Abstract:
A Printed Circuit (PC) board module is structured such that heat generated by an Integrated Circuit (IC) device can be sufficiently radiated to the outside. The PC board module includes: a first PC board having a first conductive ground pad arranged therein; a plurality of via holes contained within the first PC board and positioned below the first ground pad; a plurality of conductive via lines contained within the plurality of via holes; a second PC board arranged below the first PC board; and a second conductive ground pad arranged on the second PC board and contacting the plurality of via lines.

Description:
CLAIM OF PRIORITY 
       [0001]    This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C.§119 from an application for PRINTED CIRCUIT BOARD MODULE WITH IMPROVED HEAT RADIATION EFFICIENCY earlier filed in the Korean Intellectual Property Office on 8 Mar. 2007 and there duly assigned Serial No. 10-2007-0023096. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a Printed Circuit (PC) board module, and more particularly, the present invention relates to a PC board module with improved heat radiation efficiency. 
         [0004]    2. Description of the Related Art 
         [0005]    Several thousands to several millions of circuit elements, such as transistors, capacitors, and resistors, are formed in an Integrated Circuit (IC) device. The IC device performs various functions as the circuit elements transmit or receive signals. The IC device can process more signals as more circuit elements are formed in the IC device. 
         [0006]    An IC device generates more heat during operation as the amount of signal processing increases or when an operating voltage increases, thereby making the operation of internal circuit elements of the IC device unstable, and in serious cases, causing a malfunction of the internal circuit elements. 
         [0007]    In particular, when an IC device mounted on a PC board generates a large amount of heat, other circuit elements may be affected by the IC device, and thus, a PC board module may be discarded as being defective. Thus, in order to stabilize a PC board module, it is necessary to sufficiently radiate heat generated by an IC device mounted on a PC board. 
         [0008]    Therefore, various attempts have been made to sufficiently radiate heat generated by an IC device mounted on a PC board. However, a more effective method is needed. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention provides a PC board module which is structured such that heat generated by an IC device on the PC board can be sufficiently radiated to the outside. 
         [0010]    According to one aspect of the present invention, a Printed Circuit (PC) board module is provided, the module including: a first PC board having a conductive first ground pad arranged thereon; a plurality of via holes arranged within the first PC board and positioned below the first ground pad; a plurality of conductive via lines contained within the plurality of via holes; a second PC board arranged below the first PC board; and a second conductive ground pad arranged on the second PC board and contacting the plurality of via lines. 
         [0011]    The PC board module may further include an Integrated Circuit (IC) device arranged on the first ground pad. The IC device may include an IC chip therein, and the PC board module may further include a ground plate attached to a lower surface of the IC chip and connected to a ground terminal of the IC chip, a lower surface of the ground plate being exposed outside of the IC device. The ground plate may be attached to the first ground pad with an adhesive. The adhesive may include a conductive adhesive. 
         [0012]    The plurality of via lines may be electrically connected to the first ground pad and the second ground pad. 
         [0013]    The PC board module may further include an intermediate insulator interposed between the first PC board and the second PC board to insulate the first PC board from the second PC board. The PC board module may further include a plurality of other via lines contained within the intermediate insulator to electrically connect the plurality of via lines arranged within the first PC board to the second ground pad. 
         [0014]    The intermediate insulator may include a Pressure Conductive Rubber (PCR), and a portion of the intermediate insulator may become conductive when pressed. 
         [0015]    The first ground pad may have a wider area than that of the IC device. 
         [0016]    According to another aspect of the present invention, a Printed Circuit (PC) board module is provided, the module including: a PC board having a conductive first ground pad arranged thereon; a plurality of via holes contained within the PC board and positioned below the first ground pad; a plurality of conductive via lines contained within the plurality of via holes; and a second ground pad arranged below the PC board and contacting the plurality of via lines. 
         [0017]    The first ground pad may have a wider area than that of the second ground pad. 
         [0018]    The plurality of via lines may include solder. 
         [0019]    The PC board module may further include an Integrated Circuit (IC) device arranged on the first ground pad. The IC device may include an IC chip therein, and the PC board module may further include a ground plate attached to a lower surface of the IC chip and connected to a ground terminal of the IC chip, a lower surface of the ground plate being exposed outside of the IC device. The ground plate may be attached to the first ground pad with a conductive adhesive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    A more complete appreciation of the present invention and many of the attendant advantages thereof, will be readily apparent as the present invention 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: 
           [0021]      FIG. 1  is a sectional view of a PC board module according to an embodiment of the present invention; 
           [0022]      FIG. 2  is a plan view of the PC board module of  FIG. 1 ; 
           [0023]      FIG. 3  is a plan view of the PC board module of  FIG. 1  from which an IC device has been removed; 
           [0024]      FIG. 4  is a sectional view of an IC device of  FIG. 1 ; 
           [0025]      FIG. 5  is a sectional view of a PC board module according to another embodiment of the present invention; 
           [0026]      FIG. 6  is a sectional view of a PC board module according to still another embodiment of the present invention; 
           [0027]      FIG. 7  is a sectional view of a PC board module according to yet another embodiment of the present invention; and 
           [0028]      FIG. 8  is a sectional view of a structure wherein an insulating layer is attached to a lower surface of a PC board of  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0029]    The present invention is described more fully below with reference to the accompanying drawings, in which exemplary embodiments of the present invention are shown. The same reference numerals refer to the same constitutional elements throughout the specification. 
         [0030]      FIG. 1  is a sectional view of a PC board module according to an embodiment of the present invention,  FIG. 2  is a plan view of the PC board module of  FIG. 1 , and  FIG. 3  is a plan view of the PC board module of  FIG. 1  from which an IC device has been removed. 
         [0031]    Referring to  FIGS. 1 through 3 , a PC board module  101  includes a first PC board  111 , a second PC board  121 , an intermediate insulator  131 , and an IC device  141 . 
         [0032]    The first PC board  111  includes a first substrate  113 , a first metal line portion  115 , a first ground pad  117 , and a plurality of via lines  119 . 
         [0033]    The first substrate  113  is made of an insulating material, e.g., a ceramic or resin. 
         [0034]    The first metal line portion  115  is disposed on the first substrate  113 . The first metal line portion  115  includes a plurality of metal lines  115   a  and  115   b . The metal lines  115   a  and  115   b  are made of a conductive material, e.g., copper. The metal lines  115   a  and  115   b  electrically connect circuit devices (not shown) mounted on the first substrate  113 , including the IC device  141 . 
         [0035]    The first ground pad  117  is disposed on the first substrate  113 . The first ground pad  117  is made of the same material as the metal lines  115   a  and  115   b , e.g., copper. The first ground pad  117  may have various shapes. Preferably, the first ground pad  117  may have the same tetragonal shape as the IC device  141 . The IC device  141  is mounted on the first ground pad  117 . The first ground pad  117  reinforces the heat radiation and grounding efficiencies of the IC device  141 . 
         [0036]    The IC device  141  contains an IC chip therein (see  411  of  FIG. 4 ). Heat coming from the IC device  141  is substantially generated by the IC chip. When the PC board module  101  operates, the IC device  141  operates. Heat is generated by the IC device  141 . The heat generated by the IC device  141  is transmitted to the first ground pad  117 . The first ground pad  117  has a wider area than the IC device  141 . That is, when the IC device  141  is mounted on the first ground pad  117 , the first ground pad  117  is partially exposed out of the IC device  141 . As such, since the first ground pad  117  is partially exposed out of the IC device  141 , heat transmitted to the first ground pad  117  from the IC device  141  is radiated into the air. Thus, the IC device  141  is protected from thermal damage. However, when a large amount of heat is generated by the IC device  141 , the first ground pad  117  alone cannot timely radiate all of the heat generated by the IC device  141 . In this case, a second ground pad  127  disposed on the second PC board  121  reinforces the heat radiation efficiency of the IC device  141 . 
         [0037]    When the IC device  141  is mounted on the first ground pad  117 , a ground plate (see  431  of  FIG. 4 ) of the IC device  141  is connected to the first ground pad  117 . As such, when the ground plate of the IC device  141  is connected to the first ground pad  117 , a grounding area of the IC device  141  is increased, thereby enhancing the grounding efficiency of the IC device  141 . 
         [0038]    The via lines  119  are disposed below the first ground pad  117 . In order to form the via lines  119 , a plurality of via holes are formed in the first substrate  113  to be positioned below the first ground pad  117  and are then filled with a conductive material, e.g., solder or copper. 
         [0039]    The intermediate insulator  131  is made of an insulating material and is interposed between the first PC board  111  and the second PC board  121 . Thus, the first PC board  111  and the second PC board  121  are electrically insulated by the intermediate insulator  131 . A plurality of via lines  133  are formed in the intermediate insulator  131 . That is, a plurality of via holes are formed in the intermediate insulator  131  in such a manner that they correspond to the via lines  119  formed in the first substrate  113 , and are then filled with a conductive material so as to form the via lines  133  in the intermediate insulator  131 . 
         [0040]    The second PC board  121  includes a second substrate  123 , a second metal line portion  125 , and the second ground pad  127 . 
         [0041]    The second substrate  123  is made of an insulating material, e.g., a ceramic or resin. 
         [0042]    The second metal line portion  125  is disposed on the second substrate  123  and is comprised of a plurality of metal lines  125   a  and  125   b . The metal lines  125   a  and  125   b  are made of a conductive material, e.g., copper. The second metal line portion  125  can be electrically connected to the first metal line portion  115  via other via lines (not shown) formed in the first substrate  113 . The second metal line portion  125  is not required but is optional. 
         [0043]    The second ground pad  127  is disposed on the second substrate  123 . The second ground pad  127  is arranged to vertically correspond to the first ground pad  117 . The second ground pad  127  is made of the same material as the metal lines  125   a  and  125   b  of the second metal line portion  125 , e.g., copper. The second ground pad  127  may have various shapes. Preferably, the second ground pad  127  may have a similar shape to the first ground pad  117 . 
         [0044]    As described above, when the second ground pad  127  is electrically connected to the first ground pad  117 , an area for heat radiation of the IC device  141  is increased. That is, heat generated by the IC device  141  is transmitted to the first ground pad  117  and the second ground pad  127  via the via lines  119  and  133 , and is then rapidly radiated into the air. Thus, even when a large amount of heat is generated by the IC device  141 , all of the heat is radiated into the air via the first ground pad  117  and the second ground pad  127  without affecting the operation of the IC device  141 . Therefore, it is possible to protect the IC device  141  from thermal damage. 
         [0045]    Moreover, when the second ground pad  127  is electrically connected to the first ground pad  117 , a grounding area of the IC device  141  extends to the first ground pad  117  and the second ground pad  127 . That is, the grounding area of the IC device  141  is enlarged. As the grounding area of the IC device  141  increases, the grounding efficiency of the IC device  141  is significantly enhanced. Thus, when an external surge voltage is applied to a ground terminal of the IC device  141 , both the first ground pad  117  and the second ground pad  127  can absorb the surge voltage, thereby preventing damage to the IC device  141  due to the surge voltage. 
         [0046]    The IC device  141  includes a plurality of leads  143  protruding outward, and the leads  143  are connected to the first metal line portion  115 . Thus, the IC device  141  transmits/receive signals to/from circuit elements (not shown) disposed on the first metal line portion  115 . The IC device  141  is attached to the first ground pad  117  with an adhesive  151  (e.g., epoxy). Thus, the IC device  141  is electrically connected to the first ground pad  117 . The adhesive  151  is conductive. The structure of the IC device  141  is described in more detail below with reference to  FIG. 4 . 
         [0047]      FIG. 4  is a sectional view of the IC device  141  of  FIG. 1 . 
         [0048]    Referring to  FIG. 4 , the IC device  141  includes an IC chip  411  therein, and the IC chip  411  is sealed by a molding material  421 . The molding material  421  is an insulator. A plurality of electrode pads  413  are formed on the IC chip  411 . The electrode pads  413  are connected to one end of each of a plurality of leads  143  via bonding metal lines  451 . A ground plate  431  is attached to a lower surface of the IC chip  411 . The ground plate  431  is attached to the IC chip  411  with an adhesive  441 . The ground plate  431  is conductive. A lower surface of the ground plate  431  is exposed out of the IC device  141 . The ground plate  431  is connected to a ground terminal of the IC chip  411 . 
         [0049]    As described above, when the ground plate  431  is connected to the lower surface of the IC chip  411 , the grounding efficiency of the IC chip  411  is reinforced. Moreover, since the ground plate  431  is exposed out of the IC device  141 , heat generated by the IC chip  411  is radiated out of the ground plate  431 , thereby protecting the IC chip  411  from thermal damage. 
         [0050]    The heat radiation effect is more significant, in particular, when the IC chip  411  is a regulator or a Central Processing Unit (CPU) that generates a large amount of heat during operation. 
         [0051]    The leads  143  are connected to the IC device  141 . However, a plurality of other connectors, e.g., a plurality of bumps or conductive balls, may be substituted for the leads  143 . 
         [0052]    The structure of the IC device  141  can be changed. 
         [0053]      FIG. 5  is a sectional view of a PC board module according to another embodiment of the present invention. 
         [0054]    Referring to  FIG. 5 , a PC board module  501  includes a plurality of PC boards  111 ,  511 ,  521 , and  121 , a plurality of intermediate insulators  131  and  531 , and an IC device  141 . That is, the PC board module  501  is different from the PC board module  101  of  FIG. 1  in that the PC boards  511  and  521  are further interposed between the PC boards  111  and  121 . The intermediate insulators  131  and  531  are interposed between the PC boards  111 ,  511 ,  521 , and  121  to electrically insulate the PC boards  111 ,  511 ,  521 , and  121 . The intermediate insulators  131  and  531  are as described above with reference to  FIG. 1 . 
         [0055]    As described above, as the number of stacked PC boards increases, the heat radiation and grounding efficiencies of an IC device are further enhanced. That is, the heat radiation and grounding efficiencies of an IC device are enhanced proportionally to an increase in the number of stacked PC boards. 
         [0056]      FIG. 6  is a sectional view of a PC board module according to still another embodiment of the present invention. 
         [0057]    Referring to  FIG. 6 , a PC board module  601  includes a first PC board  111 , a second PC board  121 , an intermediate insulator  611 , and an IC device  141 . The PC board module  601  is different from the PC board module  101  of  FIG. 1  only in terms of the intermediate insulator  611  and a plurality of protrusions  621 . Thus, in order to avoid overlapping descriptions, the current embodiment of the present invention is described below only in terms of the intermediate insulator  611  and the protrusions  621 . 
         [0058]    The protrusions  621  are formed to protrude from a lower surface of the first PC board  111 . The protrusions  621  are connected to a plurality of via lines  119  formed in the first PC board  111 . 
         [0059]    The intermediate insulator  611  is interposed between the first PC board  111  and the second PC board  121 . The intermediate insulator  611  is an insulator, but when pressed, pressed portions  631  become conductive. That is, when the intermediate insulator  611  is interposed between the first PC board  111  and the second PC board  121 , the portions  631  of the intermediate insulator  611  are pressed by the protrusions  621 . Thus, the protrusions  621  are electrically connected to a second ground pad  127 . Preferably, the intermediate insulator  611  may be made of Pressure Conductive Rubber (PCR). 
         [0060]    As described above, the intermediate insulator  611  becomes conductive when pressed, and thus, it is not necessary to form a plurality of via lines (see  133  of  FIG. 1 ) in the intermediate insulator  611 . Thus, when one of the first PC board  111  and the second PC board  121  is defective, it is very easy to replace the defective PC board with a new one. That is, according to the current embodiment of the present invention, it is easy to repair a defective PC board module. 
         [0061]      FIG. 7  is a sectional view of a PC board module according to yet another embodiment of the present invention. 
         [0062]    Referring to  FIG. 7 , a PC board module  701  includes a PC board  711  and an IC device  141 . The PC board module  701  is different from the PC board module  101  of  FIG. 1  in that a second ground pad  721  is used instead of the second PC board  121  of  FIG. 1 . Thus, only the second ground pad  721  is described hereinafter. 
         [0063]    The second ground pad  721  is disposed on a lower surface of the PC board  711 . The second ground pad  721  is electrically connected to a plurality of via lines  119 . The second ground pad  721  is made of a conductive material, e.g., copper or lead. The second ground pad  721  may have various shapes, e.g., a tetragonal or circular shape. As the size of the second ground pad  721  increases, the above-described effect can be more efficiently achieved. 
         [0064]    The second ground pad  721  reinforces the heat radiation and grounding efficiencies of the IC device  141  mounted on a first ground pad  117 . That is, heat generated in the IC device  141  is transmitted to the second ground pad  721  via the first ground pad  117  and is then rapidly radiated into the air. Therefore, the IC device  141  can be protected from thermal damage. 
         [0065]    Moreover, due to further installation of the second ground pad  721 , the grounding area of the IC device  141  extends to the first ground pad  117  and the second ground pad  721 . That is, the grounding area of the IC device  141  is enlarged. As the grounding area of the IC device  141  increases, the grounding efficiency of the IC device  141  is significantly enhanced. Thus, an external surge voltage applied to a ground terminal of the IC device  141  is completely absorbed in the first ground pad  117  and the second ground pad  721 , thereby preventing damage to the IC device  141  due to the surge voltage. 
         [0066]      FIG. 8  is a sectional view of the PC board  711  of  FIG. 7  having an insulating layer  811  on a lower surface thereof. Referring to  FIG. 8 , together with  FIG. 7 , the insulating layer  811  is attached to the lower surface of the PC board  711 . Thus, it is possible to protect the second ground pad  721  disposed on a lower surface of the PC board  711  from an ambient environment. 
         [0067]    As described above, according to the present invention, a plurality of via lines are formed in a PC board on which an IC device is mounted, and a plurality of ground pads are connected to the IC device via the via lines. Thus, the heat radiation efficiency of the IC device is significantly enhanced, thereby preventing damage to the IC device due to heat generated in the IC device. 
         [0068]    Moreover, due to the above-described structural characteristics, the grounding area of the IC device is significantly increased. As such, as the grounding area of the IC device increases, an external surge voltage applied to the IC device is completely absorbed in the ground pads. Therefore, it is possible to prevent damage to the IC device due to the surge voltage. 
         [0069]    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 modifications in form and detail may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.