Abstract:
The present invention provides a radio frequency identification (RFID) package structure for improving a low data reading rate of the conventional RFID transponder structure to overcome the disadvantage of the prior art, and packages a RFID die by an adhesive according to a package technology. The RFID package structure provides different ways of improving the data reading capability, such as adding a capacitor. The capacitance of the capacity can be adjusted to provide a RFID package structure applicable for different frequencies, or the RFID package structure formed by the structure of a single substrate together with the use of an adhesive can be used for producing the RFID package structure to lower the manufacturing cost.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the invention The present invention relates to a package structure, and more particularly to a radio frequency identification (RFID) package structure.  
         [0002]     2. Description of Related Art RFID is an advanced wireless identification technology that can transmit information to a computer network through a microchip-based “tag” that is attached to or incorporated in a product for identifying, tracking and confirming the conditions of the product.  
         [0003]     A RFID system is comprised of two types of devices: a transponder and a reader, such as a card or a tag, which is a passive response device. If the RFID system is turned on, the reader will generate a wireless signal of a specific frequency to activate a program stored in a chip of the transponder in order to generate radio frequency waves, and an ID code stored in a memory will be transmitted back to the reader and decoded by a host computer for the function of determining the completion of the identification.  
         [0004]     A conventional RFID transponder is made by a direct chip attach (DCA) process and connected to a device such as a printed circuit board (PCB) or an organic flexible substrate. The direct chip attach (DCA) process is a low-price packaging process that attaches a chip directly on a substrate without encapsulating the chip. However, the lithographic process for forming metal wires is one of the expensive processes for producing RFID transponders. U.S. Pat. No. 6,529,408B1 disclosed a related technology to lower the manufacturing cost, and such patented technology uses a nozzle to spray a conductive adhesive to produce an antenna pattern, and uses the direct chip attach (DCA) process to electrically connect a RFID tag having a metal bump to a portion of the antenna pattern, and then the metal bump becomes a portion of the antenna pattern, and such arrangement can waive the lithographic process as well as the manufacturing cost.  
         [0005]     Although the direct chip attach (DCA) process can lower the manufacturing cost, the hit rate of receiving data from a RFID transponder by a RFID reader in actual applications of a RFID system is approximately 60% to 70% only. Furthermore, the moisture resisting capability and the overall structural strength of the RFID transponder are not as good either.  
       SUMMARY OF THE INVENTION  
       [0006]     In view of the foregoing shortcomings of the prior art, the present invention provides a RFID package structure to overcome the shortcomings.  
         [0007]     The RFID package structure in accordance with the present invention comprises a first substrate, a RFID die, a second substrate, at least one first circuit pattern, at least one second circuit pattern and an adhesive, wherein the first circuit pattern is formed at an upper surface of the second substrate, and the first circuit pattern includes an antenna pattern, and the second circuit patterns are formed on a lower surface of the second substrate, and the second circuit pattern includes an antenna pattern or no pattern, so as to produce a complete RFID structure.  
         [0008]     The RFID package structure in accordance with a preferred embodiment of the present invention comprises a first substrate, a RFID die, a second substrate, at least one first antenna pattern, at least one second antenna pattern and an adhesive, wherein the first antenna patterns are formed on an upper surface of the first substrate, and the second antenna patterns are formed on an upper surface of the second substrate, so that the overall area of the RFID structure can be reduced.  
         [0009]     The RFID package structure in accordance with another preferred embodiment comprises a first substrate, a RFID die, a second substrate, a capacitor and at least one first antenna pattern, wherein the first antenna patterns are formed on an upper surface of the second substrate to produce a complete RFID structure, and the capacitor constitutes a LC loop circuit for adjusting the capacitance of the capacitor to satisfy the requirement of different frequencies.  
         [0010]     The RFID package structure in accordance with a further preferred embodiment comprises a first substrate, a RFID die, a second substrate, a capacitor, at least one first antenna pattern, at least one second antenna pattern and an adhesive, wherein the first antenna patterns are formed on an upper surface of the first substrate, and the second antenna patterns are formed on an upper surface of the second substrate to produce a complete RFID structure, and the capacitor constitutes a LC loop circuit for adjusting the capacitance of the capacitor to satisfy the requirement of different frequencies.  
         [0011]     In another preferred embodiment of the invention, the RFID package structure comprises a RFID die, a first substrate, a capacitor, at least one first antenna pattern and an adhesive, wherein the first antenna pattern is formed on the upper surface of the first substrate to produce a complete RFID structure, and the capacitor constitutes a LC loop circuit for adjusting the capacitance of the capacitor to satisfy the requirement of different frequencies, and the adhesive is used for wrapping the entire RFID package.  
         [0012]     The RFID package structure of the present invention can achieve the effects of improving the moisture resisting capability, increasing the data reading rate and providing a higher overall structural strength of the RFID transponder.  
         [0013]     To make it easier for our examiner to understand the innovative features and technical content, we use preferred embodiments together with the attached drawings for the detailed description of the invention, but it should be pointed out that the attached drawings are provided for reference and description but not for limiting the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1A  is a schematic view of a RFID package structure of a first preferred embodiment of the present invention;  
         [0015]      FIG. 1B  is a schematic view of a RFID structure of a first preferred embodiment of the present invention;  
         [0016]      FIG. 1C  is a flow chart of a manufacturing method of a RFID package structure according to a first preferred embodiment of the present invention;  
         [0017]      FIG. 2  is a schematic view of a RFID package structure of a second preferred embodiment of the present invention;  
         [0018]      FIG. 3  is a schematic view of a RFID package structure of a third preferred embodiment of the present invention;  
         [0019]      FIG. 4A  is a schematic view of a RFID package structure of a fourth preferred embodiment of the present invention;  
         [0020]      FIG. 4B  is a flow chart of a manufacturing method of a RFID package structure according to a fourth preferred embodiment of the present invention;  
         [0021]      FIG. 5  is a schematic view of a RFID package structure of a fifth preferred embodiment of the present invention;  
         [0022]      FIG. 6  is a schematic view of a RFID package structure with a single substrate of a first preferred embodiment of the present invention;  
         [0023]      FIG. 7  is a flow chart of a manufacturing method of a RFID package structure with a single substrate according to the present invention;  
         [0024]      FIG. 8  is a schematic view of a RFID package structure with a single substrate of a second preferred embodiment of the present invention; and  
         [0025]      FIG. 9  is a schematic view of a RFID package structure with a single substrate of a third preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]     Referring to  FIG. 1A  for a schematic view of a RFID package structure in accordance with a first preferred embodiment of the present invention, the RFID package structure  1  comprises a first substrate  10 , a RFID die  12 , a second substrate  18 , at least one first circuit pattern  20 ,  22  and an adhesive  28 .  
         [0027]     The first substrate  10  and the second substrate  18  are made of a soft organic material or a glass fiber material, and the soft organic material includes a combination of polymer, polyester and other similar materials, or a hard material such as any combination of ceramics. The RFID die  12  comprises at least one I/O pad  14 ,  16  disposed at a lower surface of the RFID die  12 , and the RFID die  12  is installed at a lower surface of the first substrate  10 . The first circuit patterns  20 ,  22  are formed at an upper surface of the second substrate  18 , and each first circuit pattern  20 ,  22  includes a first connecting point  24 ,  26  and is connected to the I/O pad  14 ,  16  through the first connecting point  24 ,  26  for electrically connecting the RFID die  12 , wherein at least one second circuit pattern  30 ,  32  is formed, and an adhesive  28  is filled between the first substrate  10  and the second substrate  18 . The first circuit patterns  20 ,  22  and the second circuit patterns  30 ,  32  can be conducted vertically by at least one conducting region  31  according to the functions and requirements of the circuits, so that the first circuit patterns  20 ,  22  and the second circuit patterns  30 ,  32  can be connected electrically.  
         [0028]     Referring to  FIG. 1B  for a schematic view of a RFID package structure in accordance with a first preferred embodiment of the present invention, the RFID structure comprises the foregoing RFID package structure  1  and a third substrate  3 , wherein the internal structure of the RFID package structure  1  has been described above, and thus will not be described again here. However, the third substrate  3  has at least one antenna pattern  34 ,  36  disposed at an upper surface of the third substrate  3 , and each antenna pattern  34 ,  36  has a second connecting point  38 ,  40  for electrically connecting the antenna patterns  34 ,  36  and the second circuit patterns  30 ,  32 , and the RFID package structure  1  and the third substrate  3  can be combined by an automated machine easily available in the market. The third substrate  3  can be made of a soft organic material such as a combination of polymer, polyester and other similar materials, or a hard material such as any combination of ceramics.  
         [0029]     Referring to  FIG. 1C  a flow chart of a manufacturing method of a RFID package structure according to a first preferred embodiment of the present invention, the manufacturing procedure comprises the steps of: preparing a first substrate  10  (S 100 ); preparing a second substrate  18  (S 102 ), wherein the second substrate  18  forms at least one first circuit pattern  20 ,  22  on an upper surface of the second substrate  18 , and each first circuit pattern  20 ,  22  has a first connecting point  24 ,  26 ; combining a RFID die  12  with the second substrate  18  (S 104 ), wherein the RFID die  12  has at least one I/O pad  14 ,  16  at a lower surface of the RFID die  12 , and the RFID die can be combined with the second substrate  18  by a soldering method or a baking method depending on the material of the first connecting point  24 ,  26 , wherein the soldering method will be adopted if the first connecting points  24 ,  26  are made of a solder paste, and the baking method will be adopted if the first connecting points  24 ,  26  are made of a conductive adhesive.  
         [0030]     While Step (S 104 ) is being carried out, the first substrate  10  is integrated with an upper surface of the RFID die  12  by a soldering method or a baking method (S 106 ), and an adhesive  28  is formed between the first substrate  10  and the second substrate  18  by an adhesion method or an ink-jet method, and the adhesive  28  can be a liquid epoxy resin (S 108 ), and finally the baking method is adopted to solidify the adhesive  28  to form the RFID package  1  (S 110 ).  
         [0031]     The RFID package structure in accordance with the first preferred embodiment of the present invention is characterized in that the RFID die  12  is packaged to achieve the effects of improving the moisture resisting capability, increasing the data reading rate, and providing better overall structural strength of the RFID transponder.  
         [0032]     Referring to  FIG. 2  for a schematic view of a RFID package structure in accordance with a second preferred embodiment of the present invention, the RFID package structure  1  comprises a first substrate  10 , a RFID die  12 , a second substrate  18 , at least one antenna pattern  42 ,  44  and an adhesive  28 .  
         [0033]     The first substrate  10  and the second substrate  18  are made of a soft organic material or a fiber glass material, and the organic material includes a combination of polymer, polyester and other similar materials, or a hard material such as any combination of ceramics. The RFID die  12  includes at least one I/O pad  14 ,  16  disposed at a lower surface of the RFID die  12 , and the RFID die  12  is installed at a lower surface of the first substrate  10 , and at least one antenna pattern  42 ,  44  is formed at an upper surface of a second substrate  18 , and each antenna pattern  42 ,  44  has a first connecting point  24 ,  26  and is connected to the I/O pad  14  through the first connecting point  24 ,  26  for electrically connecting the RFID die  12 , and an adhesive  28  is filled between the first substrate  10  and the second substrate  18 .  
         [0034]     The major difference between the second preferred embodiment and the first preferred embodiment of the present invention resides on that the second substrate  18  of the first embodiment forms the first circuit patterns  20 ,  22  on its upper surface, and the first circuit patterns  20 ,  22  are simply electric circuits, and the second substrate  18  of the second preferred embodiment forms the antenna patterns  42 ,  44  including a complete radio frequency antenna circuit on its upper surface.  
         [0035]     The RFID package structure in accordance with the second preferred embodiment of the present invention is characterized in that the RFID die  12  is packaged, and the radio frequency antenna patterns  42 ,  44  are laid directly on the second substrate  18  to achieve the effects of improving the moisture resisting capability, increasing the data reading rate, and providing better overall structural strength, and thus the second preferred embodiment of the invention provides a complete RFID transponder without requiring an additional process for connecting another external substrate (such as the third substrate  3  adopted in the first preferred embodiment).  
         [0036]     Referring to  FIG. 3  for a schematic view of a RFID package structure of a third preferred embodiment of the present invention, the RFID package structure  5  comprises a first substrate  50 , at least one first antenna pattern  52 ,  54 , a RFID die  12 , a second substrate  56 , at least one second antenna pattern  58 ,  60  and an adhesive  28 .  
         [0037]     The first substrate  50  and the second substrate  56  are made of a soft organic material or a glass fiber material, and the organic material includes a combination of polymer, polyester and other similar materials, or a hard material such as any combination of ceramics. The first substrate  50  forms the first antenna pattern  52 ,  54  on its lower surface, and the RFID die  12  has at least one I/O pad  14 ,  16  disposed at a lower surface of the RFID, and the RFID die  12  is installed at a lower surface of the first substrate  50  and the middle of the first antenna patterns  52 ,  54 , and the second antenna patterns  58 ,  60  are formed on an upper surface of the second substrate  56 , and each second antenna pattern  58 ,  60  has a first connecting point  62 ,  64 , and is connected to the I/O pad  14 ,  16  through the first connecting point  62 ,  64  for electrically connecting the RFID die  12 , and an adhesive  2  is filled between the first substrate  50  and the second substrate  56 .  
         [0038]     The RFID package structure in accordance with the third preferred embodiment of the present invention is characterized in that the RFID die  12  is packaged, and the first radio frequency antenna patterns  52 ,  54  are laid directly on the first substrate  50  and the second radio frequency antenna patterns  58 ,  60  are laid directly on the second substrate  56  to achieve the effects of improving the moisture resisting capability, increasing the data reading rate, and providing better overall structural strength, and thus the third preferred embodiment of the invention provides a complete RFID transponder without requiring an additional process for connecting another external substrate (such as the third substrate  3  adopted in the first preferred embodiment). Further, the first antenna patterns  52 ,  54  are laid on the first substrate  50  for dispersing an overcrowded antenna pattern on a specific substrate designed for different radio frequencies. Since the inductance of a radio frequency antenna is directly proportional to the number of coils, therefore the third preferred embodiment of the invention can reduce the overall packaging area for the manufacture of a multi-layer board, and the finished goods of the RFID transponder can be connected selectively to an active component or a passive component.  
         [0039]     Referring to  FIG. 4A  for a schematic view of a RFID package structure of a fourth preferred embodiment of the present invention, the RFID package structure  7  comprises a first substrate  10 , a RFID die  12 , a second substrate  18 , at least one antenna pattern  42 ,  44 , a capacitor  70  and an adhesive  28 .  
         [0040]     The first substrate  10  and the second substrate  18  are made of a soft organic material or a glass fiber material, and the soft organic material includes a combination of polymer, polyester and other similar materials, or a hard material such as any combination of ceramics. The RFID die  12  comprises at least one I/O pad  14 ,  16  disposed at a lower surface of the RFID die  12 , at least one antenna pattern  42 ,  44  formed on an upper surface of the a second substrate  18 , and each antenna pattern  42 ,  44  has a first connecting point  24 ,  26  and is coupled to the I/O pad  14 ,  16  through the first connecting point  24 ,  26  for electrically connecting the RFID die  12 , and a capacitor  70  installed at a lower surface of the first substrate  10 , and the capacitor  70  has at least one conducting terminal  72 ,  74  coupled to the second substrate  18  through the first connecting point  24 ,  26  for electrically connecting the capacitor  70  with the second substrate  18 , and an adhesive  28  filled between the first substrate  10  and the second substrate  18 .  
         [0041]     Referring to  FIG. 4B  for a flow chart of a manufacturing method of a RFID package structure  7  according to a fourth preferred embodiment of the present invention, the manufacturing procedure comprising the steps of: preparing a first substrate  10  (S 200 ); preparing a second substrate  18  (S 202 ), wherein the second substrate  18  forms at least one antenna pattern  42 ,  44  on its upper surface, and each antenna pattern  42 ,  44  has a first connecting point  24 ,  26 ; providing a RFID die  12  and a capacitor  70  for connecting the second substrate  18  (S 204 ), wherein the RFID die  12  has at least one I/O pad  14 ,  16  on its lower surface, and the connecting process can be achieved by a soldering method or a baking method depending on the material of the first connecting point  24 ,  26 , wherein the soldering method will be adopted if the first connecting points  24 ,  26  are made of a solder paste, and the baking method will be adopted if the first connecting points  24 ,  26  are made of a conductive adhesive.  
         [0042]     While Step (S 204 ) is being carried out, the first substrate  10  is combined to an upper surface of the capacitor by a soldering method or a baking method (S 206 ), and an adhesive  28  is formed between the first substrate  10  and the second substrate  18  by an adhesion method or an ink-jet method, and the adhesive  28  can be a liquid epoxy resin, and the baking method is adopted to solidify the adhesive  28  to form the RFID package  1  (S 208 ), and the adhesive  28  is solidified by the baking method to form the RFID package  7  (S 210 ).  
         [0043]     The RFID package structure in accordance with the fourth preferred embodiment of the present invention is characterized in that the RFID die  12  is packaged to achieve the effects of improving the moisture resisting capability, increasing the data reading rate, and providing better overall structural strength, and the radio frequency antenna patterns  42 ,  44  are laid directly on the second substrate  18 . Further, the fourth preferred embodiment of the invention adds a capacitor  70  for producing LC circuit oscillations with the antenna pattern  42 ,  44  in the RFID package structure, since different frequencies can be achieved by changing the capacitance of the capacitor  70 .  
         [0044]     Referring to  FIG. 5  for a schematic view of a RFID package structure in accordance with a fifth preferred embodiment of the present invention, the RFID package structure  8  comprises a first substrate  10 , at least one first antenna pattern  80 ,  82 , a RFID die  12 , a second substrate  18 , at least one second antenna pattern  84 ,  86 , a capacitor  70  and an adhesive  28 .  
         [0045]     The first substrate  10  and the second substrate  18  are made of a soft organic material or a glass fiber material, and the soft organic material includes a combination of polymer, polyester and other similar materials, or a hard material such as any combination of ceramics. The first substrate  10  forms the first antenna pattern  80 ,  82  on its lower surface, and the RFID die  12  comprises: at least one I/O pad  14 ,  16  disposed at its lower surface; at least one second antenna pattern  84 ,  86  formed on an upper surface of the second substrate  18 , and each second antenna pattern  84 ,  86  has a first connecting point  92 ,  94  and is coupled to the I/O pad  14 ,  16  through the first connecting point  92 ,  94  for electrically connecting the RFID die  12 ; a capacitor  70  installed at a lower surface of the first substrate  10 , and the capacitor  70  has at least one conducting terminal  72 ,  74  coupled to the second substrate  18  through the first connecting point  92 ,  94  for electrically connecting the capacitor  70  with the second substrate  18 ; and an adhesive  28  filled between the first substrate  10  and the second substrate  18 .  
         [0046]     The RFID package structure in accordance with the fifth preferred embodiment of the present invention is characterized in that the RFID die  12  is packaged to achieve the effects of improving the moisture resisting capability, increasing the data reading rate, and providing better overall structural strength. Further, the first antenna patterns  80 ,  82  are laid on the first substrate  10  for dispersing an overcrowded antenna pattern on a specific substrate designed for different radio frequencies. Since the inductance of a radio frequency antenna is directly proportional to the number of coils, therefore the fifth preferred embodiment of the invention can reduce the whole packaging area for the manufacture of a multi-layer board, and the fifth preferred embodiment adds the capacitor  70  to produce LC circuit oscillations for the first antenna pattern  80 ,  82  in the RFID package structure, since different frequencies can be achieved by changing the capacitance of the capacitor  70 .  
         [0047]     Referring to  FIG. 6  for a schematic view of a RFID package structure with a single substrate of a first preferred embodiment of the present invention, the RFID package structure  9  with a single substrate comprises at least one circuit pattern  96 ,  98 , a RFID die  12 , a fourth substrate  100 , and an adhesive  28 .  
         [0048]     The differences of the RFID package structure with a single substrate of this embodiment from that of the first preferred embodiment reside on that this embodiment does not come with a first substrate  10 , and the adhesive  28  wraps the entire RFID package structure by using an ink-jet method or a printing method. Since the fourth substrate  100  and the circuit pattern  96 ,  98  do not come with a first substrate  10 , therefore the manufacturing cost can be reduced. The rest of technical characteristics of the RFID package structure is the same as those of the first preferred embodiment, and thus will not be described here.  
         [0049]     Referring to  FIG. 7  for a flow chart of a manufacturing method of a RFID package structure with a single substrate according to the present invention, the manufacturing method comprises the steps of: preparing a fourth substrate  100  (S 300 ), wherein the fourth substrate  100  forms at least one circuit pattern  96 ,  98  on its surface, and each circuit pattern  96 ,  98  has a first connecting point  24 ,  26 ; providing a RFID die  12  for connecting the fourth substrate  100  (S 302 ), wherein the RFID die  12  has at least one I/O pad  14 ,  16  disposed at its lower surface, and the RFID die  12  is connected to the fourth substrate  100  by a soldering method or a baking method depending on the material of the first connecting point  24 ,  26 , and the soldering method will be adopted if the first connecting points  24 ,  26  are made of a solder paste, and the baking method will be adopted if the first connecting points  24 ,  26  are made of a conductive adhesive.  
         [0050]     After Step S 302  is completed, an adhesive  28  is used for wrapping the RFID die  12 , the fourth substrate  100  and the circuit patterns  96 ,  98  (S 304 ), and the wrapping can be achieved by an ink-jet method or a printing method, and the adhesive  28  can be a liquid epoxy resin; and using the baking method to solidify the adhesive  28  to form the RFID package  9  (S 306 ).  
         [0051]     Referring to  FIG. 8  for a schematic view of a RFID package structure with a single substrate of a second preferred embodiment of the present invention, the RFID package structure  13  with a single substrate comprises at least one antenna pattern  130 ,  132 , a RFID die  12 , a fourth substrate  100 , and an adhesive  28 .  
         [0052]     The differences of the RFID package structure with a single substrate of this embodiment from that of the second preferred embodiment reside on that this embodiment does not come with a first substrate  10 , and the adhesive  28  wraps the entire RFID package structure by using an ink-jet method or a printing method. Since the fourth substrate  100  and the antenna pattern  130 ,  132  do not come with a first substrate  10 , therefore the manufacturing cost can be reduced. The rest of technical characteristics of the RFID package structure is the same as those of the first preferred embodiment, and thus will not be described here.  
         [0053]     Referring to  FIG. 9  for a schematic view of a RFID package structure with a single substrate of a third preferred embodiment of the present invention, the RFID package structure  15  with a single substrate comprises at least one antenna pattern  150 ,  152 , a RFID die  12 , a fourth substrate  100 , a capacitor  70 , at least one conducting terminal  72 ,  74  and an adhesive  28 .  
         [0054]     The differences of the RFID package structure with a single substrate in accordance with the third embodiment from that of the first preferred embodiment reside on that the third embodiment does not come with a first substrate  10 , and the adhesive  28  wraps the entire RFID package structure by using an ink-jet method or a printing method. Since the fourth substrate  100  and the antenna pattern  150 ,  152  do not come with a first substrate  10 , therefore the manufacturing cost can be reduced. The rest of technical characteristics of the RFID package structure is the same as those of the first preferred embodiment, and thus will not be described here.  
         [0055]     The difference between the RFID package structure of the invention and the RFID transponder of the prior art resides on that the conventional RFID transponder is manufactured in the form of a barcode, and the RFID package structure of the invention is manufactured in the form of a package. The advantages of the invention include its convenience that allows users to put the RFID package freely in almost anywhere such as putting it in a carton, and attaching it on a carton or the back cover of a book, etc. Therefore, RFID package provides a more flexible range of applications than the conventional RFID transponder.  
         [0056]     Although the present invention has been described with reference to the preferred embodiments thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.