JP2000311764A - Surge absorbing element, and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an electrostatic capacity small, and to eliminate a complicated manufacturing process. SOLUTION: This surge absorbing element has a pair of internal electrode layers 3 conducted with a pair of external electrodes 1 inside an insulating ceramic layer 2 having the external electrodes 1, and an inside diameter 5 of an insulation layer portion of a discharge space 4 formed penetratedly in the internal electrode layers 3 is larger than an inside diameter 6 of an electrode layer portion. An atmosphere inside the discharge space 4 generates electric breakdown to generate discharge by this constitution when an excessive voltage is impressed between the internal electrode layers 3, and a surge voltage is absorbed thereby.

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 used in a communication device or the like from a surge, and particularly to a surface mount type which is advantageous for automatic mounting on a printed circuit board. 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 a surge absorbing element for protecting a communication device from a surge, a varistor made of a high-resistance element having a voltage non-linear characteristic and a discharge type surge absorbing element having a discharge space sealed in an airtight container have been widely used. It's being used.

Conventional varistors have the advantage that they have excellent surge absorption responsiveness, and that it is easy to reduce the size of elements and to adopt a structure that is compatible with surface mount components. However, the conventional varistor has a drawback that it has a large capacitance and is difficult to use for a signal circuit.

[0004] Further, the conventional discharge-type surge absorbing element is widely used in signal-related circuits because of its small capacitance. However, since the surge absorbing element has an airtight structure in which the lead wire is drawn out by enclosing the glass as shown in FIG. This method requires complicated and time-consuming steps such as bending, bending, and insertion of lead wires into holes of a printed circuit board and soldering, and is not suitable for surface mounting.

[0005]

As means for solving these problems, a surface mount type surge absorbing element has been proposed. However, in the structure of the surface mount type surge absorbing element, in order to keep the micro gap airtight, evacuate and seal the cap, and form an insulating coating on the micro gap so that the cap and the micro gap do not short-circuit. There is a problem that it takes a lot of man-hours and productivity does not increase.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problem, and has an object to provide a surge absorbing element which has a small capacitance and does not require a complicated manufacturing process to increase productivity, and a method of manufacturing the same. To provide.

[0007]

According to the present invention, an external electrode is provided inside an insulating ceramic layer having a pair of external electrodes.
A pair of internal electrode layers 3 electrically connected to the inner electrode layer, wherein the inner diameter 5 of the insulating ceramic layer portion of the discharge space 4 formed through the inner electrode layers is larger than the inner diameter 6 of the internal electrode layer portion. Element.

Further, the present invention is the surge absorbing element according to the present invention, wherein a plate-like electrode layer laminated at regular intervals is provided between the internal electrode layers.

In the present invention, the insulating ceramic layer is formed in a sheet shape by a printing method or a green sheet method, the internal electrode layer is formed in a sheet shape by a printing method, and the discharge space is formed by shearing. This is a method for manufacturing a surge absorbing element in which each of the sheets is press-bonded and integrally sintered.

As shown in FIG. 1, the surge absorbing element of the present invention has a pair of internal electrode layers 3 electrically connected to the external electrodes 1 inside an insulating ceramic layer 2 having a pair of external electrodes 1. The inner diameter 5 of the insulating layer portion of the discharge space 4 formed through the electrode layer 3 is larger than the inner diameter 6 of the electrode layer portion.

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 to generate a discharge, thereby absorbing a surge voltage.

Further, by making the inner diameter 5 of the insulating ceramic layer portion of the discharge space 4 larger than the inner diameter 6 of the internal electrode layer portion, a wide discharge space 4 is ensured, and the inner diameter 5 of the insulating ceramic layer portion becomes smaller than the electrode layer. Short-circuiting due to spattering of the electrode material due to creeping discharge of the surface of the insulating ceramic layer, which occurs when the inner diameter is the same as that of the portion 6, is less likely to occur, and durability against repeated discharge is improved.

Further, the discharge starting voltage can be adjusted by the gap length between the electrodes. Furthermore, when the plate-shaped electrode layers 7 are stacked at regular intervals between the internal electrode layers 3, the discharge starting voltage is approximately proportional to the number of layers, so that the starting voltage can be easily controlled according to the purpose.

Since the capacitance of the surge absorbing element in 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.

In the surge absorbing element of the present invention, the insulating ceramic layer 2 forms a sheet by a printing method or a green sheet method, the internal electrode layer 3 forms a sheet by a printing method, and the discharge space 4 forms a sheet by a shearing process. It is manufactured by forming, sintering after pressing each sheet, and it is possible to use a conventional method with high mass productivity. In addition, external dimensions, electrode area and spacing,
The number of layers can be selected as appropriate according to the desired electrical characteristics.

As the insulating ceramic layer 2, a ceramic material having a high specific volume resistivity such as alumina, mullite, steatite, forsteatite, cordierite, glass, titania, zirconia, or the like may be used alone or in combination. It can be selected according to the purpose.

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

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, and is a cross-sectional view of the surge absorbing elements of samples No. 1 to No. 3, and FIG.
In the second embodiment of the present invention, samples No. 4 to N
It is sectional drawing of the surge absorbing element of o.9. The inner diameter 6 of each of the internal electrode layers in the discharge space 4 is 50 μm.

A steatite powder having an average particle size of about 3 μm and a borosilicate glass powder were mixed with a binder and a solvent in the ratio shown in Table 1, and a paste for an insulating layer was prepared using a bead mill. Also, 70 parts by weight of silver-3 having an average particle size of about 0.3 μm.
0 parts by weight of a palladium alloy powder was mixed with a binder and a solvent in the ratio shown in Table 2, and the mixture was subjected to a bead mill to prepare a paste for an internal electrode layer.

[0021]

[Table 1]

[0022]

[Table 2]

As shown in FIG. 3, the paste for the insulating ceramic layer 2 and the paste for the internal electrode layer 3 were screen-printed and punched to form discharge spaces. After stacking these sheets and thermocompression bonding at 110 ° C.,
C. for 5 hours. Finally, a glass-containing silver paste was applied as the external electrode 1 and sintered at 600 ° C. for 30 minutes to obtain a surface-mountable surge absorbing element.

For these surge absorbing elements, 500
The static electricity of pF-500Ω-10 kV was repeatedly applied, and the discharge starting voltage and its variation were examined. In addition, in the repeated discharge, a point where the variation of the discharge start voltage becomes ± 30% or more of the reference discharge start voltage is defined as the cycle life. Table 3 shows the results.

[0025]

[Table 3]

In all of the devices, the variation in the firing voltage after 2,000 repetitions of discharge was within ± 30%. Further, the insulation resistance was 10 ¹⁰ Ω or more, and the capacitance was 0.6 pF or less.

From the above results, the gap length of the internal electrode,
By controlling the number of layers, a surge absorbing element having a desired discharge starting voltage and low capacitance can be obtained.

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

[0029]

[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 a low capacitance and a structure that is easy to surface mount.

It should be noted that the product of the present invention is not limited to the above-described embodiment, but may be used as an insulating material or an electrode material.
The fact that other insulating ceramic materials or conductive materials can be used can be easily inferred by those skilled in the art.
Similarly, as a method of producing a printing paste, applying other techniques, and the printing lamination thickness, the thickness of the electrode layer, the conditions related to the production of the laminate such as the dimensions of each part, and the sintering conditions, The fact that conditions other than the embodiment of the present invention may be used can be easily estimated by those skilled in the art.

[0032]

As described above, according to the present invention, since a technique having high productivity such as a conventional screen printing technique is used, the production is easy and the capacitance is low. It is possible to provide a surge absorbing element having excellent surge absorbing characteristics and a method for manufacturing the same.

[Brief description of the drawings]

FIG. 1 shows samples No. 1 to No. 3 according to an embodiment of the present invention.
Sectional drawing which shows the structure of the surge absorption element of FIG.

FIG. 2 shows samples No. 4 to No. 9 according to the embodiment of the present invention.
Sectional drawing which shows the structure of the surge absorption element of FIG.

FIG. 3 is a diagram showing a method for manufacturing a surge absorbing element of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 external electrode 2 insulating ceramic layer 3 internal electrode layer 4 discharge space 5 inner diameter of insulating ceramic layer portion (of discharge space) 6 inner diameter of internal electrode layer portion (of discharge space) 7 plate-like electrode layer 8 substrate

Claims (3)

[Claims] 1. An insulating ceramic layer having a pair of external electrodes, a pair of internal electrode layers electrically connected to the external electrodes, and an inner diameter of an insulating ceramic layer portion of a discharge space formed through the internal electrode layers. Is larger than the diameter in the internal electrode layer portion. 2. The surge absorbing element according to claim 1, further comprising a plate-like electrode layer laminated at a constant interval between said internal electrode layers. 3. The insulating ceramic layer is formed in a sheet shape by a printing method or a green sheet method, the internal electrode layer is formed in a sheet shape by a printing method, and the discharge space is formed by shearing. The method for manufacturing a surge absorbing element according to claim 1, wherein the sheet is integrally sintered after pressure bonding.