JP2001210445A - Chip-type surge absorption element and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chip-type surge absorption element and its manufacturing method having a small electrostatic capacity and an easy surface mounting capability to a substrate and an easy manufacturing procedure. SOLUTION: The chip-type surge absorption element in which in the inside of a ceramic sintering object having insulation characteristic which has a pair of external electrode, a 1st internal electrode 2a, 2b with a small area, a 2nd internal electrode 3a, 3b with a large area, and an electric discharge space 4 are formed, a ratio of the area of the above first internal electrode 2a, 2b of the exposed to the electric discharge space 4 and the area of the above 2nd internal electrode 3a, 3b exposed to the electric discharge space 4 is in the range of 1 to 99, to 40 to 60, and the 2nd internal electrodes 3a, 3b are placed opposite to each other, and the 1st internal electrodes 2a, 2b exists in the middle of the distance between the 2nd internal electrode 3a and 3b so that the distance 11 between two gaps closest to each other may become equal. And moreover, the 1st internal electrodes 2a, 2b and the 2nd internal electrodes 3a, 3b do not exist on the same plane.

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 suitable for protecting electronic circuits and electronic components from surges.
The present invention relates to a multilayer chip-type surge absorbing element suitable for automatic mounting on a printed circuit board 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 composed of a high resistance element having a voltage non-linearity 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 of being excellent in responsiveness to surge absorption and of being easy to miniaturize and surface mount elements. However, there is a disadvantage that the capacitance is large and is not suitable for a signal system circuit. Conventional discharge-type surge absorbing elements have a small capacitance and are widely used in signal circuits. However, since it is necessary to have an airtight structure, the structure is such that glass is sealed and lead wires are drawn out. Therefore, mounting on a board requires a lot of man-hours by cutting and bending lead wires into appropriate lengths, and then inserting the leads into holes in the board and soldering.

[0004]

[0007] Conventional varistors include:
There were the following problems. That is, there is a disadvantage that the capacitance is large and is not suitable for a signal system circuit.

[0005] Further, in the conventional discharge type surge absorbing element,
There were the following problems. That is, in order to have an airtight structure, the structure is such that the lead wire is drawn out by enclosing the glass, but for mounting on the board, the lead wire is cut and bent to an appropriate length, The method of inserting into the hole and soldering was adopted, which required a lot of man-hours.

At present, many electronic components have been switched to surface mount type devices, and surface mount type surge absorbing elements have been proposed (Japanese Patent Application Laid-Open No. Hei 7-245878, applicant:
Mitsubishi Materials). However, this method is not suitable for mass production because it requires a lot of man-hours such as attaching several ceramic plates to keep the discharge gap airtight.

Accordingly, it is an object of the present invention to provide a low-cost chip-type surge absorbing element which has a small capacitance, is easily surface-mounted on a substrate, is easy to manufacture, and has a low cost. It is.

[0008]

According to the present invention, there is provided a chip type surge absorbing element comprising a discharge space, a first internal electrode and a second internal electrode inside an insulating ceramic sintered body having a pair of external electrodes. The formed chip type surge absorbing element,
The area ratio of the discharge space exposed surface of the first internal electrode to the discharge space exposed surface of the second internal electrode is from 1:99 to 4
The second internal electrodes having a range of 0 to 60 and having a larger area exist so as to face each other, and a second internal electrode having a small area of a different polarity is provided in the middle of the distance between the second electrodes. Exists, the two internal electrodes do not exist on the same plane as the second internal electrode, the second internal electrode and the shape of exposure to the discharge space are circular, and are formed in the gap between the electrodes. The chip-type surge absorbing element is characterized in that the discharge space is a space having a plane having a larger area than the area formed by the diameter of the circular electrode.

As described above, since the closest portion between the internal electrodes is not on the same plane as the second electrode, the discharge is started by the second internal electrode having a large area and the second electrode having a different area having a small area. However, when the discharge proceeds and reaches the arc discharge, a discharge path is formed by the second internal electrodes facing each other. Therefore, electrode damage due to the discharge of the first internal electrode having a small area is minimized.

[0010] That is, when the discharge is repeated, the discharge starts, in other words, the discharge starting voltage is stabilized, and the characteristic fluctuation due to the repeated discharge is reduced. Further, by setting the plane area of the discharge space to a space having a larger plane area than the second internal electrode, a short circuit may be caused by sputtered particles other than the second internal electrode or the electrode of the discharge space. It is possible to prolong life. That is, it is possible to prolong the life of the chip type surge absorbing element.

In addition, by equalizing the distance between the gaps at the two closest points in the middle between the first internal electrode having a small area and the second internal electrode having a large area, the element can be mounted on a substrate. It is possible to eliminate the mounting direction. Further, the element of the present invention is characterized by being manufactured by a printing method and a green sheet method, and can be mass-produced based on a conventional technique.

That is, according to the present invention, a pair of first internal electrodes having a small area, a pair of second internal electrodes having a large area, and a discharge space are provided inside an insulating ceramic sintered body having a pair of external electrodes. Is formed, the ratio of the area of the exposed portion of the pair of first internal electrodes to the discharge space to the area of the exposed portion of the second internal electrode to the discharge space is: It is in the range of 1:99 to 40:60, and a pair of second internal electrodes are present so as to face each other, and a pair of first internal electrodes is provided at two positions in the middle of the distance between the pair of electrodes. And the pair of first internal electrodes and second internal electrodes do not exist on the same plane.

Further, according to the present invention, the shape of the surface of the pair of second internal electrodes exposed to the discharge space is circular, and the plane area of the discharge space formed in the gap between the electrodes is:
The chip type surge absorbing element is larger than the area of the pair of second internal electrodes.

According to the present invention, a pair of first internal electrodes having a small area, a pair of second internal electrodes having a large area, and a discharge space are provided inside an insulating ceramic sintered body having a pair of external electrodes. The ratio of the area of the exposed portion of the pair of first internal electrodes to the discharge space to the area of the exposed portion of the second internal electrode to the discharge space. Is set in a range of 1:99 to 40:60, the pair of second internal electrodes are respectively opposed to each other, and the pair of first internal electrodes is provided in the middle of the distance between the pair of second internal electrodes. A method of manufacturing a chip-type surge absorbing element, wherein the distance between two gaps is formed to be equal, and the pair of first internal electrodes and second internal electrodes do not exist on the same plane. is there.

Further, in the present invention, the method for manufacturing a chip-type surge absorbing element is a method for manufacturing a chip-type surge absorbing element formed by a printing method or a green sheet method.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A chip type surge absorbing element and a method of manufacturing the same according to the present invention will be described below.

FIG. 1 is a side view of a chip type surge absorbing element according to an embodiment of the present invention. FIG. 2 is a sectional view taken along the line AA of the chip-type surge absorbing element of FIG.

In the chip type surge absorbing element shown in FIG.
Main component _Na 2 O · _B 2 O as the insulating ceramic 1,6
_3. Steatite to which 40% by weight of SiO ₂ glass was added. Further, the first internal electrodes 2a and 2b and the second internal electrodes 3a and 3b were formed by a screen printing method using Ag-30% Pd, and were sintered at 1000C.

In FIG. 1, a large-area second internal electrode 3
a, 3b and the small-area first internal electrodes 2a, 2b
Although the same material is used, different materials may be used. In that case, the resistance value of the first internal electrodes 2a, 2b is
It is desirable that the resistance value is smaller than the resistance values of the second internal electrodes 3a and 3b. The discharge space 4 was formed by filling a discharge space portion with a carbon paste by screen printing and burning it out during sintering. The external electrodes 5a and 5b were formed by baking an Ag electrode at 600 ° C. and then applying Ni plating.

The insulating ceramics 1, 6 and the first
The materials of the internal electrodes 2a and 2b, the second internal electrodes 3a and 3b, and the external electrodes 5a and 5b are not limited to the above materials. Further, the electrode shape of the chip type surge absorbing element is not limited to the embodiment of FIG.

In the embodiment, the second internal electrodes 3a, 3
The outer diameter of the circular electrode b is 90 μm, and the outer diameter of the circular electrodes of the first internal electrodes 2a and 2b on the surface perpendicular to this is 1 μm.
A discharge experiment was performed with 0 μm, a gap between electrodes closest to each other at 50 μm, and a long side of the discharge space 4 at 200 μm.
As a result, the DC start voltage was about 500V.

An electrostatic surge (10 kV-15) is applied to this element.
(0 pF-330Ω) was applied 10,000 times, and the variation of the DC discharge start voltage was within ± 30% of the initial value.

The ratio of the area of the pair of first internal electrodes to the area of the pair of second internal electrodes is set in the range of 1:99 to 40:60. This is because the variation in the discharge starting voltage increases. Furthermore, the insulation resistance showed a value of 10 ¹⁰ Ω or more. The result is
The characteristic value is equal to or higher than the characteristic of the conventional gap discharge type surge absorbing element.

As described above, the chip-type surge absorbing element according to the present invention is a surface-mount type surge absorbing element having excellent surge life characteristics in an easy manufacturing process utilizing a technique having high productivity such as a conventional screen printing technique. can get.

[0025]

As described above, according to the present invention, the capacitance is reduced, the surface mounting on the substrate is easy, and the manufacturing is easy.
A low-cost chip-type surge absorbing element and a method of manufacturing the same can be provided.

[Brief description of the drawings]

FIG. 1 is a side view of a chip type surge absorbing element according to an embodiment of the present invention.

FIG. 2 is an AA cross-sectional view of the chip type surge absorbing element of FIG.

[Explanation of symbols]

 1,6 Insulating ceramic 2a, 2b First internal electrode 3a, 3b Second internal electrode 4 Discharge space 5a, 5b External electrode 11 Distance between gaps of closest part

Claims (4)

[Claims] 1. A pair of first internal electrodes having a small area, a pair of second internal electrodes having a large area, and a discharge space are formed inside an insulating ceramic sintered body having a pair of external electrodes. In the chip-type surge absorbing element, the ratio of the area of the exposed portion of the pair of first internal electrodes to the discharge space to the area of the exposed portion of the second internal electrode to the discharge space is from 1:99. Range of 40:60, and a pair of second
Are present such that they face each other, and between the pair of second internal electrodes, a pair of first internal electrodes are present such that the distance between the two gaps is equal, The chip-type surge absorbing element is characterized in that the pair of first internal electrodes and second internal electrodes do not exist on the same plane. 2. The shape of the surface of the pair of second internal electrodes exposed to the discharge space is circular, and the area of the plane of the discharge space formed in the gap between the electrodes is equal to that of the pair of second internal electrodes.
The area of the internal electrode is larger than the area of the internal electrode.
The chip-type surge absorbing element as described. 3. A chip forming a pair of first internal electrodes having a small area, a pair of second internal electrodes having a large area, and a discharge space inside an insulating ceramics sintered body having a pair of external electrodes. In the method of manufacturing a type surge absorbing element,
The ratio of the area of the exposed portion of the pair of first internal electrodes to the discharge space and the ratio of the area of the exposed portion of the second internal electrode to the discharge space is in the range of 1:99 to 40:60, The pair of second internal electrodes are made to face each other, and a pair of first internal electrodes are formed so that the distance between two gaps is equal to the middle of the distance between the pair of second internal electrodes. And forming the pair of first internal electrodes and second internal electrodes so that they do not exist on the same plane. 4. The method of manufacturing a chip-type surge absorbing element according to claim 3, wherein the method of manufacturing the chip-type surge absorbing element is formed by a printing method or a green sheet method.