JP4240659B2 - Optical / electrical wiring board, manufacturing method, and mounting board - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical / electrical wiring board in which optical wiring and electrical wiring are mixed, a method for manufacturing the same, and a mounting board in which optical components and electrical components are mounted on the substrate.
[0002]
[Prior art]
In order to make a computer that can perform arithmetic processing faster, the clock frequency of the CPU tends to increase more and more, and about 1 GHz now appears. As a result, there are parts where high-frequency signals flow in the electrical wiring of copper on the printed circuit board in the computer, so malfunctions may occur due to the generation of noise, and electromagnetic waves may be generated, affecting the surroundings. It will also give.
[0003]
In order to solve such a problem, a part of the copper electrical wiring on the printed circuit board is replaced with an optical fiber or optical waveguide optical wiring, and an optical signal is used instead of the electrical signal. This is because the generation of noise and electromagnetic waves can be suppressed in the case of optical signals.
[0004]
From the viewpoint of high-density mounting or miniaturization, it is desirable to produce an optical / electrical wiring board in which electrical wiring and optical wiring are stacked on the same substrate. When mounting an optical component such as a light-emitting element or a light-receiving element, it is difficult to optically match the optical axis of the optical component and the optical axis of the optical wiring. In general, the optical components cannot be matched without relying on skilled workers. Therefore, compared with an electrical component that can be automatically soldered in a reflow furnace or the like, mounting an optical component on an optical / electrical wiring board has a drawback of becoming very expensive.
[0005]
[Problems to be solved by the invention]
The present invention has been made in view of the drawbacks of the related art, and provides an optical / electrical wiring board that can be mounted at a high density or miniaturized, and that optical components can be mounted in the same manner as electrical components. Is an issue.
[0006]
[Means for Solving the Problems]
In order to achieve the above object in the present invention, first, in the invention of claim 1, an optical / electrical device comprising an optical wiring layer having an optical fiber for propagating an optical signal as an optical wiring on a substrate having electric wiring. A wiring board, an optical wiring layer in which the optical fiber is embedded in a resin layer, a mirror provided in a part of the optical fiber, and an optical wiring layer penetrating through one end face of the wiring. A conductive protrusion for fixing an optical fiber, which is installed on the substrate, penetrates the optical wiring layer, one end face is connected to the electrical wiring, and the other end face is used to make an electrical connection with the optical component. An optical / electrical wiring board comprising a conductive protrusion.
[0007]
Further, the invention of claim 2 is based on the invention of claim 1 and penetrates the optical wiring layer, one end face is connected to the electric wiring, and the other end face is a conductive material for making an electrical connection with the electric component. And an optical / electrical wiring board characterized in that the optical / electrical wiring board is provided.
[0008]
According to a third aspect of the present invention, there is provided an optical / electrical wiring board comprising the electric wiring provided on the optical wiring layer on the premise of the inventions of the first and second aspects. .
[0009]
According to a fourth aspect of the present invention, there is provided an optical / electrical wiring board characterized in that the refractive index of the resin constituting the optical wiring layer is equal to the refractive index of the cladding layer of the optical fiber.
[0010]
According to a fifth aspect of the present invention, there is provided a method of manufacturing an optical / electrical wiring board comprising an optical wiring layer having an optical fiber for propagating an optical signal as an optical wiring on a substrate having electric wiring, A step of forming a conductive protrusion on a predetermined electric wiring of a substrate having a step, a step of fixing an optical fiber to the conductive protrusion for fixing an optical fiber, a step of forming a resin layer and embedding the optical fiber; A step of exposing the upper surface of the conductive protrusion, a step of forming an electrical wiring on the optical wiring layer, and a step of forming a mirror by perforation at a predetermined position of the optical wiring layer. This is a method for manufacturing an optical / electrical wiring board.
[0011]
According to a sixth aspect of the present invention, there is provided a mounting substrate comprising an optical component and / or an electric component mounted on the optical / electrical wiring substrate according to any one of the first to third aspects.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
1. Optical / Electrical Wiring Board FIG. 1 is a plan view of a portion on which an optical component is mounted in the optical / electrical wiring board of the present invention, and FIG.
[0013]
The optical / electrical wiring board of the present invention has a structure in which an optical wiring layer 9 is laminated on a substrate 8 provided with electrical wirings 10, 11, 12, and 13. The substrate 8 may be a single-layer insulating substrate or a multilayer wiring substrate in which electrical wiring and insulating layers are alternately stacked. The constituent material may be an insulating substrate obtained by impregnating a glass cloth with a resin, a polyimide film, or a ceramic substrate.
[0014]
In the optical wiring layer 9, an optical fiber 1 is embedded in the resin layer 3 as an optical wiring for propagating an optical signal. The optical fiber 1 includes a core layer 1b through which an optical signal propagates and a cladding layer 1a that confines the optical signal in the core layer. The optical fiber 1 is fixed between the conductive protrusions 2. Since the conductive protrusion 2 is formed by a photolithography technique and a plating technique, the position of the core layer of the optical fiber can be determined by an alignment mark (not shown) formed on the substrate 8.
[0015]
Further, the conductive protrusion 2 is placed on the conductor layers 14 and 15 formed on the substrate 8 in advance. This conductor layer is preferably independent of the electrical wiring on the substrate 8.
[0016]
The characteristics of the resin forming the resin layer 3 are preferably those having a high glass transition temperature Tg, a high insulation resistance and a low coefficient of thermal expansion, and in addition, those having the same refractive index as that of the cladding layer of the optical fiber. is there. Examples of the film forming method include thermosetting and photocuring. For example, polyimide resin or epoxy resin can be used.
[0017]
The optical fiber is formed with a mirror 16 that reflects the laser light, which is an optical signal, and changes the propagation direction to 90 °. This mirror inserts an optical signal emitted from the laser light emitting element mounted on the optical / electrical wiring board of the present invention in the vertical direction toward the substrate into an optical fiber arranged in parallel with the substrate surface. The optical signal that has propagated through the optical fiber plays a role to change the propagation direction of the optical signal vertically toward the light receiving element installed on the optical / electrical wiring board of the present invention. A surface forming 45 ° is formed. This mirror can be formed by drilling using an etching method based on a metal mask formed by photolithography on the optical wiring layer, or by drilling by laser, so that the position is the alignment formed on the substrate 8. It can be determined by a mark (not shown).
[0018]
In the periphery of the mirror 16, conductive protrusions 4, 5, 6, 7 for making electrical connection with optical components such as a laser light emitting element and a light receiving element are embedded in the optical wiring layer and formed on the substrate 9. Are connected to the electrical wirings 10, 11, 12, and 13. In addition, optical components are soldered directly to the upper surface portions 4a, 5a, 6a, and 7a. If necessary, surface treatment such as Ni / Au plating may be performed on the surfaces of the upper surface portions 4a, 5a, 6a, and 7a. On the other hand, an electrical component such as an IC is also electrically connected via an electrical wiring on the substrate 8 and a conductive protrusion. Since this conductive protrusion is also formed by photolithography and plating techniques, the position thereof can be determined by an alignment mark (not shown) formed on the substrate 8, and the above-described conductive for fixing an optical fiber. Can be formed simultaneously with the sexual protrusion.
[0019]
FIG. 3 is a cross-sectional view when the lead 24 of the laser light emitting element 22 such as a semiconductor laser is soldered on the upper surfaces 4a, 5a, 6a and 7a of the conductive protrusions. The laser light 21 emitted from the laser light emitting surface 23 of the laser light emitting element 22 is reflected by the mirror 16 and propagates through the optical fiber 1.
[0020]
FIG. 4 is a cross-sectional view when the lead 34 of the light receiving element 32 such as a photodiode is soldered on the upper surface portions 4a, 5a, 6a, and 7a of the conductive protrusions. The laser beam 31 propagating through the optical fiber 1 is reflected by the mirror 16 and enters the light receiving surface 33 of the light receiving element 32.
[0021]
As already described, the mutual positional relationship between the core layer 1b in the optical fiber 1, the conductive protrusion upper surface portions 4a, 5a, 6a, and 7a for mounting the optical components, and the mirror 16 is as follows. Since it matches the intended one with extremely high accuracy, the optical axis of the core layer 1b of the optical fiber 1 is optically aligned when the lead of the optical component is placed on the conductive protrusion upper surface portions 4a, 5a, 6a, 7a. To match. Therefore, the optical component can be automatically soldered in a reflow furnace or the like.
[0022]
On the optical wiring layer of the optical / electrical wiring board, conductive protrusions for soldering electrical components may be provided, or electrical wiring may be provided. The conductive protrusion for the electrical component is electrically connected to the wiring on the substrate in the same manner as the conductive protrusion for the optical component.
[0023]
Further, if necessary, an electrical wiring can be formed between the upper surface portions of the conductive protrusions on the optical wiring layer to make an electrical connection.
[0024]
2. Manufacturing Method of Optical / Electrical Wiring Substrate The manufacturing method of the optical / electrical wiring substrate of the present invention is basically as follows. First, conductive protrusions are formed on a substrate having electrical wiring by a photolithography technique and a plating technique. The optical fiber is fixed to the conductive protrusion for fixing the optical fiber. Resin 3 is applied from above to form an optical wiring layer. Thereafter, the resin layer 3 on the upper surface portion of the conductive protrusion is removed and exposed from the surface of the optical wiring layer. Further, a metal mask opening for electrical wiring and mirror processing is formed by photolithography technology, plating, and etching technology, and a mirror is formed by dry etching.
[0025]
Hereinafter, one embodiment will be described in accordance with the flow of FIGS. 5A to 5L with a focus on the conductive protrusions for mounting optical components that are electrically connected to the electrical wiring on the substrate.
[0026]
As shown in FIG. 5A, a metal thin film 44 made of Cr and copper is sputtered on a copper polyimide multilayer substrate 41 having a copper electrical wiring layer 42 and a conductor layer 43 connected to the optical fiber fixing conductive protrusions. Form.
[0027]
As shown in FIG. 5B, 100 μm of PMER (manufactured by Tokyo Ohka Co., Ltd.) is formed as a photoresist 45 by roll coating. Exposure and development processes are performed to form an opening 46 for an optical component connecting conductive protrusion having a diameter of 100 μm and an opening 47 for a 300 μm square optical fiber fixing conductive protrusion.
[0028]
Using the metal thin film layer 44 as a cathode, copper plating is performed up to a photoresist film thickness in a copper sulfate bath at room temperature, and further, Ni 2 μm and Au 0.05 μm are formed by electroless plating, and FIG. Thus, the conductive protrusions 48 and 49 are produced.
[0029]
As shown in FIG. 5D, the photoresist 45 is removed with a dedicated stripping solution.
[0030]
As shown in FIG. 5E, the metal thin film 44 is removed with an etching solution.
[0031]
As shown in FIG. 5F, an optical fiber 50 having a diameter of 100 μm is installed at a predetermined position.
[0032]
As shown in FIG. 5G, a fluorinated epoxy resin adjusted to the refractive index of the clad layer of the optical fiber is applied from above and cured by heating at 180 ° C. for 2 hours to form the resin layer 51. .
[0033]
As shown in FIG. 5H, the outermost surface of the substrate is uniformly dry-etched to expose the upper surface portions 48 and 49 of the conductive protrusions.
[0034]
As shown in FIG. 5 (i), a Cr and copper metal thin film 52 is formed on the outermost surface after dry etching by sputtering.
[0035]
As shown in FIG. 5J, a photoresist 53 is applied by 2 μm by spin coating, and an opening 54 for etching the underlying metal thin film 52 is formed.
[0036]
As shown in FIG. 5 (k), an opening 55 for forming a metal thin film mirror is formed with an etching solution, and the photoresist is removed with a dedicated stripping solution. Thereafter, the substrate is tilted at 45 °, and drilling is performed by reactive ion etching using oxygen gas and silicon fluoride-based gas to form the mirror 56.
[0037]
As shown in FIG. 5L, the metal thin film 52 is removed by etching to obtain the optical / electrical wiring board of the present invention.
[0038]
3. Manufacturing method of mounting substrate Optical components (laser, photodiode) and electrical components (CPU, memory) were mounted on an optical / electrical wiring substrate using solder.
[0039]
【The invention's effect】
The present invention has the following effects.
First, since an optical wiring layer is provided on a substrate having electrical wiring, there is an effect that high-density mounting or miniaturization is possible.
[0040]
Second, since the mutual positional relationship between the core layer of the optical fiber, the upper surface of the conductive projection for mounting the optical component, and the mirror coincides with the intended one with extremely high accuracy, the optical axis of the optical component It is easy to optically match the optical axis of the optical wiring, and therefore there is an effect that the optical component and the electrical component can be automatically mounted simultaneously.
[0041]
Third, when soldering an optical component or an electrical component, it is directly connected to the conductive protrusion formed by plating, so that it is not affected by solder melting heat and the connection reliability is improved. At the same time, there is an effect that the reliability of connection with the electrical wiring on the substrate is also improved.
[0042]
Fourthly, since the electrical wiring is also provided on the optical wiring layer, there is an effect that interference between the electrical wirings can be suppressed.
[0043]
[Brief description of the drawings]
FIG. 1 is a plan view of a portion where an optical component is mounted on an optical / electrical wiring board according to the present invention.
FIG. 2 is a cross-sectional view taken along an optical fiber in a portion where an optical component is mounted in the optical / electrical wiring board of the present invention.
FIG. 3 is an explanatory diagram of the propagation of laser light when a laser light emitting element is mounted on the optical / electrical wiring board of the present invention.
FIG. 4 is an explanatory view of the propagation of laser light when a light receiving element is mounted on the optical / electrical wiring board of the present invention.
FIG. 5 is an explanatory view of a method for manufacturing an optical / electrical wiring board of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Optical fiber 1a Cladding layer 1b Core layer 2 Conductive protrusion part 3 for fixing an optical fiber Resin layer 4 Conductive protrusion part 4a Upper surface part of conductive protrusion part 5 Conductive protrusion part 5a Upper surface part of conductive protrusion part 6 Conductivity Projection 6a Upper surface 7 of conductive projection 7 Conductive projection 7a Upper surface 8 of conductive projection 8 Substrate 9 Optical wiring layer 10 Electrical wiring 11 Electrical wiring 12 Electrical wiring 13 Electrical wiring 14 Conductive layer 15 Conductive layer 16 Mirror 21 Laser light 22 Laser light emitting element 23 Laser light emitting surface 24 Lead 25 Solder 31 Laser light 32 Light receiving element 33 Light receiving surface 34 Lead 35 Solder 41 Substrate 42 Electrical wiring 43 Conductive layer 44 Metal thin film 45 Photo resist 46 Conductive protrusion opening 47 Light Fiber fixing conductive projection opening 48 Conductive projection 49 Optical fiber fixing conductive projection 50 Optical fiber 51 Resin layer 52 Metal Film 53 a photoresist 54 photoresist opening 55 a metal thin film opening 56 mirror

Claims (6)

An optical / electrical wiring board comprising an optical wiring layer having an optical fiber for propagating an optical signal as an optical wiring on a substrate having electric wiring,
An optical wiring layer in which the optical fiber is embedded in a resin layer;
A mirror provided in a part of the optical fiber;
A conductive protrusion for fixing an optical fiber, penetrating the optical wiring layer and having one end face installed on a substrate having the electrical wiring;
A conductive protrusion for penetrating the optical wiring layer, one end face is connected to the electrical wiring, and the other end face is electrically connected to the optical component;
An optical / electrical wiring board comprising: Furthermore, a conductive protrusion for penetrating the optical wiring layer, one end face is connected to the electrical wiring, and the other end face is electrically connected to the electrical component;
The optical / electrical wiring board according to claim 1, comprising: Furthermore, electrical wiring provided on the optical wiring layer;
The optical / electrical wiring board according to claim 1, further comprising: 4. The optical / electrical wiring board according to claim 1, wherein a refractive index of the resin constituting the optical wiring layer is equal to a refractive index of a cladding layer of the optical fiber. A method of manufacturing an optical / electrical wiring board comprising an optical wiring layer having an optical fiber for propagating an optical signal as an optical wiring on a substrate having electric wiring,
Forming conductive protrusions on predetermined electrical wiring of a substrate having electrical wiring;
Fixing the optical fiber to the conductive protrusion for fixing the optical fiber;
Forming a resin layer and embedding the optical fiber;
Exposing the upper surface of the conductive protrusion;
Forming an electrical wiring on the optical wiring layer;
Forming a mirror by perforation at a predetermined position of the optical wiring layer;
A method of manufacturing an optical / electrical wiring board, comprising: A mounting board comprising an optical component and / or an electrical component mounted on the optical / electrical wiring board according to claim 1.

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