JPH11354248A - Surface mounting type surge absorbing element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small, easily surface-mountable and easily manufacturable surface mounting type surge absorbing element. SOLUTION: In a surface mounting type surge absorbing element 1 of a layered product, plural internal electrodes 3 included inside insulating ceramics 2 are discontinuously formed in a stairs shape, and microgaps 4 are formed between one end of one internal electrode 3 and one end of the other internal electrode 3 with a space.

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 absorbing an overvoltage applied to an electronic component such as a semiconductor element or an electronic circuit, and more particularly to a surface mount type useful for automatic mounting on a printed circuit board. A surge absorbing element.

[0002]

2. Description of the Related Art A surge absorbing element is an important element for protecting an electronic circuit of an electronic device from a surge such as an induced lightning. As the surge absorbing element, a varistor composed of a high-resistance element having a voltage non-linear characteristic, a discharge arrester containing a minute discharge gap in an airtight container, and the like have been widely used.

FIG. 3 is a view showing the appearance of a conventional surge absorbing element. As shown in FIG.
Is sealed in a glass tube 12 under reduced pressure or in an inert gas atmosphere, and lead wires 11 of about 25 mm are protruded from both ends thereof. A conductive film 8 formed on a cylindrical insulator surface and divided by a micro gap 10
Is connected to the lead wire 11 via the cap electrode 9.

[0004]

However, when mounting the surge absorbing element 7 on a printed circuit board, the lead wire 11 is cut to an appropriate length, bent, and then the lead wire 11 is connected to the printed circuit board. Must be inserted into holes and soldered. Furthermore, these conventional surge absorbing elements 7
The method requires a processing step along the surface of the cylindrical insulator, which has been an obstacle to improving productivity.

In recent years, in order to improve the complicated method of mounting such a surge absorbing element on a printed circuit board, the shift of the surge absorbing element to a surface mount type like many other electronic components is being studied. is there.

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface mount type surge absorbing element which is small in size, easy to mount on a surface, and easy to manufacture.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a surface mount type surge absorbing element having an internal electrode separating a micro gap, wherein the micro gap and the internal electrode are included in an insulating ceramic, and a plurality of internal electrodes are connected in a stepwise manner. The micro gap is a surface-mount type surge absorbing element formed discontinuously in a shape and having a space between one end of one internal electrode and one end of another internal electrode.

The surface mount type surge absorbing element of the present invention has three
It is also possible to form a plurality of internal electrodes in a discontinuous stepwise manner so as to have a plurality of micro gaps. The surface mount type surge absorbing element of the present invention is characterized in that it is a laminate.

[0009]

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

FIG. 1 is a diagram showing a surface mount type surge absorbing element according to the present invention. FIG. 1A is an external perspective view of a surface mount type surge absorbing element. FIG. 1B is an explanatory diagram showing the arrangement of the internal electrodes. FIG. 1C is a cross-sectional view of the surface mount type surge absorbing element viewed from a side of the internal electrode.

As shown in FIG. 1A, the surface-mount type surge absorbing element 1 has a block-shaped insulating ceramic 2 made of steatite, and is exposed on two opposing surfaces. The external electrodes 5 are formed.

As shown in FIGS. 1B and 1C, the inside of the block-shaped insulating ceramic 2 is
Four flat internal electrodes 10 made of conductor AgPd
Are discontinuously formed in steps. The space between the ends of the internal electrodes 3 closest to each other is a micro gap 4 in the space.
Is formed. The surface mount type surge absorbing element 1 shown in FIG. 1 includes three micro gaps 4. Out of the four, the two outermost inner electrodes 10 are connected to the outer electrodes 5 formed on the surface of the insulating ceramics 2.

The surface mount type surge absorbing element 1 is laminated by screen printing using steatite as the insulating ceramic 2 and conductor AgPd as the internal electrode 10. In the manufacturing process, the portion to be the microgap 4 is formed of a resin so as to be eliminated in a subsequent baking process to form a space. The laminate thus manufactured was integrally fired at 1300 ° C. in an air atmosphere. A silver paste was applied to the surface of the produced sintered body to which the internal electrode 3 was continuous to provide an external electrode 5, and a surface-mounted surge absorbing element 1 was obtained.

A surface-mount type surge absorbing element 1 according to the present invention.
Was repeatedly discharged 1,000 times or more in an air atmosphere. As a result, the surface-mount type surge absorbing element 1 according to the present invention does not show deposition of the internal electrode material due to sputtering or the like, damage of the internal electrode material, does not change the firing voltage, and has excellent durability. It was confirmed that.

A surface-mount type surge absorbing element 1 according to the present invention.
Since the cross-sectional area of the internal electrode 3 can be increased, heat dissipation during discharge is excellent. Furthermore, since the surface-mount type surge absorbing element 1 has a configuration in which the micro gap 4 is formed as a space inside the laminate, the capacitance is small. According to the present invention, the number of micro gaps can be increased or decreased in accordance with a target surge.

Further, since the internal electrodes 3 of the surface mount type surge absorbing element 1 are literally covered with the insulating ceramics 2, the characteristic deterioration due to oxidation is extremely small. Therefore, it is not necessary to make the micro gap 4 a vacuum or an inert atmosphere, and it is not necessary to enclose the micro gap 4 in a glass tube.
Compared with the conventional surge absorbing element, it has become not only smaller but also easier to manufacture. The manufacturing cost can be reduced as compared with the conventional surge absorbing element, and furthermore, it can be mounted on a printed circuit board in a narrow mounting space.

FIG. 2 is a view showing another embodiment of the micro gap 4 in the surface mount type surge absorbing element according to the present invention. In FIG. 1C described above, the micro gap 4 is formed between an end of one internal electrode and a surface near the other internal electrode end. On the other hand, the micro gap 4 shown in FIG. 2A forms a space over a portion that overlaps with the end of the internal electrode. The micro gap 4 shown in FIG.
Only the overlapping portions of the ends of the internal electrodes form a space. Each of these micro gaps has no difficulty in manufacturing, and can be selected according to the surge.

The insulating ceramic and the conductor need not be limited to the combination of steatite and AgPd as in the present embodiment, but it is preferable to use a combination of materials having similar firing temperatures. When a conductive ceramic such as Nb ₂ O ₅ or TiC is used for the internal electrode, it is more advantageous from the viewpoint of improving durability.

[0019]

As described above, according to the present invention,
A surface-mount type surge absorbing element that is small in size, has excellent characteristics, and is easy to manufacture and surface-mount can be obtained by utilizing a technology with high productivity such as a conventional screen printing technology.

[Brief description of the drawings]

FIG. 1 is a diagram showing a surface mount type surge absorbing element according to the present invention. FIG. 1A is an external perspective view. FIG. 1B is an explanatory diagram showing the arrangement of internal electrodes. FIG. 1C is a cross-sectional view of the internal electrode as viewed from the side.

FIG. 2 is a diagram showing another form of the micro gap in the surface mount type surge absorbing element according to the present invention.

FIG. 3 is a diagram showing the appearance of a conventional surge absorbing element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Surface mount type surge absorption element 2 Insulating ceramics 3 Internal electrode 4 Micro gap 5 External electrode 7 Surge absorption element 8 Conductive film 9 Cap electrode 10 Micro gap 11 Lead wire 12 Glass tube

Claims (3)

[Claims] 1. A surface-mounted surge absorbing element having an internal electrode separating a microgap, wherein the microgap and the internal electrode are included in an insulating ceramic, and a plurality of the internal electrodes are formed in a step-like manner. The surface-mounted surge absorbing element is formed continuously, and the micro gap is formed with a space between one end of one internal electrode and one end of another internal electrode. 2. The surface mount type surge absorbing element according to claim 1, wherein a plurality of said micro gaps are formed in series. 3. The surface mount type surge absorbing element according to claim 1, wherein the surface mount type surge absorbing element is a laminate.