JPH05268725A - Surge absorbing element - Google Patents

Abstract

PURPOSE:To form a gap without using complicated laser machining necessary for skill and to manufacture a surge absorbing element simply, efficiently and compactly. CONSTITUTION:A surge absorbing element is constituted of an insulating member 11, a pair of ceramic element bodies 12 and 13 contacted with both surfaces opposed to the insulating member 11 and wrapped with conductive films 12a and 13a, a pair of electrodes 16 and 17 contacted with the outsides of the ceramic element bodies 12 and 13 and welded with lead wires 14 and 15 to the outsides of them, and an insulating pipe body 18 wrapping the insulating member 11 and the ceramic element bodies 12 and 13 and filling with inert gas to adhere to the peripheral surfaces of the electrodes 16 and 17.

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 electronic parts from surges such as transient abnormal voltage and lightning surge that enter electronic equipment. More specifically, it relates to a gap type surge absorbing element in which a pair of electrodes facing each other is hermetically sealed in an insulating tube.

[0002]

2. Description of the Related Art This type of surge absorbing element is connected to a pair of input lines of an electronic component in parallel with the electronic component, and is configured to operate at a voltage higher than the operating voltage of the electronic component. That is, the surge absorbing element is a resistor having a high resistance value at a voltage lower than the discharge starting voltage, but becomes a resistor having a low resistance value of several tens Ω or less when the applied voltage is equal to or higher than the discharge starting voltage. When a surge voltage such as a lightning surge is momentarily applied to an electronic component, the surge absorbing element discharges and absorbs the surge voltage. As a result, the surge voltage is not applied to the electronic component, and the failure or malfunction of the electronic device due to the surge voltage is avoided.

Among the conventional gap type surge absorbers,
As shown in FIG. 4, the micro gap type discharge tube has a cylindrical ceramic body 1 whose outer peripheral surface is coated with a conductive film 1a. Cap electrodes 2 and 3 are attached to both ends of the ceramic body 1. There are several tens on the outer peripheral surface of the central portion of the ceramic body 1 to which the cap electrodes 2 and 3 are attached.
A microgap 1b of μm is formed. Sealing electrodes 6 and 7 having lead wires 4 and 5 welded to the outer surfaces thereof are in contact with the end surfaces of the cap electrodes 2 and 3, respectively. Surge absorbing element 9
Holds the ceramic body 1 with the cap electrodes 2 and 3 and the sealing electrodes 6 and 7 with the lead wires 4 and 5 in contact with each other in the glass tube 8 as shown in FIG. It is made by filling the tube 8 with an inert gas and sealing the glass tube 8 to the electrodes 6 and 7.

[0004]

In the conventional surge absorbing element described above, a microgap is formed on the outer peripheral surface of the ceramic body by trimming the conductive film with a laser beam. Since the setting of the processing conditions of this laser processing apparatus is complicated, there is a problem that it takes time to form the microgap by the laser beam. In addition, since the size of the microgap formed by the laser beam tends to vary, this processing requires a skilled technique,
There is a drawback that the surge absorbing element cannot be manufactured easily. Furthermore, in order to improve the electrical connection between the sealing electrode and the conductive film, it is necessary to cap both ends of the ceramic body with cap electrodes. There has been a problem that the ceramic element body must be lengthened to cover the cap electrode and the thickness of the ceramic element body must be increased for the laser processing.

An object of the present invention is to provide a surge absorbing element which can be simply and efficiently manufactured by forming a gap without using complicated and skillful laser processing. Another object of the present invention is to provide a surge absorbing element that can be manufactured in a short size.

[0006]

In order to achieve the above object, the structure of the present invention will be described with reference to FIGS. 1 and 2.
The surge absorbing element 19 of the present invention includes an insulating member 11 and a pair of ceramic element bodies 12, 13 abutted on opposite surfaces of the insulating member 11 and covered with conductive films 12a, 13a, respectively. And a pair of electrodes 16 and 17 that are in contact with the outer surfaces of the ceramic bodies 12 and 13 and have lead wires 14 and 15 welded to the outer surfaces, the insulating member 11 and the ceramic bodies 12 and 13. And an insulating tube 18 that is filled with an inert gas and is sealed to the outer circumferences of the electrodes 16 and 17.

The insulating member 11 is preferably made of highly insulating ceramic having a volume resistivity of 10 ¹⁴ Ωcm or more, such as alumina, mullite, steatite, forsterite or beryllia. The thickness of the insulating member 11 is determined in accordance with the surge withstand capability, the response voltage, etc., but it is preferable that the thickness of the insulating member 11 is thin in order to more easily cause arc discharge of the surge absorbing element. In addition, it is necessary that both surfaces of the insulating member be parallel to each other.
It is preferable that arc discharge between a and 13a is uniformly generated at the edge of the coating. The ceramic bodies 12 and 13 are not particularly limited as long as they are insulating materials, but may be the same material as the insulating member 11. As the conductive coatings 12a and 13a that are formed on the surfaces of the ceramic bodies 12 and 13 by encapsulating them, metal thin films having excellent conductivity such as titanium, nickel, tin oxide or titanium nitride are preferable. This film is formed by wrapping the entire element bodies 12 and 13 by sputtering, vacuum deposition or the like. The electrodes 16 and 17 are made of insulating tube 1 so that cracks or the like do not enter the tube when the insulating tube 18 is sealed.
Select a material whose thermal expansion coefficient is close to that of No. 8. When the insulating tube is a glass tube made of borosilicate glass, lead glass, or the like, Dumet wire or Invar with which the thermal expansion coefficient of the glass tube matches is preferable.
For the electrodes 16 and 17, the lead wires 14 and 15 are welded to the respective outer surfaces before the insulating tube 18 is sealed. A rare gas such as argon gas or nitrogen gas is enclosed in the insulating tube body 18.

The surge absorbing element of the present invention is manufactured by the following method. First, the one electrode 16 to which the lead wire 14 is welded is inserted into the end portion of the insulating tubular body 18,
The insulative tube 18 is erected vertically so that the other end of the is up. Then, the ceramic body 12 having the conductive coating 12a, the insulating member 11 and the ceramic body 13 having the conductive coating 13a are arranged in this order on the insulating tube 18
Drop it in. Next, the other electrode 17 having the lead wire 15 welded thereon is inserted into the insulating tubular body 18. While the insulating member 11 and the ceramic bodies 12 and 13 are held between the electrodes 16 and 17, the inside of the insulating tube body 18 is evacuated to remove air, and an inert gas is introduced instead. In this state, when the insulating tubular body 18 and the electrodes 16 and 17 are heated by the carbon heater (not shown), the insulating tubular body 18 is heated.
Are sealed to the electrodes 16 and 17.

[0009]

The conductive coatings 12a, 1 are formed on the outer surfaces of the ceramic bodies 12, 13 opposite to the contact surface of the insulating member 11.
Since it is covered with 3a, it can be electrically well connected to the electrodes 16 and 17 without providing a conventional cap electrode.
When a surge voltage is applied to the electrodes 16 and 17, the film 12 a is passed through the gap formed by the insulating member 11.
Arc discharges between and 13a. If the insulating member 11 has a smaller diameter than the ceramic bodies 12 and 13, the film 12a,
Since 13a face each other, arc discharge can be easily performed without delay in discharge.

[0010]

EXAMPLES Next, examples of the present invention will be described together with comparative examples. The invention is not limited to this example. <Example> As shown in FIGS. 1 and 2, the thickness is about 0.05.
mm and a diameter of about 1.0 mm, a pair of ceramic bodies 12 and 13 respectively covered with conductive coatings 12a and 13a made of titanium are formed on opposite surfaces of a disk-shaped insulating member 11 made of alumina. Abut. The films 12a and 13a are formed by sputtering. Each of the ceramic bodies 12 and 13 has a cylindrical shape, a length of about 0.5 mm, a diameter of about 1.3 mm, and is made of mullite. A pair of electrodes 16, 17 having lead wires 14, 15 welded to their respective outer surfaces are brought into contact with the respective outer surfaces of the ceramic bodies 12, 13. The electrodes 16 and 17 have a diameter of about 1.5.
mm dumet wire is sliced into a length of about 2 mm. Insulating member 11 and ceramic bodies 12 and 13 are sandwiched between electrodes 16 and 17 in a glass tube 18 made of lead glass. In this state, insulating tube 18 is filled with argon gas and insulating tube 18 is wrapped around electrodes 16 and 17. Is sealed to. The glass tube 18 has an outer diameter of about 2.6 mm and a length of about 5.0 mm.

<Comparative Example> The aforementioned surge absorbing element 9 shown in FIG. 4 was used as a comparative example. Here, the ceramic body 1 has a length of about 3 mm and a diameter of about 1 mm, and is made of the same mullite as the ceramic bodies 12 and 13 of the embodiment. A conductive film 1a made of the same material and having the same thickness as that of the embodiment is formed on this surface, and a microgap 1b having a width of about 50 μm is formed on the outer peripheral surface of the central portion thereof. Cap electrodes 2 and 3
Is about 2 mm long and about 1.5 mm in diameter,
Sealing electrodes 6 and 7 made of the same material as in the embodiment are brought into contact with each other. The ceramic body 1 with the cap electrodes 2 and 3 and the sealing electrodes 6 and 7 with the lead wires 4 and 5 are housed in a glass tube 8, and the glass tube 8 is filled with argon gas to form the electrodes 6 and 7. Is sealed to. The outer diameter of the glass tube 8 is about 2.6 m.
m, and the length is about 7.0 mm.

An electrostatic life test and a pseudo surge response test were conducted on the surge absorbers of the examples and comparative examples. <Electrostatic life test> Output terminal 21 of the circuit shown in FIG.
A static absorption life test was conducted by connecting the lead wires of the surge absorbing element to # 22 and # 22. In FIG. 3, 23 is a 10 kV DC power source, 24 is a capacitor having an electrostatic capacity of 1000 pF, and 25
Is a 250Ω resistor, and 26 is a charge / discharge changeover switch. The switch 26 is switched to the contact a as shown by the solid line in the figure, and a voltage of 10 kV is applied to the capacitor 24 to charge the capacitor 24. Then, the switch 26 is switched to the contact b as shown by the broken line in the figure to discharge the capacitor 24. Then, static electricity was applied to the surge absorbing element. The above static electricity was repeatedly applied 2000 times to the surge absorbing elements of the examples and comparative examples, and the discharge starting voltage, insulation resistance, and capacitance of each surge absorbing element before and after the test were measured. As a result, both the surge absorbing elements of the example and the comparative example before the test had a discharge starting voltage of 200 V, an insulation resistance value of 10 ¹¹ Ω or more, and a capacitance of 0.5 pF. When measured after the test, the surge absorption elements of Examples and Comparative Examples both had a discharge starting voltage of 200 V, an insulation resistance value of 10 ¹¹ Ω or more, and an electrostatic capacitance of 0.5 pF, and there was a change in each value. There wasn't.

<Pseudo Surge Response Test> (1.2 × 50) μsec−10 kV for the surge absorbing elements of the example and the comparative example.
Was repeatedly applied 100 times, and the operating voltage was measured. The surge absorbing elements of the examples and the comparative examples were designed to have a DC discharge inception voltage of 200V. The surge absorbing element of the comparative example started discharging at an average of 400 V and its standard deviation was 50, whereas the surge absorbing element of the example similarly started discharging at an average of 400 V and its standard deviation was 50. Met. From the above, it was found that the surge absorbing element of the example is not inferior in durability and surge absorbing characteristics to the surge absorbing element of the comparative example.

[0014]

As described above, in the surge absorbing element of the present invention, since the gap is formed without the conventional laser processing, the rate of defective products due to the variation of the gap is low, and the efficiency is simplified. It can be manufactured well and has electrical characteristics equivalent to those of conventional surge absorbing elements. Further, since the conventional cap electrode is not used, the length and the thickness can be reduced, and the mounting space for the surge absorbing element can be further reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a surge absorber according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view thereof.

FIG. 3 is an electrostatic life test circuit of Examples and Comparative Examples.

FIG. 4 is a cross-sectional view of a conventional surge absorber.

[Explanation of symbols]

 11 Insulating member 12,13 Ceramic element body 12a, 13a Conductive film 14,15 Lead wire 16,17 Electrode 18 Insulating tube body 19 Surge absorbing element

Front page continuation (72) Inventor Takaaki Ito 2270 Yokose, Yokose-cho, Chichibu-gun, Saitama Sanryo Materials Co., Ltd.

Claims (6)

[Claims] 1. An insulating member (11), and a pair of ceramic bodies (1) abutted on opposite surfaces of the insulating member (11) and respectively covered with conductive films (12a, 13a). 12, 13), and a pair of electrodes (16, 17) in which lead wires (14, 15) are welded to the outer surfaces of the pair of ceramic element bodies (12, 13), respectively, and abutted on the outer surfaces, An insulating tube body (18) that encloses the insulating member (11) and the ceramic body (12, 13) and is filled with an inert gas and sealed to the outer periphery of the electrode (16, 17). Surge absorber. 2. The insulating member (11) is made of alumina, mullite,
The surge absorbing element according to claim 1, which is steatite, forsterite or beryllia. 3. The surge absorbing element according to claim 1, wherein the conductive film (12a, 13a) is titanium, nickel, tin oxide or titanium nitride. 4. The surge absorbing element according to claim 1, wherein the insulating tube body (18) is a glass tube. 5. The surge absorbing element according to claim 4, wherein the electrodes (16, 17) are Dumet wires or amber. 6. The surge absorbing element according to claim 1, wherein the inert gas is a rare gas or a nitrogen gas.