Inductor

Abstract

This makes it easier for moisture stored in the inductor to pass through. [Solution] One aspect of the present invention is an inductor comprising a base body having a core containing magnetic powder and resin, a coil embedded in the core, and an external terminal provided on the surface of the base body, wherein the coil has a winding portion around which a conductor is wound and a lead portion drawn out from the winding portion, the lead portion has an exposed portion exposed from the base body, and the external terminal is formed by plating on an area of ​​the surface of the base body that includes at least a part of the exposed portion, and a plated break is formed between the exposed portion and the external terminal that is not connected by plating.

Description

Technical Field

[0001] The present invention relates to an inductor.

Background Art

[0002] Patent Document 1 discloses an inductor having a core containing soft magnetic particles and a resin, a coil conductor composed of a conductor having a coating layer and a fusion layer on the surface embedded in the core, wherein the metal layer of the external electrode extends up to the upper surface of the element protection film at the outer edge of the electrode formation portion and further penetrates into the element at the boundary between the electrode formation portion and the element protection layer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an inductor integrally formed using a composite material containing magnetic particles and a resin as in Patent Document 1, when exposed to a high-humidity environment, moisture is stored in the coating layer, fusion layer of the conducting wire, and the resin component of the core. Thus, since the stored moisture can evaporate when the inductor is heated by reflow mounting or the like, there is room for improvement to facilitate passage of the evaporated moisture.

[0005] An object of the present invention is to facilitate passage of moisture stored in the inductor through the element.

Means for Solving the Problems

[0006] One aspect of the present invention is an inductor comprising a base body having a core containing magnetic powder and resin, a coil embedded in the core, and an external terminal provided on the surface of the base body, wherein the coil has a winding portion around which a conductor is wound and a lead portion drawn out from the winding portion, the lead portion has an exposed portion exposed from the base body, and the external terminal is formed by plating on a region of the surface of the base body that includes at least a part of the exposed portion, and a plated break portion that is not connected by plating is formed between the exposed portion and the external terminal.

[0007] Another aspect of the present invention is an inductor comprising a base body having a core containing magnetic powder and resin, a coil embedded in the core, and an external terminal provided on the surface of the core, wherein the coil has a winding portion around which a conductor is wound and a lead portion drawn out from the winding portion, the lead portion has an exposed portion exposed from the base body, and the external terminal is formed by plating on the surface of the base body in a region including at least a part of the exposed portion, and a plated break is formed near the exposed portion where the external terminal is not formed.

[0008] Another aspect of the present invention is an inductor comprising a base body having a core containing magnetic powder and resin, a coil embedded in the core, and an external terminal provided on the surface of the core, wherein the coil has a winding portion around which a conductor is wound and a lead portion drawn out from the winding portion, the lead portion has an exposed portion exposed from the base body, the external terminal is formed by plating on a region of the surface of the base body including a part of the exposed portion, the exposed portion has an uncoated portion located outside the external terminal, and a recess is formed on the surface of the base body along the uncoated portion. [Effects of the Invention]

[0009] According to the present invention, moisture stored in the inductor can be made to pass through the substrate more easily. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view of an inductor according to Embodiment 1 of the present invention, viewed from the top side. [Figure 2] Figure 1 is a perspective view of the inductor, seen from the bottom side. [Figure 3] Figure 1 is a perspective view showing the internal structure of the inductor. [Figure 4] This is a schematic diagram of the manufacturing process for the inductor of the present invention. [Figure 5] This figure shows the end face of the inductor according to Embodiment 1 of the present invention. [Figure 6] This is a cross-sectional view taken from VI-VI in Figure 5. [Figure 7] This figure shows the end face of an inductor according to Embodiment 2 of the present invention. [Figure 8] This figure shows the end face of an inductor according to Embodiment 3 of the present invention. [Figure 9] This figure shows the end face of an inductor according to Embodiment 4 of the present invention. [Modes for carrying out the invention]

[0011] [Embodiment 1] Embodiment 1 of the present invention will be described below with reference to the drawings. Figure 1 is a perspective view of the inductor according to Embodiment 1, viewed from the top surface 12, and Figure 2 is a perspective view of the inductor of Figure 1, viewed from the bottom surface 10. The inductor of Embodiment 1 is configured as a surface-mount type electronic component and comprises a substantially rectangular parallelepiped-shaped base body 2, which is one aspect of a substantially rectangular parallelepiped shape, and a pair of external electrodes 4 provided on the surface of the base body 2. The external electrodes 4 correspond to an example of an "external terminal" in the present invention.

[0012] Hereinafter, in the base model 2, the first main surface that faces the mounting substrate (not shown) 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 the 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 the side surfaces 16. As shown in Fig. 1, the distance from the bottom surface 10 to the upper 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. Further, 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 size of the inductor is, for example, the length L dimension is 2.0 mm, the width W dimension is 1.6 mm, and the thickness T dimension is 1.1 mm.

[0013] Fig. 3 is a perspective view showing the internal structure of the inductor. The base body 2 includes a coil conductor 20 and a substantially rectangular parallelepiped core 30 in which the coil conductor 20 is embedded, and is configured as a molded inductor in which the coil conductor 20 is encapsulated in the core 30. The coil conductor 20 corresponds to an example of the "coil" in the present invention.

[0014] The core 30 is a molded body obtained by compression molding a mixed powder of magnetic powder and resin into a substantially rectangular parallelepiped shape by pressurizing and heating the mixed powder while enclosing the coil conductor 20. The magnetic powder is composed of, for example, soft magnetic particles.

[0015] The magnetic powder of Embodiment 1 includes two types of particles with different particle sizes: first magnetic particles (large particles) having a relatively large average particle size and second magnetic particles (small particles) having a relatively small average particle size. Thereby, at the time of compression molding, the second magnetic particles, which are small particles, enter between the first magnetic particles, which are large particles, together with the resin, so that the filling rate of the magnetic particles in the core 30 can be increased and the magnetic permeability can be enhanced. In Embodiment 1, the average particle sizes of the metal particles of the first magnetic particles and the second magnetic particles are 24.4 μm and 1.7 μm, respectively. The average particle size of the first magnetic particles is preferably 7 μm or more and 60 μm or less, and the average particle size of the second magnetic particles is preferably 1 μm or more and 4 μm or less. Further, by including particles having an average particle size different from that of the first magnetic particles and the second magnetic particles, the magnetic particles may include particles of three or more types of particle sizes.

[0016] Both the first magnetic particles and the second magnetic particles are particles having metal particles and an insulating film with a film thickness of not less than several nanometers and not more than several tens of nanometers covering their surfaces. By covering the metal particles with the insulating film, the insulation resistance and the withstand voltage can be increased, the generation of eddy currents can be suppressed, and the loss can be reduced. In the first magnetic particles of Embodiment 1, Fe-Si-B amorphous alloy powder is used for the metal particles, and zinc phosphate glass with a thickness of 10 nm or more and 50 nm or less is used for the insulating film. Further, in the second magnetic particles of Embodiment 1, carbonyl iron powder is used for the metal particles, and a silica film with a thickness of 5 nm or more and 15 nm or less is used for the insulating film.

[0017] Further, in the mixed powder of Embodiment 1, an epoxy resin mainly composed of a phenol aralkyl type epoxy resin is used as the resin material. In Embodiment 1, the composition of the mixed powder is such that the first magnetic particles are 75 ± 10 wt%, the second magnetic particles are 25 ± 10 wt%, and the resin is 2.7 wt% or more and 3.5 wt% or less.

[0018] As shown in FIG. 3, the coil conductor 20 includes a winding portion 22 around which a conducting wire is wound and a pair of lead portions 24 drawn from the winding portion 22. The coil conductor 20 is composed of a conducting wire and a coating layer formed on the surface of the conducting wire. The conducting wire is a rectangular cross-section strip-shaped conducting wire (so-called flat wire) made of copper. For example, its thickness is 18 μm or more and 90 μm or less, and its width is 240 μm or more and 340 μm or less. The coating layer is composed of an insulating layer formed on the surface of the strip-shaped conducting wire and a fusion layer formed on the surface of the insulating layer for adhering the strip-shaped conducting wires overlapping each other in the winding portion 22. The insulating layer is made of polyamideimide resin and has a thickness of, for example, 6 ± 2 μm. Further, the fusion layer is made of polyamide resin and has a thickness of, for example, 2.5 ± 1.0 μm. Note that the thickness surface of the coil conductor may be a curved surface. When the thickness surface is a curved surface, the width of the conducting wire includes the curved surface portion of the thickness.

[0019] The winding portion 22 of the coil conductor 20 is formed in a so-called alpha winding, in which both ends of a strip-shaped conductor (hereinafter also simply referred to as a conductor) are drawn out to the outer circumference and the conductor is wound in a spiral in two stages so that it is connected to 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 portions 24 are drawn out from the winding portion 22 to each of the pair of end faces 14, with one main surface side of the strip-shaped conductor exposed from the base body 2 and the other main surface side embedded in the base body 2. Of the lead-out portions 24, the portion exposed from the end faces 14 of the base body 2 will be referred to as the exposed portion 24A below. Also, of the lead-out portions 24, the portion connecting the winding portion 22 and the exposed portion 24A will be referred to as the connecting portion 24B below. One main surface of the strip-shaped conductor exposed from the base body 2 in the lead-out section 24 is electrically connected to the external electrode 4.

[0020] The pair of external electrodes 4 are so-called L-shaped electrodes, consisting 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.

[0021] Furthermore, a protective layer (not shown) is formed on the surface of the substrate 2, excluding the area of ​​the external electrode 4. The protective layer is, for example, a phenoxy resin and a novolac resin, and contains nanosilica as a filler. The protective layer is formed on the surface of the substrate 2 with a thickness of 10 μm to 30 μm.

[0022] Inductors with this configuration can improve DC superposition characteristics by using, for example, a soft magnetic material for the magnetic powder. Therefore, they are used as choke coils in DC-DC converter circuits that require high currents, and are found in electronic components of 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 filter circuits and rectifier / smoothing circuits, for example.

[0023] Figure 4 is a schematic diagram of the inductor manufacturing process. As shown in the figure, the inductor manufacturing process includes a coil conductor formation process, a pre-molded body formation process, a thermoforming and hardening process, a barrel polishing process, and an external electrode formation process.

[0024] The coil conductor formation process is a process of forming a coil conductor 20 from a wire. In this process, the coil conductor 20 is formed by winding the wire using a winding method called "alpha winding," resulting in a shape having the aforementioned winding portion 22 and a pair of lead portions 24. The number of turns of the coil conductor 20 is not particularly limited.

[0025] The pre-molded body formation process is the process of forming pre-molded bodies, which are called tablets. The pre-molded body is formed by pressurizing the mixed powder, which is the material for the base body 2, to create a solid that is easy to handle. In Embodiment 1, two types of tablets are formed: a first tablet with an appropriate shape (e.g., an E-shaped cross-section) having a groove for housing the coil conductor 20, and a second tablet with an appropriate shape (e.g., an I-shaped cross-section or a plate shape) covering the groove side of the first tablet.

[0026] The thermoforming and curing process involves setting the first tablet, the coil conductor 20, and the second tablet so that the tip of the lead portion 24 of the coil 20 is in contact with the molding die, and applying heat while pressing in the overlapping direction of the first and second tablets to cure them, thereby integrating the first tablet, the coil conductor 20, and the second tablet. As a result, a base body 2 is formed in which the coil conductor 20 is enclosed within the core 30 and the tip of the lead portion 24 of the coil conductor 20 is exposed from the end face of the base body. The thermoforming and curing process corresponds to the base body molding process in this disclosure.

[0027] The barrel polishing process involves barrel polishing the molded body, which rounds the corners of the base body 2.

[0028] The external electrode formation step is a step of forming the external electrode 4 on the core 30, and includes a base material protective layer formation step, a surface treatment step, and a plating layer formation step.

[0029] The base material protective layer formation process involves coating the entire surface of the molded body with an insulating resin. This process forms a base material protective layer, composed of an insulating resin, on the entire surface of the molded body.

[0030] The surface treatment process involves modifying the surface of the core 30 by irradiating the electrode area with laser light. 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 at least a portion of the exposed portion 24A of the lead-out portion 24. Specifically, by irradiating with laser light, the protective layer of the base material on the surface of the core 30 and the coating layer at the tip of the lead-out portion 24 of the coil conductor 20 are removed in the area of ​​the electrode area to form the exposed portion 24A, the resin on the surface of the core 30 is removed, and the insulating film on the surface of the magnetic powder exposed from the core 30 is removed, causing the magnetic particles to fuse together. As a result, the exposed area of ​​the metal of the magnetic powder per unit area of ​​the surface of the core 30 is larger in the electrode area compared to other parts of the core 30 surface, making it easier to form the plating. After irradiation with laser light, a cleaning process (e.g., etching) may be performed to clean the surface of the electrode area.

[0031] In the plating layer formation process, a copper plating layer is formed on the electrode area where the laser light is to be irradiated by barrel plating of copper onto the surface of the core 30. In addition, the plating layer may be formed by further adding a nickel (Ni) plating layer and a tin (Sn) plating layer on top of the copper plating layer. Alternatively, layers of aluminum (Al), silver (Ag), gold (Au), or palladium (Pd) may be used instead of the copper (Cu) layer.

[0032] Through the above-described external electrode formation process, the external electrode 4 composed of the above-described plating layer is formed. Furthermore, the external electrode 4 is not limited to an L-shaped electrode; it may also be a so-called five-sided electrode, provided from the entire surface of the end face 14 to a portion of the bottom surface 10, the top surface 12, and the pair of side surfaces 16 adjacent to the end face 14.

[0033] (Configuration of external electrodes) Figure 5 shows the end face 14 of the inductor 1 in Embodiment 1. As shown in Figure 5, in Embodiment 1, the external electrode 4 formed on the end face 14 is formed in a region that includes the entire exposed portion 24A of the coil conductor 20.

[0034] Furthermore, a plating break portion 41 is formed on the end face 14 of the external electrode 4. The plating break portion 41 is the area inside the outer edge of the external electrode 4 where the external electrode 4 is not plated.

[0035] In detail, the plating break portion 41 in Embodiment 1 is the portion where the exposed portion 24A of the lead-out portion 24 and the external electrode 4 are not connected by plating. Furthermore, the plating break portion 41 in Embodiment 1 is formed along the base portion 24C, which is the portion of the exposed portion 24A that is closer to the connection portion 24B.

[0036] In the plating break section 41 of Embodiment 1, the protective layer of the base material is removed, and the core 30 of the base material 2 is exposed. In addition, in the plating break section 41 of Embodiment 1, the coating layer covering the wires of the coil conductor 20 may remain.

[0037] In this way, the formation of the plating break 41 allows evaporated moisture to easily pass through the plating break 41 even when the inductor 1 is heated while moisture is present in the inductor 1. This is because moisture cannot pass through the metal external electrode 4, but can move through the core 30 and easily pass through the plating break 41. Furthermore, in Embodiment 1, the plating break 41 is formed along the base portion 24C located on the side of the exposed portion 24A that is closer to the connection portion 24B. Therefore, moisture contained in the inductor 1 can easily reach the plating break 41 along the interface of the coating layer, which is the resin covering the conductor wire of the coil conductor 20, and the evaporated moisture can pass through more easily.

[0038] As described later, experiments conducted by the inventors have confirmed that when the inductor 1 having the plating break 41 of Embodiment 1 is exposed to conditions of 85°C and 85% humidity for 168 hours, if the moisture content is less than 0.04 wt% by weight, the moisture evaporated by heating of the inductor 1 can be properly passed through. The moisture content of inductor 1 when exposed to a similar environment varies depending on the ratio of resin in the core 30, the thickness of the coating layer of the coil conductor 20, the material of the protective layer, etc. Furthermore, the higher the ratio of resin in inductor 1, the more likely it is to have a high moisture content.

[0039] The plating break 41 in Embodiment 1 is formed by adjusting the time spent performing barrel plating during the plating layer formation process.

[0040] At the start of the plating layer formation process, that is, after the completion of the surface treatment process, the area near the base portion 24C connected to the connection portion 24B is the part of the exposed portion 24A where the distance between the conductor and the surface of the core 30 tends to be the largest. For this reason, during barrel plating in the plating layer formation process, the external electrode 4 near the base portion 24C is plated later than the external electrode 4 in other areas. In Embodiment 1, this property is utilized to form a plated section 41 by ending the barrel plating earlier than the time at which the external electrode 4 is formed along the base portion 24C.

[0041] (Packing density of magnetic powder) Figure 6 is a cross-sectional view of Figure 5 along the line VI-VI, showing a cross-section of the inductor 1 along the length DL and width DW, including the entire length of one of the lead-out sections 24.

[0042] As shown in Figure 6, in the inductor 1, there is a region between the winding portion 22 and the lead portion 24 where no conductors exist. This region between the winding portion 22 and the lead portion 24 will be referred to as the first filling portion 51 below. In addition, there is a region inside the winding portion 22 where no conductors exist. This region inside the winding portion 22 will be referred to as the second filling portion 52 below. Furthermore, the portion of the base body 2 excluding the first filling portion 51, the second filling portion 52, and the coil conductor 20 will be referred to as the third filling portion 53 below.

[0043] In inductor 1, the filling rate of magnetic powder in the first filling section 51 is smaller than that of magnetic powder in the second filling section 52 and the third filling section 53. This is because, during the thermoforming and curing process, the space between the winding section 22 and the lead section 24, which corresponds to the first filling section 51, is narrow, making it difficult for the mixed powder of resin and magnetic powder to enter. The filling rate referred to here is the ratio of the volume occupied by magnetic powder per unit volume.

[0044] Thus, because the filling rate of magnetic powder in the first filling section 51 is smaller than that of the second filling section 52 and the third filling section 53, when the moisture in the resin of the inductor 1 evaporates due to heating, the moisture easily passes through areas other than the magnetic powder and reaches the plating break section 41. For this reason, the small filling rate of magnetic powder in the first filling section 51 allows moisture to easily pass through the inductor 1.

[0045] The fact that the filling rate of magnetic powder in the first filling section 51 is smaller than the filling rate of magnetic powder in the second filling section 52 and the third filling section 53 can be confirmed, for example, as follows: First, the inductor 1 is cut in a cross-section that includes one lead portion 24 and is parallel to the length direction DL and the width direction DW, i.e., a cross-section equivalent to that in Figure 6. Next, the ratio of the area occupied by the cross-section of the magnetic powder per unit area of ​​the first filling portion 51 is calculated in the cut cross-section. Furthermore, the ratio of the area occupied by the cross-section of the magnetic powder per unit area of ​​the second filling portion 52 and the third filling portion 53 is calculated. Then, if the calculated value for the first filling portion 51 is smaller than the values ​​for the second filling portion 52 and the third filling portion 53, it can be confirmed that the filling rate of the magnetic powder in the first filling portion 51 is smaller than the filling rate of the magnetic powder in the second filling portion 52 and the third filling portion 53.

[0046] More specifically, the ratio of the area occupied by the cross-section of magnetic powder per unit area may be the ratio of the area occupied by magnetic powder to the total area of ​​the first filling section 51, the second filling section 52, or the third filling section 53. In this case, a magnified image of a cross-section equivalent to that shown in Figure 6 of the inductor 1 is taken using a microscope or scanning electron microscope (SEM) to include the entire cross-section. Next, based on the acquired magnified image, the total area of ​​the first filling section 51, the second filling section 52, and the third filling section 53 is obtained by image processing or the like. Next, based on the acquired magnified image, the area occupied by magnetic powder in the entirety of the first filling section 51, the second filling section 52, and the third filling section 53 is obtained by image processing or the like. Then, for each of the first filling section 51, the second filling section 52, and the third filling section 53, the ratio of the area occupied by magnetic powder to the total area is calculated. Furthermore, in a cross-section equivalent to that of Figure 6, the area occupied by the first filling portion 51 may be defined, for example, as the area inside the imaginary line L1 that connects the tip 24D of the lead portion 24 to the end face of the winding portion 22 perpendicularly. Also, in a cross-section equivalent to that of Figure 6, the area occupied by the second filling portion 52 may be defined as the area inside the innermost circumference of the conductor constituting the winding portion 22. Also, in a cross-section equivalent to that of Figure 6, the area occupied by the third filling portion 53 may be defined as the area of ​​the cross-section of the inductor 1 excluding the first filling portion 51, the second filling portion 52, the coil conductor 20, the base protective layer, and the external electrode 4.

[0047] Furthermore, the ratio of the area occupied by the cross-section of the magnetic powder per unit area may be calculated from an enlarged image obtained by magnifying a portion of the first filling section 51, the second filling section 52, or the third filling section 53. In this case, for a cross-section of the inductor 1 equivalent to that shown in Figure 6, an enlarged image is taken using a microscope or SEM, magnifying a portion of each of the first filling section 51, the second filling section 52, and the third filling section 53. Next, the area occupied by the magnetic powder is obtained from each of the magnified photographs of the first filling section 51, the second filling section 52, and the third filling section 53 by image processing or the like. Then, the ratio of the area occupied by the magnetic powder to the area of ​​the field of view of the obtained enlarged image is calculated.

[0048] (experiment) The inventors created multiple inductors 1 with plating breaks 41 similar to those in Embodiment 1, exposed them to high temperature and high humidity conditions, and then heated them to confirm whether the moisture absorbed by the inductors 1 could pass through properly. The details of the experiment are described below.

[0049] (Sample preparation) The inventors adjusted the time of the plating layer formation process to create samples A1 and A4 in which no plating breaks 41 were formed, and samples A2, A3, and A5 inductors 1 in which plating breaks 41 were formed in the same manner as in Embodiment 1. The inventors created inductor 1 as sample A1, with a length L dimension of 2.5 mm, a width W dimension of 2.0 mm, a thickness T dimension of 1.1 mm, and a weight of 64.24 mg at the time of fabrication. The inventors created inductor 1 as sample A2, with a length L dimension of 2.5 mm, a width W dimension of 2.0 mm, a thickness T dimension of 1.1 mm, and a weight of 66.79 mg at the time of fabrication. The inventors created inductor 1 as sample A3, with a length L dimension of 2.0 mm, a width W dimension of 1.6 mm, a thickness T dimension of 1.2 mm, and a weight of 48.55 mg at the time of fabrication. The inventors created inductor 1 as sample A4, with a length L dimension of 2.5 mm, a width W dimension of 2.0 mm, a thickness T dimension of 1.2 mm, and a weight of 72.55 mg at the time of creation. The inventors created inductor 1 as sample A5, with a length L dimension of 3.1 mm, a width W dimension of 2.5 mm, a thickness T dimension of 1.8 mm, and a weight of 57.84 mg at the time of fabrication.

[0050] (Details of moisture absorption treatment) The inventors subjected samples A1 to A5 to a moisture absorption treatment under high temperature and high humidity conditions. In this treatment, the inventors exposed samples A1 to A5 to a constant temperature and humidity test chamber at a temperature of 85°C and a humidity of 85% for 168 hours. The moisture absorption treatment was carried out in accordance with MSL1 of the Moisture Sensitivity Level (MSL) test defined by JEDEC.

[0051] (Details of the heat treatment) The inventors heated samples A1 to A5 after the moisture absorption treatment. Each sample A1 to A5 was heated to 250°C. The moisture content of samples A1 to A5 after the moisture absorption treatment was determined by the weight of the water vapor generated from each sample, obtained by analysis using a thermogravimetric-mass spectrometer (TG-MS). The heat treatment simulates the heating process that occurs when inductor 1 is reflow-mounted in a reflow oven.

[0052] (observation) The inventors observed samples A1 to A5 after heat treatment using CT and other methods. In the observation, the inventors evaluated the crack occurrence status of samples A1 to A5 in two stages: "Good" (no cracks) and "Bad" (cracks were present). Such cracks can occur when moisture absorbed by samples A1 to A5 during the moisture absorption treatment evaporates into water vapor during the heat treatment and rapidly expands. If there is no escape route for the water vapor within samples A1 to A5, the internal pressure of samples A1 to A5 increases, causing cracks to form. Furthermore, when such cracks occur, the inductance value of samples A1 to A5 may decrease from the value at the time of creation. In determining the presence or absence of cracks, the inventors observed the cross-section of each sample A1 to A5 in addition to its external appearance.

[0053] (result) Table 1 below shows the experimental results.

[0054] [Table 1]

[0055] As shown in Table 1, the moisture content of sample A1 after the hygroscopic treatment was 0.026422 mg by weight, which was 0.04113 wt% by weight relative to the weight of sample A1 at the time of preparation. Furthermore, observations by the inventors resulted in a "Bad" judgment, indicating that cracks had formed in sample A1 after the heat treatment. In sample A2, the moisture content after the hygroscopic treatment was 0.021209 mg by weight, which was 0.03175 wt% by weight relative to the weight of sample A2 at the time of preparation. Furthermore, observations by the inventors resulted in a "Good" rating, indicating that no cracks had formed in sample A2 after the heat treatment. In sample A3, the moisture content after the hygroscopic treatment was 0.018244 mg by weight, which was 0.03758 wt% by weight relative to the weight of sample A3 at the time of preparation. Furthermore, observations by the inventors resulted in a "Good" rating, indicating that no cracks had formed in sample A3 after the heat treatment. In sample A4, the moisture content after the hygroscopic treatment was 0.040251 mg by weight, which was 0.05548 wt% by weight relative to the weight of sample A4 at the time of preparation. Furthermore, observations by the inventors resulted in a "Bad" judgment, indicating that cracks had formed in sample A4 after the heat treatment. In sample A5, the moisture content after the hygroscopic treatment was 0.015759 mg by weight, which was 0.02725 wt% by weight relative to the weight of sample A5 at the time of preparation. Furthermore, observations by the inventors resulted in a "Good" rating, indicating that no cracks had formed in sample A5 after the heat treatment.

[0056] (Conclusion) The inventors analyzed that, based on experimental results, if the moisture content of inductor 1 after dehumidification treatment is less than 0.04 wt% by weight relative to inductor 1, no cracks will occur in inductor 1 during heat treatment. Therefore, they concluded that if the moisture content of inductor 1 after exposure to conditions of 85°C and 85% humidity for 168 hours is less than 0.04 wt% by weight, the occurrence of cracks during heating such as reflow mounting can be suppressed.

[0057] Next, embodiments 2 to 4 will be described. In the following description, the differences from embodiment 1 will be explained, and the explanation of matters common to embodiment 1 will be omitted.

[0058] [Embodiment 2] Embodiment 2 will be described below. Figure 7 is a diagram showing the end face 14 of the inductor 1 according to Embodiment 2.

[0059] As shown in Figure 7, in Embodiment 2, a plating break 141 is formed in the region inside the outer edge of the external electrode 4, along the edge 24E of the exposed portion 24A. The edge 24E is the portion of the outer edge of the exposed portion 24A that extends along the width direction DW, which is the extension direction of the exposed portion 24A. The plating break 141 in Embodiment 2 is provided over substantially the entire length of the edge 24E.

[0060] In detail, the plating break portion 141 in Embodiment 2 is a portion formed between the exposed portion 24A and the external electrode 4 that is not connected by plating. Furthermore, in the plating break portion 141 of Embodiment 2, the thickness of the base material protective layer is thinner than that of the upper surface 12, side surface 16, and other portions that were not irradiated with laser light during the surface treatment process.

[0061] In Embodiment 2, the plating break portion 141 is formed by intentionally leaving a portion of the base material protective layer along the edge 24E of the exposed portion 24A during the surface treatment process, and then performing a plating layer formation process. In the surface treatment process, the laser beam is usually scanned over the entire surface of the planned electrode area multiple times until all of the base material protective layer and coating layer of the planned electrode area are removed. As a result, the magnetic powder or the metal portion of the conductor is exposed over the entire planned electrode area, and an external electrode 4 is formed that covers the entire planned electrode area. In contrast, in the surface treatment process of Embodiment 2, the intensity or number of irradiations of the laser beam is adjusted so that only the thickness of the base material protective layer is reduced, rather than all of the base material protective layer being removed, only in the area along the edge 24E of the exposed portion 24A of the planned electrode area. After that, the plating break portion 141 of Embodiment 2 is formed by performing a plating layer formation process.

[0062] As described above, in the plating break 141 of Embodiment 2, the external electrode 4 is not formed, and the thickness of the protective layer is thinner than the thickness of the protective layer in other areas such as the top surface 12 and the side surface 16. Therefore, moisture absorbed by the resin of the inductor 1 and evaporated by heating can reach the plating break 141 through the coating layer of the coil conductor 20 or the first filling portion 51, and then pass through the plating break 141 to the outside of the inductor 1.

[0063] [Embodiment 3] Embodiment 3 will be described below. Figure 8 is a diagram showing the end face 14 of the inductor 1 according to Embodiment 3.

[0064] As shown in Figure 8, in Embodiment 2, a plating break portion 241 is formed in the region inside the outer edge of the external electrode 4, located near the exposed portion 24A. In the example in Figure 8, two plating break portions 241 are formed, but the number of plating break portions 241 can be one or more.

[0065] In detail, the plating break portion 241 in Embodiment 3 is a location where the external electrode 4 is not plated. The plating break portion 241 is spaced apart from the exposed portion 24A and is located in the vicinity of the exposed portion 24A. Here, the location in the vicinity of the exposed portion 24A means, for example, a location closer to the exposed portion 24A than the imaginary line L2 that bisects the distance between the outer edge of the exposed portion 24A and the outer edge of the external electrode 4. Furthermore, it is sufficient if a portion of the plating break portion 241 is located closer to the exposed portion 24A than the imaginary line L2. In Embodiment 3, the thickness of the base material protective layer in the plating break portion 241 is thinner than the thickness of the base material protective layer in other locations such as the top surface 12 and side surfaces 16, or the base material protective layer is completely removed.

[0066] The plating break portion 241 in Embodiment 3 may be formed by intentionally leaving a portion of the base material protective layer near the exposed portion 24A during the surface treatment process, and then performing the plating layer formation process. In this case, during the surface treatment process of Embodiment 3, the intensity or number of laser irradiations is adjusted so that the entire base material protective layer is not removed, but only the thickness of the base material protective layer is reduced, only in a portion of the area near the exposed portion 24A of the planned electrode location. Subsequently, the plating break portion 241 of Embodiment 3 is formed by performing the plating layer formation process.

[0067] Furthermore, the plating break portion 241 in Embodiment 3 may be formed by removing all of the base protective layer from the planned electrode area in the surface treatment process, then peeling off the exposed magnetic powder near the exposed portion 24A of the planned electrode area, and then performing the plating layer formation process. In this case, since the external electrode 4 is less likely to be plated in the area where the magnetic powder has peeled off during the plating layer formation process, the plating break portion 241 is formed.

[0068] As described above, in the plating break 241 of Embodiment 3, the external electrode 4 is not formed, and the base material protective layer is either removed or thinner than the thickness of the base material protective layer in other areas such as the top surface 12 and side surfaces 16. Therefore, moisture absorbed by the resin of the inductor 1 and evaporated by heating can reach the plating break 241 through the coating layer of the coil conductor 20 or the first filling portion 51, and then pass through the plating break 241 to the outside of the inductor 1.

[0069] [Embodiment 4] Embodiment 4 will be described below. Figure 9 is a diagram showing the end face 14 of the inductor 1 according to Embodiment 4.

[0070] As shown in Figure 9, in Embodiment 4, the exposed portion 24A has an uncovered portion 24F that is not covered by the external electrode 4. In Embodiment 4, the uncovered portion 24F is the part of the exposed portion 24A that is not covered by the external electrode 4. In Embodiment 4, the uncovered portion 24F is formed on the tip 24D side of the exposed portion 24A. The uncovered portion 24F is exposed to the outside from the end face 14 of the base body 2. In addition, the portion of the conductor constituting the coil conductor 20 that corresponds to the uncovered portion 24F is covered by the coating layer and the base body protective layer.

[0071] Furthermore, a recess 341 is formed on the end face 14. The recess 341 is a recess extending inward from the end face 14 to the base body 2. The recess 341 is formed on the end face 14 of the base body 2 along the uncovered portion 24F. The recess 341 is also formed in a position in contact with the outer edge of the external electrode 4.

[0072] The formation of the recess 341 exposes the interface between the external electrode 4 and the protective layer to the void inside the recess 341. Therefore, when moisture contained in the inductor 1 of Embodiment 4 is evaporated by heating, it can pass through the interface between the external electrode 4 and the protective layer and out of the inductor 1 through the recess 341.

[0073] [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.

[0074] In the embodiments 1 to 3 described above, the plating breaks 41, 141, and 241 were formed entirely on the inside of the outer edge of the external electrode 4, but this is just one example. The plating breaks 41, 141, and 241 may extend to the outer edge of the external electrode 4.

[0075] In the embodiments 1 to 4 described above, the exposed portion 24A was described as being exposed from the end face 14, but this is just one example. The exposed portion 24A may also be configured to be exposed from, for example, the bottom face 10.

[0076] 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 (the so-called equivalence range).

[0077] [Configurations supported by the above embodiment]

[0078] This embodiment provides the following effects.

[0079] (Configuration 1) An inductor comprising a base body having a core containing magnetic powder and resin, a coil embedded in the core, and an external terminal provided on the surface of the base body, wherein the coil has a winding portion around which a conductor is wound and a lead portion drawn out from the winding portion, the lead portion has an exposed portion exposed from the base body, and the external terminal is formed by plating on an area of ​​the surface of the base body that includes at least a part of the exposed portion, and a plated break portion that is not connected by plating is formed between the exposed portion and the external terminal. According to the inductor described in Configuration 1, the plated gap functions as a pathway for moisture stored in the inductor to escape. This makes it easier for moisture stored in the inductor to pass through.

[0080] (Configuration 2) The inductor according to Configuration 1, wherein the plated cut portion is formed along the base of the exposed portion. In the inductor described in Configuration 2, the plating break formed along the base of the exposed portion functions as an escape route for moisture accumulated in the inductor. This makes it easier for moisture accumulated in the inductor to pass through.

[0081] (Configuration 3) The inductor according to Configuration 1, wherein the plated cut portion is formed along the edge of the exposed portion that is parallel to the extension direction of the exposed portion. In the inductor described in configuration 3, the plating break formed along the edge of the exposed portion functions as an escape route for moisture accumulated in the inductor. This makes it easier for moisture accumulated in the inductor to pass through.

[0082] (Configuration 4) An inductor comprising a base body having a core containing magnetic powder and resin, a coil embedded in the core, and an external terminal provided on the surface of the core, wherein the coil has a winding portion around which a conductor is wound and a lead portion drawn out from the winding portion, the lead portion has an exposed portion exposed from the base body, and the external terminal is formed by plating on the surface of the base body in a region including at least a part of the exposed portion, and a plated break is formed near the exposed portion where the external terminal is not formed. In the inductor described in configuration 4, the plating break formed along the edge of the exposed portion functions as an escape route for moisture accumulated in the inductor. This makes it easier for moisture accumulated in the inductor to pass through.

[0083] (Configuration 5) An inductor comprising a base body having a core containing magnetic powder and resin, a coil embedded in the core, and an external terminal provided on the surface of the core, wherein the coil has a winding portion around which a conductor is wound and a lead portion drawn out from the winding portion, the lead portion has an exposed portion exposed from the base body, the external terminal is formed by plating on a region of the surface of the base body including a part of the exposed portion, the exposed portion has an uncoated portion located outside the external terminal, and a recess is formed on the surface of the base body along the uncoated portion. According to the inductor described in configuration 5, the recess formed on the surface of the base material along the uncoated portion functions as an escape route for moisture stored in the inductor. This makes it easier for moisture stored in the inductor to pass through.

[0084] (Configuration 6) An inductor according to any one of Configurations 1 to 5, wherein the packing rate of the magnetic powder between the lead portion and the winding portion is smaller than the packing rate of the magnetic powder in other areas. According to the inductor described in configuration 6, moisture stored in the inductor can easily move to the plated gaps or recesses by passing through the region between the lead-out section and the winding section, where the magnetic powder filling rate is low. Therefore, it is possible to make it easier for moisture stored in the inductor to pass through.

[0085] (Configuration 7) An inductor according to any one of Configurations 1 to 6, wherein the moisture content when exposed for 168 hours under conditions of a temperature of 85°C and a humidity of 85% is less than 0.04 wt% by weight. The inductor described in Configuration 7 can suppress the moisture content in the inductor. Therefore, when the inductor is heated and the moisture stored in the inductor evaporates, it is possible to suppress adverse effects on the inductor while making it easier for the moisture to pass through. [Explanation of Symbols]

[0086] 1 Inductor 2. Base body 4. External electrodes (external terminals) 4A part 10 Bottom 12 Top side 14 End face 16 Side view 20 Coil conductors (coils) Volume 22 24 Drawer section 24A Exposed part 24C Root part 24E Edge 24F Uncovered section 30 cores 41 Plating break 141 Plating break 241 Plating break 341 Recess

Claims

1. A base body having a core containing magnetic powder and resin, and a coil embedded in the core, The body comprises an external terminal provided on the surface of the aforementioned body, The coil has a winding portion around which a conductor is wound, and a lead portion from which a wire is drawn out. The aforementioned pull-out portion has an exposed portion that is exposed from the base body, The external terminal is formed by plating on the surface of the base body, in an area that includes at least a portion of the exposed portion. Between the exposed portion and the external terminal, a plated gap is formed that is not connected by plating. Inductor.

2. The aforementioned plating break is formed along the base of the exposed portion, The inductor according to claim 1.

3. The plated break portion is formed along the edge of the exposed portion that is parallel to the extending direction of the exposed portion. The inductor according to claim 1.

4. A base body having a core containing magnetic powder and resin, and a coil embedded in the core, The core comprises an external terminal provided on the surface of the core, The coil has a winding portion around which a conductor is wound, and a lead portion from which a wire is drawn out. The aforementioned pull-out portion has an exposed portion that is exposed from the base body, The external terminal is formed by plating on the surface of the base body, in an area that includes at least a portion of the exposed portion. Near the exposed portion, a plated section is formed where the external terminal is not formed. Inductor.

5. A base body having a core containing magnetic powder and resin, and a coil embedded in the core, The core comprises an external terminal provided on the surface of the core, The coil has a winding portion around which a conductor is wound, and a lead portion from which a wire is drawn out. The aforementioned pull-out portion has an exposed portion that is exposed from the base body, The external terminal is formed by plating on the surface of the base body, in a region that includes a part of the exposed portion. The exposed portion has an uncovered portion located outside the external terminal, A recess is formed on the surface of the base body along the uncoated portion. Inductor.

6. The filling rate of the magnetic powder between the extraction portion and the winding portion is smaller than the filling rate of the magnetic powder in other areas. An inductor according to any one of claims 1 to 5.

7. The moisture content when exposed for 168 hours under conditions of 85°C and 85% humidity is less than 0.04 wt% by weight. An inductor according to any one of claims 1 to 5.

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