Ceramic electronic component

Abstract

The present invention addresses the problem of providing a heat-resistant, humidity-resistant, and highly reliable ceramic electronic component by, in a plating step for forming an external electrode, preventing a plating solution from intruding into a base electrode layer.　This ceramic electronic component 1 comprises: a ceramic base body that includes an internal electrode layer; and an external electrode which is disposed on the surface of said ceramic base body and is electrically connected to the internal electrode layer. The ceramic electronic component is characterized in that the external electrode 3 comprises: a base electrode layer 4 containing a SiO2-BaO-B2O3-CaO-based glass; a protective layer 5 that covers the surface of the SiO2-BaO-B2O3-CaO-based glass which is exposed on the surface of said base electrode layer, the protective layer containing at least one element selected from the group consisting of P, S, C, Si, Ba, F, N, Al, Sr and B; and a Ni plating layer 6a that covers the base electrode layer and the protective layer.

Description

Technical Field

[0001] The present invention relates to a ceramic electronic component in which an external electrode is formed on the surface of a ceramic element incorporating an internal electrode layer, such as a capacitor, an inductor, and a varistor.

Background Art

[0002] In a ceramic electronic component such as a capacitor, an external electrode that conducts with the internal electrode layer is provided on the surface of a ceramic element incorporating the internal electrode layer. Since the external electrode usually needs to be in close contact with the ceramic element, it has an underlayer electrode layer containing a conductive metal and glass, and in order to prevent erosion by solder used when mounting on an electric circuit, the surface of the underlayer electrode layer is covered with a Ni plating layer and further with a Sn plating layer.

[0003] However, since the plating solution used in the plating process is highly reactive and elutes components with poor chemical resistance, it erodes the glass exposed on the surface of the underlayer electrode layer, and further, the plating solution enters the pores generated by the erosion, resulting in a problem that the heat resistance and moisture resistance of the electronic component decrease.

[0004] In particular, in recent years, with the miniaturization and multifunctionalization of electronic products, chip components also tend to be miniaturized and highly functionalized. Therefore, the thinning of the external electrodes of ceramic electronic components has been promoted, and there is a risk that the problem of deterioration of heat resistance and the like due to the entry of the plating solution becomes more prominent.

[0005] For this reason, there is a demand for the development of a highly reliable ceramic electronic component that prevents the plating solution from entering the underlayer electrode layer in the plating process and has excellent heat resistance and moisture resistance.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a highly reliable ceramic electronic component that is excellent in heat resistance and moisture resistance by preventing the immersion of a plating solution into a base electrode layer in a plating process for forming an external electrode.

Means for Solving the Problems

[0008] As a result of investigations by the present inventors to solve the above problems, a SiO2-BaO-B2O3-CaO-based glass is incorporated into the base electrode layer of the external electrode, and the surface of the SiO2-BaO-B2O3-CaO-based glass exposed on the surface of the base electrode layer is covered with a protective layer containing at least one element selected from the group consisting of P, S, C, Si, Ba, F, N, Al, Sr, and B, thereby finding that the immersion of the plating solution into the base electrode layer can be prevented, and the present invention has been completed.

[0009] That is, the present invention is a ceramic electronic component including a ceramic element body incorporating an internal electrode layer and an external electrode disposed on the surface of the ceramic element body and electrically connected to the internal electrode layer, wherein the external electrode includes a base electrode layer containing a SiO2-BaO-B2O3-CaO-based glass, a protective layer containing at least one element selected from the group consisting of P, S, C, Si, Ba, F, N, Al, Sr, and B, which covers the surface of the SiO2-BaO-B2O3-CaO-based glass exposed on the surface of the base electrode layer, and a Ni plating layer covering the base electrode layer and the protective layer, and is characterized by comprising the above.

[0010] Furthermore, the present invention is a ceramic electronic component characterized in that the protective layer contains a P element.

[0011] Furthermore, the present invention is a ceramic electronic component characterized in that the thickness of the protective layer is 1 nm or more and 100 nm or less.

[0012] Furthermore, the present invention is a ceramic electronic component characterized in that the thickness of the thinnest part of the base electrode layer is 0.1 μm or more and 5 μm or less.

[0013] Furthermore, the present invention is a ceramic electronic component characterized in that the thickness of the dielectric layer is 0.3 μm or more and 0.45 μm or less.

Effect of the Invention

[0014] According to the present invention, in the plating process for forming the external electrode, it is possible to prevent the plating solution from entering the base electrode layer, and to provide a highly reliable ceramic electronic component with excellent heat resistance and moisture resistance.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0016] Hereinafter, a ceramic electronic component according to an embodiment of the present invention will be described. FIG. 1 is an external view of a ceramic electronic component 1. FIG. 2 is a conceptual diagram of a cross section along the line I-I of the ceramic electronic component 1 shown in FIG. 1.

[0017] (Ceramic Electronic Component) The ceramic electronic component 1 is an electronic component in which an external electrode that conducts with the internal electrode layer is provided on the surface of a ceramic body incorporating an internal electrode layer, and is incorporated into an electronic circuit such as a capacitor, an inductor, a varistor, etc., and is widely used. Hereinafter, as an embodiment of the ceramic electronic component, a multilayer ceramic capacitor 1a will be described in detail as an example.

[0018] (Multilayer Ceramic Capacitor) The multilayer ceramic capacitor 1a is a ceramic electronic component having a substantially rectangular parallelepiped shape, including a laminate 2 and a pair of external electrodes 3 provided at both ends of the laminate 2. The laminate 2 includes an inner layer portion 9 in which a plurality of dielectric layers 7 and a plurality of internal electrode layers 8 are alternately laminated.

[0019] In the following description, as terms representing the orientation of the multilayer ceramic capacitor 1a, the direction in which the pair of external electrodes 3 are provided in the multilayer ceramic capacitor 1a is defined as the length direction L. The direction in which the dielectric layers 7 and the internal electrode layers 8 are laminated is defined as the lamination direction T. The direction intersecting both the length direction L and the lamination direction T is defined as the width direction W. FIG. 1 shows an XYZ orthogonal coordinate system. In the embodiment, the width direction W is orthogonal to both the length direction L and the lamination direction T, but is not necessarily in an orthogonal relationship with each other and may be in an intersecting relationship with each other.

[0020] Also, on the six outer surfaces of the laminate 2, a pair of outer surfaces facing each other in the lamination direction T are defined as a first main surface A1 and a second main surface A2, a pair of outer surfaces facing each other in the width direction W are defined as a first side surface B1 and a second side surface B2, and a pair of outer surfaces facing each other in the length direction L are defined as a first end surface C1 and a second end surface C2. Note that the multilayer ceramic capacitor 1a of the embodiment is often used with the second main surface A2 side being the mounting direction and the first main surface A1 being on the upper side.

[0021] When there is no need to particularly distinguish and describe the first main surface A1 and the second main surface A2, they are collectively referred to as the main surface A. When there is no need to particularly distinguish and describe the first side surface B1 and the second side surface B2, they are collectively referred to as the side surface B. When there is no need to particularly distinguish and describe the first end surface C1 and the second end surface C2, they are collectively referred to as the end surface C for description.

[0022] In ceramic electronic components such as multilayer ceramic capacitors, each element listed as a component to be blended may be in any form such as a single substance, a compound, a metal, an alloy, a solid solution, etc., as long as the specified element is blended at a predetermined site.

[0023] (Multilayer body) The multilayer body 2 includes an inner layer portion 9 and outer layer portions 10 that are arranged in the stacking direction so as to sandwich the inner layer portion and form a first main surface A1 and a second main surface A2.

[0024] (Inner layer portion) The inner layer portion 9 has a plurality of dielectric layers 7 and a plurality of internal electrode layers 8 stacked thereon. The inner layer portion includes 5 or more and 100 or less dielectric layers and internal electrode layers, respectively.

[0025] (Outer layer portion) The outer layer portions 10 are arranged so as to sandwich the inner layer portion 9 in the stacking direction T and form a first main surface A1 and a second main surface A2. The outer layer portions 10 can use the same ceramic material as the dielectric layers 7 of the inner layer portion 9.

[0026] (Dielectric layer) The dielectric layer 7 can be obtained by sintering a ceramic green sheet formed into a sheet shape from a slurry in which a binder, additives such as a plasticizer and a dispersant, and an organic solvent are added to a mixture obtained by adding and mixing ceramic powder, glass particles, and, if necessary, a sintering aid. As the ceramic powder, for example, a ceramic material mainly composed of barium titanate (BaTiO3) can be used. Further, those obtained by adding sub-components such as Mn compounds, Fe compounds, Cr compounds, Co compounds, and Ni compounds to this main component may also be used.

[0027] The thickness of the dielectric layer 7 in the stacking direction T is preferably 0.3 μm or more and 0.45 μm or less. Thereby, while maintaining the capacitance and the dielectric breakdown strength and the high-temperature load life, the multilayer ceramic capacitor can be miniaturized by thinning.

[0028] (Internal electrode layer) The plurality of internal electrode layers 8 consists of a first internal electrode layer 8A and a second internal electrode layer 8B. The first internal electrode layer 8A is exposed on the first end face C1 and is connected to the first external electrode 3A. Also, the second internal electrode layer 8B is exposed on the second end face C2 and is connected to the second external electrode 3B. The first internal electrode layer 8A and the second internal electrode layer 8B are usually alternately arranged in the stacking direction T with a dielectric layer in between.

[0029] The internal electrode layer 8 is formed by applying an internal electrode paste on the surface of a ceramic green sheet constituting the dielectric layer and integrally firing it together with the dielectric layer. The internal electrode layer is not particularly limited, but the thickness in the stacking direction T can be set to 0.2 μm or more and 2.0 μm or less. As the material of the internal electrode layer, any metal such as Ni, Cu, Ag, Pd, Ti, Cr, and Au, or an alloy combining any of these can be used.

[0030] (External electrode) The external electrode 3 includes a first external electrode 3A provided on the first end face C1 of the laminate 2 and a second external electrode 3B provided on the second end face C2 of the laminate 2. The external electrode 3 can be obtained by applying a conductive paste on the entire both end faces C of the laminate and a part of both main faces A and both side faces B and baking to form a base electrode layer, and then forming a plating layer on the base electrode layer. When there is no need to particularly distinguish between the first external electrode 3A and the second external electrode 3B for explanation, they are collectively described as the external electrode 3.

[0031] (Base electrode layer) The underlying electrode layer 4 is formed by applying and baking a conductive paste containing a conductive metal and glass. The underlying electrode layer can be formed by the co-firing method that simultaneously fires with the laminate or the post-firing method that applies and bakes the conductive paste to the fired laminate. It is preferable that the thickness of the thinnest part of the underlying electrode layer in the length direction L is 0.1 μm or more and 5 μm or less. This is because if the thickness of the thinnest part is less than 0.1 μm, it is difficult to form a uniform underlying electrode layer in mass production. On the other hand, if it exceeds 5 μm, the external electrode becomes large, making it difficult to miniaturize the ceramic electronic component. Note that the thinnest part of the underlying electrode layer refers to the part that shows the smallest numerical value in the thickness in the length direction L of the underlying electrode layer 4 covering the end face C of the laminate 2.

[0032] As the conductive metal contained in the conductive paste, for example, at least one metal selected from the group consisting of Cu, Ni, Ag, Pd, Ag-Pd alloy, and Au, or an alloy combining any of these can be used.

[0033] The conductive paste contains SiO2-BaO-B2O3-CaO-based glass, and by baking the conductive paste, an underlying electrode layer 4 in which a part of the SiO2-BaO-B2O3-CaO-based glass 4b appears on the surface can be formed. The SiO2-BaO-B2O3-CaO-based glass easily reacts with P, S, C, Si, Ba, F, N, Al, and B, and a protective layer is easily formed.

[0034] (Protective layer) A protective layer 5 is formed so as to cover the surface of the SiO2-BaO-B2O3-CaO-based glass 4b exposed on the surface of the underlying electrode layer 4. The protective layer contains at least one element selected from the group consisting of P, S, C, Si, Ba, F, N, Al, and B. In particular, it is preferably contained P and B. The protective layer containing P or B is formed as a film by replacing the SiO2-BaO-B2O3-CaO-based glass by immersing the laminate on which the underlying electrode layer is formed in an aqueous phosphoric acid solution or an aqueous boric acid solution, respectively.

[0035] By covering the surface of the SiO2-BaO-B2O3-CaO-based glass 4b exposed on the surface of the base electrode layer 4 with the protective layer 5, erosion of the SiO2-BaO-B2O3-CaO-based glass by the plating solution can be prevented, and it becomes possible to prevent the generation of pores in the base electrode layer and the degradation of heat resistance and moisture resistance accompanying the intrusion of the plating solution.

[0036] If the thickness of the protective layer in the length direction L is less than 1 nm, the SiO2-BaO-B2O3-CaO-based glass cannot be reliably protected. On the other hand, if it exceeds 100 nm, the external electrode becomes large, making it difficult to miniaturize the ceramic electronic component. Therefore, it is preferably set to 1 nm or more and 100 nm or less.

[0037] (Plating layer) A Ni plating layer 6a is formed so as to cover the surfaces of the base electrode layer 4 and the protective layer 5. The Ni plating layer can be formed by electrolytic plating. Also, an Sn plating layer 6b can be formed on the surface of the Ni plating layer 6a by electrolytic plating to form a two-layer structure. The plating layer can prevent the solder used when mounting the multilayer ceramic capacitor from eroding the base electrode layer.

[0038] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to this, and various modifications are possible. Further, the present invention is not limited to multilayer ceramic capacitors and can be widely used for ceramic electronic components.

Explanation of reference numerals

[0039] A Main surface A1 First main surface A2 Second main surface B Side surface B1 First side surface B2 Second side surface C End face C1 First end face C2 Second end face 1 Ceramic electronic component 1a Multilayer ceramic capacitor 2 Laminate 3 External electrode 3A First external electrode 3B Second external electrode 4 Underlying electrode layer 4a Conductive metal 4b SiO2-BaO-B2O3-CaO-based glass 5 Protective layer 6 Plating layer 6a Ni plating layer 6b Sn plating layer 7 Dielectric layer 8 Internal electrode layer 8A First internal electrode layer 8B Second internal electrode layer 9 Inner layer part 10 Outer layer part

Claims

1. A ceramic electronic component comprising a ceramic element body incorporating an internal electrode layer, and an external electrode disposed on the surface of the ceramic element body and electrically connected to the internal electrode layer, The external electrode is SiO ２ -BaO-B ２ O ３ -CaO-based glass-containing base electrode layer, and The SiO exposed on the surface of the underlying electrode layer ２ -BaO-B ２ O ３ A protective layer covering the surface of the -CaO-based glass and containing at least one element selected from the group consisting of P, S, C, Ba, F, N, Al, and Sr a Ni plating layer covering the base electrode layer and the protective layer, characterized in that it comprises the above.

2. The ceramic electronic component according to Claim 1, wherein the protective layer contains P.

3. The ceramic electronic component according to Claim 1 or 2, wherein the thickness of the protective layer is 1 nm or more and 100 nm or less.

4. The ceramic electronic component according to Claim 1 or 2, wherein the thickness of the thinnest part of the base electrode layer is 0.1 μm or more and 5 μm or less.

5. The ceramic electronic component according to Claim 1 or 2, wherein the thickness of the dielectric layer is 0.3 μm or more and 0.45 μm or less.

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