JP2671928B2 - Multi-function element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a composite function element having a varistor function and a capacitor function, which is mainly composed of SrTiO ₃ based semiconductor porcelain and has a high resistance layer formed at a grain boundary thereof. Regarding improvement.

[Prior Art] In recent years, microcomputers have been mounted in various electronic devices, and in that case, malfunction of the devices due to noise has become a serious problem. Accordingly, the demand for varistors for absorbing voltage noise has been increasing.

As a varistor material, a semiconductor porcelain having a high resistance layer formed at a crystal grain boundary is known, and conventionally, a ZnO-based, SiC-based or SrTiO ₃ -based material has been used.

[Technical problem to be solved by the invention]

However, the ZnO-based varistor, which has been put into practical use, has excellent voltage nonlinearity, but has a problem in that it has a poor response to high-speed noise and has a small effect in absorbing electrostatic noise and the like.

On the other hand, in the case of the SiC type, the voltage non-linearity was not so good, and the noise voltage could not be absorbed in some cases.

Therefore, SrTiO ₃ -based varistors have been attracting attention.
The greatest feature of varistor using SrTiO ₃ based semiconductor porcelain is
It has a large capacitance, and has a capacitance that is about 10 times that of a ZnO-based semiconductor ceramic. Therefore, it is excellent in high-speed noise absorbing ability.

However, in terms of varistor characteristics, that is, voltage non-linearity, SrTiO ₃ -based semiconductor porcelain has about twice the performance of SiC-based semiconductor porcelain, but 1% better than ZnO-based porcelain.
It is considerably inferior to / 2 to 1/5. Therefore, since the voltage suppression effect is small, it has been a serious problem in considering the use of SrTiO ₃ based semiconductor porcelain.

Further, the driving voltage of the microcomputer is about 3 to 5V, and at present, there is no varistor capable of handling this low voltage. Therefore, there is a demand for a varistor capable of handling such a low voltage.

Therefore, an object of the present invention is to provide a SrTiO ₃ -based multi-functional device that is excellent in absorbing high-speed noise, has improved voltage nonlinearity, and can easily obtain a desired varistor voltage. It is in.

[Means for solving technical problems]

The multi-functional device of the present invention contains SrTiO ₃ as a main component and at least one selected from the group consisting of oxides of rare earth elements, Nb, W and Ta as a semiconducting agent in an amount of 0.05 to 1% by weight.
Included, which is configured using a semiconductor porcelain in which glass is diffused into the crystal grain boundaries, the glass is at least one of B ₂ O ₃ and SiO ₂ , Bi ₂ O ₃ , at least PbO, and ZnO. It is characterized by including one kind.

In the above-mentioned constitution, at least one kind of oxides of rare earth elements, Nb, W and Ta is contained in an amount of 0.05 to 1% by weight because a high resistance layer is formed at a grain boundary of a SrTiO ₃ -based porcelain to form a semiconductor. This is because it is used conventionally.

[Action and Effect of the Invention]

Conventionally, when a semiconductor porcelain containing SrTiO ₃ as a main component is prepared, an SrTiO ₃ based varistor or capacitor can be formed by oxidizing and diffusing Bi, Pb, Zn, Cu, Na, B, Si and the like. That was known.

Therefore, the inventors of the present application, while taking advantage of the characteristics of such SrTiO ₃ -based semiconductor ceramics, as a result of earnest study to obtain a composite functional element having more excellent voltage non-linearity, as described above, once in the grain boundaries. If you diffuse the vitrified oxide,
The inventors of the present invention have found that a compound functional device having more excellent voltage non-linearity can be obtained, and have completed the present invention.

That is, according to the present invention, the B ₂ O ₃ and
Since the glass containing at least one kind of SiO ₂ and at least one kind of Bi ₂ O ₃ , PbO and ZnO is diffused, while maintaining a large capacitance of the SrTiO ₃ based semiconductor porcelain, Excellent voltage nonlinearity is realized. Therefore, it is possible to effectively absorb high-speed noise, and to obtain a composite function element excellent in voltage suppression effect. Not only that, it is also easy to control the varistor voltage by adjusting the diffusion amount of the glass, and therefore it is easy to realize a varistor compatible with low voltage.

[Explanation of Example]

SrCO ₃ and TiO ₂ were mixed in a ratio to obtain SrTiO _3, and as a semiconducting agent, a mixture was prepared so that Y ₂ O ₃ was 0.05% by weight based on the total weight. The mixture thus prepared was precalcined at a temperature of 1000 ° C. to 1200 ° C. for about 3 hours and then pulverized.

Polyvinyl alcohol was mixed as an organic binder into the obtained fine powder raw material and granulated.

Next, the granulated powder was molded under a pressure of about 500 kg / cm to 2 ton / cm to obtain a disk-shaped molded body having a diameter of 7 mm and a wall thickness of 0.5 mm.
This molded body is fired in air at a temperature in the range of 1100 ° C to 1200 ° C, and further in a reducing atmosphere of N ₂ : H ₂ = 95 mol%: 5 mol% at a temperature of 1400 ° C to 1500 ° C for 3 hours. Baked.

On the surface of the obtained sintered body, 0.1% by weight of glass obtained by vitrifying the oxidizing agent having the composition shown in Table 1 below was applied, and heat-treated at a temperature of 900 ° C to 1200 ° C for 2 hours. Finally, the surface of this unit was coated with an indium-gallium alloy as an electrode, and the varistor voltage (V _1mA ), voltage non-linearity coefficient (α), capacitance C, and dielectric loss (tan δ) were measured. The results are shown in Table 2.

For comparison, a unit in which the Na oxide (non-vitrified) was diffused was similarly constructed and the characteristics were measured (samples indicated by symbol M in Tables 1 and 2). However, this comparative example is shown).

As is apparent from Table 2, the devices of the examples of the present invention show much larger capacitance than the devices of the comparative examples and also have a high voltage nonlinear coefficient α.

Next, changes in the varistor voltage and the voltage non-linearity coefficient and the addition amount of the glass additive are shown in FIGS. 1 and 2. These show the characteristics for Examples 1, 10 and 20 shown in Table 2.

As is clear from FIG. 1, the varistor voltage V _1mA increases as the coating amount of the glass additive increases. Therefore, it is understood that by controlling the coating amount of this glass additive, it is possible to realize a multi-functional device having various varistor voltages.

Further, as is clear from FIG. 2, it can be seen that the voltage non-linearity coefficient changes considerably depending on the coating amount of the glass additive. That is, when the glass coating amount is less than 0.05% by weight, the voltage non-linearity coefficient sharply decreases, while on the other hand, 1% by weight.
It can be seen that the voltage non-linearity coefficient drops sharply and the varistor characteristic almost disappears even when the value exceeds. In actual measurement, it has been found that when the content exceeds 1% by weight, the varistor characteristics almost disappear and thermal breakdown occurs during the measurement.

[Brief description of the drawings]

FIG. 1 shows the relationship between the varistor voltage and the amount of glass oxide added in the example of the present invention, and FIG. 2 shows the relationship between the voltage nonlinearity coefficient and the amount of glass oxide added in the example of the present invention. FIG.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Masayoshi Maeda 2-26-10 Tenjin Tenjin, Nagaokakyo City, Kyoto Prefecture Murata Manufacturing Co., Ltd. (72) Yasunobu Yoneda 2-26-10 Tenjin Nagaokakyo, Kyoto Prefecture Murata Manufacturing Co., Ltd. (56) Reference JP-A-56-169316 (JP, A) JP-A-57-27001 (JP, A) JP-A-61-271802 (JP, A)

Claims (1)

(57) [Claims] 1. SrTiO ₃ as a main component and at least 0.05 to 1% by weight of at least one selected from the group consisting of oxides of rare earth elements, Nb, W and Ta as a semiconducting agent, and glass is contained in the crystal grain boundaries. It is configured by using a diffused semiconductor porcelain, and the glass contains at least one of B ₂ O ₃ and SiO ₂ , and at least one of Bi ₂ O ₃ , PbO, and ZnO. Multi-function element.