Coil device

Abstract

To provide a coil device capable of realizing miniaturization while increasing current.SOLUTION: A first end 12a of a first wire 12 is connected to a first connecting wire portion 63a of a first terminal electrode 60, and a first end 14a of a second wire 14 is connected to a second connecting wire portion 63b of a first terminal electrode 60. A second end 12b of the first wire 12 is connected to a first connecting wire portion 73a of a second terminal electrode 70, and a second end 14b of the second wire 14 is connected to a second connecting wire portion 73b of the second terminal electrode 70. The first connecting wire portion 63a and the second connecting wire portion 63b of the first terminal electrode 60 are arranged at positions separated from each other. The first connecting wire portion 73a and the second connecting wire portion 73b of the second terminal electrode 70 are arranged at positions separated from each other.SELECTED DRAWING: Figure 3A

Description

Technical Field

[0001] The present invention relates to a coil device such as a power inductor used in, for example, a DC-DC converter.

Background Art

[0002] As an inductor, a coil in which a wire is wound around a core bobbin is used (Patent Document 1). In a vertical coil device in which the bobbin portion described in Patent Document 1 is perpendicular to the mounting surface, it is possible to connect the terminal electrode and the wire by laser welding on the side surface of the flange portion. Therefore, the coil device of Patent Document 1 has an advantage that a stronger and more reliable wire connection process is possible compared to a horizontal coil device.

[0003] Due to the increasing current in recent electronic devices, coil devices are also required to handle larger currents. However, in conventional coil devices, when using a thick and low-resistance wire to handle larger currents, the lead end of the thick wire is difficult to bend, making the wire connection work complicated and causing the coil device to become larger.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In view of such a situation, the present invention is made, and an object thereof is to provide a coil device capable of achieving miniaturization while increasing the current.

Means for Solving the Problems

[0006] In order to achieve the above object, a coil device according to the present invention is A magnetic core having a core portion and a flange portion, a first wire and a second wire wound around the core portion, a coil device having a first terminal electrode and a second terminal electrode attached to the flange portion in mutual insulation, a first end of the first wire is connected to a first connection portion of the first terminal electrode, a first end of the second wire is connected to a second connection portion of the first terminal electrode, a second end of the first wire is connected to a first connection portion of the second terminal electrode, a second end of the second wire is connected to a second connection portion of the second terminal electrode, the first connection portion and the second connection portion of the first terminal electrode are arranged at positions separated from each other, the first connection portion and the second connection portion of the second terminal electrode are arranged at positions separated from each other.

[0007] In the coil device of the present invention, the current between the first terminal electrode and the second terminal electrode is divided and flows through at least a coil composed of the first wire and a coil composed of the second wire. Therefore, the current flowing through one of the first wire or the second wire can be reduced, and at the same time, the total current flowing between the first terminal electrode and the second terminal electrode can be increased. Therefore, it is possible to realize a coil device that can cope with a large current without using a thick wire.

[0008] Also, since there is no need to use a thick wire, the lead end of the wire (the first end or the second end; the same applies hereinafter) is easy to bend, the connection operation becomes easy, and the reliability of the bonding strength between the lead end of the wire and the terminal electrode at the connection portion is also improved. Furthermore, since there is no need to use a thick wire, it is not necessary to increase the thickness of the flange portion of the magnetic core accordingly, and in this respect, it is also possible to reduce the size of the coil device.

[0009] Furthermore, since the first connection portions and the second connection portions of each terminal electrode are arranged at positions separated from each other, the work of separately connecting the lead ends of the wires and the terminal electrodes at each connection portion, for example, by laser welding or the like, becomes easy. In addition, the thermal influence and the like of the connection work at any one of the connection portions are less likely to adversely affect the other connection portions, and the connection reliability at these connection portions is improved.

[0010] Preferably, the first connection portion and the second connection portion of the first terminal electrode are arranged on opposite sides along one side surface of the flange portion. Also preferably, the first connection portion and the second connection portion of the second terminal electrode are arranged on opposite sides along the other side surface of the flange portion.

[0011] By configuring in this way, the first connection portion and the second connection portion of each terminal electrode are easily arranged at positions separated from each other. Therefore, the work of separately connecting the lead ends of the wires and the terminal electrodes at each connection portion, for example, by laser welding or the like, becomes easy. In addition, the thermal influence and the like of the connection work at any one of the connection portions are less likely to adversely affect the other connection portions, and the connection reliability at these connection portions is improved. Further, since the connection portion is arranged on the side surface of the flange portion and not on the outer end surface of the flange portion on the mounting surface side, the low-profile of the coil device can also be realized.

[0012] Preferably, the first connection portion of the first terminal electrode and the first connection portion of the second terminal electrode are arranged at diagonal positions with the core portion interposed therebetween. Also preferably, the second connection portion of the first terminal electrode and the second connection portion of the second terminal electrode are arranged at diagonal positions with the core portion interposed therebetween.

[0013] By configuring in this way, it becomes easier to make the length from the first connection part of the first terminal electrode to which the first end of the first wire is connected to the first connection part of the second terminal electrode to which the second end of the first wire is connected substantially the same as the corresponding length of the second wire. The corresponding length of the second wire is the length from the second connection part of the first terminal electrode to which the first end of the second wire is connected to the second connection part of the second terminal electrode to which the second end of the second wire is connected. By making these lengths substantially the same, it becomes easier to make the current flowing through the coil composed of the first wire and the current flowing through the coil composed of the second wire substantially the same. Therefore, it becomes easier to maximize the current flowing through the coil device.

[0014] Preferably, the first terminal electrode has a first attachment piece attached to the outer end face of the flange portion. Also preferably, the second terminal electrode has a second attachment piece attached to the outer end face of the flange portion. By attaching these attachment pieces to the outer end face of the magnetic core with an adhesive or the like, it becomes easier to attach the first terminal electrode and the second terminal electrode to the flange portion respectively.

[0015] Preferably, the first terminal electrode further has connection rising pieces on which the first connection part and the second connection part are respectively formed, and these connection rising pieces may be raised from the mutually opposite edges of the first attachment piece toward the side surface of the flange portion. Also preferably, the second terminal electrode further has connection rising pieces on which the first connection part and the second connection part are respectively formed, and these connection rising pieces are raised from the mutually opposite edges of the second attachment piece toward the side surface of the flange portion.

[0016] The connection rising pieces may be provided with gripping pieces for sandwiching and temporarily fixing the lead end of the wire, and the connection part is formed by, for example, bringing the lead end of the wire into contact with the connection rising pieces and performing laser welding.

[0017] Preferably, a notch is formed on the side surface of the flange portion where the vertical piece for the connecting wire is formed. By inserting the vertical piece for the connecting wire into the notch, the connecting wire portion can be accommodated inside the notch portion, preventing the connecting wire portion from protruding outside the flange portion. As a result, it contributes to the miniaturization of the coil device, reduces the risk of the connecting wire portion colliding with other components, and improves the connection reliability of the connecting wire portion.

[0018] Preferably, a recess is formed on the outer end surface of the flange portion, and the first terminal electrode or the second terminal electrode has an inner vertical piece that loosely enters the recess.

[0019] With such a configuration, when mounting the coil device on a circuit board or the like, a connecting member such as solder also enters the recess, and a fillet is formed on the outer surface of the inner vertical piece, improving the bonding strength between the circuit board and the terminal electrode.

[0020] The terminal electrode is composed of, for example, a metal terminal, and the mounting piece, which is the main part thereof, can be adhered to the outer end surface of the flange portion. Moreover, the inner vertical piece of the terminal electrode only loosely enters the recess, and the wall surface of the recess and the inner vertical piece are not fitted. Therefore, even if the coil device is exposed to a harsh temperature change environment such as -40 to 150 °C, the thermal stress acting on the terminal electrode is less likely to act on the flange portion of the magnetic core, reducing the risk of generating cracks or the like in the magnetic core. Also, even under a harsh temperature environment, the deterioration of the bonding strength between the coil device and the circuit board is small.

[0021] Preferably, a gap with a predetermined interval is formed between the side wall connected to the bottom wall of the recess and the tip of the inner vertical piece that enters the recess. With such a configuration, even if the coil device is exposed to a harsh temperature change environment, the thermal stress acting on the terminal electrode is less likely to act on the flange portion of the magnetic core, reducing the risk of generating cracks or the like in the magnetic core. Also, even under a harsh temperature environment, the deterioration of the bonding strength between the coil device and the circuit board is small.

[0022] Preferably, the first terminal electrode or the second terminal electrode further has an outer rising piece that rises from the edge of the first mounting piece or the second mounting piece toward the side surface of the flange portion. A fillet of a connection member such as solder is likely to be formed on the outer surface of the outer rising piece. Therefore, the bonding strength between the terminal electrode and a circuit board or the like is further improved.

[0023] The first mounting piece or the second mounting piece may each have a pair of separated mounting pieces connected to the first connection portion and the second connection portion, respectively, and these separated mounting pieces may be connected by the outer rising piece. Further, the first connection portion and the second connection portion of the first terminal electrode or the second terminal electrode may be connected by the first mounting piece or the second mounting piece.

Brief Description of the Drawings

[0024]

Figure 1A

Figure 1B

Figure 1C

Figure 1D

Figure 1E

Figure 2A

Figure 2B

Figure 3A

Figure 3B

Figure 4

Figure 5A

Figure 5B

Figure 5C

[0025] Hereinafter, the present invention will be described based on the embodiments shown in the drawings.

[0026] A coil device 2 according to an embodiment of the present invention shown in FIGS. 1A to 1E is used as a component such as a DC-DC converter, and particularly preferably, as a power inductor or the like.

[0027] This coil device 2 has a drum core 20 as a magnetic core. Examples of the magnetic material constituting the drum core 20 include soft magnetic materials such as metals and ferrites, but are not particularly limited. As shown in FIG. 2A, the drum core 20 has a bobbin portion 30 around which two wires (a first wire 12 and a second wire 14) constituting the coil portion 10 are wound along the winding axis direction of the core 20.

[0028] It is preferable that the periphery of the bobbin portion 30 around which the wires 12 and 14 are wound is covered with an exterior resin 15. By covering with the exterior resin 15, the coil portion 10 can be effectively protected, and short-circuit failures and the like can also be suppressed. Further, the exterior resin 15 may be composed of a magnetic material-containing resin. By configuring in this way, the magnetic material-containing exterior resin 15 serves as a path for the magnetic field, and the magnetic characteristics of the coil device 2 are improved. The magnetic material contained in the exterior resin 15 is not particularly limited, but examples thereof include magnetic material powder similar to the magnetic material powder constituting the core 20, or other magnetic material powder.

[0029] The wires 12 and 14 are not particularly limited, and for example, flat wires, round wires, stranded wires, Litz wires, braided wires, etc. made of copper or the like, or wires in which these conductive core wires are insulated and coated can be used. Specifically, known windings such as AIW (polyimide wire), UEW (urethane wire), UEW, USTC, etc. can be used. Wire 12 ,14 The wire diameter of is not particularly limited, and for example, it is 0.1 to 0.5 mm. The wire diameters and materials of the two wires 12 and 14 may be different, but it is preferable that they are the same.

[0030] At both ends of the winding core part 30 in the winding axis direction (Z-axis direction), a first flange part 40 and a second flange part 50 are integrally formed respectively. These first flange part 40 and second flange part 50 protrude in the X-Y axis plane with respect to the winding core part 30. Note that the X-axis, Y-axis, and Z-axis are perpendicular to each other, and the Z-axis coincides with the axial direction of the winding axis.

[0031] The cross section (the cross section of the X-Y axis plane) of the winding core part 30 is not particularly limited, and it may be a square cross section, a rectangular cross section, a circular cross section, or other cross-sectional shapes. In this embodiment, it is substantially circular.

[0032] As shown in FIG. 2A, the second flange part 50 has an outer end face 52 in the winding axis direction (Z-axis direction) and an inner face 53 in the winding axis direction located on the opposite side. The upper end of the coil part 10 in the Z-axis direction is positioned on the inner face 53. Also, the first flange part 40 has an outer end face 42 in the winding axis direction and an inner face 43 in the winding axis direction located on the opposite side. The lower end of the coil part 10 in the Z-axis direction is positioned on the inner face 43 in the winding axis direction. Note that the number of winding layers of the wires 12 and 14 is not particularly limited, and the winding method of the wires 12 and 14 is also not particularly limited.

[0033] The specific shape of the second flange portion 50 is not particularly limited. In the present embodiment, as shown in FIG. 1D, it has side surfaces 50a, 50a facing each other in the Y-axis direction and side surfaces 50b, 50b facing each other in the X-axis direction, and has a rectangular shape as a whole when viewed from the Z-axis direction. And chamfered portions 54 are respectively formed at four corner portions where the virtual bilateral extension surfaces of the side surfaces 50a, 50a of the second flange portion 50 intersect with the virtual bilateral extension surfaces of the side surfaces 50b, 50b. The chamfered portion 54 is integrally formed with the first flange portion 40, the second flange portion 50, and the core portion 30 when the drum core 20 shown in FIG. 3A is molded, but may be formed by cutting or polishing after integral molding.

[0034] Also, the specific shape of the first flange portion 40 is not particularly limited. In the present embodiment, as shown in FIG. 5A, it has side surfaces 40a, 40a facing each other in the Y-axis direction and side surfaces 40b, 40b facing each other in the X-axis direction, and has a rectangular shape as a whole when viewed from the Z-axis direction. And notches 44 are respectively formed at four corner portions where the virtual bilateral extension surfaces of the side surfaces 40a, 40a of the first flange portion 50 intersect with the virtual bilateral extension surfaces of the side surfaces 40b, 40b. The notch 44 is integrally formed with the first flange portion 40, the second flange portion 50, and the core portion 30 when the drum core 20 is molded, but may be formed by cutting or polishing after integral molding.

[0035] In the present embodiment, as also shown in FIG. 5A, the side surfaces 40a, 40a of the first flange portion 40 are positioned on the same virtual plane (X-Z plane) so as to be substantially flush with the side surfaces 50a, 50a of the second flange portion 50 respectively. Also, the side surfaces 40b, 40b of the first flange portion 40 are positioned on the same virtual plane (Y-Z plane) so as to be substantially flush with the side surfaces 50b, 50b of the second flange portion 50 respectively.

[0036] Moreover, in this embodiment, the size of each notch 44 of the first flange portion 40 is larger than the size of each chamfered portion 54 of the second flange portion 50. As shown in FIG. 1D, when viewing the outer end face 52 of the second flange portion 50 from above the Z-axis, the outer shape of the first flange portion 40 located below the Z-axis becomes invisible. However, a part of the continuous lines 63 and 73 shown in FIG. 1A can be seen at the portion corresponding to the chamfered portion 54 of the second flange portion 50.

[0037] That is, in this embodiment, the outer shape size of the second flange portion 50 and the outer shape size of the first flange portion 40 are almost the same. However, since the first flange portion 40 has notches 44 larger than the chamfered portions 54, if they have the same thickness, their volumes will be different. In order to make the volume of the second flange portion 50 and the volume of the first flange portion 40 substantially the same, the Z-axis thickness of the first flange portion 40 may be made larger than the Z-axis thickness of the second flange portion 50.

[0038] As shown in FIG. 5A, on the outer end face 42 of the first flange portion 40, four independent recesses 46 are arranged at positions as close as possible to the center of the outer end face 42, two by two at predetermined intervals in the X-axis and Y-axis directions respectively. Each independent recess 46 is formed long along the Y-axis direction, and the interval between adjacent independent recesses 46 along the X-axis or Y-axis is determined to be a size that ensures insulation between the adjacent terminal electrodes (the first terminal electrode 60 and the second terminal electrode 70) along the X-axis shown in FIG. 3A.

[0039] In this embodiment, as shown in FIG. 3A, a pair of terminal electrodes 60, 70 are mounted on the outer end face 42 of the first flange portion 40 in the winding axis direction. Although the details of the terminal electrodes 60, 70 will be described later, they are made of a conductive metal plate such as tough pitch steel, phosphor bronze, brass, iron, nickel, etc.

[0040] The terminal electrodes 60 and 70 each have plate-shaped mounting pieces 61 and 71 having a plane substantially parallel to the plane including the X-axis and the Y-axis. As shown in FIG. 1E, these mounting pieces 61 and 71 are adhered to the outer end face 42 in the winding axis direction of the first flange portion 40 by an adhesive or the like. A terminal mounting groove conforming to the shape of the mounting pieces 61 and 71 may be formed in the outer end face 42 of the first flange portion 40 to which the mounting pieces are adhered.

[0041] The groove depth of the terminal mounting groove is preferably smaller than the respective thicknesses of the mounting pieces, and the bottom surfaces of the mounting pieces 61 and 71 preferably protrude more than the outer end face 42 in the winding axis direction. By doing so, the mounting portions 61 and 71 of the coil device 2 can be easily connected to the wiring pattern 82 such as the circuit board 80 shown in FIG. 2B by a connecting member such as solder 84 during the mounting operation.

[0042] As shown in FIG. 3A, at both ends of the mounting piece 61 in the Y-axis direction, near the outside in the X-axis direction, a first connection rising piece 62a and a second connection rising piece 62b are integrally formed so as to rise in the Z-axis direction, respectively. Similarly, at both ends of the mounting piece 71 in the Y-axis direction, near the outside in the X-axis direction, a first connection rising piece 72a and a second connection rising piece 72b are integrally formed so as to rise in the Z-axis direction, respectively.

[0043] The first connection rising piece 62a and the first connection rising piece 72a are arranged at diagonal positions of the first flange portion 40 with the winding core portion 30 interposed therebetween. Similarly, the second connection rising piece 62b and the second connection rising piece 72b are arranged at diagonal positions of the first flange portion 40 with the winding core portion 30 interposed therebetween.

[0044] These connection rising pieces 62a, 62b, 72a, and 72b can each come into contact with the notch side face 40c of each notch 44 of the first flange portion 40. The notch side face 40c is a face drawn along the Y-axis from the side face 40a to the inside of the notch 44 and is a face substantially parallel to the side face 40a.

[0045] The tip portions of the respective rising pieces 62a, 62b, 72a, 72b for the connecting wires are bent so as to be folded back, and form gripping pieces 62a1, 62b1, 72a1, 72b1 respectively. Between the gripping piece 62a1 and the rising piece 62a for the connecting wire, the first lead portion (first end) 12a of the first wire 12 shown in FIG. 4 is sandwiched and joined, and the first connecting wire portion 63a shown in FIG. 1A is formed. In the first connecting wire portion 63a, the first lead portion 12a and the rising piece 62a of the first terminal electrode 60 are electrically connected.

[0046] Also, between the gripping piece 62b1 and the rising piece 62b for the connecting wire shown in FIG. 3A, the first lead portion (first end) 14a of the second wire 14 shown in FIG. 4 is sandwiched and joined, and the second connecting wire portion 63b shown in FIG. 1D is formed. In the second connecting wire portion 63b, the first lead portion 14a and the rising piece 62b of the first terminal electrode 60 are electrically connected.

[0047] Also, between the gripping piece 72a1 and the rising piece 72a for the connecting wire shown in FIG. 3A, the second lead portion (second end) 12b of the first wire 12 shown in FIG. 4 is sandwiched and joined, and the first connecting wire portion 73a shown in FIG. 1D is formed. In the first connecting wire portion 73a, the second lead portion 12b and the rising piece 72a of the second terminal electrode 70 are electrically connected.

[0048] Furthermore, between the gripping piece 72b1 and the rising piece 72b for the connecting wire shown in FIG. 3A, the second lead portion (second end) 14b of the second wire 14 shown in FIG. 4 is sandwiched and joined, and the second connecting wire portion 73b shown in FIG. 1D is formed. In the second connecting wire portion 73b, the second lead portion 12b and the rising piece 72b of the second terminal electrode 70 are electrically connected.

[0049] Each of the connecting wire portions 63a, 63b, 73a, 73b is preferably formed by laser welding. The laser light for welding is irradiated, for example, from below the flange portion 40 along the Z axis, and the tip portions of the lead portions 12a, 12b, 14a, 14b are laser welded to the rising pieces 62a, 62b, 72a, 72b for the connecting wires respectively to form the connecting wire portions 63a, 63b, 73a, 73b.

[0050] The connection lead-up pieces 62a, 62b, 72a, 72b to which the respective lead portions 12a, 12b, 14a, 14b shown in FIG. 4 are attached are disposed inside each notch 44 of the first flange portion 40 shown in FIG. 5A. Moreover, as shown in FIG. 1D, a part of the connection lead-up pieces 62a, 62b, 72a, 72b where the connection portions 63a, 63b, 73a, 73b are formed is disposed outside the chamfered portion 54k of the second flange portion 50. Therefore, the laser light irradiated from below the flange portion 40 along the Z axis can form the connection portions 63a, 63b, 73a, 73b without irradiating any of the flange portions 40, 50.

[0051] As shown in FIG. 3A, a pair of outer lead-up pieces 64a, 64b and a pair of outer lead-up pieces 74a, 74b are integrally formed so as to rise in the Z-axis direction at the outer ends in the X-axis direction of the attachment portions 61 and 71, respectively. The rising height of each of the outer lead-up pieces 64a, 64b, 74a, 74b is the same as the rising height of the connection lead-up pieces 62a, 62b, 72a, 72b.

[0052] Also, a pair of inner lead-up pieces 66a, 66b and a pair of inner lead-up pieces 76a, 76b are integrally formed so as to rise in the Z-axis direction at the inner ends in the X-axis direction of the attachment portions 61 and 71, respectively. The rising height of the inner lead-up pieces 66a, 66b, 77a, 77b is smaller than the rising height of the outer lead-up pieces 64a, 64b, 74a, 74b.

[0053] Also, the rising angle of the outer lead-up pieces 64a, 64b, 74a, 74b with respect to the attachment portions 61, 71 is preferably about 90 degrees, similar to the connection lead-up pieces 62a, 62b, 72a, 72b. However, the rising angle of the inner lead-up pieces 66a, 66b, 77a, 77b is preferably greater than 90 degrees, and as shown in FIG. 2B, it is preferably 95 to 160 degrees, more preferably 100 to 150 degrees.

[0054] As shown in FIG. 2B, the outer rising pieces 64b and 74a (the same applies to 64a and 74b) preferably contact the side surfaces 40b of the first flange portion 40 respectively, and the positioning of each terminal electrode 60 in the X-axis direction with respect to the outer end surface 42 of the first flange portion 40 is preferably performed. Further, as shown in FIG. 1E, the connecting wire rising pieces 62a, 62b, 72a, and 72b preferably contact the notch side surfaces 40c inside the notch 44 of the first flange portion 40 respectively. This is because the positioning of each terminal electrode 60 and 70 in the Y-axis direction is performed with respect to the outer end surface 42 of the first flange portion 40.

[0055] As shown in FIG. 2B, each inner rising piece 66a, 66b, 77a, 77b is adapted to loosely fit into each independent recess 46 formed in the outer end surface of the first flange portion 40. That is, each inner rising piece 66a, 66b, 77a, 77b is preferably separated from the inner wall surface of each independent recess 46 by a predetermined interval (predetermined gap) t1 along the X-axis, and is preferably separated from the outer wall surface of the independent recess 46 by a predetermined interval (predetermined gap) t2. Further, it is preferable that the tips of each inner rising piece 66 and 76 do not contact the bottom wall surface of each independent recess 46 either.

[0056] Although not particularly limited, the predetermined interval t1 is preferably about 1.5 to 5 times the plate thickness of each inner rising piece 66 and 76. Also, the predetermined interval t2 is preferably about 0.1 to 3 times the plate thickness of each inner rising piece 66 and 76. Further, the width in the Y-axis direction of each independent recess 46 shown in FIG. 5A is larger than the width in the Y-axis direction of the inner rising pieces 66a, 66b, 77a, 77b shown in FIG. 3A, and is preferably about 1.1 to 1.5 times.

[0057] In the present specification, "outer" means the side located in the direction away from the center of the coil device 2, and "inner" means the side close to the center of the coil device 2.

[0058] Next, a method for manufacturing the coil device 2 shown in FIGS. 1A to 5A will be described. First, the drum core 20 shown in FIGS. 3A and 5A is molded. The molding method of the drum core 20 is not particularly limited, but compression molding, CIM (Ceramic Injection Molding) molding, MIM (Metal Injection Molding) molding, etc. are conceivable. After molding, it is fired to form a sintered body.

[0059] Next, the terminal electrodes 60 and 70 are attached to the outer end surface 42 of the first flange portion 40 of the drum core 20. When attaching and fixing the terminal electrode 60 ,70 to the outer end surface 42, an adhesive is interposed only between the attachment pieces 61 and 71 and the outer end surface 42. Then, it is preferable to pay attention so that the adhesive does not enter the inside of each independent recess 46 and does not protrude toward the outer side surfaces 40a, 40b, and 40c of the first flange portion 40.

[0060] Note that each of the terminal electrodes 60 and 70 can be easily formed by punching and bending a single metal plate (for example, a copper plate). After or before attaching each of the terminal electrodes 60 and 70 to the drum core, the wires 12 and 14 shown in FIG. 4 are wound around the bobbin portion 30 of the drum core 20 shown in FIG. 5 to form the coil portion 10. When winding the wires 12 and 14 around the bobbin portion 30, the wires 12 and 14 may be wound separately, or the wires 12 and 14 may be wound simultaneously in the same direction.

[0061] With the coil portion 10 formed on the bobbin portion 30, the lead portions 12a, 12b (14a, 14b) at both ends of each of the wires 12 (14) constituting the coil portion 10 are positioned and temporarily fixed between the connection rising pieces 62a, 72a (62b, 72b) and the gripping pieces 62a1, 72a1 (62b1, 72b1) of the terminal electrode 60. In that state, laser welding is performed.

[0062] As described above, the laser light irradiated from below the flange portions 40 along the Z-axis can form the connection portions 63a, 63b, 73a, and 73b without irradiating any of the flange portions 40 and 50. Also, the connection between the lead portions 12a, 12b (14a, 14b) of the winding wire 12 (14) and the terminal electrodes 60 (70) is performed at a temperature higher than the temperature (230 to 280°C) for forming the solder fillet, such as laser welding (temperature of 1000°C or higher). Therefore, a strong and reliable wire connection process for the wire 12 (14) is possible.

[0063] In the coil device 2 according to the present embodiment, two terminal electrodes 60 and 70 are attached to the outer end surface 42 of the first flange portion 40 of the drum core 20 as the magnetic core, as shown in FIG. 1E. Therefore, at least two wires 12 and 14 are wound around the bobbin portion 30 of the coil device 2 of the present embodiment, and the respective lead portions 12a and 12b at both ends of the wire 12 are connected to each of the two terminal electrodes 60 and 70. Also, the respective lead portions 14a and 14b at both ends of the wire 14 are connected to each of the two terminal electrodes 60 and 70.

[0064] Therefore, in the coil device 2 of the present embodiment, the current between the first terminal electrode 60 and the second terminal electrode 70 is divided and flows through at least the coil formed by the first wire 12 and the coil formed by the second wire 14. Therefore, while the current flowing through one of the first wire 12 or the second wire 14 can be reduced, the total current flowing between the first terminal electrode 60 and the second terminal electrode 70 can be increased. Therefore, it is possible to realize a coil device 2 that can cope with a large current without using a thick wire.

[0065] In addition, since it is not necessary to use thick wires, the lead portions 12a, 12b, 14a, and 14b of the wires 12 and 14 are easily bent, facilitating the wire connection operation. The reliability of the bonding strength between the wires 12 and 14 and the terminal electrodes 60 and 70 at the wire connection portion is also improved. Furthermore, since it is not necessary to use thick wires, it is not necessary to increase the thickness of the flange portions 40 and 50 of the magnetic core 20 accordingly. In this regard as well, it is possible to reduce the size of the coil device 2.

[0066] Furthermore, since the first wire connection portions 63a and 73a and the second wire connection portions 63b and 73b of the respective terminal electrodes 60 and 70 are arranged at positions separated from each other, the operation of separately connecting the wires 12 and 14 and the terminal electrodes 60 and 70 at the respective wire connection portions 63a, 63b, 73a, and 73b, for example, by laser welding, becomes easy. In addition, the thermal influence of the connection operation at any of the wire connection portions 63a, 63b, 73a, and 73b is less likely to adversely affect other wire connection portions, and the connection reliability of these wire connection portions 63a, 63b, 73a, and 73b is improved.

[0067] In the coil device 2 of the present embodiment, four independent recesses 46 are formed on the outer end surface 42 of the first flange portion 40 of the drum core 20, and the inner rising pieces 66a, 66b, 76a, and 76b of the respective terminal electrodes 60 and 70 are loosely inserted into the respective recesses 46. Therefore, as shown in FIG. 2B, when the coil device 2 is mounted on a circuit board 80 or the like, a connecting member such as solder 84 also enters the inside of the recess 46, and a fillet is also formed on the outer surface of the inner rising pieces 66 and 76, improving the bonding strength between the wiring pattern 82 of the circuit board 80 and the terminal electrodes 60 and 70.

[0068] The terminal electrodes 60 and 70 are composed of, for example, metal terminals, and the attachment portions 61 and 71, which are the main parts thereof, are adhered to the outer end surface 42 of the flange portion 40. Moreover, the inner rising pieces 66a, 66b, 76a, and 76b of the respective terminal electrodes 60 and 70 only loosely enter the recessed portions 46, and the inner rising pieces 66 and 76 do not fit with the wall surfaces of the recessed portions 46. Therefore, even if the coil device 2 is exposed to an environment with severe temperature changes, such as from -40 to 150°C, the thermal stress acting on the terminal electrode 60 hardly acts on the flange portion 40 of the drum core 20, and there is little possibility of generating cracks or the like in the drum core 20. Also, even under a severe temperature environment, the deterioration of the bonding strength between the coil device 2 and the circuit board 80 is small.

[0069] Also, in the present embodiment, outer rising pieces 64a, 64b, 74a, and 74b are integrally formed at the edges of the attachment portions 61 and 71 located on the opposite side along the X-axis from the inner rising pieces 66a, 66b, 76a, and 76b, and the outer rising pieces 64a, 64b, 74a, and 74b are integrally raised along the side surface 40b of the flange portion 40. As shown in FIG. 2B, fillets such as solder 84 are likely to be formed on the outer surfaces of the rising pieces 66b and 76a (the same applies to 66a and 76b). Therefore, the bonding strength between the terminal electrodes 60 and 70 and the circuit board 80 or the like is further improved.

[0070] Also, when mounting the coil device 2 on, for example, the circuit board 80, the solder 84 attached to the lower surface of each terminal 60 also adheres to the outer surfaces of the outer rising pieces 64b and 74a (the same applies to 64a and 74b), and when viewed from above in the Z-axis direction, the state of the attached solder 84 can be confirmed without being hidden by the second flange portion 50.

[0071] Furthermore, in the present embodiment, the rising height of the outer rising pieces 64b and 74a (the same applies to 64a and 74b) is lower than the thickness in the winding axis direction of the first flange portion 40. By configuring in this way, the compactification of the coil device 2 can be realized. Also, the possibility of the exterior resin 15 shown in FIG. 1B adhering to the outer rising pieces 64a and 74b (the same applies to 64b and 74a) is reduced, and the formation of fillets during mounting is not inhibited.

[0072] Further, as shown in FIG. 1E, in the present embodiment, the inner rising pieces 66a, 66b, 76a, 76b are arranged offset from the outer rising pieces 64, 74 so as to be located near the central axis of the core portion 30 (see FIG. 2B) when viewed from the direction of the X-axis. By arranging the inner rising pieces 66a, 66b, 76a, 76b in this way, it becomes possible to move the position of the recess 46 formed in the outer end face 42 of the flange portion 40 toward the center side of the outer end face 42. As a result, the position where the recess 46 is formed corresponds to the position corresponding to the core portion 30 (see FIG. 2B). Even if the recess 46 is formed in the flange portion 40, the possibility of reducing the strength of the drum core 20 is reduced, and the recess 46 can be formed without increasing the thickness of the flange portion 40, which also contributes to the compactification of the coil device 2.

[0073] Furthermore, in the present embodiment, as shown in FIG. 3A, connection wire rising pieces 62a, 62b, 72a, 72b different from the inner rising pieces and the outer rising pieces are integrally formed on the attachment portions 61, 71. Also, each of the connection wire rising pieces 62a, 62b, 72a, 72b is integrally raised along the notch side face 40c parallel to the side face 40a of the flange portion 40. The lead portions 12a, 14a of the wire are respectively connected to the connection wire rising pieces 62a, 62b, and the lead portions 12b, 14b of the wire are respectively connected to the connection wire rising pieces 72a, 72b.

[0074] With this configuration, each of the terminal electrodes 60, 70 has six rising pieces 62a, 62b, 64a, 64b, 66a, 66b (or 72a, 72b, 74a, 74b, 76a, 76b), and these rising pieces are raised from the attachment portions 61, 71 at different positions into the side faces 40b, 40c of the flange portion 40 or the recess 46. As shown in FIG. 2B, the formation locations of the fillets of the solder 84 with the circuit board 80 increase, and the connection strength with the circuit board 80 is further improved.

[0075] Furthermore, in the present embodiment, the flange portion 40 protrudes outward in the radial direction of the core portion 30, and has a substantially square shape as a whole when viewed from the direction of the Z-axis. Notches 44 are formed at the four corners of the flange portion 40, and connection portions between the lead-up pieces 62a (or 62b, 72a, 72b) for connection lines and the lead portions 12a (or 12b, 14a, 14b) are arranged therein. By configuring in this way, without changing the outer diameter dimensions of the flange portions 40 and 50 (while maintaining the miniaturization of the coil device 2), the volume of the drum core 20 can be maximally maintained, and a decrease in inductance can be suppressed.

[0076] That is, in the present embodiment, most of the lead-up pieces 62a, 62b, 72a, 72b of the terminal electrodes 60, 70, including the connection lines 63a, 63b, 73a, 73b shown in FIG. 3A, are respectively accommodated inside the respective notches 44 of the first flange portion 40. Moreover, as shown in FIG. 1D, when viewing the outer end face 52 of the second flange portion 50 from above the Z-axis, only a part of the connection lines 63a, 63b, 73a, 73b shown in FIG. 1A can be seen at the portion corresponding to the chamfered portion 54 of the second flange portion 50. For this reason, the coil device 2 can be miniaturized, and at the same time, the volume of the magnetic material of the drum core 20 including the flange portions 40 and 50 can be maximally increased. Therefore, it is easy to improve the inductance characteristics and the like of the coil device 2.

[0077] Moreover, in the present embodiment, it is possible to minimize the protruding amount of the terminal electrodes 60, 70 with respect to the second flange portion 50 without maintaining the sizes of the flange portions 40 and 50 and reducing the inductance. During the conveyance of the coil device 2, the terminal fittings 60 and Jumper parts 63a, 63b, 73a, 73b are less likely to collide with a mounting device or the like.

[0078] Also, in the present embodiment, the concave portion 46 is configured such that an adhesive for adhering the mounting portions 61 and 71 to the outer end surface 42 of the flange portion 40 does not enter. That is, the terminal electrodes 60 are adhered to the outer end surface 42 of the flange portion 40 only by the mounting portions 61 and 71. By configuring in this way, even if the coil device 2 is exposed to an environment with severe temperature changes, the thermal stress acting on the terminal electrodes 60 and 70 is less likely to act on the flange portion 40 of the drum core 20, and there is little possibility of generating cracks or the like in the drum core 20. Also, even under a severe temperature environment, the deterioration of the bonding strength between the coil device and the circuit board is small.

[0079] Also, in the present embodiment, as shown in FIG. 2B, a gap with a predetermined interval t1 and t2 is formed between the side wall surface connected to the bottom wall surface of the concave portion 46 and the tips of the inner rising pieces 66 and 76 that enter the concave portion 46. By configuring in this way, even if the coil device 2 is exposed to an environment with severe temperature changes, the thermal stress acting on the terminal electrode 60 is less likely to act on the flange portion 40 of the drum core 20, and there is little possibility of generating cracks or the like in the drum core 20. Also, even under a severe temperature environment, the deterioration of the bonding strength between the coil device 20 and the circuit board 80 is small.

[0080] Also, the concave portion is composed of four independent concave portions 46 formed on the outer end surface 42 of the flange portion 40. By configuring the concave portion formed on the outer end surface 42 of the flange portion 40 with four independent concave portions 46, the volume reduction and strength reduction of the drum core 20 are small, and the characteristics improvement and compactification of the coil device 2 can be achieved simultaneously. Also, by configuring in this way, it is easy to ensure insulation between the terminal electrodes 60 and 70.

[0081] Furthermore, in the present embodiment, as shown in FIG. 3A, the first connecting portions 63a and 63b of the first terminal electrode 60 are arranged on opposite sides of the Y-axis along one of the side surfaces 40b of the flange portion 40. Also, the first connecting portions 72a and 72b of the second terminal electrode 70 are arranged on opposite sides of the Y-axis along the other of the side surfaces 40b of the flange portion 40.

[0082] By configuring in this way, the first connection portions 63a and 73a and the second connection portions 63b and 73b of the respective terminal electrodes 60 and 70 are easily arranged at positions separated from each other. Therefore, the work of separately connecting the lead portions 12a, 12b, 14a, and 14b of the wires 12 and 14 shown in FIG. 4 and the terminal electrodes 60 and 70 shown in FIG. 3A by, for example, laser welding or the like becomes easy. In addition, the thermal influence of the connection work in any of the connection portions 63a, 63b, 73a, and 73b is less likely to adversely affect other connection portions, and the connection reliability of these connection portions is improved. Further, since the connection portions 63a, 63b, 73a, and 73b are arranged on the side surface 40c of the flange portion and not on the outer end surface of the flange portion on the mounting surface side, the low-profile of the coil device 2 can also be realized.

[0083] Moreover, in the present embodiment, as shown in FIG. 3A, the first connection portion 63a of the first terminal electrode 60 and the first connection portion 73a of the second terminal electrode 70 are arranged at diagonal positions with the central axis of the core portion 30 interposed therebetween. Also, the second connection portion 63b of the first terminal electrode 60 and the second connection portion 73b of the second terminal electrode 70 are arranged at diagonal positions with the central axis of the core portion 30 interposed therebetween.

[0084] By configuring in this way, it becomes easy to make the length from the first connection portion 63a of the first terminal electrode 60 to which the first lead portion 12a of the first wire 12 shown in FIG. 4 is connected to the first connection portion 73a of the second terminal electrode 70 to which the second lead portion 12b of the first wire 12 is connected substantially the same as the corresponding length of the second wire 14. The corresponding length of the second wire 14 is the length from the second connection portion 63b of the first terminal electrode 60 to which the first lead portion 14a of the second wire 14 is connected to the second connection portion 73b of the second terminal electrode 70 to which the second lead portion 14b of the second wire 14 is connected. By making these lengths substantially the same, it becomes easy to make the current flowing through the coil composed of the first wire 14 and the current flowing through the coil composed of the second wire 14 substantially the same. Therefore, it becomes easy to maximize the current flowing through the coil device 2.

[0085] In addition, in this embodiment, as shown in FIG. 3B, the first attachment piece 61 may have a pair of separated attachment pieces 61a and 61b that are respectively connected to the first connection part 63a and the second connection part 63b. The separated attachment pieces 61a and 61b are separated by a notch 68 formed along the X axis at the central part of the attachment piece 61 in the Y-axis direction. These separated attachment pieces 61a and 61b are connected (mechanically and electrically) by a single outer standing piece 64 extending in the Y-axis direction.

[0086] Similarly, the second attachment piece 71 may also have a pair of separated attachment pieces 71a and 71b that are respectively connected to the first connection part 73a and the second connection part 73b. The separated attachment pieces 71a and 71b are separated by a notch 78 formed along the X axis at the central part of the attachment piece 71 in the Y-axis direction. These separated attachment pieces 71a and 71b are connected (mechanically and electrically) by a single outer standing piece 74 extending in the Y-axis direction.

[0087] Also, in this embodiment, as shown in FIG. 5B, two independent recesses 46 and 46 arranged side by side in the Y-axis direction shown in FIG. 5A may be made continuous to form two common recesses 46a and 46a. Alternatively, as shown in FIG. 5C, two common recesses 46a and 46a arranged side by side in the X-axis direction shown in FIG. 5B may be made continuous to form a single common recess 46b.

[0088] Moreover, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention.

[0089] For example, as means for forming the connection parts 63a, 63b, 73a, and 73b, not only laser welding but also thermocompression bonding (at 300°C or higher) may be used. Even in the case of thermocompression bonding, the connection between the lead parts 12a, 12b, 14a, and 14b of the winding wires 12 and 14 and the terminal electrodes 60 and 70 can be made at a temperature higher than the temperature (230 to 280°C) for forming the fillet of the solder 84 shown in FIG. 2B. Alternatively, as means for forming the other connection parts 63a, 63b, 73a, and 73b, arc welding, ultrasonic welding, etc. are exemplified.

[0090] Also, in the terminal electrodes 60 and 70 of the above-described embodiment, it is preferable that the inner surface of the mounting portions 61 and 71 in contact with the drum core 20 is not formed with a plating film in order to improve the adhesiveness with the drum core. However, on the outer surface that becomes the bonding surface with the circuit board, tin plating may be performed in order to improve the bonding property with the solder 84.

[0091] Furthermore, in the above-described embodiment, the overall shape of each flange portion 40 and 50 as viewed from the Z-axis direction is a quadrangle. However, in the present invention, it may be circular, elliptical, or other shapes.

[0092] Also, in the above-described embodiment, the recesses 46, 46a, and 46b formed on the outer end surface of the flange portion 40 are configured so that the adhesive for bonding the mounting portions 61 and 71 of each terminal electrode 60 does not enter. However, it may enter slightly. However, it is preferable that the adhesive does not enter the recesses 46, 46a, and 46b as much as possible in terms of improving the adhesive force or joining force of each terminal electrode 60 and 70 to the outer end surface 42 of the flange portion.

Explanation of Reference Numerals

[0093] 2... Coil device 10... Coil portion 12... First wire 14... Second wire 12a, 14a... First lead portion (first end) 12b, 14b... Second lead portion (second end) 15... Exterior resin 20... Drum core (magnetic core) 30... Bobbin portion 40... First flange portion 40a, 40b... Side surfaces 40c... Notched side surface 42... Outer end surface 43... Inner surface 44... Notch 46... Independent recess 46a, 46b... Common recesses 50... Second flange portion 50a, 50b... Side 52... Outer end face 53... Inner surface 54... Chamfered portion 60, 60a... First terminal electrode 70, 70b... Second terminal electrode 61, 71... Mounting piece 61a, 61b, 71a, 71b... Separated mounting piece 62a, 62b, 72a, 72b... Upright piece for connecting wire 62a1, 62b1, 72a1, 72b1... Gripping piece 63a, 73a... First connecting wire portion 63b, 73b... Second connecting wire portion 64, 64a, 64b, 74, 74a, 74b... Outer upright piece 66a, 66b, 76a, 76b... Inner upright piece 68, 78... Notch 80... Circuit board 82... Wiring pattern 84... Solder

Claims

1. A coil device having a bobbin portion, a first flange portion, and a second flange portion, a first wire and a second wire wound around the bobbin portion, a first terminal electrode, and a second terminal electrode, wherein the first terminal electrode and the second terminal electrode are attached to the first flange portion apart from each other, the first terminal electrode has a first terminal first connection portion to which a first end of the first wire is connected and a first terminal second connection portion to which a first end of the second wire is connected, the second terminal electrode has a second terminal first connection portion to which a second end of the first wire is connected and a second terminal second connection portion to which a second end of the second wire is connected, the first terminal first connection portion, the first terminal second connection portion, the second terminal first connection portion, and the second terminal second connection portion are respectively arranged at four diagonal positions on a side surface of the first flange portion, the first terminal first connection portion and the first terminal second connection portion are arranged at positions opposite to each other along one side surface of the first flange portion among the four diagonal positions on the side surface side, the second terminal first connection portion and the second terminal second connection portion are arranged at positions opposite to each other along the other side surface of the first flange portion among the four diagonal positions on the side surface side.

2. The first terminal first connection portion and the second terminal first connection portion of the second terminal electrode are arranged at diagonal positions with respect to each other among the four diagonal positions on the side surface side, The coil device according to claim 1, wherein the first terminal second connection portion and the second terminal second connection portion of the second terminal electrode are arranged at diagonal positions with respect to each other among the four diagonal positions on the side surface side.

3. The first terminal electrode has a first attachment piece attached to an outer end surface of the first flange portion, The coil device according to claim 1 or 2, wherein the second terminal electrode has a second attachment piece attached to an outer end surface of the first flange portion.

4. The first terminal electrode further has connection rising pieces on which the first terminal first connection portion and the first terminal second connection portion are respectively formed, and these connection rising pieces are raised from opposite edges of the first attachment piece toward the side surface of the first flange portion. The second terminal electrode further has lead-up pieces for connection on which the second terminal first connection part and the second terminal second connection part are respectively formed, and these lead-up pieces for connection are raised from the mutually opposite edges of the second attachment piece toward the side surface of the first flange part. The coil device according to claim 3.

5. On the side surface of the first flange part where the lead-up piece for connection is formed, a notch is formed. The coil device according to claim 4.

6. A recess is formed on the outer end surface of the first flange part, The first terminal electrode or the second terminal electrode has an inner lead-up piece that loosely enters the recess. The coil device according to any one of claims 1 to 5.

7. A gap with a predetermined interval is formed between the side wall connected to the bottom wall of the recess and the tip of the inner lead-up piece that enters the recess. The coil device according to claim 6.

8. The first terminal electrode or the second terminal electrode further has an outer lead-up piece that is raised from the edge of the first attachment piece or the second attachment piece toward the side surface of the first flange part. The coil device according to any one of claims 3 to 5.

9. The first attachment piece has a pair of separated attachment pieces respectively connected to the first terminal first connection part and the first terminal second connection part, and these separated attachment pieces are connected by the outer lead-up piece. The coil device according to claim 8.

10. The first terminal first connection part and the first terminal second connection part of the first terminal electrode are connected by the first attachment piece. The coil device according to any one of claims 3 to 8.

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