KR20220086452A - Multilayer capacitor - Google Patents

Abstract

One embodiment of the present invention includes a body including a plurality of dielectric layers and a plurality of internal electrodes stacked with the dielectric layers interposed therebetween, and external electrodes formed outside the body and connected to the internal electrodes, the plurality of dielectric layers contains a dielectric expressed by the compositional formula of BaM1 _a Ti _1-x Sn _x M2 _b O ₃ (0.008≤x≤0.05, 0.006≤a≤0.03, 0.0006≤b<0.006), where M1 contains a rare earth element and M2 provides a multilayer capacitor including at least one of Mn and V.

Description

Multilayer Capacitors {MULTILAYER CAPACITOR}

The present invention relates to a multilayer capacitor.

A capacitor is an element that can store electricity, and basically, when two electrodes are opposed to each other and a voltage is applied, electricity is accumulated in each electrode. When a DC voltage is applied, a current flows inside the capacitor as electricity is stored, but when the accumulation is completed, the current stops flowing. On the other hand, when an AC voltage is applied, an AC current flows while the polarity of the electrodes is changed.

According to the type of insulator provided between the electrodes, the capacitor includes an aluminum electrolytic capacitor comprising an electrode made of aluminum and a thin oxide film between the aluminum electrodes, a tantalum capacitor using tantalum as an electrode material, and barium titanate between the electrodes. Ceramic capacitors using dielectrics of the same high dielectric constant, Multi-Layer Ceramic Capacitors (MLCCs) using high-k ceramics as a dielectric provided between electrodes in a multi-layer structure, and polystyrene films as dielectrics between electrodes It can be divided into several types, such as film capacitors.

Among them, multilayer ceramic capacitors have excellent temperature and frequency characteristics and have the advantage that they can be implemented in a small size. Recently, attempts have been made to make the multilayer ceramic capacitor smaller, and for this purpose, a dielectric layer and an internal electrode are formed thinly. In addition, research on dielectric materials for realizing a multilayer ceramic capacitor having high capacity and excellent reliability is being conducted.

SUMMARY OF THE INVENTION One object of the present invention is to provide a multilayer capacitor having improved performance by using a dielectric material having a high dielectric constant and excellent reliability.

As a method for solving the above problems, the present invention intends to propose a novel structure of a multilayer capacitor through an example, and specifically, it includes a plurality of dielectric layers and a plurality of internal electrodes stacked with the dielectric layers interposed therebetween. a body and an external electrode formed outside the body and connected to the internal electrode, wherein the plurality of dielectric layers include BaM1 _a Ti _1-x Sn _x M2 _b O ₃ (0.008≤x≤0.05, 0.006≤a≤0.03, 0.0006≤b<0.006), wherein M1 includes a rare earth element, and M2 includes at least one of Mn and V.

In an embodiment, the rare earth element may include Dy.

In an embodiment, the dielectric may include 0.006-0.012 moles of Dy relative to 1 mole of Ba.

In an embodiment, M2 may include both Mn and V, and the dielectric may include 0.0003-0.0035 moles of Mn and 0.0003-0.0025 moles of V relative to 1 mole of Ba.

In an embodiment, the dielectric may further include an Al component of 0.003 moles or more and less than 0.012 moles relative to 1 mole of Ba.

In an embodiment, the dielectric may further include an Mg component of 0.001 mol or more and less than 0.012 mol relative to 1 mol of Ba.

In an embodiment, the dielectric may further include 0.03 moles or more of Si components relative to 1 mole of Ba.

In an embodiment, the compositional formula may satisfy the condition of 0.12≤a/x≤3.75.

In an embodiment, the compositional formula may satisfy the condition of 0.012≤b/x≤0.75.

In an embodiment, in the formula, the ratio of Ba to Ti (Ba/Ti) may be 1.010 to 1.050.

In an embodiment, at least one of the grains included in the plurality of dielectric layers may have a core-shell structure including a core and a shell part covering the core.

In one embodiment, the shell portion may have a greater content of Sn than the core.

In an embodiment, the average thickness of the dielectric layer may be 500 nm or less.

In an embodiment, the average thickness of the internal electrode may be 400 nm or less.

In the case of the multilayer capacitor according to an embodiment of the present invention, it is possible to secure a high level of capacity and has excellent reliability such as withstand voltage characteristics.

1 is a perspective view schematically illustrating an external appearance of a multilayer capacitor according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view II′ in the multilayer capacitor of FIG. 1 .
3 is a cross-sectional view II-II` in the multilayer capacitor of FIG. 1 .
4 is an enlarged schematic view of the grain of the dielectric layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to specific embodiments and the accompanying drawings. However, the embodiment of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments of the present invention are provided in order to more completely explain the present invention to those skilled in the art. Accordingly, the shapes and sizes of elements in the drawings may be exaggerated for clearer description, and elements indicated by the same reference numerals in the drawings are the same elements.

And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and the thickness is enlarged to clearly express various layers and regions, and components having the same function within the scope of the same idea are referred to as the same. It is explained using symbols. Furthermore, throughout the specification, when a part "includes" a certain element, it means that other elements may be further included, rather than excluding other elements, unless otherwise stated.

1 is a perspective view schematically illustrating an external appearance of a multilayer capacitor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line I-I` in the multilayer capacitor of FIG. 1 . 3 is a cross-sectional view II-II` in the multilayer capacitor of FIG. 1 . And Fig. 4 is a schematic view showing the enlarged grain of the dielectric layer.

1 to 3 , the multilayer capacitor 100 according to an embodiment of the present invention includes a dielectric layer 111 and a plurality of internal electrodes 121 and 122 stacked in the first direction (X direction) with the dielectric layer 111 therebetween. It includes a body 110 and external electrodes 131 and 132 including a. And the plurality of dielectric layers 111 include a dielectric expressed by the composition formula of BaM1 _a Ti _1-x Sn _x M2 _b O ₃ (0.008≤x≤0.05, 0.006≤a≤0.003, 0.0006≤b<0.006), wherein , M1 includes a rare earth element, and M2 includes at least one of Mn and V.

The body 110 includes a stacked structure in which a plurality of dielectric layers 111 are stacked in a first direction (X-direction), and may be obtained by, for example, stacking a plurality of green sheets and then sintering. By this sintering process, the plurality of dielectric layers 111 may have an integrated shape. As shown in Figure 1, the body 110 may have a shape similar to a rectangular parallelepiped. In the present embodiment, the dielectric layer 111 included in the body 110 includes a barium titanate-based ceramic dielectric, and includes Sn, a rare earth element, and a transition metal component. The inventors of the present invention have discovered that the grain size and permittivity of a dielectric can be effectively controlled by controlling the components and content of additives. In this case, when these additives are used in the form of coatings on the base material powder, grain growth of dielectric grains can be effectively controlled, and the dielectric strength characteristics and the like can be improved.

As described above, the dielectric layer 111 includes a dielectric expressed by the composition formula of BaM1 _a Ti _1-x Sn _x M2 _b O ₃ (0.008≤x≤0.05, 0.006≤a≤0.003, 0.0006≤b<0.006) and , where M1 includes a rare earth element, and M2 includes at least one of Mn and V. The Sn component may be doped in the form of a coating on the base material powder, and grain growth of dielectric grains may be suppressed during the sintering process. Accordingly, even when a dielectric is implemented using fine powder, excessive increase in grain size can be alleviated and a high dielectric constant can be secured. Specifically, in order to thin the dielectric layer 111, fine dielectric powder must be used. In the case of fine barium titanate, the sintering driving force increases, making it difficult to control grain growth during the sintering process, and excessive grain growth until the sintered body is densified. is accompanied Accordingly, the withstand voltage and high temperature reliability may be deteriorated, and the effective capacity may be reduced under a DC electric field. In this embodiment, the Sn component is added in an optimized content range to solve this problem, and further, when the Sn component is used in the form of a coating on the base material powder, the effect can be expressed more significantly.

In addition, the Sn component may serve as an acceptor to improve the reduction resistance of the dielectric material. In addition, when Ti is substituted with Sn by doping of Sn, the dielectric constant may be improved because a crystal structure having excellent dielectric constant may be changed. As described above, even when the dielectric layer 111 is implemented with a thin thickness by the addition of the Sn component, a high dielectric constant can be secured and the withstand voltage characteristic can be strengthened. The amount of Sn added is preferably 0.008-0.05 mol relative to 1 mol of Ba, and when Sn is less than 0.008 mol, the above-described effect is not clearly exhibited. In addition, when Sn is added in an amount greater than 0.05 mol, the impact resistance may deteriorate due to the formation of a network between Sn. The Sn component may be uniformly diffused in the grain during sintering, and may also exist at the interface between the dielectric layer 111 and the internal electrodes 121 and 122 . In addition, when grain growth of dielectric grains is limited, a core-shell structure may remain in the dielectric grains as shown in FIG. 4 . Referring to FIG. 4 , the dielectric grain may include both the core-shell grain 11 and the grain 12 without a core-shell structure. In the case of the core-shell grain 11 , the core 11a and the shell portion (11b). Here, the content of Sn in the shell portion 11b may be greater than that of the core 11a.

When Sn is added, the ratio of Ba to Ti (Ba/Ti) may be higher than that of general barium titanate, thereby suppressing grain growth of dielectric grains. In this case, the Ti to Ba ratio (Ba/Ti) may have a value in the range of 1.010 to 1.050. When the ratio of Ba to Ti (Ba/Ti) is 1.050 or more and has a high molar ratio, the dielectric grains can be densified by suppressing grain growth during sintering, and from this, electrical characteristics (withstanding voltage characteristics), moisture resistance reliability, etc. can be improved. .

In the dielectric, M1 is a rare earth element, and the rare earth element may include Dy. M1 is contained in 0.006-0.03 mol relative to 1 mol of Ba. When the dielectric includes Dy, the dielectric may contain 0.006-0.012 moles of Dy relative to 1 mole of Ba, and additionally include other rare earth elements (eg, Tb, Eu, Ce, Sc, Y, etc.) in addition to Dy. In this case, the total amount of the rare earth element may be 0.006-0.03 moles based on 1 mole of Ba as described above. In addition, M2 in the dielectric includes at least one of Mn and V, which are transition metals, and 0.0006-0.006 mol relative to 1 mol of Ba. In this case, M2 may include both Mn and V, where, relative to 1 mole of Ba, Mn may include 0.0003 moles or more and less than 0.0035 moles, and V may include 0.0003 moles or more and less than 0.0025 moles. Like the Sn component, the M1 and M2 components may be provided in a coated form on the base material powder, but may be uniformly diffused inside the grain during sintering. In this case, the rare earth element and the transition metal component may serve to enhance the reliability of the dielectric material by strengthening the Schottky barrier and increasing the reduction resistance of the dielectric material.

In the present embodiment, the content of M1 and M2 may satisfy a specific condition compared to the content of Sn. That is, the condition of 0.12≤a/x≤3.75 in the composition formula may be satisfied. Simultaneously or separately, the composition formula may satisfy the condition of 0.012≤b/x≤0.75. These conditions are to set the relative content of doping as an additive in an appropriate range in consideration of the functions described above for Sn, M1, and M2.

In addition to the above-described components, the dielectric may further include one or more subcomponents. Specifically, the dielectric may further include an Al component in an amount of 0.003 mol or more and less than 0.012 mol relative to 1 mol of Ba. In addition, the dielectric may further include an Mg component in an amount of 0.001 mol or more and less than 0.012 mol relative to 1 mol of Ba. In addition, the dielectric may further include 0.03 moles or more of Si components relative to 1 mole of Ba. In the case of these additional subcomponents, they may be added to the base material powder or may be added in the form of coatings on the base material powder.

On the other hand, the component of the dielectric applied to the multilayer capacitor can be analyzed, for example, by the following method. In the case of the destructive method, the multilayer capacitor is crushed, the internal electrode is removed, the dielectric part is selected, and the selected dielectric is used in an inductively coupled plasma spectrometer (ICP-OES), inductively coupled plasma mass spectrometer (ICP-MS), etc. can be used to analyze the components of the genome. And in the case of the non-destructive method, it is possible to analyze the components inside the dielectric grain in the center of the chip using TEM-EDS. Here, the Si component may be measured at the grain boundary rather than the inside of the grain.

Also, as described above, an effect of improving withstand voltage characteristics, etc. obtainable by using the dielectric material may be remarkable when the dielectric layer 111 and the internal electrodes 121 and 122 are thinner than the conventional ones. The thickness of the dielectric layer 111 may be 500 nm or less, and the thickness of the internal electrodes 121 and 122 may be 400 nm or less. Here, the thickness of the dielectric layer 111 may mean an average thickness of the dielectric layer 111 disposed between the internal electrodes 121 and 122 . As an example of the measurement standard, the average thickness of the dielectric layer 111 is an image of the cross-section in the first direction (X direction) and the third direction (Z direction) of the body 110 with a scanning electron microscope (SEM) can be measured by scanning For example, an arbitrary dielectric layer extracted from an image scanned with a scanning electron microscope (SEM) of cross-sections in the first and third directions cut from the central portion of the body 110 in the second direction (Y direction) , the average value may be measured by measuring the thickness at 30 points equally spaced in the third direction. The thickness measured at the 30 points at equal intervals may be measured in the capacitor forming part, which means a region where the internal electrodes 121 and 122 overlap each other.

Similarly, the thickness of the internal electrodes 121 and 122 may mean an average thickness. In this case, the average thickness of the internal electrodes 121 and 122 is an image of the cross-section in the first direction (X direction) and the third direction (Z direction) of the body 110 with a scanning electron microscope (SEM). It can be measured by scanning. For example, an arbitrary interior extracted from an image scanned with a scanning electron microscope (SEM) of cross-sections in the first and third directions cut from the central portion of the body 110 in the second direction (Y direction) With respect to the electrodes 121 and 122 , the thickness may be measured at 30 points equally spaced in the third direction to measure the average value. The 30 equally spaced points may be measured in the capacitor forming part, which means a region where the internal electrodes 121 and 122 overlap each other.

The plurality of internal electrodes 121 and 122 may be obtained by printing a paste including a conductive metal to a predetermined thickness on one surface of the ceramic green sheet and then sintering the paste. In this case, as shown in FIG. 2 , the plurality of internal electrodes 121 and 122 include first and second internal electrodes 121 and 121 exposed in a third direction (Z direction) facing each other of the body 110 . 122) may be included. Here, the third direction (Z direction) is a direction in which the first surface S1 and the second surface S2 of the active part 112 of the body 110 face each other is referred to as the second direction (Y direction). The direction may be perpendicular to the first direction (X direction) and the second direction (Y direction). The first and second internal electrodes 121 and 122 are connected to different external electrodes 131 and 132 and may have different polarities when driven, and are electrically separated from each other by the dielectric layer 111 disposed therebetween. can be However, the number of the external electrodes 131 and 132 or the connection method with the internal electrodes 121 and 122 may vary depending on the embodiment. The main constituent materials of the internal electrodes 121 and 122 may include nickel (Ni), copper (Cu), palladium (Pd), silver (Ag), and the like, and alloys thereof may also be used.

The external electrodes 131 and 132 are formed outside the body 110 and may include first and second external electrodes 131 and 132 respectively connected to the first and second internal electrodes 121 and 122 . have. The external electrodes 131 and 132 may be formed by making a paste of a material containing a conductive metal and then applying it to the body 110 . Examples of the conductive metal include nickel (Ni), copper (Cu), and the like. ), palladium (Pd), gold (Au), or alloys thereof. Here, the external electrodes 131 and 132 may further include a plating layer including Ni, Sn, or the like.

The inventors of the present invention manufactured dielectrics with the following composition and conducted reliability tests. Unlike the above based on 1 mole of Ba, the content of each element in the composition below is expressed as a molar ratio with respect to 100 moles of Ba. And the results of the accelerated life test (HALT) for each sample were described.

Sample Sn Dy Mn V Al Mg HALT #One 0 0.800 0.100 0.104 0.880 1.000 X #2 0 0.600 0.050 0.052 0.640 0.500 X #3 1.000 0.600 0.03 0.03 0.880 1.000 O #4 1.000 0.600 0.075 0.078 0.760 0.750 O #5 1.000 0.600 0.050 0.052 0.640 0.500 O #6 1.000 0.800 0.050 0.052 0.640 0.500 O #7 1.000 0.840 0.075 0.075 0.360 0.100 O #8 1.000 1.200 0.150 0.150 0.720 0.200 O #9 1.000 0.900 0.35 0.25 0.620 0.150 X #10 1.000 1.080 0.098 0.098 1.2 1.2 X

According to the above experimental results, samples (#4-#7) satisfying the above-described compositional formula of the present embodiment showed good results in HALT. These samples not only satisfied the intended capacity condition, but also had excellent withstand voltage characteristics and reliability. In the samples, Dy was used as a rare earth element, and when Dy was 0.6-1.2 mol relative to 100 mol of Ba, excellent reliability was obtained. However, as described above, the dielectric may further include other rare earth elements (eg, Tb, Eu, Ce, Sc, Y, etc.) in addition to Dy. In this case, the total amount of the rare earth elements is Ba 100 as a preferable condition. It may be 0.6-3.0 moles relative to moles. Unlike the samples according to the embodiment, in the case of the remaining samples according to the comparative example, at least one of the Sn content condition, the rare earth element content condition, and the transition metal content condition of the present invention were not satisfied, and the HALT withstanding voltage characteristics were relatively low. showed

The present invention is not limited by the above-described embodiments and the accompanying drawings, but by the appended claims. Accordingly, it will be apparent to those of ordinary skill in the art that various types of substitutions, modifications and changes are possible within the scope of the present invention described in the claims, and this is also included in the appended claims. It will be said to belong to the technical idea described in

100: multilayer capacitor
110: body
111: dielectric layer
121, 122: internal electrode
131, 132: external electrode
11, 12: grain
11a: core
11b: shell part

Claims (14)

a body including a plurality of dielectric layers and a plurality of internal electrodes stacked with the dielectric layers interposed therebetween; and
and an external electrode formed outside the body and connected to the internal electrode.
The plurality of dielectric layers includes a dielectric expressed by a compositional formula of BaM1 _a Ti _1-x Sn _x M2 _b O ₃ (0.008≤x≤0.05, 0.006≤a≤0.03, 0.0006≤b<0.006), where M1 is A multilayer capacitor comprising a rare earth element, and M2 comprises at least one of Mn and V.
According to claim 1,
wherein the rare earth element includes Dy.
3. The method of claim 2,
The dielectric is a multilayer capacitor comprising 0.006-0.012 moles of Dy compared to 1 mole of Ba.
According to claim 1,
Wherein M2 includes both Mn and V, and the dielectric includes 0.0003 moles or more and less than 0.0035 moles of Mn relative to 1 mole of Ba, and V is 0.0003 moles or more and less than 0.0025 moles.
According to claim 1,
The dielectric is a multilayer capacitor further comprising an Al component in an amount of 0.003 moles or more and 0.012 moles or more relative to 1 mole of Ba.
According to claim 1,
The dielectric is a multilayer capacitor further comprising an Mg component of 0.001 mole or more and less than 0.012 mole relative to 1 mole of Ba.
According to claim 1,
The dielectric is a multilayer capacitor further comprising 0.03 moles or more of Si components relative to 1 mole of Ba.
According to claim 1,
The composition formula is a multilayer capacitor satisfying the condition of 0.12≤a/x≤3.75.
9. The method of claim 1 or 8,
The composition formula is a multilayer capacitor satisfying the condition of 0.012≤b/x≤0.75.
According to claim 1,
In the above formula, the ratio of Ba to Ti (Ba/Ti) is 1.010 to 1.050.
According to claim 1,
A multilayer capacitor having a core-shell structure, wherein at least one of the grains included in the plurality of dielectric layers includes a core and a shell part covering the core.
12. The method of claim 11,
The shell portion is a multilayer capacitor having a greater Sn content than the core.
According to claim 1,
An average thickness of the dielectric layer is 500 nm or less.
According to claim 1,
and an average thickness of the internal electrode is 400 nm or less.

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