Multilayer capacitor

Abstract

A multilayer capacitor includes a capacitor body including a plurality of dielectric layers and a plurality of internal electrodes, and external electrodes respectively disposed on both end portions of the capacitor body and respectively connected to exposed portions of the internal electrodes. Each of the external electrodes includes a conductive layer formed on the capacitor body and connected to the internal electrode, an inner plating layer including nickel (Ni) and phosphorus (P) and covering the conductive layer, and an outer plating layer including palladium (Pd) and phosphorus (P) and covering the inner plating layer.

Description

[0001] This application is a divisional application of the invention patent application "Multilayer Capacitor" filed on October 29, 2019, with application number 201911035482.3. Technical Field

[0002] This disclosure relates to multilayer capacitors. Background Technology

[0003] In a typical multilayer capacitor, the plating of the external electrode can be formed using nickel plating and tin plating, and tin-based solder can be used when the multilayer capacitor is mounted on a substrate.

[0004] In the case of tin-containing solder, problems such as cracking may occur when the product requires reliability at temperatures of 150°C or higher. In recent years, there has been a trend to use conductive adhesives, which mainly consist of epoxy resin and metal fillers, as bonding materials.

[0005] However, when the aforementioned conductive adhesive is used as the bonding material and the plating of the external electrode is made of tin, the bonding strength between the conductive adhesive and the plating may decrease, which may lead to an increase in installation failures of multilayer capacitors. Summary of the Invention

[0006] One aspect of this disclosure provides a multilayer capacitor that, even when high reliability is required when the multilayer capacitor is mounted on a substrate using a conductive adhesive, prevents a decrease in the bonding strength between the conductive adhesive and the plating layer, thereby preventing mounting failures.

[0007] According to one aspect of this disclosure, a multilayer capacitor includes: a capacitor body including a dielectric layer and a plurality of inner electrodes; and a plurality of outer electrodes disposed at two ends of the capacitor body and connected to exposed portions of the inner electrodes. Each of the outer electrodes includes: a conductive layer disposed on the capacitor body and connected to the inner electrodes; an inner plating layer including nickel (Ni) and phosphorus (P) and covering the conductive layer; and an outer plating layer including palladium (Pd) and phosphorus (P) and covering the inner plating layer.

[0008] In embodiments of this disclosure, the phosphorus content of the inner coating may be greater than 4% by weight and less than or equal to 8% by weight, based on the total weight of the inner coating.

[0009] In embodiments of this disclosure, the inner plating layer may comprise nickel (Ni) and phosphorus (P), with phosphorus (P) dispersed as an impurity in the inner plating layer.

[0010] In embodiments of this disclosure, the capacitor body may include a first surface and a second surface opposite to each other, a third surface and a fourth surface connected to the first surface and the second surface and opposite to each other, and a fifth surface and a sixth surface connected to the first surface and the second surface and connected to the third surface and the fourth surface and opposite to each other, and the plurality of internal electrodes may be alternately exposed through the third surface and the fourth surface of the capacitor body, and the dielectric layer is located between the plurality of internal electrodes.

[0011] In embodiments of this disclosure, the conductive layer of the outer electrode may include: a connecting portion disposed on the third and fourth surfaces of the capacitor body and connected to the exposed portion of the inner electrode; and a bending portion extending from the connecting portion to a portion of the first surface of the capacitor body.

[0012] In embodiments of this disclosure, the inner plating layer can be formed by plating a first metal layer comprising nickel and phosphorus onto the conductive layer using an electroless plating process, and the outer plating layer can be formed by plating a second metal layer comprising palladium and phosphorus onto the inner plating layer using an electroless plating process.

[0013] In embodiments of this disclosure, the conductive layer may comprise at least one of copper and silver.

[0014] In embodiments of this disclosure, the inner coating may have a thickness of 1 μm to 10 μm.

[0015] In embodiments of this disclosure, the thickness of the inner coating may be greater than the thickness of the outer coating.

[0016] In embodiments of this disclosure, the phosphorus content of the outer coating may be greater than or equal to 2% by weight and less than or equal to 6% by weight, based on the total weight of the outer coating.

[0017] In embodiments of this disclosure, the outer plating layer may comprise nickel (Ni) and phosphorus (P), with phosphorus (P) dispersed as an impurity in the outer plating layer.

[0018] In embodiments of this disclosure, each of the external electrodes may not contain a tin (Sn) layer.

[0019] According to one aspect of this disclosure, a multilayer capacitor includes: a capacitor body including a plurality of dielectric layers and a plurality of inner electrodes; and outer electrodes disposed at two ends of the capacitor body and respectively connected to exposed portions of the inner electrodes. Each of the outer electrodes includes: a conductive layer disposed on the capacitor body and connected to the inner electrodes; an inner nickel (Ni) layer having phosphorus (P) dispersed as an impurity in the inner nickel (Ni) layer and covering the conductive layer; and an outer noble metal layer having phosphorus (P) dispersed as an impurity in the outer noble metal layer and covering the inner nickel (Ni) layer.

[0020] In embodiments of this disclosure, the outer noble metal layer may be a palladium (Pd) layer containing phosphorus (P), with phosphorus (P) dispersed as an impurity in the palladium (Pd) layer.

[0021] In embodiments of this disclosure, the phosphorus content of the inner nickel (Ni) layer may be greater than 4% by weight and less than or equal to 8% by weight, based on the total weight of the inner nickel layer.

[0022] In embodiments of this disclosure, the phosphorus content of the outer noble metal layer may be greater than or equal to 2% by weight and less than or equal to 6% by weight, based on the total weight of the outer noble metal layer.

[0023] In embodiments of this disclosure, the thickness of the inner nickel (Ni) layer may be greater than the thickness of the outer noble metal layer.

[0024] In embodiments of this disclosure, each of the external electrodes may not contain a tin (Sn) layer. Attached Figure Description

[0025] The above and other aspects, features and advantages of this disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0026] Figure 1 This is a perspective view schematically illustrating a multilayer capacitor according to an embodiment of the present disclosure.

[0027] Figure 2A and Figure 2B These are respectively shown as applied to Figure 1 A plan view of the first and second internal electrodes of a multilayer capacitor.

[0028] Figure 3 It is along Figure 1 The cross-sectional view taken from line I-I' in the diagram.

[0029] Figure 4 It is shown in Figure 3 The cross-sectional view of the external electrode forming only a conductive layer.

[0030] Figure 5It is shown in Figure 4 A cross-sectional view of an inner plating layer also formed in the outer electrode. Detailed Implementation

[0031] Preferred embodiments of the present disclosure will be described below with reference to the accompanying drawings.

[0032] However, embodiments of this disclosure may be modified into various other forms, and the scope of this disclosure is not limited to the following embodiments.

[0033] Furthermore, embodiments of this disclosure may be provided to illustrate this disclosure more fully to those skilled in the art.

[0034] For clarity, the shape and size of the elements in the accompanying drawings may be exaggerated.

[0035] In the accompanying drawings of the corresponding embodiments, the same reference numerals may be used for the same elements.

[0036] Furthermore, unless otherwise expressly stated, the use of "includes" or "contains" an element throughout the specification does not exclude other elements, but may include other elements.

[0037] In the following text, for the purpose of clearly illustrating embodiments of this disclosure, when defining the orientation of the capacitor body 110, X, Y, and Z represent the length direction, width direction, and thickness direction of the capacitor body 110, respectively. Furthermore, in this embodiment, the Z direction can be used to have the same concept as the stacking orientation of the stacked dielectric layers.

[0038] Figure 1 This is a perspective view schematically illustrating a multilayer capacitor according to an embodiment of the present disclosure. Figure 2A and Figure 2B These are respectively shown as applied to Figure 1 A plan view of the first and second internal electrodes of a multilayer capacitor. Figure 3 It is along Figure 1 A cross-sectional view taken from line I-I' in the diagram. Figure 4 It is shown in Figure 3 The external electrode in the diagram only forms a cross-sectional view of the conductive layer, and Figure 5 It is shown in Figure 4 A cross-sectional view of an inner plating layer also formed in the outer electrode.

[0039] Reference Figures 1 to 5 The multilayer capacitor 100 according to this embodiment may include a capacitor body 110, a first external electrode 130, and a second external electrode 140.

[0040] The capacitor body 110 can be formed by stacking multiple dielectric layers 111 in the Z direction and then sintering the stacked dielectric layers 111. In this case, the boundaries between adjacent dielectric layers 111 in the capacitor body 110 can be integrated to a degree that makes it difficult to confirm the boundaries without using a scanning electron microscope (SEM).

[0041] The capacitor body 110 may have a generally hexahedral shape, but this disclosure is not limited thereto. The shape and size of the capacitor body 110 and the number of dielectric layers 111 stacked are not limited to the shape and size of the capacitor body 110 and the number of dielectric layers 111 stacked shown in the accompanying drawings of this embodiment.

[0042] In this embodiment, for ease of explanation, the two surfaces of the capacitor body 110 that are opposite to each other in the Z direction can be defined as a first surface 1 and a second surface 2, respectively; the two surfaces of the capacitor body 110 that are connected to the first surface 1 and the second surface 2 and are opposite to each other in the X direction can be defined as a third surface 3 and a fourth surface 4, respectively; and the two surfaces of the capacitor body 110 that are connected to the first surface 1 and the second surface 2, connected to the third surface 3 and the fourth surface 4, and are opposite to each other in the Y direction can be defined as a fifth surface 5 and a sixth surface 6, respectively. Furthermore, in this embodiment, the mounting surface of the multilayer capacitor 100 can be the first surface 1 of the capacitor body 110.

[0043] The dielectric layer 111 may include a ceramic material with a high dielectric constant, such as barium titanate (BaTiO3) based ceramic powder, strontium titanate (SrTiO3) based ceramic powder, etc., but is not limited thereto.

[0044] In addition, ceramic additives, organic solvents, plasticizers, binders, dispersants, etc., can also be added to the dielectric layer 111 together with the ceramic powder.

[0045] Ceramic additives can be, for example, transition metal oxides or transition metal carbides, rare earth elements, magnesium (Mg), aluminum (Al), etc.

[0046] The capacitor body 110 may include: an effective region, which serves as a portion contributing to the capacitance formation of the capacitor; and an upper cover portion 112 and a lower cover portion 113, which are formed as an upper edge portion and a lower edge portion on the upper and lower surfaces of the effective region in the Z direction, respectively.

[0047] The upper cover 112 and the lower cover 113 may have the same material and construction as the dielectric layer 111, except that they do not include the inner electrode.

[0048] The upper cover 112 and the lower cover 113 can be formed by stacking a single dielectric layer or two or more dielectric layers on the upper and lower surfaces of the effective region in the Z direction, respectively; and can be used to prevent the first inner electrode 121 and the second inner electrode 122 from being damaged by physical or chemical stress.

[0049] The first inner electrode 121 and the second inner electrode 122 may be electrodes with different polarities, may be arranged alternately in the Z direction and have a dielectric layer 111 between them, and may be configured such that one end of the first inner electrode 121 and one end of the second inner electrode 122 are exposed through the third surface 3 and the fourth surface 4 of the capacitor body 110, respectively.

[0050] In this case, the first inner electrode 121 and the second inner electrode 122 can be electrically insulated from each other by the dielectric layer 111 between them.

[0051] As will be described later, the ends of the first inner electrode 121 and the second inner electrode 122, which are alternately exposed by the third surface 3 and the fourth surface 4 of the capacitor body 110, can respectively contact the first outer electrode 130 disposed on the third surface 3 of the capacitor body 110 and the second outer electrode 140 disposed on the fourth surface 4 of the capacitor body 110, and can respectively be electrically connected to the first outer electrode 130 disposed on the third surface 3 of the capacitor body 110 and the second outer electrode 140 disposed on the fourth surface 4 of the capacitor body 110.

[0052] In this embodiment, when a predetermined voltage is applied to the first external electrode 130 and the second external electrode 140, charge can accumulate between the first internal electrode 121 and the second internal electrode 122.

[0053] In this case, the electrostatic capacitance of the multilayer capacitor 100 is proportional to the overlap area of ​​the first inner electrode 121 and the second inner electrode 122 in the effective region in the Z direction.

[0054] There are no particular limitations on the materials used to form the first internal electrode 121 and the second internal electrode 122, and they can be formed using noble metal materials (such as platinum (Pt), palladium (Pd) and palladium-silver (Pd-Ag) alloys) and conductive pastes made from one or more of nickel (Ni) and copper (Cu).

[0055] In this case, the method of printing conductive paste can be screen printing, gravure printing, etc., but this disclosure is not limited thereto.

[0056] The first external electrode 130 and the second external electrode 140 may be provided with voltages of different polarities, may be provided at two ends of the capacitor body 110 in the X direction, and may respectively contact the exposed portion of the first internal electrode 121 and the exposed portion of the second internal electrode 122 and may respectively be electrically connected to the exposed portion of the first internal electrode 121 and the exposed portion of the second internal electrode 122.

[0057] The first external electrode 130 may include: a first conductive layer 131 formed on the capacitor body 110 to be connected to the first internal electrode 121; a first internal plating layer 132 formed to cover the first conductive layer 131; and a first external plating layer 133 formed to cover the first internal plating layer. The second external electrode 140 may include: a second conductive layer 141 formed on the capacitor body 110 to be connected to the second internal electrode 122; a second internal plating layer 142 formed to cover the second conductive layer 141; and a second external plating layer 143 formed to cover the second internal plating layer.

[0058] The first conductive layer 131 may include a first connecting portion 131a and a first bending portion 131b.

[0059] The first connecting portion 131a may be formed on the third surface 3 of the capacitor body 110 and may be connected to the exposed portion of the first internal electrode 121. The first bent portion 131b may be a portion extending from the first connecting portion 131a to a portion of the first surface 1 of the capacitor body 110.

[0060] In this case, the first bend 131b may also extend to a portion of the fifth surface 5, a portion of the sixth surface 6, and a portion of the second surface 2 in the capacitor body 110 to improve the fixing strength, etc.

[0061] The second conductive layer 141 may include a second connecting portion 141a and a second bent portion 141b.

[0062] The second connecting portion 141a may be formed on the fourth surface 4 of the capacitor body 110 and may be connected to the exposed portion of the second internal electrode 122. The second bent portion 141b may be a portion extending from the second connecting portion 141a to a portion of the first surface 1 of the capacitor body 110.

[0063] In this case, the second bend 141b may also extend to a portion of the fifth surface 5, a portion of the sixth surface 6, and a portion of the second surface 2 in the capacitor body 110 to improve the fixing strength, etc.

[0064] The first conductive layer 131 and the second conductive layer 141 may include at least one of copper (Cu) and silver (Ag), and may also include glass, epoxy resin, etc.

[0065] The first inner plating layer 132 and the second inner plating layer 142 may comprise nickel (Ni) and phosphorus (P). For example, the first inner plating layer 132 and the second inner plating layer 142 may primarily comprise nickel (Ni) and also include phosphorus (P), which is dispersed as an impurity in the first inner plating layer 132 and the second inner plating layer 142. In another example, the first inner plating layer 132 and the second inner plating layer 142 may be nickel (Ni) plating layers with phosphorus (P) dispersed therein as an impurity.

[0066] The first inner plating layer 132 and the second inner plating layer 142 can be formed by plating a first metal layer comprising nickel and phosphorus onto the first conductive layer 131 and the second conductive layer 141, respectively.

[0067] In this case, the first inner plating layer 132 and the second inner plating layer 142 can be formed by electroless plating processes, respectively. Compared with the coating film formed by electroplating, when the first inner plating layer 132 and the second inner plating layer 142 are formed by electroless plating processes, the formed first inner plating layer 132 and the second inner plating layer 142 can have better corrosion resistance, and the plating process can usually be performed uniformly at each location to have a uniform plating thickness, and there is no difference in plating characteristics compared with the coating film formed by electroplating processes.

[0068] Furthermore, in the electroplating process, dummy bodies such as steel balls are added to conduct electricity during barrel plating. In this embodiment, when performing an electroless plating process, plating can be performed solely on the substrate without any dummy bodies. Therefore, plating preparation and defect selection of the substrate after plating can be performed more easily.

[0069] Based on the total weight of the first inner plating layer 132 and the second inner plating layer 142, respectively, the phosphorus content in the first inner plating layer 132 and the second inner plating layer 142 can be greater than 4% by weight and less than or equal to 8% by weight.

[0070] In Table 1 below, corrosion resistance can be confirmed by salt spray testing, and it can be confirmed that the longer the time, the better the corrosion resistance.

[0071] [Table 1]

[0072]

[0073] In this case, phosphorus can play a role in determining the characteristics of the nickel coating. Referring to Table 1, #1 (excluding phosphorus (P)) can be a case where plating cannot be performed in an electroless plating process.

[0074] It can be confirmed that, in cases #2 and #3 (phosphorus content of 4 wt% or less), the corrosion resistance of the first inner coating 132 and the second inner coating 142 is reduced.

[0075] It can be confirmed that the nickel deposition rate decreases in cases #8 and #9 (where phosphorus content exceeds 8 wt%).

[0076] When the nickel deposition rate decreases, the plating time required to achieve the same plating thickness becomes longer. Therefore, the manufacturing time of the product increases, leading to reduced productivity.

[0077] The thicknesses of the first inner plating layer 132 and the second inner plating layer 142 can be greater than or equal to 1 μm and less than or equal to 10 μm. When the thicknesses of the first inner plating layer 132 and the second inner plating layer 142 are less than 1 μm, there may be insufficient nickel coverage, and the first conductive layer 131 and the second conductive layer 141 will be exposed. When the thicknesses of the first inner plating layer 132 and the second inner plating layer 142 are greater than 10 μm, excessive plating time may be required.

[0078] The first outer coating 133 and the second outer coating 143 may include palladium (Pd) and phosphorus (P). Based on the total weight of the first outer coating 133 and the second outer coating 143, the phosphorus content in the first outer coating 133 and the second outer coating 143 may be greater than or equal to 2% by weight and less than or equal to 6% by weight, respectively. For example, the first outer coating 133 and the second outer coating 143 may primarily comprise palladium (Pd) and also include phosphorus (P), with phosphorus (P) dispersed as an impurity in the first outer coating 133 and the second outer coating 143. In another example, the first outer coating 133 and the second outer coating 143 may be palladium (Pd) coatings with phosphorus (P) dispersed therein as an impurity.

[0079] The first outer plating layer 133 and the second outer plating layer 143 can be formed by plating a second metal layer containing palladium and phosphorus onto the first inner plating layer 132 and the second inner plating layer 142 respectively using an electroless plating process.

[0080] Since the first outer plating layer 133 and the second outer plating layer 143 are respectively used to prevent the nickel components in the first inner plating layer 132 and the second inner plating layer 142 from being oxidized, the first outer plating layer 133 and the second outer plating layer 143 can preferably be formed as thin by using a material comprising a noble metal that has relatively low oxidizability compared to nickel.

[0081] For example, the thickness of the first outer plating layer 133 and the second outer plating layer 143 can be less than the thickness of the first inner plating layer 132 and the second inner plating layer 142, respectively. When the thickness of the first outer plating layer 133 and the second outer plating layer 143 increases, there is a high probability that problems such as plating cracking may occur.

[0082] Compared to coatings formed by electroplating, when the first outer coating 133 and the second outer coating 143 are formed by electroless plating, the first outer coating 133 and the second outer coating 143 can have better corrosion resistance, and the plating process can usually be performed uniformly at each location to have a uniform plating thickness, and there is no difference in plating characteristics compared to coatings formed by electroplating.

[0083] The multilayer capacitor of this embodiment can be a product that is mounted on a substrate using conductive adhesive and requires reliability at temperatures of 150°C or higher.

[0084] The first outer plating layer 133 and the second outer plating layer 143 can be the parts of a multilayer capacitor that can come into contact with conductive adhesive when the multilayer capacitor is mounted on a substrate. Since they do not contain tin, the bonding strength with the substrate can be prevented from deteriorating, and there are no reliability issues at high temperatures.

[0085] According to embodiments of this disclosure, even when high reliability is required when using conductive adhesive to mount multilayer capacitors on a substrate, the bonding strength between the conductive adhesive and the plating layer can be prevented from decreasing, thereby preventing mounting failure of the multilayer capacitor.

[0086] While exemplary embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations may be made without departing from the scope of this disclosure as defined by the appended claims.

Claims

1. A multilayer capacitor, comprising: The capacitor body includes multiple dielectric layers and multiple internal electrodes; as well as External electrodes are respectively disposed at both ends of the capacitor body and respectively connected to the exposed portions of the internal electrodes. Each of the external electrodes includes: A conductive layer is disposed on the capacitor body and connected to the internal electrode; An inner plating layer, comprising nickel and phosphorus, and covering the conductive layer; and An outer plating layer, comprising palladium and phosphorus, covers the inner plating layer, and the outer plating layer is the outermost layer of the outer electrode.

2. The multilayer capacitor of claim 1, wherein, Based on the total weight of the inner coating, the phosphorus content of the inner coating is greater than 4% by weight and less than or equal to 8% by weight.

3. The multilayer capacitor of claim 2, wherein, The inner plating layer contains nickel and includes phosphorus, which is dispersed in the inner plating layer as an impurity.

4. The multilayer capacitor of claim 1, wherein, The capacitor body includes a first surface and a second surface opposite to each other, a third surface and a fourth surface connected to the first surface and the second surface and opposite to each other, and a fifth surface and a sixth surface connected to the first surface and the second surface and connected to the third surface and the fourth surface and opposite to each other, and the plurality of internal electrodes are alternately exposed through the third surface and the fourth surface of the capacitor body, and the dielectric layer is located between the plurality of internal electrodes.

5. The multilayer capacitor of claim 4, wherein, The conductive layer of the outer electrode includes: a connecting portion disposed on the third and fourth surfaces of the capacitor body and connected to the exposed portion of the inner electrode; and a bending portion extending from the connecting portion to a portion of the first surface of the capacitor body.

6. The multilayer capacitor according to claim 1, wherein The inner plating layer is formed by plating a first metal layer containing nickel and phosphorus onto the conductive layer using an electroless plating process, and The outer coating is formed by depositing a second metal layer containing palladium and phosphorus onto the inner coating using an electroless plating process.

7. The multilayer capacitor of claim 1, wherein, The conductive layer contains at least one of copper and silver.

8. The multilayer capacitor of claim 1, wherein, The inner coating has a thickness of 1 μm to 10 μm.

9. The multilayer capacitor of claim 1, wherein, The thickness of the inner coating is greater than the thickness of the outer coating.

10. The multilayer capacitor of claim 1, wherein, Based on the total weight of the outer coating, the phosphorus content of the outer coating is greater than or equal to 2% by weight and less than or equal to 6% by weight.

11. The multilayer capacitor of claim 10, wherein, The outer coating contains palladium and phosphorus, with phosphorus dispersed as an impurity in the outer coating.

12. The multilayer capacitor of claim 1, wherein, Each of the external electrodes does not contain a tin layer.

13. A multilayer capacitor, comprising: The capacitor body includes multiple dielectric layers and multiple internal electrodes; as well as External electrodes are respectively disposed at both ends of the capacitor body and respectively connected to the exposed portions of the internal electrodes. Each of the external electrodes includes: A conductive layer is disposed on the capacitor body and connected to the internal electrode; An inner nickel layer, having phosphorus dispersed as an impurity within the inner nickel layer, and covering the conductive layer; and An outer noble metal layer, having phosphorus dispersed as an impurity in the outer noble metal layer, covers the inner nickel layer, and the outer noble metal layer is the outermost layer of the outer electrode.

14. The multilayer capacitor of claim 13, wherein, The outer noble metal layer is a palladium layer containing phosphorus, with phosphorus dispersed as an impurity in the palladium layer.

15. The multilayer capacitor of claim 13, wherein, Based on the total weight of the inner nickel layer, the phosphorus content of the inner nickel layer is greater than 4% by weight and less than or equal to 8% by weight.

16. The multilayer capacitor of claim 13, wherein, Based on the total weight of the outer noble metal layer, the phosphorus content of the outer noble metal layer is greater than or equal to 2% by weight and less than or equal to 6% by weight.

17. The multilayer capacitor of claim 13, wherein, The thickness of the inner nickel layer is greater than the thickness of the outer noble metal layer.

18. The multilayer capacitor of claim 13, wherein, Each of the external electrodes does not contain a tin layer.

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