阅读说明：本技术 覆金属层叠板及电路基板 (Metal-clad laminate and circuit board ) 是由 橘髙直树 安藤智典 安藤敏男 于 2020-03-20 设计创作，主要内容包括：本发明提供一种覆金属层叠板及电路基板,其包括即便在绝缘树脂层的厚度薄的情况下,也具有高的尺寸稳定性与面内各向同性,且与金属层的粘接性优异的绝缘树脂层,并且覆金属层叠板及蚀刻金属层后的膜的卷曲也得到抑制。所述覆金属层叠板,其包括绝缘树脂层及层叠于所述绝缘树脂层的单面的金属层,且绝缘树脂层具有由非热塑性聚酰亚胺构成的非热塑性聚酰亚胺层、及与非热塑性聚酰亚胺层的至少一面相接设置的由热塑性聚酰亚胺构成的热塑性聚酰亚胺层。热塑性聚酰亚胺层介隔存在于金属层与非热塑性聚酰亚胺层之间,绝缘树脂层的厚度为2μm以上且15μm以下的范围内,并且厚度方向的双折射Δn(xy-z)为0.080～0.140的范围内。(The invention provides a metal-clad laminate and a circuit board, which include an insulating resin layer having high dimensional stability and in-plane isotropy even when the insulating resin layer is thin, and having excellent adhesion to a metal layer, and in which curling of the metal-clad laminate and a film after etching the metal layer is suppressed. The metal-clad laminate comprises an insulating resin layer and a metal layer laminated on one surface of the insulating resin layer, wherein the insulating resin layer comprises a non-thermoplastic polyimide layer made of non-thermoplastic polyimide and a thermoplastic polyimide layer made of thermoplastic polyimide and arranged in contact with at least one surface of the non-thermoplastic polyimide layer. The thermoplastic polyimide layer is interposed between the metal layer and the non-thermoplastic polyimide layer, the thickness of the insulating resin layer is in the range of 2 [ mu ] m to 15 [ mu ] m, and the birefringence [ delta ] n (xy-z) in the thickness direction is in the range of 0.080 to 0.140.)

1. A metal-clad laminate comprising an insulating resin layer and a metal layer laminated on one surface of the insulating resin layer, wherein the metal-clad laminate is characterized in that,

the insulating resin layer has

Non-thermoplastic polyimide layer composed of non-thermoplastic polyimide, and

a thermoplastic polyimide layer made of thermoplastic polyimide and provided in contact with at least one surface of the non-thermoplastic polyimide layer,

the thermoplastic polyimide layer is interposed between the metal layer and the non-thermoplastic polyimide layer,

the thickness of the insulating resin layer is in the range of 2-15 μm, and

the birefringence [ delta ] n (xy-z) in the thickness direction is in the range of 0.080 to 0.140.

2. The metal-clad laminate according to claim 1, wherein the non-thermoplastic polyimide comprises a tetracarboxylic acid residue and a diamine residue, and contains 50 parts by mole or more of a diamine residue derived from a diamine compound represented by the following formula (1) per 100 parts by mole of all diamine residues;

in the formula (1), R independently represents a halogen atom, or an alkyl or alkoxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a phenyl or phenoxy group which may be substituted with a monovalent hydrocarbon group having 1 to 6 carbon atoms or an alkoxy group, and n₁Independently represent an integer of 0 to 4, n₂Represents an integer of 0 to 1.

3. The metal clad laminate of claim 1 wherein the insulating resin layer has

A non-thermoplastic polyimide layer composed of the non-thermoplastic polyimide, and

a thermoplastic polyimide layer made of thermoplastic polyimide disposed in contact with both sides of the non-thermoplastic polyimide layer,

the thickness of the thermoplastic polyimide layer provided on the side in contact with the metal layer was T1,

The thickness of the non-thermoplastic polyimide layer was set to T2,

When the thickness of the thermoplastic polyimide layer disposed on the side opposite to the metal layer is set to T3,

the thicknesses of T1, T2 and T3 satisfy the following relational expressions (1) and (2);

(1)0.8≦T3/T1＜1.4

(2)0.20＜(T1+T3)/(T1+T2+T3)≦0.50。

4. the metal-clad laminate sheet according to any one of claims 1 to 3, wherein the CTE of the insulating resin layer is in the range of 15ppm/K or more and 30ppm/K or less,

MD side of the insulating resin layerTowards (CTE)_MD) CTE (CTE) with TD direction_TD) Satisfies the following relation (i);

|(CTE_MD-CTE_TD)/(CTE_MD+CTE_TD)|≦0.05…(i)。

5. the metal-clad laminate of any one of claims 1 to 3, wherein the width of the metal-clad laminate is 470mm or more and the deviation of the thickness of the insulating resin layer is within a range of ± 0.5 μm.

6. The metal-clad laminate according to any one of claims 1 to 3, wherein, of the insulating resin films obtained by etching and removing the metal layer, when the insulating resin films in a 50mm square after humidity conditioning for 24 hours are left to stand so that the convex surface of the central portion thereof is in contact with the flat surface under conditions of 23 ℃ and a humidity of 50% RH, the curl amount obtained by calculating the average value of the float amounts at the four corners is 10mm or less.

7. The metal-clad laminate according to any one of claims 1 to 3, wherein a diamine residue derived from a diamine compound represented by formula (1) is in a range of 50 to 99 parts by mole, and a diamine residue derived from a diamine compound represented by formula (2) below is in a range of 1 to 50 parts by mole, relative to 100 parts by mole of all diamine residues contained in the non-thermoplastic polyimide;

in the formula (2), R independently represents a halogen atom, or an alkyl group or an alkoxy group having 1 to 6 carbon atoms and being substituted with a halogen atom, or a phenyl group or a phenoxy group being substituted with a monovalent hydrocarbon group or an alkoxy group having 1 to 6 carbon atoms,

Z₁independently represents a single bond selected from-O-, -S-, -CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-CO-、-SO₂A divalent radical of-or-NH-,

n₃independently represent an integer of 0 to 4, n₄Represents an integer of 0 to 2;

wherein Z is₁At least one of (A) represents a group selected from-O-, -S-, -CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-CO-、-SO₂A divalent group of-or-NH-.

8. The metal-clad laminate according to any one of claims 1 to 3, further comprising another metal layer laminated on the insulating resin layer on a side opposite to the metal layer with reference to the insulating resin layer.

9. A circuit board obtained by processing the metal layer of the metal-clad laminate according to any one of claims 1 to 8 into a wiring.

Technical Field

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

Background

In recent years, with the progress of downsizing, weight saving, and space saving of electronic devices, there has been an increasing demand for a Flexible Printed circuit board (FPC) that is thin and lightweight, has flexibility, and has excellent durability even when repeatedly bent. Since FPCs can be mounted in a limited space in a three-dimensional and high-density manner, their applications are expanding to components such as wiring or cable (cable) of a movable portion of electronic equipment such as a Hard Disk Drive (HDD), a Digital Versatile Disc (DVD), a mobile phone, and a smart phone, and a connector (connector).

The FPC is manufactured by etching a metal layer of a metal-clad laminate having the metal layer and an insulating resin layer and performing wiring processing. In a photolithography (photolithography) process for mounting a metal-clad laminate or in a process of mounting an FPC, various processes such as bonding, cutting, exposure, etching, and the like are performed. The processing accuracy in these steps is important in maintaining the reliability of the electronic device mounted with the FPC. However, since the metal-clad laminate has a structure in which metal layers and insulating resin layers having different coefficients of Thermal Expansion (hereinafter, sometimes referred to as "CTE") are laminated, stress is generated between the layers due to a difference in the Coefficients of Thermal Expansion (CTE) between the metal layers and the insulating resin layers. The stress is released when the metal layer is etched and wiring is performed, and the stress expands and contracts, thereby causing a change in the size of the wiring pattern. Therefore, dimensional changes occur at the FPC stage, which causes poor connection between wirings or between wirings and terminals, and reduces the reliability and yield of the circuit board. Therefore, dimensional stability is a very important characteristic in a metal clad laminate as a material of a circuit board.

Electronic devices are expected to be further enhanced in functionality and miniaturized in the future. Therefore, for example, it is considered that the demand for using the FPC in a multilayered state is increasing. Further, the tendency of the circuit board itself to be thinner is also increasing in response to the reduction in thickness of the housing of electronic devices such as mobile phones and smart phones. In the circuit board, when the thickness of the insulating resin layer is reduced, finer wiring processing is required for impedance matching, and therefore, it is necessary to improve the dimensional stability to a conventional level or more and also to suppress curling. In addition, when the wiring is processed into fine wiring, adhesion is also required so that the wiring is not peeled off from the substrate.

Therefore, the following requirements for the insulating resin layer of a circuit board such as FPC are stricter than ever.

Thinning of thickness,

Low thermal expansibility (high dimensional stability),

Reduction of in-plane anisotropy (isotropy),

Low curling property (both of a metal-clad laminate state and a film state after etching),

Adhesion to the metal layer, and the like.

When the insulating resin layer is an extremely thin layer having a thickness of 15 μm or less, particularly 12 μm or less, the conventional design concept cannot be applied to satisfy the required characteristics other than the thickness, and a method different from the conventional method is required.

As the metal Clad Laminate, a Copper Clad Laminate (CCL) in which a Copper foil and a polyimide layer are laminated is widely used. A single-layer polyimide film having a thickness of 10 μm or less, which is an insulating resin layer applicable to the CCL, has been proposed (patent documents 1 to 3).

However, the polyimide films proposed in patent documents 1 to 3 are lacking in description about the reduction of in-plane anisotropy (isotropy), and are single-layer polyimide films, and therefore, when an adhesive or the like is used for lamination with a metal layer, the total thickness of the insulating resin layer becomes large, and there is room for improvement in terms of the reduction of the thickness.

Further, as a metal-clad laminate not via an adhesive layer, a metal-clad laminate having an insulating resin layer including three polyimide layers has also been proposed (patent document 4). However, patent document 4 relates to improvement of solder resistance after moisture absorption, and neither discloses nor suggests an insulating resin layer having a total thickness of 12 μm or less of three polyimide layers, and there is room for improvement in terms of further reduction in thickness. Further, warpage (curl) of the metal-clad laminate or the film after etching is also silent.

As a method for improving curling of the metal clad laminate or the etched film, the following metal clad laminate has also been proposed: a high thermal expansion polyimide layer is provided on both sides of a low thermal expansion polyimide layer, and the curl of the film is controlled by controlling the thickness ratio of the high thermal expansion polyimide layer (patent document 5). However, the insulating resin layers are all about 25 μm, and a control technique for reducing the thickness is also lacking.

Further, a polyimide film having a thickness of about 25 μm, which can reduce dimensional change at high temperature processing by controlling CTE, 0 ° retardation, and the like, has also been proposed (patent document 6). However, as the 0 ° retardation is reduced, the difference is difficult to be observed as the thickness is reduced, and there is room for improvement as an index for evaluating physical properties.

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese patent laid-open No. 2016-186031

[ patent document 2] Japanese patent laid-open No. 2014-196467

[ patent document 3] Japanese patent laid-open publication No. 2017-145325

[ patent document 4] Japanese patent laid-open No. 2016-141152

[ patent document 5] Japanese patent laid-open No. 2006-306086

[ patent document 6] Japanese patent laid-open publication No. 2017-200759

Disclosure of Invention

[ problems to be solved by the invention ]

The purpose of the present invention is to provide a metal-clad laminate which comprises an insulating resin layer that has high dimensional stability and in-plane isotropy even when the insulating resin layer is thin, and has excellent adhesion to a metal layer, and in which curling of the metal-clad laminate and the film after etching of the metal layer is suppressed.

[ means for solving problems ]

The present inventors have made extensive studies and as a result, have found that the above problems can be solved by controlling the birefringence Δ n (xy-z) in the in-plane direction and the thickness direction of the insulating resin layer, and have completed the present invention.

That is, the metal-clad laminate of the present invention includes an insulating resin layer and a metal layer laminated on one surface of the insulating resin layer.

The insulating resin layer of the metal-clad laminate of the present invention has a non-thermoplastic polyimide layer made of a non-thermoplastic polyimide, and a thermoplastic polyimide layer made of a thermoplastic polyimide provided in contact with at least one surface of the non-thermoplastic polyimide layer.

Further, the metal-clad laminate of the present invention is characterized in that: the thermoplastic polyimide layer is interposed between the metal layer and the non-thermoplastic polyimide layer, the insulating resin layer has a thickness in a range of 2 [ mu ] m or more and 15 [ mu ] m or less, and a birefringence [ delta ] n (xy-z) in a thickness direction is in a range of 0.080 to 0.140.

In the metal clad laminate of the present invention, there may be: the non-thermoplastic polyimide contains a tetracarboxylic acid residue and a diamine residue, and contains 50 parts by mole or more of a diamine residue derived from a diamine compound represented by the following formula (1) per 100 parts by mole of all diamine residues.

[ solution 1]

In the formula (1), R independently represents a halogen atom, or an alkyl or alkoxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a phenyl or phenoxy group which may be substituted with a monovalent hydrocarbon group having 1 to 6 carbon atoms or an alkoxy group, and n₁Independently represent an integer of 0 to 4, n₂Represents an integer of 0 to 1.

In the metal-clad laminate of the present invention, the insulating resin layer may have a non-thermoplastic polyimide layer made of the non-thermoplastic polyimide and a thermoplastic polyimide layer made of a thermoplastic polyimide provided in contact with both sides of the non-thermoplastic polyimide layer.

Further, in the metal-clad laminate of the present invention, there may be: when the thickness of the thermoplastic polyimide layer provided on the side in contact with the metal layer is T1, the thickness of the non-thermoplastic polyimide layer is T2, and the thickness of the thermoplastic polyimide layer provided on the side opposite to the metal layer is T3, the thicknesses of T1, T2, and T3 satisfy the following relational expressions (1) and (2).

(1)0.8≦T3/T1＜1.4

(2)0.20＜(T1+T3)/(T1+T2+T3)≦0.50

In the metal-clad laminate of the present invention, there may be: the CTE of the insulating resin layer may be in a range of 15ppm/K or more and 30ppm/K or less, and the CTE (CTE) of the insulating resin layer in a Machine Direction (MD) Direction_MD) CTE (CTE) with respect to Transverse Direction (TD) Direction_TD) Satisfies the following relation (i).

|(CTE_MD-CTE_TD)/(CTE_MD+CTE_TD)|≦0.05…(i)

In the metal-clad laminate of the present invention, the width of the metal-clad laminate may be 470mm or more and the deviation of the thickness of the insulating resin layer may be in the range of ± 0.5 μm.

In the metal-clad laminate of the present invention, when the insulating resin film, which is 50mm square after humidity conditioning for 24 hours under conditions of 23 ℃ and a humidity of 50% RH, is allowed to stand so that the convex surface of the central portion is in contact with the flat surface, the curl amount obtained by calculating the average value of the lift amount at the four corners of the insulating resin film obtained by etching away the metal layer may be 10mm or less.

In the metal-clad laminate of the present invention, the diamine residue derived from the diamine compound represented by the general formula (1) may be in the range of 50 to 99 parts by mole, and the diamine residue derived from the diamine compound represented by the following general formula (2) may be in the range of 1 to 50 parts by mole, relative to 100 parts by mole of all the diamine residues contained in the non-thermoplastic polyimide.

[ solution 2]

In the formula (2), R independently represents a halogen atom, or an alkyl group or an alkoxy group having 1 to 6 carbon atoms and being substituted with a halogen atom, or a phenyl group or a phenoxy group being substituted with a monovalent hydrocarbon group or an alkoxy group having 1 to 6 carbon atoms,

Z₁independently represents a single bond selected from-O-, -S-, -CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-CO-、-SO₂A divalent radical of-or-NH-,

n₃independently represent an integer of 0 to 4, n₄Represents an integer of 0 to 2.

Wherein Z is₁At least one of (A) represents a group selected from-O-, -S-, -CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-CO-、-SO₂A divalent group of-or-NH-.

The metal-clad laminate of the present invention may further include another metal layer laminated on the insulating resin layer on the opposite side of the insulating resin layer with respect to the insulating resin layer.

The circuit board of the present invention is obtained by processing the metal layer of any one of the metal-clad laminates into a wiring.

[ Effect of the invention ]

The metal-clad laminate of the present invention includes an insulating resin layer having a small thickness, high dimensional stability and in-plane isotropy, and excellent adhesion to a metal layer, and is suppressed from curling. Therefore, the insulating resin layer has excellent dimensional stability and is less likely to cause curling when a circuit is processed on an FPC or the like. In addition, since the insulating resin layer is thin, when applied to a multilayer substrate, the total thickness can be reduced, and high-density mounting can be achieved. Further, since the insulating resin layer has a small thickness and is excellent in adhesion to the metal layer, heat dissipation from a power device or a light-emitting diode (LED) element mounted on a circuit is also excellent, and adhesion can be secured even in a high-temperature environment. Therefore, the metal-clad laminate of the present invention is also useful for applications requiring heat release properties.

Drawings

Fig. 1 is a diagram for explaining a delay evaluation system used in the examples and comparative examples.

Fig. 2 is a schematic diagram for explaining a method of measuring a delay used in the examples and comparative examples.

[ description of symbols ]

2: polyimide film

2 a: laminated surface

2 b: casting surface

20: test specimen

21: light source

22: light-receiving part

d: thickness of

θ₁: angle of incidence

θ₂: angle of refraction

L₁、L₂、L₃: light.

Detailed Description

Next, embodiments of the present invention will be explained.

< Metal-clad laminate >

The metal-clad laminate of the present embodiment includes an insulating resin layer and a metal layer laminated on at least one surface of the insulating resin layer. The metal-clad laminate of the present embodiment may be a single-sided metal-clad laminate having a metal layer on one side of an insulating resin layer, or may be a double-sided metal-clad laminate having metal layers on both sides of an insulating resin layer.

< insulating resin layer >

In the metal-clad laminate of the present embodiment, the insulating resin layer has a thermoplastic polyimide layer on at least one side of the non-thermoplastic polyimide layer, that is, the thermoplastic polyimide layer may be provided on one side or both sides of the non-thermoplastic polyimide layer, and the thermoplastic polyimide layer is interposed between the metal layer and the non-thermoplastic polyimide layer, that is, the metal layer and the surface of the thermoplastic polyimide layer are laminated in contact with each other, and here, the non-thermoplastic polyimide is usually a polyimide which does not exhibit adhesiveness even if softened by heating, and the present invention refers to a metal-clad laminate having a storage elastic modulus at 30 ℃ of 1.0 × 10 as measured by a dynamic viscoelasticity measuring apparatus (dynamic mechanical analyzer (DMA))⁹A storage modulus of elasticity of 1.0 × 10 at 360 ℃ under Pa or above⁸Pa or more, the thermoplastic polyimide is usually a polyimide whose glass transition temperature (Tg) can be clearly confirmed, and in the present invention, it means that the storage elastic modulus at 30 ℃ as measured by using DMA is 1.0 × 10⁹Pa or above and a storage elastic coefficient of less than 1.0 × 10 at 360 DEG C⁸Pa of a polyimide.

The insulating resin layer may have a two-layer structure of a thermoplastic polyimide layer and a non-thermoplastic polyimide layer, and preferably has a three-layer structure in which a thermoplastic polyimide layer, a non-thermoplastic polyimide layer, and a thermoplastic polyimide layer are stacked in this order from the side in contact with the metal layer. For example, in the case of forming the insulating resin layer by a cast (cast) method, a two-layer structure in which a thermoplastic polyimide layer and a non-thermoplastic polyimide layer are sequentially stacked from the casting surface side may be employed, or a three-layer structure in which a thermoplastic polyimide layer, a non-thermoplastic polyimide layer, and a thermoplastic polyimide layer are sequentially stacked from the casting surface side may be employed, and a three-layer structure is preferable. The "casting surface" described here means a surface on the side of the support body when the polyimide layer is formed. The support may be a metal layer of the metal-clad laminate, or may be a support for forming a gel film or the like. In the insulating resin layer, the surface opposite to the casting surface is referred to as a "lamination surface", and in the case where there is no particular description, the metal layer may be laminated on the lamination surface or may not be laminated.

< birefringence [ delta n (xy-z) ]in the thickness direction of the insulating resin layer

In order to ensure dimensional stability, a non-thermoplastic polyimide layer with a low CTE is often included in the metal clad laminate, but the CTE of the non-thermoplastic polyimide layer tends to decrease as the thickness of the non-thermoplastic polyimide layer is reduced. The behavior is particularly evident in casting processes, for which reasons can be mentioned: in the heat treatment, the thinner the thickness is, the more the volatilization of the solvent present in the resin layer is promoted, and the more the molecular orientation proceeds. Along with the above behavior, it is considered that the smaller the thickness is, the smaller the orientation difference in the thickness direction is.

Therefore, even when the thickness ratio of the thermoplastic layer/non-thermoplastic layer of the polyimide layer having a thickness of about 25 μm in the conventional art is applied as it is to a thin insulating resin layer, the CTE is lowered, and thus a mismatch between the CTEs of the metal layer and the resin layer occurs, resulting in deterioration of dimensional stability. Further, in the case of a polyimide film including a thermoplastic layer/non-thermoplastic layer, since the orientation distribution in the thickness direction of the non-thermoplastic layer changes, if the thickness ratio of the thermoplastic layer/non-thermoplastic layer is the same as that in the conventional case, curling occurs in the film.

That is, in the extremely thin insulating resin layer, a design concept different from the conventional art is required from the viewpoint of improving the dimensional stability after circuit processing and suppressing curling.

In order to improve dimensional stability after circuit processing and suppress curling, it is necessary to control the thickness ratio of the thermoplastic layer/the non-thermoplastic layer so as to balance the CTE of each layer while taking into account the reduction in CTE and the variation in orientation distribution in the thickness direction due to thinning, and particularly in a thin region, it is difficult to separate the layers, and thus it is difficult to grasp the CTE of each layer.

Further, when the insulating resin layer is produced by a casting method, since the solvent is transmitted in one direction, the CTE is different depending on the lamination order even if the material is the same and the thickness is the same. Therefore, the CTE of each layer of the insulating resin layer formed by the casting method is different from the CTE value obtained by measuring a polyimide film separately manufactured with the same material and the same thickness as those of each layer.

Therefore, as a result of diligent studies on the balance of the layers, it was found that dimensional stability and film curl can be suppressed by evaluating the molecular orientation and the thickness ratio of the thermoplastic layer/non-thermoplastic layer by the birefringence Δ n (xy-z) in the thickness direction and controlling the ratio to be within a predetermined range. Here, "birefringence Δ n (xy-z) in the thickness direction" is a difference between a refractive index Nxy in an in-plane direction (xy plane) and a refractive index Nz in a cross-sectional direction (z direction) orthogonal to the in-plane direction in the polyimide film.

The more the molecules are oriented, the stronger the tendency of the molecules to align in the in-plane direction is, and therefore Δ n (xy-z) becomes larger, and when no orientation is performed, Δ n (xy-z) becomes smaller. In addition, the larger the proportion of non-thermoplastic layers, the larger Δ n (xy-z) will be.

Therefore, by evaluating the orientation degree of molecules and the thickness ratio of the thermoplastic layer/non-thermoplastic layer by Δ n (xy-z) and controlling them within a predetermined range, dimensional stability can be improved and film curling can be suppressed.

From this viewpoint, the insulating resin layer of the metal-clad laminate of the present embodiment has a thickness in the range of 2 μm to 15 μm, and the birefringence Δ n (xy-z) in the thickness direction is controlled in the range of 0.080 to 0.140.

The thickness of the insulating resin layer may be set to a thickness within a predetermined range according to the purpose of use, and if the thickness of the insulating resin layer is less than the lower limit, problems such as failure to secure electrical insulation properties, difficulty in handling in the manufacturing process due to a reduction in workability, and the like may occur. On the other hand, if the thickness of the insulating resin layer exceeds the upper limit, it becomes difficult to reduce the thickness of the circuit board such as FPC or to mount it at high density. Since the thinner the thickness is, the more difficult the application of the conventional design is, the effect of the present invention is exerted more in the case of being applied to the region having the thinner thickness.

Further, when the birefringence Δ n (xy-z) in the thickness direction is less than 0.080, orientation is not sufficiently performed, which causes deterioration in dimensional stability, and since a difference in orientation in the thickness direction is likely to occur, curling is also likely to occur as a film. On the other hand, if the birefringence Δ n (xy-z) in the thickness direction exceeds 0.140, the CTE is excessively lowered, and dimensional stability after circuit processing is deteriorated due to mismatch with the CTE of the metal foil.

The birefringence Δ n (xy-z) in the thickness direction is preferably 0.090 or more and 0.140 or less, more preferably 0.090 or more and 0.130 or less, and most preferably 0.090 or more and 0.120 or less. By controlling the birefringence Δ n (xy-z) within the above-mentioned predetermined range, it is possible to suppress the decrease in dimensional stability due to the curling of the film and the mismatch between the metal layer and the resin layer, and to ensure good workability in circuit processing and dimensional accuracy of fine wiring even when the thickness of the insulating resin layer is 15 μm or less, for example, 12 μm or less.

The thickness of the insulating resin layer is 15 μm or less, preferably 12 μm or less, more preferably 9 μm or less, and further preferably 5 μm or less. By setting the thickness of the insulating resin layer to 15 μm or less, preferably 12 μm or less, more preferably 9 μm or less, and further preferably 5 μm or less, an extremely thin circuit board can be produced. Therefore, the degree of freedom of application to a folded wiring or a multilayer wiring or the like in a thin frame body or the like is increased, and high-density mounting can be realized.

In the present embodiment, when the average thickness is T μm, the variation in the thickness of the insulating resin layer is preferably within a range of T ± 0.5 μm, and more preferably within a range of T ± 0.3 μm. If the thickness variation exceeds T + -0.5 μm, it may be difficult to control the birefringence Δ n (xy-z) in the thickness direction.

Thickness ratio of thermoplastic layer to non-thermoplastic layer

In the conventional design, since the orientation on the lamination surface side is promoted by the orientation difference in the thickness direction, as in patent document 5 (japanese patent laid-open No. 2006-306086), when the thickness is about 25 μm, the film curl is suppressed by slightly increasing the thickness of the thermoplastic polyimide layer on the lamination surface side. However, when the thickness of the polyimide layer is reduced to 15 μm or less, particularly 12 μm or less, the distribution of orientation becomes nearly uniform, and therefore, it is necessary to increase the thickness ratio of the thermoplastic polyimide layer on the casting surface side as compared with the conventional design.

From such a viewpoint, in order to suppress curling and improve dimensional stability after circuit processing, in the single-sided metal-clad laminate, when the thickness of the thermoplastic polyimide layer present on the side (casting surface side) in contact with the metal layer is T1, the thickness of the non-thermoplastic polyimide layer is T2, and the thickness of the thermoplastic polyimide layer present on the side (lamination surface side) opposite to the metal layer is T3, T3/T1 is preferably in the range of 0.8 or more and less than 1.4. In particular, when the thickness of the insulating resin layer exceeds 9 μm and is 12 μm or less, T3/T1 is more preferably in the range of 0.8 to 1.3, and when the thickness of the insulating resin layer is 2 μm or more and 9 μm or less, T3/T1 is most preferably in the range of 0.9 to 1.3.

If the ratio T3/T1 is less than 0.8, the influence of the thermoplastic polyimide layer on the casting surface side becomes too large, and therefore curling of the film to the casting surface side occurs. On the other hand, if the ratio T3/T1 is 1.4 or more, the influence of the thermoplastic polyimide layer on the laminated surface side becomes too large, and curling of the film to the laminated surface side occurs.

In the case where the metal-clad laminate is a double-sided metal-clad laminate in which metal layers are laminated on both sides of the insulating resin layer, when two types of single-sided metal-clad laminates are formed by removing one-sided metal layer by etching, it is sufficient that either one of the single-sided metal-clad laminates satisfies the relationship of the ratio T3/T1.

Further, as a balance between the non-thermoplastic polyimide layer and the thermoplastic polyimide layer, it is also necessary to further thicken the thermoplastic polyimide layer compared to the conventional design by utilizing the orientation promotion of the thinning. Therefore, (T1+ T3)/(T1+ T2+ T3) indicating the ratio of the thermoplastic polyimide layer to the polyimide layer is set to be in a range of exceeding 0.20 and 0.50 or less. In particular, when the thickness of the insulating resin layer exceeds 9 μm and is 12 μm or less, (T1+ T3)/(T1+ T2+ T3) is more preferably in the range of 0.25 or more and 0.50 or less, and when the thickness of the insulating resin layer is 2 μm or more and 9 μm or less, (T1+ T3)/(T1+ T2+ T3) is most preferably in the range of 0.30 or more and 0.50 or less.

When (T1+ T3)/(T1+ T2+ T3) exceeds 0.50, the CTE of the insulating resin layer tends to be increased to more than 30ppm/K because the thickness of the non-thermoplastic polyimide layer is too small. On the other hand, if (T1+ T3)/(T1+ T2+ T3) is 0.20 or less, the CTE of the insulating resin layer tends to be reduced to less than 15ppm/K because the thickness of the non-thermoplastic polyimide layer is too large.

＜CTE＞

In the metal-clad laminate of the present embodiment, in order to suppress curling and improve dimensional stability after circuit processing, it is important that the CTE of the insulating resin layer is in the range of 15ppm/K to 30ppm/K, preferably 15ppm/K to 25 ppm/K. If the CTE is less than 15ppm/K or exceeds 30ppm/K, defects such as occurrence of curling of the metal-clad laminate and reduction in dimensional stability after circuit processing may occur.

In addition, the CTE (CTE) of the insulating resin layer in the MD direction (longitudinal direction/conveyance direction)_MD) CTE (CTE) with respect to TD direction (width direction)_TD) Preferably, the relationship satisfies the following expression (i). The case where the following formula (i) is satisfied is an average value (CTE) of CTEs in the MD direction and the TD direction with respect to CTEs in the MD direction and the TD direction_AVE) The shift of (2) is 5% or less, and the anisotropy is small. Since the dimensional stability is adversely affected when the anisotropy of the insulating resin layer in the MD direction and the TD direction is large, the smaller the value on the left side in the formula (i) is, the better. In other words, when the formula (i) is satisfied, either one of the following formulas (iii) and (iv) is satisfied.

|(CTE_MD-CTE_TD)/(CTE_MD+CTE_TD)|≦0.05…(i)

CTE_AVE＝(CTE_MD+CTE_TD)/2…(ii)

|(CTE_MD-CTE_AVE)/(CTE_AVE)|≦0.05…(iii)

|(CTE_TD-CTE_AVE)/(CTE_AVE)|≦0.05…(iv)

In the insulating resin layer, the non-thermoplastic polyimide layer constitutes a polyimide layer having low thermal expansion, and the thermoplastic polyimide layer constitutes a polyimide layer having high thermal expansion. Here, the polyimide layer having low thermal expansibility is a polyimide layer having a CTE preferably in the range of 0ppm/K to 20ppm/K, more preferably 0ppm/K to 15 ppm/K. The polyimide layer having high thermal expansion is a polyimide layer having a CTE of preferably 35ppm/K or more, more preferably 35ppm/K or more and 80ppm/K or less, and still more preferably 35ppm/K or more and 70ppm/K or less. The polyimide layer can be made to have a desired CTE by appropriately changing the combination of raw materials used, the thickness, and the drying/hardening conditions.

In the metal-clad laminate of the present embodiment, the insulating resin layer is preferably formed by a casting method in which a solution of a thermoplastic or non-thermoplastic polyimide or a solution of a precursor is sequentially applied. In the case of the casting method, an extremely thin insulating resin layer having a thickness of 15 μm or less, particularly 12 μm or less, including a plurality of polyimide layers can be easily produced. On the other hand, in the case of the tenter method, for example, in order to produce an insulating resin layer having a thickness of 15 μm or less, particularly 12 μm or less, a stretched film is required, and therefore, cracking or cracking is likely to occur, and the technical difficulty is high. Further, the in-plane thickness and CTE are likely to vary, and anisotropy is likely to occur in the CTE in the MD direction and the CTE in the TD direction.

(non-thermoplastic polyimide)

In the present embodiment, it is preferable that the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer contains a tetracarboxylic acid residue and a diamine residue, and these residues each contain an aromatic group. It is considered that since both of the tetracarboxylic acid residue and the diamine residue contained in the non-thermoplastic polyimide contain an aromatic group, the ordered structure of the non-thermoplastic polyimide is easily formed, and the dimensional stability is improved.

In the present invention, the tetracarboxylic acid residue means a tetravalent group derived from a tetracarboxylic dianhydride, and the diamine residue means a diamine residueA divalent group derived from a diamine compound. Further, as for the "diamine compound", the hydrogen atoms in the terminal two amino groups may be substituted, and may be, for example, -NR₃R₄(Here, R is₃、R₄Independently represents an optional substituent such as an alkyl group).

The non-thermoplastic polyimide contained in the metal-clad laminate of the present embodiment preferably contains 50 parts by mole or more of a diamine residue derived from a diamine compound represented by the following general formula (1) per 100 parts by mole of all diamine residues.

[ solution 1]

[ in the formula (1), R independently represents a halogen atom, or an alkyl or alkoxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a phenyl or phenoxy group which may be substituted with a monovalent hydrocarbon group having 1 to 6 carbon atoms or an alkoxy group, and n₁Independently represent an integer of 0 to 4, n₂Represents an integer of 0 to 1]

The diamine residue derived from the diamine compound represented by the general formula (1) is likely to form a ordered structure and to have a low CTE, and thus, dimensional stability can be improved. In addition, since two or more benzene rings are included, it is also advantageous in terms of improvement in dimensional stability in a case where it is also helpful to reduce the imide group concentration and reduce the moisture absorption. From this viewpoint, the diamine residue derived from the diamine compound represented by the general formula (1) is contained preferably in an amount of 50 parts by mole or more, more preferably in an amount of 60 to 100 parts by mole, based on 100 parts by mole of all the diamine residues contained in the non-thermoplastic polyimide. If the amount is less than 50 parts by mole, the CTE increases and the dimensional stability deteriorates.

Preferred specific examples of the diamine residue derived from the diamine compound represented by the general formula (1) include diamine residues derived from the following diamine compounds: 2,2' -dimethyl-4,4' -diaminobiphenyl (2,2' -dimethyl-4,4' -diaminobiphenol, m-TB), 2' -diethyl-4,4' -diaminobiphenyl (2,2' -diethyl-4,4' -diaminobiphenol, m-EB), 2' -diethoxy-4,4' -diaminobiphenyl (2,2' -diethoxy-4,4' -diaminobiphenol, m-EOB), 2' -dipropoxy-4,4' -diaminobiphenyl (2,2' -diethoxy-4,4' -diaminobiphenol, m-POB), 2' -n-propyl-4,4' -diaminobiphenyl (2,2' -n-propyl-4,4 '-diaminobiphenol, m-NPB), 2' -divinyl-4,4'-diaminobiphenyl (2,2' -diaminobiphenyl-4, 4 '-diaminobiphenol, VAB), 4' -diaminobiphenyl, 4'-diamino-2,2' -bis (trifluoromethyl) biphenyl (4,4 '-diaminono-2, 2' -bis (trifluoromethyl) biphenol, TFMB), 4 "-diamino-p-terphenyl (4, 4" -diaminono-p-terphenyl, DATP), and the like. Among these, 2'-dimethyl-4,4' -diaminobiphenyl (m-TB), 2'-diethyl-4,4' -diaminobiphenyl (m-EB), 4'-diamino-2,2' -bis (trifluoromethyl) biphenyl (TFMB), and 4,4 ″ -diamino-p-terphenyl (DATP) are preferable, and particularly, 2'-dimethyl-4,4' -diaminobiphenyl (m-TB) is most preferable because it is easy to form a rank structure and reduce the imide group concentration and the moisture absorption rate.

In addition, in order to reduce the elastic coefficient of the insulating resin layer, improve the elongation, the bending resistance, and the like, it is preferable that the non-thermoplastic polyimide contains a diamine residue derived from a diamine compound represented by the following general formula (2).

[ solution 2]

Wherein in the formula (2), R independently represents a halogen atom, or an alkyl group or an alkoxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a phenyl group or a phenoxy group which may be substituted with a monovalent hydrocarbon group or an alkoxy group having 1 to 6 carbon atoms,

Z₁independently represents a single bond selected from-O-, -S-, -CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-CO-、-SO₂A divalent radical of-or-NH-,

n₃independently represent an integer of 0 to 4, n₄Represents an integer of 0 to 2.

Wherein Z is₁At least one of (A) represents a group selected from-O-, -S-, -CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-CO-、-SO₂A divalent group of-or-NH-.

Since the diamine residue derived from the diamine compound represented by the general formula (2) has a site having flexibility, flexibility can be imparted to the insulating resin layer. From such a viewpoint, the diamine residue derived from the diamine compound represented by the general formula (2) is contained more preferably in the range of 1 to 50 mol parts, and most preferably in the range of 1 to 40 mol parts, relative to 100 mol parts of all diamine residues contained in the non-thermoplastic polyimide. When the amount of the carbon black is more than 50 parts by mole, the CTE increases and the dimensional stability deteriorates. In addition, when the content is less than 1 molar part, flexibility is deteriorated, and thus bending characteristics are deteriorated. In addition, in the case where the non-thermoplastic polyimide contains both of the diamine residue derived from the diamine compound represented by the above general formula (1) and the diamine residue derived from the diamine compound represented by the general formula (2), the content of the diamine residue derived from the diamine compound represented by the general formula (1) is more preferably in the range of 50 to 99 parts by mole, and most preferably in the range of 60 to 99 parts by mole, relative to 100 parts by mole of all the diamine residues contained in the non-thermoplastic polyimide.

Preferable specific examples of the diamine compound represented by the general formula (2) include: 3,3' -diaminodiphenylmethane, 3' -diaminodiphenylpropane, 3' -diaminodiphenylsulfide, 3' -diaminodiphenylsulfone, 3-diaminodiphenylether, 3,4' -diaminodiphenylmethane, 3,4' -diaminodiphenylpropane, 3,4' -diaminodiphenylsulfide, 3,4' -diaminobenzophenone, (3,3' -diamino) diphenylamine, 1,4-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene (1,3-bis (4-aminophenoxy) bezene, TPE-R), 1,4-bis (4-aminophenoxy) benzene (1,4-bis (4-aminophenoxy) benzene, TPE-Q), 3- [4- (4-aminophenoxy) phenoxy]Aniline, 3- [3- (4-aminophenoxy) phenoxy]Aniline, 1,3-bis (3-aminophenoxy) benzene (1,3-bis (3-aminophenoxy) bezene, APB), 4' - [ 2-methyl- (1, 3-phenylene) dioxy group]Dianiline, 4' - [ 4-methyl- (1, 3-phenylene) dioxy]Bis-aniline, 4' - [ 5-methyl- (1)3-phenylene) dioxy]Dianiline, bis [4- (3-aminophenoxy) phenyl]Methane, bis [4- (3-aminophenoxy) phenyl]Propane, bis [4- (3-aminophenoxy) phenyl]Ether, bis [4- (3-aminophenoxy) phenyl]Sulfone, bis [4- (3-aminophenoxy)]Benzophenone, bis [4,4' - (3-aminophenoxy)]Benzanilides, 4- [3- [4- (4-aminophenoxy) phenoxy ] phenoxy]Phenoxy radical]Aniline, 4' - [ oxybis (3, 1-phenyleneoxy)]Dianiline, bis [4- (4-aminophenoxy) phenyl]Ether (bis [4- (4-aminophenyloxy) phenyl)]ether, BAPE), bis [4- (4-aminophenoxy) phenyl]Ketone (bis [4- (4-aminophenyloxy) phenyl)]ketone, BAPK), bis [4- (3-aminophenoxy)]Biphenyl, bis [4- (4-aminophenoxy)]Biphenyl, 2-bis (4-aminophenoxyphenyl) propane (2,2-bis (4-aminophenyloxy) propane, BAPP), and the like. Among these, n in the general formula (2) is preferable₃For example, the compound (0) is preferably 4,4' -diaminodiphenyl ether (4,4' -diaminodiphenyl ether, 4,4' -DAPE), 1,3-bis (4-aminophenoxy) benzene (TPE-R), 1,3-bis (3-aminophenoxy) benzene (APB), 1,4-bis (4-aminophenoxy) benzene (TPE-Q), or 2,2-bis (4-aminophenoxyphenyl) propane (BAPP).

In particular, other diamines which are generally used may be used in combination as a raw material of the polyimide as long as the object of the present invention is not impaired. Examples of the other diamine include p-phenylene diamine (p-PDA) and m-phenylene diamine (m-PDA).

The tetracarboxylic acid residue contained in the non-thermoplastic polyimide is not particularly limited, and examples thereof include a tetracarboxylic acid residue derived from pyromellitic dianhydride (PMDA) (hereinafter also referred to as PMDA residue), and a tetracarboxylic acid residue derived from 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA) (hereinafter also referred to as BPDA residue). These tetracarboxylic acid residues can easily form a ordered structure. The PMDA residue is a residue that plays a role in controlling CTE and controlling glass transition temperature. Further, the BPDA residue is expected to have an effect of suppressing moisture absorption of the insulating resin layer by reducing the imide group concentration of the non-thermoplastic polyimide because the tetracarboxylic acid residue has no polar group and has a relatively large molecular weight. From this viewpoint, the total amount of PMDA residues and/or BPDA residues is preferably 50 parts by mole or more, more preferably in the range of 60 parts by mole to 100 parts by mole, and most preferably in the range of 80 parts by mole to 100 parts by mole, based on 100 parts by mole of all tetracarboxylic acid residues contained in the non-thermoplastic polyimide. If the content is less than 50 parts by mole, the CTE increases and the dimensional stability deteriorates.

Examples of other tetracarboxylic acid residues contained in the non-thermoplastic polyimide include tetracarboxylic acid residues derived from the following aromatic tetracarboxylic dianhydrides: 2,3',3,4' -biphenyltetracarboxylic dianhydride, 2',3,3' -biphenyltetracarboxylic dianhydride, 3,3',4,4' -diphenylsulfonetetracarboxylic dianhydride, 4,4' -oxydiphthalic anhydride, 2',3,3' -benzophenonetetracarboxylic dianhydride, 2,3,3',4' -benzophenonetetracarboxylic dianhydride or 3,3',4,4' -benzophenonetetracarboxylic dianhydride, 2,3',3,4' -diphenylethertetracarboxylic dianhydride, bis (2, 3-dicarboxyphenyl) ether dianhydride, 3,3',4,4' -p-terphenyltetracarboxylic dianhydride, 2,3,3',4' -p-terphenyltetracarboxylic dianhydride or 2,2',3,3' -p-terphenyltetracarboxylic dianhydride, 2-bis (2, 3-dicarboxyphenyl) -propane dianhydride or 2,2-bis (3, 4-dicarboxyphenyl) -propane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride or bis (3, 4-dicarboxyphenyl) methane dianhydride, bis (2, 3-dicarboxyphenyl) sulfone dianhydride or bis (3, 4-dicarboxyphenyl) sulfone dianhydride, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride or 1, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1,2,7, 8-phenanthrene-tetracarboxylic acid dianhydride, 1,2,6, 7-phenanthrene-tetracarboxylic acid dianhydride or 1,2,9, 10-phenanthrene-tetracarboxylic acid dianhydride, 2,3,6, 7-anthracenetetracarboxylic acid dianhydride, 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-dichloronaphthalene-1, 4,5, 8-tetracarboxylic dianhydride or 2, 7-dichloronaphthalene-1, 4,5, 8-tetracarboxylic dianhydride, 2,3,6, 7-tetrachloronaphthalene-1, 4,5, 8-tetracarboxylic dianhydride or 1,4,5, 8-tetrachloronaphthalene-2, 3,6, 7-tetracarboxylic dianhydride, 2,3,8, 9-perylene-tetracarboxylic dianhydride, 3,4,9, 10-perylene-tetracarboxylic dianhydride, 4,5,10, 11-perylene-tetracarboxylic dianhydride 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, thiophene-2, 3,4, 5-tetracarboxylic dianhydride, 4' -bis (2, 3-dicarboxyphenoxy) diphenylmethane dianhydride, and the like.

The CTE, toughness, thermal expansibility, adhesiveness, glass transition temperature (Tg), and the like of the non-thermoplastic polyimide can be controlled by selecting the kind of the acid anhydride and the diamine, or by selecting the molar ratio of each of the two or more kinds of acid anhydride and diamine. In the case where the non-thermoplastic polyimide has a plurality of polyimide structural units, the polyimide structural units may be present in the form of blocks or may be present randomly, preferably randomly.

The imide group concentration of the non-thermoplastic polyimide is preferably 35% by weight or less. Here, the "imide group concentration" means the imide group (- (CO) in polyimide₂A value obtained by dividing the molecular weight of-N-) by the molecular weight of the entire structure of the polyimide. When the imide group concentration exceeds 35% by weight, the molecular weight of the resin itself becomes small and the low hygroscopicity is also deteriorated due to the increase of the polar group. By selecting the combination of the acid anhydride and the diamine compound, the molecular orientation of the non-thermoplastic polyimide is controlled, whereby an increase in CTE associated with a decrease in the imide group concentration is suppressed, and low hygroscopicity is ensured.

The weight average molecular weight of the non-thermoplastic polyimide is, for example, preferably within a range of 10,000 to 400,000, and more preferably within a range of 50,000 to 350,000. When the weight average molecular weight is less than 10,000, the strength of the insulating resin layer tends to be reduced and the insulating resin layer tends to be brittle. On the other hand, when the weight average molecular weight exceeds 400,000, the viscosity tends to increase excessively, and defects such as uneven thickness and streaks tend to occur during coating operation.

(thermoplastic polyimide)

In the present embodiment, it is preferable that the thermoplastic polyimide constituting the thermoplastic polyimide layer contains a tetracarboxylic acid residue and a diamine residue, and these residues each contain an aromatic group. Since both the tetracarboxylic acid residue and the diamine residue contained in the thermoplastic polyimide contain an aromatic group, heat resistance can be ensured.

In the present embodiment, the diamine residue contained in the thermoplastic polyimide preferably contains a diamine residue derived from the diamine compound represented by the above general formula (2). The diamine residue derived from the diamine compound represented by the general formula (2) is preferably 50 parts by mole or more, more preferably in the range of 70 to 100 parts by mole, and most preferably in the range of 80 to 100 parts by mole, based on 100 parts by mole of all diamine residues. By including 50 parts by mole or more of the diamine residue derived from the diamine compound represented by the general formula (2) per 100 parts by mole of all the diamine residues, flexibility and adhesiveness can be imparted to the thermoplastic polyimide layer, and the thermoplastic polyimide layer can function as an adhesive layer to the metal layer. Among diamine residues derived from the diamine compound represented by the general formula (2), 4 '-diaminodiphenyl ether (4,4' -DAPE), 1,3-bis (4-aminophenoxy) benzene (TPE-R), and 2,2-bis (4-aminophenoxyphenyl) propane (BAPP) are particularly preferable. Since the diamine residue derived from these diamine compounds has a site having flexibility, flexibility can be imparted by lowering the elastic coefficient of the insulating resin layer.

In the present embodiment, as the diamine residue derived from a diamine compound other than the above-mentioned general formula (2) contained in the thermoplastic polyimide, for example, a diamine residue derived from a diamine compound represented by the following formula: 2,2'-dimethyl-4,4' -diaminobiphenyl (m-TB), 2'-diethyl-4,4' -diaminobiphenyl (m-EB), 2'-diethoxy-4,4' -diaminobiphenyl (m-EOB), 2 '-dipropyloxy-4, 4' -diaminobiphenyl (m-POB), 2'-n-propyl-4,4' -diaminobiphenyl (m-NPB), 2,2' -divinyl-4,4' -diaminobiphenyl (VAB), 4' -diaminobiphenyl, 4' -diamino-2,2' -bis (trifluoromethyl) biphenyl (TFMB), p-phenylenediamine (p-PDA), m-phenylenediamine (m-PDA), and the like.

The tetracarboxylic acid residue contained in the thermoplastic polyimide is not particularly limited, and examples thereof include a tetracarboxylic acid residue derived from pyromellitic dianhydride (PMDA) (hereinafter also referred to as PMDA residue), a tetracarboxylic acid residue derived from 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA) (hereinafter also referred to as BPDA residue), and a tetracarboxylic acid residue derived from 3,3',4,4' -benzophenonetetracarboxylic dianhydride (hereinafter also referred to as BTDA residue). These tetracarboxylic acid residues can easily form a ordered structure, and the rate of change in size under a high-temperature environment is reduced. The PMDA residue is a residue that plays a role in controlling CTE and controlling glass transition temperature. Further, the BPDA residue is expected to have an effect of reducing the imide group concentration of the thermoplastic polyimide and suppressing moisture absorption of the insulating resin layer because the tetracarboxylic acid residue has no polar group and has a relatively large molecular weight. Furthermore, since BTDA residues have moderate bendability, flexibility can be provided without greatly increasing CTE. From this viewpoint, the total amount of PMDA residues, BPDA residues, and/or BTDA residues is preferably 50 parts by mole or more, more preferably in the range of 60 parts by mole to 100 parts by mole, and most preferably in the range of 80 parts by mole to 100 parts by mole, based on 100 parts by mole of all tetracarboxylic acid residues contained in the thermoplastic polyimide.

Examples of the other tetracarboxylic acid residue contained in the thermoplastic polyimide include tetracarboxylic acid residues derived from the same aromatic tetracarboxylic dianhydrides as those exemplified in the non-thermoplastic polyimide.

In the thermoplastic polyimide, the CTE, the tensile elastic modulus, the glass transition temperature, and the like can be controlled by selecting the kinds of the tetracarboxylic acid residue and the diamine residue or the molar ratio of each of the tetracarboxylic acid residue and the diamine residue when two or more kinds of tetracarboxylic acid residues or diamine residues are contained. In the case where the thermoplastic polyimide has a plurality of polyimide structural units, the thermoplastic polyimide may be present in the form of blocks or may be present randomly, preferably randomly.

The imide group concentration of the thermoplastic polyimide is preferably 35% by weight or less. Here, the "imide group concentration" means the imide group (- (CO) in polyimide₂A value obtained by dividing the molecular weight of-N-) by the molecular weight of the entire structure of the polyimide. When the imide group concentration exceeds 35% by weight, the molecular weight of the resin itself becomes small and the low hygroscopicity is also deteriorated due to the increase of the polar group. By controlling the molecular orientation of the thermoplastic polyimide by selecting the combination of the acid anhydride and the diamine compound, an increase in CTE associated with a decrease in the imide group concentration is suppressed, and low hygroscopicity is ensured.

The weight average molecular weight of the thermoplastic polyimide is, for example, preferably within a range of 10,000 to 600,000, and more preferably within a range of 50,000 to 500,000. When the weight average molecular weight is less than 10,000, the strength of the insulating resin layer tends to be reduced and the insulating resin layer tends to be brittle. On the other hand, when the weight average molecular weight exceeds 600,000, the viscosity tends to increase excessively, and defects such as uneven thickness and streaks tend to occur during coating operation.

(Synthesis of non-thermoplastic polyimide and thermoplastic polyimide)

Generally, polyimides can be made by: tetracarboxylic dianhydride and a diamine compound are reacted in a solvent to produce a polyamic acid, and then heated to be closed in a ring. For example, a tetracarboxylic dianhydride and a diamine compound are dissolved in an organic solvent in approximately equimolar amounts, and the resulting solution is stirred at a temperature in the range of 0 ℃ to 100 ℃ for 30 minutes to 24 hours to cause a polymerization reaction, thereby obtaining a polyamic acid as a precursor of a polyimide. During the reaction, the reaction components are dissolved so that the produced precursor is in the range of 5 to 30 wt%, preferably 6 to 20 wt% in the organic solvent. Examples of the organic solvent used in the polymerization reaction include: n, N-Dimethylformamide (DMF), N-dimethylacetamide (DMAc), N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, Dimethylsulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme (diglyme), triglyme (triglyme), cresol, and the like. Two or more of these solvents may be used in combination, and an aromatic hydrocarbon such as xylene or toluene may be used in combination. The amount of the organic solvent used is not particularly limited, but is preferably adjusted so that the concentration of the polyamic acid solution obtained by the polymerization reaction is about 5 to 30 wt%.

The polyamic acid synthesized is usually advantageously used in the form of a reaction solvent solution, and may be concentrated, diluted or replaced with another organic solvent as necessary. In addition, polyamic acid is generally excellent in solvent solubility and thus can be advantageously used. The viscosity of the solution of polyamic acid is preferably in the range of 500cps to 100,000 cps. If the amount is outside the above range, defects such as uneven thickness and streaks are likely to occur in the film during coating work using a coater or the like. The method for imidizing the polyamic acid is not particularly limited, and for example, heat treatment such as heating in the solvent at a temperature in the range of 80 to 400 ℃ for 1 to 24 hours is preferably employed.

< Metal layer >

Examples of the metal constituting the metal layer include metals selected from copper, aluminum, stainless steel, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, zirconium, gold, cobalt, titanium, tantalum, zinc, lead, tin, silicon, bismuth, indium, and alloys thereof. The metal layer may be formed by a method such as sputtering, vapor deposition, or plating, but a metal foil is preferably used from the viewpoint of adhesiveness. Copper foil is particularly preferable in terms of conductivity. The copper foil may be any of an electrolytic copper foil and a rolled copper foil. In the case of continuously producing the metal-clad laminate of the present embodiment, a long metal foil obtained by winding a metal foil having a predetermined thickness into a roll shape is used as the metal foil.

The metal layer is preferably a copper foil having a rust preventive layer containing nickel, zinc and cobalt on at least the surface on the side in contact with the thermoplastic polyimide layer. In this case, the surface roughness Rz of the copper foil on at least the side in contact with the thermoplastic polyimide layer is preferably 1.0 μm or less, and more preferably 0.6 μm or less. When the surface roughness Rz of the copper foil exceeds 1.0 μm, the thermoplastic polyimide layer in contact with the copper foil is damaged in an extremely thin insulating resin layer having an overall thickness of 15 μm or less, particularly 12 μm or less, and defects such as insulation property and peel strength occur.

In the metal-clad laminate of the present embodiment, when the insulating resin film of 50mm square after humidity conditioning for 24 hours is left to stand so that the convex surface of the central portion thereof is in contact with the flat surface, the curl amount obtained by calculating the average value of the floating amounts at the four corners of the insulating resin film obtained by etching and removing the metal layer is preferably 10mm or less, more preferably 8mm or less, and most preferably 5mm or less, among the insulating resin films obtained by etching and removing the metal layer. If the curl amount exceeds 10mm, workability is deteriorated and it is difficult to maintain dimensional accuracy in circuit processing.

The width (i.e., the length in the TD direction) of the metal-clad laminate of the present embodiment is preferably 470mm or more, and more preferably in the range of 470mm to 1200 mm. In general, as the width (i.e., the length in the TD direction) of the metal-clad laminate is larger, it is more difficult to control the dimensional stability and the in-plane isotropy, and the deviation tends to be larger. Therefore, the present invention is particularly useful for application to a metal-clad laminate having a width of 470mm or more, and can significantly exhibit the effects of the present invention. When the width exceeds 1200mm, the variation in-plane dimensional stability and thickness becomes large, and for example, when the film is processed into an FPC or the like, defects are likely to occur, and the yield tends to be deteriorated.

Hereinafter, a copper-clad laminate having a copper layer will be described as a preferred embodiment of the metal-clad laminate.

< copper-clad laminate >

The copper-clad laminate of the present embodiment may include an insulating resin layer and a copper layer such as a copper foil on at least one surface of the insulating resin layer. In addition, in order to improve the adhesion between the insulating resin layer and the copper layer, the layer in contact with the copper layer in the insulating resin layer is a thermoplastic polyimide layer. The insulating resin layer has the same configuration as that described for the metal-clad laminate.

The copper layer is provided on one or both sides of the insulating resin layer. That is, the copper-clad laminate of the present embodiment may be a single-sided copper-clad laminate (single-sided CCL) or a double-sided copper-clad laminate (double-sided CCL). In the case of the single-sided CCL, the copper layer laminated on one side of the insulating resin layer is referred to as "1 st copper layer" in the present invention. In the case of the double-sided CCL, the copper layer laminated on one side of the insulating resin layer is referred to as "1 st copper layer" in the present invention, and the copper layer laminated on the side opposite to the side on which the 1 st copper layer is laminated in the insulating resin layer is referred to as "2 nd copper layer" in the present invention. The "2 nd copper layer" corresponds to "another metal layer" laminated on the opposite side of the insulating resin layer from the 1 st copper layer. The copper-clad laminate of the present embodiment is used as an FPC by forming a copper wiring by performing wiring circuit processing such as etching of a copper layer.

The copper-clad laminate can be produced, for example, by: a polyimide resin film is prepared, and a seed layer (seed layer) is formed by sputtering metal thereon, and then a copper layer is formed by, for example, copper plating.

In addition, the copper-clad laminate may also be prepared by: a resin film of polyimide is prepared, and a copper foil is laminated thereon by a method such as thermocompression bonding.

Further, the copper-clad laminate may also be prepared by: a coating liquid containing polyamic acid as a precursor of polyimide is cast on a copper foil, dried to form a coating film, and then subjected to heat treatment and imidization to form a polyimide layer. In the case of forming an insulating resin layer including a plurality of polyimide layers by a casting method, the coating liquid of polyamic acid may be applied in sequence, for example, in the case where the polyimide layers are a three-layer structure, the following method is preferable: a coating solution of polyamic acid is applied to a copper foil in this order so that a precursor layer of thermoplastic polyimide, a precursor layer of non-thermoplastic polyimide, and a precursor layer of thermoplastic polyimide are laminated in this order, and then heat-treated and imidized.

(layer 1 st copper)

In the copper-clad laminate of the present embodiment, the copper foil used for the 1 st copper layer (hereinafter, sometimes referred to as "1 st copper foil") is not particularly limited, and may be, for example, a rolled copper foil or an electrolytic copper foil.

For example, when high-density mounting or bendability is required, the thickness of the 1 st copper foil is preferably 35 μm or less, more preferably in the range of 6 to 18 μm. If the thickness of the 1 st copper foil exceeds 35 μm, bending stress applied to the copper layer (or copper wiring) when the copper-clad laminate (or FPC) is bent becomes large, and thus the bending resistance is lowered. In addition, from the viewpoint of production stability and workability, the lower limit of the thickness of the 1 st copper foil is preferably set to 6 μm. In applications where heat dissipation is required, such as power modules and LED substrates, the thickness of the 1 st copper foil is preferably 18 μm or more, more preferably in the range of 18 to 50 μm, and even more preferably in the range of 35 to 50 μm. In applications requiring heat dissipation, a large current is often required depending on the required power of a device to be mounted, and it is preferable to increase the thickness of the metal layer, and if the thickness of the metal layer is less than 18 μm, the supply current to the device is limited, and if it exceeds 50 μm, the workability tends to deteriorate.

The tensile elastic modulus of the 1 st copper foil is, for example, preferably in the range of 50GPa to 300GPa, and more preferably in the range of 70GPa to 250 GPa. In the case of using a rolled copper foil as the 1 st copper foil in the present embodiment, when annealing (anneal) is performed by heat treatment, flexibility is easily increased. Therefore, if the tensile elastic coefficient of the copper foil is less than the lower limit, the rigidity of the 1 st copper foil itself is lowered by heating in the step of forming the insulating resin layer on the 1 st copper foil in length. On the other hand, if the tensile elastic modulus exceeds the upper limit value, a larger bending stress is applied to the copper wiring when the FPC is bent, and the bending resistance thereof is lowered. The rolled copper foil has a tendency that the tensile elastic modulus thereof changes depending on the heat treatment conditions at the time of forming the insulating resin layer on the copper foil, the annealing treatment of the copper foil after forming the insulating resin layer, and the like. Therefore, in the present embodiment, in the finally obtained copper-clad laminate, the coefficient of elasticity in tension of the 1 st copper foil may be within the above range.

The 1 st copper foil is not particularly limited, and a commercially available rolled copper foil can be used.

(No. 2 copper layer)

The 2 nd copper layer is laminated on the surface of the insulating resin layer opposite to the 1 st copper layer. The copper foil used for the 2 nd copper layer (2 nd copper foil) is not particularly limited, and may be, for example, a rolled copper foil or an electrolytic copper foil. In addition, a commercially available copper foil may be used as the 2 nd copper foil. In addition, the same copper foil as the 1 st copper foil may be used as the 2 nd copper foil.

As described above, the metal-clad laminate of the present embodiment includes an insulating resin layer having high dimensional stability and in-plane isotropy, excellent adhesion of the metal layer, and suppressed curling, even though the insulating resin layer has an extremely thin layer having a thickness of 15 μm or less, preferably 12 μm or less. Therefore, dimensional changes and curling due to environmental changes (e.g., high-temperature/high-pressure environments, humidity changes, etc.) during the circuit processing step, the substrate laminating step, and the component mounting step can be effectively suppressed. Further, since the thickness of the insulating resin layer is 15 μm or less, preferably 12 μm or less, high-density mounting of a circuit board such as an FPC obtained from the metal-clad laminate can be realized. Therefore, by using the metal-clad laminate of the present embodiment as a circuit board material, miniaturization of electronic devices can be coped with, and reliability and yield of the circuit board can be improved. Further, since the insulating resin layer is thin and has excellent adhesion to the metal layer, it is also useful for applications requiring heat dissipation, such as a power module and a substrate for an LED.

< Circuit Board >

The metal-clad laminate of the present embodiment is useful mainly as a material for a circuit board such as an FPC. For example, a circuit board such as an FPC according to an embodiment of the present invention can be manufactured by patterning a copper layer of the exemplary copper-clad laminate by a conventional method to form a wiring layer. Further, a multilayer circuit board or a rigid flexible board (rigid FPC) can be produced by laminating a plurality of circuit boards such as FPCs according to an embodiment of the present invention.

Further, since the insulating resin layer of the circuit board such as FPC according to an embodiment of the present invention is thin, it is useful for applications requiring heat dissipation, for example, a power module, a substrate for LED, and the like. In such applications, the thickness of the metal layer may be increased in order to increase the supply current to the device. Further, the thickness of the insulating resin layer may be reduced to improve heat dissipation. When the insulating resin layer is thinned, the thickness of the insulating resin layer is preferably in the range of 2 to 9 μm, more preferably in the range of 2 to 5 μm. If the thickness of the insulating resin layer exceeds 9 μm, the heat dissipation performance is impaired, and if it is less than 2 μm, there is a fear of troubles such as breakage at the time of circuit processing and failure to secure insulation after processing as an FPC.