Optical module, optical connector cable, and method for producing optical module

Abstract

This optical module comprises: a substrate; an optical element; an optical coupling module; and an adhesive. The substrate has a glass cloth therein. The optical element is mounted on the substrate. The optical coupling module is configured to be optically coupled to the optical element. The adhesive fixes the optical coupling module to the substrate. A cavity that is recessed from a first main surface of the substrate toward a second main surface of the substrate so as to have a bottom portion is formed in the substrate. At least a portion of the optical coupling module is housed in the cavity. The glass cloth has a protruding portion that protrudes from a lateral surface of the cavity to the inside of the cavity. The protruding portion penetrates into the adhesive located between the lateral surface and the optical coupling module.

Description

Optical module, optical connector cable, and method for manufacturing optical module

[0001] This application claims priority to Japanese Patent Application No. 2021-128966, filed on August 5, 2021, and incorporates by reference all of the contents of that application.

[0002] Patent Document 1 discloses an optical component as an example of an optical module including a substrate on which an optical element is mounted and an optical coupling module optically coupled to the optical element. In the optical module, light emitted from an optical fiber held in the optical coupling module is incident on the optical element mounted on the substrate via the optical coupling module.

[0003] Japanese Patent Application Laid-Open No. 2019-082508

[0004] The optical module of the present disclosure includes a substrate, an optical element, an optical coupling module, and an adhesive. The substrate has a glass cloth therein. The optical element is mounted on the substrate. The optical coupling module is configured to optically couple with the optical element. The adhesive fixes the optical coupling module to the substrate. The substrate has a cavity recessed from a first main surface of the substrate toward a second main surface of the substrate so as to have a bottom. At least a portion of the optical coupling module is housed in the cavity. The glass cloth has a protrusion protruding from a side surface of the cavity into the interior of the cavity. The protrusion penetrates into the adhesive located between the side surface and the optical coupling module.

[0005] The optical connector cable of the present disclosure includes the optical module described above and an optical fiber cable, the optical fiber cable having an optical fiber, and the optical fiber cable is attached to the optical module such that the optical fiber is optically coupled to an optical element via the optical coupling module.

[0006] A method for manufacturing an optical module according to the present disclosure includes the steps of: preparing a substrate including a glass cloth; forming a cavity in the substrate, the cavity being recessed from a first main surface of the substrate toward a second main surface of the substrate so as to have a bottom; placing at least a portion of an optical coupling module configured to optically couple with an optical element inside the cavity; and fixing the optical coupling module to the substrate with an adhesive. In the step of forming the cavity, a portion of the glass cloth is made to protrude from a side surface into the cavity as a protrusion. In the step of fixing the optical coupling module to the substrate, adhesive is applied to the inside of the cavity so that the protrusion penetrates into the adhesive.

[0007] FIG. 1 is a perspective view showing an end of an optical connector cable according to one embodiment. FIG. 2 is a perspective view showing the end of the optical connector cable from which a protective member has been removed. FIG. 3 is a plan view of the optical module viewed from above the first main surface of the substrate. FIG. 4 is a plan view of the optical module viewed from above the second main surface of the substrate. FIG. 5 is a cross-sectional view of the optical module cut along line V-V shown in FIG. 3. FIG. 6 is an enlarged view of the portion surrounded by dashed line A shown in FIG. 5. FIG. 7 is a perspective view showing a substrate used in the optical module shown in FIG. 3. FIG. 8 is an enlarged view of the portion surrounded by dashed line B shown in FIG. 7. FIG. 9 is a schematic view of the substrate in a plan view. FIG. 10 is a plan view of the optical coupling module accommodated in a cavity.

[0008] [Problem to be Solved by the Present Disclosure] The optical module disclosed in Patent Document 1 has a structure in which an optical coupling module is mounted on a substrate. The optical coupling module is attached to the substrate with an adhesive. However, for example, the size of the optical coupling module may be small, limiting the amount of adhesive that can be applied. Therefore, there is a need for the development of an optical module that can improve the adhesive strength of the optical coupling module to the substrate.

[0009] An object of the present disclosure is to provide an optical module, an optical connector cable, and a method for manufacturing an optical module that can improve the adhesive strength of the optical coupling module to a substrate.

[0010] Effect of the Present Disclosure According to the present disclosure, the adhesive strength of the optical coupling module to the substrate can be improved.

[0011] [Description of Embodiments of the Present Disclosure] First, the contents of the embodiments of the present disclosure will be listed and described. An optical module according to one embodiment includes a substrate, an optical element, an optical coupling module, and an adhesive. The substrate has a glass cloth therein. The optical element is mounted on the substrate. The optical coupling module is configured to be optically coupled to the optical element. The adhesive fixes the optical coupling module to the substrate. The substrate has a cavity recessed from a first main surface of the substrate toward a second main surface of the substrate, the cavity having a bottom. At least a portion of the optical coupling module is housed in the cavity. The glass cloth has a protrusion protruding from a side surface of the cavity into the interior of the cavity. The protrusion penetrates into the adhesive located between the side surface and the optical coupling module.

[0012] In this optical module, a portion of the glass cloth (a protrusion) protrudes from the side of the cavity into the cavity. The protrusion also penetrates into the adhesive that secures the optical coupling module to the substrate. This increases the contact area between the adhesive and the substrate by the surface area of ​​the protrusion, and the protrusion can function as an anchor for the adhesive. This improves the adhesive strength of the optical coupling module to the substrate.

[0013] In one embodiment, the glass cloth may be configured with glass threads as weft and warp threads. When viewed from the thickness direction of the substrate, the side surface may be formed so as to follow the extending direction of at least one of the weft and warp threads. In this case, a long protrusion is formed, further increasing the contact area between the adhesive and the substrate. This can further improve the adhesive strength of the optical coupling module to the substrate. The glass threads constituting at least one of the weft and warp threads may be formed from a bundle of multiple glass filaments, each of which may have a diameter of 10 μm or less. The weave density of the glass threads in at least one of the weft and warp threads may be 50 threads / 25 mm or more and 100 threads / 25 mm or less.

[0014] In one embodiment, the optical coupling module may be housed inside the cavity such that a gap is provided between the side surface of the cavity and the optical coupling module. The adhesive may be disposed in the gap. The width of the gap may be 50 μm or more and 750 μm or less. In this case, the adhesive can be stored in the gap where the protrusion is located, allowing the surface of the protrusion to appropriately contact the adhesive. Furthermore, by having the width of the gap be 50 μm or more and 750 μm or less, an appropriate amount of adhesive can be stored in the gap. Therefore, the adhesive strength of the optical coupling module to the substrate can be further improved.

[0015] In one embodiment, the length of the protrusion may be 100 μm or more and 1 mm or less. In this case, since the length of the protrusion is 100 μm or more, a sufficient contact area with the adhesive on the surface of the protrusion can be ensured. This can further improve the adhesive strength of the optical coupling module to the substrate. Furthermore, since the length of the protrusion is 1 mm or less, the protrusion is unlikely to interfere with the insertion of the optical coupling module into the cavity. This makes it easy to insert the optical coupling module into the cavity.

[0016] In one embodiment, the optical coupling module may have a holder that holds an end of an optical fiber that is optically coupled to an optical element via the optical coupling module. In this case, the end of the optical fiber is properly held by the holder of the optical coupling module, thereby enabling more accurate optical coupling between the optical element and the optical fiber.

[0017] In one embodiment, the cavity may have a through hole formed therein that penetrates from the bottom to the second main surface. The optical element may be mounted on the second main surface so as to overlap with the through hole when viewed from above the second main surface. In this case, the optical coupling module and the optical element mounted on the second main surface of the substrate can be optically coupled via the simple structure of the through hole.

[0018] In one embodiment, the cavity may include a first cavity and a second cavity having a second bottom located closer to the second major surface than the first bottom of the first cavity. In this case, the cavity portion that primarily accommodates components such as lenses that tend to protrude from the underside of the optical coupling module may be made deeper, while the other portions may be made shallower, thereby reducing the overall cavity area. As a result, the strength of the substrate can be maintained even when the cavity is provided in the substrate. The first bottom of the first cavity may be provided with a positioning hole recessed from the first bottom toward the second major surface. The second bottom of the second cavity may be provided with a plurality of through holes penetrating from the second bottom to the second major surface.

[0019] An optical connector cable according to one embodiment includes any one of the optical modules described above and an optical fiber cable. The optical fiber cable has at least one optical fiber. The optical fiber cable is attached to the optical module so that the optical fiber is optically coupled to an optical element via the optical coupling module. This optical connector cable can improve the adhesive strength of the optical coupling module to the substrate, similar to the optical module described above.

[0020] A method for manufacturing an optical module according to one embodiment includes the steps of: preparing a substrate including a glass cloth; forming a cavity in the substrate, the cavity being recessed from a first main surface of the substrate toward a second main surface of the substrate so as to have a bottom; placing at least a portion of an optical coupling module configured to optically couple with an optical element inside the cavity; and fixing the optical coupling module to the substrate with an adhesive. In the step of forming the cavity, a portion of the glass cloth is made to protrude from a side surface of the cavity into the cavity as a protrusion. In the step of fixing the optical coupling module to the substrate, adhesive is applied to the inside of the cavity so that the protrusion penetrates into the adhesive.

[0021] In this method for manufacturing an optical module, a portion of the glass cloth is made to protrude from the side of the cavity into the cavity as a protrusion. The adhesive is then applied so that the protrusion penetrates into the adhesive. This increases the contact area between the adhesive and the substrate by the surface area of ​​the protrusion, and the protrusion can function as an anchor for the adhesive. This improves the adhesive strength of the optical coupling module to the substrate.

[0022] [Details of the embodiments of the present disclosure] Specific examples of the optical module, optical connector cable, and method for manufacturing the optical module according to the present disclosure will be described below with reference to the drawings. The present disclosure is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. In the description of the drawings, the same elements are given the same reference numerals, and duplicate explanations will be omitted.

[0023] An optical connector cable 1 according to one embodiment will be described with reference to Figures 1 and 2. Figure 1 is a perspective view showing an end of the optical connector cable 1 according to one embodiment. Figure 2 is a perspective view showing the end of the optical connector cable 1 with the protective member 20 removed. For the sake of explanation, the width direction of the end of the optical connector cable 1 will be referred to as direction X, the extension direction of the end as direction Y, and the thickness direction of the end as direction Z. In this embodiment, direction X, direction Y, and direction Z are perpendicular to one another.

[0024] The optical connector cable 1 is a cable used, for example, to transmit and receive optical signals between devices. As shown in Figures 1 and 2, the optical connector cable 1 includes an optical fiber cable 10, a protective member 20, and an optical module 30. Although Figures 1 and 2 show one end of the optical fiber cable 10, the other end of the optical fiber cable 10 may also have a similar configuration.

[0025] As shown in FIG. 2 , the optical fiber cable 10 includes a plurality of optical fibers 11 and a cable jacket 12. Each optical fiber 11 is a component for transmitting an optical signal. A majority of each optical fiber 11 is housed inside the cable jacket 12. A tip portion of each optical fiber 11 is exposed to the outside of the cable jacket 12. The plurality of optical fibers 11 are arranged one-dimensionally along the direction X. Inside the cable jacket 12, all of the optical fibers 11 are housed closely together. Meanwhile, outside the cable jacket 12, the plurality of optical fibers 11 branch into several bundles (four to six in this embodiment), and the ends of each bundle are held by each optical coupling module 50. Each optical fiber 11 includes, for example, a glass fiber and a coating resin. The glass fiber includes, for example, a core and a cladding surrounding the core. Each optical fiber 11 may be a single-mode optical fiber (SMF) or a multimode optical fiber (MMF).

[0026] As shown in FIG. 1 , the protective member 20 is a member having a flat shape that expands in the X and Y directions. The optical module 30 is housed inside the protective member 20. The protective member 20 protects the optical module 30 from external impacts and the like. The protective member 20 has a laminated structure consisting of an inner layer 21 and an outer layer 22 that covers the inner layer 21. The inner layer 21 is made of, for example, metal. The outer layer 22 is made of, for example, resin. At the tip of the optical connector cable 1, a portion of the inner layer 21 is exposed from the outer layer 22. The exposed portion of the inner layer 21 is inserted, for example, into a socket provided in a device to which the optical connector cable 1 is connected.

[0027] Next, the optical module 30 will be described with reference to FIGS. 3 to 6. FIG. 3 is a plan view of the optical module 30 viewed from above the first main surface 41 of the substrate 40. FIG. 4 is a plan view of the optical module 30 viewed from above the second main surface 42 of the substrate 40. FIG. 5 is a cross-sectional view of the optical module 30 taken along line V-V in FIG. 3. FIG. 6 is an enlarged view of the portion surrounded by dashed line A in FIG. 5. The optical module 30 includes a substrate 40, a plurality of optical coupling modules 50, a plurality of optical elements 60, and a plurality of ICs 61.

[0028] The substrate 40 is a plate-like member on which various optical and electronic elements are mounted. The substrate 40 may be a multilayer substrate formed by stacking multiple resin layers, or a single-layer substrate formed by a single resin layer. The resin layer may be made of, for example, epoxy resin, polyimide resin, or fluororesin. In this embodiment, the thickness direction of the substrate 40 coincides with the Z direction. When viewed from the Z direction, the substrate 40 has a pair of side surfaces 40a and 40b extending along the X direction and a pair of side surfaces 40c and 40d extending along the Y direction. When viewed from the Z direction, the outer edge of the substrate 40 has a rectangular shape defined by the pair of side surfaces 40a and 40b and the pair of side surfaces 40c and 40d. In other words, the substrate 40 is a rectangular substrate. The substrate 40 has a first main surface 41 and a second main surface 42 facing each other in the Z direction. The thickness of the substrate 40 may be 0.2 mm or more and 0.8 mm or less.

[0029] The substrate 40 has at least one glass cloth 70 therein. The glass cloth 70 is a woven fabric formed using glass yarns as warp and weft threads. For ease of explanation, only a portion of the glass cloth 70 is shown in FIGS. 3 and 4 , but in this embodiment, the glass cloth 70 is provided over the entire substrate 40 when viewed from the Z direction. That is, the outer edge of the glass cloth 70 when viewed from the Z direction coincides with the outer edge of the substrate 40. When the substrate 40 is a multilayer substrate, the glass cloth 70 may be provided in each of multiple resin layers constituting the substrate 40. In this embodiment, the substrate 40 is a multilayer substrate, and multiple glass cloths 70 are stacked in the Z direction. The detailed configuration of the glass cloth 70 will be described later.

[0030] Various wirings (not shown) for electrically connecting the IC 61 and other electronic elements are provided inside the substrate 40. In the following description, the end where the side surface 40a is located in the direction Y may be referred to as the tip of the optical module 30, and the end where the side surface 40b is located may be referred to as the base end of the optical module 30. Furthermore, the surface where the first main surface 41 is located in the direction Z may be referred to as the top surface of the optical module 30, and the surface where the second main surface 42 is located may be referred to as the bottom surface of the optical module 30.

[0031] 3, the first main surface 41 is a surface extending in the X direction and the Y direction and has a rectangular shape in a plan view. A plurality of patterns 41a made of a metal film are provided in an area of ​​the first main surface 41 closer to the side surface 40a. Each pattern 41a may be connected to the IC 61 via, for example, wiring within the substrate 40. Meanwhile, a plurality of optical coupling modules 50 are mounted side by side along the X direction in an area of ​​the first main surface 41 closer to the side surface 40b.

[0032] As shown in FIG. 4 , the second main surface 42 is a surface extending in the X and Y directions and has a rectangular shape in a plan view. A plurality of optical elements 60 and a plurality of ICs 61 are mounted in an area of ​​the second main surface 42 near the side surface 40 b. For ease of explanation, each optical element 60 is indicated by a dashed line in FIG. 4 . Each optical element 60 is a light-receiving element such as a photodiode (PD). The light-receiving surface of each optical element 60 faces the optical coupling module 50. When viewing the second main surface 42 from above (in the Z direction), each optical element 60 overlaps with a corresponding through-hole 48 a provided in the substrate 40. This allows the optical element 60 to receive light from the optical coupling module 50 that faces it across the substrate 40 via the through-hole 48 a. The opening area of ​​the through-hole 48a in the second main surface 42 is smaller than the surface area of ​​the face of the optical element 60 facing the second main surface 42, so that the optical element 60 can be disposed on the second main surface 42. Each IC 61 is an integrated circuit that controls the operation of the optical element 60. Each IC 61 may be connected to the optical element 60 via, for example, wiring or bonding wires within the substrate 40. In this embodiment, one IC 61 is connected to three optical elements 60. By disposing the IC 61 near the optical element 60 (for example, adjacent to it), the communication speed between the IC 61 and the optical element 60 can be maintained high.

[0033] The optical coupling module 50 is a component that optically couples the optical fiber 11 and the optical element 60. The optical coupling module 50 is made of a material (e.g., glass or optically transparent resin) that transmits the light emitted from the optical fiber 11. As shown in FIG. 3 , the optical coupling module 50 has a substantially rectangular shape when viewed from direction Z. The optical coupling module 50 has a tip surface 50a and a pair of side surfaces 50b. The tip surface 50a is a surface that extends along direction X and direction Z, and connects the pair of side surfaces 50b. Each side surface 50b is a surface that extends along direction Y and direction Z.

[0034] 5 , the optical coupling module 50 has a groove 51, an upper surface 52, a lower surface 53, an abutting surface 54, a mirror 55, and a lens 56. The groove 51 is a V-groove (a groove having a V-shape in an XZ cross section) extending along the Y direction and serves as a holder for holding the end of the optical fiber 11. The groove 51 determines the position of the optical fiber 11 relative to the optical coupling module 50 and prevents the optical fiber 11 from shifting in the X direction. The end of the optical fiber 11 placed in the groove 51 is fixed to the groove 51 by, for example, an adhesive. The adhesive may be, for example, an ultraviolet-curable adhesive or a light-transmitting adhesive that transmits the light L emitted from the optical fiber 11. The shape of the groove 51 is not limited to a V-groove. For example, the shape of the groove 51 may be a U-groove with a rounded bottom or a rectangular groove with a bottom surface along the X direction and the Y direction. The holding portion (groove portion 51 in this embodiment) that holds the end of the optical fiber 11 does not necessarily have to be provided in the optical coupling module 50. For example, the groove portion 51 may be provided in a separate component that is different from the optical coupling module 50. When the groove portion 51 is provided in a separate component, for example, the optical coupling module 50 may have a pair of convex portions, and the separate component in which the groove portion 51 is provided may have a pair of concave portions, and the optical coupling module 50 and the separate component may be connected by fitting the convex portions of the optical coupling module 50 into the concave portions of the separate component.

[0035] The upper surface 52 is a surface located at the top of the optical coupling module 50 and extends along the X and Y directions. The upper surface 52 is located closer to the tip surface 50a of the optical coupling module 50 than the groove portion 51. The upper surface 52 is provided with a recess whose surface functions as a mirror 55. The lower surface 53 is a surface located at the bottom of the optical coupling module 50 and extends along the X and Y directions.

[0036] The abutting surface 54 is a surface against which the tip surface of the optical fiber 11 abuts, and is aligned with the X and Z directions. The abutting surface 54 connects the end of the groove 51 in the Y direction to the end of the top surface 52. Light L emitted from the optical fiber 11 passes through the abutting surface 54 and is incident on the mirror 55. The abutting surface 54 and the tip surface of the optical fiber 11 do not need to be in direct contact. For example, a light-transmitting adhesive or a refractive index matching agent that transmits light L may be inserted between the abutting surface 54 and the tip surface of the optical fiber 11.

[0037] The mirror 55 is a component that changes the propagation direction of the light L emitted from the optical fiber 11. The mirror 55 is provided at an angle with respect to both the XY plane and the XZ plane. The mirror 55 receives the light L emitted from the optical fiber 11 along the direction Y and reflects the light L along the direction Z toward the lens 56. The incident optical axis and the reflected optical axis of the light L may form a right angle, for example. The light L reflected by the mirror 55 enters the optical element 60 via the lens 56 and the through-hole 48a.

[0038] The lens 56 is a component that optically couples with the optical element 60. The lens 56 is provided on a portion of the optical coupling module 50 that protrudes toward the second main surface 42 in the direction Z. As shown in FIG. 6 , the lens 56 faces the optical element 60 in the direction Z and has a surface that is convexly curved toward the optical element 60. The focal point F of the lens 56 is located inside the optical element 60 rather than the surface of the optical element 60. The lens 56 converges the light L reflected by the mirror 55 and makes it incident on the optical element 60. Various parameters of the lens 56 (e.g., the surface shape, size, material, etc. of the lens 56) are optimized so that the focal point F of the lens 56 is located inside the optical element 60.

[0039] Next, a detailed configuration of the substrate 40 will be described with reference to FIGS. 7 and 8 . FIG. 7 is a perspective view showing the substrate 40. FIG. 8 is an enlarged view of the portion surrounded by the dashed line B shown in FIG. 7 . For convenience of explanation, the optical coupling modules 50 are not shown in FIGS. 7 and 8 . As shown in FIG. 7 , a plurality of cavities 43 are formed in the substrate 40. Each cavity 43 is a recess recessed from the first main surface 41 toward the second main surface 42. An optical coupling module 50 is housed inside each cavity 43. The plurality of cavities 43 are arranged side by side along the direction X. The number of cavities 43 may be equal to or greater than the number of optical coupling modules 50 mounted on the substrate 40. In this embodiment, the same number (four) of cavities 43 as the number of optical coupling modules 50 are formed. Each cavity 43 may be formed by, for example, countersinking. Between adjacent cavities 43, beam portions 43a are provided, which extend from the inside to the outside of the substrate 40 along direction Y. The beam portions 43a are shaped to rise from the first bottom portions 45 of the respective cavities 43 toward the first main surface 41 of the substrate 40.

[0040] Each cavity 43 includes a first cavity 44 and a second cavity 47. The first cavity 44 is a recess that constitutes most of the cavity 43 and has a first bottom 45 and a side surface 46. The first bottom 45 is a portion on which the optical coupling module 50 is placed, and in this embodiment, is a surface along the direction X and the direction Y. When viewed from the direction Z, the outer edge of the first bottom 45 has a rectangular shape with long sides along the direction Y. The first bottom 45 is large enough to accommodate the entire optical coupling module 50. Placing the optical coupling module 50 on the first bottom 45 includes not only cases in which the optical coupling module 50 is placed in direct contact with the first bottom 45, but also cases in which the optical coupling module 50 is placed on the first bottom 45 via another member such as an adhesive.

[0041] As shown in FIG. 8 , the first bottom 45 has a pair of positioning holes 45 a. Each positioning hole 45 a penetrates from the first bottom 45 toward the second main surface 42 (see FIG. 4 ). The pair of positioning holes 45 a functions as a mechanism for positioning the optical coupling module 50 relative to the cavity 43. For example, the optical coupling module 50 may be provided with a pair of protrusions corresponding to the pair of positioning holes 45 a. By placing the optical coupling module 50 so that each of the pair of protrusions is fitted into each of the pair of positioning holes 45 a, the lens 56 (see FIG. 5 ) and the optical element 60 are suitably optically coupled. While the number of positioning holes 45 a may be one, forming two or more positioning holes 45 a allows for more accurate positioning of the optical coupling module 50. Each positioning hole 45 a does not need to penetrate from the first bottom 45 to the second main surface 42 and may be a blind hole having a bottom surface.

[0042] The form of the positioning mechanism used to position the optical coupling module 50 is not limited to the positioning hole 45a. For example, marks may be provided on each of the first bottom 45 and the optical coupling module 50, and the optical coupling module 50 may be placed at a position where the marks overlap, thereby suitably optically coupling the lens 56 of the optical coupling module 50 and the optical element 60. In this case, the material of the optical coupling module 50 may be a material that transmits visible light (e.g., glass or optically transparent resin) so that the marks provided on the first bottom 45 are visible through the optical coupling module 50.

[0043] The side surface 46 is a surface that rises from the outer edge of the first bottom 45 toward the first main surface 41 of the substrate 40. The side surface 46 connects the first bottom 45 and the first main surface 41. The side surface 46 defines the outer edge of the first cavity 44 when viewed from the direction Z. The side surface 46 may be parallel to the direction Z or may be inclined relative to the direction Z. The side surface 46 includes a side surface 46a and a pair of side surfaces 46b. As shown in FIG. 7 , the side surface 46a is a surface located at the end of the first cavity 44 closer to the side surface 40a and connects the pair of side surfaces 46b together. The side surface 46a is aligned with the direction X when viewed from the direction Z. The corner where the side surface 46a and the first bottom 45 intersect may have an R-shape.

[0044] The pair of side surfaces 46b are surfaces that face each other in direction X. When viewed from direction Z, each side surface 46b extends along direction Y. The corners where each side surface 46b intersects with the first bottom 45 may have an R-shape. Furthermore, the end of the first cavity 44 closer to the side surface 40b does not have a side surface. That is, the cavity 43 opens at the side surface 40b. This allows the optical coupling module 50 to be housed inside the cavity 43 through this opening. Furthermore, with the optical coupling module 50 housed in the cavity 43, the optical fiber 11 connected to the optical coupling module 50 can be drawn out of the cavity 43 from this opening.

[0045] As shown in FIG. 8 , the second cavity 47 is a recess provided in the first bottom 45 of the first cavity 44. The second cavity 47 is formed to extend along the direction X. The second cavity 47 has a second bottom 48 and a side surface 49. The second bottom 48 is located closer to the second main surface 42 than the first bottom 45. In this embodiment, the second bottom 48 is a surface extending along the directions X and Y. When viewed from the direction Z, the outer edge of the second bottom 48 has a rectangular shape with long sides extending along the direction X. A portion of the optical coupling module 50 (the portion where the lens 56 is formed) is placed on the second bottom 48 (see FIG. 5 ). The lens 56 is housed in the second cavity 47.

[0046] A plurality of through holes 48a are formed in the second bottom 48. In this embodiment, two round holes and one elongated hole are formed as the through holes 48a for each second cavity 47. The number and shape of the through holes 48a are not limited and may be changed as appropriate depending on the number and shape of the optical elements 60 mounted on the second main surface 42. As shown in FIG. 6 , the through holes 48a penetrate from the second bottom 48 to the second main surface 42. Light L traveling from the lens 56 toward the optical elements 60 passes through the through holes 48a. The through holes 48a have a tapered shape in which the inner diameter decreases from the second bottom 48 to the second main surface 42. The inner diameter and taper angle of the through holes 48a are optimized to not obstruct the path of the light L. The through holes 48a may also be straight through holes with a constant inner diameter.

[0047] As shown in Fig. 8 , a plurality of protrusions 74, which are part of the glass cloth 70, protrude from the side surface 46 of the first cavity 44 into the cavity 43. Here, the glass cloth 70 will be described in detail with reference to Fig. 9 . Fig. 9 is a schematic diagram of the substrate 40 in a plan view. Fig. 9 shows the substrate 40 before the plurality of cavities 43 are formed. In Fig. 9 , various components such as the optical element 60 and the IC 61 provided on the substrate 40 are not shown.

[0048] As shown in FIG. 9 , a glass cloth 70 is provided inside the substrate 40. The glass cloth 70 is a woven fabric composed of glass threads 71 ​​as weft threads 72 and warp threads 73. The glass cloth 70 has a mesh-like sheet shape. In the glass cloth 70, the weft threads 72 and the warp threads 73 regularly intersect with each other. The weave density of the weft threads 72 and the weave density of the warp threads 73 are, for example, 50 threads / 25 mm or more and 100 threads / 25 mm or less. The glass threads 71 ​​constituting the weft threads 72 and the warp threads 73 are, for example, bundles of several hundred glass filaments (for example, 100 to 500 threads). The diameter of each glass filament is, for example, about several μm (for example, 1 μm to 10 μm). For ease of explanation, in FIG. 9 , the spacing between the weft threads 72 and the warp threads 73 is shown larger than the actual spacing.

[0049] The weft yarns 72 extend along direction X. That is, when viewed from direction Z, the weft yarns 72 extend along the pair of side surfaces 40a, 40b. The warp yarns 73 extend along direction Y. That is, when viewed from direction Z, the warp yarns 73 extend along the pair of side surfaces 40c, 40d. When a cavity 43 is formed in the substrate 40 on which the glass cloth 70 is arranged, for example, by countersinking, as shown in FIG. 8 , a portion of the weft yarns 72 and the warp yarns 73 protrudes as protrusions 74 from the side surfaces 46 into the cavity 43. Specifically, for example, when forming the cavity 43, some of the weft yarns 72 are cut, and the ends of the cut weft yarns 72 protrude from the side surfaces 46a as protrusions 74. Similarly, when forming the cavity 43, some of the warp yarns 73 are cut, and the ends of the cut warp yarns 73 protrude as protrusions 74 from each side surface 46b.

[0050] The side surface 46a is formed so as to align with the extension direction of the weft thread 72. The extension direction of the weft thread 72 refers to the extension direction of the weft thread 72 located inside the substrate 40 (direction X in this embodiment), not the extension direction of the protrusion 74 protruding from the side surface 46a. The protrusion 74 protruding from the side surface 46a may protrude in an irregular direction different from direction X. The length of the protrusion 74 protruding from the side surface 46a is, for example, 100 μm or more and 1 mm or less, and more preferably 100 μm or more and 200 μm or less. When multiple protrusions 74 protrude from the side surface 46a, the orientation and length of each protrusion 74 may differ from one another. Note that the length of the protrusion 74 here refers to the average length of any 10 protrusions 74. The same applies hereinafter.

[0051] Each side surface 46b is formed along the extension direction of the warp threads 73. The extension direction of the warp threads 73 refers to the extension direction of the warp threads 73 located inside the substrate 40 (direction Y in this embodiment), not the extension direction of the protrusions 74 protruding from each side surface 46b. The protrusions 74 protruding from each side surface 46b may protrude in an irregular direction different from direction Y. The length of the protrusions 74 protruding from each side surface 46b is, for example, 100 μm or more and 1 mm or less, more preferably 100 μm or more and 200 μm or less. When multiple protrusions 74 protrude from each side surface 46b, the orientation and length of each protrusion 74 may be different from each other. As such, the side surface 46 in this embodiment is aligned along the extension direction of the weft threads 72 or the warp threads 73. Therefore, compared to when the side surface 46 is inclined with respect to the extension direction of the weft threads 72 and the warp threads 73, the glass threads 71 ​​are more likely to protrude from the side surface 46, and long protrusions 74 are more likely to be formed.

[0052] The manner in which the optical coupling module 50 is accommodated in the cavity 43 will be described with reference to Figures 5 and 10. Figure 10 is a plan view of the optical coupling module 50 accommodated in the cavity 43. For ease of explanation, the distances between the weft threads 72 and between the warp threads 73 are shown larger than the actual distances in Figure 10. Furthermore, Figure 10 does not show the portion of the glass cloth 70 provided inside the substrate 40 that overlaps with the first bottom 45, but in reality, the glass cloth 70 is also provided between the first bottom 45 and the second main surface 42 (see Figure 5).

[0053] 5 , most of the optical coupling module 50 is housed in the first cavity 44, and the portion where the lens 56 is provided (the portion protruding downward in direction Z) is housed in the second cavity 47. The portion of the optical fiber 11 located on the substrate 40 (the mounting portion) extends along the first main surface 41 of the substrate 40. The central axis of the mounting portion is located inside the cavity 43. The end of the optical fiber 11 extends straight on the side surface 40b of the substrate 40 without being bent.

[0054] The depth D1 of the first cavity 44 is optimized, for example, according to the thickness T of the optical coupling module 50. Here, the depth D1 is the distance from the first main surface 41 to the first bottom 45 in the thickness direction (direction Z) of the substrate 40. The thickness T is the distance from the upper surface 52 to the lower surface 53 in direction Z. The depth D1 may be equal to or greater than half the thickness T of the optical coupling module 50. In this embodiment, the depth D1 is equal to or greater than half the thickness of the substrate 40 (the distance from the first main surface 41 to the second main surface 42). When the thickness of the substrate 40 is 10, the depth D1 may be, for example, equal to or greater than 6 and equal to or less than 8. As the depth D1 increases, a larger portion of the optical coupling module 50 is accommodated in the cavity 43, thereby reducing the thickness of the optical module 30. In this embodiment, the upper surface 52 is located outside the cavity 43 (above the first main surface 41), but the depth D1 may be greater so that the upper surface 52 is located inside the cavity 43 (at the same height as the first main surface 41 or below the first main surface 41).

[0055] The depth D2 of the second cavity 47 is greater than the depth D1. Here, the depth D2 is the distance from the first main surface 41 to the second bottom 48 in the thickness direction of the substrate 40. When the thickness of the substrate 40 is 10, the depth D2 may be, for example, 7 or more and 9 or less. The depth D2 may be optimized depending on, for example, the thickness T of the optical coupling module 50.

[0056] 10 , in this embodiment, the entire optical coupling module 50 is disposed on the substrate 40. The entire optical coupling module 50 does not have to be disposed on the substrate 40, and a portion of the optical coupling module 50 may be disposed outside the substrate 40 (at a position that does not overlap with the substrate 40 in the Z direction). For example, the base end portion of the optical coupling module 50 (the left portion in FIG. 10 ) may be disposed outside the substrate 40.

[0057] The optical coupling module 50 is accommodated in the cavity 43 such that a gap 80 is provided between the side surface 46 and the optical coupling module 50. Specifically, a gap 81 is provided between the tip surface 50a and the side surface 46a, and a gap 82 is provided between each side surface 50b and each side surface 46b. A width W1 of the gap 81 in the direction Y may be, for example, 50 μm or more and 500 μm or less. A width W2 of the gap 82 in the direction X may be, for example, 50 μm or more and 750 μm or less. The width W2 may be greater than the width W1.

[0058] The optical coupling module 50 is fixed to the substrate 40 using an adhesive 85. As shown in FIG. 5 , the adhesive 85 is disposed between the lower surface 53 and the first bottom 45. To prevent the optical path of the light L from being obstructed by the adhesive 85, the adhesive 85 does not have to be disposed inside the second cavity 47. Furthermore, as shown in FIG. 10 , the adhesive 85 is also disposed in the gap 81 and contacts the protrusions 74 protruding from the side surface 46 a. The protrusions 74 protruding from the side surface 46 a penetrate into the adhesive 85. Similarly, the adhesive 85 is also disposed in the gap 82 and contacts the protrusions 74 protruding from each side surface 46 b. The protrusions 74 protruding from each side surface 46 b penetrate into the adhesive 85. The adhesive 85 is, for example, an ultraviolet-curable adhesive or a light-transmitting adhesive. It is not necessary for all of the protrusions 74 protruding from the side surface 46 to penetrate into the adhesive 85; it is sufficient for at least some of the protrusions 74 to penetrate into the adhesive 85.

[0059] Next, a method for manufacturing the optical module 30 described above will be described. First, a substrate 40 is prepared, including a glass cloth 70 configured with glass threads 71 ​​as weft threads 72 and warp threads 73. Next, cavities 43 (first cavities 44 and second cavities 47) are formed in the substrate 40. The cavities 43 may be formed, for example, by countersinking. In the process of forming the cavities 43, the side surfaces 46 of the cavities 43 are formed so that they extend along the direction of extension of at least one of the weft threads 72 and the warp threads 73 when viewed from the Z direction. In this embodiment, the cavities 43 are formed so that the side surfaces 46a extend along the weft threads 72 and the side surfaces 46b extend along the warp threads 73. By forming the side surfaces 46 in this manner along the extension direction of the glass threads 71 ​​(weft threads 72 or warp threads 73), portions of the weft threads 72 and warp threads 73 tend to protrude from the side surfaces 46 into the cavity 43 as protrusions 74. The length and quantity (number) of the protruding portions 74 of the glass cloth 70 protruding from the side surfaces of the cavity 43 can be adjusted by adjusting processing conditions such as the countersinking. In a subsequent step of fixing the optical coupling module 50 to the substrate 40, the orientation of the protruding portions 74 may be adjusted so that they stand upright relative to the side surfaces 46, so that the protruding portions 74 can easily penetrate the adhesive 85. The orientation of the protruding portions 74 may be adjusted, for example, directly by an operator's hand, or by blowing air onto the protruding portions 74. In the step of forming the cavity 43, a plurality of through holes 48a are formed extending from the second bottom portion 48 of the second cavity 47 toward the second main surface 42.

[0060] Next, the optical coupling module 50 is placed inside the cavity 43 and fixed to the substrate 40 with adhesive 85. Specifically, the adhesive 85 is applied to an area of ​​the first bottom 45 where the second cavity 47 is not formed, and then the optical coupling module 50 is placed so that the lower surface 53 contacts the adhesive 85. At this time, as shown in FIG. 10 , the optical coupling module 50 is placed so that a gap 81 is formed between the tip surface 50a and the side surface 46a and a gap 82 is formed between each side surface 50b and each side surface 46b. The adhesive 85 is spread, for example, by the weight of the optical coupling module 50 and flows into the gaps 81 and 82. As a result, each protrusion 74 enters the adhesive 85 stored in the gaps 81 and 82. The amount of adhesive 85 applied is adjusted so that the adhesive 85 flows into the gap 80 and each protrusion 74 enters the adhesive 85. The amount of adhesive 85 applied per optical coupling module 50 is, for example, 1 mg or more and 10 mg or less.

[0061] Next, a plurality of optical elements 60 and a plurality of ICs 61 are mounted on the second main surface 42. At this time, each optical element 60 is mounted so as to overlap a corresponding one of the through holes 48a in the direction Z. This completes the manufacturing process of the optical module 30.

[0062] As described above, in the optical module 30 and optical connector cable 1 according to this embodiment, a portion of the glass cloth 70 (the protrusion 74) protrudes from the side surface 46 of the cavity 43 into the cavity 43. Furthermore, the protrusion 74 penetrates into the adhesive 85 that fixes the optical coupling module 50 to the substrate 40. This increases the contact area between the adhesive 85 and the substrate 40 by the surface area of ​​the protrusion 74, and the protrusion 74 can function as an anchor for the adhesive 85. This improves the adhesive strength of the optical coupling module 50 to the substrate 40.

[0063] In the above embodiment, the glass cloth 70 is configured with glass threads 71 ​​as weft threads 72 and warp threads 73. When viewed from direction Z, the side surface 46 is formed so as to follow the extending direction of at least one of the weft threads 72 and the warp threads 73. In this case, the protrusions 74 are formed with a large length, which further increases the contact area between the adhesive 85 and the substrate 40. This can further improve the adhesive strength of the optical coupling module 50 to the substrate 40.

[0064] In the above embodiment, the optical coupling module 50 is housed inside the cavity 43 so that a gap 80 is provided between the side surface 46 and the optical coupling module 50. The adhesive 85 is disposed in the gap 80. The widths W1 and W2 of the gap 80 may be 50 μm or more and 750 μm or less. In this case, the adhesive 85 can be stored in the gap 80 where the protrusion 74 is located, allowing the surface of the protrusion 74 to appropriately contact the adhesive 85. Furthermore, by setting the widths W1 and W2 of the gap 80 to 50 μm or more and 750 μm or less, an appropriate amount of adhesive 85 can be stored in the gap 80. This further improves the adhesive strength of the optical coupling module 50 to the substrate 40.

[0065] In the above embodiment, the length of the protrusion 74 may be 100 μm or more and 1 mm or less. In this case, because the length of the protrusion 74 is 100 μm or more, a sufficient contact area between the surface of the protrusion 74 and the adhesive 85 can be ensured. This further improves the adhesive strength of the optical coupling module 50 to the substrate 40. Furthermore, because the length of the protrusion 74 is 1 mm or less, the protrusion 74 is less likely to interfere with the insertion of the optical coupling module 50 into the cavity 43. This makes it easy to insert the optical coupling module 50 into the cavity 43.

[0066] In the above embodiment, the optical coupling module 50 has a groove 51 (holding portion) that holds the end of the optical fiber 11 that is optically coupled to the optical element 60 via the optical coupling module 50. In this case, the end of the optical fiber 11 is properly held by the groove 51 of the optical coupling module 50, so that the optical coupling between the optical element 60 and the optical fiber 11 can be more accurately achieved.

[0067] In the above embodiment, the cavity 43 has a through hole 48a formed therein, penetrating from the second bottom 48 to the second main surface 42. The optical element 60 is mounted on the second main surface 42 so as to overlap with the through hole 48a when the second main surface 42 is viewed from above (in the Z direction). In this case, the optical coupling module 50 and the optical element 60 mounted on the second main surface 42 of the substrate 40 can be optically coupled via the simple configuration of the through hole 48a.

[0068] In the above embodiment, the cavity 43 has a first cavity 44 closer to the first main surface 41 and a second cavity 47 having a second bottom 48 located closer to the second main surface 42 than the first bottom 45 of the first cavity 44. In this case, the cavity portion (second cavity 47 portion) that mainly accommodates components such as the lens 56 that tend to protrude from the lower surface 53 of the optical coupling module 50 can be made deeper, while the other portion (first cavity 44 portion) can be made shallower, thereby making the overall area of ​​the cavity 43 smaller. As a result, the strength of the substrate 40 can be maintained even when the cavity 43 is provided in the substrate 40.

[0069] In the method for manufacturing the optical module 30 according to this embodiment, a portion of the glass cloth 70 is formed as a protrusion 74, which protrudes from the side surface 46 of the cavity 43 into the cavity 43. The adhesive 85 is applied so that the protrusion 74 penetrates the adhesive 85. This increases the contact area between the adhesive 85 and the substrate 40 by the surface area of ​​the protrusion 74, and the protrusion 74 can function as an anchor for the adhesive 85. This improves the adhesive strength of the optical coupling module 50 to the substrate 40.

[0070] Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above embodiments and can be applied to various other embodiments. For example, the cavity 43 may have a uniform depth without including the second cavity 47. In this case, the bottom of the cavity 43 may be an entirely flat mounting surface, and the optical coupling module 50 may be mounted on the mounting surface. Alternatively, the first bottom 45 of the first cavity 44 may have multiple protrusions, and the optical coupling module 50 may be mounted on the multiple protrusions.

[0071] The optical module 30 in the above embodiment is configured to cause the light L emitted from the optical fiber 11 to be incident on the optical element 60, but may also be configured to cause the light emitted from the optical element 60 to be incident on the optical fiber 11. In this case, the optical element 60 may be a light-emitting element such as a VCSEL (Vertical Cavity Surface Emitting Laser). The light emitted from the optical element 60 may be converted into collimated light (parallel light) by the lens 56, reflected by the mirror 55, and then incident on the optical fiber 11.

[0072] In the above embodiment, the protrusion 74 protrudes from the side surface 46 of the first cavity 44. However, the protrusion 74 may also protrude from the side surface 49 of the second cavity 47. The side surface 49 of the second cavity 47 is a surface connecting the second bottom 48 and the first bottom 45, and is formed to rise from the outer edge of the second bottom 48 toward the first bottom 45. The side surface 49 of the second cavity 47 may be formed to align with the extension direction of at least one of the weft yarns 72 and the warp yarns 73 when viewed from direction Z. The adhesive 85 may also be disposed inside the second cavity 47 and be in contact with the protrusion 74 protruding from the side surface 49 of the second cavity 47.

[0073] DESCRIPTION OF SYMBOLS 1...Optical connector cable 10...Optical fiber cable 11...Optical fiber 12...Cable jacket 20...Protective member 21...Inner layer 22...Outer layer 30...Optical module 40...Substrate 40a, 40b, 40c, 40d...Side surface 41...First main surface 41a...Pattern 42...Second main surface 43...Cavity 43a...Beam portion 44...First cavity 45...First bottom portion 45a...Positioning hole 46, 46a, 46b...Side surface 47...Second cavity 48...Second bottom portion 48a...Through hole 49...Side surface 50...Optical coupling module 50a...Tip surface 50b...Side surface 51...Groove portion 52...Upper surface 53...Lower surface 55...Mirror 56...Lens 60...Optical element 61...IC 70...Glass cloth 71...Glass thread 72...Weft thread 73...Warp thread 74...Protrusion 80, 81, 82...Gaps 85...Adhesive F...Focus point L...Light W1...Width W2...Width

Claims

1. A substrate having a glass cloth therein; An optical element mounted on the substrate; an optical coupling module configured to optically couple with the optical element; an adhesive for fixing the optical coupling module to the substrate; Equipped with a cavity is formed in the substrate, the cavity being recessed from a first main surface of the substrate toward a second main surface of the substrate so as to have a bottom, and at least a portion of the optical coupling module is accommodated in the cavity; the glass cloth has a protruding portion protruding from a side surface of the cavity into the cavity, the protrusion is embedded in the adhesive located between the side surface and the optical coupling module; The glass cloth is formed of glass yarns as weft and warp yarns, The side surface is formed so as to extend along at least one of the weft yarns and the warp yarns when viewed from the thickness direction of the substrate. Optical module.

2. The glass yarn constituting at least one of the weft yarn and the warp yarn is formed from a bundle of a plurality of glass filaments, and each of the plurality of glass filaments has a diameter of 10 μm or less.

2. The optical module according to claim 1.

3. The weaving density of the glass yarn in at least one of the weft yarn and the warp yarn is 50 yarns / 25 mm or more and 100 yarns / 25 mm or less.

3. The optical module according to claim 1 or 2.

4. the optical coupling module is accommodated in the cavity such that a gap is provided between the side surface and the optical coupling module; The adhesive is disposed in the gap.

3. The optical module according to claim 1 or 2.

5. The width of the gap is 50 μm or more and 750 μm or less.

5. The optical module according to claim 4.

6. The length of the protrusion is 100 μm or more and 1 mm or less.

3. The optical module according to claim 1 or 2.

7. the optical coupling module has a holder for holding an end of an optical fiber that is optically coupled to the optical element via the optical coupling module; 3. The optical module according to claim 1 or 2.

8. a through hole is formed in the cavity, the through hole penetrating from the bottom to the second main surface, the optical element is mounted on the second main surface so as to overlap the through hole when viewed from above the second main surface; 3. The optical module according to claim 1 or 2.

9. The cavity includes a first cavity and a second cavity having a second bottom located closer to the second main surface than a first bottom of the first cavity.

3. The optical module according to claim 1 or 2.

10. The first bottom of the first cavity is provided with a positioning hole recessed from the first bottom toward the second main surface.

10. The optical module according to claim 9.

11. The second bottom of the second cavity is provided with a plurality of through holes penetrating from the second bottom to the second main surface.

10. The optical module according to claim 9.

12. A substrate having a glass cloth therein; A plurality of optical elements mounted on the substrate; a plurality of optical coupling modules configured to optically couple to each of the plurality of optical elements; an adhesive for fixing each of the optical coupling modules to the substrate; Equipped with a plurality of cavities are formed in the substrate, the cavities being recessed from a first main surface of the substrate toward a second main surface of the substrate so as to have a bottom, and each of the plurality of cavities accommodates a corresponding one of the plurality of optical coupling modules; the glass cloth has a plurality of protrusions protruding from each side surface of the plurality of cavities into the interior of the plurality of cavities, the plurality of protrusions are embedded in the adhesive located between each of the side surfaces and each of the plurality of optical coupling modules; Optical module.

13. The optical module according to claim 1 or 2, a fiber optic cable having at least one optical fiber; The optical fiber cable is attached to the optical module such that the optical fiber is optically coupled to the optical element via the optical coupling module.

14. Providing a substrate comprising a glass cloth; forming a cavity in the substrate, the cavity having a bottom and recessed from a first main surface of the substrate toward a second main surface of the substrate; receiving at least a portion of an optical coupling module configured to be optically coupled to an optical element within the cavity and fixing the optical coupling module to the substrate by an adhesive; Equipped with In the step of preparing a substrate including the glass cloth, the glass cloth is prepared, the glass cloth being configured with glass yarns as weft yarns and warp yarns; In the step of forming the cavity, the cavity is formed so that a side surface of the cavity is aligned along an extension direction of at least one of the weft yarns and the warp yarns when viewed from a thickness direction of the substrate, and a part of the glass cloth is made to protrude from the side surface into the cavity as a protrusion, In the step of fixing the optical coupling module to the substrate, the adhesive is applied to the inside of the cavity so that the protrusion penetrates into the adhesive. A method for manufacturing an optical module.