JPH0443584A - Gas-tight structure of surge absorbing element - Google Patents

Abstract

PURPOSE:To set a current density small even to an overcurrent, and decrease effects of a thermal stress by a local heat or the like by forming electrodes of a sealing metal having a similar thermal expansion coefficient to that of a ceramic coating material, engaging the ceramic coating material between the electrodes, and composing a gas-tight structure where the whole circumference is sealed. CONSTITUTION:A main electrode 40 is moulded of sealing metal having a similar expansion coefficient to that of a ceramic coating material 5, and an end part of a cap-like electrode 4 is fixed at a center recess of if to form an integrated electrode. For a sealing material 61, BAg-8 silver braze is used if the ceramic coating material is of ceramic, it is inserted into a step part 60 between both edge parts of the ceramic coating material and the main electrode, mixed gas 7 is enclosed in the main electrodes, and it is heated to a predetermined temperature and sealed.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an airtight structure of a surge absorbing element for protecting various electronic devices, static electricity countermeasures, and lightning protection to avoid various harmful effects caused by surges. It is.

[Prior Art] FIG. 2A is a cross-sectional view showing an airtight structure of a conventional surge absorbing element, and FIG. 2B is a cross-sectional view taken along line EE in FIG. 2A. In the figure, 11 is an insulator molded into a cylindrical shape, and 12 is an insulator 1
1, this conductive thin film 12
A micro-gap 13 with a minute width is cut out to divide it into two pieces, a cap-shaped electrode I4 is fixed to each end of the divided conductive thin film 12, and a lead wire 18 is welded and attached to this electrode 14. This is an airtight structure in which the entire body is covered with a porcelain covering material 15 in an atmosphere of a mixed gas 17, and the mixed gas 17 is sealed inside.

In this configuration, lead glass with good workability is used as the porcelain covering material 15, a Dumet wire suitable as a lead glass-enclosed wire is used as the lead wire 18, and the Dumet wire is enclosed at both ends of the lead glass. A portion 16 is formed.

The hermetic structure of the conventional surge absorption element is constructed as described above. First, when a surge voltage is applied between the lead wires 18 and 18, an electric field is concentrated in the micro gap 13, and a surge is generated due to the electric field. A first stage discharge occurs in the microgap 13 due to the electrons. Next, the electrons emitted by this first-stage discharge collide with the surrounding mixed gas 17 to ionize the mixed gas. Similarly, the phenomenon of ionizing the mixed gas 17 due to the creeping discharge along the circumference of the micro gap 13 rapidly progresses, and eventually the insulation of the mixed gas 17 is destroyed and a second Stage discharge occurs. This second stage discharge is connected to the lead wire 18.1.
As the surge current applied between 8 and 8 increases, glow discharge shifts to arc discharge. In this way, a two-stage discharge mechanism is configured.

[Problems to be Solved by the Invention] In the airtight structure of the conventional surge absorbing element as described above, when this surge absorbing element is connected to a power source with low impedance, the commercial power supply of the electric circuit after the surge discharge ends. Excessive currents occur due to follow-on currents drawn from the ground, lightning strikes, etc. This excessive current increases the current density between the leads 18, 18 and causes the joint 16 of the Dumet wire encapsulated in lead glass to become abnormally heated. As a result, cracks occur in the lead glass due to the difference in thermal expansion coefficients between the Dumet wire and the lead glass, resulting in a fatal drawback in that the airtightness is destroyed.

Additionally, when wiring this surge absorbing element to a board, etc., if the radius of curvature of the lead wire 18 is incorrectly bent, or if excessive impact is applied, the lead glass may be damaged, which is a mechanical strength problem. there were.

This invention was devised to solve these problems, and it fundamentally changes the airtight structure of the conventional Dumet wire sealed with lead glass, and has a thermal expansion coefficient similar to that of the porcelain sheathing material. The electrodes are formed using a sealing metal with a coefficient of expansion, and both edges of the porcelain covering material are fitted between the electrodes to seal them, thereby ensuring the airtightness of the mixed gas sealed between the electrodes. The object of the present invention is to provide an airtight structure for a surge absorbing element that has strong mechanical strength.

c. Means for Solving Problems] The airtight structure of the surge absorbing element according to the present invention has electrodes fixed to both ends of an insulator having a conductive thin film attached to the surface through a micro gap, and a gap between the electrodes. In a surge absorbing element in which a space is sealed with a porcelain covering material and a mixed gas is sealed in the sealed space, the electrode is made of a sealing metal having a coefficient of thermal expansion similar to that of the porcelain covering material. The above-mentioned porcelain covering material is fitted and sealed between the above-mentioned electrodes.

In the airtight structure of the surge absorbing element according to claim 2, when ceramics or hard glass is used as the porcelain coating material, the sealing metal is Kovar (Fe''N1-G).
o Electrodes are formed from a gold alloy, and a porcelain covering material is fitted and sealed between the electrodes.

The hermetic structure of the surge absorbing element according to claim 3 is such that when ceramics or hard glass is used as the porcelain covering material, 42ALLOY (F
The electrodes are made of (e-N i 42% alloy), and a porcelain covering material is fitted and sealed between the electrodes.

In the airtight structure of the surge absorption element according to claim 4, when soft glass is used as the porcelain covering material, an electrode is formed of 426ALLOY (42% Fe-Ni 6% alloy) as the sealing metal, A porcelain covering material is fitted and sealed between the electrodes.

In the airtight structure of the surge absorbing element according to claim 5, when soft glass is used as the porcelain covering material, 52'ALLOY (50% FeNi alloy) is used as the sealing metal.
electrodes are formed, and a porcelain covering material is fitted and sealed between the electrodes.

[Function] In the airtight structure of the surge absorbing element of the present invention, the surge voltage applied between the electrodes first causes a glow discharge along the microgap of the conductive thin film, and then as the current increases, an arc discharge occurs between the electrodes. A two-stage discharge mechanism is constructed in which the surge energy is absorbed. Therefore, when an excessive current is applied between the electrodes due to a lightning strike or a follow-on current, the airtight structure of the present invention forms the electrodes with a sealing metal having a thermal expansion coefficient similar to that of the porcelain covering material. However, since both edges of the porcelain covering material are fitted between the electrodes and the entire circumference is sealed, the current density is small even in the case of excessive current, and therefore the influence of thermal stress due to local heating is small. Since this is avoided, the surge absorption effect is easily and successfully achieved over a long period of time.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

[Embodiment] FIG. 1A is a sectional view showing an embodiment of the present invention, and FIG. 1B is a sectional view taken along line DD in FIG. 1A. 1 is an insulator made by extruding porcelain powder into a cylindrical shape and firing it.
is made of one selected from the group consisting of mullite porcelain, forsterite porcelain, alumina porcelain, and steatite porcelain, and its dielectric constant is extremely large at 6 to 1o.

A conductive thin layer H2 is deposited on the surface of this insulator I. The conductive thin film 2 is made of a kind of compound selected from the group consisting of conductive metal oxides and interstitial nitrides, and is a conductive ceramic thin film with a high melting point and excellent oxidation resistance and corrosion resistance. Compared to conventional two-stage discharge type arresters manufactured using conductive paints and thin films, the stability of the discharge starting voltage against the application of impulse surges and the life characteristics are far superior. ing.

Next, this conductive ceramic thin film 2 is divided into two to a plurality of parts by providing one to a plurality of microgaps 3 having a width of 2.0 .mu.m or less. This microgap 3 is cut out parallel to the circumferential direction using a laser or a diamond tool.

Cap-shaped electrodes 4 made of highly electrically conductive stainless steel or Kovar are fixed to both ends of the divided conductive ceramic thin film 2. With the above steps, a two-stage discharge element body is formed.

Hereinafter, the airtight structure of the surge absorbing element according to the present invention will be explained.

Reference numeral 40 denotes a main electrode, which is molded into the shape shown in the figure using a sealing metal having a thermal expansion coefficient similar to that of the porcelain covering material 5 described below, and the cap-shaped electrode 4 is placed in the central recess of the sealing metal. The ends of each are fixed to form an integral electrode. Furthermore, a stepped portion 60 having a depth corresponding to the thickness of the porcelain covering material 5 is provided on the outer periphery of the main electrode 40 .

61 is a sealing material, and when the above-mentioned porcelain covering material 5 is ceramic, it is B A g -8 (JIS-Z-a261
), or if the porcelain sheathing material 5 is soft glass or hard glass, glass powder is used to connect both edges of the porcelain sheathing material 5 and the main electrode 40 to the stepped portion 6.
Insert into 0. Reference numeral 6 indicates a sealing portion made up of a stepped portion 6o and a sealing material 61.

Note that when sealing the soft or hard glass and the main electrode 4o, it is also possible to heat the glass directly and seal the glass without using the sealing material 6I.

Next, the entire body on which the sealed portion 6 is formed is heated in a heating furnace atmosphere in which a discharge starting voltage is determined from a mixed gas 7 selected from argon gas, neon gas, nitrogen gas, etc. and the gas pressure. The hermetic structure of the surge absorbing element is completed by sealing the mixed gas 7 between the main electrodes 40 and 40 on the two sides to be heated to a specified temperature (780 to 900'C in the case of the silver solder) and sealed. do.

In this embodiment, when ceramic is used as the porcelain covering material 5, the sealed portion of the ceramic that fits with the main electrode 40 is metallized with Mo and Mn on the front side to facilitate soldering. I got used to it.

In the airtight structure of claim 2, when ceramics or hard glass is used as the porcelain sheathing material 5, Kovar (Fe-Ni42 %-Co17% alloy)
The main electrode 40 is formed using the main electrodes 40 and 40, and the above-mentioned porcelain covering material 5 is fitted and sealed between the main electrodes 40 and 40.

The ceramic used in this example is an alumina ceramic with an AItos component ratio of 93%, but if the AI and O8 component ratios are about 86 to 93% and have good metallization properties, AItos can be used. It does not limit the component ratio.

In the airtight structure of claim 3, when alumina ceramics or hard glass having good metallization property and having an A1*Os component ratio of about 86 to 93% as described above is used as the porcelain sheathing material 5, the porcelain sheathing material 5 42ALLOY (F
The main electrode 40 is formed using e-Ni 42% alloy,
The above-mentioned porcelain covering material 5 is fitted and sealed between the main electrodes 40° and 40°.

Incidentally, the porcelain covering material 5 does not have to be the alumina ceramic Al tOS described in the embodiment of claim 2.3 above. For example, when aluminum nitride porcelain AIN, steatite porcelain MgO・5ift, or forsterite porcelain 2MgO-S i Ot is used, a sealing metal having a thermal expansion coefficient similar to that of the aluminum nitride porcelain AIN is used, and the electrode is Of course, the same effect as described above can be obtained by forming 40.

In the airtight structure of claim 4, when soft glass is used as the porcelain sheathing material 5, 426ALL is used as the sealing metal having a thermal expansion coefficient similar to that of the porcelain sheathing material 5.
A main electrode 40 is formed using OY (42% Fe-Ni-6% Cr alloy), and a porcelain covering material 5 is fitted and sealed between the main electrodes 40 and 40.

In the airtight structure of claim 5, when soft glass is used as the porcelain sheathing material 5, 52ALLO is used as the sealing metal having a coefficient of thermal expansion close to that of the porcelain sheathing material 5.
The main electrode 40 is formed using Y (50% Fe-Ni alloy), and the above-mentioned porcelain covering material 5 is fitted and sealed between the main electrodes 40° and 40°.

[Effects of the invention] The body constitutes a mechanism that maintains the surge absorption characteristics, especially the life characteristics and the stability of the discharge starting voltage, which are the characteristics of the conventional two-stage discharge type surge absorption element, and furthermore, it The electrodes are made of a sealing metal with a thermal expansion coefficient similar to the expansion coefficient, and a porcelain covering material is fitted between the electrodes to seal the entire circumference, making it airtight. Even when an excessive current is applied, the current density is small and the influence of thermal stress due to local heating is avoided, so the surge absorption characteristics and discharge starting voltage characteristics are far superior to conventional two-stage discharge arresters etc. The industrial value of an airtight structure that is stable and has particularly excellent longevity characteristics is great.

[Brief explanation of the drawing]

FIG. 1A is a sectional view showing one embodiment of the present invention, FIG. 1B is a sectional view taken along line DD in FIG. 1A, FIG. 2A is a sectional view showing an airtight structure of a conventional surge absorbing element, and FIG. 2B is 2nd Av! :
It is an EE sectional view of J. In the figure, l: insulator 2: conductive thin film 3: microgap 4 cap-shaped electrode 5: porcelain covering material 6
: Sealing part 7 : Mixed gas 8 Lead wire 40 : Main electrode 60 : Step part 61 : Sealing material. Note that the same reference numerals in each figure indicate the same or corresponding parts. Patent applicant Ipex Co., Ltd.

Claims (1)

[Claims] 1. Electrodes are fixed to both ends of an insulator having a conductive thin film attached to the surface through a microgap, the space between the electrodes is sealed with a magnetic covering material, and the inside of the sealed space is In the surge absorbing element, the electrode is formed of a sealing metal having a coefficient of thermal expansion similar to that of the porcelain sheathing material, and the porcelain sheathing material is placed between the electrodes. The airtight structure of the surge absorption element is characterized by fitting and sealing. 2. The porcelain coating material is ceramic or hard glass, and the sealing metal is Kovar (Fe-Ni-Co).
2. The airtight structure of the surge absorbing element according to claim 1, wherein the surge absorbing element is an alloy. 3. The porcelain coating material is ceramic or hard glass, and the sealing metal is 42ALLOY (Fe-Ni
42% alloy). 4. The porcelain covering material is soft glass, and the sealing metal is 426ALLOY (42% Fe-Ni-6% Cr).
2. The airtight structure of the surge absorbing element according to claim 1, wherein the surge absorbing element is an alloy. 5. The hermetic structure of the surge absorbing element according to claim 1, wherein the porcelain covering material is soft glass, and the sealing metal is 52ALLOY (50% Fe-Ni alloy).