JP2007242800A - Common mode filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact common mode filter which can achieve a desired impedance. <P>SOLUTION: The laminate 5 of the common mode filter comprises an insulation layer 9 having a hole 20, coil conductor layer 10 having a coil 21, insulation layer 11 having a hole 24, coil conductor layer 12 having a coil 25, insulation layer 13 having a hole 28, and an insulation layer 15 having a hole 31. In a region inside the coils 21 and 25 in the laminate 5, a concave 32 for forming a magnetic path is formed by the holes 20, 24, 28, and 31. The holes 20, 24, 28, and 31 become wider, going toward the upper layer side of the laminate 5. The side face of the concave 32 for forming a magnetic path has a stepped structure, and the concave 32 for forming a magnetic path becomes wider, going toward the opening side thereof (toward the upper layer side of the laminate 5). The concave 32 for forming a magnetic path is filled with a resin J filled with magnetic powder to form a closed magnetic path. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a common mode filter used in electronic equipment and the like.

As a conventional common mode filter, for example, a common mode choke coil as described in Patent Document 1 is known. This common mode choke coil includes a laminated body in which a plurality of insulating layers and two coil patterns are alternately laminated. A hole is formed in a central region surrounded by the coil pattern in each insulating layer, and the hole is filled with a material containing an insulating adhesive containing ferrite magnetic powder. As a result, a closed magnetic circuit is formed in the common mode choke coil.
Japanese Patent Laid-Open No. 11-54326

  In recent years, miniaturization of common mode filters has been strongly demanded. However, when the above-described common mode filter is downsized, there is a possibility that a desired impedance may not be ensured.

  An object of the present invention is to provide a small common mode filter capable of obtaining a desired impedance.

  As a method of forming a closed magnetic path in a common mode filter, a resin (magnetic resin) containing a magnetic material for forming a magnetic path in a magnetic path forming recess formed by holes provided in a plurality of insulating layers ) Is generally filled. At this time, in the case where the magnetic resin is printed (applied) in the magnetic path forming concave portion and filled, the common mode filter having a chip size larger than 1210 type (about 1.2 mm × about 1.0 mm × about 0.6 mm) Although a desired impedance can be obtained, a desired impedance may not be obtained with a common mode filter having a chip size of 1210 type or less.

  Therefore, the present inventors have investigated the cause of such a problem. As the common mode filter is reduced in size, the magnetic path forming recesses are naturally reduced. However, the conditions for filling the magnetic resin in the magnetic path forming recesses (speed for moving the squeegee, viscosity of the magnetic resin, equipment, etc.) The conditions are the same regardless of the size of the recess for forming the path. For this reason, when the magnetic resin is printed and filled in the magnetic path forming recess using a squeegee, the amount of magnetic resin that embeds the air present in the magnetic path forming recess is the size of the magnetic path forming recess. It will be the same regardless. In this case, the occupation ratio of the air contained in the closed magnetic path formed of the magnetic resin increases as the magnetic path forming concave portion becomes smaller. Therefore, in a common mode filter of 1210 type or less in which the magnetic path forming recess is small, the impedance tends to decrease. As a result of repeated trial and error and further studies, the present inventors have made the magnetic resin into a magnetic path by making the magnetic path forming recess wider toward the opening side (upper layer side). It has been found that the amount of the air present in the forming recess can be reduced. The present invention has been made based on such knowledge.

  That is, the present invention is a common mode filter including a plurality of insulating layers and two coil conductor layers having a spiral coil portion, and the insulating layers and the coil conductor layers are alternately stacked. The insulating layer is formed with holes that penetrate the insulating layer in the thickness direction and constitute a part of the magnetic path forming concave portion, and the magnetic path forming concave portion is made of a magnetic material for forming the magnetic path. The contained resin is filled, and the magnetic path forming recess is formed in the insulating layer on the upper layer side from the hole formed in the insulating layer on the lower layer side so as to become wider from the lower layer side toward the upper layer side. The hole is enlarged.

  Thus, in the present invention, by making the hole on the upper layer side larger than the hole on the lower layer side, the closed magnetic path forming recess formed by each hole becomes wider toward the opening side (upper layer side). ing. For this reason, when a resin (magnetic resin) containing a magnetic material for forming a magnetic path is printed and filled in the magnetic path forming recesses in the manufacturing process of the common mode filter, the magnetic resin is used for forming the magnetic path. It is thought that it becomes easy to flow toward the bottom of the magnetic path forming recess along the side surface of the recess. In this case, since the amount of the magnetic resin that embeds the air present in the magnetic path forming concave portion is reduced, the size of the opening of the magnetic path forming concave portion can be reduced along with the downsizing of the common mode filter. The occupation ratio of the air contained in the closed magnetic path formed of the magnetic resin can be reduced. Thereby, a desired impedance can be ensured even in a small common mode filter.

  Preferably, the side surface of the magnetic path forming recess is stepped. In this case, the side surface of the hole formed in the insulating layer is not necessarily tapered. Therefore, the hole can be easily formed in the insulating layer by, for example, etching, laser beam, punching, or the like.

  Preferably, the hole is formed in a portion corresponding to the inner region of the coil portion in the insulating layer. In order to ensure the desired coil characteristics while reducing the size of the common mode filter, the space of the portion corresponding to the outer region of the coil portion is made narrower than the space of the portion corresponding to the inner region of the coil portion. Is preferred. For this reason, the area | region of a closed magnetic circuit can be increased by forming a hole in the site | part corresponding to the inner side area | region of the coil part in an insulating layer. Thereby, it is possible to ensure sufficient impedance of the common mode filter.

  At this time, it is preferable that the hole has a cross-sectional shape corresponding to the spiral shape of the coil portion. As a result, a wide space of a portion corresponding to the inner region of the coil portion in the insulating layer can be effectively used, and the region of the closed magnetic circuit can be further increased.

  According to the present invention, it is possible to obtain a common mode filter having a desired impedance while reducing the size of the common mode filter. This makes it possible to realize a small and high-quality common mode filter.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a common mode filter according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a perspective view showing an embodiment of a common mode filter according to the present invention. In the figure, the common mode filter 1 of the present embodiment is a common mode choke coil having a chip size of, for example, 1210 type (about 1.2 mm × about 1.0 mm × about 0.6 mm).

  The common mode filter 1 includes a rectangular parallelepiped laminated body 5 including a lower magnetic substrate 2, a layer structure 3, and an upper magnetic substrate 4. The layer structure 3 is disposed between the lower magnetic substrate 2 and the upper magnetic substrate 4. The lower magnetic substrate 2 and the upper magnetic substrate 4 are substrates made of a magnetic material such as sintered ferrite or composite ferrite (resin containing powdered ferrite). Terminal electrodes 6A and 6B are provided on one end face of the laminate 5, and terminal electrodes 6C and 6D are provided on the other end face of the laminate 5 so as to face the terminal electrodes 6A and 6B.

  FIG. 2 is an exploded perspective view of the laminate 5. In the figure, the layer structure 3 of the laminate 5 includes an insulating layer 7, a coil conductor layer 8, an insulating layer 9, a coil conductor layer 10, an insulating layer 11, a coil conductor layer 12, an insulating layer 13, and a coil conductor in order from the bottom. The layer 14, the insulating layer 15, the magnetic layer 16, and the adhesive layer 17 are laminated. The insulating layers 7, 9, 11, 13, and 15 are formed of an insulating resin material such as polyimide resin or epoxy resin. The coil conductor layers 8, 10, 12, and 14 are made of a metal material such as Cu or Al.

  FIG. 3 is a plan view of the insulating layers 7, 9, 11, 13, 15 and the coil conductor layers 8, 10, 12, 14. 2 and 3, a coil conductor layer 8 is laminated on the insulating layer 7. The coil conductor layer 8 has an L-shaped lead portion 18 and lead electrodes 19A to 19D. The lead portion 18 is connected to the lead electrode 19C. The extraction electrodes 19A to 19D are electrically connected to the terminal electrodes 6A to 6D.

  A coil conductor layer 10 is laminated on the coil conductor layer 8 via an insulating layer 9. A hole 20 having a circular cross section or a substantially circular cross section penetrating in the thickness direction of the insulating layer 9 is formed in the central portion of the insulating layer 9.

  The coil conductor layer 10 includes a coil portion 21, an L-shaped lead portion 22, and lead electrodes 23A to 23D. The coil portion 21 is formed in a substantially circular spiral shape so as to surround the hole portion 20. One end of the lead portion 22 is connected to the outer end of the coil portion 21, and the other end of the lead portion 22 is connected to the lead electrode 23A. The extraction electrodes 23A to 23D are electrically connected to the terminal electrodes 6A to 6D. The inner end of the coil portion 21 is electrically connected to the lead portion 18 of the coil conductor layer 8 through a contact hole (not shown) formed in the insulating layer 9. Note that the contact hole is filled with a conductive material such as Ag.

A coil conductor layer 12 is laminated on the coil conductor layer 10 via an insulating layer 11. A hole 24 having a circular cross section or a substantially circular cross section penetrating in the thickness direction of the insulating layer 11 is formed in the central portion of the insulating layer 11. The diameter D ₂ of the hole 24 is larger than the diameter D ₁ of the hole 20.

  The coil conductor layer 12 includes a coil portion 25, an L-shaped lead portion 26, and lead electrodes 27A to 27D. The coil portion 25 is formed in a substantially circular spiral shape so as to surround the hole portion 24. The coil portion 25 overlaps the coil portion 21 with the insulating layer 11 interposed therebetween. One end of the lead portion 26 is connected to the outer end of the coil portion 25, and the other end of the lead portion 26 is connected to the lead electrode 27B. The lead electrodes 27A to 27D are electrically connected to the terminal electrodes 6A to 6D.

A coil conductor layer 14 is laminated on the coil conductor layer 12 via an insulating layer 13. A hole 28 having a circular cross-section or a substantially circular cross-section penetrating in the thickness direction of the insulating layer 13 is formed in the central portion of the insulating layer 13. The diameter D ₃ of the hole 28 is larger than the diameter D ₂ of the hole 24.

  The coil conductor layer 14 has an L-shaped lead portion 29 and lead electrodes 30A to 30D. The lead portion 29 is connected to the lead electrode 30D. The lead portion 29 is electrically connected to the inner end of the coil portion 25 of the coil conductor layer 12 through a contact hole (not shown) formed in the insulating layer 13. The extraction electrodes 30A to 30D are electrically connected to the terminal electrodes 6A to 6D.

An insulating layer 15 is laminated on the coil conductor layer 14. A hole 31 having a circular cross section or a substantially circular cross section penetrating in the thickness direction of the insulating layer 15 is formed at the center of the insulating layer 15. The diameter D ₄ of the hole 31 is larger than the diameter D ₃ of the hole 28.

  A magnetic layer 16 is laminated on the insulating layer 15. The magnetic layer 16 is formed of a resin material for forming a closed magnetic path in the common mode filter 1, for example, a resin containing magnetic powder such as powdered ferrite (magnetic powder-containing resin).

  An adhesive layer 17 is laminated on the magnetic layer 16. The adhesive layer 17 is a layer that joins the magnetic layer 16 and the upper magnetic substrate 4 and is formed of an adhesive such as an epoxy resin, a polyimide resin, or a polyamide resin.

  In the layer structure 3 composed of such layers, as shown in FIG. 4, the central region surrounded by the coil portions 21 and 25 (the inner region of the coil portions 21 and 25) has the lowermost insulating layer 7 and A magnetic path forming recess 32 formed by the holes 20, 24, 28, 31 formed in the other insulating layers 9, 11, 13, 15 is provided. That is, the holes 20, 24, 28, 31 form part of the magnetic path forming recess 32, respectively. Since the diameters of the holes 20, 24, 28, 31 are gradually increased from the lower layer side to the upper layer side of the layer structure 3, the side surface of the magnetic path forming recess 32 has a stepped structure. Thus, the magnetic path forming recess 32 becomes wider toward the opening side (upper layer side).

  The magnetic path forming recess 32 is filled with the same magnetic powder-containing resin J as the magnetic layer 16. As a result, a closed magnetic path 33 is formed in the inner region of the coil portions 21 and 25 in the layer structure 3.

  At this time, in the portions corresponding to the inner regions of the coil portions 21 and 25 in the insulating layers 9, 11, 13, and 15, a wider space is provided compared to the portions corresponding to the outer regions of the coil portions 21 and 25. Yes. Moreover, the cross-sectional shape of the holes 20, 24, 28, 31 is a cross-sectional circular shape or a cross-sectional substantially circular shape corresponding to the substantially circular spiral coil portions 21, 25. Therefore, the space in the inner region of the coil portions 21 and 25 in the layer structure 3 can be effectively utilized as the closed magnetic path 33.

The diameters D _{1 to} D ₄ (see FIG. 3) of the holes 20, 24, 28, 31 that form part of the magnetic path forming recess 32 are about 360 μm, about 380 μm, about 400 μm, and about 420 μm, respectively. is there. The depth H (see FIG. 4) of the magnetic path forming recess 32 is, for example, about 40 μm.

  Next, a procedure for manufacturing the common mode filter 1 configured as described above will be described. First, the laminated body 5 is produced as follows.

  That is, for example, a resin material such as polyimide resin is applied on the lower magnetic substrate 2 by spin coating, dipping, spraying, or the like, and then exposed, developed, and cured to form the insulator layer 7.

  Subsequently, a base layer such as Cr / Cu is formed on the insulator layer 7 by sputtering, for example, a resist is applied to the surface of the base layer, exposed and developed, and further conductor plating such as Cu is applied. Then, unnecessary portions of the conductor plating are removed by etching, the resist is peeled off, and then the underlying layer is removed by etching. As a result, the coil conductor layer 8 having the pattern of the extraction portion 18 and the extraction electrodes 19 </ b> A to 19 </ b> D is formed on the insulator layer 7.

  Subsequently, the insulator layer 9 is formed on the coil conductor layer 8 in the same manner as the method for forming the insulator layer 7. Then, for example, a hole 20 and a contact hole (not shown) are simultaneously formed in the insulator layer 9 by etching, laser beam, punching, or the like. Then, a conductive material such as Ag is filled in the contact hole.

  Subsequently, the coil conductor layer 10 is formed by forming the pattern of the coil portion 21, the lead portion 22, and the lead electrodes 23A to 23D on the insulator layer 9 by the same method as the method for forming the coil conductor layer 8. . Then, the insulator layer 11 is formed on the coil conductor layer 10 and the holes 24 are formed in the insulator layer 11 in the same manner as the method for forming the insulator layers 7 and 9.

  Subsequently, the coil conductor layer 12 is formed by forming the pattern of the coil portion 25, the lead portion 26, and the lead electrodes 27 </ b> A to 27 </ b> D on the insulator layer 11 by a method similar to the method for forming the coil conductor layer 8. . Then, in the same manner as the method for forming the insulator layers 7 and 9, the insulator layer 13 is formed on the coil conductor layer 12, and the hole 28 and the contact hole (not shown) are further formed in the insulator layer 13. The contact hole is filled with a conductive material.

  Subsequently, the coil conductor layer 14 is formed by forming the pattern of the extraction portion 29 and the extraction electrodes 30 </ b> A to 30 </ b> D on the insulator layer 13 by the same method as the formation method of the coil conductor layer 8. Then, the insulator layer 15 is formed on the coil conductor layer 14 in the same manner as the method for forming the insulator layers 7 and 9, and the hole 31 is further formed in the insulator layer 15.

  As a result, as shown in FIG. 5A, the layer structure intermediate body 34 in which the coil portions 21 and 25 are incorporated is formed on the lower magnetic substrate 2. At this time, a magnetic path forming recess 32 having a step shape is formed in the inner region of the coil portions 21 and 25 in the layer structure intermediate 34 by the holes 20, 24, 28 and 31.

  Subsequently, as shown in FIG. 5B, the magnetic powder-containing resin J is embedded in the magnetic path forming recess 32 and applied to the upper surface of the layer structure intermediate 34, and the magnetic powder-containing resin J is cured in this state. Thereby, a closed magnetic path 33 including the magnetic layer 16 is formed in the layer structure intermediate 34. Application and embedding of the magnetic powder-containing resin J is performed using a screen printing method.

  Specifically, as shown in FIG. 6, a metal mask 35 having a hole is placed on the layer structure intermediate 34. Then, by pasting the paste-like magnetic powder-containing resin J with the squeegee 36 in a state where the paste-like magnetic powder-containing resin J is placed on the upper surface of the layer structure intermediate 34, the magnetic powder-containing resin J is placed in the magnetic path forming recess 32. While embedding, the magnetic powder-containing resin J is flattened on the upper surface of the magnetic layer 16.

  Subsequently, as shown in FIG. 5C, an adhesive such as an epoxy resin is applied on the magnetic layer 16 to form an adhesive layer 17. Then, the upper magnetic substrate 4 is attached to the upper surface of the adhesive layer 17. Thereby, said laminated body 5 is obtained.

  Thereafter, the terminal electrodes 6A and 6B are formed on one end face of the multilayer body 5, and the terminal electrodes 6C and 6D are formed on the other end face of the multilayer body 5. Specifically, for example, a Cr / Cu film or a Ti / Cu film is formed on the end face of the multilayer body 5 by mask sputtering, and then electroplating is performed using Cu / Ni / Sn. 6D is formed. As described above, the common mode filter 1 is completed.

  By the way, if the common mode filter is small, such as the 1210 type (described above), the opening diameter of the magnetic path forming recess 32 is naturally reduced accordingly. Therefore, as shown in FIG. 7, when the magnetic path forming recess 32 is cylindrical, the magnetic powder containing resin J having a relatively high viscosity is embedded in the magnetic path forming recess 32. The contained resin J may not be sufficiently filled in the magnetic path forming recess 32. As the cause, the following can be considered.

  That is, when the magnetic powder-containing resin J is printed and filled in the magnetic path forming concave portion 32 using the squeegee 36 as described above, the magnetic powder-containing resin J embraces the air present in the magnetic path forming concave portion 32. As shown in FIG. 7, a void X is formed at the bottom edge of the magnetic path forming recess 32, and a filling defect of the magnetic powder-containing resin J may occur. At this time, when the magnetic path forming concave portion 32 has a cylindrical shape, the amount of the air existing in the magnetic path forming concave portion 32 is embraced by the size of the opening diameter of the magnetic path forming concave portion 32. It seems to be equivalent. For this reason, the smaller the opening diameter of the magnetic path forming recess 32, the higher the occupation ratio of the air (cavity) contained in the closed magnetic path 33 formed by the magnetic powder-containing resin J. In this case, not only the impedance of the common mode filter decreases, but also the impedance of the common mode filter varies due to the difference in filling of the magnetic powder-containing resin J.

  On the other hand, in the present embodiment, the diameters of the holes 20, 24, 28, 31 that form the closed magnetic path forming recesses 32 are increased from the lower layer side to the upper layer side of the laminated body 5, thereby The stepped structure is such that the shape of the recess 32 is wider than the upper layer side (opening side) of the laminate 5. Thereby, when the magnetic powder containing resin J having a relatively high viscosity is printed and embedded in the magnetic path forming recess 32, the magnetic powder containing resin J forms a magnetic path along the fine stepped side surface of the magnetic path forming recess 32. It flows smoothly to the bottom of the concave portion 32 for use, and the amount of the magnetic powder-containing resin J embracing the air present in the concave portion 32 for forming the magnetic path is reduced. For this reason, the filling defect of the magnetic powder-containing resin J is suppressed, and the magnetic powder-containing resin J is sufficiently filled in the magnetic path forming recess 32, so that the occupation ratio of the air contained in the closed magnetic path 33 is reduced. Can do.

  Thereby, the fall of the impedance of the common mode filter 1 can be suppressed. Therefore, it is possible to secure a stable impedance characteristic while reducing the size of the common mode filter 1 and to suppress generation of noise due to leakage magnetic flux. Moreover, impedance variation occurring between the plurality of common mode filters 1 can be suppressed.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the side surface of the magnetic path forming concave portion 32 has a stepped structure, but the magnetic path forming concave portion 32 may be widened toward the upper layer side of the laminate 5. The cross-sectional shape of the side surface of the magnetic path forming recess 32 may be tapered.

  Moreover, in the said embodiment, although the coil parts 21 and 25 were formed in the substantially circular spiral shape, as the spiral shape of the coil parts 21 and 25, an ellipse shape, a square shape, etc. may be sufficient. At this time, in order to effectively use the space corresponding to the inner region of the coil portions 21 and 25 in the insulating layers 9, 11, 13, and 15 as the closed magnetic path 33, the insulating layers 9, 11, 13, and 15 are respectively provided. The cross-sectional shape of the holes 20, 24, 28, 31 to be formed is preferably an oval shape, a square shape, or the like corresponding to the spiral shape of the coil portions 21, 25.

  Furthermore, in the said embodiment, although the recessed part 32 for magnetic path formation was formed in the inner area | region of the coil parts 21 and 25 in the laminated body 5, if the space is ensured, the coil parts 21 and 25 in the laminated body 5 will be described. A magnetic path forming concave portion may be formed in the outer region of.

  Further, in the above embodiment, the holes 20, 24, 28, 31 forming the magnetic path forming recess 32 are formed in the insulating layers 9, 11, 13, 15 excluding the lowermost insulating layer 7 in the layer structure 3. Although formed, holes may also be formed in the insulating layer 7. In this case, since the area of the closed magnetic path 33 in the layer structure 3 is increased, the impedance of the common mode filter 1 can be further increased. However, in the case where no hole is formed in the lowermost insulating layer 7 as described above, it is not necessary to perform drilling or the like on the insulating layer 7 at all, so that the number of steps can be reduced.

It is a perspective view showing one embodiment of a common mode filter concerning the present invention. It is a disassembled perspective view of the laminated body shown in FIG. It is a top view which shows the insulating layer and coil conductor layer of each layer shown in FIG. It is sectional drawing of the laminated body shown in FIG. It is sectional drawing which shows the process of producing the laminated body shown in FIG. It is a perspective view which shows the method of embedding magnetic powder containing resin in the recessed part for magnetic path formation shown in FIG. It is sectional drawing which shows the state by which magnetic powder containing resin was embedded at the recessed part for magnetic path formation, when the recessed part for magnetic path formation has comprised the column shape as a comparative example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Common mode filter, 9 ... Insulating layer, 10 ... Coil conductor layer, 11 ... Insulating layer, 12 ... Coil conductor layer, 13 ... Insulating layer, 15 ... Insulating layer, 20 ... Hole, 21 ... Coil part, 24 ... Hole: 25: Coil, 28: Hole, 31: Hole, 32: Magnetic path forming recess, J: Magnetic powder-containing resin

Claims (4)

A common mode filter comprising a plurality of insulating layers and two coil conductor layers having a spiral coil portion, wherein the insulating layers and the coil conductor layers are alternately stacked;
Each of the plurality of insulating layers is formed with a hole that penetrates in the thickness direction of the insulating layer and constitutes a part of the magnetic path forming recess,
The magnetic path forming recess is filled with a resin containing a magnetic material for forming a magnetic path,
The hole portion formed in the insulating layer on the upper layer side is larger than the hole portion formed in the insulating layer on the lower layer side so that the magnetic path forming concave portion becomes wider from the lower layer side toward the upper layer side. A common mode filter characterized by   The common mode filter according to claim 1, wherein a side surface of the magnetic path forming recess is stepped.   The common mode filter according to claim 1, wherein the hole portion is formed in a portion corresponding to an inner region of the coil portion in the insulating layer.   The common mode filter according to claim 3, wherein the hole portion has a cross-sectional shape corresponding to a spiral shape of the coil portion.

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