Abstract:
A structure for electronics package for module packaging and a method of manufacturing a single chip module (SCM) or multi-chip module (MCM) for an opto-electronic package having an improved structure for heat dissipation and testing is disclosed. The optical transceivers are ideally located on a surface opposite to the electrical portion of the package. Variations on the module package include pluggable or socketed optical transceivers and card pacers that allow for the installation of multiple optical transceivers.

Description:
FIELD OF THE INVENTION 
     This invention relates to single (SCM) and multi-chip (MCM) modules. Specifically, it relates to optoelectronic modules having an optical transceiver to increase signal bandwidth density to and from the modules as well as the interconnect distance in devices ranging from high-end processors, switch and router chips that require large input/output (I/O) dataflow. 
     BACKGROUND OF THE INVENTION 
     Electrical interconnects exhibit limitations in scaling to even higher bandwidth density in tern-s of the maximum data rate per line, the interconnect distance, power and crosstalk. Optical interconnects may overcome these limitations. Parallel opto-electronic modules exist that transform several electrical signals into optical signals or vice-versa. However, the currently available modules are large in their size and the interconnect density at the electrical side is limited to the density that is available in standard printed circuit board technology. In order to enable optical technology to emerge in areas very close to the processor, the interconnect density between the processor and the optical module will have to be increased. 
     In SCM or MCM technology, the processor or switch chip is mounted onto a carrier substrate. This carrier does exhibit a large interconnect density and serves several functions. First it offers a high density interconnect between electronic components mounted on the carrier surface. Furthermore, the carrier is the interconnect medium between the processor(s) and the printed circuit board (PCB). In order to utilize the high interconnect density potential of optical technology, the optoelectronic elements have to be attached to the carrier substrate. Several approaches to bring optics to the SCM or MCM are described in the prior art. 
     In U.S. Pat. No. 6,512,861 B2 by Intel, the optoelectronic package is mounted on to the printed circuit board with embedded optical waveguides and a mirror is used to redirect the light. 
     In U.S. Pat. No. 6,611,635 B1 by Fujitsu, a variety of embodiments are disclosed where either a mirror is used to redirect the light, or the opto-electronic element is directly connected to the waveguide. 
     U.S. Pat. No. 6,439,895 B1 by Intel describes a socket compatible with optical and electrical interconnects in that it has an opening in the center to let optical signals pass through. 
     U.S. Published Patent Application No. 2006/0078248 A1 by NEC describes an opto-electronic package where the alignment between the board and the optical waveguides is achieved through pins. 
     SUMMARY OF THE INVENTION 
     It is an aspect of an embodiment of the present invention to provide a method to integrate optoelectronics onto a single chip module (SCM) or a multi-chip module (MCM) in order to increase the signal bandwidth density to and from the chip as well as the interconnect distance. 
     It is another aspect of an embodiment of the present invention to provide an optoelectronic module that is easier to lest than prior art devices. 
     It is yet another aspect of an embodiment of the present invention to provide a module package where the electrical and optical components are decoupled which will give the optics better stability. 
     It is yet a further aspect of an embodiment of the present invention to provide a short electrical via connection between the processors and the optoelectronic module to mitigate electrical signal interference. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross sectional view according to an embodiment of the present invention. 
         FIG. 2  is a cross sectional view according to a second embodiment of the present invention. 
         FIG. 3  is a cross sectional view according to a third embodiment of the present invention. 
         FIG. 4  is a cross sectional view according to a fourth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described in terms of the embodiment illustrated in  FIG. 1 .  FIG. 1  shows an opto-electronic module or package  100  having processors  101 . The processors  101  can be any of those known in the art. Preferably, the processors  101  are high-end processing chips or switch and router chips. Connected to the processors  101  is ball grid array  109 . Ball grid array  109  connects the processors  101  to carrier substrate  102 . The carrier substrate is connected to the printed circuit board  103  by ball grid arrays  109  and  104 . Those skilled in the art will recognize that the present invention may use connectors other than ball grid arrays without departing from the scope of the present invention. Having the processors  101  above the printed circuit board  103  allows for the electronics heat to be dissipated upwards while the heat generated by optical transceiver  105  is dissipated downwards. Optical transceiver  105  is installed in circuit board openings  110 . This allows for greater heat dissipation for the optical transceiver  105 . Optical transceiver  105  is connected to waveguide connector  106 . Free standing flexible connector  107  is attached to the optical transceiver  105  and to the laminated flexible waveguide layers  108  to destinations outside the module  100 . It should be noted the optical signals in waveguide layers  108  is parallel to the carrier substrate  102 . Additionally, the optical transceiver is perpendicular to the electrical elements or processors  101 . The connectors and attachments in this embodiment are exemplary only. Those skilled the art will recognize that other types of connectors, attachments and waveguides may be substituted without departing from the scope of the instant invention. The embodiment shown in  FIG. 1  provides ease of testing the electrical components separately from the optical components before assembly on the printed circuit board  103 . Additionally, the layout illustrated in  FIG. 1  allows for a smaller optical transceiver with reduced dimensions. 
       FIG. 2  is a variation of the embodiment of  FIG. 1 .  FIG. 2  shows an optoelectronic module or package  200  having processors  201 . The processors  201  are attached to a carrier substrate  202  via ball grid array  210 . Printed circuit board  203  and carrier substrate  202  are attached via ball grid arrays  204  and  210 . Adjacent to ball grid array  204  is a socket connector  205 . Socket connector or plug  205  allows for the use of socketed or pluggable optical transceivers. It is desirable to use a common transceiver design for both card edge and MCM applications because of the ease of attaching the optical transceiver components to the circuit board  203 . This may require additional space on the underside of the package so that the optical transceiver can be inserted into its electrical receptacle Additionally, this embodiment has waveguide connector  207 , free standing flexible connector  208 , circuit board openings  21   1  and laminated flexible waveguide layers  209  which are substantially similar to those discussed in reference to  FIG. 1  above. The connectors and attachments in this embodiment are exemplary only. Those skilled the art will recognize that other types of connectors, attachments and waveguides may be substituted without departing from the scope of the instant invention. 
       FIG. 3  shows another variation of the embodiment discussed in reference to  FIG. 1 . In this embodiment, the opto-electronic module or package  300  has been modified to include a card spacer  307 , a Z-axis axis connector  305 , and an electrical receptacle  306 . This spacing element  307  can accommodate multiple optical transceivers  308 , providing a spatial transform from the wiring density of the module substrate  302  to the density required from the optical transceiver  308 . The assembly steps are modified so that the electrical receptacle  306  and card spacer  307  are both attached to the module package  300 , then the pluggable optics  308  are inserted, followed by connection of the optical waveguide components  309 - 311 . The ball grid arrays  304 ,  312  and circuit board openings  313  are substantially similar to those discussed in reference to  FIG. 1 . The connectors and attachments in this embodiment are exemplary only. Those skilled the art will recognize that other types of connectors, attachments and waveguides may be substituted without departing from the scope of the instant invention. 
       FIG. 4  is another variation on the embodiment discussed in reference to  FIG. 1 . In this embodiment, the opto-electronic module or package  400  has been modified with a free standing flex with excess slack  411 . It may be desirable to provide excess slack in the waveguide/free standing flex for several reasons to allow for movement in package  400 . The flex  411  can be shaped into a serpentine fashion, and optionally tacked down to the underside of the printed circuit board  403  using a small bead of epoxy or similar adhesive. Further, this embodiment contains the processors or electrical elements  401 , a carrier substrate  402 , a printed circuit board  403 . The processors  401  are connected to the carrier substrate and printed circuit board via ball grid arrays  404  and  412 . Similar to the configuration of  FIG. 3 , the optical transceiver  408  is installed in electrical receptacle  406  with Z-axis connector  406  and card spacer  407 . Waveguide connector  409  is connected to flex  411  installed in the laminated flexible waveguide layers  410  to destinations outside the optoelectronic module  400 . As in all the embodiments, the waveguide layer  410  guides the optical signal parallel to the carrier substrate  402  or printed circuit board  403  and the printed circuit board  402  has circuit board openings  413 . The connectors and attachments in this embodiment are exemplary only. Those skilled the art will recognize that other types of connectors, attachments and waveguides may be substituted without departing from the scope of the instant invention. 
     The invention has been described in detail with particular reference to certain exemplary embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.