JP2004302325A - Method of manufacturing photoelectric compound substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method which allows an optical waveguide of a photoelectric compound substrate to be tapered simultaneously in the breadthwise direction and the thickness direction when forming the optical waveguide. <P>SOLUTION: A first resin layer made of a positive photosensitive resin 10A is formed on one side of a substrate 2 as a lower clad layer 10, and a gray mask 11 capable of giving a radiation intensity distribution is arranged on the first resin layer, and the first resin layer is exposed and developed from above the mask to form a taper groove part 13 which has the cross section reduced from the input side toward the output side of the optical waveguide, and a second resin layer 2A is formed as a core layer 2 so as to fill up the groove part, and a third resin layer 14A is formed on the second resin layer 2A as an upper clad layer 14. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing an opto-electric composite substrate in which an optical waveguide is formed on an electric wiring board, particularly such that the optical waveguide cross-sectional area is large on the light incident side and the optical waveguide cross-sectional area is small on the output side. The present invention relates to a method for manufacturing a photoelectric composite substrate having a so-called tapered optical waveguide.
[0002]
[Prior art]
All of the conventional printed circuit boards have been transmitting and receiving signals by electricity. However, a method has been proposed in which light is used for a high-speed part due to a limit of an electric transmission speed (for example, see Patent Document 1).
[0003]
FIG. 6 shows an example of a printed circuit board in which an optical waveguide and electric wiring are mixed. A waveguide element using a substrate with an optical waveguide has an electric wiring board on which a pattern of electric wiring 1 for transmitting a signal is formed, and an optical waveguide formed on a printed circuit board 3 is provided at a portion for transmitting a high-speed signal. Wave path 15 (core layer 2, clad layers 10, 14) is used. Therefore, at both ends of the optical waveguide 15, more precisely, at both ends of the core layer 2 and the lower clad layer 10, there are formed optical path conversion sections 9 each having an inclined surface for converting the optical path of an optical signal. Above 9, there are provided an LD (laser diode) 4 which is a light emitting element for converting electric-optical signals and a PD (photodiode) 5 which is a light receiving element for converting optical-electric signals. The substrate with an optical waveguide is joined to another electric wiring substrate by an adhesive layer 6.
[0004]
The LD 4 and the PD 5 are respectively provided on the LD main body and the PD main body provided on the electric wiring 1 of the substrate with the optical waveguide, and between the electric wiring 1 and the LD 4 and the PD 5, an LD for connecting them is provided. Driver 8 and PD driver 7 are provided.
[0005]
Then, the electric signal i input from the electric wiring 1 is converted into an optical signal by the LD 4, reflected by the optical path conversion unit 9 having an input-side inclined surface, input to the optical waveguide core layer 2 and transmitted. The light is reflected by the optical path conversion unit 9 having the inclined surface on the output side and enters the PD 5, where it is converted into an electric signal, and is output to the outside as an electric signal o from the electric wiring 1 of another electric wiring board via the connection layer. It is supposed to be.
[0006]
A resin material such as a polyimide resin or an epoxy resin is used for the optical waveguide, and a pattern is formed by using a mask and a UV exposure method, a formation method by RIE (Reactive on Etching) processing, and a mold. There are molding methods and the like.
[0007]
Of the signals to be transmitted, the optical waveguide core layer 2 is used for transmitting a high-speed signal of several Gbps or more, and the LD4 and PD5 are used for electric-optical and optical-electrical signal conversion. Here, in order to optically couple the light from the LD 4 to the optical waveguide core layer 2 and from the optical waveguide core layer 2 to the PD 5, an optical path conversion of 90 ° is necessary. This requires a 45 ° inclined surface formed on the end face of the optical waveguide. A mirror is used as the optical path changing unit 9.
[0008]
Here, the optical waveguide on the printed circuit board 3 transmits the signal transmitted from the LD 4 to the PD 5, but in the conventional structure, the cross section along the longitudinal direction of the optical waveguide core layer 2 was rectangular. In this case, the larger the area of the optical waveguide portion receiving the light from the LD 4, the smaller the mounting accuracy tolerance with the LD 4 can be. Therefore, the wider the optical waveguide cross section is better, but the more the light is emitted to the PD 5, the wider the beam is. The area irradiated to the light receiving area of the PD 5 is small, and a loss occurs. As a countermeasure against this, it is considered effective to increase the area of the optical waveguide portion on the LD side and reduce the area on the PD side (hereinafter referred to as “taper”) to reduce the loss by using a tapered optical waveguide.
[0009]
Conventionally, for a plastic optical fiber, a graded index fiber-type optical repeater whose core diameter decreases gradually from the optical fiber side toward the light receiving element side is interposed between the end face and the light receiving surface of the light receiving element. Is known (for example, see Patent Document 2).
[0010]
[Patent Document 1]
JP 2000-332301 A
[Patent Document 2]
Japanese Patent Application Laid-Open No. H11-125749
[Problems to be solved by the invention]
However, Patent Document 2 does not refer to the structure or manufacturing method of the photoelectric composite substrate in which an optical waveguide is formed on an electric wiring substrate.
[0013]
Further, as a method of manufacturing such a tapered optical waveguide, the above-described die method and RIE (reactive ion etching) method can be considered, but the die method is expensive in manufacturing the die. The RIE (reactive ion etching) method has a problem that the time required for etching when forming an optical waveguide pattern is long and is not suitable for a large optical waveguide.
[0014]
Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a method of manufacturing an opto-electric composite board in which an optical waveguide is formed on an electric wiring board, which is suitable for forming the optical waveguide, and which is suitable for forming the optical waveguide in the width direction. It is an object of the present invention to provide a manufacturing method capable of simultaneously forming a taper in the thickness direction.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is configured as follows.
[0016]
According to the method of manufacturing an opto-electric composite board according to the first aspect of the present invention, an optical waveguide is formed on an electric wiring board, and light reflected by an input-side optical path conversion unit and incident on the optical waveguide is converted into an output-side optical path. In a method for manufacturing a photoelectric composite substrate having a structure in which light is reflected by a conversion unit and guided to a light receiving element, a first resin layer made of a positive photosensitive resin is formed as a lower clad layer on one surface of the substrate, and the first resin layer is formed. A gray mask capable of imparting a distribution to the irradiation intensity is disposed on the resin layer, and the cross-sectional area decreases from the input side to the output side of the optical waveguide by exposing and developing the first resin layer from above the mask. Forming a groove-shaped groove, forming a second resin layer as a core layer so as to fill the groove, and forming a third resin layer as an upper clad layer on the second resin layer. .
[0017]
According to a second aspect of the present invention, in the method of manufacturing an optoelectronic composite substrate according to the first aspect, a gray mask having a gradation structure in which a light transmission amount of the mask decreases from an input side to an output side of the optical waveguide is used as the mask. By exposing and developing the first resin layer from above the mask, a tapered groove having a shallower depth from the input side to the output side of the optical waveguide is formed, and a core layer is formed so as to fill the groove. The second resin layer is formed to form a core layer whose thickness decreases from the input side to the output side of the optical waveguide.
[0018]
According to a third aspect of the present invention, in the method for manufacturing an opto-electric composite substrate according to the second aspect, when the mask pattern is exposed and developed, the width of the groove decreases from the input side to the output side of the optical waveguide. It is characterized by using a pattern.
[0019]
According to a fourth aspect of the present invention, in the method of manufacturing an opto-electric composite substrate according to any one of the first to third aspects, light emitted from the optical waveguide is supplied to a light receiving element in an optical path conversion unit on the output side of the optical waveguide. It is characterized in that a lens for focusing is provided.
[0020]
<The gist of the invention>
The gist of the present invention relates to an optical waveguide for transmitting an optical signal, and a taper type optical waveguide for reducing an optical connection loss in signal transmission is manufactured by using a UV exposure method and a gray mask, and is manufactured in a width direction and a thickness direction. At the same time is a tapered optical waveguide.
[0021]
That is, by forming a first resin layer on one surface of the substrate, disposing a mask having a predetermined pattern on the first resin layer, exposing and developing the first resin layer from above the mask A groove is formed, a second resin layer as a core layer is formed so as to fill the groove, and finally a third resin layer is formed on the second resin layer to complete the optical waveguide. At the time of the exposure and development, a positive photosensitive resin is used for the first resin layer, and a gray mask having a structure having a distribution of irradiation intensity is used for the mask. Thus, an optical waveguide in which the width direction and the thickness direction are simultaneously tapered is manufactured.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described based on the illustrated embodiments.
[0023]
FIG. 5 shows the structure of the photoelectric composite substrate to be manufactured in the present embodiment. As in the case of FIG. 6, there is an electric wiring board on which a pattern of electric wiring 1 for transmitting a signal is formed, and an optical waveguide 15 (core Layer 2, cladding layers 10, 14) are used. At both ends of the optical waveguide 15, more precisely, at both ends of the core layer 2 and the lower cladding layer 10, an optical path conversion unit 9 for converting an optical path of an optical signal is formed by a 45 ° inclined surface, and an optical path conversion unit on the input side thereof. Above 9, an LD (laser diode) 4 that is a light-emitting element that converts electric-optical signals, and above an optical path conversion unit 9 on the output side is a PD (photodiode) that is a light-receiving element that converts optical-electric signals. 5 are provided. The substrate with an optical waveguide is joined to another electric wiring substrate by an adhesive layer 6.
[0024]
However, the aperture, that is, the cross-sectional area of the optical waveguide core layer 2 is not constant in the longitudinal direction as in the case of FIG. 6, and extends from the input side (LD side) to the output side (PD side) of the optical waveguide 15. The configuration is such that the cross-sectional area of the core layer 2 is reduced.
[0025]
FIG. 1 shows a manufacturing process of the tapered optical waveguide of the present invention. First, a substrate 3 (for example, a glass epoxy substrate, a silicon substrate or the like) is prepared as shown in FIG.
[0026]
Next, as shown in FIG. 2B, a positive photosensitive resin 10A (for example, an acrylic resin, an epoxy resin, or a polyimide resin) is applied as a first resin to be the lower clad layer 10. The positive photosensitive resin 10A can be formed by a method of attaching a resin film in addition to the formation by coating.
[0027]
Next, as shown in FIG. 3C, a gray mask 11 having a predetermined pattern and capable of giving a distribution to the UV irradiation intensity is disposed above the positive photosensitive resin 10A. At this time, the gray mask 11 is as shown in FIG. 2, and it is possible to form the tapered shape in the thickness direction by giving a distribution to the irradiation intensity as well as the tapered shape in the width direction. That is, the gray mask 11 has a pattern in which the width decreases from the input side to the output side of the optical waveguide as the mask pattern 11a corresponding to the shape of the core layer 2. In the mask pattern 11a of the gray mask 11, the light transmission amount or light absorption amount in the internal region is gradually changed in the longitudinal direction of the optical waveguide, and the light of the mask is changed from the input side to the output side of the optical waveguide. It has a gradation structure in which the amount of transmission is small. This is a gradation structure in which light is hardly transmitted on the LD side and light is easily transmitted on the PD side.
[0028]
After disposing the gray mask 11, exposure light 12 (here, UV exposure light) is irradiated from above the gray mask 11, and the exposure light is applied only to a portion where a tapered portion corresponding to the core layer 2 is formed through the gray mask 11. Make sure that 12 hits.
[0029]
As shown in FIG. 1D, the positive photosensitive resin 10A that has received the exposure light 12 is developed to form a tapered groove 13 having a tapered shape in the width direction and the thickness direction. Thereby, a lower clad layer (first resin layer) 10 having a tapered portion having a tapered shape in the width direction and the thickness direction is formed. Here, the tapered groove 13 can simultaneously form a taper in the thickness direction and a taper in the width direction. The reason that the taper shape in the width direction and the thickness direction can be formed at the same time is that the width of the mask pattern 11a is gradually changed so that the output side has a taper shape with a small width, thereby enabling a taper shape in the width direction. This is because a taper in the thickness direction is made possible by using the gray mask 11 capable of giving a distribution to the irradiation intensity and reducing the light passing amount on the output side.
[0030]
Next, as shown in FIG. 3E, the second resin 2A for forming the core layer 2 is filled on the tapered portion of the lower clad layer 10, that is, in the tapered groove 13. Here, as the resin 2A, for example, a thermosetting resin or a photocurable resin can be used.
[0031]
Further, as shown in FIG. 3F, an optical waveguide is formed by applying a third resin 14A for protecting the core layer 2 on the core layer 2 and the positive photosensitive resin 10A exposed to the outside. 15 is completed. Here, the first resin of the lower cladding layer 10 and the third resin 14A of the upper cladding layer 14 may be made of the same material or different materials, but both must have a lower refractive index than the core layer 2. .
[0032]
As described above, by using a positive photosensitive resin as the cladding material of the optical waveguide and using a gray mask capable of giving a distribution to the UV irradiation intensity for pattern formation, the width direction and the thickness direction of the positive photosensitive resin are used. Can be simultaneously formed. The connection loss can be reduced by achieving a tapered shape such that the optical waveguide cross-sectional area is large on the LD side and the optical waveguide cross-sectional area is small on the PD side.
[0033]
【Example】
FIG. 3 shows an embodiment of the present invention. FIG. 4 shows a cross section taken along the line AA ′ in FIG. The optical waveguide portion corresponding to the LD has a large cross-sectional area of the optical waveguide core layer 2, so that the positional tolerance can be loosened when optically connecting to the LD4. On the other hand, on the PD side, the cross-sectional area of the optical waveguide core layer 2 is small, and the light receiving area of the PD 5 is efficiently illuminated to reduce the connection loss.
[0034]
Further, not only the taper shape in the horizontal direction, but also the taper shape in the height direction, the connection loss can be further reduced.
[0035]
As another embodiment, FIG. 5 shows a structure in which a lens 16 is attached to a 45 ° mirror portion on the PD side to collect light emitted from an optical waveguide. With this structure, light can be efficiently incident on the light receiving area of the PD 5, and connection loss with the PD can be further reduced.
[0036]
【The invention's effect】
As described above, according to the method for manufacturing a photoelectric composite substrate of the present invention, a first resin layer made of a positive photosensitive resin is formed as a lower clad layer on one surface of the substrate, and the irradiation intensity is distributed thereon. Is arranged, and the first resin layer is exposed and developed from above the mask to form a tapered groove having a smaller cross-sectional area from the input side to the output side of the optical waveguide. Is formed, and a third resin layer as an upper cladding layer is formed on the second resin layer, so that the cross-sectional area of the optical waveguide core layer is smaller than the input area of the optical waveguide. The shape of the optical waveguide that becomes smaller from the side to the output side, for example, a tapered shape in the width direction and the thickness direction can be simultaneously manufactured.
[0037]
By having such a tapered optical waveguide, for example, the optical waveguide cross-sectional area can be increased on the LD side and the optical waveguide cross-sectional area can be reduced on the PD side, and connection loss can be reduced.
[Brief description of the drawings]
FIG. 1 is a view showing a process for producing an optical waveguide of an optoelectronic composite substrate according to the present invention.
FIG. 2 is a diagram illustrating a gray mask used in the present invention.
FIG. 3 is a plan view in which an optical waveguide according to one embodiment of the present invention is arranged on a substrate.
FIG. 4 is a cross-sectional view illustrating a cross section taken along the line AA ′ in FIG. 3, illustrating an example of an optical waveguide in which a taper is also provided in a thickness direction.
FIG. 5 is a diagram showing a structure of an opto-electric composite substrate to which the present invention is applied, and is a diagram also used as another embodiment in which a lens is attached to a mirror portion of an optical waveguide 45 °.
FIG. 6 is a cross-sectional view of a conventional photoelectric composite substrate in which optical waveguides and electric wiring are mixed.
[Explanation of symbols]
2 Core layer (second resin layer)
2A Second resin 3 Printed circuit board 4 LD
5 PD
9 Optical path conversion unit (45 ° mirror)
10. Lower cladding layer (first resin layer)
10A Positive photosensitive resin (first resin)
11 Gray mask 11a Mask pattern 13 Tapered groove 14 Upper cladding layer (third resin layer)
14A Third resin 15 Optical waveguide 16 Lens

Claims (4)

An optical / electrical composite having a structure in which an optical waveguide is formed on an electric wiring board, and light reflected by an optical path conversion unit on the input side and incident on the optical waveguide is reflected by an optical path conversion unit on the output side and guided to a light receiving element. In the method for manufacturing a substrate,
Form a first resin layer made of a positive photosensitive resin as a lower clad layer on one surface of the substrate,
A gray mask capable of imparting a distribution to the irradiation intensity is arranged on the first resin layer,
Exposure and development of the first resin layer from above the mask to form a tapered groove having a smaller cross-sectional area from the input side to the output side of the optical waveguide,
Forming a second resin layer as a core layer so as to fill the groove,
A method for manufacturing a photoelectric composite substrate, comprising forming a third resin layer as an upper clad layer on the second resin layer. The method for manufacturing a photoelectric composite substrate according to claim 1,
As the mask, a gray mask having a gradation structure in which the light transmission amount of the mask decreases from the input side to the output side of the optical waveguide,
By exposing and developing the first resin layer from above the mask, a tapered groove portion whose depth decreases from the input side to the output side of the optical waveguide is formed,
Forming a second resin layer as a core layer so as to fill the groove, and forming a core layer whose thickness decreases from the input side to the output side of the optical waveguide. . The method for manufacturing a photoelectric composite substrate according to claim 2,
A method of manufacturing a photoelectric composite substrate, wherein a pattern in which the width of the groove portion decreases from the input side to the output side of the optical waveguide when exposed and developed is used as the mask pattern. The method for manufacturing a photoelectric composite substrate according to any one of claims 1 to 3,
A method for manufacturing a photoelectric composite substrate, comprising: providing a lens for condensing light emitted from an optical waveguide on a light receiving element in an optical path conversion unit on the output side of the optical waveguide.

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