Resin film and method for manufacturing the same, as well as metallized resin film and printed circuit board

Abstract

The objective is to provide a novel resin film or the like that exhibits excellent solder resistance and adhesion. [Solution] The above problem can be solved by forming a resin film in which layer A, which contains polyimide resin and fumed metal oxide, is formed on at least one surface of layer B, which is a heat-resistant resin film with a coefficient of linear expansion of 20 ppm / °C or less, and the coefficient of linear expansion of the polyimide resin is 30 ppm / °C or more and 100 ppm / °C or less.

Description

Technical Field

[0001] The present invention relates to a resin film, a method for producing the same, a metallized resin film, and a printed wiring board.

Background Art

[0002] A printed wiring board having a circuit composed of metal conductors on an insulating substrate is widely used as a component for mounting various electronic components on the printed wiring board and realizing the functions of electronic devices. With the high functionality, high performance, and miniaturization of electronic devices, there is a demand for further narrowing the pitch of circuit wiring in printed wiring boards. Specifically, there is a demand for printed wiring boards in which narrow-pitch circuits are formed on flexible film portions such as (a) flexible printed wiring boards, (b) rigid-flex substrates, (c) multilayer flexible substrates, and (d) COF (chip-on-film) that can be compactly folded and housed inside electronic devices.

[0003] As a method for coping with narrow-pitch circuit formation, Patent Document 1 discloses a method of bonding a copper foil of a thin film with a carrier to a polyimide sheet.

[0004] Further, Patent Document 2 discloses a method of forming a metal layer on a polyimide film using physical vapor deposition methods such as vacuum evaporation, sputtering, and ion plating.

[0005] Further, Patent Document 3 discloses an example in which direct copper plating is performed by electroless plating on a material containing a polyimide resin containing a silicone structure and fumed silica.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

[0007] However, the conventional technologies described above were insufficient in terms of solder resistance and adhesion, and there was room for further improvement.

[0008] One embodiment of the present invention has been made in view of the above-mentioned problems, and its purpose is to provide a novel resin film with excellent solder resistance and adhesion, a method for manufacturing the same, and a metallized resin film and printed circuit board obtained from the resin film. [Means for solving the problem]

[0009] As a result of diligent research, the inventors have found that the above problems can be overcome.

[0010] In other words, in the resin film according to one embodiment of the present invention, layer A, which contains a polyimide resin and a fumed metal oxide, is formed on at least one surface of layer B, which is a heat-resistant resin film with a coefficient of linear expansion of 20 ppm / °C or less, and the coefficient of linear expansion of the polyimide resin is 30 ppm / °C or more and 100 ppm / °C or less.

[0011] Furthermore, in a method for manufacturing a resin film according to one embodiment of the present invention, layer A, which contains a polyimide resin and a fumed metal oxide, is formed on at least one surface of layer B, which is a heat-resistant resin film with a coefficient of linear expansion of 20 ppm / °C or less, wherein the coefficient of linear expansion of the polyimide resin is 30 ppm / °C or more and 100 ppm / °C or less, and layer A, which contains a polyimide resin and a fumed metal oxide, is obtained by mixing a polyamic acid solution, which is a precursor of the polyimide resin, with a fumed metal oxide, and imidizing the resulting fumed metal oxide-dispersed polyamic acid solution. [Effects of the Invention]

[0012] According to one embodiment of the present invention, a material and method that exhibits excellent solder heat resistance and can be used for forming narrow-pitch circuits can be provided. Specifically, a resin film capable of forming an electroless plating layer that exhibits excellent solder heat resistance and strong adhesion to a low-roughness surface, a method for manufacturing the same, a metallized resin film obtained from the resin film, and a printed circuit board can be provided. [Modes for carrying out the invention]

[0013] [Technical concept of one embodiment of the present invention] As a result of diligent research by the present inventors, we have found that the technologies described in the above-mentioned prior art documents 1 to 3 have the following areas for improvement or problems.

[0014] For example, in Patent Document 1, irregularities are intentionally formed on the surface of the copper foil to ensure adhesion between the insulating substrate and the copper foil. Therefore, although the copper layer thickness in Patent Document 1 is thinner than the limit for ordinary copper foil, there are adverse effects on the circuit shape during the etching process, there are limits to narrowing the pitch, and there are adverse effects on the transmission characteristics.

[0015] Furthermore, the technology described in Patent Document 2 involves forming metals such as nickel, chromium, vanadium, titanium, and molybdenum on the substrate surface by physical vapor deposition. However, according to the technology in Patent Document 2, simply etching with an etching solution for copper during circuit formation does not completely remove metals such as nickel, chromium, and titanium. To completely remove them, it is necessary to use a different etching solution, which presents a problem of a complicated process.

[0016] Furthermore, while Patent Document 3 discloses a resin film capable of forming an electroless plating layer on a low-roughness surface, there was room for improvement in terms of solder resistance and other properties.

[0017] The present invention has been made in view of the above problems, and an object thereof is to provide a novel resin film excellent in solder resistance and adhesion, a method for producing the same, a metallized resin film obtained from the resin film, and a printed wiring board. One embodiment of the present invention, for example, exhibits excellent solder heat resistance and can handle circuit formation with a narrow pitch. The object is to provide a material (resin film) and a method thereof, specifically, a resin film having excellent solder heat resistance and capable of forming an electroless plating layer showing strong adhesion to a low-roughness surface, and a method for producing the same. Another object of one embodiment of the present invention is to provide a metallized resin film and a printed wiring board obtained from the resin film.

[0018] 〔Resin film〕 In a resin film according to an embodiment of the present invention, a layer A containing a polyimide resin and a fumed metal oxide is formed on at least one surface of a heat-resistant resin film B having a linear expansion coefficient of 20 ppm / °C or less, and the linear expansion coefficient of the polyimide resin is 30 ppm / °C or more and 100 ppm / °C or less.

[0019] The resin film according to an embodiment of the present invention has the above configuration and thus has the advantage of being excellent in solder resistance and adhesion. As an example, in this specification, adhesion is evaluated by peel strength (N / cm), and solder resistance is evaluated by moisture absorption solder heat resistance.

[0020] The layer A containing a polyimide resin and a fumed metal oxide (sometimes referred to as layer A) will be described.

[0021] <Layer A (layer A) containing a polyimide resin and a fumed metal oxide> It is an essential requirement that the layer A in one embodiment of the present invention contains a polyimide resin and a fumed metal oxide. Further, with this configuration, the adhesion between the resin film and the electroless metal plating layer, particularly the adhesion in the state immediately after forming the electroless metal plating layer without performing heating or the like, can be greatly improved. The concept of the adhesion mechanism will be described below.

[0022] The electroless metal plating process consists of multiple independent chemical baths. These chemical baths are controlled under predetermined conditions (concentration, temperature, etc.), and the surface of the object to be plated is brought into contact with these chemicals for a predetermined time by methods such as immersion and showering, and chemical changes and possibly physical shape changes occur on the surface. These chemicals contain various components, and the pH also varies depending on the type of chemical, and there are chemicals showing strong alkalinity and strong acidity. On the other hand, both the polyimide resin and the fumed metal oxide essential to one embodiment of the present invention interact with these chemicals, causing changes in chemical structure and physical shape, and are considered to affect the improvement of adhesion to electroless metal plating. The fumed metal oxide and the polyimide resin both undergo chemical changes in an alkaline environment. For example, the fumed metal oxide dissolves in an alkaline environment to form an ionic metal oxide. For example, the polyimide resin forms an amido acid group showing ionic properties by the cleavage reaction of the imide ring in an alkaline environment. These ionic compounds (such as ionic metal oxides and amido acid groups showing ionic properties) react with metal ions in the electroless metal plating bath, and compounds derived from the three components of "fumed metal oxide" - "metal (e.g., copper)" - "polyimide resin" can be formed at the interface between the polyimide resin and the metal plating. It is considered that the said compound contributes to the adhesion, and as a result, the adhesion between the polyimide resin and the metal plating becomes high.

[0023] On the other hand, the dissolution rates of polyimide resin and fumed metal oxide in an alkaline environment are thought to be influenced by the chemical structure and aggregation structure of the polyimide resin, and the chemical structure and specific surface area of ​​the fumed metal oxide, respectively. When layer A, which contains polyimide resin and fumed metal oxide according to one embodiment of the present invention, is exposed to an alkaline environment, dissolution occurs according to the dissolution rates of the polyimide resin and fumed metal oxide, respectively. Layer A of one embodiment of the present invention has a structure in which the fumed metal oxide exists embedded in the polyimide resin phase. Therefore, when layer A of one embodiment of the present invention is exposed to an alkaline environment, fine irregularities of a similar size to the particle size of the fumed metal oxide are generated on the surface of layer A according to the dissolution rates of the polyimide resin and fumed metal oxide in alkaline chemicals, and as a result, the surface area of ​​layer A may increase. This increase in the surface area of ​​layer A is also thought to contribute to the improvement of adhesion strength.

[0024] Furthermore, the fumed metal oxide essential to one embodiment of the present invention has a structure in which primary particles are aggregated and exists embedded in the polyimide resin phase. In addition, it is believed that a portion of certain structural units of the fumed metal oxide essential to one embodiment of the present invention is exposed on the surface and / or near the surface, while the other portion exists in the bulk direction, and that these two are firmly bonded together, contributing to improved adhesion strength. In other words, it is believed that (i) the increased surface area of ​​the interface where compounds derived from the three components of "fumed metal oxide" - "metal (e.g., copper)" - "polyimide resin" exist, and (ii) the fumed metal oxide being embedded in the polyimide resin phase and firmly bonded together, contribute to the increased adhesion strength with electroless metal plating. It should be noted that the present invention is not limited in any way to the above-mentioned idea (speculation) regarding the mechanism of adhesion.

[0025] <Polyimide resin of layer A> Next, the polyimide resin used for layer A will be described. Polyimide resin is characterized by containing imide groups in its chemical backbone. It is believed that these imide groups (functional groups) in the polyimide resin interact with fumed metal oxides and metal elements (for example, copper), improving adhesion to the electroless metal plating layer. Therefore, for the adhesion effect of one embodiment of the present invention to be realized, it is an essential requirement that the polyimide resin contains imide groups. On the other hand, through diligent research, the inventors have independently discovered that the coefficient of linear expansion of the polyimide resin used for layer A affects adhesion, and specifically, good adhesion is observed when it is 30 ppm / °C or higher, leading to one embodiment of the present invention. In this specification, the coefficient of linear expansion of the polyimide resin is the coefficient of linear expansion in the plane direction when the polyimide resin used for layer A is made into a film, and reflects the degree of in-plane orientation of the polyimide molecular chains within layer A. A smaller coefficient of linear expansion of the polyimide resin indicates that the polyimide molecular chains are oriented in the plane direction, while a larger coefficient indicates that the polyimide molecular chains are also oriented in the thickness direction.

[0026] It is known that the coefficient of linear expansion of polyimide resin can be controlled by the type of monomer used. To reduce the coefficient of linear expansion of polyimide resin, it is effective to use monomers with a rigid chemical structure and to increase their composition ratio. By using monomers with a rigid chemical structure and increasing their composition ratio, when processed (molded) into a film, the polyimide molecular chains can be oriented in the planar direction, and furthermore, a state in which these molecular chains are deposited in the thickness direction can be formed.

[0027] As described above, the inventors have independently discovered that if the coefficient of linear expansion of the polyimide resin in layer A is too small, the adhesion between the resin film and the electroless metal plating layer decreases. The reason for this is not clear, but it is speculated that the following may be the case. When polyimide obtained from a monomer mixture using a monomer with a rigid chemical structure and a high proportion of the monomer is exposed to an alkaline chemical solution, the polyimide molecules near the surface are converted to polyamic acid through a cleavage reaction of the imide ring, and a state is formed in which polyamic acid molecules oriented in the planar direction are deposited in the thickness direction. The cohesive force between polyamic acid molecular chains is weaker than the cohesive force between polyimide molecular chains. Therefore, when an electroless metal plating layer (film) is formed on the surface of a film obtained by exposing the polyimide to an alkaline chemical solution and the adhesion is evaluated, it is speculated that peeling occurs at the interface where the polyamic acid molecular chains with weak cohesive force are broken in layers, and as a result, the adhesion strength between the film and the plating layer (film) tends to be low. However, the present invention is not limited in any way to this speculation.

[0028] Conversely, to increase the coefficient of thermal expansion of polyimide resin, it is effective to use monomers with flexible chemical structures and to increase their composition ratio. By using monomers with flexible chemical structures and increasing their composition ratio, when molded into a film, the polyimide molecular chains tend to be oriented not only in the planar direction but also in the thickness direction, that is, they tend to exhibit random orientation.

[0029] As described above, the inventors have independently discovered that when the linear expansion coefficient of the polyimide resin in layer A is large (for example, 30 ppm / °C or higher), the adhesion between the resin film and the electroless metal plating layer is enhanced. The reason for this is not clear, but it is speculated as follows: When polyimide obtained from a monomer mixture using a monomer with a flexible chemical structure and a high composition ratio of said monomer is exposed to an alkaline chemical solution, the polyimide molecules near the surface are converted to polyamic acid by the cleavage reaction of the imide ring. However, there are many covalent bonds in the polymer chain in the thickness direction as well, and therefore, a state of high cohesive force between molecular chains is maintained. Therefore, when an electroless metal plating film is formed on the surface of a film obtained by exposing the polyimide to an alkaline chemical solution and the adhesion is evaluated, it is speculated that, as described above, the linear expansion coefficient of the polyimide is small and layered delamination between polyamic acid molecular chains does not occur as in the case of polyimide with advanced in-plane molecular orientation, and as a result, the adhesion strength with the electroless metal plating tends to increase. It should be noted that the present invention is not limited in any way to this speculation.

[0030] Therefore, from the perspective of not reducing the cohesive force of the polyimide resin itself even when exposed to an alkaline chemical solution, it is preferable that the polyimide resin used in layer A is a polyimide resin that tends to have random orientation, that is, a polyimide resin that tends to have isotropic molecular orientation, rather than a polyimide resin that has advanced in-plane molecular orientation.

[0031] With respect to polyimide resins, there is a correlation between the degree of in-plane molecular orientation and the coefficient of linear expansion. With respect to polyimide resins, when the in-plane molecular orientation is highly advanced, and as a result the peel strength between the oriented polymer chains is also weakened, the coefficient of linear expansion becomes less than 30 ppm / °C. It is preferable that the polyimide resin used in layer A has a random orientation tendency, where the molecules are oriented not only in the plane direction but also in the thickness direction, which improves adhesion with electroless metal plating. The coefficient of linear expansion of the polyimide resin is preferably 30 ppm / °C or higher, more preferably greater than 30 ppm / °C, more preferably 35 ppm / °C or higher, even more preferably 40 ppm / °C or higher, even more preferably 45 ppm / °C or higher, and particularly preferably 50 ppm / °C or higher.

[0032] On the other hand, if the coefficient of linear expansion of the polyimide resin in layer A increases, the coefficient of linear expansion of the entire resin film of the present invention, composed of layers A and B, also tends to increase. When the resin film of the present invention is used for printed circuit boards, an increase in the coefficient of linear expansion of the entire resin film tends to worsen the dimensional accuracy required in the mounting process, which is undesirable. Furthermore, in the course of diligent research, the inventors have independently obtained the novel finding that, surprisingly, setting the coefficient of linear expansion of the polyimide resin to 100 ppm or less tends to result in excellent heat resistance, such as solder heat resistance, or in other words, excellent solder resistance. Therefore, the coefficient of linear expansion of the polyimide resin of layer A is preferably 100 ppm / °C or less, more preferably 90 ppm / °C or less, more preferably 80 ppm / °C or less, more preferably 75 ppm / °C or less, even more preferably 70 ppm / °C or less, even more preferably 65 ppm / °C or less, and particularly preferably 60 ppm / °C or less.

[0033] <Heat resistance, glass transition temperature, and high-temperature modulus of the polyimide resin in layer A> The linear expansion coefficient of the polyimide resin used in layer A is preferably 30 ppm / °C or higher, and more preferably higher than 30 ppm / °C. When the linear expansion coefficient of the polyimide resin increases, the polyimide resin tends to exhibit thermoplasticity. Thermoplastic resins soften when they reach a certain temperature, and this property can be used to process them, for example, by thermocompressing them with copper foil. From the perspective of improving adhesion with electroless metal plating, which is the objective of one embodiment of the present invention, thermoplasticity is not an essential requirement.

[0034] On the other hand, if we consider the use of the resin film of one embodiment of the present invention for printed circuit boards, it is preferable that the polyimide resin can withstand the high temperatures during the processing and the high temperatures during component mounting. Therefore, it is preferable that the polyimide resin used in layer A has a high glass transition temperature and high modulus of elasticity at high temperatures, and there is no particular disadvantage to it being too high. From the above viewpoint, it is preferable that the glass transition temperature of the polyimide resin, which is an indicator of heat resistance, be as high as possible, for example, preferably 180°C or higher, and more preferably 230°C or higher. Furthermore, in order to achieve good solder heat resistance, it is preferable that the polyimide resin used in layer A has a certain modulus of elasticity even near the melting point of solder. Specifically, the polyimide resin contained in layer A has a storage modulus of elasticity of 0.2 × 10⁻⁶ at 300°C. 8 It is preferable that it is Pa or higher, 0.5 × 10 8 It is more preferable that it be Pa or higher, 0.8 × 10 8 It is even more preferable that it be Pa or higher, 1.0 × 10 8 It is particularly preferable that the value be Pa or higher.

[0035] <Solubility of the polyimide resin in layer A> It is possible to manufacture a resin film of one embodiment of the present invention by using a soluble polyimide that is soluble in organic solvents as the polyimide resin for layer A. Specifically, a soluble polyimide can be dissolved in an organic solvent, a fumed metal oxide can be dispersed in the resulting solution, and the resulting dispersion can be applied to layer B, which is a heat-resistant resin film. Then layer B can be dried to obtain a resin film of one embodiment of the present invention. However, when using the resin film of one embodiment of the present invention for printed circuit boards, it is preferable that the polyimide resin used in layer A is insoluble so that problems such as resin dissolution do not occur in processes where organic solvents are used in the manufacturing and mounting processes of the printed circuit board. Furthermore, even if the polyimide resin is insoluble in organic solvents, it is even more preferable that it does not swell in organic solvents. On the other hand, it is preferable from the viewpoint of reliability that the polyimide resin of layer A and layer B, which is a heat-resistant resin film, are firmly adhered to each other. In order to improve the adhesion between the polyimide resin of layer A and layer B, it is preferable to contact the precursor of the polyimide resin of layer A (or a solution containing the precursor) with layer B and then imidize the precursor.

[0036] As described above, the polyimide resin used in layer A can be either soluble or insoluble to achieve one embodiment of the present invention, but it is preferably insoluble. In other words, it is preferable that the polyimide resin contained in layer A is an insoluble polyimide resin. By contacting a precursor of an insoluble polyimide resin (or a solution containing the precursor) with layer B, and then imidizing the precursor, a resin film of one embodiment of the present invention comprising a layer A containing an insoluble polyimide resin can be obtained. This makes it possible to obtain a resin film with excellent solvent resistance and excellent adhesion between layer A and layer B, and is therefore preferred.

[0037] The insolubility of polyimide resins will now be explained. In this specification, insolubility of a polyimide resin means that it does not dissolve in organic solvents commonly used in industrial applications. Specifically, it is preferable that the polyimide resin does not dissolve in organic solvents at 20°C to 30°C in an amount of 10% by weight or more, and more preferably insoluble in an amount of 5% by weight or more. Examples of organic solvents include, but are not limited to, alcohol-based solvents such as methanol, ethanol, and propanol; ketone-based solvents such as acetone and methyl ethyl ketone; aromatic solvents such as toluene, xylene, cresol, and benzene; ether-based solvents such as dioxolane, dioxane, tetrahydrofuran, and diethyl ether; and aprotic polar solvents such as N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and acetonitrile.

[0038] <Formulation of the polyimide resin in layer A> Next, we will explain the monomer species used in the polyimide resin used in layer A, the polymerization method, etc. The polyimide resin used in layer A must have a coefficient of thermal expansion of 30 ppm / °C or higher and 100 ppm / °C or lower. In addition, it is preferable to appropriately control other physical properties of the polyimide resin, such as its glass transition temperature, storage modulus at high temperatures, and solubility in organic solvents. One means of controlling these properties within an appropriate range is the selection of raw materials. Polyimide resin raw material monomers include monomers with flexible skeletons and monomers with rigid skeletons. By appropriately selecting these and further adjusting the blending ratio, it is possible to achieve the desired physical properties.

[0039] Examples of diamines with a flexible skeleton include 4,4'-oxydianiline, 3,3'-oxydianiline, 3,4'-oxydianiline, bis{4-(4-aminophenoxy)phenyl}sulfone, 2,2'-bis{4-(4-aminophenoxy)phenyl}propane, bis{4-(3-aminophenoxy)phenyl}sulfone, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, and 4,4'-diaminodi Phenylthioether, 3,4'-diaminodiphenylthioether, 3,3'-diaminodiphenylthioether, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 3,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenyl Nylsulfone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, 2,2-bis[4- Examples include (3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 4,4'-bis(4-aminophenoxy)biphenyl, and 4,4'-bis(3-aminophenoxy)biphenyl.

[0040] On the other hand, diamines with a rigid skeleton include 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1,2-diaminobenzene, benzidine, 3,3'-dichlorobenzidine, 3,3'-dimethylbenzidine, 2,2'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 2,2'-dimethoxybenzidine, 3,3'-dihydroxy-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)benzidine, 1,5-diaminonaphthalene, 4,4'-diaminobenzanilide, 3,4'-diaminobenzanilide, and 3,3'-diaminobenzanilide.

[0041] Of these, in terms of controlling thermal properties and being readily available industrially, one or more diamines selected from the group consisting of 4,4'-oxydianiline, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 3,3'-oxydianiline, 3,4'-oxydianiline, 1,3-bis(4-aminophenoxy)benzene, bis{4-(4-aminophenoxy)phenyl}sulfone, 2,2'-bis{4-(4-aminophenoxy)phenyl}propane, bis{4-(3-aminophenoxy)phenyl}sulfone, 1,3-bis(3-aminophenoxy)benzene, 3,3'-diaminobenzophenone, and 4,4'-diaminobenzophenone can be preferably used as diamines having a flexible skeleton. In particular, one or more selected from the group consisting of 4,4'-oxydianiline, 1,3-bis(4-aminophenoxy)benzene, and 2,2'-bis{4-(4-aminophenoxy)phenyl}propane may be preferably used. As diamines having a rigid skeleton, one or more selected from the group consisting of 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, and 2,2'-dimethylbenzidine may be preferably used because they exhibit the effect of hardening polymer chains in relatively small amounts and are readily available industrially. In particular, at least one of 1,4-diaminobenzene (p-phenylenediamine) and 2,2'-dimethylbenzidine may be preferably used. These diamines may be used individually or in combination of two or more.

[0042] Examples of tetracarboxylic dianhydrides with a flexible skeleton include 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,4'-oxydiphthalic anhydride, 4,4'-oxydiphthalic anhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)phthalic anhydride, 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride, and 2,2-bis(3,4-dicarboxyphenyl) Examples include propane dianhydride, bis(3,4-dicarboxyphenyl)propane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, p-phenylenebis(trimellitic acid monoester anhydride), ethylenebis(trimellitic acid monoester anhydride), and bisphenol A bis(trimellitic acid monoester anhydride).

[0043] On the other hand, examples of tetracarboxylic dianhydrides with a rigid skeleton include pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, and 3,4,9,10-perylenetetracarboxylic dianhydride.

[0044] Of these, one or more selected from the group consisting of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, and 4,4'-oxydiphthalic acid anhydride can be preferably used as tetracarboxylic acid dianhydride having a flexible skeleton, in terms of controllability of thermal properties and ease of industrial availability. Among these, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride is more preferred and can be effectively used to achieve a good balance of various desired physical properties in a preferred embodiment of the present invention, namely adhesion to electroless plating films, elastic modulus at high temperatures, glass transition temperature, and coefficient of linear expansion of polyimide resin. As a tetracarboxylic dianhydride having a rigid skeleton, pyromellitic dianhydride can be preferably used because it exhibits the effect of strengthening polymer chains in relatively small amounts and is readily available industrially. Two or more of these tetracarboxylic dianhydrides may also be used in mixture form.

[0045] Many aspects of the relationship between adhesion and the chemical structure of the polyimide resin of layer A in one embodiment of the present invention remain unclear, making a clear explanation difficult. Empirically, based on the diligent research conducted by the inventors, a combination of acid dianhydrides that reduce the polarization of the imide ring of the polyimide resin and diamines tends to exhibit good adhesion. Specifically, a combination of at least one of 4,4'-oxydiphthalic acid dianhydride and 3,3',4,4'-biphenyltetracarboxylic acid dianhydride as the acid dianhydride and 2,2'-bis(trifluoromethyl)benzidine as the diamine is effective. The preferred combination of diamine and acid dianhydride is not particularly limited. It is preferable to select one or more diamines from the group consisting of 2,2'-bis(trifluoromethyl)benzidine, 4,4'-oxydianiline, 1,3-bis(4-aminophenoxy)benzene, and 2,2'-bis{4-(4-aminophenoxy)phenyl}propane as the diamine, and at least one of 4,4'-oxydiphthalic acid dianhydride and 3,3',4,4'-biphenyltetracarboxylic acid dianhydride as the acid dianhydride, and further combine them with fumed metal oxides of an appropriate type and amount. This configuration (combination) can improve adhesion to the electroless metal plating layer of one embodiment of the present invention, and is particularly preferable as it can greatly improve the initial state after the formation of the electroless metal plating layer. Furthermore, in order to achieve a good balance of elastic modulus at high temperatures, glass transition temperature, coefficient of linear expansion, etc., it is also preferable to use other diamines and acid dianhydrides in combination with the preferred diamines and acid dianhydrides described above.

[0046] The polyamic acid, which is a precursor of the polyimide in layer A, is obtained by mixing the diamine and the acidic dianhydride in an organic solvent to a substantially equimolar or nearly equimolar extent and reacting them. Any organic solvent capable of dissolving polyamic acid can be used. Preferred organic solvents include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone, with at least one of N,N-dimethylformamide and N,N-dimethylacetamide being particularly preferred. The solid content concentration of the polyamic acid is not particularly limited, but a polyamic acid with sufficient mechanical strength when formed into polyimide can be obtained within the range of 5% to 35% by weight.

[0047] The order in which the diamine and acid dianhydride are added as raw materials is not particularly limited. The properties of the resulting polyimide can be controlled not only by controlling the chemical structures of the diamine and acid dianhydride, but also by controlling their addition order.

[0048] Furthermore, when 1,4-diaminobenzene and pyromellitic dianhydride are used as raw materials, the polyimide structure obtained by the bonding of the two has low durability against desmear solution. Therefore, it is preferable to adjust the order of addition of 1,4-diaminobenzene and pyromellitic dianhydride to prevent the formation of a structure in which the two are directly bonded.

[0049] Layer A may contain resins other than the polyimide resin described above as resin components. It is preferable that the polyimide resin content in the resin components of Layer A is high. For example, it is preferable that polyimide resin accounts for 50% or more by weight of 100% by weight of the resin components in Layer A, more preferably 60% or more by weight, more preferably 70% or more by weight, more preferably 80% or more by weight, even more preferably 90% or more by weight, and most preferably 95% or more by weight. It is most preferable that polyimide resin accounts for 100% by weight of the resin components in Layer A; in other words, it is most preferable that Layer A contains only polyimide resin as its resin component.

[0050] <Fumed Metal Oxides> The fumed metal oxide used in one embodiment of the present invention is a metal oxide mainly composed of silica, alumina, titania, etc. Preferably, the fumed metal oxide used in one embodiment of the present invention is a metal oxide obtained by gas-phase synthesis. When obtained by gas-phase synthesis, due to the characteristics of the manufacturing method, the resulting fumed metal oxide has the characteristic that its structural units are structures formed by the aggregation of primary particles. In other words, it is preferable that the fumed metal oxide has structural units formed by the aggregation of primary particles (for example, having an aggregated structure like a bunch of grapes). The fumed metal oxide is mixed with a polyimide resin to constitute layer A of one embodiment of the present invention. As a result of various studies by the inventors, it is preferable that layer A has the following conditions: (i) the structural units of the fumed metal oxide are embedded in the polyimide resin with low voids; (ii) the structural units exist from the surface and / or near the surface of layer A towards the bulk direction; and (iii) the structural units are uniformly present and dispersed within layer A. Such a state is considered effective in achieving the adhesion objective of one embodiment of the present invention. Unlike fumed metal oxides having an aggregated structure which are suitably used in one embodiment of the present invention, in the case of spherical or amorphous metal oxide particles (e.g., colloidal silica) in which primary particles exist independently, the binding force with polyimide resin tends to be weaker compared to fumed metal oxides, which is undesirable.

[0051] Furthermore, as long as layer A contains polyimide resin and fumed metal oxide, layer A may further contain spherical or amorphous metal oxide particles in which primary particles exist independently. It is preferable that the amount of metal oxide particles in layer A be as small as possible. For example, in layer A, it is preferable that the amount of metal oxide particles blended per 100 parts by weight of polyimide resin precursor be less than 10 parts by weight, more preferably 5 parts by weight or less, even more preferably 1 part by weight or less, even more preferably 0.5 parts by weight or less, and particularly preferably 0.1 parts by weight or less.

[0052] In the compounding of polyimide resin and fumed metal oxide, increasing the proportion of fumed metal oxide tends to increase the porosity in layer A. When the porosity in layer A is not too high, the bonding strength between the polyimide resin and the fumed metal oxide does not decrease, and the strength of layer A itself tends to be good, resulting in good adhesion to electroless metal plating, and furthermore, good adhesion between layer A and layer B. Therefore, in the compounding of polyimide resin and fumed metal oxide, it is preferable that the proportion of fumed metal oxide is not too high. Conversely, in the compounding of polyimide resin and fumed metal oxide, decreasing the proportion of fumed metal oxide tends to decrease the porosity. When the porosity in layer A is not too low, it is preferable that sufficient adhesion to electroless metal plating is easily achieved. This is thought to be because, because the proportion of fumed metal oxide is not too low, the amount of compounds derived from the three components "fumed metal oxide" - "metal (e.g., copper)" - "polyimide resin" is sufficient. Furthermore, the present invention is not limited to such speculation.

[0053] Therefore, to achieve good adhesion, it is preferable to control the blending ratio of polyimide resin to fumed metal oxide within an appropriate range. On the other hand, fumed metal oxides come in various grades with different primary particle sizes, structures formed by aggregated primary particles, and surface treatment types, and we believe that there is an appropriate blending ratio that also takes these factors into account.

[0054] <Primary particle size and specific surface area of ​​fumed metal oxides> In the electroless metal plating process, the chemicals partially dissolve the fumed metal oxide near the surface, but it is preferable that the surface roughness of layer A does not become excessively large even after dissolution. For this reason, it is preferable that the primary particle size of the fumed metal oxide is small, specifically, preferably 5 nanometers to 1,000 nanometers, more preferably 5 nanometers to 100 nanometers, even more preferably 5 nanometers to 50 nanometers, and even more preferably 10 nanometers to 20 nanometers. The specific surface area of ​​the fumed metal oxide is also a physical property that expresses the primary particle size, and the larger the primary particle size, the smaller the specific surface area. The specific surface area of ​​the fumed metal oxide is preferably 30 square meters / gram to 400 square meters / gram, and more preferably 100 square meters / gram to 250 square meters / gram.

[0055] <Apparent specific gravity of fumed metal oxides> Fumed metal oxides are structures formed by the aggregation of primary particle sizes, and apparent specific gravity can be used as an indicator of the structural state of fumed metal oxides. A low apparent specific gravity of fumed metal oxides indicates that the structure is bulky and has large voids. Conversely, a high apparent specific gravity indicates that the structure is less bulky and has small voids.

[0056] A layer A with a low porosity can be produced by filling the voids in the structure formed by the aggregation of primary particle sizes of fumed metal oxides with polyimide resin components. The lower the apparent specific gravity of the fumed metal oxide, the more voids there are in the structure of the fumed metal oxide, and the more polyimide resin components are used to fill these voids. The higher the apparent specific gravity of the fumed metal oxide, the more polyimide resin components are needed to fill the voids in the structure of the fumed metal oxide. Conversely, when producing a layer A with a low porosity by blending fumed metal oxides with a certain amount of polyimide resin, (i) if the fumed metal oxide has a low apparent specific gravity, the upper limit of the amount of fumed metal oxide that can be blended is lower, and conversely, (ii) if the fumed metal oxide has a high apparent specific gravity, a larger amount of fumed metal oxide can be blended, i.e., the upper limit of the amount of fumed metal oxide that can be blended is higher. As mentioned earlier, if the amount of fumed metal oxide is not too high, there is no risk of excessive voids forming in layer A. As a result, the bonding strength between the polyimide resin and the fumed metal oxide does not decrease, and the strength of layer A itself tends to be good, which in turn tends to result in good adhesion to electroless metal plating, and good adhesion between layer A and layer B. Therefore, when compounding polyimide resin with fumed metal oxide, it is preferable that the ratio of fumed metal oxide is not too high. Conversely, if the ratio of fumed metal oxide is not too low, it is easier to achieve sufficient adhesion to electroless metal plating. In other words, when compounding polyimide resin with fumed metal oxide, compounding the fumed metal oxide near the upper limit of the amount is effective in achieving good adhesion.

[0057] The upper limit of the amount of fumed metal oxide to be blended with a certain amount of polyimide resin to create layer A with a low porosity varies depending on the apparent specific gravity of the fumed metal oxide and the type of surface treatment. In other words, by adjusting the amount of fumed metal oxide blended with a certain amount of polyimide resin according to the apparent specific gravity of the fumed metal oxide and the type of surface treatment, adhesion can be further improved. In one embodiment of the present invention, the apparent specific gravity of the fumed metal oxide is preferably 20 grams / liter or more and 250 grams / liter or less, and more preferably 20 grams / liter or more and 220 grams / liter or less. Furthermore, the higher the apparent specific gravity of the fumed metal oxide, the higher the upper limit of the amount of fumed metal oxide blended, and the more the adhesion tends to improve. Therefore, it is more preferable that the apparent specific gravity of the fumed metal oxide is greater than 50 grams / liter and 250 grams / liter or less, more preferably 60 grams / liter or more and 250 grams / liter or less, even more preferably 70 grams / liter or more and 250 grams / liter or less, and even more preferably 70 grams / liter or more and 220 grams / liter or less. Furthermore, the apparent specific gravity of the fumed metal oxide can also be changed by structural modification of the fumed metal oxide by applying mechanical stress such as shear to the fumed metal oxide.

[0058] Various surface treatments are possible for fumed metal oxides. Examples of fumed metal oxide surface states include silanol (untreated), dimethylsilyl, octylsilyl, trimethylsilyl, dimethylsiloxane, dimethylpolysiloxane, aminoalkylsilyl, and methacrylatesilyl, all of which are industrially available. When the polarity of the fumed metal oxide surface treatment is similar to that of the polyimide resin component, the upper limit of the fumed metal oxide blending amount tends to increase. Furthermore, if the fumed metal oxide is untreated, its wettability with the alkaline chemicals in the electroless metal plating process is too high, leading to a high dissolution rate of the fumed metal oxide and a tendency for the surface roughness of layer A to increase. Therefore, it is preferable that the surface of the fumed metal oxide be treated with an appropriate hydrophobic treatment. The apparent specific gravity of the fumed metal oxide can be measured according to ISO 787 / XI.

[0059] <Specific examples of fumed metal oxides> The following are specific examples of fumed metal oxides that can be preferably used in one embodiment of the present invention, but are not limited to these. Fumed metal oxides that satisfy the requirements of various properties, including apparent specific gravity, can be more preferably used in one embodiment of the present invention. Fumed metal oxides of various grades with different primary particle size, specific surface area, surface treatment type, apparent specific gravity, and metal oxide type are available from Nippon Aerosil Co., Ltd., Asahi Kasei Wacker Silicone Co., Ltd., and Cabot Co., Ltd., and can be preferably used. The following will be a specific example using fumed metal oxides from Nippon Aerosil Co., Ltd. Aerosil R972, R972CF, R972V, etc., which are substantially equivalent except for apparent specific gravity, can be preferably used, and among these, R972 (50 grams / liter), which has a high apparent specific gravity, can be more preferably used. Similarly, Aerosil R974, R9200, VP RS920, etc., which are equivalent except for apparent specific gravity, can be preferably used, and among these, Aerosil R9200 (200 grams / liter) and Aerosil VP RS920 (80 grams / liter to 120 grams / liter), which have high apparent specific gravity, can be more preferably used. In addition to these, as fumed metal oxides manufactured by Nippon Aerosil Co., Ltd., which have a relatively low apparent specific gravity of 70 grams / liter or less, which is one of the preferred physical properties of one embodiment of the present invention, Aerosil NX130, RY200S, R976, NAX50, NX90G, NX90S, RX200, RX300, R812, R812S, etc. can be preferably used. Furthermore, fumed metal oxides manufactured by Nippon Aerosil Co., Ltd. with a relatively high apparent specific gravity of 70 grams / liter or more, such as Aerosil 200V, AEROIDE TiO2 P90, AEROIDE TiO2 NKT90, OX50, RY50, RY51, AEROIDE TiO2 P25, R8200, RM50, RX50, AEROIDE TiO2 T805, and R7200, can also be preferably used. Note that Aerosil VP RS920 has been sold under the name "Aerosil E9200" since November 2021. Furthermore, "Aerosil" or "AEROSIL" is a registered trademark of Evonik Operations GmbH. Additionally, fumed metal oxides synthesized by gas-phase synthesis, which have a structure in which the primary particle size is aggregated, are preferably used.

[0060] Among these fumed metal oxides, fumed silicas such as Aerosil R972, 972V, NX130, R9200, VP RS920, R974, R976, and R8200 are preferred because they have a good surface shape for layer A formed by dissolution in an alkaline environment, and their surface roughness is within an appropriate range.

[0061] <Percentage of fumed metal oxide in the formulation> It is preferable that layer A, which contains a polyimide resin and a fumed metal oxide, is an imidized product of a mixture of the precursor of the polyimide resin and the fumed metal oxide (for example, a fumed metal oxide-dispersed polyamic acid solution described later). Specifically, a resin film according to one embodiment of the present invention can be obtained by mixing the fumed metal oxide with a polyamic acid solution which is a precursor of the polyimide resin constituting layer A, (a) applying the obtained mixture to a heat-resistant film of layer B, drying layer B, and imidizing the mixture, (b) applying the obtained mixture to a precursor film of layer B, drying the film, and imidizing the mixture, or (c) co-extruding the obtained mixture with the resin precursor solution of layer B or the resin solution of layer B, drying the obtained extruded product, and imidizing the mixture.

[0062] It is preferable that the amount of fumed metal oxide blended in layer A is 10 parts by weight or more and 130 parts by weight or less per 100 parts by weight of the polyimide resin precursor. As mentioned above, the preferred blending amount of fumed metal oxide to the polyimide precursor (polyimide resin) in layer A can be adjusted to some extent by the apparent specific gravity of the fumed metal oxide, but due to the influence of the surface treatment of the fumed metal oxide, etc., it is not possible to say anything definitive. Here, as an indicator, the preferred blending amount of fumed metal oxide is described.

[0063] When the apparent specific gravity of the fumed metal oxide is 20 grams / liter or more and 70 grams / liter or less, the amount of fumed metal oxide blended (relative to the solid content of the polyimide (precursor) resin) is preferably 15 to 80 parts by weight, and more preferably 20 to 60 parts by weight, per 100 parts by weight of the polyimide resin precursor.

[0064] When the apparent specific gravity of the fumed metal oxide is 70 grams / liter or more and 250 grams / liter or less, the amount of fumed metal oxide blended (relative to 100 parts by weight of polyimide (precursor) resin solids) is preferably 10 parts by weight or more and 130 parts by weight or less, more preferably 15 parts by weight or more and 120 parts by weight or less, and even more preferably 20 parts by weight or more and 100 parts by weight or less.

[0065] As described above, the preferred blending amount varies depending on the apparent specific gravity of the fumed metal oxide. The higher the apparent specific gravity of the fumed metal oxide, the greater the blending amount that can be used, and the greater the preferred blending amount tends to be. By blending the fumed metal oxide within the above range with 100 parts by weight of the polyimide resin precursor, it is possible to achieve better adhesion strength, and in particular, stronger adhesion in the initial state after the formation of the electroless plating film. It is also possible to mix (combine) multiple types of fumed metal oxides with different primary particle sizes, specific surface areas, surface treatment types, apparent specific gravity, and metal oxide types.

[0066] <Fumed metal oxide dispersed polyamic acid solution> To obtain layer A of one embodiment of the present invention, it is preferable to mix and disperse a precursor solution of the polyimide resin of layer A with a fumed metal oxide to obtain a fumed metal oxide-dispersed polyamic acid solution (hereinafter sometimes referred to as layer A dispersion). Layer A can be obtained by imidizing this layer A dispersion. In other words, it is preferable that layer A is an imidized product of a mixture of the polyimide resin precursor and the fumed metal oxide. This configuration has the advantage of improving the adhesion between layer A and layer B. The procedure for obtaining the layer A dispersion is described below in detail, but the embodiment of the present invention is not limited thereto.

[0067] (1) An organic solvent is added to the fumed metal oxide to disperse the fumed metal oxide in the organic solvent to the structural units of a structure in which primary particles have aggregated. Dispersion methods include dispersers, homogenizers, planetary mixers, bead mills, rotary mixers, rolls, kneaders, high-pressure dispersers, ultrasonics, resolvers, etc. However, it is not necessary to disperse the fumed metal oxide to the structural units in the organic solvent as long as the effects of the present embodiment are obtained. However, if the fumed metal oxide is dispersed to the structural units, the fumed metal oxide will not exist in solid form in layer A, and in that case, the surface roughness of layer A will be small, which is advantageous for the fine wiring formation properties that are the aim of the present embodiment and is therefore preferable. It is also possible to disperse and grind the fumed metal oxide under conditions that further reduce the size of the structural units. The organic solvent can be a solvent used for the polymerization of polyamic acid, and amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone can be preferably used, but are not limited to these.

[0068] (2) The liquid obtained in (1) and the precursor solution of the polyimide resin of layer A are mixed and stirred in a desired ratio to obtain a layer A dispersion. If the fumed metal oxide is already dispersed in the organic solvent in step (1), the layer A dispersion can be obtained by mixing the liquid obtained in (1) and the precursor solution and then stirring or other methods. Alternatively, the layer A dispersion can be obtained not only by stirring but also by using the various dispersion methods described in (1).

[0069] The final concentration of the resulting Layer A dispersion is not particularly limited, but it is preferable to have a concentration and viscosity suitable for the next process. Organic solvents can be used as appropriate to adjust the concentration and viscosity of the Layer A dispersion. Furthermore, amines for the purpose of imparting adhesion to Layer B, dehydrating agents for the imidation reaction of polyamic acid, catalysts, etc., may be added to the Layer A dispersion.

[0070] Furthermore, fillers may be added to the layer A dispersion to improve various film properties such as sliding properties, thermal conductivity, electrical conductivity, corona resistance, and loop stiffness. Any filler can be used, but preferred examples include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, and mica.

[0071] Furthermore, thermosetting resins such as epoxy resins and phenoxy resins, and thermoplastic resins such as polyether ketones and polyether ether ketones may be used, as long as the overall properties of the resulting resin layer are not impaired. Methods for adding these resins include adding them to the polyamic acid if they are soluble in the solvent. If the polyimide is also soluble, it may be added to the polyimide solution. A dispersion of layer A can be obtained by following these steps.

[0072] <Layer B> Layer B, which is a heat-resistant resin film of one embodiment of the present invention, has layer A formed on one or both sides thereof. From the viewpoint of dimensional stability when the resin film of one embodiment of the present invention is used for printed circuit board applications, the coefficient of linear expansion of layer B is preferably 20 ppm / °C or less. The resin composition of layer B is not particularly limited, but liquid crystal polymer films, resin films containing reinforcing fibers, resin films containing inorganic fillers, and polyimides are preferred. From the viewpoint of heat resistance, flexibility, etc., layer B is more preferably a film containing (or made of) polyimide, and even more preferably a film containing (or made of) non-thermoplastic polyimide.

[0073] It is known that the coefficient of linear expansion of polyimide resin films can be controlled by the type of monomer used. To reduce the coefficient of linear expansion of a polyimide resin film, it is effective to use monomers with a rigid chemical structure and to increase their composition ratio. By using monomers with a rigid chemical structure and increasing their composition ratio, when the film is molded (processed), the polyimide molecular chains may be oriented in the planar direction, and furthermore, a state in which molecular chains are deposited in the thickness direction may be formed. Conversely, to increase the coefficient of linear expansion of a polyimide resin film, it is effective to use monomers with a flexible chemical structure and to increase their composition ratio. By using monomers with a flexible chemical structure and increasing their composition ratio, when the film is molded, the polyimide molecular chains tend to be oriented not only in the planar direction but also in the thickness direction, that is, they tend to exhibit random orientation. When a non-thermoplastic polyimide film is used for layer B, there are no particular limitations on the diamine used in the production of the non-thermoplastic polyimide film, but the coefficient of linear expansion of the final polyimide film must be 20 ppm / °C or less. Therefore, in the production of non-thermoplastic polyimide films, it is preferable to appropriately combine and use rigid diamines and flexible diamines in accordance with the structure of the acid dianhydride.

[0074] Examples of rigid diamines suitable for use in the production of non-thermoplastic polyimide films include 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diamino-3,3'-dimethylbiphenyl, 4,4'-diamino-3,3'-dihydroxybiphenyl, 1,4-diaminobenzene, 1,3-diaminobenzene, and 4,4'-bis(4-aminophenoxy)biphenyl 4,4'-diaminobenzanilide.

[0075] Examples of flexible diamines suitably used in the production of non-thermoplastic polyimide films include 4,4'-diaminodiphenyl ether, 2,2-bis{4-(4-aminophenoxy)phenyl}propane, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, and 1,3-bis(3-aminophenoxy)benzene. In the production of non-thermoplastic polyimide films, the diamines listed when describing the polyimide resin of layer A can also be used as appropriate.

[0076] When a non-thermoplastic polyimide film is used for layer B, the acid dianhydride used in the production of the non-thermoplastic polyimide film is not particularly limited, however, the coefficient of thermal expansion of the final polyimide must be 20 ppm / °C or less. Therefore, in the production of the non-thermoplastic polyimide film, it is preferable to appropriately combine rigid and flexible acid dianhydrides in accordance with the structure of the diamine. Specific rigid acid dianhydrides suitable for use in the production of non-thermoplastic polyimide films include 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and pyromellitic acid dianhydride. Flexible acid dianhydrides suitable for use in the production of non-thermoplastic polyimide films include 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride and 4,4'-oxydiphthalic acid dianhydride. In the production of the non-thermoplastic polyimide film, it is also possible to use the acid dianhydrides listed when describing the polyimide resin of layer A as appropriate.

[0077] Polyamic acid, a precursor of polyimide, is obtained by mixing the diamine and the acidic dianhydride in an organic solvent in a substantially equimolar or nearly equimolar manner and reacting them. Any organic solvent capable of dissolving polyamic acid can be used. Preferred organic solvents include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone, with at least one of N,N-dimethylformamide and N,N-dimethylacetamide being particularly preferred. The solid content concentration of the polyamic acid is not particularly limited; a concentration within the range of 5% to 35% by weight will yield a polyamic acid with sufficient mechanical strength when formed into polyimide.

[0078] The order in which the diamine and acid dianhydride are added as raw materials is not particularly limited. The properties of the resulting polyimide can be controlled not only by controlling the chemical structures of the diamine and acid dianhydride, but also by controlling their addition order.

[0079] Fillers may be added to the polyamic acid to improve various film properties such as sliding properties, thermal conductivity, electrical conductivity, corona resistance, and loop stiffness. Any filler can be used, but preferred examples include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, and mica.

[0080] Furthermore, thermosetting resins such as epoxy resins and phenoxy resins, and thermoplastic resins such as polyether ketones and polyether ether ketones may be used, as long as they do not impair the overall properties of the resulting resin layer. Methods for adding these resins include adding them to the polyamic acid if they are soluble in the solvent. If the polyimide is soluble, it may also be added to the polyimide solution. If the polyimide is insoluble in the solvent, a method may be used in which the polyamic acid is first imidized, and then the polyimide obtained by imidization and the further added solvent-insoluble polyimide are compounded by melt kneading. However, since the solder heat resistance and / or heat shrinkage rate of the resulting flexible metal-clad laminate may deteriorate, it is desirable not to use soluble polyimides in one embodiment of the present invention. Therefore, it is desirable to use a soluble resin when mixing with the polyimide.

[0081] A method for obtaining a non-thermoplastic polyimide film preferably used in layer B of one embodiment of the present invention preferably includes the following steps (i) to (iv). (i) A step of reacting an aromatic diamine with an aromatic tetracarboxylic dianhydride in an organic solvent to obtain a polyamic acid solution, (ii) A step of casting the film-forming dope containing the polyamic acid solution onto a support, (iii) After heating the film-forming dope on the support, peel off the gel film obtained from the support, (iv) A step of further heating the gel film to imidize the polyamic acid remaining in the gel film and to dry it.

[0082] (ii) The methods for the subsequent steps are broadly classified into thermal imidation and chemical imidation. Thermal imidation is a method in which a polyamic acid solution is cast onto a support as a film-forming dope and imidation is carried out by heating alone, without using dehydrating ring-closing agents or the like. Chemical imidation, on the other hand, is a method in which a polyamic acid solution to which at least one of a dehydrating ring-closing agent and a catalyst is added as an imidation accelerator is used as a film-forming dope to promote imidation. Either method may be used, but chemical imidation is superior in productivity.

[0083] As dehydrating ring-closing agents, acid anhydrides such as acetic anhydride can be suitably used. As catalysts, tertiary amines such as aliphatic tertiary amines, aromatic tertiary amines, and heterocyclic tertiary amines can be suitably used.

[0084] Suitable supports for casting the film-forming dope include glass plates, aluminum foil, endless stainless steel belts, and stainless steel drums. Heating conditions are set according to the final film thickness and / or production rate. After partially imidizing or drying the film-forming dope, the imidized material is peeled off the support to obtain a polyamic acid film (hereinafter referred to as a gel film).

[0085] The gel film is dried while fixing its edges to prevent shrinkage during curing, and water, residual solvent, and imidization accelerator are removed from the gel film. The remaining amide acid in the gel film is then completely imidized to obtain a polyimide-containing film. The heating conditions can be appropriately set according to the final film thickness and / or production rate.

[0086] Furthermore, it is preferable to use an industrially available polyimide film as layer B in one embodiment of the present invention. Examples of commercially available polyimide films that can be used as layer B include, for example, "Apical" (manufactured by Kaneka), "Kapton" (manufactured by DuPont and Toray DuPont), and "Upirex" (manufactured by Ube Industries).

[0087] The resin film according to one embodiment of the present invention may be in the following forms: Including layer A and layer B, The aforementioned layer A comprises a polyimide resin and a fumed metal oxide. The aforementioned layer B includes a heat-resistant resin film having a coefficient of linear expansion of 20 ppm / °C or less, or is said to be the heat-resistant resin film. The aforementioned layer A is formed on at least one surface of the aforementioned layer B, A resin film in which the linear thermal expansion coefficient of the polyimide resin is 30 ppm / °C or more and 100 ppm / °C or less.

[0088] <Method for manufacturing a resin film including layers A and B> A method for producing a resin film according to one embodiment of the present invention is to form a layer A containing a polyimide resin and a fumed metal oxide on at least one surface of a heat-resistant resin film B having a coefficient of linear expansion of 20 ppm / °C or less, wherein the coefficient of linear expansion of the polyimide resin is 30 ppm / °C or more and 100 ppm / °C or less, and the layer A containing the polyimide resin and the fumed metal oxide is obtained by mixing a polyamic acid solution of a precursor of the polyimide resin with the fumed metal oxide, and imidizing the resulting fumed metal oxide-dispersed polyamic acid solution.

[0089] A method for manufacturing a resin film according to one embodiment of the present invention may be in the following forms: A method for manufacturing a resin film, Step 1 involves mixing a polyamic acid solution, a precursor of polyimide resin, with a fumed metal oxide. The process includes step 2 of imidizing the fumed metal oxide-dispersed polyamic acid solution obtained in step 1, The aforementioned resin film is Including the aforementioned layer A and the aforementioned layer B, The aforementioned layer A comprises the polyimide resin and the fumed metal oxide, The aforementioned layer B includes a heat-resistant resin film having a coefficient of linear expansion of 20 ppm / °C or less, or is said to be the heat-resistant resin film. The aforementioned layer A is formed on at least one surface of the aforementioned layer B, A method for manufacturing a resin film, wherein the linear thermal expansion coefficient of the polyimide resin is 30 ppm / °C or more and 100 ppm / °C or less.

[0090] Step 1 and the fumed metal oxide-dispersed polyamic acid solution obtained in Step 1 are the same as those described in the section on <Fumed Metal Oxide-Dispersed Polyamic Acid Solution>, so that description will be referenced and the explanation will be omitted here. The preferred embodiment described in the section on <Fumed Metal Oxide-Dispersed Polyamic Acid Solution> is also a preferred embodiment for Step 1 and the fumed metal oxide-dispersed polyamic acid solution obtained in Step 1.

[0091] The resin film of one embodiment of the present invention includes layer A and layer B. The resin film of one embodiment of the present invention is composed of layer A and layer B. Layer B of one embodiment of the present invention must be a heat-resistant resin film having a coefficient of linear expansion of 20 ppm / °C or less. Examples of layer B, i.e., the heat-resistant resin film, include liquid crystal polymer films, resin films containing reinforcing fibers, resin films containing inorganic fillers, industrially available polyimide films, and non-thermoplastic polyimide films manufactured through steps (i) to (iv) above. It is preferable to apply the layer A dispersion obtained in step 1 to the surface of these heat-resistant resin films (layer B), dry the layer A dispersion, and imidize it to obtain the resin film of one embodiment of the present invention.

[0092] Alternatively, a resin film of one embodiment of the present invention having multiple layers may be obtained by using a co-extrusion die having multiple channels in step (ii) above. Furthermore, a resin film of one embodiment of the present invention may be obtained by coating the surface of the gel film in step (iii) above with the layer A dispersion, drying both the gel film and layer A simultaneously, and imidizing them. In either case, the heating conditions may affect various film properties and / or adhesion to the electroless metal plating layer. Therefore, it is preferable to set appropriate heating temperatures and heating times. It is also preferable to set appropriate heating conditions depending on the chemical structure, concentration, solvent type of the polyamic acid contained in the layer A dispersion and / or the final thickness of layer A, and it is not possible to describe generally suitable heating conditions. For example, let's assume the thickness of layer A is 10 microns or less. In this case, it is preferable to imidize the Layer A dispersion, etc. by performing the following (1) to (3) (however, (2) may be performed as needed): (1) Dry the Layer A dispersion, etc. at a relatively low heating temperature, i.e., a heating temperature of 100°C to 200°C for 1 minute to 5 minutes; (2) Subsequently, heat the Layer A dispersion, etc. at a temperature of 200°C to 300°C as needed; (3) As a final heating condition, heat the Layer A dispersion, etc. at a temperature of 300°C to 500°C for 1 minute to 5 minutes.

[0093] There are two main methods for imidization in step 2: thermal imidization and chemical imidization. For imidization of the fumed metal oxide-dispersed polyamic acid solution (layer A dispersion), it is preferable to use thermal imidization, which proceeds with imidization solely by heating without the use of dehydrating ring-closing agents or the like.

[0094] Layer A has the function of adhering to the electroless metal plating layer. It is assumed that a copper-clad laminate is manufactured by laminating copper foil to this layer A. In this case, it is preferable that the adhesive layer has a thickness sufficient to grip the surface irregularities of the roughened surface of the copper foil. However, in one embodiment of the present invention, since layer A obtains a metal layer by depositing the electroless metal plating layer on its surface, the adhesion to the electroless metal plating layer can be achieved even if the thickness of layer A is relatively thin. From the viewpoint of forming layer A industrially stably, it is preferable that layer A has a thickness of 0.1 microns or more and 30 microns or less, and more preferably 1 micron or more and 10 microns or less. On the other hand, when the resin film of one embodiment of the present invention is used in a printed circuit board, it is preferable to appropriately design the coefficient of linear expansion, thereby making it possible to control warping due to temperature changes in the composite with the conductor layer including the electroless metal plating layer. The coefficient of linear expansion of the resin film of one embodiment of the present invention can be controlled by considering parameters such as the thickness of layer A, the coefficient of linear expansion of layer A alone, the thickness of layer B, and the coefficient of linear expansion of layer B alone. By considering the aforementioned parameters, it is preferable and feasible to match, for example, the coefficient of linear expansion of the copper in the conductive layer with the coefficient of linear expansion of the resin film in one embodiment of the present invention.

[0095] <Electroless metal plating> An electroless metal plating layer can be formed on the surface of layer A of a resin film according to one embodiment of the present invention. By forming an electroless metal plating layer on the surface of layer A, a metallized resin film can be obtained. A metallized resin film having an electroless metal plating layer formed on the surface of layer A is also one embodiment of the present invention. The electroless metal plating layer (film) obtained by electroless metal plating can be made thinner than that of general copper foil. The thickness of the electroless metal plating layer is preferably 0.01 microns to 10.00 microns, more preferably 0.10 microns to 2.00 microns, and even more preferably 0.20 microns to 1.00 microns.

[0096] In one embodiment of the present invention, electroless metal plating preferably utilizes a reduction-type electroless plating that employs a chemical reaction. Examples of metals used for electroless metal plating include copper, nickel, gold, and silver, all of which are applicable to this embodiment. Of these, electroless copper plating and electroless nickel plating are preferred, and among these, electroless copper plating is the most preferred due to its widespread and common use as a process for making the insulating resin surface of through-holes and via walls of printed circuit boards conductive. In other words, it is preferable that the electroless metal plating in this embodiment is electroless copper plating. For electroless copper plating processes widely used for printed circuit boards, the chemical solutions processes of various plating chemical manufacturers can be utilized. Furthermore, desmearing is also commonly performed before electroless copper plating. Desmearing is primarily performed to remove smear generated on the copper surface during the through-hole formation process and the laser via formation process. Desmearing also chemically alters the surface of the resin film in this embodiment and is therefore preferable. Both the desmearing process and the electroless copper plating process are carried out by sequentially treating the object to be plated with multiple chemical solutions. For example, the desmear process consists of chemicals responsible for swelling, etching, and reduction. Similarly, the electroless copper plating process consists of a series of chemicals, each performing a specific role, such as cleaning and conditioning, soft etching, pre-dipping, catalyst application, activation, and electroless copper plating. These series of processes can utilize chemical processes from various plating chemical manufacturers. For example, chemicals from Atotec, Adcopper IW from Okuno Pharmaceutical Co., Ltd., Surupap PEA from Uemura Industries Co., Ltd., chemicals from Rohm & Haas Electronic Materials Co., Ltd., and chemicals from Meltex Co., Ltd. are all applicable and can be combined as needed. While these electroless copper plating solutions may contain trace amounts of nickel, they can be used within limits that do not impair the effects of one embodiment of the present invention.Furthermore, when electroless plating is applied to layer A, electroless plating may be applied directly to layer A, or pretreatment such as alkaline treatment or desmear treatment may be applied to layer A before electroless plating is applied to the pretreated layer A. Examples of alkaline aqueous solutions for alkaline treatment include aqueous sodium hydroxide solution and aqueous potassium hydroxide solution.

[0097] In one embodiment of the present invention, the aim is to achieve sufficient adhesion between the resin film and the electroless metal plating in a metallized resin film obtained by performing only an electroless metal plating layer formation process (electroless metal plating process) on a resin film. If the adhesion is low, problems such as the circuit peeling off from the resin film substrate may occur in the subsequent circuit formation process. In order to improve the adhesion between the resin film and the electroless metal plating in a metallized resin film, the metallized resin film is sometimes heated to a temperature of 150°C or higher after the electroless plating process to improve the adhesion. However, when heating a metallized resin film, (a) the process is complicated, (b) surface oxidation of the electroless metal plating layer caused by heating may cause adverse effects and problems in subsequent processes, and (c) even if heated, a sufficient adhesion improvement effect may not be achieved. In one embodiment of the present invention, good adhesion can be obtained even without high-temperature heating of the metallized resin film, and it also has heat resistance for use as a printed circuit board. In other words, when we say that a resin film according to one embodiment of the present invention has excellent adhesion, it means that, at a minimum, for a metallized resin film obtained by forming an electroless metal plating layer on the surface of layer A of a resin film, the electroless metal plating layer in the metallized resin film exhibits excellent peel strength (for example, exhibits a peel strength of 3 N / cm or more) without performing a heat treatment of 150°C or higher on the metallized resin film. In this specification, the peel strength of the electroless metal plating layer in a metallized resin film obtained by forming an electroless metal plating layer on the surface of layer A of a resin film, and which has not been subjected to a heat treatment of 150°C or higher, may be referred to as "initial peel strength". In one embodiment of the present invention, it is preferable that, for a metallized resin film obtained by forming an electroless metal plating layer on the surface of layer A of a resin film, the electroless metal plating layer in the metallized resin film exhibits a peel strength of 3 N / cm or more, more preferably 5 N / cm or more, without performing a heat treatment of 150°C or higher on the metallized resin film.In one embodiment of the present invention, it is preferable that the metallized resin film exhibits a peel strength of 3 N / cm or more, more preferably 5 N / cm or more, without performing a heat treatment of 150°C or higher after forming the electroless metal plating layer.

[0098] Furthermore, when a substrate (resin film) is made conductive by electroless metal plating, even if good adhesion strength is achieved when there is no circuit pattern on the back surface of the substrate (resin film), sufficient adhesion strength may not be achieved when there is a circuit pattern on the back surface of the substrate (resin film). In a preferred embodiment of the present invention, good adhesion can be obtained regardless of the presence or absence of a circuit pattern on the back surface, even without heating the metallized resin film to a high temperature, and it also has heat resistance for use as a printed circuit board. In other words, although not essential, it is preferable that the electroless metal plating layer in the metallized resin film obtained by forming electroless metal plating layers on both sides of layer A of the resin film exhibits excellent peel strength (for example, exhibiting a peel strength of 3 N / cm or more) without heat treatment of 150°C or higher on the metallized resin film. In one embodiment of the present invention, it is preferable that the electroless metal plating layer in the metallized resin film obtained by forming electroless metal plating layers on both sides of layer A of a resin film exhibits a peel strength of 3 N / cm or more, more preferably 5 N / cm or more, without performing a heat treatment of 150°C or higher on the metallized resin film. In one embodiment of the present invention, it is preferable that the metallized resin film exhibits a peel strength of 3 N / cm or more, more preferably 5 N / cm or more, after forming the electroless metal plating layers on both sides, without performing a heat treatment of 150°C or higher.

[0099] Furthermore, in one embodiment of the present invention, a metallized resin film obtained by forming an electroless metal plating layer on the surface of layer A of a resin film can obtain sufficient adhesion even when dried at room temperature without active heating. If the metallized resin film obtained after the electroless metal plating layer formation process is wet with a cleaning solution such as water, problems may occur in the next process, such as the lamination process of a dry film resist. For this reason, a heat drying treatment for the purpose of drying is preferably performed on the metallized resin film obtained by the electroless metal plating layer formation process. The heating temperature in the heat drying treatment is preferably 150°C or less, more preferably less than 150°C, and even more preferably 100°C or less. The heating time in the heat drying treatment is preferably 30 minutes or less, and even more preferably 10 minutes or less. By heating and drying the metallized resin film under mild conditions within the above range, it is possible to suppress the oxidation of the electroless metal plating to a level that does not pose a practical problem, and at the same time, good adhesion can be obtained. For this reason, a heat drying treatment of the metallized resin film under mild conditions within the above range is preferably performed.

[0100] In order to suppress the peeling of circuit patterns during the circuit formation process in the manufacturing of printed circuit boards, it is preferable that the metallized resin film obtained by only performing an electroless metal plating layer formation treatment on a resin film (a metallized resin film that has not undergone heat treatment of 150°C or higher) has sufficient adhesion. The peel strength (initial peel strength) of the metallized resin film is preferably 3 N / cm or higher, more preferably 5 N / cm or higher, even more preferably 6 N / cm or higher, and even more preferably 7 N / cm or higher.

[0101] <Printed wiring board> A resin film according to one embodiment of the present invention, or a printed circuit board using a metallized resin film according to one embodiment of the present invention, is also one embodiment of the present invention. A method for manufacturing a printed circuit board using a resin film according to one embodiment of the present invention will be described below. The resin film according to one embodiment of the present invention can be a metallized resin film in which an electroless copper plating film (electroless copper plating layer) is firmly attached to the surface of a low-roughness layer A using electroless metal plating, particularly a general-purpose electroless copper plating solution. By using the resin film or metallized film according to one embodiment of the present invention, it is possible to form narrow-pitch circuits regardless of whether it is a subtractive or additive method, and without using complicated methods such as button plating. Furthermore, by using the resin film or metallized film according to one embodiment of the present invention, it is possible to obtain a conductor layer and circuit that has a narrow pitch and good circuit shape, has excellent transmission characteristics, and is thin in thickness. In other words, by using the resin film or metallized film according to one embodiment of the present invention, it is possible to manufacture a printed circuit board with high flexibility, and it is possible to manufacture flexible printed circuit boards, multilayer flexible printed circuit boards, rigidflex substrates, chip-on-film substrates, etc.

[0102] It is also possible to combine the process of forming an electroless metal plating layer on at least one surface of a resin film according to one embodiment of the present invention with known methods such as subtractive and additive circuit formation processes, multilayering, and build-up multilayering. In the case of multilayering, it is possible to combine it with a suitable adhesive and adhesive sheet. It is also possible to combine it with through-hole formation and blind via formation. For example, by performing the following methods (1) to (3) on the resin film according to one embodiment of the present invention, it is possible to obtain the various printed circuit boards described above: (1) First, through-holes are formed, and then an electroless metal plating layer is formed by performing an electroless metal plating layer formation treatment, thereby simultaneously forming an electroless metal plating layer (film) on the through-hole wall and the resin film surface; then (2) circuits are formed by a known method; and further (3) multilayering treatment, protective film formation treatment, and surface treatment are performed by a known method. It is preferable that the surface roughness of the resin film according to one embodiment of the present invention is small in order to form narrow-pitch circuits. In one embodiment of the present invention, the surface roughness Ra of the resin film (layer A) exposed by etching away the electroless metal plating layer (film) is preferably 200 nanometers or less, more preferably 150 nanometers or less, and even more preferably 100 nanometers or less. The surface roughness can be adjusted by changing the amount of fumed metal oxide added to the polyimide precursor, the type of fumed metal oxide (apparent specific gravity, surface treatment, etc.), the chemical structure of the polyimide resin of layer A, the desmear conditions, the conditions for forming the electroless metal plating layer, and so on.

[0103] A printed circuit board obtained by one embodiment of the present invention can transmit electrical signals in the GHz band by using a resin film or a metallized resin film according to one embodiment of the present invention. Transmitting electrical signals in the GHz band, as used herein, means that when the insertion loss S21 parameter is measured using a network analyzer E5071C (Keysight Technologies) and a GSG250 probe on a microstrip line transmission path having a signal line with a thickness of 12 microns, a resin film according to one embodiment of the present invention with a thickness of 25 microns, and a ground layer with a thickness of 12 microns, in order, and processed to have a characteristic impedance of 50 Ω, the transmission loss at 10 GHz is less than 7 dB / 100 mm, the transmission loss at 20 GHz is less than 11 dB / 100 mm, and the transmission loss at 30 GHz is less than 14 dB / 100 mm. Here, the signal line with a thickness of 12 microns refers to wiring consisting of a conductor layer with a total thickness of 12 microns, consisting of an electroless metal plating layer and an electrolytic copper plating layer. Furthermore, the 12-micron thick ground layer refers to a ground layer consisting of a conductive layer with a total thickness of 12 microns, comprising an electroless metal plating layer and an electrolytic copper plating layer. Also, (i) a film (laminated structure) having a signal line of 12 microns thickness and a resin film according to one embodiment of the present invention with a thickness of 25 microns in sequence, and (ii) a film (laminated structure) having a signal line of 12 microns thickness, a resin film according to one embodiment of the present invention with a thickness of 25 microns, and a ground layer of 12 microns in sequence, can also be called a metallized resin film according to one embodiment of the present invention. [1] Layer A, which contains polyimide resin and fumed metal oxide, is formed on at least one surface of layer B, which is a heat-resistant resin film with a coefficient of linear expansion of 20 ppm / °C or less. A resin film characterized in that the linear expansion coefficient of the polyimide resin is 30 ppm / °C or more and 100 ppm / °C or less. [2] The resin film according to [1], characterized in that the apparent specific gravity of the fumed metal oxide is 20 grams / liter or more and 220 grams / liter or less. [3] The resin film according to [1] or [2], characterized in that the amount of fumed metal oxide blended with 100 parts by weight of the polyimide resin precursor is 10 to 130 parts by weight. [4] The resin film according to any one of [1] to [3], characterized in that the fumed metal oxide is fumed silica. [5] The resin film according to any one of [1] to [4], characterized in that layer A, which includes the polyimide resin and the fumed metal oxide, is an imidized compound of a precursor of the polyimide resin and the fumed metal oxide. [6] The storage modulus of the polyimide resin at 300°C is 1 × 10⁻⁶ 8 A resin film according to any one of [1] to [5], characterized in that it is Pa or higher. [7] The resin film according to any one of [1] to [6], characterized in that the polyimide resin is an insoluble polyimide resin. [8] The resin film according to any one of [1] to [7], characterized in that the layer B contains a polyimide resin. A metallized resin film having an electroless metal plating layer formed on the surface of layer A, as described in any one of [9], [1] to [8].

[10] The metallized resin film according to [9], characterized in that the electroless metal plating is electroless copper plating.

[11] The metallized resin film according to [9] or

[10] , characterized in that the electroless metal plating layer of the metallized resin film is removed by etching, and the surface roughness Ra of the exposed resin film is 200 nanometers or less.

[12] The metallized resin film according to any one of [9] to

[11] , characterized in that, after forming the electroless metal plating layer, it exhibits a peel strength of 5 N / cm or more without heat treatment at 150°C or higher. A printed circuit board using a resin film described in any one of [1] to [8] or a metallized resin film described in any one of [9] to

[12] .

[14] A printed circuit board as described in

[13] capable of transmitting electrical signals in the GHz band.

[15] A method for producing a resin film, characterized in that layer A, which contains a polyimide resin and a fumed metal oxide, is formed on at least one surface of layer B, which is a heat-resistant resin film having a coefficient of linear expansion of 20 ppm / °C or less, the coefficient of linear expansion of the polyimide resin is 30 ppm / °C or more and 100 ppm / °C or less, and layer A, which contains the polyimide resin and the fumed metal oxide, is obtained by mixing a polyamic acid solution of a precursor of the polyimide resin with the fumed metal oxide, and imidizing the resulting fumed metal oxide-dispersed polyamic acid solution.

[16] A method for producing a resin film according to

[15] , characterized by applying the fumed metal oxide dispersed polyamic acid solution to the layer B made of the heat-resistant resin film, drying the fumed metal oxide dispersed polyamic acid solution, and imidizing it.

[17] A method for producing a resin film according to

[15] , characterized by co-extruding the fumed metal oxide dispersed polyamic acid solution with the precursor solution of the layer B made of the heat-resistant resin film, drying the fumed metal oxide dispersed polyamic acid solution and the precursor solution, and imidizing them. [Examples]

[0104] One embodiment of the present invention will be described in more detail below based on examples and comparative examples. However, the present invention is not limited to the following examples.

[0105] <Preparation of a single-layer film of polyimide resin for layer A> The polyamic acid solution obtained in the synthesis example was coated onto aluminum foil, and the polyamic acid solution was sequentially heated at 120°C for 360 seconds, 200°C for 60 seconds, 350°C for 200 seconds, and 450°C for 30 seconds to perform imidization. Next, the aluminum foil was dissolved and removed using an etching solution to obtain a single-layer film of polyimide resin layer A. The coefficient of linear expansion, storage modulus, glass transition temperature, and solubility were evaluated using this single-layer film.

[0106] <Measurement of linear thermal expansion coefficient> The coefficient of thermal expansion was measured using a TMA120C manufactured by Seiko Electronics Co., Ltd. The sample size was 3 mm in width and 10 mm in length. The sample was heated from 10°C to 400°C at a rate of 10°C / min with a load of 3 g. The sample was then cooled to 10°C, and then heated again at a rate of 10°C / min. The average value of the thermal expansion coefficient was calculated from the thermal expansion coefficient during the second heating cycle from 100°C to 200°C.

[0107] <Measurement of storage modulus and glass transition temperature of layer A> The single-layer film obtained in the section "Preparation of a single-layer film of polyimide resin of layer A" was used as a sample, and its storage modulus and glass transition temperature were measured using a DMS6100 manufactured by Seiko Electronics Co., Ltd. The sample size was 9 mm in width and 50 mm in length. Measurements were taken at frequencies of 1, 5, and 10 Hz, with a heating rate of 3°C / min, in the temperature range from 20°C to 400°C, and the value of the storage modulus at 300°C was read. The glass transition temperature (hereinafter referred to as "Tg") was determined from the value of the inflection point of the storage modulus.

[0108] <Solubility> The solubility of the single-layer film obtained in the section "Preparation of a single-layer film of polyimide resin of layer A" was evaluated for the following organic solvents. If any of the organic solvents dissolved the film at a concentration of 10% by weight or more, it was marked as soluble (× - poor), and if it did not dissolve at a concentration of 10% by weight or more, it was marked as insoluble (○ - good). The temperature of the organic solvents was set to 25°C. Organic solvents: methanol, methyl ethyl ketone, toluene, tetrahydrofuran, N,N-dimethylformamide <Preparation of double-sided copper-clad laminate for evaluation> The resin films obtained in the examples and comparative examples were subjected to desmear treatment, electroless copper plating, and electrolytic copper plating sequentially under the conditions shown in Tables 1-3 (Atotec Co., Ltd.) to obtain evaluation double-sided laminates. The electrolytic copper plating thickness was set to 12 microns.

[0109] [Table 1]

[0110] [Table 2]

[0111] [Table 3]

[0112] <Peel strength> In one embodiment of the present invention, regarding the adhesion between a resin film and an electroless metal plating layer in a metallized resin film, (a) In a metallized resin film obtained by performing only an electroless metal plating layer formation treatment, sufficient adhesion is achieved. (b) The metallized resin film exhibits good adhesion without requiring high-temperature heat treatment. (c) To obtain good adhesion regardless of the presence or absence of a circuit pattern on the back surface of the metallized resin film, (d) It must have heat resistance as a printed circuit board; in other words, it must maintain good adhesion even after the metallized resin film has been left at high temperatures. This makes it possible to achieve this. This avoids problems such as a decrease in the reliability of the printed circuit board due to the circuit peeling off from the resin film substrate during the circuit formation process. In consideration of the above, the peel strength was measured using the following procedure to evaluate the adhesion.

[0113] (Preparation of samples for peel strength measurement) From the metallized resin films (double-sided copper-clad laminates) obtained in the examples and comparative examples, samples for peel strength measurement were prepared: one without copper on the back surface, and another with copper on the back surface. For each peel strength measurement sample, the initial peel strength, peel strength after high-temperature heat treatment, and heat-resistant peel strength were measured.

[0114] (Form 1 - No copper on the back) The copper layer on one side of a double-sided copper-clad laminate was completely removed by etching, and a 5mm wide copper pattern was fabricated on the remaining copper layer on the other side using an etching method with masking tape. The initial peel strength, peel strength after high-temperature heat treatment, and heat-resistant peel strength were measured using the following procedure.

[0115] "Initial Peel Strength - No Copper on Backside": After pattern etching, water droplets were wiped off the double-sided copper-clad laminate, and the masking tape was removed. The peel strength was measured immediately afterward. The adhesion of the double-sided copper-clad laminate was evaluated immediately after only the electroless plating layer formation treatment, without drying or high-temperature heating.

[0116] "Peel Strength After High-Temperature Heat Treatment - No Copper on Backside": After pattern etching, water droplets were wiped off the double-sided copper-clad laminate, the masking tape was removed, and it was dried at 50°C for 10 minutes. Next, the double-sided copper-clad laminate was placed in a heat resistance test environment at 180°C for 15 minutes, and then the peel strength was measured. This was done to confirm the effect of high-temperature treatment on adhesion.

[0117] "Heat-resistant peel strength - without copper on the back": After pattern etching, water droplets were wiped off the double-sided copper-clad laminate, the masking tape was removed, and it was dried at 50°C for 10 minutes. Then, the double-sided copper-clad laminate was placed in a heat-resistant test environment at 150°C for 168 hours, and the peel strength was measured. This was done to evaluate heat resistance.

[0118] (Form 2 - with copper backing) A 5mm wide copper pattern was created on one side of a double-sided copper-clad laminate using an etching method with masking tape, and an evaluation pattern with a full copper layer was created on the reverse side. The initial peel strength, peel strength after high-temperature heat treatment, and heat-resistant peel strength were measured using the following procedure.

[0119] "Initial Peel Strength - With Copper on Backside": After pattern etching, water droplets were wiped off the double-sided copper-clad laminate, the masking tape was removed, and the peel strength was measured immediately. This was performed to evaluate the adhesion of the double-sided copper-clad laminate immediately after only the electroless plating layer formation process, without drying or high-temperature heating.

[0120] "Peel Strength After High-Temperature Heat Treatment - With Copper on the Backside": After pattern etching, water droplets were wiped off the double-sided copper-clad laminate, the masking tape was removed, and it was dried at 50°C for 10 minutes. Next, the double-sided copper-clad laminate was placed in a heat resistance test environment at 180°C for 15 minutes, and then the peel strength was measured. This was done to confirm the effect of high-temperature treatment on adhesion.

[0121] "Heat-resistant peel strength - with copper on the back": After pattern etching, water droplets were wiped off the double-sided copper-clad laminate, the masking tape was removed, and it was dried at 50°C for 10 minutes. Then, the double-sided copper-clad laminate was placed in a heat-resistant test environment at 150°C for 168 hours, and the peel strength was measured. This was done to evaluate heat resistance.

[0122] (Peel strength measurement) The six types of peel strength measurements described above were performed on a single double-sided copper-clad laminate. Peel strength was measured by peeling the laminate at a crosshead speed of 50 mm / min and a peeling angle of 180°, and the resulting load was measured.

[0123] <Heat-resistant solder with moisture absorption properties> The evaluation double-sided copper-clad laminates obtained in the examples and comparative examples were cut into 3.5 cm squares. Next, 15 samples were prepared by etching the excess copper foil layer from each 3.5 cm square evaluation double-sided copper-clad laminate, so that a 2.5 cm square copper foil layer remained in the center of one side (for convenience, referred to as side A) and the copper foil layer remained over the entire surface of the other side (for convenience, referred to as side B). The obtained samples were left for 96 hours under humid conditions of 40°C and 90% RH to absorb moisture. After the moisture absorption treatment, five samples were immersed in a solder bath at 260°C, 280°C, or 300°C for 10 seconds. In other words, five samples were used under each temperature condition. For the samples after solder immersion, the copper foil layer on side B was completely removed by etching, and the appearance of the overlapping copper foil areas was observed. If any of the following were observed in the appearance—whitening, blistering, or peeling of the copper foil layer—it was determined that there was a change in appearance. Under the condition of 300℃, if there was no change in appearance for all five samples, it was evaluated as ○ (Good). If one or more of the five samples showed a change in appearance under the condition of 300℃ but no change at 260℃, it was evaluated as △ (Pass). If one or more of the five samples showed a change in appearance at 260℃, it was evaluated as × (Poor).

[0124] <Surface roughness Ra> The copper layer of the evaluation double-sided copper-clad laminates obtained in the examples and comparative examples was dissolved and removed by etching. The surface roughness (Ra) of the exposed resin film was measured using a scanning probe microscope (SPM, Bruker AXS Dimension Icon) in accordance with JIS C 0601-2001.

[0125] (Synthesis Example 1; Synthesis of the polyimide precursor of layer A) 322.3 g of N,N-dimethylformamide (hereinafter also referred to as DMF) and 33.9 g of 1,3-bis(4-aminophenoxy)benzene (hereinafter sometimes referred to as TPE-R) were added to a 2000 ml glass flask. Next, while stirring the solution in the flask under a nitrogen atmosphere, 33.6 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter sometimes referred to as BPDA) was added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution of 0.51 g of BPDA dissolved in 9.7 g of DMF (hereinafter sometimes referred to as BPDA solution (1)) was prepared separately. BPDA solution (1) was gradually added to the reaction solution, paying attention to viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BPDA solution (1) and stirring of the reaction solution were stopped. Through this operation, a polyamic acid solution, which is a polyimide precursor, was obtained.

[0126] (Synthesis Example 2; Synthesis of the polyimide precursor of layer A) 321.4 g of N,N-dimethylformamide (hereinafter sometimes referred to as DMF), 12.5 g of 4,4'-oxydianiline (hereinafter sometimes referred to as ODA), and 18.3 g of TPE-R were added to a 2000 ml glass flask. Next, while stirring the solution in the flask under a nitrogen atmosphere, 36.4 g of BPDA was added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.55 g of BPDA in 10.5 g of DMF (hereinafter sometimes referred to as BPDA solution (2)). BPDA solution (2) was gradually added to the reaction solution, paying attention to viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BPDA solution (2) and stirring of the reaction solution were stopped. Through this operation, a polyamic acid solution, which is a polyimide precursor, was obtained.

[0127] (Synthesis Example 3; Synthesis of the polyimide precursor of layer A) 321.8 g of N,N-dimethylformamide (hereinafter also referred to as DMF), 24.7 g of TPE-R, and 7.6 g of 2,2'-dimethylbenzidine (hereinafter sometimes referred to as m-TB) were added to a 2000 ml glass flask. Next, while stirring the solution in the flask under a nitrogen atmosphere, 35.0 g of BPDA was added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.53 g of BPDA in 10.1 g of DMF (hereinafter sometimes referred to as BPDA solution (3)). BPDA solution (3) was gradually added to the reaction solution, paying attention to viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BPDA solution (3) and stirring of the reaction solution were stopped. Through this operation, a polyamic acid solution, which is a polyimide precursor, was obtained.

[0128] (Synthesis Example 4; Synthesis of the polyimide precursor of layer A) 321.9 g of N,N-dimethylformamide (hereinafter also referred to as DMF) and 35.0 g of TPE-R were added to a 2000 ml glass flask. Next, while stirring the solution in the flask under a nitrogen atmosphere, 6.5 g of pyromellitic dianhydride (hereinafter sometimes referred to as PMDA) and 25.9 g of BPDA were added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.52 g of BPDA in 10.0 g of DMF (hereinafter sometimes referred to as BPDA solution (4)). BPDA solution (4) was gradually added to the reaction solution, paying attention to viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BPDA solution (4) and stirring of the reaction solution were stopped. Through this operation, a polyamic acid solution, which is a polyimide precursor, was obtained.

[0129] (Synthesis Example 5; Synthesis of the polyimide precursor of layer A) 321.6 g of N,N-dimethylformamide (hereinafter also referred to as DMF) and 36.2 g of TPE-R were added to a 2000 ml glass flask. Next, while stirring the solution in the flask under a nitrogen atmosphere, 13.5 g of PMDA and 17.6 g of BPDA were added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.54 g of BPDA in 10.3 g of DMF (hereinafter sometimes referred to as BPDA solution (5)). BPDA solution (5) was gradually added to the reaction solution, paying attention to viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BPDA solution (5) and stirring of the reaction solution were stopped. Through this operation, a polyamic acid solution, which is a polyimide precursor, was obtained.

[0130] (Synthesis Example 6; Synthesis of the polyimide precursor of layer A) 320.4 g of N,N-dimethylformamide (hereinafter also referred to as DMF) and 27.5 g of ODA were added to a 2000 ml glass flask. Next, while stirring the solution in the flask under a nitrogen atmosphere, 39.8 g of BPDA was added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.60 g of BPDA in 11.5 g of DMF (hereinafter sometimes referred to as BPDA solution (6)). BPDA solution (6) was gradually added to the reaction solution, paying attention to the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BPDA solution (6) and stirring of the reaction solution were stopped. Through this operation, a polyamic acid solution, which is a polyimide precursor, was obtained.

[0131] (Synthesis Example 7; Synthesis of the polyimide precursor of layer A) 321.6 g of N,N-dimethylformamide (hereinafter also referred to as DMF), 25.2 g of 2,2'-bis{4-(4-aminophenoxy)phenyl}propane (hereinafter sometimes referred to as BAPP), and 6.6 g of 1,4-diaminobenzene (hereinafter sometimes referred to as p-PDA) were added to a 2000 ml glass flask. Next, while stirring the solution in the flask under a nitrogen atmosphere, 35.6 g of BPDA was added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution of 0.54 g of BPDA dissolved in 10.3 g of DMF was prepared separately (hereinafter sometimes referred to as BPDA solution (7)). BPDA solution (7) was gradually added to the reaction solution, paying attention to the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BPDA solution (7) and stirring of the reaction solution were stopped. Through this procedure, a polyamic acid solution, which is a polyimide precursor, was obtained.

[0132] (Synthesis Example 8; Synthesis of the polyimide precursor of layer A) 319.0 g of N,N-dimethylformamide (hereinafter also referred to as DMF), 14.6 g of ODA, and 7.9 g of p-PDA were added to a 2000 ml glass flask. Next, while stirring the solution in the flask under a nitrogen atmosphere, 44.7 g of 4,4'-oxydiphthalic acid dianhydride (hereinafter sometimes referred to as ODPA) was added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.68 g of ODPA in 12.9 g of DMF (hereinafter sometimes referred to as ODPA solution (1)). ODPA solution (1) was gradually added to the reaction solution, paying attention to the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of ODPA solution (1) and stirring of the reaction solution were stopped. Through this operation, a polyamic acid solution, which is a polyimide precursor, was obtained.

[0133] (Synthesis Example 9; Synthesis of the polyimide precursor of layer A) 321.1 g of N,N-dimethylformamide (hereinafter also referred to as DMF) and 35.7 g of TPE-R were added to a 2000 ml glass flask. Next, while stirring the solution in the flask under a nitrogen atmosphere, 13.3 g of PMDA and 18.3 g of ODPA were added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.56 g of ODPA in 10.8 g of DMF (hereinafter sometimes referred to as ODPA solution (2)). ODPA solution (2) was gradually added to the reaction solution, paying attention to viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of ODPA solution (2) and stirring of the reaction solution were stopped. Through this operation, a polyamic acid solution, which is a polyimide precursor, was obtained.

[0134] (Synthesis Example 10; Synthesis of the polyimide precursor of layer A) 321.7 g of N,N-dimethylformamide (hereinafter also referred to as DMF), 12.2 g of ODA, and 22.5 g of 4,4'-bis(4-aminophenoxy)biphenyl (hereinafter sometimes referred to as 4-APBP) were added to a 2000 ml glass flask. Next, while stirring the solution in the flask under a nitrogen atmosphere, 8.0 g of PMDA and 24.6 g of BPDA were added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution of 0.54 g of BPDA dissolved in 10.2 g of DMF was prepared separately (hereinafter sometimes referred to as BPDA solution (8)). BPDA solution (8) was gradually added to the reaction solution, paying attention to viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BPDA solution (8) and stirring of the reaction solution were stopped. Through this operation, a polyamic acid solution, which is a polyimide precursor, was obtained.

[0135] (Synthesis Example 11; Synthesis of Polyimide Precursor of Layer A) 323.9 g of N,N-dimethylformamide (hereinafter also referred to as DMF) and 39.6 g of BAPP were added to a 2000 ml glass flask. Next, while stirring the solution in the flask under a nitrogen atmosphere, 39.6 g of BPDA was added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.42 g of BPDA in 8.0 g of DMF (hereinafter sometimes referred to as BPDA solution (9)). BPDA solution (9) was gradually added to the reaction solution, paying attention to viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BPDA solution (9) and stirring of the reaction solution were stopped. Through this operation, a polyamic acid solution, which is a polyimide precursor, was obtained.

[0136] (Synthesis Example 12; Synthesis of the polyimide precursor of layer A) 320.0 g of N,N-dimethylformamide (hereinafter also referred to as DMF) and 26.0 g of ODA were added to a 2000 ml glass flask. Next, while stirring the solution in the flask under a nitrogen atmosphere, 41.3 g of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (hereinafter sometimes referred to as BTDA) was added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.62 g of BTDA in 11.9 g of DMF (hereinafter sometimes referred to as BTDA solution (1)). BTDA solution (1) was gradually added to the reaction solution, paying attention to viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BTDA solution (1) and stirring of the reaction solution were stopped. Through this operation, a polyamic acid solution, which is a polyimide precursor, was obtained.

[0137] (Synthesis Example 13; Synthesis of the polyimide precursor of layer A) 318.8 g of N,N-dimethylformamide (hereinafter also referred to as DMF), 14.2 g of ODA, and 7.7 g of p-PDA were added to a 2000 ml glass flask. Next, while stirring the solution in the flask under a nitrogen atmosphere, 45.3 g of BTDA was added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.68 g of BTDA in 13.1 g of DMF (hereinafter sometimes referred to as BTDA solution (2)). BTDA solution (2) was gradually added to the reaction solution, paying attention to viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of BTDA solution (2) and stirring of the reaction solution were stopped. Through this operation, a polyamic acid solution, which is a polyimide precursor, was obtained.

[0138] (Synthesis Example 14; Synthesis of Polyimide Precursor of Layer A) 11.7 g of N,N-dimethylformamide (hereinafter also referred to as DMF) and 26.6 g of ODA were added to a 2000 ml glass flask. Next, while stirring the solution in the flask under a nitrogen atmosphere, 40.7 g of ODPA was added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.61 g of ODPA in 11.7 g of DMF (hereinafter sometimes referred to as ODPA solution (3)). ODPA solution (3) was gradually added to the reaction solution, paying attention to the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of ODPA solution (3) and stirring of the reaction solution were stopped. Through this operation, a polyamic acid solution, which is a polyimide precursor, was obtained.

[0139] (Synthesis Example 15; Synthesis of the polyimide precursor of layer A) 322.0 g of N,N-dimethylformamide (hereinafter also referred to as DMF) and 32.9 g of TPE-R were added to a 2000 ml glass flask. Next, while stirring the solution in the flask under a nitrogen atmosphere, 34.4 g of ODPA was added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.52 g of ODPA in 9.9 g of DMF (hereinafter sometimes referred to as ODPA solution (4)). ODPA solution (4) was gradually added to the reaction solution, paying attention to viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of ODPA solution (4) and stirring of the reaction solution were stopped. Through this operation, a polyamic acid solution, which is a polyimide precursor, was obtained.

[0140] (Synthesis Example 16; Synthesis of Polyimide Precursor of Layer A) 321.3 g of N,N-dimethylformamide (hereinafter also referred to as DMF), 25.8 g of ODA, and 4.6 g of p-PDA were added to a 2000 ml glass flask. Next, while stirring the solution in the flask under a nitrogen atmosphere, 36.9 g of PMDA was added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.56 g of PMDA in 10.6 g of DMF (hereinafter sometimes referred to as PMDA solution). The PMDA solution was gradually added to the reaction solution, paying attention to the viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of the PMDA solution and stirring of the reaction solution were stopped. Through this operation, a polyamic acid solution, which is a polyimide precursor, was obtained.

[0141] (Synthesis Example 17; Synthesis of Polyimide Precursor of Layer A) 320.9 g of N,N-dimethylformamide (hereinafter also referred to as DMF), 10.4 g of ODA, and 18.7 g of KF-8010 manufactured by Shin-Etsu Chemical Co., Ltd. were added to a 2000 ml glass flask. Next, while stirring the solution in the flask under a nitrogen atmosphere, 38.1 g of 4,4'-(4,4'-isopropylidene diphenoxy)bis(phthalic anhydride) (hereinafter sometimes referred to as BPADA) was added to the flask, and the solution in the flask was stirred at 25°C for 1 hour. A solution was separately prepared by dissolving 0.58 g of BPADA in 11.0 g of DMF (hereinafter sometimes referred to as BPADA solution). The BPADA solution was gradually added to the reaction solution, paying attention to viscosity, and the reaction solution in the flask was stirred. When the viscosity of the reaction solution reached 1000 poise, the addition of the BPADA solution and stirring of the reaction solution were stopped. Through this operation, a polyamic acid solution, which is a polyimide precursor, was obtained. The chemical structure of KF-8010, manufactured by Shin-Etsu Chemical Co., Ltd., is shown in general formula (1).

[0142] [ka]

[0143] (Example formulation 1; Dispersion of fumed metal oxide for layer A) 20g of Aerosil R9200 manufactured by Nippon Aerosil Co., Ltd. and 80g of DMF were mixed. The resulting mixture was stirred for 5 minutes at a rotation speed of 10,000 rpm in a rotary homogenizer (rotary blade diameter 20 mm) to obtain a dispersion of fumed metal oxide.

[0144] (Example formulation 2; Dispersion of fumed metal oxide for layer A) A dispersion of fumed metal oxide was obtained by performing the same procedure as in Formula Example 1, except that Aerosil R9200 manufactured by Nippon Aerosil Co., Ltd. was replaced with Aerosil R972 manufactured by Nippon Aerosil Co., Ltd.

[0145] (Example formulation 3; Dispersion of fumed metal oxide for layer A) A dispersion of fumed metal oxide was obtained by performing the same procedure as in Formula Example 1, except that Aerosil R9200 manufactured by Nippon Aerosil Co., Ltd. was replaced with Aerosil NX130 manufactured by Nippon Aerosil Co., Ltd.

[0146] (Formulation example 4; Dispersion of fumed metal oxide for layer A) A dispersion of fumed metal oxide was obtained by performing the same procedure as in Formula Example 1, except that Aerosil R9200 manufactured by Nippon Aerosil Co., Ltd. was replaced with Aerosil VP RS920 manufactured by Nippon Aerosil Co., Ltd.

[0147] The concentration of fumed metal oxide in the dispersions of fumed metal oxide obtained in formulation examples 1-4 was 20% by weight.

[0148] (Formulation example 5; Dispersion of fumed metal oxide for layer A) A dispersion was prepared by mixing 60 g of Admanano, a dispersion of 10 nm particle size manufactured by Admatex Co., Ltd. (solvent: DMF, concentration: 30 wt / wt%) with 30 g of DMF.

[0149] (Formulation example 6; Dispersion of fumed metal oxide for layer A) Admanano, a dispersion of 50 nm particle size manufactured by Admatex Co., Ltd. (solvent DMF, concentration 20 wt / wt%), was used as the dispersion.

[0150] (Example 1) 40 g of the polyamic acid solution obtained in Synthesis Example 1 and 17 g of the dispersion from Preparation Example 1 were mixed. 40 g of DMF and 2 g of lutidine were then added to the resulting mixture to obtain Layer A dispersion. This Layer A dispersion was applied to one side of a non-thermoplastic polyimide film (Apical FP, 17 microns thick, manufactured by Kaneka Corporation) so that the final thickness of Layer A on that side was 4 microns. The Layer A dispersion was dried at 120°C for 2 minutes, and then the remaining side was coated and dried using the same procedure. Subsequently, the non-thermoplastic polyimide film coated with Layer A dispersion was heated at 450°C for 12 seconds to imidize the polyamic acid in Layer A, resulting in a resin film with a structure consisting of Layer A (containing polyimide resin and fumed metal oxide) / non-thermoplastic polyimide film / Layer A laminated in this order. Note that the non-thermoplastic polyimide film (Apical FP) corresponds to Layer B. In other words, in Example 1, layer B is made of polyimide resin, and specifically consists only of a non-thermoplastic polyimide film. Furthermore, the coefficient of linear expansion of the apical FP was 12 ppm / °C.

[0151] The aforementioned resin film was subjected to desmear treatment, electroless copper plating, and electrolytic copper plating under the conditions shown in Table 1 to obtain double-sided copper-clad laminates. Peel strength, heat resistance of moisture-absorbing solder, and surface roughness Ra were evaluated. The composition and results are shown in Tables 4 to 7.

[0152] (Example 2) Except for replacing the dispersion of Formulation Example 1 used in Example 1 with the dispersion of Formulation Example 2, the same procedure as in Example 1 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0153] (Example 3) Except for replacing the dispersion of Formulation Example 1 used in Example 1 with the dispersion of Formulation Example 3, the same procedure as in Example 1 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0154] (Example 4) Except for replacing the dispersion of Formulation Example 1 used in Example 1 with the dispersion of Formulation Example 4, the same procedure as in Example 1 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0155] (Comparative Example 1) 40 g of the polyamic acid solution obtained in Synthesis Example 1 was mixed with 40 g of DMF and 2 g of lutidine to obtain a mixture. The same procedure as in Example 1 was performed, except that the layer A dispersion used in Example 1 was replaced with the mixture, to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The initial peel strength did not show sufficient values ​​in both cases, with and without copper backing. Furthermore, after high-temperature heat treatment, the peel strength showed good adhesion in the case without copper backing, but not in the case with copper backing, indicating that the adhesion results differed depending on the presence or absence of copper backing. The composition and results are shown in Tables 4 to 7.

[0156] (Example 5) Except for changing the amount of dispersion solution in Formulation Example 2 used in Example 2 to 3.4 g, the same procedure as in Example 2 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0157] (Example 6) Except for changing the amount of dispersion solution in Formulation Example 2 used in Example 2 to 6.8 g, the same procedure as in Example 2 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0158] (Example 7) Except for changing the amount of dispersion solution in Formulation Example 2 used in Example 2 to 10.2 g, the same procedure as in Example 2 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0159] (Example 8) Except for changing the amount of dispersion solution in Formulation Example 2 used in Example 2 to 34 g, the same procedure as in Example 2 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0160] (Example 9) Except for changing the amount of dispersion solution in Formulation Example 3 used in Example 3 to 3.4 g, the same procedure as in Example 3 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0161] (Example 10) Except for changing the amount of dispersion solution of Formulation Example 3 used in Example 3 to 6.8 g, the same procedure as in Example 3 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0162] (Example 11) Except for changing the amount of dispersion solution in Formulation Example 3 used in Example 3 to 10.2 g, the same procedure as in Example 3 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0163] (Example 12) Except for changing the amount of dispersion solution in Formulation Example 3 used in Example 3 to 34 g, the same procedure as in Example 3 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0164] (Example 13) Except for changing the amount of dispersion solution of Formulation Example 1 used in Example 1 to 6.8 g, the same procedure as in Example 1 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0165] (Example 14) Except for changing the amount of dispersion solution of Formulation Example 1 used in Example 1 to 10.2 g, the same procedure as in Example 1 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0166] (Example 15) Except for changing the amount of dispersion solution of Formulation Example 1 used in Example 1 to 34 g, the same procedure as in Example 1 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0167] (Example 16) Except for changing the amount of dispersion solution of Formulation Example 1 used in Example 1 to 51 g, the same procedure as in Example 1 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0168] (Example 17) Except for changing the amount of dispersion of formulation example 4 used in Example 4 to 6.8 g, the same procedure as in Example 4 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0169] (Example 18) Except for changing the amount of dispersion solution in Formulation Example 4 used in Example 4 to 10.2 g, the same procedure as in Example 4 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0170] (Example 19) Except for changing the amount of dispersion solution in Formulation Example 4 used in Example 4 to 34 g, the same procedure as in Example 4 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0171] (Example 20) Except for changing the amount of dispersion solution in Formulation Example 4 used in Example 4 to 51 g, the same procedure as in Example 4 was followed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was performed. The composition and results are shown in Tables 4 to 7.

[0172] (Example 21) In Example 21, the same procedure as in Example 1 was followed, except that the drying process after electroless copper plating was changed to wiping off water droplets only, and the drying process after copper sulfate plating was also changed to wiping off water droplets only. A double-sided copper-clad laminate was obtained and evaluated in the same manner. The composition and results are shown in Tables 4 to 7. In the metallized resin film (double-sided copper-clad laminate) of Example 21, the six types of peel strength showed good values, similar to Example 1. That is, the metal plating layer adhered well to the resin film without heating after the electroless metal plating layer formation treatment.

[0173] (Example 22) Except for replacing the polyamic acid solution of Synthesis Example 1 used in Example 1 with the polyamic acid solution of Synthesis Example 2, the same procedure as in Example 1 was performed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was carried out. The composition and results are shown in Tables 4 to 7.

[0174] (Example 23) The same procedure as in Example 1 was followed, except that the polyamic acid solution from Synthesis Example 1 used in Example 1 was replaced with the polyamic acid solution from Synthesis Example 3. Resin films and double-sided copper-clad laminates were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0175] (Example 24) The same procedure as in Example 1 was followed, except that the polyamic acid solution from Synthesis Example 1 used in Example 1 was replaced with the polyamic acid solution from Synthesis Example 4. Resin films and double-sided copper-clad laminates were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0176] (Example 25) The same procedure as in Example 1 was followed, except that the polyamic acid solution from Synthesis Example 1 used in Example 1 was replaced with the polyamic acid solution from Synthesis Example 5. Resin films and double-sided copper-clad laminates were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0177] (Example 26) The same procedure as in Example 1 was followed, except that the polyamic acid solution from Synthesis Example 1 used in Example 1 was replaced with the polyamic acid solution from Synthesis Example 6. Resin films and double-sided copper-clad laminates were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0178] (Example 27) The same procedure as in Example 1 was followed, except that the polyamic acid solution from Synthesis Example 1 used in Example 1 was replaced with the polyamic acid solution from Synthesis Example 7. Resin films and double-sided copper-clad laminates were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0179] (Example 28) The same procedure as in Example 1 was followed, except that the polyamic acid solution from Synthesis Example 1 used in Example 1 was replaced with the polyamic acid solution from Synthesis Example 8. Resin films and double-sided copper-clad laminates were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0180] (Example 29) The same procedure as in Example 1 was followed, except that the polyamic acid solution from Synthesis Example 1 used in Example 1 was replaced with the polyamic acid solution from Synthesis Example 9. Resin films and double-sided copper-clad laminates were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0181] (Example 30) The same procedure as in Example 1 was followed, except that the polyamic acid solution of Synthesis Example 1 used in Example 1 was replaced with the polyamic acid solution of Synthesis Example 10. Resin films and double-sided copper-clad laminates were obtained and evaluated in the same manner. The compositions and results are shown in Tables 4 to 7.

[0182] (Example 31) The procedure was the same as in Example 1, except that the polyamic acid solution from Synthesis Example 1 used in Example 1 was replaced with the polyamic acid solution from Synthesis Example 11. Resin films and double-sided copper-clad laminates were obtained and evaluated in the same manner. The heat resistance evaluation of the moisture-absorbing solder was △. The composition and results are shown in Tables 4 to 7.

[0183] (Example 32) The procedure was the same as in Example 1, except that the polyamic acid solution from Synthesis Example 1 used in Example 1 was replaced with the polyamic acid solution from Synthesis Example 12. Resin films and double-sided copper-clad laminates were obtained and evaluated in the same manner. The heat resistance evaluation of the moisture-absorbing solder was △. The composition and results are shown in Tables 4 to 7.

[0184] (Comparative Example 2) The procedure was the same as in Example 1, except that the polyamic acid solution from Synthesis Example 1 used in Example 1 was replaced with the polyamic acid solution from Synthesis Example 13. Resin films and double-sided copper-clad laminates were obtained and evaluated in the same manner. The heat resistance evaluation of the moisture-absorbing solder was negative. The composition and results are shown in Tables 4 to 7.

[0185] (Example 33) The procedure was the same as in Example 1, except that the polyamic acid solution from Synthesis Example 1 used in Example 1 was replaced with the polyamic acid solution from Synthesis Example 14. Resin films and double-sided copper-clad laminates were obtained and evaluated in the same manner. The heat resistance evaluation of the moisture-absorbing solder was △. The composition and results are shown in Tables 4 to 7. (Example 34) The procedure was the same as in Example 1, except that the polyamic acid solution from Synthesis Example 1 used in Example 1 was replaced with the polyamic acid solution from Synthesis Example 15. Resin films and double-sided copper-clad laminates were obtained and evaluated in the same manner. The heat resistance evaluation of the moisture-absorbing solder was △. The composition and results are shown in Tables 4 to 7.

[0186] (Comparative Example 3) The procedure was the same as in Example 1, except that the polyamic acid solution from Synthesis Example 1 used in Example 1 was replaced with the polyamic acid solution from Synthesis Example 16. Resin films and double-sided copper-clad laminates were obtained and evaluated in the same manner. The heat resistance evaluation of the moisture-absorbing solder was negative. The composition and results are shown in Tables 4 to 7.

[0187] (Comparative Example 4) Except for replacing the polyamic acid solution of Synthesis Example 1 used in Example 1 with the polyamic acid solution of Synthesis Example 17, the same procedure as in Example 1 was performed to obtain a resin film and a double-sided copper-clad laminate, and the same evaluation was carried out. The polyimide resin of layer A contains a silicone backbone, and there is a risk of contact failure in electronic devices and process contamination due to the volatilization of siloxane components from the main chain backbone. In addition, layer A has a large coefficient of linear expansion, and the evaluation of heat resistance of hygroscopic solder was negative. It has poor dimensional stability and is soluble in organic solvents, and also has poor resistance to organic solvents in the printed circuit board manufacturing process. The composition and results are shown in Tables 4 to 7.

[0188] (Comparative Example 5) The polyamic acid solution from Synthesis Example 17 was placed in a tray coated with a fluororesin and heated under reduced pressure at 665 Pa for 120 minutes at 200°C in a vacuum oven to obtain a polyimide resin. The obtained polyimide resin was dissolved in a mixed solvent of dioxolane and toluene (mixing ratio = 50% by weight / 50% by weight) to obtain a 17% by weight polyimide solution. Separately, 20 g of Aerosil R9200 manufactured by Nippon Aerosil Co., Ltd. was mixed with 80 g of the above mixed solvent, and the resulting mixture was stirred for 5 minutes at a rotation speed of 10,000 rpm in a rotary blade homogenizer (rotary blade diameter 20 mm) to obtain a dispersion of fumed metal oxide. 40 g of the polyimide solution and 17 g of the fumed metal oxide dispersion were mixed to obtain a fumed metal oxide dispersed polyimide solution (hereinafter also referred to as Layer A solution). The Layer A solution was applied to one side of a non-thermoplastic polyimide film (Apical FP, 17 microns thick, manufactured by Kaneka Corporation) so that the final thickness of Layer A on one side was 4 microns. The Layer A solution was dried at 60°C for 5 minutes and then at 150°C for 5 minutes. The remaining side was then coated and dried using the same procedure. This operation yielded a resin film with the structure Layer A / non-thermoplastic polyimide film / Layer A. Subsequently, the same procedure as in Example 1 was performed to obtain a double-sided copper-clad laminate, which was then evaluated in the same manner. The polyimide resin of Layer A contains a silicone backbone, and there is a risk of contact failure in electronic equipment and process contamination due to the volatilization of siloxane components from the main chain backbone. Furthermore, the heat resistance evaluation of the hygroscopic solder was unsuccessful. In addition, Layer A has a large coefficient of linear expansion, poor dimensional stability, and is soluble in organic solvents, resulting in poor resistance to organic solvents in the printed circuit board manufacturing process. The composition and results are shown in Tables 4 to 7.

[0189] [Table 4]

[0190] [Table 5]

[0191] [Table 6]

[0192] Table 7

[0193] Table 8

[0194] Table 9

[0195] Table 10

[0196] Table 11

Claims

1. A metallized resin film is formed in which layer A, which contains polyimide resin and fumed metal oxide, is formed on at least one surface of layer B, which is a heat-resistant resin film with a coefficient of linear expansion of 20 ppm / °C or less, and an electroless metal plating layer is formed on the surface of layer A by electroless metal plating. The amount of the fumed metal oxide blended with 100 parts by weight of the polyimide resin precursor is 10 to 130 parts by weight. The metal type used for the electroless metal plating is a metal selected from the group consisting of copper, nickel, gold, and silver, characterized in that it is a metallized resin film.

2. The metallized resin film according to claim 1, characterized in that the electroless plating layer is 0.01 microns to 10.00 microns thick.

3. The metallized resin film according to claim 1, characterized in that the peel strength of the electroless metal plating layer in the metallized resin film is 3 N / cm or more.

4. The metallized resin film according to claim 1, characterized in that the electroless metal plating is electroless copper plating.

5. The metallized resin film according to claim 1, characterized in that the fumed metal oxide is fumed silica.

6. The metallized resin film according to claim 1, characterized in that the layer A comprising the polyimide resin and the fumed metal oxide is an imidide of a mixture of the precursor of the polyimide resin and the fumed metal oxide.

7. The metallized resin film according to claim 1, wherein the linear expansion coefficient of the polyimide resin is 30 ppm / °C or more and 100 ppm / °C or less.

8. The storage modulus of the polyimide resin at 300°C is 1 × 10⁻⁶. ８ The metallized resin film according to claim 1, characterized in that it is Pa or higher.

9. The metallized resin film according to claim 1, characterized in that the polyimide resin is an insoluble polyimide resin.

10. The metallized resin film according to claim 1, characterized in that the aforementioned layer B contains a polyimide resin.

11. The metallized resin film according to claim 1, characterized in that the apparent specific gravity of the fumed metal oxide is 20 grams / liter or more and 220 grams / liter or less.

12. The metallized resin film according to claim 1, characterized in that the electroless metal plating layer of the metallized resin film is removed by etching, and the surface roughness Ra of the exposed resin film is 200 nanometers or less.

13. The metallized resin film according to claim 1, characterized in that, after forming the electroless metal plating layer, it exhibits a peel strength of 5 N / cm or more without performing a heat treatment of 150°C or higher.

14. A printed circuit board using a metallized resin film according to any one of claims 1 to 13.

15. A printed circuit board according to claim 14, capable of transmitting electrical signals in the GHz band.

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