JP4779918B2 - Photoelectric conversion device - Google Patents

Description

  The present invention relates to a photoelectric conversion apparatus including an optical element.

  Conventionally, as a photoelectric conversion device, for example, as described in FIG. 9 of Patent Document 1, a light emitting element that emits light by converting an electric signal into an optical signal, and an electric signal for transmitting the light signal to the light emitting element An IC circuit is formed, the substrate mounted on one surface from the side opposite to the light emitting element emits light, and disposed so as to extend from the light emitting element in a direction perpendicular to one surface of the substrate, so that the light emitting element emits light. One having a waveguide for transmitting light is known. In place of the light emitting element, a light receiving element that converts a received optical signal into an electric signal may be used.

Moreover, in the photoelectric conversion apparatus described in FIG. 9 of Patent Document 1, a female electrical connector provided on the wiring board and a detachable male electrical connector are provided on the other surface of the substrate. By connecting these electrical connectors, the substrate and the wiring substrate are electrically connected.
JP 2001-42170 A

  However, in the configuration as described above, since the waveguide is disposed so as to extend from the light emitting element in a direction orthogonal to the one surface of the substrate, the height of the entire apparatus becomes considerably high.

  Here, as described in FIG. 3 of Patent Document 1, an electrical connector may be provided on the end face of the substrate so that the light emitting element emits light in a direction parallel to the wiring substrate. However, the height of the device is at least as large as the size of the light emitting element and the size of the control IC element, so that the height of the device cannot be suppressed so much.

  Therefore, the applicant of the present application mounts the optical element on one side of the mount substrate from the light emitting side or the light receiving side so that the apparatus can be reduced in height, and the optical element is mounted on the mount substrate. An IC circuit for the element is provided and an electrical connector that can be attached to and detached from the external connector is provided on one surface of the mount substrate or the other surface on the opposite side, and a waveguide that is optically coupled to the optical element is provided on one surface of the mount substrate or A photoelectric conversion device provided on the mount substrate along the other surface has been proposed.

  With this photoelectric conversion device, the overall height of the device in the thickness direction of the mount substrate can be suppressed, and the device can be reduced in height.

  In this photoelectric conversion apparatus, an interposer substrate (intermediate substrate) is disposed between the mount substrate and the electrical connector, and the electrode pattern is converted by the interposer substrate to electrically connect the mount substrate and the electrical connector. It is possible.

  In such a photoelectric conversion device, it is desired to improve the sealing performance of the optical element and the IC circuit and improve the reliability of the device.

  In view of such a demand, an object of the present invention is to provide a photoelectric conversion apparatus capable of improving the reliability of the apparatus.

  The invention of claim 1 is an optical element that converts an electrical signal into an optical signal or an optical signal into an electrical signal, and an IC circuit that transmits an electrical signal to or receives an electrical signal from the optical element, A mounting board on which the optical element is mounted; an electrical connector that can be attached to and detached from an external connector; and a waveguide that is optically coupled to the optical element, wherein the electrical connector includes the optical element on the mounting board and the optical board. An optical / electrical conversion device provided on a mount substrate along one surface of the mount substrate or the other surface on the opposite side thereof, provided on one surface on which an IC circuit is mounted, An intermediate substrate for changing an electrode pattern is provided between the substrate and the electrical connector, and further, the substrate is arranged between the mount substrate and the intermediate substrate so as to connect the two substrates. It is, and is characterized in that the frame body surrounding the light element and the IC circuit together with the mounting substrate and the intermediate substrate is provided.

  According to a second aspect of the present invention, in the photoelectric conversion apparatus according to the first aspect, the frame is provided with a through wiring for electrically connecting the mount substrate and the intermediate substrate. It is a feature.

  The invention according to claim 3 is the photoelectric conversion device according to claim 1 or 2, wherein a space surrounded by the mount substrate, the intermediate substrate, and the frame is filled with a sealing body. To do.

  According to the first aspect of the present invention, the frame is provided between the mount substrate and the intermediate substrate, and the optical element and the IC circuit are surrounded by the mount substrate, the intermediate substrate, and the frame, thereby sealing the optical element and the IC circuit. Therefore, the optical element and the IC circuit can be protected from moisture and dust. This improves the reliability of the device.

  According to the second aspect of the invention, since the frame body that seals the optical element and the IC circuit can be rationally used, the mount substrate and the intermediate substrate can be electrically connected. A solder ball that plays a role of connecting to the solder is not necessary.

  According to the invention of claim 3, the sealing property of the optical element and the IC circuit is further enhanced by the sealing body, and the heat generated in the optical element and the IC circuit is quickly moved to the sealing body, so that the optical element and The heat dissipation for the IC circuit can also be improved.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  First, with reference to FIGS. 1 to 7, the photoelectric conversion apparatus 1A previously proposed by the applicant will be described as a reference example. This photoelectric conversion device 1A includes a light emitting side photoelectric conversion unit (also referred to as an E / O module) 1A1 that is mounted on one wiring board 2 by fitting electrical connectors 6 and 7, and another wiring board 2. Similarly, a light-receiving side photoelectric conversion part (also referred to as an O / E module) 1A2 that is mounted by fitting the electrical connectors 6 and 7 and an external waveguide 9 that optically connects these conversion parts 1A1 and 1A2. I have.

  In the present specification, the vertical direction in FIG. 1 is referred to as the vertical direction, the direction orthogonal to the paper surface in FIG. 1 is referred to as the horizontal direction, and the right side in FIG. The left side of FIG. 1 is referred to as the front side and the right side is referred to as the rear side with respect to the light-receiving side photoelectric conversion unit 1A2.

  The light emission side photoelectric conversion unit 1A1 includes a mount substrate 3 having a rectangular shape extending in the front-rear direction in plan view. As shown in FIG. 2, a light emitting element 4A that converts an electric signal into an optical signal to emit light and an IC for transmitting the electric signal to the light emitting element 4A are provided on one surface 3a that is the lower surface of the mount substrate 3. An IC substrate 5A on which a circuit 50A is formed is mounted, and a header type electrical connector (hereinafter simply referred to as “header”) 6 is provided so as to cover these 4A and 5A from below. In addition, on one surface 3a of the mount substrate 3, a driving power supply line and a signal line for the light emitting element 4A are formed by a wiring pattern 36 (see FIG. 4). Further, the mount substrate 3 is provided with a mirror portion 33 that converts an optical path of light emitted by the light emitting element 4A by approximately 90 ° at a position directly above the light emitting element 4A, and optically connected to the light emitting element 4A. An internal waveguide 31 to be coupled is provided so as to extend from the mirror portion 33 to the front end surface 3 b of the mount substrate 3.

  The light emitting element 4A has a shape of a square plate that is flat in the vertical direction, emits light upward from the upper surface, and is mounted on the one surface 3a of the mount substrate 3 from the light emitting side. As the light emitting element 4A, a VCSEL (Vertical Cavity Surface Emitting Laser) which is a semiconductor laser is employed. The IC substrate 5A is a driver IC that drives the VCSEL, has a shape of a square plate that is flat in the vertical direction, and is disposed in the vicinity of the light emitting element 4A. The light emitting element 4A and the IC substrate 5A are connected to the wiring pattern 36 of the mount substrate 3 by bumps 11 (see FIG. 3) made of gold or solder. In addition, although LED etc. are employable as 4 A of light emitting elements, LED etc. are difficult to oscillate at high speed compared with laser diodes, such as VCSEL, and use in the transmission band below several hundred MHz is a condition, and in that case Is advantageous in terms of low price.

  The mount substrate 3 needs to be rigid in order to avoid the influence of heat during mounting and the influence of stress due to the use environment. Further, in the case of optical transmission, since optical transmission efficiency from the light emitting element to the light receiving element is required, it is necessary to mount the optical element with high accuracy and to suppress position fluctuation due to the influence of heat during use as much as possible. For this reason, a silicon substrate is employed as the mount substrate 3. The mount substrate 3 is preferably made of a material having a linear expansion coefficient close to that of the light emitting element 4A. In addition to silicon, the mount substrate 3 is made of a compound semiconductor such as GaAs of the same system as the VCSEL material or a ceramic such as aluminum nitride. May be.

  The mirror part 33 can be formed by depositing gold, silver, copper or aluminum on a 45 ° inclined surface formed by etching the mount substrate 3 by a method such as vapor deposition or sputtering. The 45 ° inclined surface can be formed by anisotropic etching utilizing the difference in the etching rate of silicon crystals. For the anisotropic etching, for example, a strong alkali such as a potassium hydroxide aqueous solution or a TMAH (tetramethylammonium hydroxide) aqueous solution is used.

  The internal waveguide 31 is provided along one surface 3 a of the mount substrate 3, and transmits light emitted from the light emitting element 4 </ b> A in a direction parallel to the one surface 3 a of the mount substrate 3. The internal waveguide 31 is composed of two types of resins having different refractive indexes. Specifically, as shown in FIG. 3, the internal waveguide 31 includes a core 31a made of a resin having a high refractive index and a clad 31b made of a low refractive index resin that covers the core 31a from the periphery. These are disposed in a waveguide forming groove 32 formed in the mount substrate 3. The sizes of the core 31a and the clad 31b are determined from light loss calculation based on the divergence angle of the light emitting element 4A and the light receiving diameter of the light receiving element 4B described later. In addition to the resin, the internal waveguide 31 may be made of an inorganic material as long as it is a light transmissive material such as quartz.

  The waveguide forming groove 32 can be formed by anisotropic etching as in the case of forming the 45 ° inclined surface. In addition to anisotropic etching, there is a dry etching forming method such as reactive ion etching for forming the waveguide forming groove 32.

  As shown in FIGS. 4 and 5A and 5B, when the waveguide forming groove 32 having a substantially rectangular cross section and the 45 ° inclined surface are formed by anisotropic etching, the etching conditions are different. That is, the composition of the etching solution is different. Therefore, it is necessary to perform etching in two steps. However, either may be performed first.

  Alternatively, when the waveguide forming groove 32 is formed simultaneously with the 45 ° inclined surface, as shown in FIGS. 5C and 5D, the waveguide forming groove 32 has a substantially trapezoidal cross section. The groove width of the waveguide forming groove 32 is increased. The waveguide forming groove 32 has no problem as long as it does not cover the bonding pad for the light emitting element 4A. Therefore, this is also possible.

  The external waveguide 9 is bonded to the front end surface 3b of the mount substrate 3 by an optical adhesive, and the internal waveguide 31 is optically coupled to the external waveguide 9 by this bonding. become. If the distance from the mirror portion 33 to the external waveguide 9 is short, there is a case where the loss is small even if light is simply propagated in the air. In this case, the internal waveguide 31 is omitted. The light may be directly incident on the external waveguide 9 from the mirror unit 33.

  As the external waveguide 9, it is more convenient to use a flexible film-like one in which the resin optical waveguide is thinned. That is, the film-like external waveguide 9 is excellent in flexibility, and there is no problem even if it is used for a bent portion of, for example, a mobile phone. Depending on the bending curvature, light loss may occur, but this can be reduced by increasing the refractive index difference between the core and the cladding. The external waveguide 9 may be a silica fiber or a plastic fiber other than the film-like one.

  The header 6 is detachable from a socket type electrical connector (hereinafter simply referred to as “socket”) 7 which is an external connector provided on the wiring board 2. The header 6 and the socket 7 can be interchanged with each other, the socket 7 is provided on the mount board 3, the header 6 is provided on the wiring board 2, and the header 6 may be an external connector.

  As shown in FIG. 6A, the socket 7 has a substantially rectangular shape extending in the front-rear direction in a plan view. The socket 7 includes a socket main body 72 and a terminal 71 held by the socket main body 72. The socket main body 72 is provided with a fitting recess 72a having a rectangular frame shape in plan view. The terminal 71 is exposed in the fitting recess 72a. Further, the end portion of the terminal 71 protrudes from the socket main body 72 in the left-right direction, and this end portion is connected to a not-illustrated wiring pattern formed on the upper surface of the wiring substrate 2 by unillustrated solder or the like. The socket 7 is usually mounted on the wiring board 2 by reflow.

  On the other hand, as shown in FIG. 6B, the header 6 has a substantially rectangular shape extending in the front-rear direction that is slightly smaller than the socket 7 in a bottom view. The header 6 includes a header main body 62 and terminals 61 held by the header main body 62. The header main body 62 has a rectangular frame in bottom view that can be fitted into the fitting recess 72a of the socket 7. A fitting projection 62a is provided, and the terminal 61 is exposed on the surface of the fitting projection 62a. Further, the end portion of the terminal 61 protrudes in the left-right direction from the header body 62, and this end portion is connected to the wiring pattern 36 of the mount substrate 3 by the solder ball 10. Further, for mounting the header 6 on the mount substrate 3, it is possible to use terminal posts, pins, etc. in addition to the solder balls. The height including the mount substrate 3 and the solder ball 10 is about 1 mm.

  Then, when the fitting convex part 62a of the header 6 is inserted into the fitting concave part 72a of the socket 7 and they are fitted, the terminals 61 and 71 come into contact with each other and the wiring pattern of the wiring board 2 and the wiring pattern of the mount board 3 36 is electrically connected. At this time, the height from the lower surface of the socket 7 to the upper surface of the header 6 is about 1 mm. For this reason, the height from the upper surface of the wiring board 2 to the other surface 3c serving as the upper surface of the mount board 3 when the light emitting side photoelectric conversion part 1A1 is mounted on the wiring board 2 is about 2 mm.

  Since the basic configuration of the light-receiving side photoelectric conversion unit 1A2 is the same as that of the light-emitting side photoelectric conversion unit 1A1, detailed description thereof is omitted. The light-emitting side photoelectric conversion unit 1A1 is different from the light-emitting side photoelectric conversion unit 1A1 in that a light receiving element 4B that receives light on one surface 3a of the mount substrate 3 and converts an optical signal into an electric signal, as shown in FIG. An IC substrate 5B on which an IC circuit 50B for receiving an electrical signal from 4B is formed is mounted. PD is adopted as the light receiving element 4B, and the IC substrate 5B is a TIA (Trans-impedance Amplifier) element that performs current / voltage conversion. In addition, an amplifier element may be mounted on the mount substrate 3.

  In the photoelectric conversion apparatus 1A of the reference example as described above, the header 6 is provided on the one surface 3a of the mount substrate 3 on which the light emitting element 4A or the light receiving element 4B is mounted, and the internal waveguide 31 is connected to one of the mount substrates 3. Since it is provided so as to extend in a direction parallel to the direction 3a, the height of the entire device in the plate thickness direction of the mount substrate 3 can be suppressed, and the height of the device can be reduced.

  Next, with reference to FIG. 8 and FIG. 9, the photoelectric conversion apparatus 1B according to the first embodiment of the present invention will be described. Since this photoelectric conversion apparatus 1B is an improvement of the photoelectric conversion apparatus 1A of the reference example, the same components as those of the reference example are denoted by the same reference numerals, and description thereof is omitted. Also in this photoelectric conversion device 1B, the light receiving side photoelectric conversion unit is the same as the light emission side photoelectric conversion unit, and therefore only the light emission side photoelectric conversion unit 1B1 will be illustrated and described.

  In the light emission side photoelectric conversion unit 1B1 of the first embodiment, an interposer substrate (intermediate substrate) 8 is provided between the mount substrate 3 and the header 6, as shown in FIG. That is, the upper surface of the interposer substrate 8 is connected to the one surface 3 a of the mount substrate 3 by the solder balls 15, and the header 6 is connected to the lower surface of the interposer substrate 8 by the solder 110. As a result, the mount substrate 3 and the header 6 are electrically connected by the interposer substrate 8, the solder 110 and the solder balls 15.

  Details will be described below.

  As shown in FIG. 9A, the one surface 3a of the mount substrate 3 includes an external electrical connection terminal portion 36a, a wiring portion 36b, and terminal portions 36c for the light emitting element 4A and the IC substrate 5A. A wiring pattern 36 is formed.

  Further, the interposer substrate 8 is formed of, for example, a multilayer board, and electrodes corresponding to the external electrical connection terminal portions 36a of the wiring pattern 36 are formed on the uppermost layer on the mount substrate 3 side, and on the lowermost layer on the header 6 side. A wiring pattern 81 (see FIG. 9C) having an electrode 81a corresponding to the terminal 61 of the header 6 is formed, and by electrically connecting them in the intermediate layer, the electrode pitch is converted and the electrode pattern Is to change.

  In the interposer substrate 8, the number of electrodes of the uppermost layer electrode and the lowermost layer electrode 81a do not necessarily correspond one-to-one, and the lowermost layer electrode 81a is integrated into a plurality of uppermost layer electrodes. Electrical connection is also possible. Therefore, it is possible to reduce the number of terminals of the header 6 by consolidating the electric lines with the interposer substrate 8.

  As described above, by using the interposer substrate 8, the degree of freedom of the wiring pattern of the mount substrate 3 can be improved. That is, since the light emitting element 4 </ b> A and the IC substrate 5 </ b> A are mounted on the mount substrate 3, it is difficult to match the external electrical connection terminal portion 36 a of the wiring pattern 36 of the mount substrate 3 with the terminal 61 of the header 6. In such a case, the interposer substrate 8 is particularly effective.

  In the light emission side photoelectric conversion unit 1B1, a frame 37 having a rectangular shape in plan view is interposed between the mount substrate 3 and the interposer substrate 8. As shown in FIG. 8, the frame body 37 has an upper end edge in close contact with one surface 3 a of the mount substrate 3 and a lower end edge in close contact with the upper surface of the interposer substrate 8. A substantially sealed space H is formed together with the mount substrate 3 and the interposer substrate 8.

  Further, the frame body 37 is mounted on the mount substrate 3 such that the terminal portions 36c for the light emitting elements 4A and the IC substrate 5A of the mount substrate 3 are located within the frame, while the external electrical connection terminal portions 36a are located outside the frame. Thus, the light emitting element 4A and the IC substrate 5A are sealed in the space H when the apparatus is assembled.

  Examples of the material of the frame 37 include an insulating material such as glass. The space H may be filled with a sealing body such as sealing resin or gas.

  In the first embodiment, the frame body 37 is provided between the mount substrate 3 and the interposer substrate 8, and the light emitting element 4A and the IC substrate 5A are surrounded by the mount substrate 3, the interposer substrate 8 and the frame body 37. Since the sealing performance of the light emitting element 4A and the IC substrate 5A is enhanced, the light emitting element 4A and the IC substrate 5A can be protected from moisture, dust and the like. This improves the reliability of the device.

  As described above, when the space H is filled with the sealing body, the sealing body further enhances the sealing performance of the light emitting element 4A and the IC substrate 5A, and is generated in the light emitting element 4A and the IC substrate 5A. By quickly moving the heat to the sealing body, the heat dissipation to the light emitting element 4A and the IC substrate 5A can also be improved.

  Next, with reference to FIG. 10 and FIG. 11, the photoelectric conversion apparatus 1C according to the second embodiment of the present invention will be described. Since this photoelectric conversion apparatus 1C is also an improvement of the photoelectric conversion apparatus 1A of the reference example, the same reference numerals are given to the same components as those of the reference example, and description thereof will be omitted. Also in this photoelectric conversion device 1C, since the light receiving side photoelectric conversion unit is the same as the light emission side photoelectric conversion unit, only the light emission side photoelectric conversion unit 1C1 is illustrated and described.

  The light emitting side photoelectric conversion unit 1C1 of the second embodiment is similar to the first embodiment in that an interposer substrate 8 is provided between the mount substrate 3 and the header 6, but the mount substrate 3 and the interposer A frame body 137 having a configuration different from that of the frame body 37 of the first embodiment is interposed between the substrate 8 and the interposer substrate 8 and the mount substrate 3 are electrically connected via the frame body 137. ing. For this reason, in the second embodiment, solder balls are not used as means for electrically connecting the mount substrate 3 and the interposer substrate 8.

  As shown in FIGS. 10 and 11, the frame body 137 has an outer edge shape substantially equal to that of the mount substrate 3, and through-wires are provided at positions corresponding to the external electrical connection terminal portions 36 a on the mount substrate 3. 138. The through wiring 138 also corresponds to the uppermost electrode of the interposer substrate 8, and both ends of the through wiring 138 come into contact with the external electrical connection terminal portion 36 a and the electrode of the interposer substrate 8 when the device is assembled. Thereby, the mount substrate 3 and the interposer substrate 8 are electrically connected.

  The frame 137 also forms a substantially sealed space H together with the mount substrate 3 and the interposer substrate 8 in the same manner as the frame 37 of the first embodiment, and the light emitting element 4A and the IC substrate 5A are formed in the space H. Are to be sealed. In the second embodiment, the space H may be filled with a sealing body.

  According to the second embodiment, the mount substrate 3 and the interposer substrate 8 can be electrically connected by rationally using the frame body 137 that seals the light emitting element 4A and the IC substrate 5A. Solder balls that serve to electrically connect the substrates 3 and 8 are not required.

  In the present embodiment, as the photoelectric conversion device 1B, a one-way communication type in which an optical signal is transmitted from the light emission side photoelectric conversion unit 1B1 to the light reception side photoelectric conversion unit is shown. A bidirectional communication type in which the light receiving element 4B is mounted on the light emitting side photoelectric conversion unit 1B1, the light emitting element 4A is mounted on the light receiving side photoelectric conversion unit, and a plurality of waveguides 31 are formed on the mount substrate 3. There may be. Moreover, the photoelectric conversion apparatus 1B should just be equipped with at least one of the light emission side photoelectric conversion part 1B1 or the light reception side photoelectric conversion part. Further, in both the one-way communication type and the two-way communication type, one-channel communication has been described. However, multi-channel communication may be performed by mounting an array-shaped light emitting / receiving element. Alternatively, a structure in which a plurality of waveguides are formed may be used.

It is a schematic block diagram of the photoelectric conversion apparatus of a reference example, and the wiring board to which this photoelectric conversion apparatus is connected. It is the figure which decomposed | disassembled the light emission side photoelectric conversion part of the photoelectric conversion apparatus of a reference example. (A) is a side view of a mount substrate on which an optical element is mounted, and (b) is a cross-sectional view taken along line AA of (a). It is the perspective view which looked at the mount board | substrate of the state before providing a waveguide from the downward direction. (A) is a bottom view of the mount substrate, (b) is a cross-sectional view of (a), (c) is a bottom view of the mount substrate of a modified example, and (d) is a cross-sectional view of (c). (A) is a perspective view of a socket type electrical connector, (b) is a perspective view of a header type electrical connector. It is the figure which decomposed | disassembled the light-receiving side photoelectric conversion part of the photoelectric conversion apparatus of a reference example. It is a schematic sectional drawing of the photoelectric conversion apparatus which concerns on 1st Embodiment of this invention. 1A and 1B are photoelectric conversion devices according to a first embodiment of the present invention, in which FIG. 1A is a bottom view of a mount substrate, FIG. 1B is a bottom view of a frame, and FIG. 2C is a bottom view of an interposer substrate. It is a schematic sectional drawing of the photoelectric conversion apparatus which concerns on 2nd Embodiment of this invention. It is the photoelectric conversion apparatus which concerns on 2nd Embodiment of this invention, (a) is a bottom view of a mount board | substrate, (b) is a bottom view of a frame, (c) is a bottom view of an interposer board | substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1B, 1C Photoelectric conversion apparatus 2 Wiring board 3 Mount board 3a One side 3c The other side 31 Internal waveguide 37,137 Frame body 138 Through wiring 4A Light emitting element 4B Light receiving element 5A, 5B IC board 50A, 50B IC circuit 6 Header type Electrical connector 7 Socket-type electrical connector 8 Interposer substrate 9 External waveguide H Space

Claims (3)

An optical element that converts an electrical signal into an optical signal or an optical signal into an electrical signal, an IC circuit for transmitting an electrical signal to or receiving an electrical signal from the optical element, and the optical element are mounted A mounting board; an electrical connector that can be attached to and detached from an external connector; and a waveguide that is optically coupled to the optical element. The electrical connector is mounted with the optical element and the IC circuit on the mounting board. Provided in the direction, the waveguide is a photoelectric conversion device provided on the mount substrate along one surface of the mount substrate or the other surface on the opposite side,
Between the mount substrate and the electrical connector, an intermediate substrate for changing the electrode pattern is provided,
Further, a frame body is provided between the mount substrate and the intermediate substrate so as to connect the two substrates and surrounds the optical element and the IC circuit together with the mount substrate and the intermediate substrate. A photoelectric conversion device characterized by that.   The photoelectric conversion apparatus according to claim 1, wherein the frame body is provided with a through wiring for electrically connecting the mount substrate and the intermediate substrate.   The photoelectric conversion apparatus according to claim 1, wherein a sealing body is filled in a space surrounded by the mount substrate, the intermediate substrate, and the frame body.

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