Optical module and method for manufacturing the same

Abstract

To provide an optical module which can improve the connection reliability.SOLUTION: An optical module 10 includes: a wiring substrate 11; and an optical waveguide device 60 mounted on the wiring substrate 11. The wiring substrate 11 includes: a core substrate 20; a wiring structure 30 on the upper surface of the core substrate 20; and a notch part 40 penetrating the wiring structure 30 in a thickness direction and exposing a peripheral portion of the core substrate 20. The optical waveguide device 60 is mounted on the upper surface of the wiring structure 30 located in the vicinity of the notch part 40.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical module and a method for manufacturing the optical module. [Background technology]

[0002] Conventionally, optical modules used in optical communications have been known that include a wiring board, an optical waveguide device mounted on the wiring board, and optical components connected to the optical waveguide device (see, for example, Patent Document 1). Examples of optical components include planar lightwave circuits and optical fiber arrays. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-64211 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned optical module, it is desired to improve the reliability of the connection between the optical waveguide device and the optical component. [Means for solving the problem]

[0005] According to one aspect of the present invention, there is provided a wiring board and an optical waveguide device mounted on the wiring board, wherein the wiring board has a core substrate, a wiring structure formed on an upper surface of the core substrate, and a cutout portion that penetrates the wiring structure in the thickness direction and exposes a peripheral portion of the core substrate, and the optical waveguide device is mounted on the upper surface of the wiring structure located in the vicinity of the cutout portion. [Effects of the Invention]

[0006] According to one aspect of the present invention, an effect is achieved in that connection reliability can be improved. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic cross-sectional view (cross-sectional view taken along line 1-1 in FIG. 2) showing an optical module according to an embodiment. [Figure 2] FIG. 2 is a schematic plan view showing a part of the optical module according to the embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view showing a method for manufacturing an optical module according to an embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view showing a method for manufacturing an optical module according to an embodiment. [Figure 5] FIG. 5 is a schematic cross-sectional view showing a method for manufacturing an optical module according to an embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view showing a method for manufacturing an optical module according to an embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view showing an optical module according to a modified example. [Figure 8] FIG. 8 is a schematic cross-sectional view showing an optical module according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment will be described below with reference to the accompanying drawings. For convenience, the accompanying drawings may show characteristic portions enlarged to make the features easier to understand, and the dimensional ratios of each component may differ from one drawing to another. In addition, in the cross-sectional views, some components are hatched with a matte finish to make the cross-sectional structure of each component easier to understand, and some components are not hatched at all. In the plan views, some components are hatched to make the planar shape of each component easier to understand. Each drawing illustrates mutually orthogonal X-, Y-, and Z-axes. Each drawing illustrates a first direction X1, which is one direction in the X-axis direction along the X-axis, and a first opposite direction X2, which is the opposite direction of the first direction X1. Each drawing illustrates a second direction Y1, which is one direction in the Y-axis direction along the Y-axis, and a second opposite direction Y2, which is the opposite direction of the second direction Y1. Each drawing illustrates a third direction Z1, which is one direction in the Z-axis direction along the Z-axis, and a third opposite direction Z2, which is the opposite direction of the third direction Z1. In this specification, unless otherwise specified, "planar view" refers to viewing an object from the Z-axis direction. In this specification, "planar shape" refers to the shape of an object viewed from the Z-axis direction, unless otherwise specified. Furthermore, in this specification, "facing" refers to surfaces or components facing each other, and includes not only cases where they are completely facing each other, but also cases where they are partially facing each other. In this specification, "facing" refers not only to cases where two components are separated from each other, but also to cases where two components are in contact with each other.

[0009] (Overall configuration of optical module 10) 1, the optical module 10 includes a wiring board 11 and one or more (two in this embodiment) optical waveguide devices 60 mounted on the wiring board 11. The optical module 10 includes, for example, one or more (two in this embodiment) optical fiber arrays 70 mounted on the wiring board 11 and one or more (one in this embodiment) electronic components 80 mounted on the wiring board 11.

[0010] (Configuration of wiring board 11) Wiring board 11 has a core substrate 20, a wiring structure 30 laminated on the upper surface of core substrate 20, and a wiring structure 50 laminated on the lower surface of core substrate 20. Wiring structure 30 has a structure in which a wiring layer 31, an insulating layer 32, a wiring layer 33, an insulating layer 34, a wiring layer 35, and a solder resist layer 36 are laminated in this order on the upper surface of core substrate 20. Wiring structure 50 has a structure in which a wiring layer 51, an insulating layer 52, a wiring layer 53, an insulating layer 54, a wiring layer 55, and a solder resist layer 56 are laminated in this order on the lower surface of core substrate 20.

[0011] Copper or a copper alloy, for example, can be used as the material for the wiring layers 31, 33, 35, 51, 53, and 55. The coefficient of thermal expansion (CTE) of the wiring layers 31, 33, 35, 51, 53, and 55 can be set to, for example, about 15 ppm / °C to 18 ppm / °C. The thickness of each of the wiring layers 31, 33, 35, 51, 53, and 55 can be set to, for example, about 5 μm to 20 μm.

[0012] The insulating layers 32, 34, 52, and 54 may be made of, for example, a thermosetting insulating resin. Examples of the thermosetting insulating resin include epoxy resin, polyimide resin, and cyanate resin. The insulating layers 32, 34, 52, and 54 may contain a filler such as silica or alumina. The thermal expansion coefficient of the insulating layers 32, 34, 52, and 54 may be, for example, approximately 20 ppm / °C to 40 ppm / °C. The thickness of each of the insulating layers 32, 34, 52, and 54 may be, for example, approximately 10 μm to 30 μm.

[0013] The solder resist layers 36, 56 may be made of an insulating resin whose main component is a photosensitive resin, such as a phenolic resin or a polyimide resin. The solder resist layers 36, 56 may contain a filler, such as silica or alumina. The thermal expansion coefficient of the solder resist layers 36, 56 may be, for example, approximately 20 ppm / °C to 40 ppm / °C. The thickness of each of the solder resist layers 36, 56 may be, for example, approximately 10 μm to 30 μm.

[0014] (Configuration of core substrate 20) The core substrate 20 is provided, for example, in the center of the wiring substrate 11 in the thickness direction. The core substrate 20 is formed, for example, in a flat plate shape. The planar shape of the core substrate 20 can be any shape. For example, the planar shape of the core substrate 20 can be a rectangular shape.

[0015] The core substrate 20 is an insulating layer having higher rigidity than the insulating layers 32, 34 of the wiring structure 30. The core substrate 20 is formed, for example, to be thicker than the insulating layers 32, 34. The thickness of the core substrate 20 can be, for example, approximately 50 μm to 500 μm. The material of the core substrate 20 is preferably a material having a thermal expansion coefficient close to that of the optical waveguide device 60 and the optical fiber array 70. The material of the core substrate 20 can be, for example, glass or silicon. The core substrate 20 is formed, for example, of a single layer. That is, the core substrate 20 is a single member.

[0016] The core substrate 20 has, for example, a thermal expansion coefficient similar to that of the optical waveguide device 60. The core substrate 20 has, for example, a thermal expansion coefficient similar to that of the optical fiber array 70. Here, in this specification, "similar" in "similar thermal expansion coefficient" means that the difference between the thermal expansion coefficient of the core substrate 20 and the thermal expansion coefficient of the optical waveguide device 60 or the thermal expansion coefficient of the optical fiber array 70 is in a range of 10 ppm / °C or less. The thermal expansion coefficient of the optical waveguide device 60 can be, for example, about 3 ppm / °C to 6 ppm / °C. The thermal expansion coefficient of the optical fiber array 70 can be, for example, about 3 ppm / °C to 6 ppm / °C. The thermal expansion coefficient of the core substrate 20 can be, for example, about 3 ppm / °C to 12 ppm / °C.

[0017] The difference between the thermal expansion coefficient of the core substrate 20 and the thermal expansion coefficient of the optical waveguide device 60 is smaller than, for example, the difference between the thermal expansion coefficient of the wiring structure 30 and the thermal expansion coefficient of the optical waveguide device 60. More specifically, the difference between the thermal expansion coefficient of the core substrate 20 and the thermal expansion coefficient of the optical waveguide device 60 is smaller than, for example, the difference between the thermal expansion coefficient of the wiring layers 31, 33, and 35 of the wiring structure 30 and the thermal expansion coefficient of the optical waveguide device 60. The difference between the thermal expansion coefficient of the core substrate 20 and the thermal expansion coefficient of the optical waveguide device 60 is smaller than, for example, the difference between the thermal expansion coefficient of the insulating layers 32 and 34 of the wiring structure 30 and the thermal expansion coefficient of the optical waveguide device 60. The difference between the thermal expansion coefficient of the core substrate 20 and the thermal expansion coefficient of the optical waveguide device 60 is smaller than, for example, the difference between the thermal expansion coefficient of the solder resist layer 36 of the wiring structure 30 and the thermal expansion coefficient of the optical waveguide device 60.

[0018] The difference between the thermal expansion coefficient of the core substrate 20 and the thermal expansion coefficient of the optical fiber array 70 is smaller than, for example, the difference between the thermal expansion coefficient of the wiring structure 30 and the thermal expansion coefficient of the optical fiber array 70. More specifically, the difference between the thermal expansion coefficient of the core substrate 20 and the thermal expansion coefficient of the optical fiber array 70 is smaller than, for example, the difference between the thermal expansion coefficient of the wiring layers 31, 33, and 35 and the thermal expansion coefficient of the optical fiber array 70. The difference between the thermal expansion coefficient of the core substrate 20 and the thermal expansion coefficient of the optical fiber array 70 is smaller than, for example, the difference between the thermal expansion coefficient of the insulating layers 32 and 34 and the thermal expansion coefficient of the optical fiber array 70. The difference between the thermal expansion coefficient of the core substrate 20 and the thermal expansion coefficient of the optical fiber array 70 is smaller than, for example, the difference between the thermal expansion coefficient of the solder resist layer 36 and the thermal expansion coefficient of the optical fiber array 70.

[0019] A plurality of through holes 20X are formed in the core substrate 20, penetrating the core substrate 20 in the thickness direction. A through electrode 21 is formed in each through hole 20X, penetrating the core substrate 20 in the thickness direction.

[0020] (Configuration of wiring structure 30) The wiring layer 31 is formed on the upper surface of the core substrate 20. The wiring layer 31 is electrically connected to the wiring layer 51 through the through electrodes 21. An insulating layer 32 covering the wiring layer 31 is laminated on the upper surface of the core substrate 20. A wiring layer 33 is laminated on the upper surface of the insulating layer 32. The wiring layer 33 is formed integrally with, for example, via wiring that penetrates the insulating layer 32 in the thickness direction and is electrically connected to the wiring layer 31 through the via wiring. An insulating layer 34 covering the wiring layer 33 is laminated on the upper surface of the insulating layer 32. A wiring layer 35 is laminated on the upper surface of the insulating layer 34. The wiring layer 35 is formed integrally with, for example, via wiring that penetrates the insulating layer 34 in the thickness direction and is electrically connected to the wiring layer 33 through the via wiring. The wiring layer 35 has, for example, wiring that electrically connects the electronic component 80 and the optical waveguide device 60 to each other. A solder resist layer 36 that covers the wiring layer 35 is laminated on the upper surface of the insulating layer 34. The solder resist layer 36 is the outermost insulating layer of the wiring board 11 (here, the uppermost layer).

[0021] The solder resist layer 36 has a plurality of openings 36X formed therein for exposing portions of the upper surface of the wiring layer 35 as connection pads P1. The solder resist layer 36 has a plurality of openings 36Y formed therein for exposing portions of the upper surface of the wiring layer 35 as connection pads P2. The connection pads P1 are pads for connecting to, for example, the optical waveguide device 60. The connection pads P2 are pads for connecting to, for example, the electronic component 80.

[0022] A surface treatment layer is formed, if necessary, on the upper surface of the wiring layer 35 exposed at the bottom of the openings 36X and 36Y. Examples of the surface treatment layer include a gold (Au) layer, a nickel (Ni) layer / Au layer (a metal layer formed by laminating a Ni layer and an Au layer in this order), and a Ni layer / palladium (Pd) layer / Au layer (a metal layer formed by laminating a Ni layer, a Pd layer, and an Au layer in this order). Other examples of the surface treatment layer include a Ni layer / Pd layer (a metal layer formed by laminating a Ni layer and a Pd layer in this order) and a Pd / Au layer (a metal layer formed by laminating a Pd layer and an Au layer in this order). Here, the Au layer is a metal layer made of Au or an Au alloy, the Ni layer is a metal layer made of Ni or an Ni alloy, and the Pd layer is a metal layer made of Pd or a Pd alloy. The Au layer, Ni layer, and Pd layer may be, for example, a metal layer formed by electroless plating (electroless plated layer) or a metal layer formed by electrolytic plating (electroplated layer). Alternatively, the surface treatment layer may be an OSP (organic solderability preservative) film formed by applying an anti-oxidation treatment such as an OSP treatment to the upper surface of the wiring layer 35. The OSP film may be, for example, an organic coating of an azole compound or an imidazole compound. When a surface treatment layer is formed on the upper surface of the wiring layer 35, the surface treatment layer functions as the connection pads P1 and P2.

[0023] (Configuration of wiring structure 50) The wiring layer 51 is formed on the lower surface of the core substrate 20. The wiring layer 51 is electrically connected to the wiring layer 31 through the through electrodes 21. An insulating layer 52 covering the wiring layer 51 is laminated on the lower surface of the core substrate 20. A wiring layer 53 is laminated on the lower surface of the insulating layer 52. The wiring layer 53 is formed integrally with, for example, via wiring that penetrates the insulating layer 52 in the thickness direction and is electrically connected to the wiring layer 51 through the via wiring. An insulating layer 54 covering the wiring layer 53 is laminated on the lower surface of the insulating layer 52. A wiring layer 55 is laminated on the lower surface of the insulating layer 54. The wiring layer 55 is formed integrally with, for example, via wiring that penetrates the insulating layer 54 in the thickness direction and is electrically connected to the wiring layer 53 through the via wiring. A solder resist layer 56 covering the wiring layer 55 is laminated on the lower surface of the insulating layer 54. The solder resist layer 56 is an insulating layer that is the outermost layer (here, the bottom layer) of the wiring board 11.

[0024] The solder resist layer 56 has a plurality of openings 56X formed therein to expose portions of the lower surface of the wiring layer 55 as external connection pads P3. The external connection pads P3 are connected to external connection terminals (not shown) that are used when mounting the optical module 10 on a mounting substrate such as a motherboard.

[0025] If necessary, a surface treatment layer is formed on the lower surface of the wiring layer 55 exposed at the bottom of the opening 56X. Examples of the surface treatment layer include a metal layer such as an Au layer, a Ni layer / Au layer, a Ni layer / Pd layer / Au layer, a Ni layer / Pd layer, or a Pd layer / Au layer, and an OSP film.

[0026] In this example, an external connection terminal is provided on the underside of the wiring layer 55, but the wiring layer 55 itself exposed at the bottom of the opening 56X, or if a surface treatment layer is formed on the underside of the wiring layer 55, the surface treatment layer itself may also be used as the external connection terminal.

[0027] The wiring board 11 has one or more notches 40. The wiring board 11 of this embodiment has two notches 40. Specifically, the wiring board 11 has two notches 40 corresponding to the two optical fiber arrays 70. Since the two notches 40 have the same structure, the following description will focus on the notch 40 provided on the first direction X1 side (the right side in the figure) of the two notches 40.

[0028] Each notch 40 is formed to penetrate the wiring structure 30 in the thickness direction and expose the peripheral edge of the core substrate 20. Each notch 40 is formed, for example, to expose a portion of the peripheral edge of the core substrate 20. Each notch 40 is formed to penetrate the solder resist layer 36 in the thickness direction and also to penetrate the insulating layers 32, 34 in the thickness direction.

[0029] As shown in FIG. 2, each notch 40 is formed so as to be cut out from the end face 30A of the wiring structure 30 in the first direction X1 toward the first opposite direction X2. Each notch 40 is formed so as to be recessed from the end face 30A toward the first opposite direction X2. As shown in FIG. 1, each notch 40 is formed so as to open in the first direction X1 and in the third direction Z1. As shown in FIG. 2, the planar shape of each notch 40 is formed, for example, rectangular. The planar shape of each notch 40 is not limited to a rectangular shape and can be any shape. Each notch 40 extends from the end face 30A along the first opposite direction X2 and also along the second direction Y1. Each notch 40 is provided, for example, in only a portion of the wiring structure 30 in the second direction Y1. Each notch 40 is provided, for example, at a middle position of the wiring structure 30 in the second direction Y1.

[0030] The dimension of each notch 40 along the second direction Y1 is smaller than the dimension of the wiring structure 30 along the second direction Y1. The dimension of each notch 40 along the second direction Y1 is larger than the dimension of the optical waveguide device 60 along the second direction Y1. The dimension of each notch 40 along the second direction Y1 is larger than the dimension of the optical fiber array 70 along the second direction Y1.

[0031] 1, the innermost end face of each cutout 40, i.e., the end face of each cutout 40 in the first opposite direction X2, is formed by, for example, the end face of the insulating layer 32, the end face of the insulating layer 34, and the end face of the solder resist layer 36. At the end face of each cutout 40 in the first opposite direction X2, for example, the end face of the insulating layer 32, the end face of the insulating layer 34, and the end face of the solder resist layer 36 are formed flush with each other.

[0032] For example, a recess 41 is formed on the upper surface of the core substrate 20 exposed from each cutout 40. The recess 41 is formed so as to recess from the upper surface of the core substrate 20 toward the wiring structure 50 (i.e., toward the third opposite direction Z2). The recess 41 is formed so as not to penetrate the core substrate 20 in the thickness direction. The bottom surface of the recess 41 is provided at a central position in the thickness direction of the core substrate 20. The recess 41 is formed so as to communicate with the cutout 40, for example. The recess 41 is formed on the entire upper surface of the core substrate 20 exposed from the cutout 40, for example. Therefore, the planar shape of the recess 41 is formed to be the same as the planar shape of the cutout 40. Furthermore, the planar size of the recess 41 is formed to be the same as the planar size of the cutout 40.

[0033] The wiring board 11 described above is mounted with an optical waveguide device 60, an optical fiber array 70, and an electronic component 80. Note that the wiring board 11 may be mounted with optical functional elements other than the optical waveguide device 60 and the optical fiber array 70. Examples of optical functional elements include an optical modulator, an optical amplifier, and an optical attenuator.

[0034] (Configuration of the optical waveguide device 60) Each optical waveguide device 60 has a plurality of electrode pads 61 formed on one surface (here, the bottom surface) of the optical waveguide device 60. Each optical waveguide device 60 is mounted on the top surface of the wiring substrate 11. Each optical waveguide device 60 is, for example, flip-chip mounted on the top surface of the wiring structure 30 of the wiring substrate 11. The electrode pads 61 of each optical waveguide device 60 are electrically connected to the connection pads P1 of the wiring substrate 11 via bonding members 62. As a result, each optical waveguide device 60 is electrically connected to the wiring layer 35 of the wiring substrate 11 via the electrode pads 61 and the bonding members 62.

[0035] The electrode pads 61 are provided so as to face the connection pads P1, respectively. Each electrode pad 61 is formed, for example, in a columnar shape so as to protrude downward from the lower surface of the optical waveguide device 60. Each electrode pad 61 is, for example, a metal post. Each electrode pad 61 can be made of, for example, copper or a copper alloy.

[0036] For example, gold bumps or solder bumps can be used as the bonding members 62. Materials for the solder bumps include, for example, alloys containing lead (Pb), alloys of tin (Sn) and Au, alloys of Sn and Cu, alloys of Sn and silver (Ag), and alloys of Sn, Ag, and Cu.

[0037] Since the two optical waveguide devices 60 have similar structures, the following description will focus on the optical waveguide device 60 provided on the first direction X1 side (right side in the figure) of the two optical waveguide devices 60.

[0038] 2, each optical waveguide device 60 has, for example, one or more (three in this embodiment) optical elements 63 and one or more (three in this embodiment) optical waveguides 64. The optical waveguide device 60 is, for example, a silicon photonics component. The optical waveguide 64 is, for example, a silicon optical waveguide.

[0039] Each optical element 63 may be, for example, a light-emitting element such as a vertical cavity surface-emitting laser (VCSEL) or a light-emitting diode (LED), etc. Each optical element 63 may be, for example, a light-receiving element such as a photodiode or an avalanche photodiode.

[0040] Each optical waveguide 64 is optically connected to, for example, each optical element 63. Each optical waveguide 64 connects, for example, each optical element 63 to the optical fiber array 70. Each optical waveguide 64 is formed, for example, in an elongated shape extending along the first direction X1. An end of each optical waveguide 64 in the first direction X1 is optically connected to the optical fiber array 70, and an end of each optical waveguide 64 in the first opposite direction X2 is optically connected to the optical element 63. Each optical waveguide 64 extends, for example, from each optical element 63 to an end face of the optical waveguide device 60 in the first direction X1. The multiple optical waveguides 64 are arranged side by side along, for example, the second direction Y1. Although not shown, each optical waveguide 64 has, for example, a core that propagates an optical signal and a cladding that surrounds the outer periphery of the core.

[0041] Each optical waveguide device 60 is provided near the cutout 40. Each optical waveguide device 60 is mounted on the upper surface of the wiring structure 30 located near the cutout 40. The optical waveguide device 60 is provided, for example, so that an end of the optical waveguide device 60 in the first direction X1 overlaps the cutout 40 in a plan view. That is, the end of the optical waveguide device 60 in the first direction X1 is provided so as to protrude in the first direction X1 beyond the inner end face of the cutout 40, i.e., the end face of the cutout 40 in the first opposite direction X2.

[0042] (Configuration of the optical fiber array 70) Each optical fiber array 70 has a housing 71 and one or more (three in this embodiment) optical fibers 72. The housing 71 holds three optical fibers 72. For example, the housing 71 holds the three optical fibers 72 in a state where they are lined up along the second direction Y1.

[0043] Each optical fiber 72 has, for example, a core 73 that propagates an optical signal and a cladding 74 that surrounds the outer periphery of the core 73. The core 73 extends, for example, over the entire length of the optical fiber 72 in the longitudinal direction. The cladding 74 extends, for example, over the entire length of the optical fiber 72 in the longitudinal direction. The end face of each optical fiber 72 in the first opposite direction X2 extends, for example, to the end face of the housing 71 in the first opposite direction X2. Each optical fiber 72 extends, for example, in the first direction X1 further than the end face of the housing 71 in the first direction X1.

[0044] The optical fiber array 70 is provided so as to face an end face in the first direction X1 of the optical waveguide device 60. The optical fiber array 70 is provided, for example, so that an end face in the first opposite direction X2 of each optical fiber 72 faces an end face in the first direction X1 of each optical waveguide 64. The optical fiber array 70 is provided so that the central axis of the core 73 of each optical fiber 72 coincides with the central axis of the core of each optical waveguide 64. In other words, the optical fiber array 70 is provided so that the optical axis of the core 73 of each optical fiber 72 coincides with the optical axis of the core of each optical waveguide 64.

[0045] The optical fiber array 70 is provided so as to protrude in the first direction X1 from the end face 30A of the wiring structure 30 in the first direction X1. The optical fiber array 70 is provided so that the end face of the optical fiber array 70 in the first opposite direction X2 abuts against the end face of the optical waveguide device 60 in the first direction X1. However, a gap may occur between the optical fiber array 70 and the optical waveguide device 60.

[0046] The optical fiber array 70 is bonded to the optical waveguide device 60 with an optical adhesive 75. Each optical fiber 72 is optically connected to each optical waveguide 64 of the optical waveguide device 60 with, for example, the optical adhesive 75. The optical adhesive 75 is formed, for example, to fill the gap between the optical waveguide device 60 and the optical fiber array 70. Filling the gap between the optical waveguide device 60 and the optical fiber array 70 with the optical adhesive 75 prevents air reflection and improves the coupling efficiency between each optical waveguide 64 and each optical fiber 72. The optical adhesive 75 is formed, for example, to cover the entire end face of each optical fiber 72 in the first opposite direction X2. The optical adhesive 75 is formed, for example, to cover the entire end face of each optical waveguide 64 in the first direction X1. The optical adhesive 75 can be, for example, a UV-curable optical adhesive. The optical adhesive 75 can be an optical adhesive having a refractive index close to the refractive index of the core of the optical waveguide 64 or the refractive index of the core 73 of the optical fiber 72.

[0047] As shown in FIG. 1, the optical fiber array 70 is mounted on the core substrate 20 exposed from the cutout 40. The optical fiber array 70 is fixed to, for example, the bottom surface of the recess 41. The housing 71 of the optical fiber array 70 is adhered to the bottom surface of the recess 41 by, for example, an adhesive 76. The adhesive 76 is bonded to the bottom surface of the housing 71 and also to the core substrate 20 that forms the bottom surface of the recess 41. The adhesive 76 can be, for example, an ultraviolet-curing adhesive or a thermosetting adhesive.

[0048] (Configuration of electronic component 80) The electronic component 80 has a plurality of electrode pads 81 formed on one surface (here, the lower surface) of the electronic component 80. The electronic component 80 is mounted on the upper surface of the wiring board 11. The electronic component 80 is, for example, flip-chip mounted on the upper surface of the wiring structure 30 of the wiring board 11. The electrode pads 81 of the electronic component 80 are electrically connected to the connection pads P2 of the wiring board 11 via bonding members 82. As a result, the electronic component 80 is electrically connected to the wiring layer 35 of the wiring board 11 via the electrode pads 81 and the bonding members 82. The electronic component 80 is electrically connected to the optical waveguide device 60, for example, via the wiring layers 31, 33, 35, etc. of the wiring board 11. Note that one electronic component 80 may be provided corresponding to one optical waveguide device 60, or one electronic component 80 may be provided corresponding to multiple optical waveguide devices 60.

[0049] The electronic component 80 may be, for example, an IC chip such as a driver that drives the optical element 63 (see FIG. 2) of the optical waveguide device 60. The electronic component 80 may be, for example, an IC chip incorporating a DSP (Digital Signal Processor) that processes an optical output signal from the optical element 63 (see FIG. 2) of the optical waveguide device 60, an amplifier, or the like.

[0050] The plurality of electrode pads 81 are provided so as to face the plurality of connection pads P2, respectively. Each electrode pad 81 is formed, for example, in a columnar shape so as to protrude downward from the lower surface of the electronic component 80. Each electrode pad 81 is, for example, a metal post. Each electrode pad 81 can be made of, for example, copper or a copper alloy.

[0051] For example, gold bumps or solder bumps can be used as the bonding members 82. Materials that can be used for the solder bumps include alloys containing Pb, alloys of Sn and Au, alloys of Sn and Cu, alloys of Sn and Ag, and alloys of Sn, Ag, and Cu.

[0052] (Method of manufacturing the optical module 10) Next, a method for manufacturing the optical module 10 will be described with reference to Figures 3 to 6. For ease of explanation, the parts that will ultimately become the components of the optical module 10 will be denoted by the reference numerals of the final components.

[0053] 3, a structure is formed that includes a core substrate 20, a wiring structure 30 formed on the upper surface of the core substrate 20, and a wiring structure 50 formed on the lower surface of the core substrate 20. This structure can be manufactured by a known manufacturing method, and therefore a detailed description thereof will be omitted here.

[0054] 4, a cutout 40 is formed that penetrates the wiring structure 30 in the thickness direction and exposes a portion of the core substrate 20. In this embodiment, notch 40 is formed, and at the same time, a recess 41 that communicates with notch 40 is also formed. As a result, the bottom surface of recess 41 is located lower than the upper surface of the core substrate 20. These cutout 40 and recess 41 can be formed by cutting from the upper surface side of the wiring structure 30 using, for example, a router or the like. In this embodiment, the recess 41 that communicates with notch 40 can be formed by cutting from the upper surface side of the core substrate 20 so as to thin the core substrate 20 exposed from cutout 40.

[0055] Through the above manufacturing steps, the wiring board 11 can be manufactured. 5, an optical waveguide device 60 is mounted on the wiring board 11, and an electronic component 80 is mounted on the wiring board 11. In this process, electrode pads 61 of the optical waveguide device 60 are bonded to connection pads P1 of the wiring board 11 via bonding members 62. For example, if the bonding members 62 are solder layers, the electrode pads 61 and the connection pads P1 are aligned, and then a reflow process is performed to melt the bonding members 62, which are solder layers, and electrically connect the electrode pads 61 to the connection pads P1. Also, in this process, electrode pads 81 of the electronic component 80 are bonded to connection pads P2 of the wiring board 11 via the bonding members 82. For example, if the bonding members 82 are solder layers, the electrode pads 81 and the connection pads P2 are aligned, and then a reflow process is performed to melt the bonding members 82, which are solder layers, and electrically connect the electrode pads 81 to the connection pads P2. The optical waveguide device 60 is provided so that a part of it overlaps with the notch 40 in plan view.

[0056] Next, in the step shown in FIG. 6 , the optical fiber array 70 is mounted on the core substrate 20 exposed from the cutout 40 while being optically connected to the optical waveguide device 60. More specifically, first, the optical fiber array 70 is aligned with the optical waveguide device 60. Specifically, the optical fiber array 70 is aligned with the optical waveguide device 60 so that the optical axes of the optical waveguides 64 and the optical fibers 72 coincide with each other. This alignment is performed, for example, using active alignment. At this time, by mounting the optical fiber array 70 on the core substrate 20 exposed from the cutout 40, the optical axes of the optical fibers 72 and the optical waveguides 64 can be aligned with each other in the Z-axis direction. In other words, when the optical fiber array 70 is mounted on the core substrate 20 exposed from the cutout 40, specifically on the bottom surface of the recess 41, the depth of the recess 41 is adjusted so that the optical axes of the optical fibers 72 and the optical waveguides 64 coincide with each other in the Z-axis direction.

[0057] Next, the optical waveguide device 60 and the optical fiber array 70 are bonded together with an optical adhesive 75, and the optical fiber array 70 is bonded to the bottom surface of the recess 41 with an adhesive 76. For example, using a dispenser or the like, the uncured optical adhesive 75 is applied between the optical waveguide device 60 and the optical fiber array 70, and the uncured adhesive 76 is applied between the optical fiber array 70 and the bottom surface of the recess 41. Thereafter, ultraviolet light is irradiated to cure the optical adhesive 75 and the adhesive 76. As a result, the optical waveguide device 60 and the optical fiber array 70 are bonded together with the optical adhesive 75, and the optical fiber array 70 is bonded to the bottom surface of the recess 41 with the adhesive 76.

[0058] The optical module 10 of this embodiment can be manufactured through the above manufacturing steps. Next, the effects of this embodiment will be described. (1) The optical module 10 includes a wiring substrate 11, an optical waveguide device 60 mounted on the wiring substrate 11, and an optical fiber array 70 connected to the optical waveguide device 60. The wiring substrate 11 includes a core substrate 20, a wiring structure 30 formed on the upper surface of the core substrate 20, and a cutout 40 that penetrates the wiring structure 30 in the thickness direction and exposes a portion of the core substrate 20. The optical waveguide device 60 is mounted on the upper surface of the wiring structure 30 near the cutout 40. The optical fiber array 70 is fixed on the core substrate 20 exposed from the cutout 40.

[0059] According to this configuration, the optical fiber array 70 connected to the optical waveguide device 60 is fixed on the core substrate 20. Therefore, the optical fiber array 70 is bonded to the optical waveguide device 60 and also to the core substrate 20. This improves the bonding strength of the optical fiber array 70 to the optical waveguide device 60 and the core substrate 20 compared to when the optical fiber array 70 is bonded only to the optical waveguide device 60. In other words, by bonding the optical fiber array 70 onto the core substrate 20, the bonding strength between the optical waveguide device 60 and the optical fiber array 70 can be reinforced. As a result, the connection reliability between the optical waveguide device 60 and the optical fiber array 70 can be improved. For example, even if an external force is unintentionally applied to the optical fiber array 70, the connection between the optical waveguide device 60 and the optical fiber array 70 can be suitably prevented from being released.

[0060] (2) A recess 41 is formed on the upper surface of the core substrate 20 exposed from the cutout 40, and the optical fiber array 70 is fixed to the bottom surface of the recess 41. With this configuration, the position of the optical axis of the optical fiber 72 in the Z-axis direction can be easily adjusted by adjusting the depth of the recess 41. Therefore, by adjusting the depth of the recess 41 according to the thicknesses of the wiring structure 30, the optical waveguide device 60, and the optical fiber array 70, the position of the optical axis of the optical fiber 72 in the Z-axis direction can be suitably adjusted to a desired position. Therefore, even if the thicknesses of the wiring structure 30, the optical waveguide device 60, and the optical fiber array 70 are variously changed, the optical axis of the optical fiber 72 can be suitably aligned with the optical axis of the optical waveguide 64 in the Z-axis direction by adjusting the depth of the recess 41.

[0061] (3) The end of the optical waveguide device 60 in the first direction X1 is arranged to overlap the notch 40 in a plan view. According to this configuration, the end of the optical waveguide device 60 in the first direction X1 is arranged to protrude in the first direction X1 from the inner end face of the notch 40. This makes it possible to suitably arrange the optical fiber array 70 so that the end face of the optical waveguide device 60 in the first opposite direction X2 abuts against the end face of the optical waveguide device 60 in the first direction X1.

[0062] (4) The difference between the thermal expansion coefficient of the core substrate 20 and the thermal expansion coefficient of the optical fiber array 70 is smaller than the difference between the thermal expansion coefficient of the wiring structure 30 and the thermal expansion coefficient of the optical fiber array 70. As a result, the difference between the thermal expansion coefficient of the fixed portion of the optical fiber array 70 (in this embodiment, the core substrate 20) and the thermal expansion coefficient of the optical fiber array 70 can be made smaller than when the optical fiber array 70 is fixed on the wiring structure 30. Therefore, even when the optical module 10 is exposed to a high-temperature environment, for example, it is possible to prevent a large difference from occurring between the amount of thermal deformation of the core substrate 20 and the amount of thermal deformation of the optical fiber array 70. As a result, it is possible to effectively prevent the optical axes of the optical fibers 72 from being misaligned due to a difference in the amount of thermal deformation.

[0063] (5) The difference between the thermal expansion coefficient of the core substrate 20 and the thermal expansion coefficient of the optical waveguide device 60 is smaller than the difference between the thermal expansion coefficient of the wiring structure 30 and the thermal expansion coefficient of the optical waveguide device 60. This makes it possible to reduce the difference between the thermal expansion coefficient of the core substrate 20, which serves as a fixing portion of the optical fiber array 70, and the thermal expansion coefficient of the optical waveguide device 60. Therefore, even when the optical module 10 is exposed to a high-temperature environment, for example, it is possible to prevent a large difference from occurring between the amount of thermal deformation of the core substrate 20, the amount of thermal deformation of the optical fiber array 70, and the amount of thermal deformation of the optical waveguide device 60. As a result, it is possible to effectively prevent misalignment between the optical axes of the optical fibers 72 and the optical waveguides 64 due to differences in the amount of thermal deformation.

[0064] (6) Incidentally, when a recess is provided in the wiring structure 30 and the optical fiber array 70 is fixed to the bottom surface of the recess, variations in the depth of the recess may cause variations in the thermal expansion coefficient of the fixed portion of the optical fiber array 70. More specifically, since the wiring structure 30 has a layered structure in which multiple components are stacked, different components are exposed from the recess depending on the depth of the recess, i.e., different components constitute the fixed portion of the optical fiber array 70. For this reason, variations in the depth of the recess cause variations in the thermal expansion coefficient of the fixed portion of the optical fiber array 70.

[0065] In contrast, in the optical module 10 of this embodiment, the core substrate 20 is configured from a single layer. That is, the core substrate 20 is configured from a single member. Therefore, even if the depth of the recess 41 is changed, it is possible to suitably suppress fluctuations in the thermal expansion coefficient of the core substrate 20, which is the fixing portion of the optical fiber array 70.

[0066] (7) The gap between the optical waveguide device 60 and the optical fiber array 70 is filled with an optical adhesive 75. As a result, even if a gap occurs between the optical waveguide device 60 and the optical fiber array 70, air reflection in the gap can be prevented, thereby increasing the coupling efficiency between the optical waveguide device 60 and the optical fiber array 70.

[0067] (8) The optical fiber array 70 is adhered onto the core substrate 20 by the adhesive 76. This allows the optical fiber array 70 to be firmly fixed onto the core substrate 20. (Example of change) The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0068] In the above embodiment, the recess 41 is provided on the entire upper surface of the core substrate 20 exposed from the cutout 40, but this is not limiting. For example, the recess 41 may be provided on only a portion of the upper surface of the core substrate 20 exposed from the cutout 40.

[0069] The depth of the recess 41 in the above embodiment can be changed as needed. 7, the recess 41 may be omitted. In this case, the optical fiber array 70 is fixed to the upper surface of the core substrate 20 exposed from the cutout 40. In this case, the upper surface of the core substrate 20 exposed from the cutout 40 is formed flush with the upper surface of the core substrate 20 in other parts.

[0070] In the above embodiment, the cutout 40 is provided only in a portion of the wiring structure 30 in the second direction Y1, but this is not limited to this. For example, the cutout 40 may be provided over the entire length of the wiring structure 30 in the second direction Y1. For example, the cutout 40 may be provided over the entire circumferential circumference of the wiring structure 30. In this case, the peripheral edge of the core substrate 20 is exposed from the cutout 40 over the entire circumferential circumference.

[0071] Although the optical fiber array 70 of the above embodiment is provided with three optical fibers 72, there is no particular limitation on the number of optical fibers 72. The number of optical fibers 72 provided in the optical fiber array 70 may be one or two, or may be four or more.

[0072] In the optical module 10 of the above embodiment, the optical component connected to the optical waveguide device 60 is embodied as the optical fiber array 70, but the present invention is not limited to this. 8, the optical component to be connected to the optical waveguide device 60 may be embodied as an optical connector 90. The optical connector 90 is optically connected to the optical waveguide device 60 and is fixed onto the core substrate 20 exposed from the cutout 40. For example, the optical connector 90 is bonded to the optical waveguide device 60 with an optical adhesive 75 and is also bonded onto the core substrate 20 with an adhesive 76. The optical connector 90 is configured to be detachable from a mating connector 91 having one or more optical fibers 72, for example.

[0073] Furthermore, the optical components connected to the optical waveguide device 60 may be embodied as optical components other than the optical fiber array 70 and the optical connector 90, such as a planar lightwave circuit. Although the optical waveguide device 60 of the above embodiment is provided with three optical waveguides 64, there is no particular limitation on the number of optical waveguides 64. The number of optical waveguides 64 may be one or two, or may be four or more.

[0074] Although the optical waveguide device 60 of the above embodiment is provided with three optical elements 63, there is no particular limitation on the number of optical elements 63. The number of optical elements 63 may be one or two, or may be four or more.

[0075] In the optical waveguide device 60 of the above embodiment, one optical element 63 is provided corresponding to one optical waveguide 64, but this is not limiting. For example, one optical element 63 may be provided corresponding to a plurality of optical waveguides 64.

[0076] The number of wiring layers 31, 33, 35 and insulating layers 32, 34 in the wiring structure 30 of the above embodiment, as well as the layout of the wiring, can be modified and changed in various ways. The number of wiring layers 51, 53, 55 and insulating layers 52, 54 in the wiring structure 50 of the above embodiment, as well as the layout of the wiring, can be modified and changed in various ways.

[0077] The wiring structure 50 in the above embodiment may be omitted. The solder resist layers 36, 56 in the wiring board 11 of the above embodiment may be omitted.

[0078] The number of optical waveguide devices 60, optical fiber arrays 70, and electronic components 80 in the optical module 10 of the above embodiment is not particularly limited. [Explanation of symbols]

[0079] 10 Optical Modules 11 Wiring board 20 Core Board 30 Wiring structure 30A end face 31,33,35 wiring layer 32,34 Insulating layer 40 Notch 41 Recess 60 Optical Waveguide Devices 63 Optical Elements 64 Optical waveguide 70 Optical Fiber Array 71 Housing 72 Optical Fiber 75 Optical Adhesives 76 Adhesive 80 Electronic Components 90 Optical connectors (optical components) X1 1st direction X2 1st opposite direction Y1 2nd direction

Claims

1. A wiring board; an optical waveguide device mounted on the wiring substrate, The wiring board is A core substrate; a wiring structure formed on the upper surface of the core substrate; a notch that penetrates the wiring structure in a thickness direction and exposes a peripheral edge of the core substrate, an optical module in which the optical waveguide device is mounted on an upper surface of the wiring structure located near the notch;

2. 2. The optical module according to claim 1, further comprising an optical component fixed on the core substrate exposed from the notch and connected to the optical waveguide device.

3. a recess formed on the upper surface of the core substrate exposed through the cutout, the bottom surface of the recess is provided at a middle position in the thickness direction of the core substrate, The optical module according to claim 2 , wherein the optical component is fixed to the bottom surface of the recess.

4. the notch portion is formed to cut out the wiring structure from an end face of the wiring structure in a first direction toward a first opposite direction that is a direction opposite to the first direction, The notch is open in the first direction, The optical module according to claim 2 , wherein an end portion of the optical waveguide device in the first direction is provided so as to overlap the notch portion in a plan view.

5. The optical module according to claim 4 , wherein a dimension of the notch along a second direction perpendicular to the first direction is larger than a dimension of the optical component along the second direction.

6. 3. The optical module according to claim 2, wherein a difference between the thermal expansion coefficient of said core substrate and that of said optical component is smaller than a difference between the thermal expansion coefficient of said wiring structure and that of said optical component.

7. 7. The optical module according to claim 6, wherein a difference between the thermal expansion coefficient of the core substrate and the thermal expansion coefficient of the optical waveguide device is smaller than a difference between the thermal expansion coefficient of the wiring structure and the thermal expansion coefficient of the optical waveguide device.

8. 3. The optical module according to claim 2, wherein the core substrate is configured from a single layer.

9. an optical adhesive for bonding the optical waveguide device and the optical component; an adhesive for bonding the optical component and the core substrate, 3. The optical module according to claim 2, wherein the optical adhesive fills a gap between the optical waveguide device and the optical component.

10. forming a wiring substrate having a core substrate and a wiring structure formed on an upper surface of the core substrate; forming a notch that penetrates the wiring structure and exposes a peripheral edge of the core substrate; mounting an optical waveguide device on the top surface of the wiring structure; a step of connecting an optical component to the optical waveguide device and fixing the optical component on the core substrate exposed from the notch; A method for manufacturing an optical module having the above structure.

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