JP5160346B2 - Photoelectric composite flexible wiring board and manufacturing method thereof - Google Patents

Description

  The present invention relates to a photoelectric composite flexible wiring board that is thin and excellent in bending resistance and a method for manufacturing the same.

  Mobile electronic devices represented by mobile phones, digital cameras, notebook computers, and the like are particularly strongly required to be light and thin. For this reason, in order to make mobile electronic devices lighter, thinner, and easier to use, a foldable or slide type housing design is often employed.

  In order to realize such an excellent design, it is necessary to transmit an electrical signal through the inside of a composite operation type hinge that realizes a folding structure or a sliding structure. A flexible wiring board capable of transmitting a signal even in a dynamically bent state is used to transmit an electric signal inside the composite operation type hinge. The flexible wiring board used for the hinge portion has a level of 100,000 times. It is required to endure mechanically and electrically in repeated bending operations.

  While mobile electronic devices such as mobile phones and digital cameras are required to be lighter, thinner, and smaller, the data size that electronic devices must process increases rapidly, including high-quality still image / video data. There is also a need for faster information processing. Therefore, flexible wiring boards used in electronic devices are required to be capable of transmitting higher-speed signals in addition to making the substrates themselves lighter, thinner, and smaller.

  Conventionally, flexible wiring boards transmit electrical signals using copper wiring, but to meet current and future needs for large-capacity and high-speed signal processing, attempts have been made to simultaneously transmit optical signals on flexible wiring boards. In order to perform optical signal transmission with a flexible wiring board, a composite of an optical waveguide and a conductive wiring is required.

In summary, in the present and future, the flexible wiring board is required to satisfy the following three conditions.
(a) A composite of an optical waveguide for conducting optical transmission and a conductive wiring.
(b) The wiring board has mechanical, electrical and optical bending resistance.
(c) The wiring board itself can be made light, thin and small.

  However, the conventional structure of the flexible wiring board that combines the optical waveguide and the conductive wiring has a structure in which the flexible wiring board and the optical waveguide layer are separate layers, as seen in Patent Document 1, and therefore flexible wiring As the plate increases in thickness, it becomes difficult to bend.

In addition to being difficult to bend, the center of the bending stress generated when the entire substrate is bent is the center of the optical waveguide core material layer and the conductive metal layer due to the structure in which the optical waveguide core material layer and the conductive metal layer are separate layers. Therefore, the bending stress applied to each layer also becomes larger. Therefore, the bending life of the optical waveguide core material layer and the conductive metal layer is further shortened.
Patent No. 3193500

  The present invention has been made in view of the above-described points, and an object thereof is to provide a photoelectric composite flexible wiring board that is thin and excellent in bending resistance and that can mount a semiconductor including a photoelectric conversion element, and a method for manufacturing the same.

For the purposes achieved, in the present application, it provides the invention of manufacturing methods described invention, and claim 3 things according to claim 1.

That is, according to claim 1,
In the photoelectric composite flexible wiring board provided with the optical waveguide core material pattern and the conductive metal pattern on the surface of the clad material base film,
At least in the bending flexible part, the optical waveguide core material pattern and the conductive metal pattern are arranged on the same plane,
The optical waveguide core material pattern and the conductive metal pattern are covered with a clad material coverlay ,
The thickness of the optical waveguide core material pattern is thicker than the thickness of the conductive metal pattern, and the thickness of the clad material base film in contact with the optical waveguide core material pattern is smaller than the thickness of the portion in contact with the conductive metal pattern. the photoelectric composite flexible wiring board, characterized in that there,
And claim 3,
In the method of manufacturing a photoelectric composite flexible wiring board in which an optical waveguide core material pattern and a conductive metal pattern are provided on the surface of the cladding material base film,
(a) preparing a laminate having a metal layer on at least one surface of the clad material base film,
(b) forming a conductive metal pattern by removing unnecessary portions of the metal layer;
(c) Thinly processing a part of the surface of the cladding material base film exposed by removing the metal layer ,
(d) the core material layer is laminated on a surface of the conductive metal pattern,
(e) By removing unnecessary portions of the core material layer , an optical waveguide core material pattern is formed on the clad material base film that is thinly processed at least in the bending flexible portion ;
(f) A method for producing a photoelectric composite flexible wiring board, comprising: covering a clad material coverlay so as to cover the optical waveguide core material pattern;
It is.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  FIG. 1 is a plan view showing a photoelectric composite flexible wiring board module which is an application target example of the present invention. In FIG. 1, a cable portion in which the optical waveguide core material pattern 2 and the conductive metal pattern 3 are combined, a light receiving element, an amplifier IC, a signal conversion IC and a conductive metal pattern connector mounting portion arranged on the left side of the cable portion, A light emitting element, a driver IC, and a conductive metal pattern insertion connector portion arranged on the right side of the cable portion are provided.

  This photoelectric composite flexible wiring board module is formed by combining an electrical connector mounting portion formed of a conductive metal pattern 3, a mounted connector socket or a header component, etc. on the surface of a base material such as a clad base film. Yes.

The electrical signal transmitted from the insertion connector portion is converted into an optical signal by a light emitting element such as a VCSEL (surface emitting laser) mounted and propagates through the optical waveguide. The optical signal propagated through the optical waveguide is converted back to an electrical signal by a light receiving element such as a photodiode, which is also a mounted component, and further amplified by an amplifier IC or the like, and after necessary signal conversion processing is performed, it is converted into a conductive pattern. A signal is further propagated through the connected connector part mounting part.

First embodiment

  FIG. 2 shows a first embodiment with the most basic structure according to the invention. In the first embodiment, in the photoelectric composite flexible wiring board in which the optical waveguide core material pattern 2 and the conductive metal pattern 3 are provided on the surface of the optical waveguide cladding material base film 1, at least in the bending flexible portion, The optical waveguide core material pattern 2 and the conductive metal pattern 3 are disposed on the same plane, and have a clad material coverlay 4 that covers the optical waveguide core pattern 2 and the conductive wiring pattern 3. Here, examples of the material for the clad material and the core material include polyimide resins, epoxy resins, acrylic resins, and the like.

  As a method for forming the conductive metal pattern, a semi-additive method in which wiring is formed on the seed layer by plating, or a printing method such as screen printing or ink jet printing in which metal particles are dispersed in a resin binder may be used. A subtractive method of etching a metal foil is more desirable because of its high resistance to rust.

  In FIG. 3, an example of the manufacturing method of the photoelectric composite flexible wiring board by this invention is shown. The manufacturing method of the basic structure shown in FIG. 2 will be described with respect to the cutting plane AA in FIG. This manufacturing method includes the following steps (a) to (e).

Step (a): A laminate having a metal layer on at least one surface of the clad material base film is prepared. The surface state of the metal foil 3a is preferably as smooth as possible. When copper foil is used as the metal foil 3a, the unevenness on the surface of the copper foil is transferred to the clad material base film 1, and the core material pattern 2 formed on the surface of the clad material base film 1 and the surface of the clad material base film 1 This is because the surface of the film becomes uneven, and transmission loss as an optical waveguide increases.

  Step (b): An etching resist (not shown) is formed on the metal foil 3a by exposure / development of a dry film, and unnecessary portions of the metal foil 3a are removed by etching the metal foil 3a. A conductive wiring pattern 3 is formed.

  Step (c): The photosensitive core material 2a of the optical waveguide is formed so that the space between the conductive wiring patterns 3 formed in the step (b) is filled. As a method of forming the photosensitive core material 2a, a method of forming the film-formed photosensitive core material 2a and the substrate formed in the step (b) by a laminating press or a vacuum laminating press, or a varnish-like core material 2a, A method of forming by applying and drying by screen printing or spray printing is applicable.

  Step (d): The photosensitive core material 2a formed in the step (b) is exposed and developed to form the core material pattern 2 of the optical waveguide.

  Step (e): A clad material coverlay 4 is formed so as to cover the core material pattern 2 of the optical waveguide formed in the step (d), and an opening on the conductive pad necessary for component mounting is formed.

  Thereafter, the component mounting can also be performed by performing a surface treatment such as plating on the conductive pad.

  Due to these features, the present invention has the following effects.

  According to the present invention, a conductive metal pattern for an electrical signal and an optical waveguide pattern are formed in the same plane, and the cladding material of the optical waveguide is used as a base film and a coverlay of the flexible wiring board, thereby It is possible to reduce the total thickness.

  The fact that the total thickness of the photoelectric composite flexible wiring board can be reduced according to the present invention is advantageous for lightness and thinness required for electronic devices, and by being thinned, improvement in softness and improvement in flex resistance are realized as a substrate. .

Second embodiment

  In the optical waveguide, if the surface of the clad material base film and the surface of the core pattern formed on the clad material base film are rough, the transmission loss as the optical waveguide increases, which is disadvantageous. Therefore, in the structure and the manufacturing method shown in the first embodiment, the surface of the metal foil to be used needs to be as smooth as possible.

  On the other hand, since the physical anchor effect decreases as the surface of the metal foil becomes smoother, the adhesion between the metal foil and the laminated resin material decreases. In the second embodiment, a metal foil that has been subjected to a roughening treatment necessary for obtaining practically sufficient adhesion characteristics, secures transmission loss as an optical waveguide, and further improves bending characteristics, and The structure is shown.

  FIG. 4 shows the photoelectric composite flexible wiring board described with reference to FIG. 2, in which the thickness of the optical waveguide core pattern is larger than the thickness of the conductive metal pattern, and the thickness of the clad material base film in contact with the optical waveguide core material pattern is The structure is characterized by being thinner than the thickness of the portion in contact with the pattern.

  FIG. 5 is a cross-sectional process diagram illustrating a method of manufacturing the photoelectric composite flexible wiring board shown in FIG. 4 and includes the following steps (a) to (f).

  Step (a): A laminate having a metal layer 3a on at least one surface of the clad material base film 1 is prepared. The surface of the metal foil 3 a that is in close contact with the cladding material base film 1 is subjected to a roughening treatment in order to obtain a necessary and sufficient adhesion force with the cladding material base film 1.

  Step (b): An etching resist (not shown) is formed on the metal foil 3a by exposure / development of a dry film, and unnecessary portions of the metal foil 3a are removed by etching the metal foil 3a. A conductive metal pattern 3 is formed.

  Step (c): A part of the surface of the clad base material 1 exposed by removing the metal foil 3a is cut and thinned. As a thin processing method, digging with a dicer, ablation processing with a laser, plasma etching, reactive ion etching, chemical etching with a chemical solution, or the like can be applied.

Especially in machining dug by Dicer, can it to form a working unit 5 dug Ri Kezurito irregularities of the clad material 1 of the surface by the transfer of the back surface shape of the metal foil 3a mechanically simple method, thereby A smooth surface can be obtained.

Step (d): The photosensitive core material 2a of the optical waveguide is formed so as to fill between the conductive metal patterns 3 formed in the step (c). In the figure, the conductive metal pattern 3 and the digging portion 5 are formed not only to be buried but also to cover the upper portion.

  As a method for forming the photosensitive core material 2, a method of forming a filmed core material 2a and a substrate formed in the step (c) by a laminating press or a vacuum laminating press, or a varnish-like core material 2a by screen printing. Or a method of forming by applying and drying by spray printing or the like.

  Step (e): The photosensitive core material 2a formed in the step (d) is exposed and developed to form the core material pattern 2 of the optical waveguide.

  Step (f): A clad material coverlay 4 is formed so as to cover the core material pattern 2 of the optical waveguide formed in the step (e), and an opening on the conductive pad necessary for component mounting is formed.

  It is possible to use a metal foil that has been subjected to a roughening treatment for improving adhesion by the production method including the above steps (a) to (f), and formed by a roughening treatment of the metal surface transferred to the clad material. The transferred irregularities are removed, and a smooth surface of the clad material 1 is obtained. As a result, it is possible to form the core pattern 2 having a smooth surface thereon, so that an increase in optical transmission loss in the optical waveguide portion can be suppressed.

  Moreover, by digging the clad material 1, the bending center of the core material 2 can be aligned with the bending center of the entire substrate, and the bending stress applied to the core material 2 can be reduced. As a result, the bending life of the optical waveguide is extended. It is possible. Of course, since the total thickness of the clad material base film 1 and the clad material coverlay 4 is also reduced, it becomes softer and easier to bend.

Third embodiment

  FIG. 6 shows the structure of the third embodiment of the present invention. The difference from the second embodiment shown in FIG. 4 is that a thin intermediate layer 6 of several μm is inserted between the metal foil 3 and the clad material 1.

  FIG. 7 is a cross-sectional process diagram showing the manufacturing method of the third embodiment shown in FIG. 6 and includes the following processes (a) to (f).

Step (a): A laminate having the intermediate layer 6 and the metal layer 3a on at least one surface of the clad base material 1 is prepared. Examples of the material of the intermediate layer 6 include polyimide resins, epoxy resins, acrylic resins, and the like. The surface state of the metal foil 3 a is preferably as smooth as possible, but the surface of the metal foil 3 a that is in close contact with the clad material base film 1 is necessary to obtain a necessary and sufficient adhesion with the clad material base film 1. A roughened treatment may be used.

  Step (b): An etching resist (not shown) is formed on the metal foil 3a by exposure / development of a dry film, and unnecessary portions of the metal foil 3a are removed by etching the metal foil 3a. A conductive metal pattern 3 is formed.

Step (c): From the side of the intermediate layer 6 exposed by removing the metal foil 3a, the intermediate layer 6 and the clad material base film 1 are dug to form an engraved portion 7 and processed thinly. As a thin processing method, digging with a dicer, ablation processing with a laser, plasma etching, reactive ion etching, chemical etching with a chemical solution, or the like can be applied. In particular, in the digging process with a dicer, the unevenness on the surface of the clad material 1 due to the transfer of the back surface shape of the metal foil 3a can be scraped off by a mechanically simple technique, and a smooth surface can be obtained.

  Step (d): The photosensitive core material 2 of the optical waveguide is formed so as to fill between the conductive metal patterns 3 formed in the step (c). As a method for forming the photosensitive core material 3, a method of forming the filmed core material 3 a and the substrate formed in the step (c) by a laminating press or a vacuum laminating press, or a varnish-like core material 3 a by screen printing. Or a method of forming by applying and drying by spray printing or the like.

  Step (e): The photosensitive core material 3a formed in the above step is exposed and developed to form the optical waveguide core material pattern 3.

  Step (f): A clad material coverlay 4 is formed so as to cover the core material pattern 2 of the optical waveguide formed in the step (e), and an opening on the conductive pad necessary for component mounting is formed. Thereafter, the component mounting can also be performed by performing a surface treatment such as plating on the conductive pad.

  In the third embodiment, a thin intermediate layer 6 of several μm is inserted between the metal foil 3 a and the clad material 1. Due to the characteristics of the intermediate layer 6, a photoelectric composite flexible wiring board having further improved functions can be manufactured.

  For example, by using an adhesive having high adhesion between the metal foil 3a and the clad material 1 as the intermediate layer 6, even a very smooth surface metal foil without surface roughening treatment can be used with good adhesion.

  This makes it possible to form the conductive wiring pattern 3 having a smoother front / back surface and a straight pattern edge, thereby reducing transmission loss when transmitting a high-frequency electrical signal. Thus, transmission of electrical signals at higher frequencies is possible.

  By digging the clad material base film 1, the bending center of the core material 2a is aligned with the bending center of the entire substrate, and the bending stress applied to the core material 2a can be reduced, as in the second embodiment. it can. As a result, the bending life of the optical waveguide can be extended. Of course, since the total thickness of the clad material base film 1 and the clad material coverlay 4 is also reduced, it can be made softer and easier to bend.

The top view of the photoelectric composite module which concerns on this invention. 1 is a cross-sectional configuration diagram showing a structure of a first embodiment of the present invention. Process drawing which shows the manufacturing method of the 1st Embodiment of this invention. Sectional block diagram which shows the structure of the 2nd Embodiment of this invention. Process drawing which shows the manufacturing method of the 2nd Embodiment of this invention. Sectional block diagram which shows the structure of the 3rd Embodiment of this invention. Process drawing which shows the manufacturing method of the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cladding material base film 2a Core material 2 Core material pattern 3a Metal foil 3 Conductive metal pattern 4 Cladding material coverlay 5 Excavation processing part 6 Intermediate layer
7 Digging part

Claims (4)

In the photoelectric composite flexible wiring board provided with the optical waveguide core material pattern and the conductive metal pattern on the surface of the clad material base film,
At least in the bending flexible part, the optical waveguide core material pattern and the conductive metal pattern are arranged on the same plane,
The optical waveguide core material pattern and the conductive metal pattern are covered with a clad material coverlay ,
The thickness of the optical waveguide core material pattern is thicker than the thickness of the conductive metal pattern, and the thickness of the clad material base film in contact with the optical waveguide core material pattern is smaller than the thickness of the portion in contact with the conductive metal pattern. A photoelectric composite flexible wiring board, comprising: In the photoelectric composite flexible wiring board according to claim 1,
The photoelectric composite flexible wiring board, wherein an intermediate layer made of a resin is provided between the conductive metal pattern and the clad material base film. In the method of manufacturing a photoelectric composite flexible wiring board in which an optical waveguide core material pattern and a conductive metal pattern are provided on the surface of the cladding material base film,
(a) preparing a laminate having a metal layer on at least one surface of the clad material base film,
(b) forming a conductive metal pattern by removing unnecessary portions of the metal layer;
(c) Thinly processing a part of the surface of the cladding material base film exposed by removing the metal layer ,
(d) the core material layer is laminated on a surface of the conductive metal pattern,
(e) By removing unnecessary portions of the core material layer , an optical waveguide core material pattern is formed on the clad material base film that is thinly processed at least in the bending flexible portion ;
(f) A method for producing a photoelectric composite flexible wiring board, wherein a clad material coverlay is covered so as to cover the optical waveguide core material pattern. In the manufacturing method of the photoelectric composite flexible wiring board according to claim 3 ,
(a) A laminate having an intermediate layer made of a resin and a metal layer on at least one surface of the clad material base film is prepared,
(b) forming a conductive metal pattern by removing unnecessary portions of the metal layer;
(c) removing a portion of the exposed intermediate layer from which the metal layer has been removed, and processing the exposed cladding material base film thinly;
(d) laminating a core resin layer on the surface having the conductive metal pattern;
(e) By removing unnecessary portions of the core resin layer, an optical waveguide core material pattern is formed on the clad material base film that is thinly processed at least in the bending flexible portion;
(f) A method for producing a photoelectric composite flexible wiring board, wherein a clad material coverlay is covered so as to cover the optical waveguide core material pattern.

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