Patent Publication Number: US-2021167856-A1

Title: System comprising packaged optical devices

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 16/702,209 filed Dec. 3, 2019, the contents of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field of the Disclosure 
     The present disclosure generally relates to a system comprising packaged devices and, in particular, to a system comprising packaged optical devices for optical communication. 
     2. Description of the Related Art 
     Along with the rapid growth and thriving development in optical communication industry, attention has been paid to increasing transmission rate while reducing power loss. For example, to enhance power efficiency, an optical transceiver may be placed closer to an optical switch. In addition, to improve area efficiency, the number of optical transceivers that can be served by an optical switch may be maximized to thereby increase the transceiver density. 
     SUMMARY 
     Embodiments of the present disclosure provide a system comprising optical devices. The system includes a first substrate and a first device for optical communication. The first device has a first surface, a second surface opposite to the first surface, and a first side contiguous with the first surface and the second surface. Moreover, the first side is smaller than one of the first surface and the second surface in terms of area. The first device is attached at the first side thereof to the first substrate. 
     Embodiments of the present disclosure also provide a system comprises optical devices. The system includes a substrate, a first device and a second device. The first device, for optical communication, has a first planar surface smaller than a second planar surface in terms of area. The first device is attached at the first planar surface thereof to the substrate. The second device is disposed on the substrate and serves the first device during an optical communication. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects of some embodiments of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that various structures may not be drawn to scale, and dimensions of the various structures may be arbitrarily increased or reduced for clarity of discussion. 
         FIG. 1A  is a schematic top view of a system comprising optical devices, in accordance with an embodiment of the present disclosure. 
         FIG. 1B  is a front view of the system illustrated in  FIG. 1A , taken along line AA′. 
         FIG. 1C  is a schematic perspective diagram showing an enlarged view of a first device in the system illustrated in  FIG. 1B . 
         FIG. 2A  is a schematic top view of a system comprising optical devices, in accordance with another embodiment of the present disclosure. 
         FIG. 2B  is a front view of the system illustrated in  FIG. 2A , taken along line BB′. 
         FIG. 2C  is a schematic perspective diagram showing an enlarged view of a first device in the system illustrated in  FIG. 2B . 
         FIG. 3A  is a schematic top view of a system comprising optical devices, in accordance with still another embodiment of the present disclosure. 
         FIG. 3B  is a front view of the system illustrated in  FIG. 3A , taken along line CC′. 
         FIG. 4A  is a schematic top view of a system comprising optical devices, in accordance with yet another embodiment of the present disclosure. 
         FIG. 4B  is a front view of the system illustrated in  FIG. 4A , taken along line DD′. 
     
    
    
     DETAILED DESCRIPTION 
     Common reference numerals are used throughout the drawings and the detailed description to indicate the same or similar components. Embodiments of the present disclosure will be readily understood from the following detailed description taken in conjunction with the accompanying drawings. 
     The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to explain certain aspects of the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed or disposed in direct contact, and may also include embodiments in which additional features may be formed or disposed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
     In some comparative systems, optical transceivers are attached at a relatively large surface thereof to a substrate in a “lying” posture. Consequently, the number of optical transceivers that can be arranged on the substrate is restricted. Further, the bandwidth resources provided by an optical switch device available for optical transceivers are underutilized. In some embodiments of the present disclosure, first devices that act as optical transceivers are attached at a relatively small side or planar surface thereof to a substrate in a “standing” posture. The number of first devices that can be arranged on the substrate, or the density of the first devices, is significantly increased. As a result, optimized utilization of bandwidth resources is achieved. 
       FIG. 1A  is a schematic top view of a system  100  comprising optical devices  10  and  20 , in accordance with an embodiment of the present disclosure. 
     Referring to  FIG. 1A , the system  100  includes first devices  10  and a second device  20 . The first device  10  functions to act as an optical transceiver, while the second device  20  acts as a processor or controller that serves these first devices  10  during an optical communication. The first device  10  includes a first module  11  and a second module  12  on a carrier  15 . In the present embodiment, the first module  11  includes a photonic integrated circuit (PIC) configured to, during a receiving operation, receive an optical signal from an external system and convert the received optical signal into an electric signal. In addition, the second module  12  includes an electric IC (EIC) configured to, during a receiving operation, demodulate an electric signal from the first module  11  and send the demodulated electric signal to the second device  20 . As a result, information conveyed in the optical signal from an external system is received, decoded by the first device  10  and sent to the second device  20  during a receiving operation. Moreover, the electric IC of the second module  12  is configured to, during a transmission operation, modulate the waveform of a light wave emitted from a light source  50  via an optical fiber  58  towards the first module  11 , thereby encoding information from the second device  20  in the light wave, resulting in an optical signal in the form of a carrier wave. In addition, the photonic IC of the first module  11  is configured to, during a transmission operation, transmit the optical signal to an external system. As a result, information from the second device  20  is encoded in the carrier wave and transmitted to an external system during a transmission operation. 
     The first module  11  of the first device  10  is connected via an optical fiber  58  to a corresponding light source  50 . Moreover, the second module  12  is electrically connected via a conductive line  28  such as a copper wire to the second device  20 . In the present embodiment, the light sources  50 , which may include laser light sources, are disposed on the first substrate  31 . Alternatively, a light source  50  may be disposed on the second module  12  of the first device  10  and connected to the second module  12  via an optical fiber. 
     The first devices  10  are disposed on a first substrate  31 , and the second device  20  is disposed on a second substrate  32 , which in turn is disposed on the first substrate  31 . In an embodiment, the first substrate  31  includes a coarse-pitch substrate such as a printed circuit board (PCB), which may support line width and line spacing (L/S) of approximately 100 micrometers (μm) and 100 μm, respectively. In addition, the second substrate  32  includes a fine-pitch substrate, which may support L/S smaller than approximately 2 μm/2 μm. 
     In some embodiments, the system  100  is incorporated in an electronic device such as a mobile device including, for example, a smart phone. During an optical communication, the system  100  receives an optical signal from or transmits an optical signal to an external system, such as another electronic device. 
     The second device  20  in the system  100  may support data transmission at approximately 12.8 tera (T) bytes per second, and thus offers services in a relatively large bandwidth. While the data transmission rate of the second device  20  is rapidly evolving, by comparison, the data transmission rate of the first device  10  is moving slow and may support approximately 400 giga (G) bytes per second. As a result, one such second device  20  is able to serve at least 32 (=12.8 T/400 G) such first devices  10 . To fully utilize the bandwidth resources of the second device  20 , it may be desirable to employ as many as first devices  10  affordable by the second device  20 . Moreover, to curb power loss, a first device  10  may be specified to be disposed close to a second device  20 . In an embodiment, the first device  10  is disposed within approximately 2 micrometers (mm) from the second device  20 . Consequently, given the above, it is desirable to increase the density of first devices  10 , which may be arranged to surround the second device  20  within a predetermined range of distance. 
       FIG. 1B  is a front view of the system  100  illustrated in  FIG. 1A , taken along line AA′. 
     Referring to  FIG. 1B  and also  FIG. 1A , to be densely packed, the first device  10  is attached to the first substrate  31  by way of “standing” thereon instead of “lying” on the first substrate  31  as would be so arranged in a comparative system. Generally, a standing posture of an object occupies less contact area than a lying posture. As a result, by standing the first device  10  on the first substrate  31 , more space can be created for additional first devices  10 .  FIG. 1C  is a schematic perspective diagram showing an enlarged view of a first device  10  in the system  100  illustrated in  FIG. 1B . Referring to  FIG. 1C , the first device  10  takes the form of a packaged IC having a compact, flat profile. The first device  10  in a packaged form has planar surfaces s 1 , s 2 ,  10   a  and  10   b . The planar surfaces s 1  and s 2 , also referred to as a first side and a second side, respectively, are contiguous with each other and each also contiguous with the planar surfaces  10   a  and  10   b . The planar surfaces  10   a  and  10   b , also referred to as a first surface and a second surface, respectively, are opposed to each other, and are larger than the first side s 1  and the second side s 2  in terms of area. In an embodiment, the dimension of the first device  10  is approximately 3 centimeters (or 30 mm) in length, approximately 2 centimeters (or 20 mm) in width, and approximately 2 mm in thickness. As a result, the area of each of the first surface  10   a  and the second surface  10   b  is approximately 600 mm 2 , and the areas of the first side s 1  and the second side s 2  are approximately 40 mm 2  and approximately 60 mm 2 , respectively. Accordingly, in terms of area, the first surface  10   a  or the second surface  10   b  is approximately 15 times the first side s 1  and approximately 10 times the second side s 2 . That is, each of the first surface  10   a  and the second surface  10   b  is not smaller than 10 times the first side s 1  or the second side s 2 . With the significantly small area, standing the first device  10  at the first side s 1  or the second side s 2  thereof on the first substrate  31  saves a significant amount of area of the first substrate  31 . 
     Alternatively, the first device  10  may take the form of a non-packaged structure including functional modules such as PIC  11  and EIC  12  on a carrier  15 , as in the embodiment illustrated in  FIG. 1A . The overall dimension of the first device  10  in a non-packaged form, which still has a compact, flat profile, is similar to that in a packaged form. Consequently, like the packaged form, standing the first device  10  at a relatively small-area side thereof on the first substrate  31  achieves area efficiency in the real estate of the first substrate  31 , and contributes to a significantly improved density of the first devices  10  on the first substrate  31 . 
     In some comparative systems, optical transceivers thereof are similar in device functions and physical configurations to the first device  10 . The optical transceiver is attached at a first surface  10   a  or a second surface  10   b , in a “lying” posture, to a substrate. To accommodate more optical transceivers, an increase in the substrate size is specified, which may not be allowed in the limited inner space of an electronic device, and may deviate from the downsizing trend. As a result, the number of optical transceivers available on a substrate is significantly restricted, resulting in insufficient utilization of the resources of the second device  12 . The system  100  according to the present disclosure alleviates or solves the problems that would occur in the comparative systems. 
     Referring back to  FIG. 1B , the first device  10  is attached at the first side s 1  thereof to the first substrate  31 . The first device  10  is provided with conductive pads  18  arranged at one of the first surface  10   a  and the second surface  10   b  adjacent to the first side s 1  for electrical connection to the second device  20 . Moreover, the first substrate  31  is provided with a socket corresponding in position to the conductive pads  18  so as to accommodate the conductive pads  18 . Furthermore, the first substrate  31  and the second substrate  32  are provided with a first wiring  31   w  and a second wiring  32   w , respectively, to establish a conductive path between the first device  10  and the second device  20 . Specifically, the first device  10 , when attached onto the first substrate  31 , is electrically connected via the conductive pads  18 , the first wiring  31   w  in the first substrate  31  and the second wiring  32   w  in the second substrate  32  to the second device  20 . 
       FIG. 2A  is a schematic top view of a system  200  comprising optical devices  10  and  20 , in accordance with another embodiment of the present disclosure. For simplicity, the optical fibers  58  and conductive lines  28  shown in  FIG. 1A  are omitted. 
     Referring to  FIG. 2A , the system  200  is similar to the system  100  described and illustrated with reference to  FIG. 1A  except that, for example, flexible circuits  70  replace the conductive pads  18 . The flexible circuit  70 , such as a flexible circuit board (FCB) or flexible printed circuit board, may include a thin insulating polymer film having conductive circuit patterns affixed thereto and supplied with a thin polymer coating to protect the conductor circuits. The flexible circuit  70  facilitates electrical connection between the first device  70  and the second device  20  over the space. 
       FIG. 2B  is a front view of the system  200  illustrated in  FIG. 2A , taken along line BB′.  FIG. 2C  is a schematic perspective diagram showing an enlarged view of a first device  10  in the system  200  illustrated in  FIG. 2B . 
     Referring to  FIG. 2B  and also  FIG. 2C , the first device  10  is attached at the second side s 2  thereof to the first substrate  31 . Since the second side s 2  is larger than the first side s 1  in area, the second side s 2  facilitates the first device  10  to stand more stable on the first substrate  31 . Alternatively, as in the system  100 , the first device  10  may be attached at the first side s 1  thereof to the first substrate  31 . 
       FIG. 3A  is a schematic top view of a system  300  comprising optical devices  10  and  20 , in accordance with still another embodiment of the present disclosure.  FIG. 3B  is a front view of the system  300  illustrated in  FIG. 3A , taken along line CC′. 
     Referring to  FIG. 3A  and also  FIG. 3B , the system  300  is similar to the system  100  described and illustrated with reference to  FIG. 1A  except that, for example, the first devices  10  are disposed on a second substrate  42  rather than the first substrate  31 . Moreover, the second substrate  42  is similar to the second substrate  32  described and illustrated with reference to  FIG. 1A  except that, for example, the second substrate  42  is larger than the second substrate  32  in terms of area so as to accommodate the first devices  10  in addition to the second device  20 . The first device  10  may be electrically connected to the second device  20  by conductive pads and a wiring structure as described and illustrated with reference to  FIGS. 1A and 1B . Alternatively, the first device  10  may be electrically connected to the second device  20  by a flexible circuit as described and illustrated with reference to  FIGS. 2A and 2B . In addition, as in the present embodiment, the first device  10  may be attached at the second side s 2  thereof to the first substrate  31  or, as in the system  100 , the first device  10  may be attached at the first side s 1  thereof to the first substrate  31 . 
       FIG. 4A  is a schematic top view of a system  400  comprising optical devices  10  and  20 , in accordance with yet another embodiment of the present disclosure.  FIG. 4B  is a front view of the system  400  illustrated in  FIG. 4A , taken along line DD′. For simplicity, the optical fibers  58  and conductive lines  28  shown in  FIG. 1A  are omitted. 
     Referring to  FIG. 4A  and also  FIG. 4B , the system  400  is similar to the system  100  described and illustrated with reference to  FIG. 1A  except that, for example, additional first devices  10  are shown. These additional first devices  10  together with those already shown in  FIG. 1A  substantially surround the second device  20 . Each of the first devices  10  may be disposed with a predetermined distance, for example, 2 μm from the second device  20 . In the present embodiment, the first device  10  may be attached at the second side s 2  thereof to the first substrate  31 . In other embodiments, as in the system  100 , the first device  10  may be attached at the first side s 1  thereof to the first substrate  31 . Due to the standing posture, the first devices  10  are densely packed around the second device  20 . As a result, the density of first devices  10  is increased. Moreover, the bandwidth resources of the second device  20  may be fully utilized. 
     Spatial descriptions, such as “above,” “below,” “up,” “left,” “right,” “down,” “top,” “bottom,” “vertical,” “horizontal,” “side,” “higher,” “lower,” “upper,” “over,” “under,” and so forth, are indicated with respect to the orientation shown in the figures unless otherwise specified. It should be understood that the spatial descriptions used herein are for purposes of illustration only, and that practical implementations of the structures described herein can be spatially arranged in any orientation or manner, provided that the merits of embodiments of this disclosure are not deviated from by such an arrangement. 
     As used herein, the terms “approximately,” “substantially,” “substantial” and “about” are used to describe and account for small variations. When used in conjunction with an event or circumstance, the terms can refer to instances in which the event or circumstance occurs precisely as well as instances in which the event or circumstance occurs to a close approximation. For example, when used in conjunction with a numerical value, the terms can refer to a range of variation less than or equal to ±10% of that numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. For example, two numerical values can be deemed to be “substantially” the same or equal if a difference between the values is less than or equal to ±10% of an average of the values, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. 
     Two surfaces can be deemed to be coplanar or substantially coplanar if a displacement between the two surfaces is no greater than 5 μm, no greater than 2 μm, no greater than 1 μm, or no greater than 0.5 μm. 
     As used herein, the singular terms “a,” “an,” and “the” may include plural referents unless the context clearly dictates otherwise. 
     As used herein, the terms “conductive,” “electrically conductive” and “electrical conductivity” refer to an ability to transport an electric current. Electrically conductive materials typically indicate those materials that exhibit little or no opposition to the flow of an electric current. One measure of electrical conductivity is Siemens per meter (S/m). Typically, an electrically conductive material is one having a conductivity greater than approximately 10 4  S/m, such as at least 10 5  S/m or at least 10 6  S/m. The electrical conductivity of a material can sometimes vary with temperature. Unless otherwise specified, the electrical conductivity of a material is measured at room temperature. 
     Additionally, amounts, ratios, and other numerical values are sometimes presented herein in a range format. It is to be understood that such range format is used for convenience and brevity and should be understood flexibly to include numerical values explicitly specified as limits of a range, but also to include all individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly specified. 
     While the present disclosure has been described and illustrated with reference to specific embodiments thereof, these descriptions and illustrations are not limiting. It should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the present disclosure as defined by the appended claims. The illustrations may not be necessarily drawn to scale. There may be distinctions between the artistic renditions in the present disclosure and the actual apparatus due to manufacturing processes and tolerances. There may be other embodiments of the present disclosure which are not specifically illustrated. The specification and drawings are to be regarded as illustrative rather than restrictive. Modifications may be made to adapt a particular situation, material, composition of matter, method, or process to the objective, spirit and scope of the present disclosure. All such modifications are intended to be within the scope of the claims appended hereto. While the methods disclosed herein have been described with reference to particular operations performed in a particular order, it will be understood that these operations may be combined, sub-divided, or re-ordered to form an equivalent method without departing from the teachings of the present disclosure. Accordingly, unless specifically indicated herein, the order and grouping of the operations are not limitations of the present disclosure.