The present application claims priority to Japanese Patent Application No. 2018-101486, filed May 28, 2018, the disclosure of which is incorporated herein by reference in its entirety including any and all particular combinations of the features disclosed therein.
The present invention relates to a coil component, and an electronic device.
As the demand for thinner coil components rises, coil components are used in high frequency bands (such as 10 MHz and higher), allowing the coil components to have lower inductances. As a result, coil components that use a flat coil constituted by a single layer of a spirally-wound coil conductor, have been in use in recent years. A flat coil constituted by a spirally-wound coil conductor is such that one end part is positioned on the inner side of the flat coil, while the other end part is positioned on the outer side of the flat coil. Accordingly, constitutions are known, wherein a lead conductor connected to, of the two end parts of a flat coil, the end part positioned on the inner side of the flat coil, is led out from the inner side of the flat coil to the outer side of the flat coil and then connected to an external electrode (refer to Patent Literature 1, for example).
[Patent Literature 1] Japanese Patent Laid-open 2001-102217
When a coil component is used in a high frequency band, a greater requirement is put on reducing loss. The higher the frequency at which the coil component is used, the higher the speed becomes at which magnetic flux transmitting through the coil conductor and lead conductor changes, and this increases loss due to eddy current that generates inside the conductor.
The present invention was made in light of the aforementioned problems, and its object is to suppress the increase in loss inside the conductor.
The present invention represents a coil component comprising: a base part containing a magnetic material and having insulating property; a flat coil embedded in the base part, formed by a wound coil conductor where a first end part on one side is located on the inner side of the windings, and a second end part on the other side is located on the outer side of the windings; a first lead conductor connected to the first end part of the flat coil; a second lead conductor connected to the second end part of the flat coil; a first external electrode provided on the surface of the base part and connected to the first lead conductor; and a second external electrode provided on the surface of the base part and connected to the second lead conductor; wherein, the first lead conductor is connected to the first external electrode in an area on the inner side of the flat coil when the base part and the flat coil are viewed from above in the direction of a coil axis of the flat coil
The aforementioned constitution may be such that the first lead conductor is connected from the first end part of the flat coil to the first external electrode, along a straight line.
The aforementioned constitution may be such that the first lead conductor is parallel with the coil axis.
The aforementioned constitution may be such that the first lead conductor overlaps the coil conductor when the base part and the flat coil are viewed from above in the direction of the coil axis.
The aforementioned constitution may be such that the cross-sections of the first lead conductor and the second lead conductor, in the direction perpendicular to the coil axis, have a circular shape.
The aforementioned constitution may be such that: the first lead conductor connects to the first external electrode provided on a first face, among all surfaces, of the base part; the second lead conductor connects to the second external electrode provided on the first face of the base part; and the first external electrode and the second external electrode are not provided on a second face, on the opposite side of the first face, of the base part.
The aforementioned constitution may be such that the first external electrode and the second external electrode are provided only on the first face, among all surfaces, of the base part.
The aforementioned constitution may be such that: the first external electrode is provided in a manner extending from a first face among all surfaces, via a third face that connects to the first face and a second face on the opposite side of the first face, to the second face, of the base part; and the second external electrode is provided in a manner extending from the first face, via a fourth face that connects to the first face and the second face, to the second face, of the base part.
The aforementioned constitution may be such that it further comprises: a third lead conductor connected to the first end part of the flat coil; a fourth lead conductor connected to the second end part of the flat coil; a third external electrode provided on the surface of the base part and connected to the third lead conductor; and a fourth external electrode provided on the surface of the base part and connected to the fourth lead conductor; wherein, the first lead conductor is connected to the first external electrode provided on a first face, among all surfaces, of the base part; the second lead conductor is connected to the second external electrode provided on the first face of the base part; the third lead conductor is connected to the third external electrode provided on a second face, on the opposite side of the first face, of the base part, in an area on the inner side of the flat coil, when the base part and the flat coil are viewed from above in the direction of the coil axis; and the fourth lead conductor is connected to the fourth external electrode provided on the second face of the base part.
The aforementioned constitution may be such that: the first external electrode and the third external electrode are connected on a third face that connects to the first face and the second face of the base part; and the second external electrode and the fourth external electrode are connected on a fourth face that connects to the first face and the second face of the base part.
The aforementioned constitution may be such that: the first lead conductor is connected to the first external electrode provided on a first face, among all surfaces, of the base part; the second lead conductor is connected to the second external electrode provided on the first face of the base part; end parts of the first lead conductor and the second lead conductor project from the first face of the base part; and the first external electrode and the second external electrode cover the end parts of the first lead conductor and the second lead conductor to form dome-shaped projections.
The aforementioned constitution may be such that the height of the coil component is 0.6 mm or smaller.
The present invention represents an electronic device comprising: the aforementioned coil component; and a circuit board which the coil component is mounted on or embedded in.
According to the present invention, the increase in loss inside the conductor can be suppressed.
Examples of the present invention are explained below by referring to the drawings.
The base part 10 is shaped as a rectangular solid having a bottom face 12, a top face 14, a pair of end faces 16a and 16b, and a pair of side faces 18a and 18b. The bottom face 12 is the mounting face, while the top face 14 is a face on the opposite side of the bottom face 12. The end faces 16a and 16b are faces connected to the short sides of the bottom face 12 and the top face 14, while the side faces 18a and 18b are faces connected to the long sides of the bottom face 12 and the top face 14. It should be noted that the shape of the base part 10 is not limited to a perfect rectangular solid; instead, its vertices may be rounded, ridges (boundaries between faces) may be rounded, or faces may be curved, for example. In other words, “shaped as a rectangular solid” includes having these shapes.
The base part 10 has insulating property and is formed by a material that contains magnetic metal grains, ferrite grains, or other magnetic grains. The base part 10 is formed by a material in which magnetic grains are contained as a primary component, for example. “Contained as a primary component” means magnetic grains are contained by more than 50 percent by weight, 70 percent by weight or more, or 80 percent by weight or more, for example. The base part 10 may be formed by a resin that contains magnetic grains, or it may be formed by magnetic grains of which surfaces are insulation-coated. For the magnetic metal grains, FeSi-type, FeSiCr-type, FeSiAl-type, FeSiCrAl-type, Fe, Ni, or other magnetic metals, crystalline magnetic metals, non-crystalline magnetic metals, or nanocrystalline magnetic metals are used, for example. For the ferrite grains, NiZn-type ferrites, MnZn-type ferrites, or other ferrites are used, for example. For the resins, polyimide resins, phenolic resins, or other thermosetting resins may be used, or polyethylene resins, polyamide resins, or other thermosetting resins may be used, for example. For the insulating films to coat the surfaces of magnetic grains with, silicone oxide films and other inorganic insulating films may be used, for example.
The flat coil 30 is formed by a single layer of a spirally-wound coil conductor 32, where an end part 34 on one side of the coil conductor 32 is provided on the inner side of the windings, and an end part 36 on the other side is provided on the outer side of the windings, and it is also called “flat spiral coil.” The end parts 34 and 36 may be positioned along a straight line that runs through the center of the flat coil 30 in top view and roughly in parallel with the long sides of the bottom face 12 and the top face 14, or one or both of the end parts 34 and 36 may deviate from such straight line. The coil conductor 32 is formed by copper, aluminum, nickel, silver, platinum, palladium, or other metal material or an alloyed material containing the foregoing, for example, and an insulating film may be provided on the conductor surface. The cross-section shape of the coil conductor 32 is a rectangle, for example, but it may also be a trapezoid, semi-ellipse constituted by straight lines and curved lines, or the like. The flat coil 30 has a coil axis 38 that crosses at right angles with a plane specified by the windings of the coil conductor 32. The bottom face 12 and the top face 14 of the base part 10 represent planes that cross roughly at right angles with the coil axis 38, while the end faces 16a and 16b and the side faces 18a and 18b of the base part 10 represent planes that are roughly in parallel with the coil axis 38. The coil conductor 32 has a spacing along each winding. This spacing may be air, the insulating film on the coil conductor 32, or other insulating material, so long as each winding is insulated.
The flat coil 30 is shaped as an ellipse with the coil conductor 32 being wound elliptically, for example; however, it may also be shaped as a circle with the coil conductor 32 being wound circularly, or a rectangle with the coil conductor 32 being wound rectangularly, or a so-called oval shape with the coil conductor 32 being wound in a manner combining the foregoing. Here, the shape of the flat coil 30, or specifically the wound shape of the coil conductor 32, is expressed as an ellipse, circle, rectangle, or oval by assuming that the conductor constituting the outermost periphery part of the coil conductor 32 forms a closed figure. The shape of the flat coil 30, or specifically the wound shape of the coil conductor 32, may also be expressed in the same way hereinafter. Also, the flat coil 30 is shaped as an ellipse when the ratio of a short axis length L2, to a long axis length L1, of the flat coil 30 (L2/L1) is 0.9 or smaller, while the flat coil 30 is shaped as a circle when the ratio is greater than 0.9. Also, preferably when a long direction length and a short direction length of the base part 10 are given by L3 and L4, respectively, the ratio of the long axis length L1 and the short axis length L2 of the flat coil 30 is roughly the same as the ratio of the long direction length L3 and the short direction length L4 of the base part 10 (L1:L2≈L3:L4). The coil axis 38 is defined as an axis that perpendicularly runs through the center of the wound shape of the coil conductor 32, when the conductor constituting the outermost periphery part of the coil conductor 32 is assumed to form a closed shape. If the wound shape of the coil conductor 32 is an ellipse, the center of the wound shape of the coil conductor 32 becomes a point of intersection between the long axis and the short axis; if the wound shape of the coil conductor 32 is a rectangle, the center of the wound shape of the coil conductor 32 becomes a point of intersection between the diagonal lines; if the wound shape of the coil conductor 32 is an oval, the center of the wound shape of the coil conductor 32 becomes a midpoint that equally divides the axis of symmetry into two.
Because the flat coil 30 has a so-called single-layer, spirally-wound shape where the coil conductor 32 does not overlap in the direction of the coil axis 38, the coil component 100 can be made thinner. For example, the height of the coil component 100 may be set to 0.6 mm or smaller, 0.4 mm or smaller, or 0.2 mm or smaller. Examples of the size (length×width×height) of the coil component 100 include 0.2 mm×0.1 mm×0.1 mm, 0.3 mm×0.2 mm×0.1 mm, 0.3 mm×0.2 mm×0.2 mm, 0.4 mm×0.2 mm×0.2 mm, 0.6 mm×0.3 mm×0.3 mm, 1.0 mm×0.5 mm×0.3 mm, 1.6 mm×0.8 mm×0.3 mm, 1.6 mm×0.8 mm×0.4 mm, 1.6 mm×0.8 mm×0.5 mm, 1.6 mm×1.0 mm×0.3 mm, 1.6 mm×1.0 mm×0.4 mm, 1.6 mm×1.0 mm×0.5 mm, 1.6 mm×1.2 mm×0.3 mm, 1.6 mm×1.2 mm×0.4 mm, 1.6 mm×1.2 mm×0.5 mm, 2.0 mm×1.2 mm×0.3 mm, 2.0 mm×1.2 mm×0.4 mm, 2.0 mm×1.2 mm×0.5 mm, 2.0 mm×1.2 mm×0.6 mm, 2.0 mm×1.6 mm×0.3 mm, and 2.0 mm×1.6 mm×0.5 mm, and the like.
The external electrodes 60 and 62 are external terminals used for surface mounting, and positioned in a manner partially overlapping the end parts 34, 36 of the coil conductor 32 when viewed from above in the direction of the coil axis 38. The external electrode 60 is provided on the bottom face 12 of the base part 10 at a position closer to the end face 16a. The external electrode 62 is provided on the bottom face 12 of the base part 10 at a position closer to the end face 16b. The external electrodes 60 and 62 are provided only on the bottom face 12 among all surfaces, and not provided on the top face 14, the end faces 16a and 16b, or the side faces 18a and 18b, of the base part 10. In other words, each of the external electrodes 60 and 62 is a one-face electrode provided only on one face, among all surfaces, of the base part 10. The external electrodes 60 and 62 are provided symmetrically to a center line 20 between the end faces 16a and 16b of the base part 10, for example. The external electrodes 60 and 62 may also be provided symmetrically to a center 22 of the bottom face 12 of the base part 10, for example. As the external electrodes 60 and 62 are provided symmetrically to the center line 20 and/or the center 22, the coil component 100 can be mounted on a circuit board, etc., in a well-balanced manner.
Each of the external electrodes 60 and 62 has a multi-layer structure having, for example, a bottom layer formed by copper, aluminum, nickel, silver, platinum, palladium, or other metal material, or an alloyed material containing the foregoing, a middle layer formed by silver or a conductive resin containing silver, and a top layer being a nickel, tin or copper plated layer. It should be noted that the layer structure of the external electrodes 60 and 62 is not limited to the one illustrated above, and may be such that intermediate layers are provided between the respective layers, a topmost layer is provided on top of the top layer, or the like.
Here, when the flat coil 30 is viewed from above in the direction of the coil axis 38, an area, which is delineated or surrounded by a closed figure line drawn in a manner that a circumferential length along an outermost periphery part 33 of the coil conductor 32 is shortest, is referred to as an area 42 (shaded part surrounded by a closed dotted figure line 43 in
The lead conductor 50 may connect the end part 34 of the flat coil 30 and the external electrode 60 provided on the bottom face 12 of the base part 10, along a straight line. This way, the length of the lead conductor 50 becomes shorter, so the electrical resistance can be reduced. Also, the lead conductor 50 may connect the end part 34 of the flat coil 30 and the external electrode 60 provided on the bottom face 12 of the base part 10, in parallel with the coil axis 38. This way, the length of the lead conductor 50 becomes even shorter, so the electrical resistance can be reduced further and the below-mentioned impact of eddy current suppressed effectively. It should be noted that, “in parallel with the coil axis 38” means both ends of the lead conductor 50 are overlapping when viewed from above in the direction of the coil axis 38. The shortest length can be achieved when each end part is allowed to overlap by at least a half. Also, the aforementioned “in parallel with the coil axis 38” does not only mean “parallel” in the strict sense, but also accommodates a slight inclination and/or height gap, etc., equivalent to a manufacturing error. Also, the lead conductor 50 may be provided in a manner overlapping the coil conductor 32 when viewed from above in the direction of the coil axis 38. In other words, the lead conductor 50 may be placed in a manner fitting entirely inside the width of the coil conductor 32. This ensures good connection stability between the lead conductor 50 and the coil conductor 32, allowing the connection resistance to remain constant regardless of any position deviation of the connection part.
The lead conductor 52 may connect the end part 36 of the flat coil 30 and the external electrode 62 provided on the bottom face 12 of the base part 10, along a straight line. This way, the electrical resistance of the lead conductor 52 can be reduced. The lead conductor 52 may also connect the end part 36 of the flat coil 30 and the external electrode 62 provided on the bottom face 12 of the base part 10, in parallel with the coil axis 38. This way, the electrical resistance of the lead conductor 52 can be reduced further. Also, the lead conductor 52 may be connected to the external electrode 62 on the end face 16b of the base part 10 based on any general structure.
The lead conductors 50 and 52 are formed by copper, aluminum, nickel, silver, platinum, palladium, or other metal material or an alloyed material containing the foregoing, for example. The lead conductors 50 and 52 may be formed by the same material as the coil conductor 32, or they may be formed by a different material. The cross-section shapes of the lead conductors 50 and 52 in the direction perpendicular to the coil axis 38 are a circle, for example. This way, magnetic flux transmitting through the lead conductors 50 and 52 can be kept roughly constant, even when the coil conductor 32 is wound by an arbitrarily set number of times, and consequently the impact of loss can be kept constant. The diameters of the lead conductors 50 and 52 are approx. 50 μm to 300 μm, for example. It should be noted that the cross-section shapes of the lead conductors 50 and 52 in the direction perpendicular to the coil axis 38, if not a circle, may be an ellipse, rectangle, etc., for example.
Now, how the coil component 100 in Example 1 is manufactured, is explained. The coil component 100 is formed through steps including those where multiple green sheets (insulating sheets) are stacked. A green sheet is an insulating structural precursor to the base part 10, and is formed by, for example, applying a resin material containing magnetic grains onto a film using the doctor blade method or printing method.
First, multiple green sheets are prepared. Some of these multiple green sheets are lasered, etched, or otherwise processed to form through holes at specified positions. Next, on some green sheets in which through holes have been formed, a conductive material is applied using the printing method, for example, to form precursors to the coil conductor 32 and the lead conductors 50 and 52 that form the flat coil 30. Also, on other green sheets in which through holes have been formed, a conductive material is applied using the printing method, for example, to form precursors to the lead conductors 50 and 52. When sintered, these precursors become the coil conductor 32 and the lead conductors 50 and 52.
Next, the multiple green sheets are stacked in a specified order, and a pressure is applied in the stacking direction to pressure-bond the multiple green sheets. Then, the pressure-bonded green sheets are cut to individual chips using a dicer, lever cutter, etc., after which the chips are sintered at a specified temperature. As a result of this sintering, the base part 10 is formed in which the flat coil 30 constituted by the coil conductor 32, and the lead conductors 50 and 52, are provided. The external electrodes 60 and 62 are formed by paste printing, plating, sputtering, or other method used in thin-film processes.
Next, the coil component in a comparative example is explained.
On the coil component 1000 pertaining to the comparative example, the lead conductor 51 connected to the end part 34 of the flat coil 30 is led out, through the interior of the base part 10, from the inner side of the flat coil 30 to the outer side of the flat coil 30. As a result, the lead conductor 51 intersects all windings of the coil conductor 32. This way, magnetic flux generated by the current flowing through the lead conductor 51 passes through the parts of the coil conductor 32 that intersect the lead conductor 51, and consequently eddy current generates in the coil conductor 32. This is explained using
According to Example 1, on the other hand, the lead conductor 50 is connected to the external electrode 60 in the area 42 on the inner side of the flat coil 30 when the base part 10 and the flat coil 30 are viewed from above in the direction of the coil axis 38 of the flat coil 30, as shown in
Preferably the lead conductor 50 connects the edge part 34 of the flat coil 30 and the external electrode 60 provided on the bottom face 12 of the base part 10, along a straight line. This way, eddy current generating in the coil conductor 32 and lead conductor 50 can be reduced effectively. Also, the electrical resistance of the lead conductor 50 can be made smaller.
Preferably the lead conductor 50 connects the end part 34 of the flat coil 30 and the external electrode 60 provided on the bottom face 12 of the base part 10, along a straight line in parallel with the coil axis 38 of the flat coil 30, as shown in
Preferably the lead conductor 50 is provided in a manner overlapping the coil conductor 32 when the base part 10 and the flat coil 30 are viewed from above in the direction of the coil axis 38, as shown in
As shown in
As shown in
As shown in
As shown in
According to Variation Example 2 of Example 1, the external electrode 60 connected to the lead conductor 50 is provided in a manner extending from the bottom face 12, via the end face 16a, to the top face 14, of the base part 10. The external electrode 62 connected to the lead conductor 52 is provided in a manner extending from the bottom face 12, via the end face 16b, to the top face 14, of the base part 10. This way, both the bottom face 12 and the top face 14 of the base part 10 can be used as a mounting face.
As shown in
According to Variation Example 3 of Example 1, the lead conductors 50 and 54 are connected to the end part 34, while the lead conductors 52 and 56 are connected to the end part 36, of the flat coil 30. When the base part 10 and flat coil 30 are viewed from above in the direction of the coil axis 38 of the flat coil 30, the lead conductor 50 is connected, in the area 42 on the inner side of the flat coil 30, to the external electrode 60 provided on the bottom face 12 of the base part 10, while the lead conductor 54 is connected, in the area 42 on the inner side of the same, to the external electrode 64 provided on the top face 14 of the base part 10. Also, the lead conductor 52 is connected to the external electrode 62 provided on the bottom face 12 of the base part 10, while the lead conductor 56 is connected to the external electrode 66 provided on the top face 14 of the base part 10. This way, both the bottom face 12 and the top face 14 of the base part 10 can be used as a mounting face.
Preferably the external electrodes 60, 62, 64, and 66 are provided on the bottom face 12 and the top face 14, and not on any face other than the bottom face 12 and the top face 14, of the base part 10. This allows for high-density mounting for the same reasons explained in Example 1. It should be noted that, also in Variation Example 3 of Example 1, the external electrodes provided on the surface of the base part 10 may be three-face electrodes or five-face electrodes, just like in Variation Example 2 of Example 1. In other words, the external electrode 60 provided on the bottom face 12 of the base part 10 and the external electrode 64 provided on the top face 14 of the same may be connected on the end face 16a, while the external electrode 62 provided on the bottom face 12 of the base part 10 and the external electrode 66 provided on the top face 14 of the same may be connected on the end face 16b.
As with the coil component 200 in Example 2, the board 80 having the coil conductor 32 formed on its principle face may be embedded in the base part 10. In this case, presence of the board 80 on the top face of the coil conductor 32 means absence of magnetic material over the entire top face of the flat coil 30. In other words, no magnetic material is present that penetrates through the area overlapping the flat coil 30 as viewed in the direction of the coil axis 38. As a result, generation of eddy current in the coil conductor 32 can be suppressed effectively.
As with the coil component 300 in Example 3, the lead conductors 50 and 52 may be formed by bending the conductive wire from which the coil conductor 32 has been formed. In this case, no magnetic material is present between the parts of the coil conductor 32. In other words, on a section perpendicular to the direction of the coil axis 38, no magnetic material is present that penetrates between the conductive windings of the flat coil 30 in the direction parallel with the coil axis 38. As a result, generation of eddy current in the coil conductor 32 can be suppressed effectively. It should be noted that the conductive wire is not limited to a round wire of which cross-section shape is a circle, and it may also be a rectangular wire of which cross-section shape is a rectangle.
The coil component 400 in Example 4 can be formed by a method similar to the manufacturing method explained in Example 1, for example. Here, a structure where the end parts of the lead conductors 50 and 52 project from the bottom face 12 of the base part 10 can be obtained by using, for the conductive material with which to form the lead conductors 50 and 52, a material that shrinks less, when sintered, than does the insulating material with which to form the base part 10.
According to Example 4, the end parts of the lead conductors 50 and 52 project from the bottom face 12 of the base part 10. The external electrodes 60 and 62 cover the end parts of the lead conductors 50 and 52 projecting from the bottom face 12 of the base part 10, and thereby form the dome-shaped projections 68 and 70. As a result, pressing the external electrodes 60 and 62 onto the solder applied on a circuit board for the purpose of mounting them on the circuit board, causes the projections 68 and 70 to bite into the solder. This prevents the coil component 400 from deviating from its specified position even when, for example, vibration that generates when the pickup device is raised by breaking the vacuum, or vibration that generates when the circuit board is transferred to the melting furnace, is applied to the coil component 400.
It should be noted that, while Example 5 presents an example where the coil component 100 in Example 1 is mounted on the circuit board 90, any of the coil components in Variation Example 1 of Example 1 to Example 4 may be mounted on the circuit board 90. When the coil component 400 in Example 4 is mounted on the circuit board 90, for example, position deviation problems can be prevented at the time of mounting the coil component 400 on the circuit board 90, as explained in Example 4. Also, the coil component may be embedded in the circuit board 90, and it can be made thinner in either case.
The foregoing described the examples of the present invention in detail; it should be noted, however, that the present invention is not limited to these specific examples, and various modifications/changes may be added to the extent that the results do not deviate from the key points of the present invention as described in “What Is Claimed Is.
Number | Date | Country | Kind |
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2018-101486 | May 2018 | JP | national |