Patent Publication Number: US-2015068793-A1

Title: Printed circuit board and method of manufacturing the same

Description:
CROSS REFERENCE(S) TO RELATED APPLICATIONS 
     This application claims the foreign priority benefit under 35 U.S.C. Section 119 of Korean Application No. 10-2013-0109685, entitled “Printed Circuit Board and Method of Manufacturing the Same” filed on Sep. 12, 2013, which is hereby incorporated by reference in its entirety into this application. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a printed circuit board and a method of manufacturing the same, and more particularly, to a printed circuit board capable of improving adhesive reliability of a solder ball simplifying the number of manufacturing processes and a method of manufacturing the same. 
     2. Description of the Related Art 
     In accordance with a rapid development of an electronic industry recently, since electronic components are highly integrated and have high performance, and the electronic components such as an integrated chip (IC), a central processing unit (CPU), a variety of elements, and the like are mounted, a printed circuit board which is used so as to be electrically connected to a main board is also multi-functionalized and a package using the printed circuit board is also miniaturized. 
     Particularly, in a case of a memory package, a plurality of electronic components may be laminated and installed in order to increase capacity of the package, and a thickness of the package has also become thin, as a total of thickness of a mobile device having the package mounted therein is gradually thinned. 
     The memory package as mentioned above is mainly manufactured in a form of package of package (POP) in which the package is laminated on the package, and since an upper package is mounted on a lower package, warpage variation of the package should be small. 
     RELATED ART DOCUMENT  
     Patent Document  
     (Patent Document 1) Korean Patent Laid-Open Publication No. 2009-0042569 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a printed circuit board capable of excluding a solder resist from components controlling warpage of the printed circuit board and preventing adhesion of a solder ball from being weaken, which may be caused by the exclusion of the solder resist, and a method of manufacturing the same. 
     According to an exemplary embodiment of the present invention, there is provided a printed circuit board, including: an insulation layer; pattern parts formed on both surfaces of the insulation layer; a connection pad formed on the same layer as the pattern part and having a step part; a first plated layer formed on the pattern part; an oxide film formed on a region excluding a region on which the first plated layer is formed; a second plated layer formed on the connection pad; and a solder ball covering the connection pad. 
     The insulation layer may be provided with a through-hole, and the through-hole may be filled with an interlayer plated layer to electrically connect the pattern parts to each other. 
     The connection pad may be formed to be protruded in a bump form between the pattern parts provided on a lower surface of the insulation layer, and may have the step part formed on a peripheral part to thereby form resistibility against cross section stress of the solder ball by the step part. 
     The oxide film may be formed by a brown oxide, a black oxide or an OSP process which is an organic surface protective agent. 
     According to another exemplary embodiment of the present invention, there is provided a method of manufacturing a printed circuit board, the method including: preparing a base substrate; forming a through-hole in the base substrate; forming first dry film resist patterns on both surfaces of the base substrate so that plating pattern forming position is opened; forming pattern parts and a connection pad by growing a plated layer on opened regions of the first dry film resist pattern; forming a second dry film resist pattern on the pattern parts; forming a first plated layer and a second plated layer on opened regions of the second dry film resist pattern; removing the second dry film resist pattern; and forming an oxide film on a region excluding a region on which the first plated layer of the pattern part is formed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 to 9  are process views showing a method of manufacturing a printed circuit board according to an exemplary embodiment of the present invention; 
         FIG. 1  is a cross-sectional view of a base substrate; 
         FIG. 2  is a cross-sectional view of a state in which a through-hole is formed in the base substrate; 
         FIG. 3  is a cross-sectional view of a state in which a first dry film resist pattern is formed in the base substrate having the through-hole formed therein; 
         FIG. 4  is a cross-sectional view of a state in which a plating process is performed for an opened region of the first dry film resist pattern; 
         FIG. 5  is a cross-sectional view of a state in which a second dry film resist pattern is formed on a pattern part; 
         FIG. 6  is a cross-sectional view of a state in which a Ni/Au plated layer is formed on the opened region of the second dry film resist pattern; 
         FIG. 7  is a cross-sectional view of a state in which the second dry film resist pattern is removed; 
         FIG. 8  is a cross-sectional view of a state in which an oxide film is formed on the pattern part; and 
         FIG. 9  is a cross-sectional view of the printed circuit board according to the exemplary embodiment of the present invention of a state in which a solder ball is coupled to a connection pad of a lower surface. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The acting effects and technical configuration with respect to the objects of a printed circuit board and a method of manufacturing the same according to the present invention will be clearly understood by the following description in which exemplary embodiments of the present invention are described with reference to the accompanying drawings. 
     First,  FIG. 9  is a cross-sectional view of a printed circuit board according to an exemplary embodiment of the present invention. 
     As shown, the printed circuit board  100  according to the exemplary embodiment of the present invention may be configured to include an insulation layer  110 , pattern parts  120  formed on both surfaces of the insulation layer  110 , and a connection pad  130  formed on the same layer as the pattern part  120 . In this case, in  FIG. 9 , the connection pad  130  may be disposed between the pattern parts  120  throughout the printed circuit board  100  in a state in which a portion of the printed circuit board  100  is cut. 
     In this case, the pattern part  120  may have an oxide film  121  formed on a surface thereof and the connection pad  130  formed on the insulation layer  110  and between the pattern parts  120  may have a Ni/Au plated layer  132  formed on a surface thereon. In addition, the connection pad  130  is configured in a bump form in which the step part  131  is formed, and a solder ball  140  may be coupled to the connection pad  130  so as to cover the connection pad  130 . In this case, the solder ball  140  may have improved adhesive reliability by the connection pad  130  and the step part  131 . 
     The insulation layer  110  may serve as a core of the printed circuit board according to the exemplary embodiment of the present invention and may be configured of an insulating material of a resin or an ABF material. In addition, a glass woven material such as a glass cross or a glass fabric is impregnated in the resin, such that the insulation layer  110  may be assigned with rigidity and may have resistibility against warpage caused by heat and pressure during a manufacturing process of the board. 
     In addition, the insulation layer  110  may have a via or a through-hole  111  formed therein. The through-hole  111  may be formed to penetrate through the insulation layer  110  by a mechanical drilling process or laser process and may have an inter-layer plated layer  123  filled therein to be used as a connection unit electrically connecting between upper and lower portions of the insulation layer  110 . 
     The pattern part  120  and the connection pad  130  may be formed on the insulation layer  110 . The pattern part  120  and the connection pad  130  are formed by performing a plating process on the insulation layer  110 . More specifically, a seed layer (not shown) is first formed and a plated layer is grown on the seed layer by performing an electroplating or electroless plating, such that the pattern part  120  and the connection pad  130  may be formed. In this case, the connection pad  130  may be simultaneously formed on an upper surface and a lower surface of the insulation layer  110 , or may be protruded from any one surface of the upper surface or the lower surface in a bump form. In addition, the connection pad  130  may be formed to have the same height as the pattern part  120  or the height less than the pattern part  120  in a space between the pattern parts  120 . 
     In addition, the connection pad  130  may have the step part  131  having a form in which a central portion thereof is protruded. The step part  131  is formed by growing the plated layer on the above-mentioned seed layer. The step part  131  may be formed by having a width of the seed layer greater than that of the plated layer by not removing a portion of the seed layer surrounding the plated layer at the time of removing the seed layer. 
     In addition, the connection pad  130  may further have a second plated layer  132  formed on the upper surface including the step part  131 . The second plated layer  132  may be configured of a Ni/Au plated layer and adhesive performance of the solder ball  140  may be improved by the second plated layer  132 , where a rough layer is generated by an intermetallic compound (IMC) generated while nickel is oxidized at the second plated layer  132  formed at an adhesive interface between the solder ball  140  and the connection pad  130  at the time of reflow process for adhesion of the solder ball, that is, the second plated layer  132  by the Ni/Au plating process, the adhesion between the surface of the connection pad  130  and the second plated layer  132  may be improved. 
     Meanwhile, the pattern part  120  may be formed to have the same height as the connection pad  130  and may have an oxide film  121  formed on a surface thereof. The oxide film  121  functions as the insulation layer in place of a solder resist layer formed on the pattern part and may serve to protect the pattern part from the outside. In addition, the pattern part  120  formed by performing the plating on the seed layer is formed by a copper (Cu) plating, the oxide film  121  may be formed by performing a brown oxide, a black oxide or an OSP process which is an organic surface protective agent on the surface of the pattern part  120 . 
     In addition, the first plated layer  122  may be formed on a portion in which the oxide film  121  is not applied on the pattern part  120 . The first plated layer  122  may function as a pad or pattern electrically connected to the via or the like which may be formed in the insulation layer formed on the pattern part  120  and built-up on the pattern part  120 . 
     The printed circuit board  100  according to the exemplary embodiment of the present invention having the above-mentioned configuration may decrease a thickness of the printed circuit board since the solder resist layer needs not to be separately configured, due to the oxide film  121  formed on the pattern part  120  serving as the solder resist, and may decrease warpage occurrence since the solder resist layer in which warpage is mainly generated by heat and pressure at the time of manufacturing the printed circuit board is removed. 
     A method of manufacturing the printed circuit board according to the exemplary embodiment of the present invention having the above-mentioned configuration will be described with reference to the following drawings in which the manufacturing processes are sequentially shown. 
       FIGS. 1 to 9  are process views showing a method of manufacturing a printed circuit board according to an exemplary embodiment of the present invention,  FIG. 1  is a cross-sectional view of a base substrate,  FIG. 2  is a cross-sectional view of a state in which a through-hole is formed in the base substrate,  FIG. 3  is a cross-sectional view of a state in which a first dry film resist pattern is formed in the base substrate having the through-hole formed therein, and  FIG. 4  is a cross-sectional view of a state in which a plating process is performed for an opened region of the first dry film resist pattern. 
     As shown, the printed circuit board first prepares the base substrate. As the base substrate  115 , a copper clad laminate (CCL) having copper layers  112  formed on both surfaces thereof may be used, and the copper layer  112  having a thickness of several gm or less may be separately formed on both surfaces of the insulation layer  110  to thereby configure the copper clad laminate. The base substrate  115  having the copper layer  112  formed thereon may have the through-hole  111  formed therein as shown in  FIG. 2 . The through-hole  111  may be processed by the mechanical drilling process or laser process and may be formed by forming the via holes in upper and lower portions of the base substrate. In addition, after forming the via hole, the through-hole  111  may form an inner wall surface thereof to be flat by performing a flattening process for an inclined wall surface using desmear chemicals such as sodium permanganate, or the like. 
     After the through-hole  111  is formed in the base substrate  115 , a photosensitive film or photosensitive resin is applied on the base substrate  115  and the photosensitive film is exposed and developed, such that a first dry film resist pattern  113  having an opened pattern forming position may be formed. 
     An outer region of the first dry film resist pattern  113  is a position at which the pattern part  120  will be formed and may be provided with the pattern part  120  by growing the plated layer by an electroplating or electroless plating process using the copper layer  112  as the seed layer. In this case, the pattern part  120  may simultaneously perform a copper plating process for the outer region of the first dry film resist pattern  113  and an inner portion of the through-hole  111  to thereby electrically connect the upper and lower portions of the base substrate  115 . In addition, the lower surface of the base substrate  115  may be provided with the connection pad  130  by growing the plated layer between the pattern parts  120 . 
     Next,  FIG. 5  is a cross-sectional view of a state in which a second dry film resist pattern is formed on a pattern part,  FIG. 6  is a cross-sectional view of a state in which a Ni/Au plated layer is formed on the opened region of the second dry film resist pattern, and  FIG. 7  is a cross-sectional view of a state in which the second dry film resist pattern is removed. 
     As shown in  FIGS. 5 to 7 , the photosensitive film or photosensitive resin is applied on both surface of the base substrate  115  having the pattern part  120  formed thereon and the photosensitive film or photosensitive resin is exposed and developed, such that a second dry film resist pattern  125  having an opened plated layer  122  forming position may be formed. In this case, the second dry film resist pattern  125  formed on the lower surface of the base substrate  115  may form an open region so that the copper layer  112  surrounding the connection pad  130  is exposed by a predetermined portion. The open region of the second dry film resist pattern  125  on the lower surface of the printed circuit board as described above forms a solder ball connection region. 
     The open region of the second dry film resist pattern  125  may be provided with a first plated layer  122  formed by the Ni/Au plating process by performing the electroplating. In this case, a second plated layer  132  formed by the Ni/Au plating process may also be formed on the connection pad  130  formed on the lower surface of the printed circuit board and the copper layer  112  surrounding thereof. 
     Next, when the electroplating process for forming the Ni/Au plated layers  122  and  132  in the opened region of the second dry film resist pattern  125  is completed, the second dry film resist pattern  125  is removed, such that the pattern part  120 , the plated layers  122  and  132  plated on the pattern part  120  and the connection pad  130 , and the copper layer  112  between the pattern parts  120  may be exposed. 
     Next,  FIG. 8  is a cross-sectional view of a state in which an oxide film is formed on the pattern part and  FIG. 9  is a cross-sectional view of the printed circuit board according to the exemplary embodiment of the present invention of a state in which a solder ball is coupled to a connection pad of a lower surface. 
     As shown, when the second dry film resist pattern  125  is removed, the copper layer  112  used as the seed layer for forming the pattern part  120  may be removed by etching. As portions in which the copper layer  112  is removed, the copper layer  112  in the region between the pattern parts  120 , and the region between the pattern part  120  and the connection pad  130  having the second plated layer  132  formed thereon is removed, such that the insulation layer  110  used as the base substrate is exposed and electrical short of the pattern part  120  may be made. 
     Next, an oxide film  121  may be formed to have a thickness below several μm at regions on the pattern part  120  excluding the region in which the first plated layer  122  is formed. The oxide film  121  may be formed by the brown oxide, the black oxide or the OSP process on the pattern part  120  made of the copper plated layer and may be configured as a final insulation layer on the pattern part  120  which is exposed to the outside. In this case, the pattern part  120  formed on the insulation layer  110  may form a single copper plated layer by integrating the copper layer  112  and the plated layer grown on the copper layer  112  at the same time as the formation of the oxide film  121 . Similarly, the connection pad  130  may also be formed in a pattern having the same height as the pattern part  120  by integrating the plated layer grown on the copper layer  112 , and the un-removed copper layer  112  around the connection pad  130  is configured in a land form, such that the connection pad  130  having the step part  131  may be configured. In this case, the second plated layer  132  formed by the Ni/Au plating process may be formed only on the upper surface of the connection pad  130  having the step part  131 . 
     Next, the solder ball  140  may be coupled onto the connection pad  130  formed on the lower surface of the printed circuit board. The solder ball  140  is formed on the connection pad  130  and is covered so as to include the step part  131 , such that when external force is applied from the side portion of the solder ball  140 , resistibility against cross-section stress of the solder ball  140  may be secured by the step part  131  formed on the connection pad  130 , thereby making it possible to improve adhesive reliability between the solder ball  140  and the connection pad  130 . 
     Meanwhile, the printed circuit board according to the exemplary embodiment of the present invention may form the plated layer without having a separate plating lead line for performing the Ni/Au plating process at the time of forming the second plated layer  132  by the Ni/Au plating process on the pattern layer  120  and the connection pad  130  based on  FIG. 6 . Therefore, noise occurrence in the printed circuit board caused by the plating lead line may be prevented. 
     According to the exemplary embodiment of the present invention, the printed circuit board and the method of manufacturing the same may decrease the thickness of the printed circuit board since the solder resist layer needs not to be separately configured, due to the oxide film formed on the pattern part serving as the solder resist, and may decrease warpage occurrence since the solder resist layer in which warpage is mainly generated by heat and pressure at the time of manufacturing the printed circuit board is removed. 
     In addition, since the solder ball is covered to include the step part of the connection pad, when external force is applied from the side portion of the solder ball, resistibility against cross-section stress of the solder ball may be secured by the step part, thereby making it possible to improve adhesive reliability of the solder ball. 
     Although the exemplary 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. Accordingly, such modifications, additions and substitutions should also be understood to fall within the scope of the present invention.