JP6474664B2 - Coverlay film - Google Patents

Description

  The present invention relates to a coverlay film. More specifically, the present invention relates to a coverlay film for a flexible printed wiring board.

  In recent years, the performance and miniaturization of electronic devices are rapidly progressing, and there is an increasing demand for higher density, smaller size, and thinner electronic components used in electronic devices. Along with this, further improvements in various physical properties such as heat resistance, mechanical strength, and electrical characteristics have been required for materials used for electronic components. For example, printed circuit boards on which semiconductor elements are mounted are required to have higher density, higher functionality, and higher performance.

  Under such circumstances, there is an increasing demand for flexible printed wiring boards (hereinafter referred to as FPC) capable of three-dimensional wiring and mounting in a narrow space. In general, FPC has a structure in which a circuit pattern is formed on a polyimide film having excellent heat resistance and flexibility, and an insulating resin layer having an adhesive layer, that is, a so-called coverlay film is bonded to the surface.

  In recent years, since the frequency of transmission signals in FPC has been remarkably increased, materials used for FPC are required to be able to reduce electrical signal loss in a high-frequency region, specifically, in a frequency region of 1 to 20 GHz. The coverlay film is also required to exhibit excellent electrical characteristics (low dielectric constant, low dielectric loss tangent) in a high frequency region. However, in Patent Documents 1 to 3, the loss of the electric signal in the high frequency region is not regarded as a problem, and the electrical characteristics of the coverlay film in the high frequency region have not been studied at all.

  On the other hand, Patent Document 4 discloses a coverlay film that exhibits a low dielectric constant and a low dielectric loss tangent as a coverlay film by performing a low dielectric constant and low dielectric loss tangent of the adhesive layer, and further a liquid crystal polymer for the insulating layer. Disclosed are materials that, when used, exhibit further low dielectric constant and low dielectric loss tangent of coverlay film.

JP 2008-248141 A JP 2006-169446 A JP 2005-2448048 A JP 2014-86591 A

  Coverlay films are generally composed of an adhesive layer and an insulating resin layer. In order to exhibit excellent electrical characteristics (low dielectric constant, low dielectric loss tangent) in the high frequency region, adhesives with excellent electrical characteristics have been developed. Yes. Furthermore, in order to design a coverlay film having excellent electrical characteristics, it is necessary to improve electrical characteristics not only for the adhesive layer but also for the insulating resin layer.

  The coverlay film described in Patent Document 4 provides not only the development of an adhesive layer with excellent electrical characteristics, but also the use of a liquid crystal polymer film for the insulating resin layer to provide a coverlay film with superior electrical characteristics. Yes. Further, when a polyimide film is used for the insulating resin layer, the electrical characteristics are improved by reducing the thickness ratio of the insulating resin layer to the adhesive layer.

  However, when a liquid crystal polymer film is used for the insulating resin layer of the coverlay film, there is a problem that the material cost is high and the price is higher than that of a conventional coverlay film.

  In addition, since the value of dielectric loss tangent increases as the frequency increases in the conventional polyimide, even in a coverlay film using a polyimide film for the insulating resin layer, the frequency increases in the assumed frequency range of 1 to 20 GHz. It is predicted that the value of the dielectric loss tangent increases.

  An object of this invention is to provide the cover-lay film which shows a low dielectric constant and a low dielectric loss tangent in the frequency range of 1-20 GHz.

  In order to solve the above-described problems, the present inventors use polyimide having a low dielectric constant and a low dielectric loss tangent as materials for the insulating resin layer and the adhesive layer, and the insulating resin layer and the adhesive layer. By considering the thickness ratio, the inventors have found that excellent electrical characteristics are exhibited in a high frequency region of 1 to 20 GHz and that deterioration of dielectric loss tangent accompanying an increase in frequency can be suppressed, leading to the present invention.

That is, the coverlay film of the present invention includes a polyimide insulating layer (A) and a polyimide adhesive layer (B) provided on one surface of the polyimide insulating layer (A). And the coverlay film of this invention is the structure of following i-ha:
A) The thickness (L1) of the polyimide insulating layer (A) is in the range of 12 μm to 30 μm;
B) The polyimide adhesive layer (B) has a thickness (L2) in the range of 10 μm to 40 μm;
C) When the dielectric constant of the coverlay film is Dk12 and the dielectric loss tangent is Df12, the following formula (1) is satisfied;
√Dk12 × Df12 <0.007…… (1)
It is characterized by comprising.

In the coverlay film of the present invention, the dielectric constant in the polyimide insulating layer (A) is Dk1, the dielectric loss tangent is Df1, the dielectric loss tangent at 5 GHz in the coverlay film is Df12-5 GHz, and the dielectric loss tangent at 20 GHz. In the case of Df12-20 GHz, the following formula (2), formula (3) and formula (4);
√Dk1 × Df1 <0.01 (2)
L2 / (L1 + L2)> 0.40 ... (3)
Df12-20GHz / Df12-5GHz ≦ 1 ... (4)
May be satisfied.

  In the coverlay film of the present invention, the polyimide insulating layer (A) is made of polyimide obtained by reacting an acid anhydride component and a diamine component, and the diamine component is a primary dimer acid having two terminal carboxylic acid groups. It may contain a dimer acid type diamine substituted with an aminomethyl group or an amino group.

  The cover lay film of the present invention is made of polyimide that can be manufactured at a lower cost than a liquid crystal polymer film, exhibits excellent electrical characteristics, and has a low dielectric loss tangent even in a high frequency region. Therefore, the coverlay film of the present invention can be suitably used as an electronic material that requires high-speed signal transmission.

  Embodiments of the present invention will be described below.

[Coverlay film]
The coverlay film of the present embodiment includes a polyimide insulating layer (A) and a polyimide adhesive layer (B) provided on one surface of the polyimide insulating layer (A).

The coverlay film of the present invention has the following formula (1) when the dielectric constant of the entire coverlay film is Dk12 and the dielectric loss tangent is Df12:
√Dk12 × Df12 <0.007…… (1)
Is satisfied. In the prior art, the lowering of the dielectric of the adhesive layer of the coverlay film has been studied. However, it is important not only to lower the dielectric of the adhesive layer but also to lower the dielectric of the entire coverlay film. The above-mentioned √Dk12 × Df12 serves as an index of the dielectric properties of the coverlay film, and the above formula (1) can be satisfied by reducing the dielectric of the polyimide insulating layer (A). . If the above characteristics are satisfied, the product of the square root of the dielectric constant and the dielectric loss tangent of either one of the polyimide insulating layer (A) and the polyimide adhesive layer (B) may be larger than 0.007. In order to satisfy the formula (1), it is preferable that the dielectric properties of the polyimide insulating layer (A) satisfy the formula (2) described later, and the thickness ratio of the polyimide adhesive layer (B) is described later. It is preferable to satisfy Formula (3).

  Moreover, the thickness (L1) of the polyimide insulating layer (A) is preferably in the range of 12 μm or more and 30 μm or less. The thickness (L2) of the polyimide adhesive layer (B) is preferably in the range of 10 μm or more and 40 μm or less.

Moreover, the thickness of the polyimide adhesive layer (B) with respect to the sum of the thickness (L1) of the polyimide insulating layer (A) and the thickness (L2) of the polyimide adhesive layer (B) (preferably the entire thickness of the coverlay film) (L2) is preferably higher than 40%.
That is, the following formula (3);
L2 / (L1 + L2)> 0.40 ... (3)
It is preferable to satisfy. By satisfying the formula (3), the dielectric constant and dielectric loss tangent of the polyimide adhesive layer (B) is excellent when compared with the polyimide insulating layer (A). Can be achieved, and the formula (1) can also be achieved.

In addition, when the dielectric loss tangent at 5 GHz in the entire coverlay film is Df12-5 GHz and the dielectric loss tangent at 20 GHz is Df12-20 GHz, the following formula (4):
Df12-20GHz / Df12-5GHz ≦ 1 ... (4)
Is preferably satisfied. In order to make the coverlay film usable in a high frequency range, it is important to show stable dielectric characteristics not only in a narrow frequency range but also in a wide frequency range. Therefore, it is important to design the coverlay film with a material that does not deteriorate the dielectric loss tangent even in a high frequency range. In order to achieve the formula (4), the polyimide adhesive layer (B) exhibiting a stable dielectric loss tangent even in a high frequency region is used, and the thickness of the polyimide insulating layer that tends to deteriorate the dielectric loss tangent in the high frequency region. It is important to maintain a certain ratio. In addition, the polyimide adhesive layer (B) has a material design that suppresses the rotational movement of the dipole in the molecular skeleton in order to make it difficult for the dielectric loss tangent to deteriorate in the high frequency range, that is, the dipole in the molecular skeleton is reduced. It becomes important.

Moreover, in order to suppress the curvature of a coverlay film, it is desirable that the elastic modulus of a polyimide insulating layer (A) is higher than the elastic modulus of a polyimide adhesive layer (B). Polyimide insulation layer (A)
When the elastic modulus of the adhesive layer is lower than the elastic modulus of the polyimide adhesive layer (B), the warp of the coverlay film increases due to the influence of the polyimide adhesive layer (B) having a large coefficient of thermal expansion, and the circuit wiring board is bonded. This also causes warping.

  Moreover, a coverlay film is good also as a form which bonds a release material on the surface at the side of a polyimide adhesive layer (B), and has a release material layer. The material of the release material is not particularly limited as long as it can be peeled without impairing the shape of the coverlay film. For example, resin films such as polyethylene terephthalate, polyethylene, and polypropylene, and these resin films on paper A laminate or the like can be used.

  Since the coverlay film of the present invention has excellent flexibility and thermoplasticity, the polyimide adhesive layer (B) is filled between the wirings when used as an FPC coverlay film, and the coverlay film and the wiring layer High adhesion is obtained.

  Next, the polyimide insulating layer (A) and the polyimide adhesive layer (B) will be described in detail.

[Polyimide insulation layer (A)]
The resin used for the polyimide insulating layer (A) is a polyimide obtained by reacting an acid anhydride component containing an aromatic tetracarboxylic acid anhydride component with a diamine component containing an aliphatic diamine, aromatic diamine or the like. . Since polyimide is generally produced by reacting an acid anhydride with a diamine, a specific example of polyimide can be understood by explaining the acid anhydride and diamine. Hereinafter, a preferable polyimide will be described using an acid anhydride and a diamine.

<Acid anhydride>
As acid anhydride component of polyimide raw material used for polyimide insulation layer (A), pyromellitic anhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 3,3 ', 4,4'-biphenyl Preferred examples include tetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride, and 4,4′-oxydiphthalic anhydride. Moreover, 2,2 ', 3,3'-, 2,3,3', 4'- or 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 2,3 ', 3,4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride, 2,3 ', 3,4'-diphenyl ether tetracarboxylic dianhydride Bis (2,3-dicarboxyphenyl) ether dianhydride, 3,3``, 4,4 ''-, 2,3,3``, 4 ''-or 2,2 '', 3, 3 ''-p-terphenyltetracarboxylic dianhydride, 2,2-bis (2,3- or 3,4-dicarboxyphenyl) -propane dianhydride, bis (2,3- or 3.4-di Carboxyphenyl) methane dianhydride, bis (2,3- or 3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3- or 3,4-dicarboxyphenyl) ethane dianhydride 1,2,7,8-, 1,2,6,7- or 1,2,9,10-phenanthrene-tetracarboxylic dianhydride, 2,3,6,7-anthracene tetracarboxylic acid Anhydride, 2,2-bis (3,4-dicarboxyphenyl) tetrafluoropropane dianhydride, 2,3,5,6-cyclohexane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5 , 6-Naphthalenetetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 2, 6- or 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7- (or 1,4,5,8-) tetrachloronaphthalene-1, 4,5,8- (or 2,3,6,7-) tetracarboxylic dianhydride, 2,3,8,9-, 3,4,9,10-, 4,5,10,11- Or 5,6,11,12-perylene-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride Anhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'-bis (2,3-dicarboxy Phenoxy) Examples include phenylmethane dianhydride.

<Diamine>
Dimer acid type diamine in which two terminal carboxylic acid groups of dimer acid are substituted with primary aminomethyl group or amino group as diamine component of polyimide raw material used for polyimide insulating layer (A), 4,4′- Diamino-2,2′-dimethylbiphenyl, 4,4′-diamino-3,3′-dimethylbiphenyl, 4,4′-diamino-2,2′-bis (trifluoromethyl) biphenyl, 4,4′- Diaminodiphenyl ether, 2'-methoxy-4,4'-diaminobenzanilide, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 2,2'-bis [ 4- (4-Aminophenoxy) phenyl] propane, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxy-4,4'-diaminobiphenyl, 4,4'-diaminobenzanilide 2,2-bis- [4- (3-aminophenoxy) phenyl] Lopan, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy)] biphenyl, bis [4- (3- Aminophenoxy) biphenyl, bis [1- (4-aminophenoxy)] biphenyl, bis [1- (3-aminophenoxy)] biphenyl, bis [4- (4-aminophenoxy) phenyl] methane, bis [4- ( 3-aminophenoxy) phenyl] methane, bis [4- (4-aminophenoxy) phenyl] ether, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy)] benzophenone, Bis [4- (3-aminophenoxy)] benzophenone, bis [4,4 '-(4-aminophenoxy)] benzanilide, bis [4,4'-(3-aminophenoxy)] benzanilide, 9,9-bis 4- (4-Aminophenoxy) phenyl] fluorene, 9,9-bis [4- (3-aminophenoxy) phenyl] fluorene, 2,2-bis- [4- (4-aminophenoxy) phenyl] hexafluoropropane 2,2-bis- [4- (3-aminophenoxy) phenyl] hexafluoropropane, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4 ' -Methylene-2,6-diethylaniline, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenylethane, 3,3'-diaminodiphenylethane, 4,4 ' -Diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4, 4'-diaminodiphenyl ether, 3,3-di Aminodiphenyl ether, 3,4'-diaminodiphenyl ether, benzidine, 3,3'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 4,4 ''-diamino-p-terphenyl, 3,3 ''-diamino- p-terphenyl, m-phenylenediamine, p-phenylenediamine, 2,6-diaminopyridine, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 4, 4 '-[1,4-phenylenebis (1-methylethylidene)] bisaniline, 4,4'-[1,3-phenylenebis (1-methylethylidene)] bisaniline, bis (p-aminocyclohexyl) methane, bis (p-β-amino-t-butylphenyl) ether, bis (p-β-methyl-δ-aminopentyl) benzene, p-bis (2-methyl-4-aminopentyl) benzene, p-bis (1, 1-dimethyl-5-aminopentyl) benzene, 1,5-diaminonaphthalene, 2,6-diamino Phthalene, 2,4-bis (β-amino-t-butyl) toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine , P-xylylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine and the like.

  Each of the acid anhydrides and diamines may be used alone or in combination of two or more. Also, diamines and acid anhydrides other than those described above can be used together with the above acid anhydrides or diamines. By selecting the types of acid anhydrides and diamines, and the respective molar ratios when using two or more acid anhydrides or diamines, the thermal expansibility, adhesiveness, glass transition temperature, etc. can be controlled. .

The polyimide constituting the polyimide insulating layer (A) preferably has an imide group concentration of 33% or less, and more preferably 32% or less. Here, the “imide group concentration” means a value obtained by dividing the molecular weight of the imide group (— (CO) ₂ —N—) in the polyimide by the molecular weight of the entire structure of the polyimide. When the imide group concentration exceeds 33%, the flame retardancy of the polyimide is lowered and the dielectric properties are also deteriorated due to the increase in polar groups.

  The polyimide which comprises a polyimide insulating layer (A) can be manufactured by making an acid anhydride component and a diamine component react in a solvent, producing | generating a precursor resin, and carrying out heat ring closure. For example, it is a polyimide precursor by dissolving an acid anhydride component and a diamine component in an approximately equimolar amount in an organic solvent and stirring and polymerizing at a temperature in the range of 0 to 100 ° C. for 30 minutes to 24 hours. A polyamic acid is obtained. In the reaction, the reaction components are dissolved so that the precursor to be produced is in the range of 5 to 30% by weight, preferably in the range of 10 to 20% by weight in the organic solvent. Examples of the organic solvent used for the polymerization reaction include N, N-dimethylformamide, N, N-dimethylacetamide (DMAC), N-methyl-2-pyrrolidone, 2-butanone, dimethyl sulfoxide, dimethyl sulfate, cyclohexanone, and dioxane. , Tetrahydrofuran, diglyme, triglyme and the like. Two or more of these solvents can be used in combination, and further, aromatic hydrocarbons such as xylene and toluene can be used in combination. The amount of such organic solvent used is not particularly limited, but the amount used is such that the concentration of the polyamic acid solution (polyimide precursor solution) obtained by the polymerization reaction is about 5 to 30% by weight. It is preferable to adjust and use.

  The synthesized precursor is usually advantageously used as a reaction solvent solution, but can be concentrated, diluted, or replaced with another organic solvent if necessary. Moreover, since a precursor is generally excellent in solvent solubility, it is advantageously used. The method for imidizing the precursor is not particularly limited, and for example, heat treatment such as heating in the solvent at a temperature within the range of 80 to 400 ° C. for 1 to 24 hours is suitably employed.

<Polyimide insulation layer (A) thickness>
The polyimide insulating layer (A) exhibits a function as a protective film, and is preferably 12 μm or more from the viewpoint of transportability during production and adhesive layer coating, and has a dielectric property as a coverlay film. In order to avoid deterioration, it is preferably in the range of 30 μm or less.

From the viewpoint of heat resistance, the polyimide insulating layer (A) preferably has a glass transition temperature (Tg) of 280 ° C. or higher, and more preferably 300 ° C. or higher. Also, from the viewpoint of suppressing warpage when bonded to FPC as a coverlay, the thermal expansion coefficient of the polyimide insulating layer (A) is in the range of 1 × 10 ⁻⁶ to 30 × 10 ⁻⁶ (1 / K). , Preferably 1 × 10 ^{−6 to} 25 × 10 ⁻⁶ (1 / K), more preferably 15 × 10 ^{−6 to} 25 × 10 ⁻⁶ (1 / K). .

In order to reduce dielectric loss when the polyimide insulating layer (A) is used as an insulating layer of a coverlay film on a circuit board such as an FPC, the product of the square root of the dielectric constant and the dielectric loss tangent at 5 GHz, 10 GHz, and 20 GHz, Both are preferably less than 0.01. That is, when the dielectric constant of the polyimide insulating layer (A) at 5 GHz, 10 GHz, and 20 GHz is Dk1, and the dielectric loss tangent is Df1, the following formula (2);
√Dk1 × Df1 <0.01 (2)
It is preferable to satisfy.

  If the product of the square root of dielectric constant and dielectric loss tangent at 5 GHz, 10 GHz, and 20 GHz of the polyimide insulating layer (A) exceeds 0.01, the dielectric properties as a coverlay film also deteriorate and are comparable to conventional coverlay films. Performance. From this, the imide group concentration is preferably 33% or less, and more preferably 32% or less. When the imide group concentration exceeds 33%, the increase in the polar group of the polyimide leads to deterioration of dielectric constant and dielectric loss tangent.

  The polyimide insulating layer (A) may contain an inorganic filler in the polyimide layer as necessary. Specific examples include silicon dioxide, aluminum oxide, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, and calcium fluoride. These may be used alone or in combination of two or more.

[Polyimide adhesive layer (B)]
The resin used for the polyimide adhesive layer (B) is a polyimide obtained by reacting an acid anhydride component containing an aromatic tetracarboxylic acid anhydride component with an aliphatic diamine component. An aromatic diamine may be included as a diamine component. Since polyimide is generally produced by reacting an acid anhydride with a diamine, a specific example of polyimide can be understood by explaining the acid anhydride and diamine. Hereinafter, a preferable polyimide will be described using an acid anhydride and a diamine.

  The resin used for the polyimide adhesive layer (B) is, for example, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (BTDA) or 4,4′-oxydiphthalic anhydride as a raw acid anhydride. Product (ODPA, also known as 5,5′-oxybis-1,3-isobenzofurandione), 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3 ′, 4, 4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), pyromellitic dianhydride (PMDA), 5,5 '-[1-methyl-1,1-ethanediylbis (1,4-phenylene) bisoxy] bis (Isobenzofuran-1,3-dione) (BISDA), 4,4′-diaminodicyclohexylmethane and the like can be used. These can be used alone or in combination of two or more.

<Aliphatic diamine>
The resin used for the polyimide adhesive layer (B) is, for example, a dimer acid type diamine formed by replacing two terminal carboxylic acid groups of dimer acid with primary aminomethyl groups or amino groups, as a raw material diamine component. 4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 2-methyl-1,5-diaminopentane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,3-bis ( Aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, 4,4′-methylenebis Diaminoalkanes such as cyclohexylamine, tris (2-aminoethyl) amine, N, N′-bis (2-aminoethyl) -1,3- Lopandiamine, bis (3-aminopropyl) ethylenediamine, 1,4-bis (3-aminopropyl) piperazine, diethylenetriamine, N-methyl-2,2′-diaminodiethylamine, 3,3′-diaminodipropylamine, N, Amines containing nitrogen atoms such as N-bis (3-aminopropyl) methylamine, bis (3-aminopropyl) ether, 1,2-bis (2-aminoethoxy) ethane, 3,9-bis (3 -Aminopropyl) -2,4,8,10-tetraoxaspiro [5.5] -undecane-containing amines, amines having 2,2'-thiobis (ethylamine) and other sulfur atoms It is desirable to use aliphatic diamines such as these as main components, and these can be used alone or in combination of two or more. Moreover, since the resin used for the polyimide adhesive layer (B) has a low dielectric constant and a low dielectric loss tangent and needs to be soluble, the aliphatic diamine is preferably 60 mol% based on the total diamine. As mentioned above, it is more preferable that it is 80 mol% or more.

<Aromatic diamine>
The resin used for the polyimide adhesive layer (B) is 4,4′-diamino-2,2′-dimethylbiphenyl, 4,4′-diamino-3,3′-dimethylbiphenyl, 4,4, 4′-diamino-2,2′-bis (trifluoromethyl) biphenyl, 4,4′-diaminodiphenyl ether, 2′-methoxy-4,4′-diaminobenzanilide, 1,4-bis (4-aminophenoxy) ) Benzene, 1,3-bis (4-aminophenoxy) benzene, 2,2'-bis [4- (4-aminophenoxy) phenyl] propane, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxy-4,4'-diaminobiphenyl, 4,4'-diaminobenzanilide, 2,2-bis- [4- (3-aminophenoxy) phenyl] propane, bis [4- (4- Aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, bi [4- (4-aminophenoxy)] biphenyl, bis [4- (3-aminophenoxy) biphenyl, bis [1- (4-aminophenoxy)] biphenyl, bis [1- (3-aminophenoxy)] biphenyl, Bis [4- (4-aminophenoxy) phenyl] methane, bis [4- (3-aminophenoxy) phenyl] methane, bis [4- (4-aminophenoxy) phenyl] ether, bis [4- (3-amino Phenoxy) phenyl] ether, bis [4- (4-aminophenoxy)] benzophenone, bis [4- (3-aminophenoxy)] benzophenone, bis [4,4 ′-(4-aminophenoxy)] benzanilide, bis [ 4,4 ′-(3-aminophenoxy)] benzanilide, 9,9-bis [4- (4-aminophenoxy) phenyl] fluorene, 9,9-bis [4- (3-aminophenoxy) phenyl] fluorene, 2,2-bis- [4- 4-Aminophenoxy) phenyl] hexafluoropropane, 2,2-bis- [4- (3-aminophenoxy) phenyl] hexafluoropropane, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi- 2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 4,4'-diaminodiphenylpropane, 3,3'-diaminodiphenylpropane, 4,4'-diaminodiphenylethane, 3,3 '-Diaminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylsulfone, 3 , 3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 3,3-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, benzidine, 3,3'-diaminobiphenyl, 3,3'-dimethoxybenzi Gin, 4,4 ''-diamino-p-terphenyl, 3,3 ''-diamino-p-terphenyl, m-phenylenediamine, p-phenylenediamine, 2,6-diaminopyridine, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 4,4 '-[1,4-phenylenebis (1-methylethylidene)] bisaniline, 4,4'-[1, 3-phenylenebis (1-methylethylidene)] bisaniline, bis (p-aminocyclohexyl) methane, bis (p-β-amino-t-butylphenyl) ether, bis (p-β-methyl-δ-aminopentyl) Benzene, p-bis (2-methyl-4-aminopentyl) benzene, p-bis (1,1-dimethyl-5-aminopentyl) benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2, 4-bis (β-amino-t-butyl) toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m- It may contain aromatic diamines such as xylylenediamine, p-xylylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, etc. These can be used alone or in combination of two or more. Moreover, you may combine with aliphatic diamine. In addition, the resin used for the polyimide adhesive layer (B) has a low dielectric constant and a low dielectric loss tangent and needs to be soluble. Therefore, it is necessary to reduce the ratio of aromatic diamine to total diamine. . For this reason, the aromatic diamine is preferably less than 40 mol%, more preferably less than 20 mol%, based on the total diamine. When the ratio of the aromatic diamine is increased, the solubility in the solvent during the polyimide solution is lowered. Further, since the aromatic skeleton has π electrons, the dielectric constant is increased.

  The resin used for the polyimide adhesive layer (B) can be produced by reacting the acid anhydride component and the diamine component in a solvent to form a precursor resin, and then heat-ring closure. For example, a polyimide solution can be obtained by dissolving an acid anhydride component and a diamine component in an organic solvent in an approximately equimolar amount and stirring for 30 minutes to 24 hours at a temperature within a range of 0 to 200 ° C. . In the reaction, the reaction components are dissolved so that the resulting polyimide is in the range of 5 to 50% by weight, preferably in the range of 20 to 40% by weight, in the organic solvent. Examples of the organic solvent used for the polymerization reaction include N, N-dimethylformamide, N, N-dimethylacetamide (DMAC), N-methyl-2-pyrrolidone, 2-butanone, dimethyl sulfoxide, dimethyl sulfate, cyclohexanone, and dioxane. , Tetrahydrofuran, diglyme, triglyme and the like. Two or more of these solvents can be used in combination, and a solvent azeotropic with water such as xylene and toluene may be used.

  In addition, the resin used for the polyimide adhesive layer (B) includes, in addition to the polyimide resin, other curing resin components such as a plasticizer and an epoxy resin, a curing agent, a curing accelerator, an inorganic filler, a coupling agent, Fillers, pigments, solvents, flame retardants, and the like can be appropriately blended. However, some plasticizers contain a large number of polar groups, and there is a concern that this may promote the diffusion of copper from the copper wiring. Therefore, it is preferable not to use the plasticizer as much as possible.

  The resin for the polyimide adhesive layer (B) obtained as described above has excellent flexibility and thermoplasticity when it is used to form an adhesive layer. For example, FPC, rigid flex circuit It has preferable characteristics as an adhesive for a coverlay film that protects a wiring part such as a substrate. When used as the polyimide adhesive layer (B) of the coverlay film, the adhesive resin composition is applied in a solution state (for example, a varnish containing a solvent) to one side of the film material for the polyimide insulating layer (A). Then, for example, the coverlay film of the present invention having the polyimide insulating layer (A) and the polyimide adhesive layer (B) can be formed by thermocompression bonding at a temperature of 60 to 220 ° C. When a resin component such as a crosslinking agent or an epoxy resin is contained, the crosslinking reaction or the curing reaction of the thermosetting resin can be advanced using the heat during thermocompression bonding. Moreover, even when heat condensation at the time of thermocompression bonding is not sufficient, heat treatment can be further performed after thermocompression bonding for heat condensation. When heat treatment is performed after thermocompression bonding, the heat treatment temperature is preferably, for example, 60 to 220 ° C, and more preferably 80 to 200 ° C. Moreover, after apply | coating the resin composition for polyimide adhesive layers (B) on the arbitrary base materials in the state of a solution (for example, varnish shape containing a solvent), for example, after drying at the temperature of 80-180 degreeC. By peeling, an adhesive film for the polyimide adhesive layer (B) is formed, and this adhesive film is thermocompression bonded with the film material for the polyimide insulating layer (A) at a temperature of 60 to 220 ° C., for example. Also, the coverlay film of the present embodiment can be formed. The resin for the polyimide adhesive layer (B) may be used by forming a coating film in a solution state by screen printing on an arbitrary substrate and drying it at a temperature of, for example, 80 to 180 ° C. it can. Preferably, a cured product can be formed by further heat-treating at a temperature of 130 to 220 ° C. for a predetermined time to completely cure the coating film.

  The features of the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited to the examples. In the following examples, unless otherwise specified, various measurements and evaluations are based on the following.

[Measurement of dielectric constant and dissipation factor]
Using a vector network analyzer (manufactured by Agilent, trade name E8363C) and an SPDR resonator, the dielectric constant and dielectric loss tangent of the resin sheet at a predetermined frequency were measured. In addition, the material used for the measurement was left for 24 hours under the conditions of temperature; 24-26 ° C., humidity: 45-55%.

Abbreviations used in Examples and Comparative Examples indicate the following compounds.
(A) Polyimide raw material BTDA: 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride BPDA: 3,3 ′, 4,4′-diphenyltetracarboxylic dianhydride PMDA: pyromellitic dianhydride Product m-TB: 2,2′-dimethyl-4,4′-diaminobiphenyl DDA: Aliphatic diamine having 36 carbon atoms (trade name; PRIA, manufactured by Croda Japan Co., Ltd.)
MINE 1074, amine value: 210 mg KOH / g, mixture of cyclic and chain-structured dimer diamine, content of dimer component: 95% by weight or more)
N-12: Dodecanedioic acid dihydrazide

(B) Insulating base material Insulating base material (1): material: liquid crystal polymer, thickness: 25 μm
Insulating substrate (2): Material: Polyimide, Thickness: 25 μm

(C) Release substrate Release substrate (1): Material: PET, surface treatment; silicone treatment, thickness 38 μm

(D) Copper foil Copper foil (1): Electrolytic copper foil, thickness: 12.5 μm, surface roughness Rz on the polyimide insulating layer coating side: 1.5 μm

<Resin synthesis for polyimide insulation layer>
In the formation of the polyimide insulating layer used in Examples and Comparative Examples, the synthesis of the polyamic acid used is according to Synthesis Example 1 below.

[Synthesis Example 1]
Under a nitrogen stream, a 500 ml separable flask was charged with 3.86 g DDA (0.0072 mol), 18.94 g m-TB (0.089 mol) and 255 g DMAc and stirred at room temperature. Dissolved. Next, 5.60 g of BPDA (0.019 mol) and 16.60 g of PMDA (0.076 mol) were added, and then the polymerization reaction was continued for 3 hours at room temperature to obtain a polyamic acid solution a. It was. The polyamic acid solution a had a solid content concentration of 15% by weight and a solution viscosity of 31000 cps.

<Resin synthesis for polyimide adhesive layer>
In the formation of the polyimide adhesive layer used in the examples and comparative examples, the synthesis of the polyimide used is based on the following synthesis examples 2 and 3.

[Synthesis Example 2]
Under a nitrogen stream, a 500 ml separable flask was charged with 44.98 g BTDA (0.139 mol), 75.02 g DDA (0.140 mol), 168 g N-methyl-2-pyrrolidone and 112 g xylene. The mixture was charged and mixed well at 40 ° C. for 30 minutes to obtain a polyamic acid solution. This polyamic acid solution was heated to 190 ° C., heated and stirred for 4.5 hours, and 112 g of xylene was added to obtain a polyimide solution b in which imidization was completed. The resulting polyimide solution b had a solid content of 29.1% by weight and a viscosity of 7800 cps. Moreover, the weight average molecular weight (Mw) of the polyimide solution b was 87,700.

[Synthesis Example 3]
34.4 g (10 g as a solid content) of the polyimide solution b obtained in Synthesis Example 2, 1.25 g of N-12 and 2.5 g of Exolit OP935 (manufactured by Clariant Japan Co., Ltd.) were blended, and 1.297 g of N-methyl-2-pyrrolidone and 3.869 g of xylene were added and diluted to obtain a polyimide adhesive solution c. The resulting polyimide adhesive solution c had a solid content concentration of 32.5% by weight and a viscosity of 3100 cps.

<Preparation of polyimide insulation layer film>
Production of the polyimide insulating layer films used in Examples and Comparative Examples is based on Production Examples 1 and 2 below.

[Production Example 1]
After the polyamic acid solution a obtained in Synthesis Example 1 is uniformly applied to one side (surface roughness Rz; 1.5 μm) of the copper foil (1) so that the thickness after curing is 12.5 μm, 120 The solvent was removed by heat drying at ° C. Furthermore, stepwise heat treatment was performed from 120 ° C. to 360 ° C. to complete imidization. With respect to the obtained metal-clad laminate, the copper foil was removed by etching using a ferric chloride aqueous solution to obtain a polyimide insulating layer film 1.

[Production Example 2]
A polyimide insulating layer film 2 was obtained in the same manner as in Production Example 1 except that the thickness after curing was 25 μm.

<Preparation of polyimide adhesive layer film>
The production of the polyimide adhesive layer film used in the measurement of dielectric constant and dielectric loss tangent described in Examples and Comparative Examples is according to Production Example 3 below.

[Production Example 3]
The polyimide adhesive solution c obtained in Synthesis Example 3 is applied to the silicone-treated surface of the release substrate (1) (length × width × thickness = 320 mm × 240 mm × 25 μm) so that the thickness after drying is 25 μm. And then dried by heating at 80 ° C. for 15 minutes. Furthermore, after heat-treating at 180 ° C. for 2 hours to completely remove the solvent, it was peeled from the release substrate (1) to obtain a polyimide adhesive layer film 1.

[Example 1]
The polyimide adhesive solution c obtained in Synthesis Example 3 is applied to the copper foil removal surface of the polyimide insulating layer film 1 (length × width × thickness = 320 mm × 240 mm × 25 μm) so that the thickness after drying becomes 15 μm. And then dried by heating at 80 ° C. for 15 minutes. Furthermore, heat treatment was performed at 180 ° C. for 2 hours to completely remove the solvent, and the coverlay film 1 was obtained.

[Examples 2 to 4 and Comparative Example 1]
Coverlay films 2 to 5 were produced in the same manner as in Example 1 except that the thicknesses of the polyimide insulating layer film and the polyimide adhesive layer film were combinations shown in Tables 1 and 2.

[Comparative Example 2]
A coverlay film 6 was obtained in the same manner as in Example 1 except that the insulating substrate (1) was used as the polyimide insulating layer film.

[Comparative Example 3]
A coverlay film 7 was obtained in the same manner as in Example 1 except that the insulating base material (2) was used as a polyimide insulating layer film.

  As mentioned above, although embodiment of this invention was described in detail for the purpose of illustration, this invention is not restrict | limited to the said embodiment, A various deformation | transformation is possible.

Claims (1)

A cover lay film including a polyimide insulating layer (A) and a polyimide adhesive layer (B) provided on one surface of the polyimide insulating layer (A),
The following i-ha configuration:
A) The thickness (L1) of the polyimide insulating layer (A) is in the range of 12 μm to 30 μm;
B) The polyimide adhesive layer (B) has a thickness (L2) in the range of 10 μm to 40 μm;
C) The dielectric constant at any frequency of 5 GHz, 10 GHz, and 20 GHz in the coverlay film is Dk12, the dielectric loss tangent is Df12, and at any frequency of 5 GHz, 10 GHz, and 20 GHz in the polyimide insulating layer (A). When the dielectric constant of the above is Dk1, the dielectric loss tangent is Df1, the dielectric loss tangent at 5 GHz in the coverlay film is Df12-5 GHz, and the dielectric loss tangent at 20 GHz is Df12-20 GHz, the following formula (1) : Satisfying formula (2), formula (3) and formula (4) ;
√Dk12 × Df12 <0.007…… (1)
√Dk1 × Df1 <0.01 (2)
[However, √Dk1 × Df1> 0.007]
L2 / (L1 + L2)> 0.40 ... (3)
Df12-20GHz / Df12-5GHz ≦ 1 ... (4)
A cover lay film comprising: