JPS6095901A - Positive temperature coefficient semiconductor porcelain - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a barium titanate-based positive temperature semiconductor porcelain having a positive resistance temperature coefficient, which is used as a current control element and a constant temperature heating element in various electronic devices, automobiles, etc. It is related to.

Structure of the conventional example and its problems A positive temperature coefficient semiconductor porcelain material with a positive temperature coefficient of resistance larger than that of the conventional example has been developed and has been used as various current control elements and constant temperature heating elements. It is a material that can flow a large current when it is in a low resistance state, and after a certain period of time, it is heated by self-heating due to the surreal heat of the positive temperature semiconductor porcelain itself, and becomes high temperature, causing the positive temperature semiconductor porcelain to become high temperature. As a resistor, it controls the current value by 74% and maintains a high temperature state.

Recently, there has been a trend to use positive characteristic semiconductor ceramics to perform the above-described current control even for larger currents. Therefore, there is a problem in that the power supply voltage applied to the positive characteristic semiconductor ceramic becomes large, and the positive characteristic semiconductor ceramic becomes unable to withstand the large voltage application and breaks down. Additionally, there is a trend toward using positive characteristic semiconductor porcelain as a constant temperature heating element to further increase output and efficiency. For this purpose, the power supply voltage force applied to the positive characteristic semiconductor porcelain;
Efforts have been made to improve heat dissipation efficiency, such as by adding metal plates for heat dissipation to the surface of the porcelain. However, the application of a large voltage to such positive characteristic semiconductor porcelain and the temperature difference between the surface temperature of the porcelain and its internal temperature due to improved heat dissipation efficiency can cause problems such as voltage breakdown and an increase in room temperature resistance during intermittent load tests. there were.

As mentioned above, the positive characteristic semiconductor ceramic generates heat by itself using its own Joule heat and controls the current. This self-heating of positive characteristic semiconductor porcelain occurs inside the porcelain, and heat dissipation is not as good inside the porcelain as compared to the vicinity of the surface, so it is inevitable that the temperature at the center will be high. Therefore, each part of the element has the same temperature coefficient of resistance as shown in Figure 1, so the center temperature T2 is higher than the temperature near the surface T1, and the resistance R2 at the center is much higher than the resistance R1 near the surface. becomes a large value. For this reason, most of the voltage applied to the positive characteristic semiconductor porcelain was applied to the center, causing local breakdown and an increase in room temperature resistance during the intermittent load test. In FIG. 1, TC indicates the Curie temperature [7, which is the temperature at which the resistance value is twice the room temperature resistance.

Purpose of the Invention In view of the above-mentioned drawbacks, the present invention aims to control the resistance value distribution caused by the temperature distribution difference of positive characteristic semiconductor porcelain used as a current control element and a constant temperature heating element, and to develop a withstand voltage characteristic that can sufficiently withstand large currents and large voltages. The purpose of this invention is to provide a highly reliable positive characteristic semiconductor porcelain with excellent performance and little increase in room temperature resistance during intermittent load tests.

Structure of the Invention In order to achieve this object, the positive characteristic semiconductor porcelain according to the present invention has lead, strontium, calcium, or tin with different concentrations within the element, and the Curie temperature is highest in the center of the element and near the surface. It is unique in that it is formed to have a low resistance value, suppresses the resistance value distribution in the positive temperature semiconductor porcelain during operation, and can obtain a positive temperature semiconductor porcelain with excellent withstand voltage characteristics and high reliability. It has the effect of

That is, as shown in FIG. 2, the positive characteristic semiconductor porcelain according to the present invention has a resistance temperature coefficient of 8 × Curie temperature Tc1) near the surface of the element and a resistance temperature curve B (Curie temperature TC2) of the center part. is different. In this positive characteristic semiconductor porcelain, it is inevitable that the temperature at the center T2 is higher than the temperature near the surface T1, but the temperature difference within the element (T
2-71) and the resistance temperature characteristic is the Curie temperature difference (Tc
2-Tc1), and if the resistance at room temperature and the temperature coefficient of resistance are approximately equal, the resistance R1 near the surface and the resistance R2 at the center during operation will be approximately equal, and therefore the difference in resistance value distribution will be small over the entire positive characteristic semiconductor porcelain. So,
The electric field strength applied to the positive characteristic semiconductor ceramic becomes uniform throughout, and the withstand voltage characteristics and reliability are significantly improved.

Examples of the present invention will be described in detail below.

Description of Examples BaCo3. PbO, TtO2, Nb2O,, Si
2. Exit MnO2 0.024Si02+0. Ooo4
Mn02 and (Ba0.waPb0.2o)Tio3+o, oo1oN
B2O5 + 0.024SiO2 + OΩ004MnO2, mixed in a ball mill for 20 hours, crushed and dried in a 9N Shama ball mill, and mixed with 10wt of 5wt% polyvinyl alcohol. %, and granulated, and they were made into raw material 1 and raw material 2. Next, 1.31 of raw material 1 was pressurized at 1001ψ/-, and then 1.31 of raw material 2 was added to 100. After applying pressure at lje/crlt, further adding 1.3f of raw material 1 and pressurizing at 100 Kg/ctl, the whole was press-molded at 1000 Kl/ct/l to obtain the layered molded product shown in Fig. 3. Figure 3.

1 and 3 indicate the layer of raw material 1, and 2 indicates the layer of raw material 20.
For comparison, raw material 1 and raw material 2 were each used separately for 10
At a pressure of 00Kf/cd, diameter 18mm + thickness 311
It was press-molded into a 1 m disc shape. These molded bodies thus obtained were fired at 1300°C for 1 hour, and ohmic silver electrodes were provided thereon to prepare samples 1, 2°3.

Here, Sample 1 was prepared using the molded article shown in FIG. 3 according to the present invention, and Samples 2 and 3 were prepared using Raw Materials 2 and 3 alone, respectively. The resistance-temperature characteristics of the sample thus obtained are shown in Figure 4, and Table 1 shows the withstand voltage, rate of change in resistance in the intermittent load test, specific resistance at room temperature, and Curie temperature. In FIG. 4, A indicates sample 1. B is sample 2.
C is 01, which indicates the resistance-temperature characteristics of sample 3. The withstand voltage in the table is a voltage that can be withstood for 3 minutes at a constant voltage, and the test was performed by increasing the voltage by soV. 450V means that at 400V it was held for 3 minutes, but at 450V it was destroyed within 3 minutes. Similarly, the rate of change in resistance indicates the rate of change in resistance in an intermittent load test, and indicates the rate of change in room temperature resistance when intermittent voltage application of 175 V is applied to the sample for 10 seconds and then stopped for 350 seconds is repeated 3600 times. ing. The resistivity at room temperature is the resistivity at 26°C, and the Curie temperature is the temperature at which the resistance is twice the resistance at room temperature.

As is clear from the above table, Sample 1 according to the present invention, which has a difference in PBK concentration and has a higher Curie temperature in the center, has a markedly improved withstand voltage and a smaller rate of resistance change in the room temperature intermittent load test. It has the unique effect of improving reliability.

In addition, lead, strontium, calcium, and tin may be added singly or at the same time as two or more of the above-mentioned Curie temperature transfer elements to create raw materials with different Curie temperatures,
Similar effects were obtained even when a layered structure of three or more layers was created as in the above embodiment.

Further, it is preferable that the Curie temperature difference is set by measuring the temperature distribution within the element under the actual usage conditions of the positive characteristic semiconductor porcelain.

In addition, strontium cal/rum tin is applied in the form of oxides, titanates, and various salts to the surface of the pre-sintered body at 800°C to 1000°C, fired at 125°C to 1400°C, and cured. The same effect was obtained even with one temperature distribution.As described above, the present invention provides a difference in concentration of lead, strontium, calcium, or tin in a positive characteristic barium titanate semiconductor ceramic element. By forming the device so that the Curie temperature is highest at the center and concave near the surface, it is possible to make the electric field strength applied to the positive characteristic semiconductor porcelain uniform throughout the device, and improve withstand voltage characteristics and reliability. It has the unique effect of significantly improving physical properties and is of great industrial value.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a resistance-temperature curve showing the resistance distribution caused by temperature distribution in a conventional PTC porcelain element, and Fig. 2 is a resistance-temperature curve illustrating the operating principle of the PTC semiconductor porcelain according to the present invention. FIG. 3 is a diagram showing the structure of a molded body in an example of the positive characteristic semiconductor porcelain according to the present invention, and FIG. 4 is a diagram showing a resistance-temperature curve of a sample in the example. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure → −J benefit (°C) 2nd figure → Uban no performance; (°C)

Claims (1)

[Claims] In a positive characteristic barium titanate semiconductor ceramic element,
A characteristic semiconductor porcelain characterized by having lead, strontium, calcium, and tin having different concentrations so that the Curie temperature is highest at the center of the element and lower near the surface.