JP2016157120A - Optical circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical circuit board in which electronic components are stably operated.SOLUTION: An optical circuit board A is configured such that: on an upper main surface of a wiring board 10 having a wiring conductor 14a between multiple stacked insulation layers 12a and 12b, an optical waveguide 16 formed such that a core 16b is held between a lower cladding layer 16a and an upper cladding layer 16c is disposed so as to extend along the upper main surface; and the core 16b is cut off perpendicularly to an extending direction and at a predetermined angle relative to the upper main surface, and the cut in which a cross section made by cutting off the core 16b serves as a reflection face M is also formed so as to penetrate the optical waveguide 16 from an upper surface of the upper cladding layer 16c. A metal layer S forming a bottom face of the cut is disposed above the wiring conductor 14a.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical circuit board having a reflecting surface for changing the direction of an optical signal.

FIG. 3 shows an example of a conventional optical circuit board B.
As shown in FIG. 3, the conventional optical circuit board B includes a wiring board 20 and an optical waveguide forming portion 21.

  The wiring board 20 includes a lower insulating layer 22a and an upper insulating layer 22b. Connection holes 23 are formed in the insulating layers 22a and 22b. A lower wiring conductor 24 a is formed in the upper surface of the lower insulating layer 22 a and the connection hole 23. An upper wiring conductor 24 b is formed in the upper surface of the upper insulating layer 22 b and in the connection hole 23. Further, external connection pads 25 are formed on the lower surface of the lower insulating layer 22a.

The optical waveguide forming part 21 is formed on the wiring board 20. An optical waveguide 26 and an electronic component connection pad 27 are formed in the optical waveguide forming portion 21.
The optical waveguide 26 is formed by a lower clad layer 26a, a core 26b, and an upper clad layer 26c. An optical signal is transmitted to the optical waveguide 26.
The electronic component connection pad 27 is formed on the upper surface of the upper cladding layer 26c. An electronic component (not shown) is mounted on the electronic component connection pad 27. An optical signal is exchanged between the electronic component and the optical waveguide 26.
Further, a connection hole 28 is formed in the optical waveguide forming portion 21 so as to penetrate the optical waveguide forming portion 21. A connection conductor 28 a is attached in the connection hole 28. The electronic component connection pad 27 and the upper wiring conductor 24b are connected via the connection conductor 28a.
The lower clad layer 26a and the upper clad layer 26c constituting the optical waveguide forming portion 21 are solid insulating layers. The core 26b has a thin band shape with a square cross section. The lower clad layer 26a and the upper clad layer 26c are in close contact with the surface of the core 26b and surround the core 26b.
Furthermore, the core 26b has a reflective surface M at one end thereof. The reflecting surface M has a cross section that is perpendicular to the extending direction of the core 26b and has a predetermined angle with respect to the upper main surface. An optical signal is exchanged between the optical waveguide 26 and the electronic component via the reflecting surface M.

  Next, an example of a conventional method for manufacturing an optical circuit board will be described with reference to enlarged views of main parts shown in FIGS. In addition, the same code | symbol is attached | subjected and demonstrated to the part similar to FIG.

  First, as shown in FIG. 4A, a lower insulating layer 22a having a lower wiring conductor 24a deposited on the upper surface and an external connection pad 25 deposited on the lower surface is prepared.

  Next, as shown in FIG. 4B, the upper insulating layer 22b is laminated on the upper surface of the lower insulating layer 22a, and the connection hole 23 having the lower wiring conductor 24a as the bottom surface is formed.

  Next, as shown in FIG. 4C, the wiring substrate 20 is formed by depositing the upper wiring conductor 24 b in the upper surface of the upper insulating layer 22 b and the connection hole 23.

  Next, as shown in FIG. 4D, a lower clad layer 26 a is formed on the upper surface of the wiring substrate 20.

  Next, as shown in FIG. 4E, a core 26b is formed on the upper surface of the lower cladding layer 26a.

  Next, as shown in FIG. 4F, an optical waveguide 26 is formed by forming an upper clad layer 26c on the upper surface of the core 26b.

  Next, as shown in FIG. 4G, a connection hole 28 is formed in the optical waveguide 26 to expose a part of the upper wiring conductor 24b as a bottom surface.

  Next, as shown in FIG. 4H, a connection conductor 28a is deposited in the connection hole 28, and an electronic component connection pad 27 is formed on the upper surface of the upper clad layer 26c.

  Finally, as shown in FIG. 4 (i), the core 26b is divided by irradiating a laser beam obliquely from above the optical waveguide 26, and perpendicular to the extending direction of the core 26b and with respect to the upper main surface of the wiring board 20. A conventional optical circuit board B as shown in FIG. 3 is formed by forming the reflecting surface M having a cross section having a predetermined angle.

In recent years, as electronic devices typified by portable communication devices and music players have become smaller and more functional, optical circuit boards mounted on these electronic devices are also required to be smaller and more functional. ing. For this reason, fine wiring conductors are formed at a high density with respect to the wiring conductors of the wiring board constituting the optical circuit board.
However, when the reflective surface M is formed when the conventional optical circuit board B is manufactured, a fine lower layer wiring formed at a high density by the laser irradiated obliquely from above penetrating the upper insulating layer 22b. The conductor 24a may be reached and damaged. As a result, there is a problem that an electric signal is difficult to propagate to the lower wiring conductor 24a and the electronic component does not operate stably.

JP 2006-330066 A

  The present invention prevents damage to the wiring conductor by forming a metal layer that prevents the laser at the time of forming the reflection surface from reaching the wiring conductor formed on the wiring board, thereby stabilizing the electronic component. It is an object of the present invention to provide an optical circuit board that can be operated easily.

  In the optical circuit board according to the present invention, an optical waveguide having a core sandwiched between a lower clad layer and an upper clad layer is provided along the upper main surface on the upper main surface of the wiring board having a wiring conductor between a plurality of laminated insulating layers. The core is divided at a predetermined angle with respect to the upper main surface and at a predetermined angle with respect to the upper main surface, and a cut in which the divided cross section of the core is a reflective surface is formed in the upper cladding layer. An optical circuit board is formed so as to penetrate the optical waveguide from the upper surface, and a metal layer that forms the bottom surface of the cut is disposed above the wiring conductor.

  According to the optical circuit board of the present invention, when the core is divided by irradiating the laser from obliquely above the optical waveguide, the metal layer is formed in the region where the laser irradiation axis and the upper surface of the insulating layer above the wiring conductor intersect. By forming it, the laser is prevented from reaching below the upper surface of the insulating layer above the wiring conductor. As a result, it is possible to prevent the wiring conductor from being damaged by the laser, and thus it is possible to provide an optical circuit board that can stably propagate an electric signal to the wiring conductor and stably operate an electronic component. can do.

FIG. 1 is a schematic cross-sectional view showing an embodiment of an optical circuit board according to the present invention. 2A to 2I are enlarged cross-sectional views of main parts showing one embodiment for each process of manufacturing an optical circuit board according to the present invention. FIG. 3 is a schematic sectional view showing an example of a conventional optical circuit board. 4 (a) to 4 (i) are enlarged cross-sectional views of main parts showing an example of a conventional method for manufacturing an optical circuit board.

  First, an embodiment of the optical circuit board of the present invention will be described in detail with reference to FIG.

  As shown in FIG. 1, the optical circuit board A of the present invention includes a wiring board 10 and an optical waveguide forming portion 11.

  The wiring board 10 includes a lower insulating layer 12a and an upper insulating layer 12b. Connection holes 13 are formed in both insulating layers 12a and 12b. A lower wiring conductor 14 a is formed in the upper surface of the lower insulating layer 12 a and the connection hole 13. An upper wiring conductor 14 b is formed in the upper surface of the upper insulating layer 12 b and in the connection hole 13. Further, a laser blocking metal layer S is formed on the upper surface of the upper insulating layer 12b. An external connection pad 15 is formed on the lower surface of the lower insulating layer 12a.

The optical waveguide forming portion 11 is formed on the upper main surface of the wiring board 10. An optical waveguide 16 and electronic component connection pads 17 are formed in the optical waveguide forming portion 11.
The optical waveguide 16 is formed of a lower cladding layer 16a, a core 16b, and an upper cladding layer 16c. The optical waveguide 16 is formed so as to extend along the upper main surface of the wiring substrate 10. An optical signal is transmitted to the optical waveguide 16.
The electronic component connection pad 17 is formed on the upper surface of the upper cladding layer 16c. An electronic component (not shown) is mounted on the electronic component connection pad 17. Optical signals are exchanged between the electronic component and the optical waveguide 16.
Further, a connection hole 18 is formed in the optical waveguide forming portion 11 so as to penetrate the optical waveguide forming portion 11. A connection conductor 18 a is attached in the connection hole 18. The electronic component connection pad 17 and the upper wiring conductor 14b are connected via the connection conductor 18a.
The lower clad layer 16a and the upper clad layer 16c constituting the optical waveguide forming portion 11 are solid insulating layers. The core 16b has a thin strip shape with a square cross section. The lower cladding layer 16a and the upper cladding layer 16c are in close contact with the surface of the core 16b and surround the core 16b.
Furthermore, the core 16b has a reflection surface M at one end thereof. The reflective surface M is formed of a cross section having a predetermined angle with respect to the upper main surface and perpendicular to the extending direction of the core 16b. An optical signal is exchanged between the optical waveguide 16 and the electronic component via the reflecting surface M.

  Next, an example of the manufacturing method of the optical circuit board of the present invention will be described in detail with reference to FIGS. Further, the same parts as those in FIG.

First, as shown in FIG. 2A, a lower insulating layer 12a having a lower wiring conductor 14a deposited on the upper surface and an external connection pad 15 deposited on the lower surface is prepared.
The lower insulating layer 12a is formed, for example, by impregnating a glass cloth with an epoxy resin, a bismaleimide triazine resin, or the like and thermosetting it. The lower wiring conductor 14a and the external connection pad 15 are made of a highly conductive metal such as copper by a known plating method, for example.

Next, as shown in FIG. 2 (b), the upper insulating layer 12b is laminated on the upper surface of the lower insulating layer 12a, and the connection hole 13 exposing the lower wiring conductor 14a as the bottom surface is formed.
The upper insulating layer 12b is formed, for example, by applying an insulating sheet made of bismaleimide triazine resin, polyimide resin or the like to the upper surface of the lower insulating layer 12a in a vacuum state and then thermally curing the insulating sheet.
The connection hole 13 is formed by, for example, laser processing.

Next, as shown in FIG. 2 (c), the upper wiring conductor 14b is deposited in the upper surface of the upper insulating layer 12b and in the connection hole 13, and laser irradiation is performed to form a reflection surface M to be described later. The wiring board 10 is formed by depositing a laser blocking metal layer S in a region where the shaft and the upper surface of the upper insulating layer 12b intersect.
The upper wiring conductor 14b and the metal layer S are formed of a highly conductive metal such as copper by a known plating method, for example. The thickness of the metal layer S is preferably about 10 to 15 μm. If it is thinner than 10 μm, the laser may be cut off imperfectly. On the other hand, if the thickness is greater than 15 μm, it may be difficult to reduce the thickness of the optical waveguide 16.

Next, as shown in FIG. 2D, a lower clad layer 16 a is formed on the upper surface of the wiring substrate 10.
The lower clad layer 16a is formed by, for example, applying a photosensitive sheet made of an epoxy resin or a polyimide resin on the wiring substrate 10 in a vacuum state to form a predetermined shape by exposure and development, and then thermosetting. . The thickness of the lower cladding layer 16a is about 10 to 20 μm.

Next, as shown in FIG. 2E, the core 16b is formed on the upper surface of the lower cladding layer 16a.
The core 16b is formed by depositing a photosensitive sheet made of, for example, an epoxy resin or a polyimide resin on the lower clad layer 16a in a vacuum state, forming a strip shape by exposure and development, and then thermosetting. The refractive index of the resin forming the photosensitive sheet for forming the core 16b is larger than the refractive index of the resin forming the photosensitive sheet for forming the lower and upper cladding layers 16a and 16c. The thickness of the core 16b is about 30 to 40 μm.

Next, as shown in FIG. 2F, an optical waveguide 16 is formed by forming an upper clad layer 16c on the upper surface of the core 16b.
The upper clad layer 16c is formed by applying a photosensitive sheet made of, for example, epoxy resin or polyimide resin so as to cover the lower clad layer 16a and the core 16b in a vacuum state, exposing and developing, and then thermosetting. Is done. The thickness of the upper cladding layer 16c is about 10 to 20 μm.

Next, as shown in FIG. 2G, a connection hole 18 is formed in the optical waveguide 16 to expose a part of the upper wiring conductor 14b as a bottom surface.
The connection hole 18 is formed, for example, by laser processing with the upper wiring conductor 14b as the bottom surface.

Next, as shown in FIG. 2H, a connection conductor 18a is deposited in the connection hole 18, and an electronic component connection pad 17 is formed on the upper surface of the upper clad layer 16c.
The connection conductor 18a and the electronic component connection pad 17 are formed of a highly conductive metal such as copper by a known plating method, for example.

  Finally, as shown in FIG. 2I, the core 16b is divided by irradiating the laser beam obliquely from above the optical waveguide 16 so as to be perpendicular to the extending direction of the core 16b and to the upper main surface of the wiring board 10. A reflecting surface M having a cross section having a predetermined angle is formed. Then, the optical circuit board A as shown in FIG. 1 is formed by surface-treating the divided section of the optical waveguide 16 divided by the laser with blasting or the like.

  At this time, according to the optical circuit board of the present invention, the laser blocking metal layer S is formed in a region where the laser irradiation axis for forming the reflecting surface M and the upper surface of the upper insulating layer 12b intersect. Therefore, the laser irradiated when forming the reflecting surface M is prevented from reaching below the metal layer S by the laser blocking metal layer S after dividing the core 16b. Thereby, since it is possible to avoid damage to the lower wiring conductor 14a by the laser, it is possible to stably propagate the electric signal to the lower wiring conductor 14a and to stably operate the electronic component. An optical circuit board can be provided.

  In addition, this invention is not limited to an example of the above-mentioned embodiment, A various change is possible if it is a range which does not deviate from the summary of this invention. For example, in this example, the case where the metal layer S is formed from copper is shown, but a metal such as titanium, nickel, or chromium, or an alloy layer thereof may be used.

DESCRIPTION OF SYMBOLS 10 Wiring board 12a (lower layer) insulating layer 12b (upper layer) insulating layer 14a (lower layer) wiring conductor 14b (upper layer) wiring conductor 16 Optical waveguide 16a Lower clad layer 16b Core 16c Upper clad layer A Optical circuit board M Reflection Surface S Metal layer

Claims (1)

  An optical waveguide having a core sandwiched between a lower clad layer and an upper clad layer is arranged on the upper main surface of a wiring board having a wiring conductor between a plurality of laminated insulating layers so as to extend along the upper main surface. The core is cut at a predetermined angle perpendicular to the extending direction and with respect to the upper main surface, and a cut in which the cut section of the core is a reflective surface is formed from the upper surface of the upper clad layer. An optical circuit board formed so as to penetrate the optical waveguide, wherein a metal layer forming a bottom surface of the cut is disposed above the wiring conductor.

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