JP2001007461A - Optical / electrical wiring board and mounting board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a wiring board on which an optical part can be mounted similarly to an electric part with high mounting density while reducing the size by providing an optical board, embedded with an optical waveguide for passing an optical signal, with a plurality of posts projecting from the surface thereof. SOLUTION: The optical/electrical wiring board has a structure where an optical board 9 is stacked over a board 8 provided with electric wiring 10, 11, 12, 13. The optical board 9 has a core pattern 2, i.e., optical wiring for passing an optical signal, embedded in a clad layer 1 having refractive index lower than that of the core material. A mirror 3 for reflecting an optical signal, i.e., laser light, and deflecting the laser light by 90 deg. is formed on the optical board 9. Posts 4, 5, 6, 7 for making electrical connection of a laser element or a photodetector are provided on the periphery of the mirror 3 while penetrating the optical board 9 or projecting to a constant height from the surface thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical / electrical wiring board in which optical wiring and electric wiring are mixed, and a mounting board for mounting an optical component and an electric component on the substrate.

[0002]

2. Description of the Related Art In order to produce a computer capable of performing arithmetic processing faster, the clock frequency of a CPU tends to increase more and more, and a clock frequency of about 1 GHz has recently appeared. As a result, there is a portion where high-frequency signals flow in the electric wiring made of copper on the printed circuit board in the computer, so that malfunctions occur due to generation of noise, and electromagnetic waves are generated and surrounding electronic devices are generated. Will also be affected.

In order to solve such a problem, a part of copper electric wiring on a printed circuit board is replaced by an optical fiber or an optical waveguide, and an optical signal is used instead of an electric signal. ing. This is because in the case of an optical signal, generation of noise and electromagnetic waves can be suppressed.

From the viewpoint of high-density mounting or miniaturization, it is desirable to manufacture an optical / electrical wiring board in which electric wiring and optical wiring are laminated on the same substrate. Is difficult to optically align the optical axis of the optical component with the optical axis of the optical wiring member when mounting optical components such as laser light emitting elements and light receiving elements. I wasn't allowed to. Therefore, there is a disadvantage that mounting an optical component on an optical / electrical wiring board is extremely expensive compared to an electrical component that can be automatically soldered in a reflow furnace or the like.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks of the related art, and enables high-density mounting or miniaturization, and furthermore, mounting of optical components in the same manner as mounting of electrical components. An object of the present invention is to provide a structure of an optical / electrical wiring board which can be performed.

[0006]

In order to attain the above object, the present invention is directed to an optical wiring board having an electric wiring embedded therein, wherein an optical waveguide for transmitting an optical signal is embedded in the electric wiring board. An optical / electrical wiring board for laminating formed optical substrates, wherein the optical substrate has a plurality of columns protruding from the surface of the optical substrate.

According to a second aspect of the present invention, in the optical / electrical wiring board according to the first aspect, the support is made of a conductive metal, and is electrically connected to the electric wiring board.

According to a third aspect of the present invention, in the optical / electrical wiring board according to the first or second aspect, the diameter of the column is 50 to 500 microns and the height from the substrate surface is 20 to 500 microns.
It is characterized by being 200 microns.

According to a fourth aspect of the present invention, a support formed on the optical / electrical wiring board of the optical / electrical wiring board according to any one of the first to third aspects comprises an optical component and / or an electric component. An optical component and / or an electrical component is inserted into a concave portion provided on the component side to mount the component.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. 1. Optical / Electrical Wiring Board In the optical / electrical wiring board of the present invention, FIG. 1A is a plan view of a portion where an optical component is mounted, and FIG. 1A is a sectional view taken along a core pattern 2 which is an optical wiring. Shown in b).

The optical / electrical wiring board according to the present invention comprises an electric wiring 10,
A structure in which an optical substrate 9 is laminated on a substrate 8 provided with 11, 12, and 13 is adopted. The substrate 8 may be a single-layer insulating substrate or a multilayer wiring substrate in which electric wiring and insulating layers are alternately laminated. As a constituent material, an insulating substrate in which a glass cloth is impregnated with a resin, a polyimide film, or a ceramic substrate may be used.

In an optical substrate 9, a core pattern 2 is embedded in a cladding layer 1 having a lower refractive index than the core material as an optical wiring for transmitting an optical signal. Since this core pattern is formed by a photolithography technique, its position can be determined by an alignment mark (not shown) formed on the supporting substrate.

On the optical substrate 9, there is formed a mirror 3 which reflects laser light as an optical signal and changes the propagation direction to 90 °.
This mirror inserts an optical signal emitted vertically from the laser light emitting element mounted on the optical / electrical wiring board of the present invention toward the substrate, into an optical wiring arranged parallel to the substrate surface, or conversely, The optical signal that has propagated through the optical wiring is directed toward the light receiving element installed on the optical / electrical wiring board of the present invention, and plays a role of vertically changing the propagation direction of the optical signal.
A surface forming 45 ° with respect to the substrate is formed. This mirror is processed by drilling using an etching method based on a metal mask formed on the optical substrate by photolithography technology,
Alternatively, the position can be determined by an alignment mark (not shown) formed on the substrate 8 because it can be formed by processing by laser drilling.

On the periphery of the mirror 3, there are columns 4 for making electrical connection with optical components such as a laser light emitting element and a light receiving element.
5, 6, and 7 penetrate the optical substrate or are formed on the optical substrate to protrude to a certain height when viewed from the optical substrate surface. These pillars are preferably made of a metal such as copper, and in this case, electric wirings 10, 11, 12,
13, but does not necessarily have to be conductive. It may be just a support.

The columns 4, 5, 6,
7 is comfortably accommodated in a concave portion provided on the optical component side,
The top of the support and the periphery of the optical component recess are soldered. If the shape of the concave part of the optical component and the shape of the support column are made similar to each other so as to be engaged, the movable range of the optical component is limited. Therefore, the optical axis of the light emitting laser and the optical axis of the mirror (optical waveguide) 3 having a width of several microns can be accurately matched and firmly fixed, and if necessary, can be electrically connected to the electric wiring. It is. Further, the optical component concave portion can be formed with high precision by plating by a constant method such as bump formation.

It is desirable that the columnar top be subjected to a surface treatment such as Ni / Au plating. On the other hand, electric components such as ICs are similarly electrically connected to electric wiring on the substrate 8 via conductive metal columns. Since the columns are formed by photolithography and plating, their positions can be determined by alignment marks (not shown) formed on the substrate 8.

2. Manufacturing Method of Optical / Electrical Wiring Board The configuration of the optical / electrical wiring board according to the present invention will be described in detail with reference to the drawings. (1) Manufacturing method of optical substrate A film-shaped optical substrate was formed by the following procedure (see FIG. 2). Resin 31 (which serves as a cladding layer as a supporting medium for an optical substrate that guides light) and is made of fluorinated polyamic acid or fluorinated epoxy resin which is a precursor of fluorinated polyimide resin (Selection) is applied to a thickness of about 20 to 100 microns (step (a)). In the case of a polyamic acid solution, it is baked at 350 degrees for 1 to 2 hours to imidize. If it is an epoxy resin, it is cured by UV or polymerized at 100 to 200 degrees.

Next, a resin having a refractive index suitable for the wavelength to be guided, such as a resin 32 serving as an optical waveguide, for example, a fluorine-based polyamic acid solution or a polymethyl methacrylate resin solution, is selected, and is uniformly 8 μm in an appropriate method. Apply (step (b)). If there is photosensitivity, patterning is performed by a standard photolithography method to form an optical waveguide 33, and then a curing reaction according to the material is performed. If there is no photosensitivity, after curing, a metal mask of a predetermined pattern is formed, and a waveguide pattern is formed by RIE dry etching (step (c)).
Further, the same material as that of the previously formed clad layer is similarly applied to a thickness of about 20 to 100 microns.

Next, a through hole 34 is formed at a desired position on the optical substrate.
Was formed (step (d)). Excimer laser is irradiated through a mask having a predetermined pattern to form holes. Next, when the film is peeled off from the silicon wafer, a film-shaped optical substrate 35 including a through hole can be formed.
(e)). In this method, a complete through-hole was formed, and no residue was left.

(2) Manufacturing Method of Electric Wiring Board Next, a manufacturing method of the electric wiring board will be described (FIG. 3).
reference). On a suitable insulating substrate 40 such as a glass epoxy substrate, a plating method, a sputtering method, a vapor deposition method, etc.
A copper thin film of about a micron is formed. A desired metal wiring 41 is formed by a conventional photolithography method. In order to form a plurality of columns, a metal thin film 42 is formed by sputtering (step
(f)), a dry film resist 43 is adhered thereon, and exposure and development are performed by a standard method to form an opening 44 (step (g)). Next, copper plating is performed using the metal thin film 42 as a cathode, and the inside of the opening is buried with copper as much as possible (step (h)).
). When the resist is stripped (step (i)) and the metal thin film is removed by etching, copper pillars 45 can be formed on the metal wiring (step (j)). The shape of the column is a circular column type, a square column type, or a mask having a shape corresponding to the terminal opening of the optical component. The height is controlled by the thickness of the resist or the time taken for plating. Approximately 30-200 microns in diameter and 100-high
About 200 microns is desirable.

(3) Method of Manufacturing Optical / Electrical Wiring Board A plurality of columns 45 on the electrical board are
0 is used as a guide for alignment and stacking (see FIG. 4). That is, the through holes formed in the optical substrate film are laminated so that the pillar made of a conductive metal or the like penetrates and protrudes (step (k)). It is desirable that the adhesive 14 is applied to the side of the optical substrate that comes into contact with the electric substrate, so that the optical substrate and the electric substrate are completely bonded and fixed.

Further, a metal thin film 4 is formed on the surface of the laminated substrate.
6 is formed by sputtering (step (l)), and a photoresist 47 is applied. Exposure and development are performed to form a photoresist opening 48 for mirror formation (step (m))
).

The opening 4 is formed in the metal thin film 46 by etching.
9 is formed, and a metal mask for mirror formation is formed. Further, the substrate is inclined at 45 °, a mirror 50 is formed by RIE dry etching (step (n)), and the metal mask is dissolved and removed to complete the optical / electrical wiring substrate of the present invention (step (o)). )).

As another manufacturing method of the optical / electrical wiring board, there is a build-up method. In this method, the optical substrate and the electric substrate are not separately manufactured and then laminated, but the optical substrate material is laminated while being directly patterned on the electric substrate. The columns may be formed on the electric substrate before the optical substrate is built up, or may be formed by laminating the optical substrates and then forming via holes and embedding plating.

3. FIG. 5 shows a conductive terminal side recess 24 of an optical component (laser, photodiode) 22 containing a light emitting laser as an example.
2 schematically shows a state in which a metal column protruding from above the optical substrate is accommodated and soldered. After thinly soldering the recess 24, the metal posts 5, 7 were lightly inserted into the terminal recess of the optical component. The shape of the concave portion was a circle with a radius of 80 microns and the depth was 50 microns. The number of metal pillars was four and the shape was a circle with a radius of 75 microns. Terminals for electrical components (CPU, memory) were placed on thin soldered metal pads.

After cooling in a reflow oven at a temperature of 250 ° C. for 10 seconds, the terminal of the optical component is fixed at an equilibrium position determined by the shape of the concave portion and the surface tension of the molten solder, and the optical axis of the laser is positioned at the center of the mirror. It was confirmed that it was within ± 3 microns. In the case where the flat metal terminal having no concave portion and the supporting column are bonded via solder as in the case of the electric component, the fixing position of the optical component is not stabilized, and an error of about ± 50 μm occurs. The recess not only ensures electrical continuity and high-precision alignment with the mirror for optical wiring, but also improves the reliability of connection because the top of the support is directly connected to the metal terminal on the optical component side by solder as a pad. did.

[0027]

The present invention has the following effects. First, since an optical wiring layer is provided on a substrate having electric wiring, high-density mounting or miniaturization is possible.

Second, the mutual positional relationship between the core pattern including the mirror of the optical substrate and the support for mounting the optical component coincides with the intended one with extremely high accuracy.

Third, since the terminals of the optical component are accurately accommodated in the recesses on the optical substrate, it is easy to optically match the optical axis of the optical component with the optical axis of the optical wiring. Therefore, the optical component and the electrical component can be automatically mounted at the same time.

Fourth, when soldering an optical component or an electrical component, if it is directly connected to a conductive support formed by plating, it is not affected by the heat of solder melting and the reliability of the connection is improved. I do. At the same time, the reliability of connection with the electric wiring on the substrate is improved.

[Brief description of the drawings]

FIG. 1A is a plan view of a portion on which an optical component is mounted on an optical / electrical wiring board according to the present invention. (B) A cross-sectional view of a portion of the optical / electrical wiring board according to the present invention, in which an optical component is mounted, cut parallel to the optical waveguide.

FIG. 2 is an explanatory view showing one example of a manufacturing process of the optical substrate according to the present invention.

FIG. 3 is an explanatory view showing one example of a manufacturing process of the electric wiring board according to the present invention.

FIG. 4 is an explanatory view showing an example in which an optical board and an electric wiring board according to the present invention are stacked using columns.

FIG. 5 is an explanatory diagram illustrating propagation of laser light when a laser light emitting element is mounted as an example on the optical / electrical wiring board according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 clad layer 2 optical waveguide (core layer) 3 mirror 4 support 4 a pad 5 support 5 a pad 6 support 6 a pad 7 support 7 a pad 8 substrate 9 optical substrate 10 electrical wiring 11 electrical wiring 12 electrical wiring 13 electrical wiring 14 adhesive 21 laser Light 22 Laser light emitting element 23 Laser light emitting surface 24 Conducting terminal recess 25 Solder 30 Silicon substrate 31 Cladding layer 32 Core layer 33 Waveguide 34 Through hole 35 Optical substrate 40 Insulating substrate 41 Electrical wiring 42 Metal thin film 43 Photoresist opening Photoresist opening Part 45 support 46 metal thin film 47 photoresist 48 photoresist opening 49 metal thin film opening 50 mirror

Continuing from the front page (72) Inventor Daisuke Inokuchi 1-5-1, Taito, Taito-ku, Tokyo Letterpress Printing Co., Ltd. (72) Inventor Kenta Yotsui 5-1-1 Taito, Taito-ku, Tokyo Letterpress printing In-house F-term (reference) 2H047 KA04 KB09 MA07 PA02 PA03 PA04 PA24 PA28 QA05 TA05 TA44 TA47 5E317 AA04 AA24 BB03 BB04 BB12 BB13 BB15 CC31 CC33 CC44 CC52 CD15 CD32 CD34 GG14 GG16 5E319 AA03 AB05 AC16 GG01 AC18 AA09 BB03 BB16 BC25 BC28 BC34 BC40 CC32 CC36 CC43 CC57 EE01 GG09 5E338 AA00 BB61 BB75 CC01 CC10 CD01 CD32 EE22

Claims (4)

[Claims] 1. An optical / electrical wiring board in which an optical board in which an optical waveguide for optical signal propagation is embedded is laminated on an electrical wiring board in which electric wiring is embedded, wherein the optical board protrudes from the surface of the optical board. An optical / electrical wiring board having a plurality of columns. 2. The optical / electrical wiring board according to claim 1, wherein said support pillar is made of a conductive metal and is electrically connected to said electric wiring board. 3. The method according to claim 1, wherein the diameter of the column is 50 to 500 microns.
3. The optical / electrical wiring board according to claim 1, wherein the height from the substrate surface is 20 to 200 microns. 4. The optical / electrical wiring board according to claim 1, wherein the support is inserted into a concave portion provided on an optical component and / or an electric component side to insert the support into the optical component or / and the optical component. And a mounting board on which electric components are mounted.