Abstract:
A pluggable electronic module is provided that has an electronic component and a module body enclosing the electronic component. The module body has a first surface and a second surface. The first surface has a first area substantially parallel to the second surface and a second area that defines a non-zero angle with respect to the first area. The second area contacts a thermal sink to dissipate heat generated by the electronic component. The pluggable electronic module has a reduced insertion force in comparison with conventional pluggable electronic modules.

Description:
FIELD OF THE INVENTION 
     The invention relates to electronic modules and more specifically to pluggable electronic modules. 
     BACKGROUND OF THE INVENTION 
     Electronic component manufacturers often work together to develop a multi-source agreement (MSA) that describes guidelines for manufacturing an electronic module. For example, there exists an MSA for dense wavelength division multiplexing (DWDM) pluggable transceiver modules and for XFP (10 gigabit small form factor pluggable module) devices. With reference to  FIGS. 1A and 1B , a pluggable transceiver module  10  constructed for DWDM communications includes a top module body  14 , bottom module body  18 , a transmit port  22 , a receive port  26 , and a plurality of heat transfer fins  30 . Electronic components (not shown), which are concealed by top module body  14  and bottom module body  18  can include optical transmitters, optical receivers, and various electronic circuits and devices, which provide the functionality of the pluggable transceiver module  10 . The transmit port  22  and the receive port  26  facilitate optical communication between the module  10  and other modules or components of a communications system. The ports  22 ,  26  are coupled through optical communication paths to the electronic components within the bottom module body  18 . During operation, the electronic components within bottom module body  18  generate heat, which is removed through top module body  14  to permit normal operation of the transceiver module  10 . The heat transfer fins  30  extend from the top module body  14  and help to dissipate the heat generated by the electronic components within bottom module body  18 . In other transceiver modules (not shown), the heat transfer fins  30  are not present. Instead, the top module body  14  is relatively flat in the region where the heat transfer fins  30  are typically located. 
     In some communications applications, multiple pluggable modules  10  are grouped together in an enclosure. The enclosure typically includes printed circuit boards (PCBs), circuitry, and other devices, which are part of an optical communications system. The top surface of the enclosure often is a heat sink. As the modules  10  are inserted into the enclosure, the heat transfer fins  30  make contact with the underside of the heat sink to establish a thermal path to dissipate the heat generated by the electronic components within the bottom module body  18 . The friction between the heat transfer fins  30  and the underside of the heat sink during insertion is undesirable because it increases the force necessary to insert and remove the pluggable modules  10 . 
     What is needed is a pluggable electronic module that has reduced friction during insertion and provides enhanced heat dissipation. 
     SUMMARY OF THE INVENTION 
     One object of the present invention is to provide a pluggable electronics module that interfaces with a fixed heat sink. Another object of the invention is to provide a pluggable electronics module that requires a reduced insertion force. Yet another object of the invention is to provide a pluggable electronics module that provides thermal transfer capabilities without stressing a printed circuit board (PCB) interconnect system. 
     In one aspect, the invention relates to a pluggable electronic module having an electronic component and a module body enclosing the electronic component. The module body has a first surface and a second surface. The first surface has a first area substantially parallel to the second surface and a second area that defines a non-zero angle with respect to the first area. The second area contacts a thermal sink to dissipate heat generated by the electronic component. 
     In another aspect, the invention relates to a pluggable electronic module having an electronic component and a means for dissipating heat generated by the electronic component. The means for dissipating heat substantially encloses the electronic component and has a first surface and a second surface. The first surface has a first area substantially parallel to the second surface and a second area that defines a non-zero angle with respect to the first area. The second area contacts a thermal sink. 
     In yet another aspect, the invention relates to a method of cooling an electronic module. The method includes receiving the electronic module in an opening of a thermal sink. The electronic module has a module body that encloses the electronic component. The module body has a first surface and a second surface. The first surface has a first area substantially parallel to the second surface and a second area that defines a non-zero angle with respect to the first area. The method also includes providing a thermal path between the second area and the thermal sink, and dissipating heat generated by the electronic component through the thermal path. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and further advantages of this invention may be better understood by referring to the following description in conjunction with the accompanying drawings, in which like numerals indicate like structural elements and features in various figures. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
         FIG. 1A  is an isometric view of one embodiment of a prior art pluggable electronic module. 
         FIG. 1B  is a side view of the module of  FIG. 1A . 
         FIG. 2A  is an isometric view of an embodiment of a pluggable electronic module mounted to a PCB mount rail constructed according to the principles of the invention. 
         FIG. 2B  is a side view of the module and PCB mount rail of  FIG. 2A . 
         FIG. 3  is an exploded view of a carrier used in a communications system. 
         FIG. 4A  is an exploded view of another embodiment of a pluggable electronic module and a portion of the carrier of  FIG. 3 . 
         FIG. 4B  is a side view of the pluggable electronic module and carrier of  FIG. 4A . 
         FIG. 5A  is an isometric view of an embodiment of a heat sink for use with the module of  FIG. 1A . 
         FIG. 5B  is a side of the heat sink of  FIG. 5B . 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIGS. 2A and 2B , an embodiment of a pluggable electronic module  100  constructed according to the principles of the invention includes a module body assembly  102  having a top module body  104  and a bottom module body (not shown), electronic components (not shown), a transmit port  112 , and a receive port  116 . The top module body  104  is parallel and sealed to the bottom body with an internal electromagnetic compliant (EMC) gasket that prevents electromagnetic radiation from escaping from the body assembly  102 . Electronic components within the module body assembly  102  provide the functionality of the pluggable electronics module  100  and generate heat, which is removed through the top module body  104  during operation to maintain satisfactory module performance. 
     The top module body  104  includes a first surface  120  (top) and a second surface  124  (bottom). The bottom surface  124  makes contact with the top of the bottom module body to form an EMC seal. The top surface  120  has a first area  128 , a second area  132 , and a third area  136 . The first area  128  is approximately parallel to the bottom surface  124 . The second area  132  extends at a non-zero angle θ with respect to the first area  128  towards the front of the pluggable electronics module  100 . The first area  128  and the second area  132  meet along a line P 1  at a predetermined distance D 1  from the front of the module body  104 . The distance D 1  is dependent upon the angle θ. The third area  136  is also substantially parallel to the bottom surface  124 . The second area  132  and the third area  136  meet along a line P 2  at a predetermined distance D 2  from the front of the module body  104 . In one embodiment, the predetermined distance D 2  is dependent upon the angle θ. In the illustrated embodiment, the predetermined distance D 2  is 9.5 mm. The locations of the first area  128 , the second area  132 , and the third area  138  are determined according to the location of the electronic components within the module body  104  to achieve a desired heat dissipation characteristic. 
     The module body assembly  102  can be constructed from a metal, such as aluminum. Alternatively, the module body assembly  102  can be constructed from any material that conforms to predetermined thermal requirements, such as die cast magnesium or zinc. Additionally, the top module body  104  can be constructed of aluminum and the bottom module body can be constructed of aluminum or a metal coated plastic. Constructing the bottom module body of metal coated plastic provides a path for ground currents to travel during operation. The ground currents aid in preventing noise waves from penetrating the module body assembly  102 . 
     In one exemplary configuration, the electronic module  100  is used as part of a carrier  34  as shown in  FIG. 3 . The carrier  34  includes a PCB  38 , a plurality of PCB mount rails  42 , an interface panel  46  having a plurality of openings  50  and a heat sink  54  having a topside  55  and an underside  56 . The heat sink  54  is attached to the PCB  38  at the various attachment points  58 . The heat sink  54  does not move relative to the PCB  38  once it is attached to the PCB  38 . Each electronic module  100  is inserted though a respective opening  50  in the interface panel  46 . Each of the PCB mount rails  42  receives one of the pluggable electronics modules  100 . The rear of the pluggable electronics module  100  engages an electrical connector that electrically couples the electronics module  100  to the PCB  38 . As the pluggable electronics module  100  is inserted, the first area  128  of the top surface  120  of the module body  104  does not make contact with the underside  56  of the heat sink  54 . The force required to insert the electronic module  100  into the carrier  34  is reduced because there is less friction to overcome. As the second area  132  of the top surface  120  passes through the opening  50 , a distance between the second area  132  and the underside  56  of the heat sink  54  decreases according to the angle θ and the increasing insertion length. The minimum separation between the module body  104  and the underside  56  of the heat sink  54  is achieved when the third area  136  of the top surface  120  enters the opening  50 . 
     Once the electronic module  100  is fully inserted, the PCB mount rail  42  assists in maintaining the electronic module  100  in place. However, a gap exists between the second area  132  of the first surface  120  and the underside  56  of the heat sink  54 . The gap limits the transfer of heat from the electronic module  100  to the heat sink  54 . 
     It is desirable to provide a thermal path from the module body  104  to the heat sink  54 . The thermal path increases heat transfer and improves the performance of the electronic module  100 . To provide a thermal path, a thermally conductive member is placed between the second area  132  of the top surface  120  and the underside  56  of the heat sink  54 . 
     An exploded view of a portion of the heat sink  54 , the thermally conductive member, and the pluggable electronics module  100  is shown in  FIGS. 4A and 4B . The thermally conductive member is a thermal pad  144 , which is configured to make contact with a portion of the second area  132  of the top surface  120 . The thermal pad  144  can have a variety of shapes and sizes depending on the application. In one embodiment, the thermal pad  144  has a thickness T of 3.5 mm. The thermal pad  144  is constructed of a thermally conductive material, such as a silicone elastomer or a thermally conductive foam. In one embodiment, the thermal pad  144  is constructed of SARCON HRD manufactured by Fujipoly America Corporation of Carteret, N.J. The thermal pad  144  is compressible and provides a force to the first surface  120 . The force is a function of the angle θ and the volume of the thermal pad  144 . The force is counteracted by the PCB mount rail  42  to maintain the location of the pluggable electronics module  100  in the carrier  34 . 
     A thermal spacer  148  is used in combination with the thermal pad  144  to provide a thermal path from the pluggable electronics module  100  to the heat sink  54 . The thermal spacer  148  has a first surface  152  that contacts the underside  56  of the heat sink  54  and a second surface  156  that is manufactured at an angle β, which is approximately equal to the angle θ of the pluggable electronics module  100 . The second surface  156  has a groove  160  that has a complimentary shape configured to receive the thermal pad  144 . The thermal spacer  148  is constructed of the same material as the heat sink  54  or a different material depending on the desired thermal result. 
       FIGS. 5A &amp; 5B  show an embodiment of an individual heat sink  164  that is used with the pluggable module  100  in a system when the larger heat sink  55  can not be used. The individual heat sink  164  includes a top panel  170 , a back panel  174  and a pair of side panels  178 A,  178 B. The top panel  170  and the side panels  178 A,  178 B form a generally C-shaped cross-section. The heat sink  164  also has an opening  182  opposite the back panel  174  that receives the pluggable electronics module  100 . Multiple heat transfer fins  186  extend from the top panel  170 . The side panels  178 A,  178 B and the top panel  170  are shaped complementary to the pluggable electronics module  100 . The individual heat sink  164  has an overall height H 1  that is combination of a height H 2  of the side walls  178 A,  178 B and a height H 3  of the heat transfer fins  186 . The height H 2  of the side panels  178 A,  178 B changes relative to the distance from the back panel  174 . At a predetermined point P 3 , the height H 2  of the side panels  178 A,  178 B begins to increase according to the angle β, which is complementary to the angle θ of the pluggable electronics module  100 . Similarly, at the point P 3  the height H 3  of the heat transfer fins  186  begins to decrease according to the angle β. The change in the heights H 2  and H 3  provide minimal separation or no separation between the top surface  120  of the electronics module  100  and the underside of the top panel  170  of the heat sink  164  when the module  100  is fully inserted. A PCB mount rail  42  (not shown) can be included on the inside faces of the side panels  178 A,  178 B and the back panel  174  to maintain the registration of the module  100  within the individual heat sink  164 . 
     During assembly, an EMC gasket (not shown) is inserted between a PCB  38  and the bottom perimeter of the individual heat sink  164 . The EMC gasket and the heat sink  164  create an EMC enclosure for the pluggable module  100 . One advantage of this configuration is the conduction of heat generated during the operation of the module  100  into copper planes of the PCB  38 . Another advantage is the reduction in the cost of cooling the module  100  and providing EMC shielding for the module. The reduction results from constructing the heat sink  164  of a single die cast part that guides the module  100 , seals out noise, and provides a convective heat dissipation surface that contacts the second area  132  of the top module body  104  of the pluggable module  100 . 
     While the invention has been shown and described with reference to specific preferred embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the following claims. For example, the thermal spacer  148  can be constructed as an integral part of the heat sink  54 .