Abstract:
A guidance block includes a base, a pair of opposing card guide sides supported on a common surface of the base, the sides defining a gap between the pair of opposing sides, and a spring coupled to one of the card guide sides, partially within the gap provided between the pair of opposing sides, with the card guide sides and spring member configured to align a circuit board disposed in the gap with a connector.

Description:
BACKGROUND  
       [0001]     A backplane or midplane (hereafter called backplane) is an electronic circuit board, which may include circuits, and includes sockets into which other circuit boards or cards can be plugged. For instance, in a computer the backplane (sometimes referred to as a motherboard) is a circuit board that includes sockets for cards. The cards (also referred to as expansion cards, boards, adapters and so forth) include circuits that provide a functional capability to the computer. The card is typically made of a rigid material and is plugged into one of the computer&#39;s expansion slots e.g., connectors in the backplane. Cards have a variety of sizes designed to match corresponding socket dimensions. To provide alignment of the card to the slot, the backplane can include a guide pin and the card can include a receptacle. Inserting the guide pin into the receptacle aligns the card with the slot.  
       SUMMARY OF THE INVENTION  
       [0002]     In one aspect the invention features a guidance block that includes a base and a pair of opposing card guide sides supported on a common surface of the base. The opposing card sides define a gap between the pair of opposing sides. A spring member is coupled to one of the card guide sides, partially within the gap provided between the pair of opposing sides, with the card guide sides and spring clip configured to align a circuit board disposed in the gap between with a connector.  
         [0003]     Embodiments may include one or more of the following. The base can be connected to a backplane or a midplane. The base can include an extension region. The extension region can be configured to fit into an alignment slot in the backplane. The card guide side can include a spring region configured to attach the spring. The spring region can include an overhang member. The card guide sides can be configured such that the spring can be coupled to either of the sides. The card guide sides can include a macro alignment region. The macro alignment region can include an angled end. The guidance block can include screws that attach the base to the backplane. The spring can provide alignment of a primary side of the circuit board.  
         [0004]     The sides can be configured to accept multiple thicknesses of circuit packs. The spring clip can include an electrically conductive material that provides an electrostatic discharge (ESD) path to ground. The base can include an angled outer region.  
         [0005]     In another aspect, the invention features a device that includes a backplane and a guidance block. The guidance block includes a base, a pair of opposing card guide sides supported on a common surface of the base. The opposing card guide sides define a gap between the pair of opposing sides. A spring member is coupled to one of the card guide sides, partially within the gap provided between the pair of opposing sides. The card guide sides and spring clip are configured to align a circuit board disposed in the gap with a connector.  
         [0006]     Embodiments may include one or more of the following. The base can include an extension region configured to fit into an alignment slot in the backplane. The card guide side can include a spring region configured to attach the spring. The spring region can include an overhang member. The card guide sides can be configured such that the spring can be coupled to either of the sides. The card guide sides can include a macro alignment region having an angled end. The spring can provide alignment of a primary side of the circuit board. The sides can accept multiple thicknesses of circuit boards. The spring clip can be composed of an electrically conductive material. The base can include an angled outer region  
         [0007]     In one aspect, the guidance block includes a spring to bias a card to the primary side of the guidance block. This allows a user to insert a board into the device without regard for the thickness of the board. The spring aligns the connectors on the board with the connectors in the slot.  
         [0008]     In another aspect, guidance blocks are provided in pairs. Providing the guidance blocks in pairs adds the advantage of both horizontal and vertical alignment of the card to the socket.  
         [0009]     The current invention obviates the need for the traditional guide pin and receptacle to provide macro alignment of a card to a slot. The current invention does not require additional printed circuit board (PCB) real estate for a guide pin receptacle and maximizes the height of the PCB&#39;s. This allows greater I/O density per card since the space traditionally needed for a guide receptacle can be used for additional connectors. 
     
    
     DESCRIPTION OF DRAWINGS  
       [0010]      FIG. 1  is a diagram depicting a backplane with a guidance block.  
         [0011]      FIG. 2  is a diagram a guidance block.  
         [0012]      FIG. 3  is a diagram of the spring attachment region of the guidance block and a spring.  
     
    
     DESCRIPTION  
       [0013]     Referring to  FIG. 1 , a backplane  10  includes multiple slots  16 . A user aligns and plugs a card  12  into one of the slots  16 . Each slot  16  fits a particular card thickness. Typical card thicknesses range from 0.05 inches to 0.20 inches. The shelf may include shelf card guides  18 . The shelf card guides  18  have slots  19  configured to accept the card, and are usually part of the shelf mechanical assembly. Alternately, guidance blocks  14  attached to the backplane  10  provide macro alignment of the card  12  to the slot  16  and can be easier to use than the shelf card guides  18  included in the backplane  10 . Each guidance block  14  includes a slot configured to accept the edge of a card  12 . For example, guidance block  14   a  guides a first edge (depicted as the upper edge in  FIG. 1 ) of a card  12  while guidance block  14   b  guides a second parallel edge (depicted as :the lower edge in  FIG. 1 ) of the card  12 . Using the guidance blocks in pairs, provides both horizontal and vertical alignment of the card to the sockets. The guidance blocks  14  can be removably attached to the backplane, for example by attaching the guidance blocks  14  to the backplane  10  using screws. Alternately, bonding, soldering, and so forth can permanently or semi-permanently attach the guidance blocks  14 .  
         [0014]     Referring to  FIG. 2  guidance block  14  includes a base  30  and opposing perpendicular sides  50   a  and  50   b  forming a guide slot  52 . Each side  50   a  and  50   b  includes three regions, a macro alignment region  38 , a spring region  42 , and an end region  48 . The macro alignment region  38  includes a slanted outer region  32  used to guide the card horizontally into the guide slot  52 . A slanted region  37  at the front edge of base  30  provides the ramping feature to vertically align the card  12  into slot  52 . A spring clip  44  attaches to the spring region  42  of one of the sides  50   a,    50   b.  Alternately, other types of spring members could be used instead of spring clip  44 .  
         [0015]     While the spring clip  44  provides the advantage of ease of manufacture and assembly, other types of spring members can be used. For example, a spring member could be composed of a coil spring with a flat plate attached for the sliding surface or a wire formed leaf spring, the spring could also be made of plastic and have an optional coating of a electrically conductive material.  
         [0016]     The spring clip  44  can be attached to either spring region  42   a  or  42   b  dependent on whether the guidance block  14  will be used as a top guidance block or bottom guidance block. In order to bias the card to the opposite side, the spring clip  44  is attached to the opposite spring region (i.e. attaching the spring to region  42   a  of side  50   a  biases the card towards side  50   b ). In this example ( FIG. 2 ), the spring clip  44  is shown attached to spring region  42   b.  A curved, unshaped lip  40  portion of the spring clip  44  attaches the spring clip  44  to spring region  42   b  of the guidance block  14 . Lip  40  extends around a side of spring region  42  ( FIG. 3 ). The lip  40  includes an attachment hole  82  that snaps into a raised tab  80  on the spring region  42 . The locking of the raised tab  80  into the attachment hole  82  secures the spring clip  44  to the spring region  42 . Lip  40  extends around the side of spring region  42   b.  An overhang member  46  on the spring region  42  helps to hold the spring clip  44  in place. The overhang member  46  prevents the spring clip  44  from sliding vertically and detaching from the spring region  42 .  
         [0017]     Spring clip  44  provides horizontal alignment for the circuit pack and biases the card  12  toward side  50   a  ( FIG. 2 ). This biasing aligns a connector on the primary side of a card  12  to a connector in the backplane  10 . Since the spring clip  44  can be depressed in varying amounts and slot  52  is wider than the board, guidance block  14  can accept cards  12  of varying thickness. Since guidance block  14  can accept cards  12  of varying thicknesses, a guidance block  14  can be used with a backplane without concern for the card thickness the backplane is configured to accept. The spring clip  44  can be made of an electrically conductive material, for example beryllium copper stainless steel, spring steel, copper, or aluminum. In another example the spring clip can be made of plastic provided the plastic acts as a spring, moves the card, and returns to its original position after deflection. When the spring clip  44  is composed of metal, and the guidance block  14  is composed of metal and the block is grounded, the metal provides an electrostatic discharge (ESD) path from the board to ground. If the spring was formed out of plastic it could be electro-plated to-provide the electrical path for grounding.  
         [0018]     An extension  36  from base  30  fits the shelf card guides  18 . A backplane is often configured to fit a particular card thickness. Thus, shelf card guide  18  may be included on the shelf to provide alignment of the card to the slot of the shelf. Since shelf card guide  18  is the approximate thickness of the board, it may be difficult for a user to align the board to the shelf card guide  18 . A user slides the extension  36  on the guidance block  14  into the shelf card guide  18 , thus the user can align the board using guidance block  14  instead of the shelf card guide  18  provided on the shelf. The spring clip  44  on guidance block  14  aligns the board, allowing the user to insert the card into a wider slot (slot  52 ) yet still align the card to the connectors.  
         [0019]     In one example, the base  30  and sides  50  are molded from plastic producing a unitary piece having the features discussed above. Base  30  and sides  50  could instead be composed of multiple parts bonded together to form the structure. In another example, the base  30  and sides  50  could be composed of metal (providing ESD protection) or another firm, electrically conductive material.  
         [0020]     The exact shape and attachment of spring clip  44  can vary. In the example shown in  FIG. 2  and  FIG. 3 , the spring clip  44  is attached by extension region  40  of the spring using tab  80  and hole  82 . The spring clip  44  could alternately be adhesively bonded to region  42 .  
         [0021]     While in the example described above, each guidance block  14  is individually attached to backplane  10 , multiple guidance blocks  14  can be grouped to form a larger unit. For example, a backplane might include eight card slots. Thus, a grouping of sixteen guidance blocks (one top and one bottom per slot)  14  provides alignment for each card slot in the backplane.  
         [0022]     In the above example, the guidance block  14  includes a single spring to bias the card. The guidance block  14  could alternately include two springs. In this example, each side would have opposing springs. By including two springs, the card is aligned not to one side, but to the middle of the guidance block  14 .  
         [0023]     A single part could be provided out of plastic that formed the ramp block and the spring as a single unit this could then be plated to provide the ground as well.  
         [0024]     A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.