Abstract:
A printed circuit board including: an insulation layer; a first circuit pattern formed over one surface of the insulation layer, the first circuit pattern having a side thereof slanted with respect to the insulation layer; and a second circuit pattern formed over the other surface of the insulation layer, the second circuit pattern having a side thereof slanted with respect to the insulation layer, wherein the side of the second circuit pattern is less slanted than the side of the first circuit pattern.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. divisional application filed under 37 CFR 1.53(b) claiming priority benefit of U.S. Ser. No. 12/213,703 filed in the United States on Jun. 23, 2008, which claims earlier priority benefit to Korean Patent Application No. 10-2008-0000799 filed with the Korean Intellectual Property Office on Jan. 3, 2008 the disclosures of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    The present invention relates to a printed circuit board and to a method of manufacturing the printed circuit board. 
         [0004]    2. Description of the Related Art 
         [0005]    Electronic equipment are being produced with higher performance and smaller sizes, leading to cost increases in such electronic equipment. As such, there are efforts to lower the cost of components used in electronic equipment. 
         [0006]    Methods of manufacturing a printed circuit board according to the related art include tenting processes and additive processes. 
         [0007]    Whereas tenting processes allow low manufacture costs, they are limited in forming fine-line circuit patterns. Additive processes have been developed to overcome this limitation, but these have the disadvantage of incurring higher costs. 
         [0008]    In the related art, when a copper clad laminate (CCL) is used as the material for manufacturing a printed circuit board, the method used may involve applying a tenting process on both surfaces or applying an additive process on both surfaces. One reason for this may be that both surfaces would be exposed to the etchant or the plating bath simultaneously. Thus, even in cases where a fine-line circuit pattern is required on one surface only, the same process may have to be employed for both surfaces at the same time. 
         [0009]    In the manufacture of a printed circuit board according to the related art, there may also be problems of curling or bending, etc., as the thickness of the printed circuit board is decreased. 
       SUMMARY 
       [0010]    An aspect of the invention provides a method of forming circuit patterns sequentially on both surfaces of a printed circuit board. 
         [0011]    Another aspect of the invention provides a method of manufacturing a printed circuit board that includes forming a first protective layer over one surface of a core substrate, forming a first circuit pattern over the other surface of the core substrate by a first process, removing the first protective layer, forming a second protective layer over the other surface of the core substrate, and forming a second circuit pattern over the one surface of the core substrate by a second process. 
         [0012]    Still another aspect of the invention provides a method of manufacturing a printed circuit board that includes attaching one surface of each of a pair of core substrates onto either surface of a first protective layer, forming a first circuit pattern over the other surface of each of the pair of core substrates by a first process, separating the pair of core substrates from the first protective layer, attaching the other surface of each of the pair of core substrates onto either surface of a second protective layer, and forming a second circuit pattern over the one surface of each of the pair of core substrates by a second process. 
         [0013]    Certain embodiments of the invention may include one or more of the following features. 
         [0014]    In certain embodiments, the core substrate can be a copper clad laminate (CCL). 
         [0015]    The first process can be any one selected from a group consisting of a tenting process, a semi-additive process, and an additive process. 
         [0016]    The second process can be any one selected from a group consisting of a tenting process, a semi-additive process, and an additive process. 
         [0017]    The first and second protective layers can be foam tapes. 
         [0018]    A side of the second circuit pattern may be less slanted than a side of the first circuit pattern. 
         [0019]    An interface can be formed within the first circuit pattern. 
         [0020]    Yet another aspect of the invention provides a printed circuit board, which includes an insulation layer, a first circuit pattern having a side slanted with respect to the insulation layer that is formed over one surface of the insulation layer, and a second circuit pattern having a side slanted with respect to the insulation layer that is formed over the other surface of the insulation layer. The side of the second circuit pattern may be less slanted than the side of the first circuit pattern. 
         [0021]    In certain embodiments of the printed circuit board, an interface can be formed within the first circuit pattern. 
         [0022]    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 
         [0023]      FIG. 1  is a flowchart illustrating the manufacture of a printed circuit board according to an embodiment of the invention. 
           [0024]      FIG. 2 ,  FIG. 3 ,  FIG. 4 ,  FIG. 5 ,  FIG. 6 , and  FIG. 7  are cross sectional views representing a flow diagram illustrating the manufacture of a printed circuit board according to an embodiment of the invention. 
           [0025]      FIG. 8  is a flowchart illustrating the manufacture of a printed circuit board according to another embodiment of the invention. 
           [0026]      FIG. 9 ,  FIG. 10 ,  FIG. 11 ,  FIG. 12 ,  FIG. 13 , and  FIG. 14  are cross sectional views representing a flow diagram illustrating the manufacture of a printed circuit board according to another embodiment of the invention. 
           [0027]      FIG. 15  is a cross sectional view of a printed circuit board according to yet another embodiment of the invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0028]    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. 
         [0029]      FIG. 1  is a flowchart illustrating the manufacture of a printed circuit board according to an embodiment of the invention, and  FIG. 2  through  FIG. 7  are cross sectional views representing a flow diagram illustrating the manufacture of a printed circuit board according to an embodiment of the invention. In  FIGS. 2 to 7 , there are illustrated a core substrate  11 , an insulation layer  111 , copper foils  112 , a first protective layer  12 , via holes  13 , a first circuit pattern  14 , vias  15 , a second protective layer  16 , and a second circuit pattern  17 . 
         [0030]    Operation S 11  may include forming a first protective layer  12  over one surface of a core substrate  11 , where  FIG. 2  represents a corresponding procedure. 
         [0031]    The core substrate  11  can be made from just the insulation layer. This particular embodiment, however, illustrates the use of a copper clad laminate (CCL). The copper clad laminate (CCL) can include a copper foil on just one surface of the insulation layer, or as illustrated in this particular embodiment, include copper foils  112  stacked over both surfaces of the insulation layer  111 . 
         [0032]    The thickness of a copper foil  112  can be such that allows the application of a tenting process. Also, the copper foil can be such that is thin enough to allow the application of a semi-additive process. 
         [0033]    A tape, such as a foam tape, can be used for the first protective layer  12 , whereby the surface of the core substrate  11  can be protected in a simple manner from a plating liquid or etchant, etc., making it possible to form each of the first circuit pattern  14  and second circuit pattern  17  in order. 
         [0034]    Operation S 12  may include forming a first circuit pattern  14  over the other surface of the core substrate  11  using a first process, where  FIG. 3  and  FIG. 4  represent corresponding procedures. 
         [0035]    Before forming the first circuit pattern  14 , via holes  13  can be perforated, as illustrated in  FIG. 3 , in order to form vias  15  that connect the circuit patterns  14 ,  17  on either surface. A laser can be used for perforating the via holes  13 . Afterwards, the insides of the via holes  13  can be plated to form the vias  15 . 
         [0036]    The first process can be any of a semi-additive process, tenting process, and additive process. In this particular embodiment, the first circuit pattern  14  may be formed by a tenting process. In cases where the core substrate  11  is made only of an insulation layer, an additive process may be used. An additive process may include selectively forming a circuit pattern over the insulation layer by electroless plating or electroplating. A semi-additive process may include selectively forming a circuit pattern over a thin film of copper, and then removing the exposed copper by etching. 
         [0037]    Operation S 13  may include removing the first protective layer  12 . The first protective layer  12  can be physically separated or can be removed using a chemical solution. If a foam tape is used for the first protective layer  12 , increasing the temperature can create bubbles in the tape, so that the adhesion may be lowered and the tape may easily be separated from the core substrate  11 . 
         [0038]    Operation S 14  may include forming a second protective layer  16  over the other surface of the core substrate  11 , where  FIG. 5  represents a corresponding procedure. 
         [0039]    The other surface of the core substrate  11  may already have the first circuit pattern  14  formed by the first process. Therefore, the second protective layer  16  can be attached to the other surface of the core substrate  11 , in order that the first circuit pattern  14  may not be damaged. The second protective layer  16  can be made from the same material as that of the first protective layer  12 . 
         [0040]    Operation S 15  may include forming a second circuit pattern  17  over the one surface of the core substrate  11  using a second process, where  FIG. 6  represents a corresponding procedure. 
         [0041]    The one surface of the core substrate  11  may be exposed, after the removal of the first protective layer  12 . In this particular embodiment, the core substrate  11  may be a copper clad laminate, and thus a copper foil  112  may be exposed as illustrated in  FIG. 5 . 
         [0042]    The second process can be a tenting process of removing portions of the copper foil  112 . If the copper foil is thin, it is possible to form the second circuit pattern  17  by a semi-additive process and then remove the exposed portions of the copper foil. If the one surface of the core substrate  11  is the insulation layer, an additive process can be used for forming the second circuit pattern  17 . 
         [0043]    In this particular embodiment, the first circuit pattern  14  can be formed using an additive or a semi-additive process, and the second circuit pattern  17  can be formed using a tenting process, so that the sides of the second circuit pattern  17  can form lower inclinations, with respect to the insulation layer  111 , than the sides of the first circuit pattern  14 . 
         [0044]    One reason for this may be that, because of the tenting process, the upper portions on the sides of the second circuit pattern  17  may be exposed more to the etchant than are the lower portions and may thus be removed more. 
         [0045]    The first circuit pattern  14 , on the other hand, can have an interface formed within, because of the additional plating procedure included for forming the vias  15 . 
         [0046]    Afterwards, the second protective layer  16  can be removed, and solder resists can be applied, to complete the printed circuit board  10  as illustrated in  FIG. 7 . 
         [0047]      FIG. 8  is a flowchart illustrating the manufacture of a printed circuit board according to another embodiment of the invention, and  FIG. 9  through  FIG. 14  are cross sectional views representing a flow diagram illustrating the manufacture of a printed circuit board according to another embodiment of the invention. In  FIGS. 9 to 14 , there are illustrated core substrates  21 , insulation layers  211 , copper foils  212 , a first protective layer  22 , via holes  23 , first circuit patterns  24 , vias  25 , a second protective layer  26 , and second circuit patterns  27 . 
         [0048]    Operation S 21  may include attaching one surface of each of a pair of core substrates  21  to either surface of a first protective layer  22 .  FIG. 9  represents a corresponding procedure. 
         [0049]    In this particular embodiment, the pair of core substrates  21  can be attached to both surfaces of the first protective layer  22  in a symmetrical arrangement. 
         [0050]    The core substrates  21  can be made from just the insulation layers. This particular embodiment illustrates the use of copper clad laminates (CCL). A copper clad laminate (CCL) can include a copper foil on just one surface of the insulation layer, or as illustrated in this particular embodiment, include copper foils  212  stacked over both surfaces of the insulation layer  211 . 
         [0051]    The thickness of a copper foil  212  can be such that allows the application of a tenting process. Also, the copper foil can be such that is thin enough to allow the application of a semi-additive process. 
         [0052]    A tape, such as a foam tape, can be used for the first protective layer  22 , whereby the surfaces of the core substrates  21  can be protected in a simple manner from a plating liquid or etchant, etc., making it possible to form each of the first circuit patterns  24  and second circuit patterns  27  sequentially. 
         [0053]    Operation S 22  may include forming a first circuit pattern  24  over the other surface of each of the pair of core substrates  21 , where  FIG. 10  and  FIG. 11  represent corresponding procedures. 
         [0054]    Before forming the second circuit patterns  27 , via holes  23  can be perforated, as illustrated in  FIG. 10 , to form vias  25  for connecting the circuit patterns  24 ,  27 . A laser can be used for perforating the via holes  23 . Afterwards, the insides of the via holes  23  can be plated to form the vias  25 . 
         [0055]    The first process can be any of a semi-additive process, tenting process, and additive process. In this particular embodiment, the first circuit patterns  24  may be formed by a tenting process. In cases where the core substrates  21  are made only of insulation layers, an additive process may be used. An additive process may include selectively forming a circuit pattern over the insulation layer by electroless plating or electroplating. A semi-additive process may include selectively forming a circuit pattern over a thin film of copper, and then removing the exposed copper by etching. 
         [0056]    Operation S 23  may include separating the pair of core substrates  21  from the first protective layer  22 . The first protective layer  22  can be physically separated or can be removed using a chemical solution. If a foam tape is used for the first protective layer  22 , increasing the temperature can create bubbles in the tape, so that the adhesion may be lowered and the tape may easily be separated from the core substrates  21 . 
         [0057]    Operation S 24  may include attaching the other surface of each of the pair of core substrates  21  to either surface of a second protective layer  26 , where  FIG. 12  represents a corresponding procedure. 
         [0058]    The other surface of each core substrate  21  may already have the first circuit pattern  24  formed by the first process. Therefore, the second protective layer  26  can be attached to the other surface of each core substrate  21 , in order that the first circuit pattern  24  may not be damaged. The second protective layer  26  can be made from the same material as that of the first protective layer  22 . In this embodiment, the pair of core substrates  21  can be attached to the second protective layer  26  symmetrically. 
         [0059]    Operation S 25  may include forming a second circuit pattern  27  over the one surface of each of the pair of core substrates  21  using a second process, where  FIG. 13  represents a corresponding procedure. 
         [0060]    One surface of each of the pair of core substrates  21  may be exposed, after the removal of the first protective layer  22 . In this particular embodiment, the core substrates  21  may be copper clad laminates, and thus the copper foils  212  may be exposed, as illustrated in  FIG. 12 . 
         [0061]    The second process can be a tenting process of removing portions of the copper foils  212 . If the copper foils are thin, it is possible to form the second circuit patterns  17  by a semi-additive process and then remove the exposed portions of the copper foils. If the one surface of each of the core substrates  21  is an insulation layer, an additive process can be used for forming the second circuit patterns  27 . 
         [0062]    Since the first circuit patterns  24  can be formed using an additive or a semi-additive process, and the second circuit patterns  27  can be formed using a tenting process, the sides of the second circuit patterns  27  can form lower inclinations with respect to the insulation layer  211 , compared to the sides of the second circuit patterns  27 . 
         [0063]    One reason for this may be that, because of the tenting process, the upper portions on the sides of the second circuit patterns  27  may be exposed more to the etchant than are the lower portions and may thus be removed more. 
         [0064]    The first circuit patterns  24 , on the other hand, can each have an interface formed within, because of the additional plating procedure included for forming the vias  25 . 
         [0065]    Afterwards, the second protective layer  26  can be removed, and solder resists can be applied, to complete a pair of printed circuit boards  20  as illustrated in  FIG. 14 . Each printed circuit board  20  can be a complete product in itself. 
         [0066]      FIG. 15  is a cross sectional view of a printed circuit board according to yet another embodiment of the invention. In  FIG. 15 , there are illustrated a printed circuit board  30 , an insulation layer  31 , a first circuit pattern  33 , a second circuit pattern  32 , and vias  34 . 
         [0067]    The printed circuit board  30  according to this embodiment may have a first circuit pattern  33  and a second circuit pattern  32  formed respectively on either surface. The second circuit pattern  32  can be formed by a tenting process, so that the sides  321  of the second circuit pattern  32  can be slanted with respect to the insulation layer  31 . 
         [0068]    The sides  331  of the first circuit pattern  33 , however, may be slanted by a greater inclination from the insulation layer  31  compared to the sides  321  of the second circuit pattern  32 , as the first circuit pattern  33  can be formed by an additive or a semi-additive process. 
         [0069]    A tenting process can involve removing unnecessary portions with an etchant and having the remaining portions form the circuit pattern. Here, the upper portions of the circuit pattern can be exposed more to the etchant and thus can be removed more. Therefore, the sides  321  of the second circuit pattern  32  can form a smaller inclination with the insulation layer  31  compared to those of the first circuit pattern  33 , as is illustrated in  FIG. 15 . 
         [0070]    The first circuit pattern  33  can have an interface  36  formed within, because of the extra plating procedure involved in forming the vias  34 . 
         [0071]    According to certain aspects of the invention as set forth above, circuit patterns can be formed sequentially on either surface of a printed circuit board, making it possible to apply a different process for forming the circuit pattern on each surface of the printed circuit board. 
         [0072]    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. As such, many embodiments other than those set forth above can be found in the appended claims.