Abstract:
A thermally enhanced coreless thin substrate with embedded chips, which mainly includes a patterned carrier metal layer, at least one chip, at least one dielectric layer and at least one wiring layer, is disclosed. The chip is attached to a heat sink portion of the patterned carrier metal layer. The dielectric layer is formed over the patterned carrier metal layer and covers the chip. The wiring layer is formed on the dielectric layer for electrically connecting the patterned carrier metal layer and the chip. In the process of manufacturing the thermally enhanced coreless thin substrate with embedded chips, the heat sink portion is formed by patterning the patterned carrier metal layer after finishing the formation of the wiring layer. Thus, a thin board type electronic device that combines a heat sink, a carrier substrate and embedded chips together to form an integral unit is fabricated.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the priority benefit of Taiwan application serial no. 94147759, filed Dec. 30, 2005. All disclosure of the Taiwan application is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a circuit board with an embedded chip, and more particularly, to a thermally enhanced coreless thin substrate with an embedded chip and method for manufacturing the same.  
         [0004]     2. Description of Related Art  
         [0005]     Conventionally, the circuit board, the chip package and the combination of modularized chip package components are separately manufactured and applied. In general, the electronic device so fabricated, for example, a multi-chip package module has a thicker structure and a longer route for electrical transmission.  FIG. 1  is a schematic cross-sectional view of a conventional multi-chip package module. The conventional multi-chip package module  100  in  FIG. 1  mainly comprises a circuit substrate  110 , a plurality of chips  120  and a heat sink  130 . The chips  120  can be flip chips with a plurality of bumps  121  or chip package components. The substrate  110  has a plurality of inner connecting pads  113  disposed on a top surface  111  and a plurality of outer connecting pads  114  disposed on a bottom surface  112 . The chips  120  are disposed on the top surface  111  of the substrate  110  and are electrically connected to the inner connecting pads  113  through the bumps  121 . The heat sink  130  is attached on the chips  120 . In general, a plurality of solder balls  140  are bonded to the outer connecting pads  114 . Because the substrate  110  is a printed circuit board fabricated in a laminate or build-up technique, the packaging and modular combination of these chips  120  are applied independently. Therefore, the multi-chip package module  100  is thicker than usual and the average electrical transmission paths are longer, and signal transmission is more vulnerably interfered through cross-talk effect.  
       SUMMARY OF THE INVENTION  
       [0006]     Accordingly, at least one objective of the present invention is to provide a thermally enhanced coreless thin substrate with an embedded chip. A patterned carrier metal layer inside a substrate includes at least one heat sink portion and at least one chip is disposed on the heat sink portion. A dielectric layer inside the substrate covers the chip. A wiring layer inside the substrate is formed on the dielectric layer. The wiring layer electrically connects the chip to the patterned carrier metal layer. The present invention joins a substrate, a chip and a heat sink of a conventional multi-chip package module together to form an integral thin board type electronic device. As a result, the thickness of the device is pared down and yet the structure is able to provide the embedded chip with an enhanced capacity to dissipate heat and tighter seal. Hence, its assembling ability, interconnection reliability and electrical performance are improved and its subsequent packaging density and resistance to cross-talk effect are enhanced.  
         [0007]     Another objective of the present invention is to provide a method for manufacturing a thermally enhanced coreless thin substrate with an embedded chip. The patterning of the patterned carrier metal layer in the substrate is performed after the formation of the wiring layer inside the substrate so that the patterned carrier metal layer functions as a carrier for the chip, a heat sink for the chip and an electrical connection with the chip.  
         [0008]     According to the present invention, a thermally enhanced coreless thin substrate with an embedded chip mainly comprises a patterned carrier metal layer, at least one chip, a dielectric layer and a wiring layer. The patterned carrier metal layer at least comprises a heat sink portion. The chip is disposed on the heat sink portion. Furthermore, the chip has a plurality of electrodes. The dielectric layer is formed on the patterned carrier metal layer and covers the chip. In addition, the dielectric layer has a plurality of through holes. These through holes are linked to the patterned carrier metal layer, and the dielectric layer exposes the electrodes on the chip. The wiring layer is formed on the dielectric layer. The wiring layer includes a plurality of first trace lines and a plurality of second trace lines. The first trace lines are electrically connected to the patterned carrier metal layer via the through holes and the second trace lines are electrically connected to the electrodes.  
         [0009]     It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.  
         [0011]      FIG. 1  is a schematic cross-sectional view of a conventional multi-chip package module.  
         [0012]      FIG. 2  is a schematic cross-sectional view of a thermally enhanced coreless thin substrate with embedded chips according to one embodiment of the present invention.  
         [0013]      FIGS. 3A through 3M  are schematic cross-sectional views showing the process of fabricating a thermally enhanced coreless thin substrate with embedded chips according to one embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]     Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.  
         [0015]      FIG. 2  is a schematic cross-sectional view of a thermally enhanced coreless thin substrate with embedded chips according to one embodiment of the present invention. The thermally enhanced coreless thin substrate  200  with an embedded chip mainly comprises a patterned carrier metal layer  210 , at least one first chip  220 , a first dielectric layer  230  and a first wiring layer  240 . The patterned carrier metal layer  210  at least comprises a heat sink portion  211 . The patterned carrier metal layer  210  can be fabricated by patterning a copper foil or other conductive films. In the present embodiment, the patterned carrier metal layer  210  further comprises a plurality of connecting pads  212  for electrically connecting to external devices. Preferably, the patterned carrier metal layer  210  is a wiring layer having a wiring structure capable of minimizing the number of wiring layers inside the substrate.  
         [0016]     The first chip  220  is disposed on the heat sink portion  211  by adhesion or eutectic bonding. Furthermore, the first chip  220  has a plurality of electrodes  221  and the electrodes  221  can be bonding pads or bumps. The first chip  220  further includes an integrated circuit component (not drawn).  
         [0017]     The first dielectric layer  230  is formed on the patterned carrier metal layer  210  and covers the first chip  220 . The first dielectric layer  230  is fabricated using an electrically insulating material such as polyimide (PI) or polyethylene terephthalate (PET). The first dielectric layer  230  has a plurality of through holes  231  and the through holes  231  are linked to the patterned carrier metal layer  210 . Furthermore, the first dielectric layer  230  also exposes the electrodes  221 . The first wiring layer  240  is formed on the first dielectric layer  230 . The first wiring layer  240  comprises a plurality of first trace lines  241  and a plurality of second trace lines  242 . The first trace lines  241  are electrically connected to the connecting pads  212  of the patterned carrier metal layer  210  via the through holes  231 . The second trace lines  242  are electrically connected to the electrodes  221 . The first trace lines  241  may electrically connect to the corresponding second trace lines  242  either directly or through other wiring layers.  
         [0018]     In the process of fabricating the thermally enhanced coreless thin substrate  200  with an embedded chip, the heat sink portion  211  of the patterned carrier metal layer  210  is used for supporting the first chip  220 . By forming the first dielectric layer  230  over the patterned carrier metal layer  210  and covering the first chip  220 , the first chip  220  is embedded within the patterned carrier metal layer  210  and the first dielectric layer  230  to enhance its heat dissipating capacity and reduce its package thickness. Therefore, the patterned carrier metal layer  210  can save a conventional chip carrier, a heat sink and at least one wiring layer inside the carrier substrate because it is a single component with all the foregoing functions. Furthermore, at least one chip is embedded in the interior of the thermally enhanced coreless thin substrate  200 .  
         [0019]     In the present embodiment, the thermally enhanced coreless thin substrate  200  with an embedded chip further comprises a first solder mask layer  291  formed underneath the patterned carrier metal layer  210 . The first solder mask layer  291  exposes the connecting pads  212  on the patterned carrier metal layer  210 . Furthermore, the first solder mask layer  291  has an opening  292  that exposes the heat sink portion  211  so that the heat sink portion  211  has an exposed surface for providing the thermally enhanced coreless thin substrate  200  with good heat dissipation. Preferably, the exposed surfaces of the connecting pads  212  have a plated layer  213 , for example, a nickel-gold plated layer to prevent the oxidation of the connecting pads  212 . Moreover, the plated layer  213  may also be formed on the exposed surface of the heat sink portion  211 . In the present embodiment, an additional second dielectric layer  251  may also be formed on the first wiring layer  240 . A second wiring layer  261  is formed on the second dielectric layer  251  and the second wiring layer  261  is electrically connected to the first wiring layer  240 . Because the second dielectric layer  251  is used for isolating the first wiring layer  240  from the second wiring layer  261 , the thickness of the second dielectric layer  251  can be smaller than the first dielectric layer  230 . Moreover, the number of wiring layers and dielectric layers can be gradually increased until the desired wiring structure is obtained. In the present embodiment, the thermally enhanced coreless thin substrate  200  with an embedded chip may be used to replace a conventional multi-chip module. A third dielectric layer  252  is formed on the second wiring layer  261  and a third wiring layer  262  is formed on the third dielectric layer  252 . The second wiring layer  261  and the third wiring layer  262  are used to electrically connect with the first trace lines  241  and the second trace lines  242  of the first wiring layer  240 . Furthermore, a fourth dielectric layer  253  covers the third wiring layer  262 . At least one second chip  270  can be disposed on the second wiring layer  261 . A plurality of electrodes  271  of the second chip  270  is electrically connected to the second wiring layer  261 . Preferably, the substrate  200  further comprises a patterned covering metal layer  280  formed on the second chip  270  and the fourth dielectric layer  253 . The patterned covering metal layer  280  at least comprises a heat sink portion  281  attached to the second chip  270 . In addition, a second solder mask layer  293  is formed on the uppermost layer of the substrate  200  to cover the circuit section of the patterned covering metal layer  280 . The second solder mask layer  293  has an opening  294  that exposes the heat sink portion  281  of the patterned covering metal layer  280 . If the patterned covering metal layer  280  has a plurality of connecting pads  282 , the second solder mask layer  293  also exposes the connecting pads  282 . Preferably, a plated layer  213  is formed on the exposed surfaces of the heat sink portion  281  and the connecting pads  282  to prevent oxidation. Thus, the thermally enhanced coreless thin substrate  200  with embedded chips not only has superior assembling ability and interconnection reliability, but also has a higher wiring density and thinner package dimension. Moreover, the substrate  200  has a better electrical performance. Not only are the interconnections between the chips  220  and  270  within the substrate  200  enhanced, cross-talk effect between transmission wires is also minimized as well.  
         [0020]     The method of manufacturing the thermally enhanced coreless thin substrate  200  is shown with reference to a series of cross-sectional diagrams from  FIGS. 3A through 3M . First, as shown in  FIG. 3A , a carrier metal layer  210 ′ is provided. The carrier metal layer  210 ′ can be a copper foil. At least one of the first chip  220  is attached to the carrier metal layer  210 ′ through adhesion or eutectic bonding method. Moreover, the electrodes  221  of the first chip  220  face upward and are exposed. Then, as shown in  FIG. 3B , the first dielectric layer  230  is formed on the carrier metal layer  210 ′ by a digital inkjet printing or a stencil printing method, and the first dielectric layer  230  covers the first chip  220  but exposes the electrodes  221 . Preferably, the digital inkjet printing method is used because the first dielectric layer  230  can be shaped into various kinds of patterns and its thickness in different areas can be carefully controlled. For example, the first dielectric layer  230  is thinner over the first chip  220  and thicker over the carrier metal layer  210 ′. The through holes  231  may be formed in-situ with the formation of the first dielectric layer  230  or afterwards through performing an exposure and development process. The through holes  231  are linked to the carrier metal layer  210 ′. Thereafter, as shown in  FIG. 3C , the first wiring layer  240  is formed on the first dielectric layer  230  by etching the copper foil or performing photoresist interior plating. The first trace lines  241  of the first wiring layer  240  are electrically connected to the carrier metal layer  210 ′ via the through holes  231 . The second trace lines  242  of the first wiring layer  240  are electrically connected to the electrodes  221 . Next, as shown in  FIG. 3D , the second dielectric layer  251  is formed on the first wiring layer  240 . In the present embodiment, the second dielectric layer  251  has suitable through-hole structures for exposing the first trace lines  241  and the second trace lines  242  of the first wiring layer  240 . Then, as shown in  FIG. 3E , the second wiring layer  261  is formed on the second dielectric layer  251 . The second wiring layer  261  is electrically connected to the first wiring layer  240 . After that, as shown in  FIG. 3F , the third dielectric layer  252  is formed on the second wiring layer  261 . The third dielectric layer  252  has suitable through-hole structures for exposing parts of the second wiring layer  261 . Subsequently, as shown in  FIG. 3G , a thermal compression fixture  310  is used to dispose the second chip  270  on the third dielectric layer  252 . As shown in  FIG. 3H , the electrodes  271  of the second chip  270  are electrically connected to the second wiring layer  261 . Afterwards, as shown in  FIG. 3I , the third wiring layer  262  is formed on the third dielectric layer  252 . Next, as shown in  FIG. 3J , the fourth dielectric layer  253  is formed on the third wiring layer  262 . Similarly, the digital inkjet printing technique can be used so that the outer surface of the fourth dielectric layer  253  is almost flushed with the second chip  270  and prevented from covering the second chip  270 . Then, as shown in  FIG. 3K , a covering metal layer  280 ′ is formed on the second chip  270  and the fourth dielectric layer  253 . Next, as shown in  FIG. 3L , an exposure and development process is used to form a mask  321  on the carrier metal layer  210 ′ and a mask  322  on the covering metal layer  280 ′ for etching the carrier metal layer  210 ′ and the covering metal layer  280 ′. For example, a dry film or a photoresist layer may serve as the masks  321  and  322 . Afterwards, as shown in  FIG. 3M , the carrier metal layer  210 ′ is patterned to form the patterned carrier metal layer  210  that comprises the heat sink portion  211  and the connecting pads  212 . Meanwhile, the covering metal layer  280 ′ is patterned to form the patterned covering metal layer  280  that comprises the heat sink portion  281  and the connecting pads  282 . Finally, as shown in  FIG. 2 , the first solder mask layer  291  is formed on the patterned carrier metal layer  210  and the second solder mask layer  293  is formed on the patterned covering metal layer  280  to produce the thermally enhanced coreless thin substrate  200  with embedded chips. Therefore, the carrier metal layer  210 ′ functions as a chip carrier, a heat sink and an electrical connection for the chip in the manufacturing process.  
         [0021]     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.