JP7405644B2 - Metal-clad laminates and circuit boards - Google Patents

Description

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

In recent years, as electronic devices have become smaller, lighter, and space-saving, flexible printed circuit boards (FPCs) have become thinner, lighter, more flexible, and have excellent durability even after repeated bending. Demand for circuits is increasing. FPC can be mounted three-dimensionally and with high density even in a limited space, so it can be used, for example, in the wiring of movable parts of electronic devices such as HDDs, DVDs, mobile phones, and smartphones, as well as parts such as cables and connectors. Its uses are expanding.

FPC is manufactured by etching the metal layer of a metal-clad laminate having a metal layer and an insulating resin layer to form wiring. In the photolithography process for metal-clad laminates and the FPC mounting process, various processes such as bonding, cutting, exposure, and etching are performed. Machining accuracy in these steps is important in maintaining the reliability of electronic devices equipped with FPCs. However, metal-clad laminates have a structure in which a metal layer and an insulating resin layer are laminated with different coefficients of thermal expansion (hereinafter sometimes referred to as "CTE"), so the CTE of the metal layer and the insulating resin layer is different. The difference causes stress between the layers. This stress is released when the metal layer is etched to process wiring, causing expansion and contraction, which causes a change in the dimensions of the wiring pattern. As a result, dimensional changes ultimately occur at the FPC stage, causing poor connections between wirings or between wirings and terminals, reducing the reliability and yield of the circuit board. Therefore, dimensional stability is a very important property in metal-clad laminates used as circuit board materials.

It is expected that electronic devices will become more sophisticated and smaller in the future. Therefore, for example, it is thought that the need to use FPC in a multilayered state will increase. Additionally, as the housings of electronic devices such as mobile phones and smartphones become thinner, there is a growing trend for circuit boards themselves to be thinner. When the thickness of the insulating resin layer on circuit boards becomes thinner, finer wiring processing is required to match impedance, so it is necessary to improve dimensional stability and suppress curling more than ever before. be. Adhesion is also required to prevent the wiring from peeling off from the substrate when processed into fine wiring.
Therefore, in the insulating resin layer of circuit boards such as FPC,
・Thinner thickness,
・Low thermal expansion (high dimensional stability),
・Reduction of in-plane anisotropy (isotropy),
・Low curling (both in the state of the metal-clad laminate and in the state of the film after etching),
・Adhesion to metal layer,
These characteristics will be required more strictly than ever before. When the thickness of the insulating resin layer becomes an extremely thin layer of 15 μm or less, especially 12 μm or less, conventional design concepts cannot be applied to meet the required characteristics other than thickness, and a different approach than before is required.

As a metal-clad laminate, a copper-clad laminate (CCL) in which copper foil and a polyimide layer are laminated is widely used. A single-layer polyimide film with a thickness of 10 μm or less that can be applied to the insulating resin layer of CCL has been proposed (Patent Documents 1 to 3).
However, the polyimide films proposed in Patent Documents 1 to 3 have little description of in-plane anisotropy reduction (isotropy), and since they are single-layer polyimide films, they cannot be laminated with metal layers. Sometimes, when an adhesive or the like is used, the total thickness of the insulating resin layer increases, so there is room for improvement in terms of reducing the thickness.

Furthermore, as a metal-clad laminate without an adhesive layer, a metal-clad laminate having an insulating resin layer made of three polyimide layers has also been proposed (Patent Document 4). However, Patent Document 4 is concerned with improving solder resistance after moisture absorption, and does not disclose or suggest an insulating resin layer in which the total thickness of three polyimide layers is 12 μm or less, and does not disclose or suggest an insulating resin layer in which the total thickness of three polyimide layers is 12 μm or less. There is room for improvement in terms of thinning. Furthermore, there is little description of warpage (curl) in metal-clad laminates or films after etching.
As a method for improving curl in metal-clad laminates and films after etching, we have created a high thermal expansion polyimide layer on both sides of a low thermal expansion polyimide layer and controlled the thickness ratio of the high thermal expansion polyimide layer to prevent film curl. A controlled metal-clad laminate has also been proposed (Patent Document 5). However, the thickness of each insulating resin layer is around 25 μm, and there is little description of control techniques when the thickness is reduced.

Furthermore, a polyimide film with a thickness of about 25 μm that can reduce dimensional changes during high-temperature processing by controlling CTE, 0° retardation, etc. has also been proposed (Patent Document 6). However, the thinner the thickness, the more difficult it is to find a difference in 0° retardation, and there is room for improvement as an index for evaluating physical properties.

Japanese Patent Application Publication No. 2016-186031 Japanese Patent Application Publication No. 2014-196467 Japanese Patent Application Publication No. 2017-145325 Unexamined Japanese Patent Publication No. 2016-141152 JP2006-306086A JP 2017-200759 Publication

An object of the present invention is to provide a metal-clad laminate that has an insulating resin layer that has high dimensional stability and in-plane isotropy even when the thickness of the insulating resin layer is thin, and has excellent adhesiveness with metal layers. An object of the present invention is to provide a metal-clad laminate in which curling is suppressed both in the state of the film and in the state of the film after etching the metal layer.

As a result of intensive studies, the present inventors have found that the above problem can be solved by controlling the birefringence Δn(xy-z) in the in-plane direction and the thickness direction in the insulating resin layer, and have completed the present invention. reached.

That is, the metal-clad laminate of the present invention is a metal-clad laminate including an insulating resin layer and a metal layer laminated on one side of the insulating resin layer.
In the metal-clad laminate of the present invention, the insulating resin layer includes a non-thermoplastic polyimide layer made of non-thermoplastic polyimide, and a thermoplastic polyimide layer provided in contact with at least one surface of the non-thermoplastic polyimide layer. It has a thermoplastic polyimide layer composed of.
In the metal-clad laminate of the present invention, the thermoplastic polyimide layer is interposed between the metal layer and the non-thermoplastic polyimide layer, and the insulating resin layer has a thickness of 2 μm or more and 15 μm or less. The birefringence Δn(xy-z) in the thickness direction is within the range of 0.080 to 0.140.

In the metal-clad laminate of the present invention, the non-thermoplastic polyimide contains a tetracarboxylic acid residue and a diamine residue, and a diamine compound represented by the following formula (1) is added to 100 mole parts of the total diamine residue. It may contain 50 mole parts or more of a diamine residue derived from.

In formula (1), R is independently a halogen atom, an alkyl group or alkoxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a monovalent hydrocarbon group having 1 to 6 carbon atoms or alkoxy It represents a phenyl group or a phenoxy group which may be substituted with a group, n ₁ independently represents an integer of 0 to 4, and n ₂ represents an integer of 0 to 1.

In the metal-clad laminate of the present invention, the insulating resin layer is composed of a non-thermoplastic polyimide layer made of the non-thermoplastic polyimide and a thermoplastic polyimide provided in contact with both sides of the non-thermoplastic polyimide layer. It may also have a thermoplastic polyimide layer.
In the metal-clad laminate of the present invention, the thermoplastic polyimide layer provided on the side in contact with the metal layer has a thickness of T1, the non-thermoplastic polyimide layer has a thickness of T2, and the metal layer is When the thickness of the thermoplastic polyimide layer provided on the opposite side is T3, the thicknesses of T1, T2, and T3 may 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, the CTE of the insulating resin layer may be within a range of 15 ppm/K or more and 30 ppm/K or less, and the CTE in the MD direction (CTE _MD ) and the CTE in the TD direction in the insulating resin layer (CTE _TD ) may satisfy the relationship of the following formula (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 470 mm or more, and the variation in thickness of the insulating resin layer may be within a range of ±0.5 μm.

In the metal-clad laminate of the present invention, in the insulating resin film obtained by etching and removing the metal layer, the insulating resin film of 50 mm square is dried under conditions of 23° C. and 50% RH for 24 hours. , the amount of curl obtained by calculating the average value of the amount of rise of the four corners when the sheet is left standing so that the convex surface of the central portion is in contact with a flat surface may be 10 mm 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) is 50 moles per 100 mole parts of the total diamine residues contained in the non-thermoplastic polyimide. The amount of the diamine residue derived from the diamine compound represented by the following general formula (2) may be within the range of 1 to 50 parts by mole.

In formula (2), R is independently a halogen atom, an alkyl group or alkoxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a monovalent hydrocarbon group having 1 to 6 carbon atoms or alkoxy Indicates a phenyl group or phenoxy group which may be substituted with a group,
Z ₁ is independently a single bond, -O-, -S-, -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -CO-, -SO ₂ -, or -NH - indicates a divalent group selected from
n ₃ independently represents an integer of 0 to 4, and n ₄ represents an integer of 0 to 2.
However, at least one of Z ₁ is -O-, -S-, -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -CO-, -SO ₂ -, or - Indicates a divalent group selected from NH-.

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

The circuit board of the present invention is formed by processing the metal layer of any of the metal clad laminates described above into wiring.

The metal-clad laminate of the present invention has an insulating resin layer that is thin, has high dimensional stability and in-plane isotropy, and has excellent adhesiveness to the metal layer, Curls are also suppressed. Therefore, the insulating resin layer has excellent dimensional stability and is less likely to curl when processing circuits on FPCs and the like. Furthermore, since the thickness of the insulating resin layer is thin, when applied to a multilayer board, the total thickness is reduced and high-density packaging becomes possible. In addition, because the insulating resin layer is thin and has excellent adhesion to metal layers, it has excellent heat dissipation from power devices and LED elements mounted on the circuit, and has excellent adhesion even in high-temperature environments. is guaranteed. Therefore, the metal-clad laminate of the present invention is also useful in applications where heat dissipation is required.

FIG. 2 is a drawing for explaining a retardation evaluation system used in Examples and Comparative Examples. FIG. 2 is a diagram illustrating the principle of a method for measuring retardation used in Examples and Comparative Examples.

Next, embodiments of the present invention will be described.

<Metal-clad laminate>
The metal-clad laminate of this embodiment includes an insulating resin layer and a metal layer laminated on at least one side of the insulating resin layer. Note that the metal-clad laminate of this embodiment may be a single-sided metal-clad laminate having a metal layer on one side of the insulating resin layer, or a double-sided metal-clad laminate having metal layers on both sides of the insulating resin layer. It may be.

<Insulating resin layer>
In the metal-clad laminate of this embodiment, the insulating resin layer has a thermoplastic polyimide layer on at least one of the non-thermoplastic polyimide layers. That is, the thermoplastic polyimide layer may be provided on one or both sides of the non-thermoplastic polyimide layer. Moreover, the thermoplastic polyimide layer is interposed between the metal layer and the non-thermoplastic polyimide layer. That is, the metal layer is laminated in contact with the surface of the thermoplastic polyimide layer. Here, non-thermoplastic polyimide generally refers to polyimide that does not soften or exhibit adhesive properties even when heated. A polyimide having a storage modulus of 1.0×10 ⁹ Pa or more at 360° C. and a storage modulus of 1.0×10 ⁸ Pa or more at 360° C. In addition, thermoplastic polyimide generally refers to polyimide whose glass transition temperature (Tg) can be clearly confirmed, but in the present invention, the storage modulus at 30°C measured using DMA is 1.0 × 10 ⁹ Pa or more, and a storage modulus at 360° C. of less than 1.0×10 ⁸ Pa.

The insulating resin layer may have a two-layer structure of a thermoplastic polyimide layer and a non-thermoplastic polyimide layer, but from the side in contact with the metal layer, the thermoplastic polyimide layer, the non-thermoplastic polyimide layer and the thermoplastic polyimide layer are It is preferable to have a three-layer structure laminated in sequence. For example, when forming an insulating resin layer by a casting method, it may have a two-layer structure in which a thermoplastic polyimide layer and a non-thermoplastic polyimide layer are laminated in this order from the cast side, or a thermoplastic polyimide layer and a non-thermoplastic polyimide layer are laminated from the cast side. A three-layer structure may be used in which a non-thermoplastic polyimide layer and a thermoplastic polyimide layer are laminated in this order, but a three-layer structure is preferable. The "cast surface" herein refers to the surface on the support side when forming the polyimide layer. The support may be a metal layer of a metal-clad laminate, or a support used when forming a gel film or the like. Note that the surface of the insulating resin layer opposite to the cast surface is described as a "laminate surface," but unless otherwise specified, a metal layer may or may not be laminated on the laminate surface.

<Thickness of insulating resin layer and birefringence Δn(xy-z) in the thickness direction>
To ensure dimensional stability, metal-clad laminates often include a non-thermoplastic polyimide layer with a low CTE, but the CTE of the non-thermoplastic polyimide layer tends to decrease as the thickness becomes thinner. . This behavior is particularly noticeable in the casting method, and the reason is that during the heat treatment process, the thinner the resin layer is, the more the solvent present in the resin layer evaporates and the more oriented the molecules become. Due to the above behavior, it is considered that the thinner the thickness, the smaller the orientation difference in the thickness direction.
For this reason, even if the thickness ratio of the thermoplastic layer/non-thermoplastic layer in the polyimide layer with a thickness of about 25 μm in the conventional technology is applied as is to the thin insulating resin layer, the CTE of the metal layer and the resin layer will be lowered. Mismatch occurs and dimensional stability deteriorates. Furthermore, in the case of a polyimide film composed of a thermoplastic layer and a non-thermoplastic layer, the orientation distribution in the thickness direction of the non-thermoplastic layer changes, so the thickness ratio of the thermoplastic layer and non-thermoplastic layer is the same as before. Curling occurs in the film.
In other words, an ultra-thin insulating resin layer requires a different design concept from the conventional technology from the viewpoint of improving dimensional stability after circuit processing and suppressing curling.

In order to increase the dimensional stability after circuit processing and suppress curling, the thickness ratio of the thermoplastic layer and non-thermoplastic layer must be controlled by considering lower CTE due to thinning and changes in orientation distribution in the thickness direction. However, it is necessary to balance the CTE of each layer, but it is not easy to understand the CTE of each layer because it is difficult to isolate each layer, especially in a thin region.
Furthermore, when an insulating resin layer is manufactured by a casting method, the solvent escapes in one direction, so even if the layers are made of the same material and have the same thickness, the CTE will have different values depending on the order of lamination. Therefore, the CTE of each layer of the insulating resin layer formed by the casting method differs from the CTE value obtained by measuring a polyimide film separately produced from the same material and the same thickness as each layer.

Therefore, as a result of careful consideration of the balance of each layer, we evaluated the molecular orientation and the thickness ratio of thermoplastic layer/non-thermoplastic layer using birefringence Δn (xy-z) in the thickness direction, and found that it was within a predetermined range. It was discovered that dimensional stability and film curl can be suppressed. Here, "birefringence Δn(xy-z) in the thickness direction" refers to the refractive index Nxy in the in-plane direction (xy plane) and the refractive index Nz in the cross-sectional direction (z direction) orthogonal to the in-plane direction in a polyimide film. This is the difference.
As the molecular orientation progresses, the tendency of the molecules to align in the in-plane direction becomes stronger, so Δn(xy-z) becomes larger, and when the orientation does not progress, Δn(xy-z) becomes smaller. Further, as the proportion of the non-thermoplastic layer increases, Δn(xy-z) also increases.
Therefore, by evaluating the degree of molecular orientation and the thickness ratio of the thermoplastic layer/non-thermoplastic layer using Δn (xy-z) and keeping it within a predetermined range, dimensional stability can be improved and film curl can be suppressed.

From this point of view, in the metal-clad laminate of the present embodiment, the thickness of the insulating resin layer is within the range of 2 μm to 15 μm, and the birefringence Δn(xy-z) in the thickness direction is 0.080 to 0. Control within the range of .140 or less.
The thickness of the insulating resin layer can be set within a predetermined range depending on the purpose of use, but if the thickness of the insulating resin layer is less than the lower limit above, electrical insulation cannot be guaranteed. Problems may arise, such as difficulty in handling during the manufacturing process due to decreased handling properties. On the other hand, if the thickness of the insulating resin layer exceeds the above upper limit, it becomes difficult to reduce the thickness of circuit boards such as FPCs and to implement high-density mounting. The thinner the thickness, the more difficult it becomes to apply the existing design, so the effects of the present invention are more pronounced when applied to thinner areas.
In addition, if the birefringence Δn(xy-z) in the thickness direction is less than 0.080, the orientation will not progress sufficiently, which will cause deterioration of dimensional stability, and orientation differences in the thickness direction will likely occur. The film also tends to curl. On the other hand, when the birefringence Δn(xy-z) in the thickness direction exceeds 0.140, the CTE decreases excessively, and the dimensional stability after circuit processing deteriorates due to mismatch with the CTE of the metal foil.

The birefringence Δn(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 keeping the birefringence Δn(xy-z) within the above-determined range, curling of the film and reduction in dimensional stability due to mismatch between the metal layer and the resin layer can be suppressed, and the thickness of the insulating resin layer can be reduced to 15 μm. Hereinafter, even with a thin film of, for example, 12 μm or less, good handling properties during circuit processing and dimensional accuracy of fine wiring can be ensured.

The thickness of the insulating resin layer is 15 μm or less, preferably 12 μm or less, more preferably 9 μm or less, and even more preferably 5 μm or less. When the thickness of the insulating resin layer is 15 μm or less, preferably 12 μm or less, more preferably 9 μm or less, and still more preferably 5 μm or less, it becomes possible to produce an extremely thin circuit board. Therefore, the degree of freedom in application to folded wiring, multilayer wiring, etc. inside a thin housing increases, and high-density packaging becomes possible.

Further, in this embodiment, when the average thickness of the insulating resin layer is Tμm, the thickness variation is preferably within the range of T±0.5μm, and preferably within the range of T±0.3μm. is more preferable. If the thickness variation exceeds T±0.5 μm, it may become difficult to control the birefringence Δn(xy-z) in the thickness direction.

<Thickness ratio of thermoplastic layer and non-thermoplastic layer>
In the conventional design, the orientation difference in the thickness direction promotes the orientation on the laminate side. By making the thermoplastic polyimide layer slightly thicker, curling of the film is suppressed. However, when the thickness of the polyimide layer is reduced to 15 μm or less, especially 12 μm or less, the orientation distribution becomes nearly uniform, so it is necessary to increase the thickness ratio of the thermoplastic polyimide layer on the cast surface side compared to the conventional design.
From this point of view, in order to suppress curling and improve dimensional stability after circuit processing, in a single-sided metal-clad laminate, the thickness of the thermoplastic polyimide layer existing on the side in contact with the metal layer (cast side) is T1, When the thickness of the non-thermoplastic polyimide layer is T2 and the thickness of the thermoplastic polyimide layer on the side opposite to the metal layer (laminate side) is T3, T3/T1 is 0.8 or more and less than 1.4. It is preferably within the range. In particular, when the thickness of the insulating resin layer is more than 9 μm and less than 12 μm, T3/T1 is more preferably in the range of 0.8 to 1.3, and when the thickness of the insulating resin layer is more than 2 μm and less than 9 μm, In some cases, it is most preferable that T3/T1 is within the range of 0.9 or more and 1.3 or less.
When the ratio T3/T1 is less than 0.8, the influence of the thermoplastic polyimide layer on the cast side becomes too large, and the film curls toward the cast side. On the other hand, if the ratio T3/T1 is 1.4 or more, the influence of the thermoplastic polyimide layer on the laminate surface side becomes too large, causing curling of the film toward the laminate surface side.
In addition, when the metal-clad laminate is a double-sided metal-clad laminate in which metal layers are laminated on both sides of an insulating resin layer, the metal layer on one side is removed by etching to form two types of single-sided metal-clad laminates. When forming a single-sided metal clad laminate, it is sufficient that one of the single-sided metal clad laminates satisfies the above ratio T3/T1.

Furthermore, as for the balance between the non-thermoplastic polyimide layer and the thermoplastic polyimide layer, it is necessary to make the thermoplastic polyimide layer thicker than in the conventional design due to the orientation promotion due to the thinning mentioned above. Therefore, (T1+T3)/(T1+T2+T3), which indicates the ratio of the thermoplastic polyimide layer to the polyimide layer, is set within a range of more than 0.20 and 0.50 or less. In particular, when the thickness of the insulating resin layer is more than 9 μm and less than 12 μm, it is more preferable that (T1+T3)/(T1+T2+T3) is in the range of 0.25 or more and 0.50 or less, and the thickness of the insulating resin layer is 2 μm or more and 9 μm or less, it is most preferable that (T1+T3)/(T1+T2+T3) is within the range of 0.30 or more and 0.50 or less.
When (T1+T3)/(T1+T2+T3) exceeds 0.50, the thickness of the non-thermoplastic polyimide layer is too small, and the CTE of the insulating resin layer tends to increase and exceed 30 ppm/K. On the other hand, when (T1+T3)/(T1+T2+T3) is 0.20 or less, the thickness of the non-thermoplastic polyimide layer is too large, so that the CTE of the insulating resin layer tends to become small and fall below 15 ppm/K.

<CTE>
In the metal-clad laminate of this 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 within the range of 15 ppm/K or more and 30 ppm/K or less. Yes, preferably within the range of 15 ppm/K or more and 25 ppm/K or less. If the CTE is less than 15 ppm/K or more than 30 ppm/K, problems such as curling of the metal-clad laminate and decreased dimensional stability after circuit processing occur.

Further, it is preferable that the CTE (CTE _MD ) in the MD direction (longitudinal direction/conveyance direction) and the CTE (CTE _TD ) in the TD direction (width direction) in the insulating resin layer satisfy the relationship of the following formula (i). When the following formula (i) is satisfied, the deviation of the CTE in the MD direction and the TD direction with respect to the average value of the CTE in the MD direction and the TD direction (CTE _AVE ) is 5% or less, which means that the anisotropy is small. If the anisotropy of the insulating resin layer in the MD direction and the TD direction increases, the dimensional stability will be adversely affected, so the smaller the value on the left side of equation (i), the better. In other words, when formula (i) is satisfied, both of the following formulas (iii) and (iv) are 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 low thermal expansion polyimide layer, and the thermoplastic polyimide layer constitutes a high thermal expansion polyimide layer. Here, the low thermal expansion polyimide layer refers to a polyimide layer having a CTE preferably in the range of 0 ppm/K to 20 ppm/K, more preferably in the range of 0 ppm/K to 15 ppm/K. The high thermal expansion polyimide layer is made of polyimide having a CTE of preferably 35 ppm/K or more, more preferably 35 ppm/K or more and 80 ppm/K or less, and even more preferably 35 ppm/K or more and 70 ppm/K or less. refers to a layer. The polyimide layer can be made into a polyimide layer having a desired CTE by appropriately changing the combination of raw materials used, the thickness, and drying/curing conditions.

In the metal-clad laminate of this embodiment, the insulating resin layer is preferably formed by a casting method in which a thermoplastic or non-thermoplastic polyimide solution or a precursor solution is sequentially applied. In the case of the casting method, it is easy to produce an extremely thin insulating resin layer containing a plurality of polyimide layers and having a thickness of 15 μm or less, particularly 12 μm or less. On the other hand, in the case of the tenter method, for example, in order to produce an insulating resin layer with a thickness of 15 μm or less, especially 12 μm or less, it is necessary to stretch the thin film, which tends to cause breaks and cracks, creating technical hurdles. expensive. Furthermore, in-plane thickness and CTE variations tend to occur, and anisotropy also tends to occur in CTE in the MD direction and TD direction.

(Non-thermoplastic polyimide)
In this embodiment, the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer contains a tetracarboxylic acid residue and a diamine residue, both of which preferably contain an aromatic group. The tetracarboxylic acid residue and diamine residue contained in the non-thermoplastic polyimide both contain aromatic groups, which makes it easier to form an ordered structure in the non-thermoplastic polyimide, which is thought to contribute to improved dimensional stability. .

In the present invention, a tetracarboxylic acid residue refers to a tetravalent group derived from a tetracarboxylic dianhydride, and a diamine residue refers to a divalent group derived from a diamine compound. represents something. Further, in the "diamine compound", the hydrogen atoms in the two terminal amino groups may be substituted, for example, -NR ₃ R ₄ (here, R ₃ and R ₄ are independently any arbitrary group such as an alkyl group). ) may also mean a substituent.

The non-thermoplastic polyimide contained in the metal-clad laminate of this embodiment contains diamine residues derived from a diamine compound represented by the following general formula (1) based on 100 mole parts of the total diamine residues. It is preferable that it is contained in an amount of 50 mole parts or more.

［式（１）において、Ｒは独立に、ハロゲン原子、又は炭素数１～６のハロゲン原子で置換されてもよいアルキル基若しくはアルコキシ基、又は炭素数１～６の１価の炭化水素基若しくはアルコキシ基で置換されてもよいフェニル基若しくはフェノキシ基を示し、ｎ_１は独立に０～４の整数、ｎ_２は０～１の整数を示す。］

[In formula (1), R is independently a halogen atom, an alkyl group or alkoxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a monovalent hydrocarbon group having 1 to 6 carbon atoms; It represents a phenyl group or a phenoxy group which may be substituted with an alkoxy group, n ₁ independently represents an integer of 0 to 4, and n ₂ represents an integer of 0 to 1. ]

Diamine residues derived from the diamine compound represented by the general formula (1) tend to form an ordered structure and can improve dimensional stability by lowering CTE. Furthermore, since it contains two or more benzene rings, it lowers the imide group concentration and contributes to lower moisture absorption, which is also advantageous in terms of increasing dimensional stability. From this point of view, the diamine residue derived from the diamine compound represented by general formula (1) should be contained in an amount of 50 mole parts or more based on 100 mole parts of the total diamine residues contained in the non-thermoplastic polyimide. The content is preferably within the range of 60 to 100 mole parts. If it is less than 50 mole parts, CTE increases and dimensional stability deteriorates.

Preferred specific examples of diamine residues derived from the diamine compound represented by general formula (1) include 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'- Diethyl-4,4'-diaminobiphenyl (m-EB), 2,2'-diethoxy-4,4'-diaminobiphenyl (m-EOB), 2,2'-dipropoxy-4,4'-diaminobiphenyl ( m-POB), 2,2'-n-propyl-4,4'-diaminobiphenyl (m-NPB), 2,2'-divinyl-4,4'-diaminobiphenyl (VAB), 4,4'- Diamines derived from diamine compounds such as diaminobiphenyl, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB), and 4,4''-diamino-p-terphenyl (DATP) Examples include residues. Among these, 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-diethyl-4,4'-diaminobiphenyl (m-EB), 4,4'-diaminobiphenyl Preferred examples include -2,2'-bis(trifluoromethyl)biphenyl (TFMB) and 4,4''-diamino-p-terphenyl (DATP), particularly 2,2'-dimethyl-4 , 4'-diaminobiphenyl (m-TB) is most preferred because it easily forms an ordered structure, lowers the imide base concentration, and lowers the moisture absorption rate.

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

However, in formula (2), R is independently a halogen atom, an alkyl group or alkoxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a monovalent hydrocarbon group having 1 to 6 carbon atoms. or a phenyl group or phenoxy group which may be substituted with an alkoxy group,
Z ₁ is independently a single bond, -O-, -S-, -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -CO-, -SO ₂ -, or -NH - indicates a divalent group selected from
n ₃ independently represents an integer of 0 to 4, and n ₄ represents an integer of 0 to 2.
However, at least one of Z ₁ is -O-, -S-, -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -CO-, -SO ₂ -, or - Indicates a divalent group selected from NH-.

Since the diamine residue derived from the diamine compound represented by the general formula (2) has a flexible site, it can impart flexibility to the insulating resin layer. From this point of view, the diamine residue derived from the diamine compound represented by general formula (2) should be present in an amount of 1 to 50 mole parts based on 100 mole parts of all the diamine residues contained in the non-thermoplastic polyimide. The content is more preferably within the range of 1 to 40 mole parts, and most preferably the content is within the range of 1 to 40 mole parts. If the content exceeds 50 mole parts, the CTE will increase and the dimensional stability will deteriorate. Furthermore, if the content is less than 1 part by mole, the flexibility will deteriorate, and therefore the bending properties will deteriorate. In addition, the non-thermoplastic polyimide contains both diamine residues derived from the diamine compound represented by the above general formula (1) and diamine residues derived from the diamine compound represented by the general formula (2). If contained, the content of diamine residues derived from the diamine compound represented by general formula (1) should be 50 to 99 moles per 100 moles of all diamine residues contained in the non-thermoplastic polyimide. The amount is more preferably within the range of 60 to 99 mole parts, and most preferably within the range of 60 to 99 mole parts.

Preferred specific examples of the diamine compound represented by general formula (2) include 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, 3,4' -Diaminobenzophenone, (3,3'-bisamino)diphenylamine, 1,4-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,4-bis (4-aminophenoxy)benzene (TPE-Q), 3-[4-(4-aminophenoxy)phenoxy]benzenamine, 3-[3-(4-aminophenoxy)phenoxy]benzenamine, 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, 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)]benzanilide, 4-[3-[4-(4-aminophenoxy)phenoxy]phenoxy]aniline, 4,4'-[oxybis(3,1-phenyleneoxy)]bisaniline, bis[4 -(4-aminophenoxy)phenyl]ether (BAPE), bis[4-(4-aminophenoxy)phenyl]ketone (BAPK), bis[4-(3-aminophenoxy)]biphenyl, bis[4-(4-aminophenoxy)phenyl]ketone (BAPK), -aminophenoxy)]biphenyl, 2,2-bis(4-aminophenoxyphenyl)propane (BAPP), and the like. Among these, those in which n ₃ in general formula (2) is 0 are preferred, such as 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), 2,2-bis(4-aminophenoxy) Phenyl)propane (BAPP) is preferred.

However, it is also possible to use other diamines commonly used as raw materials for polyimide, as long as they do not impede the purpose of the present invention. Examples of other diamines include p-phenylenediamine (p-PDA) and m-phenylenediamine (m-PDA).

The tetracarboxylic acid residue contained in the non-thermoplastic polyimide is not particularly limited, but for example, a tetracarboxylic acid residue derived from pyromellitic dianhydride (PMDA) (hereinafter also referred to as PMDA residue). ), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA)-derived tetracarboxylic acid residues (hereinafter also referred to as BPDA residues) are preferred. These tetracarboxylic acid residues can facilitate formation of an ordered structure. Furthermore, PMDA residues are residues that play a role in controlling CTE and glass transition temperature. Furthermore, since the BPDA residue has no polar group and has a relatively large molecular weight among tetracarboxylic acid residues, it can be expected to have the effect of lowering the imide group concentration of the non-thermoplastic polyimide and suppressing moisture absorption in the insulating resin layer. From this point of view, the total amount of PMDA residues and/or BPDA residues is preferably 50 parts by mole or more, more preferably is preferably in the range of 60 to 100 parts by mole, most preferably in the range of 80 to 100 parts by mole. When the content is less than 50 parts by mole, CTE increases and dimensional stability deteriorates.

Examples of other tetracarboxylic acid residues contained in the non-thermoplastic polyimide include 2,3',3,4'-biphenyltetracarboxylic dianhydride and 2,2',3,3'-biphenyltetracarboxylic acid residue. Acid dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 2,3',3,4'-biphenyltetracarboxylic dianhydride 2,2',3,3'-, 2,3,3',4'- or 3,3',4,4'-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 Anhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride Aromatic tetracarboxylic dianhydrides such as acid dianhydrides, thiophene-2,3,4,5-tetracarboxylic dianhydrides, and 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydrides. Examples include tetracarboxylic acid residues derived from compounds.

By selecting the types of acid anhydrides and diamines mentioned above, and when using two or more types of acid anhydrides or diamines, the molar ratio of each, the CTE, toughness, thermal expansion property, adhesiveness, etc. of the non-thermoplastic polyimide, Glass transition temperature (Tg) etc. can be controlled. Furthermore, in the case where the non-thermoplastic polyimide has a plurality of polyimide structural units, they may exist as blocks or randomly, but it is preferable that they exist randomly.

The imide group concentration of the non-thermoplastic polyimide is preferably 35% by weight or less. Here, "imide group concentration" means the value obtained by dividing the molecular weight of the imide group (-(CO) ₂ -N-) in polyimide by the molecular weight of the entire polyimide structure. When the imide group concentration exceeds 35% by weight, the molecular weight of the resin itself decreases, and the low hygroscopicity also deteriorates due to the increase in polar groups. By selecting the combination of the above acid anhydride and diamine compound, the orientation of the molecules in the non-thermoplastic polyimide can be controlled, thereby suppressing the increase in CTE due to a decrease in the imide group concentration and ensuring low hygroscopicity. ing.

The weight average molecular weight of the non-thermoplastic polyimide is, for example, preferably within the range of 10,000 to 400,000, more preferably within the 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 decreases and tends 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 and streaks tend to occur during coating operations.

(Thermoplastic polyimide)
In this embodiment, the thermoplastic polyimide constituting the thermoplastic polyimide layer contains a tetracarboxylic acid residue and a diamine residue, and it is preferable that both of these contain an aromatic group. Heat resistance can be ensured by both the tetracarboxylic acid residue and the diamine residue contained in the thermoplastic polyimide containing an aromatic group.

In this embodiment, the thermoplastic polyimide preferably contains a diamine residue derived from a diamine compound represented by the above general formula (2). The diamine residue derived from the diamine compound represented by general formula (2) is preferably 50 parts by mole or more, and within the range of 70 to 100 parts by mole, based on 100 parts by mole of the total diamine residues. More preferably, the amount is within the range of 80 to 100 mole parts. By containing at least 50 mole parts of diamine residues derived from the diamine compound represented by general formula (2) based on 100 mole parts of the total diamine residues, flexibility and adhesion are imparted to the thermoplastic polyimide layer. It can be applied as an adhesive layer to the metal layer. Furthermore, among the diamine residues derived from the diamine compound represented by general formula (2), 4,4'-diaminodiphenyl ether (4,4'-DAPE), 1,3-bis(4-aminophenoxy) Particularly preferred are benzene (TPE-R) and 2,2-bis(4-aminophenoxyphenyl)propane (BAPP). Since the diamine residues derived from these diamine compounds have flexible sites, they can reduce the elastic modulus of the insulating resin layer and impart flexibility.

In this embodiment, the diamine residue derived from a diamine compound other than the above general formula (2) contained in the thermoplastic polyimide is, for example, 2,2'-dimethyl-4,4'-diaminobiphenyl ( m-TB), 2,2'-diethyl-4,4'-diaminobiphenyl (m-EB), 2,2'-diethoxy-4,4'-diaminobiphenyl (m-EOB), 2,2'- Dipropoxy-4,4'-diaminobiphenyl (m-POB), 2,2'-n-propyl-4,4'-diaminobiphenyl (m-NPB), 2,2'-divinyl-4,4'-diamino Biphenyl (VAB), 4,4'-diaminobiphenyl, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl (TFMB), p-phenylenediamine (p-PDA), m-phenylenediamine Examples include diamine residues derived from diamine compounds such as (m-PDA).

The tetracarboxylic acid residue contained in the thermoplastic polyimide is not particularly limited, but for example, a tetracarboxylic acid residue derived from pyromellitic dianhydride (PMDA) (hereinafter also referred to as PMDA residue). , 3,3',4,4', tetracarboxylic acid residue derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) (hereinafter also referred to as BPDA residue), 3,3',4,4' -benzophenonetetracarboxylic dianhydride (hereinafter also referred to as BTDA residue) is preferably mentioned. These tetracarboxylic acid residues easily form an ordered structure and can reduce the rate of dimensional change in a high temperature environment. Furthermore, PMDA residues are residues that play a role in controlling CTE and glass transition temperature. Furthermore, since the BPDA residue has no polar group and has a relatively large molecular weight among tetracarboxylic acid residues, it can be expected to have the effect of lowering the imide group concentration of the thermoplastic polyimide and suppressing moisture absorption in the insulating resin layer. Furthermore, since BTDA residues have appropriate flexibility, flexibility can be imparted without significantly increasing CTE. From this point of view, the total amount of PMDA residues, BPDA residues and/or BTDA residues is preferably 50 parts by mole or more based on 100 parts by mole of all the tetracarboxylic acid residues contained in the thermoplastic polyimide. , more preferably within the range of 60 to 100 parts by mole, most preferably within the range of 80 to 100 parts by mole.

Other tetracarboxylic acid residues contained in the thermoplastic polyimide include tetracarboxylic acid residues derived from aromatic tetracarboxylic dianhydrides similar to those exemplified in the non-thermoplastic polyimide.

In the thermoplastic polyimide, CTE, tensile Elastic modulus, glass transition temperature, etc. can be controlled. Furthermore, when the thermoplastic polyimide has a plurality of polyimide structural units, they may exist as blocks or randomly, but it is preferable that they exist randomly.

The imide group concentration of the thermoplastic polyimide is preferably 35% by weight or less. Here, "imide group concentration" means the value obtained by dividing the molecular weight of the imide group (-(CO) ₂ -N-) in polyimide by the molecular weight of the entire polyimide structure. When the imide group concentration exceeds 35% by weight, the molecular weight of the resin itself decreases, and the low hygroscopicity also deteriorates due to the increase in polar groups. By selecting a combination of the above acid anhydride and diamine compound, the orientation of molecules in the thermoplastic polyimide can be controlled, suppressing the increase in CTE due to a decrease in imide group concentration and ensuring low hygroscopicity. There is.

The weight average molecular weight of the thermoplastic polyimide is, for example, preferably within the range of 10,000 to 600,000, more preferably within the 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 decreases and tends to become brittle. On the other hand, if the weight average molecular weight exceeds 600,000, the viscosity increases excessively and defects such as uneven thickness and streaks tend to occur during coating operations.

(Synthesis of non-thermoplastic polyimide and thermoplastic polyimide)
Generally, polyimide can be produced by reacting a tetracarboxylic dianhydride and a diamine compound in a solvent to produce a polyamic acid, which is then ring-closed by heating. For example, a polyimide precursor can be obtained by dissolving approximately equimolar amounts of tetracarboxylic dianhydride and a diamine compound in an organic solvent, stirring at a temperature within the range of 0 to 100°C for 30 minutes to 24 hours, and causing a polymerization reaction. A polyamic acid is obtained. In the reaction, the reaction components are dissolved in the organic solvent so that the amount of the precursor to be produced is within the range of 5 to 30% by weight, preferably within the range of 6 to 20% 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, dimethyl sulfoxide (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. Further, the amount of such an organic solvent to be used is not particularly limited, but it should be adjusted to an amount such that the concentration of the polyamic acid solution obtained by the polymerization reaction is about 5 to 30% by weight. is preferred.

It is usually advantageous to use the synthesized polyamic acid as a reaction solvent solution, but it can be concentrated, diluted, or replaced with another organic solvent if necessary. In addition, polyamic acids generally have excellent solvent solubility, so they are advantageously used. Preferably, the viscosity of the polyamic acid solution is within the range of 500 cps to 100,000 cps. Outside this range, defects such as uneven thickness and streaks are likely to occur in the film during coating operations using a coater or the like. The method of imidizing polyamic acid is not particularly limited, and for example, heat treatment such as heating in the above-mentioned solvent at a temperature within the range of 80 to 400° C. for 1 to 24 hours is preferably employed.

<Metal layer>
Examples of metals constituting the metal layer include copper, aluminum, stainless steel, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, zirconium, gold, cobalt, titanium, tantalum, zinc, lead, tin, silicon, and bismuth. , indium, or an alloy thereof. Although the metal layer can be formed by, for example, sputtering, vapor deposition, plating, or other methods, it is preferable to use metal foil from the viewpoint of adhesiveness. Copper foil is particularly preferred in terms of conductivity. The copper foil may be either an electrolytic copper foil or a rolled copper foil. In addition, when the metal-clad laminate of this embodiment is continuously produced, a long metal foil having a predetermined thickness is wound into a roll as the metal foil.

The metal layer is preferably a copper foil having a rust-proofing layer containing nickel, zinc, and cobalt on at least the surface in contact with the thermoplastic polyimide layer. In this case, the surface roughness Rz of the copper foil at least on the side in contact with the thermoplastic polyimide layer is preferably 1.0 μm or less, more preferably 0.6 μm or less. If the surface roughness Rz of the copper foil exceeds 1.0 μm, the thermoplastic polyimide layer in contact with the copper foil will be damaged in an ultra-thin insulating resin layer with an overall thickness of 15 μm or less, especially 12 μm or less, and the insulation will deteriorate. Problems occur in peel strength, etc.

The metal-clad laminate of this embodiment is an insulating resin film obtained by etching away a metal layer, and the insulating resin film is 50 mm square after being conditioned for 24 hours at 23° C. and 50% RH. When it is left standing so that the convex surface in the center is in contact with a flat surface, the amount of curl obtained by calculating the average value of the raised amount of the four corners is preferably 10 mm or less, and 8 mm or less. More preferably, it is 5 mm or less. When the amount of curl exceeds 10 mm, handling properties deteriorate and it becomes difficult to maintain dimensional accuracy during circuit processing.

The width (that is, the length in the TD direction) of the metal-clad laminate of this embodiment is preferably 470 mm or more, and more preferably within the range of 470 to 1200 mm. Generally, as the width (that is, the length in the TD direction) of a metal-clad laminate increases, it becomes difficult to control dimensional stability and in-plane isotropy, and variations tend to increase. From this, the present invention is particularly useful when applied to metal-clad laminates having a width of 470 mm or more, and the effects of the invention are greatly exhibited. Furthermore, if the width exceeds 1200 mm, the in-plane dimensional stability and thickness variations will increase, and problems will tend to occur during processing into, for example, FPC, and the yield will tend to deteriorate.

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

<Copper-clad laminate>
The copper-clad laminate of this embodiment may include an insulating resin layer and a copper layer such as copper foil on at least one surface of the insulating resin layer. Furthermore, in order to improve the adhesiveness between the insulating resin layer and the copper layer, the layer in the insulating resin layer that is in contact with the copper layer is a thermoplastic polyimide layer. The insulating resin layer has the same structure 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 this 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 a single-sided CCL, the copper layer laminated on one side of the insulating resin layer is referred to as the "first copper layer" in the present invention. In the case of double-sided CCL, the copper layer laminated on one side of the insulating resin layer is referred to as the "first copper layer" in the present invention, and the copper layer on the opposite side of the insulating resin layer to the side on which the first copper layer is laminated is referred to as the "first copper layer" in the present invention. The copper layer laminated on the surface is referred to as the "second copper layer" in the present invention. Note that the "second copper layer" corresponds to "another metal layer" laminated on the opposite side of the first copper layer with respect to the insulating resin layer. The copper-clad laminate of this embodiment is used as an FPC by processing a wiring circuit by etching the copper layer to form copper wiring.

A copper-clad laminate may be prepared, for example, by preparing a polyimide resin film, sputtering metal onto it to form a seed layer, and then forming a copper layer by, for example, copper plating.

Further, the copper-clad laminate may be prepared by preparing a polyimide resin film and laminating copper foil thereon by a method such as thermocompression bonding.

Furthermore, copper-clad laminates are produced by casting a coating solution containing polyamic acid, which is a precursor of polyimide, onto copper foil, drying it to form a coating film, and then heat-treating it to imidize it to form a polyimide layer. It may be prepared by When forming an insulating resin layer consisting of a plurality of polyimide layers by a casting method, a coating solution of polyamic acid can be sequentially applied. For example, if the polyimide layer has a three-layer structure, a thermoplastic polyimide precursor layer, a non-thermoplastic polyimide precursor layer, and a thermoplastic polyimide precursor layer are laminated in this order on the copper foil. A preferred method is to apply a polyamic acid coating solution and then heat-treat it to imidize it.

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

The thickness of the first copper foil is preferably 35 μm or less, more preferably within the range of 6 to 18 μm, for example when high-density packaging or flexibility is required. If the thickness of the first copper foil exceeds 35 μm, bending resistance will decrease due to increased bending stress applied to the copper layer (or copper wiring) when the copper-clad laminate (or FPC) is bent. Become. Moreover, from the viewpoint of production stability and handling property, it is preferable that the lower limit of the thickness of the first copper foil is 6 μm. Furthermore, in applications where heat dissipation is required, such as power modules and LED boards, the thickness of the first copper foil is preferably 18 μm or more, more preferably within the range of 18 μm to 50 μm, and even more preferably 35 μm to 50 μm. It is better to be within the range of . In applications where heat dissipation is required, a large current is often required due to the power requirements of the mounted device, so 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 power supply to the device will be reduced. There is a limit to the current, and if it exceeds 50 μm, workability tends to deteriorate.

Further, the tensile modulus of the first copper foil is, for example, preferably within the range of 50 to 300 GPa, more preferably within the range of 70 to 250 GPa. When a rolled copper foil is used as the first copper foil in this embodiment, flexibility tends to increase when it is annealed by heat treatment. Therefore, if the tensile modulus of the copper foil is less than the above lower limit, the rigidity of the first copper foil itself will decrease due to heating during the process of forming an insulating resin layer on the long first copper foil. Put it away. On the other hand, if the tensile modulus exceeds the above upper limit, a greater bending stress will be applied to the copper wiring when the FPC is bent, resulting in a decrease in its bending resistance. Note that the tensile modulus of rolled copper foil tends to change depending on heat treatment conditions when forming an insulating resin layer on the copper foil, annealing treatment of the copper foil after forming the insulating resin layer, and the like. Therefore, in this embodiment, it is sufficient that the tensile modulus of the first copper foil is within the above range in the copper-clad laminate finally obtained.

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

(Second copper layer)
The second copper layer is laminated on the opposite surface of the insulating resin layer from the first copper layer. The copper foil (second copper foil) used for the second copper layer is not particularly limited, and may be, for example, rolled copper foil or electrolytic copper foil. Moreover, a commercially available copper foil can also be used as the second copper foil. Note that the second copper foil may be the same as the first copper foil.

As described above, the metal-clad laminate of this embodiment has high dimensional stability and in-plane isotropy even though the insulating resin layer is an extremely thin layer with a thickness of 15 μm or less, preferably 12 μm or less. However, it has an insulating resin layer with excellent adhesion to the metal layer, and curling is also suppressed. Therefore, dimensional changes and curls due to environmental changes (for example, high temperature/high pressure environment, humidity changes, etc.) during circuit processing, board lamination, and component mounting processes are effectively suppressed. Furthermore, since the thickness of the insulating resin layer is 15 μm or less, preferably 12 μm or less, high-density mounting of circuit boards such as FPCs obtained from metal-clad laminates is possible. Therefore, by using the metal-clad laminate of this embodiment as a circuit board material, it is possible to respond to miniaturization of electronic devices, and it is also possible to improve the reliability and yield of the circuit board. Furthermore, since the insulating resin layer is thin and has excellent adhesion to metal layers, it is also useful in applications where heat dissipation is required, such as power modules and LED substrates.

<Circuit board>
The metal-clad laminate of this embodiment is mainly useful as a material for circuit boards such as FPCs. For example, a circuit board such as an FPC, which is an embodiment of the present invention, can be manufactured by processing the copper layer of the above-exemplified copper-clad laminate into a pattern by a conventional method to form a wiring layer. Further, it is possible to manufacture a multilayer circuit board or a rigid-flexible board (rigid FPC), which is an embodiment of the present invention, in which circuit boards such as FPC are laminated in multiple layers.

Furthermore, since the circuit board such as FPC, which is an embodiment of the present invention, has a thin insulating resin layer, it is also a useful material in applications where heat dissipation is required, such as power modules and LED boards. In such applications, the thickness of the metal layer may be increased to increase the current supplied to the device. Furthermore, the thickness of the insulating resin layer may be reduced in order to improve heat dissipation. When making the insulating resin layer thinner, the thickness of the insulating resin layer is preferably within the range of 2 μm to 9 μm, more preferably within the range of 2 μm to 5 μm. If the thickness of the insulating resin layer exceeds 9 μm, heat dissipation will be impaired, and if it is less than 2 μm, there are concerns that problems such as breakage during circuit processing and failure to maintain insulation properties after processing as an FPC may occur.

Examples are shown below to explain the features of the present invention more specifically. However, the scope of the present invention is not limited to the examples. In addition, in the following examples, various measurements and evaluations are as follows unless otherwise specified.

[Measurement of viscosity]
The viscosity at 25° C. was measured using an E-type viscometer (manufactured by Brookfield, trade name: DV-II+Pro). The rotational speed was set so that the torque was 10% to 90%, and the value was read when the viscosity stabilized 2 minutes after starting the measurement.

[Measurement of weight average molecular weight]
The weight average molecular weight was measured by gel permeation chromatography (manufactured by Tosoh Corporation, trade name: HLC-8220GPC). Polystyrene was used as a standard substance, and N,N-dimethylacetamide was used as a developing solvent.

[Measurement of storage modulus]
A polyimide film with a size of 5 mm x 20 mm was heated from 30°C to 400°C at a heating rate of 4°C/min using a dynamic viscoelasticity measurement device (DMA: manufactured by UBM, trade name: E4000F). When measured at a frequency of 11 Hz, the storage modulus at 30 ° C. is 1.0 × 10 ⁹ Pa or more, and the storage modulus at 360 ° C. is less than 1.0 × 10 ⁸ Pa. A material exhibiting a storage modulus of 1.0×10 ⁹ Pa or more at 30° C. and a storage modulus of 1.0×10 ⁸ Pa or more at 360° C. was defined as “non-thermoplastic.”

[Measurement of coefficient of thermal expansion (CTE)]
Using a thermomechanical analyzer (manufactured by Bruker, trade name: 4000SA), a polyimide film with a size of 3 mm x 20 mm was heated at a constant heating rate from 30 to 265 °C at 20 °C/min while applying a load of 5.0 g. The temperature was raised at a rate of 250°C to 100°C, and the temperature was further maintained for 10 minutes, and then cooled at a rate of 5°C/minute to determine the average coefficient of thermal expansion from 250°C to 100°C.

[Measurement of surface roughness of copper foil]
The surface roughness of the copper foil was measured using AFM (manufactured by Bruker AXS, trade name: Dimension Icon type SPM), probe (manufactured by Bruker AXS, trade name: TESPA (NCHV), tip radius of curvature 10 nm, Using a spring constant of 42 N/m), measurement was performed in a tapping mode over an 80 μm x 80 μm area on the surface of the copper foil, and the ten-point average roughness (Rz) was determined.

[About retardation Re and birefringence Δn(xy-z) in the thickness direction]
Birefringence Δn(xy-z) in the thickness direction was measured using a birefringence meter (manufactured by Photonic Lattice, product name: Wide Range Birefringence Evaluation System WPA-100, measurement area: MD: 20 mm x TD: 15 mm). It was measured using The birefringence Δn(xy-z) in the thickness direction was calculated from the measurement results by measuring retardation Re, which will be described later, using a known polarization state control device (for example, see JP-A-2016-126804).

First, a method for evaluating retardation Re will be explained. FIG. 1 is an explanatory diagram showing a part of the retardation Re evaluation system.
The retardation Re evaluation system uses a birefringence/phase difference evaluation device (manufactured by Photonic Lattice Co., Ltd., WPA-100) and a method (not shown) that rotates the sample to change the incident angle θ ₁ of light incident on the sample. It consists of a rotating device. In FIG. 1, reference numeral 20 indicates a sample, reference numeral 21 indicates a light source of the birefringence/phase difference evaluation apparatus, and reference numeral 22 indicates a light receiving section of the birefringence/phase difference evaluation apparatus. The wavelength of the light emitted by the light source 21 is 543 nm. The sample 20 is fixed to a rotating device (not shown) while being supported by a fixing frame.

The retardation Re was measured while changing the incident angle θ ₁ of the light incident on the sample 20 by changing the inclination angle of the sample 20 supported by the above-mentioned frame using a rotating device (not shown) (see FIG. 2). The incident angle θ ₁ was changed to 0°, ±30°, ±45°, and ±60°, and the retardation Re was measured at each angle.

Next, a method for calculating birefringence Δn(xy-z) in the thickness direction will be explained. The birefringence Δn(xy-z) in the thickness direction was calculated using the measurement results of the retardation Re. When a polyimide film is evaluated using the retardation evaluation system described above, the incident angle θ _{1 and} the refraction angle θ ₂ are shown as shown in FIG. In FIG. 2, numeral 2 indicates a polyimide film, numeral 2a indicates the laminated surface of the polyimide film 2, numeral 2b indicates the cast surface of the polyimide film 2, and d indicates the thickness of the polyimide film. Here, the light before entering the laminate surface 2a is represented by the symbol _L1 , the light in the polyimide film 2 is represented by the symbol _L2 , and the light emitted from the cast surface 2b is represented by the symbol _L3 . The X-axis, Y-axis, and Z-axis are orthogonal to each other, the XY direction is an axis parallel to the laminate surface 2a of the polyimide film 2, the Z direction is an axis perpendicular to the laminate surface 2a of the polyimide film 2, and the axis in the thickness direction It is.

As shown in the following equation (A), the retardation Re depends on the thickness d, the birefringence Δn(xy-z) in the thickness direction, and the refraction angle θ ₂ . The angle of refraction θ ₂ depends on the angle of incidence θ ₁ . Therefore, birefringence Δn(xy-z) can be calculated from a plurality of measured values of retardation Re obtained for a plurality of incident angles _θ1 .
Re=d・Δn(xy-z)・sin ² θ ₂ /cosθ ₂ ... (A)
However, the refraction angle θ ₂ is the angle between the beam inside the film and the normal line of the film, and the incident angle θ ₁ is the relationship of θ ₂ = sin ⁻¹ (sin θ ₁ /N) from Snell's law. becomes. Here, d is the film thickness, and N is the refractive index of the measurement sample.
Note that Δn(xy-z) is the difference between the refractive index in the in-plane direction and the refractive index in the thickness direction,
Δn(xy-z)=n _xy -n _z is satisfied.
n _xy : refractive index in the in-plane direction n _z : refractive index in the thickness direction

[Measurement of curl amount]
After etching away the copper foil from the metal-clad laminate sample to obtain a polyimide film, the polyimide film with a size of 50 mm x 50 mm was conditioned for 24 hours at 23°C and 50% RH, and the direction in which it curled was It was placed on a smooth table with the upper surface facing up. The amount of curl at that time was measured using calipers. At this time, the case where the film curled toward the etched surface of the base material was indicated as a plus, the case where the film curled on the opposite side was indicated as a minus, and the average of the measured values of the four corners of the film was defined as the amount of curl.

[Thickness measurement]
The copper foil was etched away from the sample of the metal-clad laminate at five points separated by about 90 mm in the width direction, and the thickness was measured after obtaining a polyimide film. The average value of the thickness at 5 points was taken as the thickness, and the difference between the average value and each point was evaluated as thickness variation.

[Measurement of peel strength]
A copper foil from a sample of a metal-clad laminate was circuit-processed into lines and spaces with a width of 1.0 mm and an interval of 5.0 mm, and then cut into 8 cm width x 4 cm length to prepare measurement sample 1. The peel strength of the cast surface side of Measurement Sample 1 was measured by the following method.
Using a Tensilon tester (manufactured by Toyo Seiki Seisakusho, product name: Strograph VE-1D), the resin layer side of measurement sample 1 was fixed to an aluminum plate with double-sided tape, and the copper foil was heated in a 180° direction at a speed of 50 mm/min. The central strength was determined when the copper foil was peeled off by 10 mm from the resin layer.

Abbreviations used in Examples and Comparative Examples indicate the following compounds.
BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride PMDA: Pyromellitic dianhydride BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl TPE-R: 1,3-bis(4-aminophenoxy)benzene TPE-Q: 1,4-bis(4-aminophenoxy)benzene DAPE: 4, 4'-diaminodiphenyl ether BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane DMAc: N,N-dimethylacetamide

(Synthesis example 1)
Under a nitrogen stream, 94.1 parts by weight of m-TB (0.40 mol parts) and 14.3 parts by weight of TPE-R (0.05 mol parts) and the solid content concentration after polymerization were added to the reaction tank. DMAc in an amount of 7.5% by weight was added and dissolved by stirring at room temperature. Next, after adding 29.4 parts by weight of BPDA (0.10 parts by mole) and 87.1 parts by weight of PMDA (0.4 parts by mole), stirring was continued for 3 hours at room temperature to carry out a polymerization reaction. Polyimide precursor resin liquid a was obtained. The solution viscosity of the polyimide precursor resin liquid a was 12,000 cps, and the weight average molecular weight was 250,000.

(Synthesis example 2)
Under a nitrogen stream, 77.8 parts by weight of BAPP (0.19 mol parts) and DMAc in an amount such that the solid content concentration after polymerization is 6.0% by weight were charged into a reaction tank, and the mixture was stirred at room temperature. Dissolved. Next, after adding 2.8 parts by weight of BPDA (0.01 mol part) and 39.4 parts by weight of PMDA (0.18 mol part), stirring was continued for 3 hours at room temperature to carry out a polymerization reaction. Polyimide precursor resin liquid b was obtained. Polyimide precursor resin liquid b had a solution viscosity of 700 cps and a weight average molecular weight of 261,000.

(Synthesis example 3)
Under a nitrogen stream, 53.5 parts by weight of DAPE (0.27 mol parts) and DMAc in an amount such that the solid content concentration after polymerization was 7.0% by weight were placed in a reaction tank, and the mixture was stirred at room temperature. Dissolved. Next, after adding 86.7 parts by weight of BTDA (0.27 parts by mole), stirring was continued for 3 hours at room temperature to carry out a polymerization reaction to obtain polyimide precursor resin liquid c. The solution viscosity of the polyimide precursor resin liquid C was 1,200 cps, and the weight average molecular weight was 140,000.

(Synthesis example 4)
Under a nitrogen stream, 35.96 parts by weight of m-TB (0.1691 mol parts), 2.75 parts by weight of TPE-Q (0.0094 mol parts) and 3.86 parts by weight of BAPP were added to the reaction tank. (0.0094 mol part) and DMAc in an amount such that the solid content concentration after polymerization was 15.0% by weight were added and dissolved by stirring at room temperature. Next, after adding 20.18 parts by weight of PMDA (0.0925 mol parts) and 27.26 parts by weight of BPDA (0.0925 mol parts), stirring was continued for 3 hours at room temperature to carry out a polymerization reaction. Polyimide precursor resin liquid d was obtained. The solution viscosity of the polyimide precursor resin liquid d was 25,000 cps, and the weight average molecular weight was 220,000.

(Synthesis example 5)
Under a nitrogen stream, 5.63 parts by weight of m-TB (0.0265 mol parts) and 30.96 parts by weight of TPE-R (0.1059 mol parts) and the solid content concentration after polymerization were added to the reaction tank. DMAc in an amount of 15.0% by weight was added and dissolved by stirring at room temperature. Next, after adding 8.53 parts by weight of PMDA (0.0391 mol parts) and 26.88 parts by weight of BPDA (0.0913 mol parts), stirring was continued for 3 hours at room temperature to carry out a polymerization reaction. A polyimide precursor resin liquid e was obtained. The solution viscosity of the polyimide precursor resin liquid e was 3,000 cps, and the weight average molecular weight was 120,000.

(Example 1)
Polyimide precursor resin liquid b was applied to the roughened surface (Rz=0.6 μm) of copper foil 1 (electrolytic copper foil, manufactured by Fukuda Metal Foil and Powder Industries Co., Ltd., product name: T49-DS-HD2, thickness: 12 μm). After uniform coating with a coating width of 500 mm using a die coater, the solvent was removed by heating and drying at 130°C. Next, polyimide precursor resin liquid a was uniformly coated with a coating width of 500 mm using a die coater so as to be laminated thereon, and the solvent was removed by heating and drying at 90 to 125°C. Further, polyimide precursor resin liquid C was uniformly applied onto the polyimide precursor resin liquid A layer using a die coater with a coating width of 500 mm, and was heated and dried at 130°C to remove the solvent. After this, the temperature is gradually raised from room temperature to 320°C for about 30 minutes to heat-treat and imidize, resulting in a total thickness of about 4.5 μm (thickness variation within ±0.3 μm) consisting of 3 polyimide resin layers. A metal-clad laminate 1 was obtained in which an insulating resin layer was formed on a copper foil 1. The thickness of the polyimide precursor resin liquid coated on the copper foil 1 after curing is approximately 0.8 μm/approximately 2.9 μm/approximately 0.8 μm in the order of b/a/c. The evaluation results of this metal-clad laminate 1 are as follows.
Thickness direction birefringence Δn(xy-z); 0.113
CTE _MD ; 20ppm/K
CTE _TD ; 20ppm/K
Film curl amount: 1.8mm
Thickness ratio of thermoplastic polyimide layer on cast side and laminate side: T3/T1=1.0
Ratio of thermoplastic layer; (T1+T3)/(T1+T2+T3)=0.36
Peel strength: 0.6kN/m

(Example 2)
Polyimide precursor resin liquid b was uniformly applied to the roughened surface of copper foil 1 with a coating width of 500 mm using a die coater, and then heated and dried at 130° C. to remove the solvent. Next, polyimide precursor resin liquid a was uniformly coated with a coating width of 500 mm using a die coater so as to be laminated thereon, and the solvent was removed by heating and drying at 90 to 125°C. Further, polyimide precursor resin liquid B was uniformly applied onto the polyimide precursor resin liquid A layer using a die coater with a coating width of 500 mm, and the solvent was removed by heating and drying at 130°C. After this, the temperature is gradually raised from room temperature to 320°C for about 30 minutes to be heat-treated and imidized, resulting in a total thickness of about 11.8 μm (thickness variation within ±0.3 μm) consisting of 3 polyimide resin layers. A metal-clad laminate 2 was obtained in which an insulating resin layer was formed on a copper foil 1. The thickness of the polyimide precursor resin liquid coated on the copper foil 1 after curing is approximately 1.8 μm/approximately 8.0 μm/approximately 2.0 μm in the order of b/a/b. The evaluation results of this metal-clad laminate 2 are as follows.
Thickness direction birefringence Δn(xy-z); 0.131
CTE _MD ; 23ppm/K
CTE _TD ; 23ppm/K
Film curl amount: -1.0mm
Thickness ratio of thermoplastic polyimide layer on cast side and laminate side: T3/T1=1.1
Ratio of thermoplastic layer; (T1+T3)/(T1+T2+T3)=0.32
Peel strength: 0.9kN/m

(Example 3)
Polyimide precursor resin liquid b was uniformly applied to the roughened surface of copper foil 1 with a coating width of 500 mm using a die coater, and then heated and dried at 130° C. to remove the solvent. Next, polyimide precursor resin liquid a was uniformly coated with a coating width of 500 mm using a die coater so as to be laminated thereon, and the solvent was removed by heating and drying at 90 to 125°C. Furthermore, polyimide precursor resin liquid B was uniformly applied onto the polyimide precursor resin liquid A layer using a die coater in a coating width of 500 mm, and was dried by heating at 130° C. to remove the solvent. After that, heat treatment is performed in a stepwise temperature raising process from room temperature to 320°C for about 25 minutes to imidize, resulting in a total thickness of about 11.1 μm (thickness variation within ±0.3 μm) consisting of 3 polyimide resin layers. A metal-clad laminate 3 was obtained in which an insulating resin layer was formed on a copper foil 1. The thickness of the polyimide precursor resin liquid coated on the copper foil 1 after curing is approximately 2.1 μm/approximately 6.8 μm/approximately 2.2 μm in the order of b/a/b. The evaluation results of this metal-clad laminate 3 are as follows.
Thickness direction birefringence Δn(xy-z); 0.138
CTE _MD ; 27ppm/K
CTE _TD ; 27ppm/K
Film curl amount: 9.3mm
Thickness ratio of thermoplastic polyimide layer on cast side and laminate side: T3/T1=1.0
Ratio of thermoplastic layer; (T1+T3)/(T1+T2+T3)=0.39
Peel strength: 0.9kN/m

(Reference example 1)
Polyimide precursor resin liquid e was uniformly applied to the roughened surface of copper foil 1 with a coating width of 500 mm using a die coater, and then heated and dried at 130° C. to remove the solvent. Next, the polyimide precursor resin liquid d was uniformly coated with a coating width of 500 mm using a die coater so as to be laminated thereon, and the solvent was removed by heating and drying at 90 to 125°C. Furthermore, the polyimide precursor resin liquid e was uniformly applied onto the polyimide precursor resin liquid layer d using a die coater with a coating width of 500 mm, and the mixture was heated and dried at 135° C. to remove the solvent. After this, the temperature is gradually raised from room temperature to 320°C for about 30 minutes to heat-treat and imidize it, resulting in a total thickness of about 24.1 μm (thickness variation within ±0.3 μm) consisting of 3 polyimide resin layers. A metal-clad laminate 4 having an insulating resin layer formed on a copper foil 1 was obtained. The thickness of the polyimide precursor resin liquid coated on the copper foil 1 after curing is approximately 2.0 μm/approximately 19.3 μm/approximately 2.8 μm in the order of e/d/e. The evaluation results of this metal-clad laminate 4 are as follows.
Thickness direction birefringence Δn(xy-z); 0.142
CTE _MD ; 23ppm/K
CTE _TD ; 23ppm/K
Film curl amount: 0.5mm
Thickness ratio of thermoplastic polyimide layer on cast side and laminate side: T3/T1=1.4
Ratio of thermoplastic layer; (T1+T3)/(T1+T2+T3)=0.20
Peel strength: >1.0kN/m

(Comparative example 1)
Polyimide precursor resin liquid a was uniformly applied to copper foil 1 with a coating width of 500 mm using a die coater, and the solvent was removed by heating and drying at 90 to 125°C. After that, the temperature was raised stepwise from room temperature to 280°C over about 5 minutes to imidize the metal, and an insulating resin layer with a thickness of about 5.2 μm (thickness variation ±0.3 μm) was formed on the copper foil 1. A stretched laminate 5 was obtained. The evaluation results of this metal-clad laminate 5 are as follows.
Thickness direction birefringence Δn(xy-z); 0.123
CTE _MD ; 22ppm/K
CTE _TD ; 21ppm/K
Film curl amount: 20mm or more (film curls and cannot be measured)
Peel strength: 0.2kN/m

(Comparative example 2)
Polyimide precursor resin liquid a was uniformly applied to copper foil 1 with a coating width of 500 mm using a die coater, and the solvent was removed by heating and drying at 90 to 125°C. Thereafter, the metal-clad laminate 6 is heat-treated from room temperature to 320°C for about 30 minutes to imidize, and an insulating resin layer with a thickness of about 4.1 μm (thickness variation ±0.3 μm) is formed on the copper foil 1. I got it. The evaluation results of this metal-clad laminate 6 are as follows.
Thickness direction birefringence Δn(xy-z); 0.140
CTE _MD ; 1ppm/K
_CTETD ; 1ppm/K
Film curl amount: 2mm
Peel strength: 0.3kN/m

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 can be modified in various ways.

2...Polyimide film, 2a...Laminate surface, 2b...Cast surface, 20...Sample, 21...Light source, 22...Light receiving part, θ1...Incidence angle, _{θ2 ...} Refraction angle, _L1 , _L2 , _L3 ...Light

Claims (9)

A metal-clad laminate comprising an insulating resin layer and a metal layer laminated on one side of the insulating resin layer,
The insulating resin layer is
a non-thermoplastic polyimide layer composed of non-thermoplastic polyimide;
a thermoplastic polyimide layer formed of thermoplastic polyimide provided in contact with at least one surface of the non-thermoplastic polyimide layer;
has
The thermoplastic polyimide layer is interposed between the metal layer and the non-thermoplastic polyimide layer,
The insulating resin layer has a thickness within a range of 2 μm or more and 15 μm or less,
A metal-clad laminate characterized in that birefringence Δn(xy-z) in the thickness direction is within the range of 0.080 to 0.140. The non-thermoplastic polyimide contains a tetracarboxylic acid residue and a diamine residue, and based on 100 mole parts of the total diamine residue, a diamine residue derived from a diamine compound represented by the following formula (1), The metal-clad laminate according to claim 1, containing 50 mole parts or more.

[In formula (1), R is independently a halogen atom, an alkyl group or alkoxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a monovalent hydrocarbon group having 1 to 6 carbon atoms; It represents a phenyl group or a phenoxy group which may be substituted with an alkoxy group, n ₁ independently represents an integer of 0 to 4, and n ₂ represents an integer of 0 to 1. ] The insulating resin layer is
a non-thermoplastic polyimide layer composed of the non-thermoplastic polyimide;
a thermoplastic polyimide layer formed of thermoplastic polyimide provided in contact with both sides of the non-thermoplastic polyimide layer;
has
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,
The thickness of the thermoplastic polyimide layer provided on the opposite side to the metal layer is T3,
The metal-clad laminate according to claim 1, wherein 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 The CTE of the insulating resin layer is within the range of 15 ppm/K or more and 30 ppm/K or less,
The metal-clad laminate according to any one of claims 1 to 3, wherein the CTE in the MD direction (CTE _MD ) and the CTE in the TD direction (CTE _TD ) of the insulating resin layer satisfy the relationship of the following formula (i).
|(CTE _MD - CTE _TD )/(CTE _MD +CTE _TD )|≦0.05... (i) The metal-clad laminate according to any one of claims 1 to 3, wherein the width of the metal-clad laminate is 470 mm or more, and the variation in thickness of the insulating resin layer is within a range of ±0.5 μm. In the insulating resin film obtained by etching and removing the metal layer, the 50 mm square insulating resin film after 24 hours of humidity conditioning at 23° C. and 50% RH is heated so that the convex surface in the center thereof is flat. The metal-clad laminate according to any one of claims 1 to 3, wherein when the metal-clad laminate is left standing in contact with a surface, the amount of curl obtained by calculating the average value of the amount of rise of the four corners is 10 mm or less. The amount of diamine residues derived from the diamine compound represented by the general formula (1) is within the range of 50 to 99 parts by mole relative to 100 parts by mole of all diamine residues contained in the non-thermoplastic polyimide. The metal cladding according to any one of claims 1 to 3, wherein the diamine residue derived from the diamine compound represented by the following general formula (2) is within the range of 1 to 50 mole parts. Laminated board.

[In formula (2), R is independently a halogen atom, an alkyl group or alkoxy group having 1 to 6 carbon atoms which may be substituted with a halogen atom, or a monovalent hydrocarbon group having 1 to 6 carbon atoms; Indicates a phenyl group or phenoxy group which may be substituted with an alkoxy group,
Z ₁ is independently a single bond, -O-, -S-, -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -CO-, -SO ₂ -, or -NH - indicates a divalent group selected from
n ₃ independently represents an integer of 0 to 4, and n ₄ represents an integer of 0 to 2.
However, at least one of Z ₁ is -O-, -S-, -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -CO-, -SO ₂ -, or - Indicates a divalent group selected from NH-. ] The metal clad laminate according to any one of claims 1 to 7, further comprising another metal layer laminated on the insulating resin layer on the opposite side of the metal layer with respect to the insulating resin layer. Board. A circuit board formed by processing the metal layer of the metal-clad laminate according to any one of claims 1 to 8 into wiring.

Images