Coil device

A coil device includes: a core including a winding core part and a flange part at an axial end part of the winding core part, a coil part including a first wire and a second wire wound around the winding core part, a first terminal electrode, formed on a flange part mounting surface and a lead-out part of the first wire is connected, and a second terminal electrode, formed on the mounting surface of the flange part spaced apart from the first terminal electrode and a lead-out part of the second wire is connected, in which the flange part includes a concave part, recessed from the upper surface of the flange part and from an outer end surface of the flange part in order to have bottoms. The coil device is easy to connect a wire and has excellent bonding strength even when the connecting part becomes the mounting surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a coil device used as, for example, an inductor.

2. Description of the Related Art

Patent Document 1 discloses a coil device on which a terminal electrode, having a wire connected on the side opposite to the mounting surface, is formed. With the coil device described in Patent Document 1, there is a possibility that sufficient bonding strength between the coil device and the circuit board cannot be ensured when the terminal electrode and the wire are connected on the mounting surface.

PRIOR ART

DISCLOSURE OF THE INVENTION

Means for Solving the Problems

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a coil device which is easy to connect a wire and has excellent bonding strength even when the connecting part becomes a mounting surface.

To achieve the above object, a coil device of the first object of the invention includes:a core including a winding core part and a flange part provided at an axial end part of the winding core part,a coil part including a first wire and a second wire wound around the winding core part,a first terminal electrode, formed on a mounting surface of the flange part and a lead-out part of the first wire is connected, anda second terminal electrode, formed on the mounting surface of the flange part spaced apart from the first terminal electrode and a lead-out part of the second wire is connected, in whichthe flange part includes a concave part, recessed from the mounting surface of the flange part and from an outer end surface of the flange part in order to have bottoms.

To achieve the above object, the core of the invention includes:a winding core part anda flange part provided at an axial end part of the winding core part, in whichthe flange part includes a concave part, recessed from a mounting surface of the flange part and from an outer end surface of the flange part in order to have bottoms.

In the coil device according to the first aspect of the present invention and the core according to the present invention, the flange part includes the concave part, recessed from the mounting surface of the flange part and from the outer end surface of the flange part in order to have bottoms. For this reason, at the time of cutting after connecting the wire, for example, a cutting position of the wire is arranged on the mounting surface side of the concave part, and the cutting is performed so as to enter the cutting tool to the bottom from the mounting surface of the concave part.

When the wire is cut while pressing a lead-out part with the cutting tool on the flange part, the flange part may be damaged, and it is not easy to cut the wire. In the present invention, since the wire can be cut in the above-described manner, the wire can be easily connected and cut.

Further, in the present invention, the concave part is recessed in order to have bottoms and is not extended to an inner end surface. Therefore, the outer end surface and the inner end surface of the flange part are not in communication with each other and are partitioned by a wall. Therefore, when cutting the wire, it can prevent cutting another wire incorrectly.

Further, with the above-described configuration, even if the concave part is formed in the flange part, the volume of the flange part does not become extremely small, and the inductance of the coil device does not decrease. In addition, even if an external force is applied to the flange from the first terminal electrode side or the second terminal electrode side, the flange part has a high strength capable of withstanding the force.

Further, by leading out the wire toward the concave part, it becomes possible to draw the wire obliquely on the electrode and bond the wire at the end part of the terminal electrode. Therefore, good solder wettability can be obtained except for the bonding part between the wire and the terminal electrode, the area of the electrode surface can be sufficiently large, and it becomes possible to increase the bonding strength between the coil device and the circuit board.

It is preferable that the concave part is located close to the second terminal electrode between the first terminal electrode and the second terminal electrode, and the lead-out part of the second wire extends obliquely from an outer periphery of the winding core part through the second terminal electrode toward the concave part, when viewed from the mounting surface.

With such configuration, the second wire can be bonded to the end part of the second terminal electrode. In this case, a good solder wettability can be obtained except at the bonding part between the lead-out part of the second wire and the second terminal electrode. Thus, the area of the electrode surface can be sufficiently large and the bonding strength between the coil device and the circuit board can be increased.

It is preferable that an end part of the lead-out part of the second wire is provided on the second terminal electrode close to the concave part. With such an arrangement, the second wire is arranged on the mounting surface side of the concave part when the second wire is cut. Thus, it becomes possible to cut the second wire while the cutting tool enters toward the bottom from the mounting surface of the concave part.

It is preferable that, an inclined part inclined from the outer periphery of the winding core toward the first terminal electrode is formed on the inner end surface provided opposite to the outer end surface of the flange part, the led-out part of the first wire extends along the inclined surface of the inclined part from the outer periphery of the winding core part toward the first terminal electrode, and a wall is formed between the bottom from the outer end surface of the concave part and the inclined part.

In this way, by forming the inclined part on the inner end surface, it is possible to draw out the first wire along the inclined surface of the inclined part, and no excessive load is generated on the lead-out part of the first wire. In addition, since a wall is formed between the bottom from the outer end surface of the concave part and the inclined part, the concave part and the inclined part do not communicate with each other, and when cutting the second wire, the first wire is prevented from being cut.

It is preferable that an outer shape of the flange part as viewed from the front and an outer shape of the flange part as viewed from the back substantially coincide with each other, when the core is reversed. In this way, it becomes possible to form the terminal electrode on both front and back of the flange part.

In order to achieve the above object, a coil device of the second object of the invention includes:a core including a winding core part, a first flange part provided at an axial end part of the winding core part, and a second flange part provided at the other axial end part of the winding core part,a coil part in which a first wire and a second wire are wound around the winding core part,a first terminal electrode, formed on a mounting surface of the first flange part and connected to one lead-out part of the first wire,a second terminal electrode, formed on the mounting surface of the first flange part spaced apart from the first terminal electrode and connected to one lead-out part of the second wire,a third terminal electrode, formed on the mounting surface of the second flange part and connected to the other lead-out part of the second wire, anda fourth terminal electrode, formed on the mounting surface of the second flange part spaced apart from the third terminal electrode and connected to the other lead-out part of the first wire, in whichthe first flange part includes a concave part, recessed from the mounting surface of the first flange part and from an outer end surface of the first flange part in order to have bottoms.

The coil device may include:a first inclined part of the first flange part, inclined from an outer periphery of the winding core toward the first terminal electrode and formed on an inner end surface opposite to the outer end surface of the first flange part, anda second inclined part of the second flange part, inclined from the outer periphery of the winding core toward the third terminal electrode and formed on an inner end surface opposite to an outer end surface of the second flange part, in whichthe one lead-out part of the first wire extends along an inclined surface of the first inclined part of the first flange part from the outer periphery of the winding core part toward the first terminal electrode,and the other lead-out part of the second wire extends along an inclined surface of the second inclined part of the second flange part from the outer periphery of the winding core part toward the third terminal electrode. With such configuration, it becomes possible to equalize the line length of the coil composed of the first wire and the line length of the coil made of the second wire.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described based on the embodiments shown by figures.

The First Embodiment

As shown inFIG. 1A, coil device1according to an embodiment of the invention includes a drum core10and a coil part30, wound around a winding core part12of the drum core10.

In the following description, the X axis indicates a direction parallel to the winding axis of the winding core12of the drum core10in a plane parallel to the mounting surface on which the coil device1is mounted. As with the X axis, the Y axis is in a plane parallel to the mounting surface and is perpendicular to the X axis. The Z axis is in normal direction to the mounting surface.

The drum core10has the winding core part12and a pair of flange parts14a,14bprovided at both ends in the X axis direction of the winding core part12. One of the flange parts14a(the first flange part) is provided at one end of the winding core part12in the axial direction. The other flange part14b(the second flange part) is provided at the other end of the winding core part12in the axial direction and faces the flange part14a.In the following description, when it is unnecessary to particularly distinguish the flange parts14aand14b, they are collectively referred to as “flange part14”. The winding core part12has a winding axis in the X axis direction and has a substantially hexagonal cross section elongated in the Y axis direction. Each of the flange parts14has the same shape, but they may be different from each other. In the present embodiment, the respective flange parts14is provided so as to be point symmetrical to each other. Although the cross sectional shape of the winding core part12is substantially hexagonal in the present embodiment, it may be rectangular, circular, or substantially octagonal, and its cross sectional shape is not particularly limited.

As shown inFIG. 1A, the first wire31and the second wire32wound around the winding core part12, and constitute the coil part30formed by winding one or more layers of the wires31,32. The wires31,32are constituted by such as coated conducting wires, and have a configuration in which a core material made of a good conductor is covered with an insulating coating film. In the present embodiment, the cross sectional areas of the conductor part of the wires31,32may be the same or different. Further, the coil part30may be formed by winding one wire in one or more layers, or may be formed by winding three or more wires in one or more layers.

In the present embodiment, although the number of turns of the wires31and32are substantially the same, they may be different depending on the use. It should be noted that “the number of turns of the wires31and32are substantially the same” refers to the ratio of the number of turns is within the range of 0.75 to 1/0.75, and preferably one.

The outer shape of each flange part14is a substantially rectangular parallelepiped shape (substantially rectangular shape) in the Y axis direction. And these flange parts14are arranged so as to be substantially parallel to each other with a predetermined interval in the X axis direction. As shown inFIG. 1B, when viewing the flange part14from the mounting surface side (the Z axis upper side in the present embodiment), the flange part14is formed so that its four corners are rounded. The cross sectional (Y-Z cross section) shape of the flange part14may be a circular shape or a substantially octagonal shape, and its cross sectional shape is not particularly limited.

As shown inFIG. 1B, the flange part14has an upper surface14A, a lower surface14B, an inner end surface14C, an outer end surface14D, the first lateral side surface14E, and the second lateral side surface14F. The upper surface14A is a surface on the upper side of the flange part14. The lower surface14B is a surface opposite to the upper surface14A. The inner end surface14C is a surface on the winding core part12side. The outer end surface14D is a surface opposite to the inner end surface14C. The first lateral side surface14E is orthogonal to the upper surface14A and the inner end surface14C, and is on the side of the first terminal electrode41described later. The second lateral side surface14F is perpendicular to the upper surface14A and the inner end surface14C and is the face on the side of the second terminal electrode42.

In the present embodiment, the upper surface14A becomes the mounting surface (a ground surface) when the coil device1is mounted on such as a circuit board. In the illustrated example, the second lateral side surface14F of one flange part14flushes with the first lateral side surface14E of the other flange part14. However, there may be a deviation in Y axis direction between the lateral side surfaces14E and14F.

The first terminal electrode41is formed on the upper surface14A (the mounting surface) of the flange part14. The first terminal electrode41formed on the first flange part14aand the first terminal electrode (the third terminal electrode)41formed on the second flange part14bhave the same configuration. As shown inFIG. 1BandFIG. 1C, according to the present embodiment, the first terminal electrode41includes the first upper surface electrode part410and the first side surface electrode part411, which are electrically connected. More specifically, the first upper surface electrode part410is parallel to the X-Y plane and is formed at one end of the upper surface14A of the flange part14in the Y axis direction. A part of the first upper surface electrode part410also extends to the first inclined part141described later. The first side surface electrode part411is a surface parallel to the Y-Z plane and is formed on the end surface14D of the flange part14. By forming the first side surface electrode part411on the flange part14, it is possible to form a sufficient solder fillet on the first terminal electrode41.

The first connecting part311, which is a connecting part of the first wire31with the lead-out part310, is formed in the first upper electrode part410formed on the first flange part14a.A first connecting part321, which is a connecting part of the second wire32to the lead-out part320, is formed on the first upper surface electrode part410formed on the second flange part14b.The connection parts311,321are formed by thermocompression bonding the lead-out parts310,320to the first upper surface electrode part410. In the present embodiment, the first upper surface electrode parts410and420also function as a mounting part that is connected to face the circuit board (not shown). More specifically, a part of the first upper surface electrode parts410,420where the first connecting parts311,321are not formed functions as a good bonding surface of solder with electrodes (lands) of the circuit board.

In general, the solder wettability decreases at the thermocompression bonded part. Therefore, it is preferable that the first connecting parts311,321are preferably provided at the end, and but not in the central part of the first upper surface electrode parts410,420. Thereby, it is possible to ensure a sufficiently large area of the first upper surface electrode part410,420having excellent solder wettability, to increase the bonding strength (fixing strength) between the coil device and the circuit substrate. In addition, even when the coil device1is downsized, it is possible to sufficiently secure the fixing strength with the circuit board.

On the upper surface14A (the mounting surface) of the flange part14, the second terminal electrode42is formed at a predetermined interval (spaced apart) from the first terminal electrode41along the Y axis direction. The second terminal electrode42formed in the first flange part14aand the second terminal electrode (the fourth terminal electrode)42formed in the second flange part14bhave the same configuration. The distance between the first terminal electrode41and the second terminal electrode42is not particularly limited as long as insulation is secured.

According to the present embodiment, the second terminal electrode42includes the second upper surface electrode part420and the second side surface electrode part421, which are electrically connected. More specifically, the second upper surface electrode part420is parallel to the X-Y plane and is formed at one end of the upper surface14A of the flange part14in the Y axis direction. A part of the second upper surface electrode part420also extends to the second inclined part142and the third inclined part described later. The second side surface electrode part421is a surface parallel to the Y-Z plane and is formed on the end surface14D of the flange part14. By forming the first side surface electrode part411on the flange part14, it is possible to form the sufficient solder fillet on the second terminal electrode42.

The second upper surface electrode part420formed on the first flange part14ais formed with the second connecting wire part321which is the connecting part with the lead out part320of the second wire32. The second upper surface electrode part420formed on the second flange part14bis formed with the first connecting part311which is a connecting part of the first wire31with the lead-out part310. The connection parts311,321are formed by thermocompression bonding the lead-out parts310,320to the second upper surface electrode part420. In the present embodiment, the second upper surface electrode part420also functions as the mounting part that is connected to be opposed to the surface of the circuit board (not shown). More specifically, the part of the second upper surface electrode part420where the connecting parts311and321are not formed functions as a good bonding surface of the solder to the electrode (land) of the circuit board.

Note that it is preferable that the connecting parts311and321are provided not at the center but on the end part of the second upper surface electrode part420. Thereby, it becomes possible to secure a sufficiently large area, where it is excellent in solder wettability. And it is possible to increase the fixing strength between the coil device and the circuit board. In addition, even when the coil device1is downsized, it is possible to sufficiently secure the fixing strength with the circuit board.

On the inner end surface14C positioned opposite to the outer end surface14D of the first flange part14a,the first inclined part (the first inclined part of the first flange part)141inclined from the outer periphery (the outer periphery on the side of second terminal electrode42) of the winding core part12(the first flange part side inclined part) is formed. Similarly, on the inner end surface14C positioned opposite to the outer end surface14D of the second flange part14b,the first inclined part (the first inclined part of the second flange part)141inclined from the outer periphery (the outer periphery on the side of the second terminal electrode42) of the winding core part12(a first flange part side inclined part) is formed. As shown inFIG. 2A, the first inclined part141is inclined so as to gradually descend from the first terminal electrode41side toward the second terminal electrode42side. The first inclined part141is formed in a range between the intersection line14C1, formed by the inner end surface14C and the outer periphery of the winding core part12, and the upper surface14A.

When viewed from the upper surface14side, the first inclined part141has an outer shape of a substantially triangular shape (approximately right triangle in the illustrated example), and gradually narrows toward the second terminal electrode42side. In the present embodiment, the lead-out part310of the first wire31extends obliquely from the outer periphery of the winding core part12toward the first terminal electrode41of the first flange part14aalong the inclined surface of the first inclined part141. The lead-out part320of the second wire32extends obliquely from the outer periphery of the winding core part12toward the first terminal electrode41of the second flange part14balong the inclined surface of the first inclined part141.

As shown inFIGS. 1A and 1B, the second inclined part142is formed on the inner end surface14C of the flange part14. The second inclined part142is inclined so as to gradually descend toward the winding core part12along the X axis direction. The second inclined part142is formed in a range between the intersection line14C1formed by the inner end surface14C and the outer periphery of the winding core part12and the upper surface14A.

In the present embodiment, the lead-out part320of the second wire32extends obliquely from the outer periphery of the winding core part12toward the second terminal electrode42of the first flange part14aalong the inclined surface of the second inclined part142. Further, the lead-out part310of the first wire31extends obliquely from the outer periphery of the winding core part12toward the second terminal electrode42of the second flange part14balong the inclined surface of the second inclined part142. Therefore, it is preferable that the lead-out parts310and320pass through the end part of the second terminal electrode42and sufficiently secure the area of the second upper surface electrode part420having excellent solder wettability as described above.

The third inclined part143is formed on the first lateral side surface14E of the flange part14. The third inclined part143is inclined so as to gradually descend toward the outer side of the flange part14along the Y axis direction.

A fourth inclined part144is formed on the second lateral side surface14F of the flange part14. The fourth inclined part144is inclined so as to gradually descend toward the outside of the flange part14along the Y axis direction.

As shown inFIG. 2A, on the inner end surface14C of the flange part14, a step part146is formed at the bonding part with the winding core part12. The step part146is used as a passage for smoothly leading out the lead-out parts310,320of the wires31,32to the second upper electrode part420of the second terminal electrode42.

As shown inFIGS. 1A and 1B, the flange part14has the concave part140recessed from the mounting surface (the upper surface14A) of the flange part and from an outer end surface of the flange part in order to have bottoms. That is, the concave part140(groove) for opening the upper surface14A side and the outer end surface14D side of the flange part14is formed at the corner part between the upper surface14A and the outer end surface14D of the flange part14.

The concave part140has a first side wall140a,a second side wall140b,a third side wall140c,and a fourth side wall140d.The first side wall140ais a side wall on the side opposite to the inner end surface14C and corresponds to the bottom from the outer end surface14D of the concave part140. The second side wall140bis a side wall on the side opposite to the first lateral end surface14E. The third side wall140cis a side wall on the side opposite to the second lateral end surface14F and is on the side opposite to the second side wall140b.The fourth side wall140dis a side wall on the side opposite to the inner end surface14C and corresponds to the bottom from the upper surface (mounting surface)14A of the concave part140.

In the present embodiment, the concave part140is located between the first terminal electrode41and the second terminal electrode42. In the present embodiment, the concave part140is provided closer to the second terminal electrode42than the first terminal electrode41. A gap of a predetermined length is formed between the concave part140and the second terminal electrode42. The gap may be omitted.

With such arrangement, the lead-out parts310,320of the wires31,32obliquely extends from the outer circumference (more precisely, the step part146) of the winding core part12, through the inclined surface of the second inclined part142and the second terminal electrode42(more precisely, the end part of the second terminal electrode42in the X axis direction), and toward the concave part140, when viewed from the upper surface (the mounting surface)14A side. End parts of the lead-out parts310and320of the wires31and32are provided on the second terminal electrode42near the concave part140(near the third side wall140c).

As shown inFIG. 1B, the concave part140has a substantially square shape when viewed from the upper surface14A side. However, the shape of the concave part140is not limited thereto, and may be, for example, a substantially rectangular shape or a substantially circular shape when viewed from the upper surface14A side.

As shown inFIG. 1B, the first side wall140a, the second side wall140b, and the third side wall140cof the concave part140are tapered surfaces, respectively. And as shown inFIG. 1C, the width in the X axis direction and the width in the Y axis direction gets narrower as the upper surface14A gets closer to the lower surface14B at the concave part140. Note that the first side wall140a,the second side wall140b,and the third side wall140cof the concave part140may be surfaces perpendicular to the upper surface14A.

As shown inFIG. 1A, a wall145is formed between the first side wall140a(the bottom from the outer end surface14D) and the first inclined part141, respectively of the concave part140. The wall145connects the first terminal electrode41side and the second terminal electrode42side of the concave part140along the Y axis direction. Therefore, a region of the height H1(seeFIG. 1C) is formed continuously through the wall145between the first terminal electrode41side and the second terminal electrode42side having the concave part140in between.

The first terminal electrode41and the second terminal electrode42are composed such as of a metal paste baking film or a metal plating film. For the terminal electrodes41and42, for example, Ag paste is applied to the surfaces of the upper surface14A and the outer end surface14D of the flange part14and baked thereof, and then the surface is subjected to, for example, electrolytic plating or electroless plating to form a plating film.

The material of the metal paste is not particularly limited, and examples thereof include Cu paste and Ag paste. Further, the plating film may be a single layer or a multiple layer, and plating films such as Cu plating, Ni plating, Sn plating, Ni—Sn plating, Cu—Ni—Sn plating, Ni—Au plating, Au plating and the like are exemplified. The thickness of the terminal electrodes41and42is not particularly limited, but it is preferably 0.1 to 15 μm.

In manufacturing the coil device1, first, the drum core10and the wires31,32are prepared. As the wires31and32, for example, a core material made of a good conductor such as copper (Cu) is covered with an insulating material such as imide-modified polyurethane and the outermost surface is covered with a thin resin film such as polyester can be used.

As the magnetic material constituting the drum core10, for example, a magnetic material having a relatively high magnetic permeability such as a Ni—Zn based ferrite, an Mn—Zn based ferrite, a metal magnetic material, or the like is exemplified. These magnetic material powders are pressed and sintered, whereby the drum core10is produced. At that time, as shown inFIG. 2A, in the drum core10, the recessed part140, the first inclined part141, the second inclined part142, the third inclined part143, and the fourth inclined part144are integrally formed in each part of the flange part14. Further, in the drum core10, the winding core part12and the pair of flange parts14are integrally formed.

Next, a metal paste is applied to the flange part14of the drum core10and baked thereof at a predetermined temperature. Then, by applying electrolytic plating or electroless plating on the surface thereof, the first terminal electrode41and the second terminal electrode42as shown inFIG. 2Bare formed.

Next, the drum core10and the wires31,32on which the terminal electrodes41,42are formed are set at a winding machine (not shown). And as shown inFIG. 2C, the first wire31(lead-out part310) is lead out from the tip of the nozzle50and connected to the first upper surface electrode part410of the first terminal electrode41. As a result, the first connecting part311is formed at the connecting part between the first upper electrode part410and the first wire31.

Similarly, the second wire32(the lead-out part320) is drawn out from the tip of the nozzle50and connected to the second upper electrode part420of the second terminal electrode42. As a result, the second connecting part321is formed at the connecting part between the second upper surface electrode part420and the second wire32.

A method for the connection is not particularly limited. For example, a heater chip is pressed so as to sandwich the wire31or32between itself and the terminal electrode41or42, and the wires31,32are thermocompression bonded. Since the insulating material covering the core wires of the wires31and32is melted by heat during thermocompression bonding, it is not necessary to remove the coating on the wires31and32.

Next, as shown inFIG. 2D, an unnecessary part of the first wire31(the lead-out part310) protruding from the first upper surface electrode part410(the first terminal electrode41) is cut by the cutting tool60. When the unnecessary part of the lead-out part310is cut, the cut part of the lead-out part310is provided around the third inclined part143, and the cutting tool60is placed (located) so that its side surface substantially flushes with the first lateral side surface14E.

Then, at that position, the cutting tool60is lowered along the first lateral side surface14E in the Z axis direction. As a result, it is possible to cut the cut part of the lead-out part310without bringing the cutting tool60into contact with the corner part of the upper surface14A and the first lateral side surface14E respectively of the flange part14, and the flange part14can be prevented from being damaged.

Similarly, an unnecessary part of the second wire32(the lead-out part320) protruding from the second upper surface electrode part420(the second terminal electrode42) is cut by the cutting tool60. At the time of cutting the unnecessary part of the lead-out part320, the cut part of the lead-out part320is arranged on the mounting surface side of the recessed part140and at least a part of the cutting tool60is provided (positioned) above the upper surface14A of the flange part14, such that the side surface thereof substantially flushes with the third side wall140c.

Then, at that position, the cutting tool60is lowered in the Z axis direction along the third side wall14ctoward the fourth side wall140d.At this time, at least a part of the cutting tool60enters the inside of the concave part140from the outside of the concave part140, cuts the cut part of the lead-out part320on the mounting surface side of the concave part140, then enters the inside of the concave part140as it is. Therefore, it is possible to cut the cut part of the lead-out part320without bringing the cutting tool60into contact with the upper surface14A of the flange part14, preventing the flange part14from being damaged.

Next, as shown inFIG. 2E, the first wire31(the lead-out part310) is drawn obliquely to the outer periphery of the winding core part12along the inclined surface of the first inclined part141and wound around the winding core part12. Similarly, the second wire32(the lead-out part320) is drawn obliquely to the outer periphery of the winding core part12along the inclined surface of the second inclined part420and wound around the winding core part12to form the coil part30. Then, the wires31,32(the lead-out parts310,320) are obliquely drawn from the outer periphery of the winding core part12so as to pass through the connecting parts420,410of the terminal electrodes42,41, and hooked and fixed to each pole70so as not to slack.

Next, as shown inFIG. 2F, the first wire31is connected to the second upper surface electrode part420of the second terminal electrode42. As a result, the first connecting part311is formed at a connecting part between the second upper surface electrode part420and the first wire31.

Similarly, the second wire32is connected to the first upper surface electrode part410of the first terminal electrode41. As a result, a second connecting part321is formed at the connecting part between the first upper surface electrode part410and the second wire32.

Next, as shown inFIG. 2G, unnecessary parts of the first wires31(the lead-out part310) protruding from the second upper surface electrode part420(the second terminal electrode42) are cut in the same manner as described inFIG. 2Dwith the cutting tool60. Similarly, unnecessary parts of the second wire32(the lead-out part320) protruding from the first upper surface electrode part410(the first terminal electrode41) is cut by the cutting tool60.

Next, as shown inFIG. 2H, the plate-shaped core20is placed on the lower surface14B of the flange part14. The lower surface14B is formed of a flat surface, and it is easy to install the plate-shaped core20. The plate-shaped core20is a flat rectangular parallelepiped having a flat surface, and has a function of increasing the inductance of the coil device1. The plate-shaped core20is preferably composed of the same magnetic member as the drum core10, but it may be composed of separate members. The plate-shaped core20is not necessarily made of a magnetic material and may be made of a non-magnetic material such as a synthetic resin.

In the present embodiment, the flange part14is formed with the concave part140that is recessed so that the bottom remains from the upper surface (mounting surface)14A and the outer end surface14D of the flange part14. Therefore, at the time of cutting after connecting the second wire32, for example, the cut point of the second wire32is provided on the side respectively of the upper surface14A of the concave part140, and the cutting tool is moved toward the bottom from the upper surface14A of the concave part140.

Further, in the present embodiment, the concave part140is recessed so that the bottom remains from the outer end surface14D, and is not formed so as to extend to the inner end surface14C. Therefore, the outer end surface14D of the flange part14and the inner end surface14C do not communicate with each other and are partitioned by the wall145. Therefore, it is possible to prevent erroneously cutting the first wire31when cutting the second wire32.

Further, with the above-described configuration, even if the concave part140is formed in the flange part14, the volume of the flange part14does not become extremely small, and the inductance of the coil device1never decreases. Even if an external force is applied to the flange part14from the first terminal electrode31side or the second terminal electrode32side, the flange part14has a high strength capable of withstanding thereof is provided.

In the present embodiment, the concave part140is provided close to the second terminal electrode42between the first terminal electrode41and the second terminal electrode42. And the lead-out part320of the second wire32extends obliquely from the outer periphery of the winding core part12through the second terminal electrode42toward the concave part140, when viewed from the upper surface14A side.

That is, in the present embodiment, by pulling the second wire32toward the concave part140, the second wire32is drawn obliquely on the second terminal electrode42, and it becomes possible to bond the second wires32to the end of the second terminal electrode42. Therefore, a good solder wettability can be obtained except for the second connecting part321which is the bonding part between the second wire32and the second terminal electrode42, and the area of the surface of the second terminal electrode42is sufficiently large. Thus, it is possible to increase the bonding strength between the coil device1and the circuit board.

Further, in the present embodiment, the end part of the lead-out part320of the second wire32is provided on the second terminal electrode42close to the concave part140. With such an arrangement, when cutting the second wire32, the second wire32is arranged on the concave part140at the upper surface14A side so that the second wire32can be cut by allowing the cutting tool to enter from the upper surface14A of the concave part140toward the bottom.

In the present embodiment, the first inclined part141inclined from the outer periphery of the winding core part12toward the first terminal electrode42is formed on the inner end surface14C positioned opposite to the outer end surface14D of the flange part14. The lead-out part310of the first wire32extends along the inclined surface of the first inclined part141from the outer periphery of the core part12toward the first terminal electrode41, and the wall145is formed between the bottom of the outer end surface14D of the concave part140and the first inclined part141.

By thus forming the first inclined part141on the inner end surface14C, the first wire32can be lead out along the inclined surface of the first inclined part141. Thus, an excessive load does not generate at the lead-out part310of the first wire31. Further, since a wall is formed between the bottom from the outer end surface14D of the concave part140and the first inclined part141, the concave part140and the first inclined part141are not communicated with each other, and it is possible to prevent erroneously cutting the first wire31at the time of cutting the wire32.

The Second Embodiment

The coil devices1A according to the second embodiment shown inFIGS. 3A to 3Chave the same configuration and exhibit the same operational effects, as the coil device1according to the first embodiment except for the following. Each member of the coil device1A shown inFIGS. 3A to 3Ccorresponds to each members of the coil device1according to the first embodiment shown in such asFIGS. 2E to 2G, and the same reference numerals are given to the corresponding members. The explanation is partly omitted.

The coil device1A has the coil part30A. The coil part30A has the first layer formed by the first wire31and the second layer provided on the outer periphery of the first layer and formed with the second wire32.

In manufacturing the coil device1A, each step shown inFIGS. 2A to 2Dis carried out in the same manner as described in the first embodiment. Next, as shown inFIG. 3A, the first wire31and the second wire32are wound around the winding core part12in two layers. Next, the lead-out part310of the first wire31is drawn out to the second upper surface electrode part420of the second terminal electrode42of the flange part14b,and connected as shown inFIG. 3Bto form the first connecting part311. Similarly, the lead-out part320of the second wire32is lead out to the first upper surface electrode part410of the first terminal electrode41of the flange part14b,and connected as shown inFIG. 3Bto form the second connecting part321. Next, as shown inFIG. 3C, an unnecessary part of the first wire31(lead-out part310) protruding from the second upper surface electrode part420and an unnecessary part of the second wire32(lead-out part320) protruding from the first upper surface electrode part410are cut by the cutting tool60.

As shown inFIG. 4, the unnecessary part of the second wire32(the lead-out part320) may be cut at a position separated from the third inclined surface143in the Y axis direction. In that case, an unnecessary part of the second wire32may remain at the tip of the second connecting part321as shown inFIG. 4. The detailed illustration is omitted, but the same is applied to cutting the unnecessary part of the first wire31(the lead-out part310) inside the concave part140.

It should be noted that the present invention is not limited to the above-described embodiments, and can be variously modified within the scope of the invention.

In the above embodiment, the widths W3, W4and the height H2of the concave part140shown inFIG. 1Bare not particularly limited, and may be appropriately changed according to the size of the cutting tool. However, from the viewpoint of easily entering at least a part of the cutting tool inside the concave part140, it is preferable that the widths W3, W4and the height H2are large, and from the viewpoint of improving the inductance of the coil device1, the widths W3, W4and the height H2are preferably as small as possible.

Specifically, the ratio W3/W1of the width W3in the X axis direction of the concave part140on the upper surface14A to the width W1in the X axis direction of the flange part14is preferably 0.1 to 0.6, more preferably 0.3 to 0.5. The width W4in the Y axis direction of the concave part140on the upper surface14A may be determined according to the distance between the first terminal electrode41and the second terminal electrode42. In the illustrated example, the width W4is substantially the same as the width W3, but it may be different. The ratio H2/H1of the height H2in the Z axis direction of the concave part140shown inFIG. 1Cto the height H1in the Z axis direction of the flange part14is preferably 0.5 to 0.9, more preferably 0.6 to 0.8.

The minimum width W5between the concave part140and the first inclined part141shown inFIG. 1Bis not particularly limited, and may be appropriately determined considering the widths W1and W3. However, the minimum width W5between the concave part140and the first inclined part141is at least 0.05 mm or more.

The size of the coil device1is not particularly limited, but the length L in X axis direction is 1.15 to 1.35 mm, the width W2in Y axis direction is 0.9 to 1.1 mm, and the height H1(seeFIG. 1C) in Z axis direction is 0.45 to 0.53 mm. The ratio W6/W2of Y axis direction width W6of the winding core part12shown inFIG. 2Ato the Y axis direction width W2of the flange parts14,14shown inFIG. 1Bis preferably 0.6 to 0.9.

Further, according to the first embodiment, each lead-out part310of the first wire31may be connected to the first terminal electrode41of the first flange part14aand the first terminal electrode41of the second flange part14b.Similarly, the lead-out parts320of the second wire32may be respectively connected to the second terminal electrode42of the first flange part14aand the second terminal electrode42of the second flange part14b.In this case, for example, before or after forming the coil part30, the first wire31and the second wire32are made to intersect (twist the pair of wires31,32), whereby the positional relation of the first wire31and the second wire32may be reversed from the example shown inFIG. 1A.

In the second embodiment, the respective lead-out parts310of the first wire31may be respectively connected to the first terminal electrode41of the first flange part14aand the first terminal electrode41of the second flange part14b.Similarly, the lead-out parts320of the second wire32may be respectively connected to the second terminal electrode42of the first flange part14aand the second terminal electrode42of the second flange part14b.

In the above embodiments, as shown inFIG. 2A, the concave part140and the first inclined part140are formed only on the upper surface14A of the flange part14. However, as shown inFIG. 5, they may be formed also on the lower surface14B of the flange part14. In this case, when the core10is reversed, it is preferable to make the direction in which the first groove part141extends and the relative position of the concave part140of the upper surface (a front surface)14A coincide with the same of lower surface (a back surface)14B, in order to make the outer shape of the flange part14as viewed from the upper surface14A substantially coincide with the outer shape of the flange part14as viewed from the lower surface14B.

Further, in each of the above embodiments, as shown inFIG. 2B, the case where the first terminal electrode41is made by the first upper surface electrode part410and the first side surface electrode part411is exemplified, however, the first side surface electrode part411may be omitted. Similarly, for the second terminal electrode42, the second side surface electrode part421may be omitted.

In each of the above embodiments, the range of the first upper surface electrode part410may be expanded to the outer side in the Y axis direction of the third inclined part143, and the end part in the Y axis direction of the flange part14may be covered with the first upper surface electrode part410. Further, the range of the first side surface electrode part411may be extended to the outer side in the Y axis direction of the flange part14, and the end part in the Y axis direction of the flange part14may be covered with the first side surface electrode part411.

Similarly, the range of the second upper surface electrode part420may be extended to the outer side of the fourth inclined part144in the Y axis direction, and the end part of the flange part14in the Y axis direction may be covered with the second upper surface electrode part420. Further, the range of the second side surface electrode part421may be expanded to the outside of the flange part14in the Y axis direction, and the end part of the flange part14in the Y axis direction may be covered with the second side surface electrode part412.

NUMERICAL REFERENCES

41. . . The First Terminal Electrode410. . . The First Upper Surface Electrode Part411. . . The First Side Surface Electrode Part

42. . . The Second Terminal Electrode420. . . The Second Upper Surface Electrode Part421. . . The Second Side Surface Electrode Part