Abstract:
A blade for a chassis-based system includes a printed circuit board (PCB) mounted at a tilt angle within the blade. The tilt angle provides space above or below the PCB at the front end of the blade, such that media interface modules can be flexibly positioned within the blade. A tilt angle that positions the PCB higher near the front end of the blade may enable media interface modules mounted in a belly-to-belly configuration on the PCB to be fitted within the front end of the blade. A tilt angle that positions the PCB lower near the front end of the blade may enable media interface modules mounted on the upper surface of the PCB to be fitted within the first end of the blade. The tilt angle also positions a backplane connector mounted on the PCB to properly engage a backplane when the blade is inserted into a slot.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is a continuation of U.S. patent application Ser. No. 12/620,361 filed Nov. 17, 2009, which application is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a blade used in a chassis-based system. More specifically, the present invention relates to the tilted installation of a printed circuit board within a blade. 
         [0004]    2. Related Art 
         [0005]      FIG. 1A  is an isometric view of a conventional rack-mountable blade  100 , which includes blade pan assembly  101 , printed circuit board (PCB)  102 , blade hardware  103 - 104 , media interface module  105 , PCB mounting structures  106 - 108  and high density backplane connector  109 .  FIG. 1B  is a cross-sectional view of blade  100  along section line B-B of  FIG. 1A .  FIG. 1B  also illustrates a portion of a chassis  120  having an associated slot  121  for receiving blade  100 , along with a portion of a backplane  130 , which is coupled to chassis  120 , and a high density backplane connector  131 , which is coupled to backplane  130 . 
         [0006]    Blade pan assembly  101  includes a flat bottom portion  101 A, and an upright faceplate portion  101 B. Blade pan assembly  101  is typically formed from sheet metal. PCB  102  is attached to the flat bottom portion  101 A of blade pan assembly  101  by PCB mounting structures  106 - 108 . As illustrated in  FIG. 1B , each of the PCB mounting structures has the same fixed height H 1 , such that PCB  102  is positioned a fixed height H 1  above, and in parallel with, the flat bottom portion  101 A. 
         [0007]    Blade hardware  103  and  104  includes integrated circuit chips, discrete circuit elements (e.g., resistors and capacitors), heat sinks and/or interconnect structures, which are located on the upper and lower surfaces of PCB  102 , respectively. As described below, the height of the upper blade hardware  103  is greater than the height of the lower blade hardware  104 . 
         [0008]    Media interface module  105  is attached to the upper surface of PCB  102 . The media interface module  105  can be fixed (as described herein) or pluggable (wherein module  105  is a connector on PCB  102 ). Media interface module  105  is coupled to electronic circuitry in blade hardware  103 / 104  by conductive traces in PCB  102 . A portion of media interface module  105  is exposed through an opening  101 C in the faceplate portion  101 B of blade pan assembly  101 . The exposed portion of media interface module  105  includes a port structure that allows for the connection of a network cable (e.g., an Ethernet cable, or an optical cable). 
         [0009]    High density backplane connector  109  is attached to the upper surface of PCB  102 , at the end opposite media interface module  105 . High density backplane connector  109  includes a plurality of connector elements (represented by dashed lines in  FIG. 1B ) that are connected to conductive traces on PCB  102  and extend to a back end  109 A of high density backplane connector  109 . 
         [0010]    Blade  100  is inserted into slot  121  within a chassis  120 . Note that this slot  121  is typically defined by side support elements of chassis  120  (not shown), which engage lateral edges of the blade pan assembly  101 . A backplane  130  is attached to the chassis  120 . Backplane  130  includes electrical pathways that allow different blades in chassis  120  to communicate. A high density backplane connector  131  is attached to backplane  130  at a predetermined fixed location within slot  121 . High-density backplane connector  131  is configured to engage with high density backplane connector  109  (i.e., in a plug/socket configuration) when blade  100  is fully inserted into slot  121 . Once engaged, the high density backplane connectors  109  and  131  provide electrical connections between PCB  102  and backplane  130 . 
         [0011]    One of the design considerations associated with blade  100  is the slot height H S . It is desirable to minimize the slot height H S  in order to maximize the number of blades that can fit in a chassis. Another design consideration associated with blade  100  is the location of particular circuit elements on PCB  102 . Shorter, cool-operating passive parts are typically located on the lower surface of PCB  102  (i.e., blade hardware  104 ), and taller, hot-operating active parts are typically located on the upper surface of PCB  102  (i.e., blade hardware  103 ). In order to minimize the height of blade  100  (and therefore the required slot height H S ) PCB  102  is positioned at a height H 1  that is relatively close to the flat bottom portion  101 A of blade pan assembly  101 . Note that positioning PCB  102  at the middle of the slot height H S  is not optimal (because such positioning would undesirably, and unnecessarily, increase the required slot height). 
         [0012]    The height H 1  is insufficient to allow a conventional media interface module (e.g., media interface module  105 ) to be mounted under the printed circuit board  102 . That is, the height of a conventional media interface module is greater than the distance H 1  that exists between the lower surface of PCB  102  and the upper surface of the flat bottom portion  101 A of pan blade assembly  101 . As a result, blade  100  is undesirably limited to a single row of media interface ports  105  across the faceplate portion  101 B of blade pan assembly  101 . (See,  FIG. 1A .) 
         [0013]      FIG. 2  is a cross-sectional view of another conventional rack-mountable blade  200 , which allows two rows of media interface ports to be located at the front surface of blade  200 . Blade  200  includes blade pan assembly  201 , media interface modules  205 - 206 , high-density backplane connector  209 , PCB (motherboard)  210 , motherboard hardware  211 - 212 , motherboard mounting structures  213 - 215 , PCB (daughterboard)  220 , daughterboard hardware  213 - 214 , daughterboard mounting structures  223 - 224 , and bridge structure  230 . Blade pan assembly  201  includes flat bottom portion  201 A and upright faceplate portion  201 B. Motherboard  210  and daughterboard  220  replace the single PCB  102  of blade  100 . Motherboard hardware  211  and daughterboard hardware  221  roughly corresponds with blade hardware  103  of blade  100  (although daughterboard hardware  221  is typically designed to have a smaller height than motherboard hardware  221 , such that the overall height of slot  121  does not have to be increased in view of the height of daughterboard  220 ). Similarly, motherboard hardware  212  and daughterboard hardware  222  roughly corresponds with blade hardware  104  of blade  100 . 
         [0014]    Motherboard  210  is attached to the flat bottom portion  201 A of blade pan assembly  201  by mounting structures  213 - 215 . As illustrated in  FIG. 2 , each of the mounting structures  213 - 215  has the same fixed height H 1  as PCB mounting structures  106 - 108  ( FIG. 1B ), such that motherboard  210  is positioned a fixed height H 1  above, and in parallel with, the flat bottom portion  201 A. As a result, high-density backplane connector  209  of blade  200  is positioned in the same manner as high-density backplane connector  109  of blade  100 . As a result, high-density backplane connector  209  properly engages high-density backplane connector  131  on backplane  130  when blade  200  is inserted into slot  121 . 
         [0015]    Daughterboard  220  is attached to the flat bottom portion  201 A of blade pan assembly  201  by mounting structures  223 - 224 . As illustrated in  FIG. 2 , each of the mounting structures  223 - 224  has the same fixed height H 2 , wherein height H 2  is greater than height H 1 . The height H 2  is selected such that media interface module  205  may be attached to the upper surface of daughterboard  220 , and media interface module  206  may be attached to the lower surface of daughterboard  220 , as illustrated. That is, media interface modules  205  and  206  are connected in a belly-to-belly configuration, on opposite sides of daughterboard  220 . As illustrated in  FIG. 2 , media interface modules  205  and  206  are exposed through openings  201 C and  201 D, respectively, in the faceplate portion  201 B of blade pan assembly  201 . Because blade  200  allows two rows of media interface modules to be implemented in a belly-to-belly configuration, blade  200  may advantageously include twice as many media interface modules as blade  100 . 
         [0016]    However, the dissimilar heights of motherboard  210  and daughterboard  220  necessitate the use of a bridge structure  230  between motherboard  210  and daughterboard  220 . Bridge structure  230  includes a plurality of conductive paths, which enable signals to be transmitted between motherboard  210  and daughterboard  220 . Bridge structure  230  can include, for example, a high-speed connector and/or ribbon cable. 
         [0017]    Blade  200  exhibits the following disadvantages with respect to blade  100 . Blade  200  will have higher materials costs than blade  100 , because blade  200  requires an extra PCB (i.e., daughterboard  220 ), as well as the additional hardware associated with the bridge structure  230 . Blade  200  will also have higher assembly costs, because blade  200  requires the installation of the extra PCB  220  and the bridge structure  230 . In addition, signal integrity is degraded by the use of bridge structure  230 , which requires that signals be transmitted off of PCBs  210  and  220 . The bridge structure  230  also creates a bottleneck for signals transmitted between PCB  210  and PCB  220 . The two-PCB structure of blade  200  also results in less effective PCB area for components, as components cannot be placed in the gap between PCB  210  and PCB  220 . 
         [0018]    It would therefore be desirable to have an improved blade structure, which allows the use of two rows of media interface modules (or larger media interface modules), but does not exhibit the disadvantages associated with the motherboard/daughterboard design of blade  200 . 
       SUMMARY 
       [0019]    Accordingly, the present invention provides an improved blade, which includes a single printed circuit board mounted at a tilt angle within a blade pan assembly. The single printed circuit board extends substantially the entire depth of the blade (i.e., from the front end of the blade to the rear end of the blade). In one embodiment, the tilt angle causes the front end of the printed circuit board (i.e., the end of the printed circuit board located adjacent to the front end of the blade) to be positioned slightly higher than the rear end of the printed circuit board (i.e., the end of the printed circuit board located adjacent to the read end of the blade). This configuration provides additional space below the printed circuit board at the front end of the blade. This configuration allows media interface modules mounted in a belly-to-belly configuration at the front end of the printed circuit board to be fitted into the front end of the blade. 
         [0020]    In another embodiment, the tilt angle causes the front end of the printed circuit board to be positioned slightly lower than the rear end of the printed circuit board. This configuration provides additional space above the printed circuit board at the front end of the blade. This configuration allows relatively tall media interface modules mounted on the upper surface of the front end of the printed circuit board to be fitted into the front end of the blade. 
         [0021]    A high-density backplane connector may be mounted at the rear edge of the printed circuit board. In one embodiment, the tilt angle of the printed circuit board is not large enough to prevent the high-density backplane connector from properly engaging a corresponding connector element on a backplane when the blade is inserted into a slot of a chassis. In an alternate embodiment, a shim that exhibits the tilt angle is located between the printed circuit board and the high-density backplane connector, thereby leveling the high-density backplane connector. In another embodiment, a surface of the high-density backplane connector that is coupled to the printed circuit board is fabricated to exhibit the tilt angle, thereby leveling the high-density backplane connector. 
         [0022]    The present invention will be more fully understood in view of the following description and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1A  is an isometric view of a conventional rack-mountable blade, which includes a single printed circuit board (PCB) and a single row of media interface modules. 
           [0024]      FIG. 1B  is a cross sectional view of the blade of  FIG. 1A  along section line B-B of  FIG. 1A . 
           [0025]      FIG. 2  is a cross-sectional view of another conventional rack-mountable blade, which includes two PCBs and two rows of media interface modules. 
           [0026]      FIG. 3  is a cross-sectional view of a rack-mountable blade in accordance with one embodiment of the present invention. 
           [0027]      FIG. 4A  is a cross-sectional view of a high-density backplane connector, which is leveled by a shim, in accordance with one embodiment of the present invention. 
           [0028]      FIG. 4B  is a cross sectional view of a modified high-density backplane connector, which can be used in the blade of  FIG. 3 , in accordance with one embodiment of the present invention. 
           [0029]      FIG. 4C  is a cross sectional view of a modified high-density backplane connector having a tilted mating interface, which can be used in the blade of  FIG. 3 , in accordance with one embodiment of the present invention 
           [0030]      FIG. 5A  is a cross-sectional view of belly-to-belly media interface modules, which are aligned with a common vertical plane in accordance with one embodiment of the present invention. 
           [0031]      FIG. 5B  is a cross-sectional view of belly-to-belly media interface modules, which are connected to a printed circuit board using shims in accordance with one embodiment of the present invention. 
           [0032]      FIG. 6  is a cross-sectional view of a rack-mountable blade in accordance with an alternate embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]      FIG. 3  is a cross-sectional view of a rack-mountable blade  300  in accordance with one embodiment of the present invention. Blade  300  includes blade pan assembly  301 , printed circuit board (PCB)  302 , blade hardware  303 - 304 , media interface modules  305 - 306 , PCB mounting structures  307 - 309 , and high-density backplane connector  310 .  FIG. 3  also illustrates a chassis  120 , slot  121 , backplane  130  and high-density interconnect socket  131 , which are described above in more detail in connection with  FIGS. 1A-1B  and  2 . 
         [0034]    PCB  302  extends from the front edge of blade  300  to the rear edge of blade  300 , as illustrated. Blade hardware  303  and  304  is located on the upper and lower surfaces of PCB  302 , respectively, as illustrated in  FIG. 3 . Blade hardware  303  and  304  may include, for example, integrated circuit chips, discrete circuit elements (e.g., resistors and capacitors), heat sinks and/or interconnect structures, which are located on the upper and lower surfaces of PCB  302 , respectively. In general, blade hardware  303 - 304  performs the required processing within blade  300 . In the described embodiments, blade hardware  103  includes the tall, heat-generating parts of blade  300 , while blade hardware  304  includes short, cooler-operating parts. Consequently, the height of blade hardware  304  is significantly less than the height of blade hardware  303 . 
         [0035]    Media interface modules  305  and  306  are mounted on the upper and lower surfaces of PCB  302 , respectively, in a belly-to-belly configuration. As described herein, a media interface module includes a socket and a transceiver, wherein the transceiver can be plugged into (or pulled out of) the socket. The socket is physically mounted to the PCB  302  and is dimensioned to receive the transceiver. The socket includes a connector element, which provides electrical connections between the transceiver and conductive traces of the PCB  302  (when the transceiver is plugged into the socket). The transceiver includes a port (e.g., and optical port or an Ethernet port), which is exposed at the front end of blade  300  when the transceiver is plugged into the socket. In the described embodiments, media interface modules  305 - 306  are conventional modules, which are identical to media interface modules  105  ( FIGS. 1A-1B ) and  205 - 206  ( FIG. 2 ). Media interface modules  305 - 306  are coupled to electronic circuitry in blade hardware  303 / 304  by conductive traces in PCB  302 . 
         [0036]    High-density backplane connector  310  is mounted on the upper surface of PCB  302 . High-density backplane connector  310 , which is identical to high-density backplane connectors  109  ( FIGS. 1A-1B ) and  209  ( FIG. 2 ) in the present embodiment, includes electrical connections to PCB  302 . As defined herein, media interface ports  305 - 306  are located at a front edge of PCB  302 , and high density connector plug  310  is located at a rear edge of PCB  302 . 
         [0037]    Blade pan assembly  301  is substantially identical to blade pan assemblies  101  ( FIGS. 1A-1B ) and  201  ( FIG. 2 ). Thus, blade pan assembly  301  includes a flat (planar) bottom portion  301 A, which forms the bottom surface of blade  300 , and an upright faceplate portion  301 B, which forms the front surface of blade  300 . Openings  301 C and  301 D, which extend through the faceplate portion  301 B of blade pan assembly  301 , expose media interface modules  305  and  306 , respectively. Blade pan assembly  301  is formed from sheet metal in the described embodiments, although blade pan assembly  301  can be formed of other materials in other embodiments. PCB  302  is attached to the flat bottom portion  301 A of blade pan assembly  301  by PCB mounting structures  307 - 309 . As illustrated in  FIG. 3 , each of the PCB mounting structures  307 - 309  has a different height, such that PCB  302  is positioned at a slight angle with respect to the flat bottom portion  301 A. In the described embodiments, the PCB mounting structures  307 ,  308  and  309  have heights H A , H B  and H C , respectively, wherein H A &gt;H B &gt;H C . In a particular embodiment, the heights H A , H B  and H C  are selected such that PCB  302  is positioned at a tilt angle A of about 0.86 degrees, with respect to the flat bottom portion  301 A of blade pan assembly  301 . However, the tilt angle A can have other values in accordance with the guidance provided below. The tilt angle A depends on specific design tolerances, connectors used, PCB size, and whether the backplane connector  310  is shimmed (as described below). 
         [0038]    The heights H A -H C  of PCB mounting structures  307 - 309  are selected such that the high-density backplane connector  310  is located at a height that allows this connector  310  to properly engage with the associated high-density backplane connector  131 . The angle and heights will vary depending on media interface type and particulars of the blade design. In one embodiment, the height of the rear edge of PCB  302  is approximately equal to the height H 1  ( FIGS. 1B and 2 ). In this embodiment, the high-density backplane connector  310  mounted on PCB  302  is located at approximately the same height as the conventional high density backplane connectors  109  ( FIG. 1B) and 209  ( FIG. 2 ). Consequently, high-density backplane connector  310  will be properly connected to the corresponding high-density backplane connector  131  when blade  300  is inserted into the slot  121  of chassis  120 . Note that even though the high-density backplane connector  310  is at a slight angle (e.g., 0.86°) with respect to the flat portion  310 A of pan blade assembly  301 , the tolerances of the high density backplane connectors  310  and  131  are sufficient to allow these connectors  310  and  131  to properly engage when blade  300  is inserted into slot  121 . Stated another way, the tilt angle A is selected such that the insertion tolerances of the backplane connectors  310  and  131  are not exceeded. 
         [0039]    When backplane connectors  310  and  131  are engaged, the tilt angle A introduces forces between the backplane  130  and PCB  302  (wherein these forces tend to straighten the tilt of PCB  302 ). Thus, in designing blade  300 , all of these forces must be analyzed to ensure that no design allowances are exceeded. 
         [0040]      FIGS. 4A and 4B  are side views of high-density backplane connector  310  and PCB  302  in accordance with alternate embodiments of the present invention. As illustrated in  FIG. 4A , a shim  401  may be inserted between high-density backplane connector  310  and PCB  302 , wherein the shim  401  inclines the connector  310  by the angle A. As a result, shim  401  levels high-speed backplane connector  310 , such that this connector  310  is positioned in parallel with the flat bottom portion  301 A of blade pan assembly  301 . In a particular embodiment, the thickest portion of shim  401  is on the order of ten thousandths of an inch. Note that the shim  401  is positioned at a location(s) where electrical connections between PCB  302  and high-density backplane connector  310  do not exist. Alternate embodiments may implement multiple shims between high-speed backplane connector  310  and PCB  302 . In the embodiment of  FIG. 4A , shim  401  may introduce forces between PCB  302  and backplane connector  310 . Thus, in designing blade  300 , all of these forces must be analyzed to ensure that no design allowances are exceeded. 
         [0041]    As illustrated in  FIG. 4B , the lower surface of high-density backplane connector  310  may be fabricated to have an angle that matches the tilt angle A of PCB  302 . For example, a portion  402  of high-density backplane connector  310  may be removed by machining, or an equivalent process (i.e., connector  310  may simply be fabricated without portion  402 ). Eliminating portion  402  of high-density backplane connector  310  advantageously levels this connector  310 , thereby improving the alignment with high-density backplane connector  131 . 
         [0042]    As illustrated in  FIG. 4C , the high-density backplane connector  310  may be fabricated such that the mating interface within connector  310  is situated at the tilt angle A, with respect to the lower surface  310 L of connector  310 . Dashed line  410  illustrates the mating interface of connector  310  in accordance with one embodiment of the present invention. Positioning the mating interface of connector  310  at the tilt angle A promotes the alignment and connection of connector  310  with high-density backplane connector  131 . 
         [0043]    Returning now to  FIG. 3 , the heights H A -H C  of PCB mounting structures  307 - 309  are further selected such that the front edge of PCB  302  is high enough to allow media interface modules  305  and  306  to be mounted in a belly-to-belly configuration on opposite sides of PCB  302 . In one embodiment, the height of the front edge of PCB  302  is approximately equal to the height H 2  of daughterboard  220  in blade  200  ( FIG. 2 ). The tilt angle A of PCB  302  is selected to provide adequate clearance for media interface module  306  between PCB  302  and the flat bottom portion  301 A of blade pan assembly  301 , while also providing adequate clearance for media interface module  306  between PCB  302  and the upper boundary of blade  300 . 
         [0044]    In the embodiment illustrated by  FIG. 3 , the front surfaces of media interface modules  305 - 306  co-planar, but are not located in parallel with the vertical faceplate portion  301 B of blade pan assembly  301 . Rather, the front surfaces of media interface modules  305 - 306  are offset from the plane of the faceplate portion  301 B by the tilt angle, A. As a result, media interface module  306  may protrude out through the faceplate portion  301 B slightly more than media interface module  305 . 
         [0045]      FIGS. 5A and 5B  are cross sectional views of media interface modules  305 - 306  and PCB  302  in accordance with alternate embodiments of the present invention. As illustrated in  FIG. 5A , media interface module  305  protrudes further past the front edge of PCB  302  than media interface module  306 . As a result, media interface modules  305  and  306  protrude out through the faceplate portion  301 B of blade pan assembly  301  by the same amount. In this embodiment, the front surfaces of media interface modules  305  and  306  are not co-planar. However, the front surfaces of media interface modules  305 - 306  are centered on a common vertical plane  500 . That is, the centers of the front surfaces of media interface modules  305 - 306  (which are shown by x&#39;s in  FIG. 5A ) are located on the same vertical plane  500 . 
         [0046]    As illustrated in  FIG. 5B , shims  501 - 502  may be inserted between media interface modules  305 - 306 , respectively, and PCB  302 . Shims  501 - 502  level media interface modules  305 - 306 , respectively, by inclining/reclining these modules by the tilt angle A. As a result, media interface modules  305 - 306  are positioned in parallel with the flat bottom portion  301 A of blade pan assembly  301 . 
         [0047]      FIG. 6  is a cross-sectional view of a rack-mountable blade  600  in accordance with an alternate embodiment of the present invention. Because blade  600  is similar to blade  300 , similar elements are labeled with similar reference numbers in  FIGS. 3 and 6 . Thus, blade  600  includes blade pan assembly  301 , PCB  302 , blade hardware  303 - 304  and high-density backplane connector  310 , which have been described above in connection with  FIG. 3 .  FIG. 6  also illustrates chassis  120 , slot  121 , backplane  130  and high-density interconnect socket  131 . 
         [0048]    PCB mounting structures  607 - 609  attach PCB  302  to the flat bottom portion  301 A of blade pan assembly  301  in blade  600 . PCB mounting structures  607 ,  608  and  609  have heights H D , H E  and H F , respectively, wherein H D &lt;H E &lt;H F . As a result, PCB  302  is positioned at a slight angle with respect to the flat bottom portion  301 A, wherein the front edge of PCB  302  is lower than the rear edge of PCB  302 . 
         [0049]    Media interface module  605  is mounted on the upper surface of PCB  302 , at the front edge of PCB  302 . Media interface module  605  has a height H M  that is greater than the heights of modules  105 ,  205 - 206  and  305 - 306 . In blade  600 , the upright faceplate portion  301 B of blade pan assembly  301  is modified to include a relatively large opening  601 C. This large opening  601 C allows the relatively tall media interface module  605  to be exposed through faceplate portion  301 B. 
         [0050]    The downward tilt angle A of PCB  302  is selected to allow the relatively high media interface module  605  to be properly positioned at the front surface of blade  600 . Note that without the downward tilt angle A, media interface module  605  would not fit within blade  600 . (That is, the combined heights of media interface module  605 , PCB  302  and blade hardware  304 , plus the required clearances, would be greater than the height of the blade  600 ). 
         [0051]    The exposed front surface of media interface module  605  is angled slightly downward in blade  600 . In one embodiment, a shim may be inserted between media interface module  605  and PCB  302 , thereby leveling media interface module  605  with respect to the flat bottom portion  301 A of pan assembly  300 . (See, e.g.,  FIG. 5B .) 
         [0052]    The heights H D -H F  of PCB mounting structures  607 - 609  are selected such that the high-density backplane connector  310  is located at a height that allows this connector  310  to properly engage with the associated high-density backplane connector  131 . The angle and heights will vary depending on media interface type and particulars of the blade design. The design considerations associated with connector  310  have been described above in connection with FIGS.  3  and  4 A- 4 B, and apply equally within blade  600 . For example, the high-density backplane connector  310  of blade  600  can be shimmed or machined in the manner described above in connection with  FIGS. 4A-4B . Note that the shim (or machined) angle used in blade  600  would be reversed with respect to  FIGS. 4A-4B . 
         [0053]    Although the present invention has been described in connection with various embodiments, it is understood that variations of these embodiments would be obvious to one of ordinary skill in the art. For example, although three PCB support structures  307 - 309  (or  607 - 609 ) are shown along the length of PCB  302 , it is understood that two (or more than three) PCB support structures can be used in alternate embodiments. Moreover, although PCB  302  has been described as being attached to the bottom portion  301 A of pan assembly  301  by PCB support structures  307 - 309 , it is understood that PCB  302  could be mounted at the tilt angle A by attaching PCB  302  to other surfaces (e.g., side surfaces) of pan assembly  301 . Thus, the present invention is limited only by the following claims.