JP2018006501A - Electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic component which can reduce the occurrence of a crack in a connection portion with a substrate or the like and which can retain good electrical conductivity.SOLUTION: A multilayer ceramic capacitor 1 comprises: a ceramic elemental body 10; an internal electrode 14 provided in the ceramic elemental body; and an external electrode 20 provided on a surface of the ceramic elemental body. The external electrode includes: a first external electrode layer 22 formed by enameling of metal paste; a second external electrode layer 24 formed on the first external electrode layer, and including a metal component and a resin component; and third external electrode layers 26, 28 formed on the second external electrode layer, and made of plated metal. The second external electrode layer includes: flake-like metal particles of 5-20 μm in diameter; and spherical metal particles of 5-100 nm in average particle diameter. In the second external electrode layer, the resin component is a thermosetting resin.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electronic component, particularly an electronic component using a ceramic material.

  Many electronic parts using ceramic materials such as capacitors and inductors are provided on the surface of the element body so as to be connected to the element body made of the ceramic material, the internal electrode provided inside the element body, and the internal electrode. The external electrode is provided. For such electronic components, conventionally, methods for suppressing cracks in the element body caused by the difference in physical properties between the element body and the external electrode have been studied.

  For example, in Patent Document 1, in a multilayer ceramic capacitor that is an example of an electronic component having the above-described structure, the external electrode has a three-layer structure including first to third external electrode layers from the element body side, and the second external electrode It describes that a layer containing a resin component is provided as a layer and that the bonding strength between the respective layers is within a predetermined range. In this multilayer ceramic capacitor, the occurrence of cracks in the element body hardly occurs due to the external force absorbed by the second conductor layer and the like.

  However, as a result of studies by the present inventors, when a thermal shock is applied to a substrate or the like on which an electronic component is mounted, the degree of expansion and contraction due to heat differs greatly between the substrate and the electronic component. It has been found that stress concentrates on the solder joint with the substrate and cracks are likely to occur. And even if such a crack is generated in the joint portion when a multilayer ceramic capacitor with reduced crack generation in the element body, such as the above-mentioned Patent Document 1, is applied, it is particularly in a severe environment such as in-vehicle use. In many cases, it could not be prevented sufficiently.

When the ratio of the resin component is relatively increased, the stress relaxation capability of the second external electrode layer is improved, so that it is possible to suppress the occurrence of cracks in thermal shock, but the conductivity is reduced. ESR (equivalent series resistance), which is one of important electrical characteristics, deteriorates.

Patent Document 2 describes, as an electronic component structure, an external electrode in which a metal component is a combination of flaky metal particles having a specific surface area of 0.5 to 4 m 2 / g and massive metal particles having an average particle size of 0.1 to 10 μm. Has been. In this electronic component, high conductivity can be secured by a combination of the flaky metal particles and the massive metal particles.

However, since the structure of the electronic component described in Patent Document 2 does not substantially have the first external electrode layer, in particular, in the case of a thin-layer multilayer electronic component, the electrical conductivity between the external electrode and the internal electrode. Connection becomes difficult, and it is difficult to develop electrical characteristics as an electronic component.

JP-A-11-219849 JP-A-10-284342

It is an object of the present invention to provide an electronic component that can reduce the occurrence of cracks at a joint portion with a substrate or the like in thermal shock and has higher conductive connectivity.

A ceramic body, an internal electrode provided inside the ceramic body, a first external electrode layer provided on a surface of the ceramic body and formed by baking a metal paste, and the first external body A second external electrode layer formed on the electrode layer and containing a metal component and a resin component; a third external electrode layer formed on the second external electrode layer and made of a plated metal; The second external electrode layer includes flaky metal particles having an average diameter of 5 to 20 μm and spherical metal particles having an average particle diameter of 5 to 100 nm, and the resin component in the second external electrode layer Is a thermosetting resin.

In the present invention, the area ratio of the flaky metal particles to the spherical metal particles in the cross-sectional area of the second external electrode layer is preferably 50:50 to 90:10.

Furthermore, it is preferable that the area ratio of the area of the flaky metal particles and the spherical metal particles and the area of the resin component in the cross-sectional area of the second external electrode layer is 40:60 to 60:40.

Furthermore, the flaky metal particles and the spherical metal particles preferably contain at least one or more of Ni, Cu, Pd, Ag, Pt, and Au.

Furthermore, the thermosetting resin is preferably an epoxy resin.

In the present invention, the first external electrode layer can be formed, for example, by baking a conductive paste containing Ag, Ag—Pd, Ni, or Cu.

  By forming the first external electrode layer, the conductive connectivity between the internal electrode and the second external electrode layer can be effectively ensured.

In the present invention, the third external electrode layer described above is preferably composed of a lower layer film made of a metal that prevents the solder from diffusing into the second external electrode layer, and a metal having good solderability. And a surface layer film. Specifically, Ni is preferable as the lower layer film and Sn is preferable as the surface layer film.

The average diameter of the flaky metal particles in the second external electrode layer is 5 to 20 μm. When the average diameter is less than 5 μm, the film strength is low, and cracks are likely to occur due to stress such as thermal shock. On the other hand, when the average diameter is larger than 20 μm, the conductivity is low and the ESR is high.

The average particle diameter of the spherical metal particles in the second external electrode layer is 5 to 100 nm. By using these fine particles, ESR was remarkably improved. This seems to be because when the thermosetting resin is cured, the fine particles are melted and conductively joined between the flaky metal particles. When the average particle size is smaller than 5 nm, the thixotropy of the paste is increased, and when the film is formed by the dipping method, the shape is deteriorated. On the other hand, when the average particle size is larger than 100 nm, the conductivity is low and the ESR is high.

  The flaky metal particles and the spherical metal particles in the second external electrode layer are at least one metal selected from Ni, Cu, Pd, Ag, Pt, and Au, or an alloy thereof, or another metal on the surface of the metal particles. Particles coated with can be used.

  The area ratio between the flaky metal particles and the spherical metal particles in the second external electrode layer is 50:50 to 90:10. When the area ratio of the flaky metal particles is lower than 50%, the conductivity is low and the ESR is high. On the other hand, when the area ratio of the flaky metal particles is higher than 90%, the thixotropy of the paste is increased, and when the film is formed by the dipping method, the shape is deteriorated.

  The resin component in the second external electrode layer is a thermosetting resin. The thermoplastic resin has almost no material having both heat resistance, adhesion strength, and solvent solubility necessary for paste preparation.

  As the thermosetting resin, for example, epoxy resin, acrylic resin, melamine resin, phenol resin, polyimide resin, resol type phenol resin, unsaturated polyester resin, fluorine resin, silicone resin, etc. are used. A thermosetting resin such as a polyimide resin or an epoxy resin is preferably used, and an ultraviolet curable resin may be used.

The area ratio between the area of the flaky metal particles and the spherical metal particles and the area of the resin component is 40:60 to 60:40. When the area ratio between the flaky metal particles and the spherical metal particles is lower than 40%, the conductivity becomes low and the ESR becomes high. On the other hand, when the area ratio between the flaky metal particles and the spherical metal particles is higher than 60%, the content of the resin component is relatively low, so that external stress cannot be absorbed, and cracks are generated, for example, in thermal shock. It becomes easy to do.

According to the present invention, even if stress is generated by bending or thermal shock when mounted on a circuit board, the ceramic body does not crack, and also has excellent ESR, resulting in high quality and long-term performance. A reliable electronic component can be provided.

Examples of the electronic component include, but are not limited to, a multilayer ceramic capacitor, a multilayer ceramic inductor, a multilayer ceramic LC component, and a multilayer ceramic substrate.

FIG. 1 is a cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention. FIG. 2 is an SEM photograph of a cross section of the second external electrode in the multilayer ceramic capacitor according to one embodiment of the present invention.

In the present embodiment, a multilayer ceramic capacitor will be described as an example of an electronic component.

Multilayer Ceramic Capacitor As shown in FIG. 1, a multilayer ceramic capacitor 1 according to an embodiment of the present invention includes a capacitor body 10 having a configuration in which dielectric layers 12 and internal electrode layers 14 are alternately stacked. A pair of external electrodes 20 are formed on both side ends of the capacitor body 10 so as to be electrically connected to the internal electrode layers 14 arranged alternately in the body 10. The internal electrode layers 14 are laminated so that the side end faces are alternately exposed on the surfaces of the two opposite ends of the capacitor body 10. The pair of external electrodes 20 are formed at both ends of the capacitor body 10 and connected to the exposed end surfaces of the alternately arranged internal electrode layers 14 to constitute a capacitor circuit.

The outer shape and dimensions of the capacitor body 10 are not particularly limited and can be appropriately set depending on the application. Usually, the outer shape is substantially a rectangular parallelepiped shape, and the dimensions are usually vertical (0.4 to 5.6 mm) × It can be about horizontal (0.2-5.0 mm) × height (0.2-1.9 mm).

The dielectric layer 12 is made of a dielectric material including a ceramic material. The ceramic material contained in the dielectric material is preferably a material having a high dielectric constant in order to obtain excellent characteristics as a capacitor. For example, barium titanate (BaTiO3) -based materials, lead composite perovskite compound-based materials, strontium titanate-based (SrTiO3) -based materials, and the like are suitable.

Examples of the internal electrode 14 include those made of Ni or Ni alloy. As the Ni alloy, an alloy containing 95% by mass or more of Ni and at least one of Mn, Cr, Co, Al and the like is preferable.

As shown in FIG. 1, the external electrode 20 includes a first external electrode layer 22 formed by baking, a second external electrode layer 24 containing a metal component and a resin component, a first plating layer 26, and a second plating layer 28. The third external electrode layer is formed from the dielectric element body 10 in this order toward the outside.

Method for Manufacturing Multilayer Ceramic Capacitor Next, an example of a method for manufacturing the multilayer ceramic capacitor 1 according to this embodiment will be described.

First, a raw material of a dielectric material that constitutes the dielectric layer 12 is prepared. For example, examples of the raw material for the ceramic material include oxides of metal elements constituting the ceramic material. After mixing this raw material, it is temporarily fired at about 800-1300 ° C. The temporarily fired product is pulverized by a jet mill, a ball mill or the like until a desired particle size is obtained. Thereafter, a binder, a plasticizer, and the like are added to the pulverized product to obtain a paste for forming the dielectric layer 12 (hereinafter referred to as “dielectric paste”).

Content of each component in a dielectric paste is not specifically limited, For example, a dielectric paste can be prepared so that about 10 to about 50 weight% of solvent may be included.

The dielectric paste may contain additives selected from various dispersants, plasticizers, dielectrics, subcomponent compounds, glass frit, insulators, and the like, if necessary. When these additives are added to the dielectric paste, the total content is desirably about 10% by weight or less.

In this embodiment, since polyvinyl butyral is used for the organic binder in the organic vehicle, the plasticizer content in this case is preferably about 25 to about 100 parts by weight with respect to 100 parts by weight of the binder.

Next, a thickness of about 0.3 to 10 μm, more preferably 0.3 to 5 μm, and even more preferably about 0.3 to 2 μm is formed on the carrier sheet using this dielectric paste by a doctor blade method or the like. Then, a ceramic green sheet is formed. The ceramic green sheet becomes the dielectric layer 2 shown in FIG. 1 after firing.

As the carrier sheet, for example, a PET film or the like is used, and a film coated with silicone or the like is preferable in order to improve peelability. Although the thickness of a carrier sheet is not specifically limited, Preferably it is 5-100 micrometers.

The ceramic green sheet is dried after being formed on the carrier sheet. The drying temperature of the ceramic green sheet is preferably 50 to 100 ° C., and the drying time is preferably 1 to 20 minutes.

Next, an electrode layer (internal electrode pattern) having a predetermined pattern to be the internal electrode layer 14 shown in FIG. 1 is formed on the surface of the ceramic green sheet formed on the carrier sheet.

The thickness of the internal electrode layer is preferably 2 μm or less, more preferably 0.3 to 1.0 μm. If the thickness of the internal electrode layer is too large, the number of stacked layers must be reduced, and the acquired capacity is reduced, making it difficult to increase the capacity. On the other hand, if the thickness is too thin, it is difficult to form uniformly, and electrode breakage is likely to occur.

The thickness of the internal electrode layer is in the above range in the current technology, but it is more desirable that the thickness is as small as possible in the range where the electrode is not interrupted.

The method for forming the internal electrode layer is not particularly limited as long as the layer can be formed uniformly. In this embodiment, a screen printing method using a conductive paste is used.

In the internal conductive paste, the same ceramic powder as the ceramic powder contained in the dielectric paste may be contained as a co-material. The common material has an effect of suppressing the sintering of the conductive powder in the firing process. The ceramic powder (co-material) is preferably contained in the conductive paste in an amount of 5 to 30 parts by weight with respect to 100 parts by weight of the conductive powder. If the amount of the co-material is too small, the sintering suppressing effect of the conductive powder is lowered, the lineability (continuity) of the internal electrode is deteriorated, and the apparent dielectric constant is lowered. On the other hand, if the amount of the co-material is too large, the lineability of the internal electrode tends to deteriorate and the apparent dielectric constant tends to decrease.

In order to improve adhesion, the conductive paste may contain a plasticizer. Examples of the plasticizer include phthalic acid esters such as benzylbutyl phthalate (BBP), adipic acid, phosphoric acid esters, glycols, and the like. In the present embodiment, preferably, dioctyl adipate (DOA), butyl butylene glycol phthalate (BPBG), didodecyl phthalate (DDP), dibutyl phthalate (DBP), benzyl butyl phthalate (BBP), dioctyl phthalate ( DOP), dibutyl sebacate and the like are used. Of these, dioctyl phthalate (DOP) is particularly preferable. The plasticizer is contained in an amount of preferably 25 to 150 parts by weight, more preferably 25 to 100 parts by weight with respect to 100 parts by weight of the organic binder in the organic vehicle. By adding the plasticizer, the adhesive force of the internal electrode layer formed using the paste is increased, and the adhesive force between the internal electrode layer and the ceramic green sheet is improved. In order to obtain such an effect, the amount of the plasticizer added is preferably 25 parts by weight or more. However, if the addition amount exceeds 150 parts by weight, it is not preferable because excessive plasticizer oozes out from the internal electrode layer formed using the paste.

The conductive paste can be obtained by kneading the above components with a ball mill or the like to form a slurry.

Next, a plurality of ceramic green sheets with internal electrode layers of a predetermined pattern formed on the surface as described above are laminated to produce a green chip, and a binder removal process, a firing process, and an annealing process performed as necessary Thus, the capacitor body 10 made of a sintered body is formed.

  Then, a metal such as Cu constituting the first external electrode layer 22 is baked on the two end surfaces of the element body 10 where the end portions of the internal electrodes 14 are exposed, and the first external electrode is formed on the surface of the end surface. Layer 22 is formed. Specifically, for example, the first external electrode layer 22 can be formed by applying a conductive paste in which a binder or the like is added to a metal to the end face and then baking at a temperature of about 800 ° C.

  Next, a conductive paste (conductive resin material) containing the above-described conductive material and epoxy resin for forming the second external electrode layer 24 is applied so as to cover the first external electrode layer 22. After application, the epoxy resin in the conductive paste is cured by heating at about 150 to 250 ° C., thereby forming the second external electrode layer 24 on the surface of the first external electrode layer 22.

  Further, a third electrode layer 26 made of Ni or the like is formed so as to cover the second electrode layer 24 by a wet plating method such as electrolytic plating. Then, a fourth electrode layer 28 made of Sn or the like is formed on the surface of the third electrode layer 26 in the same manner. In this way, the capacitor 1 having the structure shown in FIG. 1 is obtained.

As mentioned above, although embodiment of this invention has been described, this invention is not limited to the embodiment mentioned above at all, and can be variously modified within the range which does not deviate from the summary of this invention.

For example, in the above-described embodiment, the multilayer ceramic capacitor is exemplified as the multilayer ceramic electronic component according to the present invention. However, the multilayer ceramic electronic component according to the present invention is not limited to the multilayer ceramic capacitor, and may be applied to a multilayer ceramic substrate or the like. Of course, it can be applied.

Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

Example 1
First, an element body was prepared in which a dielectric layer made of barium titanate and an internal electrode layer made of nickel were arranged so that the dielectric layers were on both outer sides. Next, a conductive paste containing Cu, glass frit, and ethyl cellulose as an organic binder is applied to a pair of opposing end faces of the element body, and then fired at 800 ° C. to form first external surfaces on both end faces of the element body. An electrode layer was formed.

Next, on the surface of the first external electrode layer, bisphenol A type epoxy resin having a flake Ag powder having an average diameter of 10 μm, 58.0 wt%, a spherical Ag powder having an average particle diameter of 20 nm, 16.3% by weight, and a molecular weight of 2900. A conductive paste containing 6.5% by weight of (main agent), 1.3% by weight of novolac-type phenolic resin (curing agent), and 18% by weight of terpineol (solvent) was applied. Next, heating was performed at 200 ° C. for 60 minutes to cure the conductive paste, thereby forming a second external electrode layer on the first external electrode layer.

Thereafter, a Ni plating layer and a Sn plating layer are sequentially formed on the surface of the second external electrode layer by electrolytic plating to form a third external electrode layer, and external electrodes are provided on both end faces of the element body. A multilayer capacitor element was completed.
[Thermal shock test]

A sample in which the capacitor element was fixed on the substrate by soldering was prepared. This sample was subjected to 3000 cycles of thermal shock with cooling at −55 ° C. for 30 minutes and heating at 125 ° C. for 30 minutes as one cycle. I confirmed. Fifty samples were used for the test, and the number of samples in which cracks were observed was counted. The obtained results are shown in Table 1.
[ESR test]

An ESR at 1 kHz was measured using an impedance analyzer. The results are shown in Table 1.
[Film thickness of second external electrode layer]

  The capacitor element was polished, and the thickness of the second external electrode at the center was measured.

(Examples 2-5, Comparative Examples 1-4)
Example 1 except that the conductive paste for forming the second external electrode layer was obtained by changing the average diameter of the flaky Ag powder and the average particle diameter of the spherical Ag powder as shown in Table 1. In the same manner, a capacitor element was obtained. The results are shown in Table 1.

  As shown in Examples 1 to 5 in Table 1, when the Ag powder used for the second external electrode has an average diameter of 5 to 20 μm in the flake shape and an average particle size of 5 to 100 nm in the spherical shape, in the thermal shock test Cracks did not occur and ESR was low.

  On the other hand, in Comparative Example 1, cracks occurred in the thermal shock test. This is thought to be because the average diameter of the flaky Ag powder was as small as 3 μm, so that the film strength was low, and cracks were easily generated due to thermal shock stress.

In Comparative Example 2, ESR was high. This is probably because the average diameter of the flaky Ag powder was as large as 25 μm, so that the specific surface area was relatively low, and the contact probability between Ag powders was low.

  Moreover, in the comparative example 3, the film thickness was thick. This is probably because the spherical Ag powder has a small average particle size of 3 nm, so that the thixotropy of the paste is high, and it is difficult to level in film formation by the dipping method. When the film thickness is thus large, the length of the capacitor element may deviate from the standard, leading to a decrease in yield.

In Comparative Example 4, ESR was high. This is thought to be because the spherical Ag powder does not melt at the curing temperature of the epoxy resin because the average particle diameter of the spherical Ag powder is as large as 120 nm, so that the conductive bonding between the flaky metal particles is reduced.

(Examples 6-7, Comparative Examples 5-6)
As a conductive paste for forming the second external electrode layer, a capacitor element was obtained in the same manner as in Example 1 except that the addition amounts of flaky Ag powder and spherical Ag powder were changed as shown in Table 2. . The results are shown in Table 2.

The area ratio between the flaky Ag powder and the spherical Ag powder was determined by calculation from the added amount of each Ag powder.
As shown in Example 1 and Examples 6 to 7 in Table 2, when the area ratio of the flaky Ag powder and the spherical Ag powder used for the second external electrode is 50:50 to 80:20, thermal shock In the test, no crack was generated, the ESR was low, and the film thickness was also good.

On the other hand, in Comparative Example 5, the ESR was high. This is presumably because the contact ratio between the Ag powders was low because the area ratio of the flaky Ag powder was low.

  Moreover, in the comparative example 6, the film thickness was thick. This is presumably because the area ratio of the flaky Ag powder is high, so that the thixotropy of the paste is high, and it is difficult to level in film formation by the dipping method, so that it becomes thick.

(Examples 8-9, Comparative Examples 7-8)
As the conductive paste for forming the second external electrode layer, the same procedure as in Example 1 was conducted except that the addition amounts of flaky Ag powder, spherical Ag powder, epoxy resin and phenol resin were changed as shown in Table 3. Thus, a capacitor element was obtained. The results are shown in Table 3.

The area ratio between the Ag powder and the resin component was determined by image analysis from the cross-sectional SEM photograph of the second external electrode shown in FIG.
As shown in Example 1 and Examples 8 to 9 in Table 3, when the area ratio between the Ag powder used for the second external electrode and the resin component was 42:58 to 58:42, cracks occurred in the thermal shock test. , Low ESR, and good film thickness.

On the other hand, in Comparative Example 7, the ESR was high. This is presumably because the contact ratio between Ag powders is low because the area ratio of Ag powders is low.

  In Comparative Example 8, cracks occurred in the thermal shock test. This is presumably because the content ratio of the resin component was relatively low due to the high area ratio of Ag powder, and external stress could not be absorbed.

The present invention can be used as an external electrode of an electronic component such as a multilayer ceramic capacitor.

DESCRIPTION OF SYMBOLS 1 ... Multilayer ceramic capacitor 10 ... Capacitor body 12 ... Dielectric layer 14 ... Internal electrode layer 20 ... External electrode

Claims (5)

A ceramic body,
An internal electrode provided inside the ceramic body;
A first external electrode layer provided on the surface of the ceramic body and formed by baking a metal paste;
A second external electrode layer formed on the first external electrode layer and containing a metal component and a resin component;
A third external electrode layer made of plated metal, formed on the second external electrode layer;
The second external electrode layer includes flaky metal particles having an average diameter of 5 to 20 μm and spherical metal particles having an average particle diameter of 5 to 100 nm,
The electronic component, wherein the resin component in the second external electrode layer is a thermosetting resin. 2. The electronic component according to claim 1, wherein an area ratio of the flaky metal particles and the spherical metal particles in a cross-sectional area of the second external electrode layer is 50:50 to 90:10. The area ratio of the areas of the flaky metal particles and the spherical metal particles and the area of the resin component in the cross-sectional area of the second external electrode layer is 40:60 to 60:40. Electronic component in any one. The electronic component according to claim 1, wherein the flaky metal particles and the spherical metal particles include at least one of Ni, Cu, Pd, Ag, Pt, and Au. The electronic component according to claim 1, wherein the thermosetting resin is an epoxy resin.

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