JP2000348846A - Chip type surge absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain long life and high reliability by installing a relay electrode for relaying arc discharge separated from a discharge electrode and terminal electrodes on other surface of an insulating substrate within a discharge chamber. SOLUTION: When a surge having long duration time enters a chip type surge absorber 10, the temperature in a discharge chamber 13 becomes high by arc discharge between terminal electrodes 12, 12. By installing a relay electrode 17 in the position separated from a discharge electrode 15 and the terminal electrodes 12, 12, during arc discharge, part of discharge is passed through the relay electrode 17, and arc discharge is conducted between the relay electrode 17 and the terminal electrodes 12, 12. The amount of discharge between the discharge electrodes 12, 12 is decreased, and heat load to the discharge electrodes 12, 12 is remarkably suppressed. As a result, even if repeated surge is applied, damage of a discharge gap 14 is reduced, and the life of the chip type surge absorber 10 is lengthened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip-type surge absorber for protecting an electronic circuit or a communication device from a surge of lightning or the like, and more particularly, to a surge absorber on an insulating substrate in a discharge chamber facing a discharge gap. The present invention relates to a chip type surge absorber provided with a relay electrode for further protecting a discharge gap.

[0002]

2. Description of the Related Art Various types of surge absorbers have been developed and used effectively for the purpose of protecting electronic circuits and communication devices from surges and noise acting on circuits from inside and outside of circuits. Among them, the microgap type surge absorber of FIG. 4 is widely used because of its good surge response and excellent life characteristics.

[0003] The micro gap type surge absorber is
As shown in FIG. 4, a cap electrode 43 provided with a slag lead 45 is put on both ends of an absorber element having a conductive film 42 having a micro gap 42A formed on the surface of a cylindrical insulator 41, and sealed with a glass tube 46. It is stopped.

The micro gap type surge absorber is
It is provided in parallel with a circuit or a device to be protected and supplies a surge when a surge occurs to protect the circuit or the device, or is provided in a ground circuit to protect the circuit and the like by flowing a surge in the same manner.

The principle of operation of the surge absorber will be described. When the circuit operates in a normal state, no current flows through the surge absorber because the micro gap 42A exists. However, when a surge such as an induced lightning enters the circuit, a voltage corresponding to the surge is applied to both ends of the micro gap. If the surge voltage is equal to or higher than the discharge starting voltage of the surge absorber, insulation between the micro gaps is broken, and glow discharge occurs between the micro gaps. Furthermore, if the surge continues,
The discharge gas rises in temperature and ionizes, causing a transition from glow discharge to arc discharge, and discharge between the cap electrodes, allowing a large amount of surge to flow. As a result, no surge acts on the circuits and devices to be protected, and these circuits and devices are protected from damage.

The surge absorber is not destroyed by one discharge, but can be used about 1,000 times depending on conditions. This point is significantly different from a fuse that is destroyed by one use and needs to be installed again.

However, the microgap type surge absorber must be connected to an external circuit via a lead wire due to its structure, so that it cannot be surface-mounted.
In addition, since it is necessary to seal a cylindrical insulator inside the glass tube, miniaturization is difficult. Therefore, it has not been possible to meet the demands of industrial technology for downsizing and increasing the density of electronic circuits.

Therefore, a chip-type surge absorber shown in FIG. 3 has been proposed as a surge absorber that solves the above-mentioned problems while maintaining the performance of the conventional micro-gap surge absorber.

A chip type surge absorber 30 shown in FIG. 3 has an insulating base 31 having a penetrated cavity, and a pair of terminal electrodes 32 arranged at both ends of the insulating base so as to close the cavity. A discharge chamber 3 which is a cavity closed by the insulating base and the terminal electrode and in which a discharge gas is sealed.
3 and a pair of discharge electrodes 35 arranged with a discharge gap 34 on an insulating substrate in the discharge chamber, and the terminal electrodes and the discharge electrodes are electrically connected.

The chip type surge absorber can be surface-mounted by electrically connecting a terminal electrode and an external circuit with solder. Also, since no glass tube or cap electrode is required for encapsulation, miniaturization is possible. Furthermore, since the basic configuration and operating principle are not different from those of the micro-gap surge absorber, the performance of the surge absorber is comparable to that of the micro-gap surge absorber.

[0011]

In the chip type surge absorber, a surge enters, and if the surge continues for a long time, the glow discharge shifts to an arc discharge between the terminal electrodes. However, when transitioning to arc discharge, the chip-type surge absorber has a low internal temperature of several 10
Increase to 00 ° C. Since the discharge electrode is made of ceramic or metal having a high melting point, it is not damaged by one or two discharges. However, in a circuit in which the surge is long and easy to continue or a circuit in which the surge frequently occurs, the heat of the repetitive discharge damages the conductive film forming the discharge electrode, and the interval between the discharge gaps increases. Since the discharge start voltage depends on the interval between the discharge gaps, the discharge start voltage increases when the distance between the discharge gaps increases, and an unexpected high voltage is applied to the electronic circuit or the communication device, causing a breakdown.

[0012]

Therefore, the present invention has been studied to solve such problems and to provide a chip-type surge absorber having a long life and high reliability. Was reached.

According to a first aspect of the present invention, there is provided a rectangular parallelepiped insulating substrate (11) having a cavity penetrated therein, and the penetrated cavity is closed at both ends of the insulating substrate. Terminal electrodes (12) arranged as follows
A discharge chamber (13), which is a cavity closed by the insulating substrate and the terminal electrode and in which a discharge gas is filled, and a discharge gap (14) provided on one surface of the insulating substrate in the discharge chamber. A pair of discharge electrodes (15) arranged, and
In a chip-type surge absorber in which a discharge electrode and a terminal electrode are electrically connected, a relay for relaying an arc discharge separated from the discharge electrode and the terminal electrode to another surface of the insulating substrate in the discharge chamber. A chip-type surge absorber provided with an electrode (17).

As described above, when a surge having a long duration enters the chip-type surge absorber, the discharge chamber becomes hot due to arc discharge between the terminal electrodes. However, when the relay electrode is formed at a position separated from the discharge electrode and the terminal electrode as in the present invention, part of the discharge passes through the relay electrode during arc discharge, and arc discharge occurs between the relay electrode and the terminal electrode. Will be done. Therefore, the amount of discharge between the discharge electrodes is reduced, and the heat load on the discharge electrodes is greatly suppressed. As a result, damage to the discharge gap due to repeated application of the surge is reduced, and the life of the surge absorber is prolonged.

A second aspect of the present invention is to solve the above problem.
The invention according to claim 1, wherein the inner end surface of the insulating substrate in the discharge chamber is cut away toward the inner surface between the end of the relay electrode and the terminal electrode, and the discharge space is enlarged. It is characterized by being. In the invention of claim 2, the reason why the insulating substrate between the end portion of the free electrode on the inner end surface and the terminal electrode is cut out toward the inner surface is that the discharge space is enlarged so that the relay electrode and the terminal electrode are cut off. This is because it is possible to facilitate the arc discharge during the heat treatment and to prevent the metal vapor evaporated by the arc discharge from being deposited on the end face of the insulating base and short-circuiting the surge absorber itself.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The chip type surge absorber of the present invention will be described below in more detail by describing its structure.

In the present invention, the insulating substrate 11 is exposed to a high temperature when a surge enters as described above, and therefore is required to have both electrical insulation and heat resistance. Therefore, ceramics having excellent heat resistance can be suitably used as the insulating substrate, and among them, alumina and mullite are optimally determined by comprehensively judging from insulation, heat resistance, strength, price and the like. is there.

The insulating substrate 11 has a rectangular parallelepiped shape and has a hollow penetrating therein. This substrate can be integrally formed by hollowing out an insulating material. However, since it is difficult to form a discharge gap, a relay electrode, and the like by this method, two plate-like bodies each having a groove formed on one or both of them are laminated and bonded.

The terminal electrode 12 is formed by covering a metal cap on the end face of the insulating substrate and heat-welding the cap. Metal caps are Ag, Ag / Pd, A
It is manufactured by processing a conductive paste mainly containing a noble metal such as g / Pt or Cu. By forming the terminal electrode in this manner, the cavity in the insulating base is closed. However, since the discharge gas needs to be sealed inside the cavity, the formation of the terminal electrode is performed in an atmosphere of the discharge gas. After filling the discharge gas, this cavity
The discharge chamber 13 is formed.

Since the discharge electrode is so thin that it is difficult to establish conduction with the terminal electrode, it is necessary to form the conduction auxiliary electrode 20 at the end of the insulating base as shown in FIG. Is also possible.

Since the discharge electrode 15 requires high heat resistance, it is made of conductive ceramic or metal. Specifically, RuO ₂ , Ti, TiO, TiN, Ta, W, Si
C, SnO ₂ , BaAl, Nb, Si, C, Au, A
g, Pt, Pd, La or a mixture of two or more thereof is formed by a sputtering method, an evaporation method, an ion plating method, a printing method, a printing method, or the like. Note that the film thickness is 0.
It is about 1 to 20 μm.

The discharge gap 14 is formed by forming a discharge electrode integrally and then cutting it by laser or etching, or is formed simultaneously with the conductive film by a screen mask method or the like. The discharge gap does not need to be one, and a plurality of discharge gaps can be provided. When a plurality of discharge gaps are provided, the firing voltage is determined according to the total gap width. Also, the minimum distance between the discharge electrode and the relay electrode needs to be larger than the total gap width of the discharge gap. If this interval is smaller than the total width of the discharge gap, the first discharge is started during this interval.

As the discharge gas, any gas that can be ionized at a high temperature, including air, can be used. However, considering the stability of the gas at a high temperature and the discharge starting voltage, He, A
_{r, Ne, Xe, SF 6} , CO 2, H 2, C 2 F 6, C 3 F 8, CF
_4, it is preferable to use one or a mixture of two or more of such N _2.

The material of the relay electrode 17, which is a technical feature of the present invention, is the same as that of the discharge electrode. The relay electrode is
For that purpose, it can be formed not only at the bottom of the groove but also at the side. In addition, the shape can be freely set as long as the distance between the discharge electrode and the terminal electrode is not too small. For the formation of the relay electrode, a method similar to the formation of the discharge electrode, such as a printing method or a sputtering method, can be used.

According to the second aspect of the present invention, the discharge space is enlarged by notching the insulating substrate between the end of the relay electrode and the terminal electrode toward the inner surface. The cutout of the insulating substrate is performed by laser or dicing.

[0026]

Embodiment 1 Hereinafter, a chip type surge absorber according to claim 1 will be described with reference to FIG. The present invention is not limited to the present embodiment unless it is contrary to the gist. In this example, alumina was used for the insulating substrate, Cu was used for the terminal electrode, and RuO ₂ was used for the discharge electrode and the relay electrode.

A discharge electrode 15 was deposited on the insulating substrate by a printing method, and a gap having a width of 20 μm was formed in the discharge electrode by using a laser to form a discharge gap 14, thereby producing a discharge substrate 11a. The dimensions of the discharge substrate 11a are 3.2 mm x 1.6 mm
× 0.5 mm, discharge electrode length 1.6 mm, width 0.5
mm and a thickness of 5 μm.

A width of 0.5 mm for securing a discharge chamber,
A groove 21 having a depth of 0.25 mm was formed in the insulating substrate. Next, a relay electrode having a width of 0.48 mm, a length of 2.2 mm, and a thickness of 5 μm was formed on the bottom of the groove by a printing method, to produce a cover substrate 11b. The size of the cover substrate is 3.2
mm × 1.6 mm × 0.5 mm.

The discharge substrate 11a and the cover substrate 11b were bonded to each other with the glass paste 22, and then heated to produce the insulating substrate 11.

After caps made of metal were attached to both end surfaces of the insulating substrate, they were baked to form terminal electrodes 12. In this case, as shown in FIG. 1D, in order to ensure conduction between the discharge electrode 14 and the terminal electrode 12, the terminal electrode can be attached after the auxiliary electrode 20 is formed.

After the terminal electrodes are attached, firing is performed for 76 hours.
The process was performed in an Ar gas flow of 0 Toor, and the discharge gas was sealed simultaneously with the formation of the terminal electrodes.

[0032]

Embodiment 2 Next, a chip type surge absorber according to a second embodiment will be described in the same manner. The method of manufacturing the chip-type surge absorber of the second aspect is basically the same as the method of manufacturing the chip-type surge absorber of the first aspect. Therefore, only the different points will be described here.

According to a second aspect of the present invention, the discharge space is enlarged by notching the inner end face of the insulating base between the end of the relay electrode and the terminal electrode. Specifically, in Example 1, after forming the relay electrode, the groove is deepened from the end of the relay electrode toward the end of the groove by the laser (see FIG. 2). In the present example, the depth of the groove 21 was increased by 0.1 mm at the end of the insulating substrate. The auxiliary electrode 20
Is formed, the auxiliary electrode may be cut out.

The groove is desirably deeper toward the end of the insulating substrate. However, if the discharge space is enlarged, even if the end is shallow, there is no practical problem. The insulating substrate may be cut off before the relay electrode is formed.

[0035]

Comparative Example 1 A chip-type surge absorber similar to the conventional product was manufactured in the same manner as in Example 1 except that no relay electrode was formed on the cover substrate.

[Experimental Example] The following test was conducted to confirm the life characteristics of the chip-type surge absorbers manufactured in Examples 1 and 2 and Comparative Example 1. The width of the discharge gap of the test chip type surge absorber was 20 μm, the initial discharge start voltage was 300 V, the discharge gas was Ar, and the gas filling pressure was 760 Toor.

After charging a 1500 pF capacitor at a voltage of 10 KV, it was released and applied to a surge absorber. The number of times of application was 1500 times, and the discharge starting voltage was measured every 500 times during the application. The number of test samples was seven in each of the examples and comparative examples, and the measured values of the seven samples were averaged.
Table 1 shows the measurement results.

As shown in Table 1, in the conventional chip-type surge absorber of the comparative example, the discharge starting voltage is increased by applying a surge 500 times. Then, 1000 times, Claim 2
In the second embodiment of the invention, the discharge starting voltage does not increase even after the surge is applied 1500 times.

[Table 1]

[0039]

The chip type surge absorber according to the present invention has the following features.
Since the relay electrode is provided on the opposite side of the discharge gap, part of the discharge flows to the relay electrode at the time of arc discharge, arc discharge is performed between the relay electrode and the terminal electrode, the heat load on the discharge electrode is reduced, Thermal damage of the discharge gap was reduced, and the life of the chip type surge absorber was extended. According to the second aspect of the present invention, since the discharge space is expanded between the relay electrode and the terminal electrode, arc discharge is facilitated, the life of the surge absorber is extended, and the metal vapor scattered by the arc discharge is reduced. Short-circuiting of the surge absorber itself due to vapor deposition on the end surface of the insulating substrate can be prevented.

[Brief description of the drawings]

FIG. 1 illustrates a manufacturing process according to the first aspect of the present invention. (1) The discharge substrate 11a is illustrated. (2) The cover substrate 11b is illustrated. (3) FIG. 3 is a diagram in which a discharge substrate 11a and a cover substrate 11b are joined. (4) It is a longitudinal sectional view of the invention of claim 1.

FIG. 2 is a longitudinal sectional view of the invention according to claim 2;

FIG. 3 is a conventional chip-type surge absorber. (A) It is a perspective view of the conventional chip type surge absorber. (B) It is AA sectional drawing of FIG.3 (a).

FIG. 4 is a longitudinal sectional view of a micro gap type surge absorber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Chip type surge absorber 11 Insulating base 11a Discharge substrate 11b Cover substrate 12 Terminal electrode 13 Discharge chamber 14 Discharge gap 15 Discharge electrode 17 Relay electrode 20 Auxiliary electrode 21 Groove 22 Glass paste 23 Notch

Continued on the front page (72) Inventor Yoshiyuki Tanaka 2270 Yokoze, Yokoze-cho, Chichibu-gun, Saitama Prefecture Inside the Ceramics Factory of Mitsubishi Materials Corporation (72) Inventor Koichiro Harada 2270-Yokoze, Yoji, Yokoze-cho, Chichibu-gun, Saitama Mitsubishi Materials (72) Inventor Yasuhiro Shato 2270, Yokoze, Yokoze-cho, Chichibu-gun, Saitama Prefecture Mitsubishi Materials Corporation Ceramics Company (72) Inventor Hitoshi Inaba 2270, Yokoze, Yokoze-cho, Chichibu-gun, Saitama Mitsubishi Materials Inside the ceramics factory

Claims (3)

[Claims] 1. A rectangular parallelepiped insulating substrate (11) having a cavity penetrated therein, and a pair of terminal electrodes (12) arranged at both ends of the insulating substrate so as to close the penetrated cavity. ), A discharge chamber (13) which is a cavity closed by the insulating base and the terminal electrode and in which a discharge gas is sealed.
A discharge gap (1) is formed on one surface of the insulating substrate in the discharge chamber.
4) A chip-type surge absorber having a pair of discharge electrodes (15) arranged and provided with electrical connection between the discharge electrodes and the terminal electrodes. A chip type surge absorber characterized in that a relay electrode (17) for relaying an arc discharge separated from the discharge electrode and the terminal electrode is provided on the other upper surface. 2. The chip-type surge absorber according to claim 1, wherein an inner end surface of the insulating base is cut out toward an inner surface between an end of the relay electrode and the terminal electrode. . 3. The chip type surge absorber according to claim 1, wherein said discharge gap has a plurality of discharge gaps.