Abstract:
A method and an apparatus for integrating a surface acoustic wave (SAW) filter and a transceiver are provided to solve the problem of having a large area of the prior-art integration of a SAW filter and a transceiver; wherein a device for integrating a SAW filter and a transceiver is provided and a component stack method is used to accomplish the integration of the SAW filter and the transceiver, and thus besides featuring a low cost and a small area as well as avoiding a signal loss, the invention can further include a design of encapsulating other components and chips, or even suitable to be used for various integrated circuit packaging technologies (such as QFP and BGA, etc.)

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a method and an apparatus for integrating a surface acoustic wave (SAW) filter and a transceiver, more particularly to the design and concept of a component stack architecture. 
   2. Description of Related Art 
   As the wireless communication technology is developed rapidly, various mobile devices and wireless network products are introduced unceasingly to the market. In the wireless communication technology, a signal is received, demodulated, decoded and computed and then the signal is coded, modulated and transmitted. In general, the level of difficulty will be higher and the circuit operation will be less stable, if a high-frequency signal is converted into a digital signal. Therefore, the design of a wireless communication system includes a radio frequency (RF), an intermediate frequency (IF) and a signal operating base-band frequency (BB). In a detail circuit design, a surface acoustic wave (SAW) filter is usually added to a transceiver to filter the noise in a high-frequency signal. With the trend of the wireless communication products being light, thin, short and compact, the quantity and area of internal components of these products encounter a very big challenge. Therefore, the development of component integration has become an indispensable part of electronic products and technologies. Since the integration technology between high-frequency components and base-band components is very different due to the materials and characteristics of the components, and thus giving us plenty of room for further improvements. 
   Please refer to  FIG. 1  for the schematic view of the structure of a device for integrating a SAW filter and a transceiver according to a prior art. Under the conditions of not affecting the performance of a SAW filter  13 , most SAW filters  13  adopt a ceramic substrate package and keep their surfaces not in contact with each other to assure the performance of the SAW filter  13  due to the properties of the piezoelectric material in the SAW filter  13 . However, such design still has the problem of being unable to reduce the package size of a SAW filter  13 . Therefore, the integration between a SAW filter  13  and a transceiver  12  is accomplished by a printed circuit board  11 . The transceiver  12  and the SAW filter  13  are built on the printed circuit board  11  for filtering the noise of a radio frequency (RF) signal. 
   In view of the description above, the foregoing prior-art SAW filer and transceiver are inconvenient and still have drawbacks in the actual practice, and thus requiring further improvements. The drawbacks are listed below: 
   1. The area of the SAW filter  13  is too large; 
   2. The SAW filter  13  is installed by itself and cannot be integrated into other components effectively; 
   3. There exists a problem of losing a signal easier when the signal is transmitted by the printed circuit board; and 
   4. Poor quality of a printed circuit board may cause a signal distortion or a system failure. 
   In view of the aforementioned drawbacks, the inventor of the present invention based on years of experience of the related field to conduct extensive researches and practice the theory, and finally invented a feasible design to effectively overcome the aforementioned drawbacks. 
   SUMMARY OF THE INVENTION 
   Therefore, it is a primary objective of the present invention to solve the problem of the large area of a prior-art surface acoustic wave (SAW) filter and provide a device for integrating a SAW filter and a transceiver, wherein a component stack method is used to accomplish the integration of the SAW filter and the transceiver. Firstly, a conductive layer is formed on a substrate, and a transceiver is disposed on the substrate, and then a SAW filter is disposed on the transceiver. The SAW filter includes an air cavity covering the SAW filter and a gap being reserved between the air cavity and the SAW filter. The conductive layer, SAW filter and transceiver are electrically connected with each other by a metal lead. Finally, a molding compound encapsulates the circuit among the substrate, transceiver and SAW filter wave component. The substrate used for the device according to the present invention could be substituted by a lead frame. 
   Another objective of the present invention is to provide a method of integrating a surface acoustic wave (SAW) filter and a transceiver, which comprises the steps of: disposing a substrate first; forming a conductive layer on the substrate; coating an epoxy layer on the substrate; disposing a receiver on the substrate; forming a thin isolation layer on the transceiver; disposing a SAW filter on the transceiver; electrically connecting the SAW filter wave, the transceiver and the conductive layer by a metal lead; encapsulating the circuit among the substrate, the transceiver and the SAW filter; and finally shaping an integrated chip. The substrate used in this method can be substituted by a lead frame. 
   In addition to the advantages of having a low cost and a small area as well as avoiding a signal loss, the device for integrating the surface acoustic wave (SAW) filter can be designed to include and encapsulate other components and chips. 
   To make it easier for our examiner to further understand the features and technical contents of the present invention, please refer to the detailed description and drawings of the present invention. However, the drawings are provided for the purpose of reference and description only, but not intended for limiting the scope of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic view of the device for integrating a surface acoustic wave (SAW) filter and a transceiver according to a prior art; 
       FIG. 2  is a schematic view of the device for integrating a surface acoustic wave (SAW) filter and a transceiver according to the invention; 
       FIG. 3  is a schematic view of a device for integrating a surface acoustic wave (SAW) filter and a transceiver according to another preferred embodiment of the invention. 
       FIG. 4  is a flow chart of the method for integrating a surface acoustic wave (SAW) filter and a transceiver according to the invention; and 
       FIG. 5  is a flow chart of the method for integrating a surface acoustic wave (SAW) filter and a transceiver according to another preferred embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Please refer to  FIG. 2  for the device for integrating a surface acoustic wave (SAW) filter and a transceiver according to the present invention. The main improvement of the present invention over the prior art resides on using a component stack method to accomplish the integration of a SAW filter and a transceiver, and thus can dispose a transceiver on a SAW filter as to save the area occupied by the SAW filter and the cost incurred. The technical characteristics and features of the present inventions are described below. Please also refer to  FIG. 2 . A substrate  21  is formed on a conductive layer  221  for electrically coupling other components and the substrate  21  could be a semiconductor substrate or a glass substrate. A transceiver  22  is disposed on the substrate  21  and electrically coupled with the conductive layer  221  by a metal lead  25 . In the connection between the transceiver  22  and the conductive layer  221 , the transceiver  22  can install a plurality of pads  221  around it and the metal lead  25  can be connected to the plurality of pads  221  and the conductive layer  211  simultaneously. 
   A surface acoustic wave (SAW) filter  23  is disposed on the transceiver  22 , and an air cavity  24  covers the SAW filter  23  and keeps a gap  241  between the air cavity  24  and the SAW filter  23 , and the SAW filter  23  and the conductive layer  221  are electrically coupled by a metal lead  25 ; wherein the air cavity  24  is made of a semiconductor material or a glass material. The gap  241  could be filled with various kinds of gases or kept in a vacuum. In the connection between the SAW filter  23  and the conductive layer  221 , a plurality of pads  231  can be installed around the SAW filter  23 , and the metal lead is connected to the plurality of pads and the conductive layer  211  simultaneously by a metal lead  25 . In the design of a circuit connection, the transceiver  22 , the SAW filter  23  and the conductive layer  221  are electrically connected by a metal lead  25 . 
   Then, a molding compound  26  is used to encapsulate the circuit among the substrate  21 , the transceiver  22 , and the SAW filter  23 ; wherein the molding compound  26  is made of a ceramic material, a plastic material or a metal material. 
   Finally, a component stack method is used to integrate the SAW filter and the transceiver  22  into an integrated chip  20 . 
   Please refer to  FIG. 3  accompanied with  FIG. 2 .  FIG. 3  shows the structure of a device for integrating a SAW filter and a transceiver according to another preferred embodiment of the present invention, and their major difference resides on that the lead frame  31  as shown in  FIG. 3  can substitute the substrate  21  as shown in  FIG. 2  as to dispose the transceiver  32  on a chip substrate of the lead frame  31 . Owing to the conductivity of the lead frame  31 , the substrate  21  on the conductive layer  211  as shown in  FIG. 2  is no longer needed. Therefore, the transceiver  32 , the SAW filter  33  and the lead frame  31  can be electrically connected by a lead for the circuit design. 
   Please refer to  FIG. 4  for the flow chart of the method for integrating a SAW filter and a transceiver according to the present invention. The method comprises the steps of firstly disposing a substrate (Step  40 ); coating an epoxy layer on the substrate (Step  42 ); disposing a transceiver on the substrate (Step  44 ), forming a thin isolation layer on the transceiver (Step  46 ), disposing a SAW filter on the transceiver (Step  48 ); electrically coupling the transceiver and the conductive layer by a metal lead (Step  4   a ); encapsulating the circuit among the substrate, the transceiver and the SAW filter by a molding compound (Step  4   b ); and forming an integrated chip (Step  4   c ). 
   Please refer to  FIG. 4 . The substrate used in Step  40  could be a semiconductor substrate or a glass substrate; the epoxy layer used in Step  42  could be a silver epoxy; and the transceiver used in Step  44  could install a plurality of pads around it to facilitate a later circuit connection. Similarly, the SAW filter used in Step  48  could also install a plurality of pads around it to facilitate a later circuit connection. 
   Further, an air cavity covers the SAW filter and keeps a gap between the air cavity and the SAW filter in Step  48 , and the air cavity is made of a semiconductor material or a glass material. The gap can be filled with various gases or kept in a vacuum. The molding compound used in Step  4   b  could be a compound of a ceramic material, a plastic material or a metal material. 
   Please refer to  FIG. 5  accompanied with  FIG. 4 .  FIG. 5  shows a flow chart of the method of integrating a SAW filter and a transceiver according to another preferred embodiment of the present invention. The method comprises the steps of: disposing a lead frame (Step  50 ); coating an epoxy layer on a chip substrate of the lead frame (Step  52 ); disposing a transceiver on the chip substrate of the lead frame (Step  54 ); forming a thin isolation layer on the transceiver (Step  56 ); disposing a SAW filter on the transceiver (Step  58 ); electrically connecting the SAW filter, the transceiver and the lead frame by a metal lead (Step  5   a ); encapsulating the circuit among the lead frame, the transceiver and the SAW filter by a molding compound (Step  5   b ); and forming an integrated chip (Step  5   c ). 
   Please refer to  FIG. 4 . The epoxy layer used in Step  52  could be a silver epoxy, and the transceiver in Step  54  comprises a plurality of pads around it to facilitate a later circuit connection. Similarly, the SAW filter used in Step  58  could also install a plurality of pads around it to facilitate a later circuit connection. 
   Further, an air cavity covers the SAW filter and keeps a gap between the air cavity and the SAW filter in Step  58 , and the air cavity could be a semiconductor material or a glass material. The gap can be filled with various gases or kept in a vacuum. The molding compound used in Step  5   b  could be a compound made of a ceramic material, a plastic material or a metal material. 
   The method and apparatus for integrating a SAW filter and a transceiver according to the present invention can further integrate other components and chips into the package design to fit various integrated circuit packaging technologies (such as the QFP and BGA, etc), in addition to the advantages of having a low cost and small area as well as avoiding signal loss. 
   In summation of the above description, the present invention herein enhances the performance than the conventional structure and further complies with the patent application requirements and is submitted to the Patent and Trademark Office for review and granting of the commensurate patent rights. 
   While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.