WO2013175795A1

WO2013175795A1 - Varistor and method of manufacturing same

Info

Publication number: WO2013175795A1
Application number: PCT/JP2013/003274
Authority: WO
Inventors: 清水　基尋; 富岡　聡志; 吉田　則隆; 一郎亀山; 奥田　和弘
Original assignee: パナソニック株式会社
Priority date: 2012-05-25
Filing date: 2013-05-23
Publication date: 2013-11-28
Also published as: JP2015156406A

Abstract

A varistor has a varistor layer, a pair of internal electrodes, a pair of external electrodes, and a first insulation layer. The varistor layer has zinc oxide as the main component and has a first surface and a second surface opposite the first surface. The internal electrodes are provided within the varistor layer. The external electrodes are respectively connected to the internal electrodes and are provided outside the varistor layer. The first insulation layer is provided on the first surface of the varistor layer and has Gahnite as the main component.

Description

Varistor and manufacturing method thereof

The present invention relates to a varistor suitable for protecting an electronic device from static electricity and a manufacturing method thereof, and more particularly to a varistor functioning as a substrate for mounting an LED (light emitting diode) or a semiconductor.

In recent years, with the rapid progress of miniaturization and low power consumption of electronic devices, the withstand voltage of various electronic components constituting the circuit of electronic devices has been reduced. For this reason, when an electrostatic pulse or the like enters a conduction portion of an electronic device, various electronic components, particularly semiconductor devices, are easily destroyed.

Such semiconductor devices mainly include LEDs. LEDs are being studied for application in many products such as general lighting fixtures, backlights for televisions, strobe light sources for cameras, and the like, and demand is expected to increase in the future. In the future, LEDs are required to have higher brightness and higher output, and at the same time, LED packages are required to further improve heat dissipation.

As such an LED package, a module having a built-in varistor part and provided with a function for preventing static electricity is known. This LED package includes a ceramic substrate made of low-temperature fired glass ceramics (LTCC) and a varistor portion that is simultaneously fired integrally with the ceramic substrate (for example, Patent Document 1).

International Publication No. 2006/106717

The present invention is a varistor excellent in heat dissipation characteristics and a method for manufacturing the same. The varistor of the present invention includes a varistor layer, a pair of internal electrodes, a pair of external electrodes, and a first insulating layer. The varistor layer is mainly composed of zinc oxide, and has a first surface and a second surface opposite to the first surface. The internal electrode is provided inside the varistor layer. The external electrodes are respectively connected to the internal electrodes and provided outside the varistor layer. The first insulating layer is provided on the first surface of the varistor layer and contains garnite as a main component. Thus, it is excellent in heat dissipation by making garnite as a main component at least as the first insulating layer on one surface of the varistor layer.

FIG. 1 is a schematic cross-sectional view of a varistor in an embodiment of the present invention. FIG. 2A is a schematic cross-sectional view showing the procedure for manufacturing the varistor in the embodiment of the present invention. FIG. 2B is a schematic cross-sectional view showing the manufacturing procedure following FIG. 2A. FIG. 2C is a schematic cross-sectional view showing the manufacturing procedure following FIG. 2B. FIG. 2D is a schematic cross-sectional view showing the manufacturing procedure following FIG. 2C. FIG. 3 is a characteristic diagram showing the X-ray diffraction measurement result of the first insulating layer in the varistor shown in FIG. FIG. 4 is a graph showing the line distribution of the bismuth element concentration and the manganese element concentration of the first insulating layer and the second varistor layer of the varistor in the present invention.

Prior to the description of the embodiment of the present invention, problems in the conventional configuration will be briefly described. Generally, the thermal conductivity of the glass component is low. For this reason, the conventional configuration cannot sufficiently dissipate the heat generated during the operation of the LED. This heat affects the operation of the LED and also the varistor characteristics, and as a result, the reliability of the LED decreases.

Hereinafter, the varistor 8 according to the embodiment of the present invention will be described. FIG. 1 is a sectional view of the varistor 8. Hereinafter, as the varistor 8 in the present embodiment, a ceramic substrate in which a varistor function is incorporated in a substrate for mounting an LED such as a semiconductor will be described as an example.

The varistor 8 includes a varistor layer 2, a pair of internal electrodes 14, a pair of external electrodes such as a terminal electrode 7 and a main surface electrode 6, and the first insulating layer 1. The varistor layer 2 contains zinc oxide as a main component, and has a first surface 2C and a second surface 2D opposite to the first surface 2C. The internal electrode 14 is provided inside the varistor layer 2. The terminal electrode 7 is connected to the internal electrode 14 and provided outside the varistor layer 2. The first insulating layer 1 is provided on the first surface 2C of the varistor layer 2 and contains garnite as a main component. That is, the first insulating layer 1 has a first surface 1A in contact with the first surface 2C of the varistor layer 2, and a second surface 1B opposite to the first surface 1A. The “main component” in the first insulating layer 1 means that the occupation ratio is 70% by weight or more, and the “main component” in the varistor layer 2 means that the occupation ratio is 80% by weight or more. .

Generally, the main components of LTCC used in conventional varistors are alumina and a glass component having low thermal conductivity. The thermal conductivity of LTCC is about 2 to 3 W / m · K. On the other hand, the thermal conductivity of garnite, which is the main component of the first insulating layer 1, is 18 W / m · K. Thus, by having the 1st insulating layer 1 which contains garnite whose thermal conductivity is remarkably higher than LTCC as a main component, the varistor 8 is more excellent in heat dissipation and reliability than the conventional varistor.

Next, the configuration of the varistor 8 will be further described. As shown in FIG. 1, the varistor layer 2 includes a first varistor layer 2A and a second varistor layer 2B. The first varistor layer 2 </ b> A is a portion that is sandwiched between the internal electrodes 14 and has a varistor function, and the second varistor layers 2 </ b> B are disposed on both surfaces of the first varistor layer 2 </ b> A via the internal electrodes 14. In addition to protecting the first varistor layer 2A, the second varistor layer 2B is a first varistor layer 2A formed by diffusion of other elements when the varistor layer 2 is integrally fired with a layer made of another material, as will be described later. Inhibits composition change.

The first insulating layer 1 is provided on the first surface 2C, which is one of the main surfaces of the varistor layer 2, and the second insulating layer 3 is provided on the second surface 2D, which is the other main surface. That is, the first insulating layer 1 and the second insulating layer 3 sandwich the varistor layer 2. At least a pair of internal electrodes 14 are provided inside the varistor layer 2.

Each of the internal electrodes 14 is connected to one of the main surface electrodes 6 disposed on the upper surface of the second insulating layer 3 via a via electrode 5 penetrating the first insulating layer 1, the varistor layer 2, and the second insulating layer 3. The terminal electrode 7 disposed on the lower surface of the first insulating layer 1 is electrically connected. A semiconductor device such as an LED is mounted on the upper surface of the main surface electrode 6, and the terminal electrode 7 functions as an electrode for mounting the varistor 8 on the main substrate. The main surface electrode 6 may be provided on the lower surface of the first insulating layer 1 and the terminal electrode 7 may be provided on the upper surface of the second insulating layer 3, which are not particularly limited.

The varistor layer 2 comprises zinc oxide at 80 wt% or more, bismuth oxide as an accessory component at 0.5 wt% or more and 2.1 wt% or less, manganese oxide at 0.4 wt% or more, 0.5 wt% or less, It is formed by mixing and baking antimony oxide in an amount of 1.0 wt% or more and 1.6 wt% or less and cobalt oxide in an amount of 1.0 wt% or more and 1.4 wt% or less. With this material composition, excellent varistor characteristics can be exhibited, and the main component of the first insulating layer 1 can be garnite. Specifically, the garnite of the first insulating layer 1 has a much higher thermal conductivity than the conventional LTCC, and is advantageous in terms of higher brightness and higher output required for LED lighting and the like in the future.

The second insulating layer 3 is preferably composed of, for example, a baked substrate (hereinafter, rigid substrate) mainly composed of alumina. Alternatively, the second insulating layer 3 is preferably configured in the same manner as the first insulating layer 1. That is, the main component of the second insulating layer 3 is preferably garnite. These effects will be described later.

Next, a method for manufacturing the varistor 8 will be described with reference to FIGS. 2A to 2D. First, as shown in FIG. 2A, a hole for forming the via electrode 5 is formed by laser in a rigid substrate 23 mainly composed of alumina to be the second insulating layer 3, and a via electrode paste ( Hereinafter, paste 24 is filled.

Next, zinc oxide, bismuth oxide, manganese oxide and antimony oxide, a binder resin, a plasticizer, and a solvent are blended, and then mixed and dispersed to prepare a slurry for the varistor sheet 12. Next, the varistor sheet 12 slurry is applied by a doctor blade method onto a film of polyethylene terephthalate (PET) or the like and dried to produce the varistor sheet 12. At that time, the internal electrode paste 13 is screen-printed on a predetermined number of varistor sheets 12. A hole for forming the via electrode 5 is formed in the varistor sheet 12 by a mechanical puncher method, and the paste 24 is filled in the hole by screen printing. Thereafter, as shown in FIG. 2B, the varistor sheet 12 is laminated on the upper surface of the rigid substrate 23 so as to have a predetermined laminated structure. At that time, the paste 24 filled in the rigid substrate 23 and the paste 24 filled in each varistor sheet 12 are arranged so as to be connected.

Next, an aluminum oxide powder, a binder resin, a plasticizer, and a solvent are blended and mixed and dispersed to prepare a slurry for the first ceramic sheet 11. The main component of the first ceramic sheet 11 is aluminum oxide, and the blending amount thereof is 80% by weight or more with respect to the total amount of the first ceramic sheet 11. Next, the first ceramic sheet 11 is produced by applying a slurry for the first ceramic sheet 11 on the PET film by a doctor blade method and drying it. Similarly to the varistor sheet 12, a hole for forming the via electrode 5 is formed in the first ceramic sheet 11 by a mechanical puncher method, and a paste 24 is filled in the hole by screen printing. Thereafter, a predetermined number of the first ceramic sheets 11 are laminated on the upper surface of the varistor sheet 12 in the laminate shown in FIG. 2B to produce the laminate shown in FIG. 2C. At that time, the paste 24 filled in the varistor sheet 12 and the paste 24 filled in the first ceramic sheet 11 are arranged so as to be connected. That is, in this laminated body, the first ceramic sheet 11 is provided on the first surface of the varistor sheet 12, and the rigid substrate 23 is provided on the second surface opposite to the first surface of the varistor sheet 12. In addition, since the adhesiveness between sheets improves by laminating | stacking the 1st ceramic sheet | seat 11 and the varistor sheet | seat 12, it is preferable.

Next, as shown in FIG. 2D, a terminal electrode paste (hereinafter referred to as paste) 16 is applied to the upper surface of the first ceramic sheet 11 so as to be connected to the end of the paste 24. Further, a main surface electrode paste (hereinafter referred to as paste) 15 is applied to the lower surface of the rigid substrate 23. The pastes 15 and 16 can be applied by screen printing. Note that the

pastes

15 and 16 may be applied in advance when the sheet is manufactured before the laminate shown in FIG. 2C is formed.

Next, the laminate shown in FIG. 2D is heated to a temperature of about 400 ° C. to 600 ° C. to remove the binder, and then fired at a temperature of 950 ° C. or higher and 1050 ° C. or lower. That is, the laminate of the rigid substrate 23, the varistor sheet 12, the internal electrode paste 13, and the first ceramic sheet 11 is integrally fired at a predetermined temperature. Thereby, as shown in FIG. 1, the 2nd insulating layer 3, the varistor layer 2, a pair of internal electrode 14, and the 1st insulating layer 1 are formed. At that time, the zinc element of zinc oxide contained in the varistor sheet 12 diffuses into the first ceramic sheet 11 and reacts with the aluminum element of aluminum oxide contained in the first ceramic sheet 11 to produce garnite. As a result, the first insulating layer 1 contains garnite as a main component.

Thus, the 1st ceramic sheet | seat 11 which has an aluminum oxide powder as a main component, and the varistor sheet | seat 12 which has a zinc oxide as a main component are integrally baked, a garnite produces | generates and 1st with high heat conductivity. The insulating layer 1 can be formed. In addition, by providing the second insulating layer 3 as described above, a further excellent varistor 8 can be produced.

In addition, the terminal electrode 7 and the main surface electrode 6 can also be formed by the plating method after baking the laminated body shown to FIG. 2D.

As described above, by forming the second insulating layer 3 using the rigid substrate 23, it is possible to suppress the shrinkage in the planar direction that occurs when the first ceramic sheet 11 and the varistor sheet 12 are integrally fired. . Therefore, the dimensional accuracy of the varistor 8 can be improved.

Similarly to the first ceramic sheet 11, a sheet composed of an aluminum oxide powder and a binder resin, a plasticizer and a solvent is produced, and the varistor sheet 12 is sandwiched between the sheet and the first ceramic sheet 11. Thus, it may be integrally fired simultaneously. Thereby, the 2nd insulating layer 3 which contains garnite as a main component like the 1st insulating layer 1 can be formed. Thus, when the 1st insulating layer 1 and the 2nd insulating layer 3 contain garnite as a main component, the curvature by the difference in the shrinkage | contraction behavior at the time of baking of the 1st insulating layer 1 and the 2nd insulating layer 3 will be shown. Can be suppressed, which is preferable. Moreover, since the heat conductivity on both surfaces of the varistor layer 2 improves, it is preferable. In this case, for example, instead of using the rigid substrate 23, a plurality of sheets formed in the same manner as the first ceramic sheet 11 are laminated to produce the configuration shown in FIG. 2A. Good.

Next, the subcomponents in the varistor sheet 12 for forming the varistor layer 2 will be specifically described. The subcomponent is for causing the varistor layer 2 to function as a varistor and has the following effects. The melting point of bismuth oxide contained in the varistor sheet 12 is about 830 ° C., and if it is a eutectic composition with manganese oxide, a liquid phase is formed at a lower temperature of about 790 ° C. Therefore, when firing at about 1000 ° C., a liquid phase is formed and diffused to the first ceramic sheet 11 that becomes the first insulating layer 1. Due to this diffusion, zinc oxide in the varistor sheet 12 diffuses into the first ceramic sheet 11. And the aluminum oxide and zinc oxide of the 1st ceramic sheet | seat 11 react, and a garnite is formed. Also, the sinterability of the first insulating layer 1 itself is improved. Thus, the coexistence of manganese oxide and bismuth oxide is preferable because liquid phase formation is promoted and garnite formation is likely to proceed.

The first ceramic sheet 11 preferably contains niobium oxide. As a result, the first insulating layer 1 preferably contains niobium. The niobium oxide in the first ceramic sheet 11 has an effect of attracting the bismuth element diffused from the varistor sheet 12. Therefore, it indirectly contributes to garnite formation.

Hereinafter, the effects of the present embodiment will be described using specific examples.

First, when the total weight of the solid content of the varistor sheet 12 is 100% by weight, 88.4% by weight of the main component zinc oxide, 5.2% by weight of bismuth oxide as subcomponents, and 1.0% of manganese oxide. % By weight, 1.6% by weight of antimony oxide, and 1.9% by weight of cobalt oxide. Furthermore, a binder resin, a plasticizer, and a solvent are mixed and dispersed to prepare a slurry for the varistor sheet 12. This slurry is molded and dried to produce a varistor sheet 12.

Similarly, when the ceramic component of the first ceramic sheet 11 is 100% by weight, aluminum oxide is 90.0% by weight, manganese oxide is 2.0% by weight, bismuth oxide is 6.0% by weight, and niobium oxide is 2%. Each is blended at a ratio of 0.0% by weight. Further, a binder resin, a plasticizer, and a solvent are mixed and dispersed to prepare a slurry for the first ceramic sheet 11. The slurry is molded and dried to produce the first ceramic sheet 11.

As the second insulating layer 3, a rigid substrate 23, which is an aluminum oxide substrate, is used, and a varistor sheet 12 and a first ceramic sheet 11 are laminated to produce a laminate shown in FIG. 2C. The thickness of the varistor sheet 12 is 25 μm, the thickness of one of the first ceramic sheets 11 is 40 μm, and the thickness of the rigid substrate 23 is 180 μm. In order to form a laminated body, six varistor sheets 12 and one first ceramic sheet 11 are laminated. The breakdown of the six varistor sheets 12 includes two sheets for forming the first varistor layer 2A, two sheets for forming the second varistor layer 2B on the first varistor layer 2A, and the first varistor layer. Two sheets for forming the second varistor layer 2B under 2A.

The paste 24 for producing the pair of internal electrodes 14 provided in the varistor sheet 12, the first ceramic sheet 11, and the rigid substrate 23 contains an Ag—Pd alloy in which Ag is 80% and Pd is 20%.

Next, as shown in FIG. 2D, pastes 15 and 16 are applied to the laminate, and then the laminate is subjected to binder removal treatment at 600 ° C. for 2 hours, and then fired at 1000 ° C. for 2 hours. In this way, the varistor 8 is manufactured.

The vertical and horizontal dimensions of the varistor 8 after firing are 2.0 mm × 2.0 mm, the thickness of the first insulating layer 1 is 40 μm, the thickness of the first varistor layer 2A in the varistor layer 2 is 50 μm, and the second varistor layer 2B The thickness is 50 μm.

FIG. 3 shows the result of X-ray diffraction measurement in the first insulating layer 1. The detection peak is almost garnite (black circle), and other peaks that are thought to be a complex oxide of niobium and bismuth (white circle) are detected. In addition, it is estimated that the peak contained in the first insulating layer 1 cannot be detected because the manganese is amorphous with bismuth or the like.

In addition, as a result of performing energy dispersive X-ray analysis (EDS analysis) on the surface of the first insulating layer 1, the garnite content in the first insulating layer 1 is 100% by weight of the entire first insulating layer 1. 85% by weight. In the EDS analysis, the surface voltage of the entire visual field is analyzed with an acceleration voltage of 30 kV and an observation magnification of 5000 times.

The main component of the first ceramic sheet 11 that is the starting material of the first insulating layer 1 is aluminum oxide. The sintering temperature of aluminum oxide is about 1500 ° C. However, as described above, the laminate shown in FIG. 2D is sintered at a temperature of 950 ° C. or higher and 1050 ° C. or lower. Therefore, aluminum oxide does not contribute to the sintering of the first insulating layer 1. Therefore, the mechanical strength of the first insulating layer 1 depends on the amount of garnite produced.

The proportion of garnite contained in the first insulating layer 1 depends on the total amount of aluminum oxide contained in the first ceramic sheet 11. Therefore, it is preferable that this aluminum oxide reacts with zinc contained in the second varistor layer 2B and exists as garnite as much as possible. In the above example, the garnite content is 85% by weight, and if it is about this level, the mechanical strength as the varistor 8 is ensured. Moreover, it has been confirmed that there is no problem even at 80% by weight. Ideally, however, the aluminum element is preferably present in the first insulating layer 1 as garnite instead of aluminum oxide.

Next, the sinterability of the first insulating layer 1 in the varistor 8 and the elution degree of the first insulating layer 1 by the plating solution when the terminal electrode 7 and the main surface electrode 6 are formed by a plating method are examined. Sinterability and elution degree depend on the thickness of the first insulating layer 1. Therefore, the thickness of the first varistor layer 2A is fixed to 50 μm, the thickness of the second varistor layer 2B is fixed to 50 μm, the thickness of the first insulating layer 1 is changed, and the sinterability and the elution degree are measured. The manufacturing method of the varistor 8 is the same as that of the varistor 8 described above. Here, “thickness” means a dimension in a direction perpendicular to the first surface 2 </ b> C of the varistor layer 2.

In order to measure the sinterability of the first insulating layer 1, the varistor 8 having a different thickness of the first insulating layer 1 is sufficiently dried to measure the dry weight, and the dried varistor 8 is defoamed in water. After that, the water content is measured. Then, the difference between the moisture content and the dry weight is calculated as the water absorption rate. Since the water absorption is contrary to the sinterability, it can be determined that the sinterability is high if the water absorption is small.

In order to measure the elution degree of the first insulating layer 1, the varistor 8 after measuring the water absorption rate is immersed in the plating solution for 30 minutes, then washed and dried to measure the weight. Then, the weight loss rate before and after immersion of the plating solution is calculated. The weight loss rate determined in this way is used as an index of elution degree. (Table 1) shows the measurement results.

Generally, the water absorption rate of a ceramic that has been sufficiently sintered and densified is 0.1% or less. If the water absorption is 0.1% or less, there is no moisture penetration into the interior, and the varistor 8 can be used with sufficiently high reliability. On the other hand, when the water absorption rate exceeds 0.1%, the reliability in a high-temperature and high-humidity environment is a concern. On the other hand, even if the water absorption after firing is 0.1% or less, if the degree of elution into the plating solution, that is, the weight loss rate of the first insulating layer 1 is high, the strength of the first insulating layer 1 decreases during plating. The reliability of the varistor 8 is a concern.

As shown in Sample B to Sample K in Table 1, if the thickness of the first insulating layer 1 is 25 μm or more and 65 μm or less, the water absorption rate in the first insulating layer 1 is 0.1% or less and low weight loss The high-reliability varistor 8 can be manufactured.

As described above, bismuth oxide and manganese oxide contained in the varistor sheet 12 to be the second varistor layer 2B form a liquid phase in the firing process and contribute to densification of the varistor layer 2. In addition, the liquid phase diffuses and moves to the first ceramic sheet 11 which becomes the first insulating layer 1 in a state containing the zinc component, and contributes to densification of the first insulating layer 1.

However, when the thickness of the first insulating layer 1 is larger than 65 μm like the sample L, the liquid phase diffusing from the varistor sheet 12 to the first ceramic sheet 11 reaches the surface of the first insulating layer 1 in the firing process. do not do. For this reason, it is presumed that the surface layer of the first insulating layer 1 is not sufficiently densified and voids are formed and moisture enters.

On the other hand, when the thickness of the first insulating layer 1 is less than 25 μm, the liquid phase that diffuses from the varistor sheet 12 to the first ceramic sheet 11 becomes excessive during the firing process. Therefore, an extreme liquid phase float occurs on the surface of the first insulating layer 1. As a result, this liquid phase is eluted into the plating solution, and the weight loss rate in the first insulating layer 1 is considered to increase. As described above, the thickness of the first insulating layer 1 in the direction perpendicular to the first surface 2C of the varistor layer 2 is preferably 25 μm or more and 65 μm or less. As described above, the lower limit of the thickness of the first insulating layer 1 is a value when the main surface electrode 6 and the terminal electrode 7 are formed by plating. Therefore, when these electrodes are formed by paste printing, the lower limit of the thickness of the first insulating layer 1 may not be this value.

As described above, the sinterability of the first insulating layer 1 can be evaluated by the concentration distribution of the bismuth element and the manganese element. In the first insulating layer 1, it is preferable that the bismuth element and the manganese element are uniformly distributed in the first insulating layer 1 so as to have a constant concentration.

In order to obtain sufficient sinterability, the concentration of the bismuth element and manganese element on the second surface 1B of the first insulating layer 1 is such that the concentration of bismuth element and manganese element on the first surface 1A of the first insulating layer 1 It is preferable that it is more than the concentration.

The liquid phase component contained in the varistor sheet 12 to be the varistor layer 2 crosses the interface between the varistor sheet 12 and the first ceramic sheet 11 and sufficiently reaches the entire first ceramic sheet 11 to ensure sufficient sinterability. Is done. Moreover, garnite is sufficiently formed by zinc diffusion from the varistor sheet 12. As a result, the concentration distribution of bismuth element and manganese element as described above is obtained.

FIG. 4 shows the result of line analysis of the line 4-4 in FIG. 1 by wavelength dispersive X-ray spectroscopy (WDS analysis). The analysis target is the sample G in (Table 1). FIG. 4 shows the concentration distribution of bismuth element and manganese element in the first insulating layer 1 and the second varistor layer 2B. In the WDS analysis, the acceleration voltage is 15 kV.

The first surface 2C of the varistor layer 2 and the first surface 1A of the first insulating layer 1 are in contact with each other. In FIG. 4, the first surface 1A (the first surface 1A (the second surface 1B) having a distance of 50 μm is opposed to and in contact with the first surface 2C of the varistor layer 2 in the first insulating layer 1). Position). As is apparent from FIG. 4, the concentration of the bismuth element and the manganese element on the second surface 1B is equal to or higher than that on the first surface 1A. Therefore, it can be seen that sufficient sinterability is ensured and garnite is formed in the entire first insulating layer 1.

The varistor described above is a ceramic substrate with a built-in varistor function, but the present invention is not limited to this. For example, a chip-type laminated varistor can be applied as a configuration in which the first insulating layer 1 mainly composed of garnite is provided on one surface or both surfaces of the varistor layer 2. That is, the second insulating layer 3 is not necessarily provided. In this case, the main surface electrode 6 may not be provided. That is, the external electrode is an electrode for electrically connecting the varistor 8 to an external substrate or electronic device. When the second insulating layer 3 is not provided, a stacked body may be manufactured without the rigid substrate 23 in FIGS. 2A to 2D.

Further, the configuration of the external electrode is not limited to the terminal electrode 7 or the main surface electrode 6. The internal electrode 14 may be extended to the side surface of the varistor layer 2 to be partially exposed from the varistor layer 2, and the external electrode may be formed on the exposed portion by plating or the like. In this case, the via electrode 5 is not necessary.

The varistor according to the present invention is useful in a semiconductor device or the like, especially in a ceramic substrate or a chip-type multilayer varistor with a built-in varistor of an LED whose brightness and output are increasing.

DESCRIPTION OF SYMBOLS 1 1st insulating layer 1A 1st surface 1B 2nd surface 2 Varistor layer 2A 1st varistor layer 2B 2nd varistor layer 2C 1st surface 2D 2nd surface 3 2nd insulating layer 5 Via electrode 6 Main surface electrode 7 Terminal electrode 8 Varistor 11 First ceramic sheet 12 Varistor sheet 13 Internal electrode paste 14 Internal electrode 15 Main surface electrode paste (paste)
16 Terminal electrode paste (paste)
23 Rigid Substrate 24 Via Electrode Paste

Claims

A varistor layer mainly composed of zinc oxide and having a first surface and a second surface opposite to the first surface;
A pair of internal electrodes provided inside the varistor layer;
A pair of external electrodes respectively connected to the pair of internal electrodes and provided outside the varistor layer;
A first insulating layer provided on the first surface of the varistor layer and mainly composed of garnite;
Barista.
The varistor layer and the first insulating layer include bismuth and manganese as constituent elements,
The varistor layer is
A first varistor layer disposed between the pair of internal electrodes;
A second varistor layer disposed between one of the pair of internal electrodes and the first insulating layer;
The thickness of the first insulating layer in the direction perpendicular to the first surface of the varistor layer is 25 μm or more and 65 μm or less.
The varistor according to claim 1.
The varistor layer and the first insulating layer include bismuth and manganese as constituent elements,
The first insulating layer has a first surface in contact with the varistor layer, and a second surface opposite to the first surface;
The concentration of the bismuth element and the manganese element on the second surface of the first insulating layer is equal to or higher than the concentration of the bismuth element and the manganese element on the first surface of the first insulating layer, respectively.
The varistor according to claim 1.
A second insulating layer provided on the second surface of the varistor layer;
The varistor according to claim 1.
The main component of the second insulating layer is garnite.
The varistor according to claim 4.
The main component of the second insulating layer is alumina.
The varistor according to claim 4.
The first insulating layer includes niobium,
The varistor according to claim 1.
A varistor sheet mainly composed of zinc oxide;
A laminated body of a pair of internal electrode paste provided inside the varistor sheet and a first ceramic sheet mainly composed of aluminum oxide provided on the first surface of the varistor sheet is integrally fired at a predetermined temperature. so,
A varistor layer mainly composed of zinc oxide and having a first surface and a second surface opposite to the first surface;
A pair of internal electrodes provided inside the varistor layer;
Forming a first insulating layer provided on the first surface of the varistor layer and containing garnite as a main component;
Forming a pair of external electrodes respectively connected to the pair of internal electrodes and provided outside the varistor layer,
The garnite, which is the main component of the first insulating layer, is generated by a reaction between zinc contained in the zinc oxide and aluminum contained in the aluminum oxide.
A method for manufacturing a varistor.
A varistor sheet mainly composed of zinc oxide; a pair of internal electrode pastes provided inside the varistor sheet; a first ceramic sheet mainly composed of aluminum oxide provided on the first surface of the varistor sheet; By integrally firing a laminated body with a first ceramic sheet mainly composed of aluminum oxide provided on a second surface opposite to the first surface of the varistor sheet at a predetermined temperature,
A varistor layer mainly composed of zinc oxide and having a first surface and a second surface opposite to the first surface;
A pair of internal electrodes provided inside the varistor layer;
A first insulating layer provided on the first surface of the varistor layer, the main component being garnite;
Forming a second insulating layer provided on the second surface of the varistor layer and containing garnite as a main component;
Forming a pair of external electrodes respectively connected to the pair of internal electrodes and provided outside the varistor layer,
The garnite which is the main component of the first insulating layer and the second insulating layer is generated by a reaction between zinc contained in the zinc oxide and aluminum contained in the aluminum oxide.
A method for manufacturing a varistor.
A varistor sheet mainly composed of zinc oxide;
A pair of internal electrode paste provided inside the varistor sheet; a first ceramic sheet mainly composed of aluminum oxide provided on a first surface of the varistor sheet;
By integrally firing the laminate with the alumina substrate provided on the second surface opposite to the first surface of the varistor sheet at a predetermined temperature,
A varistor layer mainly composed of zinc oxide and having a first surface and a second surface opposite to the first surface; a pair of internal electrodes provided inside the varistor layer;
A first insulating layer provided on the first surface of the varistor layer, the main component being garnite;
Forming a second insulating layer composed of an alumina substrate provided on the second surface of the varistor layer;
Forming a pair of external electrodes respectively connected to the pair of internal electrodes and provided outside the varistor layer,
The garnite, which is the main component of the first insulating layer, is generated by a reaction between zinc contained in the zinc oxide and aluminum contained in the aluminum oxide.
A method for manufacturing a varistor.