Inductor and method for producing inductor
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- MURATA MFG CO LTD
- Filing Date
- 2024-11-22
- Publication Date
- 2026-06-03
Abstract
Description
Inductor and method for manufacturing the same
[0001] The present invention relates to an inductor and a method for manufacturing an inductor.
[0002] Patent Document 1 describes an inductor having a coil conductor, an element body containing metal magnetic particles and resin and enclosing the coil conductor, and a pair of external electrodes electrically connected to the ends of the coil conductor. In this inductor, the surface of the lead-out portion of the coil conductor is exposed on the surface of the element body, and a plating layer is formed on the portion of the element body surface where the external electrodes will be formed after the resin contained in the element body is removed. This electrically connects the metal magnetic particles contained in the element body, the lead-out portion, and the external electrodes including the plating layer.
[0003] JP 2016-58418 A
[0004] In the above-described conventional inductor, for example, when the coil conductor is formed of a lead wire having a conductor and an insulating coating, after forming an element body so that the lead portions of the coil conductor are exposed, by irradiating the external electrode formation area on the element body surface, including the exposed lead portions, with laser light, the resin on the element body surface is removed and the insulating coating of the lead portions exposed on the element body surface is also removed. During this process, there may be portions of the insulating coating of the lead wire that are not sufficiently removed near the outline of the lead portion exposed on the element body surface (i.e., the boundary between the surface of the exposed lead portion and the surrounding element body surface). Such remaining portions of the insulating coating make it difficult for the plating layer that constitutes the external electrode to adhere, which may cause dents on the surface of the external electrode or moisture to get between the external electrode and the insulating coating, causing solder explosions when the inductor is soldered to a substrate.
[0005] The object of the present invention is to prevent an external electrode from being formed on the insulating coating of the lead portion exposed on the surface of the element body in an inductor having a coil conductor with a pair of lead portions made of a conducting wire having a conductor and an insulating coating, thereby preventing the formation of a depression on the surface of the external electrode and preventing moisture, which is a cause of solder explosions when mounted on a board, from penetrating into the external electrode.
[0006] One aspect of the present invention is an inductor having a coil conductor having a pair of first and second lead portions formed by a strip-shaped conductor wire having a conductor and an insulating coating covering the outer periphery of the conductor, an element body containing magnetic particles and resin and containing the coil conductor, an element body protective film covering the surface of the element body, and an external electrode connected to the coil conductor, wherein the element body has a mounting surface that faces a mounting board when mounted, and two paired end faces that are perpendicular to the mounting surface, and each of the first and second lead portions that are strip-shaped conductor wire is provided with an insulating coating covering the strip-shaped conductor wire. One main surface of the conductor is exposed from the end face of the element body, and the exposed portions exposed on the end faces of each of the first and second lead-out portions have a planar shape that is approximately rectangular with two opposing sides that are approximately parallel to the mounting surface of the element body, and the element body protective film covers the far side of the two sides of the approximately rectangular shape formed by the exposed portions of at least one of the first and second lead-out portions, which is the side farthest from the mounting surface, and includes an overlapping portion that overlaps with the insulating coating extending over part of the exposed portion, and the external electrode extends on the surface of the overlapping portion of the element body protective film.Another aspect of the present invention comprises: an element molding step of embedding a coil conductor having a first lead portion and a second lead portion, the coil conductor being formed from a strip-shaped conductor having a conductor and an insulating coating coating coating the outer periphery of the conductor, in an element body containing magnetic particles and a resin so that the first lead portion and the second lead portion of the coil conductor are exposed from the surface of the element body; an element protective film forming step of forming an element protective film on the surface of the element body so as to cover the surface of the element body; a surface treatment step of irradiating laser light onto planned electrode locations on the surface of the element body, including exposed portions of the first lead portion and the second lead portion exposed from the element body, to remove part of the resin and the element protective film on the surface of the element body at the planned electrode locations; and a plating layer forming step of forming external electrodes by plating on the surface of the element body including the exposed portions, wherein the element body has a mounting surface that faces a mounting board when mounted, and and two paired end faces perpendicular to each other, wherein in the element body molding step, the coil conductor is embedded in the element body so that one main surface of the first lead portion and the second lead portion, which are strip-shaped conductors, is exposed from the end face of the element body, and the planar shape of the exposed portions exposed at the end faces of the first lead portion and the second lead portion is a substantially rectangular shape having two opposing sides substantially parallel to the mounting surface of the element body, in the surface treatment step, the element body protective film is removed from the surface of the element body so as to include an overlapping portion that covers a far side, which is the side farthest from the mounting surface, of the two sides of the substantially rectangular shape formed by the exposed portions of at least one of the first lead portion and the second lead portion, and overlaps with a part of the exposed portion, and in the plating layer formation step, the external electrode is formed so as to extend on the surface of the overlapping portion of the element body protective film. This specification includes the entire contents of Japanese Patent Application No. 2024-024547, filed on February 21, 2024.
[0007] According to the present invention, in an inductor having a coil conductor having a pair of lead portions made of a conducting wire having a conductor and an insulating coating, enclosed within a body containing magnetic particles and resin, it is possible to prevent an external electrode from being formed on the insulating coating of the lead portion exposed on the surface of the body, thereby preventing the occurrence of depressions on the surface of the external electrode and preventing moisture, which is a cause of solder explosions when mounted on a board, from penetrating into the external electrode.
[0008] FIG. 1 is a perspective view of an inductor according to an embodiment of the present invention, viewed from the top side. FIG. 2 is a perspective view of the inductor viewed from the mounting surface side. FIG. 3 is a see-through perspective view showing the internal configuration of the inductor. FIG. 4 is a plan perspective view of the inductor shown in FIG. 3, viewed from the top side. FIG. 5 is a V-V cross-sectional view of the inductor shown in FIG. 4. FIG. 6 is a view showing a plan view of two end faces of the element body of the inductor shown in FIG. 5. FIG. 7 is a view showing a plan view of the end face shown in FIG. 6, with an element protective film superimposed thereon. FIG. 8 is a view showing a plan view of the end face shown in FIG. 7, with an external electrode formation region superimposed thereon. FIG. 9 is a cross-sectional view taken along IX-IX in FIG. 8A. FIG. 10 is an example of an enlarged cross-sectional photograph of a portion of an element body end face including an overlapping portion of an element protective film. FIG. 11 is a diagram showing a manufacturing process for an inductor. FIG. 12 is a view showing a plan view of an element body end face of an inductor according to another embodiment, with an element protective film and an external electrode formation region superimposed thereon.
[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. [1. Inductor Configuration] First, the configuration of an inductor 1 according to this embodiment will be described. [1.1 Overall Configuration of Inductor] Fig. 1 is a perspective view of the inductor 1 according to this embodiment as viewed from the top surface 12 side, and Fig. 2 is a perspective view of the inductor 1 as viewed from the mounting surface 10 side. The inductor 1 of this embodiment is configured as a surface-mount electronic component, and includes an element body 2 having a substantially rectangular parallelepiped shape, which is one form of a substantially hexahedral shape, and a pair of external electrodes 4 provided on the surface of the element body 2.
[0010] Hereinafter, in the element body 2, a first main surface that faces a mounting board (not shown) during mounting is defined as a mounting surface 10, a second main surface opposite to the mounting surface 10 is defined as a top surface 12, a pair of third main surfaces perpendicular to the mounting surface 10 are defined as end surfaces 14, and a pair of fourth main surfaces perpendicular to the mounting surface 10 and the pair of end surfaces 14 are defined as side surfaces 16. As shown in FIG. 1 , the distance from the mounting surface 10 to the top surface 12 is defined as a thickness T of the element body 2, the distance between the pair of side surfaces 16 is defined as a width W of the element body 2, and the distance between the pair of end surfaces 14 is defined as a length L of the element body 2. Furthermore, the direction of the thickness T is defined as a thickness direction DT, the direction of the width W is defined as a width direction DW, and the direction of the length distance is defined as a length direction DL. The dimensions of the inductor 1 are, for example, a length L of 1.4 mm, a width W of 1.2 mm, and a thickness T of 0.65 mm.
[0011] 3 is a see-through perspective view showing the internal configuration of the inductor 1. The element body 2 includes a coil conductor 20 and a substantially hexahedral core 30 in which the coil conductor 20 is embedded, and is configured as a molded inductor in which the coil conductor 20 is sealed in the core 30.
[0012] The core 30 is a molded body obtained by compression molding a powder mixture of magnetic particles and resin into a substantially hexahedral shape by applying pressure and heat while the coil conductor 20 is enclosed therein.
[0013] The magnetic particles of this embodiment contain particles of two particle sizes: first magnetic particles with a relatively large average particle size and second magnetic particles with a relatively small average particle size. This allows the second magnetic particles, which are small particles, to penetrate between the first magnetic particles with the resin during compression molding, thereby increasing the magnetic particle filling rate in the core 30 and improving magnetic permeability. The average particle size (D50) of the first magnetic particles is preferably 20 μm or more and 68 μm or less, and more preferably 21.4 μm or more and 27.4 μm or less. The average particle size (D50) of the second magnetic particles is preferably 1 μm or more and 6 μm or less, and more preferably 1.5 μm or more and 1.8 μm or less. The magnetic particles may contain particles with different average particle sizes from the first magnetic particles and the second magnetic particles, thereby containing particles of three or more particle sizes.
[0014] The first magnetic particles and the second magnetic particles are both particles having metal particles and an insulating film covering the surfaces of the metal particles with a thickness of several nanometers to several tens of nanometers. Covering the metal particles with an insulating film increases the insulation resistance and withstand voltage. In the first magnetic particles of this embodiment, Fe—Si—B amorphous alloy powder is used for the metal particles, and zinc phosphate glass with a thickness of 10 nm to 50 nm is used for the insulating film. Furthermore, in the second magnetic particles of this embodiment, carbonyl iron powder is used for the metal particles, and a silica film with a thickness of 5 nm to 15 nm is used for the insulating film.
[0015] In the mixed powder of this embodiment, the resin material is an epoxy resin whose main component is a phenol alkyl epoxy resin. The amount of second magnetic particles contained in the mixed powder is, for example, 15 wt% to 30 wt% and preferably 20 wt% to 30 wt% based on the total weight of the magnetic particles. The resin content in the mixed powder is 2.0 wt% to 3.5 wt% based on the total weight of the mixed powder.
[0016] As shown in FIG. 3 , the coil conductor 20 includes a winding portion 22 around which a conductor wire is wound and a pair of lead portions 24 drawn from the winding portion 22. The coil conductor 20 does not necessarily have to be wound, but may be linear, meander-shaped, or the like. In these cases, the coil conductor 20 includes the linear or meander-shaped conductor portion instead of the winding portion 22, and a pair of lead portions 24 extending from the conductor portion. The conductor forming the coil conductor 20 includes a copper conductor and an insulating coating formed on the surface of the conductor. The conductor is a strip-shaped conductor (so-called flat conductor). The thickness of the conductor is 118 μm or less, preferably 52 μm or more. The width of the conductor is 180 μm or less, preferably 110 μm or more. The aspect ratio of the conductor is, for example, 1.2 to 3.4. The insulating coating is made of, for example, polyurethane resin, polyester resin, epoxy resin, or polyamide-imide resin, and is preferably polyamide-imide resin. The insulating coating has a thickness of, for example, 3 μm.
[0017] The conductor wire may have a bonding layer on the insulating coating for bonding overlapping conductor wires together in the winding portion 22. For example, the bonding layer is made of polyamide resin, and the thickness thereof is preferably 1 μm or more and 25 μm or less, more preferably 2 μm or more and 25 μm or less, and even more preferably 2 μm or more and 4 μm or less.
[0018] The winding portion 22 of the coil conductor 20 is formed by winding a strip-shaped conductor wire (hereinafter simply referred to as a conductor wire) in a spiral shape, with both ends drawn out to the outer periphery and connected to each other at the inner periphery. In this embodiment, the winding portion 22 is configured as a two-stage spiral along its central axis. Inside the element body 2, the coil conductor 20 is embedded in the core 30 with the central axis of the winding portion 22 oriented along the thickness direction DT of the element body 2. The draw-out portions 24 extend from the winding portion 22 to each of the pair of end faces 14, with one main surface exposed from the element body 2 and the other main surface embedded in the element body 2.
[0019] The conductor of the lead portion 24 is exposed from the insulating coating that covers the conductor at the exposed portion that is exposed from the surface of the element body 2 and is electrically connected to the external electrode 4 .
[0020] The pair of external electrodes 4 are so-called L-shaped electrodes, which are composed of L-shaped members extending from each end face 14 of the element body 2 to the mounting surface 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 extending to the mounting surface 10 is electrically connected to wiring on the circuit board by appropriate mounting means such as solder.
[0021] An element protective film 5 (not shown in FIGS. 1 to 4 ) is formed on the surface of the element body 2. The element protective film 5 is made of, for example, a phenoxy resin and a novolac resin, and contains nanosilica as a filler. The element protective film 5 is formed on the surface of the element body 2 to a thickness of 10 μm to 30 μm.
[0022] 3, when distinguishing between the upper and lower stages of the winding portion 22, which is composed of two spiral stages, the upper stage in the figure will be referred to as the upper stage 22a, and the lower stage in the figure will be referred to as the lower stage 22b. Furthermore, when distinguishing between the two lead-out portions 24, the lead-out portion 24 drawn from the upper stage 22a of the winding portion 22 will be referred to as the lead-out portion 24a, and the lead-out portion 24 drawn from the lower stage 22b of the winding portion 22 will be referred to as the lead-out portion 24b. Furthermore, when distinguishing between the two end faces 14, the left end face 14 in the figure, where one main surface of the lead-out portion 24a, which is a strip-shaped conductor, is exposed, will be referred to as the end face 14a, and the right end face 14 in the figure, where one main surface of the lead-out portion 24b, which is exposed, will be referred to as the end face 14b (not shown in FIG. 3). Furthermore, when distinguishing between the two external electrodes 4, the external electrode 4 on the left side of the figure, which is connected to the lead-out portion 24a exposed on the end face 14a, will be referred to as external electrode 4a, and the external electrode 4 on the right side of the figure, which is connected to the lead-out portion 24b exposed on the end face 14b, will be referred to as external electrode 4b.
[0023] The inductor 1 having such a configuration can improve the DC bias characteristics by using a soft magnetic material for the magnetic particles, and is therefore used as an electronic component in electric circuits through which large currents flow, a choke coil in DC-DC converter circuits and power supply circuits, and as an electronic component in electronic devices such as personal computers, DVD players, digital cameras, TVs, mobile phones, smartphones, car electronics, medical and industrial machinery, etc. However, the uses of the inductor 1 are not limited to this, and it can also be used, for example, in tuning circuits, filter circuits, rectifying and smoothing circuits, etc.
[0024] [1.2 Configuration of the Boundary Between the Lead Portion and the External Electrode] As described above in relation to the background art, in conventional inductors, the insulating coating of the lead portion's conductor wire that remains near the outline of the lead portion exposed on the surface of the element body (i.e., the boundary between the exposed surface of the lead portion and the surrounding surface of the element body) makes it difficult for the plating layer that constitutes the external electrode to adhere to the insulating coating, which can cause dents in the surface of the external electrode or allow moisture to enter the external electrode, which can cause solder to explode when the inductor is mounted on a board.
[0025] For this reason, in the inductor 1 according to this embodiment, particularly on the exposed surface of the lead portion 24 exposed on the surface of the element body 2, the insulating coating extending onto part of this exposed surface is covered with the element body protective film 5 of the element body 2, and the external electrode 4 is formed to overlap it. This prevents the external electrode 4 from being formed on the insulating coating of the lead portion 24 exposed on the surface of the element body 2 at the boundary area covered with the element body protective film 5, thereby suppressing the occurrence of depressions on the surface of the external electrode and preventing moisture from penetrating inside the external electrode 4.
[0026] Fig. 4 is a planar perspective view of the inductor 1 shown in Fig. 1 and Fig. 3 as viewed from the side of the top surface 12. Fig. 5 is a cross-sectional view of the inductor 1 shown in Fig. 4 taken along the line VV.
[0027] 5, an element body protective film 5 (hatched portion in the figure) is formed on the surface of the element body 2 including the core 30 and the coil conductor 20. The winding portion 22 of the coil conductor 20 is composed of an upper stage 22a and a lower stage 22b. The lead-out portion 24a, which is drawn from the upper stage 22a to the end face 14a on the left side in the figure, is positioned farther away from the mounting surface 10 than the lead-out portion 24b, which is drawn from the lower stage 22b to the end face 14b on the right side in the figure.
[0028] Figure 6 shows plan views of the end faces 14a and 14b of the element body 2 of the inductor 1 shown in Figures 4 and 5, as viewed from the +DL and -DL directions, respectively. Figure 6A shows a plan view of the end face 14a, and Figure 6B shows a plan view of the end face 14b. In Figure 6, the element body protective film 5 and external electrodes 4 formed on the surface of the element body 2 are omitted from the illustration.
[0029] 6 , lead-out portion 24 is a strip-shaped conductor, one main surface of which is exposed from end surface 14. Furthermore, exposed portion 240 exposed at end surface 14 of lead-out portion 24 has a generally rectangular shape in plan view having two opposing sides that are generally parallel to mounting surface 10 of element body 2. Of the two sides of the generally rectangular shape of exposed portion 240 in plan view, the side farther from mounting surface 10 is referred to as far side 241, and the side closer to mounting surface 10 is referred to as near side 242.
[0030] Here, when distinguishing between the two exposed portions 240 corresponding to the two drawers 24, the exposed portion 240 of drawer 24a will be referred to as exposed portion 240a, and the exposed portion 240 of drawer 24b will be referred to as exposed portion 240b. When distinguishing between the far sides 241 of the two exposed portions 240 corresponding to the two drawers 24, the far side 241 of exposed portion 240a will be referred to as far side 241a, and the far side 241 of exposed portion 240b will be referred to as far side 241b. Similarly, when distinguishing between the near sides 242 of the two exposed portions 240 corresponding to the two drawers 24, the near side 242 of exposed portion 240a will be referred to as near side 242a, and the near side 242 of exposed portion 240b will be referred to as near side 242b.
[0031] The lead-out portion 24 is a part of the coil conductor 20 made up of a conductor wire 60, which is a flat conductor wire, and the conductor wire 60 has a conductor 61 and an insulating coating 62. As shown in Figures 6A and 6B, the insulating coating 62 is removed from the end surface 14 of each lead-out portion 24, exposing the conductor 61.
[0032] 6, the removed range of the insulating coating 62 in the exposed portions 240a and 240b of the lead-out portions 24a and 24b is different. That is, at the end face 14b where the lead-out portion 24 is located closer to the mounting surface 10 (FIG. 6B), the conductor 61 is exposed over almost the entire surface of the exposed portion 240b of the lead-out portion 24b. In contrast, in this embodiment, at the end face 14b where the lead-out portion 24 is located farther from the mounting surface 10 (FIG. 6A), the insulating coating 62 is formed to extend downward from the far side 241a of the lead-out portion 24a to a position where it covers a portion of the conductor 61.
[0033] 7 is a plan view of the end face 14 shown in FIG. 6 , with the element body protective film 5 (hatched portion in the figure) formed on the surface of the element body 2 superimposed thereon. In this embodiment, at the end face 14 a where the lead portion 24 is located farther from the mounting surface 10 ( FIG. 7A ), the element body protective film 5 is formed to extend to a position covering the far side 241 a of the lead portion 24 a. That is, the element body protective film 5 covers the insulating coating 62 extending from the far side 241 a of the lead portion 24 a to part of the exposed portion 240 a, and includes an overlapping portion 50 (hatched portion with left-hand diagonal lines in the figure) that overlaps with part of the exposed portion 240 a.
[0034] 8 is a diagram showing the formation area of the external electrode 4 (the area within the rectangular frame shown with two-dot chain lines) superimposed on the plan view of the end face 14 shown in Fig. 7. In this embodiment, on the end face 14a where the lead portion 24 is located farther from the mounting surface 10 ( Fig. 8A ), the external electrode 4a extends onto the surface of the overlapping portion 50 of the element protective film 5.
[0035] 9 is a cross-sectional view taken along the line IX-IX in FIG. 8A. In the exposed portion 240a of the lead portion 24a exposed on the surface of the end face 14a, in addition to the conductor 61, the insulating coating 62 extending from above in the figure to a part of the exposed portion 240a is also exposed from the end face 14a.
[0036] The external electrode 4a extends over the surface of the overlapping portion 50 of the element protective film 5, which covers the insulating coating 62 and overlaps with a portion of the exposed portion 240a. Therefore, even if the insulating coating 62 is exposed on the end face 14a above the exposed portion 240a of the lead portion 24a, depressions in the external electrode and infiltration of moisture into the external electrode are unlikely to occur. Furthermore, the amount of protrusion of the insulating coating 62 exposed on the end face 14a (lower in the figure) toward the end face 14a can be reduced by adjusting the sweep direction of the laser beam in the vertical direction in FIG. 9 when removing the element protective film 5 by irradiating it with laser light in the surface treatment step (S52) of the manufacturing process of the inductor 1 described below. Therefore, in the inductor 1, depressions on the surface of the external electrode 4 are suppressed overall, and infiltration of moisture, which can cause solder explosions when the inductor 1 is mounted on a substrate, can be suppressed.
[0037] It is preferable that the area of the portion of the exposed portion 240 of the lead portion 24 that is covered by the overlapping portion 50 of the element protective film 5 is 20% or less of the area of the exposed portion 240 (see, for example, FIG. 8A ). This makes it possible to maintain the bonding strength and low DC resistance of the connection portion between the lead portion 24 and the external electrode 4, while suppressing the occurrence of dents on the surface of the external electrode and suppressing the intrusion of moisture into the external electrode, which is a cause of solder explosions when the external electrode is mounted on a board.
[0038] 10 is an example of an enlarged cross-sectional photograph of a portion of the fabricated inductor 1 corresponding to the cross-section of the end face 14a shown in Fig. 9. The portion indicated by the dotted oval in the figure is the overlapping portion 50 of the element protective film 5 that covers the insulating coating 62 of the conductor 60 that forms the lead portion 24a. The external electrode 4a is formed on the surface of the overlapping portion 50, and the insulating coating 62 of the lead portion 24a and the external electrode 4a are not in direct contact.
[0039] 11 is a diagram showing the manufacturing process of the inductor 1. The manufacturing process of the inductor 1 includes a coil conductor forming step (S1), a preform forming step (S2), an element molding step (S3), a barrel polishing step (S4), and an external electrode forming step (S5).
[0040] The coil conductor forming step (S1) is a step of forming the coil conductor 20 from a conductive wire. In this step, the coil conductor 20 is formed into a shape having the above-mentioned winding portion 22 and a pair of lead-out portions 24 by winding the conductive wire using a winding method known as "alpha winding," for example. Alpha winding refers to a state in which the lead-out portions 24 at the beginning and end of the conductive wire, which functions as a conductor, are wound in two spiral stages so that they are located on the outer periphery. The number of turns of the coil conductor 20 is not particularly limited.
[0041] The preform formation step (S2) is a step of forming a preform called a tablet. The preform is formed by pressing the mixed powder, which is the material of the element body 2, into a solid form that is easy to handle. In this embodiment, two types of tablets are formed: a first tablet of an appropriate shape (e.g., E-shaped) having a groove into which the coil conductor 20 fits, and a second tablet of an appropriate shape (e.g., I-shaped or plate-shaped) that covers the groove of the first tablet.
[0042] In the element molding step (S3), the first tablet, the coil conductor, and the second tablet are set in a molding die, and while applying heat, pressure is applied in the overlapping direction of the first tablet and the second tablet to harden them, integrating the first tablet, the coil conductor, and the second tablet, thereby molding the element 2 in which the coil conductor 20 is enclosed in the core 30.
[0043] In this embodiment, in the element body molding process (S3), the coil conductor 20 is embedded in the element body 2 so that one main surface of the lead-out portion 24, which is a strip-shaped conductor, is exposed from the end face 14 of the element body 2, and so that the planar shape of the exposed portion 240 exposed on the end face 14 of the lead-out portion 24 is approximately rectangular with two opposing sides that are approximately parallel to the mounting surface 10 of the element body 2.
[0044] The barrel polishing step (S4) is a step of barrel polishing this molded body, and by this step, the corners of the element body 2 are rounded.
[0045] The external electrode forming step (S5) is a step of forming the external electrodes 4 on the core 30, and includes an element protective film forming step (S51), a surface treatment step (S52), and a plating layer forming step (S53).
[0046] The element protective film forming step (S51) is a step of coating the entire surface of this molded body with an insulating resin.
[0047] The surface treatment step (S52) is a step of modifying the surface of the planned electrode area by irradiating the area with laser light. Here, the planned electrode area refers to the area on the surface of the core 30 where the external electrode 4 is to be formed, including the area where the lead-out portion 24 is exposed. Specifically, by irradiating the laser light, the element protective film 5 on the surface of the core 30 and the coating layer on the lead-out portion 24 of the coil conductor 20 are removed from the planned electrode area, the resin on the surface of the core 30 is removed, and the insulating film on the surface of the magnetic particles exposed from the core 30 is removed. As a result, the exposed area of the metal of the magnetic particles per unit area of the surface of the core 30 is larger in the planned electrode area than in other surface areas of the core 30. After irradiating the laser light, a cleaning process (e.g., etching) may be performed to clean the surface of the planned electrode area.
[0048] In this embodiment, particularly in the surface treatment process (S52), the element protective film 5 is removed from the surface of the element 2 so that after irradiation with laser light, an overlapping portion 50 remains, covering the far side 241, which is the side farthest from the mounting surface 10, of the two sides of the approximately rectangular shape formed by the exposed portion 240 of the pull-out portion 24, and overlapping with a portion of the exposed portion 240.
[0049] In the plating layer forming step (S53), copper is barrel-plated on the surface of the core 30 to form a copper plating layer at the electrode-planed location irradiated with the laser light, thereby forming the external electrode 4. The external electrode 4 may be formed by further providing a Ni plating layer and a Sn plating layer on the copper plating layer.
[0050] In this embodiment, particularly in the plating layer formation step (S53), the external electrodes 4 are formed so as to extend onto the surface of the overlapping portion 50 of the element protective film 5. The formation of the external electrodes 4 on the surface of the overlapping portion 50 can be achieved, for example, by adjusting the barrel plating processing time to be longer when forming the copper plating layer described above, thereby causing the copper plating layer formed on the conductor 61 of the exposed portion 240 to grow toward the surface of the overlapping portion 50.
[0051] 3. Other Embodiments
[0052] In the above-described embodiment, the element protective film 5 has an overlapping portion 50 at the far side 241 of the exposed portion 240 of one of the two lead portions 24, the lead portion 24 farther from the mounting surface 10. However, the element protective film 5 may have an overlapping portion 50 at each of the two lead portions 24. FIG. 12 is a diagram showing an example of the arrangement of the lead portions 24, the element protective film 5, and the external electrodes 4 at the two end faces 14 in another embodiment of such an inductor 1. FIG. 12 corresponds to FIG. 8 , which shows the configuration at the two end faces 14 a, 14 b in the above-described embodiment. In FIG. 12 , the same components as those shown in FIG. 8 are denoted by the same reference numerals as those shown in FIG. 8 , and the description of FIG. 8 above is incorporated herein by reference.
[0053] As shown in Fig. 12, the overlapping portion 50 of the element protective film 5 can be formed on both the exposed portion 240a of the lead portion 24a at the end face 14a shown in Fig. 12(A) and the exposed portion 240b of the lead portion 24b at the end face 14b shown in Fig. 12(B). In Fig. 12, in order to distinguish between the two overlapping portions 50 formed on the end face 14a and the end face 14b, the overlapping portion 50 formed on the end face 14a is referred to as overlapping portion 50a, and the overlapping portion 50 formed on the end face 14b is referred to as overlapping portion 50b. The overlapping portion 50a is formed in the same portion as the overlapping portion 50 in Fig. 8(A).
[0054] 12B, the element protective film 5 includes an overlapping portion 50b that covers the far side 241b of the exposed portion 240b of the lead-out portion 24b and overlaps with a part of the exposed portion 240b. The external electrode 4b extends from the mounting surface 10 along the end face 14b onto the surface of the overlapping portion 50b.
[0055] Furthermore, in the above-described embodiment, the coil conductor 20 includes the alpha-wound winding portion 22 as an example, but the coil conductor 20 does not necessarily have to include the winding portion 22. The portion of the coil conductor 20 corresponding to the winding portion 22 may be configured in a linear shape, a meandering shape, or the like. In these cases, a pair of lead-out portions 24 extending from the linear or meandering conductor portion can be disposed at positions at approximately the same distance from the mounting surface 10.
[0056] In the above-described embodiment, the exposed portion 240 of the drawer portion 24 has a planar shape at the end face 14 that is approximately rectangular and long along the width direction DW, but it may also have an approximately rectangular shape that is long along the thickness direction DT.
[0057] All of the above-described embodiments and modifications are merely examples of one aspect of the present invention, and can be modified and applied as desired without departing from the spirit of the present invention. Furthermore, unless otherwise specified, the horizontal, vertical, and other directions, various numerical values, shapes, and materials in the above-described embodiments include a range that provides the same action and effect as those directions, numerical values, shapes, and materials (so-called equivalent ranges).
[0058] 4. Configurations Supported by the Above-described Embodiments The above-described embodiments support the following configurations.
[0059] (Configuration 1) An inductor having a coil conductor having a pair of first and second lead portions formed by a strip-shaped conductor wire having a conductor and an insulating coating covering the outer periphery of the conductor, an element body containing magnetic particles and resin and containing the coil conductor, an element body protective film covering the surface of the element body, and an external electrode connected to the coil conductor, wherein the element body has a mounting surface that faces a mounting board when mounted, and two paired end faces that are perpendicular to the mounting surface, and each of the first and second lead portions that are strip-shaped conductor wires is one of the ends of the strip-shaped conductor wire. an inductor having a main surface exposed from the end face of the element body, and an exposed portion exposed from each of the end faces of the first lead portion and the second lead portion, which has a planar shape that is approximately rectangular having two opposing sides that are approximately parallel to the mounting surface of the element body, and the element body protective film covers the far side of the two sides of the approximately rectangular shape formed by the exposed portion of at least one of the first lead portion and the second lead portion, which is the side farthest from the mounting surface, and includes an overlapping portion that overlaps with the insulating coating extending over a portion of the exposed portion, and the external electrode extends on the surface of the overlapping portion of the element body protective film. According to the inductor of configuration 1, in an inductor in which a coil conductor having a pair of lead portions consisting of a strip-shaped conductor wire having a conductor and an insulating coating is enclosed within a body containing magnetic particles and resin, the formation of an external electrode on the insulating coating of the lead portion exposed on the surface of the body is prevented by the body protective film formed on the surface of the body 2, thereby preventing the occurrence of depressions on the surface of the external electrode and preventing moisture, which is a cause of solder explosions when mounted on a substrate, from penetrating into the external electrode.
[0060] (Configuration 2) An inductor according to configuration 1, wherein the external electrodes each extend from a respective one of the opposing end faces to the mounting surface adjacent to the respective end face, the first lead portion and the second lead portion each have an exposed portion exposed from a surface of a different one of the two end faces, the far sides of the exposed portions of the first lead portion and the second lead portion are at different distances from the mounting surface, and in the first lead portion or the second lead portion whose far side is farther from the mounting surface, the element protective film covers the far side of the first lead portion or the second lead portion and includes the overlapping portion overlapping with the insulating coating extending over part of the exposed portion, and the external electrode extends from the mounting surface along the end face to the surface of the overlapping portion of the element protective film. According to the inductor of configuration 2, the occurrence of depressions on the surface of at least one of the pair of external electrodes can be suppressed, and moisture, which is a cause of solder cracking when mounted on a substrate, can be prevented from penetrating into the external electrode.
[0061] (Configuration 3) The inductor according to Configuration 1, wherein the element protective film includes an overlapping portion that covers the far sides of the first lead portion and the second lead portion and overlaps with the insulating coating that extends to part of the exposed portion in both the first lead portion and the second lead portion, and the external electrodes extend from the mounting surface along the end face to the surface of the overlapping portion of the element protective film in both the first lead portion and the second lead portion. The inductor of Configuration 3 can suppress the occurrence of depressions on the surfaces of the external electrodes in both of a pair of external electrodes and can suppress the intrusion of moisture into the external electrodes, which can cause solder splashes when mounted on a substrate.
[0062] (Configuration 4) An inductor according to any one of Configurations 1 to 3, wherein the area of the portion of the exposed portion of at least one of the first lead portion and the second lead portion that is covered by the overlapping portion of the element body protective film is 20% or less of the area of the exposed portion. The inductor of Configuration 4 can maintain the bonding strength and low DC resistance of the connection portion between the lead portion and the external electrode, while suppressing the occurrence of dents on the surface of the external electrode and suppressing the penetration of moisture into the external electrode, which is a cause of solder bursting when mounted on a substrate.
[0063] (Configuration 5) A method for manufacturing a semiconductor device comprising: an element molding step of embedding a coil conductor having a first lead portion and a second lead portion, the coil conductor being formed by a strip-shaped conductor having a conductor and an insulating coating coating coating the outer periphery of the conductor, in an element body containing magnetic particles and a resin so that the first lead portion and the second lead portion of the coil conductor are exposed from the surface of the element body; an element protective film forming step of forming an element protective film on the surface of the element body so as to cover the surface of the element body; a surface treatment step of irradiating laser light onto planned electrode locations on the surface of the element body, including exposed portions of the first lead portion and the second lead portion exposed from the element body, to remove part of the resin and the element protective film on the surface of the element body at the planned electrode locations; and a plating layer forming step of forming external electrodes by plating on the surface of the element body including the exposed portions, wherein the element body has a mounting surface that faces a mounting board when mounted, and a metal layer that is formed on the mounting surface. a pair of end faces that are perpendicular to each other, wherein in the element body molding process, the coil conductor is embedded in the element body so that one main surface of the first lead portion and the second lead portion, which are strip-shaped conductors, is exposed from the end face of the element body, and the planar shape of the exposed portions exposed at the end faces of the first lead portion and the second lead portion is a substantially rectangular shape having two opposing sides that are substantially parallel to the mounting surface of the element body; in the surface treatment process, the element body protective film is removed from the surface of the element body so as to include an overlapping portion that covers the far side of the two sides of the substantially rectangular shape formed by the exposed portions of at least one of the first lead portion and the second lead portion, which is the side farthest from the mounting surface, and overlaps with a part of the exposed portion; and in the plating layer formation process, the external electrode is formed so as to extend on the surface of the overlapping portion of the element body protective film. According to the inductor manufacturing method of configuration 5, in an inductor having a coil conductor with a pair of lead portions made of a strip-shaped conductor wire having a conductor and an insulating coating enclosed within a body containing magnetic particles and resin, the formation of an external electrode on the insulating coating of the lead portion exposed on the surface of the body is prevented by the body protective film formed on the surface of the body 2, thereby preventing the occurrence of depressions on the surface of the external electrode and preventing moisture, which could cause solder explosions when mounted on a substrate, from penetrating into the external electrode.
[0064] 1...inductor, 2...element body, 4, 4a, 4b...external electrode, 5...element body protective film, 10...mounting surface, 12...upper surface, 14, 14a, 14b...end surface, 16...side surface, 20...coil conductor, 22...winding portion, 22a...upper section, 22b...lower section, 24, 24a, 24b...drawing portion, 30...core, 50, 50a, 50b...overlapping portion, 60...conductor, 61...conductor, 62...insulating coating, 240, 240a, 240b...exposed portion, 241, 241a, 241b...far side, De...depression, Mo...moisture
Claims
1. An inductor comprising: a coil conductor having a pair of first and second lead portions formed from a strip-shaped conductor wire having a conductor and an insulating coating covering the outer periphery of the conductor; an element body containing magnetic particles and resin and encapsulating the coil conductor; an element body protective film covering the surface of the element body; and an external electrode connected to the coil conductor, wherein the element body has a mounting surface that faces the mounting board when mounted, and two paired end surfaces that are perpendicular to the mounting surface, and each of the first and second lead portions, which are strip-shaped conductor wires, has one main surface exposed from the end surface of the element body, and the exposed portions exposed at the end surfaces of the first and second lead portions have a generally rectangular shape in plan view with two opposing sides that are generally parallel to the mounting surface of the element body, an inductor, wherein the element protection film covers one of the two sides of a substantially rectangular shape formed by the exposed portion of at least one of the first lead portion and the second lead portion, which is the side farthest from the mounting surface, and includes an overlapping portion that overlaps with the insulating coating extending over part of the exposed portion, and the external electrode extends over the surface of the overlapping portion of the element protection film.
2. The inductor according to claim 1, wherein the external electrodes extend from each of the opposing end faces to the mounting surface adjacent to the respective end face, the first and second lead portions each have an exposed portion exposed from the surface of a different one of the two end faces, the far sides of the exposed portions of the first and second lead portions are at different distances from the mounting surface, and in the first or second lead portion whose far side is farther from the mounting surface, the element protective film covers the far side of the first or second lead portion and includes the overlapping portion that overlaps with the insulating coating extending over part of the exposed portion, and the external electrode extends from the mounting surface along the end face to the surface of the overlapping portion of the element protective film.
3. An inductor as described in claim 1, wherein the element protective film covers the far sides of both the first and second lead portions and includes an overlapping portion that overlaps with the insulating coating that extends over part of the exposed portion, and the external electrode extends from the mounting surface along the end face to the surface of the overlapping portion of the element protective film in both the first and second lead portions.
4. An inductor according to any one of claims 1 to 3, wherein the area of the exposed portion of at least one of the first lead portion and the second lead portion that is covered by the overlapping portion of the element protective film is 20% or less of the area of the exposed portion.
5. A method for manufacturing a semiconductor device comprising: an element molding step of embedding a coil conductor having a first lead portion and a second lead portion, the coil conductor being formed from a strip-shaped conductor wire having a conductor and an insulating coating coating the outer periphery of the conductor, in an element body containing magnetic particles and a resin so that the first lead portion and the second lead portion of the coil conductor are exposed from the surface of the element body; an element protective film forming step of forming an element protective film on the surface of the element body so as to cover the surface of the element body; a surface treatment step of irradiating laser light onto planned electrode locations on the surface of the element body, including exposed portions of the first lead portion and the second lead portion exposed from the element body, to remove part of the resin and the element protective film on the surface of the element body at the planned electrode locations; and a plating layer forming step of forming external electrodes by plating on the surface of the element body including the exposed portions, wherein the element body has a mounting surface that faces the mounting board when mounted, and two paired end faces that are perpendicular to the mounting surface, a first lead portion and a second lead portion, which are strip-shaped conductors, embedded in the element body so that one main surface of each of the first lead portion and the second lead portion is exposed from the end face of the element body, and the planar shape of the exposed portions exposed on the end faces of the first lead portion and the second lead portion is a substantially rectangular shape having two opposing sides substantially parallel to the mounting surface of the element body; a surface treatment process in which the element body protective film is removed from the surface of the element body so as to include an overlapping portion that covers the far side of the two sides of the substantially rectangular shape formed by the exposed portions of at least one of the first lead portion and the second lead portion, which is the side farthest from the mounting surface, and overlaps with a part of the exposed portion; and a plating layer formation process in which the external electrode is formed so as to extend on the surface of the overlapping portion of the element body protective film.