JP6376992B2 - Multilayer ceramic capacitor - Google Patents

Description

  The present invention relates to a multilayer ceramic capacitor including a multilayer body in which dielectric layers and internal electrode layers are alternately stacked.

  In recent years, there is a high demand for miniaturization of electronic components accompanying the increase in the density of electronic circuits used in digital electronic devices such as mobile phones and tablet terminals, and the miniaturization and large size of multilayer ceramic capacitors (MLCC) constituting the circuits are high. Capacity is rapidly increasing.

  The capacitance of the multilayer ceramic capacitor is proportional to the dielectric constant of the constituent material of the dielectric layer constituting the capacitor and the number of laminated dielectric layers, and inversely proportional to the thickness per dielectric layer. Therefore, in order to meet the demand for miniaturization, it is required to increase the dielectric constant of the material and reduce the thickness of the dielectric layer to increase the number of laminated layers.

  By the way, in the multilayer ceramic capacitor, protective regions such as a cover layer and a side margin portion that cover the multilayer body that is a capacitance layer are provided. However, when the number of stacked dielectric layers is increased in order to increase the capacitance of the capacitor, it is necessary to make the thickness of the cover layer provided as the outermost layer in the stacking direction thinner in order to fit within a specified chip size. In addition, even when the crossing area of the internal electrode layers is increased in order to increase the capacity, the thickness of the side margin portions provided on both side surfaces orthogonal to the stacking direction of the stacked body must be reduced.

  For example, Patent Document 1 discloses a multilayer ceramic capacitor having a cover layer thickness of 15 μm or less. Further, Patent Document 2 proposes that an identification unit for identifying the upper and lower parts of the ceramic body according to the difference in brightness or hue is provided in any one of the upper and lower cover layers of the multilayer ceramic capacitor. This identification part includes a dielectric layer to which one or more metals selected from Ni, Mn, Cr and V are added, suggesting that a difference in brightness or hue can be recognized outside the ceramic body. ing.

JP 2014-11449 A JP 2014-22722 A

  As described above, in a monolithic ceramic capacitor with a reduced size and increased capacity, the thickness of the protective layer (protective region) such as the cover layer and the side margin portion must be made thinner. However, if the thickness of the protective layer is reduced, the internal electrode may be recognized as a discolored portion through the thin protective layer in the chip appearance image inspection. It is difficult to discriminate the difference between the color difference portion where the internal electrode can be seen through and the color difference between the portion without the internal electrode and the actual defect portion such as a crack or delamination in the ceramic by image recognition processing. Therefore, for example, in a multilayer ceramic capacitor having a thin protective layer having a thickness of 15 μm or less, there has been a problem that the end of the internal electrode seen through from the outside is mistaken as a defective portion and erroneously determined.

  Therefore, the present invention provides a multilayer ceramic capacitor that is downsized and increased in capacity, and improves the accuracy of chip appearance inspection by preventing the internal electrodes in the ceramic sintered body from being seen through from the outside. It is aimed.

  In order to solve the above problems, the present invention is a multilayer ceramic capacitor comprising a laminate in which dielectric layers and internal electrode layers are alternately laminated, and a protective region covering at least a part of the laminate. A dye component for darkening the protective region is added to the protective region.

  In the multilayer ceramic capacitor, the thickness of the protective region is preferably 15 μm or less.

  In the multilayer ceramic capacitor, the protective region contains Ba and Ti as main components, and the dye component contains at least one element selected from the group consisting of V, Mo, Nb, Ta, W, and Mn. It is preferable to do.

  In the multilayer ceramic capacitor, it is preferable that the protective region contains 0.2 mol or more of the dye component with respect to 100 mol of Ba or Ti as the main component element.

  In the multilayer ceramic capacitor, the composition amount of the subcomponent in the dielectric layer is preferably smaller than the composition amount of the dye component in the protection region. In this case, the ratio a / b of the composition amount a of the dye component in the protection region to the composition amount b of the subcomponent in the dielectric layer satisfies the relational expression of 1.5 ≦ a / b ≦ 5.0. It is preferable.

  In the multilayer ceramic capacitor, the protective region includes at least one element selected from Sr and Ca as a main component element and at least one element selected from Ti and Zr, and the dye component includes V, Mo, Nb, It is preferable to contain at least one element selected from the group consisting of Ta, W, and Mn.

  In the multilayer ceramic capacitor, the protective region to which the dye component is added is provided on both sides of the cover layer, which is the outermost layer in the stacking direction of the multilayer body, and / or orthogonal to the stacking direction of the multilayer body. A side margin is preferable.

  According to the present invention, by adding a dye component to the protective region of the laminate, the internal electrode layer is not seen through in appearance image inspection. Thereby, it is possible to prevent erroneous determination due to the internal electrode layer being image-recognized and to improve the accuracy of the image inspection.

FIG. 1 is a perspective view schematically showing a partial cross section of a multilayer ceramic capacitor according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a II cross section of the multilayer ceramic capacitor of FIG. FIG. 3 is a schematic view showing a III cross section of the multilayer ceramic capacitor of FIG.

[Multilayer ceramic capacitor]
FIG. 1 is a perspective view schematically showing a partial cross section of a multilayer ceramic capacitor 1 according to the present invention. The multilayer ceramic capacitor 1 is formed on a ceramic sintered body 10 having a chip size and a shape (for example, a 1.0 × 0.5 × 0.5 mm rectangular parallelepiped) defined by a standard, and on both sides of the ceramic sintered body 10. And a pair of external electrodes 20. The ceramic sintered body 10 is mainly composed of particle crystals containing Ba and Ti, and a laminated body 11 (“internal active layer” or “capacitor” in which dielectric layers 12 and internal electrode layers 13 are alternately laminated. And a protective region 14 that covers at least a part of the laminate 11. The protection region 14 includes a cover layer 15 formed as the outermost layer above and below the stack 11 in the stacking direction, and side margin portions 16 provided on both sides orthogonal to the stacking direction of the stack 11.

  In the multilayer body 11, the thickness of the dielectric layer 12 sandwiched between the two internal electrode layers 13 is 0.8 μm or less in accordance with specifications such as capacitance and required breakdown voltage, and the total number of laminated layers is It has hundreds to hundreds of high-density multilayer structures.

  The cover layer 15 formed in the outermost layer portion of the multilayer body 11 and the side margin portions 16 provided on both surface sides orthogonal to the stacking direction of the multilayer body 11 provide moisture from the outside to the dielectric layer 12 and the internal electrode layer 13. It is provided to protect against contamination such as contamination and contamination and to prevent their deterioration over time.

  Further, the internal electrode layer 13 has its edges alternately drawn out to a pair of external electrodes 20 having different polarities at both ends in the length direction of the dielectric layer 12.

The dielectric layer 12 of the multilayer ceramic capacitor 1 includes ceramic particles having a main component element including Ba and Ti and a subcomponent including the element X. The main component of the ceramic particles is, for example, BaTiO ₃ . Specifically, the subcomponent element X is at least one element selected from the group consisting of Mo, Ta, Nb, and W. The ceramic particles further contain rare earth elements (Y, Sm, Eu, Tb, Gd, Dy, Ho, Er, Tm, Yb) and Si compounds such as SiO ₂ as additive components.

  Further, the composition amount (concentration) of the subcomponent element X in the dielectric layer 12 is not particularly limited, but from the viewpoint of the life characteristics and bias characteristics of the multilayer ceramic capacitor 1, the amount of Ti in the dielectric layer 12 is 100 mol. It is preferable that it is 0.05-0.3 mol with respect to it.

  The average particle diameter of such ceramic particles is not particularly limited, but is preferably 80 to 800 nm from the viewpoint of thinning the dielectric layer 12. In this specification, the average particle size means that the ceramic particles are observed with a scanning electron microscope (SEM) or a TEM, and the magnification is adjusted to be about 80 particles in one image. This is the average value of the Feret diameters obtained by obtaining a plurality of photographs and measuring the total number of particles on the photographs. The Feret diameter is a fixed tangent diameter defined by the distance between two parallel tangents that sandwich the particle.

  The conductive material for forming the internal electrode layer 13 is not particularly limited, but may contain at least one metal element selected from the group consisting of Ag, Pb, Pt, Ni, and Cu, for example.

The cover layer 15 and the side margin portion 16 which are the protection regions 14 of the stacked body 11 contain Ba and Ti as main component elements. The main component of the cover layer 15 and the side margin portion 16 is the same as the main component of the dielectric layer 12, and is preferably BaTiO ₃ , for example. The cover layer 15 and the side margin 16 are formed to have a thickness of 15 μm or less from the viewpoint of obtaining the maximum capacity within the chip dimensions defined by the standard. Here, the “thickness” of the cover layer refers to the shortest distance between the cover layer surface and the internal electrode closest to the cover layer surface (see FIG. 2). The “thickness” of the side margin refers to the shortest distance between the surface of the side margin and the end of the internal electrode closest to the surface of the side margin (see FIG. 3). That is, the “thickness” of the protection region refers to the shortest distance between the surface of the protection region and the internal electrode closest to the protection region surface.

The cover layer 15 and / or the side margin portion 16 is added with a dye component that darkens the protective region 14 as a subcomponent. The subcomponent (pigment component) added to the protective region 14 may contain the same element as the subcomponent of the dielectric layer 12, but in addition, from the group consisting of V, Mo, Nb, Ta, W, Mn It may contain at least one element selected. It is preferable that the cover layer 15 and / or the side margin portion 16 contain 0.2 mol or more of a subcomponent (pigment component) with respect to 100 mol of Ba or Ti as a main component element. The ceramic sintered body 10 to which an auxiliary component of 0.2 mol% or more is added is in a state of not allowing visible light to pass beyond a depth (thickness) of at least 15 μm.
Moreover, it is preferable that the quantity of the subcomponent (pigment component) added to the cover layer 15 and / or the side margin part 16 is 10 mol or less with respect to 100 mol of Ba or Ti which is a main component element.

The composition amount of the subcomponent (dye component) in the cover layer 15 and / or the side margin portion 16 is larger than the composition amount of the subcomponent in the dielectric layer 12. Specifically, the pigment component composition amount a of the cover layer 15 is preferably at least 1.5 times or more the subcomponent composition amount b of the dielectric layer 12. When the pigment component amount a of the cover layer 15 is 1.5 times or more the subcomponent amount b of the subcomponent of the dielectric layer 12, the cover layer 15 is sufficiently darkened, and the inner electrode of the outermost layer in the chip appearance image inspection 13 is not recognized through the cover layer 15. Thereby, erroneous determination of ceramic particle structural defects can be prevented. Further, when the pigment component composition amount a of the side margin portion 16 is 1.5 times or more of the subcomponent composition amount b of the dielectric layer 12, the side margin portion 16 is darkened and the end portion of the internal electrode layer 13 is Is not recognized through the side margin 16.
Further, if the dye component composition amount “a” of the cover layer 15 and / or the side margin portion 16 is larger than five times the subcomponent composition amount “b” of the dielectric layer 12, a part of the dye component diffuses into the dielectric layer 12. This affects the sinterability and dielectric constant of the dielectric layer 12. When it exceeds 5 times, the dielectric constant decreases by 10% or more from the dielectric constant at 1.5 times due to diffusion due to the concentration difference.

  Therefore, the composition amount (mol ratio relative to the main component) a of the pigment component in the cover layer 15 and / or the side margin portion 16 is at least 1. of the composition amount (mol ratio relative to the main component) b of the subcomponent in the dielectric layer 12. The pigment component composition amount a is 5 times or less, preferably 3 times or less, preferably 3 times or less of the subcomponent composition amount b. That is, it is preferable that the ratio of the pigment component composition amount a to the subcomponent composition amount b satisfies the relational expression of 1.5 ≦ a / b ≦ 5.0.

  The pigment component added to the cover layer 15 and / or the side margin portion 16 preferably contains at least one element selected from the group consisting of V, Mo, Nb, Ta, W, and Mn. These elements can darken the cover layer 15 and / or the side margin 16 to a hue close to the internal electrode layer 13 containing Ni. That is, by adding the dye component containing these elements, the ratio (a / b) of the dye component amount a of the protective region 14 to the subcomponent amount b of the dielectric layer 12 is made as small as possible. And the influence on the sinterability and dielectric constant of the dielectric layer 12 can be reduced.

  The protective region to which the dye component is added may be both the cover layer 15 and the side margin portion 16 or only one of the cover layer 15 and the side margin portion 16. It is also considered effective to apply a dark paint or the like on the surface of the cover layer 15 and / or the side margin portion 16 in order to eliminate the see-through of the internal electrode from the outside of the chip.

  Further, in the present invention, the ceramic particles constituting the laminate 11 and the dielectric layer 12 include, as main component elements, at least one element selected from Sr and Ca and at least one element selected from Ti and Zr. For example, it can be applied to a temperature compensation capacitor. Since the ceramic particles having such a composition are lighter in color than the ceramic particles containing Ba and Ti as main components, it is easy to cause an erroneous determination due to the internal electrode layer 13 being seen through and image recognition. Also in such a multilayer ceramic capacitor, the cover layer 15 and / or the side margin portion 16 includes a subcomponent (pigment) containing at least one element selected from the group consisting of V, Mo, Nb, Ta, W, and Mn. By adding the component, the internal electrode layer 13 cannot be seen through, and the effects of the present invention can be exhibited particularly effectively.

[Manufacturing method of multilayer ceramic capacitor]
Hereinafter, a method for manufacturing the multilayer ceramic capacitor 1 described above will be described.
First, raw material powder for forming the dielectric layer 12 is prepared. The dielectric includes Ba and Ti, which are usually included in the dielectric layer 12 in the form of a sintered body of barium titanate (BaTiO ₃ ) particles.

  Barium titanate is a tetragonal compound having a perovskite structure and exhibits a high dielectric constant. This barium titanate is generally obtained by synthesizing barium titanate by reacting a titanium raw material such as titanium dioxide with a barium raw material such as barium carbonate. Various methods for synthesizing the barium titanate have been known. For example, a solid phase method, a sol-gel method, a hydrothermal method, and the like are known. Any of these can be used in the present invention.

  In this method, preferably, the above-mentioned subcomponent compound containing the subcomponent element X is first mixed with the barium titanate particles, and calcined at 820 to 1150 ° C. Subsequently, the calcined barium titanate particles are wet-mixed together with additive component compounds such as rare earth compounds and Si compounds, dried and pulverized to prepare ceramic powder. The amount of the subcomponent compound added to the dielectric layer is 0.05 to 0.3 mol with respect to 100 mol of Ti. The amount of the rare earth compound is 0.05 to 0.5 mol with respect to 100 mol of Ti, and the amount of the Si compound is 0.5 to 1.5 mol with respect to 100 mol of Ti.

  A binder such as polyvinyl butyral (PVB) resin, an organic solvent such as ethanol and toluene, and a plasticizer such as dioctyl phthalate (DOP) are added to the ceramic powder and wet mixed. Using the obtained slurry, a strip-like dielectric green sheet having a thickness of 1.2 μm or less is applied on a substrate by, for example, a die coater method or a doctor blade method and dried.

  The green sheet (cover sheet) serving as the cover layer is also prepared through the same process as the above-described dielectric green sheet. Further, the dielectric paste that becomes the side margin portion is also prepared through the same process as the above-described slurry. However, for these protective layers, as a pigment component for darkening, at least 1.5 times or more, preferably 0.2 mol% or more of the subcomponent of the subcomponent added to the dielectric layer, Mixed into barium titanate particles. The subcomponent compound added to the protective layer may be the same as the subcomponent compound added to the dielectric green sheet, but in addition, at least one selected from the group consisting of V, Mo, Nb, Ta, W, Mn It may contain an element.

  Then, a metal conductive paste containing an organic binder is printed on the surface of the dielectric green sheet by screen printing, thereby arranging patterns of internal electrode layers that are alternately drawn to a pair of external electrodes having different polarities. As the metal, nickel is widely adopted from the viewpoint of cost. In the metal conductive paste, barium titanate having an average particle diameter of 50 nm or less may be uniformly dispersed as a co-material.

  Thereafter, the dielectric green sheet on which the internal electrode layer pattern is printed is punched out to a predetermined size, and the punched dielectric green sheet is peeled off from the base material with the internal electrode layer 13 and the dielectric layer 12 being peeled off. And the internal electrode layers are alternately exposed to the pair of external electrodes having different polarities by alternately exposing the edges on the both end faces in the length direction of the dielectric layer. For example, 100 to 500 layers) are stacked. A 15 μm-thick cover sheet to be the cover layer 15 is laminated on the upper and lower sides of the laminated dielectric green sheets and pressed. Then, the laminate is cut into a predetermined chip size so that the side portion of the electrode is exposed, and a dielectric paste is applied to both cut surfaces perpendicular to the stacking direction where the electrode is exposed to a thickness of 15 μm. The side margin portion 15 is formed by drying.

  Thereafter, a Ni conductive paste to be the external electrode 20 is applied to both sides of the cut laminate and dried. Thereby, a molded body of the multilayer ceramic capacitor 1 is obtained. In addition, you may vapor-deposit an external electrode on the both end surfaces of a laminated body by sputtering method.

The molded body of the multilayer ceramic capacitor thus obtained is debindered in an N ₂ atmosphere at 250 to 500 ° C., and then fired at 1100 to 1300 ° C. for 10 minutes to 2 hours in a reducing atmosphere. Each compound constituting the dielectric green sheet sinters and grows. In this way, the laminated body 11 in which the dielectric layers 12 and the internal electrode layers 13 made of a sintered body are alternately laminated, the cover layer 15 formed as the outermost layer above and below the lamination direction, and both sides in the lamination direction A multilayer ceramic capacitor 1 having a side margin portion 16 formed on the side is obtained.

  In the present invention, the reoxidation treatment may be further performed at 600 to 1000 ° C. As another embodiment relating to the method for manufacturing a multilayer ceramic capacitor, the external electrode and the dielectric may be fired in separate steps. For example, the external electrode may be formed by firing a laminated body in which dielectrics are laminated and then baking a conductive paste on both ends thereof.

[Example]
Table 1 shows the manufacturing conditions and evaluation results of the prototyped MLCC. Sample No. In Nos. 1 to 26, 0.5 mol of holmium oxide and 100 mol of silicon dioxide were added to 100 mol of Ti as additional components. Sample No. In Nos. 27 to 33, 0.1 mol of holmium oxide and 100 mol of silicon dioxide were added as additive components to 100 mol of the main component. Moreover, the shape of the sample was a rectangular parallelepiped shape of 1.0 mm × 0.5 mm × 0.5 mm.

(Sample Nos. 1 to 26)
Sample No. 1 to 26 are MLCCs mainly composed of BaTiO ₃ . For these, a defective product having an image defect rate of 0% and a relative dielectric constant greater than 4000 was determined to be a conforming product. Among these samples, when the sub-component amount b in the dielectric layer is 0.05 to 0.3 mol%, the dye component amount a1 in the cover layer (thickness 13 to 15 μm) is 0.2 mol% or more, and the side margin Good results were obtained with samples (No. 1, 2, 8 to 10, 18, 20 to 26) in which the pigment component amount a2 in the parts (thickness 13 to 15 μm) was 0.2 mol% or more. The pigment component / subcomponent ratios in these examples were 1.5b ≦ a1 ≦ 5b and 1.5b ≦ a2 ≦ 5b.

  Sample No. in which no pigment component was added to the cover layer and / or the side margin. 3, 17 and sample Nos. With less pigment component of about 0.1 mol%. In 12, 15, etc., the image defect rate was as high as 30% and 60%. In addition, the sample ratios of the pigment component / subcomponent component ratios a1 / b and a2 / b are as small as about 1.0, respectively. 4 and 15 also had slightly higher image defect rates of 30% and 60%.

  Sample No. with a pigment component / subcomponent ratio exceeding 5.0 For 5, 6, 13, 14, and 19, the image defect rate was as good as 0%, but the relative dielectric constant was 4000 or less. Therefore, in order to obtain a small-sized and large-capacity multilayer ceramic capacitor, the pigment component / subcomponent component ratios a1 / b and a2 / b are preferably in the range of 1.5 to 5.0, respectively.

  Sample No. For 16 MLCCs, the amount of the dye component was 1.0 mol% (the dye component / subcomponent ratio was 1.0), but the image defect rate was 0%. The reason why the image defect rate is 0% is considered to be that the thickness of the cover layer and the side margin portion is as relatively large as 17 μm, and the internal electrode layer was not seen through from the outside.

(Sample No. 27-33)
Sample No. 27 to 33 are MLCCs mainly composed of other than BaTiO ₃ , and are samples containing at least one element selected from Sr and Ca and at least one element selected from Ti and Zr as main components. For these, an image defect rate of 0% was determined as a conforming product. For example, in sample No. 2 in which the amount of the dye component in the cover layer and the side margin is 0.2 mol%. With respect to 27 to 30, an image defect rate of 0% was achieved and good.

DESCRIPTION OF SYMBOLS 1 Multilayer ceramic capacitor 10 Ceramic sintered body 11 Laminated body 12 Dielectric layer 13 Internal electrode layer 15 Cover layer 16 Side margin part 20 External electrode

Claims (7)

A multilayer ceramic capacitor comprising a laminate in which dielectric layers and internal electrode layers are alternately laminated, and a protective region covering at least a part of the laminate,
A dye component that darkens the protected area is added to the protected area ;
The protective region to which the dye component is added is a cover layer that is an outermost layer in the stacking direction of the stacked body and a side margin portion that is provided on both sides orthogonal to the stacking direction of the stacked body. Multilayer ceramic capacitor.   The multilayer ceramic capacitor according to claim 1, wherein the protective region has a thickness of 15 μm or less. The protective region contains Ba and Ti as main component elements,
The multilayer ceramic capacitor according to claim 1 or 2, wherein the pigment component contains at least one element selected from the group consisting of V, Mo, Nb, Ta, W, and Mn.   The multilayer ceramic capacitor according to claim 3, wherein the protective region contains 0.2 mol or more of the dye component with respect to 100 mol of Ba or Ti as the main component element.   The multilayer ceramic capacitor according to any one of claims 1 to 4, wherein a composition amount of a subcomponent in the dielectric layer is smaller than a composition amount of the dye component in the protection region.   The ratio a / b of the composition amount a of the dye component in the protection region to the composition amount b of the subcomponent in the dielectric layer satisfies a relational expression of 1.5 ≦ a / b ≦ 5.0. The multilayer ceramic capacitor according to any one of -5. The protective region includes at least one element selected from Sr and Ca as a main component element and at least one element selected from Ti and Zr;
The multilayer ceramic capacitor according to claim 1 or 2, wherein the pigment component contains at least one element selected from the group consisting of V, Mo, Nb, Ta, W, and Mn.