Abstract:
A method and apparatus for coupling electrical connectors to a printed circuit board. The first and second clamp member are held in an open position with electrical connectors therebetween. While in the open position, the clamp is positioned over a printed circuit board, with the first and second clamp members aligned for connection to the circuit board. The clamp is then partially closed, to a preloaded position which aligns the electrodes in the clamping assembly with the electrodes on the circuit board. After the initial alignment has occurred, the clamp is firmly fastened to the printed circuit board, to electrically couple the electrodes of the connectors and the clamp to the electrodes on the printed circuit board.

Description:
TECHNICAL FIELD 
     This invention relates to electrical connectors, and more particular to electrical connectors for coupling circuits on printed circuit boards. 
     BACKGROUND OF THE INVENTION 
     Many computing devices, such as desktop computers, workstations, main-frame and super-computers employ multiple printed circuit boards (“PCB”) that include various microprocessors, printed circuits and other components that must be electrically coupled together to transmit data and/or power. The electrical traces on one or more layers of the PCB form the printed circuits and typically terminate in one or more terminals or contacts for making connections. Every decreasing element sizes, such a pitch (i.e., the spacing between successive components), width, and height, exacerbate the problem of providing secure and reliable connections between the printed circuits. Precise positioning on the order of thousandths of an inch is often necessary. Consistent pressure across each of the many contacts is also desirable to assure a reliable connection. A single failed or intermittent connection can result in large amounts of “down-time” for the computing device, and costly troubleshooting by highly skilled technicians. 
     Highly parallel processing super-computers present a particularly significant problem in terms of space constraints. Super computers rely on a high number of connections between circuit boards that each carry one or more microprocessors. The nature of parallel processing places high demands on the timing of signals, including clock signals across the various computer components. The PCBs are spaced relatively close together to reduce the length of the connections between the PCBs in an effort to improve the timing of the signals. The tight spacing hinders the ability of technicians to access particular computer components, such as the PCBs and electrical connectors. This presents a particular problem to computer manufacturers and owners who desire a modular design that permits failed components to be quickly and easily replaced. If serviceable, a modular design would also permit the addition of new or additional processors as desired, for example when more processing power is required or when the processors become more affordable. This could significantly extend the life of the computing device. 
     SUMMARY OF THE INVENTION 
     According to principles of the present invention, a clamp for an electrical connector to a printed circuit board is structured to provide quick and accurate connection. 
     The electrical connector is positioned inside the clamp and has electrodes organized in a pattern for contact with the printed circuit board. The clamping assembly which holds the electrical connector has alignment members to ensure precise and accurate alignment with the printed circuit board. In order to provide quick attachment and release, the clamp assembly has three positions during the clamping and unclamping sequence. In a first position, the clamp is fully open and the electrical connector is held in the position so that it may be placed over a printed circuit board in preparation for attachment. In a second configuration, the clamping assembly is clipped into a preloaded position to properly align the electrical connectors and hold the clamping assembly into position for final attachment. In the third, final attachment stage, the clamping assembly is solidly connected to the printed circuit board with rigid bolts extending through the clamp assembly, through the printed circuit board and to a clamping member in the clamp assembly so as to hold the electrodes on the electrical connectors in complete electrical contact with the electrodes on the printed circuit board. 
     The clamp assembly may be easily attached and removed from the printed circuit board with high reliability. All electrical connections between electrodes will be properly made and that it can be quickly removed without damage to the electrical contacts. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, identical reference numbers identify similar elements or acts. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale and various elements and portions of elements may be are arbitrarily enlarged and positioned to improve drawing legibility. 
     FIG. 1 is an isometric view of a connector according to the present invention coupling a pair of circuits on two printed circuit boards in side-by-side relation. 
     FIG. 2 is a top plan view of the connector according to the present invention coupling a pair of circuits on two printed circuit boards in parallel relation. 
     FIG. 3 is a top, isometric view of the inventive connector. 
     FIG. 4 is a partial, bottom, rear isometric view of the connector of FIG.  3 . 
     FIG. 5 is an isometric view of the clamp assembly in the preloaded condition, prior to final clamping. 
     FIG. 6 is a front elevational view of the clamping assembly in a fully open position. 
     FIG. 7 is a side elevational view of the fully open position of FIG.  6 . 
     FIG. 8 is a side elevational view of the clamp assembly in a preloaded condition, ready for clamping. 
     FIG. 9 is a side elevational view of the clamping assembly in a fully clamped position. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a connector  10  coupling printed circuit boards  12  (“PCBs”) according to the present invention. The connector  10  includes a first and second clamps  24 ,  26 , and a first set of electrical connectors, such as four flexible circuit substrates  28 - 34 , electrically coupling circuits on the first PCB  14  to circuits on the second PCB  16 . The connector  10  also includes a flexible support member  50  that provides mechanical support and stability to the connection. 
     FIG. 1 shows the first printed circuit board (“PCB”)  14 , and the second PCB  16 , in a side-by-side, parallel arrangement. FIG. 2 shows the connector  10  coupling circuits on the first and second PCBs boards  14 ,  16 , where the PCBs  14 ,  16 , are in the same plane. The circuit boards are of a type used in a super computer or large mainframe computer. Thus, each board will have many electronic components, including many microprocessors. A single computer may have a dozen or more boards with different positions with respect to each other that must be connected. While parallel and side-by-side connections are shown, they may also be stacked, one above another or be arranged in some other configuration. 
     The PCBs  12  are formed from one or more layers of an insulating material, such as FR-4 epoxy-fiberglass laminate. The PCBs  12  are typically sufficiently thick to form a rigid substrate, although minor amounts of bending or deflection can occur. The printed circuits include electrically conductive circuit traces  13  and various electrical and electronic components (not shown) on one or both surfaces  18  and  20 . Each layer of the PCB  14 ,  16  can also carry circuit traces (not shown) where the PCB  14 ,  16  is a laminate structure. Through-holes  17  can provide connections between circuit traces  13  on outer surfaces  18 ,  20  and/or inner layers of the PCB  14 ,  16 . The printed circuits include electrical contacts  22  to coupled the printed circuits to other electrical circuits. The electrical contacts  22  are located close to the edges of the PCB  14 ,  16  to make the coupling easier. 
     Electrical conductors  28 - 34  extend into the clamps and have exposed electrodes  103  for connecting to electrodes contacts on the printed circuit board (see FIG.  3 ). The details of this electrical connection need not be described here since other types of electrical contacts can be used within the concept of this invention. 
     The electrical connectors  28 - 34  can be of any acceptable type. Ribbon cable strips, electrical cables, or flexible circuit substrates can be used. The invention is particularly helpful with ribbon strips and flexible substrates as will now be explained. Use of flexible circuit substrates  28 - 34  provide low resistance, low impedance connections. Such electrical connectors are particularly desirable in parallel processing systems, where the timing of signals is critical. The flexible circuit substrates  28 - 34  include electrical traces formed on one or more layers (approximately 2-8) of insulated substrate material. The substrate can be printed circuit board material (e.g., polyimide film, FR-4 epoxy-fiberglass laminate), or any acceptable alternatives. The resulting substrate is highly flexible, hence convenient for making connections in tight spaces and/or at an angle and yet is quite strong. 
     Over-flexing of electrical connectors, such as ribbon cables and flexible circuit substrates can lead to defects in electrical conductors and traces and/or layers thus causing open circuits and/or short circuits. The flexible circuit substrates  28 - 34  are particularly susceptible to failure caused by twisting or rotation about a longitudinal axis  44  of the traces, where the traces typically run along the length of the flexible circuit substrate  28 - 34  between a set of electrodes  103  located at each end  48  of the flexible circuit substrate  28 - 34 . The present invention solves this problem. 
     The connector  10  also includes a mechanical support  50  coupling the first and second clamps  24 ,  26  to each other. The support  50  can be any acceptable flexible member, such as a leaf spring, metal plate or other mechanical support, to significantly reduce twisting or rotation about the longitudinal axis  44  of the traces and flexible circuit substrates  28 - 34 . Use of a leaf spring  50  for the support provides a resiliently deformable steel plate, having a prebuilt curve or camber  52  that permits translation along a longitudinal axis  56  while reducing rotation about the longitudinal axis  56 . The curve is selected to permit easy manipulation of the connector  10  in space restricted areas, such as between PCBs  14 ,  16  inside super computers. The leaf spring  50  is designed in each application to be sufficiently stiff to support the weight of the clamps  24 ,  26 . The stiffness is a function of the material, the thickness, width, length and curvature or camber of the leaf spring  50 . The leaf spring  50  is made sufficiently stiff to prevent the weight of the first clamp  24  from causing twisting or rotating the flexible circuit substrates  28 - 34  about the longitudinal axis  56  if it is unclamped from the respective PCB  16  while the second clamp  26  is connected. Twisting can particularly be a problem when the PCBs  14 ,  16  are arranged as shown in FIG. 2, where gravity would tend to pull the clamp  24  downward if it is disconnected. The leaf spring  50  thus provides the mechanical support to ensure that the electrical connectors  28 - 42  are not destroyed when one of the clamps is disconnected and hangs free at one end. 
     The shape of the leaf spring  50  is selected to be strong, yet flexible. An enlarged portion  55  connects to the respective clamps  24  and  26 . A necked down region  57  has a smooth curve to gradually reduce the body width  59  of the leaf spring to the desired value with the proper spring constant and flexibility, yet sufficient strength. The width and thickness of the body  59  are selected to provide the desired strength and flexibility. A wider and/or thicker body will have a higher spring constant and will be more stiff. A somewhat thinner leaf spring body  59  provides more flexibility yet less support strength. The width and thickness of the leaf spring body  59  is selected to provide the adequate strength and spring constant with sufficient flexibility based on the weight of the clamps and the respective orientation of the PCBs being connected. 
     The leaf spring  50  has a preselected spring bias loaded in a certain direction as manufactured. This is well-known for leaf springs, and upon manufacture can be predesigned to have a desired curvature and camber when unstretched, as will now be explained. 
     FIGS. 3 and 4 illustrate examples of the leaf spring  50  in an unloaded and unstretched condition. The leaf spring  50  has a curvature and preset camber as determined when it was manufactured. The strength of its spring force is based on its width, thickness, and type of materials, as described herein. In an at-rest condition, the leaf spring  50  holds the clamps  24  and  26  a preselected distance away from each other. The electrical connectors  28 - 42  are assured of being retained in a smooth nonbinding relationship since they are held in position by the leaf spring  50 . The electrical connectors  28 - 42  therefore will not twist, turn, or become entangled when at rest since the leaf spring extended between the clamps  24  and  26  with the support  50  holding them in a selected orientation. The connector  10  can thus remain at rest or be shipped from one location to another with high reliability and assurance that the electrical connectors  28 - 34  will not be damaged nor entangled. 
     The connector  10  is installed on the printed circuit boards  14  and  16  as follows. The connector  24  is positioned in the correct location to provide proper electrical contact to the printed circuit board  14  at the contact points on the printed circuit board. Alignment pins  76  in the connector extend through holes in the printed circuit board to ensure proper alignment. Frame members  31  and  33  hold the ends of the conductors  28 - 34  with the electrodes  103  thereon. While this alignment is being carried out, the leaf spring  50  holds the electrical connectors  28 - 34  in a firm, yet flexible orientation. The operator thus does not need to be concerned about entangling or damaging the electrical connectors while first clamp  24  is being aligned with the circuit board  14 . Upon alignment being completed, the first connector  24  is coupled to a first printed circuit board  14  with the second end hanging free. 
     After the clamp  24  is connected, the user then connects clamp  26  to the other circuit board. This is done by stretching the leaf spring  50  so as to bias it in a spring-loaded condition. Once the leaf spring  50  is biased to its proper location, the clamp  26  is connected to the second printed board  16 . The leaf spring  50  is thus in a loaded condition providing a resilient connection between the clamps  24  and  26  to the printed circuit boards  14  and  16 . It is generally a very light spring force to not place an undue load on PCBs  14  and  16 . The electrical connectors  28 - 34  thus do not carry the stress of supporting the clamps  24  and  26 . The leaf spring  50  provides mechanical support for the electrical connectors so that they may rest upon the leaf spring and be supported thereby if desired. Other types of electrical connectors, such as the flexible circuit substrates, will be spaced above and generally not touch the leaf spring. In one embodiment, the electrical connectors are side by side as shown in FIGS. 1 and 2; in other embodiments, they may be spaced one above the other in a stacked relationship, as seen from connectors  28  and  36  having a space  38  therebetween, shown in FIG.  3 . 
     FIGS. 3 and 4 show the first and second clamps  24 ,  26 , and the flexible circuit substrates  28 - 34  in more detail than FIGS. 1 and 2. Only one of the clamps is described since the first and second clamps  24 ,  26  are similar structures. The clamps  24  and  26  each include a first clamping member  58  and a second clamping member  60  in opposed, spaced apart relation. The first and second clamping members  58 ,  60  are elongated metal plates with a surface for supporting electrical connectors therebetween. 
     The leaf spring  50  is bolted to the clamps  24  and  26  by a bolt  72  and a nut  102 , best seen in FIG. 4. A spring clip  73  is coupled by bolt  72  and nut  102  to the clamping assembly  26 . It has an aperture  75  which is aligned to mate with pin  77  when the clamp  26  is in the preloaded position. 
     As shown in FIGS. 3,  4 , and  6 , a pair of coil compression springs  78  bias the first and second clamping members  58 ,  60  away from each other, toward an unclamped position. This holds the clamp  26  in the open position. The coil compression springs  78  are disposed about the rear fasteners  72 , at the rear of the clamping members  58 ,  60  to retain the coil compression springs  78  on the respective clamping member  58 , 60 . The spring clip  73  can be used to place the clamp  26  in the preloaded position, as will now be explained. 
     FIG. 5 illustrates the clamping assembly  26  alone. It is shown in the preloaded position. The two front fasteners  74  are threaded and serve as the final fasteners at the front of the clamping members  58 ,  60  to hold the electrical connections in a solid position between the clamping members  58 ,  60 . The rear fasteners  72  align the clamping members  58  and  60  in the open position. The threads of the front fasteners  74  engage a respective portion of the first and second clamping members  58 ,  60  to move the first and second clamping members  58 ,  60  with respect to one another. For example, a lower threaded portion of the front fasteners  74 , see FIGS. 3 and 4, engages a thread in the hole  76  of the second clamping member  60 , while an upper threaded portion of the front fastener  74  engages a thread in the hole  76  of the first clamping member  58 . Thus, the distance or space  80  between the clamping members  58 ,  60  can be adjusted by rotating the front fasteners  74 . 
     The clamping assembly  26  is designed to provide quick and easy clamping, and has significant advantages as will now be explained. The clamp  26  as shown in FIGS. 3,  4  and  6  is in the fully open position. The open position is characterized by fastener  72  at the rear of the clamp holding the two clamp members  58  and  60  connected to each other with a solid connection. Spring  78  biases the clamping members  58  and  60  away from each other to hold the clamp in the fully open position. Spring clip  73  connected to the clamping member  68  is not connected to the other clamping member  58  so that the two clamping members are held together by the rear fastener  72 . Since the spring  78  is biasing it into the open position, a user may easily grasp the clamp and position it over a printed circuit board with good clearance on each side so that it may be quickly and easily positioned. Once the clamp  26  is positioned over the edge of the printed circuit board, it is advanced from the fully open position to the preloaded position, see FIGS. 5 and 7. This is accomplished by slightly depressing clamping member  58  towards clamping member  60 , compressing spring  78 . 
     The connecting sequence can be seen by comparing FIGS. 6,  7 ,  8  and  9 . As clamping member  58  is compressed, pin  77  contacts spring clip  73  and slowly pushes it away from the clamping member  58 . As the clamping member  58  continues to be depressed, the pin  77  enters aperture  75  of spring clip  73 . Once it enters aperture  75 , the spring clip  73  will hold the clamp  26  in the preloaded position, FIG.  8 . 
     While the user, whether manually by hand or via a robot is depressing the clamp  26 , it is carefully held in position so that alignment posts  76  are properly positioned in the printed circuit board. Other alignment posts or alignment members may also be positioned from the clamp  26  to the printed circuit board  14 , or from the printed circuit board  14  to the clamp  26 . Thus, in the fully open position there is no connection between the clamping assembly  26  and the printed circuit board  14 . As it is advanced to the preloaded position, the alignment members of the clamping assembly  26  and the printed circuit board  14  are aligned with each other so that in the preloaded condition, the clamping assembly is held in a properly aligned position on the printed circuit board. This position is shown in FIG.  8 . The spring clip  73  is retaining the clamping members  58  and  60  in a relative position with each other while the fastener  72  provides proper horizontal and vertical alignment but does not provide compression force to hold the clamping members to each other. The spring clip  73  holds with sufficient strength to overcome the compression spring  78 . 
     The clamp  26  can be held in the preloaded position for an extended period of time if desired until it is time for the fasteners  74  to connect the clamp in a locked position. When the clamping assembly  26  is to be fully attached in the clamped position to the printed circuit board  14  then fasteners  74  are threaded down tightly to firmly press clamping member  58  and  60  into each side of the printed circuit board. Electrodes  103  are held in firm contact with the corresponding exposed electrodes on the printed circuit board as the fastener  74  is threaded tightly down to clamp the clamping assembly  26  firmly to the printed circuit board  14 . This locked, final clamp position is shown in FIG.  9 . The printed circuit board has been omitted in FIGS. 6-9 for ease in illustration. However, as will be appreciated during use, the printed circuit board  14  is positioned within the clamping assembly  26  between frame members  31  and  33 . Rubber pads  35  press the frame  31  and  33  with the conductors  28 - 42  thereon into engagement with printed circuit board  14 . The electrical connections are thus properly made from the connectors  28 - 42  to the circuit board  14  via the electrode  103 . In this final clamped position, the fasteners  74  are holding members  58  and  60  to each other and the spring clip  73  is not needed to provide this function. The spring clip  73  held the clamp in the correctly aligned, preloaded position so that fastener  74  could be quickly and easily attached with a high degree of assurance that the circuit board  14  would be properly aligned with its electrodes contacting those on the clamping assembly  26 . 
     The clamping assembly  26  remains on the printed circuit board for an extended period of time as desired. When it is desired to remove the clamping assembly  26  from the printed circuit board, the operation is carried out in reverse. The threaded fasteners  74  are removed from holding clamping members  58  and  60  to each other. This slowly releases the clamping members  58  and  60  in a controlled fashion as compression spring  78  pushes the clamps away from each other. Spring clip  73 , which still engages pin  77  through its aperture  75  continues to hold clamping members  50  and  60  in the preloaded condition. The clamping member is still properly aligned and the electrodes  103  are still properly aligned with the electrodes on the printed circuit board  14  so that no damage is done as the clamping assembly  26  is removed from the printed circuit board. When it is desirable to provide complete removal of the clamping assembly  26  from the printed circuit board the spring clips  73  are pushed laterally away from member  58  so that pin  77  is disengaged from aperture  75 . Once pin  77  is disengaged from aperture  75 , then compression springs  78  force clamping member  58  and  60  further away from each other so they are stopped and held in position by the head of the fastener  72 . The clamping assembly  26  is now in the fully open position and the clamp can be removed from the printed circuit board  14  under control of the user and the leaf spring  50  as will now be explained. 
     The leaf spring  50  remains in its spring-loaded condition while the circuit boards  14  and  16  are within the housing of the computer, normally a supercomputer which may have dozens of such boards therein. At some time, it may be necessary to remove one of the boards  16  from the super computer and replace it with a different board. The connector  10  makes such a change quick and easy, while assuring that no damage will be done to the electrical connectors  28 - 42  or to any adjacent boards. According to principles of the present invention, the clamp  26  is loosened and removed from the board  16 . The operator can then let go of the clamp  26  and let one end hang free so that the entire connector  10  is supported by the circuit board  14 . The leaf spring  50 , since it is preshaped, will automatically move back to the rest position and thus will spring away from circuit board  16  in a motion which does not interfere with or impact other portions of the circuit board  16 . The clamp  26  thus is automatically swung free by the retraction of the leaf spring  50  and can be assured of not impacting or causing damage to other locations inside the supercomputer when it is not connected. The leaf spring  50  returns to its rest condition and holds the clamp  26  in a suspended location determined by the preset shape of the spring  50  when manufactured, as previously discussed. The clamp  26  can thus hang free for an extended period of time while the electrical connectors  28 - 42  are supported without fear of entanglement or damage. When a new board  16  is provided in the slot in the supercomputer, it is slid into location quickly and easily. Since the clamp  26  is held by the leaf spring  50  in a preset position, the user can be assured of inserting the board  16  smoothly and cleanly without becoming entangled in the electrical connectors. Once the board is in place, the operator engages the clamp  26  onto the board  16  by stretching the leaf spring  50  as desired and clamping the connector  10  to the board  16 . The electrical connection is thus quickly and cleanly made to the circuit board  16  and operation of the supercomputer continues. Indeed, if used in a super computer, the invention may permit it to remain operating while the board is being replaced, and the connector  10  assures that no damage to the electrical circuits nor interference with other boards will occur during the replacement. 
     In an alternative embodiment, the mechanical support  50  is not a leaf spring. Instead it is a support member that holds the electrical connectors in a safe position to prevent damage to the wires or tangling of wires. Thus, in the embodiment when the connector  50  is not a spring, it will hold the clamps  24  and  26  in the proper position, as well as the electrical wires  28 - 34  but it will not spring back into position to automatically swing away from the board  26  when it is unclamped. 
     Although specific embodiments of and examples for, the invention are described herein for illustrative purposes, various equivalent modifications can be made without departing from the spirit and scope of the invention, as will be recognized by those skilled in the relevant art. The teachings provided herein of the invention can be applied to other electrical connectors, not necessarily the exemplary clamping electrical connector generally described above. Aspects of the invention can be modified, if necessary, to employ systems, circuits and concepts of the various patents, applications and publications to provide yet further embodiments of the invention.