Electronic component

Abstract

The purpose of the present invention is to suppress removal of a coating layer from an element.　One embodiment of the present invention is an electronic component comprising: an element provided with a core that contains metal magnetic particles and first resin; and a coating layer that covers the surface of the element and contains second resin. At the interface between the element and the coating layer, the surface roughness Ra of the element is 2.0 μm-6.0 μm.

Description

Electronic component

[0001] The present invention relates to an electronic component.

[0002] Patent Document 1 discloses a power inductor comprising: an internal electrode coil pattern; a magnetic body having respective ends of the internal electrode coil pattern exposed at opposing both end faces; external electrodes provided on both end faces of the magnetic body so as to be connected to respective ends of the internal electrode coil pattern; and an anti-plating film covering the magnetic body between the external electrodes.

[0003] Japanese Patent Application Laid-Open No. 2016-139789

[0004] In Patent Document 1, forming an anti-plating film suppresses reduction in reliability caused by diffusion of plating in a plating step for forming external electrodes. However, when covering an element body such as a magnetic body with a coat layer such as an anti-plating film, if the adhesion between the coat layer and the element body is weak, the coat layer may peel off from the element body due to factors such as impact.

[0005] An object of the present invention is to suppress peeling of the coat layer from the element body.

[0006] This specification includes the entire content of Japanese Patent Application No. 2025-048527 filed on March 24, 2025. One aspect of the present invention is an electronic component comprising: an element body including a core containing metal magnetic particles and a first resin; and a coat layer coating a surface of the element body and containing a second resin, wherein a surface roughness Ra of the element body at an interface between the element body and the coat layer is 2.0 µm or more and 6.0 µm or less.

[0007] According to the present invention, peeling of the coat layer from the element body can be suppressed.

[0008] Fig. 1 is a perspective view of an inductor according to an embodiment of the present invention viewed from a top surface side. Fig. 2 is a perspective view of the inductor viewed from a bottom surface side. Fig. 3 is a transparent perspective view showing the internal configuration of the inductor. Fig. 4 is a schematic diagram of a manufacturing process of the inductor. Fig. 5 is a perspective view of a first tablet having an E-shaped cross-section. Fig. 6 is a schematic cross-sectional view of the inductor.

[0009] Embodiments of the present invention will be described below with reference to the drawings.

[0010] [1. Embodiments] [1.1. Inductor Configuration] Figure 1 is a perspective view of the inductor 1 according to this embodiment, viewed from the top surface 12, and Figure 2 is a perspective view of the inductor 1, viewed from the bottom surface 10. The inductor 1 of this embodiment is configured as a surface-mount type electronic component and comprises a substantially rectangular parallelepiped base body 2 and a pair of external electrodes 4 provided on the surface of the base body 2. In addition, the portion of the surface of the base body 2 excluding the external electrodes 4 is covered with a coating layer 50. The inductor 1 corresponds to an example of an "electronic component" in this disclosure.

[0011] Hereinafter, in the base body 2, the first main surface facing the mounting board (not shown in the figure) during mounting is defined as the bottom surface 10, the second main surface opposite the bottom surface 10 is called the top surface 12, the pair of third main surfaces perpendicular to the bottom surface 10 are called end surfaces 14, and the pair of fourth main surfaces perpendicular to the bottom surface 10 and the pair of end surfaces 14 are called side surfaces 16. As shown in Figure 1, the distance from the bottom surface 10 to the top surface 12 is defined as the thickness T of the base body 2, the distance between the pair of side surfaces 16 is defined as the width W of the base body 2, and the distance between the pair of end surfaces 14 is defined as the length L of the base body 2. Furthermore, the direction of the thickness T is defined as the thickness direction DT, the direction of the width W is defined as the width direction DW, and the direction of the length distance is defined as the length direction DL. The dimensions of the inductor 1 are, for example, a length L of 2.0 mm, a width W of 1.2 mm, and a thickness T of 0.9 mm.

[0012] Figure 3 is a perspective view showing the internal structure of the inductor 1. The base body 2 comprises a coil conductor 20 and a roughly hexahedral core 30 in which the coil conductor 20 is embedded, and is configured as a conductor-encapsulated magnetic component in which the coil conductor 20 is sealed within the core 30.

[0013] The core 30 is a molded body formed by compressing a mixed powder of metallic magnetic particles and resin into a roughly hexahedral shape by pressurizing and heating the powder while enclosing the coil conductor 20.

[0014] Furthermore, the metallic magnetic particles of this embodiment include two types of particle sizes: first magnetic particles with a relatively large average particle size and second magnetic particles with a relatively small average particle size. As a result, during compression molding, the second magnetic particles are interwoven with the resin between the first magnetic particles, increasing the packing density of the metallic magnetic particles in the core 30 and also increasing the magnetic permeability.

[0015] The D50 particle size (median diameter) of the first magnetic particles is preferably 10 μm or more and 50 μm or less, and the D50 particle size of the second magnetic particles is preferably 1 μm or more and 5 μm or less. Furthermore, the magnetic powder may contain particles with D50 particle sizes different from those of the first and second magnetic particles, thereby containing three or more different particle sizes.

[0016] In this embodiment, both the first magnetic particles and the second magnetic particles are particles having a metal particle and an insulating coating covering its surface with a thickness of several nanometers to tens of nanometers. Fe-Si amorphous alloy powder is used for the metal particle, and zinc phosphate glass is used for the insulating coating. Covering the metal particle with the insulating coating increases the insulation resistance and dielectric strength.

[0017] For the first and second magnetic particles, metal particles of the Fe system, such as Fe (pure iron) or Fe alloys, can be used. As an example of an Fe alloy, one or more alloys selected from the group consisting of alloys containing Fe and Ni, alloys containing Fe and Co, alloys containing Fe and Si, alloys containing Fe, Si and Cr, alloys containing Fe, Si and Al, alloys containing Fe, Si, B and C, alloys containing Fe, Si, B and Cr, and alloys containing Fe, P, Cr, Si, B, Nb and C can be used.

[0018] The composition of the metal particles of the first magnetic particle and the composition of the metal particles of the second magnetic particle may be the same or different from each other. In this embodiment, the first magnetic particle has particles of an alloy containing Fe, Ni, Sn, and C. The second magnetic particle has particles of Fe (pure iron).

[0019] The insulating coating formed on the surface of the metal particles of the first and second magnetic particles may be one or more insulating coatings selected from the group consisting of, for example, inorganic glass coatings, organic-inorganic hybrid coatings, and inorganic insulating coatings formed by the sol-gel reaction of metal alkoxides. In addition, for the first and second magnetic particles, other phosphates (such as magnesium phosphate, calcium phosphate, manganese phosphate, cadmium phosphate, etc.) or resin materials (such as silicone resins, epoxy resins, phenolic resins, polyamide resins, polyimide resins, and polyphenylene sulfide resins) may be used for the insulating coating.

[0020] In the mixed powder of this embodiment, epoxy resin or the like is used as the resin material. Hereinafter, the resin used in the mixed powder and constituting the core 30 will be referred to as the "first resin". In this embodiment, the first resin is an epoxy resin mainly composed of bisphenol A type epoxy resin. The epoxy resin may also be a phenol novolac type epoxy resin. Furthermore, the material of the first resin may be something other than epoxy resin. Also, the first resin may be a mixture of two or more types of resins rather than just one type of resin. For example, in addition to epoxy resin, thermosetting resins such as phenol resin, polyester resin, polyimide resin, and polyolefin resin can be used as the material of the first resin.

[0021] As shown in Figure 3, the coil conductor 20 comprises a winding section 22 around which a conductor is wound, and a pair of lead-out sections 24 that are drawn out from the winding section 22 and at least a portion of which is exposed from the base body 2. The coil conductor 20 is composed of a conductor and a coating layer formed on the surface of the conductor. The conductor is a strip-shaped conductor with a rectangular cross-section made of copper (a so-called flat rectangular conductor). Note that the coil conductor 20 does not necessarily have to be wound; it may also be in a straight shape, meander shape, etc.

[0022] The winding portion 22 of the coil conductor 20 is formed by winding a strip-shaped wire (hereinafter also simply referred to as a wire) in a spiral shape so that both ends of the wire are drawn out to the outer circumference and connected to each other on the inner circumference. Inside the base body 2, the coil conductor 20 is embedded in the core 30 with the central axis of the winding portion 22 aligned with the thickness direction DT of the base body 2. The lead-out portion 24 is drawn out from the winding portion 22 to each of a pair of end faces 14, with one main surface exposed from the base body 2 and the other main surface embedded in the base body 2. The one main surface of the lead-out portion 24 that is exposed from the base body 2 is electrically connected to the external electrode 4.

[0023] The pair of external electrodes 4 are so-called L-shaped electrodes, composed of L-shaped members extending from each end face 14 of the base body 2 to the bottom face 10. Each external electrode 4 is connected to the lead-out portion 24 of the coil conductor 20 at the end face 14, and the portion 4A (Figure 2) extending to the bottom face 10 is electrically connected to the wiring of the circuit board by appropriate mounting means such as soldering. Note that the external electrodes 4 are not limited to the above L-shaped electrodes, but may also be a so-called five-sided electrode structure, or a bottom-face electrode.

[0024] Inductors with this configuration can improve DC superposition characteristics by using soft metal magnetic particles instead of metallic magnetic particles, and are therefore used as electronic components in electrical circuits where large currents flow, as well as as choke coils in DC-DC converter circuits and power supply circuits. They are also used as electronic components in electronic devices such as personal computers, DVD players, digital cameras, TVs, mobile phones, smartphones, car electronics, and medical and industrial machinery. However, the applications of inductors are not limited to these; they can also be used in tuning circuits, filter circuits, and rectifier / smoothing circuits, for example.

[0025] [1.2. Inductor Manufacturing Process] Figure 4 is a schematic diagram of the manufacturing process of the inductor 1. As shown in the figure, the manufacturing process of the inductor 1 may include a pre-molded body formation process (S1), a coil conductor formation process (S2), a base body molding process (S3), a surface irregularity formation process (S4), a coating layer formation process (S5), and an external electrode formation process (S6).

[0026] The pre-molded body formation step (S1) is a step in which a pre-molded body called a tablet is formed. The pre-molded body is formed into an easy-to-handle solid form by pressurizing the mixed powder, which is the material of the base body 2. In the pre-molded body, the resin contained in the mixed powder is in a semi-cured or uncured state. In this embodiment, as an example, a first tablet with an E-shaped cross-section and a groove into which the coil conductor 20 is inserted is formed.

[0027] Figure 5 is a perspective view of the first tablet 30a having an E-shaped cross-section. As shown in Figure 5, the first tablet 30a has an E-shaped form with three protrusions. The shape of the pre-molded body is not limited to the E-shaped form exemplified in Figure 5, and may be an I-shaped form (plate-like) without protrusions, a T-shaped form with one protrusion in the center of the I-shaped form, or a form with a total of five protrusions in the center and at the four corners of the I-shaped form. Furthermore, multiple pre-molded bodies may be used in combination.

[0028] The coil conductor formation step (S2) is a step in which a coil conductor 20 is formed from a wire. The coil conductor 20 is formed by winding the wire, for example, into a shape having an alpha winding portion 22 and a pair of lead portions 24. As mentioned above, the coil conductor 20 does not necessarily have to be wound, and may be in a straight shape, meander shape, etc.

[0029] In the base body molding process (S3), the coil conductor 20 is housed in the first tablet 30a. At this time, the protrusion of the first tablet 30a is inserted into the winding core portion of the coil conductor 20. Furthermore, the above-mentioned mixed powder may be used to coat the coil conductor 20 with the mixed powder. In the base body forming process (S3), the molding die containing these coil conductors 20, the first tablet 30a, and the mixed powder is introduced into a compression molding machine. The first tablet 30a and the mixed powder inside the molding die are heated and pressurized to harden the resin contained in the first tablet 30a and the mixed powder. As a result, a base body 2 with the coil conductor 20 enclosed in the core 30 is molded. The conditions during compression molding of the base body 2 are, for example, a temperature of 150°C to 200°C, a pressure of 5 MPa to 50 MPa, and a pressurization time of 60 s to 1800 s.

[0030] The surface roughness formation step (S4) is a step in which fine irregularities are formed on the surface of the base body 2 formed in the base body molding step (S3). In the surface roughness formation step (S4), irregularities are formed on the surface of the base body 2 by applying blasting, laser irradiation, dry barreling, or wet barreling, etc. The surface roughness Ra of the surface of the base body 2 is adjusted to a predetermined value by the surface roughness formation step (S4). In this embodiment, blasting is applied to the surface of the base body 2 in the surface roughness formation step (S4). In this case, the surface roughness Ra on the surface of the base body 2 can be adjusted by the blasting treatment time and the spray particle size. Specifically, by increasing the blasting treatment time or increasing the spray particle size, the surface roughness Ra on the surface of the base body 2 can be increased, and by decreasing the blasting treatment time or decreasing the spray particle size, the surface roughness Ra on the surface of the base body 2 can be decreased. In this specification, surface roughness Ra refers to the arithmetic mean roughness as defined in JIS B 0601-2013.

[0031] In the coating layer formation step (S5), a coating layer 50 is formed on the surface of the base body 2, which has been formed with irregularities in the irregularity formation step (S4). In the coating layer formation step (S5), the coating liquid, which is the coating layer 50 before curing, is applied to the surface of the base body 2 by any method such as spraying, dipping, dispensing, or various printing methods. At this time, it is preferable to use a coating liquid that has high wettability on the surface of the base body 2. By using a coating liquid with high wettability, the coating liquid can easily penetrate into the irregularities on the surface of the base body 2, and the coating layer 50 can easily penetrate into the irregularities on the surface of the base body 2.

[0032] In this embodiment, during the coating layer formation step (S5), multiple substrates 2 are placed in a drum, and the coating liquid is applied to the substrates 2 by spraying while the drum is rotated to prevent excessive impact from being applied to the substrates 2.

[0033] Next, the spraying of the coating liquid inside the drum is stopped, and the coating liquid on the surface of the base body 2 is allowed to dry to the extent that it no longer adheres to other objects. In this embodiment, when drying the coating liquid on the surface of the base body 2, high-temperature drying gas is blown into the drum to accelerate the drying of the coating liquid. The drying gas is, for example, nitrogen gas. By adjusting the flow rate of the drying gas blown into the drum, the surface roughness Ra of the surface 52 (see Figure 6) of the coating layer 50 formed on the base body 2 can be adjusted. Specifically, by increasing the flow rate of the drying gas, the coating liquid dries faster, and the surface roughness Ra of the surface 52 of the coating layer 50 increases. By decreasing the flow rate of the drying gas, the drying of the coating liquid slows down, and the surface roughness Ra of the surface 52 of the coating layer 50 decreases.

[0034] After the coating liquid dries, the base body 2 is removed from the drum and subjected to heat treatment, which hardens the coating liquid and forms a coating layer 50, thus completing the coating layer formation process (S5).

[0035] Furthermore, the base body 2 created in the base body molding process (S3) may be subjected to barrel polishing to round the edges of the base body 2. In this embodiment, when forming the coating layer 50 on the base body 2 in the coating layer formation process (S5), the base body 2 is simultaneously barrel polished.

[0036] In the external electrode formation step (S6), the external electrodes 4 are formed on the base body 2 after the coating layer formation step (S5). The external electrodes 4 can be formed by methods such as plating, applying a conductive paste to the base body and baking it, or sputtering.

[0037] For example, when forming the external electrode 4 by plating, the surface of the electrode area on the surface of the base body 2 may be modified by irradiating the area with laser light, and then the external electrode 4 may be formed on the electrode area by electroplating. Here, the electrode area refers to the area on the surface of the core 30 where the external electrode 4 should be formed, and includes the portion where the lead-out portion 24 is exposed. By irradiating with laser light, the coating layer of the lead-out portion 24 of the coil conductor 20 and the coating layer 50 of the base body 2 are removed in the area of ​​the electrode area, as well as the resin on the surface of the core 30 and the insulating film on the surface of the metal magnetic particles exposed from the core 30. As a result, the area of ​​metal exposure of the metal magnetic particles per unit area of ​​the surface of the core 30 is larger in the area of ​​the electrode area compared to other parts of the surface of the core 30.

[0038] [1.3. Coat Layer Composition]

[0039] Figure 6 is a schematic cross-section of the inductor 1, and shows a magnified schematic of the interface between the coating layer 50 and the base body 2 in the cross-section of the inductor 1. As shown in Figure 6, in the inductor 1, the interface 51 between the base body 2 and the coating layer 50 is rougher and has more irregularities than the surface 52 of the coating layer 50, which is the surface opposite the interface 51. In detail, the surface roughness Ra of the base body 2 at interface 51 is greater than or equal to the surface roughness Ra of the surface 52 of the coating layer 50.

[0040] The inventors have confirmed through experiments described later that a suitable range for the surface roughness Ra of the base body 2 at the interface 51 between the base body 2 and the coating layer 50 is 2.0 μm or more. A surface roughness Ra of 2.0 μm or more at the interface 51 increases the contact area between the base body 2 and the coating layer 50, making it difficult for the coating layer 50 to peel off from the base body 2. Furthermore, a surface roughness Ra of 6.0 μm or less at the interface 51 is preferable. A surface roughness Ra of 6.0 μm or less at the interface 51 ensures the effective volume of the base body 2 in the inductor 1 and suppresses a decrease in the inductance of the inductor 1. In this embodiment, the surface roughness Ra of the base body 2 at the interface 51 is between 2.0 μm and 6.0 μm.

[0041] Furthermore, the inventors have confirmed through experiments described later that a suitable range for the surface roughness Ra on the surface 52 of the coating layer 50 is 2.0 μm or less. A surface roughness Ra of 2.0 μm or less on the surface 52 of the coating layer 50 makes it less likely for the surface 52 to catch on a parts feeder or the like when the inductor 1 is passed through one. Therefore, peeling of the coating layer 50 starting from the surface 52 can be suppressed. In this embodiment, the surface roughness Ra on the surface 52 of the coating layer 50 is 2.0 μm or less.

[0042] The surface roughness Ra of the base material 2 at interface 51 and the surface roughness Ra of the coating layer 50 at surface 52 can be determined as follows. First, the inductor 1 is embedded in resin and polished to the center in the DW direction to form polished cross sections along the DL and DT directions. At this time, ion milling or the like may be applied to the polished cross sections. Next, the coating layer 50 on the bottom surface 10 side at the center in the DL direction of the polished cross section is observed. In the observation, elemental analysis mapping is performed on a 75 μm × 100 μm field of view of the observed object using FE-SEM / EDX (field emission scanning electron microscope with energy dispersive X-ray analyzer). Furthermore, the interface 51 and surface 52 are drawn using image analysis. Then, the surface roughness Ra of the base material 2 at interface 51 within the field of view and the surface roughness Ra of the coating layer 50 at surface 52 are determined based on JIS B 0601-2013. This allows us to determine the surface roughness Ra of the base material 2 at interface 51 and the surface roughness Ra of the coating layer 50 at surface 52 for one inductor 1. The same operation is applied to each of the 10 inductors, one location at a time for each polished cross section of one inductor 1. Then, the average value of the obtained surface roughness Ra for each inductor 1 is calculated. This allows us to determine the average value of the surface roughness Ra of the base material 2 at interface 51 and the average value of the surface roughness Ra of the coating layer 50 at surface 52 for inductors of the same type 1.

[0043] The coating layer 50 contains a base resin. Hereinafter, the base resin in the coating layer 50 will be referred to as the "second resin." As the second resin, for example, epoxy resin, urethane resin, acrylic resin, polyimide resin, polyimideamide resin, or polyamide resin can be used. Alternatively, one of these resins may be used as the second resin, or a resin made by mixing multiple of these resins may be used. In this embodiment, the second resin is epoxy resin. The second resin may be the same type of resin as the first resin contained in the core 30 of the base body 2.

[0044] Furthermore, the coat layer 50 contains fine particles as a filler. By including the fine particles in the coat layer 50, the mechanical strength of the coat layer 50 can be improved. The fine particles contained in the coat layer 50 may be inorganic filler metal particles such as titanium oxide, silicon dioxide, alumina, and calcium carbonate. Furthermore, the coat layer 50 may contain one type of these inorganic filler metal particles as fine particles, or may contain a plurality of types. In the present embodiment, the coat layer 50 contains silicon dioxide as the fine particles.

[0045] The weight ratio of the second resin to the fine particles contained in the coat layer 50 is preferably second resin : fine particles = 1:1.5 to 1:2.5. In the present embodiment, the weight ratio of the second resin to the fine particles is second resin : fine particles = 1:2.

[0046] Furthermore, it has been confirmed by experiments conducted by the inventors of the present invention described later that a suitable average particle diameter of the fine particles contained in the coat layer 50 is 100 nm or less. When the average particle diameter of the fine particles contained in the coat layer 50 is 100 nm or less, the fine particles easily enter the irregularities at the interface 51 between the element body 2 and the coat layer 50. Unlike the case where the fine particles do not enter the irregularities of the interface 51, this makes it easy to uniformize the distribution of the fine particles between the anchor portions that have entered the irregularities of the interface 51 in the coat layer 50 and the portions of the coat layer 50 excluding the anchor portions. For this reason, composition deviation between the anchor portion and other portions in the coat layer 50 can be suppressed, and intra-film fracture in the coat layer 50 can be suppressed. In the present embodiment, the average particle diameter of the fine particles contained in the coat layer 50 is 100 nm. Note that the average particle diameter herein refers to the average value of equivalent circle diameters.

[0047] Still, the average particle size of the fine particles may be measured from the finished inductor 1 as follows. First, the inductor 1 is embedded in resin, and the inductor 1 is polished to the center in the DW direction to form a polished cross-section along the DL direction and the DT direction. At this time, ion milling or the like may be applied to the polished cross-section. Next, observation is performed targeting the coat layer 50 on the bottom surface 10 side at the center in the DL direction within the polished cross-section. In the observation, elemental analysis mapping is performed on the 75 μm×100 μm visual field of the observation target using FE-SEM / EDX. Next, the equivalent circle diameter of each fine particle in the visual field is obtained from the results of the elemental analysis mapping using image analysis or the like. By obtaining the average value of these equivalent circle diameters, the average particle size of the fine particles for one inductor 1 can be obtained. The same operation is applied one position per polished cross-section of one inductor 1 to each of 10 inductors. Then, by calculating the average value of all the obtained equivalent circle diameters, the average particle size of the fine particles for the same type of inductor 1 can be obtained.

[0048] [1.4. Effects of the Embodiment] According to the present embodiment, the following effects are obtained.

[0049] The inductor 1 of the present embodiment includes: an element body 2 including a core 30 containing metal magnetic particles and a first resin; and a coat layer 50 that covers a surface of the element body 2 and contains a second resin. At an interface 51 between the element body 2 and the coat layer 50, the surface roughness Ra of the element body 2 is 2.0 μm or more and 6.0 μm or less. According to this inductor 1, the contact area between the element body 2 and the coat layer 50 can be secured. Therefore, peeling of the coat layer 50 from the element body 2 can be suppressed.

[0050] As in the present embodiment, the inductor 1 may be configured such that, in the coat layer 50, the surface roughness Ra on a surface 52 that is a surface opposite to the interface 51 with the element body 2 is 2.0 μm or less. According to this inductor 1, unevenness on the surface of the coat layer 50 is less likely to catch on other objects. Therefore, peeling of the coat layer 50 from the element body 2 can be suppressed.

[0051] As in this embodiment, the coating layer 50 in the inductor 1 may be configured to contain fine particles, the average particle size of which is 100 nm or less. This suppresses compositional misalignment between the anchor portion and the other portions of the coating layer 50, and suppresses intrafilm fracture in the coating layer 50. Therefore, peeling of the coating layer 50 from the substrate 2 can be suppressed.

[0052] [2. Example 1] In order to suppress the peeling of the coating layer 50, the inventors conducted the following experiment to verify a suitable range of surface roughness Ra of the substrate 2 at the interface 51 and a suitable range of surface roughness Ra of the surface 52 of the coating layer 50.

[0053] [2.1. Preparation of Samples] Based on the above embodiment, the inventors prepared samples A1 to A3, A7 to A9, and A12 to A14 as comparative examples of the above embodiment, and samples A4 to A6 and A10 to A11 as examples of the above embodiment. The inventors changed the surface roughness Ra of the base material 2 at the interface 51 of each sample A1 to A14 by adjusting the processing time of the blast treatment in the unevenness formation process. The inventors also changed the surface roughness Ra of the surface 52 of each sample A1 to A14 by adjusting the flow rate of the drying gas in the coating layer formation process. The average values ​​of the surface roughness Ra of the base material 2 at the interface 51 and the average values ​​of the surface roughness Ra of the surface 52 of the coating layer 50 for each type of sample A1 to A14 were confirmed by the method described in the embodiment.

[0054] [2.2. Evaluation Method] The inventors prepared 50,000 inductors 1 for each type of sample A1 to A14. Then, each inductor 1 for each sample A1 to A14 was passed through a parts feeder and then visually sorted using a visual sorting machine. In the visual sorting, it was determined from the appearance whether or not peeling of the coating layer 50 had occurred on each inductor 1, and the number of inductors 1 with peeling was determined for each type of sample A1 to A14. According to the inventors' observations, peeling of the coating layer 50 mainly occurred at the interface 51 between the base body 2 and the coating layer 50.

[0055] [2.3. Results] Table 1 shows the results of the above evaluation. However, in the "Judgment" column in Table 1, "G" indicates a pass and "NG" indicates a fail. In this experiment, for 50,000 inductors 1, if the number of inductors 1 that delaminated was 5 or less, it was judged as "G", and if the number was 6 or more, it was judged as "NG".

[0056]

[0057] As shown in Table 1, sample A1 had an average surface roughness Ra of 0.5 μm at interface 51, an average surface roughness Ra of 0.6 μm at surface 52, and 103 peels, and was judged as "NG". Sample A2 had an average surface roughness Ra of 1.0 μm at interface 51, an average surface roughness Ra of 0.5 μm at surface 52, and 72 peels, and was judged as "NG". Sample A3 had an average surface roughness Ra of 1.5 μm at interface 51, an average surface roughness Ra of 0.6 μm at surface 52, and 27 peels, and was judged as "NG". Sample A4 had an average surface roughness Ra of 2 at interface 51, an average surface roughness Ra of 0.6 μm at surface 52, and 0 peels, and was judged as "G". Sample A5 had an average surface roughness Ra of 2 at interface 51 of 2.5 μm, an average surface roughness Ra of 0.7 μm at surface 52, and 0 peels, and was judged as "G". Sample A6 had an average surface roughness Ra of 3.0 μm at interface 51 of 2, an average surface roughness Ra of 0.5 μm at surface 52, and 0 peels, and was judged as "G". Sample A7 had an average surface roughness Ra of 1.5 μm at interface 51 of 2, an average surface roughness Ra of 1.3 μm at surface 52, and 32 peels, and was judged as "NG". Sample A8 had an average surface roughness Ra of 1.5 μm at interface 51 of 2, an average surface roughness Ra of 2.0 μm at surface 52, and 35 peels, and was judged as "NG". Sample A9 had an average surface roughness Ra of 1.5 μm at interface 51, an average surface roughness Ra of 2.3 μm at surface 52, and 54 peels, and was judged as "NG". Sample A10 had an average surface roughness Ra of 2.0 μm at interface 51, an average surface roughness Ra of 1.3 μm at surface 52, and 0 peels, and was judged as "G". Sample A11 had an average surface roughness Ra of 2.0 μm at interface 51, an average surface roughness Ra of 2.0 μm at surface 52, and 0 peels, and was judged as "G".Sample A12 had an average surface roughness Ra of 2.0 μm at interface 51, an average surface roughness Ra of 2.3 μm at surface 52, and 3 peels, and was judged as "G". Sample A13 had an average surface roughness Ra of 2.0 μm at interface 51, an average surface roughness Ra of 2.5 μm at surface 52, and 4 peels, and was judged as "G". Sample A14 had an average surface roughness Ra of 3.0 μm at interface 51, an average surface roughness Ra of 2.5 μm at surface 52, and 0 peels, and was judged as "G".

[0058] [2.4. Conclusion] Based on the above evaluation results, the inventors concluded that if the surface roughness Ra of the base material 2 at interface 51 is 2.0 μm or more, the peeling of the coating layer 50 from the base material 2 can be suppressed. In addition, although samples A12 and A13 were judged as "G", several cases of peeling of the coating layer 50 occurred, so the inventors concluded that it is preferable for the surface roughness Ra of the surface 52 of the coating layer 50 to be 2.0 μm or less. Note that in Example 1, the surface roughness Ra of the base material 2 at interface 51 was only evaluated up to 3.0 μm, but it can take values ​​such as 3.5 μm, 4.0 μm, 4.5 μm, 5.0 μm, 5.5 μm, and 6.0 μm.

[0059] [3. Example 2] The inventors conducted the following experiment to verify the effect of the average particle size of the fine particles contained in the coating layer 50 on the ease of peeling of the coating layer 50.

[0060] [3.1. Preparation of Samples] Based on the above embodiment, the inventors prepared samples B1 to B3 as comparative examples of the above embodiment, and samples B4 to B6 as examples of the above embodiment. The inventors changed the average particle size of the fine particles in the coating layer 50 in each sample B1 to B6 by adjusting the average particle size of the fine particles used in preparing the coating liquid. The inventors also adjusted the processing time of the blast treatment in the unevenness formation process to make the average surface roughness Ra of the base material 2 at the interface 51 of each sample B1 to B6 2.0 μm. Furthermore, the inventors adjusted the flow rate of the drying gas in the coating layer formation process to make the average surface roughness Ra of the surface 52 of the coating layer 50 in each sample B1 to B6 0.5 μm or more and 0.7 μm or less.

[0061] [3.2. Evaluation Method] The inventors prepared 500 inductors 1 for each type of sample B1 to B6. Then, using the inductors 1 for each sample B1 to B6, they performed a 90-degree tape peel test as specified in JIS Z 0237:2009 and determined the number of inductors 1 that peeled. The inventors' observations confirmed that in this experiment, the peeling of the coating layer 50 mainly occurred within the film of the coating layer 50.

[0062] [3.3. Results] Table 2 shows the results of the above evaluation.

[0063]

[0064] As shown in Table 2, in sample B1, the average surface roughness Ra of the base material 2 at interface 51 was 2.0 μm, the average surface roughness Ra at surface 52 was 0.6 μm, the average particle size of the fine particles in the coating layer 50 was 250 nm, and the number of inductors 1 that delaminated was 70. In sample B2, the average surface roughness Ra of the base material 2 at interface 51 was 2.0 μm, the average surface roughness Ra at surface 52 was 0.5 μm, the average particle size of the fine particles in the coating layer 50 was 180 nm, and the number of inductors 1 that delaminated was 41. In sample B3, the average surface roughness Ra of the base material 2 at interface 51 was 2.0 μm, the average surface roughness Ra at surface 52 was 0.7 μm, the average particle size of the fine particles in the coating layer 50 was 120 nm, and the number of inductors 1 that delaminated was 3. In sample B4, the average surface roughness Ra of the base material 2 at interface 51 was 2.0 μm, the average surface roughness Ra at surface 52 was 0.6 μm, the average particle size of the fine particles in the coating layer 50 was 100 nm, and the number of inductors 1 that had delaminated was 0. In sample B5, the average surface roughness Ra of the base material 2 at interface 51 was 2.0 μm, the average surface roughness Ra at surface 52 was 0.5 μm, the average particle size of the fine particles in the coating layer 50 was 80 nm, and the number of inductors 1 that had delaminated was 0. In sample B6, the average surface roughness Ra of the base material 2 at interface 51 was 2.0 μm, the average surface roughness Ra at surface 52 was 0.5 μm, the average particle size of the fine particles in the coating layer 50 was 50 nm, and the number of inductors 1 that had delaminated was 0.

[0065] [3.4. Conclusion] From the results of the above evaluation, the inventors found that in samples B4 to B6, where the average particle size of the fine particles in the coating layer 50 was 100 nm or less, no peeling of the coating layer 50 occurred. They concluded that if the average particle size of the fine particles in the coating layer 50 is 100 nm or less, peeling of the coating layer 50 can be suppressed.

[0066] [4. Other Embodiments] The embodiments described above illustrate one aspect of the present invention and can be arbitrarily modified and applied without departing from the spirit of the invention. Furthermore, it is possible to arbitrarily combine the elements of the embodiments described above to create new embodiments.

[0067] In the embodiments described above, an inductor 1 was explained as an example of an electronic component, but this is merely an example. However, the application of the present invention is not limited to inductors, and it can be applied to any electronic component other than an inductor.

[0068] In the embodiments described above, the horizontal and vertical directions, various numerical values, shapes, and materials include, unless otherwise specified, a range that produces the same effects as those directions, numerical values, shapes, and materials (a so-called equivalence range).

[0069] 1...Inductor (electronic component), 2...Base body, 4...External electrode, 10...Bottom surface, 12...Top surface, 14...End surface, 16...Side surface, 20...Coil conductor, 22...Winding section, 24...Outlet section, 30...Core, 30a...First tablet, 50...Coating layer, 51...Interface, 52...Surface

Claims

1. An electronic component comprising: a base body having a core containing metallic magnetic particles and a first resin; and a coating layer covering the surface of the base body and containing a second resin, wherein the surface roughness Ra of the base body at the interface between the base body and the coating layer is 2.0 μm or more and 6.0 μm or less.

2. The electronic component according to claim 1, wherein the surface roughness Ra of the coating layer on the side opposite to the interface with the substrate is 2.0 μm or less.

3. The electronic component according to claim 1 or 2, wherein the coating layer contains fine particles, and the average particle size of the fine particles is 100 nm or less.

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