JPH03246902A - Manufacture of positive temperature coefficient thermistor - Google Patents

Abstract

PURPOSE:To easily manufacture a thermistor which has different Curie points in one part of a magnetic element body and in the other part and is free from cracks and the like, by baking a molded body of calcined powder of BaTiO3 based porcelain in an atmosphere containing the shifter element of Curie point. CONSTITUTION:In the manufacturing method of a planar PTC thermistor which has different Curie points in one part of a magnetic element body constituting a planar part and the other part, a molded body of calcined powder of BaTiO3 based porcelain is baked in an atmosphere of Pb or the like as the shifter of Curie point; or a molded body of BaTiO3 based porcelain or a molded body of the calcined powder is baked in an atmosphere of halogen gas such as F and Cl which decrease the resistance value. By this constitution, each component in the atmosphere is subjected to vapor phase diffusion and permeates from the surface of the molded body. Hence the surface layer part and the central part of an obtained PTC thermister have different characteristics, so that a degauss element part and a heater element part are formed in a magnetic ele ment body.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a PTC thermistor, and more particularly to a method of manufacturing a PTC thermistor used for controlling a demagnetizing current.

Conventionally, this type of PTC thermistor has been used as a demagnetizing element for controlling a demagnetizing current, and FIG. A cross-sectional view of a demagnetizing element 30 is shown.

In the demagnetizing element 30, 31 is a first PTC thermistor, electrodes 32a and 32b are formed on both sides of the first PTC thermistor, and the Curie point is set at 50°C. P
A second PTC thermistor 33 is arranged in parallel on the side of the TC thermistor 31, electrodes 34a and 34b are formed on both sides of the second PTC thermistor 33, and the Curie point is 12.
It is set to 0°C. Then, the opposing electrode surfaces 3
A lead terminal 35 is interposed between 2b and 34a and fixed with solder 38. In addition, PTC thermistor 31
A lead terminal 36 is fixed to another electrode surface 32a of the PTC thermistor 33, and a lead terminal 37 is fixed to another electrode surface 34b of the PTC thermistor 33 by solder 38. The outer peripheries of these two PTC thermistors 31 and 33 are covered with an insulating resin 39.

FIG. 8 is a circuit diagram showing an example of the use of the degaussing element having the above structure.

In the figure, reference numeral 40 denotes a PTC thermistor for degaussing, which is connected in series with a degaussing coil 41 wound around a cathode ray tube in a color television receiver.
The thermistor 42 is coupled (hereinafter referred to as "thermally coupled") so that heat transfer occurs between the two.

PTC thermistors are usually composed of semiconductor ceramics mainly composed of BaTiOs, and have a characteristic that their resistance is low up to a certain temperature (Curie point), and the resistance increases rapidly at temperatures above the Curie point8. Therefore, when voltage is applied to this PTC thermistor, a large current flows because the resistance is low at first, and as a result, the PTC thermistor
The thermistor itself generates heat and its temperature rises. When this temperature rise reaches the Curie point, the resistance increases rapidly, the current decreases, and the amount of heat generated decreases, so the PT
The C thermistor reaches thermal equilibrium and becomes stable.

That is, when an alternating current voltage is applied to the degaussing coil 41 in FIG. 8, a large current flows through the degaussing coil 41 because the resistance is initially low, and a large alternating magnetic field is generated. Moreover, the demagnetizing PTC thermistor 40 itself generates heat by itself due to this large current flowing into it, and its temperature rises. When this temperature rise reaches the Curie point, the resistance increases rapidly and the flowing current decreases, and the magnetic field generated in the demagnetizing coil 41 also decreases accordingly, and demagnetization is performed.

Further, in synchronization with this, a voltage is also applied to the heater PTC thermistor 42, and the heater PTC thermistor 42 itself generates heat. The heat generated by the heater PTC thermistor 42 is transmitted to the demagnetizing PTC thermistor 40, which promotes an increase in the thermal equilibrium temperature of the demagnetizing PTC thermistor 40, thereby increasing its resistance value further. Therefore, the current flow in the demagnetizing PTC thermistor 40 in the thermal equilibrium state is reduced, and the magnetic field in the stable state becomes smaller, promoting demagnetization.

As described above, the method for manufacturing the degaussing element 30, which is composed of two PTC thermistors 31 and 33 for degaussing (degaussing element part) and for heater (heater element part), is conventional in that a molded body for forming a demagnetizing element part and a heater are used. The molded body for forming the element part was fired separately and then thermally bonded. In addition, as another manufacturing method, a method has been attempted in which the molded body for forming the demagnetizing element part and the molded body for forming the heater element part are combined, integrally molded, and fired at the same time.This method requires fewer steps ( However, in the configuration of the conventional degaussing element 30 described above, one degaussing element 30 has two elements, one for degaussing and one for heater. P
Since the TC thermistors 31 and 33 are required, the shape of the degaussing element 30 becomes large, which not only takes up space when installed (but also increases cost).

Furthermore, in the conventional manufacturing method of the demagnetizing element 30, the molded body for forming the demagnetizing element part and the molded body for forming the heater element part are fired separately and then thermally combined, which reduces the number of steps in the manufacturing process. The problem was that it took too much time and effort.

On the other hand, after combining the above-mentioned image molded bodies and molding them into one,
In the simultaneous firing method, since the component compositions of the image molded bodies are different, the optimum firing conditions and shrinkage rates are different for each molded body, which causes cracks to occur, and simultaneous firing is difficult in practice. there were.

Furthermore, the characteristics of the BaTiO3-based PTC thermistor vary greatly depending on the firing conditions. In particular, additives having a low melting point (such as Pb) scatter during firing, causing a compositional deviation between the surface and the inside of the PTC thermistor. In this way, Pb, which is also a shifter of the Curie point,
There was a problem in that the original characteristics of the PTC thermistor would change due to the scattering of the particles.

The present invention was invented in view of the above-mentioned problems, and
It is an object of the present invention to provide an efficient manufacturing method for a PTC thermistor that has a degaussing function and a heater function in one PTC thermistor and is miniaturized.

In order to achieve the above-mentioned objects, the method for manufacturing a PTC cermisk according to the present invention comprises a flat plate shape in which one part of the porcelain body constituting the flat part and the other parts have different Curie points. A method for manufacturing a PTC thermistor, characterized in that a molded body of calcined powder of Ba Ti 03-based porcelain is fired in an atmosphere containing a shifter element at the Curie point, and a part of the porcelain body constituting the flat plate part. A method for producing a flat plate-shaped PTC zamister in which the resistivity of the PTC zamister and other parts are different, characterized by firing a molded body of BaTiO-based porcelain or a molded body of calcined powder in an atmosphere of halogen gas. It is said that

In the manufacturing method of the above-mentioned 1-C thermistor, Ba
Either the molded body of the calcined powder of the Ti 03 series G main device is fired in an atmosphere such as PB which is a shifter of the Cunot point, or the molded body of the BaTtO3 type porcelain or the molded body of the calcined powder is reduced in resistance value. By firing in a halogen gas atmosphere at a temperature of 0.degree. F., 0.degree. C., etc., each component in the atmosphere diffuses in a vapor phase and permeates through the surface of the molded article. Therefore, in the surface layer and center of the obtained PTC thermistor, P
The properties as a TC thermistor are different,
The demagnetizing element part and the heat element part are formed in one ceramic body. That is, a PTC thermistor with excellent characteristics can be obtained by reversely utilizing the compositional deviation phenomenon of PTC thermistors, which has been a problem in the past.

Among the elements to be diffused in the gas phase, compounds such as Pb, Sr, Zr, and Ca, which are Gury's shifters, are generally difficult to vaporize. It is preferable to use compounds such as chlorides of Sr, Zr, Ca, etc.

In addition, the Curie point shifter is solidified within the grains of BaTiOa porcelain and has the function of moving the Curie point.
It is necessary to diffuse and solidify the shifter within the grains of B a TiOa-based porcelain. For this reason, it is necessary to carry out vapor phase diffusion of these Curie point shifters into a molded body of BaTiOs-based porcelain in the form of calcined powder. On the other hand, halogen elements such as F and C2, which lower specific resistance, segregate at grain boundaries and have the effect of lowering resistance. It suffices to diffuse these halogen elements into the grain boundaries of the system porcelain, and the vapor phase diffusion of these halogen elements is B a
The process may be performed on a molded body of T i 03 series porcelain.

In this way, by selecting the manufacturing method depending on the type of element that causes the vapor phase diffusion effect, the above effect can be fully exhibited.

By the way, when firing is performed by vapor-phase diffusion of the above-mentioned elements, it is necessary to consider the shape of the BaT103-based porcelain molded body or the calcined powder molded body (sample molded body).

For example, a disk-shaped P as shown in Fig. 4(a')
When trying to create a porcelain body for TC thermistor,
When the specimens formed in the shape of a disk from the beginning are stacked and fired, diffusive elements such as PB enter through the gaps between the specimen moldings by gas phase diffusion, and the electrodes on the center side of the specimen moldings enter. These elements penetrate into the constituent surfaces. Therefore, in order to form the central electrode on the surface of the obtained porcelain body as shown in Section 4 (b), it is necessary to polish the surface.

Therefore, by first firing a sample molded body formed into a cylindrical shape in an atmosphere of a gas-phase diffusion element, and then cutting it into a disk shape, the P can be obtained without going through the process of surface polishing.
A 6R element body for a TC thermistor is created.

In the porcelain body obtained in this way, the outer peripheral part where the element is diffused in vapor phase is used for the heater, and the central part is used for demagnetization, so that one PTC thermistor has two functional characteristics. Demagnetization is further promoted by increasing the thermal equilibrium temperature in the demagnetizing portion and reducing the current flow in the thermal equilibrium state.

EXAMPLE An embodiment of the method for manufacturing a PTC thermistor according to the present invention will be described below with reference to the drawings. Note that components having the same functions as those of the conventional example are given the same reference numerals.

In FIG. 1, 10 is a semi-closed container that can supply the oxygen necessary for firing and also maintain the atmosphere of the vapor-phase diffusion elements (atmosphere also enters and exits).
It is composed of a plate material 11 made of magnesia and a case 12 made of magnesia (length: 40 cm, width: 40 cm, height: 10 cm). Several cylindrical sample molded bodies 13 are placed in this semi-closed container 10 to prepare for firing.

First, P, which is a shifter of the Curie point, is used as a gas phase diffusive element.
The case where b is used will be explained.

Since Pb is a compound that is in the form of an oxide and easily vaporizes, a certain amount of Pb oxide 14 is placed in the semi-closed container 10 together with the sample molded body 13 .

Then, by firing both of them at the same time, the sample molded body 13 is fired in an atmosphere of vaporized PB.

However, the amount of pb oxide 14 used is determined depending on the amount of sample molded body 13 prepared.

On the other hand, when using halogen elements such as F and Cβ that reduce specific resistance, these halogen elements are originally gaseous, so they are introduced into the semi-sealed container 10 as they are in gaseous form, and are heated in an atmosphere of halogen gas. The sample molded body 13 is fired.

Next, the cylindrical sample molded body 13 fired in the atmosphere of the vapor phase diffusion element is cut into a disk shape as shown in FIG. 4(a), and then as shown in FIG. 4(b). As described above, electrodes 21, 22, and 23 are formed on both the front and back surfaces of a disk-shaped ceramic body (hereinafter referred to as a substrate) 19. Then, connect the lead terminals 24, 25, 26 to the electrodes 22, 23, 21, respectively.
After connecting to the PTC thermistor 20, the PTC thermistor 20 was manufactured by covering with a resin layer 27 (FIG. 2).

FIG. 2 shows a cross-sectional view of the PTC thermistor 20, in which a ring-shaped electrode 21 and a circular electrode 22 are formed on one side of a disk-shaped substrate 19, and a circular electrode 22 is formed on the other side almost over the entire surface. An electrode 23 is formed. A lead terminal 26 is attached to the electrode 21, a lead terminal 24 is attached to the electrode 22,
Lead terminals 25 are connected to the electrodes 23, respectively, and the substrate 19, electrodes 21, 22, 23, and node terminals 24, 25, 26 are covered with a resin layer 27 for protection and insulation.

In the PTC thermistor 20 having the above configuration, the heater element portion 19a formed on the outer periphery of the substrate 19 and the demagnetizing element portion 19b formed at the center have different Curie points or specific resistances.

FIG. 3 shows a specific example of the dimensions of the PTC thermistor 20. The thickness T of the substrate 19 is approximately 2 mm, the diameter is approximately 22 mm, the width W of the electrode 21 is approximately 3 mm, the diameter d of the electrode 22 is approximately 14 mm, and the interval between the electrodes 21 and 22 is 1 mm. degree is ensured.

The component composition of the PTC thermistor 20 having such a configuration is as follows:
Generally, for 100 moε of the main component consisting of Ba Ti 03 and S r Ti O 3, 0.02 to 0.5 moI of D3/2O3 is used as a semiconducting agent, and a smaller amount of TiO2 and SiO2 is used as a sintering aid. One type has 0.1 to 5.0 moff, Mn as a PTC effect improver.
O is contained in a range of 0 to 1.0 moI2.

In Example 1.2 described below, the component composition of the sample molded body was as shown in Table 1 below. After producing the PTC thermistor 20 according to the above manufacturing method, the resistance-temperature characteristics of each were investigated.

Note that R1 in FIGS. 5 and 6 described below indicates the specific resistance between the lead terminals 24 and 25, and R2 indicates the specific resistance between the lead terminals 25 and 26. In addition, a comparative example was prepared in which the sample was fired in an air atmosphere.

<Example 1> Using the calcined powder ■ shown in Table 1, a cylindrical molded body 13 with a diameter of 27 mm and a height of 8 cm was created, and a semi-sealed container 1 was prepared.
10 of the molded bodies 13 and 100 g of Pb 04, which is the Pb oxide 14, were placed in
Baked for an hour. Then, the molded body 13 is cut to a thickness of about 2 mm by the above method, and electrodes are formed to form PT.
A C thermistor 20 was manufactured.

FIG. 5 shows the PTC thermistor 2 obtained in Example 1 above.
0 shows the resistance-temperature characteristics of 0. As is clear from this graph, R2 has a higher Curie point than R1. This is because the outer peripheral portion (heater element portion 19a) of the substrate 19 contains pb, which is a Curie point shifter, and is affected by intragranular diffusion of pb.

Therefore, when a degaussing circuit as shown in FIG. 8 is designed, the heater element portion 19a having a high Curie point acts like a heater on the demagnetizing element portion 19b (center portion) having a low Curie point. Therefore, the demagnetizing element portion is maintained at a higher temperature than when it exists alone, and its equilibrium point current becomes smaller, so that demagnetization is further promoted.

<Example 2> Using the calcined powder ■ shown in Table 1, a cylindrical molded body 13 with a diameter of 27 mm and a height of 8 cm was created, and a semi-sealed container 1 was prepared.
Ten of the molded bodies 13 were placed in a vacuum chamber and fired at 1320° C. for about 2 hours while introducing CCG4 gas, which is a halogen compound gas, at a flow rate of 20 mff/min. A PTC thermistor 20 was produced by cutting the cylindrical molded body 13 to a thickness of about 2 mm and forming electrodes using the above method.

FIG. 6 shows the PTC thermistor 2 obtained in Example 2 above.
0 shows the resistance-temperature characteristics of 0. As is clear from this graph, R2 has a smaller resistivity than R1. This is the outer peripheral part of the substrate 19 (heater element part 19
This is because b) contains (l) and is affected by the grain boundary diffusion of CI2.

Therefore, when a degaussing circuit as shown in FIG. 8 is designed, the heater element portion 19a having a small resistivity exerts a heater-like effect on the demagnetizing element portion 19b. Therefore, the demagnetizing element portion 19b is maintained at a higher temperature than when it exists alone, and its equilibrium point current becomes smaller, so that demagnetization is further promoted.

The results for Example 1.2 above were expressed numerically as shown in Table 2 above.

Further, as a comparative example, a molded body 13 was formed using the calcined powder (1), and the atmosphere in which the molded body 13 was fired was air.

In the method for manufacturing the second PTC thermistor 20, a molded body of calcined powder of Ba Ti 03 series porcelain is converted into a molded body of calcined powder of Ba Ti 03 series porcelain, a molded body of PB, etc., which is a Curie point shifter, a molded body of Ba Ti 03 series porcelain, or a molded body of calcined powder. By firing in an atmosphere containing halogen elements such as F and C1 that reduce resistivity, the Curie point or resistivity characteristics can be varied.

In other words, without installing two PTC thermistors, one for demagnetization and one for heater, in the PTC thermistor 20, one PTC thermistor can be used.
It becomes possible to provide the TC thermistor 20 with a demagnetizing function and a heater function without causing cracks in the ceramic substrate. And the PTC thermistor 2 manufactured in this way
0, due to the function of the heater element part 19a, the demagnetizing element part 1
The thermal equilibrium temperature at 9b can be maintained at a high temperature,
By making the equilibrium point current smaller, the demagnetizing current in the thermal equilibrium state can be efficiently controlled. Further, it is possible to achieve a compact size and to produce it at a low cost.

As described above, in the method for manufacturing a PTC thermistor according to the present invention, the number of steps in the manufacturing process is reduced compared to the conventional manufacturing method in which two PTC thermistors are installed, making it possible to simplify the work and reduce costs. You can try to bring it down.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be modified without departing from the spirit of the invention. for example,
When adjusting the atmosphere using a vapor phase diffusion element during firing, it is desirable to consider and use various diffusion concentrations depending on the desired PTC characteristics or the type of diffusion element.

older brother! L and Hiroshi As is clear from the above explanation, in the method for manufacturing a flat PTC thermistor according to the present invention, BaTi
By firing a molded body of calcined powder of 03 series porcelain in an atmosphere containing a shifter element with a Cunot point, one part of the porcelain body constituting the flat plate part and the other parts have different Curie points. A PTC thermistor can be easily manufactured without causing cracks or the like in the ceramic body.

In addition, by firing a molded body of BaTiOz-based porcelain or a molded body of calcined powder in an atmosphere of a halogen element,
A PTC thermistor having different specific resistances in one part and other parts of the porcelain body constituting the flat plate portion can be easily manufactured without causing cracks or the like in the porcelain body.

Therefore, in the PTC thermistor manufactured by the above method, it is possible to provide a degaussing function and a heater function in one PTC thermistor without installing two PTC thermistors, one for degaussing and one for heater. can. The function of the heater element allows the thermal equilibrium temperature in the demagnetizing element to be maintained at a high temperature, and by making the equilibrium point current smaller, the demagnetizing current in the thermal equilibrium state can be efficiently controlled, making demagnetization more effective. It can be promoted.

In addition, it is possible to manufacture a PTC thermistor that is compact in shape and at a low cost.

As described above, by using the method for manufacturing a PTC thermistor according to the present invention, one PTC thermistor can have multiple functions, while reducing the number of steps in the manufacturing process and simplifying the work compared to the conventional manufacturing method. It is possible to aim for
Moreover, cost reduction can be achieved.

[Brief explanation of drawings]

FIG. 1 is a perspective view for explaining the method of manufacturing a PTC thermistor according to the present invention, FIG. 2 is a sectional view showing an example of a PTC thermistor manufactured by the method according to the present invention, and FIG.
4 is a sectional view showing an example of dimensions of a manufactured PTC thermistor, FIG. 4 is a perspective view for explaining the method of manufacturing a PTC thermistor according to the present invention, and FIG. A graph showing the resistance-temperature characteristics of a PTC thermistor manufactured by the method according to the present invention, FIG. 7 is a sectional view showing a conventional demagnetizing element, and FIG. 8 is a circuit diagram using the demagnetizing element. 13 ... BaTiO3 ceramic molded body or calcined powder molded body 14 ... Pb oxide (Curie point shifter element compound) 0 ... PTC Samista patent applicant Agent Sumitomo Metal Industries, Ltd. Person Patent Attorney Bennai Ryuji Diagram (a)

Claims (2)

[Claims] (1) A positive characteristic of a flat plate in which one part of the porcelain body constituting the flat part and the other parts have different Curie points (hereinafter referred to as PTC).
) In the method for manufacturing a thermistor, BaTiO_
A method for producing a PTC thermistor, which comprises firing a molded body of calcined powder of type 3 porcelain in an atmosphere containing a shifter element at the Curie point. (2) In the manufacturing method of a flat PTC thermistor in which one part of the porcelain body constituting the flat plate part and the other parts have different resistivities, a molded body of BaTiO_3-based porcelain or a molded body of calcined powder is treated with halogen. A method for manufacturing a PTC thermistor, characterized by firing in a gas atmosphere.