JP5380903B2 - 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.

  As a promising technology for solving problems that hinder high-speed communication, such as increasing the speed of processing signals and reducing electrical noise, it is possible to send and receive information at high transmission speeds by using optical signals. The technology that uses simple optical wiring 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.

  In particular, in the mounting of the light receiving / emitting element and the optical waveguide, a method has been reported in which the optical waveguide is fixedly mounted using a bridge girder and the height of the optical waveguide and the light receiving / emitting element is matched (Non-Patent Document 1). However, this method has a problem that the mounting reliability of the optical waveguide is lowered and a problem that the position of the tip of the optical waveguide is shifted and the optical connection efficiency is lowered. In addition, a technique has been reported in which a silicon substrate is etched, a light emitting / receiving element is embedded in an etched portion, and an optical waveguide is mounted thereon (Patent Document 1). However, this method has a problem that the light receiving / emitting element and the optical waveguide are separated by the height of wire bonding, and the optical connection efficiency is lowered. Further, there is a problem that the etched silicon substrate becomes expensive.

M.M. Usui, N .; Matsuura et al. , 10th LEOS '97, 51 (1997) JP 05-002766 A

  The present invention has been made in view of the drawbacks of the prior art, and provides a structure in which a light emitting / receiving element, an optical waveguide, and an optical signal path conversion component are connected by an inexpensive and simple process. Furthermore, the mounting reliability of the connecting portion is improved. Accordingly, it is an object of the present invention to provide an optical substrate with low cost and good connection characteristics and a method for manufacturing the same.

The first invention, and the electric wiring forming electrical wiring by patterning the metal layer of the insulating resin film having a least metal layer on the first surface even in the insulating resin layer, by patterning the insulating resin layer An insulating resin layer forming step of providing an opening, an insulating resin substrate installation step of bonding an insulating resin film on the support base with the first surface facing outside, and a light receiving and emitting surface in the opening of the first A light emitting / receiving element mounting step for installing the light emitting / receiving element so as to be on the surface side, and an insulating resin in which the light emitting / receiving surface and the light input / output surface of the optical waveguide are aligned to optically connect with the light receiving / emitting element It is the manufacturing method of the optical board | substrate which has an optical waveguide mounting process which installs an optical waveguide on a film, and a support base material removal process which removes the said support base material.

The second invention, photosensitive insulating resin layer to form the opening the insulating resin layer is patterned by photolithography to least well of made of a resin insulating resin layer insulating resin film having a metal layer on the first surface Forming step, insulating resin substrate installation step of bonding the insulating resin film on the supporting base material with the first surface outside, an electric wiring step of patterning the metal layer to form an electric wiring, and the opening A light emitting / receiving element mounting step for installing the light emitting / receiving element so that the light emitting / receiving surface of the light emitting / receiving element is on the first surface side, and the light emitting / receiving unit optically connected to the light emitting / receiving element An optical substrate manufacturing method comprising: an optical waveguide mounting step of installing an optical waveguide on an insulating resin film so that the light input / output surfaces of the optical waveguide are aligned; and a support base material removal step of removing the support base material .

The third invention is the method of manufacturing an optical substrate according to claim 1 or 2 , further comprising a control chip mounting step of mounting a control chip of the light emitting / receiving element on the electric wiring.

A fourth invention, the light receiving and emitting surface, the light board according to any of claims 1 to 3, characterized in that it has the light input surface and the transparent resin filling step of filling a transparent resin into the gap It is a manufacturing method.

5th invention has the mold resin formation process which covers at least one part of an insulating resin layer with mold resin, The manufacturing method of the optical substrate in any one of Claim 1 to 3 characterized by the above-mentioned.

The present invention has the following effects.
First, it is possible to match the height of the surface of the insulating resin layer and the light emitting / receiving surface of the light emitting / receiving element by matching the thickness of the light emitting / receiving element and the insulating resin and embedding the light receiving / emitting element in the insulating resin layer. It becomes. Thereby, the place which mounts an optical waveguide can be made flat, and there exists an effect which improves the mounting reliability of an optical waveguide and simplifies the mounting difficulty.

  Second, by fixing the light emitting / receiving element in the insulating resin layer, the connection between the light emitting / receiving element and the electric wiring becomes easy. Since the entire light emitting / receiving element is fixed to the substrate, the element does not move even under high-temperature heating conditions such as wire bonding, and wire bump formation is facilitated. This has the effect of improving the mounting yield and reducing the manufacturing cost.

  Third, by installing both the light emitting / receiving surface of the light emitting / receiving element and the pad surface for electrical connection above the substrate, the general-purpose light emitting / receiving element can be used as it is. A light emitting / receiving element having the light emitting / receiving surface as the lower surface and the pad surface for electrical connection as the upper surface is expensive and the manufacturing cost increases. By using a general-purpose light emitting / receiving element, there is an effect of reducing the manufacturing cost.

A cross-sectional view of the optical substrate of the present invention is shown in FIG.
The optical substrate 110 of the present invention includes an insulating resin layer 10 having an electric wiring 21 having a metal layer patterned on a first surface. An opening is formed in the insulating resin layer, and the light emitting / receiving element 60 is installed in the opening so that the light receiving / emitting element 61 is fitted toward the outer surface, that is, the electric wiring side. An optical waveguide 50 for inputting / outputting optical signals between the light receiving / emitting element and the optical wiring is disposed on the light receiving / emitting surface.

  The insulating resin layer 10 can select any organic material and inorganic material. Specifically, acrylic materials, silicone materials, silicon wafers, metal materials, glass materials, prepregs, laminated plate materials, and the like can be used. Furthermore, it is possible to perform patterning with high accuracy by forming an insulating resin layer by a photolithography method using a photosensitive resin. Therefore, the opening shape can be matched with the light emitting / receiving element and can be installed with high positional accuracy. Because. As a result, the light receiving / emitting element embedding part can be shaped with high accuracy, and the light receiving / emitting element can be mounted by aligning the outer shape. Examples of the photosensitive resin include a photosensitive polyimide resin, a photosensitive acrylic resin, a photosensitive epoxy resin, and a photosensitive epoxy acrylate resin obtained by polymerizing these.

  In the present invention, as described later, an optical substrate is manufactured by a process using a support substrate to provide an opening that penetrates the insulating resin layer, and a light emitting / receiving element is installed in the opening. For this reason, the insulating resin layer can be thinned to a thickness substantially equal to the thickness of the light emitting / receiving element, and a high-density optical substrate can be realized.

  As the optical waveguide 50, a general optical wiring optical waveguide composed of a core and a clad covering the outer periphery of the core can be used. As the material, polymer materials such as carbonate, epoxy, acrylic, imide, urethane, norbornene, and inorganic materials such as quartz can be used. As the transmission mode, a single mode, a multi mode, a single multi mixed wiring, or the like can be employed. Further, the optical waveguide may be a single layer or a laminate of a plurality of layers.

  In the optical substrate of FIG. 1, the end surface of the optical waveguide on the side of the light receiving / emitting element is cut at 45 degrees to form a mirror surface that reflects an optical signal. Alternatively, a mirror may be formed by forming a metal layer on the end face. Thereby, the leakage of the optical signal by mold resin at the time of covering with mold resin can be prevented. By arranging the light emitting / receiving section 61 of the light emitting / receiving element and the light input / output surface of the end face of the optical waveguide to coincide with each other, both are optically connected.

  As the light emitting / receiving element 60, 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. The light emitting / receiving element 60 can be mounted by wire bonding or the like.

  In the present invention, the light emitting / receiving element is fixed in the insulating resin layer, thereby facilitating connection between the light emitting / receiving element and the electric wiring. This is because since the entire light receiving and emitting element is fixed to the substrate, the element does not move even under high-temperature heating conditions such as wire bonding, and wire bump formation is facilitated. Thereby, the mounting yield can be improved and the manufacturing cost can be reduced.

  In addition, a transparent resin 80 can be filled between the light emitting / receiving surface of the light emitting / receiving element 60 and the light input / output surface of the optical waveguide 50 as necessary. As the transparent resin 80, a generally used polymer material can be used. Specifically, a carbonate material, an epoxy material, an acrylic material, an imide material, a urethane material, a silicone material, an organic material mixed with an inorganic filler, and the like can be used. However, the material is not limited thereto. It is desirable to use an optical resin having a refractive index equivalent to that of the optical waveguide 50 in order to eliminate the difference in refractive index at the interface. Thereby, the refractive index mismatch between the light emitting / receiving element and the optical waveguide can be improved, the optical connection characteristics can be improved, and the environmental reliability can be improved.

  Furthermore, the control chip 40 of the light emitting / receiving element 60 can be mounted on the copper foil 20 as necessary. It can be connected to the optical wiring in the vicinity of the control chip, and the light emitting / receiving element and the control chip can be connected without passing the photoelectric signal through the inside of the substrate. Can be suppressed. The control chip 40 can be mounted by die bonding, wire bonding, flip chip mounting, or the like.

  By molding the entire first surface on which the electrical wiring of the optical substrate is formed or an arbitrary portion including the optical waveguide and the light receiving and emitting elements with the molding resin 70, it is possible to improve the environmental reliability of the substrate and the mounted components. . In that case, in order to prevent mold resin from entering the interface between the light emitting / receiving element 60 and the optical waveguide 50, it is desirable to fill the transparent resin 80 in advance.

  Since the lower surface of the optical substrate is formed flat, the connector can be installed with high accuracy. Specifically, an LGA, a PGA, a small electrical connector, or the like can be installed. FIG. 1 shows an example in which the wiring board 110 is connected via the solder bump 90.

  The optical substrate of the present invention is effective for electronic devices or optical components that involve a large amount of information input / output. Specific examples of electronic devices equipped with optical substrates include input and output of large information such as various electronic computers including notebook computers and large commercial computers, home game machines, recording / playback machines, televisions, and routers. Use in information / communication equipment is effective because it enables efficient signal transmission and reception without being affected by noise. In addition, specific examples of the optical component on which the optical substrate 1 is mounted include an optical interconnection (photoelectric wiring board), an optical connector, an optical coupler, an optical coupler, an optical switch, an optical splitter, or an optical transceiver, The same effect can be expected by mounting on optical components.

Next, the manufacturing method of the optical board | substrate of this invention is demonstrated.
First, the insulating resin layer and metal layer of an insulating resin film having a metal layer such as copper foil formed on one side are patterned before and after the formation of electrical wiring, and openings and via holes for installing light emitting and receiving elements. The insulating resin layer removed portion is removed.

  As a specific method of the above steps, first, a metal layer is patterned to form a wiring pattern and a mounting pad. As a patterning method for the metal layer, a known metal processing method can be used. Specifically, a resist pattern is formed according to the wiring pattern and the mounting pad, and the wiring pattern is formed by etching. Further, if necessary, Ni, Au plating or solder resist printing may be performed. Next, an insulating resin layer removing portion such as an opening or a via hole in which the light emitting and receiving element is installed can be removed by using an insulating resin processing method such as laser processing. Next, the patterned insulating resin film is pasted on the support substrate with the surface on which the electrical wiring is formed facing outside.

  In the case where the insulating resin layer is formed of a photosensitive resin, as a photolithography process, exposure is performed using a mask corresponding to the pattern of the photosensitive resin, development is performed, the insulating resin layer is patterned, and openings are formed. Can be formed. Next, after laminating on the supporting substrate with the electric wiring forming surface as a table, the metal layer can be patterned by the above-described method.

  Each of the above steps may be appropriately combined. A general laminating method can be used for laminating the supporting substrate and the insulating resin film. A commonly used material can be used for the supporting substrate. Specifically, a carbonate material, an epoxy material, an acrylic material, an imide material, a urethane material, a silicone material, an organic material mixed with an inorganic filler, and the like can be used. However, the material is not limited thereto. Further, an ultraviolet peelable pressure-sensitive adhesive layer can be provided on the support substrate. By performing each process on the supporting base material, the lower surface of the optical substrate can be made flat. Accordingly, the mounting difficulty of the optical waveguide can be simplified and the mounting reliability can be improved, so that the connector can be installed with high accuracy on the lower surface of the optical substrate. Specifically, an LGA, a PGA, a small electrical connector, or the like can be installed. Further, since the insulating resin layer is held and fixed by the support base material, the optical substrate can be stably mounted even when the insulating resin layer is thin.

  Next, the light emitting / receiving element is mounted on the light emitting / receiving element installation portion from which the insulating resin layer has been removed. By making the thickness of the insulating resin layer substantially the same as the thickness of the light receiving and emitting element, it is possible to minimize loss at the connection portion with the optical waveguide. If the thickness of the insulating resin layer is substantially the same as the thickness of the light emitting / receiving element, that is, at least a part of the light receiving / emitting surface of the light receiving / emitting element can be brought into contact with the light input / output portion of the optical waveguide for photoelectric conversion. It is.

  Further, a control chip for the light emitting / receiving element may be mounted as necessary before or after the mounting process of the light receiving / emitting element. In this case, the control chip of the light emitting / receiving element can be mounted on the electric wiring. The control chip 40 can be mounted by wire bonding or flip chip mounting.

  Next, the optical waveguide is mounted so that the light input / output unit of the optical waveguide and the light emitting / receiving unit of the light emitting / receiving element are connected. If necessary, an optical adhesive may be filled in the interface between the light emitting / receiving element and the optical waveguide. Optical loss at the connection portion between the light emitting / receiving element and the optical waveguide can be reduced.

  Next, the entire substrate or an arbitrary portion can be molded with a molding resin. In this case, after the molding step, the carrier film is finally peeled off to obtain the optical substrate of the present invention. Note that in the case where an ultraviolet peelable adhesive layer is provided on the support substrate, the support substrate can be peeled off by ultraviolet irradiation.

  Specific examples of the method for producing an optical substrate according to the present invention are shown below with reference to the following examples, but the present invention is not construed as being limited thereto.

<Example 1>
First, a patterned copper foil 20 was obtained by forming an etching resist pattern 25 on a copper foil of a Toray single-sided copper foil polyimide substrate (copper foil 12 μm thickness, polyimide 350 μm thickness) and etching the copper foil ( FIG. 2b).

  Next, the insulating resin 10 was processed with a carbon dioxide laser to obtain a patterned insulating resin layer (FIG. 2c).

  Next, the insulating resin layer 10 was laminated on the support substrate 30 (PET: manufactured by Toyo Ink) (FIG. 2d).

  Next, the control chip 40 (VCSEL driver chip 350 μm thickness: manufactured by HELIX AG) was mounted on the copper foil 20, and electrical connection was performed by wire bonding (FIG. 2e).

  Next, the light emitting / receiving element 60 (4ch VCSEL: manufactured by ULM) was mounted on the carrier film from which the insulating resin was removed by patterning (FIG. 2f). The installation position alignment performed abutment alignment using the outer shape of the insulating resin layer 11.

  Next, an optical waveguide film 50 (multimode epoxy optical waveguide film: manufactured by NTT-AT) was placed on the insulating resin layer 10 and the light emitting / receiving element 61 (FIG. 2g). For installation and fixing, an epoxy-based refractive index matching optical adhesive (manufactured by NTT-AT) was used.

  Next, the insulating resin layer 10 was covered with a mold resin 70 (FIG. 2h).

  Next, the support base material 30 was peeled off to manufacture the optical substrate 100 (FIG. 2i).

  As a result of evaluating the optical characteristics of the produced optical substrate, a stable light output of 0.9 to 1.1 mW was confirmed in each channel.

<Example 2>
First, as a photosensitive insulating material, 52 parts by weight of bisphenol A type epoxy acrylate (Lipoxy VR-90: Showa High Polymer) and 15 parts by weight of phthalic anhydride are stirred in a propylene glycol monomethyl ether acetate solvent at 110 ° C. for 30 minutes for alkali development. Type photosensitive insulating resin varnish raw material was prepared. Furthermore, 50 parts by weight of the alkali-developable photosensitive insulating resin varnish raw material, 17 parts by weight of an alicyclic epoxy compound (EHPE3150: Daicel Chemical), 30 parts by weight of a photocurable epoxy resin (Cyclomer M100: Daicel Chemical), Propylene glycol monomethyl ether acetate solvent was added to 3 parts by weight of a photoinitiator (LucirinTPO: BASF) and dispersed in a continuous horizontal sand mill for about 3 hours to prepare an alkali development type photosensitive insulating resin varnish.

  Next, the alkali development type photosensitive insulating resin varnish is applied on a copper foil with a slit coater and dried at 70 ° C. for 20 minutes to form a semi-cured photosensitive insulating resin layer having a thickness of about 350 μm. A photosensitive insulating resin with a foil was produced (FIG. 3a).

Next, a photomask was brought into close contact with the photosensitive insulating resin layer 10, exposed to 500 mJ / cm ² with an ultra-high pressure mercury lamp, and cured with ultraviolet rays. Thereafter, development with about 5% organic amine alkali aqueous solution, washing with water, and sufficient drying in a 90 ° C. oven were performed to obtain a patterned insulating resin layer (FIG. 3 b).

  Next, the insulating resin layer 10 was laminated on the support substrate 30 (PET: manufactured by Toyo Ink) (FIG. 3c).

  Next, an etching resist pattern 25 was formed on the copper foil 20, and the copper foil was etched to obtain a patterned copper foil 21 (FIG. 3d).

  Next, a control chip 40 (VCSEL driver chip: manufactured by HELIX AG) was mounted on the copper foil 20, and electrical connection was performed by wire bonding (FIG. 3e).

  Next, the light emitting / receiving element 60 (4ch VCSEL: manufactured by ULM) was mounted on the carrier film from which the insulating resin was removed by patterning (FIG. 3f). The installation position alignment performed abutment alignment using the outer shape of the insulating resin layer 11.

  Next, an optical waveguide film 50 (multimode epoxy optical waveguide film: manufactured by NTT-AT) was placed on the insulating resin layer 10 and the light emitting / receiving element 60 (FIG. 3g). For installation and fixing, an epoxy-based refractive index matching optical adhesive (manufactured by NTT-AT) was used.

  Next, the insulating resin layer 10 was covered with a mold resin 70 (FIG. 3h).

  Next, the support base material 30 was peeled off to manufacture the optical substrate 100 (FIG. 3i).

  As a result of evaluating the optical characteristics of the produced optical substrate, a stable light output of 0.9 to 1.1 mW was confirmed in each channel.

Sectional drawing of the optical board | substrate of this invention. Explanatory drawing (Example 1) of the manufacturing method of the optical board | substrate of this invention. Explanatory drawing of the manufacturing method of the optical board | substrate of this invention (Example 2).

Explanation of symbols

10 Insulating resin layer 20 Metal layer (copper foil)
DESCRIPTION OF SYMBOLS 30 Support base material 40 Control chip 50 Optical waveguide 60 Light emitting / receiving element 61 Light receiving / emitting part 70 Mold resin 80 Transparent resin 90 Solder bump 100 Optical board 110 Wiring board

Claims (5)

And the electric wiring forming electrical wiring by patterning the metal layer of the insulating resin film having a least metal layer on the first surface even in the insulating resin layer,
An insulating resin layer forming step of patterning the insulating resin layer to provide an opening;
An insulating resin substrate installation step of bonding the insulating resin film on the support base with the first surface facing outside; and
A light emitting / receiving element mounting step of installing the light emitting / receiving element so that the light receiving / emitting surface is on the first surface side in the opening;
An optical waveguide mounting step of installing an optical waveguide on an insulating resin film by matching the light input / output surface of the optical waveguide and the light input / output surface of the optical waveguide so as to be optically connected to the light emitting / receiving element;
A supporting substrate removing step of removing the supporting substrate;
The manufacturing method of the optical board | substrate which has this. An insulating resin layer forming step of forming an opening the insulating resin layer of the insulating resin film also has a metal layer on the first surface and less of a photosensitive resin insulating resin layer is patterned by photolithography,
An insulating resin substrate installation step of bonding the insulating resin film on the support base with the first surface facing outside; and
An electrical wiring step of patterning the metal layer to form electrical wiring;
A light emitting / receiving element mounting step of installing the light emitting / receiving element such that the light receiving / emitting surface of the light emitting / receiving element is on the first surface side in the opening;
An optical waveguide mounting step of installing an optical waveguide on an insulating resin film by matching the light input / output surface of the optical waveguide with the light emitting / receiving portion so as to be optically connected to the light emitting / receiving element;
A supporting substrate removing step of removing the supporting substrate;
The manufacturing method of the optical board | substrate which has this.   The method for manufacturing an optical substrate according to claim 1, further comprising a control chip mounting step of mounting a control chip of the light emitting / receiving element on the electric wiring.   4. The method of manufacturing an optical substrate according to claim 1, further comprising a transparent resin filling step of filling a transparent resin into a gap between the light emitting / receiving surface and the light input / output surface.   4. The method for producing an optical substrate according to claim 1, further comprising a mold resin forming step of covering at least a part of the insulating resin layer with a mold resin.