Abstract:
Disclosed is a radiant heat printed circuit board, which has improved heat-radiating properties and reliability, and a method of fabricating the same.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2007-0044101, filed May 7, 2007, entitled “Radiant heat printed circuit board and fabricating method of the same”, which is hereby incorporated by reference in its entirety into this application. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates, in general, to a radiant heat printed circuit board and a method of fabricating the same, and more particularly, to a radiant heat printed circuit board that has improved heat-radiating properties and reliability and to a method of fabricating the same. 
         [0004]    2. Description of the Related Art 
         [0005]    Generally, a printed circuit board (PCB) has a plurality of conductive patterns designed to comprise a predetermined circuit pattern, and thus, high-temperature heat is generated by the conductive pattern and the mounted or embedded devices. 
         [0006]    However, when heat of a predetermined level or more is generated by the mounted or embedded devices, circuit errors, including operational failure or breakage of the circuit, occur. In order to dissipate heat generated by the mounted or embedded devices, a PCB in which an aluminum core is inserted into the center thereof has been proposed. 
         [0007]    The PCB, in which the aluminum core is inserted into the center thereof is fabricated through the method shown in  FIGS. 1A to 1D . 
         [0008]      FIGS. 1A to 1D  are sectional views illustrating the process of fabricating the radiant heat PCB according to a conventional technique. 
         [0009]    As illustrated in  FIG. 1A , prepared is a PCB  100 , in which an insulating layer  104 , a copper clad laminate (CCL) having inner circuit patterns  112  on both sides thereof, and a single-sided CCL (RCC) having a copper foil  110  on one side thereof are sequentially laminated on each of both surfaces of an aluminum core  102  for dissipating heat generated by the devices mounted on or embedded in the PCB. 
         [0010]    After the preparation of the PCB  100 , a via hole  114  is formed through the PCB using a CNC drill, as illustrated in  FIG. 1B . 
         [0011]    The via hole  114  functions to electrically connect the upper portion of the PCB  100  to the lower portion thereof. 
         [0012]    After the formation of the via hole  114 , deburring is conducted to remove burrs on the copper foil, dust particles on the inner wall of the via hole, dust on the copper foil, and fingerprints, generated upon drilling. 
         [0013]    Subsequently, desmearing is conducted to remove smears attached to the inner wall of the via hole caused by melting of the resin constituting the PCB, for example, the insulating layer  104  laminated on both surfaces of the aluminum core  102 , the insulating layer  106  of the CCL  106 ,  112  having the insulating layer  106  and the inner circuit patterns  112  on both sides thereof, and the insulating layer  108  of the RCC  108 ,  110  having the insulating layer  108  and the copper foil  110  on one side thereof, attributable to heat generated by the drill bit upon drilling. 
         [0014]    After the desmearing is conducted, an electroless copper plating layer  116  and a copper electroplating layer  118  are formed on the inner wall of the via hole  114  and the copper foil  110  through electroless copper plating and copper electroplating, as illustrated in  FIG. 1C . 
         [0015]    After the formation of the electroless copper plating layer  116  and the copper electroplating layer  118 , a dry film (not shown) is applied on the copper electroplating layer  118 , after which the portion of the dry film, other than the portion of the dry film that covers the portion of the copper electroplating layer corresponding to an outer circuit pattern, is removed through exposure and development. 
         [0016]    Subsequently, the portion of the copper electroplating layer  118  from which the dry film is removed, and the electroless copper plating layer  116  and the copper foil  110 , corresponding thereto, are removed using an etchant, thus forming the outer circuit pattern  120 , as illustrated in  FIG. 1D . 
         [0017]    After the formation of the outer circuit pattern  120 , the dry film remaining on the outer circuit pattern  120  is removed. 
         [0018]    However, the method of fabricating the radiant heat PCB according to the conventional technique is disadvantageous because smears are removed using a polishing agent and water or by spraying water into the via hole  114  using a high-pressure washer, and thus the degree of removal thereof is decreased, so that the subsequently formed electroless copper plating layer is not efficiently formed on the inner wall of the via hole, undesirably decreasing the reliability of the PCB. 
         [0019]    Further, the method of fabricating the radiant heat PCB according to the conventional technique is disadvantageous because the acid or alkali used in the electroless copper plating melts the aluminum core  102 , which is weakly resistant thereto, and thus the electroless copper plating layer is not efficiently formed on the inner wall of the via hole where the aluminum core  102  is located, so that the upper portion of the PCB is not electrically connected to the lower portion thereof, undesirably decreasing the reliability of the PCB. 
       SUMMARY OF THE INVENTION 
       [0020]    Accordingly, the present invention provides a radiant heat PCB, which has improved heat-radiating properties and reliability, and a method of fabricating the same. 
         [0021]    According to the present invention, a radiant heat PCB may include an aluminum core; a plurality of insulating layers laminated on both surfaces of the aluminum core; an inner circuit pattern formed between the insulating layers; an outer circuit pattern formed on the outermost insulating layer; a via hole formed through the aluminum core and the plurality of insulating layers; and a nickel plating layer formed on the aluminum core exposed to the inner wall of the via hole to protect the aluminum core exposed to the inner wall of the via hole. 
         [0022]    In addition, a method of fabricating a radiant heat PCB may include a) preparing a PCB, in which a first insulating layer, a CCL having a second insulating layer and inner circuit patterns on both sides thereof, and a single-sided CCL having a third insulating layer and a copper foil on one side thereof are sequentially laminated on each of both surfaces of an aluminum core; b) forming a via hole through the PCB; c) removing smears from the inner wall of the via hole using plasma; d) forming a nickel plating layer on the aluminum core exposed to the inner wall of the via hole; and e) forming an outer circuit pattern on the third insulating layer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIGS. 1A to 1D  are sectional views sequentially illustrating the process of fabricating a radiant heat PCB, according to a conventional technique; 
           [0024]      FIG. 2  is a sectional view illustrating the radiant heat PCB, according to the present invention; and 
           [0025]      FIGS. 3A to 3E  are sectional views sequentially illustrating the process of fabricating a radiant heat PCB, according to the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    Hereinafter, a detailed description will be given of the preferred embodiments of the present invention, with reference to the appended drawings. 
         [0027]      FIG. 2  is a sectional view illustrating the radiant heat PCB, according to the present invention. 
         [0028]    With reference to  FIG. 2 , the radiant heat PCB, according to the present invention, includes an aluminum core  12 , first insulating layers  14 , second insulating layers  16 , third insulating layers  18 , inner circuit patterns  22 , outer circuit patterns  34 , a via hole  24 , and a nickel plating layer  30 . 
         [0029]    The aluminum core  12  is inserted into the center of the PCB to thus dissipate heat generated by the devices mounted on or embedded in the PCB, and is used as a ground. 
         [0030]    The first insulating layer  14  is laminated on each of both surfaces of the aluminum core  12  and thus functions to electrically disconnect the aluminum core  12  from the exterior. 
         [0031]    The second insulating layer  16  is laminated on the first insulating layer  14 , and functions to electrically disconnect the inner circuit patterns  22 , formed on both sides thereof, from each other. 
         [0032]    Specifically, the second insulating layer  16  electrically disconnects the inner circuit pattern  22  formed thereon from the inner circuit pattern  22  formed thereunder. 
         [0033]    The third insulating layer  18  is laminated on the second insulating layer  16 , and functions to electrically disconnect the outer circuit pattern  34 , formed on the outermost layer of the PCB, from the inner circuit pattern  22 . 
         [0034]    The via hole  24  is formed through the aluminum core  12 , the first insulating layers  14 , the second insulating layers  16 , and the third insulating layers  18 , in order to electrically connect the upper portion of the PCB to the lower portion thereof. 
         [0035]    The nickel plating layer  30  is formed on the aluminum core  12  exposed to the inner wall of the via hole  24  so that the aluminum core  12 , exposed to the inner wall of the via hole  24 , is prevented from being melted when an electroless copper plating layer is formed. 
         [0036]      FIGS. 3A to 3E  sequentially illustrate the process of fabricating the radiant heat PCB, according to the present invention. 
         [0037]    As illustrated in  FIG. 3A , prepared is a PCB, in which the fist insulating layer  14 , the CCL having the second insulating layer  16  and the inner circuit patterns  22  on both sides thereof, and the single-sided CCL (RCC) having the third insulating layer  18  and the copper foil  20  on one side thereof are sequentially laminated on each of both surfaces of the aluminum core  12 . 
         [0038]    As the first insulating layer  14 , a prepreg is used, and, as the second insulating layer  16  and the third insulating layer  18 , FR-4, in which glass fiber is impregnated with epoxy resin, is mainly used. 
         [0039]    Here, the PCB  10  may be formed through one of the three methods mentioned below. 
         [0040]    The first method follows. 
         [0041]    The CCL, including the insulating layer  16  and the copper foils on both sides thereof, is prepared. 
         [0042]    Thereafter, a dry film (not shown) is applied on the copper foil of the CCL, after which the portion of the dry film, other than the portion of the dry film that covers the portion of the copper foil corresponding to the inner circuit pattern  22 , is removed through exposure and development. 
         [0043]    After the removal of the dry film, the portion of the copper foil from which the dry film is removed is etched using an etchant. 
         [0044]    Accordingly, the inner circuit pattern  22 , which is the portion of the copper foil on which the dry film remains, is formed on both sides of the second insulating layer  16 . 
         [0045]    After the formation of the inner circuit pattern  22 , the dry film remaining on the inner circuit pattern  22  is removed. 
         [0046]    Subsequently, the fist insulating layer  14 , the CCL having the second insulating layer  16  and the inner circuit patterns  22  on both sides thereof, and the RCC having the third insulating layer  18  and the copper foil on one side thereof are sequentially formed on each of both surfaces of the aluminum core  12 , and are then heated and compressed using a press, thus forming the PCB  10 . 
         [0047]    In addition to the formation of the inner circuit pattern  22  using only the copper foil, the inner circuit pattern  22  may be formed by forming the electroless copper plating layer and the copper electroplating layer on the copper foil and then applying the dry film. 
         [0048]    Specifically, the second method of forming the PCB  10  includes forming the electroless copper plating layer and the copper electroplating layer on the copper foil laminated on both sides of the second insulating layer  16  and then applying the dry film on the copper electroplating layer. 
         [0049]    The subsequent procedure is conducted in the same manner as in the first method, including applying the dry film on the copper foil to form the inner circuit pattern  22 , thus forming the inner circuit pattern  22 . After the formation of the inner circuit pattern  22 , the fist insulating layer  14 , the CCL having the second insulating layer  16  and the inner circuit patterns  22  on both sides thereof, and the RCC having the third insulating layer  18  and the copper foil  20  on one side thereof are sequentially formed on each of both surfaces of the aluminum core  12 , and are then heated and compressed using a press, thereby forming the PCB  10 . 
         [0050]    In addition, the inner circuit pattern  22  may be formed by forming the electroless copper plating layer and the copper electroplating layer on both sides of the second insulating layer  16  and then applying the dry film. 
         [0051]    Specifically, the third method of forming the PCB  10  includes forming the electroless copper plating layer and the copper electroplating layer on both sides of the second insulating layer  16  and then applying the dry film on the copper electroplating layer. 
         [0052]    The subsequent procedure is conducted in the same manner as in as the first method, including applying the dry film on the copper foil to form the inner circuit pattern  22 , thus forming the inner circuit pattern  22 . After the formation of the inner circuit pattern  22 , the fist insulating layer  14 , the CCL having the second insulating layer  16  and the inner circuit patterns  22  on both sides thereof, and the RCC having the third insulating layer  18  and the copper foil  20  on one side thereof are sequentially formed on each of both surfaces of the aluminum core  12 , and are then heated and compressed using a press, thereby forming the PCB  10 . 
         [0053]    Alternatively, the PCB  10  may be formed by sequentially forming, on each of both surfaces of the aluminum core  12 , the fist insulating layer  14 , the CCL having the second insulating layer  16  and the inner circuit patterns  22  on both sides thereof, the third insulating layer  18 , and the copper foil  20 , and then heating and compressing them using a press. 
         [0054]    After the preparation of the PCB  10 , the via hole  24  is formed through the PCB  10  using a CNC drill, as illustrated in  FIG. 3B . 
         [0055]    The via hole  24  plays a role in electrically connecting the upper portion of the PCB  10  to the lower portion thereof. 
         [0056]    After the formation of the via hole  24 , deburring is conducted to remove burrs on the copper foil, dust particles on the inner wall of the via hole, dust on the copper foil, and fingerprints, generated upon drilling. 
         [0057]    Thereafter, smears attached to the inner wall of the via hole  24  caused by melting of the resin constituting the PCB, for example, the first insulating layer  14 , the second insulating layer  16 , and the third insulating layer  18 , attributable to heat generated by the drill bit upon drilling, are removed using plasma, composed of nitrogen, CF4 and oxygen. 
         [0058]    Because plasma decomposes and removes the smears, the smears attached to the inner wall of the via hole  24  are completely removed using plasma. 
         [0059]    After the removal of the smears, the nickel plating layer  30  is formed on the aluminum core  12  exposed to the inner wall of the via hole  24  through plating, as illustrated in  FIG. 3C . 
         [0060]    The nickel plating layer  30  functions to prevent the aluminum core  12  from being melted by the acid or alkali subsequently used in electroless copper plating. 
         [0061]    After the formation of the nickel plating layer  30 , the electroless copper plating and the copper electroplating are sequentially conducted, thus forming the electroless copper plating layer  26  and the copper electroplating layer  28  on the inner wall of the via hole  24  and the copper foil  20 , as illustrated in  FIG. 3D . 
         [0062]    After the formation of the electroless copper plating layer  26  and the copper electroplating layer  28 , a dry film (not shown) is applied on the copper electroplating layer  28 , after which the portion of the dry film, other than the portion of the dry film covering the portion of the copper electroplating layer corresponding to an outer circuit pattern, is removed through exposure and development. 
         [0063]    Subsequently, the portion of the copper electroplating layer  28  from which the dry film is removed, and the electroless copper plating layer  26  and the copper foil  20 , corresponding thereto, are removed using an etchant, thus forming the outer circuit pattern  34 , as illustrated in  FIG. 3E . 
         [0064]    After the formation of the outer circuit pattern  34 , the dry film remaining on the outer circuit pattern  34  is removed. 
         [0065]    In the radiant heat PCB and the method of fabricating the same according to the present invention, after the formation of the via hole  24 , the smears attached to the inner wall of the via hole  24  are decomposed and removed using plasma, thereby completely removing them. Hence, the subsequent electroless copper plating layer is efficiently formed, consequently increasing the reliability of the PCB. 
         [0066]    In the radiant heat PCB and the method of fabricating the same according to the present invention, after the formation of the via hole  24 , the nickel plating layer  30  is formed on the aluminum core  12  exposed to the inner wall of the via hole  24 , thereby preventing the aluminum core  12  from being melted by the acid or alkali subsequently used in electroless copper plating, so that the electroless copper plating layer  26  and the copper electroplating layer  28  are uniformly formed on the inner wall of the via hole  24 , consequently increasing the reliability of the PCB. 
         [0067]    In the radiant heat PCB and the method of fabricating the same according to the present invention, because the aluminum core  12  is inserted into the center of the PCB, heat generated by the mounted or embedded devices is dispersed into the aluminum core  12 , thus improving heat-radiating properties. 
         [0068]    As described hereinbefore, the present invention provides a radiant heat PCB and a method of fabricating the same. According to the present invention, after a via hole is formed, smears attached to the via hole can be completely removed through decomposition and removal using plasma, so that a subsequent electroless copper plating layer can be efficiently formed, consequently increasing the reliability of the PCB. 
         [0069]    Further, after the formation of the via hole, a nickel plating layer is formed on the aluminum core exposed to the inner wall of the via hole, thus preventing the melting of the aluminum core attributable to an acid or alkali subsequently used in electroless copper plating, so that the electroless copper plating layer and the copper electroplating layer can be uniformly formed on the inner wall of the via hole, consequently increasing the reliability of the PCB. 
         [0070]    Furthermore, because the aluminum core is inserted into the center of the PCB, heat generated by the mounted or embedded device is dispersed in the aluminum core, thus improving heat-radiating properties. 
         [0071]    Although the 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.