KR102464310B1 - Multi-layered ceramic capacitor - Google Patents

Abstract

The present invention includes a body including a dielectric layer and an internal electrode, and an external electrode disposed on one surface of the body, the external electrode comprising: a first conductive resin layer in contact with the internal electrode; and a second conductive resin layer disposed on the first conductive resin layer, wherein the first and second conductive resin layers include a plurality of metal particles, an intermetallic compound surrounding the plurality of metal particles, and a base resin. and wherein the area fraction of the intermetallic compound of the first conductive resin layer is higher than that of the second conductive resin layer.

Description

Multilayer Ceramic Capacitor {MULTI-LAYERED CERAMIC CAPACITOR}

The present invention relates to a multilayer ceramic capacitor.

Multi-Layered Ceramic Capacitors (MLCCs) are important chip components used in industries such as communications, computers, home appliances, and automobiles due to their small size, high capacity, and easy mounting. It is a core passive element used in various electric, electronic and information communication devices such as , digital TV.

In recent years, the multilayer ceramic capacitor has also been miniaturized and has a high capacity due to the miniaturization and high performance of electronic devices. As such, the importance of securing high reliability of the multilayer ceramic capacitor is increasing.

In order to secure the high reliability of the multilayer ceramic capacitor, a conductive resin layer is formed on the external electrode to absorb tensile stress generated in a mechanical or thermal environment to prevent cracks caused by stress. A technique for applying is disclosed.

The conductive resin layer is formed using a paste containing Cu, glass frit, and a thermosetting resin, and serves to electrically and mechanically bond between the sintered electrode layer and the plating layer of the external electrode of the multilayer ceramic capacitor, It serves to protect the multilayer ceramic capacitor from mechanical and thermal stress according to the process temperature and the bending impact of the board during circuit board mounting.

However, when a paste containing Cu, glass frit, and a thermosetting resin is used, there is a possibility that the physical properties of the reliability item may change due to bending shock or thermal shock, moisture absorption such as moisture or chlorine water, depending on the basic physical properties of the material. There is this.

That is, when a paste containing Cu, glass frit, and a thermosetting resin is used, residual stress may exist inside the chip, and the bending shock is transmitted to the ceramic body as it is, and the chemical resistance depends on the components of the glass frit. There is a problem that characteristics may be weakened.

Korean Patent Publication No. 2015-0086343

SUMMARY OF THE INVENTION It is an object of the present invention to provide a multilayer ceramic capacitor having excellent moisture resistance, low internal equivalent series resistance (ESR), and excellent resistance to mechanical stress.

One embodiment of the present invention includes a body including a dielectric layer and an internal electrode, and an external electrode disposed on one surface of the body, the external electrode comprising: a first conductive resin layer in contact with the internal electrode; and a second conductive resin layer disposed on the first conductive resin layer, wherein the first and second conductive resin layers include a plurality of metal particles, an intermetallic compound surrounding the plurality of metal particles, and a base resin. and wherein the area fraction of the intermetallic compound of the first conductive resin layer is higher than that of the second conductive resin layer.

According to an embodiment of the present invention, by including the first conductive resin layer having a high area fraction of the intermetallic compound, moisture resistance is improved, internal equivalent series resistance (ESR) is low, bending strength, etc. It has the effect of improving resistance to mechanical stress and chemical resistance properties.

1 is a perspective view schematically illustrating a multilayer ceramic capacitor according to an exemplary embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along line II′ of FIG. 1 .
FIG. 3 is an enlarged cross-sectional view of region B of FIG. 2 .
4 is a photograph of a cross-section in the vicinity of region B of a conventional multilayer ceramic capacitor.
5 is a photograph of a cross-section in the vicinity of region B of the multilayer ceramic capacitor according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to specific embodiments and the accompanying drawings. However, the embodiment of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments of the present invention are provided in order to more completely explain the present invention to those skilled in the art. Accordingly, the shapes and sizes of elements in the drawings may be exaggerated for clearer description. In addition, components having the same function within the scope of the same idea shown in the drawings of each embodiment will be described using the same reference numerals.

And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and the thickness is enlarged to clearly express various layers and regions, and components having the same function within the scope of the same idea are referred to as the same. It is explained using symbols. Furthermore, throughout the specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

1 is a perspective view schematically illustrating a multilayer ceramic capacitor according to an exemplary embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II′ of FIG. 1 .

1 and 2 , a multilayer ceramic capacitor 100 according to an exemplary embodiment includes a body 110 and first and second external electrodes 130 and 140 .

The body 110 may include an active region as a portion contributing to the formation of capacitance of the capacitor, and upper and lower covers 112 and 113 formed at upper and lower portions of the active region as upper and lower margins, respectively.

In one embodiment of the present invention, the body 110 is not particularly limited in shape, but may have a substantially hexahedral shape.

That is, the body 110 may not have a perfect hexahedral shape, but may have a substantially hexahedral shape due to a difference in thickness according to the arrangement of the internal electrodes and polishing of the corners.

When the direction of the cube is defined to clearly describe the embodiment of the present invention, in the drawings, the X direction is the first direction or the longitudinal direction, the Y direction is the second direction or the width direction, and the Z direction is the third direction, the thickness direction, or It can be defined as the stacking direction.

In addition, in the body 110 , both surfaces facing each other in the Z direction are defined as first and second surfaces 1 and 2 , connected to the first and second surfaces 1 and 2 and facing each other in the X direction. defined as the third and fourth surfaces 3 and 4, connected to the first and second surfaces 1 and 2, connected to the third and fourth surfaces 3 and 4, and mutually in the Y direction The opposite surfaces are defined as fifth and sixth surfaces 5 and 6 . In this case, the first surface 1 may be a mounting surface.

The active region may have a structure in which a plurality of dielectric layers 111 and a plurality of first and second internal electrodes 121 and 122 are alternately stacked with the dielectric layers 111 interposed therebetween.

The dielectric layer 111 may include a ceramic powder having a high dielectric constant, for example, a barium titanate (BaTiO ₃ )-based or strontium titanate (SrTiO ₃ )-based powder, but the present invention is not limited thereto.

At this time, the thickness of the dielectric layer 111 can be arbitrarily changed according to the capacitance design of the multilayer ceramic capacitor 100 , and the thickness of the first layer is configured to be 0.1 to 10 μm after firing in consideration of the size and capacity of the body 110 . However, the present invention is not limited thereto.

The first and second internal electrodes 121 and 122 may be disposed to face each other with the dielectric layer 111 interposed therebetween.

The first and second internal electrodes 121 and 122 are a pair of electrodes having different polarities. The dielectric layer 111 is interposed between the first and second internal electrodes 121 and 122 by printing a conductive paste including a conductive metal to a predetermined thickness on the dielectric layer 111 . may be formed so as to be alternately exposed through the third and fourth surfaces 3 and 4 of the body 110 along the stacking direction of the dielectric layer 111 and electrically to each other by the dielectric layer 111 disposed in the middle. can be insulated.

The first and second internal electrodes 121 and 122 are first and second external electrodes 130 and 140 through portions alternately exposed through the third and fourth surfaces 3 and 4 of the body 110 . and may be electrically connected to each other.

Accordingly, when a voltage is applied to the first and second external electrodes 130 and 140 , electric charges are accumulated between the first and second internal electrodes 121 and 122 facing each other, and in this case, the electrostatic charge of the multilayer ceramic capacitor 100 . The capacitance is proportional to the area of the overlapping regions of the first and second internal electrodes 121 and 122 .

The thickness of the first and second internal electrodes 121 and 122 may be determined according to the purpose, for example, may be determined to be in the range of 0.2 to 1.0 μm in consideration of the size and capacity of the ceramic body 110, The present invention is not limited thereto.

In addition, the conductive metal included in the first and second internal electrodes 121 and 122 may be nickel (Ni), copper (Cu), palladium (Pd), or an alloy thereof, and the present invention is not limited thereto. not.

The upper and lower covers 112 and 113 may have the same material and configuration as those of the dielectric layer 111 of the active region, except that they do not include internal electrodes.

That is, it can be seen that the upper and lower covers 112 and 113 are formed by stacking a single dielectric layer or two or more dielectric layers on the upper and lower surfaces of the active region in the Z-direction, respectively, and are basically formed by first and second dielectric layers caused by physical or chemical stress. It may serve to prevent damage to the second internal electrodes 121 and 122 .

The first and second external electrodes 130 and 140 include the first conductive resin layers 131 and 141 , the second conductive resin layers 132 and 142 and the plating layer disposed on the first conductive resin layers 131 and 141 . (133, 134, 143, 144), respectively.

The plating layers 133 , 134 , 143 , and 144 may have, for example, a structure in which nickel plating layers 133 and 143 and tin plating layers 134 and 144 are sequentially stacked.

FIG. 3 is an enlarged cross-sectional view of region B of FIG. 2 .

Although the region B is illustrated with an enlarged portion of the first external electrode 130 , the first external electrode 130 is electrically connected to the first internal electrode 121 , and the second external electrode 130 is connected to the second external electrode 130 . The configuration of the first external electrode 130 and the second external electrode 140 is similar only with a difference in connection with the internal electrode 122 . Therefore, the following description will be based on the first external electrode 130 , but this It is considered that the description of the external electrode 140 is included.

As shown in FIG. 3 , the first and second conductive resin layers 131 and 132 include a plurality of metal particles 131a and 132a, intermetallic compounds 131b and 132b surrounding the plurality of metal particles, and a base. The resins 131c and 132c are included, and the area fraction of the intermetallic compound 131b of the first conductive resin layer 131 is higher than the area fraction of the intermetallic compound 132b of the second conductive resin layer 132 . high.

In the first and second conductive resin layers 131 and 132 , a plurality of metal particles 131a and 132a are dispersed in base resins 131c and 132c, and intermetallic compounds 131b and 132b are formed by the metal particles 131a, 132a) in the form surrounding it.

The first and second conductive resin layers 131 and 132 serve to electrically and mechanically bond the internal electrode 121 and the plating layer 133 to each other. By absorbing the generated tensile stress, cracks may be prevented from occurring, and the multilayer ceramic capacitor may be protected from bending impact of the substrate.

The metal particles 131a and 132a may include at least one of Ag and Cu, more preferably Ag.

The intermetallic compounds 131b and 132b surround the plurality of metal particles 131a and 132a in a molten state and serve to connect them to each other, thereby minimizing the stress inside the body 110, and providing high temperature load and moisture resistance load characteristics. can be improved

In this case, the intermetallic compounds 131b and 132b may include a metal having a lower melting point than the curing temperature of the base resin 132c.

That is, since the intermetallic compounds 131b and 132b contain a metal having a melting point lower than the curing temperature of the base resin 132c, the metal having a melting point lower than the curing temperature of the base resin 132c is dried and cured. It is melted in the process of passing, and forms an intermetallic compound with a portion of the metal particles to surround the metal particles 132a. In this case, the intermetallic compound may preferably include a low-melting-point metal of 300° C. or less.

For example, it may include Sn having a melting point of 213 to 220°C. In the process of drying and curing, Sn is melted, and the molten Sn wets high-melting-point metal particles such as Ag or Cu by capillary action, and reacts with a part of Ag or Cu metal particles to form Ag ₃ Sn, Intermetallic compounds such as Cu ₆ Sn ₅ and Cu ₃ Sn are formed. Ag or Cu not participating in the reaction remains in the form of metal particles 131a and 132a as shown in FIG. 3 . The area fraction of the intermetallic compound 131b of the first conductive resin layer 131 is higher than the area fraction of the intermetallic compound 132b of the second conductive resin layer 132 . As shown in FIG. 5 , which is a photograph of a cross-section in the vicinity of region B of the multilayer ceramic capacitor according to an embodiment of the present invention, an intermetallic compound is densely formed in the first conductive resin layer, whereas the second conductive resin layer is densely formed. The intermetallic compound of the conductive resin layer is formed in a network form.

Since the first conductive resin layer is densely formed with intermetallic compounds, the moisture penetration path is reduced and moisture resistance is improved, the electrical connectivity with the internal electrode is improved, the ESR (Equivalent Series Resistor) is lowered, and mechanical properties such as bending strength are reduced. Resistance to adverse stresses is also increased.

In this case, the first conductive resin layer may include an intermetallic compound in an area of 60 to 75%, and the second conductive resin layer may include an intermetallic compound in an area of 50% or less (excluding 0 area%).

When the intermetallic compound of the first conductive resin layer is less than 60 area%, moisture resistance reliability may be inferior, and when it exceeds 75 area%, adhesiveness with the body may be inferior.

When the amount of the intermetallic compound in the second conductive resin layer exceeds 50 area%, it is difficult to form the intermetallic compound in the first conductive resin layer by 60 area% or more, and the lower limit thereof is not particularly limited, but for example, 10 It may be greater than or equal to area %.

On the other hand, the intermetallic compound 131b of the first conductive resin layer is formed by combining the low melting point metal of the intermetallic compound with the metal component of the internal electrode at the interface between the internal electrode 121 and the intermetallic compound 131b. compounds may be included.

The base resin 132c may include a thermosetting resin having electrical insulation properties.

In this case, the thermosetting resin may be, for example, an epoxy resin, but the present invention is not limited thereto.

The base resin 132c serves to mechanically bond between the body 110 and the plating layer 133 .

When the conductive resin layer is formed using a conventional paste containing Cu, glass frit, and a thermosetting resin, the glass frit component helps to form an alloy between the Cu particles and the Ni internal electrode and acts as a binder. It performs the role of sealing (sealing). That is, when the melting temperature of the glass frit component, the sintering temperature of Cu, and the alloy formation temperature between Cu and Ni are similar, sintering of copper particles occurs and densification proceeds. and the glass frit component fills the empty space. However, the formation temperature is made at 700 ~ 900 ℃, the residual stress remains, problems such as radiation cracks may occur. In addition, depending on the component of the glass frit, there may be a problem in that the chemical resistance to the plating solution may be weakened.

On the other hand, in the present invention, the first and second conductive resin layers can be formed by using a low-melting-point paste including Ag powder, Sn-based solder powder, and a base resin, and an intermetallic compound is formed at a low temperature, By allowing the intermetallic compound to be densely formed in the first conductive resin layer, the above-described problems can be solved.

In the case of a low-melting-point paste containing Ag powder, Sn-based solder powder and base resin, the generation of residual stress is relatively small because it is formed through epoxy curing. It can suppress the generation of residual stress more effectively than the expanding Cu-Ni alloy. In addition, since the intermetallic compound is densely formed in the first conductive resin layer, electrical connectivity with the internal electrode may be improved, and paths such as moisture absorption or penetration of the plating solution may be blocked, thereby improving moisture resistance reliability.

4 is a microscopic photograph of a cross-section near region B of a conventional multilayer ceramic capacitor in which a conductive resin layer is formed using a paste including Cu, glass frit, and a thermosetting resin. 5 is a microscopic photograph of a cross-section in the vicinity of region B of the multilayer ceramic capacitor according to an embodiment of the present invention in which a conductive resin layer is formed using a low-melting-point paste including Ag powder, Sn-based solder powder, and a base resin; it's one picture

In the case of FIG. 4 , one conductive resin layer having a uniform density is formed, but in FIG. 5 , the intermetallic compound is densely formed in the first conductive resin layer, and the intermetallic compound in the second conductive resin layer is a network It can be seen that the shape is formed.

In this case, in the low-melting-point paste including Ag powder, Sn-based solder powder, and the base resin, the Sn-based solder powder may include two or more kinds of Sn-based solders having different melting points.

For example, Ag powder, Sn-based solder powder containing two or more Sn-based solders having different melting points, and a base resin are mixed, and then a paste is prepared by dispersing it using a 3-roll mill. can After the paste is applied to the body and dried, the temperature is raised to 350° C. at a temperature increase rate of 4.6° C./min and maintained to perform curing. During curing, the Sn-based solder having a low melting point is melted first, so that the fluidity is increased, so that the amount of the solder component in the liquid phase moving toward the internal electrode increases, so that the first conductive resin layer having a more dense structure can be formed.

In addition, in the low-melting-point paste including Ag powder, Sn-based solder powder, and base resin, the Sn-based solder powder may include two or more kinds of Sn-based solders having different particle sizes.

For example, Ag powder, Sn-based solder powder including two or more Sn-based solders having different particle sizes, and a base resin are mixed, and then a paste is prepared by dispersing it using a 3-roll mill. can do. After the paste is applied to the body and dried, the temperature is raised to 350° C. at a temperature increase rate of 4.6° C./min, and cured by maintaining it. During thermosetting, the larger the particle size of the Sn-based solder, the greater the fluidity. Therefore, the larger Sn-based solder first moves toward the internal electrode to form the first conductive resin layer having a more dense structure.

The Sn-based solder powder may include, for example, at least one selected from Sn, Sn _96.5 Ag _3.0 Cu _0.5 , Sn ₄₂ Bi ₅₈ and Sn ₇₂ Bi ₂₈ .

The particle size of Ag contained in the Ag powder may be 0.5 to 3 μm, and the shape is not particularly limited.

Although the embodiment of the present invention has been described in detail above, the scope of the present invention is not limited thereto, and various modifications and variations are possible within the scope without departing from the technical matters of the present invention described in the claims. It will be apparent to those of ordinary skill in the art.

100: multilayer ceramic capacitor
110: body
111: dielectric layer
121, 122: first and second internal electrodes
130, 140: first and second external electrodes
131, 141: first conductive resin layer
132, 142: second conductive resin layer
131a, 132a: metal particles
131b, 132b: intermetallic compounds
131c, 132c: base resin
133, 134, 143, 144: plating layer

Claims (10)

a body comprising a dielectric layer and an internal electrode; and
Including; an external electrode disposed on the body;
The external electrode includes a first conductive resin layer and a second conductive resin layer disposed on the first conductive resin layer,
The first and second conductive resin layers include a plurality of metal particles, an intermetallic compound containing a metal element having a melting point of 300° C. or less, and a base resin,
The multilayer ceramic capacitor wherein the area fraction of the intermetallic compound of the first conductive resin layer is higher than that of the second conductive resin layer.
According to claim 1,
The first conductive resin layer contains an intermetallic compound in an area % of 60 to 75,
The second conductive resin layer includes an intermetallic compound in an area % of 50 or less (excluding 0 area %).
According to claim 1,
wherein the metal particles include at least one of Ag and Cu.
According to claim 1,
The intermetallic compound includes at least one of Ag ₃ Sn, Cu ₆ Sn ₅ and Cu ₃ Sn.
According to claim 1,
The external electrode is
The multilayer ceramic capacitor further comprising a plating layer disposed on the second conductive resin layer.
According to claim 1,
The first and second conductive resin layers are manufactured by thermosetting a paste including Ag powder, Sn-based solder powder, and a base resin.
7. The method of claim 6,
The paste is a multilayer ceramic capacitor, wherein the Sn-based solder powder includes two or more kinds of Sn-based solders having different particle sizes.
7. The method of claim 6,
The Sn-based solder powder includes at least two kinds of Sn-based solders having different melting points.
7. The method of claim 6,
The Sn-based solder powder includes at least one selected from Sn, Sn _96.5 Ag _3.0 Cu _0.5 , Sn ₄₂ Bi ₅₈ and Sn ₇₂ Bi ₂₈ .
7. The method of claim 6,
A multilayer ceramic capacitor having a particle size of 0.5 to 3 μm of Ag included in the Ag powder.

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