TWI909954B - Manufacturing methods of conductor substrates, wiring substrates, expandable elements, and wiring substrates - Google Patents

Abstract

A conductor substrate has a stretchable resin layer and a conductor foil disposed on the stretchable resin layer. The stretchable resin layer comprises a cured resin composition containing (A) a rubber component, (B) a crosslinking component having epoxy groups, and (C) an ester-based curing agent.

Description

Manufacturing methods of conductor substrates, wiring substrates, expandable elements, and wiring substrates

One aspect of the invention relates to a wiring substrate with high scalability and a method for manufacturing the same. Another aspect of the invention relates to a conductor substrate that can be used to form the wiring substrate. Yet another aspect of the invention relates to a stretchable element using the wiring substrate.

In recent years, in fields such as wearable devices and healthcare-related devices, there is a need for devices that can be used along the curves of the body or joints, and that are flexible and elastic enough to prevent poor connections even when put on and taken off. To construct such devices, wiring boards or substrates with high elasticity are required.

Patent 1 describes a method for sealing semiconductor devices such as memory chips using a stretchable resin composition. Patent 1 primarily studies the application of stretchable resin compositions in sealing applications. [Prior Art Documents] [Patent Documents]

[Patent Document 1] International Publication No. 2016/080346

[Problem to be Solved by the Invention] As described in Patent 1, by making the sealing material elastic, it is possible to realize elastic components that are difficult to achieve in conventional sealing materials. On the other hand, the substrate material does not have elasticity, and therefore it is difficult to achieve higher elasticity. Therefore, there is a need for a wiring board with higher elasticity.

Furthermore, from the perspective of improving heat resistance, crosslinking components with reactive functional groups were investigated as materials for substrates used in the fabrication of wiring boards. However, if crosslinking components with reactive functional groups are used, the following problems arise: the dielectric loss tangent of the resulting substrate tends to increase, and the transmission loss of the wiring disposed on the substrate tends to increase.

In this context, one objective of the present invention is to provide a conductor substrate with high scalability and low dielectric loss tangent, a wiring substrate using the conductor substrate, a scalable element, and a method for manufacturing the wiring substrate. [Means for Solving the Problem]

To achieve the aforementioned objective, one aspect of the present invention provides a conductor substrate having: a stretchable resin layer; and a conductor foil disposed on the stretchable resin layer, the stretchable resin layer comprising a cured resin composition containing (A) a rubber component, (B) a crosslinking component having epoxy groups and (C) an ester-based curing agent.

Another aspect of the present invention provides a conductor substrate having: a stretchable resin layer; and a conductor coating disposed on the stretchable resin layer. The stretchable resin layer comprises a cured resin composition containing (A) a rubber component, (B) a crosslinking component having epoxy groups, and (C) an ester-based curing agent.

According to the aforementioned conductor substrate, high elongation can be obtained by using a stretchable resin layer containing (A) a rubber component as its base material. Furthermore, it is believed that the increase in dielectric loss tangent when using a crosslinking component with reactive functional groups as the material for fabricating the stretchable resin layer is due to the formation of hydroxyl groups during the curing reaction. Hydroxyl groups are small, highly polarizable functional groups; therefore, materials containing hydroxyl groups generally increase the dielectric loss tangent. On the other hand, the inventors have found that by combining (B) an epoxy-containing crosslinking component as a crosslinking component with (C) an ester-based curing agent as a curing agent, the formation of hydroxyl groups during the curing reaction of the crosslinking component can be significantly suppressed. The reason is that the curing reaction between the epoxy groups of the crosslinking component and the ester-based curing agent does not involve the formation of hydroxyl groups, and it is difficult to form hydroxyl groups after curing. Furthermore, these cured products do not adversely affect the extensibility. Therefore, according to the conductor substrate having the above-described structure, a low dielectric loss tangent can be achieved by using crosslinking components that can maintain high extensibility and improve heat resistance.

Another aspect of the present invention provides a wiring substrate comprising the conductor substrate of the present invention, wherein the conductor foil or conductor plating forms a wiring pattern. The wiring substrate is a substrate in which the conductor foil or conductor plating forms the wiring pattern within the conductor substrate of the present invention, and the wiring substrate includes a stretchable resin layer having the specific configuration, thus exhibiting high stretchability. Furthermore, by using crosslinking components, it exhibits high heat resistance and can have a low dielectric loss tangent, thereby significantly reducing the transmission loss of the wiring pattern.

Another aspect of the present invention provides a stretchable element comprising: the wiring substrate of the present invention; and an electronic device mounted on the wiring substrate. The stretchable element includes the wiring substrate of the present invention, comprising a stretchable resin layer having the specific configuration described above, thus exhibiting high stretchability, and possessing high heat resistance and low dielectric loss tangent through the use of crosslinking components, thereby significantly reducing transmission losses in the wiring pattern.

Another aspect of the present invention provides a conductor substrate for forming a wiring substrate. The wiring substrate includes a conductor substrate having a stretchable resin layer and a conductor foil or conductor film disposed on the stretchable resin layer, the conductor foil or conductor film forming a wiring pattern.

Another aspect of the present invention provides a method for manufacturing the wiring substrate of the present invention, comprising: a step of preparing a multilayer having a stretchable resin layer and a conductor foil deposited on the stretchable resin layer; a step of forming an etching resist on the conductor foil; a step of exposing the etching resist and developing the exposed etching resist to form an etching resist pattern covering a portion of the conductor foil; a step of removing the portion of the conductor foil not covered by the etching resist pattern; and a step of removing the etching resist pattern.

Another aspect of the present invention provides a method for manufacturing the wiring substrate of the present invention, comprising: a step of forming a coating resist on a stretchable resin layer; a step of exposing the coating resist and developing the exposed coating resist to form a resist pattern covering a portion of the stretchable resin layer; a step of forming a conductor film on the surface of the portion of the stretchable resin layer not covered by the resist pattern by electroless plating; and a step of removing the resist pattern.

Another aspect of the present invention provides a method for manufacturing the wiring substrate of the present invention, comprising: a step of forming a conductor film on a stretchable resin layer by electroless plating; a step of forming a coating resist on the conductor film; exposing the coating resist and developing the exposed coating resist to form a coating covering the stretchable resin layer. The steps include: a step of forming a partial resist pattern; a step of further forming a conductor film by electroplating on the portion of the conductor film not covered by the resist pattern; a step of removing the resist pattern; and a step of removing the portion of the conductor film formed by electroless plating that was not covered by the conductor film formed by electroplating.

Another aspect of the present invention provides a method for manufacturing the wiring substrate of the present invention, comprising: a step of forming an etching resist on a conductor film formed on a stretchable resin layer; a step of exposing the etching resist and developing the exposed etching resist to form an etching resist pattern covering a portion of the stretchable resin layer; a step of removing the portion of the conductor film not covered by the etching resist pattern; and a step of removing the etching resist pattern.

The aforementioned manufacturing method allows for the efficient fabrication of the wiring substrate of this invention, which uses conductor foil or conductor plating to form wiring patterns. [Effects of the Invention]

According to one aspect of the present invention, a conductor substrate with high scalability and low dielectric loss tangent, a wiring substrate using the conductor substrate, a scalable element, and a method for manufacturing the wiring substrate can be provided.

The following describes several embodiments of the present invention in detail. However, the present invention is not limited to the following embodiments.

According to one embodiment of a conductor substrate, it has a stretchable resin layer and a conductor layer disposed on one or both sides of the stretchable resin layer. The stretchable resin layer includes a cured resin composition containing (A) a rubber component, (B) a crosslinking component having epoxy groups, and (C) an ester-based curing agent. Another embodiment of a wiring substrate has a stretchable resin layer containing the cured resin composition and a conductor layer disposed on one or both sides of the stretchable resin layer and forming a wiring pattern. The conductor layer may be a conductor foil or a conductor coating.

<Conductor Substrate> [Conductor Foil] The elastic coefficient of the conductor foil can be 40 GPa to 300 GPa. With an elastic coefficient of 40 GPa to 300 GPa, breakage of the conductor foil due to elongation of the wiring substrate is less likely to occur. From the same perspective, the elastic coefficient of the conductor foil can be 50 GPa or higher, or 60 GPa or higher, or 280 GPa or lower, or 250 GPa or lower. The elastic coefficient of the conductor foil here can be a value measured using the resonance method.

Conductor foil can be metal foil. Examples of metal foils include: copper foil, titanium foil, stainless steel foil, nickel foil, permalloy foil, 42 alloy foil, Kovar foil, nickel-chromium foil, beryllium copper foil, phosphor bronze foil, brass foil, zinc white copper foil, aluminum foil, tin foil, lead foil, zinc foil, solder foil, iron foil, tantalum foil, niobium foil, molybdenum foil, zirconium foil, gold foil, silver foil, palladium foil, Monel foil, Inconel foil, and Hastelloy foil, among others. From the perspective of appropriate elasticity, the conductor foil can be selected from copper foil, gold foil, nickel foil, and iron foil. From the perspective of wiring formation, the conductor foil can be copper foil. Copper foil can be easily formed into wiring patterns by photolithography without damaging the properties of the stretchable resin layer.

There are no particular restrictions on the copper foil used; for example, electrolytic copper foil and roll-rolled copper foil used in copper-clad laminates and flexible wiring boards can be used. Commercially available electrolytic copper foils include, for example: F0-WS-18 (manufactured by Furukawa Electric Industries, Ltd., trade name), NC-WS-20 (manufactured by Furukawa Electric Industries, Ltd., trade name), YGP-12 (manufactured by Nippon Electrolytic Co., Ltd., trade name), GTS-18 (manufactured by Furukawa Electric Industries, Ltd., trade name), and F2-WS-12 (manufactured by Furukawa Electric Industries, Ltd., trade name). Examples of rolled copper foils include: TPC foil (manufactured by JX Metals Co., Ltd., trade name), HA foil (manufactured by JX Metals Co., Ltd., trade name), HA-V2 foil (manufactured by JX Metals Co., Ltd., trade name), and C1100R (manufactured by Sumitomo Mitsui Metal Mining Shinco Co., Ltd., trade name). From the viewpoint of adhesion to the stretchable resin layer, copper foil with a roughening treatment can be used. From the viewpoint of folding endurance, roll-rolled copper foil can be used.

The metal foil may have a roughened surface formed by a roughening treatment. In this case, the metal foil is typically disposed on the stretchable resin layer with the roughened surface in contact with the stretchable resin layer. From the viewpoint of the adhesion between the stretchable resin layer and the metal foil, the surface roughness Ra of the roughened surface can be 0.1 μm to 3 μm, or 0.2 μm to 2.0 μm. To facilitate the formation of fine wiring, the surface roughness Ra of the roughened surface can be 0.3 μm to 1.5 μm.

Surface roughness Ra can be measured, for example, using the Wyko NT9100 surface shape measuring device (manufactured by Veeco) under the following conditions: Measurement Conditions Inner lens: 1x Outer lens: 50x Measurement range: 0.120 × 0.095 mm Measurement depth: 10 μm Measurement method: Vertical scanning interferometry (VSI)

There is no particular limitation on the thickness of the conductor foil, which can range from 1 μm to 50 μm. If the thickness of the conductor foil is greater than 1 μm, it is easier to form wiring patterns. If the thickness of the conductor foil is less than 50 μm, it is particularly easy to etch and process.

Conductor foils are disposed on one or both sides of the stretchable resin layer. By disposing conductor foils on both sides of the stretchable resin layer, warping caused by heating for hardening, etc., can be suppressed.

There are no particular limitations on the method of setting the conductor foil. For example, there are methods such as: directly coating a resin composition for forming a scalable resin layer onto a metal foil; and coating a resin composition for forming a scalable resin layer onto a carrier film to form a resin layer (scalable resin layer before curing), and depositing the formed resin layer onto the conductor foil.

[Conductor Coating] Conductor coatings can be formed using conventional coating methods employed in addition or semi-additive methods. For example, after treatment with a palladium-adhesive coating catalyst, a stretchable resin layer is immersed in an electroless plating solution to deposit an electroless plating layer (conductor layer) with a thickness of 0.3 μm to 1.5 μm on the entire surface of the primer. Further electroplating (electrodecoration) can be performed as needed to adjust the thickness to the desired level. Any electroless plating solution can be used without particular limitation. Conventional methods can also be employed for electroplating without particular limitation. From the perspectives of cost and resistance, conductor coatings (electrode-coating and electroplating) can be copper-plated films.

Furthermore, unwanted portions can be etched away to form the circuit layer. The etching solution used in the etching process can be appropriately selected depending on the type of plating layer. For example, in the case of copper plating, the etching solution used in the etching process can be a mixture of concentrated sulfuric acid or hydrogen peroxide water, or a ferric chloride solution, etc.

To improve adhesion to the conductor coating, unevenness can be pre-formed on the stretchable resin layer. One method for forming unevenness is, for example, transferring the roughened surface of the copper foil. For the copper foil, examples include YGP-12 (manufactured by Nippon Electrolytic Co., Ltd., trade name), GTS-18 (manufactured by Furukawa Electric Industries, Ltd., trade name), or F2-WS-12 (manufactured by Furukawa Electric Industries, Ltd., trade name).

Methods for transferring the roughened surface of copper foil include: directly applying a resin composition used to form a stretchable resin layer to the roughened surface of the copper foil; and a method of coating a resin composition used to form a stretchable resin layer onto a carrier film and then forming a resin layer (the stretchable resin layer before curing) on the copper foil. By forming a conductor coating on both sides of the stretchable resin layer, warping caused by heating for curing, etc., can be suppressed.

Surface treatments can be applied to stretchable resin layers for the purpose of achieving high adhesion of conductor coatings. Examples of surface treatments include roughening treatments (de-smearing), ultraviolet (UV) treatment, and plasma treatment used in the general wiring board manufacturing process.

As a process for removing adhesive residue, methods used in the general wiring board manufacturing process can be employed, such as using an aqueous solution of sodium permanganate.

[Expandable Resin Layer] Expandable resin layers can have, for example, a recovery rate of 80% or more after tensile deformation to a strain of 20%. This recovery rate is determined in a tensile test of a test sample using an expandable resin layer. Let X be the strain (displacement) applied in the first tensile test, then let Y be the difference between X and the position at which the load is first applied when the sample returns to its initial position and is subjected to tensile testing again. R is calculated using the formula: R (%) = (Y/X) × 100%, and this R is defined as the recovery rate. The recovery rate can be measured by setting X to 20%. Figure 1 shows the stress-strain curve for a measurement example of the recovery rate. In terms of tolerance to repeated use, the recovery rate can be above 80%, 85%, or 90%. The upper limit of the recovery rate by definition is 100%.

The elastic modulus (tensile elastic modulus) of the stretchable resin layer can be 0.1 MPa or higher and 1000 MPa or lower. If the elastic modulus is 0.1 MPa or higher and 1000 MPa or lower, it tends to have particularly excellent workability and flexibility as a substrate. From this point of view, the elastic modulus can be 0.3 MPa or higher and 100 MPa or lower, or 0.5 MPa or higher and 50 MPa or lower.

The elongation at break of the extensible resin layer can be 100% or higher. If the elongation at break is 100% or higher, there is a tendency to easily obtain sufficient extensibility. From this perspective, the elongation at break can be 150% or higher, 200% or higher, 300% or higher, or 500% or higher. There is no particular upper limit to the elongation at break, and it is usually around 1000% or lower.

The dielectric loss tangent (Df) of the stretchable resin layer can be 0.004 or less. If the dielectric loss tangent is 0.004 or less, there is a tendency to sufficiently reduce the transmission loss of wiring patterns disposed on the stretchable resin layer. From this perspective, the dielectric loss tangent can be 0.0035 or less, 0.003 or less, or 0.0025 or less. There is no particular limitation on the lower limit of the dielectric loss tangent, which is usually around 0.0005 or more.

The dielectric constant (Dk) of the stretchable resin layer can be 4.0 or less. If the dielectric constant is 4.0 or less, there is a tendency to sufficiently reduce the transmission loss of the wiring pattern disposed on the stretchable resin layer. From this point of view, the dielectric constant can be 3.5 or less, 3.0 or less, or 2.5 or less.

The stretchable resin layer can be a layer in which there are no absorption peaks attributable to the stretching vibrations of hydroxyl groups in its infrared absorption spectrum. This sufficiently reduces the dielectric loss tangent of the stretchable resin layer, and there is a tendency to sufficiently reduce the transmission loss of wiring patterns disposed on the stretchable resin layer.

The stretchable resin layer comprises a cured resin composition (curing resin composition) containing (A) a rubber component, (B) an epoxy-containing crosslinking component, and (C) an ester-based curing agent. That is, the stretchable resin layer contains a crosslinked polymer of (B) the epoxy-containing crosslinking component. Stretchability is readily imparted to the stretchable resin layer primarily by means of the rubber component (A).

(A) The rubber component may include, for example, at least one rubber selected from the group consisting of acrylic rubber, isoprene rubber, butyl rubber, styrene-butadiene rubber, butadiene rubber, acrylonitrile-butadiene rubber, silicone rubber, urethane rubber, chloroprene rubber, ethylene propylene rubber, fluororubber, vulcanized rubber, epichlorohydrin rubber, and chlorinated butyl rubber. From the viewpoint of protecting the wiring from damage caused by moisture absorption, a rubber component with low air permeability may be used. Therefore, (A) the rubber component may include at least one selected from styrene-butadiene rubber, butadiene rubber, and butyl rubber. By using styrene-butadiene rubber, the tolerance of the stretchable resin layer to various chemicals used in the coating process can be improved, and wiring boards can be manufactured with high yield.

Commercially available acrylic rubber products include, for example, the "Nipol AR series" from ZEON Corporation of Japan and the "KURARITY series" from Kuraray Corporation.

Commercially available isoprene rubber products include, for example, the "Nipol IR series" from ZEON Corporation of Japan.

Commercially available butyl rubber products include, for example, JSR Corporation's "BUTYL" series.

Commercially available styrene-butadiene rubber products include, for example, JSR Corporation's "Dynaron SEBS series" and "Dynaron HSBR series", Kraton Polymers Japan Co., Ltd.'s "Kraton D Polymer series", and Aronkasei Co., Ltd.'s "AR series".

Commercially available butadiene rubber products include, for example, the "Nipol BR series" from ZEON Corporation of Japan.

Commercially available acrylonitrile butadiene rubber products include, for example, JSR Corporation's "JSR NBR series".

Commercially available silicone rubber products include, for example, Shin-Etsu Silicone Co., Ltd.'s "KMP series".

Commercially available products made of ethylene propylene rubber include, for example, JSR Corporation's "JSR EP series".

Commercially available fluororubber products include, for example, Daikin Corporation's "DAIEL series".

Commercially available epichlorohydrin rubber products include, for example, the "Hydrin series" from ZEON Corporation of Japan.

(A) Rubber components can also be synthesized. For example, acrylic rubber can be obtained by reacting (meth)acrylic acid, (meth)acrylate, aromatic vinyl compounds, cyanide vinyl compounds, etc.

(A) The rubber component may also include rubber with cross-linking groups. By using rubber with cross-linking groups, there is a tendency to easily improve the heat resistance of the stretchable resin layer. The cross-linking group is any reactive group that enables the reaction of cross-linking the molecular chains of the (A) rubber component. Examples include reactive groups, anhydride groups, amino groups, hydroxyl groups, epoxy groups, and carboxyl groups possessed by the cross-linking component (B) described later.

(A) The rubber component may also include rubber having at least one cross-linking group among an anhydride group and a carboxyl group. Examples of rubber having an anhydride group include rubber partially modified with maleic anhydride. Rubber partially modified with maleic anhydride is a polymer containing constituent units derived from maleic anhydride. Commercially available examples of rubber partially modified with maleic anhydride include, for instance, the styrene-based elastomer "Tufprene 912" manufactured by Asahi Kasei Corporation.

Partially modified rubber using maleic anhydride can also be a partially modified hydrogenated styrene-based elastomer using maleic anhydride. Hydrogenated styrene-based elastomers are also expected to have improved weather resistance and other effects. Hydrogenated styrene-based elastomers are elastomers obtained by reacting hydrogen with the unsaturated double bonds of a styrene-based elastomer having soft chains containing unsaturated double bonds. Examples of commercially available hydrogenated styrene-based elastomers that have been partially modified with maleic anhydride include "FG1901" and "FG1924" from Kraton Polymers Japan Co., Ltd., and "TufTech M1911", "TufTech M1913" and "TufTech M1943" from Asahi Kasei Corporation.

From a coating perspective, (A) the weight-average molecular weight of the rubber component can be 20,000–200,000, 30,000–150,000, or 50,000–125,000. Here, the weight-average molecular weight (Mw) represents the standard polystyrene conversion value obtained by gel permeation chromatography (GPC).

In the resin composition, based on the total amount of (A) rubber component, (B) crosslinking component, and (C) ester-based hardener, the content of (A) rubber component is preferably 60% to 95% by mass, more preferably 65% to 90% by mass, and even more preferably 70% to 85% by mass. If the content of (A) rubber component is 60% by mass or more, there is a tendency to obtain more sufficient elasticity, and the rubber component and crosslinking component are thoroughly mixed. If the content of (A) rubber component is 95% by mass or less, there is a tendency for the elastic resin layer to have particularly excellent properties in terms of adhesion, insulation reliability, and heat resistance. Based on the quality of the stretchable resin layer, the content of (A) rubber component in the stretchable resin layer can be within the range described.

(B) Crosslinking components with epoxy groups are components that crosslink during the curing reaction to form crosslinked polymers. (B) There are no particular limitations on the presence of epoxy groups within the molecule in crosslinking components; for example, they can be ordinary epoxy resins. As epoxy resins, they can be monofunctional, difunctional, or polyfunctional without particular limitation, but difunctional or polyfunctional epoxy resins can be used to obtain sufficient curability.

Examples of epoxy resins include: bisphenol A type, bisphenol F type, phenolic varnish type, naphthalene type, dicyclopentadiene type, and cresol varnish type. Aliphatic chain modified epoxy resins impart softness. Commercially available aliphatic chain modified epoxy resins include, for example, EXA-4816 manufactured by DIC Corporation. From the perspectives of curability, low viscosity, and heat resistance, phenolic varnish type, cresol varnish type, naphthalene type, or dicyclopentadiene type epoxy resins can be selected. These epoxy resins can be used alone or in combination of two or more.

By combining rubbers with maleic anhydride or carboxyl groups with epoxy compounds (epoxy resins), particularly excellent effects can be obtained in terms of the heat resistance and low moisture permeability of the stretchable resin layer, the adhesion between the stretchable resin layer and the conductive layer, and the low viscosity of the stretchable resin layer. If the heat resistance of the stretchable resin layer is improved, for example, the degradation of the stretchable resin layer during heating steps such as nitrogen reflux can be suppressed. If the stretchable resin layer has low viscosity, the conductor substrate or wiring substrate can be handled with good workability.

The resin composition may contain crosslinking components other than (B) the epoxy-containing crosslinking component, to the extent that it does not significantly impair the effects of the invention. From the viewpoint of more sufficiently reducing the dielectric loss tangent of the stretchable resin layer, the content of other crosslinking components is preferably less than 10 parts by mass relative to 100 parts by mass of (B) the epoxy-containing crosslinking component.

(C) Ester-based hardeners are compounds that participate in the hardening reaction themselves, which can improve the heat resistance of stretchable resin layers and reduce dielectric loss tangent.

There are no particular limitations on ester-based curing agents, but from the viewpoint of more fully obtaining the effects of improved heat resistance and reduced dielectric loss tangent, compounds with one or more highly reactive ester groups per molecule, such as phenolic esters, thiophenolic esters, N-hydroxyamine esters, and heterocyclic hydroxyl compounds, are preferable. More specifically, examples of ester-based curing agents include "EPICLON HPC8000-65T", "EPICLON HPC8000-L-65MT", and "EPICLON HPC8150-60T" (all trade names manufactured by DIC Corporation). These can be used alone or in combination.

It is believed that the ester-based curing agent reacts with the crosslinking component (B) as shown in formula (I) below during the curing reaction. It is believed that no hydroxyl groups are generated in the reaction between the ester-based curing agent (C) and the crosslinking component (B). Furthermore, even if side reactions occur, it is difficult to generate hydroxyl groups, resulting in a low dielectric loss tangent.

[Chemistry 1] In the formula, ^R1 , ^R2 and ^R3 each independently represent a monovalent organic group, and in order to more fully obtain the effects of the invention, they can also be monovalent organic groups with aromatic rings.

The resin composition may contain curing agents other than (C) ester-based curing agent to a extent that does not significantly impair the effects of the invention. From the viewpoint of more sufficiently reducing the dielectric loss tangent of the stretchable resin layer, the content of other curing agents is preferably less than 10 parts by weight relative to 100 parts by weight of (C) ester-based curing agent.

In the resin composition, using the total amount of (A) rubber component, (B) crosslinking component and (C) ester-based hardener as a benchmark, the total content of (B) crosslinking component and (C) ester-based hardener is preferably 5% to 40% by mass, more preferably 10% to 35% by mass, and even more preferably 15% to 30% by mass. If the total content of (B) crosslinking component and (C) ester-based hardener is 5% by mass or more, there is a tendency to obtain more complete curing and the extensible resin layer has particularly excellent properties in terms of adhesion, insulation reliability and heat resistance. If the total content of (B) crosslinking component and (C) ester-based curing agent is less than 40% by mass, there is a tendency to obtain more sufficient elasticity and for the rubber component and crosslinking component to be fully mixed.

In the resin composition, the preferred content ratio of (B) crosslinking component to (C) ester-based hardener is within the range of 4:5 to 5:4, calculated as the equivalent ratio of epoxy groups in (B) epoxy resin to ester bonds in (C) ester-based hardener. Within this content range, there is a tendency to obtain more complete curing, and the elastomeric resin layer exhibits particularly excellent properties in terms of adhesion, insulation reliability, and heat resistance.

The resin composition may further contain a (D) curing accelerator. The (D) curing accelerator is a compound that functions as a catalyst for the curing reaction. The (D) curing accelerator may also be selected from tertiary amines, imidazoles, organic acid metal salts, phosphorus compounds, Lewis acids, amine complex salts, and phosphines. Among these, imidazoles may be used from the viewpoint of the storage stability and curing properties of the varnish of the resin composition. In cases where the (A) rubber component contains rubber partially modified using maleic anhydride, a compatible imidazole may also be selected.

In the resin composition, relative to 100 parts by mass of the total amount of (A) rubber component, (B) crosslinking component, and (C) ester-based curing agent, the content of (D) curing accelerator can be 0.1 parts by mass to 10 parts by mass. If the content of (D) curing accelerator is 0.1 parts by mass or more, there is a tendency to obtain more sufficient curing. If the content of (D) curing accelerator is 10 parts by mass or less, there is a tendency to obtain more sufficient heat resistance. Based on the above considerations, the content of (D) curing accelerator can be 0.3 parts by mass to 7 parts by mass, or 0.5 parts by mass to 5 parts by mass.

In addition to the aforementioned components, the resin composition may also include, as needed and to the extent that it does not significantly impair the effects of the invention, antioxidants, anti-yellowing agents, ultraviolet absorbers, visible light absorbers, colorants, plasticizers, stabilizers, fillers, flame retardants, leveling agents, etc.

In particular, the resin composition may contain at least one anti-deterioration agent selected from the group consisting of antioxidants, heat stabilizers, light stabilizers, and anti-hydrolysis agents. Antioxidants inhibit deterioration caused by oxidation. Furthermore, antioxidants impart sufficient heat resistance to the stretchable resin layer at high temperatures. Heat stabilizers impart stability to the stretchable resin layer at high temperatures. Examples of light stabilizers include: ultraviolet absorbers that prevent deterioration caused by ultraviolet radiation, light-blocking agents that block light, and matting agents that have the function of stabilizing organic materials by accepting the light energy absorbed by the organic materials. Anti-hydrolysis agents inhibit deterioration caused by moisture. Anti-degradation agents may be at least one selected from the group consisting of antioxidants, heat stabilizers, and ultraviolet absorbers. As an anti-degradation agent, only one of the ingredients listed above may be used, or two or more may be used in combination. For better results, two or more anti-degradation agents may be used in combination.

Antioxidants may be one or more selected from the group consisting of phenolic antioxidants, amine antioxidants, sulfur-based antioxidants, and phosphite antioxidants. For better results, two or more antioxidants may be used in combination. Phenolic antioxidants and sulfur-based antioxidants may also be used in combination.

Phenolic antioxidants can be compounds with sterically hindering substituents such as t-butyl and trimethylsilyl groups adjacent to the phenolic hydroxyl group. Phenolic antioxidants are also known as hindered phenolic antioxidants.

Phenolic antioxidants can be, for example, one or more compounds selected from the group consisting of 2-tert-butyl-4-methoxyphenol, 3-tert-butyl-4-methoxyphenol, 2,6-ditert-butyl-4-ethylphenol, 2,2'-methylene-bis(4-methyl-6-tert-butylphenol), 4,4'-thiobis(3-methyl-6-tert-butylphenol), 4,4'-butylenebis(3-methyl-6-tert-butylphenol), 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene and tetra-[methylene-3-(3',5'-ditert-butyl-4'-hydroxyphenyl)propionate]methane. Phenolic antioxidants can be represented by high molecular weight phenolic antioxidants such as 1,3,5-trimethyl-2,4,6-tris(3,5-ditert-butyl-4-hydroxybenzyl)benzene and tetra-[methylene-3-(3',5'-ditert-butyl-4'-hydroxyphenyl)propionate]methane.

Phosphite antioxidants can be selected from triphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, 4,4'-butylene-bis(3-methyl-6-tert-butylphenyl)-di(tetrazyl) phosphite, cyclonepentanetetrayl-bis(nonylphenyl) phosphite, cyclonepentanetetrayl-bis(dinonylphenyl) phosphite, cyclonepentanetetrayl-tris(nonylphenyl) phosphite, and cyclonepentanetetrayl-tris(di(di)) phosphite. One or more compounds from the group consisting of nonylphenyl phosphite, 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphenanthroline-10-oxide, 2,2-methylenebis(4,6-ditert-butylphenyl)-2-ethylhexyl phosphite, diisodecyl pentaerythritol diphosphite and tris(2,4-ditert-butylphenyl) phosphite may be tris(2,4-ditert-butylphenyl) phosphite.

Examples of other antioxidants include hydroxyamine antioxidants, represented by N-methyl-2-dimethyl amino acetohydroxamic acid, and sulfur-based antioxidants, represented by dilauryl 3,3'-thiodipropionate.

The antioxidant content can also be based on the mass of the resin composition (total solid content) and ranges from 0.1% to 20% by mass. If the antioxidant content is above 0.1% by mass, sufficient heat resistance of the stretchable resin layer can be easily obtained. If the antioxidant content is below 20% by mass, exudation and blooming can be inhibited.

From the perspective of preventing sublimation during heating, the molecular weight of antioxidants can be 400 or higher, 600 or higher, or 750 or higher. When two or more antioxidants are included, the average molecular weight of these antioxidants can be within the above range.

Examples of heat stabilizers (heat deterioration preventers) include: metal soaps or inorganic salts such as combinations of zinc and barium salts of higher fatty acids; organotin compounds such as organotin maleate and organotin thiolate; and fullerenes (e.g., hydroxylated fullerenes).

Examples of UV absorbers include: benzophenone-based UV absorbers, represented by 2,4-dihydroxybenzophenone; benzotriazole-based UV absorbers, represented by 2-(2'-hydroxy-5'-methylphenyl)benzotriazole; and cyanoacrylate-based UV absorbers, represented by 2-ethylhexyl-2-cyano-3,3'-diphenylacrylate.

Examples of hydrolytic agents include: carbodiimide derivatives, epoxy compounds, isocyanate compounds, acid anhydrides, oxazoline compounds, and melamine compounds.

Other anti-deterioration agents include, for example, hindered amine light stabilizers, ascorbic acid, propyl gallate, catechin, oxalic acid, malonic acid, and phosphites.

The stretchable resin layer can be manufactured, for example, by means of: dissolving or dispersing (A) a rubber component, (B) a crosslinking component and (C) an ester-based curing agent, and other components as needed, in an organic solvent to obtain a resin varnish; and forming the resin varnish onto a conductor foil or carrier film by means of the method described later.

There are no particular restrictions on the organic solvents used here. Examples include: aromatic hydrocarbons such as toluene, xylene, mesitylene, cumene, and p-isopropyltoluene; cyclic ethers such as tetrahydrofuran and 1,4-dioxane; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and 4-hydroxy-4-methyl-2-pentanone; esters such as methyl acetate, ethyl acetate, butyl acetate, methyl lactate, ethyl lactate, and γ-butyrolactone; carbonates such as ethyl carbonate and propyl carbonate; and acetamides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone. Toluene or N,N-dimethylacetamide may also be used from the perspective of solubility and boiling point. These organic solvents can be used alone or in combination of two or more. The concentration of solid components (other than organic solvents) in resin varnishes can be 20% to 80% by mass.

There are no particular limitations on the carrier film. Examples include: polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, and other polyesters; polyethylene, polypropylene, and other polyolefins; polycarbonate, polyamide, polyimide, polyamide-imide, polyether-imide, polyether sulfide, polyether ketone, polyphenylene ether, polyphenylene sulfide, polyarylate, polyether, liquid crystal polymers, and other films. In terms of flexibility and toughness, films made of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polypropylene, polycarbonate, polyamide, polyimide, polyamide-imide, polyphenylene ether, polyphenylene sulfide, polyarylate, or polyurethane can also be used as carrier films.

There is no particular limitation on the thickness of the carrier film, which can range from 3 μm to 250 μm. If the thickness of the carrier film is 3 μm or more, the film strength is sufficient; if the thickness of the carrier film is less than 250 μm, sufficient flexibility can be obtained. From the above point of view, the thickness can be 5 μm to 200 μm or 7 μm to 150 μm. From the viewpoint of improving the peelability from the stretchable resin layer, films that have undergone release treatment using silicone-based compounds, fluorine-containing compounds, etc., can also be used as needed.

If necessary, the protective film can also be attached to the stretchable resin layer to form a laminated film with a three-layer structure including a conductor foil or carrier film, a stretchable resin layer and a protective film.

There are no particular limitations on the protective film used; examples include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PET), and polyethylene naphthalate (PET); and polyolefin films such as polyethylene and polypropylene. From the perspective of flexibility and toughness, polyester films such as polyethylene terephthalate and polyolefin films such as polyethylene and polypropylene can be used as protective films. From the perspective of improving the peelability from the stretchable resin layer, the protective film can be treated with silicone-based compounds or fluorinated compounds for release.

The thickness of the protective film can be appropriately varied depending on the desired flexibility, and can range from 10 μm to 250 μm. A thickness of 10 μm or more tends to provide sufficient film strength, while a thickness of less than 250 μm tends to provide sufficient flexibility. Based on these considerations, a thickness of 15 μm to 200 μm, or 20 μm to 150 μm, is suitable.

[Manufacturing Method of Wiring Substrate] A wiring substrate having a conductor foil in one embodiment can be manufactured, for example, by a method comprising: preparing a multilayer board (conductor substrate) having a stretchable resin layer and a conductor foil deposited on the stretchable resin layer; forming an etching resist on the conductor foil; exposing the etching resist and developing the exposed etching resist to form an etching resist pattern covering a portion of the conductor foil; removing the portion of the conductor foil not covered by the etching resist pattern; and removing the etching resist pattern.

As a method for obtaining a laminate (conductor substrate) having a scalable resin layer and a conductor foil, any method can be used, including applying a varnish of the resin composition used to form the scalable resin layer to the conductor foil; and a method for forming a scalable resin layer by depositing the conductor foil onto a carrier film using a vacuum press, laminator, or the like. The scalable resin layer can be formed by heating the resin composition and carrying out a crosslinking reaction (curing reaction) of the crosslinking components.

The method for depositing a stretchable resin layer on a carrier film onto a conductor foil can be any method, such as using a roller laminator, a vacuum laminator, or a vacuum press. From the viewpoint of production efficiency, a roller laminator or a vacuum laminator can be used for forming.

The thickness of the dried stretchable resin layer is not particularly limited, and is typically 5 μm to 1000 μm. Within this range, sufficient strength of the stretchable resin layer can be easily obtained, and due to thorough drying, the amount of residual solvent in the stretchable resin layer can be reduced.

Alternatively, a conductor foil can be further laminated on the opposite side of the conductor foil in the stretchable resin layer, thereby creating a laminate with conductor foils on both sides of the stretchable resin layer. By providing conductor layers on both sides of the stretchable resin layer, warping of the laminate during curing can be suppressed.

As a method for forming wiring patterns on the conductor foil of a laminate (a laminate for forming a wiring substrate), methods such as etching can be used. For example, when copper foil is used as the conductor foil, the etching solution can be a mixture of concentrated sulfuric acid and hydrogen peroxide, or a ferric chloride solution.

Examples of etching resists used in etching include: Photec H-7025 (manufactured by Hitachi Chemical Co., Ltd., trade name) and Photec H-7030 (manufactured by Hitachi Chemical Co., Ltd., trade name), and X-87 (manufactured by Taiyo Holdings Co., Ltd., trade name). The etching resist is typically removed after the wiring pattern is formed.

One embodiment of a method for manufacturing a wiring substrate having a conductor coating includes: a step of forming a conductor coating on a stretchable resin layer by electroless plating; a step of forming a coating resist on the conductor coating; and a step of exposing the coating resist and developing the exposed coating resist to form a coating covering the stretchable resin layer. The steps include: partially forming an anti-corrosion pattern; further forming a conductor film by electroplating on the portion of the conductor film not covered by the anti-corrosion pattern; removing the anti-corrosion pattern; and removing the portion of the conductor film formed by electroless plating that is not covered by the conductor film formed by electroplating.

Another embodiment of the method for manufacturing a wiring substrate includes: a step of forming an etching resist on a conductor film formed on a stretchable resin layer; a step of exposing the etching resist and developing the exposed etching resist to form an resist pattern covering a portion of the stretchable resin layer; a step of removing the portion of the conductor film not covered by the resist pattern; and a step of removing the resist pattern.

Examples of coating corrosion inhibitors used as masks for plating include: Photech RY3325 (manufactured by Hitachi Chemical Co., Ltd., trade name), Photech RY-5319 (manufactured by Hitachi Chemical Co., Ltd., trade name), and MA-830 (manufactured by Taiyo Holdings Co., Ltd., trade name). Furthermore, details regarding electroless plating and electroplating are as described above.

Scalable components can be obtained by mounting various electronic devices on a wiring board. [Example]

The present invention is further illustrated by the following embodiments. However, the present invention is not limited to these embodiments.

(Example 1) <Preparation of Resin Varnish for Forming a Strength-Expanding Resin Layer> While (A) is composed of 80 parts by weight (amount of non-volatile component) of maleic anhydride-modified styrene-vinyl butadiene rubber (trade name "FG1924GT" manufactured by KRATON Corporation), diluted with toluene and adjusted to a non-volatile component of 25% by weight, and (B) 11 parts by weight of dicyclopentadiene-type epoxy resin (trade name "EPICLON HP7200H" manufactured by DIC Corporation), diluted with toluene and adjusted to a non-volatile component of 25% by weight. 0.1 parts by weight (amount of non-volatile components), 25% by weight of an ester-based hardener (DIC Corporation trade name "HPC8000-65T") diluted with toluene to achieve a non-volatile content as component (C), 8.9 parts by weight of a dicyclopentadiene-type diphenol compound (amount of non-volatile components), and 3 parts by weight of 1-benzyl-2-methylimidazolium (Shikoku Chemical Co., Ltd. trade name "1B2MZ") as component (D), are stirred and mixed to obtain a resin varnish.

<Fabrication of the Lamination Film> A release-treated polyethylene terephthalate (PET) film (Teijin DuPont Films Co., Ltd., trade name "Purex A31", 25 μm thick) was prepared as the carrier film. The resin varnish was applied to the release-treated surface of the PET film using a doctor blade coater (Kangjing Precision Machinery Co., Ltd., trade name "SNC-350"). The coating was then dried in a dryer (Futaba Science Co., Ltd., trade name "MSO-80TPS") at 100°C for 20 minutes to form a 100 μm thick resin layer (the stretchable resin layer before curing). A PET film with the same release treatment as the carrier film is attached as a protective film to the formed resin layer, with the release treatment surface facing the resin layer side, to obtain a laminated film.

<Conductor Substrate Fabrication> The protective film of the laminated film is peeled off. On the exposed resin layer, an electrolytic copper foil with a roughened surface Ra of 1.5 μm (trade name "F2-WS-12" manufactured by Furukawa Electric Industries, Ltd.) is overlapped with the resin layer facing outwards. In this state, the electrolytic copper foil layer is pressed onto the resin layer using a vacuum pressure laminator (trade name "V130" manufactured by Nikko Materials Co., Ltd.) under conditions of 0.5 MPa pressure, 90°C temperature, and 60 seconds of pressing time. Subsequently, the substrate was heated at 180°C for 60 minutes in a dryer (manufactured by Futaba Science Co., Ltd., under the trade name "MSO-80TPS") to obtain a conductive substrate having a stretchable resin layer as the resin layer and an electrolytic copper foil as the conductive layer.

(Examples 2 to 6 and Comparative Examples 1 to 2) Except for changing the composition of the resin varnish to the composition shown in Table 1, the resin varnish, the laminated film and the conductor substrate are manufactured in the same manner as in Example 1. Furthermore, in Table 1, "HP5000" is a phenolic varnish-type epoxy resin (manufactured by DIC Corporation under the trade name "EPICLON HP5000"), "HPC8000-L-65MT" is an ester-based hardener (manufactured by DIC Corporation under the trade name "EPICLON HPC8000-L-65MT", a low molecular weight grade of HPC8000-L-65MT), and "HPC8150-60T" is an ester-based hardener (manufactured by DIC Corporation under the trade name "EPICLON HPC8150-60T", a compound with a naphthalene skeleton). Additionally, the amounts of each component in Table 1 are the amounts of non-volatile components, expressed in parts by mass.

[Determination of Tensile Elasticity and Elongation at Break] The laminated films obtained in the Examples and Comparative Examples were heated to 180°C for 60 minutes to harden the resin layer and form a stretchable resin layer. The carrier film and protective film were removed, and the stretchable resin layer was cut into strips 40 mm long and 10 mm wide to obtain test pieces. Tensile tests were performed on these test pieces using an autograph (manufactured by Shimadzu Corporation, trade name "EZ-S") to obtain stress-strain curves. The tensile elasticity and elongation at break were determined from the obtained stress-strain curves. Tensile tests were conducted with a clamp spacing of 20 mm and a tensile speed of 50 mm/min. The tensile elastic coefficient was determined based on the slope of the stress-strain curve in the stress range of 0.5 N to 1.0 N. The strain at the point of fracture was recorded as the elongation at break. The results are shown in Table 1.

[Determination of Recovery Rate] Similar to the determination of tensile elasticity coefficient and elongation at break, a strip of extensible resin layer, 40 mm in length and 10 mm in width, was prepared. Using an automatic plotter (Shimadzu Corporation, trade name "EZ-S"), the test piece was stretched at a speed of 100 mm/min until the strain reached 20%. After releasing the stress and returning to the initial position, a tensile test was performed again. The recovery rate R is calculated by setting the strain (displacement) applied in the first tensile test as X, and the difference between the position at which the load was first applied in the second tensile test and X as Y, using the following formula. In this test, X was 20%. The results are shown in Table 1. R (%) = Y/X × 100

[Determination of Dielectric Constant (Dk) and Dielectric Loss Tangent (Df)] Similar to the determination of tensile elasticity and elongation at break, test pieces of stretchable resin layers measuring 80 mm × 80 mm were prepared. Using these test pieces, Dk and Df were calculated using the cavity resonator method. Measurements were performed using a vector network analyzer E8364B (manufactured by Keysight Technologies), a CP531 (manufactured by Kanto Electronics Applications Development Co., Ltd.), and a CPMA-V2 (program), at an ambient temperature of 25°C and a frequency of 10 kHz. The results are shown in Table 1.

[Evaluation of Heat Resistance] The laminated films obtained in Examples 1 to 6 and Comparative Examples 1 to 2 were heated to 180°C for 60 minutes to harden the resin layer and form a stretchable resin layer. After removing the carrier film and protective film, the stretchable resin layer was subjected to a heat resistance test using a nitrogen reflux system (trade name "TNV-EN" manufactured by Tamura Manufacturing Co., Ltd.). The heat resistance test was performed by repeating the heating process 10 times using the temperature distribution shown in Figure 3 of IPC/JEDEC J-STD-020. After the heat resistance test, the tensile elasticity, elongation at break, and recovery rate of the stretchable resin layer were measured using the same method. The results, along with the results of the tests conducted before the heat resistance test, are shown in Tables 2 and 3.

[Determination of Infrared Absorption Spectroscopy (IR)] Regarding the resin layer of the laminated film of Comparative Example 1 (the stretchable resin layer before curing) and the stretchable resin layer after curing by heating it at 180°C for 60 minutes, and the stretchable resin layer after curing by heating the resin layer of the laminated film of Example 1 and Comparative Example 3 at 180°C for 60 minutes, after removing the carrier film and protective film, the infrared absorption spectrum was determined by transmission using a Fourier transform infrared spectrophotometer (trade name "FTS3000MX" manufactured by Bio-Rad Corporation). Figure 4 shows the infrared absorption spectra of the stretchable resin layers of Comparative Example 1 before and after curing, and Figure 5 shows the infrared absorption spectra of the stretchable resin layers of Examples 1, 3, and 1 after curing.

As shown in Figure 4, in the stretchable resin layer of Comparative Example 1, an absorption peak near 3400 ^cm⁻¹ belonging to the stretching vibrations of hydroxyl groups, which was not present before curing, was observed after curing, indicating that hydroxyl groups were generated through the curing reaction. Furthermore, as shown in Figure 5, in the stretchable resin layers of Examples 1 and 3, the absorption peak of the stretching vibrations belonging to hydroxyl groups was almost absent, and the formation of hydroxyl groups was suppressed.

[Fabrication and Evaluation of Wiring Substrate] A test wiring substrate 1 as shown in Figure 2 was fabricated. The test wiring substrate 1 has a stretchable resin layer 3 and a conductor foil (electrolytic copper foil) formed on the stretchable resin layer 3 as a conductor layer 5 and having a wave pattern. First, an etching resist (trade name "Photec RY-5325" manufactured by Hitachi Chemical Co., Ltd.) was laminated onto the conductor layer of the conductor substrate obtained in the embodiments and comparative examples where the surface of the stretchable resin layer has an uneven surface, using a roller laminator, and a photomask with a wave pattern was formed on it. The etching resist was exposed using an EXM-1201 exposure machine manufactured by ORC Corporation at an energy of 50 mJ/ ^cm² . Then, it was spray-developed for 240 seconds in a 1% sodium carbonate aqueous solution at 30°C to dissolve the unexposed portions of the etching resist, forming a resist pattern with wavy openings. Next, the copper foil not covered by the resist pattern was removed using an etching solution. Subsequently, the etching resist was removed using a stripping solution, resulting in a wiring substrate 1 with a conductor layer 5 on a stretchable resin layer 3, forming a wavy wiring pattern with a wiring width of 50 μm that meanders along a predetermined direction X.

The obtained wiring substrate is stretched and deformed in the X direction until the strain reaches 10%, and the stretchable resin layer and the waveform wiring pattern are observed when it returns to its original state. As a result, the wiring substrate of either the embodiment or the comparative example does not experience breakage of the stretchable resin layer or the wiring pattern during stretching.

[Table 1] Implementation Example 1 Implementation Example 2 Implementation Example 3 Implementation Example 4 Implementation Example 5 Implementation Example 6 Comparative example 1 Comparative example 2 (A) Ingredients FG1924 80 80 80 80 80 80 80 80 (B) Components HP7200H 11.1 11.2 10.9 - - - 20 - HP5000 - - - 10.6 10.7 10.5 - 20 (C) Components HPC8000-65T 8.9 - - 9.4 - - - - HPC8000-L-65MT - 8.8 - - 9.3 - - - HPC8150-60T - - 9.1 - - 9.5 - - (D) Component 1B2MZ 3 3 3 3 3 3 3 3 Tensile elasticity coefficient (MPa) 3.8 3.4 3.4 3.1 2.9 2.9 3.5 2.9 Elongation at break (%) 860 800 800 770 740 810 550 690 Recovery rate (%) 94 94 94 94 94 94 94 94 Dielectric constant Dk 2.4 2.3 2.2 2.3 2.3 2.2 2.5 2.4 Dielectric loss tangent Df 0.0023 0.0021 0.0016 0.0024 0.0024 0.0018 0.0050 0.0048

[Table 2] Implementation Example 1 Implementation Example 2 Implementation Example 3 Implementation Example 4 Before heat resistance test After heat resistance test Before heat resistance test After heat resistance test Before heat resistance test After heat resistance test Before heat resistance test After heat resistance test Tensile elasticity coefficient (MPa) 3.8 3.8 3.4 3.3 3.4 3.4 3.1 3.1 Elongation at break (%) 860 690 800 710 800 740 770 690 Recovery rate (%) 94 94 94 94 94 94 94 94

[Table 3] Implementation Example 5 Implementation Example 6 Comparative example 1 Comparative example 2 Before heat resistance test After heat resistance test Before heat resistance test After heat resistance test Before heat resistance test After heat resistance test Before heat resistance test After heat resistance test Tensile elasticity coefficient (MPa) 2.9 2.9 2.9 2.8 3.5 3.4 2.9 2.9 Elongation at break (%) 740 650 810 690 550 440 690 600 Recovery rate (%) 94 94 94 93 94 94 94 94

As shown in Table 1, the conductor substrates of Examples 1 to 6 exhibit superior scalability and low dielectric loss tangent compared to the conductor substrates of Comparative Examples 1 to 2. Furthermore, as shown in Tables 2 and 3, the conductor substrates of Examples 1 to 6 maintain good scalability and elasticity even after heat resistance testing. [Industrial Applicability]

The conductor substrate and the wiring substrate obtained therefrom of the present invention are expected to be used as substrates for, for example, wearable devices.

1: Wiring substrate 3: Extensible resin layer 5: Conductor layer (conductor foil or conductor coating) X: Strain (displacement) applied in the first tensile test Y: Difference between the starting position when the load is applied in the subsequent tensile test and X

Figure 1 is a stress-strain curve showing the recovery rate measurement example. Figure 2 is a plan view showing one embodiment of the wiring substrate. Figure 3 is a temperature profile curve showing the heat resistance test. Figure 4 is a graph showing the infrared absorption spectra of the stretchable resin layer before and after curing in Comparative Example 1. Figure 5 is a graph showing the infrared absorption spectra of the cured stretchable resin layers of Examples 1, 3, and 1.

1: Wiring board

3: Extensible resin layer

5: Conductor layer (conductor foil or conductor coating)

X: Strain (displacement) applied in the first tensile test

Claims (21)

A conductor substrate comprising: a stretchable resin layer; and a conductor foil disposed on the stretchable resin layer, the stretchable resin layer comprising a cured resin composition, the resin composition comprising (A) a rubber component, (B) a crosslinking component having epoxy groups and (C) an ester-based curing agent, the (A) rubber component comprising a styrene-based elastomer having crosslinking groups, the styrene-based elastomer having crosslinking groups being a styrene-butadiene rubber comprising an anhydride group or a carboxyl group. A conductor substrate comprising: a stretchable resin layer; and a conductor foil disposed on the stretchable resin layer, the stretchable resin layer comprising a cured resin composition, the resin composition comprising (A) a rubber component, (B) a crosslinking component having epoxy groups and (C) an ester-based curing agent, the (A) rubber component comprising a styrene-based elastomer having crosslinking groups, the styrene-based elastomer having crosslinking groups being a styrene-based elastomer having an anhydride group. A conductor substrate comprising: a stretchable resin layer; and a conductor foil disposed on the stretchable resin layer, the stretchable resin layer comprising a cured resin composition, the resin composition comprising (A) a rubber component, (B) a crosslinking component having epoxy groups and (C) an ester-based curing agent, the (A) rubber component comprising a styrene-based elastomer having crosslinking groups, and the recovery rate of the stretchable resin layer after being stretched to a strain of 20% is 80% or more. A conductor substrate comprising: a stretchable resin layer; and a conductor foil disposed on the stretchable resin layer, the stretchable resin layer comprising a cured resin composition, the resin composition comprising (A) a rubber component, (B) a crosslinking component having epoxy groups, (C) an ester-based curing agent and an antioxidant, wherein the (A) rubber component comprises a styrene-based elastomer having crosslinking groups. The conductor substrate as described in any one of claims 1 to 4, wherein the elastic coefficient of the conductor foil is 40 GPa to 300 GPa. A conductor substrate comprising: a stretchable resin layer; and a conductor coating disposed on the stretchable resin layer, the stretchable resin layer comprising a cured resin composition, the resin composition comprising (A) a rubber component, (B) a crosslinking component having epoxy groups and (C) an ester-based curing agent, the (A) rubber component comprising a styrene-based elastomer having crosslinking groups, the styrene-based elastomer having crosslinking groups being a styrene-butadiene rubber comprising an anhydride group or a carboxyl group. A conductor substrate comprising: a stretchable resin layer; and a conductor coating disposed on the stretchable resin layer, the stretchable resin layer comprising a cured resin composition, the resin composition comprising (A) a rubber component, (B) a crosslinking component having epoxy groups and (C) an ester-based curing agent, the (A) rubber component comprising a styrene-based elastomer having crosslinking groups, the styrene-based elastomer having crosslinking groups being a styrene-based elastomer having an anhydride group. A conductor substrate comprising: a stretchable resin layer; and a conductor coating disposed on the stretchable resin layer, the stretchable resin layer comprising a cured resin composition, the resin composition comprising (A) a rubber component, (B) a crosslinking component having epoxy groups and (C) an ester-based curing agent, the (A) rubber component comprising a styrene-based elastomer having crosslinking groups, and the recovery rate of the stretchable resin layer after being stretched to a strain of 20% is 80% or more. A conductor substrate comprising: a stretchable resin layer; and a conductor coating disposed on the stretchable resin layer, the stretchable resin layer comprising a cured resin composition, the resin composition comprising (A) a rubber component, (B) a crosslinking component having epoxy groups, (C) an ester-based curing agent and an antioxidant, wherein the (A) rubber component comprises a styrene-based elastomer having crosslinking groups. The conductor substrate as described in claim 2 or claim 7, wherein the styrene elastomer having an anhydride group is a hydrogenated styrene elastomer partially modified with maleic anhydride. The conductor substrate as described in any one of claims 1 to 4 and claims 6 to 9, wherein the resin composition further contains a (D) curing accelerator. The conductor substrate as described in any one of claims 1 to 4 and claims 6 to 9, wherein the total amount of the (A) rubber component, the (B) crosslinking component and the (C) ester curing agent is used as a reference, and the content of the (A) rubber component is 60% to 95% by mass. A wiring substrate comprising a conductor substrate as described in any one of claims 1 to 4, wherein the conductor foil forms a wiring pattern. A wiring substrate comprising a conductor substrate as described in any one of claims 6 to 9, wherein the conductor is coated to form a wiring pattern. A retractable element includes: a wiring substrate as described in claim 13 or claim 14; and an electronic device mounted on the wiring substrate. A conductor substrate as described in any one of claims 1 to 4, used to form a wiring substrate, the wiring substrate comprising a conductor substrate having a stretchable resin layer and a conductor foil disposed on the stretchable resin layer, the conductor foil forming a wiring pattern. A conductor substrate as described in any one of claims 6 to 9, used to form a wiring substrate, the wiring substrate comprising a conductor substrate having a stretchable resin layer and a conductor coating disposed on the stretchable resin layer, the conductor coating forming a wiring pattern. A method for manufacturing a wiring substrate, the wiring substrate being as described in claim 13, the method comprising: a step of preparing a multilayer board having a stretchable resin layer and a conductor foil deposited on the stretchable resin layer; a step of forming an etching resist on the conductor foil; a step of exposing the etching resist and developing the exposed etching resist to form an etching resist pattern covering a portion of the conductor foil; a step of removing the portion of the conductor foil not covered by the etching resist pattern; and a step of removing the etching resist pattern. A method for manufacturing a wiring substrate, comprising: forming a coated resist on a stretchable resin layer; exposing the coated resist and developing the exposed coated resist to form a resist pattern covering a portion of the stretchable resin layer; forming a conductor film on the surface of the portion of the stretchable resin layer not covered by the resist pattern by electroless plating; and removing the resist pattern. A method for manufacturing a wiring substrate, comprising the method described in claim 14, wherein the method includes: forming a conductor film on a stretchable resin layer by electroless plating; forming a coating resist on the conductor film; exposing the coating resist and developing the exposed coating resist to form a resist pattern covering a portion of the stretchable resin layer; further forming a conductor film on the portion of the conductor film not covered by the resist pattern by electroplating; and removing the resist pattern. The step of removing the portion of the conductor film formed by electroless plating that was not covered by the conductor film formed by electroplating. A method for manufacturing a wiring substrate, comprising the method described in claim 14, the method comprising: forming an etching resist on a conductor film formed on a stretchable resin layer; exposing the etching resist and developing the exposed etching resist to form an etching resist pattern covering a portion of the stretchable resin layer; removing the portion of the conductor film not covered by the etching resist pattern; and removing the etching resist pattern.