Abstract:
A bifurcated conductive pad positioned on an electrical mating component, such as a circuit card, a contact portion of a cable assembly, or the like, having a main body and a mating edge. The bifurcated conductive pad receives a mating element having a built-up charge. The conductive pad comprises an initial contact portion and a final contact portion. The initial contact portion is configured to receive the mating element before the final contact portion receives the mating element, and wherein at least one of the initial and final contact portions is grounded so that the final contact portion receives a reduced amount of the built-up charge.

Description:
BACKGROUND OF THE INVENTION 
   Certain embodiments of the present invention generally relate to conductive pads or contacts of electronic circuit cards, electrical cable assemblies, electrical components and the like, and more particularly to conductive pads that protect against electrical and electrostatic charge and build up on electrical elements that are mated with the conductive pads. 
   Various electronic systems, such as computers, comprise a wide array of components mounted on circuit boards, such as daughtercards and motherboards that are interconnected to transfer signals and power throughout the systems. Circuit cards having mating contacts are used to transfer signals and power between the circuit boards and other components of the systems. Various cable assemblies are used as well to transfer signals between components. 
     FIG. 1  is an isometric view of a conventional circuit card  10  housed in a connector to interconnect circuit boards and other components. The circuit card  10  includes a mating edge  12 , a top edge  14  and a channel edge  16  defining a main body  17  therebetween. The circuit card  10  includes a plurality of conductive pads  18  (signal and ground conductive pads) arranged along the mating edge  12  of the main body  17 . Conductive pads  22  (ground and signal pads) are arranged along the channel edge  16  of the main body  17 . Traces  26  connect corresponding conductive pads  18  and  22 . The traces  26  are staggered on opposite sides of the circuit card  10  and connected to corresponding conductive pads  18  and  22  through vias  20  and  24 , respectively. The traces  26  may also be positioned to electrically connect two or more vias  20  or  24 . 
   The channel edge  16  is received and retained within a channel of a connector housing (not shown). Typically, contact pins (not shown) engage the conductive pads  22  through cavities within the channels. Also, contacts (not shown) electrically connect conductive pads  18  on one circuit card  10  to conductive pads  18  on another circuit card  10 . 
   Different types of circuit cards, which may be used in various applications, are known in the art. The circuit cards may be housed or retained in a wide variety of housings. The circuit card  10  is merely an example of a typical circuit card having conventional conductive pads  18  and  22 . Typically, conductive pads  18  and  22 , which may be used on circuit cards and on other electrical components, are single unitary conductive pieces directly connected to traces  26 . 
   In order to establish electrical contact with the circuit card, a mating element of a corresponding circuit board or electrical component contacts the conductive pad. Often, electrostatic or other electrical energy builds up in the mating element. Often, an electrical charge may arc from the mating element to the circuit card. Also, when the mating element initially contacts the conductive pad, electrostatic energy built up on the mating element is discharged into the conductive pad. The electrostatic or electrical charge travels from the conductive pad through the electrical path emanating from the conductive pad. Typically, the electrical path leads to another component. The circuitry of the component, however, may not be able to handle the surge of electrostatic energy. Often, the electrostatic or electrical charge, or surge, may degrade or destroy the circuitry of components within an electrical system. 
   Thus, a need exists for a conductive pad that protects against the harmful effects of an electrostatic discharge. 
   BRIEF SUMMARY OF THE INVENTION 
   Certain embodiments of the present invention provide a circuit card or electrical mating component having a conductive pad configured to join a mating element having a charge build-up. The conductive pad comprises first and second contact portions separate and distinct from one another and a charge-controlling device. The first contact portion is configured to receive the mating element before the second contact portion receives the mating element. The charge-controlling device is connected to the first contact portion to establish an electrical path in which the charge build-up is discharged through the charge-controlling device. The charge-controlling device may be surface mounted, or positioned within the circuit card or electrical mating component. 
   Certain embodiments of the present invention also provide a bifurcated conductive pad positioned on a circuit card having a main body and a mating edge. The bifurcated conductive pad receives a mating element having a built-up charge. The conductive pad comprises an initial contact portion and a final contact portion, wherein the initial contact portion is configured to receive the mating element before the second contact portion receives the mating element. At least one of the initial and final contact portions is grounded so that the final contact portion receives a reduced amount of the built-up charge. Certain embodiments of the present invention also provide a circuit board comprising a main body and a charge-controlling conductive pad system. The charge-controlling conductive pad system includes at least one surface mount pad positioned on said main body; and a resistor mounted on said at least one surface mount pad, wherein said at least one surface mount pad is connected to ground 

   
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  illustrates an isometric view of a conventional circuit card configured to be mounted in a connector housing. 
       FIG. 2  illustrates a side view of a circuit card formed according to an embodiment of the present invention. 
       FIG. 3  illustrates a side view of a portion of a circuit card formed according to an embodiment of the present invention. 
       FIG. 4  illustrates a partial end view of a mating edge of a circuit card formed according to an embodiment of the present invention. 
       FIG. 5  illustrates a partial plan view of a top edge of a circuit card formed according to an embodiment of the present invention. 
       FIG. 6  illustrates a schematic diagram representative of a charge-controlling system according to an embodiment of the present invention. 
       FIG. 7  illustrates a side view of a circuit card formed according to an alternative embodiment of the present invention. 
       FIG. 8  illustrates a partial plan view of a top edge of a circuit card formed according to an alternative embodiment of the present invention. 
       FIG. 9  illustrates a side view of a circuit card formed according to an alternative embodiment of the present invention. 
       FIG. 10  illustrates a partial sectional view of the circuit card of  FIG. 9  taken along line  10 — 10  in  FIG. 9 . 
     The foregoing summary, as well as the following detailed description of certain embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, certain embodiments. It should be understood, however, that the present invention is not limited to the arrangements and instrumentalities shown in the attached drawings. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 2  illustrates a side view of a circuit card  28  according to an embodiment of the present invention. One or more circuit cards  28  may be mounted in connector housings having a variety of shapes and sizes. The circuit card  28  includes a mating edge  30 , a top edge  32 , a back edge (not shown) and a bottom edge (not shown) that define a main body  34 . The circuit card  28  also includes a plurality of charge-controlling pads  36 , which may be signal or ground pads. The charge-controlling pads  36  may be used to control electrical charges exchanged between the circuit cards  28  and matable components during mating. For example, the charge-controlling pads  36  may control electrostatic discharge (ESD) from a mating element to the circuit card  28 . The charge-controlling pads  36  are bifurcated pads in that they include an initial contact portion  38  and a final contact portion  40  separated by a gap  41  of non-conductive circuit board material. The initial contact portion  38  and the final contact portion  40  include vias  42  and  44 , respectively, that interconnect parallel initial and final contact portions  38  and  40  located on opposite sides of the circuit card  28 . The final contact portions  40  may be connected to traces  46 , which provide an electrical connection to other conductive pads, electrical components, etc., on the circuit card  28 . 
   It is to be understood that the charge-controlling pads  36  may be used with circuit cards, or any elements or component that have a conductive surface that is mated with another conductive surface. That is, the charge-controlling pads  36  may be used within electrical connectors, electrical cable assemblies, chassis assemblies, motherboards, daughtercards, and various other electrical components in which electrical mating between two elements is needed. For example, the charge controlling pads  36  may be utilized with electrical cable assemblies such as those disclosed in U.S. Pat. No. 5,766,027, issued to Fogg (the &#39;027 patent), which is herein incorporated by reference in its entirety. The charge-controlling pads  36  may be used on, or as, contact portions of the electrical cable assemblies disclosed within the &#39;027 patent. 
   A charge-controlling device  47 , such as a resistor, is positioned within or on the surface of the circuit card  28  proximate the gap  41 . The charge-controlling device  47  may be connected to the initial and final contact portions  38  and  40  through traces. The initial contact portion  38  and the final contact portion  40  may be electrically connected through the charge-controlling device  47 . A variety of charge-controlling devices  47  may be used depending on the configuration.  FIGS. 3–5  show exemplary configurations for charge-controlling devices  47 . The charge-controlling device  47  may be surface mounted or deposited (such as a carbon deposit on a thick film circuit board) on the circuit card  28  between the initial contact portion  38  and the final contact portion  40 . Alternatively, the charge-controlling device  47  may be embedded within the circuit card  28 . The charge-controlling device  47  may be any suitable material that safely and efficiently resists a predetermined voltage threshold. 
   In operation, an electrically conductive mating element  45 , such as a terminal contact, is moved along the direction of arrow A to mate with the charge-controlling conductive pad  36  such that the mating element  45  engages the initial contact portion  38  before engaging the final contact portion  40 . That is, the mating process includes two stages, namely an initial mating stage and a final mating stage. 
   During the initial mating stage, the mating element  45  may discharge an electrostatic surge or spike, which has been stored on or within the mating element  45  and/or circuitry connected thereto. Also, an electrical surge, such as a power signal, may arc from the mating element to the charge-controlling pad  36 . The electrostatic or electrical surge travels from the initial contact portion  38  into the via  42 . The electrostatic or electrical surge then travels through the via  42  to a trace (not shown) connected to the charge-controlling device  47 , which impedes, diminishes, attenuates or otherwise resists the flow of the electrostatic or electrical surge. A diminished electrical signal then travels from the charge-controlling device  47  to a trace that is electrically connected to the via  44  of the final contact portion  40 . 
   Optionally, the initial contact portion  38  may not be electrically connected to the final contact portion  40 . Instead, the via  42  may be electrically connected to a trace and the charge-controlling device  47 , which in turn is electrically grounded through a trace. The grounding trace need not be electrically connected to any portion of the final contact portion  40 . Thus, as the mating element  45  is slid or otherwise moved into position over the charge-controlling conductive pad  36 , an electrostatic or other electrical charge is received by the initial contact portion  38 , and discharged through the charge-controlling device  47 . Hence, the full electrostatic or electrical charge is not introduced onto the final contact portion  40 , where the electrical path from the initial contact portion  38  is grounded. Because the initial contact portion  38  is grounded, the charge-controlling conductive pad  36 , and consequently the circuit card  28 , does not store or experience excess charge. As the mating element  45  is moved beyond the initial mating position into a final mating position over the final contact portion  40 , the possibility of an electrostatic or other electrical surge traveling from the final contact portion  40  to any electrically connected component is minimized due to the mating element  45  first discharging an electrostatic or other electrical charge through the initial contact portion  38 . 
     FIG. 3  illustrates a sectional view of the circuit card  28  according to an alternative embodiment of the present invention. The charge-controlling conductive pads  36  may include a charge-controlling device  48 , such as a resistor, surface mounted on gap  41  and connecting the initial contact portion  38  to the final contact portion  40 . In this embodiment, the initial contact portion  38  need not be grounded. Instead, the resistive qualities of the charge-controlling device  48  are sufficient to adequately dissipate the electrostatic or other electrical charge between the initial contact portion  38  and the final contact portion  40 . 
     FIG. 4  illustrates an end view of a portion of a circuit card  28  formed according to an alternative embodiment of the present invention. As shown in  FIG. 4 , the arrow A (depicted by X) is oriented into the page. The initial contact portions  38  and final contact portions  40  (shown in  FIG. 3 ) are positioned proximate the mating edge  30  on the sides of the circuit card  28  such that a charge-controlling device  50  (such as a resistor) and trace segments  51  provide an electrical path between each side of the initial and final contact portions  38  and  40 , respectively. The charge-controlling device  50  may be positioned in, or formed integrally with, vias  42  (and also vias  44 ). The electrical path including the charge-controlling device  50  may also be grounded. 
     FIG. 5  illustrates a partial plan view of a top edge of a circuit card formed according to an alternative embodiment of the present invention. The initial and final contact portions  38  and  40  are positioned on the sides of circuit card  28  such that the vias  42  and  44  provide an electrical path between each side of the circuit card  28 . A charge-controlling device  52 , such as a resistor, may be positioned between the via  42  of the initial contact portion  38  and the via  44  of the final contact portion  40 . Additionally, the electrical path including the charge-controlling device  52  may be grounded. 
     FIG. 6  illustrates a schematic diagram representative of a charge-controlling system  54  according to an embodiment of the present invention. The system  54  includes initial and final contact portions  38  and  40  connected by way of a trace  56 . The trace  56  is in turn electrically connected to a charge-controlling device  58 , which is in turn connected to ground  60  (that is, the charge-controlling device  58  is grounded). Electrostatic or other electrical surges or spikes travel from the initial contact portion  38  into the charge-controlling device  58  (such as a resistor). The electrostatic or electrical surges or spikes are dissipated by the charge-controlling device  58  and then passed to ground  60 . 
   Optionally, more than one charge-controlling device may be used within the conductive pad  36 . For example, one charge-controlling device may be positioned between the initial contact portion  38  and the ground, while another charge-controlling device may be positioned between the initial contact portion  38  and the final contact portion  40 . Also, multiple ESD-controlling devices may be positioned within a single electrical path. For example, two ESD-controlling devices may be positioned in series or in parallel between the initial contact portion  38  and the ground. 
   Additionally, the conductive pad  36  may be bifurcated into more than two parts. That is, the conductive pad  36  may include an initial, intermediate and final contact portions. Further, a plurality of intermediate contact portions may be positioned between the initial and final contact portions. The intermediate contact portions, similar to the initial contact portions, may be grounded and/or connected to the final contact portions through charge controlling devices and/or traces. 
     FIG. 7  illustrates a side view of a circuit card  100  formed according to an alternative embodiment of the present invention. One or more circuit cards  100  may be mounted in connector housings having a variety of shapes and sizes. The circuit card  100  includes a mating edge  102 , a top edge  104 , a back edge (not shown) and a bottom edge (not shown) that define a main body  106 . The circuit card  100  also includes a plurality of charge-controlling pads  108 . The charge-controlling pads  108  include an initial contact portion  110  and a final contact portion  112  separated by a gap  114 . A surface mounted resistor  116  is disposed within the gap  114  and connects the initial contact portion  110  to the final contact portion  112 . The initial contact portion  110  includes a via  118 . The via  118  interconnects the initial contact portion  110  to a ground plane (shown with respect to  FIG. 8 ) located on the opposite side of the circuit card  100 . The final contact portions  112  may be connected to traces  120 , which provide an electrical connection to other conductive pads, electrical components, etc., on the circuit card  100 . 
   The charge-controlling pads  108  may be utilized with electrical cable assemblies such as those disclosed in the &#39;027 patent. The charge-controlling pads  108  may be used on, or as, contact portions of the electrical cable assemblies disclosed within the &#39;027 patent. 
   A variety of charge-controlling devices  116  may be used depending on the configuration. For example, the charge controlling devices  116  may be 1.0 to 10.0 MOhm resistors. In this way, when a mating element (such as mating element  45  shown with respect to  FIG. 2 ) contacts the initial contact portion  110 , any electrostatic discharge from the mating element travels from the initial contact portion  110  to the ground plane through the via  110 . Further, electrostatic charge is dissipated by shorting the final contact portions  112  to the ground plane through the charge-controlling devices  116   
     FIG. 8  illustrates a partial plan view of the top edge  114  of the circuit card  100  formed according to an alternative embodiment of the present invention. The initial contact portion  110  on a first side  122  of the circuit card  100  is electrically connected to a ground plane  124  on the second side  126  through the via  118 . As shown in  FIG. 8 , the charge-controlling device  116  is surface mounted on the first side  122  and electrically connects the initial contact portion  110  to the final contact portion  112 . Electrostatic charge does not build up on the circuit card  100  because any such charge is dissipated through the charge-controlling device  116 , and/or passed to the ground plane  124 . Optionally, no via  118  may connect the initial contact portion  110  to the ground plane  124 . Instead, any electrostatic energy may be sufficiently dissipated through the charge-controlling device  116 . 
   In general, embodiments of the present invention may be used with a variety of electrical components, such as electrical connectors, electrical cable assemblies and chassis assemblies. Embodiments of the present invention provide an improved conductive pad that may be used with electrical components that mate with other electrical components. Further, the bifurcated conductive pads provide electrical mating between electrical components that safeguards against electrostatic discharge (ESD), arcing, and other electrical spikes or surges from one component to the other. 
     FIG. 9  illustrates a side view of a circuit card  200  formed according to an alternative embodiment of the present invention. Circuit card  200  includes a mating edge  212 , a top edge  214 , a back edge (not shown) and a bottom edge (not shown) that define a main body  216 . Circuit card  200  includes a charge controlling system  218  that includes a contact pad  220 , a first surface mount pad  222 , an additional surface mount pad  224 , and a charge controlling device  226  surface mounted between surface mount pad  222  and surface mount pad  224 . Surface mount pad  222  is also connected to a signal trace  227  on circuit card  200 . In an exemplary embodiment, charge controlling device  226  is a resistor. Surface mount pad  224  includes a via  228  that connects surface mount pad  224  to a ground plane (see  FIG. 10 ). The ground plane may be an internal layer of circuit card  200  and/or on the opposite surface of the circuit card  200 . This embodiment provides for flexibility in the circuit layout since the charge controlling device  226  need not be immediately proximate the contact pad  220  or the card mating edge  212 . 
     FIG. 10  illustrates a partial sectional view of the circuit card  200  of  FIG. 9  viewed from the line of sight  10 — 10  in  FIG. 9 . The via  228  is shown extending through circuit card  200  and connecting surface mount pad  224  to ground at  230  at the surface of the circuit card  200  and/or alternatively at  232  representing an internal layer at ground within circuit card  200 . Charge controlling device  226  is surface mounted between surface mount pads  222  and  224 . Electrostatic charges are dissipated in charge controlling device  226  and/or passed to ground. 
   While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.