Patent Publication Number: US-2011048777-A1

Title: Component-Embedded Printed Circuit Board

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a circuit board, and more particularly to a printed circuit board having an embedded component. 
     2. The Prior Arts 
     Embedded passives are passive components disposed between layers of a multi-layer circuit board. The electronic components, such as capacitors or resistors are directly formed on an inner layer of the circuit board by etching or printing. Then, at least one outer layer of the circuit board is laminated onto the inner circuit board to bury the electronic component inside the multi-layer circuit board. The embedded passives are adapted to replace those discrete passives soldered to the circuit board, so as to free up space on the circuit board to pack more circuitry and active components. 
     Buried resistor technologies are first proposed by Ohmega Technologies, Inc., a manufacturer of OHMEGA-PLY® resistor-conductor material. The buried resistor is a thin film of a phosphorus-nickel alloy serving as a resistive element plated onto a matt side of a copper foil of an inner layer. Then, they are compressed to configure a thin core, and later processed by photo-resist processing twice and etching processing thrice, so as to configure a desired thin film resistor at a certain position. Such a thin film resistor is disposed between the layers, and thus called buried resistor. 
     In 1992, Zycon, a U.S. PCB manufacturer, proposed to further provide an extremely thin dielectric inner layer, e.g., 2 to 4 mils, in a high level multilayer circuit board in addition to original Vcc/GND inner layers. An integral capacitor is configured by the parallel copper layers of the circuit board, which provide a large area of the copper layer. Because the capacitor is disposed between the layers, it is named as buried capacitor (BC). The buried capacitor has advantages of avoiding noise, providing charging power, and stabilizing voltage, during operating at a basic frequency. With respect to the BC, Zycon owns several U.S. patents, i.e., U.S. Pat. No. 5,079,069, U.S. Pat. No. 5,161,086, and U.S. Pat. No. 5,155,655. 
     Recently, the concept of the embedded passives is applied to fabricate active components in the circuit board for increasing a packaging density. Accordingly, a recess is formed in an insulating layer, and an electronic component is embedded in the recess. However, the circuit board still has the insulating layer remained beneath the electronic component. Therefore, the overall thickness of the circuit board and density of the circuitry can be further improved. 
     SUMMARY OF THE INVENTION 
     A primary objective of the present invention is to provide a component-embedded printed circuit board, which includes a detachable carrier plate having a metalized layer disposed thereon and disposes a component on the metalized layer. The detachable carrier plate replaces an inseparable insulating layer of a conventional component-embedded PCB, thereby reducing the thickness of the PCB and increasing the density of circuitry. 
     In order to achieve the objective, a component-embedded PCB according to the present invention includes a carrier plate having a metalized layer, i.e. a plating metal layer, plated thereon, an electronic component disposed on the metalized layer of the carrier plate, and a metal layer laminated onto the metalized layer and the carrier plate by a dielectric film. The carrier plate is then removed to expose the metalized layer and at least one of the metal layer and the exposed metalized layer is patterned to form a circuit layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be apparent to those skilled in the art by reading the following detailed description of preferred embodiments thereof, with reference to the attached drawings, in which: 
         FIG. 1A  is a schematic drawing illustrating a carrier plate and a metalized layer of a component-embedded printed circuit board according to a first embodiment of the present invention; 
         FIG. 1B  is a schematic drawing illustrating surface mount technology (SMT) fiducial marks being provided on the metalized layer of  FIG. 1A ; 
         FIG. 1C  is a schematic drawing illustrating an electronic component being disposed on the metalized layer of  FIG. 1B ; 
         FIGS. 1D-1E  are schematic drawings illustrating the carrier plate, the metalized layer and the electronic component of  FIG. 1C  and a metal layer having a dielectric film; 
         FIG. 1F  is a schematic drawing illustrating an opening corresponding to the electronic component being formed; 
         FIG. 1G  is a schematic drawing illustrating the carrier plate of  FIG. 1F  being removed; 
         FIG. 1H  is a schematic drawing illustrating the metal layer and the metalized layer of  FIG. 1G  being patterned to form circuit layers; 
         FIG. 2A  is a partial exploded view illustrating a component-embedded PCB according to a second embodiment of the present invention before the carrier plate is removed; and 
         FIG. 2B  is a partial exploded view illustrating a component-embedded PCB according to a third embodiment of the present invention before the carrier plate is removed. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIGS. 1A to 1H  are schematic diagrams illustrating steps of fabricating a component-embedded PCB according to a first embodiment of the present invention. Referring to  FIG. 1A , a metalized layer  12 , e.g. a plating metal layer, is disposed on a carrier plate  10 . The carrier plate  10  is made of a conductive material or an insulating material, and the metalized layer  12  is made of copper. 
     As shown in  FIG. 1B , a plurality of surface mount technology (SMT) fiducial marks  14  are provided on the metalized layer  12  for positioning purpose. Referring to  FIG. 1C , an electronic component  16  is disposed on the metalized layer  12  of the carrier plate  10 . Referring to  FIGS. 1D-1E , a metal layer  20  is laminated onto the metalized layer  12  having the electronic component  16  disposed thereon by a dielectric film  18 . As shown in  FIG. 1F , an opening  22  corresponding to the electronic component  16  is formed for the convenience of later processing a through hole (not shown) for the electronic component  16  to output signals. The carrier plate  10  is then removed from the laminated metal layer  20 , the dielectric film  18 , the metalized layer  12  and the carrier plate  10  to expose the metalized layer  12  as shown in  FIG. 1G . Then, at least one of the metal layer  20  and the exposed metalized layer  12  is patterned to form a circuit layer  24  as shown in  FIG. 1H . Therefore, the component-embedded PCB has the circuit layer  24  but does not have any insulating layer remained beneath the electronic component  16 , thereby reducing a thickness of the component-embedded PCB. The component-embedded PCB according to the present invention has a higher density of circuitry than a conventional component-embedded PCB does. 
     The electronic component  16  may be an active component or a passive component, such as a capacitor, a resistor, or an inductance. In order to enhance the bonding between the carrier plate  10  and the metalized layer  12 , the carrier plate  10  is configured with a rough surface. 
     In addition to the steps as shown in  FIGS. 1D-1E , there are another ways to laminate the metal layer  20  onto the metalized layer  12  having the electronic component  16  disposed thereon. 
     Referring to  FIG. 2A , a component-embedded PCB according to a second embodiment of the present invention further includes a dielectric layer  13  disposed on the metalized layer  12  to enhance the electrical insulation. The electronic component  16  is disposed on the dielectric layer  13 . Then, the metal layer  20  is laminated onto the dielectric layer  13  by the dielectric film  18  similar to  FIGS. 1D-1E . 
     If the electronic component  16  is too thick, the electronic component  16  is likely to be damaged during the metal layer  20  being laminated onto the carrier plate  10  and the metalized layer  12  by the dielectric film  18 . Referring to  FIG. 2B , a component-embedded PCB according to a third embodiment of the present invention further includes two dielectric sheets  26  to prevent the electronic component  16  from damage. Each of the dielectric sheets  26  includes a cavity  26   a  corresponding to the electronic component  16 . The dielectric sheets  26  are disposed on the metalized layer  12  and the electronic component  16  is located in the cavities of the dielectric sheets  26 . Then, the carrier plate  10  and the metalized layer  12  having the electronic component  16  disposed thereon, the dielectric sheets  26 , and the metal layer  20  having the dielectric film  18  are laminated together similar to  FIGS. 1D-1E . 
     Although the present invention has been described with reference to the preferred embodiments thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.