Patent Publication Number: US-9425502-B2

Title: Wireless module with integrated antenna by using rigid-flex board

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a built-in wireless module for handheld electronic device and more particularly, to a wireless module with integrated antenna by using rigid-flex board having the characteristics of small size, low loss, low cost, and design and optimization facilitation. 
     2. Description of the Related Art 
     With new advances in technology, all kinds of handheld electronic products are used widely and developed with the tread toward deeper integration and smaller handheld sizes. In consequence, built-in electronic communication module is inevitably developed towards the same trend. 
     Conventional wireless module designs commonly have the communication IC and the antenna be mounted in one single printed circuit board. This design has the drawback of large size, not facilitating locational optimization of the antenna. Therefore, this design is not suitable for use in a small-sized electronic product. In order to eliminate this problem, another prior art design of wireless module was created. This prior art design uses a RF connector and a cable to connect separated communication IC and antenna, facilitating optimization of the antenna in the internal space of the electronic product. However, according to this design, the RF connector and the cable must use special materials and design techniques to reduce high-frequency loss, resulting in significant increase in component costs. A pin connector can be used to substitute for the aforesaid RF connector and cable for high-frequency loss reduction, however the impedance matching problem in signal transmission greatly increase the degree of design difficulty. 
     In view of the above-mentioned problems, U.S. Pat. No. 8,344,955 discloses a wireless module, entitled “Integrated antenna with e-flex technology”. This design enables a communication IC and an antenna to be respectively mounted in a rigid PC board and a flex PC board, wherein the flex PC board has at least one part thereof joined to one end of the rigid PC board to constitute a rigid-flex board. However, because the power layer and the ground layer are interruptedly mounted in the rigid PC board and a flex PC board, this design not only increases circuit complexity, but also may introduce unnecessary noises. Therefore, there is still room for improvement. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide a wireless module with integrated antenna by using rigid-flex board, which integrates an antenna and a communication IC into a rigid-flex board to reduce loss and costs, providing reliable signal quality. 
     To achieve this and other objects of the present invention, a wireless module with integrated antenna by using rigid-flex board of the invention comprises a flex substrate comprising opposing first surface and second surface and a signal layer and a ground layer, an antenna integrated in one side of the flex substrate and comprising a radiator and a feed-in segment and a grounding segment extended from the radiator and respectively electrically connected to the signal layer and ground layer of the flex substrate, a first rigid substrate stacked on the first surface of the flex substrate at an opposite side remote from the antenna, and a communication unit integrated in the first rigid substrate and electrically connected to the signal layer. 
     Thus, the signal layer and the ground layer are continuously arranged on one same flex substrate. This arrangement is helpful to decrease the uncertainty and loss of RE signal transmission path, to improve signal transmission performance and quality, and to reduce component costs. Further, the characteristic of flexibility of the flex substrate facilitates optimization of the antenna. Further, integrating the flex substrate and the first rigid substrate into a rigid-flex board is helpful in reducing the size of the wireless module and facilitating the installation. 
     Further, the antenna can be, but not limited to, planar inverted F antenna, near field communication antenna, monopole antenna or dipole antenna. 
     Further, the optimal design of the invention is to package the communication unit on the rigid substrate using the technique of SiP (System In Package, facilitating application. 
     Other and further benefits, advantages and features of the present invention will be understood by reference to the following specification in conjunction with the accompanying drawings, in which like reference characters denote like elements of structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic drawing illustrating the structural architecture of a wireless module in accordance with the first embodiment of the present invention. 
         FIG. 2  is a sectional view taken along line  2 - 2  of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 and 2 , a wireless module  10  in accordance with the present invention is shown. The wireless module  10  comprises a flex substrate  20 , an antenna  30  integrated in one side of the flex substrate  20 , two rigid substrates  41  and  42  stacked on an opposite side of the flex substrate  20  remote from the antenna  30 , and a communication unit  50  integrated in the rigid substrate  41 . The structural features of the aforesaid components are outlined hereinafter. 
     The flex substrate  20  comprises a first surface  21 , a second surface  22  opposite to the first surface  21 , an electrically conducting signal layer  23  integrated in the first surface  21 , and an electrically conducting ground layer  24  integrated in the second surface  22 . 
     The antenna  30  is integrated in the first surface  21  of the flex substrate  20 . In this embodiment, the antenna  20  is a NFC (Near Field Communication) antenna, comprising a radiator  31 , and a feed-in segment  32  and a grounding segment  33  extended from the radiator  31  and respectively connected to the signal layer  23  and the ground layer  24 . To a person having ordinary skill in the art, changing the antenna into a planar inverted-F antenna, monopole antenna or dipole antenna would have been obvious. 
     The rigid substrates  41  and  42  are respectively stacked on the first surface  21  and second surface  22  of the flex substrate  20  at one side remote from the antenna  30  using a lamination process, and thus the rigid substrates  41  and  42  and the flex substrate  20  are combined to constitute a rigid-flex board  40 . This rigid-flex board  40  is connected to a main board through aboard to board connector or any other interface means. The rigid-flex board  40  comprises a plurality of conductive vias  43  respectively electrically connected to the signal layer  23 , the ground layer  24  and the power trace  12 , signal trace  13  and ground trace  14  of the main board  11 . 
     The communication unit  50  comprises at least one communication IC  51  packaged on the rigid substrate  41  of the rigid-flex board  40  using a semiconductor packaging technique, such as SiP (System in Package), MCP (Multi-Chip Package) or PoP (Package on Package) and electrically connected to the aforesaid conductive vias  43 , joining the antenna  30  to perform wireless communication functions. 
     In addition to the aforesaid components, this embodiment further comprises a grounding component  60  having a conducting structure  61  electrically connected to the connection between the ground layer  24  of the flex substrate  20  and the grounding segment  33  of the antenna  30 . 
     With the foregoing structure, the wireless module  10  of the invention uses the flex substrate  20  and the rigid substrates  41  and  42  to constitute a rigid-flex board  40  that is then integrated with the antenna  30  and the communication unit  50 . Further, the antenna  30  is directly connected to the signal layer  23  and ground layer  24  of the flex substrate  20 , and then connected to the communication unit  50  through the conductive vias  43 . Therefore, the high-frequency signal transmission path is quite simple, and proper measures can be taken in advance in response to the problem of impedance matching. Further, this design does not need to face the high-frequency connectors and cables uncertainty, and can significantly reduce the difficulty of development and component costs. Further, with modular design to reduce the size of the wireless module  10 , the wireless module  10  can easily be installed in the main board  11  of a mobile electronic device, enabling the allocation of the antenna  30  to be optimized using the characteristic of high flexibility of the flex substrate  20 , so as to achieve the purpose of the present invention. 
     It is to be noted that the number of the rigid substrates of the rigid-flex board can be reduced to one, i.e., the rigid substrate  42  at the second surface  22  is adapted for use as a reinforcing material to reinforce the mechanical strength. By means of changing the geometric configuration of the rigid substrate  41  can overcome this problem. 
     Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.