Patent Grant
12131862
The present invention relates to an electronic component having a terminal electrode.
As shown in Patent Document 1, an electronic component having a terminal electrode (may be referred to as “external electrode”) formed on an outer surface of an element body is known. In this electronic component, the terminal electrode is connected to an internal electrode or a leadout electrode such as a lead provided in the element body.
For example, as shown in Patent Document 1, this terminal electrode can be formed by applying firing type paste containing a metal powder and a glass component to the outer surface of the element body, and by subjecting this paste-applied part to a baking treatment at a temperature of approximately 700° C. or at a temperature equal to or higher than the temperature. However, in the case of forming the terminal electrode by performing the baking treatment at a high temperature as described above, a defect such as cracks may occur in the element body due to an influence of a thermal stress.
In addition, Patent Document 2 discloses a method of forming a terminal electrode by using thermosetting paste containing a metal powder and a thermosetting resin. In this case, when forming the terminal electrode, a heating treatment may be performed at a hardening temperature of the resin, and the baking treatment at the high temperature is not necessary. However, in the terminal electrode disclosed in Patent Document 2, problems arise in that joining strength to the leadout electrode cannot be sufficiently secured and contact resistance of a joining portion becomes high.
[Patent Document 1] JP 2013-045926 A
[Patent Document 2] JP H6-267784 A
The present invention has been made in view of above circumstances, and an object thereof is to provide an electronic component in which joining reliability of a terminal electrode is high and a terminal electrode has low resistance.
To accomplish the above object, the electronic component according to the present invention includes:
a leadout electrode portion provided on an outer surface of an element main body; and
a resin electrode layer formed at a part of the outer surface of the element main body and connected to the leadout electrode portion,
wherein the leadout electrode portion contains copper as a main component,
the resin electrode layer includes a conductor powder containing silver, and a resin, and
a diffusion layer containing copper oxide and silver is formed at an interface between the leadout electrode portion and the resin electrode layer.
In the electronic component according to the present invention, by having the above configuration, joining reliability between the leadout electrode portion and the terminal electrode (resin electrode layer) can be sufficiently secured. In addition, a reduction in resistance of the terminal electrode can be realized.
The thickness of the diffusion layer may be at least 30 nm or greater. In addition, the diffusion layer can be recognized as a region in which a concentration gradient of silver occurs from an outermost surface of the leadout electrode portion toward the resin electrode layer.
Preferably, the conductor powder of the resin electrode layer includes first particles having a particle size of a micrometer order, and second particles having a particle size of a nanometer order. Since the resin electrode layer has the above configuration, joining reliability of the terminal electrode is further improved, and a resistance of the terminal electrode can be further reduced.
Preferably, the first particles have a flat shape, and the second particles aggregate among the first particles.
Due to the above configuration, the second particles electrically connect among the first particles, and the resistance of the terminal electrode can be further reduced.
The diffusion layer may intermittently exist along the interface between the leadout electrode portion and the resin electrode layer.
Further, an oxidized film mainly containing copper oxide may be formed on a surface side of the leadout electrode portion. In this case, the diffusion layer is located between the oxidized film and the resin electrode layer. In the electronic component according to the present invention, even when the oxidized film exists on the surface side of the leadout electrode portion, the diffusion layer is formed between the leadout electrode portion and the resin electrode. Accordingly, the joining strength of the terminal electrode can be sufficiently secured, and the resistance of the terminal electrode can be reduced.
FIG .4B is an enlarged cross-sectional view of a region IVB shown in
Hereinafter, the present invention is described in detail based on an embodiment shown in the drawings.
As shown in
The element main body 4 includes an upper surface 4a, a bottom surface 4b locate on an opposite side of the upper surface 4a in a Z-axis direction, and four side surfaces 4c to 4f. Dimensions of the element main body 4 are not particularly limited. For example, a dimension of the element main body 4 in an X-axis direction can be set to 1.2 to 6.5 mm, a dimension of that in a Y-axis direction can be set to 0.6 to 6.5 mm, and a dimension of that in a height (Z-axis) direction can be set to 0.5 to 5.0 mm.
As shown in
In addition, the element main body 4 includes a coil portion 6α at the inside thereof. The coil portion 6α is constituted by winding a wire 6 as a conductor in a coil shape. In
The wire 6 constituting the coil portion 6α includes a conductor portion mainly containing copper, and an insulating layer covering an outer periphery of the conductor portion. More specifically, the conductor portion is constituted by pure copper such as oxygen-free copper and tough pitch copper, a copper-containing alloy such as phosphor bronze, brass, red brass, beryllium copper, and silver-copper alloy, or a copper-coated steel wire. On the other hand, the insulating layer is not particularly limited as long as the insulating layer has an electrical insulating property. Examples thereof include an epoxy resin, an acrylic resin, polyurethane, polyimide, polyamide-imide, polyester, nylon, and the like, or a synthetic resin obtained by mixing at least two or more kinds of the above resins. In addition, as shown in
As shown in
The magnetic material contained in the core portions 41 and 42 can be constituted, for example, by a ferrite powder or a metal magnetic powder. Examples of the ferrite powder include Ni—Zn-based ferrite and Mn—Zn-based ferrite. In addition, the metal magnetic powder is not particularly limited, and examples thereof include an Fe—Ni alloy, an Fe—Si alloy, an Fe—Co alloy, an Fe—Si—Cr alloy, an Fe—Si—Al alloy, an Fe-containing amorphous alloy, an Fe-containing nano-crystalline alloy, and other soft magnetic alloys. Note that, subcomponents may be appropriately added to the ferrite powder or the metal magnetic powder.
In addition, for example, both of the first core portion 41 and the second core portion 42 may be constituted by the same kind of magnetic material, and relative permeability μ1 of the first core portion 41 and relative permeability μ2 of the second core portion 42 may be set to be the same as each other. Alternatively, the composition of the magnetic materials may be different between the first core portion 41 and the second core portion 42.
Further, with regard to the magnetic material (that is, the ferrite powder or the metal magnetic powder) constituting the first core portion 41 or the second core portion 42, a median diameter (D50) thereof can be set to 5 to 50 μm. Moreover, the magnetic material may be constituted by mixing a plurality of particle groups different in D50. For example, large diameter powder of which D50 is 8 to 15 μm, a median diameter powder of which D50 is 1 to 5 μm, and a small diameter powder of which D50 is 0.3 to 0.9 μm may be mixed.
In the case of mixing the plurality of particle groups as described above, a ratio of the large diameter powder, the median diameter powder, and the small diameter powder is not particularly limited. In addition, the large diameter powder, the median diameter powder, and the small diameter powder can be constituted by the same kind of material, or can be constituted by different materials. As described above, since the magnetic material contained in the first core portion 41 or the second core portion 42 is constituted by the plurality of particle groups, a packing density of the magnetic material contained in the element main body 4 can be increased. As a result, various characteristics of the inductor 2 such as permeability, eddy current loss, and DC bias characteristics are improved.
Here, the particle size of the magnetic material can be measured by observing the cross-section of the element main body 4 with a scanning electron microscope (SEM), a scanning transmission electron microscope (STEM), or the like, and performing image analysis of an obtained cross-section photograph with software. At this time, it is preferable that the particle size of the magnetic material is measured in terms of an equivalent circle diameter.
Moreover, in a case where the first core portion 41 or the second core portion 42 is constituted by the metal magnetic powder, particles constituting the powder are preferably insulated from each other. Examples of an insulating method include a method of forming an insulation coating on a particle surface. Examples of the insulation coating include a film formed from a resin or an inorganic material, and an oxidized film formed by oxidizing the particle surface through heat treatment. In the case of forming the insulation coating with a resin or an inorganic material, examples of the resin include a silicone resin, and an epoxy resin. Examples of the inorganic material include phosphates such as magnesium phosphate, calcium phosphate, zinc phosphate, and manganese phosphate, silicates such as sodium silicate (water glass), soda lime glass, borosilicate glass, lead glass, aluminosilicate glass, borate glass, and sulfate glass. By forming the insulation coating, insulation properties among particles can be enhanced, and a withstand voltage of the inductor 2 can be improved.
Further, the resin included in the first core portion 41 and the second core portion 42 is not particularly limited, and for example, thermosetting resins such as an epoxy resin, a phenol resin, a melamine resin, a urea resin, a furan resin, an alkyd resin, a polyester resin, and a diallyl phthalate resin, thermoplastic resins such as an acrylic resin, polyphenylene sulfide (PPS), polypropylene (PP), and a liquid crystal polymer (LCP), or the like can be used.
As shown in
The winding core portion 41b is located above the flange portions 41a in the Z-axis direction, and is formed integrally with the flange portions 41a. Further, the winding core portion 41b has a shape of approximately elliptical column protruding toward an upward side in the Z-axis, and is inserted to an inner side of the coil portion 6α. The shape of the winding core portion 41b is not limited to the shape shown in
The notched portions 41c are located among the flange portions 41a, and four pieces of the notched portions 41c are formed at corners of an X-Y plane. That is, the notched portions 41c are formed in the vicinity of sites at which the side surfaces 4c to 4f of the element main body 4 intersect each other. The notched portions 41c are used as a passage through which the lead portion 6a drawn from the coil portion 6α passes. In addition, the notched portions 41c also function as a passage when a molding material constituting the second core portion 42 flows from a front surface side to a rear surface side of the first core portion 41 in a manufacturing process. In
As shown in
As shown in
Here, a height h from the bottom surface 4b of the element main body 4 to the first flange portions 41ax in the Z-axis direction is shorter than an outer diameter of each of the lead portions 6a. Accordingly, the majority of the lead portion 6a is accommodated at the inside of the element main body 4 (particularly, the second core portion 42), but a part of an outer periphery of the lead portion 6a is exposed to the bottom surface 4b of the element main body 4, under the first flange portions 41ax. Each of the lead portions 6a is constituted by the wire 6, but at a site exposed to the bottom surface 4b, the insulating layer existing on the outer periphery of the wire 6 is removed, and the conductor portion of the wire 6 is exposed. In this embodiment, as shown in
In this embodiment, as shown in
The terminal electrode 8 includes at least a resin electrode layer 81. In addition, the terminal electrode 8 may have a stacked structure including the resin electrode layer 81 and other electrode layers. In a case where the terminal electrode 8 is set to have the stacked structure, the resin electrode layer 81 is formed so as to be in direct contact with the leadout electrode portion 61. Then, the other electrode layers are stacked on an outside-surface of the resin electrode layer 81. That is, the other electrode layers are stacked on an opposite side of the leadout electrode portion 61. The other electrode layers may be a single layer or a plurality of layers, and a material thereof is not particularly limited. For example, the other electrode layers can be constituted by a metal such as Sn, Au, Ni, Pt, Ag, and Pd, or alloy containing at least one kind of the above metal elements. Further, the other electrode layers can be formed by plating or sputtering. Moreover, an entire average thickness of the terminal electrodes 8a and 8b is preferably set to 10 to 60 μm, and an average thickness of the resin electrode layer 81 is preferably set to 10 to 20 μm.
In addition, in this embodiment, the conductor powder 83 of the resin electrode layer 81 is constituted by two particle groups different in a particle size distribution, that is, first particles 83a and second particles 83b. The first particles 83a are a group of particles on the order of micrometers. In this embodiment, “particles on the order of micrometers” mean particles having an average particle size of 0.05 μm or more and several tens of μm or less. The average particle size of the first particles 83a is preferably 1 to 10 μm in a cross-section shown in
In addition, a shape of the first particles 83a can be a shape close to a sphere, a long spherical shape, an irregular block shape, a needle shape, or a flat shape, and more preferably the needle shape or the flat shape. In this embodiment, particles having an aspect ratio of 2 to 30 in the cross-section as shown in
On the other hand, the second particles 83b are a group of particles on the order of nanometers, and have a smaller average particle size than the first particles 83a. The second particles 83b are aggregated and exist in the vicinity of an outer periphery of the first particles 83a and/or particle gaps of the first particles 83a as shown in
In addition, both the first particles 83a and the second particles 83b contain Ag as a main component. In a case where a metal element other than Ag is also contained in the conductor powder 83, an existence aspect of the metal element is not particularly limited. For example, the metal element other than Ag may exist as particles other than the first particles 83a and the second particles 83b, or may be solidly dissolved in the first particles 83a.
In addition, in the cross-section of the resin electrode layer 81 as shown in
Here, the area occupied by each of the elements can be measured by observing the cross-section of the resin electrode layer 81 as shown in
As shown in
In this embodiment, a diffusion layer 68 is formed at the interface between the leadout electrode portion 61 and the resin electrode layer 81. This diffusion layer 68 exists in the region R3 where the second particles 83b are in contact with the outermost surface of the leadout electrode portion 61 as shown in
This diffusion layer 68 contains at least copper oxide and Ag, and may contain voids or the resin component 82. In addition, the thickness T1 of the diffusion layer 68 is at least 30 nm or greater, preferably 30 to 500 nm, and more preferably 50 to 250 nm.
Note that, as shown in
In this embodiment, even when the oxidized film 61a is formed by performing exposure of the leadout electrode portion 61 or formation of the resin electrode layer 81 under a predetermined condition to be described later, the diffusion layer 68 may be formed at the interface between the leadout electrode portion 61 and the resin electrode layer 81. In this case, the diffusion layer 68 may be located between the oxidized film 61a of the leadout electrode portion 61 and the resin electrode layer 81. In addition, the thickness T2 of the oxidized film 61a can be approximately 5 to 100 nm, and is preferably within a range of 5 to 30 nm.
Note that,
In this embodiment, since the diffusion layer 68 is formed at the interface between the leadout electrode portion 61 and the terminal electrode 8, adhesion strength of the resin electrode layer 81 to the leadout electrode portion 61 can be improved. As a result, joining reliability of the terminal electrode 8 with respect to the element main body 4 can be improved, and the resistance of the terminal electrode 8 can be reduced.
The diffusion layer 68 contains copper oxide and Ag as described above, and existence or non-existence of the diffusion layer 68 can be recognized through line analysis using STEM-EPMA (electron probe micro analyzer), mapping analysis, or the like.
For example, in the line analysis by STEM-EPMA, a measurement line is drawn in a direction approximately orthogonal to the interface between the leadout electrode portion 61 and the resin electrode layer 81, and quantitative analysis is performed on the measurement line with constant intervals. Here, in the above analysis, a sample for STEM observation can be prepared by a micro sampling method using a focused ion beam (FIB). In addition, in the line analysis, a size of each measurement point (spot size) is preferably set to have a diameter of 1.5 nm or less, and an interval of the measurement point is preferably set to 1.0 nm or less.
Further, when the outermost surface side of the leadout electrode portion 61 is set as a starting point of the diffusion layer 68 on the measurement line VIA, an end point of the diffusion layer 68 is set to a position where the content rate of Ag is stable.
Moreover, a line analysis result as shown in
Note that, in the line analysis with the EPMA, an element existing in a depth direction of the measurement point, or an element existing in the vicinity of the outer periphery of the measurement point has an influence on a component analysis result. Therefore, even in a case where the diffusion layer 68 does not exist as in
In addition, in a case where it is difficult to specify the diffusion layer 68 with only the concentration gradient of Ag, the diffusion layer 68 is specified also in consideration of a concentration gradient of Cu. The concentration gradient of Cu also occurs in a range having the thickness T1 from the outer surface of the leadout electrode portion 61 toward the resin electrode layer 81 as shown in
Moreover, the diffusion layer 68 may be specified based on the following definition in addition to the above method. That is, the diffusion layer 68 is a region in which both the content rate of Ag and the content rate of Cu are 5 wt % or greater on the resin electrode layer 81 side in comparison to the outermost surface of the leadout electrode portion 61. Alternatively, the diffusion layer 68 is a region in which the content rate of Ag fluctuates within a range of 5 to 100 wt %, and the content rate of Cu fluctuates within a range of 5 to 100 wt %.
On the other hand, in the case of measuring the diffusion layer 68 with the mapping analysis using the STEM-EPMA, mapping images as shown in
When comparing the mapping images of the respective elements (Ag, Cu, and O), it can be seen that a region where Cu and O overlap each other exists in the diffusion layer 68. In addition, it can be seen that Cu and O exist at a part where the amount of Ag detected is less, and the region where Cu and O overlap each other exists at a grain boundary of Ag particles. That is, a Cu component contained in the diffusion layer 68 does not exist as pure copper or an Ag—Cu alloy, but exists as copper oxide. Further, the copper oxide in the diffusion layer 68 exists at the grain boundary of the Ag particles.
As described above, in the case of performing the mapping analysis on the interface between the leadout electrode portion 61 and the resin electrode layer 81, the diffusion layer 68 can be recognized as a site where the Ag particles and the copper oxide are mixed.
Next, a method of manufacturing the inductor 2 according to this embodiment is described.
First, the first core portion 41 is prepared by a press method such as heating and pressing molding method, or an injection molding method. In preparation of the first core portion 41, a raw material powder of a magnetic material, a binder, a solvent, and the like are kneaded to obtain a granule and the granule is used as a molding raw material. In a case where the magnetic material is constituted by a plurality of particle groups, magnetic powders different in a particle size distribution are prepared, and may be mixed in a predetermined ratio.
Next, the coil portion 6α is mounted on the obtained first core portion 41. The coil portion 6α is a coreless coil obtained by winding the wire 6 in a predetermined shape in advance, and the coreless coil is inserted into the winding core portion 41b of the first core portion 41. Alternatively, the coil portion 6α can be formed by directly winding the wire 6 around the winding core portion 41b of the first core portion 41. After combining the first core portion 41 and the coil portion 6α, the pair of lead portions 6a is drawn from the coil portion 6α, and is disposed under the first flange portions 41ax, as shown in
Next, the second core portion 42 is prepared by the insert injection molding. In preparation of the second core portion 42, first, the first core portion 41 equipped with coil portion 6α is putted in a mold. It is preferable to spread a release film on an inner surface of the mold in advance. A flexible sheet-shaped member such as a PET film can be used as the release film. Since the release film is used, the lead portion 6a existing under the first flange portions 41ax comes into close contact with the release film, when putting the first core portion 41 in the mold. Therefore, a part of the outer periphery of the lead portion 6a is covered with the release film, and a part of the outer periphery of the lead portion 6a is exposed from the bottom surface 4b of the element main body 4 after forming the second core portion 42.
As a raw material constituting the second core portion 42, a material having fluidity at the time of molding is used. Specifically, a composite material obtained by kneading a raw material powder of a magnetic material, and a binder such as the thermoplastic resin or the thermosetting resin may be used. A solvent, a dispersant, or the like may be appropriately added to the composite material. The above composite material is introduced into the mold in a slurry state, in the insert injection molding. At this time, the introduced slurry passes through the notched portion 41c of the first core portion 41 and is also filled under the first flange portions 41ax. Then, during the injection molding, heat is appropriately applied according to the type of the binder of the composite material. In this manner, the element main body 4 is obtained, in which the first core portion 41, the second core portion 42, and the coil portion 6α are integrated.
Next, a planned electrode portion is formed by irradiating the laser for a part of the bottom surface 4b of the element main body 4, that is, a part where the pair of terminal electrodes 8 in
The laser used in the above process is preferably a UV laser of which a wavelength is a short wavelength of 400 nm or less. In laser processing, a green laser (wavelength: 532 nm) is typically used, but the principle of removing a target (the insulating layer of the lead portion 6a, the resin of the core portion, or the like) is different between the green laser and the UV laser. In the case of the green laser, a surface temperature of the target rapidly rises due to the laser irradiation, and the target is melted or evaporates (thermally decomposed) to be removed. Accordingly, when using the green laser, an oxidized film having a thickness greater than 100 nm is likely to be formed on the surface of the exposed leadout electrode portion 61, and generation of the diffusion layer 68 is suppressed. On the other hand, in the case of the UV laser, molecular bonds of an organic compound constituting the target are decomposed by the UV laser. Thereby, the target is removed. Even in the case of using the UV laser, slight temperature rise also occurs and thermal decomposition also occurs. However, formation of the oxidized film is much more difficult in the case of using the UV laser than in the case of using the green laser. Therefore, the diffusion layer 68 is likely to be formed by using the UV laser.
Note that, mechanical polishing, a blast treatment, a chemical corrosion treatment, and the like are also considered as a method of forming the planned electrode portion, but a film (an oxidized film or a corrosion layer) having a thickness greater than 100 nm is likely to be formed even in these methods. Therefore, the planned electrode portion is preferably formed through irradiation of UV laser as described above.
Next, resin electrode paste is applied to the planned electrode portion by a method such as a printing method. A binder becoming the resin component 82 and a metal raw material powder becoming the conductor powder 83 are contained in the resin electrode paste used in this case. More specifically, the metal raw material powder is constituted by micro-particles having a particle size of the micrometer order, and nano-particles having a particle size of the nanometer order. The micro-particles are particles becoming the first particles 83a after hardened the paste, and an average particle size thereof is preferably 1 to 10 μm, and more preferably 3 to 5 μm. On the other hand, the nano-particles are particles becoming the second particles 83b after hardened the paste, and an average particle size thereof is preferably 5 to 30 nm, and more preferably 5 to 15 nm.
Note that, in printing of the resin electrode paste, conditions such as the amount of application are controlled so that the average thickness of the resin electrode layer 81 after a heating treatment becomes 10 to 20 μm. Since the thickness of the resin electrode layer 81 is adjusted to the above range, the diffusion layer 68 is likely to be formed.
After applying the resin electrode paste to the planned electrode portion, the element main body 4 is subjected to a heating treatment under predetermined conditions to harden the binder (the resin component 82) in the paste. As the conditions in the heating treatment, a treatment temperature (holding temperature) is preferably 170° C. to 230° C., and a holding time is preferably 60 to 90 minutes. When performing the heating treatment under the above conditions, the resin electrode layer 81 is formed at the planned electrode portion of the element main body 4.
Here, a method of forming the diffusion layer 68 is described. In this embodiment, the diffusion layer 68 is formed by 1) forming the planned electrode portion through irradiation with the UV laser, 2) applying the resin electrode paste containing nano-particles to the planned electrode portion in a predetermined thickness (thickness with which the thickness of the resin electrode layer 81 after a heating treatment becomes 10 to 20 μm), and 3) performing the heating treatment under predetermined conditions. Further, the thickness T1 of the diffusion layer 68 can be controlled by the conditions at the time of the heating treatment. For example, at the time of the heating treatment, as heat energy applied increases (the holding temperature is raised or the holding time is lengthened), the thickness T1 of the diffusion layer 68 tends to increase. Note that, the formation conditions of the diffusion layer 68 are illustrative only, and the diffusion layer 68 can be formed under conditions other than the above conditions.
After forming the resin electrode layer 81, a plating film or a sputtering film may be appropriately formed on the outer surface of the resin electrode layer 81. For example, by formed a plating film of Ni, Cu, Sn, or the like on the outer surface of the resin electrode layer 81, solder wettability is improved.
The inductor 2 having the pair of terminal electrodes 8 formed in the element main body 4 is obtained by the above manufacturing method.
Summary of Embodiment
In the inductor 2 of this embodiment, the terminal electrode 8 includes the resin electrode layer 81. This resin electrode layer 81 is formed by subjecting the resin component 82 to a hardening treatment, and a baking treatment at a high temperature is not necessary during a manufacturing process. Further, in the inductor 2 of this embodiment, the diffusion layer 68 containing Ag and copper oxide is formed at the interface between the leadout electrode portion 61 and the resin electrode layer 81. Since the diffusion layer 68 is formed, adhesion strength of the resin electrode layer 81 to the leadout electrode portion 61 can be improved. As a result, the joining reliability of the terminal electrode 8 is improved, and the resistance of the terminal electrode 8 can be reduced.
In addition, in this embodiment, the conductor powder 83 of the resin electrode layer 81 is constituted by the second particles 83b obtained from nano-particles as a raw material and the first particles 83a having a flat shape and a particle size of the micrometer order. According to this configuration, the adhesion strength of the resin electrode layer 81 to the leadout electrode portion 61 is further improved, and the joining reliability of the terminal electrode 8 is further improved. Further, due to the above configuration, the second particles 83b aggregate in particle gaps of the first particles 83a, and play a role of electrically connecting the gaps of the first particles 83a. As a result, the resistance of the terminal electrode 8 can be further reduced.
Further, in this embodiment, the oxidized film 61a may be formed on at least a part of the surface of the leadout electrode portion 61. Even when the oxidized film 61a exists, the diffusion layer 68 may be formed by forming the resin electrode layer 81 under the above conditions. Accordingly, even in a case where the oxidized film 61a exists, the joining reliability of the terminal electrode 8 can be improved, and the resistance of the terminal electrode 8 can be reduced.
Hereinbefore, the embodiment of the present invention has been described, but the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention. For example, in
In addition, in the above embodiment, the terminal electrode 8 is formed on the bottom surface 4b of the element main body 4. However, the position of the terminal electrode 8 is not limited thereto, and may be formed on the upper surface 4a or the side surfaces 4c to 4f, or may be formed over a plurality of surfaces.
Further, the conductor powder 83 of the resin electrode layer 81 may be constituted by only the second particles 83b obtained from nano-particles as a raw material. Alternatively, particles having a specific surface area greater than that of the micro-particles (first particles 83a) may be used instead of the second particles 83b.
In addition, the first core portion 41 constituting the element main body 4 can also be a sintered body of a ferrite powder or a metal magnetic powder. Further, the element main body 4 itself may be a dust core or a sintered body core of an FT type, an ET type, an EI type, a UU type, an EE type, an EER type, a UI type, a drum type, a pot type, or a cup type, and the inductor may be constituted by winding the coil around the core. In this case, it is not necessary to embed the lead portion inside the element main body, and the lead portion may be drawn along an outer periphery of the core to be connected to the outer surface of the terminal electrode 8.
The electronic component according to the present invention is not limited to the inductor, and may be an electronic component such as a capacitor, a transformer, a choke coil, and a common mode filter. For example, in a case where the electronic component is a stacked ceramic capacitor, a portion of inner electrode layers exposed to an end surface of a stacked body becomes the leadout electrode portion 61. Further, in the stacked ceramic capacitor, the terminal electrode 8 is formed on the end surface of the stacked body in conformity to the exposed portion of the inner electrode layers.
Hereinafter, the present invention is further described with reference to detailed examples, but the present invention is not limited to the examples.
In an example, an inductor sample shown in
In a comparative example, an inductor sample was prepared by using resin electrode paste containing only Ag micro-particles as a conductor powder. Further, with respect to the comparative example, the interface between the leadout electrode portion and the terminal electrode was line-analyzed with the STEM-EPMA. As a result, in the comparative example, it could be found that the same analysis result as in
A DC resistance of the inductor sample obtained above and a contact resistance of the terminal electrode were measured. The DC resistance and the contact resistance were measured at ten sites in the example and the comparative example, and an average value thereof, and a CV value (fluctuation coefficient) were calculated. As a result, it could be found that the contact resistance was further reduced by 4% in the example having the diffusion layer than in the comparative example. Further, from comparison of the CV value of the DC resistance between the example and the comparative example, the CV value in the example was approximately ⅓ of the comparative example. Therefore, it could be seen that the resistance of the terminal electrode can be reduced and a deviation of the resistance can be reduced by forming the diffusion layer at the interface between the leadout electrode portion and the terminal electrode.
In addition, a high-temperature load test (acceleration test) was performed to check the joining reliability of the terminal electrode. In the high-temperature load test, the inductor sample was exposed to a high-temperature environment of 100° C. or higher for a long time while applying a voltage to the inductor sample, and an increase rate of the DC resistance after the exposure was measured. As a result, the increase rate of the DC resistance in the example after the test was suppressed to ½ or less of the comparative example. Therefore, it could be found that the joining reliability of the terminal electrode is improved by forming the diffusion layer.
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