JP2001076839A - Surface mounting type surge absorbing element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce capacitance by forming an inner diameter larger than the other inner diameter in a part not contacting with internal electrode layers of a discharge space formed between a pair of internal electrode layers arranged inside an insulating layer composed of an insulating ceramic sintered body. SOLUTION: A part of an insulating layer 2 between internal electrode layers 3 is desirably constituted of a multilayer not less than three layers, an inner diameter 5 of a discharge space 4 of a layer not contacting with the internal electrode layers 3 among the insulating layer 2 is formed larger than an inner diameter 6 of the discharge space 4 of a layer contacting with the internal electrode layers 3, and a layer not contacting with the internal electrode layers 3 is constituted by at least one layer or more so that the discharge space 4 has a projecting shape outside. Even when performing creeping discharge, since a projecting part is hardly sputtered, a short circuit is hardly caused, so that durability to repetitive discharge is improved. Desirably, the insulating layer 2 is formed by a printing method, the internal electrode layers 3 are formed by a printing method, the discharge space 4 is formed by shearing work, and these are manufactured by being integrally sintered after press-fitting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surge absorbing element for protecting an electronic circuit or an electronic component of a communication device or the like from a surge, and a method of manufacturing the same. The present invention relates to a surge absorbing element and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as this type of surge absorbing element,
A varistor made of a high-resistance element having a voltage non-linear characteristic, a discharge type surge absorbing element having a discharge space sealed in an airtight container, and the like are widely used.

A conventional varistor has excellent responsiveness of surge absorption, and has an advantage that it is easy to reduce the size of an element and to adopt a structure corresponding to a surface mount component. It has a drawback that it is difficult to use for system circuits.

[0004] Further, the conventional discharge-type surge absorbing element is widely used in signal-related circuits because of its small capacitance. However, the structure is that the lead wire is drawn out by encapsulating glass as an airtight structure.When mounting on a printed circuit board, it is necessary to cut and bend the lead wire to an appropriate length, and then A lead wire was inserted into the hole and soldered. While many electronic components have been shifted to surface-mounted electronic components, such a mounting method on a printed circuit board has been a time-consuming method.

As a means for solving these problems, a surface mount type surge absorbing element has been proposed. However, in order to keep the micro gap airtight, vacuum evacuation and sealing of a cap are required.
The man-hours required to form an insulating film on the microgap so as not to short-circuit the cap and the microgap are required, and there is a problem that productivity is not improved.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in order to solve such a problem, and has a small capacitance.
Moreover, it is an object of the present invention to provide a surface mount type surge absorbing element which is easy to manufacture and a method of manufacturing the same.

[0007]

According to the present invention, there is provided an insulating layer made of an insulating ceramic sintered body having a pair of external electrodes, wherein a pair of internal electrode layers electrically connected to the external electrodes are provided inside the insulating layer. A surface-mounted surge absorbing element having a discharge space between electrode layers, wherein the inner diameter of a part of the discharge space not in contact with the internal electrode layer is larger than other inner diameters.

Further, the present invention is the above-mentioned method for manufacturing a surface mount type surge absorbing element, wherein the insulating layer between the internal electrode layers is formed of three or more sheets.

Further, the present invention provides a method for forming a sheet to be the insulating layer by a printing method or a green sheet method, forming a sheet to be the internal electrode layer by a printing method, and forming a hole to be the discharge space in the sheet. Formed by shearing,
This is a method for manufacturing the above surface mount type surge absorbing element, in which each sheet is pressed and then integrally sintered.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the surface mount type surge absorbing element of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the surface mount type surge absorbing element according to the present invention includes a pair of external electrodes 1 electrically connected to an insulating layer 2 made of an insulating ceramic sintered body having a pair of external electrodes 1. , And a discharge space 4 between the internal electrode layers 3.

With this configuration, when an excessive voltage is applied between the internal electrode layers 3, the atmosphere in the discharge space 4 causes dielectric breakdown, and a discharge is generated, so that a surge voltage can be absorbed.

Further, the insulating layer portion between the internal electrode layers 3 is composed of three or more layers, and among the insulating layers, the internal electrode layer 3
The inner diameter 5 of the discharge space 4 of the layer not in contact with the inner electrode layer 3 is made larger than the inner diameter 6 of the discharge space 4 of the layer in contact with the internal electrode layer 3, and at least one layer not in contact with the internal electrode layer 3 is formed. By doing so, the discharge space 4 has an outwardly convex shape.

When the inner diameters 5 and 6 of the discharge space 4 of the insulating layer are the same, creeping discharge easily occurs along the surface of the insulating layer, and a short circuit may occur due to the electrode material being sputtered on the surface of the insulating layer. However, in the structure of the present invention, a part of the insulating layer between the two internal electrode layers 3 has a shape that is convex outward, and even when creeping discharge occurs, the convex part is not easily sputtered. Therefore, a short circuit does not easily occur, and durability against repeated discharge is improved.

Further, the discharge starting voltage can be adjusted by the gap length between the internal electrode layers. Further, at the time of sintering, by replacing the discharge gas and sealing the glass, it is possible to obtain an element having excellent repeated discharge durability.

Since the capacitance of the surface mount type surge absorbing element according to the present invention is determined by the area of the opposing portion of the electrode, it is possible to reduce the capacitance according to the application.

Such a surface mount type surge absorbing element is
An insulating ceramic layer is formed by a printing method or a green sheet method, an internal electrode layer is formed by a printing method, a hole serving as a discharge space is formed by shearing, and each sheet is pressed and then integrally sintered. Since it is manufactured, it is possible to use a conventional method with high mass productivity.
The external dimensions, electrode area, spacing, and number of layers can be selected as appropriate according to desired electrical characteristics.

As the insulating ceramic layer, alumina,
Ceramic materials having a high specific volume resistivity, such as mullite, steatite, forsteatite, cordierite, glass, titania, and zirconia, can be used alone or in combination, and can be selected according to the purpose.

For the internal electrode layer, a material having excellent conductivity such as a low-resistance metal such as copper, silver, aluminum, and nickel, and an alloy material such as carbon, stainless steel, and Kovar can be used. In addition, SnO ₂ , Nb ₂ O ₅ , Mo
O ₃ , WO ₃ , TiC, SiC, ZrC, WC, Hf
Conductive ceramic materials such as oxides, carbides, and nitrides such as C, VC, TiN, TaN, VN, ZrN, and NbN can also be used. When these conductive ceramic materials are used, deterioration of the electrodes due to melting or oxidation during gas discharge can be suppressed. These electrode materials may be used alone or in combination of a metal material and a ceramic material, but may be used in combination.

[0020]

Next, an embodiment of the surface mount type surge absorbing element of the present invention will be described with reference to the drawings.

First, a steatite powder having an average particle size of about 3 μm and a borosilicate glass powder were mixed at a ratio shown in Table 1 with a binder and a solvent, and a paste for an insulating layer was prepared using a bead mill.

[0022]

[Table 1]

Also, 70 parts by weight of silver-30 parts by weight of palladium alloy powder having an average particle size of about 0.3 μm were mixed with a binder and a solvent in the ratio shown in Table 2, and a paste for an internal electrode layer was prepared using a bead mill. .

[0024]

[Table 2]

These were screen-printed as shown in FIG. 2 and punched (sheared) to form holes serving as discharge spaces. The inner diameter 6 of the discharge space was 500 μm, and the inner diameter 5 of the discharge space was 700 μm. Overlay these sheets,
Thermocompression bonding was performed at 110 ° C. At 1000 ° C in air,
It was sintered for 5 hours. Finally, a glass-containing silver paste was applied as an external electrode, and sintered at 600 ° C. for 30 minutes to obtain a surface-mountable surge absorbing element.

For these surge absorbing elements, 500p
F-500Ω-10 kV static electricity was repeatedly applied 2000 times, and the discharge starting voltage and its variation were examined. Also,
The cycle life was defined as the point at which the variation of the discharge start voltage in repeated discharge became ± 30% or more of the reference discharge start voltage. Table 3 shows the results.

[0027]

[Table 3]

In Table 3, the variation in the firing voltage of all the elements was ± 22 after 2000 repeated discharges.
%. Also, the insulation resistance exceeds 10 ¹⁰ Ω,
The capacitance was 0.7 pF or less.

From the above results, by controlling the gap length between the internal electrode layers, a desired discharge starting voltage can be obtained,
It has become possible to obtain a surge absorbing element having a low capacitance.

Table 4 shows a comparison between the conventionally used surge absorbing element and the product of the present invention.

[0031]

[Table 4]

From Table 4, it can be seen that the surge absorbing element according to the present invention has a feature that it has the same low capacitance as that of the conventional discharge type surge absorbing element and has a structure that can be easily mounted on the surface. You can see that there is.

It should be noted that the present invention is not limited to the above embodiment, and those skilled in the art can easily estimate that other insulating ceramic materials or conductive materials can be used as the insulating material and the electrode material. it can. Similarly, the conditions relating to the production of the laminate, such as the application of other methods as the production method of the paste, the thickness of the printed laminate, the thickness of the internal electrode layer, the dimensions of each part, and the sintering conditions, etc. It can be easily inferred by those skilled in the art that the conditions other than the embodiment may be used.

[0034]

As described above, according to the present invention,
A surface mount type surge absorbing element having a small capacitance and easy to manufacture, and a method for manufacturing the same can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the structure of a surface mount type surge absorbing element according to an embodiment of the present invention. FIG. 1A is a sectional view, and FIG.
(B) is an AA cross-sectional view of FIG. 1 (a). FIG. 1 (c)
FIG. 1A is a cross-sectional view taken along the line BB, and FIG.
CC sectional view of FIG.

FIG. 2 is a diagram illustrating a method for manufacturing a surface-mount type surge absorbing element according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 external electrode 2 insulating layer 3 internal electrode layer 4 discharge space 5, 6 inner diameter of discharge space 7 substrate

Claims (3)

[Claims] 1. A surface having a pair of internal electrode layers electrically connected to said external electrodes inside an insulating layer made of an insulating ceramic sintered body having a pair of external electrodes, and having a discharge space between said internal electrode layers. A surface-mounted surge absorbing element, wherein an inner diameter of a part of the discharge space not in contact with the internal electrode layer is larger than another inner diameter. 2. The method according to claim 1, wherein the insulating layer between the internal electrode layers is formed of three or more sheets. 3. A sheet to be the insulating layer is formed by a printing method or a green sheet method, a sheet to be the internal electrode layer is formed by a printing method, and a hole to be the discharge space is formed in the sheet by a shearing process. 3. The method for manufacturing a surface-mounted surge absorbing element according to claim 1, wherein each of the sheets is pressure-bonded and then integrally sintered.