JP3287871B2 - Printed circuit board manufacturing method - Google Patents

Abstract

PURPOSE:To constitute the printed circuit board in such a manner that a part of its electric conductor circuit plays the role of a photoconductor path and to minimize the use of photoconductor path elements by forming a part of the electric conductor circuit as a light reflection surface of the photoconductor path. CONSTITUTION:Copper plating layers 3a, 3b constituting the electric conductor circuit and the photoconductor path 4 consisting of the photoconductor path element of a light transmissive member are integrally embedded in a substrate 2 consisting of an epoxy resin, etc. The photoconductor path element constituting the photoconductor path 4 is formed of a transparent resin material or transparent rubber material having good light transmittance. The light reflection surfaces 5a, 5b are formed in the corner parts which are a part of the copper plating layers 3a, 3b in such a manner that a light signal reflects and transmits the inside of such photoconductor path 4. Namely, the light signal entering from the end face of the photoconductor path 4a from the arrow (a) side is reflected perpendicularly an the light reflection surface 5a of the copper plating layer 3a, is introduced horizontally to the photoconductor path 4b, is reflected perpendicularly an the light reflection surface 5b of the copper plating layer 3b, is passed through the photoconductor path 4c and is emitted from the end face like an arrow (b).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is a printed circuit board and is embedded in the substrate by integrating the optical conductor with an electrical conductor circuit
The present invention relates to the manufacturing method .

[0002]

2. Description of the Related Art In recent years, in a device such as an acoustic product or a power supply, an electric conductor circuit for obtaining an electric signal and an optical waveguide element formed of a light transmitting member for obtaining an optical signal are formed on a single printed circuit board. The technology of burying and integrating into a building is increasing, and this trend is expected to increase further in the future.

[0003]

In the above-described printed circuit board configured as described above, an optical path is formed on the printed circuit board by using the optical path element, and the optical path element is formed on the printed circuit board. The technology has not yet been developed. Also, since the optical signal passing through the light guide path has linearity, it is impossible to pass the light signal when the light guide path element has an angle, so that a method of forming the light guide path element needs to be devised. . In addition, forming a light reflecting structure in the optical waveguide device requires a special technical device.

[0004] Further, since the optical waveguide element is generally expensive, there is a problem that the manufacturing cost of the printed circuit board is high, and therefore, it is necessary to minimize the use of the optical waveguide.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and provides a printed circuit board in which an optical conductor path is integrally buried together with an electric conductor circuit. It is an object to obtain a printed circuit board having:

[0006]

In order to achieve the above-mentioned object, a method of manufacturing a printed circuit board according to the present invention is characterized in that an electric conductor circuit and a light guide path made of a light transmitting member are integrated with the substrate. In a method of manufacturing a printed circuit board embedded therein, a step of forming a photoresist layer on a substrate and forming a plurality of openings by photolithography,
After cutting the corners of the photoresist layer left between the openings to form an inclined surface and forming a conductor layer in the openings, the photoresist layer is removed to form an electric conductor circuit having a light reflecting surface. removing the step, a step of forming a light guide path is filled with a transparent material between the electric conductor circuit, an integrated solidified substrate to form a resin layer on the entire surface including the electrical conductor circuits and optical interconnects for And a transfer step.

[0007]

Printed circuit board manufacturing method of the present invention [act was above mentioned, the
The light reflecting surface of the light guide path can be manufactured simultaneously with the electric conductor circuit.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of a printed circuit board according to the present embodiment, and FIG. 2 is a sectional view taken along line AA of FIG.

In FIGS. 1 and 2, a printed circuit board generally designated by a reference numeral 1 is composed of a board 2 made of epoxy epoxy or the like, copper plating layers 3a and 3b serving as electric conductor circuits, and an optical conductor of a light transmitting member. Optical waveguide 4 composed of optical path elements is on the same plane
And are buried adjacently and integrally.

More specifically, the copper plating layers 3a and 3b are
Are embedded in a meandering manner at predetermined intervals, and are embedded in a meandering manner such that the optical waveguide 4 is sandwiched between the copper plating layers 3a and 3b. The light guide path element constituting the light guide path 4 is made of a transparent resin material or a transparent rubber material having good light transmittance.

The transparent resin material is, for example, an optical material such as an acrylic resin, a polycarbonate resin or an epoxy resin, and the transparent rubber material is a two-component curing type silicon for optical applications used for optical fibers and the like. Rubber is preferred. Silicon rubber is chemically stable and heat-resistant, and a two-component curing type is particularly transparent and easy to handle.

As described above, the optical waveguide 4 buried in a meandering shape is a part of the copper plating layers 3a and 3b in order to reflect an optical signal in the optical waveguide 4 and transmit the light. Light reflecting surfaces 5a and 5b are formed at certain corners. That is, an optical signal incident from the end of the light guide path 4a from the arrow a side is reflected at right angles to the light reflecting surface 5a of the copper plating layer 3a and is guided horizontally to the light guide path 4b, from which the copper plating layer 3
b, the light is reflected at right angles to the light reflecting surface 5b, passes through the light guide path 4c, and exits the light guide path 4 from the end face of the light guide path 4c.

Here, the light reflecting surfaces 5a and 5b will be described. The copper plating layer 3 forming the light reflecting surfaces 5a and 5b
Since a and 3b are made of copper, if the light reflectance on the light reflecting surfaces 5a and 5b is insufficient, a metal having a high reflectance at a wavelength to be used, for example, tin, nickel, or the like is used.
The problem can be solved by plating silver, gold or an alloy thereof, and mirror-finish the plating. Alternatively, aluminum or the like may be vapor-deposited or sputtered on the light reflecting surfaces 5a and 5b, and a method of pressing a metal having good spreadability such as gold, or a method of heating and applying a low melting point alloy such as solder For example, a method such as attaching

FIG. 3 shows an embodiment of the entrance and exit of the optical signal to the light guide path 4 of the printed circuit board 1. Also in this case, as in FIG. 1, the reflection of the optical signal is enabled by using a part of the copper plating layer. That is, the optical signal emitted perpendicularly to the surface of the printed circuit board 1 from the photodiode 6 mounted on the printed circuit board 1 is perpendicular to the light reflecting surface 5c formed on the copper plating layer 3c embedded in the printed circuit board 1. The photosensor is mounted on the printed circuit board 1 by being reflected and guided to the light guide path 4 and reflecting the optical signal upward at right angles to the reflecting surface 5d of another copper plating layer 3d embedded in the printed circuit board 1. 7 can be detected. Of course, if the light reflecting surfaces 5c and 5d also have insufficient light reflectance, the same metal having the high reflectance at the wavelength to be used may be used.

Next, a manufacturing process of a printed circuit board in which a part of an electric conductor circuit can be used as a reflection surface of a light guide path will be described with reference to FIGS. 4 and 5 by taking the embodiment of FIG. 3 as an example.

First, as shown in FIG. 4A, a thin-film copper 9 is bonded to the surface of a conductor plate 8 such as stainless steel having a predetermined thickness.

Next, as shown in FIG. 4B, a photoresist layer 10 having a thickness of about 30 to 40 μm is formed on the thin-film copper 9, and the photoresist layer 10 is exposed and developed to form a photoresist layer 10. The two openings 10a and 10a of the copper plating layer which becomes the electric conductor circuit from which the above-mentioned is removed are formed.

Next, as shown in FIG. 4C, the openings 10a,
The corners of the photoresist layer 10 left between 10a are precisely cut at an angle of 45 °, for example, mechanically or by a laser to form inclined surfaces 10b, 10b.

Next, as shown in FIG. 4D, copper plating is performed using the thin film copper 9 exposed through the openings 10a, 10a of the photoresist layer 10 as an electrode, and copper plating is performed in the openings 10a, 10a of the photoresist layer 10. The layers 3c and 3d are formed. At this time, the inclined surface 1 of the photoresist layer 10
The reflecting surfaces 5c and 5d of the optical waveguide are formed on the copper plating layers 3c and 3d by the layers 0b and 10b.

Next, as shown in FIG. 5A, the photoresist layer 10 is removed with a predetermined solution, and the copper plating layers 3c and 3d are left on the thin-film copper 9.

Next, as shown in FIG. 5B, the space 11 between the copper plating layers 5c and 5d formed in FIG. 5A is filled with a transparent resin or a transparent rubber, and the transparent resin or the transparent rubber is solidified. Thus, the light guide path 4 is formed.

Next, as shown in FIG. 5C, the prepreg epoxy resin and hot press (1
(80 ° C., 75 minutes), the copper plating layer 3
A resin layer 12 serving as a material of a printed circuit board is formed and coated on the entire surface including the light guide path 4c, 3d, and the light guide path 4;
2 is solidified and integrated with the copper plating layers 3 c and 3 d and the optical waveguide 4.

Finally, as shown in FIG. 5D, the resin layer 12
After the conductor plate 8 is peeled off from the resin layer 12, the thin film copper 9 is removed by etching, so that the copper plating layers 3c and 3d
When the resin layer 12 is solidified by a heat treatment, the printed circuit board is completed. Thereafter, by mounting the photodiode 6 and the photosensor 7 on the printed board 1, the printed board 1 shown in FIG. 3 can be manufactured.

In the manufacture of the printed circuit board described above, the reflecting surfaces 5c and 5d for reflecting the light from the upper surface of the printed circuit board 1 in the right angle direction cannot be formed by ordinary pattern mask exposure. Leave the photoresist layer on the reflective surface unexposed and partially expose it at an angle with ultraviolet laser irradiation, etc., or mechanically cut or polish the photoresist after development to create a reflective surface, The surface may be plated with copper. Alternatively, it may be chemically removed using an excimer laser so as not to affect the copper plating of the base.

In the case of the reflection surfaces 5a and 5b of the printed circuit board 1 shown in FIG. 1, forming the angle in the photoresist layer when the printed circuit board is viewed from above is a matter of CA in wiring design.
This is possible at the D stage. However, it should be noted that it is necessary to select a material that causes less shrinkage of the photoresist layer 10 formed on the thin-film copper 9. This is the photoresist layer 10
Even if an appropriate angle is formed, unevenness is generated due to shrinkage of the photoresist, and light reflection becomes insufficient. In this case, after the photoresist is plated with copper to remove the photoresist, the copper surface is partially polished or modified with a spreadable metal such as gold or a low-melting alloy such as solder. You may.

In the manufacture of the printed circuit board described above, a transparent resin or a transparent rubber constituting the light guide path 4 is used.
Thermal contact with the resin layer 12 constituting the substrate must be avoided as much as possible. For example, a Teflon-based material has little effect as a substrate material, but a typical epoxy resin contains an amine component as a cross-linking agent, and may cause a transparent resin or a transparent rubber to become clouded by hot contact. Therefore, it is desirable to form a film acting as a barrier on the surface of the transparent resin or the transparent rubber. As the coating material, a coating or coating material of a fluororesin such as Teflon or vinylidene fluoride, or protection with an inorganic substance is preferable.

In the printed circuit board according to the present invention configured as described above, a part of the copper plating layer integrally embedded in the board is made to be the light reflecting surface of the light guide path. It can play the role of a conductor path, which enables expensive light guide elements to be used with a minimum of use, as well as the surface mounting and height of optical devices, which have hitherto been technically difficult. Density mounting can be easily performed.

Further, since the light reflecting surface of the light guide path is a part of the copper plating layer, the light guide path can be formed more easily and the precision of the light reflecting surface can be improved as compared with the case where the light guide element is difficult to fix. Adhesive fixing is unnecessary.

Further, since the light reflecting surface of the optical waveguide can be manufactured simultaneously with the copper plating layer, problems such as adhesiveness and displacement which are likely to occur when the optical waveguide element is fixed can be solved.

The present invention is not limited to the embodiment described above and shown in the drawings, and various modifications can be made without departing from the scope of the invention. For example, the copper plating layer does not necessarily have to function as an electric circuit, and may be patterned at the same time as patterning the copper plating layer in the manufacturing process.

[0031]

According to the printed board manufacturing method of the present invention described above, according to the present invention, it is possible to manufacture a light guide path having a light reflective structure with minimum use of high cost optical conductor element. As a result, it is possible to prevent a rise in the manufacturing cost of the printed circuit board, and it is possible to mount optical devices on the surface and at a high density, which have been technically difficult in the past.

Also, a method of manufacturing a printed circuit board according to the present invention
According to the method, the light reflecting surface of the light guide path is part of the electrical conductor circuit.
Therefore, it is easier to manufacture compared to the difficult way of fixing the optical waveguide element, and the precision of the light reflecting surface is good and the fixing by bonding is not necessary, and the light reflecting surface of the optical waveguide is manufactured at the same time as the electric conductor circuit. By doing so, it is possible to solve problems such as adhesiveness and displacement that are likely to occur when the optical waveguide element is fixed.

The fields of application of the printed circuit board according to the present invention include, for example, televisions, audio equipment,
The present invention can be widely applied to photocouplers such as household electric appliances and power supply devices, and optical communication and information processing fields such as optical controllers, optical repeaters, optical computers, and optical IC cards.

[Brief description of the drawings]

FIG. 1 is a plan view of a printed circuit board according to the present embodiment.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view of a printed circuit board according to another example of the present embodiment.

FIG. 4 is a diagram (part 1) illustrating a process of manufacturing a printed circuit board in the embodiment of FIG. 3;

FIG. 5 is a diagram (part 2) illustrating a process of manufacturing the printed circuit board in the embodiment of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printed board 2 Substrate 3a-3d Copper plating layer 4, 4a-4c Light guide path 5a-5d Light reflection surface 6 Photodiode 7 Photosensor 8 Conductor plate 9 Thin film copper 10 Photoresist layer 10a Opening 12 Resin layer

Claims (1)

(57) [Claims] 1. A method of manufacturing a printed circuit board in which an electric conductor circuit and an optical waveguide made of a light-transmitting member are integrated into a substrate and embedded in the substrate, wherein a photoresist layer is formed on the substrate. Forming a plurality of openings by photolithography, cutting the corners of the photoresist layer left between the openings to form an inclined surface, forming a conductive layer in the openings, Forming an electric conductor circuit having a light reflecting surface by removing the resist layer; filling a transparent material between the electric conductor circuits to form an optical conductor path; It solidified integrally forming a resin layer on the whole surface including the conductive path, the method of manufacturing a printed circuit board, characterized by comprising a transfer step of removing the substrate.