Abstract:
A line card includes a metal frame that includes a front section, and a bottom section connected to the front section via an angled section, where the angled section results in an opening between the line card and a second line card, when the line card is installed above the second line card in a rack, and where the opening allows directed air to enter the rack from a front direction; a printed circuit board attached to the metal frame; and a group of front panel connectors attached to the front section of the metal frame.

Description:
RELATED APPLICATION 
       [0001]    This application is a continuation application of U.S. patent application Ser. No. 12/877,710, filed Sep. 8, 2010, the entire contents of which is hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    An electronic device may include components, such as integrated circuits (ICs), which may need to be secured to a mechanically rigid substrate. Such components may be mounted on a printed circuit board (PCB), which may provide structural stability. The PCB may be incorporated into a line card which may include connectors for interacting with other electronic devices. Multiple line cards may be mounted into a chassis of a rack. During operation, electronic components of the line card, such as ICs, may generate heat. It may be necessary to cool line cards mounted in a rack to ensure that the line cards do not exceed a safe operating temperature. However, cooling components of line cards mounted in a rank unit may prove to be particularly challenging. 
       SUMMARY OF THE INVENTION 
       [0003]    According to one aspect, a line card may include a metal frame including a front section, and a bottom section connected to the front section via an angled section, where the angled section results in an opening between the line card and a second line card, when the line card is installed above the second line card in a rack, and where the opening allows directed air to enter the rack from a front direction; a PCB attached to the metal frame; and a group of front panel connectors attached to the front section of the metal frame. 
         [0004]    According to another aspect, a rack may include a group of line cards mounted in the rack; and a group of openings located between adjacent ones of the group of line cards, a particular opening extending substantially a width of the rack and located between a first particular line card and a second particular line card, where the first particular line card is mounted immediately above the second particular line card, and where the group of openings allow directed air to enter the rack from a front direction. 
         [0005]    According to another aspect, a method, of forming a metal frame for a line card, may include forming a front section of the metal frame; forming an angled section, where the angled section connects a bottom section of the metal frame to the front section, where the angled section results in an opening between the line card and a second line card, when the line card is installed above the second line card in a rack, and where the opening allows directed air to enter the rack from a front direction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate the invention and, together with the description, explain the invention. In the drawings, 
           [0007]      FIG. 1  is a diagram illustrating an example system according to an implementation described herein; 
           [0008]      FIG. 2  is a diagram illustrating an example rack according to an implementation described herein; 
           [0009]      FIG. 3A  is a diagram illustrating a first view of a line card according to a first implementation described herein; 
           [0010]      FIG. 3B  is a diagram illustrating a second view of a line card according to the first implementation described herein; 
           [0011]      FIG. 4A  is a diagram illustrating the rack of  FIG. 2  with installed line cards according to an implementation described herein; 
           [0012]      FIG. 4B  is a diagram illustrating air flow in a rack with line cards according to the first implementation described herein; 
           [0013]      FIG. 5A  is a diagram illustrating a line card according to a second implementation described herein; 
           [0014]      FIG. 5B  is a diagram illustrating air flow in a rack with line cards according to the second implementation described herein; 
           [0015]      FIG. 6A  is a diagram illustrating a line card according to a third implementation described herein; 
           [0016]      FIG. 6B  is a diagram illustrating air flow in a rack with a line card according to the third implementation described herein; and 
           [0017]      FIG. 7  is a diagram of a flow chart illustrating an example process for forming a line card according to an example implementation described herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The following detailed description of the invention refers to the accompanying drawings. The same reference numbers may be used in different drawings to identify the same or similar elements. Also, the following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims and equivalents. 
         [0019]    A rack may include line cards mounted onto the chassis of the rack. The line cards may include a high density of connectors that utilize most of the front panel area. A computer room with racks may be implemented with an air conditioning (AC) cooling system that employs a front to back cooling scheme. As a result of the high density of the front panel connectors, and because individual line cards may be mounted closely together, it may be difficult to achieve efficient front to back cooling, as there may not be a way for air to enter the rack from the front. As the incoming cooling air may not be able to enter the rack from the front, the air may need to enter from the sides of the rack, which may result in inefficient cooling of the electronic components of the line cards. 
         [0020]    An implementation described herein may relate to a chassis system with front cooling air intake. A line card may include a modified metal frame with a recessed bottom. A recessed bottom may be achieved by including an angled section in the bottom of the line card frame, resulting in an opening with the shape of a long slot with a length that is substantially equal to a width of the line card, when the line card is mounted in a chassis of a rack. The resulting opening in a first line card provides a way for the air to enter the rack from the front, allowing the air to cool the components of a second line card located below the first line card. 
         [0021]    Another implementation described herein may include a line card with a modified metal frame with a recessed bottom and an extended upper part of the frame. The extended upper part of a second line card may abut the angled portion of a recessed bottom of a first line card located on top of the second line card, when the first and second line cards are mounted onto a chassis of a rack. The extended upper part of the line card frame may include one or more openings to allow for air flow. The openings may be small enough to prevent electromagnetic (EM) interference, while allowing air to enter the space between two line cards. 
         [0022]    Yet another implementation described herein may include a line card with a modified metal frame with a recessed bottom and an extended upper part of the frame that includes openings of varying density. The density of the openings in the extended upper part of the frame may be increased at locations corresponding to locations of heat generating components. The increased density of the openings may allow more air to flow through the location corresponding to the heat generating components, causing the heat generating components to be cooled at a higher rate than other areas of a PCB of the line card. Furthermore, a backplane of the rack may be designed with exhaust fans and/or openings that line up with an area of increased density of openings, allowing more air to flow across the heat generating components in a front-to-back direction in relation to the rack. 
         [0023]      FIG. 1  is a diagram illustrating an example system  100  according to an implementation described herein. As shown in  FIG. 1 , system  100  may include one or more racks  110  (referred to herein as “racks  110 ” collectively and “rack  110 ” individually), located in a computer room  101 , and an air conditioning (AC) unit  120 . Racks  110  in computer room  101  may be arranged sequentially next to each other so that the front panels of racks  110  face AC unit  120 . 
         [0024]    Rack  110  may include a chassis with a front panel  112 , with line cards mounted on front panel  112 , a backplane  114  that includes connectors to connect to the line cards and allow communication between particular line cards, and/or a power supply (not shown in  FIG. 1 ) to supply electrical power to the line cards and to the backplane. Rack  110  may provide structural stability for line cards mounted in rack  110 , may provide a space-efficient way to store and organize line cards, may provide EM shielding for the line cards, and may provide a mechanism that allows communications between individual line cards (e.g., via a backplane). Fronts of line cards, mounted in front panel  112 , may include front connectors for connecting particular line cards with other devices. 
         [0025]    AC unit  120  may cool racks  110 . AC unit  120  may be located within computer room  101  or outside computer room  101  and may generate entry air flow  130 . Entry air flow  130  may be directed at front panels of racks  100 . Front panel  112  of racks  100  may include openings for allowing entry air flow  130  to enter racks  110  substantially in a front-to-back direction. Backplane  114  of rack  110 , which may be located parallel to front panel  112 , may include openings and/or exhaust fans for facilitating exit air flow  140 . 
         [0026]    Although  FIG. 1  shows example components of system  100 , in other implementations, system  100  may include fewer components, different components, differently arranged components, or additional components than depicted in  FIG. 1 . Additionally or alternatively, one or more components of system  100  may perform the tasks described as being performed by one or more other components of system  100 . 
         [0027]      FIG. 2  is a diagram illustrating an example rack  110  according to an implementation described herein.  FIG. 2  depicts rack  110  as an empty rack without any installed line cards. As shown in  FIG. 2 , rack  110  may include a chassis frame  210  and a backplane  114 . Chassis frame  210  may provide structural stability to rack  110  and may include front panel  112 . Front panel  112  may include mounting area  215 . Mounting area  215  may include, for example, holes that may accommodate screws used to mount particular line cards. Chassis frame  210  may include panels that cover the top, bottom, and sides of rank  110  (not shown in  FIG. 2 ), to provide additional structural stability to rack  110 , protect line cards from the outside environment, to provide EM shielding of line cards, to give rack  110  a more esthetic appearance, etc. 
         [0028]    Backplane  114  may be mounted on a back surface of chassis frame  210  in a direction substantially parallel to front panel  112 . Backplane  114  may include one or more line card connectors  212 , a bus  214 , one or more openings  216  (referred to herein collectively as “openings  216 ” and individually as “opening  216 ”), and one or more exhaust fans  218  (referred to herein collectively as “exhaust fans  218 ” and individually as “exhaust fan  218 ”). 
         [0029]    Line card connectors  212  may electrically connect particular line cards to backplane  114 . Bus  214  may connect to line card connectors  212  and may allow communications between particular line cards. Opening  216  may facilitating exit air flow  140  by allowing air, entering via front panel  112 , to exit rack  110 . Additionally or alternatively, exhaust fan  218  may facilitate exit air flow  140  by directing air, entering via front panel  112 , to exit rack  112  via rotating fan blades. Rack  114  may include a power supply (not shown in  FIG. 2 ), located either inside rack  110  or outside rack  110 , for supplying electrical power to backplane  114  and to any line cards installed in rack  110 . 
         [0030]    Although  FIG. 2  shows example components of rack  110 , in other implementations, rack  110  may include fewer components, different components, differently arranged components, or additional components than depicted in  FIG. 2 . Additionally or alternatively, one or more components of rack  110  may perform the tasks described as being performed by one or more other components of rack  110 . 
         [0031]      FIGS. 3A and 3B  are diagrams illustrating a line card  300  according to a first implementation described herein.  FIG. 3A  depicts a three-dimensional view of line card  300  and  FIG. 3B  depicts a side view of line card  300 . As shown in  FIGS. 3A and 3B , line card  300  may include a cookie sheet frame  310 , mounting hardware  320 , front connectors  330 , and a PCB  340 . 
         [0032]    Cookie sheet frame  310  may include a metal frame for providing structural stability to PCB  340  and front connectors  330 . Cookie sheet frame  310  may have a width that extends substantially the width of front panel  112  (i.e., an inside width of rank  110 ), so that line card  300  fits inside front panel  112  and may be mounted onto front panel  112  via mounting area  215 . Cookie sheet frame  310  may have a depth substantially the depth of chassis frame  210 , so that line card  300  fits inside rack  110  and so that a connector  212  of backplane  114  connects to a back connector (not shown in  FIGS. 3A and 3B ) of PCB  340 . Cookie sheet frame  310  may provide partial or complete EM shielding to PCB  340  and/or to front connectors  330 . 
         [0033]    Cookie sheet frame  310  may include a top portion  312 , a front portion  314 , and a bottom portion  316 . Top portion  312  may facilitate handling of line card  300  during installation. Front portion  314  may secure connectors  330  in place and may partially secure PCB  340  in place. Front portion  314  may include mounting hardware  320 . Mounting hardware  320  may include, for example, screws to mount line card  300  using mounting area  215 . 
         [0034]    Bottom portion  316  may include an angled section  318 . Angled section  318  may provide a recessed area that may create an opening between line card  300  and another line card mounted below line card  300 . The opening may allow entry air flow  130  to enter an area above PCB  340  of the line card mounted below line card  300  and cool components mounted on PCB  340  of the line card mounted below line card  300 . 
         [0035]    Front connectors  330  may provide electrical and/or optical connectors to cables that may provide electrical and/or optical connections to other electronic devices (e.g., other line cards mounted on rack  110  or line cards mounted in another rack). The number of front connectors  330  included in line card  300  may depend on a size of rack  110  and line card  300  and may be maximized to take up most of the area of front portion  314  of cookie sheet frame  310 . For example, for a standard 19 inch rack, connectors  330  may include 48 connectors, in two rows of 24. 
         [0036]    PCB  340  may provide a structurally stable substrate for mounting electrical and/or optical components of line card  300  and may include electrical and/or optical connections between the electrical and/or optical components. PCB  340  may include one or more components  350  (referred to herein collectively as “components  350 ” and individually as “component  350 ”). 
         [0037]    Component  350  may include, for example, ICs such as processors or processing logic (e.g., application specific integrated circuits (ASICs) or field programmable gate arrays (FPGAs)) that may interpret and execute instructions, and/or memory devices, such as a random access memory (RAM) device or another type of dynamic storage device, a read only memory (ROM) device or another type of static storage device, a magnetic and/or optical recording memory device and its corresponding drive, and/or a removable form of memory, such as a flash memory. 
         [0038]    Although  FIGS. 3A and 3B  show example components of line card  300 , in other implementations, line card  300  may include fewer components, different components, differently arranged components, or additional components than depicted in  FIGS. 3A and 3B . Additionally or alternatively, one or more components of line card  300  may perform the tasks described as being performed by one or more other components of line card  300 . 
         [0039]      FIG. 4A  is a diagram illustrating rack of  110  with installed line cards according to an implementation described herein.  FIG. 4B  is a diagram illustrating a side view of rack  110  and depicts air flow in rack  110 , with installed line cards  300 , according to the first implementation described herein. As shown in  FIGS. 4A and 4B , line cards  300  are installed with front connectors  330  located in the area of front panel  112 . As a result of angled sections  318 , which provide a recessed area in bottom portion  314 , an opening  410  is created between a first line card and a second line card mounted below the first line card. 
         [0040]    The height of opening  410  may be determined based on the length and angle of angled section  318 . The width of opening  410  may extend substantially the width of rack  110 . Opening  410  allows entry air flow  130  to enter an area between cookie sheet frame  310  of a first line card and a PCB  340  of a second line card, which is mounted below the first line card in rack  110 . When entry air flow  130  enters the area, the cool air may cool components  350  of the second line card. After cooling air components  350 , the air may proceed to exit the area through opening  216  and/or exhaust fan  218  of backplane  114 . 
         [0041]      FIGS. 5A and 5B  are diagrams illustrating a line card  500  according to a second implementation described herein.  FIG. 5A  depicts a three-dimensional view of line card  500 .  FIG. 5B  depicts a side view of rack  110  and depicts air flow in rack  110 , with installed line cards  500 , according to the second implementation described herein. As shown in  FIGS. 5A and 5B , line card  500  may include a cookie sheet frame  510 , mounting hardware  320 , front connectors  330 , and PCB  340 . 
         [0042]    Cookie sheet frame  510  may include a metal frame for providing structural stability to PCB  340  and front connectors  330 . Cookie sheet frame  510  may have a width that extends substantially the width of front panel  112 , so that line card  500  fits inside front panel  112  and may be mounted onto front panel  112  via mounting area  215 . Cookie sheet frame  510  may have a depth substantially the depth of chassis frame  210 , so that line card  500  fits inside rack  110  and so that a connector  212  of backplane  114  connects to a back connector (not shown in  FIGS. 5A and 5B ) of PCB  340 . Cookie sheet frame  510  may provide partial or complete EM shielding to PCB  340  and/or to front connectors  330 . 
         [0043]    As shown in  FIG. 5B , cookie sheet frame  510  may include an extended top portion  512 , a front portion  514 , and a bottom portion  516 . Extended top portion  512  may extend in a direction away from front connectors  330 , so that when line card  500  is installed in rack  110 , the extended top portion contacts the bottom portion of the cookie sheet frame of a line card installed above line card  500 . Extended top portion  512  may include openings  520 . In one implementation, openings  520  may be of equal size and distributed evenly across substantially all of extended top portion  512 . In another implementation, openings  520  may not all be of equal size, and/or may not be distributed evenly, and/or may not be distributed across all of extended top portion  512 . 
         [0044]    Extended top portion  512  may shield line card  500  from EM interference. Extended top portion  512  of cookie sheet frame  510  of line card  500 , together with bottom portion  516  of cookie sheet frame  510  of line card  500 , bottom portion  516  of cookie sheet frame  510  of a line card installed above line card  500 , and side panels of rack  110 , may form a Faraday cage around PCB  340  of line card  500 , thus protecting PCB  340  from external EM radiation. 
         [0045]    Openings  520  may render extended top portion  512  transparent to air flow and not transparent to EM interference. In other words, openings  520  may be large enough to allow entry air flow  130  to pass through extended top portion  512  and small enough to prevent EM radiation of particular frequencies to pass through extended top portion  512 . Openings  520  may be smaller than a wavelength of any EM radiation that is to be prevented from penetrating extended top portion  512 . For example, openings in the range of 1-3 mm in diameter may block EM radiation in the GHz range. 
         [0046]    Front portion  514  may include mounting hardware  320 . Mounting hardware  320  may include, for example, screws to mount line card  500  using mounting area  215 . Bottom portion  516  may include an angled section  518 . Angled section  518  may provide a recessed area that may create an opening  530  between line card  500  and another line card mounted below line card  500 . Opening  530  may allow entry air flow  130  to enter, through openings  520  of extended top portion  512 , the area above the PCB of the line card mounted below line card  500  and cool components mounted on the PCB of the line card mounted below line card  500 . 
         [0047]    Front connectors  330  may provide electrical and/or optical connectors to cables that may provide electrical and/or optical connections to other electronic devices (e.g., other line cards mounted on rack  110  or line cards mounted in another rack). The number of front connectors  330  included in line card  500  may depend on a size of rack  110  and line card  500  and may be maximized to take up most of the area of front portion  514  of cookie sheet frame  510 . For example, for a standard 19 inch rack, connectors  330  may include 48 connectors, in two rows of 24. 
         [0048]    PCB  340  may provide a structurally stable substrate for mounting electrical and/or optical components of line card  500  and may include electrical and/or optical connections between the electrical and/or optical components. PCB  340  may include one or more components  350 . 
         [0049]    Although  FIGS. 5A and 5B  show example components of line card  500 , in other implementations, line card  500  may include fewer components, different components, differently arranged components, or additional components than depicted in  FIGS. 5A and 5B . Additionally or alternatively, one or more components of line card  500  may perform the tasks described as being performed by one or more other components of line card  500 . 
         [0050]      FIGS. 6A and 6B  are diagrams illustrating a line card  600  according to a third implementation described herein.  FIG. 6A  depicts a three-dimensional view of line card  600 .  FIG. 6B  depicts air flow across line card  600 , according to the third implementation described herein. As shown in  FIGS. 6A and 6B , line card  600  may include a cookie sheet frame  610 , mounting hardware  320 , front connectors  330 , and PCB  340 . 
         [0051]    Cookie sheet frame  610  may include a metal frame for providing structural stability to PCB  340  and front connectors  330 . Cookie sheet frame  610  may have a width that extends substantially the width of front panel  112 , so that line card  600  fits inside front panel  112  and may be mounted onto front panel  112  via mounting area  215 . Cookie sheet frame  610  may have a depth substantially the depth of chassis frame  210 , so that line card  600  fits inside rack  110  and so that a connector  212  of backplane  114  connects to a back connector (not shown in  FIGS. 6A and 6B ) of PCB  340 . Cookie sheet frame  610  may provide partial or complete EM shielding to PCB  340  and/or to front connectors  330 . 
         [0052]    Cookie sheet frame  610  may include an extended top portion  612 , a front portion  614 , and a bottom portion  616 . Extended top portion  612  may extend in a direction away from front connectors  330 , so that when line card  600  is installed in rack  110 , extended top portion  612  contacts bottom portion  616  of the cookie sheet frame of a line card installed above line card  600 . Extended top portion  612  may include openings  620 . 
         [0053]    Extended top portion  612  may shield line card  600  from EM interference. Extended top portion  612  of cookie sheet frame  610  of line card  600 , together with bottom portion  616  of cookie sheet frame  610  of line card  600 , bottom portion  616  of cookie sheet frame  610  of a line card installed above line card  600 , and side panels of rack  110 , may form a Faraday cage around PCB  340  of line card  600 , thus protecting PCB  340  from external EM radiation. 
         [0054]    Openings  620  may render extended top portion  612  transparent to air flow and not transparent to EM interference. In other words, openings  620  may be large enough to allow entry air flow  130  to pass through extended top portion  612  and small enough to prevent EM radiation of particular frequencies to pass through extended top portion  612 . Openings  620  may be smaller than a wavelength of any EM radiation that is to be prevented from penetrating extended top portion  612 . 
         [0055]    Extended top portion  612  may include an increased density area  630 . Increased density area  630  may include an area with an increased density of openings  620 . Increased density area  630  may correspond to a location of component  350  (for example, a heat generating component) mounted on PCB  340 . As shown in  FIG. 6B , the increased density of the openings in increased density area  630  may allow increased air flow  640 , of entry air flow  130 , to flow through the location corresponding to component  350  (for example, a heat generating component), causing heat generating component  350  to be cooled at a higher rate than other areas of PCB  340 . While  FIGS. 6A and 6B  depict a single increased density area  630  aligned with a particular component  150 , line card  600  may include multiple increased density areas  630 . For example, line card  600  may include a particular increased density area  630  aligned with each particular component  350  that is determined to need increased air flow. 
         [0056]    Exhaust fan  218  may be aligned with increased density area  630  to allow more air to flow over component  350  and pull air out of rack  110 . While  FIG. 6B  depicts a single exhaust fan  218  aligned with a single increased density area  630 , if line card  600  includes multiple increased density areas  630 , rack  110  may include multiple exhaust fans  218 . For example, rack  110  may include a particular exhaust fan  218  aligned with each increased density area  630 . Additionally or alternatively, opening  216  may be aligned with increased density area  630  to allow more air to flow over component  350  and exit rack  110  with less resistance (not shown in  FIG. 6B ). 
         [0057]    Front portion  614  may include mounting hardware  320 . Mounting hardware  320  may include, for example, screws to mount line card  600  using mounting area  215 . Bottom portion  616  may include an angled section  618 . Angled section  618  may provide a recessed area that may create an opening between line card  600  and another line card mounted below line card  600 . The opening may allow entry air flow  130  to enter, through openings  620  of extended top portion  612 , the area above PCB  340  of the line card mounted below line card  600  and cool components mounted on PCB  340  of the line card mounted below line card  600 . 
         [0058]    Front connectors  330  may provide electrical and/or optical connectors to cables that may provide electrical and/or optical connections to other electronic devices (e.g., other line cards mounted on rack  110  or line cards mounted in another rack). The number of front connectors  330  included in line card  600  may depend on a size of rack  110  and line card  600  and may be maximized to take up most of the area of front portion  614  of cookie sheet frame  610 . 
         [0059]    PCB  340  may provide a structurally stable substrate for mounting electrical and/or optical components of line card  600  and may include electrical and/or optical connections between the electrical and/or optical components. PCB  340  may include one or more components  350 . 
         [0060]    Although  FIGS. 6A and 6B  show example components of line card  600 , in other implementations, line card  600  may include fewer components, different components, differently arranged components, or additional components than depicted in  FIGS. 6A and 6B . Additionally or alternatively, one or more components of line card  600  may perform the tasks described as being performed by one or more other components of line card  600 . 
         [0061]      FIG. 7  is a diagram of a flow chart illustrating an example process for forming a line card according to an example implementation described herein. The process of  FIG. 7  may include selecting a height of an air flow opening (block  710 ). The height of opening  410  (or of opening  530 ) may be based on, for example, one or more of a height of connectors  330 , a spacing of holes in mounting area  215 , a spacing of line card connectors  212  of backplane  114 , and/or a particular air flow requirement. For example, a first line card with components that generate more heat may require more air flow and, therefore, a second line card with a higher opening may be installed above the first line card to allow for more air flow. 
         [0062]    An angled section of a line card may be formed based on the selected height (block  720 ). For example, angled section  318  (or angled sections  518  or  618 ) may be formed at an angle based on the selected height of opening  410  (or opening  530 ) and based on the desired length of angled section  318 . The angled section of the line card may be formed, for example, by deforming the cookie sheet frame of the line card. 
         [0063]    The process of  FIG. 7  may include determining whether to incorporate EM shielding (block  730 ). For example, a first line card may include components that are more sensitive to EM interference or may include components that generate EM interference and may, therefore, require EM shielding. A second line card may not need EM shielding or may include components that should not be shielded (e.g., wireless receivers or transmitters). 
         [0064]    If the determination is made that EM shielding is not to be incorporated (block  730 —NO), processing may proceed to installing front panel connectors and a PCB (block  790 , described below). If the determination is made that EM shielding is to be incorporated (block  730 —YES), an extended top section of the line card frame may be formed based on the depth of the angled section (block  740 ). For example, cookie sheet frame  510  may be fabricated with extended top section  512 . Cookie sheet frame  510  may be deformed to form extended top section  512 . 
         [0065]    Openings in the extended top section of the line card frame may be formed (block  750 ). For example, in one implementation, openings  520  may be drilled into extended top section  512  to form circular openings. In another implementation, openings  520  may be formed by a process other than drilling, such as via micromachining, laser cutting, or stamping. Using a process other than drilling may allow for forming openings with a shape other than a circular shape. For example, openings  520  may be formed as narrow slits. The size of the openings in the extended top section may be based on a wavelength of EM interference from which the line card is to be shielded. For example, the openings may be smaller than the wavelength of the highest frequency EM interference that is to be prevented from passing through the extended top section of the line card. 
         [0066]    The process of  FIG. 7  may include determining whether to incorporate concentrated air flow (block  760 ). For example, a first line card may include a component (e.g., a processor) at a particular location of PCB  340  that generates a significantly larger amount of heat than components at other locations of PCB  340 . Thus, it may be determined to incorporate concentrated air flow into the first line card. A second line card may include components distributed on PCB  340  in such a way that there is not a significant difference in heat generation at particular locations of PCB  340 . Thus, it may be determined that concentrated air flow need not be incorporated into the second line card. 
         [0067]    If the determination is made that concentrated air flow is not to be incorporated (block  760 —NO), processing may proceed to installing front panel connectors and a PCB (block  790 , described below). If the determination is made that concentrated air flow is to be incorporated (block  760 —YES), a location of heat generating components may be determined (block  770 ). For example, extended top section  620  may be aligned with PCB  340  to determine a region of extended top section  620  that corresponds to a location of a heat generating component located on PCB  340 . 
         [0068]    A density of openings at locations corresponding to locations of heat generating components may be increased (block  780 ). For example, increased density area  630  may be formed by forming additional openings  620 . The density of openings in increased density area  630  may be based on an amount of increased air flow that is to be achieved through increased density area  630 . For example, a first heat generating component may be aligned with a first increased density area and a second heat generating component, which generates less heat than the first heat generating component, may be aligned with a second increased density area with a smaller density of openings than the first increased density area. 
         [0069]    Front panel connectors and a PCB may be installed (block  790 ). Once the cookie sheet frame has been fabricated, the PCB and the front panel connectors may be installed to the cookie sheet frame. For example, openings for front panel connectors  330  may be formed in front section  314  (or front section  514  or  614 ) and front panel connectors  330  may be snapped into place (or attached with a fastener and/or an adhesive). The PCB may be attached to the cookie sheet frame with fasteners and/or an adhesive. 
       CONCLUSION 
       [0070]    The foregoing description provides illustration and description, but is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. 
         [0071]    For example, while a series of blocks has been described with respect to  FIG. 7 , the order of the blocks may be modified in other implementations. Further, non-dependent blocks may be performed in parallel. 
         [0072]    It will be apparent that aspects, as described above, may be implemented in many different forms of software, firmware, and hardware in the implementations illustrated in the figures. The actual software code or specialized control hardware used to implement these aspects should not be construed as limiting. Thus, the operation and behavior of the aspects were described without reference to the specific software code—it being understood that software and control hardware could be designed to implement the aspects based on the description herein. 
         [0073]    It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps, or components, but does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. 
         [0074]    Even though particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the invention. In fact, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. 
         [0075]    No element, act, or instruction used in the description of the present application should be construed as critical or essential to the invention unless explicitly described as such. Also, as used herein, the article “a” is intended to include one or more items. Where only one item is intended, the term “one” or similar language is used. Further, the phrase “based on,” as used herein is intended to mean “based, at least in part, on” unless explicitly stated otherwise.