U.S. patent application number 14/956484 was filed with the patent office on 2017-06-08 for thermal management of optical coupling systems.
The applicant listed for this patent is International Business Machines Corporation. Invention is credited to Mark D. Schultz, Shurong Tian.
Application Number | 20170160501 14/956484 |
Document ID | / |
Family ID | 58798225 |
Filed Date | 2017-06-08 |
United States Patent
Application |
20170160501 |
Kind Code |
A1 |
Schultz; Mark D. ; et
al. |
June 8, 2017 |
THERMAL MANAGEMENT OF OPTICAL COUPLING SYSTEMS
Abstract
An optical coupling system includes a substrate, an electronic
die comprising a plurality of coupling holes for passing light, an
optical element die attached to a bottom surface of the electronic
die, the electronic die attached to the substrate such that the
electronic die covers a cavity in the substrate and the optical
element die resides within the cavity of the substrate. The system
may also include a thermally conductive lid that covers and
contacts the electronic die and the substrate and has a coupling
aperture that enables light that passes through the coupling holes
to pass through the thermally conductive lid. The system may also
include an optical cable coupler comprising a coupling section that
laterally fits within the coupling aperture and a body section
disposed above the coupling section that is laterally larger than
the coupling section. A method for providing the above system is
also disclosed herein.
Inventors: |
Schultz; Mark D.; (Ossining,
NY) ; Tian; Shurong; (Mount Kisco, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
International Business Machines Corporation |
Armonk |
NY |
US |
|
|
Family ID: |
58798225 |
Appl. No.: |
14/956484 |
Filed: |
December 2, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 6/4245 20130101;
G02B 6/4267 20130101; G02B 6/4269 20130101; G02B 6/4272 20130101;
G02B 6/4242 20130101; G02B 6/4244 20130101 |
International
Class: |
G02B 6/42 20060101
G02B006/42; G02B 6/32 20060101 G02B006/32 |
Goverment Interests
GOVERNMENT RIGHTS
[0001] This invention was made with government support under
contract number H98230-13-D-0122 awarded by the United States
Department of Defense. The United States Government has certain
rights to this invention.
Claims
1. An optical coupling system comprising: a substrate having a
cavity formed on a top surface thereof; an electronic die
comprising a plurality of coupling holes for passing light; an
optical element die attached to a bottom surface of the electronic
die; the electronic die attached to the substrate such that the
electronic die at least partially covers the cavity and the optical
element die resides within the cavity of the substrate, the optical
element die comprising one or more optical elements for providing
light to, or receiving light from, the coupling holes; a thermally
conductive lid that covers and contacts at least a portion of the
electronic die and the substrate, the thermally conductive lid
comprising a coupling aperture that encompasses the plurality of
coupling holes and enables light that passes through the coupling
holes to pass through the thermally conductive lid; and an optical
cable coupler comprising a coupling section and a body section, the
coupling section laterally fitting within the coupling aperture and
the body section disposed above the coupling section and laterally
larger than the coupling aperture.
2. The system of claim 1, further comprising a heat sink thermally
attached to the thermally conductive lid.
3. The system of claim 2, further comprising a thermal interface
material disposed between the heat sink and the thermally
conductive lid.
4. The system of claim 1, wherein the thermally conductive lid is a
heat sink.
5. The system of claim 1, wherein the thermally conductive lid
comprises air cooling elements or water cooling elements.
6. The system of claim 1, wherein the electronic die comprises a
driving circuit.
7. The system of claim 6, wherein the driving circuit is
electrically connected with an electro-optical element on the
optical element die.
8. The system of claim 1, further comprising a lensing element.
9. The system of claim 8, wherein the lensing element reduces
divergence of a light beam that passes through a coupling hole.
10. The system of claim 1, further comprising a thermal interface
layer comprising a thermal interface material.
11. The system of claim 10, wherein the thermal interface layer is
disposed between the electronic die and the thermally conductive
lid.
12. The system of claim 10, wherein the thermal interface layer is
disposed between the electronic die and the substrate.
13. The system of claim 10, wherein the thermal interface layer is
disposed between the thermally conductive lid and the
substrate.
14. The system of claim 10, wherein the thermal interface layer is
disposed between the electronic die and the optical element
die.
15. The system of claim 10, wherein the thermal interface layer is
a pad.
16. The system of claim 10, wherein the thermal interface material
is a gel.
17. The system of claim 10, wherein the thermal interface material
is cured.
18. The system of claim 1, wherein the one or more optical elements
comprise a laser.
19. The system of claim 1, wherein the one or more optical elements
comprise a photodiode.
20. An optical coupling method comprising: providing a substrate
having a cavity formed on a top surface thereof; providing an
electronic die comprising a plurality of coupling holes for passing
light; connecting an optical element die to a bottom surface of the
electronic die; attaching the electronic die and the optical
element die to the substrate such that the electronic die covers
the cavity and the optical element die resides within the cavity of
the substrate, the optical element die comprising one or more
optical elements for providing light to, or receiving light from,
the coupling holes; covering the electronic die and the optical
element die with a thermally conductive lid that covers and
contacts at least a portion of the electronic die and the
substrate, the thermally conductive lid comprising a coupling
aperture that encompasses the plurality of coupling holes and
enables light that passes through the coupling holes to pass
through the thermally conductive lid; and optically coupling an
optical cable coupler to the one or more optical elements, the
optical cable coupler comprising a coupling section that laterally
fits within the coupling aperture and a body section disposed above
the coupling section that is laterally larger than the coupling
aperture.
Description
BACKGROUND OF THE INVENTION
[0002] The present invention relates generally to the field of
optical coupling systems, and more particularly to thermal
management in optical coupling systems.
[0003] Active optical elements such as electro-optic transceivers
often produce substantial thermal loads and are usually optically
coupled to large optical connectors which hinder access to cooling
elements such as heat sinks. Furthermore, the optical coupling
pathways between the active optical elements and the optical
connectors comprise materials that are thermally insulating and
reduce the ability to cool the active optical elements.
Additionally, the continued increase in channels carried on optical
fibers along with the potential for multicore fiber applications
increases the need for better thermal management in optical
coupling systems.
SUMMARY
[0004] As disclosed herein, an optical coupling system includes a
substrate having a cavity formed on a top surface thereof, an
electronic die comprising a plurality of coupling holes for passing
light, an optical element die attached to a bottom surface of the
electronic die, the electronic die attached to the substrate such
that the electronic die covers the cavity and the optical element
die resides within the cavity of the substrate. The optical element
die may comprise one or more optical elements for providing light
to, or receiving light from, the coupling holes. The system may
also include a thermally conductive lid that covers and contacts at
least a portion of the electronic die and the substrate and
comprises a coupling aperture that encompasses the plurality of
coupling holes and enables light that passes through the coupling
holes to pass through the thermally conductive lid. The system may
also include an optical cable coupler provided with a coupling
section that laterally fits within the coupling aperture and a body
section disposed above the coupling section that is laterally
larger than the coupling aperture.
[0005] One method corresponding to the above system includes:
providing a substrate having a cavity formed on a top surface
thereof, providing an electronic die comprising a plurality of
coupling holes for passing light, connecting an optical element die
to a bottom surface of the electronic die, attaching the electronic
die and the optical element die to the substrate such that the
electronic die covers the cavity and the optical element die
resides within the cavity of the substrate. The optical element die
may include one or more optical elements for providing light to, or
receiving light from, the coupling holes. The method may also
include covering the electronic die and the optical element die
with a thermally conductive lid that covers and contacts at least a
portion of the electronic die and the substrate. The thermally
conductive lid may include a coupling aperture that encompasses the
plurality of coupling holes and enables light that passes through
the coupling holes to pass through the thermally conductive lid.
The method may also include optically coupling an optical cable
coupler to the one or more optical elements, the optical cable
coupler provided with coupling section that laterally fits within
the coupling aperture and a body section disposed above the
coupling section that is laterally larger than the coupling
aperture.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a flowchart diagram depicting one example of an
electro-optic packaging method in accordance with at least one
embodiment of the present invention;
[0007] FIG. 2 is a perspective view drawing depicting one example
of an optical element die in accordance with at least one
embodiment of the present invention;
[0008] FIG. 3 is a perspective view drawing depicting one example
of an electronic die in accordance with at least one embodiment of
the present invention;
[0009] FIG. 4 is a perspective view drawing depicting one example
of a substrate in accordance with at least one embodiment of the
present invention;
[0010] FIG. 5 is a perspective view drawing depicting one example
of an electro-optic device in accordance with at least one
embodiment of the present invention;
[0011] FIG. 6 is a perspective view drawing depicting one example
of a lidded electro-optic device in accordance with at least one
embodiment of the present invention; and
[0012] FIG. 7 is a cross-sectional view depicting one example of an
optical coupling system in accordance with at least one embodiment
of the present invention.
DETAILED DESCRIPTION
[0013] The embodiments disclosed herein recognize that the optical
coupling pathways in optical coupling systems are thermally
insulating and reduce the ability to cool active elements (e.g.,
driving circuits and electro-optic transceivers) that produce
substantial thermal loads. Furthermore, the embodiments disclosed
herein recognize that reducing the coupling area in such systems
can improve the ability to cool the active elements that produce
substantial thermal loads. The embodiments disclosed herein also
recognize that long and/or narrow thermal paths within optical
coupling systems reduce the ability to cool the active elements
that produce substantial thermal loads and that short and/or broad
thermally conductive paths can improve the ability to cool the
active elements that produce substantial thermal loads.
[0014] Various embodiments will now be described in reference to
the Figures. For example, FIG. 1 is a flowchart diagram depicting
one example of an electro-optic packaging method 100 in accordance
with at least one embodiment of the present invention. As depicted,
the electro-optic packaging method 100 includes providing (110) one
or more optical element die, connecting (120) to an electronic die,
providing (130) a substrate, attaching (140) the electronic die to
the substrate, covering (150) with an apertured thermally
conductive lid, and coupling (160) to an optical cable coupler. The
electro-optic packaging method 100 enables forming an optical
coupling system with improved thermal cooling characteristics.
[0015] Providing (110) one or more optical element die includes
providing one or more die with one or more optical elements thereon
such as optical transmitters, receivers, or transceivers. The
optical elements may be electro-optic elements that convert an
electronic signal to an optical signal and/or an optical signal to
an electronic signal.
[0016] One example of a set of optical element die is depicted in
the perspective view drawing of FIG. 2 as optical die 200. As
depicted, optical die 200 include a transmitting die 200A, a
receiving die 200B, optical elements 210 and thermal solder pad(s)
220. The optical die 200 contain optical elements 210 that enable
transmitting and/or receiving optical signals such as data
modulated laser beams. In some embodiments, the optical die 200
comprises a semiconductor material such as GaAs.
[0017] The thermal solder pad 220 provides an external thermal
pathway for heat dissipation. In the depicted embodiment, the
thermal solder pad is disposed on the perimeter of the optical die
200 and (substantially completely) encompasses the optical elements
210. In addition to thermal solder pads, the optical die may
contain electronic solder pads (not shown) that provide an external
pathway for electrical power and electrical signals such as
transmit signals and receive signals. The thermal solder pad 220
and the electronic solder pads may be used to thermally,
electrically, and physically attach the optical element die to an
electronic die or substrate.
[0018] Referring again to FIG. 1, connecting (120) an electronic
die may include physically, electrically, and thermally connecting
an electronic die to the optical element die. The electronic die
may have one or more electronic circuits thereon such as receiving
circuits and/or driving circuits. The electronic circuits may be
electrically or otherwise operably connected with optical
(including electro-optical) elements on the optical element die.
The electronic die may also have one or more coupling holes for
passing light provided by, or received by, the optical elements on
the optical element die. The coupling holes may enable optical
elements on the optical element die to optically couple to external
elements such as fiber optic cables.
[0019] One example of an electronic die that can be connected with
an optical element die is depicted in FIG. 3. As depicted, the
electronic die 300 includes one or more coupling holes 310 for
passing light. In some embodiments, the electronic die comprises a
semiconductor material that is conducive to forming circuits
thereon such as driving (e.g., transmitting) circuits and receiving
circuits. Consequently, the electronic die 300 may have one or more
electronic circuits formed thereon such as driving circuits and
receiving circuits (not explicitly shown in FIG. 3). The various
circuits may be operably connected to optical elements (including
electro-optical elements) on one or more optical die 200 attached
to the electronic die 300.
[0020] Referring again to FIG. 1, providing (130) a substrate may
include providing a substrate with a cavity formed therein that is
sufficiently large enough to contain the optical element die. One
example of such a substrate is depicted in FIG. 4 as substrate 400.
As depicted, substrate 400 is provided with a cavity 410 and
connection areas 420. The cavity 410 may be sufficiently large
enough to contain the optical die 200. The connection areas 420 may
be sized and placed to contact the undersurface of the electronic
die 300 without overlapping with the optical die 200 that is
attached (e.g., soldered) to the undersurface of the electronic die
300. In some embodiments, the substrate 400 is also provided with
connection areas 420 on the bottom surface to facilitate connection
with a system board, a motherboard, or the like.
[0021] The connection areas 420 may be formed of a material of high
thermal and electrical conductivity. In some embodiments, the
connections areas are patterned (not shown) with signal traces and
pads that support the transfer of electrical signals (e.g., to/from
the electronic die 300) and thermal interface pads that support the
transfer of thermal energy. The thermal interface pads of the
connection areas 420 may conform to irregularities in the surfaces
that they contact in order to maximize heat transfer. For example,
the thermal interface pads of the connection areas 420 may be
formed of a pad material, a gel, or a paste. In some embodiments,
the thermal interface pads of the connection areas 420 are formed
of a cured material.
[0022] Attaching (140) the electronic die to the substrate may
include physically and thermally attaching the electronic die to
the substrate in a manner that places the optical element die
within the cavity of the substrate. One example of an electronic
die that is attached to a substrate having such a cavity is
depicted in FIG. 5 as the electro-optic device 500. As depicted,
the electro-optic device 500 includes the substrate 400 with the
electronic die 300 placed over the cavity 410 (not shown in FIG. 5)
such that the optical die 200 (not shown in FIG. 5) that is
attached to the electronic die 300, fits within the cavity 410. A
thermal interface layer 510 and the connection areas 420 (not seen
in FIG. 5, see FIG. 7) may improve the thermal conductivity between
the electronic die 300 and the other elements of the the
electro-optic device 500.
[0023] Covering (150) with an apertured thermally conductive lid
may include covering the electronic die with a thermally conductive
lid that has an aperture that is just sufficiently large enough to
encompass the coupling holes so that light that passes through the
coupling holes will not be blocked (e.g., give manufacturing and
coupling tolerances). Furthermore, the contact area between the
thermally conductive lid and the electronic die may be
substantially maximized.
[0024] The thermally conductive lid may be formed of a material of
high thermal conductivity (e.g., >180 W/m K) such as aluminum,
copper or diamond. In some embodiments, the thermally conductive
lid is a heat sink that incorporates air cooling or water cooling
elements. In other embodiments, the thermally conductive lid is in
thermal communication with (e.g., in contact with) a heat sink. One
example of an electronic die covered with a thermally conductive
lid is depicted in FIG. 6 as a lidded electro-optic device 600. As
depicted, the lidded electro-optic device 600 includes the
electo-optic device 500 covered with a thermal lid 610 that has an
aperture 620 formed therein that enables light to pass through the
coupling holes 310.
[0025] Referring again to FIG. 1, coupling (160) to an optical
cable coupler may include coupling to an optical cable coupler that
has a coupling section that is sufficiently narrow to fit within
the aperture of the apertured thermally conductive lid. One example
of such an optical cable coupler is depicted in the cross sectional
view of FIG. 7 which depicts an optical coupling system 700.
[0026] As depicted in FIG. 7, the optical coupling system 700
includes substrate 400 with cavity 410 formed therein that contains
the optical die 200A and 200B. The optical die 200A and 200B are
attached to the backside of the electronic die 300. The thermally
conductive lid 610 covers and contacts at least a portion of the
electronic die 300 and the substrate 400. The thermally conductive
lid 610 includes a coupling aperture 620 that encompasses the
coupling holes 310 (see FIG. 3) and enables light that passes
through the coupling holes 310 to pass through the thermally
conductive lid 610. An optical cable coupler 710 includes a
coupling section 720 that fits laterally within the coupling
aperture 620, a body section 730 disposed above the coupling
section that is laterally larger than the coupling aperture, and a
heat sink 750 that provides cooling capabilities to the lid 610 and
potentially the optical cable coupler 710 as well. In some
embodiments, the heat sink 750 is thermally attached to the
thermally conductive lid and opposing sidewalls of the body section
of the optical cable coupler 710.
[0027] The optical cable coupler 710 may also include various
mechanical elements (not shown) which enable connecting the optical
cable coupler 710 to an optical cable (not shown) and thereby
enable optical coupling between the optical elements on the optical
die 200 and the optical cable. The various mechanical elements may
hold a coupling surface (not shown) of the optical cable adjacent
to, and in contact with, a coupling surface 740 of the body section
730. Index matching fluids may also be used to fill in gaps between
coupling surfaces and improve optical coupling.
[0028] In some embodiments, the optical coupling system 700
includes one or more lensing elements (not shown) disposed between
optical elements on the optical die 200 and the coupling section
720 of the optical cable coupler 710. The lensing elements may
reduce the divergence of, or focus, light beams that pass through
the coupling holes 310. In some embodiments, the lensing elements
are disposed within, or adjacent to, the coupling holes 310.
[0029] One of skill in the art may appreciate that the narrowed
coupling section 720 of the optical coupler 710 relative to the
body section 730 and coupling surface 740 provides for an increased
contact area with the electronic die 300 and an improved thermal
path through the thermally conductive lid 610 to the heatsink 750.
The increased contact area may significantly improve the thermal
performance of the optical coupling system 700 relative to
conventional coupling systems that do not have a narrowed coupling
section 720 along with a narrowed coupling aperture 620. In some
embodiments, the diameter of the narrowed coupling section 720 is
less than 80 percent of the width of the body section 730. In
certain embodiments, the diameter of the narrowed coupling section
720 is less than 60 percent of the width of the body section
730.
[0030] The embodiments disclosed herein also recognize that, due to
laser divergence, the optical cable coupler 710 must be close to
the coupling holes 310 (not shown in FIG. 7) on the electronic die
300. The embodiments disclosed herein also recognize that the
potentially high heat loads from the active elements on the optical
element die 200 and the electronic die 300 require short and broad
thermal pathways (e.g., as provided by the thermally conductive lid
610) to cooling elements such as the heat sink 750. Providing short
and broad thermal pathways enables the optical coupling system 700
to maintain reasonable operating temperatures for optical elements
on the optical element die 200 (e.g., VCSEL lasers) and electronic
circuits on the electronic die 300 such as driving circuits and
receiving circuits.
[0031] It should be noted that this description is not intended to
limit the invention. On the contrary, the embodiments presented are
intended to cover some of the alternatives, modifications, and
equivalents, which are included in the spirit and scope of the
invention as defined by the appended claims. Further, in the
detailed description of the disclosed embodiments, numerous
specific details are set forth in order to provide a comprehensive
understanding of the claimed invention. However, one skilled in the
art would understand that various embodiments may be practiced
without such specific details.
[0032] Although the features and elements of the embodiments
disclosed herein are described in particular combinations, each
feature or element can be used alone without the other features and
elements of the embodiments or in various combinations with or
without other features and elements disclosed herein.
[0033] This written description uses examples of the subject matter
disclosed to enable any person skilled in the art to practice the
same, including making and using any devices or systems and
performing any incorporated methods. The patentable scope of the
subject matter is defined by the claims, and may include other
examples that occur to those skilled in the art.
[0034] Such other examples are intended to be within the scope of
the claims.
* * * * *