JP2017204627A - Laminated type capacitor and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated type capacitor which enables a low-temperature rapid firing process, and by which both of a high dielectric constant and high reliability can be ensured.SOLUTION: A laminated type capacitor and a method for manufacturing the same are provided according to the present invention. The capacitor laminated type capacitor comprises a main body including dielectric layers having a core-shell structure and including a ferroelectric. The capacitor laminated type capacitor is arranged by laminating at least two or more layers composed of blocks of a ceramic composition with a coating film of 1-2 nm in thickness formed on a shell part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a multilayer capacitor and a method for manufacturing the same.

  A multilayer capacitor (MLCC) is an electronic component that has an advantage of being small in size but having a high capacity and being easy to be mounted, and includes a liquid crystal display (LCD) and a plasma display panel. Chips that are attached to circuit boards of various electronic products such as video devices such as (PDP: Plasma Display Panel), computers, personal digital assistants (PDAs) and mobile phones, and charge or discharge electricity It is a condenser of the form.

  In recent years, along with the trend toward downsizing and speeding up of electronic products, the above-mentioned multilayer capacitors are also required to be downsized and high capacity, and to prevent a decrease in capacity when a DC voltage is applied. Therefore, high reliability having excellent DC characteristics and withstand voltage characteristics is required.

  Therefore, in order to realize the high reliability of the multilayer capacitor, not only the dielectric layer and the internal electrode need to be thinned, but also the firing in which the product is rapidly fired at a low temperature during the firing in the product manufacturing process. Since a process is required, development of a material suitable for such a low temperature / rapid firing process is required.

Korean Published Patent No. 2007-0023228 JP 2011-256091 A

  An object of the present invention is to provide a multilayer capacitor that can be rapidly fired at a low temperature and that can simultaneously ensure a high dielectric constant and high reliability, and a method for manufacturing the same.

  According to one aspect of the present invention, there is provided a core-shell structure in which a dielectric layer of a capacitor body includes a ferroelectric and includes an inner portion (core portion) and an outer shell portion (shell portion). Provided is a multilayer capacitor formed by laminating at least two layers of a plurality of block-like ceramic compositions having a shell part and further having a coating film having a thickness of 1 to 2 nm.

According to another aspect of the present invention, a ceramic composition used for a ceramic sheet for forming a dielectric layer is manufactured. The ceramic composition is seeded by adding a metal foreign substance and TiO ₂ to Ba (OH) _2. Adding a grain growth inhibitor to the seed and then growing the grain to form the seed into a core-shell structure, adjusting the molar ratio of the seed, and the surface of the seed After patching the monomolecular adsorbent to the substrate, a metal ion in the form of nitrate or hydrochloride is added and reacted to form a coating film of 1 to 2 nm, and the coating film is formed. And drying the seed to produce a block-like powder, and a method for producing a multilayer capacitor.

  According to an embodiment of the present invention, there is an effect that a high dielectric constant and high reliability of a multilayer capacitor can be secured at the same time.

1 is a perspective view illustrating a schematic structure of a multilayer ceramic capacitor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the multilayer ceramic capacitor when the II ′ line shown in FIG. 1 is taken as a cut surface. It is sectional drawing which expanded and showed A part in FIG. FIG. 2 is an exploded perspective view showing a laminated structure of internal electrodes in FIG. 1. 2 is a photograph showing a ceramic composition according to an embodiment of the present invention by STEM-EDS. 3 is a flowchart sequentially illustrating a method of manufacturing a ceramic composition according to an embodiment of the present invention. 3 is a flowchart sequentially illustrating a method of manufacturing a multilayer capacitor according to an embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention can be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. In addition, the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art. Accordingly, the shape and size of elements in the drawings may be enlarged or reduced (or highlighted or simplified) for a clearer description.

  Note that components having the same functions within the scope of the same idea shown in the drawings of the embodiments will be described using the same reference numerals.

  Further, in the entire specification, “including” a certain component does not mean that other components are excluded unless specifically stated otherwise, and may include other components. It means that you can do it.

  Referring to FIGS. 1 and 2, the multilayer ceramic capacitor 100 according to the present embodiment includes a main body 110 and first and second external electrodes 131 and 132.

  When the direction of the main body 110 is defined to clearly describe the present embodiment, L, W, and T displayed on the drawing indicate a length direction, a width direction, and a thickness direction, respectively.

  Here, the thickness direction can be used as the same concept as the stacking direction in which the dielectric layers 111 are stacked.

  In addition, the shape of the main body 110 is not particularly limited, and can have, for example, a substantially hexahedral shape.

  In the present embodiment, for convenience of explanation, a pair of surfaces facing each other in the thickness direction T among the wall surfaces of the main body 110 formed by stacking the dielectric layers 111 are defined as a first surface and a second surface, A pair of surfaces connecting the first surface and the second surface and facing each other in the length direction L are a third surface and a fourth surface, a pair perpendicular to the third surface and the second surface, and facing each other in the width direction. The surfaces are defined as the fifth surface and the sixth surface.

  The main body 110 includes an active region 115 and an upper cover 112 and a lower cover 113 which are margin portions.

  The active region 115 is a part that contributes to the capacitance formation of the capacitor 100, and includes a plurality of dielectric layers 111, a plurality of first internal electrodes 121, and a plurality of second internal electrodes 122.

  The active region 115 includes a plurality of dielectric layers 111 and first and second internal electrodes 121 and 122 that are alternately arranged with the dielectric layers 111 interposed therebetween in the thickness direction T. And then fired.

  The dielectric layer 111 is in a sintered state, and the boundary between the adjacent dielectric layers 111 is difficult to be confirmed without using a scanning electron microscope (SEM: Scanning Electron Microscope). It can be in an integrated state.

  Referring to FIG. 3, the dielectric layer 111 is configured by laminating at least two layers, preferably 3 to 5 layers, of a high dielectric constant ceramic powder 111 a containing a ferroelectric.

The material forming the ceramic powder 111a is, for example, a BaTiO ₃ (barium titanate) -based material, in which Ca (calcium), Zr (zirconium), and the like are partly dissolved in BaTiO ₃ (Ba _1-x Ca _x ) TiO ₃ , Ba (Ti _1-y Ca _y ) O ₃ , (Ba _1-x Ca _x ) (Ti _1-y Zr _y ) O ₃ , or Ba (Ti _1-y Zr _y ) O ₃ The material for forming the ceramic powder according to the present invention can be included, but is not limited thereto.

  Further, the ceramic powder 111a has a core-shell structure including an inner core part (core) and a shell part (shell) which is a surface layer part, and as shown in FIG. A coating film having a thickness is further formed, and each is formed into a block shape formed of a substantially tetrahedron.

  At this time, if the thickness of the coating film exceeds 2 nm, the coating films of the respective powders are aggregated with each other, so that the form of the film is not maintained, and the agglomerates are in the form of islands (like scattered islands) There is a risk that a problem will occur. On the other hand, when the thickness of the coating film is less than 1 nm, the form of the layer is not stably maintained, and on the contrary, it may cause the sinterability during firing to be hindered.

  The coating film can be formed by reacting a monomolecular adsorbent containing alkali metal atoms with an additive in the form of nitrate or hydrochloride.

  At this time, as the monomolecular adsorbent, for example, a molecular electrolyte or a ketone-based substance can be used, and the alkali metal is an alkali metal element having an atomic number of 20 or less, for example, Na ( Sodium), K (potassium), or Li (lithium).

  On the other hand, since the produced ceramic powders 111a are all in different sizes (particle sizes, etc.), voids may be generated between the ceramic powders 111a when stacked one above the other. . Therefore, the dielectric layer 111 further includes glass 111b in order to remove the voids caused by the variation in the size of the grains as described above and to make the height when the ceramic powder 111a is laminated as designed. Can be made.

  At this time, the glass 111b may be included so that the content ratio (molar ratio) is 1 to 5 mol% with respect to 100 mol of the ceramic powder 111a. When the content ratio of the glass 111b is less than 1 mol%, there may occur a problem that the dielectric layer is not sufficiently sintered when the main body 110 is fired. Further, when the content ratio of the glass 111b exceeds 5 mol%, there may occur a problem that the dielectric characteristics of the main body 110 are not sufficiently exhibited.

  Referring to FIG. 4, the first internal electrode 121 and the second internal electrode 122 are electrodes having different polarities, and are disposed to face each other in the stacking direction of the dielectric layer 111. The dielectric layers 111 disposed between the second internal electrodes 122 may be electrically insulated from each other.

  Each of the first internal electrode 121 and the second internal electrode 122 extends along the length direction L in the main body 110, and each of the first internal electrode 121 and the second internal electrode 122 has one end portion. Can be arranged so as to be exposed on the third surface and the fourth surface forming both end surfaces in the length direction L of the main body 110, respectively.

  Further, one end of the first internal electrode 121 and the second internal electrode 122 exposed on the third surface and the fourth surface forming both end surfaces in the length direction L of the main body 110 is the length direction L of the main body 110. The first external electrode 131 and the second external electrode 132 can be electrically connected to portions exposed on the third and fourth surfaces forming both end surfaces of the first external electrode 131 and the second external electrode 132, respectively.

  With the above-described configuration, when a predetermined voltage is applied to the first and second external electrodes 131 and 132, charges are accumulated between the first internal electrode 121 and the second internal electrode 122 facing each other. . At this time, the capacitance of the multilayer capacitor 100 is proportional to the area of the overlapping region where the first internal electrode 121 and the second internal electrode 122 overlap with each other along the stacking direction of the dielectric layer 111.

  The thicknesses of the first and second internal electrodes 121 and 122 can be determined according to the application, and are within a range of 0.05 to 2.5 μm in consideration of the size of the main body 110, for example. However, the thicknesses of the internal electrodes 121 and 122 in the present invention are not limited to such dimensions.

  The first and second internal electrodes 121 and 122 are formed of a conductive metal. In this embodiment, a material such as nickel (Ni) or a nickel (Ni) alloy can be used. , 122 are not limited to these.

  A screen printing method or a gravure printing method can be used as the conductive metal printing method, but the conductive metal printing method in the present invention is not limited to these.

  The cover includes an upper cover 112 and a lower cover 113.

  Referring to the drawing, the upper cover 112 is a portion formed to have a predetermined thickness on the upper surface of the first internal electrode 121 disposed at the top in the active region 115, and the lower cover 113 is formed of the active region 115. 2 is a portion formed to have a predetermined thickness on the lower surface of the second internal electrode 122 disposed at the bottom.

  For example, the upper cover 112 and the lower cover 113 are formed by stacking at least one dielectric layer 111 included in the active region 115 on the upper and lower portions of the active region 115 in the main body 110 of the capacitor 100. can do.

  The first and second external electrodes 131 and 132 are disposed on the third and fourth surfaces forming both end surfaces in the length direction L of the main body 110, and the first and second internal electrodes 121 and 122 are connected to the third surface. The parts exposed on the fourth surface are in contact with each other and are electrically connected.

  At this time, the first and second external electrodes 131 and 132 can be provided so as to extend to a part of the first surface and the second surface facing each other in the thickness direction T of the wall surface of the main body 110. .

  Further, the first and second external electrodes 131 and 132 are provided so as to extend to a part of the fifth surface and the sixth surface facing each other in the width direction W of the wall surface of the main body 110 as necessary. Accordingly, the fixing strength of the external electrodes 131 and 132 to the main body 110 can be improved.

  The first and second external electrodes 131 and 132 can be formed by a method of printing or applying a conductive paste containing a conductive metal.

  The conductive metal can include nickel (Ni), copper (Cu), palladium (Pd), gold (Au), or an alloy thereof, but the conductive material used in the present invention is limited to these. Is not to be done.

  On the other hand, if necessary, a plating layer (not shown) can be further formed on the surfaces of the first and second external electrodes 131 and 132 using nickel (Ni) or tin (Sn).

Manufacturing Method of Multilayer Capacitor Hereinafter, a manufacturing method of the multilayer capacitor 100 according to an embodiment of the present invention will be described with reference to the flowcharts shown in FIGS. 6 and 7.

  First, a method for producing a ceramic composition used for forming the dielectric layer 111 of the present invention will be described.

In the ceramic composition according to the present embodiment, first, Ba (OH) ₂ is prepared (step S10), and metal foreign matter is added to the Ba (OH) ₂ in order to increase the value of the crystal axis ratio (step S21). , TiO ₂ is further added (step S22), and a seed is synthesized (step S20).

  Next, a grain growth inhibitor is added to the seed (step S31), and grains are grown while increasing the crystallinity of the dielectric powder to form a seed in a core-shell structure (step S30).

  Next, the molar ratio of the seed having grown grains is adjusted (step S40).

  The seed having the adjusted molar ratio is dispersed in a slurry form having a solid content of an aqueous system and a weight ratio of about 20 to 40% by weight.

  Therefore, after adding a monomolecular type adsorbent to the seed and patching the surface of the seed, a metal ion in the form of nitrate or hydrochloride is added and reacted (step S51), as shown in FIG. A coating film having a thickness of 1 to 2 nm is formed on the seed shell (step S50).

  At this time, a molecular electrolyte or a ketone-based substance can be used as the monomolecular adsorbent, and the alkali metal atom can be a metal element such as Na (sodium) or K (potassium).

  Next, the seed on which the coating film is formed is dried (step S60), thereby completing a ceramic composition having a block-like powder form.

  In order to manufacture the multilayer capacitor 100 of the present embodiment, first, a plurality of ceramic sheets are manufactured using the ceramic composition manufactured by the method as described above (step S110).

  The ceramic sheet is for forming the active region 115 of the main body 110 and the dielectric layer 111 included in the upper cover 112 and the lower cover 113.

  The ceramic sheet is prepared by mixing a ceramic powder, a polymer, a solvent, and the like, and a slurry having a thickness of several μm is obtained by applying the slurry to a carrier film using a doctor blade or the like and drying the slurry. It is possible to manufacture it so that it becomes a shape.

  At this time, as an additional material, glass may be further added so as to be disposed between the ceramic compositions.

  The glass may be included so that the content ratio (molar ratio) to 100 mol of the ceramic composition is 1 to 5 mol%.

  Next, the first and second internal electrodes 121 and 122 are printed on at least one surface of each of the ceramic sheets by printing a conductive paste containing a conductive powder such as nickel so as to form a layer having a predetermined thickness. Is formed (step S120).

  In addition, each of the first and second internal electrodes 121 and 122 is such that one end portion in the length direction L of the ceramic sheet is exposed to both end surfaces (third surface and fourth surface) of the main body portion 110. Can be formed.

  At this time, a screen printing method or a gravure printing method can be used as a method for printing the conductive paste, but the printing method in the present invention is not limited to these.

  Next, the plurality of ceramic sheets on which the first and second internal electrodes 121 and 122 are formed are arranged so that the first and second internal electrodes 121 and 122 face each other with the ceramic sheets interposed therebetween. Laminate. And after arrange | positioning the ceramic sheet | seat in which the internal electrodes 121 and 122 are not formed in the upper surface and the lower surface, a laminated body is manufactured by pressing (step S130).

  Next, the laminate is cut into regions corresponding to one capacitor to form chips, and fired to have first and second surfaces facing each other in the thickness direction T as wall surfaces, One end of each of the first and second internal electrodes 121 and 122 is alternately exposed, and further includes third and fourth surfaces forming both end surfaces in the length direction L as wall surfaces, and each other in the width direction W. The main body 110 further having the fifth and sixth surfaces facing each other as a wall surface is manufactured (step S140).

  At this time, the ceramic composition in the ceramic sheet constituting the laminate has a block-like structure and is fired in a state where the mutual contact is not point contact but surface contact. be able to.

  In addition, such surface contact between the ceramic compositions has an effect of suppressing the entire diffusion of the additive of the ceramic sheet within the grains, and therefore, the core portion of the ceramic composition has a high dielectric constant. An area can be secured.

  Therefore, the effect of simultaneously improving the dielectric constant and reliability of the multilayer capacitor 100 can be expected due to the characteristics of the ceramic sheet.

  Next, the first and second internal electrodes 121 and 122 are electrically connected to the exposed portions on the third and fourth surfaces forming both end surfaces in the length direction L of the main body 110, respectively. As described above, the first and second external electrodes 131 and 132 are formed using a conductive paste (step S150).

  At this time, the first and second external electrodes 131 and 132 can be formed by a method such as dipping or roller, but the method of forming the external electrodes 131 and 132 in the present invention is not limited to these methods. Absent.

  Next, the capacitor formed as described above is fired to complete the multilayer capacitor 100 (step S160).

A conventional method for manufacturing the dielectric layer 111 is to mix BaTiO ₃ having a spherical particle shape as a base material and amorphous metal oxide powder as an additive, and uniformly disperse the organic solvent as a solvent. It was manufactured by forming it into a sheet and then drying it.

  However, due to the high activation energy of the metal oxide powder used as an additive, the dielectric layer 111 is excessively grain-grown and has a low reliability. Therefore, although firing under conditions of low speed and high temperature is possible, there has been a problem that baking under conditions of rapid and low temperature and baking in a thin layer state are difficult.

In order to solve the above problems, a technique for producing a metal oxide powder used as an additive into a nano metal oxide having a particle size of 20 nm or less and a technique for coating an additive on the surface of BaTiO ₃ are known. ing.

  However, in the case of the above nanometal oxide, due to the limitation of fine particle dispersion, the effect of firing under a rapid and low temperature condition or firing in a thin layer state is not high.

Further, in the case of the technique of coating the additive on the surface of BaTiO ₃ , the generation of excessive grain growth can be partially suppressed, but the geometric characteristic indicating the sintering characteristic of the point contact between the particles. Therefore, a long baking time is still required.

  As described above, according to the present embodiment, the ceramic composition forming the dielectric layer has a core-shell structure, and a coating film having a thickness of 1 to 2 nm is formed on the shell portion. Additives such as hydrochloride react fast with the base material, but generally react only at the shell and only minimally diffuse to the core, so rapid firing at low temperatures Is possible.

  Therefore, when the dielectric layer 111 and the main body 110 of the capacitor 100 are manufactured using such materials, the high dielectric constant and high reliability of the multilayer capacitor 100 can be secured at the same time.

  As mentioned above, although embodiment of this invention was described in detail, the scope of the present invention is not limited to this, and various correction and deformation | transformation are within the range which does not deviate from the technical idea of this invention described in the claim. It will be apparent to those having ordinary knowledge in the art.

DESCRIPTION OF SYMBOLS 100 Multilayer capacitor 110 Main body 111 Dielectric layer 111a Ceramic composition 111b Glass 112 Upper cover 113 Lower cover 115 Active region 121,122 1st and 2nd internal electrode 131,132 1st and 2nd external electrode

Claims (9)

A main body including a plurality of dielectric layers, and first and second internal electrodes arranged alternately with each of the plurality of dielectric layers interposed therebetween;
The first and second portions are respectively disposed on both end surfaces in the longitudinal direction of the main body, and are electrically connected to portions where the first and second internal electrodes are respectively exposed on the both end surfaces. A second external electrode,
Each of the plurality of dielectric layers has a core-shell structure including a ferroelectric, and a coating film having a thickness of 1 to 2 nm is further formed on the surface of the shell portion constituting the core-shell structure. A multilayer capacitor in which at least two layers of the plurality of block-shaped ceramic compositions are laminated.   The multilayer capacitor according to claim 1, wherein the coating film is formed by reacting a monomolecular adsorbent containing an alkali metal atom with an additive in the form of nitrate or hydrochloride.   The multilayer capacitor according to claim 2, wherein the monomolecular adsorbent contains a molecular electrolyte or a ketone-based substance, and the alkali metal atom is Na (sodium) or K (potassium).   4. The multilayer capacitor according to claim 1, wherein each of the plurality of dielectric layers further includes a glass disposed between the plurality of block-shaped ceramic compositions. 5. .   Each of the plurality of dielectric layers is formed of a material containing glass with respect to ceramic powder, and the glass is included so that the content ratio with respect to 100 mol of ceramic powder is 1 to 5 mol%. The multilayer capacitor according to claim 4. Laminating at least two layers of block-shaped ceramic composition to produce a ceramic sheet;
Forming the first and second internal electrode patterns on the ceramic sheet using a conductive paste,
Alternately laminating the ceramic sheets on which the first and second internal electrode patterns are formed, and then pressurizing to produce a laminate; and
Cutting the laminate so that a part of the first and second internal electrode patterns are exposed, and then firing the laminate to manufacture a main body including the first and second internal electrodes;
Forming first and second external electrodes using a conductive paste on the main body so as to be electrically connected to the exposed portions of the first and second internal electrodes, respectively;
Firing the body on which the first and second external electrodes are formed, and
The ceramic composition is
Adding a metal foreign substance and TiO ₂ to Ba (OH) ₂ to synthesize a seed;
Adding a grain growth inhibitor to the seed and then growing the grain to form a seed in a core-shell structure;
Adjusting the molar ratio of the seeds;
After patching the surface of the seed with a monomolecular adsorbent, adding a metal ion in the form of nitrate or hydrochloride to react to form a coating film having a thickness of 1 to 2 nm;
A step of producing a block-like powder by drying the seed on which the coating film is formed.   In the method for producing a ceramic composition, the monomolecular adsorbent contains an alkali metal atom and a molecular electrolyte or a ketone-based substance, and the alkali metal atom is Na (sodium) or K (potassium). A method for producing a multilayer capacitor according to claim 6.   8. The method of manufacturing a multilayer capacitor according to claim 6, wherein, in the step of manufacturing the ceramic sheet, the ceramic sheet is manufactured by further arranging glass between the stacked ceramic compositions.   The method for manufacturing a multilayer capacitor according to claim 8, wherein the ceramic sheet contains glass so that a content ratio of 100 mol of the ceramic composition is 1 to 5 mol%.