JP2001059911A - Printed wiring board for mounting optical fiber and manufacture of printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to mount optical fiber without using a fixing terminal on a printed wiring board and to provide the printed wiring board capable of easily performing the fixture at the time of mounting optical fiber and suppressing the damage of the optical fiber. SOLUTION: A resin layer 3a of a prescribed thickness is formed on the surface for mounting the optical fiber 3f of a substrate 3d. Further, a groove 3g for fixing optical fiber in which the optical fiber is stored is formed and, at the same time, an overhanging part 3e which is narrower in width than the inside of the fixing groove 3g is preferably formed on the opening part of the fixing groove 3g by inwardly facing an opening edge of the resin layer 3a and extendedly disposing the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board for mounting an optical fiber used in an electronic circuit for handling an optical signal and a method for manufacturing the printed wiring board.

[0002]

2. Description of the Related Art Conventionally, as the operating frequency of a device has been increased, an example in which a part of the circuit of the device is constituted by an optical circuit has been increasing.
No. 4 proposes this. In this technique, as shown in FIG. 7, an optical terminal 1a for external connection and an optical module 1d for converting light into an electronic signal are connected by an optical fiber 1b. It is structured to be fixed to the printed wiring board 1e by fixing terminals 1c.

[0003]

By the way, in such a conventional printed circuit board for mounting an optical fiber, when the radius of curvature R of the optical fiber 1b becomes smaller than an allowable value, light is radiated and loss occurs. Therefore, the fixing terminal 1c is mounted in consideration of the radius of curvature R. Also, since the optical fiber 1b was fixed at several places, the fixing terminal 1c was used.
However, the number of components increases, the cost increases, and the mounting area of the fixing terminal 1c hinders the improvement of the mounting density of the pattern mounting area of the printed wiring board 1e. When the optical fiber 1b is fixed by the fixing terminal 1c, the optical fiber 1b is barely fixed on the printed wiring board 1e. There was a risk of damage.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem. In a printed wiring board on which an optical fiber is mounted, the optical fiber can be mounted without using a fixing terminal on the printed wiring board. The present invention also provides a printed wiring board for mounting an optical fiber and a method for manufacturing the printed wiring board, which can be easily fixed at the time of mounting the optical fiber and can suppress damage to the optical fiber.

[0005]

According to a first aspect of the present invention, there is provided a printed wiring board for mounting an optical fiber, wherein a resin layer having a predetermined thickness is provided on an optical fiber mounting surface of a substrate. Is formed in the resin layer, an optical fiber fixing groove for accommodating the optical fiber is formed, and an opening of the fixing groove is formed with an overhang portion narrower than the inside of the fixing groove. It is characterized by having. In the printed wiring board for mounting an optical fiber according to claim 2 of the present invention, the overhang portion according to claim 1 is formed by extending an opening edge of the resin layer inward. It is characterized by being. The printed wiring board for mounting an optical fiber according to a third aspect of the present invention is characterized in that the overhang portion according to the first aspect is formed by a second resin layer laminated on the resin layer. And A printed wiring board for mounting an optical fiber according to a fourth aspect of the present invention is characterized in that the overhang portion according to the first aspect is formed of a metal foil laminated on the resin layer. In the method of manufacturing a printed wiring board according to claim 5 of the present invention, a resin mixed with a curing agent is applied to a surface of a substrate to form a resin layer, and a metal foil is integrally laminated on the surface of the resin layer. And on the surface of this metal foil,
An etching resist for forming an etching resist pattern along the mounting path of the optical fiber is laminated, an opening is formed by etching and removing the metal foil by the etching resist pattern, and then the resin layer is formed by the opening. Etching is performed wider than the opening, and then, the resin layer is cured to form an optical fiber fixing groove having an overhang portion having a narrower opening. According to a method of manufacturing a printed wiring board according to claim 6 of the present invention, a resin mixed with a curing agent is applied to a surface of a substrate to form a resin layer, and an optical fiber mounting path is formed on the surface of the resin layer. An etching resist is formed to form an etching resist pattern along the opening. The etching resist pattern is used to remove the resin layer by etching to form an opening. Then, the opening forms the opening in the resin layer. Etching wider than that, and then curing the etching resist and the resin layer, thereby forming an optical fiber fixing groove having an overhang portion with a narrow opening in the resin layer. . In the method for manufacturing a printed wiring board according to claim 7 of the present invention, a resin layer made of an ultraviolet curable resin is formed on a surface of a substrate, and an ultraviolet mask along an optical fiber mounting path is formed on the surface of the resin layer. After lamination, the resin layer is cured by irradiating ultraviolet rays, and then a metal foil is laminated on the surface of the resin layer, and an etching resist pattern is formed on the surface of the metal foil along an optical fiber mounting path. An etching resist is laminated, and the metal foil is removed by etching with the etching resist pattern to form an opening.
The resin layer is etched wider by the opening than the opening to form an optical fiber fixing groove having an overhang portion having a narrower opening. In the method for manufacturing a printed wiring board according to claim 8 of the present invention, after forming a resin layer made of a thermosetting resin on the surface of a release sheet, the resin layer is adjusted to the mounting path of an optical fiber. The resin has a shape, and is pressed against the release sheet while deforming the resin layer by pushing a molding die having a cross-sectional shape whose tip gradually narrows, and in this state, the resin layer is dried to form the resin. An optical fiber fixing groove is formed in the layer, and then, after the resin layer is integrally attached to the surface of the substrate, by peeling the release sheet, the optical fiber fixing groove is formed on the surface of the resin layer. A continuous narrow opening is formed, and then the resin layer is cured. Further, in the method for manufacturing a printed wiring board according to claim 9 of the present invention, after forming a resin layer on the surface of the substrate and forming an optical fiber fixing groove along the optical fiber mounting path in the resin layer, By laminating a resin film on the surface of the resin layer and then subjecting the resin film to laser processing, an opening is formed along the optical fiber fixing groove and narrower than the optical fiber fixing groove. It is characterized by doing. Furthermore, the method for manufacturing a printed wiring board according to claim 10 of the present invention includes a step of forming a printing screen in which a mold having an optical fiber fixing groove is bonded, and filling the printing screen mold with calcium carbonate. Transferring the calcium carbonate onto a substrate using the printing screen, drying and solidifying the calcium carbonate, and forming and solidifying a resin around the calcium carbonate on the substrate up to the height of the calcium carbonate. And then,
The step of dissolving and removing the calcium carbonate forms the optical fiber fixing groove.

[0006]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the printed wiring board of the present invention, as shown in FIG. 1, the optical fiber 2b connecting the optical connector 2a and the optical element 2d is securely fixed by the optical fiber fixing groove 2c formed in the printed wiring board 2e. can do. The optical fiber fixing groove 2c is shown in FIG.
As shown in (c), both sides of the optical fiber 3f are bank-shaped. Hereinafter, a method of forming the optical fiber fixing groove 3g will be described in detail based on each embodiment described later.

(First Embodiment) In this embodiment, a resin 3a containing a curing agent, for example, a thermosetting resin obtained by mixing a curing agent in an epoxy resin or the like is used as shown in FIG.
It is applied to a printed wiring board 3d, which is an insulating substrate on which a copper wiring pattern is formed, having a thickness of 50 μm to 200 μm. Next, it is dried in a hot air oven at 80 ° C. for 20 minutes, and has a thickness of about 15
An adhesive layer of 0 μm to 200 μm was formed. Then,
Copper plating 3b is applied to the resin surface, an etching resist is applied thereon, a mask image is exposed on the etching resist through a mask film to form an etching resist pattern, and the copper plating 3b is protected by the etching resist pattern, Other portions of the copper plating 3b are etched to provide windows 3c. When the resin is used as a solvent through the window 3c, for example, when an epoxy resin is used, the overhang 3e is formed by over-etching with a mixed solution of acetone and methyl ethyl ketone as a solvent and dissolving the resin as shown in FIG. . Alternatively, an alkali-soluble epoxy resin can be used as the curing agent-containing resin 3a. In this case, the alkali-soluble epoxy resin is overetched and dissolved with a sodium carbonate solution at 40 degrees Celsius as a solvent. .

Next, this substrate is heated at 150 ° C. for 30 minutes to cure the resin composition, and as shown in FIG.
A printed wiring board having the optical fiber fixing groove 3g is formed.

As shown in FIG. 2C, an optical fiber 3f is provided on the bank of the printed wiring board 3d thus formed.
In between. Also, as the printed wiring board 3d, it is possible to use a printed wiring board 3d in which a copper wiring pattern is formed on the surface and an insulating resin is applied in advance.
Also, an alkali-soluble ultraviolet-curable epoxy resin is directly applied as an etching resist on the surface of the curing agent-containing resin 3a without passing through the copper plating 3b, and a mask image is exposed on the etching resist through a mask film,
It is developed with a sodium carbonate solution to form an etching resist pattern, and the hardening agent-containing resin 3a is over-etched with the etching resist pattern by a solution of a mixture of acetone and methyl ethyl ketone to dissolve as shown in FIG. Forming an overhang 3e,
Next, an epoxy resin containing a curing agent and an alkali-soluble ultraviolet-curing epoxy resin used as an etching resist are mixed with 150.
By heating and curing at 30 ° C. for 30 minutes, a printed wiring board 3 d having an optical fiber fixing groove 3 g can be formed.

In the printed wiring board 3d according to the present embodiment having the above-described configuration, the optical fiber 3f is formed by the optical fiber fixing groove 3g from the optical connector to the optical component without using the optical fiber fixing terminal. The optical fiber 3f can be fixed to the route that has been
It is also possible to reduce the number of parts of the device. Further, the depth of the optical fiber fixing groove 3g is larger than the diameter of the optical fiber 3f, and when the optical fiber 3f is settled, there is no interference from other components.
f can be prevented from being damaged. That is, in the present invention,
Since the depth of the optical fiber fixing groove 3g is equal to or greater than the diameter of the optical fiber 3f with respect to the diameter of the optical fiber 3f (125 μm), the light enters the optical fiber fixing groove 3g while maintaining the curvature radius R of the optical fiber 3f. The fiber 3f can be fixed. Also,
Since the optical fiber fixing groove 3g has an overhang structure, the optical fiber 3f is difficult to come out of the groove. Further, the optical fiber 3f is the optical fiber fixing groove 3
g, the structure prevents damage to the optical fiber 3f after the optical fiber 3f is mounted.

(Second Embodiment) As a second embodiment, an alkali-soluble resin such as a photosensitive epoxy resin, a photosensitive polyimide resin, a photosensitive epoxy acrylate resin, a photosensitive epoxy methacrylate resin, or a photosensitive urethane acrylate resin is used. An ultraviolet curable resin is applied to the printed wiring board in a thickness of 150 μm to 200 μm, and then dried in a hot air oven at 80 ° C. for 20 minutes to obtain a thickness of about 150 μm to 200 μm.
m of the resin layer was formed. Next, the resin layer is cured by exposing the resin layer to ultraviolet rays through an ultraviolet mask to the portion outside the optical fiber housing area. Next, copper plating is applied to the surface of the adhesive layer, an etching resist is applied thereon, and the etching resist is exposed to ultraviolet rays through a mask film to mask a window area smaller than the optical fiber housing area. The exposed image is exposed and developed to form a pattern of etching resist that masks the outside of the window area. A window is provided by etching the copper plating with the etching pattern. Next, by dissolving the alkali-soluble ultraviolet-curable resin from the window of the substrate with an aqueous solution of sodium carbonate and over-etching the resin, etching the resin that is not irradiated with ultraviolet light in the copper foil window and the copper foil base, Form an overhang under the copper foil. Next, heating is performed at 150 ° C. for 30 minutes to cure the resin composition.

According to the present embodiment, there is an advantage that a region in which the resin can be dissolved can be designated and controlled by exposing the ultraviolet-curable resin in advance and making it insoluble in alkali.

(Third Embodiment) In a third embodiment, an alkali-soluble thermosetting resin composition having a thickness of 150 to 200 μm is applied to a roughened surface of a copper foil having a thickness of 8 μm. Dry at 20 ° C. for 20 minutes to form a layer of the resin composition. Next, a sheet is formed by laminating a PET film coated with silicone as a protective film thereon. Next, this sheet is placed on both sides of the printed wiring board by PE
75 ° C
To make a double-sided copper-clad board. Next, as in the first embodiment, the copper surface is etched with a mask pattern image, and the alkali-soluble resin layer is over-etched with an aqueous solution of sodium carbonate and dissolved using the copper pattern as a mask. A hang is formed and then the substrate is heated at 150 ° C. for 30
Heat for a minute to cure the resin composition.

According to this embodiment, since the film formed in advance is attached to the printed wiring board, there is no need to control the thickness of the resin applied to the printed circuit boards of various dimensions, and there is an effect that the production becomes easy. .

(Fourth Example) As a fourth embodiment, as shown in FIG. 3, a silicone-coated PET film 4b is coated with a curing agent-containing resin 4d as shown in FIG. Apply with a thickness of ~ 200 [mu] m. Next, a mold with a tapered tip formed on the mounting portion of the optical fiber is pressed, dried in a hot air oven at 80 ° C. for 20 minutes, and the shape of the mold is transferred to form a PET film 4.
Optical fiber fixing groove 4c having overhang on b side
And a sheet on which the adhesive 4e is formed. Next, this sheet is placed on both sides of the printed wiring board 4a, and the printed wiring board 4a is placed on the opposite side of the PET film 4b.
, And laminated by a metal roll at 75 ° C., and the PET film 4b is peeled off. Next, this substrate is heated at 150 ° C. for 30 minutes to cure the resin composition, thereby obtaining a printed wiring board 4 a having an optical fiber fixing groove 4 c formed thereon as shown in FIG. 3B. . Here, a metal foil is used instead of the PET film 4b, and PET is used.
The step of peeling the film 4b can replace the above-described manufacturing method by etching the metal foil.

In the present embodiment, in order to form the overhang shape of the mounting portion of the optical fiber by transfer of a mold, a step of melting the hardening agent-containing resin 4d to form an overhang of the hardening agent-containing resin 4d. Has the feature that it is omitted and the production becomes easy.

(Fifth Embodiment) In this embodiment, first, a resin containing a curing agent, for example, a thermosetting resin such as an epoxy resin is applied to a silicone-coated PET film in a thickness of 20 μm to 30 μm. Then, a resin film 5c dried in a hot air oven at 80 ° C. for 20 minutes is prepared.
Next, as shown in FIG. 4B, a hardener-containing resin 5b made of a thermosetting resin or the like such as an epoxy resin is removed by a 150 μm
It is applied to the printed wiring board 5a with a thickness of about 200 μm.
Next, the substrate is heated at 150 ° C. for 30 minutes to cure the resin composition. Next, as shown in FIG. 4C, a width b (about 150 μm) larger than the diameter of the optical fiber is applied to the cured resin 5b containing a curing agent by a carbon dioxide gas pulse laser.
In step m), a groove is formed. Next, the previously formed resin film 5c is superposed on the substrate surface on the side opposite to the PET film, and is laminated with a metal roll at 75 ° C.
Peel off the T film. Next, the substrate was heated at 150 ° C. for 3 hours.
Heat for 0 minutes to cure the resin composition. Next, a through-hole having a width a (about 130 μm) is formed in the resin film 5c facing the groove having the width b by using a pulsed carbon dioxide gas laser, and as shown in FIG. Groove 5d
To form an overhang structure.

According to this embodiment, since the holes of the resin film 5c are formed by the pulsed carbon dioxide laser, no solution is used, so that the residue of the solution does not remain in the optical fiber fixing groove 5d. In addition, there is no need to wash the residue, which has the effect of facilitating production.

(Sixth Embodiment) In this embodiment, as shown in FIG. 5, an optical fiber 6e for fixing an extra length of an optical fiber 6e connecting the optical connector 6b and the optical element 6f.
Optical fiber 6e which is shifted at a constant pitch in the surface direction of the printed wiring board 6a and is supported by the optical fiber fixing groove 6c.
Is always only one, and the intersection 6d of the two optical fibers 6e is not provided with the fixing groove and the resin of the fixing part. As a result, the groove depth can be reduced to 150 μm.
m to 200 μm, which has the effect of reducing the increase in thickness due to the overlap of the optical fibers 6e.

(Seventh Embodiment) This embodiment is different from FIG.
As shown in (a), calcium carbonate having a trapezoidal cross-section corresponding to the height of an optical fiber having a diameter of 0.125 mm and having a thickness of 0.14 mm thicker and a width of an upper base smaller than that of a lower base. The wall 7a is formed in the optical fiber fixing groove forming portion on the metal flat plate 7b. Next, as shown in FIG. 6 (b), a thermosetting resin 7c is applied around the calcium carbonate wall 7a to a height of 0.14 mm to the upper end of the wall. Next, as shown in FIG. 6 (c), the thermosetting resin 7c is pressed against the printing screen cloth 7d to be thermoset to bond them together, and then the calcium carbonate wall 7a is peeled off, and the optical fiber is placed at the position where the optical fiber is arranged. Thermosetting resin 7 having trapezoidal groove 7f
The printing screen 7e having the pattern c is formed. This printing screen 7e can be created by another manufacturing method. For example, it is also possible to form a metal optical fiber fixing groove 7k mold and attach a printing screen to it.

Next, a groove 7f having a trapezoidal cross section of the mold of the printing screen 7e is filled with a bank-like paste 7h of calcium carbonate, and the printing screen 7e is pressed against a substrate 7i, as shown in FIG. The bank paste 7h of calcium carbonate is extruded from the printing screen 7e with 7g of compressed air and transferred onto the substrate 7i to form a bank, and the bank paste 7h of calcium carbonate is dried and solidified.

Thereafter, as shown in FIG. 6 (e), a thermosetting resin 7j is applied to the substrate 7i up to the height of the top surface of the calcium carbonate formed in a bank shape on the substrate, and is cured by heating. Next, the calcium carbonate exposed on the surface of the cured thermosetting resin 7j is dissolved and removed with acetic acid, and as shown in FIG. 6 (f), an optical fiber fixing groove 7k whose surface width is smaller than the bottom surface width is formed. Form. Thus, 0.1
An optical fiber fixing groove 7k having an overhang toward the inside is formed in the thermosetting resin 7j applied to a thickness of 4 mm. According to the present embodiment, calcium carbonate was transferred onto the substrate 7i using the printing screen 7e in which the mold was attached to the shape of the optical fiber fixing groove 7k, and a resin layer was formed around the calcium carbonate wall. Since the calcium carbonate is dissolved and removed later, and the resin layer having the optical fiber fixing groove 7k is formed on the substrate 7i without dissolving the resin, the production cost can be reduced.

The various shapes, dimensions, and the like of the components shown in the above-described embodiments are merely examples, and can be variously changed based on design requirements and the like.

[0024]

Since the present invention is configured as described above, the optical fiber can be connected to the optical fiber from the optical connector to the optical component in the intended path by the optical fiber fixing groove without using the optical fiber fixing terminal. Can be fixed, thereby reducing the number of parts of the apparatus. Also, the depth of the optical fiber fixing groove is larger than the diameter of the optical fiber, and when the optical fiber is settled, there is no interference from others, so that damage to the optical fiber at the time of mounting components, etc. can be prevented. .

[Brief description of the drawings]

FIG. 1 is an external perspective view schematically showing the present invention.

FIG. 2 is a longitudinal sectional view of a main part showing the first embodiment of the present invention.

FIG. 3 is a longitudinal sectional view of a main part showing a fourth embodiment of the present invention.

FIG. 4 is a longitudinal sectional view of a main part showing a fifth embodiment of the present invention.

FIG. 5 is a plan view showing a sixth embodiment of the present invention.

FIG. 6 is a longitudinal sectional view of a main part showing a seventh embodiment of the present invention.

FIG. 7 is a plan view showing a conventional example.

[Explanation of symbols]

 1a Optical terminal 1b Optical fiber 1c Fixing terminal 1d Optical module 1e Printed wiring board 2a Optical connector 2b Optical fiber 2c Optical fiber fixing groove 2d Optical element 2e Printed wiring board 3a Resin containing hardener 3b Copper plating 3c Window 3d Printed wiring board 3e Overhang 3f Optical fiber 3g Optical fiber fixing groove 4a Printed wiring board 4b PET film 4c Optical fiber fixing groove 4d Hardener-containing resin 4e Adhesive 5a Printed wiring board 5b Hardener-containing resin 5c Resin film 5d Optical fiber fixing Groove 6a Printed wiring board 6b Optical connector 6c Optical fiber fixing groove 6d Intersection 6e Optical fiber 6f Optical element 7a Calcium carbonate wall 7b Metal flat plate 7c Thermosetting resin 7d Printing screen cloth 7e Printing screen 7f Trapezoidal groove 7g Bank-like paste 7i substrate 7j thermosetting resin 7k optical fiber fixing grooves of the compressed air 7h calcium carbonate

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takeshi Shimura 5-7-1 Shiba, Minato-ku, Tokyo Inside NEC Corporation (72) Inventor Takao Saito 5-7-1 Shiba, Minato-ku, Tokyo Japan Inside Electric Co., Ltd.

Claims (10)

[Claims] 1. A resin layer having a predetermined thickness is formed on an optical fiber mounting surface of a substrate, and an optical fiber fixing groove for accommodating the optical fiber is formed in the resin layer. A printed wiring board for mounting an optical fiber, wherein an overhang portion narrower than the inside of the fixing groove is formed in the opening. 2. The printed wiring board for mounting an optical fiber according to claim 1, wherein the overhang portion is formed by extending an opening edge of the resin layer inward. . 3. The printed circuit board according to claim 1, wherein the overhang portion is formed by a second resin layer laminated on the resin layer. 4. The printed wiring board for mounting an optical fiber according to claim 1, wherein the overhang portion is formed of a metal foil laminated on the resin layer. 5. A resin layer mixed with a curing agent is applied to the surface of a substrate to form a resin layer, and a metal foil is integrally laminated on the surface of the resin layer. An etching resist for forming an etching resist pattern along the mounting path is laminated, the metal foil is removed by etching with the etching resist pattern to form an opening, and then the resin layer is formed by the opening.
Manufacturing the printed wiring board, wherein the opening is formed to be wider than the opening, and then the resin layer is cured to form an optical fiber fixing groove having the overhang having a narrower opening. Method. 6. An etching resist for forming a resin layer by applying a resin mixed with a curing agent on the surface of a substrate, and forming an etching resist pattern along the optical fiber mounting path on the surface of the resin layer. Are laminated, and the resin layer is etched and removed by this etching resist pattern to form an opening. Then, the opening is used to etch the resin layer wider than the opening,
Then, an optical fiber fixing groove having an overhang portion having a narrow opening is formed in the resin layer by curing the etching resist and the resin layer. 7. A resin layer made of an ultraviolet curable resin is formed on a surface of a substrate, and an ultraviolet mask is laminated on the surface of the resin layer along a mounting path of an optical fiber, and then the resin layer is irradiated with ultraviolet light. Then, a metal foil is laminated on the surface of the resin layer, and an etching resist for forming an etching resist pattern along a mounting path of the optical fiber is laminated on the surface of the metal foil. The metal foil is removed by etching to form an opening, and the opening is used to etch the resin layer wider than the opening, so that the opening has an overhang portion having a narrower width. A method for manufacturing a printed wiring board, comprising forming a fiber fixing groove. 8. After a resin layer made of a thermosetting resin is formed on the surface of the release sheet, the resin layer has a shape matching the optical fiber mounting path and a cross-sectional shape whose tip gradually narrows. Depressing the formed mold and pressing the release sheet while deforming the resin layer, in this state,
By drying the resin layer, an optical fiber fixing groove is formed in the resin layer, and then, after the resin layer is integrally attached to the surface of the substrate, the release sheet is peeled off, thereby removing the resin. A method for manufacturing a printed wiring board, comprising: forming a narrow opening continuous with the optical fiber fixing groove on a surface of a layer; and curing the resin layer. 9. A resin layer is formed on the surface of the substrate, an optical fiber fixing groove is formed in the resin layer along an optical fiber mounting path, and then a resin film is laminated on the surface of the resin layer. A method for manufacturing a printed wiring board, characterized in that an opening along the optical fiber fixing groove and narrower than the optical fiber fixing groove is formed by subjecting the resin film to laser processing. 10. A step of forming a printing screen in which a mold having an optical fiber fixing groove is bonded, filling the printing screen mold with calcium carbonate, and using the printing screen to deposit the calcium carbonate on a substrate. Transferring, drying and solidifying the calcium carbonate, forming a resin up to the height of the calcium carbonate around the calcium carbonate on the substrate and solidifying the resin, and then dissolving and removing the calcium carbonate Forming a groove for fixing an optical fiber by a process.