JP4405356B2 - Control method of resistivity distribution of composite sintered body - Google Patents

Description

The present invention is related to method of controlling the resistivity distribution in the composite sintered body containing an insulating ceramics and the conductive material. More specifically, the present invention relates to a method for controlling the specific resistance value distribution of the composite sintered body with a simple operation .

For example, as a method of manufacturing a resistor having a specific resistance value of about 1 × 10 ⁶ to 1 × 10 ¹³ Ωcm, for example, Japanese Patent Application Laid-Open No. 9-283606 (Patent Document 1) and Japanese Patent Application Laid-Open No. 9-283607 (Patent) As shown in Reference 2), a mixed powder obtained by adding a specific amount of heat-resistant conductive material powder to insulating ceramic powder is molded and sintered to form a sintered body, and this composite sintered body is used as a composite resistor. A method (first method) for performing this is conventionally known.

Although the specific resistance value of the resistor obtained by the first method is mainly determined by the addition amount of the heat-resistant conductive material, the specific resistance value of the resistor changes rapidly before and after the threshold value. Therefore, in the first method for manufacturing the resistor, a resistor having a desired specific resistance value within a range of, for example, 1 × 10 ⁶ to 1 × 10 ¹³ Ωcm at room temperature is manufactured in the laboratory. Although possible, it is difficult to manufacture on an industrial scale.
In the first resistor manufacturing method, the specific resistance value at room temperature is, for example, about 1 × 10 ⁶ to 1 × 10 ¹³ Ωcm by controlling the distribution of the heat-resistant conductive material in the sintered body. It is not easy to manufacture a resistor whose specific resistance distribution in the resistor is arbitrarily controlled, and it is virtually impossible to manufacture this on an industrial scale.

On the other hand, as a second method for producing a resistor in which the specific resistance distribution in the resistor is arbitrarily controlled, for example, in Japanese Patent Laid-Open No. 7-69756 (Patent Document 3), It is known that a specific resistance distribution of a carbon-ceramic composite material is controlled by energizing a carbon-ceramic composite material having a specific resistance of 2 × 10 ^{−4 to 1} Ωcm at room temperature and adjusting the position of the current-carrying electrode. Yes.

In this second resistor manufacturing method, the carbon in the carbon-ceramic composite material is oxidized and removed by current heating, and the specific resistance distribution of the resistor is controlled by increasing the specific resistance value of the portion where the carbon is oxidized and removed. To do. Therefore, it is essential that the composite material to be used has a specific resistance at room temperature in the range of 2 × 10 ^{−4 to 1} Ωcm. When the resistance value of the composite material used exceeds 1 Ωcm, the amount of electricity flowing through the composite material is reduced and heat generation is not sufficiently performed, so that carbon cannot be sufficiently oxidized and removed. For example, the resistance value cannot be controlled to about 1 × 10 ⁶ to 1 × 10 ¹³ Ωcm.

JP-A-9-283606 JP-A-9-283607 JP-A-7-69756

The present invention is intended to provide a method for controlling the specific resistance value distribution of a composite sintered body of an insulating ceramic and a conductive material simply and with high efficiency.
According to the method of the present invention , the specific resistance value distribution of the composite resistor can be made substantially uniform, or regions having different specific resistance values can be distributed in the obtained composite resistor .

  As a result of intensive studies to solve the above problems, the present inventor has found that when a voltage is applied to a composite sintered body of an insulating ceramic and a conductive material, the specific resistance value in the vicinity of the voltage application portion decreases, and the specific resistance value It was found that the amount of decrease depends on the voltage value to be applied, the application time, etc., and the present invention was completed based on this finding.

The method for controlling the specific resistance value distribution of the composite sintered body of the insulating ceramic and the conductive material according to the present invention comprises molding a mixture of insulating ceramic particles made of aluminum oxide particles and conductive material particles made of silicon carbide. -The electric field strength is 1 to 20 kV / mm in the desired part of the composite sintered body obtained by sintering and having a specific resistance value at room temperature of 1 x 10 ⁷ Ω · cm to 1 x 10 ¹⁸ Ω · cm. A specific voltage is applied to reduce the specific resistance value of the voltage application portion.
In the control method of the present invention, the content of the conductive material particles in the composite sintered body is 5% by volume or more based on the total volume of the composite sintered body, and the conductive material particles It is preferable that 10% by volume or more has a particle size of 0.2 μm or less.
In the control method of the present invention, it is preferable that the average particle diameters of the aluminum oxide particles and the silicon carbide particles in the composite sintered body are 2 μm or less and 0.5 μm or less, respectively.
In the control method of the present invention, it is preferable that a voltage applied to a desired portion of the composite sintered body is equal to or higher than a predetermined use voltage of the composite sintered body.
In the control method of the present invention, it is possible to measure a specific resistance value of a portion of the composite sintered body to which a voltage is applied, and to adjust the applied voltage according to the measured value.
In the control method of the present invention, when the measured value of the specific resistance value of the composite sintered body is higher than the surrounding specific resistance value, the voltage application is applied to the high specific resistance value portion. As a result, the specific resistance value can be lowered until it becomes substantially equal to the surrounding specific resistance value.
In the control method of the present invention, the specific resistance value distribution of the obtained composite resistor can be controlled by adjusting the position of the voltage marking electrode used for the voltage application.
In the control method of the present invention, a voltage application electrode is arranged for each of two or more regions having the desired pattern of the composite sintered body, and voltage application by each electrode is performed in a desired ratio. By applying until the resistance value is reached, a desired pattern can be distributed in the high specific resistance value region and the low specific resistance value region.

According to the control method of the present invention, the specific resistance value distribution of the composite sintered body of the insulating ceramic and the conductive material can be efficiently controlled by a simple method of applying a voltage. In addition, according to the method of the present invention, a composite resistor having a substantially uniform specific resistance value distribution can be manufactured at a low cost on an industrial scale from a composite sintered body of an insulating ceramic and a conductive material.

In the present invention, a mixed powder containing insulating ceramic material particles and conductive material particles is molded and sintered to produce a composite sintered body.
Insulating ceramic material particles include aluminum oxide (Al ₂ O ₃ ) particles, yttrium oxide (Y ₂ O ₃ ) particles, silicon oxide (SiO ₂ ) particles, zirconium oxide (ZrO ₂ ) particles, and aluminum nitride (AlN) particles. Silicon nitride (Si ₃ N ₄ ) particles, mullite (3Al ₂ O ₃ .2SiO ₂ ) particles, and the like are known. Aluminum oxide Of these (Al ₂ O ₃₎ particles are excellent in heat resistance at low cost, since the mechanical properties of the composite sintered body is also good, used to identify in the present invention.

The conductive material particles are not particularly limited as long as they can withstand high temperatures during sintering. For example, conductive silicon carbide (SiC) particles, molybdenum (Mo) particles, tungsten (W) particles, tantalum High melting point metal particles such as (Ta) particles, carbon (C) particles, and the like are known. Among these, when conductive silicon carbide (SiC) particles are compounded with aluminum oxide (Al ₂ O ₃ ) particles, the resulting composite sintered body has less temperature dependency of the specific resistance value, It is excellent in corrosion resistance to gas, has excellent heat resistance and thermal shock resistance, and has a low risk of damage due to thermal stress when used at high temperatures, so it is specifically used in the present invention.

The mixing ratio of the insulating ceramic particles and the conductive particles is not particularly limited, but the specific resistance value at room temperature of the composite sintered body (before voltage application) is 1 × 10 ⁷ Ωcm or more. It is preferable to use a mixing ratio.
That is, in the case of a composite sintered body having a specific resistance value at room temperature of less than 1 × 10 ⁷ Ωcm before voltage application of the composite sintered body, the amount of current flowing through the composite sintered body becomes too large, There is also a possibility that the sintered body is completely destroyed, and the specific resistance value cannot be controlled efficiently. The upper limit of the specific resistance value at room temperature before voltage application of the composite sintered body is not particularly limited, but the practical upper limit is usually 1 × 10 ¹⁸ Ωcm, preferably 1 × 10 ¹⁶ Ωcm.

  The particle size of the insulating ceramic particles, the particle size of the conductive particles, and the sintering conditions for sintering are not particularly limited, but the content of the conductive material particles in the composite sintered body Is preferably 5% by volume or more with respect to the volume of the composite sintered body, and 10% by volume or more of the conductive material particles preferably have a particle size of 0.2 μm or less.

  The content ratio of the conductive material particles contained in the composite sintered body to which the voltage is applied is 5% by volume or more, and the content of the conductive material particles having a particle size of 0.2 μm is the conductive material particles. When the total volume is 10% by volume or more, the specific resistance value is gradually decreased by voltage application, and it becomes easy to obtain the target specific resistance value. In addition, the specific resistance existing before voltage application Variations in value can be reduced.

  A plurality of voltage application electrodes are attached to a desired portion of the composite sintered body of the obtained insulating ceramic and conductive material, and a voltage is applied. The applied voltage may be either a DC voltage or an AC voltage, but it is preferable to use a DC voltage from the viewpoint of work safety. When a voltage is applied, the specific resistance in the vicinity of the voltage application portion decreases. The voltage application time is set to a time sufficient for the specific resistance value in the vicinity of the voltage application portion to be a desired value.

Specific voltage application conditions are: type of composite sintered body of insulating ceramics and conductive material, blending ratio of insulating ceramics and heat-resistant conductive material, shape of composite sintered body, desired specific resistance value In the present invention, the applied voltage is set so that the electric field strength is 1 to 20 kV / mm . The upper limit value of the applied electric field strength is set to 20 kV / mm from the viewpoint of safety .
There is no limitation on the atmosphere in applying the voltage, and it is usually preferable to apply the voltage in the air.

  When manufacturing a composite resistor according to the present invention, the voltage to be applied is set to be equal to or higher than the working voltage of the composite resistor. Here, the “voltage used by the resistor” refers to a voltage applied when the composite resistor manufactured by the resistor manufacturing method of the present invention is actually used for various applications. Even if the applied voltage is equal to or lower than the “use voltage of the resistor”, the specific resistance value of the composite sintered body is lowered, but the final manufactured composite resistor has a voltage higher than the applied voltage at the time of manufacture. When a voltage is applied, the specific resistance value of the resistor continues to decrease, and the practicality of the resulting resistor is lost.

The attachment position of the application electrode may be determined according to the distribution of the desired specific resistance value to be obtained after voltage application. In the method of the present invention, the ratio of only the vicinity of the application part to which the voltage is applied is determined . Since the resistance decreases, the distribution of the specific resistance value in the composite resistor can be controlled by adjusting the mounting position of the voltage application electrode.

That is, it consists of a composite sintered body of insulating ceramics and a conductive material, provided that a voltage is applied to the high resistance region of the composite resistor where the distribution of specific resistance values is not uniform, and the specific resistance value in the vicinity of this application part. Is reduced to a specific resistance value in a region where no voltage is applied, so that the specific resistance distribution is almost uniformized in the composite resistor , so that a composite resistor having a substantially constant resistance value can be produced on an industrial scale. Can be obtained at low cost.
Further, by adjusting the position of the voltage application electrode, inexpensively obtained Rukoto an industrial scale a composite resistors region having an area and a low resistivity having a high specific resistance value are distributed in any pattern also it can.

In the method of controlling the specific resistance value, while measuring the specific resistance value of the voltage application unit, or according to the voltage application conditions (applied voltage, application time) obtained experimentally in advance, It is preferable to apply a voltage. In this way, by applying the voltage while measuring the specific resistance value of the composite sintered body, or by applying a voltage according to voltage application conditions (applied voltage, application time) obtained experimentally in advance. Thus, a composite resistor having an accurate desired specific resistance value distribution can be obtained on an industrial scale at a low cost.

  As described above, the reason why the specific resistance in the vicinity of the voltage application portion is reduced by applying a voltage to the composite sintered body of the insulating ceramic and the conductive material is not necessarily clear, but the voltage was applied. This is considered to be because the tissue rich in insulation in the vicinity of the voltage application portion changes to a tissue rich in conductivity.

Hereinafter, using aluminum oxide (Al ₂ O ₃ ) as the insulating ceramic, and using conductive silicon carbide (SiC) as the heat-resistant conductive material,
(1) The specific resistance distribution is uniformed in the obtained composite resistor, and the composite resistor has a constant resistance value. (2) The high specific resistance region and the low specific resistance region are distributed in an arbitrary pattern. A compound resistor,
The present invention will be further described in detail by taking the case of obtaining the above.

As the conductive silicon carbide (SiC) particles used for the aluminum oxide (Al ₂ O ₃ ) -silicon carbide (SiC) composite sintered body, it is preferable to use particles obtained by a plasma CVD method. In particular, a raw material gas of a silane compound or silicon halide and hydrocarbon is introduced into a plasma in a non-oxidizing atmosphere, and a gas phase reaction is performed while controlling the pressure of the reaction system in the range of less than 1 atm to 0.1 torr. Conductive silicon carbide (SiC) ultrafine particles having an average particle size of 0.1 μm or less are excellent in sinterability, high purity, and spherical in particle shape. Is good.

On the other hand, the aluminum oxide (Al ₂ O ₃ ) powder is not particularly limited as long as it has a high purity. Moreover, excessive oxidation of silicon carbide (SiC) during sintering can be suppressed by setting the atmosphere during sintering to a non-oxidizing atmosphere.
In addition, there is no special limitation regarding the shaping | molding method and sintering method at the time of preparation of the said composite sintered compact, For example, conventional means, such as a hot press method, are employable. Moreover, there is no limitation also about the dimension shape of a composite sintered compact.

A specific resistance distribution is made uniform in the resistor, and a composite resistor having a constant resistance value is measured. The specific resistance value distribution in the aluminum oxide (Al ₂ O ₃ ) -silicon carbide (SiC) composite sintered body is measured. . For example, microelectrodes are respectively arranged in desired portions on the upper and lower surfaces of the composite sintered body, a direct current voltage of about 100 V / mm is applied between the electrodes, and the flowing current value is measured. Measure by calculating the specific resistance value.

Then, as shown in FIG. 1, a voltage applying electrode 2 is disposed in a region having a high specific resistance value on the surface 1a (upper surface in FIG. 1) of the composite sintered body 1, and further, the composite firing is performed. On the back surface 1b of the bonded body 1 (the lower surface in FIG. 1), a counter electrode 3 for applying voltage is disposed. The specific resistance of the voltage application unit in the voltage applied, for example, the above temporarily suspended the application of the voltage for reducing the resistance, separately, so that the electric field intensity is approximately 100 V / mm between the electrodes a DC voltage is applied to the current flowing is measured and determined by calculating the specific resistance from Ohm's law.

  While applying a voltage higher than the working voltage of the finally obtained composite resistor between the voltage application electrodes 2 and 3 arranged as shown in FIG. 1, the specific resistance of the voltage application section is applied. While measuring the value, when the application of the voltage is stopped when the specific resistance value in the low resistance region of the composite sintered body is obtained, the distribution of the specific resistance value is almost uniform in the composite resistor, A composite resistor having a certain resistance value distribution is obtained.

A composite resistor in which a high specific resistance value region and a low specific resistance value region are distributed in a desired pattern . For example, the voltage application electrodes 12a and 12b having the pattern shapes shown in FIGS. The aluminum oxide (Al ₂ O ₃ ) -silicon carbide (SiC) composite sintered body 10 is disposed on the surface 10a (upper surface in FIG. 2), and further on the back surface 10b of the composite sintered body 10 (FIG. In FIG. 2, a counter electrode 13 for applying a flat plate voltage is disposed on the lower surface. The specific resistance value of the voltage application unit during voltage application is, for example, temporarily interrupting the application of the voltage for reducing the resistance and separately applying a DC voltage of about 100 V / mm between the electrodes. Measure the value of the flowing current and calculate the specific resistance value from Ohm's law.

  While applying a voltage higher than the working voltage of the finally obtained composite resistor between the voltage application electrodes 12a and 12b and the voltage application electrode 13 thus arranged, the voltage application unit When the application of the voltage is stopped when a desired specific resistance value is obtained while measuring the specific resistance value, the pattern shape of the low specific resistance value region corresponds to the arrangement pattern shape of the voltage application electrode. A composite resistor in which the specific resistance value region and the low specific resistance value region are distributed in a desired pattern is obtained.

The examples are given to further illustrate the present invention.
Example 1
Conductive silicon carbide (SiC) ultrafine particles having an average particle size of 0.05 μm were vapor-phase synthesized by a plasma CVD method. The silicon carbide (SiC) ultrafine particles 10% by volume and the commercially available aluminum oxide (Al ₂ O ₃ ) particles 90% by volume having an average particle diameter of 0.5 μm were mixed for 5 hours using an ultrasonic disperser. The mixed powder was dried, molded, and sintered for 3 hours under the conditions of an argon atmosphere and a temperature of 1700 ° C. to produce a disc-shaped composite sintered body having a radius of 200 mm and a thickness of 2 mm.
And the particle size distribution of the silicon carbide (SiC) particle | grains in this composite sintered compact was measured by the SEM observation method. The results are shown in Table 1.
Moreover, the distribution of the specific resistance value of this composite sintered body at room temperature (25 ° C.) was measured. The result is shown in FIG .

As is clear from FIG. 4, the specific resistance value distribution of the composite sintered body before voltage application was low in the central portion and high in the outer peripheral portion.
Therefore, as shown in FIG. 3, ring-shaped voltage application electrodes 31 are disposed on the surfaces of the outer peripheral regions 30a and 30b having a high specific resistance value of the composite sintered body 30, and further, the composite On the back surface of the outer peripheral area of the sintered body, a counter electrode plate-like voltage application electrode 32 is arranged, and finally obtained between the voltage application electrodes 31 and 32 (2 mm) thus arranged. A voltage of 9 kV, that is , a voltage at which the electric field strength is 4.5 kV / mm is applied for 10 minutes as a voltage higher than the working voltage of the resistor to be used, and the room temperature (25 ° C.) of the composite sintered body thus subjected to voltage application is applied. ) Was measured in the same manner, as shown in FIG. 4, the ratio of the specific resistance value in the high specific resistance region to the specific resistance value in the low specific resistance region was, as shown in FIG. What was more than 100 times before voltage application is 5 times after voltage application It had dropped to below.

Example 2
A square plate-shaped composite sintered body having a length, width: 300 mm, and thickness 2 mm was produced in the same manner as in Example 1. However, the amount of silicon carbide (SiC) ultrafine particles was changed to 9% by volume, the amount of aluminum oxide (Al ₂ O ₃ ) particles was changed to 91% by volume, and the sintering temperature was changed to 1800 ° C. did.

  The particle size distribution of silicon carbide (SiC) particles in this composite sintered body was measured by SEM observation. The results are shown in Table 2.

2 (a) and 2 (b), voltage application electrodes 12a and 12b having the pattern shape shown in FIG. 2 (a) are disposed on the surface 10a of the composite sintered body 10, Further, a counter electrode voltage application electrode 13 was disposed on the back surface 12 b of the composite sintered body 10. Between the voltage application electrodes 12a and 12b arranged in this way and the voltage application electrode 13 (2 mm) , a DC voltage of 24 kV, that is, an electric field as a voltage higher than the working voltage of the finally obtained resistor is obtained. A voltage with an intensity of 12 kV / mm was applied for 10 minutes.
In the resistor thus obtained, the specific resistance value in the region to which the voltage was applied was 1 × 10 ¹¹ Ωcm to 1 × 10 ¹² Ωcm, and the specific resistance value in the region to which the voltage was not applied was 10 ¹⁴ Ωcm or more.

  The method of the present invention can efficiently control the specific resistance value distribution of a composite sintered body containing an insulating ceramic and a conductive material by a simple method, and has a desired specific resistance value distribution. Resistors (such as those having a uniform distribution, or those in which a high specific resistance value region and a low specific resistance value region are distributed in a desired pattern) can be manufactured efficiently and with a simple operation, Its practical effect is extremely high.

Explanatory drawing of the one aspect | mode of the control method of the specific resistance value distribution of the composite sintered compact of this invention. 2A is an explanatory plan view of an example of an apparatus used in the method of manufacturing a composite resistor of the present invention, and FIG. 2B is an explanatory cross-sectional view taken along line YY of the apparatus of FIG. . Sectional explanatory drawing of the other example of the apparatus used for the manufacturing method of the composite resistor of this invention. The graph which shows ratio with respect to the specific resistance value of the low specific resistance value area | region of the specific resistance value of a high specific resistance value area | region in the composite resistor manufactured by the apparatus of FIG. 3, and its raw material composite sintered compact.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,10 Composite sintered body 1a, 10a Front surface of composite sintered body 1b, 10b Back surface of composite sintered body 2,3 Voltage application electrode 12a, 12b Voltage application electrode (surface side)
13 Voltage application electrode (back side)
30 Disc-shaped composite sintered body 30a, 30b Peripheral part of composite sintered body (region with high specific resistance)
31 Front side ring-shaped voltage application electrode 32 Back side voltage application electrode

Claims (8)

It is obtained by molding and sintering a mixture of insulating ceramic particles made of aluminum oxide particles and conductive material particles made of silicon carbide, and has a resistivity value of 1 × 10 ⁷ Ω · cm to 1 × 10 at room temperature. A voltage is applied to a desired portion of the composite sintered body of ¹⁸ Ω · cm so that the electric field strength is 1 to 20 kV / mm, and the specific resistance value of the voltage application portion is reduced. A method for controlling the specific resistance value distribution of a composite sintered body of an insulating ceramic and a conductive material.   The content of the conductive material particles in the composite sintered body is 5% by volume or more with respect to the total volume of the composite sintered body, and 10% by volume or more of the conductive material particles The control method according to claim 1, which has a particle size of 0.2 μm or less.   2. The control method according to claim 1, wherein average particle sizes of the aluminum oxide particles and the silicon carbide particles in the composite sintered body are 2 μm or less and 0.5 μm or less, respectively. The control method according to claim 1, wherein a voltage applied to a desired portion of the composite sintered body is equal to or higher than a predetermined use voltage of the composite sintered body. The control method according to claim 4, wherein a specific resistance value of a portion to which a voltage is applied of the composite sintered body is measured, and the applied voltage is adjusted in accordance with the measured value. When the measured value of the specific resistance value of the portion to which voltage is applied of the composite sintered body is higher than the surrounding specific resistance value, the voltage is applied to the high specific resistance value portion, and the specific resistance value The control method according to claim 5, wherein the value is decreased until it becomes substantially equal to a specific resistance value of the surroundings. The control method according to claim 4, wherein a specific resistance value distribution of the obtained composite resistor is controlled by adjusting a position of a voltage marking electrode used for applying the voltage. A voltage application electrode is arranged for each of two or more regions having the desired pattern of the composite sintered body, and voltage application by each electrode is performed until the region reaches a desired specific resistance value. The control method according to claim 7, wherein the high specific resistance region and the low specific resistance region are distributed in a desired pattern.

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