CN114929474A

CN114929474A - Flexible metal-clad laminated board with microstrip line structure

Info

Publication number: CN114929474A
Application number: CN202180008908.5A
Authority: CN
Inventors: 秋山贵善; 细贝诚二; 立石和幸; 斋藤隼平
Original assignee: Kaneka Corp
Current assignee: Kaneka Corp
Priority date: 2020-02-18
Filing date: 2021-01-27
Publication date: 2022-08-19
Also published as: JPWO2021166572A1; KR20220143009A; TW202202338A; WO2021166572A1

Abstract

The present invention addresses the problem of achieving further reduction in transmission loss of a flexible metal-clad laminate. The present invention can solve the above-described problems by using a flexible metal clad laminate characterized by having a microstrip line structure, the flexible metal clad laminate having at least a signal line (3)/a 1 st polyimide layer (2)/a ground layer (1) in this order, the thickness of the 1 st polyimide layer (2) being 75 to 200 μm and the dielectric loss at 10GHz being 0.008 or less.

Description

Flexible metal-clad laminated board with microstrip line structure

Technical Field

The present invention relates to a flexible metal-clad laminate having a microstrip line structure.

Background

Polyimide films are widely used for electronic substrate materials because of their excellent mechanical strength, heat resistance, electrical insulation properties, and chemical resistance. For example, a flexible copper clad laminate (hereinafter, also referred to as FCCL) in which at least a copper foil is laminated on one surface thereof, a flexible printed circuit board (hereinafter, also referred to as FPC) in which a circuit is formed, and the like are manufactured using a polyimide film as a substrate material and used in various electronic devices.

With the recent high-speed signal transmission of electronic devices, there has been an increasing demand for polyimide as a substrate material to have a low dielectric constant and a low dielectric loss tangent in order to increase the frequency of electric signals transmitted through circuits. The tendency toward higher frequencies is progressing, and in the future, materials having low dielectric constants and low dielectric loss tangents are demanded in the region of, for example, 5GHz or more, and further 10GHz or more. And the propagation speed of signals in electronic circuits decreases as the dielectric constant of the substrate material increases. In addition, if the dielectric constant and the dielectric loss tangent are increased, the transmission loss of the signal is also increased. Therefore, it is important to improve the performance of electronic devices that polyimide, which is a substrate material, has a low dielectric constant and a low dielectric loss tangent, and that the transmission loss in a state where it is formed into an FPC is small.

As a film that can be used for a circuit board with a high frequency, an insulating resin layer in which a resin powder with a low dielectric constant is mixed with a polyimide resin is known. For example, patent document 1 discloses an example in which a polyimide containing a fine powder of a fluorine-based resin is used for a circuit board.

Patent document 2 describes that polyimide, which is a substrate material, is effective in reducing dielectric constant and dielectric loss. As a representative method for wiring a high-speed transmission line in an FPC, a strip line and a microstrip line are known. The microstrip line has a simple structure, and a transmission line is wired on the surface layer of the substrate, so that the microstrip line has excellent signal characteristics and can be manufactured at low cost. In addition, the strip line is covered with 2 GND planes, and thus has a feature that electromagnetic interference (EMI) can be suppressed compared to the microstrip line. In recent years, requirements for low transmission characteristics among the characteristics have been intensified, and microstrip lines having excellent transmission characteristics have been increasingly used. On the other hand, it describes: in order to reduce transmission loss by using a strip line, it is effective to reduce the dielectric constant and the dielectric loss of polyimide as a substrate material (patent document 2).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication "Japanese unexamined patent publication No. 2017-78102"

Patent document 2: japanese laid-open patent publication No. 2018-145303 "

Disclosure of Invention

Problems to be solved by the invention

However, patent document 2 relates only to a reduction in the transmission loss of polyimide as a substrate material, and cannot realize a further reduction in the transmission loss of a flexible metal-clad laminate. Polyimide has a limit to lower dielectric constant and lower dielectric loss, and it is an object to provide a method for producing a flexible metal-clad laminate and a flexible metal-clad laminate having a low transmission loss in order to further reduce the transmission loss of the flexible metal-clad laminate.

Means for solving the problems

As a result of intensive studies, the present inventors have found that the above problems can be solved by the following configurations. That is, the present invention forms this structure as follows.

One embodiment of the present invention relates to a flexible metal clad laminate having a microstrip line structure, the flexible metal clad laminate having at least a signal line/a 1 st polyimide layer/a ground layer in this order, the 1 st polyimide layer having a thickness of 75 to 200 μm and a dielectric loss at 10GHz of 0.008 or less.

Another embodiment of the present invention relates to a method for manufacturing a flexible metal-clad laminate having a microstrip line structure, wherein the flexible metal-clad laminate includes at least a signal line, a1 st polyimide layer, and a ground layer in this order, and a polyimide film having a thickness of 75 to 200 μm and a dielectric loss at 10GHz of 0.008 or less is used as the 1 st polyimide layer.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a method for manufacturing a flexible metal clad laminate capable of easily preventing transmission loss of the flexible metal clad laminate, and a flexible metal clad laminate with low transmission loss. The flexible metal-clad laminate can be suitably used for a coaxial cable requiring a high-speed and high-frequency transmission line instead of a flexible application or an antenna application.

Drawings

Fig. 1 is a schematic cross-sectional view of a flexible metal clad laminate with microstrip lines.

Fig. 2 is a schematic cross-sectional view of a flexible metal-clad laminate having a microstrip line with a plurality of signal lines.

Fig. 3 is a schematic diagram showing an example of a method for manufacturing a flexible metal clad laminate having a microstrip line.

Fig. 4 is a schematic cross-sectional view of a flexible metal clad laminate with tape lines.

Fig. 5 is a schematic cross-sectional view of a flexible metal clad laminate with tape lines.

Fig. 6 is a schematic cross-sectional view of a flexible metal clad laminate with tape lines.

Fig. 7 is a schematic view showing a manufacturing method of a flexible metal clad laminate having strip lines.

Fig. 8 is a schematic view showing a method of laminating a polyimide adhesive sheet.

Fig. 9 is a schematic view showing a manufacturing method of a single-sided flexible metal clad laminate used in the flexible metal clad laminate.

Fig. 10 is a schematic view showing a manufacturing method of a single-sided flexible metal clad laminate used in the flexible metal clad laminate.

Fig. 11 is a schematic view showing a manufacturing method of a single-sided flexible metal clad laminate used in the flexible metal clad laminate.

Fig. 12 is a schematic view showing a manufacturing method of a double-sided flexible metal clad laminate used in the flexible metal clad laminate.

Fig. 13 is a schematic view showing a manufacturing method of a double-sided flexible metal clad laminate used in the flexible metal clad laminate.

Detailed Description

The flexible metal-clad laminate of the present invention is characterized by having a microstrip line structure, and the flexible metal-clad laminate has at least a signal line/a 1 st polyimide layer/a ground layer in this order, and the thickness of the 1 st polyimide layer is 75 to 200 [ mu ] m and the dielectric loss at 10GHz is 0.008 or less.

The flexible metal-clad laminate of the present invention further comprises a ground layer/2 nd polyimide layer/adhesive layer, and at least a ground layer/2 nd polyimide layer/adhesive layer/signal line/1 st polyimide layer/ground layer in this order, wherein the thickness of the 2 nd polyimide layer is 75 to 200 μm, and the dielectric loss at 10GHz may be 0.008 or less.

In the present specification, the phrase "flexible metal clad laminate having a microstrip line structure" refers to "flexible metal clad laminate having at least a signal line/1 st polyimide layer/ground layer in this order". The "flexible metal clad laminate having a strip line structure" refers to a "flexible metal clad laminate having at least a ground layer/a 2 nd polyimide layer/an adhesive layer/a signal line/a 1 st polyimide layer/a ground layer in this order".

First, a polyimide film used for the 1 st polyimide layer and the 2 nd polyimide layer of the present invention will be described. The thickness of the polyimide film used for the 1 st polyimide layer and the 2 nd polyimide layer is 75 to 200 [ mu ] m, and the dielectric loss at 10GHz is 0.008 or less. By using the polyimide film, the insertion loss at 10GHz of the flexible metal-clad laminate having a microstrip line structure and the flexible metal-clad laminate having a strip line structure can be made to be-3.2 dB or more and 0dB or less.

It is preferable that the 1 st polyimide layer has a thermoplastic polyimide layer and a non-thermoplastic polyimide layer, or the 1 st polyimide layer and the 2 nd polyimide layer each have a thermoplastic polyimide layer and a non-thermoplastic polyimide layer, since a flexible metal clad laminate can be easily manufactured.

The polyimide film used for each of the 1 st polyimide layer and the 2 nd polyimide layer is not particularly limited as long as the thickness is 75 to 200 μm and the dielectric loss at 10GHz is 0.008 or less. On the other hand, a polyimide film having a multilayer structure having a 3-layer structure in which thermoplastic polyimide layers are provided on both sides of a non-thermoplastic polyimide layer is preferably used. In this case, although the number of steps for bonding is increased as compared with the case of a polyimide having a single layer, the total manufacturing cost of the film tends to be reduced, which is preferable.

As the polyimide film used for each of the 1 st polyimide layer and the 2 nd polyimide layer, the following films are particularly preferable. Specifically, a polyimide film having a thickness of less than 75 μm and having a 3-layer structure comprising thermoplastic polyimide layers on both sides of a non-thermoplastic polyimide layer is laminated (pressure-bonded) at least 2 sheets to form a film having a thickness of 75 to 200 μm. This is desirable because the total manufacturing cost of the film can be minimized.

(polyimide adhesive sheet: polyimide film having 3-layer Structure comprising thermoplastic polyimide layers on both sides of non-thermoplastic polyimide layer)

Hereinafter, a polyimide film having a 3-layer structure in which thermoplastic polyimide layers are provided on both sides of a non-thermoplastic polyimide layer will be described. For convenience, a polyimide film having a 3-layer structure in which thermoplastic polyimide layers are provided on both sides of a non-thermoplastic polyimide layer is referred to as a polyimide adhesive sheet. First, the raw material monomer of the polyamic acid that is a precursor of the non-thermoplastic polyimide used for the non-thermoplastic polyimide layer, the production of the polyamic acid that is a precursor of the non-thermoplastic polyimide, the production method of the non-thermoplastic polyimide film, and the order of the thermoplastic polyimide layer will be described in detail.

(raw material monomer of polyamic acid as precursor of non-thermoplastic polyimide)

The raw material monomer of the polyamic acid which is a precursor of the non-thermoplastic polyimide in the present invention is not particularly limited as long as the non-thermoplastic polyimide obtained by imidizing the polyamic acid which is a precursor satisfies the following requirements. That is, the non-thermoplastic polyimide is not particularly limited as long as it has solder heat resistance, dimensional stability, and flame retardancy required for a conventional flexible printed circuit board material, and the solder heat resistance, dimensional stability, and flame retardancy can be controlled by a single structure and a manufacturing method. As the raw material monomer, for example, diamine and acid dianhydride which are generally used for synthesis of polyamic acid can be used.

The diamine is not particularly limited as long as the effect of the present invention can be exhibited, and examples thereof include 2,2 '-bis [4- (4-aminophenoxy) phenyl ] propane, 4' -diaminodiphenylpropane, 4 '-diaminodiphenylmethane, 4' -diaminodiphenylsulfide, 3 '-diaminodiphenylsulfone, 4' -oxydianiline, 3 '-oxydianiline, 3, 4' -oxydianiline, 4 '-diaminodiphenyldiethylsilane, 4' -diaminodiphenylsilane, 4 '-diaminodiphenylethylphosphine oxide, 4' -diaminodiphenyl-N-methylamine, 4 '-diaminodiphenyl-N-phenylamine, 4' -diaminodiphenyl-N-phenylamine, and the like, 1, 4-diaminobenzene (p-phenylenediamine), bis {4- (4-aminophenoxy) phenyl } sulfone, bis {4- (3-aminophenoxy) phenyl } sulfone, 4 '-bis (4-aminophenoxy) biphenyl, 4' -bis (3-aminophenoxy) biphenyl, 1, 3-bis (3-aminophenoxy) benzene, 3 '-diaminobenzophenone, 4' -diaminobenzophenone, 2-bis (4-aminophenoxyphenyl) propane and the like, and these may be used singly or in combination in plural.

Examples of the diamine which is advantageous for realizing low dielectric loss include aliphatic diamines having 36 carbon atoms, 1, 4-diaminobenzene (p-phenylenediamine), 1, 3-bis (4-aminophenoxy) benzene, 1, 3-bis (3-aminophenoxy) benzene, 4 '-diamino-2, 2' -dimethylbiphenyl, 4 '-diamino-3, 3' -dimethylbiphenyl, 4,4 '-diamino-2, 2' -bis (trifluoromethyl) biphenyl, 4 '-diamino-p-terphenyl, bis (4-aminophenyl) terephthalate, 2-bis (4-aminophenoxyphenyl) propane, 2-bis (4-aminophenoxyphenyl) hexafluoropropane, 4' -bis (4-aminophenoxy) biphenyl, and the like. The diamine is preferably contained in an amount of 30 to 100 mol%, more preferably 50 to 100 mol%, and still more preferably 70 to 100 mol% based on the total diamine component.

The acid dianhydride-based compound that can be used as a raw material monomer of polyamic acid is not particularly limited as long as the effect of the present invention can be exhibited, and examples thereof include pyromellitic dianhydride, 2,3,6, 7-naphthalenetetracarboxylic dianhydride, 3,3 ', 4, 4' -biphenyltetracarboxylic dianhydride, 1,2,5, 6-naphthalenetetracarboxylic dianhydride, 2 ', 3, 3' -biphenyltetracarboxylic dianhydride, 3,3 ', 4, 4' -benzophenonetetracarboxylic dianhydride, 2 ', 3, 3' -benzophenonetetracarboxylic dianhydride, 4,4 '-oxydiphthalic dianhydride, 3, 4' -oxydiphthalic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 3,4,9, 10-perylenetetracarboxylic dianhydride, bis (3, 4-dicarboxyphenyl) propane dianhydride, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, bis (3, 4-dicarboxyphenyl) ethane dianhydride, oxydiphthalic dianhydride, bis (3, 4-dicarboxyphenyl) sulfonic acid dianhydride, p-phenylene bis (trimellitic acid monoester anhydride), ethylene bis (trimellitic acid monoester anhydride), bisphenol A bis (trimellitic acid monoester anhydride), and the like.

Examples of the acid dianhydride which is advantageous for realizing a low dielectric loss include 3,3 ', 4, 4' -biphenyltetracarboxylic acid dianhydride, p-phenylene bis (trimellitic acid anhydride), 4,4 '-oxydiphthalic acid dianhydride, 2' -bis (4- (3, 4-dicarboxyphenoxy) phenyl) propane dianhydride, pyromellitic acid dianhydride, and the like. The amount of the acid dianhydride is preferably 30 to 100 mol%, more preferably 50 to 100 mol%, and still more preferably 70 to 100 mol% based on the total amount of the acid dianhydride.

The 1 st polyimide layer and the 2 nd polyimide layer can be manufactured by the following method, for example. That is, the polyamic acid can be produced by a method in which the diamine and the acid dianhydride are used as raw materials, a ring-opening addition polymerization reaction is performed in a solvent to obtain a polyamic acid solution, and then the polyamic acid is heated to perform a dehydrative cyclization reaction (imidization). Thus, the dielectric loss at 10GHz of the 1 st and 2 nd polyimide layers can be controlled to be 0.008 or less.

(production of Polyamic acid as precursor of non-thermoplastic polyimide)

The organic solvent used for producing the polyamic acid as the precursor of the non-thermoplastic polyimide may be any solvent as long as it dissolves the non-thermoplastic polyamic acid. For example, N-dimethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone, and the like, which are amide solvents, are preferable, and N, N-dimethylformamide and N, N-dimethylacetamide are more preferably used. The solid content concentration of the polyamic acid as a precursor of the non-thermoplastic polyimide is not particularly limited, and when it is in the range of 5 to 35% by weight, a polyamic acid as a precursor of the non-thermoplastic polyimide having sufficient mechanical strength when formed into a non-thermoplastic polyimide film can be obtained.

The order of addition of the aromatic diamine and the aromatic acid dianhydride as the raw materials is not particularly limited, and the properties of the resulting non-thermoplastic polyimide can be controlled not only by controlling the chemical structure of the raw materials but also by controlling the order of addition.

The non-thermoplastic polyamic acid may be added with a filler for the purpose of improving various characteristics of the film such as slidability, thermal conductivity, electrical conductivity, corona resistance, and ring stiffness. Any filler can be used, and preferable examples thereof include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica, and the like.

(method for producing non-thermoplastic polyimide film)

In order to obtain the non-thermoplastic polyimide film of the present invention, it is preferable to include the following steps:

i) a step of reacting an aromatic diamine and an aromatic acid dianhydride in an organic solvent to obtain a polyamic acid solution (hereinafter, also referred to as a non-thermoplastic polyamic acid) which is a precursor of a non-thermoplastic polyimide;

ii) a step of casting a film-forming dope containing the non-thermoplastic polyamic acid solution from a die onto a support to form a resin layer (also referred to as a liquid film);

iii) heating the resin layer on a support to form a self-supporting gel film, and then peeling the gel film from the support;

iv) heating the resultant mixture to imidize the remaining amic acid and drying the imidized amic acid to obtain a non-thermoplastic polyimide film.

in the subsequent steps ii), the methods of imidization are roughly classified into a thermal imidization method and a chemical imidization method. The thermal imidization method is a method in which a polyamic acid solution is cast as a film forming dope onto a support without using a dehydration ring-closing agent or the like, and imidization is performed only by heating. Another chemical imidization method is a method of accelerating imidization by using, as a film-forming coating material, a solution obtained by adding at least one of a dehydration ring-closing agent and a catalyst as an imidization accelerator to a polyamic acid solution. Any of these methods can be used, and the chemical imidization method is more excellent in productivity.

As the dehydration ring-closing agent, an acid anhydride represented by acetic anhydride can be suitably used. As the catalyst, tertiary amines such as aliphatic tertiary amines, aromatic tertiary amines, and heterocyclic tertiary amines can be suitably used.

As the support on which the film forming dope is cast, a glass plate, an aluminum foil, an endless stainless steel belt, a stainless steel drum, or the like can be suitably used. Heating conditions are set according to the thickness and production rate of the finally obtained film, and at least one of imidization and drying is partially performed, and then the film is peeled from the support to obtain a polyamic acid film (hereinafter referred to as a gel film).

The ends of the gel film are fixed, and the gel film is dried while avoiding shrinkage during curing, and after removing water, residual solvent, and imidization accelerator from the gel film, the remaining amic acid is completely imidized to obtain a polyimide-containing film. The heating conditions may be appropriately set depending on the thickness of the finally obtained film and the production rate.

(thermoplastic polyimide (layer))

The thermoplastic polyimide contained in the thermoplastic polyimide (layer) in the present invention is obtained by imidizing a polyamic acid as a precursor thereof.

The aromatic diamine and the aromatic tetracarboxylic dianhydride used in the polyamic acid, which is a precursor of the thermoplastic polyimide used in the present invention, may be the same as those used in the non-thermoplastic polyimide layer. On the other hand, in order to produce a thermoplastic polyimide film, it is preferable to react a diamine having flexibility with an acid dianhydride. Examples of the diamine having flexibility include 4,4 ' -diaminodiphenyl ether, 4 ' -bis (4-aminophenoxy) biphenyl, 4 ' -bis (3-aminophenoxy) biphenyl, 1, 3-bis (3-aminophenoxy) benzene, 1, 3-bis (4-aminophenoxy) benzene, 2-bis (4-aminophenoxyphenyl) propane, and the like. In order to adjust the glass transition temperature (Tg) of the polyimide film, the diamine may be used in combination with 1, 4-diaminobenzene and/or 4,4 '-diamino-2, 2' -dimethylbiphenyl. Examples of the acid dianhydride suitable for combination with these diamines include pyromellitic dianhydride, 3 ', 4,4 ' -benzophenonetetracarboxylic dianhydride, 3 ', 4,4 ' -biphenyltetracarboxylic dianhydride, and 4,4 ' -oxydiphthalic dianhydride.

In the method for producing a thermoplastic polyamic acid according to the present invention, any known method may be used as long as the obtained thermoplastic polyimide satisfies the following requirements. That is, any known method may be used as long as the thermoplastic polyimide obtained by imidizing the obtained polyamic acid has adhesion to a metal foil, solder heat resistance, dimensional stability, and flame retardancy required for conventional flexible printed wiring board materials.

For example, it can be produced by the following steps (A-a) to (A-c):

(A-a) a step of reacting an aromatic diamine and an aromatic acid dianhydride in an organic solvent in the state where the aromatic diamine is in excess to obtain a prepolymer having amino groups at both ends;

(A-b) a step of additionally adding an aromatic diamine having a structure different from that of the aromatic diamine used in the step (A-a);

(A-c) further adding an aromatic acid dianhydride different in structure from the aromatic acid dianhydride used in step (A-a) to the aromatic diamine and the aromatic acid dianhydride in the step so that the aromatic diamine and the aromatic acid dianhydride are substantially equimolar and polymerizing.

Alternatively, the polyamic acid may be obtained by performing the following steps (B-a) to (B-c):

(B-a) a step of reacting an aromatic diamine and an aromatic acid dianhydride in an organic polar solvent in a state where the aromatic acid dianhydride is excessive, to obtain a prepolymer having acid anhydride groups at both ends;

(B-B) a step of additionally adding an aromatic acid dianhydride having a structure different from that of the aromatic acid dianhydride used in the step (B-a);

(B-c) a step of adding an aromatic diamine having a structure different from that of the aromatic diamine used in the step (B-a) so that the aromatic diamine and the aromatic acid dianhydride are substantially equimolar in the whole step, and polymerizing the mixture.

(solid content concentration of Polyamic acid)

The solid content concentration of the polyamic acid of the present invention is not particularly limited, and is usually obtained at a concentration of 5 to 35% by weight, preferably 10 to 30% by weight. At a concentration within this range, an appropriate molecular weight and solution viscosity are obtained.

(method for producing polyimide adhesive sheet)

The method for producing the laminate having the thermosetting resin layer and the polyimide layer in the present invention will be described in detail. The method for producing the laminate of the present invention may be, for example, a method in which a non-thermoplastic polyamic acid is synthesized in the above-described i), and then a thermoplastic polyamic acid is applied to both sides of the temporarily collected non-thermoplastic polyimide film, and then imidized, after the steps of the above-described ii) to iv). A polyimide adhesive sheet can also be produced by applying a thermoplastic polyimide solution capable of forming a thermoplastic polyimide layer on both sides of the non-thermoplastic polyimide film and drying the solution.

As another method, the following method can be mentioned. In the above i), a non-thermoplastic polyamic acid is synthesized, and a polyamic acid (hereinafter, a thermoplastic polyamic acid) which is a precursor of a thermoplastic polyimide is separately synthesized. In the step ii), the coating material containing the thermoplastic polyamic acid/the film-forming coating material containing the non-thermoplastic polyamic acid solution/the coating material containing the thermoplastic polyamic acid is cast from a die onto a support so as to form 3 layers, thereby forming a resin layer (which may be referred to as a liquid film). The steps of iii) and iV) are performed in the same manner as described below, whereby the polyimide adhesive sheet of the present invention can be produced.

< Flexible Metal-clad laminate with microstrip line Structure >

A flexible metal clad laminate characterized by having a microstrip line structure, comprising a signal line, a1 st polyimide layer and a ground layer in this order, wherein the thickness of the 1 st polyimide layer is 75 to 200 [ mu ] m, and the dielectric loss at 10GHz is 0.008 or less.

As shown in fig. 1, the flexible metal-clad laminate having a microstrip line structure of the present invention sequentially includes a signal line, a1 st polyimide layer, and a ground layer. The polyimide layer 1 is a polyimide film having a thickness of 75 to 200 [ mu ] m and a dielectric loss of 0.008 or less at 10 GHz. This makes it possible to set the insertion loss at 10GHz to-2.4 dB or more and 0dB or less.

As shown in fig. 2, a plurality of signal lines may be provided.

< method for manufacturing flexible metal-clad laminate having microstrip line structure >

As shown in fig. 3, a plurality of polyimide adhesive sheets (polyimide films having a 3-layer structure in which thermoplastic polyimide layers are provided on both sides of a non-thermoplastic polyimide layer) were sandwiched between 2 copper foils and collectively bonded. Then, the signal line is formed by etching, whereby the microstrip line structure can be easily formed.

Instead of the polyimide adhesive sheet, a single-layer thermoplastic polyimide film may be used in the following manner. That is, for example, the copper foil/single-layer thermoplastic polyimide/non-thermoplastic polyimide/single-layer thermoplastic polyimide/copper foil may be laminated in this order and collectively laminated in the same manner. The total thickness of the thermoplastic polyimide and the non-thermoplastic polyimide (thickness of the polyimide layer) in this case is preferably 75 μm or more.

(thermoplastic polyimide (Single layer))

The thermoplastic polyimide (single layer) is obtained by imidizing the same polyamic acid as the polyamic acid described in the section "thermoplastic polyimide (layer)" which is a precursor of the thermoplastic polyimide, and forming a sheet (film). The production of the thermoplastic polyimide (single layer) is preferably carried out by the same method as the production method of the non-thermoplastic polyimide film.

(non-thermoplastic polyimide (Single layer))

The non-thermoplastic polyimide (single layer) is a sheet (film) formed by imidizing the same polyamic acid as a precursor of the non-thermoplastic polyimide to form a single layer. The production of the non-thermoplastic polyimide (single layer) is preferably carried out by the same method as the production method of the non-thermoplastic polyimide film.

Various known methods can be applied as a method of lamination, and a thermocompression bonding method obtained by bonding by thermocompression bonding is preferable in that generation of wrinkles and the like in the single-sided flexible metal-clad laminate can be suppressed. Examples of the method for bonding the polyimide adhesive sheet and the metal foil include a thermal compression bonding method using a batch process using a single-plate press, and a thermal compression bonding method using a continuous process using a hot roll laminating apparatus (also referred to as a thermal laminating apparatus) or a Double Belt Press (DBP) apparatus. Among them, a thermal compression bonding method using a heat roll laminating apparatus having one or more pairs of metal rolls is preferable in terms of productivity and equipment cost including maintenance cost. The "heat roll laminating apparatus having one or more pairs of metal rolls" as used herein is not particularly limited as long as it has a metal roll for heating and pressurizing a material.

The surface roughness (Ra) of the signal line on the 1 st polyimide layer side is preferably small in view of contributing to low transmission loss, and adhesion must be secured. Therefore, it is preferably 0.05 to 0.5. mu.m, more preferably 0.08 to 0.3. mu.m, and still more preferably 0.1 to 0.2. mu.m. The surface roughness is based on the surface roughness of the polyimide layer side and can therefore be controlled by the metal foil used.

As a method of forming the ground layer, a method of attaching a metal foil is described, and one or both of the ground layers may be formed by applying a conductive paste and drying, or may be formed by attaching a conductive shielding film.

Various known methods can be applied as a method of lamination, and a thermocompression bonding method obtained by bonding by thermocompression bonding is preferable in that occurrence of appearance defects and the like of the double-sided flexible metal-clad laminate can be suppressed. Examples of the bonding method include a thermal compression bonding method using a batch process by a single plate press, a thermal compression bonding method using a continuous process by a heat roll laminating apparatus (also referred to as a thermal laminating apparatus) or a Double Belt Press (DBP) apparatus, and the like. From the viewpoint of productivity and equipment cost including maintenance cost, a thermocompression bonding method using a heat roll laminating device having at least one pair of metal rolls is preferable. The "heat roll laminating apparatus having one or more pairs of metal rolls" as used herein is not particularly limited as long as it has a metal roll for heating and pressurizing a material.

In this thermocompression bonding method, the metal foil is subjected to 2 times of high heat treatment in the production of the single-sided flexible metal clad laminate and in the production of the double-sided flexible metal clad laminate, and therefore there is a problem that the metal foil is likely to cause poor appearance due to heat burning and heat deformation. In order to improve the thermal deformation, among the thermocompression bonding methods, the thermocompression bonding method using a heat roll laminating device having at least one pair of metal rolls is preferably used to control the tension of the metal foil and the single-sided flexible metal-clad laminate or the tension of the metal foil and the double-sided flexible metal-clad laminate. Specifically, the tension before thermocompression bonding is preferably set to be high, and the lead-out tension of the single-sided flexible metal-clad laminate or the lead-out tension of the double-sided flexible metal-clad laminate is preferably set to be 40kgf/270mm or more. In addition, in order to improve the heat burning, it is preferable to use a protective film at the time of hot roll lamination.

The heating method of the material to be laminated in the thermocompression bonding method is not particularly limited, and for example, a conventionally known heating method capable of heating at a predetermined temperature such as a heat cycle method, a hot air heating method, an induction heating method, or the like can be used. Similarly, the pressure application method of the material to be laminated by the thermocompression bonding method is not particularly limited, and for example, a conventionally known method that can apply a predetermined pressure such as a hydraulic method, an air pressure method, or an inter-gap pressure method may be used.

The heating temperature in the thermocompression bonding step, that is, the pressure bonding temperature (lamination temperature), may be the lowest temperature at which the polyimide adhesive sheet on the side that is in close contact with the metal foil can be in close contact with the metal foil in the production of the single-sided flexible metal-clad laminate. The polyimide adhesive sheet on the side not in close contact with the metal foil may be at a temperature at which the sheet is not stuck to other materials, peripheral members, or the like. Therefore, the laminating temperature in the production of the single-sided flexible metal-clad laminate can be set to the glass transition temperature (Tg) +20 ℃ to (Tg) +60 ℃ of the polyimide adhesive sheet to be used.

When the polyimide adhesive sheet is heated at a temperature exceeding Tg, the polyimide adhesive sheet softens as the heating temperature increases, and the polyimide adhesive sheet easily adheres to peripheral members. In this case, the polyimide adhesive sheet on the side not in close contact with the metal foil may contact with peripheral members during processing, and therefore, the adhesiveness is preferably low. Therefore, the above lamination temperature is preferably employed.

On the other hand, in the production of a double-sided flexible metal-clad laminate, a situation in which the adhesion strength of all layers is high is desired. Therefore, the lamination can be performed at a higher temperature than the single-sided flexible metal clad laminate. Therefore, the laminating temperature in the production of the double-sided flexible metal-clad laminate is preferably a temperature of glass transition temperature (Tg) +20 ℃ to (Tg) +90 ℃ of the polyimide adhesive sheet to be used, and more preferably Tg +50 ℃ to (Tg) +80 ℃ of the adhesive sheet (C).

The lamination speed in the thermocompression bonding step is preferably 0.5 m/min or more, and more preferably 1.0 m/min or more. When the thickness is 0.5 m/min or more, sufficient thermocompression bonding can be achieved, and when the thickness is 1.0 m/min or more, productivity can be further improved.

The higher the pressure in the thermocompression bonding step, that is, the higher the lamination pressure, the lower the lamination temperature and the higher the lamination speed, but generally, if the lamination pressure is too high, the dimensional change of the obtained metal-clad laminate tends to be deteriorated. Conversely, the lower the lamination pressure, the lower the adhesion strength of the metal foil of the obtained metal-clad laminate tends to be. Therefore, the laminating pressure is preferably in the range of 49N/cm to 490N/cm (5kgf/cm to 50kgf/cm), more preferably in the range of 98N/cm to 294N/cm (10kgf/cm to 30 kgf/cm). When the amount is within this range, three conditions of the laminating temperature, the laminating speed, and the laminating pressure can be made favorable, and the productivity can be further improved.

In order to obtain the single-sided flexible metal-clad laminate or the double-sided flexible metal-clad laminate of the present invention, a heat roll laminating apparatus that continuously heats and pressure-bonds a material to be laminated is preferable. In the heat roller laminating apparatus, a laminated material leading-out means for leading out the laminated material may be provided at a front stage of the thermal laminating means, or a laminated material winding means for winding the laminated material may be provided at a rear stage of the thermal laminating means. By providing these means, the productivity of the heat roller laminating apparatus can be further improved. The specific configuration of the means for leading out the material to be laminated and the means for winding up the material to be laminated is not particularly limited, and examples thereof include a known roll winder capable of winding up an adhesive sheet, a metal foil, or the obtained metal-clad laminate.

It is more preferable to further provide a winding means and a drawing means for winding or drawing the protective film. If these take-up means and take-out means are provided, the protective film that has been used once in the thermocompression bonding step can be taken up and set on the take-out side again to reuse the protective film. Further, when the protective film is wound, an end position detecting means and a winding position correcting means may be provided so that both ends of the protective film are aligned. This enables the end portions to be aligned and wound up with high accuracy, and therefore, the efficiency of reuse can be improved. The specific configurations of the winding means, the deriving means, the edge position detecting means, and the winding position correcting means are not particularly limited, and various conventionally known devices can be used.

(Metal foil)

The metal foil that can be used in the present invention is not particularly limited. When the flexible metal-clad laminate of the present invention is used in electronic and electrical equipment applications, examples thereof include foils made of copper or a copper alloy, stainless steel or an alloy thereof, nickel or a nickel alloy (including 42 alloy), and aluminum or an aluminum alloy. In general, a copper foil such as a rolled copper foil or an electrolytic copper foil is often used for a flexible laminate, and it is also preferably used in the present invention. The surface of these metal foils may be coated with a rust-proof layer, a heat-resistant layer, or an adhesive layer. The thickness of the metal foil is not particularly limited, and may be any thickness that can provide sufficient functions according to the application.

The transmission loss is mainly composed of a conductor loss due to the copper foil and a dielectric loss due to the insulating resin base material. Since the conductor loss is affected by the skin effect of the copper foil which appears more remarkably at higher frequencies, a copper foil with a low roughness is required to suppress the transmission loss in high-frequency applications. Further, it is known that the conductivity of an alloy containing a magnetic material such as nickel or cobalt, which is used for rust prevention or improvement of adhesiveness, changes depending on the frequency, and the transmission loss may be deteriorated, and thus care must be taken in use.

The thickness of the metal foil is, for example, preferably 3 μm to 30 μm, more preferably 5 μm to 20 μm. The surface roughness (Ra) of the metal foil is preferably 0.05 to 0.5. mu.m, more preferably 0.08 to 0.3. mu.m, and still more preferably 0.1 to 0.2. mu.m, in view of adhesion to the polyimide layer. When the surface roughness (Ra) is smaller than this range, the adhesion to the polyimide layer becomes low, and when Ra is larger than this range, the conductor loss becomes large, so that it is difficult to reduce the transmission loss.

< surface treatment of polyimide adhesive sheet >

Since the polyimide adhesive sheet has an adhesive layer as the outermost layer, it is not necessary to perform a general surface treatment for improving the adhesion force. However, when the adhesive sheets are bonded to each other, since they are made of the same material, the surface state is the same, and the anchoring effect is small and the adhesion tends to be low. In this case, the adhesion force between the polyimide adhesive sheets can be improved by applying a surface treatment to the adhesive layer, which is not usually applied, to at least one surface of the bonding surface.

The method of surface treatment is not particularly limited, and for example, corona treatment, plasma treatment, blast treatment, or the like can be used.

< Flexible Metal-clad laminate having strip line Structure >

A flexible metal clad laminate having a strip line structure and having at least a ground layer/a 2 nd polyimide layer/an adhesive layer/a signal line/a 1 st polyimide layer/a ground layer in this order will be described.

As shown in fig. 4, the flexible metal clad laminate having a strip line structure of the present invention includes a ground layer/2 nd polyimide layer/adhesive layer (adhesive layer 1)/signal line/1 st polyimide layer/ground layer in this order. Further, polyimide films having a thickness of 75 to 200 μm and a dielectric loss of 0.008 or less at 10GHz are used for the 1 st polyimide layer and the 2 nd polyimide layer, respectively. This makes it possible to set the insertion loss at 10GHz to-3.2 dB or more and 0dB or less.

As shown in fig. 5, an adhesive layer (adhesive layer 2) may be provided between the copper layer as the signal line and the 1 st polyimide layer.

Further, as shown in fig. 6, a plurality of signal lines may be provided.

The flexible metal clad laminate having a strip line structure of the present invention can be manufactured by bonding a single-sided flexible metal clad laminate (ground layer/2 nd polyimide layer) to an adhesive layer (bonding sheet) or a double-sided flexible metal clad laminate as shown in fig. 7. Here, an example is described in which an adhesive layer is used as the adhesive sheet. On the other hand, the flexible metal-clad laminate can be similarly produced by applying an adhesive to the polyimide surface of the single-sided flexible metal-clad laminate or the polyimide surface of the double-sided flexible metal-clad laminate, instead of the bonding sheet, and bonding the two.

< method for producing single-sided flexible metal-clad laminate >

In the present invention, the single-sided flexible metal-clad laminate is obtained by laminating a metal foil (ground layer) on the thermoplastic polyimide layer as an adhesive layer of the polyimide adhesive sheet (a polyimide film having a 3-layer structure in which thermoplastic polyimide layers are provided on both sides of a non-thermoplastic polyimide layer). As shown in fig. 8, a single-sided flexible metal-clad laminate can be produced by laminating (laminating) a plurality of polyimide adhesive sheets having a thickness of 75 μm or less to form an adhesive layer having a thickness of 75 μm or more and then laminating a metal layer on one side. Alternatively, as shown in fig. 9, a single-sided flexible metal-clad laminate may be produced by collectively bonding a metal foil and a plurality of polyimide adhesive sheets.

Fig. 9 shows an example in which a polyimide adhesive sheet (a polyimide film having a 3-layer structure in which thermoplastic polyimide layers are provided on both sides of a non-thermoplastic polyimide layer) is used, but may be bonded in the order of metal foil (ground layer)/thermoplastic polyimide (single layer)/non-thermoplastic polyimide (single layer) as shown in fig. 10. The total thickness of the thermoplastic polyimide and the non-thermoplastic polyimide in this case is preferably 75 μm or more.

(thermoplastic polyimide (Single layer))

The thermoplastic polyimide (single layer) is the same as the thermoplastic polyimide (single layer) in the flexible metal-clad laminate having a microstrip line structure of the present invention (hereinafter referred to as "flexible metal-clad laminate 1"). That is, the present invention is a sheet (film) obtained by imidizing the same polyamic acid as the polyamic acid described in the section "thermoplastic polyimide (layer)" which is a precursor of the thermoplastic polyimide. The production of the thermoplastic polyimide (single layer) is preferably carried out by the same method as the production method of the non-thermoplastic polyimide film.

(non-thermoplastic polyimide (Single layer))

The non-thermoplastic polyimide (single layer) is the same as the non-thermoplastic polyimide (single layer) in the flexible metal clad laminate 1. That is, the present invention is a sheet (film) in which the same polyamic acid as a precursor of the non-thermoplastic polyimide is imidized to form a single layer. The production of the non-thermoplastic polyimide (single layer) is preferably carried out by the same method as the production method of the non-thermoplastic polyimide film.

As shown in fig. 11, the metal foil (ground layer)/thermoplastic polyimide/non-thermoplastic polyimide may be laminated in this order so that a plurality of layers of (thermoplastic polyimide/non-thermoplastic polyimide) are repeated. The sum of the thicknesses of the thermoplastic polyimide and the non-thermoplastic polyimide in this case is 75 μm or more.

As a method of lamination, various known methods can be applied, and the same method as the lamination method in the above-described method of manufacturing the flexible metal clad laminate 1 can be used.

< method for producing double-sided flexible metal-clad laminate >

In the present invention, the double-sided flexible metal-clad laminate can be obtained by laminating a metal foil on the thermoplastic polyimide layer as the adhesive layer of the polyimide adhesive sheet (polyimide film having a 3-layer structure in which thermoplastic polyimide layers are provided on both sides of a non-thermoplastic polyimide layer). As shown in fig. 12, a metal foil/a plurality of polyimide adhesive sheets/a metal foil may be collectively laminated to form a double-sided flexible metal-clad laminate (b in fig. 12). Instead of the plurality of polyimide adhesive sheets, a plurality of polyimide adhesive sheets having a thickness of 75 μm or less may be laminated (laminated) as shown in fig. 13. Next, a signal line is formed by etching one surface of the double-sided flexible metal-clad laminate (b in fig. 12 and b in fig. 13). The signal line may be plural as shown in fig. 6. As described above, a double-sided flexible metal clad laminate (c in fig. 12 and c in fig. 13) can be produced.

The surface roughness (Ra) of the signal line on the 1 st polyimide layer side is preferably small in terms of contributing to reduction of transmission loss. However, since it is also necessary to ensure the adhesion, it is preferably 0.05 μm to 0.5. mu.m, more preferably 0.08 μm to 0.3. mu.m, and still more preferably 0.1 μm to 0.2. mu.m. The surface roughness is based on the surface roughness of the 1 st polyimide layer side of the metal foil laminated on the double-sided flexible metal-clad laminate, and thus can be controlled by the metal foil used.

The method of forming the ground layer is described as the method of bonding the metal foil, but the same method as the method of forming the ground layer in the above-described method of manufacturing the flexible metal clad laminated sheet 1 may be adopted. That is, one or both of the ground layers may be formed by applying and drying the conductive paste, or the conductive shield film may be laminated.

(Metal foil)

The flexible metal clad laminate having a strip line structure of the present invention may be a metal foil, and is not particularly limited, and the same metal foil as that in the flexible metal clad laminate 1 may be used.

< surface treatment of polyimide adhesive sheet >

The polyimide adhesive sheet in the flexible metal-clad laminate having a tape structure has an adhesive layer on the outermost layer, similarly to the polyimide adhesive sheet in the flexible metal-clad laminate 1 described above. Therefore, it is not necessary to perform a general surface treatment for improving the adhesion force. However, when the adhesive sheets are bonded to each other, since they are made of the same material, the surface state is the same, and the anchoring effect is small and the adhesion tends to be low. In this case, the adhesion force between the polyimide adhesive sheets can be improved by applying a surface treatment to the adhesive layer, which is not usually applied, to at least one surface of the bonding surface.

The present invention may include the inventions shown below.

(A1) A multilayer flexible metal-clad laminate characterized by having a microstrip line structure, the flexible metal-clad laminate having at least a signal line, a polyimide layer and a ground layer in this order, the polyimide layer having a thickness of 75 to 200 μm and a dielectric loss at 10GHz of 0.008 or less.

(A2) The flexible metal clad laminate according to (A1), wherein an insertion loss at 10GHz is-2.4 dB or more and 0dB or less.

(A3) The flexible metal clad laminate according to (a1) or (a2), wherein the polyimide layer has a thermoplastic polyimide layer and a non-thermoplastic polyimide layer.

(A4) The flexible metal-clad laminate according to any one of (A1) to (A3), wherein the polyimide layer has A3-layer structure including a thermoplastic polyimide layer on both sides of a non-thermoplastic polyimide.

(A5) The flexible metal-clad laminate according to (A4), wherein the polyimide layer is a laminate of 2 or more sheets of a polyimide film having a thickness of less than 75 μm and having the 3-layer structure.

(A6) The flexible metal clad laminate according to any one of (A1) to (A5), wherein the laminate has 2 or more signal lines.

(A7) The flexible metal-clad laminate according to any one of (A1) to (A6), wherein the surface roughness (Ra) of the signal line on the polyimide layer side is 0.05 μm to 0.5 μm.

(A8) A method for manufacturing a flexible metal-clad laminate, characterized in that the flexible metal-clad laminate has a microstrip line structure, the multilayer flexible metal-clad laminate has at least a signal line/a polyimide layer/a ground layer in this order, and the polyimide layer uses a polyimide film having a thickness of 75 to 200 [ mu ] m and a dielectric loss at 10GHz of 0.008 or less.

(A9) The method for manufacturing a flexible metal clad laminate according to (A8), wherein an insertion loss of the flexible metal clad laminate at 10GHz is-2.4 dB or more and 0dB or less.

(A10) The method of producing a flexible metal clad laminate according to (A8) or (a9), wherein the polyimide layer has a thermoplastic polyimide layer and a non-thermoplastic polyimide.

(A11) The method for producing a flexible metal-clad laminate according to any one of (A8) to (A10), wherein the polyimide layer is formed by laminating a thermoplastic polyimide film and a non-thermoplastic polyimide.

(A12) The method for producing a flexible metal-clad laminate according to any one of (A8) to (A11), wherein the polyimide layer has A3-layer structure including a thermoplastic polyimide layer on both surfaces of a non-thermoplastic polyimide.

(A13) The method of producing a flexible metal-clad laminate according to (A12), wherein the polyimide layer is formed by laminating at least 2 or more polyimide films having a thickness of less than 75 μm and a 3-layer structure.

(A14) The method for manufacturing a flexible metal-clad laminate according to any one of (A8) to (a13), wherein the flexible metal-clad laminate has 2 or more signal lines.

(A15) The method for producing a flexible metal-clad laminate according to any one of (A8) to (A14), wherein the surface roughness (Ra) of the signal line on the polyimide layer side is 0.05 μm to 0.5 μm.

(B1) A multilayer flexible metal-clad laminate having a strip line structure, characterized in that the multilayer flexible metal-clad laminate has at least a ground layer/a 1 st polyimide layer/an adhesive layer/a signal line/a 2 nd polyimide layer/a ground layer in this order, the thickness of the 1 st polyimide layer and the 2 nd polyimide layer is 75 to 200 [ mu ] m, and the dielectric loss at 10Hz is 0.008 or less.

(B2) The multilayer flexible metal clad laminate according to (B1), wherein an insertion loss at 10GHz is-3.2 dB or more and 0dB or less.

(B3) The multilayer flexible metal clad laminate according to (B1) or (B2), wherein the 1 st polyimide layer and the 2 nd polyimide layer have a thermoplastic polyimide layer and a non-thermoplastic polyimide layer.

(B4) The multilayer flexible metal clad laminate according to any one of (B1) to (B3), wherein the 1 st polyimide layer and the 2 nd polyimide layer have a 3-layer structure including thermoplastic polyimide layers on both surfaces of non-thermoplastic polyimide.

(B5) The multilayer flexible metal clad laminate according to (B4), wherein the 1 st polyimide layer and the 2 nd polyimide layer are a laminate of 2 or more sheets of polyimide films having a thickness of less than 75 μm and the 3-layer structure.

(B6) The multilayer flexible metal-clad laminate of any one of (B1) to (B5), wherein an adhesive layer is further provided between the copper layer as the signal line and the second polyimide layer.

(B7) The multilayer flexible metal clad laminate according to any one of (B1) to (B6), wherein the laminate has 2 or more signal lines.

(B8) The multilayer flexible metal-clad laminate according to any one of (B1) to (B7), wherein the surface roughness (Ra) of the signal line on the 2 nd polyimide layer side is 0.05 to 0.5. mu.m.

(B9) A method for manufacturing a multilayer flexible metal clad laminate having a strip line structure, wherein the multilayer flexible metal clad laminate has at least a ground layer/a 1 st polyimide layer/an adhesive layer/a signal line/a 2 nd polyimide layer/a ground layer in this order, and polyimide films having a thickness of 75 to 200 [ mu ] m and a dielectric loss at 10Hz of 0.008 or less are used for the 1 st polyimide layer and the 2 nd polyimide layer.

(B10) The method for producing a multilayer flexible metal clad laminate according to (B9), wherein an insertion loss of the multilayer flexible metal clad laminate at 10GHz is-3.2 dB or more and 0dB or less.

(B11) The method for producing a multilayer flexible metal clad laminate according to (B9) or (B10), wherein the 1 st polyimide layer and the 2 nd polyimide layer each comprise a thermoplastic polyimide layer and a non-thermoplastic polyimide.

(B12) The method for producing a multilayer flexible metal-clad laminate according to any one of (B9) to (B11), wherein the 1 st polyimide layer and the 2 nd polyimide layer are laminated by laminating a thermoplastic polyimide film and a non-thermoplastic polyimide.

(B13) The method for producing a multilayer flexible metal-clad laminate according to any one of (B9) to (B12), wherein the 1 st polyimide layer and the 2 nd polyimide layer have a 3-layer structure including thermoplastic polyimide layers on both surfaces of non-thermoplastic polyimide.

(B14) The method for producing a multilayer flexible metal-clad laminate according to (B13), wherein the 1 st polyimide layer and the 2 nd polyimide layer are formed by laminating at least 2 or more polyimide films having a thickness of less than 75 μm and having the 3-layer structure.

(B15) The method for producing a multilayer flexible metal-clad laminate according to any one of (B9) to (B14), further comprising an adhesive layer between the copper layer as the signal line and the second polyimide layer.

(B16) The method for manufacturing a multilayer flexible metal-clad laminate according to any one of (B9) to (B15), wherein the multilayer flexible metal-clad laminate has 2 or more signal lines.

(B17) The method for producing a multilayer flexible metal-clad laminate according to any one of (B9) to (B16), wherein the signal line has a surface roughness (Ra) of 0.05 μm to 0.5 μm on the 2 nd polyimide layer side.

(C1) A flexible metal-clad laminate characterized by having a microstrip line structure, the flexible metal-clad laminate having at least a signal line/a 1 st polyimide layer/a ground layer in this order, the thickness of the 1 st polyimide layer being 75 to 200 μm and the dielectric loss at 10GHz being 0.008 or less.

(C2) The flexible metal-clad laminate according to (C1), further comprising a ground layer/2 nd polyimide layer/adhesive layer, wherein the flexible metal-clad laminate comprises at least a ground layer/2 nd polyimide layer/adhesive layer/signal line/1 st polyimide layer/ground layer in this order,

the thickness of the 2 nd polyimide layer is 75 to 200 μm, and the dielectric loss at 10GHz is 0.008 or less.

(C3) The flexible metal clad laminate according to (C1) or (C2), wherein the insertion loss at 10GHz is-3.2 dB or more and 0dB or less.

(C4) The flexible metal clad laminate according to any one of (C1) to (C3), wherein the 1 st polyimide layer has a thermoplastic polyimide layer and a non-thermoplastic polyimide layer, or the 1 st polyimide layer and the 2 nd polyimide layer each have a thermoplastic polyimide layer and a non-thermoplastic polyimide layer.

(C5) The flexible metal-clad laminate according to any one of (C1) to (C4), wherein the 1 st polyimide layer has a 3-layer structure in which thermoplastic polyimide layers are provided on both surfaces of a non-thermoplastic polyimide layer, or each of the 1 st polyimide layer and the 2 nd polyimide layer has a 3-layer structure in which thermoplastic polyimide layers are provided on both surfaces of a non-thermoplastic polyimide layer.

(C6) The flexible metal-clad laminate according to (C5), wherein the 1 st polyimide layer is a laminate of 2 or more sheets of polyimide films having a thickness of less than 75 μm and having a 3-layer structure, or each of the 1 st polyimide layer and the 2 nd polyimide layer is a laminate of 2 or more sheets of polyimide films having a thickness of less than 75 μm and having a 3-layer structure.

(C7) The flexible metal-clad laminate according to any one of (C1) to (C6), wherein the signal line is a copper layer,

an adhesive layer is further provided between the copper layer and the 1 st polyimide layer.

(C8) The flexible metal clad laminate according to any one of (C1) to (C7), wherein the laminate has 2 or more signal lines.

(C9) The flexible metal-clad laminate according to any one of (C1) to (C8), wherein the surface roughness (Ra) of the signal line on the 1 st polyimide layer side is 0.05 μm to 0.5 μm.

(C10) A method for manufacturing a flexible metal-clad laminate, characterized in that the flexible metal-clad laminate has a microstrip line structure, the flexible metal-clad laminate has at least a signal line/a 1 st polyimide layer/a ground layer in this order, and a polyimide film having a thickness of 75 to 200 [ mu ] m and a dielectric loss at 10GHz of 0.008 or less is used as the 1 st polyimide layer.

(C11) The method for producing a flexible metal-clad laminate according to (C10), further comprising a ground layer/2 nd polyimide layer/adhesive layer, wherein the flexible metal-clad laminate comprises at least the ground layer/2 nd polyimide layer/adhesive layer/signal line/2 nd polyimide layer/ground layer in this order,

the 2 nd polyimide layer is formed of a polyimide film having a thickness of 75 to 200 [ mu ] m and a dielectric loss of 0.008 or less at 10 GHz.

(C12) The method for manufacturing a flexible metal clad laminate according to (C10) or (C11), wherein an insertion loss of the flexible metal clad laminate at 10GHz is-3.2 dB or more and 0dB or less.

(C13) The method of manufacturing a flexible metal clad laminate according to any one of (C10) to (C12), wherein the 1 st polyimide layer has a thermoplastic polyimide layer and a non-thermoplastic polyimide layer, or the 1 st polyimide layer and the 2 nd polyimide layer each have a thermoplastic polyimide layer and a non-thermoplastic polyimide layer.

(C14) The method for producing a flexible metal-clad laminate according to any one of (C10) to (C13), wherein a thermoplastic polyimide film and a non-thermoplastic polyimide are laminated to form the 1 st polyimide layer, or a thermoplastic polyimide film and a non-thermoplastic polyimide are laminated to form the 1 st polyimide layer and the 2 nd polyimide layer, respectively.

(C15) The method for producing a flexible metal-clad laminate according to any one of (C10) to (C14), wherein the 1 st polyimide layer has a 3-layer structure in which thermoplastic polyimide layers are provided on both sides of a non-thermoplastic polyimide layer, or each of the 1 st polyimide layer and the 2 nd polyimide layer has a 3-layer structure in which thermoplastic polyimide layers are provided on both sides of a non-thermoplastic polyimide layer.

(C16) The method for producing a flexible metal-clad laminate according to (C15), wherein the 1 st polyimide layer is formed by laminating at least 2 or more polyimide films having a thickness of less than 75 μm and a structure of the 3 layers, or each of the 1 st polyimide layer and the 2 nd polyimide layer is formed by laminating at least 2 or more polyimide films having a thickness of less than 75 μm and a structure of the 3 layers.

(C17) The method of manufacturing a flexible metal-clad laminate according to any one of (C10) to (C16), wherein the signal line is a copper layer,

(C18) The method for manufacturing a flexible metal-clad laminate according to any one of (C10) to (C17), wherein the flexible metal-clad laminate has 2 or more signal lines.

(C19) The method for producing a flexible metal-clad laminate according to any one of (C10) to (C18), wherein the surface roughness (Ra) of the signal line on the 1 st polyimide layer side is 0.05 μm to 0.5 μm.

Examples

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The methods for evaluating the dielectric constant, dielectric loss tangent, transmission characteristics of FPC, peel strength, film thickness, and surface roughness of copper foil of the polyimide films in the synthesis examples, and comparative examples are as follows.

(measurement of dielectric constant and dielectric loss tangent)

The dielectric constant and the dielectric loss tangent of the multilayer polyimide film were measured at the following frequencies using a cavity resonator perturbation complex dielectric constant evaluation device (manufactured by kanto electronic application and development co., ltd.).

Measuring frequency: 10GHz

The measurement conditions were as follows: the temperature is 22-24 ℃, and the humidity is 45-55%

Measurement of the sample: the sample left standing under the aforementioned measurement conditions for 24 hours was used.

(production of FCCL, measurement of microstrip line and strip line Transmission characteristics)

The polyimide film and the copper foil were laminated under the following conditions to obtain a double-sided FCCL.

Copper foil used: has a thickness of 12 μm and a surface roughness of 0.45 μm or less

Lamination conditions of polyimide and copper foil: the laminating temperature is 360 ℃, the laminating pressure is 0.8 ton and the laminating speed is 1m/min

In the production of the microstrip line circuit, one surface of the double-sided FCCL is etched to produce a microstrip line having a line length of 10cm, and the circuit portion and the terminal portion are plated with copper. The circuit width was calculated from the thickness, dielectric constant, and dielectric loss tangent of the constituent material so that the characteristic impedance became 50 Ω.

Then, the microstrip line circuit was bonded to the adhesive layer (bonding sheet) via one surface FCCL by heating at 160 ℃ under reduced pressure for 30 minutes to produce an FPC test piece having a strip line structure. The circuit width was calculated from the thickness, dielectric constant, and dielectric loss tangent of the constituent material so that the characteristic impedance became 50 Ω.

The obtained flexible metal clad laminate having a microstrip line circuit and the obtained flexible metal clad laminate having a strip line circuit were subjected to the following processes. That is, after drying at 150 ℃ for 30 minutes, humidity control was carried out in a laboratory adjusted to 23 ℃ and 55% RH for 24 hours or more. Then, measurement of the insertion loss S21 parameter was performed using a network analyzer E5071C (Keysight Technologies) and a GSG250 probe, and the transmission loss (dB/100mm) at the measurement frequency of 10GHz was obtained.

(method of measuring peeling Strength)

The FCCL was analyzed in accordance with "6.5 peel strength" of JISC 6471. Specifically, a metal foil portion having a width of 1mm was peeled off at a peeling angle of 90 degrees under a condition of 100 mm/min, and the load was measured. Regarding the peel strength, the peel strength was evaluated as "O" (good) when the peel strength was 12N/cm or more, and as "X" (poor) when the peel strength was less than 12N/cm.

(thickness of film)

The thickness of the film was measured by using a contact thickness gauge, LASER HOLOGAGE manufactured by Mitsutoyo corporation.

(surface roughness Ra of copper foil)

The arithmetic mean roughness was measured under the following conditions using a light wave interference surface roughness meter (new view5030 system manufactured by ZYGO).

(measurement conditions)

An objective lens: 50-fold mirror zoom: 2

FDA Res：Normal

Analysis conditions:

Remove：Cylinder

Filter：High Pass

Filter Low Waven：0.002mm

(Synthesis example 1)

11.64kg of 1, 3-bis (4-aminophenoxy) benzene (hereinafter, also referred to as TPE-R) and 11.28kg of 4,4 '-diamino-2, 2' -dimethylbiphenyl (hereinafter, also referred to as m-TB) were added to 328.79kg of N, N-dimethylformamide (hereinafter, also referred to as DMF) while the reaction system was kept at 20 ℃ and stirred under a nitrogen atmosphere. After the dissolution of TPE-R, m-TB was visually confirmed, 14.66kg of 3,3 ', 4, 4' -biphenyltetracarboxylic dianhydride (hereinafter, also referred to as BPDA) and 7.39kg of pyromellitic anhydride (hereinafter, also referred to as PMDA) were added thereto and the mixture was stirred for 30 minutes. Subsequently, 4.31kg of p-phenylenediamine (hereinafter, also referred to as PDA) and 9.85kg of PMDA were added thereto and the mixture was stirred for 30 minutes.

Finally, 0.9kg of PMDA was dissolved in DMF so that the solid content concentration became 7% to prepare a solution, and the solution was gradually added to the reaction solution while paying attention to the increase in viscosity, and the polymerization was terminated when the viscosity reached 3000 poise.

To the polyamic acid solution, an imidization accelerator composed of acetic anhydride/isoquinoline/DMF (weight ratio 2.0/0.7/4.0) was added at a weight ratio of 50%, and the mixture was continuously stirred by a mixer, extruded from a T die, and cast onto a stainless steel belt. After heating the resin film at 130 ℃ for 100 seconds, the self-supporting gel film was peeled off from the endless belt and fixed to tenter clips, and the film was dried and imidized at 250 ℃ for 17 seconds, 350 ℃ for 17 seconds, and 400 ℃ for 120 seconds to obtain a polyimide film having a thickness of 17 μm.

(Synthesis example 2)

15.76kg of 4, 4' -diaminodiphenyl ether (hereinafter, also referred to as ODA) was added to 328.94kg of DMF while the reaction system was kept at 20 ℃ and stirred under a nitrogen atmosphere. After confirming the dissolution of ODA by visual observation, 17.37kg of BPDA and 2.57kg of PMDA were added and stirred for 30 minutes. Subsequently, 11.14kg of m-TB and 12.30kg of PMDA were added thereto and the mixture was stirred for 30 minutes.

Finally, a solution was prepared by dissolving 0.9kg of PMDA in DMF so that the solid concentration became 7%, and this solution was gradually added to the reaction solution while noting the increase in viscosity, and the polymerization was terminated when the viscosity reached 3000 poise.

(Synthesis example 3)

While the reaction system was kept at 20 ℃ C, 32.39kg of ODA10.53kg and 2, 2-bis [4- (4-aminophenoxy) phenyl ] propane (hereinafter, also referred to as BAPP) were added to 657.82kg of DMF, and the mixture was stirred under a nitrogen atmosphere. After confirming visually that ODA and BAPP were dissolved, 16.95kg of 3,3 ', 4, 4' -benzophenonetetracarboxylic dianhydride (hereinafter, also referred to as BTDA) and 14.34kg of PMDA were added, and the mixture was stirred for 30 minutes. Then, 14.22kg of PDA and 29.83kg of PMDA were added thereto and the mixture was stirred for 30 minutes.

Finally, a solution was prepared by dissolving 1.7kg of PDA in DMF so that the solid content concentration became 10%, and this solution was gradually added to the reaction solution while noting the increase in viscosity, and the polymerization was terminated when the viscosity reached 3000 poise.

(Synthesis of thermoplastic polyimide precursor (Polyamic acid))

29.8g of BAPP are dissolved in 249g of DMF which is cooled to 10 ℃. 21.4g of BPDA was added thereto and dissolved, followed by stirring for 30 minutes to form a prepolymer. Further, a DMF solution of BAPP prepared separately (BAPP 1.57g/DMF 31.4g) was carefully added to the solution, and the addition was stopped when the viscosity reached about 1000 poise. Stirring was carried out for 1 hour to obtain a polyamic acid solution having a solid content of about 17% by weight and a rotational viscosity of 1000 poise at 23 ℃.

< Flexible Metal-clad laminate with microstrip line Structure >

(example 1)

After the thermoplastic polyamic acid solution was diluted with DMF until the solid content concentration became 10 wt%, polyamic acid was applied to one side of the film obtained in synthesis example 1 with a comma coater so that the final thickness of the one side became 4 μm, and the film was heated in a drying furnace set at 140 ℃ for 1 minute. The other side was similarly coated with polyamic acid to a final thickness of 4 μm, and then heated in a drying furnace set at 140 ℃ for 1 minute. Then, the resultant was subjected to a heat treatment in a far-infrared heating furnace at an atmospheric temperature of 360 ℃ for 20 seconds to obtain a polyimide laminate having a total thickness of 25.0. mu.m. Further, 3 copper foils were stacked in this order of a copper foil/polyimide laminate having a total thickness of 25.0. mu.m, and the laminate was thermally laminated at a lamination temperature of 360 ℃ and a lamination pressure of 0.8 ton at a lamination speed of 1.0 m/min by using a hot roll laminator to produce a double-sided copper clad laminate (double-sided FCCL) (copper foil: CF-T49A-HD2, Ra: 0.15. mu.m, thickness of polyimide layer: 75. mu.m). The 3-fold polyimide laminate corresponds to the "1 st polyimide layer".

One surface of a double-sided FCCL including a polyimide layer was etched to form a microstrip line having a line length of 10cm, and a circuit portion and a terminal portion were plated with copper to form a test piece of a flexible metal-clad laminate of the microstrip line. The circuit width was calculated from the thickness, dielectric constant, and dielectric loss tangent of the constituent material so that the characteristic impedance became 50 Ω.

(example 2)

A test piece of a flexible metal-clad laminate was produced in the same manner as in example 1, except that 4 polyimide laminates having a total thickness of 25.0 μm obtained in example 1 were stacked. The polyimide laminate 4 corresponds to the "1 st polyimide layer".

(example 3)

A test piece of a flexible metal-clad laminate was produced in the same manner as in example 1, except that 6 polyimide laminates having a total thickness of 25.0 μm obtained in example 1 were stacked. The polyimide laminate 6 corresponds to the "1 st polyimide layer".

(example 4)

A test piece of a flexible metal-clad laminate was produced in the same manner as in example 1, except that 8 polyimide laminates having a total thickness of 25.0 μm obtained in example 1 were stacked. The polyimide laminate 8 corresponds to the "1 st polyimide layer".

It was confirmed from examples 1 to 4 that the insertion loss of the flexible metal clad laminate decreased as the thickness of the polyimide laminate became thicker.

(example 5)

The film obtained in synthesis example 2 was coated with a thermoplastic polyamic acid solution and dried and heat-treated in the same manner as in example 1 to obtain a polyimide laminate. Further, a test piece of a flexible metal-clad laminate was produced using the same copper foil as in example 1 under the same bonding conditions as in example 1.

Comparative example 1

A test piece of a flexible metal-clad laminate was produced in the same manner as in example except that only 1 polyimide laminate having a total thickness of 25.0 μm obtained in example 1 was used and the thickness of the polyimide laminate was set to 25 μm. The polyimide laminate 1 corresponds to the "1 st polyimide layer".

Comparative example 2

A test piece of a flexible metal-clad laminate was produced in the same manner as in example 1, except that 2 polyimide laminates having a total thickness of 25.0 μm obtained in example 1 were stacked and the thickness of the polyimide laminate was set to 50 μm. The polyimide laminate 2 corresponds to the "1 st polyimide layer".

From example 1 and comparative examples 1 and 2, it was confirmed that the insertion loss of the flexible metal-clad laminate was deteriorated (the absolute value was increased) as the thickness of the polyimide laminate was decreased.

Comparative example 3

A test piece of a flexible metal-clad laminate was produced by stacking 3 polyimide laminates having a total thickness of 25.0 μm in the same manner as in example 2, except that the film obtained in synthesis example 3 was used.

It was confirmed from example 2 and comparative example 3 that the insertion loss of the flexible metal-clad laminate is deteriorated when the polyimide laminate having a large dielectric loss is used. Further, it is understood from example 1 and comparative example 3 that, when a polyimide laminate having a large electrical loss is used, the insertion loss of the flexible metal-clad laminate is deteriorated even if the thickness of the laminate is large. From the above results, it is found that it is essential to use a polyimide laminate having a low dielectric loss and laminate the polyimide laminate to be thick in order to obtain a good insertion loss.

The dielectric constant and the dielectric loss tangent of the flexible metal-clad laminates (multilayer polyimide films) obtained in examples 1 to 5 and comparative examples 1 to 3, and the peel strength of the double-sided FCCL obtained from the polyimide film are shown in table 1. Further, the transmission loss measurement results at 10GHz measured using the FPC test piece obtained under the above conditions using the double-sided FCCL are shown in table 1.

[ Table 1]

	Dielectric constant	Dielectric loss tangent	Thickness (μm)	Peel strength (N/cm)	Insertion loss (dB) @10GHz
						Example 1	3.1	0.008	75	12.4	-2.4
Example 2	3.1	0.008	100	12.1	-2.1
						Example 3	3.1	0.008	150	11.4	-1.8
Example 4	3.1	0.008	200	10.3	-1.6
						Example 5	3.2	0.006	75	12.1	-2.2
Comparative example 1	3.1	0.008	25	14.3	-4.5
						Comparative example 2	3.1	0.008	50	13.5	3.0
Comparative example 3	3.3	0.018	100	11.7	-3.4

< Flexible Metal clad laminate having strip line Structure >

(example 6)

After the thermoplastic polyamic acid solution was diluted with DMF until the solid content concentration became 10 wt%, polyamic acid was applied to one side of the film obtained in synthesis example 1 with a comma coater so that the final thickness of the one side became 4 μm, and the film was heated in a drying furnace set at 140 ℃ for 1 minute. The other side was similarly coated with polyamic acid so that the final thickness became 4 μm, and then heated in a drying furnace set at 140 ℃ for 1 minute. Next, the polyimide laminate was subjected to a heat treatment in a far infrared heating furnace at an atmospheric temperature of 360 ℃ for 20 seconds to obtain a polyimide laminate having a total thickness of 25.0. mu.m. Further, a copper foil/3 polyimide laminates having a total thickness of 25.0 μm were stacked in this order, and the resultant was thermally laminated at a lamination temperature of 360 ℃, a lamination pressure of 0.6 ton and a lamination speed of 1.0 m/min by using a hot roll laminator to produce a double-sided copper clad laminate (double-sided FCCL) (copper foil: CF-T49A-HD2, Ra: 0.15 μm, thickness of polyimide laminate: 75 μm). The polyimide laminate 3 corresponds to the "1 st polyimide layer".

Further, 3 pieces of the polyimide laminate having a total thickness of 25.0 μm were stacked in this order of copper foil/the total thickness, and heat-laminated using a hot roll laminator at a laminating temperature of 360 ℃, a laminating pressure of 0.8 ton and a laminating speed of 1.0 m/min to produce a single-sided copper clad laminate (single-sided FCCL) (copper foil: CF-T49A-HD2, Ra: 0.15 μm, thickness of polyimide laminate: 75 μm). The polyimide laminate 3 corresponds to the "polyimide layer 2".

One surface of the double-sided FCCL including the 1 st polyimide layer was etched to form a microstrip line having a line length of 10cm, and the circuit portion and the terminal portion were plated with copper. The microstrip circuit is bonded to a single-sided FCCL including a2 nd polyimide laminate by heating under reduced pressure at 150 ℃ for 30 minutes and 1 to 2MPa via a bonding sheet SAFY made of NIKKAN INDUSTRIES Co., Ltd. Thus, a test piece having a flexible metal clad laminate with a tape structure was produced. The circuit width was calculated from the thickness, dielectric constant, and dielectric loss tangent of the constituent material so that the characteristic impedance became 50 Ω, and the upper and lower grounds were electrically connected to each other through a via hole to reduce noise (fig. 4).

(example 7)

Test pieces of double-sided FCCL, single-sided FCCL, and flexible metal-clad laminate were produced in the same manner as in example 6, except that 4 polyimide laminates having a total thickness of 25.0 μm obtained in example 6 were stacked. The polyimide laminate 4 corresponds to the "1 st polyimide layer".

(example 8)

Test pieces of double-sided FCCL, single-sided FCCL, and flexible metal-clad laminate were prepared in the same manner as in example 6 except that 6 sheets of the polyimide laminate having a total thickness of 25.0 μm obtained in example 6 were stacked. The polyimide laminate 6 corresponds to the "1 st polyimide layer".

(example 9)

Test pieces of double-sided FCCL, single-sided FCCL, and flexible metal-clad laminate were produced in the same manner as in example 6, except that 8 polyimide laminates having a total thickness of 25.0 μm obtained in example 6 were stacked. The polyimide laminate 8 corresponds to the "1 st polyimide layer".

It was confirmed from examples 6 to 9 that the insertion loss decreased as the thickness of the polyimide laminate increased.

(example 10)

The film obtained in synthesis example 2 was coated with a thermoplastic polyamic acid solution and dried and heat-treated in the same manner as in example 6 to obtain a polyimide laminate. Further, test pieces of double-sided FCCL, single-sided FCCL, and flexible metal-clad laminate were produced using the same bonding conditions as in example 6 and the same copper foil as in example 6.

Comparative example 4

Test pieces of double-sided FCCL, single-sided FCCL, and flexible metal-clad laminate were produced in the same manner as in example 6, except that only 1 polyimide laminate having a total thickness of 25.0 μm obtained in example 6 was used and the thicknesses of the 1 st and 2 nd polyimide layers were each set to 25 μm. Comparative example 5

Test pieces of double-sided FCCL, single-sided FCCL, and flexible metal-clad laminate were prepared in the same manner as in example 6 except that 2 sheets of the polyimide laminate having a total thickness of 25.0 μm obtained in example 6 were stacked and the thicknesses of the 1 st and 2 nd polyimide layers were set to 50 μm, respectively.

From example 6 and comparative examples 4 and 5, it was confirmed that the insertion loss was deteriorated (the absolute value was increased) as the thickness of the polyimide laminate was decreased.

Comparative example 6

Test pieces of double-sided FCCL, single-sided FCCL, and flexible metal-clad laminate were prepared by stacking 3 polyimide laminates having a total thickness of 25.0 μm in the same manner as in example 6, except that the films obtained in synthesis example 3 were used.

It was confirmed from example 7 and comparative example 6 that the insertion loss is deteriorated when a polyimide laminate having a large dielectric loss is used. Further, it is understood from example 6 and comparative example 6 that, when a polyimide laminate having a large dielectric loss is used, the insertion loss is deteriorated even if the thickness of the laminate is large. From the above results, it is found that in order to obtain a good insertion loss, it is essential to use a polyimide laminate having a low dielectric loss and to laminate the polyimide laminate in a thick layer.

The dielectric constant and the dielectric loss tangent of the flexible metal-clad laminates (multilayer polyimide films) obtained in examples 6 to 10 and comparative examples 4 to 6, and the peel strength of the double-sided FCCL obtained from the polyimide film are shown in table 2. Table 2 shows transmission loss measurement results at 10GHz measured using the FPC test piece obtained under the above conditions using double-sided FCCL.

[ Table 2]

Description of the reference numerals

1. Grounding layer

2. 1 st polyimide layer

3. Copper layer as signal line

4.2 nd polyimide layer

5. Adhesive layer 1

6. Adhesive layer 2

7. Single-side flexible metal-clad laminated plate

8. Adhesive layer (bonding sheet)

9. Double-sided flexible metal-clad laminated plate

10. Non-thermoplastic polyimide

11. Thermoplastic polyimide

Claims

1. A flexible metal-clad laminate is characterized by having a microstrip line structure, the flexible metal-clad laminate being provided with at least a signal line/1 st polyimide layer/a ground layer in this order, the thickness of the 1 st polyimide layer being 75 to 200 [ mu ] m, and the dielectric loss at 10GHz being 0.008 or less.

2. The flexible metal clad laminate of claim 1 further comprising a ground layer/2 nd polyimide layer/adhesive layer, and at least sequentially comprising a ground layer/2 nd polyimide layer/adhesive layer/signal line/1 st polyimide layer/ground layer,

the thickness of the 2 nd polyimide layer is 75 to 200 [ mu ] m, and the dielectric loss at 10GHz is 0.008 or less.

3. The flexible metal clad laminate according to claim 1 or 2, wherein an insertion loss at 10GHz is-3.2 dB or more and 0dB or less.

4. The flexible metal clad laminate of any one of claims 1 to 3 wherein the 1 st polyimide layer has a thermoplastic polyimide layer and a non-thermoplastic polyimide layer or the 1 st polyimide layer and the 2 nd polyimide layer each have a thermoplastic polyimide layer and a non-thermoplastic polyimide layer.

5. The flexible metal clad laminate according to any one of claims 1 to 4, wherein the 1 st polyimide layer has a 3-layer structure having a thermoplastic polyimide layer on both sides of a non-thermoplastic polyimide layer, or the 1 st polyimide layer and the 2 nd polyimide layer each have a 3-layer structure having a thermoplastic polyimide layer on both sides of a non-thermoplastic polyimide layer.

6. The flexible metal-clad laminate of claim 5 wherein the 1 st polyimide layer is a laminate of 2 or more polyimide films having the 3-layer structure and a thickness of less than 75 μm, or wherein the 1 st polyimide layer and the 2 nd polyimide layer are each a laminate of 2 or more polyimide films having the 3-layer structure and a thickness of less than 75 μm.

7. The flexible metal clad laminate according to any one of claims 1 to 6,

the signal line is a copper layer,

there is also an adhesive layer between the copper layer and the 1 st polyimide layer.

8. The flexible metal clad laminate of any one of claims 1 to 7 wherein there are 2 or more signal lines.

9. The flexible metal clad laminate according to any one of claims 1 to 8, wherein the surface roughness (Ra) of the signal line on the 1 st polyimide layer side is 0.05 to 0.5 μm.

10. A method for manufacturing a flexible metal-clad laminate, characterized in that the flexible metal-clad laminate has a microstrip line structure, the flexible metal-clad laminate has at least a signal line/1 st polyimide layer/ground layer in this order, and as the 1 st polyimide layer, a polyimide film having a thickness of 75 to 200 [ mu ] m and a dielectric loss at 10GHz of 0.008 or less is used.

11. The method of claim 10, wherein the flexible metal-clad laminate further comprises a ground layer/2 nd polyimide layer/adhesive layer, and at least the ground layer/2 nd polyimide layer/adhesive layer/signal line/2 nd polyimide layer/ground layer in this order,

the 2 nd polyimide layer is a polyimide film having a thickness of 75 to 200 [ mu ] m and a dielectric loss of 0.008 or less at 10 GHz.

12. The method of manufacturing a flexible metal clad laminate according to claim 10 or 11, wherein the insertion loss of the flexible metal clad laminate at 10GHz is-3.2 dB or more and 0dB or less.

13. The method of manufacturing a flexible metal clad laminate according to any one of claims 10 to 12 wherein the 1 st polyimide layer has a thermoplastic polyimide layer and a non-thermoplastic polyimide layer, or the 1 st polyimide layer and the 2 nd polyimide layer each have a thermoplastic polyimide layer and a non-thermoplastic polyimide layer.

14. The method of producing a flexible metal-clad laminate according to any one of claims 10 to 13, wherein the 1 st polyimide layer is formed by laminating a thermoplastic polyimide film and a non-thermoplastic polyimide, or the 1 st polyimide layer and the 2 nd polyimide layer are formed by laminating a thermoplastic polyimide film and a non-thermoplastic polyimide, respectively.

15. The method for producing a flexible metal clad laminate according to any one of claims 10 to 14, wherein the 1 st polyimide layer has a 3-layer structure having thermoplastic polyimide layers on both sides of a non-thermoplastic polyimide layer, or each of the 1 st polyimide layer and the 2 nd polyimide layer has a 3-layer structure having thermoplastic polyimide layers on both sides of a non-thermoplastic polyimide layer.

16. The method of manufacturing a flexible metal clad laminate according to claim 15, wherein the 1 st polyimide layer is laminated by at least 2 polyimide films having the 3-layer structure and a thickness of less than 75 μm, or each of the 1 st polyimide layer and the 2 nd polyimide layer is laminated by at least 2 polyimide films having the 3-layer structure and a thickness of less than 75 μm.

17. The method for producing a flexible metal clad laminate according to any one of claims 10 to 16,

the signal line is a copper layer,

18. The method of manufacturing a flexible metal clad laminate according to any one of claims 10 to 17, wherein the flexible metal clad laminate has 2 or more signal lines.

19. The method for manufacturing a flexible metal-clad laminate according to any one of claims 10 to 18, wherein the surface roughness (Ra) of the signal line on the 1 st polyimide layer side is 0.05 μm to 0.5 μm.