JP2019175991A - Capacitor - Google Patents

Abstract

To provide a capacitor increasing a mechanical intensity.SOLUTION: A sinter body contains a dielectric layer 11 and a cover part 9 having a plurality of ceramic particles. When a region of the dielectric layer 11 adjacent to the cover part 9 and an inner electrode layer 13 of two layers nipping them is a cover neighbor layer, a region other than the cover part neighbor layer is a middle layer, two layers nipping the cover part neighbor layer is a first inner electrode layer 13a, and an electrode layer in the middle layer is a second inner electrode layer 13b, one part of the inner electrode layer 13 is lacked, a non-coated part 13c not partially coating the dielectric layer 11 is included, and co-material particles 13d having a main component similar to the ceramic particles in the non-coated part 13c exists in the first inner electrode layer 13a. At least one of the cover part 9 to which the co-material particles 13d is adjacent or the adjacent dielectric layers 11 is connected, and the first inner electrode layer 13a has an area rate of the non-coated part 13c higher than that of the second inner electrode layer 13b.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to capacitors.

  In recent years, multilayer ceramic capacitors (hereinafter referred to as “capacitors”) have higher capacitance per unit volume due to higher dielectric constants of dielectric materials or thinner dielectric layers and internal electrode layers. Increasingly. For this reason, the size of the capacitor is reduced, and the capacitor is also developed in a large size region such as the 3216 type (see, for example, Patent Document 1).

JP2015-138909A

  A capacitor according to the present disclosure includes a capacitor main body having an effective portion in which a plurality of dielectric layers and internal electrode layers are alternately stacked to develop a capacitance, and a cover portion disposed on the surface of the effective portion in the stacking direction. And a pair of external electrodes provided on opposing end faces of the capacitor body, the internal electrode layer is connected to the pair of external electrodes, and the dielectric layer and the cover portion are a plurality of ceramics. A sintered body including particles, and a region of the effective portion of the dielectric layer adjacent to the cover portion and the two internal electrode layers sandwiching the dielectric layer is defined as a cover portion vicinity layer. A region other than the cover portion vicinity layer is a middle layer, the two internal electrode layers sandwiching the cover portion vicinity layer are first internal electrode layers, and the internal electrode layer in the middle layer is a second internal electrode The internal power The layer has a non-coated portion that is partially missing and does not partially cover the dielectric layer, and the first internal electrode layer has the same main component as the ceramic particles in the non-coated portion. There are co-material particles having, and the co-material particles are bonded to at least one of the adjacent cover portion or the adjacent dielectric layer, and the first internal electrode layer is The area ratio of the uncovered portion is higher than that of the second internal electrode layer.

It is a perspective view which shows the external shape of the capacitor | condenser of embodiment. It is the ii-ii sectional view taken on the line of FIG. It is the cross-sectional schematic diagram which expanded the A section of FIG. It is a cross-sectional schematic diagram which shows a state when the capacitor of the embodiment is mounted on a wiring board and a load is applied by bending. It is a cross-sectional schematic diagram of the capacitor | condenser which shows the other aspect of embodiment, and shows a state with many non-covering parts in the site | part close | similar to an external electrode. FIG. 10 is a schematic cross-sectional view of a capacitor showing another aspect of the embodiment and in a state in which the frequency of the uncovered portion in the internal electrode layer decreases from the cover portion side toward the center of the effective portion. FIG. 7 is a cross-sectional view showing another aspect of the embodiment of the capacitor showing a state in which the internal electrode layer having many uncovered portions is provided at the center in the stacking direction of the effective portion in addition to the position adjacent to the cover portion. It is a cross-sectional schematic diagram.

FIG. 1 is a perspective view illustrating an external shape of a capacitor according to an embodiment. 2 is a cross-sectional view taken along line ii-ii in FIG. FIG. 3 is an enlarged schematic cross-sectional view of a portion A in FIG.
The capacitor according to the embodiment includes a capacitor body 1 and an external electrode 3. The capacitor body 1 has a rectangular parallelepiped shape. The external electrode 3 is provided on the opposite end face 5 of the capacitor body 1. In this case, the external electrode 3 may be a single base electrode composed of metallization, or may have one or more plating films on the surface of the base electrode.

  The capacitor body 1 includes an effective portion 7 and cover portions 9 provided on both the upper and lower surfaces of the effective portion 7. The effective portion 7 has a configuration in which the dielectric layers 11 and the internal electrode layers 13 are alternately stacked. In this case, the effective portion 7 is a portion that develops capacitance in the capacitor body 1. The cover portion 9 is provided to protect the effective portion 7 environmentally or to protect the effective portion 7 from mechanical impacts or the like. The dielectric layer 11 and the cover portion 9 are a sintered body including a plurality of ceramic particles 11a. The ceramic particles 11a are bonded via a grain boundary phase such as a glass phase.

  In the capacitor according to the embodiment, the area formed by the dielectric layer 11 adjacent to the cover portion 9 and the two internal electrode layers 13 sandwiching the dielectric layer 11 in the effective portion 7 is in the vicinity of the cover portion. This is layer 7A. Further, a region other than the cover portion vicinity layer 7A of the effective portion 7 is set as a middle layer 7B. In other words, the middle layer 7B is sandwiched between the cover vicinity layers 7A. Hereinafter, the two internal electrode layers 13 in the cover portion vicinity layer 7A may be referred to as a first internal electrode layer 13a, and the internal electrode layer 13 in the middle layer 7B may be referred to as a second internal electrode layer 13b.

  Both the first internal electrode layer 13a and the second internal electrode layer 13b have uncovered portions 13c that are partially missing and do not partially cover the dielectric layer 11. In the uncovered portion 13c, there are ceramic particles 11a having the same main component as the ceramic particles 11a constituting the dielectric layer 11. Hereinafter, the ceramic particles 11a existing in the non-covered portion 13c may be referred to as common material particles 13d. The same main component means that the components (here, metal oxides) contained most in the uncovered portion 13c and the dielectric layer 11 are the same. The common material particles 13d are bonded to at least one of the space between the cover portion 9 adjacent to the cover portion vicinity layer 7A and the space between the adjacent dielectric layers 11. Further, the area ratio of the uncovered portion 13c in the first internal electrode layer 13a is higher than that in the second internal electrode layer 13b. If the first internal electrode layer 13a constituting the cover vicinity layer 7A has a high area ratio of the uncovered portion 13c, the mechanical strength of the portion around the cover vicinity layer 7A in the capacitor body 1 is increased. Can be increased.

  The reason will be described below with reference to the drawings. The capacitor shown below is a conventional capacitor for convenience. In the following description of the conventional capacitor, reference numerals are not given, but the names of the parts in the conventional capacitor correspond to the parts in the capacitor of the embodiment shown in FIG. In the conventional capacitor, the area ratio of the uncovered portion in the internal electrode layer located in the cover portion vicinity layer is equal to the internal electrode layer (second internal electrode layer 13b) in the middle portion. That is, in the case of the conventional capacitor, the area ratio of the uncovered portion in the internal electrode layer located in the vicinity of the cover portion is lower than that of the capacitor of the embodiment shown in FIG. In this conventional capacitor, for example, the area ratio of the non-covered portion provided in the internal electrode layer located in the layer near the cover portion and the area ratio of the non-covered portion provided in the internal electrode layer located in the middle step are both 30. %. Also in this case, ceramic particles having the same main component as the ceramic particles constituting the dielectric layer are present as co-material particles in the non-covered portion. Further, the co-material particles are bonded to at least one of the space between the cover portion adjacent to the cover portion adjacent layer or the space between the adjacent dielectric layers.

Thus, when the area ratio of the non-covered part in the layer near the cover part is equivalent to the internal electrode layer in the middle part, and the area ratio of the non-covered part in the cover part near layer is as low as less than 30%, the area near the cover part The frequency of the co-material particles bonded to the cover layer and the dielectric layer in the middle layer in the internal electrode layer in the layer is low. For this reason, the dielectric layer in the cover vicinity layer and the cover layer laminated via the first internal electrode layer and the dielectric layer in the middle step are not firmly bonded. As a result, the layer near the cover part has the same level as the middle stage part in which the area ratio of the non-covering part is relatively low, and the mechanical strength is low.

  Specifically, in a conventional capacitor, when deformation occurs in the wiring board after the capacitor is mounted on the wiring board, the cover part extends from the cover side facing the wiring board to the end face. Cracks penetrating the neighboring layers diagonally tend to occur. Also, delamination is likely to occur between the dielectric layer constituting the cover portion vicinity layer and the first internal electrode layer.

  FIG. 4 is a schematic cross-sectional view showing a state when the capacitor of the embodiment is mounted on a wiring board and a load is applied due to bending. In the capacitor of the embodiment shown in FIG. 4, the area ratio of the uncovered portion 13c in the internal electrode layer 13 (the first internal electrode layer 13a and the second internal electrode layer 13b) is, for example, 30% or more. On the other hand, the area ratio of the non-covered portion 13c in the internal electrode layer 13 (second internal electrode layer 13b) located in the middle step portion 7B is less than 30% as in the conventional capacitor described above. The capacitor shown in FIG. 4 includes the common material particles 13d bonded to the cover portion 9 and the dielectric layer 11 in the middle layer 7B in the internal electrode layer 13 (first internal electrode layer 13a) in the cover portion vicinity layer 7A. The frequency is higher than conventional capacitors. For this reason, the capacitor shown in FIG. 4 has a higher mechanical strength near the cover portion vicinity layer 7A than the conventional capacitor described above. As a result, even after the capacitor is mounted on the wiring board 21, even if the wiring board 21 is bent and deformed, the crack C that obliquely penetrates the cover portion vicinity layer 7 </ b> A from the cover portion 9 to the end surface 5 hardly occurs. . Further, delamination is unlikely to occur between the dielectric layer 11 constituting the cover vicinity layer 7A and the first internal electrode layer 13a. This is because the uncovered portion 13c formed on the first internal electrode layer 13a constituting the cover portion vicinity layer 7A includes a large amount of the common material particles 13d, and the common material particles 13d are adjacent to the cover portion 9 or This is because the dielectric layer 11 is firmly bonded and cross-linked.

  In the capacitor of the embodiment, the area ratio of the uncovered portion 13c in the first internal electrode layer 13a constituting the cover portion neighboring layer 7A is preferably 30% or more and 50% or less. When the area ratio of the non-covering portion 13c is 30% or more, the joint strength between at least one of the adjacent cover portion 9 and the dielectric layer 11 is increased by the common material particles 13d existing in the non-covering portion 13c. Can do. On the other hand, when the area ratio of the uncovered portion 13c is 50% or less, the effective area of the first internal electrode layer 13a can be increased, so that a capacitor having a high capacitance can be obtained.

  On the other hand, the area ratio of the uncovered portion 13a in the second internal electrode layer 13b disposed in the region other than the cover portion vicinity layer 7A of the effective portion 7 is lower than 30% because the capacitance of the capacitor is increased. Is good.

  In addition, in the first internal electrode layer 13a and the second internal electrode layer 13b, the ratio of the locations where the uncoated portion 13c contains the co-material particles 13d is 80% or more in terms of the number ratio of the uncovered portion 13c. Is good.

FIG. 5 shows another aspect of the embodiment, and is a schematic cross-sectional view of a capacitor showing a state where there are many uncovered portions near the external electrodes. The capacitor according to the embodiment may have a structure in which the non-covered portion 13c in which the common material particles 13d are present in the first internal electrode layer 13a is provided at a high frequency in a portion close to the external electrode 3. Here, the portion close to the external electrode 3 is a region on the external electrode 3 side when the capacitor is equally divided into three in the direction of the pair of external electrodes 3 facing each other. When a deflection test is performed after mounting such a capacitor on the wiring board 21, cracks are usually likely to occur near the end surface 5 of the capacitor body 1 where the external electrode 3 is provided. For this reason, generation | occurrence | production of a crack can be suppressed effectively by localizing the non-coating part 13c in the site | part close | similar to the external electrode 3. FIG. In addition, since the frequency of the non-covering portion 13c at a position away from the external electrode 3 can be reduced, the effective area of the first internal electrode layer 13a can be increased, so that the capacitance of the capacitor can be increased.

  In the capacitor according to the embodiment, in the first internal electrode layer 13a constituting the cover portion vicinity layer 7A, the difference in the area ratio of the uncovered portion 13c on both surfaces of the dielectric layer 11 is 5 points or less in% display. good. If the difference in the area ratio of the uncovered portion 13c in the first internal electrode layer 13a constituting the cover portion vicinity layer 7A is small at the positions of both surfaces of the dielectric layer 11, the dielectric layer 11 constituting the cover portion vicinity layer 7A and Adjacent cover 9 and the dielectric layer 11 of the effective portion 7B can be firmly coupled. Thereby, the deformation of the cover portion vicinity layer 7A can be further reduced. As a result, it is possible to further reduce the probability that a crack will occur in the cover portion vicinity layer 7A.

  In the capacitor of the embodiment, it is preferable that the first internal electrode layer 13a having a higher area ratio of the uncovered portion 13c than the second internal electrode layer 13b is provided on both sides of the effective portion 7 in the stacking direction. When the cover vicinity layer 7A having the first internal electrode layer 13a having a higher area ratio of the uncovered portion 13c than the second internal electrode layer 13b is provided on both sides in the stacking direction of the effective portion 7, the capacitor is wired Even if it is mounted on the substrate in any direction of the stacking direction, the cover portion vicinity layer 7A having the first internal electrode layer 13a having a higher area ratio of the non-covered portion 13c than the second internal electrode layer 13b is used as the wiring substrate. It becomes possible to arrange them closer. As a result, it is possible to reduce the probability that the capacitor will crack after being mounted on the wiring board.

  As described above, the cover portion vicinity layer 7A in which the area ratio of the uncovered portion 13c in the first internal electrode layer 13a is higher than that on the second internal electrode layer 13b side is provided on the cover portion 9 in the stacking direction of the effective portion 7. However, the capacitor of the embodiment is not limited to this. FIG. 6 is a cross-sectional view showing another aspect of the embodiment. FIG. 6 is a schematic cross-sectional view of a capacitor having a structure in which the frequency of the uncovered portion in the internal electrode layer decreases from the cover portion side toward the center of the effective portion. As another aspect of the capacitor of the embodiment, there are a plurality of internal electrode layers 13 and dielectric layers 11 in which the area ratio of the uncovered portion 13c is the same as that of the first internal electrode layer 13a from the cover vicinity layer 7A to the middle step portion 7B side. The structure may be repeated across the layers. The number of the internal electrode layers 13 having the same area ratio of the uncovered portion 13c provided in the middle step portion 7B as that of the first internal electrode layer 13a is preferably 1 to 3 layers. Further, the area ratio of the non-covering portion 13c may have a tendency to gradually decrease from the cover portion 9 side toward the center in the stacking direction of the effective portion 7B. In a capacitor that is mounted on the wiring board 21 and undergoes a deflection change, the crack usually tends to progress from the cover portion 9 side to the effective portion 7 side. Under such circumstances, when the structure is such that the area ratio of the non-covered portion 13c gradually decreases from the cover portion 9 side toward the center in the stacking direction of the effective portion 7B, the capacitor cover portion 9 side to the effective portion 7 side. It is possible to more efficiently suppress the developing cracks. This is because the distortion of the capacitor due to the deflection of the wiring board 21 is smaller in the center than the cover portion 9 side of the capacitor. In this case, conversely, since the coverage of the internal electrode layer 13 increases from the cover portion 9 toward the center, the effective area of the internal electrode layer 13 can be increased in the entire capacitor body 1.

In the case of the capacitor of the embodiment, as shown in FIG. 7, the internal electrode layer 13 with many uncovered portions 13 c is provided in the central portion 7 c in the stacking direction of the effective portion 7 in addition to the position adjacent to the cover portion 9. May be. In this case, it is preferable that two or three internal electrode layers 13 with many uncovered portions 13c are provided at the position of the central portion 7c. Here, the area ratio of the non-covering portion 13c may be approximately the same as the ratio in the cover portion vicinity layer 7A. When a layer corresponding to the cover portion vicinity layer 7A is provided in the central portion 7c in the stacking direction of the middle step portion 7B, the occurrence of delamination that tends to occur in the central portion 7c in the stacking direction of the effective portion 7 is suppressed. Can do. If the number of the internal electrode layers 13 with many uncovered portions 13c is 2 to 3, the possibility of covering a portion where delamination occurs is increased, and the internal electrode layers 13 due to the increase in the number of uncovered portions 13c. This is because the decrease in effective area can be reduced and the decrease in capacitance can be suppressed.

  The capacitor according to the embodiment described above is suitable for the capacitor body 1 whose outer shape is a rectangular parallelepiped, and in particular, the length (thickness) of the lamination method of the dielectric layer 11 and the internal electrode layer 13 is such a dielectric. A so-called thin plate-like one shorter than the length in the width direction of the layer 11 and the internal electrode layer 13 is more preferable. That is, the capacitor body 1 has a length in the direction of the opposing external electrode L, a length perpendicular to the length L and a direction along the plane direction of the dielectric layer 11 or the internal electrode layer 13. It is suitable for the case where the thickness t is shorter than the width W, where the width W is the thickness t when the length in the stacking direction of the dielectric layer 11 and the internal electrode layer 13 is the thickness t. If the thickness t of the capacitor is shorter than the width W, it is easy to mount the capacitor in the direction perpendicular to the wiring substrate 21 when the capacitor is mounted on the wiring substrate 21. As a result, it is possible to mount the cover portion vicinity layer 7A having a high area ratio of the uncovered portion 13c in the capacitor in a state facing the wiring substrate 21 side, and the effect of this capacitor can be easily enjoyed.

  In the capacitor according to the embodiment, the ceramic particles constituting the dielectric layer 11 in the cover vicinity layer 7A should have a larger average particle diameter than the ceramic particles constituting the dielectric layer 11 in the middle layer 7B. When the size of the ceramic particles constituting the dielectric layer 11 in the cover portion vicinity layer 7A is larger than the size of the ceramic particles constituting the dielectric layer 11 in the middle layer 7B, when a crack occurs from the cover portion 9 In the dielectric layer 11 of the cover portion vicinity layer 7A, the probability that cracks will occur along the grain boundaries can be reduced. As a result, cracks penetrating through the cover vicinity layer 7A in the thickness direction are less likely to occur, and a more durable capacitor can be obtained.

  As a material for forming the dielectric layer 11 and the cover portion 9, for example, a dielectric material mainly composed of barium titanate exhibiting ferroelectricity is suitable, but not limited thereto, titanium oxide. Similar effects can be obtained with dielectric materials exhibiting paraelectric properties such as strontium titanate and calcium titanate. In this case, as the dielectric material, for example, a material containing magnesium, rare earth element, and manganese oxides may be applied to the above-described main component.

  Suitable materials for the internal electrode layer 11 and the external electrode 3 (base electrode) include base metal materials such as nickel and copper in addition to noble metal materials such as silver and palladium.

  Next, a method for manufacturing the capacitor according to the embodiment will be described. The capacitor of the embodiment specifies a pattern sheet in which the content of dielectric powder used as a co-material in the internal electrode pattern is different from that of other layers as a pattern sheet in which the internal electrode pattern is formed on the dielectric green sheet. The capacitor can be produced by a conventional manufacturing method except that it is disposed at the position of and laminated. Specifically, an internal electrode pattern in which the content of the dielectric powder is increased as compared with the pattern sheet used for the middle layer 7B is used for the pattern sheet corresponding to the cover portion vicinity layer 7A. As a result, the area ratio of the non-covered portion 13c in the internal electrode layer 13 (first internal electrode layer 13a) of the cover portion neighboring layer 7A is the same as that of the non-covered portion in the internal electrode layer 13 (second internal electrode layer 13b) of the middle step portion 7B. A capacitor higher than the area ratio can be obtained. Hereinafter, the embodiment will be described in detail.

Hereinafter, a multilayer ceramic capacitor was specifically produced as an example of the capacitor, and the characteristics were evaluated. First, as a raw material powder, 0.5 atom of purity is 99.9%, Ba / Ti molar ratio is 1.005, and (Ba + Ca) / Ti molar ratio is 1.005. % Barium titanate powder was prepared, and the following components were added thereto to prepare a dielectric powder. The composition of the dielectric powder is 0.05 mole of V ₂ O ₅ powder, 0.7 mole of MgO powder, and 0 rare earth element (Dy ₂ O ₃ ) oxide powder with respect to 100 moles of barium titanate powder. 4 mol, 0.2 mol of MnCO ₃ powder, and further sintering aid (glass powder of SiO ₂ = 55, BaO = 20, CaO = 15, Li ₂ O = 10 (mol%)) as raw material powder ( 1 part by mass was added to 100 parts by mass of barium titanate powder or barium titanate powder containing calcium).

  Next, the obtained dielectric powder was put into a mixed solvent of polyvinyl butyral resin and toluene and alcohol, and wet-mixed using a zirconia ball having a diameter of 0.5 mm to prepare a ceramic slurry, doctor blade method Thus, a dielectric green sheet having an average thickness of 6 μm was produced.

  Next, a plurality of conductor pastes mainly composed of nickel (Ni) were formed on the upper surface of the dielectric green sheet so as to form a rectangular internal electrode pattern. Nickel powder having an average particle size of 0.2 μm was used as the conductor paste for forming the internal electrode pattern. What added 10-20 mass parts of barium titanate powder as a co-material particle | grain with respect to 100 mass parts of this nickel was used. For the internal electrode pattern having a low coverage, a conductive paste having a content of co-material particles of 10% was used. For internal electrode patterns having a high coverage, a conductor paste having a common material particle content of 20% was used. The content of the common material particles is a value when the total amount of the nickel powder and the common material particles is 100% by mass. As the barium titanate powder used as the co-material particles, those having an average particle diameter of 0.1 μm and 0.3 μm were used. Sample No. shown in Table 1 For No. 3, a mixed powder obtained by mixing barium titanate powder having an average particle size of 0.1 μm and barium titanate powder having an average particle size of 0.3 μm was used for the pattern sheet to be the cover portion vicinity layer 7A. In this case, both powders were equally divided. Sample No. Pattern sheets and sample Nos. 1 and 2 used for the effective portions of the multilayer ceramic capacitors of 1, 2, 4, and 5 Barium titanate powder having an average particle size of 0.1 μm was used for the pattern sheet used for the middle step 7B of the multilayer ceramic capacitor 3.

Next, 200 pattern sheets on which internal electrode patterns were formed were laminated on ceramic green sheets, and 20 ceramic green sheets on which the internal electrode patterns were not printed were laminated on the upper and lower surfaces, respectively, to prepare a temporary laminate. Thereafter, the temporary laminate is closely adhered using a press machine at a temperature of 60 ° C., a pressure of 10 ⁷ Pa, and a time of 10 minutes to produce a laminate, and then the laminate is cut into predetermined dimensions. A green molded body to be a capacitor body was formed.

  Next, the raw molded body was degreased in nitrogen, then fired at a maximum temperature of 1200 ° C. in a reducing atmosphere adjusted with a forming gas, and a holding time at the maximum temperature of 2 hours. Was made. A batch firing furnace was used for this firing. The forming gas was introduced into the firing furnace after passing through the wetting device.

  Next, reoxidation treatment was performed on the manufactured capacitor body. The conditions for the reoxidation treatment were set to a maximum temperature of 1000 ° C. and a holding time of 5 hours in a nitrogen atmosphere.

The capacitor body obtained after firing had a length of 3.2 mm, a width of 1.6 mm, and a thickness of 1.6 mm. The average thickness of the dielectric layer was 5 μm. The average thickness of the internal electrode layer was 1 μm. The effective area per internal electrode layer was 1.78 mm ² . Here, the effective area is an area of overlapping portions of the internal electrode layers formed alternately in the stacking direction so as to be exposed at different end faces of the capacitor body.

Next, after barrel-polishing the capacitor body, a base electrode paste containing Cu powder and glass was applied to both ends of the capacitor body and baked at 850 ° C. to form a base electrode. Then, using an electrolytic barrel machine, Ni plating and Sn plating films were sequentially formed on the surface of the base electrode to produce a multilayer ceramic capacitor.

  Each of the produced samples had a structure in which layers near the cover part having a high area ratio of the non-covered part were provided on both upper and lower surfaces of the effective part.

  The sample (sample No. 3 in Table 1) in which the uncovered portion is biased toward the end face side of the capacitor body uses co-material particles having an average particle size larger than that of the nickel powder as co-material particles. It produced using the screen for printing from which an aperture ratio differs in a position. When manufacturing a multilayer ceramic capacitor, if it says about one internal electrode pattern, let the center part of the longitudinal direction be a cutting location. For this reason, the screen used for printing was such that when the internal electrode pattern was divided into three equal parts in the longitudinal direction, the opening ratio of the central part was higher than the opening ratios of both sides. In this case, it was utilized that the common material particles having a larger average particle diameter than the nickel powder protrude toward the larger opening ratio.

  The produced samples (sample Nos. 2 to 5) are the average of the ceramic particles constituting the dielectric layer in the middle layer in which the average particle diameter of the ceramic particles constituting the dielectric layer in the cover portion vicinity layer is the average in all the samples. It was larger than the particle size. Sample No. 1 and the average particle diameter of the ceramic particles constituting the dielectric layer in the middle layer, and the sample no. The average particle diameter of the ceramic particles constituting the dielectric layer in the middle layer of 2 to 5 multilayer ceramic capacitors was 0.4 μm for all the samples. In this case, co-material particles exist in the non-covered part, and the thickness of the dielectric layer from the ceramic particles combined with the co-material particles together with the ceramic particles on the dielectric layer side combined with the dielectric layer. In the range of 2 to 3 ceramic particles, it was confirmed that these ceramic particles grew more than the ceramic particles in other regions, and the average particle size was larger. Further, in any of the prepared samples, the difference in the area ratio of the non-covered portion on both surfaces of the dielectric layer was 5 points or less in the first internal electrode layer constituting the layer near the cover portion.

  Next, the following evaluation was performed on the produced multilayer ceramic capacitor. The evaluation of the non-covered portion is performed by polishing the produced capacitor and exposing the cross section as shown in FIG. 2, and then observing and photographing a predetermined range with a scanning electron microscope. The number, the presence ratio of the co-material particles, the area ratio of the uncovered portion, and whether or not the co-material particles are bonded to the cover portion and the dielectric layer were evaluated. These evaluations were performed by extracting one from each sample. The notation “first internal electrode layer” in Table 1 means an internal electrode layer having a high area ratio of the non-covered portion in the cover portion vicinity layer. The expression “second internal electrode layer” means an internal electrode layer in which the area ratio of the uncovered portion in the middle step is lower than that of the first internal electrode layer. The range in which the photograph was taken was a range having a length of 100 μm at the center in the longitudinal direction of the capacitor (the direction of the opposing external electrode). The area ratio of the non-covered portion was determined from the ratio with the total length of the non-covered portion when the total length of the internal electrode layer in the photographed image was 1. The presence ratio of the co-material particles was determined from the ratio of the number of the co-material particles existing in the non-covered portion when the total number of the non-cover portions existing in the photographed area was 1. In any of the samples prepared, the co-material particles present in the uncoated portion were bonded to the adjacent cover portion and dielectric layer.

  The average particle size of the ceramic particles in the cover portion vicinity layer was obtained from a photograph taken for evaluating the uncoated portion. In this case, the area is determined from the outline of the ceramic particles existing in the range of 20 μm in the center in the longitudinal direction of the capacitor (in the direction of the opposing external electrode), the obtained area is defined as the area of the circle, and the diameter is determined from the area. The particle size of each ceramic particle was calculated. Next, the average particle size was determined by averaging the particle sizes determined for each ceramic particle.

  The capacitance of the capacitor was measured at room temperature (25 ° C.) using an LCR meter under the conditions of a temperature of 25 ° C., a frequency of 1.0 kHz, and an AC voltage of 1.0 Vrms. The number of samples was 10 and the average value was obtained.

  Moreover, the capacitor | condenser produced was soldered to the wiring board made from FR-4, and the sample for a bending test was produced. The number of samples in the deflection test was 100. The amount of deflection in the deflection test was 5 mm and 10 mm. Samples that had cracks or lamination in the capacitor after the deflection test were counted as defective.

  As is clear from the results of Tables 1 and 2, samples (sample Nos. 2 to 5) in which the area ratio of the non-covered portion of the internal electrode layer in the cover vicinity layer is higher than the same area ratio in the middle stage portion are covered. The number of defects in the deflection test was smaller than that of the sample (sample No. 1) in which the same area ratio in the part vicinity layer and the same area ratio in the middle stage part were equivalent. These samples (Sample Nos. 2 to 5) had a capacitance of 2.05 μF or more.

  Among these samples, a sample (sample No. 3) in which the position of the non-covered portion is biased toward the external electrode side, and three internal electrode layers with a high area ratio of the non-covered portion are provided on both the upper and lower surfaces of the effective portion. The provided sample (sample No. 4), the sample (sample No. 5) in which the internal electrode layer having a high area ratio of the non-covered portion is added to the cover vicinity layer and is also arranged in the center in the stacking direction of the effective portion, Compared with the sample (sample No. 2) in which two internal electrode layers having a high area ratio of the covering portion were provided on both the upper and lower surfaces of the effective portion, the number of defects when the deflection amount was 10 mm was small.

  The sample (sample No. 1) in which the area ratio of the non-covered portion of the internal electrode layer in the cover vicinity layer was equivalent to the same area ratio in the middle stage portion had a high capacitance of 2.2 μF. The number of defects of Sample No. The number was 20/100 or more compared to 2-5.

1 ... Capacitor body 3 ... External electrode 5 ... End face 7 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Part 9 ············································· Dielectric layer 11a 13... Internal electrode layer 13 a... First internal electrode layer 13 b. Internal electrode layer 13c ···································································· Wiring substrate

Claims (5)

A capacitor body having an effective portion in which a plurality of dielectric layers and internal electrode layers are alternately stacked to develop a capacitance, and a cover portion disposed on the surface of the effective portion in the stacking direction;
A pair of external electrodes provided on opposite end faces of the capacitor body,
The internal electrode layer is connected to the pair of external electrodes;
The dielectric layer and the cover part are sintered bodies containing a plurality of ceramic particles,
Of the effective portion, a region between the dielectric layer adjacent to the cover portion and the two internal electrode layers sandwiching the dielectric layer is defined as a cover portion vicinity layer, and a region other than the cover portion vicinity layer. Is the middle layer, the two internal electrode layers sandwiching the cover vicinity layer are the first internal electrode layers, and the internal electrode layer in the middle layer is the second internal electrode layer,
The internal electrode layer has a non-coated portion that is partially missing and does not partially cover the dielectric layer,
In the first internal electrode layer, co-material particles having the same main component as the ceramic particles are present in the uncovered portion, and the dielectric layer is adjacent to or adjacent to the cover portion where the co-material particles are adjacent. And at least one of
The first internal electrode layer has a higher area ratio of the uncovered portion than the second internal electrode layer,
Capacitor.   The capacitor according to claim 1, wherein the cover portion vicinity layer having the first internal electrode layer is provided on both sides in the stacking direction of the effective portion.   3. The capacitor according to claim 1, wherein the first internal electrode layer has a coverage difference of the uncovered portion between the two internal electrode layers sandwiching the cover portion vicinity layer, which is 5 points or less in% display. 4. .   4. The ceramic particle constituting the dielectric layer in the cover portion vicinity layer has an average particle size larger than that of the ceramic particle constituting the dielectric layer in the middle layer. 5. The capacitor described.   The capacitor body has a width in a direction perpendicular to the length L and a direction in a direction perpendicular to the length L and along the planar direction of the dielectric layer or the internal electrode layer. 5. The thickness according to claim 1, wherein the thickness t is shorter than the width W, where W is the thickness t of the dielectric layer and the internal electrode layer in the stacking direction. The capacitor described.

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