Patent Publication Number: US-11664627-B2

Title: Shielded Board-to-Board Connector

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/229,326, filed on Apr. 13, 2021, which is a continuation of U.S. patent application Ser. No. 16/737,621, filed on Jan. 8, 2020, now U.S. Pat. No. 11,031,737, which is a continuation of U.S. patent application Ser. No. 16/334,170, filed on Mar. 18, 2019, now U.S. Pat. No. 10,566,742, which is a national stage of International Application No. PCT/CN2016/099350, filed on Sep. 19, 2016. All of the aforementioned applications are hereby incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a connector, and more particularly, a board-to-board connector for connecting printed boards to each other. 
     BACKGROUND 
     It is desirable to make a board-to-board connector adaptable to high speed signal transmission, where the board-to-board connector is mounted in the smartphone and is for connecting a mother board and another board in the smartphone. 
     High speed signal transmission in a connector tends to increase EMI (electromagnetic interference) noise emitted from a connection section between signal contact elements of the connector. The board-to-board connector adaptable to high speed signal transmission needs to be capable of shielding the EMI noise. 
     Conventional board-to-board connectors for smartphones, which have a lower height, e.g. about 0.6 to 0.7 mm, are not provided with an electromagnetic interference shield. On the other hand, conventional board-to-board connectors for computers or televisions are provided with an electromagnetic interference shield. However, since these board-to-board connectors with an electromagnetic interference shield have a height considerably larger than that of the board-to-board connectors for smartphones, it may be impossible to apply the structure of conventional board-to-board connectors with an electromagnetic interference shield to the board-to-board connectors for smartphones. 
     In addition, conventional board-to-board connectors with an electromagnetic interference shield have a structure in which only either one of a plug and a receptacle comprises the shield which is configured to surround both a plug housing and a receptacle housing when the plug has been inserted into the receptacle. These conventional board-to-board connectors cannot completely shield EMI noise. For example, in conventional board-to-board connectors with an electromagnetic interference shield, EMI noise may leak out by passing through a gap between the exterior of the plug housing and the interior of the receptacle housing and through the plug housing and the receptacle housing made of resin. 
     Japanese Unexamined Patent Application, First Publication No. 2012-54173 discloses a board-to-board connector comprising a plug and a receptacle which is fittable to the plug, wherein the plug comprises an insulation plug housing and a plurality of plug shield members which are fixed to the plug housing, and the receptacle comprises an insulation receptacle housing and a plurality of receptacle shield members which are fixed to the receptacle housing, and wherein ground contact portions extending from the plug shield members are respectively in direct contact with ground contact portions extending from the plug shield members. However, the plug shield members as well as the receptacle shield members are aligned in the longitudinal direction of the connector, but they are not provided on the opposite ends in the longitudinal direction of the connector, that is, the short side section of the periphery of the connector. Therefore, EMI noise may leak out by passing through the opposite end portions of the plug housing and the receptacle housing, which are positioned at the opposite ends. Furthermore, since there is a gap between the plug shield members and the receptacle shield members, EMI noise may leak out by passing through the gap. 
     Japanese Unexamined Patent Application, First Publication No. 2010-97759 discloses a board-to-board connector comprising a receptacle and a plug, wherein the receptacle comprises an insulation stationary housing, a movable housing which is provided on the stationary housing, a first shield cover surrounding the exterior of the stationary housing, and a second shield cover surrounding the exterior of the movable housing, and the plug comprises an insulation plug housing configured to be insertable into the movable housing and a plug shield cover surrounding the exterior of the plug housing. The second shield cover is provided with a plurality of bending tabs which are in direct contact with the plug shield cover when the plug has been fitted to the receptacle. However, the bending tabs are provided on the short side section of the periphery of the connector, but they are not provided on the long side section of the periphery of the connector. Therefore, EMI noise may leak out by passing through a gap between the long side section of the plug shield cover and the long side section of the movable housing and through the long side section of the movable housing. 
     Japanese Unexamined Patent Application, First Publication No. 2008-243703 discloses a board-to-board connector comprising a receptacle and a plug, wherein the receptacle comprises an insulation receptacle housing and a receptacle shield member surrounding an exterior of the receptacle housing, and the plug comprises an insulation plug housing and plug shield members covering the opposite ends of the plug housing. The receptacle shield member is provided with a plurality of bending tabs which are in direct contact with the plug shield members when the plug has been fitted to the receptacle. However, the bending tabs are provided on the short side section of the periphery of the connector, but they are not provided on the long side section of the periphery of the connector. Therefore, EMI noise may leak out by passing through a gap between the long side section of the plug housing and the long side section of the receptacle housing and through the long side section of the plug housing and the long side section of the receptacle housing. 
     There exists a need to address the aforementioned unresolved problems of conventional board-to-board connectors, in particular, to improve the EMI noise shielding performance of board-to-board connectors. 
     SUMMARY 
     An object of the present invention is to provide a board-to-board connector capable of eliminating or reducing a leakage of EMI noise generated by the signal contact elements of the receptacle and the plug. 
     This object is achieved by means of a board-to-board connector for connecting printed boards to each other, the connector comprising: a receptacle comprising a plurality of signal contact elements to be electrically connected to one of the printed boards, and a plug comprising a plurality of signal contact elements to be electrically connected to the other of the printed boards, the signal contact elements being configured so that each of the signal contact elements of the plug is in contact with the corresponding signal contact element of the receptacle when the plug has been inserted into the receptacle, wherein the receptacle comprises an electromagnetic interference shield which continuously or discontinuously surrounds the plurality of signal contact elements of the receptacle, and the plug comprises an electromagnetic interference shield which continuously or discontinuously surrounds the plurality of signal contact elements of the plug, and wherein the shield of the receptacle and the shield of the plug are configured to be in direct contact with each other when the plug has been inserted into the receptacle, the contact arrangement being provided in the entire perimeter of the connector. 
     By means of this board-to-board connector, when the plug is inserted into the receptacle and each of the signal contact elements of the plug is in contact with the corresponding signal contact element of the receptacle, EMI noise generated by the signal contact elements of the receptacle and the plug is shielded by the shields of the receptacle and the plug in the entire perimeter of the connector. 
     In one embodiment of the board-to-board connector, the receptacle comprises an electrical insulation receptacle housing in which the plurality of signal contact elements of the receptacle are installed, the receptacle housing including a peripheral portion surrounding the plurality of signal contact elements of the receptacle. The shield of the receptacle covers the interior of the peripheral portion of the receptacle housing. In addition, the plug comprises an electrical insulation plug housing in which the plurality of signal contact elements of the plug are installed, the plug housing including a peripheral portion surrounding the plurality of signal contact elements of the plug, the peripheral portion of the plug housing being configured to be insertable into the peripheral portion of the receptacle housing. The shield of the plug covers the exterior of the peripheral portion of the plug housing. 
     In a preferred embodiment of the board-to-board connector, the shield of the plug is provided with a plurality of abutment portions for bringing the shield of the plug into direct contact with the shield of the receptacle. The abutment portions are positioned at intervals around the entire shield of the plug. In this embodiment, the abutment portions may be formed like a leaf spring. The abutment portions formed like a leaf spring outwardly project from a surface of the shield of the plug in an oblique direction, and the abutment portions are configured to be elastically deformed by abutment with the shield of the receptacle when the plug has been inserted into the receptacle. 
     In another preferred embodiment of the board-to-board connector, the shield of the receptacle is provided with a plurality of abutment portions for bringing the shield of the receptacle into direct contact with the shield of the plug. The abutment portions are positioned at intervals around the entire shield of the receptacle. In this embodiment, the abutment portions are formed like a leaf spring. The abutment portions formed like a leaf spring inwardly project from a surface of the shield of the receptacle in an oblique direction, and the abutment portions are configured to be elastically deformed by abutment with the shield of the plug when the plug has been inserted into the receptacle. 
     In a further preferred embodiment of the board-to-board connector, the shield of the plug is provided with a plurality of first abutment portions for bringing the shield of the plug into direct contact with the shield of the receptacle, and the shield of the receptacle is provided with a plurality of second abutment portions for bringing the shield of the receptacle into direct contact with the shield of the plug. The first abutment portions are positioned at intervals around the entire shield of the plug, and the second abutment portions are positioned at intervals around the entire shield of the receptacle. In this embodiment, the first abutment portions are formed like a leaf spring. The first abutment portions formed like a leaf spring outwardly project from a surface of the shield of the plug in an oblique direction, and the first abutment portions are configured to be elastically deformed by abutment with the shield of the receptacle when the plug has been inserted into the receptacle. In addition, the second abutment portions are formed like a leaf spring. The second abutment portions like a leaf spring inwardly project from a surface of the shield of the receptacle in an oblique direction, and the second abutment portions are configured to be elastically deformed by abutment with the shield of the plug when the plug has been inserted into the receptacle. Preferably, the first and second abutment portions may be positioned so that the first abutment portions are arranged alternately with the second abutment portions when the plug has been inserted into the receptacle. 
     In the above-mentioned embodiments of the board-to-board connector, the shield of the receptacle may comprise a grounding portion to be electrically connected to one of the printed boards. In addition, the shield of the plug may comprise a grounding portion to be electrically connected to the other of the printed boards. 
     Furthermore, in the above-mentioned embodiments of the board-to-board connector, each signal contact element of the receptacle includes a soldering section to be soldered on one of the printed boards, and a bottom portion of the receptacle housing may be provided with at least one opening through which soldering sections of a plurality of signal contact elements of the receptacle are visible from the insertion port side of the receptacle. 
     In a preferred embodiment of the board-to-board connector, the connector is adapted to be mounted in a smartphone. Nevertheless, the board-to-board connector according to the present application may be mounted in other kinds of electronic devices, such as mobile phones, tablet-type computers, notebook-type computers, desk calculators, electronic notebooks, portable televisions, digital cameras, medical apparatuses, or the like. 
     The term “printed board” should be understood to mean various electronic boards including, for example, PCBs (printed circuit boards), PWBs (printed wiring boards), FPCs (flexible printed circuits), or the like. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be better understood from the following detailed description of non-limiting embodiments thereof, and on examining the accompanying drawings, in which: 
         FIG.  1    shows one cross-sectional schematic diagram of a board-to-board connector according to a first embodiment of the present application, and this is a cross-sectional view along line A-A shown in  FIGS.  3  and  4   ; 
         FIG.  2    shows another cross-sectional schematic diagram of the board-to-board connector according to the first embodiment of the present application, and this is a cross-sectional view along line B-B shown in  FIGS.  3  and  4   ; 
         FIG.  3    shows a planar schematic diagram of a receptacle in the board-to-board connector according to the first embodiment of the present application; 
         FIG.  4    shows a planar schematic diagram of a plug in the board-to-board connector according to the first embodiment of the present application; 
         FIG.  5    shows a cross-sectional schematic diagram of a variation of a receptacle in the board-to-board connector according to the first embodiment of the present application; 
         FIG.  6    shows a cross-sectional schematic diagram of another variation of a receptacle in the board-to-board connector according to the first embodiment of the present application; 
         FIG.  7    shows a cross-sectional schematic diagram of a board-to-board connector according to a second embodiment of the present application; 
         FIG.  8    shows a cross-sectional schematic diagram of a board-to-board connector according to a third embodiment of the present application, and this is a cross-sectional view along line C-C shown in  FIGS.  9  and  10   ; 
         FIG.  9    shows a planar schematic diagram of a receptacle in the board-to-board connector according to the third embodiment of the present application; 
         FIG.  10    shows a planar schematic diagram of a plug in the board-to-board connector according to the third embodiment of the present application; and 
         FIG.  11    shows a cross-sectional schematic diagram of a single-row-type board-to-board connector according to a fourth embodiment of the present application. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     First Embodiment 
     The board-to-board connector  1  shown in  FIGS.  1  to  4    is for connecting two boards (a first board  2  and a second board  3 ) together, and in particular, enables signal transmission between the first and second boards  2  and  3 . The board-to-board connector  1  is suitable for a smartphone and is adapted to be mounted in a smartphone. Both first and second boards  2  and  3  to be connected to each other by the board-to-board connector  1  are pails which may be mounted in the smartphone. 
     As shown in  FIGS.  1  and  2   , the board-to-board connector  1  comprises a receptacle  10  and a plug  20  which are fittable to each other. The receptacle  10  is mounted on the first board  2 , such as a mother board of the smartphone, and the plug  20  is mounted on the second board  3 , such as the other board to be connected to the mother board. Alternatively, the second board  3  on which the plug  20  is mounted may be the mother board, and the first board  2  on which the receptacle  10  is mounted may be the other board to be connected to the mother board. 
     Referring to  FIGS.  1  to  3   , the receptacle  10  is a female connector part configured to be able to receive the plug  20 , and has the appearance of a substantially rectangular parallelepiped as a whole. The receptacle  10  comprises an electrical insulation receptacle housing  11 , a plurality of signal contact elements  12 , an electromagnetic interference shield  13 , and power contact elements  14 . 
     Referring to  FIGS.  1 ,  2 , and  4   , the plug  20  is a male connector configured to be insertable into the receptacle  10 , and has the appearance of a substantially rectangular parallelepiped as a whole. The plug  20  comprises an electrical insulation plug housing  21 , a plurality of signal contact elements  22 , an electromagnetic interference shield  23 , and power contact elements  24 . 
     Referring to  FIGS.  1  to  4   , the receptacle housing  11  as well as the plug housing  21  are each a molded component made of one or more electrical insulation materials such as synthetic resin. The receptacle housing  11  and the plug housing  21  are formed so as to be engageable with each other, and in particular, shaped so that the plug housing  21  is insertable into the receptacle housing  11 . Specifically, an outer rectangular loop-shaped recess no as well as an inner rectangular recess in which is located within the outer recess no are formed on the receptacle housing  11 . On the other hand, the plug housing  21  comprises an outer peripheral portion  211  insertable into the outer recess no of the receptacle housing  11  and an inner peripheral portion  212  insertable into the inner recess in of the receptacle housing  11 . 
     In more detail, referring to  FIGS.  1  to  3   , the receptacle housing  11  comprises a bottom portion  112 , an outer peripheral portion  113 , and an inner peripheral portion  114  which define the outer recess no and the inner recess  111 . The bottom portion  112  is shaped into an approximate rectangle and is located adjacent and parallel to the first board  2 . The outer peripheral portion  113  has an approximately rectangular-cylindrical shape and comprises four walls, that is, a pair of long side walls  113   a  opposite to each other and a pair of short side walls  113   b  opposite to each other. Each wall  113   a ,  113   b  projects from an outer periphery of the bottom portion  112  in a direction away from the first board  2 . The inner peripheral portion  114  has an approximately rectangular-cylindrical shape smaller than the interior of the outer peripheral portion  113  and is small enough to be located inside the outer peripheral portion  113  with an approximately rectangular-cylindrically shaped space. That is, the outer peripheral portion  113  and the inner peripheral portion  114  define the outer rectangular loop-shaped recess no therebetween. The inner peripheral portion  114  comprises four walls, that is, a pair of long side walls  114   a  opposite to each other and a pair of short side walls  114   b  opposite to each other. Each wall  114   a ,  114   b  projects from a central site of the bottom portion  112  in a direction away from the first board  2 . The space inside the inner peripheral portion  114  is the inner recess  111 . The inner peripheral portion  114  is arranged in the same orientation as the outer peripheral portion  113  and shares a central point with the outer peripheral portion  113 . The inner peripheral portion  114  has substantially the same height as the outer peripheral portion  113 . 
     The bottom portion  112  of the receptacle housing  11  is provided with two openings  115  which are vertically formed therethrough. The openings  115  are shaped into an approximate rectangle and extend in the longitudinal direction of the board-to-board connector  1 . The openings  115  are symmetrically arranged on both sides interposing the inner peripheral portion  114 . That is, one of the openings  115  is located between one of the long side walls  113   a  of the outer peripheral portion  113  and one of the long side walls  114   a  of the inner peripheral portion  114 , and the other of the openings  115  is located between the other of the long side walls  113   a  of the outer peripheral portion  113  and the other of the long side walls  114   a  of the inner peripheral portion  114 . 
     Referring to  FIGS.  1 ,  2 , and  4   , the plug housing  21  comprises a bottom portion  210  in addition to the outer peripheral portion  211  and the inner peripheral portion  212 . The bottom portion  210  is shaped into an approximate rectangle and is located adjacent and parallel to the second board  3 . The outer peripheral portion  211  has an approximately rectangular-cylindrical shape and comprises four walls, that is, a pair of long side walls  211   a  opposite to each other and a pair of short side walls  211   b  opposite to each other. Each wall  211   a ,  211   b  projects from an outer periphery of the bottom portion  210  in a direction away from the second board  3 . The inner peripheral portion  212  has an approximately rectangular parallelepiped shape smaller than the interior of the outer peripheral portion  211  and is small enough to be located inside the outer peripheral portion  211  with an approximately rectangular-cylindrical shaped space. That is, the outer peripheral portion  211  and the inner peripheral portion  212  define a rectangular loop-shaped recess  213  therebetween. The inner peripheral portion  212  is arranged in the same orientation as the outer peripheral portion  211  and shares a central point with the outer peripheral portion  211 . The inner peripheral portion  212  has substantially the same height as the outer peripheral portion  211 . 
     Referring to  FIGS.  1  to  4   , each of signal contact elements  12  and  22  is a narrow strip component made of one or more electro-conductive materials such as copper, copper alloy, or the like, and is formed by being bent into a desired shape. Each signal contact element  12  of the receptacle  10  is installed in the receptacle housing  11  in such a manner that a portion thereof is embedded in the receptacle housing  11 . Each signal contact element  22  of the plug  20  is installed in the plug housing  21  in such a manner that a portion thereof is embedded in the plug housing  21 . The plurality of signal contact elements  12  of the receptacle  10  are surrounded by the outer peripheral portion  113  of the receptacle housing  11 , and the plurality of signal contact elements  22  of the plug  20  are surrounded by the outer peripheral portion  211  of the plug housing  21 . The plurality of signal contact elements  12  of the receptacle  10  as well as the plurality of signal contact elements  22  of the plug  20  are arranged at equal intervals in the longitudinal direction of the board-to-board connector  1  and form two rows. The first and second rows of the signal contact elements  12  of the receptacle  10  are symmetrically arranged on both sides interposing the inner recess  111 . The first and second rows of signal contact elements  22  of the plug  20  are symmetrically arranged on both sides interposing the inner peripheral portion  212 . The plurality of signal contact elements  12  of the receptacle  10  and the plurality of signal contact elements  22  of the plug  20  are arranged and configured to be respectively electrically connected to each other when the plug  20  has been inserted into the receptacle  10  so as to enable signal transmission between signal transmitting lines on the first board  2  and signal transmitting lines on the second board  3 . Specifically, the plurality of signal contact elements  12  and  22  are formed so that the plurality of signal contact elements  12  of the receptacle  10  are respectively engageable with the plurality of signal contact elements  22  of the plug  20 , and in particular, are shaped so that each signal contact element  12  of the receptacle  10  is insertable into and contactable to the corresponding signal contact element  22  of the plug  20 . 
     In more detail, referring to  FIGS.  1  to  3   , the signal contact element  12  of the receptacle  10  comprises a contact section  120 , a soldering section  121 , and an anchor section  122 . The contact section  120  is exposed so as to be capable of contacting the signal contact elements  22  of the plug  20 . The contact section  120  has a convex shape, and extends along an inner surface, a tip surface, and an outer surface of the long side wall  114   a  of the inner peripheral portion  114  of the receptacle housing  11 . The anchor section  122  extends from an end of the contact section  120  to an end of the soldering section  121  and is embedded and fixed in the bottom portion  112 . The soldering section  121  is exposed for soldering on the signal transmitting line on the first board  2  by SMT (surface mounted technology) or PIP (pin in paste technology). The soldering section  121  protrudes from the bottom portion  112  into the opening  115  in the bottom portion  112  so that the soldering section  121  is visible from the insertion port side of the receptacle  11 . Due to such a soldering section  121 , the entire length of the signal contact element  12  can be made shorter than a configuration wherein the soldering section of the signal contact elements of the receptacle protrudes from the outer peripheral portion of the receptacle housing, and thereby it is possible to reduce material cost for the signal contact elements  12  to lower than that of the above-mentioned configuration. In addition, since the soldering section  121  of the signal contact elements  12  can be shorter, a high co-planarity of the soldering sections  121  of the plurality of the signal contact elements  12  can be obtained so as to prevent defective soldering in the soldering section  121 . Furthermore, since the soldering section  121  is visible from the insertion port side of the receptacle  11  through the opening  115 , the co-planarity of the soldering sections  121  and the soldered portion in the soldering sections  121  can be easily inspected. 
     Referring to  FIGS.  1 ,  2 , and  4   , the signal contact element  22  of the plug  20  comprises a contact section  220 , a soldering section  221 , and an anchor section  222 . The contact section  220  is positioned within the recess  213  of the plug housing  21  and is exposed so as to be capable of contacting the signal contact elements  12  of the receptacle  10 . The contact section  220  has a concave shape such that the contact section  120  of the signal contact element  12  of the receptacle  10  can be inserted therein. The contact section  220  is elastically deformable so that contact can be reliably maintained between the contact sections  120 ,  220 . The soldering section  221  is exposed for soldering on the signal transmitting line on the second board  3  by SMT or PIP. The soldering section  221  protrudes from the outer peripheral portion  211 . The anchor section  222  extends from an end of the contact section  220  to an end of the soldering section  221  and is embedded and fixed in the outer peripheral portion  211 . 
     Referring to  FIGS.  1  to  4   , the shield  13  as well as the shield  23  are each a cover component capable of shielding EMI noise. These shields  13  and  23  are made of one or more electromagnetic wave shielding materials, for example, a metal plate material such as copper alloy, stainless steel, or the like, and are formed by pressing the metal plate material. Alternatively, the shields may be made of other materials such as metal mesh material, metal foam material, metal plating material, a metal-containing coating material, a metal-containing polymer material, electromagnetic shielding film material, or the like. 
     Referring to  FIGS.  1  to  3   , the shield  13  of the receptacle  10  is arranged and configured to continuously surround the plurality of signal contact elements  12  of the receptacle  10 . Specifically, the shield  13  is attached to the outer peripheral portion  113  of the receptacle housing  11  such that the shield  13  covers the interior, a tip surface, and the exterior of the outer peripheral portion  113 . The shield  13  comprises an interior section  130 , tip sections  131 , exterior sections  132 , and an inner flange section  133 . The interior section  130  has an approximately rectangular-cylindrical shape along the interior of the outer peripheral portion  113  of the receptacle housing  11  and is configured to cover the entire interior of the outer peripheral portion  113  of the receptacle housing  11 . Each tip section  131  has a rectangular shape along the tip surface of the outer peripheral portion  113  of the receptacle housing  11  and is configured to cover the tip surface of the corresponding wall  113   a ,  113   b  of the outer peripheral portion  113 . Each tip section  131  extends over the overall length of an inner surface of the corresponding wall  113   a ,  113   b . Each tip section  131  is integrally provided in the interior section  130  and extends outward from a top end (an end on the insertion port side) of the interior section  130 . The corners between the interior section  130  and the tip section  131  are chamfered in a flat planar form or a round form so as to facilitate the insertion of the plug  20  into the receptacle  10 . Each exterior section  132  has a rectangular shape along the exterior of the outer peripheral portion  113  of the receptacle housing  11  and is configured to cover the outer surface of the corresponding wall  113   a ,  113   b  of the outer peripheral portion  113 . Each exterior section  132  extends over the overall length of the tip section  131 . Each exterior section  132  is integrally provided in the tip section  131  and is hung from the outer side end of the tip section  131 . Each exterior section  132  is provided with at least one grounding portion  135  to be electrically connected to the first board  2 . Each grounding portion  135  is a tab extending outward from a proximal end (an end on the side of the first board  2 ) of the exterior section  132 . Each grounding portion  135  can be soldered on the first board  2  by SMT or PIP so as to allow electrical grounding of the shield  13 . The inner flange section  133  has a rectangular loop shape along the outer periphery of the bottom portion  112  of the receptacle housing  11  and is configured to cover the outer periphery of the bottom portion  112 . In addition, the shield  13  may be divided into a plurality of parts, and the shield  13  may be configured to discontinuously surround the plurality of the signal contact elements  12  of the receptacle  10 . 
     The exterior section  132  does not necessarily need to extend over the overall length of the tip section  131  and to cover most of the exterior of the outer peripheral portion  113  of the receptacle housing  11 . For example, as shown in  FIG.  5   , the width of the exterior sections  132 ′ of the shield  13 ′ of the receptacle  10  may be similar to the width of the grounding portion  135  so as to merely connect the tip section  131  to the grounding portion  135 . Also, the shield  13  of the receptacle  10  does not necessarily need to include the inner flange section  133 . For example, as shown in  FIG.  6   , there may be no inner flange section in the shield  13 ″ of the receptacle  10 . 
     Referring to  FIGS.  1 ,  2 , and  4   , the shield  23  of the plug  20  is arranged and configured to continuously surround the plurality of signal contact elements  22  of the plug  20 . Specifically, the shield  23  is attached to the outer peripheral portion  211  of the plug housing  21  such that the shield  23  covers the tip surface and exterior of the outer peripheral portion  211 . The shield  23  comprises an exterior section  230  and a tip section  231 . The exterior section  230  has an approximately rectangular-cylindrical shape along the exterior of the outer peripheral portion  211  of the plug housing  21  and is configured to cover substantially the entire exterior of the outer peripheral portion  211  of the plug housing  21 . The exterior section  230  is provided with cutouts  230   a  through which the soldering section  221  of the signal contact elements  22  is exposed. The cutouts  230   a  are formed on both long-side walls of the exterior section  230 . The tip section  231  has a rectangular loop shape along the tip surface of the outer peripheral portion  211  of the plug housing  21  and is configured to cover the entire tip surface of the outer peripheral portion  211 . The tip section  231  is integrally provided in the exterior section  230  and extends inward from a tip end of the exterior section  230 . The corners between the exterior section  230  and the tip section  231  are chamfered in a flat planar form or a round form so as to facilitate the insertion of the plug  20  into the receptacle  10 . The exterior section  230  is provided with at least one grounding portion  233  to be electrically connected to the second board  3 . Each grounding portion  233  is a tab extending outward from a proximal end (an end on the side of the second board  3 ) of the exterior section  230 . Each grounding portion  233  can be soldered on the second board  3  by SMT or PIP so as to allow electrical grounding of the shield  23 . In addition, the shield  23  may be divided into a plurality of parts, the shield  23  may be configured to discontinuously surround the plurality of the signal contact elements  22  of the plug  20 . 
     Referring to  FIGS.  1  to  4   , the shield  13  of the receptacle  10  and the shield  23  of the plug  20  are configured to be in direct contact with each other when the plug  20  has been inserted into the receptacle  10  in order to prevent EMI noise generated by the signal contact elements  12 ,  22  from leaking out. In particular, in order to eliminate a path through which EMI noise may pass, the contact arrangement of the shields  13  and  23  is provided in the entire perimeter of the connector  1 . The contact arrangement does not necessarily need to be continuous in the entire perimeter of the connector  1 , and may be discontinuous so that EMI noise is substantially shielded completely. 
     Specifically, as shown in  FIGS.  1 ,  2 , and  4   , the exterior section  230  of the shield  23  of the plug  20  is provided with a plurality of abutment portions  232  for bringing the shield  23  of the plug  20  into direct contact with the shield  13  of the receptacle  10 . Each abutment portion  232  is formed like a leaf spring having a rectangular shape. Each abutment portion  232  outwardly projects from an outer surface of the shield  23  of the plug  20  in an oblique direction so as to abut the interior section  130  of the shield  13  of the receptacle  10  when the plug  20  has been inserted into the receptacle  10 . The abutment portion  232  is configured to be elastically deformed by abutment with the interior section  130  of the shield  13  of the receptacle  10  when the plug  20  has been inserted into the receptacle  10 . Such abutment portion  232  is formed by cutting the metal plate material of the shield  13  into a channel shape and folding outward a portion surrounded by the cutting line. The folding line of the abutment portion  232  is provided on the side closer to the tip section  231  and the abutment portion  232  is opened on the side closer to the second board  3 . The plurality of abutment portions  232  are positioned at intervals around the entire exterior section  230  of the shield  23  of the plug  20 . The interval between the plurality of abutment portions  232  can be decided according to the frequency band of the EMI noise to be shielded by the shields  13  and  23 . 
     Referring to  FIGS.  2  to  4   , the power contact elements  14  of the receptacle  10  and the power contact elements  24  of the plug  20  are current-transmitting elements for enabling high-current transmission between the first board  2  and the second board  3 . These power contact elements  14  and  24  are each a wide strip component made of one or more electro-conductive materials such as copper, copper alloy, or the like, and are formed by being bent into a desired shape. The strip material of the power contact elements  14  and  24  is wider than that of the signal contact elements  12  and  22  so that a high current such as 5.0 A or more can flow through the power contact elements  14  and  24  which have been electrically connected to each other. Each power contact element  14  of the receptacle  10  is installed in the receptacle housing  11  in such a manner that a portion thereof is embedded in the receptacle housing  11 . Each power contact element  24  of the plug  20  is installed in the plug housing  21  in such a manner that a portion thereof is embedded in the plug housing  21 . The power contact element  14  of the receptacle  10  and the power contact element  24  of the plug  20  are arranged and configured to be respectively electrically connected to each other when the plug  20  has been inserted into the receptacle  10 . 
     In more detail, referring to  FIGS.  2  and  3   , the power contact element  14  of the receptacle  10  comprises a contact section  140  and an anchor section  141 . The contact section  140  is exposed so as to be capable of contacting the power contact element  24  of the plug  20 . The contact section  140  has a convex shape, and extends along an inner surface, a tip surface, and an outer surface of the short side wall  114   b  of the inner peripheral portion  114  of the receptacle housing  11 . The anchor section  141  is embedded and fixed in the bottom portion  112 . The power contact element  14  of the receptacle  10  can be soldered on the current transmitting line on the first board  2  by SMT or PIP. 
     Referring to  FIGS.  2  and  4   , the power contact element  24  of the plug  20  comprises a contact section  240 , a soldering section  241 , and an anchor section  242 . The contact section  240  is positioned within the recess  213  of the plug housing  21  and is exposed so as to be capable of contacting the contact section  140  of the power contact element  14  of the receptacle  10 . The contact section  240  is elastically deformable so that contact can be reliably maintained between the contact sections  140 ,  240 . The soldering section  241  is exposed for soldering on the current transmitting line on the second board  3  by SMT or PIP. The soldering section  241  protrudes from the outer peripheral portion  211 . The anchor section  242  extends from an end of the contact section  240  to an end of the soldering section  241  and is embedded and fixed in the outer peripheral portion  211 . 
     Second Embodiment 
       FIG.  7    shows the board-to-board connector  1 A according to the second embodiment of the present application. The board-to-board connector  1 A has common characteristics with the board-to-board connector  1  of the above-described first embodiment, and a detailed description of these common characteristics is omitted. The following is a detailed description of different characteristics of the board-to-board connector  1 A as compared to the board-to-board connector  1  of the first embodiment. 
     As shown in  FIG.  7   , the interior section  130  of the shield  13  of the receptacle  10  is provided with a plurality of abutment portions  134  for bringing the shield  13  of the receptacle  10  into direct contact with the shield  23  of the plug  20 . Each abutment portion  134  is formed like a leaf spring having a rectangular shape. Each abutment portion  134  inwardly (toward the inside of the outer recess no of the receptacle housing  11 ) projects from an inner surface of the shield  13  of the receptacle  10  in an oblique direction so as to abut the exterior section  230  of the shield  23  of the plug  20  when the plug  20  has been inserted into the receptacle  10 . The abutment portion  134  is configured to be elastically deformed by abutment with the exterior section  230  of the shield  23  of the plug  20  when the plug  20  has been inserted into the receptacle  10 . Such abutment portion  134  is formed by cutting the metal plate material of the shield  23  into a channel shape and folding inward a portion surrounded by the cutting line. The folding line of the abutment portion  134  is provided on the side closer to the tip section  131  and the abutment portion  134  is opened on the side closer to the first board  2 . The plurality of abutment portions  134  are positioned at intervals around the entire interior section  130  of the shield  13  of the receptacle  10 . The interval between the plurality of abutment portions  134  can be decided according to the frequency band of the EMI noise to be shielded by the shields  13  and  23 . 
     In contrast to the board-to-board connector  1  according to the first embodiment of the present application, an abutment portion like a leaf spring is not provided on the exterior section  230  of the shield  23  of the plug  20  in the board-to-board connector  1 A according to the second embodiment. 
     Third Embodiment 
       FIGS.  8  to  10    show the board-to-board connector  1 B according to the third embodiment of the present application. The board-to-board connector  1 B has common characteristics with the board-to-board connectors  1  and  1 A of the above-described first and second embodiments, and a detailed description of these common characteristics is omitted. The following is a detailed description of different characteristics of the board-to-board connector  1 B as compared to the board-to-board connectors  1  and  1 A of the first and second embodiments. 
     As shown in  FIG.  8   , both the exterior section  230  of the shield  23  of the plug  20  and the interior section  130  of the shield  13  of the receptacle  10  are provided with a plurality of abutment portions  232  and  134  for bringing the shield  23  of the plug  20  and the shield  13  of the receptacle  10  into mutual direct contact with each other. 
     Specifically, as shown in  FIGS.  8  and  9   , each of the first abutment portions  232  provided on the exterior section  230  of the shield  23  of the plug  20  is formed like a leaf spring having a rectangular shape. Each first abutment portion  232  outwardly projects from an outer surface of the shield  23  of the plug  20  in an oblique direction so as to abut the interior section  130  of the shield  13  of the receptacle  10  when the plug  20  has been inserted into the receptacle  10 . The first abutment portion  232  is configured to be elastically deformed by abutment with the interior section  130  of the shield  13  of the receptacle  10  when the plug  20  has been inserted into the receptacle  10 . Such first abutment portion  232  is formed by cutting the metal plate material of the shield  13  into a channel shape and folding outward a portion surrounded by the cutting line. The folding line of the first abutment portion  232  is provided on the side closer to the tip section  231  and the first abutment portion  232  is opened on the side closer to the second board  3 . 
     As shown in  FIGS.  8  and  10   , each of the second abutment portions  134  provided on the interior section  130  of the shield  13  of the receptacle  10  is formed like a leaf spring having a rectangular shape. Each second abutment portion  134  inwardly (toward the inside of the outer recess no of the receptacle housing  11 ) projects from an inner surface of the shield  13  of the receptacle  10  in an oblique direction so as to abut the exterior section  230  of the shield  23  of the plug  20  when the plug  20  has been inserted into the receptacle  10 . The second abutment portion  134  is configured to be elastically deformed by abutment with the exterior section  230  of the shield  23  of the plug  20  when the plug  20  has been inserted into the receptacle  10 . Such second abutment portion  134  is formed by cutting the metal plate material of the shield  23  into a channel shape and folding inward a portion surrounded by the cutting line. The folding line of the second abutment portion  134  is provided on the side closer to the tip section  131  and the second abutment portion  134  is opened on the side closer to the first board  2 . 
     Referring to  FIGS.  8  to  10   , the first and second abutment portions  232  and  134  are positioned at intervals around the entire exterior section  230  of the shield  23  of the plug  20  and around the entire interior section  130  of the shield  13  of the receptacle  10 . In particular, the plurality of first abutment portions  232  and the plurality of second abutment portions  134  are positioned so that the first abutment portions  232  can be arranged alternately with the second abutment portions  134  in a peripheral direction of the exterior section  230  of the shield  23  and the interior section  130  of the shield  13  when the plug  20  has been inserted into the receptacle  10 . That is, the board-to-board connector  13  exhibits a relative positional relationship between the first abutment portions  232  and the second abutment portions  134  such that they can be displaced from each other in the peripheral direction and be away from each other without overlapping when the plug  20  has been inserted into the receptacle  10 . The interval between the adjacent first and second abutment portions  232  and  134  can be decided according to the frequency band of the EMI noise to be shielded by the shields  13  and  23 . 
     Fourth Embodiment 
       FIG.  11    shows a single-row type board-to-board connector  1 C according to the fourth embodiment of the present application. The board-to-board connector  1 C has common characteristics with the board-to-board connector  1  of the above-described first embodiment, and a detailed description of these common characteristics will be omitted. The following is a detailed description of different characteristics of the board-to-board connector  1 C as compared to the board-to-board connector  1  of the first embodiment. 
     As shown in  FIG.  11   , a rectangular loop-shaped recess  110 ′ is formed on the receptacle housing  11  instead of the outer rectangular-loop shaped recess no and the inner rectangular shaped recess  111  shown in  FIGS.  1  to  3   . On the other hand, the plug housing  21  comprises a peripheral portion  211 ′ insertable into the recess  110 ′ of the receptacle housing  11 . 
     In more detail, the receptacle housing  11  comprises the bottom portion  112 , the outer peripheral portion  113 , and an inner wall portion  114 ′ which define the recess  110 ′. The inner wall portion  114 ′ has an approximately rectangular shape and is located inside the outer peripheral portion  113  with an approximately rectangular-cylindrically shaped space. That is, the outer peripheral portion  113  and the inner wall portion  114 ′ define the rectangular loop-shaped recess  110 ′ therebetween. The inner wall portion  114 ′ projects from a central site of the bottom portion  112  in a direction away from the first board  2 . The inner wall portion  114 ′ is arranged in the same orientation as the outer peripheral portion  113 . The inner wall portion  114 ′ has substantially the same height as the outer peripheral portion  113 . The bottom portion  112  of the receptacle housing  11  is provided with one opening  115  which is vertically formed therethrough. The opening  115  is located between one of the long side walls  113   a  of the outer peripheral portion  113  and the inner wall portion  114 ′. The plurality of signal contact elements  12  of the receptacle  10  are installed in the inner wall portion  114 ′ of the receptacle housing  11 . The plurality of signal contact elements  12  of the receptacle  10  are arranged at equal intervals in the longitudinal direction of the board-to-board connector  1 C and form a single row. The contact section  120  of the signal contact elements  12  extends along one of the opposed side surfaces, a tip surface, and the other of the opposed side surfaces of the inner wall portion  114 ′ of the receptacle housing  11 . 
     The opposed long side walls  211   a  and the opposed short side walls  211   b  of the peripheral portion  211 ′ define a rectangular-shaped recess  213 ′ therebetween. The plurality of signal contact elements  22  of the plug  20  are installed in one of the opposed long side walls  211   a  of the peripheral portion  211 ′. The plurality of signal contact elements  22  of the plug  20  are arranged at equal intervals in the longitudinal direction of the board-to-board connector  1 C and form a single row. The contact section  220  of the signal contact elements  22  is positioned within the recess  213 ′ of the plug housing  21 . 
     Due to the board-to-board connector  1 ,  1 A,  1 B, or  1 C, the shielding performance in the connector  1 ,  1 A,  1 B, or  1 C can be improved. As the result, a leakage of EMI noise generated by the signal contact elements  12  and  22  of the receptacle  10  and the plug  11  can be eliminated or reduced, and interference between the EMI noise and an RF signal in the electronic device such as a smartphone can be eliminated or reduced. Accordingly, a device in which the connector  1 ,  1 A,  1 B, or  1 C is mounted can improve antenna performance and can be adaptable to high speed signal transmission. 
     The number of rows of the plurality of signal contact elements of the receptacle and the plug can be appropriately changed, and the plurality of signal contact elements may form three rows or more. In addition, the shield of the receptacle and the shield of the plug may be in direct contact with each other continuously in the entire perimeter of the connector. 
     Although preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions, and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.