JPH05101903A - Semiconductor porcelain having resistance with positive temperature characteristic - Google Patents

Abstract

PURPOSE:To improve static pressure tightness by composing so that a surface area of a semiconductor porcelain may be not less than a specific area per unit volume. CONSTITUTION:This semiconductor porcelain is made up by molding and firing a granular raw material where the surface area of the semiconductor porcelain is not less than 40cm<2> per volume 1cm<3>. Further, a gratin diameter of the grains composing the semiconductor porcelain after firing is not to exceed 8mum. Thereby, a radiation effect in the inside of the semiconductor porcelain during high voltage impression is improved, static pressure tightness is improved so as to heighten reliability of an element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor ceramic having a positive resistance temperature characteristic, and more particularly to a semiconductor ceramic excellent in static withstand voltage.

[0002]

2. Description of the Related Art In recent years, barium titanate-based semiconductor porcelain having a large positive resistance temperature characteristic has been developed and used, and when the Curie temperature is exceeded, the resistance value rapidly increases,
Since it reduces the amount of current passing through it, it is widely used for applications such as circuit overcurrent protection and degaussing of the cathode ray tube frame of television receivers.

On the other hand, an element using a barium titanate-based semiconductor porcelain (semiconductor porcelain element) has a problem that the positive resistance-temperature characteristic, that is, the static breakdown voltage deteriorates when the thickness thereof becomes a certain amount or less. In order to meet this demand, there has been proposed a method of preventing the deterioration of static withstand voltage characteristics by making the thickness of the semiconductor porcelain element 5 times or more the average particle diameter of the particles constituting the porcelain (Japanese Patent Application No. 62-168341). issue).

[0004]

However, this method is intended to improve the static breakdown voltage simply by adjusting the grain size and the thickness of the semiconductor ceramic element, and it is not always necessary to sufficiently improve the static breakdown voltage. There was a problem that I could not do it.

The present invention solves the above problems, and an object of the present invention is to provide a semiconductor porcelain having a positive resistance temperature characteristic excellent in static withstand voltage.

[0006]

In order to achieve the above object, the semiconductor porcelain having a positive resistance temperature characteristic of the present invention has a positive resistance temperature characteristic formed by molding and firing a granular raw material. The semiconductor porcelain is characterized in that the surface area of the semiconductor porcelain is 40 cm ² or more per 1 cm ^{3 of} volume.

This effect can be further assured by setting the particle size of the particles constituting the semiconductor porcelain after firing to 8 μm or less.

In the present specification, the term "surface area" means an apparent surface area. For example, in the case of a disk-shaped semiconductor porcelain, the sum of the areas of the front and back surfaces and the outer peripheral surface is the "surface area", and when the semiconductor porcelain is in the shape of a rectangular plate (rectangular etc.), The sum of the areas is the "surface area" referred to here, and is not the sum of the surface areas of the individual particles forming the semiconductor porcelain.

The present invention has been made by earnestly studying in order to obtain a semiconductor porcelain element having an excellent static withstand voltage, and as a result, was found to know that the control of the heat radiation state when a high voltage is applied is deeply related to the static withstand voltage. , The surface area of semiconductor porcelain is 40 cm
^{When it is 2} / cm ³ or more, it is based on the fact that the heat dissipation effect inside the semiconductor porcelain during high voltage application is improved and the static withstand voltage is improved. This effect can be obtained by setting the particle size after firing to 8 μm or less. Can be made more reliable.

[0010]

EXAMPLES The features of the present invention will be described in more detail below with reference to examples of the present invention.

BaCO ₃ , TiO ₂ , SrCO ₃ , Y ₂ O _3
Are mixed at a ratio such that a predetermined composition represented by the following formula (1): (Ba _0.9459 Sr _0.05 Y _0.004 ) TiO ₃ + 0.0001Mn + 0.007SiO ₂ (1) is obtained. Then, this is put in a polyethylene pot together with pure water and zirconia balls, pulverized and mixed for 5 hours, dried, and calcined at 1100 ° C. for 2 hours. This calcined powder is put into a polyethylene pot together with pure water and zirconia balls and crushed to adjust the particle size so that the average particle size is 0.8 μm to 3 μm.

The calcined powder with the adjusted particle size is put in a polyethylene pot, and zirconia balls, a plasticizer, an organic binder, a dispersant and the like are mixed so as to form a slurry having a predetermined viscosity, and they are mixed for 16 hours. A sheet having a thickness of 100 μm is formed from this slurry by using a doctor blade method, and a plurality of the sheets are laminated and pressure-bonded. Then, this is punched out to obtain a disk-shaped molded body. Then, the molded body is fired at 1350 ° C. for 1 hour to obtain a fired body (semiconductor porcelain). And on both main surfaces of this semiconductor porcelain,
An In-Ga alloy is applied to form an electrode, which is used as a sample for characteristic measurement.

The surface area per unit volume (surface volume ratio) was changed by the following method. The diameter of the molded body is fixed at 10 mm, and its thickness is
This is changed by changing the number of sheets to be pressure-bonded (Example 1). The thickness of the molded body is kept constant at 1.0 mm and its diameter is changed (Example 2).

With respect to each sample of Example 1 in Table 1 and Example 2 in Table 2, the static breakdown voltage at room temperature (25 ° C.) (current when the voltage applied quasi-statically to the device was increased) The minimum voltage value, V / mm) and the specific resistance (Ω · cm) are shown.

[0015]

[Table 1]

[0016]

[Table 2]

In Tables 1 and 2, the samples and parameters marked with * are outside the scope of the present invention. Table 1,
As shown in Table 2, when the surface volume ratio becomes large, that is, when the surface volume ratio becomes 40 cm ² / cm ³ or more, the static resistance is greatly improved although the specific resistance does not change significantly. In particular, when the particle size is 8 μm or less, a static breakdown voltage of 100 V / mm or more can be obtained. On the other hand, when the particle size is 15 μm,
Compared with the case where the particle size is 8 μm, the effect of improving the static pressure resistance obtained by increasing the surface volume ratio is small, and is about 85 V / mm at 60 cm ² / cm ³ , for example. As described above, the surface volume ratio is preferably 40 cm ² / cm ³ or more, and it is more preferable that the particle size is 8 μm or less in order to surely improve the static pressure resistance.

[0018]

As described above, the semiconductor porcelain having the positive resistance temperature characteristic of the present invention has a surface area of the semiconductor porcelain of 1 cm.
Since it is configured to be 40 cm ² or more per ³ cm, the heat dissipation effect inside the semiconductor porcelain when a high voltage is applied is improved, the static breakdown voltage is greatly improved, and the reliability of the element is improved.

This effect can be further ensured by setting the particle size of the particles constituting the semiconductor porcelain after firing to 8 μm or less.

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[Procedure amendment]

[Submission date] November 19, 1992

[Procedure Amendment 1]

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[Correction target item name] 0015

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[0015]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

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[0016]

Claims (2)

[Claims] 1. A semiconductor porcelain having a positive resistance temperature characteristic formed by molding and firing a granular raw material, wherein the surface area of the semiconductor porcelain is 40 cm ² or more per 1 cm ^{3 of} volume. Semiconductor porcelain having resistance temperature characteristics. 2. The particle size of the particles constituting the semiconductor porcelain after firing is 8 μm or less.
A semiconductor porcelain having the described positive resistance-temperature characteristic.