JPH0346201A - Semiconductor porcelain possessing positive resistance-temperature characteristic - Google Patents

Abstract

PURPOSE:To avoid the destruction of an element when voltage is applied suddenly by a method wherein the Curie point, to be transferred to a high resistance element from a low resistance element, is set in such a manner that it becomes higher as going into the inner part and it becomes lower as going to the outer part. CONSTITUTION:The inner layer 2 of high Curie point is laminated by pinching it with the outer layers 3 and 3 having low Curie point in such a manner that the Curie point becomes higher as going into the inner part from outside part of a semiconductor porcelain. Accordingly, even when heat is generated when a current is limited, the resistance of the inner layer 2 can be made equal to or lower than the resistance of the outer layers 3. To be more precise, the resistance of the inner layer is liable to abnormal increase of resistance due to the fact that heat is hardly generated there, and its temperature rises easily, but the increase of resistance can be suppressed by constituting the inner layer with a high Curie point material. As a result, the thermal stress breakdown due to the difference in temperature distribution of a ceramic element and especially the destruction of the element due to sudden application of voltage can be avoided.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a semiconductor ceramic electronic component having a positive resistance-temperature characteristic used, for example, for starting a motor, and particularly relates to a semiconductor ceramic electronic component that is used for starting a motor and has a thermal stress fracture when a sudden voltage is applied. The present invention relates to an element structure that avoids this.

[Conventional technology]

Generally, semiconductor porcelain is known which exhibits positive resistance-temperature characteristics by mixing small amounts of impurities and additives with BaTloi, and conventionally there is a structure as shown in FIG. 4, for example. This semiconductor ceramic 10 is constructed by forming electrodes 12 on both main surfaces of a disk-shaped ceramic element 11, and connecting lead wires 13 to the electrodes 12. This semiconductor porcelain 10 is capable of, for example, temperature detection, temperature control, temperature compensation, constant temperature heating element, overcurrent protection, atmosphere detection, and motor starting.

Or, for example, in a motor starting circuit used in an automatic degaussing circuit, etc., in order to start the motor,
It is necessary to have a function that first applies a large alternating current and then gradually attenuates the current after the motor starts moving.
The above semiconductor ceramic lO is employed in this motor starting circuit. That is, the semiconductor ceramic 10 has the function of passing a large current at the start of current application, and limiting and attenuating the current by increasing the resistance value over time due to heat generation of the ceramic element 11. A motor starting circuit can be formed with a single element. The above rate is adopted because it is used for such purposes.

The body ceramic 10 is required to have low resistance and withstand voltage, and in particular, is required to withstand voltage against sudden voltage application.

[Problem that the invention seeks to solve]

However, the conventional semiconductor ceramic 10 described above has a problem in that the ceramic element 11 is easily destroyed by sudden voltage application. This is because the ceramic element 11 is made of a single material, so 1! When heat is generated during flow restriction, there is a difference in temperature distribution between the inside 11a (the elliptical portion) and the outside 11b of the element 11. In other words, external 11b
Since the inside 11a is in contact with the atmosphere, heat diffusion is fast, the temperature is relatively low, and the resistance is small. However, since heat dissipation is slow in the inside 11a, the resistance is higher than that of the outside 11b, and as a result, the inside 11a
This is because thermal stress fracture occurs faster in a than in the outside. Especially when a sudden voltage is applied, the internal 11a and external 11b
Destruction is likely to occur because there is a large difference in the rate of thermal equilibrium between the two.

The present invention has been made in view of the above-mentioned conventional situation, and an object of the present invention is to provide a semiconductor ceramic electronic component that can avoid thermal stress destruction due to differences in temperature distribution of ceramic elements, particularly destruction when a sudden voltage is applied. .

Means for Solving Problem c] The present inventors have determined that the internal resistance value of the ceramic element when it generates heat is equal to or equal to the external resistance value, even though the temperature tends to rise due to heat dissipation. The present invention was developed based on the idea that thermal stress fracture could be avoided if the temperature could be lowered.

Therefore, the invention of item 1 of the present application is characterized in that semiconductor porcelain having positive resistance-temperature characteristics is made of a material whose Curie point is higher on the inside than on the outside, that is, with a material that becomes higher in resistance at higher temperatures. It is said that The second aspect of the invention is characterized in that an outer layer made of a ceramic material having a low Curie point is laminated on both sides of an inner layer made of a ceramic material having a high Curie point, and these are integrally sintered.

Here, the semiconductor porcelain of the present invention is characterized in that the Curie point, which transitions from a low-resistance element to a high-resistance element, is set higher on the inside and lower on the outside. This can be realized by adopting at least a three-layer structure consisting of an inner layer and an outer layer having different Curie points. In this case, the present invention is of course not limited to this three-layer structure, but also includes a multi-layer structure of three or more layers. Just set it.

[Effect]

According to the semiconductor porcelain according to the present invention, since the Curie point increases from the outside to the inside of the semiconductor porcelain,
Specifically, since the inner layer with a high Curie point is sandwiched between the outer layers with a low Curie point and is laminated, the resistance of the inner layer can be made equal to or lower than the resistance of the outer layer even if heat is generated during current limitation. I can do it.

In other words, since the inner layer is difficult to dissipate heat and easily rises in temperature, its resistance tends to rise abnormally. However, by being made of a material with a high Curie point, the rise in resistance can be suppressed, and as a result, the resistance of the element due to sudden voltage application can be suppressed. Destruction can be avoided.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 to 3 are diagrams for explaining semiconductor ceramics according to an embodiment of the present invention.

In the figure, 1 is a semiconductor ceramic having positive resistance-temperature characteristics, which is made by laminating a rectangular plate-shaped inner layer 2 and a pair of rectangular plate-shaped outer layers 3.3 facing each other with the inner layer 2 in between.
Electrodes 5.5 are formed at the center of both main surfaces of the ceramic element 4 which is integrally sintered, and lead wires 6 are connected to each electrode 5 for titc.

The inner layer 2 is made of a ceramic material having a Curie temperature of, for example, 65°C, and the outer layer 3 has a Curie temperature of, for example, 65°C.
For example, it is made of ceramic material at a temperature of 115°C.

Next, a method for manufacturing the semiconductor ceramic l of this example will be explained.

1. First, 0.05-01% of yttrium oxide was mixed as a semiconducting agent with 1% of barium titanate 74mo1% and strontium titanate 24°95mo1%,
To this, 5 wt% of SiOtO is added as a mineralizing agent, and 2 wt% of Mn0xO is added as a property improving agent, mixed and pulverized, and calcined at 1000° C. for 2 hours.

Next, this pre-fired material is crushed again, and a vinyl acetate binder and a dispersant are mixed therein to give a thickness of 1.5 mm.
A green sheet of sn is formed. As a result, an outer layer 3 having a Curie point of 115° C. is formed.

ii, while barium titanate 91 mo 1%, strontium titanate 2.95 moj! %, 0.05-01% yttrium oxide as a semiconducting agent, and S i O! as a mineralizing agent. 0.3 wL%, Af! ○s
O, 2wt%.

2 wt% of MnOtO is added as a property improving agent, mixed and pulverized, and calcined at 1000°C for 2 hours.Next, the calcined material is crushed again, and a vinyl acetate binder and a vinyl acetate binder are added to it. A green sheet with a thickness of 2°0fi is formed by mixing the dispersant. This results in a Curie point of 65
The inner layer 2 of ℃ takes shape.

iii.Next, the inner layer 2 is sandwiched between the two outer layers 3, 3, stacked and thermocompressed to form a ceramic element 4 having a thickness of 5n. Then, the element 4 is
It is integrally fired at ℃ for 2 hours to obtain a sintered body. Thereafter, for example, Ag paste is printed and baked on both main surfaces of the ceramic element 4 to form electrodes 55, and each of the electrodes 5 is
Solder the lead wire 6 to. In this way, the semiconductor ceramic 1 of this example is manufactured.

The table shows the results of characteristic tests conducted to confirm the effects of this example.

In this test, semiconductor porcelain produced by the manufacturing method of this example was used, and its resistance value, temperature coefficient, static withstand voltage, and dynamic withstand voltage were measured. The semiconductor ceramic was shaped like a disk with a diameter of 10 mm and each outer layer was 1.5 m thick and the inner layer was 2.0 fl thick. For comparison, 2 fl [conventional samples A and 13] were prepared and the same measurements were performed. The above-mentioned conventional sample A uses the ceramic material (Curie point: 115°C) used for the above-mentioned outer layer, and has a diameter of 10 cm and a thickness of 5°.
The conventional sample B used the same ceramic material (Curie point: 65° C.) for the inner layer and had the same shape.

As is clear from the same table, in the case of conventional samples A and H, the temperature coefficient is 25%/L28%/L, the static withstand voltage is 100V,
120v1 dynamic withstand voltage was 85V and 95V. On the other hand, in the case of the sample of this example, the temperature coefficient was 20%/, the static withstand voltage was 130 V, and the withstand voltage was 115 V, which were all improved, and as is clear from the test results, the inner layer 2 of the semiconductor ceramic By setting the outer layer 3 to a high Curie point and the outer layer 3 to a low Curie point, it is possible to suppress the difference in speed of thermal equilibrium during heat generation of the ceramic element 4, avoid thermal stress fracture, and obtain an electronic component with excellent withstand voltage, especially dynamic voltage resistance. It will be done.

In addition, in this example, thermal stress fracture can be avoided by laminating outer and inner layers with different Curie points, so it is not necessary to take measures to increase the size of conventional ceramic elements, which allows for miniaturization of electrical equipment. can contribute to the development of

In addition, in the above embodiment, the case where a three-layer structure consisting of an inner layer 2 and two outer layers 3°3 was used was explained as an example, but the present invention is not limited to this structure, and can be applied to a multilayer structure having three or more layers. In this case as well, the ceramic material of each layer may be selected so that the Curie temperature is lower toward the outside, and in the case of this multilayer structure, thermal stress fracture can be more effectively avoided.

〔Effect of the invention〕

As described above, according to the semiconductor porcelain according to the present invention, the Curie point is higher on the inside than on the outside of the semiconductor porcelain, and specifically, the inner layer with a high Curie point is sandwiched between the outer layers with a low Curie point and laminated. This has the effect of avoiding thermal stress breakdown of the ceramic element, particularly breakdown when a sudden voltage is applied.

[Brief explanation of drawings]

1 to 3 are diagrams for explaining semiconductor porcelain according to an embodiment of the present invention, in which FIG. 1 is a sectional view thereof, FIG. 2 is an exploded perspective view showing its manufacturing process, and FIG. 4 is a perspective view showing the laminated state, and FIG. 4 is a sectional view showing the conventional semiconductor ceramic. In the figure, 1 is semiconductor porcelain, 2 is inner layer, 3 is outer layer, 4
is a ceramic element.

Claims (2)

[Claims] (1) In a semiconductor porcelain having a positive resistance-temperature characteristic that transitions from a low resistance to a high resistance at a predetermined Curie point, the inside is made of a ceramic material with a higher Curie point than the outside. Semiconductor porcelain with resistance temperature characteristics. (2) A patent characterized in that the semiconductor porcelain is formed by laminating an outer layer made of a ceramic material with a lower Curie point than the inner layer on both sides of an inner layer made of a ceramic material with a lower Curie point, and firing these together. A semiconductor ceramic having a positive resistance temperature characteristic according to claim 1.