Abstract:
A heat sink for conducting a coolant is provided. The heat sink includes a casing and a porous material layer. The porous material layer is disposed inside the casing, and the coolant is conducted into the porous material layer. Moreover, a package structure that dissipates heat by use of a coolant is provided. The package structure includes a carrier, a chip, and the aforementioned heat sink. The chip is disposed on the carrier, and the heat sink is disposed on the carrier or above the chip. The heat dissipation efficiency of the package structure can be improved by the heat sink.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the priority benefit of Taiwan application serial no. 94100957, filed on Jan. 13, 2005. All disclosure of the Taiwan application is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of Invention  
         [0003]     The present invention relates to a heat sink and a package structure. More particularly the present invention relates to a heat sink and a package structure having high heat dissipation efficiency.  
         [0004]     2. Description of Related Art  
         [0005]     Recently, with the continuous increase in the integration of the internal circuitry of the integrated circuit (IC), the heat produced by the IC is also increased continuously. For the personal computer, ICs with high integration, such as the Central Processing Unit or graphic chip, produce heat. To allow said ICs to continue normal operation, the IC must be kept under a preferable operating temperature, in order to avoid degradation of the performance or damage due to overheating. In other words, with the continuous improvement of the processing speed and the data processing capacity of the IC, the heat dissipation requirements are also needed to be enhanced relatively. Therefore, at present, some package structures have heat sinks.  
         [0006]     As described above, since the heat sink in the conventional package structure is a passive heat dissipation element, in the situation in which the integration of the inner circuit of the chip is continuously increasing, the heat generated by the chip is also increased continuously. Therefore, the passive heat sink cannot meet the heat dissipation requirements of the chip.  
       SUMMARY OF THE INVENTION  
       [0007]     Accordingly, the present invention is directed to provide an active heat sink which dissipates heat mainly by use of a coolant so as to improve the heat dissipation efficiency of the heat sink.  
         [0008]     The present invention is directed to provide a package structure, wherein an active heat sink is disposed on a carrier and the heat sink dissipates heat mainly by a coolant, in order to improve the heat dissipation efficiency of the package structure.  
         [0009]     The present invention is directed to provide a package structure, wherein an active heat sink is disposed above the chip, and the heat sink dissipates heat mainly by a coolant in order to improve the heat dissipation efficiency of the package structure.  
         [0010]     As embodied and broadly described herein, the present invention provides a heat sink suitable for conducting a coolant. This heat sink comprises a casing and a porous material layer. The porous material layer is disposed in the casing and the coolant is suitable to be conducted into the porous material layer.  
         [0011]     As embodied and broadly described herein, the present invention further provides a package structure suitable for dissipating heat by use of a coolant. The package structure comprises a carrier, a chip, and a heat sink. The chip is disposed on the carrier and is electrically connected to the carrier, and the heat sink is disposed on the carrier. Moreover, the heat sink comprises a casing and a porous material layer. The porous material layer is disposed in the casing, and the coolant is suitable to be conducted into the porous material layer.  
         [0012]     In an embodiment of the present invention, the above package structure, for example, further comprises an encapsulant for fixing the chip on the carrier.  
         [0013]     In an embodiment of the present invention, the carrier is, for example, a leadframe comprising a die pad and a plurality of leads. The die pad has a first attaching surface and a corresponding first rear surface, wherein the chip is disposed on the first attaching surface and the heat sink is disposed on the first rear surface, and the leads are arranged around the die pad.  
         [0014]     In an embodiment of the present invention, the carrier is, for example, a printed circuit board (PCB). Moreover, the carrier has, for example, a second attaching surface and a corresponding second rear surface, wherein the chip is disposed on the second attaching surface. Additionally, the heat sink is disposed, for example, on the second attaching surface of the carrier or on the second rear surface of the carrier. Furthermore, the chip and the heat sink are stacked, for example, on the second attaching surface of the carrier.  
         [0015]     In an embodiment of the present invention, the above package structure further comprises, for example, a plurality of solder balls disposed on the second attaching surface of the carrier or the second rear surface of the carrier.  
         [0016]     As embodied and broadly described herein, the present invention further provides a package structure suitable for dissipating heat by a coolant. The package structure comprises a carrier, a chip, and a heat sink. The chip is disposed on the carrier and is electrically connected to the carrier, and the heat sink is disposed above the chip. Moreover, the heat sink comprises a casing and a porous material layer, wherein the porous material layer is disposed in the casing and the coolant is suitable to be conducted into the porous material layer.  
         [0017]     In an embodiment of the present invention, the above package structure further comprises, for example, an encapsulant for fixing the chip on the carrier. Moreover, the heat sink is embedded, for example, in the encapsulant above the chip.  
         [0018]     In an embodiment of the present invention, the carrier is, for example, a leadframe. The leadframe comprises, for example, a die pad and a plurality of leads. The die pad has a first attaching surface and a corresponding first rear surface, and the chip is disposed on the first attaching surface. Moreover, the leads are arranged around the die pad.  
         [0019]     In an embodiment of the present invention, the carrier is, for example, a PCB. The carrier has, for example, a second attaching surface and a corresponding second rear surface, wherein the chip is disposed on the second attaching surface.  
         [0020]     In an embodiment of the present invention, the above package structure further comprises, for example, a plurality of solder balls disposed on the second attaching surface of the carrier or the second rear surface of the carrier.  
         [0021]     In the above heat sink and the two package structures, the casing has, for example, an inlet and an outlet, wherein the coolant is injected into the porous material layer through the inlet and is output through the outlet. Moreover, the casing is, for example, a plate casing, a strip casing, a frame casing, or a U-shape casing. Additionally, the material of the casing is, for example, metal.  
         [0022]     In the above heat sink and the two package structures, the material of the porous material layer is, for example, metal. Moreover, the porous material layer is, for example, a metal sinter.  
         [0023]     In the heat sink of the present invention, the porous material layer has many pores, so the contact area between the coolant and the porous material layer are enlarged, thus enabling the coolant to dissipate the heat of the heat sink rapidly. Therefore, the heat sink of the present invention has high heat dissipation efficiency.  
         [0024]     Moreover, since the above heat sink is disposed on the carrier or above the chip according to the package structure of the present invention, the heat sink can rapidly absorb the heat of the surface with which it is in contact and can rapidly dissipate the absorbed heat by use of a coolant. Therefore, the heat dissipation efficiency of the package structure according to the present invention is relatively high.  
         [0025]     In order to the make the aforementioned and other objects, features and advantages of the present invention more comprehensible, preferred embodiments accompanied with appended drawings are described in detail below. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]      FIGS. 1A-1C  are sectional views depicting three package structures according to one preferred embodiment of the present invention;  
         [0027]      FIGS. 2A and 2B  two sectional views depicting the heat sink;  
         [0028]      FIG. 3  is a sectional view depicting another package structure according to one preferred embodiment of the present invention;  
         [0029]      FIGS. 4A and 4B  are sectional views depicting yet another two package structures according to one preferred embodiment of the present invention; and  
         [0030]      FIGS. 5A and 5B  are sectional views depicting still another two package structures according to one preferred embodiment of the present invention.  
     
    
     DESCRIPTION OF EMBODIMENTS  
       [0031]      FIGS. 1A-1C  are sectional views depicting three package structures according to one preferred embodiment of the present invention.  FIG. 2A  and  FIG. 2B  are two sectional views depicting the heat sink. Referring to  FIGS. 1A, 1B ,  2 A, and  2 B, a package structure  200   a  of the present embodiment is adapted to dissipate heat by a coolant (not shown). The package structure  200   a  comprises a carrier  210   a , a chip  220 , and a heat sink  230 . The chip  220  is disposed on the carrier  210   a  and the heat sink  230  is disposed above the chip  220  (as shown in  FIG. 1A ) or on the carrier  210   a  (as shown in  FIG. 1B ). Moreover, the heat sink  230  comprises a casing  232  and a porous material layer  234 , wherein the porous material layer  234  is disposed in the casing  232 , and the coolant is adapted to be conducted into and flow within the porous material layer  234 .  
         [0032]     The above package structure  200   a  further comprises, for example, an encapsulant  240  for fixing the chip  220  on the carrier  210   a . Moreover, the casing  232  of the heat sink  230  has, for example, an inlet  232   a  and an outlet  232   b , and the coolant  100  is injected into the porous material layer  234  through the inlet  232   a  and is output through the outlet  232   b.    
         [0033]     As described above, since the heat sink  230  is disposed on the carrier  210   a  or above the chip  220  according to the package structure  200   a  of the embodiment, the casing  232  of the heat sink  230  can absorb the heat of the surface (the surface of the carrier or the encapsulant) contacting it. Moreover, since the porous material layer  234  has many pores  234   a  inside, when the coolant  100  is injected into the porous material layer  234  through the inlet  232   a , the contact area between the coolant  100  and the porous material layer  234  is large, thus enabling the coolant  100  to absorb the heat of the heat sink  230  rapidly and then dissipate it. Therefore, the package structure  200   a  of the embodiment has high heat dissipation efficiency.  
         [0034]     In the embodiment, the material of the casing  232  of the heat sink  230  is, for example, metal. Moreover, the material of the porous material layer  234  is, for example, sintered metal. In the embodiment, the metal is, for example, sintered into a metal sinter having many pores  234   a , or the metal is made to have many pores  234   a  by penetrating or other methods to serve as the passage for passing the coolant  100 .  
         [0035]     It should be noted that the shape of the casing  232  depicted in the  FIG. 2B  is for the purpose of illustration only, and not for that of limiting the present invention. In fact, the casing  232  of the embodiment can be a strip casing, a plate casing, a frame casing, a U-shape casing, or a casing of another shape. Moreover, the package structure of the embodiment has various configurations, and a plurality of preferred configurations given below are for the purpose of illustration only, and not that of limiting the present invention. It should be known to any of those skilled in the art that proper modifications can be made according to the present invention without departing the scope of the invention.  
         [0036]     Referring to  FIGS. 1A-1C , in one preferred embodiment of the present invention, the carrier  210   a  can be a printed circuit board (PCB), a leadframe or other carriers. The carrier  210   a  depicted in the  FIGS. 1A-1C  is a PCB having a attaching surface  212   a  and a corresponding rear surface  214   a . The chip  220  is disposed on the attaching surface  212   a . Moreover, the heat sink  230  is, for example, embedded in the encapsulant  240  above the chip  220   a  (as shown in  FIG. 1A ), or is disposed on the attaching surface  212   a  of the carrier  210   a  (as shown in  FIG. 1B ). In addition, in one embodiment, the chip  220  and the heat sink  230  are, for example, stacked on the attaching surface  212   a  of the carrier  210   a  (as shown in  FIG. 1C ).  
         [0037]     As described above, the package structure  200   a  of the embodiment further comprises, for example, a plurality of solder balls  250  disposed on the rear surface  214   a  of the carrier  210   a . The package structure  200   a  is electrically connected to the other elements by the solder balls  250 . Moreover, the package structure  200   a  further comprises, for example, a plurality of bonding wire  260  connected between the chip  220  and the carrier  210   a , such that the chip  220  is electrically connected to the carrier  210   a  by the bonding wire  260 . It should be noted that the bonding wire  260  of the embodiment can also be replaced by bumps (not shown).  
         [0038]      FIG. 3  is a sectional view depicting another package structure according to one preferred embodiment of the present invention. Referring to  FIG. 3 , in the package structure  200   a ′ of the present embodiment, the carrier  210   a  is, for example, a PCB having a attaching surface  212   a  and a rear surface  214   a  corresponding to the attaching surface  212   a . The chip  220  is disposed on the attaching surface  212   a  and is electrically connected to the carrier  210   a  by the bump  270 . Moreover, the heat sink  230  is disposed above the chip  220  and the solder balls  250  are disposed on the rear surface  214   a  of the carrier  210   a.    
         [0039]      FIGS. 4A and 4B  are sectional views depicting another two package structures according to one preferred embodiment of the present invention. Referring to  FIGS. 4A and 4B , in the package structure  200   a ″ of the present embodiment, the carrier  210   a  is, for example, a PCB, wherein the attaching surface  212   a  thereof has a cavity  216   a , and the chip  220  is disposed on the bottom of the cavity  216   a . Moreover, the heat sink  230  is disposed on the rear surface  214   a  of the carrier  210   a  (as shown in  FIG. 4A ), or is disposed in the encapsulant  240  above the chip  220  (as shown in  FIG. 4B ). The solder balls  250  are disposed on the attaching surface  212   a  of the carrier  210   a.    
         [0040]     As described above, the heat sink  230  according to the package structure  200   a ″ of the present invention can be disposed on the attaching surface  212   a  of the carrier  210   a  (as shown in  FIGS. 1B and 1C ), on the rear surface  214   a  of the carrier  210   a  (as shown in  FIG. 4A ), above the chip  220  (as shown in  FIG. 3 ), or embedded in encapsulant  240  above the chip  220  (as shown in  FIGS. 1B and 4B ). Moreover, the solder balls  250  can be disposed on the attaching surface  212   a  of the carrier  210   a  (as shown in  FIGS. 4A and 4B ) or on the rear surface  214   a  of the carrier  210   a  (as shown in  FIGS. 1A-1C  and  FIG. 3 ).  
         [0041]      FIGS. 5A and 5B  are sectional views depicting still another two package structures according to one preferred embodiment of the present invention. Referring to  FIGS. 5A and 5B , in the package structure  200   b  of the present embodiment, the carrier  200   b  is, for example, a leadframe having a die pad  212   b  and a plurality of leads  214   b . The chip  220  is disposed on the die pad  212   b , and the leads  214   b  are arranged around the die pad  212   b  and are electrically connected to the chip  220 . Moreover, the die pad  212   b  has, for example, a attaching surface  216   b  and a corresponding rear surface  218   b . The chip  220  is disposed on the attaching surface  216   b  and the heat sink  230  is, for example, disposed on the rear surface  218   b  of the die pad  212   b  (as shown in  FIG. 5A ) or in the encapsulant  240  above the chip  220  (as shown in  FIG. 5B ).  
         [0042]     The above package structure  200   b  further comprises, for example, a plurality of bonding wire  260  connected between the chip  220  and the leads  214   b  to make the chip  220  electrically connected to the lead  214   b . Of course, the bonding wire  260  in the package structure  200   b  can be replaced by bumps (not shown).  
         [0043]     It should be noted that, in the above various package structures  200   a ,  200   a ′,  200   a ″, and  200   b , the shape of the casing of the heat sink  230  is not limited to the shapes shown in the drawings. That is, the casing can be a strip casing, a plate casing, a frame casing, a U-shape casing, or a casing of another shape.  
         [0044]     In view of the above, the package structure of the present invention has at least the following advantages:  
         [0045]     1. Since the porous material layer of the heat sink has many pores therein, the contact area between the coolant and the porous material layer can be enlarged, thus enabling the coolant to dissipate the heat of the heat sink rapidly. Therefore, the heat sink in the package structure of the present invention has high heat dissipation efficiency.  
         [0046]     2. Since the heat sink is disposed on the carrier or above the chip, the heat sink with high heat dissipation efficiency can rapidly absorb the heat of the surface with which it is in contact, thus improving the heat dissipation efficiency of the package structure.  
         [0047]     Although the present invention is disclosed as above by preferred embodiments, they are not intended to limit the present invention. Various variations and modifications can be made by any of those skilled in the art without departing from the spirit and scope of the present invention, and the scope of the present invention shall be defined by the appended claims.