JPH01293503A - Semiconductor porcelain having positive temperature coefficient of resistance - Google Patents

Abstract

PURPOSE:To form external electrodes easily and improve the productivity by a method wherein ceramics layers and internal electrodes are alternately laminated to form a laminated unit, the terminals of the internal electrodes are exposed on both the sides of the laminated unit, an insulating layer is formed over the surface of the laminated unit except the exposed parts of the internal electrodes and external electrodes are formed by electrolytic plating so as to cover the exposed parts of the respective internal electrodes. CONSTITUTION:Ceramics layers 2 and internal electrodes 3 are alternately laminated to form a laminated unit 4. The left and right terminals of the internal electrodes 3 are alternately exposed on both the left and right sides 4a and 4b of the laminated unit 4 respectively. An insulating layer 5 is formed over the surface of the laminated unit 4 except the exposed parts 3a of the internal electrodes 3 and then external electrodes 6 are formed by electrolytic plating so as to cover the exposed parts 3a of the respective internal electrodes 3. For instance, the BaTiO3 ceramics layers 2 and the internal electrodes 3 made of tin are alternately laminated to form the laminated unit 4 and the insulating layer 5 made of Bi2O3 is formed over the surface of the laminated unit 4 except the exposed parts 3a of the internal electrodes 3. Then the first external electrodes 6 made of Ni are formed on both the sides 4a and 4b and, further, second external electrodes 7 made of tin are formed on the surfaces of the first extarnal electrodes 6.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to semiconductor porcelain, which is made up of alternately laminated ceramic layers and internal electrodes and has positive resistance-temperature characteristics, and is particularly applicable to mass production. , relates to a structure of semiconductor porcelain that can improve productivity.

(Prior Art) Generally, semiconductor porcelain used as a positive temperature coefficient thermistor has the property of transitioning from a conductor to an insulator at a certain predetermined temperature.
There is a structure as shown in the figure (Japanese Unexamined Patent Publication No. 61-153
This semiconductor ceramic 20 has ceramic layers 21 and internal electrodes 22 alternately laminated, and external electrodes 24 are formed on both sides 23a and 23b of a sintered body 23 that is integrally sintered.
It is composed of the following. In addition, each of the internal electrodes 22
The left and right end faces of the sintered body 23 are alternately led out to the left side 23a and the right side 23b of the sintered body 23 and connected to the external electrode 24.

By the way, when forming the external electrode 24 on the sintered body 23, conventionally, a conductive paste is applied and then baked.
For example, an ohmic silver electrode is formed.

[Problem that the invention seeks to solve]

However, the above-mentioned conventional method for forming external electrodes involves a step of applying conductive paste to both sides of the sintered body, so there is a problem in that productivity is low.

An object of the present invention is to provide a semiconductor ceramic in which the above-mentioned external Ti can be easily formed and productivity can be improved.

[Means for solving problems]

In order to solve the above-mentioned conventional problems, the present inventors studied the structure of semiconductor ceramics, especially the external electrodes, and focused on forming the external electrodes by electrolytic plating. According to this electrolytic plating, the equipment is simple and a large amount can be processed at one time, so it can be expected to improve productivity compared to the case of applying a conventional conductive paste. However, when electrolytic plating is applied to the sintered body, since the entire unit of the sintered body is a semiconductor, a problem arises in that metal is deposited on the entire unit, and electrolytic plating cannot be used as it is. There was found.

Therefore, we have come up with the idea that if an insulating layer is formed on the outer surface of the sintered body in areas where metal deposition is unnecessary, it is possible to prevent the metal from breaking due to electrolytic plating in the unnecessary areas, and the present invention has been completed.

Therefore, in a semiconductor ceramic having positive resistance-temperature characteristics, the end face of the internal electrode is exposed on the side surface of a laminate formed by alternately laminating ceramic layers and internal electrodes. The present invention is characterized in that an insulating layer is formed on the outer surface portion excluding exposed portions, and external electrodes are formed by electrolytic plating so as to cover the exposed portions of each of the internal electrodes.

Here, the m-edge layer is formed by, for example, forming an internal electrode gap layer in the laminate during the process of forming the internal tti, and then filling this into a magnetic container together with an oxidizing agent such as Bbf)s. The oxidizing agent can be thermally diffused by heating the oxidizing agent.

[Effect]

According to the semiconductor porcelain having positive resistance-temperature characteristics according to the present invention, since the insulating layer is formed on the outer surface at a portion other than the exposed portion of the internal electrode, the external electrode can be formed by electrolytic plating. That is, by immersing the above-mentioned laminate in a plating solution and performing electrolytic plating, metal as the external electrode is deposited only on the exposed portions of the above-mentioned internal electrodes, and this metal grows to form the respective internal electrodes on the sides of the laminate. An external electrode is formed to cover the exposed portion. In addition, the insulating layer in this case can be easily formed by placing a large number of laminates in a ceramic container, adding an oxidizing agent thereto, and thermally diffusing the oxidizing agent, and the electrolytic plating process described above can be performed at once. Since it can be processed in large quantities, productivity can be greatly improved compared to conventional paste application work.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 to 4 are diagrams for explaining semiconductor ceramics according to an embodiment of the present invention.

In FIG. 1, 1 is the semiconductor porcelain of this example, and its external shape is a rectangular parallelepiped with a length of 10 m, a width of 5 fl, and a thickness of about 2 days. The semiconductor ceramic 1 has a laminate 4 formed by alternately laminating barium titanate ceramic layers 2 and internal electrodes 3 made of a base metal such as tin, and has left and right side surfaces 4a and 4b of the laminate 4. The left and right end faces of the internal electrodes 3 are exposed alternately, and an insulating layer 5 made of Bl and Q is formed on the outer surface of the laminate 4 except for the exposed portions 3a. Further, first external electrodes 6 made of N1 are formed on both side surfaces 4a and 4b of the laminate 4, and the first external electrodes 6 are made of N1. The paddle 6 is connected to the exposed portion 3a of the rod 3 inside.

Further, on the outer surface of the first external electrode 6, a second external electrode 7 made of tin, a low melting point metal, is formed.

Next, a method for manufacturing the semiconductor ceramic 1 of this embodiment will be explained with reference to FIGS. 2 to 4.

■ First, 3aTiOt as the main component, YxOs as a semiconducting agent, SiO and Altos as a mineralizing agent.
, MnOt is added as a property improving agent, mixed and pulverized, and an acrylic organic binder is mixed thereto to produce a slurry-like ceramic material. Then, this ceramic material is formed into a green sheet with a predetermined uniform thickness.

(2) On the other hand, a paste is prepared by mixing BaTiOs sintered powder with carbon and Fes. Then, this paste is printed on the top surface of the green sheet in a shape corresponding to the polar pattern inside, and this is cut into a rectangular shape. As a result, only one side portion 8a of the paste 8 extends to the outer edge of the green sheet 9, and the other side portion 8b is located inward.Next, as shown in FIG. Each green sheet 9 is MM'l so that one side portion 8a is exposed to the outside alternately, and ceramic sheets 1 as a dummy are placed above and below the laminated sheets 9.
0 are piled up to form a laminate, and this laminate is pressed in the lamination direction using a press.

(2) The above-mentioned laminate is heated to about 1300° C. in air and fired. Then, the carbon in the paste 8 is burned out, and a sintered body 4 in which a porous layer 1) is formed in the paste 8 portion is obtained (see FIG. 3 (al)).

■ Next, the sintered body 4 is placed in a cylindrical porcelain pot 12 as shown in FIG.
i□0. Add the powder and heat to 1000° C. while rotating the pot 12. Then, the powder 3i, ○, thermally diffuses to the outer surface of the sintered body 4 and turns the surface portion into an insulator, thereby forming the insulating layer 5 (see FIG. 3~), where: The opening portion of the porous layer 1) is not made into an insulator even by the above-mentioned thermal diffusion, and therefore the insulation layer 5 is formed on the outer surface of the sintered body 4 excluding the opening of the porous layer 1). It will be formed in parts.

■ Next, the sintered body 4 on which the insulating layer 5 has been formed is heated with a low melting point heavy metal I4 (tin, lead, etc. or an alloy thereof), for example w
It is immersed in solution A, and tin is injected into the porous Nll under pressure. As a result, the porous Ji1) portion becomes the internal electrode 3, and the end surface 3a of the electrode 3 is exposed to the side surfaces 4a and 4b of the sintered body 4 (see FIG. 3 (C1)).

(2) The sintered body 4 on which the internal electrodes 3 have been formed is immersed in a Ni plating solution, and electrolytic plating is performed by passing a direct current through the Ni plating solution. This precipitates only on the side surface 4b, and grows while spreading on the side surface 4b, thereby forming the first external electrode 6 on the side surface 4b. Furthermore, in order to improve soldering properties on the surface of the first external electrode 6, a second external electrode 7 made of tin is formed by electrolytic plating or sputtering (see FIG. 3 (C1)). , the semiconductor ceramic 1 of this example will be manufactured.

Next, the effects of this embodiment will be explained.

According to the semiconductor ceramic 1 of this embodiment, the internal ti of the sintered body 4
Since the insulation M5 is formed on the outer surface except for the exposed portion 3a of 3, electrolytic plating can be used when forming the external electrodes 6 and 7, productivity can be improved, and component costs can be reduced accordingly.

In the above embodiment, the external electrode 6 was formed by forming the insulation N5 on the outer surface of the sintered body 4, then injecting the base metal under pressure, and performing electrolytic plating, but in the present invention, the following procedure was performed. For example, the insulating layer 5 may form an external electrode.
After forming, a porous external electrode layer may be formed first, a base metal may be injected under pressure into both this porous external electrode layer and the porous layer 1), and then electrolytic plating may be performed. In this case, the processing time required for electrolytic plating is significantly shortened.

(Effects of the Invention) As described above, according to the semiconductor porcelain having positive resistance-temperature characteristics according to the present invention, since an insulating layer is formed on the outer surface of the laminate except for the exposed portion of the internal electrode, the formation of the external electrode In addition, the electrolytic plating process left behind in mass production can be used, which has the effect of greatly improving productivity.

[Brief explanation of the drawing]

1 to 4 are diagrams for explaining a semiconductor ceramic according to an embodiment of the present invention, in which FIG. 1 (δ) is a perspective view thereof, FIG. 1 Cb1 is a sectional view thereof, and FIGS. Fig. 4 is a diagram for explaining the manufacturing method, Fig. 2 is an exploded perspective view thereof, Fig. 3 (al to Fig. 3 fe) is a cross-sectional view, and Fig. 4 is a surface of the semiconductor porcelain. FIG. 5 is a front view showing a porcelain pot used for forming an insulating layer on a semiconductor porcelain pot, and FIG. 5 is a sectional view showing a conventional semiconductor porcelain pot. In the figure, ■ is semiconductor porcelain, 2 is a ceramic layer, 3 is an internal electrode, 3a is an exposed part of the internal electrode, 4 is a sintered body (laminate), 4a and 4b are the side surfaces of the sintered body, and 5 is an insulating layer. , 6 are external electrodes. Patent applicant Murata Manufacturing Co., Ltd. Representative Patent attorney Tsutomu Shimoichi Figure 1 Figure 2

Claims (1)

[Claims] (1) In semiconductor ceramics that have positive resistance characteristics that transform from a conductor to an insulator at a predetermined temperature, ceramic layers and internal electrodes are alternately laminated to form a laminate, and the left and right sides of the laminate are The left and right end faces of the internal electrodes are alternately exposed, and an insulating layer is formed on the outer surface of the laminate excluding the exposed parts of the internal electrodes, and electrolyzed so as to cover the exposed parts of each internal electrode. A semiconductor porcelain having positive resistance-temperature characteristics characterized by having an external electrode formed by plating.