Glass substrate and optical connection component
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Filing Date
- 2025-11-11
- Publication Date
- 2026-03-11
Smart Images
Figure 2024253098000001
Abstract
Description
Glass substrates and optical connection parts
[0001] This application claims priority to Japanese Patent Application No. 2023-095677, filed on June 9, 2023, and incorporates by reference all of the contents of that application.
[0002] Patent Document 1 discloses a perforated glass plate for holding a plurality of glass fibers. The perforated glass plate has a glass plate body with a plurality of through holes formed therein, into which the glass fibers are respectively inserted. The glass plate body is formed, for example, by a process combining laser modification and etching, or by a laser-based hole drilling technique.
[0003] International Publication No. 2020 / 027125
[0004] A glass substrate according to one embodiment of the present disclosure comprises a substrate body made of a glass material, including a first surface and a second surface opposite the first surface. The substrate body has at least one through-hole formed therein, the through-hole penetrating from the first surface to the second surface and allowing insertion of at least one glass fiber. The outer diameter of the glass fiber is 125 μm or less. The inner diameter of the through-hole is larger than the outer diameter of the glass fiber, and the surface roughness Rz of the inner surface of the through-hole is 1 μm or less. The ratio of the inner diameter of the through-hole to the surface roughness Rz is 127 or less.
[0005] FIG. 1 is a perspective view showing a state in which an optical connecting component according to this embodiment is connected to an electronic component. FIG. 2A is a perspective view showing the optical connecting component of FIG. 1. FIG. 2B is a plan view of the optical connecting component of FIG. 2A as viewed from the electronic component side. FIG. 3 is a perspective view showing a glass substrate provided in the optical connecting component of FIG. 1. FIG. 4 is a perspective view showing an enlarged view of a portion of the glass substrate of FIG. 3. FIG. 5 is a graph for explaining a method for calculating the surface roughness Rz. FIG. 6A is a perspective view showing a state in which glass fibers are inserted into each through-hole of the glass substrate of FIG. 4. FIG. 6B is a cross-sectional view of the glass substrate taken along line A1-A1 of FIG. 6A. FIG. 7A is an enlarged perspective view showing another example of the glass substrate. FIG. 7B is a cross-sectional view of the glass substrate taken along line A2-A2 of FIG. 7A. FIG. 8 is a plan view showing another example of the shape of the through-hole of the glass substrate.
[0006] [Problem to be Solved by the Present Disclosure] When a through hole is formed in a glass plate body using the manufacturing method described above, the manufacturing method tends to cause surface roughness on the inner surface of the through hole. If the surface roughness causes irregularities on the inner surface of the through hole, the irregularities can cause stress concentration on the glass fiber, resulting in damage such as breakage of the glass fiber. In order to reduce the occurrence of such damage to the glass fiber, for example, it is conceivable to increase the inner diameter of the through hole in advance, taking into account the height of the irregularities that may occur on the inner surface of the through hole. However, increasing the inner diameter of the through hole in this way may reduce the positional accuracy of the glass fiber inserted into the through hole.
[0007] The present disclosure provides a glass substrate and an optical connecting component that can increase the positional accuracy of a glass fiber while reducing damage to the glass fiber.
[0008] Effect of the Present Disclosure The glass substrate and optical connecting component according to the present disclosure can reduce damage to the glass fiber while increasing the positional accuracy of the glass fiber.
[0009] [Description of Embodiments of the Present Disclosure] First, the contents of the embodiments of the present disclosure will be listed and described.
[0010] (1) A glass substrate according to one embodiment of the present disclosure comprises a substrate body made of a glass material, including a first surface and a second surface opposite the first surface. The substrate body has at least one through-hole formed therein, the through-hole penetrating from the first surface to the second surface and allowing insertion of at least one glass fiber. The outer diameter of the glass fiber is 125 μm or less. The inner diameter of the through-hole is larger than the outer diameter of the glass fiber. The surface roughness Rz of the inner surface of the through-hole is 1 μm or less. The ratio of the inner diameter of the through-hole to the surface roughness Rz is 127 or less.
[0011] The glass substrate holds the glass fiber so that the glass fiber is maintained at a predetermined connection position relative to the electronic component to which it is connected. The optical coupling efficiency of the glass fiber to such an electronic substrate largely depends on the positional accuracy of the glass fiber. For example, a positional deviation of the glass fiber on the order of μm can cause a large optical connection loss of the glass fiber. From the viewpoint of reducing such optical connection loss, it is desirable to precisely maintain the position of the glass fiber on the order of μm. In the glass substrate, the surface roughness Rz of the inner surface of the through hole into which the glass fiber is inserted is set to 1 μm or less. Furthermore, assuming that a standard glass fiber having an outer diameter of 125 μm or less is inserted into the through hole, the ratio of the inner diameter of the through hole to the surface roughness Rz is set to 127 or less. In this case, the inner diameter of the through hole can be made as small as possible so as to avoid damage to the glass fiber due to stress concentration on the glass fiber caused by unevenness that may be formed on the inner surface of the through hole, and to allow for adhesive between the inner surface of the through hole and the glass fiber. In other words, the positional deviation of the glass fiber inserted into the through hole can be minimized on the order of μm while maintaining the maximum height of the convex portion that can be formed on the inner surface and the minimum space that can accommodate the adhesive injected into the through hole between the inner surface of the through hole and the glass fiber. As a result, it is possible to increase the positional accuracy of the glass fiber held in the glass substrate while reducing the occurrence of damage to the glass fiber due to stress concentration on the glass fiber caused by the unevenness of the through hole.
[0012] (2) In the glass substrate described in (1) above, the substrate body may be formed with a plurality of through holes into which a plurality of glass fibers can be inserted, respectively. In this case, it is possible to increase the positional accuracy of each glass fiber held in the glass substrate while reducing the occurrence of damage to each of the plurality of glass fibers, thereby effectively achieving the above-mentioned effects.
[0013] (3) In the glass substrate described in (1) or (2) above, a plurality of convex portions may be formed on the inner surface of the through hole, aligned along the extension direction of the through hole and the circumferential direction of the through hole. The arrangement pitch of two adjacent convex portions in the extension direction may be larger than the arrangement pitch of two adjacent convex portions in the circumferential direction. In this case, the number of convex portions formed along the extension direction can be reduced compared to when the arrangement pitch of the convex portions in the extension direction is equal to the arrangement pitch of the convex portions in the circumferential direction. In other words, the number of convex portions with which the glass fiber comes into contact while inserting the glass fiber into the through hole along the extension direction from the first surface to the second surface can be reduced. As a result, the opportunity for stress concentration in the glass fiber due to the convex portions can be reduced, and damage to the glass fiber due to stress concentration can be more reliably reduced.
[0014] (4) In the glass substrate described in any one of (1) to (3) above, the through hole may include an expanded diameter portion connected to the first surface and expanding in diameter as it approaches the first surface. In a cross section of the substrate body taken along a plane passing through the central axis of the through hole, the inner surface of the expanded diameter portion may have a curved shape that is bent so as to move away from the central axis as it approaches the first surface. For example, when a glass fiber is inserted into the through hole from the first surface, stress concentration is likely to occur in the glass fiber due to irregularities that may be formed on the inner surface of the through hole near the first surface. In contrast, in the above configuration, the through hole includes an expanded diameter portion that expands in diameter as it approaches the first surface, and the inner surface of the expanded diameter portion has a curved shape that is bent so as to move away from the central axis as it approaches the first surface. In this case, stress concentration on the glass fiber due to irregularities that may be formed on the inner surface of the expanded diameter portion can be reduced, thereby more reliably reducing damage to the glass fiber due to stress concentration.
[0015] (5) In the glass substrate described in (4) above, the inner surface of the enlarged diameter portion may be bent at the cut surface so that the curvature of the inner surface increases toward the first surface. In this case, stress concentration on the glass fiber due to irregularities that may be formed on the inner surface of the enlarged diameter portion can be more reliably reduced, thereby making it possible to more reliably reduce damage to the glass fiber due to stress concentration.
[0016] (6) In the glass substrate described in any one of (1) to (5) above, a groove extending from the first surface to the second surface may be formed. In this case, the groove formed on the inner surface of the through hole can be used as an escape groove for escaping excess adhesive injected into the through hole to fix the glass fiber to the substrate body. Use of this escape groove eliminates the need to adjust the through hole, such as by designing it larger in advance to take into account the amount of adhesive to be injected into the through hole. This makes it possible to minimize the inner diameter of the through hole while maintaining the shape of the inner surface of the through hole in a shape corresponding to the shape of the glass fiber. This more reliably achieves the aforementioned effect of increasing the positional accuracy of the glass fiber inserted into the through hole.
[0017] (7) An optical connecting component according to an embodiment of the present disclosure may include the glass substrate according to any one of (1) to (6) above, and a glass fiber inserted into the through hole and fixed to the substrate body with an adhesive. Because this optical connecting component includes any one of the glass substrates described above, it is possible to increase the positional accuracy of the glass fiber while reducing the occurrence of damage to the glass fiber, as described above.
[0018] (8) In the optical connecting component described in (7) above, the glass fiber may include a first straight portion extending along the extension direction of the through hole and inserted into the through hole, a second straight portion extending along a cross direction intersecting the extension direction, and a curved portion extending between the first straight portion and the second straight portion and connecting the first straight portion and the second straight portion. In this case, it is possible to achieve the above-mentioned effects of reducing damage to the glass fiber and improving the positioning accuracy of the glass fiber while reducing the height of the glass fiber.
[0019] [Details of the embodiments of the present disclosure] Specific examples of glass substrates and optical connecting components according to the present disclosure will be described below with reference to the drawings. The present disclosure is not limited to the following examples, but is set forth in the claims, and is intended to include all modifications within the scope of equivalents to the claims. In the description of the drawings, identical or corresponding elements are given the same reference numerals, and redundant explanations will be omitted as appropriate. For ease of understanding, some parts of the drawings may be simplified or exaggerated, and dimensional ratios and the like are not limited to those shown in the drawings. An XYZ coordinate system is shown in the drawings as necessary. The X-axis direction, Y-axis direction, and Z-axis direction intersect (e.g., are perpendicular to) each other.
[0020] Fig. 1 is a perspective view showing a state in which an optical connecting part 1 according to this embodiment is connected to an electronic substrate 2. Fig. 2A is a perspective view showing the optical connecting part 1 of Fig. 1. Fig. 2B is a plan view of the optical connecting part 1 of Fig. 2A as seen from the electronic substrate 2 side.
[0021] 1, the optical connecting part 1 includes, for example, a fiber ribbon 10 and a fiber fixing part 20. The fiber ribbon 10 has a curved portion midway, and a first end of the fiber ribbon 10 is connected to an electronic board 2 via the fiber fixing part 20. A second end of the fiber ribbon 10 is connected to on-site wiring via, for example, a connector. The electronic board 2 may be, for example, a chip substrate such as a silicon photonics chip (SPC) that inputs and outputs light.
[0022] The fiber ribbon 10 includes, for example, a plurality of optical fibers 13 arranged in a row along the Y-axis direction, and a coating resin layer 15 that collectively coats the plurality of optical fibers 13 with a ribbon resin. Each of the plurality of optical fibers 13 may be, for example, a single-core optical fiber having a single core, or a multi-core optical fiber having multiple cores. Each optical fiber 13 includes at least a glass fiber 11.
[0023] 2A , the glass fiber 11 includes, for example, a straight portion P1 (an example of a "second straight portion" in the present disclosure), a curved portion P2, and a straight portion P3 (an example of a "first straight portion" in the present disclosure). The straight portion P1 extends from the coating resin layer 15 in the X-axis direction (an example of a "crossing direction" in the present disclosure). The curved portion P2 is bent from the straight portion P1 in the Z-axis direction (an example of an "extending direction" in the present disclosure). The straight portion P3 extends from the curved portion P2 in the Z-axis direction and is connected to the fiber fixing component 20. The curved portion P2 extends between the straight portion P1 and the straight portion P3 while curving so as to connect the straight portion P1 and the straight portion P3. The curved portion P2 is formed, for example, by heating the glass fiber 11.
[0024] The fiber fixing component 20 includes at least a glass substrate 25. The glass substrate 25 is placed on the electronic substrate 2 and holds each glass fiber 11 connected to the electronic substrate 2. The fiber fixing component 20 may further include ferrules that are placed on the glass substrate 25 and support each glass fiber 11. The glass substrate 25 is fixed to the electronic substrate 2 by, for example, an ultraviolet-curing adhesive. The glass substrate 25 is formed of a glass material that is transparent to ultraviolet light. Examples of materials for the glass substrate 25 include fused silica glass and borosilicate glass. Being transparent to ultraviolet light means, for example, that a material with a thickness of 1 mm has a transmittance of 10% or more when irradiated with ultraviolet light having a wavelength of 350 nm or more and 400 nm or less.
[0025] FIG. 3 is a perspective view showing the glass substrate 25. FIG. 4 is an enlarged perspective view showing a portion of the glass substrate 25 of FIG. 3. As shown in FIG. 3, the glass substrate 25 includes, for example, a rectangular plate-shaped substrate main body 26. The substrate main body 26 includes a rectangular front surface 26a (an example of a "first surface" in the present disclosure) and a rectangular back surface 26b (an example of a "second surface" in the present disclosure) disposed opposite the front surface 26a. The front surface 26a and the back surface 26b extend along the X-axis direction and the Y-axis direction, respectively, and are aligned with each other along the Z-axis direction. The back surface 26b faces the electronic substrate 2 (see FIG. 1) in the Z-axis direction. The back surface 26b is fixed to the electronic substrate 2 with, for example, the aforementioned ultraviolet-curing adhesive. The thickness of the substrate main body 26 between the front surface 26a and the back surface 26b may be, for example, approximately 1 mm.
[0026] The substrate body 26 is formed with a plurality of through holes 27 penetrating in the Z-axis direction from the rear surface 26b to the front surface 26a. The plurality of through holes 27 are arranged in a line along the Y-axis direction so as to correspond to the plurality of glass fibers 11 (see FIG. 1) arranged along the Y-axis direction. The shape of each through hole 27 as viewed along the Z-axis direction is, for example, circular. The inner diameter D27 (see FIG. 4) of each through hole 27 may be constant at each position along the Z-axis direction. That is, each through hole 27 may have a constant inner diameter D27 from the front surface 26a to the rear surface 26b.
[0027] Each through hole 27 can be formed using, for example, a laser-based drilling technique. When forming each through hole 27, a process combining photolithography and dry etching such as reactive ion etching (RIE) may be used. In this embodiment, each through hole 27 is formed using laser irradiation and etching. For example, a portion of the substrate body 26 is modified by laser irradiation, and the modified portion is removed by etching. As a result, each through hole 27 is formed in the substrate body 26.
[0028] As shown in FIG. 4 , the inner surface 27 a has surface roughness due to the formation method, such as laser irradiation and etching. As a result, minute irregularities are formed on the inner surface 27 a. For convenience of explanation, FIG. 4 shows multiple protrusions 27 b formed on the inner surface 27 a, but in reality, multiple recesses are also formed on the inner surface 27 a. The multiple protrusions 27 b are arranged side by side on the inner surface 27 a, for example, along the Z-axis direction in which the central axis CL of the through hole 27 extends and along the circumferential direction D centered on the central axis CL. Each protrusion 27 b has a shape extending in the Z-axis direction, for example.
[0029] 4, the arrangement pitch W1 of two adjacent protrusions 27b in the Z-axis direction is larger than the arrangement pitch W2 of two adjacent protrusions 27b in the circumferential direction D. The arrangement pitches W1, W2 of two adjacent protrusions 27b may be, for example, the distance between the centers of the two protrusions 27b when viewed along the normal direction of the inner surface 27a.
[0030] The level of unevenness on the inner surface 27a can be evaluated, for example, by the surface roughness Rz. The surface roughness Rz is calculated as the sum of the maximum peak height and the maximum valley depth of the profile curve over a reference length. The surface roughness Rz refers to the maximum height roughness defined in JIS B 0601:2013, "Geometric Properties of Products (GPS) - Surface Texture: Profile Curve Method - Terms, Definitions, and Surface Texture Parameters." The surface roughness Rz is a value measured in accordance with the description in JIS B 0601:2013.
[0031] Fig. 5 is a graph illustrating a method for calculating the surface roughness Rz. The horizontal axis of Fig. 5 represents the position of the inner surface 27a along the circumferential direction D of the through hole 27. The vertical axis of Fig. 5 represents the height of the irregularities on the inner surface 27a. In graph G10 of Fig. 5, the height of the highest convex portion 27b (maximum peak height) within a reference length along the circumferential direction of the inner surface 27a is represented as Zp, and the depth of the lowest concave portion (maximum valley depth) is represented as Zv. In this case, the surface roughness Rz is defined as the difference between the maximum peak height Zp and the maximum valley depth Zv (Zp - Zv).
[0032] Depending on the magnitude of the surface roughness Rz, i.e., the height of the convex portions 27b on the inner surface 27a, the glass fiber 11 inserted into the through hole 27 may come into contact with the convex portions 27b on the inner surface 27a, and stress may be concentrated at the contact portion between the glass fiber 11 and the convex portions 27b. Such stress concentration may cause damage to the glass fiber 11, such as breakage. Therefore, from the viewpoint of reducing damage to the glass fiber 11, it is desirable that the surface roughness Rz of the inner surface 27a be small.
[0033] In this embodiment, the surface roughness Rz of the inner surface 27a is set to be equal to or greater than 0 μm and equal to or less than 1 μm. The upper limit of the surface roughness Rz is not limited to 1 μm, and may be 0.8 μm or less, 0.6 μm or less, or 0.4 μm or less. The inner diameter D27 of the through hole 27 is set to decrease depending on the surface roughness Rz. In this embodiment, the inner diameter D27 is set so that the ratio of the inner diameter D27 to the surface roughness Rz is 127 or less. For example, when the surface roughness Rz is 1 μm, the inner diameter D27 of the through hole 27 may be 127 μm.
[0034] The surface roughness Rz of the inner surface 27a can be adjusted by changing the laser irradiation conditions and etching conditions when forming the through-holes 27 in the substrate body 26. For example, by changing the irradiation pitch when irradiating the substrate body 26 with a laser and changing the etching process time, it is possible to obtain the inner surface 27a having a surface roughness Rz of 1 μm or less.
[0035] Fig. 6A is a perspective view showing a state in which glass fibers 11 are inserted into each through-hole 27 of the glass substrate 25 of Fig. 4. Fig. 6B is a cross-sectional view of the glass substrate 25 taken along line A1-A1 of Fig. 6A. As shown in Fig. 6A, each glass fiber 11 includes a core 11a and a clad 11b surrounding the core 11a. The core 11a and the clad 11b include, for example, silica-based glass. The outer diameter D11 of each glass fiber 11 may be, for example, 125 µm. The outer diameter D11 of each glass fiber 11 may be, for example, 80 µm or more and 125 µm or less.
[0036] 6B , each glass fiber 11 is inserted into each through-hole 27 from the surface 26a of the substrate body 26, and an ultraviolet-curing adhesive A is injected into each through-hole 27. When this adhesive A hardens, each glass fiber 11 is fixed to the substrate body 26. The core 11a of each glass fiber 11 fixed to the substrate body 26 is optically connected to each input / output unit of the electronic board 2 (see FIG. 1 ) on which the substrate body 26 is mounted.
[0037] 6B , it is assumed that the outer diameter D11 of the glass fiber 11 is 125 μm, the inner diameter D27 of the through hole 27 is 127 μm, and the surface roughness Rz is 1 μm or less. In this case, when the glass fiber 11 is inserted into the through hole 27 (strictly speaking, when the glass fiber 11 is arranged so that the optical axis of the glass fiber 11 coincides with the central axis CL of the through hole 27), the gap G1 between the glass fiber 11 and the inner surface 27 a is 2 μm. When the surface roughness Rz is 1 μm or less, the maximum height H of the convex portions 27 b from the inner surface 27 a is 1 μm, and therefore a gap G2 of at least 1 μm is maintained between the convex portions 27 b and the glass fiber 11. In this case, it is possible to insert the glass fiber 11 into the through hole 27 while reducing the occurrence of damage to the glass fiber 11 due to stress concentration on the glass fiber 11 by the convex portions 27 b.
[0038] As described above, the glass fiber 11 is fixed to the substrate body 26 by the adhesive A, and therefore a space is required between the glass fiber 11 and the inner surface 27a that allows the adhesive A to be injected. In this embodiment, a gap G2 of at least 1 μm is maintained between the glass fiber 11 and the protrusion 27b, and therefore a space is maintained between the glass fiber 11 and the inner surface 27a that allows the adhesive A to be injected. Therefore, in this embodiment, the glass fiber 11 can be inserted into the through hole 27 without damaging the glass fiber 11, while maintaining a space that allows the adhesive A to be injected between the glass fiber 11 and the inner surface 27a.
[0039] The effects obtained by the glass substrate 25 and the optical connecting part 1 according to this embodiment described above will be described below.
[0040] The glass substrate 25 holds the glass fiber 11 so that the glass fiber 11 is maintained at a predetermined connection position relative to the electronic substrate 2. The optical coupling efficiency of the glass fiber 11 relative to the electronic substrate 2 depends greatly on the positional accuracy of the glass fiber 11. For example, a positional deviation of the glass fiber 11 on the order of μm can cause a large optical connection loss of the glass fiber 11. From the viewpoint of reducing such optical connection loss, it is desirable to maintain the position of the glass fiber 11 precisely on the order of μm.
[0041] In this embodiment, the surface roughness Rz of the inner surface 27a into which the glass fiber 11 is inserted is set to 1 μm or less, and further, assuming that a glass fiber 11 having a standard outer diameter D11 of 125 μm or less is inserted into the through hole 27, the ratio of the inner diameter D27 of the through hole 27 to the surface roughness Rz is set to 127 or less. In this case, the inner diameter D27 of the through hole 27 can be made as small as possible to a degree that does not cause damage to the glass fiber 11 due to stress concentration on the glass fiber 11 by the convex portions 27b of the inner surface 27a, and that allows adhesive A to be applied between the inner surface 27a and the glass fiber 11.
[0042] That is, it is possible to minimize the positional deviation of the glass fiber 11 inserted into the through hole 27, on the order of μm, while maintaining a minimum space between the inner surface 27a and the glass fiber 11 that is sufficient to accommodate the convex portions 27b of the inner surface 27a and the adhesive A injected into the through hole 27. As a result, it is possible to increase the positional accuracy of the glass fiber 11 held on the glass substrate 25, while reducing the occurrence of damage to the glass fiber 11 due to stress concentration on the glass fiber 11 caused by the convex portions 27b.
[0043] In this embodiment, the substrate body 26 is formed with a plurality of through holes 27 into which the plurality of glass fibers 11 can be inserted, respectively. In this case, it is possible to increase the positional accuracy of each glass fiber 11 held on the glass substrate 25 while reducing the occurrence of damage to each of the plurality of glass fibers 11, and therefore the above-mentioned effects can be effectively obtained.
[0044] In the present embodiment, the arrangement pitch W1 of two adjacent convex portions 27 b in the Z-axis direction is larger than the arrangement pitch W2 of two adjacent convex portions 27 b in the circumferential direction D. In this case, the number of convex portions 27 b formed along the Z-axis direction can be reduced compared to when the arrangement pitch W1 of each convex portion 27 b in the Z-axis direction is equal to the arrangement pitch W2 of each convex portion 27 b in the circumferential direction D. In other words, the number of convex portions 27 b that come into contact with the glass fiber 11 while the glass fiber 11 is being inserted into the through hole 27 along the Z-axis direction from the front surface 26 a to the back surface 26 b can be reduced. As a result, the chance of stress concentration occurring in the glass fiber 11 due to contact of the glass fiber 11 with the convex portions 27 b can be reduced, and damage to the glass fiber 11 caused by stress concentration can be more reliably reduced.
[0045] In this embodiment, the optical connecting part 1 includes a glass substrate 25 and a glass fiber 11 that is inserted into the through hole 27 and fixed to the substrate body 26 with adhesive A. Because the optical connecting part 1 includes the above-mentioned glass substrate 25, it is possible to increase the positional accuracy of the glass fiber 11 while reducing the occurrence of damage to the glass fiber 11, as described above.
[0046] In this embodiment, the glass fiber 11 includes a straight portion P1 extending along the Z-axis direction and inserted into the through-hole 27, a straight portion P3 extending along the X-axis direction, and a curved portion P2 extending between the straight portion P1 and the straight portion P3 while curving to connect the straight portion P1 and the straight portion P3. In this case, the height of the glass fiber 11 can be reduced, and the above-mentioned effects of reducing damage to the glass fiber 11 and improving the positional accuracy of the glass fiber 11 can be obtained.
[0047] The present disclosure is not limited to the above-described embodiments, and can be modified as appropriate within the scope of the claims.
[0048] Fig. 7A is an enlarged perspective view of a glass substrate 25A, which is another example of the glass substrate 25. Fig. 7B is a cross-sectional view of the glass substrate 25A taken along line A2-A2 in Fig. 7A. The glass substrate 25A in Fig. 7A differs from the glass substrate 25 of the above-described embodiment in the shape of each through-hole formed in the substrate body.
[0049] As shown in FIG. 7B , each through hole 27A of the substrate body 26A includes a constant diameter portion P21 and an expanding diameter portion P22. The constant diameter portion P21 extends in the Z-axis direction from the back surface 26b toward the front surface 26a and has a constant inner diameter. The expanding diameter portion P22 extends in the Z-axis direction from the constant diameter portion P21 to the front surface 26a and expands in diameter as it approaches the front surface 26a. The inner diameter D21 of the constant diameter portion P21 is set, for example, to be larger than the outer diameter D11 of the glass fiber 11 (see FIG. 6A ) and to be 127 μm or less in relation to the surface roughness Rz. For example, if the outer diameter D11 of the glass fiber 11 is 125 μm and the surface roughness Rz is 1 μm or less, the inner diameter D21 of the constant diameter portion P21 may be 127 μm.
[0050] The inner diameter D22 of the expanded diameter portion P22 gradually increases as it approaches the surface 26a from the constant diameter portion P21. In the cross section of Figure 7B, the inner surface 27a of the expanded diameter portion P22 is curved so as to move away from the central axis CL of the through hole 27A as it approaches the surface 26a. As a result, in the cross section of Figure 7B, the distance d22 in the X-axis direction between the inner surface 27a and the central axis CL of the through hole 27A increases as the inner surface 27a of the expanded diameter portion P22 approaches the surface 26a. The cross section of Figure 7B is a cut surface of the substrate main body 26 taken along the central axis CL of the through hole 27A, i.e., a cut surface of the substrate main body 26 taken on a plane passing through the central axis CL of the through hole 27A.
[0051] In the cross section of Figure 7B, the inner surface 27a of the expanded diameter portion P22 is curved so that the curvature of the inner surface 27a increases as it approaches the surface 26a. As a result, the curvature of the inner surface 27a is minimum at the connection portion P23 between the expanded diameter portion P22 and the constant diameter portion P21 and maximum at the surface 26a. The inner diameter D22 of the expanded diameter portion P22 at the surface 26a is larger than the inner diameter D21 of the constant diameter portion P21. For example, if the inner diameter D21 of the constant diameter portion P21 is 127 μm or less, the inner diameter D22 of the expanded diameter portion P22 at the surface 26a may be 250 μm or less. For convenience of explanation, the cross section of Figure 7B omits possible irregularities formed on the inner surface 27a. However, in reality, irregularities may be formed on the inner surface 27a, as in the above-described embodiment.
[0052] Even with this configuration, the same effects as those of the above-described embodiment can be obtained. Furthermore, in the glass substrate 25A, the through hole 27A includes an expanding portion P22 whose diameter expands toward the surface 26a, and the inner surface 27a of the expanding portion P22 has a curved shape that is bent so as to move away from the central axis CL toward the surface 26a. In this case, stress concentration on the glass fiber 11 due to unevenness of the inner surface 27a of the expanding portion P22 can be reduced, and damage to the glass fiber 11 caused by stress concentration can be more reliably reduced.
[0053] In the glass substrate 25A, the inner surface 27a of the expanded diameter portion P22 is bent so that the curvature of the inner surface 27a increases as it approaches the surface 26a. In this case, it is possible to more reliably reduce the occurrence of stress concentration on the glass fiber 11 due to unevenness of the inner surface 27a of the expanded diameter portion P22, and therefore it is possible to more reliably reduce damage to the glass fiber 11 due to stress concentration.
[0054] 8A to 8F are plan views showing other examples of the shape of the through hole 27. In FIGS. 8A to 8F, the outer shape of the glass fiber 11 is also shown by a two-dot chain line. For example, the shape of the through hole 27 viewed along the Z-axis direction may be rectangular like the through hole 27B in FIG. 8A, elliptical like the through hole 27C in FIG. 8B, triangular like the through hole 27D in FIG. 8C, or rhombic like the through hole 27E in FIG. 8D. Alternatively, the shape of the through hole 27 viewed along the Z-axis direction may be another polygonal shape.
[0055] As shown in Fig. 8(e) , two grooves 28a, 28b may be formed in a circular through-hole 27F. The two grooves 28a, 28b may extend along the Z-axis direction from the front surface 26a to the back surface 26b. The grooves 28a, 28b may be formed, for example, at a pair of positions in the through-hole 27F that face each other across the central axis CL. The shape of each groove 28a, 28b as viewed along the Z-axis direction may be, for example, rectangular.
[0056] These grooves 28a and 28b can be used as relief grooves to allow excess adhesive A used to secure the glass fiber 11 to escape. By utilizing these relief grooves, it is not necessary to preliminarily design the through hole 27F to be larger in consideration of the amount of adhesive A to be injected into the through hole 27F. This eliminates the need to make adjustments such as reducing the size of the through hole 27F. This allows the inner diameter of the through hole 27F to be minimized while maintaining the shape of the through hole 27F in accordance with the shape of the glass fiber 11. This more reliably achieves the aforementioned effect of improving the positional accuracy of the glass fiber 11 inserted into the through hole 27F. As shown in FIG. 8(f), three grooves 29a, 29b, and 29c may be formed in the through hole 27G. The number of grooves formed in the through hole in this manner can be changed as appropriate.
[0057] In the above-described embodiment, the glass substrate 25 holds one fiber ribbon 10. However, the glass substrate of the present disclosure may hold multiple fiber ribbons. The number of through holes formed in the glass substrate of the present disclosure can be changed as appropriate depending on the number of glass fibers to be inserted into the through holes. For example, the glass substrate may have one through hole formed therein for holding one glass fiber.
[0058] DESCRIPTION OF SYMBOLS 1...Optical connecting part 2...Electronic substrate 10...Fiber ribbon 11...Glass fiber 11a...Core 11b...Cladding 13...Optical fiber 15...Coating resin layer 20...Fiber fixing part 27, 27A, 27B, 27C, 27D, 27E, 27F, 27G...Through hole 25, 25A...Glass substrate 26a...Front surface (an example of the "first surface" of the present disclosure) 26b...Back surface (an example of the "second surface" of the present disclosure) 27a...Inner surface 27b...Convex portion 28a, 28b, 29a, 29b, 29c...Groove A...Adhesive CL...Central axis D...Circumferential direction D11...Outer diameter D21, D22...Inner diameter D27...Inner diameter d22...Distance G1, G2...Gap P1...Straight portion (an example of the "second straight portion" of the present disclosure) P2...Curved portion P3: Straight portion (an example of the "first straight portion" of the present disclosure) P21: Constant diameter portion P22: Expanded diameter portion P23: Connection portion W1, W2: Arrangement pitch
Claims
1. a substrate body including a first surface and a second surface opposite to the first surface, the substrate body being made of a glass material; the substrate body has at least one through-hole formed therein, the through-hole penetrating from the first surface to the second surface and allowing insertion of at least one glass fiber; The outer diameter of the glass fiber is 125 μm or less, an inner diameter of the through hole is larger than the outer diameter of the glass fiber; The surface roughness Rz of the inner surface of the through hole is 1 μm or less, a ratio of the inner diameter of the through hole to the surface roughness Rz is 127 or less; Glass substrate.
2. The substrate body is formed with a plurality of through holes into which the plurality of glass fibers can be inserted, respectively. The glass substrate according to claim 1 .
3. a plurality of protrusions are formed on the inner surface of the through hole, the protrusions being aligned along an extension direction of the through hole and a circumferential direction of the through hole; an arrangement pitch of two adjacent protrusions in the extension direction is larger than an arrangement pitch of two adjacent protrusions in the circumferential direction; The glass substrate according to claim 1 .
4. the through hole includes an expanding portion connected to the first surface and expanding in diameter as it approaches the first surface, In a cross section of the substrate body taken along a plane passing through a central axis of the through hole, the inner surface of the expanded diameter portion has a curved shape that is bent so as to move away from the central axis as it approaches the first surface. The glass substrate according to claim 1 .
5. In the cut surface, the inner surface of the enlarged diameter portion is bent so that the curvature of the inner surface increases toward the first surface. The glass substrate according to claim 4 .
6. A groove extending from the first surface to the second surface is formed on the inner surface of the through hole. The glass substrate according to claim 1 .
7. The glass substrate according to any one of claims 1 to 6, the glass fiber inserted into the through hole and fixed to the substrate body by an adhesive; Optical connection parts.
8. The glass fiber is a first linear portion extending along the extension direction of the through hole and inserted into the through hole; a second linear portion extending along a cross direction intersecting the extension direction; a curved portion extending between the first straight portion and the second straight portion so as to connect the first straight portion and the second straight portion while curving, The optical connecting part according to claim 7 .