JP2016192477A - Multilayer ceramic electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer ceramic electronic component that keeps continuity of an inner electrode film even when the inner electrode film is thinned.SOLUTION: A multilayer ceramic electronic component includes a dielectric layer 2 and an inner electrode layer 3. The inner electrode layer 3 includes a first metal and a second metal. The second metal is included within the range of 0.5 to 4.0 vol.% against the first metal and at least thereof exists in an interface between the dielectric layer 2 and the inner electrode layer 3. The wettability of the second metal to a dielectric constituting the dielectric layer 2 is higher than that of the first metal to the dielectric. The first metal is Ni, and the second metal is selected from at least one of Ca, Mg, Ba, and Mn.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a multilayer ceramic electronic component.

  A multilayer ceramic capacitor, which is an example of an electronic component, is obtained by, for example, printing a predetermined pattern of internal electrodes on a ceramic green sheet made of a predetermined dielectric ceramic composition, alternately stacking them, and then integrating them. Manufactured by firing chips.

  Since the internal electrode of the multilayer ceramic capacitor is integrated with the ceramic dielectric by firing, it is necessary to select a material that does not react with the dielectric. For this reason, expensive noble metals such as Pt and Pd have been conventionally used as a material constituting the internal electrode layer.

  However, in recent years, dielectric ceramic compositions that can use inexpensive base metals such as Ni and Cu have been developed, and a significant cost reduction has been realized. In particular, Ni having high oxidation resistance and high melting point is mainly used.

  In addition, there is a high demand for miniaturization of electronic components due to the increase in the density of electronic circuits, and the miniaturization and increase in capacity of multilayer ceramic capacitors are rapidly progressing. For this reason, the dielectric layers and internal electrodes are made thinner. The method is adopted.

  As a method of thinning the internal electrode layer using Ni, it is known that Ni powder having a particle diameter of 0.1 μm to 1.0 μm is used as a material for the internal electrode layer in the conductive paste.

  However, the Ni powder of the internal electrode layer has a difference in shrinkage behavior because the sintering start temperature is lower than the sintering start temperature of the ceramic powder of the dielectric layer. As the difference in the shrinkage behavior increases, a larger stress is caused in the multilayer body, and structural defects such as cracks and delamination as the multilayer ceramic capacitor are likely to occur. Furthermore, when fine Ni powder is used for the purpose of thinning the layer, the sintering start temperature of Ni powder is lowered, and Ni in the internal electrode layer is spheroidized to become discontinuous as a film. Causes a decrease in acquired capacitance.

  In addition, when firing in an inert atmosphere or reducing atmosphere to prevent oxidation of Ni powder, the temperature at which Ni powder starts to be sintered becomes even lower, and sometimes sintering starts at a low temperature of 400 ° C. or lower. is there. On the other hand, the temperature at which the ceramic powder of the dielectric layer starts to be sintered is high, and is usually about 1200 ° C. even when firing in an inert atmosphere or a reducing atmosphere. Therefore, the continuity of the internal electrode film is lowered.

Conventionally, the following improvement methods have been proposed for the above problems.

  Patent Document 1 proposes a method for increasing the filling rate of Ni and the common material of the internal electrode film in order to improve the continuity of the internal electrode film. By increasing the filling rate of Ni, interruption can be prevented and the continuity of the internal electrode film can be improved.

JP 2002-245874 A

However, when the dielectric layer and the internal electrode layer are made thinner in order to further reduce the size and capacity, the following problems occur.

When Ni powder and co-material are atomized in order to make the internal electrode layer thinner, the sintering start temperature of both Ni powder and co-material is lowered. Therefore, high filling of Ni and co-material as introduced in Patent Document 1 It is difficult to maintain the continuity of the internal electrode film only by making it easy.

  The present invention has been made in view of the above, and an object thereof is to provide a multilayer ceramic electronic component capable of maintaining the continuity of an internal electrode film even when the internal electrode layer is thinned.

  In order to solve the above-described problems and achieve the object, a multilayer ceramic electronic component of the present invention has a dielectric layer and an internal electrode layer, and the internal electrode layer includes a first metal and a second metal, The second metal is included in the range of 0.5 to 4.0% by volume with respect to the first metal, and at least a part of the second metal is present at the interface between the dielectric layer and the internal electrode layer. The wettability of the second metal to the dielectric constituting the dielectric layer is higher than the wettability of the first metal to the dielectric constituting the dielectric layer. Note that there is no problem even if the second metal is present in the internal electrode layer.

  The wettability of the present invention is a property evaluated as follows. This will be described with reference to FIG.

First, a target for each metal was prepared, and a metal 33 was vapor-deposited at room temperature on a dielectric substrate 21 having the same composition as that of the dielectric layer of the multilayer ceramic capacitor described in the examples to prepare a sample. The state of the deposited metal 33 of the obtained sample was observed with a scanning tunneling microscope (STM).

The state of the metal 33 is roughly divided into three types. When the metal 33 grows in a plane so as to increase the contact area with the dielectric substrate 21, when it grows in an island shape so as to reduce the contact area with the dielectric substrate as much as possible, the plane and the island-like growth are mixed. It is a case. It shows that the metal 33 has a better wettability with the dielectric as it grows in a plane so as to increase the contact area with the dielectric substrate 21.

Since the first metal has low affinity with the dielectric that is an oxide, the wettability is poor, and the surface tension of the metal acts by the heat of the firing process to shrink and spheroidize, so that the film tends to be discontinuous. On the other hand, since the second metal has a high affinity with the dielectric and good wettability, it is likely to exist at the interface between the dielectric layer and the internal electrode layer. In addition, since the second metal is in a non-oxidized state, the affinity for the first metal is high. By causing the second metal that tends to exist in both the dielectric layer and the internal electrode layer to exist in the non-oxidized state at the interface between the dielectric layer and the internal electrode layer, the first metal having poor wettability with the dielectric layer and The dielectric layers can be connected and the first metal can be kept continuous.

The second metal has higher wettability with respect to the dielectric than the first metal. Further, the second metal is preferably a component contained in the dielectric layer. The reason is that the wettability of the second metal to the dielectric layer is improved when the same element as the second metal contained in the internal electrode layer is also contained in the dielectric layer. Furthermore, even when the second metal diffuses into the dielectric layer, the probability of undesirably changing the dielectric characteristics is reduced.

  The first metal described above is preferably Ni, and the second metal is preferably Ca, Mg, Ba, or Mn.

  The present invention has an effect that it is possible to obtain a multilayer ceramic electronic component that maintains the continuity of the internal electrode film even when the internal electrode layer is thinned.

1 is a cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention. It is an example of the lamination | stacking state of the green sheet and exterior green sheet before baking, (a) is sectional drawing which shows the state decomposed | disassembled partially, (b) is sectional drawing which shows a laminated body. 3 is a flowchart illustrating a method for manufacturing a multilayer ceramic capacitor according to an embodiment of the present invention. It is the figure which expanded the internal electrode layer vicinity of FIG. The state of growth when a metal is vapor-deposited on a dielectric substrate is shown in a schematic diagram, (a) is a diagram of planar growth, (b) is a diagram of a mixture of planar growth and island growth, (c ) Is an island-like growth.

  Hereinafter, a multilayer ceramic capacitor as an example of a multilayer ceramic electronic component to which the present invention is applied will be described with reference to the drawings.

A multilayer ceramic capacitor 1 according to an embodiment of the present invention has an element body having a plurality of dielectric layers 2 and internal electrode layers 3. The electrode layer 3 is laminated so that the electrode end faces are alternately exposed on the opposite end faces of the element body, and is formed so as to be electrically connected to the pair of external electrodes 4 disposed on both end faces of the element body. The In the element body, the exterior dielectric layer 5 is disposed on both outermost layers in the stacking direction of the dielectric layer 2 and the internal electrode layer 3.

First, an interior green sheet 11 constituting the dielectric layer 2 after firing and an exterior green sheet 12 constituting the exterior dielectric layer 5 are prepared. A raw material ceramic powder is mixed and pulverized together with an organic vehicle and a dispersant using a ball mill to prepare a paint. The prepared paint was applied onto PET with a doctor blade and dried to obtain an interior green sheet 11 and an exterior green sheet 12.

Next, a conductive paste for forming an internal electrode film after firing was prepared. 5 to 30 parts by weight of a co-material, 10 to 100 parts by weight of an organic vehicle, and a second metal of Mn resinate with respect to 100 parts by weight of the first metal Ni powder, the metal component of the Ni powder is 0. 5-4.0% by volume was added. Ni powder, common material, organic vehicle, and second metal were mixed and dispersed by a three-roll mill to produce a conductive paste.

Next, a conductive paste containing components constituting the electrode layer 3 after firing is formed on the interior green sheet by screen printing or the like.

A plurality of interior green sheets printed with a conductive paste are stacked, and exterior green sheets 12 are stacked in a single layer or multiple layers on both sides in the stacking direction, and cut into predetermined dimensions to form a stacked body 14.

The laminated body was debindered and fired under predetermined conditions, the end face of the sintered body was polished by sand blasting, and then external electrodes were formed on both end faces of the sintered body to obtain a laminated ceramic capacitor 1.

The common material contained in the dielectric layer 2, the exterior dielectric layer 5, and the internal electrode layer 3 forming the element is composed of a dielectric ceramic composition. The dielectric ceramic composition includes a composition formula ABO ₃ (wherein the A site is composed of at least one element selected from Sr, Ca and Ba. The B site is at least one element selected from Ti and Zr). It is preferable that a composite oxide having a perovskite crystal structure is contained as a main component. Among the dielectric oxides, it is preferable that the A site is mainly composed of Ba and the B site is mainly composed of Ti to form barium titanate.

  The dielectric ceramic composition may include various subcomponents in addition to the main component. Subcomponents are selected from oxides of Sr, Zr, Y, Gd, Tb, Dy, V, Mo, Zn, Cd, Ti, Sn, W, Ba, Ca, Mn, Mg, Cr, Si and P. At least one is illustrated. By adding the subcomponent, low temperature firing is possible without deteriorating the dielectric properties of the main component. Further, the reliability failure when the dielectric layer 2 is thinned is reduced, and the lifetime can be extended. From the viewpoint of improving the continuity of the internal electrode layer, Ca, Mg, Ba, and Mn are preferable. This is because the wettability of the second metal to the dielectric layer is improved when the same element as the second metal contained in the internal electrode layer is also contained in the dielectric layer.

  Various conditions such as the number and thickness of the dielectric layers 2 constituting the interior portion 15 may be appropriately determined according to the application. From the viewpoint of reducing the size and capacity of the multilayer ceramic capacitor, it is preferably 0.5 μm to 1.0 μm and the number of layers is preferably 150 layers or more. What is necessary is just to determine the thickness of the exterior dielectric layer 5 suitably according to a use, for example, it is about 20 micrometers-several hundred micrometers.

  The conductive paste used to form the internal electrode layer 3 includes a first metal, a second metal having better dielectric and wettability than the first metal, a dielectric layer 2 forming an element, and an exterior dielectric. It is composed of a co-material having the same composition as the layer 5 and an organic vehicle.

  In the conductive paste, the first metal is preferably Ni, and the second metal is preferably Ca, Mg, Ba, or Mn.

  The second metal is preferably added as a metal resinate or alloyed with the first metal. This is because Ca, Mg, Ba, and Mn preferable as the second metal are easily oxidized in the air when added in a single metal state.

  The second metal present at the interface between the dielectric layer and the internal electrode layer is preferably a single metal state. Although it may exist as an alloy with the first metal, it is considered that the wettability with the dielectric layer is lower than in the case of a single substance, and the amount of the interface may be reduced.

  The amount of the second metal present in the internal electrode layer is preferably 0.5 to 4.0% by volume. When the amount of the second metal is less than 0.5% by volume, the coverage is not improved. The reason is that the amount is small and the effect of connecting the first metal and the dielectric layer cannot be exhibited. If the amount of the second metal is more than 4.0% by volume, the product characteristics change undesirably. This is because the dielectric layer is reduced when fired in a strong reducing atmosphere in order to keep the second metal that is easily oxidized in a non-oxidized state.

An organic vehicle is obtained by dissolving a binder in an organic solvent. The binder used for the organic vehicle is not particularly limited, and may be appropriately selected from usual various binders such as ethyl cellulose and polyvinyl butyral. Moreover, the organic solvent used for the organic vehicle is not particularly limited, and may be appropriately selected from various organic solvents such as terpineol, butyl carbitol, acetone, and toluene.

  The thickness of the internal electrode layer 3 may be appropriately determined according to the application, and is, for example, about 0.3 to 1.0 μm. From the viewpoint of reducing the size and capacity of the multilayer ceramic capacitor, 0.3 μm to 0.00 μm. It is preferable that it is 8 micrometers.

The binder removal and firing conditions were performed in a mixed atmosphere of N ₂ —H ₂ —H ₂ O that does not oxidize the second metal with reference to the Ellingham diagram and the like. This is because when the second metal is oxidized, the effect of improving the wettability of the first metal to the dielectric cannot be exhibited, or the characteristics of the multilayer ceramic capacitor are undesirably changed. This is because when Ni is sintered, it diffuses together with the co-material to the dielectric layer side and cannot exist at the interface between the internal electrode layer and the dielectric layer.

  The contents of the present invention will be described in further detail using examples and comparative examples. However, the present invention is not limited to the following examples.

Example 1
First, an interior green sheet 11 and an exterior green sheet 12 were prepared. The raw material ceramic powder was mixed with an organic vehicle and a dispersant using a ball mill and pulverized to prepare a paint. The prepared paint was applied onto PET with a doctor blade and dried to obtain an interior green sheet 11 and an exterior green sheet 12.

  Next, a conductive paste for forming an internal electrode film after firing was prepared. 16 parts by weight of 15 parts by weight of co-material, 60 parts by weight of organic vehicle, and second metal of Mn resinate were added to 100 parts by weight of Ni powder of the first metal. Mn resinate has a metal component of 2.0% by volume with respect to Ni powder. Ni powder, common material, organic vehicle, and second metal were mixed and dispersed by a three-roll mill to produce a conductive paste.

  The conductive paste was printed on the interior green sheet by screen printing 13. The printing amount was adjusted by the total amount of the first metal and the second metal so that the thickness was 0.50 μm when the coverage after firing was 90%. The exterior green sheet was laminated so that there were 20 layers and the dielectric layer sandwiched between the internal electrode layers was 200 layers, and cut into 0.75 mm × 0.38 mm to obtain a laminate 14.

The laminate was baked at 650 ° C. with a binder removed and 1230 ° C. in an atmosphere in which N ₂ —H ₂ —H ₂ O was mixed so that Mn as the second metal was not oxidized. After polishing the end face of the obtained 0.60 mm × 0.30 mm sintered body by sand blasting, external electrodes were formed on both end faces of the sintered body to obtain a multilayer ceramic capacitor 1.

(Examples 2 to 4)
In Examples 2 to 4, multilayer ceramic capacitors were produced in the same manner as in Example 1 except that the second metal was changed as shown in Table 1.

(Example 5)
In Example 5, a multilayer ceramic capacitor was fabricated in the same manner as in Example 1 except that the addition form of the second metal was changed as shown in Table 1.

(Examples 6 and 7)
In Examples 6 and 7, the addition amount of the second metal was changed as shown in Table 1, and the others were made in the same manner as in Example 1 to produce a multilayer ceramic capacitor.

(Comparative Example 1)
In Comparative Example 1, a multilayer ceramic capacitor was produced in the same manner as in Example 1 except that the second metal was not added.

(Comparative Examples 2 and 3)
In Comparative Examples 2 and 3, the second metal was changed as shown in Table 1, and the others were the same as in Example 1 to produce a multilayer ceramic capacitor.

(Comparative Example 4)
In Comparative Example 4, a multilayer ceramic capacitor was manufactured in the same manner as in Example 1 except that the binder removal atmosphere of the multilayer body was changed as shown in Table 1.

(Comparative Example 5)
In Comparative Example 5, a multilayer ceramic capacitor was fabricated in the same manner as in Example 1 except that the firing atmosphere of the multilayer body was changed as shown in Table 1.

  In Comparative Examples 6 and 7, the addition amount of the second metal was changed as shown in Table 1, and the others were made in the same manner as in Example 1 to produce a multilayer ceramic capacitor.

(Evaluation of wettability)
The evaluation of the wettability of each metal type with respect to the dielectric was determined in the direction in which the metal 33 grows on the dielectric substrate 21. First, a deposition source of each metal and a dielectric substrate having the same composition as the dielectric layer of the multilayer ceramic capacitor described in the examples were prepared. A metal was deposited on a dielectric substrate in a vacuum of 3.0 × 10 ⁻⁵ Torr or less using a vacuum deposition apparatus so that the film thickness was 1 to 20 nm, thereby preparing a sample. The state of the deposited metal of the obtained sample was observed with a scanning tunneling microscope (STM) in a range of 50 nm × 50 nm.

The case where the metal 33 grows in a plane so as to increase the contact area with the dielectric substrate 21 is “◯”, and the case where the metal 33 grows in an island shape so as to minimize the contact area with the dielectric substrate is “x”. . A case where plane growth and island-shaped growth coexist was defined as “Δ”. “◯” indicates a metal having good wettability with a dielectric.

(Continuity evaluation of internal electrode film)
The continuity of the internal electrode film was evaluated by the coverage. The produced multilayer ceramic capacitor is filled with resin, polished to the center to expose the surface perpendicular to the lamination direction, and an electrode layer based on an image obtained by observation with a scanning electron microscope (SEM) The ratio of the total length of the actually continuous portion to the length when the was completely continuous was calculated as the coverage.

(Distribution of second metal)
The produced multilayer ceramic capacitor is filled with resin, polished to the center to expose the surface perpendicular to the lamination direction, and the polished surface is observed with an electron beam microanalyzer (EPMA). The second metal is a dielectric. The presence of the interface between the electrode layer and the electrode layer and the inside of the electrode layer were examined. The case where it existed was indicated as “◯”, and the case where it did not exist was indicated as “x”. Based on the mapping image of EPMA, the distribution amount was calculated by calculating the ratio of the area of the second metal 32 to the area of the first metal 31 and expressed in volume%.

(Acquisition capacity)
The obtained capacity of the produced multilayer ceramic capacitor was measured. The acquired capacity in Table 1 is a percentage of the capacity measurement result of each sample with respect to the capacity when the coverage of the internal electrode is 100%.

  When Examples 1-7 were compared with Comparative Examples 1-7, in the case of Examples 1-7, the coverage of the internal electrode was 90% or more, and a multilayer ceramic capacitor having high continuity of the internal electrode film was obtained. . In the case of Examples 1-7, the internal electrode layer was thinned compared with Comparative Examples 1-7 because the coverage was 90% or more. Since the amount of metal is the same, it is considered that the higher the coverage, the thinner the internal electrode layer.

  When the distribution state of the second metal in the internal electrode layer was analyzed, Examples 1 to 7 and Comparative Examples 2 and 3 existed in the metal state in the interface between the internal electrode layer and the dielectric layer and in the internal electrode layer. Was. Since Comparative Examples 4 and 5 were not present in the internal electrode layer and were present as oxides at the interface between the internal electrode layer and the dielectric layer, the amount of the dielectric layer was smaller than the amount added. It is highly probable that it has spread.

  Comparative Example 7 could not be characterized. This is probably because the proportion of the second metal in the internal electrode layer increased and the conductivity could not be secured.

  As described above, the multilayer ceramic electronic component according to the present invention is useful for obtaining a structure having high continuity of the internal electrode film even when the internal electrode layer becomes thin.

DESCRIPTION OF SYMBOLS 1 Multilayer ceramic capacitor 2 Dielectric layer 3 Internal electrode layer 4 External electrode 5 Exterior dielectric layer 11 Interior green sheet 12 Exterior green sheet 13 Electrode precursor layer 14 Laminated body 15 Interior part 16 Exterior part 21 Dielectric substrate 31 1st Metal 32 second metal 33 metal

Claims (2)

Having a dielectric layer and an internal electrode layer;
The internal electrode layer includes a first metal and a second metal,
The second metal is included in a range of 0.5 to 4.0% by volume with respect to the first metal,
At least a portion of the second metal is present at the interface between the dielectric layer and the internal electrode layer;
The wettability of the second metal with respect to the dielectric constituting the dielectric layer is as follows:
The multilayer ceramic electronic component according to claim 1, wherein the first metal has higher wettability with respect to a dielectric constituting the dielectric layer. 3. The multilayer ceramic electronic component according to claim 1, wherein the first metal is Ni, and the second metal is selected from at least one of Ca, Mg, Ba, and Mn.

Images