JP2002110405A - Overvoltage protective device material and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide material used for an overvoltage protective device which has a low leakage current, a small capacitance, and a high response speed and is kept very stable in a manufacturing process, and a method of manufacturing the same. SOLUTION: At least two kinds of ceramic powder are uniformly mixed together; the mixed ceramic powder is pre-baked and formed into powder material with a PN junction; the powder material is uniformly dispersed in a solvent containing a binder for the formation of paste material; the paste material is filled in a gap between electrodes; the powder material contained in the paste material is bonded together by sintering to turn the paste material into a porous structure; and thus an overvoltage protective device can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a kind of overvoltage protection device and a method of manufacturing the same.

[0002]

2. Description of the Related Art Materials and structures of known zinc oxide variable resistors include zinc oxide, B, Bi, Ba, Si, Sr,
It is composed of an oxide of an element selected from the group consisting of Pb, Pr, Co, Mn, Sb or Cr or a mixture thereof, and bismuth oxide or the like forms a crystal interface layer between particles of zinc oxide. What is required for the structure of the material is a structure that can be manufactured with a material density close to the theoretical density. Generally, a product having a theoretical density of 90% or more is a commercialized product. However, such devices have the disadvantage of high capacitance. The crystalline interface layer is similar in electrical representation to a capacitor, so that a variable resistor made of such a material has a relatively high capacitance and is not suitable for high frequency circuits. This was one significant drawback of such a variable resistor. The material of the overvoltage protection device according to the present invention belongs to a porous structure, and therefore, if the same material composition and the same device structure are used, since the material belongs to the porous material structure, it has relatively low capacitance and leakage current, and has a high frequency. It can be applied in a circuit.

[0003] There is a relationship between the breakdown voltage of a zinc oxide variable resistor and the zinc oxide crystal grains between the two electrodes. According to the microstructure of the known zinc oxide variable resistor shown in FIG.
One crystal interface layer exists between the zinc oxide crystal grains, and this crystal interface layer is made of an oxide such as bismuth oxide, and is generally a rich bismuth region, and a pn junction is formed between the zinc oxide and the rich bismuth region. If the zinc oxide semiconductor is represented by N and the rich bismuth region is represented by P from one end of the electrode to the other end, the pn junction structure of the variable resistor becomes EPNPNP-N-. .....- NP
−NPE can be displayed. Among them, E is a conductor electrode, and it is hypothesized that a breakdown voltage Vb1 exists at each pn junction and that a total of X pn junctions exist between the electrodes. If the breakdown voltage Vb is Vb = ＶVb1
Is displayed.

[0004] The present invention provides a porous material having a pn junction, the material structure of which is as shown in FIG. 2 or FIG. 3, wherein a zinc oxide semiconductor is indicated by P from one end of the electrode to the other end. For example, when a coating layer made of, for example, an oxide containing bismuth oxide is denoted by N, the pn junction of the overvoltage protection element provided by the present invention is EP-N-P-P-S-P-N-P-.
······· −PNPPPSNPE Among them, PNP represents one crystal grain, S is a spacer layer between crystal grains, S is an insulator such as air or glass, and a breakdown voltage between them is represented by Vs. Further, if the crystal grains are brought into contact with each other to make S nonexistent and one breakdown voltage Vb2 exists for each P-N-P, a plurality of crystal grains are formed between the electrodes. Thus, the breakdown voltage of the element can be expressed as Vb = ΣVb2 + ΣVs. Thereby, the principle of the overvoltage protection device of the present invention is different from that of the well-known overvoltage protection device.

As a material of an overvoltage protection device previously published, there is a material described in US Pat. No. 4,726,991. The material structure is such that a conductor or semiconductor powder is covered with a single insulating layer. This insulating layer has a thickness of less than several hundreds of mm, and such a material structure has a practical disadvantage. That is, the thickness of the insulating layer is only within a few hundred square meters, the difficulty of the manufacturing process of this thickness is extremely high, if the thickness of the insulating layer to cover is too thin, it is easy to form a short circuit of the element, If the thickness of the insulating layer is slightly thick, the breakdown voltage becomes high, which is a drawback of the structure in which the surface of the conductor or the semiconductor powder is covered with the insulating layer.

[0006] Similarly, the structure of the coating-type material described in US Patent No. 5,294,374 is a mixture of conductor powder coated with one insulating layer and an uncoated semiconductor mixture, The coating thickness is between 70 ° and 1 micron, and the coating layer material is a semiconductor, which is basically an insulating or semiconductive material that blocks the passage of current, Has achieved the purpose of electrical resistance. However, the thickness of the coating layer directly affected the breakdown voltage of the device, and therefore, the uniformity of the thickness became sufficiently important.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a material and a method for manufacturing an overvoltage protection element.
The overvoltage protection material provided by the present invention is a powder material,
The granule itself of the powder material has a pn junction, and due to the presence of the pn junction, the powder itself has a characteristic of low leakage current,
When the voltage suddenly increases in a situation where a surge occurs in the circuit, the material instantaneously breaks down, and the material instantaneously becomes a conductor and can be used as a material of the overvoltage protection element.

[0008] The present invention also provides a method of uniformly dispersing a powder material in a solvent, or uniformly dispersing the powder material in a solvent containing a binder, or uniformly dispersing a glass powder in a solvent containing a binder. An appropriate paste is formed, filled between electrodes having gaps, dried and sintered to form a porous structure, and the density of the porous material is set to 30-9 of the theoretical density.
The next object is to control to 0% so that devices manufactured using this have the advantages of low capacitance and low leakage current.

A well-known overvoltage protection material is a material in which a conductor or a semiconductor powder is isolated by an insulating material. In the manufacture of an element made of this material, when the conductor powder is sprayed on the insulating material, the conductor powder is placed in one place. However, in view of this problem, according to the present invention, the powder material itself has a pnp junction, thereby greatly reducing the electric resistance value. Even if the powder and the powder are concentrated in one place, it does not affect the characteristics of the element, does not cause a similar short circuit phenomenon, can greatly increase the production yield, and has stable characteristics. Another object is to provide a manufacturing process.

A well-known overvoltage protection material is a material obtained by coating the surface of a conductor or semiconductor powder with an insulating material.
Alternatively, the insulating material is made of a material in which a conductor or semiconductor powder is isolated, and the thickness of the insulating material directly affects the breakdown voltage of the device. In the present invention, the overvoltage protection material is such that the powder material itself has a crystal interface layer, whereby the breakdown voltage of the element is not directly related to the thickness of the coating layer, and the number of pnp junctions and the breakage of the interface are reduced. Yet another object is to make the down-voltage relevant, thereby facilitating the control of the breakdown voltage.

[0011]

According to a first aspect of the present invention, there is provided a powder material in which at least two kinds of ceramic powders are sufficiently mixed and then prebaked to form a pn junction. It is used as the material of the protection element. According to the invention of claim 2, one of the ceramic powders in the powder material is a ceramic powder containing zinc oxide, and the other is B, Bi, Ba, Si, Sr, Pb, P
The material of the overvoltage protection device according to claim 1, wherein the material is a ceramic powder composed of an oxide of an element selected from the group consisting of r, Co, Mn, Sb, and Cr or a mixture thereof. I have. The invention of claim 3 is
One of the ceramic powders in the powder material is barium titanate, strontium titanate, ceramic powder which is a calcium titanate or a mixture thereof,
The overvoltage protection element according to claim 1, wherein the B powder is a ceramic powder composed of an oxide of an element selected from the group consisting of Nb, Mn, Cu, Co, and Si or a mixture thereof. Of the material. According to a fourth aspect of the present invention, there is provided the overvoltage protection element material according to the first aspect, wherein the powder material has an average particle size of 0.1 to 100 μm. The invention according to claim 5 is that, after sufficiently mixing at least two types of ceramic powders, prebaking is performed, and the powder material having a pn junction formed is uniformly dispersed in a solvent to obtain a paste-like material. Filling the paste-like material between two electrodes having a gap, bringing the paste-like material into contact with both electrodes, drying and baking this paste-like material, joining the powder of the material, and obtaining a porous material body And an overvoltage protection element. In the invention according to claim 6, one of the ceramic powders in the powder material is a ceramic powder containing zinc oxide, and the other is B, Bi, Ba, Si, Sr, Pb, Pr, C
The overvoltage protection device according to claim 5, wherein the ceramic powder is made of an oxide of an element selected from the group consisting of o, Mn, Sb, and Cr or a mixture thereof. According to a seventh aspect of the present invention, one of the ceramic powders in the powder material is a ceramic powder that is barium titanate, strontium titanate, calcium titanate or a mixture thereof, and the B powder is N powder.
The overvoltage protection element according to claim 5, wherein the ceramic powder is composed of an oxide of an element selected from the group consisting of b, Mn, Cu, Co, and Si or a mixture thereof. The invention according to claim 8 is the overvoltage protection element according to claim 5, wherein the material density of the porous material body is set to 30 to 90% of the theoretical density. According to the ninth aspect of the invention, at least two types of ceramic powders are sufficiently mixed and then pre-baked, and a powder material having a pn junction formed is uniformly dispersed in a solvent to obtain a paste-like material. Filling the paste-like material between the two electrodes having a gap, bringing the paste-like material into contact with both electrodes, drying and baking this paste-like material, bonding the powder of the material, and forming a porous material body A method for manufacturing an overvoltage protection element, in which an overvoltage protection element is obtained. In the invention according to claim 10, one of the ceramic powders in the powder material is a ceramic powder containing zinc oxide, and the other is B, B
i, Ba, Si, Sr, Pb, Pr, Co, Mn, Sb
Alternatively, there is provided a method for manufacturing an overvoltage protection element according to claim 9, wherein the ceramic powder is composed of an oxide of an element selected from the group consisting of Cr or a mixture thereof. The invention according to claim 11, wherein one of the ceramic powders in the powder material is barium titanate,
Ceramic powder which is strontium titanate, calcium titanate or a mixture thereof, and B powder is Nb,
The method for manufacturing an overvoltage protection element according to claim 9, wherein the ceramic powder is made of an oxide of an element selected from the group consisting of Mn, Cu, Co, and Si or a mixture thereof. A twelfth aspect of the present invention is the overvoltage protection device according to the ninth aspect, wherein the material density of the porous material body is 30 to 90% of the theoretical density. According to a thirteenth aspect of the present invention, a paste material is obtained by sufficiently mixing at least two types of ceramic powders, pre-baking, and uniformly dispersing a powder material having a pn junction formed in a solvent containing a binder. Then, the paste-like material is filled between two electrodes having a gap, the paste-like material is brought into contact with both electrodes, dried, and the paste-like material is baked.
The method is a method for manufacturing an overvoltage protection element, in which powders of materials are joined to form a porous material body to obtain an overvoltage protection element. According to a fourteenth aspect of the present invention, one of the ceramic powders in the powder material is a ceramic powder containing zinc oxide, and the other is B, Bi, Ba, Si, Sr, P
14. A ceramic powder comprising an oxide of an element selected from the group consisting of b, Pr, Co, Mn, Sb or Cr or a mixture thereof.
The method for manufacturing an overvoltage protection element described in (1). The invention according to claim 15 is one in which one of the ceramic powders in the powder material is a ceramic powder that is barium titanate, strontium titanate, calcium titanate or a mixture thereof, and the B powder is Nb, Mn, Cu, Co, S
14. A method for manufacturing an overvoltage protection device according to claim 13, wherein the ceramic powder is composed of an oxide of an element selected from the group consisting of i or a mixture thereof. The invention according to claim 16 is the overvoltage protection element according to claim 13, wherein the material density of the porous material body is 30 to 90% of the theoretical density.
The invention according to claim 17 is that, after sufficiently mixing at least two types of ceramic powders, prebaking is performed, and the powder material and the glass powder having the pn junction formed are dispersed in a solvent to obtain a paste-like material. This paste material is filled between two electrodes having a gap, the paste material is brought into contact with both electrodes, dried and baked, and the powder of the material is joined to form a porous material body. To obtain an overvoltage protection element. In the invention according to claim 18, one of the ceramic powders in the powder material is a ceramic powder containing zinc oxide, and the other is B, B
i, Ba, Si, Sr, Pb, Pr, Co, Mn, Sb
Alternatively, there is provided a method for manufacturing an overvoltage protection element according to claim 17, wherein the ceramic powder is composed of an oxide of an element selected from the group consisting of Cr or a mixture thereof. In the invention of claim 19, one of the ceramic powders in the powder material is a ceramic powder which is barium titanate, strontium titanate, calcium titanate or a mixture thereof, and the B powder is N powder.
18. The method for manufacturing an overvoltage protection device according to claim 17, wherein the ceramic powder is composed of an oxide of an element selected from the group consisting of b, Mn, Cu, Co, and Si or a mixture thereof. I have. The invention of claim 20 is
The material density of the porous material body is 30-90 of the theoretical density.
%. The overvoltage protection element according to claim 17, wherein The invention according to claim 21 is that, after at least two kinds of ceramic powders are sufficiently mixed, prebaking is performed, and the powder material and the glass powder having the pn junction formed are dispersed in a solvent containing a binder to form a paste-like material. Get,
This paste material is filled between two electrodes having a gap, the paste material is brought into contact with both electrodes, dried and baked, and the powder of the material is joined to form a porous material body. To obtain an overvoltage protection element. In the invention according to claim 22, one of the ceramic powders in the powder material is a ceramic powder containing zinc oxide, and the other is B, Bi, Ba, S
22. The ceramic powder according to claim 21, wherein the ceramic powder is composed of an oxide of an element selected from the group consisting of i, Sr, Pb, Pr, Co, Mn, Sb or Cr, or a mixture thereof. This is a method for manufacturing an overvoltage protection element. The invention of claim 23 is the ceramic powder in which one of the ceramic powders in the powder material is barium titanate, strontium titanate, calcium titanate or a mixture thereof, and the B powder is Nb, Mn, C
22. The method for manufacturing an overvoltage protection device according to claim 21, wherein the ceramic powder is made of an oxide of an element selected from the group consisting of u, Co, and Si or a mixture thereof. An invention according to claim 24 is the overvoltage protection device according to claim 21, wherein the material density of the porous material body is 30 to 90% of the theoretical density.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 In the fine structure of the powder material shown in FIGS. 2 and 3, reference numeral 10 denotes zinc oxide powder, zinc oxide itself is an n-type semiconductor, and resistance at room temperature. The value is only several Ω-cm, and the coating layer 12 is, for example, B,
Bi, Ba, Si, Sr, Pb, Pr, Co, Mn, S
It is composed of a p-type semiconductor that is an oxide of an element selected from the group consisting of b or Cr or a mixture thereof, a pn junction is formed between this coating layer and zinc oxide, and the powder is a p-type semiconductor and n-type. A semiconductor-covered state emerges, which results in a pnp structure, whereby under normal working voltage,
A high electrical resistance situation emerges, the voltage increases rapidly when surges appear, and when the total breakdown voltage at the interface is reached, the material instantaneously breaks down, with only a few resistances at this time. Ω-cm, large current is passed, surge energy is introduced into the ground wire, and after the surge energy passes, the interface recovers to the original high electrical resistance form, and the process protection circuit is achieved by this process. I do.

The method of manufacturing the overvoltage protection material of the present invention is as shown in FIG. 4, and each step is as follows. Steps (1) and (2): Zinc oxide and a p-type semiconductor powder such as bismuth oxide powder are uniformly mixed. Among them, zinc oxide powder accounts for 50 to 97% by weight. (3), (4) Step: The mixed oxide powder obtained in the step (2) is pre-baked at a temperature of 800 to 1600 ° C. After pre-baking (3) and polishing (4), the crystal grain structure of the material becomes as shown in FIG. 2, and a pn junction state is formed between the p-type semiconductor 12, for example, bismuth oxide and zinc oxide 10. (5) Step: The powder material and the glass powder obtained in the step (4) are uniformly dispersed in a solvent containing a binder to obtain a paste-like material. (6) Step: The paste-like material obtained in the step (5), as shown in FIG.
, And the drying (7) and (8) baking steps are performed to obtain a product of the overvoltage protection element.

Embodiment 2: Another kind of material composition of the material of the overvoltage protection element of the present invention is two kinds of ceramic powder, so-called A powder and B powder, wherein A powder is barium titanate, strontium titanate, Ceramic powder which is calcium titanate or a mixture thereof is used.
An oxide of an element selected from the group consisting of b, Mn, Cu, Co, and Si or a mixture thereof. The method of manufacturing an overvoltage protection element using this material is as shown in FIG. 6, and the respective steps are as follows: (1), (2) Step: A powder and B powder are uniformly mixed . Among them, the powder A is desirably 70 to 90% by weight. (3), (4) step: Pre-baking the mixed oxide powder of the step (2) at 800 to 1500 ° C. (3)
Then, polishing (4) is performed to form a pn junction between both semiconductors. (5) Step: The material obtained in the step (4) is evenly dispersed in a solvent containing a binder to obtain a paste-like material. (6) Step: As shown in FIG. 5, the electrodes 21 and 22 and the base 30 are covered with the paste-like material obtained in the step (5), and further dried (7) and baked (8). To obtain a product of the overvoltage protection element.

In the overvoltage protection element manufactured from this powder material, the structure of the material has a porous structure. As shown in the electron micrograph of FIG.
0, the relatively deep color is the air chamber 50, and the material density is controlled to 30-90% of the theoretical density.

FIG. 8 is a voltage response curve of the electrostatic discharge of the present invention, and FIG. 9 is a current response curve of the electrostatic discharge of the present invention.
The static power source is set to 8 kV, and the figure clearly shows the situation after the material breakdown. At this time, a large amount of current passes through the element (FIG. 8), and the peak voltage is only 300 V or less (see FIG. 9). ).

[0017]

The overvoltage protection material of the present invention has the novelty and practicality of the overvoltage protection material, and the voltage protection element obtained by modifying the structure of the overvoltage protection material has stability in production and characteristics, and has low stability. It has the advantages of leakage current and low capacitance,
Ensure compliance with patent requirements. It should be noted that any modification or alteration of details that can be made based on the present invention belongs to the claims of the present invention.

[Brief description of the drawings]

FIG. 1 is a structural explanatory view of a known zinc oxide variable resistor.

FIG. 2 is an explanatory diagram of a microscopic structure of a material of an overvoltage protection element of the present invention.

FIG. 3 is a diagram illustrating another microscopic structure of the material of the overvoltage protection element of the present invention.

FIG. 4 is a manufacturing flowchart of the overvoltage protection device of the present invention.

FIG. 5 is an embodiment diagram of an overvoltage protection device manufactured according to the present invention.

FIG. 6 is another manufacturing flowchart of the overvoltage protection device of the present invention.

FIG. 7 is an electron micrograph of the overvoltage protection material of the present invention.

FIG. 8 is an electrostatic discharge protection voltage response curve of the overvoltage protection device of the present invention.

FIG. 9 is an electrostatic discharge protection current response curve of the overvoltage protection device of the present invention.

[Description of Signs] 1 Zinc oxide 12 Mixture of bismuth oxide 21 Electrode 22 Electrode 23 Overvoltage protection material 30 Substrate 40 Powder material 50 Air chamber

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E032 BA03 BA07 BA15 BA21 BB11 CA02 CC06 CC09 5E034 CA10 CB02 CB04 CB06 CC02 CC03 CC04 CC05 CC06 CC07 CC10 CC11 CC12 CC18 CC19 DA02 DB01 DB03 DC01 DE07 EA08 EB01 5G013 AA01 DA02 CB

Claims (24)

[Claims] 1. A material for an overvoltage protection element, wherein the material is a powder material in which at least two kinds of ceramic powders are sufficiently mixed and then prebaked to form a pn junction. 2. One of the ceramic powders in the powder material is a ceramic powder containing zinc oxide, and the other is B, Bi, Ba, Si, Sr, Pb, Pr,
2. The material for an overvoltage protection device according to claim 1, wherein the ceramic powder is made of an oxide of an element selected from the group consisting of Co, Mn, Sb, and Cr or a mixture thereof. 3. One of the ceramic powders in the powder material is a ceramic powder which is barium titanate, strontium titanate, calcium titanate or a mixture thereof, and B powder is Nb, Mn, Cu, Co, S
The material for an overvoltage protection device according to claim 1, wherein the material is a ceramic powder composed of an oxide of an element selected from the group consisting of i or a mixture thereof. 4. The powder material has an average particle size of 0.1-1.
2. The material for an overvoltage protection element according to claim 1, wherein the thickness is set to 00 μm. 5. A powdery material in which at least two kinds of ceramic powders are sufficiently mixed and then pre-baked to form a pn junction are uniformly dispersed in a solvent to obtain a paste-like material. It is manufactured by filling the material between two electrodes with a gap, bringing the pasty material into contact with both electrodes, drying and baking this pasty material, joining the material powder, and obtaining a porous material body An overvoltage protection element, characterized in that: 6. One of the ceramic powders in the powder material is a ceramic powder containing zinc oxide, and the other is B, Bi, Ba, Si, Sr, Pb, Pr,
6. The overvoltage protection device according to claim 5, wherein the ceramic powder is made of an oxide of an element selected from the group consisting of Co, Mn, Sb, and Cr or a mixture thereof. 7. One of the ceramic powders in the powder material is a ceramic powder which is barium titanate, strontium titanate, calcium titanate or a mixture thereof, and B powder is Nb, Mn, Cu, Co, S
6. The overvoltage protection device according to claim 5, wherein the ceramic powder is composed of an oxide of an element selected from the group consisting of i or a mixture thereof. 8. The method according to claim 5, wherein the material density of the porous material is 30 to 90% of the theoretical density.
3. The overvoltage protection device according to claim 1. 9. A paste material is obtained by sufficiently mixing at least two types of ceramic powders and then pre-baking, and uniformly dispersing the powder material having formed a pn junction in a solvent to obtain a paste material. Filling the material between the two electrodes having a gap, bringing the pasty material into contact with both electrodes, drying and baking this pasty material, joining the material powder, forming a porous material body, A method for manufacturing an overvoltage protection element, which obtains a protection element. 10. One of the ceramic powders in the powder material is a ceramic powder containing zinc oxide, and the other is B, Bi, Ba, Si, Sr, Pb, Pb.
The method for manufacturing an overvoltage protection device according to claim 9, wherein the ceramic powder is made of an oxide of an element selected from the group consisting of r, Co, Mn, Sb, and Cr or a mixture thereof. . 11. One of the ceramic powders in the powder material is a ceramic powder that is barium titanate, strontium titanate, calcium titanate or a mixture thereof, and B powder is Nb, Mn, Cu, Co, S
The method for manufacturing an overvoltage protection element according to claim 9, wherein the ceramic powder is composed of an oxide of an element selected from the group consisting of i or a mixture thereof. 12. The overvoltage protection device according to claim 9, wherein a material density of the porous material body is set to 30 to 90% of a theoretical density. 13. At least two kinds of ceramic powders are sufficiently mixed and then pre-baked, and a powder material having a pn junction formed is uniformly dispersed in a solvent containing a binder to obtain a paste-like material. This paste material is filled between two electrodes having a gap, the paste material is brought into contact with both electrodes, dried and baked, and the powder of the material is joined to form a porous material body. A method for producing an overvoltage protection element, comprising: 14. One of the ceramic powders in the powder material is a ceramic powder containing zinc oxide, and the other is B, Bi, Ba, Si, Sr, Pb, Pb.
The method for manufacturing an overvoltage protection device according to claim 13, wherein the ceramic powder is made of an oxide of an element selected from the group consisting of r, Co, Mn, Sb, and Cr or a mixture thereof. . 15. One of the ceramic powders in the powder material is a ceramic powder that is barium titanate, strontium titanate, calcium titanate or a mixture thereof, and B powder is Nb, Mn, Cu, Co, S
The method for manufacturing an overvoltage protection element according to claim 13, wherein the ceramic powder is composed of an oxide of an element selected from the group consisting of i or a mixture thereof. 16. The overvoltage protection device according to claim 13, wherein a material density of the porous material body is set to 30 to 90% of a theoretical density. 17. A method in which at least two types of ceramic powders are sufficiently mixed and then prebaked, and a powder material and a glass powder having a pn junction formed therein are dispersed in a solvent to obtain a paste-like material. Filling the paste-like material between the two electrodes having a gap, bringing the paste-like material into contact with both electrodes, drying and baking this paste-like material, bonding the powder of the material, and forming a porous material body; A method for manufacturing an overvoltage protection element, which obtains an overvoltage protection element. 18. One of the ceramic powders in the powder material is a ceramic powder containing zinc oxide, and the other is B, Bi, Ba, Si, Sr, Pb, Pb.
The method for manufacturing an overvoltage protection element according to claim 17, wherein the ceramic powder is made of an oxide of an element selected from the group consisting of r, Co, Mn, Sb, and Cr or a mixture thereof. . 19. One of the ceramic powders in the powder material is a ceramic powder which is barium titanate, strontium titanate, calcium titanate or a mixture thereof, and B powder is Nb, Mn, Cu, Co, S
18. The method for manufacturing an overvoltage protection device according to claim 17, wherein the ceramic powder is composed of an oxide of an element selected from the group consisting of i or a mixture thereof. 20. The overvoltage protection device according to claim 17, wherein a material density of the porous material body is set to 30 to 90% of a theoretical density. 21. After sufficiently mixing at least two types of ceramic powders, prebaking is performed, and a powder material and a glass powder having a pn junction formed are dispersed in a solvent containing a binder to obtain a paste-like material. The paste-like material is filled between two electrodes having a gap, the paste-like material is brought into contact with both electrodes, dried and baked, and the powder of the material is joined to form a porous material body. A method for manufacturing an overvoltage protection element, which is formed to obtain an overvoltage protection element. 22. One of the ceramic powders in the powder material is a ceramic powder containing zinc oxide, and the other is B, Bi, Ba, Si, Sr, Pb, Pb.
The method for manufacturing an overvoltage protection device according to claim 21, wherein the ceramic powder is made of an oxide of an element selected from the group consisting of r, Co, Mn, Sb, and Cr or a mixture thereof. . 23. One of the ceramic powders in the powder material is a ceramic powder which is barium titanate, strontium titanate, calcium titanate or a mixture thereof, and B powder is Nb, Mn, Cu, Co, S
22. The method for manufacturing an overvoltage protection device according to claim 21, wherein the ceramic powder is composed of an oxide of an element selected from the group consisting of i or a mixture thereof. 24. The overvoltage protection device according to claim 21, wherein the material density of the porous material body is 30 to 90% of the theoretical density.