JP2001043954A - Surge absorbing element and manufacture of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surge absorbing element of low capacity and high productivity without complex processes, by providing the inside of an insulating ceramic layer having a pair of external electrodes, with internal electrodes conducting with the external electrodes and a space, and confining a discharge gas in the discharging space. SOLUTION: An insulating ceramic sheet 2 and internal electrodes 6 on the insulating ceramic sheet 2 are formed by screen printing, and a hole 5 as a discharging space is punched out. When the excess voltage is applied between the internal electrodes 6, the dielectric breakdown occurs in the atmosphere in the discharging space, the discharging is generated, and the serge voltage is absorbed. Preferably, a sheet having an insulating ceramic layer is formed, a hole as the discharging space is formed on the sheet, the internal electrodes and the hole are formed on another sheet, and the sheets are stacked, crimped, and then integrally sintered, further the sheets and the internal electrodes are formed by a printing method or a green sheet method, and the holes are formed by the shearing work or the laser beam machining to form a surge absorbing element.

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 more particularly to a surface mount type surge absorbing element advantageous for automatic mounting on a printed circuit board. It concerns the manufacturing method.

[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 the element and make the structure compatible with surface mount components. However, it also has a disadvantage that the capacitance is large and it is difficult to use it for a signal system circuit.

[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 an airtight structure that draws out lead wires by encapsulating glass, so when mounting on a printed circuit board, cutting, bending, cutting,
Furthermore, it requires a complicated and time-consuming process such as insertion of a lead wire into a hole in a printed circuit board and soldering, and is not suitable for surface mounting.

[0005]

As means for solving the drawbacks of these conventional products, a surface mount type surge absorbing element has been proposed. However, in the structure of the surface mount type surge absorbing element, the cap is sealed by evacuating to keep the micro gap airtight. At this time, there is a problem that man-hours such as forming an insulating film on the microgap are required to prevent short-circuit between the cap and the microgap, thereby reducing productivity.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a surge absorbing element having a small capacitance and a high productivity which does not require complicated manufacturing steps, and a method of manufacturing the same. It is in.

[0007]

According to the present invention, there is provided an insulating ceramic layer having a pair of external electrodes, an internal electrode and a discharge space which are electrically connected to the external electrode, and a discharge gas is confined in the discharge space. This is a surge absorbing element characterized by the above.

The present invention also relates to a method of manufacturing a surge absorbing element having an internal electrode and a discharge space, which are electrically connected to the external electrodes, inside the insulating ceramic layer having a pair of external electrodes. Forming a sheet that forms the discharge space in the sheet, forming the internal electrode in the sheet, and then forming a hole in the sheet. A method of manufacturing a surge absorbing element, comprising stacking, crimping, and integrally sintering sheets.

Further, the present invention is the above-mentioned method for manufacturing a surge absorbing element, wherein the sheet and the internal electrode are formed by a printing method or a green sheet method.

Further, the present invention is the method for manufacturing a surge absorbing element, wherein the holes are formed by shearing or laser processing.

The surge absorbing element according to the present invention is provided with an internal electrode and a discharge space electrically connected to the external electrode inside the insulating ceramic layer having the external electrode. With this configuration, an excessive voltage is applied between the internal electrodes. Then, the surge voltage can be absorbed by the atmosphere in the discharge space causing a dielectric breakdown to generate a discharge.

Further, at the time of integral sintering, the gas is replaced with a discharge gas,
By encapsulating the glass, an element having excellent durability against repeated discharge can be obtained.

Further, the discharge starting voltage can be adjusted by the gap length between the internal electrodes, and can be adjusted by changing the type of discharge gas.

Since the capacitance is determined by the area of the opposing portion of the electrode, the capacitance can be reduced according to the application.

Further, the surge absorbing element of the present invention can use a manufacturing method which is conventionally high in mass productivity. That is, the insulating ceramic layer and the internal electrode are formed in a sheet shape by a printing method or a green sheet method, the discharge space is formed by shearing or laser processing, and each sheet is integrally sintered after being pressed. It is manufactured by The external dimensions, electrode area and interval, and the number of layers can be selected as appropriate according to desired electrical characteristics.

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

For the internal electrode, 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 copearl can be used. 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. These electrode materials may be used alone or in combination of a metal material and a ceramic material, or may be used in combination.

[0018]

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

(First Embodiment) A first embodiment of the present invention will be described with reference to FIGS. 1 to 4 and Tables 1 to 3.

FIG. 1 is a perspective view of a surge absorbing element according to the present invention. FIG. 2 is an exploded perspective view of FIG. FIG.
FIG. 2 is a sectional view taken along line AA of FIG. FIG. 4 is a sectional view perpendicular to the line AA of FIG. These figures show the samples No. 1 to No. 3 and the sample No. 7 shown in Table 3.
No. 9 to No. 9.

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 insulating ceramics was prepared using a bead mill. Also, 70 parts by weight of silver and 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 the mixture was subjected to a bead mill to prepare an internal electrode paste.

[0022]

[Table 1]

[0023]

[Table 2]

Using these, the insulating ceramic sheet 2 and the internal electrodes 6 are formed on the insulating ceramic sheet 2 by screen printing in the shape pattern (pattern 1) shown in the insulating ceramic sheet 4 having the internal electrodes in FIG. Then, a hole 5 for the discharge space was formed by punching.

Next, as shown in FIG. 6, the insulating ceramic sheet 2, the perforated insulating ceramic sheet 3, and the insulating ceramic sheet 4 having the internal electrodes formed thereon are stacked and thermocompression-bonded at 110.degree. After doing
It was integrally sintered at 1000 ° C. for 5 hours. Finally, as shown in FIG. 1, a glass-containing silver paste was applied as the external electrode 1, sintered at 600 ° C. for 30 minutes, and surface-mountable samples No. 1 to No. 3 and No. No. 0.7 to No. 9 were obtained. FIG. 3 is a cross-sectional view taken along a line AA in FIG. 1, and FIG. 4 is a cross-sectional view taken along a line AA in FIG.

The surge absorbing element sample thus obtained was repeatedly supplied with static electricity of 500 pF-500 Ω-10 kV, and the discharge starting voltage and its variation were examined. Note that, 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.

[0027]

[Table 3]

As is evident from Table 3, the variation in the firing voltage of all the samples was within ± 30% after 2000 repetitive discharges. The insulation resistance is 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 atmosphere in the discharge space, it is possible to obtain a surge absorbing element having a desired discharge start and a low capacitance.

(Second Embodiment) A second embodiment of the present invention will be described with reference to FIGS. 5 to 8 and a table.

FIG. 5 is a perspective view of a surge absorbing element according to the present invention. FIG. 6 is an exploded perspective view of FIG. FIG.
FIG. 6 is a sectional view taken along line BB of FIG. FIG. 8 is a sectional view perpendicular to BB of FIG. These figures correspond to samples No. 4 to No. 6 shown in Table 3.

Steatite powder having an average particle size of about 3 μm and borosilicate glass powder were mixed with a binder and a solvent at the ratios shown in Table 1, and a paste for insulating ceramics was prepared using a bead mill. In addition, silver 70 having an average particle size of about 0.3 μm
Parts by weight—30 parts by weight of palladium alloy powder were 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.

In each of these shapes (pattern 2) shown in FIG. 6, an insulating ceramic sheet and internal electrodes 6 were formed by screen printing, and holes for discharge spaces were formed by punching.

Next, as shown in FIG. 6, the insulating ceramic sheet 2, the perforated insulating ceramic sheet 3, and the insulating ceramic sheet 4 having internal electrodes formed thereon are stacked and heated at 110 ° C. After crimping, 10
It was integrally sintered at 00 ° C. for 5 hours. Finally, as shown in FIG. 5, a silver paste containing glass was applied as the external electrode 1 and sintered at 600 ° C. for 30 minutes, and the surge absorption of the surface-mountable samples No. 4 to No. 6 shown in Table 3 was performed. An element was obtained. Note that FIG. 7 shows a cross-sectional view of the surge absorbing element 20 obtained in FIG. 5, which is horizontal to the line BB, and FIG. 8 shows a cross-sectional view perpendicular to the line BB.

A static electricity of 500 pF-500 Ω-10 kV was repeatedly applied to the surge absorbing element sample thus obtained, and the discharge starting voltage and its variation were examined. Note that, 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.

As is evident from Table 3, the variation in the firing voltage of all the samples was within ± 30% after 2000 repetitive discharges. The insulation resistance is 10 ¹⁰
Ω or more, and the capacitance was 0.6 pF or less. The variation (%) of the discharge starting voltage and the cycle life
This is at the same level as the product sample No. 1 to No. 3 of the present invention in the embodiment.

From the above results, the gap length of the internal electrode,
By controlling the atmosphere in the discharge space, it is possible to obtain a surge absorbing element having a desired discharge starting voltage and low capacitance.

As apparent from the first and second embodiments, 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 mount on a surface. You can see that there is. Table 4 shows a comparison between a conventionally used surge absorbing element and the present invention.

[0039]

[Table 4]

As is clear from Table 4, the product of the present invention has a smaller capacitance than the conventional varistor for surface mounting. Further, the product of the present invention can be a surface-mount type surge absorbing element that does not require a lead wire required by a conventional discharge type surge absorbing element.

It should be noted that the product of the present invention is not limited to the above-described embodiment, and it is easily understood by those skilled in the art that other insulating ceramic materials or conductive materials can be used as the insulating material and the electrode material. It can be analogized to: Similarly, the conditions for producing the paste for printing, applying other methods, and the conditions for producing the laminate, such as the thickness of the printed laminate, the thickness of the electrode layer, and the dimensions of each part, and the sintering conditions are described in this book. The fact that conditions other than the embodiment of the invention may be used can be easily estimated by those skilled in the art.

[0042]

As described above, according to the present invention, since a technology having high productivity such as a conventional screen printing technology is used, it is easy to manufacture, and the capacitance is low and the surge is low. A surface mount type surge absorbing element having excellent absorption characteristics can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view of a surge absorbing element according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view of the surge absorbing element according to the first embodiment of the present invention.

FIG. 3 is a sectional view taken along the line AA of FIG. 1;

FIG. 4 is a sectional view taken along a line AA of FIG. 1;

FIG. 5 is a perspective view of a surge absorbing element according to a second embodiment of the present invention.

FIG. 6 is an exploded perspective view of a surge absorbing element according to a second embodiment of the present invention.

FIG. 7 is a sectional view taken along the line BB of FIG. 5;

FIG. 8 is a sectional view perpendicular to the line BB in FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 External electrode 2 Insulating ceramics sheet 3 Perforated insulating ceramics sheet 4 Insulating ceramics sheet having an internal electrode 5 Holes 6 Internal electrode 7 Insulating ceramics layer 8 Discharge space 9 Side glass coating layer 10 Upper and lower glass coating layers 20 Surge Absorption element

Claims (4)

[Claims] 1. A surge absorbing element comprising: an insulating ceramic layer having a pair of external electrodes; and an internal electrode and a discharge space that are electrically connected to the external electrode, wherein a discharge gas is confined in the discharge space. . 2. A method of manufacturing a surge absorbing element having an internal electrode and a discharge space, which are electrically connected to an external electrode, inside a insulating ceramic layer having a pair of external electrodes, wherein a sheet constituting the insulating ceramic layer is formed. And forming holes forming the discharge space in the sheet, and forming the holes after forming the internal electrodes in the sheet, and stacking the sheets obtained from each of the steps. A method for producing a surge absorbing element, comprising: crimping and integrally sintering. 3. The method according to claim 2, wherein the sheet and the internal electrode are formed by a printing method or a green sheet method. 4. The hole according to claim 2, wherein the hole is formed by shearing or laser processing.
A method for manufacturing the surge absorbing element as described in the above.