Patent Publication Number: US-2022240410-A1

Title: Opto-electric module

Description:
TECHNICAL FIELD 
     The present invention relates to an opto-electric module, and more particularly, to a mounting structure for an opto-electric module. 
     BACKGROUND ART 
     In opto-electric modules provided with a large number of electronic components and optical components (for example, see PTL 1 and 2), as the speed of transmission signals increases, the heat generated by each component continues to increase. 
     CITATION LIST 
     Patent Literature 
     PTL 1: International Publication No. WO 2015/012213 
     PTL 2: International Publication No. WO 2014/156962 
     SUMMARY OF INVENTION 
     Technical Problem 
     The present invention has been devised in the light of the above points, and one objective thereof is to provide an opto-electric module that can be cooled efficiently. 
     Solution to Problem 
     To solve the problem described above, one aspect of the present invention is an opto-electric module comprising: an opto-electric hybrid device provided with an electronic circuit and an optical circuit driven by the electronic circuit, the opto-electric hybrid device having a first surface and a second surface on an opposite side from the first surface, such that an electrical input and output unit with respect to the electronic circuit and an optical input and output unit with respect to the optical circuit are disposed on the first surface; an interface substrate which is disposed near the first surface of the opto-electric hybrid device and which is provided with an electrical interconnect coupled to the electrical input and output unit, an optical interconnect coupled to the optical input and output unit, an electrical interface which is connected to the electrical interconnect and also connectible to an external electrical interconnect, and an optical interface which is connected to the optical interconnect and also connectible to an external optical interconnect; and a heat-dissipating member disposed in contact with the second surface of the opto-electric hybrid device. 
     Also, another aspect of the present invention is an opto-electric module in which, in the above aspect, the second surface of the opto-electric hybrid device is a flat surface with no steps. 
     Also, another aspect of the present invention is an opto-electric module in which, in the above aspect, the heat-dissipating member contacts the entirety of the flat second surface. 
     Also, another aspect of the present invention is an opto-electric module in which, in the above aspect, the opto-electric hybrid device is provided with an optical waveguide disposed perpendicularly or obliquely to the first surface, and the optical input and output unit of the opto-electric hybrid device is an end of the optical waveguide near the first surface. 
     Also, another aspect of the present invention is an opto-electric module in which the above aspect further comprises an optical coupling unit that optically couples the optical input and output unit of the opto-electric hybrid device to the optical interconnect of the interface substrate. 
     Also, another aspect of the present invention is an opto-electric module in which, in the above aspect, the optical coupling unit is a mirror formed on an end face of the optical interconnect. 
     Also, another aspect of the present invention is an opto-electric module in which, in the above aspect, the optical coupling unit is a mirror built inside or mounted on the surface of the interface substrate. 
     Also, another aspect of the present invention is an opto-electric module in which, in the above aspect, the mirror is a condensing mirror. 
     Also, another aspect of the present invention is an opto-electric module in which, in the above aspect, the optical coupling unit includes a transparent medium of a solid or a gel filling a space between the optical input and output unit of the opto-electric hybrid device and the end face of the optical interconnect of the interface substrate. 
     Advantageous Effects of Invention 
     According to the present invention, an opto-electric module can be cooled efficiently. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross section view of an opto-electric hybrid device that is one element constituting an opto-electric module according to an embodiment of the present invention; 
         FIG. 2  is a cross section view of an opto-electric hybrid device according to another example that may be used as a structural element in an opto-electric module according to an embodiment of the present invention; 
         FIG. 3  is a cross section view of an opto-electric module according to an embodiment of the present invention; and 
         FIG. 4  is a cross section view of an opto-electric module according to another embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described in detail and with reference to the drawings. 
       FIG. 1  is a cross section view of an opto-electric hybrid device  100  that is one element constituting an opto-electric module according to an embodiment of the present invention. The opto-electric hybrid device  100  is provided with a substrate  102 , a semiconductor laser  103 , an optical modulator  104 , a first optical waveguide  105 , a second optical waveguide  106 , a grating coupler  107 , a driver IC  108 , and an electrical interconnect  109 . The electrical interconnect  109  includes a via  109   a  for providing electrical continuity between a first surface  100 A (in  FIG. 1 , the upper surface) of the opto-electric hybrid device  100  and the surface of the substrate  102 , and an electrical interconnect  109   b  formed on the surface of the substrate  102 .  FIG. 1  is a view of the opto-electric hybrid device  100  from the cross-sectional direction and therefore a single set of the semiconductor laser  103 , the optical modulator  104 , the first optical waveguide  105 , the second optical waveguide  106 , the grating coupler  107 , and the electrical interconnect  109  is illustrated, but a plurality of sets of the semiconductor laser  103 , the optical modulator  104 , the first optical waveguide  105 , the second optical waveguide  106 , the grating coupler  107 , and the electrical interconnect  109  may be arranged in the direction perpendicular to the cross section in  FIG. 1 . Additionally, the opto-electric hybrid device  100  may also be provided with a plurality of driver ICs  108 . 
     The substrate  102  is a silicon (Si) substrate or a silicon on insulator (SOI) substrate, and the optical modulator  104 , the first optical waveguide  105 , the grating coupler  107 , and the electrical interconnect  109   b  are formed on the surface thereof. The optical modulator  104  is optically connected to the grating coupler  107  through the first optical waveguide  105 . The optical modulator  104 , the first optical waveguide  105  (for example, an Si waveguide), and the grating coupler  107  can be formed on the surface of the substrate  102  using silicon photonics technology. The back surface of the substrate  102  (the surface on the opposite side from the surface on which the optical modulator  104 , the first optical waveguide  105 , the grating coupler  107 , and the electrical interconnect  109   b  are formed) is a flat surface with no steps, and forms a second surface  100 B of the opto-electric hybrid device  100 . 
     Additionally, the semiconductor laser  103  and the driver IC  108  are mounted on the surface of the substrate  102 . The semiconductor laser  103  is disposed near one end of the first optical waveguide  105  such that emitted light therefrom enters the first optical waveguide  105 . The driver IC  108  is mounted on the substrate  102  using a connecting electrode  115  (such as a ball grid array (BGA), for example) electrically connecting an electric terminal (not illustrated) on the driver IC  108  side and the electrical interconnect  109   b  on the substrate  102  side to each other. The driver IC  108  is connected to the semiconductor laser  103 , the optical modulator  104 , and the via  109   a  through the electrical interconnect  109   b,  and is configured to drive the semiconductor laser  103  and the optical modulator  104  on the basis of an electrical signal inputted from the via  109   a.    
     In addition, the second optical waveguide  106  is formed on the substrate  102  standing upright or obliquely with respect to the substrate  102 . The inclination angle of the second optical waveguide  106  with respect to the substrate  102  is in the range from 0° to 10°, for example. The end of the second optical waveguide  106  on the substrate  102  side is positioned directly above the grating coupler  107 , while the opposite end of the second optical waveguide  106  away from the substrate  102  is positioned on the first surface  100 A of the opto-electric hybrid device  100 . 
     Note that the second optical waveguide  106  erected on the substrate  102  as above can be produced by using a narrow UV light beam from above the substrate  102  to irradiate a UV-curing resin applied to have a predetermined thickness on the substrate  102 , and thereby cure the UV-curing resin in a columnar shape only where the UV light beam passed through. In a configuration in which the second optical waveguide  106  is erected and formed obliquely with respect to the substrate  102 , to keep unintended portions of the UV-curing resin from being cured due to oblique reflections of the UV light beam off the surface of the substrate  102 , a UV absorption layer (not illustrated) for absorbing the UV light beam and suppressing reflections is preferably formed in advance on the surface of the substrate  102 . 
     In the opto-electric hybrid device  100  configured as above, an electrical signal for operating the driver IC  108  is inputted into the via  109   a  through the first surface  100 A of the opto-electric hybrid device  100 . The driver IC  108  drives the semiconductor laser  103  and the optical modulator  104  on the basis of the electrical signal. Light emitted from the semiconductor laser  103  is modulated by the optical modulator  104  and then diffracted by the grating coupler  107  to convert the light path to a direction substantially perpendicular to the substrate  102 , and the light passes through the second optical waveguide  106  and is outputted from the first surface  100 A of the opto-electric hybrid device  100 . In this way, electrical signals and optical signals in the opto-electric hybrid device  100  are inputted and outputted at the first surface  100 A. 
       FIG. 2  is a cross section view of an opto-electric hybrid device  101  according to another example that may be used as a structural element in an opto-electric module according to an embodiment of the present invention. In  FIG. 2 , structural elements that are the same as the structural elements in  FIG. 1  described above are denoted with the same signs. The opto-electric hybrid device  101  is provided with a light-receiving element (photodiode)  110  underneath the second optical waveguide  106  on the substrate  102  instead of the semiconductor laser  103 , the optical modulator  104 , the first optical waveguide  105 , and the grating coupler  107  in the opto-electric hybrid device  100  of  FIG. 1 . 
     The light-receiving element  110  can be formed directly on the surface of the substrate  102  using silicon photonics technology, or chip-type light-receiving element  110  produced separately may be mounted on the substrate  102 . The light-receiving element  110  is connected to the driver IC  108  through the electrical interconnect  109   b.  The driver IC  108  may also be a transimpedance amplifier (TIA) for performing IV (current-to-voltage) conversion of a photoelectrically converted current signal outputted from the light-receiving element  110 . 
     In the opto-electric hybrid device  101  having the configuration of  FIG. 2 , an optical signal supplied from an external optical interconnect (not illustrated in  FIG. 2 ) is inputted into the second optical waveguide  106  through the first surface  100 A of the opto-electric hybrid device  100  and is incident on the light-receiving element  110 . The light-receiving element  110  photoelectrically converts the optical signal to generate a current signal. The current signal is sent to the driver IC  108  through the electrical interconnect  109   b,  and the driver IC  108  IV-converts the current signal to generate and output a voltage signal. The electrical signal from the driver IC  108  passes through the via  109   a  and is outputted from the first surface  100 A of the opto-electric hybrid device  100 . In this way, like the opto-electric hybrid device  100  of  FIG. 1 , electrical signals and optical signals in the opto-electric hybrid device  101  are inputted and outputted at the first surface  100 A. 
     Note that the configuration of an opto-electric hybrid device is not limited to the configurations illustrated in  FIGS. 1 and 2 . For example, an opto-electric hybrid device provided with both an optical transmission function like the opto-electric hybrid device  100  of  FIG. 1  and an optical reception function like the opto-electric hybrid device  101  of FIG.  2  may be used as a structural element of an opto-electric module according to an embodiment of the present invention. 
       FIG. 3  is a cross section view of an opto-electric module  10  according to an embodiment of the present invention. An opto-electric module  10  is provided with the opto-electric hybrid device  100  described with reference to  FIG. 1 , an interface substrate  200 , and a heat-dissipating member  300 . The opto-electric module  10  may also be provided with the opto-electric hybrid device  101  described with reference to  FIG. 2  or an opto-electric hybrid device that includes optical transmission and reception functions through a combination of the configurations of both the device  100  of  FIG. 1  and the device  101  of  FIG. 2  instead of the opto-electric hybrid device  100  of  FIG. 1 . Note that the following description relates to a configuration in which the opto-electric module  10  is provided with the opto-electric hybrid device  100  of  FIG. 1 . 
     The interface substrate  200  is provided with an electrical interconnect  202 , an optical interconnect  203 , an electrical interface  204 , and an optical interface  205 . The interface substrate  200  can be configured using a rigid substrate or a flexible substrate. The electrical interconnect  202  is a single-layer or multilayer electrical interconnect, and is electrically connected to the electrical interface  204 . At least a portion of the electrical interconnect  202  is exposed on the surface (the upper surface in  FIG. 3 ) of the interface substrate  200 , thereby allowing an electrical connection between the exposed portion and the opto-electric hybrid device  100 . The electrical interface  204  may also be a pin grid array (PGA) for example, and by inserting the PGA into an IC socket  401  provided on a motherboard  400 , the interface substrate  200  can be mechanically and electrically connected to the motherboard  400 . 
     The optical interconnect  203  may be an optical fiber or polymer optical waveguide, and is laid out on the surface of the interface substrate  200  on the same side where the portion of the electrical interconnect  202  is exposed (that is, the upper surface in  FIG. 3 ). An optical coupling unit  203   a  (described later) is formed or disposed on one end of the optical interconnect  203 , and the optical interface  205  (optical connector) is connected to the other end. The optical interface  205  can be connected to a corresponding external optical connector or the like (not illustrated). 
     In the opto-electric module  10  of  FIG. 3 , the opto-electric hybrid device  100  is mounted on the interface substrate  200  with the first surface  100 A facing the interface substrate  200  (flip chip mounting) side. As described above with reference to  FIG. 1 , one end of the via  109   a  and one end of the second optical waveguide  106  are positioned on the first surface  100 A of the opto-electric hybrid device  100 . The via  109   a  of the opto-electric hybrid device  100  is connected to the electrical interconnect  202  exposed on the surface of the interface substrate  200  through a connecting electrode  250  such as a BGA, for example. Additionally, the second optical waveguide  106  is optically connected to the optical interconnect  203  of the interface substrate  200  through the optical coupling unit  203   a.    
     The optical coupling unit  203   a  can be configured as a total internal reflection mirror produced by forming the end face of the optical interconnect  203  (an optical fiber or polymer optical waveguide) obliquely with respect to the optical axis, for example. The reflective surface of the total internal reflection mirror  203   a  may be any of planar, spherical, or aspherical. The reflective surface of the total internal reflection mirror  203   a  preferably is spherical or aspherical because the mirror  203   a  thereby functions as a condensing mirror, such that light emitted from the second optical waveguide  106  of the opto-electric hybrid device  100  is condensed by the mirror  203   a  and coupled to the optical interconnect  203  of the interface substrate  200  with high efficiency. The optical coupling unit  203   a  may also be a mirror installed on the interface substrate  200  near the end of the optical interconnect  203 . 
     As above, the opto-electric hybrid device  100  is flip-chip mounted on the interface substrate  200 , and consequently the second surface  100 B of the opto-electric hybrid device  100  (that is, the flat surface with no steps on the back surface of the substrate  102  forming the opto-electric hybrid device  100 ) faces the opposite side away from the interface substrate  200 . The heat-dissipating member  300  is disposed on the second surface  100 B of the opto-electric hybrid device  100 . The heat-dissipating member  300  is a metal (copper or aluminum) or ceramic member (a heatsink) shaped to have a heat-dissipating surface (in  FIG. 3 , the upper surface) with a large surface area. The surface of the heat-dissipating member  300  near the opto-electric hybrid device  100  (in  FIG. 3 , the lower surface) is configured as a flat surface that closely contacts the second surface  100 B of the opto-electric hybrid device  100  (that is, the flat back surface of the substrate  102 ). A grease or adhesive having a high thermal conductivity may also be provided between the contacting surfaces. 
     In the opto-electric module  10  according to the present embodiment, by causing the heat-dissipating member  300  to contact the second surface  100 B of the opto-electric hybrid device  100  over a wide area (namely, the entire back surface of the substrate  102 ), heat generated in the electronic circuits and optical circuits (for example, the driver IC  108  and the semiconductor laser  103 ) and other heat-generating components inside the opto-electric hybrid device  100  is transmitted to the heat-dissipating member  300  efficiently. For this reason, a larger amount of heat from the opto-electric hybrid device  100  can be dissipated through the heat-dissipating member  300 , and the cooling performance of the opto-electric module  10  can be raised. 
       FIG. 4  is a cross section view of an opto-electric module  11  according to another embodiment of the present invention. In  FIG. 4 , structural elements that are the same as the structural elements in  FIG. 3  described above are denoted with the same signs. The opto-electric module  11  is provided with the opto-electric hybrid device  100  described with reference to  FIG. 1 , an interface substrate  201 , and a heat-dissipating member  300 . Like the opto-electric module  10  described above, the opto-electric module  11  may also be provided with the opto-electric hybrid device  101  described with reference to  FIG. 2  or an opto-electric hybrid device that includes optical transmission and reception functions through a combination of the configurations of both the device  100  of  FIG. 1  and the device  101  of  FIG. 2  instead of the opto-electric hybrid device  100  of  FIG. 1 . Note that the following description relates to a configuration in which the opto-electric module  11  is provided with the opto-electric hybrid device  100  of  FIG. 1 . 
     The interface substrate  201  is provided with an electrical interconnect  202 , an optical interconnect  203 , an electrical interface  204 , and an optical interface  205 . Of these, the configurations of the electrical interconnect  202 , the electrical interface  204 , and the optical interface  205  are the same as the interface substrate  200  in  FIG. 3 . The optical interconnect  203  of the interface substrate  201  is embedded in the interface substrate  201 . Furthermore, as illustrated in  FIG. 4 , the interface substrate  201  includes a hole  206 , and one end of the embedded optical interconnect  203  is positioned in a side wall of the hole  206 . A mirror  207  is disposed near the end of the optical interconnect  203  inside the hole  206 . Also, the opto-electric hybrid device  100  is mounted on the interface substrate  201  such that the first surface  100 A faces the interface substrate  201  side similarly to  FIG. 3 , and also such that the end of the second optical waveguide  106  is positioned over the hole  206 . 
     For example, the mirror  207  may be a mirror obtained by mirror-polishing a metal member or a mirror obtained by forming a metal film or a dielectric multilayer film on the surface of a plastic member. The reflective surface of the mirror  207  may be any of planar, spherical, or aspherical. The reflective surface of the mirror  207  preferably is spherical or aspherical because the mirror  207  thereby functions as a condensing mirror, such that light emitted from the second optical waveguide  106  of the opto-electric hybrid device  100  is condensed by the mirror  207  and coupled to the optical interconnect  203  of the interface substrate  201  with high efficiency. 
     The inside of the hole  206  of the interface substrate  201  and also the space above the hole  206  and below the bottom surface of the opto-electric hybrid device  100  mounted on the interface substrate  201  are filled with a transparent medium  208  containing a solid or a gel. When the opto-electric module  11  is actually used, the opto-electric module  11  may be immersed in an inert liquid to cool the heat-generating IC and the like efficiently (immersion cooling). By filling the space from the light output unit on the opto-electric hybrid device  100  side to the light input unit on the interface substrate  201  side with the solid or gel transparent medium  208 , even if the opto-electric module  11  is immersion-cooled, the inert liquid does not intrude into the space and affect the propagation of light. Consequently, the opto-electric module  11  can be immersion-cooled without degrading the optical characteristics of the opto-electric module  11 . 
     Also, in the opto-electric module  11  according to the present embodiment, the configuration and arrangement of the opto-electric hybrid device  100  and the heat-dissipating member  300  are the same as the opto-electric module  10  of  FIG. 3 . Consequently, in the opto-electric module  11  according to the present embodiment, like the opto-electric module  10  of  FIG. 3 , by causing the heat-dissipating member  300  to contact the second surface  100 B of the opto-electric hybrid device  100  over a wide area (namely, the entire back surface of the substrate  102 ), heat generated in the electronic circuits and optical circuits (for example, the driver IC  108  and the semiconductor laser  103 ) and other heat-generating components inside the opto-electric hybrid device  100  is transmitted to the heat-dissipating member  300  efficiently. For this reason, a larger amount of heat from the opto-electric hybrid device  100  can be dissipated through the heat-dissipating member  300 , and the cooling performance of the opto-electric module  11  can be raised. 
     The above describes embodiments of the present invention, but the present invention is not limited thereto, and various modifications are possible within a scope that does not depart from the gist of the present invention. 
     REFERENCE SIGNS LIST 
     
         
           10  opto-electric module 
           11  opto-electric module 
           100  opto-electric hybrid device 
           101  opto-electric hybrid device 
           100 A first surface 
           100 B second surface 
           102  substrate 
           103  semiconductor laser 
           104  optical modulator 
           105  first optical waveguide 
           106  second optical waveguide 
           107  grating coupler 
           108  driver IC 
           109  electrical interconnect 
           109   a  via 
           109   b  electrical interconnect 
           110  light-receiving element 
           115  connecting electrode 
           200  interface substrate 
           202  electrical interconnect 
           203  optical interconnect 
           203   a  optical coupling unit, total internal reflection mirror 
           204  electrical interface 
           205  optical interface 
           206  hole 
           207  mirror 
           208  transparent medium 
           250  connecting electrode 
           300  heat-dissipating member 
           400  motherboard 
           401  IC socket