-mentioned problems,
The aim is to provide a method for treating pores in ceramics that can maintain the airtightness stably without being affected by changes in temperature and environment by filling the microvoids present in the ceramics with inorganic substances. Things.

[0008]

A method for treating pores in ceramics according to the present invention for achieving the above object is a method for treating pores for filling fine voids in ceramics. It is characterized in that the fine voids of the ceramic are filled by impregnation with methyl silicate.

Methyl silicate is liquid and highly permeable,
It is possible to satisfactorily impregnate the fine voids existing in the ceramic. Methyl silicate is a decomposable material, and when heated at room temperature or higher (for example, at 10 ° C. or higher),
The methyl group and the hydroxyl group evaporate, leaving silicon dioxide (SiO ₂ ) in the fine voids of the ceramic, thereby improving the airtightness. Since silicon dioxide (SiO ₂ ) is inorganic, it is hardly affected by changes in temperature or environment.

[0010] In addition, when a vacuum state is maintained for a predetermined time while the sintered ceramic is immersed in methyl silicate, permeability is improved.

That is, when the ceramic is immersed in an alcohol solution of methyl silicate and pulled by a vacuum device, air, water vapor, and the like existing in fine voids in the ceramic are replaced with methyl silicate. The vacuum state (reduced pressure state) is maintained for about one hour, and the operation is continued until no bubbles are generated in the methyl silicate.

Further, the concentration of the methyl silicate is 1%
It is preferable that the ratio is not less than 15%. A more preferred concentration of methyl silicate is 2.5% or more and 7.5% or less. Methyl silicate can be used, for example, by dissolving Ceramate C-513 (trade name) manufactured by Catalyst Chemical Industry Co., Ltd. in the above-mentioned concentration in methyl alcohol, ethyl alcohol, isopropyl alcohol, or the like.

When the concentration of methyl silicate is set low, the viscosity decreases, the permeability into the ceramics can be improved, the processing time can be shortened, and the fine cavities can be filled. I can do it.

It is preferable that the sintered ceramic is impregnated with methyl silicate and then washed with alcohol before drying the methyl silicate to remove excess methyl silicate. When the methyl silicate is dried, silicon dioxide (SiO ₂ ) remains white on the surface of the ceramic, and is washed with alcohol for the purpose of removing it. Methyl silicate is diluted with alcohol and can be easily removed.

Further, after the sintered ceramic is impregnated with methyl silicate, excess methyl silicate is removed by alcohol washing before drying of the methyl silicate, and heat treatment is performed at 200 ° C. or more and 800 ° C. or less. Is preferred.

After the sintered ceramics are impregnated with methyl silicate, the methyl silicate is washed with alcohol before drying to remove excess methyl silicate, and the alcohol-washed ceramics are arranged so as not to overlap. Thereafter, at a temperature of 10 ° C. or more and 100 ° C. or less, a drying treatment is performed in a vacuum state (reduced pressure state) or a drying treatment at an atmospheric pressure state to remove alcohol.
Heat treatment at 0 ° C. or less is preferable. The heat treatment time depends on the type of ceramic to be treated.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the method for treating pores in ceramics according to the present invention will be specifically described with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of an air permeability measuring device for measuring the hermeticity of ceramics, FIG. 2 is a diagram showing the hermeticity of ceramics sealed by a method for treating pores of ceramics according to the present invention, FIG. 3 is a diagram showing the airtightness according to the concentration of methyl silicate, and FIG. 4 is a diagram showing the pore distribution of ceramics sealed by the method for treating pores of ceramics according to the present invention.

The method for treating pores of ceramics according to the present invention is a method for treating pores for filling microscopic voids in ceramics. For example, ceramics is treated with an alcohol solution of methyl silicate (for example, Ceramate C manufactured by Catalyst Chemical Industry Co., Ltd.). -513 (trade name)).

At this time, the amount of methyl silicate is such that the entire surface of the ceramic is soaked, and the concentration of the methyl silicate may be as low as 1% or more and 15% or less. Methyl silicate can be diluted with alcohol to disperse solute and reduce viscosity, improve permeability, shorten processing time, and impregnate even finer voids to ensure filling. . A more preferred concentration of methyl silicate is 2.5% or more and 7.5%.

In a state where the ceramic is immersed in the methyl silicate, the vacuum is maintained for a predetermined time (for example, about 1 hour) by a vacuum device (for example, about one hour) to promote the impregnation of the ceramic with the methyl silicate. Excessive methyl silicate on the surface of is washed with alcohol and dried.

Excess methyl silicate is removed by washing with alcohol before drying the methyl silicate, and after the methyl silicate is dried and the methyl and hydroxyl groups are evaporated, silicon dioxide (SiO ₂ ) remains white on the ceramic surface. Can be prevented.

The vacuum drying of methyl silicate after alcohol washing is performed at room temperature or higher. For example, at least 10 ° C. and 1
Drying at a temperature of 00 ° C. or less is preferred. Methyl silicate is decomposed by infiltrating and drying the ceramic with the methyl silicate, the methyl group is evaporated as methyl alcohol, and inorganic silicon dioxide (SiO ₂ )
Remains in the fine voids in the ceramic.

As a result, the hermeticity of the ceramics is improved, and the hermeticity of the ceramics is remarkably improved as compared with the conventional surface treatment using an organic resin such as an epoxy resin, and silicon dioxide (SiO ₂ ) is obtained. Since is inorganic, it is possible to provide a stable and highly airtight ceramic which is hardly affected by changes in temperature and environment.

In particular, the present invention is effective when applied to ceramics for protection of electronic parts and the like that do not like air and water vapor, and the airtightness can be greatly improved by eliminating fine voids from the inside of the ceramics.

The alcohol solution of methyl silicate is a highly permeable and decomposable material. For example, Ceramate C-513 (trade name) manufactured by Catalysis Kasei Kogyo is preferably used. This ceramate C-513 is represented by the following chemical formula.

[0026]

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In the drying process, when these substances exceed their solubility, they repeatedly undergo dehydration and dealcoholization reactions to form crosslinks.
Changes to silica glass with a three-dimensional structure. At this time, the concentration of methyl silicate used is 1% or more and 15% or less, preferably 2.5% or more and 7.5% or less.

By using methyl silicate having a low concentration, by diluting with alcohol, the solute is dispersed to lower the viscosity, the permeability is increased, and the airtightness is improved (FIG. 2).
And FIG. 3). As a result, the processing time can be reduced,
It is possible to fill finer voids.

Specific processing steps will be described below. First, the pressure of the sintered ceramic is reduced by a vacuum device in a state of being immersed in an alcohol solution of methyl silicate. Here, air, water vapor, and the like existing in the ceramics are replaced with methyl silicate. The processing time at this time is about 1 hour,
Continue until no more bubbles are generated in the methyl silicate.

Next, alcohol washing is performed to prevent white methyl silicate from remaining on the surface of the ceramic. Alcohol-washed ceramics are arranged so that they do not overlap,
Room temperature or higher in a vacuum state (reduced pressure state), that is, 10 ° C. or higher,
Drying is performed at a temperature of 100 ° C. or less to remove alcohol.

After vacuum drying, the temperature is 200 ° C. or more and 800
Sintered by heat treatment at a temperature of not more than ℃. The heat treatment time at this time depends on the ceramic to be treated. In addition, the above-mentioned treatment of drying at a temperature of 10 ° C. or more and 100 ° C. or less to remove alcohol is omitted, and a temperature of 200 ° C.
The sintering may be performed by heat treatment at a temperature of not more than ℃.

FIG. 4 shows that the same ceramics as described above with reference to FIG. 6 are subjected to the above-described method for treating pores of a ceramic according to the present invention for comparison with the untreated ceramics, and then the ceramic is subjected to mercury injection. It is a figure which shows the pore distribution measured by the porosimeter. In FIG. 4, the horizontal axis indicates the pore diameter (μm), and the vertical axis indicates the volume (c
c) is shown.

In the untreated ceramic of FIG. 6, there are large voids in the range A having a pore size of 10 μm to 20 μm, and further, there are voids in the range B of 0.05 μm or less.
It can be seen that, after the above-described method for treating pores of a ceramic according to the present invention, voids having pore diameters in the range of 10 μm to 20 μm and voids having pore diameters of 0.05 μm or less have almost disappeared.

<Embodiment> A detailed example of a sealing process for a cap-shaped ceramic 1 serving as a container for accommodating electronic components as shown in FIG. 1 will be described below. Electronic components that extremely dislike air and water vapor must be used in containers that are impermeable to them.

In the surface treatment using the epoxy resin as in the conventional example, only the surface is coated with the resin, and the airtightness is not uniform as shown in FIG. Therefore, it is more useful to fill all voids existing in the ceramics 1.

As the method, a sealing process is carried out by using methyl silicate as a filler and infiltrating methyl silicate into minute voids.

First, the sintered ceramics 1 is immersed in a liquid methyl silicate having a concentration of 5.0% in a vacuum apparatus, and is pulled in a vacuum state (reduced pressure state) for about 1 hour.
After taking out of the vacuum device, the surface of the ceramics 1 is washed with alcohol, and again placed on a water-absorbing paper in the vacuum device so that the opening of the ceramics 1 does not overlap. After drying for about 1 hour,
After being taken out of the vacuum device, it is placed in a dryer and heat-treated at about 200 ° C. for about 1 hour.

The airtightness of the treated ceramics 1 is measured using an air permeability measuring device manufactured by Wing Hi-Cera Corporation shown in FIG. The air permeation measuring device shown in FIG. 1 has a small hole 3a in a decompression chamber 3 to which a vacuum pump 2 is connected.
Is opened, and the injection needle 4 is inserted into the hole 3a from the inside of the decompression chamber 3,
The gap between the hole 3a and the injection needle 4 is filled with the silicon sheet 5 and sealed so that no air leaks.

A ceramic 1 serving as a sample for measuring the airtight performance is placed on a silicon sheet 5 so as to cover the injection needle 4, and a silicon grease 6 is interposed in a gap between the ceramic 1 and the silicon sheet 5.
And the silicon sheet 5 are brought into close contact with each other, and sealing is performed so that air does not leak from the gap between the ceramics 1 and the silicon sheet 5.

Then, the entire outer surface of the ceramics 1 is covered with an airtight plastic container (not shown), and the vacuum pump 2 is driven to reduce the pressure in the decompression chamber 3 to a vacuum (reduced pressure), and then the plastic container is removed. 1 minute, 2 minutes, 5 minutes, 10 minutes after removing the plastic container
FIG. 2 shows a graph obtained by reading the scale of a vacuum gauge 7 provided between the vacuum pump 2 and the decompression chamber 3 after a lapse of 20 minutes.

FIG. 2 shows the results obtained by measuring five ceramics 1 samples in the same manner as described above.
In FIG. 2, the horizontal axis represents elapsed time (minutes), and the vertical axis represents the degree of vacuum (× 10 ⁻⁴ Pa). In the surface treatment with the epoxy resin of the conventional example shown in FIG. 5 described above, only the surface is coated with the resin, and a curve in which the degree of vacuum is reduced by the passing air over time is drawn. This curve can be a pressure rising speed. The pressure rising speed is measured, and the lower the pressure rising speed (the gentler the curve, the lower the degree of vacuum), the better the airtight performance and the higher the sealing effect.

In FIG. 2, the five samples were substantially uniform and the degree of vacuum was hardly reduced. Therefore, the airtightness is improved by impregnating and drying the ceramic 1 with methyl silicate, and it is possible to perform a uniform and stable sealing process with higher airtightness as compared with the surface treatment using an epoxy resin or the like as in the conventional example. found.

FIG. 3 shows a graph in the case where the concentration of methyl silicate is different, and is the same as above except for the concentration of methyl silicate. Also in FIG. 3, the horizontal axis indicates elapsed time (minutes), and the vertical axis indicates the degree of vacuum (× 10 ⁻⁴ Pa). Graph a has a methyl silicate concentration of 10%, graph b has a methyl silicate concentration of 7.5%, and graph c.
Has a methyl silicate concentration of 5%.

As shown in FIG. 3, it was found that the lower the concentration of methyl silicate, the higher the airtightness and the more stable the sealing process.

[0045]

As described above, the present invention has the above-described structure and function. Therefore, not only the surface treatment as in the prior art, but also the effect of the temperature and environment changes by filling the fine voids existing inside the ceramics with an inorganic material. It is hard to receive and can maintain airtightness stably.

That is, by impregnating and drying the ceramic with methyl silicate, silicon dioxide (SiO ₂ ) remains in the fine voids of the ceramic, thereby improving the airtightness as compared with the conventional surface treatment using an epoxy resin or the like. . Since silicon dioxide (SiO ₂ ) is inorganic, it is hardly affected by changes in temperature or environment.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of an air permeability measuring device for measuring the airtightness of ceramics.

FIG. 2 is a view showing the hermeticity of ceramics subjected to sealing treatment by the method for treating pores of ceramics according to the present invention.

FIG. 3 is a diagram showing airtightness according to methyl silicate concentration.

FIG. 4 is a view showing a pore distribution of ceramics subjected to a sealing treatment by the ceramic pore treating method according to the present invention.

FIG. 5 is a diagram showing airtightness when a surface of a conventional ceramic is coated with an epoxy resin.

FIG. 6 is a diagram showing a pore distribution of untreated ceramics.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ceramics 2 ... Vacuum pump 3 ... Decompression chamber 3a ... Hole 4 ... Injection needle 5 ... Silicon sheet 6 ... Silicon grease 7 ... Vacuum gauge

Claims (6)

[Claims] 1. A method of treating pores for filling fine voids in ceramics, the method comprising impregnating methyl silicate into sintered ceramics to fill the fine voids in the ceramics. Processing method. 2. The method according to claim 1, wherein a vacuum state is maintained for a predetermined time while the sintered ceramic is immersed in methyl silicate. 3. The method according to claim 1, wherein the concentration of the methyl silicate is 1% or more and 15% or less. 4. The method according to claim 1, wherein the sintered ceramic is impregnated with methyl silicate, and then the alcohol is washed with alcohol before drying the methyl silicate to remove excess methyl silicate. 4. The method for treating pores in ceramics according to claim 1. 5. After the sintered ceramic is impregnated with methyl silicate, an excess methyl silicate is removed by alcohol washing before drying the methyl silicate,
The method according to claim 1, wherein the heat treatment is performed at a temperature of 200 ° C. or more and 800 ° C. or less. 6. After the sintered ceramic is impregnated with methyl silicate, an excess of methyl silicate is removed by alcohol washing before drying of the methyl silicate,
After that, after a drying treatment in a vacuum state or an atmospheric pressure state at a temperature of 10 ° C. or more and 100 ° C. or less and a dealcoholization, a heat treatment is performed at a temperature of 200 ° C. or more and 800 ° C. or less. Item 4. The method for treating pores in ceramics according to any one of Items 1 to 3.