Abstract:
The present disclosure discloses a contact structure for electromechanical switch. The contact structure is using the design including a PCB and a moving contact to allow the actuations and have great switch characteristics whose range is from DC to high frequency.

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 13/204,668, filed on Aug. 6, 2011, which claims priority to Taiwan Application Serial Number 100119622, filed on Jun. 3, 2011. The entire disclosures of both applications are hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     1. Technical Field 
     This disclosure relates to an electromechanical switch, more particularly relates to a contact structure for electromechanical switch utilizing a PCB based construction and a moving contact to allow the actuations and have excellent switch performances, such as high isolation and low insertion loss, and the electromechanical switch is capable of transmitting electronic signals ranged from DC to microwave. 
     2. Description of Related Art 
     The electronic signal transmission speed is requested growing fast with the technology progress, so that the control switches or relays are required to be capable of processing the 1 GHz or higher frequency signal. The electromechanical switches or relays are for connecting or disconnecting current or circuitry with mechanical design. Conventional contact structure of those electromechanical switches or relays does not consider the problem of high frequency transmission while designing, so that the contact structure is only capable of transmitting DC or extremely low frequency signals. If the present contact structure with mechanical design desires to be added a processing device for high frequency signals, it will meet the problems which are the cost increase in large scale and hard to mass production. 
     The MEMS switch or relay is used for resolving the problems mentioned above. In brief, it is fabricated on the silicon wafer with semiconductor technology and having the potential of mass production. The micro design is capable of minimizing the volume of the switches or relays. The typical MEMS switch  5 , shown as  FIGS. 1 and 2 , has a pair of electrodes  11  and  14  which are separated by a thin dielectric layer  12  and an air gap or cavity  13  defined by a dielectric standoff  16 . The electrode  14  is mounted on a diaphragm or a moving beam capable of mechanical displacement, and the other electrode  11  is jointed on a substrate and cannot move freely. The switch  5  has two states, that is open (shown as  FIG. 1 ) or close (shown as  FIG. 2 ). 
     The MEMS switch is very small, so that the charged dielectric medium and effects of static friction always interference the stable actuation and release. And the MEMS switch needs low insertion loss and high isolation while transmitting the high frequency electronic signals, so as to define the gap between the electrodes  11  and  14 . Therefore, the MEMS switch is restricted while being used for transmitting the high frequency electronic signals. 
     In addition, the MEMS switch is fabricated with semiconductor technology, and the processes are including repeatedly oxidizing, depositing, transferring, and etching. The processes are complicated and the steps are numerous. If one of the processes is error, the total element must be reworked, so as to make the manufacturing time and cost higher. 
     SUMMARY  
     The objective of this disclosure is providing a contact structure for electromechanical switch, which provides stable switch characteristics, such as low insertion loss while ON, and high isolation while OFF. 
     The contact structure of this disclosure matches the condition of low driving power. 
     The contact structure of this disclosure allows many kinds of actuations, such as electrostatic force, electro-magnetic force, piezoelectric effect, or heating effect. 
     The contact structure of this disclosure applies to the switch or relay with the application range from DC to microwave, and is capable of processing the 1 GHz or higher frequency signal. 
     The contact structure of this disclosure is using PCB structure and suitable for low cost mass production. Compared to conventional MEMS switch, the switch of this disclosure has lower manufacturing cost and simpler manufacturing method. 
     The contact structure of this disclosure is capable of minimizing the volume of the MEMS switch. 
     The contact structure of this disclosure utilizes PCB and moving contact. Although the PCB has been already used in RF switch and thin film switch, there are still many characteristics different from the RF switch and the thin film switch, which comprise:
         (a) The RF switch is capacitive type, it is not suitable for directing current and cannot be a current switch or relay. But the switch of this disclosure is suitable for being a current switch or relay.   (b) The RF switch is driven by electrostatic force which needs high driving voltage and very small actuation gap that does not match the conditions of low driving power and large separated gap.   (c) The printed circuits of the RF switch are integrated on a PCB, but the contact structure of this disclosure is an individual configuration.   (d) The thin film switch generally means a push switch, not an electromechanical switch, which is suitable for the conditions with a switch power lower than 1 W, 42V(DC) or 25V(DC) maximum operating voltage, minimum operating current smaller than 100 mA. The thin film switch is not suitable for matching conventional electromechanical actuating device, and further not suitable for processing high frequency signal.       

     In one embodiment, the contact structure of this disclosure is capable of transmitting high frequency signals in a one-in-multi-out, a multi-in-one-out or a multi-in-multi-out mode. 
     Other features or advantages of the present disclosure will be apparent from the following drawings and detailed description of several embodiments, and also from the appending claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows: 
         FIG. 1  shows a cross-section diagram of a typical MEMS switch. 
         FIG. 2  shows a cross-section and schematic diagram of the typical MEMS switch while being actuated. 
         FIG. 3  shows an exploded diagram of the contact structure according to this disclosure. 
         FIG. 3A  shows a schematic diagram of one example of the structure of the moving contact and the static contact. 
         FIG. 3B  shows a schematic diagram of another example of the structure of the moving contact and the static contact. 
         FIG. 3C  shows a schematic diagram of still another example of the structure of the moving contact and the static contact. 
         FIG. 4  shows a cross-section diagram of the contact structure according to this disclosure. 
         FIG. 5  shows a schematic diagram of the contact structure according to this disclosure while being actuated. 
         FIG. 6  shows a schematic diagram of a first embodiment of the electromechanical switch with the contact structure according to this disclosure. 
         FIG. 7  shows a schematic diagram of a second embodiment of the electromechanical switch with the contact structure according to this disclosure. 
         FIG. 8  shows a schematic diagram of a first embodiment while packaging the contact structure and an actuating device according to this disclosure. 
         FIG. 9  shows a schematic diagram of a second embodiment while packaging the contact structure and an actuating device according to this disclosure. 
         FIG. 10  shows a section view of another embodiment of the contact structure according to this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
     Please refer to  FIG. 3 , a contact structure  20  is stacked by a plurality of PCBs, which comprise a basic layer  21 , a spacing layer  22 , and a top layer  23  from top to bottom. 
     The basic layer  21  is rigid material but not limited to insulation material, such as FR4, or a material capable of responding microwave with some frequency range, such as RO4003 high frequency circuit board material. A lower surface of the basic layer  21  has a grounding structure (not shown) which is formed by metalizing the lower surface of the basic layer  21 . An upper surface of the basic layer  21  is set signal traces by printed circuit technology to become static contacts  211 . A static contact  211  is formed on an upper surface of the basic layer  21  via printed circuit technology. The static contact  211  can be viewed as a metal signal trace. 
     The spacing layer  22  is stacked on the upper surface of the basic layer  21 . The spacing layer  22  can be made from various PCB materials, such as kapton, typical FR4, or solid bonding film made from acrylic with a predetermined thickness. The spacing layer  22  includes a window  221  to make the static contacts  211  of the basic layer  21  be not covered by the spacing layer  22 . 
     The top layer  23  is stacked on an upper surface of the spacing layer  22 , and made from a flexible circuit board material. A static contact  211  is formed on an upper surface of the basic layer  21  via printed circuit technology. The static contact  211  can be viewed as a metal signal trace. A nick  232  is specifically machined at the flexible circuit board surrounding the moving contacts  231 , so that a floating area  233  is surrounding the moving contacts  231 . The floating area  233  can be moved downwardly while a force is applied and moved upwardly to become flat while the force is released. 
     Finally, the basic layer  21 , the spacing layer  22  and the top layer  23  are stacked together, shown as  FIG. 4 . 
     The static contacts  211  and the moving contacts  231  are metal printed conducting paths with specified geometry, which are defined in accordance with different application range. Therefore, the layouts of the paths of the static contacts  211  and the moving contacts  231  are defined according to the performance of the switch or relay. That makes the application range of the contact structure  20  wider. It is suitable for the application range from DC to microwave, especially capable of processing 1 GHz or higher frequency signal, and capable of performing low insertion loss. 
     The static contacts  211  and the moving contacts  231  have specified impedance, normally 50Ω. The static contacts  211  and the moving contacts  231  are micro strip lines. The micro strip line is a kind of signal transmission line having good impedance control and capable for passing high frequency signals. 
     Commonly when the static contacts  211  and the moving contacts  231  are contacted for conducting a waveguide to transmit signals, an overlapping area is formed. The overlapping area can be referred as a capacitor. At high frequency, signal can couple through the capacitor. Therefore, even the static contacts  211  and the moving contacts  231  are not contacted (switch is OFF), the signal is not isolated. Insufficient isolation will reduce performance of the devices such as switch or relay utilizing the contact structure  20 . Owing to the isolation is related to the overlapping area, to minimize the phenomena of insufficient isolation, the overlapping area should be reduced. For example, in  FIG. 3A , the static contacts  211  and the moving contacts  231  has converging portion  211   a  and converging portion  231   a  respectively. Via the structure of the converging portion  211  and the converging portion  231 , isolation between the static contacts  211  and the moving contacts  231  will be enhanced. It should be known that the geometry of the converging portions  211   a ,  231   a  can be specifically designed in accordance with various situations. For example, in  FIG. 3A , the converging portions  211   a ,  231   a  are triangle with spiky end, and in  FIG. 3B , the converging portions  211   a ,  231   a  are triangle with circle end. In  FIG. 3C , the converging portions  211   a ,  231   a  can be formed by combination of two portions with gradually reduced width. By the converging portions  211   a ,  231   a , it is possible to keep sufficient isolation and capable of transmitting high frequency signals. 
     However, the impedance variation occurred owing to line width change of the static contacts  211  and the moving contacts  231 . Therefore, a compensation structure is set along the metal printed conducting paths to compensate the impedance variation. In this embodiment, a tuning circuit  212  and a tuning circuit  234  adjacent to the static contacts  211  and the moving contacts  231  are utilized for compensating the impedance variation. The tuning circuit  212  and the tuning circuit  234  have specifically designed geometry for effectively compensating the impedance variation. 
     The gap between the static contacts  211  and the moving contacts  231  is defined by the thickness of the spacing layer  22  and the required electric power for actuating the contact structure  20 . However, the narrow gap is preferable to make sure that the moving contacts  231  are certainly contacting with the static contacts  211  and in a condition of low driving power. The gap can be controlled by controlling the thickness of the spacing layer  22 . 
     Please refer to  FIG. 5 , the contact structure  20  with an actuation makes the top layer  23  having the floating area  233  move downwardly, and the window  221  of the spacing layer  22  allows the moving contacts  231  moving downwardly to contact the static contacts  211  of the basic layer  21 . The actuation can be performed by an actuating device with electrostatic force, electromagnetic force, piezoelectric effect, or heating effect. The actuating device is coupled to the contact structure  20  and a transmission portion of the actuating device is contacting the top layer  23  having the floating area  233 . 
     Please refer to  FIG. 6 , the actuating device  30  is electromechanical type. A supporting member  31  is welded to a lead frame  54  disposed at the bottom of the basic layer  21  via the window  221  of the spacing layer  22  and a via  53  disposed at the basic layer  21  in advance. The transmission portion  32  of the actuating device  30  is contacting the top layer  23  having the floating area  233 . The movement of the transmission portion  32  is driving the floating area  233  to move downwardly and then makes the moving contacts  231  contact the static contacts  211 . 
     Please refer to  FIG. 7 , the actuating device  40  is electromagnetic type. In the circuit printing process of the contact structure  20 , a printed coil  41  is constructed at the bottom of the basic layer  21 , and a magnetic material  42  is constructed at the top of the top layer  23  and coating the printed coil  41 . The current is passed through the printed coil  41 , and the moving contacts  231  are move downwardly to contact the static contacts  211  via the magnetic material  42 . 
     Embodiments of packaging processes of the contact structure  20  and the actuating device  30  are showed in  FIGS. 8 and 9 . The switch structure may not be packaged individually; switch meshes may be formed on the printed circuit board first and the packaging processes are then performed. 
     Please refer to  FIG. 9 , the actuating device  30  has already been coupled to the contact structure  20 . One part of the contact structure  20  is packaged. The lower surface of the basic layer  21  is presetting layouts of a ground and leads, and the printed conducting paths arranged at the upper surface of the basic layer  21  are connected to relative leads through a via  55  of the basic  21 . The basic layer  21  is coupled to a lead frame  54  matched each other. The supporting member  31  of the actuating device  30  is welded at the lead frame  54  through the window  221  of the spacing layer  22  and the preset via  53  of the basic layer  21 . An outer cover  60  is closing the whole configuration. 
     Please refer to  FIG. 10 . A contact structure  300  is formed by stacking a plurality of PCBs. The contact structure  300  includes a top layer  310 , a spacing layer  320 , a basic layer  330 , at least two RF layers  340  and at least one control layer  350 . The top layer  310 , the spacing layer  320 , the basic layer  330 , the RF layers  340  and the control layer  350  are stacked in order from up to down. The structure of the top layer  310 , the spacing layer  320  and the basic layer  330  are similar to the top layer  23 , spacing layer  22  and the basic layer  21  in the aforementioned embodiment. In the embodiment, a space between the top layer  310  and the basic layer  330  is separated into multiple sub-spaces  312  by the spacing layer  320 , and the top layer  310  includes multiple moving contacts  311 . In the embodiment, two sub-spaces  312  and two moving contacts  311  are used, but it should be mentioned that the number of the sub-space  312  or the moving contact  311  is not limited. The basic layer  330  includes a static contact  331  on an upper surface, and one of the RF layers  340  includes a trace  341  on an upper surface. The static contact  331  is a micro strip line for allowing transmitting high frequency signals such as RF signals, and the trace  341  is a strip line for RF connection between devices. Main difference between the contact structure  300  and the aforementioned contact structure  20  is that the contact structure  20  is only capable of transmitting the signals in a one-in-one-out mode, but the contact structure  300  is further capable of transmitting the signals in a one-in-multi-out, a multi-in-one-out or a multi-in-multi-out mode. To reach this purpose, in the contact structure  300 , two RF layers  340  are stacked under the basic layer  330 , and the static contact  331  of the basic layer  330  is electrically connected to the trace  341  of the RF layer  340 . In  FIG. 3 , the contact static  331  is electrically connected to the trace  341  via two RF interconnections  401 . Therefore, by the two moving contacts  311  and the two RF interconnections  401 , the signals can be transmitted through a 2×2 variant, such as one-in-one-out, one-in-two-out, two-in-one-out and two-in-two out. Moreover, the control layer  350  is stacked under the RF layer  340  for providing logic and driving control of the actuators that make switching action. It can also include other non-RF functions as it separated by ground layers  342  between the RF layer  340  and the control layer  350 . 
     In on example, two grounding interconnections  402  are used to connect the ground layer  342  located on a back surface of the basic layer  330  and the ground layer  342  located on a back surface of the RF layer  340 . 
     In the aforementioned embodiment, the number of the moving contacts  311  and the RF interconnections  401  can be varied with different applications, thereby achieving multi-in-multi-out functionality. 
     In summary, this disclosure provides a contact structure for electromechanical switch utilizing PCB process and moving contact. Therefore, the volume of the electromechanical switch can be substantially minimized, the production and manufacturing cost of the electromechanical switch is low, various kinds of actuations can be allowed, various kinds of actuating devices can be matched, and the electromechanical switch has excellent performances, such as high isolation and low insertion loss. And the application range can be from DC to microwave. 
     Although the present disclosure has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims.