Abstract:
An expanding standoff connector is disclosed including a collar having a slit through a wall of the collar, a tapered interior surface and an exterior surface configured to engage an interior of a mounting opening of the circuit board. A fastener including a threaded portion and a substantially cone shaped portion configured to mate with the tapered interior surface of the collar is placed within the collar and advanced to expand the collar to mount the circuit board. A related method for mounting a circuit board is also disclosed. Since the expansion is horizontal only (purely radial), a more uniform radial expansion from top-to-bottom of the collar is applied to the circuit board and a best-fit alignment between a circuit board and heatsink can be maintained.

Description:
BACKGROUND OF THE INVENTION 
   1. Technical Field 
   The present invention relates generally to circuit board connectors, and more particularly, to a precision-locking standoff connector for mounting a circuit board with a slit collar. 
   2. Related Art 
   Electronic circuit board assembly requires the ability to securely lock a circuit board in place for proper operation. For example, typical personal computer (PC) circuit board operation requires locking the board into position after it, and in particular a chip connected thereto, has been “best-fit” to a copper heatsink or coldplate. The term “best-fit” refers to how the circuit board is coupled to the heatsink via thermal transmission materials in a near-perfectly parallel fashion. Establishing a thin, uniform thermal interface between chip and heatsink is critical for achieving adequate thermal performance for high powered applications. Variable height standoffs are sometimes used to accommodate variations in stack-up height and tilt. Non-parallelism between chip and heatsink will increase a thermal interface gap, thus decreasing thermal performance. Variable position standoffs enable parallel assembly between chip and heatsink while accommodating non-parallelism between circuit card and chassis. Referring to  FIG. 1 , one conventional approach for locking a circuit board  6  into position is shown. Circuit board  6  includes a chip  8  mounted to a heatsink or coldplate  10  via thermal transmission material. In this approach, as shown in  FIG. 2 , split expanding plastic standoff connectors  12  are used to mount circuit board  6 . Returning to  FIG. 1 , in this setting, expanding plastic standoff connectors  12  are mounted to a chassis  14  and mounting openings  16  of circuit board  6  are placed over ends  18  of standoff connectors  12 . As shown in  FIG. 2 , as threaded fastener  20  is tightened into end  18  of a standoff connector  12 , slit portion  22  of standoff connector  12  expands against an interior of mounting opening  16 . A drawback of this type mount is that, as standoff connector  12  expands, it tends to move circuit board  6  vertically and disturb the best-fit alignment of circuit board  6  (i.e., chip  8  thereof) to the heatsink/coldplate  10 . For example, slit portion  22  tends to vertically move (with a V-shaped expansion profile) the circuit board  6  rather than simply horizontally clamp it in position. 
   In view of the foregoing, there is a need in the art for a standoff connector for maintaining a best-fit alignment between a circuit board and heatsink. 
   SUMMARY OF THE INVENTION 
   The invention includes an expanding standoff connector including a collar having a slit through a wall of the collar, a tapered interior surface and an exterior surface configured to engage an interior of a mounting opening of the circuit board. A fastener including a threaded portion and a substantially cone shaped portion configured to mate with the tapered interior surface of the collar is placed within the collar and advanced to expand the collar to mount the circuit board. A related method for mounting a circuit board is also disclosed. Since the expansion is horizontal only (purely radial), a more uniform radial expansion from top-to-bottom of the collar is applied to the circuit board and a best-fit alignment between a circuit board and heatsink can be maintained. 
   A first aspect of the invention is directed to an expanding standoff connector for mounting a circuit board, the connector comprising: a collar including a slit through a wall of the collar, a tapered interior surface and an exterior surface configured to engage an interior of a mounting opening of the circuit board; and a fastener including a threaded portion and a substantially cone shaped portion, the substantially cone shaped portion configured to mate with the tapered interior surface of the collar, wherein advancement of the fastener through the collar forces the substantially cone shaped portion against the tapered interior surface to expand the exterior surface of the collar against the interior of the mounting opening to mount the circuit board. 
   A second aspect of the invention includes an expanding standoff connector for mounting a circuit board, the connector comprising: a collar including an expanding slit region having a tapered interior surface and an exterior surface for engaging an interior of a mounting opening of the circuit board; and a fastener including a threaded portion and a substantially cone shaped portion, the substantially cone shaped portion configured to mate with the tapered interior surface of the collar, wherein advancement of the fastener through the collar forces the substantially cone shaped portion against the tapered interior surface to expand the exterior surface of the collar against the interior of the mounting opening to mount the circuit board. 
   A third aspect of the invention includes a method for mounting a circuit board using an expandable standoff connector, the method comprising the steps of: inserting a collar of the expandable standoff connector within an interior of a mounting opening of the circuit board, the collar including a slit through a wall of the collar, a tapered interior surface and an exterior surface configured to engage an interior of a mounting opening of the circuit board; providing a fastener including a threaded portion and a substantially cone shaped portion, the substantially cone shaped portion configured to mate with the tapered interior surface of the collar; and advancing the fastener through the collar to force the substantially cone shaped portion against the tapered interior surface to expand the exterior surface of the collar against the interior of the mounting opening to mount the circuit board. 
   The foregoing and other features of the invention will be apparent from the following more particular description of embodiments of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The embodiments of this invention will be described in detail, with reference to the following figures, wherein like designations denote like elements, and wherein: 
       FIG. 1  shows a side view of a conventional circuit board expanding standoff connector. 
       FIG. 2  shows a detailed side view of the connector of  FIG. 1 . 
       FIG. 3  shows an exploded perspective view of a first embodiment of a slit collar expandable standoff connector according to the invention. 
       FIG. 4A  shows a cross-sectional side view of the connector of  FIG. 3  in a non-actuated position. 
       FIG. 4B  shows a cross-sectional side view of the connector of  FIG. 3  in an actuated position. 
       FIG. 5  shows a cross-sectional side view of an alternative embodiment of a fastener. 
       FIGS. 6A–B  show perspective views of alternative embodiments of a collar. 
       FIG. 6C  shows a plan view of the collar of  FIG. 6B . 
       FIG. 6D  shows a perspective view of another alternative embodiment of a collar. 
       FIG. 7  shows an exploded perspective view of a second embodiment of a slit collar expandable standoff connector according to the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   With reference to the accompanying drawings, FIGS.  3  and  4 A–B show a first embodiment of an expanding standoff connector  100  for mounting a circuit board according to the invention. Connector  100  includes a collar  102  and a fastener  104 . As shown in  FIG. 3 , collar  102  includes a slit  106  through a wall  108  of collar  102  that allows expansion of the collar, as will be described in more detail below. Collar  102  also includes a tapered interior surface  110  that is substantially conical. In addition, as shown in  FIGS. 4A–B , collar  102  may also include a substantially cylindrical surface  111 , although this is not necessary as shown in  FIG. 3 . An exterior surface  112  of collar  102  is configured to engage an interior  114  ( FIG. 4A–B ) of a mounting opening  116  ( FIG. 4A ) of circuit board  118 . In particular, exterior surface  112  preferably has a shape configured to substantially match interior  114  of mounting opening  116 . 
   Fastener  104  may be provided in a number of forms. In any embodiment, fastener  104  includes a threaded portion  140  and a substantially cone shaped portion  142 . Substantially cone shaped portion  142  is configured to mate with tapered interior surface  110  of collar  102 .  FIGS. 3 ,  4 A– 4 B illustrate a first embodiment of fastener  104  in which substantially cone-shaped portion  142  includes an opening  144  extending longitudinally therethrough, and threaded portion  140  includes a separate bolt  146  that extends through opening  144  to fasten into a chassis  150  to which circuit board  118  is mounted. Sufficient clearance is provided about separate bolt  146  to enable standoff  100  to be self-centering. 
     FIG. 5  illustrates a second embodiment of a fastener  204  in which a threaded portion  240  and substantially cone-shaped portion  242  are integral parts of fastener  204 . That is, fastener  204  is provided as a bolt  246  having a substantially conical neck portion  248 . In either situation, as fastener  104 ,  204  is advanced through collar  102 , i.e., by threading of threaded portion  140 ,  240  into chassis  150 , the fastener forces substantially cone shaped portion  140 ,  240  against tapered interior surface  110  to expand exterior surface  112  of collar  102  against interior  114  of mounting opening  116  to mount circuit board  118 . Fastener  104 ,  204  also may include a tool engaging member  152  such as a screwdriver opening, fluting for a socket driver, hex head, threaded opening for a slide hammer, etc., for engaging by a tool (not shown) for adjusting the fastener. 
   Referring to FIGS.  3  and  6 A–B, the collar can also be provided in a variety of forms. As shown in  FIG. 3 , collar  102  includes slit  106  that extends an entire longitudinal length L of the collar. However, this is not necessary. For example, as shown in  FIG. 6A , a collar  202  includes at least one slit  206  (and preferably numerous slits  206 ) that extend only part of longitudinal length L of the collar. The extent to which slits  206  extend may be user defined depending on, for example, the amount of expansion of the collar desired. In one embodiment, numerous slits  206  are uniformly placed about the collar to ensure uniform expansion. In another embodiment, shown in  FIGS. 6B–C , a collar  262  is illustrated including numerous slits  266 T,  266 B that only extend part of longitudinal length L of the collar. In this embodiment, slits  266 T,  266 B are uniformly placed about the collar to ensure uniform expansion. In contrast to the  FIG. 6A  embodiment, however, slits  266 T,  266 B overlap vertically within collar  262 . Slits  266 T extends from a top  268  of collar  26  and terminate prior to a bottom  270  of collar  262 , while slits  266 B extend from bottom  270  and terminate prior to top  268 . Again, the extent to which slits  266 T,  266 B extend may be user defined depending on, for example, the amount of expansion of the collar desired. Collar  262  can expand substantially uniformly.  FIG. 6D  shows another embodiment of a collar  290  including one slit  292  that extends the entire longitudinal length L of the collar, and at least one (and preferably numerous) slits  296  that extend only part of longitudinal length L of the collar. The partial length slit  296  counteracts the collar&#39;s tendency to expand more at the top than at the bottom. Again, the extent to which slits  296  extend may be user defined depending on, for example, the amount of expansion of the collar desired. 
   Referring to  FIG. 7 , a second embodiment of an expandable standoff connector  300  is illustrated. In this embodiment, connector  300  includes a collar  302  and a fastener  304 . As shown in  FIG. 7 , collar  302  includes an expanding slit region  360  having a tapered interior surface  310  and an exterior surface  312  for engaging an interior of a mounting opening of the circuit board (not shown). Collar  302  may also include a substantially cylindrical interior surface  311  adjacent tapered interior surface  310 , but this is not necessary. Collar  302  also includes a base  362  with a relieved area  364  between base  362  and expanding slit region  360 . Base  362  is coupled to a chassis (not shown) in any now known or later developed fashion. In this embodiment, fastener  304  includes a threaded portion  340  provided along a substantially cone-shaped portion  342 , and tapered interior surface  310  includes mating threads  370  to threaded portion  340  such that fastener  304  can be threaded into collar  302 . As shown, threaded portion  340  and substantially cone-shaped portion  342  are integral parts of fastener  304 , however, this is not necessary. Expanding slit region  360  includes a plurality of slits  306  through a wall  308  of collar  302  that allows expansion of the collar as fastener  304  is advanced into expanding slit region  360 . Relieved area  364  provides additional flexibility of collar  302  during expansion. Advancement of fastener  304  into collar  302  forces substantially cone shaped portion  340  against tapered and threaded interior surface  310  to expand exterior surface  312  of collar  302  against the interior of the mounting opening to mount the circuit board. 
   As in the previous embodiments, an exterior surface  312  of collar  302  is configured to engage the interior of the mounting opening of the circuit board (not shown) by, for example, having a shape configured to substantially match the interior of the mounting opening. In addition, fastener  304  may also include a tool engaging member  352 , as described above, for engaging by a tool for adjusting the fastener. 
   The invention also includes a method for mounting a circuit board using an expandable standoff connector  100 ,  300 . The method includes inserting a collar  102 ,  202 ,  302  within an interior  114  of a mounting opening  116  of circuit board  118 . The collar includes a slit  106 ,  206 ,  306  through a wall of the collar, a tapered interior surface  110 ,  310  and an exterior surface  112 ,  312  configured to engage an interior of a mounting opening of the circuit board. Next, a fastener  104 ,  304  is provided including a threaded portion  140 ,  240 ,  340  and a substantially cone shaped portion  142 ,  242 ,  342  where the substantially cone shaped portion is configured to mate with tapered (and perhaps threaded) interior surface  110 ,  310  of the collar. Next, the fastener is advanced through (i.e., through or into) the collar to force the substantially cone shaped portion  141 ,  242 ,  342  against the tapered interior surface  110 ,  310  to expand the exterior surface of the collar against the interior of the mounting opening to mount the circuit board. As noted above, as shown in  FIGS. 3 ,  4 AB and  5 , the advancing step may include threading the threaded portion into a chassis  150  to which the circuit board is mounted. Alternatively, as shown in  FIG. 7 , where threaded portion  340  is provided along substantially cone-shaped portion  342 , and tapered interior surface  310  includes mating threads to the threaded portion, the advancing step may include threading threaded portion  342  into interior surface  310  of the collar. 
   Standoff connectors  100 ,  300 , as described above, are also easily removable by rotatingly removing fastener  104 ,  204 ,  304 , which allows easy removal of a circuit board for assembly rework or repair. 
   While this invention has been described in conjunction with the specific embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the embodiments of the invention as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention as defined in the following claims.