Abstract:
A circuit board includes a board part including a pattern portion on one surface thereof, the pattern portion being electrically connected to a semiconductor chip, and an under-fill layer disposed on the board part and exposing the pattern portion to the outside, the under-fill layer flowing to cover the pattern portion by heat generated in mounting the semiconductor chip.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of Korean Patent Application No. 10-2009-0082209 filed on Sep. 1, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a circuit board, a semiconductor package, and a method of manufacturing the same, and more particularly, to a circuit board including a separate under-fill layer, a semiconductor package including the circuit board, and a method of manufacturing the circuit board. 
         [0004]    2. Description of the Related Art 
         [0005]    One of main technique development trends in the semiconductor industry is a reduction in the size of semiconductor devices. 
         [0006]    In order to realize slim and light semiconductor devices, the followings are required: techniques for reducing the sizes of individual mounting components, system-on-chip (SOC) techniques for implementing a plurality of individual devices as a single chip, and techniques for integrating a plurality of individual devices into a single package. 
         [0007]    In general, a semiconductor device is mounted on a circuit board using flip-chip bonding. In this case, a solder ball is mounted on the bottom of the semiconductor device, and this solder ball contacts a connection pad on the surface of the circuit board. Thereafter, heat is applied to the vicinity of the solder ball so as to achieve an electrical connection between the semiconductor device and the connection pad. In addition, a liquid under-fill resin is filled between the semiconductor device and a solder resist layer of the circuit board and then cured (hardened). 
         [0008]    However, an existing under-fill process requires high unit costs, and is susceptible to defects such as the undesired absence of an under-fill portion around a pattern portion placed inside. Therefore, techniques allowing for the omission of such a process are currently in demand. 
       SUMMARY OF THE INVENTION 
       [0009]    An aspect of the present invention provides a circuit board including an under-fill layer formed on a board part, a semiconductor package, and a method of manufacturing the circuit board. 
         [0010]    According to an aspect of the present invention, there is provided a circuit board including: a board part including a pattern portion on one surface thereof, the pattern portion being electrically connected to a semiconductor chip; and an under-fill layer disposed on the board part to expose the pattern portion to the outside, the under-fill layer flowing to cover the pattern portion by heat generated in mounting the semiconductor chip. 
         [0011]    The under-fill layer may be disposed on the board part and includes an opening wider than the pattern portion. 
         [0012]    The under-fill layer may be disposed on the board part and exposes the pattern portion in part. 
         [0013]    The circuit board may further include a solder resist layer disposed between the board part and the under-fill layer to protect a circuit pattern formed in the board part. 
         [0014]    The solder resist layer may include an opening to expose the pattern portion to the outside, and the under-fill layer may include an opening having a size that is equal to or greater than the opening of the solder resist layer. 
         [0015]    According to another aspect of the present invention, there is provided a semiconductor package including: a semiconductor chip including a conductive adhesive attached on a bottom surface thereof; and a circuit board including a board part including a pattern portion on one surface thereof, the pattern portion being electrically connected to the semiconductor chip, and an under-fill layer disposed on the board part and exposing the pattern portion to the outside, the under-fill layer flowing to cover the pattern portion by heat generated in mounting the semiconductor chip. 
         [0016]    The semiconductor package may further include a solder resist layer disposed between the board part and the under-fill layer to protect a circuit pattern formed in the board part. 
         [0017]    The solder resist layer may have an opening to expose the pattern portion to the outside, and the under-fill layer may have an opening having a size that is equal to or greater than the opening of the solder resist layer. 
         [0018]    According to another aspect of the present invention, there is provided a method of manufacturing a circuit board, the method including: forming a pattern portion on a top surface of a board part; forming an under-fill layer on the board part to cover the pattern portion by heat generated in mounting a semiconductor chip; and exposing the pattern portion to the outside through the under-fill layer. 
         [0019]    The forming of the pattern portion on the top surface of the board part may include forming a solder resist layer for protecting an upper portion of the pattern portion. 
         [0020]    The exposing of the pattern portion may include forming the under-fill layer using a mask placed on the pattern portion so as to expose the pattern portion to the outside. 
         [0021]    The exposing of the pattern portion may include forming an opening in the under-fill layer by using a laser, corresponding to a location of the pattern portion. 
         [0022]    The exposing of the pattern portion may include forming an opening in the under-fill layer by emitting light thereto, the under-fill layer being formed of a photosensitive material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0024]      FIG. 1  is a cross-sectional view illustrating a circuit board according to an exemplary embodiment of the present invention; 
           [0025]      FIGS. 2A through 2C  are cross-sectional views for explaining a method of manufacturing a semiconductor package according to an exemplary embodiment of the present invention; 
           [0026]      FIGS. 3A through 3D  are cross-sectional views for explaining a method of manufacturing a circuit board according to an exemplary embodiment of the present invention; 
           [0027]      FIGS. 4A through 4C  are cross-sectional views for explaining a method of manufacturing a circuit board according to another exemplary embodiment of the present invention; and 
           [0028]      FIGS. 5A through 5C  are cross-sectional views for explaining a method of manufacturing a circuit board according to another exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0029]    Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. 
         [0030]    In the drawings, like reference numerals in the drawings denote like elements. 
         [0031]    A circuit board, a semiconductor package and a method of manufacturing a circuit board will now be described in detail with reference to  FIGS. 1 through 5C . 
         [0032]      FIG. 1  is a cross-sectional view illustrating a circuit board according to an exemplary embodiment of the present invention. 
         [0033]    Referring to  FIG. 1 , a circuit board  100  may include a board part  110 , a solder resist layer  120  and an under-fill layer  130 . 
         [0034]    Pattern portions  112  are provided on the surface of the board part  110  for an electrical connection with a semiconductor chip (see  200  in  FIGS. 2A through 2C ). The board part  110  may utilize an organic board, a ceramic board employing low-temperature co-fired ceramics, or the like. 
         [0035]    In addition, the solder resist layer  120  and the under-fill layer  130  may be placed sequentially on the board part  110  around the pattern portions  112 . The board part  110  may be manufactured using a plurality of layers, and a circuit pattern may be provided in order to electrically connect the plurality of layers. 
         [0036]    The solder resist layer  120  is provided on the surface of the board part  110  in the vicinity of the pattern portions  112  so as to expose the pattern portions  112 . 
         [0037]    The solder resist layer  120  serves for the alleviation of thermal stress as well as for electrical insulation, and may be formed of an insulating material containing a polymer. The solder resist layer  120  may be formed of an insulating material containing a photosensitive polymer in order to allow for the exposure of the pattern portions  112  to the outside. The insulating material may be selectively subjected to light-exposure and development to thereby expose the pattern portions  112  to the outside. 
         [0038]    Although this embodiment includes the solder resist layer  120 , the present invention is not limited to the description and the solder resist layer  120  may be omitted. 
         [0039]    The under-fill layer  130  is disposed on the solder resist layer  120 , and may have the same size as the solder resist layer  120 . Thus, like the solder resist layer  120 , the under-fill layer  130  may also be provided, exposing the pattern portions  112 . 
         [0040]    The under-fill layer  130  serves to enhance bonding strength with the semiconductor chip against external impact. 
         [0041]    Therefore, the under-fill layer  130  is formed of a polymer having fluidity, so that the under-fill layer  130  flows to the exposed pattern portions  112  when heated in the process of mounting the semiconductor chip  200 . 
         [0042]    According to this embodiment, the under-fill layer  130  is automatically melted and flows toward the pattern portions  112  at the time of mounting the semiconductor chip on the circuit board. Consequently, a reflow process that is performed after injecting a separate under-fill material is omitted, thereby simplifying the manufacturing process and thus enhancing productivity. 
         [0043]    Moreover, according to this embodiment, the under-fill layer  130 , formed in the vicinity of the pattern portions  112 , flows to an empty area in the circuit board  100  during thermal processing to thereby completely fill the empty area. Accordingly, a defect such as the undesired absence of the under-fill layer  130  in the board part  110  can be prevented. 
         [0044]      FIGS. 2A through 2C  are cross-sectional views illustrating a semiconductor package according to an exemplary embodiment of the present invention. 
         [0045]    Referring to  FIGS. 2A through 2C , a semiconductor package may include a semiconductor chip  200  and the circuit board. 
         [0046]    The semiconductor chip  200  is connected onto a board part  110 , and may include solder balls  210  formed of a conductive adhesive and mounted on the bottom of the semiconductor chip  200 . The solder balls  210  on the bottom of the semiconductor chip  200  are spaced apart from each other, corresponding to the locations of the pattern portions  112  of the board part  110 . 
         [0047]    The circuit board may include the board part  110 , a solder resist layer  120  and an under-fill layer  130 , and detailed description thereof may be omitted since it has the same construction as in the above-described construction. 
         [0048]    Referring to  FIG. 2A , the semiconductor chip  200  is disposed on the board part  110  with its solder balls  210  corresponding to the pattern portions  112  of the circuit board  100 . 
         [0049]    Referring to  FIG. 2B , the semiconductor chip  200  and the board part  110  are made to contact each other so that the solder balls  210  of the semiconductor chip  200  contact the pattern portions  112  of the board part  110 , respectively. 
         [0050]    Thereafter, heating is performed to thereby melt the solder balls  210  of the semiconductor chip  200  and cause them to contact the pattern portions  112  for an electrical connection therebetween. At this time, by this heating, the under-fill layer  130  is also melted and flows towards the pattern portions  112  as shown in  FIG. 2C . 
         [0051]    That is, the under-fill layer on the board part  110  is automatically melted in the process of mounting the semiconductor chip  200 , and flows toward the pattern portions  112 . This allows for the omission of a reflow process that is performed after the injection of a separate under-fill material. Accordingly, the semiconductor package of this embodiment can be manufactured using simpler processes with higher productivity. 
         [0052]      FIGS. 3A through 3D  are cross-sectional views for explaining a method of manufacturing a circuit board according to an exemplary embodiment of the present invention. 
         [0053]    As shown in  FIG. 3A , the method of manufacturing the circuit board  100  may include forming pattern portions  112  on the top surface of a board part  110 . 
         [0054]    As shown in  FIG. 3B , a solder resist layer  120  is formed on the board part  110  to cover the pattern portions  112 . Here, the solder resist layer  120  may be formed of a glass material. 
         [0055]    After the solder resist layer  120  is formed on the pattern portions  112 , as shown in  FIG. 3C , an under-fill layer  130  of a polymer material may be disposed on the solder resist layer  120 . 
         [0056]    Subsequently, laser processing (see arrows in  FIG. 3C ) is performed according to the location of the pattern portions  112  and melts the solder resist layer  120  and the under-fill layer  130 . Consequently, as shown in  FIG. 3D , the solder resist layer  120  and the under-fill layer  130  are formed around the pattern portions  112 , exposing the pattern portions  112  entirely. 
         [0057]    However, the present invention is not limited to exposing the pattern portions  112  entirely across the circuit part  110 , and the pattern portions  112  may be partially exposed. 
         [0058]      FIGS. 4A through 4C  are cross-sectional views for explaining a method of manufacturing a circuit board according to another exemplary embodiment of the present invention. 
         [0059]    Referring to  FIG. 4A , the method of manufacturing a circuit board  100  may include forming pattern portions  112  on the top surface of a board part  110 . 
         [0060]    After the pattern portions  112  are formed on the top surface of the board part  110 , a solder resist layer  120  is formed to cover the upper portions of the pattern portions  112  on the board part  110 . 
         [0061]    Here, the solder resist layer  120  may be formed of an insulating layer containing a photosensitive polymer in order to expose the pattern portions  112 . The solder resist layer  120  may be subjected to light-exposure and development processes so as to expose the pattern portions  112  and the vicinity thereof to the outside. 
         [0062]    Subsequently, as shown in  FIG. 4B , a mask M having openings is placed on the solder resist layer  120  for the process of forming an under-fill layer  130 . 
         [0063]    After the solder resist layer  120  is formed on the board part  110 , as shown in  FIG. 4C , an under-fill layer  130  having the same size as the solder resist layer  120  may be provided on the solder resist layer  120  by using a screen-printing process through the openings of the mask M. 
         [0064]    Accordingly, the solder resist layer  120  and the under-fill layer  130  may have openings of the same size in order to expose the pattern portions  112  to the outside. However, the present invention is not limited to the above description, the openings of the under-fill layer  130  may be greater than those of the solder resist layer  120 . 
         [0065]      FIGS. 5A through 5C  are cross-sectional views for explaining a method of manufacturing a circuit board according to another exemplary embodiment of the present invention. 
         [0066]    Referring to  FIG. 5A , the method of manufacturing a circuit board  100  may include forming pattern portions  112  on the top surface of a board part  110 . 
         [0067]    After the pattern portions  112  are formed on the board part  110 , a solder resist layer  120  is formed to cover the upper portions of the pattern portions  112 . 
         [0068]    The solder resist layer  120  may be formed of a photosensitive polymer in order to expose the pattern portions  112 . The solder resist layer  120  may be subjected to light-exposure and development processes to thereby expose the pattern portions  112  and the vicinity of the pattern portions  112 . 
         [0069]    Also, an under-fill layer  130  may be formed in a way that covers the solder resist layer  120  and the pattern portions  112 . A laser is emitted toward the pattern portions  112  (see arrows in  FIG. 5B ) so that the pattern portions  112  and the vicinity thereof are completely exposed. Through the above process, the under-fill layer  130  may be provided only on the solder resist layer  120  as shown in  FIG. 5C . 
         [0070]    In this embodiment, the pattern portions  112  are opened by melting the under-fill layer  130  using a laser process. However, the invention is not limited to the description, and an etching process may be used. 
         [0071]    Accordingly, the method of manufacturing a circuit board according to this embodiment forms the under-fill layer  130  on the board part  110 , thereby simplifying a manufacturing process and thus allowing for the omission of a reflow process performed after an under-fill material is injected. 
         [0072]    Moreover, since the under-fill layer  130  is formed on the board part  110  so as to expose the pattern portions  112  to the outside, the under-fill layer  130  re-flows into each empty area, and thus completely fills such empty areas. Accordingly, the circuit board, the semiconductor package and the method of manufacturing the circuit board, according to this embodiment, can prevent a defect such as the undesired absence of the under-fill layer  130 . 
         [0073]    As set forth above, in the circuit board, the semiconductor package and the method of manufacturing the circuit board according to exemplary embodiments of the invention, a reflow process performed after the injection of a separate under-fill material is omitted since an under-fill layer is formed on a board part, thereby simplifying the manufacturing process thereof. 
         [0074]    In addition, in the circuit board, the semiconductor package and the method of manufacturing the circuit board according to exemplary embodiments, the under-fill layer is formed near each empty area around pattern portions to thereby flow to each empty area during thermal processing. Accordingly, the defect of the undesired random absence of the under-fill layer in the board part can be prevented. 
         [0075]    While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.