JP2010072472A - Photoelectric composite substrate and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric composite substrate that dispenses with the need of making through-holes or the like on the substrate for printed circuit board for the purpose of input/output of light from a core, and that forms an optical waveguide with lamination of two layers of transparent resin. <P>SOLUTION: The photoelectric composite substrate includes a printed circuit board 3 formed by installing an electrical circuit 2 on one side of a transparent substrate 1 which is manufactured by impregnating, with the glass fiber base material, a resin composition adjusted to substantially the same refractive index as a glass fiber base material and by curing it. Also, the photoelectric composite substrate includes an optical waveguide 9 having the transparent substrate 1 as the first cladding CL1 and having a second cladding CL2 that is formed by laminating a transparent resin 4 with a higher refractive index than that of the transparent substrate 1 on the side of the transparent substrate 1 without the electrical circuit 2 arranged, and that is formed, in a place corresponding to the light receiving/emitting face 6 of a light receiving/emitting element 5 mounted by connecting to the electrical circuit 2, by laminating a core CO with a mirror 7 arranged for deflecting an optical path in the direction of the light receiving/emitting face 6 and, over the core CO, a transparent resin 8 with substantially the same refractive index as that of the transparent substrate 1 on the surface of the transparent substrate 1, covering the core CO. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a photoelectric composite substrate provided with an optical waveguide formed of a resin material and an electric circuit, and a method for manufacturing the same.

  In addition to the need for high-speed processing of optical communications represented by the Internet, there is a growing need to adopt high-speed processing and avoid electromagnetic noise by adopting optical transmission in the field of transmitting a large amount of image information within the apparatus. For this purpose, in-device interconnection that transmits light between LSI and IC chips instead of conventional electrical transmission is an important technology. In this field, the optical input / output unit and the light emitting / receiving element of the optical waveguide are not a single mode waveguide having a cross section using wavelengths of 1.3 μm or 1.5 μm or less, which is used in long-distance optical communication, and having a wavelength of 10 μm or less. In order to facilitate alignment, a multimode waveguide having a cross section of 30 to 100 μm is optimal.

  In order to form high-speed transmission in the apparatus, a multimode waveguide is optimal, but low-speed transmission is also necessary, and a power supply circuit is always necessary. For this reason, a photoelectric composite substrate in which an optical waveguide (optical circuit) and an electric circuit are integrated is desired.

  As a photoelectric composite substrate that combines such an optical waveguide and an electric circuit, a printed wiring board provided with an electric circuit is used, and an optical waveguide is formed by laminating a transparent resin as a clad or core on the printed wiring board substrate. The thing which made it do is proposed conventionally (for example, refer patent document 1, patent document 2, etc.).

In such a photoelectric composite substrate, a light receiving and emitting element is mounted on a printed wiring board in a state of being connected to the electric circuit, a through hole is formed in the substrate, and a 45 ° inclined surface is formed in the core. A light transmission / reception element and a mirror are optically coupled through a through hole to form a mirror by processing the above and so on, so that light transmission through an optical waveguide is performed.
International Publication WO01 / 01176 Pamphlet JP 2004-20767 A

  Since the substrate of the printed wiring board generally does not transmit light, the through hole or the like is processed into the substrate as described above, and light is transferred between the light emitting / receiving element and the optical waveguide through the through hole or the like. It is.

  The process of forming a through hole in the printed wiring board substrate must be performed before the optical waveguide is formed in the substrate. If the through hole is opened in the substrate in this way, the surface of the substrate is used for cladding. When the optical waveguide is formed by the build-up method in which the resin and the core resin are sequentially laminated, the formation of the mirror becomes difficult because the optical waveguide is uneven at the through-hole portion. For this reason, the optical waveguide cannot be formed by a build-up method, and a wasteful method of forming the optical waveguide in a separate process and transferring the optical waveguide to the printed wiring board substrate must be employed. It was something that I did not get. If the build-up method is used, the through-holes formed in the printed wiring board substrate are filled with a transparent material or temporarily filled to flatten the surface of the substrate, and then the cladding resin or core is used. Therefore, there is a problem in that the number of man-hours increases.

  Also, when producing an optical waveguide on the surface of a printed wiring board substrate by a build-up method, after laminating a transparent resin as a first cladding on the surface of the substrate, a transparent resin having a higher refractive index than the first cladding is used. A core is formed by stacking on the surface of the first cladding, and a transparent resin having the same refractive index as that of the first cladding is stacked on the surface of the first cladding from above the core to form a second cladding. It was necessary to laminate the transparent resin in three layers.

  The present invention has been made in view of the above points, and it is not necessary to provide a through hole or the like in a printed wiring board substrate, and a photoelectric composite substrate in which an optical waveguide can be formed by laminating two transparent resins. And it aims at providing the manufacturing method.

  The photoelectric composite substrate according to claim 1 of the present invention has an electric circuit on one side of a transparent substrate 1 produced by impregnating and curing a glass fiber substrate with a resin composition adjusted to substantially the same refractive index as that of the glass fiber substrate. A surface of the transparent substrate 1 on which the electric circuit 2 is not provided, with the printed wiring board 3 formed by providing 2 and the transparent substrate 1 as the first cladding CL1 and the transparent resin 4 having a refractive index higher than that of the transparent substrate 1 The light receiving / emitting surface 6 is connected to the electric circuit 2 and corresponds to the light emitting / receiving surface 6 of the light emitting / receiving element 5 mounted on the surface of the transparent substrate 1 provided with the electric circuit 2. A core CO provided with a mirror 7 that deflects in the direction of the substrate and a transparent resin 8 having substantially the same refractive index as that of the transparent substrate 1 are laminated on the surface of the transparent substrate 1 opposite to the surface provided with the electric circuit 2 from above the core CO. Second clad CL formed to cover the core CO It is characterized in that formed by including an optical waveguide 9 having and.

  According to this invention, by using the printed wiring board 3 formed by providing the electric circuit 2 on the transparent substrate 1, the mirror 7 of the core CO and the light emitting / receiving surface 6 of the light emitting / receiving element 5 mounted on the printed wiring board 3. Can be performed through the transparent substrate 1, and there is no need to provide a through hole in the printed wiring board 3 for the optical coupling. When forming the optical waveguide 9 by the build-up method, the transparent substrate 1 of the printed wiring board 3 is used as the first clad CL1, and the transparent resin 4 for the core CO and the transparent resin 8 for the second clad CL2 are laminated. Thus, the optical waveguide 9 can be formed by laminating two layers of transparent resins 4 and 8.

  Further, the present invention is characterized in that the second printed wiring board 10 is laminated on the surface of the second clad CL2 opposite to the printed wiring board 3.

  According to the present invention, the printed wiring boards 3 and 10 can be disposed on both sides of the photoelectric composite substrate, and the electrical transmission path can be increased, and of course, the dimensional stability is improved and the reliability is improved. Is something that can be done.

  Further, the present invention is characterized in that the substrate 11 of the second printed wiring board 10 is a transparent substrate having substantially the same refractive index as that of the second cladding CL2.

  According to the present invention, a part of the second cladding CL2 can be formed by the substrate 11 of the second printed wiring board 10, and the thickness of the second cladding CL2 can be reduced. It is.

  In the present invention, the surface of the printed wiring board 3 on which the electric circuit 2 is formed is covered with the solder resist 12 except for the portion corresponding to the mirror 7 of the core CO and the mounting portion of the light emitting / receiving element 5. It is characterized by this.

  According to the present invention, the surface of the transparent substrate 1 can be covered with the solder resist 12 except for a portion necessary for inputting / outputting light to / from the mirror 7 of the core CO, and light that becomes noise passes through the transparent substrate 1 to the core. It is possible to prevent the generation of noise by preventing CO from entering.

  The method for producing a photoelectric composite substrate according to the present invention comprises an electric circuit 2 on one side of a transparent substrate 1 produced by impregnating and curing a glass fiber substrate with a resin composition adjusted to substantially the same refractive index as that of the glass fiber substrate. Using the printed wiring board 3 formed by providing the transparent substrate 1 as the first clad CL1, the transparent substrate 4 having a refractive index higher than that of the transparent substrate 1 is provided on the surface of the transparent substrate 1 where the electric circuit 2 is not provided. A step corresponding to the light emitting / receiving surface 6 of the light emitting / receiving element 5 that is mounted on the surface of the transparent substrate 1 that is connected to the electric circuit 2 and mounted on the surface provided with the electric circuit 2. , The step of processing the core CO at a position positioned with respect to the electric circuit 2 to form a mirror 7 for deflecting the optical path in the direction of the light receiving and emitting surface, and transparent resin 8 having a refractive index substantially the same as that of the transparent substrate 1 is transparent. Set up the electric circuit 2 of the substrate Surface and laminated on the opposite side from the top of the core from CO, and forming a second cladding covering the core, is characterized in that to form an optical waveguide 9.

  According to this invention, by using the printed wiring board 3 formed by providing the electric circuit 2 on the transparent substrate 1, the mirror 7 of the core CO and the light emitting / receiving surface 6 of the light emitting / receiving element 5 mounted on the printed wiring board 3. Can be performed through the transparent substrate 1, so that it is not necessary to process a through hole in the printed wiring board 3 for the optical coupling, and the transparent substrate 1 of the printed wiring board 3 is eliminated. Is formed as a first clad CL1 by laminating the transparent resin 4 for the core CO and the transparent resin 8 for the second clad CL2 to build up the two layers of the transparent resins 4 and 8, thereby forming the optical waveguide 9 It can be formed. In addition, when the mirror 7 is formed on the core CO, it is possible to align the electric circuit 2 connecting the light emitting / receiving element 5 while looking through the transparent substrate 1, and the mirror 7 can be formed with positional accuracy. It can be done high.

  According to the present invention, by using the printed wiring board 3 formed by providing the electric circuit 2 on the transparent substrate 1, the mirror 7 of the core CO and the light emitting / receiving surface 6 of the light emitting / receiving element 5 mounted on the printed wiring board 3. Can be performed through the transparent substrate 1, and there is no need to provide a through hole in the printed wiring board 3 for the optical coupling. When forming the optical waveguide 8 by the build-up method, the transparent substrate 1 of the printed wiring board 3 is used as the first clad CL1, and the transparent resin 4 for the core CO and the transparent resin 8 for the second clad CL2 are laminated. Thus, the optical waveguide 9 can be formed by laminating the two layers of the transparent resins 4 and 8, and the optical waveguide 9 can be formed with fewer man-hours.

  Hereinafter, the best mode for carrying out the present invention will be described.

  The printed wiring board 3 used in the present invention is formed by providing the electric circuit 2 on one side of the transparent substrate 1.

  And this transparent substrate 1 mixes high refractive index resin with a larger refractive index than glass fiber, and low refractive index resin with a smaller refractive index than glass fiber so that a refractive index may approximate the refractive index of glass fiber. The prepared resin composition can be used by impregnating and curing the resin composition in a glass fiber substrate.

  It is preferable to use a cyanate ester resin as a resin having a higher refractive index than the glass fiber. The cyanate ester resin is obtained by polymerization of a cyanate ester compound having two or more cyanate groups in one molecule by generating a triazine ring by trimerization. Examples of the cyanate ester compound include 2,2-bis ( Aromatic cyanate ester compounds such as 4-cyanatophenyl) propane, bis (3,5-dimethyl-4-cyanatophenyl) methane, 2,2-bis (4-cyanatophenyl) ethane, and derivatives thereof Can be used. These may be used alone or in combination of a plurality of types. This cyanate ester resin has a rigid molecular skeleton, and therefore imparts a high glass transition temperature to the cured product. Further, since cyanate ester resin is solid at normal temperature, it becomes easy to dry by touch when preparing a prepreg by impregnating a resin composition into a glass fiber substrate and drying it as described later. The prepreg is easy to handle.

  Here, when the refractive index of the glass fiber is, for example, 1.56, the cyanate ester resin used as the high refractive index resin preferably has a refractive index of around 1.6. When the refractive index of the glass fiber is n, n + 0 It is desirable that it is in the range of 0.03 to n + 0.06. In the present invention, the refractive index of the resin refers to the refractive index in the state of the cured resin, and is a value tested by ASTM D542.

  On the other hand, as the resin having a lower refractive index than the glass fiber, any epoxy resin can be used as long as it has a low refractive index, but it is preferable to use a hydrogenated bisphenol type epoxy resin. When the refractive index of the glass fiber is 1.56, for example, the low refractive index epoxy resin preferably has a refractive index of around 1.5. When the refractive index of the glass fiber is n, n−0.04 It is desirable to be in the range of ˜n−0.08.

  In the low refractive index hydrogenated bisphenol type epoxy resin, as the bisphenol type, bisphenol F type, bisphenol S type and the like can be used in addition to the bisphenol A type.

  Further, as the hydrogenated bisphenol type epoxy resin having a low refractive index, it is preferable to use a solid type hydrogenated bisphenol type epoxy resin that is solid at room temperature. Liquid type hydrogenated bisphenol type epoxy resin that is liquid at normal temperature can be used, but when preparing a prepreg, it can only be dried to a sticky state with the touch, and the prepreg is easy to handle. Since it becomes worse, it is preferable to use a solid-type hydrogenated bisphenol-type epoxy resin. Furthermore, it is possible to use other than the hydrogenated bisphenol type epoxy resin as the low refractive index epoxy resin. For example, an epoxy resin containing 1,2-epoxy-4- (2-oxiranyl) cyclohexane is used in combination. be able to. This epoxy resin is used together to finely adjust the refractive index, and is an optimal resin for facilitating the molding of the transparent substrate 1 because it is solid at room temperature.

  Then, the above-described high refractive index cyanate ester resin is mixed with an epoxy resin such as a low refractive index hydrogenated bisphenol type epoxy resin to prepare and use a resin composition that approximates the refractive index of glass fiber. is there. The mixing ratio of the high refractive index cyanate ester resin and the low refractive index epoxy resin is arbitrarily adjusted so as to approximate the refractive index of the glass fiber. Here, it is desirable that the refractive index of the resin composition be as close as possible to the refractive index of the glass fiber. However, when the refractive index of the glass fiber is n, the refractive index is adjusted so as to approximate in the range of n−0.02 to n + 0.02. It is preferable to do this.

  The resin composition is preferably prepared such that the cured resin has a glass transition temperature (Tg) of 170 ° C. or higher. When the glass transition temperature is 170 ° C. or higher, the heat resistance of the transparent substrate 1 can be increased. The upper limit of the glass transition temperature is not particularly set, but practically about 280 ° C. is the upper limit of the glass transition temperature. The glass transition temperature can be adjusted by changing the blending ratio of the cyanate ester resin in the resin composition, and depends on the type of low refractive index resin used together. If the cyanate ester resin is about 30% by mass or more in the resin component, the glass transition temperature of the resin composition can be adjusted to 170 ° C. or more. Here, in this invention, a glass transition temperature is the value measured based on JISC6481 TMA method.

  Furthermore, a curing initiator (curing agent) can be blended in the resin composition. An organic metal salt can be used as the curing initiator. Examples of the organic metal salt include salts of organic acids such as octanoic acid, stearic acid, acetylacetonate, naphthenic acid, and salicylic acid with metals such as Zn, Cu, and Fe. These may be used alone or in combination of two or more. Among them, zinc octoate is preferable. By using zinc octoate as the curing initiator, the glass transition temperature of the cured resin can be increased. The content of the organic metal salt such as zinc octoate in the resin composition is not particularly limited, but is preferably in the range of 0.01 to 0.1 PHR.

  A cationic curing agent can also be used as the curing initiator. Thus, by using a cationic curing agent, the transparency of the resin can be enhanced. The cationic curing agent is not particularly limited, and aromatic sulfonium salts, aromatic iodonium salts, ammonium salts, aluminum chelates, boron trifluoride amine complexes, and the like can be used. The content of the cationic curing agent in the resin composition is not particularly limited, but is preferably in the range of 0.2 to 3.0 PHR.

  Further, a curing catalyst such as a tertiary amine such as triethylamine or triethanolamine, 2-ethyl-4-imidazole, 4-methylimidazole, 2-ethyl-4-methyl-imidazole (2E4MZ) may be used as a curing initiator. it can. The content of the curing catalyst in the resin composition is not particularly limited, but is preferably in the range of 0.5 to 5 PHR.

  As described above, a resin composition can be prepared by blending an epoxy resin such as a high refractive index cyanate ester resin, a low refractive index hydrogenated bisphenol type epoxy resin, and a curing initiator. This resin composition is used as a resin varnish after being dissolved or dispersed in a solvent as required. The solvent is not particularly limited, but benzene, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, acetone, methanol, ethanol, isopropyl alcohol, 2-butanol, ethyl acetate, butyl acetate, propylene glycol monomethyl ether, Propylene glycol monomethyl ether acetate, diacetone alcohol, N, N′-dimethylacetamide and the like can be used.

  On the other hand, the glass fiber is preferably E glass or NE glass in view of the effect of increasing the impact resistance of the transparent substrate 1. E glass is also called non-alkali glass and is a glass that is widely used as a glass fiber for resin reinforcement, and NE glass is NewE glass. Moreover, it is preferable to surface-treat glass fiber with the silane coupling agent normally used as a glass fiber processing agent in order to improve impact resistance. The refractive index of the glass fiber is preferably in the range of 1.55 to 1.57, and more preferably in the range of 1.555 to 1.565. If the refractive index of glass fiber is this range, the transparent substrate 1 excellent in visibility can be obtained. As the glass fiber base material, a glass fiber woven fabric or non-woven fabric can be used.

  A prepreg can be prepared by impregnating a glass fiber base material with a varnish of a resin composition, heating and drying. The drying conditions are not particularly limited, but a drying temperature of 100 to 160 ° C. and a drying time of 1 to 10 minutes are preferable.

  Next, one or a plurality of the prepregs are stacked and heated and pressed to cure the resin composition, whereby the transparent substrate 1 can be obtained. The conditions for the heat and pressure molding are not particularly limited, but a temperature range of 150 to 200 ° C., a pressure of 1 to 4 MPa, and a time of 10 to 120 minutes are preferable.

  At this time, the metal-clad transparent substrate 1 can be produced by heating and pressing as described above in a state where a metal foil such as a copper foil is laminated on one side of the prepreg, and is transparent. An electric circuit 2 can be formed by performing printed wiring processing such as exposure and etching on a metal foil laminated on one side of the substrate 1, and the electric circuit is formed on one side of the transparent substrate 1 as shown in FIG. The printed wiring board 3 provided with 2 can be obtained.

  Here, in the transparent substrate 1 produced as described above, a resin matrix formed by polymerizing an epoxy resin such as a high refractive index cyanate ester resin and a low refractive index hydrogenated bisphenol type epoxy resin, By containing cyanate ester resin, the glass transition temperature is high, and the transparent substrate 1 excellent in heat resistance can be obtained. Epoxy resins such as cyanate ester resin and hydrogenated bisphenol type epoxy resin are all excellent in transparency, and a transparent substrate 1 that ensures high transparency can be obtained. In the transparent substrate 1, the content of the glass fiber base material is preferably in the range of 25 to 65% by mass, and within this range, high impact resistance can be obtained due to the reinforcing effect of the glass fiber. Sufficient transparency can be obtained.

  Moreover, as a glass fiber base material, in order to obtain high transparency, it is preferable to use a plurality of thinly laminated ones. Specifically, it is preferable to use a glass fiber substrate having a thickness of 50 μm or less and to use two or more glass fiber substrates having a thickness of 50 μm or less. Although the minimum of the thickness of a glass fiber base material is not specifically limited, About 10 micrometers is a practical minimum. The number of glass fiber substrates is not particularly limited, but about 20 is the practical upper limit. Thus, when manufacturing the transparent substrate 1 using a plurality of glass fiber base materials, each glass fiber base material is impregnated with a resin composition and dried to prepare a prepreg, and a plurality of the prepregs are stacked and heated. The transparent substrate 1 can be obtained by pressure molding, but a prepreg is prepared by impregnating and drying a resin composition in a state where a plurality of glass fiber base materials are stacked, and this prepreg is heated and pressure-molded. The transparent substrate 1 may be obtained.

  The present invention manufactures a photoelectric composite substrate by using a printed wiring board 3 provided with an electric circuit 2 on one side of the transparent substrate 1 as described above. First, the surface of the transparent substrate 1 provided with the electric circuit 2 and The transparent resin 4 is laminated on the opposite surface as shown in FIG. As this transparent resin 4, what has a refractive index higher than the refractive index of the transparent substrate 1 is used, It is preferable that it is resin of the same system as resin which forms the transparent substrate 1. FIG. The laminated thickness of the transparent resin 4 is not particularly limited, but is preferably about 20 to 100 μm. In order to improve the adhesion between the transparent substrate 1 and the transparent resin 4, it is preferable to perform plasma treatment on at least one of them.

  For example, as shown in FIG. 3A, the transparent resin 4 is laminated on the transparent substrate 1 by laminating a layer of the transparent resin 4 on the transfer film 16 and a cover film 17 on the surface of the layer of the transparent resin 4. After the film is used and the transparent resin 4 layer is pasted and transferred to the surface of the transparent substrate 1 with the cover film 17 peeled off, the transfer film 16 is peeled off from the transparent resin 4 layer. . Of course, the present invention is not limited to this, and the transparent resin 4 may be laminated by applying a coating solution of the transparent resin 4 to the surface of the transparent substrate 1 by a coating method such as spin coating or dip coating. .

  Thus, after laminating the transparent resin 4 on one surface of the transparent substrate 1, the transparent resin 4 is processed into a pattern shape as shown in FIG. 2C to form the core CO of the optical waveguide 9. The patterning process is performed by, for example, overlaying a mask with an optical circuit pattern on the surface of the uncured transparent resin 4 and irradiating light such as ultraviolet rays from the mask to make the transparent resin 4 a part of the optical circuit pattern. The transparent resin 4 can be left in the shape of an optical circuit pattern by curing only and dissolving and removing the uncured portion with a developer. As the developer, an organic solvent can be used, and examples thereof include acetone, isopropyl alcohol, toluene, and ethylene glycol. Also, an aqueous developer disclosed in Japanese Patent Application Laid-Open No. 2007-292964 can be used satisfactorily. As a developing method, an arbitrary method such as a method of spraying a developer by spraying or a method using ultrasonic cleaning can be adopted.

  Next, the mirror 7 is formed on the core CO as shown in FIG. The mirror CO is for bending the optical path of the optical waveguide 6 at a right angle so that light is input to and output from the optical waveguide 6. As shown in FIG. 1 to be described later, since the light receiving / emitting element 5 is mounted on the transparent substrate 1 on the opposite side of the printed wiring board 3 where the optical waveguide 6 is provided, The mirror 7 is formed in the core CO at the corresponding position.

  For example, as shown in FIG. 3B, the mirror 7 can be formed by cutting both ends of the core CO at a 45 ° angle with a processing tool 19 such as a dicing or a router. Positioning of the position where the mirror 7 is formed on the core CO can be performed, for example, by providing an alignment mark on the transparent substrate 1 and using this alignment mark as a reference. The 45 ° inclined surface of the mirror 7 is formed so that the inclined outer surface faces the opposite side of the transparent substrate 1. In order to reduce the roughness of the inclined surface processed by the mirror 7, it is preferable to smooth the surface using a laser or to coat a resin having a refractive index close to that of the core CO so as to increase the reflectance. Further, by forming a metal reflection film on this inclined surface of the mirror 7 by vapor deposition or sputtering, the reflection efficiency of the mirror 7 can be further increased. As the metal of the reflective film, gold is most preferable from the viewpoint of reliability, but other metals may be used for use in applications where reliability is not strictly required.

  Here, the light emitting / receiving element 5 mounted on the surface of the transparent substrate 1 of the printed wiring board 3 as shown in FIG. 1 is mounted in a state of being connected to the electric circuit 2 provided on the transparent substrate 1. The position of the circuit 2 and the position of the light emitting / receiving element 5 are relatively determined. Accordingly, the position of the light emitting / receiving element 5 mounted on the transparent substrate 1 can be specified with reference to the pattern of the electric circuit 2, and the pattern of the electric circuit 2 passes through the transparent substrate 1 from the core CO side. It can be visually recognized. Therefore, in the present invention, while the electric circuit 2 is viewed through the transparent substrate 1, the electric circuit 2 is positioned as a reference to position the formation position of the mirror 7 of the core CO, and the mirror 7 is processed into the core CO in this state. Thus, the mirror 7 can be formed on the core CO with high positional accuracy without the need for providing an alignment mark on the transparent substrate 1.

  After the mirror 7 is formed on the core CO as described above, the transparent resin 8 is applied on the surface of the transparent substrate 1 opposite to the surface on which the electric circuit 2 is formed, as shown in FIG. Laminate and cover the core CO with the transparent resin 8. The transparent resin 8 has a refractive index lower than that of the core CO and has substantially the same refractive index as that of the transparent substrate 1, and is preferably the same resin as that forming the transparent substrate 1. As long as is substantially the same as that of the transparent substrate 1, another resin may be used.

  For example, as illustrated in FIG. 3C, the transparent resin 8 is laminated using a laminate film in which a layer of the transparent resin 8 is laminated on the transfer film 16 and a cover film 17 is stretched on the surface of the layer of the transparent resin 8. After the film 17 is peeled off, the layer of the transparent resin 8 is applied to the surface of the transparent substrate 1 from the top of the core CO and transferred, and then the transfer film 16 is peeled off from the layer of the transparent resin 8. . Of course, the present invention is not limited to this, and the transparent resin 8 is laminated by applying a coating solution of the transparent resin 8 on the surface of the transparent substrate 1 from above the core CO by a coating method such as spin coating or dip coating. You may do it.

  Then, by curing the transparent resin 8 by light irradiation, heating, or the like, the transparent substrate 1 of the printed wiring board 3 becomes the first clad CL1, the cured layer of the transparent resin 8 becomes the second clad CL2, and the core CO is formed. An optical waveguide 9 provided between the clads CL1 and CL2 can be formed. As shown in FIG. 1, the electric circuit 2 provided on the printed wiring board 3 and the optical waveguide 9 are integrally provided. The photoelectric composite substrate A can be obtained. On the photoelectric composite substrate A, the light receiving / emitting element 5 including the light emitting element 5a and the light receiving element 5b is mounted on the printed wiring board 3 while being electrically connected to the electric circuit 2.

  Thus, in the photoelectric composite substrate A on which the light emitting / receiving element 5 is mounted, the light emitted from the light emitting surface 6 on the lower surface of the light emitting element 5a is transmitted through the transparent substrate 1 of the printed wiring board 3 and one of the cores CO. The light beam is reflected by the mirror 7 at the end, and the optical path is deflected by the mirror 7 so that it enters the core CO and propagates through the core CO. The light propagated in the core CO is reflected by the mirror 7 at the other end of the core CO, and is emitted from the core CO by changing the optical path again. The light is then transmitted through the transparent substrate 1 and received by the light receiving element. The light is received by the light receiving surface 6b. In this way, the light emitted from the light emitting element 5a propagates through the core CO of the optical waveguide 9 and is received by the light receiving element 5b, whereby information can be transmitted at high speed by optical transmission.

  Here, the printed wiring board 3 is interposed between the light emitting / receiving element 5 and the mirror 7 of the core CO. Since the printed wiring board 3 uses the transparent substrate 1 as a substrate, the light emitting / receiving element 5 and the core CO Light is transmitted to and received from the mirror 7 through the transparent substrate 1, and it is not necessary to provide a through hole in the printed wiring board 3. Can be optically coupled. Since there is no need to provide a through hole in the printed wiring board 3 as described above, the optical waveguide 9 is formed by the build-up method in which the transparent resins 4 and 8 are sequentially laminated on the transparent substrate 1 of the printed wiring board 3 as described above. It will be easy to do.

  The optical waveguide 9 formed as described above is formed by using the transparent substrate 1 of the printed wiring board 3 as the first cladding CL1. Therefore, the optical waveguide 9 can be formed in a two-layer structure in which the transparent resin 4 for forming the core CO and the transparent resin 8 for forming the second cladding CL2 are stacked on the surface of the transparent substrate 1. In other words, the optical waveguide 9 can be formed with less man-hours.

  FIG. 4A shows another embodiment of the present invention, in which a second printed wiring board 10 is laminated on the surface of the second cladding CL opposite to the printed wiring board 3. It is. By laminating the second printed wiring board 10 in this way, the electric circuit 2 of the printed wiring board 3 and the electric circuit 21 provided on the second printed wiring board 10 are placed on both sides of the photoelectric composite substrate A. It can be formed and can increase the number of electrical transmission lines. In addition, by forming the core CO and the second clad CL2 made of resin alone on both sides of the printed wiring boards 3 and 10 reinforced with the glass fiber base material, high-strength photoelectric The composite substrate A can be obtained, and shrinkage and warping when the resin is cured, and dimensional changes due to temperature changes in the use environment can be suppressed, and a highly reliable photoelectric composite substrate A can be obtained. It can be done. By forming the through hole 22 in the photoelectric composite substrate A, the electric circuits 2 and 21 on both sides can be connected through the through hole 22. The through hole 22 can be formed to, for example, 10 μmφ by irradiating an excimer laser. The surface of the through hole 2 is subjected to surface treatment with permanganate desmear and soft etching treatment with a peroxidized water system, followed by panel plating. May be formed.

  As the second printed wiring board 3, an ordinary opaque substrate 11 can be used, and an electric circuit 21 is provided on one surface, both surfaces, or any portion inside the substrate 11. There may be. Further, the second printed wiring board 3 is laminated by laminating a transparent resin 8 as shown in FIG. 2E and curing it to produce a second clad CL2. Then, an adhesive is applied to the surface of the second clad CL. This can be done by attaching the second printed wiring board 3.

  Alternatively, as shown in FIG. 4B, a layer of the transparent resin 8 is laminated on the surface of the substrate 11 of the second printed wiring board 10 and a cover film 17 is stretched on the surface of the layer of the transparent resin 8, In the step of FIG. 2D, after the cover film 17 is peeled off, the layer of the transparent resin 8 is attached to the surface of the transparent substrate 1 from the top of the core CO, and then the second resin is cured. The formation of the clad CL2 and the lamination of the second printed wiring board 10 may be performed simultaneously.

  Further, as the second printed wiring board 10, in addition to the opaque substrate 11, a substrate having a transparent substrate having substantially the same refractive index as that of the second cladding CL 2 may be used. As such a transparent substrate, the same substrate as the transparent substrate 1 of the printed wiring board 3 can be used, but other substrates may be used as long as the refractive index is substantially the same as that of the second cladding CL2. . As described above, when the substrate 11 of the second printed wiring board 10 is a transparent substrate having substantially the same refractive index as that of the second cladding CL2, a part of the second cladding CL2 is formed by the transparent substrate 11. As shown in FIG. 5, the thickness of the second cladding CL2 can be reduced. Therefore, it is possible to reduce the thickness of the photoelectric composite substrate A. In this case, it is desirable that the electric circuit 21 is not provided on the surface of the transparent substrate 11 on the second clad CL2 side.

  In mounting the light emitting / receiving element 5 on the printed wiring board 3 of the photoelectric composite substrate A as described above, the light receiving / emitting element 5 is connected to the electric circuit 2 on the surface of the printed wiring board 3 on which the electric circuit 2 is formed. The soldering process is performed with the solder resist 12 covered and the electric circuit 2 protected with the solder resist 12 except for the places where the other mounting parts are connected by soldering. In the present invention, the electric circuit 2 of the transparent substrate 1 is formed except for the portion corresponding to the mirror 7 of the core CO in addition to the portion where the mounting components such as the light receiving and emitting element 5 are connected to the electric circuit 2 and mounted. The solder resist 12 is coated on the surface. A portion corresponding to the mirror 7 is a portion where light passes between the mirror 7 and the light emitting / receiving surface 6 of the light emitting / receiving element 5. The solder resist 12 is preferably opaque.

As a method of covering the surface of the transparent substrate 1 with the solder resist 12 except for a portion such as a portion corresponding to the mirror 7 or a portion where the light emitting / receiving element 5 is mounted, a portion where the solder resist 12 is applied to the entire surface of the transparent substrate 1 and not covered There is a method in which the exposed portion is cured by masking and the exposed portion is cured, and then developed and the solder resist 12 in the unexposed portion is dissolved and removed. Further, after the solder resist 12 is cured, it may be partially removed by a physical method. For example, a method of partially evaporating the solder resist 12 by laser irradiation, or mechanically removing the solder resist 12. There is a method of cutting. As the laser, an ultraviolet laser typified by an excimer laser of KrF or ArF, or an infrared laser typified by an Nd—YAG or CO ₂ laser can be used. As a method of mechanically cutting, there is a drilling process. In this case, it is necessary to flatten the tip so as to match the pad diameter. Further, it is desirable to control the cutting depth at 1 μm or less so as not to damage the electric circuit 2 as much as possible. In either case, a mechanism that can visually recognize and specify a processing position using a CCD camera or the like, and a mechanism that can process the position specified by NC control or the like with high accuracy are required. The processing position accuracy is generally required to be 10 μm or less in consideration of a positional deviation amount for efficiently inputting / outputting light, but it is preferable that the processing position accuracy is as small as possible.

  By covering the surface of the transparent substrate 1 with the solder resist 12 in this way, the solder resist 12 becomes a shielding film, and the light of the light emitting elements other than the light receiving and emitting elements 5 and other external light are transmitted to the transparent substrate. 1 can be blocked and prevented from leaking into the core CO of the optical waveguide 9. Accordingly, it is possible to prevent external light from entering from the transparent substrate 1 of the printed wiring board 3 and generating noise, and the light can be shielded by using the solder resist 12. Thus, there is no need to use a special member for light shielding.

  Next, the present invention will be specifically described with reference to examples.

Example 1
As a high refractive index resin, 49 parts by mass of a solid type bisphenol type epoxy resin (“Epicoat 1006” manufactured by Japan Epoxy Resin Co., Ltd .: refractive index 1.60) and a liquid type bisphenol F type epoxy resin (DIC Corporation) ) “Epiclon 830S”: refractive index 1.60), 7 parts by mass, low refractive index resin, solid hydrogenated bisphenol A type epoxy resin (“YL7170” manufactured by Japan Epoxy Resins Co., Ltd.): refractive index 1. 50) is mixed with 44 parts by mass, and 1.8 parts by mass of Sb-F6 sulfonium salt (“SI-150L” manufactured by Sanshin Chemical Industry Co., Ltd.) is added as a cationic curing agent. Then, 50 parts by mass of methyl ethyl ketone was added and stirred and dissolved at a temperature of 70 ° C. to prepare a varnish of the epoxy resin composition. Refractive index of the cured product of the resin composition is 1.56, also the glass transition temperature Tg of 110 ° C..

Next, a glass fiber cloth (“3313 type” manufactured by Asahi Sebel Co., Ltd .: fiber diameter 6 μm, mass 80.0 g / m ² , E glass, refractive index 1.562, Abbe number 58) and the above epoxy resin composition A prepreg was prepared by impregnating the varnish of the product and heating at 150 ° C. for 5 minutes to remove the solvent and to semi-cur the epoxy resin.

  Then, a copper foil having a thickness of 18 μm is overlaid on the prepreg, and this is set in a press machine, and heat-pressed under conditions of 170 ° C., 2 MPa, 15 minutes, thereby laminating a copper foil on one side of a thickness of 0.08 mm. A transparent substrate 1 was obtained.

  Next, a photosensitive resist is applied to the surface of the copper foil, and a photomask is aligned and set on the copper foil. Then, exposure is performed by irradiating with ultraviolet rays, and further development is performed to remove the uncured resist. Then, the electric circuit 2 was formed by passing through an etching solution and dissolving the copper foil in a portion not covered with the resist. Thus, the printed wiring board 3 which provided the electric circuit 2 on the single side | surface of the transparent substrate 1 was produced (FIG. 2 (a)).

  On the other hand, 8 parts by mass of an epoxy resin having a 3,4-epoxycyclohexenyl skeleton (“Celoxide 2021P” manufactured by Daicel Chemical Industries, Ltd.) and 1,2-bis-1,2-bis (hydroxymethyl) -1-butanol 12 parts by mass of epoxy resin of epoxy-4- (2-oxanyl) cyclohexane adduct (“EHPE3150” manufactured by Daicel Chemical Industries, Ltd.), solid bisphenol A type epoxy resin (“Epicoat 1006FS” manufactured by Japan Epoxy Resin Co., Ltd.) ), 37 parts by mass of solid trifunctional epoxy resin (“VG-3101” manufactured by Mitsui Chemicals, Inc.), 18 parts by mass of solid novolac epoxy resin (“EPPN201” manufactured by Nippon Kayaku Co., Ltd.) Part, 10 parts by mass of a liquid bisphenol type epoxy resin (“Epiclon 850S” manufactured by DIC Corporation), An epoxy resin is prepared by blending 1 part by mass of a cationic curing initiator (“SL-170” manufactured by Adeka Co., Ltd.), adding 15 parts by mass of toluene and 35 parts by mass of methyl ethyl ketone, and stirring and dissolving at 60 ° C. A varnish of the composition was prepared.

  Then, a PET film (“OX-50” manufactured by Teijin DuPont Co., Ltd.) is used as the transfer film 16, and this resin varnish is applied to the surface of the transfer film 16 using a multi coater (manufactured by Hirano Tech Seed Co., Ltd.). Then, by drying this, a layer of transparent resin 4 made of a solid epoxy resin and having a thickness of 40 μm was formed. The refractive index after curing of the transparent resin 4 was 1.58.

  Next, a pressure type vacuum laminator (Nichigo Morton Co., Ltd. “V-130”) is used on one side of the printed wiring board 3 where the transparent substrate 1 is not provided with the electric circuit 2, and the conditions are 60 ° C. and 0.2 MPa. Then, the transparent resin 4 was laminated (FIG. 2B).

Then, the negative mask formed with slits of a linear pattern with a width of 40 μm and a length of 120 mm is aligned so that the alignment mark provided on the negative mask matches the alignment mark provided when etching the copper foil, and transparent Overlaid on the surface of the resin 4. Next, it exposed by irradiating on the conditions of ³ J / cm < ² > with an ultrahigh pressure mercury lamp, and the transparent resin 4 of the part corresponding to the slit of a negative mask was photocured. Further, after heat treatment at 140 ° C. for 2 minutes, development is performed with an ultrasonic cleaner using an aqueous flux cleaner (“Pine Alpha ST-100SX” manufactured by Arakawa Chemical Industries, Ltd.) adjusted to 55 ° C. as a developer. By processing, the unexposed portion of the transparent resin 4 was dissolved and removed, washed with water and air blown, and then dried at 100 ° C. for 10 minutes. In this way, a core CO made of a cured product of the transparent resin 4 was formed (FIG. 2 (c)).

  Thereafter, positions corresponding to the light emitting / receiving surfaces 6 of the light emitting / receiving elements 5 at both ends of the core CO are positioned with reference to the alignment mark produced by etching the copper foil, and the guided light is inclined at an angle of 90 °. A micromirror 7 to be deflected was formed. That is, a rotating blade (“# 5000” manufactured by DISCO Corporation) with a cutting blade apex angle of 90 ° is used as the processing tool 19 and moves across the core CO under the conditions of a rotational speed of 10000 rpm and a moving speed of 0.1 mm / s. As a result, the V-groove was cut in the core CO to form a 45 ° inclined surface (FIG. 3B).

Next, the resin varnish used for the production of the transparent substrate 1 diluted 50 times with a mixed solvent of toluene: MEK = 3: 7 was applied to the inclined surface of the V groove of the core CO with a brush, and 100 After heating and drying at 30 ° C. for 30 minutes, exposure is further performed by irradiating ultraviolet rays with an ultrahigh pressure mercury lamp at 1 J / cm ² , followed by heat treatment at 120 ° C. for 10 minutes, thereby smoothing the surface of the inclined surface. Was done. Thereafter, gold was deposited by covering a metal mask having an opening in the V-groove, thereby forming a 1000-thick gold thin film on the inclined surface, and the mirror 7 was finished. The interval length between the mirrors 7 of the core CO was set to 10 cm (FIG. 2 (d)).

  On the other hand, the second printed wiring board 10 in which the electric circuit 21 was provided on one side of the transparent substrate 11 was manufactured by the same procedure as that for manufacturing the printed wiring board 3 described above. The material of the transparent substrate 11 is the same as that of the transparent substrate 1 of the printed wiring board 3 described above. Then, the epoxy resin varnish used for manufacturing the transparent substrate 1 of the printed wiring board 3 is applied to the surface of the transparent substrate 11 where the electric circuit 21 is not provided by an automatic bar coater, and dried at 130 ° C. for 30 minutes. As a result, a layer of transparent resin 8 having a thickness of 50 μm was formed.

  Then, a layer of the transparent resin 8 provided on the second printed wiring board 10 is formed on the surface of the printed wiring board 3 on which the core CO of the transparent substrate 1 is formed, from above the core CO, and a pressure type vacuum laminator (Nichigo Morton ( Co., Ltd. “V-130”) was laminated under the conditions of 80 ° C. and 0.2 MPa.

  Then, the transparent resin 8 is cured by heat treatment at 150 ° C. for 60 minutes, the transparent substrate 1 of the printed wiring board 3 becomes the first clad CL1, the cured layer of the transparent resin 8 becomes the second clad CL2, and the core CO Was formed between the clads CL1 and CL2 to produce an optical waveguide 9 to obtain a photoelectric composite substrate A (FIG. 5).

  Next, the surface on which the electric circuit 2 of the transparent substrate 1 of the printed wiring board 3 is formed and the surface of the second printed wiring board 10 on which the electric circuit 21 of the transparent substrate 11 is formed correspond to the mirror 7 of the core CO. The solder resist 12 was covered except for the place and the mounting portion of the light emitting / receiving element 5. That is, first, the solder resist 12 is applied, heated and dried by touching the coating film, then exposed through a photomask except for the portion corresponding to the mirror 7 of the core CO, and developed with a developing solution. The solder resist 12 was dissolved and removed, and further heated to cure the solder resist 12. Next, the solder resist 12 was removed by laser irradiation at a portion where the light emitting / receiving element 5 was mounted on the electric circuit 2.

  The characteristics of the optical waveguide 9 of the photoelectric composite substrate A produced as described above were evaluated. That is, of the mirrors 7 provided at both ends of the core CO, one end is connected to an LED light source having a wavelength of 850 nm on the surface of the transparent substrate 1 of the printed wiring board 3 at a position corresponding to one of the mirrors 7. , The other end of the optical fiber of NA 0.21 is closely contacted via silicone oil matching oil, and one end is connected to the power meter on the surface of the transparent substrate 1 at a position corresponding to the other mirror 7, a core diameter of 200 μm, The other end of the NA0.21 optical fiber was brought into close contact with silicone oil matching oil. Then, the light emitted from the LED light source was incident on the core CO, the light emitted from the core CO was received by a power meter, and the light power (P1) at this time was measured. In addition, the light emitted from the LED light source was directly received by a power meter in a state where the other ends of the respective optical fibers were brought into contact with each other, and the power (P0) of the light at this time was measured. The insertion loss of the optical waveguide 9 was calculated by introducing P1 and P0 measured in this way into the calculation formula of −10 log (P1 / P0), and it was 2.5 dB. It was confirmed to be excellent.

It is sectional drawing which shows an example of embodiment of the photoelectric composite board | substrate of this invention. Each process of manufacture of a photoelectric composite board same as the above is shown, (a)-(e) is sectional drawing, respectively. Each process of manufacture of a photoelectric composite substrate same as the above is shown, (a)-(c) is sectional drawing, respectively. It shows an example of another embodiment of the photoelectric composite substrate of the same, (a) is a cross-sectional view, (b) is a cross-sectional view showing a manufacturing process. It is sectional drawing which shows an example of other embodiment of a photoelectric composite board same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Electric circuit 3 Printed wiring board 4 Transparent resin 5 Light emitting / receiving element 6 Light receiving / emitting surface 7 Mirror 8 Transparent resin 9 Optical waveguide 10 2nd printed wiring board 11 Board | substrate 12 Solder resist

Claims (5)

  A printed wiring board formed by providing an electric circuit on one side of a transparent substrate produced by impregnating and curing a glass fiber substrate with a resin composition adjusted to substantially the same refractive index as that of the glass fiber substrate, and a transparent substrate Is formed by laminating a transparent resin having a refractive index higher than that of the transparent substrate on the surface of the transparent substrate not provided with the electric circuit, and connecting the electric circuit with the electric circuit of the transparent substrate. A core provided with a mirror that deflects the optical path in the direction of the light receiving / emitting surface at a location corresponding to the light receiving / emitting surface of the light emitting / receiving element mounted on the substrate, and a transparent resin having substantially the same refractive index as the transparent substrate An optoelectronic composite substrate comprising: an optical waveguide having a second clad formed on the surface opposite to the surface on which the core is provided and laminated from above the core.   2. The photoelectric composite substrate according to claim 1, wherein a second printed wiring board is laminated on a surface of the second clad opposite to the printed wiring board.   The photoelectric composite substrate according to claim 2, wherein the substrate of the second printed wiring board is a transparent substrate having a refractive index substantially the same as that of the second cladding.   The surface of the printed circuit board on which the electric circuit is formed is covered with a solder resist except for a portion corresponding to the mirror of the core and a mounting portion of the light receiving and emitting element. A photoelectric composite substrate according to any one of the above.   A transparent substrate using a printed wiring board formed by providing an electric circuit on one side of a transparent substrate prepared by impregnating and curing a glass fiber substrate with a resin composition adjusted to substantially the same refractive index as the glass fiber substrate As a first cladding, a transparent resin having a refractive index higher than that of the transparent substrate is laminated on the surface of the transparent substrate on which the electric circuit is not provided, and a patterning process is performed to form a core, and the transparent circuit is connected to the electric circuit. Mirror that processes the core at a position positioned with respect to the electrical circuit at a position corresponding to the light emitting / receiving surface of the light emitting / receiving element mounted on the surface on which the electrical circuit of the substrate is provided, and deflects the optical path in the direction of the light receiving / emitting surface And forming a second clad that covers the core by laminating a transparent resin having substantially the same refractive index as the transparent substrate on the surface of the transparent substrate opposite to the surface on which the electric circuit is provided. From the process to The photoelectric composite substrate manufacturing method characterized by forming an optical waveguide.

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