Abstract:
Disclosed herein is a printed circuit board including: a base substrate in which a connection pad is formed; a solder resist layer formed on the base substrate and comprising a trench exposing a surface of the base substrate; and a dam formed on the solder resist layer and burying the inside of the trench.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2012-0154684, filed on Dec. 27, 2012, entitled “Printed Circuit Board and Method of Manufacturing the Same”, which is hereby incorporated by reference in its entirety into this application. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field The present invention relates to a printed circuit board and a method of manufacturing the same. 
         [0003]    2. Description of the Related Art 
         [0004]    As electronic devices have been recently thin, small size, and highly functional, a packaging technology of loading electronic devices on substrates requires high density mounting, and accordingly, a mounting technology of a chip scale package form appears. 
         [0005]    In a case where an electronic device is mounted on a printed circuit board, a connection between the printed circuit board and the electronic device is reinforced by filling a gap formed between the electronic device and the printed circuit board with an underfill so as to secure connection reliability of the electronic device (U.S. Pat. No. 8,039,761). In a case where such an underfill is liquid resin and is injected into the gap between the printed circuit board and the electronic device, a predetermined amount of the underfill is ejected to a peripheral portion. 
         [0006]    However, since the electronic device tends to be mounted on the printed circuit board at high density and a circuit pattern tends to be formed at high density according to a recent development of the electronic device, in a case where the underfill is ejected to an approaching connection pad or circuit pattern, the connection pad or the circuit pattern is contaminated, which causes a defective product. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention has been made in an effort to provide a printed circuit board that forms a dam having an enhanced adhesion and a method of manufacturing the same. 
         [0008]    According to a first preferred embodiment of the present invention, there is provided a printed circuit board including: a base substrate in which a connection pad is formed; a solder resist layer formed on the base substrate and comprising a trench exposing a surface of the base substrate; and a dam formed on the solder resist layer and burying the inside of the trench. 
         [0009]    A roughness may be formed in an upper portion of the solder resist layer and an inner wall of the trench. 
         [0010]    The surface of the base substrate exposed by the trench may expose at least one of an insulation layer and a circuit pattern of the base substrate. 
         [0011]    The solder resist layer may further include an opening portion exposing the connection pad to the outside. 
         [0012]    The printed circuit board may further include: a bump formed on the connection pad. 
         [0013]    The printed circuit board may further include: an electronic device mounted on the bump. 
         [0014]    The printed circuit board may further include: underfill resin injected between the electronic device and the base substrate. 
         [0015]    An upper portion of the dam may be formed in a semispherical shape. 
         [0016]    According to a second preferred embodiment of the present invention, there is provided a method of manufacturing a printed circuit board, the method including: providing a base substrate in which a connection pad is formed; forming a solder resist layer comprising a trench exposing a surface of the base substrate on the base substrate; and forming a dam on the solder resist layer and burying the inside of the trench. 
         [0017]    The forming of the solder resist layer may include: stacking the solder resist layer on the base substrate; and removing the solder resist layer from a location at which the dam is to be formed and forming the trench exposing the surface of the base substrate. 
         [0018]    The method may further include: after the forming of the solder resist layer, forming a bump on the connection pad. 
         [0019]    The method may further include: before the forming of the bump, forming an opening portion in the solder resist layer so as to allow the connection pad to be exposed to the outside. 
         [0020]    The method may further include: after the forming of the solder resist layer, forming a roughness in an upper portion of the solder resist layer and an inner wall of the trench. 
         [0021]    In the forming of the roughness, the roughness may be formed using a plasma polishing method or a chemical polishing method. 
         [0022]    In the forming of the dam, the dam may be formed by filling and curing the inside of the trench with dam ink. 
         [0023]    The method may further include: after the forming of the bump, mounting an electronic device on the bump. 
         [0024]    The method may further include: injecting underfill resin between the electronic device and the base substrate. 
         [0025]    In the forming of the dam, the dam ink may be filled inside the trench using an inkjet printing method. 
         [0026]    An upper portion of the dam may be formed in a semispherical shape. 
         [0027]    In the forming of the solder resist layer, the surface of the base substrate exposed by the trench may expose at least one of an insulation layer and a circuit pattern of the base substrate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
           [0029]      FIG. 1  is an exemplary view of a printed circuit board according to an embodiment of the present invention; 
           [0030]      FIGS. 2 through 8  are exemplary views for explaining a method of manufacturing a printed circuit board according to an embodiment of the present invention; 
           [0031]      FIG. 9  is an exemplary view of a printed circuit board in which a dam is formed according to an embodiment of the prior art; 
           [0032]      FIG. 10  is an exemplary view of a printed circuit board in which a dam is formed according to another embodiment of the prior art; and 
           [0033]      FIG. 11  is an exemplary view of a printed circuit board in which a dam is formed according to an embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]    The objects, features and advantages of the present invention will be more clearly understood from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant descriptions thereof are omitted. Further, in the following description, the terms “first”, “second”, “one side”, “the other side” and the like are used to differentiate a certain component from other components, but the configuration of such components should not be construed to be limited by the terms. Further, in the description of the present invention, when it is determined that the detailed description of the related art would obscure the gist of the present invention, the description thereof will be omitted. 
         [0035]    Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. 
         [0036]    Printed Circuit Board 
         [0037]      FIG. 1  is an exemplary view of a printed circuit board  100  according to an embodiment of the present invention. 
         [0038]    Referring to  FIG. 1 , the printed circuit board  100  may include a base substrate  110 , a solder resist layer  130 , a dam  150 , a bump  140 , and underfill resin  170 . 
         [0039]    The base substrate  110  may be usually complex polymer resin used as an interlayer insulation material. For example, the printed circuit board  100  may be manufactured to be thinner by employing prepreg as the base substrate  110 . Alternatively, a fine circuit may be easily implemented by employing an Ajinomoto build up film (ABF) as the base substrate  110 . In addition, the base substrate  110  may use epoxy based resin such as FR-4, Bismaleimide Triazine (BT), etc., but is not particularly limited thereto. A copper clad laminate (CCL) may be used as the base substrate  110 . 
         [0040]    In the present embodiment, the base substrate  110  may include the connection pad  120 . The connection pad  120  may be an element that is electrically connected to an external electronic device  160 . The connection pad  120  may be formed of electrically conductive metal. A circuit layer such as a circuit pattern (not shown) and a via (not shown) as well as the connection pad  120  may be formed on the base substrate  110 . 
         [0041]    Meanwhile, although the base substrate  110  is configured as a single layer in  FIG. 1 , the present invention is not limited thereto. That is, the base substrate  110  may be a build-up layer consisting of an insulation layer and a circuit layer of a multilayer or a monolayer and the via. 
         [0042]    The solder resist layer  130  may be formed on the base substrate  110 . The solder resist layer  130  may be formed so as to prevent the circuit layer from being damaged during soldering for mounting the electronic device  160  on the base substrate  110 . 
         [0043]    An opening portion  135  and a trench  131  may be formed in the solder resist layer  130 . The opening portion  135  may be formed in an upper portion of the connection pad  120 . The opening portion  135  may allow the connection pad  120  to be exposed from the solder resist layer  130 . 
         [0044]    The trench  131  may be formed passing through the solder resist layer  130 . The trench  131  may allow a surface of the base substrate  110  to be exposed from the solder resist layer  130 . An area of the base substrate  110  exposed by the trench  131  may be the insulation layer formed of the interlayer insulation material. Alternatively, the area of the base substrate  110  exposed by the trench  131  may be the circuit layer formed of the electrically conductive metal. Alternatively, the trench  131  may concurrently expose the insulation layer and the circuit layer of the base substrate  110 . The trench  131  may be formed outside of the connection pad  120  to surround the connection pad  120 . That is, the trench  131  may be formed to surround the outside of the electronic device  160  that will be mounted later. 
         [0045]    Also, a roughness may be formed in a surface of the solder resister layer  130 . That is, the roughness may be formed in both an upper portion of the solder resist layer  130  and an inner wall of the trench  131 . 
         [0046]    The dam  150  may be formed inside the trench  131  and the upper portion of the solder resist layer  130 . The dam  150  is an element to prevent underfill resin  170  injected between the electronic device  160  that will be mounted later and the base substrate  110  from being ejected to the outside. The dam  150  may be formed outside the printed circuit board  100 . For example, the dam  150  may be formed outside the electronic device  160  that will be mounted later to surround the electronic device  160 . The dam  150  may be formed of a solder resist material. The dam  150  may be formed by filling and hardening the trench  131  with dam ink using an inkjet printing method. The dam  150  formed using the inkjet printing method may have a hemispherical shape with an upper portion convex and curved. 
         [0047]    The bump  140  may be formed on the connection pad  120 . That is, the bump  140  may be formed on the connection pad  120  exposed from the solder resist layer  130 . The electronic device  160  may be mounted on the bump  140 . The bump  140  may bond the connection pad  120  and the electronic device  160  and electrically connect the connection pad  120  and the electronic device  160 . 
         [0048]    The underfill resin  170  may be injected between the electronic device  160  and the base substrate  110 . The underfill resin  170  may function as an adhesive agent for fixing the electronic device  160  to the printed circuit board  100 . The underfill resin  170  may function as protecting the electronic device  160  and the printed circuit board  100  from an external shock. 
         [0049]    According to an embodiment of the present invention, the dam  150  may be formed by forming the trench  131  that passes through the solder resist layer  130  and burying the inside of the trench  131 . In this regard, the roughness may be formed on the upper portion of the solder resist layer  130  and the inner wall of the trench  131 . The dam  150  is formed in this way, and thus a bonding area between the dam  150 , the solder resist layer  130 , and the base substrate  110  may be maximized. That is, the bonding area between the dam  150  and the printed circuit board  100  is maximized, and thus reliability may be also enhanced. 
         [0050]    Method of Manufacturing Printed Circuit Board 
         [0051]      FIGS. 2 through 8  are exemplary views for explaining a method of manufacturing the printed circuit board  100  according to an embodiment of the present invention. Referring to  FIG. 2 , the base substrate  110  may be provided. The base substrate  110  may be usually complex polymer resin used as an interlayer insulation material. For example, the printed circuit board  100  may be manufactured to be thinner by employing prepreg as the base substrate  110 . Alternatively, a fine circuit may be easily implemented by employing an Ajinomoto build up film (ABF) as the base substrate  110 . In addition, the base substrate  110  may use epoxy based resin such as FR-4, Bismaleimide Triazine (BT), etc., but is not particularly limited thereto. A copper clad laminate (CCL) may be used as the base substrate  110 . 
         [0052]    In the present embodiment, the base substrate  110  may include the connection pad  120 . The connection pad  120  may be an element that is electrically connected to an external electronic device ( 160  of  FIG. 8 ). The connection pad  120  may be formed of electrically conductive metal. A circuit layer such as a circuit pattern (not shown) and a via (not shown) as well as the connection pad  120  may be formed on the base substrate  110 . 
         [0053]    Meanwhile, although the baser substrate  110  is configured as a single layer in  FIG. 2 , the present invention is not limited thereto. That is, the base substrate  110  may be a build-up layer consisting of an insulation layer and a circuit layer of a multilayer or a monolayer and the via. Referring to  FIG. 3 , the solder resist layer  130  may be formed on the base substrate  110 . The solder resist layer  130  may be formed to surround the connection pad  120  formed in the base substrate  110 . 
         [0054]    Referring to  FIG. 4 , the trench  131  and the an opening portion  135  may be formed in the solder resist layer  130 . The trench  131  may be formed passing through the solder resist layer  130 . That is, the base substrate  110  may be exposed in a lower surface of the trench  131 . In this regard, an area of the base substrate  110  exposed by the trench  131  may be the insulation layer formed of the interlayer insulation material. Alternatively, the area of the base substrate  110  exposed by the trench  131  may be the circuit layer formed of the electrically conductive metal. Alternatively, the trench  131  may concurrently expose the insulation layer and the circuit layer of the base substrate  110 . The trench  131  may be formed outside of the connection pad  120  to surround the connection pad  120 . That is, the trench  131  may be formed to surround the outside of the electronic device  160  that will be mounted later. 
         [0055]    The opening portion  135  may be formed in an upper portion of the connection pad  120 . The opening portion  135  may expose the connection pad  120  to form a space in which the bump  140  is to be formed later. 
         [0056]    The trench  131  and the opening portion  135  may be separately or concurrently formed. For example, the trench  131  and the opening portion  135  may be formed by performing exposure and developing operations. Alternatively, the trench  131  and the opening portion  135  may be formed by using laser. That is, a method of forming the trench  131  and the opening portion  135  is not limited to a specific method, and may be easily selected by one of ordinary skill in the art from the well-known technologies. 
         [0057]    Referring to  FIG. 5 , the bump  140  may be formed. The bump  140  may be formed on the connection pad  120 . The bump  140  may be generally formed as a solder. The bump  140  may be formed by inserting a solder paste or a solder ball in the opening portion  135  of the solder resist layer  130  and performing a reflow. The bump  140  may function as electrically connecting the connection pad  120  and the electronic device ( 160  of  FIG. 8 ) that will be mounted later. 
         [0058]    Referring to  FIG. 6 , a roughness  137  may be formed in the solder resister layer  130 . The roughness  137  may be formed by performing plasma etching or chemical etching on a surface of the solder resist layer  130 . The roughness  137  may be concurrently formed an inner wall of the trench  131  as the roughness  137  is formed in the surface of the solder resist layer  130 . 
         [0059]    Referring to  FIG. 7 , the dam  150  may be formed. The dam  150  may be formed by coating the inside of the trench  131  with dam ink. The dam ink may be formed of a liquid solder resist material. The dam ink may be coated using an inkjet printing method. In this regard, the dam ink may bury the inside of the trench  131  and concurrently may be formed to protrude from an upper portion of the solder resist layer  130  at a predetermined height. The dam  150  may be formed by hardening the coated dam ink. The dam  150  formed using the inkjet printing method may have a hemispherical shape with an upper portion convex and curved. The above-formed dam  150  may be bonded to the surface of the solder resist layer  130  and the inner wall of the trench  131  in which the roughness  137  is formed. The dam  150  may be also bonded to at least one of the insulation layer and the circuit layer that are the surface of the base substrate  110 . In this regard, the roughness  137  may be formed in the insulation layer or the circuit layer that is bonded to the dam  150 . A bonding area between the dam  130  according to the embodiment of the present invention and the printed circuit board  100  may be maximized. 
         [0060]    The dam  150  is bonded to the printed circuit board  100  in which the roughness  137  is formed at the maximum, which prevents the dam  150  from being detached, thereby enhancing reliability. 
         [0061]    Referring to  FIG. 8 , the electronic device  160  may be mounted. The electronic device  160  may be mounted on the bump  140 . The electronic device  160  may be bonded to the printed circuit board  100  through the bump  140 . The electronic device  160  may be to electrically connected to the connection pad  120  through the bump  140 . The underfill resin  170  may be injected after mounting the electronic device  160  on the bump  140 . The underfill  170  may be injected between the electronic device  160  and the printed circuit board  100 . In this regard, the underfill resin  170  in a liquid state may be prevented from being ejected to the outside owing to the dam  150  formed outside the electronic device  160 . 
         [0062]      FIGS. 9 through 11  are exemplary views for comparing an adhesion test result of a dam. 
         [0063]    The adhesion test of  FIGS. 9 through 11  may be conducted by evaluating a pencil hardness of the dam. The pencil hardness may be evaluated by comparing a hardness ( 9 H to  6 B) of a pencil lead of KS G2603 and a hardness of the dam by using a pencil hardness test equipment. This comparison may be made by scraping the pencil lead against a surface of the dam at an angle of 45 with a uniform load and speed. The stronger the pencil hardness of the dam, the higher the hardness and adhesion of the dam. The pencil hardness may be classified as  9 H,  8 H,  7 H,  6 H,  5 H,  4 H,  3 H,  2 H, H, F, B,  2 B,  3 B,  4 B,  5 B, and  6 B. In this regard,  9 H is the strongest hardness, and hardness sequentially becomes low toward  6 B. 
         [0064]      FIG. 9  is an exemplary view of a printed circuit board in which a dam  250  is formed according to an embodiment of the prior art. 
         [0065]    Referring to  FIG. 9 , the dam  250  according to the prior art may be formed on a solder resist layer  230 . In this regard, a lower surface of the dam  250  may be bonded to only an upper portion of the solder resist layer  230 . A pencil hardness of the dam  250  may be from  2 B to H. 
         [0066]      FIG. 10  is an exemplary view of a printed circuit board in which a dam  350  is formed according to another embodiment of the prior art. 
         [0067]    Referring to  FIG. 10 , the dam  350  according to the prior art may be formed on a solder resist layer  330 . The dam  350  may be inserted into the solder resist layer  330 . In this regard, a lower surface of the dam  350  may be inserted into the center of the solder resist layer  330 . A pencil hardness of the dam  350  may be from  2 H to  4 H. 
         [0068]      FIG. 11  is an exemplary view of a printed circuit board in which a dam  150  is formed according to an embodiment of the present invention. 
         [0069]    Referring to  FIG. 11 , the dam  150  may be formed on the solder resist layer  130 . The dam  350  may be inserted into the solder resist layer  130 . In this regard, the dam  350  may be formed passing through the solder resist layer  130 . That is, a lower surface of the dam  150  may be bonded to a surface of the base substrate  110 . A pencil hardness of the dam  150  may be from  7 H to  8 H. 
         [0070]    As a result of comparing  FIGS. 9 through 11 , it may be confirmed that a bonding area between the dam  130  of  FIG. 11  according to the embodiment of the present invention and the printed circuit board  100  structurally increases. The greater the bonding area between the dam  130  and the printed circuit board  100 , the higher the adhesion therebetween. This may be confirmed from the test result that the pencil hardness of the dams  230  and  330  according to the prior art is between  2 B and H and between  2 H and  4 H, whereas the pencil hardness of the dam  150  according to an embodiment of the present invention is between  8 H and  9 H. 
         [0071]    As described above, a printed circuit board and a method of manufacturing the same according to the embodiments of the present invention can form a dam having an enhanced adhesion. 
         [0072]    Although the embodiments of the present invention have been disclosed for illustrative purposes, it will be appreciated that the present invention is not limited thereto, and 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. 
         [0073]    Accordingly, any and all modifications, variations or equivalent arrangements should be considered to be within the scope of the invention, and the detailed scope of the invention will be disclosed by the accompanying claims.