Abstract:
An exemplary method for manufacturing a circuit board includes, firstly, providing a substrate made of heat conductive, electrically insulative material. Then a copper layer is formed on the substrate. After that, nickel is plated on the copper layer to form a nickel layer. Finally, gold is and plated on the nickel layer to form a gold layer.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to circuit boards and methods for manufacturing circuit boards, and more particularly, to a circuit board typically used to mount LEDs (light emitting diodes) thereon and a method for manufacturing such circuit board. 
         [0003]    2. Description of Related Art 
         [0004]    LEDs have many advantages, such as high luminosity, low operational voltage, low power consumption, compatibility with integrated circuits, easy driving, long term reliability, and environmental friendliness. Such advantages have promoted the widespread use of LEDs as a light source. Nowadays, LED lamps are commonly applied in lighting. However, the wavelength of the light emitted by such an LED lamp has red shift once the LED lamp overheats. Therefore the LED lamp needs to be maintained at a relatively cool temperature. Generally, a heat sink is fixed to a printed circuit board (PCB) on which one or more LEDs are mounted, for dissipating heat from the LEDs. However, a conventional PCB has low heat conductivity, resulting in a rather poor heat dissipation effect for the LED lamps. 
         [0005]    What is needed, therefore, is a circuit board providing a high heat dissipation effect for associated components such as LED lamps, and a method for manufacturing such a circuit board. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. 
           [0007]      FIG. 1  is a flow chart showing a method for manufacturing a circuit board in accordance with an embodiment of the present disclosure. 
           [0008]      FIG. 2  is a schematic, cross-sectional view of an exemplary circuit board manufactured by the method of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    Referring to  FIGS. 1-2 , these show aspects of a method for manufacturing a circuit board  10  of an embodiment of the present disclosure. 
         [0010]    In step S 1 , a flat substrate  20  is provided. The substrate  20  is made of electrically insulative, thermally conductive material such as rubber, ceramic, or silicon. In addition, the substrate  20  is not limited to the flat shape described and shown. The substrate  20  can have other shapes such as spherical, conical, or frustoconical, depending on the actual requirements. 
         [0011]    In step S 2 , a copper layer  30  is formed on the substrate  20  by sputtering deposition under a temperature of about 373 K (Kelvin). The copper layer  30  covers a top surface of the substrate  20 . Such plating of the copper layer  30  to the substrate  20  can increase a joint force therebetween, whereby the copper layer  30  does not easily separate from the substrate  20 . A thickness of the copper layer  30  is larger than a thickness of the substrate  20 . 
         [0012]    In step S 3 , a circuit is formed in the copper layer  30  by patterning the copper layer  30 , for example by etching. Thereby, a plurality of linear slots  31  is formed in the copper layer  30 . Each linear slot  31  extends from a bottom face to a top face of the copper layer  30 . Alternatively, the linear slots  31  can be formed in the copper layer  30  by other suitable methods. 
         [0013]    In step S 4 , a nickel layer  40  is formed on the copper layer  30  by plating nickel material on the copper layer  30 . The nickel layer  40  is also filled into the linear slots  31 . Since nickel material has high corrosion resistance, the nickel layer  40  made of one or more nickel materials can prevent the copper layer  30  from corrosion (such as rusting) even after the circuit board  10  has been used for a long period. Thus, a circuit structure of the copper layer  30  is protected. 
         [0014]    In step S 5 , a gold layer  50  is formed on the nickel layer  40  by plating gold on the nickel layer  40 . Since gold has inactive chemical properties, the gold layer  50  can further prevent the circuit structure of the copper layer  30  from corrosion. That is, the circuit structure of the copper layer  30  is doubly protected. Due to the excellent metallic ductility of gold, the gold layer  50  can be made thin, and still have the advantages of anti-corrosion, good electrical conductivity, and good thermal conductivity. 
         [0015]    Referring to  FIG. 2 , the circuit board  10  includes the substrate  20 , the copper layer  30 , the nickel layer  40  and the gold layer  50 . Electronic components are set on the gold layer  50 . Heat generated by the electronic components is transferred through the gold layer  50 , the nickel layer  40  and the copper layer  30  to the substrate  20  in sequence. A thermal conductivity of pure copper is 401 W/[m*K] (watts per meter*Kelvin). A thermal conductivity of pure nickel is 90 W/[m*K]. A thermal conductivity of pure gold is 317 W/[m*K]. Therefore, the heat generated by the electronic components can be transferred from the gold layer  50  to the substrate  20  quickly. 
         [0016]    In summary, the substrate  20  is made of material having good thermal conductivity, and the three metal layers  30 ,  40 ,  50  on the substrate  20  are all made of metallic materials having good thermal conductivity. Thus, a thermal conductivity of the circuit board  10  is improved. Furthermore, the substrate  20  can be made of transparent material such as glass or thermally conductive epoxy, for meeting special demands. 
         [0017]    It is believed that the present disclosure and its advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the present disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments.