Abstract:
A coupling and grounding structure of a plasma display device for grounding a circuit board effectively, and fixing the circuit board stably. The plasma display device includes a plasma display panel having a display area, on which images are displayed; a chassis base coupled to a back surface of the plasma display panel; at least one circuit board, on which at least one electronic element for driving the plasma display panel is mounted, the circuit board having a conductive portion and at least one coupling hole to be coupled to the chassis base by a bolt member penetrating the coupling hole; and at least a conductive member which contacts the conductive portion and the bolt member in the coupling hole.

Description:
CLAIM OF PRIORITY 
   This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C §119 from an application entitled PLASMA DISPLAY DEVICE HAVING STRUCTURES FOR COUPLING AND GROUNDING OF CIRCUIT BOARD earlier filed in the Korean Industrial Property Office on 10 Oct. 2003, and there duly assigned Serial No. 2003-70595 by that Office. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a plasma display panel (PDP), and more particularly, to coupling and grounding structures of a circuit board in a plasma display device. 
   2. Description of the Related Art 
   In general, a plasma display panel (PDP) displays images using gas discharge operations, and has excellent display characteristics such as display capacitry, brightness, contrast, residual image, and viewing angle. Thus, the PDP can substitute for a cathode ray tube (CRT). In the PDP, a discharge occurs in a gas between electrodes due to a direct current (DC) or alternating current (AC) being applied to the electrodes, and phosphors are excited by ultraviolet rays caused by the discharge operation and emit lights. 
   The PDP can be classified into an AC type and a DC type according to a discharge mechanism thereof. The DC type PDP includes the electrodes that are directly exposed in the gas layer filled in discharge cells, and voltage applied to the electrodes is applied to the discharge gas layer. In addition, in the AC type PDP, electrodes are separated by both the discharge gas layer and a dielectric layer, the electrodes do not absorb charged particles generated in the discharge operation to form wall charges, and the discharge operation is performed using the wall charge. 
   In the general PDP, the panel is attached to a chassis base while interposing a heat-radiation sheet having thermal conductivity. In addition, a circuit board, on which a plurality of electronic elements are mounted, is coupled to a boss that is formed on the chassis base. The circuit board is coupled to the boss using bolts by arranging a plurality of coupling holes that are formed on the circuit board with the boss. Therefore, the bolts must be coupled tightly. 
   I have determined that in such a case, the circuit board may be damaged or distorted due to the bolts being over tightened. Additionally, the bolts may be loosened during thermal distortion or vibration of the circuit board. Accordingly, the grounding is performed poorly. Also, if the grounding of the circuit board is performed poorly, current and voltage noises cannot be controlled effectively, and electromagnetic interference (EMI) characteristics will be lowered. 
   SUMMARY OF THE INVENTION 
   The present invention provides a plasma display device having coupling and grounding structures that can effectively ground a circuit board, and stably fix the circuit board to a chassis of the plasma display device. 
   According to an aspect of the present invention, there is provided a plasma display device including: a chassis base coupled to a back surface of a plasma display panel having a display area; at least a circuit board, on which at least one electronic element for driving the plasma display panel is mounted, including a conductive portion and at least one coupling hole to be coupled to the chassis base by a bolt member penetrating the coupling hole; and at least a conductive member which contacts the conductive portion and the bolt member in the coupling hole. 
   According to another aspect of the present invention, there is provided a plasma display device including: a chassis base coupled to a back surface of a plasma display panel having a display area; at least a circuit board, on which at least one electronic element for driving the plasma display panel is mounted, including a conductive portion and at least one coupling hole to be coupled to the chassis base by a bolt member penetrating the coupling hole; and at least a conductive member that contacts the conductive portion and the bolt member and has a guide unit inserted into a portion of the chassis base, to which the circuit board is coupled. The chassis base further includes a coupling recess corresponding to the guide unit on the portion where the circuit board is coupled. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the present invention, and many of the attendant advantages thereof, will become readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
       FIG. 1  is a partially exploded perspective view showing an example of a coupling structure of a circuit board and a boss unit; 
       FIG. 2  is a cross-sectional view showing the structure of  FIG. 1 ; 
       FIG. 3  is an exploded perspective view showing a plasma display device according to the principles of the present invention; 
       FIG. 4  is a perspective view showing a coupling structure of a circuit board and a chassis base according to a first embodiment according to the principles of the present invention; 
       FIG. 5  is a cross-sectional view showing the structure of  FIG. 4 ; 
       FIG. 6  is a perspective view showing a coupling structure of a circuit board and a chassis base according to a second embodiment according to the principles of the present invention; 
       FIG. 7  is a cross-sectional view showing the structure of  FIG. 6 ; 
       FIG. 8  is a cross-sectional view showing a modified example of the structure shown in  FIG. 6 ; 
       FIG. 9  is a perspective view showing a coupling structure of a circuit board and a chassis base according to a third embodiment according to the principles of the present invention; 
       FIG. 10  is a cross-sectional view showing the structure of  FIG. 9 ; 
       FIG. 11  is a perspective view showing a coupling structure of a circuit board and a chassis base according to a fourth embodiment according to the principles of the present invention; 
       FIG. 12  is a cross-sectional view showing the structure of  FIG. 11 ; 
       FIG. 13  is a perspective view showing a coupling structure of a circuit board and a chassis base according to a fifth embodiment according to the principles of the present invention; 
       FIG. 14  is a cross-sectional view showing the structure of  FIG. 13 ; 
       FIG. 15  is a cross-sectional view showing a modified example of the structure shown in  FIG. 13 ; and 
       FIGS. 16 through 19  are cross-sectional views showing the coupling structures of different embodiments according to the principles of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Shown in  FIG. 1  is a plurality of soldering units  42  for grounding formed around a coupling hole  41  for bolt member  5 . Circuit board  4  is grounded to a chassis base  3  through a boss  31  as shown in  FIGS. 1 and 2 . 
   The soldering units  42  penetrate circuit board  4  as shown in  FIG. 2 . In general, the circuit board  4  has a multi-layered structure, and a plurality of circuit ground wires  43  are built-in the cross section of the board. The soldering units  42  penetrate the ground wires  43 , and upper end portions of the soldering units  42  are exposed on outer upper side of the circuit board  4 . 
   As shown in  FIG. 2 , the head of the coupling bolt member  5  contacts the soldering units  42  to form a ground. That is, the ground wires  43  of the circuit board  4  are grounded to the chassis base  3  through the soldering units  42  and the bolt member  5 . 
   In the above grounding structure, however, since the soldering units  42  protrude on the upper surface of the circuit board  4 , the bolt member  5  should be coupled to the soldering units  42  tightly in order to ground the soldering units  42 . If the bolt member  5  is coupled to the soldering units  42  loosely, the bolt member  5  may not contact some of the soldering units  42 . Therefore, the bolt member  5  must be coupled tightly. In this case, the circuit board  4  may be damaged or distorted, and thus the bolt member  42  may be loosened during thermal distortion or vibration of the circuit board  4 . Accordingly, the grounding is performed poorly. In addition, if the grounding of the circuit board  4  is performed poorly, current and voltage noises cannot be reduced effectively, and electromagnetic interference (EMI) characteristics may be lowered. 
     FIG. 3  is a partially exploded perspective view showing a plasma display device according to an embodiment of the present invention. 
   Referring to  FIG. 3 , the plasma display device of the present invention includes a plasma display panel (PDP)  1  having a first substrate  11  and a second substrate  12  formed of a transparent glass material. The PDP  1  is fixedly attached to a chassis base  3 , and a heat radiation sheet  2  that is formed of a thermal conductive material may further be disposed between the PDP  1  and the chassis base  3 . In addition, at least one or more circuit boards  6 , on which various electronic elements for driving the PDP  1  are mounted, are coupled to the chassis base  3 . The PDP  1  coupled to the chassis base  3  is received in an additional case (not shown), and a filter member may be further coupled to a front surface of the PDP  1 . 
   In the present invention, the PDP  1  can be any type of PDP, for example, an alternating current (AC) type surface discharge PDP can be used as the PDP  1 . 
   On the other hand, the circuit board  6  that is coupled to the chassis base  3  includes at least one or more coupling holes  61 . In addition, bolt members  7  penetrate the coupling holes  61  to be coupled to chassis base  3 , and accordingly, the circuit board  6  is fixedly coupled to the chassis base  3 . 
   In an embodiment of the present invention, the chassis base may include boss units  31  corresponding to the coupling holes  61 , and the bolt members  7  can be coupled to the boss units  31 . However, the coupling structure is not limited to above described structure, and any type of structure can be used if it fixes the circuit board  6  by coupling the bolt members  7  to the chassis base  3 . 
   In addition, it is desirable that the bolt member  7  is formed of a conductive material for grounding the circuit board  6 . Also, various kinds of coupling members can be used, for example, a rivet can be used as the coupling member instead of bolt member  7 . 
   On the other hand, as shown in  FIGS. 4 and 5 , the bolt member  7  is coupled to the circuit board  6  after interposing an additional conductive member  8  therebetween. The conductive member  8  can be formed of a conductive material such as aluminum, and nickel can be plated on the surface of the conductive member  8  for reinforcing the strength. In addition, according to the present invention shown in  FIGS. 4 and 5 , the conductive member  8  includes a ground portion  81  that is inserted through a slot  6   a  into the circuit board  6  in a thickness direction thereof, and a supporting portion  82   a  that surrounds the coupling hole  61 . 
   The circuit board  6  can be formed in a multi-layered structure, and a conductive portion  63  is disposed on each layer. The conductive portion  63  should be completely grounded onto the chassis base  3  to reduce current noise and voltage noise of the plasma display device, and to prevent the operating errors. 
   Therefore, as shown in  FIG. 5 , the additional conductive member  8  can be disposed for the grounding. The conductive member  8  is formed as a flat plate as shown in  FIG. 4 , and includes a grounding portion  81  on an end portion thereof so that the grounding portion  81  is inserted into the circuit board  6  in the thickness direction thereof and contacts the conductive portions  63  in the circuit board  6 . The supporting portion  82   a  is formed to surround the coupling hole  61  on a portion corresponding to the coupling hole  61 . The supporting portion  82   a  is also formed by perforating a hole, having a smaller diameter than that of the coupling hole  61 , through the conductive member  8  of plate type, and a circumferential portion of the hole is bent during a burring operation so as to form a bent portion  82   b  that engages and is inserted into the coupling hole  61 . In addition, the bolt member  7  is coupled to the supporting portion  82   a  and coupled to the boss unit  31 . 
   When the conductive member  8  of plate type and the grounding portion  81  disposed on the end portion of the conductive member  8  are inserted into the circuit board  6  according to the present invention, the total area that the conductive portion  63  of the circuit board  6  and the bolt member  7  are in contact can be increased, thus the grounding can be performed completely. Also, when the bolt member  7  is coupled to the boss unit  31 , the bolt member  7  and the supporting portion  82   a  can have an increased area of contact, thus the force exerted by tightening bolt member  7  can be evenly distributed which lowers pressure exerted on circuit board  6  at coupling hole  61 . Accordingly, the distortion or damage of the circuit board  6  can be prevented, and the bolt member  7  is not loosened. 
     FIGS. 6 and 7  show a conductive member according to another embodiment of the present invention, the conductive member  8  includes a first conductive member  83  that is coupled on the upper surface of the circuit board  6 , and a second conductive member  84  that is disposed on a lower surface of the circuit board  6 , that is, a surface facing the chassis base  3 . 
   The conductive member  8  including the first and second conductive members  83  and  84  also electrically connects the conductive portion  63  of the circuit board  6  and the bolt member  7  in order to perform a grounding. 
   As shown in  FIGS. 6 and 7 , the first conductive member  83  and the second conductive member  84  can be connected at end portions thereof. Therefore, the conductive member  8  can be formed to be longer than that of  FIGS. 4 and 5 , and bent around the coupling hole  61  of the circuit board  6  to form the connected first and second conductive members  83  and  84 . 
   The first and second conductive members  83  and  84  also respectively include first and second grounding portions  83   a  and  84   a  that are inserted through slot  6   a  into the circuit board  6  in the thickness direction of the circuit board, and first and second supporting portions  83   b  and  84   b  that surround and extend into the coupling hole  61 . 
   When the conductive member  8  is formed to have the first and second conductive members  83  and  84 , the area of contact between the circuit board  6  and the conductive portion  63  increases, and thus improve the grounding capacity. In addition, since the first and second conductive members  83  and  84  are connected to each other, the distortion of the circuit board  6  can be limited when the bolt member  7  couples the circuit board  6  to chassis  3 . 
   The structure including the first and second conductive members  83  and  84  is not limited to the above described structure, and the first and second conductive members  83  and  84  may not be connected to each other, as shown in  FIG. 8 . 
   Alternatively, as shown in  FIGS. 9 and 10 , in a state where the first and second conductive members  83  and  84  are connected to each other, the first conductive member  83  can include a penetration grounding portion  85  that is inserted into the coupling hole  61  and extends nearly all the way through coupling hole  61 . The penetration grounding portion  85  is formed to contact conductive portion  63  at the inner surface of the coupling hole  61  to increase the contacting area of the circuit board  6  with the conductive member  8 . Accordingly, the grounding reliability of the circuit board  6  to the chassis base  3  can be improved more. Since the first and second conductive members  83  and  84  are connected to each other, the distortion of the circuit board  6  can be prevented more effectively. 
     FIGS. 11 and 12  show a conductive member  8  according to still another embodiment of the present invention. As shown in  FIGS. 11 and 12 , the conductive member  8  can be formed as a conductive tube  86 , an outer circumferential surface of which contacts the inner surface of the coupling hole  61 . In this case, an outer diameter of the conductive tube  86  is formed to be slightly less than an inner diameter of the coupling hole  61 . In addition, a length of the conductive tube  86  is formed to be equal to the thickness of the circuit board  6 . 
   Accordingly, the conductive tube  86  electrically contacts the conductive portion  63  of the circuit board  6  through the inner surface of the coupling hole  61 , and an upper portion or a lower portion of the conductive tube  86  contacts the bolt member  7  and is grounded to the chassis base  3 . Therefore, the grounding area is increased by the conductive tube  86 , and the distortion of the circuit board  6  is eliminated to reduce the risk of the bolt member  7  of being loosened. 
   As shown in  FIGS. 13 and 14 , the conductive tube  86  may include a flat portion, hereafter, flange portion  86   a , on a portion contacting the head of bolt member  7 . The flange portion  86   a  can be formed by expanding an upper portion of the tube  86  and bending the expanded portion. The flange portion  86   a  can increase the area of contact between the circuit board  6  and the bolt member  7 , and the bolt member  7  can be coupled to the circuit board  6 . 
   The conductive tube  86  can further include a second flange portion  86   b  on an opposite end of tube  86  from flange portion  86   a , flange portion  86   b  contacting to boss unit  31  of the chassis base  3  as shown in  FIG. 15 . The flange portion  86   b  can be formed by elongating the conductive tube  86 , expanding the upper and lower portions of the tube  86 , and bending the expanded portions, characterized in that the outer surface area of tube  86  between flange portions  86   a  and  86   b  is equal to the thickness of circuit board  6 . When the flange portions are formed on both end portions of conductive tube  86 , the contacting area of the conductive tube  86   b  with bolt member  7  and boss unit  31  increases the grounding efficiency of the circuit board  6  and coupling the bolt member  7  while reducing the risk of distorting the circuit board  6 . 
   On the other hand, according to the present invention, a guide unit that is inserted into the boss  31  of chassis base  3  can be further formed on a portion of the conductive member  8 , which is coupled to the chassis base  3 , and a coupling recess corresponding to the guide unit can be formed in boss  31  on the coupling portion of the chassis base  3  so that the circuit board  6  and the chassis base  3  can be coupled to each other more firmly. 
   That is, as shown in  FIG. 16 , as compared to  FIG. 5 , it is desirable that a guide unit  87  extends from the supporting portion  82   a  that surrounds the coupling hole  61 , and a coupling recess  32  is formed in the boss unit  31  so as to correspond to the guide unit  87  in the structure of the conductive member  8 . Note that the upper surface of boss  31  remains in contact with a bottom surface of circuit board  6  to ensure a tight fit. 
   An embodiment of the invention in  FIG. 17 , as compared to the embodiment shown in  FIG. 10 , shows a guide unit  87   b  can be formed by bending an extended portion of the second conductive member  84 . In this case, coupling recess  32  in boss  31  is provided corresponding to the guide unit  87   b.    
   In addition, an embodiment of the invention in  FIG. 18 , as compared to the embodiment shown in  FIG. 12 , shows a guide unit  87   c  can be formed by extending an end portion of the conductive tube  86 , which faces the boss unit  31 , and inserting the guide unit  87   c  into the coupling recess  32  of the boss unit  31 . 
   Further, an embodiment of the invention in  FIG. 19 , as compared to the embodiment shown in  FIG. 14 , shows a guide unit  87   d  can be formed by extending an end portion of the conductive tube  86 , which faces the boss unit  31 , and inserting the guide unit  87   d  into the coupling recess  32  of the boss unit  31 . 
   The structures of the guide unit and the coupling recess can be applied to all embodiments of the present invention. The conductive member can be fixedly coupled to the boss unit due to the guide unit and the coupling recess, and the coupling position of the conductive member can be set accurately. 
   According to the plasma display device of the present invention, the grounding area of the circuit board can be increased by adopting the conductive member, thus the current and voltage noises or erroneous operations caused by the ground defects can be prevented. 
   In addition, the connecting structure between the circuit board and the chassis base can be formed fixedly. Since the distortion of the circuit board due to pressure by the bolt member can be prevented, and the bolt member will not accidentally loosen. 
   In addition, the mounting position of the circuit board can be known easily. 
   While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.