JP2006215289A - Substrate for optical circuit, and manufacturing method of optical circuit substrate using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an opto-electric hybrid substrate that facilitates mutual positioning between electric circuit wiring and an optical waveguide, that mitigates load for designing an optical waveguide in designing the electric circuit wiring, and that increases latitude of design for the electric circuit wiring, in manufacturing the opto-electric hybrid substrate. <P>SOLUTION: The substrate for the optical circuit is characterized in that a plurality of cores are arranged side by side through a clad at least on a part of a face parallel to the substrate face, and that an identification code for specifying a core is formed near each core. The manufacturing method of the optical circuit substrate includes a process of forming an incidence/emission part of light in this substrate for the optical circuit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polymer optical waveguide, and more particularly to a method of manufacturing an optical integrated circuit, an optical component for optical interconnection, an opto-electric hybrid board, and the like.

  As base materials for optical components or optical fibers, inorganic materials such as quartz glass and multicomponent glass, which have the characteristics of low light propagation loss and wide transmission band, are widely used. System materials have also been developed and are attracting attention as materials for optical waveguides because they are superior in processability and price compared to inorganic materials. For example, a flat plate type having a core-clad structure in which a polymer having excellent transparency such as polymethyl methacrylate (PMMA) or polystyrene is used as a core and a polymer having a refractive index lower than that of the core material is used as a cladding material. An optical waveguide is produced (Patent Document 1). On the other hand, a low-loss flat optical waveguide is realized using polyimide, which is a transparent polymer with high heat resistance (Patent Document 2).

As one of uses of the polymer optical waveguide, an opto-electric hybrid board is considered. As the opto-electric hybrid board, a laminated structure of a polymer optical waveguide and an electric printed wiring board, or a substrate in which electrical wiring is directly performed on the polymer optical waveguide is considered. In these opto-electric hybrid boards, the surface on which the electric circuit is formed differs from the surface on which the optical waveguide is formed. For this reason, it is difficult to align the electrical circuit wiring pattern and the core pattern constituting the optical waveguide separately. Furthermore, because the location of light input / output differs depending on the use and design of the opto-electric hybrid board, it is necessary to design the optical circuit according to the design of the opto-electric hybrid board and to produce a core pattern according to it. .
Japanese Patent Laid-Open No. 03-188402 Japanese Patent Laid-Open No. 04-9807

The object of the present invention is to facilitate the mutual alignment of the electric circuit wiring and the optical waveguide in the manufacture of the opto-electric hybrid board, and to design the optical copper waveguide when designing the electric circuit wiring in order to avoid the above-mentioned problems. It is an object of the present invention to provide an opto-electric hybrid board that reduces the burden on the circuit board and increases the degree of freedom in designing electrical circuit wiring.

As a result of intensive studies, the present inventor has found that the above-mentioned problems can be solved by forming an optical waveguide to which core position information is given, and has completed the present invention. That is, in the present invention, a plurality of cores are arranged in parallel via a clad on at least a part of a plane parallel to the substrate surface, and an identification code for identifying the core is formed in the vicinity of each core. It is the board | substrate for optical circuits characterized by having.

A plurality of second cores that further intersect with the core may be formed in parallel.
In the present invention, it is a preferred embodiment that a conductor layer is formed on the surface where the core is not formed. This conductor layer may be unpatterned, and the electrical wiring may be patterned.

  According to another aspect of the invention, there is provided a step of identifying a core to be guided by the optical circuit substrate and forming a reflecting surface by providing a hole for cutting the core at a position where the light to be guided enters or exits the core. The manufacturing method of the optical circuit board containing this.

  Furthermore, the present invention is directed to an optical circuit substrate in which a plurality of cores are arranged in parallel via a cladding on at least a part of a plane parallel to the substrate surface, and the detection light focused on the core crosses the core. Specify the core by scanning in the direction and counting the change in reflected or transmitted light intensity, and form a reflecting surface by providing a hole to cut the core at the location where the light to be guided to or output from the specified core The manufacturing method of the optical circuit board | substrate including the process to do.

  An optical circuit or an electric circuit using at least one of the plurality of cores is formed on a surface opposite to the surface on which the plurality of cores are formed. For example, when the light-emitting element is an element of the circuit, in the design of the light-emitting element and the electric circuit wiring for driving the light-emitting element, the installation position of the light-emitting element is even determined as the position projected on the range where the plurality of cores are formed. Then, the optical path from the light emitting element to the core is formed by selecting the core closest to the installation position and making a hole that guides the light from the light emitting element to the core and at the same time forming a reflective surface that cuts the core. can do.

  The smaller the pitch of the cores arranged in parallel, the greater the degree of freedom in the place where the light emitting / receiving elements and optical elements connected to the electric circuit are installed. On the other hand, if the core pitch is too small, light leaks to the adjacent core, and loss increases. The pitch between the cores is preferably 5 μm or more and 1 mm or less as an interval between the cores. More preferably, it is 10 μm or more and 500 μm or less. Further, it is desirable that 20 to 300 cores are formed in parallel via a clad so as to fill at least a width of 10 mm.

  When the cores intersect, the pitch of the parallel cores is suitably at least twice the core width. As a result, interference between the intersecting cores can be reduced, and the position of the light input / output portion can be easily set.

  In the present invention, among the plurality of cores arranged in parallel via the clad, some are actually used, and other cores are not used, so-called dummy. Since a plurality of cores can be collectively formed by photolithography, for example, the number of core forming steps can be changed without changing the number of core forming steps as compared with a case where a core pattern is previously formed in accordance with an electric circuit.

  Here, the optical circuit substrate is a substrate including an optical waveguide provided with at least a core and a clad, and does not have an input / output unit for light to the core. This optical circuit board is further processed to form electrical wiring, and if necessary, various electronic elements and photoelectric elements are mounted, and an input / output unit for light to the core is formed to become an opto-electric hybrid board, or electrical It is laminated with an electric wiring board on which various electronic elements and photoelectric elements are mounted as necessary, and an optical input / output unit to the core is formed to form an opto-electric hybrid board.

  An opto-electric hybrid board is a board having both an optical waveguide and an electric circuit. Examples of the electric circuit include an electric circuit for driving a light receiving and emitting element, and light guided through the optical waveguide is electro-optics outside the optical waveguide or outside the optical waveguide. A circuit for applying an electric field for producing an effect can be mentioned. An optical circuit board is an optical circuit board having an optical waveguide and a light input / output section formed in a necessary core. Here, not only a substrate having only an optical circuit that does not include electrical wiring but also an optical / electrical hybrid substrate is referred to as an optical circuit substrate.

  Since the optical circuit board according to the present invention can cope with various signal transmission paths, it is not necessary to change the design of the core pattern of the optical waveguide for each optical circuit board including the opto-electric hybrid board, and the photomask used for the production thereof. Can use the same thing. Also, when designing the electrical circuit wiring of the opto-electric hybrid board, it is possible to design the optimal wiring for the electrical circuit wiring and select the core that is close to the place where optical coupling is necessary, so that the optimal circuit design Therefore, the degree of freedom can be increased and the substrate cost can be reduced as a whole.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Here, a polyimide optical waveguide will be described as an example of the optical waveguide layer, but it is of course possible to use a resin other than polyimide as a material for the optical waveguide and the electric wiring board. In addition to a structure in which an optical waveguide layer and an electrical wiring board layer are laminated as an opto-electric hybrid board, it is possible to have direct electrical wiring on the optical waveguide, or even a single optical waveguide It is. In addition, it is preferable that the core and the clad are made of resin because processing becomes easy.

FIG. 1 shows an example of the optical waveguide of the present invention. In the optical waveguide composed of the clad 1 and the core 2, the core is a straight line and many wires are arranged at a certain pitch. Here, the core has drawn a straight line pattern, but a pattern other than a straight line may be used. When designing a circuit, one of the plurality of cores arranged in parallel is selected.
There are the following methods for specifying the core used in the optical waveguide.

  In one method, as shown in FIG. 2, numbers or letters that are identification codes 4 for identifying the cores are attached along the cores 2 in the vicinity of each core. Various identification codes such as numerals and Roman letters can be used for this identification code. If this identification code is repeatedly formed in a certain cycle along the direction in which the core extends, the identification code can be easily found. This identification code may be engraved at the same time when the core is formed by photolithography.

  Another method for identifying the core is to change the intensity of the reflected light when crossing the core by scanning the detection light focused on the core position with a beam of moderate size and focused on the core position. By counting the number of times, the core can be specified by obtaining the number of cores. You may obtain | require the intensity change of transmitted light instead of reflected light. If necessary, a marker serving as a mark may be formed in the vicinity of the identified core. This marker can also be formed by irradiating a laser beam. By these methods, it is possible to specify a location where an optical connection is to be made, for example, a core where an optical input portion to the core, an output portion from the core, or a reflection portion within the core is to be formed.

Next, a method for forming the light input / output portion at the necessary portion of the identified core will be described.
In the cross section of the optical waveguide shown in FIG. 7, the core 2 is sandwiched between the top and bottom of the clad 1 (FIG. 7 (a)). The input / output portion of the optical waveguide is irradiated with laser from an oblique direction to form an oblique hole 33 and cut the core (FIG. 7B). The cut surface of the core becomes a mirror. If the angle of inclination of the mirror is 45 degrees, the optical path 34 in the direction perpendicular to the core can be obtained (FIG. 7 (c)). Rather than irradiating the laser obliquely, a light input / output portion can be formed by puncturing a hole vertically and inserting a short optical waveguide or optical fiber with a mirror to be an optical pin into the hole. .

  FIG. 8 shows a mirror forming method for an optical waveguide embedded type opto-electric hybrid board. Here, since the electric wiring layers 35 are formed on both surfaces of the optical waveguide composed of the core 2 and the clad 1 (FIG. 8A), the core 2 may not be seen from above. In that case, a hole 36 that does not reach the core is formed in the electric wiring layer by using a substrate without an electric wiring board in the light input / output unit or by irradiating an excimer laser (FIG. 8B). The identification code is recognized through this hole. Thereafter, an excimer laser is irradiated obliquely to form a mirror (FIG. 8C). Even when the core of the optical waveguide cannot be observed because the optical waveguide is surrounded by an opaque layer, the position information is obtained by using a layer with a hole or a hole in advance, and the input / output of light to be the optical path 34 The part can be formed (FIG. 8D).

  In addition to providing a plurality of cores arranged in parallel in the entire substrate or only in one region, the substrate can be divided into a plurality of regions, and a plurality of cores arranged in parallel in some of the regions can be provided. In that case, the core pattern may be different in different regions. FIG. 4 shows an example of dividing into four areas 11 and performing optical transmission in each area. Although not shown, a number for identifying the core may be displayed between the core 12 and the core.

  Next, FIG. 5 shows an example in which a plurality of cores 22 arranged in parallel via the clad 21 and a plurality of parallel cores orthogonal to the cores 22 are formed, and the core pattern has a mesh shape. As a result, it is possible to guide light in another direction as well as in one direction. Although some loss occurs at the location where the cores intersect, the loss can be made acceptable by design. According to the circuit design, a 90 ° conversion mirror may be formed by drilling a hole where light input / output is necessary.

  Further, by using such a pattern, light can be input / output at an arbitrary location in the substrate. In FIG. 6, as in FIG. 5, the core 22 is formed in a mesh shape in the optical waveguide composed of the clad 21 and the core 22. Here, a mirror is formed at the intersection of the cores. An example of a method for forming a mirror is laser processing. By irradiating the part where the mirror is formed vertically with a laser to form a hole 31 for vertically cutting a part of the core, the cut surface of the core becomes a mirror. By performing optical path conversion through this mirror, it is transmitted to a desired location. The optical input / output unit 32 can be used by forming a hole at a desired location and inserting a 90 ° conversion micro mirror, or by directly forming a 90 ° conversion oblique hole in the optical waveguide and using the core cross section as a mirror. That's fine. In this way, the optical path 23 indicated by the dotted line can be obtained. At this time, a core to be used can be specified by assigning a number as an identification code to each straight waveguide. The intersection forming the mirror is a combination of two numbers.

  Further, as shown in FIG. 9, by forming a hole 41 having a rectangular cross section having a vertex at the center of the intersection by laser processing, not only simple optical path conversion but also one-to-two optical branching is possible. It becomes. The rectangular holes at the intersections are punctured vertically by irradiating an excimer laser through a photomask of the same shape. The light propagating in the optical path 42 that is formed as a part of the wall of the hole 41 toward the core end surface is demultiplexed at the core end surface, and the branched light is respectively transmitted to the two-way optical paths 43 and 43 ′ in which the optical paths are changed by 90 degrees. Go ahead. By using this method, not only one-to-one but one-to-many optical transmission can be performed at any place in the substrate.

  FIG. 3A shows a form in which the entire substrate is divided into four regions and an infinite number of cores 12 are connected from one region 11 to the other three regions. Here, the intersection 13 where the cores intersect is made to intersect at an angle as close to 90 degrees as possible as shown in FIG. In the case where there are many intersections and loss is a problem, it is preferable that the optical circuit layer has a structure of two or more layers. At that time, the place of light input / output may be adjusted. Furthermore, if necessary, all patterns are made of equal length wiring. Also in this case, a number may be given to each core pattern as position information as shown in FIG.

  The optical waveguide layer has a multi-layer structure, and by using any one or each of the patterns shown in FIGS. 1, 3, 4, and 5 for each layer configuration, it is possible to select an allowable loss value and a route according to the application. Therefore, the optical waveguide and the opto-electric hybrid board are easy to use for the user. This can be achieved simply by adjusting the position of the light input / output mirror. At this time, the light input / output unit may be a place where the patterns do not overlap.

  Subsequently, the present invention will be described in more detail using several examples. It is obvious that an unlimited number of optical waveguides and opto-electric hybrid substrates can be obtained by using various polymers having different molecular structures. Therefore, the present invention is not limited only to these examples.

Example 1
2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 2,2-bis (trifluoromethyl) -4,4'-diaminobiphenyl (TFDB) on a 5-inch silicon wafer ) And a polyimide formed from a copolymerized polyamic acid solution of 6FDA and TFDB and 6FDA and 4,4′-oxydianiline (ODA) as a core, and embedded by photolithography and dry etching technology. Type optical waveguide film was prepared. At this time, as the core pattern, a net-like core pattern composed of a core parallel to each other at a pitch of 250 μm in one direction in a 7 cm square and a core crossing the core was formed. Each core width was 35 μm and the height was 30 μm. Further, numbering for identification was made at a position of 40 μm on the left side of the core in a 1 mm cycle from the end to 1 to 140 from the end. This was formed simultaneously with the patterning of the core by assigning this number to the mask pattern at the time of core formation.

  Next, an optical input / output micromirror was formed. Micromirror formation was performed on the core of No. 50. The optical waveguide was tilted at 51 degrees, and a micromirror was formed by KrF excimer laser processing. A mask projection method was used for excimer laser processing. A mask having a square shape with a side of 200 μm was used on the optical waveguide. With this, a hole having a side of 200 μm can be formed. The optical waveguide was irradiated at 200 pulses / second for 3 seconds. The irradiation intensity was about 0.4 mJ / pulse on the optical waveguide. This irradiation was performed at two locations, which were the light input side and the output side, respectively. The light from the outside was converted by 90 degrees to input / output light. When light with a wavelength of 850 nm is inserted from the optical input section with an optical fiber and the light reflected by the 90-degree optical path changing micromirror is observed with the CCD camera at the optical output section, a reflected spot is observed and light propagation can be confirmed. It was.

(Example 2)
An optical waveguide pattern exactly the same as in Example 1 was formed.
Next, two polyimide films with a single-sided copper foil as a flexible wiring board were prepared, and an opto-electric hybrid board was prepared. Thermoplastic polyimide was spin-coated on both sides of the fluorinated polyimide optical waveguide as a bonding layer so as to have a thickness of 10 μm after the heat treatment, followed by heat treatment. As the thermoplastic polyimide, a polyimide made of oxydiphthalic dianhydride (ODPA) and aminophenoxybenzene (APB) was used.
Next, two polyimide films with single-sided copper foil were bonded and fixed to both sides of the polyimide film surface of the optical waveguide film coated with the thermoplastic polyimide film by a hot press. The hot press was performed at a press temperature of 250 ° C., a press pressure of 2 MPa, and a press time of 4 hours.

  Next, an optical input / output micromirror was formed. Micromirror formation was performed on the core of No. 50. The copper layer was wet etched with an aqueous ferric chloride solution. When it was difficult to see the core due to the material of the substrate, a KrF excimer laser was irradiated in the vicinity of No. 50 using a mask having an irradiation diameter of 1 mm on one side on the opto-electric hybrid substrate. The optical waveguide was irradiated at 200 pulses / second for 0.6 seconds. The irradiation intensity was about 0.4 mJ / pulse on the optical waveguide. This irradiation was performed at two locations on the light input side and output side, and the surface layer at that location was removed. Next, in the same manner as in Example 1, the substrate was tilted by 51 degrees, and excimer laser was irradiated back and forth on the light input side and output side to form holes. Irradiation was performed for 3 seconds at 200 pulses / second using a mask having an irradiation diameter of 200 μm on one side on the opto-electric hybrid board. In this manner, micromirrors having core cut surfaces were formed at two locations, the input side and the output side. When light having a wavelength of 850 nm is inserted from the light input portion of the substrate through an optical fiber and the light reflected by the 90 ° optical path changing micromirror is observed at the light output portion of the substrate with a CCD camera, a reflected spot is observed, Propagation was confirmed.

(Example 3)
An optical waveguide pattern exactly the same as in Example 1 was formed.
Next, an optical transmission path was formed using this optical waveguide pattern. In the vertical 1 core, a light incident portion is provided in the middle of the intersection between the horizontal 1 core and the horizontal 2 core, and in the horizontal 140 core, the middle of the intersection between the vertical 140 core and the vertical 139 core. It was designed to provide a light emitting part. In other words, this is an optical path that propagates through the core of the length 140, changes the optical path by 90 ° in the plane at the intersection of the length 1 core and the width 140 core, and propagates the core of the width 140. First, by KrF excimer laser processing, a hole 31 penetrating the core was vertically drilled by KrF excimer laser processing at the intersection of one vertical core and 140 horizontal core as shown in FIG. The optical path can be changed 90 degrees in the plane by the core cut surface formed at this time. As a condition for drilling, a mask having an irradiation diameter of 200 μm on one side was used on the optical waveguide. With this, a hole having a side of 200 μm can be formed. The optical waveguide was irradiated at 200 pulses / second for 2 seconds. The irradiation intensity was about 0.4 mJ / pulse on the optical waveguide.

  Next, a light input / output mirror was formed. The cut surface of the core formed by making an oblique hole with a laser at each of the light incident portion and the light emitting portion is a mirror. In the formation method, the optical waveguide was tilted at 51 degrees, and the same input mask was used to irradiate the light input / output part with a KrF excimer laser for 3 seconds with the same amount of irradiation as before. As a result, the light perpendicularly incident on the substrate surface from the outside was subjected to an optical path change by 90 degrees, and the light was input to one vertical core. When light with a wavelength of 850 nm is inserted from the optical input section with an optical fiber and the light reflected by the 90-degree optical path conversion mirror is observed with a CCD camera in the optical output section of the horizontal 140 core, a reflected spot is observed, and light propagation Was confirmed. Before making holes for input / output and optical path conversion in this optical waveguide, it is bonded to an electric wiring board, and these holes are made through the electric wiring board to form an electric mixed board.

The figure which shows an example of the optical waveguide of this invention The figure which shows an example of the identification code | symbol of the optical waveguide of this invention The figure which shows an example of the optical waveguide of this invention The figure which shows an example of the optical waveguide of this invention The figure which shows an example of the optical waveguide of this invention The figure which shows an example of the in-plane optical path conversion in the optical waveguide of this invention The figure which shows an example of the formation method of the light input / output part in the optical waveguide of this invention The figure which shows an example of the formation method of the optical input / output part in the opto-electric hybrid board of this invention The figure which shows an example of 2 branches using the optical waveguide of this invention

Explanation of symbols

1: cladding, 2: core, 4: identification code,
11: Region, 12: Core, 13: Intersection of core, 21: Clad,
22: Core, 31: Hole, 32: Optical input / output unit,
33: hole, 34: optical path, 35: electrical wiring layer,
36: hole, 41: hole, 42: optical path, 43: optical path

Claims (5)

A plurality of cores are arranged in parallel through a clad in at least a part of a plane parallel to the substrate surface, and an identification code for identifying the core is formed in the vicinity of each core. Optical circuit board. The optical circuit board according to claim 1, wherein a plurality of second cores that further intersect with the core are formed in parallel. The optical circuit board according to claim 1, wherein a conductor layer is formed on a surface on which the core is not formed. 4. A core to be guided by the optical circuit substrate according to claim 1 is specified, and a reflecting surface is formed by providing a hole for cutting the core at a position where light to be guided enters or exits the core. The manufacturing method of the optical circuit board characterized by including the process to perform. Reflects detection light focused on a core in a direction across the core on an optical circuit board in which a plurality of cores are arranged in parallel via a clad on at least part of the plane parallel to the board surface. Including a step of identifying a core by counting a change in light or transmitted light intensity, and forming a reflecting surface by providing a hole for cutting the core at a position where light to be guided to or emitted from the identified core is incident An optical circuit board manufacturing method characterized by the above.