JP2005134451A - Optic/electric mixed mounting substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce optical propagation loss in the optical path along the substrate thickness direction of an optic/electric mixed mounting substrate. <P>SOLUTION: An optic/electric mixed mounting substrate 1 is provided with an electric wiring 3 which is formed on the surface of a substrate 2, an optical wiring (a waveguide core) 4 which is formed inside the substrate 2, a vertical direction waveguide 5 which guides optical signals along the thickness direction of the substrate 2 and an optical path changing structure 6 which is used to optically couple the optical wiring 4 and the vertical direction waveguide 5. The vertical direction waveguide 5 is formed by conducting partial material reform at a point P where laser light beams LB are irradiated using the electric wiring 3 as a reference for positioning. The optical path changing structure 6 is formed in a similar manner as in the case of the vertical direction waveguide 5. The vertical direction waveguide 5 is formed without conducting a mechanical elimination process and a material filling process. Therefore, the optic/electric mixed mounting substrate, in which conventional optical propagation loss caused by bubble generation due to resin filling and resin hardening deformation or the like is reduced, is obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an opto-electric hybrid board in which electrical wiring and optical wiring are mixed.

  2. Description of the Related Art Conventionally, in an opto-electric hybrid board, which is a composite board in which electrical wiring and optical wiring (optical waveguide) are mixed, a photoelectric conversion element that converts between an optical signal mounted on the substrate surface and an electrical signal from the optical waveguide inside the board And an optical path between optical waveguides that are separated from each other in the thickness direction of the substrate. As such an opto-electric hybrid board having an optical path (optical waveguide) for propagating an optical signal in a direction perpendicular to the substrate surface, for example, the one shown in FIG. 9 is known (see, for example, Patent Document 1). ).

A method for forming this conventional opto-electric hybrid board will be described. First, as shown in FIG. 9A, an electrode 91 for installing a photoelectric conversion element is provided on an electrical wiring substrate 90, and a through hole 92 is formed. As shown in FIG. 9B, an optical waveguide plate composed of a core 93 and a clad 94 is formed of resin on the lower surface of the electric wiring board 90, and the clad material 93 is filled and cured in the through holes. As shown in FIG. 2, a through hole 96 penetrating the whole is further formed. Next, as shown in FIG. 9 (d), the core material 97 is filled and cured in the through holes 96. Subsequently, as shown in FIG. 9E, a mirror 98 is formed from the lower surface of the substrate by cutting or etching, and an optical waveguide from the direction in the substrate plane toward the substrate thickness direction is formed.
Republished patent WO01 / 001176

  However, in the opto-electric hybrid board having the optical waveguide in the thickness direction of the board formed by the method as described above, a process of removing a part of the members constituting the board is necessary, and the work efficiency in manufacturing the board is reduced. Not good. Further, in the method of making an optical path by making a hole in the clad portion and filling the core material into the through hole, it is difficult to prevent bubbles that cause light propagation loss in the optical path. Moreover, time is required for processing, hardening of the core material, and the like. Furthermore, if shrinkage occurs when the filled resin is cured, there is a problem that the propagation loss of the optical path is significantly reduced.

  The present invention solves the above-described problems, and an object thereof is to provide an opto-electric hybrid board with reduced light propagation loss in an optical path in the thickness direction of the board.

  In order to achieve the above object, an invention according to claim 1 includes an electric wiring for propagating an electric signal formed on a substrate, an optical wiring for propagating an optical signal formed on the substrate in an in-plane direction of the substrate, and the substrate In an opto-electric hybrid board including a vertical waveguide that guides an optical signal in the thickness direction of the optical path, an optical path changing structure that deflects light so as to optically couple between the optical wiring and the vertical waveguide is provided, The vertical waveguide is formed by irradiating a laser beam at a position on the substrate determined with the electric wiring as a reference for positioning and performing material modification, and is an opto-electric hybrid board. is there.

  According to a second aspect of the present invention, in the opto-electric hybrid board according to the first aspect, the cross-sectional areas at both ends of the vertical waveguide are different from each other.

  According to a third aspect of the present invention, in the opto-electric hybrid board according to the first aspect, the end of the vertical waveguide has a convex lens shape.

  According to a fourth aspect of the present invention, in the opto-electric hybrid board according to the first aspect, the substrate is subjected to material modification by irradiating femtosecond laser light.

  According to a fifth aspect of the present invention, in the opto-electric hybrid board according to the first aspect, the vertical waveguide includes an outer peripheral portion having a low refractive index and a central portion having a high refractive index.

  According to a sixth aspect of the present invention, in the opto-electric hybrid board according to the first aspect, the vertical waveguide is composed of a plurality of optical waveguides.

  A seventh aspect of the present invention is the opto-electric hybrid board according to the first aspect, wherein a photonic crystal is formed by laser light irradiation around the vertical waveguide and / or the optical path changing structure. .

  According to the invention of claim 1, by performing partial material modification by irradiating laser light, a vertical waveguide is formed without performing mechanical removal processing or material filling. An opto-electric hybrid board with reduced generation of light propagation loss due to resin curing deformation or the like can be obtained. It is also possible to form a very fine optical path. Further, since the vertical waveguide is formed with the electrical wiring as a reference for positioning, similarly, the photoelectric conversion element can be mounted with high positional accuracy with respect to the vertical waveguide by using the electrical wiring as a reference for positioning.

  According to the invention of claim 2 or claim 3, for example, by forming the larger cross-sectional area of both ends of the vertical waveguide as the light incident side, at the time of light entering and exiting the vertical waveguide Optical loss can be reduced.

  According to the invention of claim 4, since the local modification of the substrate material can be easily performed using the femtosecond laser, the vertical waveguide can be easily formed. Even if the laser beam is not scanned in the vertical direction, as the vertical waveguide is formed by the material modification inside the substrate, the vertical waveguide is sequentially moved to the substrate surface side by the self-focusing function of the laser beam. It can also be made to form toward.

  According to invention of Claim 5 or Claim 6, the optical propagation loss of an optical path can be reduced.

  According to the invention of claim 7, even if the internal reforming portion is not formed in a strict continuous state, light can be confined in the optical path by the photonic crystal, and the vertical waveguide can be easily formed. Further, by forming a photonic crystal around the optical path changing structure, it is possible to reduce the optical loss during the optical path deflection.

  Hereinafter, an opto-electric hybrid board according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an opto-electric hybrid board 1 and a manufacturing method thereof. As shown in FIG. 1A, the opto-electric hybrid board 1 includes an electric wiring 3 that propagates an electric signal formed on the surface of the substrate 2 and an optical wiring that propagates an optical signal formed inside the substrate 2. (Waveguide core) 4, a vertical waveguide 5 for guiding an optical signal in the thickness direction of the substrate 2, and an optical path changing structure for deflecting light so as to optically couple the optical wiring 4 and the vertical waveguide 5 6 is provided. The optical wiring 4 is formed by being surrounded by a waveguide clad 41 having a refractive index smaller than that of the optical wiring 4. The vertical waveguide 5 is formed in the internal region of the substrate 2 from the surface of the substrate 2 to the surface of the clad 41.

  As shown in FIG. 1B, the above-described vertical waveguide 5 partially improves the material at a point P irradiated with the laser beam LB at a position on the substrate determined by using the electrical wiring 3 as a positioning reference. It is formed so as to guide the optical signal in the thickness direction of the substrate by performing the quality. Similarly to the vertical waveguide 5, the optical path changing structure 6 is also formed by partial material modification by laser light irradiation.

  Here, an outline of the entire manufacturing process of the opto-electric hybrid board 1 will be described. First, the substrate 2 and the inner optical waveguide (that is, the optical wiring 4 and the clad 41) are made by molding or photolithography using resin for the substrate, the clad, and the optical wiring having different refractive indexes. Are formed by stacking. Next, the electrical wiring 3 is formed on the surface of the substrate 2 having a waveguide inside. Next, the optical path changing structure 6 is formed on the optical path of the optical wiring 3 using laser light, and the vertical waveguide 5 is formed using laser light. In addition, the order of these manufacturing processes can be changed suitably.

  This partial material modification by laser light irradiation (called photoinduced refractive index change) can be performed locally at the point P irradiated with the laser light, and by scanning the irradiation point in the XYZ directions. The material modified region having an arbitrary three-dimensional shape can be formed relatively easily. For each of the above-described resins forming the opto-electric hybrid board 1, it is necessary to use a material that undergoes material modification by laser light irradiation, that is, a resin that changes a desired light-induced refractive index by laser light irradiation.

  Further, in order to guide light in a desired direction, a linear continuous region (that is, an optical path) having a refractive index larger than that of the surroundings may be formed. Therefore, the waveguide is formed by focusing the laser beam on the optical path formation position and increasing the refractive index by modifying the laser beam irradiation section while moving the laser beam focus along the desired formation position. Is done. The moving speed of the focal point needs to be equal to or lower than the speed at which the modified region cannot be interrupted.

  As a method of forming the vertical waveguide 5 by moving the focal point, for example, a modified region is formed by adjusting the focal position of the laser beam to a predetermined depth inside the substrate at a desired formation position, and the depth thereof is adjusted as necessary. A method in which the modified region is expanded by laser beam scanning in the in-plane direction (XY direction) and the focal position is moved to the substrate surface side (Z direction) to further form a continuous modified region. It is good. It is not preferable to reverse this procedure, that is, to form the modified portion from the shallower side to the deeper side because the laser beam is scattered in the modified portion.

  As the laser light, femtosecond laser light or the like that hardly affects the surroundings of the laser light irradiation portion is desirable. The laser processing conditions are, for example, a laser wavelength of 800 nm, a pulse width of 100 fs, a laser repetition frequency of 82 MHz, and a laser output of 1 to 7 nJ / pulse. As for partial material modification by laser light irradiation, for example, an invention by the present applicant is disclosed in Japanese Patent Laid-Open No. 2002-14246.

  Since the opto-electric hybrid board 1 manufactured in this way forms the vertical waveguide 5 without performing mechanical removal processing or material filling, the conventional machining hole is filled with resin to guide the vertical guide. Unlike the formation of a waveguide, this is an opto-electric hybrid board provided with a vertical waveguide in which generation of light propagation loss due to bubble generation, resin hardening deformation, or the like is reduced. Further, since the forming method does not depend on machining, it is possible to form a finer vertical waveguide 5 and this opto-electric hybrid board 1 can cope with integration of optical wiring and miniaturization of the board. .

  The above-described positioning on the substrate 2 using the electrical wiring 3 as a positioning reference will be described. In a composite substrate (an opto-electric hybrid board) in which the electrical wiring 3 for propagating the electrical signal and the optical wiring 4 for propagating the optical signal are mixed, the optical signal propagating through the optical wiring 4 is taken out in the vertical direction, and FIG. As shown by the dotted line in FIG. 2, the optical signal emitted from the surface-emitting laser or the like mounted on the substrate surface is propagated to the photoelectric conversion element C such as a photodiode mounted on the substrate surface. It is necessary to propagate to the optical wiring provided in parallel. At this time, the loss of the optical signal propagating in the vertical direction (photoelectric coupling loss) depends on the absorptance and reflectance of the material through which the light propagates, the light spread angle, and the propagation distance. In addition, in particular, the alignment accuracy between the position of the light incident / exit end face of the vertical waveguide 5 and the position of the light receiving / emitting portion C1 of the photoelectric conversion element C greatly affects the magnitude of the photoelectric coupling loss.

  Therefore, the vertical waveguide 5 is formed using the electrical wiring 3 as a positioning reference, and thereafter, the alignment between the photoelectric conversion element C and the vertical waveguide 5 is similarly performed using the electrical wiring 3 as the positioning reference. By mounting the photoelectric conversion element C, the alignment accuracy is improved and the photoelectric coupling loss can be reduced. That is, first, the position of the optical wiring 4 and the optical path changing structure 6 and the position of the land 31 that is a part of the electrical wiring 3 on which the photoelectric conversion element C is mounted are measured. The position of the light emitting / receiving section C1 of the photoelectric conversion element C can be calculated from the measured position of the land 31. From the calculated position, a position (a space region in the substrate 2) where the vertical waveguide 5 is formed can be obtained, and the vertical waveguide 5 can be formed with high accuracy.

  By the way, as a result of the position measurement, the position where the vertical waveguide 5 can be formed is limited. In this case, taking advantage of the property that partial material modification by laser light irradiation is possible for the three-dimensional distribution region, not the optical waveguide strictly along the vertical line but the light emitting / receiving unit C1 and the optical path changing structure 6 The vertical waveguide 5 is formed along a straight line or a curve connecting the two. The opto-electric hybrid board 1 provided with the vertical waveguide 5 formed in this way has a small opto-electric coupling loss.

  Next, an opto-electric hybrid board according to another embodiment of the present invention will be described with reference to FIG. The vertical waveguide 5 of the opto-electric hybrid board 1 is formed in a region from the surface of the board 2 to the inside of the optical wiring 4 through the clad 41. This opto-electric hybrid board 1 has less opto-electric coupling loss than the opto-electric hybrid board shown in FIG. In forming the vertical waveguide 5, attention is paid so as not to damage the optical path changing structure 6.

  Next, an opto-electric hybrid board according to still another embodiment of the present invention will be described with reference to FIG. The opto-electric hybrid board 1 includes a vertical waveguide 50 that optically couples a plurality of optical wirings 4 formed at different positions in the thickness direction of the board 2. An optical path changing structure 6 is provided at a position corresponding to the upper and lower optical wirings 4, and a vertical waveguide 50 is formed therebetween. The opto-electric hybrid board 1 has a multilayer optical wiring structure in which a vertical waveguide 50 between layers is formed by partial material modification by laser light irradiation, like the optical path changing structure 6 and the vertical waveguide 5. Light propagation.

  Next, an opto-electric hybrid board according to still another embodiment of the present invention will be described with reference to FIGS. These opto-electric hybrid boards 1 reduce the optical coupling loss between the light emitting / receiving section of the photoelectric conversion element and the vertical waveguide. As shown in FIG. 4A, a photoelectric conversion element such as a surface emitting laser is mounted on the electrical wiring 3 on the surface of the substrate 2 (not shown), and an optical signal is transmitted from the surface of the substrate 2 to the optical wiring 4. In the case of waveguide, the vertical waveguide 5 is formed so that the cross section on the surface side of the substrate 2 has a larger taper shape than the cross section on the inner side of the substrate.

  On the other hand, as shown in FIG. 4B, when the optical signal propagating through the optical wiring 4 is propagated to the vertical waveguide 5 and is received by a photodiode or the like (not shown) of the substrate 2, The vertical waveguide 5 is formed so that the cross section on the inner side of the substrate is tapered more than the cross section on the substrate surface side. As described above, the vertical waveguide 5 having different sizes at both ends is processed by scanning a laser beam over a wide range, for example, on the inner side, and defocusing the laser beam on the surface side of the substrate 2. can do.

  Next, an opto-electric hybrid board according to still another embodiment of the present invention will be described with reference to FIG. In this opto-electric hybrid board 1, the shape of the end face inside the vertical waveguide 5 is a convex lens. With this convex lens on the end face, it is possible to reduce optical loss when light enters and exits between the optical wiring 4 and the vertical waveguide 5. The convex lens shape can be formed by a method using the energy distribution of laser light or a method of condensing and processing laser light with a high-power lens only at the tip of the convex lens portion.

  Next, an opto-electric hybrid board according to still another embodiment of the present invention will be described with reference to FIG. The vertical waveguide 5 of the opto-electric hybrid board 1 includes a central core 51 having a high refractive index and a clad 52 having a low refractive index around it. Such a double structure has energy higher than that of the laser beam used to form the vertical waveguide with respect to the vertical waveguide of the opto-electric hybrid board shown in FIG. The laser beam is used to cause a material modification at the central portion of the vertical waveguide and further increase the refractive index. The low-refractive-index vertical waveguide 5 formed in advance is formed in advance widely in order to form a high-refractive index region to be formed later. When a material whose refractive index is lowered by laser irradiation is used, a double structure can be formed by lowering the refractive index by irradiating laser light around a previously formed vertical waveguide.

  Next, an opto-electric hybrid board according to still another embodiment of the present invention will be described with reference to FIG. The vertical waveguide 5 of the opto-electric hybrid board 1 is formed as an assembly of a plurality of unit waveguides 53. The spread of light from the vertical waveguide 5 having a small light incident / exit end of each unit waveguide 53 is smaller than the spread of light from the vertical waveguide having a single large light incident / exit end. That is, when light is emitted from the vertical waveguide 5 to the optical wiring 4, optical loss can be reduced. The vertical waveguide 5 is formed by adjoining individual unit waveguides 53 formed by narrowing laser light.

  Next, an opto-electric hybrid board according to still another embodiment of the present invention will be described with reference to FIG. The vertical waveguide 5 of the opto-electric hybrid board 1 is such that the region where the optical signal is guided remains the material of the substrate 2 and the surroundings are modified by laser light irradiation so that the light enters the vertical waveguide 5. It is formed to be confined. The material modification in this case is to form a photonic crystal, which is a crystal having a structure in which substances having different refractive indexes are periodically arranged by focusing the laser beam on the modified portion and performing internal processing. In addition, even if the internal modified portion that is a photonic crystal is not formed in a strictly continuous state, light can be confined in the optical path by the photonic crystal, and a vertical waveguide can be easily formed. Furthermore, by forming this photonic crystal also around the optical path changing structure 6, it is possible to reduce optical loss when changing the optical path. As a laser used for forming the photonic crystal, a femtosecond laser or the like that hardly affects the surroundings is suitable. The present invention is not limited to the above-described configuration, and various modifications can be made.

(A) is sectional drawing of the opto-electric hybrid board which concerns on one Embodiment of this invention, (b) is sectional drawing which shows the manufacturing method of the opto-electric hybrid board. Sectional drawing of the opto-electric hybrid board | substrate which concerns on other one Embodiment of this invention. Sectional drawing of the opto-electric hybrid board | substrate which concerns on another one Embodiment of this invention. (A) (b) is sectional drawing of the opto-electric hybrid board | substrate which concerns on another one Embodiment of this invention. Sectional drawing of the opto-electric hybrid board | substrate which concerns on another one Embodiment of this invention. Sectional drawing of the opto-electric hybrid board | substrate which concerns on another one Embodiment of this invention. Sectional drawing of the opto-electric hybrid board | substrate which concerns on another one Embodiment of this invention. Sectional drawing of the opto-electric hybrid board | substrate which concerns on another one Embodiment of this invention. (A)-(e) Sectional drawing which shows the conventional opto-electric hybrid board | substrate and its manufacturing process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Opto-electric hybrid board 2 Substrate 3 Electric wiring 4 Optical wiring 5 Vertical waveguide 6 Optical path change structure 51 Center part 52 Outer part 63 Optical waveguide LB Laser light

Claims (7)

An electric wiring for propagating an electric signal formed on the substrate, an optical wiring for propagating the optical signal formed on the substrate in the in-plane direction of the substrate, and a vertical waveguide for guiding the optical signal in the thickness direction of the substrate; In an opto-electric hybrid board with
An optical path changing structure for deflecting light so as to optically couple between the optical wiring and the vertical waveguide,
2. The opto-electric hybrid board according to claim 1, wherein the vertical waveguide is formed by irradiating a laser beam to a position on the board determined with the electric wiring as a reference for positioning and modifying the material.   The opto-electric hybrid board according to claim 1, wherein the cross-sectional areas at both ends of the vertical waveguide are different from each other.   The opto-electric hybrid board according to claim 1, wherein an end of the vertical waveguide has a convex lens shape.   The opto-electric hybrid board according to claim 1, wherein the vertical waveguide is formed by modifying the substrate by irradiating femtosecond laser light.   The opto-electric hybrid board according to claim 1, wherein the vertical waveguide includes a central portion having a high refractive index and an outer peripheral portion having a low refractive index.   The opto-electric hybrid board according to claim 1, wherein the vertical waveguide is composed of a plurality of optical waveguides.   The opto-electric hybrid board according to claim 1, wherein a photonic crystal is formed by laser light irradiation around the vertical waveguide and / or the optical path changing structure.

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