JPH0851004A - Chip thermister - Google Patents

Abstract

PURPOSE:To obtain a ceramic thermister in which the interlayer exfoliation, i.e., delamination, is prevented while sustaining a low resistance for B constant inherent to the material of thermister and thereby sustaining a large area for a pair of inner electrodes. CONSTITUTION:A green sheet 12 principally comprising a ceramic and provided with a conductor layer for forming one 13 of a pair of inner electrodes is laminated alternately with a green sheet 15 provided with a conductor layer for forming the other 14 of the pair of inner electrodes to obtain a chip ceramic thermister where the pair of inner electrodes are formed alternately on the opposite sides of the green sheet 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermistor which utilizes a resistance change of a semiconductor due to a temperature change, and more particularly to a chip type ceramic thermistor mainly composed of a semiconductor ceramic.

[0002]

2. Description of the Related Art Thermistors are widely used for temperature compensation of electronic equipment, current control, temperature detection and the like.

In recent years, the degree of integration of electronic parts has further increased,
There is a demand for small parts that can be surface-mounted. Thermistors, like other electronic components such as resistors, capacitors, and inductors, are becoming chips for surface mounting.

Most of the thermistors formed into chips have a prismatic shape or a rectangular plate shape as in the case of a multilayer ceramic chip capacitor, and external electrodes serving as terminals for connection are respectively provided on both end faces of these. It is provided.

A more recent chip-type thermistor has an internal structure, as shown in FIG.
It has been announced that it has the same structure as a capacitor.

Here, the monolithic ceramic electronic component means that a conductor layer is formed on a green sheet containing ceramic as a main component, and the green sheets are laminated, pressure-bonded, and fired to form an electronic component in the ceramic body. The device and the electronic circuit are configured. The green sheet refers to a flexible green ceramic sheet obtained by molding a suspension obtained by adding a solvent, a binder, a plasticizer, etc., mainly to alumina powder, and drying the suspension.

Here, FIG. 2 will be briefly described. FIG. 2 is a sectional end view showing a conventional example of a chip-type ceramic thermistor. In FIG. 2, (a) is a sectional end view of the first conventional example viewed from above. FIG. 1B is a sectional end view of the first conventional example seen from the front, and FIG. 7C is a sectional end view of the second conventional example seen from the front.

The cross-sectional end view of FIG. 2 (c) seen from the plane is the same as that of FIG. 2 (a), and is not shown.

Reference numeral 21 in FIG. 2 is a rectangular plate-shaped laminated ceramic body which constitutes a thermistor.
For example, a conductor layer to be a pair of internal electrodes 23, 24 is formed on substantially the entire end portions of both upper surfaces of a slightly thick green sheet 22, respectively, and another slightly slightly thicker surface is formed on the upper surface of the green sheet 22. It is manufactured by stacking thick green sheets 25.

Reference numeral 26 in FIG. 2 is a rectangular box-shaped laminated ceramic body which is another conventional example.
For example, three green sheets 22 having conductor layers for the internal electrodes 23 and 24 that are paired on the left and right on the same plane are stacked, and three layers are stacked on the top surface of the uppermost green sheet 22.
It is manufactured by stacking another green sheet 25.

Therefore, the conductor layers forming the pair of internal electrodes 23, 24 are formed on almost both ends of the green sheet 22 except for the center of the upper surface thereof, and the resistance for a predetermined B constant is obtained. It was decided that the resistance would be lowered. The constant B is used in the relational expression between the resistance value and the temperature, which expresses the characteristics of the thermistor, and is specific to the material of the thermistor.

However, in these conventional examples, a pair of internal electrodes 23,
Since the conductor layer 24 is coated, the coating area becomes large, and as a result, the laminated ceramic body 21 or 26, which is the base material of the ceramic thermistor, is delaminated, that is, delaminated. ) There was a drawback that defects were likely to occur.

[0013]

As described above, if the area of the pair of internal electrodes is increased to reduce the resistance value with respect to a predetermined B constant, delamination, which is delamination, is likely to occur. There was a problem.

The present invention is unique to B thermistor materials.
It was developed for the purpose of providing a ceramic thermistor which lowers the resistance value with respect to a constant and at the same time does not cause delamination failure.

In other words, the present invention was developed for the purpose of increasing the area of the pair of internal electrodes and preventing the delamination of the ceramic thermistor.

[0016]

A ceramic thermistor of the present invention is a chip-type ceramic thermistor produced by laminating green sheets whose main component is ceramic, and is a conductor which becomes one internal electrode of a pair. The green sheets on which the layers are formed and the green sheets on which the conductor layers to be the other internal electrodes of the pair are formed are laminated alternately, and the internal electrodes forming the pairs are the same in the green sheet laminate. It is characterized in that the layers are formed so as to be offset from each other by at least one layer.

That is, according to the present invention, first, external electrodes serving as connection terminals are provided on a pair of opposed vertical end faces of a prism or a rectangular plate-shaped ceramic body, and one end is connected to each of the left and right external electrodes. A chip thermistor having a pair of left and right inner electrode conductor layers that horizontally extend to the position where the other end does not reach the center toward the center of the body. Secondly, a chip thermistor, characterized in that the layers are arranged in different shelves on different planes parallel to each other, secondly, is connected to a pair of opposed vertical end faces of a prismatic or rectangular plate-shaped ceramic body, respectively. It has an external electrode that serves as a terminal, one end is connected to each of the left and right external electrodes, and the other end extends horizontally toward the center of the body to a position where it does not reach the center. A chip thermistor having several pairs of internal electrode conductor layers, characterized in that the conductor layers of each pair are arranged in different shelves on different planes parallel to each other. By doing so, the above problem was solved.

[0018]

Since the green sheet and the conductor layer have different expansion coefficients, the larger the area of the coated portion of the conductor layer, the greater the strain due to thermal stress during expansion or contraction.

In the present invention, since the pair of internal electrodes are formed in different layers of the green sheet, in other words, the layers of the green sheet are changed to form a pair of internal electrodes. Since the coating area of the conductor layer for the internal electrode for one sheet layer can be made small, the delamination failure can be significantly reduced.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings with reference to its embodiments.

FIG. 1 is a sectional end view showing an embodiment according to the present invention, in which FIG. 1 (a) shows a chip according to the first embodiment.
Sectional end view of the thermistor seen from above, (b) in the figure
[FIG. 3] is a sectional end view of the first embodiment as seen from the front, and (c) in the drawing is a sectional end view of the chip thermistor as the second embodiment as seen from the front.

The sectional end view of FIG. 1 (c) viewed from the plane is the same as FIG. 1 (a), and is not shown.

Reference numeral 11 in FIG. 1 is a rectangular plate-shaped laminated ceramic body which constitutes the chip thermistor of the present invention. The laminated ceramic body 11 is, for example, almost entirely on one end of the upper surface of a slightly thin green sheet 12. , A conductor layer to be one internal electrode 13 is formed, and a slightly thin green sheet 15 having a conductor layer to be the other internal electrode 14 is further laminated on the upper surface of the green sheet 12, and the green sheet While stacking another slightly thick green sheet 16 on the upper surface of the sheet 15, the green sheet 12
It is formed by stacking another slightly thin green sheet 18 on the lower surface of. The phantom line (one-dot chain line) in the figure represents the interface between the green sheets.

Reference numeral 17 in FIG. 1 is a rectangular box-shaped laminated ceramic body according to another embodiment of the present invention. The laminated ceramic body 17 is, for example, slightly thin in which a conductor layer to be the internal electrode 13 is formed. On the upper surface of the green sheet 12 of
By stacking the slightly thin green sheets 15 on which the conductor layers to be the other internal electrodes 14 are formed, the three pairs of internal electrodes 13 and 14 are displaced by one green sheet layer between the right and left electrodes for each pair. 3 sets are stacked in a different shelf-like arrangement, and another slightly thick green sheet 16 is stacked on the upper surface of the uppermost green sheet 15, and another slightly thin sheet is formed on the lower surface of the lowermost green sheet 12. It is formed by stacking the green sheets 18.

On the other hand, a conventional chip thermistor having the structure shown in FIG. 2 was manufactured.

In order to compare the conventional example and the example, the above-mentioned respective samples were formed and compared under the same conditions as much as possible.

First, a valence control agent and a sintering aid are added to predetermined amounts of manganese oxide and cobalt oxide, and the mixture is stirred in a wet ball mill, dehydrated, dried, calcined, and then again. After stirring with a wet ball mill, dehydration and drying were performed to obtain a powder material for producing a chip-type ceramic thermistor (NTC characteristic).

A powder containing this ceramic as a main component, a predetermined amount of a polyvinyl butyral binder, and a plasticizer,
After adding a toluene-based solvent and stirring with a wet ball mill, the resulting suspension is degassed, and the resulting solution is coated with a doctor blade to form a sheet, which is a 100 μm-thick green sheet. I got a green sheet.

After that, by screen printing, Ag-
Print the Pd-based internal electrodes on the green sheet, press-fit,
After cutting and debinding at 400 ° C for 2 hours, firing is performed at 1200 ° C for 2 hours in the air, and the chip-shaped ceramic thermistor substrate shown in Figs. 1 and 2 is used. A certain laminated ceramic body 1
1, 17, 21, and 26 were obtained.

For each of the sample bases, 10
The result of checking delamination by 0
It is shown below.

In the case of the first conventional example, that is, in the case of the laminated ceramic body 21 structure based on FIG. 2B,
When 100 sample base materials were examined, the delamination was 2.

In the case of the second conventional example, that is, in the case of the laminated ceramic body 26 structure based on FIG.
When 100 sample base materials were examined, the delamination was 5.

On the other hand, in the case of the first embodiment, that is, the laminated ceramics body 11 based on FIG.
In the case of the structure, when 100 sample base materials were examined,
The delamination was 0.

In the case of the second embodiment, that is, in the case of the laminated ceramic body 17 structure based on FIG.
When 100 sample base materials were examined, the delamination was 0.

As is clear from the above comparison, when the internal electrodes 13 and 14 forming a pair have different electrode structures of the green sheets, the resistance value with respect to the B constant peculiar to the thermistor material can be kept low, and It has been found that delamination defects can be significantly reduced.

In other words, the green sheets 12, 15
Of the internal electrodes 13 and 14 forming a pair by alternately stacking the layers of
Because it is composed of different layers, one green sheet 1
Since the coating area of the conductor layers for the internal electrodes in the 2 and 15 layers can be made small, as a result, the resistance value with respect to the B constant can be lowered, and the delamination failure can be greatly reduced.

[0037]

As described above, according to the present invention, in a ceramic thermistor manufactured by laminating green sheets whose main component is ceramic, a conductor layer to be one internal electrode of a pair is partially formed. Since the green sheets are alternately stacked and the internal electrodes forming the pair are formed in different layers of the green sheets, the resistance value for the B constant, which is unique to the material of the thermistor, is kept low. At the same time, it is possible to supply a ceramic thermistor having no delamination defect, and as a result, it is possible to greatly contribute to the improvement of the reliability of the electronic device and the cost reduction.

[Brief description of drawings]

FIG. 1 is a cross-sectional end view showing an embodiment according to the present invention, in which (a) is a cross-sectional end view of the embodiment as seen from a plane,
(B) in the drawing is a sectional end view of the first embodiment as seen from the front, and (c) in the drawing is a sectional end view of the second embodiment as seen from the front.

FIG. 2 is a sectional end view showing a conventional example, in which (a) is
It is the cross-sectional end view which looked at the prior art example from the plane, and (b) in the figure
[Fig. 3] is a sectional end view of the first conventional example as viewed from the front, and (c) in the figure is a sectional end view of the second conventional example as viewed from the front.

[Explanation of symbols]

 11 laminated ceramic body 12 green sheet 13 internal electrode 14 internal electrode 15 green sheet 16 green sheet 17 laminated ceramic body 18 green sheet

Claims (2)

[Claims] 1. A prism or a rectangular plate-shaped ceramic body has a pair of opposing vertical end faces each having an external electrode serving as a connection terminal, and one end is connected to each of the left and right external electrodes, and the other end is A chip thermistor having a pair of left and right inner electrode conductor layers that horizontally extend to a position that does not reach the center toward the center of the body, and the pair of conductor layers are different from each other in parallel. A chip thermistor characterized by being arranged like a shelf on a flat surface. 2. A prism or a rectangular plate-shaped ceramic body has external electrodes serving as connection terminals on a pair of opposing vertical end faces, and one end is connected to each of the left and right external electrodes, and the other end is A chip thermistor having a plurality of pairs of left and right inner electrode conductor layers that horizontally extend to a position that does not reach the center toward the center of the body. A chip thermistor characterized by being arranged in different shelves on different planes parallel to each other.