Resin film, method for producing the same, metal-clad laminate, and circuit board

Abstract

To provide a resin film having transparency, capable of reducing transmission loss in high frequency transmission, and having excellent dimensional stability.SOLUTION: A resin film includes a polyimide insulating layer P and fluorine-based resin layers F1, F2 laminated on one surface or both surfaces of the polyimide insulating layer P and satisfies a condition (i) in which the total light transmittance of the entire resin film A is 80% or more and a condition (ii) in which the thermal expansion coefficient of the entire resin film A is 30 ppm / K or less. In the resin film A, it is preferable that the dielectric loss tangent of the entire resin film A measured by a split post dielectric resonator (an SPDR resonator) at a frequency of 10 GHz is 0.008 or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a resin film useful as an electronic component material, a method for producing the same, a metal-clad laminate, and a circuit board.

Background Art

[0002] In recent years, with the progress of miniaturization, weight reduction, and space saving of electronic devices, there has been an increasing demand for flexible printed circuit boards (FPCs) that are thin, lightweight, flexible, and have excellent durability even when repeatedly bent. Since FPCs enable three-dimensional and high-density mounting even in limited spaces, their applications are expanding to wirings in movable parts of electronic devices such as HDDs, DVDs, portable information terminals, and smartphones, as well as components such as cables and connectors.

[0003] As a material for the insulating resin layer constituting a circuit board typified by FPCs, polyimide, which is excellent in heat resistance, chemical resistance, flexibility, mechanical properties, and electrical properties, is widely used. Since polyimide generally exhibits a yellowish-brown color, it has been proposed to enhance transparency by using a raw material monomer containing a fluorine atom in order to apply it to applications where transparency is required (for example, Patent Documents 1 and 2).

[0004] By the way, in recent years, due to the progress of high performance of devices, it has also become necessary to cope with the high frequency of transmission signals. When transmitting a high-frequency signal, if the transmission loss in the transmission path is large, problems such as loss of electrical signals and long signal delay times occur. Therefore, in the future, reduction of transmission loss will also be important in FPCs.

[0005] In order to improve the 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 of a circuit board (for example, Patent Documents 3 and 4). Since the insulating resin layers of Patent Documents 3 and 4 use a fluororesin, they are excellent in terms of dielectric properties, but there are problems in dimensional stability. In particular, when applied to an FPC, there is a concern that the dimensional changes before and after circuit processing by etching and the dimensional changes before and after heat treatment will increase.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0007] In order to lower the dielectric tangent of a polyimide layer alone, it is effective to form an ordered structure. However, in order to increase the total light transmittance of polyimide, it is necessary to make the CT interaction less likely to occur and make it difficult to form an ordered structure. That is, in the polyimide layer, it is considered that an improvement in the total light transmittance and a reduction in the dielectric tangent are in a trade-off relationship.

[0008] An object of the present invention is to provide a resin film having high transparency, capable of reducing transmission loss even in high-frequency transmission, and excellent in dimensional stability.

Means for Solving the Problems

[0009] As a result of intensive research, the present inventors have found that by laminating a fluororesin layer on a polyimide insulating layer, it becomes 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 a plurality of layers, and includes a polyimide insulating layer and a fluororesin 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 condition ii); i) The total light transmittance of the entire resin film is 80% or more. ii) The coefficient of thermal expansion of the entire resin film is 30 ppm / K or less. It is characterized by satisfying the above.

[0010] The resin film of the present invention may have a dielectric tangent of 0.008 or less at a frequency of 10 GHz of the entire resin film measured by a split post dielectric resonator (SPDR resonator).

[0011] The resin film of the present invention may have a thickness of the entire resin film in the range of 10 to 150 μm, and the ratio of the thickness of the polyimide insulating layer to the thickness of the entire resin film may be in the range of 0.5 to 0.9.

[0012] The polyimide insulating layer of the resin film of the present invention may be composed of a single layer or a plurality of polyimide layers. In this case, the polyimide constituting the polyimide layer (i) having a thickness of 50% or more with respect to 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. Also, the proportion of fluorine atoms contained in the polyimide layer (i) may be in the range of 10 to 40% by weight with respect to the entire polyimide.

[0013] The metal-clad laminate of the present invention includes any of the above resin films and a metal layer laminated on the surface of the fluororesin layer in the resin film.

[0014] Another aspect of the metal-clad laminate of the present invention is that a first metal layer, a fluororesin adjacent layer provided adjacent to one side of the first metal layer, a second metal layer, a fluororesin adjacent layer provided adjacent to one side of the second metal layer, a plurality of resin layers interposed between the two fluororesin adjacent layers, and are provided. In this case, a resin laminate is formed by the two fluororesin adjacent layers and the plurality of resin layers, and the resin laminate has at least two or more polyimide layers, and a fluororesin intermediate layer laminated between the polyimide layers. and has.

[0015] The circuit board of the present invention is formed by wiring the metal layer of any of the above metal-clad laminates.

[0016] The method for manufacturing a resin film of the present invention is a method for manufacturing any of the above resin films, a step of applying a solution containing fluororesin particles on a substrate and heat-treating to melt the fluororesin particles to form the fluororesin layer; a step of applying a polyimide precursor solution on the fluororesin layer and heat-treating to imidize and form the polyimide layer; and includes.

[0017] The method for manufacturing a resin film of the present invention further a step of further applying a solution containing fluororesin particles on the polyimide layer and heat-treating to melt the fluororesin particles to form the second fluororesin layer, and may include.

Advantages of the Invention

[0018] The resin film of the present invention can achieve high transparency and dimensional stability by laminating a fluorine-based resin layer on a polyimide insulating layer, and further aims to achieve both transparency and low dielectric tangent. Therefore, a circuit board applying the resin film of the present invention 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. Accordingly, when the resin film and the metal-clad laminate of the present invention are applied to, for example, a circuit board for transmitting a high-frequency signal with a frequency of 10 GHz or more, it becomes possible to effectively reduce the transmission loss.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0020] Embodiments of the present invention will be described with appropriate reference to the drawings.

[0021] [Resin Film] The resin film according to an embodiment of the present invention is a resin film having a laminated structure composed of a plurality of layers. The resin film of the present embodiment includes a polyimide insulating layer and a fluorine-based resin layer laminated on one or both sides of the polyimide insulating layer.

[0022] FIG. 1 is a schematic diagram showing a configuration example of a resin film according to an embodiment of the present invention. The resin film A includes a polyimide insulating layer P, a first fluorine-based resin layer F1 laminated on one surface of the polyimide insulating layer P, and a second fluorine-based resin layer F2 laminated on the surface of the polyimide insulating layer P opposite to the first fluorine-based resin layer F1. The resin film A has a sandwich structure in which the polyimide insulating layer P is sandwiched between the first fluorine-based resin layer F1 and the second fluorine-based resin layer F2. Note that the resin film A may have only one of the first fluorine-based resin layer F1 or the second fluorine-based resin layer F2. Also, the first fluorine-based resin layer F1 and the second fluorine-based resin layer F2 may have the same configuration or different configurations.

[0023] [Polyimide insulating layer] The polyimide insulating layer P is composed of a single layer or a plurality of polyimide layers. The polyimide insulating layer P preferably has a main polyimide layer (i) having a thickness of 50% or more with respect to the total thickness of the polyimide insulating layer P. Here, "main" means having the largest thickness among the plurality of polyimide layers constituting the polyimide insulating layer P, preferably having a thickness of 50% or more, more preferably 60% or more with respect to the total thickness of the polyimide insulating layer P. The polyimide insulating layer P may be composed of only the main polyimide layer (i).

[0024] When the polyimide insulating layer P is composed of a plurality of polyimide layers, although not shown, the polyimide insulating layer P preferably has a structure in which thermoplastic polyimide layers containing thermoplastic polyimide as a resin component are laminated on both sides of the main polyimide layer (i). Note that "thermoplastic polyimide" generally refers to a polyimide in which the glass transition temperature (Tg) can be clearly confirmed. In the present invention, however, it refers to a polyimide having a storage elastic modulus at 30 ° C. measured using DMA of 1.0 × 10 9 Pa or more and a storage elastic modulus at 350 ° C. of less than 1.0 × 10 8 Pa.

[0025] The polyimide that constitutes 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 material tetracarboxylic dianhydride and diamine compound are reacted in approximately equimolar amounts, 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, when the term "polyimide" is used, it means a resin composed of a polymer having an imide group in its molecular structure, such as polyamideimide, polyetherimide, polyesterimide, polysiloxaneimide, polybenzimidazoleimide, etc., in addition to polyimide.

[0026] The polyimide that constitutes 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 in order to make the total light transmittance of the resin film A 80% or more. The proportion of fluorine atoms contained in the polyimide that constitutes 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, with respect to the entire polyimide. If the fluorine concentration of the main polyimide layer (i) exceeds 40% by weight and is too high, the total light transmittance of the entire resin film A will increase, but the ordered structure will be difficult to form, the dielectric loss tangent will deteriorate, and the adhesiveness (compatibility) with the first fluorine-based resin layer F1 and the second fluorine-based resin layer F2 will also deteriorate. 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 will decrease.

[0027] The main polyimide constituting the main polyimide layer (i) preferably contains a fluorine-containing acid dianhydride residue. Since the fluorine-containing acid dianhydride residue has a bulky group containing a fluorine atom, it reduces the interactions such as π-π stacking between polymer chains. As a result, it is considered that charge transfer (CT) between the aromatic tetracarboxylic acid residue and the aromatic diamine residue is less likely to occur, and the polyimide can be made closer to transparent.

[0028] Examples of the fluorine-containing acid dianhydride residue include acid dianhydride residues derived from acid dianhydride components such as 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, 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, etc.

[0029] In addition, 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), which is represented by the following formula (1), in order to control the coefficient of thermal expansion (CTE) of the polyimide layer (i). The PMDA residue is preferably contained in an amount of 50 mol parts or more, more preferably in the range of 60 mol parts or more and 100 mol parts or less, based on 100 mol parts in total of all acid dianhydride residues. If the PMDA residue is less than 50 mol parts, the CTE of the polyimide layer (i) becomes high and the dimensional stability of the entire resin film A decreases.

[0030]

Chemical formula

[0031] In addition, the main polyimide constituting the polyimide layer (i) may contain an acid dianhydride residue derived from an acid dianhydride component generally used in the synthesis of polyimide as an acid dianhydride residue other than those described above. As such an acid dianhydride residue, an aromatic tetracarboxylic acid residue is preferable.

[0032] The main polyimide constituting the polyimide layer (i) preferably contains a fluorine-containing diamine residue. Since the fluorine-containing diamine residue has a group containing a bulky fluorine atom, it reduces the interaction such as π-π stacking between polymer chains. As a result, it is considered that the charge transfer (CT) between the aromatic tetracarboxylic acid residue and the aromatic diamine residue can be made difficult to occur, and the polyimide can be made closer to transparent.

[0033] Examples of the fluorine-containing diamine residue 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, 2,2-bis-[4-(3-aminophenoxy)phenyl]hexafluoropropane, etc.

[0034] Among the fluorine-containing diamine residues, it is more preferable to contain a diamine residue (hereinafter sometimes referred to as "diamine (2) residue") derived from a diamine compound represented by the following general formula (2).

[0035] [Chemical formula]

[0036] In the general formula (2), the substituent X independently represents an alkyl group having 1 to 3 carbon atoms substituted with a fluorine atom, and m and n independently represent an integer of 1 to 4.

[0037] Since 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, it easily forms an ordered structure and promotes the orientation in the in-plane direction of the molecular chain. Therefore, an increase in the CTE of the main polyimide layer (i) can be suppressed, and the dimensional stability of the entire resin film A can be enhanced. From such a viewpoint, it is preferable that the main polyimide constituting the main polyimide layer (i) contains 50 mol parts or more of the diamine (2) residue with respect to a total of 100 mol parts of all diamine residues, and more preferably contains it within the range of 50 mol parts or more and 100 mol parts or less.

[0038] Preferable specific 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.

[0039] The main polyimide constituting the main polyimide layer (i) may contain, as diamine residues other than those described above, diamine residues derived from diamine components generally used in the synthesis of polyimide.

[0040] The polyimide of the present embodiment can be produced by reacting the above acid dianhydride component and diamine component in a solvent to form a polyamic acid and then subjecting it to thermal ring closure. For example, the acid dianhydride component and the diamine component are dissolved in an organic solvent in approximately equimolar amounts and stirred at a temperature in the range of 0°C to 100°C for 30 minutes to 24 hours to carry out a polymerization reaction, whereby a polyamic acid, which is a precursor of polyimide, can be obtained. In the reaction, the reaction components are dissolved so that the resulting precursor is in the range of 5% by weight or more and 30% by weight or less, preferably in the range of 10% by weight or more and 20% by weight or less, in the organic solvent. Examples of the organic solvent 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, γ-butyrolactone, etc. These solvents can also be used in combination of two or more, and furthermore, a combination with aromatic hydrocarbons such as xylene and toluene is also possible. Also, the amount of such an organic solvent used is not particularly limited, but it is preferably adjusted to an amount such 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.

[0041] In the synthesis of polyimide, only one kind of the above acid dianhydride and diamine may be used, or two or more kinds may be used in combination. By selecting the types of the acid dianhydride and diamine and the respective molar ratios in the case of using two or more kinds of acid dianhydrides or diamines, transparency, dielectric properties, thermal expansibility, adhesiveness, glass transition temperature, etc. can be controlled.

[0042] The synthesized polyamic acid is usually advantageously used as a reaction solvent solution, but can be concentrated, diluted or replaced with another organic solvent if necessary. Also, since polyamic acid generally has excellent solvent solubility, it is advantageously used. The method of imidizing the polyamic acid is not particularly limited, and for example, heat treatment such as heating in the above solvent at a temperature condition in the range of 80°C to 400°C for 1 hour to 24 hours is preferably employed.

[0043] The weight average molecular weight of the polyamic acid is preferably in the range of, for example, 10,000 or more and 400,000 or less, more preferably in the range of 50,000 or more and 350,000 or less. When 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, when the weight average molecular weight exceeds 400,000, the viscosity increases excessively and defects such as film thickness unevenness and streaks tend to occur during the coating operation.

[0044] [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 all of the resin component. The main component of the resin component means a component contained in an amount exceeding 50% by weight with respect to all the resin components. The fluororesin has high transparency and very excellent dielectric properties.

[0045] The fluororesin constituting the first fluororesin layer F1 and the second fluororesin layer F2 is not particularly limited. For example, 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. may be mentioned. Among these fluororesins, PFA, FEP, ETFE, and EFEP, which are tetrafluoroethylene-based fluororesins, are preferable, and PFA is more preferable. Among PFAs, from the perspective of appropriately controlling the balance between mechanical strength and melting point, a copolymer having a molar ratio of tetrafluoroethylene (TFE) units to perfluoroalkyl vinyl ether copolymer (PAVE) units (TFE units:PAVE units) of 10:90 to 90:10 is most preferred.

[0046] For the first fluororesin layer F1 and the second fluororesin layer F2, in order to maintain good dielectric properties of the entire resin film A, as single substances, the relative permittivity at 10 GHz is preferably in the range of 1.9 to 3.1, more preferably in the range of 2.0 to 2.5, and the dielectric loss tangent is preferably 0.001 or less, more preferably 0.0008 or less.

[0047] 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, it is 290 °C or higher. If the melting point is lower than 260 °C, it may melt during the manufacturing process of electronic devices or the like, causing changes in characteristics.

[0048] The glass transition temperatures (Tg) of the first fluororesin layer F1 and the second fluororesin layer F2 are preferably 200 °C or lower, and more preferably 180 °C or lower. By setting the Tg of the first fluororesin layer F1 and the second fluororesin layer F2 to 200 °C or lower, thermocompression bonding at low temperature becomes possible, so the internal stress generated during lamination with a metal-clad laminate or the like can be relaxed, and dimensional changes after circuit processing can be suppressed. If the Tg of the first fluororesin layer F1 and the second fluororesin layer F2 exceeds 200 °C, the thermocompression bonding temperature when the resin film A is interposed and adhered between a metal-clad laminate or the like becomes high, and there is a risk of impairing the dimensional stability after circuit processing.

[0049] Note that the first fluororesin layer F1 and the second fluororesin layer F2 may have the same or different configurations such as thickness, physical properties, and materials, but it is preferable that they have the same configuration.

[0050] The resin film A of this embodiment satisfies the following conditions i) and ii).

[0051] 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 to applications that require transparency. It is more preferable that the total light transmittance of the entire resin film is 85% or more.

[0052] Condition ii): The coefficient of thermal expansion of the entire resin film A is 30 ppm / K or less. By satisfying Condition ii), high dimensional stability can be obtained. When the coefficient of thermal expansion of the entire resin film exceeds 30 ppm / K, it becomes difficult to obtain dimensional accuracy after circuit processing. The coefficient of thermal expansion of the entire resin film is preferably in the range of 20 - 30 ppm / K.

[0053] Furthermore, it is preferable that the resin film of this embodiment satisfies the following Condition iii). Condition iii): The dielectric loss tangent of the entire resin film A at a frequency of 10 GHz measured by a split post dielectric resonator (SPDR resonator) is 0.008 or less. By satisfying Condition iii), when applied to a circuit board or the like that transmits high-frequency signals in the GHz band (for example, a frequency of 10 GHz or more), it becomes 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. Note that the relative permittivity of the entire resin film A at 10 GHz is preferably in the range of 2.0 - 4.0, and more preferably in the range of 2.5 - 3.5.

[0054] Regarding the above conditions i) to iii), in the case of a resin film composed of a polyimide alone, it has been difficult to achieve both high total light transmittance and low dielectric loss tangent. The reason is that in order to increase the total light transmittance, it is necessary to make the CT interaction of the polyimide less likely to occur and make it difficult to form an ordered structure. On the other hand, in order to lower the dielectric loss tangent of the polyimide, it is effective to form an ordered structure. Therefore, an improvement in the total light transmittance and a reduction in the dielectric loss tangent are in a trade-off relationship. On the other hand, a resin film composed of a fluororesin alone can achieve high total light transmittance and low dielectric loss tangent. However, since the fluororesin has a glass transition temperature (Tg) of 94 °C and a melting point of about 300 °C (in the case of PFA), it lacks heat resistance and dimensional stability. The resin film of this embodiment can achieve 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 the polyimide insulating layer, it is possible to ensure high transparency even for a relatively thick resin film with a thickness of 50 μm or more.

[0055] The resin film A preferably has a yellowness index (YI) of 10 or less, more preferably 8 or less. By controlling the YI to 10 or less, the resin film A can be made almost colorless. On the other hand, when the YI exceeds 10, the yellow to yellowish-brown coloring becomes strong, and the visibility of the resin film decreases.

[0056] [Thickness] The thickness of the entire resin film A is preferably in the range of, for example, 10 to 150 μm, more preferably in the range of 10 to 125 μm. Also, the thickness T of the polyimide insulating layer P P is preferably in the range of, for example, 5 to 75 μm, more preferably in the range of 8 to 50 μm. Here, the thickness T of the polyimide insulating layer P A with respect to the thickness T of the entire resin film A P The ratio of (T P / T A) is preferably in the range of 0.5 to 0.9, and 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 less than 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 cannot 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. Also, if the thickness of the fluorine-based resin layer (that is, the total thickness of the first fluorine-based resin layer F1 and the second fluorine-based resin layer F2) is too large, the dimensional stability of the entire resin film A will deteriorate. Conversely, if it is too small, the adhesiveness will decrease, and the total light transmittance and dielectric properties of the entire resin film A will deteriorate.

[0057] The resin film A of the present embodiment may contain an inorganic filler and / or an organic filler as optional components, as long as the effects of the invention are not inhibited. Examples of the inorganic filler include silicon dioxide, aluminum oxide, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, calcium fluoride, etc. Examples of the organic filler include liquid crystal polymer, etc. These fillers can be used alone or in combination of two or more. Also, as long as the effects of the invention are not inhibited, the resin film A may be appropriately blended with optional components such as a plasticizer, other cured resin components such as an epoxy resin, a curing agent, a curing accelerator, a coupling agent, a flame retardant, etc., as necessary.

[0058] The resin film A of the present embodiment may be in a state laminated on a base material such as a resin sheet such as a copper foil, a glass plate, a polyimide-based film, a polyamide-based film, a polyester-based film, etc.

[0059] [Manufacturing method of resin film] The method for manufacturing the resin film A of this embodiment is not particularly limited. When the resin film A has a structure in which a first fluororesin layer F1 / polyimide insulating layer P / second fluororesin layer F2 as shown in FIG. 1 are laminated, the following method can be exemplified.

[0060] The first method uses the casting method, and on an arbitrary substrate, the first fluororesin layer F1, polyimide insulating layer P, and second fluororesin layer F2 are formed and laminated in this order by the casting method, and the resin film A is manufactured by peeling from the substrate as necessary. The first method is a preferable method when it is desired to form the first fluororesin layer F1 and the second fluororesin layer F2 with a small thickness.

[0061] The second method uses the film lamination method. Two fluororesin films and one polyimide film are prepared, and the polyimide film is sandwiched between the fluororesin films and laminated by pressing, and the resin film A is manufactured. The second method is a preferable method when it is desired to form the first fluororesin layer F1 and the second fluororesin layer F2 with a large thickness. In the film lamination method, a large thickness that is difficult to thicken in the first method can also be formed, and transparency can be maintained when thickened.

[0062] Here, the first method will be described in detail with reference to FIG. 2. First, a particle dispersion liquid in which fluororesin particles F0 are dispersed in an arbitrary solvent is applied onto an arbitrary substrate B and dried, so that as shown in Fig. 2(a), a plurality of fluororesin particles F0 are adhered onto the substrate B (Step 1). The substrate B to be used is not particularly limited, but as a heat-resistant material, for example, it is preferable to use a metal foil such as a copper foil having a thickness in the range of 5 to 35 μm. In the first method, by using a copper foil as the substrate B, a resin film A can be manufactured, and at the same time, a copper-clad laminate provided with the resin film A and a copper foil layer can be manufactured. As an arbitrary solvent, for example, a highly volatile organic solvent is preferable. As the fluororesin particles F0, those having an average particle diameter measured by a laser diffraction / scattering measurement method in the range of 1 to 5 μm are preferable, and for example, commercially available products such as Fluon+ TM EA-2000 powder (manufactured by AGC Inc.) can be used.

[0063] Next, the fluororesin particles F0 are heat-treated together with the substrate B, melted, and then cooled and solidified to form a film, so that 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 may be equal to or higher than the melting point of the fluororesin. For example, in the case of PFA, it is preferably set to about 320°C.

[0064] Next, a solution of a polyimide precursor is applied onto the first fluororesin layer F1 of the formed first laminate, dried, and heat-treated to imidize it, thereby forming a polyimide insulating layer P as shown in Fig. 2(c) to produce a second laminate (Step 3). The method of applying the solution of the polyimide precursor onto the substrate is not particularly limited, and for example, it can be applied using a coater such as comma, die, knife, lip, etc. The heat treatment temperature for imidization can be, for example, 360°C. When the polyimide insulating layer P is composed of multiple layers, heat treatment may be performed each time the solution of the polyimide precursor is applied and dried, or after repeating the steps of applying and drying the solution of the polyimide precursor multiple times, heat treatment may be performed all at once. Also, by multi-layer extrusion, after simultaneously applying and drying a laminated structure of polyamic acid, imidization may be performed. The second laminate can be made into a resin film A having a structure with the first fluororesin layer F1 on one side of the polyimide insulating layer P by peeling the substrate B as necessary. Also, when using a metal foil as the substrate B, the second 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.

[0065] 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 dried, thereby attaching 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.

[0066] Next, the fluororesin particles F0 are heat-treated together with the second laminate, melted, and then cooled and solidified to form a film, thereby forming a second fluororesin layer F2 on the polyimide insulating layer P as shown in Fig. 2(e) 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 the base material B as necessary. When a metal foil is used as the base material 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. Further, the third laminate can be made into a double-sided metal-clad laminate by using a metal foil as the base material B and forming a metal layer on the surface of the resin film A opposite to the base material B.

[0067] As described above, in the resin film A obtained in this way, fluororesin layers (the first fluororesin layer F1 and / or the second fluororesin layer F2) are laminated on one side or both sides of the polyimide insulating layer P, so that both improvement of the total light transmittance and reduction of the dielectric tangent are achieved. In addition to high transparency and excellent dielectric properties, it has high dimensional stability.

[0068] [Metal-clad laminate] The metal-clad laminate according to an embodiment of the present invention includes the above resin film A and a metal layer laminated on the surface of the fluororesin layer in the resin film A. In this case, the resin film A may have a configuration as shown in FIG. 1 having 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 configuration having a fluororesin layer (the first fluororesin layer F1 or the second fluororesin layer F2) only on one side of the polyimide insulating layer P (not shown). That is, the metal-clad laminate of this embodiment may be a single-sided metal-clad laminate or a double-sided metal-clad laminate.

[0069] The metal-clad laminate of this embodiment can be manufactured by a method of laminating a metal foil on the resin film A or by using a metal foil as the base material B for preparing the resin film A as described above.

[0070] Next, with reference to FIGS. 3 to 5, application examples of the metal-clad laminate of this embodiment will be described. FIG. 3 is a schematic diagram showing the configuration of a metal-clad laminate according to an embodiment of the present invention. The metal-clad laminate 10A of the present embodiment includes a first metal layer M1, a fluororesin adjacent layer F10 provided adjacent to one side of the first metal layer M1, a second metal layer M2, a fluororesin adjacent layer F20 provided adjacent to one side of the second metal layer M2, a plurality of resin layers interposed between the fluororesin adjacent layer F10 and the fluororesin adjacent layer F20, and is provided with. The first metal layer M1 and the second metal layer M2 are each located on the outermost side, and the fluororesin adjacent layer F10 and the fluororesin adjacent layer F20 are disposed in contact with their inner sides. Further, between the fluororesin adjacent layer F10 and the fluororesin adjacent layer F20, a plurality of resin layers including a plurality of polyimide insulating layers P and a fluororesin intermediate layer F30 are interposed. 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. Since the metal-clad laminate 10A is provided with a fluororesin adjacent layer F10 or a fluororesin adjacent layer F20 having a low dielectric tangent at positions adjacent to a pair of metal layers (the first metal layer M1 and the second metal layer M2 serving as wirings), the transmission loss in high-frequency signal transmission can be effectively suppressed.

[0071] As shown in FIG. 3, a resin laminate 40 is formed by the fluororesin adjacent layer F10, the fluororesin adjacent layer F20, and a plurality of resin layers. 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 addition to the fluororesin adjacent layer F10 and the fluororesin adjacent layer F20. In this way, by providing a laminated 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, low dielectric tangent is realized while ensuring high dimensional stability. Note that the resin laminate 40 may have any resin layer other than those described above, but it is preferably formed only by the resin layers having the above-described functions.

[0072] The metal-clad laminate 10A shown in FIG. 3 has two polyimide insulating layers P and one fluororesin intermediate layer F30. However, the number of polyimide insulating layers P may be two or more, and there is no particular limitation on the number of fluororesin intermediate layers F30. For example, a configuration having three polyimide insulating layers P and two fluororesin intermediate layers F30 as in the metal-clad laminate 10B shown in FIG. 4 may be used, or a configuration having five polyimide insulating layers P and four fluororesin intermediate layers F30 as in the metal-clad laminate 10C shown in FIG. 5 may be used.

[0073] In the metal-clad laminate 10, the configurations of the first metal layer M1 and the second metal layer M2 may be the same or different, but it is preferable that they have the same material, the same physical properties, and the same thickness.

[0074] Also, the configurations of the fluororesin adjacent layer F10 and the fluororesin adjacent layer F20 may be the same or different, but it is preferable that they have the same material, the same physical properties, and the same 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 for reducing transmission loss when manufacturing a high-frequency transmission circuit board.

[0075] 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 have the same material and the same physical properties in order to improve the dielectric properties of the entire resin laminate 40 and effectively suppress the transmission loss of high-frequency signals.

[0076] The configurations of the plurality of polyimide insulating layers P may be the same or different, but it is preferable that they have the same material, the same physical properties, the same thickness, and the same layer structure because it becomes easier to design the mechanical strength and dimensional accuracy when manufacturing a circuit board.

[0077] From the perspective of suppressing the transmission loss of high-frequency signals, the dielectric tangent Df1 at 10 GHz in the fluororesin adjacent layers F10 and F20 and the fluororesin intermediate layer F30 is preferably 0.001 or less, more preferably 0.0008 or less.

[0078] Also, the dielectric tangent Df2 of the polyimide insulating layer P at 10 GHz is desirably as low as possible. However, since it is a layer that ensures dimensional accuracy and mechanical strength, it is preferably 0.01 or less, more preferably 0.009 or less. Even if the dielectric tangent Df2 of the polyimide insulating layer P is somewhat high, by laminating it with the fluororesin adjacent layers F10 and F20 and the fluororesin intermediate layer F30 having a lower dielectric tangent and considering the thickness ratio with these, it is possible to ensure a low dielectric tangent for the entire resin laminate 40.

[0079] The total thickness T of the plurality of polyimide insulating layers P PA is the total thickness T of the resin laminate 40 (that is, the fluororesin adjacent layers F10 and F20, one or more fluororesin intermediate layers F30, and the plurality of polyimide insulating layers P) 40 and the ratio (T PA / T 40 ) is preferably in the range of 0.5 to 0.9, more preferably in 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 reduction of transmission loss of high-frequency signals while maintaining dimensional accuracy and mechanical strength when the metal-clad laminates 10A, 10B, and 10C are circuit-processed. From this perspective, the ratio (T PA / T 40 ) is preferably in the range of 50 to 90%.

[0080] Here, the thickness of each layer in the resin laminate 40 is not particularly limited as it can be appropriately set according to the purpose of use, but can be exemplified as follows. The thickness of one layer of the fluororesin adjacent layers F10 and F20 is preferably in the range of 1 to 100 μm, more preferably in the range of 2 to 75 μm. The thickness of one layer of the polyimide insulating layer P is preferably in the range of 5 to 100 μm, more preferably in the range of 10 to 50 μm. The thickness of one layer of the fluororesin intermediate layer F30 is preferably in the range of 1 to 150 μm, more preferably in the range of 2 to 100 μm. The total thickness T of the resin laminate 40 is preferably in the range of 50 to 300 μm, more preferably in the range of 75 to 200 μm.

[0081] Hereinafter, each layer constituting the metal-clad laminates 10A, 10B, and 10C will be described.

[0082] [Metal layer] The materials of the first metal layer M1 and the second metal layer M2 are not particularly limited. For example, copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof can be mentioned. Among these, copper or a copper alloy is particularly preferable. Note that the material of the wiring layer in the circuit board of the present embodiment described later is also the same as that of the first metal layer M1 and the second metal layer M2.

[0083] The thicknesses of the first metal layer M1 and the second metal layer M2 are not particularly limited. For example, when using a metal foil such as a copper foil, it is preferably 35 μm or less, more preferably in the range of 5 to 25 μm. From the viewpoints of production stability and handling properties, the lower limit value of the thickness of the metal foil is preferably 5 μm. Note that when using a copper foil, either a rolled copper foil or an electrolytic copper foil may be used. Also, as the copper foil, a commercially available copper foil can be used.

[0084] In addition, the metal foil may be subjected to surface treatment with, for example, rust prevention treatment or for the purpose of improving adhesion, such as siding, aluminum alcoholate, aluminum chelate, silane coupling agent, etc.

[0085] [Manufacture 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 combines these methods.

[0086] In Method A, a fluororesin adjacent layer F10 is formed on the first metal layer M1 by a casting method, and separately, a fluororesin adjacent layer F20 is formed on the second metal layer M2. Next, on each of the fluororesin adjacent layer F10 and the fluororesin adjacent layer F20, a polyimide insulating layer P and / or a fluororesin intermediate layer F30 are formed by a casting method so as to have the required number of layers, and two single-sided metal-clad laminates are separately produced. The formation of each layer by the casting method can be carried out in the same manner as described for the resin film A. Thereafter, the metal-clad laminates 10A, 10B, and 10C can be manufactured by bonding the resin surfaces of the two single-sided metal-clad laminates.

[0087] In Method B, resin sheets corresponding to the fluororesin adjacent layer F10, the fluororesin adjacent layer F20, a plurality of polyimide insulating layers P, and one or more fluororesin intermediate layers F30 are prepared by a film lamination method, and these resin sheets are arranged and bonded between the first metal layer M1 and the second metal layer M2 and thermocompression bonded to manufacture the metal-clad laminates 10A, 10B, and 10C.

[0088] Method C is a method that combines Method A and Method B. For example, two single-sided metal-clad laminates are separately formed by a casting method so as to have the required number of layers, and the required number of resin sheets corresponding to the polyimide insulating layer P and the fluororesin intermediate layer F30 prepared separately are arranged and bonded between the resin surfaces of these two single-sided metal-clad laminates and thermocompression bonded to manufacture the metal-clad laminates 10A, 10B, and 10C.

[0089] The metal-clad laminates 10A, 10B, and 10C of the present embodiment obtained as described above can be used to manufacture a circuit board such as a single-sided FPC or a double-sided FPC by performing wiring circuit processing such as etching the first metal layer M1 and / or the second metal layer M2.

[0090] [Circuit board] Metal-clad laminates using resin film A as the insulating resin layer, and metal-clad laminates 10A, 10B, and 10C are mainly useful as circuit board materials such as FPCs and rigid-flex circuit boards. By forming a wiring layer by processing one or both of the metal layers in the metal-clad laminate in a pattern by a conventional method, a circuit board such as an FPC according to an embodiment of the present invention can be manufactured. The circuit board of this embodiment includes, although not shown, an insulating resin layer (resin film A or resin laminate 40) and a wiring layer provided on one or both sides of this insulating resin layer. The insulating resin layer has high transparency, can reduce transmission loss even in high-frequency transmission, and has excellent dimensional stability.

Example

[0091] Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, various measurements and evaluations are as follows.

[0092] [Calculation of yellowness index (YI)] The yellowness index (YI) of a resin film (50 mm × 50 mm) was measured with a UV-3600 spectrophotometer manufactured by Shimadzu Corporation. 1) YI (yellowness index) It was calculated based on the calculation formula represented by the following formula (1) in accordance with JIS Z 8722. YI = 100×(1.2879X - 1.0592Z) / Y ···(1) X, Y, and Z: Tristimulus values of the test piece

[0093] [Measurement of coefficient of thermal expansion (CTE)] A resin film (3 mm × 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 with a thermomechanical analysis (TMA) apparatus, and then cooled. The coefficient of thermal expansion was measured from the amount of elongation (linear expansion) of the resin film from 250°C to 100°C during cooling.

[0094] [Calculation of Total Light Transmittance (T.T.)] A resin film (50 mm × 50 mm) was measured for total light transmittance (T.T.) in accordance with JIS K 7136 using a haze meter NDH500 manufactured by Nippon Denshoku Industries Co., Ltd. For the insulating resin layer of the metal-clad laminate, etching of single-sided or double-sided metal foil was performed to obtain a resin film, which was measured in the same manner.

[0095] [Measurement of Relative Dielectric Constant (Dk) and Dissipation Factor (Df)] The relative dielectric constant (Dk) and dissipation factor (Df) of the resin films obtained by etching away the copper foil of the copper-clad laminates prepared in each example and comparative example were measured at a frequency of 10 GHz using a vector network analyzer (manufactured by Agilent Technologies, product name: E8363C) and a split post dielectric resonator (SPDR resonator). The resin films used for the measurement were left standing for 24 hours under the conditions of temperature: 24 to 26 °C and humidity: 45 to 55%.

[0096] [Measurement of Viscosity] The viscosity was measured at 25 °C for the polyamic acid solution obtained in the synthesis example using a cone-plate viscometer with a constant temperature bath (manufactured by Tokimec Inc.).

[0097] [Measurement of Surface Roughness of Copper Foil] The sample was cut into a size of approximately 10 mm square, fixed to the sample stage with double-sided tape, irradiated with soft X-rays to remove the static electricity on the copper foil surface, and then the ten-point average roughness Rz (RzJis) of the copper foil surface was measured under the following measurement conditions using a scanning probe microscope (AFM, manufactured by Bruker AXS Inc., product name: Dimension Icon type SPM). The measurement conditions are as follows. Measurement mode; Tapping mode Measurement area; 1 μm × 1 μm Scan speed; 1 Hz Probe; Manufactured by Buruker, RTESP-300

[0098] The abbreviations used in the examples, etc. 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’-Biphenyltetracarboxylic Dianhydride DMAc: N,N-Dimethylacetamide

[0099] Synthesis Examples 1 - 9 To synthesize polyamic acid solutions A - I, under a nitrogen stream, into a 200 ml separable flask, DMAc as the solvent was added to achieve the solid content concentration shown in Table 1, and the diamine component and acid anhydride component shown in Table 1 were heated and dissolved at 45°C for 2 hours while stirring. Then, the solution was continuously stirred at room temperature for 2 days to conduct the polymerization reaction, and viscous solutions A - I of polyamic acid were prepared.

[0100] [Table 1]

[0101] [Example 1] On copper foil 1 (electrolytic copper foil, manufactured by Fukuda Metal Foil Powder Industry Co., Ltd., product name; CF-T9DA-SV-12, thickness; 12 μm, Rzjis; 0.8 μm), PFA fine particles 1 (manufactured by AGC Inc., product name; Fluon+ TM EA-2000 powder, D 50; 3 μm, maximum particle size; 10 μm) of 30 wt% was uniformly applied to a DMAc solution so that the final thickness was 15 μm, and then heated and dried at 90 °C for 3 minutes and at 120 °C for 3 minutes to remove the solvent. After that, it was heated at 320 °C for 3 minutes to form a PFA film on 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 heated and dried at 125 °C to remove the solvent. After that, a stepwise heat treatment was performed from 125 °C to 360 °C to complete imidization and form polyimide layer A. Further, on polyimide layer A, a DMAc solution in which 30 wt% of PFA fine particles 1 was dispersed was uniformly applied so that the final thickness was 15 μm, and then heated and dried at 90 °C for 3 minutes and at 120 °C for 3 minutes to remove the solvent. After that, it was heated at 320 °C for 3 minutes to form an insulating resin layer 1 with a thickness of 60 μm composed of a PFA layer / polyimide layer A / PFA layer, and a metal-clad laminate 1 was prepared.

[0102] Using an aqueous ferric chloride solution, copper foil 1 was etched away to prepare resin film 1. Table 2 shows the measurement results of T.T., YI, CTE, relative permittivity, and dielectric tangent for resin film 1.

[0103] [Example 2] On copper foil 1, PFA dispersion 1 (manufactured by AGC, trade name; Fluon + TM EA-2000 Dispersion, D 50; 3 μm, maximum particle size; 10 μm, 50 wt% dispersed in DMAc solution; the same applies hereinafter) was uniformly coated so that the final thickness was 5 μm, 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 copper foil 1. Next, a diluted solution of polyamic acid solution B (viscosity; 17300 cP) was uniformly coated on the PFA film so that the cured thickness was 15 μm, then heated and dried at 125 °C to remove the solvent, and then subjected to a stepwise heat treatment from 125 °C to 360 °C to complete imidization and form a polyimide layer B. Further, on the polyimide layer B, PFA dispersion 1 was uniformly coated so that the final thickness was 5 μm, 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 2 with a thickness of 25 μm composed of a PFA layer / polyimide layer B / PFA layer, and a metal-clad laminate 2 was prepared.

[0104] Using an aqueous ferric chloride solution, copper foil 1 was etched away to prepare resin film 2. Table 2 shows the measurement results of T.T., YI, CTE, relative permittivity, and dielectric tangent for resin film 2.

[0105] [Example 3] On copper foil 1, PFA dispersion 1 was uniformly coated so that the final thickness was 1 μm, 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 copper foil 1. Next, a diluted solution of polyamic acid solution C (viscosity; 23000 cP) was uniformly coated on the PFA film so that the cured thickness was 10 μm, then heated and dried at 125 °C to remove the solvent, and then subjected to a stepwise heat treatment from 125 °C to 360 °C to complete imidization and form a polyimide layer C. Further, on the polyimide layer C, PFA dispersion 1 was uniformly coated so that the final thickness was 1 μm, 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 with a thickness of 12 μm composed of a PFA layer / polyimide layer C / PFA layer, and a metal-clad laminate 3 was prepared.

[0106] Using an aqueous solution of ferric chloride, copper foil 1 was etched away to prepare resin film 3. Table 2 shows the measurement results of T.T., YI, CTE, relative permittivity, and dielectric tangent for resin film 3.

[0107] [Example 4] A diluted solution of polyamic acid solution A (viscosity: 13700 cP) was uniformly coated on base film 1 (polyimide film, manufactured by Ube Industries, Ltd., trade name; Upilex 75S, thickness 75 μm) so that the cured thickness would be 50 μm. After heating and drying at 125 °C to remove the solvent, stepwise heat treatment was performed from 125 °C to 360 °C to complete imidization and form polyimide layer A. Polyimide layer A was peeled off from base film 1 to prepare polyimide film A. On copper foil 1, PFA film 1 (manufactured by AGC, trade name; Fluon + TM EA-2000 film, thickness: 25 μm), polyimide film A, PFA film 1 (thickness: 25 μm), and copper foil 1 were laminated in sequence, and heating and pressing were performed at 320 °C and 7.5 MPa for 20 minutes under a vacuum atmosphere to prepare double-sided metal-clad laminate 4.

[0108] Using an aqueous solution of ferric chloride, copper foil 1 was etched away to prepare resin film 4. Table 2 shows the measurement results of T.T., YI, CTE, relative permittivity, and dielectric tangent for resin film 4.

[0109] [Example 5] On the copper foil 1, a diluted solution of polyamic acid solution D (viscosity: 3200 cP) was uniformly applied so that the thickness after curing would be 1.0 μm, and then it was dried by heating 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 would be 8 μm, and then it was dried by heating at 125°C to remove the solvent. Further, a diluted solution of polyamic acid solution E (viscosity: 1700 cP) was uniformly applied thereon so that the thickness after curing would be 1.0 μm, and then it was dried by heating at 125°C to remove the solvent. In this way, after forming a three-layer polyamic acid layer, a stepwise heat treatment was carried out from 125°C to 360°C over 30 minutes to complete imidization, and a 10-μm-thick polyimide layer 5 composed of polyimide layer D / polyimide layer B / polyimide layer E was formed to prepare a metal-clad laminate 5. The copper foil 1 of the obtained metal-clad laminate 5 was etched and removed using an aqueous solution of ferric chloride to prepare a polyimide film 5. Next, on the copper foil 1, PFA dispersion liquid 1 was uniformly applied so that the final thickness would be 2 μm, and then it was dried by heating at 90°C for 3 minutes and at 120°C for 3 minutes to remove the solvent, and then it was heated at 320°C for 3 minutes to prepare a metal laminate film 5 having a PFA film formed on the copper foil 1. On the PFA film of the obtained metal laminate film 5, the polyimide film 5 was laminated thereon such that the PFA film was in contact with the polyimide, and heating and pressing were carried out at 320°C and 7.5 MPa for 20 minutes under a vacuum atmosphere to prepare a double-sided metal-clad laminate plate 5.

[0110] The copper foil 1 was etched and removed using an aqueous solution of ferric chloride to prepare a resin film 5. Table 2 shows the measurement results of T.T., YI, CTE, relative permittivity, and dielectric tangent for the resin film 5.

[0111] [Example 6] On the copper foil 1, the PFA dispersion liquid 1 was uniformly coated so that the final thickness became 5 μm, and then heated and dried at 90°C for 3 minutes and at 120°C for 3 minutes to remove the solvent. After that, it was heated at 320°C for 3 minutes to form a PFA film on the copper foil 1. Next, a diluted solution of the polyamic acid solution F (viscosity: 18400 cP) was uniformly coated on the PFA film so that the thickness after curing became 20 μm, and then heated and dried at 125°C to remove the solvent. After that, a stepwise heat treatment was performed from 125°C to 360°C to complete imidization and form a polyimide layer F. Further, on the polyimide layer F, the PFA dispersion liquid 1 was uniformly coated so that the final thickness became 5 μm, and then heated and dried at 90°C for 3 minutes and at 120°C for 3 minutes to remove the solvent. After that, it was heated at 320°C for 3 minutes to form a second PFA film. Next, a diluted solution of the polyamic acid solution F (viscosity: 18400 cP) was uniformly coated on the second PFA film so that the thickness after curing became 20 μm, and then heated and dried at 125°C to remove the solvent. After that, a stepwise heat treatment was performed from 125°C to 360°C to complete imidization and form a polyimide layer F. Further, on the polyimide layer F, the PFA dispersion liquid 1 was uniformly coated so that the final thickness became 5 μm, and then heated and dried at 90°C for 3 minutes and at 120°C for 3 minutes to remove the solvent. After that, it was heated at 320°C for 3 minutes to form an insulating resin layer 6 with a thickness of 55 μm composed of a PFA layer / polyimide layer F / PFA layer / polyimide layer F / PFA layer, and a metal-clad laminate 6 was prepared.

[0112] Using an aqueous ferric chloride solution, the copper foil 1 was etched away to prepare a resin film 6. Table 2 shows the measurement results of T.T., YI, CTE, relative permittivity, and dielectric loss tangent for the resin film 6.

[0113] [Example 7] On the copper foil 1, after uniformly applying the PFA dispersion liquid 1 so that the final thickness becomes 2 μm, it was 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 C (viscosity: 23000 cP) was uniformly applied on the PFA film so that the thickness after curing became 21 μm, then heated and dried at 125 °C to remove the solvent, and then subjected to a stepwise heat treatment from 125 °C to 360 °C to complete imidization and form a polyimide layer C. Further, on the polyimide layer C, after uniformly applying the PFA dispersion liquid 1 so that the final thickness becomes 2 μm, it was 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 with a thickness of 25 μm composed of a PFA layer / polyimide layer C / PFA layer, and a metal-clad laminate 7 was prepared. Two obtained metal-clad laminates 7 were overlapped so that the copper foil 1 was located on 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.

[0114] Using an aqueous ferric chloride solution, the copper foil 1 was etched away to prepare a resin film 7. Table 2 shows the measurement results of T.T., YI, CTE, relative permittivity, and dielectric tangent for the resin film 7.

[0115] [Example 8] On the copper foil 1, after uniformly applying the PFA dispersion liquid 1 so that the final thickness becomes 1 μm, it was 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 so that the thickness after curing became 15 μm, then heated and dried at 125 °C to remove the solvent, and then subjected to a stepwise heat treatment from 125 °C to 360 °C to complete imidization and form a polyimide layer B, and a metal-clad laminate 8 was prepared. A PFA film 1 (thickness: 25 μm) was placed on the polyimide of the obtained metal-clad laminate 8, and then the metal-clad laminate 8 was laminated so that the copper foil 1 was located on the outermost layer. Heat and pressure were applied at 320 °C and 7.5 MPa for 20 minutes under a vacuum atmosphere to prepare a double-sided metal-clad laminate 8.

[0116] Using an aqueous ferric chloride solution, the copper foil 1 was etched away to prepare a resin film 8. Table 2 shows the measurement results of T.T., YI, CTE, relative permittivity, and dielectric tangent for the resin film 8.

[0117] [Example 9] On the copper foil 1, the PFA dispersion liquid 1 was uniformly coated so that the final thickness was 1 μm, and then heated and dried at 90 °C for 1 minute and 120 °C for 1 minute. After removing the solvent, it was 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 the polyamic acid solution B (viscosity: 17300 cP) was uniformly coated on the PFA film so that the cured thickness was 10 μm, and then heated and dried at 125 °C to remove the solvent. Then, a stepwise heat treatment was performed from 125 °C to 360 °C to complete imidization and form a polyimide layer B. Further, on the polyimide layer B, the PFA dispersion liquid 1 was uniformly coated so that the final thickness was 1 μm, and then heated and dried at 90 °C for 1 minute and 120 °C for 1 minute. After removing the solvent, it was heated at 320 °C for 1 minute and 30 seconds to form an insulating resin layer 9 with a thickness of 12 μm composed of a PFA layer / polyimide layer B / PFA layer, and a metal-clad laminate 9 was prepared. A diluted solution of the polyamic acid solution G (viscosity: 22400 cP) was uniformly coated on the base film 1 in advance so that the cured thickness was 10 μm, and then heated and dried at 125 °C to remove the solvent. Then, a stepwise heat treatment was performed from 125 °C to 360 °C to complete imidization and form a polyimide layer G. A polyimide film G was prepared by peeling it from the base film 1. The polyimide film G was placed on the PFA layer of the metal-clad laminate 9, and then the metal-clad laminate 9 was laminated so that the copper foil 1 was on the outermost layer. Heat and pressure were applied at 320 °C and 7.5 MPa for 20 minutes under a vacuum atmosphere to obtain a double-sided metal-clad laminate 9.

[0118] Using an aqueous ferric chloride solution, copper foil 1 was etched away to prepare resin film 9. Table 2 shows the measurement results of T.T., YI, CTE, relative permittivity, and dielectric tangent for resin film 9.

[0119]

Table 2

[0120] (Comparative Example 1) On copper foil 1, PFA dispersion 1 was uniformly coated to a final thickness of 6 μm, 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 copper foil 1. Next, a diluted solution of polyamic acid solution G (viscosity: 22400 cP) was uniformly coated on the PFA film to a cured thickness of 12.5 μm, then heated and dried at 125°C to remove the solvent, and then subjected to a stepwise heat treatment from 125°C to 360°C to complete imidization and form polyimide layer G. Further, on polyimide layer G, PFA dispersion 1 was uniformly coated to a final thickness of 6 μm, 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 with a thickness of 24.5 μm composed of a PFA layer / polyimide layer G / PFA layer, and a metal-clad laminate 10 was prepared.

[0121] Using an aqueous ferric chloride solution, copper foil 1 was etched away to prepare resin film 10. Table 3 shows the measurement results of T.T., YI, CTE, relative permittivity, and dielectric tangent for resin film 10.

[0122] (Comparative Example 2) On one side of a polyimide film (manufactured by Ube Industries, Ltd., trade name: Upilex 25S, thickness 25 μm, total light transmittance: 55%), PFA dispersion 1 was uniformly coated to a final thickness of 6 μm, 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 polyimide film. Furthermore, after uniformly applying PFA dispersion liquid 1 onto the polyimide film surface to a final thickness of 6 μm, it was heated and dried at 90 °C for 3 minutes and then 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 with a thickness of 37 μm composed of a PFA layer / polyimide film / PFA layer.

[0123] Table 3 shows the measurement results of T.T., YI, CTE, relative permittivity, and dielectric tangent for the resin film 11.

[0124] (Comparative Example 3) A diluted solution of polyamic acid solution H (viscosity: 19000 cP) was uniformly applied onto the base film 1 to a cured thickness of 50 μm, then heated and dried at 125 °C to remove the solvent, and then subjected to a 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 to prepare a polyimide film H. On the copper foil 1, 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 sequence, and heated and pressed at 320 °C and 7.5 MPa for 20 minutes under a vacuum atmosphere to prepare a double-sided metal-clad laminate 12.

[0125] Using an aqueous ferric chloride solution, the copper foil 1 was etched away to prepare a resin film 12. Table 3 shows the measurement results of T.T., YI, CTE, relative permittivity, and dielectric tangent for the resin film 12.

[0126] (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 a polyamic acid solution I.

[0127] Using an aqueous ferric chloride solution, the copper foil 1 was etched away to prepare a resin film 13. Table 3 shows the measurement results of T.T., YI, CTE, relative permittivity, and dielectric tangent for the resin film 13.

[0128] (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 H of Comparative Example 3 was changed to the polyamic acid solution G.

[0129] Using an aqueous solution of ferric chloride, the copper foil 1 was etched away to prepare a resin film 14. Table 3 shows the measurement results of T.T., YI, CTE, relative permittivity, and dielectric tangent for the resin film 14.

[0130]

Table 3

[0131] As described above, the embodiments of the present invention have been described in detail for illustrative purposes. However, the present invention is not limited to the above embodiments, and various modifications are possible.

Explanation of Reference Numerals

[0132] 10A, 10B, 10C... metal-clad laminates, 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

1. A resin film having a laminated structure composed of a plurality of layers, a polyimide insulating layer, a fluororesin layer laminated on one or both sides of the polyimide insulating layer, and comprising the polyimide insulating layer is composed of a single layer or a plurality of polyimide layers, and the polyimide constituting the polyimide layer (i) having a thickness of 50% or more with respect to the total thickness of the 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, and the proportion of fluorine atoms contained in the polyimide layer (i) is in the range of 10 to 40% by weight with respect to the total polyimide, the total thickness of the resin film is in the range of 34 to 150 μm, the ratio of the thickness of the polyimide insulating layer to the total thickness of the resin film is in the range of 0.5 to 0.9, and the following conditions i) and condition ii); i) the total light transmittance of the entire resin film is 80% or more, ii) the coefficient of thermal expansion of the entire resin film is 30 ppm / K or less, A resin film characterized by satisfying the above.

2. The resin film according to claim 1, wherein the dielectric loss tangent of the entire resin film at a frequency of 10 GHz measured by a split post dielectric resonator (SPDR resonator) is 0.008 or less.

3. The resin film according to claim 1 or 2, wherein the total thickness of the resin film is in the range of 50 to 150 μm.

4. A metal-clad laminate comprising the resin film according to any one of claims 1 to 3 and a metal layer laminated on the surface of the fluororesin layer in the resin film.

5. A first metal layer, A fluororesin adjacent layer provided adjacent to one side of the first metal layer, A second metal layer, A fluororesin adjacent layer provided adjacent to one side of the second metal layer, A plurality of resin layers interposed between the two fluororesin adjacent layers, Comprising, A resin laminate is formed by the two fluororesin adjacent layers and the plurality of resin layers, The resin laminate, At least two or more polyimide layers, A fluororesin intermediate layer laminated between the polyimide layers, The metal-clad laminate according to claim 4, having.

6. A circuit board formed by wiring the metal layer of the metal-clad laminate according to claim 4 or 5.

7. A method for manufacturing a resin film according to any one of claims 1 to 3, A step of applying a solution containing fluororesin particles on a substrate and performing heat treatment to melt the fluororesin particles to form the fluororesin layer; A step of applying a polyimide precursor solution on the fluororesin layer and performing heat treatment to imidize and form the polyimide layer; A method for manufacturing a resin film including.

8. Furthermore, A step of applying a solution containing fluororesin particles on the polyimide layer and performing heat treatment to melt the fluororesin particles to form the second fluororesin layer, The method for manufacturing a resin film according to claim 7, including.

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