KR20190004631A - Multi-layered ceramic capacitor - Google Patents

Abstract

According to the present invention, disclosed is a stacked ceramic capacitor with excellent moisture resisting reliability, low equivalent series resistor (ESR), and excellent resistance to mechanical stress. The stacked ceramic capacitor comprises: a body which includes a dielectric layer and an internal electrode; and an external electrode arranged in one side of the body. The external electrode includes a first conductive resin layer coming in contact with the internal electrode, and a second conductive resin layer arranged on the first conductive resin layer. The first and second resin layers include a plurality of metal particles, an intermetallic compound surrounding the plurality of metal particles, and a base resin. An area fraction of the intermetallic compound of the first conductive resin layer is greater than that of the second conductive resin layer.

Description

[0001] MULTI-LAYERED CERAMIC CAPACITOR [0002]

The present invention relates to a multilayer ceramic capacitor.

Multilayer Ceramic Capacitor (MLCC) is an important chip component used in industries such as communication, computer, home appliance, and automobile due to its small size, high capacity, and easy mounting. Especially, , Digital TV, and other electric, electronic, and information communication devices.

In recent years, with the miniaturization and high performance of electronic devices, multilayer ceramic capacitors are also becoming smaller and higher in capacity, and the importance of ensuring high reliability of multilayer ceramic capacitors is increasing with this trend.

In order to secure high reliability of such a multilayer ceramic capacitor, in order to absorb tensile stress generated in a mechanical or thermal environment and to prevent cracks caused by stress, a conductive resin layer Is disclosed.

The conductive resin layer is formed using a paste containing Cu, glass frit, and a thermosetting resin. The conductive resin layer electrically and mechanically bonds the sintered electrode layer of the external electrode of the multilayer ceramic capacitor and the plating layer, And serves to protect the multilayer ceramic capacitor from mechanical and thermal stresses depending on the process temperature and the bending impact of the substrate during circuit board mounting.

However, when a paste containing Cu, glass frit and a thermosetting resin is used, the physical properties of the reliability item may be changed due to moisture absorption such as warpage, thermal shock, water or chlorine due to the basic physical properties of the material .

That is, when a paste containing Cu, glass frit and a thermosetting resin is used, residual stress may exist in the chip, and the bending impact may be transmitted to the ceramic body as it is. Depending on the composition of the glass frit, There is a problem that the characteristics can be weakened.

Korean Patent Laid-Open Publication No. 2015-0086343

An object of the present invention is to provide a multilayer ceramic capacitor excellent in moisture and humidity reliability, low in internal equivalent series resistance (ESR), and excellent in resistance to mechanical stress.

According to an embodiment of the present invention, there is provided a plasma display panel comprising a body including a dielectric layer and an internal electrode, and an external electrode disposed on one side of the body, wherein the external electrode is 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 comprise a plurality of metal particles, an intermetallic compound surrounding the plurality of metal particles, and a base resin And an area fraction of the intermetallic compound of the first conductive resin layer is higher than that of the second conductive resin layer.

According to one embodiment of the present invention, by including the first conductive resin layer having a high area fraction of the intermetallic compound, moisture resistance can be improved, and an equivalent equivalent series resistance (ESR) There is an effect that resistance to mechanical stress and chemical resistance characteristics can be improved.

1 is a perspective view schematically showing a multilayer ceramic capacitor according to an embodiment of the present invention.
2 is a sectional view taken along the line I-I 'in Fig.
3 is an enlarged cross-sectional view of the region B in Fig.
4 is a photograph of a cross section of a conventional multilayer ceramic capacitor in the vicinity of the B region.
5 is a photograph of a cross section of a multilayer ceramic capacitor according to an embodiment of the present invention in the vicinity of a region B;

Hereinafter, embodiments of the present invention will be described with reference to specific embodiments and the accompanying drawings. However, the embodiments of the present invention can be modified into 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 for a more complete description of the present invention to the ordinary artisan. Accordingly, the shapes, sizes, etc. of the elements in the drawings may be exaggerated for clarity. In the drawings, like reference numerals are used to designate like elements that are functionally equivalent to the same reference numerals in the drawings.

It is to be understood that, although the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, Will be described using the symbols. Further, throughout the specification, when an element is referred to as " including " an element, it means that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise.

1 is a perspective view schematically showing a multilayer ceramic capacitor according to an embodiment of the present invention. 2 is a sectional view taken along the line I-I 'in Fig.

Referring to FIGS. 1 and 2, a multilayer ceramic capacitor 100 according to an embodiment of the present invention includes a body 110 and first and second external electrodes 130 and 140.

The body 110 may include an active area serving as a part contributing to capacity formation of the capacitor and upper and lower covers 112 and 113 formed respectively on upper and lower parts of the active area as upper and lower margin parts.

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

That is, the body 110 may have a substantially hexahedral shape but not a complete hexahedral shape due to the thickness difference due to the arrangement of the internal electrodes and the polishing of the corner portions.

In order to clearly explain the embodiment of the present invention, when defining the direction of the hexahedron, the X direction is the first direction or the longitudinal direction, the Y direction is the second direction or the width direction, the Z direction is the third direction, And can be defined as a lamination direction.

In the body 110, both surfaces opposite to each other in the Z direction are defined as first and second surfaces 1 and 2, and are connected to the first and second surfaces 1 and 2, Is defined as a third and a fourth surface 3 and 4 and connected to the first and second surfaces 1 and 2 and connected to the third and fourth surfaces 3 and 4, The opposing both surfaces are defined as the fifth and sixth surfaces 5 and 6. At this time, 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 inner electrodes 121 and 122 are alternately stacked with a dielectric layer 111 sandwiched therebetween.

The dielectric layer 111 may include a ceramic powder having a high dielectric constant, for example, a barium titanate (BaTiO ₃ ) -based or a 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 capacity design of the multilayer ceramic capacitor 100. In consideration of the size and the capacity of the body 110, the thickness of one layer is 0.1 to 10 μm after firing However, the present invention is not limited thereto.

The first and second internal electrodes 121 and 122 may be arranged 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 and a conductive paste containing a conductive metal with a predetermined thickness is printed on the dielectric layer 111 to sandwich the dielectric layer 111 between the electrodes. And alternately exposed through the third and fourth surfaces 3 and 4 of the body 110 along the stacking direction of the dielectric layers 111. The dielectric layers 111 are electrically connected to each other Can be insulated.

The first and second internal electrodes 121 and 122 are electrically connected to the first and second external electrodes 130 and 140 through alternately exposed portions through the third and fourth faces 3 and 4 of the body 110, Respectively.

Therefore, when a voltage is applied to the first and second external electrodes 130 and 140, charges are accumulated between the first and second internal electrodes 121 and 122 opposing each other. At this time, the electrostatic charge of the multilayer ceramic capacitor 100 The capacitance is proportional to the area of the overlapping region 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 depending on the application and may be determined to fall within a range of 0.2 to 1.0 탆 in consideration of the size and capacity of the ceramic body 110, The present invention is not limited thereto.

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. no.

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

That is, the upper and lower covers 112 and 113 may be 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. Basically, The second internal electrodes 121 and 122 can be prevented from being damaged.

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

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

3 is an enlarged cross-sectional view of the region B in Fig.

The first external electrode 130 is electrically connected to the first internal electrode 121 and the second external electrode 130 is electrically connected to the second external electrode 130. In this case, Since the first external electrode 130 and the second external electrode 140 are similar in configuration to each other, the first external electrode 130 will be described below with reference to the second external electrode 130, It is assumed that 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, The area fraction of the intermetallic compound 131b of the first conductive resin layer 131 is larger than the area fraction of the intermetallic compound 132b of the second conductive resin layer 132, high.

The first and second conductive resin layers 131 and 132 are formed by dispersing a plurality of metal particles 131a and 132a in the base resin 131c and 132c and intermetallic compounds 131b and 132b in the metal particles 131a and 132b, 132a.

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. When the multilayer ceramic capacitor is mounted on a substrate, It is possible to prevent a crack from occurring by absorbing tensile stress generated and to protect the multilayer ceramic capacitor from the bending impact of the substrate.

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

The intermetallic compounds 131b and 132b surround the plurality of metal particles 131a and 132a in a molten state to connect the metal particles 131a and 132a to each other and minimize the stress in the body 110, Can be improved.

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

That is, since the intermetallic compounds 131b and 132b include 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 subjected to the drying and curing process And melts in the process of passing, forming an intermetallic compound with a part of the metal particles to enclose the metal particles 132a. At this time, the intermetallic compound may preferably contain a low melting point metal at 300 캜 or lower.

For example, Sn having a melting point of 213 to 220 캜. During the drying and curing process, Sn is melted. The molten Sn is precipitated by the capillary phenomenon of metal particles having a high melting point such as Ag or Cu and reacts with a part of Ag or Cu metal particles to form Ag ₃ Sn, Cu ₆ Sn ₅ , and Cu ₃ Sn. Ag or Cu not participating in the reaction remains in the form of metal particles 131a and 132a as shown in FIG. 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 section of the multilayer ceramic capacitor according to the embodiment of the present invention taken near the B region, an intermetallic compound is densely formed in the first conductive resin layer, The intermetallic compound of the conductive resin layer is formed in a network form.

The intermetallic compound is densely formed in the first conductive resin layer to reduce moisture infiltration path, thereby improving the moisture resistance reliability. The electrical connection with the internal electrode is improved to lower the ESR (Equivalent Series Resistor) The resistance to stress is also increased.

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

When the intermetallic compound of the first conductive resin layer is less than 60% by area, moisture resistance reliability may be poor. When the intermetallic compound is more than 75% by area, adhesiveness to the body may be poor.

When the intermetallic compound of the second conductive resin layer is more than 50% by area, it is difficult to form the intermetallic compound of the first conductive resin layer by 60% or more by area. The lower limit of the intermetallic compound is not particularly limited, Area%.

On the other hand, the intermetallic compound 131b of the first conductive resin layer is formed by interposing a metal having a low melting point 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 ≪ / RTI > compounds.

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

At this time, 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 the body 110 and the plating layer 133 together.

In the case of forming a conductive resin layer by using a paste containing conventional Cu, glass frit and thermosetting resin, the glass frit component helps to form an alloy between the Cu particle and the Ni inner electrode and acts as a binder To perform sealing. That is, when the temperature at which the glass frit component melts, the sintering temperature of Cu, and the alloy forming temperature between Cu and Ni are similar, sintering of the copper particles occurs and densification proceeds. As a result of the alloy formation between Cu and Ni, And the glass frit component serves to fill the void space. However, the formation temperature is 700 to 900 DEG C, residual stress remains, and problems such as spinning cracks may occur. Further, there may arise a problem that the chemical resistance property to the plating solution may be weakened depending on the glass frit component.

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

In the case of low-melting paste containing Ag powder, Sn-based solder powder, and base resin, since the epoxy resin is formed through epoxy curing, the residual stress is relatively less generated and the volume decreases as the intermetallic compound is formed. The generation of residual stress can be effectively suppressed as compared with the alloy of Cu-Ni expanding. Further, since the intermetallic compound is densely formed in the first conductive resin layer, the electrical connection with the internal electrode can be improved and the path such as moisture absorption or plating solution penetration can be blocked, thereby improving the moisture resistance reliability.

4 is a photograph of a cross section of a conventional multilayer ceramic capacitor in the vicinity of region B, which is formed by using a paste containing Cu, glass frit, and a thermosetting resin, to form a conductive resin layer. 5 is a sectional view of a 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 containing Ag powder, Sn-based solder powder, and base resin, It's a picture.

In FIG. 4, one conductive resin layer having uniform density is formed. In the case of 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 As shown in FIG.

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

For example, an Ag powder, a Sn-based solder powder including two or more Sn-based solders having different melting points, and a base resin are mixed and dispersed using a 3-roll mill to prepare a paste . The paste is coated on the body and dried, and then heated to 350 DEG C at a temperature raising rate of 4.6 DEG C / minute to hold and cure the paste. The Sn-based solder having a low melting point at the time of curing is first melted to increase the fluidity, and the liquid solder component moving toward the internal electrode is increased, so that the first conductive resin layer having a more dense structure can be formed.

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

For example, an Ag powder, a Sn-based solder powder containing two or more Sn-based solders having different particle sizes, and a base resin are mixed and dispersed using a 3-roll mill to prepare a paste can do. The paste is coated on the body and dried, and then heated to 350 DEG C at a temperature raising rate of 4.6 DEG C / minute to hold and cure the paste. As the particle size of the Sn-based solder increases, the fluidity increases as the Sn-based solder is thermally cured, so that the Sn-based solder having a large particle size first moves toward the internal electrode, thereby forming the first conductive resin layer having a more dense structure.

Sn-based solder powder, for example, Sn-based solder powder is Sn, Sn _{96 . 5} Ag _{3 . 0} Cu _{0 .5,} may include Sn ₄₂ Bi and Sn ₅₈ Bi _{72 28} at least one selected from.

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

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, and that various changes and modifications may be made therein without departing from the scope of the invention. It will be obvious to those of ordinary skill in the art.

100: Multilayer Ceramic Capacitor
110: Body
111: dielectric layer
121 and 122: first and second inner electrodes
130, 140: first and second outer electrodes
131, 141: the first conductive resin layer
132, 142: a second conductive resin layer
131a, 132a: metal particles
131b, 132b: intermetallic compound
131c and 132c: base resin
133, 134, 143, 144: Plating layer

Claims (10)

A body including a dielectric layer and an internal electrode, and an external electrode disposed on one side of the body,
Wherein the external electrode comprises: 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 comprise a plurality of metal particles, an intermetallic compound surrounding the plurality of metal particles, and a base resin, wherein an area fraction of the intermetallic compound in the first conductive resin layer A multilayer ceramic capacitor higher than the conductive resin layer.
The method according to claim 1,
Wherein the first conductive resin layer contains 60 to 75% by area of an intermetallic compound,
Wherein the second conductive resin layer contains 50% by area or less of intermetallic compound (excluding 0% by area).
The method according to claim 1,
Wherein the metal particles comprise at least one of Ag and Cu.
The method according to claim 1,
Wherein the intermetallic compound comprises at least one of Ag ₃ Sn, Cu ₆ Sn _5, and Cu ₃ Sn.
The method according to claim 1,
The external electrode
And a plating layer disposed on the second conductive resin layer.
The method according to claim 1,
Wherein the first and second conductive resin layers are formed by thermally curing a paste containing Ag powder, Sn-based solder powder, and base resin.
The method according to claim 6,
Wherein the Sn-based solder powder includes two or more Sn-based solders having different particle sizes.
The method according to claim 6,
Wherein the Sn-based solder powder includes two or more Sn-based solders having different melting points.
The method according to claim 6,
The Sn-based solder powder is Sn, Sn _{96 . 5} Ag _{3 . 0} Cu _{0 .5,} a multilayer ceramic capacitor comprising a Sn ₄₂ Bi and Sn ₅₈ Bi _{72 28} at least one selected from.
The method according to claim 6,
Wherein the Ag powder contained in the Ag powder has a particle size of 0.5 to 3 占 퐉.

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