JP2011029385A - Flexible multilayered substrate and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible multilayered substrate obtaining desirable bendability. <P>SOLUTION: The flexible multilayered substrate includes a flexible core material 10 and a plurality of layers α, β having a wiring pattern 20 formed on the core material 10. The plurality of layers α, β are laminated and integrated with each other to constitute a laminate. When viewed from a laminated direction of the plurality of layers α, β, a first region A which is relatively liable to bend and a second region B which is relatively hard to bend are formed. In the wiring pattern 20, a part (a wiring pattern 21) disposed at least on the first region A is made of a conductive resin with conductive powder adhered thereto with a resin. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a flexible multilayer substrate formed by laminating a plurality of layers each including a flexible core material and a wiring pattern formed on the core material, and a method for manufacturing the same.

  Japanese Patent Laid-Open No. 8-330683 (Patent Document 1) discloses a printed wiring board in which one insulating layer of a multilayer printed board is made of a material that bends flexibly and only the layer is formed. .

  In JP 2008-235594 A (Patent Document 2), an electrode formed on a rigid printed board and an electrode formed on a wiring board assembly are electrically connected via a conductive adhesive. It is shown.

JP-A-8-330683 JP 2008-235594 A

  In the substrate described in Patent Document 1, the flexibility of the copper foil formed on the insulating layer is not always sufficient, so that the desired flexibility may not be obtained.

  Further, the wiring board assembly described in Patent Document 2 is completely different from the present invention in its premise and configuration.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a flexible multilayer substrate capable of obtaining desired flexibility.

  The flexible multilayer substrate according to the present invention includes a plurality of layers including a flexible core material and a wiring pattern formed on the core material, and is laminated by laminating and integrating the plurality of layers. And a first region that is relatively easy to bend and a second region that is relatively difficult to bend when viewed from the stacking direction of the plurality of layers, and at least the first region of the wiring pattern is formed. The upper portion is made of a conductive resin in which conductive powder is fixed with resin.

  According to the above configuration, the wiring pattern formed in the first region, which is relatively easy to bend, is configured with the conductive resin in which the conductive powder is fixed with the resin, so that the wiring pattern of the part is configured with the metal thin film. Compared with the case where it does, the flexibility of a flexible multilayer substrate can be improved.

  In one embodiment, in the flexible multilayer substrate, the conductive powder contained in the conductive resin is at least one conductive powder selected from the group consisting of copper, gold, silver, nickel, and tin.

  In one embodiment, in the flexible multilayer substrate, the average particle size of the conductive powder is 0.5 μm or more and 20 μm or less.

In the present specification, “average particle size” means the D ₅₀ average particle size measured by the method shown in JIS R1629.

  In one embodiment, in the flexible multilayer substrate, the resin contained in the conductive resin is a thermoplastic resin.

  In one embodiment, in the flexible multilayer substrate, the glass transition point of the thermoplastic resin is 20 ° C. or less.

  In one embodiment, in the flexible multilayer substrate, the core material is constituted by a thermoplastic resin sheet.

  In one embodiment, in the flexible multilayer substrate, the plurality of layers include a first layer having a wiring pattern made of a conductive resin formed on a surface thereof, and a metal harder than the wiring pattern made of a conductive resin. And a second layer having a wiring pattern made of a thin film formed on the surface thereof.

  The method for producing a flexible multilayer substrate according to the present invention includes a step of forming a plurality of layers including a flexible core material and a wiring pattern formed on the core material, and laminating the plurality of layers. Forming a laminate by integrating, and forming a first region that is relatively easy to bend and a second region that is relatively difficult to bend when viewed from the stacking direction of the plurality of layers. In the wiring pattern, at least a portion located on the first region is made of a conductive resin in which conductive powder is fixed with a resin.

  According to the above method, the wiring pattern formed in the first region that is relatively easily bent is formed of the conductive resin in which the conductive powder is fixed with the resin, so that the wiring pattern of the portion is formed of the metal thin film. Compared with the case where it does, the flexibility of a flexible multilayer substrate can be improved.

  According to the present invention, the wiring pattern formed in the first region, which is relatively easy to bend, is composed of the conductive resin in which the conductive powder is fixed with the resin, so that the flexibility of the first region in the flexible multilayer substrate is achieved. Can be improved.

It is sectional drawing which shows the flexible multilayer substrate which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the flexible multilayer substrate which concerns on Embodiment 2 of this invention. It is a figure which shows the 1st process in the manufacturing process of the flexible multilayer substrate which concerns on Embodiment 1,2. It is a figure which shows the 2nd process in the manufacturing process of the flexible multilayer substrate which concerns on Embodiment 1,2. It is a figure which shows the 3rd process in the manufacturing process of the flexible multilayer substrate which concerns on Embodiment 1,2. It is a figure which shows the 4th process in the manufacturing process of the flexible multilayer substrate which concerns on Embodiment 1,2. It is a figure which shows the 5th process in the manufacturing process of the flexible multilayer substrate which concerns on Embodiment 1,2. It is a figure which shows the 6th process in the manufacturing process of the flexible multilayer substrate which concerns on Embodiment 1,2. It is a figure which shows the state which looked at the flexible multilayer substrate shown in FIG. 1 from the lamination direction of the 1st layer and the 2nd layer.

  Embodiments of the present invention will be described below. Note that the same or corresponding portions are denoted by the same reference numerals, and the description thereof may not be repeated.

  Note that in the embodiments described below, when referring to the number, amount, and the like, the scope of the present invention is not necessarily limited to the number, amount, and the like unless otherwise specified. In the following embodiments, each component is not necessarily essential for the present invention unless otherwise specified.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing a flexible multilayer substrate according to the first embodiment. Referring to FIG. 1, the flexible multilayer substrate according to the present embodiment includes a core material 10, a wiring pattern 20, and a via conductor 30.

  The core material 10 is made of a flexible material. The core material 10 is an insulating layer made of, for example, a liquid crystal polymer (hereinafter referred to as “LCP”), polyethylene terephthalate (hereinafter referred to as “PET”), polyimide, and the like. . The core material 10 is typically composed of a thermoplastic resin sheet such as LCP.

  When the core material 10 is made of LCP, it is possible to obtain a flexible multilayer substrate having excellent dimensional stability, high frequency characteristics, and the like. The reason why the high frequency characteristics are improved when the core material 10 is made of LCP is that LCP has low water absorption, and deterioration of the high frequency characteristics due to the dielectric constant of the moisture absorbed by the core material is suppressed.

  The core material 10 is classified into one included in the first layer α that is a bent layer (first core material) and one included in the second layer β that is a non-bent layer (second core material).

  The wiring pattern 20 includes a first wiring pattern 21 included in the first layer α and a second wiring pattern 22 included in the second layer β.

  The first wiring pattern 21 and the second wiring pattern 22 are made of different materials. More specifically, the second wiring pattern 22 is formed of a metal thin film, whereas the first wiring pattern 21 is formed of a conductive resin in which conductive powder is fixed with a resin. This conductive resin film is more flexible than a metal thin film such as a copper foil. Therefore, the first wiring pattern 21 is more flexible than the second wiring pattern 22. In this specification, the core material 10 having the first wiring pattern 21 formed on the surface thereof is referred to as a “bending layer” (first layer α), and the core material having the second wiring pattern 22 formed on the surface thereof. 10 is referred to as a “non-bent layer” (second layer β).

As said electroconductive powder, copper, gold | metal | money, silver, nickel, tin, and those mixtures are used for the electroconductive powder contained in electroconductive resin, for example. Preferably, the average particle diameter (D ₅₀ ) of the conductive powder is about 0.5 μm or more and 20 μm or less.

If the diameter of the conductive powder is too large, there is a concern about the reproducibility of the wiring shape and the deterioration of the fine wiring property. On the other hand, if the diameter of the conductive powder is too small, there is a concern that the reliability of the conductivity of the first wiring pattern 21 is lowered. Such a concern is wiped out by setting the average particle diameter (D ₅₀ ) of the conductive powder to about 0.5 μm or more and 20 μm or less. In addition, it is preferable that the ratio of the electroconductive powder in an electroconductive resin film shall be about 30-80 vol% considering the balance of conduction | electrical_connection reliability and flexibility.

  As the resin contained in the conductive resin, for example, a thermoplastic resin is used. Preferably, the glass transition point of this thermoplastic resin is about 20 ° C. or less. That is, when the glass transition point is 20 ° C. or lower, the conductive resin film is plastically deformed at approximately room temperature, and once it is deformed, its shape is easily maintained.

  If the glass transition point of the thermoplastic resin is too high, the flexibility tends to decrease at room temperature. By setting the glass transition point of the thermoplastic resin to about 20 ° C. or less, a flexible multilayer substrate having excellent flexibility can be obtained.

  The via conductor 30 is embedded in a via hole formed in the core material 10. The via conductors 30 electrically connect the wiring patterns 20 located on both surfaces of the core material 10. A predetermined wiring pattern 20 is formed on the core material 10, and the wiring elements 20 are electrically connected by the via conductors 30, thereby forming an electric element that realizes a desired function. As described above, when an LCP material is used as the core material 10, a flexible multilayer substrate suitable for a high-frequency element that transmits a high-frequency signal can be obtained. The high-frequency element is used for various applications such as a mobile phone, a digital camera, a game machine, and a high-speed transmission cable.

  In the flexible multilayer substrate according to the present embodiment, the first wiring pattern 21 and the second wiring pattern when viewed from the stacking direction of the first layer α and the second layer β (that is, the vertical direction in FIG. 1). 22, a first region (bent portion) A in which only the first wiring pattern 21 is formed, and a second region (non-bent portion) B in which both the first wiring pattern 21 and the second wiring pattern 22 are formed. And are formed.

  As described above, only the first wiring pattern 21 made of the conductive resin film is formed in the first region A serving as the bent portion (flexible area). Therefore, the flexibility of the first region A is improved as compared with the case where the second wiring pattern 22 is provided in the first region A instead of the first wiring pattern 21. That is, a flexible multilayer substrate having high flexibility can be obtained.

  On the other hand, in addition to the first wiring pattern 21, a second wiring pattern 22 made of a metal film is formed in the second region B serving as a non-bent portion (rigid area). Therefore, the second region B has higher shape retention than the first region A. Therefore, the second region B can be easily used as a connection portion when the flexible multilayer substrate is mounted on the base substrate.

  The first region A, which is relatively easy to bend, and the second region B, which is relatively difficult to bend, can be distinguished, for example, in the following manner. As an example, in the second region B which is a non-bent portion, the via conductor 30 for electrically connecting the wiring patterns 20 of each layer is formed in the core material 10, whereas the first portion which is a bent portion. In the region A, the via conductor 30 is not formed. In addition, in the second region B which is a connection portion with the base substrate, the wiring pattern 20 (second wiring pattern 22) is formed on the outermost surface of the stacked body, whereas it becomes a bent portion. In the first region A that does not become a connection portion, the wiring pattern 20 is not formed on the outermost surface of the stacked body.

  As described above, according to the flexible multilayer substrate according to the present embodiment, the first wiring pattern 21 formed in the first region A, which is relatively easily bent, is made of conductive resin in which conductive powder is fixed with resin. By comprising, the flexibility of a flexible multilayer substrate can be improved compared with the case where the wiring pattern of the said part is comprised with a metal thin film.

  The inventor of the present application conducted an experiment for evaluating the flexibility of several combinations of the core material 10 and the first wiring pattern 21 in order to confirm the above-described effects. The results are shown in Table 1.

  In the experiment whose results are shown in Table 1, the flexible multilayer substrate shown in FIG. 1 was used, and a flexible film having a thickness of 25 μm was used as the core material 10 (specifically, polyimide, PET, LCP as shown in Table 1). Etc.) are used. As the first wiring pattern 21, a conductor layer having a thickness of 18 μm shown in Table 1 is used. In addition, the average particle diameter of copper powder is 3.0 micrometers. As the second wiring pattern 22, a copper foil having a thickness of 18 μm is used. The via conductor 30 is formed by filling a via hole by screen printing with silver (Ag) particles dispersed in a printing resin solution.

  In Table 1, the flexibility was evaluated by a folding resistance test defined in JIS C6471. Specifically, the folding resistance test was performed at room temperature (25 ° C.), and those that showed folding resistance of 500 times or more were evaluated as good (◯), and those that were less than 500 were rated as poor (×). .

  As shown in Table 1, it was confirmed that in Examples 1 to 3 in which a conductive resin film was applied to the wiring pattern 21, it was possible to achieve better flexibility than the comparative example in which the wiring pattern was formed of copper foil.

  As another example, the inventor of the present application also bent an example in which the wiring pattern 21 was formed of a conductive resin in which copper powder as a conductive material was fixed with a resin such as PMMA (Polymethylmethacrylate) or PMMA copolymer. An experiment to confirm the sex was conducted. In this example, since the glass transition point of the resin is about 45 ° C. to 100 ° C. and the glass transition point is higher than that of Examples 1 to 3, the improvement in flexibility at room temperature is shown in Examples 1 to 3. It was a thing of the grade which did not reach. In other words, it was confirmed that the flexibility at room temperature is remarkably improved by setting the glass transition point of the resin of the resin to which the conductive powder is fixed to 20 ° C. or less.

(Formation 2)
FIG. 2 is a sectional view showing a flexible multilayer substrate according to the second embodiment. As shown in FIG. 2, the flexible multilayer substrate according to the present embodiment is a modification of the flexible multilayer substrate according to Embodiment 1, and is a first layer α that is a bent portion in a first layer α that is a bent layer. In the region A, the wiring pattern 20 is constituted by a wiring pattern 21 made of a conductive resin, and in the second region B which is a non-bent portion, the wiring pattern 20 is constituted by a wiring pattern 22 made of a metal thin film. Also in the present embodiment, the flexibility of the first region A can be improved as in the first embodiment.

  Since matters other than those described above are the same as in the first embodiment, detailed description will not be repeated.

(Further variations)
In the above-described embodiment, the material constituting the conductive powder contained in the conductive resin and the average particle diameter thereof are exemplified. However, the conductive powder is not limited to the above-described material, and the conductive powder The average particle size is not limited to the above range.

  In the above-described embodiment, the range of the glass transition point of the thermoplastic resin included in the conductive resin is exemplified, but the range of the glass transition point of the thermoplastic resin is not limited to the above.

  In the embodiment described above, the first layer α in which the wiring pattern 21 made of a conductive resin is formed on the surface and the wiring pattern 22 made of a metal thin film harder than the wiring pattern 21 is formed on the surface. Although an example in which a laminated structure is formed with the layer β has been shown, the scope of the present invention is not limited to this, and all the wiring patterns 20 may be constituted by the wiring patterns 21 made of a conductive resin.

  In the embodiment described above, a plurality (two layers) of the first layers α are stacked. However, the scope of the present invention is not limited to this, and the first layer α may be only one layer.

(Production method)
Below, the manufacturing method of the flexible multilayer substrate which concerns on Embodiment 1, 2 mentioned above is demonstrated, referring FIGS. Here, the example which comprised the core material 10 with LCP resin is demonstrated as an example.

  As shown in FIG. 3, for the core material 10 having the wiring pattern 20 disposed on one surface, a via conductor extending in the thickness direction is installed so as to be electrically connected to the wiring pattern 20. A process of drilling is performed. This drilling can be performed, for example, by irradiation with laser light 40 as shown in FIG.

  As a result of the drilling process, as shown in FIG. 4, a part of the core material 10 is removed to obtain the hole 10A. The hole 10A is depicted as a straight vertical hole in the figure, but may actually be a tapered hole. FIG. 4 shows a state immediately after the irradiation with the laser beam 40. The LCP resin originally present in the hole 10A is removed by laser irradiation, and there is a region where the LCP resin is melted in the vicinity of the inner wall of the hole 10A. Thereafter, as the temperature slowly decreases, as shown in FIG. 5, the LCP resin melted in the vicinity of the inner wall of the hole 10A is re-solidified.

  As shown in FIG. 6, the via conductor 30 is disposed in the hole 10A. This can be performed by forming a film with a metal that will be the material of the via conductor 30 on the upper surface of the core material 10 and then removing the excess metal film. The via conductor 30 can be formed of Cu, for example.

  As shown in FIG. 7, a plurality of layers including the core material 10 on which the via conductors 30 are formed are laminated. In addition to stacking, as shown in FIG. 8, all the core members 10 included in the laminate are integrated. This step can be performed by heating and pressurizing (high pressure vacuum press).

(State seen from the stacking direction of the first layer and the second layer)
The flexible multilayer substrate according to the first and second embodiments described above includes a laminated body formed by laminating and integrating the first layer α and the second layer β, and this laminated body is the first layer. FIG. 9 shows a state viewed from the stacking direction of α and the second layer β. In FIG. 9, the pattern 21 </ b> A of the first wiring pattern 21 is indicated by a broken line in the drawing, and the pattern 22 </ b> B of the second wiring pattern 22 is indicated by an alternate long and short dash line in the drawing. 9 corresponds to the cross-sectional view of FIG.

  As shown in FIG. 9, only the first wiring pattern 21A is formed in the first region A, and both the first wiring pattern 21A and the second wiring pattern 22B are formed in the second region B.

  Although the embodiments of the present invention have been described above, the embodiments disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  10 core material, 10A hole, 20 wiring pattern, 21 first wiring pattern, 22 second wiring pattern, 30 via conductor, 40 laser light, A first region (bent portion), B second region (non-bent portion), α first layer (bending layer), β second layer (non-bending layer).

Claims (8)

A plurality of layers including a flexible core material and a wiring pattern formed on the core material;
A laminate is configured by laminating and integrating the plurality of layers,
When viewed from the stacking direction of the plurality of layers, a first region that is relatively easy to bend and a second region that is relatively difficult to bend are formed,
Of the wiring pattern, at least a portion located on the first region is a flexible multilayer substrate made of a conductive resin in which conductive powder is fixed with a resin.   The flexible multilayer substrate according to claim 1, wherein the conductive powder contained in the conductive resin is at least one conductive powder selected from the group consisting of copper, gold, silver, nickel, and tin.   The flexible multilayer substrate according to claim 2, wherein the conductive powder has an average particle size of 0.5 μm or more and 20 μm or less.   The flexible multilayer substrate according to any one of claims 1 to 3, wherein the resin contained in the conductive resin is a thermoplastic resin.   The flexible multilayer substrate according to claim 4, wherein a glass transition point of the thermoplastic resin is 20 ° C. or less.   The flexible multilayer substrate according to any one of claims 1 to 5, wherein the core material is constituted by a thermoplastic resin sheet.   The plurality of layers include a first layer having a wiring pattern made of the conductive resin formed on the surface and a wiring pattern made of a metal thin film harder than the wiring pattern made of the conductive resin on the surface. The flexible multilayer substrate according to any one of claims 1 to 6, comprising a second layer formed. Forming a plurality of layers including a flexible core material and a wiring pattern formed on the core material;
And laminating and integrating the plurality of layers to form a laminate,
Forming a first region that is relatively easy to bend and a second region that is relatively difficult to bend when viewed from the stacking direction of the plurality of layers;
A method for manufacturing a flexible multilayer substrate, wherein at least a portion of the wiring pattern located on the first region is formed of a conductive resin in which conductive powder is fixed with a resin.

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