JP5477576B2 - Optical substrate manufacturing method - Google Patents

Description

  The present invention relates to an optical substrate having electrical wiring and optical wiring, and a method for manufacturing the same.

  With the advancement of advanced information technology in recent years, the performance improvement of information processing devices such as routers and servers used for information communication has progressed remarkably, and further speeding up of communication signals is required in these devices. . In this speeding up, the communication quality of the electrical wiring in the electronic circuit or the electric circuit becomes an obstacle to improving the performance, so that this obstacle cannot be ignored in increasing the communication speed. Therefore, as a promising technology for solving problems that hinder high-speed communication, such as speeding up processing signals and reducing electrical noise, information can be transmitted and received at high transmission speeds using optical signals. The technology using optical wiring that can be used is attracting attention. In particular, in order to realize large-capacity optical interconnection using optical wiring, high density optical wiring and low loss connection are important, and various technical studies for high performance and cost reduction have been conducted. Yes.

  The optical signal is diffused when output from the light emitting element or the optical wiring. For this reason, it is necessary to connect the optical signal connection components at intervals as close as possible. Further, since the optical signal leaks and loses when the connection position of the optical connection is shifted, it is necessary to accurately connect the positions. In addition, since the optical waveguide for propagating the optical signal is provided in the horizontal direction in the substrate plane, it is necessary to convert the optical signal path by approximately 90 ° in order to input / output the optical signal to / from the light emitting / receiving surface of the light emitting / receiving element. is there.

  As a structure for converting an optical signal by 90 °, it is a known technique to form a mirror structure in which an end portion of an optical waveguide is cut at approximately 45 °.

  As a method of incorporating optical wiring onto an electronic substrate, there is a method of mounting a photoelectric module on a substrate, which is a collection of optical wiring, elements that convert light into electricity, element control units, and the like. Various methods for manufacturing such an optical substrate are currently being studied.

  There have been many reports on optical substrates in which an optical waveguide is laminated on the outermost layer of the substrate as in, for example, Patent Document 1, but recently, optical waveguides in the substrate as in Patent Document 2 have been made. There are also reports on the interior structure. The reason for this tendency is that by installing the optical waveguide in the substrate, the degree of freedom in pattern design is increased, and further high-density mounting of the substrate becomes possible.

  However, in this type of optical waveguide interior structure, when the substrate is manufactured by a laminating process, it is conceivable that the end portion of the optical waveguide is particularly deformed by pressure in the laminating process. If the end portion of the optical waveguide is deformed, the optical signal may not be transmitted due to the displacement of the optical connection.

JP 2009-122162 A Japanese Patent No. 4292476

  The present invention has been made in view of such conventional problems, and provides an optical substrate in which an optical waveguide is embedded in the substrate by an inexpensive material and a highly productive process. In particular, when an optical waveguide interior substrate is obtained by a lamination process, deformation of the waveguide end is suppressed. Accordingly, it is an object to provide an optical substrate having low cost and good connectivity and a manufacturing method thereof.

In order to solve the above problems, the invention according to claim 1 is a method of manufacturing an optical substrate in which an optical waveguide for transmitting an optical signal is embedded,
Spacers built in the optical substrate and built in the entire outer periphery or a part of the outer periphery of the optical waveguide, an insulating resin layer in which electrical wiring is patterned on at least the front and back, and a light emitting / receiving element provided on the electrical wiring And a method of manufacturing an optical substrate having a light emitting / receiving element control element provided on the electrical wiring,
Adhering the optical waveguide to the first surface of the first insulating resin layer;
Laminating spacers on the entire outer periphery or a part of the outer periphery of the optical waveguide;
Opening an adhesive layer in accordance with the light input / output part of the optical waveguide;
A step of thermocompression bonding the second insulating resin layer to the first surface of the first insulating resin layer with the adhesive layer;
Providing a through hole in the outermost layer of the insulating resin layer;
Forming an electrical wiring by patterning on the outermost layer of the insulating resin layer;
Providing an opening in the second insulating resin layer so that an optical signal input / output portion of the optical waveguide is exposed, and mounting a light emitting / receiving element that performs optical input / output on the electrical wiring;
Providing a light emitting and receiving element control element on the electrical wiring;
It is a manufacturing method of the optical board | substrate characterized by having.

  The present invention has the following effects. According to the first invention, in the optical substrate in which the optical waveguide is built, the spacer is disposed on the entire outer periphery of the optical waveguide or a part thereof. As a result, in the heating / compression process in which the substrate is laminated on the surface on which the waveguides are laminated via an adhesive layer such as a prepreg, the thermal stress applied to the waveguides is absorbed by the spacers arranged, so that the optical waveguides in particular. The deformation of the end can be greatly suppressed.

  Further, according to the second aspect, by using a metal spacer material, it is possible to reduce the deformation of the spacer due to thermal stress as compared with the case where a resin-based spacer is used.

  Further, according to the third invention, the optical path conversion mirror is formed in the light input / output part of the optical waveguide, and the metal film is provided on the mirror, so that the reliability is higher than that in the air mirror without the metal film. A mirror with less light loss.

  According to the fourth aspect of the present invention, a low-loss optical waveguide-incorporated optical substrate can be provided by arranging spacers on the outer periphery of the optical waveguide. In particular, since the optical substrate is manufactured by a lamination process, the optical substrate can be provided at a lower cost than the build-up method.

It is sectional drawing which shows an example which concerns on the manufacturing method of the optical board | substrate of this invention. It is sectional drawing which shows an example which concerns on the manufacturing method of the optical board | substrate of this invention following FIG. It is sectional drawing which shows an example which concerns on the manufacturing method of the optical board | substrate of this invention following FIG. It is sectional drawing which shows an example which concerns on the manufacturing method of the optical board | substrate of this invention following FIG.

  The optical substrate and the manufacturing method thereof according to the present invention will be described in more detail.

  A completed drawing of the optical substrate 100 of the present invention is shown in FIG. In the optical substrate 100 of the present invention, the optical waveguide 11 provided with the mirror 12 is first laminated on the insulating resin substrate 10a. The optical waveguide 11 is generally fixed with an epoxy optical adhesive, but is not limited thereto.

  Arbitrary organic materials and inorganic materials can be used for the insulating resin layer 10a. Specifically, an acrylic material, a silicone material, a silicon wafer, a metal material, a glass material, a prepreg, a laminated plate material, or the like can be used, but is not limited thereto.

  As the optical waveguide 11, an optical waveguide in which a general optical wiring is formed on an optical waveguide film can be used. As the film material of the optical waveguide film, polymer materials such as carbonate, epoxy, acrylic, imide, urethane, norbornene, and inorganic materials such as quartz can be used. As a transmission mode of the formed optical wiring, it is possible to adopt a configuration such as a single mode, a multimode, and a single multi mixed wiring. Moreover, it is not limited to a film, A thin wire optical fiber array can also be used.

  The mirror 12 is not particularly limited as long as it is a material having a high reflectance with respect to the wavelength of propagating light. For example, a metal film made of gold, silver, aluminum, or an alloy thereof can be used. In addition, these metal materials are preferable in that they have a high reflectance with respect to light having a wavelength of 850 nm used as a light emitting element.

  After the optical waveguide 11 is fixed, spacers 13 are installed around the mirrors at both ends of the optical waveguide. For fixing, a general epoxy adhesive for printed wiring boards was used, but the present invention is not limited to this.

  As long as the spacer 13 is a peripheral portion of the optical waveguide 11, the spacer 13 may be installed at a plurality of locations and the entire periphery of the optical waveguide 11, but it is more preferable to separately install the spacer 13 at two locations around the mirror portion 12 at both ends.

  Arbitrary organic materials and inorganic materials can be used as the material of the spacer 13. Specific examples include inorganic materials such as stainless steel, copper, iron, and aluminum, and organic materials such as polyimide, acrylic, and phenolic resins. Stainless steel is more preferable from the viewpoint of cost and durability.

  Subsequently, an opening 15 is provided in the adhesive layer in accordance with the light input / output portion of the optical waveguide 11, and the insulating resin layers 10 a and 10 b are heated and pressure-bonded via the adhesive layer 14.

  The opening 15 provided in the adhesive layer 14 is formed by a drill machine, a router processing machine, a laser processing machine, or the like. Further, the adhesive layer 14 needs to be laminated by aligning the opening 15 and the mirror part 12 which is an input / output part of the optical waveguide.

  As the material for the adhesive layer 14, aramid fiber, carbon fiber prepreg, and other insulating adhesives for printed wiring boards can be used, but glass fiber prepreg is more preferable from the viewpoint of heat resistance, reliability, and low linear expansion coefficient.

  After the insulating resin was heated and pressure-bonded, the via hole 16 and the through hole 17 were opened, and the via hole 18 and the through hole 19 were formed by plating.

  As a method for forming the via hole, laser processing is preferable. There are carbon dioxide laser, YAG laser (fundamental wave, 2nd harmonic, 3rd harmonic, or 4th harmonic) or excimer laser, etc., but both conductor layer and insulating resin layer are processed. A YAG laser (third harmonic or fourth harmonic), or an excimer laser, which is a short wavelength laser of 400 nm or less capable of simultaneously processing the laser beam, is more preferable.

  The hole for through hole can be formed by drilling with a drilling machine.

  The plating process includes an electroless copper plating or direct plating process for forming an electroplating seed layer on the insulating resin surface, and an electroplating process for plating using the seed layer as a power supply pattern.

  Next, an etching resist 20 is formed by using a known photolithography technique such as exposure and development. Thereafter, etching and peeling are performed to form the conductive layer 21 patterned on the electric wiring and the mounting pad. If necessary, Ni / Au plating and solder resist printing are also performed.

  Further, an optical through hole 22 is opened. For this purpose, it is preferable to form a marking indicating the opening position in advance by patterning, whereby a necessary size and depth can be opened at a predetermined position. Since high-precision processing is required for the opening, a YAG laser (third harmonic or fourth harmonic) or excimer laser is more preferable.

  Thereafter, the light emitting / receiving element control element 23 can be mounted on a mounting pad formed of a metal foil pattern as necessary. The light emitting and receiving element control element 23 can be mounted by die bonding, wire bonding 24, flip chip mounting, or the like.

  Finally, the light emitting / receiving element 25 is mounted so that the light input / output part of the optical waveguide 11 and the light receiving / emitting part of the light receiving / emitting element 25 are connected.

  As the light receiving and emitting element 25, a single channel or a plurality of channels of optical elements can be used. Specifically, an edge-emitting LD, a surface-emitting LD, a surface-receiving PD, or the like can be used. For the connection between the light emitting / receiving element 25 and the electric wiring formed by the patterned conductive layer, a method such as wire bonding or soldering can be used.

  Examples will be described below, but the present invention should not be construed as being limited thereto. Moreover, although the following description demonstrates the optical waveguide 11 of the optical board | substrate 100 as a single layer optical waveguide film, it does not necessarily need to be 1 layer. Moreover, although the following description demonstrates the optical waveguide 11 as multimode, it does not necessarily need to be multimode.

(Example) An optical waveguide 11 (multi-mode epoxy optical waveguide film: manufactured by NTT-AT) was placed on a non-woven glass cloth epoxy substrate (500 μm thick, FIG. 1A) as an insulating layer (FIG. 1B). . An epoxy-based refractive index matching optical adhesive (manufactured by NTT-AT) was used for installation and fixing. Here, gold is sputtered on the mirror 12 of the optical waveguide 11.

  Next, a stainless steel spacer (height: 100 μm) was placed around the mirror 12 on the insulating resin 10a. As the adhesive, an epoxy metal adhesive (manufactured by Three Bond) was used (FIG. 1 (c), FIG. 1 (d)).

  Next, a glass cloth prepreg (manufactured by Hitachi Chemical Co., Ltd.) was used as the adhesive layer 14, and an opening corresponding to the input / output part of the optical waveguide 11 was provided on the glass cloth prepreg (FIG. 1 (e)). Subsequently, the insulating resin layers 10a and 10b were heated and pressure-bonded via the adhesive layer 14 (FIG. 2 (f)).

  Next, via holes 16 were formed by processing with an ultraviolet laser (YAG third harmonic) with a wavelength of 355 nm, and through holes 17 were formed with a drilling machine (FIG. 2 (g)). . The hole diameters for via holes and through holes processed here were 60 μm and 120 μm, respectively.

  Next, in order to remove the resin residue deposited in the hole for the via hole, potassium permanganate and sodium hydroxide were dissolved in ion exchange water at a ratio of 3 to 2, and heated to about 50 ° C. The substrate was immersed in this mixed solution to remove the resin residue.

  Next, the copper plating process was performed and the via hole 18 and the through hole 19 were formed (FIG.2 (h)).

  Next, in order to form a wiring pattern, a dry film resist for wiring formation was heated and pressed with a laminator to form a resist layer. Further, using a photomask having a predetermined pattern, exposure was performed with parallel light using an ultrahigh pressure mercury lamp as a light source, and development was performed with a 1% aqueous sodium carbonate solution to obtain a desired etching resist pattern (FIG. 2). (I)).

  Copper was etched by etching with an aqueous ferric chloride solution having a specific gravity of 1.40. Thereafter, the resist was stripped with a 3% aqueous sodium hydroxide solution to obtain a circuit pattern (FIG. 3 (j)).

  Next, an optical through hole 22 was formed (FIG. 3 (k)). For this, it is preferable to process with an ultraviolet laser (YAG third harmonic) having a wavelength of 355 nm.

  Next, the light emitting / receiving element control element 23 (VCSEL driver chip 350 μm thickness: manufactured by HELIX AG) was mounted on the patterned copper foil 21, and electrical connection was performed by wire bonding 24 (FIG. 3L).

  Next, the light emitting / receiving element 25 is mounted on the patterned copper foil 21 so that the light input / output part of the optical waveguide 11 and the light emitting / receiving part of the light receiving / emitting element 25 (4cH VCSEL 150 μm thickness: made by ULM) are connected. (FIG. 4 (m)).

(Comparative example)
As a comparative example, the light output of two optical substrates produced in substantially the same manner as in the example was confirmed. One is an optical substrate 100 manufactured by the same manufacturing method as the embodiment, and the other is an optical substrate in which the spacer 13 is not provided.

  As a result of evaluating the optical characteristics of the optical substrate 100, an optical output of 0.9 to 1.3 mW was confirmed in each channel of the optical waveguide.

  As a method for evaluating the optical characteristics, first, light (850 nm) having an intensity of 5.0 mW was emitted from the light emitting element. This 5.0 mW optical signal enters from the end of each core channel of the optical waveguide, exits from the other end of the optical waveguide, and is received by the light receiving element. The light intensity at this time was measured with a light intensity measuring device.

  For the optical substrate that did not have a spacer as a comparative example, the mirror, which is the light input / output part, was deformed after the heating / compression process of the glass cloth prepreg used as the adhesive layer, and at this point the light input / output was completely I can't do it.

  Therefore, by using the optical substrate manufacturing method of the present invention, the thermal stress applied to the waveguide is absorbed by the spacer disposed after the heating / compression step of laminating the substrate via the adhesive layer. The deformation of the portion can be greatly suppressed, and a low-loss optical waveguide-embedded optical substrate can be manufactured.

DESCRIPTION OF SYMBOLS 10a ... Insulating resin layer 10b ... Insulating resin layer 11 ... Optical waveguide 12 ... Mirror 13 ... Spacer 14 ... Adhesive layer 15 ... Adhesive layer opening 16 ... For via holes Hole 17 ... through hole 18 ... via hole 19 ... through hole 20 ... etching resist 21 ... patterned conductive layer 22 ... light through hole 23 ... light emitting / receiving element control Element 24 ... Wire bonding 25 ... Light emitting / receiving element 100 ... Optical substrate

Claims (1)

It is a method of manufacturing an optical substrate with an optical waveguide for transmitting an optical signal,
Spacers built in the optical substrate and built in the entire outer periphery or a part of the outer periphery of the optical waveguide, an insulating resin layer in which electrical wiring is patterned on at least the front and back, and a light emitting / receiving element provided on the electrical wiring And a method of manufacturing an optical substrate having a light emitting / receiving element control element provided on the electrical wiring,
Adhering the optical waveguide to the first surface of the first insulating resin layer;
Laminating spacers on the entire outer periphery or a part of the outer periphery of the optical waveguide;
Opening an adhesive layer in accordance with the light input / output part of the optical waveguide;
A step of thermocompression bonding the second insulating resin layer to the first surface of the first insulating resin layer with the adhesive layer;
Providing a through hole in the outermost layer of the insulating resin layer;
Forming an electrical wiring by patterning on the outermost layer of the insulating resin layer;
Providing an opening in the second insulating resin layer so that an optical signal input / output portion of the optical waveguide is exposed, and mounting a light emitting / receiving element that performs optical input / output on the electrical wiring;
Providing a light emitting and receiving element control element on the electrical wiring;
A method for manufacturing an optical substrate, comprising: