JP2002329872A - Material of protection element for transient overvoltage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material of a protection element for transient overvoltages. SOLUTION: In the material of the protection element for transient overvoltages, at least two kinds of powder materials are mixed. One kind of them has a nonlinear-resistance interface, and both of a pn-junction and a Schottky barrier belong to the nonlinear-resistance interface. The other kind is conductor powder. By mixing uniformly these powders with an appropriate bonding agent, a structure for a protection element configured in the mode of distributed depositions of these powders is obtained. As a result, the total number of the pn-junctions present between the electrodes of the protection element is reduced by the presence of the conductors to lower the breakdown voltage of the protection element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for a kind of transient overvoltage protection device having a breakdown voltage. Body material, this interface or a so-called non-linear resistance interface, the other kind is a conductor powder, and the conductor powder is dispersed between powder materials having a pn junction, so that the two A material for a transient overvoltage protection device, wherein the total number of pn junctions is relatively reduced, thereby relatively lowering the breakdown voltage of the device.

[0002]

2. Description of the Related Art The material and structure of a known zinc oxide variable resistor include zinc oxide, B, Bi, Ba, Si, Sr, and P.
It is composed of an oxide such as b, Pr, Co, Mn, Sb or Cr or a mixed material thereof. For example, bismuth oxide forms one crystal intermediate layer between zinc oxide particles, and the structure of such a material is In addition, it is required to manufacture the structure so that the material density approaches the theoretical density. Generally, 90% or more of the theoretical density is a product to be commercialized. However, such devices have the disadvantage of high capacitance. The crystalline intermediate 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 compatible in high frequency circuits,
This is one significant drawback of such a variable resistor. The material of the transient overvoltage protection device of the present invention belongs to the powder diffusion structure, and therefore, even if the same material composition and the same device design are used, the material belongs to the powder diffusion structure, so that the relatively low capacitance and leakage current are obtained. It has a current and therefore is applied in high frequency circuits and antennas.

[0003] The breakdown voltage of a zinc oxide variable resistor is related to the number of zinc oxide grains between the two electrodes, and there is a single crystal intermediate layer between the zinc oxide grains. This crystal intermediate layer is made of bismuth oxide or another oxide, and is generally called a rich bismuth area. A nonlinear resistance interface, a pn junction or a Schottky barrier is formed between the zinc oxide and the rich bismuth area. If the zinc oxide semiconductor is represented by N and the rich bismuth area is represented by P from one end to the other end of the electrode, the PN structure of this resistor is EPNPNPN ... ...- N-P-N-P-
E. Among them, E is a conductor electrode, and each P-N-P junction has one breakdown voltage Vb1, and if there are a total of several P-N-P junctions between the electrodes, the breakdown voltage becomes Vb can be described as the sum of Vb1.

[0004] In the prior invention, a material structure in which a powder having a pn junction is diffused and deposited is described in a patent pending. If a pn-junction powder formed by coating a P-type semiconductor with an N-type semiconductor is taken as an example, a powder having a pn junction is simply referred to as a pn powder, and between the two electrodes of the element, There are a plurality of pn powders.
When an N-type semiconductor is displayed, the pn junction between the electrodes is displayed as follows. EPNPPPSPNPPP ... PNP
-SPNPPE Among them, PNP represents condyle powder, S represents a spacer layer between powders, and S represents air or glass insulator. , The breakdown voltage between them is denoted by Vs. Alternatively, the crystal grains may come into contact with each other and S may not be present. Each PNP has a breakdown voltage Vb2, which is composed of several crystal grains between the electrodes, whereby the breakdown voltage Vb of the device can be expressed as the sum of Vs of the sum of Vb2 and Vs2. It is.

[0005] US Pat. No. 4,726,991, which has a material structure in which a conductor or semiconductor powder is covered with a single insulating layer. The thickness of this insulating layer is less than several hundred square meters, and such a material structure has one disadvantage in practice. First, the thickness of the insulating layer is within several hundred square meters, and the difficulty of the manufacturing process to control this thickness is extremely high. When the thickness of the insulating layer to cover is very thin, it is easy to form a short circuit of the element. When the thickness of the insulating layer is slightly thicker, the breakdown voltage may be increased, which is a drawback of the technique of covering the surface of the conductor or semiconductor powder with the insulating layer.

[0006] Similarly, US Pat.
No. 5,294,374, whose material structure is a mixture of a conductor powder coated with one insulating layer and an uncoated semiconductor.
It can be between Å and 1 micron, and semiconductors can be used for the coating layer material. Basically, any of these materials is an insulating material or a semiconductor material that blocks the passage of electric current and achieves the purpose of high electric resistance. However, since the thickness of the coating layer directly affects the breakdown voltage of the device, uniformity of the thickness has become sufficiently important.

A variable resistance material in which various conductor powders, semiconductor powders or non-conductor powders are uniformly mixed in a material containing a binder has already been published in US patents, for example, US Pat. 685,026,3,685,0
28, 4,977,357, 5,068,634, 5,
068,634, 5,260,848, 5,294,3
74, 5,393,596, 5,807,509. The powders of these material structures themselves do not have non-linear resistance characteristics. Its breakdown properties are exhibited by the composition of these powders, and this principle is different from that described in the present invention. The material structure of the present invention has novelty and practicality.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a kind of transient overvoltage protection element material, which comprises mixing at least two kinds of powder materials, one of which is a non-linear resistance interface. The pn junction and the Schottky barrier both belong to the non-linear resistance interface, and the other type is a conductive powder, and these powders are mixed uniformly with an appropriate adhesive to form these. The structure is such that the powder is formed by a diffusion deposition method.
The total number of n-junctions is reduced by the presence of the conductor, thus lowering the breakdown voltage of the device.

[0009]

According to the first aspect of the present invention, at least one kind of powder material having a nonlinear resistance interface is uniformly mixed, and the powder material is filled between both electrodes of the device. Characterized in that a non-linear resistance characteristic is provided between the two electrodes. According to a second aspect of the present invention, the powder material having the non-linear resistance interface comprises zinc oxide powder, B, Bi, Ba, Si, S
The material for a transient overvoltage protection device according to claim 1, wherein the material has an interface formed by an oxide of r, Pb, Pr, Co, Mn, Sb, or Cr. Claim 3
In the invention, the average particle size of the powder material is 0.01-100.
The material of the transient overvoltage protection device according to claim 1, wherein the material is μm. According to a fourth aspect of the present invention, there is provided the transient overvoltage protection device according to the first aspect, wherein the powder material has an average particle diameter of 0.01 to 100 μm. According to a fifth aspect of the present invention, at least two types of powder materials are uniformly mixed, one of which is a powder material having a non-linear resistance interface, the other is a conductor powder, and the conductor powder and the non-linear resistance interface are mixed. The transient overvoltage protection device is characterized in that a powder material obtained by uniformly mixing powder materials having the following characteristics is used to provide a nonlinear resistance characteristic between both electrodes of the device. The invention of claim 6 is
The powder material having the non-linear resistance interface is composed of zinc oxide powder, B, Bi, Ba, Si, Sr, Pb, Pr, Co,
The material of the transient overvoltage protection device according to claim 5, wherein the material has an interface formed by an oxide of Mn, Sb, or Cr. The invention according to claim 7 is the material for the transient overvoltage protection element according to claim 5, wherein the conductor powder is metal powder. The invention according to claim 8 is the material for the transient overvoltage protection element according to claim 5, wherein the conductor powder is a non-metallic powder. According to a ninth aspect of the present invention, there is provided the transient overvoltage protection element material according to the fifth aspect, wherein the powder material has an average particle diameter of 0.01 to 100 μm. The invention according to claim 10 is that the powder material has an average particle diameter of 0.01-
The material of the transient overvoltage protection element according to claim 5, wherein the thickness is between 100 μm. Claim 11
In the invention, the metal powder is any one of aluminum, silver, palladium, platinum, gold, nickel, copper, tungsten, chromium, iron, zinc, titanium, niobium, molybdenum, ruthenium, lead, and iridium powder. The material of the transient overvoltage protection element according to claim 7 characterized by the following. The invention according to claim 12 is characterized in that the metal powder is any one of aluminum, silver, palladium, platinum, gold, nickel, copper, tungsten, chromium, iron, zinc, titanium, niobium, molybdenum, ruthenium, lead and iridium. The material of the transient overvoltage protection element according to claim 7, wherein the material is an alloy powder of one element. Claim 13
The invention according to claim 8, wherein the non-metallic powder is graphite powder, wherein the material is a transient overvoltage protection element according to claim 8. The invention according to claim 14 is characterized in that the non-metallic powder is tungsten carbide, titanium carbide, niobium carbide, or a compound powder that can be used instead of these compound powders. Of the transient overvoltage protection element.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The material of the transient overvoltage protection device according to the present invention is a mixture of at least two kinds of powder materials, one of which has a non-linear resistance interface, and the pn junction and the Schottky barrier are both Belongs to the nonlinear resistance interface,
The other type is a structure in which these powders are dispersed and deposited by uniformly mixing these powders and an appropriate adhesive, which is used as a conductor powder. The total number of pn junctions is reduced by the presence of the conductor, thus lowering the breakdown voltage of the device.

The transient overvoltage protection device manufactured using this material system can be applied to various types of device structures. For example,
As shown in FIG. 1, an insulating substrate 20 is a main component, first, conductor electrodes 22 and 24 are formed on a substrate, two conductor electrodes are on the same plane, and a gap 2 is formed between the electrodes.
There are eight. The powder material 28 of the present invention is filled in this gap, and by appropriate heat treatment, the powder material is deposited and the diffused structure is respected, that is, a kind of element structure is obtained.

Another viable element structure is, as shown in FIG. 2, mainly composed of a powder material 30 of the present invention.
Sintered to form a block, an electrode 34 is formed above the material, and another electrode 32 is formed below the material, thus forming a sandwich-structured element, ie, another type of transient overvoltage protection. It has an element structure.

[0013]

EXAMPLE According to the microscopic structure of the powder material shown in FIG. 3, reference numeral 10 denotes zinc oxide powder, zinc oxide itself is an N-type semiconductor, and coating layer 12 is a P-type semiconductor. Its composition is B, Bi, Ba, Si, Sr, Pb, Pr, Co,
It is composed of an oxide such as Mn, Sb or Cr or a mixed material thereof. The coating layer material contains bismuth oxide, and a pn junction is formed between the coating layer and the zinc oxide, which is an insulating layer having a high electrical resistance, and thus, under a normal working voltage, a high electrical resistance state is obtained. When the surge occurs, the voltage increases rapidly, and when the breakdown voltage of the pn junction is reached, the material instantaneously breaks down, and the electrical resistance of the material at this time is slightly several Ω-cm. This allows the passage of large currents, introduces surge energy into the ground wire, and after the surge energy passes, the pn junction recovers to its original high resistance state, thereby achieving the purpose of circuit protection by this process. The process can be repeated.

The charge is from zinc oxide powder A to zinc oxide powder C
When there is a need to transfer to A.B.C., there are three types of relatively short paths as shown in FIG.
When the coating layer is represented by P and the zinc oxide is represented by N, this route is represented by N-P-N-P-N, and both routes are two PN or NP regardless of the polarity of the electric charge. It is necessary to go through bonding. The second type is A-D-C, and this route can be expressed as N-P-D-P-N, and all pass through one PN or NP junction and one space D regardless of the polarity of the charge. I do. The breakdown voltage of these two paths is relatively high. The third type is A-E-C, E is a conductive powder, and this path is denoted by N-P-E-P-N.
Since E is a conductor, it must therefore all pass through a single PN or NP junction, regardless of the polarity of the charge, so that the breakdown voltage is the lowest of the three paths and the breakdown voltage The value of the voltage and the content of the conductor powder are related, and the higher the content of the conductor powder,
Its breakdown voltage will be lower.

When the zinc oxide powder is composed of a plurality of zinc oxide crystal lattices, that is, a plurality of coating layers are contained in one powder, that is, there is one or more PNP junctions. And the relative circumstances apply to the description of the invention.

The conductor powder is a metal conductor powder or a non-metal conductor powder, and the metal conductor powder is aluminum, silver, palladium, platinum, gold, nickel, copper, tungsten, chromium, iron, zinc, titanium, Powders of niobium, molybdenum, ruthenium, lead and iridium elements are preferred. The non-metallic conductive powder may be tungsten carbide or titanium carbide or niobium carbide powder in graphite powder or conductive carbide. Metal conductor powders also include aluminum, silver, palladium, platinum, gold, nickel, copper, tungsten, chromium,
Iron, zinc, titanium, niobium, molybdenum, ruthenium,
It can be an alloy powder of any one element in the lead and iridium powders.

FIG. 4 shows a method of manufacturing a material for a transient overvoltage protection device according to the present invention, and each step will be described below.

Steps 1 and 2: The zinc oxide powder material and the bismuth oxide powder are uniformly mixed. Among them, zinc oxide is an N-type powder, and the applied average particle size is 0.01.
-100 μm, and particularly preferably an average particle diameter of 0.1-100 μm. The size of the particle size used affects the amount of powder between the electrodes, and thus affects the breakdown voltage of the device, and its weight percentage is 50%. -97% is preferred. The bismuth oxide powder is a P-type powder, and the bismuth oxide is a P-type powder, and its weight percentage is preferably 3 to 50%. Step 3: The mixed powder of steps 1 and 2 is
Prebake at a temperature of 1600 ° C. In the process of pre-baking, the powder containing bismuth oxide forms a liquid phase at high temperature,
The surface of bismuth oxide is coated to form a crystal lattice interface between the coating phase and zinc oxide, and this interface is called a kind of pn junction or a non-linear resistance interface, or is called a Schottky barrier. Step 4: polishing the material obtained in step 3,
It is formed into a powder, and this powder has the characteristics of a non-linear resistance interface. Step 5: Add the powder material obtained in step 4 to a known binder or solvent and conductive powder. Well-known binders include, for example, ethylcellulose and other polymers, and solvents are mechanical alcohols and mechanical esters. After sufficiently uniform mixing, an operable paste-like material state is obtained. Step 6: This paste-like material is applied on a substrate having a pair of electrodes by a thick-film printing method and brought into contact with both electrodes. Step 7: Sinter the paste-like material to remove the binder and solvent, complete the manufacture of the device and, if necessary, form a further protective phase above the material to protect the material.

EXAMPLE 2 FIG. 5 shows a reaction curve of the electrostatic discharge of the present invention. Curve 1 is a response curve of a current passing element of an electrostatic discharge. The electrostatic source is 8 kV, and the situation after material breakdown can be seen from the figure. At this time, a large amount of current is allowed to pass through the element. The maximum passing current is greater than 30A. Curve 2 shows the voltage curve with a peak voltage of only 30
At 0V or less, that is, at the appearance of 8 kV electrostatic, it passes through the device of the present invention, and the voltage drops to 300V or less, thereby sufficiently achieving the function of protecting the electronic circuit. Other electrical expressions are, for example, a capacitance of about 0.5 pF and a leakage current of about 1 n.
A.

[0020]

The transient overvoltage protection material of the present invention has the novelty and practicality of the transient overvoltage protection material, and the transient overvoltage protection element obtained by the modification of the structure of the transient overvoltage protection material further has manufacturing and characteristics. It has the advantages of high stability, low leakage current and small capacitance, and conforms to the provisions of the patent. The above is a description of a specific embodiment of the present invention, and when modifications and alterations performed in accordance with the concept of the present invention do not cause the resulting functional action to exceed the spirit shown in the specification and drawings, any of the modifications fall within the scope of the present invention. I state here that I belong.

[Brief description of the drawings]

FIG. 1 is a structural representation of a feasible transient overvoltage protection device of the present invention.

FIG. 2 is another structural schematic view of a feasible transient overvoltage protection device according to the present invention.

FIG. 3 is a microscopic structural view of the powder material of the present invention.

FIG. 4 is a flowchart of a method for producing a transient overvoltage protection material according to the present invention.

FIG. 5 is a reaction curve diagram of the electrostatic discharge of the present invention.

[Explanation of symbols]

 Reference Signs List 10 zinc oxide 12 coating layer bismuth oxide mixture 20 insulating substrate 22 conductor electrode 24 conductor electrode 26 transient overvoltage protection material 28 electrode gap 30 transient overvoltage protection material 32 conductor electrode 34 conductor electrode A zinc oxide powder B zinc oxide powder C oxidation Zinc powder D space E Conductive powder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02H 9/04

Claims (14)

[Claims] At least one kind of powder material having a non-linear resistance interface is uniformly mixed, and the powder material is filled between both electrodes of the device to provide a non-linear resistance characteristic between both electrodes of the device. A material for a transient overvoltage protection element, characterized in that: 2. The powder material having the non-linear resistance interface includes zinc oxide powder, B, Bi, Ba, Si, Sr, P
The material of the transient overvoltage protection device according to claim 1, wherein the material has an interface formed by an oxide of b, Pr, Co, Mn, Sb, or Cr. 3. The powder material has an average particle size of 0.01-1.
The material of the transient overvoltage protection device according to claim 1, wherein the material is 00 µm. 4. The powder material has an average particle size of 0.01-1.
The material for a transient overvoltage protection device according to claim 1, characterized in that it is between 00 µm. 5. At least two kinds of powder materials are uniformly mixed, one of which is a powder material having a non-linear resistance interface, the other is a conductor powder, and has a non-linear resistance interface with the conductor powder. A material for a transient overvoltage protection element, wherein a non-linear resistance characteristic is provided between both electrodes of the element by a powder material obtained by uniformly mixing the powder material. 6. The powder material having the non-linear resistance interface comprises zinc oxide powder, B, Bi, Ba, Si, Sr, P
The material of the transient overvoltage protection device according to claim 5, wherein the material has an interface formed by an oxide of b, Pr, Co, Mn, Sb, or Cr. 7. The material for a transient overvoltage protection device according to claim 5, wherein the conductor powder is a metal powder. 8. The material for a transient overvoltage protection device according to claim 5, wherein the conductive powder is a non-metallic powder. 9. The powder material having an average particle size of 0.01-1.
The material of the transient overvoltage protection device according to claim 5, wherein the thickness is 00 µm. 10. The powder material having an average particle size of 0.01-
The material for a transient overvoltage protection device according to claim 5, characterized in that it is between 100 m. 11. The method according to claim 11, wherein the metal powder is aluminum, silver,
Palladium, platinum, gold, nickel, copper, tungsten,
8. The material for a transient overvoltage protection device according to claim 7, wherein the material is any one of chromium, iron, zinc, titanium, niobium, molybdenum, ruthenium, lead, and iridium powder. 12. The method according to claim 12, wherein the metal powder is aluminum, silver,
Palladium, platinum, gold, nickel, copper, tungsten,
8. The material for a transient overvoltage protection device according to claim 7, wherein the material is an alloy powder of any one of chromium, iron, zinc, titanium, niobium, molybdenum, ruthenium, lead, and iridium. 13. The material for a transient overvoltage protection device according to claim 8, wherein said non-metallic powder is graphite powder. 14. The non-metallic powder is tungsten carbide,
9. The material for a transient overvoltage protection device according to claim 8, wherein the material is a compound powder that can be used in place of titanium carbide, niobium carbide, or a compound powder thereof.