Abstract:
A metal clad laminate and a method of manufacturing the metal clad laminate are disclosed. The metal clad laminate can include a barrier layer made of a metallic material, a metal foil formed on one side of the barrier layer and coupled with the barrier layer by plating, and an insulator attached to the metal foil. By utilizing the metal clad laminate, the metal foil can be prevented from being perforated when processing a via hole using laser, so that a VOP structure may be implemented with a higher level of reliability.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2008-0062637 filed with the Korean Intellectual Property Office on Jun. 30, 2008, the disclosure of which is incorporated herein by reference in its entirety. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a metal clad laminate and a method of manufacturing the metal clad laminate. 
         [0004]    2. Description of the Related Art 
         [0005]    In manufacturing current rigid boards, a copper clad laminate (CCL) may generally be used for the core material, where build-up layers can be stacked over the copper clad laminate to form a multi-layer board. Here, a copper clad laminate refers to a material in which copper foils  2 ,  3  are formed over both sides of an insulator  1  reinforced with glass fibers, etc., as illustrated in  FIG. 1 . 
         [0006]    In accordance with the increasing demand for lighter and thinner portable electronic products that provide a greater number of functions, so also is the demand increasing for printed circuit boards that provide smaller thicknesses and higher densities. 
         [0007]    Responding to such trends towards higher densities and higher levels of integration in a board, a structure has been proposed, as illustrated in  FIG. 2 , in which a via  6  that penetrates the insulator  1 , on which a circuit pattern  4  is formed, is connected directly with a pad  6 , and in which a solder ball (not shown) is coupled to this pad  5 . This structure is referred to as a VOP (via on pad) structure. 
         [0008]    In implementing this VOP structure, the process for forming a via hole  6   a  may be performed using a CO 2  laser drill, as illustrated in  FIG. 3 . However, in cases where the via hole  6   a  is formed in a board having thin copper foils  2 ,  3 , such as in the case of a copper clad laminate, the CO 2  laser drill may cause the lower copper foil  3  to be perforated as well. Reference numeral  3   a  of  FIG. 3  shows a lower copper foil  3  perforated by CO 2  laser. 
       SUMMARY 
       [0009]    An aspect of the invention provides a metal clad laminate and a method of manufacturing the metal clad laminate, in which a metal foil can be prevented from being perforated when processing a via hole using laser. 
         [0010]    Another aspect of the invention provides a metal clad laminate that includes: a barrier layer made of a metallic material, a metal foil formed on one side of the barrier layer and coupled with the barrier layer by plating, and an insulator attached to the metal foil. 
         [0011]    Here, the barrier layer can be made of a material containing at least one of nickel (Ni), aluminum (Al), and chromium (Cr), while the metal foil can be made of a material containing copper (Cu). 
         [0012]    A metal layer can be formed on the other side of the barrier layer, where the barrier layer can be formed on the metal layer by plating. In this case, the barrier layer can be made of a material containing at least one of nickel (Ni), aluminum (Al), and chromium (Cr), and the metal foil and the metal layer can be made of materials containing copper (Cu). 
         [0013]    Yet another aspect of the invention provides a method of manufacturing a metal clad laminate that includes: forming a barrier layer over one side of a metal layer by performing plating, forming a metal foil over one side of the barrier layer by performing plating, and attaching an insulator to one side of the metal foil. 
         [0014]    The barrier layer can be made of a material containing at least one of nickel (Ni), aluminum (Al), and chromium (Cr), and the metal foil and the metal layer can be made of materials containing copper (Cu). 
         [0015]    The attaching operation can be performed by hot pressing the insulator in a semi-cured (B-stage) state with a metal foil. 
         [0016]    Still another aspect of the invention provides a method of manufacturing a metal clad laminate that includes: attaching a metal foil to one or either side of an insulator, and forming a barrier layer over the metal foil by way of electroplating. 
         [0017]    Here, the metal foil can be made of a material containing copper (Cu), and the barrier layer can be made of a material containing at least one of nickel (Ni), aluminum (Al), and chromium (Cr). 
         [0018]    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 
         [0019]      FIG. 1  is a cross sectional view illustrating a metal clad laminate according to the related art. 
           [0020]      FIG. 2  is a cross sectional view illustrating a VOP (via on pad) structure. 
           [0021]      FIG. 3  is a cross sectional view illustrating the processing of a via hole in a metal clad laminate according to the related art. 
           [0022]      FIG. 4  is a cross sectional view illustrating a first disclosed embodiment of a metal clad laminate according to an aspect of the invention. 
           [0023]      FIG. 5  is a cross sectional view illustrating a second disclosed embodiment of a metal clad laminate according to an aspect of the invention. 
           [0024]      FIG. 6  is a flowchart illustrating a first disclosed embodiment of a method of manufacturing a metal clad laminate according to another aspect of the invention. 
           [0025]      FIG. 7  is a flowchart illustrating a second disclosed embodiment of a method of manufacturing a metal clad laminate according to another aspect of the invention. 
           [0026]      FIG. 8  through  FIG. 16  and  FIG. 17  through  FIG. 24  are cross sectional views representing flow diagrams for methods of forming a VOP structure using a metal clad laminate according to an aspect of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to particular modes of practice, and it is to be appreciated that all changes, equivalents, and substitutes that do not depart from the spirit and technical scope of the present invention are encompassed in the present invention. In the description of the present invention, certain detailed explanations of related art are omitted when it is deemed that they may unnecessarily obscure the essence of the invention. 
         [0028]    The terms used in the present specification are merely used to describe particular embodiments, and are not intended to limit the present invention. An expression used in the singular encompasses the expression of the plural, unless it has a clearly different meaning in the context. In the present specification, it is to be understood that the terms such as “including” or “having,” etc., are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof disclosed in the specification, and are not intended to preclude the possibility that one or more other features, numbers, steps, actions, components, parts, or combinations thereof may exist or may be added. 
         [0029]    The metal clad laminate and method of manufacturing the metal clad laminate 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. 
         [0030]      FIG. 4  is a cross sectional view illustrating a first disclosed embodiment of a metal clad laminate according to an aspect of the invention. In  FIG. 4 , there are illustrated a metal clad laminate  10 , an insulator  11 , metal foils  12 , barrier layers  13 , and metal layers  14 . 
         [0031]    A metal clad laminate  10  according to this embodiment can be structured to have a metal foil  12 , a barrier layer  13 , and a metal layer  14  formed in order on either side of an insulator  11 . 
         [0032]    The insulator  11  may serve to electronically separate the circuit patterns formed on both sides by patterning. The insulator  11  can include glass fibers impregnated with epoxy resin. Other insulating materials may also be used for the insulator  11 . 
         [0033]    The metal foil  12  facing the insulator  11  can be formed with a maximum thickness of about 2 μm, where the metal foil can be made mainly of copper (Cu). 
         [0034]    The barrier layer  13  formed over the metal foil  12  can be formed with a thickness of about 4 μm, where the barrier layer can be made of a different material from that of the metal foil  12 . In cases where the metal foil  12  is made of copper as described above, the barrier layer  13  can be made of a material containing at least one of nickel (Ni), aluminum (Al), and chromium (Cr). For example, the barrier layer  13  can be made of a material containing nickel sulfonate. 
         [0035]    The metal layer  14  formed over the barrier layer  13  can be formed with a thickness of about 12 μm or more, where the metal layer  14  can be made of a different material from that of the barrier layer  13 . For instance, in cases where the barrier layer  13  is made of a material containing nickel sulfonate as mentioned above, the metal layer  14  can be made of a material containing copper. 
         [0036]    The metal foil  12 , barrier layer  13 , and metal layer  14  mentioned above can be coupled together by plating. For example, the barrier layer  13  can be formed on the metal layer  14  by electroplating, and the metal foil  12  can be formed on the barrier layer  13  by electrolytic plating. 
         [0037]    That is, plating can be performed to form the barrier layer  13  on one side of the metal layer  14  by plating (S 110  of  FIG. 6 ), after which plating can be performed again to form the metal foil  12  on one side of the barrier layer  13  (S 120  of  FIG. 6 ), and then the insulator  11  can be attached to one side of the metal foil  12  (S 130  of  FIG. 6 ), to produce a metal clad laminate  10  as presented in the embodiment. 
         [0038]    Of course, the opposite is also possible. That is, after plating the barrier layer  13  on the metal foil  12 , the metal layer  14  can again be plated on the barrier layer  13 . 
         [0039]    In attaching the metal foil  12  and the insulator  11  together, a method can be used of compressing a semi-cured (B-stage) insulator  11  onto the metal foil  12  under a high-temperature, high-pressure environment. 
         [0040]    Further, as a modified version of the metal clad laminate  10  disclosed in the embodiment described above, a metal clad laminate  10 ′ may also be utilized, which is structured as shown in  FIG. 5 . 
         [0041]      FIG. 5  is a cross sectional view illustrating a second disclosed embodiment of a metal clad laminate according to an aspect of the invention, where  FIG. 5  illustrates a metal clad laminate  10 , an insulator  11 , metal foils  12 , and barrier layers  13 . 
         [0042]    As illustrated in  FIG. 5 , the metal layers  14  situated on the outermost layers of the structure described in the first disclosed embodiment can be excluded in the structure of the metal clad laminate  10 ′ according to this embodiment. 
         [0043]    To manufacture this type of metal clad laminate  10 ′, a method can be used of attaching the metal foil  12  onto one side or both sides of the insulator  11  (S 210  of  FIG. 7 ), and afterwards forming the barrier layer  13  on the metal foil  12  by electroplating (S 220  of  FIG. 7 ). 
         [0044]    A method of attaching the metal foil  12  to the insulator  11  can include pressing a carrier (not illustrated), to which the metal foil  12  is attached, onto the insulator  11 , and then removing the carrier (not illustrated). Furthermore, it is to be appreciated that the metal foil  12  can also be formed directly on the insulator  11 , for example, using a method of electroplating. 
         [0045]    A description will now be provided on a method of manufacturing a printed circuit board, in particular, a VOP structure, using a metal clad laminate having a structure set forth above. 
         [0046]      FIG. 8  through  FIG. 16  and  FIG. 17  through  FIG. 24  are cross sectional views representing flow diagrams for methods of forming a VOP structure using a metal clad laminate according to an aspect of the invention. According to  FIG. 8  through  FIG. 24 , a metal clad laminate  10 , an insulator  11 , metal foils  12 , barrier layers  13 , metal layers  14 , a via  15 , a via hole  15   a , seed layers  16 , plating resists  17 , circuit patterns  18 , and a pad  19  are illustrated. 
         [0047]    First of all, a metal clad laminate  10  having a structure based on the first disclosed embodiment can be prepared, as illustrated in  FIG. 8 , and then the metal layers  14  formed on the outermost layers can be removed, as illustrated in  FIG. 9 . A method of removing the metal layers  14  can include chemical etching. 
         [0048]    As described above, the metal layers  14  and the barrier layers  13  can be made of different materials, so that the barrier layers  13  may not be harmed in the process of removing the metal layers  14  using an etchant. 
         [0049]    Furthermore, as described above, the structure of a metal clad laminate  10 ′ according to the second disclosed embodiment is similar to the structure of a metal clad laminate  10  according to the first disclosed embodiment with the metal layers  14  removed. Thus, one approach may include using the metal clad laminate  10 ′ according to the second disclosed embodiment from the beginning, instead of preparing the metal clad laminate  10  according to the first embodiment as mentioned above and then removing the metal layers  14 . 
         [0050]    Afterwards, a via hole  15   a  can be processed using CO 2  laser, as illustrated in  FIG. 10 . In a metal clad laminate  10  according to this embodiment, a barrier layer  13  can be formed under the lower metal foil  12  to reinforce the metal foil  12 , whereby damage to the lower metal foil  12  can be minimized during the process of forming the via hole  15   a  using CO 2  laser. 
         [0051]    Then, the barrier layers  13  can be removed, as illustrated in  FIG. 11 . The method of removing the barrier layers  13  can employ chemical etching. Since the barrier layers  13  and metal foils  12  may be made of different materials, as described above, the metal foils  12  may not be harmed during the process of removing the barrier layer  13  using an etchant for eliminating the barrier layer  13 . 
         [0052]    Afterwards, seed layers  16  can be formed on the surfaces of the metal foils  12  and on the inner wall of the via hole  15   a , as shown in  FIG. 12 , and plating resists  17  can be formed, as shown in  FIG. 13 . Then, circuit patterns  18  and a pad  19  can be formed using electroplating, as illustrated in  FIG. 14 . 
         [0053]    Next, the plating resists  17  can be removed, as illustrated in  FIG. 15 , and parts of the seed layers  16  and metal foils  12  can be removed by flash etching, as illustrated in  FIG. 16 , to complete the VOP structure. 
         [0054]    In the description provided above, a method of forming the seed layers  16  has been disclosed, in which the processing of the via hole  15   a  using CO 2  laser is followed by removing the barrier layers  13  and then forming the seed layers  16 . It is to be appreciated, however, that the seed layers  16  can also be formed without removing the barrier layers  13 . 
         [0055]    That is, after forming the via hole  15   a , as illustrated in  FIG. 17 , the seed layers  16  can be formed on the surfaces of the barrier layers  13  and on the inner wall of the via hole  15   a , as shown in  FIG. 18 . 
         [0056]    Then, plating resists  17  can be formed on the seed layers  16 , as illustrated in  FIG. 19 , and an electroplating process can be performed, as shown in  FIG. 20 , after which the plating resists  17  can be removed, as illustrated in  FIG. 21 . 
         [0057]    In this case, since the barrier layers  13  may remain, the manufacture of the VOP structure can include removing the seed layers  16  using flash etching, as illustrated in  FIG. 22 , removing portions of the barrier layers  13 , as shown in  FIG. 23 , and finally removing portions of the metal layers  14 , as shown in  FIG. 24 . 
         [0058]    According to certain aspects of the invention as set forth above, the metal clad laminate can be produced without perforation in the metal foil during the processing of the via hole using laser. 
         [0059]    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. 
         [0060]    Many embodiments other than those set forth above can be found in the appended claims.