Multilayer capacitor

Abstract

To provide a laminate type capacitor.SOLUTION: A laminate type capacitor according to an embodiment of the present invention includes: a main body including a laminate structure having a plurality of dielectric layers stacked and a plurality of internal electrodes that are stacked with the dielectric layers held therebetween; an external electrode formed outside the main body, connected to the internal electrodes, and including a first electrode layer disposed on a first surface of the main body where the internal electrodes are exposed and a second electrode layer covering the first electrode layer; a first insulating coating layer disposed between the first and second electrode layers and including a discontinuous region; and a second insulating coating layer including a discontinuous region so as to cover a part of a surface of the main body where the external electrode is not disposed.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a multilayer capacitor.

Background Art

[0002] A capacitor is an element that can store electricity, and generally utilizes the principle that when a voltage is applied with two electrodes facing each other, electricity is accumulated on each electrode. When a DC voltage is applied, a current flows inside the capacitor while electricity is being stored, but when the accumulation is complete, the current stops flowing. On the other hand, when an AC voltage is applied, an alternating current flows while the polarity of the electrodes is reversed.

[0003] Such capacitors can be classified into various types depending on the type of insulator provided between the electrodes, such as an aluminum electrolytic capacitor having electrodes made of aluminum and a thin oxide film provided between the aluminum electrodes, a tantalum capacitor using tantalum as an electrode material, a ceramic capacitor using a dielectric with a high dielectric constant such as barium titanate between the electrodes, a multilayer ceramic capacitor (MLCC) using a high dielectric constant ceramic as a dielectric between the electrodes in a multilayer structure, a film capacitor using a polystyrene film as a dielectric between the electrodes, and the like.

[0004] Among them, multilayer ceramic capacitors have advantages such as excellent temperature characteristics and frequency characteristics and being able to be realized in a small size, and thus have been widely applied in various fields such as high-frequency circuits in recent years. In recent years, in order to further reduce the size of multilayer ceramic capacitors, attempts have been continuously made to form dielectric layers and internal electrodes thinner.

[0005] Recently, in the field of multilayer capacitors, many attempts have been made to improve moisture resistance reliability by reducing defects caused by the penetration of moisture and plating solutions. One method involves forming a thicker cover layer or external electrodes on the capacitor body, but this increases the size of the component, which leads to a decrease in capacitance for the same size. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] One objective of the present invention is to provide a multilayer capacitor with improved moisture resistance reliability. [Means for solving the problem]

[0007] To solve the above-mentioned problems, the present invention proposes a new structure for a multilayer capacitor, by example. Specifically, it includes a multilayer structure in which a plurality of dielectric layers are stacked, a main body including a plurality of internal electrodes stacked with the dielectric layers in between, an external electrode including a first electrode layer formed outside the main body, connected to the internal electrodes and positioned on a first surface of the main body where the internal electrodes are exposed, and a second electrode layer covering the first electrode layer, a first insulating coating layer positioned between the first and second electrode layers and having a discontinuous region, and a second insulating coating layer having a discontinuous region so as to cover a portion of the surface of the main body where the external electrode is not positioned.

[0008] In one embodiment, the first insulating coating layer includes a number of aggregates, and the regions between the number of aggregates can correspond to the discontinuous regions.

[0009] In one embodiment, grooves are formed on the surface of the first electrode layer, and the first insulating coating layer can fill the grooves of the first electrode layer.

[0010] In one embodiment, the region of the first insulating coating layer that fills the grooves of the first electrode layer can be used to coat the inner walls of the grooves of the first electrode layer.

[0011] In one embodiment, the first electrode layer may be a fired electrode, and the second electrode layer may be a plated layer.

[0012] In one embodiment, grooves are formed on the surface of the main body, and the second insulating coating layer can be configured to fill these grooves.

[0013] In one embodiment, the region of the second insulating coating layer that fills the groove of the main body can be used to coat the inner wall of the groove of the main body.

[0014] In one embodiment, the first and second insulating coating layers can be connected to each other.

[0015] In one embodiment, the first and second insulating coating layers may contain the same material as each other.

[0016] In one embodiment, the second electrode layer can cover a portion of the second insulating coating layer.

[0017] In one embodiment, the first and second insulating coating layers may include at least one of Si-based and F-based polymer polymers.

[0018] In one embodiment, the area occupied by the first discontinuous region in the first insulating coating layer can be greater than 90%.

[0019] In one embodiment, the area occupied by the second discontinuous region in the second insulating coating layer can be greater than 70%.

[0020] In one embodiment, the thickness of the first insulating coating layer can be 2 μm or less.

[0021] In one embodiment, the thickness of the second insulating coating layer can be 2 μm or less.

[0022] In one embodiment, the discontinuous region of the first insulating coating layer can be filled with the second electrode layer.

Advantages of the Invention

[0023] In the case of the multilayer capacitor according to an example of the present invention, the moisture resistance reliability can be improved.

Brief Description of the Drawings

[0024] [Figure 1] It is a perspective view schematically showing the appearance of the multilayer capacitor according to an embodiment of the present invention. [Figure 2] In the multilayer capacitor of FIG. 1, it is a cross-sectional view taken along line I-I'. [Figure 3] In the multilayer capacitor of FIG. 1, it is a cross-sectional view taken along line II-II'. [Figure 4] It shows an enlarged view of a partial region of FIG. 2. [Figure 5] It shows an enlarged view of a partial region of FIG. 2. [Figure 6] It shows an enlarged view of a partial region of FIG. 2. [Figure 7] It shows an enlarged view of a partial region of FIG. 2. [Figure 8] It shows an enlarged view of a partial region of FIG. 2.

Embodiments for Carrying Out the Invention

[0025] Embodiments of the present invention will be described below with reference to specific embodiments and accompanying drawings. However, embodiments of the present invention can be modified into several other forms, and the scope of the present invention is not limited to the embodiments described below. Furthermore, embodiments of the present invention are provided to give a more complete explanation of the present invention to a person of the ordinary skill. Accordingly, the shapes and sizes of elements in the drawings may be enlarged or reduced (or highlighted or simplified) for a clearer explanation, and elements indicated by the same reference numerals in the drawings are the same elements.

[0026] Furthermore, in order to clearly illustrate the present invention in the drawings, parts unrelated to the explanation have been omitted, and the thickness has been enlarged to clearly represent multiple layers and regions. Components with the same function within the scope of the same concept are described using the same reference numerals. Moreover, throughout the specification, when a part "includes" a component, unless otherwise stated to the contrary, it does not mean that other components are excluded, but rather that other components may be further included.

[0027] Figure 1 is a schematic perspective view showing the external appearance of a multilayer capacitor according to one embodiment of the present invention. Figures 2 and 3 are cross-sectional views taken along lines I-I' and II-II', respectively, of the multilayer capacitor of Figure 1. Figures 4 to 8 show enlarged views of a portion of Figure 2.

[0028] Referring to Figures 1 to 3, a multilayer capacitor 100 according to one embodiment of the present invention includes a main body 110 including a dielectric layer 111 and a plurality of internal electrodes 121, 122 stacked on either side of it, external electrodes 131, 132, and first and second insulating coating layers 151, 152. Here, the first and second insulating coating layers 151, 152 can prevent the intrusion of moisture, plating liquid, etc. from the outside. The first insulating coating layer 151 has a first discontinuous region D1, and the second insulating coating layer 152 has a second discontinuous region D2.

[0029] The main body 110 includes a plurality of dielectric layers 111, which can be obtained, for example, by laminating a plurality of green sheets and then sintering them. This sintering process allows the plurality of dielectric layers 111 to have an integrated form. As shown in Figure 1, the main body 110 can have a shape similar to a rectangular parallelepiped. The dielectric layers 111 contained in the main body 110 can include ceramic materials having a high dielectric constant, such as BT-based ceramics, i.e., barium titanate (BaTiO3) ceramics, but other materials known in the art can also be used as long as sufficient capacitance can be obtained. The dielectric layers 111 may further contain, if necessary, additives, organic solvents, plasticizers, binders, and dispersants, along with the ceramic material as the main component. In the case of additives, these can be added in the form of metal oxides during the manufacturing process. Examples of such metal oxide additives include at least one of MnO2, Dy2O3, BaO, MgO, Al2O3, SiO2, Cr2O3, and CaCO3.

[0030] Multiple internal electrodes 121, 122 can be obtained by printing a paste containing a conductive metal to a predetermined thickness on one surface of a ceramic green sheet, and then sintering it. In this case, the multiple internal electrodes 121, 122 may include first and second internal electrodes 121, 122 exposed on the main body 110 in mutually opposing directions (Z direction with respect to the drawing), and the surface on the main body 110 where the first and second internal electrodes 121, 122 are exposed is defined as the first surface S1. The first and second internal electrodes 121, 122 can be connected to different external electrodes 131, 132 and have different polarities when driven, and can be electrically isolated from each other by a dielectric layer 111 placed between them. However, the number of external electrodes 131, 132 and the method of connection with the internal electrodes 121, 122 can vary depending on the embodiment. Examples of main constituent materials for the internal electrodes 121, 122 include Cu and Ni, and alloys of these can also be used.

[0031] The external electrodes 131 and 132 are formed on the outside of the main body 110 and may include first and second external electrodes 131 and 132 that are connected to first and second internal electrodes 121 and 122, respectively. The external electrodes 131 and 132 include a first electrode layer 141 and a second electrode layer 142.

[0032] The first electrode layer 141 is positioned on the first surface S1 of the main body 110, where the first surface S1 is the surface on which the internal electrodes 121 and 122 are exposed. The first electrode layer 141 is connected to the internal electrodes 121 and 122 and can be formed from a conductive material, such as Cu, Ni, or alloys thereof. The first electrode layer 141 can be formed by transferring a conductive paste to the first surface S1 of the main body 110, or by printing or dipping. In this way, the first electrode layer 141 can be realized in the form of a fired electrode. In this case, the first electrode layer 141 can be formed not only on the first surface S1 of the main body 110, but also on the second surfaces S2 and S3 perpendicular to the stacking direction (X direction) of the internal electrodes 121 and 122, and on the third surface S3 perpendicular to the first surface S1 and the second surface S2. However, depending on the embodiment, the first electrode 141 can be formed only on the first surface S1 of the main body 110. The second electrode layer 142 covers the first electrode layer 141 and can be a plating layer. The second electrode layer 142 can be realized as a multilayer structure containing Ni, Sn, etc.

[0033] The first insulating coating layer 151 is positioned between the first and second electrode layers 141 and 142 and has a first discontinuity region D1 as shown in Figure 4. The first insulating coating layer 151 can effectively block the penetration of plating solution and the like into the main body 110 through the first electrode layer 141. In this case, the first insulating coating layer 151 fills in the gaps in the first electrode layer 141, such as surface grooves of the first electrode 141, preventing the second electrode layer 152 from penetrating into the main body 110 and enabling the formation of a structurally dense and stable structure. Considering this function, in this embodiment, the first insulating coating layer 151 is realized with an insulating material that can be coated relatively thinly and uniformly, for example, a water-repellent material, in an attempt to improve moisture-resistant barrier properties while maintaining a small size for the external electrodes 131 and 132. It is preferable to select the material constituting the first insulating coating layer 151 with this function in mind, and for example, the first insulating coating layer 151 may include at least one of Si-based and F-based polymer polymers.

[0034] In the case of the first insulating coating layer 151, it includes a first discontinuous region D1, of which at least a portion is filled with at least one of the first and second electrode layers 141 and 142, and the first and second electrode layers 141 and 142 can be connected to each other. Here, when the first insulating coating layer 151 and the second electrode layer 142 are formed after firing the first electrode layer 141, the first discontinuous region D1 can be filled with the second electrode layer 142, as shown in the form in Figure 2. Such a first discontinuous region D can form an electrical connection path between the first and second electrode layers 141 and 142. The first discontinuous region D of the first insulating coating layer 151 can be obtained by removing a portion of it after the first insulating coating layer 151 has been formed, by polishing or etching, etc. As an example of a specific form of the first insulating coating layer 151, as shown in Figure 4, the first insulating coating layer 151 can include a number of aggregates A, and the region between such a number of aggregates A corresponds to the discontinuous region.

[0035] As shown in the embodiments in Figures 5 and 6, the first insulating coating layer 151 can fill grooves formed on the surface of the first electrode layer 141, effectively preventing moisture and plating solution from penetrating through defects in the first electrode layer 141. In this case, the area of ​​the first insulating coating layer 151 that fills the grooves of the first electrode layer 141 may be a shape that coats the inner wall of the grooves of the first electrode layer 141 (the two upper areas in Figures 5 and 6), or it may be a shape that completely fills the grooves of the first electrode layer 141 (the one lower area in Figures 5 and 6). As shown in the embodiments, various shapes of the first insulating coating layer 151 can be used in combination, and it is not necessary to completely fill the grooves of the first electrode layer 141. In this embodiment, a first discontinuous region D1 is formed in the first insulating coating layer 151 to secure electrical connection paths between the first and second electrode layers 141 and 142, and to enable the second electrode layer 142 to be formed densely and stably. This reduces plating defects when the second electrode layer 142 is made of a plating layer. When the first insulating coating layer 151 is removed by polishing or etching, as shown in the embodiment of Figure 6, all areas other than the area filling the grooves of the first electrode layer 141 can be removed. Furthermore, the area occupied by the first discontinuous region D1 in the first insulating coating layer 151 is determined considering the function of the first discontinuous region D1, and preferably the area occupied by the first discontinuous region D1 in the first insulating coating layer 151 can be greater than 90%. In addition, the thickness of the first insulating coating layer 151 can be 2 μm or less, but if the first insulating coating layer 151 is too thick, it may interfere with the formation of the second electrode layer 142, and the electrical characteristics of the external electrodes 131 and 132 may deteriorate. The thickness of the first insulating coating layer 151 can be measured, for example, based on the thickest area.

[0036] The second insulating coating layer 152 covers at least a portion of the surface of the main body 110 where the external electrodes 131 and 132 are not located. In this embodiment, the second insulating coating layer 152 covers the second surface S2 and the third surface S3 of the main body 110. However, the second insulating coating layer 152 may cover only one of the first surface S2 and the third surface S3. As shown in the embodiment in Figure 2, the first and second insulating coating layers 151 and 152 can be connected to each other. Furthermore, the first and second insulating coating layers 151 and 152 can contain the same material. For example, the second insulating coating layer 152 can contain at least one of Si-based and F-based polymer polymers. The first and second insulating coating layers 151 and 152 can each be formed from the same material at the same time to cover the first electrode layer 141 and the main body 110, respectively. When the second electrode layer 142 is formed after the first and second insulating coating layers 152 have been formed, the second electrode layer 142 can cover a portion of the second insulating coating layer 152, as shown in the illustrated embodiment.

[0037] The second insulating coating layer 152 includes a second discontinuity region D2, and the second discontinuity region D2 can be formed by polishing or etching the second insulating coating layer 152, similar to the first insulating coating layer 151. The inventors of the present invention have found that the more the second insulating coating layer 152 covers the surface of the main body 110, the more advantageous it is in terms of moisture resistance reliability, but that this can cause mounting misalignment problems when mounting the multilayer capacitor 100 on a substrate or the like. This can be attributed to the fact that if the second insulating coating layer 152 is made of a water-repellent material, static electricity is easily induced due to charging phenomena with external contact materials, causing misalignment of the component during mounting. Furthermore, if a large amount of the second insulating coating layer 152 is present around the second electrode layer 142, less wetting occurs between the solder and the second insulating coating layer 152 during mounting of the multilayer capacitor 100, which can lead to reflow defects. To reduce such side effects, a second discontinuous region D2 is formed in the second insulating coating layer 152, in which case the proportion occupied by the second discontinuous region D2 can be greater than 70%. Since the functions of the first discontinuous region D1 and the second discontinuous region D2 are different, their proportions can also be different from each other, and the relative proportion of the first discontinuous region D1 can be even higher.

[0038] As shown in the embodiments in Figures 7 and 8, the second insulating coating layer 152 can fill grooves formed on the surface of the main body 110, effectively preventing moisture and plating solution from penetrating through defects in the main body 110. In this case, the area of ​​the second insulating coating layer 152 that fills the grooves of the main body 110 may be shaped to coat the inner wall of the grooves of the main body 110 (the two on the left in Figures 6 and 7), or it may be shaped to completely fill the grooves of the main body 110 (the one on the right in Figures 6 and 7). As shown in the embodiments, various shapes of the second insulating coating layer 152 can be used in combination, and it is not necessary to completely fill the grooves of the main body 110.

[0039] As described above, forming a second discontinuous region D2 in the second insulating coating layer 151 can reduce component mounting defects. When the second insulating coating layer 152 is removed by polishing or etching, as shown in the embodiment of Figure 8, all areas other than the area filling the groove of the main body 110 can be removed. Also, similar to the first insulating coating layer 151, the thickness of the second insulating coating layer 151 can be 2 μm or less, but if the second insulating coating layer 152 becomes too thick, there is a tendency for mounting defects to increase. The thickness of the second insulating coating layer 152 can be measured, for example, based on the thickest area.

[0040] The following describes the experimental results of the effects of the above-described embodiments of the present invention. As shown in Table 1 below, plating defects, mounting defects, and high-temperature accelerated lifetime tests were conducted by varying the proportion of discontinuous regions in the first and second insulating coating layers, the coating type, and the coating thickness. Here, the presence or absence of plating defects was observed by inspecting points selected at regular intervals in the cross-section of the sample to see if the plating layer was cut or not (25 samples). Mounting defects were determined based on whether or not a secondary phase occurred in order to observe whether or not soldering defects occurred when mounting the component to the substrate (400 samples). High-temperature accelerated lifetime (HALT) tests were conducted on 80 samples to measure the reliability of the multilayer capacitor, such as its voltage withstand characteristics.

[0041] [Table 1]

[0042] As can be seen from the experimental results above, when an insulating coating layer was not formed, there were no plating or mounting defects, but the withstand voltage characteristics were poor (increased failure rate in high-temperature accelerated experiments), which is understood to be due to the penetration of moisture or plating solution through defects in the electrode layer and the main body. Also, when no discontinuous region was formed in the insulating coating layer (0%), the plating defect rate was very high, and the mounting defect rate was also high. Even when the first discontinuous region was present but its proportion was low, it was confirmed that the plating defect rate due to the plating being cut off was high, and when the proportion of the first discontinuous region was greater than 90%, a stable plating layer could be achieved. However, when the insulating coating layer was thick (more than 2.0 μm), it was confirmed that there were constraints on the formation of the plating layer and some plating defects occurred. When the proportion of the second discontinuous region was low, some mounting defects occurred, and when it was greater than 70%, it was confirmed that no mounting defects occurred.

[0043] The present invention is not limited by the embodiments described above and the accompanying drawings, but is limited by the claims provided. Accordingly, it is obvious to those with ordinary skill in the art that various forms of substitution, modification, and alteration are possible without departing from the technical idea of ​​the present invention as described in the claims, and this can also be said to be within the scope of the technical idea described in the claims. [Explanation of Symbols]

[0044] 100: Multilayer capacitor 110: Main unit 111: Dielectric layer 121, 122: Internal electrode 131, 132: External electrode 141:First electrode layer 142:Second electrode layer 151: First insulating coating layer 152: Second insulating coating layer

Claims

1. A laminated structure in which multiple dielectric layers are stacked, a main body including multiple internal electrodes stacked with the multiple dielectric layers sandwiched between them, An external electrode comprising a first electrode layer formed on the outside of the main body, connected to the plurality of internal electrodes, and positioned on the first surface of the main body where the plurality of internal electrodes are exposed, and a second electrode layer covering the first electrode layer, A first insulating coating layer having a discontinuous region is disposed between the first and second electrode layers, The main body comprises a second insulating coating layer having a discontinuous region that covers a portion of the surface where the external electrodes are not arranged, The first insulating coating layer contains a large number of aggregates, and the regions between the large number of aggregates correspond to the discontinuous regions. A multilayer capacitor in which grooves are formed on the surface of the first electrode layer, and the first insulating coating layer fills the grooves of the first electrode layer.

2. The layered capacitor according to claim 1, wherein the region in the first insulating coating layer that fills the grooves of the first electrode layer coats the inner wall of the grooves of the first electrode layer.

3. The first electrode layer is a fired electrode, The multilayer capacitor according to claim 1 or 2, wherein the second electrode layer is a plating layer.

4. A laminated capacitor according to any one of claims 1 to 3, wherein grooves are formed on the surface of the main body, and the second insulating coating layer fills the grooves.

5. The laminated capacitor according to claim 4, wherein the region in the second insulating coating layer that fills the groove of the main body coats the inner wall of the groove of the main body.

6. The multilayer capacitor according to any one of claims 1 to 5, wherein the first and second insulating coating layers are connected to each other.

7. A multilayer capacitor according to any one of claims 1 to 6, wherein the first and second insulating coating layers contain the same material as each other.

8. The multilayer capacitor according to any one of claims 1 to 7, wherein the second electrode layer covers a portion of the second insulating coating layer.

9. The multilayer capacitor according to any one of claims 1 to 8, wherein the first and second insulating coating layers include at least one of Si-based and F-based polymer polymers.

10. The multilayer capacitor according to any one of claims 1 to 9, wherein the area occupied by the discontinuous region in the first insulating coating layer is greater than 90%.

11. The multilayer capacitor according to any one of claims 1 to 10, wherein the area occupied by the discontinuous region in the second insulating coating layer is greater than 70%.

12. The multilayer capacitor according to any one of claims 1 to 11, wherein the thickness of the first insulating coating layer is 2 μm or less.

13. The multilayer capacitor according to any one of claims 1 to 12, wherein the thickness of the second insulating coating layer is 2 μm or less.

14. A multilayer capacitor according to any one of claims 1 to 13, wherein the discontinuous region of the first insulating coating layer is filled with the second electrode layer.

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