JP2005266623A - Optical printed board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain integration and multilayer structure especially by optically connecting a light emitting element and an optical wire as to an optical printed board whose practical use is expected in an optical communication field. <P>SOLUTION: A plurality of holes 5 are pierced on one or more optical wires 4 laminated on a photoelectric mixed substrate A comprising electric wires 2 and the optical wires 4 orthogonally to the optical axis 4a on the optical wires 4 and vertically to the surface of the photoelectric mixed substrate A. Optical pins 7 whose one end face is cut as a 45° mirror surface 7a are inserted into and fixed on respective holes 5 and both the 45° faces of both the optical pins 7 are formed so as to be opposed to each other on the optical wires 4 and on the optical axis 4a. The other end face 7b of each optical pin 7 is formed at the same height as the upper surface of the photoelectric mixed substrate A. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical printed circuit board that is expected to be put to practical use in the field of optical communication, and more particularly to an optical printed circuit board that can be integrated and multilayered by optically coupling a light emitting element and an optical wiring.

  In the past few years, the infrastructure of backbone and metro systems has been opticalized, and the opticalization of access systems represented by FTTH and FTTB has entered the commercial stage. The amount of information handled by devices such as exchanges continues to increase. Accordingly, it is required to increase the processing speed within and between the electronic circuit boards constituting these devices. However, in conventional electric signals, problems of propagation delay due to signal interference between wirings and lengthening of wiring distances are becoming prominent.

  As a means for solving such problems, attention has been focused on opticalizing signals within and between electronic circuit boards. Compared to electrical signals, there is no problem of mutual interference in propagation of optical signals, and parallel mounting can be performed. Therefore, opticalization of signals within and between electronic circuit boards is suitable for high-speed and large-capacity transmission. This circuit constitutes a so-called optical circuit in which an electrical signal from an electronic device is OE converted by a light emitting element mounted on a substrate and transmitted to a photodetector through an optical transmission medium such as an optical waveguide to change OE.

  Speeding up is achieved by replacing part of the electronic circuit with an optical circuit, but there are significant differences in the handling of electrons and photons as carriers. In the case of an optical circuit, alignment with respect to a propagating optical wiring or the like is very important because the light emitted from the light emitting element spreads and goes straight. In the case of electronic circuits, if they are joined by soldering, the movement of electrons is performed regardless of the displacement of the transmission path, and signals are transmitted and received. In the case of an electronic circuit board, a solder bump is usually provided on the printed circuit board or the electronic device side for connection between the electronic device and the printed circuit board. A technique such as a lead insertion type in which pins are inserted into a printed board and soldered is used. In order to realize the opticalization of the wiring in the apparatus and between the transmission lines, it is necessary to positively apply the bonding process of these electronic devices to the bonding of light.

  Features of the surface mounting type that uses the solder bumps described above include easy wiring density, short wiring length from the substrate, and self-alignment by solder reflow. An optical model using a lens has been reported as a surface mount type light coupling utilizing this feature. This is an optical model that achieves high coupling efficiency by forming a lens on the array between the light emitting / receiving element to be mounted and the optical wiring, and is suitable for multichannel use (for example, using a microlens). Optical I / O package technology). There are lenses used by ion exchange, those manufactured by a dispenser method, and an ink jet method. The lens is mounted on the light emitting surface of the light emitting element or the substrate on which the light emitting element is mounted. In addition, there is a type in which a light emitting element to be mounted, a driver, and the like are mounted in a hybrid by an interposer and optical coupling is realized without using a lens. For example, a chip-to-chip optical interconnection technique using an active interposer. In any surface mount type coupling, since the light emitting / receiving element to be mounted and the optical axis in the substrate are orthogonal to each other, a 45 degree mirror that turns back 90 degree light is required. As a method of manufacturing this mirror, a method of manufacturing a 45-degree mirror surface in an optical wiring formed in a substrate by using a diamond blade or the like is generally used [FIGS. 12A, 12B, 12C, and 13]. (See (A), (B), (C)).

  As described above, in the surface mounting type optical coupling method, since the optical axes of the light emitting element and the light receiving element to be mounted and the optical wiring are orthogonal to each other, a 45 degree mirror surface that turns back 90 degree light is used. It must be provided in the substrate and is made using a diamond blade or the like. However, in the above method, as a manufacturing process problem, it is difficult to form a 45-degree mirror surface locally at an arbitrary position in the optical printed circuit board, and there is a concern that the wiring arranged nearby may be disconnected. is there.

  In the above method, it is assumed that the optical wiring layer is on the uppermost surface of the substrate, and there are few examples in which a multilayer structure such as a conventional electronic printed circuit board is applied to the optical wiring. Since the coupling between the optical wirings adopts the shape of a directional coupler, a single mode optical waveguide is used. In the optical interconnection between chips in the same board, a data link using a multimode is generally used from the viewpoint of alignment and the like. This is because when two or more optical wiring layers are provided, the length of the optical path to the lower optical wiring is increased, causing a number of problems. Here, the optical wiring layer on the uppermost surface of the substrate is referred to as the first floor, the second floor, the third floor,.

Currently, VCSELs with excellent features such as low cost and arraying are attracting attention as light sources for short-distance communications, and many research institutions researching optical circuits use these light-emitting elements as light sources for optical wiring. Adopted. Assume that the multilayer optical wiring uses the VCSEL as a light emitting element for E / O conversion that converts a signal from an electronic device into light. Here, even if the pitch in the vertical direction with respect to the substrate of the multilayer optical wiring is 250 μm, the optical wiring length on the second floor including the upper cladding of several tens of μm becomes about 300 μm, and increases by 250 μm thereafter. It will be. At present, the spread angle of a VCSEL is about 15 degrees (@ 1 / e ² ) even in a single mode VCSEL. When the optical path length from the light emitting surface is 300 μm, the beam radius of a VCSEL with a divergence angle of 15 degrees is approximately 80 μm (300 × tan 15 °) by simple calculation, and does not fit in a core with a radius of about 20 to 25 μm. It will occur.

  It is conceivable that the VCSEL can be applied to an optical model in which this spread is suppressed using a lens and the optical path length is long. However, in an optical model using a lens, there is a concern that the coupling efficiency fluctuates greatly due to the displacement of the light source (see FIGS. 14A and 14B). This is based on the lateral magnification determined by the distance between the light emitting element such as a laser and the lens and the optical wiring, but since the lens is used for condensing the light emitted from the light emitting element such as the VCSEL, the light emitting element and the lens The distance between them becomes shorter (see FIG. 14C). Since the distance between the lens and the optical wiring is longer than this distance, the lateral magnification is inevitably increased. As a result, a very high accuracy is required for the positional deviation of the light source. As described above, it is difficult to stack the optical wiring because of the long optical path length from the light source to the optical wiring. However, the conventional printed circuit board made of electrical wiring has been integrated by stacking multiple layers by pasting or building up, and in order to realize optical wiring, Integration can be a major bottleneck.

Therefore, it is considered to apply a lead insertion type joining method in which pins of an electronic device are inserted into a printed board and soldered. For example, an optical pin that performs optical connection by inserting an optical fiber into a hole penetrating an optical wiring is known. Examples of mounting using the optical pins are shown in FIGS. 15 and 16A, 16B, and 16C. An optical wiring is formed in the substrate, and a hole is provided in the optical wiring. An optical fiber or optical wiring whose end face is processed at 45 degrees is attached to a package side having a light emitting element and a driver, and the optical pin is inserted into the hole by mounting the device with the optical pin, so that the optical axes thereof are orthogonal to each other. This is an optical model that is optically coupled to the optical wiring in the substrate (see FIGS. 15A, 15B, and 15C). Alternatively, it is an optical model that realizes the same optical coupling by inserting an optical pin cut to the depth of the hole and mounting a device in which a light emitting element or the like is packaged on the optical pin [FIG. , (B), (C)]. With this method, optical signals can be transmitted and received at an arbitrary location. However, since an optical fiber having a diameter of 125 μm is used, it is easy to be broken and difficult to handle during assembly or insertion. The length of the optical pin in FIG. 15 and FIG. 16 is assumed to be about 200 μm, but with this length, several optical pins are arranged in one-dimensional or two-dimensional directions to consider multi-channeling. When considering the case or multi-layer, it is expected that it will be difficult to mount short optical pins on the package side or insert into the hole with high accuracy, especially in terms of handling, and is not suitable for integration and multi-layering. Not realistic. Further, Patent Document 1 has a problem that it cannot be multilayered.
JP2004-31456

  The present invention has been made paying attention to such conventional problems, and its purpose is to insert an optical pin whose end face is processed at 45 degrees into a hole on an optical wiring provided in the substrate in advance. By fixing, an optical printed circuit board that shares a manufacturing process with a conventionally used printed circuit board and can introduce the concept of an optical circuit into a flexible circuit board is provided. Also, by inserting and fixing in advance the optical pins whose end faces of different lengths are processed at 45 degrees into the holes on the laminated optical wiring, not only the mounting process of the electronic printed circuit board that has been used in the past. The present invention provides an optical printed circuit board that can be multi-layered by introducing the concept of multi-layering into an optical circuit and sharing a design process.

  Accordingly, as a result of intensive studies and studies by the inventors to solve the above problems, the invention of claim 1 is applied to an optical wiring that is laminated with one or more layers in an opto-electronic hybrid substrate composed of electrical wiring and optical wiring. A plurality of holes perpendicular to the optical axis on the optical wiring and perpendicular to the opto-electronic hybrid substrate surface, and an optical pin cut with one end surface being a 45-degree mirror surface is inserted and fixed in the hole, The 45-degree surfaces of the optical pins are provided so as to face each other on the optical wiring and on the optical axis, and the other end surface of the optical pin has the same height as the upper surface of the opto-electronic hybrid substrate. The above-mentioned problems have been solved by using an optical printed circuit board characterized by being formed in the above. Further, in the above configuration, the above-mentioned problem is solved by providing an optical printed board characterized in that a synthetic resin for connection is filled between the hole and the optical pin.

  Further, in the above configuration, the optical pin is an optical fiber or an optical waveguide, or the optical printed circuit board is characterized in that the optical wiring is an optical fiber or an optical waveguide. Furthermore, the said problem was solved by having set it as the optical printed circuit board characterized by having vapor-deposited the metal film with a high reflectance on the 45 degree processed surface of the said optical pin in the said structure. Moreover, the said subject was solved by setting it as the optical printed circuit board characterized by the said structure having two or more layers of the said optical wiring laminated | stacked.

  In the present invention, in the opto-electronic hybrid board, optical pins whose end faces are processed at 45 degrees are inserted and fixed in advance in holes on the optical wiring provided in the substrate so that the optical axes are orthogonal to each other. An optical printed circuit board capable of realizing optical coupling between elements can be manufactured. In addition, by using the multilayer type optical printed circuit board of the present invention, selective optical coupling to the laminated optical wiring becomes possible, and stable optical coupling efficiency can be obtained without depending on the wiring depth. It is possible to provide an optical printed circuit board that can be used.

  First, the outline of the present invention will be described. The optical printed circuit board of the present invention is for selectively and optically coupling light emitted from an optical element mounted with the light emitting surface facing the substrate side to an optical wiring such as an optical waveguide laminated in the substrate. In addition, it has the following configuration. In-substrate optical wiring such as an optical waveguide is formed in a flat substrate so that the optical axis is parallel to the substrate surface. In addition, a part of the optical waveguide has a hole formed by a laser or a drill with respect to the optical axis. An optical pin whose end face is processed at 45 degrees is inserted into the prepared hole. A synthetic resin for connection (thermosetting or photocurable resin) is filled in the hole before or after insertion, and the optical pin is fixed. When two or more layers of optical wiring are stacked, the optical pins to be inserted are different in length in order to selectively couple to the respective optical wiring layers. The light emitting element on the transmission side is a semiconductor laser such as a surface emitting laser, and is a light receiving element such as a photodiode when receiving an optical signal propagating through an optical waveguide in the substrate. The optical pin is obtained by cutting an end face of an optical fiber or an optical waveguide at 45 degrees using a diamond blade or the like. This configuration enables optical coupling between a light-emitting / receiving element mounted on the surface with an optical pin and an optical waveguide without using an optical system such as a lens or a prism, and shares the process with the conventional printed circuit board fabrication. In addition, an optical printed circuit board can be provided at low cost. In addition, it is possible to provide a multilayer type optical printed circuit board capable of optical coupling to the laminated optical wiring.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1D is an optical printed circuit board according to the present invention, on a printed circuit board 1 on which electrical wirings 2, 2,. An optical wiring layer 3 having an optical waveguide 40 as the optical wiring 4 is provided. The printed board 1 and the optical wiring layer 3 are collectively referred to as an opto-electronic mixed board A. A plurality of holes 5 are perforated in the optical wiring layer 3 perpendicular to the optical axis 4a of the optical wiring 4 and perpendicular to the surface of the optical wiring layer 3 or the opto-electronic hybrid substrate A. The optical pin 7 cut with the one end face as a 45 degree mirror surface 7a is inserted and fixed. The 45-degree mirror surfaces 7a and 7a of the optical pins 7 and 7 are provided so as to face each other on the optical wiring 4 and on the optical axis 4a. The other end surface 7b of the optical pin 7 is formed to have the same height as the upper surface of the optical wiring layer 3 or the optoelectronic hybrid substrate A.

  An example of manufacturing an optical printed circuit board according to the present invention will be described. First, an optical wiring layer having an optical waveguide 40 as an optical wiring 4 on or inside a printed circuit board 1 on which conventional electrical wirings 2, 2,. 3 is provided. When the optical wiring layer 3 is provided on the uppermost surface of the printed circuit board 1, the printed circuit board 1 for the electrical wiring 2 is prepared once, and the optical waveguide 40 is manufactured using the printed circuit board 1 as a base and using a photosensitive technique or a transfer technique. Alternatively, a method in which the optical waveguide 40 and the printed circuit board 1 are separately manufactured and attached can be considered. When the optical wiring layer 3 is provided in the printed board 1, the produced optical waveguide 40 is sandwiched between the printed boards 1 on which the electric wiring 2 is laminated. The method of manufacturing the optical waveguide 40 is not limited to the above, and any method may be used as long as the core and clad waveguide structure can be manufactured in the printed circuit board 1 or on the upper surface of the printed circuit board 1. Holes 5 are drilled by a laser or a drill up to a predetermined layer where the manufactured optical waveguide 40 is located.

  As shown in FIG. 1D, when the optical wiring layer 3 is provided on the uppermost surface of the printed circuit board 1, holes 5 are provided in advance by a laser or a drill at a predetermined position on the optical waveguide 40 side. 1 (A)], the optical wiring layer 3 having the optical waveguide 40 is attached on the printed circuit board 1 [see FIG. 1 (B)]. As shown in FIG. 2D, when the optical wiring layer 3 is sandwiched between the upper and lower printed circuit boards 1 and 1, the optical wiring layer 3 is once bonded to the lower side of the printed circuit board 1 on the upper surface side. After the hole 5 is formed by a drill or a drill (see FIG. 2A), the printed circuit board 1 on the lower surface side is joined (see FIG. 2B). Through the above process, the hole 5 for inserting the optical pin can obtain the shape of a blind via hole in which the bottom exists in the optical wiring layer 3, and the alignment of the 45-degree mirror surface 7a and the optical wiring 4 in the height direction is as follows. Passive alignment. However, if the jig for handling the optical pin 7 can be controlled at the time of inserting the optical pin and the length of insertion of the optical pin 7 can be adjusted, the hole 5 needs to have a structure like a blind via. Alternatively, a hole penetrating to the lower surface of the substrate may be used. Also, when drilling holes, if a device that can precisely control the depth from the upper surface of the optical wiring 4 to the hole 5 is used, the hole processing is performed after laminating the electrical and optical wiring layers. Can do.

  Next, in the step of inserting the optical pin 7 into the hole 5 of the optical wiring layer 3, the inserted optical pin 7 has a length that can be handled by a jig or the like, and reaches the blind portion as described above. Until the mirror surface 7a and the optical wiring layer 3 are aligned with each other. For fixing the optical pin, a connecting synthetic resin (thermosetting or photocurable synthetic resin) 6 is used, and before or after insertion, the hole 5 is filled with the connecting synthetic resin 6 and thermoset. The optical pin 7 is fixed by light curing. Here, in order to ease the handling, the fixed optical pin 7 is set to be longer than the distance from the upper surface of the opto-electronic hybrid substrate A to the optical wiring layer 3 (excess part is protruded from the upper surface of the substrate). The optical pin 7 is configured as the other end surface 7b of the optical pin 7 so as to have the same height as the upper surface of the opto-electronic hybrid substrate A by cutting the upper end portion of the optical pin 7 with polishing or a blade. As a result, an optical printed circuit board that is an opto-electronic mixed circuit board A in which the printed circuit board 1 having the electrical wiring 2 and the optical wiring layer 3 are mixedly mounted can be manufactured.

  When producing a multilayer type optical printed circuit board, the operation of the single layer type optical printed circuit board shown in FIGS. 1 and 2 is repeated. When two or more optical wirings 4 are stacked on the uppermost surface, the optical wiring 4 side is multilayered before the optical waveguide 40 and the optical printed circuit board are bonded together by the manufacturing method shown in FIG. For example, in the case of a two-layer type multilayer optical printed circuit board, a hole 5 is processed into the optical wiring 4 on the first basement floor, the substrate is laminated with the optical wiring layer 3 on the second basement floor, and then the hole 5 for the second basement floor. Is processed. By laminating the laminated optical wiring 4 with the electrical wiring layer, the bottom 5 (blind via) is formed in the hole 5 of the optical wiring layer 3 so that passive optical coupling is performed when the optical pin 7 is inserted. A substrate having a shape can be obtained. Further, when the electrical wiring layer and the optical wiring layer 3 are alternately laminated, a one-layer optical printed circuit board obtained by the production method shown in FIG. 2 is produced, and the substrates are obtained by further laminating them. be able to. A multi-layer type optical printed circuit board can be obtained by inserting the optical pin 7 after fabrication and fixing, cutting, and polishing by the method described above. That is, the conventional optical pins shown in FIG. 15 and FIG. 16 have the disadvantages that in addition to handling problems, optical pins having different lengths must be prepared in advance in order to perform optical coupling to each layer. In the present invention in which the surface is cut and polished after insertion, the length of the prepared optical pin 7 may be any length that can be handled, and there is no requirement for accuracy. Therefore, it is possible to share parts, leading to cost reduction.

  The use of the connecting synthetic resin 6 at the time of fixing the optical pin is also effective in that attenuation such as reflection and scattering of propagating light due to processing roughness generated at the time of hole processing with a laser or a drill can be reduced. However, if the entire hole is filled with an optical adhesive such as the synthetic resin 6 for connection, the difference in refractive index is eliminated at the 45 ° mirror surface 7a necessary for 90 ° optical path conversion, and thus light goes straight downward. Therefore, the light is forcibly turned back by depositing a highly reflective metal film on the 45-degree mirror surface 7a. In an optical model that realizes 90-degree light conversion by using total reflection of light at a mirror surface that is not limited to the optical pin 7 and whose end face is processed at 45 degrees, a part of the light propagating through the core is totally reflected. The light is transmitted without satisfying the conditions, which is a major factor of attenuation. By using the optical pin 7 (metal coated optical pin) on which the metal film is deposited, attenuation due to the transmitted light is improved, and an optical adhesive can be used when fixing the optical pin. However, when 90-degree optical path conversion is realized by utilizing the total reflection phenomenon due to the difference in refractive index without depositing a metal film on the 45-degree mirror surface 7a, the bonding by the connecting synthetic resin 6 is 45 degrees of the optical pin 7. This is performed at a place other than the mirror surface 7a.

  FIG. 3 is a diagram schematically showing an embodiment in which an opto-electronic hybrid board A is manufactured using the optical printed board of the present invention. First, on the fabricated optical printed circuit board, optical elements that transmit and receive optical signals such as light emitting elements and light receiving elements, electronic circuits that drive and modulate the light emitting elements with electric signals, and light receiving elements are detected and converted. An electronic device such as an LSI is mounted together with an electronic circuit that amplifies the electric signal. An electrical signal from an electronic device such as an LSI mounted on the electronic substrate is E / O converted by a light emitting element via a driver. The light emitting element is mounted on the upper part of the optical pin 7 inserted in advance in the optical printed circuit board so that the optical axes thereof coincide with each other and the emission surface is on the optical pin side (lower surface). The light that has undergone E / O conversion by the light emitting element propagates through the optical pin 7 and undergoes a 90-degree optical path change at the 45-degree mirror surface 7a, and the light is coupled to the optical waveguide 40 provided in or on the substrate. An optical signal is output to the device. On the other hand, the optical signal propagated through the optical waveguide through the above process is incident on the 45-degree mirror surface 7a of the optical pin 7, is optically changed by 90 degrees, and propagates through the optical pin 7 toward the upper surface of the substrate. The light emitted from the end face of the optical pin 7 is coupled to a light receiving element mounted so that the light receiving surface faces the optical pin side (lower surface) and the optical axis 4a coincides with the optical pin 7, and O / This is a configuration for E conversion. Here, considering the optical coupling between the light emitting element and the optical pin shown in FIG. 1, the optical elements are close to the bump thickness, and the light emitting surface of the light emitting element mounted on the optical pin is 5 to 5. Since it is about 10 μm, it is easy to make light incident on a 50 μmφ core, which is rough compared to the requirements for mounting accuracy such as an optical model using a lens. Note that the optical coupling between the light receiving element and the optical pin can be further rougher than the mounting accuracy of the light emitting element by using a light receiving element having a large light receiving surface.

  4 and 5 show an embodiment of a multilayer optical printed circuit board according to the present invention. First, a multilayer optical wiring having an optical waveguide 40 is provided on or inside a printed circuit board on which conventional electrical wiring is laminated. When the optical wiring layer 3 is laminated on the top surface of the substrate, when the multilayer optical wiring is sandwiched between the electric wiring layers, the electric wiring layer and the optical wiring layer 3 are alternately laminated, and so on. In any case, the hole 5 is first made by a laser or a drill from the upper part of the substrate to the predetermined layer where the optical wiring 4 is produced in a form orthogonal to the optical axis 4a of the optical wiring 4. The hole manufacturing method may be any method as long as circular or rectangular hole processing is possible, and the hole diameter is larger than the diameter of the optical pin 7 to be inserted. Also, a guide pin hole is provided for rough engraving on the multilayer optical printed circuit board during mounting.

  The optical surface mount device shown in FIGS. 4 and 5 is a package of light emitting / receiving elements, electronic devices, driving circuits, etc. mounted on the end face of the optical fiber of the multilayer type optical printed circuit board (the top surface of the cut substrate). It has been The packaged surface mount device is provided with guide pins for prealignment, and the guide pins also serve as electric wiring for driving electronic devices and light emitting elements. By inserting this guide pin into the guide pin hole provided on the substrate, the optical pin 7 is inserted into the hole 5 or slit provided on the optical wiring, and passive alignment can be realized.

  FIG. 6 is a schematic view showing an example in which the multilayer type optical printed circuit board of the present invention is applied to an optical drive type. According to the present invention, since the optical wiring 4 can be multilayered, the electric wiring 2 used for driving the light emitting element can be replaced with the optical wiring 4. FIG. 3 shows a model in which POF (Plastic Optical Fiber) is applied to the power supply optical wiring. A layer in which CW oscillation light for power supply propagates is provided under the optical wiring layer 3 for signals, and the light extracted locally using the optical pin 7 and converted by the light receiving element is The power source is used to drive an electronic device or a light emitting element. In the conventional electronic printed circuit board, the laminated electric wiring 2 includes a power supply layer and a ground layer in addition to the signal layer, and is connected by a via hole or the like so that each layer functions. In realizing the opto-electronic hybrid board A, the ability to share not only the lamination of the optical wiring 4 but also the functional design process is effective in terms of evaluation and the like when considering commercialization.

  FIG. 7 is a diagram showing a model for changing the level of an optical signal or branching an optical signal to each level using the multilayer type optical printed circuit board of the present invention. In the case of FIG. 7, the optical signal that has propagated through the optical waveguide 40 on the first floor is transmitted to the light receiving element by the optical pin 7, and after being processed by the electronic device, is transmitted to the light emitting element. The optical signal transmitted from the light emitting element is mounted so as to be connected to the optical pins 7 having different lengths, and can be selectively coupled to the optical waveguide 40 on the first floor or the optical waveguide 40 on the second floor. Become. The light-emitting element shown in the figure assumes a VCSEL having a light-emitting surface of 2ch in the Z-axis direction. However, if an N-channel VCSEL is applied in the Z-axis or X-axis direction according to the number of stacked optical wirings, N × Nch A matrix-like data link becomes possible.

  The hole 5 is processed so that a predetermined inclined surface (hereinafter referred to as a taper angle) is generated. The taper angle is provided inside the hole to prevent the operation of the laser from becoming unstable when the reflected light at the end face of the optical waveguide returns to the optical element and enters the active region of the laser that emitted the light. is there. However, as described above, by adopting a method in which a metal film is deposited on the 45-degree mirror surface 7a of the optical pin 7 and the hole is filled with resin and fixed, the influence of reflected light is reduced. Is not necessary.

  The light emitting element is a semiconductor laser such as a surface emitting laser. The light receiving element is a photodiode. The gap between the light emitting element, the light receiving element, and the optical pin is desirably filled with a resin having a refractive index after curing that is the same as the core of the optical pin (underfill). This is because when the gap is an air gap, as described above, the operation of the light emitting and receiving element becomes unstable due to the influence of the reflected light. In addition, there is a concern that light may be scattered due to rough processing of the end face during the optical pin cutting described above, and this is to prevent these noise factors.

  The optical waveguide 40 may be an optical fiber. Further, a flexible optical printed circuit board can be realized by replacing the optical waveguide 40 with a bendable element such as an optical fiber or a film waveguide. In this case, the optical pin 7 is also made of an element having similar features. In the mounting example shown in FIG. 3, the multi-channel optical wiring is realized by arranging the optical waveguide 40, the light emitting element, and the light receiving element on the X axis on the array.

  In order to confirm how much optical coupling efficiency can be obtained by using the optical printed circuit board of the present invention, an optical pin was actually fabricated, and a coupling measurement to be inserted into a hole fabricated on the optical waveguide was performed. The measurement system is as shown in FIG. For measurement, an end face of GI-MMF mirrored at 45 degrees was used as an optical pin. The length of the optical pin is about 1 m, and one has an FC connector. In order to confirm the effect of the metal coating on the end face as described above, an optical pin having Au deposited on the end face (hereinafter referred to as an Au coated optical pin. On the contrary, an uncoated optical pin is hereinafter referred to as a non-coated optical pin). Also made. The specifications of the optical waveguide are: core refractive index: 1.489, cladding refractive index: 1.471, and core diameter of 40 × 40 μm. A hole for inserting an optical pin was prepared by laser ablation, and after the hole processing, a cleaning process was performed by oxygen plasma ashing. At the time of laser irradiation, irradiation is performed through a mask having a diameter of 200 μm, and the manufactured hole diameter is 220 μm on the top surface and 190 μm on the bottom surface. The above-mentioned two types of optical pins were inserted into the holes, and transmission / reception coupling loss was measured.

  Here, assuming that a light emitting element is placed on the top of the optical pin, transmission is performed when light is incident from the optical pin, and assuming that a light receiving element is disposed on the top of the optical pin and light is incident from the MMF. You are receiving. The measurement is based on the output of the light source, and the coupling efficiency is calculated by observing with a power meter the light that has propagated through the optical pin and the optical waveguide after 90-degree optical path conversion. For the experiment to confirm the effect of filling the Au coated optical pin with resin, matching oil was used instead of resin this time. The measurement result takes into account the propagation loss of the optical waveguide, the coupling loss between the optical waveguide and the incident light, and the light receiving fiber (GI-MMF used because the PD light receiving surface cannot be brought close to the end surface of the waveguide). Further, an optical model similar to that of the above measurement system was produced using a three-dimensional ray tracing method, and optical coupling was performed. However, since the shape inside the actually produced hole is not an optical cylindrical shape, modeling is difficult. Therefore, the analysis was performed assuming that the taper angle of the analysis optical model is an ideal hole based on the above-mentioned top surface hole diameter and bottom surface hole diameter. The coupling efficiency in the analysis is calculated from the light beam that has reached the other end face after 90 ° optical path conversion, based on 100,000 light beams incident from the optical pin or the optical waveguide side.

  The experiment and analysis results are shown in FIG. As a result, there is a large difference between the analysis value and the actual measurement value in the non-coated optical pin. On the other hand, the Au-coated optical pin also has a difference of about 1.6 dB between the actual measurement value and the analysis value, but almost the same result is obtained when compared with the measurement value when matching oil is used. This is because the analysis value calculates the coupling efficiency under ideal conditions, while the measurement value does not. The effects of misalignment, such as the pinning of the optical pin, can also be considered, but the rough machining of the hole and the complicated shape inside the hole can be almost ignored by using matching oil, and an ideal optical model is used. This is because the analysis and conditions are close.

  In the non-coated optical pin, the coupling loss differs greatly depending on the difference in the relative angle between the 45 ° mirror surface of the optical pin and the end face of the optical waveguide, which is generated by the taper angle of the hole or the bending of the optical pin. On the other hand, Au-coated optical pins are not easily affected by them, and by using a resin whose refractive index after curing is the same as the matching oil used this time, the effect of the end face shape of the processed hole is reduced, as described above. As described above, it is effective to deposit a metal film on the mirror surface of 45 degrees and fix the optical pin with resin.

Next, in order to confirm how effective the multilayer optical printed circuit board of the present invention was, analysis was performed using a three-dimensional ray tracing method. This analysis was compared with the optical model using the lens described above. This is because, as described above, it is possible to efficiently couple light to the optical wiring on the second floor, the third floor, etc. by using the lens, but the optical path length from the lens to the optical wiring layer becomes longer. The requirement for the mounting accuracy of the light source becomes severe due to the expansion of the lateral magnification of the optical system. Therefore, as shown in FIG. 10, the extent to which the light coupled to the optical wiring is changed with respect to the positional deviation of the light source is analyzed depending on whether the optical pin is used or the lens is used. The VCSEL used has a wavelength of 850 nm, a spread angle of 15 deg. (Half angle: @ 1 / e ² ), and a beam waist of 5 μm (radius).

The optical pin in FIG. 10 is assumed to have an end face of a GI type multimode fiber with a core diameter of 50 μm cut at 45 degrees, and an optical having a metal film with a reflectance of 100% on the 45 degree mirror surface. A model was created. The refractive index of the core is 1.5, the refractive index of the cladding is 1.485, and the refractive index distribution coefficient α of the core is 2.0. The lens shown in FIG. 10 has a curvature R of 45 μm, a diameter of 45 μm, and a refractive index of 1.5. A mirror having a reflectance of 100% is installed for 90-degree optical path conversion. The modeled optical waveguide of FIG. 10 has a core diameter of 40 × 40 μm, a core refractive index of 1.5, and a cladding refractive index of 1.45. The distance between the VCSEL, the optical pin, and the lens is fixed to 30 μm, the distance from the optical pin and the lens to the center of the optical wiring layer (the center of the optical waveguide core) is L, and L is 250 μm (first floor), 500 μm ( 2nd floor), 750 μm (3rd floor), and 1000 μm (4th floor), and the change in the coupling efficiency with respect to the displacement of the VCSEL in the X-axis direction was analyzed. In addition, when changing L of an optical pin, the length of an optical pin is changed. The calculation method of the coupling efficiency was calculated from the following equation by obtaining light (N lines) that reached the end face of the optical waveguide after being converted by 90 ° optical path with reference to 100,000 rays emitted from the VCSEL.

  The analysis results are shown in FIG. When L in FIG. 11A is 250 μm (first floor), the coupling efficiency is better when the lens is used, but the coupling efficiency increases as the amount of displacement of the VCSEL increases (at a point where the displacement is 10 μm or more). The optical pin is better. This is because, as described above, the beam on the incident surface of the optical waveguide is greatly shifted due to the lateral magnification of the lens. When L in FIG. 11B is 500 μm (second floor), the maximum coupling efficiency is about the same for the optical pin and the lens, and the amount of reduction in coupling efficiency with respect to displacement is larger for the lens. The maximum coupling efficiency of the lens decreases as L in FIG. 11C increases to 750 μm (3rd floor) and L in FIG. 11D increases to 1000 μm (4th floor). Significantly smaller than pins. For optical pins, the change in coupling efficiency with respect to the change in L is very small. This is because the spread angle of the VCSEL is 15 deg. And there is light that does not satisfy the NA of the fiber of the optical pin and leaks to the cladding. Because it was obtained. Even if the lengths of the optical pins are different, the transmission loss with respect to the distance can be almost ignored at a distance of about several millimeters or less.

  The above analysis results show that the same effect can be obtained for a one-layer type optical printed circuit board, and it can be seen that the present invention is effective for one or more optical printed circuit boards. As described above, by realizing the multilayer optical printed circuit board of the present invention, the concept of multilayering is introduced into the optical wiring in the same manner as the conventional electronic printed circuit board, and selective optical coupling to the multilayered optical wiring is achieved. It becomes possible.

(A)-(C) are the state diagrams of the manufacturing process of the optical printed circuit board of this invention, (D) is sectional drawing of this invention of manufacture completion. (A)-(C) are the state diagrams of the manufacturing process of the optical printed circuit board of another embodiment of this invention, (D) is sectional drawing of this invention of completion of manufacture. It is the schematic diagram which showed the example of mounting of the optoelectronic hybrid board | substrate using the optical printed circuit board of this invention. (A) is sectional drawing of the manufacturing process of embodiment of the optoelectronic hybrid board | substrate using the multilayer type optical printed circuit board of this invention, (B) is a perspective view of (A). (A) is sectional drawing of the manufacturing process of embodiment of the optoelectronic hybrid board | substrate using the multilayer type optical printed circuit board of this invention, (B) is a perspective view of (A). It is the 1st schematic diagram which showed embodiment of the optoelectronic hybrid board | substrate which applied the multilayer type optical printed circuit board of this invention. It is the 2nd schematic diagram which showed embodiment of the optoelectronic hybrid board | substrate which applied the multilayer type optical printed circuit board of this invention. It is the figure which showed the experiment and analysis method of the basic examination performed in order to implement | achieve the optical printed circuit board of this invention. It is the figure which showed the experiment and analysis result of the basic examination performed in order to implement | achieve the optical printed circuit board of this invention. It is the analysis model performed in order to compare the multilayer type optical wiring which applied the prior art, and the multilayer type optical printed circuit board of this invention. (A) is an analysis result performed to compare the optical wiring to which the conventional technology is applied and the optical printed circuit board of the present invention, and (B) to (D) are multilayer optical wirings to which the conventional technology is applied. And the results of an analysis performed to compare the multilayer optical printed circuit board of the present invention. (A)-(C) are process drawings of the conventional first technique in an optical printed circuit board. (A)-(C) are process drawings of the conventional second technique in an optical printed circuit board. (A)-(C) are process drawings of the conventional third technique in an optical printed circuit board. (A)-(C) are process drawings of the conventional 4th technique in an optical printed circuit board. (A)-(C) are process drawings of the conventional fifth technique in an optical printed circuit board.

Explanation of symbols

Electrical wiring 2, printed circuit board 1, optical wiring 4, optical axis 4a, optical wiring layer 3, hole 5,
Synthetic resin 6 for connection, optical pins 7, 7a ... 45 degree mirror surface, 7b ... other end surface, optical waveguide 40,
Optoelectronic mixed substrate A.

Claims (6)

In an opto-electronic hybrid substrate composed of electrical wiring and optical interconnect, a plurality of holes are formed on the optical interconnect laminated in one or more layers perpendicular to the optical axis on the optical interconnect and perpendicular to the opto-electronic hybrid substrate surface. In the hole, an optical pin cut with a mirror surface at one end is inserted and fixed, and both the 45-degree surfaces of both optical pins are provided on the optical wiring and on the optical axis. The optical printed circuit board, wherein the other end surface of the optical pin is formed to have a height equivalent to the upper surface of the opto-electronic hybrid substrate. 2. The optical printed circuit board according to claim 1, wherein a synthetic resin for connection having a refractive index comparable to that of the optical pin or the optical wiring is filled between the hole and the optical pin. . 3. The optical printed circuit board according to claim 1, wherein the optical pin is an optical fiber or an optical waveguide. 3. The optical printed circuit board according to claim 1, wherein the optical wiring is an optical fiber or an optical waveguide. 5. The optical printed circuit board according to claim 1, wherein a metal film having a high reflectance is vapor-deposited on a 45-degree processed surface of the optical pin. 6. The optical printed circuit board according to claim 1, wherein the optical wiring is laminated in two or more layers.

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