JP2011258490A - Overvoltage protection component and method of manufacturing the same - Google Patents

Abstract

An object of the present invention is to obtain an overvoltage protection component having a low operating voltage and high reliability.
An overvoltage protection component according to the present invention has a space between a tip portion of a lower voltage-dependent resistance layer 3 formed on an insulating substrate 2 and a first discharge electrode 4 formed thereon. Opposing second discharge electrode 5, upper voltage dependent resistance layer 6 covering a part thereof, lower voltage dependent resistance layer 3, first discharge electrode 4, second discharge electrode 5, and upper voltage dependency A discharge space 7 which is a space surrounded by the resistance layer 6, and the lower voltage-dependent resistance layer 3 and the upper voltage-dependent resistance layer 6 are usually insulators and have a property of conducting electricity when an overvoltage is applied. The conductive particles are dispersed so as not to be short-circuited, the height of the side wall surface of the discharge space 7 is equal to the thickness of the first discharge electrode 4, and the insulating substrate 2 is made of alumina.
[Selection] Figure 1

Description

  The present invention relates to an overvoltage protection component that protects an electronic component or an electronic circuit from overvoltage and a method of manufacturing the same.

  As a method to protect electronic components and electronic circuits from overvoltage such as static electricity, it functions as an insulator in normal use conditions. When overvoltage is applied, the impedance of the component itself is greatly reduced or discharged inside the component. For example, a method of connecting an overvoltage protection component that conducts electricity by connecting between an input or output terminal of an electronic component or the like to be protected and a ground is widely known.

  As an overvoltage protection component, an insulating ceramic containing glass is used as a base body, and a pair of discharge electrodes are arranged in the interior thereof with a space at the tip portion. Further, there is also known one in which the height of the space is the same as the thickness of the discharge electrode (see Patent Document 1).

  On the other hand, an overvoltage protection component is also known in which a pair of discharge electrodes are disposed on an alumina substrate so that their tip portions face each other (see Patent Document 2).

  An overvoltage protection component that lowers the discharge start voltage by dispersing conductive particles between a pair of discharge electrodes is also known (see Patent Document 3).

JP 2000-277229 A Japanese Patent Laid-Open No. 2004-14466 International Publication No. 2009/001649

  In recent years, two performances have been particularly required for overvoltage protection components.

  The first is to lower the operating voltage. In recent years, electronic components have been reduced in resistance to static electricity and the like due to miniaturization and the like, and are often damaged by an overvoltage that is lower than conventional ones. For this reason, the overvoltage protection component has been required to operate at a low voltage. Here, the operation of the overvoltage protection component means that the impedance is greatly reduced or that electricity is conducted by discharging inside the component, and the operating voltage is because the overvoltage protection component operates as described above. Say the lowest voltage. That is, the overvoltage protection component conducts electricity at a voltage equal to or higher than the operating voltage and exhibits the properties of a conductor.

  The second is high reliability. Overvoltage protection components have been required to be reliable when a higher voltage is applied or the number of times of overvoltage is significantly repeated. This is because the required reliability increases depending on the electronic equipment where the overvoltage protection component is used, the place where the electronic equipment is used, the application, and the usage environment, and the reliability is higher than the original required level. This is based on the idea of increasing the safety factor against overvoltage by asking for overvoltage protection components, in other words, securing a large margin. For example, there is a case where a higher voltage is applied and a reliability test in which such a voltage is repeatedly applied is performed. In particular, there may be a test in which a short pulse high voltage is continuously applied repeatedly.

  As described above, the high-voltage pulse test is a very severe test compared to the actual application of static electricity, but such a test method is also used in order to increase the safety factor as described above. . In such a test, there is a case where a short circuit occurs due to dissolution or deformation of a discharge electrode or a conductive material existing between a pair of discharge electrodes.

  Lowering the operating voltage and increasing the reliability are not required independently, but improvements in both characteristics have been demanded.

  The present invention solves the above-described conventional problems, and an object thereof is to obtain an overvoltage protection component having low operating voltage and high reliability.

  In order to achieve the above object, the present invention has the following means.

  The invention according to claim 1 is an insulating substrate, a lower voltage-dependent resistance layer formed on the insulating substrate, and a first discharge electrode having at least a tip portion formed on the lower voltage-dependent resistance layer. A second discharge electrode having at least a tip thereof formed on the lower voltage-dependent resistance layer and facing the tip of the first discharge electrode with a space therebetween, the first discharge electrode, The second discharge electrode, the lower voltage-dependent resistance layer, and the upper voltage-dependent resistance layer formed on the insulating substrate are opposed to the tip portion of the first discharge electrode and the tip portion of the second discharge electrode. A discharge space that is a space surrounded by the first discharge electrode, the second discharge electrode, the lower voltage-dependent resistance layer, and the upper voltage-dependent resistance layer, A lower voltage dependent resistance layer and the upper voltage dependent The resistance layer is usually an insulator and has a property of conducting electricity when an overvoltage is applied, and is present in a dispersed manner so that conductive particles do not short-circuit at least on the surface in contact with the discharge space, The height of the side wall surface of the discharge space is equal to the thickness of the first discharge electrode, and the insulating substrate is made of alumina.

  The invention according to claim 1 has the following effects.

  Since the height of the side wall surface of the discharge space is made equal to the thickness of the first discharge electrode, when the discharge is started, any path of the lower voltage-dependent resistance layer and the upper voltage-dependent resistance layer can be taken. Damage due to discharge due to the applied overvoltage can be dispersed, and reliability can be improved.

  The lower voltage-dependent resistance layer and the upper voltage-dependent resistance layer are usually insulators, and have characteristics that creeping discharge through these resistance layer surfaces is very likely to occur when an overvoltage is applied, and at least the discharge space Since the conductive particles are dispersed on the surface in contact with the surface so as not to be short-circuited, the operating voltage can be lowered.

  Moreover, since the insulating substrate is made of alumina, it has excellent heat dissipation characteristics and can improve reliability.

  The invention described in claim 2 includes a glass protective layer mainly composed of glass that covers the upper voltage-dependent resistance layer, and a resin protective layer made of a resin that covers the glass protective layer.

  With this configuration, there is an effect that reliability with respect to moisture and moisture can be improved.

  According to a third aspect of the present invention, the lower voltage-dependent resistance layer is located at least below the discharge space, below the tip of the first discharge electrode, and below the tip of the second discharge electrode. And covered with the glass protective layer.

  With this configuration, there is an effect that the reliability with respect to moisture and moisture can be further improved.

  According to a fourth aspect of the present invention, there is provided a first step of forming a lower resistance paste layer by applying a paste containing a voltage dependent material to be a lower voltage dependent resistance layer on an upper surface of an insulating substrate, and a discharge electrode paste. By applying the first discharge electrode paste layer serving as the first discharge electrode and the second discharge electrode paste layer serving as the second discharge electrode on the upper surface side of the insulating substrate, the tip portions thereof are opposed to each other. And a third step of forming at least a tip portion of the first discharge electrode paste layer and a tip portion of the second discharge electrode paste layer on the lower resistance paste layer; A fourth step of forming a discharge space paste layer by applying a substance to be applied between a front end portion of the first discharge electrode paste layer and a front end portion of the second discharge electrode paste layer; the discharge space paste layer; A top resistance paste layer is formed by applying a paste containing a voltage dependent material to be an upper voltage dependent resistance layer so as to cover the front end of the first discharge electrode paste layer and the front end of the second discharge electrode layer. And a firing step of burning the discharge space paste layer by firing after the fifth step to form a discharge space.

  With this manufacturing method, the discharge electrode can be formed with high accuracy, and the operation voltage can be lowered.

  As described above, the overvoltage protection component and the manufacturing method thereof according to the present invention have an effect of obtaining high reliability while reducing the operating voltage.

Front sectional drawing of the overvoltage protection component in Embodiment 1 of this invention Side cross-sectional view of the same overvoltage protection component Front sectional view showing the manufacturing method of the overvoltage protection component Front sectional view showing the manufacturing method of the overvoltage protection component Front sectional view showing the manufacturing method of the overvoltage protection component Front sectional view showing the manufacturing method of the overvoltage protection component Plan view showing the manufacturing method of the overvoltage protection component Plan view showing the manufacturing method of the overvoltage protection component Plan view showing the manufacturing method of the overvoltage protection component Plan view showing the manufacturing method of the overvoltage protection component The top view of the manufacturing process of the overvoltage protection component in Embodiment 2 of this invention The top view of the manufacturing process of the overvoltage protection component in Embodiment 3 of this invention

(Embodiment 1)
Hereinafter, the present invention will be described using the first embodiment.

  FIG. 1 is a front sectional view of an overvoltage protection component according to Embodiment 1 of the present invention, and FIG. 2 is a side sectional view of the overvoltage protection component.

  The overvoltage protection component 1 exhibits the property of an insulator in normal times, but conducts electricity when an overvoltage is applied. Hereinafter, the configuration of the overvoltage protection component 1 will be described.

  The insulating substrate 2 is a plate-like substrate made of alumina. Alumina is an insulator and has excellent strength and thermal conductivity.

The lower voltage-dependent resistance layer 3 is formed on the insulating substrate 2, is an insulator at a normal voltage, and has a characteristic that creeping discharge through the surface of the resistance layer is very likely to occur when an overvoltage is applied. As the composition, zinc oxide or the like used for varistors and glass mixed with conductor particles can be used. As the conductor particles, Cu, TiB ₂ , ZrB ₂ , CuNi, AgPd, or the like can be used. Further, the conductor particles only have to be dispersed at least on the surface in contact with the discharge space 7, and after the mixture of zinc oxide or the like and glass is formed in layers on the insulating substrate 2, the conductor particles are arranged on the surface. Also good.

  Here, the lower voltage-dependent resistance layer 3 is formed to be smaller than the width of the insulating substrate 2 in the left-right direction of FIG.

  Both the first discharge electrode 4 and the second discharge electrode 5 are formed on the lower voltage-dependent resistance layer 3, and are opposed to each other with a space at the tip. A current flows through the first discharge electrode 4 and the second discharge electrode 5 when an overvoltage is applied. However, since the impedance should be significantly lower than the impedance of an electronic circuit or the like to be protected at that time, the first discharge electrode 4 and the second discharge electrode 5 are excellent in conductivity. It is made of copper. However, the material is not limited to copper, and gold having excellent chemical stability may be used, and tungsten having a high specific resistance but a very high melting point and being hardly damaged by discharge can be used. This selection may be determined in consideration of conductivity, resistance to discharge damage, and cost. The first discharge electrode 4 and the second discharge electrode 5 are formed narrower in the width direction than the lower voltage-dependent resistance layer 3. The reason for this will be described in the description of the manufacturing method described later.

  The upper voltage-dependent resistance layer 6 is formed on the lower voltage-dependent resistance layer 3, the first discharge electrode 4, the second discharge electrode 5 and the insulating substrate 2, and the composition thereof is the same as that of the lower voltage-dependent resistance layer 3. In the same manner as the lower voltage-dependent resistance layer 3, the conductive particles are dispersed at least on the surface in contact with the discharge space 7.

  The discharge space 7 is a space surrounded by the lower voltage-dependent resistance layer 3, the first discharge electrode 4, the second discharge electrode 5, and the upper voltage-dependent resistance layer 6, and the first discharge electrode 4 and the second discharge electrode It is located between the tips of the electrodes 5. The height of the wall surface of the discharge space 7 is equal to the thickness of the first discharge electrode 4. Here, the height of the side wall surface of the discharge space 7 refers to the length of the portion serving as the wall in contact with the discharge space 7 in the vertical direction of the drawing in FIGS. Since only the first discharge electrode 4 exists between the lower voltage-dependent resistance layer 3 and the upper voltage-dependent resistance layer 6 at the front end portion of the first discharge electrode 4, The side wall surface is the end surface at the tip of the first discharge electrode 4 and, of course, the height of the side wall surface of the discharge space 7 is equal to the thickness of the first discharge electrode 4.

  The glass protective layer 8 is made of glass and is configured to cover the upper voltage dependent resistance layer 6. Since the upper voltage-dependent resistance layer 6 may have fine voids, the glass protective layer 8 has a function of preventing moisture and moisture from entering the discharge space 7 and the like. Moreover, since the glass protective layer 8 has better adhesion to the insulating substrate 2 made of alumina than the protective film made of resin, it is possible to prevent moisture from entering between the insulating substrate 2 and the glass protective layer 8. Thus, by forming the glass protective layer 8, moisture resistance can be improved.

  The resin protective layer 9 is made of resin, covers the glass protective layer 8, and has a function of protecting the inside from mechanical force and impact. As the material, polyamide, phenol resin, polyimide, or the like can be used.

  The top electrode layer 10 is formed on a part of the top surface of the first discharge electrode 4 and a part of the top surface of the second discharge electrode 5, respectively.

  The lower electrode layer 11 is formed on both ends of the lower surface of the insulating substrate 2.

  The end face electrodes 12 are respectively formed around both end faces of the insulating substrate 2 and have a function of electrically connecting the first discharge electrode 4 or the second discharge electrode 5 and the lower surface electrode layer 11. . The end face electrode 12 is preferably made of a material having excellent conductivity. Specifically, a material mainly composed of silver or copper is preferable. In view of solderability to a printed circuit board, it is preferable to form a nickel plating layer on the underlying electrode of silver or copper and further form a tin plating layer on the surface thereof.

  A method for manufacturing the overvoltage protection component 1 configured as described above will be described below.

  3 to 10 show a manufacturing method, in which FIGS. 3 to 6 are front sectional views showing a manufacturing method of the overvoltage protection component according to Embodiment 1 of the present invention, and FIGS. 7 to 10 show the same overvoltage. It is a top view which shows the manufacturing method of a protection component.

  First, as shown in FIGS. 3A and 7A, an insulating substrate 2 is prepared.

  Next, as shown in FIGS. 3B and 7B, a lower resistance paste layer 20 that will eventually become the lower voltage-dependent resistance layer 3 is formed on the insulating substrate 2 by printing. The material of the lower resistance paste layer 20 is a paste obtained by mixing the resin having the composition of the lower voltage-dependent resistance layer 3 with a resin. The width of the lower voltage dependent resistance layer 3 is narrower than the width of the insulating substrate 2.

  Next, as shown in FIGS. 3C and 7C, a first discharge electrode paste layer 21 and a second discharge electrode paste layer 22 are applied on the lower resistance paste layer 20 by printing. Ultimately, the first discharge electrode paste layer 21 corresponds to the first discharge electrode 4, and the second discharge electrode paste layer 22 corresponds to the second discharge electrode 5. The first discharge electrode paste layer 21 and the second discharge electrode paste layer 22 are formed to face each other with a gap at the tip. In order to reduce the operating voltage, this interval may be narrowed. For this purpose, the first discharge electrode paste layer 21 and the second discharge electrode paste layer 22 are formed as a single layer and then cut with a laser to form a narrow gap between the first discharge electrode paste layer 21 and the first discharge electrode paste layer 21. 2 discharge electrode paste layers 22 can be formed. However, when a laser is used, the lower voltage dependent resistance layer 3 may be cut or a groove may be formed in the lower voltage dependent resistance layer 3, which is not preferable in terms of characteristics. Therefore, the first discharge electrode paste layer 21 and the second discharge electrode paste layer 22 are formed by printing. The distance between the first discharge electrode paste layer 21 and the second discharge electrode paste layer 22 is 20 to 60 μm. Here, both the first discharge electrode paste layer 21 and the second discharge electrode paste layer 22 are formed on the lower resistance paste layer 20 and do not protrude from the lower resistance paste layer 20. By doing in this way, it becomes possible to form the 1st discharge electrode paste layer 21 and the 2nd discharge electrode paste layer 22 with sufficient precision. When the first discharge electrode paste layer 21 or the second discharge electrode paste layer 22 is formed so as to protrude from the lower resistance paste layer 20, the first discharge electrode paste layer 21 or the second discharge electrode paste layer 22 is formed. Part of the paste constituting the portion flows out onto the protruding portion, that is, the insulating substrate 2, thereby deteriorating the accuracy of the shapes of the first discharge electrode paste layer 21 and the second discharge electrode paste layer 22. End up. Therefore, both the first discharge electrode paste layer 21 and the second discharge electrode paste layer 22 are formed on the lower resistance paste layer 20.

  Next, as shown in FIGS. 4A and 8A, the discharge space paste layer 23 is applied to a portion where the first discharge electrode paste layer 21 and the second discharge electrode paste layer 22 face each other. To do. The discharge space paste layer 23 is made of a material that is burned off by subsequent firing, and for example, acrylic beads can be used. The space where the discharge space paste layer 23 exists burns away to form the discharge space 7.

  Next, as shown in FIGS. 4B and 8B, the upper resistance paste layer 24 is replaced with the lower resistance paste layer 20, the first discharge electrode paste layer 21, the second discharge electrode paste layer 22, and the discharge. It is formed on the space paste layer 23. The upper resistance paste layer 24 is formed so as to cover the entire discharge space paste layer 23, and is formed so as to cover at least the front ends of the first discharge electrode paste layer 21 and the second discharge electrode paste layer 22. Yes. The upper resistance paste layer 24 finally corresponds to the upper voltage dependent resistance layer 6.

  Next, as shown in FIGS. 4C and 8C, the glass paste layer 25 is formed so as to cover the upper resistance paste layer 24. The glass paste layer 25 finally corresponds to the upper voltage dependent resistance layer 6.

  Thereafter, firing is performed to burn out the discharge space paste layer 23, and further, the lower resistance paste layer 20, the first discharge electrode paste layer 21, the second discharge electrode paste layer 22, the discharge space paste layer 23, and the upper resistance paste. The layer 24 and the glass paste layer 25 are fired. As a result, the lower resistance paste layer 20 is applied to the lower voltage dependent resistance layer 3, the first discharge electrode paste layer 21 is applied to the first discharge electrode 4, and the second discharge electrode paste layer 22 is applied to the second discharge electrode 5. The space where the discharge space paste layer 23 existed becomes the discharge space 7, the upper resistance paste layer 24 becomes the upper voltage dependent resistance layer 6, and the glass paste layer 25 becomes the glass protective layer 8, respectively. The figure after this baking is FIG. 5 (a) and FIG. 9 (a).

  Next, as shown in FIGS. 5B and 9B, the upper electrode layer 10 is formed. The top electrode layer 10 can be formed by printing and baking.

  Next, as shown in FIGS. 5C and 9C, the resin protective layer 9 is formed so as to cover the glass protective layer 8. The resin protective layer 9 can be formed by a method of printing, applying, and then drying a paste of the resin constituting the resin protective layer 9.

  Finally, as shown in FIGS. 6 and 10, the end face electrode 12 is formed. The end face electrode 12 is printed and coated with a paste containing a conductor constituting the end face electrode 12 so as to be in contact with the end face of the insulating substrate 2 and the upper face electrode layer 10 and the lower face electrode layer 11, and then dried or fired. Further, a nickel plating layer and a tin plating layer are formed on the surface of the nickel plating layer by a barrel plating method.

  Next, the operation of the overvoltage protection component 1 will be described.

  The overvoltage protection component 1 is connected between the input of an electronic component or electronic circuit to be protected from an overvoltage such as static electricity and the ground. Specifically, the first discharge electrode 4 is connected to the input side of an electronic component or the like, and the second discharge electrode 5 is connected to the ground side. Normally, the potential of the signal transmitted to the input is also applied to the first discharge electrode 4, and a potential difference occurs between the second discharge electrode 5 facing the first discharge electrode 4. Since the two are separated by an insulator, no current flows between them. That is, the overvoltage protection component 1 functions as an insulator, and a signal transmitted to the input is transmitted to an electronic component or the like as it is.

  On the other hand, when an overvoltage is applied, a discharge is generated between the first discharge electrode 4 and the second discharge electrode 5. In this case, the discharge does not begin to occur between the first discharge electrode 4 and the second discharge electrode 5 through the direct discharge space 7, but first, the lower voltage-dependent resistance layer 3 or the upper voltage that is in contact with the discharge space 7 is used. Discharge occurs through the surface of the dependent resistance layer 6. Here, in the lower voltage-dependent resistance layer 3 and the upper voltage-dependent resistance layer 6, conductor powder is dispersed at least on the surface thereof, and thus creeping discharge is easily generated through the conductor powder. Once a discharge occurs, a discharge occurs between the first discharge electrode 4 and the second discharge electrode 5 through the discharge space 7 thereafter.

  When the overvoltage is not applied and only the signal is transmitted to the input, the potential difference between the first discharge electrode 4 and the second discharge electrode 5 is also reduced, so that the discharge between them is stopped and the overvoltage protection component 1 is used as an insulator. Only the signal that functions and is sent to the input will flow through the electronic components and the like.

  The overvoltage protection component 1 may be used by connecting to the signal line to which the overvoltage is applied, and may be connected to the output side. In this case, the same effects as when connected to the input side are obtained.

  Here, in the overvoltage protection component 1 of the present embodiment, since the height of the wall surface of the discharge space 7 and the thickness of the first discharge electrode 4 are equal, the first discharge electrode 4 and the lower voltage dependent resistance layer 3 are in contact with each other. The first discharge electrode 4 and the upper voltage dependent resistance layer 6 are also in contact with each other, and the distance between them is the same. The same applies to the second discharge electrode 5 having the same thickness as the first discharge electrode 4. Therefore, the first discharge can occur in either the lower voltage dependent resistance layer 3 or the upper voltage dependent resistance layer 6. In general, the discharge start location is likely to be generated from a pointed location or a location where the discharge distance is shortened, but the shapes of the tips of the first discharge electrode 4 and the second discharge electrode 5 are as follows. Even if unevenness is generated microscopically, there is no unevenness macroscopically and the distance between the electrodes is constant, so that the place where the discharge is started is not determined in one place. Further, the path through which the discharge current flows at the start of discharge is not determined by only one of the lower voltage-dependent resistance layer 3 and the upper voltage-dependent resistance layer 6. Therefore, the lower voltage-dependent resistance layer 3 and the upper voltage-dependent resistance layer 6 are both in contact with the first discharge electrode 4 and the second discharge electrode 5, so that the discharge at the start of discharge is But it is happening. Thereby, damage due to discharge at the start of discharge can be dispersed, and reliability can be improved.

  The lower voltage-dependent resistance layer 3 and the upper voltage-dependent resistance layer 6 that are in contact with the discharge space 7 are not formed by dispersing conductive particles in an insulator, but by dispersing conductive particles in those that are energized when an overvoltage is applied. Therefore, the surface discharge is easier than that in which the conductive particles are simply dispersed in the insulator, and the discharge start voltage can be further reduced. In order to reduce the discharge start voltage, it is preferable to increase the conductor powder, but if it is increased too much, there is a possibility of a short circuit. Therefore, the operating voltage can be lowered while preventing short-circuiting by using a material that can be a varistor material as a main component. In the case of the configuration in which the conductor powder is dispersed in the insulator, it is disadvantageous in terms of lowering the operating voltage compared to the present embodiment, but it can be used when the required operating voltage is not so low. .

  Further, since the insulating substrate 2 is made of alumina and only the lower voltage dependent resistance layer 3 is interposed between the discharge space 7 and the heat generated by the discharge generated in the discharge space 7 can be dissipated through the insulating substrate 2. it can. Thereby, the damage to the 1st discharge electrode 4 and the 2nd discharge electrode 5 by discharge can be reduced. In the overvoltage protection component 1 of the present embodiment, the strength as a component can be ensured by the insulating substrate 2, and therefore the lower voltage-dependent resistance layer 3 is not required to have strength as a component, thereby reducing the thickness. Therefore, it is preferable to dissipate heat from the discharge through the insulating substrate 2. In particular, this configuration is very useful when a high voltage and short pulse overvoltage is repeatedly applied.

  In the present embodiment, the firing process is performed in the state shown in FIGS. 4C and 8C, and the lower resistance paste layer 20, the first discharge electrode paste layer 21, and the second discharge electrode paste layer. 22, firing of the upper resistive paste layer 24 and the glass paste layer 25 and burning of the discharge space paste layer 23 are performed at once. Considering the difficulty of stacking many layers by printing, firing is performed several times. It may be divided into For example, after the first discharge electrode paste layer 21 and the second discharge electrode paste layer 22 of FIGS. 3C and 7C are formed, first baking is performed at about 850 ° C., and then FIG. b) After the upper resistance paste layer 24 of FIG. 8B is formed, the second baking is performed at about 850 ° C., and after the glass paste layer 25 of FIG. 4C and FIG. A method of performing the second baking at about 650 ° C. can also be adopted.

  Further, in the manufacturing method of the present embodiment, the process of manufacturing one overvoltage protection component 1 has been described. However, as in the manufacturing method used in a chip resistor or the like, a single large alumina substrate is used. A plurality of overvoltage protection components 1 may be manufactured. In this case, it is sufficient to manufacture with one large alumina substrate until the end face electrode 12 is formed, and to divide into pieces before forming the end face electrode 12.

(Embodiment 2)
FIG. 11 is a plan view of the manufacturing process of the overvoltage protection component in the second embodiment of the present invention, and corresponds to FIG. 7B, which is a diagram of the manufacturing process in the first embodiment. In the first embodiment, the lower resistance paste layer 20 is formed from the left end to the right end on the upper surface of the insulating substrate 2 as shown in FIG. 7B. In the second embodiment, the central portion on the upper surface of the insulating substrate 2 is formed. You may make it provide only. Then, on the upper surface of the insulating substrate 2, the region where the lower protective paste layer 20 is formed, that is, the region where the lower voltage dependent resistance layer 3 is formed, so that the region where the glass protective layer 8 is formed completely includes. Then, the reliability with respect to moisture and humidity can be improved. In this case, the end of the lower resistance paste layer 20 in the left-right direction in FIG. 11, that is, the end of the insulating substrate 2 in the end face direction, is the first discharge electrode paste layer 21 and the second discharge electrode paste layer 22. Should be far enough away from the tip. As described in the first embodiment, when the first discharge electrode paste layer 21 and the second discharge electrode paste layer 22 protrude outside the lower resistance paste layer 20, the paste is formed on the insulating substrate 2 during printing. This is because the shape accuracy of the first discharge electrode paste layer 21 and the second discharge electrode paste layer 22 deteriorates. By setting the positions sufficiently apart, it is possible to prevent deterioration in accuracy of the tip portions of the first discharge electrode paste layer 21 and the second discharge electrode paste layer 22 that affect the discharge characteristics.

(Embodiment 3)
FIG. 12 is a plan view of the manufacturing process of the overvoltage protection component in the third embodiment of the present invention, and corresponds to FIG. 8 (a), which is a diagram of the manufacturing process in the first embodiment. In Embodiment 1, the width of the discharge space 7 is made wider than the width of the first discharge electrode 4 and the second discharge electrode 5, but they may be the same width as shown in FIG. In this case, since the discharge may be started through the wall surfaces in the thickness direction of the first discharge electrode 4 and the second discharge electrode 5 on the inner wall of the discharge space 7, damage due to the start of the discharge can be further dispersed. .

  The overvoltage protection component and the manufacturing method thereof according to the present invention can be applied to electronic devices and the like.

DESCRIPTION OF SYMBOLS 1 Overvoltage protection component 2 Insulation board | substrate 3 Lower voltage dependence resistance layer 4 1st discharge electrode 5 2nd discharge electrode 6 Upper voltage dependence resistance layer 7 Discharge space 8 Glass protection layer 9 Resin protection layer 20 Lower resistance paste layer 21 1st Discharge electrode paste layer 22 Second discharge electrode paste layer 23 Discharge space paste layer 24 Upper resistance paste layer 25 Glass paste layer

Claims (4)

An insulating substrate;
A lower voltage-dependent resistance layer formed on the insulating substrate;
A first discharge electrode having at least a tip thereof formed on the lower voltage-dependent resistance layer;
A second discharge electrode having at least a tip portion formed on the lower voltage-dependent resistance layer and facing the tip portion of the first discharge electrode with a space therebetween;
The first discharge electrode, the second discharge electrode, the lower voltage-dependent resistance layer, and an upper voltage-dependent resistance layer formed on the insulating substrate;
The first discharge electrode, the second discharge electrode, and the lower voltage-dependent resistance layer have a space in which a tip portion of the first discharge electrode and a tip portion of the second discharge electrode are opposed to each other. And a discharge space that is a space surrounded by the upper voltage-dependent resistance layer,
The lower voltage-dependent resistance layer and the upper voltage-dependent resistance layer are usually insulators and have a property of conducting electricity when an overvoltage is applied, and at least a surface that is in contact with the discharge space does not short-circuit the conductive particles. Exist in a distributed manner,
The height of the side wall surface of the discharge space is equal to the thickness of the first discharge electrode,
The insulating substrate is an overvoltage protection component made of alumina. The overvoltage protection component according to claim 1, further comprising: a glass protective layer mainly composed of glass covering the upper voltage-dependent resistance layer; and a resin protective layer made of a resin covering the glass protective layer. The lower voltage dependent resistance layer is located at least below the discharge space, below the tip of the first discharge electrode, and below the tip of the second discharge electrode, and is covered with the glass protective layer. The overvoltage protection component according to claim 2. A first step of forming a lower resistive paste layer by applying a paste containing a voltage dependent material to be a lower voltage dependent resistive layer on an upper surface of an insulating substrate;
By applying a discharge electrode paste, the first discharge electrode paste layer to be the first discharge electrode and the second discharge electrode paste layer to be the second discharge electrode are formed on the upper surface side of the insulating substrate. A third portion is formed so that the front end portions are opposed to each other and at least the front end portion of the first discharge electrode paste layer and the front end portion of the second discharge electrode paste layer are positioned on the lower resistance paste layer. Process,
A fourth step of forming a discharge space paste layer by applying a material to be burned by heat between the tip portion of the first discharge electrode paste layer and the tip portion of the second discharge electrode paste layer;
Applying a paste containing a voltage-dependent material serving as an upper voltage-dependent resistance layer so as to cover the discharge space paste layer, the tip of the first discharge electrode paste layer, and the tip of the second discharge electrode layer A fifth step of forming a resistive paste layer;
A method for manufacturing an overvoltage protection component, comprising: a firing step of burning the discharge space paste layer by firing after the fifth step to form a discharge space.

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