JP2010278398A - Method for evaluation of element distribution of object to be evaluated, and method of manufacturing electronic component using evaluation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of quantitatively evaluating spatial dispersion of element distribution from element distribution data of objects to be evaluated. <P>SOLUTION: In the method of evaluating the element distribution, the element distribution of the objects to be evaluated is obtained as a two-dimensional image signal of the number X×Y of pixels. When X and Y have a relation of X≤Y, and f (x, y) is expressed as an element concentration in a position (x, y) of an arbitrary pixel, and u and v are expressed as arbitrary spatial frequencies, and a frequency r is expressed as r=(u<SP>2</SP>+v<SP>2</SP>)<SP>1/2</SP>, the method has a step of performing two-dimensional Fourier transformation of the two-dimensional image signal to obtain a frequency spectrum F (u, v), a step of acquiring the sum P (r) of the spectrum intensity in the frequency r about the frequency spectrum F (u, v), and a step of evaluating the element distribution of the objects to be evaluated by using an inclination in a specified frequency range found based on a graph in which a horizontal axis indicates the frequency r and a vertical axis indicates the sum P (r) of the spectrum intensity. The inclination is obtained by using linear approximation. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an element distribution evaluation method for an object to be evaluated and an electronic component manufacturing method using the evaluation method.

  Multilayer ceramic capacitors are widely used as small-sized, large-capacity, and high-reliability electronic components, and the number used in electrical and electronic devices is large. In recent years, with the miniaturization and high performance of devices, the demand for further miniaturization, larger capacity, lower cost, and higher reliability of multilayer ceramic capacitors has become increasingly severe.

  A multilayer ceramic capacitor is usually manufactured by laminating an internal electrode paste and a dielectric slurry (paste) by a sheet method, a printing method, or the like, followed by firing. In general, Pd and Pd alloys have been used for the internal electrodes. However, since Pd is expensive, relatively inexpensive Ni and Ni alloys are being used. By the way, when the internal electrode is formed of Ni or Ni alloy, there is a problem that the electrode is oxidized if firing is performed in the atmosphere. For this reason, generally, after debinding, the dielectric layer is reoxidized by firing at an oxygen partial pressure lower than the equilibrium oxygen partial pressure of Ni and NiO, followed by heat treatment.

  However, when fired in a reducing atmosphere, there is a problem that the dielectric layer is reduced, the insulation resistance (IR) is reduced, and the high-temperature load life is also reduced.

  Thus, for example, Patent Document 1 and Patent Document 2 propose a dielectric material having a predetermined CV value as a reduction-resistant dielectric material that is not reduced even when fired in a reducing atmosphere. This is because the presence of a phase called a segregation phase in which the subcomponent is present at a higher concentration than the main phase mainly composed of the main component at the grain boundary of the dielectric layer reduces the high temperature load life. It is considered as one of the factors, and the CV value is used as an indicator of the presence of segregation phase.

Specifically, in Patent Document 1, in order to obtain a multilayer ceramic capacitor having a low IR failure rate (initial insulation resistance failure rate), excellent high temperature load life, and high reliability, the CV value of SiO ₂ distribution is: It is described as 250 or less.

Patent Document 2 describes that the CV value of Al ₂ O ₃ distribution is 100 or less in order to obtain a multilayer ceramic capacitor having a high withstand voltage, excellent high-temperature load life, and high reliability. Yes.

The CV value is a value calculated from the following formula, and indicates the degree of dispersion from the average value. In general, when the CV value is low, the segregation phase does not exist, the segregation phase is small, or even if the segregation phase is present, the concentration of elements constituting the segregation phase tends to be low.
CV value = (standard deviation σ of detection intensity / average detection intensity x) × 100

By the way, when the dielectric ceramic composition contains Si, Mg, and Ca as subcomponents, the presence of a relatively large segregation phase having a size of 2.0 μm ² or more tends to cause a decrease in high temperature load life. is there.

However, when the small regions with high concentration of small elements of about 1.0 μm ² or less, called “clusters”, are adjacent to each other at an interval of twice or less the diameter, and gathered in the range of 2.0 μm ² or more. As in the case where the segregation phase is present, it is known to cause a decrease in the high temperature load life.

  On the other hand, as described above, the CV value can be evaluated for the degree of dispersion from the average value, but since spatial variation cannot be detected, it is necessary to grasp the existence of a cluster (cluster) of small elements. I can't. Hereinafter, the CV value and the spatial variation will be further described with reference to FIG.

  6A is a schematic diagram of an element distribution in a state in which no segregation phase and clusters exist (state in which the distribution of element concentration is uniform), and FIG. 6B shows that a cluster exists. It is a schematic diagram of the element distribution in the assumed state (state where the distribution of element concentration is locally biased). Here, in FIGS. 6A and 6B, when the white portion represents the concentration 1 of an element and the black portion represents the concentration 0 of an element, the average concentration in FIG. The standard deviation is 0.09, and the CV value of the concentration is 0.9.

  On the other hand, when the CV value is similarly obtained for FIG. 6B, the CV value of FIG. 6B is 0.9, which is the same as FIG. 6A.

  Thus, the CV value shows the same value both when the segregation phase and the cluster are not present (FIG. 6A) and when the cluster is present (FIG. 6B). As described above, this is because the CV value is an index that cannot detect spatial variation, and the presence of a cluster cannot be detected depending on the CV value.

  As a conventional technique, it is possible to visually recognize the presence of clusters from an element distribution image by EPMA, STEM-EDS, or the like. However, visual recognition of images is an evaluation method unsuitable for mass production, and there is a problem in that there is room for the viewer's subjectivity and lack of objectivity.

JP 2006-5222 A JP 2006-66835 A Ryoma Kitagaki, Manabu Kanematsu, Takafumi Noguchi, “Study on quantitative evaluation of exposed concrete visual information by two-dimensional Fourier transform”, Structural Papers, November 2005, No. 597, p. 33 Ryoma Kitagaki, Manabu Kanematsu, Takafumi Noguchi, “Study on the analysis method of visual information change of exposed concrete by two-dimensional Fourier transformation”, Structural papers, November 2005, No. 597, p. 39

  The present invention has been made in view of such a situation, and an object thereof is to provide a method for quantitatively evaluating spatial variations in element distribution from element distribution data of an object to be evaluated.

  Another object of the present invention is to provide a method for producing an electronic component having a dielectric ceramic composition having a good high temperature load life using the above method.

  As a result of intensive studies to achieve the above object, the present inventor has found that the spatial variation of the element distribution can be quantitatively evaluated from a predetermined evaluation value obtained from the element distribution data. It was.

Thus, according to the present invention, the following [1] to [7] are provided.
[1] Obtaining the element distribution of the object to be evaluated as a two-dimensional image signal having the number of pixels X × Y,
X and Y are in a relationship of X ≦ Y,
f (x, y) is expressed as an element concentration at an arbitrary pixel position (x, y),
u and v are expressed as arbitrary spatial frequencies,
When the frequency r is represented by r = (u ² + v ² ) ^1/2 ,
Obtaining a frequency spectrum F (u, v) by performing a two-dimensional Fourier transform on the two-dimensional image signal;
Obtaining a sum P (r) of spectral intensities at a frequency r for the frequency spectrum F (u, v);
Evaluating the element distribution of the object to be evaluated using a slope in a predetermined frequency range obtained from a graph in which the horizontal axis is the frequency r and the vertical axis is the sum of spectral intensities P (r),
The element distribution evaluation method, wherein the slope is obtained by linear approximation.
[2] The element distribution evaluation method according to [1], wherein the object to be evaluated is a ceramic sintered body.
[3] The element distribution evaluation method according to [1], wherein the object to be evaluated is a dielectric ceramic composition.
[4] When r is R when R is X / 2,
The element distribution evaluation method according to [3] above, wherein a range of a predetermined frequency with respect to the inclination is in a range of 7R / 256 or more and 27R / 256 or less.
[5] In the above [3] or [4], when the evaluation value is in the range of 0 or more and 0.003 or less, it is determined that segregation and clusters of the element distribution have not occurred. Evaluation method of element distribution of description.
[6] The dielectric ceramic composition includes at least one of Si, Mg, and Ca as an element, and at least one of Si, Mg, and Ca is an evaluation target [3] ] The element distribution evaluation method according to any one of [5] to [5].
[7] A method for producing an electronic component having a dielectric ceramic composition,
Firing a device body in which a plurality of dielectric layers and internal electrode layers are alternately arranged; and
The dielectric layer is composed of a dielectric ceramic composition;
A step of evaluating the dielectric ceramic composition by the element distribution evaluation method according to any one of [3] to [6];
A method of making an electronic component having a dielectric ceramic composition whose evaluation value is not included in a predetermined range as a defective product.

  According to the present invention, it is possible to provide a method for quantitatively evaluating the spatial variation of the element distribution from the element distribution data of the object to be evaluated. Further, by applying such an evaluation method, for example, It is possible to provide a method for manufacturing an electronic component having a dielectric ceramic composition having a good high temperature load life.

FIG. 1 is a schematic view showing the evaluation method of the present invention. FIG. 2 is a cross-sectional view of a multilayer ceramic capacitor according to an embodiment of the present invention. FIG. 3 is a table summarizing a table showing elemental distributions of subcomponents expressed by STEM-EDS analysis of the fine structure of the dielectric layer according to the example of the present invention. FIG. 4 is a frequency obtained by performing two-dimensional Fourier transform on the element concentration based on the diagram showing the elemental distribution of subcomponents expressed by STEM-EDS analysis of the fine structure of the dielectric layer according to the embodiment of the present invention. FIG. FIG. 5 is a frequency spectrum graph obtained from the frequency spectrum diagram according to the embodiment of the present invention. FIG. 6 is a schematic diagram showing an element concentration distribution.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

Element Distribution Evaluation Method First, how to obtain an element distribution evaluation value in this embodiment will be described with reference to the process schematic diagram shown in FIG.

First, element distribution data of an object to be evaluated is obtained. The object to be evaluated is not particularly limited as long as the elements are distributed, and examples thereof include elemental analysis on a ceramic sintered body, a magnetic recording medium, or a thin film. As the ceramic sintered body, a dielectric ceramic composition is preferable. In the present evaluation method, the composition of the dielectric ceramic composition is not limited.
It should be noted that an object to be evaluated used in this evaluation method is preferably one in which elements are not uniformly distributed.

  Further, the element distribution may be any as long as it includes a two-dimensional image signal ((A) in FIG. 1). As a method for obtaining the element distribution data, for example, EPMA (Electron Probe Micro Analysis), SEM-EDS, STEM -Measurement by EDS and TEM-EF (energy filter) is mentioned.

  The two-dimensional image signal needs to represent the element concentration f (x, y) at the position (x, y) of an arbitrary pixel. In this case, the two-dimensional image signal may be binarized or continuously changed (grayscale).

  Next, f (x, y) is subjected to a two-dimensional Fourier transform to obtain a frequency spectrum F (u, v).

  Here, when the element distribution is obtained as a two-dimensional pixel signal having the number of pixels X × Y shown in FIG. 1, for example, the position (x, y) represents the position of an arbitrary pixel in the element distribution data, and 0 ≦ x ≦ X−1, 0 ≦ y ≦ Y−1. U and v represent arbitrary spatial frequencies.

  Further, the frequency spectrum F (u, v) is represented by the equation (1), the spectrum intensity is represented by the equation (2), and the horizontal axis is v and the vertical axis is u, for example, a frequency spectrum diagram ( (B1) in FIG. 1 is obtained. In the frequency spectrum diagram, the distance from the center indicates “frequency”, the direction from the center indicates “the direction of the sine wave”, and the color shading indicates “the spectral intensity of the wave having the frequency / direction”.

  FIGS. 1A and 1B1 are schematic views. When f (x, y) representing FIG. 1A is two-dimensional Fourier transformed, FIG. 1B1 is obtained. The indicated F (u, v) cannot be obtained.

・・・（１）

・・・（２）

... (1)

... (2)

  Next, as shown in FIG. 1 (B2), the sum of the spectral intensities included in the donut-shaped range having a spacing of Δr divided into concentric circles centered on the origin of the frequency spectrum diagram. Ask for.

  For the description of this process, F (u, v) is represented by polar coordinates F (r, θ). Here, F (u, v) = F (r, θ), r means frequency, and is expressed by equation (3), and θ is expressed by equation (4). By expressing in this way, the sum of the spectrum intensities is expressed by equation (5) as the sum of the spectrum intensities P (r) at an arbitrary frequency r. That is, P (r) can be said to be expressed as a frequency r function by canceling the directionality of the sine wave.

・・・（３）

・・・（４）

・・・（５）

... (3)

... (4)

... (5)

  This technique is used as a method for evaluating the appearance in Non-Patent Document 1 and Non-Patent Document 2.

  Next, as shown in FIG. 1C, the slope is determined from a graph (hereinafter referred to as a frequency spectrum graph) in which the horizontal axis is the frequency r and the vertical axis is the sum of spectral intensities P (r). The present invention is characterized in that the slope is a slope in a predetermined frequency range.

The inclination is obtained by linear approximation.
The present invention is characterized in that an evaluation value is a slope in a predetermined frequency range. By using the slope as the evaluation value, it is possible to quantitatively evaluate the spatial variation of the element distribution.

  In the dielectric ceramic composition as the evaluation object according to an embodiment of the present invention, the evaluation object has a predetermined frequency with respect to the inclination, where r is R when r is X / 2. The range is from 7R / 256 to 27R / 256. If the frequency is larger than this range, it has a noise component in the measurement and is not suitable for obtaining an evaluation value. In addition, effective evaluation cannot be performed even if a slope smaller than this range is entered.

  In the dielectric ceramic composition as an object to be evaluated according to an embodiment of the present invention, the predetermined range for the evaluation value is preferably in the range of 0 to 0.003. When the evaluation value is less than 0, segregation and clusters are large, and the high temperature load life tends to decrease. On the other hand, when the evaluation value is greater than 0.003, the dielectric constant tends to decrease.

  By using this evaluation method for the dielectric ceramic composition, it is possible to infer the presence of clusters that could not be detected by the conventional method using the CV value as well as the segregated phase, and the dielectric ceramic having a good high temperature load life. A composition can be obtained.

Multilayer ceramic capacitor 1
The electronic component manufactured by the manufacturing method according to one embodiment of the present invention is not particularly limited. In this embodiment, a multilayer ceramic capacitor is illustrated.

  As shown in FIG. 2, a multilayer ceramic capacitor 1 as an electronic component according to an embodiment of the present invention includes a capacitor element body 10 having a configuration in which dielectric layers 2 and internal electrode layers 3 are alternately stacked. At both ends of the capacitor element body 10, a pair of external electrodes 4 are formed which are electrically connected to the internal electrode layers 3 arranged alternately in the element body 10. The shape of the capacitor element body 10 is not particularly limited, but is usually a rectangular parallelepiped shape. Moreover, there is no restriction | limiting in particular also in the dimension, What is necessary is just to set it as a suitable dimension according to a use.

  The internal electrode layers 3 are laminated so that the end faces are alternately exposed on the surfaces of the two opposite ends of the capacitor element body 10. The pair of external electrodes 4 are formed at both ends of the capacitor element body 10 and are connected to the exposed end surfaces of the alternately arranged internal electrode layers 3 to constitute a capacitor circuit.

Dielectric layer 2
The dielectric layer 2 contains a dielectric ceramic composition composed of a main component and a subcomponent, and the segregation phase is segregated from the subcomponent, and these are compared with a main phase mainly composed of the main component. This is a portion where the subcomponent of is present at a high concentration. In the present embodiment, the segregation phase is present at the grain boundary of the dielectric layer and / or the interface between the dielectric layer and the electrode.

  The composition of the dielectric ceramic composition is not particularly limited, but in the present invention, the segregation phase in the dielectric layer 2 preferably contains at least one of Si, Mg, and Ca.

In this embodiment, the dielectric ceramic composition is represented by a composition formula Ba _m TiO _{2 + m} , _m in the composition formula is 0.995 ≦ m ≦ 1.010, and the ratio of Ba and Ti is It contains a main component satisfying 0.995 ≦ Ba / Ti ≦ 1.010 and other subcomponents.

In this embodiment, it is preferable to contain the following 1st-5th subcomponents.
A first subcomponent containing at least one selected from MgO, CaO, BaO and SrO; a second subcomponent containing silicon oxide as a main component; and at least selected from V ₂ O ₅ , MoO ₃ and WO ₃ A third subcomponent including one kind and an oxide of R (where R is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) And a fourth subcomponent including at least one selected from Lu and a fifth subcomponent including CaZrO ₃ or CaO + ZrO ₂ .

The ratio of each subcomponent to the main component is 100 mol of the main component.
1st subcomponent: 0-3.0 mol (however, 0 is not included),
Second subcomponent: 2 to 10 mol,
Third subcomponent: 0.01 to 0.5 mol,
4th subcomponent: 0.5-7 mol 5th subcomponent: 5 mol or less (however, 0 is not included).

The ratio of each of the subcomponents to the main component is preferably 100 mol of the main component,
1st subcomponent: 0.5-2.5 mol,
Second subcomponent: 2 to 5 mol,
Third subcomponent: 0.1 to 0.4 mol,
Fourth subcomponent: 0.5 to 5 mol Fifth subcomponent: 0 to 3 mol.

The ratio of the fourth subcomponent is not the molar ratio of the oxide of R, but the molar ratio of R alone. That is, for example, when an oxide of Yb is used as the fourth subcomponent, the ratio of the fourth subcomponent is 1 mol. The ratio of Yb ₂ O ₃ is not 1 mol but the ratio of Yb is 1 mol. It means that.

  In the present embodiment, the temperature characteristics of the capacitance can be improved by including the first to fifth subcomponents in the dielectric ceramic composition.

  Note that, in this specification, each oxide constituting the main component and each subcomponent is represented by a stoichiometric composition, but the oxidation state of each oxide may be out of the stoichiometric composition. . However, the said ratio of each subcomponent is calculated | required by converting into the oxide of the said stoichiometric composition from the metal amount contained in the oxide which comprises each subcomponent.

  The reasons for limiting the contents of the subcomponents are as follows.

  If the content of the first subcomponent (MgO, CaO, BaO, and SrO) is too small, the capacity-temperature change rate becomes large. On the other hand, when there is too much content, while sinterability will deteriorate, it exists in the tendency for a high temperature load life to deteriorate. The composition ratio of each oxide in the first subcomponent is arbitrary.

The second subcomponent contains silicon oxide as a main component, and is preferably contained as a composite oxide represented by a composition formula (Ba, Ca) _x SiO _{2 + x} . BaO and CaO in the composition formula (Ba, Ca) _x SiO _{2 + x} are also included in the first subcomponent, but (Ba, Ca) _x SiO _{2 + x} , which is a composite oxide, has a low melting point and thus has a reactivity to the main component. Since it is good, in the present invention, BaO and / or CaO is also added as the composite oxide.

When the content of the second subcomponent is too small, the capacity-temperature characteristic is deteriorated and IR (insulation resistance) is lowered. On the other hand, if the content is too large, the high temperature load life becomes insufficient and the dielectric constant is drastically reduced. _{X in} (Ba, Ca) _x SiO _{2 + x} is preferably 0.8 to 1.2, more preferably 0.9 to 1.1. When x is too small, that is, when SiO ₂ is too much, it reacts with the main component Ba _m TiO _{2 + m} and deteriorates dielectric properties. On the other hand, if x is too large, the melting point becomes high and the sinterability is deteriorated, which is not preferable. In the second subcomponent, the ratio of Ba and Ca is arbitrary, and may contain only one.

The third subcomponent (V ₂ O ₅ , MoO ₃ and WO ₃ ) exhibits the effect of flattening the capacity-temperature characteristics above the Curie temperature and the effect of improving the high temperature load life. If the content of the third subcomponent is too small, such an effect becomes insufficient. On the other hand, when there is too much content, IR will fall remarkably. The constituent ratio of each oxide in the third subcomponent is arbitrary.

  The fourth subcomponent (R oxide) exhibits the effect of shifting the Curie temperature to the high temperature side and the effect of flattening the capacity-temperature characteristics. When there is too little content of a 4th subcomponent, such an effect will become inadequate and a capacity | capacitance temperature characteristic will worsen. On the other hand, if the content is too large, the sinterability tends to deteriorate. Among the fourth subcomponents, Y oxide and Yb oxide are preferable because they have a high effect of improving characteristics and are inexpensive.

The fifth subcomponent (CaZrO ₃ or CaO + ZrO ₂ ) shifts the Curie temperature to the high temperature side, flattens the capacitance-temperature characteristics, improves the insulation resistance (IR), improves the breakdown voltage, reduces the firing temperature, etc. It has the effect of.

Internal electrode layer 3
The conductive material contained in the internal electrode layer 3 is not particularly limited, but a relatively inexpensive base metal can be used because the constituent material of the dielectric layer 2 has reduction resistance. As the base metal used as the conductive material, Ni or Ni alloy is preferable. The Ni alloy is preferably an alloy of Ni and one or more elements selected from Mn, Cr, Co and Al, and the Ni content in the alloy is preferably 95% by weight or more. In addition, in Ni or Ni alloy, various trace components, such as P, may be contained about 0.1 wt% or less. The thickness of the internal electrode layer 3 may be appropriately determined according to the application and the like, but is usually 0.1 to 3 μm, particularly preferably about 0.2 to 2.0 μm.

External electrode 4
The conductive material contained in the external electrode 4 is not particularly limited, but in the present invention, inexpensive Ni, Cu, and alloys thereof can be used. The thickness of the external electrode 4 may be appropriately determined according to the application and the like, but is usually preferably about 10 to 50 μm.

Manufacturing Method of Multilayer Ceramic Capacitor A manufacturing method of a multilayer ceramic capacitor as an electronic component according to an embodiment of the present invention is not particularly limited, but, as with conventional multilayer ceramic capacitors, a normal printing method or sheet method using a paste The green chip is manufactured by firing, and after firing, the external electrode is printed or transferred and fired. Hereinafter, the manufacturing method will be specifically described.

First, a dielectric ceramic composition powder contained in a dielectric layer paste is prepared, a main component and subcomponents are mixed, and this is made into a paint to prepare a dielectric layer paste.
The mixing time is preferably 15 hours or longer. When the mixing time is less than 15 hours, the segregation phase of subcomponents becomes large and the high temperature load life tends to be reduced.

  The dielectric layer paste may be an organic paint obtained by mixing a dielectric ceramic composition powder and an organic vehicle, or may be a water-based paint.

  As the dielectric ceramic composition powder, the above-described oxides, mixtures thereof, and composite oxides can be used. In addition, various compounds that become the above-described oxides and composite oxides by firing, such as carbonates and An acid salt, a nitrate, a hydroxide, an organometallic compound, or the like can be appropriately selected and mixed for use. What is necessary is just to determine content of each compound in a dielectric ceramic composition powder so that it may become a composition of the above-mentioned dielectric ceramic composition after baking. The particle size of the dielectric ceramic composition powder is usually about 0.1 to 1 [mu] m in average before the coating.

  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. Further, the organic solvent to be used is not particularly limited, and may be appropriately selected from various organic solvents such as terpineol, butyl carbitol, acetone, toluene, and the like, depending on a method to be used such as a printing method or a sheet method.

  Further, when the dielectric layer paste is used as a water-based paint, a water-based vehicle in which a water-soluble binder or a dispersant is dissolved in water and a dielectric material may be kneaded. The water-soluble binder used for the water-based vehicle is not particularly limited, and for example, polyvinyl alcohol, cellulose, water-soluble acrylic resin, or the like may be used.

  The internal electrode layer paste is prepared by kneading the above-mentioned organic vehicle with various conductive metals and alloys as described above, or various oxides, organometallic compounds, resinates, etc. that become the above-mentioned conductive materials after firing. Prepare.

  The external electrode paste may be prepared in the same manner as the internal electrode layer paste described above.

  There is no restriction | limiting in particular in content of the organic vehicle in each above-mentioned paste, For example, what is necessary is just about 1-5 weight% of binders, for example, about 10-50 weight% of binders. Each paste may contain additives selected from various dispersants, plasticizers, dielectrics, insulators, and the like as necessary. The total content of these is preferably 10% by weight or less.

  When the printing method is used, the dielectric layer paste and the internal electrode layer paste are laminated and printed on a substrate such as PET, cut into a predetermined shape, and then peeled from the substrate to obtain a green chip.

  When the sheet method is used, a dielectric layer paste is used to form a green sheet, the internal electrode layer paste is printed thereon, and these are stacked to form a green chip.

Before firing, the green chip is subjected to binder removal processing. The binder removal treatment may be appropriately determined according to the type of the conductive material in the internal electrode layer paste. However, when a base metal such as Ni or Ni alloy is used as the conductive material, the oxygen partial pressure in the binder removal atmosphere is 10 It is preferable to be ⁻⁴⁵ to 10 ⁵ Pa. When the oxygen partial pressure is less than the above range, the binder removal effect is lowered. If the oxygen partial pressure exceeds the above range, the internal electrode layer tends to oxidize.

As other binder removal conditions, the temperature rising rate is preferably 5 to 300 ° C./hour, more preferably 10 to 100 ° C./hour, and the holding temperature is preferably 180 to 400 ° C., more preferably 200 to 350. The temperature holding time is preferably 0.5 to 24 hours, more preferably 2 to 20 hours. The firing atmosphere is preferably air or a reducing atmosphere, and as an atmosphere gas in the reducing atmosphere, for example, a mixed gas of N ₂ and H ₂ is preferably used after being humidified.

The atmosphere at the time of green chip firing may be appropriately determined according to the type of conductive material in the internal electrode layer paste, but when a base metal such as Ni or Ni alloy is used as the conductive material, the oxygen content in the firing atmosphere The pressure is preferably 10 ⁻⁷ to 10 ⁻³ Pa. When the oxygen partial pressure is less than the above range, the conductive material of the internal electrode layer may be abnormally sintered and may be interrupted. Further, when the oxygen partial pressure exceeds the above range, the internal electrode layer tends to be oxidized.

  In this embodiment, the holding temperature during firing is preferably 1200 to 1380 ° C. If the holding temperature is less than the above range, densification becomes insufficient, and if it exceeds the above range, segregation of subcomponents becomes large.

As other firing conditions, the rate of temperature rise is preferably 50 to 500 ° C./hour, more preferably 200 to 300 ° C./hour, and the temperature holding time is preferably 0.5 to 8 hours, more preferably 1 to 3 hours. The time and cooling rate are preferably 50 to 500 ° C./hour, more preferably 200 to 300 ° C./hour. Further, the firing atmosphere is preferably a reducing atmosphere, and as the atmosphere gas, for example, a mixed gas of N ₂ and H ₂ is preferably used by humidification.

  When firing in a reducing atmosphere, it is preferable to anneal the capacitor element body. Annealing is a process for re-oxidizing the dielectric layer, which can significantly increase the high-temperature load life, thereby improving reliability.

The oxygen partial pressure in the annealing atmosphere is preferably 10 ^{−1 to} 10 Pa. When the oxygen partial pressure is less than the above range, it is difficult to reoxidize the dielectric layer, and when it exceeds the above range, the internal electrode layer tends to be oxidized.

  The holding temperature at the time of annealing is preferably 1100 ° C. or less, particularly 500 to 1100 ° C. When the holding temperature is lower than the above range, the dielectric layer is not sufficiently oxidized, so that the IR is low and the high temperature load life is likely to be shortened. On the other hand, when the holding temperature exceeds the above range, not only the internal electrode layer is oxidized and the capacity is lowered, but the internal electrode layer reacts with the dielectric substrate, the capacity temperature characteristic is deteriorated, the IR is lowered, and the high temperature is increased. The load life is likely to decrease. Note that annealing may be composed of only a temperature raising process and a temperature lowering process. That is, the temperature holding time may be zero. In this case, the holding temperature is synonymous with the maximum temperature.

As other annealing conditions, the temperature holding time is preferably 0 to 20 hours, more preferably 2 to 10 hours, and the cooling rate is preferably 50 to 500 ° C./hour, more preferably 100 to 300 ° C./hour. . Further, as the annealing atmosphere gas, for example, humidified N ₂ gas or the like is preferably used.

In the above-described binder removal processing, firing and annealing, for example, a wetter or the like may be used to wet the N ₂ gas or mixed gas. In this case, the water temperature is preferably about 5 to 75 ° C.

  The binder removal treatment, firing and annealing may be performed continuously or independently.

  In the present invention, the capacitor element body obtained as described above is evaluated by the above-described evaluation method. The evaluation may be performed on the capacitor element body or the multilayer ceramic capacitor. Below, the case where evaluation with the above-mentioned evaluation method is performed with respect to the capacitor element body will be described.

  In order to detect a cluster contained in the dielectric ceramic composition as the evaluation object according to an embodiment of the present invention, the number of pixels of the two-dimensional image signal is 128 × 128 or more, more preferably 256 × 256. The magnification is 10,000 times to 100,000 times, more preferably 20,000 times to 50,000 times.

A capacitor element body whose evaluation value is not included in the predetermined range may be a defective product. Further, the manufacturing conditions may be changed so that the inclination falls within a predetermined range based on such an evaluation result. On the other hand, the capacitor element body in which the evaluation body is included in a predetermined range is subjected to end surface polishing by, for example, barrel polishing or sand blasting, and the external electrode paste is printed or transferred and fired to form the external electrode 4. The firing conditions of the external electrode paste are preferably, for example, about 10 minutes to 1 hour at 600 to 800 ° C. in a humidified mixed gas of N ₂ and H ₂ . Then, if necessary, a coating layer is formed on the surface of the external electrode 4 by plating or the like.

  The multilayer ceramic capacitor of the present invention thus manufactured is mounted on a printed circuit board by soldering or the like and used for various electronic devices.

  As mentioned above, although embodiment of this invention has been described, this invention is not limited to the embodiment mentioned above at all, and can be variously modified within the range which does not deviate from the summary of this invention.

  For example, in the above-described embodiment, the multilayer ceramic capacitor is exemplified as the electronic component according to the present invention. However, the electronic component according to the present invention is not limited to the multilayer ceramic capacitor, and is composed of a dielectric ceramic composition having the above composition. Any material having a dielectric layer can be used.

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

Example First, as a starting material for producing a dielectric ceramic composition, a main component material (BaTiO ₃ ) having an average particle size of 0.3 μm and the following first to fifth subcomponent materials were prepared.
MgO (first subcomponent): 1.0 mol (Ba _0.6 Ca _0.4 ) SiO ₃ (second subcomponent): 3.0 mol V ₂ O ₅ (third subcomponent): 0.1 mol Y ₂ O ₃ (fourth subcomponent): 2.0 mol Yb ₂ O ₃ (fourth subcomponent): 1.75 mol CaZrO ₃ (fifth subcomponent): 1.5 mol The amount of the component added is the number of moles relative to 100 moles of BaTiO _{3 as} the main component.

  Next, the raw materials of these main components and subcomponents were wet-mixed by a ball mill for 5 to 30 hours and dried to obtain a dielectric ceramic composition powder. The mixing time of each sample (sample numbers 1 to 8 and A to C) is shown in Table 1 and FIG.

  Next, 100 parts by weight of the obtained dielectric ceramic composition powder after drying, 4.8 parts by weight of acrylic resin, 100 parts by weight of ethyl acetate, 6 parts by weight of mineral spirit, and 4 parts by weight of toluene were mixed with a ball mill. The mixture was made into a paste to obtain a dielectric layer paste.

  Furthermore, 44.6 parts by weight of Ni particles, 52 parts by weight of terpineol, 3 parts by weight of ethyl cellulose, and 0.4 parts by weight of benzotriazole were kneaded with three rolls and slurried to obtain an internal electrode layer paste. It was.

  Using these pastes, the multilayer ceramic chip capacitor 1 shown in FIG. 2 was manufactured as follows.

  First, a green sheet was formed on a PET film using the obtained dielectric layer paste. After the internal electrode paste was printed thereon, the sheet was peeled from the PET film. Next, these green sheets and protective green sheets (not printed with internal electrode layer paste) were laminated and pressure-bonded to obtain green chips.

Next, the green chip was cut into a predetermined size and subjected to binder removal processing, firing and annealing under the following conditions to obtain a multilayer ceramic fired body. The binder removal treatment conditions were temperature rising rate: 30 ° C./hour, holding temperature: 260 ° C., temperature holding time: 8 hours, and atmosphere: in the air. Firing conditions are: temperature rising rate: 200 ° C./hour, holding temperature: 1050 to 1450 ° C., temperature holding time: 2 hours, cooling rate: 300 ° C./hour, atmospheric gas: humidified N ₂ + H ₂ mixed gas (oxygen content) Pressure: 10 ⁻² Pa). The annealing conditions were as follows: temperature rising rate: 200 ° C./hour, holding temperature: 1000 ° C., temperature holding time: 2 hours, cooling rate: 300 ° C./hour, atmospheric gas: humidified N ₂ gas (oxygen partial pressure: 10 ⁻¹ Pa). Note that a wetter with a water temperature of 5 to 75 ° C. was used for humidifying the atmospheric gas during firing and annealing.

  Specific firing temperatures of the samples (sample numbers 1 to 8 and A to C) are shown in Table 1 and FIG.

  Next, after polishing the end face of the obtained multilayer ceramic fired body by sandblasting, In-Ga was applied as an external electrode to obtain a sample of the multilayer ceramic capacitor shown in FIG.

  The size of the obtained capacitor sample was 3.2 mm × 1.6 mm × 0.6 mm, the number of dielectric layers sandwiched between internal electrode layers was 4, and the thickness of the dielectric layers per layer (interlayers) Thickness) was 2.7 μm, and the thickness of the internal electrode layer was 1.2 μm.

  As a method for measuring the thickness of the dielectric layer, first, the obtained capacitor sample was cut along a plane perpendicular to the internal electrode, and an SEM photograph of the cut surface was taken. Next, on the SEM photograph, a line perpendicular to the internal electrode was drawn, and the distance between the internal electrode and the adjacent internal electrode was measured. This was performed 20 times, and the average of the measured values was obtained, and this was taken as the thickness of the dielectric layer.

  For each of the obtained capacitor samples, the evaluation value, CV value, high temperature load life (average life) and relative dielectric constant of the dielectric layer were measured by the methods shown below.

Evaluation Value First, STEM-EDS analysis was performed on the dielectric layer of the obtained capacitor sample to obtain elemental mapping of the minor component Mg. This mapping diagram was measured at 256 pixels in length and width, and the magnification was 40000 times (FIG. 3).

  Next, the concentration distribution shown in this figure was subjected to two-dimensional Fourier transform to obtain a frequency spectrum diagram (FIG. 4).

  Further, the obtained frequency spectrum diagram is divided into 62 donuts (Δr = 2.0) from a distance of 3.5 pixels to a distance of 127.5 pixels from the center, and each donut is included in the inside thereof. The sum of the spectrum intensities was obtained, and a frequency spectrum graph was obtained with the frequency (r) on the horizontal axis and the sum of the spectrum intensities (P (r)) on the vertical axis (FIG. 5). In FIG. 5, P (3.5) to P (13.5) are plotted.

  The slope of this graph was obtained by linear approximation and used as an evaluation value. The evaluation value is preferably as large as possible. In this example, the evaluation value is preferably 0 or more. The results are shown in Table 1.

CV value The CV value of the subcomponent Mg was calculated by the following formula (6), and then the obtained results were obtained by averaging. The results are shown in Table 1.
CV value [%] = (standard deviation σ of sub-component detection intensity / average sub-component detection intensity x) × 100 (6)

High temperature load life (average life)
A high temperature load life (average life) was measured by maintaining a DC voltage of 8.0 V / μm at 200 ° C. with respect to the capacitor sample. This high temperature load life was evaluated by measuring 10 life samples and measuring the average life time. In this example, the time from the start of application until the insulation resistance drops by an order of magnitude was defined as the lifetime. The longer the lifetime, the better. In the present embodiment, it is preferably 10 hours or longer. The results are shown in Table 1.

Dielectric constant (εs)
The capacitance of the capacitor sample was measured with a digital LCR meter (YHP 4274A) at a reference temperature of 25 ° C. under the conditions of a frequency of 1 kHz and an input signal level (measurement voltage) of 1 Vrms. Then, the relative dielectric constant (no unit) was calculated from the obtained capacitance. In this embodiment, it is preferably 3000 or more. The results are shown in Table 1.

  In Sample No. 5, the firing temperature was low, the dielectric layer was not sufficiently densified, and measurement was not possible.

  FIG. 3 is a mapping diagram showing the element distribution of the dielectric layers of the sample numbers 1 to 9, FIG. 4A is a frequency spectrum diagram of the sample number 4 of FIG. 3, and FIG. The frequency spectrum figure of the sample number 7 is shown. 5A shows a frequency spectrum graph for FIG. 4A, and FIG. 5B shows a frequency spectrum graph for FIG. 4B.

  From Table 1, it can be seen that when the evaluation value is included in the range of 0 to 0.003, the high temperature load life and the relative dielectric constant show good values (Sample Nos. 6, 7 and 9).

  Further, as apparent from Table 1, Sample Nos. 2 and 8 resulted in a low high temperature load life even though the CV values were lower than Sample Nos. 6, 7 and 9. This is presumably because Sample Nos. 2 and 8 have a collection (cluster) of minute regions with a high concentration of small elements that cannot be detected by the CV value.

DESCRIPTION OF SYMBOLS 1 ... Multilayer ceramic capacitor 2 ... Dielectric layer 3 ... Internal electrode layer 4 ... External electrode 10 ... Capacitor element main body

Claims (7)

Obtain the element distribution of the object to be evaluated as a two-dimensional image signal with the number of pixels X × Y
X and Y are in a relationship of X ≦ Y,
f (x, y) is expressed as an element concentration at an arbitrary pixel position (x, y),
u and v are expressed as arbitrary spatial frequencies,
When the frequency r is represented by r = (u ² + v ² ) ^1/2 ,
Obtaining a frequency spectrum F (u, v) by performing a two-dimensional Fourier transform on the two-dimensional image signal;
Obtaining a sum P (r) of spectral intensities at a frequency r for the frequency spectrum F (u, v);
Evaluating the element distribution of the object to be evaluated using a slope in a predetermined frequency range obtained from a graph in which the horizontal axis is the frequency r and the vertical axis is the sum of spectral intensities P (r),
The element distribution evaluation method, wherein the slope is obtained by linear approximation.   The element distribution evaluation method according to claim 1, wherein the object to be evaluated is a ceramic sintered body.   2. The element distribution evaluation method according to claim 1, wherein the object to be evaluated is a dielectric ceramic composition. When r is R when r is X / 2,
4. The element distribution evaluation method according to claim 3, wherein a range of a predetermined frequency with respect to the inclination is in a range of 7R / 256 or more and 27R / 256 or less.   5. The element distribution evaluation according to claim 3, wherein when the evaluation value is in a range of 0 to 0.003, it is determined that segregation and clusters of the element distribution do not occur. Method.   The dielectric ceramic composition includes at least one of Si, Mg, and Ca as an element, and at least one of Si, Mg, and Ca is an evaluation target. The element distribution evaluation method according to any one of the above. A method for producing an electronic component having a dielectric ceramic composition,
Firing a device body in which a plurality of dielectric layers and internal electrode layers are alternately arranged; and
The dielectric layer is composed of a dielectric ceramic composition;
The step of evaluating the dielectric ceramic composition by the element distribution evaluation method according to any one of claims 3 to 6,
A method of making an electronic component having a dielectric ceramic composition whose evaluation value is not included in a predetermined range as a defective product.

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