Plastic composite lens array in optical networks

An optoelectronic assembly may include a PCB and an optical lens. The PCB includes a top surface where at least a portion of the top surface includes a first material with a first thermal property. The optical lens includes a lens frame and an optical portion positioned within the lens frame. The lens frame is coupled to the top surface of the PCB. The lens frame includes a second material with a second thermal property, the second material being different from the first material. The optical portion positioned includes a third material with a third thermal property, the third material being different from the first material and the second material. The third material is optically transparent.

FIELD

The application relates generally to a plastic composite lens array in optical networks.

BACKGROUND

Optoelectronic components may be used in the conversion of optical signals to electrical signals and/or electrical signals to optical signals. The manner in which various optoelectronic components are assembled or coupled together, including materials thereof, may affect a quality or amount of conversion efficiency for a desired signal output. For example, material properties of some materials used in lens arrays may lead to coupling losses or efficiency losses.

SUMMARY

Some embodiments described herein generally relate to a plastic composite lens array in optical networks, e.g., that may be implemented as or in one or more optoelectronic assemblies.

In an example embodiment, an optoelectronic assembly may include a printed circuit board (PCB) including a top surface, at least a portion of the top surface including a first material with a first thermal property. Additionally, the optoelectronic assembly may include an optical lens. The optical lens may include a lens frame coupled to the top surface of the PCB, the lens frame including a second material with a second thermal property, the second material being different from the first material. The optical lens may also include an optical portion positioned within the lens frame, the optical portion including a third material with a third thermal property, the third material being different from the first material and the second material, and the third material being optically transparent.

In another example embodiment, a method to manufacture an optoelectronic assembly may include forming an optical lens. The optical lens may include a lens frame including a lens frame material with a lens frame thermal property. The optical lens may also include an optical portion positioned within the lens frame, the optical portion including an optical portion material with an optical portion thermal property, the optical portion material being different from the lens frame material, and the optical portion material being optically transparent. Additionally, the method may include coupling the optical lens to a top surface of a printed circuit board (PCB) that includes a PCB material with a PCB thermal property, in which coupling the optical lens to the top surface of the PCB includes coupling the lens frame to the top surface of the PCB.

all arranged in accordance with at least one embodiment described herein.

DESCRIPTION OF EMBODIMENTS

In some products or designs, a lens array may be made of one type of plastic, e.g., a single type of plastic formed as a single unitary component coupled to a printed circuit board (PCB). A portion of the lens array may be coupled to the PCB and/or other components of the product, and light may be transmitted through another portion of the lens array. The portion of the lens array coupled to the PCB may be referred to as a lens frame and the portion of the lens array through which light passes may be referred to as an optical portion to distinguish between the two portions. However, both the lens frame and the optical portion are not typically distinguishable as they typically form a unitary component of a single type of plastic in existing lens arrays. Such products or designs may experience lens displacement and/or stress, for example, due to component temperatures during epoxy curing processes and/or normal/max operation of the lens array. Specifically, for example, temperatures of the lens frame and the PCB during epoxy curing processes and/or normal/max operation may cause lens displacement and/or stress due to certain material properties, such as coefficient of thermal expansion (CTE). In particular, a greater mismatch between a CTE of the lens frame and a CTE of the PCB may lead to greater coupling losses or efficiency losses for the lens array. In contrast, a decreased mismatch between the CTE of the lens frame and the CTE of the PCB may decrease coupling losses and/or efficiency losses for the lens array.

Aspects of the present disclosure may include one or more embodiments to decrease the mismatch between the CTE of the lens frame and the CTE of the PCB compared to the other products or designs mentioned above by including a composite lens array. The composite lens array of the present disclosure may incorporate two or more types of plastic in contrast to prior techniques mentioned above that include a single type of plastic for both the lens frame coupled to the PCB and the optical portion positioned within the lens frame. In the techniques mentioned above, translucent plastics (e.g., polyetherimide, polycarbonate, polyurethane, Trivex®, and other translucent plastics) are used as the single plastic material for both the lens frame and the optical portion within the lens frame. Such translucent plastics, however, typically include a relatively high CTE. For example, a CTE of Ultem® (an example polyetherimide) is about 50×10−6m/m ° C., which in some cases, may result in too much displacement and/or stress in the lens array (e.g., too large of an optical coupling loss) when used as the material for both the lens frame and the optical portion within the lens frame.

Aspects of the present disclosure address these and other example problems of other techniques, such as the other products and designs mentioned above. For example, according to one or more embodiments of the present disclosure, the optical portion of the lens array may include a first type of plastic, e.g., a translucent plastic that allows optical signals to pass therethrough. The lens frame, which houses the optical portion of the lens and is coupled to the PCB, may include a second type of plastic different from the first type of plastic. The second type of plastic may have a CTE that is the same as or similar to the CTE of the PCB. By incorporating the second type of plastic in the lens frame, lateral displacement and/or stress of the lens array may be reduced. Additionally or alternatively, a greater number of optical channels may be included in the optical portion of the lens array given a reduced amount of lateral displacement and/or stress.

Reference will now be made to the drawings to describe various aspects of example embodiments of the invention. It is to be understood that the drawings are diagrammatic and schematic representations of such example embodiments, and are not limiting of the present invention, nor are they necessarily drawn to scale.

FIG. 1illustrates a top perspective view of an example optoelectronic module100, arranged in accordance with at least one embodiment of the present disclosure. A top housing of the optoelectronic module100is depicted (for illustration purposes) in a transparent manner to illustrate various components within the optoelectronic module100. As illustrated, the optoelectronic module100may include a ferrule105, a lens110, and a printed circuit board (PCB)115. The optoelectronic module100may additionally include one or more optical signal sources (e.g., one or more lasers or LEDs) and/or one or more optical receivers (e.g., one or more photodiodes). The optical signal sources and/or optical receivers may be mounted to the PCB115, an interposer, or other suitable structure between the PCB115and the lens110and may be optically coupled through the lens to one or more optical fibers. In these or other embodiments, the optoelectronic module100may be part of a host connection to an optical network. For example, the ferrule105may include or be coupled to the one or more optical fibers configured for transmitting optical signals within the optical network. For instance, in some embodiments, inbound optical signals may propagate from the optical fiber(s), through the ferrule105, through the lens110, and to the optical receiver(s). Outbound optical signals may be transmitted from the optical signal source(s) through the lens110, through the ferrule105, and into the optical fiber(s).

In these or other embodiments, the lens110may be physically coupled, either directly or indirectly, to the PCB115as described further below with respect toFIG. 3.

FIG. 2illustrates the lens110of the optoelectronic module100ofFIG. 1, arranged in accordance with at least one embodiment of the present disclosure. As illustrated, the lens110may include an optical portion220with optical channels222(only one channel222is labeled inFIG. 2and other FIGS. for simplicity), a lens frame225, and legs230(only one leg230is labeled inFIG. 2and other FIGS. for simplicity).

In these or other embodiments, the optical portion220may be positioned (e.g., housed) within the lens frame225. In some embodiments, the optical portion220may be configured to receive and/or transmit optical signals, e.g., via the optical channels222that are configured to connect with a ferrule (such as the ferrule105ofFIG. 1). Each of the optical channels222may include at least one convex lens structure, and possibly more (e.g., two) aligned convex lens structures (e.g., located on opposite sides (in a light propagation direction) of the optical portion220and aligned in the light propagation direction), or other suitable structures. The convex lens structure(s) of each optical channel222may, for example, collimate an optical signal as the optical signal enters the optical portion220and/or focus the optical signal as it exits the optical portion220.

The optical portion220is illustrated in one or more of the figures, includingFIGS. 4 and 5, as including a total of sixteen optical channels222. In some examples, eight of the optical channels222may be transmit optical channels, e.g., for output optical signals, while the remaining eight of the optical channels222may be receive optical channels. Other arrangements are possible.

Additionally or alternatively, the optical portion220may be made of a plastic material. The plastic material of the optical portion220may be optically transparent, at least with respect to one or more target wavelengths of the optical signals transmitted and/or received by the optoelectronic module100. The term translucent as used herein may indicate an optical transmissivity of at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, or at least 95% with respect to given wavelength. The plastic material of the optical portion220may include one or more of polyetherimide (e.g., Ultem®), polycarbonate, polyurethane, Trivex®, and other translucent plastics. In these or other embodiments, the optically transparent plastic of the optical portion220may include a thermal property, such as coefficient of thermal expansion (CTE). The CTE of the optically transparent plastic of the optical portion220may be higher than that of other plastics, such as the plastic used in the lens frame225, and/or than that of a printed circuit board (such as the PCB115ofFIG. 1). For example, Ultem® (an example polyetherimide) may have a CTE of about 50×10−6m/m ° C., whereas a material of the lens frame225and/or of the PCB115may have a CTE of, e.g., 14×10−6m/m° C.

In these or other embodiments, the lens frame225may be made of a different plastic than the optically transparent plastic of the optical portion220. For example, the lens frame225may include polyether ether ketone (PEEK). Additionally or alternatively, the lens frame225may include glass fiber. In these or other embodiments, a CTE of PEEK may be about 14×10−6m/m ° C., and a CTE of glass fiber-filled PEEK may be about 6×10−6m/m ° C. Thus, in some embodiments, the lens frame225may be made of a different material with a lower CTE relative to the optically transparent plastic of the optical portion220, such that the lens110is a composite component made of two or more portions with differing CTE properties.

Additionally or alternatively, the plastic of the lens frame225may be selected to match or approximate a CTE of a structure to which the lens110is coupled (e.g., the PCB115ofFIG. 1). In these or other embodiments, the material of the lens frame225may be configured to reduce displacement and/or stress of the lens110as described in greater detail with respect toFIG. 3. Additionally or alternatively, the material of the lens frame225may enable a number of the optical channels222to be increased to about 20 optical channels, about 22 optical channels, about 24 optical channels, or another suitable number of optical channels as also described in greater detail with respect toFIG. 3.

In some embodiments, one or more portions of the lens frame225may be molded. For example, one or more portions of the lens frame225may be molded prior to the optical portion220. In these or other embodiments, the lens frame225may include a plastic material with a higher melting temperature than the optically transparent plastic of the optical portion220. Additionally or alternatively, the optical portion220may be overmolded. For example, an optical portion220made of Ultem® (having a mold temperature of about 135° C. to about 165° C.) may be overmolded with a lens frame225made of PEEK (having a melting temperature of about 343° C.).

In these or other embodiments, the legs230may extend downward from a bottom surface of the lens frame225. Additionally or alternatively, the legs230may be configured to interface with (e.g., bond/mount to) a structure, such as the PCB115ofFIG. 1. A manner in which the legs230interface with a corresponding structure is described in additional detail with respect toFIG. 3.

FIG. 3illustrates an example environment300in which the lens110is coupled (e.g., bonded/mounted) to the PCB115, arranged according to at least one embodiment of the present disclosure. As illustrated, the environment300includes the lens110, the PCB115, the optical portion220, the optical channels222, the lens frame225, the legs230, a top surface332of the PCB115, an underfill layer335, a chip on glass assembly (COGA)340, a structural epoxy bond345, and a UV epoxy bond348.

In these or other embodiments, the underfill layer335may be positioned on a top surface332of the PCB115, for example between the COGA340and the PCB115. In some embodiments, the underfill layer335may be configured to couple a bottom surface of the COGA340to the top surface332of the PCB115.

In some embodiments, the COGA340may be positioned on a top surface of the underfill layer335, for example between the underfill layer335and a bottom surface of the lens110, and may be electrically coupled to the PCB115, e.g., via one or more electrical connections. The COGA340may include one or more optical signal sources and/or optical receivers, such as one or more lasers, one or more photodiodes, a laser array, and/or a photodiode array, mounted thereon. Each optical signal source and/or each optical receiver may be optically aligned with a corresponding one of the optical channels222of the optical portion220of lens110. Additionally or alternatively, the COGA340may be spatially separated from the bottom surface of the lens110(e.g., based on a height of the legs230).

In some embodiments, the lens frame225may be coupled to the top surface332of the PCB115via the structural epoxy bond345. In these or other embodiments, the structural epoxy bond345may couple at least a portion of the bottom surface of the lens110to the top surface332of the PCB115. Thus, in some embodiments, the structural epoxy bond345may have a height, in some positions, equal to a distance spanning between the top surface332of the PCB115and the bottom surface of the lens110. Additionally or alternatively, the structural epoxy bond345may couple outer edge portions of the lens frame225to the top surface332of the PCB115. Thus, in some embodiments, the structural epoxy bond345may have a height, in some positions, greater than a distance spanning between the top surface332of the PCB115and the bottom surface of the lens110. In these or other embodiments, the structural epoxy bond345may be cured at about 150° C.

Additionally or alternatively, the lens frame225may be coupled to the top surface332of the PCB115via the UV epoxy bond348between the legs230and the top surface332of the PCB115. In these or other embodiments, the UV epoxy bond348may include a thickness (e.g., a height for consistency of terminology) of about 10 μm. In some embodiments, the UV epoxy bond348may be cured at about 35° C.

In some embodiments, the material of the lens frame225may be configured to reduce lateral displacement of the lens110in a direction parallel and/or approximately parallel to the top surface332of the PCB115. For example, during curing of the structural epoxy bond345at about 150° C., the material of the lens frame225may limit lateral displacement of the lens110to be an absolute amount of lateral displacement in a closed range of [−12 μm, 12 μm] (seeFIG. 5). Additionally or alternatively, during an operational temperature of about 75° C., the material of the lens frame225may limit lateral displacement of the lens110to be an absolute amount of lateral displacement in a closed range of [−6 μm, 6 μm] (seeFIG. 4). In these or other embodiments, the lateral displacement of the lens110may be reduced due to the CTE of the PCB115and the CTE of the lens frame225being similar (e.g., approximately equal) and/or identical to each other. As used herein, two values may be approximately equal if within about 30%, about 20%, or about 10% of each other.

In some embodiments, the material of the lens frame225may be configured to reduce stress (e.g., a bending stress) of the lens110. For example, during curing of the structural epoxy bond345at about 150° C., the material of the lens frame225may limit bending stress of the lens110to be an amount of bending stress in a closed range of [0 MPa, 200 MPa] (seeFIG. 7). Additionally or alternatively, during an operational temperature of about 75° C., the material of the lens frame225may limit bending stress of the lens110to be an amount of bending stress in a closed range of [0 MPa, 50 MPa] (seeFIG. 6). In these or other embodiments, the bending stress of the lens110may be reduced due to the CTE of the PCB115and the CTE of the lens frame225being similar (e.g., approximately equal) and/or identical to each other.

In some embodiments, the material of the lens frame225may enable an increase in a number of optical channels222. In some other techniques involving lenses having a single material, a relatively high degree of CTE mismatch between the lens and the PCB has heretofore limited the number of optical channels (e.g., in a row or column of optical channels). Thus, in some embodiments of the present disclosure, the material of the lens frame225configured to decrease CTE mismatch may enable an increase in the number of optical channels222to about 20 optical channels, about 22 optical channels, about 24 optical channels, or another suitable number of optical channels (albeit the number of optical channels222depicted inFIGS. 2-7is 16 optical channels).

FIG. 4illustrates the lens110under lateral displacement analysis (e.g., finite element analysis) at 75° C., the lens110arranged according to at least one embodiment of the present disclosure. As illustrated, the lens110includes the optical portion220, the optical channels222, the lens frame225, the legs230, and displacement markers450. In these or other embodiments, the displacement markers450may indicate a respective amount of lateral displacement for a corresponding position (e.g., a specific optical channel222). As shown by the displacement markers450inFIG. 4, an absolute amount of lateral displacement of the lens110may be in a closed range of [−6 μm, 6 μm] given that the lens frame225inFIG. 4includes PEEK. In other embodiments, an absolute amount of lateral displacement of the lens110at 75° C. may be in a closed range of [−3 μm, 3 μm] given a lens frame225including glass fiber-filled PEEK. In comparison, some other techniques (e.g., including Ultem® for both the fiber-filled PEEK In comparison, some other techniques (e.g., including Ultem® for both the optical portion220and the lens frame225) at 75° C. may result in an absolute amount of lateral displacement of a corresponding lens being in a closed range of [−20 μm, 20 μm].

FIG. 6illustrates an example environment600in which the lens110, the PCB115, and other components are under stress analysis (e.g., finite element analysis) at 75° C., the environment600arranged according to at least one embodiment of the present disclosure. As illustrated, the environment600includes the lens110, the PCB115, the optical portion220, the optical channels222, the lens frame225, the legs230, the top surface332of the PCB115, the underfill layer335, the COGA340, the structural epoxy bond345, and the UV epoxy bond348. In these or other embodiments, the legend and associated color shading ofFIG. 6may indicate a respective amount of stress for a corresponding position in the environment600. As shown inFIG. 6, an amount of stress at 75° C. in the environment600may be in a closed range of [0 MPa, 50 MPa] given, for example, that the lens frame225inFIG. 6includes PEEK. In comparison, some other techniques (e.g., including Ultem® for both the optical portion220and the lens frame225) at 75° C. may result in stress of a corresponding environment being in a closed range of [0 MPa. 150 MPa],

FIG. 7illustrates an example environment700in which the lens110, the PCB115, and other components are under stress analysis (e.g., finite element analysis) at 150° C., the environment700arranged according to at least one embodiment of the present disclosure. As illustrated, the environment700includes the lens110, the PCB115, the optical portion220, the optical channels222, the lens frame225, the legs230, the top surface332of the PCB115, the underfill layer335, the COGA340, the structural epoxy bond345, and the UV epoxy bond348. In these or other embodiments, the legend and associated color shading ofFIG. 7may indicate a respective amount of stress for a corresponding position in the environment700. As shown inFIG. 7, an amount of stress at 150° C. in the environment700may be in a closed range of [0 MPa, 200 MPa] given, for example, that the lens frame225inFIG. 7includes PEEK. In comparison, some other techniques (e.g., including Ultem® for both the optical portion220and the lens frame225) at 150° C. may also result in stress of a corresponding environment700being in a closed range of [0 MPa, 200 MPa]. At 150° C., the highest stress may occur near the interface between the COGA340and the PCB115. Given the same material for the COGA340and the PCB115for both of a single-material lens (e.g., an Ultem® lens) and a composite lens as described herein, the stress near the prior-mentioned interface is about same.

FIG. 8illustrates a flow diagram of an example method800to manufacture an optoelectronic assembly, arranged in accordance with at least one embodiment described herein. The method800may be arranged to manufacture at least one of the embodiments described herein. In these and other embodiments, some or all of the steps of the method800may be performed based on the execution of computer-readable instructions stored on one or more non-transitory computer-readable media. Although illustrated as discrete blocks, various blocks may be divided into additional blocks, combined into fewer blocks, or eliminated, depending on the desired implementation.

The method800may begin at block805at which an optical lens may be formed. The optical lens may include a lens frame including a lens frame material with a lens frame thermal property. The optical lens may also include an optical portion positioned within the lens frame, the optical portion including an optical portion material with an optical portion thermal property, the optical portion material being different from the lens frame material, and the optical portion material being optically transparent. Block805may be followed by block810.

At block810, the optical lens may be coupled to a top surface of a PCB that includes a PCB material with a PCB thermal property. In these or other embodiments, coupling the optical lens to the top surface of the PCB may include coupling the lens frame to the top surface of the PCB.

In an example embodiment, the PCB, lens frame, and optical portion thermal properties may include CTE. The PCB thermal property of the PCB material and the lens frame thermal property of the lens frame material may be matched. For example, the PCB thermal property and the lens frame thermal property may be similar or identical to each other. Alternatively or additionally, the optical portion thermal property of the optical portion of the lens may be different than the PCB and lens frame thermal properties. Specifically, for instance, the PCB and lens frame thermal properties may each include a CTE in a range from about 5×10−6m/m ° C. to about 20×10−6m/m ° C., while the optical portion thermal property may include a CTE in a range from about 45×10−6m/m ° C. to about 55×10−6m/m ° C.

One skilled in the art will appreciate that, for these processes, operations, and methods, the functions and/or operations performed may be implemented in differing order. Furthermore, the outlined functions and operations are only provided as examples, and some of the functions and operations may be optional, combined into fewer functions and operations, or expanded into additional functions and operations without detracting from the essence of the disclosed embodiments.

However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations.