JP2012069882A - Optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical module capable of suppressing a loss to high frequency, by shortening an electrically connecting distance between an optical element and an IC substrate.SOLUTION: An optical module comprises a substrate 15, an internal waveguide 21, a mirror portion 20, an optical element 33 (33a and 33b), and an external waveguide 25. A holding member 30 is provided, which holds a light-emitting surface or a light-receiving surface of the optical element 33 on a back surface so as to keep a predetermined clearance from a surface of the substrate 15. On a surface of the holding member 30 and near the optical element 33, an IC substrate 34a is mounted. A metal circuit 35a for electrically connecting a through-hole wiring 30b of the optical element 33 of the holding member 30 and the IC substrate 34a is provided.

Description

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

  The optical module shown in FIG. 8 includes an internal waveguide 2 provided in a groove 1a formed on the surface of a first substrate (mount substrate) 1, and an optical path conversion mirror formed at the tip of the groove 1a. Part 3 is provided. Further, it is mounted on the surface of the first substrate 1 so as to face the mirror part 3, and emits an optical signal to the core part of the internal waveguide 2 through the mirror part 3, or the internal waveguide through the mirror part 3. The optical element 4 which receives the optical signal from the core part of 2 is provided. Furthermore, an external waveguide (optical fiber) 5 that is optically coupled to the core portion of the internal waveguide 2 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 Patent Document 1, flip chip mounting is performed on the surface of the first substrate 1 with bumps using the light emitting surface or the light receiving surface of the optical element 4 as a mounting surface.

  Further, the first substrate 1 is installed on the surface of another second substrate (interposer substrate) 6, and an electrical signal is transmitted to the optical element 4 on the surface of the second substrate 6 or an electrical signal from the optical element 4 is transmitted. An IC substrate 7 on which an IC circuit for receiving is formed is mounted.

  The metal circuit (patterning circuit by copper or gold sputtering) 1b of the optical element 4 formed on the surface of the first substrate 1 and the IC substrate 7 of the second substrate 6 are usually electrically connected by wire bonding 8. It is connected to the. In addition, 9 is a pressing plate for pressing and fixing the optical fiber 5 to the first substrate 1, and 10 is a connector for electrically connecting the IC substrate 7 to another circuit device.

JP 2009-260227 A

  However, since the optical element 4 of the first substrate 1 and the IC substrate 7 of the second substrate 6 are electrically connected by the metal circuit 1b and the wire bonding 8, this electrically connecting distance L becomes long.

  For this reason, during high-frequency transmission (for example, 10 Gbps or more), there is a desire to improve the loss due to high frequency loss. In particular, the influence is significant on the light receiving side (light receiving element side) of the optical element 4.

  The present invention has been made to meet the above-mentioned demand, and provides an optical module capable of suppressing loss against high frequency by shortening the distance of electrical connection between an optical element and an IC substrate. It is intended.

  In order to solve the above-mentioned problems, the present invention provides an internal waveguide provided in a first groove formed on the surface of a substrate, an optical path conversion mirror part formed at the tip of the first groove, It is mounted on the surface side of the substrate so as to face this mirror part, and emits an optical signal to the core part of the internal waveguide through the mirror part, or an optical signal from the core part of the internal waveguide through the mirror part In an optical module including an optical element that receives light and an external waveguide that is optically coupled to the core portion of the internal waveguide, the optical element is mounted on the back surface that is fixed to the surface of the substrate and faces the surface Mounted on the surface opposite to the back surface of the holding member and in the vicinity of the optical element. The holding member holds the light emitting surface or the light receiving surface of the optical element so as to be separated from the surface of the substrate by a predetermined gap. Transmit an electrical signal to this optical element or light An IC substrate on which an IC circuit for receiving an electrical signal from a child is formed; a through-hole wiring of an optical element provided in the holding member; and a through-hole wiring provided on a surface of the holding member; An optical module including a metal circuit that electrically connects an IC substrate is provided.

  The holding member can be configured to be insulative.

  An optical fiber as the external waveguide is provided in a second groove formed continuously with the first groove on the surface of the substrate, and has a fiber core portion optically coupled to the core portion of the internal waveguide. The holding member may also serve as a pressing plate that presses and fixes the optical fiber to the substrate.

  A concave portion is formed on the back surface of the pressing plate, the optical element is mounted on the bottom surface of the concave portion, and the optical element is hermetically sealed by filling the concave portion with a transparent adhesive or a transparent resin. It can be set as the structure currently made.

  The optical element may be configured to be hermetically sealed with a transparent resin.

  The pressing plate can be formed of a resin molded body.

  According to the present invention, the optical element is mounted on the back surface of the holding member fixed to the front surface of the substrate, and the IC substrate is mounted on the surface of the holding member and in the vicinity of the optical element. The through hole wiring and the metal circuit of the IC substrate are electrically connected.

  Accordingly, since the optical element and the IC substrate can be mounted on the back surface and the front surface of the holding member, the distance for electrical connection between the optical element and the IC substrate can be shortened, and thus loss against high frequency can be suppressed.

  Further, since the light emitting surface or the light receiving surface of the optical element faces upward (surface opposite to the bump mounting surface), foreign matter inspection after mounting of the optical element can be performed.

1 is a schematic side view of an optical module according to the present invention. It is the 1st board | substrate of the optical module of the light emission side of FIG. 1, (a) is side surface sectional drawing, (b) is II sectional view taken on the line of (a), (c) is II-II line of (a). It is sectional drawing. 2A is a perspective view, and FIG. 3B is a perspective view in which an internal waveguide is formed and an optical fiber is fixed by a pressing plate. FIG. 2 is a schematic drawing of a first substrate of the light-emitting side optical module in FIG. 1, (a) is a side cross-sectional view, and (b) is a side cross-sectional view of a pressing plate in which a light-emitting element is sealed with a transparent resin. (A) is a side sectional view of a pressing plate in which a recess is formed, (b) is a side sectional view of a pressing plate in which an IC substrate is mounted right above the light emitting element, and (c) is a transparent resin or transparent adhesive in the recess. It is side surface sectional drawing of the filled pressing board. It is side surface sectional drawing of a holding member different from a pressing plate. It is a top view of a pressing plate. It is a schematic side sectional view of a conventional light emitting side optical module.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic side view of an optical module according to the present invention. 2 is a first substrate 15 of the optical module on the light emitting side of FIG. 1, (a) is a side sectional view, (b) is a sectional view taken along line II of (a), and (c) is a sectional view of (a). It is II-II sectional view taken on the line. 3A and 3B show the first substrate 15, in which FIG. 3A is a perspective view, and FIG. 3B is a perspective view in which an internal waveguide 21 is formed and the optical fiber 17 is fixed by a pressing plate 30.

  In FIG. 1, the optical module includes a first substrate (mount substrate) 15 on the light emitting side, a first substrate (mount substrate) 16 on the light receiving side, and an optical element 33 (light emitting elements 33a, 16) of the first substrates 15 and 16. And an optical fiber 17 for optically coupling the light receiving element 33b).

  The first substrates 15 and 16 need to have rigidity 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 the optical transmission efficiency from the light emitting element 33a to the light receiving element 33b is required, it is necessary to mount the optical element 33 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 substrates 15 and 16 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 [using this groove, a highly accurate mirror portion 20 (described later) and an internal waveguide 21 ( (To be described later). ]. In addition, the silicon substrate has good flatness.

  The first substrates 15 and 16 are respectively installed on the surface (upper surface) of a second substrate (another substrate... Interposer substrate) 18 having a larger size. Connectors 19 for electrically connecting to other circuit devices are attached to the back surface (lower surface) of each second substrate 18.

  As shown in detail in FIGS. 2 and 3A, the surface of the first substrate 15 has a substantially trapezoidal first groove (waveguide forming groove) 15a and a substantially V shape deeper than the first groove 15a. A character-shaped second groove 15b is formed continuously in the front-rear direction.

  At the tip of the first groove 15a, an optical path changing mirror 20 for bending the optical path by 90 degrees is formed at a position directly below the light emitting element 33a (described later).

  In the first groove 15a of the first substrate 15, an internal waveguide 21 that is optically coupled to the light emitting element 33a is provided. The internal waveguide 21 extends from the mirror portion 20 in the direction of the second groove 15b, and is flush with the rear end portion 15d of the first groove 15a (see FIG. 3A).

  As shown in FIG. 2C, the internal waveguide 21 includes a core part 22 having a substantially square cross section with a high refractive index through which light propagates, and a clad part 23 having a refractive index lower than that.

  The left and right surfaces and the upper surface of the core part 22 are covered with a clad part 23. The back surface of the core portion 22 is in contact with the bottom surface of the first groove 15 a that is wider than the core portion 22. The first groove 15a may be a substantially V-shaped groove shallower than the second groove 15b.

  As shown in FIGS. 1 and 3B, the optical fiber 17 includes a core portion 22 of the inner waveguide 21 of the first substrate 15 on the light emitting side and a core portion of the inner waveguide 21 of the first substrate 16 on the light receiving side. And a fiber core portion 25 that can be optically coupled to the inside. And it is a cord type comprised by the fiber clad part 26 which surrounds the outer periphery of this fiber core part 25, and the coating | coated part 27 which coat | covers the outer periphery of this fiber clad part 26. The fiber core portion 25, the fiber clad portion 26, and the covering portion 27 are circular.

  As shown in FIG. 1, the optical fiber 17 has the covering portion 27 peeled off in the vicinity of the second groove 15 b of the first substrate 15 to expose the fiber clad portion 26.

  Then, as shown in FIGS. 2A and 2B, the fiber clad portion 26 of the optical fiber 17 is installed in the second groove 15b of the first substrate 15, and the rising slope 15c at the boundary with the first groove 15a. The fiber clad part 26 is positioned. At this time, it is optically coupled with the optical axis of the core portion 22 of the internal waveguide 21 of the first substrate 15 and the fiber core portion 25 of the optical fiber 17 aligned.

  The gap between the end face of the core portion 22 of the internal waveguide 21 of the first substrate 15 and the end face of the fiber core portion 25 of the optical fiber 17 is 200 μm or less. In general, the gap 0 is preferable, in which the coupling efficiency is zero, but in this configuration, the gap is 60 nm to 100 nm due to restrictions on the groove width of the first substrate 15 and the outer diameter size of the optical fiber clad portion 26. .

  On the surface side of the first substrate 15, as shown in FIG. 2A and FIG. 3B, a pressing plate (holding member) 30 is disposed on the upper portion of the fiber clad portion 26 of the optical fiber 17. The space between the first groove 15b and the second groove 15b is filled with an adhesive 31. The pressing plate 30 is preferably formed of a transparent insulating member such as glass.

  As described above, the distal end side of the fiber clad portion 26 of the optical fiber 17 is bonded and fixed to the first substrate 15 together with the pressing plate 30 with the adhesive 31 while being pressed against the second groove 15 b by the pressing plate 30. become.

  The holding plate 30 bonded and fixed to the surface of the first substrate 15 with the adhesive 31 has a stepped extension extending above the internal waveguide 21 with a certain distance from the surface of the first substrate 15. The part 30a is integrally formed.

  On the back surface (lower surface) of the extending portion 30 a facing the surface of the first substrate 15, the light emitting element 33 a that is located directly above the mirror portion 20 of the internal waveguide 21 and converts an electric signal into an optical signal emits light. It is flip-chip mounted with bumps with the surface facing down. That is, the light emitting surface of the light emitting element 33a is held by the extending portion 30a of the pressing plate 30 such that the light emitting surface of the light emitting element 33a is separated from the surface of the first substrate 15 by a predetermined gap.

  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 33a. The light emitting element 33a may be an LED or the like. The IC substrate 34a described below is a driver IC that drives the VCSEL.

  Further, an IC in which an IC circuit for transmitting an electrical signal to the light emitting element 33a is formed on the surface (upper surface) opposite to the back surface (lower surface) of the extending portion 30a is located in the vicinity of the light emitting element 33a. A substrate (signal processing unit) 34a is mounted.

  As shown in FIG. 4A, the extending portion 30a of the pressing plate 30 is provided with a through hole wiring 30b of the light emitting element 33a in the vertical direction. The through hole wiring 30b has copper or the like on the inner surface of the hole. The plated conductive foil is electrically connected to the terminal of the light emitting element 33a.

  As shown in FIG. 7, a metal circuit (patterning circuit by copper or gold sputtering) 35a for electrically connecting the through-hole wiring 30b and the IC substrate 34a is formed on the surface of the extending portion 30a of the pressing plate 30. Is provided.

  Further, a metal circuit (patterning circuit by copper or gold sputtering) 35b of the IC substrate 34a on the surface of the extending portion 30a is a metal circuit for supplying IC power to the second substrate 18 by wire bonding 36 (patterning circuit by copper or gold sputtering). ) 18a.

  Returning to FIG. 1, the basic configuration of the first substrate 16 on the light receiving side is the same as that of the first substrate 15 on the light emitting side.

  However, a light receiving element 33b that converts an optical signal into an electric signal is mounted instead of the light emitting element 33a that converts an electric signal into an optical signal. The first substrate on the light emitting side is that an IC substrate (signal processing unit) 34b on which an IC circuit for transmitting an electric signal to the light receiving element 33b is formed is mounted on the surface of the second substrate 18. 15 and different. As the light receiving element 33b, a PD (Photo Diode) is adopted, and the IC substrate 34b is an element such as a TIA (Trans-impedance Amplifier) that performs current / voltage conversion.

  If the optical module is configured as described above, the light emitting element 33a (the same applies to the light receiving element 33b) is mounted on the back surface of the extending portion 30a of the pressing plate (holding member) 30 fixed to the surface of the first substrate 15. ing. In addition, the IC substrate 34a is mounted on the surface of the pressing plate 30 and in the vicinity of the light emitting element 33a (in this example, immediately lateral position), and the through hole wiring 30b of the light emitting element 33a and the metal circuit 35a of the IC substrate 34a. And are electrically connected.

  Thereby, since the light emitting element 33a and the IC substrate 34a can be mounted on the back surface and the front surface of the pressing plate 30, the distance L1 (see FIG. 7) for electrical connection between the light emitting element 33a and the IC substrate 34a can be shortened. Therefore, the loss with respect to a high frequency can be suppressed.

  In addition, since the light emitting surface of the light emitting element 33a faces upward (surface opposite to the bump mounting surface), foreign matter inspection after the light emitting element 33a is mounted can be performed.

  Furthermore, if the presser plate 30 is formed of an insulating member, the light emitting element 33a can be mounted on the insulating presser plate 30, so that loss against high frequency can be further suppressed.

  As shown in FIG. 4B, if the light emitting element 33a is hermetically sealed with a transparent resin 37 such as silicone rubber, the light emitting element 33a is protected and the mounting strength is improved. Furthermore, since water molecules do not enter the light emitting element 33a, reliability in a high humidity environment can be maintained. Further, if the transparent resin 37 is formed into a condensing lens shape, the optical coupling is improved.

  Further, since the pressing plate 30 of the optical fiber 17 also serves as a holding member that holds the light emitting element 33a, the structure can be simplified.

  Furthermore, if an organic / inorganic hybrid resin, for example, is used as the resin molded body for molding the presser plate 30, in addition to the effect of expanding the degree of freedom in the shape of the resin molding (complicated concave structure can be mass-produced at low cost), moisture resistance The effect of improving the property can also be added.

  In the embodiment of FIGS. 4A and 4B, the light emitting element 33a is flip-chip mounted on the back surface (lower surface) of the stepped extension 30a of the pressing plate 30 with bumps. On the other hand, as in the embodiment of FIG. 5A, the pressure plate (holding member) 30 has the same thickness and extends above the internal waveguide 21 along the surface of the first substrate 15. The extending part 30a can also be formed integrally. In this case, the recess 30c can be formed on the back surface of the extending portion 30a, and the light emitting element 33a can be flip-chip mounted on the bottom surface (lower surface) of the recess 30c with bumps.

  In FIG. 5A, the IC substrate 34a is mounted at a position immediately beside the light emitting element 33a. However, as shown in FIG. 5B, the IC substrate 34a can be mounted at a position directly above the light emitting element 33a. is there.

  Further, as shown in FIG. 5C, the light emitting element 33a can be hermetically sealed by filling the concave portion 30c with a transparent resin (or transparent adhesive) 37.

  In this way, by filling the recess 30c with the transparent resin 37, the light emitting element 33a is protected and the mounting strength is improved. Further, it is possible to prevent foreign matters such as dust and dust from entering the recess 30c. Furthermore, since water molecules do not enter the light emitting element 33a, reliability in a high humidity environment can be maintained. It should be noted that a transparent adhesive may be used as the adhesive 31 for adhering and fixing the presser plate 30 to the first substrate 15, and a part of the adhesive 31 may be filled in the recess 30c at the time of bonding. .

  In each of the above embodiments, the holding plate 30 of the optical fiber 17 also serves as a holding member that holds the light emitting element 33a. However, as shown in FIG. 6, the holding plate that holds the light emitting element 33a separately from the holding plate 30. A member 38 can also be provided. In this case, the light emitting element 33a is flip-chip mounted on the bottom surface (lower surface) of the recess 30c with bumps, and an extension portion similar to that shown in FIG. 4A is formed, and the back surface (lower surface) of the extension portion. Further, the light emitting element 33a can be flip-chip mounted with bumps.

  As described above, the optical module according to the present invention includes the internal waveguide provided in the first groove formed on the surface of the substrate, and the optical path conversion mirror portion formed at the tip of the first groove. Mounted on the surface side of the substrate so as to face this mirror part, and emits an optical signal to the core part of the internal waveguide through the mirror part, or light from the core part of the internal waveguide through the mirror part In an optical module including an optical element that receives a signal and an external waveguide that is optically coupled to the core portion of the internal waveguide, the optical element is fixed to the surface of the substrate, and the optical element is disposed on the back surface facing the surface. A holding member that is mounted and holds the light emitting surface or light receiving surface of the optical element so as to be separated from the surface of the substrate by a predetermined gap, and a surface opposite to the back surface of the holding member and in the vicinity of the optical element. It is mounted and an electric signal is transmitted to this optical element. Is an IC substrate on which an IC circuit for receiving an electrical signal from the optical element is formed, a through-hole wiring of the optical element provided in the holding member, and a through-hole wiring provided on the surface of the holding member. And a metal circuit that electrically connects the IC substrate.

  According to this, the optical element is mounted on the back surface of the holding member fixed to the front surface of the substrate, and the IC substrate is mounted on the surface of the holding member and in the vicinity of the optical element. The through-hole wiring and the metal circuit of the IC substrate are electrically connected.

  Accordingly, since the optical element and the IC substrate can be mounted on the back surface and the front surface of the holding member, the distance for electrical connection between the optical element and the IC substrate can be shortened, and thus loss against high frequency can be suppressed.

  In addition, since the light emitting surface or light receiving surface of the optical element faces upward (surface opposite to the bump), foreign matter inspection after mounting the optical element can be performed.

  The holding member can be configured to be insulative.

  According to this, since the optical element can be mounted on the insulating holding member, the loss with respect to the high frequency can be further suppressed.

  An optical fiber as the external waveguide is provided in a second groove formed continuously with the first groove on the surface of the substrate, and has a fiber core portion optically coupled to the core portion of the internal waveguide. The holding member may also serve as a pressing plate that presses and fixes the optical fiber to the substrate.

  According to this, since the holding member also serves as a pressing plate for the optical fiber, the structure can be simplified.

  A concave portion is formed on the back surface of the pressing plate, the optical element is mounted on the bottom surface of the concave portion, and the optical element is hermetically sealed by filling the concave portion with a transparent adhesive or a transparent resin. It can be set as the structure currently made.

  According to this, by filling the recess with the transparent adhesive or the transparent resin, the optical element is protected and the mounting strength is improved. Moreover, it can prevent that foreign materials, such as dust and dust, penetrate | invade in a recessed part. Furthermore, since water molecules do not enter the optical element, the reliability in a high humidity environment can be maintained.

  The optical element may be configured to be hermetically sealed with a transparent resin.

  According to this, the optical element is hermetically sealed with the transparent resin, so that the optical element is protected and the mounting strength is improved. In addition, since water molecules do not enter the optical element, the reliability in a high humidity environment can be maintained. Further, if the transparent resin is molded into a condensing lens shape, the optical coupling is improved.

  The pressing plate can be formed of a resin molded body.

  According to this, in addition to the effect of expanding the degree of freedom of shape of resin molding (complicated concave structure etc. can be mass-produced at low cost) by using a resin molding, for example, organic / inorganic hybrid resin, the effect of improving moisture resistance is also added it can.

15 First substrate (substrate)
16 Second substrate (substrate)
17 Optical fiber (external waveguide)
20 Mirror part 21 Internal waveguide 22 Core part 25 Fiber core part 30 Holding plate (holding member)
30a Extension part 30b Through-hole wiring 30c Recess 31 Adhesive 33 Optical element 33a Light emitting element 33b Light receiving element 34a, 34b IC substrate 35a Metal circuit 37 Transparent resin 38 Holding member

Claims (6)

An internal waveguide provided in the first groove formed on the surface of the substrate, an optical path converting mirror formed at the tip of the first groove, and the surface of the substrate facing the mirror And an optical element that emits an optical signal to the core part of the internal waveguide via the mirror part or receives an optical signal from the core part of the internal waveguide via the mirror part, and the core of the internal waveguide In an optical module having an external waveguide optically coupled to a portion,
A holding member fixed to the surface of the substrate, the optical element being mounted on the back surface facing the surface, and holding the light emitting surface or the light receiving surface of the optical element so as to separate the substrate surface from a predetermined gap;
An IC substrate that is mounted on the surface opposite to the back surface of the holding member and in the vicinity of the optical element, and on which an IC circuit for transmitting an electrical signal or receiving an electrical signal from the optical element is formed. When,
Through hole wiring of an optical element provided in the holding member;
An optical module comprising a metal circuit provided on a surface of the holding member and electrically connecting the through hole wiring and the IC substrate.   The optical module according to claim 1, wherein the holding member is insulative.   An optical fiber as the external waveguide is provided in a second groove formed continuously with the first groove on the surface of the substrate, and has a fiber core portion optically coupled to the core portion of the internal waveguide. The optical module according to claim 1, wherein the holding member also serves as a pressing plate that presses and fixes the optical fiber to the substrate.   A concave portion is formed on the back surface of the pressing plate, the optical element is mounted on the bottom surface of the concave portion, and the optical element is hermetically sealed by filling the concave portion with a transparent adhesive or a transparent resin. The optical module according to claim 3, wherein the optical module is provided.   The optical module according to claim 3, wherein the optical element is hermetically sealed with a transparent resin.   The optical module according to claim 1, wherein the pressing plate is made of a resin molded body.

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