Abstract:
A system and method of establishing an electrical connection between first and second circuit boards includes the use of a multi-function fastener. The fastener is inserted between the circuit boards and serves to physically connect the circuit boards to each other and to a support or base. The fastener bears against conductive edge portions of the first and second circuit boards to also establish electrical conductivity between the circuit boards. Fasteners may be provided to communicate a grounding voltage, as well as, a power supply voltage. By providing a series of circuit boards and fasteners, it is possible to establish common ground and power supply voltage levels in multi-circuit board assemblies, without providing separate ground and power supply bars.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to electrical and physical connections of circuit boards. 
     2. Description of the Relevant Art 
     Often a single electronic device will include multiple circuit boards. Each circuit board is firmly attached within a housing of the electronic device. Further, each circuit board is electrically connected to a common ground voltage, and usually to a common power supply voltage, such as 5 volts. In order to establish the common ground voltage and common supply voltage for the multiple circuit boards, it is common to provide a grounding bar and a power supply bar. 
     FIGS. 1 and 2 illustrate an electrical assembly in accordance with the background art, such as a network interface device (NID), as commonly employed in the telecommunications art. In FIGS. 1 and 2, an electrical box of the NID includes a base  1  and a cover  2 . The cover  2  is attached to the base  1  by a hinge  3 . FIG. 1 is a top view, illustrating the NID with its cover  2  open, providing access to the contents of the base  1 . FIG. 2 is a cross sectional view illustrating the NID with its cover  2  closed. 
     Inside the base  1 , a grounding bar  4  is connected to a floor of the base  1 , via first screws  5 . A power supply bar  6  is connected to the floor of the base  1 , via second screws  7 . Electrical conductivity does not exist between the grounding bar  4  and power supply bar  6 . A plurality of first threaded studs  8  extend away from an upper surface of the grounding bar  4 . Likewise, a plurality of second threaded studs  9  extend away from an upper surface of the power supply bar  6 . 
     A plurality of circuit boards  10 , such as printed circuit boards, are attached between the grounding bar  4  and the power supply bar  6 . Each circuit board  10  includes a first through hole  11  surrounded by a first electrically conductive ring  12  and a second through hole  13  surrounded by a second electrically conductive ring  14 . One of the first threaded studs  8  is passed through the first through hole  11 , and one of the second threaded studs  9  is passed through one of the second through holes  13 . A first washer  15  and first nut  16  are applied to the first threaded stud  8 . Likewise, a second washer  17  and second nut  22  are applied to the second threaded stud  9 . 
     As illustrated in FIG. 1, a first wire  18  is passed through a first port  19  formed by the base  1  and cover  2 . The first wire  18  is electrically connected to the grounding bar  4 , via one of the first screws  5 , or one of the first nuts  16 . The first wire  18  provides the common grounding voltage. A second wire  20  is passed through a second port  21  formed by the base  1  and cover  2 . The second wire  20  is electrically connected to the power supply bar  6 , via one of the second screws  7 , or one of the second nuts  22 . The second wire  20  provides the common power supply voltage. 
     By the arrangement of FIGS. 1 and 2, each printed circuit board  10  is firmly connected to the base  1 . Also, a common ground voltage and a common power supply voltage are provided to the first electrically conductive ring  12  and the second electrically conductive ring  14  of each printed circuit board  10 , respectively. 
     The arrangement of FIGS. 1 and 2 suffers drawbacks. The grounding bar  4  and power supply bar  6  are bulky and rather expensive. Therefore, the overall size of the NID be enlarged to accommodate the grounding bar  4  and the power supply bar  6 . Further, the overall cost of manufacturing the NID must be increased by the material costs of the grounding bar  4  and the power supply bar  6 , as well as, by the labor costs associated with installing the grounding bar  4  and the power supply bar  6 . 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to overcome one or more of the drawbacks associated with the background art. 
     It is a further object of the present invention to provide a system and method of grounding and/or powering multiple circuit boards which is less expensive and/or less labor intensive. 
     It is an additional object of the present invention to provide a system and method of grounding and/or powering multiple circuit boards which consumes less space within an enclosure, housing the circuit boards. 
     These and other objects are accomplished by providing an electrical assembly comprising a base; a first circuit board disposed on said base; a first electrically conductive portion associated with said first circuit board; a second circuit board disposed on said base; a second electrically conductive portion associated with said second circuit board; a first fastener located between said first circuit board and said second circuit board and attaching said first circuit board to said second circuit board; and a third electrically conductive portion associated with said first fastener electrically connecting said first conductive portion to said second conductive portion. 
     Further, these and other objects are accomplished by providing an electrical assembly comprising: a circuit board having a first surface, a first edge and a second edge; a first electrically conductive portion formed on said first surface; a first cutout formed along said first edge adjacent said first electrically conductive portion; and a second cutout formed along said second edge adjacent said first electrically conductive portion. 
     Moreover, these and other objects are accomplished by a method of forming an electrical assembly comprising the steps of: providing a base, a first circuit board with a first electrically conductive portion, a second circuit board with a second electrically conductive portion, and a first fastener with a third electrically conductive portion; disposing the first and second circuit boards on the base, inserting the first fastener between the first and second circuit boards; and contacting the third electrically conductive portion with the first and second electrically conductive portions to establish a common circuit. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is a top view illustrating electrical and physical interconnections between multiple circuit boards, in accordance with the background art; 
     FIG. 2 is a cross sectional view illustrating the interconnections of FIG. 1; 
     FIG. 3 is a top view of a circuit board, in accordance with the present invention; 
     FIG. 4 is top view illustrating electrical and physical interconnections between multiple circuit boards, in accordance with the present invention; 
     FIG. 5 is a cross sectional view illustrating the interconnections of FIG. 4; 
     FIG. 6 is a cross sectional view illustrating an alternative embodiment for electrically interconnecting the circuit boards; 
     FIG. 7 is a cross sectional view illustrating a first embodiment for connecting a ground wire or power supply wire; and 
     FIG. 8 is a cross sectional view illustrating a second embodiment for connecting a ground wire or power supply wire. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to FIG. 3, a circuit board  30 , in accordance with the present invention, includes a first surface  31 , a first edge  32  and a second edge  33 . A first electrically conductive portion  34  is formed on the first surface  31  at a first end of the circuit board  30 . A second electrically conductive portion  35  is formed on the first surface  31  at a second end of the circuit board  30 . The first and second electrically conductive portions  34 ,  35  may be metallic traces formed on, or applied to, the first surface  31  of the circuit board  30 . 
     A first cutout  36  is formed along the first edge  32  adjacent to the first electrically conductive portion  34 . A second cutout  37  is formed along the second edge  33  adjacent to the first electrically conductive portion  34 . A third cutout  38  is formed along the first edge  32  adjacent to the second electrically conductive portion  35 . A fourth cutout  39  is formed along the second edge  33  adjacent to the second electrically conductive portion  35 . The cutouts  36 ,  37 ,  38 ,  39  are illustrated as semi-circular in shape, however it should be noted that other shapes may also be suitable. 
     Inside the first electrically conductive portion  34 , there is provided a first through hole  40 . A first through slot  41  and a second through slot  42  are provided adjacent to the first through hole  40  and open into the first through hole  40 . Residing between the first through slot  41  and the second through slot  42  is a first flexible portion  43  of the circuit board  30 . A third through slot  44 , fourth through slot  45  and second flexible portion  46  may be provided on an opposite side of the first through hole  40  in a mirror symmetrical fashion. 
     Inside the second electrically conductive portion  35 , there is provided a second through hole  47 . A fifth through slot  48  and a sixth through slot  49  are provided adjacent to the second through hole  47  and open into the second through hole  47 . Residing between the fifth through slot  48  and the sixth through slot  49  is a third flexible portion  50  of the circuit board  30 . A seventh through slot  51 , eighth through slot  52  and fourth flexible portion  53  may be provided on an opposite side of the second through hole  47  in a mirror symmetrical fashion. 
     In application, a plurality of circuitry components (not illustrated), such as transistors, diodes, capacitors, and resistors, would be present upon the first, and perhaps a back surface of the circuit board  30 . The circuitry components could be fill scale, or integrate components on a printed circuit board, such as employed in large scale integration (LSI) or very large scale integration (VLSI), etc. In order to power the circuitry components, a grounding voltage would be established at the first electrically conductive portion  34 , and a power supply voltage, such as 5 volts, would be established at the second electrically conductive portion  35 . Soldering, or printed metallic traces, would interconnect the appropriate circuitry components between the first electrically conductive portion  34  and the second electrically conductive portion  35 . 
     Now, with reference to FIGS. 4 and 5, the interconnections of a plurality of circuit boards  30  will be explained. In FIG. 4, a modified electrical box of the NID includes a modified base  60  and the cover  2 . The cover  2  is attached to the modified base  60  by the hinge  3 . FIG. 4 is a top view, illustrating the NID with the cover  2  open, providing access to the contents of the modified base  60 . FIG. 2 is a cross sectional view illustrating the NID with its cover  2  closed. 
     Inside the modified base  60 , there is provided a first bank of threaded holes  63  and a second bank of threaded holes  64 . When assembling the NID, the circuit boards  30  are laid side-by-side on the modified base  60 , with a center of the cutouts  36 ,  37 ,  38 ,  39  being located above respective ones of the threaded holes  63 ,  64 . First fasteners, such as first screws  65 , are threaded into respective threaded holes of the first bank of threaded holes  63 . Likewise, second fasteners, such as second screws  66 , are threaded into respective threaded holes of the second bank of threaded holes  64 . 
     Each of the first and second screws  65 ,  66  includes a threaded shaft and a third electrically conductive portion, such as a head constructed of an electrically conductive material. As illustrated in FIG. 5, once the first screws  65  are tightened down, the conductive heads will physically contact the first electrically conductive portions  34  of the circuit boards  30 . The physical contact will secure the circuit boards  30  to the modified base  60 , as well as, establish electrical conductivity between the first electrically conductive portions  34  of the circuit boards  30 . Once the second screws  66  are tightened down, the conductive heads will physically contact the second electrically conductive portions  35  of the circuit boards  30 . The physical contact will secure the circuit boards  30  to the modified base  60 , as well as, establish electrical conductivity between the second electrically conductive portions  35  of the circuit boards  30 . 
     FIG. 6 is a close-up view of an alternative embodiment for the first fasteners. In FIG. 6, the third electrically conductive portion is a conductive washer  67 , disposed under a head of the first screw  65 . The conductive washer  67  establishes electrical conductivity between the first electrically conductive portions  34  of adjacent circuit boards  30 . Therefore, in the first screws  65  need not be constructed of an electrically conductive material. 
     As in FIG. 1, the first wire  18  is passed through the first port  19  formed by the modified base  60  and the cover  2 . The first wire  18  must be electrically connected to the first electrically conductive portions  34  of the circuit boards  30 , in order to provide a common grounding voltage. The second wire  20  is passed through the second port  21  formed by the modified base  60  and the cover  2 . The second wire  20  must be electrically connected to the second electrically conductive portions  35  of the circuit boards  30 , in order to provide a common power supply voltage. 
     FIG. 7 illustrates a first embodiment for electrically connecting the first wire  18  to the first electrically conductive portions  34 . A terminal  68  on an end of the first wire  18  is sandwiched between two conductive washers  69 . One of the conductive washers  69  bears against a head of the first screw  65  and the other of the conductive washers  69  bears against the first electrically conductive portion  34  of one of the circuit boards  30 . By tightening the first screw  65 , electrical conductivity is established between the common ground voltage of the first wire  18  and the first electrically conductive portions  34 . Of course, a similar arrangement could be employed to electrically connect the second wire  20  to the second electrically conductive portions  35 . 
     FIG. 8 illustrates a second embodiment for electrically connecting the first wire  18  to the first electrically conductive portions  34 . The terminal  68  on the end of the first wire  18  is sandwiched between a conductive washer  69  and a head of a third fastener  70 . The conductive washer  69  bears against the first electrically conductive portion  34  of one of the circuit boards  30 . The third fastener  70  is threaded into the first through hole  40  (see FIG. 3) and tightened to establish electrical conductivity between the common ground voltage of the first wire  18  and the first electrically conductive portion  34 . By the second embodiment, it is possible to use third fasteners  70  of various diameters, since the first and second flexible portions  43 ,  46  of the circuit board  30  will yield to accommodate the diameter of the third fastener  70 . Of course, a similar arrangement could be employed to electrically connect the second wire  20  to the second electrically conductive portions  35 . 
     Although screws have been illustrated as the first, second and third fasteners, it should be apparent after reading the disclosure, that other types of fasteners, such as snaps or specialty fasteners, could be used. Further, although the first and second electrically conductive portions have been illustrated at the ends of the circuit boards, it should be apparent that the present invention would be equally applicable if the conductive portions were place at other, consistent locations on the circuit boards. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.