JP5409262B2 - Photoelectric wiring board manufacturing method and optoelectric wiring board - Google Patents

Description

  The present invention relates to a method for manufacturing an optoelectric wiring board and an optoelectric wiring board.

  In recent years, with the improvement of information processing capability of computers, in an integrated circuit (IC) such as a semiconductor large scale integrated circuit element (LSI, VLSI) used as a microprocessor, the degree of integration of transistors has been increased. The operating speed of the IC has reached the GHz level at the clock frequency. Along with this, there has been a demand for higher density and finer electrical wiring for electrically connecting electrical elements.

  However, increasing the density and miniaturization of electrical wiring tends to cause crosstalk and propagation loss of electrical signals. For this reason, an optical transmission technique in which an electrical signal inputted to and outputted from a semiconductor element is converted into an optical signal, and the optical signal is transmitted through an optical wiring such as an optical waveguide formed on a mounting substrate has been studied.

  For example, as an optical transmission technique, for example, Patent Document 1 discloses an optoelectric wiring board in which an optical waveguide manufactured in a separate process is attached to a printed wiring board.

JP 2004-4427 A

  However, as in Patent Document 1, in order to align and paste the end portion of the optical waveguide and the end portion of the substrate, it is necessary to accurately align the core of the optical waveguide, and the alignment is very fine and difficult. There was a problem of becoming.

  It is also conceivable to produce a photoelectric wiring substrate by forming a light guide on a substrate by photolithography using a photosensitive light guide material. However, when a printed wiring board is used as the substrate, the build-up layer of the printed wiring board generally contains a white filler such as silica, so that light reaching the build-up layer during light irradiation causes irregular reflection. . As a result, there is a problem that the core is formed in a place other than the desired place. In particular, when a plurality of cores are formed in one optical waveguide, the cores may be manufactured without being separated from each other, and it is difficult to integrate the plurality of cores.

  An object of the present invention is to provide an opto-electric wiring board manufacturing method and an opto-electric wiring board capable of producing a plurality of cores with high accuracy using photolithography.

  A method for manufacturing an optoelectronic wiring board according to an embodiment of the present invention is a method for manufacturing an optoelectronic wiring board in which an optical waveguide having a lower clad, a plurality of cores, and an upper clad is formed on a printed wiring board. A conductive layer that absorbs light of a specific wavelength and a resin insulating layer that absorbs light of the specific wavelength on the printed wiring board, and the resin insulating layer is connected to the end of the printed wiring board from the conductive layer. A step of forming the lower clad on the conductive layer and the resin insulating layer, and a photosensitive resin having photosensitivity to the light of the specific wavelength. Laminating on the clad, irradiating light of the specific wavelength and patterning the photosensitive resin to produce a plurality of cores, and covering the periphery of the plurality of cores together with the lower clad Comprising the steps of preparing a cladding, the.

The step of producing the conductive layer and the resin insulation layer and the step of producing the lower clad are performed using an epoxy resin as the resin insulation layer and the lower clad.
The step of producing the conductive layer and the resin insulating layer preferably includes a step of aligning the upper surface of the resin insulating layer and the upper surface of the conductive layer so as to be flush with each other.

  The step of producing the conductive layer and the resin insulating layer preferably includes a step of providing the resin insulating layer so as to surround the periphery of the conductive layer.

  The light having the specific wavelength is preferably ultraviolet light.

  The conductive layer preferably has an oxidized surface.

It is preferable that the method further includes a step of irradiating a laser on a position overlapping with the conductive layer to perforate the optical waveguide positioned at a position overlapping with the conductive layer .

An optical semiconductor having a step of forming a through conductor that conducts from the conductive layer to the upper surface of the optical waveguide, and that is electrically connected to the through conductor and optically coupled to the plurality of cores on the through conductor It is preferable to further include a step of providing an element.

An optoelectric wiring board according to an embodiment of the present invention includes a printed wiring board, a resin insulating layer provided on an end of the printed wiring board, on the printed wiring board, and inside the resin insulating layer. A conductive layer having a blackened surface, and provided on the conductive layer and the resin insulating layer up to an end of the printed wiring board, and includes the lower clad, the plurality of cores, and the upper clad comprising an optical waveguide that is, the, the lower cladding, that are placed in contact with the conductive layer.
Moreover, the photoelectric wiring board concerning one Embodiment of this invention is the said structure. WHEREIN: The upper surface of the said conductive layer and the upper surface of the said resin insulating layer are the same surfaces.

An optoelectric wiring board according to an embodiment of the present invention includes a printed wiring board, a resin insulating layer provided on an end of the printed wiring board, on the printed wiring board, and inside the resin insulating layer. A conductive layer having a blackened surface, and provided on the conductive layer and the resin insulating layer up to an end of the printed wiring board, and includes the lower clad, the plurality of cores, and the upper clad The upper surface of the conductive layer and the upper surface of the resin insulating layer are flush with each other.
Moreover, the photoelectric wiring board concerning one Embodiment of this invention is the said structure, The said lower clad is arrange | positioned in contact with the said conductive layer.

  According to this embodiment, a plurality of cores can be produced with high accuracy using photolithography.

It is sectional drawing of the optoelectric wiring board of the 1st Embodiment of this invention. (A)-(c) is sectional drawing which shows the manufacturing method of the optoelectronic wiring board of the 1st Embodiment of this invention. (D) And (e) is the manufacturing method of the optoelectronic wiring board of the 1st Embodiment of this invention, Comprising: It is sectional drawing which shows the process after FIG.2 (c). It is a top view of the conductive layer 2a and the resin insulating layer 2b in FIG.2 (b). It is an expanded sectional view when the core 3b in FIG.2 (c) is seen from the side surface.

  Hereinafter, a method for manufacturing an opto-electric wiring board and an opto-electric wiring board according to an embodiment of the present invention will be described in detail with reference to the drawings. However, these drawings are only examples of the embodiments, and the present invention includes them. It is not limited.

  FIG. 1 shows an example of an optoelectric wiring board according to an embodiment of the present invention. The optoelectric wiring board in FIG. 1 includes a printed wiring board 1, a resin insulating layer 2b, a conductive layer 2a, and an optical waveguide 3. 1 further includes an optical semiconductor element 5 and an optical path changing unit 9, but the present invention is not limited to this. 1 uses a light-emitting element as the optical semiconductor element 5 and irradiates signal light such as infrared light from the optical semiconductor element 5 and causes the optical path of the signal light to pass through the optical path conversion unit 9. Is converted into the optical waveguide 3 (see the arrow in FIG. 1).

  FIG. 2 shows a method for manufacturing an optoelectric wiring board according to an embodiment of the present invention.

  FIG. 2A shows the printed wiring board 1. The printed wiring board 1 includes a base body 1a, a resin insulating layer 1bb in a buildup layer formed on both surfaces of the base body 1a, and a conductive layer 1ba in the buildup layer.

  The substrate 1a has a thickness of 0.2 to 2 mm, and a glass epoxy substrate, a BT resin substrate, a polyimide substrate, or the like is used. The substrate 1a may be a single layer or a laminate, and electrical wiring is formed on both sides and inside of the substrate 1a with a through conductor or the like.

  The build-up layer is composed of a resin insulating layer 1bb and a conductive layer 1ba. The resin insulating layer 1bb is made of a thermosetting epoxy resin or the like and has a thickness of 10 to 50 μm. Since the thickness is small, it is possible to make fine holes with a laser, and it can be laminated to route a complicated electric wiring pattern or to be integrated in a narrow range. The conductive layer 1ba in the buildup layer is electrically connected to a through electrode formed on the base 1a.

  The printed wiring board 1 shown in FIG. 2A is a multilayer board in which a buildup layer is provided on each of the front and back layers of the base 1a. The number of resin insulation layers 1bb and conductive layers 1ba in the build-up layer can be increased according to the required number. Alternatively, a single-layer substrate having only the substrate 1a may be used without the build-up layer.

  In FIG. 2B, a conductive layer 2a that absorbs light of a specific wavelength and a resin insulating layer 2b that absorbs light of the specific wavelength are formed on the printed circuit board shown in FIG. 2A. A process is shown.

  The conductive layer 2a and the resin insulating layer 2b both absorb light having a specific wavelength. The light having a specific wavelength is light having a wavelength at which a photosensitive resin used in a process described later exhibits photosensitivity. I mean.

  The conductive layer 2a is made of, for example, copper that is generally used as an electrical wiring. The surface of the conductive layer 2a is blackened to absorb light of a specific wavelength. This blackening treatment means oxidizing the surface with sodium chlorite or the like. By the blackening treatment, the surface of the conductive layer 2a is blackened and can absorb light having a specific wavelength. Further, by the blackening treatment, minute irregularities of about 0.2 to 2 μm are formed on the surface.

  Since the conductive layer 2a absorbs light of a specific wavelength, in the process described later, when a plurality of cores are formed by irradiating light of a specific wavelength and patterning a photosensitive resin, Reflection can be suppressed. Furthermore, by having irregularities on the surface, it is possible to improve the adhesion with the lower clad 3a formed on the upper part.

  As the resin insulating layer 2b, for example, a material in which an absorber that absorbs light of a specific wavelength is mixed with a resin such as an epoxy resin is used.

  In the process shown in FIG. 4, the resin insulating layer 2b is formed so as to be positioned on the end side of the printed wiring board 1 with respect to the conductive layer 2a. Thereby, the exposure of the conductive layer 2a to the outside can be suppressed as much as possible, and the occurrence of defects such as leakage or corrosion can be suppressed. Further, under high heat conditions required in the subsequent manufacturing process and mounting process, peeling is likely to occur from an interface having greatly different thermal expansion coefficients, but the thermal expansion coefficient of the resin insulating layer 2b provided on the end side is Since the thermal expansion coefficients of the resins 1bb and 3a positioned above and below the thermal expansion coefficient of the conductive layer 2a are closer, the separation of the optical waveguide 3 from the printed wiring board 1 is suppressed. In this step, as shown in FIG. 4, it is preferable to provide the resin insulating layer 2b so as to surround the conductive layer 2a.

  In addition, in the top view of the conductive layer 2a and the resin insulating layer 2b in FIG. 4, the center is represented by white, but this white is obtained by omitting the pattern of the central conductive layer 2a. A pattern 2a is formed.

  Moreover, since it is usually difficult to provide the conductive layer 2a on the end side, the light absorption effect by the conductive layer 2a cannot be obtained in the patterning of the plurality of cores 3b on the end side. Although it was not obtained, since the resin insulating layer 2b was produced closer to the end side of the printed wiring board 1 than the conductive layer 2a, the resin insulating layer 2b exhibited a light absorption effect on the end side. It is possible to produce a plurality of cores 3b having an excellent shape.

  When the conductive layer 2a and the resin insulating layer 2b are formed adjacent to each other, it is preferable to align the upper surface of the resin insulating layer 2b and the upper surface of the conductive layer 2a so that they are flush with each other. Specifically, the upper surface of the resin insulating layer 2b is aligned with the upper surface of the conductive layer 2a by making the thicknesses equal. The thicknesses need not be perfectly equal, but are preferably equal between ± 20%. By aligning the upper surface of the resin insulating layer 2b with the upper surface of the conductive layer 2a, the occurrence of a step between the upper surface of the resin insulating layer 2b and the upper surface of the conductive layer 2a is suppressed, and the shape change due to the step in a later step. A small optical waveguide 3 can be produced. In addition, since the thickness of the optical waveguide 3 can be reduced compared to the case where the unevenness caused by the conductive layer 2a is filled with the lower cladding layer, the warp of the printed wiring board 1 can be suppressed. A highly reliable electrical connection between the upper and lower sides is obtained.

  In FIG. 2 (c), a lower clad 3a is formed on the conductive layer 2a and the resin insulating layer 2b, and a photosensitive resin having photosensitivity to light of a specific wavelength is laminated on the lower clad 3a. Irradiating the light of the specific wavelength and patterning the photosensitive resin to produce a plurality of cores 3b; and producing the upper clad 3c so as to cover the periphery of the plurality of cores 3b together with the lower clad 3a; , Indicate.

  The step of producing the lower clad 3a on the conductive layer 2a and the resin insulating layer 2b is achieved, for example, by laminating a photosensitive resin film and performing exposure, development and baking in this order. When a photosensitive liquid resin is used, it is applied by spin coating or a doctor blade, and exposure, development, and baking are performed. As described above, when the upper surface of the resin insulating layer 2b and the upper surface of the conductive layer 2a are aligned, the film having a desired film thickness does not need to be considered for the film thickness necessary to absorb the step. Can be used. In addition, a flat liquid resin can be applied without being affected by a step. By forming the lower clad 3a flat, the core 3b in the next process also has no positional fluctuation in the vertical direction of the substrate, the thickness variation is suppressed, and the low-loss optical waveguide 3 is obtained.

  In the step of laminating a photosensitive resin having photosensitivity to light of a specific wavelength on the lower clad 3a, for example, a resin film that is sensitive to ultraviolet light is laminated, and then exposure, development, and baking are performed in this order. By doing so, a pattern of a plurality of cores 3b is produced. At this time, as described above, due to the light absorption effect of the conductive layer 2a and the resin insulating layer 2, the pattern of the core 3b reflects the photomask shape even on the end side of the printed wiring board, and a good shape is obtained. It is done. For example, as shown in FIG. 5, the cores have shapes that are separated from each other. In the method for manufacturing an opto-electric wiring board according to an embodiment of the present invention, the interval A between the cores 3b exposed at the end of the printed wiring board can be formed to be as small as 10 to 215 μm.

  The step of producing the upper clad 3c so as to cover the periphery of the plurality of cores 3b together with the lower clad 3a is achieved by, for example, laminating a photosensitive resin film and performing exposure, development, and baking in this order.

  The lower clad 3a, the core 3b, and the upper clad 3c are made of a resin that can be used for a direct exposure method such as photosensitive epoxy resin, acrylic resin, polyimide resin, or a resin that can be used for a refractive index change method such as polysilane. Can be mentioned. As described above, the direct exposure method refers to the formation of the lower clad 3a, the coating of the material of the core 3b, the formation of the core 3b by mask exposure, and the further application of the upper cladding 3c on the upper and side surfaces thereof. This is a method of forming an optical waveguide. In addition, the refractive index changing method is performed by using the characteristics of a polysilane polymer material or the like whose refractive index is lowered by UV (ultraviolet) irradiation, and performing UV irradiation on a portion other than the portion that becomes the core 3b, and the portion other than the portion that becomes the core 3b. This is a method for producing an optical waveguide by lowering the refractive index of the optical waveguide.

  The core 3b has a higher refractive index than that of the lower cladding 3a and the upper cladding 3c (preferably a relative refractive index difference of 1 to 5% with respect to the refractive index of the lower cladding 3a and the upper cladding 3c), and can confine an optical signal. it can. The cross-sectional size of the core 3b is, for example, 35 to 100 μm square.

  In the embodiment of the present invention, only the core 3b is exposed and developed to produce a desired shape. However, the lower clad 3a and the upper clad 3c can be similarly shaped by exposure and development.

  On the back surface of the printed wiring board, as shown in FIG. 2C, a back surface insulating layer 10 and a back surface conductive layer 11 are formed. This is provided to prevent the substrate from warping when the optical waveguide 3 is formed, and it may be provided with a single layer as shown in the figure or a plurality of layers. Further, this layer may be used for surface protection of the back surface of the substrate instead of the solder resist layer. In that case, the portions that need to be exposed can be removed by exposure and development. Further, although not shown, a solder resist layer can be formed. In order to minimize the warpage of the substrate, it is ideal that the upper and lower layer structures are symmetrical, but from the viewpoint of productivity and cost, it is necessary to suppress warpage by making the upper and lower layer structures asymmetric. It is also possible to form a minimal layer.

  Through the above steps, an optoelectric wiring board can be manufactured.

  As shown in FIG. 1, when producing an optoelectric wiring board having the optical semiconductor element 5, the through conductor 4 is produced from the conductive layer 2a to the upper surface of the optical waveguide 3 as shown in FIG. It is preferable to further comprise a step of performing. The through conductor 4 is provided so as to penetrate the entire optical waveguide 3 or to penetrate only the lower clad 3a and the upper clad 3c. The number of layers penetrating is determined by the shape of the core 3b and the location where the through conductor 4 is formed. The through-conductor 4 and the electrode pad 6 can be obtained by drilling a desired position of the optical waveguide 3 with a laser or the like, then performing surface treatment and copper plating. Since the processing position by the laser or the pattern position of the electrode pad 6 can be formed while confirming the alignment marker of the conductive layer 2a through the transparent optical waveguide 3, highly accurate positioning is possible. The electrode pad 6 can be mounted with an optical element by performing Ni / Au plating or the like on the copper surface formed by plating.

  As shown in FIG. 1, in order to provide the optical semiconductor element 5 on the electrode pad 6, an electrical connection portion 7 is necessary. As the electrical connection portion 7, any conductive member suitable for high-speed signal transmission can be used. For example, a metal member such as gold, silver, or copper, and the form thereof is not limited to a ball, and may be a columnar shape or a bump shape.

  The solder resist layer 8 is formed on the upper portion of the optical waveguide 3 and has effects such as maintaining insulation between the electrode pads 6 and protecting the surface of the optical waveguide 3, the electrode pads 6, and the exposed portions of the optical waveguide 3. The portions other than those where the opening of the electrode pad 6 is necessary are covered with the solder resist 8.

  As shown in FIG. 1, when producing the optoelectric wiring board which has the optical path conversion part 9, it is preferable to further comprise the process of producing the optical path conversion part 9, as shown in FIG.3 (e).

  The optical path conversion unit 9 is preferably an inclined surface that is inclined with respect to the extending direction of the core 3b. The inclined surface converts the light traveling direction from the upper part in the substrate vertical direction into the light traveling direction in the core 3b, or converts the light traveling direction in the core 3b into the light traveling direction in the upper substrate vertical direction. To play a role. For example, the optical path direction of light is changed by 90 degrees by an inclined surface inclined at 45 degrees with respect to the optical axis direction.

  The optical path conversion unit 9 has a high reflectance with respect to light guided through the core 3b, such as gold (Au), silver (Ag), platinum (Pt), aluminum (Al), copper (Cu), and the like. It is preferable that the film is formed on the surface.

  In the production of the optical path conversion unit 9, first, a groove structure having an inclined surface and a vertical surface of the optical waveguide 3 is produced for the core 3b by embossing, etching, dicing, laser processing or the like. Then, a film having a high reflectance is formed on the inclined surface, and the groove structure is formed by filling a resin transparent to propagating light like the optical waveguide 3. Even if the groove structure has a spatial structure in which no resin is filled, light can be propagated using the optical path changing unit 9, but in that case, foreign matter or the like may enter the groove structure and increase the light propagation loss. In order to improve reliability, it is desirable to fill the resin, and it is most preferable to use a material having the same refractive index as that of the core 3b. However, a resin having a higher refractive index than the lower clad 3a or the upper clad 3c is filled. May be. Thus, the optical path changing unit 9 can be manufactured.

  The present invention is not limited to the above embodiment, and various modifications may be made without departing from the scope of the present invention.

1: Printed wiring board 1a: Base 1ba: Conductive layer 1bb in the buildup layer: Resin insulating layer 2a in the buildup layer: Conductive layer 2b: Resin insulating layer 3: Optical waveguide 3a: Lower cladding 3b: Core 3c: Upper Clad 4: Penetration conductor 5: Optical semiconductor element 6: Electrode pad 7: Electrical connection part 8: Solder resist 9: Optical path conversion part 10: Back surface insulating layer 11: Back surface conductive layer A: Distance between adjacent cores 3b

Claims (11)

An optical circuit board manufacturing method for producing an optical waveguide having a lower clad, a plurality of cores and an upper clad on a printed circuit board,
On the printed wiring board, a conductive layer that absorbs light of a specific wavelength and a resin insulating layer that absorbs light of the specific wavelength, the resin insulating layer is closer to the end of the printed wiring board than the conductive layer A step of making it to be located at
Producing the lower clad on the conductive layer and the resin insulating layer;
Laminating a photosensitive resin having photosensitivity to the light of the specific wavelength on the lower clad, irradiating the light of the specific wavelength and patterning the photosensitive resin to produce a plurality of cores; ,
Producing the upper cladding so as to cover the periphery of the plurality of cores together with the lower cladding;
The manufacturing method of the optoelectric wiring board which comprises this.   The method of manufacturing an optoelectric wiring board according to claim 1, further comprising the step of irradiating a laser on a position overlapping with the conductive layer to perforate the optical waveguide positioned at a position overlapping with the conductive layer.   3. The photoelectric wiring board according to claim 1, wherein the step of producing the conductive layer and the resin insulation layer and the step of producing the lower clad are performed using an epoxy resin as the resin insulation layer and the lower clad. Production method.   The photoelectric process according to any one of claims 1 to 3, wherein the step of producing the conductive layer and the resin insulating layer includes a step of aligning the upper surface of the resin insulating layer and the upper surface of the conductive layer so as to be flush with each other. A method for manufacturing a wiring board.   5. The method of manufacturing an optoelectronic wiring board according to claim 1, wherein the step of producing the conductive layer and the resin insulating layer includes a step of providing the resin insulating layer so as to surround the periphery of the conductive layer.   6. The method for manufacturing an optoelectric wiring board according to claim 1, wherein the conductive layer has an oxidized surface. Producing a through conductor that conducts from the conductive layer to the top surface of the optical waveguide;
7. The method according to claim 3, further comprising a step of providing an optical semiconductor element electrically connected to the through conductor and optically coupled to the plurality of cores on the through conductor. The manufacturing method of the optoelectric wiring board as described. A printed wiring board;
On the printed wiring board, a resin insulating layer provided at an end of the printed wiring board, a conductive layer provided on the inner side of the resin insulating layer, and the surface of which is blackened,
An optical waveguide provided on the conductive layer and the resin insulating layer up to an end of the printed wiring board, and comprising a lower clad, a plurality of cores, and an upper clad ;
The lower cladding is photoelectric circuit board that is disposed in contact with the conductive layer.
The optoelectric wiring board according to claim 8 , wherein an upper surface of the conductive layer and an upper surface of the resin insulating layer are flush with each other.
A printed wiring board;
On the printed wiring board, a resin insulating layer provided at an end of the printed wiring board, a conductive layer provided on the inner side of the resin insulating layer, and the surface of which is blackened,
An optical waveguide provided on the conductive layer and the resin insulating layer up to an end of the printed wiring board, and comprising a lower clad, a plurality of cores, and an upper clad ;
Photoelectric circuit board upper surface of the upper surface and the resin insulating layer of the conductive layer that has a same plane.
The optoelectric wiring board according to claim 10 , wherein the lower clad is disposed in contact with the conductive layer.