JP2022155041A - Flexible metal-clad laminate sheet and flexible circuit board - Google Patents

Abstract

To provide excellent crease resistance to an FPC formed from a flexible metal-clad laminate sheet, even when a polyimide insulation layer thickness is set to 50 μm or more in order to apply the flexible metal-clad laminate sheet on which a polyimide insulation layer as a dielectric is laminated on a metal layer to high frequency use.SOLUTION: A flexible metal-clad laminate sheet used for a flexible circuit board that is folded and housed in a housing of an electronic device by folding so that an upper surface side is turned by 180 degrees and is folded to be a lower surface side, has: an insulation resin layer having a thickness of 50 μm or more and 150 μm or less and a tensile elastic modulus (TM1) within a range of 1 GPa or more and 7 GPa or less; and a metal layer laminated on at least one surface of the insulating resin layer. A tensile elastic modulus (TM2) in a range of 5 μm in a thickness direction from an interface with the metal layer in the insulating resin layer is in a range of 2 GPa or more and 10 GPa or less, and the tensile elastic modulus (TM2) is larger than the tensile elastic modulus (TM1).SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a flexible metal-clad laminate and a flexible circuit board.

In recent years, a flexible circuit board (FPC) obtained by processing the copper foil of a flexible metal-clad laminate in which a polyimide insulating layer is provided on a copper foil into a wiring circuit is placed at an angle of 180 degrees to the upper surface side (circuit formation side). A technique has been proposed in which an FPC is folded by "sweep folding" in which an FPC is inverted and folded so that it faces the bottom side, and the folded FPC (that is, FPC for folding use) is housed in a thin housing of a light, thin, and small electronic device. (Patent Document 1). In this technology, in order to prevent the occurrence of disconnection or cracking due to "folding" in the wiring circuit of the FPC, the polyimide insulating layer of the FPC is a laminate of two types of polyimide layers with different coefficients of thermal expansion. In addition, the thickness and tensile modulus of the entire polyimide insulating layer are set within a specific range, the surface roughness of the copper foil is set within a specific range, and a predetermined bending coefficient is set within a specific range. is proposed.

By the way, when a flexible metal-clad laminate for FPC is applied to high-frequency applications, it is widely practiced to increase the thickness of a polyimide insulating layer, which is a dielectric, in order to improve high-frequency characteristics. For this reason, attempts have been made to increase the thickness of the polyimide insulating layer of the folded FPC described in Patent Document 1 so as to apply it to high frequency applications.

Patent No. 6320031

However, in the FPC for folding use of Patent Document 1, the thickness range of the polyimide insulating layer can only be accommodated within the range of 5 to 30 μm. It was concluded that the realization of good "folding resistance" has not been studied at all, and rather, the folding resistance is greatly reduced when an FPC with a polyimide insulating layer having a thickness of more than 30 μm is folded. (see paragraph 0020 of Patent Document 1).

An object of the present invention is to provide a flexible metal-clad laminate in which a polyimide insulating layer is laminated as a dielectric on a metal layer. An object of the present invention is to impart good creasing resistance to an FPC made from a plate.

As a result of extensive research, the present inventors have found that, in order to apply FPC to high-frequency applications, the polyimide insulating layer of the flexible metal-clad laminate, which is the material for manufacturing FPC, is made thicker by laminating a plurality of polyimide layers. In this case, it was found that not only the tensile elastic modulus of the entire polyimide insulating layer but also the tensile elastic modulus of the metal layer adjacent region of the polyimide insulating layer is greatly related to the folding resistance of the FPC. completed.

That is, the present invention provides a flexible metal-clad laminate used for a flexible circuit board that is folded and housed in a housing of an electronic device by folding so that the upper surface side is turned 180 degrees to become the lower surface side,
an insulating resin layer having a thickness in the range of 50 μm or more and 150 μm or less and a tensile elastic modulus (TM1) in the range of 1 GPa or more and 7 GPa or less;
a metal layer laminated on at least one surface of the insulating resin layer,
The tensile elastic modulus (TM2) in the range of 5 μm in the thickness direction from the interface with the metal layer in the insulating resin layer is in the range of 2 GPa or more and 10 GPa or less, and the tensile elastic modulus (TM2) is the tensile elastic modulus ( To provide a flexible metal-clad laminate characterized by being larger than TM1).

In the flexible metal ^- clad laminate of the present invention, the value (RF/L ³ ) is preferably in the range of 400 N/mm ⁵ or more and 1200 N/mm ⁵ or less.

Moreover, in the flexible metal-clad laminate of the present invention, the thickness of the metal layer is preferably in the range of 6 μm or more and 15 μm or less.

Furthermore, in the flexible metal-clad laminate of the present invention, the insulating resin layer is formed by laminating a plurality of polyimide layers, has a polyimide layer (A) as a central layer of the plurality of polyimide layers, and the polyimide layer (A ) is preferably in the range of 0.5 to 0.96 with respect to the total thickness of the insulating resin layer.

Such a polyimide layer (A) preferably has a tensile modulus of 1 GPa or more and 5 GPa or less.

The present invention provides a flexible circuit board in which the metal layer of the above flexible metal-clad laminate is wired. The flexible circuit board is preferably folded such that the metal layer is folded inwards.

The flexible metal-clad laminate of the present invention comprises an insulating resin layer having a thickness in the range of 50 μm to 150 μm and a tensile modulus (TM1) in the range of 1 GPa to 7 GPa, and at least one surface of the insulating resin layer. and a laminated metal layer. In this insulating resin layer, the tensile elastic modulus (TM2) within a range of 5 μm in the thickness direction from the interface with the metal layer is in the range of 2 GPa or more and 10 GPa or less, and the tensile elastic modulus (TM2) is the tensile elastic modulus. greater than the rate (TM1). Therefore, the flexible metal-clad laminate of the present invention, in which an insulating resin layer is laminated on a metal layer, exhibits good resistance to folding and is useful as a material for manufacturing FPCs suitable for high-frequency applications. ing.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing which shows the structure of the flexible single-sided metal-clad laminate of one embodiment of this invention. FIG. 4 is a schematic cross-sectional view showing the configuration of a flexible double-sided metal-clad laminate according to another embodiment of the present invention; FIG. 2 is a schematic cross-sectional view showing the configuration of a preferred embodiment of the flexible single-sided metal-clad laminate of FIG. 1; FIG. 3 is a schematic cross-sectional view showing the configuration of a preferred embodiment of the flexible double-sided metal-clad laminate of FIG. 2; It is a cross-sectional explanatory view of a multilayer polyimide layer for calculating the average tensile modulus. FIG. 3 is a plan explanatory view showing the state of copper wiring of a test circuit board piece used in Examples. FIG. 10 is a side explanatory view showing the state of the sample stage and the test circuit board piece in the bending test (a state diagram in which the test circuit board piece is fixed on the sample stage); FIG. 10 is a side explanatory view showing the state of the sample stage and the test circuit board piece in the bending test (state diagram before pressing the bending portion of the test circuit board piece with a roller). FIG. 10 is a side explanatory view showing the state of the sample stage and the test circuit board piece in the bending test (a diagram showing the state in which the bent portion of the test circuit board piece is pressed by a roller). FIG. 10 is a side explanatory view showing the state of the sample stage and the test circuit board piece in the bending test (the state diagram of the test piece being returned to a flat state by opening the bending portion); FIG. 10 is a side explanatory view showing the state of the sample stage and the test circuit board piece in the bending test (a state diagram of flattening the crease portion of the bending portion by pressing with a roller). It is cross-sectional explanatory drawing (part) of a flexible circuit board. FIG. 3 is a schematic cross-sectional view of a laminate used for calculation of equivalent bending rigidity of a flexible metal-clad laminate.

Embodiments of the present invention will be described with reference to the drawings as appropriate.

[Flexible metal-clad laminate]
FIG. 1 is a schematic cross-sectional view showing the configuration of a flexible single-sided metal-clad laminate according to one embodiment of the present invention. The flexible single-sided metal-clad laminate (CA) of this embodiment has a metal layer (MA) and an insulating resin layer (X) laminated on one side of the metal layer (MA). The insulating resin layer (X) has a structure in which a bottom insulating resin layer (PA) and an adhesive layer (BA) are laminated, and the bottom insulating resin layer (PA) is arranged on the metal layer (MA) side. . The bottom insulating resin layer (PA) and the adhesive layer (BA) are preferably each composed of a polyimide layer.

FIG. 2 is a schematic cross-sectional view showing the configuration of a flexible double-sided metal-clad laminate according to another embodiment of the present invention. This flexible double-sided metal-clad laminate (C) has a structure in which a pair of metal layers (M1, M2) sandwich an insulating resin layer (X). It has a structure in which (CA) is bonded with an adhesive layer (B). That is, the flexible double-sided metal-clad laminate (C) includes a first single-sided metal-clad laminate (C1), a second single-sided metal-clad laminate (C2), and these first single-sided metal-clad laminates (C1 ) and the adhesive layer (B) laminated between the second single-sided metal-clad laminate (C2). Here, the first single-sided metal-clad laminate (C1) comprises a first metal layer (M1) and a first insulating resin layer laminated on at least one surface of the first metal layer (M1). (P1) and The second single-sided metal-clad laminate (C2) comprises a second metal layer (M2) and a second insulating resin layer (P2) laminated on at least one surface of the second metal layer (M2). and have The adhesive layer (B) is arranged so as to contact the first insulating resin layer (P1) and the second insulating resin layer (P2). That is, the flexible double-sided metal-clad laminate (C) comprises a first metal layer (M1)/first insulating resin layer (P1)/adhesive layer (B)/second insulating resin layer (P2)/second of metal layers (M2) are laminated in this order. The first metal layer (M1) and the second metal layer (M2) are positioned on the outermost side, respectively, and the first insulating resin layer (P1) and the second insulating resin layer (P2) are located inside them. Further, an adhesive layer (B) is interposed between the first insulating resin layer (P1) and the second insulating resin layer (P2). The first insulating resin layer (P1), the second insulating resin layer (P2), and the adhesive layer (B) are each preferably composed of a polyimide layer.

(Layer thickness of insulating resin layer)
The insulating resin layer (X) constituting the flexible metal-clad laminate of the present invention has a layer thickness of 50 μm or more and 150 μm or less, preferably 50 μm or more and 125 μm or less, in order to produce an FPC for high frequency applications from the flexible metal-clad laminate. have. If the layer thickness is below this range, the wiring width becomes narrow from the viewpoint of impedance control, which is essential for high-frequency FPC boards, and it becomes difficult to control variations in wiring width during wiring processing in the subtractive method. As a result, there is a tendency that impedance mismatching tends to occur at the junction with other parts.

(tensile modulus of the entire insulating resin layer)
In the flexible metal-clad laminate of the present invention, the insulating resin layer (X) as a whole exhibits a tensile elastic modulus (TM1) of 1 GPa or more and 7 GPa or less, preferably 2 GPa or more and 6 GPa or less. If the tensile modulus of elasticity (TM1) is less than this range, the rigidity of the substrate itself is low when it is mounted on an electronic device after being severely bent at 180 degrees. As a result, if it is exceeded, the flexural rigidity of the substrate itself increases, which tends to cause problems such as springback when mounted on an electronic device. Therefore, if the tensile modulus of elasticity (TM1) is within this range, even a substrate using a thick insulator is less likely to cause problems when mounted on an electronic device. The tensile modulus of elasticity is measured by removing the metal layer by etching and removing the remaining insulating resin layer (X) under an environment of a temperature of 23° C. and a relative humidity of 50% using a commercially available tensile elasticity tester (for example, It can be carried out using Strograph R-1) manufactured by Toyo Seiki Seisakusho.

(Tensile elastic modulus in the vicinity of the metal layer of the insulating resin layer)
In the flexible metal-clad laminate of the present invention, not only the tensile modulus (TM1) of the entire insulating resin layer (X) but also the insulating resin layer (X) within a range of 5 μm in the thickness direction from the interface with the metal layer Focusing on the tensile modulus (TM2) of This is because, when the substrate is severely bent at 180 degrees as described above, if the rigidity of the insulating resin layer near the metal wiring is low, the bending tip of the wiring becomes a sharp angle. This is because the damage to the copper wiring increases. Therefore, the flexible metal-clad laminate of the present invention exhibits a tensile modulus (TM2) of 2 GPa or more and 10 GPa or less, preferably 4 GPa or more and 7 GPa or less. If the tensile modulus (TM2) is below this range, the rigidity in the vicinity of the interface with the copper foil cannot be expressed, and if it exceeds this range, the rigidity tends to be too high and the copper foil tends to be damaged. Therefore, if the tensile modulus of elasticity (TM2) is within this range, the wire shape at the tip of the bent portion does not become sharp, and good bending resistance can be maintained.

The tensile modulus (TM2) should be greater than the tensile modulus (TM1), preferably more than 1 and 3 times or less. This is because if the tensile elastic modulus (TM2) is equal to or lower than the tensile elastic modulus (TM1), there is concern that the rigidity of the entire insulating resin layer will become too high.

(equivalent bending stiffness)
In the flexible metal-clad laminate of the present invention, attention is focused on the equivalent bending rigidity (RF) [N/mm ² ]. If the numerical value of the equivalent bending rigidity becomes small, there is concern that the flexible metal-clad laminate will not be able to maintain the minimum necessary rigidity as a copper wiring board. This is because there is concern that problems such as springback may develop due to the high repulsive force when mounted on an electronic device. Therefore, the equivalent bending rigidity (RF) [N/mm ² ] of the flexible metal-clad laminate of the present invention is preferably 0.1 N/mm ² or more and 3.0 N/mm ² or less, more preferably 0.5 N/mm ² or more and 2.0 N/mm ² or less. The equivalent bending stiffness can be calculated according to paragraphs 0030 to 0038 and 0055 to 0058 of JP-A-2016-146419.

As described above, the flexible metal-clad laminate of the present invention has an equivalent bending stiffness within a preferable numerical range, but the equivalent bending stiffness increases as the total thickness increases. Therefore, as a parameter in a state where the influence of the total thickness is minimized, the numerical value obtained by dividing the numerical value of the equivalent bending rigidity by the cube of the total thickness (L) [mm] of the flexible metal-clad laminate (RF/L ³ ) Evaluate with The dimension of this numerical value (RF/L ³ ) is [N/mm ⁵ ].

In the flexible metal-clad laminate of the present invention, the numerical range of such “RF/L ³ ” is preferably 400 N/mm ⁵ or more and 1200 N/mm ⁵ or less, more preferably 400 N/mm ⁵ or more and 900 N/mm ⁵ or less. is. If the numerical range of “RF/L ³ ” falls below this range, the copper wiring board cannot maintain the minimum necessary rigidity, and if it exceeds this range, the repulsive force tends to increase.

(When the insulating resin layer is composed of multiple polyimide layers)
In the flexible metal-clad laminate of the present invention, the insulating resin layer (X) may be a single polyimide layer, but it is preferably constructed by laminating a plurality of polyimide layers as shown in FIGS. This makes it easier to increase the thickness of the insulating resin layer (X), thereby lowering the hurdles in applying the FPC to high-frequency applications. In the case of the single-sided metal layer type as shown in FIG. 1, the insulating resin layer (X) is preferably a laminate of two polyimide layers. , The insulating resin layer (X) is preferably a laminate of three polyimide layers.

When the insulating resin layer (X) of the flexible metal-clad laminate of the present invention is composed of a laminate of a plurality of polyimide layers, the thickness of the polyimide layer (A) as the central layer of the insulating resin layer (X) is The total thickness of the insulating resin layer (X) is preferably 0.5 or more and 0.96 or less. If the ratio of the thickness of the polyimide layer (A) to the total thickness of the insulating resin layer (X) is below this range, the dielectric loss tangent of the insulating resin layer (X) becomes insufficient, and sufficient dielectric properties cannot be obtained. If it exceeds, there is a tendency that problems such as deterioration of the dimensional stability of the insulating resin layer (X) occur. Here, the center layer of the insulating resin layer (X) is the polyimide layer laminated in the middle when three or more odd-numbered polyimide layers are laminated, and four or more even-numbered polyimide layers. is the thicker of the two middle adjacent polyimide layers. When two polyimide layers are laminated, it means the polyimide layer directly laminated on the polyimide layer in contact with the metal layer. Accordingly, the polyimide layer (A) corresponds to the adhesive layer (BA) in FIG. 1, and the polyimide layer (A) corresponds to the adhesive layer (B) in FIG.

The tensile modulus of the polyimide layer (A) contained in the insulating resin layer (X) of the flexible metal-clad laminate of the present invention is preferably in the range of 0.1 GPa or more and 5 GPa or less, more preferably 0.2 GPa or more and 3 GPa or less. is. If the tensile modulus of the polyimide layer (A) is within this range, it is possible to reduce the occurrence of wrinkles, prevent air bubbles from being trapped during lamination, and improve handling properties. Further, for the polyimide layer (A), it is preferable to specify the storage elastic modulus in addition to the tensile elastic modulus from the viewpoint of stress relaxation during thermocompression bonding. Specifically, the storage modulus of the polyimide layer (A) at 50° C. is preferably 1800 MPa or less, and the maximum value of the storage modulus at 180 to 260° C. is preferably 800 MPa or less, more preferably 500 MPa or less. is. By controlling the storage elastic modulus within such a range, warping is less likely to occur even after the solder reflow process after circuit processing. The storage elastic modulus can be measured using a commercially available viscoelasticity measuring device.

<Flexible single-sided metal-clad laminate>
The configuration of the flexible single-sided metal-clad laminate (CA) and the pair of single-sided metal-clad laminates (C1, C2) is not particularly limited, and general FPC materials can be used, and commercially available copper-clad laminates can be used. and so on. The configurations of the first single-sided metal-clad laminate (C1) and the second single-sided metal-clad laminate (C2) may be the same or different.

(metal layer)
Materials for the metal layer (MA), the first metal layer (M1) and the second metal layer (M2) are not particularly limited, but examples include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, Indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, alloys thereof, and the like. Among these, copper or a copper alloy is particularly preferable. The materials of the wiring layers in the circuit board of this embodiment, which will be described later, are also the same as those of the metal layer (MA), the first metal layer (M1) and the second metal layer (M2).

The thicknesses of the metal layer (MA), the first metal layer (M1) and the second metal layer (M2) are not particularly limited, but from the viewpoint of production stability and handling properties, preferably 5 μm or more and 35 μm or less. , and more preferably 25 μm or less. Particularly preferably, the thickness is 6 μm or more and 15 μm or less. When a metal foil such as copper foil is used as the metal layer, the thickness is preferably 35 μm or less, more preferably in the range of 5 to 25 μm. The lower limit of the thickness of the metal foil is preferably 5 μm from the viewpoint of production stability and handling. When copper foil is used, it may be rolled copper foil or electrolytic copper foil. Moreover, as a copper foil, the copper foil marketed can be used.

In addition, the metal foil may be subjected to surface treatment with, for example, siding, aluminum alcoholate, aluminum chelate, silane coupling agent, etc., for the purpose of rust prevention treatment and adhesion strength improvement.

(insulating resin layer)
The insulating resin layer (X) has a structure in which a bottom insulating resin layer (PA) and an adhesive layer (BA) are laminated in FIG. It has a structure in which two insulating resin layers (P2) sandwich the adhesive layer (B).

(Bottom insulating resin layer, first insulating resin layer, second insulating resin layer)
The bottom insulating resin layer (PA), the first insulating resin layer (P1), and the second insulating resin layer (P2) are not particularly limited as long as they are made of a resin having electrical insulation. For example, polyimide, epoxy resin, phenol resin, polyethylene, polypropylene, polytetrafluoroethylene, silicone, ETFE, etc. can be used, but polyimide is preferred. In addition, the bottom insulating resin layer (PA), the first insulating resin layer (P1) and the second insulating resin layer (P2) are not limited to single layers, and may be laminated with a plurality of resin layers. good. In the present invention, the term "polyimide" means a resin composed of a polymer having an imide group in its molecular structure, such as polyamideimide, polyetherimide, polyesterimide, polysiloxaneimide, and polybenzimidazoleimide, in addition to polyimide.

(adhesion layer)
The adhesive layer (BA) and the adhesive layer (B) constituting the insulating resin layer (X) are the polyimide layers when the insulating resin layer (X) is formed by laminating a plurality of polyimide layers. Thermoplastic polyimide corresponding to (A) and containing a tetracarboxylic acid residue derived from a tetracarboxylic dianhydride and a diamine residue derived from a diamine compound (hereinafter referred to as "adhesive polyimide" there is).

In the present invention, the term "tetracarboxylic acid residue" means a tetravalent group derived from a tetracarboxylic dianhydride, and the term "diamine residue" refers to a divalent group derived from a diamine compound. means the basis of The term "thermoplastic polyimide" generally refers to a polyimide whose glass transition temperature (Tg) can be clearly identified. A polyimide having a storage modulus of 1.0×10 ⁸ Pa or more at 300° C. and less than 3.0×10 ⁷ Pa at 300° C. In addition, "non-thermoplastic polyimide" generally refers to polyimide that does not soften or exhibit adhesiveness when heated.
A polyimide having a storage modulus of 1.0×10 ⁹ Pa or more at 0° C. and a storage modulus of 3.0×10 ⁸ Pa or more at 300° C.

(tetracarboxylic acid residue)
The adhesive polyimide can contain, without particular limitation, a tetracarboxylic acid residue derived from a tetracarboxylic dianhydride generally used in thermoplastic polyimides. , a total of 90 tetracarboxylic acid residues (hereinafter sometimes referred to as “tetracarboxylic acid residues (1)) derived from a tetracarboxylic dianhydride represented by the following general formula (1) It is preferable to contain the tetracarboxylic acid residue (1) in a total of 90 mol parts or more with respect to 100 mol parts of the tetracarboxylic acid residue, thereby improving the flexibility and heat resistance of the adhesive polyimide. If the total amount of tetracarboxylic acid residues (1) is less than 90 mol parts, the solubility of the adhesive polyimide in solvents tends to decrease.

In general formula (1), X represents a single bond or a divalent group selected from the following formulae.

In the above formula, Z represents -C ₆ H ₄ -, -(CH ₂ ) _n - or -CH ₂ -CH(-O-C(=O)-CH ₃ )-CH ₂ -, where n is 1 Indicates an integer from ~20.

Tetracarboxylic dianhydrides for deriving the tetracarboxylic acid residue (1) include, for example, 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3′, 4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), 4,4'-oxydiphthalic dianhydride (ODPA ), 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propanoic dianhydride (BPADA), Examples include p-phenylene bis(trimellitic acid monoester dianhydride) (TAHQ), ethylene glycol bisanhydrotrimellitate (TMEG), and the like.

The adhesive polyimide can contain a tetracarboxylic acid residue derived from an acid anhydride other than the tetracarboxylic dianhydride represented by the above general formula (1) as long as the effects of the invention are not impaired. . Such tetracarboxylic acid residues are not particularly limited, but examples include pyromellitic dianhydride, 1,4-phenylenebis(trimellitic acid monoester) dianhydride, 4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'- or 2,3,3',4'-benzophenonetetracarboxylic 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-dicarboxyphenyl)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-anthracenetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)tetrafluoropropane dianhydride, 2,3,5,6-cyclohexane dianhydride, 1,2, 5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-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, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride anhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride, ethylene glycol bisanhydrotri Examples include tetracarboxylic acid residues derived from aromatic tetracarboxylic dianhydrides such as mellitate.

(diamine residue)
The adhesive polyimide contains 20 mol parts or more, preferably 40 mol parts or more, more preferably 60 mol parts or more of the dimer acid-type diamine residue derived from the dimer acid-type diamine with respect to 100 mol parts of the diamine residue. contains. By containing the dimer acid-type diamine residue in the above amount, the dielectric properties of the adhesive layers (BA) and (B) are improved, and the glass transition temperature of the adhesive layers (BA) and (B) is lowered ( By lowering the Tg, the thermocompression bonding property can be improved, and by lowering the elastic modulus of the adhesive layers (BA) and (B), the internal stress can be relaxed. When the dimer acid-type diamine residue is less than 20 mol parts with respect to 100 mol parts of the diamine residue, the bottom insulating resin layer (PA), the first insulating resin layer (P1) and the second insulating resin layer The adhesive layers (BA) and (B) interposed between (P2) may not have sufficient adhesiveness, and the elastic modulus of the adhesive layers (BA) and (B), which have high thermal expansibility is high, the post-etching dimensional change rate of the metal layer (MA), the first metal layer (M1) and the second metal layer (M2) may deteriorate.

Here, the dimer acid-type diamine means that the two terminal carboxylic acid groups (-COOH) of the dimer acid are substituted with primary aminomethyl groups (-CH ₂ -NH ₂ ) or amino groups (-NH ₂ ). means a diamine consisting of Dimer acid is a known dibasic acid obtained by an intermolecular polymerization reaction of unsaturated fatty acids, and its industrial production process is almost standardized in the industry. It is obtained by dimerization with Etc. Industrially obtained dimer acid is mainly composed of dibasic acid with 36 carbon atoms obtained by dimerizing unsaturated fatty acids with 18 carbon atoms such as oleic acid and linoleic acid. , any amount of monomeric acids (18 carbon atoms), trimer acids (54 carbon atoms), and other polymerized fatty acids of 20 to 54 carbon atoms. In the present invention, it is preferable to use dimer acid whose content is increased to 90% by weight or more by molecular distillation. Moreover, although a double bond remains after the dimerization reaction, in the present invention, the dimer acid includes the one which is further hydrogenated to reduce the degree of unsaturation.

As a feature of the dimer acid-type diamine, it is possible to impart properties derived from the skeleton of the dimer acid to the polyimide. That is, the dimer acid-type diamine is a macromolecular aliphatic with a molecular weight of about 560 to 620, so that the molar volume of the molecule can be increased and the polar groups of the polyimide can be relatively reduced. Such features of the dimer acid-type diamine are considered to contribute to improving the dielectric properties by reducing the dielectric constant and the dielectric loss tangent while suppressing the deterioration of the heat resistance of the polyimide. In addition, since it has two freely moving hydrophobic chains having 7 to 9 carbon atoms and two chain aliphatic amino groups having a length close to 18 carbon atoms, it not only gives the polyimide flexibility, Since polyimide can have an asymmetrical chemical structure or a non-planar chemical structure, it is thought that a low dielectric constant and a low dielectric loss tangent of polyimide can be achieved.

Dimer acid-type diamines are commercially available, for example, PRIAMINE 1073 (trade name), PRIAMINE 1074 (trade name), and PRIAMINE 1075 (trade name) manufactured by Croda Japan, Versamin 551 (trade name) manufactured by BASF Japan. ), Versamin 552 (trade name), and the like.

Further, the adhesive polyimide contains a diamine residue derived from at least one diamine compound selected from diamine compounds represented by the following general formulas (B1) to (B7), based on 100 mol parts of all diamine components. The total content is preferably in the range of 20 to 80 mol parts, more preferably in the range of 20 to 60 mol parts. Since the diamine compounds represented by the general formulas (B1) to (B7) have a flexible molecular structure, by using at least one diamine compound selected from these in an amount within the above range, the polyimide molecule It can improve chain flexibility and impart thermoplasticity. If the total amount of the diamine compounds represented by the general formulas (B1) to (B7) exceeds 80 mol parts per 100 mol parts of all the diamine components, the flexibility of the polyimide becomes insufficient and Tg increases. , the residual stress due to thermocompression bonding increases, and the post-etching dimensional change rate tends to deteriorate.

In formulas (B1) to (B7), R ₁ independently represents a monovalent hydrocarbon group having 1 to 6 carbon atoms or an alkoxy group, and the linking group A independently represents -O-, -S-, -CO- , -SO-, -SO ₂ -, -COO-, -CH ₂ -, -C(CH ₃ ) ₂ -, -NH- or -CONH-, n1 is independently 0 Indicates an integer from ~4. However, the formula (B3) that overlaps with the formula (B2) is excluded, and the formula (B5) that overlaps with the formula (B4) is excluded.

The term "independently" means that in one or more of the above formulas (B1) to (B7), multiple linking groups A, multiple R1 or multiple n1 may be the same or , which means it can be different. Further, in formulas (B1) to (B7), the hydrogen atoms in the two terminal amino groups may be substituted, for example —NR ₂ R ₃ (wherein R ₂ and R ₃ are independently alkyl (meaning any substituent such as a group).

The diamine represented by formula (B1) (hereinafter sometimes referred to as "diamine (B1)") is an aromatic diamine having two benzene rings. In this diamine (B1), the amino group directly attached to at least one benzene ring and the divalent linking group A are at the meta position, so that the degree of freedom of the polyimide molecular chain is increased and has high flexibility. It is thought that it contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, the use of the diamine (B1) enhances the thermoplasticity of the polyimide. Here, the linking group A is preferably -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -CO-, -SO ₂ -, -S-, or -COO-.

Diamine (B1) includes, for example, 3,3'-diaminodiphenylmethane, 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,3-diaminodiphenyl ether , 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylpropane, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminobenzophenone, (3,3'-bisamino ) diphenylamine and the like.

The diamine represented by formula (B2) (hereinafter sometimes referred to as "diamine (B2)") is an aromatic diamine having three benzene rings. This diamine (B2) has an amino group directly attached to at least one benzene ring and a divalent linking group A at the meta position, so that the degree of freedom of the polyimide molecular chain is increased and has high flexibility. It is thought that it contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, the use of the diamine (B2) enhances the thermoplasticity of the polyimide. Here, the connecting group A is preferably -O-.

Examples of the diamine (B2) include 1,4-bis(3-aminophenoxy)benzene, 3-[4-(4-aminophenoxy)phenoxy]benzenamine, 3-[3-(4-aminophenoxy)phenoxy] Benzenamine and the like can be mentioned.

The diamine represented by formula (B3) (hereinafter sometimes referred to as "diamine (B3)") is an aromatic diamine having three benzene rings. This diamine (B3) has two divalent linking groups A directly connected to one benzene ring at the meta-position to each other, so that the degree of freedom of the polyimide molecular chain is increased and has high flexibility. It is thought that this contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, the use of the diamine (B3) enhances the thermoplasticity of the polyimide. Here, the connecting group A is preferably -O-.

Examples of the diamine (B3) include 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,3-bis(3-aminophenoxy)benzene (APB), 4,4'-[2- Methyl-(1,3-phenylene)bisoxy]bisaniline, 4,4'-[4-methyl-(1,3-phenylene)bisoxy]bisaniline, 4,4'-[5-methyl-(1,3-phenylene) ) bisoxy] bisaniline and the like.

The diamine represented by formula (B4) (hereinafter sometimes referred to as "diamine (B4)") is an aromatic diamine having four benzene rings. This diamine (B4) has high flexibility due to the fact that the amino group directly connected to at least one benzene ring and the divalent linking group A are in the meta position, and improve the flexibility of the polyimide molecular chain. considered to contribute. Therefore, the use of the diamine (B4) enhances the thermoplasticity of the polyimide. Here, the linking group A is preferably -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -SO ₂ -, -CO-, or -CONH-.

Diamines (B4) include bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]ether, bis Examples include [4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)]benzophenone, bis[4,4'-(3-aminophenoxy)]benzanilide and the like.

The diamine represented by formula (B5) (hereinafter sometimes referred to as "diamine (B5)") is an aromatic diamine having four benzene rings. This diamine (B5) has two divalent linking groups A directly connected to at least one benzene ring at the meta position to each other, so that the degree of freedom of the polyimide molecular chain is increased and has high flexibility. It is thought that it contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, the use of the diamine (B5) enhances the thermoplasticity of the polyimide. Here, the connecting group A is preferably -O-.

Examples of the diamine (B5) include 4-[3-[4-(4-aminophenoxy)phenoxy]phenoxy]aniline, 4,4'-[oxybis(3,1-phenyleneoxy)]bisaniline, and the like. .

The diamine represented by formula (B6) (hereinafter sometimes referred to as "diamine (B6)") is an aromatic diamine having four benzene rings. Since this diamine (B6) has at least two ether bonds, it has high flexibility, and is considered to contribute to the improvement of the flexibility of the polyimide molecular chain. Therefore, the use of the diamine (B6) enhances the thermoplasticity of the polyimide. Here, the linking group A is preferably -C(CH ₃ ) ₂ -, -O-, -SO ₂ -, or -CO-.

Examples of the diamine (B6) include 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), bis[4-(4-aminophenoxy)phenyl]ether (BAPE), bis[4 -(4-aminophenoxy)phenyl]sulfone (BAPS), bis[4-(4-aminophenoxy)phenyl]ketone (BAPK) and the like.

The diamine represented by formula (B7) (hereinafter sometimes referred to as "diamine (B7)") is an aromatic diamine having four benzene rings. Since this diamine (B7) has highly flexible divalent linking groups A on both sides of the diphenyl skeleton, it is believed that this contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, the use of the diamine (B7) enhances the thermoplasticity of the polyimide. Here, the connecting group A is preferably -O-.

Examples of the diamine (B7) include bis[4-(3-aminophenoxy)]biphenyl, bis[4-(4-aminophenoxy)]biphenyl and the like.

The adhesive polyimide may contain a diamine residue derived from a diamine compound other than the dimer acid-type diamine and diamines (B1) to (B7) as long as the effects of the invention are not impaired. As the diamine residue derived from a diamine compound other than the dimer acid-type diamine and the diamines (B1) to (B7), those generally used as diamine compounds used in thermoplastic polyimides can be used without limitation. .

In the adhesive polyimide, by selecting the types of the tetracarboxylic acid residue and the diamine residue, and the respective molar ratios when applying two or more tetracarboxylic acid residues or diamine residues, the thermal expansion coefficient , tensile modulus, glass transition temperature, etc. can be controlled. Moreover, when the adhesive polyimide has a plurality of polyimide structural units, they may exist as blocks or may exist randomly, but preferably exist randomly.

The imide group concentration of the adhesive polyimide is preferably 20% by weight or less. Here, "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 20% by weight, the molecular weight of the resin itself becomes small, and the low hygroscopicity deteriorates due to the increase in polar groups, resulting in an increase in Tg and elastic modulus.

The weight average molecular weight of the adhesive polyimide is, for example, preferably within the range of 10,000 to 400,000, more preferably within the range of 20,000 to 350,000. If the weight-average molecular weight is less than 10,000, the strength of the adhesive layers (BA) and (B) will be lowered and they will tend to become brittle. On the other hand, if the weight-average molecular weight exceeds 400,000, the viscosity increases excessively, and defects such as uneven thickness of the adhesive layers (BA) and (B) and streaks tend to occur during coating operations. .

Adhesive polyimides are most preferably fully imidized structures. However, part of the polyimide may be amic acid. The imidization rate is 1015 cm by measuring the infrared absorption spectrum of the polyimide thin film by the single reflection ATR method using a Fourier transform infrared spectrophotometer (commercial product: FT/IR620 manufactured by JASCO Corporation). Based on the benzene ring absorber around ⁻¹ , it can be calculated from the absorbance of C═O stretching derived from the imide group around 1780 cm ⁻¹ .

(crosslink formation)
When the adhesive polyimide has a ketone group, the ketone group is reacted with the amino group of an amino compound having at least two primary amino groups as functional groups to form a C=N bond, thereby cross-linking. Structures can be formed. By forming a crosslinked structure, the heat resistance of the adhesive polyimide can be improved. Preferred tetracarboxylic dianhydrides for forming adhesive polyimides having ketone groups include, for example, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), and diamine compounds such as Examples thereof include aromatic diamines such as 4,4'-bis(3-aminophenoxy)benzophenone (BABP) and 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene (BABB).

Examples of amino compounds that can be used for crosslinking the adhesive polyimide include dihydrazide compounds, aromatic diamines, and aliphatic amines. Among these, dihydrazide compounds are preferred. Aliphatic amines other than dihydrazide compounds tend to form a crosslinked structure even at room temperature, but there is concern about the storage stability of the varnish, while aromatic diamines require high temperatures to form a crosslinked structure. When a dihydrazide compound is used, both the storage stability of the varnish and the shortening of the curing time can be achieved. Examples of dihydrazide compounds include oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, and maleic acid. dihydrazide, fumaric acid dihydrazide, diglycolic acid dihydrazide, tartaric acid dihydrazide, malic acid dihydrazide, phthalic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, 2,6-naphthoedioic acid dihydrazide, 4,4-bisbenzene dihydrazide, 1,4 Dihydrazide compounds such as -naphthoic acid dihydrazide, 2,6-pyridinedioic acid dihydrazide, and itaconic acid dihydrazide are preferred. The above dihydrazide compounds may be used alone or in combination of two or more.

The adhesive polyimide can be produced by reacting the tetracarboxylic dianhydride and the diamine compound in a solvent to form a polyamic acid, followed by heat ring closure. For example, a tetracarboxylic dianhydride and a diamine compound are dissolved in an organic solvent in approximately equimolar amounts and stirred at a temperature within the range of 0 to 100° C. for 30 minutes to 24 hours for a polymerization reaction to form a polyimide precursor. A polyamic acid is obtained. In the reaction, the reaction components are dissolved in the organic solvent so that the resulting precursor is within the range of 5 to 50% by weight, preferably within the range of 10 to 40% by weight. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2 -butanone, dimethylsulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, cresol and the like. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. The amount of such an organic solvent to be used is not particularly limited, but the amount used is adjusted so that the concentration of the polyamic acid solution obtained by the polymerization reaction is about 5 to 50% by weight. is preferred.

It is usually advantageous to use the synthesized polyamic acid as a reaction solvent solution, but if necessary, it can be concentrated, diluted, or replaced with another organic solvent. Polyamic acid is also advantageously used because it is generally excellent in solvent solubility. The viscosity of the polyamic acid solution is preferably in the range of 500 cps to 100,000 cps. If the thickness is out of this range, for example, defects such as thickness unevenness and streaks are likely to occur in the film during the coating operation using a coater or the like.

The method of imidizing polyamic acid to form an adhesive polyimide is not particularly limited, for example, heat treatment such as heating in the above solvent at a temperature within the range of 80 to 400 ° C. for 1 to 24 hours is preferable. adopted by

When cross-linking the adhesive polyimide obtained as described above, the above amino compound is added to the resin solution containing the adhesive polyimide having a ketone group, and the ketone group in the adhesive polyimide and the amino compound are combined. Condensation reaction with primary amino groups. Due to this condensation reaction, the resin solution is cured into a cured product. In this case, the amount of the amino compound added is 0.004 mol to 1.5 mol, preferably 0.005 mol to 1.2 mol, more preferably 0.005 mol to 1.2 mol in total of the primary amino group per 1 mol of the ketone group. The amino compound can be added at 0.03 mol to 0.9 mol, most preferably 0.04 mol to 0.5 mol. If the amino compound is added in such an amount that the total amount of primary amino groups is less than 0.004 mol with respect to 1 mol of the ketone group, the cross-linking of the adhesive polyimide by the amino compound is not sufficient. The adhesive layers (BA) and (B) tend to exhibit less heat resistance, and if the amount of amino compound added exceeds 1.5 mol, the unreacted amino compound acts as a thermoplastic, , (B) tends to lower the heat resistance.

The condensation reaction conditions for cross-linking are not particularly limited as long as the ketone groups in the adhesive polyimide react with the primary amino groups of the amino compound to form imine bonds (C=N bonds). The temperature of the heat condensation is, for example, 120° C. for reasons such as releasing water generated by the condensation to the outside of the system, or simplifying the condensation step when the heat condensation reaction is subsequently performed after the synthesis of the adhesive polyimide. It is preferably within the range of -220°C, more preferably within the range of 140-200°C. The reaction time is preferably about 30 minutes to 24 hours, and the end point of the reaction is, for example, 1670 cm by measuring the infrared absorption spectrum using a Fourier transform infrared spectrophotometer (commercial product: FT/IR620 manufactured by JASCO Corporation). It can be confirmed by the reduction or disappearance of the absorption peak derived from the ketone group in the polyimide resin around ⁻¹ and the appearance of the absorption peak derived from the imine group around 1635 cm ⁻¹ .

The thermal condensation of the ketone group of the adhesive polyimide and the primary amino group of the amino compound can be performed, for example, by (a) a method of adding an amino compound and heating following synthesis (imidation) of the adhesive polyimide, ( b) A method in which an excessive amount of an amino compound is charged in advance as a diamine component, and following the synthesis (imidization) of the adhesive polyimide, the adhesive polyimide is heated together with the remaining amino compound that does not participate in imidization or amidation, or , (c) a method of heating an adhesive polyimide composition to which an amino compound is added after processing it into a predetermined shape (for example, after applying it to an arbitrary substrate or after forming it into a film), and the like. can be done.

In order to impart heat resistance to the adhesive polyimide, the formation of the imine bond has been described as the formation of the crosslinked structure, but the method is not limited to this. can be mixed and cured.

By using the adhesive polyimide obtained as described above, the adhesive layers (BA) and (B), ie, the polyimide layer (A), have excellent flexibility and dielectric properties (low dielectric constant and low dielectric loss tangent). will have. In addition, as will be described later, the adhesive polyimide has a sufficiently low storage elastic modulus in a temperature range of around 100 ° C., so the adhesion temperature is significantly lowered compared to other adhesive resins such as fluorine resins. be able to.

<Thermal expansion coefficient of insulating resin layer>
The bottom insulating resin layer (PA), the first insulating resin layer (P1), and the second insulating resin layer (P2), which constitute the insulating resin layer (X) of the flexible metal-clad laminate of the present invention, have a thermal expansion coefficient (CTE) is preferably 10 ppm/K or more, preferably 10 ppm/K or more and 30 ppm/K or less, more preferably 15 ppm/K or more and 25 ppm/K or less. If the CTE is less than 10 ppm/K or more than 30 ppm/K, warping will occur and dimensional stability will decrease. A polyimide layer having a desired CTE can be obtained by appropriately changing the combination of raw materials to be used, thickness, and drying/curing conditions.

The adhesive polyimide constituting the adhesive layers (BA) and (B) has high thermal expansion but low elasticity, so even if the CTE exceeds 30 ppm / K, the internal stress generated during lamination can be relaxed. can be done.

Moreover, in the flexible single-sided metal-clad laminate (CA) of FIG. It is in the range of 10 ppm/K or more and 30 ppm/K or less, more preferably 15 ppm/K or more and 25 ppm/K or less. If the CTE is less than 10 ppm/K or more than 30 ppm/K, warping will occur and dimensional stability will decrease.

Moreover, in the flexible double-sided metal-clad laminate (C) of FIG. is preferably in the range of 10 ppm/K or more and 30 ppm/K or less, more preferably in the range of 15 ppm/K or more and 25 ppm/K or less. If the CTE is less than 10 ppm/K or more than 30 ppm/K, warping will occur and dimensional stability will decrease.

<Glass Transition Temperature (Tg) of Adhesive Polyimide Constituting Adhesive Layers (BA) and (B)>
The adhesive polyimide preferably has a glass transition temperature (Tg) of 250° C. or lower, more preferably 40° C. or higher and 200° C. or lower. When the Tg of the adhesive polyimide is 250° C. or less, thermocompression bonding can be performed at a low temperature, so that internal stress generated during lamination can be relaxed and dimensional change after circuit processing can be suppressed. When the Tg of the adhesive polyimide exceeds 250° C., the temperature at which it is laminated on the bottom insulating resin layer (PA) and the gap between the first insulating resin layer (P1) and the second insulating resin layer (P2) The temperature becomes high when interposing and adhering, and there is a risk of impairing the dimensional stability after circuit processing.

<Storage Elastic Modulus of Adhesive Polyimide Constituting Adhesive Layers (BA) and (B)>
The adhesive polyimide is characterized by having a temperature range of 40 to 250° C. in which the storage elastic modulus sharply decreases with increasing temperature. Such properties of the adhesive polyimide are considered to be the factors that relax the internal stress during thermocompression bonding and maintain the dimensional stability after circuit processing. The adhesive polyimide preferably has a storage modulus of 5×10 ⁷ [Pa] or less at the upper limit temperature of the temperature range, and is within the range of 1×10 ⁵ to 5×10 ⁷ [Pa]. is more preferred. With such a storage elastic modulus, even if the upper limit of the above temperature range is taken as the upper limit, thermocompression bonding is possible at 250° C. or less, ensuring adhesion and suppressing dimensional change after circuit processing.

<Dielectric loss tangent of insulating resin layer (X)>
The bottom insulating resin layer (PA), the first insulating resin layer (P1), and the second insulating resin layer (P2) are, for example, applied to a circuit board, in order to suppress deterioration of dielectric loss at 10 GHz. The dielectric loss tangent (Tan δ) is preferably 0.02 or less, more preferably 0.0005 or more and 0.01 or less, and still more preferably 0.001 or more and 0.008 or less. When the dielectric loss tangent at 10 GHz of the bottom insulating resin layer (PA), the first insulating resin layer (P1), and the second insulating resin layer (P2) exceeds 0.02, a high frequency signal is generated when applied to a circuit board. Inconveniences such as loss of electrical signals are likely to occur on the transmission path. On the other hand, the lower limit of the dielectric loss tangent at 10 GHz of the bottom insulating resin layer (PA), the first insulating resin layer (P1) and the second insulating resin layer (P2) is not particularly limited, but the insulating resin layer of the circuit board Considering the physical property control of

The adhesive layers (BA) and (B) preferably have a dielectric loss tangent (Tan δ) at 10 GHz of preferably 0.004 or less, more preferably 0, in order to suppress deterioration of dielectric loss when applied to a circuit board, for example. It is preferably in the range of 0.0005 to 0.004, more preferably in the range of 0.001 to 0.0035. If the dielectric loss tangent of the adhesive layers (BA) and (B) exceeds 0.004 at 10 GHz, problems such as loss of electrical signals on high-frequency signal transmission paths are likely to occur when applied to a circuit board. On the other hand, the lower limit of the dielectric loss tangent at 10 GHz of the adhesive layers (BA) and (B) is not particularly limited.

<Dielectric constant of insulating resin layer (X)>
When the bottom insulating resin layer (PA), the first insulating resin layer (P1) and the second insulating resin layer (P2) are applied as insulating layers of a circuit board, for example, the insulating layers as a whole have a relative dielectric constant at 10 GHz. A ratio of 4.0 or less is preferred. When the dielectric constant at 10 GHz of the bottom insulating resin layer (PA), the first insulating resin layer (P1), and the second insulating resin layer (P2) exceeds 4.0, when applied to a circuit board, the bottom This leads to deterioration of the dielectric loss of the insulating resin layer (PA), the first insulating resin layer (P1) and the second insulating resin layer (P2), causing problems such as loss of electric signals on the transmission path of high frequency signals. easier.

The adhesive layers (BA) and (B) preferably have a dielectric constant of 4.0 or less at 10 GHz in order to ensure impedance matching when applied to a circuit board, for example. If the dielectric constant of the adhesive layers (BA) and (B) at 10 GHz exceeds 4.0, the dielectric loss of the adhesive layers (BA) and (B) will be deteriorated when applied to a circuit board, and the high frequency signal will be deteriorated. Inconveniences such as loss of electric signals tend to occur on the transmission path.

[Manufacturing of flexible metal-clad laminate]
The flexible metal-clad laminate of the present invention can be produced by a conventional method. For example, an adhesive layer is formed on a release film as a resin sheet. Separately, a single-sided metal-clad laminate consisting of a metal layer and a polyimide layer is prepared by coating and drying one or more polyamide solutions on the metal layer. Subsequently, a resin sheet is attached onto the polyimide layer of the single-sided metal-clad laminate, and the release film is removed to obtain the flexible single-sided metal-clad laminate shown in FIG. Alternatively, the flexible double-sided metal-clad laminate shown in FIG. 2 can be obtained by placing the polyimide layers of a pair of single-sided metal-clad laminates facing each other, sandwiching a resin sheet from which the release film has been removed, and bonding the entire laminate. The flexible metal-clad laminate of the present invention can also be produced by methods other than those described above.

[Flexible circuit board]
The flexible metal-clad laminate of the present embodiment as shown in FIGS. ) and/or the second metal layer (M2), a circuit board such as single-sided FPC or double-sided FPC can be manufactured.

[Preferred Configuration Example 1 of Flexible Metal-clad Laminate]
Next, regarding the flexible single-sided metal-clad laminate (CA) of FIG. 1, the case where both the bottom insulating resin layer (PA) and the adhesive layer (BA) are polyimide will be taken as an example and will be described more specifically with reference to FIG. explained in detail.

FIG. 3 is a schematic cross-sectional view showing the structure of flexible single-sided metal-clad laminate 100A of the present embodiment. As shown in FIG. 3, the flexible single-sided metal-clad laminate 100A includes a metal layer 101A as a metal layer (MA), a bottom polyimide layer 110A as a bottom insulating resin layer (PA), and an adhesive layer (BA) as and an adhesive polyimide layer 120A. Here, the bottom polyimide layer 110A and the adhesive polyimide layer 120A correspond to the insulating resin layer (X).

The bottom polyimide layer 110A may have a structure in which a plurality of polyimide layers are laminated. For example, in the embodiment shown in FIG. 3, the base layer includes a non-thermoplastic polyimide layer 111A made of non-thermoplastic polyimide and thermoplastic polyimide layers 112A made of thermoplastic polyimide provided on both sides thereof. It has a layered structure. Note that the bottom polyimide layer 110A is not limited to a three-layer structure.

In the flexible one-sided metal-clad laminate 100A shown in FIG. 3, the adhesive polyimide layer 120A is an adhesive layer for bonding the flexible one-sided metal-clad laminate 100A to another member, while ensuring dimensional stability. , has the function of improving the dielectric properties of the flexible single-sided metal-clad laminate 100A. The adhesive polyimide constituting the adhesive polyimide layer 120A is as described for the adhesive layer (BA).

Next, the non-thermoplastic polyimide layer 111A and the thermoplastic polyimide layer 112A that constitute the bottom polyimide layer 110A will be briefly described.

Non-thermoplastic polyimide layer:
The polyimide used for the non-thermoplastic polyimide layer 111A is obtained by reacting an acid dianhydride component containing an aromatic tetracarboxylic dianhydride component with a diamine component containing an aliphatic diamine and/or an aromatic diamine. Non-thermoplastic polyimides are preferred. As the acid dianhydride and the diamine, monomers generally used for synthesizing non-thermoplastic polyimides can be used, so description thereof is omitted here. Thermal expansibility, adhesion, glass transition temperature, etc. can be controlled by selecting the types of acid anhydrides and diamines, and the respective molar ratios when two or more acid anhydrides or diamines are used. .

The polyimide constituting the non-thermoplastic polyimide layer 111A preferably has an imide group concentration of 33% or less, more preferably 32% or less. When the imide group concentration exceeds 33%, the flame retardancy of the polyimide is lowered, and the increase in polar groups also deteriorates the dielectric properties.

The thickness of the non-thermoplastic polyimide layer 111A is preferably in the range of 6 μm or more and 100 μm or less from the viewpoint of securing the function as a base layer and transportability during manufacturing and thermoplastic polyimide coating, and is preferably 9 μm. More preferably, the thickness is in the range of 50 μm or more. If the thickness of the non-thermoplastic polyimide layer 111A is less than the above lower limit, the electrical insulation and handleability will be insufficient, and if it exceeds the upper limit, productivity will decrease.

From the viewpoint of heat resistance, the non-thermoplastic polyimide layer 111A preferably has a glass transition temperature (Tg) of 280° C. or higher, more preferably 300° C. or higher.

Further, from the viewpoint of suppressing warpage, the coefficient of thermal expansion of the non-thermoplastic polyimide layer 111A is within the range of 1 ppm/K or more and 30 ppm/K or less, preferably 1 ppm/K or more and 25 ppm/K or less, more preferably It is preferably in the range of 15 ppm/K or more and 25 ppm/K or less.

In addition, the non-thermoplastic polyimide used for the non-thermoplastic polyimide layer 111A may include optional components such as a plasticizer, other curing resin components such as epoxy resin, a curing agent, a curing accelerator, a coupling agent, a filler, and a solvent. , a flame retardant, etc. can be appropriately added. However, some plasticizers contain a large amount of polar groups, which may promote the diffusion of copper from the copper wiring. Therefore, it is preferable not to use plasticizers as much as possible.

Thermoplastic polyimide layer:
The polyimide used for the thermoplastic polyimide layer 112A is obtained by reacting an acid anhydride component containing an aromatic tetracarboxylic dianhydride component with a diamine component containing an aliphatic diamine component and/or an aromatic diamine component. A plastic polyimide is preferred. As acid anhydrides and diamines, monomers generally used for synthesizing thermoplastic polyimides can be used, and description thereof is omitted here. Thermal expansibility, adhesion, glass transition temperature, etc. can be controlled by selecting the types of acid anhydrides and diamines, and the respective molar ratios when two or more acid anhydrides or diamines are used. . From the viewpoint of improving dielectric properties, it is preferable to use an adhesive polyimide for forming an adhesive polyimide layer 120A as an adhesive layer (BA) as the polyimide used for the thermoplastic polyimide layer 112A.

The polyimide constituting the thermoplastic polyimide layer 112A preferably has an imide group concentration of 33% or less, more preferably 32% or less. When the imide group concentration exceeds 33%, the flame retardancy of the polyimide is lowered, and the increase in polar groups also deteriorates the dielectric properties.

The thickness of the thermoplastic polyimide layer 112A is preferably in the range of 1 μm or more and 10 μm or less, more preferably in the range of 1 μm or more and 5 μm or less, from the viewpoint of ensuring the adhesion function. When the thickness of the thermoplastic polyimide layer 112A is less than the above lower limit, the adhesiveness becomes insufficient, and when it exceeds the upper limit, the dimensional stability tends to deteriorate.

From the viewpoint of suppressing warpage, the thermoplastic polyimide layer 112A has a thermal expansion coefficient of 30 ppm/K or more, preferably 30 ppm/K or more and 100 ppm/K or less, more preferably 30 ppm/K or more and 80 ppm/K or less. should be within range.

In addition to polyimide, the resin used for the thermoplastic polyimide layer 112A includes optional components such as plasticizers, other curing resin components such as epoxy resins, curing agents, curing accelerators, inorganic fillers, coupling agents, Fillers, solvents, flame retardants, and the like can be blended as appropriate. However, some plasticizers contain a large amount of polar groups, which may promote the diffusion of copper from the copper wiring. Therefore, it is preferable not to use plasticizers as much as possible.

In the flexible single-sided metal-clad laminate 100A, in order to ensure dimensional stability after circuit processing, the overall thermal expansion coefficient of the bottom polyimide layer 110A and the adhesive polyimide layer 120A is preferably 10 ppm/K or more, preferably 10 ppm/K. It is preferably in the range of K or more and 30 ppm/K or less, more preferably in the range of 15 ppm/K or more and 25 ppm/K or less.

In the flexible single-sided metal-clad laminate 100A, the ratio of the thickness of the adhesive polyimide layer 120A to the total thickness of the bottom polyimide layer 110A and the adhesive polyimide layer 120A is as described with reference to FIG.

[Circuit board]
The flexible single-sided metal-clad laminate 100A of the present embodiment is mainly useful as a circuit board material for FPCs, rigid-flex circuit boards, and the like. That is, the metal layer 101A of the flexible metal-clad laminate 100A of the present embodiment is processed into a pattern by a conventional method to form a wiring layer, thereby forming a circuit board such as an FPC according to one embodiment of the present invention. can be manufactured.

[Preferred Configuration Example 2 of Flexible Metal-clad Laminate]
Next, regarding the flexible double-sided metal-clad laminate (C) of FIG. A more specific description will be given with reference to FIG. 4 as an example.

FIG. 4 is a schematic cross-sectional view showing the structure of the flexible double-sided metal-clad laminate 100 of this embodiment. As shown in FIG. 4, the metal-clad laminate 100 includes metal layers 101 and 101 as a first metal layer (M1) and a second metal layer (M2), a first insulating resin layer (P1) It has polyimide layers 110, 110 as a second insulating resin layer (P2) and an adhesive polyimide layer 120 as an adhesive layer (B). Here, the metal layer 101 and the polyimide layer 110 form a single-sided metal-clad laminate 130 as a first single-sided metal-clad laminate (C1) or a second single-sided metal-clad laminate (C2). In this aspect, the first single-sided metal-clad laminate (C1), the second single-sided metal-clad laminate (C2), and the single-sided metal-clad laminate 130 have the same configuration. Here, the polyimide layers 110, 110 and the adhesive polyimide layer 120 correspond to the insulating resin layer (X).

Each of the polyimide layers 110 and 110 may have a structure in which a plurality of polyimide layers are laminated. For example, in the embodiment shown in FIG. 4, non-thermoplastic polyimide layers 111 and 111 made of non-thermoplastic polyimide are provided as base layers, and thermoplastic polyimide layers 112 and 112 made of thermoplastic polyimide are provided on both sides of the layers. It has a three-layer structure with Note that the polyimide layers 110, 110 are not limited to a three-layer structure.

In the flexible double-sided metal-clad laminate 100 shown in FIG. 4, the inner thermoplastic polyimide layers 112, 112 of the two single-sided metal-clad laminates 130, 130 are each laminated to the adhesive polyimide layer 120 to form the flexible metal-clad laminate. 100 are formed. The adhesive polyimide layer 120 is an adhesive layer for bonding the two single-sided metal-clad laminates 130, 130 together in the metal-clad laminate 100, and the flexible metal-clad laminate 100 while ensuring dimensional stability. It has the function of improving the dielectric properties of The adhesive polyimide constituting the adhesive polyimide layer 120 is as described for the adhesive layer (B) above.

Next, the non-thermoplastic polyimide layer 111 and the thermoplastic polyimide layer 112 constituting the polyimide layers 110, 110 will be briefly described.

Non-thermoplastic polyimide layer:
The polyimide used for the non-thermoplastic polyimide layer 111 is obtained by reacting an acid dianhydride component containing an aromatic tetracarboxylic dianhydride component with a diamine component containing an aliphatic diamine and/or an aromatic diamine. Non-thermoplastic polyimides are preferred. As the acid dianhydride and the diamine, monomers generally used for synthesizing non-thermoplastic polyimides can be used, so description thereof is omitted here. Thermal expansibility, adhesiveness, glass transition temperature, etc. can be controlled by selecting the types of acid anhydrides and diamines, and the respective molar ratios when two or more acid dianhydrides or diamines are used. can.

The polyimide constituting the non-thermoplastic polyimide layer 111 preferably has an imide group concentration of 33% or less, more preferably 32% or less. When the imide group concentration exceeds 33%, the flame retardancy of the polyimide is lowered, and the increase in polar groups also deteriorates the dielectric properties.

The thickness of the non-thermoplastic polyimide layer 111 is preferably in the range of 6 μm or more and 100 μm or less from the viewpoint of ensuring the function as a base layer and transportability during manufacturing and thermoplastic polyimide coating, and is 9 μm. More preferably, the thickness is in the range of 50 μm or more. If the thickness of the non-thermoplastic polyimide layer 111 is less than the above lower limit, the electrical insulation and handleability will be insufficient, and if it exceeds the upper limit, productivity will decrease.

From the viewpoint of heat resistance, the non-thermoplastic polyimide layer 111 preferably has a glass transition temperature (Tg) of 280° C. or higher, more preferably 300° C. or higher.

In addition, from the viewpoint of suppressing warpage, the thermal expansion coefficient of the non-thermoplastic polyimide layer 111 is within the range of 1 ppm/K or more and 30 ppm/K or less, preferably 1 ppm/K or more and 25 ppm/K or less, more preferably It is preferably in the range of 15 ppm/K or more and 25 ppm/K or less.

In addition, the non-thermoplastic polyimide used for the non-thermoplastic polyimide layer 111 may include optional components such as a plasticizer, other curing resin components such as epoxy resin, a curing agent, a curing accelerator, a coupling agent, a filler, and a solvent. , a flame retardant, etc. can be appropriately added. However, some plasticizers contain a large amount of polar groups, which may promote the diffusion of copper from the copper wiring. Therefore, it is preferable not to use plasticizers as much as possible.

Thermoplastic polyimide layer:
The polyimide used for the thermoplastic polyimide layer 112 is obtained by reacting an acid dianhydride component containing an aromatic tetracarboxylic dianhydride component with a diamine component containing an aliphatic diamine component and/or an aromatic diamine component. Thermoplastic polyimides are preferred. As acid anhydrides and diamines, monomers generally used for synthesizing thermoplastic polyimides can be used, and description thereof is omitted here. Thermal expansibility, adhesion, glass transition temperature, etc. can be controlled by selecting the types of acid anhydrides and diamines, and the respective molar ratios when two or more acid anhydrides or diamines are used. . From the viewpoint of improving dielectric properties, it is preferable to use an adhesive polyimide for forming the adhesive polyimide layer 120 as the adhesive layer (B) as the polyimide used for the thermoplastic polyimide layer 112 .

The polyimide constituting the thermoplastic polyimide layer 112 preferably has an imide group concentration of 33% or less, more preferably 32% or less. When the imide group concentration exceeds 33%, the flame retardancy of the polyimide is lowered, and the increase in polar groups also deteriorates the dielectric properties.

The thickness of the thermoplastic polyimide layer 112 is preferably in the range of 1 μm or more and 10 μm or less, more preferably in the range of 1 μm or more and 5 μm or less, from the viewpoint of ensuring the adhesion function. When the thickness of the thermoplastic polyimide layer 112 is less than the above lower limit, the adhesiveness becomes insufficient, and when it exceeds the upper limit, the dimensional stability tends to deteriorate.

From the viewpoint of suppressing warpage, the thermoplastic polyimide layer 112 has a thermal expansion coefficient of 30 ppm/K or more, preferably 30 ppm/K or more and 100 ppm/K or less, more preferably 30 ppm/K or more and 80 ppm/K or less. should be within range.

In addition to polyimide, the resin used for the thermoplastic polyimide layer 112 includes optional components such as plasticizers, other curing resin components such as epoxy resins, curing agents, curing accelerators, inorganic fillers, coupling agents, Fillers, solvents, flame retardants and the like can be appropriately blended. However, some plasticizers contain a large amount of polar groups, which may promote the diffusion of copper from the copper wiring. Therefore, it is preferable not to use plasticizers as much as possible.

In order to ensure dimensional stability after circuit processing in the flexible metal-clad laminate 100, the overall thermal expansion coefficient of the two polyimide layers 110 and the adhesive polyimide layer 120 is preferably 10 ppm/K or more, preferably 10 ppm/K. It is preferably in the range of K or more and 30 ppm/K or less, more preferably in the range of 15 ppm/K or more and 25 ppm/K or less.

In the flexible metal-clad laminate 100, the thickness ratio of the adhesive polyimide layer 120 to the total thickness of the two polyimide layers 110 and the adhesive polyimide layer 120 is as described with reference to FIG.

[Circuit board]
Flexible metal-clad laminate 100 of the present embodiment is mainly useful as a circuit board material such as FPC and rigid-flex circuit board. That is, one or both of the two metal layers 101 of the flexible metal-clad laminate 100 of the present embodiment are processed into a pattern by a conventional method to form a wiring layer. A circuit board such as a certain FPC can be manufactured.

EXAMPLES Examples are given below to more specifically describe the features of the present invention. 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 as follows.

[Measurement of tensile modulus]
Using Strograph R-1 manufactured by Toyo Seiki Seisakusho Co., Ltd., the tensile modulus was measured under an environment of a temperature of 23° C. and a relative humidity of 50%. A sample for measurement was measured under conditions of MD; 250 mm×TD; 12.7 mm, load cell; 500 N, tensile speed; 50 mm/min, and distance between chucks; 50 mm.

[Measurement of average tensile modulus]
The average tensile elastic modulus is the tensile elastic modulus within a range of 5 μm in the thickness direction from the interface with the metal layer in the insulating resin layer, and is calculated by the following formula (1).

In formula (1), M _i is the tensile elastic modulus (unit: GPa) of the i-th polyimide layer from the interface of the metal layer, and T _i is the thickness of the i-th polyimide layer (unit: μm). and n is an integer of 1 or more.

[Measurement of storage modulus]
It was measured using a dynamic viscoelasticity device (DMA: manufactured by UBM, trade name: E4000F). A polyimide having a storage modulus of 1.0×10 ⁹ Pa or more at 30° C. and a storage modulus of 3.0×10 ⁸ Pa or more at 280° C. is defined as a “non-thermoplastic polyimide”. A polyimide having a storage elastic modulus of 1.0×10 ⁸ Pa or more at 280° C. and a storage elastic modulus of less than 3.0×10 ⁷ Pa at 280° C. was defined as “thermoplastic polyimide”.

[Evaluation of dielectric properties]
Using a vector network analyzer (Agilent, trade name: Vector Network Analyzer E8363C) and an SPDR resonator, a polyimide film (polyimide film after curing) was measured at a temperature of 23° C. and a humidity of 50% RH for 24 hours. After standing, the relative permittivity (ε) and dielectric loss tangent (Tan δ) at a frequency of 10 GHz were measured.

[Glass transition temperature (Tg)]
Temperature; 160 ° C.; RSA-G2 (manufactured by Mento Co., Ltd., product name: RSA-G2), measurement is performed from 30 ° C. to 200 ° C. at a temperature increase rate of 4 ° C./min and a frequency of 11 GHz, and the temperature at which the change in elastic modulus (tan δ) becomes maximum is determined as the glass transition temperature. temperature.

[Measurement of seam folding (bending test)]
As described in Japanese Patent No. 6320031, the metal foil of the flexible metal-clad laminate is etched, and 10 rows of copper wiring with a line width of 100 μm, a space width of 100 μm and a length of 40 mm are formed along the longitudinal direction. A test piece (test circuit board piece) was prepared (FIG. 6). As shown in FIG. 6 showing only the conductor wiring in the test piece, the 10 rows of copper wiring 51 in the test piece 40 are all continuously connected via the U-shaped portion 52, and the resistors are connected at both ends thereof. An electrode portion (not shown) for value measurement is provided. The test piece 40 was fixed on the sample stages 20 and 21 that can be folded in two, and wiring for resistance value measurement was connected to start monitoring the resistance value (FIG. 7). In the bending test, a urethane roller 22 was used on the 10 rows of copper wiring 51 at the exact central portion in the longitudinal direction so that the gap G at the bending portion 40C was 0.5 to 1.5 mm. After bending all 10 rows of copper wiring 51 by moving the rollers in a controlled manner parallel to the bending lines (FIGS. 8 and 9), the bent portions are opened to return the test piece to a flat state (FIG. 10), The folded part was moved again while being held down by the roller (Fig. 11), and this series of steps was counted as one fold. While constantly monitoring the resistance value of the wiring, the bending test was repeated, and when the wiring reached a predetermined resistance (3000Ω), it was determined that the wiring was broken.

[Calculation of midplane position]
As described in Japanese Patent No. 6320031, the lower surface of the first layer shown in FIG. 12 is used as the reference surface SP. A case will be considered below in which the laminated body is bent so that the reference plane SP has a downward convex shape in FIG. In FIG. 12, symbol NP represents the neutral plane of the laminate. A neutral plane position [NP] (Neutral Plane position) is calculated by the following equation (2). Here, E is the modulus of elasticity, B is the width of the depth (usually assumed to be the unit width of the entire layer and Bi = 1), h is the distance between the central plane of the layer and the reference plane, and t is the thickness of the layer.

[Calculation of equivalent bending stiffness]
As described in Japanese Patent No. 6320031, the equivalent bending rigidity [BR] (Equivalent Bending Rigidity), which is the bending rigidity of the entire flexible circuit board, is calculated by the following equation (3).

In equation (2), as shown in FIG. 12, ai is the distance between the top surface of the i-th layer and the neutral plane NP, bi is the distance between the bottom surface of the i-th layer and the neutral plane NP, and E is The tensile modulus of elasticity, B is the width of the depth (usually assumed to be the unit width of the entire layer and Bi = 1), h is the distance between the central plane of the layer and the reference plane, and t is the thickness of the layer. Σ _{i =1} ⁿ E _i (ai ³ -bi ³ )/3 is the sum of the values of E _i (ai ³ -bi ³ )/3 for i from 1 to n. Regarding the i-th layer, Bi(a _i ³ -b _i ³ )/3 is a parameter representing the geometrical characteristic of the cross section, which is generally called the moment of inertia of the area, which is related to the formula (2). A value obtained by multiplying the geometrical moment of inertia of the i-th layer by the tensile elastic modulus of the i-th layer is the flexural rigidity of the i-th layer.

The abbreviations used in Examples and Reference Examples represent the following compounds.
BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride PMDA: pyromellitic dianhydride m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl TPE-R: 1 ,3-bis(4-aminophenoxy)benzenebisaniline-M: 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene NMP: N-methyl-2-pyrrolidone DMAc: N,N -Dimethylacetamide BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride DDA: Aliphatic diamine having 36 carbon atoms (manufactured by Croda Japan Co., Ltd., trade name: PRIA
MINE1074, amine value: 205 mgKOH/g, mixture of dimer diamine with cyclic structure and chain structure, content of dimer component: 95% by weight or more)
BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane N-12: Dodecanedioic acid dihydrazide OP935: Organic phosphinate aluminum salt (manufactured by Clariant Japan, trade name; E
xolit OP935)

[Synthesis Example 1]
(Preparation of polyimide solution 1)
In a 500 mL 4-necked flask equipped with a nitrogen inlet tube, stirrer, thermocouple, Dean-Stark trap, and condenser, 44.92 g BTDA (0.139 mol), 75.08 g DDA (0.141 mol), 168 g of NMP and 112 g of xylene were charged and mixed at 40° C. for 30 minutes to prepare a polyamic acid solution. This polyamic acid solution was heated to 190° C., heated and stirred for 4 hours, and distilled water and xylene were removed from the system. Then, the polyimide solution 1 (solid content: 29.5% by weight, weight average molecular weight: 75,700) in which imidation was completed by cooling to 100 ° C., adding 112 g of xylene and stirring, and further cooling to 30 ° C. was prepared.

[Synthesis Example 2]
(Preparation of polyamic acid solution 1)
Under a nitrogen stream, 64.20 g of m-TB (0.302 mol) and 5.48 g of bisaniline-M (0.016 mol) were added to the reactor, and an amount that would give a solid content concentration of 15% by weight after polymerization. of DMAc was added and dissolved by stirring at room temperature. Next, after adding 34.20 g of PMDA (0.157 mol) and 46.13 g of BPDA (0.157 mol), the polymerization reaction was carried out at room temperature for 3 hours with continuous stirring, polyamic acid solution 1 (viscosity: 26,500 cps) were prepared.

[Synthesis Example 3]
(Preparation of polyamic acid solution 2)
69.56 g of m-TB (0.328 mol), 542.75 g of TPE-R (1.857 mol), DMAc in an amount to give a solids concentration of 12% by weight after polymerization, 194.39 g of PMDA ( A polyamic acid solution 2 (viscosity: 2,650 cps) was prepared in the same manner as in Synthesis Example 2 except that 0.891 mol) and 393.31 g of BPDA (1.337 mol) were used as the raw material composition.

[Production example 1]
(Preparation of resin sheet 1 from polyimide varnish 1)
169.49 g (50 g as solids) of polyimide solution 1 was blended with 1.8 g of N-12 (0.0036 mol) and 12.5 g of OP935, and 6.485 g of NMP and 19.345 g of xylene were added. to prepare polyimide varnish 1.

Polyimide varnish 1 was applied to the silicone-treated surface of the release substrate (vertical × horizontal × thickness = 320 mm × 240 mm × 25 μm) so that the thickness after drying was 50 μm, and then dried by heating at 80 ° C. for 15 minutes. A resin sheet 1 (thickness: 50 μm) was produced by peeling from the release substrate. The resin sheet 1 had a Tg of 78° C. and a dielectric constant (Dk) and a dielectric loss tangent (Df) of 2.68 and 0.0028, respectively. Further, the storage elastic modulus characteristics of the resin sheet 1 were as follows.

Steep temperature range of storage modulus: 40 to 74°C
Storage modulus (40° C.); 5.0×10 ⁸ Pa
Storage modulus (74° C.); 1.1×10 ⁷ Pa
Storage modulus (250° C.); 3.0×10 ⁶ Pa

[Production Examples 2 to 5]
(Preparation of resin sheets 2 to 5 from polyimide varnish 1)
Resin sheet 2 (thickness; 75 μm), resin sheet 3 (thickness; 25 μm), resin sheet 4 (thickness; 19 μm) and resin sheet 5 (thickness; 38 μm).

[Production example 6]
(Production of single-sided metal-clad laminate 1)
Copper foil 1 (Electrolytic copper foil CF-T49A-DS-HD2 manufactured by Fukuda Metal Co., Ltd., thickness: 12 μm, surface roughness Rz on the resin layer side: 0.6 μm, tensile modulus: 30 GPa) Polyamic acid solution 2 was uniformly applied so that the thickness after curing was about 2 to 3 μm, and dried by heating at 120° C. to remove the solvent. Next, polyamic acid solution 1 was uniformly applied thereon so that the thickness after curing was about 21 μm, and dried by heating at 120° C. to remove the solvent. Further, the polyamic acid solution 3 was evenly applied thereon so that the thickness after curing was about 2 to 3 μm, and then dried by heating at 120° C. to remove the solvent. Further, stepwise heat treatment was performed from 120° C. to 360° C. to complete imidation, and a flexible single-sided metal-clad laminate 1 (resin layer thickness: 25 μm) was produced.

[Production example 7]
(Production of single-sided metal-clad laminate 2)
A single-sided metal-clad laminate 2 (resin layer thickness: 12 μm) was produced in the same manner as in Production Example 6, except that the polyamic acid solution was applied so as to have a thickness of about 8 μm after curing.

[Production example 8]
(Production of single-sided metal-clad laminate 3)
A single-sided metal-clad laminate 3 (resin layer thickness: 38 μm) was produced in the same manner as in Production Example 6, except that the polyamic acid solution was applied so that the thickness after curing was about 34 μm.

[Example 1]
(Production of flexible circuit board 1)
Two single-sided metal-clad laminates 1 were prepared, and the respective resin layer side surfaces were superposed on both sides of the resin sheet 1 and crimped at 180° C. for 2 hours under a pressure of 3.5 MPa to form a flexible metal. A tension laminate 1 was produced. Next, after the metal layer on one side of the flexible metal-clad laminate 1 is removed by etching using an aqueous solution of ferric chloride to prepare a single-sided metal-clad laminate, the other metal layer is subjected to a predetermined wiring process. A flexible circuit board 1 was prepared. Table 1 shows the evaluation results of the flexible circuit board 1 .

[Example 2]
(Fabrication of flexible circuit board 2)
Two single-sided metal-clad laminates 2 are prepared, and the respective resin layer side surfaces are superimposed on both sides of the resin sheet 2 to produce a flexible metal-clad laminate 2 in the same manner as in Example 1. A circuit board 2 was produced. Table 1 shows the evaluation results of the flexible circuit board 2 .

[Example 3]
(Production of flexible circuit board 3)
Two single-sided metal-clad laminates 1 are prepared, and the respective resin layer side surfaces are superimposed on both sides of the resin sheet 1 to produce a flexible metal-clad laminate 3 in the same manner as in Example 1. A circuit board 3 was produced. Table 1 shows the evaluation results of the flexible circuit board 3 .

[Example 4]
(Fabrication of flexible circuit board 4)
Two single-sided metal-clad laminates 3 are prepared, and the respective resin layer side surfaces are superposed on both sides of the resin sheet 3 to produce a flexible metal-clad laminate 4 in the same manner as in Example 1. A circuit board 4 was produced. Table 1 shows the evaluation results of the flexible circuit board 4 .

[Example 5]
(Fabrication of flexible circuit board 5)
Two single-sided metal-clad laminates 1 are prepared, the resin layer side surfaces of each are superimposed on both sides of a resin sheet 2, and a flexible metal-clad laminate 5 is produced in the same manner as in Example 1. A circuit board 5 was produced. Table 1 shows the evaluation results of the flexible circuit board 5 .

[Reference example 1]
(Production of Reference Circuit Board 1)
A resin sheet 1 is placed on a copper foil 1, and a polyimide film 1 (manufactured by Toray DuPont Co., Ltd., trade name: Kapton EN-S, thickness: 25 μm) is placed on top of it. Vacuum lamination was performed under the conditions of 0.85 MPa for 1 minute, and then heated in an oven at a temperature of 160° C. for 1 hour to prepare a metal-clad laminate 1 . A reference circuit board 1 was produced by subjecting the metal layer of the obtained metal-clad laminate 1 to a predetermined wiring process. Table 2 shows the evaluation results of the reference circuit board 1.

[Reference example 2]
(Production of Reference Circuit Board 2)
A metal-clad laminate 2 was produced in the same manner as in Reference Example 1, with a resin sheet 4, a polyimide film 1, a resin sheet 4 and a copper foil 1 stacked in this order on a copper foil 1. After the metal layer on one side of the obtained metal-clad laminate 2 is removed by etching using an aqueous solution of ferric chloride to prepare a single-sided metal-clad laminate, the other metal layer is subjected to a predetermined wiring process. A reference circuit board 2 was produced. Table 2 shows the evaluation results of the reference circuit board 2 .

[Reference example 3]
(Production of Reference Circuit Board 3)
A metal-clad laminate 3 was produced in the same manner as in Reference Example 1, with a resin sheet 3, a polyimide film 1, a resin sheet 3 and a copper foil 1 stacked in this order on a copper foil 1. After the metal layer on one side of the obtained metal-clad laminate 3 is removed by etching using an aqueous solution of ferric chloride to produce a single-sided metal-clad laminate, the other metal layer is subjected to a predetermined wiring process. A reference circuit board 3 was produced. Table 2 shows the evaluation results of the reference circuit board 3.

[Reference Example 4]
(Production of Reference Circuit Board 4)
A metal-clad laminate 4 was produced in the same manner as in Reference Example 1, with a resin sheet 5, a polyimide film 1, a resin sheet 5 and a copper foil 1 stacked in this order on a copper foil 1. After the metal layer on one side of the obtained metal-clad laminate 4 is removed by etching using an aqueous solution of ferric chloride to produce a single-sided metal-clad laminate, the other metal layer is subjected to a predetermined wiring process. A reference circuit board 4 was prepared. Table 2 shows the evaluation results of the reference circuit board 4 .

[Reference Example 5]
(Production of Reference Circuit Board 5)
A metal-clad laminate 5 was prepared in the same manner as in Reference Example 1, with a resin sheet 1, a polyimide film 1, a resin sheet 1 and a copper foil 1 stacked in this order on a copper foil 1. After the metal layer on one side of the obtained metal-clad laminate 5 is removed by etching using an aqueous solution of ferric chloride to produce a single-sided metal-clad laminate, the other metal layer is subjected to a predetermined wiring process. A reference circuit board 5 was prepared. Table 2 shows the evaluation results of the reference circuit board 5 .

<Preparation of sample for measurement of tensile modulus of polyimide layer>
After uniformly applying a predetermined polyamic acid solution to a predetermined thickness on the copper foil 1, it is dried by heating at 120°C to remove the solvent, and is subjected to stepwise heat treatment from 120°C to 360°C. Upon completion of imidization, a single-sided metal-clad laminate was prepared. A polyimide film was prepared by etching away the copper foil layer of a single-sided metal-clad laminate using an aqueous solution of ferric chloride. The tensile elastic modulus of this polyimide film was defined as the tensile elastic modulus of a single polyimide layer.

<Calculation of equivalent bending stiffness>
Calculation of the equivalent bending rigidity of a flexible metal-clad laminate will be described using a laminate as shown in FIG. 13 as an example. Assuming the state of the sample in the above-mentioned folding test, it is calculated by the above formula (3) with a layer structure in which a copper foil is attached to one side of the insulating resin layer. Numerical values used for the calculation of the equivalent bending stiffness of the laminate were all values measured as a single-layer insulator. When applied to the case of Example 1, the copper foil layer (tensile modulus M1: 30.0 GPa, thickness T1: 12 μm) is the first layer, and the second layer insulator (tensile modulus M2: 3.4 GPa, thickness T2: 2 μm), third layer insulator (tensile modulus M3: 8.0 GPa, thickness T3: 21 μm), fourth layer insulator (tensile modulus M4: 3.4 GPa, Thickness T4: 2 μm), fifth layer insulator (tensile modulus M5: 0.8 GPa, thickness T5: 12 μm), the equivalent bending rigidity is 0.15 N / mm ² , total thickness (87 μm) The value obtained by dividing by the cube of is 234 N/mm ² .

The evaluation results of Examples 1 to 5 and Reference Examples 1 to 5 are summarized in Tables 1 and 2.

<Summary>
By comparing Example 1 with Reference Examples 1 and 3, Examples 2 to 4 with Reference Example 4, and Example 5 with Reference Example 5, even if the layer thickness of the insulating resin layer is the same, It can be seen that the number of folding tests is greatly increased in the case of . Although the number of folds in Reference Example 2 is relatively large at 94 times, the results of Examples 1 to 5 are obtained with the flexible metal-clad laminate of the present invention in which the insulating resin layer has the same thickness as in Reference Example 2. (The number of folds tends to increase as the insulating resin layer becomes thinner).

Although the embodiments of the present invention have been described above in detail for the purpose of illustration, the present invention is not limited to the above embodiments and various modifications are possible.

C, CA Flexible metal-clad laminate C1 First single-sided metal-clad laminate C2 Second single-sided metal-clad laminate MA, M1, M2 Metal layer PA Bottom insulating resin layer P1 First insulating resin layer P2 Second insulation Resin layer B, BA Adhesive layer X Insulating resin layer
100, 100A flexible metal-clad laminate 101, 101A metal layer 110, 110A polyimide layer 111, 111A non-thermoplastic polyimide layer 112, 112A thermoplastic polyimide layer 120, 120A adhesive polyimide layer 130, 130A single-sided metal-clad laminate

Claims (7)

A flexible metal clad laminate used for a flexible circuit board that is folded and housed in a housing of an electronic device by folding so that the upper surface side is turned 180 degrees and bent to the lower surface side,
an insulating resin layer having a thickness in the range of 50 μm or more and 150 μm or less and a tensile elastic modulus (TM1) in the range of 1 GPa or more and 7 GPa or less;
a metal layer laminated on at least one surface of the insulating resin layer,
The tensile elastic modulus (TM2) in the range of 5 μm in the thickness direction from the interface with the metal layer in the insulating resin layer is in the range of 2 GPa or more and 10 GPa or less, and the tensile elastic modulus (TM2) is the tensile elastic modulus ( A flexible metal-clad laminate characterized by being larger than TM1). The value obtained by dividing the equivalent bending rigidity (RF) [N/mm ² ] of the flexible metal-clad laminate by the cube of the overall thickness (L) [mm] (RF/L ³ ) is 400 N/mm ⁵ or more and 1200 N/ The flexible metal-clad laminate according to claim 1, wherein the thickness is within the range of ^mm5 or less. 3. The flexible metal-clad laminate according to claim 1, wherein the metal layer has a thickness in the range of 6 [mu]m to 15 [mu]m. The insulating resin layer is formed by laminating a plurality of polyimide layers, and has a polyimide layer (A) as a central layer of the plurality of polyimide layers, and the thickness of the polyimide layer (A) is equal to the entire thickness of the insulating resin layer. 4. The flexible metal-clad laminate according to any one of claims 1 to 3, wherein the ratio is in the range of 0.5 or more and 0.96 or less. 5. The flexible metal-clad laminate according to claim 4, wherein the polyimide layer (A) has a storage modulus of 1800 MPa or less at 50° C. and a maximum storage modulus of 800 MPa or less at 180 to 260° C. A flexible circuit board obtained by wiring the metal layer in the flexible metal-clad laminate according to any one of claims 1 to 5. 7. The flexible circuit board according to claim 6, wherein the metal layer is bent inward.

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