JP4265321B2 - surge absorber - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surge absorber used to protect various devices from surges and prevent accidents.
[0002]
[Prior art]
Abnormal current (surge current) and abnormal voltage (surge voltage) such as lightning surge, static electricity, etc., such as the part where electronic devices for communication equipment such as telephones, facsimiles, modems, etc. are connected to communication lines, power lines, antennas or CRT drive circuits. The surge absorber is connected to the portion that is easily subjected to electric shock due to the electrical shock in order to prevent the electronic device and the printed circuit board on which the device is mounted from being damaged due to thermal damage or fire.
[0003]
Conventionally, for example, a surge absorber using a surge absorbing element having a micro gap has been proposed. In this surge absorber, a so-called microgap is formed on the peripheral surface of a cylindrical ceramic member coated with a conductive film, and a surge absorbing element having a pair of cap electrodes at both ends of the ceramic member is placed in a glass tube together with a sealing gas. It is a discharge type surge absorber in which sealed electrodes having lead wires at both ends of a cylindrical glass tube are sealed by high-temperature heating (see, for example, Patent Document 1).
[0004]
In recent years, with the miniaturization of equipment, surface-mounting is also progressing in such a discharge type surge absorber. As an example applicable to the surge absorber, there is a surface mount type (Melph type) that has no lead wire on the sealing electrode, and when mounting, the sealing electrode and the substrate side are connected and fixed by soldering. is there.
[0005]
[Patent Document 1]
JP 2002-110311 A (page 3-4, FIG. 1)
[0006]
[Problems to be solved by the invention]
However, the following problems remain in the conventional surge absorber. In other words, for applications that require high surge resistance, such as communication lines and power lines, there is a demand for characteristics that can be used more fully, and the surface mount type can break the glass tube during mounting. Therefore, it has been considered that the glass tube used in the surge absorber is a ceramic tube.
[0007]
In a conventional surge absorber using a glass tube, a cylindrical ceramic is put in the glass tube, and sealing electrodes are arranged on both ends of the glass tube, and the glass tube is melted in a high-temperature furnace and fixed tightly to the sealing electrode. It has a stop process.
In this cooling process from sealing, since the glass tube generates residual stress in the compression direction due to the difference in thermal expansion coefficient with the cylindrical ceramic, the ohmic contact between the sealing electrode and the cylindrical ceramic conductive film is sufficient. Have been able to get. However, when a ceramic tube is used instead of a glass tube, the difference in thermal expansion coefficient between the ceramic tube and the columnar ceramic is small compared to the above, so that the residual stress generated in the cooling process from sealing is small. Insufficient ohmic contact between the electrode and the cylindrical ceramic conductive film may not be obtained, resulting in inconvenience that electrical characteristics such as a discharge start voltage are not stable.
[0008]
The present invention has been made in view of the above-described problems, and an object thereof is to provide a surge absorber having stable electrical characteristics such as a discharge start voltage.
[0009]
[Means for Solving the Problems]
The present invention employs the following configuration in order to solve the above problems. That is, the surge absorber according to the present invention includes a columnar insulating member in which a conductive film is divided and formed on a peripheral surface through a central discharge gap, and opposed to both ends of the insulating member. A surge absorber comprising a pair of terminal electrode members that are in contact with each other, and an insulating tube that is formed of a ceramic material and that has the pair of terminal electrode members disposed at both ends and seals the insulating member together with a sealing gas The terminal electrode member includes a peripheral edge bonded to the end surface of the insulating tube with a brazing material, and a support concave portion that supports the insulating member on a radially inner side surface. A contact surface between the support recess and the conductive film is formed by press-fitting or fitting an insulating member, and a Vickers hardness Hv of the terminal electrode member satisfies 100 <Hv <200. You It is characterized in.
[0010]
According to the present invention, a belt-like contact surface on the circumference is formed between the support recess and the conductive coating by press-fitting or fitting an insulating member into the support recess, thereby increasing the contact surface and ensuring the contact surface. With this contact, a sufficient ohmic contact can be obtained, and the electrical characteristics such as the discharge start voltage of the surge absorber are stabilized.
In addition, since the terminal electrode member has a suitable hardness, it is possible to prevent damage to the insulating member when press-fitted and contact failure between the insulating member and the terminal electrode member during assembly, and one terminal electrode A contact failure between the other terminal electrode member and the insulating member can be suppressed due to excessive penetration of the insulating member into the member.
[0011]
In the surge absorber according to the present invention, the absolute value δ (1 / ° C.) of the difference in average thermal expansion coefficient of the terminal electrode member and the insulating tube around room temperature satisfies δ <10 × 10 ^−6. Is preferred.
During the brazing and cooling process, a large residual stress is generated at the joint between the insulating tube and the terminal electrode member due to the difference in thermal expansion coefficient between the terminal electrode member and the insulating tube, and the insulating tube is damaged or sealed. There is a risk of poor airtightness due to poor stoppage.
According to the present invention, since the difference in the average value of the thermal expansion coefficient between the terminal electrode member and the insulating tube is suitable, the generation of residual stress due to the difference in the thermal expansion coefficient is suppressed in the cooling process from brazing, and the It is possible to prevent airtight defects due to breakage of the sex tube and poor sealing.
[0012]
In the surge absorber according to the present invention, it is preferable that the terminal electrode member is made of Kovar (KOVAR), which is an alloy of Fe (iron), Ni (nickel), and Co (cobalt).
In the surge absorber according to the present invention, the terminal electrode member is preferably Kovar subjected to an annealing treatment.
According to the present invention, by performing the annealing treatment, it is possible to obtain a terminal electrode member having a hardness lower than that of ordinary Kovar and satisfying the above conditions.
[0013]
In the surge absorber according to the present invention, it is preferable that the conductive coating and the support recess are in contact with each other through a metal member having a hardness lower than that of the insulating member.
According to this invention, since the insulating member and the support recess are in contact with each other through the metal member having a lower hardness than the insulating member, the low hardness metal member is pressed when the insulating member is press-fitted or fitted. However, it is possible to form a better contact surface by closely attaching the insulating member and the support recess to both surfaces.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of a surge absorber according to the present invention will be described with reference to FIGS. 1 to 3.
As shown in FIG. 1, the surge absorber 1 according to the present embodiment is a discharge type surge absorber using a so-called microgap, and a conductive coating 3 is dividedly formed on a peripheral surface via a central discharge gap 2. The cylindrical ceramics (insulating member) 4, a pair of terminal electrode members 5 that are disposed opposite to both ends of the cylindrical ceramics 4 and are in contact with the conductive coating 3 by press-fitting the cylindrical ceramics 4, and the pair The terminal electrode member 5 is disposed at both ends, and the cylindrical ceramic 4 is sealed together with a sealing gas 6 such as Ar (argon) whose composition is adjusted in order to obtain desired electrical characteristics. A cylindrical ceramic (insulating tube) 7 is provided.
[0015]
The cylindrical ceramic 4 is made of a ceramic material such as a mullite sintered body, and has a conductive coating 3 on the surface thereof, such as TiN (titanium nitride) by a thin film forming technique such as physical vapor deposition (PVD) method or chemical vapor deposition (CVD) method. A thin film is formed.
1 to 100 discharge gaps 2 having a width of 0.01 to 1.5 mm are formed by processing such as laser cutting, dicing, and etching. In the present embodiment, one discharge gap 2 is formed with a thickness of 70 μm.
[0016]
The pair of terminal electrode members 5 is made of Kovar, which is an alloy of Fe (iron), Ni (nickel), and Co (cobalt), and is subjected to an annealing process of heating at 900 ° C. for 30 minutes in a hydrogen atmosphere. ing.
As shown in FIG. 2, the pair of terminal electrode members 5 includes a rectangular peripheral portion 5 </ b> A having an aspect ratio of 1 or less bonded to an end surface of the cylindrical ceramic 7 and a brazing material 8, and a cylindrical shape. A protruding support part (supporting recess) 9 that protrudes in the axial direction in the ceramic 7 and supports the cylindrical ceramics 4 is provided, and is surrounded by the protruding support part 9 so as to face the end of the cylindrical ceramics 4. A central region 5B is formed. It is desirable for the protruding support portion 9 to have a slightly tapered shape on the radially inner side surface so that the radially inner side surface and the end of the cylindrical ceramic 4 can be easily press-fitted or fitted. Moreover, the mutually opposing surface of the front-end | tip of the protrusion support part 9 is made into the main discharge surface.
The pair of projecting support portions 9 form a contact surface 10 by press-fitting or fitting the cylindrical ceramics 4 to the projecting support portion 9 on the inner peripheral surface, thereby obtaining sufficient ohmic contact with the conductive coating 3. .
[0017]
Cylindrical ceramic 7 is composed of, for example, Al 2 _O 3 _(alumina) or the like of the insulating ceramic has a rectangular cross section, both end faces outline is substantially equal to the outer peripheral dimensions of the peripheral portion 5A.
In such a configuration, the absolute value δ of the difference in average thermal expansion coefficient between the terminal electrode member 5 and the cylindrical ceramic 7 and the Vickers hardness Hv of the terminal electrode member 5 are δ <10 × 10 ⁻⁶ , 100 <Hv. It is formed to satisfy both <200 conditions simultaneously.
[0018]
Next, a method for manufacturing the surge absorber 1 of the present embodiment having the above configuration will be described.
First, the pair of terminal electrode members 5 are subjected to an annealing process of heating at 900 ° C. for 30 minutes in a hydrogen atmosphere, for example, and then integrally formed into a desired shape by punching.
[0019]
Subsequently, in order to improve the wettability with the brazing material 8 on both end faces of the cylindrical ceramic 7, for example, metallized layers each including one molybdenum (Mo) -tungsten (W) layer and one Ni layer are provided. Form.
Then, the cylindrical ceramic 4 is placed on the central region 5B of the one terminal electrode member 5 by press-fitting or fitting the cylindrical ceramic 4 into the projecting support portion 9, so that the radially inner side surface and the cylindrical ceramic 4 are placed. Make contact with the end face. At this time, the contact surface 10 is formed. The cylindrical ceramic 7 is placed on the peripheral edge 5 </ b> A of the other terminal electrode member 5 with the brazing material 8 sandwiched between the peripheral edge 5 </ b> A and the end surface of the cylindrical ceramic 7.
Further, the terminal electrode member 5 is placed so that the upper side of the columnar ceramic 4 faces the central region 5B, and the radially inner side surface and the terminal electrode member 5 are brought into contact with each other. Then, the brazing material 8 is sandwiched between the peripheral portion 5 </ b> A and the end surface of the cylindrical ceramic 7.
[0020]
In the temporarily assembled state as described above, after sufficiently evacuating, it is heated as a sealing gas atmosphere until the brazing material 8 is melted, the cylindrical ceramics 4 are sealed by melting the brazing material 8, and then cooled rapidly. The surge absorber 1 is manufactured.
For example, as shown in FIG. 3, the surge absorber 1 manufactured in this way is mounted on a substrate B having a mounting surface 7 </ b> A which is one side surface of the cylindrical ceramic 7 on a substrate B such as a printed circuit board. B and the outer surfaces of the pair of terminal electrode members 5 are used by being bonded and fixed with solder S.
[0021]
According to the above configuration, the strip-shaped contact surface 10 is formed between the conductive coating 3 and the projecting support portion 9 by press-fitting or fitting the cylindrical ceramics 4 into the projecting support portion 9, and a good ohmic contact As a result, electrical characteristics such as the discharge start voltage of the surge absorber 1 are stabilized. Further, since the terminal electrode member 5 is made of an annealed Kovar, the Vickers hardness Hv of the terminal electrode member 5 and the absolute value δ of the average thermal expansion coefficient difference between the terminal electrode member 5 and the cylindrical ceramic 7 are Is a suitable value. Accordingly, it is possible to prevent damage to the cylindrical ceramics 4 during press-fitting or fitting and contact failure during assembly, and to suppress contact failure due to excessive entry of the conductive coating 3 into one terminal electrode member 5. Further, in the cooling process from brazing, the occurrence of residual stress due to the difference in thermal expansion coefficient between the terminal electrode member 5 and the cylindrical ceramic 7 can be suppressed, and the confidentiality failure due to breakage of the cylindrical ceramic 7 or defective sealing can be prevented. .
[0022]
Next, a second embodiment will be described with reference to FIG.
The basic configuration of the embodiment described here is the same as that of the first embodiment described above, and another element is added to the first embodiment described above. Therefore, in FIG. 4, the same components as those in FIG.
[0023]
The difference between the second embodiment and the first embodiment is that, in the first embodiment, the cylindrical ceramic 4 is directly press-fitted or fitted into the protruding support portion 9, whereas the second embodiment is different from the second embodiment. The surge absorber 20 in this embodiment is that the cylindrical ceramic 4 is press-fitted into the protruding support portion 9 via a pair of cap electrodes (metal members) 21 formed in a bowl shape.
The pair of cap electrodes 21 is made of a metal having a lower hardness than the cylindrical ceramic 4, such as stainless steel, and has an outer peripheral portion extending inward in the axial direction from the tip of the protruding support portion 9 of the terminal electrode member 5. It is formed in a U shape and serves as a main discharge surface.
[0024]
Next, a method for manufacturing the surge absorber 20 of the present embodiment having the above configuration will be described.
First, after the annealing treatment is performed on the pair of terminal electrode members 5, they are integrally formed by punching.
Thereafter, the pair of cap electrodes 21 are engaged with both ends of the cylindrical ceramic 4, and the surge absorber 20 is manufactured by the same method as in the first embodiment.
[0025]
According to the above configuration, since the cap electrode 21 having a lower hardness than the cylindrical ceramic 4 and capable of plastic deformation is provided, the cap electrode 21 closely attaches the cylindrical ceramic 4 and the protruding support portion 9 to both surfaces. Better contact surface can be formed.
[0026]
In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.
For example, the Vickers hardness Hv preferably satisfies 140 <Hv <180 in order to prevent contact failure due to breakage of the insulating member or excessive press-fitting.
In order to further reduce the residual stress, the absolute value δ of the difference in average thermal expansion coefficient preferably satisfies δ <8 × 10 ⁻⁶ .
[0027]
The conductive film may be Ag, Ag / Pd alloy, SnO ₂ , Al, Ni, Cu, Ti, Ta, W, SiC, BaAl, C, Ag / Pt alloy, TiO, TiC, TiCN, or the like.
Further, the metallized layers on both end faces of the cylindrical ceramic may be Ag, Cu, Au, or may be sealed only with an active metal brazing material without using the metallized layer.
The sealing gas may be, for example, the atmosphere (air) whose composition is adjusted to sell desired electrical characteristics, such as Ar, N ₂ , Ne, He, Xe, H ₂ , SF ₆ , CF _4. , C ₂ F ₆ , C ₃ F ₈ , CO ₂ or the like, and a mixed gas thereof may be used.
[0028]
【The invention's effect】
As described above, according to the surge absorber of the present invention, it is possible to obtain a good ohmic contact between the conductive coating and the support recess by an increase in the contact area and reliable contact. Therefore, electrical characteristics such as the discharge start voltage can be stabilized over a long period of time.
[Brief description of the drawings]
FIG. 1 is an axial sectional view showing a surge absorber according to a first embodiment of the present invention.
FIGS. 2A and 2B show a terminal electrode member according to a first embodiment of the present invention, in which FIG. 2A is a plan view and FIG. 2B is a cross-sectional view taken along line XX in FIG.
FIG. 3 is a cross-sectional view when the surge absorber according to the first embodiment of the present invention is mounted on a substrate.
FIG. 4 is an axial sectional view showing a surge absorber according to a second embodiment of the present invention.
[Explanation of symbols]
1, 20 Surge absorber 2 Discharge gap 3 Conductive coating 4 Cylindrical ceramics (insulating member)
5 Terminal electrode member 5A Peripheral part 6 Sealing gas 7 Cylindrical ceramics (insulating tube)
8 Brazing material 9 Protruding support (support recess)
10 Contact surface 21 Cap electrode (metal member)

Claims (5)

A columnar insulating member having a conductive film divided and formed on the peripheral surface through a central discharge gap, a pair of terminal electrode members disposed opposite to both ends of the insulating member and in contact with the conductive film, and ceramics A surge absorber comprising an insulating tube that is formed of a material and is arranged at both ends with the pair of terminal electrode members disposed therein and sealing the insulating member together with a sealing gas,
The terminal electrode member is bonded to the end surface of the insulating tube with a brazing material;
A support recess for supporting the insulating member on the radially inner side surface,
A contact surface between the support recess and the conductive coating is formed by press-fitting or fitting the insulating member into the support recess,
A surge absorber characterized in that a Vickers hardness Hv of the terminal electrode member satisfies 100 <Hv <200. The surge absorber according to claim 1,
The surge absorber, wherein an absolute value δ (1 / ° C.) of an average coefficient of thermal expansion difference between the terminal electrode member and the insulating tube near room temperature satisfies δ <10 × 10 ⁻⁶ . The surge absorber according to claim 1 or 2,
A surge absorber, wherein the terminal electrode member is made of an alloy including Fe (iron), Ni (nickel), and Co (cobalt). The surge absorber according to any one of claims 1 to 3,
A surge absorber, wherein the terminal electrode member is Kovar (registered trademark) subjected to an annealing treatment. The surge absorber according to any one of claims 1 to 4,
The surge absorber, wherein the conductive coating and the support recess are in contact with each other through a metal member having a hardness lower than that of the insulating member.

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