Abstract:
A printed circuit board (PCB) and appertaining method of manufacturing are provided. The method includes: coating a metal layer on the entire surface of a substrate having an outer surface on which an interconnection pattern is formed; partially removing the metal layer from the surface of the substrate to form a window for a chip to be mounted therein and partially exposing the interconnection pattern to form a bonding finger; forming a first insulating layer on the metal layer by primarily anodizing the metal layer; electroplating a surface of the bonding finger by supplying power to the metal layer; and forming a second insulating layer disposed below the first insulating layer by entirely and secondarily anodizing the metal layer. A gold electroplating process can be performed without a lead wire, and an oxide layer formed by an anodizing process can protect circuits formed on the substrate and electrically insulate them.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2007-0108407, filed Oct. 26, 2007, the contents of which are hereby incorporated herein by reference in their entirety. 
       BACKGROUND 
       [0002]    The present invention relates to a method of manufacturing a printed circuit board (PCB) and a PCB manufactured by the same, and more particularly, to a method of manufacturing a PCB in which an oxide layer for protecting a circuit pattern formed on a substrate is formed using an anodizing process, and a PCB manufactured by the method. 
         [0003]    In recent years, as electronic appliances are scaled down and their functions are more complex, multi-chip packages (MCPs) or stacked chip scale packages in which integrated circuit (IC) chips are stacked are being widely employed. An IC package substrate used for the MCP or the stacked chip scale package must have a predetermined thickness or less so that the MCP or the stacked chip scale package can be applied to small-sized electronic appliances with complex functions. 
         [0004]    A conventional method of manufacturing a printed circuit board (PCB) necessarily includes a process of coating solder resist in order to prevent oxidation of an exposed circuit pattern (or interconnection pattern) on an outer surface of a substrate and electrically insulate circuit patterns from one another. The solder resist is a kind of paint and is obtained by corroding copper foil coated on the substrate. Basically, the solder resist is a bare wire that is not coated with an insulating material. 
         [0005]      FIG. 1  is a block diagram of a conventional gold electroplating process using a lead wire, and  FIGS. 2A through 2C  are diagrams illustrating a conventional method of manufacturing a PCB using a gold electroplating process. 
         [0006]    Referring to  FIGS. 1 , and  2 A through  2 C, in step S 10 , an interconnection pattern  2  and a lead wire pattern  3  are formed on a surface of a substrate  1 , and a solder resist  4  formed of an insulating material is coated on the entire surface of the substrate  1 . 
         [0007]    Thereafter, in step S 20 , a dry process, an exposure process, and a developing process are performed, thereby forming a window  5  in which a chip (not shown) is mounted on a predetermined portion of the substrate  1  so that a bonding finger  2   a  is exposed on the substrate  1 . 
         [0008]    Subsequently, in step S 30 , a power source  6  is connected to the lead wire pattern  3  and the bonding finger  2   a  is electroplated with gold  2   a ′ in order to improve bonding efficiency. 
         [0009]    However, since it is necessary to form a gold-plating lead wire in order to electroplate the bonding finger  2   a  with gold, manufacturing the conventional PCB is complicated and costly. 
         [0010]    Also, the conventional solder resist has a high moisture absorption rate and a high coefficient of thermal expansion, so that the conventional PCB cannot ensure high reliability. 
         [0011]    Furthermore, when the substrate  1  has a very small thickness, a stiffened plate must be further adhered to the substrate  1 , and thus moving or handling the PCB at an interval between process steps during a package assembly process is difficult. 
       SUMMARY 
       [0012]    An exemplary embodiment of the invention provides a method of manufacturing a printed circuit board (PCB), in which a bonding finger is electroplated with gold by a primary anodizing process and an insulating layer is formed on the surface of a substrate by a secondary anodizing process so that a gold electroplating process can be performed without a lead wire, and a PCB manufactured by the method. 
         [0013]    Another exemplary embodiment of the invention provides a method of manufacturing a PCB, in which an oxide layer formed by anodization can effectively protect a circuit pattern formed on a substrate and electrically insulate circuits from one another to enhance reliability, and a PCB manufactured by the method. 
         [0014]    Yet another exemplary embodiment of the invention provides a method of manufacturing a PCB, in which the surface of a substrate is coated with ceramic so that the substrate can maintain stiffness to make it unnecessary to adhere a stiffened plate to the substrate with a small thickness, and thus moving or handing the PCB at an interval between process steps during a package assembly process is very easy, and a PCB manufactured by the same. 
         [0015]    In one aspect, the present invention is directed to a method of manufacturing a PCB. The method includes: coating a metal layer on the entire surface of a substrate having an outer surface on which an interconnection pattern is formed; partially removing the metal layer from the surface of the substrate to form a window for a chip to be mounted therein and partially exposing the interconnection pattern to form a bonding finger; forming a first insulating layer on the metal layer by primarily anodizing the metal layer; electroplating a surface of the bonding finger by supplying power to the metal layer; and forming a second insulating layer disposed below the first insulating layer by entirely and secondarily anodizing the metal layer. 
         [0016]    According to various embodiments of the present invention, when the bonding finger is electroplated, the interconnection pattern may not include a plating lead wire. 
         [0017]    The metal layer may be formed of any one of Al, Mg, Zn, Ti, Ta, Hf, and Nb. 
         [0018]    Partially exposing the interconnection pattern may be performed by an exposure process, a developing process, and an etching process. 
         [0019]    Electroplating of the surface of the bonding finger may be performed by a gold electroplating process. Here, the first and second insulating layers may be oxide layers. 
         [0020]    In another aspect, the present invention is directed to a PCB. The PCB includes: an interconnection pattern disposed on an outer surface of a substrate. A bonding finger formed by partially exposing the interconnection pattern on the surface of the substrate is electroplated with gold. An unexposed portion of the interconnection pattern is coated with an oxide layer. 
         [0021]    The oxide layer may be an aluminum oxide (Al2O3) layer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The foregoing and other objects, features and advantages of the invention will be apparent from the more particular description of exemplary embodiments of the invention, as illustrated in the accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
           [0023]      FIG. 1  is a block diagram of a conventional gold electroplating process using a lead wire; 
           [0024]      FIGS. 2A-2C  are diagrams illustrating a conventional method of manufacturing a printed circuit board (PCB) using a gold electroplating process; 
           [0025]      FIG. 3  is a flowchart illustrating a method of manufacturing a PCB according to an embodiment of the present invention; 
           [0026]      FIGS. 4A-4D  are diagrams illustrating a method of manufacturing a PCB according to an embodiment of the present invention; and 
           [0027]      FIGS. 5A-5F  are diagrams illustrating a method of manufacturing a PCB according to an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0028]    Various embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. In the drawings, the thicknesses of layers and regions may be exaggerated for clarity. It will also be understood that when a layer is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate or intervening layers may also be present. Like reference numerals refer to like elements throughout the specification. 
         [0029]      FIG. 3  is a flowchart illustrating a method of manufacturing a PCB according to various embodiments of the present invention, and  FIGS. 4A through 4D  are diagrams illustrating a method of manufacturing a PCB according to various embodiments of the present invention. 
         [0030]    Referring to  FIGS. 3 , and  4 A through  4 D, a method of manufacturing a PCB according to various embodiments of the present invention includes coating a metal layer  113  on the entire surface of a substrate  110  having an outer surface on which an interconnection pattern  111  is formed (step S 110 ). In step S 120 , the metal layer  113  is partially removed from the surface of the substrate  110  to form a window for a chip (not shown) to be mounted therein and partially expose the interconnection pattern  111  on the surface of the substrate  110  to form a bonding finger  111   a . In step S 130 , the metal layer  113  is primarily anodized to form an insulating layer  113   a  on a surface of the metal layer  113 . In step S 140 , a surface of the bonding finger  111   a  is electroplated with gold  111   a ′ by supplying power  115  to the metal layer  113 . In step S 150 , the metal layer  113  is secondarily anodized so that the entire metal layer  113  (i.e., both the surface and inside of the metal layer  113 ) is formed of an insulating material or oxide. 
         [0031]    Only the surface of the metal layer  113  is oxidized during the primary anodizing process, while not only the surface of the metal layer  113  but also the inside thereof are oxidized during the secondary anodizing process. 
         [0032]    During the primary anodizing process, only the surface of the metal layer  113  is oxidized so that the metal layer  113  can be electrically connected to the interconnection pattern  111  formed of copper foil and the bonding finger  111   a  of the interconnection pattern  111  can be electroplated with gold  111   a′.    
         [0033]    The metal layer  113  may be coated by a sputtering process or an evaporation process. 
         [0034]    In step S 120 , exposing the bonding finger  111   a  of the interconnection pattern  111  to be electroplated with gold  111   a ′ may be performed by an exposure process, a developing process and an etching process, and the etching process may be performed using a material used for etching aluminum, for example, sodium hydroxide or a mixture of nitric acid, phosphoric acid, and acetic acid. 
         [0035]    In the method of manufacturing a PCB according to various embodiments of the present invention, when the bonding finger  111   a  is electroplated with gold  111   a ′, the interconnection pattern  111  does not include a plating lead wire. In other words, since electroplating with gold  111   a ′ is performed without a lead wire, the lead wire is not prepared during formation of the interconnection pattern  111 . 
         [0036]    In step S 140 , electroplating of the surface of the bonding finger  111   a  may be performed by electroplating with gold  111   a ′. Here, the bonding finger  111   a  refers to a portion of the interconnection pattern  111 , which is electrically connected to a bonding pad of the chip. 
         [0037]    Also, when the metal layer  112  is secondarily anodized, the metal layer  112  is entirely oxidized. 
         [0038]    During anode-oxidization (or anodization), a metal layer provided as an anode is electrolyzed in a diluted acid solution so that the metal layer reacts with oxygen generated by the anode to thereby form a metal oxide layer having good adhesive characteristics with a base metal. 
         [0039]    Typically, an anodizing process may be performed on an aluminum (Al) layer. However, magnesium (Mg), zinc (Zn), titanium (Ti), tantalum (Ta), hafnium (Hf), or niobium (Nb) may be anodized. 
         [0040]    When an Al layer is electrolyzed at an anode, half the thickness of a surface of the Al layer is corroded, and the other half has aluminum oxide (Al2O3). In this case, the properties of the Al2O3 layer may depend on process conditions of the anodizing process, specifically, the composition and concentration of a solution, the type of an additive, the temperature of the solution, voltage, and current. The anodizing process results in formation of an oxide coating layer with a high corrosion resistance. Also, the PCB can be improved in appearance since the anodizing process produces a decorative effect. 
       Embodiment 1 
       [0041]      FIGS. 5A through 5F  are diagrams illustrating a method of manufacturing a PCB according to an exemplary embodiment of the present invention. 
         [0042]    Referring to  FIG. 5A , interconnection patterns  211 , for example, copper patterns, are formed on both surfaces of a substrate  210  and electrically connected to each other by a via  212 . 
         [0043]    Referring to  FIG. 5B , a metal layer  213 , for example, an Al layer  213 , is coated on the entire surface of the substrate  210 . In this case, the metal layer  213  may be coated to a thickness of several of μm by a sputtering process or an evaporation process. More specifically, the metal layer  213  may be formed to such a thickness so as not to allow resistance to exceed about 0.3 MΩ, and thus the flow of current may not be impeded during a subsequent process. 
         [0044]    Referring to  FIG. 5C , exposure, developing, and etching processes are performed so that the metal layer  213  is partially removed from a surface of the substrate  210  to form a window for a chip (not shown) to be mounted therein. Thus, the window is formed to partially expose the interconnection pattern  211  to form a bonding finger  211   a.    
         [0045]    Referring to  FIG. 5D , the metal layer  213  is primarily anodized so that an oxide layer  213   a  is formed only on the metal layer  213 . 
         [0046]    Referring to  FIG. 5E , a current is supplied to the metal layer  213  so that a surface of the bonding finger  211   a  is electroplated with gold  211   a ′. Since the oxide layer  213   a  is formed only on the metal layer  213 , the bonding finger  211   a , but not the metal layer  213 , is electroplated with gold  211   a′.    
         [0047]    Referring to  FIG. 5F , in order to prevent oxidation of the interconnection pattern  211 , the metal layer  213  is secondarily anodized so that the metal layer  213  is entirely oxidized to form a metal oxide layer  213   b , for example, an aluminum oxide (Al 2 O 3 ) layer, which functions as a solder resist. 
         [0048]    As shown in  FIG. 5F , a PCB according to an embodiment of the present invention, which is manufactured by the above-described method, includes the interconnection pattern  211  coated on an outer surface of the substrate  210 , the bonding finger  211   a  of the interconnection pattern  211 , which is exposed on the surface of the substrate  210  and electroplated with gold  211   a ′, and the metal oxide layer  213   b  coated on an unexposed portion of the interconnection pattern  211 . 
         [0049]    According to the embodiments of the present invention as described above, a gold electroplating process can be performed without a lead wire, and an oxide layer formed by an anodizing process can protect a circuit pattern formed on a substrate and electrically insulate circuits from one another. Also, since a PCB according to various embodiments of the present invention described above has a lower moisture absorption rate and a lower coefficient of thermal expansion than a conventional solder resist, the PCB can be highly reliable. 
         [0050]    For the purposes of promoting an understanding of the principles of the invention, reference has been made to the preferred embodiments illustrated in the drawings, and specific language has been used to describe these embodiments. However, no limitation of the scope of the invention is intended by this specific language, and the invention should be construed to encompass all embodiments that would normally occur to one of ordinary skill in the art. 
         [0051]    The present invention may be described in terms of functional block components and various processing steps. Such functional blocks may be realized by any number of components configured to perform the specified functions. Furthermore, the present invention could employ any number of conventional techniques for electronics configuration, signal processing and/or control, data processing and the like. 
         [0052]    The particular implementations shown and described herein are illustrative examples of the invention and are not intended to otherwise limit the scope of the invention in any way. For the sake of brevity, conventional aspects may not be described in detail. Furthermore, the connecting lines, or connectors shown in the various figures presented are intended to represent exemplary functional relationships and/or physical or logical couplings between the various elements. It should be noted that many alternative or additional functional relationships, physical connections or logical connections may be present in a practical device. Moreover, no item or component is essential to the practice of the invention unless the element is specifically described as “essential” or “critical”. 
         [0053]    The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural. Furthermore, recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. Finally, the steps of all methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The word mechanism is intended to be used generally and is not limited solely to mechanical embodiments. Numerous modifications and adaptations will be readily apparent to those skilled in this art without departing from the spirit and scope of the present invention.