JP2005062377A - Optical and electric combined substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical and electric combined substrate being a board-level optical interconnection realized at a low cost to avoid problems of light loss, a rise in cost, small and unstable input/output intensity, and contamination. <P>SOLUTION: Disclosed is the optical and electric combined substrate in which optical wiring and a surface type light emitting element 1 or surface type light receiving element 2 are mounted; and the surface type light emitting element or surface type light receiving element and the optical wiring 7 are connected by an optical waveguide 10 which is bent, and a light emission end part of the surface type light emitting element or a light reception end part of the surface type light receiving element and one end of the optical waveguide, and the other end part of the optical waveguide and an end part of the optical wiring are connected directly to each other. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polymer optical waveguide, and more particularly to an opto-electric hybrid board used in an optical integrated circuit, an optical component for optical interconnection, and the like, and a manufacturing method thereof.

  As base materials for optical components or optical fibers, inorganic materials such as quartz glass and multicomponent glass, which have the characteristics of low light propagation loss and wide transmission band, are widely used. These materials have also been developed and are attracting attention as materials for optical waveguides because they are superior in processability and price compared to inorganic materials. For example, a flat plate type having a core-clad structure in which a polymer having excellent transparency such as polymethyl methacrylate (PMMA) or polystyrene is used as a core and a polymer having a refractive index lower than that of the core material is used as a cladding material. An optical waveguide has been produced (Japanese Patent Laid-Open No. 3-188402). On the other hand, a low-loss flat optical waveguide is realized using polyimide, which is a transparent polymer having high heat resistance (Japanese Patent Laid-Open No. 2-110500). In the field of optical interconnection due to demands such as cost, surface emitting lasers (VCSELs) are about to be mounted. When laser light emitted perpendicular to the substrate is incident on an optical waveguide that is horizontal to the substrate, An optical path change of about 90 ° is required. The polymer optical waveguide is cut to about 45 ° by a dicing saw to enable 90 ° optical path conversion (Patent Document 1: Japanese Patent Laid-Open No. 10-300961). However, when cutting with a dicing saw, it may be cut at 45 ° other than the necessary place, there is a risk of contamination at the time of cutting, and further, it is difficult to make the interval between the light emitting and receiving elements 50 μm or less, Since there is no light collecting function by cutting alone, there is a problem that light diverges and causes loss.

  As shown in FIG. 3, it has also been proposed to collect light using a microlens 5 formed by an inkjet method or the like. Microlenses 5 are formed on the substrate side and the package side between the light emitting element 1 or the light receiving element 2 provided on the interposer substrate 4 of the printed wiring board 8 and the optical waveguide 7 cut by 45 degrees. As a result, positional accuracy is relaxed, and optical coupling is possible only with ordinary solder mounting. However, this increases the cost of managing the viscosity of the lens resin and the wettability of the waveguide surface. Further, since it propagates in the air, reflection occurs, the input / output intensity becomes small and unstable, and there are problems such as contamination.

A method of bending a flexible plastic optical waveguide and coupling it to a light emitting / receiving element has been proposed (Patent Document 2: JP-A-5-281428).
However, this method requires a hole or curved surface of the substrate to be accurately processed, resulting in high costs.

Further, as shown in FIG. 2, a method of inserting a pin 9 cut at an end face of 45 degrees for optical path conversion into a hole formed in a printed wiring board 8 having a light emitting element 1, a light receiving element 2 and an optical wiring 7 is also proposed. ing. In this case, the pin is obtained by cutting the optical fiber short, but it is necessary to produce a length of about 1 mm with an accuracy of several microns, and high precision processing is required such as the required position accuracy of the hole is very high. Therefore, the cost becomes high. There is also a method of bending the optical waveguide without passing through the substrate and wiring the upper surface in the air, but it is difficult to realize when the height is limited.
Japanese Patent Laid-Open No. 10-300961 JP-A-5-281428

  An object of the present invention is to provide an opto-electric hybrid board serving as a board level optical interconnection that can be realized at a low cost in order to avoid the above-described problems.

  As a result of diligent study, the present inventor did not perform 90 ° conversion using a pin, a mirror, or the like to optically couple the surface light emitting element or the surface light receiving element and the optical wiring formed on the substrate. The inventors have found that the above problems can be solved by directly coupling a surface light emitting element or a surface light receiving element and an optical wiring using a waveguide film, and have completed the present invention.

  That is, the present invention is an opto-electric hybrid board on which an optical wiring and a surface light emitting element or a surface light receiving element are mounted, and is an optical waveguide in which a space between the surface light emitting element or the surface light receiving element and the optical wiring is bent. The light emitting end of the surface edge light emitting element or the light receiving end of the surface light receiving element and one end of the optical waveguide, and the other end of the optical waveguide and the end of the optical wiring are directly coupled to each other. It is an opto-electric hybrid board.

  At this time, the optical wiring is provided on a surface opposite to the side on which the surface light emitting element or the surface light receiving element is attached, and the optical waveguide passes through a through hole provided in the opto-electric hybrid board. Since it contributes to thickness reduction, it is preferable.

  The present invention also relates to a method of manufacturing an opto-electric hybrid board on which an optical wiring and a surface light emitting element or a surface light receiving element are mounted. After directly joining one end of the optical waveguide, the surface light emitting element or the surface light receiving element is fixed to the opto-electric hybrid board, and the optical waveguide penetrating through the through-hole provided in the optical hybrid board is bent, And a step of directly joining the end portion of the optical wiring attached to the surface opposite to the side on which the surface light emitting element or the surface light receiving element is attached to the other end portion of the optical waveguide. It is a manufacturing method of a mixed board. The optical waveguide may be penetrated through the through-hole before or after being directly bonded to the surface light emitting element or the surface light receiving element.

  The opto-electric hybrid board is composed of a single substrate, and a surface type light emitting element or a surface type light receiving element may be mounted on the front surface, and an optical wiring may be provided on the back surface. The convex substrate mounted on the inside of the shape substrate may be attached to the front surface of the main substrate of the opto-electric hybrid board, and optical wiring may be provided on the back surface of the main substrate. This optical wiring may be a normal optical waveguide that is affixed on the substrate surface, or may be an optical waveguide formed on the substrate surface.

  When optical coupling between an optical waveguide and an optical element such as a surface light emitting element or a surface light receiving element is performed after the optical element is mounted on a substrate, the optical element is affected by the warp of the substrate or a short optical waveguide is bent. However, since it is difficult to hold it vertically, the optical coupling efficiency is lowered. In addition, when there are many places where optical coupling is performed, it is necessary to move the jig each time, so that the time for optical coupling is also increased.

If the optical coupling between the optical waveguide and the optical element is performed first, the above will not occur.
Further, the optical coupling between the optical waveguide and the optical wiring has a low required position accuracy and can be coupled relatively easily.

   By using the opto-electric hybrid board structure according to the present invention, a low-cost opto-electric hybrid board having good coupling efficiency and excellent mass productivity can be manufactured.

Hereinafter, the present invention will be described in detail. Here, a polyimide optical waveguide, a surface light emitting type or a surface light receiving type optical element will be described as an example, but it is of course possible to optically couple using an optical material resin other than polyimide as the material of the optical waveguide. .

  First, the manufacturing method of an optical waveguide film is demonstrated as an example of the optical waveguide used for this invention. A lower cladding layer is formed on the silicon wafer. A core layer is formed thereon. Next, a resist pattern is formed using a mask pattern on which a desired core pattern is drawn. Using this resist as a mask, dry etching is performed with oxygen plasma. Next, the remaining resist is removed with a stripping solution. Next, an upper cladding layer is formed from above. Next, the optical waveguide is peeled off from the silicon wafer by dipping in a hydrofluoric acid aqueous solution. The optical waveguide film thus obtained is cut into a desired shape with a dicing saw or the like. The length of the optical waveguide film is a length obtained by adding several millimeters to the thickness of the substrate, and the length is adjusted so that the optical waveguide comes out from the back surface of the substrate after package mounting.

  Next, an example of the manufacturing method of the optical hybrid board of this invention is shown using FIG. The strip optical waveguide 10 created as described above is directly abutted and coupled to the surface light emitting element 1 or the surface light receiving element 2 mounted inside the convex interposer substrate 4. That is, the end face obtained by cutting at right angles to the length direction of the optical waveguide is directly abutted on and fixed to the light emitting part of the surface light emitting element or the light receiving part of the surface light receiving element.

  The interposer substrate 4 may be provided with an IC chip 3 for electrically processing an optical signal passing through the surface light emitting / receiving element. A marker may be used as an alignment method at the time of coupling, or alignment may be performed so that the intensity of light that is emitted and guided in the strip optical waveguide is maximized. Bonding is performed using an adhesive at a position where the core center of the optical waveguide and the center of the light receiving and emitting diameter of the light receiving and emitting element overlap. In this manner, the light emitting / receiving element can be directly coupled to the end face of the optical waveguide without using a lens or a reflecting surface (FIG. 1 (a)).

  After the optical element is sealed with a resin sealing material 11 or the like, the optical waveguide is passed through the through hole 6 of the printed wiring board 8 formed by a drill or a laser, and soldered to an interposer substrate (for example, BGA: ball grid array substrate). Solder mounting is performed using the balls 12 (FIG. 1B). Although electrical mounting is described here using solder, various electrical mounting methods can be used. Thereafter, the strip-shaped optical waveguide 10 directly coupled to the optical element is connected to the optical wiring 7 bonded to the inside or the back surface of the printed wiring board. That is, the end face obtained by cutting the optical waveguide at right angles to the length direction and the end faces obtained by cutting the optical wiring at right angles to the length direction were abutted and fixed. At this time, a marker may be used to align the optical axis, or the center position serving as the optical axis may be obtained from the outer shape of the optical waveguide and the optical wiring. If necessary, the connecting portion is fixed using the adhesive 13 (FIG. 1 (c)).

  Thereby, compared with the case where the optical waveguide or optical fiber cut by 45 ° is used, the coupling loss can be greatly reduced, and a low-cost opto-electric hybrid board can be formed.

Subsequently, the present invention will be described in more detail with reference to examples. It is apparent that the polymer optical waveguide and the opto-electric hybrid board of the present invention can be obtained by using various polymer solutions having different molecular structures. Therefore, the present invention is not limited only to these examples.
2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 2,2-bis (trifluoromethyl) -4,4'-diaminobiphenyl (TFDB) on a 4-inch silicon wafer An optical waveguide film is formed by photolithography and dry etching techniques using a polyimide formed from (3) as a cladding and a polyimide formed from 6FDA and 4,4′-oxydianiline (ODA) as a core. Thereafter, the optical waveguide on the silicon wafer was immersed in a 5 wt% hydrofluoric acid aqueous solution, and the optical waveguide was peeled off from the silicon wafer to produce a film optical waveguide. The thickness of the film waveguide was about 50 μm. A strip optical waveguide was cut out by a dicing saw so as to have a length of 5 mm and a width of 3 mm.

  This optical waveguide was directly coupled to a surface emitting laser diode and a surface light receiving photodetector mounted on a BGA substrate. At this time, alignment was performed by emitting a surface emitting laser. Bonding was performed using a UV curable epoxy adhesive at a position where the center of the core of the optical waveguide and the center of the light receiving / emitting element overlap each other. In this way, the optical element was directly abutted and coupled to the end face of the optical waveguide. Thereafter, the BGA package was solder-mounted on a printed wiring board in which an optical waveguide film was bonded to the back surface as an optical wiring. At this time, a hole through which the strip optical waveguide passes is formed in the printed wiring board. The strip optical waveguide penetrating the hole was bent and connected to the end face of the optical waveguide of the optical wiring. After alignment, it was fixed with an adhesive. In this way, an opto-electric hybrid board could be manufactured.

    The present invention can be applied to an opto-electric hybrid board that mounts both a light emitting / receiving element and an electric circuit and performs relay processing of optical signals and optical communications.

It is a figure which shows an example of the optical coupling structure of the optical element and optical wiring by this invention. It is a figure which shows the prior art example of the optical coupling structure of the optical element and optical wiring which used the optical pin. It is a figure which shows the prior art example of the optical coupling structure of the optical element and optical wiring using a micro lens.

Explanation of symbols

1: light emitting element, 2: light receiving element, 3: IC chip,
4: Interposer substrate, 5: Micro lens, 6: Through hole,
7: Optical wiring, 8: Printed wiring board, 9: Pin,
10: optical waveguide, 11: sealing material, 12: solder ball,
13: Adhesive

Claims (3)

An opto-electric hybrid board on which an optical wiring and a surface light emitting element or a surface light receiving element are mounted, the surface light emitting element or the surface light receiving element and the optical wiring being connected by a bent optical waveguide, The light emitting end of the light emitting element or the light receiving end of the surface light receiving element and one end of the optical waveguide, and the other end of the optical waveguide and the end of the optical wiring are directly coupled to each other. Photoelectric mixed board. The optical wiring is provided on a surface opposite to the side on which the surface light emitting element or the surface light receiving element is attached, and the optical waveguide passes through a through hole provided in the opto-electric hybrid board. The opto-electric hybrid board according to 1. A method of manufacturing an opto-electric hybrid board on which an optical wiring and a surface light emitting element or a surface light receiving element are mounted, wherein one end portion of an optical waveguide is provided at a light emitting end portion of the surface light emitting element or a light receiving end portion of the surface light receiving element. After the direct bonding, the surface light emitting element or the surface light receiving element is fixed to the opto-electric hybrid board, and the optical waveguide penetrating the through hole provided in the optical hybrid board is bent, so that the surface light emitter Or manufacturing an opto-electric hybrid board, comprising a step of directly joining an end portion of an optical wiring attached to a surface opposite to a side on which a surface light receiving element is attached and the other end portion of the optical waveguide. Method.

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