JPS59101801A - Temperature sensitive resistance element - 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 The present invention relates to a temperature sensitive resistance element, and more particularly to a temperature sensitive resistance element for electric power.

A temperature-sensitive resistance element (positive temperature coefficient thermistor) is a ceramic semiconductor whose resistance increases rapidly when the temperature rises above a certain temperature, and is made of barium titanate as a base material doped with a monovalent or trivalent metal oxide. In the field of home appliances,
It is used as a constant temperature heating element, non-contact switch, constant current device, or current limiting element.

However, the above-mentioned temperature-sensitive resistance element is for power use (large current use)
When used as a current-limiting element in There are problems such as rapid temperature rise due to current and thermal breakdown.

The present invention was made in view of the above-mentioned problems, and its purpose is to reduce the specific resistance (at room temperature) and increase the mechanical strength.
An object of the present invention is to provide a temperature-sensitive resistance element that can be used as a current-limiting element for electric power. Embodiments of the present invention will be described in detail below with reference to the drawings.

The temperature-sensitive resistance element according to the present invention is used, for example, on a power current-limiting element connected to the power supply side in order to reduce the load on a circuit breaker in a circuit, and is used on a power current-limiting element connected to the power supply side of the circuit breaker in order to reduce the load on the circuit breaker. A molded body of mixed powder containing 5 to 35% by weight of copper powder is sintered at a temperature of 1150 to 1400°C in a vacuum, reducing or inert atmosphere, and the sintered body is odor-free in an oxidizing atmosphere. It is then subjected to oxidation treatment at a temperature of 950 to 1150°C.

Here, if the ratio of copper to barium titanate exceeds 35% by weight, sintering becomes difficult, and as mentioned above, the sintering temperature is a temperature higher than the melting point of copper (1083°C). It is important that the copper contained in the barium titanate powder is molten and sintered to promote sintering and to bond the barium titanate powder together after sintering. It is possible to increase the strength, that is, the mechanical strength of the element itself, and it can reach up to 1400 m? : If the temperature exceeds , the copper melts excessively and the composition after sintering becomes uneven! l) The characteristics of the device become unstable.

Furthermore, the reason why the sintered body is oxidized is to increase the specific resistance Rt(7) ratio Rt'/Ro at high temperature to the specific resistance Ro at room temperature of the element.

To manufacture the temperature-sensitive resistance element described above, first, pure water is added to barium titanate powder whose particle size is 50 to 100% below 1 μm, and this is placed in a ball mill with a glass lining (Teflon coating). Using a spherical agate ball of ~12ψ, run a ball mill at 75 to 85 revolutions per minute for 6 to 3 minutes.
The powder was pulverized by operating for 0 hours, and then dried in air at 120° C. for more than two days and nights, passing through a 30-mesh sieve to obtain 130-mesh barium titanate powder.

Further, copper powder with a purity of 99.9% is passed through a 500 mesh sieve to obtain copper powder with a size of 25 μm or less.

Next, -30 mesh of barium titanate powder and 0
．． 5-35% by weight (preferably 5-25% by weight) of 25
Copper powder of less than μm in size is mixed with dialcohol (reagent special grade ethanol) in a gold glass ■-shaped rotary mixer for 30 to 60 minutes so that it is evenly mixed, and then the alcohol is dispersed and evaporated. Remove the residue to obtain a dry mixed powder.

The above-mentioned mixed powder is put into the mold, and 250Ky/
A disk-shaped molded body with a predetermined diameter and thickness taking into account shrinkage due to sintering is produced by pressurizing the body at a pressure of 1.5 cal.The molded body is placed in a porcelain (alumina) pod and placed in an inert atmosphere (
Sintering is performed in argon gas) at a temperature of 1150 to 1400°C (preferably 1250 to 1350°C) for 0.5 to 10 hours.

Note that the rate of temperature rise and fall during heating and cooling is 5 oocA or less and 200° C./h is appropriate from the viewpoint of stabilizing properties and productivity. Further, the sintering atmosphere is not limited to an inert atmosphere, and may be a vacuum or a reducing atmosphere (hydrogen gas).

Finally, the above-mentioned sintered body was placed in air at a temperature of 95 to 11
When the oxidation treatment is performed at a temperature of 50° C. for 0.5 to 10 hours, a desired temperature-sensitive resistance element is completed.

Note that the rate of temperature rise and fall during the oxidation treatment is 300° C./h or less, as in the case of sintering. Further, the atmosphere for the oxidation treatment is not limited to air, but may be oxygen-rich air or an oxidizing atmosphere such as oxygen.

The temperature-sensitive resistance element (diameter 3
0 m/m, thickness 10 m/m), to avoid affecting the RT characteristics of the element (In-Ga).
Figure 1 shows a comparison of the RT% properties measured by brush-coating the alloy powder paste to form electrodes and the conventional one. In other words, in Figure 1, the horizontal axis shows the temperature T (°C),
The vertical axis shows the molded body of powder of barium titanate, which is sintered in air at a temperature of 1250°C for 1 hour, and the curve B shows the molded body of barium titanate powder. 1 at a temperature of 1250°C in argon gas.
Something that took a long time to sinter, -! The curve y indicates that a barium titanate powder compact is sintered in argon gas at a temperature of 1250°C for 1 hour, and this sintered body is sintered in air at a temperature of 1050°C for 1 hour. Curve C shows the RT characteristics of a molded body of a mixed powder of barium titanate and copper in an argon gas at a temperature of 1250°C.

Therefore, it can be seen that the specific resistance of the temperature-sensitive resistance element according to the present invention at room temperature is about 4Ω·α, which is about 1/25 of that of the conventional one.

Further, in the temperature-sensitive resistance element according to the present invention, when the addition (containment) ratio (wt%) of copper to barium titanate is changed, the specific resistance Ro (Ω・Crn) at room temperature and the specific resistance RO at room temperature are Ratio Rt/R of specific resistance Rt (Ω・m) at temperature (240°C).

are as shown in FIG. 2(a) and FIG. 2(to), respectively.

Therefore, the content of copper for barium titanate is
It has been found that 0.5-35% by weight, preferably 5-25% by weight gives good results.

Furthermore, the temperature-sensitive resistance element according to the present invention has a specific resistance Ro (
Rt/R
o are now shown in Fig. 3(a) o and Fig. 3(to), respectively.

Therefore, it can be seen that the oxidation treatment temperature is preferably in the range of 950 to 1150°C. It should be noted that the reason why the specific resistance R○ at room temperature suddenly increases when the temperature exceeds 1150°C is due to the oxidation of copper.

In addition, the sintering temperature T (℃) of the compact and the density f' (
The relationship with g/+:4> is as shown in FIG.

Therefore, it can be seen that the sintering temperature is preferably in the range of 1250 to 1350°C, and the product can be made more compact.

The mechanical strength of the temperature-sensitive resistance element is improved because the copper contained in the proportion mentioned above acts as a binder that binds the barium titanate particles, and the heat dissipation efficiency is improved by improving the thermal conductivity of the element itself. This seems to be due to the increase in

As described above, since the present invention is a temperature-sensitive resistance element made by oxidizing a sintered body of barium titanate containing 0.5 to 35% copper, it is more stable at room temperature than conventional ones. The specific resistance can be greatly reduced, the mechanical strength can be improved, and the effects such as being able to be used as a current limiting element for electric power are reduced.

[Brief explanation of drawings]

Fig. 1 is an RT characteristic diagram comparing the temperature-sensitive resistance element according to the present invention with a conventional one, Fig. 2 (a) and Fig. 2 (to).
3(a) and 3(a) are characteristic diagrams showing the specific resistance at room temperature and the ratio of specific resistance at a given temperature to the specific resistance at room temperature when the content ratio of copper to barium titanate is changed, respectively. ) are characteristic diagrams showing the specific resistance at room temperature and the ratio of specific resistance at a predetermined temperature to the specific resistance at room temperature when the oxidation treatment temperature is changed, respectively. Figure 4 shows the relationship between the sintering temperature and the density of the element. T('C) 0 10 20 30 40 W(kai%) W(weight%) 900 1000 ++00 1200T("
C) 900 1000 +100 1200Figure 4

Claims (1)

[Claims] A temperature-sensitive resistance element formed by oxidizing a sintered body of barium titanate containing 0.5 to 35% by weight of copper.