Multilayer ceramic electronic components

Abstract

The present invention provides a multilayer ceramic electronic component that can improve moisture resistance while suppressing adverse effects on the electrical characteristics of the capacitance section. [Solution] The device comprises a dielectric layer 11, internal electrode layers 12 facing each other with the dielectric layer 11 in between, a cover layer 13, and a side margin 16. At least a portion of the outer peripheral portion 30 consisting of the cover layer 13 and the side margin 16, region 60, is mainly composed of barium titanate, and when the titanium content of the barium titanate is 100 mol%, it contains 0.1 mol% or more of boron, 1.0 mol% or more of silicon, and 1.0 mol% or more of aluminum, with less than 0.1 mol% of magnesium and less than 0.1 mol% of manganese, and the aluminum concentration is equal to or greater than the aluminum concentration of the dielectric layer 11.

Description

Technical Field

[0001] The present invention relates to multilayer ceramic electronic components.

Background Art

[0002] In high-frequency communication systems represented by mobile phones, multilayer ceramic electronic components such as multilayer ceramic capacitors (MLCCs) are used to remove noise (see, for example, Patent Documents 1 to 5).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0004] In multilayer ceramic electronic components, a difference in sintering state may occur between the outer peripheral portion surrounding the capacitance portion and the dielectric layer of the capacitance portion, which may reduce the moisture resistance. On the other hand, if an attempt is made to improve the moisture resistance, it may have an adverse effect on the electrical characteristics of the capacitance portion.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a multilayer ceramic electronic component capable of improving the moisture resistance while suppressing an adverse effect on the electrical characteristics of the capacitance portion.

Means for Solving the Problems

[0006] The multilayer ceramic electronic component according to the present invention comprises a dielectric layer, internal electrode layers facing each other with the dielectric layer in between, a cover layer provided outside the outermost internal electrode layer in a first direction which is the stacking direction of the dielectric layer and the internal electrode layers, a side margin adjacent to the dielectric layer and the internal electrode layer in a second direction perpendicular to the first direction, and an external electrode provided adjacent to the internal electrode layer and electrically connected to the internal electrode layer in a third direction perpendicular to the first and second directions, wherein at least a portion of the outer peripheral area consisting of the cover layer and the side margin is mainly composed of barium titanate, and when the titanium content of the barium titanate is 100 mol%, it contains 0.1 mol% or more of boron, 1.0 mol% or more of silicon, and 1.0 mol% or more of aluminum, with magnesium content of less than 0.1 mol%, manganese content of less than 0.1 mol%, and the aluminum concentration being equal to or greater than the aluminum concentration of the dielectric layer.

[0007] In at least a portion of the above-mentioned multilayer ceramic electronic component, the concentration of aluminum may be 10.0 mol% or less when the titanium content of the barium titanate is set to 100 mol%.

[0008] In at least a portion of the above-mentioned multilayer ceramic electronic component, the silicon concentration may be 3.0 mol% or less when the titanium content of the barium titanate is set to 100 mol%.

[0009] In at least a portion of the above-mentioned multilayer ceramic electronic component, the concentration of boron may be 2.5 mol% or less, assuming that the titanium content of the barium titanate is 100 mol%.

[0010] In the above-described multilayer ceramic electronic component, at least a portion of the region may contain dielectric particles, and silicon and aluminum may exist as amorphous phases or needle-shaped segregates at the grain boundaries and grain boundary triple points of the dielectric particles.

[0011] In the above-described multilayer ceramic electronic component, the aluminum concentration may differ between the cover layer and the side margin, with the aluminum concentration in the side margin being greater than that of the cover layer.

[0012] In the above-described multilayer ceramic electronic component, the average particle size of dielectric particles contained in the cover layer or the side margin may be greater than twice the average particle size of dielectric particles contained in the dielectric layer. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a multilayer ceramic electronic component that can improve moisture resistance while suppressing adverse effects on the electrical characteristics of the capacitance section. [Brief explanation of the drawing]

[0014] [Figure 1] This is a partial cross-sectional perspective view of a multilayer ceramic capacitor. [Figure 2] This is a cross-sectional view along line AA in Figure 1. [Figure 3] This is a cross-sectional view along line BB in Figure 1. [Figure 4] (a) and (b) are magnified views of the area around the external electrodes. [Figure 5] (a) to (d) are diagrams illustrating the outer perimeter. [Figure 6] This is a backscattered electron image taken with a scanning electron microscope (SEM) of a portion of the cross-section of the outer periphery, which is mainly composed of barium titanate. [Figure 7] (a) and (b) are diagrams illustrating borosilicate glass. [Figure 8] This diagram illustrates a flow chart of the manufacturing process for multilayer ceramic capacitors. [Figure 9](a) and (b) are diagrams illustrating the printing process. [Figure 10] It is a diagram illustrating the crimping process.

Mode for Carrying Out the Invention

[0015] Hereinafter, embodiments will be described with reference to the drawings.

[0016] (Embodiment) FIG. 1 is a partial cross-sectional perspective view of a multilayer ceramic capacitor 100 according to an embodiment. FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1. FIG. 3 is a cross-sectional view taken along line B-B of FIG. 1. As illustrated in FIGS. 1 to 3, the multilayer ceramic capacitor 100 includes a base body 10 having a substantially rectangular parallelepiped shape, and external electrodes 20a and 20b provided on two opposing end faces of the base body 10. Among the four surfaces of the base body 10 other than the two end faces, the two surfaces other than the upper and lower surfaces in the stacking direction are referred to as side surfaces. The external electrodes 20a and 20b extend to the upper surface, lower surface, and two side surfaces of the base body 10 in the stacking direction. However, the external electrodes 20a and 20b are spaced apart from each other.

[0017] In FIGS. 1 to 3, the Z-axis direction (first direction) is the stacking direction and is the direction in which each internal electrode layer faces. The X-axis direction (second direction) is the length direction of the base body 10, is the direction in which the two end faces of the base body 10 face each other, and is the direction in which the external electrode 20a and the external electrode 20b face each other. The Y-axis direction (third direction) is the width direction of the internal electrode layer and is the direction in which two side surfaces other than the two end faces of the four side surfaces of the base body 10 face each other. The X-axis direction, the Y-axis direction, and the Z-axis direction are orthogonal to each other.

[0018] The base body 10 has a structure in which dielectric layers 11 containing a ceramic material that functions as a dielectric and internal electrode layers 12 are alternately stacked. The edges of each internal electrode layer 12 are alternately exposed to the end face of the base body 10 where the external electrode 20a is provided and the end face where the external electrode 20b is provided. As a result, each internal electrode layer 12 is alternately electrically connected to the external electrode 20a and the external electrode 20b. In the laminate of dielectric layers 11 and internal electrode layers 12, the inner electrode layer 12 is arranged as the outermost layer in the stacking direction, and the upper and lower surfaces of the laminate are covered by a cover layer 13. The cover layer 13 is mainly composed of ceramic material. For example, the composition of the cover layer 13 may be the same as or different from that of the dielectric layer 11. Note that the configuration is not limited to Figures 1 to 3, as long as the inner electrode layer 12 is exposed to two different surfaces and electrically connected to different external electrodes.

[0019] The dimensions of the multilayer ceramic capacitor 100 are, for example, 0.25 mm in length, 0.125 mm in width, and 0.125 mm in height, or 0.4 mm in length, 0.2 mm in width, and 0.2 mm in height, or 0.6 mm in length, 0.3 mm in width, and 0.3 mm in height, or 1.0 mm in length, 0.5 mm in width, and 0.5 mm in height, or 3.2 mm in length, 1.6 mm in width, and 1.6 mm in height, or 4.5 mm in length, 3.2 mm in width, and 2.5 mm in height, but are not limited to these dimensions.

[0020] The internal electrode layer 12 is mainly composed of base metals such as nickel (Ni), copper (Cu), tin (Sn), or alloys containing these. Precious metals such as platinum (Pt), palladium (Pd), silver (Ag), and gold (Au), or alloys containing these, may also be used as the internal electrode layer 12. The thickness of the internal electrode layer 12 is, for example, 5.0 μm or less, 3.0 μm or less, or 1.0 μm or less. The thickness of the internal electrode layer 12 can be measured by observing the cross-section of the multilayer ceramic capacitor 100 with an SEM (scanning electron microscope), measuring the thickness at 10 points for each of 10 different internal electrode layers 12, and deriving the average value of all measurement points.

[0021] The dielectric layer 11 is a porcelain composition according to the embodiment, and for example, mainly comprises a ceramic material having a perovskite structure represented by the general formula ABO3. Note that this perovskite structure is an ABO3 that deviates from the stoichiometric composition. 3-α It includes. For example, barium titanate (BaTiO3) can be used as the ceramic material. For example, in the dielectric layer 11, the main component ceramic is contained in an amount of 90 at% or more. The thickness of the dielectric layer 11 is, for example, 5.0 μm or less, 3.0 μm or less, and 1.0 μm or less. The thickness of the dielectric layer 11 can be measured by observing the cross-section of the multilayer ceramic capacitor 100 with an SEM (scanning electron microscope), measuring the thickness at 10 points for each of 10 different dielectric layers 11, and deriving the average value of all measurement points.

[0022] The dielectric layer 11 may contain additives. Examples of additives to the dielectric layer 11 include oxides of zirconium (Zr), hafnium (Hf), magnesium (Mg), manganese (Mn), molybdenum (Mo), vanadium (V), chromium (Cr), rare earth elements (yttrium (Y), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), and ytterbium (Yb)), or oxides containing cobalt (Co), nickel (Ni), lithium (Li), boron (B), sodium (Na), potassium (K), or silicon (Si), or glass containing cobalt, nickel, lithium, boron, sodium, potassium, or silicon.

[0023] As illustrated in Figure 2, the region where the internal electrode layer 12 connected to the external electrode 20a and the internal electrode layer 12 connected to the external electrode 20b face each other is a region in the multilayer ceramic capacitor 100 where capacitance is generated. Therefore, this region where capacitance is generated is referred to as the capacitance section 14. In other words, the capacitance section 14 is a region where adjacent internal electrode layers 12 connected to different external electrodes face each other.

[0024] The region where internal electrode layers 12 connected to external electrode 20a face each other without being connected to an internal electrode layer 12 connected to external electrode 20b is called the end margin 15. Similarly, the region where internal electrode layers 12 connected to external electrode 20b face each other without being connected to an internal electrode layer 12 connected to external electrode 20a is also called the end margin 15. In other words, the end margin 15 is the region where internal electrode layers 12 connected to the same external electrode face each other without being connected to an internal electrode layer 12 connected to a different external electrode. The end margin 15 is a region where no capacitance is generated.

[0025] As illustrated in Figure 3, in the element 10, the side margin 16 is a region provided to cover the two side edges (the edges in the Y-axis direction) of the dielectric layer 11 and the internal electrode layer 12. In other words, the side margin 16 is a region provided outside the capacitance portion 14 in the Y-axis direction. The side margin 16 is also a region that does not generate capacitance.

[0026] In the YZ cross-section, the cover layer 13 and the side margins 16 form the outer periphery of the capacitance portion 14. Therefore, in the following, the portion forming the outer periphery of the capacitance portion 14 in the YZ cross-section may be collectively referred to as the outer periphery portion 30. The cover layer 13 refers to the portion of the outer periphery portion 30 in the Y-axis direction that is above the uppermost internal electrode layer 12. Thus, the capacitance portion 14 and a pair of side margins are sandwiched between the two cover layers 13.

[0027] Figure 4(a) is an enlarged cross-sectional view near the external electrode 20a. Figure 4(b) is an enlarged cross-sectional view near the external electrode 20b. Hatches are omitted in Figures 4(a) and 4(b). As illustrated in Figures 4(a) and 4(b), the external electrodes 20a and 20b have a structure in which a plating layer 22 is provided on a base layer 21. The base layer 21 mainly consists of nickel, copper, etc. The base layer 21 may also contain ceramic particles as a co-material, or it may contain glass components. The plating layer 22 mainly consists of metals such as nickel, copper, aluminum, zinc, tin, or alloys of two or more of these. The plating layer 22 may be a plating layer of a single metal component, or it may be multiple plating layers of different metal components. For example, the plating layer 22 has a structure in which a first plating layer 23, a second plating layer 24, and a third plating layer 25 are formed in order from the base layer 21 side. The first plating layer 23 is, for example, a copper plating layer. The second plating layer 24 is, for example, a nickel plating layer. The third plating layer 25 is, for example, a tin plating layer.

[0028] Here, we will explain the delay in sintering in multilayer ceramic capacitors. In multilayer ceramic capacitors, during firing, in the capacitance portion, metal elements (e.g., nickel, copper, etc.) that are components of the internal electrode layer diffuse into the dielectric layer, promoting sintering. However, this mechanism does not act on the dielectric in the outer peripheral portion, which does not contain the internal electrode layer. Therefore, a problem arises in that sintering is slower in the outer peripheral portion than in the capacitance portion. Consequently, if firing is performed at a temperature that allows the capacitance portion to sinter and densify properly, the densification of the outer peripheral portion will be insufficient, making it easier for moisture to penetrate from the outside, thus worsening the moisture resistance of the multilayer ceramic capacitor. On the other hand, if the outer peripheral portion is fired to a level that ensures sufficient moisture resistance, over-sintering occurs in the capacitance portion, which may lead to dielectric grain growth, breaks in the internal electrode layer, a reduced lifespan, and adverse effects on electrical characteristics.

[0029] Typically, firing conditions are set to strike a balance between moisture resistance and electrical properties while still dealing with this trade-off. However, this state is not the best sintering state for either the outer casing or the capacitance, which can lead to the production of defective products (individual capacitors) that do not meet the specified values ​​for moisture resistance or electrical properties when mass-produced. To produce multilayer ceramic capacitors for applications requiring extremely high reliability, such as automotive multilayer ceramic capacitors, fundamental solutions are needed rather than simply finding a compromise in the sintering properties of the outer casing and capacitance.

[0030] Therefore, one possible method to promote sintering in the outer periphery is to increase the amount of silicon and boron, which are sintering aids in glass. However, with this method, the boron and silicon added to the outer periphery may cause grain growth in the dielectric layer of the capacitance portion, potentially reducing its lifespan. Therefore, a method is needed to retain the boron and silicon in the outer periphery.

[0031] Next, a method can be considered in which barium titanate powder with nickel solid solution is used as the main phase of the outer periphery instead of pure barium titanate. This method focuses on the fact that the sinterability of the capacitance part depends on the diffusion of nickel in the internal electrode layer, and attempts to eliminate the difference in sintering between the inside and outside by applying this effect to the outer periphery as well. Moreover, this method is superior in that it does not simply supply nickel in the form of nickel metal powder or nickel oxide, which precipitates as metal on the surface of the multilayer ceramic capacitor after firing in a reducing atmosphere. This is because if nickel appears as metal on the surface of the multilayer ceramic capacitor, it can cause plating expansion and soldering defects, which is undesirable. However, this method also has one drawback. When nickel solid-solution barium titanate is used, the density of the outer periphery becomes too high, resulting in increased internal stress. This may not be a problem for very small multilayer ceramic capacitors, but it can make the product more prone to cracking in relatively large multilayer ceramic capacitors used in automotive applications. In the first place, nickel diffusion from the electrodes in the capacitance region does not result in solid solution throughout the entire barium titanate particle, but rather mainly provides nickel to the grain boundaries and the regions near the surface of particles in contact with the grain boundaries (shell regions). Therefore, incorporating nickel into the main phase of the outer periphery cannot achieve the same state as the capacitance region. It is known that there are other metallic elements that improve sinterability when dissolved in barium titanate, and methods of adding these metallic elements to the outer periphery are known. In particular, methods of adding large amounts of magnesium or manganese to the outer periphery are known.

[0032] For example, a simple method is to include a large amount of magnesium, an element that promotes the sintering of barium titanate, in the outer periphery. While this method is effective due to its simplicity, problems can arise, such as the magnesium diffusing from the outer periphery to the capacitive region through concentration diffusion, which can lower the dielectric constant of the capacitive region, or the magnesium excessively dissolving in the barium titanate as an acceptor, increasing oxide ion defects and reducing the lifetime.

[0033] Next, in addition to adding "sintering aid components," such as magnesium and manganese, to the outer periphery to promote sintering, it is conceivable to suppress the unidirectional diffusion of magnesium and manganese from the outer periphery to the capacitive part by creating a region between the outer periphery and the capacitive part where the concentration of sintering aid components is low. While this is certainly a very effective method for eliminating the difference between the inside and outside of sintering, it requires creating a complex double structure to prevent internal diffusion of the sintering aid, which is time-consuming and costly. Therefore, a simpler method that can achieve the same effect is needed.

[0034] Therefore, one possible approach is to combine a method in which both the outer periphery and the capacitive region contain at least one of magnesium, nickel, manganese, aluminum, or chromium, with a higher concentration in the outer periphery, with the outer periphery being A-rich in the A / B ratio (ratio of A-site elements to N-site elements in a perovskite crystal). This can suppress cracking. However, this method does not prevent the diffusion of magnesium and manganese into the capacitive region as described above, and A-rich in barium titanate means Ba-rich. Barium, like magnesium and manganese, can also be diffused from the high-concentration outer periphery to the capacitive region, which is a convenient method for reducing the dielectric constant of the capacitive region, but it is not a fundamental solution.

[0035] As a result of diligent research by the inventors, it has been discovered that by adding aluminum to the outer periphery 30 in addition to boron and silicon, the boron and silicon can be retained in the outer periphery 30, thereby matching the sintering state of the capacity portion 14 with that of the outer periphery 30.

[0036] As a result of further intensive research by the inventors, it was discovered that at least a portion of the outer periphery 30 is mainly composed of barium titanate, and when the titanium content of the barium titanate is set to 100 mol%, it contains 0.1 mol% or more of boron, 1.0 mol% or more of silicon, and 1.0 mol% or more of aluminum, with less than 0.1 mol% of magnesium and less than 0.1 mol% of manganese, and the aluminum concentration is equal to or greater than the aluminum concentration of the dielectric layer 11 of the capacitance portion 14. This suppresses adverse effects on the electrical properties of the capacitance portion 14, eliminates the difference in sintering speed between the outer periphery 30 and the capacitance portion 14, and improves moisture resistance.

[0037] At least a portion of the outer periphery 30 described above is referred to as region 60. Region 60 may be a portion of the cover layer 13, as illustrated in Figure 5(a). Alternatively, region 60 may be the entire cover layer 13, as illustrated in Figure 5(b). Alternatively, region 60 may be a portion of the side margin 16. Alternatively, region 60 may be the entire side margin 16.

[0038] First, by reducing the amount of magnesium and manganese in region 60 to less than 0.1 mol%, the amount of magnesium and manganese is sufficiently suppressed, thereby preventing adverse effects on the electrical properties of the capacitance section 14 due to magnesium and manganese diffusion from region 60.

[0039] Next, by setting the amount of boron in region 60 to 0.1 mol% or more, the amount of silicon to 1.0 mol% or more, and the amount of aluminum to 1.0 mol% or more, for example, an aluminum-containing borosilicate glass can be obtained. This aluminum-containing borosilicate glass not only promotes the sintering of region 60, which is mainly composed of barium titanate, but also tends to remain without being ejected from the gaps between particles called grain boundaries and triple points. Furthermore, by setting the aluminum concentration in region 60 to be equal to or higher than that of the dielectric layer 11 of the capacitance section 14, the tendency for the glass component to remain in region 60 becomes more pronounced. Note that the aluminum concentration in the dielectric layer 11 of the capacitance section 14 is the mol% of aluminum when the titanium content of barium titanate, the main component of the dielectric layer 11, is set to 100 mol%.

[0040] From the above, the multilayer ceramic capacitor 100 according to this embodiment suppresses adverse effects on the electrical characteristics of the capacitance portion 14, and eliminates the difference in sintering speed between the region 60 and the capacitance portion 14, thereby improving moisture resistance. As a result, it becomes possible to achieve a higher level of balance between moisture resistance and electrical characteristics than multilayer ceramic capacitors that were previously manufactured by firing at a compromise point between the outer periphery and the capacitance portion. Consequently, it becomes possible to realize a multilayer ceramic capacitor that is more suitable for applications requiring extremely high reliability, such as automotive applications.

[0041] Figure 6 shows backscattered electron images taken by SEM of a portion of the cross-section of the outer periphery, which is mainly composed of barium titanate. The upper part of Figure 6 shows backscattered electron images when the amount of titanium is 100 mol%, the amount of boron is 0.1 mol% or more, the amount of silicon is 1.0 mol% or more, and the amount of aluminum is 1.0 mol% or more. As shown in the upper part of Figure 6, it can be seen that a dark phase (light elements, representing the glass phase) exists between and in the gaps of the particles, thoroughly wetting the entire particle.

[0042] In contrast, the lower panel of Figure 6 shows a backscattered electron image when the amount of titanium is 100 mol%, the amount of boron is 0.1 mol% or more, and the amount of silicon is 1.0 mol% or more, but no aluminum is added. As shown in the lower panel of Figure 6, it is clearly visible that segregated deposits, which are aggregates of the glass phase ejected from the grain boundaries, are scattered throughout the material.

[0043] To fully obtain the effect of boron as a sintering aid, it is preferable that the boron content in region 60 be as high as possible. In this embodiment, when the titanium content of barium titanate in region 60 is set to 100 mol%, it is preferable that the boron content be 0.5 mol% or more, and more preferably 1.0 mol% or more.

[0044] On the other hand, if the boron content is too high, it may affect the appearance of the multilayer ceramic capacitor 100. Therefore, it is preferable to set an upper limit on the boron content in region 60. In this embodiment, in region 60, when the titanium content of barium titanate is 100 mol%, it is preferable to set the boron content to 2.5 mol% or less, more preferably to 2.0 mol% or less, and even more preferably to 1.5 mol% or less.

[0045] Next, in order to fully obtain the effect of silicon as a sintering aid, it is preferable that the silicon content in region 60 be as high as possible. In this embodiment, when the titanium content of barium titanate in region 60 is set to 100 mol%, it is preferable that the silicon content be 1.5 mol% or more, and more preferably 2.0 mol% or more.

[0046] On the other hand, if the silicon content is too high, it may affect the appearance of the multilayer ceramic capacitor 100. Therefore, it is preferable to set an upper limit on the silicon content in region 60. In this embodiment, in region 60, when the titanium content of barium titanate is 100 mol%, it is preferable to set the silicon content to 3.0 mol% or less, more preferably to 2.7 mol% or less, and even more preferably to 2.5 mol% or less.

[0047] Next, in order to retain a sufficient amount of boron and silicon in region 60, it is preferable that the aluminum content in region 60 be higher. In this embodiment, in region 60, when the titanium content of barium titanate is 100 mol%, it is preferable that the aluminum content be 2.0 mol% or more, and more preferably 4.0 mol% or more.

[0048] On the other hand, if the aluminum content is too high, it may affect the appearance of the multilayer ceramic capacitor 100. Therefore, it is preferable to set an upper limit on the aluminum content in region 60. In this embodiment, in region 60, when the titanium content of barium titanate is 100 mol%, it is preferable to set the aluminum content to 10.0 mol% or less, more preferably to 8.0 mol% or less, and even more preferably to 5.0 mol% or less.

[0049] Next, in order to sufficiently retain the aluminum-containing borosilicate glass in region 60, it is preferable to keep the aluminum concentration in region 60 higher than that of the dielectric layer 11 of the capacitance portion 14. In this embodiment, the aluminum concentration in region 60 is preferably higher than that of the aluminum concentration in the dielectric layer 11 of the capacitance portion 14, more preferably 1.0 mol% or more higher, and even more preferably 2.0 mol% or more higher.

[0050] As illustrated in Figure 7(a), region 60 has a structure in which multiple dielectric particles 31 are sintered. Therefore, grain boundaries 32 and grain boundary triple points 33 are formed between the multiple dielectric particles 31. It is preferable that the silicon, boron, and aluminum contained in region 60 exist as amorphous borosilicate glass at the grain boundaries 32 or grain boundary triple points 33.

[0051] For example, as illustrated in Figure 7(b), it is preferable that the borosilicate glass exists as particulate segregates 71 or as needle-shaped segregates 72 at the grain boundary 32 or grain boundary triple point 33 in Figure 7(a). Here, particulate segregates 71 are segregates that have a substantially circular shape in cross-section. Needle-shaped segregates 72 are segregates that, for example, have a rectangular shape or other shape in cross-section where a major axis and a minor axis are observed, and the major axis is three times or more the minor axis.

[0052] From the viewpoint of mitigating residual stress after sintering (stress caused by the difference in thermal expansion coefficients between the electrode metal and ceramics), the average particle size of the dielectric particles 31 included in region 60 is preferably greater than twice the average particle size of the dielectric particles included in the dielectric layer 11 of the capacitance portion 14, more preferably 2.5 times or more, and even more preferably 3.0 times or more. The dielectric layer 11 of the capacitance portion 14 also has a structure in which multiple dielectric particles are sintered, as explained in Figure 7(a). The average particle size of the dielectric particles 31 included in region 60 and the average particle size of the dielectric particles included in the dielectric layer 11 of the capacitance portion 14 can be measured by reading an image taken with a scanning electron microscope (SEM) of a cross-section of the element polished to a mirror surface using image analysis software and calculating the ferret diameter.

[0053] Furthermore, the side margin 16 tends to have a lower density than the cover layer 13, resulting in slower sintering. This is because the side margin portion, which is in the same plane as the internal electrode layer, is a void because the internal electrode layer is not printed therein. Therefore, when the entire outer peripheral portion 30 is region 60, it is preferable that the aluminum concentration differs between the cover layer 13 and the side margin 16, with the aluminum concentration of the side margin 16 being higher than that of the cover layer 13. In this embodiment, it is preferable that the aluminum concentration of the side margin 16 is 0.5 mol% or higher than that of the cover layer 13, more preferably 1.5 mol% or higher, and even more preferably 2.0 mol% or higher.

[0054] Next, the manufacturing method of the multilayer ceramic capacitor 100 will be described. Figure 8 is a diagram illustrating the flow of the manufacturing method of the multilayer ceramic capacitor 100.

[0055] (Process for producing raw material powder) First, a dielectric material for forming the dielectric layer 11, a cover material for forming the cover layer 13, and an inverse pattern material for forming the side margin 16 are prepared. The dielectric material, cover material, and inverse pattern material include barium titanate powder having a perovskite structure. For example, barium titanate is a tetragonal compound having a perovskite structure and exhibits a high dielectric constant. Barium titanate powder can generally be synthesized by reacting a titanium raw material such as titanium dioxide with a barium raw material such as barium carbonate. Various methods for synthesizing barium titanate powder are conventionally known, such as the solid-phase method, the sol-gel method, and the hydrothermal method. Any of these can be used in this embodiment.

[0056] The obtained barium titanate powder is then mixed with a predetermined additive compound according to the purpose to produce dielectric material, cover material, and reverse pattern material, respectively. Examples of additive compounds include oxides of zirconium, hafnium, magnesium, manganese, molybdenum, vanadium, chromium, rare earth elements (yttrium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, and ytterbium), or oxides containing cobalt, nickel, lithium, boron, sodium, potassium, or silicon, or glasses containing cobalt, nickel, lithium, boron, sodium, potassium, or silicon.

[0057] Here, the amount of additive compounds added to the dielectric material, cover material, and reverse pattern material is adjusted so that the region 60 obtained after the firing process described later contains 0.1 mol% or more of boron, 1.0 mol% or more of silicon, and 1.0 mol% or more of aluminum, with the titanium content of barium titanate being 100 mol%, while the magnesium content is less than 0.1 mol%, the manganese content is less than 0.1 mol%, and the aluminum concentration is equal to or greater than the aluminum concentration of the dielectric layer 11 of the capacitance portion 14.

[0058] (Coating process) A dielectric material is wet-mixed with a binder such as polyvinyl butyral (PVB) resin, an organic solvent such as ethanol or toluene, and a plasticizer. Using the resulting slurry, a dielectric green sheet 51 is coated onto a substrate by, for example, a die coater or a doctor blade and then dried. The substrate is, for example, polyethylene terephthalate (PET) film.

[0059] (Printing process) Next, as illustrated in Figure 9(a), a metal conductive paste for forming internal electrodes containing an organic binder is printed on the surface of the dielectric green sheet 51 by screen printing, gravure printing, or the like, thereby arranging an internal electrode pattern 52 that is alternately drawn out to a pair of external electrodes with different polarities. Ceramic particles are added to the metal conductive paste as a co-material. The main component of the ceramic particles is not particularly limited, but it is preferable that it is the same as the main component ceramic of the dielectric layer 11. For example, barium titanate with an average particle diameter of 50 nm or less may be uniformly dispersed.

[0060] Next, an ethylcellulose-based binder and an organic solvent such as terpineol-based solvent are added to the reverse pattern material and kneaded in a roll mill to obtain a reverse pattern paste. As illustrated in Figure 9(a), the reverse pattern 53 is placed on the dielectric green sheet 51 by printing the reverse pattern paste in the peripheral area where the internal electrode pattern 52 is not printed, thereby filling the step between it and the internal electrode pattern 52. The dielectric green sheet 51 with the internal electrode pattern 52 and the reverse pattern 53 printed on it is called a laminated unit.

[0061] Subsequently, as illustrated in Figure 9(b), stacking units are carried out so that the internal electrode layer 12 and the dielectric layer 11 are staggered, and the edges of the internal electrode layer 12 are alternately exposed on both ends of the dielectric layer 11 in the longitudinal direction, alternately leading to a pair of external electrodes 20a and 20b with different polarities. For example, the number of stacked internal electrode patterns 52 is set to 100 to 1000 layers.

[0062] (Crimping process) Next, an ethylcellulose-based binder and an organic solvent such as terpineol-based solvent are added to the cover material and kneaded in a roll mill to obtain a cover sheet 54. As illustrated in Figure 10, a predetermined number of cover sheets 54 are laminated on the top and bottom of a laminate in which laminated units are stacked and then heat-pressed together. After that, they are cut to predetermined chip dimensions (for example, 1.0 mm x 0.5 mm).

[0063] (Coating process) The ceramic laminate obtained in this way is then subjected to a binder removal treatment in an N2 atmosphere, an air atmosphere, etc., and then a metal paste, which will serve as the base layer for the external electrodes 20a and 20b, is applied by a dipping method.

[0064] (Firing process) Subsequently, oxygen partial pressure 10 -10 ~10 -7 The ceramic laminate is fired in an ATM reducing atmosphere at 1100-1300°C for 10 minutes to 2 hours.

[0065] (Re-oxidation process) Subsequently, a re-oxidation treatment may be performed in an N2 gas atmosphere at 600°C to 1000°C.

[0066] (Plating process) Subsequently, a metal coating of Cu, Ni, Sn, etc. is applied to the underlayer of the external electrodes 20a and 20b by plating. Through these steps, the multilayer ceramic capacitor 100 is completed.

[0067] In the embodiments described above, multilayer ceramic capacitors were explained as examples of multilayer ceramic electronic components, but the invention is not limited to them. For example, other multilayer ceramic electronic components such as varistors and thermistors may be used. [Examples]

[0068] Below, a multilayer ceramic capacitor according to the embodiment was fabricated and its characteristics were investigated.

[0069] (Comparative Example 1) Using barium titanate with an average particle size of 100 nm, prepared by solid-phase synthesis, as the main phase, 0.5 mol% B2O3 (1.0 mol% as element B), 2.0 mol% SiO2, 1.0 mol% BaCO3, and 0.5 mol% Ho2O3 (1.0 mol% as element Ho) were weighed out. This mixed powder was dispersed with ethanol, toluene, and a dispersant using zirconia beads, and the dispersion was stopped when the median diameter of the barium titanate particle size distribution reached 100 nm. After this dispersion, the slurry was passed through a filter to separate it from the zirconia beads, and then PVB (polyvinyl butyral) resin was mixed in as a binder to prepare a dielectric slurry for the internal electrode intersection.

[0070] The slurry thus prepared was coated onto a PET film using a die coater to form a 4.0 μm thick dielectric green sheet. After drying this dielectric green sheet, nickel paste was printed to create the internal electrode pattern. 101 layers of dielectric green sheets with printed internal electrode patterns were laminated. At this time, the positive electrode pattern and negative electrode pattern were laminated alternately. Dielectric layers of the same composition, each 50 μm thick, were stacked above and below as protective layers and heat-pressed. After sintering the resulting plate-shaped molded body, it was cut into individual pieces (chips) with dimensions of 1.0 mm × 0.5 mm. Nickel paste was dipped into the two opposing surfaces of the cut chips where the internal electrode lead-out portions were exposed to form terminal electrodes.

[0071] The prepared chip was debindered by heating it to 800°C at a rate of 100°C / h in a reducing atmosphere using a mixed gas of N2-H2-H2O. Then, the heating rate was increased to 6000°C / h, the temperature was raised to 1250°C and held for 1 minute, and then the temperature was lowered to room temperature. The sintered chip was then re-oxidized at 800°C in a dry N2 atmosphere. This yielded a multilayer ceramic capacitor with a total of 100 effective dielectric units (Comparative Example 1). The average dielectric thickness of each layer after sintering was 3.2 μm. This multilayer ceramic capacitor did not contain aluminum in either the capacitance layer or the cover layer.

[0072] (Comparative Example 2) In Comparative Example 2, the cover layer was prepared so that the aluminum content was 0.5 mol% when the titanium content of the barium titanate was 100 mol%. Fine Al2O3 powder (<50 nm) was used to ensure sufficient dissolution in the borosilicate glass. Therefore, the amount of Al2O3 added was half the concentration of aluminum element. Consequently, the Al2O3 concentration in Comparative Example 2 was 0.25 mol%. All other conditions were the same as in Comparative Example 1.

[0073] (Examples 1-4) Multilayer ceramic capacitors were fabricated using the same method as in Comparative Examples 1 and 2 above, but with varying amounts of aluminum added to the cover layer. In the cover layer, when the titanium content of barium titanate is set to 100 mol%, the amount of aluminum was set to 1.0 mol% in Example 1, 5.0 mol% in Example 2, 10.0 mol% in Example 3, and 15.0 mol% in Example 4. Other conditions were the same as in Comparative Example 1. In these examples, since no aluminum is added to the capacitance portion, the relationship that aluminum concentration in the dielectric layer of the capacitance portion < aluminum concentration in the cover layer holds true in all cases, and the relationship that the amount of aluminum added to the cover layer is 1.0 mol% or more also holds true.

[0074] (Humidity resistance test and high-temperature accelerated life test) The multilayer ceramic capacitors from Comparative Examples 1 and 2 and Examples 1 to 4, after re-oxidation, were reflow-soldered onto a printed circuit board with a parallel circuit and connected to a stabilized power supply. This was then placed in a humidity-controlled constant temperature chamber and a DC voltage was applied. The humidity resistance test was conducted at 40°C, 90-95%RH, and 100V for 500 hours with 1000 test units, and the failure rate after 500 hours was expressed as a percentage. Only those with a 0% failure rate under these conditions were considered pass, and all others were considered fail. The high-temperature accelerated life test was conducted in a constant temperature chamber at 125°C with 100V and 100 test units. Life was defined as when all samples reached a short-circuit state or when the resistance value decreased to 1 / 1000 of the initial value. The time was automatically recorded for each sample, and the average was used as the average life value. Under these conditions, an average life of 48 hours or longer was considered pass, and anything less was considered fail. Products that passed both the humidity resistance test and the high-temperature accelerated life test were deemed to have passed overall, while those that failed either test were deemed to have failed.

[0075] (Evaluation results) Comparative Examples 1 and 2 both failed the humidity resistance test. This is thought to be because the borosilicate glass could not properly wet and densify the sintered body of the cover layer due to the absence or insufficient amount of aluminum added. In contrast, Examples 1 to 4 all passed the humidity resistance test. This is thought to be because the cover layer contained 0.1 mol% or more of boron, 1.0 mol% or more of silicon, and 1.0 mol% or more of aluminum, with the aluminum concentration being higher than or equal to the aluminum concentration of the dielectric layer in the capacitance portion. Furthermore, all of Examples 1 to 4 also passed the high-temperature accelerated lifetime test without any problems. This is thought to be because the magnesium and manganese in the cover layer were less than 0.1 mol%. Thus, Examples 1 to 4 yielded remarkably good results that were not obtained in Comparative Examples 1 and 2.

[0076] In Example 4, where the amount of aluminum was increased to 15 mol%, there were no problems in terms of electrical characteristics, but glass-like stains were noticeable on the surface of the multilayer ceramic capacitor. In such cases, the actual product may have a defective appearance. Therefore, it was found that it is preferable to limit the amount of aluminum added to the cover layer to 10 mol% or less.

[0077] (Example 5) In Example 5, the aluminum content in the cover layer was set to 1.0 mol% when the titanium content of the barium titanate was set to 100 mol%. Furthermore, the aluminum content in the dielectric layer of the capacitance portion was also set to 1.0 mol% when the titanium content of the barium titanate was set to 100 mol%. In other words, the aluminum concentration of the cover layer was matched to that of the dielectric layer of the capacitance portion. Other conditions were the same as in Comparative Example 1.

[0078] (Comparative Example 3) In Comparative Example 3, the cover layer was configured so that the amount of aluminum was 1.0 mol% when the titanium content of barium titanate was 100 mol%. In the dielectric layer of the capacitance portion, the amount of aluminum was configured so that the amount of aluminum was 2.0 mol% when the titanium content of barium titanate was 100 mol%. In other words, the aluminum concentration in the dielectric layer of the capacitance portion was higher than the aluminum concentration in the outer periphery. All other conditions were the same as in Comparative Example 1.

[0079] (Comparative Example 4) In Comparative Example 4, the cover layer was configured so that the amount of aluminum was 1.0 mol% when the titanium content of barium titanate was 100 mol%. In the dielectric layer of the capacitance portion, the amount of aluminum was configured so that the amount of aluminum was 3.0 mol% when the titanium content of barium titanate was 100 mol%. In other words, the aluminum concentration in the dielectric layer of the capacitance portion was higher than the aluminum concentration in the outer periphery. All other conditions were the same as in Comparative Example 1.

[0080] In both Comparative Examples 3 and 4, the high-temperature accelerated lifetime test was unsuccessful. In Comparative Example 3, this is thought to be because, even though the burning of the cover layer was stopped at an appropriate point, the internal electrode layer began to break down and spheroidize. In Comparative Example 4, this is thought to be because grain growth occurred in the dielectric layer of the capacitance section. In contrast, Example 5 passed both the humidity resistance test and the high-temperature accelerated lifetime test. This is thought to be because the cover layer contained 0.1 mol% or more of boron, 1.0 mol% or more of silicon, and 1.0 mol% or more of aluminum, with less than 0.1 mol% of magnesium and manganese, and the aluminum concentration was equivalent to that of the dielectric layer of the capacitance section. Thus, Example 5 yielded surprisingly good results that were not obtained in Comparative Examples 3 and 4.

[0081] (Comparative Examples 5, 6) In Comparative Example 5, no silicon was added to the cover layer. In Comparative Example 6, the silicon concentration in the cover layer was set to 0.5 mol% when the titanium content of barium titanate was set to 100 mol%. Other conditions were the same as in Comparative Example 1.

[0082] (Examples 6-8) In Example 6, the silicon concentration in the cover layer was set to 1.0 mol% when the titanium content of barium titanate was set to 100 mol%. In Example 7, the silicon concentration in the cover layer was set to 3.0 mol% when the titanium content of barium titanate was set to 100 mol%. In Example 8, the silicon concentration in the cover layer was set to 4.0 mol% when the titanium content of barium titanate was set to 100 mol%. Other conditions were the same as in Comparative Example 1.

[0083] In both Comparative Examples 5 and 6, the humidity resistance test was unsuccessful. This is thought to be because the silicon concentration in the cover layer was less than 1.0 mol%. In contrast, all of Examples 6 to 8 passed both the humidity resistance test and the high-temperature accelerated life test. This is thought to be because the cover layer contained 0.1 mol% or more of boron, 1.0 mol% or more of silicon, and 1.0 mol% or more of aluminum, with magnesium less than 0.1 mol%, manganese less than 0.1 mol%, and the aluminum concentration was greater than or equal to the aluminum concentration in the dielectric layer of the capacitance portion. Thus, in Examples 6 to 8, remarkably good results were obtained that were not obtained in Comparative Examples 5 and 6.

[0084] In Example 8, where the silicon content was increased to 4.0 mol%, there were no problems in terms of electrical characteristics, but glass-like stains were noticeable on the surface of the multilayer ceramic capacitor. In such cases, the actual product may have a defective appearance. Therefore, it was found that it is preferable to keep the amount of silicon added to the cover layer to 3.0 mol% or less.

[0085] (Comparative Example 7) In Comparative Example 7, boron was not added to the cover layer. All other conditions were the same as in Comparative Example 1.

[0086] (Examples 9-11) In Example 9, the boron concentration in the cover layer was set to 0.1 mol% when the titanium content of barium titanate was set to 100 mol%. In Example 10, the boron concentration in the cover layer was set to 2.5 mol% when the titanium content of barium titanate was set to 100 mol%. In Example 11, the silicon concentration in the cover layer was set to 5.0 mol% when the titanium content of barium titanate was set to 100 mol%. Other conditions were the same as in Comparative Example 1.

[0087] Comparative Example 7 failed the humidity resistance test. This is thought to be because the boron concentration in the cover layer was less than 0.1 mol%. In contrast, all of Examples 9 to 11 passed both the humidity resistance test and the high-temperature accelerated life test. This is thought to be because the cover layer contained 0.1 mol% or more of boron, 1.0 mol% or more of silicon, and 1.0 mol% or more of aluminum, with magnesium less than 0.1 mol%, manganese less than 0.1 mol%, and the aluminum concentration was greater than or equal to the aluminum concentration in the dielectric layer of the capacitance portion. Thus, Examples 9 to 11 yielded surprisingly good results that were not obtained in Comparative Example 7.

[0088] As shown in Example 9, the humidity resistance test was passed even with a boron concentration of 0.1 mol%. Comparing Examples 9, 1, 10, and 11, the high-temperature accelerated life was maximized when the boron concentration was between 1 mol% and 2.5 mol%, suggesting that around 1 mol% is preferable. In Example 11, where the boron content was increased to 5.0 mol%, there were no problems in terms of electrical characteristics, but glass-like stains were noticeable on the surface of the multilayer ceramic capacitor. In such cases, this could result in a cosmetic defect in the actual product. Therefore, it was found that it is preferable to limit the amount of boron added to the cover layer to 2.5 mol% or less.

[0089] The results are shown in Table 1. Although Examples 1 to 11 focused on the cover layer, the side margin also forms part of the outer periphery. Therefore, if similar experiments were performed on the side margin, it is considered that the material would pass the humidity resistance test and the accelerated lifetime test as long as it contains 0.1 mol% or more of boron, 1.0 mol% or more of silicon, and 1.0 mol% or more of aluminum, with less than 0.1 mol% of magnesium and manganese, and the aluminum concentration is equal to or greater than the aluminum concentration of the dielectric layer in the capacitance portion. [Table 1]

[0090] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0091] 10 Base Body 11 Dielectric layer 12 Internal electrode layer 13. Cover layer 14 Capacity part 15 End margin 16 Side margins 20a,20b external electrode 31 Dielectric Particles 32 grain boundaries 33 Grain boundary triple point 50 Outer periphery 51 Dielectric Green Sheet 52 Internal electrode pattern 53 Reverse Pattern 54 Cover Sheets 60 areas 70 Borosilicate glass 100 Multilayer Ceramic Capacitors

Claims

1. Dielectric layer and The dielectric layer is sandwiched between two internal electrode layers facing each other, In the first direction, which is the stacking direction of the dielectric layer and the internal electrode layer, a cover layer is provided outside the outermost internal electrode layer, In a second direction perpendicular to the first direction, the side margin adjacent to the dielectric layer and the internal electrode layer, In a third direction perpendicular to the first and second directions, the external electrode is provided adjacent to the internal electrode layer and electrically connected to the internal electrode layer, A multilayer ceramic electronic component wherein at least a portion of the outer peripheral area consisting of the cover layer and the side margin is mainly composed of barium titanate, and when the titanium content of the barium titanate is 100 mol%, it contains 0.1 mol% or more of boron, 1.0 mol% or more of silicon, and 1.0 mol% or more of aluminum, with magnesium content being less than 0.1 mol%, manganese content being less than 0.1 mol%, and the aluminum concentration being equal to or greater than the aluminum concentration of the dielectric layer.

2. The multilayer ceramic electronic component according to claim 1, wherein in at least a portion of the aforementioned region, the concentration of boron is 2.5 mol% or less when the titanium content of the barium titanate is 100 mol%.

3. The multilayer ceramic electronic component according to claim 1, wherein in at least a portion of the region, the concentration of silicon is 3.0 mol% or less when the titanium content of the barium titanate is 100 mol%.

4. The multilayer ceramic electronic component according to claim 1, wherein in at least a portion of the region, when the titanium content of the barium titanate is 100 mol%, the concentration of aluminum is 10.0 mol% or less.

5. The multilayer ceramic electronic component according to claim 1, wherein at least a portion of the region comprises dielectric particles, and silicon and aluminum are present as amorphous phases or needle-shaped segregates at the grain boundaries and grain boundary triple points of the dielectric particles.

6. The multilayer ceramic electronic component according to claim 1, wherein the aluminum concentration differs between the cover layer and the side margin, and the aluminum concentration in the side margin is greater than that of the cover layer.

7. The multilayer ceramic electronic component according to claim 1, wherein the average particle size of dielectric particles contained in the cover layer or the side margin is greater than twice the average particle size of dielectric particles contained in the dielectric layer.

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