JP7696740B2 - Resin film, its manufacturing method, metal-clad laminate and circuit board - Google Patents

Description

The present invention relates to a resin film useful as an electronic component material, its manufacturing method, a metal-clad laminate, and a circuit board.

In recent years, with the progress of miniaturization, weight saving, and space saving of electronic devices, there is an increasing demand for flexible printed circuits (FPCs) that are thin, lightweight, flexible, and have excellent durability even when repeatedly bent. Because FPCs allow three-dimensional and high-density mounting even in a limited space, their applications are expanding to include wiring for moving parts of electronic devices such as HDDs, DVDs, mobile information terminals, and smartphones, as well as components such as cables and connectors.

Polyimide, which has excellent heat resistance, chemical resistance, flexibility, mechanical properties, and electrical properties, is widely used as a material for the insulating resin layers that make up circuit boards such as FPCs. Since polyimide generally has a yellowish brown color, it has been proposed to use raw material monomers containing fluorine atoms to increase transparency for applications that require transparency (e.g., Patent Documents 1 and 2).

In recent years, as equipment performance has improved, there is also a need to accommodate higher frequencies for transmitted signals. When transmitting high-frequency signals, if there is a large transmission loss in the transmission path, problems such as loss of electrical signals and longer signal delay times will occur. For this reason, reducing transmission loss will become important in the future, even in FPCs.

In order to improve high-frequency transmission characteristics, it has been proposed to use a laminate in which a fluororesin layer is laminated on a polyimide layer as an insulating resin layer for a circuit board (for example, Patent Documents 3 and 4). The insulating resin layers in Patent Documents 3 and 4 use fluororesin, and therefore have excellent dielectric properties, but have issues with dimensional stability. In particular, when applied to FPCs, there is concern that dimensional changes before and after circuit processing by etching and before and after heat treatment will be significant.

JP 2010-155360 A International Publication No. WO2020/262450 JP 2019-166844 A International Publication No. WO2020/213515

In order to reduce the dielectric loss tangent of a single polyimide layer, it is effective to form an ordered structure, but in order to increase the total light transmittance of polyimide, it is necessary to make it difficult for CT interactions to occur and difficult to form an ordered structure. In other words, it is thought that there is a trade-off between improving the total light transmittance and reducing the dielectric loss tangent in a polyimide layer.

The object of the present invention is to provide a resin film that has high transparency, is capable of reducing transmission loss even in high-frequency transmission, and has excellent dimensional stability.

As a result of extensive research, the present inventors have found that by laminating a fluororesin layer on a polyimide insulating layer, it is possible to improve transparency, reduce transmission loss, and maintain dimensional accuracy.
That is, the resin film of the present invention is a resin film having a laminated structure composed of multiple layers, and includes a polyimide insulating layer and a fluorine-based resin layer laminated on one or both sides of the polyimide insulating layer. The resin film of the present invention satisfies the following conditions i) and ii);
i) the total light transmittance of the entire resin film is 80% or more;
ii) the thermal expansion coefficient of the entire resin film is 30 ppm/K or less;
The present invention is characterized in that:

The resin film of the present invention may have a dielectric loss tangent of 0.008 or less at a frequency of 10 GHz for the entire resin film as measured using a split post dielectric resonator (SPDR resonator).

The resin film of the present invention may have a total thickness within the range of 10 to 150 μm, and the ratio of the thickness of the polyimide insulating layer to the total thickness of the resin film may be within the range of 0.5 to 0.9.

In the resin film of the present invention, the polyimide insulating layer may be composed of a single layer or multiple polyimide layers. In this case, the polyimide constituting the polyimide layer (i) having a thickness of 50% or more of the total thickness of the polyimide insulating layer may contain a diamine residue derived from an aromatic diamine compound containing a fluorine atom and/or an acid dianhydride residue derived from an aromatic tetracarboxylic dianhydride containing a fluorine atom.
The proportion of fluorine atoms contained in the polyimide layer (i) may be within the range of 10 to 40% by weight based on the total weight of the polyimide.

The metal-clad laminate of the present invention comprises any one of the above resin films and a metal layer laminated on the surface of the fluororesin layer of the resin film.

The metal-clad laminate according to another aspect of the present invention is
a first metal layer;
a fluorine-based resin adjacent layer provided adjacent to one side of the first metal layer;
a second metal layer; and
a fluorine-based resin adjacent layer provided adjacent to one side of the second metal layer;
a plurality of resin layers interposed between the two adjacent fluororesin layers;
In this case, a resin laminate is formed by the two fluororesin adjacent layers and the plurality of resin layers, and the resin laminate is
At least two polyimide layers;
a fluorine-based resin intermediate layer laminated between the polyimide layers;
It has.

The circuit board of the present invention is formed by wiring the metal layer of any of the above metal-clad laminates.

The method for producing a resin film of the present invention is a method for producing any one of the above-mentioned resin films,
A step of applying a solution containing fluororesin particles onto a substrate and performing heat treatment to melt the fluororesin particles to form the fluororesin layer;
a step of applying a polyimide precursor solution onto the fluororesin layer and imidizing the solution by heat treatment to form the polyimide layer;
It includes.

The method for producing a resin film of the present invention further comprises:
a step of applying a solution containing fluororesin particles onto the polyimide layer and heat-treating the solution to melt the fluororesin particles to form a second fluororesin layer;
may also include

The resin film of the present invention is capable of realizing high transparency and dimensional stability by laminating a fluororesin layer onto a polyimide insulating layer, and furthermore, achieves both transparency and low dielectric loss tangent. Therefore, a circuit board in which the resin film of the present invention is applied to an insulating resin layer can effectively suppress transmission loss in high-frequency signal transmission while ensuring the transparency and dimensional stability of the insulating resin layer. Therefore, when the resin film and metal-clad laminate of the present invention are applied to a circuit board or the like that transmits high-frequency signals, for example, at a frequency of 10 GHz or more, it becomes possible to effectively reduce transmission loss.

1 is a schematic diagram showing a configuration of a resin film according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing a manufacturing process of a resin film. 1 is a schematic diagram showing a configuration of a metal-clad laminate according to one embodiment of the present invention. FIG. FIG. 2 is a schematic cross-sectional view showing the configuration of a metal-clad laminate according to another embodiment of the present invention. FIG. 4 is a schematic cross-sectional view showing the configuration of a metal-clad laminate according to still another embodiment of the present invention.

The embodiment of the present invention will be explained with reference to the drawings as appropriate.

[Resin film]
A resin film according to an embodiment of the present invention is a resin film having a laminated structure made up of multiple layers, which includes a polyimide insulating layer and a fluorine-based resin layer laminated on one or both sides of the polyimide insulating layer.

Figure 1 is a schematic diagram showing an example of the structure of a resin film according to one embodiment of the present invention. The resin film A includes a polyimide insulating layer P, a first fluororesin layer F1 laminated on one side of the polyimide insulating layer P, and a second fluororesin layer F2 laminated on the side of the polyimide insulating layer P opposite to the first fluororesin layer F1. The resin film A has a sandwich structure in which the polyimide insulating layer P is sandwiched between the first fluororesin layer F1 and the second fluororesin layer F2. The resin film A may have only one of the first fluororesin layer F1 or the second fluororesin layer F2. The first fluororesin layer F1 and the second fluororesin layer F2 may have the same structure or different structures.

[Polyimide insulating layer]
The polyimide insulating layer P is composed of a single layer or multiple polyimide layers. The polyimide insulating layer P preferably has a main polyimide layer (i) having a thickness of 50% or more of the total thickness of the polyimide insulating layer P. Here, "main" means having the largest thickness among the multiple polyimide layers constituting the polyimide insulating layer P, and preferably has a thickness of 50% or more, more preferably 60% or more of the total thickness of the polyimide insulating layer P. The polyimide insulating layer P may be composed of only the main polyimide layer (i).

When the polyimide insulating layer P is composed of multiple polyimide layers, although not shown in the figure, the polyimide insulating layer P is preferably structured such that thermoplastic polyimide layers containing thermoplastic polyimide as a resin component are laminated on both sides of the main polyimide layer (i). Note that, while the term "thermoplastic polyimide" generally refers to a polyimide whose glass transition temperature (Tg) can be clearly confirmed, in the present invention, it refers to a polyimide whose storage modulus at 30°C is 1.0 x ¹⁰⁹ Pa or more and whose storage modulus at 350°C is less than 1.0 x ¹⁰⁸ Pa, as measured using DMA.

The polyimide constituting the main polyimide layer (i) contains an acid dianhydride residue derived from a tetracarboxylic dianhydride component and a diamine residue derived from a diamine component. Here, the "tetracarboxylic acid residue" refers to a tetravalent group derived from a tetracarboxylic dianhydride, and the "diamine residue" refers to a divalent group derived from a diamine compound. When the raw materials, tetracarboxylic dianhydride and diamine compound, are reacted in approximately equal moles, the types and molar ratios of the tetracarboxylic acid residues and diamine residues contained in the polyimide can be made to correspond approximately to the types and molar ratios of the raw materials.
In the present invention, the term "polyimide" refers to a resin made of a polymer having an imide group in the molecular structure, such as polyimide, polyamideimide, polyetherimide, polyesterimide, polysiloxaneimide, polybenzimidazoleimide, etc.

In order to make the total light transmittance of the resin film A 80% or more, the polyimide constituting the main polyimide layer (i) preferably contains an acid dianhydride residue derived from an aromatic tetracarboxylic dianhydride containing a fluorine atom and/or a diamine residue derived from an aromatic diamine compound containing a fluorine atom. The ratio of fluorine atoms contained in the polyimide constituting the main polyimide layer (i) is preferably in the range of 10 to 40% by weight, more preferably in the range of 15 to 35% by weight, based on the total polyimide. If the fluorine concentration of the main polyimide layer (i) is high, exceeding 40% by weight, the total light transmittance of the entire resin film A is high, but an ordered structure is difficult to form, the dielectric loss tangent is deteriorated, and the adhesion (compatibility) with the first fluorine-based resin layer F1 and the second fluorine-based resin layer F2 is also deteriorated. On the other hand, if the fluorine concentration of the main polyimide layer (i) is less than 10% by weight, the total light transmittance of the entire resin film A is low.

The main polyimide constituting the main polyimide layer (i) preferably contains a fluorine-containing acid dianhydride residue. The fluorine-containing acid dianhydride residue has a group containing a bulky fluorine atom, and therefore reduces interactions such as π-π stacking between polymer chains. As a result, it is believed that charge transfer (CT) between the aromatic tetracarboxylic acid residue and the aromatic diamine residue is less likely to occur, making it possible to make the polyimide closer to transparency.

Examples of fluorine-containing acid dianhydride residues include 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), (trifluoromethyl)pyromellitic dianhydride, di(trifluoromethyl)pyromellitic dianhydride, di(heptafluoropropyl)pyromellitic dianhydride, pentafluoroethylpyromellitic dianhydride, bis{3,5-di(trifluoromethyl)phenoxy}pyromellitic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, ) hexafluoropropane dianhydride, 5,5'-bis(trifluoromethyl)-3,3',4,4'-tetracarboxybiphenyl dianhydride, 2,2',5,5'-tetrakis(trifluoromethyl)-3,3',4,4'-tetracarboxybiphenyl dianhydride, 5,5'-bis(trifluoromethyl)-3,3',4,4'-tetracarboxydiphenyl ether dianhydride, 5,5'-bis(trifluoromethyl)-3,3',4,4'-tetracarboxybenzophenone dianhydride , bis{(trifluoromethyl)dicarboxyphenoxy}benzene dianhydride, bis{(trifluoromethyl)dicarboxyphenoxy}, trifluoromethylbenzene dianhydride, bis(dicarboxyphenoxy)trifluoromethylbenzene dianhydride, bis(dicarboxyphenoxy)bis(trifluoromethyl)benzene dianhydride, bis(dicarboxyphenoxy)tetrakis(trifluoromethyl)benzene dianhydride, 2,2-bis{(4-(3,4-dicarboxyphenoxy)phenyl}hexafluoropropane dianhydride, bis{(trifluoromethyl)dicarboxyphenoxy}biphenyl dianhydride, bis{(trifluoromethyl)dicarboxyphenoxy}bis(trifluoromethyl)biphenyl dianhydride, bis{(trifluoromethyl)dicarboxyphenoxy}diphenyl ether dianhydride, bis(dicarboxyphenoxy)bis(trifluoromethyl)biphenyl dianhydride, and other acid dianhydride residues derived from acid dianhydride components.

In addition, in order to control the coefficient of thermal expansion (CTE) of the polyimide layer (i), the main polyimide constituting the polyimide layer (i) preferably contains a tetravalent acid dianhydride residue (hereinafter, sometimes referred to as "PMDA residue") derived from pyromellitic dianhydride (PMDA) represented by the following formula (1). The PMDA residue is preferably contained in an amount of 50 molar parts or more relative to a total of 100 molar parts of all acid dianhydride residues, and more preferably in the range of 60 molar parts to 100 molar parts. If the PMDA residue is less than 50 molar parts, the CTE of the polyimide layer (i) becomes high and the dimensional stability of the entire resin film A decreases.

The main polyimide constituting the polyimide layer (i) may contain, as an acid dianhydride residue other than the above, an acid dianhydride residue derived from an acid dianhydride component generally used in the synthesis of polyimides. As such an acid dianhydride residue, an aromatic tetracarboxylic acid residue is preferred.

The main polyimide constituting the polyimide layer (i) preferably contains a fluorine-containing diamine residue. The fluorine-containing diamine residue has a group containing a bulky fluorine atom, and therefore reduces interactions such as π-π stacking between polymer chains. As a result, it is believed that charge transfer (CT) between the aromatic tetracarboxylic acid residue and the aromatic diamine residue is less likely to occur, making the polyimide closer to transparency.

Examples of fluorine-containing diamine residues include diamine residues derived from diamine compounds such as 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB), 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene, 3,4-diamino-2,2'-bis(trifluoromethyl)biphenyl, 4,4'-bis(2-(trifluoromethyl)-4-aminophenoxy)biphenyl, 2,2-bis(4-(2-(trifluoromethyl)-4-aminophenoxy)phenyl)hexafluoropropane, 4,4'-bis(3-(trifluoromethyl)-4-aminophenoxy)biphenyl, 4,4'-bis(3-(trifluoromethyl)-4-aminophenoxy)biphenyl, p-bis(2-trifluoromethyl)-4-aminophenoxy]benzene, and 2,2-bis-[4-(3-aminophenoxy)phenyl]hexafluoropropane.

Among the fluorine-containing diamine residues, it is more preferable to contain a diamine residue derived from a diamine compound represented by the following general formula (2) (hereinafter, sometimes referred to as "diamine (2) residue").

In general formula (2), the substituents X each independently represent an alkyl group having 1 to 3 carbon atoms substituted with a fluorine atom, and m and n each independently represent an integer from 1 to 4.

The diamine (2) residue is an aromatic diamine residue and has a biphenyl skeleton in which two benzene rings are connected by a single bond, and therefore it is easy to form an ordered structure and promotes the in-plane orientation of the molecular chains, thereby suppressing an increase in the CTE of the main polyimide layer (i) and improving the dimensional stability of the entire resin film A. From this perspective, the main polyimide constituting the main polyimide layer (i) preferably contains 50 molar parts or more of diamine (2) residues relative to a total of 100 molar parts of all diamine residues, and more preferably contains diamine (2) residues in the range of 50 molar parts to 100 molar parts.

Specific preferred examples of the diamine (2) residue include diamine residues derived from diamine compounds such as 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB) and 3,4-diamino-2,2'-bis(trifluoromethyl)biphenyl.

The main polyimide constituting the main polyimide layer (i) may contain, as a diamine residue other than the above, a diamine residue derived from a diamine component generally used in the synthesis of polyimides.

The polyimide of this embodiment can be produced by reacting the above-mentioned acid dianhydride component and diamine component in a solvent, generating polyamic acid, and then heating and ring-closing the polyamic acid. For example, the acid dianhydride component and the diamine component are dissolved in an organic solvent in approximately equal moles, and the mixture is stirred at a temperature in the range of 0°C to 100°C for 30 minutes to 24 hours to polymerize, thereby obtaining polyamic acid, which is a precursor of polyimide. In the reaction, the reaction components are dissolved so that the precursor generated is in the range of 5% by weight to 30% by weight, preferably 10% by weight to 20% by weight, in the organic solvent. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide, N,N-dimethylacetamide (DMAC), N-methyl-2-pyrrolidone, 2-butanone, dimethyl sulfoxide, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, and γ-butyrolactone. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. The amount of such organic solvents used is not particularly limited, but it is preferable to adjust the amount used so that the concentration of the polyamic acid solution (polyimide precursor solution) obtained by the polymerization reaction is about 5% by weight to 30% by weight.

In the synthesis of polyimide, the above-mentioned dianhydrides and diamines may be used alone or in combination of two or more. By selecting the types of dianhydrides and diamines, or the molar ratios of two or more dianhydrides or diamines, the transparency, dielectric properties, thermal expansion, adhesion, glass transition temperature, etc. can be controlled.

The synthesized polyamic acid is usually advantageously used as a reaction solvent solution, but it can be concentrated, diluted, or replaced with another organic solvent if necessary. Polyamic acid is also advantageously used because it generally has excellent solvent solubility. There are no particular limitations on the method for imidizing polyamic acid, and a suitable method is, for example, heat treatment in the solvent at a temperature in the range of 80°C to 400°C for 1 to 24 hours.

The weight average molecular weight of the polyamic acid is, for example, preferably in the range of 10,000 to 400,000, and more preferably in the range of 50,000 to 350,000. If the weight average molecular weight is less than 10,000, the strength of the film tends to decrease and it tends to become brittle. On the other hand, if the weight average molecular weight exceeds 400,000, the viscosity increases excessively, and defects such as uneven film thickness and streaks tend to occur during the coating process.

[First fluororesin layer, second fluororesin layer]
The first fluororesin layer F1 and the second fluororesin layer F2 may be layers containing a fluororesin as the main component of the resin component, preferably 70% by weight or more of the resin component, more preferably 90% by weight or more of the resin component, and most preferably the entire resin component. The main component of the resin component means a component contained in more than 50% by weight of the total resin component. Fluorine-based resin has high transparency and very excellent dielectric properties.

The fluorine-based resin constituting the first fluorine-based resin layer F1 and the second fluorine-based resin layer F2 is not particularly limited, but examples thereof include tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-tetrafluoroethylene-hexafluoropropylene copolymer (EFEP), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), etc. Among these fluorine-based resins, tetrafluoroethylene-based fluorine-based resins such as PFA, FEP, ETFE, and EFEP are preferred, and PFA is more preferred.
Furthermore, among PFAs, from the viewpoint of appropriately controlling the balance between mechanical strength and melting point, a copolymer having a molar ratio of tetrafluoroethylene (TFE) units and perfluoroalkyl vinyl ether copolymer (PAVE) units (TFE units:PAVE units) of 10:90 to 90:10 is most preferred.

In order to maintain good dielectric properties of the entire resin film A, the first fluororesin layer F1 and the second fluororesin layer F2 each have, as a single layer, a relative dielectric constant at 10 GHz that is preferably in the range of 1.9 to 3.1, more preferably in the range of 2.0 to 2.5, and a dielectric loss tangent that is preferably 0.001 or less, more preferably 0.0008 or less.

The melting points of the first fluororesin layer F1 and the second fluororesin layer F2 are preferably, for example, 260°C or higher. More preferably, they are 290°C or higher. If the melting point is below 260°C, they may melt during the manufacturing process of electronic devices, etc., causing changes in their characteristics.

The first fluororesin layer F1 and the second fluororesin layer F2 each preferably have a glass transition temperature (Tg) of 200°C or less, and more preferably 180°C or less. By setting the Tg of the first fluororesin layer F1 and the second fluororesin layer F2 to 200°C or less, thermocompression bonding at a low temperature is possible, which alleviates the internal stress generated when laminating with a metal-clad laminate or the like, and suppresses dimensional changes after circuit processing. If the Tg of the first fluororesin layer F1 and the second fluororesin layer F2 exceeds 200°C, the thermocompression bonding temperature becomes high when the resin film A is interposed between metal-clad laminates or the like and bonded, and there is a risk of impairing dimensional stability after circuit processing.

The first fluororesin layer F1 and the second fluororesin layer F2 may be the same or different in thickness, physical properties, material, etc., but it is preferable that they have the same configuration.

The resin film A of this embodiment satisfies the following conditions i) and ii).

Condition i) The total light transmittance of the entire resin film A is 80% or more.
By satisfying condition i), high transparency can be ensured. If the total light transmittance of the entire resin film A is less than 80%, it becomes difficult to apply the film to applications requiring transparency. It is more preferable that the total light transmittance of the entire resin film is 85% or more.

Condition ii) The thermal expansion coefficient of the entire resin film A is 30 ppm/K or less.
By satisfying condition ii, high dimensional stability can be obtained. If the thermal expansion coefficient of the entire resin film exceeds 30 ppm/K, it becomes difficult to obtain dimensional accuracy after circuit processing. The thermal expansion coefficient of the entire resin film is preferably within the range of 20 to 30 ppm/K.

Furthermore, the resin film of the present embodiment preferably satisfies the following condition iii).
Condition iii) The dielectric loss tangent of the entire resin film A at a frequency of 10 GHz, as measured by a split post dielectric resonator (SPDR resonator), is 0.008 or less.
By satisfying condition iii, when the resin film is applied to a circuit board or the like that transmits a high-frequency signal in the GHz band (for example, a frequency of 10 GHz or more), it is possible to effectively reduce transmission loss. It is more preferable that the dielectric loss tangent of the entire resin film at a frequency of 10 GHz is 0.005 or less.
The relative dielectric constant of the entire resin film A at 10 GHz is preferably within a range of 2.0 to 4.0, and more preferably within a range of 2.5 to 3.5.

Regarding the above conditions i) to iii), it has been difficult to achieve both high total light transmittance and low dielectric loss tangent in a resin film composed of a single polyimide. The reason for this is that in order to increase the total light transmittance, it is necessary to make it difficult for the CT interaction of polyimide to occur and difficult to form an ordered structure, while in order to decrease the dielectric loss tangent of polyimide, it is effective to form an ordered structure, so there is a trade-off between improving the total light transmittance and reducing the dielectric loss tangent.
On the other hand, a resin film composed solely of a fluororesin can achieve high total light transmittance and low dielectric tangent. However, since the glass transition temperature (Tg) of the fluororesin is 94°C and the melting point is about 300°C (in the case of PFA), the resin film is lacking in heat resistance and dimensional stability.
The resin film of the present embodiment can realize high transparency and dimensional stability by laminating a polyimide insulating layer and a fluororesin layer having different properties, and can also achieve both transparency and low dielectric loss tangent. In addition, by laminating a fluororesin layer on a polyimide insulating layer, high transparency can be ensured even for a relatively thick resin film having a thickness of 50 μm or more.

The resin film A preferably has a yellowness index (YI) of 10 or less, and more preferably 8 or less. By controlling the YI to 10 or less, the resin film A can be made nearly colorless. On the other hand, if the YI exceeds 10, the yellow to yellowish brown coloring becomes stronger, and the visibility of the resin film decreases.

[Thickness]
The thickness of the entire resin film A is preferably, for example, in the range of 10 to 150 μm, more preferably in the range of 10 to 125 μm. The thickness T _P of the polyimide insulating layer P is preferably, for example, in the range of 5 to 75 μm, more preferably in the range of 8 to 50 μm. Here, the ratio (T _P /T _A ) of the thickness T _P of the polyimide insulating layer P to the thickness T _A of the entire resin film A is preferably in the range of 0.5 to 0.9, more preferably in the range of 0.5 to 0.8. If the polyimide insulating layer P is too thin and the ratio (T _P /T _A ) is below 0.5, the Tg and heat resistance of the entire resin film A will decrease, the dimensional stability will deteriorate, and the required performance as an insulating resin layer of a circuit board such as an FPC will not be maintained. On the other hand, if the polyimide insulating layer P is too thick and the ratio (T _P /T _A ) exceeds 0.9, it will be difficult to achieve high transparency and low dielectric tangent of the entire resin film A. Furthermore, if the thickness of the fluororesin layer (i.e., the total thickness of the first fluororesin layer F1 and the second fluororesin layer F2) is too large, the dimensional stability of the entire resin film A will be deteriorated, and conversely, if it is too small, the adhesion will be reduced and the total light transmittance and dielectric properties of the entire resin film A will be deteriorated.

The resin film A of the present embodiment may contain an inorganic filler and/or an organic filler as an optional component, as long as the effect of the invention is not impaired. Examples of inorganic fillers include silicon dioxide, aluminum oxide, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, calcium fluoride, etc. Examples of organic fillers include liquid crystal polymers, etc. These fillers may be used alone or in a mixture of two or more types. In addition, the resin film A may contain, as necessary, optional components such as plasticizers, other curable resin components such as epoxy resins, curing agents, curing accelerators, coupling agents, and flame retardants, as long as the effect of the invention is not impaired.

The resin film A in this embodiment may be laminated to a substrate such as a resin sheet, for example, a copper foil, a glass plate, a polyimide film, a polyamide film, or a polyester film.

[Method of manufacturing resin film]
There is no particular limitation on the method for producing the resin film A of the present embodiment. When the resin film A has a laminated structure of a first fluororesin layer F1/a polyimide insulating layer P/a second fluororesin layer F2 as shown in Fig. 1, the following method can be exemplified.

The first method is a method of producing a resin film A by forming and laminating a first fluororesin layer F1, a polyimide insulating layer P, and a second fluororesin layer F2 in this order by a casting method on an arbitrary substrate, and peeling them off from the substrate as necessary. The first method is a preferred method when it is desired to form the first fluororesin layer F1 and the second fluororesin layer F2 to have small thicknesses.

The second method utilizes a film lamination method, in which two fluororesin films and one polyimide film are prepared, and the polyimide film is sandwiched between the fluororesin films and laminated by pressing to produce a resin film A. The second method is preferred when it is desired to form the first fluororesin layer F1 and the second fluororesin layer F2 to a large thickness. The film lamination method makes it possible to form a large thickness that is difficult to achieve using the first method, and transparency can be maintained even when the thickness is increased.

Here, the first method will be described in detail with reference to FIG.
First, a particle dispersion liquid in which fluororesin particles F0 are dispersed in a solvent is applied onto an arbitrary substrate B, and then dried, so that a plurality of fluororesin particles F0 are attached onto the substrate B as shown in FIG. 2(a) (step 1). The substrate B to be used is not particularly limited, but it is preferable to use a metal foil such as copper foil having a thickness of 5 to 35 μm as a heat-resistant material. In the first method, by using copper foil as the substrate B, a copper-clad laminate having the resin film A and the copper foil layer can be produced at the same time as the production of the resin film A. As the arbitrary solvent, for example, a highly volatile organic solvent is preferable. As the fluororesin particles F0, those having an average particle diameter of 1 to 5 μm as measured by a laser diffraction/scattering measurement method are preferable, and for example, a commercially available product such as Fluon+ ^TM EA-2000 powder (manufactured by AGC) can be used.

Next, the fluororesin particles F0 are heat-treated together with the substrate B, melted, and then cooled and solidified to form a film, and as shown in FIG. 2(b), a first fluororesin layer F1 is formed on the substrate B to produce a first laminate (step 2). The heat treatment temperature for melting the fluororesin particles F0 should be equal to or higher than the melting point of the fluororesin, and in the case of PFA, for example, it is preferable to set it to about 320°C.

Next, a polyimide precursor solution is applied to the first fluororesin layer F1 of the formed first laminate, dried, and heat-treated to form a polyimide insulating layer P, as shown in FIG. 2(c), to produce a second laminate (step 3). The method of applying the polyimide precursor solution to the substrate is not particularly limited, and it is possible to apply it with a coater such as a comma, die, knife, or lip. The temperature of the heat treatment for imidization can be, for example, 360°C. When the polyimide insulating layer P is composed of multiple layers, the polyimide precursor solution may be applied and heat-treated each time it is applied and dried, or the process of applying the polyimide precursor solution and drying may be repeated multiple times and then heat-treated all at once. In addition, the polyamic acid laminate structure may be applied and dried at the same time by multi-layer extrusion, and then imidization may be performed. The second laminate is formed into a resin film A having a structure in which the first fluororesin layer F1 is formed on one side of the polyimide insulating layer P by peeling off the substrate B as necessary. Furthermore, when a metal foil is used as the substrate B, the second laminate becomes a single-sided metal-clad laminate having an insulating resin layer made of resin film A on one side of the metal layer.

Next, a particle dispersion liquid in which fluororesin particles F0 are dispersed in an arbitrary solvent is applied onto the polyimide insulating layer P of the formed second laminate, and then dried to adhere a plurality of fluororesin particles F0 onto the polyimide insulating layer P, as shown in FIG. 2(d) (Step 4). This Step 4 can be carried out in the same manner as Step 1.

Next, the fluororesin particles F0 are heat-treated together with the second laminate to melt, and then cooled and solidified to form a film, and as shown in Fig. 2(e), a second fluororesin layer F2 is formed on the polyimide insulating layer P to produce a third laminate (step 5). This step 5 can be carried out in the same manner as step 2.
The third laminate becomes a resin film A having a first fluororesin layer F1 on one side of the polyimide insulating layer P and a second fluororesin layer F2 on the other side by peeling off the substrate B as necessary. When a metal foil is used as the substrate B, the third laminate becomes a single-sided metal-clad laminate having an insulating resin layer made of the resin film A on one side of the metal layer as it is. Furthermore, the third laminate can also be a double-sided metal-clad laminate by using a metal foil as the substrate B and forming a metal layer on the side of the resin film A opposite to the substrate B.

The resin film A obtained in the above manner has a fluororesin layer (first fluororesin layer F1 and/or second fluororesin layer F2) laminated on one or both sides of the polyimide insulating layer P, thereby achieving both improved total light transmittance and low dielectric tangent, and has high dimensional stability in addition to high transparency and excellent dielectric properties.

[Metal-clad laminate]
The metal-clad laminate according to one embodiment of the present invention comprises the above-mentioned resin film A and a metal layer laminated on the surface of the fluororesin layer of the resin film A. In this case, the resin film A may have a configuration as shown in FIG. 1 in which the resin film A has fluororesin layers (the first fluororesin layer F1 or the second fluororesin layer F2) on both sides of the polyimide insulating layer P, or may have a fluororesin layer (the first fluororesin layer F1 or the second fluororesin layer F2) on only one side of the polyimide insulating layer P (not shown). In other words, the metal-clad laminate according to this embodiment may be a single-sided metal-clad laminate or a double-sided metal-clad laminate.

The metal-clad laminate of this embodiment can be manufactured by laminating a metal foil onto a resin film A, or by using a metal foil as the substrate B for preparing the resin film A, as described above.

Next, application examples of the metal-clad laminate of this embodiment will be described with reference to FIGS.
FIG. 3 is a schematic diagram showing a configuration of a metal-clad laminate according to an embodiment of the present invention. The metal-clad laminate 10A according to the present embodiment has:
a first metal layer M1;
a fluorine-based resin adjacent layer F10 provided adjacent to one side of the first metal layer M1;
A second metal layer M2; and
a fluorine-based resin adjacent layer F20 provided adjacent to one side of the second metal layer M2;
a plurality of resin layers interposed between the fluorine-based resin adjacent layer F10 and the fluorine-based resin adjacent layer F20;
The first metal layer M1 and the second metal layer M2 are located on the outermost side, and a fluororesin adjacent layer F10 and a fluororesin adjacent layer F20 are arranged in contact with the inner side of the first metal layer M1 and the second metal layer M2. Furthermore, a plurality of resin layers including a plurality of polyimide insulating layers P and a fluororesin intermediate layer F30 are interposed between the fluororesin adjacent layer F10 and the fluororesin adjacent layer F20. Here, the fluororesin adjacent layer F10 is adjacent to one polyimide insulating layer P, and the fluororesin adjacent layer F20 is in contact with another polyimide insulating layer P. The metal-clad laminate 10A has a fluororesin adjacent layer F10 or a fluororesin adjacent layer F20, each of which has a low dielectric tangent, arranged in a position adjacent to a pair of metal layers (the first metal layer M1 and the second metal layer M2, which are wiring), and therefore can effectively suppress transmission loss in high-frequency signal transmission.

As shown in Fig. 3, a resin laminate 40 is formed by a fluororesin adjacent layer F10, a fluororesin adjacent layer F20, and a plurality of resin layers. In addition to the fluororesin adjacent layer F10 and the fluororesin adjacent layer F20, this resin laminate 40 has at least two or more polyimide insulating layers P and a fluororesin intermediate layer F30 laminated between the polyimide insulating layers P. In this way, by providing a laminate structure of the polyimide insulating layer P and the fluororesin intermediate layer F30 between the fluororesin adjacent layer F10 and the fluororesin adjacent layer F20, a low dielectric tangent is realized while ensuring high dimensional stability.
The resin laminate 40 may have any resin layers other than those described above, but is preferably formed only from resin layers having the above functions.

The metal-clad laminate 10A shown in FIG. 3 has two polyimide insulating layers P and one fluororesin intermediate layer F30, but there is no particular limit to the number of fluororesin intermediate layers F30 as long as there are two or more polyimide insulating layers P. For example, the metal-clad laminate 10B shown in FIG. 4 may have three polyimide insulating layers P and two fluororesin intermediate layers F30, or the metal-clad laminate 10C shown in FIG. 5 may have five polyimide insulating layers P and four fluororesin intermediate layers F30.

In the metal-clad laminate 10, the first metal layer M1 and the second metal layer M2 may have the same or different configurations, but it is preferable that they be made of the same material, have the same physical properties, and have the same thickness.

The fluororesin adjacent layer F10 and the fluororesin adjacent layer F20 may have the same or different configurations, but preferably have the same material, physical properties, and thickness. For example, by making the dielectric tangent and thickness of the fluororesin adjacent layer F10 and the fluororesin adjacent layer F20 the same, it becomes easier to design a circuit board for high-frequency transmission to reduce transmission loss.

Furthermore, the configurations of the two fluororesin adjacent layers F10, F20 and the fluororesin intermediate layer F30 may be the same or different, but it is preferable that they be made of the same material and have the same physical properties in order to improve the dielectric properties of the entire resin laminate 40 and effectively suppress transmission loss of high-frequency signals.

The configuration of the multiple polyimide insulating layers P may be the same or different, but it is preferable that they be made of the same material, have the same physical properties, are the same thickness, and have the same layer structure, as this makes it easier to design the mechanical strength and dimensional accuracy when manufacturing the circuit board.

From the viewpoint of suppressing transmission loss of high frequency signals, the dielectric loss tangent _Df1 at 10 GHz of each of the fluororesin adjacent layers F10, F20 and the fluororesin intermediate layer F30 is preferably 0.001 or less, and more preferably 0.0008 or less.

In addition, it is desirable that the dielectric loss tangent _Df2 at 10 GHz of the polyimide insulating layer P is as low as possible, but since this is a layer that ensures the maintenance of dimensional accuracy and mechanical strength, it is preferably 0.01 or less, and more preferably 0.009 or less. Even if the dielectric loss tangent _Df2 of the polyimide insulating layer P is somewhat high, the low dielectric loss tangent of the entire resin laminate 40 can be ensured by laminating it with the fluorine-based resin adjacent layers F10, F20 and the fluorine-based resin intermediate layer F30, which have lower dielectric loss tangents, and by taking into consideration the thickness ratios of these layers.

The ratio (T PA /T 40 ) of the total thickness T _PA of the multiple polyimide insulating layers P to the total thickness T ₄₀ of the resin laminate 40 (i.e., the fluororesin adjacent layers F10, F20, the one or more fluororesin intermediate layers F30, and the multiple polyimide insulating _{layers P} ) is preferably within the range of 0.5 to 0.9, and more preferably within the range of 0.5 to 0.8.
By setting the ratio (T _PA /T ₄₀ ) within the above range, it is possible to achieve high transparency and reduced transmission loss of high frequency signals while maintaining the dimensional accuracy and mechanical strength when the metal-clad laminates 10A, 10B, and 10C are circuit-processed. From this viewpoint, the ratio (T _PA /T ₄₀ ) is preferably within the range of 50 to 90%.

Here, the thickness of each layer in the resin laminate 40 is not particularly limited as it can be appropriately set depending on the intended use, but examples thereof include the following.
The thickness of each of the fluororesin adjacent layers F10 and F20 is preferably within the range of 1 to 100 μm, and more preferably within the range of 2 to 75 μm.
The thickness of each polyimide insulating layer P is preferably within the range of 5 to 100 μm, and more preferably within the range of 10 to 50 μm.
The thickness of one layer of the fluororesin intermediate layer F30 is preferably within the range of 1 to 150 μm, and more preferably within the range of 2 to 100 μm.
The total thickness T of the resin laminate 40 is preferably within a range of 50 to 300 μm, and more preferably within a range of 75 to 200 μm.

Below, we will explain each layer that makes up metal-clad laminates 10A, 10B, and 10C.

[Metal layer]
The material of the first metal layer M1 and the second metal layer M2 is not particularly limited, but examples thereof include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof. Among these, copper or a copper alloy is particularly preferable. The material of the wiring layer in the circuit board of this embodiment, which will be described later, is the same as that of the first metal layer M1 and the second metal layer M2.

The thickness of the first metal layer M1 and the second metal layer M2 is not particularly limited, but when a metal foil such as copper foil is used, it is preferably 35 μm or less, and more preferably in the range of 5 to 25 μm. From the viewpoint of production stability and handling, it is preferable that the lower limit of the thickness of the metal foil is 5 μm. When copper foil is used, it may be rolled copper foil or electrolytic copper foil. In addition, commercially available copper foil may be used as the copper foil.

The metal foil may also be surface-treated with, for example, siding, aluminum alcoholate, aluminum chelate, silane coupling agent, etc., for the purpose of, for example, rust prevention or improving adhesion.

[Production of metal-clad laminate]
The metal-clad laminates 10A, 10B, and 10C can be manufactured, for example, by the following method A, method B, or method C, which is a combination of these.

In method A, a fluororesin adjacent layer F10 is formed on the first metal layer M1 by a casting method, and a fluororesin adjacent layer F20 is separately formed on the second metal layer M2. Next, a polyimide insulating layer P and/or a fluororesin intermediate layer F30 is formed by a casting method on each of the fluororesin adjacent layers F10 and F20 so as to obtain the required number of layers, thereby separately producing two single-sided metal-clad laminates. The formation of each layer by the casting method can be carried out by the method described for resin film A. Then, the resin surfaces of the two single-sided metal-clad laminates can be bonded together to produce metal-clad laminates 10A, 10B, and 10C.

In method B, resin sheets corresponding to the fluororesin adjacent layer F10, the fluororesin adjacent layer F20, the multiple polyimide insulating layers P, and one or multiple fluororesin intermediate layers F30 are prepared by a film lamination method, and these resin sheets are placed between the first metal layer M1 and the second metal layer M2, bonded together, and thermocompression bonded to produce metal-clad laminates 10A, 10B, and 10C.

Method C is a combination of Method A and Method B. For example, two single-sided metal-clad laminates are formed separately by a casting method so that the required number of layers is obtained, and the required number of resin sheets corresponding to the separately prepared polyimide insulating layer P and fluororesin intermediate layer F30 are placed between the resin surfaces of these two single-sided metal-clad laminates, bonded together, and thermocompression bonded to produce metal-clad laminates 10A, 10B, and 10C.

The metal-clad laminates 10A, 10B, and 10C of the present embodiment obtained as described above can be used to manufacture circuit boards such as single-sided FPCs or double-sided FPCs by processing the wiring circuitry, for example by etching the first metal layer M1 and/or the second metal layer M2.

[Circuit board]
The metal-clad laminate using the resin film A as the insulating resin layer and the metal-clad laminates 10A, 10B, and 10C are useful mainly as circuit board materials such as FPCs and rigid-flex circuit boards. One or both of the metal layers in the metal-clad laminate are processed into a pattern by a conventional method to form a wiring layer, thereby manufacturing a circuit board such as an FPC, which is one embodiment of the present invention. Although not shown, the circuit board of this embodiment includes an insulating resin layer (resin film A or resin laminate 40) and a wiring layer provided on one or both sides of the insulating resin layer, and the insulating resin layer has high transparency, can reduce transmission loss even in high-frequency transmission, and has excellent dimensional stability.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. In the following examples, various measurements and evaluations are as follows, unless otherwise specified.

[Calculation of Yellowness Index (YI)]
The yellowness index (YI) of the resin film (50 mm×50 mm) was measured using a UV-3600 spectrophotometer manufactured by Shimadzu Corporation.
1) YI (yellowness)
In accordance with JIS Z 8722, calculation was performed based on the calculation formula represented by the following formula (1).
YI=100×(1.2879X-1.0592Z)/Y...(1)
X, Y and Z: Tristimulus values of the test piece

[Measurement of coefficient of thermal expansion (CTE)]
A resin film (3 mm x 15 mm) was heated from 30°C to 280°C at a heating rate of 10°C/min while applying a load of 5.0 g in a thermomechanical analysis (TMA) device, and then cooled. The thermal expansion coefficient was measured from the elongation (linear expansion) of the resin film from 250°C to 100°C during cooling.

[Calculation of total light transmittance (T.T.)]
The total light transmittance (TT) of the resin film (50 mm x 50 mm) was measured in accordance with JIS K 7136 using a product name: HAZE METER NDH500 manufactured by Nippon Denshoku Industries Co., Ltd. For the insulating resin layer of the metal clad laminate, a resin film was prepared by etching a single-sided or double-sided metal foil, and this was measured in the same manner.

[Measurement of dielectric constant (Dk) and dielectric loss tangent (Df)]
The relative dielectric constant (Dk) and dielectric loss tangent (Df) of the resin film obtained by etching away the copper foil of the copper-clad laminate prepared in each Example and Comparative Example were measured at a frequency of 10 GHz using a vector network analyzer (manufactured by Agilent, product name: E8363C) and a split post dielectric resonator (SPDR resonator). The resin film used for the measurement was left for 24 hours under the conditions of temperature: 24 to 26°C and humidity: 45 to 55%.

[Viscosity measurement]
The viscosity of the polyamic acid solution obtained in each Synthesis Example was measured at 25° C. using a cone-plate viscometer equipped with a thermostatic water bath (manufactured by Tokimec Co., Ltd.).

[Measurement of copper foil surface roughness]
The sample was cut into a size of about 10 mm square, fixed to a sample stage with double-sided tape, irradiated with soft X-rays to remove static electricity from the copper foil surface, and then measured for the ten-point average roughness Rz (RzJis) of the copper foil surface under the following measurement conditions using a scanning probe microscope (AFM, manufactured by Bruker AXS, product name: Dimension Icon type SPM).
Measurement mode: tapping mode Measurement area: 1 μm x 1 μm
Scan speed: 1Hz
Probe: Bruker, RTESP-300

The abbreviations used in the examples represent the following compounds.
PFA: Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer TFMB: 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl PMDA: Pyromellitic dianhydride 6FDA: 2,2-bis(3,4-dicarboxyphenyl)-hexafluoropropane dianhydride ODPA: 4,4'-oxydiphthalic dianhydride BAPS: Bis[4-(aminophenoxy)phenyl]sulfone APB: 1,3-bis(3-aminophenoxy)benzene m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl TPE-R: 1,3-bis(4-aminophenoxy)benzene BPDA: 3,3',4,4'-biphenyl tetracarboxylic dianhydride DMAc: N,N-dimethylacetamide

Synthesis Examples 1 to 9
To synthesize polyamic acid solutions A to I, a solvent, DMAc, was added to a 200 ml separable flask under a nitrogen gas flow so as to give a solid content concentration shown in Table 1, and the diamine component and acid anhydride component shown in Table 1 were dissolved by heating at 45° C. for 2 hours while stirring. Thereafter, the solution was stirred at room temperature for 2 days to carry out a polymerization reaction, and viscous solutions of polyamic acid A to I were prepared.

[Example 1]
A DMAc solution in which PFA microparticles 1 (manufactured by AGC, product name: Fluon+™ EA-2000 powder, D50: 3 μm, maximum particle size: 10 μm) were dispersed at 30% by weight was uniformly applied onto copper foil 1 (electrolytic copper foil, manufactured by Fukuda Metal Foil & Powder Co., Ltd., product name: CF- ^T9DA -SV-12, thickness: 12 _μm , Rzjis: 0.8 μm) to a final thickness of 15 μm, and then the coating was dried by heating at 90° C. for 3 minutes and at 120° C. for 3 minutes to remove the solvent, and then heated at 320° C. for 3 minutes to form a PFA film on the copper foil 1. Next, a diluted solution of polyamic acid solution A (viscosity; 13700 cP) was uniformly applied on the PFA film so that the thickness after curing was 30 μm, and then the solution was heated and dried at 125 ° C. to remove the solvent, and then heat treatment was performed stepwise from 125 ° C. to 360 ° C. to complete the imidization and form a polyimide layer A. Furthermore, a DMAc solution in which PFA fine particles 1 were dispersed at 30 wt % was uniformly applied on the polyimide layer A so that the final thickness was 15 μm, and then the solution was heated and dried at 90 ° C. for 3 minutes and at 120 ° C. for 3 minutes, and after removing the solvent, the solution was heated at 320 ° C. for 3 minutes to form an insulating resin layer 1 having a thickness of 60 μm consisting of a PFA layer / polyimide layer A / PFA layer, and a metal clad laminate 1 was prepared.

Copper foil 1 was etched away using an aqueous solution of ferric chloride to prepare resin film 1. The measurement results of T.T., YI, CTE, relative dielectric constant, and dielectric loss tangent for resin film 1 are shown in Table 2.

[Example 2]
On the copper foil 1, PFA dispersion 1 (manufactured by AGC, trade name: Fluon+ ^™ EA-2000 dispersion, D ₅₀ : 3 μm, maximum particle size: 10 μm, 50 wt% dispersed DMAc solution; the same applies below) was uniformly applied to a final thickness of 5 μm, and then heated and dried at 90° C. for 3 minutes and at 120° C. for 3 minutes to remove the solvent, and then heated at 320° C. for 3 minutes to form a PFA film on the copper foil 1. Next, a diluted solution of polyamic acid solution B (viscosity: 17300 cP) was uniformly applied on the PFA film to a thickness of 15 μm after curing, and then heated and dried at 125° C. to remove the solvent, and then heat-treated stepwise from 125° C. to 360° C. to complete imidization and form a polyimide layer B. Furthermore, PFA dispersion 1 was uniformly applied onto polyimide layer B to a final thickness of 5 μm, and then heated and dried at 90° C. for 3 minutes and at 120° C. for 3 minutes to remove the solvent, and then heated at 320° C. for 3 minutes to form insulating resin layer 2 having a thickness of 25 μm and consisting of PFA layer/polyimide layer B/PFA layer, thereby preparing metal clad laminate 2.

The copper foil 1 was etched away using an aqueous solution of ferric chloride to prepare a resin film 2. The measurement results of the T.T., YI, CTE, relative dielectric constant, and dielectric tangent of the resin film 2 are shown in Table 2.

[Example 3]
On the copper foil 1, the PFA dispersion 1 was uniformly applied to a final thickness of 1 μm, and then the coating was dried by heating at 90° C. for 1 minute and at 120° C. for 1 minute to remove the solvent, and then heated at 320° C. for 1 minute and 30 seconds to form a PFA film on the copper foil 1. Next, a diluted solution of polyamic acid solution C (viscosity: 23000 cP) was uniformly applied on the PFA film to a thickness of 10 μm after curing, and then the coating was dried by heating at 125° C. to remove the solvent, and then heat treatment was performed stepwise from 125° C. to 360° C. to complete imidization and form a polyimide layer C. Furthermore, PFA dispersion 1 was uniformly applied onto the polyimide layer C to a final thickness of 1 μm, and then heated and dried at 90° C. for 1 minute and at 120° C. for 1 minute to remove the solvent, and then heated at 320° C. for 1 minute and 30 seconds to form an insulating resin layer 3 having a thickness of 12 μm and consisting of a PFA layer/polyimide layer C/PFA layer, thereby preparing a metal clad laminate 3.

The copper foil 1 was etched away using an aqueous solution of ferric chloride to prepare a resin film 3. The measurement results of the T.T., YI, CTE, relative dielectric constant, and dielectric loss tangent of the resin film 3 are shown in Table 2.

[Example 4]
A diluted solution of polyamic acid solution A (viscosity; 13,700 cP) was uniformly applied onto a base film 1 (polyimide film, manufactured by Ube Industries, Ltd., product name: Upilex 75S, thickness 75 μm) so that the thickness after curing would be 50 μm, and then the solution was dried by heating at 125° C. to remove the solvent, and then was subjected to stepwise heat treatment from 125° C. to 360° C. to complete imidization and form a polyimide layer A. The polyimide layer A was peeled off from the base film 1, and polyimide film A was prepared.
A PFA film 1 (manufactured by AGC, product name: Fluon+ ^™ EA-2000 film, thickness: 25 μm), polyimide film A, PFA film 1 (thickness: 25 μm), and copper foil 1 were laminated in that order on top of copper foil 1, and heated and pressed at 320° C. and 7.5 MPa for 20 minutes in a vacuum atmosphere to prepare a double-sided metal-clad laminate 4.

The copper foil 1 was etched away using an aqueous solution of ferric chloride to prepare a resin film 4. The measurement results of the T.T., YI, CTE, relative dielectric constant, and dielectric tangent of the resin film 4 are shown in Table 2.

[Example 5]
A diluted solution of polyamic acid solution D (viscosity; 3200 cP) was uniformly applied on the copper foil 1 so that the thickness after curing was 1.0 μm, and then heated and dried at 125 ° C to remove the solvent. Next, a diluted solution of polyamic acid solution B (viscosity; 17300 cP) was uniformly applied thereon so that the thickness after curing was 8 μm, and then heated and dried at 125 ° C to remove the solvent. Furthermore, a diluted solution of polyamic acid solution E (viscosity; 1700 cP) was uniformly applied thereon so that the thickness after curing was 1.0 μm, and then heated and dried at 125 ° C to remove the solvent. In this way, after forming three polyamic acid layers, a stepwise heat treatment from 125 ° C to 360 ° C was performed over 30 minutes to complete the imidization, and a polyimide layer 5 having a thickness of 10 μm consisting of polyimide layer D / polyimide layer B / polyimide layer E was formed, and a metal clad laminate 5 was prepared.
The copper foil 1 of the obtained metal clad laminate 5 was removed by etching using an aqueous solution of ferric chloride to prepare a polyimide film 5.
Next, the PFA dispersion liquid 1 was uniformly applied onto the copper foil 1 so as to give a final thickness of 2 μm, and then the coating was dried by heating at 90° C. for 3 minutes and at 120° C. for 3 minutes to remove the solvent, and then heated at 320° C. for 3 minutes to prepare a metal laminated film 5 in which a PFA film was formed on the copper foil 1.
A polyimide film 5 was laminated on the PFA film of the obtained metal laminated film 5, and then a metal laminated film 5 was laminated on top of that so that the PFA film was in contact with the polyimide.Then, heating and pressing were performed for 20 minutes at 320°C and 7.5 MPa in a vacuum atmosphere to prepare a double-sided metal-clad laminate 5.

The copper foil 1 was etched away using an aqueous solution of ferric chloride to prepare a resin film 5. The measurement results of the T.T., YI, CTE, relative dielectric constant, and dielectric tangent of the resin film 5 are shown in Table 2.

[Example 6]
On the copper foil 1, the PFA dispersion 1 was uniformly applied so that the final thickness was 5 μm, and then it was heated and dried at 90 ° C for 3 minutes and 120 ° C for 3 minutes, and after removing the solvent, it was heated at 320 ° C for 3 minutes to form a PFA film on the copper foil 1. Next, a diluted solution of polyamic acid solution F (viscosity; 18400 cP) was uniformly applied on the PFA film so that the thickness after curing was 20 μm, and then it was heated and dried at 125 ° C to remove the solvent, and then it was subjected to a stepwise heat treatment from 125 ° C to 360 ° C to complete the imidization and form a polyimide layer F. Furthermore, on the polyimide layer F, the PFA dispersion 1 was uniformly applied so that the final thickness was 5 μm, and then it was heated and dried at 90 ° C for 3 minutes and 120 ° C for 3 minutes, and after removing the solvent, it was heated at 320 ° C for 3 minutes to form a second PFA film. Next, a diluted solution of polyamic acid solution F (viscosity; 18400 cP) was uniformly applied on the second PFA film so that the thickness after curing was 20 μm, and then the solution was heated and dried at 125 ° C. to remove the solvent, and then heat treatment was performed stepwise from 125 ° C. to 360 ° C. to complete the imidization and form a polyimide layer F. Furthermore, PFA dispersion liquid 1 was uniformly applied on the polyimide layer F so that the final thickness was 5 μm, and then heated and dried at 90 ° C. for 3 minutes and at 120 ° C. for 3 minutes, and after removing the solvent, heated at 320 ° C. for 3 minutes to form an insulating resin layer 6 having a thickness of 55 μm consisting of a PFA layer / polyimide layer F / PFA layer / polyimide layer F / PFA layer, and a metal clad laminate 6 was prepared.

The copper foil 1 was etched away using an aqueous solution of ferric chloride to prepare a resin film 6. The measurement results of the T.T., YI, CTE, relative dielectric constant, and dielectric loss tangent of the resin film 6 are shown in Table 2.

[Example 7]
On the copper foil 1, the PFA dispersion 1 was uniformly applied to a final thickness of 2 μm, and then the coating was dried by heating at 90° C. for 1 minute and at 120° C. for 1 minute to remove the solvent, and then heated at 320° C. for 1 minute and 30 seconds to form a PFA film on the copper foil 1. Next, a diluted solution of polyamic acid solution C (viscosity: 23000 cP) was uniformly applied on the PFA film to a thickness of 21 μm after curing, and then the coating was dried by heating at 125° C. to remove the solvent, and then heat treatment was performed stepwise from 125° C. to 360° C. to complete imidization and form a polyimide layer C. Furthermore, PFA dispersion 1 was uniformly applied onto the polyimide layer C so that the final thickness would be 2 μm, and then heated and dried at 90° C. for 1 minute and at 120° C. for 1 minute to remove the solvent, and then heated at 320° C. for 1 minute and 30 seconds to form an insulating resin layer 7 having a thickness of 25 μm and consisting of a PFA layer/polyimide layer C/PFA layer, thereby preparing a metal clad laminate 7.
Two of the obtained metal clad laminates 7 were stacked together so that the copper foil 1 was positioned as the outermost layer, and heated and pressed at 320° C. and 7.5 MPa for 20 minutes in a vacuum atmosphere to prepare a double-sided metal clad laminate 7 .

The copper foil 1 was etched away using an aqueous solution of ferric chloride to prepare the resin film 7. The measurement results of the T.T., YI, CTE, relative dielectric constant, and dielectric tangent of the resin film 7 are shown in Table 2.

[Example 8]
On the copper foil 1, the PFA dispersion 1 was uniformly applied to a final thickness of 1 μm, and then heated and dried at 90° C. for 1 minute and at 120° C. for 1 minute to remove the solvent, and then heated at 320° C. for 1 minute and 30 seconds to form a PFA film on the copper foil 1. Next, a diluted solution of polyamic acid solution B (viscosity: 17300 cP) was uniformly applied on the PFA film to a thickness of 15 μm after curing, and then heated and dried at 125° C. to remove the solvent, and then heat-treated stepwise from 125° C. to 360° C. to complete imidization, form a polyimide layer B, and prepare a metal clad laminate 8.
A PFA film 1 (thickness: 25 μm) was placed on top of the polyimide of the obtained metal clad laminate 8, and then a metal clad laminate 8 was laminated on top of that so that the copper foil 1 was positioned as the outermost layer. The resulting laminate was heated and pressed at 320° C. and 7.5 MPa for 20 minutes in a vacuum atmosphere to prepare a double-sided metal clad laminate 8.

The copper foil 1 was etched away using an aqueous solution of ferric chloride to prepare a resin film 8. The measurement results of the T.T., YI, CTE, relative dielectric constant, and dielectric loss tangent of the resin film 8 are shown in Table 2.

[Example 9]
On the copper foil 1, the PFA dispersion 1 was uniformly applied to a final thickness of 1 μm, and then the coating was dried by heating at 90° C. for 1 minute and at 120° C. for 1 minute to remove the solvent, and then heated at 320° C. for 1 minute and 30 seconds to form a PFA film on the copper foil 1. Next, a diluted solution of polyamic acid solution B (viscosity: 17300 cP) was uniformly applied on the PFA film to a thickness of 10 μm after curing, and then the coating was dried by heating at 125° C. to remove the solvent, and then heat treatment was performed stepwise from 125° C. to 360° C. to complete imidization and form a polyimide layer B. Furthermore, PFA dispersion 1 was uniformly applied onto polyimide layer B to a final thickness of 1 μm, and then heated and dried at 90° C. for 1 minute and at 120° C. for 1 minute to remove the solvent, and then heated at 320° C. for 1 minute and 30 seconds to form an insulating resin layer 9 having a thickness of 12 μm and consisting of a PFA layer/polyimide layer B/PFA layer, thereby preparing metal clad laminate 9.
A diluted solution of polyamic acid solution G (viscosity: 22,400 cP) was uniformly applied onto the substrate film 1 in advance so that the thickness after curing would be 10 μm, and then the solution was heated and dried at 125° C. to remove the solvent, and then heat treatment was performed stepwise from 125° C. to 360° C. to complete imidization and form a polyimide layer G. The polyimide film G was prepared by peeling it off from the substrate film 1, and the polyimide film G was laminated on the PFA layer of the metal clad laminate 9, and the metal clad laminate 9 was laminated on top of the polyimide film G so that the copper foil 1 was the outermost layer. The polyimide film G was heated and pressed at 320° C. and 7.5 MPa for 20 minutes in a vacuum atmosphere to obtain a double-sided metal clad laminate 9.

The copper foil 1 was etched away using an aqueous solution of ferric chloride to prepare a resin film 9. The measurement results of the T.T., YI, CTE, relative dielectric constant, and dielectric loss tangent of the resin film 9 are shown in Table 2.

(Comparative Example 1)
On the copper foil 1, the PFA dispersion 1 was uniformly applied to a final thickness of 6 μm, and then heated and dried at 90° C. for 3 minutes and at 120° C. for 3 minutes to remove the solvent, and then heated at 320° C. for 3 minutes to form a PFA film on the copper foil 1. Next, a diluted solution of polyamic acid solution G (viscosity: 22400 cP) was uniformly applied on the PFA film to a thickness of 12.5 μm after curing, and then heated and dried at 125° C. to remove the solvent, and then heat treatment was performed stepwise from 125° C. to 360° C. to complete imidization and form a polyimide layer G. Furthermore, PFA dispersion 1 was uniformly applied onto the polyimide layer G to a final thickness of 6 μm, and then heated and dried at 90° C. for 3 minutes and at 120° C. for 3 minutes to remove the solvent, and then heated at 320° C. for 3 minutes to form an insulating resin layer 10 having a thickness of 24.5 μm and consisting of a PFA layer/polyimide layer G/PFA layer, thereby preparing a metal clad laminate 10.

The copper foil 1 was etched away using an aqueous solution of ferric chloride to prepare a resin film 10. The measurement results of the T.T., YI, CTE, relative dielectric constant, and dielectric loss tangent of the resin film 10 are shown in Table 3.

(Comparative Example 2)
PFA dispersion 1 was uniformly applied to one side of a polyimide film (manufactured by Ube Industries, Ltd., product name: Upilex 25S, thickness 25 μm, total light transmittance: 55%) so that the final thickness would be 6 μm, and then the film was heated and dried at 90° C. for 3 minutes and at 120° C. for 3 minutes to remove the solvent, and then heated at 320° C. for 3 minutes to form a PFA film on the polyimide film.
Furthermore, PFA dispersion 1 was uniformly applied to the polyimide film surface to a final thickness of 6 μm, and then heated and dried at 90° C. for 3 minutes and at 120° C. for 3 minutes to remove the solvent, and then heated at 320° C. for 3 minutes to prepare a resin film 11 having a thickness of 37 μm and consisting of a PFA layer/polyimide film/PFA layer.

The measurement results of T.T., YI, CTE, relative dielectric constant, and dielectric tangent for resin film 11 are shown in Table 3.

(Comparative Example 3)
A diluted solution of polyamic acid solution H (viscosity; 19000 cP) was uniformly applied onto the base film 1 so that the thickness after curing would be 50 μm, and then the solution was dried by heating at 125° C. to remove the solvent, and then was subjected to stepwise heat treatment from 125° C. to 360° C. to complete imidization and form a polyimide layer H. The polyimide layer H was peeled off from the base film 1, and a polyimide film H was prepared.
A PFA film 1 (thickness: 25 μm), a polyimide film H, a PFA film 1 (thickness: 25 μm), and a copper foil 1 were laminated in that order on top of the copper foil 1, and heated and pressed at 320° C. and 7.5 MPa for 20 minutes in a vacuum atmosphere to prepare a double-sided metal-clad laminate 12.

The copper foil 1 was etched away using an aqueous solution of ferric chloride to prepare a resin film 12. The measurement results of the T.T., YI, CTE, relative dielectric constant, and dielectric tangent of the resin film 12 are shown in Table 3.

(Comparative Example 4)
A double-sided metal-clad laminate 13 was prepared in the same manner as in Comparative Example 3, except that the polyamic acid solution H in Comparative Example 3 was changed to the polyamic acid solution I.

The copper foil 1 was etched away using an aqueous solution of ferric chloride to prepare a resin film 13. The measurement results of the T.T., YI, CTE, relative dielectric constant, and dielectric loss tangent of the resin film 13 are shown in Table 3.

(Comparative Example 5)
A double-sided metal-clad laminate 14 was prepared in the same manner as in Comparative Example 3, except that the polyamic acid solution G was used instead of the polyamic acid solution H in Comparative Example 3.

The copper foil 1 was etched away using an aqueous solution of ferric chloride to prepare a resin film 14. The measurement results of the T.T., YI, CTE, relative dielectric constant, and dielectric loss tangent of the resin film 14 are shown in Table 3.

The above describes in detail the embodiment of the present invention for illustrative purposes, but the present invention is not limited to the above embodiment and various modifications are possible.

10A, 10B, 10C...metal-clad laminate, 40...resin laminate, A...resin film,
M1: first metal layer; M2: second metal layer; F1: first fluororesin layer; F2: second fluororesin layer; F10, F20: fluororesin adjacent layers; F30: fluororesin intermediate layer; P: polyimide insulating layer

Claims (8)

A resin film having a laminated structure composed of multiple layers,
A polyimide insulating layer;
a fluorine-based resin layer laminated on one or both sides of the polyimide insulating layer;
Equipped with
the polyimide insulating layer is composed of a single layer or a plurality of polyimide layers, the polyimide constituting the polyimide layer (i) having a thickness of 50% or more of the thickness of the entire polyimide insulating layer contains a diamine residue derived from an aromatic diamine compound containing a fluorine atom and/or an acid dianhydride residue derived from an aromatic tetracarboxylic dianhydride containing a fluorine atom, the proportion of fluorine atoms contained in the polyimide layer (i) is within the range of 10 to 40% by weight based on the entire polyimide,
The thickness of the entire resin film is within a range of 34 to 150 μm, and the ratio of the thickness of the polyimide insulating layer to the thickness of the entire resin film is within a range of 0.5 to 0.9;
Conditions i) and ii) below:
i) the total light transmittance of the entire resin film is 80% or more;
ii) the thermal expansion coefficient of the entire resin film is 30 ppm/K or less;
A resin film characterized by satisfying the above. The resin film according to claim 1, in which the dielectric loss tangent of the entire resin film at a frequency of 10 GHz measured using a split post dielectric resonator (SPDR resonator) is 0.008 or less. The resin film according to claim 1 or 2, wherein the overall thickness of the resin film is within the range of 50 to 150 μm. A metal-clad laminate comprising the resin film according to any one of claims 1 to 3 and a metal layer laminated on a surface of the fluororesin layer of the resin film. a first metal layer;
a fluorine-based resin adjacent layer provided adjacent to one side of the first metal layer;
a second metal layer; and
a fluorine-based resin adjacent layer provided adjacent to one side of the second metal layer;
a plurality of resin layers interposed between the two adjacent fluororesin layers;
Equipped with
a resin laminate is formed by the two fluororesin adjacent layers and the plurality of resin layers,
The resin laminate is
At least two polyimide layers;
a fluorine-based resin intermediate layer laminated between the polyimide layers;
The metal-clad laminate according to claim 4 , comprising: A circuit board obtained by wiring the metal layer of the metal-clad laminate according to claim 4 or 5 . A method for producing the resin film according to any one of claims 1 to 3 , comprising the steps of:
A step of applying a solution containing fluororesin particles onto a substrate and performing heat treatment to melt the fluororesin particles to form the fluororesin layer;
a step of applying a polyimide precursor solution onto the fluororesin layer and imidizing the solution by heat treatment to form the polyimide layer;
A method for producing a resin film comprising the steps of: moreover,
a step of applying a solution containing fluororesin particles onto the polyimide layer and heat-treating the solution to melt the fluororesin particles to form a second fluororesin layer;
The method for producing a resin film according to claim 7 , comprising:

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