JP2016038452A - Optical wiring substrate and optical transmission module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical wiring substrate and an optical transmission module that are capable of optically connecting to other optical means with high degrees of efficiency.SOLUTION: An optical wiring substrate 1 includes: a substrate 2; a lower cladding part 3 that is disposed on the substrate 2 and has a groove part extending from an outer periphery of the substrate 2 to a further inner side than the outer periphery; a core part 4 that is disposed on the lower cladding part 3 and extends to the groove part; an upper cladding part 5 that is disposed on the lower cladding part 3 and covers the core part 4; and an optical fiber a portion of which is disposed in the groove part and that has a core connected optically to the core part 4.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an optical wiring board having an optical waveguide and an optical transmission module.

  In recent years, in order to improve information processing capability, it has been studied to change electrical transmission between electronic devices to optical transmission. Therefore, an optical wiring board on which an optical waveguide for optical transmission between electronic devices is formed is known. The optical wiring board is optically connected to an optical means such as a light emitting element, a light receiving element, or an optical fiber to construct a high-speed optical transmission circuit (see, for example, Patent Document 1).

JP 2008-241956

  In the research and development of such an optical wiring board, a structure of an optical wiring board that can be efficiently optically connected to other optical means is required.

  The present invention has been conceived under the above circumstances, and an object of the present invention is to provide an optical wiring board that can be efficiently optically connected to other optical means.

  The optical wiring board of the present invention is disposed on the substrate 2, the lower cladding portion 3 having the groove 3 a disposed on the substrate 2 and extending from the outer periphery of the substrate 2 to the inside of the outer periphery, and the lower cladding portion 3. Further, the core part 4 extending to the groove part 3a, the upper clad part 5 covering the core part 4 disposed on the lower clad part 3, and the core part 4 partially disposed in the groove part 3a are optically coupled. And an optical fiber 6 having a connected core.

  An optical transmission module of the present invention includes the above-described optical wiring board and an optical element that is mounted on the board and optically connected to the core portion.

  According to the optical wiring board and the optical transmission module of the present invention, it is possible to optically connect with other optical means efficiently.

1 is a perspective view showing a schematic configuration of an optical transmission module including an optical wiring board according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the optical transmission module of FIG. 1 and corresponds to a cross section taken along line A-A ′ of FIG. 1. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates an embodiment of an optical wiring board according to the present invention, where (a) corresponds to a plan view viewed from above, and (b) is a cross-sectional view taken along line BB ′ in (a). (C) is equivalent to sectional drawing when cut | disconnected by CC 'line | wire of (a). BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of an optical wiring board according to the present invention, where (a) corresponds to a plan view seen from above, and (b) is a cross-sectional view taken along the line DD 'in (a). (C) is equivalent to sectional drawing when cut | disconnected by the EE 'line | wire of (a). BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of an optical wiring board according to the present invention, where (a) corresponds to a plan view viewed from above, and (b) is a cross-sectional view taken along line FF ′ of (a). (C) is equivalent to sectional drawing when cut | disconnected by the GG 'line | wire of (a). BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of an optical wiring board according to the present invention, where (a) corresponds to a plan view seen from above, and (b) is a cross-sectional view taken along line HH ′ in (a). It corresponds to. FIG. 7 shows an embodiment of the optical wiring board of the present invention, corresponding to an enlarged plan view in which part of FIG. 6A is enlarged, and FIG. 6B being taken along line HH ′ of FIG. This corresponds to a cross-sectional view taken along the corresponding line II ′. 1 shows an embodiment of an optical wiring board of the present invention, which corresponds to a cross section taken along line A-A ′ of FIG. 1.

  An optical wiring board and an optical transmission module according to an embodiment of the present invention will be described below. As shown in FIGS. 1 to 8, the optical wiring board 1 according to this embodiment includes a substrate 2, a lower clad part 3, a core part 4, an upper clad part 5, and an optical fiber 6. Such an optical wiring substrate 1 is used as an optical transmission module 200 having an optical element 8 optically connected to the core portion 4.

<Optical transmission module>
An optical transmission module 200 including the optical wiring board 1 of the present embodiment is shown in FIGS. The optical transmission module 200 includes an optical wiring board 1 and an optical element 8 mounted on the optical wiring board 1 and optically connected to the core portion 4. For example, a light emitting device such as a surface emitting laser or a light receiving device such as a photodiode can be used as the optical element 8.

  The optical element 8 may be directly mounted on the wiring conductor 106 formed on the substrate 2, or may be mounted on the wiring conductor 106 of the substrate 2 through the through-hole substrate 100. In the present embodiment, the optical element 8 is mounted via the through-hole substrate 100.

  The through-hole substrate 100 has a through-hole 101 that penetrates in the vertical direction (D1 and D2 directions). The inside of the through hole 101 may be a cavity, or an optical transmission structure including the core body 120 and the clad body 121 may be disposed. An optical element 8 is mounted on the through-hole substrate 100. The optical element 8 and the core portion 4 are optically connected by a through hole 101. In the present embodiment, a case where an optical transmission structure is disposed in the through hole 101 will be described.

  As the clad body 121, for example, epoxy resin, polyimide resin, phenol resin, acrylic resin, or the like can be used. Inside the clad body 121, an optical waveguide hole 121a penetrating in the thickness direction (D1, D2 direction) is provided. A plurality of optical waveguide holes 121 a may be formed inside the clad body 121.

  A core body 120 is provided in the optical waveguide hole 121a. The core body 120 is made of a material having a higher refractive index than that of the clad body 121. Examples of the diameter of the core body 120 include a range of 1 μm to 300 μm. Since the core body 120 is filled in the optical waveguide hole 121a, the core body 120 has substantially the same diameter as the optical waveguide hole 121a, and is set according to the shape and diameter of the optical waveguide hole 121a.

The driving of the optical element 8 is controlled by the control element 102. The optical element 8 and the control element 102 are electrically connected by an electric wiring 103 formed on the through-hole substrate 100. The optical element 8 and the control element 102 are mounted on the electric wiring 103. The through-hole substrate 100 is provided with a through conductor 104 therein. The through conductor 104 may be made of any material that can be electrically connected.

  The through-hole substrate 100 is mounted on the wiring conductor 106 via the bump conductor 105 as shown in FIG. A through hole 7 a is provided in the optical waveguide layer 7, and the wiring conductor 106 on the substrate 2 is exposed. The bump conductor 105 can be made of a material that can be electrically connected and can fix the through-hole substrate 100 and the substrate 2. For example, a conductor material made of solder can be used.

  Since a fitting structure is provided on the lower surface of the through-hole substrate 100 and the upper surface of the optical waveguide layer 7, the through-hole substrate 100 is aligned when mounted on the optical wiring substrate 1. As a fitting structure, it is comprised by the recessed part or the convex part, for example.

<Optical wiring board>
The thickness of the board | substrate 2 is provided so that it may become the range of 0.01 mm or more and 1 cm or less, for example. One side (D3, D4 direction or D5, D6 direction in FIG. 1) of the substrate 2 can be set to, for example, 1 cm or more and 10 cm or less.

  The substrate 2 is made of, for example, a ceramic material or an organic material. As a specific ceramic material, for example, materials such as zirconia, alumina, silicon carbide, boron nitride, beryllia, low-temperature fired glass ceramic, mullite, glass ceramic, or silicon nitride can be used, and these may be used in combination. . On the other hand, when an organic material is used as the material of the substrate 2, for example, an epoxy resin, a bismaleimide-triazine resin, a cyanate resin, a polyphenylene ether resin, an aromatic polyamide resin, or a polyimide resin can be used.

  The substrate 2 may be a single layer substrate or a laminate in which a plurality of sub-substrates are stacked. As a material of the substrate 2, for example, a ceramic material or an organic material such as an epoxy resin can be used. In the present embodiment, a substrate made of a single layer ceramic material is employed. On the substrate 2, wiring conductors connected to an electric circuit or the like are formed. The wiring conductor is made of, for example, metalized metal.

  An optical waveguide layer 7 is formed on the substrate 2. For the optical waveguide layer 7, for example, a material based on an epoxy resin, an acrylic resin, and a polyimide resin can be used. The thickness of the optical waveguide layer 7 can be set to be, for example, 50 μm or more and 1 mm or less.

  The optical waveguide layer 7 is generally composed of a lower clad part 3, a core part 4 and an upper clad part 5. The refractive index of the core portion 4 is set to be larger than the refractive indexes of the lower cladding portion 3 and the upper cladding portion 5 in the range of 0.8% to 4%. Since the lower clad part 3 and the upper clad part 5 are arranged around the core part 4, light can be confined in the core part 4 and light can be transmitted. Hereinafter, each structure of the lower clad part 3, the core part 4, and the upper clad part 5 is demonstrated.

  The lower cladding part 3 is disposed on the substrate 2. The thickness of the lower cladding part 3 can be set to be 20 μm or more and 500 μm or less, for example. The thickness of the lower clad part 3 may be set according to the thickness of the clad 6b so that the center axes of the core 6a and the core part 4 of the optical fiber 6 are aligned when the optical fiber 6 described later is disposed on the substrate 2. . In this embodiment, since the optical fiber 6 having a diameter of 125 μm is used, the thickness of the lower clad portion 3 is set to about 45 μm.

The lower clad part 3 has a groove part 3a in a part thereof. As shown in FIG. 3A, the groove 3a is arranged so as to extend from the outer periphery of the substrate 2 to the inner side of the outer periphery when viewed in plan. The inner side of the outer periphery refers to a region surrounded by the outer periphery of the substrate 2 when viewed in plan. The groove part 3a may penetrate so that the upper surface of the board | substrate 2 may be exposed, and may be arrange | positioned so that the upper surface of the board | substrate 2 may not be exposed.

  When the groove 3a penetrates so as to expose the upper surface of the substrate 2, the optical wiring substrate 1 can be reduced in height. On the other hand, when the upper surface of the substrate 2 is not exposed, for example, the lower cladding portion 3 can be formed of two layers. In this case, when the flatness is poor because the wiring conductor 106 is provided on the substrate 2, the lower clad portion 3 is disposed at a place where the optical fiber 6 is placed, and the optical fiber The flatness of the place which mounts 6 can be improved.

  The groove 3a is set so that the lateral width matches, for example, the width of the optical fiber 6 in plan view. Here, the width of the optical fiber 6 does not necessarily have to be a diameter, and as shown in FIG. 3C, the optical fiber 6 can be accurately placed even when the lateral width of the groove 3a is shorter than the diameter. . In the present embodiment, the optical fiber 6 is placed on the substrate 2 so as to be in contact with the substrate 2, but the present invention is not limited to this. By making the lateral width of the groove 3 a smaller than the width of the optical fiber 6, the optical fiber 6 May be arranged away from the substrate 2.

  The core part 4 is disposed on the lower cladding part 3. In this embodiment, the core part 4 is set so that the cross-sectional shape of a cross section perpendicular | vertical with respect to the advancing direction of light may be inscribed in the circular outer periphery which is the cross-sectional shape of the core 6a of the optical fiber 6. The cross-sectional shape of the core part 4 is formed to be rectangular, for example. The core portion 4 is formed so that the cross-sectional area of the cross section perpendicular to the light traveling direction is approximately the same as that of the core 6 a of the optical fiber 6. The width of the core part 4 is set to be, for example, 10 μm or more and 300 μm or less.

  In this embodiment, although the cross-sectional shape of the core part 4 and the cross-sectional shape of the core 6a of the optical fiber 6 are different, the size of the core part 4 is set to be smaller than the core 6a in this way. The connection loss of light can be reduced regardless of the traveling direction of light (when used for both transmission and reception). As a result, since the optical transmission module 200 can be used for transmission and reception, it can be made highly versatile.

  On the other hand, the optical connection loss can be further reduced by setting the size of the core portion 4 in consideration of the traveling direction of light. That is, when light travels from the core part 4 to the optical fiber 6, the core part 4 is made smaller than the core 6a, and when light travels from the optical fiber 6 to the core part 4, the core part 4 is made larger than the core 6a. Can be optically connected efficiently.

  The core part 4 is arranged so that the end face 4a connected to the optical fiber 6 extends to the groove part 3a. The end surface 4a of the core part 4 is substantially flush with the edge of the groove part 3a. The end surface 4a of the core portion 4 only needs to be optically connected to the core 6a of the optical fiber 6, and may be disposed on the inner side of the edge of the groove portion 3a or may protrude to the groove portion 3a side. . In addition, although this embodiment demonstrates the case where the one core part 4 is formed, multiple core parts 4 may be formed.

  The core portion 4 has a light incident / exit surface 4b on the side opposite to the end surface 4a. The light incident / exit surface 4b is optically connected to a light receiving / emitting surface of an optical element 8 such as a light emitting element or a light receiving element. An optical path changing surface 4c is formed on the light incident / exit surface 4b side, and when the light receiving / emitting surface and the light incident / exit surface 4b are not in a straight line, the light traveling direction is changed to connect the two.

In the optical path conversion surface 4c, a part of the core portion 4 may be exposed, or a reflective film may be formed on the upper surface. The material of the reflective film may be selected in consideration of the reflectance depending on the wavelength of light to be transmitted. For example, a material mainly composed of aluminum, silver, gold, or the like can be used. By forming the reflective film, the light whose optical path is changed can be easily totally reflected. The inclination angle of the optical path conversion surface 4 c can be set to 40 ° or more and 52 ° or less with respect to the optical axis of the core portion 4, for example.

  The upper cladding part 5 is disposed on the lower cladding part 3. The upper clad part 5 is disposed so as to cover the core part 4 other than the end face 4 a of the core part 4. The upper clad part 5 is formed thicker than the core part 4, and is formed with a thickness of 20 μm or more and 500 μm or less, for example.

  The lower cladding part 3, the core part 4, and the upper cladding part 5 are formed by, for example, a photolithography method. By using a photolithography method, after forming materials for the lower clad part 3, the core part 4 and the upper clad part 5, exposure and development can be performed to pattern the material into an arbitrary shape.

  As a method of forming the lower clad part 3, the core part 4, and the upper clad part 5, for example, a laminating method can be used. As a method for laminating the film, for example, a vacuum laminating method, a roll laminating method or the like can be used. The film thickness can be controlled by adjusting the film thickness of the film. The optical waveguide layer 7 may be formed by spin coating. The optical waveguide layer 7 is formed by spin-coating a resin material to be the optical waveguide layer 7 on the substrate 2. In the case of the spin coating method, the film thickness can be controlled by adjusting the rotational speed or the viscosity of the resin material.

  Specifically, after forming a resin material to be the lower clad portion 3 on the substrate 2, the lower clad portion 3 is formed by exposing and developing so as to form the groove 3a. Thereafter, after a resin material to be the core portion 4 is formed on the lower clad portion 3, the core portion 4 is formed by exposing and developing in an arbitrary shape so as to extend to the groove portion 3a. Then, after the resin material to be the upper clad part 5 is formed on the lower clad part 3 so as to cover the core part 4, the upper clad part 5 can be formed by performing exposure and development.

  The lower clad part 3, the core part 4, and the upper clad part 5 are patterned with high precision because the resin material is exposed using a photomask (reticle) in which position information is recorded with high precision. Therefore, the groove portion 3a can be formed with high absolute positional accuracy in the lower cladding portion 3, and the core portion 4 can also be formed with high absolute positional accuracy. As a result, the groove portion 3a and the core portion 4 are formed. It can be formed with high relative positional accuracy.

  The optical fiber 6 includes a core 6a and a clad 6b that covers the core 6a. For example, the core 6a is configured to have a refractive index higher by 0.2% or more and 3% or less than the cladding 6b. The optical fiber 6 may be composed of a single mode optical fiber or a multimode optical fiber. As the multimode optical fiber, a graded index optical fiber having a refractive index that gradually decreases (in a stepwise manner) from the optical axis of the core toward the cladding in a cross section perpendicular to the light traveling direction can be used. The diameter of the core 6a is, for example, 50 μm, and the diameter of the optical fiber 6 is, for example, 125 μm. The core 6a has a circular cross section perpendicular to the light traveling direction, and the optical fiber 6 is also configured to have a substantially circular cross section.

The optical fiber 6 is placed in the groove 3a, whereby a part of the optical fiber 6 is disposed in the groove 3a. The core 6 a of the optical fiber 6 may be optically connected to the core portion 4 and may be separated from the end surface 4 a of the core portion 4. In this embodiment, the core 6a of the optical fiber 6 is
It arrange | positions so that the end surface 4a of the core part 4 may contact.

  In the optical wiring board of the present embodiment, the optical fiber 6 is placed in the groove 3 a formed in a part of the lower cladding portion 3, whereby the core portion 4 of the optical waveguide layer 7 and the core 6 a of the optical fiber 6 Are optically connected. Since the groove portion 3a and the core portion 4 are formed with high positional accuracy, the optical waveguide layer 7 and the optical fiber 6 can be optically coupled with high accuracy and easily by placing the optical fiber 6 in the groove portion 3a. it can.

(Modification 1 of optical wiring board)
On the lower clad part 3, as shown in FIG.4 (c), you may have the core member 4d. 4 d of core members have the 2nd groove part 4e in the position which overlaps with the groove part 3a. The core member 4d is formed on the lower clad part 3 constituting the groove part 3a so as to constitute the second groove part 4e. The horizontal width of the second groove portion 4e may be formed with the same horizontal width as the groove portion 3a, or may be formed larger than the horizontal width of the groove portion 3a. The core member 4d is set to the same thickness as the core portion 4. The core member 4d is formed by patterning at the same time when the core portion 4 is formed.

  Thus, since the 2nd groove part 4e is arrange | positioned on the groove part 3a, when the optical fiber 6 is mounted, it can fix more firmly. Further, since the patterning is performed simultaneously with the core portion 4, the relative positional accuracy between the end surface 4a of the core portion 4 and the second groove portion 4e is formed with the accuracy of the photomask. Therefore, by mounting the optical fiber 6 in the second groove 4e, it is possible to mount with higher positional accuracy.

  Further, as shown in FIG. 5, a clad member 5b having a third groove portion 5a may be provided on the core member 4d so as to overlap the groove portion 3a and the second groove portion 4e. The lateral width of the third groove portion 5a may be the same lateral width as that of the second groove portion 4e, or may be wider than that of the second groove portion 4e. The clad member 5 b is set to the same thickness as the upper clad portion 5. The clad member 5b is formed by patterning at the same time when the upper clad portion 5 is formed.

  Thus, by forming the 3rd groove part 5a, the effect similar to the case where the 2nd groove part 4e is formed can be acquired. In this modification, the case where the second groove portion 4e is formed has been described. However, when the third groove portion 5a is provided without providing the second groove portion 4e, the third groove portion 5a is formed so as to overlap the groove portion 3a. do it. In this case, the clad member 5b is formed on the lower clad part 3 constituting the groove part 3a.

(Modification 2 of the optical wiring board)
As shown in FIG. 6, the end surface 4 a on the optical fiber 6 side of the core portion 4 may protrude from the end surface 5 c on the optical fiber 6 side of the upper cladding portion 5. The core part 4 is arrange | positioned so that it may project from 1 micrometer or more and 50 micrometers or less, for example from the end surface 5c of the upper clad part 5 in planar view. The protruding portion of the core portion 4 is disposed on the lower cladding portion 3 and is exposed from the upper cladding portion 5. The protruding portion of the core portion 4 may be formed so as to be exposed when the upper clad portion 5 is patterned.

  As described above, the end surface 4a of the core portion 4 protrudes from the end surface 5c of the upper clad portion 5, so that the position of the core 6a of the optical fiber 6 with respect to the end surface 4a of the core portion 4 when the optical fiber 6 is placed. Can be easily confirmed.

  Moreover, as shown in FIG.7 (b), the part which the core part 4 protruded may protrude also from the end surface by the side of the optical fiber 6 (groove part 3a) of the lower clad part 3. As shown in FIG. That is, the core part 4 may protrude from the upper clad part 5 and the lower clad part 3. Furthermore, as shown in FIG. 7A, the protruding portion of the core portion 4 may have a convex shape that protrudes toward the optical fiber 6 toward the center of the end surface 4a in plan view.

  By adopting such a convex shape, the contact property can be improved regardless of the angle at which the optical fiber 6 is in contact with the end face 4 a of the core portion 4. That is, the optical fiber 6 can be optically connected even if the angle deviates from the end surface 4a of the core portion 4 when the optical fiber 6 is brought into contact therewith. Such a convex shape of the core portion 4 can be patterned when the core portion 4 is formed by a photomask.

(Modification 3 of the optical wiring board)
As shown in FIG. 8, the optical wiring board 1 may have an optical path conversion surface 4 c provided on the light incident / exit surface 4 b side of the core portion 4 filled with an upper cladding portion 5. By thus filling the optical path conversion surface 4c with the upper clad portion 5, the optical path conversion surface 4c is not exposed to the air, so that the light receiving / emitting surface of the optical element 8 and the light incident / exit surface 4b are efficiently optically coupled. Easy to do. Also, as shown in FIG. 8, through holes 7a are formed in the optical waveguide layer 7, and bump conductors 105 that are electrically connected to the optical elements 8 are disposed in the through holes 7a. The optical transmission module 200 including the height can be reduced.

DESCRIPTION OF SYMBOLS 1 Optical wiring board 2 Board | substrate 3 Lower clad part 3a Groove part 4 Core part 4a End surface 4b Light incident / exit surface 4c Optical path conversion surface 4d Core member 5 Upper clad part 5a 3rd groove part 5b Clad member 5c End surface 6 Optical fiber 6a Core 6b Clad 7 Optical waveguide layer 8 Optical element 100 Through hole substrate 101 Through hole 102 Control element 103 Electrical wiring 104 Through conductor 105 Bump 106 Wiring conductor 120 Core body 121 Clad body 121a Optical waveguide hole 200 Optical transmission module

Claims (7)

A substrate,
A lower clad portion having a groove portion disposed on the substrate and extending from the outer periphery of the substrate to the inner side of the outer periphery;
A core portion disposed on the lower cladding portion and extending to the groove portion;
An upper clad portion disposed on the lower clad portion and covering the core portion;
An optical wiring board comprising: an optical fiber having a core optically connected to the core part, a part of which is disposed in the groove part. The optical fiber has a cladding covering the core;
The optical wiring board according to claim 1, wherein the clad has the same thickness as the lower clad portion.   The optical wiring board according to claim 1, further comprising a core member disposed on the lower clad portion and having a second groove portion at a position overlapping the groove portion.   The optical wiring board according to claim 3, further comprising: a clad member disposed on the core member and having a third groove portion at a position overlapping the groove portion and the second groove portion.   5. The optical wiring board according to claim 1, wherein an end surface on the optical fiber side of the core portion protrudes from an end surface on the optical fiber side of the upper clad portion.   The optical wiring board according to claim 1, wherein the core portion protrudes toward the optical fiber toward the center. The optical wiring board according to any one of claims 1 to 6,
An optical transmission module mounted on the substrate and having an optical element optically connected to the core portion.

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