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Description  |
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BACKGROUND OF THE INVENTION
This invention, relates in general, to optoelectronic devices and, more
particularly, to molded waveguides.
As the amount of information, as well as the speed of transferring
information between electronic components increases, optoelectronic
techniques or methods used for this transfer become more important. For
example, in some high speed computers, optoelectronic techniques are used
for clock distribution, thereby enabling standard electronic components to
be timed correctly so as to manage the transfer of information more
efficiently. However, at present, use of optoelectronic techniques has
several major drawbacks or problems, such as being complex, inefficient,
costly, and generally not suitable for high volume manufacturing. Thus, as
the amount of information and the speed at which this information needs to
be transferred, a need for a structure and a fabrication method that
allows for efficient and cost effective manufacturing, as well as use of
optoelectronic methods and optoelectronic devices will be required.
Conventionally, waveguides are manufactured by a combination of
photolithographic and etching processes. For example, a conventional
waveguide is fabricated by applying a suitable optical material onto an
interconnect substrate, such as a printed board. A photoresist material is
then applied onto the optical material and subsequently patterned by a
photolithographic process. The pattern defined by the photolithographic
process is subsequently transferred into the optical material by an
etching process that removes exposed portions that are not covered by the
photoresist material. The circuit board with the etched pattern is
subsequently cleaned, which removes the residual photoresist material and
leaves a resultant optical layer in place on the circuit board. As
described above, conventional fabrication of optical layers used for
waveguides using this sequence of events is not only complicated and
expensive, but also does not lend themselves to high volume manufacturing.
It can be readily seen that conventional methods for manufacturing
waveguides have severe limitations. Also, it is evident that conventional
processes that are used to fabricate waveguides are not only complex and
expensive but also not amenable to high volume manufacturing. Therefore, a
method and a structure that lends itself for making waveguides and
integrating these waveguides into a circuit board is highly desirable.
SUMMARY OF THE INVENTION
Briefly stated, a method and an article for making a molded optical
interconnect is provided. An interconnect substrate having a major surface
is provided. A plurality of electrical tracings is disposed on the major
surface of the interconnect substrate with the plurality of electrical
tracings having a contact apparatus to receive and to transmit electrical
signals. An optoelectronic module having an optical surface and a photonic
device that is operably mounted and coupled to the plurality of electrical
tracings. A molded optical portion having a core region with a first end
and a cladding region is positioned with the first end of the core region
being adjacent and operably coupled to the optical surface of the
optoelectronic module so as to operably couple the first end of the core
region to the optical surface of the integrated circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a greatly enlarged simplified sectional view of a molded optical
interconnect;
FIG. 2 illustrates an enlarged simplified partially exploded view of an
optoelectronic module;
FIG. 3 illustrates a highly enlarged simplified sectional view of an
optoelectronic integrated circuit;
FIG. 4 is an enlarged simplified perspective view of an embodiment of the
molded optical interconnect; and
FIG. 5 is an enlarged simplified perspective view of another embodiment of
the molded optical interconnect.
DETAILED DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates an enlarged simplified sectional view of an embodiment
of a molded optical interconnect 100 having optoelectronic modules 123 and
124. It should be understood that molded optical interconnect 100 is a
sectional view, thereby enabling molded optical interconnect 100 to
continue into and out of FIG. 1. Further, molded optical interconnect 100
may also be expanded across FIG. 1, as well as incorporating other
standard electronic components in the overall design of molded optical
interconnect 100. Also, it should be understood that molded optical
interconnect 100, as shown in FIG. 1, is only a simplified illustration,
thus allowing a wide range of design modifications to be incorporated into
molded optical interconnect 100.
Molded optical interconnect 100 is made of several components or elements,
such as an interconnect substrate 101 with a surface 141, a plurality of
electrical tracings 102, a molded optical portion 116 illustrated as
having a first optical portion 117, a second optical portion 118, a core
region 119, and a cladding region 120 that surrounds core region 119,
optical modules 123 and 124 having optical surfaces 125 and 126,
respectively, and connecting apparatus 129 illustrated as a leadframe
member 130 and a pin 131 from a variety of pin connecting structures.
Generally, interconnect substrate 101 is made of any suitable interconnect
substrate, such as a circuit board (PCB), a printed wireboard (PWB), a
ceramic interconnect substrate, or the like. However, in a preferred
embodiment of the present invention, interconnect substrate is a printed
wireboard. As shown in FIG. 1, the plurality of electrical tracings 102
are disposed on and throughout interconnect substrate 101 by any suitable
method. The plurality of electrical tracings 102 are further illustrated
by electical tracings 103 through 112 shown in a variety of levels or
layers in interconnect substrate 101. Electrical tracings 103, 104, 105,
and 106 serve as bonding pads to electrically and mechanically couple
optical modules 124 and 123, respectively, to the plurality of electrical
tracings 102. Further, it should be understood that complexities
illustrated in interconnect substrate 101 are not necessary for the
practice the present invention. For example, interconnect substrate 101
can have a single level of the plurality of electrical tracings 102.
Electrical coupling of molded optical interconnect 100 to other electronic
components is achieved by any suitable method. As shown by connecting
apparatus 129, two such methods are illustrated, i.e., electrical tracing
107 is electrically coupled to leadframe member 130 and electrical tracing
113 is electrically coupled to pin 131, thereby enabling electrical
signals to be inputted and outputted through connecting apparatus 129, as
well as operably coupling optical modules 123 and 124.
Optical modules 123 and 124 can be any suitable optoelectronic device, such
as an integrated circuit having photonic capabilities, optoelectronic
interface, or the like.
Generally, optoelectronic modules 123 and 124 communicate or pass signals
by both electrically coupling and optically coupling optoelectronic
modules 123 and 124 with interconnect substrate 101. Electrical
communication is achieved by any suitable method, such as sockets and
pins, bump bonding, formed leadframe members, and the like. As shown in
FIG. 1, electrical communication from optoelectronic modules 123 and 124
to interconnect substrate 101 ifs accomplished by bumps 132, 133, 134, and
135 that are conductive, thereby electrically and mechanically coupling
optoelectronic modules 123 and 124 to electrical traces 106, 105, 104, and
103, respectively, of the plurality of electrical traces 102. Electrical
coupling of optoelectronic modules 123 and 124 to the plurality of
electrical traces 102 of interconnect substrate 101 enables electrical
signals to be inputted through connecting apparatus 129 from outside
electronic components and systems, such as other electronic boards, other
integrated circuits, and the like to affect optoelectronic modules 123 and
124. Alternatively, electrical coupling of optoelectronic modules 123 and
124 to interconnect substrate 102 enables optical signals that enter
optoelectronic modules 123 and 124 that are subsequently converted to
electrical signals to be sent to the plurality of electrical traces 102 of
interconnect substrate 101 through conductive bumps 132, 133, 134, and 135
and subsequently into electrical traces 106, 105, 104, and 103 which are
further routed and outputted through connecting apparatus 129 to effect
outside electronic components, such as other electronic boards, other
IC's, other electronic systems, and the like.
As illustrated in FIG. 1, optoelectronic modules 123 and 124 each have
optical surfaces 125 and 126, respectively, that enable light signals,
illustrated by arrows 140, to enter and leave optical modules 123 and 124,
thereby optically linking optical modules 123 and 124 to core region 119
of molded optical portion 116.
Further, as shown in FIG. 1, optoelectronic modules 123 and 124 are
optically linked by core region 119, thus enabling optical communication
between optoelectronic modules 123 and 124. Also it will be understood
that while FIG. 1 illustrates optical linking of optoelectronic modules
123 and 124, many more optoelectronic modules can be located throughout
molded optical interconnect 100 that are optically linked, as well as
other standard electronic components. It will be further understood that
IC's can be mounted throughout molded optical interconnect 101 and
electrically coupled to the plurality of electrical traces 102 of
interconnect substrate 101, thereby incorporating optical communication
and electrical coupling with standard electronic components.
By optically linking optical modules 123 and 124, as well as other
optoelectronic modules, information is communicated between optical
modules 123 and 124 at a much faster speed than if the information was
routed electrically through the plurality of electrical traces 102,
thereby enhancing speed of communication between optical modules 123 and
124, enhancing speed of communication between other electronic components
and optoelectronic components, and reducing electromagnetic interference
(EMI).
Molded optical portion 116 is made by any suitable molding or overmolding
process. Generally, molded optical portion 116 is made including first
optical portion 117 and second optical portion 118. Fabrication of optical
portion 116 is achieved by placing interconnect substrate 101 into a
molding system (not shown). A molding system delineates a channel,
illustrated in FIG. 1 as finished core region 119, and openings 142 and
143 having exposed bonding pads or electrical traces 103, 104, 105, and
106 of the plurality of electrical traces 102, thereby allowing optical
modules 123 and 124 to be electrically and mechanically mounted to
interconnect substrate 101 in openings 142 and 143. Further, molded
optical portion 116 is made so that the channel is aligned or positioned
for eventual optical coupling between optical surfaces 125 and 126 of
optoelectronic modules 123 and 124 and finished core region 119, thereby
providing optical communication between optical modules 123 and 124.
Typically, a molding compound or molding material is injected into the
molding system and on surface 141 of interconnect substrate 101, thereby
forming first optical portion 117 with the groove and openings 142 and
143.
The molding compound injected into the mold is made of optically
transparent materials, such as polymers, epoxies, plastics, polyimides, or
the like that are selected to be transparent at a desired wavelength of
light. Generally, refractive indexes of these optically transparent
materials range from 1.4 to 1.7. However, in a preferred embodiment of the
present invention, the refractive indexes of the optically transparent
materials range from 1.54 to 1.58.
Processing conditions for these molding materials or molding compounds
range from 22.0 to 200.0 degrees Celcuis for molding temperatures and
200.0 to 2,200 pounds per square inch for molding pressures. A subsequent
curing process such as ultraviolet light treatment, temperature
treatments, or the like is done which permanently transfers intricacies or
negative images of the mold into first optical portion 117.
Once the curing processes are complete, the molding system and first molded
optical portion 117 attached to interconnect substrate 101 is exposed and
subsequently removed from the molding system.
Generally, second optical portion 118 is made in a similar manner and
simultaneously with first optical portion 117, thereby enabling rapid and
automated manufacturing of molded optical portion 116 with cladding region
120 surrounding core region 119. Optical portion 117 with attached
interconnect substrate 101 is further processed by applying an optical
media such as an epoxy, a polyimide, a plastic, or the like to the grooves
formed in first optical portion 117. Subsequently, first optical portion
117 and second optical portion 118 are adhered or joined together to form
optical portion 116 having core region 119 surrounded by cladding region
120.
Typically, the optical media fills the grooves to form core region 119 and
adheres second optical portion 118 to first optical portion 117.
Application of second optical portion 120 to first optical portion 117
completes cladding region 120 which surrounds core region 119. However, it
should be understood that light signals 140 traveling through core region
119 are capable of traveling to their destinations without second optical
portion 120 being applied to first optical portion 117. However, it should
be further understood by not completing or surrounding cladding region
around core region 119 optical signals are not as effectively transferred
and guided through core region 119.
FIG. 2 illustrates a simplified partial exploded pictorial view of a
portion of optoelectronic module 200. A molded optical waveguide 201 is
electrically coupled to standard electronic components on interconnect
board 206 by any suitable method, such as wire bonding, tab bonding, bump
bonding, or the like. However, while any suitable method for coupling
molded optical waveguide 201 to interconnect substrate 206 are
appropriate, wire bonding and leadframe bonding are specifically
illustrated in FIG. 2, as being the most preferred in the present
invention. By way of example, a wire bond 216 operably couples tab 207 to
bonding pad 217 and lead frame members 211, 212 are operably coupled to
bonding pads 213, 214, respectively. Further, it should be understood that
optoelectronic module 200 is one example of many methods of making optical
electronic module 200 that are capable of being used in the present
invention.
Molded optical waveguide 201 having a plurality of core regions 203 is
fitted with photonic components 208 such as a phototransmitter or laser
202, a photodetector or photodiode 205, or a combination of both lasers
and detectors. Alternatively, array 204 is mounted on waveguide 202 which
can include a variety of different photonic components.
Photonic components 208 are mounted to molded optical waveguide 201 in a
manner that individual working portions, indicated by arrow 240, of
photonic components 208 are aligned to individual core regions of the
plurality of core regions 203 of waveguide 201, thus providing maximum
light transmission through the individual core regions of the plurality of
core regions 203 of waveguide 201.
For example, laser 202 is mounted to tab 207 and a tab (not shown) by an
electrical and mechanical connection 209. Typically, electrical and
mechanical connection 209 is achieved by any suitable method, such as
conductive bumps, e.g., solder bumps, gold bumps, conductive epoxy bumps,
or the like. By accurately mounting laser 202 to molded optical waveguide
201 and making electrical and mechanical connections 209, light
transmission from a working portion of laser 209 is guided through one of
the core regions of the plurality of core regions 203 of molded optical
waveguide 201.
Molded optical waveguide 201 including photonic components 208 is attached
to interconnect board 206 by any suitable method such as adhering, press
fitting, molding, or the like. However, in a preferred embodiment of the
present invention, an epoxied adhesive is applied to interconnect board
206 in an approximate location where molded optical waveguide 201 and
interconnect board 206 are to be bonded or joined. Waveguide 201 is then
placed onto the adhesive by an automated system such as a robotic arm,
thereby providing accurate placement and orientation of waveguide 201.
Electrical coupling of standard electronic components on interconnect board
206 through optical components 208 is illustrated by wire bond 216 from
bonding pad 217 to tab 207, as well as by leadframe members 211 and 212
being mounted and electrically coupled to bonding pads 213 and 214,
respectively. It should be evident by one skilled in the art that many
more electrical couplings typically are necessary to fully utilize inputs
and outputs of both the standard electronic components and the optical
components. It should be further evident that standard output and input
means, represented by leads 218, bumps 209, and the like are capable of
being used to optically and electrically couple photonic components 208
and waveguide 201 together.
Further, plastic encapsulation of interconnect substrate 206 and molded
optical waveguide 201 typically is achieved by an overmolding process,
represented by plastic pieces 220 which encapsulates interconnect
substrate 206 and optical waveguide 201, whereby access to core regions of
waveguide 201 are easily utilized, as well as being able to convert
electrical signals into optical signals.
FIG. 3 is a highly enlarged, simplified sectional view of an optoelectronic
integrated circuit 300. Optoelectronic integrated circuit 300 illustrates
a portion of optoelectronic integrated circuit 300 that includes a
reflective surface 301, a molded optical portion 302, a photonic device
303 having a working portion 304, a coupling apparatus 320 having
conductive bumps 305, 306, bonding pads 308, 307, respectively, integrated
circuit substrate 309, light signals, represented by arrows 316 and 317,
flag 311, and connecting apparatus 312. It should be understood that only
a small portion of optoelectronic integrated circuit 300 is shown so as to
more clearly illustrate the present invention.
Photonic device 303 is mounted to integrated circuit substrate 309 by any
suitable method, such as bump bonding, wire bonding, or the like. However,
as shown in FIG.3, photonic device 303 is mounted to integrated circuit
substrate 309 through conductive bumps 305, 306 and bonding pads 308, 307,
thereby electrically and mechanically coupling photonic device 303 to
integrated circuit substrate 309. Once photonic device 303 is mounted to
integrated circuit substrate 309, integrated circuit substrate 309 is
placed in molding system and overmolded. Additionally, during overmolding
of integrated circuit substrate 309, reflective surface 301 is positioned
in the molding system so that reflective surface 301 is incorporated into
optoelectronic integrated circuit 300. Additionally, reflective surface
301 is made of any suitable material, such as a plastic, e.g., a plastic
having a different refractive index, a metal, e.g., leadframe member, or
the like.
Generally, molding materials used for molded optical portion 302 are
similar, if not the same, as discussed hereinabove with reference to
FIG.1. Briefly, any suitable material is used for making molded optical
portion 302, such as plastics, epoxies, polyimides, or the like having a
suitable refractive index 1.3 to 1.7 with a preferred range of refractive
index being between 1.4 and 1.5. However, since optoelectronic integrated
circuit 300 is to be placed in molded optical interconnect 100 having core
region 119 with a specific refractive index, molding material selection is
made so that the refractive index of molded optical portion 302 matches or
is similar to the refractive index of core region 119 of molded optical
interconnect 100. Thus, transmission of light signals 304 and 317 are
enhanced so as to facilitate transmission of light signals 304 and 317
into and out of molded optical portion 302.
In function, optical signals of light signals, indicated by arrows 316 and
317, travel through molded optical portion 302 so as to communicate
information to and from optoelectronic integrated circuit 300. As
illustrated in FIG.3, light signals 316 emanating from working portion 304
of photonic device 303 are reflected off of reflective surface 301 and
toward optical surface 315. If, for instance, optoelectronic integrated
circuit 300 is mounted in molded optical interconnect 100 shown
hereinabove, optical signals 317 reflected from reflective surface 301 and
through molded optical portion 302 would pass through optical surface 315
and into core region 119. Alternatively, light striking optical surface
315 and entering molded optical portion 302, as shown by arrows 317,
strikes and is reflected off of reflective surface 301. Light signals 317
reflected off of reflective surface 301, indicated by arrows 304, are
directed towards photonic device 303.
FIG. 4 shows a greatly enlarged partial view of multichip module (MCM) 400,
with a portion 410 thereof removed, illustrating several main elements or
features of MCM 400, such as molded optical portions 401 having a first
molded optical portion 402 and a second molded optical portion 403, a
plurality of core regions 404 having a plurality of optical surfaces or
ends 405, an interconnect substrate 406, an optical connector 407, an
optical module 408 having a plurality of optical surfaces 409, a plurality
of bonding pads 411, openings 413 and 414, and integrated circuit 420.
Interconnect substrate 406 is similar to interconnect substrate 101 of FIG.
1 discussed hereinabove, thus not requiring further discussion at present.
As shown in FIG. 4 with portion 410 removed from MCM 400 and with optical
module 408 elevated, internal workings of MCM 400 are more clearly
viewable. The plurality of core regions 404 are exposed and can be seen to
travel throughout first optical portion 403.
Opening 413 of molded optical portion 401 exposes a plurality of bonding
pads 411 on interconnect substrate 406 as well as a plurality of optical
surfaces 405 of the plurality of core regions 404 that terminate at
opening 413. Mounting of optical module 408 to interconnect substrate 406
is achieved by any suitable method described herein and above. However,
for illustrative purposes only, bonding pads 411 are electrically coupled
to optical module 408 by a conductive bump method, thereby electrically
and mechanically coupling optical module 408 and interconnect substrate
406, as well as positioning optical surfaces 414 of optical module 408 to
optical surfaces or ends 405 of the plurality of core regions 404. Once
optical module 408 is mounted into opening 413 and operably coupled to
bonding pads 411, the plurality of optical surfaces 409 of optical module
408 are aligned and operably coupled to the plurality of optical surfaces
405 of the plurality of core regions 404, thereby both electrically and
optically coupling optical module 408 to interconnect substrate 406, thus
integrating standard electronic components with optical components.
Further, optical connector 407 illustrates optical coupling from another
source, such as another board, another optoelectronic system, or the like
to MCM 400, thereby enabling light signals, i.e., information, to be
inputted and outputted of MCM 400 opticallly. More specifically, optical
fibers (not shown) in optical connector 407 are aligned to optical
surfaces 416 of core regions 417, there by operably coupling MCM 400 with
optical connector 407.
Integrated circuit 420 illustrates an incorporation or integration of
standard electronic components into MCM 400, thereby uniting standard
electronic components with optical components so that greater speed or
movement of information is achieved.
FIG. 5 is a greatly enlarged simplified perspective view of an embodiment
of the present invention. As can be seen in FIG. 5, multichip module (MCM)
500 is made having several main components or features, such as
interconnect substrate 501 with a surface 522 having a plurality of
electrical tracings 509 illustrated by bonding pads 511, 512, 513, 514,
516, and electrical traces 517, 518, 519, and 520, an optical module 508,
a molded optical portion 521 with optical portions 541, 542, having a
plurality of core regions 527, optical connection site 524, an integrated
circuit 530, and optoelectronic sockets 525, 528, and 540.
Generally, interconnect substrate 501 is similar to previously described
interconnect substrates 101, 206, 309, and 406, thus not necessitating an
in-depth description of interconnect substrate 501. However, since
interconnect substrate 501, as shown in FIG. 5, is viewed as a perspective
illustration, several features or elements are illustrated more clearly
than in previous illustrations. As shown in FIG. 5, the plurality of
electrical tracings 509 are disposed on surface 522 of interconnect
substrate 501. More specifically, electrical tracings 517 through 520
illustrate electrical tracings that conduct electrical signals throughout
interconnect substrate 522. These electrical tracings 517 through 520 also
conduct electrical signals to appropriate bonding pads so as to conduct
electrical signals to appropriate integrated circuits and optical modules,
illustrated by integrated circuit 530 and optical module 508, thereby
integrating standard electronic components and optical modules on
interconnect substrate 501.
Molded optical portion 521 is disposed on surface 522 of interconnect
substrate 501 as described hereinabove; however, in this particular
embodiment of the present invention, molded optical portion 521 is
disposed on surface 522 so as to guide a plurality of core regions 123 to
their appropriate destinations without entirely overmolding on surface
522, thereby leaving portions of surface 522 of interconnect substrate 501
open or clear of molding compounds used for making molded optical portion
521.
As can be seen in FIG. 5, molded optical portion 521 is made having an
optical connection port 524 which is optically coupled to optoelectronic
socket 525 through molded optical portion 526 having core region 527.
Optoelectronic socket 525 is operably coupled to optoelectronic socket 540
which is also operably coupled to optoelectronic socket 528 through molded
optical portions 541 and 542, respectively. Further, it should be
understood that optoelectronic sockets 525, 540, and 528 include bonding
pads 514, 516, and 513, thus enabling optoelectronic modules to be mounted
into optoelectronic sockets, thereby enabling integration of both
optoelectronics and standard electronic components, such as integrated
circuit 530 together in a multichip format.
By now, it should be appreciated that a novel optoelectronic multichip
device and method of making has been described. The optoelectronic
multichip interconnect incorporates optoelectronics and standard
electronic components using molded optical waveguides to operably couple
standard electronic components with optical device, thereby taking
advantage of speed of optoelectronics while still maintaining or
incorporating standard electronic components. Further, use of molded
optical waveguides and molded optical modules enable cost effective
manufacturing of multichip modules. Additionally, the methods of making
both molded waveguides for interconnect substrates incorporates standard
electronic components with optical modules in a highly manufacturable
process.
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