Patent Publication Number: US-9899141-B2

Title: Common mode filter and method of manufacturing the same

Description:
CROSS REFERENCE(S) TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. Section 119 of Korean Patent Application Serial No. 10-2012-0153494, entitled “Common Mode Filter and Method of Manufacturing the Same” filed on Dec. 26, 2012, which is hereby incorporated by reference in its entirety into this application. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a common mode filter, and more particularly, to a common mode filter having a coil electrode formed on both surfaces of a core layer and a method of manufacturing the same. 
     2. Description of the Related Art 
     In accordance with a development of technology, electronic devices such as a portable phone, home appliances, a personal computer (PC), a personal digital assistant (PDA), a liquid crystal display (LCD) and the like have converted from the analog method to the digital method and have high-speed characteristics due to an increase in an amount of data to be processed. Therefore, USB 2.0, USB 3.0, and a high-definition multimedia interface (HDMI) have come into wide use as a high-speed signal transmission interface and have been used in many digital devices such as a personal computer and a digital high-definition television. 
     These interfaces employ a differential signal system transmitting a differential signal (a differential mode signal) using a pair of signal lines unlike a single-end transmission system generally used for a long time. 
     Therefore, in order to remove common mode noise, a common mode filter is generally used in a high-speed differential signal line and the like. Here, the common mode noise is noise generated in the differential signal line, and the common mode filter removes the noise capable of being removed by an existing electromagnetic interference (EMI) filter. 
     Referring to Japanese Patent Laid-Open Publication No. 2012-015494, a general common mode filter according to the related art has a structure in which a pair of primary and secondary conductor coils are included in an insulating layer and the primary and secondary conductor coils are spaced from each other having an insulating resin configuring the insulating layer therebetween. In order to manufacture the common mode filter having the above-mentioned structure, processes of applying the insulating resin and plating the coil electrode are needed to be repeatedly performed by generally performing a build-up process. 
     However, this causes an increase in process number according to a laminating number of the conductor coils to thereby become a factor of decreasing productivity and increasing manufacturing costs. Therefore, a technology capable of manufacturing the common mode filter using a simpler method is urgently demanded. 
     RELATED ART DOCUMENT 
     Patent Document 
     (Patent Document 1) Japanese Patent Laid-Open Publication No. 2012-015494 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a common mode filter capable of forming coil electrodes and an external electrode terminal without performing a build-up process and a method of manufacturing the same, thereby solving a decrease in productivity and an increase in manufacturing costs due to an increase in process number. 
     According to an exemplary embodiment of the present invention, there is provided a common mode filter, including: a core insulating layer; coil electrodes formed on both surfaces of the core insulating layer; external electrode terminals connected to end portions of the coil electrode; and an external insulating layer covering a surface of the core insulating layer, wherein the external electrode terminals are formed to face both surfaces of the core insulating layer and are connected by a connection electrode. 
     The coil electrodes formed on both surfaces of the core insulating layer may be connected to each other by a via penetrating through the core insulating layer. 
     The coil electrodes may be configured of a first coil electrode and a second coil electrode alternatively disposed on the same layer. 
     The external insulating layer may have the same diameter as that of the external electrode terminal. 
     The common mode filter may further include a surface electrode formed on one surface of the external insulating layer and bonded to the external electrode terminal. 
     According to another exemplary embodiment of the present invention, there is provided a method of manufacturing a common mode filter, the method including: preparing a core insulating layer having metal layers laminated on both surfaces thereof; performing half etching on the remainder region with exception of a region forming an external electrode terminal in the metal layers; selectively etching the metal layers of the half etched region to form a coil electrode; forming a connection electrode connecting the external electrode terminals to each other formed to face both surfaces of the core insulating layer; and forming an external insulating layer covering a surface of the core insulating layer. 
     The metal layer laminated on both surfaces of the prepared core insulating layer may have the same thickness as that of the external electrode terminal. 
     After the forming of the coil electrode, a hall penetrating through the coil electrode and the core insulating layer may be processed and an inner portion of the hall may be filled and plated to thereby form a via. 
     In the forming of the external insulating layer, the external insulating layer may be formed up to a height of the external electrode terminal. 
     A surface electrode bonded to the external electrode terminal may be formed on one surface of the external insulating layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a common mode filter according to an exemplary embodiment of the present invention; 
         FIG. 2  is a cross-sectional view taken along the line I-I′ of  FIG. 1 ; and 
         FIGS. 3 to 10  are process views sequentially showing a method of manufacturing the common mode filter according to the exemplary embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Various advantages and features of the present invention and methods accomplishing thereof will become apparent from the following description of embodiments with reference to the accompanying drawings. However, the present invention may be modified in many different forms and it should not be limited to the embodiments set forth herein. These embodiments may be provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
     Terms used in the present specification are for explaining the embodiments rather than limiting the present invention. Unless explicitly described to the contrary, a singular form includes a plural form in the present specification. The word “comprise” and variations such as “comprises” or “comprising,” will be understood to imply the inclusion of stated constituents, steps, operations and/or elements but not the exclusion of any other constituents, steps, operations and/or elements. 
       FIG. 1  is a perspective view of a common mode filter according to an exemplary embodiment of the present invention and  FIG. 2  is a cross-sectional view taken along the line I-I′ of  FIG. 1 . Additionally, components shown in the accompanying drawings are not necessarily shown to scale. For example, sizes of some components shown in the accompanying drawings may be exaggerated as compared with other components in order to assist in the understanding of the exemplary embodiments of the present invention. For simplification and clearness of illustration, a general configuration scheme will be shown in the accompanying drawings, and a detailed description of the feature and the technology well known in the art will be omitted in order to prevent a discussion of exemplary embodiments of the present invention from being unnecessarily obscure. 
     Referring to  FIGS. 1 and 2 , a common mode filter  100  according to the exemplary embodiment of the present invention may include a core insulating layer  110 , coil electrodes  111  and  112  of upper and lower layers formed on both surface of the core insulating layer  110 , external electrode terminals  120  connected to the coil electrodes  111  and  112 , and an external insulating layer  130  covering a surface of the core insulating layer  110 . The common mode filter  100  according to the exemplary embodiment of the present invention may further include surface electrodes  140  formed on one surface of the external insulating layer  130 . 
     The core insulating layer  110  electrically insulates between the coil electrodes  111  and  112  of the upper and lower layers, and the external insulating layer  130  is a layer protecting the coil electrodes  111  and  112  from the outside and a configuration material of the external insulating layer  130  may be appropriately selected in consideration of an insulating property, a heat-resisting property, a water-resisting property, and the like. For example, examples of optimal polymer materials configuring the core insulating layer  110  and the external insulating layer  130  include a thermosetting resin such as an epoxy resin, a phenol resin, a urethane resin, a silicon resin, a polyimide resin and like, a thermoplastic resin such as a polycarbonate resin, an acrylic resin, a polyacetal resin, a polypropylene resin, and the like. 
     Meanwhile, as described below, since the common mode filter  100  according to the exemplary embodiment of the present invention is manufactured using the core insulating layer  110  having metal layers laminated on both surfaces thereof, the core insulating layer  110  may use a resin (for example, prepreg) in which a reinforcement material such as a glass fiber or an inorganic filler is impregnated in the above described materials in order to enhance hardness thereof. 
     The coil electrodes  111  and  112  which are a conductor plated in a spiral shape on a co-plane, may be formed by patterning the metal layer laminated on the core insulating layer  110 . 
     The above-mentioned coil electrodes  111  and  112  may be configured of a first coil electrode and a second coil electrode electromagnetically coupled to each other, wherein the first coil electrode and the second coil electrode may be alternatively disposed on the same layer. That is, the coil electrode  111  of the upper layer may be configured of the first coil electrode and the second coil electrode which are alternatively disposed and the coil electrode  112  of the lower layer may also be configured of the first coil electrode and the second coil electrode which are alternatively disposed. 
     In this case, the first coil electrode of the upper layer and the first coil electrode of the lower layer may be connected to each other through a via  151  penetrating through the core insulating layer  110 , and the second coil electrode of the upper layer and the second coil electrode of the lower layer may also be connected to each other through the via  151  penetrating through the core insulating layer  110 . 
     The external electrode terminals  120  connected to the end portions of the coil electrodes  111  and  112  are formed at an edge of the core insulating layer  110  and are formed to face both surfaces of the core insulating layer  110 . In addition, the external electrode terminals  120  formed to face both surfaces of the core insulating layer  110  may be electrically connected by a connection electrode  152  formed on a side wall of an element. 
     For example, assuming that the coil electrodes  111  and  112  are configured of the first coil electrode and the second coil electrode as described above, first external electrode terminals  121   a  and  121   b  of upper and lower layers formed to face both surfaces of the core insulating layer  110  are electrically connected to each other by the connection electrode  152 , and the first external electrode terminal  121   a  of the upper layer or the first external electrode terminal  121   b  of the lower layer is connected to one end of the first coil electrode of the same layer. In addition, the other end of the first coil electrode is connected to the external electrode terminal positioned at an opposite side of the first external electrode terminal  121  in the same structure as that of one end of the first coil electrode. 
     Similarly, second external electrode terminals  122   a  and  122   b  of upper and lower layers formed to face both surfaces of the core insulating layer  110  are electrically connected to each other by the connection electrode  152 , and the second external electrode terminal  122   a  of the upper layer or the second external electrode terminal  122   b  of the lower layer is connected to one end of the second coil electrode of the same layer. In addition, the other end of the second coil electrode is connected to the external electrode terminal positioned at an opposite side of the second external electrode terminals  122   a  and  122   b  in the same structure as that of one end of the second coil electrode. 
     The external insulating layer  130  may be formed with the same thickness as the external electrode terminal  120  in the remainder portion with the exception of a region in which the external electrode terminal  120  is formed from the core insulating layer  110 . 
     The surface electrode  140  which is an electrode for securing connectivity between a circuit wiring on a substrate and the external electrode terminal  120 , is formed on one surface of the external insulating layer  130  and is bonded to the external electrode terminal  120 . 
     Meanwhile, although the drawings show that the external electrode terminal  120  and the connection electrode  152 , the surface electrode  140  and the connection electrode  152 , and the external electrode terminal  120  and the surface electrode  140  are separated therebetween, respectively, in order to easily describe the present invention, in the case in which the external electrode terminal  120 , the connection electrode  152 , and the surface electrode  140  are configured of the same material, they may be formed integrally with one another without being separated in external appearance. 
     Hereinafter, a method of manufacturing a common mode filter  100  according to an exemplary embodiment of the present invention will be described. 
       FIGS. 3 to 10  are process views sequentially showing a method of manufacturing the common mode filter  100  according to the exemplary embodiment of the present invention and the method of manufacturing the common mode filter  100  according to the exemplary embodiment of the present invention first prepares the core insulating layer  110  having metal layers  110   a  and  110   b  laminated on both surfaces thereof as shown in  FIG. 3 . 
     The metal layers  110   a  and  110   b , which are layers forming the coil electrodes  111  and  112  and the external electrode terminal  120 , may be made of metal material such as Ni, Pd, Ag—Pd, and Cu. 
     As described above, when the core insulating layer  110  having the metal layers  110   a  and  110   b  laminated on both surfaces thereof is prepared, half etching is performed on surfaces of the metal layers  110   a  and  110   b  as shown in  FIG. 4 . In this case, a mask (not shown in the drawings) is closely adhered to a predetermined region B of the metal layers  110   a  and  110   b  so that the metal layers  110   a  and  110   b  are not etched. 
     Therefore, metal layers  111 ′ and  112 ′ in a region A in which the half etching is performed become base layers for forming the coil electrodes  111  and  112 , and the metal layer in the region B in which etching is not performed due to the mask becomes the external electrode terminal  120 . Therefore, in  FIG. 3 , thicknesses of the metal layers  110   a  and  110   b  laminated on the core insulating layer  110  may be determined according to a thickness of the external electrode terminal  120 . 
     Next, as shown in  FIG. 5 , the metal layers  111 ′ and  112 ′ in the region A are selectively etched, such that the coil electrode  111  and  112  are formed. This may use a known pattern forming technology. 
     When the coil electrodes  111  and  112  are formed, a via for electrically connecting between layers is formed. In order to form the via, a hall penetrating through the coil electrode  111  of the upper layer (or the coil electrode  112  of the lower layer) and the core insulating layer  110  is first processed at a predetermined position as shown in  FIG. 6 . Next, as shown in  FIG. 7 , an inner portion of the hall is filled and plated to form a via  151 , thereby connecting the coil electrodes  111  and  112  of the upper and lower layers to each other. 
     Next, as shown in  FIG. 8 , the connection electrode  152  connecting the external electrode terminals  120  formed to face both surfaces of the core insulating layer  110  is formed. The forming of the connection electrode  152  is not necessarily performed after forming the coil electrodes  111  and  112 , but it may be performed regardless of the order when the core insulating layer  110  having the metal layers  110   a  and  110   b  laminated on both surfaces thereof as shown in  FIG. 3 . However, in the case in which the connection electrode  152  is formed in advance, the connection electrode  152  needs not to be etched at the time of the half etching for forming the coil electrodes  111  and  112 . Therefore, the forming of the connection electrode  152  is advantageously performed after forming the coil electrodes  111  and  112 . 
     Next, as shown in  FIG. 9 , the external insulating layer  130  having the same thickness as that of the external electrode terminal  120  is formed on the core insulating layer  110  using a dip coating method, a spin coating method or the like, and finally, as shown in  FIG. 10 , the surface electrode  140  bonded to the external electrode terminal  120  is plated, thereby finally completing the common mode filter  100  according to the exemplary embodiment of the present invention. 
     As described above, the present invention forms the coil electrodes  111  and  112  by directly patterning the metal layers  110   a  and  110   b  laminated on both surfaces of the core insulating layer  110  while not using the build-up process, thereby making it possible to significantly decrease the process number. 
     In addition, the external electrode terminal  120  is naturally formed while a specific region of the metal layers  110   a  and  110   b  is not etched, such that a process for forming the external electrode terminal  120  as in the related art needs not to be separately performed. 
     According to the exemplary embodiment of the present invention, coil electrodes and an external electrode terminal are formed using a metal layer laminated on a core insulating layer without using a build-up process as in the related art, thereby making it possible to increase productivity of a product and decrease manufacturing costs. 
     The above detailed description has illustrated the present invention. Although the exemplary embodiments of the present invention have been described, the present invention may be also used in various other combinations, modifications, and environments. In other words, the present invention may be changed or modified within the range of concept of the invention disclosed in the specification, the range equivalent to the disclosure and/or the range of the technology or knowledge in the field to which the present invention pertains. The exemplary embodiments described above have been provided to explain the best state in carrying out the present invention. Therefore, they may be carried out in other states known to the field to which the present invention pertains in using other inventions such as the present invention and also be modified in various forms required in specific application fields and usages of the invention. Therefore, it is to be understood that the invention is not limited to the disclosed embodiments. It is to be understood that other embodiments are also included within the spirit and scope of the appended claims.