Abstract:
An assembly of a printed circuit board mounted in a housing of a slim portable computer is described. The printed circuit board mounting assembly has a printed circuit board with penetration holes. A boss with a hole having a supporter formed around the circumference of the boss is installed in a housing of the portable computer and inserted into the penetration hole. A cap covering a top surface of the boss protrudes towards the upper side of the printed circuit board through the penetration hole and is in contact with the upper side, and a coupling member fastens to the boss through the cap to secure the printed circuit board to the housing.

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 A Printed Circuit Board Mounting Assemble earlier filed in the Korean Industrial Property Office on Mar. 13, 1999, and there duly assigned Ser. No. 99-8508 by that Office. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a printed circuit board mounting assembly and, more particularly, to a printed circuit board mounting assembly installed in a housing of a thin electrical system such as a portable computer. 
     2. Discussion of Related Art 
     The development of computer technology induced various models of a computer such as a notebook computer, wallet personal computer (PC), personal digital assistant (PDA), and a hand-held personal computer (HPC). Therefore, the scope of usage has rapidly expanded. The computer trend is towards miniaturization and a slim design to allow for portability. 
     In the course of trying to make smaller and thinner portable computers, the space taken to mount a printed circuit board has become a design limitation. The circuit boards such as the main board, also called the motherboard, has key electronics for the function of the portable computer such as a microprocessor or a central processing unit (CPU) that controls the function of the portable computer, disk controllers that control permanent storage, and the random access memory for temporary data storage. A certain amount of space is needed in the housing of the portable computer to mount such a circuit board. As the portable computer becomes thinner, the mounting structures are reduced also and thereby losing some stability in the process. A stable circuit board is very important because if it is not stable then key components of the portable computer may be damaged. 
     Another problem in portable computers has been reducing the noise caused by electromagnetic interference (herein after referred to as “EMI”). Excessive amounts of EMI can affect the electrical functioning of the portable computer and outside electrical devices. Because of the size limitations, special structures that may take up space for reducing the EMI are discouraged. 
     An exemplar of the prior art Ohgami et al. (U.S. Pat. No. 5,689,400, Portable Electronic Apparatus Including Space-saving Component Mounting Features, Nov. 18, 1997) discloses a fairly large bracket that is used to mount the printed circuit board in a portable computer. Annis et al. (U.S. Pat. No. 5,436,803, EMI Shielding having Flexible Conductive Envelope, Jul. 25, 1995) discloses an electrically insulating flexible sheet such as polyethylene with embedded conductive fibers that forms an electromagnetic interference shielding enclosure for a circuit card within a portable computer. Such a structure takes up valuable space. Nakamura et al. (U.S. Pat. No. 5,784,256, Portable Computer having a Circuit Board Including a Heat-Generating IC Chip and a Metal Frame Supporting the Circuit Board, Jul. 21, 1998) discloses raised bosses supported by relatively large supporting walls around part of the bosses. The supporting walls subdivides the portable computer into smaller sections thereby limiting the available surface area needed to include other electrical structures. Nigro, Jr. et al. (U.S. Pat. No. 4,742,478, Housing for a Portable Computer, May 3, 1988) discloses fairly long bosses for mounting printed circuit boards. Lin et al (U.S. Pat. No. 5,036,313, Portable Computer with Improved Assembly Design, July 1991) discusses a portable computer housing assembly. The upper housing is connected to the lower housing using fasteners inserted though a bosses molded on the lower housing. A separate rail molding allowing for the printed circuit board to slide in is used. The rails take up more space needed for electronic parts. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a printed circuit board mounting assembly capable of stably and strongly securing a printed circuit board and smoothly draining noise caused by EMI. 
     It is another object to provide a circuit board mounting structure that is not only very stable but also very small. 
     It is a further object to provide a circuit board mounting assembly that does not take extra space when providing for the draining of the noise caused by the EMI. 
     It is yet another object to provide a mounting structure for a circuit board that can be easily assembled. 
     According to features of the present invention, a circuit board mounting assembly has a printed circuit board that has a penetration hole pierced from the upper side to the lower side of the circuit board. A boss with a hole has a supporter formed around the circumference of the boss which is installed in a housing and inserted into the penetration hole of the circuit board. A cap covering a top surface of the boss is protruding towards the upper side of the printed circuit board through the penetration hole and in contact with the upper side, and a coupling member is fastened to the boss through the cap to secure the printed circuit board to the housing. 
     A conductive paint is coated on a surface of the cap and a metal layer is coated on an upper side of the printed circuit board connected to the cap. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of this invention, and many of the attendant advantages thereof, will be 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 shows a portable computer having a main board mounting assembly; 
     FIG. 2 shows a portable computer having a main board mounting assembly according to the present invention; 
     FIG. 3 is a partially enlarged view of “a” shown in FIG. 2; 
     FIGS. 4A-4B sequentially show a mounting state of a main board in a portable computer according to one embodiment of the invention; 
     FIG. 5 shows a mounting state of a main board in a portable computer according to a second embodiment of the invention; and 
     FIG. 6 shows a mounting state of a main board in a portable computer according to a third embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Now turning to the drawings, referring to FIG. 1, a portable computer  100  has a main body  110  upon which a keyboard  122  is mounted and a display unit  120  in which a liquid crystal display  124  is contained. A variety of printed circuit boards such as a main board  114  are installed in the housing  112  constituting the main body  110 . As shown in FIG. 1, in a mounting assembly of an existing main board, multiple bosses are installed upon a bottom surface  112   a  of the housing  112  in which the main board  114  is installed. In the main board  114 , a penetration hole  115  is formed at a position corresponding to the boss  116 . For example, the main board  116  is mounted upon the housing  112  by placing the main board  114  upon the boss  166  and coupling a screw  118  to the boss  116  through the penetration hole  115 . 
     In the portable computer  100  having such a main board mounting assembly, the height of the bosses  116  are minimized to which the main board is secured. The minimized bosses  116  lower the installation height of the main board  114 . However, coupling the screw  118  to the boss  116  of a low height is not strong, so that the main board  118  is unstably secured. As a result, any minor shock to the computer  100  may lead to the movement of the main board  114  and therefore severe damage to the computer  100 . 
     Further, in the main board mounting assembly, noise caused by electromagnetic interference (EMI) is drained to the housing  112  through the screw  118  contacted with an upper side of the main board  114 . 
     As shown in FIGS. 2 and 3, a portable computer  10  has a main body housing  12 , a display unit  20 , and a main board  30 . 
     The display unit  20  is pivotally coupled to the main body housing  12  by using a hinge assembly  14  in the back of the main body housing  12 . A display screen  16  disposed in front of the display unit  20  may be a display device such as a video monitor or liquid crystal display. 
     The main body housing  12  has a top housing  12   a  and a bottom housing  12   b . In the portable computer  10 , coupling the top housing  12   a  to the bottom housing  12   b  forms an internal space. The main board  30  and various electrical elements are received in the internal space. Examples of the electrical elements are a power supply device such as a battery, storage devices such as a hard disk drive and a floppy disk drive, and a pointing device. 
     Referring to FIGS. 2 and 3 again, the following is the description of a main board mounting assembly according to one embodiment of the invention. A penetration hole  36  is formed in the main board  30 , penetrating from an upper side  32  to a lower side  34  (shown in FIG.  4 A). A metal layer  38 , serving as a ground plate, is adhered to the upper side  32  of the main board  30 . A central processing unit (CPU) is mounted upon the upper side  32  thereof. For example, numerous semiconductor integrated circuit devices may be mounted upon the main board  30 . Multiple bosses  40  may be installed on a bottom surface of the housing  12  in which the main board  30  is installed. The boss  40  is so high that it may protrude through the penetration hole  36  to the upper side  32 . A supporter  42  for supporting the lower side  34  is formed in a periphery of the boss  40 . The boss  40  may have an insert  46  in which a screw hole  46   a  is formed. A cap  50  is coupled to a top surface  44  of the boss  40 . A groove  52  (shown in FIG. 4A) is formed in a bottom surface of the cap  50  so as to cover the top surface  44 . For example, the cap  50  covers the top surface  44  of the boss  40  that is protruding through the penetration hole  36  towards the upper side  32  of the main board  30 . At this time, the lower side  56  of the cap  50  is contacted with the metal layer  38  that is adhered to the upper side  32 . The metal layer  38 , although adhered to the upper side  32 , may be adhered to the lower side  34  contacting with the supporter  42  and an outer surface of the boss  40 , and an inner surface of the penetration hole  36 . The main board  30  is secured to the housing  12  by means of a screw  60  which is coupled to the screw hole  46   a  of the boss  40  through a hole  54  of the cap  50 . Further, a surface of the cap  50  is coated with a conductive paint. It will be understood with the benefit of the invention that surfaces of the housing  12  and the boss  40  are also coated with the conductive paint. For example, noise caused by EMI that is created in the main board  30  is drained from the metal layer  38  through the cap  50  to the housing  12 . 
     One assembly feature of the invention can be described as follows. Although installation height of a main board  30  is not increased, height of a boss  40  may be increased as high as the installation height because the boss is protruding through a penetration hole  36  to the upper side  32  of the main board  30 . 
     Another assembly feature of the invention is to have a cap  50  that covers an upper side  44  of a boss  40  protruding towards a top surface  32  of a main board  30  and presses the top surface thereof while coupling a screw  60 , enabling the main board  30  to be firmly placed on a supporter  42  of the boss  40 . 
     Further another assembly feature of the invention is to smoothly drain noise caused by EMI to a housing because a metal plate adhered to an upper side  32  of a main board  30 , a bottom surface  62   a  of a cap, a boss  40 , and a screw  60  are contacting one another through a wide portion. In this case, the EMI is created in the main board through the contacted wide portion. 
     A method of installing a main board  30  in a bottom housing  12   b  will be described with reference to FIGS. 4A-4B. First, a boss  40  is inserted into a penetration hole  36  of the main board  30  so that a lower side  34  may be placed on a supporter  42  of the boss  40 . A cap  50  covers the upper side  44  of the boss  40  protruding towards the upper side  32  of the main board  30  through the penetration hole  36 . If the screw  60  is then coupled to a screw hole  46   a  of the boss  40  through a hole  54  of the cap  50 , the cap  50  presses the main board  30 . Since the main board  30  is placed on the supporter  42  of the boss  40 , installation height of the main board  30  may maximally be reduced irrespective of the height of the boss  40 . A shorter boss  40  will still be stable. Formed as high as the thickness of the main board  30 , the boss  40  may have a screw hole as deep as such. The screw  60  may strongly be coupled to the boss  40 , and the main board  30  may firmly be secured to the boss  40 . 
     Such a main board mounting assembly of the invention may effectively be applied to, in particular, a slim portable computer. A lower side  56  of the cap  50  is in contact with the metal layer  38  adhered to the upper side  32  of the main board  30 . The cap  50  is in contact with the screw  60  and the upper side  44  of the boss  40 . The screw  60  is in contact with the boss  40 . In this regard, a ground metal plate  38  adhered to the upper side  32  of the main board  30 , the cap  50 , the boss  40 , and the screw  60  are in contact with one another through a wide portion. Accordingly, EMI noise created in a main board may be smoothly drained from the main board  30  through the contacted wide portion  38  to a housing  12 . 
     A main board mounting assembly shown in FIG. 5 is similar to the assembly as described in FIGS. 2 through 4B with one of the differences being the omission of a cap  50  below the head of a screw  60  and the addition of the cap to a head  62  of a screw  60 ′. In the assembly features, the screw  60 ′ has a groove  64  on which an upper side  44  of the boss  40  is located. The head  62  is so wide that a lower side  62   a  may be contacted with the metal layer  38 . If the screw  60 ′ is coupled to a screw hole  46   a  of the boss  40 , an upper side  44  of the boss  40  is inserted into the groove  64 . A lower side  62   a  of the head  62  is in contact with a metal layer  38  adhered to the upper side  32  of the main board  30 . The main board mounting assembly of this embodiment shown in FIG. 5 omits a cap  50  of one embodiment as shown in FIGS. 3 through 4B to improve assembly capability, and reduces coupling height to as much as the thickness of the cap. 
     As shown in FIG. 6, an upper side  44  of a boss  40  is inserted into a penetration hole  36  of a main board  30 . At this time, it is undesirable that the upper side  44  of the boss  40  should be protruding towards the upper side  32  of the main board  30 . A screw  60 ″ is coupled to the boss  40  inserted through the penetration hole  36 . At this time, it is desirable that the screw  60 ″ should use a head  62 ′ of a wide type so as to be in contact with a metal layer  38  of the main board  30 . In a main board mounting assembly according to this embodiment, a boss is not protruding towards an upper side  32  of a main board  30  through a penetration hole  36 . Consequently, the height of coupling a screw  60 ″ with a boss  40  of a portable computer  10  may be reduced as much as the screw  60 ″ itself. 
     Such a main board mounting assembly may effectively be used in different kinds of computers such as a notebook computer, Wallet PC (personal computer), PDA (personal digital assistant), HPC (hand-held personal computer), and Mobile Computer in which a printed circuit board is installed. 
     Although a boss is not high, a main board can strongly and stably be coupled thereto. Therefore, it is possible to highly minimize installation height of the main board. Further, a ground metal plate adhered to the main board, a cap, a boss, and a screw are in contact with one another through a wide surface area, enabling EMI noise created in the main board to be smoothly drained through the contacted wide portion. As a result, problems related to the EMI noise can be minimized. 
     The invention has been described using exemplary preferred embodiments. However, it is to be understood that the scope of the invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements. The scope of the claims, therefore, should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.