Abstract:
A PCB footprint consisting of a plurality of pads, positioned such that many different electronic components can be mounted which would otherwise require a custom circuit board. One or more of the leads can be connected via a low-impedance path to a ground plane, making a suitable platform for prototyping high-frequency designs.

Description:
RELATED APPLICATIONS 
       [0001]    U.S. Pat. No. 5,683,788 
         [0002]    U.S. Pat. No. 5,805,428 
         [0003]    U.S. Pat. No. 6,405,920 
         [0004]    U.S. Pat. No. 5,266,747 
         [0005]    U.S. Patent Application 2012/0236,516 
       STATEMENT OF FEDERALLY SPONSORED RESEARCH 
       [0006]    Not Applicable 
       NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT 
       [0007]    Not Applicable 
       SEQUENCE LISTING 
       [0008]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0009]    Modern electronic components are typically mounted on Printed Circuit Boards (PCB). A PCB is typically made by etching a desired pattern into a copper layer, where multiple such copper layers may be sandwiched together using a non-conductive substrate. 
         [0010]    To mount a component to a PCB, a pattern which matches the ‘footprint’ of the device must be etched into that PCB. Each ‘lead’ on the device correct matches a ‘pad’ on the PCB, and can be joined by soldering the component to the PCB. 
         [0011]    When prototyping designs, it is desirable to have a method of testing a part or design without requiring a new PCB to be designed and etched. This is difficult as electronic components come in a variety of package sizes. Previous multi-function footprints were often limited to 2 or 3-terminal devices, such as U.S. Pat. No. 5,683,788 or U.S. Pat. No 5,805,428. Such patterns are also unsuitable for high-frequency components, as no consideration has been given to the requirement of impedance matching and low-impedance ground paths. 
       SUMMARY OF THE INVENTION 
       [0012]    A footprint which can be used with most popular packages of high-frequency component. Packages that can be mounted include SOT-23, SOT-363, SOT-343, SOT-89, 4-pin round plastic, SOIC-8, ceramic filter package, and many custom devices. The careful mounting of a ground connection allows a low-impedance ground path which works with most of the packages. 
         [0013]    The above footprint is implemented in a circuit board which contains additional features for prototyping, such as the ability to chain multiple PCBs together without connectors. Many variations of the design of this footprint or PCB are possible to those knowledgeable in the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a view of an implementation of the footprint 
           [0015]      FIG. 2  is a view of an implementation of the footprint with a low-impedance ground path on the central pad 
           [0016]      FIG. 3  is a view of the prototyping PCB using the footprint from  FIG. 1 . 
           [0017]      FIG. 4  is a view of the prototyping PCB using the footprint from  FIG. 2 . 
           [0018]      FIG. 5A  is a view of the SOT-23-5 device mounted 
           [0019]      FIG. 5B  is a view of the SOT-363 device mounted 
           [0020]      FIG. 5C  is a view of the SOT-343 device mounted with three transmission lines and a ground pad 
           [0021]      FIG. 5D  is a view of the SOT-89 device mounted with a ground pad 
           [0022]      FIG. 5E  is a view of the SOIC-8 device mounted 
           [0023]      FIG. 5F  is a view of the ceramic filter device mounted 
           [0024]      FIG. 6  is a view of interconnected prototyping PCBs 
       
    
    
     DETAILED DESCRIPTION 
       [0025]      FIG. 1  and  FIG. 2  show two possible embodiments of the footprint. The footprint is mounted on a substrate  100 . The plurality of copper pads  101  and  102  can be used for component mounting. When a specific component is mounted a plurality of pads may be used, not all pads are used for every component type. The central pad  101  may optionally have via(s)  200  connecting to a ground plane under the central footprint. 
         [0026]      FIG. 3  and  FIG. 4  show a prototyping PCB using the footprint, where  FIG. 3  has a footprint as in  FIG. 1  and  FIG. 4  has a footprint as in  FIG. 2 . The board is etched onto a substrate  100 , and portions of the board may be connected to a ground plane using vias  300 . Additional pads such  301  are used for prototyping through hole and surface mount parts. The transmission lines  304  extend to the edge of the board. Slots  305  are made in the transmission line to allow placing of components such as resistors across the divide. The transmission line can connect to the plurality of fingers  102  of the central footprint. 
         [0027]      FIG. 5  shows several different components mounted using the boards from  FIG. 3  and  FIG. 4 . 
         [0028]    In  FIG. 5   a  a Small Outline Transistor (SOT) 23-5 is shown. The main body  501  of the transistor overlaps the central pad  502 ; pad  502  is not electrically connected in this example. The plurality of leads from the transistor  503  connect to the plurality of pads  504 . Bridging material  505  and  506  connects to the transmission line  507  and  508  respectively. The bridging material would typically be solder, but could also be a conductive ink or other conductive material. 
         [0029]    In  FIG. 5   b  a SOT-363 device  509  is mounted. Again the central pad  502  is not electrically used in this example, and the bridging material  505  and  506  is connecting two of the leads  503  to the transmission lines  507  and  508 . 
         [0030]    In  FIG. 5   c  a SOT-343 device  510  is mounted, such as typically used in a mixer device. This example uses the central pad  502  shorted to the ground plane with via  511 , which provides a low-impedance path to the ground lead  512  of the mixer part. Three transmission lines  507 ,  508 , and  513  are connected to the parts leads  514 ,  515 , and  516  respectively through use of solder and bridging material  505  and  506 . 
         [0031]    In  FIG. 5   d  a SOT-89 device  517  is mounted, where the plurality of vias such as  511  provide a low-impedance path to ground for the device ground tab  518 . The transmission lines  507  and  508  on the PCB are coupled to the device leads  519  and  520  via the bridging material  505  and  506 . 
         [0032]    In  FIG. 5   e  additional pads  521  and  522  are added outside of the main footprint, demonstrating the extensions on which parts mount need not be directly in line with the main pad. A Small Outline Integrated Circuit (SOIC-8) package  523  is mounted, where leads of the device connect to the pads. Again the central pad is connected to the ground plane via a plurality of vias  511 . This allows the bridging material  524  to form a low-impedance path to ground for the device grounding pins  525 . The connection to transmission lines  507  and  508  is again made with a bridging material  505  and  506  such as solder. 
         [0033]    In  FIG. 5   f  a ceramic filter  526  is mounted. The ceramic filter has three connections: input  527 , ground  528 , and output  529 . The plurality of vias  511  provides a low-impedance ground path. The bridging material  506  connections the transmission line  508  to the input, and bridging material  505  connects the output to transmission line  507 . 
         [0034]      FIG. 6  shows an embodiment of the design, where several PCBs  600  are interconnected along the edge. Bridging material  601  is used to connect the ground planes of the PCBs along the edges, along with bridging material  602  connecting the planar transmission lines. The edges of the boards  603  are suitable for mounting end-launch connectors, such as SMA connectors for connecting the boards to additional systems.