Wiring-forming member, method for forming wiring layer using wiring-forming member, and wiring-forming member

Abstract

A member 1 for forming wiring is provided with an adhesive layer 10 and a metal foil layer 20. The adhesive layer 10 is composed of an adhesive composition including electrically conductive particles 12. The metal foil layer 20 is disposed on the adhesive layer 10. In the member 1 for forming wiring, the ratio of a surface coarseness Rz of a first surface 20a of the metal foil layer 20 on the side adhered to the adhesive layer 10 to an average particle diameter of the electrically conductive particles 12 is 0.05 to 3.

Description

[Technical Field]

[0001] The present disclosure relates to a wiring-forming member, a method for forming a wiring layer using the wiring-forming member, and the wiring-forming member. [Background technology]

[0002] Patent Document 1 discloses a method for manufacturing a printed wiring board incorporating electronic components such as IC chips. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-191204 Summary of the Invention [Problem to be solved by the invention]

[0004] In a conventional method for manufacturing a component-embedded substrate, as shown in FIGS. 7A and 7B, insulating resin layers 102 and 103 are formed on both sides of an electronic component 101, on which an electrode 101a is provided, in the stacking direction. Then, as shown in FIGS. 7C and 7D, via electrodes 104 and 105 are formed in the insulating resin layers 102 and 103, respectively, by performing processes such as laser drilling, plating, and etching to form electrodes. Then, as shown in FIGS. 8A to 8C, a component-embedded substrate 110 is formed by repeating the processes of forming further insulating resin layers 106 and 107, forming a via electrode 108 by laser drilling and plating, and etching to form electrodes. However, in such a method for manufacturing a component-embedded substrate, many processes are performed to form one conductive layer (via electrode), and these processes must be repeated to form multiple conductive layers, making the manufacturing process very complicated.

[0005] Therefore, we investigated an adhesive with conductive particles and laminated metal foil as a wiring material. However, when using an adhesive simply laminated with metal foil, the conductive particles get caught in the recessed parts on the adhesive side of the metal foil, and the conductive particles do not deform into a flat shape (a condition for stable conduction) sufficiently during mounting (pressure application), resulting in unstable conduction.

[0006] Therefore, the present disclosure aims to provide a wiring forming member that can more reliably and stably establish electrical conduction between wirings and simplify the process of forming a wiring layer that connects the wirings, a method for forming a wiring layer using the wiring forming member, and a wiring forming member. [Means for solving the problem]

[0007] One aspect of the present disclosure relates to a wiring-forming member. The wiring-forming member includes an adhesive layer made of an adhesive composition containing conductive particles, and a metal foil layer disposed on the adhesive layer. In this wiring-forming member, the ratio of the surface roughness Rz of the surface of the metal foil layer that is bonded to the adhesive layer to the average particle size of the conductive particles is 0.05 to 3. This ratio can be expressed as surface roughness Rz / average particle size.

[0008] In this wiring-forming member, the ratio of the surface roughness Rz of the surface of the metal foil layer bonded to the adhesive layer to the average particle size of the conductive particles is 0.05 to 3. Therefore, compared to when the ratio of the surface roughness Rz of the surface of the metal foil layer bonded to the adhesive layer to the average particle size of the conductive particles is greater than 3 (see, for example, FIG. 3), the conductive particles can be more reliably flattened to increase the contact area of ​​the conductive particles with the metal foil layer (see, for example, FIG. 4). As a result, electrical conduction between the metal foil layer that will become a wiring pattern or wiring after processing and another wiring pattern or wiring to which the adhesive layer is adhered can be stabilized. Furthermore, the resistance value in this electrical conduction can be reduced. Furthermore, this wiring-forming member allows for a construction method using an adhesive layer, thereby simplifying the process of forming a wiring layer connecting wirings compared to conventional processes such as laser processing and fill plating.

[0009] In another aspect, the present disclosure relates to a wiring-forming member. The wiring-forming member includes an adhesive layer made of an adhesive composition containing conductive particles, and a metal foil layer disposed on the adhesive layer. In the wiring-forming member, the surface of the metal foil layer that is bonded to the adhesive layer has a surface roughness Rz of less than 20 μm.

[0010] In this wiring-forming member, the surface roughness Rz of the metal foil layer on the side bonded to the adhesive layer is less than 20 μm, reducing the surface roughness of the metal foil layer surface bonded to the adhesive layer. Therefore, compared to when the surface roughness of the metal foil layer on the adhesive layer side is rough (see, for example, Figure 3), the conductive particles can be more reliably flattened to increase the contact area of ​​the conductive particles with the metal foil layer (see, for example, Figure 4). As a result, electrical conduction between the metal foil layer that will become the wiring pattern or wiring after processing and other wiring patterns or wiring to which the adhesive layer is adhered can be stabilized. Furthermore, the resistance value of this electrical conduction can be reduced. Furthermore, because this wiring-forming member allows for a construction method using an adhesive layer, the process of forming a wiring layer connecting wirings can be simplified compared to conventional processes such as laser processing and fill plating.

[0011] In the wiring-forming member, the metal foil layer may have a surface roughness Rz of 0.5 μm or more and 10 μm or less, which allows the conductive particles in the metal foil layer to be more reliably deformed into a flat shape, thereby stabilizing electrical conduction between the metal foil layer that will become a wiring pattern or wiring after processing and another wiring pattern or wiring to which the adhesive layer is adhered.

[0012] In the wiring-forming member, the conductive particles may have an average particle size of 2 μm or more and 20 μm or less, which allows the wiring-forming member itself to be made thinner, and also allows the wiring layer produced by the wiring-forming member and the substrate including the wiring layer to be made thinner.

[0013] In the wiring-forming member, the shortest distance from the surface of the metal foil layer in contact with the adhesive layer to the surface of the conductive particles may be greater than 0 μm and less than 1 μm. In this case, the conductive particles are arranged on the metal foil layer side, so that the metal foil layer can more reliably crush the multiple conductive particles into a uniform flat shape. Furthermore, by distributing the conductive particles unevenly on the metal foil side in this way, the capture rate of the conductive particles in the wiring (electrodes) can be improved, further stabilizing the conduction.

[0014] In the wiring-forming member described above, the adhesive layer may include a first adhesive layer containing conductive particles in its adhesive component and a second adhesive layer, and the first adhesive layer may be located between the metal foil layer and the second adhesive layer. In this case, the conductive particles are located on the metal foil layer side, allowing the metal foil layer to more reliably crush the conductive particles into a uniform flat shape, thereby enhancing conductivity. Furthermore, by distributing the conductive particles more uniformly on the metal foil side, the rate at which the conductive particles are captured by wiring (electrodes) or the like can be improved, further stabilizing electrical conduction. The second adhesive layer may also be configured so that conductive particles are not contained in its adhesive component, thereby enabling more reliable insulation of areas that should be insulated. In this case, the second adhesive layer may contain a filler or other material.

[0015] The wiring-forming member may further include a release film. In this case, the wiring-forming member becomes easier to handle as a member, and the work efficiency when forming a wiring layer using the wiring-forming member can be improved. In addition, this release film can be used, for example, by being disposed on the surface of the adhesive layer opposite to the metal foil layer.

[0016] In yet another aspect, the present disclosure relates to a wiring-forming member, which includes a metal foil layer and an adhesive layer formed from an adhesive composition containing conductive particles, and which is provided as separate bodies, and which can be adhered to the metal foil layer during use. In this wiring-forming member, the ratio of the surface roughness Rz of the metal foil layer on the side that is adhered to the adhesive layer to the average particle size of the conductive particles is 0.05 to 3. In this case, as described above, it is possible to stabilize electrical conduction between the metal foil layer that will become a wiring pattern or wiring after processing and another wiring pattern or wiring to which the adhesive layer is adhered. It is also possible to reduce the resistance value of this electrical conduction. Furthermore, because the adhesive layer and the metal foil layer can be prepared separately (as a set of wiring-forming members), it is possible to improve the operational flexibility when fabricating wiring layers using the wiring-forming member, such as by selecting a wiring-forming member with a more optimal material composition.

[0017] In yet another aspect, the present disclosure relates to a wiring-forming member having a metal foil layer and an adhesive layer formed from an adhesive composition containing conductive particles, the adhesive layer being separately provided, and capable of adhering to the metal foil layer during use. In this wiring-forming member, the surface of the metal foil layer that is adhered to the adhesive layer has a surface roughness Rz of less than 20 μm. In this case, as with the above, stable electrical conduction can be achieved between the metal foil layer that will become a wiring pattern or wiring after processing and another wiring pattern or wiring to which the adhesive layer is adhered.

[0018] In yet another aspect, the present disclosure relates to a method for forming a wiring layer using any of the above-described wiring-forming members. This wiring layer forming method includes the steps of: preparing any of the above-described wiring-forming members; preparing a substrate on which wiring is formed; placing the wiring-forming member on the surface of the substrate on which the wiring is formed so that the adhesive layer faces the substrate to cover the wiring; thermocompressing the wiring-forming member to the substrate; and performing a patterning process on the metal foil layer. This forming method can significantly simplify the processing process compared to conventional methods. Furthermore, this forming method can easily thin the formed wiring layer.

[0019] In yet another aspect, the present disclosure relates to a wiring-forming member. This wiring-forming member includes a substrate having wiring, and a cured product of any of the above wiring-forming members disposed on the substrate so as to cover the wiring. In this wiring-forming member, the wiring is electrically connected to the metal foil of the wiring-forming member or to another wiring formed from the metal foil. According to this aspect, a wiring-forming member with a thin wiring layer can be obtained. [Effects of the Invention]

[0020] According to the present disclosure, electrical conduction between wirings can be more reliably and stably achieved, and the process of forming a wiring layer that connects the wirings can be simplified. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a cross-sectional view showing a wiring formation member according to an embodiment of the present disclosure. [Figure 2] 2(a) to 2(d) are diagrams for sequentially explaining a method for forming a wiring layer using the wiring formation member shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view illustrating a wiring-forming member according to a comparative example and a state in which the wiring-forming member is pressure-bonded. [Figure 4] FIG. 4 is a cross-sectional view illustrating a wiring-forming member according to an embodiment of the present disclosure and a state in which the wiring-forming member is pressure-bonded. [Figure 5] 5(a) to 5(c) are cross-sectional views showing wiring-forming members according to another embodiment of the present disclosure and the state when these wiring-forming members are pressure-bonded together. [Figure 6] 6(a) to 6(e) are cross-sectional views sequentially showing a conventional method for manufacturing a redistribution layer. [Figure 7] 7(a) to 7(d) are cross-sectional views for sequentially explaining a method for manufacturing a conventional component-embedded substrate. [Figure 8] 8(a) to 8(c) are cross-sectional views for sequentially explaining a method for manufacturing a conventional component-embedded substrate, showing steps subsequent to those in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, a wiring-forming member according to an embodiment of the present disclosure and a method for forming a wiring layer using the wiring-forming member will be described with reference to the drawings. In the following description, the same or equivalent parts will be denoted by the same reference numerals, and duplicated explanations will be omitted. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios of the drawings are not limited to those shown.

[0023] In this specification, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. Furthermore, in numerical ranges described in stages in this specification, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in numerical ranges described in this specification, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples.

[0024] Fig. 1 is a cross-sectional view showing a wiring-forming member according to an embodiment of the present disclosure. As shown in Fig. 1, the wiring-forming member 1 is configured to include an adhesive layer 10 and a metal foil layer 20. The wiring-forming member 1 is a member that can be used, for example, when fabricating a rewiring layer, a build-up multilayer wiring board, a component-embedded board, and the like, but is not limited thereto. The wiring-forming member 1 may also be used for EMI shielding, etc.

[0025] The adhesive layer 10 is configured to include conductive particles 12 and an adhesive layer 14 containing an insulating adhesive component in which the conductive particles 12 are dispersed. The adhesive layer 10 has a thickness of, for example, 5 μm to 20 μm. The adhesive component of the adhesive layer 14 is defined as solid content other than the conductive particles 12. Before the wiring layer is formed using the wiring-forming member 1, the adhesive layer 14 may be in a B-stage state in which the surface has been dried, i.e., in a semi-cured state.

[0026] [Conductive particle composition] The conductive particles 12 are substantially spherical particles having electrical conductivity, and are composed of metal particles made of metals such as Au, Ag, Ni, Cu, solder, or conductive carbon particles made of conductive carbon. The conductive particles 12 may be coated conductive particles having a core containing non-conductive glass, ceramic, plastic (polystyrene, etc.), or the like, and a coating layer containing the above metal or conductive carbon that coats the core. Among these, the conductive particles 12 may be metal particles formed of a heat-fusible metal, or coated conductive particles having a core containing plastic and a coating layer containing metal or conductive carbon that coats the core.

[0027] In one embodiment, the conductive particles 12 include a core made of a polymer particle (plastic particle) such as polystyrene, and a metal layer covering the core. The polymer particle may have substantially the entire surface covered with the metal layer, or a portion of the surface of the polymer particle may be exposed without being covered with the metal layer, as long as the function as a connecting material is maintained. The polymer particle may be, for example, a particle containing a polymer containing at least one monomer selected from styrene and divinylbenzene as a monomer unit.

[0028] The metal layer may be formed of various metals such as Ni, Ni / Au, Ni / Pd, Cu, NiB, Ag, or Ru. The metal layer may be an alloy layer made of an alloy of Ni and Au, an alloy of Ni and Pd, or the like. The metal layer may have a multilayer structure made of multiple metal layers. For example, the metal layer may be made of a Ni layer and an Au layer. The metal layer may be formed by plating, vapor deposition, sputtering, soldering, or the like. The metal layer may be a thin film (for example, a thin film formed by plating, vapor deposition, sputtering, or the like).

[0029] The conductive particles 12 may have an insulating layer. Specifically, for example, in the conductive particles of the above embodiment, which include a core (e.g., a polymer particle) and a coating layer such as a metal layer that coats the core, an insulating layer may be provided on the outside of the coating layer. The insulating layer may be the outermost layer located on the outermost surface of the conductive particle. The insulating layer may be a layer formed from an insulating material such as silica or acrylic resin.

[0030] The average particle size Dp of the conductive particles 12 may be 1 μm or more, 2 μm or more, or 5 μm or more, from the viewpoint of excellent dispersibility and conductivity. The average particle size Dp of the conductive particles may be 50 μm or less, 30 μm or less, or 20 μm or less, from the viewpoint of excellent dispersibility and conductivity. From the above viewpoints, the average particle size Dp of the conductive particles may be 1 to 50 μm, 5 to 30 μm, 5 to 20 μm, or 2 to 20 μm.

[0031] The maximum particle size of the conductive particles 12 may be smaller than the smallest interval between electrodes in the wiring pattern (the shortest distance between adjacent electrodes). From the viewpoint of excellent dispersibility and conductivity, the maximum particle size of the conductive particles 12 may be 1 μm or more, 2 μm or more, or 5 μm or more. From the viewpoint of excellent dispersibility and conductivity, the maximum particle size of the conductive particles may be 50 μm or less, 30 μm or less, or 20 μm or less. From the above viewpoints, the maximum particle size of the conductive particles may be 1 to 50 μm, 2 to 30 μm, or 5 to 20 μm.

[0032] In this specification, the particle size of 300 random particles (pcs) is measured by observation using a scanning electron microscope (SEM), the average value of the obtained particle sizes is defined as the average particle size Dp, and the largest value obtained is defined as the maximum particle size of the particle. Note that if the particle has protrusions or is not spherical, the particle size is defined as the diameter of the circle circumscribing the particle in the SEM image.

[0033] The content of the conductive particles 12 is determined depending on the fineness of the electrodes to be connected. For example, the amount of the conductive particles 12 is not particularly limited, but may be 0.1 vol% or more, or 0.2 vol% or more, based on the total volume of the adhesive components (components in the adhesive composition excluding the conductive particles). A blending amount of 0.1 vol% or more tends to prevent a decrease in conductivity. The blending amount of the conductive particles 12 may be 30 vol% or less, or 10 vol% or less, based on the total volume of the adhesive components (components in the adhesive composition excluding the conductive particles 12). A blending amount of 30 vol% or less tends to reduce the occurrence of short circuits. Note that the "volume percent" is determined based on the volume of each component before curing at 23°C, but the volume of each component can be converted from weight to volume using specific gravity. Alternatively, the volume of a component can be determined by adding the component to a measuring cylinder or other container containing an appropriate solvent (water, alcohol, etc.) that thoroughly wets the component without dissolving or swelling it, and then measuring the increased volume.

[0034] [Adhesive layer / adhesive component composition] The adhesive components constituting the adhesive layer 14 contain a curing agent, a monomer, and a film-forming material. When an epoxy resin monomer is used, the curing agent can be an imidazole, a hydrazide, a boron trifluoride-amine complex, a sulfonium salt, an amine imide, a polyamine salt, or dicyandiamide. Microencapsulating the curing agent by coating it with a polyurethane or polyester polymeric substance is preferable because it extends the usable time. When an acrylic monomer is used, the curing agent can be a peroxide compound, an azo compound, or the like that decomposes upon heating to generate free radicals.

[0035] When an epoxy monomer is used, the curing agent is appropriately selected depending on the target connection temperature, connection time, storage stability, etc. From the viewpoint of high reactivity, the curing agent may have a gel time of 10 seconds or less with the epoxy resin composition at a predetermined temperature, and from the viewpoint of storage stability, the curing agent may have a gel time that does not change with the epoxy resin composition after storage in a thermostatic chamber at 40°C for 10 days. From these viewpoints, the curing agent may be a sulfonium salt.

[0036] When an acrylic monomer is used, the curing agent is appropriately selected depending on the desired connection temperature, connection time, storage stability, etc. From the viewpoint of high reactivity and storage stability, the curing agent may be an organic peroxide or azo compound having a 10-hour half-life temperature of 40°C or higher and a 1-minute half-life temperature of 180°C or lower, or an organic peroxide or azo compound having a 10-hour half-life temperature of 60°C or higher and a 1-minute half-life temperature of 170°C or lower. These curing agents may be used alone or in combination, and may be used in combination with a decomposition accelerator, inhibitor, etc.

[0037] Whether an epoxy monomer or an acrylic monomer is used, in order to obtain a sufficient reaction rate when the connection time is 10 seconds or less, the amount of curing agent may be 0.1 to 40 parts by mass, or 1 to 35 parts by mass, relative to 100 parts by mass of the total of the monomer and film-forming material described below. If the amount of curing agent is less than 0.1 parts by mass, a sufficient reaction rate cannot be obtained, and it tends to be difficult to obtain good adhesive strength and low connection resistance. On the other hand, if the amount of curing agent is more than 40 parts by mass, the fluidity of the adhesive tends to decrease, the connection resistance tends to increase, and the storage stability of the adhesive tends to decrease.

[0038] Furthermore, when an epoxy resin monomer is used as the monomer, bisphenol-type epoxy resins derived from epichlorohydrin and bisphenol A, bisphenol F, bisphenol AD, or the like, epoxy novolac resins derived from epichlorohydrin and phenol novolac or cresol novolac, and various epoxy compounds having two or more glycidyl groups in one molecule, such as glycidyl amine, glycidyl ether, biphenyl, and alicyclic epoxy compounds, can be used.

[0039] When an acrylic monomer is used, the radical polymerizable compound may be a substance having a functional group that polymerizes by radicals. Examples of such radical polymerizable compounds include (meth)acrylates, maleimide compounds, and styrene derivatives. The radical polymerizable compound may be used in either a monomer or an oligomer state, or a mixture of a monomer and an oligomer may be used. One of these monomers may be used alone, or two or more may be used in combination.

[0040] The film-forming material is a polymer that facilitates handling of the low-viscosity composition containing the curing agent and monomer. The use of the film-forming material prevents the film from easily tearing, cracking, or becoming sticky, resulting in an adhesive layer 10 that is easy to handle.

[0041] Thermoplastic resins are preferably used as film-forming materials, including phenoxy resins, polyvinyl formal resins, polystyrene resins, polyvinyl butyral resins, polyester resins, polyamide resins, xylene resins, polyurethane resins, polyacrylic resins, and polyester urethane resins. Furthermore, these polymers may contain siloxane bonds or fluorine substituents. These resins may be used alone or in combination of two or more. Among the above resins, phenoxy resins may be used from the viewpoints of adhesive strength, compatibility, heat resistance, and mechanical strength.

[0042] The larger the molecular weight of the thermoplastic resin, the easier it is to obtain film-forming properties, and the melt viscosity, which affects the fluidity of the film, can be set over a wider range. The molecular weight of the thermoplastic resin may be a weight-average molecular weight of 5,000 to 150,000, or 10,000 to 80,000. By setting the weight-average molecular weight to 5,000 or more, good film-forming properties are easily obtained, and by setting it to 150,000 or less, good compatibility with other components is easily obtained.

[0043] In the present disclosure, the weight average molecular weight refers to a value measured by gel permeation chromatography (GPC) using a calibration curve based on standard polystyrene under the following conditions. (Measurement conditions) Equipment: Tosoh GPC-8020 Detector: Tosoh Corporation RI-8020 Column: Gelpack GLA160S+GLA150S manufactured by Hitachi Chemical Co., Ltd. Sample concentration: 120mg / 3mL Solvent: tetrahydrofuran Injection volume: 60μL Pressure: 2.94 x 106 Pa (30 kgf / cm 2 ) Flow rate: 1.00mL / min

[0044] The content of the film-forming material may be 5 to 80% by weight, or 15 to 70% by weight, based on the total amount of the curing agent, monomer, and film-forming material. By setting the content to 5% by weight or more, good film-forming properties are likely to be obtained, and by setting the content to 80% by weight or less, the curable composition tends to exhibit good fluidity.

[0045] In addition, the adhesive layer forming the adhesive layer 10 may further contain fillers, softeners, accelerators, antioxidants, colorants, flame retardants, thixotropic agents, coupling agents, phenolic resins, melamine resins, isocyanates, etc.

[0046] When a filler is contained, further improvement in connection reliability can be expected. The maximum diameter of the filler may be less than the particle diameter of the conductive particles 12, and the content of the filler may be 5 to 60 parts by volume per 100 parts by volume of the adhesive layer. When the content of the filler is 5 to 60 parts by volume, good connection reliability tends to be obtained.

[0047] [Metal foil layer composition] The surface roughness Rz of one surface and the opposite surface of the metal foil layer 20 may be the same or different. The metal foil layer 20 has a thickness of, for example, 5 μm to 200 μm. The thickness of the metal foil layer here refers to a thickness including the surface roughness Rz. The metal foil layer 20 is, for example, copper foil, aluminum foil, nickel foil, stainless steel, titanium, or platinum foil.

[0048] The adhesive layer 10 is disposed on the first surface 20a of the metal foil layer 20. The surface roughness Rz of the first surface 20a of the metal foil layer 20 may be 0.3 μm or more, 0.5 μm or more, or 1.0 μm or more. The surface roughness Rz of the first surface 20a of the metal foil layer 20 may be 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, less than 20 μm, 17 μm or less, 10 μm or less, 8.0 μm or less, 5.0 μm or less, or 3.0 μm or less. The surface roughness Rz of the first surface 20a of the metal foil layer 20 may be, for example, 0.3 μm or more and 20 μm or less, 0.3 μm or more and less than 20 μm, or more specifically, 0.5 μm or more and 10 μm or less. The surface roughness Rz of the second surface 20b of the metal foil layer 20 may be, for example, 20 μm or more, and may be rougher than the surface roughness Rz of the first surface 20a, may be the same as the surface roughness of the first surface 20a, or may not be rougher than the surface roughness Rz of the first surface 20a. If the surface roughness Rz of the first surface 20a of the metal foil layer 20 is too smooth (for example, the surface roughness Rz is 0.2 μm), the adhesion between the metal foil layer 20 and the adhesive layer 10 may not be maintained over a long period of time, and peeling may occur. For this reason, the surface roughness Rz of the first surface 20a of the metal foil layer 20 may be 0.3 μm or more. However, by adopting a material or connection configuration that ensures adhesion, the surface roughness Rz of the first surface 20a of the metal foil layer 20 may be less than 0.3 μm.

[0049] Surface roughness Rz refers to the ten-point average roughness Rzjis measured in accordance with the method specified in the JIS standard (JIS B 0601-2001), and refers to the value measured using a commercially available surface roughness profile measuring instrument. For example, measurement can be performed using a nano search microscope (Shimadzu Corporation's "SFT-3500").

[0050] Here, the relationship between the average particle diameter Dp of the conductive particles 12 and the surface roughness Rz of the first surface 20a of the metal foil layer 20 will be described below. In this embodiment, the ratio of the surface roughness Rz of the first surface 20a of the metal foil layer 20 to the average particle diameter Dp of the conductive particles 12, "surface roughness / average particle diameter," may be 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.5 or more, or 1 or more. Furthermore, the ratio of the surface roughness Rz of the first surface 20a of the metal foil layer 20 to the average particle diameter Dp of the conductive particles 12, "surface roughness / average particle diameter," may be 3 or less, 2 or less, 1.7 or less, or 1.5 or less. The "surface roughness / average particle size", which is the ratio of the surface roughness Rz of the first surface 20a of the metal foil layer 20 to the average particle size Dp of the conductive particles 12, may be, for example, 0.05 or more and 3 or less, and more specifically, 0.06 or more and 2 or less. In this embodiment, the surface roughness Rz of the first surface 20a of the metal foil layer 20 and the average particle size Dp of the conductive particles 12 are controlled so that the "surface roughness / average particle size", which is the ratio of the surface roughness Rz of the first surface 20a of the metal foil layer 20 to the average particle size Dp of the conductive particles 12, is in the range of 0.05 to 3.

[0051] Another aspect of the present disclosure relates to a method for forming a wiring layer using a wiring-forming member. The method for forming a wiring layer using the above-described wiring-forming member 1 will be described with reference to Fig. 2. (a) to (d) of Fig. 2 are diagrams illustrating a method for forming a wiring layer using the wiring-forming member shown in Fig. 1.

[0052] First, as shown in (a) of FIG. 2, a wiring-forming member 1 is prepared. Furthermore, a base material 30 on which wiring 32 is formed is prepared. Then, the wiring-forming member 1 is placed so that the adhesive layer 10 side of the wiring-forming member 1 faces the base material 30. Thereafter, as shown in (b) of FIG. 2, lamination is performed so as to cover the wiring 32, and the wiring-forming member 1 is attached to the base material 30.

[0053] Next, as shown in FIG. 2(c), the wiring-forming member 1 is heated and pressurized as desired, and is then pressed against the substrate 30. At this time, since the first surface 20a of the metal foil layer 20 of the wiring-forming member 1 is flat, the conductive particles 12, which must ensure electrical conductivity, can be more reliably deformed into flattened conductive particles 12a. In the pressed wiring-forming member 1a, the flattened conductive particles 12a (which destroy the insulating layer and expose the conductive portion) are arranged on the wiring 32, ensuring reliable electrical conduction between the metal foil layer 20 and the wiring 32. At this time, the adhesive layer 14 is also crushed, resulting in a thinner adhesive layer 14a.

[0054] Next, as shown in Fig. 2(d), the metal foil layer 20 is subjected to a predetermined patterning process (e.g., etching process) to process it into a predetermined wiring pattern 20c (another wiring). At this time, the second surface 20b of the metal foil layer 20 may be processed to form a smooth surface. The above-mentioned processes shown in Fig. 2(a) to (d) may be repeated a predetermined number of times to form a wiring layer.

[0055] That is, the method for forming a wiring layer using a wiring forming member comprises the steps of preparing a wiring forming member, preparing a base material on which wiring is formed, placing the wiring forming member on the surface of the base material on which wiring is formed so that the adhesive layer side faces the substrate and covers the wiring, heating and pressing the wiring forming member to the base material, and performing a patterning process on the metal foil layer.

[0056] In this way, the wiring-forming member 1b is formed. This wiring-forming member 1b includes a substrate 30 having wirings 32, and a cured product of the wiring-forming member 1 (a thermocompression-bonded wiring-forming member) placed on the substrate 30 so as to cover the wirings 32. In this wiring-forming member 1b, the wirings 32 and the metal foil 20 of the wiring-forming member 1 or the wirings 20c formed (for example, by etching) from the metal foil 20 are electrically connected by the conductive particles 12a. Note that when the processes of (a) to (d) in FIG. 2 are repeated a predetermined number of times, the wiring-forming member 1b may have a configuration having multiple wiring layers (layers in which the above-mentioned wirings are connected to each other).

[0057] Here, the stabilization of conduction by the conductive particles 12, 12a in the wiring-forming member 1 will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a cross-sectional view for explaining a wiring-forming member 101 according to a comparative example and a state in which the wiring-forming member 101 is pressure-bonded. Fig. 4 is a cross-sectional view for explaining a wiring-forming member 1 according to an embodiment of the present disclosure and a state in which the wiring-forming member 1 is pressure-bonded.

[0058] As shown in FIG. 3 , when the metal foil layer 120 of the wiring-forming member 101 according to the comparative example is positioned with its matte surface (surface roughness Rz1) facing the adhesive layer 110, the ratio of the surface roughness Rz1 of the matte surface of the metal foil layer 120 to the average particle diameter Dp of the conductive particles 112, or "surface roughness / average particle diameter," may be greater than 3. When pressure-bonding is performed in such a case, as shown in the diagram after pressure-bonding (right), the conductive particles 112 may enter the recesses of the uneven matte surface of the metal foil layer 120. In this case, the conductive particles 112 are not crushed by the metal foil layer 120 and remain nearly granular rather than flattened, resulting in a small contact area. Furthermore, if the conductive particles 112 have an insulating layer on their outermost layer, the insulating layer is not sufficiently destroyed. Therefore, the wiring-forming member 1 according to this comparative example does not provide stable conduction between the wires.

[0059] In contrast, as shown in Fig. 4, in the wiring-forming member 1, the first surface 20a of the metal foil layer 20 is disposed facing the adhesive layer 10, so that the conductive particles 12 can be more reliably crushed and deformed into the desired flat shape when pressed. Even if the conductive particles 12 have an insulating layer on their outermost layer, the conductive particles 12 are sufficiently crushed, so that the insulating layer can be destroyed and the internal conductive portions can be exposed. In this case, a sufficient and wide area can be secured for the conductive portions of the conductive particles 12a to contact the metal foil layer 20 and other wiring, thereby more reliably stabilizing the conduction between the wiring.

[0060] As described above, in the wiring-forming member 1 according to this embodiment, the ratio of the surface roughness Rz of the first surface 20a of the metal foil layer 20 bonded to the adhesive layer 10 to the average particle diameter of the conductive particles 12 is 0.05 to 3. Therefore, compared to a comparative example in which the "surface roughness / average particle diameter" (the ratio of the surface roughness Rz1 of the matte surface of the metal foil layer 120 to the average particle diameter Dp of the conductive particles 112) is greater than 3 (see FIG. 3), the conductive particles 12, 12a can be more reliably flattened to increase the contact area of ​​the conductive particles 12, 12a with the metal foil layer 20 (see FIG. 4). As a result, electrical conduction between the metal foil layer 20, which will become a wiring pattern or wiring after processing, and another wiring pattern or wiring to which the adhesive layer 10 is bonded can be stabilized. Furthermore, this wiring-forming member 1 allows for a construction method using an adhesive layer, thereby simplifying the process of forming a wiring layer connecting wirings compared to conventional construction methods.

[0061] In the wiring-forming member 1, the surface roughness Rz of the first surface 20a of the metal foil layer 20 may be less than 20 μm, or may be 0.5 μm or more and 10 μm or less. In this case, the first surface 20a of the metal foil layer 20 can more reliably deform the conductive particles 12 into a flat shape, thereby more reliably and stably establishing electrical conduction between the metal foil layer 20, which will become a wiring pattern or wiring after processing, and another wiring pattern or wiring to which the adhesive layer 10 is adhered.

[0062] In the wiring-forming member 1, the conductive particles 12 may have an average particle size of 2 μm or more and 20 μm or less. In this case, the wiring-forming member 1 itself can be made thinner, and the wiring layer produced by the wiring-forming member 1 and the substrate including the wiring layer can also be made thinner.

[0063] Furthermore, the method of forming a wiring layer using the wiring formation member 1 can greatly simplify the processing process compared to the conventional method (see FIG. 6). Furthermore, this formation method makes it possible to easily thin the formed wiring layer.

[0064] Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above embodiments and can be applied to various other embodiments. For example, in the above embodiment, as shown in FIG. 5(a), the conductive particles 12 are randomly or evenly dispersed within the adhesive layer 10 in the wiring-forming member 1. However, as shown in FIG. 5(b), the conductive particles 12 may be arranged (distributed unevenly) on the metal foil layer 20 side. In this case, the conductive particles 12 are not exposed on the second surface 10b of the adhesive layer 10 opposite the metal foil layer 20, and the thickness of the adhesive layer 10 between the conductive particles 12 and the first surface 20a of the metal foil layer 20 may be greater than 0 μm or 0.1 μm and less than 1 μm. In this case, since the conductive particles 12 are arranged on the metal foil layer 20 side, the metal foil layer 20 can more reliably flatten the conductive particles 12 in the wiring layer 1d. Furthermore, by distributing the conductive particles 12 unevenly on the metal foil layer 20 side, the capture rate of the conductive particles 12 in wiring (electrodes) and the like can be improved. That is, the conduction can be made more stable. The distance between the conductive particles 12 and the first surface 20a of the metal foil layer 20 (the thickness of the adhesive layer 10 therebetween) refers to the shortest distance from the surface of the metal foil layer 20 in contact with the adhesive layer 10 to the surface of the conductive particles 12, and is, for example, the average value at any 30 points. This distance is measured by sandwiching the wiring-forming member between two pieces of glass (thickness: approximately 1 mm) and casting a resin composition consisting of 100 g of bisphenol A-type epoxy resin (trade name: JER811, manufactured by Mitsubishi Chemical Corporation) and 10 g of a curing agent (trade name: Epomount Curing Agent, manufactured by Refine Tech Co., Ltd.), polishing the cross section using a polishing machine, and then using a scanning electron microscope (SEM, trade name: SE-8020, manufactured by Hitachi High-Tech Science Corporation).

[0065] Alternatively, as shown in FIG. 5(c), the adhesive layer 10d may be formed separately into a first adhesive layer 10e and a second adhesive layer 10f. The adhesive components constituting the first adhesive layer 10e and the second adhesive layer 10f may be the same as those constituting the adhesive layer 10 described above, but the difference is that the conductive particles 12 are not dispersed, i.e., not contained, in the second adhesive layer 10f. In this modified wiring-forming member 1e, the conductive particles 12 are dispersed, i.e., contained, in the first adhesive layer 10e. In this case, as in the modified example shown in FIG. 5(b), the conductive particles 12 are disposed on the metal foil layer 20 side, which allows the metal foil layer 20 to more reliably flatten the conductive particles 12 in the wiring layer 1f. Furthermore, by distributing the conductive particles 12 more uniformly on the metal foil layer 20 side, the capture rate of the conductive particles 12 in the wiring (electrodes) can be improved. In other words, the electrical continuity can be more stable.

[0066] The wiring-forming member 1, 1c, or 1e may further include a release film. The release film may be attached to the adhesive layer 10, 10c, or 10d on the side opposite to the side to which the metal foil layer 20 is attached, or may be attached to the side of the metal foil layer 20 opposite to the side to which the adhesive layer 10, 10c, or 10d is attached. The first surface 20a of the metal foil layer 20 may be attached to the adhesive layer 10, 10c, or 10d. In this case, the wiring-forming member becomes easier to handle, and the work efficiency when forming a wiring layer using the wiring-forming member can be improved.

[0067] Furthermore, although the above description has been given taking as an example a case where the wiring-forming member is a member formed by bonding the adhesive layer 10 and the metal foil layer 20, the wiring-forming member in this embodiment may be configured as a set product in which the adhesive layer 10 and the metal foil layer 20 are provided as separate bodies and the adhesive layer 10 can be bonded to the first surface 20a of the metal foil layer 20 during use. In this case, the adhesive layer 10 and the metal foil layer 20 can be prepared separately (as a set of wiring-forming members), which improves the degree of freedom in the work when fabricating a wiring layer using the wiring-forming member, such as by selecting a wiring-forming member with a more optimal material composition. [Example]

[0068] The present disclosure will be described in more detail below with reference to examples, although the present disclosure is not limited to these examples.

[0069] (1) Preparation of wiring forming materials The materials for producing the conductive adhesive layer and the insulating adhesive layer were prepared as follows.

[0070] (Preparation of thermoplastic resin) As the thermoplastic resin, a phenoxy resin (product name: FX-316, manufactured by Nippon Steel Chemical Co., Ltd.) was prepared.

[0071] (Synthesis of acrylic rubber) A polymerization reactor equipped with a thermometer and a stirrer was charged with 200 parts of water, 2 parts of sodium lauryl sulfate, 29.25 parts by mass of ethyl acrylate (EA, manufactured by Aldrich), 39.25 parts by mass of butyl acrylate (BA, manufactured by Aldrich), acrylonitrile (AN, manufactured by Aldrich), and 3 parts by mass of glycidyl methacrylate (GMA, manufactured by Aldrich). After sufficient removal of oxygen by vacuum degassing and nitrogen substitution three times, emulsion polymerization was carried out at normal pressure and 30°C for 5 hours. The resulting suspension polymerization liquid was coagulated with an aqueous calcium chloride solution, washed with water, and dried to obtain an acrylic rubber.

[0072] (Preparation of latent hardener) As a latent curing agent, a masterbatch-type latent curing agent (trade name: Novacure 3941, active temperature 125°C, manufactured by Asahi Kasei Chemicals) was prepared, which was a microcapsule-type curing agent with an average particle size of 5 μm, consisting of an imidazole modified product as the core and its surface coated with polyurethane, dispersed in a liquid bisphenol F-type epoxy resin.

[0073] (Preparation of conductive particles A1) Conductive particles A1 were prepared by forming a 0.2 μm thick nickel layer on the surface of a particle with a polystyrene core, and then forming a 0.02 μm thick gold layer on the outside of this nickel layer, resulting in conductive particles with an average particle size of 5 μm and a specific gravity of 2.3.

[0074] (Preparation of conductive particles A2) Conductive particles A2 were prepared by forming a 0.2 μm thick nickel layer on the surface of a particle with a polystyrene core, and then forming a 0.02 μm thick gold layer on the outside of this nickel layer, resulting in conductive particles with an average particle size of 10 μm and a specific gravity of 2.1.

[0075] (Preparation of conductive particles A3) To prepare conductive particles A3, a 0.2 μm thick nickel layer was formed on the surface of a particle with a polystyrene core, and then a 0.02 μm thick gold layer was formed on the outside of this nickel layer, resulting in conductive particles with an average particle size of 3 μm and a specific gravity of 2.5.

[0076] (Preparation of conductive particles B) Conductive particles B: average particle size 4 μm, apparent density 2.1 g / cm 3 Ni particles were prepared.

[0077] Example 1 20 parts by mass of phenoxy resin (FX-316, Nippon Steel Chemical Co., Ltd.), 20 parts by mass of acrylic rubber (ACM), and 60 parts by mass of latent curing agent "Novacure 3941" were dissolved in 100 parts by mass of toluene, and then the conductive particles shown in Table 1 were added to prepare a coating liquid for forming an adhesive layer.

[0078] This coating solution was applied to one side (the side to be coated with the coating solution) of a copper foil shown in Table 1 using a coating device (manufactured by Yasui Seiki Co., Ltd., product name: Precision Coater), and then dried with hot air at 70°C for 10 minutes to produce an adhesive film with a thickness of 18 μm on the copper foil. Note that the surface roughness Rz shown in Table 1 indicates the surface roughness of the copper foil on the adhesive film side.

[0079] (Examples 2 to 13, Comparative Examples 1 to 4) An adhesive film was prepared on copper foil in the same manner as in Example 1, except that the type and amount of conductive particles, as well as the surface roughness and thickness of the copper foil, were changed to those shown in Table 1.

[0080] [Table 1]

[0081] [Connection resistance measurement] As a reference example, a circuit board (PWB) having three copper circuits with a line width of 1000 μm, a pitch of 10000 μm, and a thickness of 15 μm was attached to a glass cloth-reinforced epoxy substrate using the copper foil adhesives of Examples 1 to 13 and Comparative Examples 1 to 4. This was connected over a width of 2 mm by heating and pressurizing at 180°C and 2 MPa for 10 seconds using a thermocompression bonding device (heating method: constant heat type, manufactured by Toray Engineering Co., Ltd.), to produce a connection.

[0082] The resulting connectors, coated with resist, were immersed in an etching solution and swung. The etching solution was adjusted to 100 g / L copper chloride and 100 ml / L hydrochloric acid. Once the desired copper foil area was gone, the specimen was rinsed with pure water. The resist was then peeled off to obtain the desired evaluation sample. The resistance between the remaining copper foil area on the circuit and the copper circuit on the board was measured with a multimeter immediately after bonding and after 250 hours in a high-temperature, high-humidity chamber at 85°C and 85% RH (post-test). The resistance value was the average of 37 resistance points between the remaining copper foil area on the circuit and the copper circuit on the board. The resistance results are shown in Table 2.

[0083] [Table 2]

[0084] As is clear from Table 2 above, in Examples 1 to 13, the resistance values ​​were all low, confirming that the conductive particles were reliably crushed, resulting in more reliable and stable electrical conduction between the wirings. On the other hand, in Comparative Examples 1 to 3, the resistance values ​​were high, suggesting that the conductive particles were not sufficiently crushed. Furthermore, in Comparative Example 4, although the resistance value immediately after bonding was low, if the surface was too smooth, adhesion could not be maintained over a long period of time, resulting in peeling and making measurement impossible. Thus, it was confirmed that by using a wiring-forming member in which the ratio of the surface roughness Rz of the surface of the metal foil layer bonded to the adhesive layer to the average particle size of the conductive particles is 0.05 to 3, good connection can be ensured even after reliability testing. [Explanation of symbols]

[0085] 1, 1c, 1e...wiring forming member, 1a, 1d, 1f...wiring layer, 1b...wiring forming member, 10, 10c, 10d...adhesive layer, 10a...first surface, 10b...second surface, 10e...first adhesive layer, 10f...second adhesive layer, 12, 12a...conductive particles, 14, 14a...adhesive layer, 20...metal foil layer, 20a...first surface, 20b...second surface.

Claims

1. an adhesive layer made of an adhesive composition containing conductive particles; a metal foil layer disposed on the adhesive layer; Equipped with A wiring-forming member, wherein the ratio of the surface roughness Rz of the surface of the metal foil layer that is bonded to the adhesive layer to the average particle size of the conductive particles is 0.5 to 1.

7.

2. A wiring formation member as described in claim 1, wherein the surface roughness Rz of the surface of the metal foil layer that is adhered to the adhesive layer is less than 20 μm.

3. The surface roughness Rz of the metal foil layer is 0.5 μm or more and 10 μm or less. The wiring forming member according to claim 1 or 2.

4. The conductive particles have an average particle size of 2 μm or more and 20 μm or less. The wiring forming member according to any one of claims 1 to 3.

5. the shortest distance from the surface of the metal foil layer in contact with the adhesive layer to the surface of the conductive particle is greater than 0 μm and not greater than 1 μm; The wiring forming member according to any one of claims 1 to 4.

6. the adhesive layer has a first adhesive layer in which the conductive particles are contained in an adhesive component, and a second adhesive layer, and the first adhesive layer is located between the metal foil layer and the second adhesive layer; The wiring forming member according to any one of claims 1 to 5.

7. Further, a release film is provided. The wiring forming member according to any one of claims 1 to 6.

8. A wiring-forming member, comprising: an adhesive layer made of an adhesive composition containing conductive particles; and a metal foil layer, which are provided as separate bodies, and the adhesive layer can be adhered to the metal foil layer during use; A wiring-forming member, wherein the ratio of the surface roughness Rz of the surface of the metal foil layer that is bonded to the adhesive layer to the average particle size of the conductive particles is 0.5 to 1.

7.

9. A wiring formation member as described in claim 8, wherein the surface roughness Rz of the surface of the metal foil layer that is adhered to the adhesive layer is less than 20 μm.

10. A step of preparing the wiring forming member according to any one of claims 1 to 9; A step of preparing a substrate on which wiring is formed; a step of placing the wiring forming member on the surface of the base material on which the wiring is formed so as to cover the wiring, with the adhesive layer facing the base material; a step of thermocompressing the wiring forming member to the base material; A step of patterning the metal foil layer; A method for forming a wiring layer, comprising:

11. a substrate having wiring; a cured product of the wiring-forming member according to any one of claims 1 to 9, which is placed on the substrate so as to cover the wiring; Equipped with A wiring-forming member, wherein the wiring is electrically connected to the metal foil of the wiring-forming member or to another wiring formed from the metal foil.

Images