JP6971580B2 - Multilayer polyimide film and flexible metal-clad laminate - Google Patents

Description

The present invention relates to a multilayer polyimide film that can be suitably used for a high frequency circuit board, and a flexible metal-clad laminate having metal foils on one or both sides thereof.

Polyimide is widely used as an electronic substrate material because it has excellent mechanical strength, heat resistance, electrical insulation, and chemical resistance. For example, a flexible metal-clad laminate (hereinafter, also referred to as FCCL) in which a polyimide film is used as a substrate material and a copper foil or the like is laminated on at least one side, and a flexible printed circuit board (hereinafter, also referred to as FPC) in which a circuit is created are manufactured. It is used in various electronic devices. In recent years, in the high frequency of electric signals transmitted through circuits accompanying high-speed signal transmission of electronic devices, there is an increasing demand for low dielectric constant and low dielectric loss tangent of polyimide as a substrate material. For example, there is a demand for a material having a low dielectric constant and a dielectric loss tangent in a high frequency (1 GHz or more) region. Further, the signal propagation speed in the electronic circuit decreases as the dielectric constant of the substrate material increases. Further, if the permittivity and the dielectric loss tangent increase, the signal transmission loss also increases. Therefore, lowering the dielectric constant of polyimide, which is a substrate material, lowering the dielectric loss tangent, and having a small transmission loss in the state of being an FPC are indispensable for improving the performance of electronic devices.

The mainstream study of FCCL suitable for high frequency and the film used for it is to develop an insulating resin layer in which a resin powder having a low dielectric constant is mixed with a polyimide resin, and polyimide layers are provided on both sides of the polyimide resin containing a fluororesin. Flexible copper-clad laminates, etc., which are laminated and further arranged with copper foil, have been developed. Patent Document 1 discloses a multilayer polyimide film as a substrate material containing polytetrafluoroethylene (PTFE) powder in polyimide.

On the other hand, since the FCCL substrate material also requires adhesiveness between the substrate material and the metal foil, it is common to have a multilayer structure having an adhesive layer. Patent Document 2 discloses a substrate for a printed circuit using a multilayer film having an adhesive layer having an adhesive force with a conductive metal layer (metal foil) formed on a heat-resistant film and having excellent dimensional stability. ..

Special table 2014-526399 JP-A-2005-026542

However, it is difficult to uniformly disperse the fluororesin in the polyimide resin by the approach of blending the fluororesin with the polyimide resin as in Patent Document 1. As a result, the characteristics tend to vary depending on the location of the film, and for example, the dielectric constant and the dielectric loss tangent are different, which makes it difficult to use as a circuit board.

In the efforts using the multilayer polyimide film as in Patent Document 2, no attention has been paid to the study of reducing the transmission loss.

Therefore, there is a need to develop a film that has uniform dielectric constant and dielectric loss tangent in the film and can be used for a high frequency circuit board (FCCL) that achieves both dimensional stability, peel strength, and reduction of transmission loss.

An object of the present invention is to provide a multilayer polyimide film and a flexible metal-clad laminate that can be suitably used for a high-frequency circuit board capable of reducing transmission loss by reducing the dielectric loss tangent and hygroscopicity of the resin layer. That is.

As a result of diligent research to solve the above problems, the present inventors have made a multilayer polyimide having a non-thermoplastic polyimide layer having low dielectric adpositivity without using a fluororesin having poor dispersibility in other resins. We have found that the above-mentioned problems can be solved by the film, and have completed the present invention.

That is, the present invention has a structure in which a thermoplastic polyimide layer is provided on at least one side of a non-thermoplastic polyimide film via a non-thermoplastic polyimide layer having a dielectric loss tangent at 10 GHz of 0.001 to 0.009. It relates to a featured multilayer polyimide film.

In a preferred embodiment, the non-thermoplastic polyimide layer having a dielectric loss tangent of 0.001 to 0.009 has a moisture absorption rate of 0.8 wt% or less, and a relative permittivity at 10 GHz of 3.3 or less, and at 10 GHz. The present invention relates to the above-mentioned multilayer polyimide film having a dielectric loss tangent of 0.007 or less.

In a preferred embodiment, the multilayer polyimide is characterized in that the moisture absorption rate is 1.0 wt% or less, the relative permittivity at 10 GHz is 3.5 or less, and the dielectric loss tangent at 10 GHz is 0.009 or less. Regarding film.

A preferred embodiment relates to a flexible metal-clad laminate having a metal foil on at least one side of the multilayer polyimide film described above.

In a preferred embodiment, the non-thermoplastic polyimide layer having a dielectric tangent at 10 GHz of 0.001 to 0.009 is at least 2,2'-dimethylbiphenyl-4,4'-diamine as the aromatic acid dianhydride. , 1,3-Bis (4-aminophenoxy) benzene, as an aromatic diamine, at least 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 3,3', 4,4 ′ -The above-mentioned multilayer polyimide film comprising a polyimide having any one of a benzophenone tetracarboxylic acid dianhydride and a pyromellitic acid dianhydride.

According to the multilayer polyimide film according to the present invention, there is an effect that a material having a low transmission loss can be provided. Therefore, it can cope with high frequency of electronic products, and is useful, for example, when developing a high frequency circuit board of 1 GHz or more.

It is sectional drawing which shows an example of the multilayer polyimide film which concerns on this invention.

Embodiments of the present invention will be described below. However, the present invention is not limited to this, and can be carried out in a mode in which various modifications are added within the range described.

Unless otherwise specified in the present specification, "A to B" representing a numerical range means "A or more (including A and larger than A), B or less (including B and smaller than B)".

(Non-thermoplastic polyimide layer with low dielectric loss tangent property)
The insulating resin film used in the conventional FCCL is generally composed of a substrate material (hereinafter, also referred to as a core layer) and an adhesive layer for adhering the core layer and the metal foil. In order to satisfy the general characteristics such as dimensional stability and peeling strength that have been required in the past, the core layer mainly secures the physical properties necessary for heat resistance and dimensional stabilization, and the adhesive layer is mainly made of metal leaf. It plays a role in ensuring the physical properties required for the peeling strength of the material. Further, it is also necessary that the multilayer film including the core layer and the adhesive layer and the metal foil can be easily manufactured when laminated by a thermal laminating method or the like.

The multilayer polyimide film of the present invention has a non-thermoplastic polyimide layer having a dielectric positive contact at 10 GHz of 0.001 to 0.009 on at least one side of the non-thermoplastic polyimide film (hereinafter, non-thermoplastic polyimide having low dielectric positive contact). A layer (also referred to as an intermediate layer) is laminated, and further has a thermoplastic polyimide layer.

The low dielectric loss tangent property in the present invention means that the dielectric loss tangent property at 10 GHz is 0.001 to 0.009. That is, the non-thermoplastic polyimide layer having a low dielectric loss tangent property in the present invention means a non-thermoplastic polyimide layer having a dielectric loss tangent property of 0.001 to 0.009 at 10 GHz.

In order to impart low transmission loss characteristics, it is necessary to reduce the dielectric constant, low dielectric loss tangent, and low moisture absorption of the insulating resin film, and it is necessary to share these characteristics between the core layer and the adhesive layer.

However, there is a trade-off between the physical properties required for the above general characteristics and the characteristics required for low transmission loss, and the core layer and the adhesive layer have the high heat resistance and dimensional stabilization that have been conventionally required. It was difficult to achieve both peel strength and low transmission loss characteristics. As a result of various studies, the present inventors have found that the dielectric constant and the dielectric loss tangent of the insulating resin film using the polyimide film are generally additive, and have low dielectric loss tangent property excellent in improvement of low transmission loss characteristics. The multilayer polyimide film having a thermoplastic polyimide layer has realized both general characteristics and low transmission loss characteristics.

Specifically, the core layer and the adhesive layer ensure the physical characteristics required for heat resistance, dimensional stabilization, and peeling strength with metal foil, which are conventionally required, and the intermediate layer is required for low transmission loss. This is a method for ensuring the physical properties of low dielectric constant, low dielectric loss tangent, and low moisture absorption.

As described above, the intermediate layer of the present invention is a material having an excellent low dielectric constant, low dielectric loss tangent, and low moisture absorption rate that affects transmission loss, and is characterized by a low moisture absorption rate unlike the non-thermoplastic polyimide used for the core layer. It is necessary to select a combination of materials that have been converted.

The intermediate layer in the present invention needs to have a low dielectric loss tangent. Specifically, it is more preferably 0.001 to 0.009, and particularly preferably 0.001 to 0.007. When the dielectric loss tangent is in this range, the transmission loss of the FPC is small, which is preferable.

The intermediate layer in the present invention preferably has a low relative permittivity. It is more preferably 2.7 to 3.5, and particularly preferably 2.7 to 3.3. When the relative permittivity is in this range, the transmission loss of the FPC becomes small, which is preferable.

Since the hygroscopicity also affects the transmission loss, it is preferable that the hygroscopicity of the intermediate layer of the present invention is low. It is more preferably 0.1% to 1.0%, and particularly preferably 0.1% to 0.8%. When the hygroscopicity is in this range, the transmission loss of the FPC becomes small, which is preferable.

The intermediate layer of the present invention is not particularly limited as long as the dielectric loss tangent is in the range of 0.001 to 0.009, and various polyamic acids can be used.

Polyamic acid is obtained by reacting an aromatic diamine with an aromatic acid dianhydride. More specifically, usually, aromatic diamine and aromatic acid dianhydride are dissolved in an organic solvent so as to have substantially the same molar amount, and the obtained solution is subjected to controlled temperature conditions. Below, it is produced by stirring until the polymerization of the aromatic acid dianhydride and the aromatic diamine is completed. The solution containing the polyamic acid thus obtained is usually obtained in a concentration of 5% by weight to 35% by weight, more preferably 10% by weight to 30% by weight. When the concentration is in this range, an appropriate molecular weight and solution viscosity are obtained. The polymerization method is not particularly limited, and the order of addition, the combination of monomers, and the composition (addition amount) are not particularly limited. For example, it may be random polymerization, or sequence polymerization capable of producing a block component.

The aromatic diamine is not particularly limited, but is, for example, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 2,2'-dimethylbiphenyl-4. , 4'-diamine, 2,2-bis {4- (4-aminophenoxy) phenyl} propane, 2,2-bis {4- (4-aminophenoxy) phenyl} hexafluoropropane, bis {4- (3) -Aminophenoxy) phenyl} sulfone, bis {4- (4-aminophenoxy) phenyl} sulfone, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1, 4-Bis (4-aminophenoxy) benzene, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-dichlorobenzidine, 3,3'-dimethylbenzidine, 2,2'-dimethylbenzidine , 3,3'-dimethoxybenzidine, 2,2'-dimethoxybenzidine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene (m-phenylenediamine), 4,4'-diaminodiphenyl Sulfone, 3,3'-diaminodiphenylsulfone, 9,9-bis (4-aminophenyl) fluorene, 4,4'-(1,4-phenylenebis (1-methylethylidene)) bisaniline, 4, 4'- (1,3-Phenylenebis (1-methylethylidene)) bisaniline, 4,4'-diaminobenzanilide and the like, or a combination of two or more thereof can be mentioned.

The aromatic acid dianhydride is not particularly limited, but for example, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 2,2', 3,3'-benzophenone. Tetracarboxylic acid dianhydride, 4,4'-oxydiphthalic acid dianhydride, 3,4'-oxyphthalic acid dianhydride, ethylenebis (trimellitic acid monoesteric anhydride), bisphenol A bis (trimellitic acid mono) Esteric acid anhydride), pyromellitic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 3,3', 4,4'-Diphenylsulfone tetracarboxylic acid dianhydride, 3,3', 4,4'-dimethyldiphenylsilanetetracarboxylic acid dianhydride, 3,3', 4,4'-tetraphenylsilanetetracarboxylic acid Dianhydride, 1,2,3,4-frantetracarboxylic acid dianhydride, 4,4'-bis (3,4-dicarboxyphenoxy) diphenylpropane dianhydride, 4,4'-hexafluoroisopropyrid Dendiphthalic anhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 2,3,3', 4'-biphenyltetracarboxylic acid dianhydride, p-phenylenebis (trimertic acid) Monoester anhydride), aromatic tetracarboxylic acid dianhydride such as p-phenylenediphthalic anhydride, or a combination of two or more thereof can be mentioned.

Preferred examples of aromatic diamines for exhibiting low dielectric adpositivity and low water absorption include 2,2'-dimethylbiphenyl-4,4'-diamine and 2,2-bis {4- (4-amino). Phenoxy) phenyl} propane, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, paraphenylenediamine, 4,4'-diamino-2,2'-bis ( Trifluoromethyl) Fluoromono such as biphenyl may be used alone or in combination of two or more. Preferred examples of aromatic acid dianhydrides for exhibiting low dielectric adpositivity and low water absorption include 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydrides and pyromellitic acid dianhydrides. , 4,4'-oxydiphthalic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, alone or in combination.

The organic solvent used as the polymerization solvent for producing the polyamic acid is not particularly limited as long as it dissolves the aromatic diamine, the aromatic acid dianhydride, and the obtained polyamic acid. If, for example, N, N-dimethylformamide, N, N-diethylformamide, N-methyl-2-pyrrolidone, N, N-dimethylacetamide or the like is used as the polymerization solvent, the obtained polyamic acid solution can be used as it is. , Polyimide film can be used.

The reaction temperature for producing the polyamic acid is preferably −10 ° C. to 50 ° C. Within such a range, the reaction proceeds at a good reaction rate and the productivity is excellent, which is preferable. The reaction time is not particularly limited, but is usually several minutes to several hours.

The polyimide is produced by a method typified by heat curing or chemical curing of the above polyamic acid. Thermal curing promotes imidization only by heat treatment. Chemical cure is a method of imidizing by mixing with a curing agent and heat-treating. The curing agent includes a dehydrating agent and a catalyst. Here, the dehydrating agent is not particularly limited as long as it is a dehydrating ring-closing agent for polyamic acid. Examples thereof include aliphatic acid anhydrides, aromatic acid anhydrides, N, N'-dialkylcarbodiimides, lower aliphatic halides, halogenated lower aliphatic acid anhydrides, aryl sulfonic acid dihalides, thionyl halides and the like. Can be done. These may be used alone or in combination of two or more as appropriate. Among these, aliphatic acid anhydrides and aromatic acid anhydrides can be preferably used, and acetic anhydride is particularly preferable. The catalyst is not particularly limited as long as it is a component having an effect of promoting the dehydration ring closure action of the dehydrating agent on the polyamic acid. For example, aliphatic tertiary amines, aromatic tertiary amines, heterocyclic tertiary amines and the like can be mentioned. Among these, for example, nitrogen-containing heterocyclic compounds such as imidazole, benzimidazole, isoquinoline, quinoline, diethylpyridine or β-picoline are particularly preferably used.

The term "non-thermoplastic" in the present invention refers to a molded product obtained by subjecting a combination of raw material monomers to solution polymerization, drying the obtained polyamic acid solution, and at least one method of thermal imidization or chemical imidization (mainly). A film) that retains its shape without being deformed such as wrinkles or elongation when heated at 450 ° C. for 1 minute.

(Non-thermoplastic polyimide film)
By using a non-thermoplastic polyimide film as a core layer, the multilayer polyimide film of the present invention can be formed.

The non-thermoplastic polyimide film may contain other resins together with the non-thermoplastic polyimide as long as the characteristics of the non-thermoplastic polyimide film are not impaired.

The non-thermoplastic polyimide film (core layer) of the present invention preferably has a low dielectric loss tangent. Specifically, it is more preferably 0.001 to 0.012, and particularly preferably 0.001 to 0.010. When the dielectric loss tangent is in the above range, the dielectric loss tangent of the multilayer polyimide film can be controlled to 0.009 or less in the intermediate layer.

It is preferable that the non-thermoplastic polyimide film layer (core layer) of the present invention also has a low hygroscopicity. Specifically, it is more preferably 0.1% to 1.7%, and particularly preferably 0.1% to 1.4%.

The coefficient of linear thermal expansion (CTE) of the core layer is preferably 1 ppm to 15 ppm, more preferably 2 to 12 ppm, in order to suppress the dimensional change rate before and after etching of the flexible metal-clad laminate. When the CTE is in the above range, the dimensional change rate of the multilayer polyimide film can be controlled in an appropriate range in the intermediate layer.

(Non-thermoplastic polyimide) The non-thermoplastic polyimide contained in the non-thermoplastic polyimide film (core layer) is produced by imidizing using a polyamic acid as a precursor.

The monomer constituting the polyamic acid which becomes a non-thermoplastic polyimide by imidization is not particularly limited as long as it can exhibit non-thermoplasticity. For example, the same thing as the monomer constituting the intermediate layer can be exemplified.

Examples of aromatic diamines preferably used for non-thermoplastic polyimides contained in non-thermoplastic polyimide films (core layers) are 2,2'-dimethylbiphenyl-4,4'-diamines and 2,2-bis. {4- (4-Aminophenoxy) phenyl} propane, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, paraphenylenediamine, 4,4'-diaminodiphenyl Propane, 4,4'-bis (4-aminophenoxy) biphenyl, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfide, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2, Examples thereof include 2-bis (4-aminophenoxyphenyl) propane, 3,3'-dihydroxy-4,4'-diamino-1,1'-biphenyl, and the like, which may be used alone or in combination of two or more. Examples of aromatic acid dianhydrides suitably used for designing non-thermoplastic polyimides contained in non-thermoplastic polyimide films (core layers) are pyromellitic acid dianhydrides, 2, 3, 6,. 7-Naphthalenetetracarboxylic acid dianhydride, 2,2', 3,3'-biphenyltetracarboxylic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 2,2- Bis (3,4-dicarboxyphenyl) propanoic acid dianhydride, p-phenylene bis (trimellitic acid monoesteric acid anhydride), 4,4'-oxydiphthalic acid dianhydride, etc. are mentioned, and these are used alone. Alternatively, a plurality of them can be used in combination.

The polymerization method, polymerization solvent, reaction temperature and reaction time of the non-thermoplastic polyimide contained in the non-thermoplastic polyimide film (core layer) are not particularly limited.

The curing agent and curing conditions when the polyamic acid is used as polyimide are not particularly limited. For example, the same ones used for manufacturing the intermediate layer can be used.

(Thermoplastic polyimide layer)
The thermoplastic polyimide layer (also referred to as an adhesive layer) according to the present invention is a thermoplastic polyimide layer contained in the adhesive layer as long as it can exhibit desired characteristics such as an adhesive force with a metal foil such as a copper foil and a suitable linear expansion coefficient. The content, molecular structure, and thickness are not particularly limited. However, it is preferable to contain 50 wt% or more of the thermoplastic polyimide in order to develop desired properties such as a significant adhesive force and a suitable coefficient of linear expansion.

It is preferable that the dielectric loss tangent of the thermoplastic polyimide layer (adhesive layer) of the present invention is also low. Specifically, it is more preferably 0.001 to 0.012, and particularly preferably 0.001 to 0.010. If the dielectric loss tangent exceeds the above range, it becomes difficult to reduce the dielectric loss tangent of the multilayer polyimide film in the intermediate layer.

It is preferable that the hygroscopicity is also low. Specifically, it is more preferably 0.1% to 1.3%, and particularly preferably 0.1% to 0.9%.

The thermoplastic polyimide in the present invention has a glass transition temperature (Tg) in the range of 150 ° C. to 300 ° C. from the viewpoint of exhibiting adhesive strength with a metal foil and not impairing the heat resistance of the obtained metal-clad laminate. ) Is preferable. In addition, Tg can be obtained from the value of the inflection point of the storage elastic modulus measured by the dynamic viscoelasticity measuring device (DMA).

The thermoplastic polyimide contained in the thermoplastic polyimide layer according to the present invention is obtained by a conversion reaction of its precursor from a polyamic acid. As a method for producing the polyamic acid, any known method can be used as in the precursor of the non-thermoplastic polyimide, that is, the precursor of the highly heat-resistant polyimide layer.

For the purpose of controlling the characteristics of the thermoplastic polyimide layer according to the present invention, an inorganic or organic filler and other resins may be added, if necessary.

(Thermoplastic polyimide)
As the thermoplastic polyimide contained in the thermoplastic polyimide layer, a thermoplastic polyimide, a thermoplastic polyamideimide, a thermoplastic polyetherimide, a thermoplastic polyesterimide or the like can be preferably used. Among them, thermoplastic polyimide is particularly preferably used from the viewpoint of dimensional stability and adhesion.

The polyamic acid used as a precursor of the thermoplastic polyimide used in the present invention is not particularly limited, and any known polyamic acid can be used. Regarding the production of the polyamic acid solution, raw materials such as aromatic acid dianhydride and aromatic diamine used for producing a precursor of non-thermoplastic polyimide, a solvent, and the above-mentioned production conditions can be used in exactly the same manner.

In addition, although various characteristics of thermoplastic polyimide can be adjusted by combining various raw materials to be used, in general, when the ratio of aromatic diamines having a rigid structure is large, the glass transition temperature becomes high and the storage elasticity during heat is increased. It is not preferable because the rate increases and the adhesiveness and workability decrease. The ratio of the aromatic diamine used in the rigid structure is preferably 40 mol% or less, more preferably 30 mol% or less, and particularly preferably 20 mol% or less.

Examples of aromatic diamines particularly preferably used in the present invention are 1,3-bis (4-aminophenoxy) benzene, 2,2'-dimethylbiphenyl-4,4'-diamine, 4,4'-bis (4). -Aminophenoxy) Biphenyl, 2,2-bis [4- (4-aminophenoxy) phenyl] propane and the like can be mentioned, and these can be used alone or in combination of two or more.

Examples of aromatic acid dianhydrides particularly preferably used in the present invention are 4,4'-oxydiphthalic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, and pyromellitic dianhydride. Anhydrous and the like can be mentioned, and these can be used alone or in combination of two or more.

The polymerization method, polymerization solvent, reaction temperature and reaction time of the thermoplastic polyimide are not particularly limited.

The curing agent for using the polyamic acid as the polyimide is not particularly limited, and for example, the same curing agent used for producing the intermediate layer can be used.

(Multilayer polyimide film)
The multilayer polyimide film of the present invention is thermoplastic via a non-thermoplastic polyimide layer (intermediate layer) having a dielectric loss tangent at 10 GHz of 0.001 to 0.009 on at least one surface of the non-thermoplastic polyimide film (core layer). It is characterized by having a structure in which a polyimide layer (adhesive layer) is provided.

Since the multilayer polyimide film of the present invention is used for a substrate for a high frequency circuit or the like, it is preferable that the hygroscopicity is low. Specifically, it is more preferably 0.1% to 1.3%, and particularly preferably 0.1% to 1.0%. It is preferable that the multilayer polyimide film of the present invention also has a low relative permittivity. Specifically, it is more preferably 2.8 to 3.6, and particularly preferably 2.8 to 3.5.

It is preferable that the dielectric loss tangent of the multilayer polyimide film of the present invention is also low. Specifically, it is more preferably 0.001 to 0.011 and particularly preferably 0.001 to 0.009.

The total thickness of the multilayer polyimide film of the present invention is not particularly limited. For example, 12 μm to 54 μm is preferable, and 16.5 μm to 48 μm is more preferable. If the total thickness is within this range, the flexible wiring board will have appropriate hardness and bendability, and the handleability will be good, and there will be troubles such as tearing during transportation and not passing through the manufacturing process. It is less likely to occur.

The total thickness of the core layer and the intermediate layer of the present invention is not particularly limited. For example, 8 μm to 50 μm is preferable, and 12.5 μm to 44 μm is more preferable. The thickness of the core layer and the intermediate layer can be arbitrarily determined within a preferable range of the total thickness. For example, in the range of total thickness, the thickness of the intermediate layer is more preferably 3 μm to 40 μm, and particularly preferably 6 μm to 35 μm. Further, the composition ratio of the thickness of the intermediate layer to the total thickness is more preferably 30% to 80%, particularly preferably 40% to 70%. When the thickness of the intermediate layer is within this range, the dielectric loss tangent of the multilayer polyimide film can be controlled to 0.009 or less in the intermediate layer.

The thickness (one side) of the adhesive layer is not particularly limited. For example, 1.7 μm to 16 μm is preferable, 1.7 μm to 6 μm is more preferable, and 1.7 μm to 4 μm is further preferable. When the thickness (one side) of the adhesive layer is within this range, the adhesion to the metal foil is good and the dimensional change rate after etching tends to be good, although it depends on the roughness of the surface of the metal foil. Further, when the adhesive layer is thick and the thickness composition ratio of the adhesive layer to the total thickness of the multilayer polyimide film is 50% or less, the dimensional change rate when processed into a flexible metal-clad laminate is good. The thickness composition ratio of the adhesive layer to the total thickness of the multilayer polyimide film is more preferably 8% to 32%, and particularly preferably 12% to 24%. When the thickness composition ratio of the adhesive layer to the total thickness of the multilayer polyimide film is within this range, the peel strength and the dimensional stability are good, which is preferable.

(Manufacturing method of multilayer polyimide film)
In the method for producing a multilayer polyimide film of the present invention, the means for providing the thermoplastic polyimide layer on at least one surface of the non-thermoplastic polyimide film via the non-thermoplastic polyimide layer having low dielectric loss tangent property is not particularly limited, and the conventional method is not limited. A known method can be used. For example, (i) a method of forming a non-thermoplastic polyimide layer having a low dielectric adjacency as an intermediate layer on a non-thermoplastic polyimide layer to be a core layer and forming a thermoplastic polyimide layer to be an adhesive layer. (Ii) A method of simultaneously molding the core layer and the intermediate layer by multi-layer extrusion or the like to form a thermoplastic polyimide layer to be an adhesive layer, (iii) Simultaneously molding the core layer, the intermediate layer and the adhesive layer by multi-layer extrusion or the like. The method and the like are preferably exemplified.

When the intermediate layer is produced by the means of (i) above, for example, after applying the precursor solution of the intermediate layer to the core layer, most of the organic solvent in the intermediate layer solution is first removed, so that the temperature is relatively low. Perform heating. The temperature at this stage is preferably in the range of 50 ° C to 200 ° C. Next, the precursor solution of the adhesive layer is applied, and heating is performed at a relatively low temperature in order to remove most of the organic solvent in the adhesive layer solution. The temperature is preferably in the range of 50 ° C to 200 ° C.

Finally, the multilayer polyimide film is heat-treated at a high temperature in order to remove the solvent slightly remaining in the intermediate layer and the adhesive layer in the multilayer polyimide film and to imidize the polyamic acid in the intermediate layer and the adhesive layer. .. The heat treatment temperature at this stage is preferably 250 ° C. or higher. When the heat treatment is performed at a temperature of 250 ° C. or higher, the dimensional stability and the peeling strength are good. When almost no solvent remains in the adhesive layer, heating is performed at this stage by applying a temperature higher than the melting point of the thermoplastic polyimide to remove the solvent, imidize the thermoplastic polyimide in the adhesive layer, and melt the adhesive layer. You may do it all together in the process. The temperature above the melting point of the thermoplastic polyimide may be as high as 390 ° C, and if it is rapidly cooled after heating, the multilayer polyimide film may shrink rapidly and the appearance may deteriorate. Therefore, the ambient temperature is gradually lowered. It is preferable to slowly cool the film.

When the multilayer polyimide film is produced by the means of (ii), the core layer and the intermediate layer are simultaneously molded by multilayer extrusion or the like, and then heated to remove the solvent, the core layer, the imidization of the intermediate layer, the core layer, and the intermediate layer. Melt. Next, an adhesive layer is formed and heated to remove the solvent, imidize the adhesive layer, and melt the adhesive layer. The steps may be performed in the same manner as in (i).

When the multilayer polyimide film is produced by the means of (iii), the core layer, the intermediate layer and the adhesive layer are simultaneously molded by multi-layer extrusion or the like, and then heated to remove the solvent, imidize and melt. The temperature step may be performed in the same manner as in (i).

The heating means is not particularly limited, and examples thereof include a hot air method and a far infrared method, and these may be used in combination. Further, as the heating method, either batch treatment or continuous treatment may be used, but from the viewpoint of productivity of the multilayer polyimide film, continuous treatment is preferable.

In the method for producing the intermediate layer, the adhesive layer and the core layer according to the present invention, either the thermal cure method or the chemical cure method may be adopted, but in consideration of the production efficiency, the chemical cure method is adopted for the core layer. Is particularly preferable.

(Metal leaf)
The metal leaf that can be used in the present invention is not particularly limited. For example, when the flexible metal-clad laminate of the present invention is used for electronic equipment / electrical equipment applications, for example, copper or copper alloy, stainless steel or alloy thereof, nickel or nickel alloy (including 42 alloy), aluminum or aluminum. A foil made of an alloy can be mentioned. In general flexible laminated plates, copper foils such as rolled copper foils and electrolytic copper foils are often used, but they can also be preferably used in the present invention. The surface of these metal foils may be coated with a rust preventive, a heat resistance imparting agent, or an adhesive. Further, the thickness of the metal foil is not particularly limited, and may be any thickness as long as it can exhibit sufficient functions according to its use. A smooth surface of the metal foil is preferable for reducing transmission loss, and a copper foil having a Ra of 1.0 μm or less can be preferably used. Smooth copper foil for high-speed transmission is commercially available from various companies. Since the adhesive layer of the multilayer polyimide film used in the present invention is a thermoplastic polyimide, it has high adhesion to copper foil, and in general, good adhesion can be obtained even with smooth copper foil, which makes it difficult to obtain an anchor effect. Are better.

(Flexible metal-clad laminate)
In order to manufacture the flexible metal-clad laminate of the present invention, as a method of laminating a multilayer polyimide film and a metal foil, for example, continuous treatment by a thermal roll laminating apparatus having a pair or more of metal rolls or a double belt press (DBP). Can be used. Above all, it is preferable to use a thermal roll laminating apparatus having a pair or more of metal rolls because the apparatus configuration is simple and it is advantageous in terms of maintenance cost. Further, since the dimensional change is particularly likely to occur when the heat roll laminating device having a pair or more of metal rolls is used to bond the metal foil, the multilayer polyimide film of the present invention is bonded to the metal foil by the heat roll laminating device. In some cases, it exhibits a remarkable effect. The "thermal roll laminating device having a pair or more of metal rolls" here may be any device having a metal roll for heating and pressurizing a material, and the specific device configuration thereof is particularly limited. It's not a thing.

The specific configuration of the means for carrying out the thermal laminating is not particularly limited, but a protective material is arranged between the pressure surface and the metal foil in order to improve the appearance of the obtained laminated board. It is preferable to do so. Examples of the protective material include materials that can withstand the heating temperature of the heat laminating process, that is, metal foils such as heat-resistant plastics, copper foils, aluminum foils, and SUS foils, and have a heat resistance of 50 ° C. or higher higher than the laminating temperature. A material having the above is preferably used. Further, the thickness of the protective material is not particularly limited as long as it can sufficiently fulfill the functions of cushioning and protection at the time of laminating. For example, the thickness of the protective material is preferably 75 μm or more.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples. The present invention is not limited to the following examples.

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

(Measurement of hygroscopicity)
The hygroscopicity was calculated from the weight loss under the condition of heating at 20 ° C./min from 20 ° C. to 120 ° C. and holding at 120 ° C. for 2 hours by STD Q600 manufactured by TA Instruments Japan. The sample was measured by allowing it to stand at 23 ° C./55% RH for 1 week and adjusting the humidity.

(Measurement of permittivity and dielectric loss tangent)
The permittivity and the dielectric loss tangent were measured using a network analyzer 8719C manufactured by HewlettPACKARD and a cavity resonator vibration method dielectric constant measuring device CP511 manufactured by Kanto Denshi Applied Development Co., Ltd. The sample was cut into 2 mm × 100 mm, and the measurement was performed after humidity control for 24 hours in a 23 ° C./55% RH environment. The measurement was performed at 10 GHz.

(Peeling strength)
A sample was prepared according to JIS C6471 "6.5 Peeling Strength", and the metal leaf part with a width of 3 mm was peeled off at a peeling angle of 90 degrees and a condition of 200 mm / min, and the load (N / cm) was applied. It was measured.

(Measurement of dimensional change rate)
Based on JIS C6481, four holes were formed in the flexible copper-clad laminate, and the distance between each hole was measured. Next, an etching step was carried out to remove the metal foil from the flexible copper-clad laminate, and then the metal leaf was allowed to stand at 23 ° C./55% RH for 24 hours for humidity control. After that, the distances of each of the above four holes were measured in the same manner as before the etching process. The measured value of the distance of each hole before removing the metal foil was set to D1, and the measured value of the distance of each hole after removing the metal foil was set to D2, and the dimensional change rate before and after etching was obtained by the following equation. Dimensional change rate (%) = {(D2-D1) / D1} × 100 Subsequently, the measured sample after etching was heated at 250 ° C. for 30 minutes and then left at 23 ° C./55% RH for 24 hours. Then, the distances of each of the above four holes were measured. Taking the measured value of the distance of each hole after heating as D3, the dimensional change rate before and after heating was obtained by the following formula. Dimensional change rate (%) = {(D3-D2) / D2} × 100 The dimensional change rate was measured in both the MD direction and the TD direction, and the average value thereof was taken as the dimensional change rate.

(Method of manufacturing flexible metal-clad laminate (FCCL))
A rolled copper foil (GHY5-93F-HA; manufactured by JX Nikko Nisseki Co., Ltd.) having a thickness of 12 μm is placed on both sides of the multilayer polyimide film, and a protective material (Apical 125 NPI; manufactured by Kaneka, 125 μm thick) is placed on both sides thereof. Using a laminating machine, heat laminating was continuously performed under the conditions of a laminating temperature of 360 ° C., a laminating pressure of 245 N / cm2 (25 kgf / cm), and a laminating speed of 1.0 m / min to prepare a flexible metal-clad laminate.

(Measurement of transmission loss)
Using the obtained flexible metal-clad laminate, a microstrip line having a line length of 10 cm and a line width of 100 μm was produced. Specifically, after undergoing drilling, through-hole plating, and patterning, a coverlay film CISV1225 manufactured by Nikkan Kogyo Co., Ltd. was bonded, and the measurement pad portion was gold-plated to prepare a microstripline-shaped FPC test piece. The obtained microstrip line was heated and dried at 120 ° C./24 hours, then allowed to stand at 23 ° C./55% RH for 48 hours to adjust the humidity, and then the transmission loss S21 parameter was set using a network analyzer and a probe station. It was measured. The signal frequency at -3 dB / 10 cm, where the signal strength is halved, was recorded.

Since the transmission characteristics are easily affected by moisture, it is necessary to perform drying and humidity control of the flexible metal-clad (copper-clad) laminated board with high accuracy.

(Synthesis Example 1: Synthesis of precursor solution of non-thermoplastic polyimide 1 having low dielectric loss tangent property)
To a reaction vessel having a capacity of 100 L, 62.9 kg of dimethylformamide (DMF) and 2.3 kg of para-phenylenediamine (PDA) were added, and 3,3', 4,4'-biphenyltetracarboxylic acid was stirred under a nitrogen atmosphere. 5.6 kg of dianhydride (BPDA) was gradually added. Subsequently, 2.6 kg of 1,3-bis (4-aminophenoxy) benzene (TPE-R) and 1.1 kg of BPDA were added, 0.5 kg of pyromellitic acid dianhydride (PMDA) was added, and the mixture was stirred for 1 hour. Was dissolved. A solution prepared by dissolving 0.2 kg of PMDA in 2.5 kg of DMF was separately prepared, and this solution was gradually added to the above reaction solution and stirred while paying attention to the viscosity. When the viscosity reached 1000 poise, the addition and stirring were stopped to obtain a polyamic acid solution.

(Synthesis Example 2: Synthesis of precursor solution of non-thermoplastic polyimide 2 having low dielectric loss tangent property)
59.5 kg of dimethylformamide (DMF) and 2.4 kg of PDA were added to a reaction vessel having a capacity of 100 L, and 5.9 kg of BPDA was gradually added while stirring under a nitrogen atmosphere. Subsequently, 3.9 kg of 2,2-bis [4- (4-aminophenoxy) phenyl] propane (BAPP) was added, and 0.7 kg of BPDA and 2.7 kg of 4,4'-oxydiphthalic anhydride (ODPA) were added. It was added and stirred for 1 hour to dissolve it. A solution prepared by dissolving 0.3 kg of ODPA in 5.6 kg of DMF was separately prepared, and this solution was gradually added to the above reaction solution and stirred while paying attention to the viscosity. When the viscosity reached 1000 poise, the addition and stirring were stopped to obtain a polyamic acid solution.

(Synthesis Example 3: Synthesis of Precursor Solution of Thermoplastic Polyimide)
64.1 kg of dimethylformamide (DMF) and 7.7 kg of BPDA were added to a reaction vessel having a capacity of 100 L, and 1.1 kg of TPE-R was gradually added while stirring under a nitrogen atmosphere. A solution prepared by dissolving 2 kg of TPE-R in 40 kg of DMF was separately prepared, and this was gradually added to the above reaction solution while paying attention to the viscosity and stirred. When the viscosity reached 1000 poise, the addition and stirring were stopped to obtain a polyamic acid solution.

(Example 1)
A 9 μm-thick high heat-resistant polyimide film (Apical (registered trademark) 9FP, manufactured by Kaneka) is used as a core layer, and the polyamic acid solution obtained in Synthesis Example 1 has a solid content concentration of 8.0% by weight on both sides of the core layer. After applying a polyamic acid solution to the solution diluted with DMF until it becomes 5 μm so that the final one-sided thickness of the non-thermoplastic polyimide (which becomes the intermediate layer) having low dielectric adjunctivity is 5 μm, it is carried out at 120 ° C. for 2 minutes. Heating was performed at 180 ° C. for 5 minutes. Subsequently, the polyamic acid solution obtained in Synthesis Example 3 was added to the outer surface of the intermediate layer coated on both sides of the core layer so that the final one-sided thickness of the thermoplastic polyimide (which becomes the adhesive layer) was 3 μm. After applying a polyamic acid solution diluted with DMF until the concentration reached 8.0% by weight, heating was performed at 120 ° C. for 2 minutes. Subsequently, heating was performed at 250 ° C. for 7 seconds, 450 ° C. for 14 seconds, and 350 ° C. for 7 seconds to obtain a multilayer polyimide film having a total thickness of 25 μm.

A rolled copper foil (GHY5-93F-HA; manufactured by JX Nippon Oil Co., Ltd.) having a thickness of 12 μm was heat-laminated on the obtained multilayer polyimide film to obtain a flexible copper foil laminated plate.

The relative permittivity, dielectric loss tangent, and moisture absorption of the multilayer polyimide film were measured, and the transmission loss of the flexible copper foil laminated plate was measured. The evaluation results are shown in Table 1.

In Example 1, the frequency at which the signal is halved is high, and it was confirmed that the transmission loss was reduced.

(Comparative Example 1)
A multilayer polyimide film and a flexible copper-clad laminate were obtained in the same manner as in Example 1 except that the polyamic acid solution prepared in Synthesis Example 1 was changed to Synthesis Example 2, and evaluated. The results are shown in Table 1.

In Comparative Example 1, the characteristics of the intermediate layer were insufficient, the dielectric loss tangent of the multilayer polyimide film did not reach the target, and the reduction of transmission loss was insufficient.

(Comparative Example 2)
It was produced in the same manner as in Example 1 except that the intermediate layer was not applied, and a multilayer polyimide film and a flexible copper-clad laminate were obtained and evaluated. The results are shown in Table 1.

From Example 1 and Comparative Example 2, it was confirmed that Example 1 achieved low transmission loss while maintaining the dimensional stability and peeling strength of the flexible copper-clad laminate by using the intermediate layer.

1. 1. Non-thermoplastic polyimide film 2. Non-thermoplastic polyimide layer with low dielectric loss tangent property 3. Thermoplastic polyimide layer 4. Multilayer polyimide film

Claims (6)

A thermoplastic polyimide layer (adhesive layer) is provided on both sides of the non-thermoplastic polyimide film (core layer) via a non-thermoplastic polyimide layer (intermediate layer) having a dielectric loss tangent at 10 GHz of 0.001 to 0.009. structure have a to be,
In the intermediate layer, the aromatic diamine constituting the intermediate layer is 2,2'-dimethylbiphenyl-4,4'-diamine, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis ( 4-Aminophenoxy) Benzene, paraphenylenediamine, or 4,4'-diamino-2,2'-bis (trifluoromethyl) biphenyl, or a combination of two or more of these, which constitutes the intermediate layer. The group acid dianhydride is 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, pyromellitic acid dianhydride, or 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride. , Or a combination of two or more of these (except when diamine-type diamine is included as the diamine).
The thickness composition ratio of the adhesive layer to the total thickness of the multilayer polyimide film is 8% to 32%, and the ratio of the thickness of the intermediate layer to the total thickness of the intermediate layer and the core layer is 30% to 80%. A multilayer polyimide film characterized by being present. The first aspect of the present invention is characterized in that the hygroscopicity of the intermediate layer is 0.8 wt% or less, the relative permittivity at 10 GHz is 3.3 or less, and the dielectric loss tangent at 10 GHz is 0.007 or less. Multilayer polyimide film. The multilayer polyimide according to claim 1 or 2 , wherein the moisture absorption rate is 1.0 wt% or less, the relative permittivity at 10 GHz is 3.5 or less, and the dielectric loss tangent at 10 GHz is 0.009 or less. the film. The intermediate layer is an aromatic acid dianhydride, which is at least one of 2,2'-dimethylbiphenyl-4,4'-diamine and 1,3-bis (4-aminophenoxy) benzene as an aromatic diamine. At least one of 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, and pyromellitic acid dianhydride. The multilayer polyimide film according to any one of claims 1 to 3, further comprising a polyimide having the above. The multilayer polyimide film according to any one of claims 1 to 4, wherein the intermediate layer contains 1,3-bis (4-aminophenoxy) benzene and para-phenylenediamine as an aromatic diamine. .. A flexible metal-clad laminate having a metal foil on at least one side of the multilayer polyimide film according to any one of claims 1 to 5.

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