Abstract:
A printed circuit board and a method of manufacturing the printed circuit board are disclosed. The method of manufacturing a printed circuit board, by forming at least one bump for interlayer conduction on a surface of a board and stacking an insulation layer on the surface of the board, can include the operations of forming at least one dam on the surface of the board that surrounds a region corresponding to the bump, forming the bump by printing conductive paste onto the region corresponding to the bump, and stacking the insulation layer onto the surface of the board. This method can be utilized to improve productivity and resolve the problem of spreading.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 10-2007-0059323 filed with the Korean Intellectual Property Office on Jun. 18, 2007, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a printed circuit board and to a method of manufacturing the printed circuit board. 
     2. Description of the Related Art 
     Among the various methods for manufacturing a printed circuit board, one method currently being used to manufacture a high-density printed circuit board is illustrated in  FIGS. 1A to 1H , which includes forming bumps  3  on a board  2 , stacking on an insulation layer  4 , and stacking this in turn onto a multi-layer board  1 , etc., while applying heat and pressure. This is referred to as a B2it method. With the B2it method, vias for interlayer conduction can be formed in a simple manner, whereby manufacturing efficiency can be increased. 
     The B2it method includes forming paste bumps, using copper (Cu), silver (Ag), etc., on a copper foil, piling an insulation layer with the copper foil, and then applying heat and pressure for stacking. In the B2it method, the process of printing the paste has to be performed such that the bumps have a height sufficient to penetrate the insulation layer. Thus, as illustrated in  FIGS. 2A and 2B , the conductive paste  3   a ,  3   b  may be printed on the lands  9  formed on an insulation layer  4 ′ over a series of four or five repetitions. As such, the repeated printing intended for forming the bumps to a particular height can lower productivity, and can cause spreading at the lower ends of the bumps. 
     SUMMARY 
     An aspect of the invention is to provide a printed circuit board and a method of manufacturing the printed circuit board, which improve productivity and resolve the problem of spreading. 
     One aspect of the invention provides a method of manufacturing a printed circuit board by forming at least one bump for interlayer conduction on a surface of a board and stacking an insulation layer on the surface of the board. The method includes forming at least one dam on the surface of the board that surrounds a region corresponding to the bump, forming the bump by printing conductive paste onto the region corresponding to the bump, and stacking the insulation layer onto the surface of the board. 
     Forming the dam can be performed by selectively etching a metal layer stacked on the surface of the board, and the dam can be made of a material including copper. 
     Another aspect of the invention provides a printed circuit board that includes a board, a bump formed on a surface of the board, a dam formed on the surface of the board that surrounds an edge of the bump, and a first insulation layer stacked on the surface of the board. 
     The board can be a copper clad laminate (CCL), which has a copper foil stacked on a second insulation layer, in which case the dam may be shaped by selectively removing the copper foil. 
     Additional aspects and advantages of the present invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A ,  FIG. 1B ,  FIG. 1C ,  FIG. 1D ,  FIG. 1E ,  FIG. 1F ,  FIG. 1G , and  FIG. 1H  are cross-sectional views representing a flow diagram for a method of manufacturing a printed circuit board according to the related art. 
         FIG. 2A  and  FIG. 2B  are cross-sectional views representing a flow diagram for a method of forming bumps according to the related art. 
         FIG. 3  is a flowchart illustrating a method of manufacturing a printed circuit board according to an aspect of the invention. 
         FIG. 4A ,  FIG. 4B ,  FIG. 4C ,  FIG. 4D ,  FIG. 4E ,  FIG. 4F ,  FIG. 4G , and  FIG. 4H  are cross-sectional views representing a flow diagram for the method illustrated in  FIG. 3 . 
         FIG. 5  is a plan view illustrating a board on which dams have been formed. 
         FIG. 6A  and  FIG. 6B  are cross-sectional views representing a flow diagram for a method of forming bumps. 
         FIG. 7  is a cross-sectional view of a printed circuit board according to another aspect of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The printed circuit board and method of manufacturing the printed circuit board according to certain embodiments of the invention will be described below in more detail with reference to the accompanying drawings. Those components that are the same or are in correspondence are rendered the same reference numeral regardless of the figure number, and redundant explanations are omitted. 
     First, the method of manufacturing a printed circuit board according to one aspect of the invention will be described as follows. 
       FIG. 3  is a flowchart illustrating a method of manufacturing a printed circuit board according to an aspect of the invention, and  FIG. 4A  through  FIG. 4H  are cross-sectional views representing a flow diagram for the method illustrated in  FIG. 3 . In  FIGS. 4A to 4H  are illustrated a four-layer board  10 , insulation layers  20   a ,  20   b , patterns  22   a ,  22   b , dams  24 , bumps  30 , and bump boards  40 . 
     First, dams  24  may be formed, which surround regions corresponding to bumps  30 , on a surface of a board (S 10 ). The board may provide the position where the bumps  30  are to be formed, and in this particular embodiment, an insulation layer  20   a  can be used for the board. Of course, the board can take a form other than an insulation layer  20   a . For example, a double-sided printed circuit board can be used that already has particular patterns formed on either side. 
     The insulation layer  20   a  may serve to electrically insulate the upper and lower layers of the printed circuit board. A particular pattern may be formed on the lower surface of the insulation layer  20   a , and may even have several layers of boards stacked thereon. 
     A dam  24  can serve to confine the region of a bump that interconnects layers, as well as to provide support for the bump  30 . A method of forming the dams  24  will be described in more detail as follows. 
     First, an etching resist (not shown) may be formed on a metal layer (not shown) stacked on a surface of the insulation layer  20   a  (S 11 ). The etching resist (not shown) can be formed to cover the metal layer (not shown) in positions where the dams  24  are to be formed. This etching resist (not shown) can be formed using a mask, by a method of exposure and development, etc. A copper clad laminate (CCL), which has a copper foil stacked on either side of an insulating layer, can be used for the insulation layer  20   a  and the metal layer (not shown) stacked on the insulation layers  20   a.    
     Next, an etchant may be provided (S 12 ). Using an etchant, the portions other than those portions covered by the etching resist (not shown) can be removed. Afterwards, the etching resist (not shown) may be removed (S 13 ). 
     In cases where the dams  24  are formed by the method described above, the dams  24  can be formed simultaneously during the process for forming the patterns  22   a , etc., on the insulation layer  20   a . As such, since there is no need for a separate process in forming the dams  24 , the manufacturing process can be simplified. An example of the patterns  22   a  and dams  24  formed on the insulation layer  20   a  is illustrated in  FIG. 4B  and  FIG. 5 . 
     After thus forming the dams  24 , conductive paste may be printed to form the bumps  30  (S 20 ). As illustrated in  FIGS. 6A and 6B , the regions where the conductive paste  30   a ,  30   b  are printed may be surrounded by the dams  24 . Therefore, during the procedure for forming the bumps  30  by printing the conductive paste  30   a ,  30   b , the lower ends of the bumps  30  may be supported by the dams  24 , and the areas of the board occupied by the bumps  30  can be limited by the dams  24 . 
     In this way, the lower ends of the bumps  30  can be prevented from spreading to a wider area than that intended. Also, compared to those cases in which dams  24  are not formed, relatively larger amounts of conductive paste  30   a ,  30   b  can be printed in one round. 
     Therefore, the number of repetitions of printing for forming the bumps  30  to a particular height can be reduced, to confer an aspect of increased productivity. The results of repeatedly printing the conductive paste  30   a ,  30   b  are illustrated in  FIGS. 6A and 6B , and the bumps  30  thus formed can be seen also in  FIG. 4C . 
     Next, an insulation layer may be stacked on to form a bump board (S 30 ). The insulation layer  20   b  can be stacked over the insulation layer  20   a  on which the bumps  30  and the pattern  22   a  are formed, where the bumps  30  can be made to penetrate the insulation layer  20   b . The insulation layer  20   b  may serve to provide electrical insulation between layers, and can be made, for example, from Prepreg. 
     Bump boards  40  formed as above may be stacked onto a four-layer board  10 , as illustrated in  FIG. 4E , to implement a multi-layer printed circuit board such as that illustrated in  FIG. 4F . 
     Afterwards, holes  26  can be perforated in the outermost layers, as illustrated in  FIG. 4G , and interlayer conduction can be provided at the outermost layers using a method such as forming plating layers  28  in the holes  26 . 
     An example of a printed circuit board manufactured by the method described above is illustrated in  FIG. 7 .  FIG. 7  is a cross-sectional view of a printed circuit board according to another aspect of the invention. In  FIG. 7  are illustrated a four-layer board  10 , insulation layers  20   a ,  20   b , patterns  22   a ,  22   b , dams  24 , bumps  30 , and bump boards  40 . 
     In the case of the printed circuit board according to this embodiment, conduction between layers can be implemented by elements including the bumps  30  which penetrate the insulation layers, and the plating layers which are formed in the holes  26 . A dam  24  can be formed around the edge of a bump  30  to surround the bump  30 , where such dams  24  may facilitate the forming of the bumps  30  while preventing spreading. 
     The insulation layers  20   a , on which the dams  24  are formed, and the patterns  22   a ,  22   b  formed on these insulation layers  20   a  can be formed by selectively removing the copper foils of a copper clad laminate, where the dams  24  can be formed by the same method, as already described above. 
     According to certain embodiments of the invention as set forth above, by forming dams and printing the bumps for interlayer conduction inside the dams, productivity can be improved and the problem of spreading can be resolved. 
     While the spirit of the invention has been described in detail with reference to particular embodiments, the embodiments are for illustrative purposes only and do not limit the invention. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the invention.