JP2017212420A - Coil component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coil component that can be made high in frequency because of a difference in diameter between a large-diameter part and a small-diameter part of a core part, and also higher in frequency (wider in band).SOLUTION: A coil component has a core part including a cone-shaped part, and a winding wound spirally along an outer peripheral surface of the core part. The winding 9 has a wire-shaped center conductor 10 and an outer layer part 11 covering a peripheral surface of the center conductor 10, and the outer layer part 11 includes a magnetic material layer 12 in contact with the peripheral surface of the center conductor 10 and an insulation coating layer 13 covering the magnetic material layer 12. The magnetic material layer 12 functions as a loss material and lowers Q. Consequently, resonance is made smooth and an abrupt decrease in impedance is suppressed so as to improve high-frequency characteristics.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a wire-wound coil component, and more particularly, to a coil component including a winding core portion including a cone-shaped portion whose diameter decreases from one end portion toward the other end portion. .

  A coil component that is of interest to the present invention and that includes a core portion including a cone-shaped portion is described in, for example, Japanese Patent Application Laid-Open No. 2004-6696 (Patent Document 1).

  More specifically, the coil component described in Patent Document 1 is a wire-wound inductor, in which a rectangular parallelepiped collar is formed at both ends of a conical core, and a winding in the core. A winding wound around the outer peripheral surface of the core part, and a rectangular parallelepiped exterior body covering the core and the winding are provided. Then, two external electrode terminals are attached and formed at lower positions on both side surfaces of the exterior body, and these external electrode terminals are connected to terminal portions formed at both ends of the winding.

  As described above, according to the coil component including the core portion including the cone-shaped portion, the winding diameter of the winding on the core portion is smaller than that of the coil component in which the diameter of the core portion is constant. Since it can be changed, it is described in Patent Document 1 that it can have a plurality of self-resonant frequencies and can therefore be used in a wide frequency range.

JP 2004-6696 A

  According to the technology for widening the usable frequency as described above, the larger the difference in diameter between the large diameter portion and the small diameter portion in the core portion, the wider the band (higher frequency) is possible. It can be said that there is. For this reason, it is considered effective to increase the diameter on the large-diameter portion side of the winding core portion and to decrease the diameter on the small-diameter portion side.

  However, if the diameter of the large-diameter portion of the winding core portion is made larger, miniaturization of the component is hindered. On the other hand, if the diameter of the small-diameter portion of the core portion is made smaller, the strength of the connecting portion between the core portion and the flange portion formed at the end thereof is lowered. Therefore, there is a limit to increasing the diameter of the large diameter part of the core part and reducing the diameter of the small diameter part, and as a result, it can be used by manipulating the diameter of the core part. There is a limit to increasing the frequency of a wide band (broadband).

  Accordingly, an object of the present invention is to increase the frequency even further by adopting a means different from this in addition to increasing the frequency due to the difference in diameter between the large diameter portion and the small diameter portion in the core portion ( An object is to provide a coil component capable of achieving a wide band.

  The present invention includes a core having a cone-shaped portion having a smaller diameter from one end portion toward the other end portion, and spirally wound along the outer peripheral surface of the core portion. In order to solve the technical problem described above, the winding includes a wire-shaped center conductor and an outer layer portion covering the peripheral surface of the center conductor. The outer layer portion includes a magnetic layer that is in contact with the peripheral surface of the central conductor, and an insulating coating layer that covers the magnetic layer.

  The inventor of the present invention has focused on reducing Q (Quality Factor) as a means for improving the characteristics of the coil component in the high frequency range. As a result, it is possible to improve the characteristics in the high frequency range by smoothing the resonance and suppressing the steep drop in impedance. Therefore, as a method of lowering Q, a method of disposing a material (for example, a magnetic material such as ferrite or a conductor such as metal) that generates a loss in the high frequency region near the wire-shaped central conductor in the winding is conceivable. . In this case, the lossy material can have a lower Q as the position where it is placed is closer to the center conductor of the winding.

  However, in a normal configuration, there is an insulating coating around the center conductor of the winding, so that lossy material cannot be placed near the center conductor of the winding. In contrast, in the present invention, since the magnetic layer is disposed so as to be in contact with the peripheral surface of the central conductor in the winding, that is, very close to the central conductor, Q can be effectively reduced. .

  The magnetic layer is preferably made of a metallic magnetic material rather than a ferrite magnetic material. Ferrite magnetic materials have (1) very low electrical conductivity, so that almost no loss in the high frequency region due to electrical resistance component occurs; (2) loss that occurs other than the electrical resistance component of ferrite (complex permeability μ ”And the loss due to the hysteresis curve) are lost in the frequency range of 10 GHz or higher; in contrast, in the case of a metal-based magnetic material, most of the generated loss is complex such as ferrite. It is not caused by the magnetic permeability μ ″ but by macroscopic conductivity. Here, the macro conductivity means the conductivity of the entire magnetic layer with respect to the case where the conductivity of each particle of the metal-based magnetic material is a micro conductivity. The macroscopic conductivity can be adjusted by changing the specific surface area by adjusting the particle size of the metal-based magnetic material and adjusting the ratio of the relatively high particle spacing between the electrical resistances, as in ferrite. The loss does not disappear above a certain frequency. For this reason, as a magnetic body arranged so as to be in contact with the peripheral surface of the central conductor in the winding, the metal type can cope with higher frequencies than the ferrite type.

  The center conductor of the winding is preferably made of copper. Copper exhibits good electrical conductivity and is relatively inexpensive and readily available.

  In the present invention, the core is preferably made of a magnetic material such as ferrite or alumina. As a result, the usable band can be further increased in frequency.

  In the coil component according to the present invention, preferably, the core has first and second flange portions respectively provided at one end portion and the other end portion of the winding core portion. The first and second terminal electrodes are respectively provided on the same side of the peripheral surface of each of the flange portions, and one end and the other end of the winding are connected to the first and second terminal electrodes, respectively. According to this configuration, the coil component can be of a surface mount type.

  In the preferred configuration described above, it is more preferable that an exterior material including a resin is disposed so as to cover at least the side of the outer periphery of the winding that is opposite to the side on which the first and second terminal electrodes are provided. The exterior material can function to provide a vacuum suction surface when the coil component is picked up by the vacuum suction chuck in the coil component mounting step.

  According to the present invention, the Q can be reduced by the presence of the magnetic layer in contact with the peripheral surface of the central conductor in the winding. Therefore, the self-resonance in the band exceeding the self-resonance frequency can be made inconspicuous (attenuation characteristics are made flat), and the usable band can be increased in frequency. That is, in the technical field of coil parts, which generally aim to improve Q, lowering Q is an inconvenient event. However, in the present invention, the lowering of Q is used in reverse.

1 is a front view showing a coil component 1 according to an embodiment of the present invention. It is sectional drawing which expands and shows the coil | winding 9 with which the coil component 1 shown in FIG. 1 is equipped. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining the process leading to the completion of the present invention, in which (A) is an equivalent circuit diagram showing a case where a resistor R is connected in series with an inductance L, and (B) is a Q in this case. It is a figure which shows the frequency characteristic. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining a process leading to the completion of the present invention, in which (A) is an equivalent circuit diagram showing a case where a resistor R is connected in parallel to an inductance L, and (B) is a Q in this case. It is a figure which shows the frequency characteristic. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining the process leading to the completion of the present invention, in which (A) is an LC series resonance circuit diagram, and (B) is a resonance circuit when C is an ideal capacitor in LC series resonance. It is a figure showing how the impedance at the time of resonance changes with Q of. It is a figure which compares and compares the frequency characteristic of an impedance with the Example within the range of this invention, and the comparative example out of range.

  With reference to FIG. 1 and FIG. 2, the coil component 1 by one Embodiment of this invention is demonstrated. The coil component 1 is a self-supporting chip type.

  The coil component 1 includes a core 2 first. The core 2 has a winding core portion 4 including a cone-shaped portion 3 whose diameter becomes smaller from one end portion toward the other end portion. In this embodiment, the entire core 2 including the cone-shaped portion 3 has a quadrangular cross section. The cone-shaped portion 3 has a tapered surface that appears in the front view shown in FIG. In addition, although not shown in figure, about the outline which appears in a top view and a bottom view, it may become a taper surface or may have a shape used as a parallel surface.

  The shape of the cone-shaped portion 3 may be another pyramid shape or a shape other than the pyramid shape, for example, a cone shape. In this embodiment, the entire core part 4 is substantially composed of the cone-shaped part 3, but only a part of the core part is composed of the cone-shaped part, and the remainder of the core part is formed. The portion may be formed of a shape portion having a uniform diameter such as a prism or a cylindrical shape.

  The core 2 also has first and second flange portions 5 and 6 provided at one end and the other end of the core 4, respectively. The eaves parts 5 and 6 have, for example, a rectangular cross section.

  First and second terminal electrodes 7 and 8 are provided on the first and second flange portions 5 and 6, respectively. In order to make the coil component 1 an electronic component that can be surface-mounted, the first and second terminal electrodes 7 and 8 face the same side of the peripheral surfaces of the first and second flange portions 5 and 6. 1 is provided on each of the first and second flanges 5 and 6 having a quadrangular cross section. The terminal electrodes 7 and 8 are formed by baking a conductive paste, plating a conductive metal, sticking a conductive metal piece, or the like.

  The coil component 1 includes a winding 9 wound spirally along the outer peripheral surface of the winding core portion 4. As well shown in FIG. 2, the winding 9 has a wire-shaped center conductor 10 made of, for example, copper, and an outer layer portion 11 that covers the peripheral surface of the center conductor 10. The outer layer portion 11 includes a magnetic layer 12 that is in contact with the peripheral surface of the central conductor, and an insulating coating layer 13 that covers the magnetic layer 12.

  The magnetic layer 12 is preferably made of a metal-based magnetic material in which a magnetic metal powder such as iron powder or nickel powder is dispersed in a resin. The magnetic layer 12 functions as a loss material that lowers Q in a frequency range (several GHz or more) exceeding the self-resonance frequency. As described above, when a metal-based magnetic material is used as the magnetic material constituting the magnetic layer 12, it can function as a loss material up to a higher frequency range than when a ferrite-based magnetic material is used.

  The insulating coating layer 13 is made of, for example, a resin such as polyurethane, polyesterimide, or polyamideimide.

  Winding 9, more specifically, one end and the other end of center conductor 10 are electrically connected to first and second terminal electrodes 7 and 8, respectively. For the connection between the winding 9 and the terminal electrodes 7 and 8, for example, thermocompression bonding is applied.

  In the coil component 1 configured as described above, the magnetic layer 12 in contact with the peripheral surface of the center conductor 10 of the winding 9 acts as a resistance connected in parallel to the inductance component of the winding 9. As a result, as will be described in detail later, the Q in the high frequency region of the coil component 1 can be lowered. In the technical field of inductors, which generally aim to improve Q, lowering Q is an inconvenient event, but in this embodiment, the lowering of Q is used in reverse. That is, in this embodiment, the Q of the coil component 1 can be lowered even when series resonance occurs due to the reduction of the Q of the coil component 1 in the high frequency region as described above. Can be reduced. Therefore, according to this embodiment, it is possible to obtain the coil component 1 having a relatively flat electrical characteristic up to a higher frequency range.

  In order to further increase the usable frequency range, it is preferable that the core portion 4 is made of a magnetic material such as ferrite or alumina.

  Moreover, in this embodiment, as shown in FIG. 1, the winding density of the winding 9 on the core part 4 is not constant. More specifically, the winding density is lower as the diameter of the core part 4 is smaller. In this way, by changing the winding density, the line capacitance generated between the turns of the winding 9 can be varied depending on the location. This makes it possible to adjust the capacity provided by the coil component 1.

  The coil component 1 includes, for example, an exterior material 14 mainly composed of a resin so as to cover at least the side of the outer periphery of the winding 9 opposite to the side on which the first and second terminal electrodes 7 and 8 are provided. Is arranged. In addition, the outer periphery of the winding 9 here means the outer periphery of the entire shape of the winding 9 wound around the core 4, for example, not the outer periphery in the cross section of the winding 9. Should be noted.

  The exterior material 14 forms a flat surface on the upper surface thereof. This flat surface can be a vacuum suction surface to which the vacuum suction chuck is applied when the coil component 1 is picked up by the vacuum suction chuck in the mounting process of the coil component 1. Therefore, the reliability and reliability of the mounting process can be improved.

  Hereinafter, in order to complete this invention, the thought which this inventor advanced is described.

  By providing the cone-shaped portion 3 in the winding core portion 4, the inductance of each turn of the winding 9 spirally wound along the periphery thereof, and the stray capacitance of each turn and the adjacent turn can be obtained. It changes little by little. Therefore, the resonance frequency of each turn is slightly shifted. In particular, when the diameter of the core part 4 decreases, the resonance frequency shifts to the high frequency side, and the amount of shift correlates with the diameter of the core part 4. Therefore, when the diameter of the core 4 is gradually reduced as in the coil component 1 shown in FIG. 1, the resonance frequency of each turn of the winding 9 wound around it is shifted to the high frequency side and is slightly different from each other. Sneak away. Therefore, in such a configuration, adjacent resonance points are very close to each other and are generated in large quantities.

  The “resonance frequency” here is the resonance frequency of the parallel resonance, and the impedance is increased at the time of the parallel resonance, and there is no problem with respect to the performance as the inductor. The problem is that a series resonance always occurs at the frequency between the parallel resonance and the parallel resonance (this is established by the theory of “reactance two-terminal network” in electric circuit theory). At the time of series resonance, unlike the case of parallel resonance, the impedance is lowered, which causes a problem with respect to the performance as an inductor. On the other hand, in the configuration of the coil component 1 shown in FIG. 1, adjacent parallel resonance points are very close to each other and are generated in large quantities. In such a case, since the frequency of the series resonance and the frequency of the parallel resonance are very close to each other, the rise and fall of the impedance are canceled out and the series resonance that should have occurred is masked by the nearby parallel resonance. The resonance point becomes inconspicuous. For this reason, when the winding 9 is wound around the periphery of the core portion 4 including the cone-shaped portion 3, it seems that high impedance is obtained in a wide band.

  On the other hand, if it is attempted to secure impedance in a higher frequency range by this method, it is necessary to make the diameter of the core part 4 smaller. However, in the configuration in which the core portion 4 includes the cone-shaped portion 3 as in the coil component 1 shown in FIG. 1, when the diameter of the core portion 4 is reduced, the strength of the core 2, particularly the flange portions 5 and 6. The strength at the joint between the core 4 and the core 4 cannot be maintained. That is, in the above method, there is a problem in achieving both a small and self-supporting core strength and securing an impedance in a higher frequency range.

  There is another way to make the resonance point as mentioned above inconspicuous. That is, by reducing the Q of the resonance circuit (an equivalent circuit provided by the coil component 1), the amount of impedance reduction due to series resonance is reduced. In particular, the present inventor has paid attention to the fact that if the Q of the resonance circuit at the time of series resonance in the high frequency region can be lowered, a wider band can be achieved.

  There are two methods for reducing the Q of the resonant circuit: increasing the loss of the capacitance component and increasing the loss of the inductance component. However, it is hard to find that there are many high-frequency losses due to capacitance. Therefore, it is more realistic to increase the loss of the inductance component.

  If you want to increase the loss of the inductance component, you can often think of increasing the loss of the center conductor itself, but this is not a good idea. This is because, if a conductor having a low conductivity is used as the center conductor, the DC resistance component increases, and above all, considering the frequency characteristics of the Q of the center conductor, the higher the frequency, the higher the Q.

  This considers the Q of the circuit as a circuit in which the coil component 1 is connected in series with the inductance L with the resistor R as shown in FIG. 3A which is modeled including the resistance component of the winding itself. And easy to understand. The Q of the circuit is represented by jωL / R, and basically the Q of the circuit increases as the frequency increases. The portion of R, which is the denominator, actually has an effect called the skin effect, and R itself has frequency characteristics, but it rises in proportion to the square root of the frequency. One molecular side jωL is proportional to the frequency. Therefore, as shown in FIG. 3B showing the frequency characteristic of Q in the circuit of FIG. 3A, the Q of the circuit becomes very high at a high frequency. FIG. 3B shows, as an example, the specific value of Q when L is fixed to 5 nH and R is fixed to 1Ω, but what is the tendency of Q excluding the absolute value? The same applies to the values of R. Therefore, in the method of increasing the loss of the central conductor 10 itself in the winding 9, it is difficult to reduce Q at a high frequency.

  Therefore, the present inventor paid attention to a method of increasing the loss of the inductance component by arranging, for example, the magnetic layer 12 so as to be in contact with the peripheral surface of the central conductor 10 in the winding 9. According to this configuration, as shown in FIG. 4A, the coil component 1 can be regarded as a circuit including a resistor R in parallel with the inductance L. Since the Q of the circuit is represented by R / jωL, contrary to FIG. 3B, as shown in FIG. 4B, the Q of the circuit is high in the low frequency range and low in the high frequency range. FIG. 4B shows, as an example, a specific value of Q when L is fixed to 5 nH and R is fixed to 2 kΩ, but what is the tendency of Q excluding the absolute value? The same applies to the values of R.

  On the other hand, in a wideband choke that must maintain a high impedance at the time of LC series resonance, Q at the time of series resonance must be a very small value in order to further reduce the amount of decrease in impedance at the time of series resonance. FIG. 5 (A) shows an LC series resonance circuit, and FIG. 5 (B) shows how the impedance at resonance is caused by Q of the resonance circuit when C is an ideal capacitor in LC series resonance. It is a figure showing whether it changes. FIG. 5B shows a case where L is fixed to 5 nH and C is fixed to 0.01 pF.

  As shown in FIG. 5B, if an inductor with a very low Q having a Q of about 1 or less can be realized, resonance can be suppressed. However, since the target value of impedance usually requires several hundreds of Ω or more, in practice, the impedance does not reach the target value only by the technique of lowering Q. Referring to FIG. 5B, it can be seen that even if Q is a very low value, for example, Q = 1/5, the impedance does not reach several hundred Ω. In view of this, the present inventor further reduces the above-described Q by a method of preventing a decrease in impedance at the time of series resonance by winding the winding 9 along the periphery of the core portion 4 having the cone-shaped portion 3. We came up with achieving the target value by combining.

  In order to perform the above combination, in practice, the Q does not have to be as low as Q = 1 as shown in FIG. 5B, but in any case, the parallel resistance is suitable for suppressing resonance. It is clear that In particular, the present inventors have found that it is preferable to use the magnetic layer 12 in contact with the peripheral surface of the center conductor 10 as the parallel resistance.

  FIG. 6 shows a coil component (solid line) wound with a winding having a magnetic layer as an embodiment of the present invention and a coil component (dotted line) wound with a winding without a magnetic layer as a comparative example. ) And the impedance frequency characteristics. In both the examples and the comparative examples, the central conductor of the winding was made of copper wire. In the examples, a magnetic plating wire “2-UEFPW 10.7” manufactured by Furukawa Electric was used as the winding.

  In particular, when compared in a frequency range exceeding 10 GHz, in the comparative example in which a winding without a magnetic layer is wound, as shown by a dotted line in FIG. On the other hand, in the embodiment in which the winding including the magnetic layer is wound, as shown by the solid line in FIG. 6, a sharp drop in impedance is suppressed. From this, according to the coil component wound with the winding provided with the magnetic layer, the effect of making the series resonance inconspicuous by gradually decreasing the diameter of the core part (very close to each other and a large number of parallel resonance points), Combining with the effect of reducing the amount of impedance reduction in series resonance by lowering the Q of the resonant circuit at the high frequency at which series resonance occurs, impedance reduction due to series resonance can be prevented, and as a result, it exceeds 10 GHz. It can be seen that good electrical characteristics up to the frequency range, that is, flat electrical characteristics can be realized.

  Although the present invention has been described with reference to the illustrated embodiment, it should be pointed out that the illustrated embodiment is an example, and modifications other than those illustrated are possible.

DESCRIPTION OF SYMBOLS 1 Coil components 2 Core 3 Cone-shaped part 4 Core part 5, 6 Gutter part 7, 8 Terminal electrode 9 Winding 10 Center conductor 11 Outer layer part 12 Magnetic body layer 13 Insulation coating layer

Claims (6)

A core having a core portion including a cone-shaped portion having a diameter that decreases from one end portion toward the other end portion;
A winding wound spirally along the outer peripheral surface of the core, and
With
The winding has a wire-shaped center conductor and an outer layer portion covering a peripheral surface of the center conductor,
The outer layer portion includes a magnetic layer in contact with the peripheral surface of the central conductor, and an insulating coating layer covering the magnetic layer.
Coil parts.   The coil component according to claim 1, wherein the magnetic layer is made of a metal-based magnetic material.   The coil component according to claim 1, wherein the central conductor is made of copper.   The coil component according to claim 1, wherein the core portion is made of a magnetic material. The core includes first and second flange portions provided on the one end portion and the other end portion of the core portion, respectively.
A first terminal electrode and a second terminal electrode provided on the same side of each of the peripheral surfaces of the first and second flanges, respectively connected to one end and the other end of the winding; The coil component according to any one of claims 1 to 4.   The outer periphery of the said coil | winding is further equipped with the exterior material containing resin arrange | positioned so that the side opposite to the side in which the said 1st and 2nd terminal electrode was provided may be covered at least. Coil parts.

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