Abstract:
A semiconductor package with a flash-proof device is proposed, in which at least one chip and at least one passive device mounted on a substrate are covered by a flash-proof device dimensionally designed for positioning the substrate in a conventional mold and preventing a molding resin from flashing on the substrate in a molding process, and thus quality of the fabricated package can be assured. Due to no need of a specifically designed mold, fabrication costs are reduced. Furthermore, the flash-proof device has its top side exposed to outside of an encapsulant formed in the molding process, thereby allowing heat dissipating efficiency to be improved. Moreover, the flash-proof device provides shielding for the chip and the passive device received therein, so that external electromagnetic interference with performance of the semiconductor package can be reduced.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to semiconductor packages, and more particularly, to a semiconductor package used as a multi-media card (MMC).  
         BACKGROUND OF THE INVENTION  
         [0002]    Illustrated in FIG. 9 is a semiconductor package miniaturized in profile and currently used as a multi-media card (MMC) as disclosed in U.S. Pat. No. 6,040,622. In the semiconductor package  1 , on a front side  100  of a substrate  10  there are mounted at least one memory chip  11  and at least one passive device  12  (only one of each is illustrated in the drawing respectively), both of which are electrically connected to the substrate  10 ; whereas on a back side  101  of the substrate  10  there are formed a plurality of connecting terminals  102  for electrically connecting the memory chip  11  and passive device  12  to an external device. The semiconductor package  1  further includes an encapsulant  13  for encapsulating the memory chip  11 , the passive device  12  and the substrate  10  in a manner that, the back side  101  and the connecting terminals  102  of the substrate  10  are exposed to outside of the encapsulant  13  to be in direct contact with the atmosphere.  
           [0003]    Furthermore, during a molding process, the substrate  10  having the memory chip  11  and passive device  12  is clamped between an upper mold  140  and a lower mold  141  of a mold  14 , as shown in FIG. 10. Prior to molding, since the portion of the substrate  10  which is arranged to be exposed to outside of the encapsulant  13  is not clamped by the mold  14 , the substrate  10  is adsorbed with vacuum onto the lower mold  141  through a via  141   a  formed in the lower mold  141  in a manner that, the back side  101  of the substrate  10  closely abuts the lower mold  141 , so as to prevent a molding resin from flashing on the back side  101  or the connecting terminals  102  of the substrate  10  during molding.  
           [0004]    However, several drawbacks are generated in the foregoing semiconductor package  1 . First, the foregoing vacuum adsorption can not be applied to a conventional mold, and a specific mold having a vacuum adsorption function used herein is more expensive than the conventional mold, thereby making complexity and costs in fabrication both increased. Furthermore, the semiconductor package  1  encapsulates relatively more electronic and semiconductor components, and accordingly generates more heat during operation than a semiconductor package merely encapsulating a single semiconductor chip; this causes a problem of how to effectively dissipate the heat for the semiconductor package  1 . In addition, as more electronic and semiconductor components are encapsulated in the semiconductor package  1 , electronic performance of the semiconductor package  1  may be easily affected by external electromagnetic interference (EMI) detrinentally.  
         SUMMARY OF THE INVENTION  
         [0005]    A primary objective of the present invention is to provide a semiconductor package with a flash-proof device, in which a molding resin can be effectively prevented from flashing on a back side of a substrate, and heat dissipating efficiency is significantly improved, as well as electricity and reliability of the semiconductor package can be assured.  
           [0006]    According to the above and other objectives, the semiconductor package of the invention includes: a substrate having a first side for disposing a plurality of conductive traces thereon, and a second side for forming a plurality of electrical connection terminals thereon; at least one chip attached to the first side of the substrate and electrically connected to the substrate; at least one passive device attached to the first side of the substrate and electrically connected to the substrate; a flash-proof device attached to the first side of the substrate for forming a space for receiving the chip and the passive device therein; and an encapsulant for encapsulating the chip, the passive device, the flash-proof device and the substrate in a manner that, a top side of the flash-proof device is exposed to outside of the encapsulant; wherein a height between the top side of the flash-proof device and the first side of the substrate is slightly greater than a depth of a molding cavity of a mold used for forming the encapsulant in a molding process. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    The present invention can be more fully understood by reading the following detailed description of the preferred embodiments, with reference made to the accompanying drawings, wherein:  
         [0008]    [0008]FIG. 1 is a sectional view of a semiconductor package of a first preferred embodiment of the invention;  
         [0009]    [0009]FIG. 2 is a perspective view of a flash-proof device used in a first preferred embodiment of the invention;  
         [0010]    [0010]FIG. 3 is a schematic diagram of a semiconductor package of a first preferred embodiment of the invention in a molding process;  
         [0011]    [0011]FIG. 4 is a sectional view of a semiconductor package of a second preferred embodiment of the invention;  
         [0012]    [0012]FIG. 7 is a perspective view of a flash-proof device used in a third preferred embodiment of the invention;  
         [0013]    [0013]FIG. 8 is a sectional view of a semiconductor package of a fourth preferred embodiment of the invention;  
         [0014]    [0014]FIG. 9 (PRIOR ART) is a sectional view of a conventional MMC semiconductor package; and  
         [0015]    [0015]FIG. 10 (PRIOR ART) is a schematic diagram showing a conventional MMC semiconductor package in a molding process. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     First Preferred Embodiment  
       [0016]    Illustrated in FIG. 1 is a sectional view of a semiconductor package of a first preferred embodiment of the invention. The semiconductor package  2  includes a substrate  20  having a first side  200  for disposing a plurality of conductive traces  202  thereon, and a second side  201  for forming a plurality of electrical connection terminals  203  thereon, which are electrically connected to the conductive traces  202  via conductive vias or interconnecting wires (not shown). The substrate  20  can be made of polyimide resin, bismaleimide triazine (BT), epoxy resin glass (FR4) or a ceramic material, etc.  
         [0017]    On the first side  200  of the substrate  20  there are attached a chip  21  and a passive device  22  at predetermined positions, wherein numbers of the chip  21  and passive device  22  can be optionally increased. The chip  21  is electrically connected to the conductive traces  202  on the substrate  20  via a plurality of gold wires  23 ; besides, the electrical connection between the chip  21  and the conductive traces  202  can also be accomplished by using a flip chip or tape automated bonding (TAB) technique. Similarly, the passive device  22  is electrically connected to the conductive traces  202  on the substrate  20  through the use of a SMT (Surface Mount Technology) techniques. As a result, the chip  21  and the passive device  22  electrically connected to the first side  200  of the substrate  20  can therefore be electrically connected to external devices through the use of the electrical connection terminals  203  on the second side  201  of the substrate  20 .  
         [0018]    After the chip  21  and the passive device  22  are mounted on the substrate  20 , a flash-proof device  24  is attached to a predetermined position on the first side  200  of the substrate  20  by means of a thermally conductive and elastic adhesive  25 . Referring to FIG. 2, the flash-proof device  24  is a hollow rectangular frame with a cavity  240  formed therein. After attaching the flash-proof device  24  to the substrate  20 , the chip  21  and the passive device  22  can be accommodated in the cavity  240  without coming into contact with the flash-proof device  24 . Moreover, in order to encompass more or larger-sized chips and passive devices in the cavity  240 , an outer sidewall  241  of the flash-proof device  24  is preferably aligned with a side edge  204  of the substrate  20  for maximizing surface area of the first side  200  of the substrate  20  contained in the cavity  240 .  
         [0019]    The semiconductor package  2  further includes an encapsulant  26  for encapsulating the chip  21  and the passive device  22  to be hermetically isolated from exterior, and for partially encapsulating the flash-proof device  24  and the substrate  20 , wherein the second side  201  of the substrate and a top side  242  of the flash-proof device  24  are exposed to outside of the encapsulant  26 . This therefore exposes the electrical connection terminals  203  on the second side  201  of the substrate  20  to be electrically connected to external devices.  
         [0020]    Referring to FIG. 3, the encapsulant  26  is formed by using a conventional mold  27  having an upper mold  270  and a lower mold  271  The upper mold  270  is formed with a molding cavity  270   a  for receiving the chip  21 , the passive device  22  and the flash-proof  20 , wherein the second side  201  of the substrate and a top side  242  of the flash-proof device  24  are exposed to outside of the encapsulant  26 . This therefore exposes the electrical connection terminals  203  on the second side  201  of the substrate  20  to be electrically connected to external devices.  
         [0021]    Referring to FIG. 3, the encapsulant  26  is formed by using a conventional mold  27  having an upper mold  270  and a lower mold  271 . The upper mold  270  is formed with a molding cavity  270   a  for receiving the chip  21 , the passive device  22  and the flash-proof device  24  therein. When the upper mold  270  is engaged with the lower mold  271 , a peripheral portion  20   a  of the substrate  20  (i.e. the portion outside the molding cavity  270   a ) not encapsulated by the encapsulant  26  is clamped by the upper mold  270  and the lower mold  271  for positioning the substrate  20  in the molding cavity  270   a . Further, as a height H from the top side  242  of the flash-proof device  24  to the first side  200  of the substrate  20  is made to be slightly greater than a depth h of the molding cavity  270   a , after engaging the upper mold  270  with the lower mold  271 , the top side  242  of the flash-proof device  24  closely abuts and is pressed by a top wall  270   b  of the molding cavity  270   a . This accordingly makes the second side  201  of the substrate  20  hermetically abut the lower mold  271  without forming a gap between the substrate  20  and the lower mold  271 . Therefore, during a molding process, a molding resin used for forming the encapsulant  26  can be prevented from flashing on the second side  201  of the substrate  20 , which makes the semiconductor package  2  qualitatively fabricated and the electrical connection terminals  203  on the substrate  20  free of flash to be electrically connected to external devices. As a result, with the use of the flash-proof device  24 , the encapsulant  26  can be formed by using the conventional mold without needing a specific mold for providing vacuum adsorption, so that costs and processes in fabrication can be reduced and simplified, respectively.  
         [0022]    Additionally, the flash-proof device  24  is formed with a plurality of vias  243 ; during the molding process, the molten molding resin flows through the vias  243  into the cavity  240  of the flash-proof device  24  for encapsulating the chip  21  and the passive device  22 . Moreover, the resin flowing through the vias  243  can further enhance bonding between the flash-proof device  24  and the cured encapsulant  26  after the molding process is completed.  
         [0023]    In order to improve heat dissipating efficiency of the semiconductor package  2 , the flash-proof device  24  can be made of a metallic material with good thermal conductivity, such as copper, aluminum, copper alloy, aluminum alloy or a mixture thereof. Furthermore, as the top side  242  of the flash-proof device  24  is exposed to the outside of the encapsulant  26 , heat transmitted to the flash-proof device  24  can be directly dissipated to the atmosphere from the top side  242  thereof.  
       Second Preferred Embodiment  
       [0024]    Illustrated in FIG. 4 is a sectional view of a semiconductor package of a second preferred embodiment of the invention. The semiconductor package  3  of the second embodiment differs from that of the first embodiment in that, a flash-proof device  34  of the semiconductor package  3  is a rectangular box, as shown in FIG. 5. The flash-proof device  34  has a rectangular frame  344  and a plate  345  connected to one end of the rectangular frame  344 , both of which define a cavity  340  for receiving a chip  31  and a passive device  32  therein. On the plate  345  there are formed a plurality of protrusions  342  for making a height from top ends  342   a  of the protrusions  342  to a first side  300  of a substrate  30  slightly greater than a depth of a molding cavity of a mold (not shown) used for forming an encapsulant  36 , which is used to encapsulate the chip  31 , the passive device  32  and the flash-proof device  34 . Thus, during a molding process, the top ends  342   a  of the protrusions  342  closely abut a top wall of the molding cavity of the mold for preventing a molding resin from flashing on a second side  301  of the substrate  30 . Moreover, the rectangular frame  344  is formed with a plurality of vias  344   b  for allowing the molten molding resin to flow into the cavity  340  of the flash-proof device  34  through the vias  344   b . Furthermore, at conductive traces  302  on the first side  300  of the substrate  30  there are formed ground traces  302   a  at positions corresponding to a bottom side  344   a  of the rectangular frame  344 , so as to electrically connect the flash-proof device  34  to the ground traces  302   a  after the flash-proof device  34  is attached to the substrate  30  through an electrically conductive adhesive  35 , so that electricity of the semiconductor package  3  can be increased. In addition, as the chip  31  and the passive device  32  are covered by the flash-proof device  34 , influence of external electromagnetic interference (EMI) on the chip  31  during the high-frequency operation can be reduced due to a shielding effect of the flash-proof device  34 , and thus the electricity of the semiconductor package  3  can be further enhanced.  
       Third Preferred Embodiment  
       [0025]    Illustrated in FIG. 6 is a sectional view of a semiconductor package of a third preferred embodiment of the invention. The semiconductor package  4  of the third preferred embodiment differs from that of the second preferred embodiment in that, the semiconductor package  4  is not formed with any protrusion on a plate  445  of a flash-proof device  44 , as shown in FIG. 7. That is, the plate  445  has a top side  445   a  thereof completely exposed to outside of an encapsulant  46  for being in direct contact with the atmosphere after the encapsulant  46  is cured. Therefore, a height from the top side  445   a  of the plate  445  to a first side  400  of a substrate  40  needs to be slightly greater than a depth of a molding cavity of a mold (not shown) used for forming the encapsulant  46 . This makes a second side  401  of the substrate  40  closely abut a lower mold (not shown) of the mold for preventing a molding resin from flashing on the second side  401  of the substrate  40 . Similarly, the flash-proof device  44  is also formed with a plurality of vias  444   b  in a rectangular frame  444  thereof for allowing the molten molding resin-to flow through the vias  444   b.    
       Fourth Preferred Embodiment  
       [0026]    Illustrated in FIG. 8 is a sectional view of a semiconductor package of a fourth preferred embodiment of the invention. The semiconductor package  5  of the fourth preferred embodiment differs from that of the third preferred embodiment in that, the semiconductor package  5  is formed with step-like recesses  542   a  at side edges of a plate  545  of a flash-proof device  54  so as to prevent a molding resin from flashing on the plate  545 .  
         [0027]    The invention has been described using exemplary preferred embodiments. However, it is to be understood that the scope of the invention is not limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements. The scope of the claims, therefore, should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.