JPH05152103A - Manufacture of thermistor element - Google Patents

Abstract

PURPOSE:To obtain a thermistor element with a high allowable current value and a high selective degree of freedom of a resistance value. CONSTITUTION:Paste for forming a porous layer into which sintering components are mixed is applied onto one plane of each ceramic green sheet to form a specific pattern. The ceramic green sheets are laminated so that an end part on the extending side of each specific pattern can be arranged in a location opposing alternately. Further, a thermistor element is manufactured, containing a process of forming a laminated body in which an end surface of an end part on the extending side is exposed on a different side surface, and a process of forming an internal electrode 6 within a specific pattern which has become porous after a sintered body 4 obtained by sintering this laminated body is abruptly cooled and of forming an external electrode 7 on each side surface of the sintered body 4 in which each end surface of these internal electrodes 6 has been exposed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thermistor element characterized in that its electric resistance changes rapidly at a certain temperature.

[0002]

2. Description of the Related Art Among the thermistor elements (CTRs) currently in practical use, those having a basic composition of VO ₂ have a temperature-resistance characteristic in which the electric resistance sharply decreases due to a temperature rise in a certain temperature range, so-called. It has a negative thermistor characteristic, and this characteristic is obtained by the transition of the crystal structure of VO ₂ between semiconductor and metal at around 70 ° C. Further, this thermistor element is composed of B, Si, P, Mg, Ca, and V ₂ O ₅ which are basic materials.
One or two kinds of oxides such as Sr, Ba, La and Pb are added and mixed, and the resulting mixture is mixed with 800
After heat treatment in a reducing atmosphere of about 900 ° C. and crushing and forming into a so-called bead type, 1
It is generally manufactured by firing in a reducing atmosphere of about 000 ° C. and then quenching.

[0003]

By the way, it is known that the thermistor characteristics in such a thermistor element largely depend on the manufacturing process, and in order to obtain good thermistor characteristics, fine manufacturing conditions are set from the beginning. You need to do it. In particular, the quenching process after firing is
Similar to the heat treatment in a reducing atmosphere, it has the greatest effect on the thermistor characteristics, and in order to obtain good thermistor characteristics, it is necessary to perform quenching treatment from a temperature range of 900 ° C or higher.

Therefore, it becomes difficult to obtain good thermistor characteristics with a large-sized thermistor element such as a disk type which is difficult to perform homogeneous quenching. Therefore, at present, a small type called a bead type or a thin film type is used. The thermistor element is used as a product in the mainstream. However, in these small thermistor elements,
Not only is the allowable current value limited to several tens of mA or less, but the degree of freedom in selecting the resistance value in the operating temperature range becomes low, so it is possible to sufficiently meet a wide range of demands such as applications as an inrush current suppressing element. It was the current situation that I could not.

The present invention was devised in view of such inconvenience, and an object thereof is to provide a method for manufacturing a thermistor element having a high allowable current value and a high degree of freedom in selecting a resistance value. ..

[0006]

In order to achieve such an object, the method for manufacturing a thermistor element according to the present invention is made of carbon (carbon) or the like on one surface of each of the ceramic green sheets having thermistor characteristics. The process of applying a porous layer-forming paste mixed with burned components and forming a predetermined pattern that extends to one end of each ceramic green sheet, and the extension side end of each predetermined pattern alternate Stacking the respective ceramic green sheets so as to be arranged at positions facing each other, and forming a laminated body in which the end faces of the extension side end portions of the respective predetermined patterns are exposed on different side faces, and this laminated body is formed. After quenching the fired body obtained by firing, internal electrodes are formed in a predetermined pattern having a porous shape, and each of these internal electrodes is formed. In which the end face of which is characterized in that a step of forming an external electrode on each side surface of the sintered body was exposed.

[0007]

In the above method, when the ceramic green sheet laminate is fired, the burned component in the porous layer forming paste applied on each ceramic green sheet is lost. Each of the predetermined patterns is left as a porous passage inside the fired body. Therefore, the inside of this fired body has the same structure as being thinly divided by the thickness corresponding to the ceramic green sheet through each of the porous passages. Even when the outer shape is larger than that of the disk type in the conventional example, it is effectively and uniformly performed through the porous passage.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method of the present invention will be described below with reference to the drawings.

1 to 3 show the manufacturing procedure of the thermistor element according to this embodiment. FIG. 1 is a perspective view showing a disassembled state of a laminated body constituting the thermistor element, and FIG. 2 is an internal structure of the laminated body. Is a sectional view showing the internal structure of the fired body, and FIG. 4 is a sectional view showing the internal structure of the completed thermistor element.

First, V ₂ O ₅ which is a basic material, P ₂ O ₅ and BaO as oxides to be added thereto are prepared, and these are weighed in a required amount and uniformly mixed, and the obtained mixture is obtained. After making it into a glass by heating and melting,
This is heat-treated in a reducing atmosphere and then pulverized to prepare a raw material powder. Then, after adding a vinyl acetate binder, a dispersant and a plasticizer to this raw material powder, a ceramic green sheet having thermistor characteristics is formed by the doctor blade method, and this is cut to obtain a rectangular 50 mm × 30 mm rectangle. A plurality of shaped ceramic green sheets 1 are formed. At this time, a paste for forming a porous layer is formed by adding a burn-out component such as carbon to the raw material powder and mixing them. Then, a paste for forming a porous layer is applied (printed) onto one surface of each of the ceramic green sheets 1, and as shown in FIG. 1, a predetermined pattern 2 whose end portion extends to one end portion of each ceramic green sheet 1. To form.

Next, these ceramic green sheets 1 are laminated on each other. At this time, as shown in FIG.
After the respective ceramic green sheets 1 are laminated while the extension side end portions 2a and 2b of the respective predetermined patterns 2 are alternately arranged at the opposite positions, the extension sides of the respective predetermined patterns 2 are bonded by pressure bonding. The stacked body 3 is formed so that the end portions 2a and 2b have different end faces and are exposed on the respective side surfaces 3a and 3b. It should be noted that the ceramic green sheet 1 in a state where a predetermined pattern of the porous layer forming paste is not formed is pressure-bonded to the uppermost portion of the laminated body 3. Therefore, in this laminated body 3, as shown in FIG. 2, the end surface of the extension side end portion 2a of the one predetermined pattern 2 is on the right side surface 3a of the laminated body 3 and the other predetermined pattern 2 is extended. The end surface of the output side end 2b is exposed on the left side surface 3b.

Then, the porous layer forming paste for forming the predetermined pattern 2 is dried, and then the laminated body 3 in which a plurality of ceramic green sheets 1 are laminated is formed.
It is fired by being placed in an inert atmosphere such as N ₂ at 0 to 1000 ° C. Then, carbon and the like which are burned out components in the porous layer forming paste applied on each ceramic green sheet 1 are burned off and lost. As shown in FIG. Each of the predetermined patterns 2 is left inside the body 4 as a porous passage 5 made of only the raw material powder. That is, the fired body 4 thus obtained has the same structure as that of the fired body 4 which is thinly divided by the thickness corresponding to the original ceramic green sheet 1 through each of the passages 5 having a porous shape. There will be.

Therefore, when the fired body 4 obtained by this firing is taken out from the firing furnace and then rapidly cooled, the quenching treatment for this fired body 4 is effectively performed through the porous passage 5 having the predetermined pattern 2. And it will be done homogeneously. Therefore, even if the outer shape of the fired body 4 is larger than that of the disk type or the like in the conventional example, the quenching treatment is carried out uniformly and without any inconvenience.

Next, the fired body 4 subjected to the quenching treatment is deaerated in a vacuum, and then immersed in a metal solution prepared by melting a low melting point metal such as Sn or Pb. Then, as shown in FIG. 4, the internal electrode 6 in which the metal solution penetrates is formed in the predetermined pattern 2 which was the porous passage 5. Furthermore, the side surfaces 4a of the fired body 4 in which the respective end surfaces of the internal electrodes 6 are exposed,
When a conductive paste is applied and baked on 4b, a pair of external electrodes 7 connected to each of the internal electrodes 6 is formed on these side surfaces 4a and 4b, thus completing the thermistor element.

By the way, in FIGS. 1 to 4 according to the method of this embodiment described above, the ceramic green sheet 1 is used.
Also, although the number of ceramic layers made of these is shown small, the inventors of the present invention measured the thermistor characteristics after setting the number of ceramic layers in the thermistor element to practical 50 layers. For example, as shown in FIG. 5, the initial resistance value is about 10 ² Ω, which is 1/100 or less of that of the conventional general thermistor element. Also, the allowable current value of the thermistor element formed by the method of this embodiment is about 1 A, which is about 10 times that of the conventional thermistor element. In addition,
In FIG. 5, which shows the thermistor characteristics, the horizontal axis represents temperature ° C and the vertical axis represents electrical resistance value Ω.

[0016]

As described above, according to the method of manufacturing a thermistor element according to the present invention, the burned components in the porous layer forming paste coated on each ceramic green sheet are lost by firing the laminate. I was destroyed,
Since each of the predetermined patterns is left as a porous passage inside the fired body, the inside of the fired body is divided into thin pieces by the thickness corresponding to the ceramic green sheet through each of the porous passages. It has the same structure as Therefore, the quenching treatment for the fired body is effectively and uniformly performed through the porous passage, and it is possible to obtain extremely good thermistor characteristics even when the outer shape is large. ..

Further, in the method of the present invention, since the ceramic layers exhibiting the thermistor characteristics are multi-layered, the capacity of the thermistor element as a whole is increased and a thermistor element having a high allowable current value can be obtained. Furthermore, the initial resistance value can be set over a wide range by adjusting the size of each ceramic layer and the number of laminated layers, and the effect that it can be used as an inrush current suppressing element can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing an exploded state of a laminated body constituting a thermistor element according to the present embodiment.

FIG. 2 is a cross-sectional view showing an internal structure of a laminated body.

FIG. 3 is a cross-sectional view showing an internal structure of a fired body.

FIG. 4 is a sectional view showing an internal structure of a completed thermistor element.

FIG. 5 is an explanatory diagram showing the thermistor characteristics.

[Explanation of symbols]

 1 Ceramic Green Sheet 2 Predetermined Patterns 2a, 2b Extension Side Ends 3 Laminates 3a, 3b Sides 4 Burned Body 4a, 4b Sides 6 Internal Electrodes 7 External Electrodes

Claims (1)

[Claims] 1. A ceramic green sheet (1) having a thermistor property is coated with a porous layer-forming paste containing a burn-out component on one surface thereof and extended to one end of each ceramic green sheet (1). A step of forming the predetermined pattern (2), and extending side end portions (2a, 2) of the predetermined pattern (2)
b) are laminated so that the ceramic green sheets (1) are alternately arranged at opposite positions, and the end faces of the extension side end parts (2a, 2b) of the respective predetermined patterns (2) are different side faces (3a). , 3b) to form the exposed laminated body (3) on each of them, and the fired body (4) obtained by firing the laminated body (3) is rapidly cooled, and then has a predetermined pattern in a porous shape. (2)
A step of forming an internal electrode (6) inside and forming an external electrode (7) on each side surface (4a, 4b) of the fired body (4) in which end faces of each of the internal electrodes (6) are exposed. A method for manufacturing a thermistor element including: