JP2020181719A - Surge protective element and manufacturing method thereof - Google Patents

Abstract

To provide a surge protective element and a manufacturing method thereof which can suppress the generation of bubbles, obtain high bonding strength and sealing property, and can keep the amount of discharge control gas confined constant.SOLUTION: A surge protective element includes an insulating tube 2 made of glass, and a pair of sealing electrodes 3 arranged so as to seal discharge control gas inside by closing openings at both ends of the insulating tube and separating facing surfaces 3a from each other, and the pair of sealing electrodes are each formed in a trapezoidal cross-section whose inner end face which is a facing surface has a larger area than an outer end face 3b, and the insulating tube is joined to the entire outer peripheral surface 3d of the sealing electrode.SELECTED DRAWING: Figure 1

Description

The present invention relates to a surge protective element used to protect various devices from surges generated by lightning strikes and the like and to prevent accidents, and a method for manufacturing the same.

Abnormal voltages such as lightning surges and static electricity in parts where electronic devices for communication devices such as telephones, facsimiles, and modems connect to communication lines, power lines, antennas or CRTs, image display drive circuits such as LCD TVs and plasma TVs, etc. A surge protective element is connected to a portion susceptible to electric shock due to (surge voltage) in order to prevent thermal damage or ignition of an electronic device or a printed substrate on which the device is mounted due to an abnormal voltage.

Conventionally, for example, Patent Document 1 describes a microgap type surge protective element in which a conductively coated member is sandwiched between opposing metal members in a glass tube. This microgap type surge protection element has a structure in which a slit (gap) of several μm to several tens of μm is provided in the center of the conductively coated member so that current does not flow between opposing metal members below a specified voltage. .. When the voltage exceeds the set voltage, an arc discharge is generated between the slits, and a current flows between the opposing metal members.

This surge protective element is a device that utilizes the shape-changing ability of a glass tube due to glass softening and the bonding characteristics with a metal, and is used in a wide range of fields because of its excellent mass productivity.
Further, Patent Document 2 includes surge protection provided with a cylindrical body made of ceramics, glass, or the like and a pair of electrodes facing each other with a space of a predetermined distance interposed therebetween by interposing an electrically insulating ring-shaped spacer. The elements are described. Like such a surge protective element, a surge protective element in which the counter electrode is sealed with a ceramic cylinder such as alumina is called an arrester.

Special Publication No. 63-57918 Japanese Unexamined Patent Publication No. 63-318805

The following problems remain in the above-mentioned conventional technique.
That is, the glass-coated microgap type surge protection element has good bondability between glass and a metal member, and has excellent reliability such as gas sealing property and air and moisture blocking property. However, since the width of the slit forming the microgap is narrow and the thickness of the conductive coating forming the periphery of the microgap is as thin as several tens of μm, the surge resistance is limited to about 1500 A. Further, a film forming process of the conductive coating and a laser processing process for forming a microgap are required, which has a disadvantage that the process becomes complicated, the production takes time, and the cost increases.

On the other hand, the arrester type surge protective element has a withstand capacity of 2000 A in a product having a diameter of 5 mm and a withstand capacity of 5000 A in a product having a diameter of 8 mm, and has a surge tolerance characteristic higher than that of a glass-coated microgap type surge protective element. There is. Such arrester-type surge protective elements are used for large household appliances, solar power generation, water and sewage, and other infrastructure equipment that require high reliability. The arrester type surge protection element requires an expensive bonding agent (silver brazing material) or an alumina cylindrical member, which is more expensive than the glass cylindrical member, in joining the metal and the ceramics. Furthermore, very high technology is required for joining ceramics and metal parts, and an electrode auxiliary material (graphite, etc.) is provided inside the electrode, and a dielectric material is used on the surface of the counter electrode for the purpose of protecting the electrode and promoting discharge. It is necessary to give it, which complicates the manufacturing process. Therefore, the manufacturing cost tends to increase significantly as compared with the glass-coated microgap type surge protective element.

Therefore, it is required to use a glass cylindrical member in terms of cost, but as shown in FIG. 2, a state in which a pair of sealing electrodes 103 are inserted in a glass insulating tube 102 with a gap between them. Then, when the insulating tube 102 and the sealing electrode 103 are joined by heating, the discharge control gas remaining between the outer peripheral surface of the sealing electrode 103 and the insulating tube 102 thermally expands to form bubbles B. You may be trapped. In the portion of the bubbles B remaining in this way, the sealing electrode 103 and the insulating tube 102 are not bonded, and there is a problem that the bonding strength and the sealing property are lowered. Further, the discharge control gas may flow to the outer peripheral surface side of the sealing electrode 103, the discharge control gas between the pair of sealing electrodes 103 becomes thin, and the discharge start voltage Vs may decrease.

The present invention has been made in view of the above-mentioned problems, and is a surge protective element capable of suppressing the generation of bubbles, obtaining high bonding strength and sealing property, and keeping the amount of discharge control gas to be confined constant. And its manufacturing method.

The present invention has adopted the following configuration in order to solve the above problems. That is, the surge protection element according to the first invention closes the glass insulating tube and the openings at both ends of the insulating tube to seal the discharge control gas inside and separate the facing surfaces from each other. The insulating tube is provided with a pair of sealing electrodes arranged so as to face each other, and the pair of sealing electrodes are formed in a trapezoidal cross section in which the inner end face, which is the facing surface, has a larger area than the outer end face. , It is characterized in that it is bonded to the entire outer peripheral surface of the sealing electrode.

In this surge protective element, a pair of sealing electrodes are formed in a trapezoidal cross-section whose inner end face, which is a facing surface, has a larger area than the outer end face, and an insulating tube is joined to the entire outer peripheral surface of the sealing electrode. Therefore, it is possible to suppress the generation of air bubbles between the outer peripheral surface of the sealing electrode and the insulating tube as compared with the columnar sealing electrode at the time of joining at the time of manufacturing, and the bonding strength and sealing are high. Sex is obtained. Further, the bonding strength and sealing property are improved by increasing the bonding area between the outer peripheral surface of the sealing electrode and the insulating tube as compared with the columnar sealing electrode. Further, since the pair of sealing electrodes has a tapered shape in which the outer diameter gradually decreases toward the outer end face, the movement of the pair of sealing electrodes in the direction in which they are separated from each other is restricted by the anchor effect on the insulating tube. It is possible to prevent the gap between the pair of sealing electrodes from expanding.

The method for manufacturing a surge protection element according to the second invention is a method for manufacturing a surge protection element according to the first invention, in which a pair of sealing electrodes are insulated from each other with their facing surfaces separated from each other. After the sealing electrode insertion step of inserting into the sex tube and the sealing electrode insertion step, the insulating tube is heated and softened to join the insulating tube and the pair of sealing electrodes, and the pair of sealing. It has an electrode joining step in which both ends of the insulating tube are closed with electrodes to seal the discharge control gas inside, and the pair of sealing electrodes are provided with the inner end faces, which are facing surfaces, on the outer side. It is characterized in that it is formed into a trapezoidal cross section having a larger area than the end face.

That is, in this method of manufacturing a surge protective element, since the pair of sealing electrodes are formed in a trapezoidal cross-section in which the inner end face, which is the facing surface, has a larger area than the outer end face, the bonding is from the facing surface side. By advancing to the outer end surface, it is difficult for the discharge control gas to remain on the joint surface between the insulating tube and the sealing electrode, and the generation of bubbles can be suppressed.
In the electrode joining step, the bonding starts from the contact portion between the insulating tube and the outer edge of the facing surface of the sealing electrode, and the bonding proceeds toward the outer end surface of the sealing electrode, and the insulating tube and the sealing electrode are joined. By pushing the discharge control gas between the outer peripheral surface and the outer end surface, it becomes difficult for the discharge control gas to remain on the joint surface between the insulating tube and the sealing electrode. Further, since the insulating tube is first joined from the contact portion between the outer edge of the facing surface of the sealing electrode, the amount of the discharge control gas confined in the gap between the pair of sealing electrodes can be kept constant.

In the second invention, the surge protective element according to the third invention makes the angle between the inner peripheral surface of the insulating tube and the outer peripheral surface of the sealing electrode 2 to 30 ° in the sealing electrode insertion step. It is characterized by setting.
That is, in this method of manufacturing a surge protection element, the angle between the inner peripheral surface of the insulating tube and the outer peripheral surface of the sealing electrode is set to 2 to 30 ° in the sealing electrode insertion step, so that glass is used in the electrode joining step. When the insulating tube of the tube softens, the bonding between the insulating tube and the outer peripheral surface of the sealing electrode can proceed smoothly from the facing surface side toward the outer end surface, and the discharge control gas can be pushed out satisfactorily. it can.
If the angle is less than 2 °, the extrusion effect of the discharge control gas may be insufficient, and if it exceeds 30 °, the insulating tube and the outer peripheral surface of the sealing electrode are formed at the outer end. The gap between the two may become too large, resulting in insufficient bonding at the outer end face.

According to the present invention, the following effects are obtained.
That is, according to the surge protective element and the manufacturing method thereof according to the present invention, the pair of sealing electrodes are formed in a trapezoidal cross section in which the inner end face, which is a facing surface, has a larger area than the outer end face, and is an insulating tube. However, since it is bonded to the entire outer peripheral surface of the sealing electrode, the bonding strength and sealing property are improved by increasing the bonding area between the outer peripheral surface of the sealing electrode and the insulating tube as compared with the columnar sealing electrode. improves. Further, since the bonding proceeds from the facing surface side to the outer end surface, the discharge control gas is unlikely to remain on the bonding surface between the insulating tube and the sealing electrode, and the generation of bubbles can be suppressed.
Therefore, the surge protection element according to the present invention is suitable for a power supply circuit section or a communication circuit section of an electric device that requires a compact, inexpensive, and highly reliable product. In particular, the surge protection element of the present invention is suitable for a wide range of applications including measures against static electricity for mounting on a substrate.

It is sectional drawing in the axial direction which shows the surge protection element before the electrode joining process (a) and after the electrode joining process (b) in one Embodiment of the surge protection element and its manufacturing method which concerns on this invention. It is sectional drawing in the axial direction which shows the surge protection element in the prior art example of the surge protection element which concerns on this invention and the manufacturing method thereof.

Hereinafter, an embodiment of a surge protective element and a method for manufacturing the same according to the present invention will be described with reference to FIG. In the drawings used in the following description, the scale is appropriately changed in order to make each member recognizable or easily recognizable.

As shown in FIG. 1, the surge protective element 1 of the present embodiment closes the glass insulating tube 2 and the openings at both ends of the insulating tube 2 to seal the discharge control gas inside and each other. It includes a pair of sealing electrodes 3 arranged so as to face each other with the facing surfaces 3a separated from each other.
In the pair of sealing electrodes 3, the inner end surface, which is the facing surface 3a, is formed in a trapezoidal cross section having a larger area than the outer end surface 3b, and the insulating tube 2 covers the entire outer peripheral surface 3d of the sealing electrode 3. It is joined.

The insulating tube 2 is, for example, cylindrical and is made of a glass tube such as lead glass.
The discharge control gas sealed in the insulating tube 2 is an inert gas or the like, for example, He, Ar, Ne, Xe, Kr, SF ₆ , CO ₂ , C ₃ F ₈ , C ₂ F ₆ , CF ₄ , H ₂ , air, etc. and a mixed gas thereof are adopted.

The sealing electrode 3 is formed of, for example, a Jumet wire, 42 alloy (Fe: 58 wt%, Ni: 42 wt%), Cu, or the like in a truncated conical shape.
A base end portion of a lead wire 5 projecting outward is embedded in each sealing electrode 3.
Further, a cuprous oxide film is formed on the outer peripheral surface 3d of the sealing electrode 3 in order to improve the wettability with glass.
As the sealing electrode 3 and the lead wire 5, so-called slag leads formed of the Jumet wire may be adopted.

In the method for manufacturing the surge protection element 1 of the present embodiment, as shown in FIG. 1A, a pair of sealing electrodes 3 are placed in a glass insulating tube 2 with the facing surfaces 3a separated from each other. After the sealing electrode insertion step and the sealing electrode insertion step, the insulating tube 2 is heated and softened to form the insulating tube 2 and the pair of sealing electrodes 3. It has an electrode joining step of joining and sealing the openings at both ends of the insulating tube 2 with a pair of sealing electrodes 3 to seal the discharge control gas inside.

The pair of sealing electrodes 3 are formed in a trapezoidal cross section in which the inner end surface, which is the facing surface 3a, has a larger area than the outer end surface 3b.
Further, in the sealing electrode insertion step, the angle θ between the inner peripheral surface of the insulating tube 2 and the outer peripheral surface 3d of the sealing electrode 3 is set to 2 to 30 °.

As described above, in the surge protection element 1 of the present embodiment, the pair of sealing electrodes 3 are formed in a trapezoidal cross-section in which the inner end surface, which is the facing surface 3a, has a larger area than the outer end surface 3b, and the insulating tube 2 However, since it is bonded to the entire outer peripheral surface 3d of the sealing electrode 3, the bonding area between the outer peripheral surface 3d of the sealing electrode 3 and the insulating tube 2 is increased as compared with the columnar sealing electrode 3. Strength and sealability are improved. Further, since the pair of sealing electrodes 3 have a tapered shape in which the outer diameter gradually decreases toward the outer end surface 3b, the pair of sealing electrodes 3 move in a direction away from each other due to the anchor effect on the insulating tube 2. Is limited, and it is possible to prevent the gap between the pair of sealing electrodes 3 from expanding.

Further, in the method of manufacturing the surge protection element 1 of the present embodiment, the pair of sealing electrodes 3 are formed in a trapezoidal cross section having an inner end surface having a facing surface 3a having a larger area than the outer end surface 3b. Since the bonding proceeds from the facing surface 3a side to the outer end surface 3b, it is difficult for the discharge control gas to remain on the bonding surface between the insulating tube 2 and the sealing electrode 3, and the generation of bubbles can be suppressed. ..

That is, in the electrode bonding step, the bonding starts from the contact portion between the insulating tube 2 and the outer edge 3c of the facing surface of the sealing electrode 3, and the bonding proceeds toward the outer end surface 3b of the sealing electrode 3 and is insulated. By pushing the discharge control gas between the sex tube 2 and the outer peripheral surface 3d of the sealing electrode 3 toward the outer end surface 3b (in the direction of the arrow in the figure), the bonding surface between the insulating tube 2 and the sealing electrode 3 It becomes difficult for the discharge control gas to remain. Further, since the insulating tube 2 and the sealing electrode 3 are first joined from the contact portion with the outer edge 3c of the facing surface, the amount of the discharge control gas confined in the gap between the pair of sealing electrodes 3 can be kept constant.

Further, since the angle θ between the inner peripheral surface of the insulating tube 2 and the outer peripheral surface 3d of the sealing electrode 3 is set to 2 to 30 ° in the sealing electrode insertion step, the insulating tube of the glass tube is set in the electrode joining step. When 2 is softened, the bonding between the insulating tube 2 and the outer peripheral surface 3d of the sealing electrode 3 can proceed smoothly from the facing surface 3a side toward the outer end surface 3b, and the discharge control gas can be pushed out satisfactorily. Can be done.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

1 ... Surge protective element, 2 ... Insulating tube, 3 ... Sealing electrode, 3a ... Facing surface (of sealing electrode), 3b ... Outer end surface (of sealing electrode), 3d ... Outer circumference (of sealing electrode) surface

Claims (3)

Insulated glass tube and
It is provided with a pair of sealing electrodes which are arranged so as to seal the discharge control gas inside by closing the openings at both ends of the insulating tube and to separate the facing surfaces from each other.
The pair of sealing electrodes are formed in a trapezoidal cross section in which the inner end face, which is the facing surface, has a larger area than the outer end face.
A surge protective element characterized in that the insulating tube is joined to the entire outer peripheral surface of the sealing electrode. The method for manufacturing the surge protective element according to claim 1.
A sealing electrode insertion step of inserting a pair of sealing electrodes into a glass insulating tube with the facing surfaces separated from each other.
After the sealing electrode insertion step, the insulating tube is heated and softened to join the insulating tube and the pair of sealing electrodes, and the pair of sealing electrodes close both ends of the insulating tube. It has an electrode joining process that seals the discharge control gas inside.
A method for manufacturing a surge protective element, characterized in that the pair of sealing electrodes are formed in a trapezoidal cross-section in which the inner end face, which is the facing surface, has a larger area than the outer end face. In the method for manufacturing a surge protective element according to claim 2,
A method for manufacturing a surge protective element, characterized in that the angle between the inner peripheral surface of the insulating tube and the outer peripheral surface of the sealing electrode is set to 2 to 30 ° in the sealing electrode insertion step.

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