JP2000286104A - Manufacture of positive temperature coefficient thermistor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain baking conditions or to easily obtain a low specific resis tance, without impairing the R-T characteristic or breakdown voltage of a positive temperature coefficient thermistor. SOLUTION: A positive temperature coefficient thermistor is manufactured, in such a way that the raw material or the thermistor is prepared by mixing raw materials with a slurry, which is prepared previously by mixing a semiconducting element with pure water. Then the raw material is calcined, and the calcined raw material is pulverized, granulated, and molded. Finally, a sintered body is obtained by baking the molded body and electrodes formed on the sintered body. Therefore, a low specific resistance of the thermistor can be made, without impairing the R-T characteristic or breakdown voltage of the thermistor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a positive temperature coefficient thermistor used as a constant temperature heating element such as a current control switching element or a hot air heater.

[0002]

2. Description of the Related Art A conventional method of manufacturing a positive temperature coefficient thermistor is as follows.
BaCO ₃ , TiO ₂ , PbO, CaCO ₃ , Y ₂ O ₃ , S
iO ₂ , Al ₂ O ₃ , Mn (NO ₃ ) _2, etc. are blended so as to have a predetermined composition, all the raw materials are mixed at the same time, the calcined material is pulverized, granulated, formed after granulation, and formed into a compact. An electrode was formed on the sintered body obtained by firing the above. Therefore, when lowering the specific resistance of the element with the same material, the desired specific resistance has been obtained by changing the firing conditions or reducing the thickness of the element.

[0003]

When a low specific resistance is obtained by changing the firing conditions such as the firing temperature, the firing time and the cooling rate by the above-mentioned conventional method, the RT characteristic (temperature characteristic of resistance value) of the device is obtained. Changed, and it was difficult to obtain a predetermined RT characteristic. Further, when the element thickness is reduced to obtain a low specific resistance, there is a problem that the withstand voltage of the element is reduced.

[0004] The present invention solves the above-mentioned problems.
An object of the present invention is to obtain a positive temperature coefficient thermistor having a low specific resistance without deteriorating the -T characteristic or withstand voltage.

[0005]

In order to achieve this object, the present invention relates to a method of mixing and mixing raw materials for a positive temperature coefficient thermistor, which comprises first mixing a semiconducting element with pure water to form a slurry, and then mixing other raw materials. Is a method of forming electrodes after calcination, pulverizing and calcining the calcined material, and thereafter sintering the molded body, thereby forming an electrode on the sintered body without impairing the RT characteristics and withstand voltage. A positive temperature coefficient thermistor having a specific resistance can be obtained. This is thought to be because the dispersibility of the semiconducting element is improved and the microscopic non-uniform distribution of the semiconducting element ions is averaged, and as a result, the solid solution is easily uniformly dissolved in the bulk of the particles and the specific resistance can be reduced. Can be

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of manufacturing a positive temperature coefficient thermistor according to claim 1 of the present invention comprises the steps of first mixing and mixing a positive temperature coefficient thermistor comprising a semiconductor element such as barium titanate and yttrium oxide. A semiconductor element is mixed with pure water to form a slurry, then mixed with other raw materials, then calcined, pulverized, granulated and formed, and the formed body is sintered to form an electrode on a sintered body. It is. As a result, the dispersibility of the semiconductor element is improved, the specific resistance can be easily reduced, and the intended purpose can be achieved without changing the firing conditions, the thickness of the element, and the like.

According to a second aspect of the present invention, there is provided a method for manufacturing a positive temperature coefficient thermistor, comprising the steps of mixing and mixing a positive temperature coefficient thermistor made of a semiconductor element such as barium titanate and yttrium oxide together with a semiconductor element. A part of other raw materials are mixed to form a slurry, then mixed with other raw materials, and calcined, pulverized, granulated, and shaped,
An electrode is formed on a sintered body obtained by firing the formed body. This makes it possible to easily lower the specific resistance without changing the firing conditions or the shape of the positive temperature coefficient thermistor using the same material.

According to a third aspect of the present invention, there is provided a method of manufacturing a positive temperature coefficient thermistor, wherein a positive temperature coefficient thermistor comprising barium titanate and yttrium oxide or the like is mixed and mixed. Mixing and drying to form a powder, then blending and mixing with other raw materials, pulverizing and calcining the calcined product, forming the product, and forming the electrode on a sintered body obtained by firing the formed product It is. This makes it possible to easily lower the specific resistance without changing the firing conditions or the shape of the positive temperature coefficient thermistor using the same material.

(Embodiment 1) An embodiment of the present invention will be described below.

Commercially available BaCO ₃ , TiO ₂ , PbO, Ca
CO ₃ , Y ₂ O ₃ , SiO ₂ , Al ₂ O ₃ , and Mn (NO ₃ ) ₂ are weighed so as to have the composition shown in Chemical Formula 1. Next, the weighed Y ₂ O ₃ was placed in a polypot, and 200 cc of pure water was added thereto.
And 200 g of zirconia balls were added and wet-mixed for 3 hours.

[0011]

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Next, raw materials other than Y ₂ O ₃ were put in a 1-liter pot, 500 cc of pure water and 600 g of zirconia balls having a diameter of 5 mm were added, and Y was mixed in a polypot.
_{The 2} O ₃ slurry was added and wet-mixed for 3 hours. Then, after calcining the mixed material at a temperature of 1100 ° C. for 2 hours,
The calcined powder was placed in a 1-liter pot, 500 cc of pure water and 600 g of zirconia balls having a diameter of 5 mm were added, wet-ground for 3 hours, and dried.

Next, 10% by weight of a 5% aqueous solution of polyvinyl alcohol was added to the obtained pulverized powder, and the mixture was granulated with a raikai machine for 5 minutes, and then passed through a 20-mesh sieve to prepare granulated powder. Thereafter, the granulated powder is formed at a pressure of 1000 kgf / cm ² , and the formed body is heated in a firing furnace at a heating rate of 250 kgf / cm ^2.
After calcination at a maximum temperature of 1250 ° C. for 2 hours, the mixture was gradually cooled to room temperature at a cooling rate of 200 ° C./hr. An aluminum electrode is sprayed on both surfaces of the obtained sintered body to produce a positive temperature coefficient thermistor. Then, the resistivity and RT characteristics at room temperature are measured, and the results are compared with the positive temperature coefficient thermistor by the conventional method ( The results are shown in Table 1).

The conventional PTC thermistor is manufactured using commercially available BaCO ₃ , TiO ₂ , PbO, CaCO ₃ , Y
₂ O ₃ , SiO ₂ , Al ₂ O ₃ , and Mn (NO ₃ ) ₂ were weighed so as to have the same composition as in the present invention, and all the raw materials were simultaneously placed in a 1-liter pot and 500 cc of pure water. And 600 g of a zirconia ball having a diameter of 5 mm were added and wet-mixed for 3 hours.

Thereafter, the mixed material is heated at a temperature of 1100 ° C. for 2 hours.
After calcining for one hour, the calcined powder is put into a 1-liter pot, and 500 cc of pure water and 600 g of zirconia balls having a diameter of 5 mm are placed.
And wet-pulverized for 3 hours, followed by drying.

Next, 10% by weight of a 5% aqueous polyvinyl alcohol solution was added to the obtained ground powder, and the mixture was granulated for 5 minutes with a raikai machine, and then passed through a 20-mesh sieve to prepare granulated powder. Thereafter, the granulated powder is formed at a pressure of 1000 kgf / cm ² , and then the formed body is heated in a firing furnace at a heating rate of 250 ° C./hr and a maximum temperature of 1250 without changing the firing conditions.
After calcination for 2 hours at a temperature of 200 ° C. and then gradually cooled to room temperature at a cooling rate of 200 ° C./hr, a conventional example is shown. Further, in the conventional example, the firing conditions were changed to lower the specific resistance, the firing was performed in a firing furnace at a heating rate of 250 ° C./hr and a maximum temperature of 1250 ° C. for 1 hour, and then gradually cooled to room temperature at a cooling rate of 250 ° C./hr. Is shown in the conventional example.

[0017]

[Table 1]

As shown in Table 1, in the conventional example, a predetermined RT characteristic could be obtained, but the specific resistance was high, and in the conventional example, a low specific resistance could be obtained. In the −T characteristic, the switching temperature (the temperature at which a resistance value twice as large as the resistance value measured at 25 ° C. is obtained) changes, and the resistance temperature coefficient (the amount of change in the resistance value with respect to temperature change) changes. It was difficult to obtain the characteristics.
On the other hand, according to the first embodiment of the present invention, the specific resistance was low, and the switching temperature and the temperature coefficient of resistance were not significantly changed from the conventional example, and the predetermined values could be obtained.

(Embodiment 2) Hereinafter, another embodiment of the present invention will be described.

As in the first embodiment, a commercially available BaCO_Three,
TiO_Two, PbO, CaCO_Three, Y_TwoO _Three, SiO_Two, Al_Two
O_Three, Mn (NO_Three)_TwoIs weighed so that it has the composition of Chemical Formula 1.
Weigh. Next, the weighed Y_TwoO_Three, SiO_Two, Al_TwoO_ThreePassing
And BaCO_Three200cc pure water
And 200 g of zirconia balls with a diameter of 5 mm
Wet mixing was performed.

Next, the remaining raw materials are placed in a 1 liter pot.
500cc of pure water and 5mm diameter zirconia ball 6
00g and further mixed in a polypot._TwoO_Three, S
iO _Two, Al_TwoO_ThreeAnd BaCO_Three3 o'clock with the slurry
Wet mixing was performed. Hereinafter, the same as Embodiment 1 of the present invention
It was produced by the method described above. Aluminum on both sides of the obtained sintered body
After producing a positive temperature coefficient thermistor by spraying the
The resistance value and the RT characteristic were measured, and the results were obtained as shown in Table 1.
This is shown in the second embodiment.

As shown in Table 1, it can be seen that the positive temperature coefficient thermistor according to the second embodiment of the present invention can have a lower specific resistance than the conventional positive temperature coefficient thermistor without changing the RT characteristics.

(Embodiment 3) Hereinafter, still another embodiment of the present invention will be described.

100 g of Y ₂ O ₃ is placed in a polypot and pure water 2
00 cc and 200 g of zirconia balls having a diameter of 5 mm were added and wet-mixed for 3 hours, followed by drying to obtain a mixed powder of Y ₂ O ₃ . Next, commercially available BaCO ₃ , TiO ₂ , PbO, CaC
A mixed powder of O ₃ , SiO ₂ , Al ₂ O ₃ , Mn (NO ₃ ) _2, and Y ₂ O ₃ is weighed so as to have a composition represented by the following chemical formula 1. Then, put these raw materials in a 1 liter pot and add 50
0 cc and 600 g of zirconia balls having a diameter of 5 mm were added and wet-mixed for 3 hours. First Embodiment of the Present Invention
It was prepared in the same manner as described above.

An aluminum electrode was sprayed on both surfaces of the obtained sintered body to produce a positive temperature coefficient thermistor, and then the room temperature resistance and the RT characteristic were measured. The results are shown in Table 1.

As shown in Table 1, the positive temperature coefficient thermistor according to the third embodiment of the present invention can have a lower specific resistance than the conventional positive temperature coefficient thermistor without significantly changing the RT characteristic. I understand.

As described above, Embodiment 1 of the present invention
According to Nos. 1 to 3, it is possible to lower the specific resistance without deteriorating the withstand voltage because the thickness of the element is not reduced, and there is no remarkable change in the RT characteristic.

Table 2 shows the results of the sedimentation test of the simulated samples according to the first to third embodiments of the present invention and the Y ₂ O ₃ of the conventional example, and evaluation of the dispersibility. First, as the embodiment sample of the present invention, to prepare a powder of Y ₂ O ₃ was pretreated drying stirring and mixing with a previously purified water then also not performed the pretreatment as a sample of the conventional example Was prepared. Next, a predetermined amount of the sample was placed in a test tube containing water, and the mixture was stirred. After standing for a predetermined time, the height of Y ₂ O ₃ precipitated at the bottom of the test tube was measured, and the height was set as the sedimentation height. Recorded. At this time, those having a low sedimentation height or those having a long sedimentation time have excellent dispersibility. Therefore, as compared with the simulated sample according to the embodiment of the present invention, the average particle diameter of Y ₂ O ₃ is almost the same in the conventional example, but the sedimentation height is lower in the simulated sample according to the embodiment of the present invention. It is considered that the dispersibility was improved without changing the particle size of Y ₂ O ₃ , and it was considered that a low specific resistance could be obtained without impairing the RT characteristics by improving the dispersibility.

[0029]

[Table 2]

In the embodiment of the present invention, the semiconductor element is Y ₂ O ₃ , but the same effect can be obtained with other semiconductor elements such as Nb and La.

[0031]

As described above, according to the present invention, when compounding and mixing a positive temperature coefficient thermistor, first, a semiconductor element is mixed to form a slurry or powder, and then, when other raw materials are mixed and mixed, By adding the compound, a positive temperature coefficient thermistor having a low specific resistance can be obtained without impairing the RT characteristic and the withstand voltage, and the specific resistance can be easily reduced without changing the shape such as the firing conditions and the thickness of the element. It becomes possible.

Claims (3)

[Claims] 1. In a compounding / mixing step of a positive temperature coefficient thermistor composed of a semiconducting element such as barium titanate and yttrium oxide, first, a semiconducting element is mixed with pure water to form a slurry, and then mixed with other raw materials. A method for producing a positive temperature coefficient thermistor in which a mixture is calcined, pulverized, granulated, molded, and then sintered to form an electrode on a sintered body. 2. In a compounding / mixing step of a positive temperature coefficient thermistor composed of a semiconducting element such as barium titanate and yttrium oxide, first, a part of other raw materials are mixed together with the semiconducting element to form a slurry, A method for producing a positive temperature coefficient thermistor in which a mixture is mixed with other raw materials, calcined, pulverized, granulated, and molded, and an electrode is formed on a sintered body obtained by calcining the molded body. 3. In a compounding / mixing step of a positive temperature coefficient thermistor made of a semiconducting element such as barium titanate and yttrium oxide, the semiconducting element is first mixed, dried to form a powder, and then the other elements are mixed. Combined with raw materials
A method for producing a positive temperature coefficient thermistor in which a mixture is calcined, pulverized, granulated, molded, and then sintered to form an electrode on a sintered body.