Wiring board

Abstract

To improve the degree of freedom of designing a wiring board.SOLUTION: A wiring board 100 comprises: a circuit board 200; and an optical guide 50 that comprises a core 5 transmitting light and a clad 52 surrounding the core 5, and is disposed on the circuit board 200. The wiring board 100 has a first component mounting region A1 and a second component mounting region A2. The optical guide 50 has a first optical guide 5a and a second optical guide 5b, and has an optical junction 50x to be combined with a connection member C and exchanging light with the connection member C. The first optical guide 5a has a first light-input / output part 50a for exchanging light with a mounted component in the first component mounting region A1 and includes a portion of the optical junction 50x. The second optical guide 5b has a second light-input / output 50b for exchanging light with a mounted component in the second mounting region A2 and includes a portion of the optical junction 50x.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a wiring board.

Background Art

[0002] Patent Document 1 discloses a microelectronic package structure including a substrate including a waveguide, an integrated circuit and a photonic engine mounted on the substrate, and an optical coupling coupled to the waveguide.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] The substrate of the microelectronic package structure disclosed in Patent Document 1 is only provided with a waveguide that provides an optical path between the optical coupling and one photonic engine. It is difficult to realize a complex circuit including transmission portions for both optical signals and electrical signals, which includes a plurality of components including optoelectronic elements such as photonic engines, and the degree of freedom in arranging optical components is considered to be low. In some cases, it is not possible to sufficiently cope with the complexity of circuits including an optical signal transmission portion and the high degree of design freedom required for the arrangement of optical components accompanying such complexity.

Means for Solving the Problem

[0005] The wiring board of the present invention includes a circuit board including an insulating layer and a conductive layer, and an optical waveguide placed on the circuit board, which includes a core portion that transmits light and a cladding portion surrounding the core portion. The wiring board has a first component mounting area and a second component mounting area, and the optical waveguide includes a first optical waveguide and a second optical waveguide, and has an optical coupling portion that is combined with a connector member to transfer light to and from the connector member, the first optical waveguide has a first input / output light portion that transfers light to and from a component mounted in the first component mounting area, and includes a part of the optical coupling portion, and the second optical waveguide has a second input / output light portion that transfers light to and from a component mounted in the second component mounting area, and includes a part of the optical coupling portion.

[0006] According to embodiments of the present invention, in a wiring board that includes an optical signal transmission unit and an electrical signal transmission unit, it is possible to facilitate the realization of more complex circuits and improve the degree of freedom in the arrangement of optical components. [Brief explanation of the drawing]

[0007] [Figure 1] A cross-sectional view showing an example of a wiring board according to one embodiment of the present invention. [Figure 2] A plan view showing an example of a wiring board in a plan view, as shown in Figure 1. [Figure 3] A cross-sectional view showing an enlarged view of part III in Figure 1. [Figure 4] A plan view of an example of an optical waveguide in a wiring board according to one embodiment. [Figure 5] Cross-sectional view of the VV line of the optical waveguide in the example shown in Figure 4. [Figure 6A] A plan view of another example of an optical waveguide in a wiring board according to one embodiment. [Figure 6B] A plan view of yet another example of an optical waveguide in a wiring board according to one embodiment. [Figure 7] A cross-sectional view showing an enlarged modified example of part III in Figure 1. [Figure 8] A cross-sectional view showing another example of the combination of optical waveguides and components in the wiring board of the embodiment. [Figure 9A] A cross-sectional view showing an example of the manufacturing process for a wiring board according to an embodiment. [Figure 9B] A cross-sectional view showing an example of the manufacturing process for a wiring board according to an embodiment. [Figure 9C] A cross-sectional view showing an example of the manufacturing process for a wiring board according to an embodiment. [Figure 9D] A cross-sectional view showing an example of the manufacturing process for a wiring board according to an embodiment. [Figure 9E] A cross-sectional view showing an example of the manufacturing process for a wiring board according to an embodiment. [Figure 10A] A cross-sectional view showing an example of the manufacturing process for an optical waveguide according to the embodiment. [Figure 10B] A cross-sectional view showing an example of the manufacturing process for an optical waveguide according to the embodiment. [Figure 10C] A cross-sectional view showing an example of the manufacturing process for an optical waveguide according to the embodiment. [Figure 10D] A cross-sectional view showing an example of the manufacturing process for an optical waveguide according to the embodiment. [Modes for carrying out the invention]

[0008] A wiring board according to one embodiment of the present invention will be described with reference to the drawings. Figure 1 is a cross-sectional view showing a wiring board 100, which is an example of a wiring board of one embodiment, and Figure 2 shows an example of the wiring board 100 of Figure 1 in plan view (Figure 1 is a cross-sectional view taken along line II of Figure 2). Note that "plan view" means viewing the wiring board of the embodiment from a line of sight along its thickness direction. Circle B, drawn with a dashed line in Figure 2, shows an enlarged view of part II of Figure 2. Figure 3 shows an enlarged view of part III of Figure 1. The wiring board 100 is merely an example of a wiring board of this embodiment. The laminated structure of the wiring board of the embodiment, and the number of conductor layers and insulating layers, respectively, are not limited to the laminated structure of the wiring board 100 of Figure 1, and the number of conductor layers and insulating layers, respectively, included in the wiring board 100. Also, in the drawings referenced in the following description, certain parts may be enlarged to facilitate understanding of the disclosed embodiment, and the size and length of each component may not be depicted in the exact proportions between them.

[0009] As shown in FIG. 1, the wiring board 100 includes a circuit board 200 and an optical waveguide 50 disposed on the circuit board 200. The circuit board 200 includes an insulating layer and a conductor layer. Specifically, the circuit board 200 in the example of FIG. 1 includes a core substrate 3, an insulating layer 21 and a conductor layer 11 sequentially stacked on a first surface 3a of the core substrate 3, and an insulating layer 22 and a conductor layer 12 sequentially stacked on a second surface 3b of the core substrate 3. Via conductors 20 that connect conductor layers sandwiching the insulating layer are formed in each of the insulating layer 21 and the insulating layer 22. The core substrate 3 includes an insulating layer 32 and conductor layers 31 formed on both surfaces of the insulating layer 32. The insulating layer 32 is provided with through-hole conductors 33 that penetrate the insulating layer 32 and connect the conductor layers 31 on both sides. The inside of the cylindrical through-hole conductor 33 is filled with a filler 34 formed of an insulating resin such as epoxy resin or a conductive resin containing metal particles, for example.

[0010] In the description of the embodiment, in the thickness direction of the wiring board 100, the side farther from the insulating layer 32 is also referred to as "upper side", "upper direction", or simply "upper", and the side closer to the insulating layer 32 is also referred to as "lower side", "lower direction", or simply "lower". Furthermore, for each component of the wiring board 100, the surface facing the opposite side of the insulating layer 32 is also referred to as an "upper surface", and the surface facing the insulating layer 32 side is also referred to as a "lower surface". The thickness direction of the wiring board 100 is also referred to as the "Z direction".

[0011] The circuit board 200 further includes solder resists 23 respectively formed on the first surface 3a side and the second surface 3b side of the core substrate 3. The solder resist 23 partially covers each of the insulating layer 21 and the conductor layer 11, or partially covers each of the insulating layer 22 and the conductor layer 12. The solder resist 23 is formed of, for example, photosensitive epoxy resin, polyimide resin, or the like.

[0012] The circuit board 200 further includes conductor posts 13 and 14 formed on the conductor layer 11. A connection layer 15 is formed on the surfaces of the conductor posts 13 and 14 using, for example, tin-based solder or gold-based solder. The conductor posts 13 and 14 are conductors having, for example, a columnar shape, extending from the conductor layer 11 toward the direction opposite to the insulating layer 21. An external component Ea1 (first component) is connected to the conductor post 13, and an external component Eb is connected to the conductor post 14. Therefore, the wiring board 100 has a component mounting area A1 (first component mounting area) where the component Ea1 is placed when the wiring board 100 is in use. In the component mounting area A1, the component Ea1 is connected to the conductor layer 11 via the connection layer 15 and the conductor post 13, and is optically coupled to the optical waveguide 50.

[0013] Although not shown in FIG. 1, the wiring board 100 further has a component mounting area A2 (second component mounting area) where an external component Ea2 (second component) is placed when the wiring board 100 is in use, as shown in FIG. 2. In the component mounting area A2, the component Ea2 is connected to the conductor layer 11 via a connection means provided on the circuit board 200 similarly to the connection layer 15 and the conductor post 13, and is optically coupled to the optical waveguide 50.

[0014] Component Ea1 and component Ea2, respectively, which are placed in component mounting areas A1 and A2 when the wiring board 100 is in use, are optical components including photoelectric elements such as light-receiving elements and / or light-emitting elements that have a photoelectric conversion function. Component Ea1 in the examples in Figures 1 to 3 comprises an electrode E1a and a light-receiving or light-emitting part E1b. The light-receiving or light-emitting part E1b has a light-receiving or light-emitting surface E1c (see Figure 3) facing sideways and downwards of component Ea1. Although not shown, component Ea2 may also comprise an electrode and a light-receiving or light-emitting part similar to the electrode E1a and light-receiving or light-emitting part E1b. The electrode E1a and the light-receiving or light-emitting part E1b are provided on the side of component Ea1 facing the wiring board 100. That is, in the examples in Figures 1 to 3, component Ea1 and component Ea2 are mounted in a so-called face-down mounting (flip-chip mounting) manner. Furthermore, the wiring board 100 may have a component mounting area A3 (third component mounting area), as will be described later with reference to Figures 6A and 6B, and may have any number of component mounting areas on which optical components are mounted.

[0015] Examples of components Ea1 and Ea2 include light-receiving elements such as photodiodes, and light-emitting elements such as light-emitting diodes (LEDs), organic light-emitting diodes (OLEDs), laser diodes (LDs), and vertical-cavity surface-emitting lasers (VCSELs). When component Ea1 is a light-emitting element, it generates light based on an electrical signal input to electrode E1a and emits light from a light-receiving or light-emitting part E1b that functions as a light-emitting part. When component Ea1 is a light-receiving element, an electrical signal is generated based on the light that enters the light-receiving or light-emitting part E1b that functions as a light-receiving part, and is output from electrode E1a. Similarly to component Ea1, if component Ea2 is a light-emitting element, it emits light according to the input electrical signal, and if it is a light-receiving element, it outputs an electrical signal according to the incoming light.

[0016] On the other hand, component Eb may be an electronic component such as a semiconductor device that generates electrical signals to cause components Ea1 and Ea2 to emit light, and / or processes the electrical signals generated by components Ea1 and Ea2. Examples of component Eb include semiconductor devices such as general-purpose operational amplifiers, driver ICs, microcontrollers, and programmable logic devices (PLDs).

[0017] The insulating layers 21, 22, and 32 may be formed using thermosetting insulating resins such as epoxy resin, bismaleimide triazine resin (BT resin), or phenolic resin. The insulating layers 21, 22, and 32 may also be formed using thermoplastic insulating resins such as fluororesin, liquid crystal polymer (LCP), fluoroethylene (PTFE) resin, polyester (PE) resin, and modified polyimide (MPI) resin. Each insulating layer may be formed from any material capable of providing insulation between the conductive layers in the circuit board 200. Although not shown, each insulating layer may contain a core material (reinforcement) formed from glass fibers or aramid fibers, and may contain inorganic fillers consisting of fine particles such as silica (SiO2), alumina, or mullite.

[0018] The conductor layers 11, 12, and 31, the through-hole conductor 33, the via conductor 20, and the conductor posts 13, 14 can be formed using any metal with suitable conductivity, such as copper or nickel. Although each of these conductors is simplified and depicted as a single layer in Figure 1, it may have a multilayer structure including two or more films. For example, the conductor layers 11 and 12 may have a two-layer structure including an electroless plating film and an electrolytic plating film. The conductor posts 13 and 14 are formed, for example, by plating metal deposited by electroless plating and / or electrolytic plating.

[0019] Conductor layers 11, 12, and 31 may each contain any conductor pattern. In the example in Figure 1, conductor layer 11 includes conductor pads 11a and 11b. Conductor posts 13 are formed on conductor pad 11a, and electrode E1a of component Ea1 is electrically connected to conductor pad 11a via conductor post 13. Similarly, conductor posts 14 are formed on conductor pad 11b, and electrode E2a of component Eb is electrically connected to conductor pad 11b via conductor post 14.

[0020] The optical waveguide 50 includes a core portion 5 and a cladding portion 52 that transmit light. As shown in Figure 2, the optical waveguide 50 included in the wiring board 100 each includes two or more (i.e., multiple) core portions 5 that transmit light. The optical waveguide 50 includes a first optical waveguide 5a and a second optical waveguide 5b, each including a core portion 5 and a cladding portion 52. In the example in Figure 2, the first optical waveguide 5a and the second optical waveguide 5b each include multiple core portions 5. However, the number of core portions 5 included in the first optical waveguide 5a and the second optical waveguide 5b is not limited to a specific number, and each optical waveguide may include any number of core portions 5.

[0021] Each core section 5 is arranged side by side along a direction intersecting the extension direction of each core section 5 (i.e., the direction of light propagation within each core section 5). The cladding section 52 is provided around each core section 5. The cladding section 52 sandwiches the core section 5 in any direction perpendicular to the direction of light propagation. Therefore, the cladding section 52 surrounds each core section 5 in a plane perpendicular to the direction of light propagation.

[0022] One end of the first optical waveguide 5a is located in the component mounting area A1. The first optical waveguide 5a has a first input / output light section 50a that exchanges light with a mounted component (component Ea1 in the example in Figures 1 to 3) located in the component mounting area A1. At the other end of the first optical waveguide 5a, there is a first optical coupling section 50x1 which is part of the optical coupling section 50x described later.

[0023] One end of the second optical waveguide 5b is located in the component mounting area A2. The second optical waveguide 5b has a second input / output light section 50b that exchanges light with a mounted component (component Ea2 in the example in Figure 2) located in the component mounting area A2. At the other end of the second optical waveguide 5b, there is a second optical coupling section 50x2, which is part of the optical coupling section 50x described later.

[0024] The core portion 5 constituting the first optical waveguide 5a has two ends in the direction of extension of the core portion 5 (a first end portion 5α1 and a second end portion 5β1 which is the end opposite to the first end portion 5α1). Light propagating through the core portion 5 of the first optical waveguide 5a enters the core portion 5 from the exposed surface of the core portion 5 at the first end portion 5α1 or the second end portion 5β1, and exits the core portion 5 from the exposed surface of the core portion 5 at the first end portion 5α1 or the second end portion 5β1.

[0025] The core portion 5 constituting the second optical waveguide 5b has two ends in the direction of extension of the core portion 5 (a first end portion 5α2, and a second end portion 5β2 which is the end opposite to the first end portion 5α2). Light propagating through the core portion 5 of the second optical waveguide 5b enters the core portion 5 from the exposed surface of the core portion 5 at the first end portion 5α2 or the second end portion 5β2, and exits the core portion 5 from the exposed surface of the core portion 5 at the first end portion 5α2 or the second end portion 5β2.

[0026] In the optical waveguide 50 examples shown in Figures 1 and 2, the first ends 5α1 and 5α2 of each core section 5 are located near one of two opposing sides of the optical waveguide 50, which has a rectangular planar shape, while the second ends 5β1 and 5β2 are located near the other of the two opposing sides.

[0027] The end faces of the core portion 5 on the second end sides 5β1 and 5β2 are positioned to face and optically couple with the optical fiber F that is connected to the optical waveguide 50 when the wiring board 100 is in use, as shown in Figures 1 and 2. For example, as shown in Figure 1, the optical fiber F and the optical waveguide 50 are connected using a connector member C. In the example in Figures 1 and 2, the connector member C is an optical connector that optically couples the optical fiber F and the optical waveguide 50. In the example in Figures 1 and 2, the ends of the core portion 5 on the second end sides 5β1 and 5β2 of the optical waveguide 50 protrude to the outside of the circuit board 200. Therefore, it is considered that the connector member C can be easily attached to the optical waveguide 50, and that the optical coupling between the end faces of the core portion 5 on the second end sides 5β1 and 5β2 and the optical fiber F is easy.

[0028] Thus, the optical waveguide 50 is combined with a connector member C in the form of an optical connector or optical fiber array and has an optical coupling section 50x, which is a region where light is exchanged between the waveguide and the connector member C. As described above, the optical coupling section 50x is composed of a first optical coupling section 50x1 included in the first optical waveguide 5a and a second optical coupling section 50x2 included in the second optical waveguide 5b. In the optical waveguide 50, light is exchanged between the waveguide and the connector member C at the first optical coupling section 50x1 and the second optical coupling section 50x2, respectively. The first optical waveguide 5a extends between the component mounting area A1 and the first input / output optical section 50a and the optical coupling section 50x. The second optical waveguide 5b extends between the component mounting area A2 and the second input / output optical section 50b and the optical coupling section 50x.

[0029] Furthermore, the "connector member" can be an optical member for relaying or connecting, such as an optical connector, optical fiber array, or optical coupler, which provides an optical path between an optical waveguide (internal optical connector) that propagates light emitted or received by components on a wiring board and an external optical connector such as an optical fiber located outside the wiring board. In addition, the "connector member" may be just an external optical connector that propagates light from one end to the other of an optical path having a predetermined length, such as an optical fiber F. Therefore, in the example shown in Figure 1, if the optical fiber F is directly connected to the optical waveguide 50 without an optical connector or the like, the optical fiber F can become a connector member C that exchanges light with the optical coupling part 50x.

[0030] The optical coupling section 50x is combined with the connector member C. The "connector member" is itself a single unit, but can have any number of optical paths, such as a multi-core optical connector or optical fiber array. However, in the connector member C, such any number of optical paths are integrated or bundled with resin so that they can be treated as a single unit externally. Each core section 5 of the optical waveguide 50 has an exposed portion in the optical coupling section 50x that is not covered by the cladding section 52 (in the examples of Figures 1 and 2, the end faces on the second ends 5β1 and 5β2 of each core section 5). In the optical coupling section 50x, light from the connector member C enters through the exposed portion of each core section 5, and light is emitted from the exposed portion of each core section 5 to the connector member C.

[0031] On the other hand, the first ends 5α1 and 5α2 of the core portion 5 overlap with the component mounting area A1 or component mounting area A2 in a plan view, as shown in the examples of Figures 1 to 3. As shown within circle B in Figure 2 and in Figure 3, at the first end 5α1, the core portion 5 of the first optical waveguide 5a is positioned to face the light-receiving or light-emitting portion E1b of component Ea1 when the wiring board 100 is in use. Although not shown, the core portion 5 of the second optical waveguide 5b is positioned to face the light-receiving or light-emitting portion of component Ea2 when the wiring board 100 is in use. Components Ea1 and Ea2 either emit light propagating through the core portion 5 or receive light propagating through the core portion 5 from the core portion 5. Specifically, as shown in Figure 3, the optical waveguide 50 is positioned so that the surface 51a of the core portion 5 and the light-receiving or light-emitting surface E1c of component Ea1 face each other and are optically coupled (adiabatically coupled). Furthermore, optical coupling is not limited to adiabatic coupling, and may also take the form of a waveguide with mirrors, etc.

[0032] Thus, the optical waveguide 50 has a first input / output light section 50a (see Figures 2 and 3), which is a region for exchanging light with component Ea1, and a second input / output light section 50b (see Figure 2), which is a region for exchanging light with component Ea2. In the example shown in Figures 2 and 3, the first input / output light section 50a overlaps with the component mounting area A1 in a plan view, and the second input / output light section 50b overlaps with the component mounting area A2 in a plan view. In the first input / output light section 50a, the exposed portion of the core portion 5 of the first optical waveguide 5a faces the light-receiving or light-emitting portion E1b of component Ea1. As described above, light from component Ea1 enters the core portion 5, and light is emitted from the core portion 5 to component Ea1. Similarly, in the second light input / output section 50b, the exposed portion of the core section 5 of the second optical waveguide 5b faces a light receiving or light emitting section such as the light receiving or light emitting section E1b in component Ea2. Light from component Ea2 enters the core section 5, and light is emitted from the core section 5 to component Ea2.

[0033] In the examples shown in Figures 1 to 3, the portion of the cladding 52 covering the upper side of the core 5 is not formed up to the outer edge of the optical waveguide 50 on the first ends 5α1 and 5α2 of the core 5. Therefore, at the first ends 5α1 and 5α2 of each core 5, as shown in Figure 3, the surface 51a of the side of the core 5 that is aligned with the direction of light propagation (X direction) within the core 5 and facing away from the circuit board 200 is exposed without being covered by the cladding 52. In other words, in the examples shown in Figures 1 to 3 where the first ends 5α1 and 5α2 overlap with the component mounting area A1 or component mounting area A2, the surface 51a of each core 5 is exposed without being covered by the cladding 52 at the first input / output light section 50a and the second input / output light section 50b.

[0034] Since the surface 51a of each core portion 5 of the first optical waveguide 5a faces the light-receiving or light-emitting surface E1c of component Ea1 without being interposed by the cladding portion 52, it is believed that highly efficient coupling can be achieved. It is also believed that highly efficient optical coupling can be obtained between the core portion 5 of the second optical waveguide 5b, which faces component Ea2, and the light-receiving and light-emitting portion of component Ea2 (not shown). In addition, in the first input / output light section 50a and the second input / output light section 50b, not only the surface 51a of each core portion 5, but the entire core portion 5, excluding the surface on the circuit board 200 side, may be exposed without being covered by the cladding portion 52.

[0035] Light propagating through the optical fiber F enters the optical waveguide 50 from the optical coupling section 50x, propagates through each core section 5, and enters components Ea1 and Ea2 from the first input / output section 50a or the second input / output section 50b. This light is converted into an electrical signal within each component and output from electrode E1a. The output electrical signal is input to component Eb via the conductor layer 11 and processed. On the other hand, the electrical signal output from component Eb is input to components Ea1 and Ea2 via electrode E1a and converted into light. This light is emitted from the light receiving or light emitting section E1b, enters the optical waveguide 50 from the first input / output section 50a or the second input / output section 50b, propagates through each core section 5, and is output to the optical fiber F from the optical coupling section 50x.

[0036] In the examples shown in Figures 1 to 3, the wiring board 100 further includes a support plate 6, and the optical waveguide 50 is placed on the support plate 6. The support plate 6 provides rigidity to the optical waveguide 50. In the examples shown in Figures 1 to 3, the support plate 6 with the optical waveguide 50 is placed on the surface of the circuit board 200. The optical waveguide 50 may be formed on the support plate 6 and fixed to the circuit board 200 together with the support plate 6, or it may be formed separately from the support plate 6 and fixed to the support plate 6 with, for example, any adhesive (not shown). The optical waveguide 50 can be fixed to the support plate 6 by any means. The support plate 6 can also be fixed to the circuit board 200 by any means such as an adhesive.

[0037] The support plate 6 is preferably made of a material having higher rigidity than the optical waveguide 50. The support plate 6 may further be made of a material having a lower coefficient of thermal expansion than the coefficient of thermal expansion of the optical waveguide 50. This is thought to suppress the decrease in optical coupling efficiency between the optical waveguide 50 and the optical fiber F and / or components Ea1, Ea2 due to temperature changes. Examples of materials for the support plate 6 include glass such as soda-lime glass, borosilicate glass, and quartz glass, various metals such as tungsten, titanium, and molybdenum, and various ceramics such as alumina, silicon nitride, and silicon oxide.

[0038] Since the optical waveguide 50 is supported by the support plate 6 in this manner, the first ends 5a1 and 5α2 of the core portion 5 can be easily positioned to couple with the light-receiving and light-emitting portions of components Ea1 and Ea2 with sufficient efficiency. Similarly, the second ends 5β1 and 5β2 can be easily positioned to couple with the optical fiber F with sufficient efficiency. Therefore, even if the rigidity of the optical waveguide 50 itself is low, it is considered that the optical waveguide 50, components Ea1 and Ea2, and the optical fiber F can be optically coupled with sufficient efficiency. In particular, the ends of the core portion 5 on the second end 5β1 and 5β2 side of the support plate 6 protrude to the outside of the circuit board 200 together with the optical waveguide 50, supporting the protruding portion of the optical waveguide 50. Therefore, it is considered that the end faces on the second end 5β1 and 5β2 side of each core portion 5 can be easily and efficiently optically coupled to the optical fiber F.

[0039] The optical waveguide 50 will be further described with reference to Figures 4 and 5. Figure 4 is a plan view of an example of the optical waveguide 50 in the wiring board of this embodiment, and Figure 5 is a cross-sectional view of the optical waveguide 50 in Figure 4 along the VV line. In Figure 4, for ease of understanding, the outer edges of each core portion 5, including the portion covered by the cladding portion 52, are shown with solid lines. Also, in Figure 2, which was referred to earlier, each core portion 5 was simplified and shown with a single dashed line, but in Figure 4, each core portion 5 is drawn with an exemplary width from its first end 5α1, 5α2 to its second end 5β1, 5β2.

[0040] As described above, in this embodiment, the optical waveguide 50 includes a first optical waveguide 5a and a second optical waveguide 5b, and has an optical coupling section 50x that exchanges light with the connector member C. The first optical waveguide 5a has a first input / output light section 50a that exchanges light with component Ea1, and the second optical waveguide 5b has a second input / output light section 50b that exchanges light with component Ea2. Both the first optical waveguide 5a and the second optical waveguide 5b include a part of the optical coupling section 50x. Because the optical waveguide 50 includes such first and second optical waveguides 5a and 5b, the wiring board of this embodiment can realize a more complex circuit having an optical signal transmission path, such as one that includes multiple optical components, each having a photoelectric conversion function.

[0041] Furthermore, the degree of freedom in arranging multiple photoelectric conversion elements on a wiring board may be improved. In other words, constraints on the relative positions between each photoelectric conversion element and a connector member C, such as an optical connector, may be relaxed. For example, multiple photoelectric conversion elements may be prepared as separate components (e.g., component Ea1 and component Ea2), and these components may be arranged spaced apart rather than adjacent to each other.

[0042] Furthermore, in the wiring board of this embodiment, it may not be necessary to individually prepare, i.e., multiple, connector members C such as optical connectors for multiple optical components such as component Ea1 and component Ea2, and combine them with an optical waveguide. Therefore, according to this embodiment, it may be possible to miniaturize the wiring board that realizes a circuit including multiple optical components.

[0043] In the example shown in Figure 4, the first optical waveguide 5a and the second optical waveguide 5b each contain three core sections 5. However, in this embodiment, the first optical waveguide 5a and the second optical waveguide 5b may contain one or more arbitrary numbers of core sections 5.

[0044] In the example in Figure 4, the core portion 5 constituting the first optical waveguide 5a and the core portion 5 constituting the second optical waveguide 5b are arranged side by side in the optical coupling portion 50x so as to be aligned along a predetermined direction. In the example in Figure 4, each core portion 5 is aligned along the Y direction, which is the direction in which the outer edge 502 of the optical waveguide 50 adjacent to the optical coupling portion 50x extends. The first optical waveguide 5a in the example in Figure 4 extends linearly from the optical coupling portion 50x to the first input / output optical portion 50a along the X2 direction, which is perpendicular to the Y direction and indicated by arrow X2 in Figure 4. The center line 5ac of the first optical waveguide 5a extends linearly along the X2 direction. The "center line of the first optical waveguide 5a" and the "center line of the second optical waveguide 5b," which will be described later, are lines that bisect the distance between the center lines of the two most spaced core portions 5 in each optical waveguide.

[0045] In particular, the central core portion 5 of the three core portions 5 constituting the first optical waveguide 5a extends linearly without bending along the X2 direction. Thus, the first optical waveguide 5a includes a core portion 5 that extends linearly without bending along a direction substantially perpendicular to the direction in which the core portions 5 are juxtaposed in the optical coupling portion 50x. At least one of the core portions 5 constituting the first optical waveguide 5a and the second optical waveguide 5b may extend linearly without bending along the X2 direction (second direction) perpendicular to the Y direction (first direction) in which the core portions 5 are aligned.

[0046] In the example shown in Figure 4, the second optical waveguide 55b extends from the optical coupling section 50x to the second input / output section 50b, and as a whole, it moves away from the first optical waveguide 5a. Therefore, the distance between the first optical waveguide 5a and the second optical waveguide 5b between the first input / output section 50a and the second input / output section 50b is wider than the distance between the first optical waveguide 5a and the second optical waveguide 5b within the optical coupling section 50x. As a result, optical interference between component Ea1 and component Ea2, and the effects of heat generation by each component, may be mitigated. Note that the "distance between the first optical waveguide 5a and the second optical waveguide 5b" is the distance between the closest core sections 5 between the first optical waveguide 5a and the second optical waveguide 5b.

[0047] In the example in Figure 4, the center line 5bc of the second optical waveguide 5b, which extends from the optical coupling section 50x to the second input / output light section 50b so as to be separated from the first optical waveguide 5a, extends at a non-zero angle with respect to the center line 5ac of the first optical waveguide 5a, which is aligned in the X2 direction. For example, the center line 5bc of the second optical waveguide 5b may include a portion that forms an angle of 10° or more and 30° or less with respect to the X2 direction (second direction). This can be done to avoid an excessive increase in the size of the optical waveguide 50, while ensuring that components Ea1 and Ea2 are sufficiently spaced apart, thereby mitigating the effects of optical interference and heat generation.

[0048] In the example in Figure 4, the arrangement pitch P1 at the first ends 5α1 and 5α2 of the core portion 5 is smaller than the arrangement pitch P2 at the second ends 5β1 and 5β2. For example, the optical fibers F coupled to each core portion 5 at the second ends 5β1 and 5β2 may not be arranged at a pitch as small as the arrangement pitch of the light-receiving or light-emitting parts E1b (see Figure 1) provided on parts Ea1 and Ea2. In the example in Figure 4, each core portion 5 is arranged at a minimum pitch larger at the second ends 5β1 and 5β2 than at the first ends 5α1 and 5α2. Therefore, it is considered that each core portion 5 and the light-receiving or light-emitting parts of parts Ea1 and Ea2, or the optical fibers F, can be appropriately coupled at the first ends 5α1 and 5α2 and the second ends 5β1 and 5β2, respectively, without requiring a separate pitch conversion means.

[0049] The minimum arrangement pitch P1 of the core portion 5 at the first ends 5α1 and 5α2 is preferably, for example, 10 μm or more and 100 μm or less, and preferably 30 μm or more and 80 μm or less. Similarly, the minimum arrangement pitch P2 of the core portion 5 at the second ends 5β1 and 5β2 is preferably, for example, 50 μm or more and 400 μm or less, and preferably 80 μm or more and 300 μm or less. However, the arrangement pitch of the core portion 5 at each end, particularly the minimum arrangement pitch, is not limited to these numerical examples.

[0050] In the example shown in Figure 4, the width of each core portion 5 in the first input / output light section 50a (the distance between opposing outer edges of each core portion 5 in a direction perpendicular to the direction of light propagation in a plan view) is smaller than the width of each core portion 5 in the optical coupling section 50x. Similarly, the width of each core portion 5 in the second input / output light section 50b is smaller than the width of each core portion 5 in the optical coupling section 50x. That is, the width of each core portion 5 in the first ends 5α1 and 5α2 is smaller than the width of each core portion 5 in the second ends 5β1 and 5β2.

[0051] As mentioned above, the optical fibers F coupled with each core portion 5 at the optical coupling portion 50x may not be arranged at a pitch as small as the arrangement pitch of the light-receiving or light-emitting portions E1b (see Figure 1) provided on components Ea1 and Ea2. In other words, the optical fibers F may have a core diameter larger than the width of the light-receiving or light-emitting portions E1b of components Ea1 and Ea2. If the core portion 5 has a width greater than the width at the optical coupling portion 50x at the first and / or second input / output optical portions 50a and 50b, it is thought that much of the emitted light between the optical waveguide 50 and the optical fibers F and / or components Ea1 and Ea2 will be lost without being able to enter the receiving side. However, in the example of Figure 4, the width of each core portion 5 is smaller than the optical coupling portion 50x at the first input / output optical portion 50a and the second input / output optical portion 50b, so it is thought that light is less likely to be lost between the optical waveguide 50 and the optical fibers F and / or components Ea1 and Ea2. Therefore, the required luminous intensity of the light source (not shown) is low, and consequently, the power consumption of the light source can be reduced.

[0052] In the example shown in Figure 4, the width of each core section 5 decreases continuously from the second ends 5β1 and 5β2 to the first ends 5α1 and 5α2. It is thought that light propagating within each core section 5 is more likely to undergo total internal reflection without being transmitted from the core section 5 into the cladding section 52. However, the width of the core section 5 may change in steps between both ends. Furthermore, the width of each core section 5 does not have to be different between the first ends 5α1 and 5α2 and the second ends 5β1 and 5β2.

[0053] In the optical waveguide 50 example shown in Figure 4, as shown in Figure 5, the thickness of each core portion 5 differs between the first end 5α1 and the second end 5β1, with the thickness of the core portion 5 at the first end 5α1 being smaller than the thickness of the core portion 5 at the second end 5β1. That is, the thickness of each core portion 5 at the first input / output light section 50a and the thickness of each core portion 5 at the second input / output light section 50b (see Figure 4) are smaller than the thickness of each core portion 5 at the optical coupling section 50x. Note that the "thickness of the core portion 5" is the distance between the two furthest points in the Z direction on the outer circumference of the cross-section of the core portion 5, perpendicular to the direction of light propagation, at each position between the first ends 5α1, 5α2 and the second ends 5β1, 5β2.

[0054] As described above, the optical fiber F (see Figure 4) optically coupled with the core portion 5 at the optical coupling portion 50x may have a core diameter larger than the width of the light-receiving or light-emitting portion E1b (see Figure 1) of components Ea1 and Ea2 optically coupled with the core portion 5 at the first input / output portion 50a or the second input / output portion 50b. In terms of ease of formation of the core portion 5, it is preferable that the core portion 5 has a width that is approximately the same as or greater than its thickness. If the core portion 5 has a thickness greater than or equal to the thickness at the optical coupling portion 50x at the first input / output portion 50a or the second input / output portion 50b, much of the emitted light may be lost between the optical waveguide 50 and the optical fiber F, and / or between the optical waveguide 50 and components Ea1 and Ea2, without being able to enter the receiving side. However, the thickness of the core portion 5 in the first input / output light section 50a (and the second input / output light section 50b shown in Figure 4) in the example of Figure 5 is smaller than the thickness of the core portion 5 in the optical coupling section 50x. Therefore, light can be transmitted efficiently in the first input / output light section 50a, the second input / output light section 50b, and the optical coupling section 50x. As mentioned above, power consumption can be reduced.

[0055] In the example in Figure 5, the thickness of the core portion 5 decreases gradually from the end face on the second end 5β1 side to the end face on the first end 5α1 side. However, the thickness of the core portion 5 may decrease continuously from the second end 5β1 side to the first end 5α1 side. Also in Figure 5, the distance between the interface I1 between the core portion 5 and the cladding portion 52 below the core portion 5 and the lower surface 501 of the optical waveguide 50 is longer at the first end 5α1 than at the second end 5β1, and the distance between the lower surface 501 of the optical waveguide 50 and the upper surface (surface 51a) of the core portion 5 is approximately constant. However, unlike the example in Figure 5, the distance between the lower surface 501 of the optical waveguide 50 and the surface 51a of the core portion 5 may be shorter at the first end 5α1 side than at the second end 5β1 side, and the distance between the interface I1 and the lower surface 501 of the optical waveguide 50 may be approximately constant. Furthermore, the distance between the interface I1 and the lower surface 501 of the optical waveguide 50 may be longer at the first end 5α1 than at the second end 5β1, and the distance between the lower surface 501 of the optical waveguide 50 and the surface 51a of the core portion 5 may be shorter at the first end 5α1 than at the second end 5β1. The thickness of the core portion 5 of the second optical waveguide 5b shown in Figure 4 may also vary in various ways between the first end 5α2 and the second end 5β2. Note that the thickness of each core portion 5 does not have to be different between the first ends 5α1, 5α2 and the second ends 5β1, 5β2.

[0056] The width and thickness of the core portion 5 at the first ends 5α1 and 5α2 (for example, on the optical component side) are, for example, 2 μm or more and 15 μm or less, respectively. The width and thickness of the core portion 5 at the second ends 5β1 and 5β2 (for example, on the optical fiber side) are, for example, 2 μm or more and 15 μm or less, respectively. When the core portion 5 has such thickness and width, highly efficient optical coupling between the core portion 5 and optical components such as components Ea1 and Ea2 and optical fiber F (see Figure 4) can be achieved.

[0057] The optical waveguide 50, i.e., the core portion 5 and the cladding portion 52, is formed from any translucent material. The optical waveguide 50 may be composed of, for example, an organic material (organic substance), an inorganic material (inorganic substance), or a hybrid material containing organic and inorganic components, such as an inorganic polymer. Examples of inorganic materials include quartz glass and silicon, while examples of organic materials include acrylic resins such as polymethyl methacrylate (PMMA), polyimide resins, polyamide resins, polyether resins, and epoxy resins. An optical waveguide 50 composed of organic material tends to be lightweight and have high toughness.

[0058] The core portion 5 and the cladding portion 52 may be composed of different materials, or they may be composed of materials of the same type. However, the core portion 5 is made of a material with a higher refractive index than the material used for the cladding portion 52, so that total internal reflection of light at the interface between the core portion 5 and the cladding portion 52 is possible. The core portion 5 and the cladding portion 52 may be formed from materials with the same refractive index, and then a difference in refractive index between the core portion 5 and the cladding portion 52 may be created by appropriate processing. A single-mode optical waveguide 5 may be obtained depending on the combination of materials for the core portion 5 and the cladding portion 52, and the design of the core portion 5 and the cladding portion 52.

[0059] Figures 6A and 6B show other examples of the optical waveguide 50 in this embodiment. In Figures 6A and 6B, each core portion 5 is depicted with a uniform width, but even in the examples in Figures 6A and 6B, the width (and thickness) of each core portion 5 may vary between one end and the other.

[0060] The optical waveguide 50 in the examples of Figures 6A and 6B includes a first optical waveguide 5a and a second optical waveguide 5b, as well as a third optical waveguide 5c composed of any number of core portions 5 and surrounding cladding portions 52. In the examples of Figures 6A and 6B, the third optical waveguide 5c includes multiple core portions 5. The wiring board of the embodiment including the optical waveguide 50 in the examples of Figures 6A and 6B has a component mounting area A3 (third component mounting area) adjacent to component mounting area A2 with component mounting area A1 in between. Component Ea3 (third component) is placed in component mounting area A3. Component Ea3, like component Ea1, is an optical component including a photoelectric element such as a photodetector and / or light-emitting element that has a photoelectric conversion function.

[0061] One end of the third optical waveguide 5c is located in the component mounting area A3. The third optical waveguide 5c has a third input / output light section 50c that exchanges light with a mounted component (component Ea3 in the example of Figures 6A and 6B) located in the component mounting area A3. At the other end of the third optical waveguide 5c, it includes a portion of the optical coupling section 50x. The third optical waveguide 5c extends between the component mounting area A3 and the third input / output light section 50c and the optical coupling section 50x.

[0062] The core portion 5 constituting the third optical waveguide 5c has an exposed portion in the third input / output portion 50c that is not covered by the cladding portion 52. This exposed portion faces a light-receiving or light-emitting portion (not shown) in component Ea3, similar to the light-receiving or light-emitting portion E1b (see Figure 1) of component Ea1. Light from component Ea3 enters the third optical waveguide 5c, and light from the third optical waveguide 5c enters component Ea3. In the example in Figure 6A, the first input / output portion 50a, the second input / output portion 50b, and the third input / output portion 50c are arranged in a line along the outer edge near each of these input / output portions in the optical waveguide 50. The third input / output portion 50c and the second input / output portion 50b are arranged with the first input / output portion 50a sandwiched between them.

[0063] As shown in the examples in Figures 6A and 6B, the optical waveguide 50 in this embodiment may have more than two input / output light sections that exchange light with the optical components mounted on the wiring board of the embodiment. The optical waveguide 50 in this embodiment may have any number of input / output light sections, two or more, corresponding to the number of optical components mounted on the wiring board of the embodiment. Furthermore, each core section 5 of the optical waveguide 50 in this embodiment may extend between each of the more than two input / output light sections of the optical waveguide (the first to third input / output light sections 50a to 50c in the example of Figure 6A, etc.) and the optical coupling section 50x. More complex circuits including photoelectric elements can be realized on the wiring board with a high degree of freedom regarding the arrangement of photoelectric elements.

[0064] In the examples shown in Figures 6A and 6B, the second optical waveguide 5b and the third optical waveguide 5c extend away from the first optical waveguide 5a from the optical coupling section 50x to the second input / output section 50b and the third input / output section 50c. That is, the second optical waveguide 5b and the third optical waveguide 5c are curved in opposite directions from the optical coupling section 50x to the second input / output section 50b and the third input / output section 50c, and extend away from each other. As a result, the first optical waveguide 5a, the second optical waveguide 5b, and the third optical waveguide 5c as a whole extend radially from the optical coupling section 50x toward the region where the first input / output section 50a, the second input / output section 50b, and the third input / output section 50c are located. On the optical coupling section 50x side, the empty areas obtained on both sides of the first to third optical waveguides 5a to 5c can be effectively utilized for purposes other than optical paths. Note that two or more connector members C (see Figure 1) may be arranged.

[0065] The second optical waveguide 5b and the third optical waveguide 5c, which are bent between the optical coupling section 50x and the second input / output section 50b and the third input / output section 50c, are each composed of a core section 5 having a bent portion. In the examples of Figures 6A and 6B, the core section 5 constituting the second optical waveguide 5b and the third optical waveguide 5c each includes a portion that bends in an arc. Therefore, in the examples of Figures 6A and 6B, compared to the case where each core section 5 includes a portion that bends at a specific angle, less light is transmitted from each core section 5 to the cladding section 52, and thus light can be transmitted with higher efficiency. Thus, it is preferable that the bent portion of the core section 5 forms an R shape, and the specific numerical values ​​such as curvature that represent the R shape are not particularly limited.

[0066] In the example in Figure 6B, the optical waveguide 50 further includes a sub-optical waveguide 5d which contains core portions 5 other than those that constitute the first to third optical waveguides 5a to 5c. The sub-optical waveguide 5d extends between component mounting area A2 and component mounting area A3. The example in Figure 6B which includes a core portion 5 that extends between component mounting area A2 and component mounting area A3 (i.e., provides an optical path between component Ea2 and component Ea3) can further increase the degree of freedom in connecting photoelectric elements in the circuit realized on the wiring board of the embodiment. In Figure 6B, the sub-optical waveguide 5d is composed of two core portions 5, but the sub-optical waveguide 5d may contain any number of core portions 5.

[0067] As mentioned above, in the example of Figure 6B, component mounting area A2 and component mounting area A3 are aligned with component mounting area A1 in between. The sub-optical waveguide 5d is located on the optical coupling section 50x side of the first input / output optical section 50a. Therefore, the sub-optical waveguide 5d intersects with the first optical waveguide 5a. The sub-optical waveguide 5d and the first optical waveguide 5a may intersect three-dimensionally via the cladding section 52, but in the example of Figure 6B, the sub-optical waveguide 5d and the first optical waveguide 5a are in contact with each other and connected at the intersection. Therefore, the sub-optical waveguide 5d enables direct optical transmission between component Ea2 and component Ea3. As a result, there is no transmission loss compared to the case where optical transmission between photoelectric conversion elements is converted to electricity. Note that the path of the sub-optical waveguide 5d is not limited to the example shown in Figure 6B, as long as the two optical components can be optically connected to each other. For example, the sub-optical waveguide 5d may be provided on the side opposite to the optical coupling 50x with respect to the component mounting area A1.

[0068] Furthermore, due to the straight-line propagation of light within the core portion 5, it is considered that the light propagating through the core portion 5 of the sub-optical waveguide 5d, even at the intersection with the first optical waveguide 5a, does not enter the core portion 5 of the first optical waveguide 5a, but instead propagates further into the core portion 5 of the sub-optical waveguide 5d. Similarly, it is considered that the light propagating through the core portion 5 of the first optical waveguide 5a does not enter the sub-optical waveguide 5d side, but instead propagates within the first optical waveguide 5a.

[0069] Figure 7 shows an enlarged view of a modified example of part III in Figure 1. In the example in Figure 7, the core portion 5 of the optical waveguide 50 is not formed to the outer edge of the optical waveguide 50 at the first end 5α1 side. The core portion 5 has its end face exposed on the upper surface 52a of the cladding portion 52, which is closer to the circuit board 200 than the core portion 5. The exposed end face of the core portion 5 faces the component mounting area A1 in the direction (X direction) along the direction of light propagation within the core portion 5. Then, as shown in Figure 7, when component Ea1 is placed on the exposed portion of the upper surface 52a of the cladding portion 52, the exposed end face of the core portion 5 faces the light-receiving or light-emitting surface E1c of the light-receiving or light-emitting portion E1b, which faces sideways. Therefore, light is transferred between the exposed end face of the core portion 5 and the light-receiving or light-emitting portion E1b of component Ea1.

[0070] In the example shown in Figure 7, a portion of the optical waveguide 50 overlaps with the component mounting area A1 in a plan view, but the first input / output light section 50a, which transfers light to and from component Ea1, is adjacent to the component mounting area A1 without overlapping in a plan view. Although not shown, the second input / output light section 50b (see Figure 2) may also be formed in the same way as the first input / output light section 50a in the example shown in Figure 7. Thus, either or both of the first input / output light section 50a and the second input / output light section 50b do not need to overlap with a component mounting area such as the component mounting area A1 in a plan view. In that case, the surface 51a of each core section 5 facing the opposite direction from the circuit board 200 does not need to be exposed in either or both of the first input / output light section 50a and the second input / output light section 50b.

[0071] Figure 8 shows another example of the combination of the optical waveguide 50 and component Ea1 in the wiring board 100 of the embodiment. In the example in Figure 8, the optical waveguide 50 and support plate 6 are arranged on solder resist 23 covering the insulating layer 21 and the conductor layer 11. Also in the example in Figure 8, the light-receiving or light-emitting portion E1b of component Ea1 is provided together with electrode E1a on the upper surface of component Ea1 facing away from the circuit board 200. Electrode E1a is electrically connected to the conductor post 13 via an electrode (not shown) that penetrates component Ea1. The core portion 5 of the optical waveguide 50 is provided such that its end face on the first end 5α1 side faces the light-receiving or light-emitting portion E1b provided on the upper surface of component Ea1. For example, the height of the core portion 5 from the surface of the circuit board 200 can be adjusted by appropriately selecting the thickness of the support plate 6 and the thickness of the cladding portion 52 on the circuit board 200 side of the core portion 5. Thus, the core portion 5 can be positioned to optically couple with the light-receiving or light-emitting portion E1b, regardless of whether the light-receiving or light-emitting portion E1b is located on the lower surface or the upper surface of the component Ea1 facing the circuit board 200.

[0072] Next, an example of a method for manufacturing the wiring board of the embodiment will be explained using the wiring board 100 in Figure 1 as an example, with reference to Figures 9A to 9E.

[0073] As shown in Figure 9A, insulating layers 21, 22 and conductive layers 11, 12 are formed on both sides of the core substrate 3. For example, a conductive layer 31 having a desired conductive pattern and a through-hole conductor 33 are formed on a double-sided copper-clad laminate substrate including an insulating layer that will become the insulating layer 32 of the core substrate 3 by a subtractive method. The inside of the cylindrical through-hole conductor 33 is filled with a filler 34 by injecting a suitable resin, such as epoxy resin. Then, an insulating layer 21 is formed on the first surface 3a of the core substrate 3, and an insulating layer 22 is formed on the second surface 3b. The insulating layers 21 and 22 are formed, for example, by laminating a film-like epoxy resin onto the core substrate 3 and then thermocompressing it. Through holes for forming via conductors 20 are formed in each insulating layer, for example by irradiation with carbon dioxide laser light. Then, a conductive layer 11 is formed on the insulating layer 21, and a conductive layer 12 is formed on the insulating layer 22. The conductive layer 11 is formed to include predetermined conductive patterns such as conductive pads 11a, 11b. Conductor layer 11 and conductor layer 12 are formed, for example, by a semi-additive method. Along with the formation of conductor layers 11 and 12, via conductors 20 are formed in through holes provided in insulating layers 21 and 22.

[0074] As shown in Figure 9B, the conductor post 13 is formed. Figure 9B shows an enlarged view of section IXB in Figure 9A after the formation of the conductor post 13. Although not shown in Figure 9B, the conductor post 14 (see Figure 9C) is also formed together with the conductor post 13. In the formation of the conductor layer 11 and the like by the semi-additive method, as shown in Figure 9B, a metal film 111 is formed over the entire surface of the insulating layer 21, for example by electroless plating. The plated film 112 is formed by pattern plating, including electroplating, using the metal film 111 as a power supply layer.

[0075] After the plating resist (not shown) used for pattern plating is removed, the metal film 111 remains completely intact, and a plating resist R1 having openings R1a at the locations where the conductor posts 13 are formed is formed on the conductor layer 11 and the insulating layer 21. For example, the openings R1a are formed using photolithography technology. Then, the conductor posts 13 are formed within the openings R1a, for example, by electroplating using the metal film 111 as a power supply layer.

[0076] Furthermore, as shown in Figure 9B, a connecting layer 15 is formed on the end face of the conductor post 13 by electroplating, for example, using a metal film 111 as the power supply layer. The connecting layer 15 is formed by a metal film made of, for example, tin, a tin alloy, or a gold alloy. After the connecting layer 15 is formed, the plating resist R1 is removed using an appropriate stripping agent. Then, the portion of the metal film 111 that is not covered by the plating film 112 is removed, for example, by quick etching.

[0077] As shown in Figure 9C, a solder resist 23 is formed covering the insulating layer 21, the conductor layer 11, the conductor posts 13 and 14, and the connecting layer 15. The solder resist 23 is formed by supplying, for example, a liquid or sheet-like epoxy resin or polyimide resin onto the insulating layer 21 and each component on its surface by methods such as printing, coating, spraying, or lamination. The solder resist 23 is fully cured or partially cured by heating or ultraviolet irradiation as needed. Solder resist 23 is also formed on the second surface 3b side of the core substrate 3 by coating or laminating epoxy resin or polyimide resin.

[0078] As shown in Figure 9D, a portion of the solder resist 23 in the thickness direction is removed. The reduction in the thickness of the solder resist 23 exposes the ends of the conductor posts 13 and 14 opposite to the insulating layer 21, and the connecting layer 15. The portion of the solder resist 23 can be removed by dry etching, such as plasma etching using carbon tetrafluoride (CF4) gas, or by blasting.

[0079] As shown in Figure 9E, the portion of the solder resist 23 corresponding to the area where the optical waveguide 50 is located is removed, for example, by irradiation with a carbon dioxide laser. The area of ​​the insulating layer 21 surface where the optical waveguide 50 is located is exposed. This laser processing can form an opening 23a in the solder resist 23. The circuit board 200 is completed.

[0080] If an optical waveguide 50 is provided and a wiring board 100 as shown in the example in Figure 1 is manufactured, a support plate 6 is also provided. The optical waveguide 50 is formed using, for example, photolithography, Mosquito, or imprint printing. As will be described later, the optical waveguide 50 may be formed on a support plate 6 made of, for example, glass, or it may be bonded to a separately prepared support plate 6 using any adhesive (not shown) after the optical waveguide 50 has been formed.

[0081] An adhesive Gu, such as a thermosetting, room-temperature curing, or photocuring adhesive, is applied to a predetermined portion of the surface of the insulating layer 21 exposed from the solder resist 23, and the support plate 6 and optical waveguide 50 are mounted on top of it. If necessary, the adhesive Gu is cured by heating or other means, and the optical waveguide 50 and support plate 6 are fixed to the circuit board 200. Furthermore, the connecting layer 15 is melted by a reflow process or the like and shaped into a hemispherical form. By going through the above steps, the wiring board 100 shown in the example in Figure 1 is completed.

[0082] Referring to Figures 10A to 10D, an example of a method for forming the optical waveguide 50 illustrated in Figures 4 and 5 is described, which involves using an imprint method on a support plate 6. As shown in Figure 10A, for example, a glass plate is prepared as the support plate 6, and a lower cladding layer 521 is formed on the surface of the support plate 6. For example, a material described above as a constituent material for the cladding portion 52 (see Figure 10C), such as PMMA, is formed into a film and heat-pressed onto the support plate 6.

[0083] The mold M is pressed against the lower cladding layer 521. The mold M is provided with a plurality of rib-shaped protrusions M1 on the surface that is pressed against the lower cladding layer 521, each having a shape corresponding to the core portion 5 (see Figures 4 and 5) that constitute the first and second optical waveguides 5a and 5b. The tips of the protrusions M1 are provided with steps corresponding to the steps that the surface of the core portion 5 on the support plate 6 side should have. By pressing the mold M against the lower cladding layer 521, a plurality of grooves 523 are formed in the lower cladding layer 521, each having a shape corresponding to the shape of the core portion 5 (see Figure 10B). Steps are formed on the bottom surface of the grooves 523, corresponding to the steps that the core portion 5 should have on the surface on the support plate 6 side.

[0084] As shown in Figure 10B, a core portion 5 is formed in the groove 523. The core portion 5 is formed by coating or printing a material that can constitute the core portion 5, such as an acrylic resin as described above, onto the surface of the lower cladding layer 521, or by forming it into a sheet and then laminating it. Specifically, the core portion 5 is formed by filling the groove 523 with the constituent material of the core portion 5 supplied onto the surface of the lower cladding layer 521 by coating or the like. The constituent material of the core portion 5 is supplied to the entire surface of the lower cladding layer 521, and then may be removed, for example, by exposure and development, except for the portion that fills the groove 523. The constituent material of the core portion 5 may also be supplied only to the inside of the groove 523 by printing using an appropriate mask.

[0085] As shown in Figure 10C, the upper cladding layer 522 is formed on the lower cladding layer 521 and the core portion 5. For example, similar to the formation of the lower cladding layer 521, the constituent material of the cladding portion 52, such as PMMA, is formed into a film and heat-pressed onto the lower cladding layer 521 and the core portion 5. The upper cladding layer 522 integrates with or at least adheres to the lower cladding layer 521, thereby forming the cladding portion 52 surrounding the core portion 5.

[0086] As shown in Figure 10D, the portion of the upper cladding layer 522 that covers the first end 5α1 of the core portion 5 is removed. In the formation of the optical waveguide 50 in the example of Figures 4 and 5, the portion of the upper cladding layer 522 that covers the areas that will become the first input / output portion 50a and the second input / output portion 50b (see Figure 4) is removed. As a result, a portion of the core portion 5 is exposed in the first input / output portion 50a and the first end 5α1, 5α2 (see Figure 4) of the second input / output portion 50b. The removed portion of the upper cladding layer 522 can be removed by, for example, exposure and development, or laser processing. In the process shown in Figure 10C, the constituent material of the cladding portion 52 may be heat-compressed so that a portion of the first end 5α1, 5α2 side of the core portion 5 is not covered. For example, the optical waveguide 50 illustrated in Figures 4 and 5 is formed by going through the process shown in Figures 10A to 10D.

[0087] The wiring boards of the embodiments are not limited to those having the structures illustrated in each drawing, or the structures, shapes, and materials illustrated herein. As stated above, the wiring boards of the embodiments may have any laminated structure. For example, the wiring boards of the embodiments may be coreless boards that do not include a core board. The wiring boards of the embodiments may include any number of conductor layers and insulating layers. Conductor pads 11b and conductor posts 14 are not required to be formed, and conductor posts 13 are not necessarily provided. Also, the three or more input and output light portions of the optical waveguide do not have to be arranged in a row. The arrangement pitch of the core portions may be substantially the same at one end and the other end, and the width and thickness of the core portions may be substantially constant from one end to the other. Although width and thickness are used as dimensions to indicate the size of the core portions, the core portions may have any cross-sectional shape other than a rectangle. Furthermore, all core portions constituting each optical waveguide may extend in a straight line without bending, or all core portions may be bent. [Explanation of Symbols]

[0088] 100 Wiring boards 11, 12 Conductor layers 21, 22 Insulating layer 200 circuit boards 5. Core section 5a First optical waveguide 5ac First optical waveguide centerline 5b Second optical waveguide 5bc Centerline of the second optical waveguide 5c Third optical waveguide 5d Sub-Optical Waveguide 50 Optical waveguide 50a First light inlet / outlet section 50b Second light input / output section 50c Third light inlet / outlet section 50x optical coupler 51a Surface (side) of the core 52 Clad section A1-A3 Component mounting area (1st to 3rd component mounting area) C connector component (optical connector) Ea1 Component (First Component) Ea2 part (second part)

Claims

1. A circuit board including an insulating layer and a conductive layer, An optical waveguide, which includes a core portion that transmits light and a cladding portion that surrounds the core portion, and is placed on the circuit board, A wiring board including, The aforementioned wiring board has a first component mounting area and a second component mounting area. The optical waveguide is, It includes a first optical waveguide and a second optical waveguide, and The first optical waveguide has an optical coupling portion that is combined with a connector member to transfer light between the connector member and the waveguide, and the first optical waveguide has a first input / output light portion that transfers light between the waveguide and the mounted component to the first component mounting area, and includes a part of the optical coupling portion. The second optical waveguide has a second input / output light section that transfers light to and from the mounted component in the second component mounting area, and also includes a part of the optical coupling section. The core portion constituting the first optical waveguide and the core portion constituting the second optical waveguide are arranged side by side in the optical coupling portion so as to be aligned along a predetermined first direction. At least one of the core portions constituting the first optical waveguide extends linearly along a second direction substantially perpendicular to the first direction.

2. A circuit board including an insulating layer and a conductive layer, An optical waveguide, which includes a core portion that transmits light and a cladding portion that surrounds the core portion, and is placed on the circuit board, A wiring board including, The aforementioned wiring board has a first component mounting area and a second component mounting area. The optical waveguide is, It includes a first optical waveguide and a second optical waveguide, and The first optical waveguide has an optical coupling portion that is combined with a connector member to transfer light between the connector member and the waveguide, and the first optical waveguide has a first input / output light portion that transfers light between the waveguide and the mounted component to the first component mounting area, and includes a part of the optical coupling portion. The second optical waveguide has a second input / output light section that transfers light to and from the mounted component in the second component mounting area, and also includes a part of the optical coupling section. The wiring board further has a third component mounting area that is adjacent to the second component mounting area with the first component mounting area in between, The optical waveguide further includes a third optical waveguide which has a third input / output light section for transferring light to and from a component mounted in the third component mounting area, and which also includes a part of the optical coupling section.

3. A circuit board including an insulating layer and a conductive layer, An optical waveguide, which includes a core portion that transmits light and a cladding portion that surrounds the core portion, and is placed on the circuit board, A wiring board including, The aforementioned wiring board has a first component mounting area and a second component mounting area. The optical waveguide is, It includes a first optical waveguide and a second optical waveguide, and The first optical waveguide has an optical coupling portion that is combined with a connector member to transfer light between the connector member and the waveguide, and the first optical waveguide has a first input / output light portion that transfers light between the waveguide and the mounted component to the first component mounting area, and includes a part of the optical coupling portion. The second optical waveguide has a second input / output light section that transfers light to and from the mounted component in the second component mounting area, and also includes a part of the optical coupling section. The thickness of the core portion in the first light input / output section and the thickness of the core portion in the second light input / output section are smaller than the thickness of the core portion in the light coupling section. The width of the core portion in the first light input / output section and the width of the core portion in the second light input / output section are smaller than the width of the core portion in the light coupling section.

4. A wiring board according to any one of claims 1 to 3, wherein the first optical waveguide includes a plurality of core portions, and the second optical waveguide includes a plurality of core portions.

5. A wiring board according to claim 2 or 3, The core portion constituting the first optical waveguide and the core portion constituting the second optical waveguide are arranged side by side in the optical coupling portion so as to be aligned along a predetermined first direction. At least one of the core portions constituting the first optical waveguide extends linearly along a second direction substantially perpendicular to the first direction.

6. The wiring board according to claim 5, wherein the center line of the second optical waveguide includes a portion that forms an angle of 10° or more with respect to the second direction.

7. The wiring board according to claim 5, wherein the core portion constituting the second optical waveguide includes a portion that bends in an arc.

8. A wiring board according to claim 1 or 3, further comprising a third component mounting area adjacent to the second component mounting area with the first component mounting area in between, The optical waveguide further includes a third optical waveguide which has a third input / output light section for transferring light to and from a component mounted in the third component mounting area, and which also includes a part of the optical coupling section.

9. The wiring board according to claim 8, wherein the first optical waveguide, the second optical waveguide, and the third optical waveguide as a whole extend radially from the optical coupling portion toward the region where the first input / output light portion, the second input / output light portion, and the third input / output light portion are located.

10. The wiring board according to claim 8, wherein the optical waveguide further includes a sub-optical waveguide extending between the second component mounting area and the third component mounting area.

11. The wiring board according to claim 10, wherein the core portion constituting the sub-optical waveguide intersects with the core portion constituting the first optical waveguide.

12. A wiring board according to claim 1 or 2, The thickness of the core portion in the first light input / output section and the thickness of the core portion in the second light input / output section are smaller than the thickness of the core portion in the light coupling section. The width of the core portion in the first light input / output section and the width of the core portion in the second light input / output section are smaller than the width of the core portion in the light coupling section.

13. A wiring board according to any one of claims 1 to 3, wherein in the first input / output light portion and the second input / output light portion, the side surface of the core portion is exposed without being covered by the cladding portion.

14. A wiring board according to claim 13, The first light input / output section overlaps with the first component mounting area in a plan view, and the second light input / output section overlaps with the second component mounting area in a plan view.

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