JP2007200923A - Laminated common mode choke coil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated common mode choke coil where a disconnection defect of a conductor pattern in baking is prevented, and an impedance characteristic in a high frequency is sufficiently obtained. <P>SOLUTION: A coil layer 10 comprising the conductor pattern 1 and a non-magnetic layer 11 are laminated in a proper order. A via-hole is formed in a prescribed position of the non-active layer sandwiched between the coil layers so as to connect the conductor pattern. Thus, two coils are incorporated inside a laminated object, and the two coils are arranged to perform an electric complementary operation. The coil layer is formed so that a non-magnetic ferrite 4 such as Zn ferrite is positioned at a periphery of the conductor pattern. The non-magnetic layer is formed of a dielectric whose dielectric constant is lower than magnetic ferrite such as alumina, and silica. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laminated common mode choke coil. More specifically, in a laminated structure in which two coils are built in a laminated body, the composition and arrangement of a film layer region that covers and includes the coil pattern is improved. About.

  As is well known, a differential transmission system is widely used for data transmission in digital electronic devices such as personal computers. This differential transmission method is a method of transmitting two types of signals having opposite phases to a pair of transmission lines at a time, and has an advantage of being resistant to external noise and generating less noise and suitable for high-speed data transmission. It is used for many high-speed digital communications such as IEEEl394, LVDS. However, in the differential transmission method, there is a problem that a common mode component (common mode) is generated due to a slight difference in transmission characteristics between a pair of transmission lines, resulting in a noise current. A mode choke coil is used.

  The common mode choke coil consists of two coils with the same number of turns. For the normal differential signal (differential mode), the magnetic flux generated in the two coils cancels each other and passes the signal as it is. In this case, the magnetic fluxes generated in the two coils are strengthened to generate a large impedance, and therefore, the operation for removing the common mode noise is performed.

As the common mode choke coil, there is a winding type in which a wire is wound around a core. However, as seen in Patent Document 1, for example, there is a laminated type in which a coil is built in a laminated body. It is preferred because it can be downsized.
Japanese Patent No. 2949244

  However, the conventional laminated common mode choke coil has the following problems. The coil layer in which the conductor pattern constituting the coil is present has a structure in which a nonmagnetic material exists around the conductor pattern, and the material (Ag paste, etc.) constituting the conductor pattern and the material constituting the nonmagnetic material Due to the difference in thermal contraction rate from (alumina, silica, etc.), stress may be applied to the conductor pattern having a narrow line width at the boundary between the nonmagnetic materials of the conductor pattern during firing, and the conductor pattern may be disconnected.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a multi-layer common mode choke coil that has a multi-layer structure that can be miniaturized and that can prevent a disconnection failure of a conductor pattern during firing.

  In order to achieve the above object, a laminated common mode choke coil according to the present invention comprises a coil layer including a conductor pattern and a nonmagnetic layer laminated in an appropriate order, and the coil layer and the nonmagnetic layer are predetermined. A laminated common in which two coils are built in the laminated body by providing vias (concepts including through holes) at positions and connecting the conductor patterns, and the two coils are arranged to be electrically complementary to each other. In the mode choke coil, the conductor pattern is formed in a spiral shape, and the laminated body is formed with a spiral central portion and an outer portion of the conductor pattern from a magnetic body, and upper and lower outermost layers are also magnetic bodies with respect to the two coils. A central yoke and an outer yoke, and the coil layer has the conductor pattern and a non-magnetic frame positioned around the conductor pattern. And light, and configured to contain. Since the coil layer is provided with nonmagnetic ferrite around the conductor pattern, stress applied to the conductor pattern during firing is reduced, and disconnection failure is prevented.

  The nonmagnetic layer may be composed of a dielectric having a lower dielectric constant than magnetic ferrite such as alumina or silica. The nonmagnetic layer may be made of nonmagnetic ferrite. The nonmagnetic ferrite can be Zn ferrite.

  By disposing a dielectric having a low dielectric constant in the nonmagnetic layer in contact with the conductor pattern, the stray capacitance between the coils is greatly reduced, and the high frequency characteristics are improved.

  In the laminated common mode choke coil according to the present invention, since the nonmagnetic material of the coil layer in which the narrow conductor burn is formed is composed of nonmagnetic ferrite, the difference in heat shrinkage between the nonmagnetic ferrite and the conductor pattern is small, and the conductor Suppresses stress applied to the pattern and prevents disconnection failure of the conductor pattern during firing

  1 to 3 show a preferred embodiment of the present invention. The laminated common mode choke coil according to the present embodiment has a configuration in which a magnetic layer 12 is arranged on the uppermost layer and the lowermost layer of a laminated body in which a coil layer 10 including a conductor pattern 1 and a nonmagnetic layer 11 are laminated in an appropriate order. .

  The coil layer 10 includes a conductor pattern 1 patterned in a spiral shape and a nonmagnetic ferrite 4 positioned around the conductor pattern 1. Further, a rectangular magnetic body 3 a is provided at the center of the coil layer 10, and both side edges on the long side are provided. The belt-like magnetic body 3b is provided. The conductor pattern 1 is formed by, for example, silver paste. The nonmagnetic ferrite 4 is, for example, Zn ferrite. Thereby, the thermal contraction rate of the conductor pattern 1 and the nonmagnetic ferrite 4 becomes relatively close, and the stress applied to the conductor pattern 1 during firing can be suppressed.

  Most of the nonmagnetic layer 11 is composed of a dielectric 6, and a rectangular magnetic body 3 a is formed at a central portion thereof, and a strip-shaped magnetic body 3 b is formed on both side edges on the long side. Furthermore, a via 2 is formed at a predetermined position, and the conductor patterns 1 of the coil layer 10 positioned above and below are conducted through the via 2. The dielectric 6 is made of a material having a low dielectric constant (for example, about ε = 5) such as alumina or silica.

  Further, vias 2 are provided at predetermined positions of the coil layer 10 and the nonmagnetic layer 11, and the conductor pattern 1 is appropriately connected by the vias 2 so that two coils are built in the laminate. The two coils are arranged so as to operate in an electrically complementary manner.

  The spiral conductor pattern 1 formed on the coil layer 10 is connected in such a manner that the upper and lower adjacent coil layers are connected to each other, and the two coil patterns are alternately engaged with each other. That is, the spiral conductor pattern 1 is formed on the second, fourth, sixth, and eighth layers, and the second and sixth layer conductor patterns 1 are connected by providing vias 2 that penetrate the third to fifth layers. Then, this is used as one coil A, and the conductive patterns 1 of the fourth and eighth layers are connected by providing vias 2 penetrating the fifth to seventh layers, and this is used as the other coil B.

  The magnetic body 3a of the coil layer 10 and the magnetic body 3a of the nonmagnetic layer 11 are arranged so as to overlap in the vertical direction. Similarly, the magnetic body 3b of the coil layer 10 and the magnetic body 3b of the nonmagnetic layer 11 are arranged. Is arranged so as to overlap in the vertical direction. Further, the upper and lower ends of these magnetic bodies 3a and 3b are connected to the magnetic layer 12, respectively. The magnetic body 3a constitutes a central yoke, and the magnetic bodies 3b and 12 constitute an outer yoke. The magnetic bodies constituting the magnetic bodies 3a and 3b and the magnetic layer 12 are ordinary magnetic ferrites. This magnetic ferrite has a dielectric constant of about 10.

  In the present embodiment, the second to eighth layers that are intermediate layers are formed by lamination printing. Further, as shown in FIG. 2, the first layer and the ninth layer serving as upper and lower surfaces were formed into a film layer having a predetermined thickness by pressing a plurality of magnetic sheets 5 by a sheet forming method. However, the present invention is not limited to this. For example, one magnetic layer 12 may be formed by pressing a magnetic sheet having a predetermined thickness by a sheet forming method, and various manufacturing methods can be used. .

  In the present invention, since the non-magnetic ferrite 4 such as Zn ferrite is positioned around the conductor pattern 1 in which the coil layer 10 is formed in a narrow and spiral shape, the coil layer applied to the conductor pattern 1 during firing. Ten plane stresses are suppressed. In addition, since the nonmagnetic layer 11 is formed of the dielectric 6, the thermal contraction rate is different from that of the conductor pattern 1, but the stress applied from the dielectric 6 to the conductor pattern 1 during firing is the conductor pattern 1 and the dielectric 6. Since the contact surface is in a direction parallel to the surface and does not increase so much, and the stress in that direction becomes stronger due to the presence of the non-magnetic ferrite 4, the occurrence of disconnection of the conductor pattern 1 can be suppressed.

  Further, as the common mode choke coil, the larger the impedance in the common mode, the better the noise removal effect, and the smaller the impedance in the differential mode, the more smoothly the signal can pass. These characteristics are determined by the inductance (L) of the coil, the stray capacitance (C) and the coupling between the two coils, and in order to obtain good characteristics, it is necessary to increase L, improve the coupling between the coils, and decrease C. There is.

  From this point of view, since the conductor pattern 1 of each layer is a spiral coil pattern, it is possible to increase the number of winding turns per layer, and thus to obtain a high inductance while maintaining a low number of layers. Can do. As a result, both high inductance and miniaturization can be achieved and the common mode impedance can be increased.

  Since the spiral conductor pattern 1 of each layer is not connected in the stacking order, it is connected so as to jump over the adjacent conductor pattern layers vertically adjacent to each other, and the two coil patterns are stacked in an alternately meshing state. The coupling between the coils is improved. As a result, the differential mode impedance can be kept low, and the common mode impedance can be increased. In addition, a decrease in common mode impedance at high frequencies can be reduced, and the frequency characteristics can be improved.

  Furthermore, in this embodiment, since the nonmagnetic layer 11 is composed of the dielectric 4 having a low dielectric constant, the stray capacitance between the coils is greatly reduced. For this reason, the impedance characteristic in a high frequency can be acquired favorably.

  FIG. 4 shows another embodiment of the present invention. In the present embodiment, the nonmagnetic layer 11 is also formed using nonmagnetic ferrite such as Zn ferrite. That is, the formation region of the dielectric 6 shown in FIGS. 1 to 3 is formed by the nonmagnetic ferrite 4. As a result, the entire periphery of the conductor pattern 1 in the three-dimensional direction is covered with nonmagnetic ferrite, and the stress applied to the conductor pattern 1 during firing is further reduced due to the difference in thermal expansion coefficient, further suppressing the possibility of pattern disconnection. Is done.

  FIG. 5 shows another example. In this example, similarly to the embodiment shown in FIGS. 1 to 3, the nonmagnetic layer 11 is formed of a dielectric 6 having a low dielectric constant (of course, the magnetic bodies 3 and 3b constituting the yoke are provided). In this example, the coil layer 10 is configured to dispose a dielectric 6 having a low dielectric constant (for example, about ε = 5) such as aluminum or silica around the conductor pattern 1. Of course, this coil layer 10 is also provided with the magnetic bodies 3 and 3a constituting the yoke. In other words, the formation region of the nonmagnetic ferrite 4 shown in FIGS. Thereby, the dielectric constant of the whole element falls, and the stray capacitance between coils can be reduced more significantly. For this reason, the impedance characteristic in a high frequency can be acquired more favorably.

  In order to demonstrate the effect of the present invention, analysis calculations were performed on a plurality of configuration examples, and impedance characteristics were evaluated. The configuration examples according to the present invention are shown in FIG. 3 according to the present invention 1 according to the multilayer configuration shown in FIG. 3, the present invention 2 according to the multilayer configuration shown in FIG. 4, and FIG. Example 1 with a laminated configuration was prepared. That is, according to the present invention 1, as shown in FIG. 3, the coil layer 10 includes Zn ferrite as the nonmagnetic ferrite 4 around the conductor pattern 1, and the nonmagnetic layer 11 has a dielectric 6 having a dielectric constant ε of about 5. It is formed by. In the present invention 2, as shown in FIG. 4, the entire film layer region covering and including the conductor pattern 1 is formed of Zn ferrite, and Example 1 covers and covers the conductor pattern 1 as shown in FIG. All the film layer regions to be formed are formed of the dielectric 6 having a dielectric constant ε of about 5.

  When the frequency characteristics of impedance were analyzed for these configuration examples, the results shown in FIGS. 6 and 7 were obtained. That is, as apparent from FIG. 6, in the present invention 1 and Example 1, the stray capacitance can be reduced because a dielectric having a low dielectric constant is used for at least the non-magnetic layer 11. Compared with the present invention 2 in which Zn ferrite is used for all layers, the common mode impedance is less likely to decrease at high frequencies, and the action and effect of reducing noise can be obtained more greatly.

  Further, as can be seen from FIG. 7, in Example 1 using a dielectric, the differential mode impedance has a resonance frequency shifted to a high frequency, so that the signal can be transmitted to a higher frequency. Since the stray capacitance is substantially determined by the width of the conductor pattern 1, the distance between the coils A and B, and the dielectric constant of the member between the coils, the present invention uses only the film layer between the layers in contact with the conductor pattern 1 as a dielectric. Even if it is 1, it can be foreseen that the impedance in the high frequency region can be improved, and as a result of analysis, it was confirmed that impedance characteristics equivalent to those of Example 1 can be obtained.

FIG. 2 is a perspective view showing a preferred embodiment of a laminated common mode choke coil according to the present invention, with each layer shown separately. It is a perspective view explaining the manufacturing process of the outermost layer in the laminated body shown in FIG. It is sectional drawing explaining the inside of the laminated body shown in FIG. 1, FIG. It is sectional drawing which shows other embodiment of this invention. It is sectional drawing which shows another example. It is the graph which computed the impedance characteristic in the common mode about the laminated structure which concerns on this invention. It is the graph which computed the impedance characteristic in differential mode about the laminated structure which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductor pattern 2 Via 3a, 3b Magnetic body 4 Nonmagnetic ferrite 5 Magnetic body sheet 6 Dielectric body 10 Coil layer 11 Nonmagnetic layer 12 Magnetic layer

Claims (4)

A coil layer including a conductor pattern and a nonmagnetic layer are laminated in an appropriate order, and vias are provided at predetermined positions of the coil layer and the nonmagnetic layer to connect the conductor pattern to the inside of the laminate. In a laminated common mode choke coil that includes two coils and the two coils are arranged to be electrically complementary to each other,
The conductor pattern has a spiral shape, and the laminate has a spiral central portion and an outer portion of the conductor pattern formed from a magnetic material, and the upper and lower outermost layers are also magnetic materials, and a central yoke and an outer yoke for the two coils. age,
A laminated common mode choke coil, wherein the coil layer includes the conductor pattern and a nonmagnetic ferrite positioned around the conductor pattern.   2. The laminated common mode choke coil according to claim 1, wherein the nonmagnetic layer is made of a dielectric having a lower dielectric constant than that of magnetic ferrite such as alumina or silica.   The multilayer common mode choke coil according to claim 1, wherein the nonmagnetic layer is made of nonmagnetic ferrite. 4. The laminated common mode choke coil according to claim 1, wherein the nonmagnetic ferrite is Zn ferrite. 5.

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