Abstract:
A package structure is disclosed. The package structure includes at least a lead, for delivering at least a signal; at least a routing layer, connected to the at least a lead, where at least a first hole is formed through the at least a routing layer; a die, disposed on the at least a routing layer, where at least a second hole is formed through the die, and the die generates or receives the at least a signal; and a molding cap, for covering the at least a routing layer and the die; where the at least a signal is delivered through the at least a first hole and the at least a second hole.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a package structure and a three dimensional (3D) package structure, and more particularly, to a package structure and a 3D package structure capable of reducing high frequency loss. 
         [0003]    2. Description of the Prior Art 
         [0004]    In general, high frequency or extremely high frequency mobile communication systems operate at an operating frequency which is higher than 10 GHz. The package technology in the prior art has significant loss when the operating frequency is higher than 10 GHz. For example, the common technology is surface mount technology (SMT). The components using SMT are mass produced and assembled as various mobile devices. However, the components using SMT in the prior art have poor high frequency properties. When the operating frequency is higher than 6 GHz, the frequency is more significant as the operating frequency increases, which degrades the performance. 
         [0005]    In detail,  FIG. 1  is a schematic diagram of a sectional side view of a package structure  10  in the prior art. The package structure  10  comprises a die  100  and leads  102 . By a wire bonding process, the die  100  is connected to the leads  102  through metal wires  104 . By a molding process, a molding cap  106  is formed to cover the die  100  and the metal wires  104 . Notably, the metal wires  104  are covered within the molding cap  106 . When an operating frequency is higher than 6 GHz, a parasitic inductive effect is formed since the metal wires  104  contact the molding cap  106 . Further, the higher the operating frequency, the larger the inductance brought by the parasitic inductive effect. Hence, high frequency loss of the package structure  10  is larger and the performance of the package structure  10  is degraded. 
         [0006]    Therefore, how to reduce high frequency loss is a significant objective in the field. 
       SUMMARY OF THE INVENTION 
       [0007]    It is therefore a primary objective of the present invention to provide a package structure and a 3D package structure capable of reducing high frequency loss, to improve over disadvantages of the prior art. 
         [0008]    The present invention discloses a package structure. The package structure comprises at least a lead, for delivering at least a signal; at least a routing layer, connected to the at least a lead, wherein at least a first hole, or a material capable of electrically conducting at least a lead frame of the package structure, is formed within the at least a routing layer; a die, disposed on the at least a routing layer, wherein at least a second hole is formed within the die, the die generates or receives the at least a signal, and the at least a signal is delivered between a first side and a second side of the die through the at least a second hole; and a molding cap, for covering the at least a routing layer and the die; wherein the at least a signal is delivered between the die and the at least a lead through the at least a first hole and the at least a second hole, or through the at least a lead frame. 
         [0009]    The present invention further discloses a three dimensional (3D) package structure. The 3D package structure comprises at least a lead, for delivering at least a signal; at least a routing layer, connected to the at least a lead, wherein at least a first hole, or a material capable of electrically conducting at least a lead frame of the 3D package structure, is formed within the at least a routing layer; a plurality of dies, stacked with each other, disposed on the at least a routing layer, wherein at least a second hole is formed within at least a first die of the plurality of dies, and the at least a first die generates or receives the at least a signal; and a molding cap, for covering the at least a routing layer and the plurality of dies; wherein the at least a signal is delivered between the at least a first die and the at least a lead through the at least a first hole and the at least a second hole, or through the at least a lead frame. 
         [0010]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a schematic diagram of a sectional side view of a package structure in the prior art. 
           [0012]      FIG. 2  is a schematic diagram of a sectional side view of a package structure according to an embodiment of the present invention. 
           [0013]      FIG. 3  is a frequency response diagram of transmission coefficient of the package structures in  FIG. 1  and  FIG. 2 . 
           [0014]      FIG. 4  is a schematic diagram of a sectional side view of a 3D package structure according to an embodiment of the present invention. 
           [0015]      FIG. 5  is a schematic diagram of a sectional side view of a package structure according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]      FIG. 2  is a schematic diagram of a sectional side view of a package structure  20  according to an embodiment of the present invention. In the current embodiment, the package structure  20  is a quad flat no-lead package (QFN) comprising leads  202 _ 1 - 202 _N. The leads  202 _ 1 - 202 _N are disposed under the package structure  20 . For brevity,  FIG. 2  only illustrates two leads  202 _ a ,  202 _ b  among the leads  202 _ 1 - 202 _N. As shown in  FIG. 2 , the package structure  20  comprises a die  200 , routing layers  208 _ 1 ,  208 _ 2 , the leads  202 _ 1 - 202 _N and a molding cap  206 . The die  200  is disposed on the routing layers  208 _ 1 ,  208 _ 2  to realize all the functions of a monolithic microwave integrated circuit (MMIC). In other words, the die  200  generates or receives a plurality of signals. The package structure  20  may be coupled to an external circuit board (not illustrated in  FIG. 2 ) through the leads  202 _ 1 - 202 _N by welding. The leads  202 _ 1 - 202 _N are configured to deliver the plurality of signals between the die  200  and the external circuit board. Moreover, signals RF_a, RF_b are high frequency signals among the plurality of signals. In an embodiment, the leads  202 _ a ,  202 _ b  are configured to deliver the signals RF_a, RF_b to the external circuit board. The routing layers  208 _ 1 ,  208 _ 2  are electrically connected to the leads  202 _ 1 - 202 _N, disposed between the die  200  and the leads  202 _ 1 - 202 _N, and configured to provide routing between the die  200  and the leads  202 _ 1 - 202 _N. The molding cap  206  maybe made of molding compound such as epoxy, air-cavity, etc., and not limited thereto. The molding cap  206  is configured to cover the routing layers  208 _ 1 ,  208 _ 2  and the die  200 , such that an appearance of the package structure  20  is a QFN. 
         [0017]    In detail, the plurality of holes  200 _via may be formed inside the die  200  via a hot via process, and a plurality of holes  208 _via may be formed inside the routing layers  208 _ 1 ,  208 _ 2  by drilling. The signals of the die  200  are passed through the holes  200 _via from a top side of the die  200  (the side of the die  200  contacting the molding cap  206 ) to a bottom side of the die  200  (the side of the die  200  contacting the routing layer  208 _ 1 ), and electrically connected to the holes  208 _via inside the routing layer. In other words, the routing layers  208 _ 1 ,  208 _ 2  utilize conductive material such as microstrip line to provide routing between the die  200  and the leads  202 _ a ,  202 _ b , through the holes  208 _via. Therefore, in the current embodiment, the signals RF_a, RF_b are passed through the holes  200  via and the holes  208 _via from the leads  202 _ a ,  202 _ b  to the die  200  (or from the die  200  to the leads  202 _ a ,  202 _b). In addition, the routing layers  208 _ 1 ,  208 _ 2  maybe a laminate print circuit board (PCB). The routing layers  208 _ 1 ,  208 _ 2  may also be made of ceramic material, or conductive material conducting with a lead frame (not illustrated in  FIG. 2 ) of the package structure  20 , and not limited thereto. In addition, by the hot via process, a die-ground  200 _gnd of the die  200  is electrically connected to a ground-lead  202 _gnd of the package structure  20 , such that the package structure  20  and the die  200  has better heat dissipation property. 
         [0018]    Notably, the high frequency signals RF_a, RF_b may electrically connected to the leads  202 _ a ,  202 _ b  through the holes  200 _via,  208 _via (or the lead frame). Thereby, the holes  200 _via,  208 _via of the present invention may replace the wire bonding method delivering the signals of the die to the leads of the package structure, so as to avoid unnecessary inductive effect. Thus, the package structure  20  would have rare (even no) parasitic inductive effect operating at high frequency (greater than 6 GHz). High frequency loss of the package structure  20  is significantly reduced. Please refer to  FIG. 3 , which is a frequency response diagram of transmission coefficient of the package structure  10  in  FIG. 1  and the package structure  20  in  FIG. 2 , wherein the dashed line represents the frequency response of transmission coefficient of the package structure  10 , and the solid line represents the frequency response of transmission coefficient of the package structure  20 . As can be seen from  FIG. 3 , since the metal wires  104  contact the molding cap  106  in the package structure  10  in the prior art and the parasitic inductive effect is formed when the frequency is high, the transmission coefficient of the package structure  10  degrades drastically when the frequency is higher than 20 GHz, i.e., the loss of the package structure  10  is significant when the frequency is higher than 20 GHz. In comparison, even when the package structure  20  of the present invention operates at frequency higher than 20 GHz, the loss of the package structure  20  is extremely small, which is less than 1 dB. 
         [0019]    Therefore, the package structure of the present invention may significantly reduce loss at high frequency. In addition, the package structure of the present invention may be applied to surface mount technology (SMT), which maybe mass produced and assembled as various mobile devices. Furthermore, the present invention utilizes the hot via process to form the holes  200 _via in the die  200 . In comparison to the flip chip technology, there is no need to re-design a circuit layout of the die  200  to accommodate the wiring layout of the flip chip package. Also, the die  200  of the present invention has better heat dissipation property brought by the hot via process. 
         [0020]    Notably, the embodiments stated in the above are utilized for illustrating concepts of the present invention. Those skilled in the art may make modifications and alternations accordingly, and not limited herein. For example, in the package structure  20 , an area of the die  200  is usually smaller than an area of the package structure  20 , and performing vertical drilling on the laminate PCB is a well-known technology. Hence, vertical drilling may be performed on the two routing layers  208 _ 1 ,  208 _ 2  to deliver the signals RF_a, RF_b from the leads  202 _ a ,  202 _ b  to the die  200  (or from the die  200  to the leads  202 _ a ,  202 _ b ). Nevertheless, the package structure of the present invention is not limited to comprise two routing layers. The package structure may comprise only one routing layer. For example,  FIG. 5  is a schematic diagram of a sectional side view of a package structure  50  according to an embodiment of the present invention. The package structure  50  is similar to the package structure  20 . Different from the package structure  20 , the package structure  50  comprises only one routing layer  508 . Since a die  500  in the package structure  50  has an area larger than the die  200 , a projection result of the die  500  overlaps with leads  502 _ a ,  502 _ b . Hence, vertical drilling may be performed on the routing layer  508  to form the holes  508 _via, to build routing between the die  500  and the leads  502 _ a ,  502 _ b . Notably, the method forming the holes in the routing layer may be modified according to practical requirement, which may be formed by oblique drilling or curved drilling, and not limited thereto. In other words, as long as holes are formed in the routing layer to build connections between the die and the leads, the requirements of the present invention is met, which is under the scope of the present invention. 
         [0021]    In another perspective, in the previous embodiment, the package structure  20  utilizes the holes to deliver the high frequency signals RF_a, RF_b between the die  200  and the leads  202 _ a ,  202 _ b , which is not limited thereto. All of the signals generated or received by the die may be delivered by the holes formed in the die and the routing layer between the die and the leads. Alternatively, if some of the signals generated or received by the die are low frequency signals or direct current (DC) signals, then the high frequency signals may be delivered between the die and the leads through the hole and the remaining low frequency signals or DC signals may be delivered between the die and the leads via wires which are formed by the wire bonding process. That is, as long as one signal is delivered through the hole (s) in the die and the holes (s) in the routing layer, the requirements of the present invention are met, which is under the scope of the present invention. 
         [0022]    In addition, the package structure  20  may be variation of QFN packages, e.g., power QFN (PQFN) package, thin QFN (TQFN) package, ultra thin QFN (UTQFN) package, extreme thin QFN (XQFN) package, etc., which are all under the scope of the present invention. In addition, the package structure  20  may also be dual flat no-lead (DFN) package and the variations thereof, e.g., power DFN (PDFN) package, thin DFN (TDFN) package, ultra thin DFN (UTDFN) package, extreme thin DFN (XDFN) package, etc., which are all under the scope of the present invention. 
         [0023]    The package structure  20  illustrates an embodiment packing a single die in the package structure, wherein the high frequency loss is reduced. In addition, the present invention may be applied for packing multiple dies in the package structure. For examples, the dies may be stacked in a vertical direction, and a three dimensional (3D) package structure is formed. For example,  FIG. 4  is a schematic diagram of a sectional side view of a 3D package  40  structure according to an embodiment of the present invention. The package structure  40  is a quad flat no-lead package (QFN) comprising leads  402 _ 1 - 402 _N. The leads  402 _ 1 - 402 _N are disposed under the package structure  40 . 
         [0024]    As shown in  FIG. 4 , the 3D package structure  40  comprises dies  400 _ 1 -_, routing layers  408 _ 1 ,  408 _ 2  and a molding cap  406 . For brevity,  FIG. 4  only illustrates two leads  402 _ a ,  402 _ b  within the leads  402 _ 1 - 402 _N. The leads  402 _ a ,  402 _ b  are configured to deliver the signals RF_a, RF_b to the external circuit board. The routing layers  408 _ 1 ,  408 _ 2  are electrically connected to the leads  402 _ a ,  402 _ b , disposed between the die  400 _ 3  and the leads  402 _ a ,  402 _ b . Holes  408  via are formed inside the routing layers  408 _ 1 ,  408 _ 2 . The routing layers  408 _ 1 ,  408 _ 2  may be made of conductive material conducting with a lead frame (not illustrated in  FIG. 4 ) of the package structure  40 . The dies  400 _ 1 - 400 _ 3  are stacked with each other (i.e., the die  400 _ 1  is disposed on a top of the die  400 _ 2  and the die  400 _ 2  is disposed on a top of the die  400 _ 3 ) and disposed on the routing layer  408 _ 1 . Holes  400 _via are formed inside the dies  400 _ 1 - 400 _ 3  by the hot via process. The dies  400 _ 1 - 400 _ 3  generate or receive the high frequency signals RF_a, RF_b. The molding cap  406  may be made of molding compound such as epoxy, air-cavity, etc., and not limited thereto. The molding cap  406  is configured to cover the routing layers  408 _ 1 ,  408 _ 2  and the dies  400 _ 1 - 400 _ 3 , such that an outward appearance of the package structure  40  is the same as a QFN. Therefore, the signals RF_a, RF_b are passed through the holes  400 _via and the holes  408 _via from the leads  402 _ a ,  402 _ b  to the dies  400 _ 1 - 400 _ 3  (or from the dies  400 _ 1 - 400 _ 3  to the leads  402 _ a ,  402 _ b ), i.e., the holes  400 _via and the holes  408  via are utilized to provide routing between the dies  400 _ 1 - 400 _ 3  and the leads  402 _ a ,  402 _ b . Notably, the 3D package  40  stated in the above is utilized for illustrating concepts of the present invention. Those skilled in the art may make modifications and alternations accordingly, and not limited herein. For example, a number of dies packed within the 3D package structure is not limited. The 3D package structure may comprise a plurality of dies. As long as the holes  400 _via are formed by the hot via process in one die of the plurality of dies, the requirements of the present invention are satisfied, which is under the scope of the present invention. In addition, a number of the routing layers of the 3D package structure is not limited to be two. The 3D package structure may comprise only one routing layer. The holes in the routing layers may be formed by vertical drilling, oblique drilling, curved drilling, and not limited thereto. Other modification may be referred to related paragraph in the above, which is not narrated here for brevity. 
         [0025]    In summary, the package structure of the present invention utilizes holes formed in the die and the routing layer to deliver high frequency signal, so as to avoid the signal path delivering high frequency signal contacting with the molding cap. Rarely (even no) parasitic inductive effect is formed. In comparison to the prior art, the package structure of the present invention has low high frequency loss, and is able to be applied to SMT, which may be mass produced and assembled as various mobile devices. 
         [0026]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.