JP2013137468A - Photoelectric hybrid wiring board and method of manufacturing photoelectric hybrid board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric hybrid wiring board made thinner than conventional ones, and a manufacturing method thereof.SOLUTION: The photoelectric hybrid wiring board includes an insulating substrate 11b like a thin plate and an electric circuit 11a and an optical waveguide 12 which are formed on a first principal surface of the substrate 11b. The optical waveguide has a light input/output part 13a for inputting/outputting an optical signal in a direction of the substrate 11b, in a region where the electric circuit 11a does not exist on the substrate 11b in plan view, and the substrate 11b includes a first via hole 16 for electric connection to the electric circuit 11a from a second principal surface of the substrate 11b and a second via hole 17a for optical connection to the light input/output part 13a from the second principal surface.

Description

  The present invention relates to a photoelectric composite wiring board and a method for manufacturing a photoelectric composite wiring board.

  High-speed transmission is required in the field of medium- and long-distance communication, specifically in the field of FTTH (Fiber To The Home) and in-vehicle, and in order to realize this, an optical fiber cable is used as a transmission medium. Has been.

  High-speed transmission has been demanded even in short-distance communication, for example, communication within 1 m. Also, in the field of such short distance communication, performance that is difficult to achieve with optical fiber cables is also required. Specifically, the required performance includes high-density wiring such as narrow pitch, branching, crossing, and multilayering, surface mountability, integration with an electric circuit board, and a small radius of curvature. For example, it can be bent. As a basis for satisfying these requirements, it is conceivable to use an optical wiring board having an optical waveguide.

  In addition, in such an optical wiring board, a light emitting element such as a vertical cavity surface emitting laser (VCSEL), a light receiving element such as a photodiode (PD), A semiconductor element such as an integrated circuit (IC) is preferably mounted. In order to drive these elements, an electric circuit needs to be provided on the optical wiring board or the like. From this, it is preferable that the photoelectric composite wiring board is provided with not only an optical waveguide but also an electric circuit. Examples of such a photoelectric composite wiring board include a bendable photoelectric composite flexible wiring board. This opto-electric composite flexible wiring board can be used in place of a flexible wiring board disposed across a hinge of a small terminal device, for example, and has attracted attention.

  Examples of such an opto-electric composite flexible wiring board include those described in Non-Patent Document 1.

  Non-Patent Document 1 describes an opto-electric composite flexible wiring board in which an optical waveguide film as an optical wiring layer and an electric flexible wiring board as an electric wiring layer are laminated. This photoelectric composite flexible wiring board is provided with an electric circuit of an electric flexible wiring board so that an electric circuit formed on the electric flexible wiring board can connect a light emitting element such as a VCSEL or a light receiving element such as a PD. An optical waveguide film is laminated on the surface on the non-side.

Toru Nakashiba and two others, “Optical / electric composite flexible wiring board”, Matsushita Electric Works Technical Report, Matsushita Electric Works, Ltd., September 2006, Vol. 54, No. 3, p. 38-43

  According to Non-Patent Document 1, it is disclosed that a highly reliable material having excellent optical characteristics such as insertion loss and little deterioration due to bending can be obtained.

  Moreover, the optoelectric composite wiring board is required to be thin as the equipment to be mounted is miniaturized. The photoelectric composite flexible wiring board described in Non-Patent Document 1 has an electric circuit exposed so that a light emitting element such as a VCSEL or a light receiving element such as a PD can be connected. For this reason, finally, it is necessary to coat this electric circuit with an insulating layer such as a cover film or a resist. Further, in the opto-electric composite flexible wiring board described in Non-Patent Document 1, an electric circuit and an optical waveguide are formed on the opposite side when viewed from the base material of the electric flexible wiring board. For these reasons, it is required to further reduce the thickness of the photoelectric composite wiring board by reducing the number of members other than the member for exhibiting the function of the photoelectric composite wiring board.

  This invention is made | formed in view of this situation, Comprising: It aims at providing the optoelectric composite wiring board thinner than the conventional optoelectric composite wiring board, and its manufacturing method.

  The photoelectric composite wiring board according to one aspect of the present invention includes a thin plate-like insulating base material, an electric circuit formed on the first main surface of the base material, and an optical waveguide. And the said optical waveguide has a light in / out part for making an optical signal go in and out toward the said base material in the area | region where the said electric circuit does not exist on the said base material by planar view. In addition, a first via hole for electrical connection from the second main surface to the electric circuit and a second via hole for optical connection from the second main surface to the light input / output portion are formed in the base material. Has been.

  In the opto-electric composite wiring board, it is preferable that an electronic component is mounted on the second main surface of the base material and is electrically connected to the electric circuit through the first via hole.

  In the opto-electric composite wiring board, the base material is long, and at least a part of the electronic component is an optical element, and corresponds to the second via hole in the second main surface of the base material. It is preferable that the optical element is mounted at a position and is optically connected to the light input / output unit via the second via hole.

  Further, in the photoelectric composite wiring board, the electronic component is sealed on the second main surface side of the base material, and a part of the electric circuit is not sealed and exposed at a peripheral portion of the base material. It is preferable that an external connection terminal is provided.

  In the photoelectric composite wiring board, the base material is preferably a flexible base material.

  According to another aspect of the present invention, there is provided a method for manufacturing an opto-electric composite wiring board, wherein a first cladding layer is formed on a first main surface of a thin plate-like insulating base material on which an electric circuit is formed. A first clad layer forming step, a core portion forming step of forming a core portion on the first clad layer, and a direction of the base material in a region where the electric circuit does not exist on the base material in a plan view. A light input / output portion forming step for forming an optical input / output portion in the core portion for inputting / outputting an optical signal toward the head, and a second cladding layer so as to embed the core portion formed on the first cladding layer. A second clad forming step to be formed; and a via hole forming step of forming a via hole penetrating and opening from the second main surface of the substrate toward the electric circuit and the light output / input section.

  ADVANTAGE OF THE INVENTION According to this invention, the photoelectric composite wiring board thinner than the conventional photoelectric composite wiring board and its manufacturing method are obtained.

It is a schematic sectional drawing which shows the photoelectric composite wiring board which concerns on one Embodiment of this invention. It is the schematic for demonstrating the manufacturing method of the photoelectric composite wiring board which concerns on one Embodiment of this invention. It is the schematic for demonstrating the manufacturing method of the photoelectric composite wiring board which concerns on one Embodiment of this invention. It is the schematic which shows the thin-plate-shaped insulating base material (electric wiring board) in which the electric circuit was formed used with the manufacturing method of the photoelectric composite wiring board which concerns on one Embodiment of this invention. It is the schematic which shows the photomask used with the manufacturing method of the photoelectric composite wiring board which concerns on one Embodiment of this invention. It is the schematic for demonstrating the mounting state of the electronic component to the photoelectric composite wiring board which concerns on one Embodiment of this invention.

  Hereinafter, although the embodiment concerning the present invention is described, the present invention is not limited to these.

  FIG. 1 is a schematic cross-sectional view showing a photoelectric composite wiring board according to an embodiment of the present invention.

  As shown in FIG. 1, an optoelectric composite wiring board 10 according to an embodiment of the present invention first includes a thin plate-like insulating base material 11b, and an electrical circuit is formed on the first main surface of the base material 11b. The electrical wiring board 11 is configured by forming the circuit 11a. On this electric wiring board 11, the optical waveguide 12 is provided so as to be provided side by side with the electric circuit 11a on the same surface side as the electric circuit 11a. The optical waveguide 12 is formed on the surface of the electric wiring board 11 on the electric circuit 11a side. The optical waveguide 12 includes a core portion 13 and a clad layer that covers the core portion 13. As shown in FIG. 1, the clad layer includes a first clad layer 14 and a second clad layer 15. In addition, the optical waveguide 12 includes a light output unit 13a that inputs and outputs an optical signal toward the base material 11b in a region where the electric circuit 11a does not exist on the base material 11b in plan view. Specifically, as shown in FIG. 1, the light output portion 13 a is provided at both ends in the longitudinal direction of the core portion 13 of the optical waveguide 12, and the electric circuit 11 a exists in the thickness direction of the optical waveguide 12. It exists in the area that does not. Examples of the shape of the light output unit 13a include an inclined surface capable of reflecting light as shown in the figure. This inclined surface is designed to reflect the guided light of the core portion 13 so as to go toward the base material 11b. The base 11b is formed with a first via hole 16 for electrical connection from the second main surface to the electric circuit 11a. Further, a second via hole 17 is formed in the base material 11b for optical connection from the second main surface to the light input / output portion 13a.

  In this opto-electric composite wiring board 10, the electric circuit 11a and the optical waveguide 12 are formed on the same surface of the base material 11b, that is, the first main surface, and the via holes 16 and 17 are formed. It can be mounted only on one side of the material 11b, that is, the half facing surface, that is, the second main surface side. That is, the photoelectric composite wiring board 10 has the first via hole 16 for electrical connection to the electric circuit 11a from the second main surface of the base material 11b. 12 can be electrically connected to various electronic components such as an element for inputting and outputting light guided in the light. Furthermore, since the optoelectric composite wiring board 10 has the second via hole 17 for optically connecting to the light input / output part 13a from the second main surface of the base material 11b, the second via hole 17 is used to make the optical An optical signal from an element for inputting / outputting light guided in the waveguide 12 can be input / output. As described above, the photoelectric composite wiring board 10 is configured such that the electric circuit 11a and the optical waveguide 12 are provided on one surface with the base material 11b interposed therebetween, and an electronic component or the like is disposed on one side on the other surface. Therefore, the photoelectric composite wiring board 10 can be thinned.

  Furthermore, when the base material 11b is a flexible base material, the photoelectric composite wiring board 10 can be bent. Since the electric circuit 11a and the optical waveguide 12 are formed on the same side when viewed from the base material 11b of the electric wiring board 11, the electric circuit 11a and the optical waveguide 12 are close to each other, and the photoelectric composite wiring board is bent. In this case, the radius of curvature of the electric circuit 11a and the optical waveguide 12 becomes closer. For this reason, it is possible to suppress the occurrence of deterioration due to bending, such as peeling between the electric circuit 11a and the optical waveguide 12, when the photoelectric composite wiring board is bent. From these things, the structure of this embodiment is useful when the electrical wiring board 11 is a flexible wiring board.

  In the photoelectric composite wiring board 10, an electronic component is mounted on the second main surface of the base material 11 b, and the electronic component is preferably electrically connected to the electric circuit 11 a through the first via hole 16. . In addition, when the first via hole 16 is used to electrically connect various electronic components, balls such as solder and gold are formed in the first via hole 16. Since the first via hole 16 holds the ball, various electronic components are preferably mounted, and a highly reliable product can be obtained.

  Furthermore, the portion of the base material 11b on the first main surface where the electric circuit 11a does not exist often removes the metal when forming the electric circuit 11a. In that case, irregularities are often formed on the surface. For this reason, since the photoelectric composite wiring board 10 forms the optical waveguide 12 on the first main surface of the base material 11b, the base material 11b of the electrical wiring board 11 and the optical waveguide 12 are formed due to the presence of the irregularities. It is thought that the adhesiveness with is excellent.

  Further, at least a part of the electronic components mounted on the photoelectric composite wiring board 10 is an optical element, and the optical element is mounted at a position corresponding to the second via hole 17 on the second main surface of the substrate 11b. In addition, it is preferable that the light input / output part 13 a is optically connected through the second via hole 17.

  Moreover, the photoelectric composite wiring board 10 is long as shown in FIG. That is, the base material 11b has a long shape. And an electronic component is sealed in the 2nd main surface side of the base material 11b. And it is preferable that a part of electric circuit 11a is exposed to the peripheral part of the base material 11b without being sealed. As described above, the electrical circuit 11a can be provided with an external connection terminal that can be electrically connected to an electrical circuit other than the photoelectric composite wiring board 10 by exposure, thereby facilitating external connection.

  The light input / output part 13a of the core part 13 guides light incident from the outside of the photoelectric composite wiring board 10 into the core part 13 or guides light guided through the core part 13 into the photoelectric composite wiring board. 10 is an inclined surface leading out to the outside. Examples of such an inclined surface include an inclined surface having an angle of 45 ° with the surface direction of the photoelectric composite wiring board 10. And in order to raise the reflectance of light on the inclined surface, as shown in FIG. 1, you may use the thing provided with the metal layer 18 as the light in / out part 18. Further, in the photoelectric composite wiring board 10, for example, as indicated by the arrow direction in FIG. Then, the light is reflected by the light entrance / exit part 13 a and emitted to the outside of the photoelectric composite wiring board 10.

  Next, the manufacturing method of the optoelectric composite wiring board according to the present embodiment will be described with reference to FIGS. 2 and 3 are schematic views for explaining the method for manufacturing the photoelectric composite wiring board according to the present embodiment.

  First, as shown to Fig.2 (a), the base material 11b (electrical wiring board 11) in which the electric circuit 11a was formed is prepared.

  Next, as shown in FIG. 2 (b), the second main surface of the substrate 11b (the surface on the side opposite to the surface on which the electric circuit 11a is formed) is temporarily attached via the adhesive layer 21. The substrate 22 is stacked. The temporary substrate 22 is not particularly limited as long as it is peeled off after the optical waveguide 12 is formed or the like and is not damaged and cannot maintain its shape in each step. The adhesive layer 21 is not particularly limited as long as the electrical wiring board 11 and the temporary substrate 22 can be bonded. Specifically, for example, a double-sided pressure-sensitive adhesive tape can be used.

  Next, as shown in FIG. 2C, the first cladding layer 14 is formed on the first main surface of the base material 11b (the surface on the side where the electric circuit 11a is formed). This step corresponds to the first cladding layer forming step.

  The method for forming the first cladding layer 14 is not particularly limited as long as the first cladding layer 14 can be formed on the first main surface of the substrate 11b. Specifically, the following method is mentioned, for example. As a first example, a resin film made of a curable resin material having a predetermined refractive index for forming the first cladding layer 14 is bonded onto the first main surface of the substrate 11b, and then cured. A method is mentioned. As a second example, there is a method in which a liquid curable resin material for forming the first cladding layer 14 is applied and then cured. As a third example, there is a method in which a varnish of a curable resin material for forming the first cladding layer 14 is applied and then cured. In addition, when forming the 1st clad layer 14, in order to improve adhesiveness, it is preferable to perform the plasma processing etc. previously on the surface of the base material 11b, especially the 1st main surface.

  In addition, as a specific method for curing the resin film after bonding the resin film to form the first cladding layer 14, for example, the following method is used. First, a resin film made of a curable resin is placed on the first main surface of the substrate 11b so as to be stacked, and then bonded by a hot press, or from a curable resin on the first main surface of the substrate 11b. The resulting resin film is bonded with a transparent adhesive. And it hardens | cures by irradiating energy rays, such as light, to the bonded resin film, or heating.

  Moreover, as a more specific method of curing after applying a liquid curable resin material or a varnish of the curable resin material for forming the first cladding layer 14, for example, the following method Is used. First, a liquid curable resin material or a varnish of a curable resin material is applied onto the first main surface of the substrate 11b by using a spin coating method, a bar coating method, a dip coating method, or the like. Then, the applied liquid curable resin material or the varnish of the curable resin material is irradiated with energy rays such as light or is cured by heating.

  As the curable resin material for forming the first cladding layer 14, a material having a lower refractive index at the transmission wavelength of the guided light than the material of the core portion 13 to be formed later is used. Specifically, the refractive index at the transmission wavelength is, for example, about 1.5 to 1.55. Examples of such curable resin materials include epoxy resins, acrylic resins, polycarbonate resins, polyimide resins, and the like having such a refractive index.

  The curable resin material used when forming the first cladding layer 14 is not particularly limited as long as it can be used as a cladding layer that satisfies the above-described refractive index after curing. Specifically, for example, as described above, those that are cured by energy rays such as light or heat can be used. More specifically, a photosensitive material etc. are mentioned, for example. The resin film made of the curable resin material is specifically a dry film obtained by applying a semi-cured photosensitive polymer material to a polyethylene terephthalate (PET) film or the like, for example, a so-called dry film. Examples thereof include a photoresist (also simply referred to as “photosensitive film”).

  The thickness of the first cladding layer 14 is not particularly limited. Specifically, it is preferable that it is about 5-15 micrometers, for example.

  Next, as shown in FIG. 2D, the core portion 13 is formed on the first cladding layer 14. This step corresponds to the core portion forming step.

  At that time, first, a core material layer made of a photosensitive material is formed on the outer surface of the formed first cladding layer 14.

  Here, the photosensitive material is a material in which the solubility of a portion irradiated with energy rays with respect to a liquid used in development described later changes. Specifically, for example, a material that is difficult to dissolve in a liquid used in development described later before irradiation with energy rays, but is easily dissolved after irradiation with energy rays can be used. As another example, there is a material that easily dissolves in a liquid used in development described later before irradiation with energy rays, but is difficult to dissolve after irradiation with energy rays. Specific examples of the photosensitive material include a photosensitive polymer material. The energy beam is not particularly limited as long as the solubility can be changed. Specifically, ultraviolet rays are preferably used from the viewpoint of ease of handling. As the photosensitive material, generally, a photosensitive polymer material whose solubility changes in a portion irradiated with ultraviolet rays is preferably used. More specifically, a photosensitive polymer material that is hard to dissolve in a liquid used in development described later is preferably used by curing the portion irradiated with ultraviolet rays.

  The method for forming the core material layer is not particularly limited as long as the core material layer can be formed. Specifically, the following method is mentioned, for example. As a first example, there is a method in which a resin film (photosensitive film) made of a photosensitive polymer material having a predetermined refractive index for forming a core material layer is bonded to the outer surface of the first cladding layer 14. Can be mentioned. As a second example, there is a method of applying a liquid photosensitive polymer material for forming a core material layer. As a third example, there is a method in which a varnish of a photosensitive polymer material for forming a core material layer is applied and then dried. In addition, when forming the core material layer, it is preferable to perform a plasma treatment or the like in advance in order to activate the outer surface of the first cladding layer 14 and improve the adhesion.

  As a more specific method of bonding the resin film to form the core material layer, for example, the following method is used. After placing the resin film made of a curable resin on the outer surface of the first cladding layer 14, the first clad layer 14 is bonded by a hot press.

  Moreover, as a more specific method of applying the liquid curable resin material for forming the core material layer or the varnish of the curable resin material, for example, the following method is used. A liquid curable resin material or a curable resin material varnish is applied to the outer surface of the first cladding layer 14 by using a spin coating method, a bar coating method, a dip coating method, or the like, and then dried as necessary. Let

  Examples of the resin film (photosensitive film) made of a photosensitive polymer material include a dry film obtained by applying a semi-cured photosensitive polymer material to a polyethylene terephthalate (PET) film or the like. Such a dry film is usually protected by a protective film.

  As the photosensitive polymer material for forming the core material layer, a material having a higher refractive index at the transmission wavelength of the guided light than the material of the first cladding layer 14 is used. Specifically, the refractive index at the transmission wavelength is, for example, about 1.55 to 1.6. As a kind of photosensitive polymer material for forming the core material layer, a photosensitive material having such a refractive index and having an epoxy resin, an acrylic resin, a polycarbonate resin, a polyimide resin, or the like as a resin component Is mentioned. Among these, bisphenol type epoxy resins are particularly preferable. Therefore, as a photosensitive polymer material for forming the core material layer, a resin composition containing a bisphenol-type epoxy resin and a photocationic curing agent can provide a highly heat-resistant waveguide. It is preferable because it can be combined with the above. From the viewpoint of adhesion between the core material layer and the first cladding layer 14, the photosensitive polymer material for forming the core material layer is the same as the curable resin material for forming the first cladding layer 14. It is preferable that it is a system | strain.

  The thickness of the core material layer is not particularly limited. Specifically, it is preferable that it is about 20-100 micrometers, for example.

  Before the core material layer is exposed and cured, the core material layer may be heat treated. By doing so, the irregularities, bubbles, voids, etc. on the surface of the core material layer disappear and become smooth. The heat treatment temperature is preferably a temperature at which the unevenness, bubbles, voids and the like on the surface of the core material layer disappear and become smooth, and is appropriately selected depending on the type of the curable resin material forming the core material layer. Further, the heat treatment time is preferably about 10 to 30 minutes from the viewpoint of sufficiently obtaining the effect of eliminating the irregularities, bubbles, voids and the like on the surface of the core material layer and smoothing. The means for heat treatment is not particularly limited, and a method such as a method of treating in an oven set at a predetermined temperature or a method of heating with a hot plate is used.

  Next, the core material layer is irradiated with exposure light through a photomask to perform pattern exposure of a predetermined shape on the core material layer. Examples of the photomask include those in which slits corresponding to the shape of the core portion are arranged, and specifically, those shown in FIG. Moreover, such exposure can be used without any limitation as long as it is a method of exposing light having a wavelength that can change (harden, etc.) the photosensitive material with light with a necessary amount of light. Specifically, for example, a method using energy rays such as ultraviolet rays can be used as the exposure light used here. In view of ease of handling, ultraviolet rays are preferably used. Also, contact exposure in which a photomask is placed so as to be in contact with the surface of the core material layer and exposure, projection type exposure in which exposure is performed while maintaining a predetermined distance so as not to contact the outer surface of the core material layer Any of these exposure methods may be used.

The exposure conditions are appropriately selected according to the type of the photosensitive material. For example, conditions for exposure using an ultrahigh pressure mercury lamp to 500 to 3500 mJ / cm ² are selected.

  And after performing such exposure, post-curing with heat is also effective from the viewpoint of ensuring curing. As post-curing conditions, a temperature of about 80 to 160 ° C. and a time of about 20 to 120 minutes are preferable. However, it is not particularly limited to this range, and it is needless to say that optimization by the photosensitive material is important.

  Next, the core part 13 as shown in FIG.2 (d) is formed by performing a development process.

  As a development process for forming the core portion 13, when the photosensitive material of the core material layer is a positive type, the unexposed portion is washed away. When the negative photosensitive type is used, the exposed portion is washed away with a developer. This is a step of removing unnecessary portions. Examples of the developer used here include acetone, isopropyl alcohol, toluene, ethylene glycol, or a mixture of these in a predetermined ratio. Further, for example, an aqueous developer as disclosed in JP-A-2007-292964 can be preferably used. Examples of the developing method include a method of spraying a developer by spraying and a method using ultrasonic cleaning.

  Next, as shown in FIG. 2 (e), a light entrance / exit portion 13 a for reflecting light is formed in the core portion 13. This process corresponds to a light input / output part forming process. The method is not particularly limited as long as the inclined surface as described above can be formed. Specific methods for forming the inclined surface include, for example, a method of cutting with a dicing blade, a method by laser ablation, and the like. More specifically, for example, one surface of the blade edge is a surface parallel to the surface direction of the blade, and the other surface is a surface whose angle with respect to the surface direction of the blade is a predetermined angle, for example, 45 °. The method etc. which cut the core part 13 using a blade are mentioned. The blade is a disc-shaped rotary blade having a cutting edge at the circumferential portion, such as a dicing blade.

  When cutting the core portion 13 with a blade, the core portion 13 may be cut while being softened by heating the electrical wiring board 11 or the blade, if necessary. Further, the cutting edge of the blade may be cut so as to reach the first cladding layer 14 or may be cut so as not to reach it.

  Next, as shown in FIG. 2 (f), it is preferable to form a metal layer 18 on the light input / output portion 13a formed as described above. As described above, the metal layer 18 may not be provided, but is preferably provided in order to increase the reflectance of light. It does not specifically limit as a method of forming a metal layer, A well-known method can be used. Specifically, for example, a vapor deposition method such as a vacuum vapor deposition method, a sputtering method, a nano paste method, and the like can be given.

  The thickness of the metal layer 18 is not particularly limited as long as it can reflect light, and examples thereof include a thickness of about 1000 mm.

  Next, as shown in FIG. 2 (g), the second cladding layer 15 is formed so as to embed the core part 13 formed as described above, thereby covering the core part 13 and the core part. 14 and 15 are formed. This step corresponds to a second cladding layer forming step.

  A method for forming the second cladding layer 15 is not particularly limited. Specific examples include the following methods. As a first example, there is a method in which a liquid curable resin material for forming the second cladding layer 15 is applied so as to embed the core portion 13 and then cured by energy rays such as light, heat, or the like. Can be mentioned. As a second method, there is a method in which a varnish of a curable resin material for forming the second cladding layer 15 is applied and then cured by energy rays such as light, heat or the like. As a third example, there is a method in which a resin film made of a curable resin material for forming the second cladding layer 15 is bonded and then cured by energy rays such as light, heat or the like.

  The curable resin material for forming the second cladding layer 15 is not particularly limited as long as it is a curable resin material having a lower refractive index at the transmission wavelength of the guided light than the material of the core portion 13. Usually, the same kind of curable resin material as that used to form the first cladding layer 14 is used.

  Further, the thickness of the second cladding layer 15 is not particularly limited, but it is preferable that the second cladding layer 15 has the same thickness as the first cladding layer 14 on the core portion 13.

  The formed optical waveguide is formed by the core portion 13 and the cladding layers (the first cladding layer 14 and the second cladding layer 15) covering the core portion 13, and the core portion 13 includes the first cladding layer 14 and The refractive index is higher than that of the second cladding layer 15, and light propagating inside is confined in the core by total reflection. Such an optical waveguide is mainly formed as a multimode waveguide. The size of the core portion 13 of the optical waveguide is, for example, a rectangular shape of 20 to 100 μm, and the thickness of the lower first cladding layer 14 and the upper second cladding layer 15 excluding the thickness of the layer including the core portion is 5 to 5, respectively. The refractive index difference between the core part and the cladding layer is suitably about 0.5 to 3%, but is not limited to this.

  Next, as shown in FIG. 3A, an insulating layer 23 such as a coverlay layer may be laminated on the second cladding layer 15. By forming the insulating layer 23, the optical waveguide can be protected. Specifically, a method of laminating a coverlay layer having an adhesive layer after performing an oxygen plasma treatment on the second clad layer 15 is exemplified. As the insulating layer 23, a material generally used as a coverlay layer can be used without limitation.

  Next, as shown in FIG. 3B, the temporary substrate 42 is peeled off, and the adhesive layer 41 is also removed together with the temporary substrate 42. Then, via holes such as the first via hole 16 and the second via hole 17 as described above are formed in the base material 11b. Specifically, the first via hole 16 penetrating the base material 11b is formed from the second main surface of the base material 11b toward the electric circuit 11a. Moreover, the 2nd via hole 17 which penetrates the base material 11b is formed toward the light entrance / exit part 13a from the 2nd main surface of the base material 11b. This process corresponds to a via hole forming process. By doing so, the photoelectric composite wiring board 10 shown in FIG. 1 can be manufactured.

  The method for forming these via holes is not particularly limited as long as a predetermined via hole can be formed. Specifically, drilling by irradiating with a laser can be mentioned.

  Next, as shown in FIG. 3C, various electronic components such as a light emitting element 24, a light receiving element 25, and a semiconductor element 26 are mounted on the obtained photoelectric composite wiring board 10. Specifically, a ball 27 such as solder or gold is formed in the first via hole 16, and the light emitting element 24 and the light receiving element 25 are mounted through the ball 27. Thereafter, the space between the light emitting element 24 or the light receiving element 25 and the electric wiring board 11 may be sealed with the underfill material 28. Further, the semiconductor element 26 may be connected by bonding via the wire 29, that is, wire bonding.

  Finally, as shown in FIG. 3 (d), a region other than the region where the electric circuit 11a is exposed at the end in the longitudinal direction of the electric wiring board 11 is sealed with the sealing resin 31. Is preferred. That is, it is preferable that various electronic components such as the light emitting element 24, the light receiving element 25, and the semiconductor element 26 are sealed with the sealing resin 31 and the region where the electric circuit 11a is exposed is not sealed. And by providing the connector 32 in the area | region where the electric circuit 11a is exposed, it can electrically connect with electric circuits other than the electric circuit of a photoelectric composite wiring board.

  Next, the electric wiring board 11 shown in FIG. FIG. 4 is a schematic view showing a base material 11b (electric wiring board 11) on which an electric circuit 11a is formed, which is used in the method for manufacturing an opto-electric composite wiring board according to the present embodiment. The electric wiring board 11 is a wiring board in which an electric circuit 11a as shown in FIG. 4 is formed on a base material 11b. FIG. 4A is a schematic view showing the electrical wiring board 11 as viewed from the side where the optical waveguide 12 is not formed, that is, a top view. FIG. 4B is a schematic cross-sectional view of the electrical wiring board 11 shown in FIG. FIG. 4C is a schematic view showing the electrical wiring board 11 viewed from the side on which the optical waveguide 12 is formed, that is, a bottom view. In practice, the optical waveguide 12 is formed using a plurality of electrical wiring boards 11 connected as shown in FIG. Therefore, the electrical wiring board 11 shown in FIG. 4 is a part corresponding to the electrical wiring board 11 of the photoelectric composite wiring board obtained by the above manufacturing method.

  Moreover, the photomask used at the core part formation process of the manufacturing method of the optoelectric composite wiring board according to the present embodiment is, for example, a photomask as shown in FIG. FIG. 5 is a schematic view showing an example of a photomask used in the method for manufacturing an optoelectric composite wiring board. The photomask 51 includes a plurality of linear slits 52 corresponding to the shape of the core portion 13. As the photomask 51, for example, 20 linear slits 52 arranged at a pitch of 4 mm may be used. Further, the photomask 51 may include a mirror alignment mark 53, a waveguide alignment mark 54, and the like for alignment.

  FIG. 6 is a schematic diagram for explaining a mounting state of the electronic component on the photoelectric composite wiring board. 6A to 6C are views seen from the electric wiring board 11 side of the photoelectric composite wiring board shown in FIGS. 3B to 3D.

  As shown in FIG. 6A, a first via hole 16 and a second via hole 17 are provided outside the electric wiring board 11. The electrical circuit 11a is exposed at the end of the electrical wiring board 11 in the longitudinal direction.

  Further, when elements such as the light emitting element 24, the light receiving element 25, and the semiconductor element 26 are mounted on such a photoelectric composite wiring board, for example, the state shown in FIG. 6B is obtained.

  Furthermore, when these elements are covered with the sealing resin 31, for example, a state as shown in FIG. As described above, various electronic components such as the light emitting element 24, the light receiving element 25, and the semiconductor element 26 are sealed with the sealing resin 31, and the region where the electric circuit 11a is exposed is not sealed. It can be electrically connected to an electric circuit other than the electric circuit of the composite wiring board.

DESCRIPTION OF SYMBOLS 10 Opto-electric composite wiring board 11 Electric wiring board 11a Electric circuit 11b Base material 12 Optical waveguide 13 Core part 13a Light entrance / exit part 14 1st cladding layer 15 2nd cladding layer 16 1st via hole 17 2nd via hole 18 Metal layer

Claims (6)

A thin plate-like insulating substrate, an electric circuit formed on the first main surface of the substrate, and an optical waveguide,
The optical waveguide has a light input / output portion for allowing an optical signal to enter and exit toward the base material in a region where the electric circuit does not exist on the base material in a plan view,
A first via hole for electrically connecting the second main surface to the electric circuit and a second via hole for optical connection from the second main surface to the light input / output portion are formed in the base material. A photoelectric composite wiring board characterized by comprising:   The photoelectric composite wiring board according to claim 1, wherein an electronic component is mounted on the second main surface of the base material and is electrically connected to the electric circuit through the first via hole. The base material is elongated,
At least a part of the electronic component is an optical element, the optical element is mounted at a position corresponding to the second via hole in the second main surface of the base material, and light is input to the light input / output portion via the second via hole. The photoelectric composite wiring board according to claim 2, which is connected.   The electronic component is sealed on the second main surface side of the base material, and a peripheral portion of the base material is provided with an external connection terminal exposed without being partly sealed of the electric circuit. Item 4. The photoelectric composite wiring board according to Item 2 or 3.   The photoelectric composite wiring board according to claim 1, wherein the substrate is a flexible substrate. A first clad layer forming step of forming a first clad layer on the first main surface of the thin plate-like insulating base material on which the electric circuit is formed;
A core part forming step of forming a core part on the first cladding layer;
In a region where the electric circuit does not exist on the base material in a plan view, a light input / output portion forming step for forming a light input / output portion in the core portion for inputting / outputting an optical signal toward the base material, and
A second cladding forming step of forming a second cladding layer so as to bury the core portion formed on the first cladding layer;
A via hole forming step of forming a via hole penetrating and opening from the second main surface of the base material toward the electric circuit and the light input / output portion;
A method for manufacturing an opto-electric composite wiring board.

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