Capacitor with conductive resin electrode layer, method for manufacturing the same, and inspection method

Abstract

The objective is to provide a multilayer ceramic capacitor that ensures the reliability of electronic component mounting and reliable formation of the plating layer on the terminal electrodes of electronic components, as well as a method for manufacturing and inspecting the same. [Solution] A multilayer ceramic capacitor 1000 comprises a laminate 1300 including a dielectric 1100 and internal electrodes 1200 (internal electrodes 1210, internal electrodes 1220), and external electrodes 1400 exposed on the outer surface of the laminate, wherein the external electrodes 1400 comprises at least a base electrode layer 1410, a conductive resin electrode layer 1420 containing a fluorescent substance, and a plated electrode layer 1430. By providing a conductive resin electrode layer 1420 between the base electrode layer and the plated electrode layer instead of a configuration in which a plated layer is applied on top of copper baked electrodes, the mechanical strength and durability of the multilayer ceramic capacitor are improved, in particular flexibility is improved, and unexpected cracks, chips, and breaks are suppressed.

Description

TECHNICAL FIELD

[0001] The present invention relates to a ceramic capacitor that has higher quality and can improve product yield, and particularly relates to a multilayer ceramic capacitor, as well as a manufacturing method and an inspection method thereof.

BACKGROUND ART

[0002] Various ceramic capacitors, typified by multilayer ceramic capacitors, are a type of capacitor that uses a ceramic material as an insulator / dielectric, and are used in various electronic circuits as electronic components that temporarily store electrical energy. Ceramic capacitors are particularly compact, inexpensive, and highly durable, and since ceramic materials have high insulating properties, they are also excellent in heat resistance and moisture resistance.

[0003] In addition, they have a wide capacitance range, can provide capacitances from very small values (on the order of picofarads) to relatively large values, are small in size, low-cost, compact and lightweight, and have low manufacturing costs, enabling low-cost mass production, so they are used in a wide range of applications. Furthermore, ceramic capacitors are suitable for processing high-frequency signals, and can also be used in wireless communication devices and the like.

[0004] For example, Patent Document 1 below aims to provide a multilayer ceramic electronic component that allows the orientation of internal electrodes to be easily determined, and a multilayer ceramic capacitor as an example of the multilayer ceramic electronic component includes a laminate having a plurality of stacked ceramic layers and first and second internal electrodes formed along the interfaces between the ceramic layers, wherein external electrodes are formed on the outer surface of the laminate, and an invention is disclosed in which a phosphor is disposed on a part of the outer surface of the laminate where no external electrode is formed.

[0005] Furthermore, Patent Document 2 discloses a conductive paste that is advantageous for forming an external electrode mainly composed of copper on the outer surface of a laminate having an internal conductive film mainly composed of nickel, and which can prevent the internal conductive film from thickening due to excessive diffusion of copper contained in the external electrode into the internal conductive film, thereby preventing cracks from occurring in the laminate. The invention provides a conductive paste containing copper powder, iron oxide powder, glass powder, and an organic vehicle, wherein the iron oxide powder is contained in an amount of 3 to 40 volume percent relative to the total volume of the copper powder and iron oxide powder, and the glass powder is contained in an amount of 10 to 25 volume percent relative to the total volume of the copper powder, iron oxide powder, and glass powder.

[0006] Furthermore, paragraph 2 of the said patent document

[0054] states, "The 'density' was evaluated by vacuum impregnating each sample of the multilayer ceramic capacitor with a fluorescent liquid, then electrolytically stripping the tin-plated film, nickel-plated film, and copper-based external electrodes formed on the multilayer ceramic capacitor, and observing the fluorescent liquid that reached the surface of the laminate. If the fluorescent liquid was observed, the density was poor and was indicated with "×" in Table 2, and if the fluorescent liquid was not observed, the density was good and was indicated with "○" in Table 2."

[0007] The description in paragraph 2 of Patent Document

[0054] describes a technical concept for destructive testing of a ceramic capacitor, in which a fluorescent liquid is vacuum-impregnated into the ceramic capacitor, the external electrodes are electrolytically peeled off, and the fluorescent liquid that has been impregnated into and reached the surface of the laminate is observed. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2014 / 147898 [Patent Document 2] International Publication No. 2005 / 055257 [Overview of the project] [Problems that the invention aims to solve]

[0009] In the process of forming a conductive resin electrode layer, the resin may be formed unintentionally to be too thick or too thin, or the resin components and conductive frit may not be uniformly distributed, resulting in uneven distribution of components. Such non-uniform areas do not possess the desired conductivity characteristics locally, and differences in conductivity characteristics compared to surrounding areas can adversely affect the subsequent formation of metal electrodes and conductive electrode layers, such as plated electrodes.

[0010] For example, if the resin component is unevenly distributed, resulting in areas with insufficient conductive frit, then during the subsequent plating process, the plating layer will not adhere to those areas, leading to defects in plating adhesion. If the plating layer does not adhere, there is a concern that the soldering in those areas will be poor, which in turn can lead to manufacturing defects and a decrease in product reliability.

[0011] The present invention has been made in view of the above-mentioned problems, and aims to provide a capacitor, a method for manufacturing the same, and an inspection method, which can improve reliability and yield and throughput by early detection of the presence and degree of uneven distribution or irregularity of resin components and conductive frit in the conductive resin electrode layer. [Means for solving the problem]

[0012] The present invention relates to a capacitor comprising a laminate including a dielectric and internal electrodes, and external electrodes exposed on the outer surface of the laminate, wherein the external electrodes comprise at least a base electrode layer, a conductive resin electrode layer containing a fluorescent substance, and a plated electrode layer.

[0013] The capacitor of the present invention is preferably characterized in that the resin component on the plated electrode layer side of the conductive resin electrode layer is greater than the resin component on the base electrode layer side, and the resin component is unevenly distributed on the plated electrode layer side in the conductive resin electrode layer.

[0014] The capacitor of the present invention is more preferably characterized in that the dielectric is ceramic.

[0015] The present invention relates to a method for manufacturing a capacitor comprising a laminate including a dielectric and internal electrodes, and external electrodes exposed on the outer surface of the laminate, characterized in that the method includes the step of sequentially forming at least a base electrode layer, a conductive resin electrode layer containing a fluorescent substance, and a plated electrode layer as the external electrodes.

[0016] The method for manufacturing a capacitor of the present invention is preferably characterized by having a step of performing an appearance inspection of the conductive resin electrode layer by irradiating it with light that causes a fluorescent substance to emit light, after the step of forming the conductive resin electrode layer and before the step of forming the plated electrode layer.

[0017] The method for manufacturing a capacitor of the present invention is preferably characterized by having a step of irradiating light that causes a fluorescent substance to emit light after the step of forming a conductive resin electrode layer and after the step of forming a plated electrode layer, to perform a visual inspection to determine whether or not there is an exposed conductive resin electrode layer where the plated electrode layer has not adhered.

[0018] The capacitor inspection method of the present invention described above is characterized by irradiating the conductive resin electrode layer with light that causes a fluorescent substance to emit light, and then sorting out defective products.

[0019] Preferably, the capacitor inspection method of the present invention described above is characterized in that the sorting inspection of defective products is based on at least one of the following: the presence or absence of light emission in the conductive resin electrode layer, the presence or absence of uneven distribution of light emission, the range of light emission, and the intensity of light emission.

[0020] The present invention is characterized by detecting the presence or absence of unattached portions of the electrode or a structure that may have unattached portions by causing the fluorescent substance contained in the conductive resin to emit light in a structure comprising a conductive resin mixed with a fluorescent substance and an electrode disposed on at least a portion of the conductive resin. [Effects of the Invention]

[0021] It is possible to provide a capacitor, and its manufacturing method, inspection method and the like, which can grasp the presence / absence and degree of uneven distribution and irregularity of the resin component and conductive frit in the conductive resin electrode layer at an early stage, further improve reliability, and enhance yield and throughput. It is also possible to provide a capacitor and a manufacturing method capable of ensuring mounting reliability of electronic components and reliably forming a plating layer on the terminal electrode of an electronic component. [Brief Description of the Drawings]

[0022] [Figure 1] It is a diagram illustrating the configuration of a multilayer ceramic capacitor. [Figure 2] It is a perspective view illustrating the external appearance of the multilayer ceramic capacitor according to the first embodiment. [Figure 3] It is an A-A' cross-sectional view of the multilayer ceramic capacitor of FIG. 2. [Figure 4] It is a diagram for explaining a microscopic photograph. [Mode for Carrying Out the Invention]

[0023] (First Embodiment: Typical Configuration of Ceramic Capacitor) FIG. 1 illustrates the cross-sectional internal configuration of a multilayer ceramic capacitor 1000. In the multilayer ceramic capacitor 1000, for example, internal electrodes 1200 (internal electrodes 1210 and 1220 are collectively referred to as internal electrodes 1200) sandwiched between sheet-shaped dielectrics 1100 are formed, alternately laminated, and sintered to form a laminated body 1300.

[0024] The internal electrodes 1200 are exposed at one end of the laminated body 1300. Further, external electrodes 1400 are formed at both ends of the laminated body 1300, and are connected to the internal electrodes 1210 or the internal electrodes 1220. Note that FIG. 1 illustrates and describes the structure around the end portion including one external electrode 1400 of the laminated body 1300.

[0025] At the other end of the laminate 1300 (not shown), an internal electrode 1220 is exposed and connected to the other external electrode, which has a similar structure to the external electrode 1400. Furthermore, as shown in Figure 1, the external electrode 1400 can have a three-layer structure. For example, a copper electrode 1410 is formed on the exposed portion of the internal electrode 1210 exposed at both ends of the laminate 1300, and then an external electrode 1400 having a conductive resin electrode layer 1420 and a plated electrode layer 1430 is formed on top of that in sequence.

[0026] In mounting such a multilayer ceramic capacitor 1000 onto a substrate, the plating layer of the external electrode 1400 and the substrate are generally electrically connected by solder. By providing a conductive resin electrode layer 1420 between the copper-plated electrode and the plating layer, instead of the conventional configuration in which a plating layer is applied on top of a copper-plated electrode, the mechanical strength and durability of the multilayer ceramic capacitor 1000 are improved, and in particular, the flexibility is improved, which makes it possible to suppress unexpected cracks, chips, and breaks. The plating electrode layer 1430 may also be a two-layer structure in which nickel (Ni) and tin (Sn) are arranged in order.

[0027] The conductive resin electrode layer 1420 is said to have good overall conductivity by mixing conductive frit (metal particles or metal powder, etc.) into the resin paste. However, while conductive frit is a particulate solid substance, the resin paste before curing is often gel-like, slime-like, or semi-liquid. Even after a sufficient mixing process, unexpected component imbalances, i.e., uneven distribution of conductive frit or resin, may occur. Generally, conductive frit does not dissolve in the resin paste. Such metal particles may include flattened particles, spherical particles, and flaky particles, and the particle shape is arbitrary. Specifically, the particle size of the conductive frit may be, for example, around 10 μm to 50 nm.

[0028] The thermosetting resin contained in the conductive resin electrode layer 1420 is not particularly limited, but for example, phenolic resin, acrylic resin, silicone resin, epoxy resin, polyimide resin, etc. can be used. The conductive resin layer 1420 relieves the stress on the external electrode 1400, and the conductive frit contained in the conductive resin layer 1420 ensures good conductivity and reliable electrical connection.

[0029] In this embodiment, the conductive resin electrode layer 1420 contains a fluorescent substance, and it is possible to determine whether or not the resin is unevenly distributed by fluorescence emission (also called luminescence) caused by irradiation with a UV lamp or the like, and if so, where it is located.

[0030] Therefore, for example, after the formation of the conductive resin electrode layer 1420, by irradiating it with a UV lamp or the like to identify the presence and location of uneven distribution of the resin, it is possible to remove the excess resin from those areas by cutting or polishing, thereby eliminating the uneven distribution of the resin and ensuring good overall conductivity. The fluorescent substance does not dissolve or synthesize with conductive frit such as metal particles or metal powder, but dissolves in the resin component. Furthermore, by visual inspection of the conductive resin electrode layer 1420, defective products can be sorted based on the presence or absence of fluorescence emission, the presence or absence of uneven emission (uneven emission), the range of emission, and the intensity of emission.

[0031] Furthermore, in the process of forming the conductive resin electrode layer 1420, even after applying the conductive resin by dip or the like, areas with resin segregation or fewer conductive frits can be identified by irradiation with a UV lamp or the like, even before the solvent has completely dried or cured. However, since the solvent may flow during the drying and curing process, altering the arrangement of resin components and conductive frits, it is preferable to confirm the fluorescence emission in the solidified state after drying or curing. Also, "after the formation of the conductive resin electrode layer" refers to the state in which the applied conductive paste has gelled or solidified.

[0032] This process of identifying and resolving resin uneven distribution can be performed at any time after the formation of the conductive resin electrode layer 1420 and before the soldering and mounting of the multilayer ceramic capacitor 1000 to the substrate. Specifically, this process of identifying and resolving resin uneven distribution can be performed after the formation of the conductive resin electrode layer 1420 and before the formation of the plated electrode layer 1430.

[0033] Furthermore, after forming the conductive resin electrode layer 1420 and then the plated electrode layer 1430, the process of identifying and resolving such uneven distribution of resin can be performed. In areas where there is an excessive amount of resin, it becomes difficult for the plated electrode layer 1430, especially the nickel (Ni) layer 1431, to adhere. Therefore, even after the formation of the plated electrode layer 1430, there are many cases where the areas of the conductive resin electrode layer 1420 with excessive resin distribution remain unplated and exposed. Consequently, it is possible to identify and define such areas by fluorescence emission caused by irradiation with a UV lamp or the like.

[0034] Fluorescent substances are a general term for materials that absorb light of a specific wavelength and emit light of a different wavelength, and are also commonly called phosphors. Furthermore, fluorescent substances are compounds that react to light and have a unique electron configuration, resulting in characteristic absorption and emission spectra, and the wavelengths emitted by fluorescent substances are often lower in energy than the light they absorb.

[0035] Fluorescent substances are known to exist across a wide wavelength range, from ultraviolet to near-infrared. Known applications include their widespread use in fluorescent lamps, fluorescent paints, cathode ray tubes, luminescent paints, and discharge lamps, and they are also known to be useful as detection reagents in cell and tissue research. Specific examples of fluorescent substances include fluorescein, eosin, merocyanine, perylene, acridine, luciferin, pyranine, stilbene, and rhodamine.

[0036] Figures 2 and 3 illustrate the configuration of a multilayer ceramic capacitor 1000 according to the first embodiment. Figure 2 is a perspective view illustrating the external appearance of the multilayer ceramic capacitor 1000. Note that Figure 2 is just one example of the external appearance, and the multilayer ceramic capacitor 1000 according to the present invention is not limited to the external shape shown in Figure 2. That is, in Figure 2, the multilayer ceramic capacitor 1000 is illustrated as a rectangular parallelepiped.

[0037] However, the multilayer ceramic capacitor 1000 may be a cube or other hexahedron. Furthermore, the multilayer ceramic capacitor 1000 may have chamfered edges. Also, the multilayer ceramic capacitor 1000 may have rounded edges. Furthermore, the multilayer ceramic capacitor 1000 may have a shape where the six faces of a rectangular prism or similar protrude outwards in a rounded manner. The multilayer ceramic capacitor 1000 is preferably 7 mm or less, more preferably 5 mm or less, and most preferably 3 mm or less. If the multilayer ceramic capacitor 1000 is too large, there is a greater concern that the substrate may bend during or after mounting, leading to cracking or chipping.

[0038] As shown in Figure 2, electrodes 1400(1) and 1400(2) are formed on the first and second end faces of the multilayer ceramic capacitor 1000, respectively. When referring to the external electrodes 1400(1) and 1400(2) collectively, they are simply referred to as the external electrode 1400. Here, the configuration of the AA' cross-section of the multilayer ceramic capacitor 1000 shown in Figure 2 will be explained using Figure 3(a).

[0039] Figure 3(a) is a cross-sectional view AA' of the multilayer ceramic capacitor 1000 shown in Figure 2. As shown in Figure 3(a), the multilayer ceramic capacitor 1000 comprises a laminate 1300 including a ceramic dielectric 1100, a first internal electrode 1210, and a second internal electrode 1220, a first external electrode 1400(1) on the first end face side of the laminate 1300, and a second external electrode 1400(2) on the second end face side. The ceramic dielectric 1100 is also referred to as the ceramic element.

[0040] Furthermore, the laminate 1300 is sometimes referred to as a capacitor element. In the laminate 1300, the ceramic dielectric 1100 and the first internal electrode 1210 and the second internal electrode 1220 form a layered structure. That is, it has a structure in which the first internal electrode 1210 and the second internal electrode 1220 are alternately stacked with the dielectric 1100 in between. Note that the first internal electrode 1210 and the second internal electrode 1220 are sometimes simply referred to as the internal electrode 1200.

[0041] The external electrode 1400(1) covers at least the entire first end face of the layer structure of the laminate 1300 and is electrically connected to the first internal electrode 1210. The external electrode 1400(2) covers at least the entire second end face of the laminate 1300 opposite to the first end face and is electrically connected to the second internal electrode 1220.

[0042] For example, a BaTiO3 (barium titanate) ceramic is used as the dielectric 1100 of this laminate 1300. As another dielectric material, a (Ba,Ca,Sr)(Ti,Zr)O3 ceramic may be used, in which some of the Ba (barium) in the BaTiO3 ceramic is replaced with Ca or Sr, or some of the Ti (titanium) is replaced with Zr.

[0043] Furthermore, dielectric materials 1100 may be used in which minor components such as Mn compounds, Fe compounds, Cr compounds, Co compounds, and Ni compounds are added to the main component. Also, the thickness of the ceramic layer of the dielectric material 1100, i.e., the ceramic body, can be, for example, 0.5 μm to 10 μm.

[0044] While all ceramics are strong, their high hardness means they are less flexible. Therefore, when subjected to bending stress or localized compressive force, the ceramic itself does not have a particularly high ability to withstand such stress.

[0045] The internal electrode 1200 may be made of noble metals such as Ag, Ag-Pd, Pd, and Au, or alloys thereof, as well as base metals such as Ni, Cu, and Al. Alternatively, an alloy may be appropriately selected from these noble and base metals. The external electrode 1400 may be made of a conductive metal such as Cu or Ag, and the plated electrode layer 1430 is preferably made of a solderable metal. If the plated electrode layer 1430 is made of multiple plating layers, it is preferable to use a solderable metal for the outermost plating layer. The thickness of each internal electrode 1200 can be, for example, 0.2 μm to 2 μm, but the thickness of the internal electrode 1200 is not particularly limited.

[0046] Figure 3(b) is a diagram illustrating the general configuration of the external electrode 1400(2). The external electrode 1400(2) is provided with, in order from the inside out, a copper (Cu) electrode layer 1410, a conductive resin electrode layer 1420, a nickel (Ni) layer 1431, and a tin (Sn) layer 1432. That is, the nickel (Ni) layer 1431 and the tin (Sn) layer 1432 are plated electrode layers 1430. The copper (Cu) electrode layer 1410 can be a baked electrode. The external electrode 1400(1) can also have the same configuration as the external electrode 1400(2).

[0047] The nickel (Ni) layer 1431 can be formed by electroplating the surface of the conductive resin electrode layer 1420 with Ni, and its thickness may be, for example, 1 μm to 5 μm. The nickel (Ni) layer 1431 also functions as a barrier layer.

[0048] Furthermore, the tin (Sn) layer 1432 can be formed by electroplating the surface of the nickel (Ni) layer 1431 with Sn, and its thickness may be, for example, 1 μm to 5 μm. The tin (Sn) layer 1432 also functions to improve soldering characteristics. The plated electrode layer 1430 may be formed by electroplating or electroless plating, or the metal electrode layer may be formed by, for example, vapor deposition or sputtering.

[0049] As shown in Figure 1, the external electrode 1400 has a three-layer hierarchical structure. Specifically, the external electrode 1400 has a bottom copper electrode layer 1410 that serves as the base, a conductive resin electrode layer 1420 above the copper electrode layer 1410, and a plated electrode layer 1430. The copper electrode layer 1410 can be described as the first base electrode connected to the first internal electrode 1210. As shown in Figure 1, the copper electrode layer 1410 covers the first end face to form the first base electrode and extends to cover the ends of the upper and bottom surfaces of the ceramic dielectric 1100 that form the four sides sandwiched between the first and second end faces.

[0050] The copper electrode layer 1410 is formed in layers near the first or second end face, which is the cross-section of the layered structure of the laminate 1300. Although not shown in Figure 1, the copper electrode layer 1410 extends to cover the top and bottom surfaces of the laminate 1300, as well as the ends of two opposing sides. The copper electrode layer 1410 can be made of a sintered metal layer, and its thickness may be, for example, 10 μm to 30 μm.

[0051] Furthermore, the conductive resin electrode layer 1420, as the first conductive resin electrode, covers the copper electrode layer 1410, which is the first base electrode, and extends to cover a portion of the ceramic dielectric 1100 that forms the four sides sandwiched between the first and second end faces of the laminate 1300.

[0052] Thus, the conductive resin electrode layer 1420 is formed in layers so as to completely or partially cover the copper electrode layer 1410. Furthermore, the plated electrode layer 1430 is provided so as to cover the conductive resin electrode layer 1420.

[0053] Furthermore, the structure and configuration of the external electrode 1400(2) are identical to those of the external electrode 1400(1). That is, the external electrode 1400(2) can comprise a bottom copper electrode layer 1410 as the base, a conductive resin electrode layer 1420 above the copper electrode layer 1410, and a plated electrode layer 1430.

[0054] Furthermore, the conductive resin electrode layer 1420 also extends to the second end face side, acting as a second conductive resin electrode, covering the copper electrode layer 1410 which is the second base electrode, and covering a portion of the four sides sandwiched between the first and second end faces of the laminate 1300.

[0055] Furthermore, it is preferable that the resin component on the plated electrode layer 1430 side of the conductive resin electrode layer 1420 is greater than the resin component on the base electrode (typically a Cu electrode) side (i.e., the resin is more unevenly distributed on the plated electrode layer 1430 side than on the base electrode side). After forming the conductive resin electrode layer 1420 by dipping or coating, the solvent will evaporate during the drying process. Due to the evaporation of the solvent, the resin, which has relatively high fluidity, will flow to the surface side, raising concerns about uneven distribution. When such uneven distribution of resin occurs, the resin containing the fluorescent agent will be unevenly distributed towards the surface side, allowing for efficient and accurate product inspection using fluorescence emission in the subsequent inspection stage to grasp the uneven distribution of resin. This enables the detection of defective products that could not be detected at that stage in the past to be detected at an earlier stage of the process, resulting in a reduction in the defective product ratio.

[0056] (Confirmation experiment and its results) To improve the mechanical strength (and flexibility) of ceramic capacitors, an external electrode structure is known in which a conductive resin electrode layer is formed on a Cu-baked electrode and then Ni / Sn plating is applied. The conductive resin electrode layer is formed by applying a paste, which is a mixture of conductive frit, resin, and organic solvent, to the end face of the element by dipping or coating, and then drying or curing the paste to form the electrode layer.

[0057] In this structure, a certain amount of resin is necessary to increase the flexibility of the resin electrode layer, but if the resin component is increased too much, the content ratio of conductive frit will decrease. Furthermore, there is a concern that areas with a high resin component may occur due to inappropriate thickness (especially if the resin electrode layer is excessively thick) or uneven shape during the process of forming the resin electrode layer.

[0058] Figure 4(a) shows a surface photograph of a multilayer ceramic element with uneven distribution of resin components, including both a normal resin electrode layer (A) and a region (B) containing a large amount of resin components. Figure 4(b) is a magnified view of the normal resin electrode layer (A), and Figure 4(c) is a magnified view of the surface of the unplated resin electrode layer in the region where the resin components are unevenly distributed (A). Figure 4(b) illustrates a typical example of a surface condition to which plating can be applied. The metal particles of the conductive frit are relatively densely distributed, resulting in good conductivity. On the other hand, Figure 4(c) shows the surface condition of the unplated region in Figure 4(a). Due to the excess resin component, the density of the metal particles of the conductive frit is low, resulting in insufficient conductivity. Therefore, even after plating, a defective area remains unplated in that region.

[0059] Areas with an excess of resin components have poor surface conductivity, making plating difficult. As a result, some areas with excess resin components remain unplated. These unplated areas cannot be soldered, negatively impacting the quality, performance, and function of the capacitor element.

[0060] One possible solution is to improve the accuracy of resin coating to more precisely control the thickness and shape of the resin. However, this method is considered unsuitable for mass production because it reduces product performance and throughput, and requires excessive time and effort.

[0061] Another possible method is to visually inspect the product after plating to identify any unplated areas. However, since the threshold for identification may not be clearly defined, this method may not always be accurate. In particular, if the frit in the resin electrode layer is silver-colored, such as silver metallic, it is difficult to distinguish it from the appearance of the plating, making identification even more challenging.

[0062] Therefore, in this experiment, a fluorescent agent that reacts to a UV lamp is added to the conductive resin paste in advance, and the resin electrode layer is coated, dried, and cured according to the conventional process. If areas with a high concentration of resin components occur as described above, these areas also contain a large amount of the fluorescent agent, and when irradiated with a UV lamp, they will reflect or emit fluorescence more brightly than areas with a high concentration of conductive frit.

[0063] Therefore, by performing visual inspection while irradiating with a UV lamp after the resin electrode layer formation process, it becomes possible to identify and remove potentially defective products that are unlikely to be plated before the plating process.

[0064] In this experiment, as an example, a commercially available fluorescent liquid was added to a resin electrode paste at a concentration of approximately 1 wt%, and the mixture was stirred to create a conductive resin paste containing the fluorescent material. Then, a 5.7 mm × 5.0 × 1.5 mm dummy fired body was used as a ceramic element and dipped or blotted into the conductive resin paste, after which it was dried and cured in a constant temperature bath.

[0065] Figure 4(d) shows the sample prepared above after being irradiated with white light in the visible light range for visual observation, and Figure 4(e) shows the sample after being irradiated with UV light to induce fluorescence and then observed. In both figures, the area enclosed by the dotted ellipse indicates the area where the resin component of the resin electrode layer is excessively concentrated and unevenly distributed. With white light irradiation, there is no difference between the area within and outside the dotted ellipse, and it is not possible to distinguish between the two. However, with fluorescence emission under UV light irradiation, the areas with excess resin, i.e., the areas enclosed by the dotted ellipse, can be clearly distinguished and recognized from other parts. The areas enclosed by the dotted ellipse glow brighter than the surrounding areas due to fluorescence emission. Furthermore, depending on the intensity, range, and emission characteristics of the fluorescence emission, it is possible to non-destructively determine the size and range of the excess resin and whether it is at an acceptable level or not. Therefore, in actual product manufacturing processes, it is possible to perform highly accurate defect detection in UV light visual inspection before and after the soldering process.

[0066] (Applicable products and manufacturing methods that utilize the present invention) The present invention can be applied not only to external electrodes of electronic components but also to circuit formation methods on substrates. For example, a conductive resin paste is applied to a substrate by inkjet or printing to form the base pattern. If sufficient conductivity and allowable current values ​​cannot be obtained by contact with conductive frit alone, a plating process is performed to plate the electrode pattern surface. In such cases, a certain amount of resin is required to ensure adhesion to the substrate, which raises concerns about poor conductivity due to incomplete plating caused by excessive or uneven distribution of resin.

[0067] Even in such cases, by mixing a fluorescent agent into the resin paste and performing a visual inspection by illuminating the resin paste with a UV lamp or the like after it has hardened but before the plating process, it is possible to identify and extract areas where the resin is unevenly distributed or product lot numbers that will result in poor plating adhesion during the subsequent plating process. This allows for the removal of the affected product from the production line or for taking countermeasures such as polishing the surface of the resin-unevenly distributed areas to remove the excess resin. Specifically, this method can also be applied to manufacturing methods in which an ink or paste, which is a mixture of resin and conductive frit in a solvent, is printed onto a substrate using inkjet or screen printing, and then metal is grown on the printed pattern during the plating process to form a circuit.

[0068] In other words, when a conductive resin containing a fluorescent agent is applied to a substrate by inkjet printing, the adhesion characteristics between the substrate and the resin are preferable when there is a certain amount of resin, as this allows for better and tighter adhesion at the interface. Next, when a plating layer is placed on top of the conductive resin, too much resin will lead to poor plating adhesion, but a good plating process can be achieved when there is a lot of conductive frit (i.e., relatively little resin).

[0069] Conductive resins are made by mixing conductive metal powders or metal particles, or other frits, into a resin. However, the two do not melt and become one; they are merely mixed together, and generally, they exhibit completely opposite properties in relation to other substances. For this reason, uniform properties are most desirable through the uniform mixing of the resin itself and the conductive frit. However, in reality, it is not uncommon to obtain a hardened conductive resin that is not uniform, with areas of excess resin or uneven distribution of frit.

[0070] In this invention, uneven distribution or excess of resin can be identified by a simple visual inspection based on UV irradiation, etc., so that products with uneven resin distribution can be excluded from the production line as defective products, or that only products with good properties that do not have uneven resin distribution can be selected and used without cost.

[0071] For example, when applying conductive resin to a flexible substrate, a certain amount of resin component improves adhesion to the substrate. Therefore, materials with a high resin content near the interface between the substrate and the conductive resin can be selected for good adhesion. Conversely, if there is little resin component and a high concentration of conductive frit near the interface between the substrate and the conductive resin, it can be judged as having poor adhesion to the substrate.

[0072] Furthermore, for example, when applying a plating layer on a conductive resin, a relatively low resin content improves adhesion characteristics with the plating layer. Therefore, samples with less resin near the interface between the plating layer and the conductive resin may be selected for good adhesion. Conversely, if there is little resin and a high concentration of conductive frit near the interface between the plating layer and the conductive resin, it can be judged that the adhesion to the plating layer is good. Moreover, by performing a visual inspection of fluorescence emission using UV light irradiation on the surface of the cured conductive resin before the plating layer is applied, it becomes possible to predict and detect in advance any adhesion defects in the plating layer.

[0073] (Manufacturing method) The following describes an example of a manufacturing method for a multilayer ceramic capacitor 1000 in order of steps. A ceramic dielectric sheet is formed as an example of a dielectric 1100, and internal electrodes 1200 are formed on its surface by coating or printing, and a ceramic dielectric layer is formed on top of it. Note that the internal electrodes 1200 are not limited to one per layer, but may be arranged in multiples. On top of this ceramic dielectric layer, internal electrodes 1200 are further formed by coating or printing so that they are laminated. In this case as well, one or more internal electrodes 1200 may be formed in multiples per layer.

[0074] Furthermore, a ceramic dielectric layer is formed on top of the internal electrode 1200. This lamination process is repeated until the number of layers (number of electrodes in the layer direction) corresponding to the required capacitance is reached, forming a laminated block. After cutting out the laminated body 1300 from the laminated block as a capacitor element chip, the laminated body 1300 can be fired. For example, the laminated body 1300 may be an element chip with one internal electrode 1200 in each layer, or it may be an element chip having multiple internal electrodes 1200 in each layer in the planar direction.

[0075] Then, a metal (copper) paste is applied to a pair of opposing end faces of the laminate 1300 and heat-treated to form copper electrodes 1410. Furthermore, a layer of conductive resin material is formed by coating or printing using a dip method or the like to form a conductive resin electrode layer 1420 (silver electrode layer) mixed with a fluorescent agent. Then, a plated electrode layer 1430 is formed sequentially using, for example, a nickel (Ni) layer 1431 and a tin (Sn) layer 1432.

[0076] According to the illustrated manufacturing method, the ends of the alternately arranged first internal electrodes 1210 can be exposed on the first end face side of the laminate 1300. In addition, the ends of the second internal electrodes 1220 can be exposed on the second end face side of the laminate 1300 (the side opposite the first end face).

[0077] Layers of copper electrodes 1410, which serve as base electrodes, are formed on the first and second end faces of the laminate 1300, respectively. A first internal electrode 1210 is connected to one of these copper electrodes 1410, and a second internal electrode 1220 is electrically connected to the other copper electrode 1410. A layer of conductive resin electrode layer 1420, which contains a fluorescent agent, is formed on top of each layer of copper electrode 1410. Furthermore, a plated electrode layer 1430 is formed on top of each layer of conductive resin electrode layer 1420.

[0078] In the manufacturing method of the multilayer ceramic capacitor 1000 of this embodiment, before forming the plated electrode layer 1430, a layer of conductive resin electrode layer 1420 containing a fluorescent agent is formed, and a visual inspection is performed to check the presence and degree of uneven distribution of the resin by irradiating it with a fluorescent lamp or the like to cause it to emit fluorescence. This makes it possible to improve throughput and prevent the occurrence of defective products by separating and removing products that may cause defects in the plated electrode layer 1430 due to excessive resin distribution. When the multilayer ceramic capacitor 1000 is mounted, for example, a heating process in a reflow oven may be performed. [Industrial applicability]

[0079] The present invention is suitable for various types of ceramic capacitors, such as multilayer ceramic capacitors, and various electronic components having a structure in which a metal layer is provided on a conductive resin by electrolytic plating or electroless plating, as well as for methods of manufacturing and inspecting the above-mentioned electronic components. [Explanation of Symbols]

[0080] 1000... Multilayer ceramic capacitor, 1100... Dielectric, 1200... Internal electrode, 1300... Laminate, 1400... External electrode.

Claims

1. A capacitor comprising a laminate including a dielectric and internal electrodes, and external electrodes exposed on the outer surface of the laminate, The external electrode comprises at least a base electrode layer, a conductive resin electrode layer containing a fluorescent substance, and a plated electrode layer. A capacitor characterized by the following features.

2. In the capacitor according to claim 1, The resin component on the plated electrode layer side of the conductive resin electrode layer is greater than the resin component on the underlayer electrode layer side. A capacitor characterized by the following features.

3. In the capacitor according to claim 1 or claim 2, The dielectric is ceramic. A capacitor characterized by the following features.

4. A method for manufacturing a capacitor comprising a laminate including a dielectric and internal electrodes, and external electrodes exposed on the outer surface of the laminate, The process of forming the external electrode includes, in order, at least a base electrode layer, a conductive resin electrode layer containing a fluorescent substance, and a plated electrode layer. A method for manufacturing a capacitor characterized by the following:

5. In the method for manufacturing a capacitor according to claim 4, The process includes a step of performing an appearance inspection of the conductive resin electrode layer by irradiating it with light that causes the fluorescent substance to emit light, after the step of forming the conductive resin electrode layer and before the step of forming the plated electrode layer. A method for manufacturing a capacitor characterized by the following:

6. In the method for manufacturing a capacitor according to claim 4, The process includes a step, after the step of forming the conductive resin electrode layer and after the step of forming the plated electrode layer, in which light that causes the fluorescent substance to emit light is irradiated to perform a visual inspection to determine whether or not there is any conductive resin electrode layer that is exposed due to the plated electrode layer not adhering to it. A method for manufacturing a capacitor characterized by the following:

7. In the capacitor inspection method according to claim 1 or claim 2, The conductive resin electrode layer is irradiated with light that causes the fluorescent substance to emit light, and defective products are sorted and inspected. A method for inspecting capacitors, characterized by the following features.

8. In the capacitor inspection method described in claim 7, The sorting inspection of the defective products is performed based on at least one of the following in the conductive resin electrode layer: presence or absence of light emission, presence or absence of uneven distribution of light emission, range of light emission, and intensity of light emission. A method for inspecting capacitors, characterized by the following features.

9. A structure comprising a conductive resin mixed with a fluorescent substance and an electrode disposed on at least a portion of the conductive resin is used to detect the presence or absence of unattached portions of the electrode, or the structure in which there are potential unattached portions, by causing the fluorescent substance contained in the conductive resin to emit light. A testing method characterized by the following features.

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