Manufacturing method for optical fiber fixed substrate and through-hole substrate

Abstract

The present invention provides an optical fiber fixing substrate that can suppress misalignment of optical fibers. [Solution] The optical fiber fixing substrate 1 of the present invention is a substrate for fixing an optical fiber, having a first main surface 1a and a second main surface 1b facing each other, a plate thickness of 0.5 mm or more and 2 mm or less, a plurality of through holes 1c that penetrate from the first main surface 1a to the second main surface 1b arranged in a matrix of two or more rows and two or more columns, and when the surface forming the plurality of through holes 1c is considered the inner surface 1d of the plurality of through holes 1c, the arithmetic mean roughness Ra of the inner surface 1d of the plurality of through holes 1c is 0.04 μm or more and 0.24 μm or less.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an optical fiber fixing substrate and a through-hole substrate.

Background Art

[0002] Conventionally, when connecting an optical fiber to an element, a jig for fixing the optical fiber has been used. In Patent Document 1 below, an example of a multi-core microcapillary for fixing an optical fiber is disclosed. In this multi-core microcapillary, a plurality of through-holes in a row are provided in a ceramic member. An optical fiber is inserted into these through-holes.

[0003] In the invention of Patent Document 1, optical fibers are inserted into two through-holes of a multi-core microcapillary, and alignment is performed between the multi-core microcapillary and an optical waveguide circuit. Next, after removing the optical fibers from the through-holes of the multi-core microcapillary, the multi-core microcapillary and the optical waveguide circuit are joined with an adhesive. Then, a plurality of optical fibers are inserted into the plurality of through-holes of the multi-core microcapillary.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Substrates for fixing optical fibers, such as multi-core microcapillaries, are expected to be used in CPO (Co-Packaged Optics). When the above substrate is used in CPO, it is desired that the substrate be small from the viewpoint of facilitating position adjustment during mounting.

[0006] However, when the substrate for fixing the optical fiber is small, the conditions for suppressing displacement of the optical fiber have not been sufficiently investigated. Therefore, even if alignment is performed between the substrate and the optical waveguide circuit, there is a risk that the optical fiber may be significantly misaligned when it is subsequently inserted into the through-hole of the substrate. As a result, there is a risk that optical loss cannot be sufficiently suppressed.

[0007] The present invention has been made in view of the above problems, and aims to provide an optical fiber fixing substrate that can suppress optical fiber misalignment. Furthermore, the present invention aims to provide a method for manufacturing a through-hole substrate that can suppress optical fiber misalignment. [Means for solving the problem]

[0008] The optical fiber fixing substrate according to Embodiment 1 of the present invention is a substrate for fixing an optical fiber, having a first main surface and a second main surface facing each other, a plate thickness of 0.5 mm or more and 2 mm or less, a plurality of through holes penetrating from the first main surface to the second main surface arranged in a matrix of two or more rows and two or more columns, and when the surface forming the plurality of through holes is considered the inner surface of the plurality of through holes, the arithmetic mean roughness Ra on the inner surface of the plurality of through holes is 0.04 μm or more and 0.24 μm or less.

[0009] In the optical fiber fixing substrate of embodiment 2, in embodiment 1, when the optical fiber is inserted into the through hole, it is preferable that L < [(ab) / 2], where L is the displacement of the center of the optical fiber from the center of the through hole, a is the inner diameter of the through hole, and b is the diameter of the optical fiber.

[0010] In the optical fiber fixing substrate of Embodiment 3, in Embodiment 1 or Embodiment 2, when a first virtual line is defined as a virtual line connecting the center of the through-hole located at one end and the center of the through-hole located at the other end in any row or column of the matrix in which the plurality of through-holes are arranged, it is preferable that the distance between the first virtual line and the center of each through-hole is 1 μm or less in any row and any column of the matrix in which the plurality of through-holes are arranged.

[0011] In the optical fiber fixing substrate of Embodiment 4, in any one embodiment of Embodiments 1 to 3, in any row or column of the matrix in which the plurality of through holes are arranged, the position of the center of each of the plurality of through holes is defined as the position in the xy coordinate system, the origin in the xy coordinate system is defined as the position of the center of the through hole located at one end of the row or column in which the xy coordinate system is defined, the x direction in the xy coordinate system is defined as the direction connecting the center of the through hole located at the other end of the row or column and the origin, the y direction in the xy coordinate system is defined as the direction orthogonal to the x direction, and a second virtual line is defined as a virtual line drawn by the least squares method based on the position of the center of each of the plurality of through holes in the row or column, it is preferable that in any row and any column of the matrix in which the plurality of through holes are arranged, the distance between the second virtual line and the center of each of the through holes is 1 μm or less.

[0012] In the optical fiber fixing substrate of embodiment 5, in any one embodiment from embodiment 1 to embodiment 4, it is preferable that the inner surface of at least one of the through holes has a laser processing mark.

[0013] In the optical fiber fixing substrate of embodiment 6, in any one embodiment from embodiment 1 to embodiment 5, when the substantially normal direction of the first main surface is the through-direction of the plurality of through-holes, at least one of the through-holes has an inclined portion, which is the portion in which the inner surface is inclined with respect to the through-direction and opens to the first main surface, and a straight portion, which is the portion in which the inner surface extends parallel to the through-direction and is connected to the inclined portion, wherein the dimension of the inclined portion along the through-direction is smaller than the dimension of the straight portion along the through-direction, and in the through-hole having the inclined portion and the straight portion, the area of ​​the portion opening to the first main surface is larger than the area of ​​the portion opening to the second main surface.

[0014] In the optical fiber fixing substrate of Embodiment 7, in any one embodiment from Embodiments 1 to 5, when the substantially normal direction of the first main surface is the through-direction of the plurality of through-holes, it is preferable that the inner surface of at least one of the through-holes is inclined with respect to the through-direction from the edge on the first main surface side to the edge on the second main surface side, and that in at least one of the through-holes, the area of ​​the portion opening to the first main surface is larger than the area of ​​the portion opening to the second main surface.

[0015] In the optical fiber fixing substrate of embodiment 8, it is preferable that it be a glass substrate in any one embodiment from embodiment 1 to embodiment 7.

[0016] A method for manufacturing a through-hole substrate according to aspect 9 of the present invention comprises the steps of: preparing a substrate having a first main surface and a second main surface facing each other; and forming a plurality of through-holes in the substrate that penetrate from the first main surface to the second main surface, arranged in a matrix of two or more rows and two or more columns, wherein, when the inner surface of the substrate facing the plurality of through-holes is considered the inner surface of the plurality of through-holes, the arithmetic mean roughness Ra of the inner surface of the plurality of through-holes is 0.04 μm or more and 0.24 μm or less; and in the step of forming the plurality of through-holes in the substrate, the plurality of through-holes are formed by a laser having a wavelength of 250 nm or more and 2000 nm or less, and a pulse width of 50 fs or more and 50 ps or less. [Effects of the Invention]

[0017] The optical fiber fixing substrate according to the present invention can suppress misalignment of optical fibers. Furthermore, the manufacturing method of the through-hole substrate according to the present invention can provide a through-hole substrate that can suppress misalignment of fibers. [Brief explanation of the drawing]

[0018] [Figure 1] Figure 1 is a schematic plan view showing an optical fiber fixing substrate according to the first embodiment of the present invention. [Figure 2] Figure 2 is a schematic cross-sectional view along line II in Figure 1. [Figure 3] Figure 3 is a schematic cross-sectional view showing an optical fiber fixing substrate according to a modified example of the first embodiment of the present invention. [Figure 4] Figure 4 is a schematic plan view showing an example of a state in which an optical fiber is inserted into a through-hole of an optical fiber fixing substrate according to the first embodiment of the present invention. [Figure 5] Figure 5 is a schematic plan view showing an example of the first imaginary line. [Figure 6] Figure 6 is a schematic plan view showing an example of a second imaginary line drawn in any row of a matrix of through holes. [Figure 7]FIG. 7 is a schematic plan view showing an example of a second virtual line drawn in any column in a matrix of a plurality of through holes. [Figure 8] FIG. 8 is a schematic cross-sectional view showing an optical fiber fixing substrate according to a second embodiment of the present invention. [Figure 9] FIGS. 9(a) and 9(b) are schematic cross-sectional views for explaining a method of manufacturing a through-hole substrate according to a third embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0019] Hereinafter, preferred embodiments of the present invention will be described. However, the following embodiments are merely illustrative, and the present invention is not limited to the following embodiments. Also, in each drawing, members having substantially the same function may be referred to by the same reference numerals.

[0020] (Optical fiber fixing substrate) (First embodiment) FIG. 1 is a schematic plan view showing an optical fiber fixing substrate according to a first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view taken along line I-I in FIG. 1.

[0021] The optical fiber fixing substrate 1 shown in FIG. 1 is a substrate for fixing an optical fiber. Specifically, a plurality of through holes 1c are provided in the optical fiber fixing substrate 1. In each through hole 1c, an optical fiber is fixed by, for example, an adhesive or the like. The optical fiber fixed to the optical fiber fixing substrate 1 is connected to, for example, an optical waveguide circuit or the like. Light is transmitted to the optical waveguide circuit or the like through the optical fiber.

[0022] The optical fiber fixing substrate 1 is a glass substrate in this embodiment. More specifically, borosilicate glass is used as the material of the optical fiber fixing substrate 1. Note that the material of the optical fiber fixing substrate 1 is not limited to the above, and for example, non-alkali glass, soda lime glass, or the like can also be used. Alternatively, an appropriate ceramic or the like may be used as the material of the optical fiber fixing substrate 1.

[0023] As shown in Figure 2, the optical fiber fixing substrate 1 has a first main surface 1a and a second main surface 1b. The first main surface 1a and the second main surface 1b face each other. In this embodiment, the optical fiber fixing substrate 1 has a rectangular plate shape. A rectangular plate shape means a plate shape in which the shape of the main surface is rectangular. However, the shape of the optical fiber fixing substrate 1 is not limited to the above, and for example, it may be plate-shaped in which the shape of the main surface is a circle, ellipse, or a polygon other than a rectangle.

[0024] In the optical fiber fixing substrate 1, the multiple through holes 1c penetrate from the first main surface 1a to the second main surface 1b. In this specification, the surface forming the multiple through holes 1c in the optical fiber fixing substrate 1 is referred to as the inner surface 1d of the multiple through holes 1c.

[0025] In this embodiment, each of the multiple through holes 1c has an inclined portion 1e and a straight portion 1f. Specifically, the inclined portion 1e is the portion where the inner surface 1d is inclined with respect to the through-direction P, when the direction approximately normal to the first main surface 1a is defined as the through-direction P of the multiple through holes 1c. In addition, the inclined portion 1e is the portion that opens into the first main surface 1a. On the other hand, the straight portion 1f is the portion where the inner surface 1d extends parallel to the through-direction P and is connected to the inclined portion 1e. In addition, in this embodiment, the straight portion 1f is the portion that opens into the second main surface 1b.

[0026] Here, the "normal direction" of the first principal surface 1a refers to the direction in which the angle it makes with the first principal surface 1a in a cross-sectional view is 90°. On the other hand, the "approximately normal direction" of the first principal surface 1a refers to the direction in which the angle it makes with the first principal surface 1a in a cross-sectional view is 80° or more and 100° or less. If the angle is obtuse, then the angle is 80° or more and 90° or less.

[0027] The angle is preferably 90°, and the penetration direction P is preferably the normal direction of the first main surface 1a. On the other hand, if the angle is not 90°, it is possible to suppress reflected light that would become noise. This effect is obtained because, when the angle is not 90°, the light reflected at the junction surface between the optical fiber and the optical waveguide circuit is emitted out of the optical fiber.

[0028] For example, in the modified version of the first embodiment shown in Figure 3, the angle between the through-direction P of the multiple through-holes 1x and the first main surface 1a is not 90°. However, the through-direction P is approximately normal to the first main surface 1a. Even in this modified version, the effects of the present invention described later can be obtained.

[0029] In this specification, the configuration in which the inner surface 1d extends parallel to the through-direction P includes not only the configuration in which the angle between the direction in which the inner surface 1d extends and the through-direction P is exactly 0°, but also the configuration in which the angle is 1° or less.

[0030] The dimension of the inclined portion 1e along the through-direction P is smaller than the dimension of the straight portion 1f along the through-direction P. In a through-hole 1c having an inclined portion 1e and a straight portion 1f, the area of ​​the portion opening to the first main surface 1a is larger than the area of ​​the portion opening to the second main surface 1b. However, the shape of the inner surface 1d of each through-hole 1c is not limited to the above. For example, all parts of the inner surface 1d in multiple through-holes 1c may extend parallel to the through-direction P, or they may extend inclined with respect to the through-direction P.

[0031] Returning to Figure 1, the multiple through-holes 1c are arranged in a matrix of 4 rows and 5 columns. Here, a row refers to a group of multiple through-holes 1c arranged horizontally in Figure 1. Here, a column refers to a group of multiple through-holes 1c arranged vertically in Figure 1. Note that the number of rows and columns of the multiple through-holes 1c are not limited to the above. The multiple through-holes 1c only need to be arranged in a matrix of 2 or more rows and 2 or more columns.

[0032] In this embodiment, the direction in which the rows of through-holes 1c extend is perpendicular to the direction in which the columns extend. However, the direction in which the rows of through-holes 1c extend and the direction in which the columns extend do not necessarily have to be perpendicular. The direction in which the rows of through-holes 1c extend and the direction in which the columns extend may intersect. However, it is preferable that the direction in which the rows of through-holes 1c extend and the direction in which the columns extend are perpendicular, as in this embodiment.

[0033] An optical fiber is inserted into each through-hole 1c. For example, after the optical fiber is inserted into the through-hole 1c, adhesive is filled into the through-hole 1c, and the optical fiber is fixed in place as the adhesive hardens.

[0034] The thickness of the optical fiber fixing substrate 1 of the present invention is 0.5 mm or more and 2 mm or less. This allows the optical fiber fixing substrate 1 to be made sufficiently small. This makes it possible to easily adjust the position of the optical fiber fixing substrate 1 when using it in CPO (Co-Packaged Optics).

[0035] The features of this embodiment are that the plate thickness is 0.5 mm or more and 2 mm or less, and the arithmetic mean roughness Ra on the inner surface 1d of the multiple through holes 1c is 0.04 μm or more and 0.24 μm or less. In this specification, the arithmetic mean roughness Ra is based on JIS B 0601:2013. With the above configuration, displacement of the optical fiber when an optical fiber is inserted into each through hole 1c can be suppressed. As a result, when the optical fiber is connected to an optical waveguide circuit or the like, the loss of light transmitted to the optical waveguide circuit or the like can be suppressed more reliably.

[0036] In addition, the multiple through-holes 1c are arranged in a matrix of two or more rows and two or more columns. This allows for a suitable increase in the number of optical fibers to be fixed, even when the optical fiber fixing substrate 1 is made smaller.

[0037] The following describes preferred configurations of the present invention. In the optical fiber fixing substrate 1, the arithmetic mean roughness Ra on the inner surface 1d of the through hole 1c is preferably 0.08 μm or more, and more preferably 0.1 μm or more. This allows for even more reliable suppression of optical fiber displacement. On the other hand, the arithmetic mean roughness Ra on the inner surface 1d of the through hole 1c is preferably 0.22 μm or less, and more preferably 0.2 μm or less. This allows for even more reliable suppression of optical fiber displacement and makes the optical fiber less susceptible to damage.

[0038] Figure 4 is a schematic plan view showing an example of a state in which an optical fiber is inserted into a through-hole of an optical fiber fixing substrate according to the first embodiment.

[0039] When the optical fiber 10 is inserted into the through-hole 1c, let L be the displacement of the center C2 of the optical fiber 10 from the center C1 in the through-hole 1c, let a be the inner diameter of the through-hole 1c, and let b be the diameter of the optical fiber. More specifically, the inner diameter a of the through-hole 1c is the inner diameter of the portion that opens to the second main surface 1b. It is preferable that the relationship between the displacement L, inner diameter a, and diameter b is L < [(ab) / 2]. In this case, the displacement of the optical fiber within the through-hole 1c can be suppressed more reliably.

[0040] The difference between the inner diameter a of the through-hole 1c and the diameter b of the optical fiber is preferably 1 μm or less. In this case, displacement of the optical fiber within the through-hole 1c can be more reliably suppressed.

[0041] The specific value of the displacement L of the center C2 of the optical fiber 10 from the center C1 in the through-hole 1c is preferably L ≤ 0.3 μm, more preferably L ≤ 0.2 μm, and even more preferably L ≤ 0.1 μm. In this case, the displacement of the optical fiber within the through-hole 1c can be suppressed more reliably.

[0042] It is preferable that the distance between the first or second virtual line shown in Figures 5 to 7 below and the center of each through-hole is 1 μm or less. In these cases, the accuracy of the position of each through-hole in the optical fiber fixing substrate can be more reliably improved.

[0043] Figure 5 is a schematic plan view showing an example of the first imaginary line. In Figure 5, examples of the first imaginary line A are shown in one of the four rows and one of the five columns. However, the first imaginary line A can be drawn in any row and any column.

[0044] The first imaginary line A is an imaginary line connecting the center C3 of a through-hole 1c located at one end and the center C4 of a through-hole 1c located at the other end in any row or column of the matrix in which multiple through-holes 1c are arranged. The double arrow d in Figure 5 indicates the distance between the first imaginary line A and the center of each through-hole 1c. The same applies to figures other than Figure 5. In any row and any column of the matrix in which multiple through-holes 1c are arranged, it is preferable that the distance between the first imaginary line A and the center of each through-hole 1c is 1 μm or less.

[0045] For example, if the positions of each through-hole 1c in the optical fiber fixing substrate 1 deviate significantly from their designed positions, the center positions of each optical fiber 10 fixed to the optical fiber fixing substrate 1 will also deviate significantly from their designed positions. In contrast, the above configuration makes it possible to more reliably improve the accuracy of the positions of each through-hole 1c in the optical fiber fixing substrate 1. In this case, deviations from the designed positions of the center positions of each optical fiber 10 fixed to the optical fiber fixing substrate 1 can be effectively suppressed. As a result, when each optical fiber is connected to an optical waveguide circuit, the loss of light transmitted to the optical waveguide circuit, etc., can be suppressed more reliably and effectively.

[0046] In particular, in the optical fiber fixing substrate 1 according to the present invention, the arithmetic mean roughness Ra on the inner surface of the through-hole 1c is within the aforementioned range, and the positional accuracy of each through-hole 1c is as described above, so that the position of the center of each optical fiber 10 fixed to the optical fiber fixing substrate 1 does not deviate from the design position, which can be effectively suppressed. As a result, when each optical fiber 10 is connected to an optical waveguide circuit or the like, the loss of light transmitted to the optical waveguide circuit or the like can be suppressed more reliably and effectively.

[0047] In the matrix of multiple through-holes 1c, the distance between the first virtual line A and the center of each through-hole 1c is preferably 1 μm or less, more preferably 0.5 μm or less, even more preferably 0.4 μm or less, and particularly preferably 0.3 μm or less in any row and any column. This makes it possible to more reliably and effectively suppress deviations in the position of the center of each optical fiber fixed to the optical fiber fixing substrate 1 from the design position.

[0048] Figure 6 is a schematic plan view showing an example of a second imaginary line drawn in any row of a matrix of multiple through-holes. Figure 7 is a schematic plan view showing an example of a second imaginary line drawn in any column of a matrix of multiple through-holes. Note that in Figure 6, an example of the second imaginary line B is shown in one of the four rows. In Figure 7, an example of the second imaginary line B is shown in one of the five columns. However, the second imaginary line B can be drawn in any row and any column.

[0049] As shown in Figure 6, in any row of the matrix in which multiple through-holes 1c are arranged, the position of the center of each of the multiple through-holes 1c is defined as the position in the xy coordinate system. The origin O in the xy coordinate system is defined as the position of the center of the through-hole 1c located at one end of the row in which the xy coordinate system is defined. The x-direction in the xy coordinate system is defined as the direction connecting the center C4 of the through-hole 1c located at the other end of the row and the origin O, and the y-direction in the xy coordinate system is defined as the direction perpendicular to the x-direction. The second virtual line B is a virtual line drawn by the least squares method based on the position of the center of each of the multiple through-holes 1c in the row.

[0050] Similarly, as shown in Figure 7, in any column of a matrix in which multiple through holes 1c are arranged, the position of the center of each of the multiple through holes 1c is defined as the position in the xy coordinate system. The origin O in the xy coordinate system is defined as the position of the center of the through hole 1c located at one end of the column in which the xy coordinate system is defined. The x direction in the xy coordinate system is defined as the direction connecting the center C4 of the through hole 1c located at the other end of the column and the origin O, and the y direction in the xy coordinate system is defined as the direction perpendicular to the x direction. The second virtual line B is a virtual line drawn by the least squares method based on the position of the center of each of the multiple through holes 1c in the column.

[0051] In the matrix of multiple through-holes 1c, it is preferable that the distance between the second virtual line B and the center of each through-hole 1c is 1 μm or less in every row and every column. This makes it possible to more reliably improve the accuracy of the position of each through-hole 1c in the optical fiber fixing substrate 1. In this case, the deviation of the center position of each optical fiber 10 fixed to the optical fiber fixing substrate 1 from the design position can be effectively suppressed. As a result, when each optical fiber 10 is connected to an optical waveguide circuit or the like, the loss of light transmitted to the optical waveguide circuit or the like can be suppressed more reliably and effectively.

[0052] In the matrix of multiple through-holes 1c, the distance between the second virtual line B and the center of each through-hole 1c is preferably 1 μm or less, more preferably 0.5 μm or less, even more preferably 0.4 μm or less, and particularly preferably 0.3 μm or less in any row and any column. This makes it possible to more reliably and effectively suppress deviations in the position of the center of each optical fiber fixed to the optical fiber fixing substrate 1 from the design position.

[0053] The thermal expansion coefficient of the optical fiber fixing substrate 1 is 50 × 10 -7It is preferable that the temperature is 20 × 10⁻¹⁰ or less. In this case, when the temperature around the optical fiber fixing substrate 1 changes, displacement of the optical fiber can be suppressed. On the other hand, the thermal expansion coefficient of the optical fiber fixing substrate 1 is 20 × 10⁻¹⁰ -7 It is preferable that the temperature is above [ / K]. In this case, the substrate that will be used as the material for the optical fiber fixing substrate 1 can be easily obtained, and productivity can be increased.

[0054] It is preferable that borosilicate glass be used as the material for the optical fiber fixing substrate 1. In this case, the coefficient of thermal expansion of the optical fiber fixing substrate 1 is, for example, 35 × 10⁻⁶. -7 [K]. Therefore, the optical fiber fixing substrate 1 has excellent productivity and, by reducing the mismatch in thermal expansion coefficient with silicon, which is the main material of the optical waveguide circuit, it is possible to suppress displacement of the optical fiber even when the temperature changes.

[0055] Returning to Figure 2, it is preferable that at least one through-hole 1c is provided in the same manner as in the first embodiment. Specifically, it is preferable that at least one through-hole 1c has an inclined portion 1e and a straight portion 1f, and that the dimension of the inclined portion 1e along the through-direction P is smaller than the dimension of the straight portion 1f along the through-direction P. Furthermore, in the through-hole 1c having the inclined portion 1e and the straight portion 1f, it is preferable that the area of ​​the portion opening to the first main surface 1a is larger than the area of ​​the portion opening to the second main surface 1b. In this case, the optical fiber 10 can be suitably guided from the inclined portion 1e into the at least one through-hole 1c.

[0056] However, the through hole 1c does not necessarily have to have an inclined portion 1e and a straight portion 1f. An example of a through hole 1c different from that of the first embodiment is shown in the second embodiment.

[0057] (Second embodiment) Figure 8 is a schematic cross-sectional view showing an optical fiber fixing substrate according to the second embodiment.

[0058] In the optical fiber fixing substrate 11 of this embodiment, the inner surfaces 11d of the multiple through holes 11c are inclined with respect to the through-direction P from the edge on the first main surface 1a side to the edge on the second main surface 1b side. In the multiple through holes 11c, the area of ​​the portion opening to the first main surface 1a is larger than the area of ​​the portion opening to the second main surface 1b.

[0059] Furthermore, the inner surface 11d of at least one through hole 11c may be inclined with respect to the through-direction P from the edge on the first main surface 1a side to the edge on the second main surface 1b side. In addition, the area of ​​the portion of the at least one through hole 11c that opens to the first main surface 1a may be larger than the area of ​​the portion that opens to the second main surface. In this case, the optical fiber 10 can be suitably guided into the at least one through hole 11c.

[0060] In addition, in this embodiment as well, similar to the first embodiment, the thickness of the optical fiber fixing substrate 11 is 0.5 mm or more and 2 mm or less, and the arithmetic mean roughness Ra on the inner surface 11d of the multiple through holes 11c is 0.04 μm or more and 0.24 μm or less. This makes it possible to suppress misalignment of the optical fiber when an optical fiber is inserted into each through hole 11c. As a result, when the optical fiber is connected to an optical waveguide circuit or the like, the loss of light transmitted to the optical waveguide circuit or the like can be suppressed more reliably.

[0061] In the through-hole 11c, it is preferable that the difference between the inner diameter of the portion opening to the first main surface 1a and the inner diameter of the portion opening to the second main surface 1b is 5 μm or more. In this case, it is easier to guide the optical fiber into the through-hole 11c. On the other hand, in the through-hole 11c, it is preferable that the difference between the inner diameter of the portion opening to the first main surface 1a and the inner diameter of the portion opening to the second main surface 1b is 10 μm or less. In this case, it is easier to form the through-hole 11c.

[0062] In the optical fiber fixing substrate 11 according to the present invention, it is preferable that at least one through hole 11c is formed by a laser. That is, it is preferable that the inner surface of at least one through hole 11c has a laser processing mark.

[0063] It is preferable that the inner surfaces of the multiple through-holes 11c have laser processing marks. In this case, the multiple through-holes 11c can be easily formed during the manufacturing process. Therefore, the productivity of the optical fiber fixing substrate 11 can be effectively increased.

[0064] The optical fiber fixing substrate 11 according to the present invention is a substrate for fixing optical fibers. However, a through-hole substrate having a similar configuration to the optical fiber fixing substrate 11 according to the present invention can also be used to fix fibers other than optical fibers. An example of a method for manufacturing such a through-hole substrate will be described below.

[0065] (Manufacturing method for through-hole circuit boards) (Third embodiment) Figures 9(a) and 9(b) are schematic cross-sectional views illustrating a method for manufacturing a through-hole substrate according to a third embodiment of the present invention.

[0066] As shown in Figure 9(a), a substrate 21A is prepared. The substrate 21A has a first main surface 21a and a second main surface 21b. The first main surface 21a and the second main surface 21b face each other. The substrate 21A is, for example, a glass substrate. However, the substrate 21A may also be a ceramic substrate.

[0067] Next, as shown in Figure 9(b), multiple through-holes 21c are formed in the substrate 21A, penetrating from the first main surface 21a to the second main surface 21b, arranged in a matrix of two or more rows and two or more columns. More specifically, the multiple through-holes 21c are formed such that the arithmetic mean roughness Ra on the inner surface 21d of each is 0.04 μm or more and 0.24 μm or less.

[0068] More specifically, in the process of forming multiple through-holes 21c in the substrate 21A, the multiple through-holes 21c are formed using a laser with a wavelength of 250 nm or more and 2000 nm or less, and a pulse width of 50 fs or more and 50 ps or less.

[0069] In the through-hole substrate 21 obtained by the manufacturing method of the present invention, the arithmetic mean roughness Ra of the inner surface 21d of the multiple through-holes 21c is 0.04 μm or more and 0.24 μm or less. This suppresses misalignment of the fiber when it is inserted into the through-hole substrate 21. In addition, multiple through-holes 21c can be easily formed by a laser. Therefore, the productivity of the through-hole substrate 21 can be effectively increased.

[0070] When forming each through-hole 21c with a laser, the laser wavelength is preferably 300 nm or higher, more preferably 330 nm or higher, and even more preferably 340 nm or higher. On the other hand, the laser wavelength is preferably 1500 nm or lower, more preferably 1200 nm or lower, and even more preferably 1100 nm or lower. This makes it possible to more reliably set the arithmetic mean roughness Ra on the inner surface 21d of the through-hole 21c to 0.04 μm or higher and 0.24 μm or lower. Therefore, fiber displacement can be more reliably suppressed in any of the through-holes 21c.

[0071] When forming each through-hole 21c with a laser, the laser pulse width is preferably 100 fs or more, more preferably 150 fs or more, and even more preferably 180 fs or more. On the other hand, the laser pulse width is preferably 40 ps or less, more preferably 30 ps or less, and even more preferably 20 ps or less. This makes it possible to more reliably set the arithmetic mean roughness Ra on the inner surface 21d of the through-hole 21c to 0.04 μm or more and 0.24 μm or less. Therefore, fiber displacement can be more reliably suppressed in each through-hole 21c.

[0072] Incidentally, when forming the through-hole 21c with a laser, at least one of the laser wavelength and pulse width may be changed. By forming the through-hole 21c while appropriately changing at least one of the laser wavelength and pulse width, for example, the inclined portion 1e and the straight portion 1f shown in Figure 2 may be formed.

[0073] (Examples) Further details of the present invention will be described below based on specific examples and comparative examples. It should be noted that the present invention is not limited in any way to the following examples, and can be implemented with appropriate modifications without altering its essence.

[0074] (Example 1) First, a substrate having a first main surface and a second main surface was prepared. The thickness of the substrate was 1 mm. Next, multiple through holes were formed in the substrate, arranged in a matrix of 2 rows and 10 columns, from the first main surface to the second main surface. Specifically, multiple through holes were formed using a laser. More specifically, multiple through holes were formed by ablation processing using a galvanometer scanner. At this time, the laser wavelength was 355 nm and the pulse width was 10 ps. The inner diameter of each through hole formed in the substrate was 126 μm. A substrate for fixing optical fibers was then fabricated.

[0075] Next, 20 optical fibers, each with a diameter of 125 μm, were inserted into the through-holes of the optical fiber fixing substrate. Then, adhesive was filled into each through-hole, and the adhesive was allowed to harden. This fixed the optical fibers to the optical fiber fixing substrate.

[0076] (Example 2) Except for setting the laser wavelength to 520 nm and the pulse width to 200 fs when forming multiple through-holes in the substrate, an optical fiber fixing substrate was fabricated in the same manner as in Example 1, and an optical fiber was fixed to the optical fiber fixing substrate.

[0077] (Example 3) Except for setting the laser wavelength to 1040 nm and the pulse width to 400 fs when forming multiple through-holes in the substrate, an optical fiber fixing substrate was fabricated in the same manner as in Example 1, and an optical fiber was fixed to the optical fiber fixing substrate.

[0078] (Example 4) Except for setting the laser wavelength to 1064 nm and the pulse width to 5 ps when forming multiple through-holes in the substrate, an optical fiber fixing substrate was fabricated in the same manner as in Example 1, and an optical fiber was fixed to the optical fiber fixing substrate.

[0079] (Comparative example) An optical fiber fixing substrate was prepared in the same manner as in Example 1, except that multiple through holes were formed in the substrate by grinding with a drill and the inner surface of each through hole was polished, and an optical fiber was fixed to the optical fiber fixing substrate.

[0080] (Measurement of arithmetic mean roughness Ra) The through-holes in the optical fiber fixing substrate were exposed by polishing. Then, the arithmetic mean roughness Ra of the inner surface of the exposed through-holes was measured using a laser microscope (KEYENCE, part number "VK-X250"). This process was repeated to measure the arithmetic mean roughness Ra of the inner surface of all through-holes. The average values ​​of the arithmetic mean roughness Ra for each of Examples 1-4 and the comparative example are shown in Table 1 below.

[0081] (Measurement of displacement in through holes) An automatic dimension measuring machine (Nikon Corporation, model number "NEXIV VMR-3020") was used to measure the positional displacement of all through-holes in the optical fiber fixing substrate. Specifically, the distance between the design center position and the actual center position was measured for all through-holes. The maximum positional displacement values ​​for each through-hole in Examples 1 to 4 and the comparative example are shown in Table 1 below.

[0082] (Measurement of misalignment in optical fibers) For each optical fiber, the portion located outside each through-hole in the optical fiber fixing substrate was removed by polishing. Then, using an automatic dimension measuring machine (Nikon Corporation, model number "NEXIV VMR-3020"), the distance between the center of each through-hole and the center of the optical fiber fixed within that through-hole was measured. The maximum positional displacement for each optical fiber in Examples 1 to 4 and the comparative example is shown in Table 1 below.

[0083] [Table 1]

[0084] As shown in Table 1, in Examples 1 to 4, the average value of the arithmetic mean roughness Ra on the inner surface of the through-holes was within the range of 0.04 μm or more and 0.24 μm or less. Although not shown in Table 1, in Examples 1 to 4, the arithmetic mean roughness Ra on the inner surface of all through-holes was within the range of 0.04 μm or more and 0.24 μm or less. Furthermore, in Examples 1 to 4, the maximum displacement of the optical fiber was small, at 0.1 μm.

[0085] In Examples 1-4 and the Comparative Example, the difference between the inner diameter of the through-hole and the diameter of the optical fiber was 1 μm. Therefore, in Examples 1-4, the distance between the inner surface of the through-hole and the optical fiber was sufficiently long.

[0086] On the other hand, in the comparative example, the arithmetic mean roughness Ra on the inner surface of the through-hole was 0.02 μm, which was outside the above range. Also, in the comparative example, the displacement of the optical fiber was 0.5 μm. That is, in the comparative example, the optical fiber was eccentric and in contact with the inner wall of the through-hole. There was no difference in the maximum displacement of the through-hole between Examples 1 to 4 and the comparative example.

[0087] Based on the above, in Examples 1 to 4, the displacement of the optical fiber was effectively suppressed. On the other hand, in the comparative example, the displacement of the optical fiber was not effectively suppressed. [Explanation of Symbols]

[0088] 1…Optical fiber fixing substrate 1a, 1b…First and second main surfaces 1c...Through hole 1d...Inner self 1e…Slope part 1f…Straight section 1x…Through hole 10… Fiber optic 11…Optical fiber fixing substrate 11c...Through hole 11d...Inner self 21…Through-hole circuit board 21A... Circuit board 21a, 21b… First and second main surfaces 21c...Through hole 21d...Inner self

Claims

1. A substrate for fixing optical fibers, It has a first main surface and a second main surface that are facing each other, The plate thickness is 0.5 mm or more and 2 mm or less. Multiple through holes extending from the first main surface to the second main surface are arranged in a matrix of two or more rows and two or more columns. An optical fiber fixing substrate in which, when the surface forming the plurality of through holes is considered the inner surface of the plurality of through holes, the arithmetic mean roughness Ra on the inner surface of the plurality of through holes is 0.04 μm or more and 0.24 μm or less.

2. The optical fiber fixing substrate according to claim 1, wherein when the optical fiber is inserted into the through-hole, L is the displacement of the center of the optical fiber from the center of the through-hole, a is the inner diameter of the through-hole, and b is the diameter of the optical fiber, such that L < [(a - b) / 2].

3. The optical fiber fixing substrate according to claim 1 or 2, wherein, in any row or column of the matrix of multiple through holes, when a first virtual line is defined as a virtual line connecting the center of a through hole located at one end and the center of a through hole located at the other end, the distance between the first virtual line and the center of each through hole is 1 μm or less in any row and any column of the matrix of multiple through holes.

4. In any row or column of the matrix of multiple through-holes, the position of the center of each of the multiple through-holes is defined as the position in the xy coordinate system, the origin in the xy coordinate system is defined as the position of the center of the through-hole located at one end of the row or column where the xy coordinate system is defined, the x direction in the xy coordinate system is defined as the direction connecting the center of the through-hole located at the other end of the row or column and the origin, the y direction in the xy coordinate system is defined as the direction perpendicular to the x direction, and a second virtual line is drawn by the least squares method based on the position of the center of each of the multiple through-holes in the row or column, wherein in any row and any column of the matrix of multiple through-holes, the distance between the second virtual line and the center of each of the through-holes is 1 μm or less.

5. The optical fiber fixing substrate according to claim 1 or 2, wherein the inner surface of at least one of the through holes has a laser processing mark.

6. When the approximate normal direction of the first main surface is defined as the through-direction of the plurality of through-holes, at least one of the through-holes has an inclined portion, which is the part in which the inner surface is inclined with respect to the through-direction and opens to the first main surface, and a straight portion, which is the part in which the inner surface extends parallel to the through-direction and is connected to the inclined portion. The dimension of the inclined portion along the through-direction is smaller than the dimension of the straight portion along the through-direction. The optical fiber fixing substrate according to claim 1 or 2, wherein in the through hole having the inclined portion and the straight portion, the area of ​​the portion opening to the first main surface is larger than the area of ​​the portion opening to the second main surface.

7. When the approximate normal direction of the first main surface is defined as the through-direction of the plurality of through-holes, the inner surface of at least one of the through-holes is inclined with respect to the through-direction from the edge on the first main surface side to the edge on the second main surface side. The optical fiber fixing substrate according to claim 1 or 2, wherein in the at least one through hole, the area of ​​the portion opening to the first main surface is larger than the area of ​​the portion opening to the second main surface.

8. The optical fiber fixing substrate according to claim 1 or 2, wherein the substrate is a glass substrate.

9. A step of preparing a substrate having a first main surface and a second main surface facing each other, The process of forming a plurality of through holes in the substrate that penetrate from the first main surface to the second main surface, arranged in a matrix of two or more rows and two or more columns, Equipped with, When the inner surface of the substrate facing the plurality of through holes is considered the inner surface of the plurality of through holes, the arithmetic mean roughness Ra of the inner surface of the plurality of through holes is 0.04 μm or more and 0.24 μm or less. A method for manufacturing a through-hole substrate, comprising the step of forming the plurality of through-holes in the substrate, wherein the plurality of through-holes are formed using a laser having a wavelength of 250 nm or more and 2000 nm or less, and a pulse width of 50 fs or more and 50 ps or less.

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