JPH09162007A - Manufacturing method of positive temperature coefficient thermistor - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] In a method of manufacturing a positive temperature coefficient thermistor used for a hot air heater, a switching element of a degaussing circuit of a television receiver, or the like, there is one that has a small variation in resistance value and an excellent step-up pressure resistance characteristic. An obtained manufacturing method is provided. SOLUTION: By using Ba ₄ Y ₂ O ₇ as a raw material of yttrium added as a semiconducting element, a positive temperature coefficient thermistor in which grain growth during sintering is uniformly advanced and the distribution of yttrium atoms is uniform. can get.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive temperature coefficient thermistor used in a self-temperature control heating element such as a warm air heater or a switching element of a degaussing circuit of a television receiver, the resistance value of which increases rapidly at a specific temperature. Manufacturing method.

[0002]

2. Description of the Related Art A method of manufacturing a conventional PTC thermistor will be described below. Conventional PTC thermistor porcelain
Barium carbonate and titanium oxide, which are the main raw materials, and lead oxide, yttrium oxide, aluminum oxide, silicon oxide, and the like, which are additives, are weighed and mixed, and calcined, crushed, granulated,
It was produced by a method of firing in the air after molding.

This manufacturing method will be described in more detail. First, barium titanate, which is the main component, is formed by a solid-phase reaction from barium carbonate and titanium oxide by mixing raw materials and calcining. At this time, lead oxide is added as a shift agent for moving the temperature at which the resistance value rapidly increases to a temperature higher than 120 ° C. Aluminum oxide and silicon oxide are added in small amounts as a role of a mineralizing agent for improving sinterability and as a raw material having an effect of suppressing grain growth.
Further, yttrium oxide is added in a trace amount as a semiconductor element. Mixing is carried out by a wet method in order to disperse these uniformly. After obtaining barium titanate by calcination, pulverization, granulation, and molding are performed by a general porcelain manufacturing method,
The desired positive temperature coefficient thermistor porcelain is obtained by firing in air.

[0004]

However, in the above-mentioned conventional manufacturing method, since the addition amount of yttrium oxide, which is a semiconducting element, is extremely small, it is difficult to uniformly disperse the yttrium oxide at the time of mixing, and it is difficult at the time of molding. Also, a non-uniform distribution of yttrium atoms occurs, which hinders uniform grain growth during sintering. Generally, it is said that the progress of semiconducting progresses at the same time as the grain growth.
There is a problem that the particle diameters vary and the variation in the room temperature resistance value becomes very large.

The present invention solves the above-mentioned problems of the prior art, and enables the grain growth of the positive temperature coefficient thermistor to proceed uniformly, reduces variations in the room temperature resistance value, and improves the boost withstand voltage characteristic. It is an object of the present invention to provide a manufacturing method capable of obtaining a positive temperature coefficient thermistor.

[0006]

In order to achieve this object, the method for producing a positive temperature coefficient thermistor according to the present invention uses Ba ₄ Y ₂ O ₇ as a raw material for yttrium used as a semiconductor element.
Is used.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As in claim 1 of the present invention, Ba ₄
By using Y ₂ O ₇ , even if the distribution of yttrium atoms inside the compact becomes non-uniform, grain growth during sintering can be progressed uniformly, variation in room temperature resistance can be reduced, and It is possible to improve the step-up breakdown voltage characteristic.

[0008]

An embodiment of the present invention will be described below.

Compositional formula of positive temperature coefficient thermistor Ba _0.8 Pb
_{0.2 TiO 3 -xBa 4 Y 2 O} 7 -0.02SiO 2 -0.0
In 01Al ₂ O ₃ -0.003MnO ₂ (where x is 0 <x ≦ 0.002 in the number of moles), positive temperature coefficient thermistor porcelains in which x was variously changed were prepared as follows. First, barium carbonate, lead oxide, titanium oxide, barium yttrium oxide, silicon oxide, aluminum oxide and manganese dioxide were weighed out so as to have a predetermined composition, and they were mixed, then calcined and pulverized. Further, it was formed into a desired shape and fired in the atmosphere at a maximum temperature of 1400 ° C. to obtain a disk-shaped positive temperature coefficient thermistor having a diameter of 13 mm and a thickness of 2.5 mm. An electrode was formed by fusing metallic aluminum to this, and used as a sample for measurement.

As a conventional example, B in the above composition formula
A sample in which a ₄ Y ₂ O ₇ was not used (when Y ₂ O ₃ was used) was also prepared, and the same measurement as this example was performed. In addition, when x exceeds 0.002, the room temperature resistance value becomes so large that it becomes unsuitable as a positive temperature coefficient thermistor, so it was excluded. Table 1 shows the measurement results of the variation in room temperature resistance value and the boost withstand voltage of the samples of the present example and the conventional example.

[0011]

[Table 1]

In Table 1, No. is the sample number, x
Is the x value in the above composition formula, and R ₂₅ is 50 for each sample.
The average value of the room temperature resistance value, the variation is the ratio of the standard deviation σ _n-1 and R ₂₅ of the room temperature resistance value, σ _n-1 / R ₂₅ is shown in percentage, and the step-up withstand voltage is in 20 V steps. 3 for the sample
The voltage value is shown as the voltage value at which the sample is destroyed by gradually increasing the voltage while applying it for 0 seconds. Further, sample numbers (1 to 8) are according to the present invention, and (9 to 16) are conventional examples.

As is clear from (Table 1), the positive temperature coefficient thermistor according to the present embodiment has an excellent effect that the variation in the room temperature resistance value is small and the boost withstand voltage characteristic is excellent.

[0014]

As described above, according to the present invention, by using Ba ₄ Y ₂ O ₇ as a raw material to which yttrium is added, in a method of manufacturing a positive temperature coefficient thermistor using barium titanate as a main component and yttrium as a semiconductor element. Thus, a positive temperature coefficient thermistor porcelain having a small variation in room temperature resistance value and an excellent step-up breakdown voltage characteristic can be obtained.

Claims (1)

[Claims] 1. A method for producing a positive temperature coefficient thermistor comprising barium titanate as a main component and yttrium as a semiconductor element, wherein B is used as a raw material for the yttrium.
A method of manufacturing a positive temperature coefficient thermistor, which comprises using a ₄ Y ₂ O ₇ .