JP2006294357A - Discharge element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact, low-cost discharge element excellent in characteristics stability, heat resistance, and anti-surge characteristics. <P>SOLUTION: The discharge element is provided with an envelope member 2 made of an electric insulating material and fitted with a through-hole 3, and discharge electrode members 4, 5 forming a sealing space 6 to be a discharge gap between themselves and installed opposed to each other so as to close each open end of the through-hole 3. The envelope member 2 is made of electric insulating oxide containing Zn and Ti. The discharge electrode members 4, 5 is made of low-resistance oxide containing rare earth elements, alkali earth metal elements and Mn, and that, with a specific resistance within the range of 10<SP>-4</SP>to 1 Ωcm. The sealing space 6 is filled with oxygen gas. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a discharge element and a method for manufacturing the same, and more particularly, to an improvement for reducing the size, performance, and cost of the discharge element.

  In recent years, home information home appliance systems in which a telephone line is connected to an information terminal device and further connected to other home appliances are becoming widespread. However, in a home information home appliance system, lightning surges or the like can easily enter a general home appliance from a telephone line, and the reverse process is also conceivable, and damage due to lightning surges is expected to increase.

  An arrester is used as an element for preventing damage as described above. The arrester has a function of absorbing a lightning surge (including an induced lightning surge) by discharge, and generally has an ability to withstand a large surge. In addition, the arrester has a feature that it has a small electrostatic capacity and is unlikely to adversely affect high-frequency signals.

  In general, the arrester has a structure in which an inert gas is sealed inside an alumina bobbin, and electrode members made of a metal such as Cu are sealed to both ends of the alumina bobbin (for example, patents) Reference 1) and laser processing a dielectric, thereby creating a gap, and sealing this together with an inert gas in a glass tube.

  On the other hand, some home appliances have a smaller size and higher performance due to the built-in computer, and as a result, noise resistance tends to decrease. Therefore, the arrester is required to be downsized and the discharge voltage to be lowered.

  However, the discharge voltage of the arresters currently on the market is 100 V or higher, and it is difficult to cause discharge at a lower voltage. This is because there are structural problems such as the distance of the gap (discharge) to be discharged, and there is a problem in the material that triggers the discharge.

Further, the conventional arrester having the structure as described above has a limit in miniaturization. Further, in the conventional arrester, since metal and ceramic are combined, gas leakage may be caused due to a difference in thermal expansion behavior between the metal and ceramic due to heat generation during discharge. Furthermore, in the arrester having a conventional structure, a relatively complicated process is required in which the components constituting the arrester are separately prepared and then assembled, resulting in an increase in cost.
JP-A-8-102355

  Accordingly, an object of the present invention is to provide a discharge element such as an arrester and a method for manufacturing the same that can solve the above-described problems.

The discharge element according to the present invention is formed of an electrically insulating material and has a through hole in a state of facing each other while forming a sealing space serving as a discharge gap between the outer member and the through hole provided therein. The first and second discharge electrode members are provided so as to close the respective open ends, and the surrounding member is made of an electrically insulating oxide containing Zn and Ti, The first and second discharge electrode members are made of a low-resistance oxide containing a rare earth element, an alkaline earth metal element, and Mn, and having a specific resistance in the range of 10 ^{−4 to 1} Ω · cm. Is characterized by being filled with oxygen gas.

  In the discharge element according to the present invention, it is preferable that a plating film is formed on the surface exposed to the outside of each of the first and second discharge electrode members. The plating film described above may be divided into a first plating film and a second plating film formed in a state of being separated from each other. The first plating film and the second plating film may be divided for both the first and second discharge electrode members or for either one of them.

  The through-hole provided in the surrounding member has a substantially rectangular vertical cross-sectional shape, and each of the first and second discharge electrode members includes an electrode portion inserted into each end portion of the through-hole, and the surrounding It is preferable that the electrode portion has a substantially rectangular vertical cross-sectional shape that is in close contact with the inner peripheral surface of the through hole.

  The surrounding member includes first and second surrounding members arranged in series on the same axis, and the first discharge electrode member is provided in each of the through holes provided in the first and second surrounding members. The second discharge electrode member is provided so as to close the opening end located outside each of the holes, and the second discharge electrode member is an opening located inside each of the through holes provided in the first and second surrounding members. You may provide so that an end may be closed in common. Such a structure constitutes a three-pole type discharge element.

  The present invention is also directed to a method for manufacturing a discharge element.

The method for manufacturing a discharge element according to the present invention includes a step of preparing an insulating green sheet including an electrically insulating oxide containing Zn and Ti and provided with a through-hole penetrating in the thickness direction, and a rare earth and alkali A step of preparing a low-resistance green sheet containing a low-resistance oxide containing an earth metal element and Mn and having a specific resistance in the range of 10 ^{−4 to 1} Ω · cm; and a rare earth element and an alkaline earth metal element And a step of preparing a low-resistance paste containing a low-resistance oxide having a specific resistance in the range of 10 ^{−4 to 1} Ω · cm, and a step of preparing a filler made of a material that disappears by firing Filling the through hole of the insulating green sheet with a low-resistance paste to form a first insulating green sheet; filling the through hole of the insulating green sheet with a filler; A step of forming a green laminate, a step of producing a green laminate in which the first insulating green sheet is sandwiched between the second insulating green sheets and the low resistance green sheet is sandwiched between the second insulating green sheets and the green And firing the laminate in an atmosphere having an oxygen concentration higher than that of the atmosphere.

  According to the present invention, since the discharge element can be manufactured by the manufacturing method as described above, the discharge element can be reduced in size and cost, and the gap between the first and second discharge electrode members can be reduced. Since the dimensions can be arbitrarily set, discharge can be generated at a lower voltage as required.

  Further, the low resistance oxide constituting the first and second discharge electrode members is stable at a high temperature and can flow a large current, and further, an electrically insulating oxide constituting the outer member and Since there is almost no difference in thermal expansion coefficient between them, cracks and the like caused by the difference in thermal expansion behavior due to heat generation when a large surge flows can be advantageously prevented.

  In addition, since both the electrically insulating oxide and the low resistance oxide used in the discharge element according to the present invention are resistant to oxidation and reduction at high temperatures, there is no need to worry about deterioration due to oxidation, and in a sealed space. As the filling gas, oxygen gas can be selected. Therefore, according to the discharge element of the present invention, discharge stability at a lower voltage can be realized.

  Further, the low-resistance oxide constituting the first and second discharge electrode members has a composition containing at least a rare earth element, an alkaline earth metal element, and Mn. By changing this composition ratio, The specific resistance of the low resistance oxide can be adjusted. In this connection, for example, in the gap type arrester, since the secondary discharge voltage is low, there is a case where a discharge subsequent flow occurs in which the current continues to flow for a long time after the discharge. In order to prevent this, an appropriate resistor is connected in series to the arrester. According to the discharge element of the present invention, as described above, since the specific resistance of the low resistance oxide constituting the first and second discharge electrode members can be adjusted, these first and second discharges can be adjusted. The electrode member can also function as a resistor for preventing a discharge subsequent flow. Therefore, since it is not necessary to add a separate resistor, it is possible to save space and simplify the mounting process.

  In the discharge element according to the present invention, when a plating film made of a conductive metal is formed on the surface exposed to the outside of each of the first and second discharge electrode members, these discharge electrode members and other electric It is possible to obtain a stable electrical connection state between the discharge element and the resistance value provided by the discharge electrode member.

  When the above-described plating film is divided into a first plating film and a second plating film formed in a state of being separated from each other, a resistance is generated between the first plating film and the second plating film. Therefore, a state in which a resistor is connected in parallel to the discharge element can be obtained, and the effect of suppressing overvoltage can be enhanced.

  In the discharge element according to the present invention, the through-hole has a substantially rectangular vertical cross-sectional shape, and the discharge electrode member is disposed on the outer surface of the surrounding member and the electrode portion inserted into each end portion of the through-hole. And the electrode part has a substantially rectangular vertical cross-sectional shape that is in close contact with the inner peripheral surface of the through hole, the airtightness of the sealed space can be improved, and the first and first Since each electrode part of 2 discharge electrode members can be made into the state which opposed only in each end surface, discharge stability can be improved more.

  1 to 6 are for explaining a first embodiment of the present invention. Here, FIG. 6 shows the discharge element 1, and FIGS. 1 to 5 show several steps performed to manufacture the discharge element 1.

  First, the discharge element 1 as a finished product will be described with reference to FIG. 6A is a longitudinal sectional view of the discharge element 1, and FIG. 6B is an equivalent circuit diagram of the discharge element 1. In the equivalent circuit diagram of FIG. 6B, elements corresponding to the elements shown in FIG. 6A are given the same reference numerals so that the correspondence can be easily understood.

  The discharge element 1 includes an enclosing member 2 made of an electrically insulating material. The surrounding member 2 is provided with a through hole 3. The through-hole 3 has a substantially rectangular vertical cross-sectional shape, as well shown in FIG. Here, the reason why the vertical cross-sectional shape of the through hole 3 is “substantially rectangular” is due to a problem in the manufacturing method described later, and when laser processing, die punching, or the like is applied to form the through hole 3. This is because the through-holes 3 are inevitably tapered and deviate from the “rectangular shape” in a strict sense.

  The discharge element 1 also includes first and second discharge electrode members 4 and 5. The first and second discharge electrode members 4 and 5 are provided so as to close the respective open ends of the through-holes 3 in a state of facing each other while forming a sealing space 6 serving as a discharge gap between them. Yes. More specifically, the first and second discharge electrode members 4 and 5 are disposed on the outer surfaces of the surrounding member 2 and the electrode portions 7 and 8 inserted into the end portions of the through hole 3, respectively. Terminal portions 9 and 10 are provided. The electrode portions 7 and 8 have a substantially rectangular vertical cross-sectional shape that is in close contact with the inner peripheral surface of the through hole 3.

  Although not shown in FIG. 6A, the cross-sectional shape of each of the through-hole 3 and the electrode portions 7 and 8 is usually circular, but is not limited thereto, and may be a rectangle or the like.

  On the surface exposed to the outside of each of the first and second discharge electrode members 4 and 5, more specifically, on the surface exposed to the outside of the terminal portions 9 and 10, a plating film made of a conductive metal 11 and 12 are formed. The plating films 11 and 12 are composed of, for example, a Ni film and a Zn or Sn film formed thereon.

In such a discharge element 1, the surrounding member 2 is made of an electrically insulating oxide containing Zn and Ti. The first and second discharge electrode members 4 and 5 are made of a low resistance oxide containing a rare earth element, an alkaline earth metal element, and Mn and having a specific resistance in the range of 10 ^{−4 to 1} Ω · cm. Become. The sealed space 6 is filled with oxygen gas. Preferably, the sealed space 6 is filled with 100% oxygen gas.

For the resistivity, ^10-4 The reason for limiting the range of ~1Ω · cm is, ^10-4 Omega · cm is the minimum value of the specific resistance of the material, on the other hand, when it exceeds 1 [Omega · cm, discharge is suppressed This is because it is not preferable.

  Next, with reference to FIG. 1 thru | or FIG. 5, the preferable manufacturing method of the discharge element 1 is demonstrated.

First, as shown in FIG. 1, an insulating green sheet 21 is prepared. The insulating green sheet 21 contains an electrically insulating oxide containing Zn and Ti. Such an insulating green sheet 21 is made into a slurry by, for example, adding a binder, a solvent, a dispersant and a plasticizer to a calcined powder obtained by calcining a mixture of ZnO powder and TiO ₂ powder. It can be obtained by molding this into a sheet.

On the other hand, a low resistance green sheet 22 is prepared as shown in FIG. The low-resistance green sheet 22 contains a low-resistance oxide containing rare earth, an alkaline earth metal element, and Mn, and having a specific resistance in the range of 10 ^{−4 to 1} Ω · cm. Such a low resistance green sheet 22 is prepared by mixing a rare earth element oxide powder such as La ₂ O ₃ , an alkaline earth metal carbonate powder such as SrCO ₃ and a Mn ₃ O ₄ powder. The calcined powder obtained by baking can be obtained by adding a binder, a solvent, a dispersant and a plasticizer to form a slurry, which is then formed into a sheet.

  Next, as shown in FIG. 3, the insulating green sheet 21 shown in FIG. 1 is provided with a through hole 23 that penetrates in the thickness direction. The through hole 23 is formed by, for example, laser or die punching. As shown in FIG. 3 (a), the through-hole 23 filled with the low resistance paste 24 is the first insulating green sheet 21a. On the other hand, as shown in FIG. A material in which the hole 23 is filled with the filler 25 is the second insulating green sheet 21b.

Here, as the low resistance paste 24, a paste having the same composition as the slurry prepared for producing the low resistance green sheet 22 described above is used. Therefore, the low-resistance paste 24 contains a low-resistance oxide containing a rare earth element, an alkaline earth metal element, and Mn and having a specific resistance in the range of 10 ^{−4 to 1} Ω · cm.

  Further, the filler 25 is made of a material that disappears as a result of a firing step described later, and can be made of a resin material such as vinyl acetate or made of carbon powder.

  Next, as shown in FIG. 4, the laminating process is performed in a laminating sequence in which the second insulating green sheet 21b is sandwiched by the first insulating green sheet 21a and the outside is sandwiched by the low resistance green sheet 22. And these are crimped | bonded and the green laminated body 26 as shown in FIG. 5 is produced.

  The green laminated body 26 shown in FIG. 5 is in a mother state from which a plurality of discharge elements 1 can be taken out. Therefore, next, the green laminated body 26 is cut along the cut line 27 and then fired. In this firing step, an atmosphere having a higher oxygen concentration than the atmosphere, for example, an atmosphere of 100% oxygen is applied.

  Next, electroplating is applied, and the plating films 11 and 12 are formed.

  When the above steps are completed, the discharge element 1 as shown in FIG. 6 is completed. In the discharge element 1 shown in FIG. 6, the surrounding member 2 is derived from the first and second insulating green sheets 21a and 21b. The through-hole 3 is derived from the through-hole 23, and in particular the sealed space 6 is provided by the through-hole 23 left as a result of the disappearance of the filler 25 by firing. Further, the electrode portions 7 and 8 of the first and second discharge electrode members 4 and 5 are derived from the low-resistance paste 24 filled in the through holes 23 of the first insulating green sheet 21 and are also terminals. The parts 9 and 10 are derived from the low resistance green sheet 22.

  Further, as described above, by firing in an atmosphere having a higher oxygen concentration than the atmosphere, the sealed space 6 is filled with oxygen gas after firing.

  The thickness of each of the insulating green sheets 21a and 21b and the low resistance green sheet 22 used in the manufacturing method described above, the number of stacked sheets, and the cross-sectional dimensions of the through holes 23 can be arbitrarily changed as necessary. it can. In particular, it is possible to easily adjust the gap size between the first and second discharge electrode members 4 and 5 in the obtained discharge element 1 by changing the thickness and number of the second insulating green sheets 21b. it can.

As described above, the surrounding member 2 is made of an electrically insulating oxide containing Zn and Ti. This electrically insulating oxide basically has a Zn ₂ TiO ₄ spinel structure, but not only this but also ZnTiO ₃ or ZnO, for example, may be included.

  Here, the reason why Zn is essential is to use the secondary electron emission effect of the above-described Zn oxide. When charged particles (such as primary electrons or ions) collide with the target material from the outside, electrons are emitted from the target material by the energy. This is called the secondary electron emission effect. Secondary ions are emitted by collision of oxygen ions ionized in the initial discharge by voltage application with the Zn oxide. In order to improve the ease of discharge and the stability, it is necessary to increase the number of carriers that carry charges in the gas, and the emission of secondary electrons increases the number of carriers. Zn oxide emits secondary electrons, but its electrical insulation does not deteriorate. The emitted secondary electrons only work as carriers in the gas and do not serve as carriers in the Zn oxide, so that leakage on the wall surface can be suppressed and discharge can be easily generated.

Ti is essential because it reacts with an alkaline earth metal in the low resistance oxide constituting the discharge electrode members 4 and 5, and if the alkaline earth metal is, for example, Sr, an SrTiO ₃ -based reaction layer is formed. This is because the adhesiveness between the surrounding member 2 and each of the discharge electrode members 4 and 5 is increased by forming them at the interface.

Further, the electrically insulating oxide constituting the surrounding member 2 and the low resistance oxide constituting the discharge electrode members 4 and 5 have very close shrinkage curves in the sintered region, and as described above, SrTiO _{Since a three-} system reaction layer is formed, the two can be closely bonded. In addition, SrTiO ₃ and the above-mentioned low-resistance oxide have the same perovskite crystal structure and the difference in lattice constant can be less than 1%, so that the generation of stress due to lattice constant mismatch is suppressed. You can also.

In addition, the electrical insulating oxide may contain additives other than Zn and Ti to the extent that the above effects are not hindered. As an example, it has been confirmed that an electrically insulating oxide to which 50 mol% of Al ₂ O ₃ atomized so as not to inhibit the sinterability can be used without any problem.

As described above, the discharge electrode members 4 and 5 are made of a low-resistance oxide containing a rare earth element, an alkaline earth metal element, and Mn. This low-resistance oxide is basically a perovskite type compound such as (La, Sr) MnO ₃ , but does not preclude inclusion of a heterogeneous phase.

As described above, Ti contained in the electrically insulating oxide and the alkaline earth metal (in some cases, the rare earth element) contained in the low resistance oxide form a reaction layer. As a result, the electrically insulating oxide Zn remains in the low-resistance oxide, but this Zn reacts with Mn to form a reaction layer made of Mn ₂ ZnO ₄ , which also forms the surrounding member 2 and the discharge electrode members 4 and 5. It contributes to the joint between. Further, since the above reaction occurs within a thickness range of several tens of μm, the conductivity of a substantial part of the discharge electrode members 4 and 5 is not lowered.

  As described above, according to the discharge element 1, the electrically insulating oxide constituting the surrounding member 2 and the low resistance oxide constituting the discharge electrode members 4 and 5 are both ceramics, and have a thermal expansion coefficient. Are very close, almost no thermal stress is generated between them, and the lattice constants of the two are also approximated. From these things, it is possible to realize a dense joined state between the surrounding member 2 and the discharge electrode members 4 and 5, and therefore effectively prevent leakage of oxygen gas filled in the sealed space 6. it can.

  As described above, the sealed space 6 is filled with oxygen gas because the electrically insulating oxide constituting the envelope member 2 and the low resistance oxide constituting the discharge electrode members 4 and 5 are in oxygen gas. It is easy to sinter and brings about the advantage that gas sealing and sintering can be performed at the same time, oxygen gas is easily ionized, can be a discharge carrier, and discharge between the electrode parts 7 and 8 is easy. This is because it can be generated.

  In the discharge element 1, the resistance value provided by the discharge electrode members 4 and 5 can be controlled relatively freely by changing the composition ratio of the low-resistance oxides constituting the discharge electrode members 4 and 5. As a result, by providing appropriate resistance to the discharge electrode members 4 and 5 themselves, the resistors R1 and R2 connected in series are incorporated into the discharge element 1 as shown in the equivalent circuit of FIG. Can do. These resistors R1 and R2 effectively act to suppress the discharge subsequent flow.

  7A and 7B are diagrams for explaining a second embodiment of the present invention. FIG. 7A is a longitudinal sectional view of the discharge element 1a, and FIG. 7B is an equivalent circuit diagram of the discharge element 1a. In FIG. 7, elements corresponding to those shown in FIG. 6 are denoted by the same reference numerals, and redundant description is omitted.

  The discharge element 1a according to the second embodiment is formed on the surface exposed to the outside of the terminal portion 9 of the first discharge electrode member 4 with the first and second plating films 11a and 11b being separated from each other. It is characterized by having. As a result, as shown in FIG. 7B, it is possible to obtain a state in which the resistors R11 and R12 are connected in parallel, thereby providing an overvoltage suppressing effect.

  8A and 8B are diagrams for explaining a third embodiment of the present invention. FIG. 8A is a longitudinal sectional view of the discharge element 1b, and FIG. 8B is an equivalent circuit diagram of the discharge element 1b. In FIG. 8, elements corresponding to those shown in FIG. 6 or 7 are denoted by the same reference numerals, and redundant description is omitted.

  The discharge element 1b according to the third embodiment is separated from each other even on the surface exposed to the outside of the terminal portion 10 of the second discharge electrode member 5, as compared with the discharge element 1a according to the second embodiment. The first and second plating films 12a and 12b are formed in the above. As a result, as shown in FIG. 8B, a state in which the resistors R21 and R22 are connected in parallel is obtained also on the second discharge electrode member 5 side, and the overvoltage suppressing effect can be further enhanced.

  FIGS. 9A and 9B are diagrams for explaining a fourth embodiment of the present invention. FIG. 9A is a longitudinal sectional view of the discharge element 1c, and FIG. 9B is an equivalent circuit diagram of the discharge element 1c. In FIG. 9, elements corresponding to those shown in FIG. 6 are denoted by the same reference numerals, and redundant description is omitted.

  The discharge element 1c according to the fourth embodiment is characterized by being a three-pole type. More specifically, the discharge element 1c includes two surrounding members 2 arranged in series on the same axis. The first discharge electrode member 4 is provided so as to close the opening end located outside each of the through holes 3 provided in each of the two surrounding members 2, and the second discharge electrode member 5 is The opening end located inside each of the through holes 3 provided in each of the two surrounding members 2 is provided so as to be closed in common.

  When the discharge element 1c according to the fourth embodiment is compared with the discharge element 1 according to the first embodiment, the shape of the second discharge electrode member 5 is different. That is, in the discharge element 1 c, the second discharge electrode member 5 has a shape in which the electrode portions 8 are formed so as to protrude from both main surfaces of the flange-shaped terminal portion 10. The plating film 12 formed on the surface exposed to the outside of the second discharge electrode member 5 is formed on the outer peripheral surface of the terminal portion 10 so as to go around the outer periphery of the discharge element 1c.

  The discharge element 1c according to the fourth embodiment can be manufactured by a manufacturing method substantially similar to the manufacturing method described with reference to FIGS. 1 to 5 for the discharge element 1 according to the first embodiment. That is, when manufacturing the discharge element 1c, the first insulating green sheet 21a and the second insulating green are formed on the uppermost low resistance green sheet 22 in the stacking process shown in FIG. The sheet 21b, the first insulating green sheet 21a, and the low resistance green sheet 22 may be further laminated in this order.

  Below, this invention is demonstrated based on an Example.

1. Preparation of Low Resistance Green Sheet and Low Resistance Paste Oxides of rare earth elements such as La ₂ O ₃ , carbonates of alkaline earth metal elements such as SrCO ₃ and Mn ₃ O ₄ as Mn, the composition ratio shown in Table 1 Next, pure water was added at a ratio of 1 to the total powder weight 1, PSZ (partially stabilized zirconia) beads having a diameter of 2 mm were added, and the mixture was pulverized for 50 hours by a ball mill. A slurry in which the powder was dispersed was obtained.

  Next, after the moisture of this slurry is evaporated at a temperature of 150 ° C. and the mixed powder is taken out, this mixed powder is calcined at a temperature of 900 to 1100 ° C. for 2 hours and then coarsely pulverized with a pulverizer, Pure water was added at a ratio of 1 to 1 by weight, and the mixture was again pulverized with PSZ beads having a diameter of 2 mm until the average powder diameter became 0.5 μm. Next, the slurry in which the calcined powder was dispersed was dehydrated and dried, and the calcined powder was taken out.

  Next, to this calcined powder, a solvent mixed with ethanol and toluene and a dispersant are added, and after sufficiently dispersing, a binder and a plasticizer are added to form a slurry, and a doctor blade method is applied thereto to obtain a thickness. A 50 μm low resistance green sheet was prepared.

  On the other hand, as described above, a low-resistance paste was prepared by adding a similar solvent and binder to the calcined powder that had been pulverized to an average powder diameter of 0.5 μm to form a paste.

  In Table 1, “specific resistance” is measured after obtaining a discharge element as a finished product.

2. Preparation of Insulating Green Sheet ZnO powder having an average particle diameter of about 0.5 μm and TiO ₂ (rutile) powder having an average particle diameter of about 0.4 μm are listed in the column “Insulating oxide composition ratio” in Table 2. As shown, the elemental ratios of Zn and Ti were blended at ratios of 1: 1, 1.5: 1, 2: 1, 2.5: 1, and 3: 1, and then the powder Pure water was added at a ratio of 1 to 1 in total weight, PSZ beads having a diameter of 2 mm were added, and the mixture was pulverized with a ball mill for 50 hours to obtain a slurry in which the mixed powder was dispersed.

  Next, after the moisture of this slurry is evaporated at a temperature of 150 ° C. and the mixed powder is taken out, the mixed powder is calcined at a temperature of 900 to 1100 ° C. for 2 hours, and then coarsely pulverized with a pulverizer. Pure water was added at a ratio of 1 to 1 by weight, and the mixture was again pulverized with PSZ beads having a diameter of 2 mm until the average powder diameter became 0.5 μm. Next, the slurry in which the calcined powder was dispersed was dehydrated and dried, and the calcined powder was taken out.

  Next, a solvent mixed with ethanol and toluene and a dispersant are added to the calcined powder, and after sufficiently dispersing, a binder and a plasticizer are added to form a slurry, and a doctor blade method is applied to the slurry, Two types of insulating green sheets having a thickness of 2 μm and a thickness of 10 μm were produced. The reason why the two types of insulating green sheets having different thicknesses are prepared in this way is to allow fine adjustment of the discharge gap dimension.

  Next, a laser was applied to the insulating green sheet to provide a through hole having a diameter of 150 μm.

3. Filling the through hole of the insulating green sheet with the low resistance paste Among the insulating green sheets prepared in the above two steps, the low resistance prepared in one step in the through holes of the desired number of insulating green sheets. The paste was filled using a screen printing method and dried.

  As for the low-resistance paste, among the 15 types of low-resistance oxides shown in Table 1, those corresponding to the composition symbols shown in the column of “Low-resistance oxide composition symbol” in Table 2 are used. Using.

4). Filling the through hole of the insulating green sheet with a filler A commercially available vinyl acetate resin was prepared as an adhesive. Then, among the insulating green sheets produced in the second step, vinyl acetate resin was filled as a filler into the through holes of the desired number of insulating green sheets by a screen printing method and dried.

5). Lamination and cutting Low resistance green sheet prepared in step 1 Insulating green sheet prepared in step 3, filled with low resistance paste, and insulating green filled in filler prepared in step 4 The sheets are laminated in the order shown in FIG. 4 and then pressed in the lamination direction by applying a pressure of 20 t / cm ^2. Then, the obtained green laminate is arranged in the lamination direction as shown in FIG. Cut with a dicer to obtain a chip-like green laminate chip.

  In the above-described lamination step, the insulating green sheet filled with the vinyl acetate resin produced in step 4 is 42 μm thick (that is, 42 μm gap size) as a result of the subsequent firing step. An insulating green sheet having a thickness of 2 μm and an insulating green sheet having a thickness of 10 μm were appropriately combined.

  In addition, the low resistance green sheet used in the stacking has the composition symbol shown in “Low Resistance Oxide Composition Symbol” in Table 2 among the 15 types of low resistance oxides shown in Table 1. The corresponding one was used.

6). Firing After degreasing the green laminate chip produced in the above step 5 at a temperature of 600 ° C., the temperature is raised to a temperature of 900 to 1100 ° C. in an oxidizing atmosphere. As shown in the column, Samples 1 to 20, 22 and 23 were fired at a temperature of 1100 to 1300 ° C. for 5 hours in an atmosphere of 100% oxygen and Sample 21 in air. In this firing step, a gas pressure of 230 Torr (about 3.1 × 10 ⁻² MPa) was applied.

7). Formation of plating film By applying an electroplating method to each sample obtained in the above step 6, an Ni plating film and an Sn plating film thereon are formed on the surface exposed to the outside of each discharge electrode member. Formed.

  Here, as shown in the column of “Structure Reference Drawing” in Table 2, for Samples 1 to 21, a plating film formation mode as shown in FIG. 6 is adopted, and for Sample 22, FIG. A plating film formation mode as shown in FIG. 8 was adopted, and for the sample 23, a plating film formation mode as shown in FIG.

  As described above, the discharge element according to each sample was obtained. In these discharge elements, the outer diameter was 1.0 mm × 0.5 mm × 0.5 mm, the discharge gap was 42 μm, and the diameter of the sealed space defining the discharge gap was 110 μm.

8). Evaluation As shown in Table 2, the “DC discharge start voltage”, the “impulse discharge start voltage”, the “surge withstand capability” and the “discharge resistance” were evaluated for the discharge elements according to the respective samples obtained in the above step 7. .

  The “DC discharge start voltage” is obtained by applying a voltage to the first and second discharge electrode members of the discharge element according to each sample while gradually increasing the voltage, and measuring the DC discharge start voltage with a peak voltmeter. .

  As for “impulse discharge start voltage”, a voltage surge having a triangular voltage waveform of 1.2 × 50 μsec is applied in a terminal open state, and the impulse discharge start voltage is observed with a storage scope.

  With regard to “surge tolerance”, a surge current having a triangular current waveform of 8 × 20 μsec is applied 10 times in increments of 100 A, and the peak current at which the discharge voltage of the discharge element changes by 10% or more is measured. Is what we asked for.

  As for “discharge resistance”, in order to examine the direct current resistance, a rectangular current was passed at a length of 0.5 A and 2 ms, and the discharge resistance was measured.

  In Table 2, according to Samples 1 to 15, 17 to 20, 22 and 23, discharge elements having good characteristics are obtained.

  On the other hand, in the sample 16, the low resistance oxide having the composition symbol k shown in Table 1 is used, and since this low resistance oxide does not contain an alkaline earth metal element, the surge resistance is low. It was relatively low.

In sample 21, air was used as the firing atmosphere, so surge resistance was low. This is presumably because CO ₂ contained in the air was ionized and carbon was deposited between the discharge gaps.

FIG. 7 is a cross-sectional view illustrating an insulating green sheet 21 prepared for manufacturing the discharge element 1 shown in FIG. 6 for explaining the first embodiment of the present invention. It is sectional drawing which shows the low resistance green sheet 22 prepared in order to manufacture the discharge element 1 shown in FIG. It is sectional drawing which shows the 1st and 2nd insulating green sheets 21a and 21b produced in order to manufacture the discharge element 1 shown in FIG. It is sectional drawing which shows the insulating green sheets 21a and 21b and the low resistance green sheet 22 according to the lamination | stacking order in the lamination process implemented in order to manufacture the discharge element 1 shown in FIG. It is sectional drawing which shows the green laminated body 26 obtained by implementing a lamination process according to the lamination order shown in FIG. 1 shows a discharge element 1 according to a first embodiment of the present invention, in which (a) is a longitudinal sectional view and (b) is an equivalent circuit diagram. The discharge element 1a by the 2nd Embodiment of this invention is shown, (a) is a longitudinal cross-sectional view, (b) is an equivalent circuit schematic. The discharge element 1b by 3rd Embodiment of this invention is shown, (a) is a longitudinal cross-sectional view, (b) is an equivalent circuit schematic. The discharge element 1c by 4th Embodiment of this invention is shown, (a) is a longitudinal cross-sectional view, (b) is an equivalent circuit schematic.

Explanation of symbols

1, 1a, 1b, 1c Discharge element 2 Surrounding member 3, 23 Through hole 4, 5 Discharge electrode member 6 Sealing space 7, 8 Electrode portion 9, 10 Terminal portion 11, 11a, 11b, 12, 12a, 12b Plating Film 21 Insulating green sheet 21a First insulating green sheet 21b Second insulating green sheet 22 Low resistance green sheet 24 Low resistance paste 25 Filler 26 Green laminate

Claims (6)

An envelope member made of an electrically insulating material and provided with a through hole;
Provided with first and second discharge electrode members provided to close each open end of the through hole in a state of facing each other while forming a sealing space serving as a discharge gap between each other,
The surrounding member is made of an electrically insulating oxide containing Zn and Ti,
The first and second discharge electrode members are made of a low-resistance oxide containing a rare earth element, an alkaline earth metal element, and Mn, and having a specific resistance in the range of 10 ^{−4 to 1} Ω · cm,
The sealed space is filled with oxygen gas,
Discharge element.   The discharge element according to claim 1, further comprising a plating film made of a conductive metal, formed on a surface exposed to the outside of each of the first and second discharge electrode members.   The discharge element according to claim 2, wherein the plating film includes first and second plating films formed in a state of being separated from each other.   The through-hole provided in the surrounding member has a substantially rectangular vertical cross-sectional shape, and each of the first and second discharge electrode members is inserted into each end of the through-hole. And a terminal portion disposed on the outer surface of the surrounding member, and the electrode portion has a substantially rectangular vertical cross-sectional shape so as to be in close contact with the inner peripheral surface of the through hole. The discharge element according to any one of 1 to 3.   The surrounding member includes first and second surrounding members arranged in series on the same axis, and the first discharge electrode member is provided on the first and second surrounding members. In addition, the second discharge electrode member is provided so as to close the open end located outside each of the through holes, and the second discharge electrode member is provided in each of the through holes provided in the first and second surrounding members. The discharge element according to any one of claims 1 to 4, wherein the discharge element is provided so as to commonly close the open ends located on the inside. A step of preparing an insulating green sheet including an electrically insulating oxide containing Zn and Ti and provided with a through-hole penetrating in the thickness direction;
Providing a low-resistance green sheet containing a low-resistance oxide containing a rare earth element, an alkaline earth metal element, and Mn and having a specific resistance in the range of 10 ^{−4 to 1} Ω · cm;
Providing a low-resistance paste containing a low-resistance oxide containing a rare earth element, an alkaline earth metal element, and Mn, and having a specific resistance in the range of 10 ^{−4 to 1} Ω · cm;
Preparing a filler made of a material that disappears upon firing;
Filling the through hole of the insulating green sheet with the low-resistance paste to form a first insulating green sheet;
Filling the through hole of the insulating green sheet with the filler to form a second insulating green sheet;
Producing a green laminate in which the first insulating green sheet is sandwiched between the second insulating green sheets and the low resistance green sheet is further sandwiched between the second insulating green sheets;
And firing the green laminate in an atmosphere having a higher oxygen concentration than the atmosphere.

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