JP7297117B2 - Multilayer ceramic capacitor - Google Patents

Description

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

In recent years, with the increasing density of electronic circuits used in digital electronic devices such as mobile phones and tablet terminals, there is a strong demand for miniaturization of electronic components. Capacity is increasing rapidly.

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

By the way, a laminated ceramic capacitor is provided with protective regions such as a cover layer and a side margin portion for covering a laminated body, which is a capacitive layer. However, when the number of laminated dielectric layers is increased in order to increase the capacity of the capacitor, it is necessary to reduce the thickness of the cover layer provided as the outermost layer in the lamination direction in order to fit within the specified chip size. Further, even when the intersecting area of the internal electrode layers is increased in order to increase the capacity, the thickness of the side margin portions provided on both sides perpendicular to the stacking direction of the stack must be made thinner.

For example, Patent Document 1 discloses a laminated ceramic capacitor having a cover layer with a thickness of 15 μm or less. In addition, Patent Document 2 proposes providing an identification portion for identifying upper and lower portions of a ceramic body based on a difference in brightness or color in either one of upper and lower cover layers of a multilayer ceramic capacitor. It is suggested that this identification part includes a dielectric layer to which one or more metals selected from Ni, Mn, Cr and V are added, whereby 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 multilayer ceramic capacitor that is miniaturized and has a large capacity, the thickness of protective layers (protective regions) such as cover layers and side margins must be made thinner. However, when the thickness of the protective layer is reduced, the internal electrodes may be recognized as a discolored portion through the thin protective layer in an external image inspection of the chip. It is difficult to distinguish the difference between the color difference between the discolored portion where the internal electrodes are visible and the portion where the internal electrodes are absent, and the actual defective portion such as cracks and delamination in the ceramic by image recognition processing. Therefore, in a multilayer ceramic capacitor having a thin protective layer of, for example, 15 μm or less in thickness, the end of an internal electrode that is visible from the outside is erroneously identified as a defective portion, resulting in an erroneous determination of failure.

Therefore, the present invention is a multi-layer ceramic capacitor with a reduced size and increased capacity, in which the internal electrodes of the ceramic sintered body are prevented from being seen through from the outside and recognized as an image, thereby improving the accuracy of the appearance inspection of the chip. purpose.

In order to solve the above problems, the present invention provides a laminate in which dielectric layers and internal electrode layers are alternately laminated, a cover layer which is the outermost layer in the lamination direction of the laminate, and A multilayer ceramic capacitor comprising protection regions that are side margin portions provided on both sides perpendicular to the direction in which the internal electrodes of the laminate are led out, wherein a dye component is added to the protection regions. In the laminated ceramic capacitor, the thickness of the side margin portion is thinner than the thickness of the cover layer, and the concentration of the pigment component in the side margin portion is higher than the concentration of the pigment component in the cover layer.

In the multilayer ceramic capacitor, the protection region preferably contains 0.2 mol or more of the dye component with respect to 100 mol of Ba or Ti as the main component element.

Also, in the laminated ceramic capacitor, the thickness of the protective region is preferably 15 μm or less.

Further, in the laminated ceramic capacitor, it is preferable that the thickness of the dielectric layers sandwiched between the internal electrodes is 0.8 μm or less.

Further, in the multilayer ceramic capacitor, the protective region preferably contains 10 mol or less of the dye component with respect to 100 mol of Ba or Ti as the main component element.

Further, in the multilayer ceramic capacitor, the pigment component is preferably at least one element selected from the group consisting of V, Mo, Nb, Ta, W and Mn.

According to the present invention, by adding a dye component to the protective region of the laminate, the internal electrode layers are not seen through in an external image inspection. As a result, it is possible to prevent erroneous determination due to image recognition through the internal electrode layers, and to improve the accuracy of the image inspection.

FIG. 1 is a perspective view schematically showing a partial cross section of a laminated ceramic capacitor according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing the II cross section of the multilayer ceramic capacitor of FIG. FIG. 3 is a schematic diagram showing the 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 laminated ceramic capacitor 1 according to the present invention. The multilayer ceramic capacitor 1 includes a ceramic sintered body 10 having chip dimensions and a shape defined by a standard (for example, a rectangular parallelepiped of 1.0×0.5×0.5 mm) and formed 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 grain crystals containing Ba and Ti, and has a laminated body 11 (“internal electric active layer” or “capacitor layer”) in which dielectric layers 12 and internal electrode layers 13 are alternately laminated inside. ) and a protective region 14 that covers at least a portion of the laminate 11 . The protection region 14 includes cover layers 15 formed as upper and lower outermost layers of the laminate 11 in the stacking direction, and side margin portions 16 provided on both sides of the laminate 11 perpendicular to the stacking direction.

The laminated body 11 has a thickness of 0.8 μm or less for the dielectric layer 12 sandwiched between the two internal electrode layers 13 according to specifications such as capacitance and required withstand voltage, and the total number of laminated bodies is It has a high-density multilayer structure of hundreds to hundreds.

The cover layer 15 formed on the outermost layer portion of the laminate 11 and the side margin portions 16 provided on both sides perpendicular to the lamination direction of the laminate 11 protect the dielectric layers 12 and the internal electrode layers 13 from moisture from the outside. It is provided to protect from contamination such as contamination and to prevent their deterioration over time.

Further, the edges of the internal electrode layers 13 are alternately led out to a pair of external electrodes 20 having different polarities at both ends of the dielectric layer 12 in the longitudinal direction.

The dielectric layer 12 of the multilayer ceramic capacitor 1 contains ceramic particles having main component elements including Ba and Ti and subcomponents including the element X. The main component of the ceramic particles is eg BaTiO ₃ . The subcomponent element X is specifically 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.

In addition, 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, 100 mol of Ti in the dielectric layer 12 It is preferably 0.05 to 0.3 mol.

Although the average particle size of such ceramic particles is not particularly limited, it is preferably 80 to 800 nm from the viewpoint of thinning the dielectric layer 12 . In this specification, the average particle size refers to observing ceramic particles with a scanning electron microscope (SEM) or TEM, adjusting the magnification so that there are about 80 particles in one image, and 300 particles or more in total. It is the average value of Feret diameters obtained by obtaining a plurality of photographs and measuring the total number of particles on the photographs. Note that the Feret diameter is a unidirectional tangent diameter defined by the distance between two parallel tangents that sandwich a particle.

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

The cover layer 15 and the side margin portions 16, which are the protective regions 14 of the laminate 11, contain Ba and Ti as main constituent elements. The main component of the cover layer 15 and the side margin portions 16 is the same as that of the dielectric layer 12, and is preferably BaTiO ₃ , for example. The thicknesses of the cover layer 15 and the side margin portions 16 are formed to be 15 μm or less from the viewpoint of obtaining the maximum capacity within the standardized chip dimensions. Here, the “thickness” of the cover layer means 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 portion means the shortest distance between the surface of the side margin portion and the end portion of the internal electrode closest to the surface of the side margin portion (see FIG. 3). That is, the "thickness" of the protection area means the shortest distance between the surface of the protection area and the internal electrode closest to the surface of the protection area.

The cover layer 15 and/or the side margin portions 16 are added with a pigment component for darkening the protective region 14 as an accessory component. The subcomponent (dye component) added to the protective region 14 may contain the same element as the subcomponent of the dielectric layer 12, but in addition to that, may be selected from the group consisting of V, Mo, Nb, Ta, W, and Mn. It may contain at least one selected element. The cover layer 15 and/or the side margin portions 16 preferably contain 0.2 mol or more of the subcomponent (dye component) with respect to 100 mol of Ba or Ti, which is the main component element. The ceramic sintered body 10 to which 0.2 mol % or more of the subcomponent is added becomes a state in which visible light does not pass through at least beyond a depth (thickness) of 15 μm.
Also, the amount of the subcomponent (dye component) added to the cover layer 15 and/or the side margin portions 16 is preferably 10 mol or less with respect to 100 mol of Ba or Ti, which is the main component element.

The composition amount of the subcomponent (pigment component) in the cover layer 15 and/or the side margin portions 16 is greater than the composition amount of the subcomponent in the dielectric layer 12 . Specifically, it is preferable that the dye component composition amount a of the cover layer 15 is at least 1.5 times the subcomponent composition amount b of the dielectric layer 12 . When the amount a of the dye component of the cover layer 15 is 1.5 times or more the amount b of the subcomponent of the dielectric layer 12, the cover layer 15 is sufficiently darkened, and the internal electrode of the outermost layer is detected in the external image inspection of the chip. 13 becomes invisible through the cover layer 15 . This can prevent erroneous determination of ceramic grain structural defects. Also, when the dye component composition amount a of the side margin portions 16 is set to 1.5 times or more of the subcomponent composition amount b of the dielectric layer 12, the side margin portions 16 are darkened, and the end portions of the internal electrode layers 13 are darkened. is not recognized through the side margin portion 16. - 特許庁
Further, when the dye component composition amount a of the cover layer 15 and/or the side margin portions 16 is more than five times the subcomponent composition amount b of the dielectric layer 12, part of the dye component diffuses into the dielectric layer 12. and affects the sinterability and dielectric constant of the dielectric layer 12 . If it exceeds 5 times, the dielectric constant will decrease by 10% or more from the dielectric constant at 1.5 times due to diffusion due to the concentration difference.

Therefore, the composition amount (molar ratio to the main component) a of the dye component in the cover layer 15 and/or the side margin portions 16 is at least 1.5 times the composition amount (molar ratio to the main component) b of the subcomponent in the dielectric layer 12 . It is preferably 5 times or more, and the dye component composition amount a is preferably 5 times or less, preferably 3 times or less, the accessory component composition amount b. That is, it is preferable that the ratio of the dye component composition amount a to the subcomponent composition amount b satisfies the relational expression of 1.5≦a/b≦5.0.

The dye component added to the cover layer 15 and/or the side margin portions 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 portions 16 to a hue close to that of the internal electrode layers 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. It is possible to reduce the influence on the sinterability and dielectric constant of the dielectric layer 12 .

The protective region to which the dye component is added may be both the cover layer 15 and the side margin portions 16, or only one of the cover layer 15 and the side margin portions 16. FIG. In order to prevent the internal electrodes from being seen through from the outside of the chip, it is also considered effective to apply a dark paint or the like to the surface of the cover layer 15 and/or the side margin portion 16 .

Further, according to the present invention, the ceramic particles constituting the laminate 11 and the dielectric layer 12 contain at least one element selected from Sr and Ca and at least one element selected from Ti and Zr as main component elements. For example, it can also be applied to a temperature compensating capacitor. Since the ceramic particles having such a composition are lighter in color than the ceramic particles containing Ba and Ti as main components, erroneous determination is likely to occur due to image recognition through the internal electrode layers 13 . In such a multilayer ceramic capacitor as well, the cover layer 15 and/or the side margin portions 16 contain at least one element selected from the group consisting of V, Mo, Nb, Ta, W, and Mn. By adding the component), the internal electrode layers 13 are not seen through, and the effects of the present invention can be exhibited particularly effectively.

[Manufacturing method of multilayer ceramic capacitor]
A method for manufacturing the laminated ceramic capacitor 1 described above will be described below.
First, raw material powder for forming the dielectric layer 12 is prepared. The dielectric includes Ba and Ti, which are typically included in dielectric layer 12 in the form of sintered 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 reacting a titanium raw material such as titanium dioxide with a barium raw material such as barium carbonate to synthesize barium titanate. As a method for synthesizing the barium titanate, various methods are conventionally known, for example, a solid phase method, a sol-gel method, a hydrothermal method, and the like. Any of these can be employed in the present invention.

In this method, barium titanate particles are preferably first mixed with a subcomponent compound containing the subcomponent element X described above and calcined at 820 to 1150°C. Subsequently, the calcined barium titanate particles are wet-mixed with additional 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 per 100 mol of Ti. The amount of the rare earth compound is 0.05-0.5 mol per 100 mol of Ti, and the amount of the Si compound is 0.5-1.5 mol per 100 mol of Ti.

Then, 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-shaped dielectric green sheet having a thickness of 1.2 μm or less is coated on the substrate by, for example, a die coater method or a doctor blade method, and dried.

A green sheet (cover sheet) that serves as a cover layer is also prepared through the same steps as those for the dielectric green sheet described above. Also, the dielectric paste that forms the side margins is prepared through the same steps as those for the slurry described above. However, for these protective layers, as a dye component for darkening, the amount of the subcomponent added to the dielectric layer is at least 1.5 times or more, preferably 0.2 mol % or more, mixed with 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. It may contain elements.

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 led to a pair of external electrodes having different polarities. Nickel is widely used as the metal from the viewpoint of cost. Barium titanate having an average particle size of 50 nm or less may be uniformly dispersed in the metal conductive paste as a common material.

After that, the dielectric green sheet on which the internal electrode layer pattern is printed is punched into a predetermined size, and the punched dielectric green sheet is separated into the internal electrode layer 13 and the dielectric layer 12 in a state where the base material is peeled off. and so that the internal electrode layers are alternately exposed on both end faces in the length direction of the dielectric layers and alternately led out to a pair of external electrodes having different polarities. For example, 100 to 500 layers) are laminated. A cover sheet having a thickness of 15 μm 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 was cut into a predetermined chip size so that the side portions of the electrodes were exposed, and dielectric paste was applied to a thickness of 15 μm on both cut surfaces perpendicular to the stacking direction where the electrodes were exposed. The side margin portions 15 are formed by drying.

After that, a Ni conductive paste, which becomes the external electrodes 20, is applied to both side surfaces of the cut laminate and dried. Thereby, a molded body of the laminated ceramic capacitor 1 is obtained. The external electrodes may be thick-film-deposited on both end surfaces of the laminate by a sputtering method.

The molded body of the laminated ceramic capacitor thus obtained is subjected to binder removal in an N ₂ atmosphere at 250 to 500° C., and then fired in a reducing atmosphere at 1100 to 1300° C. for 10 minutes to 2 hours to obtain the above-mentioned Each compound forming the dielectric green sheet is sintered and grains grow. In this manner, a laminated body 11 in which dielectric layers 12 and internal electrode layers 13 made of sintered bodies are alternately laminated inside, cover layers 15 formed as upper and lower outermost layers in the laminating direction, and both sides in the laminating direction A laminated ceramic capacitor 1 having a side margin portion 16 formed on the side is obtained.

Further, in the present invention, reoxidation treatment may be performed at 600 to 1000.degree. In another embodiment of the method for manufacturing a multilayer ceramic capacitor, the external electrodes and the dielectric may be fired in separate steps. For example, after firing a laminate in which dielectrics are laminated, a conductive paste may be baked on both ends of the laminate to form the external electrodes.

[Example]
Table 1 shows the manufacturing conditions and evaluation results of the prototype MLCCs. In addition, sample No. 1 to 26 further added 0.5 mol of holmium oxide per 100 mol of Ti and 1.0 mol of silicon dioxide per 100 mol of Ti as additive components. Also, sample no. Nos. 27 to 33 further added 0.1 mol of holmium oxide per 100 mol of the main component and 1.0 mol of silicon dioxide per 100 mol of the main component. The shape of the sample was a rectangular parallelepiped of 1.0 mm×0.5 mm×0.5 mm.

(Sample Nos. 1 to 26)
Sample no. 1 to 26 are MLCCs based on BaTiO ₃ . Regarding these, those having an image defect rate of 0% and a dielectric constant of greater than 4000 were judged to be conforming products. Among these samples, when the subcomponent 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 is Good results were obtained with samples (Nos. 1, 2, 8 to 10, 18, 20 to 26) having a dye component amount a2 of 0.2 mol % or more in a portion (thickness of 13 to 15 μm). The dye component/auxiliary component ratios in these examples were 1.5b≦a1≦5b and 1.5b≦a2≦5b.

Sample No. in which the dye component was not added to the cover layer and/or the side margins. 3 and 17, and sample Nos. 1 and 2, which have a low dye component of about 0.1 mol %. In No. 12, No. 15, etc., the image defect rate increased to 30% and 60%. In addition, sample No. 1 has a low colorant component/auxiliary component ratio a1/b and a2/b of about 1.0, respectively. 4 and 15 also showed slightly higher image defect rates of 30% and 60%.

Sample No. where the dye component/auxiliary component content ratio exceeds 5.0. Regarding Nos. 5, 6, 13, 14 and 19, the image defect rate was as good as 0%, but the dielectric constant was 4000 or less. For this reason, in order to obtain a small-sized, large-capacity multilayer ceramic capacitor, it is preferable that the colorant component/auxiliary component volume ratios a1/b and a2/b are in the range of 1.5 to 5.0, respectively.

In addition, sample No. MLCC No. 16 had an image defect rate of 0%, although the dye component amount was too small at 1.0 mol % (the dye component/auxiliary component amount ratio was 1.0). The reason why the image defect rate is 0% is considered to be that the thickness of the cover layer and the side margin portions is relatively thick, ie, 17 μm, so that the internal electrode layers could not be seen through from the outside.

(Sample Nos. 27-33)
Sample no. Samples 27 to 33 are MLCCs containing other than BaTiO ₃ as the main component, and 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 products, an image defect rate of 0% was determined as a conforming product. For example, sample No. 1 in which the dye component amount in the cover layer and the side margin portion is 0.2 mol %. For 27 to 30, an image defect rate of 0% was achieved, which was good.

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 (6)

A laminated body in which dielectric layers and internal electrode layers are alternately laminated, a cover layer which is the outermost layer in the lamination direction of the laminated body, and an internal electrode of the laminated body which is orthogonal to the lamination direction of the laminated body A multilayer ceramic capacitor comprising protection regions that are side margins provided on both sides perpendicular to the direction in which the is drawn out,
A dye component is added to the protection region,
the thickness of the side margin portion is thinner than the thickness of the cover layer,
A multilayer ceramic capacitor, wherein the concentration of the pigment component in the side margin portion is higher than the concentration of the pigment component in the cover layer. 2. The multilayer ceramic capacitor according to claim 1, wherein said protective region contains 0.2 mol or more of said dye component with respect to 100 mol of said main component element Ba or Ti. 3. The multilayer ceramic capacitor according to claim 1, wherein said protective region has a thickness of 15 [mu]m or less. 4. The multilayer ceramic capacitor according to claim 1, wherein the dielectric layers sandwiched between the internal electrodes have a thickness of 0.8 μm or less. 5. The multilayer ceramic capacitor according to claim 1, wherein said protective region contains 10 mol or less of said dye component per 100 mol of Ba or Ti as said main component element. 6. The multilayer ceramic capacitor according to claim 1, wherein said pigment component is at least one element selected from the group consisting of V, Mo, Nb, Ta, W and Mn.

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