JPH06181101A - Semiconductor ceramic having positive resistance-temperature characteristic - Google Patents

Abstract

PURPOSE:To provide semiconductor ceramic having such a positive resistance- temperature characteristic that the magnitude and fluctuation of the resistance value can be reduced by increasing the ohmic resistance. CONSTITUTION:The title laminated semiconductor or ceramic 1 is constituted by integrally sintering a laminated body formed by alternately piling up semiconductor ceramic layers 2 and internal electrodes 2 and forming first external electrodes 7 connected to one end faces 3a of the electrodes 3 on the left and right end faces of the sintered laminated body 4. Ni or an Ni alloy is used for the electrodes 3 and a metallic material composed mainly of Ni, Cu, Fe, or Co is used for at least the parts of the electrodes 7 which are brought into contact with the electrodes 3. In addition, the thickness of the electrodes 7 is controlled to 1mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated semiconductor porcelain having a positive resistance-temperature characteristic in which an electric resistance value changes with temperature, and more specifically, a combination of metal materials used for internal electrodes and external electrodes. The present invention relates to a structure of an electrode material capable of improving ohmic characteristics to reduce resistance and reducing variation in resistance value.

[0002]

2. Description of the Related Art BaTiO ₃ having a positive resistance temperature characteristic
The system semiconductor porcelain has a characteristic that the resistance value sharply increases above the Curie point. There is. Further, in order to cope with the recent low resistance, a laminated semiconductor ceramic has been proposed as an alternative to the disk type. In this laminated semiconductor ceramic, semiconductor ceramic layers and internal electrodes are alternately laminated and integrally sintered, and external electrodes are formed on the left and right end faces of the sintered body. It has a structure in which one end face of is connected alternately.

In such a laminated semiconductor ceramic, a Pd-Ag system or a Pt-Pd system is conventionally used as a metal material adopted for the internal electrode in order to cope with high temperature firing, and the metal of the external electrode is used. Ag or the like is used as the material (see JP-A-55-88304 and JP-A-57-60802).

[0004]

However, in the above conventional laminated semiconductor ceramics, when the metal material such as Pt is used for the internal electrode, it is difficult to obtain ohmic contact between the internal electrode and the ceramic layer, and as a result, There is a problem that the resistance value increases significantly. Further, when Ag or the like is used for the external electrodes, there is a problem that the resistance value tends to vary.

The present invention has been made in view of the above-mentioned conventional circumstances, and it is possible to improve the ohmic contact of the internal electrodes to reduce the resistance value and to reduce the variation in the resistance value. Is intended to provide.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have studied to solve the above-mentioned problems of increase and variation in resistance value, and found that a combination of metal materials used for internal electrodes and external electrodes was used. I paid attention. As a result of various studies to find such a metal material, it was found that Ni is suitable as a metal material that can cope with the firing temperature of the semiconductor porcelain and can obtain ohmic contact. On the other hand, when this Ni is used as the internal electrode, the external electrodes connected to the electrode are Ni, Cu, F
The inventors of the present invention have found that e and Co are effective, and thought that combining both of them can solve the problems of both increase and variation in resistance value.

Therefore, according to the present invention, a semiconductor ceramic layer and an internal electrode are alternately laminated and integrally sintered, and an external electrode to which the internal electrode is connected is formed on an end surface of the sintered body. In a semiconductor porcelain having temperature characteristics, the internal electrodes are made of Ni or a Ni alloy, and
At least a portion of the external electrode that is in contact with the internal electrode is N
It is characterized in that it is made of a metal material containing any one of i, Cu, Fe and Co as a main component.

Here, it is desirable that the thickness of the external electrode is within 1 mm. This is because Ni, C
This is because when u, Fe, and Co are adopted, it becomes clear that if the thickness of u, Fe, and Co is increased, they may peel due to thermal contraction.

[0009]

According to the semiconductor porcelain having the positive resistance temperature characteristic according to the present invention, since Ni and Ni alloy are adopted for the internal electrodes, the ohmic property with the ceramic layer is improved while ensuring the heat resistance against high temperature firing. As a result, the resistance value can be reduced. In addition, the external electrode connected to the internal electrode has N
Since i, Cu, Fe, and Co are used, it is possible to avoid variations in resistance value when Ni is used for the internal electrodes, and improve reliability of quality.

When the thickness of the external electrode is 1 mm or less, the problem of peeling due to heat shrinkage can be solved, and the reliability of the quality can be improved also from this point.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are views for explaining a semiconductor ceramic having a positive resistance temperature characteristic according to an embodiment of the present invention.
In the figure, reference numeral 1 is a laminated semiconductor ceramic of this embodiment.
The semiconductor porcelain 1 has a rectangular parallelepiped shape, and semiconductor ceramic layers 2 containing BaTiO ₃ as a main component and internal electrodes 3 are alternately laminated, and the laminated bodies are integrally sintered to form a sintered body 4. It is configured. Further, one end surface 3a of each internal electrode 3 is
Are alternately exposed on the left and right end faces 4a, 4b of the sintered body 4, and the remaining end faces are located inside the ceramic layer 2 and embedded in the sintered body 4.

A first external electrode 7 is formed on the left and right end surfaces 4a and 4b of the sintered body 4 so as to cover it. The thickness of the first external electrode 7 is set to 1 mm or less, and the first external electrode 7 and one end surface 3a of each internal electrode 3 are electrically connected. In addition, the end surfaces 4a and 4b of the sintered body 4 are
The outer surface of the first outer electrode 7 is covered with the second outer electrode 5, and the outer electrode 5 is made of a metal material of Ag-Pd.

Then, Ni or Ni alloy is adopted for the internal electrodes 3. Further, at least a portion of the first external electrode that is in contact with the internal electrode is made of Ni, Cu, F
A metal material whose main component is one selected from e and Co is adopted.

Next, one of the laminated semiconductor porcelain 1 of this embodiment is manufactured.
The manufacturing method will be described. First, as a raw material, BaCO
₃, CaCO₃, TiO₂, La₂O₃, MnO ₂, S
iO₂To prepare the following composition. (Ba_0.848Ca_0.15La_0.002)_1.01TiO₃+0.01 SiO₂
+0.001 MnO₂ The above raw materials were mixed with pure water and zirconia balls.
Put in an ethylene pot, crush and mix for 5 hours, then dry
Then, calcination is performed at 1100 ° C. for 2 hours.

Next, the calcined body is pulverized again to form a calcined powder, and the calcined powder is mixed with an organic binder, a solvent, and
And a dispersant are mixed to form a ceramic green sheet having a thickness of 0.1 mm. Next, add this green sheet to 7.5 x
A large number of semiconductor ceramic layers 2 are formed by punching into a rectangular shape so as to have a size of 6.5 mm ² .

Next, an electrode paste prepared by mixing varnish with Ni powder is prepared. This electrode paste is screen-printed on the upper surface of each ceramic layer 2 to form the internal electrodes 3. In this case, only one end surface 3a of each internal electrode 3 extends to the end edge of the ceramic layer 2, and the other end surface is located inside.

As shown in FIG. 2, the ceramic layers 2 and the internal electrodes 3 are alternately overlapped with each other, and the one end faces 3a of the internal electrodes 3 are alternately located on the left and right end faces of the ceramic layer 2. Ten layers are stacked, and ceramic layers 6 and 6 as dummy are stacked and stacked on the upper and lower surfaces thereof. Then
This is pressed and pressed by a press to form a laminate. As a result, only one end surface 3a of the internal electrode 3 is on the left side of the laminated body,
It is exposed on the right end face, and the remaining part is enclosed in the laminated body.

Next, a metal paste containing any one of Ni, Cu, Fe and Co as a main component is prepared. This metal paste is applied to the left and right end surfaces of the above-mentioned laminated body to form the first external electrodes 7.

Next, the above laminated body is heated in the atmosphere to burn the binder, and then fired in a reducing atmosphere of H ₂ / N ₂ = 3% at 1350 ° C. for 2 hours to obtain a sintered body 4. . After that, Ag-Pd (70:30) paste is applied to the surfaces of the first external electrodes 7 on the left and right end faces 4a and 4b of the sintered body 4 to form the second external electrodes 5, and then in the air. Reoxidize at 800 ℃ for 2 hours. As a result, the laminated semiconductor ceramic 1 of this embodiment is manufactured.

[0020]

[Table 1]

Table 1 shows the results of tests conducted to confirm the effects of the semiconductor ceramics of this example. In this test, the sample Nos. 1 to 4 of the respective examples were prepared by the above-described manufacturing method, and the first external electrodes of the respective sample Nos. 1 to 4 were made of Ni (Examples).
No. 1), Co (Example No. 2), Fe (Example No. 2)
3), a metal material containing Cu (Example No. 4) as a main component was adopted. In addition, in Example No. 4, the paste of Cu and AgPd was sequentially applied to the sintered body after firing, and then reoxidized.

For comparison, Comparative Sample Nos. 1 to 6 were prepared by the above manufacturing method. This comparative sample No. 1
Nos. 3 to 3 are conventional Pt (Comparative Example No. 1) for the first external electrodes, respectively.
1), Pd (Comparative Example No. 2), and AgPd = 70: 30 (Comparative Example No. 3). In Comparative Example No. 3, the Ag-Pd paste was applied to a sintered body after firing and then reoxidized.
Further, in Comparative Samples Nos. 4 to 6, the first external electrode was Ni, and the internal electrodes were made of conventional Pt (Comparative Example No. 4),
Pd (Comparative Example No. 5) and PdAg = 80: 20 (Comparative Example N)
The metal material consisting of o. 6) was used. Then, the resistance value (Ω) at room temperature of each of the above samples was measured, and the variation in the resistance value (ρ / average value%) was examined. Here, the thickness of the first external electrode of each of the above samples was 5 μm.

As is apparent from Table 1, in the case of Comparative Examples Nos. 4 to 6 in which the conventional metal material was used for the internal electrodes, the ohmic contact was not obtained, and the resistance value was 150 to.
It is as high as 200Ω. In addition, Comparative Example No. 1 in which Ni is used for the internal electrode and a conventional metal material is used for the external electrode
In case of ~ 3, resistance value is 0.3 ~ due to improvement of ohmic property
Although it is as low as 0.5 Ω, it varies from 15 to 35%.
Therefore, there is a problem in the combination of both electrodes.

On the other hand, Example Nos. 1 to 1 in which Ni was used for the internal electrodes and the metal material of the present invention was used for the first external electrodes
In the case of No. 4, all samples had low resistance values of 0.21 to 0.23 Ω at room temperature, and variations in resistance values were 5 to 6%. In this way, Ni at the contact with the Ni electrode,
It can be seen that by adopting the external electrodes made of Co, Fe, and Cu, the resistance can be reduced and the variation in the resistance value can be greatly reduced.

[0025]

[Table 2]

Table 2 shows that Ni metal is used for the internal electrode and the first external electrode, and the thickness of the first external electrode is 0.01 μm.
The test results of observing the peeling state of the electrode and changing the resistance value and the variation in the resistance value when the thickness is changed to ˜2 mm are shown.

As is clear from Table 2, when the thickness of the first external electrode is 1.2 mm and 1.5 mm, peeling occurs in the electrode, and as a result, both the resistance value and the variation increase. On the other hand, when the thickness is 1 mm or less, peeling of the electrode does not occur at all, and the resistance value is 0.22 to 0.25Ω and the variation is 5 to 7%, which is a satisfactory value.

[0028]

As described above, according to the semiconductor porcelain having the positive resistance temperature characteristic according to the present invention, Ni or Ni alloy is adopted for the internal electrode, and at least the external electrode connected to the internal electrode is used. N on the part that contacts the internal electrode
Since a metal material composed of i, Co, Fe, and Cu is adopted, the ohmic contact can be improved to reduce the resistance value, and the variation in the resistance value can be reduced, so that the reliability of the quality can be improved. To be

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a semiconductor ceramic having a positive resistance temperature characteristic according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of the semiconductor porcelain of the above embodiment.

[Explanation of symbols]

 1 Laminated Semiconductor Porcelain 2 Semiconductor Ceramic Layer 3 Internal Electrode 4 Sintered Body 7 First External Electrode (External Electrode Connected to Internal Electrode)

Claims (2)

[Claims] 1. A positive resistance-temperature characteristic is obtained by alternately stacking semiconductor ceramic layers and internal electrodes and integrally sintering them, and forming external electrodes to which the internal electrodes are connected at the end faces of the sintered body. In the semiconductor porcelain having the above-mentioned internal electrodes, Ni,
Or a positive electrode characterized by being made of a Ni alloy, and at least a portion of the outer electrode in contact with the inner electrode is made of a metal material containing any one of Ni, Cu, Fe and Co as a main component. Semiconductor porcelain having resistance temperature characteristics. 2. The semiconductor porcelain according to claim 1, wherein the external electrode has a thickness of 1 mm or less.