Optical circuit board and optical component mounting structure using the same

Abstract

The invention comprises a wiring board and an optical waveguide. The wiring board has an upper surface comprising a mounting region for an optical component. The optical waveguide is located adjacent to the mounting region for the optical component on the wiring board, and comprises a lower cladding layer from an upper surface side of the wiring board, a plurality of cores comprising a signal core as well as alignment cores located across from the signal core, and an upper cladding layer. The alignment cores have a first end surface on the optical component mounting region side, the first end surface being inclined with respect to the upper surface of the wiring board.

Description

[Technical field]

[0001] The present invention relates to an optical circuit board and an optical component mounting structure using the same. [Background technology]

[0002] In recent years, optical fibers capable of communicating large volumes of data at high speeds have come to be used in information communications (for example, Patent Document 1). Optical signals are transmitted and received between the optical fibers and optical elements (silicon photonics devices). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6290742 Summary of the Invention [Means for solving the problem]

[0004] The optical waveguide includes a wiring board and an optical waveguide. The wiring board has an upper surface including an area for mounting an optical component. The optical waveguide is located adjacent to the area for mounting the optical component on the wiring board, and includes, from the upper surface side of the wiring board, a lower clad layer, a signal core, and a plurality of cores including an alignment core located between the signal core, and an upper clad layer. The alignment core has a first end face on the side of the area for mounting the optical component, and the first end face is inclined with respect to the upper surface of the wiring board. The optical component mounting structure according to the present disclosure includes the above-mentioned optical circuit board and optical component.

[0005] A method for manufacturing an optical circuit board according to the present disclosure includes the steps of obtaining a wiring board having an upper surface including an optical waveguide forming region and an optical component mounting region, a first conductor layer located on the upper surface between the optical waveguide forming region and the optical component mounting region, and a solder resist covering the first conductor layer, stacking in order from the optical waveguide forming region to the first upper surface of the solder resist, a lower cladding layer, a signal core, and a plurality of cores including an alignment core located between the signal core, and an upper cladding layer, to form an optical waveguide precursor such that a first end face on the optical component mounting region side is inclined with respect to the upper surface of the wiring board, and removing the signal core located on the first upper surface of the solder resist and the solder resist located below the signal core in the optical waveguide precursor such that the signal core is aligned along the upper surface of the wiring board, to form an optical waveguide. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1A is a plan view showing an optical component mounting structure in which a silicon photonics device and electronic components are mounted on an optical circuit board according to an embodiment of the present disclosure, and FIG. 1B is an enlarged explanatory view for illustrating a cross section passing through a signal core in region X shown in FIG. [Diagram 2] FIG. 1C is a plan view of region Y shown in FIG. 1B (excluding the upper cladding layer of the silicon photonics device and the optical waveguide). [Diagram 3] 3A is an explanatory diagram for illustrating a cross section passing through an alignment core as viewed from the direction of arrow A shown in FIG. 2, (B) is an explanatory diagram for illustrating a cross section passing through a signal core when cut along line BB shown in FIG. 2, and (C) is an explanatory diagram for illustrating a cross section when the optical waveguide shown in (B) has a cavity. [Figure 4] 1A to 1C are plan views of the vicinity of the region Y in each manufacturing process of the wiring board. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] When mounting optical components such as silicon photonics devices on optical circuit boards, active alignment with higher accuracy is being adopted. "Active alignment" is a method of determining the mounting position of an optical component by irradiating an alignment core with light and moving and adjusting the optical component and the optical circuit board so that the peak of the received light is maximized. However, due to the structure of conventional optical circuit boards, it is difficult to adopt high-precision active alignment. In other words, the end face of the alignment core, which is the light inlet / outlet, is close to the surface of the wiring board, making it difficult to efficiently transmit and receive light between the alignment light source.

[0008] Therefore, there is a demand for an optical circuit board that can employ active alignment when mounting optical components such as silicon photonics devices and that can mount optical components with high precision.

[0009] According to the optical circuit board of the present disclosure, optical components can be mounted with high accuracy. Furthermore, according to the manufacturing method of the optical circuit board of the present disclosure, it is possible to easily perform a continuity test of the optical waveguide.

[0010] An optical circuit board according to an embodiment of the present disclosure will be described with reference to Figures 1 to 3. Figure 1(A) is a plan view showing an optical component mounting structure 10 in which a silicon photonics device (optical component) 4 is mounted on an optical circuit board 1 according to an embodiment of the present disclosure.

[0011] An optical circuit board 1 according to an embodiment of the present disclosure includes a wiring board 2 and an optical waveguide 3. An example of the wiring board 2 included in the optical circuit board 1 according to an embodiment is a wiring board generally used for optical circuit boards.

[0012] Although not specifically illustrated, such a wiring board 2 includes, for example, a core board and build-up layers laminated on both sides of the core board. The core board is not particularly limited as long as it is made of an insulating material. Examples of insulating materials include resins such as epoxy resin, bismaleimide-triazine resin, polyimide resin, and polyphenylene ether resin. Two or more of these resins may be mixed and used. The core board usually has a through-hole conductor to electrically connect the upper and lower surfaces of the core board.

[0013] The core substrate may contain a reinforcing material. Examples of the reinforcing material include insulating fabric materials such as glass fiber, glass nonwoven fabric, aramid nonwoven fabric, aramid fiber, and polyester fiber. Two or more types of reinforcing materials may be used in combination. Furthermore, the core substrate may have inorganic fillers such as silica, barium sulfate, talc, clay, glass, calcium carbonate, and titanium oxide dispersed therein.

[0014] The build-up layer has a structure in which insulating layers and conductor layers are alternately laminated. A part of the outermost conductor layer (the conductor layer located on the upper surface of the wiring board) includes the second conductor layer 21b where the optical waveguide 3 is located. The conductor layer is a metal layer made of a metal such as copper. The insulating layer included in the build-up layer is not particularly limited as long as it is made of an insulating material, similar to the core board. Examples of the insulating material include resins such as epoxy resin, bismaleimide-triazine resin, polyimide resin, and polyphenylene ether resin. Two or more of these resins may be mixed together.

[0015] When the build-up layer has two or more insulating layers, the insulating layers may be made of the same resin or different resins. The insulating layers and the core substrate included in the build-up layer may be made of the same resin or different resins. The build-up layer usually has via-hole conductors for electrically connecting the layers.

[0016] Furthermore, the insulating layer included in the build-up layer may have inorganic fillers such as silica, barium sulfate, talc, clay, glass, calcium carbonate, and titanium oxide dispersed therein.

[0017] As shown in Fig. 1(B), an optical waveguide 3 included in an optical circuit board 1 according to an embodiment is located on the surface of a second conductor layer 21b on the surface of a wiring board 2. Fig. 1(B) is an enlarged explanatory view illustrating a cross section of a region X shown in Fig. 1(A). The optical waveguide 3 has a structure in which a lower clad layer 31, a core 32, and an upper clad layer 33 are laminated in this order from the second conductor layer 21b side.

[0018] The lower cladding layer 31 included in the optical waveguide 3 is located on the surface of the wiring board 2, specifically, on the surface of the second conductor layer 21b located on the surface of the optical waveguide forming region R1 of the wiring board 2. The material forming the lower cladding layer 31 is not limited, and examples thereof include epoxy resin, silicone resin, etc.

[0019] The upper cladding layer 33 included in the optical waveguide 3 is also formed of the same material as the lower cladding layer 31. The lower cladding layer 31 and the upper cladding layer 33 may be made of the same material or different materials. Furthermore, the lower cladding layer 31 and the upper cladding layer 33 may have the same thickness or different thicknesses. The lower cladding layer 31 and the upper cladding layer 33 each have a thickness of, for example, about 5 μm or more and 150 μm or less.

[0020] The core 32 included in the optical waveguide 3 is a portion through which light that has entered the optical waveguide 3 propagates. The material forming the core 32 is not limited, and is appropriately set in consideration of, for example, the light transmittance and the wavelength characteristics of the propagating light. Examples of the material include epoxy resin and silicone resin. The core 32 has a thickness of, for example, about 3 μm or more and 50 μm or less.

[0021] As shown in Fig. 2, one optical waveguide 3 has a plurality of cores 32. This is a plan view of region Y shown in Fig. 1(B) (excluding the silicon photonics device 4 and the upper cladding layer 33 of the optical waveguide 3). The core 32 includes a signal core 32a and an alignment core 32b. There are a plurality of signal cores 32a, and two alignment cores 32b are positioned so as to sandwich the plurality of signal cores 32a. The signal cores 32a and the alignment cores 32b may be formed of the same material (resin) or different materials (resins).

[0022] At one end of the optical waveguide 3, the signal core 32a is positioned to face a silicon waveguide (Si waveguide) 41 included in the silicon photonics device 4. That is, an end face of the Si waveguide 41 and an end face of the signal core 32a of the optical waveguide 3 are positioned to face each other. At this end, optical signals are transmitted and received between the signal core 32a and the Si waveguide 41.

[0023] As shown in FIG. 3(A), the alignment core 32b has a first end surface 3a on the mounting region R2 side of the optical component 4 inclined with respect to the upper surface of the wiring board 2. FIG. 3(A) is an explanatory diagram for explaining a side view seen from the direction of the arrow A shown in FIG. 2. The structure in which the first end surface 3a is inclined with respect to the upper surface of the wiring board 2 is not limited, and an example of the structure shown in FIG. 3(A) can be given. Specifically, on the upper surface of the wiring board 2, the first conductor layer 21a is located between the optical waveguide 3 and the mounting region R2 of the optical component 4, and the solder resist 8 is located so as to cover this first conductor layer 21a. A part of the optical waveguide 3 including the first end surface 3a of the alignment core 32b is located on this solder resist 8. For this reason, for example, the angle between the end surface of the signal core 32a and the upper surface of the wiring board 2 is different from the angle between the end surface (first end surface 3a) of the alignment core 32b and the upper surface of the wiring board 2. The solder resist 8 is made of a resin, and an example of the resin is an acrylic modified epoxy resin.

[0024] In this way, when the first end face 3a is inclined with respect to the upper surface of the wiring board 2, light can be easily transmitted and received between the light source and the alignment core 32b. Therefore, when mounting the optical component 4 on the optical circuit board 1 according to the embodiment, active alignment can be adopted. As a result, the optical component 4 can be mounted with high accuracy on the optical circuit board 1 according to the embodiment. As shown in FIG. 3(C), the alignment core 32b may have a cavity C on the mounting region R2 side of the optical component 4, and one surface constituting the cavity C may be the first end face 3a.

[0025] The angle of the first end face 3a is not limited as long as it is inclined with respect to the upper surface of the wiring board 2. For example, the angle between the upper surface of the wiring board 2 and the first end face 3a is, for example, 1° or more and 30° or less. When the angle between the upper surface of the wiring board 2 and the first end face 3a is such an angle, light can be easily exchanged between the light source and the alignment core 32b. As a result, the function as an active alignment is fully exhibited.

[0026] As shown in Fig. 3(B), the signal core 32a is positioned so as to be parallel to the upper surface of the wiring board 2. Fig. 3(B) is an explanatory diagram for explaining a cross section when cut along line BB shown in Fig. 2. As shown in Fig. 2, no solder resist 8 is present under the end face of the signal core 32a on the side of the mounting area for the optical component 4.

[0027] By positioning the signal core 32a so as to be parallel to the upper surface of the wiring board 2, optical signals are efficiently transmitted and received between the mounted optical component 4. In this specification, "parallel" is not limited to completely parallel. Even when there is an inclination of a few degrees (for example, 5° or less) with respect to the upper surface of the wiring board 2, it is defined as "parallel."

[0028] The method for producing the optical circuit-board 1 according to an embodiment is not particularly limited as long as the optical circuit-board 1 having the above-mentioned structure can be produced. The method for producing the optical circuit-board according to an embodiment of the present disclosure includes the following steps (a) to (c).

[0029] Step (a): A step of obtaining a wiring board having an upper surface including an optical waveguide forming region and an optical component mounting region, a first conductor layer located on the upper surface between the optical waveguide forming region and the optical component mounting region, and a solder resist covering the first conductor layer. Step (b): A step of sequentially stacking a lower cladding layer, a signal core, a plurality of cores including an alignment core positioned between the signal core, and an upper cladding layer from an optical waveguide forming region to a first upper surface of the solder resist, so as to form an optical waveguide precursor such that a first end face on the optical component mounting region side is inclined with respect to the upper surface of the wiring board. Step (c): A step of forming an optical waveguide by removing the signal core located on the first upper surface of the solder resist and the solder resist located below the signal core in the optical waveguide precursor so that the signal core is aligned along the upper surface of the wiring board.

[0030] In step (a), as shown in FIG. 4(A), the wiring board 2 is prepared. On the upper surface of the wiring board 2, there are provided an optical waveguide forming region R1, an optical component 4 mounting region R2, a first conductor layer 21a located between the optical waveguide forming region R1 and the optical component 4 mounting region R2, a first conductor layer 21b located in the optical waveguide forming region R1, an electrode 21c located in the mounting region R2, and a solder resist 8 covering the mounting region R2 and the first conductor layer 21a. The conductor layers such as the first conductor layer 21a included in the wiring board 2 are formed by metal plating such as copper plating, or metal foil such as copper foil. The electrode 21c is located within an opening of the solder resist 8. The solder resist 8 is obtained by, for example, using a sheet formed of the above-mentioned resin and performing exposure, development, and the like.

[0031] 4(B), an optical waveguide precursor 3P is formed on the upper surface of the obtained wiring board 2 from the optical waveguide forming region R1 to the first upper surface of the solder resist 8 on the first conductor layer 21a. The optical waveguide precursor 3P is obtained by sequentially laminating a lower cladding layer 31, a plurality of cores 32 including a signal core 32a and an alignment core 32b, and an upper cladding layer 33.

[0032] Specifically, the lower cladding layer 31, the cores 32, and the upper cladding layer 33 are obtained by using sheets made of the above-mentioned resin and performing exposure, development, etc. The signal cores 32a and the alignment cores 32b may be sheets made of the same resin or different resins.

[0033] In the optical waveguide precursor 3P, the end face of the core 32 on the mounting region R2 side of the optical component 4, including the first end face 3a of the alignment core 32b, is located on the first upper surface of the solder resist 8 on the first conductor layer 21a. Therefore, as shown in Fig. 3(A), the first end face 3a of the alignment core 32b is inclined with respect to the upper surface of the wiring board 2. The angle between the upper surface of the wiring board 2 and the first end face 3a is as described above, and a detailed description thereof will be omitted.

[0034] In step (b), the end face of the signal core 32a on the mounting region R2 side is also inclined with respect to the upper surface of the wiring board 2, similar to the first end face 3a of the alignment core 32b. Therefore, between step (b) and step (c) described later, light can be easily transmitted and received between the end face of the signal core 32a on the mounting region R2 side and the light source. As a result, the optical waveguide continuity test can be easily performed in the manufacturing process of the optical circuit board.

[0035] In this way, after the step of forming the optical waveguide precursor 3P (step (b)), the signal core 32a may further include an optical continuity inspection step between the end face on the mounting area R2 side and the end face opposite the mounting area R2.

[0036] In step (c), as shown in Fig. 4(C), in the optical waveguide precursor 3P, the signal core 32a located on the first upper surface of the solder resist 8 and the solder resist 8 located below the signal core 32a are removed. Specifically, as shown in Fig. 2, the first conductor layer 21a located below the signal core 32a may be exposed from the solder resist 8 in plan view. The signal core 32a and the solder resist 8 located below the signal core 32a are removed by, for example, laser processing.

[0037] By removing the signal core 32a located on the first upper surface of the solder resist 8 and the solder resist 8 located below the signal core 32a, only the portion of the signal core 32a that is parallel to the upper surface of the wiring board 2 remains. As a result, the optical waveguide 3 is formed on the upper surface of the wiring board 2. In this manner, the optical circuit board 1 according to one embodiment is obtained.

[0038] Next, an optical component mounting structure according to the present disclosure will be described. An optical component mounting structure 10 according to an embodiment of the present disclosure has a structure in which a silicon photonics device 4 and an electronic component 6 are mounted on an optical circuit board 1 according to an embodiment. Examples of the electronic component 6 include an ASIC (Application Specific Integrated Circuit) and a driver IC.

[0039] 1(B), the silicon photonics device 4 is electrically connected to an electrode 21c located in an optical component mounting region of the wiring board 2 via solder 7. The electrode 21c is a part of a conductor layer located on the upper surface of the wiring board 2, and is located so as to be exposed from an opening in the solder resist 8.

[0040] The silicon photonics device 4 is a type of optical waveguide having, for example, silicon (Si) as a core and silicon dioxide (SiO2) as a cladding. The silicon photonics device 4 includes the Si waveguide 41 as described above, and further includes a passivation film, a light source unit, a light detection unit, and the like, which are not shown. As described above, the Si waveguide 41 is located at one end of the optical waveguide 3 so as to face the signal core 32a included in the optical waveguide 3.

[0041] For example, an electrical signal from the wiring board 2 is propagated to a light source section included in the silicon photonics device 4 via the solder 7. The light source section receives the propagated electrical signal and emits light. The emitted optical signal is propagated via the Si waveguide 41a for signal propagation and the signal core 32a of the optical waveguide 3 to the optical fiber 5 connected via the optical connector 5a. [Explanation of symbols]

[0042] 1 Optical circuit board 2. Wiring board 21a First conductor layer 21b Second conductor layer 21c electrode 23 Insulating layer 3 Optical waveguide 31 Lower cladding layer 32 cores 32a signal core 32b Alignment Core 33 Upper cladding layer 3a 1st end surface 4. Silicon photonics devices (optical components) 41 Silicon Waveguide (Si Waveguide) 5. Fiber Optics 5a Optical Connector 6. Electronic Components 7 Solder 8 Solder Resist 10 Optical component mounting structure R1 Optical waveguide formation area R2 Mounting area C Cavity

Claims

1. A wiring board and an optical waveguide are included. the wiring board has an upper surface including an area for mounting optical components; the optical waveguide is located adjacent to a mounting region of the optical component on the wiring board, and includes, from the upper surface side of the wiring board, a lower clad layer, a signal core, a plurality of cores including an alignment core positioned between the signal core, and an upper clad layer; the alignment core has a first end surface inclined with respect to the upper surface of the wiring board on a side of a mounting region of the optical component; the signal core has a second end surface located on a side of a mounting area for the optical component, the second end surface is located at a position facing an optical waveguide included in the optical component when the optical component is mounted in the mounting region of the optical component, an angle between the first end surface and the upper surface of the wiring substrate is different from an angle between the second end surface and the upper surface of the wiring substrate; Optical circuit board.

2. a first conductor layer located between the optical waveguide and a mounting region for the optical component, and a solder resist covering the first conductor layer are provided on the upper surface of the wiring board; 2. The optical circuit board according to claim 1, wherein a portion of the optical waveguide including the first end face of the alignment core is located on the solder resist, and the portion including the first end face is inclined so as to move away from the top surface of the wiring board as it approaches the first end face.

3. 2. The optical circuit board according to claim 1, wherein the alignment core has a cavity, and one surface constituting the cavity is the first end surface.

4. the wiring board has a second conductor layer on the upper surface; 4. The optical circuit board according to claim 1, wherein the optical waveguide is located on the second conductor layer.

5. 5. An optical component mounting structure comprising the optical circuit board according to claim 1 and an optical component.

6. the optical component is a silicon photonics device, the silicon photonics device having a silicon waveguide; The optical component mounting structure according to claim 5 , wherein the silicon waveguide is positioned so as to face the signal core.

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