JP2013038223A - Varistor and light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a varistor which allows for reliable electrical connection.SOLUTION: A varistor 1 includes a varistor element 10 expressing voltage nonlinear characteristics and having first and second principal surfaces 10a, 10b facing each other, first and second internal electrodes 30, 35 disposed in the varistor element 10 so as to sandwich a portion thereof and facing the opposing direction of the first and second principal surfaces 10a, 10b, a first external electrode 20 disposed on the first principal surface 10a, a second external electrode 25 disposed on the second principal surface 10b, a first conductor 40 connecting the first internal electrode 30 and the first external electrode 20 electrically, and a second conductor 45 connecting the second internal electrode 35 and the second external electrode 25 electrically. The first external electrode 20 has a recess 50 which is concave in the opposing direction of the first and second principal surfaces 10a, 10b.

Description

  The present invention relates to a varistor and a light emitting device including the varistor.

  As a varistor, a varistor element that exhibits voltage non-linear characteristics, a pair of internal electrodes arranged inside the varistor element with a part of the varistor element in between, and an outer surface of the varistor element There is known one provided with an external electrode (see, for example, Patent Document 1). As one application of such varistors, it is proposed to use these varistors as countermeasures against ESD (Electrostatic Discharge) of electronic elements such as LEDs that have been conventionally performed by Zener diodes (see, for example, Patent Document 2). It has come to be.

JP 2006-245367 A JP 2001-036140 A

  By the way, in order to protect the LED chip from the ESD surge, when trying to mount the varistor described in Patent Document 1 on the same substrate as the LED chip as it is, the longitudinal direction of the varistor is arranged along the surface direction of the substrate. Therefore, there is a problem that it is difficult to reduce the size of the light emitting device including the LED chip. On the other hand, in order to reduce the mounting area of the varistor, if the varistor is arranged to be perpendicular to the surface direction of the substrate, there is a possibility that the light emission of the LED chip may be hindered.

  Therefore, the appearance of a varistor having a reduced mounting area and a reduced height is desired. However, as the varistor becomes smaller and thinner, it becomes more difficult to connect the varistor terminals by wire bonding or the like when mounting the varistor. A new problem has occurred.

  An object of this invention is to provide the varistor which can perform an electrical connection reliably, and the light-emitting device provided with the said varistor.

  The varistor according to the present invention is arranged in the varistor body so as to sandwich the varistor element body having a first and second main surfaces facing each other and a part of the varistor element body while exhibiting a voltage non-linear characteristic. The first and second internal electrodes facing each other in the opposing direction of the first and second main surfaces, the first external electrode disposed on the first main surface, and the second main surface The second external electrode, the first conductor portion that electrically connects the first internal electrode and the first external electrode, and the second internal electrode and the second external electrode are electrically connected And a second conductor portion. In this varistor, the first external electrode has a first recess that is recessed in the opposing direction of the first and second main surfaces.

  As described above, the varistor according to the present invention has the first concave portion on the first main surface side which is terminal-connected by wire bonding or the like. In this case, when the metal used for the wire bond connection or the solder used for the solder connection is melted, the melt easily accumulates in the concave portion. Therefore, it is easy to align the terminal connection by wire bonding or the like. An electrical connection can be ensured. Further, since the metal or solder used for wire bonding or the like enters the recess in a melted state, these are firmly connected by the anchor effect, and the electrical connection of the varistor can be made more reliable.

  In the varistor, it is preferable that the first conductor portion and the first concave portion are arranged so that at least a part thereof overlaps when viewed from the opposing direction of the first and second main surfaces. In this case, when the terminals are connected by wire bonding or the like, the first conductor portion having higher flexibility than the varistor element body can absorb the mechanical load applied during the connection operation, so that the varistor element body or the like It is possible to prevent cracks from occurring.

  In the above varistor, the first and second conductor portions may have tapered through-hole electrodes whose diameter narrows in a direction from the first main surface to the second main surface. In this case, the center of the conductor portion is easily recessed, and the first recess can be easily provided on the first main surface side.

  In the varistor, the first and second conductor portions have tapered through-hole electrodes whose diameters are narrowed in the direction from the first and second main surfaces to the first and second internal electrodes, respectively. It may be. In this case, since the directionality of the varistor is lost, it is easy to use.

  In the above varistor, at least one of the first and second conductor portions has a relay electrode that extends in a plane direction intersecting the opposing direction of the first and second main surfaces and that connects the through-hole electrodes. It may be. In this case, the connection of the through-hole electrodes can be ensured. In addition, the heat dissipation effect can be enhanced by spreading the relay electrode in the plane direction. For example, the heat dissipation effect when heat is generated in the varistor when ESD is thrown in can be enhanced, and deterioration of the varistor characteristics due to heat generation can be suppressed. it can.

  In the varistor, the second external electrode may have a second recess that is recessed in a direction opposite to the first and second main surfaces. In this case, the electrical connection of the varistor can be reliably performed regardless of the terminal connection on any main surface.

  The light-emitting device according to the present invention includes any of the varistors described above and a light-emitting element connected in parallel to the varistor. In this case, it is possible to obtain a light emitting device having a varistor that is reliably electrically connected.

  According to the present invention, it is possible to provide a varistor capable of reliably performing electrical connection and a light-emitting device including the varistor.

It is a perspective view of the varistor which concerns on one Embodiment of this invention. It is the II-II sectional view taken on the line of the varistor shown in FIG. FIG. 2 is an exploded perspective view of the varistor (excluding external electrodes) shown in FIG. 1. It is a top view of the varistor shown in FIG. It is a figure which shows the relationship between the external electrode of the varistor shown in FIG. 1, an internal electrode, and a conductor part. It is a side view of the light-emitting device provided with the varistor shown in FIG. It is one aspect | mode of the modification of the varistor which concerns on this invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  First, with reference to FIGS. 1-3, the structure of the varistor 1 which concerns on this embodiment is demonstrated. The varistor 1 includes a varistor element body 10, a first external electrode 20, a second external electrode 25, a first internal electrode 30, a second internal electrode 35, a first conductor portion 40, And a second conductor portion 45. The varistor 1 having such a configuration has a substantially rectangular parallelepiped shape as a whole. In this embodiment, for example, the length in the X-axis and Y-axis directions is about 250 μm, and the thickness in the Z-axis direction is about 150 μm. It is a varistor with a small and low profile.

  The varistor element body 10 has a rectangular parallelepiped shape, and has first and second main faces 10a and 10b, first and second side faces 10c and 10d, and third and fourth side faces 10e and 10f. ing. The first and second main surfaces 10a and 10b have a square shape in which both sides extending in the X-axis direction and the Y-axis direction have the same length, and are opposed to each other. The first and second side surfaces 10c and 10d extend in the X-axis direction and face each other so as to connect the first and second main surfaces 10a and 10b. The third and fourth side surfaces 10e and 10f extend in the Y-axis direction and face each other so as to connect the first and second main surfaces 10a and 10b.

  The varistor element body 10 is a sintered body made of a semiconductor ceramic and exhibiting voltage non-linear characteristics (varistor characteristics). The varistor element body 10 is configured as a laminated body in which a plurality of varistor layers 11 to 17 (see FIG. 3) are laminated. In the actual varistor 1, the plurality of varistor layers 11 to 17 are integrated to such an extent that the boundary between them cannot be visually recognized. The varistor layers 11 to 17 include ZnO (zinc oxide) as a main component, and rare earth metal elements, Co, IIIb group elements (B, Al, Ga, In), Si, Cr, Mo, and alkali metals as subcomponents. It contains simple metals such as elements (K, Rb, Cs) and alkaline earth metal elements (Mg, Ca, Sr, Ba) and oxides thereof. The thickness of the varistor layers 11 to 17 is, for example, 5 to 60 μm.

  The first external electrode 20 is disposed on the first main surface 10 a so as to cover substantially the entire surface of the first main surface 10 a of the varistor element body 10. The first external electrode 20 has a substantially square shape when viewed from the Z-axis direction where the first and second main surfaces 10a and 10b are opposed to each other, and has a predetermined thickness. The first external electrode 20 is multi-layered, and for example, Cu, Ni, Ag—Pd or the like is used for the inner layer in contact with the varistor element body 10, and for example, Ni plating or Au is used for the outer layer. Plating is applied.

  The second external electrode 25 is disposed on the second main surface 10 b so as to cover substantially the entire surface of the second main surface 10 b of the varistor element body 10. The second external electrode 25 has a substantially square shape when viewed from the Z-axis direction and has a predetermined thickness. The second external electrode 25 is disposed so as to face the first external electrode 20 in the Z-axis direction with the varistor element body 10 interposed therebetween. The second external electrode 25 is made of the same material as that of the first external electrode 20. The first and second external electrodes 20 and 25 are electrically and mechanically connected to the first and second conductor portions 40 and 45, respectively.

  As shown in FIGS. 2 and 3, the first and second internal electrodes 30 and 35 are a pair of internal electrodes, and the Z-axis direction so as to sandwich the varistor layer 14 constituting the varistor element body 10. The varistor element body 10 is disposed in a state of facing the varistor. As shown in FIG. 5, the first and second inner electrodes 30, 35 have a square shape with a side length L <b> 2, and the planes of the first and second outer electrodes 20, 25 ( The length of one side is slightly smaller than L1).

  That is, the first and second internal electrodes 30 and 35 have an area B between 20% and 92% of the area A, where A is the area (L1 × L1) of the external electrodes 20 and 25. Preferably, the size is such that the area B is between 50% and 92% of the area A. Thus, since the area of the internal electrodes 30 and 35 is large, the electrostatic capacity can be increased and the clamp voltage can be suppressed. Further, as described above, since the first internal electrodes 30 and 35 have a configuration in which only the varistor layer 14 is sandwiched therebetween, this configuration also increases the capacitance and suppresses the clamp voltage. Is possible. The first and second internal electrodes 30 and 35 are formed using Ag, Ag-Pd, Au, or the like as a main component.

  The first conductor portion 40 is an electrode portion that electrically connects the first external electrode 20 and the first internal electrode 30 in the varistor element body 10. The first conductor portion 40 includes a through-hole electrode 42 extending in the Z direction and a relay electrode 41 that connects the through-hole electrodes 42 to each other.

  The through-hole electrode 42 is an electrode filled in a taper-shaped through-hole provided at substantially the center of the varistor layers 11 to 13, and the through-hole electrode 42 extends in the direction from the first main surface 10a to the second main surface 10b. It has a frustoconical shape (tapered shape) with a gradually decreasing diameter. The relay electrode 41 has a circular shape extending in the XY plane direction intersecting the Z-axis direction and has a predetermined thickness. The through-hole electrodes 42 and the relay electrodes 41 are alternately arranged along the Z-axis direction, and are electrically and mechanically connected to each other. The relay electrode 41 on the first main surface 10 a side is connected to the first external electrode 20, and the through-hole electrode 42 on the second main surface 10 b side is connected to the first internal electrode 30.

  Further, the through-hole electrode 42 and the relay electrode 41 are arranged so that their centers substantially overlap when viewed from the Z-axis direction. Note that the diameter D1 (see FIG. 5) of the relay electrode 41 is, for example, about 50 μm, and is formed larger than the diameter of the through-hole electrode 42. Therefore, the through-hole electrodes 42 are temporarily shifted from each other in the XY axis direction. Even in the case of being closed, the connection of the through-hole electrode 42 is not hindered. For this reason, the relay electrode 41 ensures the electrical connection between the first external electrode 20 and the first internal electrode 30.

  The second conductor portion 45 is an electrode portion that electrically connects the second external electrode 25 and the second internal electrode 35 in the varistor element body 10. The second conductor portion 45 includes a through-hole electrode 47 extending in the Z direction and a relay electrode 46 that connects the through-hole electrodes 47.

  The through-hole electrode 47 is an electrode filled in a taper-shaped through-hole provided substantially at the center of the varistor layers 15 to 17. Like the through-hole electrode 42, the through-hole electrode 47 extends from the first main surface 10 a to the second through-hole electrode 47. It has a truncated cone shape whose diameter gradually narrows in the direction toward the main surface 10b. Similar to the relay electrode 41, the relay electrode 46 has a circular shape extending in the XY plane direction intersecting the Z-axis direction, and has a predetermined thickness. The through-hole electrodes 47 and the relay electrodes 46 are alternately arranged along the Z-axis direction and are electrically and mechanically connected to each other. The relay electrode 46 on the second main surface 10 b side is connected to the second external electrode 25, and the through-hole electrode 47 on the first main surface 10 a side is connected to the second internal electrode 35.

  Further, the through-hole electrode 47 and the relay electrode 46 are arranged so that their centers substantially overlap when viewed from the Z-axis direction, like the first conductor portion 40. Further, since the diameter of the relay electrode 46 is formed larger than the diameter of the through-hole electrode 47, even if the through-hole electrodes 47 are displaced from each other in the XY axis direction, There is no problem in connection. The through-hole electrodes 42 and 47 and the relay electrodes 41 and 46 are made of substantially the same material as the internal electrode 30 and the like.

  In the present embodiment, the first and second conductor portions 40 and 45 are composed of three through-hole electrodes 41 and 46 and three relay electrodes 42 and 47, depending on the thickness of the varistor 1. The number may be increased or decreased, but is not limited thereto.

  As shown in FIGS. 1 and 4, the varistor 1 having such a configuration further includes a recess 50 that is recessed in the Z-axis direction in the first external electrode 20. The recess 50 has an inverted frustoconical shape, the size of the bottom surface of the recess 50 corresponds to the circular shape of the through-hole electrode 42, and the size of the surface on the opening side of the recess 50 is a circle of the relay electrode 41. It corresponds to the shape. The recess 50 is formed at substantially the center of the first external electrode 20 and substantially overlaps the first and second conductor portions 40 and 45 when viewed from the Z-axis direction.

  Then, the manufacturing method of the varistor 1 mentioned above is demonstrated.

  First, ZnO which is a main component constituting each varistor layer 11 to 17 of the varistor element body 10, and a small amount of additive such as Pr, Co, Cr, Ca, Si, K and Al metals or oxides are predetermined. After weighing each so as to obtain a ratio, each component is mixed to prepare a varistor material. Thereafter, an organic binder, an organic solvent, an organic plasticizer, and the like are added to the varistor material, and mixed and pulverized for about 20 hours using a ball mill or the like to obtain a slurry.

Next, this slurry is applied onto a film made of, for example, polyethylene terephthalate (PET) by a known method such as a doctor blade method and dried to form a film having a predetermined thickness. Next, through holes for filling the through hole electrodes 42 and 47 are formed at predetermined positions of the film using a CO ₂ laser or the like. When forming a through hole using a CO ₂ laser or the like, in this embodiment, the formed through hole has a tapered shape in which the opening on the near side on the laser irradiation side is wide and gradually narrows toward the back. Processing is performed as follows. The film with through holes thus obtained is peeled from the PET film, and green sheets corresponding to the varistor layers 11 to 17 are obtained.

  Next, electrode patterns corresponding to the through-hole electrodes 42 and 47, the relay electrodes 41 and 46, and the internal electrodes 30 and 35 are formed on the green sheets corresponding to the varistor layers 11 to 17 so as to have the configuration shown in FIG. Form each one. These electrode patterns are formed by printing a conductive paste, in which an organic binder and an organic solvent are mixed in a metal powder containing Ag particles as a main component, on a green sheet corresponding to the varistor layers 11 to 17 and drying it. . When the electrode patterns corresponding to the relay electrodes 41 and 46 are printed, the electrode patterns corresponding to the through-hole electrodes 42 and 47 are also formed together.

  Next, a green sheet for the varistor layers 11 to 13 on which electrode patterns corresponding to the relay electrode 41 and the through-hole electrode 42 are formed, and varistor layers 14 to 15 on which electrode patterns corresponding to the internal electrodes 30 and 35 are formed. 3 and the green sheets for varistor layers 16-17 on which electrode patterns corresponding to the relay electrode 46 and the through-hole electrode 47 are formed are stacked in the order shown in FIG. 3 to form a sheet laminate. To do. And the obtained sheet | seat laminated body is cut | disconnected per chip | tip, and the some divided | segmented green body is obtained.

  Next, the divided green body is subjected to a heat treatment at a temperature of 180 to 400 ° C. for about 0.5 to 24 hours to perform binder removal. Thereafter, baking is further performed at a temperature of 850 to 1400 ° C. for about 0.5 to 8 hours. As a result, a sintered laminate including the varistor element body 10, the first and second internal electrodes 30, 35, and the first and second conductor portions 40, 45 is obtained. During the heat treatment and firing described above, the conductive paste for the through-hole electrodes 42 and 47 filled in the tapered through-holes is thermally contracted and slightly pulled below the taper, and thus sintered. A recessed portion corresponding to the recessed portion 50 is formed on the laminate.

  Next, a conductive paste such as Cu is applied to the first and second main surfaces 10a and 10b of the varistor element body 10 so as to cover substantially the entire main surfaces 10a and 10b. Thereafter, the applied conductive paste is baked, and further Ni plating or Au plating is performed, whereby the first and second external electrodes 20 and 25 are formed. Since the recessed part has already been formed on the sintered laminate, the recessed part 50 is also formed by applying the conductive paste described above. Thus, the varistor 1 having the recess 50 is completed.

  As described above, the varistor 1 according to the present embodiment has the recess 50 on the first main surface 10a side that is terminal-connected by wire bonding or the like. For this reason, when the metal used for wire bond connection or the solder used for solder connection is melted, the melt easily accumulates in the recess 50, and the position of the terminal connection by wire bonding or the like is facilitated. The electrical connection can be ensured.

  In addition, since metal or solder used for wire bonding or the like enters the recess 50 in a melted state, they are firmly connected by the anchor effect, and the electrical connection of the varistor 1 can be made more reliable. it can.

  Further, in the varistor 1, the first conductor portion 40 and the concave portion 50 are disposed so as to substantially overlap each other when viewed from the Z-axis direction. For this reason, when performing terminal connection by wire bonding or the like, the first conductor portion 40 having higher flexibility than the varistor element body 10, the mechanical load applied during the connection work can be absorbed. It is possible to prevent cracks from occurring in the varistor element body 10 or the like.

  In the varistor 1, the first and second conductor portions 40 and 45 have tapered through-hole electrodes 42 and 47 whose diameters are narrowed in the direction from the first main surface 10a to the second main surface 10b. Have. For this reason, the center of the conductor parts 40 and 45 becomes easy to dent, and the recessed part 50 can be easily provided in the 1st main surface 10a side using this.

  In the varistor 1, the first and second conductor portions 40 and 45 have relay electrodes 41 and 46 that extend in the XY plane direction intersecting the Z-axis direction and connect the through-hole electrodes 42 and 47. . For this reason, the connection of the through-hole electrodes 42 and 47 can be ensured. Further, since the relay electrodes 41 and 46 spread in the surface direction, the heat dissipation effect of the varistor 1 can also be enhanced. For example, the heat dissipation effect when heat is generated in the varistor 1 by the introduction of ESD is increased. Degradation of varistor characteristics can also be suppressed.

  Here, the light-emitting device 60 provided with the varistor 1 mentioned above is demonstrated easily. As shown in FIG. 6, the light emitting device 60 includes an LED chip 61 (light emitting element) and the varistor 1 described above, and the LED chip 61 and the varistor 1 are mounted on an alumina substrate 62. . In this light emitting device 60, since the LED chip 61 and the varistor 1 are electrically connected in parallel, the LED chip can be protected from an ESD surge, and the varistor 1 can be reduced in size and height. Therefore, the light emission of the LED chip is not hindered. In addition, as described above, when the varistor 1 is to be connected by the wire W or the like, the distal end portion of the wire W can be easily positioned using the recess 50 of the varistor 1, so that the electrical connection of the varistor 1 is ensured. It can also be.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the above-described embodiments, and various modifications are possible. For example, in the embodiment described above, the taper directions of the through-hole electrodes 42 and 47 constituting the first and second conductor portions 40 and 45 are the same, but as shown in FIG. By reversing the taper direction of the through-hole electrode 47a of 45a, the first and second conductor portions 40, 45a are connected to the first and second internal electrodes 30, from the first and second main surfaces 10a, 10b, respectively. You may make it have the taper-shaped through-hole electrodes 42 and 45a whose diameter becomes narrow in the direction which goes to 35. FIG.

  If the through-hole electrodes 42 and 45a are arranged in this way, the second external electrode 25 of the varistor 1a can be easily configured to have a recess 52 that is recessed in the Z-axis direction. Thus, by providing the recesses 50 and 52 in both the first and second external electrodes 20 and 25, the varistor 1a can be electrically connected regardless of the terminal connection to any of the external electrodes 20 and 25. Since it can be performed reliably, handling of the varistor 1a becomes easy.

DESCRIPTION OF SYMBOLS 1,1a ... Varistor, 10 ... Varistor element body, 20, 25 ... External electrode, 30, 35 ... Internal electrode, 40, 45, 45a ... Conductor part, 41, 46 ... Relay electrode, 42, 47, 47a ... Through-hole Electrode, 50, 52 ... concave portion, 60 ... light emitting device, 61 ... LED chip.

Claims (7)

A varistor element body that exhibits voltage non-linear characteristics and has opposing first and second main surfaces;
First and second internal electrodes disposed in the varistor element body so as to sandwich a part of the varistor element body and facing in the opposing direction of the first and second main surfaces;
A first external electrode disposed on the first main surface;
A second external electrode disposed on the second main surface;
A first conductor portion that electrically connects the first internal electrode and the first external electrode;
A second conductor portion that electrically connects the second internal electrode and the second external electrode, and
The varistor is characterized in that the first external electrode has a first recess recessed in a direction opposite to the first and second main surfaces.   The first conductor portion and the first recess are arranged so that at least a part thereof is overlapped when viewed from the opposing direction of the first and second main surfaces. Item 2. A varistor according to item 1.   The said 1st and 2nd conductor part has a taper-shaped through-hole electrode from which a diameter becomes narrow in the direction which goes to a said 2nd main surface from the said 1st main surface. The varistor according to 1 or 2.   The first and second conductor portions have tapered through-hole electrodes whose diameters are narrowed in a direction from the first and second main surfaces to the first and second internal electrodes, respectively. The varistor according to claim 1 or 2, characterized by the above.   At least one of the first and second conductor portions has a relay electrode that extends in a plane direction intersecting the opposing direction of the first and second main surfaces and connects the through-hole electrodes. The varistor according to claim 3 or 4, wherein   The varistor according to any one of claims 1 to 5, wherein the second external electrode has a second recess that is recessed in a direction opposite to the first and second main surfaces. . A light emitting device comprising the varistor according to claim 1 and a light emitting element connected in parallel to the varistor.

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