Inductor

Abstract

In a ductor where a coil is sandwiched between two cores, high reliability is achieved even when exposed to high temperatures during use. [Solution] The inductor comprises a coil conductor having a first end face and a second end face facing each other along the winding shaft, a first core and a second core having walls surrounding the outer circumference of the coil conductor and sandwiching the coil conductor from the first and second end faces, and two external electrodes connected to the ends of two lead-out portions of the coil conductor. Each wall has a notch that forms a lead-out window through which the lead-out portion passes. Of the four sections of the coil conductor defined by a first surface passing through the center in the width direction of the winding shaft and the lead-out window, and a second surface passing through the winding shaft and perpendicular to the first surface, the first end face is bonded to the first core in the first section closest to one external electrode along the lead-out portion on the first end face side, and the second end face is bonded to the second core in the second section closest to the other external electrode along the lead-out portion on the second end face side.

Description

Technical Field

[0001] The present invention relates to an inductor.

Background Art

[0002] Patent Document 1 discloses an inductor including a coil obtained by alpha-winding a rectangular flat conductor with a rectangular cross-section, a first core having an E-shaped cross-section with a convex portion at the center of the main surface, and a second core having an I-shaped cross-section. The inductor is configured by sandwiching the coil between the first core and the second core in a state where the convex portion of the first core is inserted into the air-core portion of the coil. The first core and the second core are made of, for example, ferrite. The upper surface of the protrusion of the first core is bonded to the main surface of the second core, the coil is accommodated between the first core and the second core, and the winding end of the coil is drawn out from the accommodation space in the core and connected to an external electrode provided on the outer surface of the core. Usually, the height of the protrusion of the first core is set larger than the thickness of the coil, so that the two end faces in the thickness direction of the coil are bonded and fixed to the first core and the second core with a thermosetting resin to prevent the coil from moving in the space between the first core and the second core.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] In the inductor configured as described above, depending on the heating conditions of reflow soldering during mounting on a circuit board and the environmental temperature conditions after mounting, due to the difference in linear expansion coefficient between the core and the conductor, the expanded coil conductor pushes up the second core, causing a gap between the second core and the first core, which may change the inductance, or cause mechanical deterioration at the joint between the end of the coil conductor and the external electrode, leading to reduced reliability.

[0005] The objective of the present invention is to achieve high reliability in an inductor composed of a coil sandwiched between two cores, even when exposed to high temperatures during manufacturing and drastic temperature changes during use. [Means for solving the problem]

[0006] One aspect of the present invention is a coil conductor having an air core portion and a first end face and a second end face facing each other along the winding axis, wherein the conductor is wound in a spiral in two stages such that the two lead-out portions of the conductor, the beginning and the end of the winding, are located on the outer circumference, and the coil conductor is sandwiched from the sides of the first end face and the second end face, respectively, and the first core and the front The first and second cores each have a wall portion having a notch that forms a pull-out window for pulling the two pull-out portions outwards from the wall portion, and the coil conductor is divided into four sections, defined by a first surface that includes the winding shaft and passes through the center of the pull-out window in the width direction, and a second surface that includes the winding shaft and is perpendicular to the first surface, and the first end of the coil conductor The surface is bonded to the first core in the first section closest to one of the external electrodes along the lead-out portion drawn out from the side of the first end face, in one of the two sections closer to the draw-out window than the second surface, and in three sections different from the first section, it is not bonded to the first core, or in at least one section different from the first section, it is bonded to the first core with a lower adhesive force than in the first section. The second end face of the coil conductor is bonded to the second core in the second section closest to the other external electrode along the lead-out portion drawn out from the side of the second end face, in the other section of the two sections closer to the draw-out window than the second surface, and in three sections different from the second section, it is not bonded to the second core, or in at least one section different from the second section, it is bonded to the second core with a lower adhesive force than in the second section. [Effects of the Invention]

[0007] According to the present invention, an inductor composed of a coil sandwiched between two cores can achieve high reliability even when exposed to high temperatures during manufacturing, use, etc. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a perspective view of an inductor according to one embodiment of the present invention, viewed from the top. [Figure 2] Figure 2 is a quadrature view of the inductor, adding the bottom view to the three views showing the front, top, and side. [Figure 3] Figure 3 is a perspective view of the top surface of the inductor. [Figure 4] Figure 4 is a three-view drawing showing the configuration of the first core. [Figure 5] Figure 5 is a cross-sectional view of the first core shown in Figure 4, taken along the VV line. [Figure 6] Figure 6 shows the state in which the coil conductor is attached to the first core. [Figure 7] Figure 7 is an explanatory diagram illustrating the bonding configuration between the coil conductor and the first and second cores. [Figure 8] Figure 8 is an explanatory diagram illustrating the stress reduction effect in the draw-out portion of the adhesive configuration shown in Figure 7. [Figure 9] Figure 9 is a schematic diagram showing the IX-IX cross-section of the inductor shown in Figure 7. [Figure 10] Figure 10 is an explanatory diagram illustrating the stress generated at the lead-out portion in a conventional inductor. [Figure 11] Figure 11 is an explanatory diagram illustrating the separation of the adhesive surfaces between two cores in a conventional inductor. [Modes for carrying out the invention]

[0009] [1. Embodiments] Embodiments of the present invention will be described below with reference to the drawings. Figures 1, 2, and 3 show the configuration of an inductor 1 according to one embodiment of the present invention. Figure 1 is a perspective view of the inductor 1 as seen from the top surface 12, and Figure 2 is a quadrature view of the inductor 1, which includes the front 14a, top surface 12, side surface 16, and bottom surface 10. Figure 3 is a perspective view of the top surface 12 of the inductor 1.

[0010] In this embodiment, in the inductor 1, the first main surface that faces the mounting substrate (e.g., a circuit board) not shown during mounting is defined as the bottom surface 10, and the second main surface opposite the bottom surface 10 is called the top surface 12. Of the two pairs of main surfaces that are perpendicular to the bottom surface 10 and face each other, the main surface on which the lead-out window 5 from which the lead-out portion 24 of the coil conductor 20 is led out to the outside is called the front surface 14a, and the main surface opposite the front surface 14a is called the back surface 14b. Furthermore, the pair of main surfaces perpendicular to the bottom surface 10, the front surface 14a, and the back surface 14b are called the side surfaces 16.

[0011] The two ridges where the front surface 14a and the pair of side surfaces 16 intersect have chamfered corners in a plan view from the top surface 12, forming a pair of electrode holding surfaces 18, 18. Similarly, the two portions where each of the back surfaces 14b and the pair of side surfaces 16 intersect have chamfered corners in a plan view. As a result, the inductor 1 has a roughly octagonal shape in a plan view.

[0012] As shown in Figure 1, the distance from the bottom surface 10 to the top surface 12 is defined as the height H of the inductor 1, the distance between the front surface 14a and the back surface 14b is defined as the length L of the inductor 1, and the distance between the pair of side surfaces 16 is defined as the width W of the inductor 1. Furthermore, the direction of height H is defined as the height direction DH, the direction of length L is defined as the length direction DL, and the direction of width W is defined as the width direction DW.

[0013] An inductor 1 includes a first core 30a and a second core 30b both formed of a magnetic material, and a coil conductor 20 sandwiched between the first core 30a and the second core 30b. The first core 30a and the second core 30b are combined to sandwich the coil conductor 20 therebetween, thereby forming a substantially octagonal-prism magnetic core 50.

[0014] The magnetic material constituting the first core 30a and the second core 30b is, for example, ferrite. The ferrite may be, for example, Ni-Zn ferrite or Mn-Zn ferrite. Instead of ferrite, the first core 30a and the second core 30b may be formed of a magnetic material obtained by compression-molding a mixed powder of magnetic powder such as metallic magnetic material and resin.

[0015] The coil conductor 20 includes a wound portion 22 formed by winding a conductive wire having an insulating coating and a fusion-bonding layer on the insulating coating, and a pair of lead-out portions 24 led out from the wound portion 22 (Figure 3). The coil conductor 20 is, for example, a coil having an air-core portion, in which the conductive wire is alpha-wound. The wound portion 22 is formed by spirally winding the conductive wire in two stages such that the two lead-out portions 24 at the winding start and winding end of the conductive wire are located on the outer periphery, and then fusion-bonding the wound conductive wire, and has an air-core portion. The conductive wire is, for example, a rectangular wire with a rectangular cross-section.

[0016] The inductor 1 includes a pair of external electrodes 4, 4 provided extending on a bottom surface 10 (FIG. 2(d)). Each of the external electrodes 4 is a metal fitting formed by processing a metal (e.g., copper) plate so as to extend from the bottom surface 10 to an electrode holding surface 18, and is adhesively fixed to the bottom surface 10.

[0017] The distal ends of the pair of lead-out portions 24, 24 of the coil conductor 20 are pre-soldered in advance, led out from lead-out windows 5 of the magnetic core 50, and connected to the pair of external electrodes 4, 4 respectively. The pair of external electrodes 4, 4 are provided with clamps that clamp and fix the conductive wires of the pair of lead-out portions 24, 24, and the coil conductor and the external electrodes are heated and pressurized by a heater chip or the like to be electrically connected (FIG. 1, FIG. 2(a)).

[0018] Figure 4 is a three-view drawing showing the configuration of the first core 30a. Figure 4(a) is a plan view of the first core 30a, Figure 4(b) is a front view of the first core 30a, and Figure 4(c) is a side view of the first core 30a. Figure 5 is a cross-sectional view of the first core 30a shown in Figure 4, taken along the VV line. In this embodiment, the second core 30b has the same configuration as the first core 30a shown in Figure 4.

[0019] The first core 30a has a roughly octagonal shape in plan view, with the four corners of a square being chamfered (Figure 4(a)). On one main surface (the surface shown in Figure 4(a)), the first core 30a has a convex portion 31 in the central part of the roughly octagonal outer shape in plan view, and a wall portion 32 along the outer circumference of the roughly octagon (Figure 4(a)). As a result, the VV cross section of the first core 30a has an E-shape (Figure 5).

[0020] The wall portion 32 has a notch portion 33, which is a part cut out along the front surface 14a. When the coil conductor 20 is sandwiched between the first core 30a and the second core 30b, the notch portion 33, together with the notch portion 33 of the second core 30b, forms a pull-out window 5 that pulls the pull-out portion 24 of the coil conductor 20 out of the magnetic core 50. The surface opposite the surface on which the protrusion 31 is formed corresponds to the bottom surface 10 of the first core 30a, and to the top surface 12 of the second core 30b, which has the same configuration as the first core 30a.

[0021] The first core 30a and the second core 30b are placed facing each other, and their respective protrusions 31 are inserted into the air core of the coil conductor 20. By adhesively fixing the opposing surfaces of the protrusions 31 of the first core 30a and the protrusions of the second core 30b, the coil conductor 20 is held within the magnetic core 50 composed of the first core 30a and the second core 30b. In this state, the opposing surfaces of the wall portion 32 of the first core 30a and the wall portion 32 of the second core 30b are spaced apart, suppressing magnetic saturation in the magnetic core 50 (Figures 1 and 2(c)).

[0022] In this embodiment, the notch 33 is positioned so that its center is offset from the center line Cw of the width W of the first core 30a (in the example of Figure 4(a), it is offset to the right in the illustration). Since the first core 30a and the second core 30b are configured identically, when the coil conductor 20 is sandwiched between the first core 30a and the second core 30b, the notch 33 of the first core 30a and the notch 33 of the second core 30b that constitute the drawer window 5 are positioned offset from each other in a direction perpendicular to the center line Cw in the width direction of the drawer window 5 (see Figure 2(b)).

[0023] Figure 6 shows the state in which the coil conductor 20 is attached to the first core 30a. As described above, the coil conductor 20 is alpha wound, and the winding portion 22 is wound in two stages, upper and lower, along the winding shaft. As shown in Figure 6, when the coil conductor 20 is attached to the first core 30a, the pair of lead-out portions 24 of the coil conductor 20 intersect near the notch 33 and are pulled out in the left and right directions shown in the figure. In the example of Figure 6, of the two stages of winding portion 22, one lead-out portion 24 (hereinafter referred to as lead-out portion 24a) is pulled out from the stage closer to the first core 30a (hereinafter referred to as the lower stage) toward the right side shown in the figure from the notch 33.

[0024] Furthermore, since the notch 33 of the first core 30a is shifted to the right in the diagram with respect to the center line Cw of the width W, as described above, the lead-out portion 24a drawn out from the lower part of the winding portion 22 can reach the position of one of the external electrodes 4 (hereinafter referred to as external electrode 4a) on the right side of the diagram by drawing a natural curve without bending. This prevents the generation of long-term stress in the lead-out portion 24a.

[0025] Furthermore, as can be easily inferred from the description in Figure 6, when a second core 30b having the same configuration as the first core 30a is placed over the first core 30a on which the coil conductor 20 is attached, one of the two winding sections 22, the section furthest from the first core 30a and therefore closer to the second core 30b (hereinafter referred to as the upper section), will be pulled out from the notch 33 toward the left in the figure.

[0026] Furthermore, since the notch 33 of the second core 30b, which has the same configuration as the first core 30a, is positioned to the left of the center line Cw of the width W in Figure 6, the lead-out portion 24b drawn out from the upper part of the winding portion 22 can reach the position of the other external electrode 4 (hereinafter referred to as external electrode 4b) to the left of the figure by drawing a natural curve without bending. This prevents the generation of long-term stress in the lead-out portion 24b.

[0027] In conventional inductors, which have a configuration in which a coil conductor is sandwiched between two E-shaped cores, the two end faces of the coil conductor in the thickness direction are bonded and fixed to the two cores to prevent the coil conductor from moving within the space between them. As a result, due to the difference in the coefficient of thermal expansion between the coil conductor and the two cores, stress may be generated between the lead-out portion of the coil conductor and the external electrode, or lifting may occur at the bonding surface between the two cores.

[0028] Figure 10 is an explanatory diagram illustrating the stress at the lead-out portion that can occur in a conventional inductor due to adhesion between the two cores and the coil conductor. In Figure 10, the first end face e81 and the second end face e82 of the coil conductor 81 of a conventional inductor 80, which face each other in the winding axis direction, are highlighted. The coil conductor 81 is an alpha-winding coil in which the conductor is wound in a spiral in two stages. The coil conductor 81 is sandwiched between the two cores from above and below along the winding axis Cb. Note that the two cores are omitted from the diagram to simplify the drawing and facilitate understanding.

[0029] The first end face e81 of the coil conductor 81 is bonded to the lower core of the two cores, and the second end face e82 is bonded to the upper core, holding it between the two cores. A lead-out portion 83a extends from the side of the first end face e81 of the coil conductor 81, and its end 84a (hatched portion) is connected to an external electrode fixed to the lower core. Similarly, a lead-out portion 83b extends from the side of the second end face e82 of the coil conductor 81, and its end 84b (hatched portion) is connected to an external electrode fixed to the upper core.

[0030] Conventionally, the bonding points between the first end face e81 and the second end face e82 and the two cores are generally provided on both the left and right sides when viewed from the direction of the white arrows shown in the figure, centered on the portion where the two lead-out portions 83a and 83b of the coil conductor 81 are drawn out, and the bonding points of the first end face e81 and the bonding points of the second end face e82 generally face each other.

[0031] In the example shown in Figure 10, the first end face e81 has adhesive points ap91 and ap92 on both the left and right sides, and the second end face e82 has adhesive points ap93 and ap94 on both the left and right sides, and adhesive points ap91 and ap92 are located opposite adhesive points ap93 and ap94, respectively.

[0032] Here, since the ends 84a and 84b of the lead-out sections 83a and 83b are fixed to external electrodes fixed to the core, when the overall temperature of the inductor 80 rises due to the heating of reflow soldering during mounting on the circuit board or the ambient temperature after mounting, the difference in the coefficient of linear expansion between the coil conductor 81 and the two cores causes stress on the lead-out sections 83a and 83b between the ends 84a and 84b and the external electrodes in the direction of the dotted arrows shown in the figure. Such stress can cause disconnection of the lead-out sections 83a and 83b or poor connection between the ends 84a and 84b and the external electrodes.

[0033] Figure 11 is an explanatory diagram illustrating the lifting of the bonding surface between two cores that can occur in a conventional inductor due to the bonding between the two cores and the coil conductor. Figure 11 is a cross-sectional view including the two cores 85a and 85b that were omitted in Figure 10, and includes the XI-XI cross-section in Figure 10.

[0034] The two cores 85a and 85b each have protrusions 86a and 86b, respectively, giving them an E-shaped cross-section. Cores 85a and 85b are bonded together by adhesive joints ap95 between protrusions 86a and 86b. The coil conductor 81 has a first end face e81 and a second end face e82 that face each other along the winding axis, and these are bonded to cores 85a and 85b at adhesive joints ap92 and ap94 that face each other.

[0035] Here, when the overall temperature of the inductor 80 rises due to the heating during reflow soldering when mounting it on the circuit board or the ambient temperature after mounting, the coil conductor 81 expands in the vertical direction as shown by the dashed arrows in the figure, generating a peeling force on the protrusions 86a and 86b that is biased to the right side of the figure relative to the adhesive point ap95 shown by the solid arrows in the figure. As a result, a gap (or lift) occurs between the protrusions 86a and 86b, and the inductance of the inductor 80 decreases.

[0036] To solve these problems, the inductor 1 of this embodiment has a different bonding configuration between the coil conductor 20 and the first core 30a and the second core 30b compared to the conventional configuration described above.

[0037] Figure 7 is a perspective view of the inductor 1 as seen from the top surface 12, and is a diagram for explaining the bonding configuration between the coil conductor 20 and the first core 30a and the second core 30b. In the coil conductor 20, four sections are defined by a first surface S1 that includes the winding shaft Ca and passes through the center in the width direction of the pull-out window 5, and a second surface that includes the winding shaft Ca and is perpendicular to the first surface S1. Here, the center in the width direction of the pull-out window 5 refers to the center in the width direction of the entire area of ​​the pull-out window 5, which is composed of the notch 33 of the first core 30a and the notch 33 of the second core 30b.

[0038] Furthermore, in Figure 7, the first surface S1 and the second surface S2 refer to planes that extend in the direction normal to the front and back of the paper, including the dashed-dotted and double-dotted lines that represent the first surface S1 and the second surface S2, respectively. Note that in Figure 7, the projections 31 and wall portions 32 are omitted from the illustration to simplify the drawing and facilitate understanding. As described above, the first core 30a and the second core 30b are fixed to each other by bonding between their respective projections 31.

[0039] The four sections defined above are designated as follows: the section closest to the drawer window 5 on the second surface S2 and close to the external electrode 4b to which the drawer portion 24b drawn out from the upper part of the coil conductor 20 is connected is designated as the first section D1; and the sections are designated as the second section D2, third section D3, and fourth section D4, moving counterclockwise around the winding shaft Ca.

[0040] The coil conductor 20, which is alpha-wound in two stages, has a lower stage (the stage closer to the first core 30a) and an upper stage (the stage closer to the second core 30b), and the winding portion 22 composed of the upper and lower stages has two end faces that face each other along the winding axis Ca. Here, of the two end faces, the end face closer to the first core 30a is called the first end face e1, and the end face closer to the second core 30b is called the second end face e2. The above four sections are defined on the first end face e1 and the second end face e2, respectively. Figure 7 is a perspective view of the inductor 1 as seen from the top surface 12 side, so the coil conductor 20 shown in Figure 7 is the upper second end face e2. On the first end face e1, the sections opposite the first section D1, second section D2, third section D3, and fourth section D4 of the second end face e2 are similarly the first section D1, second section D2, third section D3, and fourth section D4.

[0041] The two lead-out portions 24a and 24b of the coil conductor 20 are drawn out from the side of the first end face e1 and the side of the second end face e2, respectively, in two directions perpendicular to the winding shaft Ca, intersecting each other and extending outward from the lead-out window 5. The respective ends of the lead-out portions 24a and 24b are fixedly connected to the external electrodes 4a and 4b.

[0042] Furthermore, the first end face e1 of the coil conductor 20 is bonded to the first core 30a in the first section D1, which is closest to one of the external electrodes 4a to which the lead portion 24a is connected, along the lead portion 24a that is drawn out from the side of the first end face e1, among the first section D1 and second section D2 which are closer to the lead window 5 than the second surface S2. On the other hand, in the other three sections different from the first section D1 (i.e., the second section D2, the third section D3, and the fourth section D4), the first end face e1 is not bonded to the first core 30a.

[0043] Furthermore, the upper second end face e2 of the coil conductor 20 is bonded to the second core 30b in the second section D2, which is closest to the other external electrode 4b to which the lead portion 24b is connected, along the lead portion 24b that is drawn out from the side of the second end face e2, among the first section D1 and the second section D2, which are closer to the lead window 5 than the second face S2. On the other hand, in the other three sections different from the second section D2 (i.e., the first section D1, the third section D3, and the fourth section D4), the second end face e2 is not bonded to the second core 30b.

[0044] In the example shown in Figure 7, the first end face e1 of the coil conductor 20 is bonded and fixed to the first core 30a only at the bonding point ap42 within the first section D1, and the second end face e2 is bonded and fixed to the second core 30b only at the bonding point ap43 within the second section D2.

[0045] Furthermore, the adhesives used for bonding between the protrusions 31a and 31b of the first core 30a and the second core 30b, between the first end face e1 of the coil conductor 20 and the first core 30a, and between the second end face e2 of the coil conductor 20 and the second core 30b are preferably rubber-modified epoxy resins, from the viewpoint of reducing the stress generated at these bonding locations.

[0046] Figure 8 is a diagram illustrating the stress reduction effect at the lead-out portion 24 of the inductor 1 shown in Figure 7, and corresponds to Figure 10 for the prior art. Figure 8 highlights the first end face e1 and the second end face e2 of the coil conductor 20 of the inductor 1 that are facing the direction of the winding axis Ca. Note that the first core 30a and the second core 30b are omitted from the drawing to simplify the drawing and facilitate understanding.

[0047] Unlike conventional technology, in inductor 1, the second end face e2 of the coil conductor 20 is not bonded to the second core 30b at the position of the second end face e2 opposite the bonding point ap42 where the first end face e1 of the coil conductor 20 and the first core 30a are bonded. Also, the first end face e1 is not bonded to the first core 30a at the position of the first end face e1 opposite the bonding point ap43 where the second end face e2 of the coil conductor 20 and the second core 30b are bonded. Therefore, in inductor 1, the stress that may occur between each lead portion 24 and the external electrode 4 due to the temperature rise of inductor 1 can be reduced compared to conventional configurations.

[0048] Furthermore, in the inductor 1, the first end face e1 of the coil conductor 20 is bonded to the first core 30a in a first section D1 that is susceptible to tensile force from the lead portion 24a drawn out from the side of the first end face e1, and the second end face e2 is bonded to the second core 30b in a second section D2 that is susceptible to tensile force from the lead portion 24b drawn out from the side of the second end face e2. As a result, in the inductor 1, the coil conductor 20 can be fixed to the first core 30a and the second core 30b while mitigating the above-mentioned stress.

[0049] Figure 9 is a schematic diagram showing the IX-IX cross section of the inductor 1 shown in Figure 7, passing through adhesive points ap42 and ap43, and corresponds to Figure 11 of the prior art. In Figure 8, the protrusions 31 of the first core 30a and the second core 30b are identified as protrusions 31a and 31b. In Figure 8, the first core 30a and the second core 30b are bonded and fixed to each other by the adhesive point ap41 between the respective protrusions 31a and 31b.

[0050] Then, the first end face e1 of the coil conductor 20 is bonded to the first core 30a at the bonding point ap42 within the first section D1, while the second end face e2 is not bonded in the first section D1. As a result, even if the overall temperature of inductor 1 rises due to the heating during reflow soldering when mounted on the circuit board and the ambient temperature after mounting, causing the coil conductor 20 to expand in the vertical direction as shown by the dashed arrow, the end face on the side facing the adhesive point ap43 is not bonded, which effectively reduces the peeling force generated on the protrusions 31a and 31b. Consequently, the occurrence of floating (or gaps) between protrusions 31a and 31b is prevented, and the inductance characteristics of inductor 1 can be stably realized.

[0051] [2. Other Embodiments] In the embodiment described above, the first end face e1 of the coil conductor 20 is bonded to the first core 30a only in the first section D1, and not in the other three sections (i.e., the second section D2, the third section D3, and the fourth section D4). Similarly, the second end face e2 of the coil conductor 20 is bonded to the second core 30b only in the second section D2, and not in the other three sections (i.e., the first section D1, the third section D3, and the fourth section D4).

[0052] Alternatively, the first end face e1 of the coil conductor 20 may be bonded to the first core 30a in the first section D1, and in at least one of the other three sections different from the first section D1, it may be bonded to the first core 30a with a lower adhesive force than that in the first section D1. Similarly, the second end face e2 of the coil conductor 20 may be bonded to the second core 30b in the second section D2, and in at least one of the other three sections different from the second section D2, it may be bonded to the second core 30b with a lower adhesive force than that in the second section D2. Even with such a configuration, the same effects as the inductor 1 shown in the embodiment can be achieved.

[0053] For example, the first end face e1 may be bonded to the first core 30a in at least one of the three sections excluding the first section D1, with a bonding area smaller than that in the first section D1. Alternatively, the first end face e1 may be bonded to the first core 30a in at least one of the three sections excluding the first section D1, using an adhesive with weaker bonding strength than that used in the first section D1. The same applies to the second end face e2.

[0054] In the embodiment described above, the area of ​​the adhesive point ap41, etc., was shown as an ellipse, but of course, the adhesive area of ​​the adhesive point ap41, etc., is not limited to an ellipse and may be irregular in shape.

[0055] It should be noted that the present invention is not limited to the configuration of the embodiments described above, and can be implemented in various forms without departing from the spirit of the invention.

[0056] [3. Configurations supported by the above embodiments] The embodiments described above support the following configurations.

[0057] (Configuration 1) The coil conductor comprises an air core portion, a coil conductor having a first end face and a second end face facing each other along the winding axis, the air core portion of which the wire is wound in a spiral in two stages such that the two lead-out portions at the beginning and end of the winding are located on the outer circumference, a first core and a second core each having a protrusion inserted into the air core portion of the coil conductor and a wall portion surrounding the outer circumference of the coil conductor on one main surface, the coil conductor being sandwiched from the sides of the first end face and the second end face, and two external electrodes arranged on the outer surfaces of the first core and the second core, respectively, and connected to the ends of the two lead-out portions, respectively, the wall portions of the first core and the second core each having a notch that constitutes a pull-out window for pulling the two lead-out portions out of the wall portion, and of the four sections of the coil conductor defined by a first surface including the winding axis and passing through the center in the width direction of the pull-out window, and a second surface including the winding axis and perpendicular to the first surface, the first end face of the coil conductor is An inductor wherein the coil conductor is bonded to the first core in one of the two compartments closer to the draw-out window than the second surface, along the draw-out portion drawn out from the side of the first end face, in the first compartment closest to one of the external electrodes, and in three other compartments, it is not bonded to the first core, or in at least one of the compartments, it is bonded to the first core with a lower adhesive force than in the first compartment, and the second end face of the coil conductor is bonded to the second core in the other of the two compartments closer to the draw-out window than the second surface, along the draw-out portion drawn out from the side of the second end face, in the second compartment closest to the other external electrode, and in three other compartments, it is not bonded to the second core, or in at least one of the compartments, it is bonded to the second core with a lower adhesive force than in the second compartment. This configuration allows for high reliability in an inductor, which consists of a coil conductor sandwiched between a first core and a second core, by reducing the stress applied to the lead-out portion of the coil conductor and preventing the occurrence of floating between the first and second cores, even when exposed to high temperatures during manufacturing and use.

[0058] (Configuration 2) The inductor according to Configuration 1, wherein the protrusions of the first core and the protrusions of the second core, which face each other, are bonded and fixed together, and the walls of the first core and the walls of the second core, which face each other, are spaced apart. This configuration allows for high reliability even in a configuration where a gap is provided between the wall of the first core and the wall of the second core to suppress magnetic saturation.

[0059] (Configuration 3) The inductor according to Configuration 1 or 2, wherein the notch portion of the first core and the notch portion of the second core constituting the drawer window are positioned offset from each other in a direction perpendicular to the center line in the width direction of the drawer window. With this configuration, the lead-out section can be drawn out from the coil conductor in a natural curve without bending, thus preventing the long-term stress from developing in the lead-out section. [Explanation of Symbols]

[0060] 1, 80…Inductor, 4, 4a, 4b…External electrodes, 5…Drawer window, 10…Bottom surface, 12…Top surface, 14a…Front, 14b…Back, 16…Side, 18…Electrode holding surface, 20, 81…Coil conductor, 22…Winding section, 24, 24a, 24b, 83a, 83b…Drawer section, 30a…First core, 30b…Second core, 50…Magnetic core, 31, 31a, 31b, 86a, 86b…Protrusions, 32…Wall Section, 33...notch section, 84a, 84b...end section, 85a, 85b...core, ap41, ap42, ap43, ap44, ap91, ap92, ap93, ap94...bonding section, Ca, Cb...winding shaft, Cw...centerline in the width direction, D1...first section, D2...second section, D3...third section, D4...fourth section, e1, e81...first end face, e2, e82...second end face, S1...first surface, S2...second surface.

Claims

1. A coil conductor having an air core portion and a first end face and a second end face facing each other along the winding axis, wherein the conductor is wound in a spiral shape in two stages such that the two lead-out portions at the beginning and end of the winding are located on the outer circumference, The coil conductor has a protrusion inserted into the air core portion and a wall surrounding the outer circumference of the coil conductor, each having a main surface, and the coil conductor is sandwiched between a first core and a second core from the sides of the first and second end faces, respectively. Two external electrodes are arranged on the outer surfaces of the first core and the second core, and are connected to the ends of the two lead-out portions, respectively. Equipped with, Each of the walls of the first core and the second core has a notch that forms a drawer window for pulling out the two drawer sections to the outside of the wall, Of the four sections of the coil conductor defined by a first surface that includes the winding shaft and passes through the center in the width direction of the drawer window, and a second surface that includes the winding shaft and is perpendicular to the first surface, The first end face of the coil conductor is bonded to the first core in one of the two sections closer to the draw-out window than the second face, along the draw-out portion drawn out from the side of the first end face, in the first section closest to one of the external electrodes, and in three sections different from the first section, it is not bonded to the first core, or in at least one section different from the first section, it is bonded to the first core with a lower adhesive force than in the first section. The second end face of the coil conductor is bonded to the second core in the other of the two sections closer to the draw-out window than the second face, along the draw-out portion drawn out from the side of the second end face, in the other second section closest to the external electrode, and in three sections different from the second section, it is not bonded to the second core, or in at least one section different from the second section, it is bonded to the second core with a lower adhesive force than in the second section. Inductor.

2. The protrusions of the first core and the protrusions of the second core, which face each other, are bonded and fixed together. The wall portion of the first core and the wall portion of the second core, which face each other, are spaced apart. The inductor according to claim 1.

3. The notches of the first core and the second core that constitute the drawer window are positioned offset from each other in a direction perpendicular to the center line in the width direction of the drawer window. The inductor according to either claim 1 or 2.

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