JP2018145303A - Multilayer polyimide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film that has a small dielectric constant and a small dielectric tangent without impairing basic characteristics required of FPC, can uniformly exhibit those characteristics and can be used for a coverlay for a high frequency circuit.SOLUTION: A multilayer polyimide film has at least one layer of a non-thermoplastic polyimide resin layer, has a thickness of 25 μm or more and has a transmission loss of 6 dB/10 cm or less at 10 GHz when laminating the multilayer polyimide film and a copper foil at a laminating temperature of 360°C, a laminating pressure of 0.8 ton and a laminating speed of 1 m/min and measuring the transmission loss.SELECTED DRAWING: None

Description

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

  In recent years, there has been an increasing demand for low dielectric constant and low dielectric loss tangent of polyimide, which is a substrate material, in order to increase the frequency of electrical signals transmitted through circuits associated with high-speed signal transmission of electronic devices. The trend toward higher frequencies is advancing, and in the future, it is considered that a material having a low dielectric constant and dielectric loss tangent will be required even in the region of, for example, 5 GHz or more, and further 10 GHz or more. Furthermore, the propagation speed of signals in electronic circuits decreases as the dielectric constant of the substrate material increases. If the dielectric constant and dielectric loss tangent increase, the signal transmission loss also increases. Therefore, lowering the dielectric constant and lowering the dielectric loss tangent of polyimide, which is a substrate material, and further reducing transmission loss in an FPC state are important for improving the performance of electronic devices.

  An insulating resin layer in which a resin powder having a low dielectric constant is mixed with a polyimide resin is well known as a film used for a circuit board that can be adapted to high frequency. For example, Patent Document 1 discloses a multilayer polyimide film as a substrate material in which polytetrafluoroethylene (PTFE) powder is contained in polyimide.

  In addition, since the dielectric constant and dielectric loss tangent tend to increase as the water absorption rate of the resin increases, a film using a resin with a high water absorption rate, such as polyimide resin, is not suitable as a film for high-frequency circuit boards. In Patent Document 2, it is proposed to provide a resin substrate having a high transmission speed and a small transmission loss by using a resin that does not contain a highly water-absorbing functional group such as an amide group, an imide group, or an ester group. Has been.

  On the other hand, Patent Document 3 discloses a laminate having a polyimide resin layer obtained by reacting a diamino compound containing 4,4′-diamino-2,2′-dimethylbiphenyl and a tetracarboxylic acid.

JP 2002-144476 A JP 2012-221968 A International Publication WO2002 / 085616

  However, in the case of blending the fluororesin with the polyimide resin, it may be difficult to uniformly disperse the fluororesin, and there is a problem that the characteristics are likely to vary depending on the location of the film.

  In order to reduce the water absorption of the polyimide film for the purpose of reducing the dielectric constant and dielectric loss tangent, the concentration of imide groups in the polyimide polymer must be lowered, and as a result, the polyimide film can be used for FPC. There is a problem that characteristics that are necessary basic characteristics are impaired. Specifically, the subject that a linear expansion coefficient becomes large or the transparency of a film is impaired arises.

  Accordingly, an object of the present invention is to provide a polyimide film that can be used for a high-frequency circuit board that has a low dielectric constant and dielectric loss tangent and does not impair the basic characteristics required for FPC, and that these characteristics are uniformly expressed. Is to provide.

  The present invention can solve the above problems by the following novel non-thermoplastic polyimide resin layer and a multilayer polyimide film having at least one non-thermoplastic polyimide.

1) A multilayer polyimide film having at least one non-thermoplastic polyimide resin layer, having a thickness of 25 μm or more and laminating copper foil under the following conditions to form a flexible copper-clad laminate, the flexible copper-clad laminate A multilayer polyimide film characterized by having a transmission loss of 6 dB / 10 cm or less at 10 GHz when a flexible printed circuit board on which a circuit is formed using a board is measured.
(Conditions for copper foil lamination)
Copper foil to be used: Thickness of 12 μm, roughness of the surface to be bonded to the multilayer polyimide film is 0.45 μm or less Lamination conditions of multilayer polyimide and copper foil: laminating temperature 360 ° C., laminating pressure 0.8 ton, laminating speed 1 m / min
(Flexible printed circuit board)
Wiring width: Z = (d / ε × w) ^ 0.5
Z: Characteristic impedance. D: thickness of the multilayer polyimide film (μm)
ε: Dielectric constant of multilayer polyimide film w: Width (μm) width accuracy of copper foil ± 3%
Cover lay: CISV1225 (Nikkan Kogyo)
Laying condition of coverlay: 160 ° C., 90 minutes.
2) The non-thermoplastic polyimide film includes at least pyromellitic dianhydride as an acid dianhydride and at least 4,4′-diamino-2,2′-dimethylbiphenyl as a diamine. 1) The multilayer polyimide film as described.

  Since the multilayer polyimide film of the present invention exhibits low transmission loss, it has excellent adhesion strength with a copper foil required when used as an FPC substrate, and can also be used for a high-frequency circuit substrate.

  Embodiments of the present invention will be described below, but the present invention is not limited thereto. In addition, all the academic literatures and patent literatures described in this specification are incorporated by reference in this specification. Unless otherwise specified in this specification, “A to B” representing a numerical range means “A or more (including A and greater than A) and B or less (including B and less than B)”.

  The multilayer polyimide film of the present invention is a multilayer polyimide film having at least one non-thermoplastic polyimide resin layer, and has a thickness of 25 μm or more, and has a transmission loss of 10 GHz when measured by laminating copper foils under the following conditions. The multilayer polyimide film is characterized by being 6 dB / 10 cm or less.

(Copper foil lamination conditions)
Copper foil to be used: Thickness of 12 μm, roughness of the surface to be bonded to the multilayer polyimide film is 0.45 μm or less Lamination conditions of multilayer polyimide and copper foil: laminating temperature 360 ° C., laminating pressure 0.8 ton, laminating speed 1 m / min

(Flexible printed circuit board)
Wiring width: Z = (d / ε × w) ^ 0.5
Z: Characteristic impedance. 50Ω.
d: Thickness (μm) of multilayer polyimide film
ε: Dielectric constant of multilayer polyimide film w: Width (μm) width accuracy of copper foil ± 3%
Cover lay: CISV1225 (Nikkan Kogyo)
Laying condition of coverlay: 160 ° C, 90 minutes

(Non-thermoplastic polyimide resin layer)
In the present invention, by using a specific monomer, a non-thermoplastic polyimide resin layer that can be used as a circuit board having a low transmission rate and high transmission loss can be produced by reducing the dielectric constant and dielectric loss tangent.

  An example of the method for producing the non-thermoplastic polyimide resin layer of the present invention will be described in detail. The polyamic acid (hereinafter also referred to as polyamic acid), which is a polyimide precursor used in the present invention, is substantially equimolar in an organic solvent with at least one diamine and at least one acid dianhydride. It is obtained by mixing and reacting.

  The diamine used in the polyamic acid of the present invention is not particularly limited, but 2,2-bis {4- (4-aminophenoxy) phenyl} propane, 1,3-bis (4-aminophenoxy) Benzene, 1,4-bis (4-aminophenoxy) benzene, paraphenylenediamine, 4,4′-diaminodiphenylpropane, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl sulfide, 2,2′-dimethyl-4,4′-diaminobiphenyl, 2,2-bis (4-aminophenoxyphenyl) propane, 3,3′-dihydroxy-4,4′- Diamino-1,1′-biphenyl, 4,4′-diamino-2,2′-dimethylbiphenyl, 4,4′-diamino-3,3′-di Methylbiphenyl, 4,4′-diamino-3,3′-hydroxybiphenyl, 1,4-diaminobenzene, 1,3-diaminobenzene, 4,4′-bis (4-aminophenoxy), 4,4′- Diaminodiphenyl ether, 2,2-bis {4- (4-aminophenoxy) phenyl} propane, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3 -Bis (3-aminophenoxy) benzene and the like.

  Among these, it is preferable to use a monomer having a biphenyl structure. The amount of the monomer having a biphenyl structure is preferably 20 mol% or more based on 100 mol% of the diamine component, preferably 20 mol% to 60 mol%, more preferably 30 mol% to 40 mol%. It is preferable to use within a range. In particular, it is preferable to use 4,4'-diamino-2,2'-dimethylbiphenyl.

  The acid dianhydride is not particularly limited. Specifically, pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,2 ′, 3, 3'-biphenyltetracarboxylic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic dianhydride 2,2- Examples thereof include bis (3,4-dicarboxyphenyl) propanoic acid dianhydride, p-phenylenebis (trimellitic acid monoester acid anhydride), 4,4′-oxydiphthalic acid dianhydride, and the like.

  Among these, it is preferable to use a monomer having a biphenyl structure. The amount of the monomer having a biphenyl structure is preferably 20% or more with respect to 100 mol% of the acid dianhydride component, preferably 30 mol% to 70 mol%, and more preferably 40 mol% to 60 mol. % Is preferably used.

  The polyamic acid, which is a precursor of non-thermoplastic polyimide, can be obtained by mixing and reacting the diamine and acid dianhydride in an organic solvent so as to be substantially equimolar. Any organic solvent may be used as long as it dissolves polyamic acid, but amide solvents, that is, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, etc. N, N-dimethylformamide and N, N-dimethylacetamide can be used particularly preferably. The solid content concentration of the polyamic acid is not particularly limited, and a polyamic acid having sufficient mechanical strength when obtained as a polyimide can be obtained as long as it is within the range of 5 wt% to 35 wt%.

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

  A filler may be added to the polyamic acid for the purpose of improving various film properties such as slidability, thermal conductivity, conductivity, corona resistance, and loop stiffness. Any filler may be used, but preferred examples include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica and the like.

  In addition, a thermosetting resin such as an epoxy resin or a phenoxy resin, or a thermoplastic resin such as polyether ketone or polyether ether ketone may be mixed within a range that does not impair the characteristics of the obtained non-thermoplastic polyimide resin layer as a whole. good. Examples of a method for adding these resins include a method for adding them to the polyamic acid as long as it is soluble in a solvent. If the polyimide is also soluble, it may be added to the polyimide solution. As long as it is insoluble in the solvent, a method may be mentioned in which the polyamic acid is first imidized and then combined by melt kneading. However, it is desirable to use a soluble resin to be mixed with polyimide.

(Method for producing non-thermoplastic polyimide resin layer)
In order to obtain the non-thermoplastic polyimide resin layer of the present invention, the following step i) a step of reacting an aromatic diamine and an aromatic tetracarboxylic dianhydride in an organic solvent to obtain a polyamic acid solution,
ii) a step of casting a film-forming dope containing the polyamic acid solution on a support;
iii) a step of peeling the gel film from the support after heating on the support;
iv) further heating to imidize and dry the remaining amic acid,
It is preferable to contain.

  ii) Subsequent steps are roughly divided into a thermal imidization method and a chemical imidization method. The thermal imidization method is a method in which a polyamic acid solution is used as a film-forming dope without using a dehydrating ring-closing agent or the like, and imidation is advanced only by heating and heating. One chemical imidization method is a method in which imidization is promoted by using a polyamic acid solution to which at least one of a dehydrating cyclization agent and a catalyst is added as an imidization accelerator as a film-forming dope. Either the thermal imidization method or the chemical imidization method may be used, but the chemical imidization method is superior in productivity.

  As the dehydrating ring-closing agent, acid anhydrides typified 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.

  In the subsequent steps, a glass plate, an aluminum foil, an endless stainless steel belt, a stainless steel drum, or the like can be suitably used as the support for casting the film forming dope. A heating condition is set according to the thickness and production rate of the finally obtained film, and after partially imidizing and drying, the film is peeled off from the support and then a polyamic acid film (hereinafter referred to as a gel film). Or a gel film).

  iv) In the subsequent steps, the gel film is fixed at the end to avoid shrinkage during curing, and the water, the residual solvent, the imidization accelerator remaining in the film are removed, and the remaining amic A film containing polyimide is obtained by completely imidizing the acid. The ends of the gel film are preferably not only fixed, but also stretched in the transport direction or in the direction perpendicular to the transport direction.

  The polyimide film thus obtained can be suitably used as a high-frequency compatible circuit board because of its low dielectric constant and dielectric loss tangent.

(Multilayer polyimide film)
In the present invention, the above-described at least one non-thermoplastic polyimide resin layer may be used as a core film, and a multilayer polyimide film having two or more polyimide resin layers provided with another polyimide resin layer may be used. It is preferable to further have a polyimide resin layer.

(Thermoplastic polyimide film)
Examples of the diamine and acid dianhydride used for the thermoplastic polyimide film are the same as those used for the non-thermoplastic polyimide resin layer. However, in order to obtain a thermoplastic polyimide film, a flexible diamine is used. It is preferable to react dianhydride with acid dianhydride. Examples of flexible diamines include 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 2,2-bis (4-aminophenoxyphenyl) ) Propane and the like. Examples of acid dianhydrides that can be suitably combined with these diamines include pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4, 4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, etc. are mentioned.

(Manufacturing method of multilayer polyimide film)
In the present invention, as a method for producing a multilayer polyimide film, a multi-layered resin layer may be formed at the same time using a coextrusion die having a plurality of flow paths in the step ii). ) After proceeding to the process and collecting the polyimide resin layer once, a new resin layer may be formed thereon by coating or the like. For example, in the case of obtaining a multilayer polyimide film having a thermoplastic polyimide film on at least one side of the above-described core polyimide film, a core polyimide precursor and a thermoplastic polyimide precursor are coextruded using a die. It can be obtained by casting on a support and carrying out the steps after iii).

  Since a very high temperature is required for imidization, when the resin layer other than polyimide is provided, it is preferable to take the latter means in order to suppress thermal decomposition. When a thermoplastic polyimide film is provided by coating, a thermoplastic polyimide precursor may be applied and then imidized, or a thermoplastic polyimide solution may be applied and dried.

  Moreover, a thermoplastic polyimide film may be obtained by casting a polyimide solution and cooling it instead of casting a polyamic acid solution on a support in the above-described steps.

  The multilayer polyimide film of the present invention has a thickness of 25 μm or more. If the thickness of the multilayer polyimide film is less than 25 μm, the transmission loss increases, and it is not suitable for a high-frequency circuit board. On the other hand, from the viewpoint of reducing transmission loss, the upper limit of the thickness of the multilayer polyimide film is not particularly limited, but it is preferably 50 μm or less in view of ease of manufacturing the multilayer polyimide film, productivity, and the like.

(Flexible metal foil laminate)
The multilayer polyimide film thus obtained can be formed into a flexible metal foil laminate by providing a metal foil on at least one side of the multilayer polyimide film. As a means of forming a metal foil on the multilayer polyimide film,
a) Means for obtaining a flexible metal foil laminate by bonding a metal foil by heating and pressing after obtaining a multilayer polyimide film as described above b) Casting an organic solvent solution containing polyamic acid on the metal foil And a means for obtaining a flexible metal foil laminate by removing the solvent and imidizing by heating. C) Casting a molten liquid containing non-thermoplastic polyimide on the metal foil, and cooling the flexible metal foil laminate. Means to obtain are mentioned. Among these, if the non-thermoplastic polyimide is made meltable, the heat resistance and the heat shrinkage rate of the obtained flexible metal foil laminate may be deteriorated. Therefore, the means a) or b) should be used. Is preferred. If the non-thermoplastic polyimide is solvent-soluble, an organic solvent solution containing non-thermoplastic polyimide may be used instead of the organic solvent solution containing polyamic acid. Details of a) and b) will be described below.

  In the means a), the flexible metal foil laminate of the present invention is obtained by bonding a metal foil to the obtained multilayer polyimide film by heating and pressing (laminating). The means and conditions for bonding the metal foil may be appropriately selected from conventionally known ones.

  In the means b), the means for casting the organic solvent solution containing polyamic acid on the metal foil is not particularly limited, and conventionally known means such as a die coater, comma coater (registered trademark), reverse coater, knife coater and the like. Can be used. Conventionally known means can be used as the heating means for removing the solvent and imidizing, and examples thereof include a hot air furnace and a far infrared furnace.

  Similarly to the means a), the heating time can be shortened by the chemical imidization method, and the productivity can be improved. However, since an acid is generated from an acid anhydride, which is a dehydrating ring-closing agent, in the imidization process, oxidation may proceed depending on the type of the metal foil. The addition of the dehydrating ring-closing agent is preferably selected as appropriate according to the type of metal foil and heating conditions.

  When providing other polyimide layers on the non-thermoplastic polyimide film, or when providing resin layers other than polyimide, repeat the above casting and heating steps multiple times, or use multiple layers by coextrusion or continuous casting. A means for forming and heating at a time can be suitably used.

  By means of b), the immobilization is completed and the flexible metal foil laminate of the present invention is obtained at the same time. When providing a metal foil layer on both surfaces of the resin layer, the metal foil may be bonded to the opposite resin layer surface by heating and pressing.

(Metal foil)
Although it does not specifically limit as metal foil which can be used in this invention, When using the flexible metal-clad laminated board of this invention for an electronic device and an electric equipment use, for example, copper or copper alloy, stainless steel Or the foil which consists of the alloy, nickel or a nickel alloy (a 42 alloy is also included), aluminum, or an aluminum alloy can be mentioned. In general flexible laminates, copper foil such as rolled copper foil and electrolytic copper foil is frequently used, but it can also be preferably used in the present invention. In addition, the antirust layer, the heat-resistant layer, or the contact bonding layer may be apply | coated to the surface of these metal foil. Moreover, it does not specifically limit about the thickness of the said metal foil, According to the use, what is necessary is just the thickness which can exhibit a sufficient function.

(Flexible printed circuit board)
The flexible printed circuit board obtained by etching the metal layer of the flexible metal-clad laminate according to the present invention is a high-frequency circuit board having a high transmission speed and a small transmission loss.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples. In addition, the dielectric constant of a polyimide film, a dielectric loss tangent, the measurement of the transmission characteristic of FPC, the peel strength, the thickness of a film, and the surface roughness of copper foil in a synthesis example, an Example, and a comparative example are as follows.

(Measurement of dielectric constant and dielectric loss tangent)
A cavity resonator perturbation method complex permittivity evaluation apparatus (manufactured by Kanto Electronics Application Development Co., Ltd.) was used as a measurement apparatus, and the dielectric constant and dielectric loss tangent of the multilayer polyimide film were measured at the following frequencies.
Measurement frequency: 10 GHz
Measurement conditions: temperature 22 ° C to 24 ° C, humidity 45% to 55%
Measurement sample: A sample that was allowed to stand for 24 hours under the above measurement conditions was used.

(Manufacture of FCCL, measurement of transmission characteristics of FPC)
A multilayer polyimide film and a copper foil were laminated under the following conditions to obtain a double-sided FCCL.
Copper foil to be used: Thickness of 12 μm, roughness of the surface to be bonded to the multilayer polyimide film is 0.45 μm or less Lamination conditions of multilayer polyimide and copper foil: laminating temperature 360 ° C., laminating pressure 0.8 ton, laminating speed 1 m / min
Wiring width: Z = (d / ε × w) ^ 0.5
Z: Characteristic impedance. 50Ω.
d: Thickness (μm) of multilayer polyimide film
ε: Dielectric constant of multilayer polyimide film w: Width (μm) width accuracy of copper foil ± 3%
A microstrip line having a line length of 10 cm was prepared using a double-sided FCCL obtained from a multilayer polyimide film and copper foil. Specifically, after drilling, through-hole plating, and patterning steps, a coverlay film CISV1225 made by Nikkan Kogyo Co., Ltd. was heated and bonded at 160 ° C. for 90 minutes, and the measurement pad part was gold-plated and microstrip A line-shaped FPC test piece was produced. Transmission loss is measured after drying for 30 minutes at 150 ° C. and after conditioning in a test room adjusted to 23 ° C. and 55% RH for at least 24 hours, using network analyzer E5071C (Keysight Technologies) and probe station GSG250. The S21 parameter was measured to obtain a transmission loss (dB / 100 mm) at a measurement frequency of 10 GHz.

(Measurement method of peel strength)
FCCL was analyzed according to “6.5 Peel strength” of JIS C6471. Specifically, a 1 mm wide metal foil portion was peeled off at a peeling angle of 90 degrees and 100 mm / min, and the load was measured. The case where the peel strength was 12 N / cm or more was evaluated as “◯”, and the case where the peel strength was less than 12 N / cm was evaluated as “x”.

(Film thickness)
The thickness of the film was measured using LASER HOLOGAGE manufactured by Mitsutoyo.

(Surface roughness Ra of copper foil)
The arithmetic mean roughness under the following conditions was measured using a light wave interference type surface roughness meter (NewView 5030 system manufactured by ZYGO).

(Measurement condition)
Objective lens: 50x Mirau image zoom: 2
FDA Res: Normal
Analysis conditions:
Remove: Cylinder
Filter: High Pass
Filter Low Wave: 0.002mm

(Synthesis Example 1)
With the reaction system maintained at 20 ° C., 328.79 kg of N, N-dimethylformamide (hereinafter also referred to as DMF) and 1,3-bis (4-aminophenoxy) benzene (hereinafter also referred to as TPE-R). ) 11.64 kg, 11.28 kg of 4,4′-diamino-2,2′-dimethylbiphenyl (hereinafter also referred to as m-TB) was added and stirred under a nitrogen atmosphere. After confirming that TPE-R and m-TB were dissolved, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (hereinafter also referred to as BPDA) 14.66 kg, pyromellitic anhydride 7.39 kg of product (hereinafter also referred to as PMDA) was added and stirred for 30 minutes. Subsequently, 4.31 kg of paraphenylenediamine (hereinafter also referred to as PDA) and 9.85 kg of PMDA were added and stirred for 30 minutes.
Finally, a solution in which 0.9 kg of PMDA was dissolved in DMF so as to have a solid content concentration of 7% was prepared, and this solution was gradually added to the above reaction solution while paying attention to an increase in viscosity, and the viscosity was 3000 poise. The polymerization was terminated when the value reached.

  To this polyamic acid solution, an imidization accelerator consisting of acetic anhydride / isoquinoline / DMF (weight ratio 2.0 / 0.7 / 4.0) was added at a weight ratio of 50% with respect to the polyamic acid solution. The mixture was stirred with a mixer, extruded from a T die, and cast onto a stainless steel endless belt. This resin film is heated at 130 ° C. for 100 seconds, and then the self-supporting gel film is peeled off from the endless belt and fixed to the tenter clip. At 250 ° C. for 17 seconds, 350 ° C. for 17 seconds, and 400 ° C. for 120 seconds. Drying and imidization were performed to obtain a polyimide film having a thickness of 17 μm.

(Synthesis Example 2)
With the inside of the reaction system kept at 20 ° C., 15.76 kg of 4,4′-diaminodiphenyl ether (hereinafter also referred to as ODA) was added to 328.94 kg of DMF, and the mixture was stirred under a nitrogen atmosphere. After visually confirming that ODA was dissolved, 17.37 kg of BPDA and 2.57 kg of PMDA were added and stirred for 30 minutes. Subsequently, 11.14 kg of m-TB and 12.30 kg of PMDA were added and stirred for 30 minutes.
Finally, a solution in which 0.9 kg of PMDA was dissolved in DMF so as to have a solid content concentration of 7% was prepared, and this solution was gradually added to the above reaction solution while paying attention to an increase in viscosity, and the viscosity was 3000 poise. The polymerization was terminated when the value reached.

  To this polyamic acid solution, an imidization accelerator consisting of acetic anhydride / isoquinoline / DMF (weight ratio 2.0 / 0.7 / 4.0) was added at a weight ratio of 50% with respect to the polyamic acid solution. The mixture was stirred with a mixer, extruded from a T die, and cast onto a stainless steel endless belt. This resin film is heated at 130 ° C. for 100 seconds, and then the self-supporting gel film is peeled off from the endless belt and fixed to the tenter clip. At 250 ° C. for 17 seconds, 350 ° C. for 17 seconds, and 400 ° C. for 120 seconds. Drying and imidization were performed to obtain a polyimide film having a thickness of 17 μm.

(Synthesis Example 3)
With the inside of the reaction system kept at 20 ° C., 10.53 kg of ODA and 32.39 kg of 2,2-bis [4- (4-aminophenoxy) phenyl] propane (hereinafter also referred to as BAPP) were added to 657.82 kg of DMF. And stirred under a nitrogen atmosphere. After visually confirming that ODA and BAPP were dissolved, 3,95 ′, 4,4′-benzophenonetetracarboxylic dianhydride (hereinafter also referred to as BTDA) 16.95 kg and PMDA 14.34 kg were added, and 30 Stirring was performed for a minute. Subsequently, 14.22 kg of PDA and 29.83 kg of PMDA were added and stirred for 30 minutes.

  Finally, a solution in which 1.7 kg of PDA is dissolved in DMF so as to have a solid content concentration of 10% is prepared, and this solution is gradually added to the reaction solution while paying attention to increase in viscosity, and the viscosity is 3000 poise. The polymerization was terminated when the value reached.

  To this polyamic acid solution, an imidization accelerator consisting of acetic anhydride / isoquinoline / DMF (weight ratio 2.0 / 0.7 / 4.0) was added at a weight ratio of 50% with respect to the polyamic acid solution. The mixture was stirred with a mixer, extruded from a T die, and cast onto a stainless steel endless belt. This resin film is heated at 130 ° C. for 100 seconds, and then the self-supporting gel film is peeled off from the endless belt and fixed to the tenter clip. At 250 ° C. for 17 seconds, 350 ° C. for 17 seconds, and 400 ° C. for 120 seconds. Drying and imidization were performed to obtain a polyimide film having a thickness of 17 μm.

(Synthesis of thermoplastic polyimide precursor (polyamic acid))
29.8 g of BAPP was dissolved in 249 g of DMF cooled to 10 ° C. After 21.4 g of BPDA was added and dissolved, the mixture was stirred for 30 minutes to form a prepolymer. Further, a DMF solution of BAPP (BAPP 1.57 g / DMF 31.4 g) separately prepared was carefully added to this solution, and the addition was stopped when the viscosity reached about 1000 poise. Stirring was performed for 1 hour to obtain a polyamic acid solution having a solid content concentration of about 17% by weight and a rotational viscosity at 23 ° C. of 1000 poise.

Example 1
After diluting the thermoplastic polyamic acid solution with DMF until the solid content concentration becomes 10% by weight, polyamic acid is applied to one side of the film obtained in Synthesis Example 1 with a comma coater so that the final single-sided thickness is 4 μm. Heating was performed for 1 minute through a drying furnace set at ° C. Similarly, the other surface was coated with polyamic acid so that the final thickness was 4 μm, and then heated in a drying furnace set at 140 ° C. for 1 minute. Subsequently, heat treatment was performed for 20 seconds in a far-infrared heater furnace having an atmospheric temperature of 360 ° C. to obtain a polyimide laminate having a total thickness of 25.0 μm. Furthermore, using a hot roll laminator, the copper foil and the obtained polyimide laminate were heat laminated under the conditions of a laminating temperature of 360 ° C., a laminating pressure of 0.6 tons, and a laminating speed of 1.0 m / min, (Double-sided FCCL) was prepared (copper foil: CF-T49A-HD2, Ra = 0.28 μm).

(Example 2)
In the same manner as in Example 1, the film obtained in Synthesis Example 2 was coated / dried / heat treated with a thermoplastic polyamic acid solution to obtain a polyimide laminate. Furthermore, a double-sided FCCL was produced using the same lamination conditions and copper foil as in Example 1.

(Comparative Example 1)
In the same manner as in Example 1, the film obtained in Synthesis Example 3 was coated / dried / heat treated with a thermoplastic polyamic acid solution to obtain a polyimide laminate. Furthermore, a double-sided FCCL was produced using the same lamination conditions and copper foil as in Example 1.

  Table 1 shows the dielectric constant, dielectric loss tangent, and peel strength of the double-sided FCCL obtained from the multilayer polyimide film obtained in Examples 1 and 2 and Comparative Example 1. Furthermore, Table 2 shows the transmission loss measurement results at 10 GHz measured using the FPC test piece obtained under the above-described conditions using the double-sided FCCL.

Claims (2)

A multilayer polyimide film having at least one non-thermoplastic polyimide resin layer, having a thickness of 25 μm or more, and laminating copper foil under the following conditions to form a flexible copper-clad laminate, A multilayer polyimide film characterized by having a transmission loss of 6 dB / 10 cm or less at 10 GHz when a flexible printed circuit board having a circuit formed thereon is measured.
(Conditions for copper foil lamination)
Copper foil to be used: Thickness of 12 μm, roughness of the surface to be bonded to the multilayer polyimide film is 0.45 μm or less Lamination conditions of multilayer polyimide and copper foil: laminating temperature 360 ° C., laminating pressure 0.8 ton, laminating speed 1 m / min
(Flexible printed circuit board)
Wiring width: Z = (d / ε × w) ^ 0.5
Z: Characteristic impedance. 50Ω.
d: Thickness (μm) of multilayer polyimide film
ε: Dielectric constant of multilayer polyimide film w: Width (μm) width accuracy of copper foil ± 3%
Cover lay: CISV1225 (Nikkan Kogyo)
Laying condition of coverlay: 160 ° C, 90 minutes The non-thermoplastic polyimide film includes at least pyromellitic dianhydride as an acid dianhydride and at least 4,4'-diamino-2,2'-dimethylbiphenyl as a diamine. 1. The multilayer polyimide film according to 1.