Coil component and wireless communication circuit using the same

Abstract

To increase the magnetic permeability of a magnetic layer in a coil component having a structure in which a coil pattern is covered by the magnetic layer.SOLUTION: A coil component 1 comprises a coil pattern 3 and a magnetic layer 4 covering the coil pattern. The coil pattern 3 has a flat shape in which a thickness is smaller than a width in a radial direction. Magnetic powder 4a included in the magnetic layer 4 has a flat shape in which a thickness in a direction perpendicular to a substrate 2 is smaller than a diameter in a direction parallel to the substrate. Some of the magnetic powder 4a is such that its height position based on a surface 2a of the substrate 2 is present within a height range of the coil pattern 3. As described above, the coil pattern 3 and the magnetic powder 4a both have the flat shape, and thus the magnetic permeability of the magnetic layer 4 is increased.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a coil component, and more particularly to a coil component that functions as an antenna coil by being connected to a communication circuit and a wireless communication circuit using the same.

Background Art

[0002] As a coil component that functions as an antenna coil by being connected to a communication circuit, the coil component described in Patent Document 1 is known. FIG. 8 of Patent Document 1 discloses a method of forming a magnetic layer by directly applying a paste containing magnetic powder to a coil pattern.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the coil pattern described in Patent Document 1 has a problem that it is difficult for magnetic powder to enter between coil patterns adjacent in the radial direction because the aspect ratio (the ratio of the thickness to the width of the coil pattern) is large. In order to make it easier for magnetic powder to enter between coil patterns adjacent in the radial direction, spherical magnetic powder produced by an atomization method may be used as described in Patent Document 2, but it is difficult to increase the magnetic permeability of the magnetic layer with spherical magnetic powder.

[0005] Therefore, an object of the present invention is to increase the magnetic permeability of a magnetic layer in a coil component having a structure in which a coil pattern is covered with a magnetic layer.

Means for Solving the Problems

[0006] The coil component according to the present invention comprises a substrate, a coil pattern formed on one surface of the substrate, and a composite material in which magnetic powder is dispersed in resin, and includes a magnetic layer formed on one surface of the substrate so as to cover the coil pattern. The coil pattern has a flat shape in which the thickness is smaller than the width in the radial direction, and the magnetic powder has a flat shape in which the thickness in the direction perpendicular to one surface of the substrate is smaller than the diameter in the direction parallel to one surface of the substrate. A part of the magnetic powder is characterized in that the height position with respect to one surface of the substrate exists within the height range of the coil pattern.

[0007] According to the present invention, since the magnetic powder has a flat shape and is oriented in the direction parallel to the surface of the substrate, the magnetic permeability of the magnetic layer is increased. Moreover, since the coil pattern also has a flat shape, it becomes possible to arrange magnetic powder also at both side positions in the radial direction of the coil pattern, and it becomes possible to obtain high magnetic characteristics.

[0008] In the present invention, the cross section in the radial direction of the coil pattern may have a chamfered shape such that the width becomes smaller as the height position with respect to one surface of the substrate becomes higher. According to this, since the magnetic powder is arranged obliquely along the chamfered shape portion, it becomes possible to align the direction of the magnetic field generated by the coil pattern and the orientation direction of the magnetic powder. In this case, the average value of the diameter of the magnetic powder may be 1 / 5 or more and 10 times or less the width in the radial direction of the chamfered shape portion. According to this, the direction of the magnetic field and the orientation direction of the magnetic powder become more easily aligned.

[0009] In the present invention, the average value of the diameter of the magnetic powder is 30 μm or more, and the width of the coil pattern may be 1 to 10 times the average value of the diameter of the magnetic powder. According to this, it is possible to sufficiently secure the magnetic permeability of the magnetic layer and reduce the inter-wire capacitance of the coil pattern through the magnetic powder. As a result, when a wireless communication circuit is configured by connecting a communication circuit that supplies a signal of 10 MHz or more to the coil pattern, it is possible to prevent a decrease in the self-resonant frequency.

Advantages of the Invention

[0010] Thus, according to the present invention, in a coil component having a structure in which a coil pattern is covered with a magnetic layer, it is possible to increase the magnetic permeability of the magnetic layer.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0013] FIG. 1 is a schematic exploded perspective view for explaining the structure of the coil component 1 according to an embodiment of the present invention. Further, FIG. 2 is a schematic plan view of the coil component 1.

[0014] As shown in FIGS. 1 and 2, the coil component 1 according to the present embodiment includes a substrate 2 made of an insulating resin material such as PET resin, a planar spiral coil pattern 3 made of copper (Cu) or the like formed on one surface 2a of the substrate 2, and a magnetic layer 4 formed on the surface 2a of the substrate 2 so as to cover the coil pattern 3. In the example shown in FIGS. 1 and 2, the number of turns of the coil pattern 3 is 6 turns, but the number of turns of the coil pattern 3 is not particularly limited and may be 1 turn. The outer peripheral end and the inner peripheral end of the coil pattern 3 are respectively connected to terminal electrodes 5 and 6 formed on the other surface 2b of the substrate 2 through via holes 2c and 2d provided in the substrate 2. The coil pattern 3 can be formed by plating.

[0015] Since the magnetic layer 4 functions as a magnetic path for the magnetic field generated by the coil pattern 3, a high magnetic permeability is required. The magnetic layer 4 used in this embodiment is made of a composite material in which magnetic powder is dispersed in a resin. After forming the coil pattern 3 on the surface 2a of the substrate 2, the composite material is directly applied to the surface 2a of the substrate 2 so as to cover the coil pattern 3. For this reason, no non-magnetic material other than the resin constituting the magnetic layer 4, such as a film, is interposed between the coil pattern 3 and the magnetic layer 4, and a part of the magnetic layer 4 is also filled between adjacent coil patterns 3. As a result, higher magnetic characteristics can be obtained compared with the case where the magnetic layer 4 is formed on the coil pattern 3 via a film or the like. Whether or not the magnetic layer 4 is directly applied to the surface 2a of the substrate 2 can be determined by whether or not a separate member such as a film is interposed between the coil pattern 3 and the magnetic layer 4, and whether or not a part of the magnetic layer 4 is filled within the height range of the coil pattern 3 with respect to the surface 2a of the substrate 2. When the magnetic layer 4 is directly applied, the distance between the coil pattern 3 and the magnetic powder becomes very close, and there are also portions where the two are in contact partially.

[0016] As shown in FIG. 3, the coil component 1 having such a configuration constitutes a wireless communication circuit 10 by being connected to the communication circuit 11. A pair of terminal electrodes provided in the communication circuit 11 are connected to the terminal electrodes 5 and 6 of the coil component 1, respectively. The communication circuit 11 causes the coil pattern 3 to function as an antenna coil of the wireless communication circuit 10 by supplying a signal of 10 MHz or more to the coil pattern 3. As an example, if a signal of 13.56 MHz is supplied to the coil pattern 3, it can be used as an antenna coil for near-field communication (NFC).

[0017] FIG. 4 is a schematic cross-sectional view taken along line A-A shown in FIG. 2.

[0018] As shown in Fig. 4, the cross-section along the radial direction of the coil pattern 3 has a flat shape where the thickness H is smaller than the width W1. The width W1 is the width at the portion in contact with the surface 2a of the substrate 2. As shown in Fig. 4, in the cross-section in the radial direction of the coil pattern 3, the upper corner portions have a chamfered shape such that the width becomes smaller as the height position with respect to the surface 2a of the substrate 2 increases. For this reason, the width W2 at the flat portion on the upper surface of the coil pattern 3 is smaller than the width W1 at the portion in contact with the surface 2a of the substrate 2. The width a in the radial direction of the chamfered shape portion is (W1 - W2) / 2. As specific sizes, although not particularly limited, the width W1 of the coil pattern 3 is about 0.15 to 2 mm, the thickness H is about 10 to 70 μm, the width a of the chamfered shape portion is about 20 to 70 μm, and the space S between the coil patterns 3 adjacent in the radial direction is about 0.1 to 0.25 mm. The width a of the chamfered shape portion can be controlled by the plating conditions when forming the coil pattern 3.

[0019] Regarding the thickness H of the coil pattern 3, the thicker it is, the lower the DC resistance. However, if the frequency of the signal flowing through the coil pattern 3 is 10 MHz or higher, since the current only flows in the surface layer of the coil pattern 3 due to the skin effect, it is sufficient to set it to about 10 to 70 μm. In particular, if the frequency of the signal flowing through the coil pattern 3 is 13.56 MHz, a thickness H of about 20 μm is sufficient, and considering manufacturing variations and the like, it is optimal to design the thickness H to be about 30 μm.

[0020] Fig. 5 is a schematic diagram for explaining the shape of the magnetic powder 4a contained in the magnetic layer 4, where (a) is a schematic plan view and (b) is a schematic cross-sectional view taken along the B - B line shown in (a).

[0021] As shown in Fig. 5, the magnetic powder 4a contained in the magnetic layer 4 is disk-shaped and has a flat shape. Since a large number of magnetic powders 4a are contained in the magnetic layer 4, there are variations in the size and shape of the magnetic powders 4a, but the average diameter R is about 20 to 70 μm, and the average thickness T is about 0.5 to 2 μm. In order to specify the average diameter R and the average thickness T, the cross-section of the sample may be observed by SEM, and the thickness and diameter of the magnetic powders 4a existing in a predetermined region may be measured and averaged. The average value may be the thickness or diameter at which the cumulative frequency of the thickness or diameter becomes 50%. Further, as shown in Fig. 6, the planar shape of the magnetic powder 4a may be elliptical. In this case, the major axis R1 is about 20 to 70 μm, and the ratio (R1 / R2) of the major axis R1 to the minor axis R2 is about 1 to 1.5.

[0022] Fig. 7 is a schematic diagram for explaining the orientation of the magnetic powder 4a in the magnetic layer 4. (a) shows the state before magnetic field orientation, and (b) shows the state after magnetic field orientation.

[0023] The magnetic layer 4 is a composite material in which the magnetic powder 4a is dispersed in a resin 4b as a binder. As shown in Fig. 7(a), in the state before magnetic field orientation, the orientation of the magnetic powder 4a is in a state close to random. When a strong external magnetic field φ1 is applied in this state, the magnetic powder 4a is oriented in the direction along the external magnetic field φ1. Therefore, if an external magnetic field φ1 in the direction along the surface 2a of the substrate 2 is applied, as shown in Fig. 7(b), most of the magnetic powders 4a are in a horizontal state, that is, they are oriented so that the thickness direction becomes the z direction. As a result, the magnetic layer 4 has a higher magnetic permeability in the horizontal direction (xy plane direction) than in the thickness direction (z direction), and anisotropy is imparted to the magnetic permeability. Here, in order to sufficiently increase the magnetic permeability of the magnetic layer 4 in the horizontal direction, it is preferable that the average diameter R of the magnetic powder 4a is 30 μm or more.

[0024] On one hand, in the region where the coil pattern 3 and the magnetic powder 4a interfere, the magnetic powder 4a is not horizontal but is oriented in an oblique direction along the chamfered shape. However, in this region, since the magnetic field φ2 generated by the coil pattern 3 also travels in an oblique direction, as a result, the effective magnetic permeability is improved. That is, in the region where the magnetic field φ2 travels in the horizontal direction, such as the upper part of the coil pattern 3, the magnetic powder 4a is oriented almost horizontally, and in the region where the magnetic field φ2 travels in an oblique direction, such as near the corner of the coil pattern 3, the magnetic powder 4a is also oriented in an oblique direction. Therefore, most of the magnetic field φ2 passes through the magnetic powder 4a, and the magnetic field component passing through the resin 4b is reduced. Here, in order to make the orientation of the magnetic powder 4a located near the corner of the coil pattern 3 closer to the direction of the magnetic field φ2, it is preferable that the average diameter R (or R1) of the magnetic powder 4a is 1 / 5 or more and 10 times or less of the width a in the radial direction of the chamfered shape portion.

[0025] In this embodiment, since the magnetic powder 4a has a flat shape, if the aspect ratio of the coil pattern 3 is high, it becomes difficult for the magnetic powder 4a to enter between the adjacent coil patterns 3. However, in this embodiment, the coil pattern 3 itself has a flat shape, and thus the aspect ratio is less than 1, preferably in the range of 0.2 to 0.05. Therefore, it is possible to easily allow the magnetic powder 4a having a flat shape to enter between the coil patterns 3. In other words, it is possible to surely arrange a part of the magnetic powder 4a within the height range of the coil pattern 3 with respect to the surface 2a of the substrate 2.

[0026] Also, when the frequency of the signal flowing through the coil pattern 3 is 10 MHz or higher, since the parasitic capacitance between the coil patterns 3 has a great influence on the self-resonant frequency, it is necessary to reduce the parasitic capacitance between the coil patterns 3 as much as possible. Also in this regard, in the present embodiment, since the coil pattern 3 has a flat shape, it is possible to reduce the parasitic capacitance. That is, as shown in Fig. 8(a), when the aspect ratio of the coil pattern 3 is 1 or more, a horizontal electric field line E1 is generated between adjacent coil patterns 3, and thus a large parasitic capacitance is generated in this portion. However, as shown in Fig. 8(b), if the aspect ratio of the coil pattern 3 is reduced to less than 1, the facing area of the coil patterns 3 adjacent in the radial direction is reduced, and thus the electric field line E1 decreases. Thereby, even when the space S between the coil patterns 3 is relatively narrow, it is possible to reduce the parasitic capacitance between the coil patterns 3.

[0027] In order to further reduce the parasitic capacitance between adjacent coil patterns 3, in addition to setting the aspect ratio of the coil pattern 3 to less than 1, it is preferable to narrow the width W1 of the coil pattern 3. In the present embodiment, since the magnetic powder 4a constituting the magnetic layer 4 is oriented in the horizontal direction, if the width W1 of the coil pattern 3 is large, the electric field line E2 connecting the upper surfaces of the coil patterns 3 via the magnetic powder 4a cannot be ignored. As described above, in order to sufficiently ensure the magnetic permeability of the magnetic layer 4, it is preferable that the average diameter R of the magnetic powder 4a is 30 μm or more. Considering this point, the width W1 of the coil pattern 3 is preferably 1 to 10 times the diameter R of the magnetic powder 4a. For example, if the average diameter R (or R1) of the magnetic powder 4a is 30 μm, it is preferable that the width W1 of the coil pattern 3 is 300 μm or less.

[0028] As described above, according to the present embodiment, it is possible to provide a coil component suitable for an antenna coil for transmitting and receiving a signal of 10 MHz or higher.

[0029] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention, and it goes without saying that those are also included in the scope of the present invention.

Explanation of Reference Numerals

[0030] 1 Coil component 2 Substrate 2a One surface of the substrate 2b The other surface of the substrate 2c, 2d Via holes 3 Coil pattern 4 Magnetic layer 4a Magnetic powder 4b Resin 5, 6 Terminal electrodes 10 Wireless communication circuit 11 Communication circuit E1, E2 Electric lines of force φ1, φ2 Magnetic fields

Claims

1. A substrate, A coil pattern formed on one surface of the substrate, A magnetic layer made of a composite material in which magnetic powder is dispersed in resin, and formed on the one surface of the substrate so as to cover the coil pattern, The coil pattern has a flat shape in which the thickness is smaller than the width in the radial direction, The magnetic powder has a flat shape in which the average thickness is smaller than the average diameter, Most of the magnetic powder is oriented such that the direction of the diameter is along the surface of the substrate, Some of the magnetic powder is at least partially present within the height range of the coil pattern at the height position with respect to the one surface of the substrate, The thickness of the coil pattern is smaller than the diameter of the magnetic powder, The coil pattern has a lower region including a lower surface in contact with the one surface of the substrate, and an upper region including an upper surface located on the opposite side of the lower surface, The cross-section in the radial direction of the upper region of the coil pattern has a chamfered shape portion that is chamfered such that the decrease in the width in the radial direction per unit height becomes larger as the height position with respect to the one surface of the substrate increases, A coil component, wherein the thickness of the upper region is thicker than the thickness of the lower region.

2. The coil component according to claim 1, wherein the average value of the diameter of the magnetic powder is 1 / 5 or more and 10 times or less of the width in the radial direction of the chamfered shape portion.

3. The average value of the diameter of the magnetic powder is 30 μm or more, The coil component according to claim 1 or 2, wherein the width of the coil pattern is 1 time or more and 10 times or less of the average value of the diameter of the magnetic powder.

4. A wireless communication circuit, comprising the coil component according to claim 3 and a communication circuit that supplies a signal of 10 MHz or more to the coil pattern.

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