JP2012098411A - Optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical module capable of performing high speed transmission without degrading a high frequency signal by reducing the length of wiring (wire bonding).SOLUTION: An optical module comprises first substrates 1 on which an optical device 12a of a light-emitting side and an optical device 12b of a light-receiving side are respectively mounted. The optical module further comprises an external waveguide 2 for optically connecting the optical device 12a of the light-emitting side and the optical device 12b of the light-receiving side to each other. With the first substrate 1 of the light-emitting side and the first substrate 1 of the light-receiving side thus provided, the optical module further comprises second substrates 6 on which a signal processing part 4a for sending an electric signal to the optical device 12b and a signal processing part 4b for receiving an electric signal from the optical device 12b are respectively mounted. A lowering portion 1g is formed on the surface of the first substrate 1, so that a land 12e formed on the side of the optical device 12a may be lowered toward a land 4c of the signal processing part 4a formed on the side of the optical device 12a.

Description

  The present invention relates to an optical module that transmits or receives an optical signal.

  An optical module 50 shown in FIG. 9 includes an internal waveguide 52 provided in a groove formed on the surface of each first substrate 51 of the light emitting (transmitting) side optical module 50A and the light receiving (receiving) side optical module 50B, An optical path changing mirror 53 formed at the tip of the groove is provided. Further, it is mounted on the surface of each first substrate 51 and emits an optical signal to the core portion of the internal waveguide 52 via the mirror portion 53, or light from the core portion of the internal waveguide 52 via the mirror portion 53. A light emitting element (optical element) 54A and a light receiving element (optical element) 54B for receiving signals are provided. Further, an external waveguide (optical fiber) 55 optically coupled to the core portion of each internal waveguide 52 of the light emitting element 54A and the light receiving element 54B is provided (see Patent Document 1). In Patent Document 1, a flexible film-like one in which a resin optical waveguide is thinned is used as an external waveguide.

  In this patent document 1, the surface of each first substrate 51 is flip-chip mounted with bumps using the light emitting surface of the light emitting element 54A and the light receiving surface of the light receiving element 54B as mounting surfaces.

  Each first substrate 51 is installed on the surface of another second substrate (interposer substrate) 56. On the surface of each second substrate 56, a signal processing unit (IC substrate) 57A on which an IC circuit for transmitting an electric signal to the light emitting element 54A is formed, and an electric signal for receiving the electric signal from the light receiving element 54B. A signal processing unit (IC substrate) 57B on which an IC circuit is formed is mounted.

  The light emitting element 54A, the light receiving element 54B, and the signal processing parts 57A and 57B of each second substrate 6 are electrically connected by a loop wire bonding 58, respectively. Further, the connector 59 for electrically connecting the signal processing units 57A and 57B to other circuit devices and the signal processing units 57A and 57B are electrically connected by a loop-shaped wire bonding 60, respectively. Yes.

JP 2009-260227 A

  By the way, in the optical module as described above, considering high-speed transmission of 10 Gbs or more, it is conceivable to increase the speed per line or increase the number of channels.

  In the case of speeding up per line, the impedance mismatch due to the inductance component of the wire bonding portion makes it impossible to ignore the deterioration of the high-frequency signal due to the delay due to signal reflection. Here, since the inductance component is proportional to the length of wire bonding, it is necessary to shorten the length of wire bonding (wiring) in order to increase the speed per line.

  Further, in the case of increasing the number of channels, an increase in crosstalk between wirings becomes a problem. In general, crosstalk occurs due to capacitive coupling between wirings, and examples of measures for reduction include shortening the wiring length, increasing the wiring interval, and shielding in the GND circuit. However, the wire bonding portion cannot be shielded by the GND circuit, and there is a demerit that the optical module becomes larger when the wiring interval is increased. Therefore, it is necessary to shorten the length of wire bonding (wiring) even when considering multi-channeling.

  The present invention has been made to solve the above problems, and provides an optical module that enables high-speed transmission without deteriorating a high-frequency signal by shortening the wiring (wire bonding) length. It is the purpose.

  In order to solve the above-described problems, the present invention provides an optical element that emits light by converting an electrical signal into an optical signal, or a first substrate on which an optical element that converts a received optical signal into an electrical signal is mounted; An external waveguide path for optically connecting the light-emitting side optical element and the light-receiving side optical element, and the first substrate on the light-emitting side and the first substrate on the light-receiving side are installed on the surface, and an electrical signal is sent to the optical element. In an optical module including a signal processing unit for transmitting or a second substrate on which a signal processing unit for receiving an electrical signal from an optical element is mounted, a land on the optical element side is formed on the surface of the first substrate. It is an object of the present invention to provide an optical module characterized in that a concave step portion is formed to be lowered in the direction of the land on the optical element side of the signal processing portion.

  The concave step portion of the first substrate may be formed simultaneously with a groove for positioning the external waveguide on the first substrate.

  The land on the optical element side of the first substrate may be configured to have a height that substantially coincides with the land on the optical element side of the signal processing unit.

  A connector for electrically connecting the signal processing unit to another circuit device is mounted on the second substrate, and the first substrate and the signal processing unit are dropped on the surface of the second substrate. A concave portion to be installed is formed, and the land on the connector side of the signal processing unit dropped into the concave portion has a height substantially coincident with the land of the connector on the surface of the second substrate.

  A connector for electrically connecting the signal processing unit to another circuit device is mounted on the second substrate, and a recess for dropping the first substrate is installed on the surface of the second substrate. The land on the optical element side of the first substrate that has been formed and dropped into the recess is substantially the same height as the land on the connector side of the surface of the second substrate, and the signal processing unit It is possible to adopt a configuration in which flip-chip mounting is performed on the land on the optical element side and the land on the connector of the second substrate.

  According to the present invention, by reducing the land on the optical element (light emitting element and light receiving element) side at the concave step formed on the first substrate, the height difference from the land on the optical element side of the signal processing unit is small. Become. As a result, the length of wiring (wire bonding) connecting the land on the optical element side of the first substrate and the land on the optical element side of the signal processing unit can be shortened, so that deterioration of the high-frequency signal can be suppressed and high-speed transmission can be achieved. Is possible. In addition, since the height difference is reduced, the loop height of the wire bonding can be suppressed, so that the height of the optical module can be reduced.

It is side surface sectional drawing of the optical module which concerns on this invention. FIG. 2 is a first substrate of the light emitting side optical module of FIG. 1, (a) is a side sectional view, (b) is a sectional view taken along line II in (a), and (c) is a sectional view taken along line II-II in (a) FIG. 2A is a perspective view of the first substrate of FIG. 2, and FIG. 3B is a perspective view in which an internal waveguide is formed. 2A is a perspective view in which a light emitting element is mounted, and FIG. 2B is a perspective view in which an optical fiber is inserted. It is a schematic side sectional view of the light emitting side optical module of the first embodiment. It is a schematic side sectional view of the light emitting side optical module of the second embodiment. It is a schematic side sectional drawing of the light emission side optical module of 3rd Embodiment. It is a schematic side sectional drawing of the light emission side optical module of 4th Embodiment. It is side surface sectional drawing of the conventional optical module.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is a side sectional view of an optical module 40 according to the present invention. 2A and 2B show the light-emitting side optical module 40A of FIG. 1, in which FIG. 2A is a side cross-sectional view, FIG. 2B is a cross-sectional view taken along line II in FIG. FIG. 3A and 3B show the first substrate 1. FIG. 3A is a perspective view, and FIG. 3B is a perspective view in which an internal waveguide 16 is formed. 4A and 4B show the first substrate 1, in which FIG. 4A is a perspective view in which the light emitting element 12a is mounted, and FIG. 4B is a perspective view in which the optical fiber 2 is inserted.

  In FIG. 1, the optical module 40 includes a light emitting side optical module 40A, a light receiving side optical module 40B, and an optical fiber 2 that optically couples the light emitting side and the light receiving side optical modules 40A and 40B.

  The first substrate (mount substrate) 1 of the light emitting side optical module 40A and the first substrate (mount substrate) 1 of the light receiving side optical module 40B are rigid in order to avoid the influence of heat during mounting and the stress due to the use environment. is required. Further, in the case of optical transmission, since optical coupling 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 during use as much as possible. For this reason, a silicon (Si) substrate is employed as the first substrate 1 in the present embodiment.

  In particular, in the case of a silicon substrate, it is possible to process a highly accurate etching groove on the surface by utilizing the crystal orientation of silicon [a highly accurate mirror portion 15 (described later) using this groove, and an internal waveguide 16 ( (To be described later). ]. In addition, the silicon substrate has good flatness.

  The first substrate 1 is installed on the surface (upper surface) of a second substrate (interposer substrate) 6 having a larger size. Connectors 7 for electrically connecting to other circuit devices are respectively attached to the back surface (lower surface) of each second substrate 6.

  On the surface (upper surface) of the first substrate 1, light emission for converting an electrical signal into an optical signal is sent to a metal circuit (patterning circuit by copper or gold sputtering) 12d (see FIG. 5) formed on the surface of the first substrate 1. The element 12a is flip-chip mounted with bumps 12c (see FIG. 5) with the light emitting surface facing downward.

  In the present embodiment, a surface emitting laser (VCSEL (Vertical Cavity Surface Emitting Laser)) that is a semiconductor laser is employed as the light emitting element 12a. The light emitting element 12a may be an LED or the like.

  A signal processing unit (IC substrate) 4a on which an IC circuit for transmitting an electrical signal to the light emitting element 12a is formed is mounted on the surface of the second substrate 6. The signal processing unit 4a is a driver IC that drives the VCSEL, and is disposed in the vicinity of the light emitting element 12a. In addition, the mounting method of the signal processing unit 4a will be individually described in the description of each embodiment in FIGS.

  On the surface of the first substrate 1, as shown in FIG. 3 (a), a substantially trapezoidal first groove (waveguide forming groove) 1a and a substantially V-shaped second deeper than the first groove 1a. The groove 1b is formed continuously in the front-rear direction. The first groove 1a may be a substantially V-shaped groove that is shallower than the second groove 1b.

  At the tip of the first groove 1a, an optical path changing mirror 15 for bending the optical path by 90 degrees is formed at a position directly below the light emitting element 12a.

  As shown in FIG. 3B, an internal waveguide 16 that is optically coupled to the light emitting element 12a of the first substrate 1 is provided in the first groove 1a of the first substrate 1. The internal waveguide 16 extends from the mirror portion 15 in the direction of the second groove 1b and is flush with the rear end portion 1d of the first groove 1a.

  The internal waveguide 16 includes a core portion 17 having a substantially square cross section with a high refractive index through which light propagates, and a cladding portion 18 having a refractive index lower than that. As shown in FIG. 2C, the left and right surfaces of the core portion 17 are covered with the cladding portion 18. When the first groove 1a is a shallow V-shaped groove that is shallower than the second groove 1b, the core portion 17 is not substantially square in cross section, but is substantially pentagonal in cross section along the substantially V-shaped groove. Form into shape. Further, the internal waveguide 16 is not necessarily provided in the first groove 1a.

  As shown in FIG. 4A, a light emitting element 12a is mounted at a predetermined position on the surface of the first substrate 1 on which the internal waveguide 16 is provided, and the space between the light emitting element 12a and the core portion 17 is mounted. As shown in FIG. 2A, the optical transparent resin 13 is filled.

  Returning to FIG. 1, the first substrate 1 of the light-receiving side optical module 40B will be described. The basic configuration of the first substrate 1 of the light receiving side optical module 40B is the same as that of the first substrate 1 of the light emitting side optical module 40A. However, a light receiving element 12b for converting an optical signal into an electric signal is flip-chip mounted with bumps on the surface (upper surface) of the first substrate 1 of the light receiving side optical module 40B with the light receiving surface facing downward. Further, a signal processing unit (IC substrate) 4b on which an IC circuit for transmitting an electrical signal to the light receiving element 12b is mounted on the surface of the second substrate 6, and the light emitting side optical module 40A is mounted. Different from the first substrate 1. A PD (Photo Diode) is adopted as the light receiving element 12b, and the signal processing unit 4b is an element such as a TIA (Trans-impedance Amplifier) that performs current / voltage conversion.

  Next, the optical fiber 2 will be described. As shown in FIG. 1 and FIG. 4B, the optical fiber 2 includes the core portion 17 of the internal waveguide 16 of the first substrate 1 of the light emitting side optical module 40A and the inside of the first substrate 1 of the light receiving side optical module 40B. A fiber core portion 21 that can be optically coupled to the core portion 17 of the waveguide 16 is provided inside. And it is a cord type comprised by the fiber cladding part 22 surrounding the outer periphery of this fiber core part 21, and the coating | coated part 23 which coat | covers the outer periphery of this fiber cladding part 22. FIG. The fiber core portion 21, the fiber clad portion 22, and the covering portion 23 are circular.

  As shown in FIG. 1, the optical fiber 2 has the covering portion 23 peeled off in the vicinity of the second groove 1 b of the first substrate 1 to expose the fiber cladding portion 22.

  Then, as shown in FIGS. 2A, 2C, and 4B, the fiber clad portion 22 of the optical fiber 2 is installed in the second groove 1b of the first substrate 1, and the boundary portion with the first groove 1a. The fiber clad portion 22 is positioned on the inclined surface 1c. At this time, it is optically coupled with the optical axis of the core part 17 of the internal waveguide 16 of the first substrate 1 and the fiber core part 21 of the optical fiber 2 being aligned.

  The gap between the end face of the core portion 17 of the internal waveguide 16 of the first substrate 1 and the end face of the fiber core portion 21 of the optical fiber 2 is 200 μm or less. In general, the gap 0 is preferable in which the optical coupling efficiency is 100%. However, in this configuration, the gap is 60 μm to 100 μm due to restrictions on the groove width of the first substrate 1 and the outer diameter size of the fiber clad portion 22. It becomes.

  At the position of the surface of the first substrate 1, as shown in FIGS. 2 (a) and 2 (b), a holding block 24 is disposed on the upper portion of the fiber cladding portion 22 of the optical fiber 2, and the holding block 24 and the second groove 1 b The space between is filled with the adhesive 14.

  As described above, the front end side of the fiber clad portion 22 of the optical fiber 2 is bonded and fixed to the first substrate 1 together with the pressing block 24 with the adhesive 14 while being pressed against the second groove 1 b by the pressing block 24. become.

  In the light emitting side optical module 40A, an optical signal is emitted from the light emitting element 12a to the fiber core portion 21 of the optical fiber 2 via the mirror portion 15. In the light receiving side optical module 40B, the light signal from the fiber core portion 21 of the optical fiber 2 is received by the light receiving element 12b via the mirror portion 15.

  FIG. 5 is a schematic side sectional view of the light emitting side optical module 40A-1 (the same applies to the light receiving side optical module 40B) of the first embodiment. On the surface of the first substrate 1, there is formed a recessed step portion 1g composed of an inclined surface 1e inclined obliquely downward from the vicinity of the bump 12c of the light emitting element 12a and a horizontal surface 1f horizontal from the lower end of the inclined surface 1e. Has been.

  A metal circuit (a patterning circuit using copper or gold sputtering) 12d connected to the bumps 12c of the light emitting element 12a is formed along the inclined surface 1e and the horizontal surface 1f. As a result, a land 12e on the light emitting element 12a side, which is lowered in the direction of the land 4c on the light emitting element 12a side of the signal processing unit 4a, is formed on the horizontal surface 1f of the recessed step portion 1g.

  The land 12e on the light emitting element 12a side and the land 4c on the light emitting element 12a side of the signal processing unit 4a are electrically connected by a loop-shaped wire bonding 26.

  Further, the land 4 d on the connector 7 side of the signal processing unit 4 a and the land 7 a of the connector 7 on the surface of the second substrate 6 are electrically connected by a loop-shaped wire bonding 27. The land 7 a of the connector 7 is electrically connected to the connector 7 through the through hole wiring 6 a of the second substrate 6.

  In the light emitting side optical module 40A-1 according to the first embodiment, the land 12e on the light emitting element 12a side is lowered by the concave step portion 1g formed on the first substrate 1, whereby the light emitting element 12a of the signal processing unit 4a. The height difference H from the side land 4c is reduced. As a result, since the length of the wire bonding (wiring) 26 that connects the land 12e on the light emitting element 12a side of the first substrate 1 and the land 4c on the light emitting element 12a side of the signal processing unit 4a can be shortened, the high-frequency signal is deteriorated. Can be suppressed, and high-speed transmission is possible. In addition, since the height difference H is reduced, the loop height of the wire bonding 26 can be suppressed, so that the height of the optical module 40 can be reduced. Incidentally, the reason why the wire bondings 26 and 27 are formed in a loop shape is to prevent the land 12e and 4c from having a height difference (step) H from being caught by the edge portion and being disconnected. If H is small, the loop height can be suppressed. Therefore, as in the second embodiment to be described later, if there is no difference in level (step), the wire bonding 26 can be made linearly.

  Further, the concave step portion (groove) 1g of the first substrate 1 can be formed at the same time as the second groove 1b for positioning the fiber clad portion 22 of the optical fiber 2 which is an external waveguide on the first substrate 1, so that the groove is formed. Since the etching process does not increase, the cost is not increased.

  FIG. 6 is a schematic side cross-sectional view of the light-emitting side optical module 40A-2 of the second embodiment. 5 differs from the light emitting side optical module 40A-1 of the first embodiment in FIG. 5 in that the land 12e on the light emitting element 12a side of the first substrate 1 substantially matches the land 4c on the light emitting element 12a side of the signal processing unit 4a. It is the point which becomes height to do.

  In the light emitting side optical module 40A-2 of the second embodiment, the height difference between the lands 12e and the lands 4c is made substantially equal so that the height difference H is eliminated and the wire bonding 26 can be made linearly. As a result, since the wire length for the loop of the wire bonding 26 can be further shortened, deterioration of the high-frequency signal can be further suppressed.

  FIG. 7 is a schematic side cross-sectional view of the light-emitting side optical module 40A-3 of the third embodiment. 5 is different from the light emitting side optical module 40A-1 of the first embodiment in FIG. 5 in that the concave portions 6b and 6c for dropping and installing the first substrate 1 and the signal processing unit 4a on the surface of the second substrate 6 are provided. It is a point that is formed. Further, the land 4d on the connector 7 side of the signal processing unit 4a dropped into the recess 6c is a point that is substantially coincident with the land 7a of the connector 7 on the surface of the second substrate 6.

  In the light emitting side optical module 40A-3 of the third embodiment, the height difference between the land 4d and the land 7a is made substantially equal to each other so that the height difference H is eliminated and the wire bonding 27 can be made linearly. As a result, the wire length for the loop of the wire bonding 27 can be shortened, so that the deterioration of the high-frequency signal can be further suppressed.

  FIG. 8 is a schematic side cross-sectional view of the light emitting side optical module 40A-4 of the fourth embodiment. 5 is different from the light emitting side optical module 40A-1 of the first embodiment in FIG. 5 in that a recess 6b is formed on the surface of the second substrate 6 so that the first substrate 1 is dropped. Further, the land 12e on the light emitting element 12a side of the first substrate 1 dropped into the recess 6b has a height substantially matching the land 7a on the surface of the second substrate 6 on the connector 7 side. Furthermore, the signal processing unit 4a is flip-chip mounted on the land 12e on the light emitting element 12a side of the first substrate 1 and the land 7a of the connector 7 on the second substrate 6 with bumps 4e.

  In the light emitting side optical module 40A-4 of the fourth embodiment, wire bonding between the land 12e and the land 4c and between the land 4d and the land 7a in the first to third embodiments (FIGS. 5 to 5). 7 and 26) can be replaced with flip chip mounting by the bump 4e. As a result, the wiring length can be further shortened.

  As described above, the optical module according to the present invention includes an optical element that converts an electrical signal into an optical signal and emits light, or a first substrate on which an optical element that converts a received optical signal into an electrical signal is mounted; An external waveguide path for optically connecting the light emitting side optical element and the light receiving side optical element, a light emitting side first substrate and a light receiving side first substrate are provided on the surface, and an electric signal is transmitted to the optical element. And a second substrate having a signal processing unit for transmitting an electric signal from an optical element mounted on a surface thereof, a land on the optical element side is provided on the surface of the first substrate. A concave step portion for lowering the signal processing portion in the direction of the land on the optical element side is formed.

  According to this, by reducing the land on the optical element (light emitting element and light receiving element) side in the concave step formed on the first substrate, the height difference from the land on the optical element side of the signal processing unit is reduced. . As a result, the length of wiring (wire bonding) connecting the land on the optical element side of the first substrate and the land on the optical element side of the signal processing unit can be shortened, so that deterioration of the high-frequency signal can be suppressed and high-speed transmission can be achieved. Is possible. In addition, since the height difference is reduced, the loop height of the wire bonding can be suppressed, so that the height of the optical module can be reduced.

  The concave step of the first substrate may be formed simultaneously with a groove for positioning the external waveguide on the first substrate.

  According to this, since the groove for positioning the external waveguide can be formed on the first substrate at the same time as the concave step (groove) can be formed, the etching process for forming the groove does not increase, so the cost does not increase. .

  The land on the optical element side of the first substrate may be configured to have a height that substantially coincides with the land on the optical element side of the signal processing unit.

  According to this, by making the lands on the optical element side of the first substrate substantially coincide with the lands on the optical element side of the signal processing section, there is no difference in height and wire bonding can be performed linearly. As a result, the wire length for the wire bonding loop can be shortened, so that the deterioration of the high-frequency signal can be further suppressed.

  In addition, a connector for electrically connecting the signal processing unit to another circuit device is mounted on the second substrate, and the first substrate, the signal processing unit, and the like are mounted on the surface of the second substrate. And a land on the connector side of the signal processing unit dropped into the recess is substantially the same height as the land of the connector on the surface of the second substrate. .

  According to this, the height of the land on the connector side of the signal processing unit dropped into the concave portion of the second board is made to substantially coincide with the height of the land of the connector of the second board, so that the height difference is eliminated and linearized. Wire bonding is possible. As a result, the wire length for the wire bonding loop can be shortened, so that the deterioration of the high-frequency signal can be further suppressed.

  Further, a connector for electrically connecting the signal processing unit to another circuit device is mounted on the second substrate, and a recess for installing the first substrate by dropping on the surface of the second substrate. And the land on the optical element side of the first substrate dropped into the recess is substantially the same height as the land on the connector side of the surface of the second substrate, and the signal processing unit It is possible to perform flip-chip mounting on the land on the optical element side and the land on the connector of the second substrate.

  According to this, between the land on the optical element side of the first substrate and the land on the optical element side of the signal processing unit, and between the land on the connector side of the signal processing unit and the land on the connector side of the second substrate. Wire bonding can be replaced with flip chip mounting. As a result, the wiring length can be further shortened.

1 1st board | substrate 1a 1st groove | channel 1b 2nd groove | channel (groove)
1g Concave Step 2 Optical Fiber 4a, 4b Signal Processing Unit 4c, 4d Land 4e Bump 6 Second Substrate 6b, 6c Concave 7 Connector 7a Land 12a Light Emitting Element (Optical Element)
12b Light receiving element (optical element)
12e Land 15 Mirror part 16 Internal waveguide 26, 27 Wire bonding 40 Optical module 40A Light emitting side optical module 40B Light receiving side optical module H Height difference

Claims (5)

An optical element that emits light by converting an electrical signal into an optical signal, or a first substrate on which an optical element that converts a received optical signal into an electrical signal is mounted, the optical element on the light emitting side, and the optical element on the light receiving side, An optical waveguide for optically connecting the light emitting side first substrate and the light receiving side first substrate on the surface, and a signal processing unit for transmitting an electric signal to the optical element, or an electric from the optical element In an optical module comprising a second substrate on which a signal processing unit for receiving a signal is mounted,
An optical module, wherein a concave step portion is formed on the surface of the first substrate for lowering the land on the optical element side in the direction of the land on the optical element side of the signal processing unit.   The optical module according to claim 1, wherein the concave step portion of the first substrate is formed simultaneously with a groove for positioning the external waveguide on the first substrate.   3. The optical module according to claim 1, wherein a land on the optical element side of the first substrate has a height that substantially coincides with a land on the optical element side of the signal processing unit.   A connector for electrically connecting the signal processing unit to another circuit device is mounted on the second substrate, and the first substrate and the signal processing unit are dropped on the surface of the second substrate. The connector-side land of the signal processing unit dropped into the recess is formed to have a height substantially coincident with the connector land on the surface of the second substrate. The optical module as described in any one of -3.   A connector for electrically connecting the signal processing unit to another circuit device is mounted on the second substrate, and a recess for dropping the first substrate is installed on the surface of the second substrate. The land on the optical element side of the first substrate that has been formed and dropped into the recess is substantially the same height as the land on the connector side of the surface of the second substrate, and the signal processing unit The optical module according to any one of claims 1 to 3, wherein flip-chip mounting is performed on the land on the optical element side and the land on the connector of the second substrate.

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