Abstract:
A printed circuit board disclosed. One embodiment of the present invention provides a printed circuit board that includes: an insulation layer having multiple layers of circuit wirings formed therein; a via formed along a perimeter of the insulation layer and configured for connecting circuit wirings formed on different layers of the insulation layer, the via being formed in such a way that an inside thereof is hollow; and an electromagnetic wave absorbing part contained in the via.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 10-2012-0084117, filed with the Korean Intellectual Property Office on Jul. 31, 2012, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a printed circuit board that reduces electro-magnetic noise that is emitted to an outside. 
     2. Background Art 
     Generally, electronic devices, such as smart phones, tablet PCs and the like, are required to have higher operating frequencies, broadband, multiband, etc. in order to be more functional and smaller and transmit more data faster. 
     As the electronic devices have higher operating frequencies and become smaller, electromagnetic noise such as EMI (electromagnetic interference) can be generated between electronic devices or between internal modules or parts. The electromagnetic noise can cause the electronic devices to malfunction. 
     Korean Patent Publication 2010-0071435 (laid open on Jul. 3, 2012) disclosed an electromagnetic band-gap structure with an active element, a semiconductor chip having the same, and a method of manufacturing the same. 
     SUMMARY 
     An embodiment of the present invention provides a printed circuit board that can reduce electro-magnetic noise that is emitted to an outside. 
     An aspect of the present invention features a printed circuit board, which comprises: an insulation layer having multiple layers of circuit wirings formed therein; a via formed along a perimeter of the insulation layer and configured for connecting circuit wirings formed on different layers of the insulation layer, the via being formed in such a way that an inside thereof is hollow; and an electromagnetic wave absorbing part contained in the via. 
     The via can be arranged in a row along the perimeter of the insulation layer. 
     The via can be formed in groups of a plurality of vias and arranged along the perimeter of the insulation layer. 
     The electromagnetic wave absorbing part can be made of a metallic material different from that of the via. 
     The electromagnetic wave absorbing part can comprise a dielectric material and a metallic material. 
     The electromagnetic wave absorbing part can comprise a magnetic material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts one embodiment of a printed circuit board according to the present invention. 
         FIG. 2  depicts the printed circuit board shown in  FIG. 1 . 
         FIG. 3  depicts a via and an electromagnetic wave absorbing material shown in  FIG. 1 . 
         FIG. 4  depicts another embodiment of the printed circuit board according to the present invention. 
         FIG. 5  depicts a via shown in  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
     Since there can be a variety of permutations and embodiments of the present invention, certain embodiments will be illustrated and described with reference to the accompanying drawings. This, however, is by no means to restrict the present invention to certain embodiments, and shall be construed as including all permutations, equivalents and substitutes covered by the ideas and scope of the present invention. Throughout the description of the present invention, when describing a certain relevant conventional technology is determined to evade the point of the present invention, the pertinent detailed description will be omitted. 
     Hereinafter, some embodiments of a printed circuit board according to the present invention will be described in detail with reference to accompanying drawings. 
       FIG. 1  depicts one embodiment of a printed circuit board according to the present invention, and  FIG. 2  depicts the printed circuit board shown in  FIG. 1 , and  FIG. 3  depicts a via and an electromagnetic wave absorbing material shown in  FIG. 1 . 
     Referring to  FIGS. 1 through 3 , a printed circuit board  100  can include an insulation layer  110 , a via  120  and an electromagnetic wave absorbing part  130 . 
     The insulation layer  110  can have multiple layers of circuit wirings formed therein, and circuit wirings on the plurality of layers may be formed on the insulation layer  110 . The circuit wirings  113  can include a plurality of inner layer circuit wirings  113  formed inside the insulation layer  110  and outer layer circuit wirings  113  formed on either surface of the insulation layer  110 . The insulation layer  110  can be made of various kind of non-conductive materials. 
     The via  120  can be formed along a perimeter of the insulation layer  110 . For example, the via  120  can be arranged in a row along the perimeter of the insulation layer  110 . The via  120  can be equally spaced along the perimeter of the insulation layer  110 . Since the via  120  is arranged in a row along the perimeter of the insulation layer  110 , the electromagnetic wave absorbing part  130  placed inside the via  120  can prevent electromagnetic noise from being emitted to an outside through the perimeter of the insulation layer  110 . 
     The via  120  can penetrate the insulation layer  110  to connect the circuit wirings  113  that are on different layers. Here, the via  120  can connect the circuit wiring  113  of every layer or the circuit wirings of some layers. 
     The via  120  can be formed in such a way that an inside thereof is hollow. The inside of the via  120  can be formed to be hollow by forming a via hole in the insulation layer  110  and then forming a plating layer on an inner wall of the via hole. The via  120  can be formed by plating the inner wall of the via hole. The via  120  can be formed when the outer layer circuit wirings  113  are formed or independently from the outer layer circuit wirings  113 . The via  120  can be formed in a cylindrical shape, of which an inside is hollow. 
     The via  120  can be connected with a ground wiring, among the outer layer circuit wirings  113 . The ground wiring can be separated from the circuit wirings  113  that transfer electrical signals. 
     The electromagnetic wave absorbing part  130  can be contained inside the via  120 . Since the electromagnetic wave absorbing part  130  is contained inside the via  120 , it becomes possible to prevent electromagnetic noise from being emitted to an outside through an internal space of the via  120 . Accordingly, it is possible to reduce the emission of electromagnetic noise to the outside dramatically. Also, since the electromagnetic wave absorbing part  130  is arranged along the perimeter of the insulation layer  110 , it is also possible to prevent the electromagnetic noise from being emitted through a perimeter of the printed circuit board. 
     The electromagnetic wave absorbing part  130  can be made of metallic materials that are different from the via  120 . For example, the via  120  can be made of a copper-plated material, and the electromagnetic wave absorbing part  130  can be made of ferrite. Here, the electromagnetic wave absorbing part  130  can be ferrite consisting of one or more of Mn—Zn group, Mn—Mg group, Ni—Zn group, Ba and Sr. 
     The electromagnetic wave absorbing part  130  can include a dielectric material and the aforementioned metallic material. The electromagnetic wave absorbing part  130  can be formed by mixing a powder form of the dielectric material with a powder form of the metallic material. After filling the inside of the via  120  with the powder form of the electromagnetic wave absorbing part  130 , either end of the via  120  can be sealed with, for example, a cover. 
     The electromagnetic wave absorbing part  130  can have a magnetic material. As a magnetic material is used as the electromagnetic wave absorbing part  130 , the electromagnetic noise can be absorbed more effectively. The electromagnetic wave absorbing part  130  can be constituted entirely or partially with the magnetic material. 
     The insulation layer  110  can further have a metallic shield plate on a top surface and a bottom surface thereof. The shield plate can prevent the electromagnetic noise from being emitted in directions of the top surface and the bottom surface. 
     Since the printed circuit board described hitherto has the via  120  with the electromagnetic wave absorbing part  130  arranged along the perimeter of the insulation layer  110 , the electromagnetic noise that propagates in the direction of a plane of the insulation layer  110  can be absorbed by the electromagnetic wave absorbing part  130 . Therefore, the amount of emission of electromagnetic noise from the printed circuit board can be reduced. 
       FIG. 4  depicts another embodiment of the printed circuit board according to the present invention, and  FIG. 5  depicts a via. 
     Referring to  FIGS. 4 and 5 , a printed circuit board  100  can include an insulation layer  110 , a via  120  and an electromagnetic wave absorbing part  130 . 
     The insulation layer  110  can have multiple layers of circuit wirings. Circuit wiring  113  can include a plurality of inner layer circuit wirings  113  formed inside the insulation layer  110  and outer layer circuit wirings  133  formed on either surface of the insulation layer  110 . The insulation layer  110  can be made of various kinds of non-conductive materials. 
     The via  120  can be formed along a perimeter of the insulation layer  110 . For example, groups of a plurality of the vias  120  can be arranged along the perimeter of the insulation layer  110 . Here, the groups of the vias  120  can be equally spaced along the perimeter of the insulation layer  110 . Since the groups of the vias  120  are arranged along the perimeter of the insulation layer  110 , the electromagnetic wave absorbing part  130  placed inside the via  120  can prevent electromagnetic noise from being emitted to an outside through the perimeter of the insulation layer  110 . 
     The via  120  can penetrate the insulation layer  110  to connect the circuit wirings  113  that are on different layers. Here, the via  120  can connect the circuit wirings  113  of every layer or the circuit wirings  113  of some layers. 
     The via  120  can be formed in such a way that an inside thereof is hollow. The inside of the via  120  can be formed to be hollow by forming a via hole in the insulation layer  110  and then forming a plating layer on an inner wall of the via hole. The via  120  can be formed by plating the inner wall of the via hole. The via  120  can be formed when the outer layer circuit wirings  113  are formed or independently from the outer layer circuit wirings  113 . The via  120  can be formed in a cylindrical shape, of which an inside is hollow. 
     The via  120  can be connected with a ground wiring, among the outer layer circuit wirings  113 . The ground wiring can be separated from the circuit wirings  113  that transfer electrical signals. 
     The electromagnetic wave absorbing part  130  can be contained inside the via  120 . Since the electromagnetic wave absorbing part  130  is contained inside the via  120 , it becomes possible to prevent electromagnetic noise from being emitted to an outside through an internal space of the via  120 . Accordingly, it is possible to reduce the emission of electromagnetic noise to the outside dramatically. Also, since the electromagnetic wave absorbing part  130  is arranged along the perimeter of the insulation layer  110 , it is also possible to prevent the electromagnetic noise from being emitted through a perimeter of the printed circuit board. 
     The electromagnetic wave absorbing part  130  can be made of metallic materials that are different from the via  120 . For example, the via  120  can be made of a copper-plated material, and the electromagnetic wave absorbing part  130  can be made of ferrite. Here, the electromagnetic wave absorbing part  130  can be ferrite consisting of one or more of Mn—Zn group, Mn—Mg group, Ni—Zn group, Ba and Sr. 
     The electromagnetic wave absorbing part  130  can include a dielectric material and the aforementioned metallic material. The electromagnetic wave absorbing part  130  can be formed by mixing a powder form of the dielectric material with a powder form of the metallic material. After filling the inside of the via  120  with the powder form of the electromagnetic wave absorbing part  130 , either end of the via  120  can be sealed with, for example, a cover. 
     The electromagnetic wave absorbing part  130  can have a magnetic material. As a magnetic material is used as the electromagnetic wave absorbing part  130 , the electromagnetic noise can be absorbed more effectively. The electromagnetic wave absorbing part  130  can be constituted entirely or partially with the magnetic material. 
     The insulation layer  110  can further have a metallic shield plate on a top surface and a bottom surface thereof. The shield plate can prevent the electromagnetic noise from being emitted in directions of the top surface and the bottom surface. 
     Since the printed circuit board described hitherto has the groups of the vias  120  with the electromagnetic wave absorbing part  130  arranged along the perimeter of the insulation layer  110 , the electromagnetic noise that propagates in the direction of a plane of the insulation layer  110  can be absorbed by the electromagnetic wave absorbing part  130 . Therefore, an amount of emission of electromagnetic noise from the printed circuit board can be reduced. In addition, since the groups of the vias  120  form multiple rows of electromagnetic noise shielding structure along the perimeter of the insulation layer  110 , the electromagnetic noise can be shielded much more effectively. 
     Although certain embodiments of the present invention have been described, the embodiments are for illustrative purposes only, and the present invention shall not be restricted to the described embodiments. It is to be appreciated that those skilled in the art can implement other embodiment(s) by supplementing, modifying, deleting and/or adding any elements without departing from the technical ideas of the invention.