JP2004127614A - Surge absorber and manufacturing method of same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surge absorber which can be easily miniaturized, and manufacturing method of the same capable of manufacturing the surge absorber in large quantity at a time. <P>SOLUTION: A plurality of insulation materials 23, 23 are laminated, and at least two lamination interfaces 25a, 25b are formed. An airtight discharging space 29 is formed by a hole 27 perforated through the lamination interfaces 25a, 25b. Discharging electrodes 31a, 31b, arranged on the lamination interfaces 25a, 25b respectively, are made to face each other in the discharging space with a distance larger than the distance between two lamination interfaces 25a, 25b. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surge absorber that absorbs a surge voltage and a method of manufacturing the same, and more particularly, to an improved technique that enables downsizing.
[0002]
[Prior art]
Chip-type surge absorbers are connected to parts where electronic devices such as telephones and modems are connected to communication lines, or to parts that are susceptible to electric shock such as lightning surges or static electricity, such as CRT drive circuits. Is used to prevent destruction.
[0003]
As shown in FIG. 7, a conventional chip-type surge absorber 1 has discharge electrodes 5 and 7 formed opposite to each other on a plate surface of an insulating substrate 3 made of an insulating material such as alumina and the like. A discharge gap 9 called a microgap is provided between the two (see, for example, Patent Document 1 described later). The discharge electrode 5 and the discharge electrode 7 can be formed as an integrated print pattern facing each other across the discharge gap 9 by screen-printing the electrode material.
[0004]
Above these discharge electrodes 5 and 7, a box-shaped ceramic lid 13 is attached on the insulating substrate 3 so as to form the internal space 11. Gas atmosphere. The lid 13 is covered with an adhesive 15 applied around the insulating substrate 3 so that the outer ends of the discharge electrodes 5 and 7 protrude outside. Terminal electrodes 17 and 19 are formed on both ends of the lid 13 and the insulating substrate 3 by plating or the like, and the terminal electrodes 17 and 19 are connected to the respective discharge electrodes 5 and 7.
[0005]
[Patent Document 1]
JP-A-2002-15832 (paragraph 0003, FIG. 3)
[0006]
In the surge absorber 1 having such a configuration, when a large surge voltage exceeding the discharge starting voltage flows through the discharge electrodes 5 and 7, the glow discharge a is triggered through the discharge gap 9 between the distal ends of the discharge electrodes 5 and 7. Then, as shown by the arrow b, this discharge gradually extends in the internal space 11 in the form of a creeping discharge to the outer end sides of the two discharge electrodes 5 and 7, and further, as shown in c, the discharge electrodes 5 and 7 An arc discharge occurs between the outer ends, thereby absorbing a surge voltage generated between the circuits.
[0007]
[Problems to be solved by the invention]
However, the conventional surge absorber described above has a difficulty in downsizing because it covers the box-shaped lid to form an internal space. Moreover, since the lids are attached to the insulating substrate on which the discharge electrodes are formed while positioning the lids one by one in an inert gas and assembling them, a large amount of sealing cannot be performed at once.
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a surge absorber and a method of manufacturing the surge absorber, which can be easily reduced in size, and can easily obtain a large amount of surge absorbers at once.
[0008]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a surge absorber according to the first aspect of the present invention, wherein a plurality of insulating materials are stacked to form at least two stacked boundary surfaces, and the surge absorber is perforated across the two stacked boundary surfaces. A closed discharge space is formed by the holes, and the discharge electrodes formed on each of the two stacked boundary surfaces face each other in the discharge space at a distance larger than the distance between the two stacked boundary surfaces. Features.
[0009]
In this surge absorber, the discharge space is formed in the laminated body of the insulating material, and it is not necessary to cover the box-shaped lid to form the internal space unlike the conventional structure. Also, a pair of discharge electrodes are opposed to each other via a discharge space formed by the hole, and by changing the shape and size of the hole, the distance between the discharge electrodes while maintaining a constant lamination thickness (thinness) is maintained. Can be freely set.
[0010]
According to a second aspect of the present invention, in the surge absorber according to the first aspect, a plurality of pairs of a pair of discharge electrodes facing each other in the discharge space are provided.
[0011]
In this surge absorber, when the discharge electrode that has been discharged first cannot be discharged due to long-term use, the discharge moves to the discharge electrode that is easily discharged next, and the discharge start voltage is kept low for a long time. Continue to be.
[0012]
The method for manufacturing a surge absorber according to claim 3, wherein a strip-shaped discharge electrode is formed on at least two ceramic green sheets, with one end reaching the sheet end face and the other end reaching the sheet center, and A hole larger than the width of the discharge electrode for cutting the discharge electrode is formed in the center of each of the two ceramic green sheets so that the holes coincide with each other and the discharge electrodes do not overlap each other. Are laminated, and another ceramic green sheet is laminated on and under the laminated ceramic green sheet and pressed, and the pressed plurality of ceramic green sheets are integrally fired.
[0013]
In this method for manufacturing a surge absorber, a plurality of holes and a discharge electrode are arranged at predetermined positions, and a ceramic green sheet is laminated, so that a pair of discharge electrodes can be simultaneously opposed to each discharge space, and a large number of surge absorbers can be disposed. Can be manufactured easily and all at once.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of a surge absorber and a method of manufacturing the surge absorber according to the present invention will be described in detail with reference to the drawings.
1 is a longitudinal sectional view of a surge absorber according to the present invention, FIG. 2 is a view taken along the line AA of FIG. 1, FIG. 3 is an exploded perspective view of the surge absorber shown in FIG. 1, and FIG. FIG. 5 is an exploded perspective view showing a modification of the surge absorber, FIG. 5 is an enlarged view of a main part of FIG. 1, and FIG. 6 is an enlarged view of a main part showing another modification of the surge absorber shown in FIG.
[0015]
In the surge absorber 21 according to the present embodiment, a plurality of insulating materials 23 are stacked to form at least two stacked boundary surfaces 25a and 25b. A closed discharge space 29 is formed in the stacked body in which the plurality of insulating materials 23 are stacked by a hole 27 formed over the two stacked boundary surfaces 25a and 25b. Discharge electrodes 31a and 31b are formed on each of the two stacked boundary surfaces 25a and 25b, and the discharge electrodes 31a and 31b are separated by a distance L larger than a distance T between the two stacked boundary surfaces 25a and 25b as shown in FIG. In the discharge space 29. In FIG. 1, reference numerals 32a and 32b denote terminal electrodes connected to the discharge electrodes 31a and 31b exposed on the end face of the laminate of the insulating material 23.
[0016]
Here, the distance T between the two laminated boundaries 25a and 25b means the thickness of the insulating material 23 interposed between the two laminated boundaries 25a and 25b. Therefore, if the discharge electrodes 31a and 31b are disposed in a vertically overlapping relationship with the insulating material 23 interposed therebetween, the distance between the end faces of the discharge electrodes 31a and 31b exposed in the discharge space 29 will be smaller than the lamination boundary. It is equal to the distance T between the surfaces 25a and 25b. That is, the discharge distance between the pair of discharge electrodes 31a and 31b depends on the thickness of the intervening insulating material 23.
[0017]
On the other hand, in the present embodiment, the pair of discharge electrodes 31a and 31b face each other with a distance L larger than the distance T between the two stacked boundary surfaces 25a and 25b. In other words, the pair of discharge electrodes 31a and 31b are arranged in a positional relationship such that they do not overlap vertically with the insulating material 23 interposed therebetween. In the illustrated example, the right end of the upper discharge electrode 31a reaches the right end of the sheet, and the left end reaches the center of the sheet. The left end of the lower discharge electrode 31b reaches the left end of the sheet, and the right end reaches the center of the sheet. That is, they are arranged on the same straight line. By arranging in such a relative positional relationship, the end surfaces of the pair of discharge electrodes 31a and 31b can be opposed to each other across the discharge space 29 without depending on the thickness.
[0018]
Thus, the pair of discharge electrodes 31a and 31b are opposed to each other via the discharge space 29, and by changing the shape and size of the hole, the facing distance between the discharge electrodes 31a and 31b is maintained while maintaining a constant lamination thickness. It can be set freely.
[0019]
Note that the relative positions of the pair of discharge electrodes 31a and 31b are arranged on the same straight line as described in the present embodiment, and if they do not overlap vertically as described above, May be arranged at a predetermined angle in the rotation direction. For example, the discharge electrodes 31b indicated by broken lines in FIG. 2 extend in the vertical direction in FIG.
[0020]
Here, in order to make the end faces of the pair of discharge electrodes 31a and 31b face each other with the discharge space 29 interposed therebetween, the distal ends 33 of the discharge electrodes 31a and 31b (see FIG. It must be separated from the part 35. This can be achieved by making the size of the hole 27 larger than the width W of the discharge electrodes 31a and 31b. With this configuration, it is possible to prevent the distal end portion 33 of one discharge electrode 31a from facing the base end portion 35 of the other discharge electrode 31b in the thickness direction. The discharge electrodes 31a and 31b may be cut off by the holes 27 so that the tip 33 does not remain.
[0021]
According to the surge absorber 21, the discharge space 29 is formed in the laminated body of the insulating material 23, and it is not necessary to cover the box-shaped lid to form the internal space unlike the conventional structure. Further, a pair of discharge electrodes 31a and 31b are opposed via a discharge space 29 formed by the hole 27, and by changing the shape and size of the hole 27, the discharge electrode 31a The opposing distance between 31b can be set freely.
[0022]
In the above-described embodiment, the case where the discharge electrodes 31a and 31b are formed on the two stacked boundary surfaces 25a and 25b has been described as an example. However, the surge absorber according to the present invention has, as shown in FIG. Discharge electrodes 31a, 31b, 31c, and 31d are formed on each of the plurality of insulating materials 23 (four in the illustrated example), and a plurality of pairs (two in the illustrated example) of a pair of discharge electrodes facing each other in the discharge space 29 are provided. May be used. With such a configuration, when the discharge electrodes 31a and 31b that have been discharged first cannot be discharged due to long-term use, the discharge can be transferred to the discharge electrodes 31c and 31d that are easily discharged next. it can. As a result, the discharge starting voltage can be kept low.
[0023]
Next, a method of manufacturing the surge absorber 21 configured as described above will be described. First, for example, a material obtained by adding a sintering aid to a powder of an insulating material such as alumina (Al ₂ O ₃ ) such as corundum, mullite, corundum mullite, etc., is processed into a sheet having a thickness of 1 μm to 200 μm to obtain a ceramic. A green sheet (a material before sintering the insulating material 23) is prepared. Here, as sintering aids, SiO ₂ (silicon dioxide), B ₂ O ₃ (boron oxide), PbO (lead oxide), Na ₂ O (disodium oxide), Li ₂ O (lithium oxide), BaO (Barium oxide), CaO (calcium oxide), ZnO (zinc oxide), MgO (magnesium oxide), TiO ₂ (titanium oxide), or a mixture of two or more of Al ₂ O ₃ is used. be able to.
Subsequently, as shown in FIG. 3, one end (base end 35) reaches at least one of the ceramic green sheets 23 a and 23 b on the sheet end surface, and the other end (tip end 33) reaches the center of the sheet. The discharge electrodes 31a and 31b are formed.
The discharge electrodes 31a and 31b are formed in a band shape having a width of, for example, 0.01 mm to 0.70 mm and a length of 0.6 mm to 1.5 mm, and are formed of, for example, RuO ₂ (ruthenium oxide) -glass. Ag / Pd (silver / palladium), SnO ₂ (tin dioxide), Al (aluminum), Ni (nickel), Cu (copper), Ti (titanium), TiN (titanium nitride), Ta (tantalum), W (Tungsten), SiC (silicon carbide), BaAl (barium aluminum), Nb (niobium), Si (silicon), C (carbon), Ag (silver), Ag / Pt (silver / platinum), ITO (indium-tin) Oxide) or the like. The discharge electrodes 31a and 31b may be formed by, for example, screen printing, or may be formed by a sputtering method, a CVD method, an ion plating method, a printing method, or a vapor deposition method.
[0024]
Next, holes 27 of the same shape, which are larger than the widths of the discharge electrodes 31a and 31b, for cutting the discharge electrodes 31a and 31b are formed in the respective center portions of the ceramic green sheets 23a and 23b. The hole 27 has a diameter of, for example, 0.03 mm to 0.75 mm, and its cross-sectional shape can be a perfect circle, an ellipse, or a polygon such as a triangle or more.
Next, two ceramic green sheets 23a and 23b are laminated in an inert gas such that the holes 27 are aligned with each other and the discharge electrodes 31a and 31b do not overlap vertically. In the present embodiment, the ceramic green sheet 23a is laminated on the surface of the ceramic green sheet 23b on which the discharge electrode 31b is formed so that the surface on which the discharge electrode 31a is not formed faces the ceramic green sheet 23b. I have.
Next, other ceramic green sheets 23c and 23d are laminated on and under the laminated ceramic green sheets 23a and 23b, and these are pressed. In the pressure bonding step, the laminate of the ceramic green sheets 23a, 23b, 23c, and 23d is heated to 50 ° C. to 90 ° C. and pressure bonded to apply a pressure of 98.1 MPa to 490.3 MPa.
[0025]
Finally, the plurality of pressed ceramic green sheets 23a, 23b, 23c, and 23d are placed in an inert gas (atmospheric pressure of 13330 Pa to 133300 Pa) at 600 ° C. to 1100 ° C. using a tunnel furnace or a batch furnace. And fired for 1 minute to 3 hours to perform an integral firing. Here, the inert gas used in the firing is He (helium), Ar (argon), Ne (neon), Xe (xenon), SF ₆ (sulfur hexafluoride), CO ₂ (carbon dioxide), C ₃ F ₈ (perfluoropropane), C ₂ F ₆ (perfluoroethane), CF ₄ (tetrafluoromethane), H ₂ (hydrogen molecular gas), atmosphere, and a mixed gas thereof can be used.
Thereafter, a conductive paste such as an Ag (silver) conductive paste is applied to both sides of the sintered body on which the discharge electrodes 31a and 31b are exposed, and baked at, for example, 600 ° C. to form the terminal electrodes 32a and 32b. I do.
Here, the terminal electrodes 32a and 32b may be manufactured using a conductive resin paste. The firing temperature in this case is set to 120 ° C to 250 ° C.
[0026]
According to the method of manufacturing the surge absorber 21, by stacking the ceramic green sheets in which the plurality of holes 27 and the discharge electrodes 31 a and 31 b are arranged at predetermined positions, a pair of discharge electrodes 31 a for each discharge space 29 is formed. 31b can be simultaneously arranged facing each other, and as a result, a large number of surge absorbers 21 can be easily and simultaneously manufactured. Further, according to the method of manufacturing the surge absorber 21, since it is not necessary to form a micro gap by using a laser or the like, the number of steps can be reduced and the manufacturing cost can be reduced.
[0027]
Here, in the method of manufacturing the surge absorber 21, when the hole 27 at the center of the ceramic green sheets 23a, 23b is formed by punching or the like, the discharge electrodes 31a, 31b provided on the ceramic green sheets 23a, 23b. In some cases, dripping may occur at the portion located at the edge of the hole 27, and the discharge electrodes 31 a and 31 b may enter the inner surface of the hole 27.
When such ceramic green sheets 23a and 23b are stacked such that the discharge electrodes 31a and 31 are vertically overlapped, the discharge electrode that has entered the hole 27 of one ceramic green sheet is placed on the other ceramic green sheet. May be in contact with the discharge electrode, and the surge absorber obtained by firing this may be a defective product in which the discharge electrode is short-circuited.
On the other hand, in the method of manufacturing the surge absorber 21 according to the present invention, the ceramic green sheets 23a and 23b are stacked so that the discharge electrodes 31a and 31b do not overlap one another, so that the two-dot chain line is shown in FIG. As shown, even if the discharge electrode 31a enters the hole 27, the discharge electrodes 31a and 31b do not come into contact with each other and short-circuit, so that the yield is high.
Further, by adjusting the punching conditions when the hole 27 is formed in the ceramic green sheet to intentionally cause such a dripping of the discharge electrode, the discharge electrode that has entered the hole 27 causes the main discharge ( (Arc discharge), the life characteristics of the surge absorber 21 are improved. In this case, the hole 27 is formed so that the tip 33 of the discharge electrodes 31a and 31b remains, and a part of the tip 33 of the discharge electrode 31a also enters the hole 27 and is connected to the discharge electrode 31b. As a result, the distal end 33 of the discharge electrode 31a has the same polarity as the discharge electrode 31b, and the distance between the two electrodes is further reduced, so that arc discharge is likely to occur between them.
[0028]
In the above embodiment, the case where the discharge electrodes 31a and 31b are formed on the pair of ceramic green sheets 23a and 23b, respectively, and the ceramic green sheets 23a and 23b are pressure-bonded has been described as an example. As a result, other stacked structures may be used as long as the discharge electrodes 31a and 31b are arranged to face each other with the discharge space 29 interposed therebetween. That is, as shown in FIG. 4, a discharge electrode 31a is formed on the lower surface of one ceramic green sheet 23a, and a discharge electrode 31b is formed on the upper surface of the other ceramic green sheet 23b. The ceramic green sheets 23a, 23b, 23c, 23d, and 23e may be integrally fired after being press-bonded with another ceramic green sheet 23e having a hole 27 interposed therebetween.
[0029]
【Example】
Step 1.
First, a powder of Al ₂ O _{3 and} a powder of SiO ₂ are weighed so as to have a weight ratio of 4: 6, and an organic binder, a solvent, a dispersant, and a plasticizer are added thereto, and mixed with a ball mill for 24 hours. Then, a slurry was prepared, and this slurry was processed into a single-layer ceramic green sheet having a thickness of 50 μm by a doctor blade method.
Eight single-layer ceramic green sheets were stacked, and a pressure of 196 MPa was applied thereto while being heated to a temperature of 70 ° C., and they were pressed together to form a single stacked sheet. A total of two such stacked sheets were produced. . These laminated sheets constitute the insulator layers that form the upper and lower surfaces of the surge absorber.
[0030]
Step 2.
Next, one piece of the above-mentioned 50 μm-thick ceramic green sheet was prepared, and on one surface thereof, a band of RuO ₂ -glass paste was formed in a region forming each surge absorber from one edge of this region to the center of the region. And dried to form one discharge electrode. Here, the discharge electrode was formed in a band shape having a width of 0.30 mm, a length of 1.00 mm, and a thickness of 5 μm.
Then, on the surface of the ceramic green sheet on which one discharge electrode is formed, three ceramic green sheets each having a thickness of 50 μm are further laminated, and a pressure of 196 MPa is applied while heating to a temperature of 70 ° C. It was crimped to form one laminated sheet.
Further, on the surface of the laminated sheet opposite to the surface formed by the ceramic green sheet on which one of the discharge electrodes is formed, the area forming each surge absorber is separated from the edge of one of the discharge electrodes in this region. A RuO ₂ -glass-based paste was printed in a band shape from different edges to the center of the region, and dried to form another discharge electrode having the same shape as one discharge electrode.
Then, one ceramic green sheet having a thickness of 50 μm is further laminated on the surface of the laminated sheet on which the other discharge electrode is to be formed, and a pressure of 196 MPa is applied while heating to a temperature of 70 ° C. to press them together. Thus, one laminated sheet was obtained.
Further, holes (via holes) having a diameter of 0.5 mm were formed by punching in the center of the regions forming the respective surge absorbers in the laminated sheet, and the end faces of the respective discharge electrodes were exposed in the holes.
[0031]
Step 3.
One of the laminated sheets formed in step 1 is laminated and pressed on one surface of the laminated sheet formed in step 2, and the via holes of the laminated sheet formed in step 2 are inserted into an organic vehicle (organic binder and solvent). After that, another laminated sheet formed in the step 1 was laminated on the other surface of the laminated sheet formed in the step 2 and pressed. Here, these laminated sheets were pressure-bonded by applying a pressure of 196 MPa while heating to a temperature of 70 ° C.
[0032]
Step 4.
Thereafter, the laminated body of the laminated sheet is cut into regions forming respective surge absorbers to form chip-shaped laminated bodies, and these chip-shaped laminated bodies are heated in the air to be degreased, and then inert gas (Ar, It was heated to 900 ° C. in an atmosphere pressure of 106656 Pa) and held for 2 hours for firing.
The chip-shaped sintered body thus obtained is subjected to barrel polishing to remove corners, and then an Ag conductive paste is applied to the surface of the sintered body where the electrodes are exposed, and fired at 600 ° C. in the air. Then, a terminal electrode was formed.
Further, by applying Ni plating and solder plating to the terminal electrodes, a small chip type surge absorber of 1.6 mm × 0.8 mm × 0.8 mm was manufactured.
[0033]
【The invention's effect】
As described in detail above, according to the surge absorber according to claim 1 of the present invention, the insulating material is laminated to form two laminated boundary surfaces, and the holes formed over the laminated boundary surfaces are formed. The discharge electrodes formed on each of the stacked boundary surfaces are opposed to each other in the discharge space with a distance larger than the distance between the two stacked boundary surfaces. It is not necessary to cover the box-shaped lid to form an internal space unlike the conventional structure, and the size can be easily reduced. Further, since the pair of discharge electrodes face each other via the discharge space formed by the holes, the facing distance between the discharge electrodes can be freely set while maintaining a constant laminated thickness by changing the shape and size of the holes. be able to.
[0034]
According to the surge absorber of the second aspect, in the surge absorber of the first aspect, a plurality of pairs of the discharge electrodes facing each other in the discharge space are provided. Even in the case where the discharge becomes impossible, the discharge electrode which is easily discharged next discharges, and the discharge starting voltage can be kept low.
[0035]
According to the surge absorber and the method of manufacturing the same according to the third aspect, the discharge electrode is formed on the ceramic green sheet, and a hole for cutting the discharge electrode is formed in the center of the ceramic green sheet so that the holes coincide with each other. In addition to laminating ceramic green sheets, and laminating other ceramic green sheets on top and bottom and pressing and firing integrally, by laminating ceramic green sheets having a plurality of holes and discharge electrodes arranged at predetermined positions. In addition, a pair of discharge electrodes can be opposed to each discharge space at the same time, and a large amount of surge absorber can be obtained easily and at once.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a surge absorber according to the present invention.
FIG. 2 is a view as viewed in the direction of arrows AA in FIG. 1;
FIG. 3 is an exploded perspective view of the surge absorber shown in FIG.
FIG. 4 is an exploded perspective view showing a modification of the surge absorber shown in FIG.
FIG. 5 is an enlarged view of a main part of FIG. 1;
FIG. 6 is an enlarged view of a main part showing another modification of the surge absorber shown in FIG.
FIG. 7 is a longitudinal sectional view of a conventional surge absorber.
[Explanation of symbols]
21 ... Surge absorber 23 ... Insulating materials 23a to 23e ... Ceramic green sheets 25a and 25b ... Lamination boundary surface 27 ... Hole 29 ... Discharge spaces 31a and 31b ... Discharge electrodes 33 ... Top end (other end)
35 ... base end (one end)
T: distance between the lamination boundaries

Claims (3)

A plurality of insulating materials are stacked to form at least two stacked boundary surfaces,
A sealed discharge space is formed by the holes formed over the two stacked boundary surfaces,
A surge absorber, wherein discharge electrodes formed on each of the two stacked boundary surfaces face each other in the discharge space with a distance larger than a distance between the two stacked boundary surfaces. The surge absorber according to claim 1,
A surge absorber, wherein a plurality of pairs of a pair of discharge electrodes facing each other in the discharge space are provided. A band-shaped discharge electrode is formed on at least two ceramic green sheets, with one end reaching the sheet end surface and the other end reaching the center of the sheet,
Drilling a hole larger than the width of the discharge electrode for cutting the discharge electrode at the center of each of the ceramic green sheets,
The two ceramic green sheets are stacked so that the holes coincide with each other and the discharge electrodes do not overlap each other, and another ceramic green sheet is stacked on and under the stacked ceramic green sheets and pressed. And
A method for manufacturing a surge absorber, wherein the plurality of pressed ceramic green sheets are integrally fired.

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