Metal-clad laminate and circuit board

Abstract

To provide a metal-clad laminated plate and a circuit board that can reduce transmission loss even in high frequency transmission and are excellent in dimension stability.SOLUTION: A metal-clad laminated plate 10 comprises: a first metal layer M1; a first transmission loss prevention layer BS1 that is adjacent to one side thereof; a second metal layer M2; a second transmission loss prevention layer BS2 that is adjacent to one side thereof; and a plurality of resin layers that is interposed between the first transmission loss prevention layer BS1 and the second transmission loss prevention layer BS2. A resin laminate 20 has the first transmission loss prevention layer BS1 and the second transmission loss prevention layer BS2, at least two or more layers of dimensional accuracy maintaining layers PL, and an intermediate transmission loss prevention layer BS3 that is laminated between the dimensional accuracy maintaining layers PL. In the metal-clad laminated plate 10, a total thickness of the dimensional accuracy maintaining layers PL is within a range of 25 to 60% of a total thickness of the resin laminate 20.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a metal-clad laminate and a circuit board useful as electronic components.

Background Art

[0002] In recent years, with the progress of miniaturization, weight reduction, and space saving of electronic devices, there has been an increasing demand for flexible printed circuit boards (FPCs) that are thin, lightweight, flexible, and have excellent durability even when repeatedly bent. Since FPCs enable three-dimensional and high-density mounting even in limited space, their applications are expanding, for example, to wirings in movable parts of electronic devices such as HDDs, DVDs, and smartphones, and to components such as cables and connectors.

[0003] In addition to the above-mentioned high density, with the progress of high performance of devices, it has also become necessary to cope with higher frequencies of transmission signals. When transmitting high-frequency signals, if the transmission loss in the transmission path is large, problems such as loss of electrical signals and long signal delay times occur. Therefore, in the future, reduction of transmission loss will also be important in FPCs.

[0004] In order to improve high-frequency transmission characteristics, it has been proposed to use a laminate in which films made of a fluororesin are laminated on both sides of a polyimide film as an insulating resin layer (Patent Document 1). Since the insulating resin layer of Patent Document 1 uses a fluorine-based resin, it is excellent in terms of dielectric properties, but there are problems in dimensional stability. In particular, when applied to FPCs, there is concern that the dimensional changes before and after circuit processing by etching and the dimensional changes before and after heat treatment will increase.

[0005] In order to improve high-frequency transmission characteristics, it has been proposed to laminate two single-sided metal-clad laminates by means of an adhesive layer into which specific diamine residues are introduced, and to control the thickness of the entire resin layer and the adhesive layer (Patent Document 2). However, in Patent Document 2, since the insulating layer of the single-sided metal-clad laminate increases the distance between the adhesive layer with a low dielectric tangent and the metal layer (wiring), there is room for further improvement in the effect of reducing transmission loss.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a metal-clad laminate and a circuit board capable of reducing transmission loss even in high-frequency transmission and having excellent dimensional stability.

Means for Solving the Problems

[0008] As a result of intensive research, the present inventors have provided a transmission loss suppression layer with a low dielectric tangent in contact with a pair of metal layers (wiring), respectively, and provided a structure in which a plurality of dimensional accuracy maintenance layers are laminated by an intermediate transmission loss suppression layer between the transmission loss suppression layers, and by setting the total thickness ratio of the dimensional accuracy maintenance layers to the thickness of the entire resin layer to a certain value or more, it is possible to suppress displacement of the wiring even when the thickness of the entire resin layer is increased, and it has been found that both reduction of transmission loss and maintenance of dimensional accuracy can be achieved.

[0009] The metal-clad laminate of the present invention includes a first metal layer, a first transmission loss suppression layer provided in contact with one side of the first metal layer, a second metal layer, a second transmission loss suppression layer provided in contact with one side of the second metal layer, and a plurality of resin layers interposed between the first transmission loss suppression layer and the second transmission loss suppression layer. In the metal-clad laminate of the present invention, a resin laminate is formed by the first transmission loss suppression layer, the second transmission loss suppression layer, and the plurality of resin layers. The resin laminate has at least two or more dimensional accuracy maintenance layers and an intermediate transmission loss suppression layer laminated between the dimensional accuracy maintenance layers. And the metal-clad laminate of the present invention satisfies the following conditions i and ii; i) The dielectric tangent at 10 GHz measured by a split post dielectric resonator (SPDR) after humidity conditioning for 24 hours under constant temperature and humidity conditions (normal state) of 23°C and 50% RH. When the dielectric tangents of the first transmission loss suppression layer and the second transmission loss suppression layer are Df1 and the dielectric tangent of the dimensional accuracy maintenance layer is Df2, the relationship Df1 < Df2 holds; ii) The total thickness of the dimensional accuracy maintenance layers is within the range of 25 to 60% of the total thickness of the resin laminate; is satisfied.

[0010] The circuit board of the present invention includes a first wiring layer, a first transmission loss suppression layer provided in contact with one side of the first wiring layer, a second wiring layer, a second transmission loss suppression layer provided in contact with one side of the second wiring layer, and a plurality of resin layers interposed between the first transmission loss suppression layer and the second transmission loss suppression layer. In the circuit board of the present invention, a resin laminate is formed by the first transmission loss suppression layer, the second transmission loss suppression layer, and the plurality of resin layers. The resin laminate has at least two or more dimensional accuracy maintenance layers and an intermediate transmission loss suppression layer laminated between the dimensional accuracy maintenance layers. has. And the circuit board of the present invention satisfies the following conditions i and ii; i) The dielectric tangent at 10 GHz measured by a split post dielectric resonator (SPDR) after humidity conditioning for 24 hours under the constant temperature and humidity conditions (normal state) of 23°C and 50% RH, where the dielectric tangent of the first transmission loss suppression layer and the second transmission loss suppression layer is Df1 and the dielectric tangent of the dimensional accuracy maintenance layer is Df2, and the relationship Df1 < Df2 holds; ii) The total thickness of the dimensional accuracy maintenance layer is within the range of 25 to 60% of the total thickness of the resin laminate; is satisfied.

[0011] In the metal-clad laminate or circuit board of the present invention, the dimensional accuracy maintenance layer may have a minimum value of the storage modulus in the temperature range from 100°C to 250°C within the range of 1.0 to 8.0 GPa, or may be a low coefficient of thermal expansion polyimide layer having a coefficient of thermal expansion within the range of 15 to 25 ppm / K.

[0012] In the metal-clad laminate or circuit board of the present invention, the resin constituting the first transmission loss suppression layer and the second transmission loss suppression layer is a polyimide formed by reacting an acid anhydride component and a diamine component, and contains 50 mol parts or more of a dimer diamine in which two terminal carboxylic acid groups of dimer acid are substituted with primary aminomethyl groups or amino groups with respect to 100 mol parts of the total amount of the diamine component.

Advantages of the Invention

[0013] In the metal-clad laminate of the present invention, since transmission loss suppression layers having a low dielectric tangent are provided so as to be in contact with a pair of metal layers (wiring), respectively, transmission loss in high-frequency signal transmission can be effectively suppressed. Further, a structure in which a plurality of dimensional accuracy maintenance layers and intermediate transmission loss suppression layers are laminated between the transmission loss suppression layers is provided, and the ratio of the total thickness of the dimensional accuracy maintenance layers to the thickness of the entire resin layer is set to be a certain value or more, so that low dielectric properties are realized while ensuring high dimensional stability. Therefore, when the metal-clad laminate of the present invention is applied to, for example, a circuit board for transmitting a high-frequency signal having a frequency of 10 GHz or more, it is possible to effectively reduce transmission loss.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

[0015] Embodiments of the present invention will be described with reference to the drawings as appropriate.

[0016] [Metal-Clad Laminate] FIG. 1 is a schematic diagram showing the configuration of a metal-clad laminate according to an embodiment of the present invention. The metal-clad laminate 10 of the present embodiment includes a first metal layer M1, a first transmission loss suppression layer BS1 provided in contact with one side of the first metal layer M1, a second metal layer M2, a second transmission loss suppression layer BS2 provided in contact with one side of the second metal layer M2, a plurality of resin layers interposed between the first transmission loss suppression layer BS1 and the second transmission loss suppression layer BS2, and. Since the metal-clad laminate 10 is provided with the first transmission loss suppression layer BS1 and the second transmission loss suppression layer BS2 having a low dielectric tangent at positions closest to the pair of metal layers (the first metal layer M1 and the second metal layer M2 serving as wirings), respectively, the transmission loss in high-frequency signal transmission can be effectively suppressed. Here, the resin laminate 20 is formed by the first transmission loss suppression layer BS1, the second transmission loss suppression layer BS2, and a plurality of resin layers. In addition to the first transmission loss suppression layer BS1 and the second transmission loss suppression layer BS2, this resin laminate 20 has at least two or more dimensional accuracy maintenance layers PL and an intermediate transmission loss suppression layer BS3 laminated between the dimensional accuracy maintenance layers PL. In this way, by providing a laminated structure of the dimensional accuracy maintenance layer PL and the intermediate transmission loss suppression layer BS3 between the first transmission loss suppression layer BS1 and the second transmission loss suppression layer BS2, low dielectric constant is achieved while ensuring high dimensional stability. Note that the resin laminate 20 may have any resin layers other than those described above, but it is preferably formed only by the resin layers having the above-described respective functions.

[0017] As shown in FIG. 1, the first metal layer M1 and the second metal layer M2 are each located on the outermost side, and the first transmission loss suppression layer BS1 and the second transmission loss suppression layer BS2 are disposed in contact with the inside thereof. Further, between the first transmission loss suppression layer BS1 and the second transmission loss suppression layer BS2, a plurality of resin layers including a plurality of dimensional accuracy maintenance layers PL and an intermediate transmission loss suppression layer BS3 are interposed. Here, the first transmission loss suppression layer BS1 is adjacent to one dimensional accuracy maintenance layer PL, and the second transmission loss suppression layer BS2 is in contact with another dimensional accuracy maintenance layer PL.

[0018] The metal-clad laminate 10 shown in FIG. 1 has two dimensional accuracy maintenance layers PL and one intermediate transmission loss suppression layer BS3, but the dimensional accuracy maintenance layer PL may be two or more layers, and there is no particular limitation on the number of layers of the intermediate transmission loss suppression layer BS3. For example, as shown in FIG. 2, a configuration having three dimensional accuracy maintenance layers PL and two intermediate transmission loss suppression layers BS3 may be used, or as shown in FIG. 3, a configuration having five dimensional accuracy maintenance layers PL and four intermediate transmission loss suppression layers BS3 may be used.

[0019] In the metal-clad laminate 10, the configurations of the first metal layer M1 and the second metal layer M2 may be the same or different, but it is preferable that they have the same material, the same physical properties, and the same thickness.

[0020] Also, the configurations of the first transmission loss suppression layer BS1 and the second transmission loss suppression layer BS2 may be the same or different, but it is preferable that they have the same material, the same physical properties, and the same thickness. For example, by making the dielectric tangent and thickness of the first transmission loss suppression layer BS1 and the second transmission loss suppression layer BS2 the same, the design for reducing transmission loss when manufacturing a high-frequency transmission circuit board becomes easier.

[0021] Furthermore, the configurations of the first transmission loss suppression layer BS1, the second transmission loss suppression layer BS2, and the intermediate transmission loss suppression layer BS3 may be the same or different, but it is preferable that they have the same material and the same physical properties in order to improve the dielectric characteristics of the entire resin laminate 20 and effectively suppress the transmission loss of high-frequency signals.

[0022] The configurations of the plurality of dimensional accuracy maintaining layers PL may be the same or different, but it is preferable that they have the same material, the same physical properties, the same thickness, and the same layer structure because it facilitates the design of the mechanical strength and dimensional accuracy when manufacturing the circuit board.

[0023] The metal-clad laminate 10 satisfies the following conditions i and ii.

[0024] Condition i: When the dielectric tangent of the first transmission loss suppression layer BS1 and the second transmission loss suppression layer BS2 is Df1 and the dielectric tangent of the dimensional accuracy maintaining layer PL is Df2, they satisfy the relationship Df1 < Df2. By designing the dielectric tangents Df1 of the first and second transmission loss suppression layers BS1 and BS2, which are to be circuit wirings as transmission paths for high-frequency signals, to be lower than the dielectric tangent Df2 of the dimensional accuracy maintenance layer PL, respectively, the transmission loss of the high-frequency signal can be effectively suppressed. Even when the dielectric tangents of the first transmission loss suppression layer BS1 and the second transmission loss suppression layer BS2 are different, it is necessary that both satisfy the relationship Df1 < Df2. Unless otherwise specified in the present invention, the dielectric constant and the dielectric tangent mean the dielectric constant and the dielectric tangent at 10 GHz measured by a split post dielectric resonator (SPDR) after humidity conditioning for 24 hours under the constant temperature and humidity conditions (normal state) of 23°C and 50% RH.

[0025] From the viewpoint of suppressing the transmission loss of the high-frequency signal, the dielectric tangent Df1 of the first and second transmission loss suppression layers BS1 and BS2 at 10 GHz is preferably 0.005 or less, and more preferably 0.003 or less.

[0026] The dielectric tangent Df3 of the intermediate transmission loss suppression layer BS3 at 10 GHz measured in the same manner as in condition i is preferably 0.005 or less, more preferably 0.003 or less, and most preferably the same as the dielectric tangent Df1 of the first and second transmission loss suppression layers BS1 and BS2, from the viewpoint of suppressing the transmission loss of the high-frequency signal.

[0027] Also, the dielectric tangent Df2 of the dimensional accuracy maintenance layer PL is desirably as low as possible. However, since it is a layer mainly for maintaining dimensional accuracy and mechanical strength, on the premise of satisfying condition i, it is preferably 0.012 or less, and more preferably 0.010 or less. Even if the dielectric tangent Df2 of the dimensional accuracy maintenance layer PL becomes somewhat high, by laminating it with the first and second transmission loss suppression layers BS1 and BS2 and the intermediate transmission loss suppression layer BS3 having lower dielectric tangents and considering the thickness ratio with these, low dielectric properties of the entire resin laminate 20 can be ensured.

[0028] Condition ii: The total thickness T of the dimensional accuracy maintenance layer PL PLis within the range of 25 to 60% of the total thickness T of the resin laminate 20 (i.e., the first and second transmission loss suppression layers BS1, BS2, one or more intermediate transmission loss suppression layers BS3, and a plurality of dimensional accuracy maintenance layers PL). The total thickness T of the plurality of dimensional accuracy maintenance layers PL PL By setting the ratio of the total thickness T of the metal-clad laminate 10 to the total thickness T of the resin laminate 20 within the above range, it is possible to reduce the transmission loss of high-frequency signals while maintaining the dimensional accuracy and mechanical strength when the metal-clad laminate 10 is circuit-processed. From this perspective, the ratio of the thickness T PL to the total thickness T is preferably within the range of 25 to 50%.

[0029] Here, the thickness of each layer in the resin laminate 20 is not particularly limited because it can be appropriately set according to the purpose of use, but can be exemplified as follows. The thickness of one layer of the first and second transmission loss suppression layers BS1, BS2 is preferably within the range of 2 to 100 μm, and more preferably within the range of 5 to 75 μm. The thickness of one layer of the dimensional accuracy maintenance layer PL is preferably within the range of 10 to 100 μm, and more preferably within the range of 12 to 50 μm. The thickness of one layer of the intermediate transmission loss suppression layer BS3 is preferably within the range of 12 to 150 μm, and more preferably within the range of 25 to 100 μm. The total thickness T of the resin laminate 20 is preferably within the range of 50 to 300 μm, and more preferably within the range of 75 to 200 μm.

[0030] In addition, in order to reduce the dielectric constant of the entire resin laminate 20, the total thickness T B of the first and second transmission loss suppression layers BS1, BS2 and the intermediate transmission loss suppression layer BS3 is preferably within the range of 40 to 75% with respect to the total thickness T of the resin laminate 20, and more preferably within the range of 50 to 75%.

[0031] Hereinafter, each layer constituting the metal-clad laminate 10 will be described.

[0032] [Metal layer] The materials of the first metal layer M1 and the second metal layer M2 are not particularly limited. For example, copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof can be mentioned. Among these, copper or a copper alloy is particularly preferable. Note that the material of the wiring layer in the circuit board of the present embodiment described later is the same as that of the first metal layer M1 and the second metal layer M2.

[0033] The thicknesses of the first metal layer M1 and the second metal layer M2 are not particularly limited. For example, when using a metal foil such as a copper foil, it is preferably 35 μm or less, more preferably in the range of 5 to 25 μm. From the viewpoints of production stability and handleability, the lower limit value of the thickness of the metal foil is preferably 5 μm. When using a copper foil, either a rolled copper foil or an electrolytic copper foil may be used. Also, as the copper foil, a commercially available copper foil can be used.

[0034] Further, the metal foil may be subjected to surface treatment with, for example, rust prevention treatment or for the purpose of improving adhesion, such as siding, aluminum alcoholate, aluminum chelate, silane coupling agent, etc.

[0035] [Transmission Loss Suppression Layer] The resin constituting the first and second transmission loss suppression layers BS1, BS2 and the intermediate transmission loss suppression layer BS3 (hereinafter, these may be collectively referred to as "transmission loss suppression layers BS1 to BS3") preferably has a glass transition temperature (Tg) of 180 °C or lower, more preferably 160 °C or lower. By setting the glass transition temperature of the transmission loss suppression layers BS1 to BS3 to 180 °C or lower, thermocompression bonding at a low temperature becomes possible, so that the internal stress generated during lamination can be relaxed and dimensional changes after circuit processing can be suppressed. If the Tg of the transmission loss suppression layers BS1 to BS3 exceeds 180 °C, the temperature during adhesion with the dimensional accuracy maintenance layer PL interposed therebetween becomes high, and there is a risk of impairing the dimensional stability after circuit processing.

[0036] The storage elastic modulus maximum value of the transmission loss suppression layers BS1 to BS3 in the temperature range from 100°C to 250°C is preferably 1.0 GPa or less. With such a storage elastic modulus, the internal stress during thermocompression bonding can be relaxed, and the dimensional stability after circuit processing can be maintained. Also, warping is less likely to occur even after the solder reflow process after circuit processing.

[0037] The resins constituting the first and second transmission loss suppression layers BS1, BS2 and the intermediate transmission loss suppression layer BS3 are preferably polyimides, and the two terminal carboxylic acid groups of the dimer acid are replaced with primary aminomethyl groups or amino groups with respect to 100 mol parts of the total amount of the acid anhydride component and the diamine component. It is more preferably a thermoplastic polyimide obtained by imidizing a polyamic acid of a precursor obtained by reacting a diamine component containing 50 mol parts or more of a dimer diamine (hereinafter sometimes referred to as "DDA-based polyimide") or a crosslinked cured product thereof. In the present invention, when referring to polyimide, it means a resin composed of a polymer having an imide group in its molecular structure, such as polyamideimide, polyetherimide, polyesterimide, polysiloxaneimide, polybenzimidazoleimide, etc., in addition to polyimide.

[0038] <DDA-based polyimide> DDA-based polyimide is an aliphatic thermoplastic polyimide, rich in flexibility, having sufficient toughness even when a large amount of liquid crystal polymer filler is added, and having a high ability to maintain its shape when forming a resin film.

[0039] The DDA-based polyimide contains a tetracarboxylic acid residue derived from a tetracarboxylic dianhydride as a raw material and a diamine residue derived from a diamine compound as a raw material. In the present invention, the tetracarboxylic acid residue refers to a tetravalent group derived from a tetracarboxylic dianhydride, and the diamine residue refers to a divalent group derived from a diamine compound. By reacting the raw material tetracarboxylic dianhydride and diamine compound in approximately equimolar amounts, the types and amounts of the tetracarboxylic acid residue and diamine residue contained in the DDA-based polyimide can be made to substantially correspond to the types and amounts of the raw materials.

[0040] (Anhydride component) The DDA-based polyimide can generally use a tetracarboxylic dianhydride used as a thermoplastic polyimide as a raw material without particular limitation, but it is preferably contained in a total amount of 90 mol% or more of the tetracarboxylic dianhydride represented by the following general formula (1) and / or (2) with respect to the total anhydride component. In other words, the DDA-based polyimide preferably contains a total of 90 mol parts or more of the tetracarboxylic acid residue derived from the tetracarboxylic dianhydride represented by the following general formula (1) and / or (2) with respect to 100 mol parts of the total tetracarboxylic acid residues. By containing a total of 90 mol parts or more of the tetracarboxylic acid residue derived from the tetracarboxylic dianhydride represented by the following general formula (1) and / or (2) with respect to 100 mol parts of the tetracarboxylic acid residue, it is easy to achieve both flexibility and heat resistance of the DDA-based polyimide, which is preferable. If the total of the tetracarboxylic acid residues derived from the tetracarboxylic dianhydride represented by the following general formula (1) and / or (2) is less than 90 mol parts, the solvent solubility of the DDA-based polyimide tends to decrease.

[0041] [Chemical formula]

[0042] In general formula (1), X represents a single bond or a divalent group selected from the following formulas. In general formula (2), the cyclic moiety represented by Y forms a cyclic saturated hydrocarbon group selected from a 4-membered ring, a 5-membered ring, a 6-membered ring, a 7-membered ring, or an 8-membered ring.

[0043] [Chemical formula]

[0044] In the above formula, Z represents -C6H4-, -(CH2)n-, or -CH2-CH(-O-C(=O)-CH3)-CH2-, where n represents an integer from 1 to 20.

[0045] Examples of the tetracarboxylic dianhydride represented by the general formula (1) include 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), 4,4'-oxydiphthalic anhydride (ODPA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), p-phenylenebis(trimellitic monoester anhydride) (TAHQ), ethylene glycol bisanhydrotrimellitate (TMEG), and the like. Among these, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) is particularly preferred. When using BTDA, since the carbonyl group (ketone group) contributes to adhesiveness, the adhesiveness of the DDA-based polyimide can be improved. In addition, BTDA may react with the amino group of the amino compound for crosslinking formation and the ketone group present in the molecular skeleton to form a C=N bond, and it is easy to exhibit the effect of improving heat resistance. From such a viewpoint, it is preferable to contain 50 mol parts or more, more preferably 60 mol parts or more, of the tetracarboxylic acid residue derived from BTDA with respect to 100 mol parts of the tetracarboxylic acid residue.

[0046] Examples of the tetracarboxylic dianhydride represented by the general formula (2) include 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,4,5-cycloheptanetetracarboxylic dianhydride, 1,2,5,6-cyclooctanetetracarboxylic dianhydride, and the like.

[0047] The DDA-based polyimide can contain a tetracarboxylic acid residue derived from an acid anhydride other than the tetracarboxylic acid anhydride represented by the above general formula (1) and general formula (2) within a range not impairing the effects of the invention.Such tetracarboxylic acid residues are not particularly limited, and examples thereof include pyromellitic dianhydride, 2,3',3,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'- or 2,3,3',4'-benzophenone tetracarboxylic 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-anthracene tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)tetrafluoropropane dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic 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, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride, and other tetracarboxylic acid residues derived from aromatic tetracarboxylic dianhydrides.

[0048] (Diamine component) The DDA-based polyimide uses, as a raw material, a diamine component containing 50 mol parts or more, more preferably 70 mol parts or more, of a dimer diamine in which two terminal carboxylic acid groups of dimer acid are substituted with primary aminomethyl groups or amino groups, based on 100 mol parts of the total amount of the diamine component. By containing the dimer diamine in the above amount, the dielectric properties of the polyimide can be improved, and the thermocompression bonding properties can be improved due to a decrease in the glass transition temperature (low Tg) of the polyimide, and the internal stress can be relaxed due to a decrease in the elastic modulus.

[0049] The dimer diamine means a diamine in which two terminal carboxylic acid groups (-COOH) of dimer acid are substituted with primary aminomethyl groups (-CH2-NH2) or amino groups (-NH2). Dimer acid is a known dibasic acid obtained by an intermolecular polymerization reaction of unsaturated fatty acids, and its industrial manufacturing process is almost standardized in the industry, and is obtained by dimerizing unsaturated fatty acids having 11 to 22 carbon atoms with a clay catalyst or the like. Industrially obtained dimer acid is mainly composed of a dibasic acid having 36 carbon atoms obtained by dimerizing unsaturated fatty acids having 18 carbon atoms such as oleic acid, linoleic acid, and linolenic acid, but contains an arbitrary amount of monomer acid (18 carbon atoms), trimer acid (54 carbon atoms), and other polymerized fatty acids having 20 to 54 carbon atoms depending on the degree of purification. Further, although double bonds remain after the dimerization reaction, in the present invention, those further hydrogenated to reduce the degree of unsaturation are also included in the dimer acid. The dimer diamine can be defined as a diamine compound obtained by substituting the terminal carboxylic acid groups of a dibasic acid compound in the range of 18 to 54 carbon atoms, preferably in the range of 22 to 44 carbon atoms, with primary aminomethyl groups or amino groups.

[0050] As a characteristic of the dimer diamine, it is possible to impart characteristics derived from the skeleton of the dimer acid. That is, since the dimer diamine is a large aliphatic molecule with a molecular weight of about 560 to 620, it can increase the molar volume of the molecule and relatively reduce the polar groups of the DDA-based polyimide. Such characteristics of the dimer acid type diamine are considered to contribute to improving the dielectric properties by reducing the dielectric constant and the dielectric loss tangent while suppressing the decrease in the heat resistance of the DDA-based polyimide. In addition, since it has two freely moving hydrophobic chains with 7 to 9 carbon atoms and two chain-like aliphatic amino groups with a length close to 18 carbon atoms, it not only imparts flexibility to the DDA-based polyimide, but also makes the DDA-based polyimide have an asymmetric chemical structure or a non-planar chemical structure, so it is considered that the dielectric constant can be reduced.

[0051] The dimer diamine used in the present invention is preferably purified for the purpose of reducing components other than the dimer diamine. The purification method is not particularly limited, but known methods such as distillation method and precipitation purification are suitable. The dimer diamine before purification can be obtained as a commercially available product, and examples include PRIAMINE 1073 (trade name), PRIAMINE 1074 (trade name), PRIAMINE 1075 (trade name), etc. manufactured by Croda Japan.

[0052] Examples of diamine compounds other than dimer diamine used in DDA-based polyimide include aromatic diamine compounds and aliphatic diamine compounds. Specific examples thereof include 1,4-diaminobenzene (p-PDA; paraphenylenediamine), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-n-propyl-4,4'-diaminobiphenyl (m-NPB), 4-aminophenyl-4'-aminobenzoate (APAB), 2,2-bis-[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)biphenyl, bis[1-(3-aminophenoxy)]biphenyl, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)]benzophenone, 9,9-bis[4-(3-aminophenoxy)phenyl]fluorene, 2,2-bis-[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis-[4-(3-aminophenoxy)phenyl]hexafluoropropane, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 3,3'-diaminodiphenylethane, 3,3'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 3,3''-diamino-p-terphenyl, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisaniline, 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisaniline, bis(p-aminocyclohexyl)methane, bis(p-β-amino-t-butylphenyl)ether, bis(p-β-methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-aminopentyl)benzene, p-bis(1,1-dimethyl-5-aminopentyl)benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis(β-amino-t-butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine, 2,6-diaminopyridine, 2,Examples of the diamine compounds include 5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, 2'-methoxy-4,4'-diaminobenzanilide, 4,4'-diaminobenzanilide, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, 6-amino-2-(4-aminophenoxy)benzoxazole, 1,3-bis(3-aminophenoxy)benzene, etc.

[0053] The DDA-based polyimide can be produced by reacting the above acid anhydride component and diamine component in a solvent to form a polyamic acid and then subjecting it to thermal cyclization. For example, the acid anhydride component and diamine component are dissolved in an organic solvent in approximately equimolar amounts and stirred at a temperature in the range of 0 to 100 °C for 30 minutes to 24 hours to carry out a polymerization reaction, whereby a polyamic acid, which is a precursor of the polyimide, is obtained. In the reaction, the reaction components are dissolved so that the resulting precursor is in the range of 5 to 50% by weight, preferably in the range of 10 to 40% by weight, in the organic solvent. Examples of the organic solvent 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, methylcyclohexane, dioxane, tetrahydrofuran, diglyme, triglyme, methanol, ethanol, benzyl alcohol, cresol, etc. These solvents can also be used in combination of two or more, and further, a combination with aromatic hydrocarbons such as xylene and toluene is also possible. Also, the amount of such an organic solvent used is not particularly limited, but it is preferably adjusted to an amount such that the concentration of the polyamic acid solution obtained by the polymerization reaction is about 5 to 50% by weight.

[0054] The synthesized polyamic acid is usually advantageously used as a reaction solvent solution, but can be concentrated, diluted or replaced with other organic solvents if necessary. Also, since polyamic acid generally has excellent solvent solubility, it is preferably used. The viscosity of the polyamic acid solution is preferably in the range of 500 mPa·s to 100,000 mPa·s. If it is outside this range, defects such as film thickness unevenness and streaks are likely to occur during coating operations using a coater or the like.

[0055] The method of imidizing polyamic acid to form polyimide is not particularly limited. For example, heat treatment such as heating in the above solvent at a temperature condition in the range of 80 to 400 °C for 1 to 24 hours is preferably employed. Also, the temperature may be heated under constant temperature conditions, or the temperature may be changed during the process.

[0056] In DDA-based polyimide, by selecting the types of the above acid anhydride component and diamine component, and the respective molar ratios when applying two or more acid anhydride components or diamine components, dielectric properties, coefficient of thermal expansion, tensile elastic modulus, glass transition temperature, etc. can be controlled. Also, in DDA-based polyimide, when it has a plurality of structural units of polyimide, it may be present as a block or randomly, but it is preferably present randomly.

[0057] The weight average molecular weight of DDA-based polyimide is preferably in the range of, for example, 10,000 to 200,000. If it is within such a range, it becomes easy to control the weight average molecular weight of the polyimide. Also, for example, when applied as an adhesive for FPC, the weight average molecular weight of DDA-based polyimide is more preferably in the range of 20,000 to 150,000, and even more preferably in the range of 40,000 to 150,000. When applied as an adhesive for FPC, if the weight average molecular weight of DDA-based polyimide is less than 20,000, the flow resistance tends to deteriorate. On the other hand, when the weight average molecular weight of DDA-based polyimide exceeds 150,000, the viscosity increases excessively and it becomes insoluble in the solvent, and defects such as thickness unevenness and streaks of the adhesive layer are likely to occur during coating operations.

[0058] The imide group concentration of the DDA-based polyimide is preferably 22% by weight or less, more preferably 20% by weight or less. Here, the "imide group concentration" means the value obtained by dividing the molecular weight of the imide group (- (CO) 2-N-) in the polyimide by the molecular weight of the entire structure of the polyimide. When the imide group concentration exceeds 22% by weight, the molecular weight of the resin itself decreases, and the low moisture absorption property deteriorates due to the increase in polar groups, and the Tg and elastic modulus increase.

[0059] The DDA-based polyimide most preferably has a completely imidized structure. However, a part of the polyimide may be an amic acid. The imidization rate can be measured by measuring the infrared absorption spectrum of the polyimide thin film by the single reflection ATR method using a Fourier transform infrared spectrophotometer (commercially available product: FT / IR620 manufactured by JASCO Corporation), and based on the benzene ring absorber near 1015 cm -1 It can be calculated from the absorbance of the C=O stretching derived from the imide group at 1780 cm -1 of.

[0060] In the DDA-based polyimide, as optional components, for example, plasticizers, other cured resin components such as epoxy resins, curing agents, curing accelerators, inorganic fillers, coupling agents, fillers, solvents, flame retardants, etc. can be appropriately blended.

[0061] [Crosslink formation of DDA-based polyimide] When the DDA-based polyimide has a ketone group, a crosslinked structure can be formed by reacting the ketone group with the amino groups of an amino compound having at least two primary amino groups as functional groups (hereinafter sometimes referred to as "amino compound for crosslink formation"). By forming the crosslinked structure, the heat resistance of the DDA-based polyimide can be improved. Preferred tetracarboxylic dianhydrides for forming the DDA-based polyimide having a ketone group include, for example, 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), and preferred diamine compounds include, for example, aromatic diamines such as 4,4'-bis(3-aminophenoxy)benzophenone (BABP) and 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene (BABB).

[0062] For the purpose of forming a crosslinked structure, in particular, it is preferable to include the above DDA-based polyimide containing a BTDA residue derived from BTDA, preferably 50 mol% or more, more preferably 60 mol% or more, based on all the tetracarboxylic acid residues, and the amino compound for crosslink formation. In the present invention, the "BTDA residue" means a tetravalent group derived from BTDA.

[0063] Examples of the amino compound for forming a bridge include (I) dihydrazide compounds, (II) aromatic diamines, (III) aliphatic amines, etc. Among these, dihydrazide compounds are preferred. Aliphatic amines other than dihydrazide compounds are likely to form a crosslinked structure even at room temperature, raising concerns about the storage stability of the varnish. On the other hand, aromatic diamines need to be heated to a high temperature to form a crosslinked structure. Thus, when using a dihydrazide compound, it is possible to achieve both the storage stability of the varnish and the shortening of the curing time. Examples of the dihydrazide compound include dihydrazide compounds such as oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, diglycolic acid dihydrazide, tartaric acid dihydrazide, malic acid dihydrazide, phthalic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, 2,6-naphthalenedicarboxylic acid dihydrazide, 4,4-bisbenzenedihydrazide, 1,4-naphthoic acid dihydrazide, 2,6-pyridinedicarboxylic acid dihydrazide, itaconic acid dihydrazide. The above dihydrazide compounds may be used alone or in combination of two or more.

[0064] In addition, amino compounds such as the above (I) dihydrazide compounds, (II) aromatic diamines, and (III) aliphatic amines can also be used in combination of two or more across categories, such as a combination of (I) and (II), a combination of (I) and (III), and a combination of (I), (II), and (III).

[0065] Also, from the viewpoint of making the network structure formed by crosslinking with the amino compound for crosslinking formation denser, the amino compound for crosslinking formation used in the present invention preferably has a molecular weight (weight average molecular weight when the amino compound for crosslinking formation is an oligomer) of 5,000 or less, more preferably 90 to 2,000, and still more preferably 100 to 1,500. Among these, an amino compound for crosslinking formation having a molecular weight of 100 to 1,000 is particularly preferred. When the molecular weight of the amino compound for crosslinking formation is less than 90, one amino group of the amino compound for crosslinking formation only forms a C=N bond with the ketone group of the DDA-based polyimide, and the periphery of the remaining amino groups becomes sterically bulky, so the remaining amino groups tend to be less likely to form a C=N bond.

[0066] When crosslinking the ketone group in the DDA-based polyimide and the amino compound for crosslinking formation, the above-mentioned amino compound for crosslinking formation is added to the resin solution containing the DDA-based polyimide, and the ketone group in the DDA-based polyimide and the primary amino group of the amino compound for crosslinking formation are subjected to a condensation reaction. By this condensation reaction, the resin solution is cured to form a cured product. In this case, the addition amount of the amino compound for crosslinking formation can be such that the total amount of the primary amino groups is 0.004 mol to 1.5 mol, preferably 0.005 mol to 1.2 mol, more preferably 0.03 mol to 0.9 mol, and most preferably 0.04 mol to 0.6 mol per 1 mol of the ketone group. When the addition amount of the amino compound for crosslinking formation is such that the total amount of the primary amino groups is less than 0.004 mol per 1 mol of the ketone group, the crosslinking by the amino compound for crosslinking formation is not sufficient, so the heat resistance after curing tends not to be exhibited. When the addition amount of the amino compound for crosslinking formation exceeds 1.5 mol, the unreacted amino compound for crosslinking formation acts as a plasticizer and tends to lower the heat resistance as an adhesive layer.

[0067] The conditions for the condensation reaction for crosslink formation are not particularly limited as long as the ketone group in the DDA-based polyimide reacts with the primary amino group of the amino compound for crosslink formation to form an imine bond (C=N bond). The temperature for the heat condensation is preferably in the range of, for example, 120 to 220°C, more preferably in the range of 140 to 200°C, for reasons such as releasing the water generated by the condensation out of the system or simplifying the condensation process when the heat condensation reaction is subsequently carried out after the synthesis of the DDA-based polyimide. The reaction time is preferably about 30 minutes to 24 hours. The end point of the reaction can be confirmed, for example, by measuring the infrared absorption spectrum using a Fourier transform infrared spectrophotometer (commercially available product: FT / IR620 manufactured by JASCO Corporation), by the decrease or disappearance of the absorption peak derived from the ketone group in the polyimide resin near 1670 cm -1 and the appearance of the absorption peak derived from the imine group near 1635 cm -1 .

[0068] The heat condensation of the ketone group of the DDA-based polyimide and the primary amino group of the amino compound for crosslink formation can be carried out, for example, (1) A method of adding the amino compound for crosslink formation and heating it following the synthesis (imidization) of the DDA-based polyimide, (2) A method of previously charging an excessive amount of the amino compound as the diamine component, and following the synthesis (imidization) of the DDA-based polyimide, heating it together with the DDA-based polyimide using the remaining amino compound that does not participate in imidization or amidization as the amino compound for crosslink formation, or, (3) A method of heating the composition of the DDA-based polyimide added with the above-mentioned amino compound for crosslink formation after processing it into a predetermined shape (for example, after coating it on an arbitrary substrate or forming it into a film shape), etc.

[0069] For imparting heat resistance to the DDA-based polyimide, the formation of an imine bond by forming a crosslinked structure was described, but it is not limited thereto. As a method for curing the polyimide, for example, it is also possible to blend and cure a compound having an unsaturated bond such as an epoxy resin, an epoxy resin curing agent, maleimide, an activated ester resin, or a resin having a styrene skeleton.

[0070] [Dimensional accuracy maintaining layer] In order to maintain the mechanical strength of the metal-clad laminate 10, the dimensional accuracy maintaining layer PL preferably has a minimum value of the storage modulus in the temperature range of 100°C to 250°C within the range of 1.0 to 8.0 GPa, and more preferably within the range of 2.0 to 6.0 GPa is more preferable. If the minimum value of the storage modulus of the dimensional accuracy maintaining layer PL is less than 1.0 GPa, sufficient mechanical strength and dimensional accuracy after circuit processing cannot be obtained. When the minimum value of the storage modulus exceeds 8.0 GPa, warping is likely to occur during the lamination press.

[0071] Also, in order to maintain the dimensional accuracy when the metal-clad laminate 10 is circuit-processed, the coefficient of thermal expansion (CTE) of the dimensional accuracy maintaining layer PL is preferably within the range of 15 to 25 ppm / K, and more preferably within the range of 16 to 23 ppm / K. If the CTE of the dimensional accuracy maintaining layer PL is less than 15 ppm / K, warping is likely to occur in the metal-clad laminate 10, and if it exceeds 25 ppm / K, dimensional accuracy after circuit processing cannot be obtained.

[0072] The dimensional accuracy maintaining layer PL is not particularly limited as long as it is composed of a resin having electrical insulation properties. For example, polyimide, epoxy resin, phenolic resin, polyethylene, polypropylene, polytetrafluoroethylene, silicone, ETFE, etc. can be mentioned, but it is preferably composed of polyimide. That is, the dimensional accuracy maintaining layer PL is preferably a low thermal expansion polyimide layer composed of a single layer or multiple layers.

[0073] When the dimensional accuracy maintaining layer PL is a single-layer polyimide layer, it can have the same configuration as the non-thermoplastic polyimide layer 31 described later. As the single-layer polyimide layer, for example, commercially available products such as Kapton EN (trade name; manufactured by Toray DuPont Co., Ltd.) and Apical NPI (trade name; manufactured by Kaneka Corporation) can be used.

[0074] When the dimensional accuracy maintaining layer PL is composed of a plurality of polyimide layers, the dimensional accuracy maintaining layer PL may have, for example, a structure in which thermoplastic polyimide layers 33 containing thermoplastic polyimide as a resin component are laminated on both sides of a non-thermoplastic polyimide layer 31 containing non-thermoplastic polyimide as a resin component, as shown in FIG. 4. Note that the "non-thermoplastic polyimide" generally refers to a polyimide that does not show softening or adhesiveness even when heated. In the present invention, however, it refers to a polyimide having a storage elastic modulus at 30°C of 1.0×10 9 Pa or more and a storage elastic modulus at 350°C of 1.0×10 8 Pa or more, as measured using a dynamic viscoelasticity measuring device (DMA). Also, the "thermoplastic polyimide" generally refers to a polyimide having a clearly confirmed glass transition temperature (Tg). In the present invention, however, it refers to a polyimide having a storage elastic modulus at 30°C of 1.0×10 9 Pa or more and a storage elastic modulus at 350°C of less than 1.0×10 8 Pa, as measured using DMA.

[0075] Next, preferred configuration examples of the non-thermoplastic polyimide layer 31 and the thermoplastic polyimide layer 33 for forming the dimensional accuracy maintaining layer PL will be described.

[0076] Non-thermoplastic polyimide layer: The non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 31 contains a tetracarboxylic acid residue and a diamine residue. The polyimide preferably contains an aromatic tetracarboxylic acid residue derived from an aromatic tetracarboxylic dianhydride and an aromatic diamine residue derived from an aromatic diamine.

[0077] (Tetracarboxylic acid residue) The non-thermoplastic polyimide that constitutes the non-thermoplastic polyimide layer 31 preferably contains a tetracarboxylic acid residue derived from at least one of 3,3’,4,4’-biphenyltetracarboxylic dianhydride (BPDA) and 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ) as a tetracarboxylic acid residue, and a tetracarboxylic acid residue derived from at least one of pyromellitic dianhydride (PMDA) and 2,3,6,7-naphthalenetetracarboxylic dianhydride (NTCDA).

[0078] The tetracarboxylic acid residue derived from BPDA (hereinafter also referred to as “BPDA residue”) and the tetracarboxylic acid residue derived from TAHQ (hereinafter also referred to as “TAHQ residue”) are likely to form an ordered structure of the polymer, and can reduce the dielectric tangent and hygroscopicity by suppressing the movement of molecules. The BPDA residue can impart self-supportability to the gel film of the polyamic acid as the polyimide precursor, but on the other hand, it increases the CTE after imidization and tends to lower the glass transition temperature and reduce the heat resistance.

[0079] From such a viewpoint, the non-thermoplastic polyimide that constitutes the non-thermoplastic polyimide layer 31 is controlled to contain the total of the BPDA residue and the TAHQ residue preferably in the range of 30 to 60 mol parts, more preferably in the range of 40 to 50 mol parts, per 100 mol parts of all the tetracarboxylic acid residues. If the total of the BPDA residue and the TAHQ residue is less than 30 mol parts, the formation of the ordered structure of the polymer becomes insufficient, resulting in a decrease in moisture absorption resistance or insufficient reduction of the dielectric tangent. If it exceeds 60 mol parts, in addition to an increase in CTE and an increase in the change amount of in-plane retardation (RO), there is a risk of a decrease in heat resistance.

[0080] In addition, the tetracarboxylic acid residue derived from pyromellitic dianhydride (hereinafter also referred to as "PMDA residue") and the tetracarboxylic acid residue derived from 2,3,6,7-naphthalene tetracarboxylic dianhydride (hereinafter also referred to as "NTCDA residue") have rigidity, so they enhance the in-plane orientation, suppress the CTE to a low level, and play a role in controlling the in-plane retardation (RO) and the glass transition temperature. On the other hand, since the PMDA residue has a small molecular weight, if its amount becomes too large, the imide group concentration of the polymer increases, the polar groups increase, the hygroscopicity increases, and the dielectric tangent increases due to the influence of moisture inside the molecular chain. In addition, the NTCDA residue tends to make the film brittle due to the highly rigid naphthalene skeleton and increase the elastic modulus. Therefore, the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer preferably contains the total of the PMDA residue and the NTCDA residue in the range of 40 to 70 mole parts, more preferably 50 to 60 mole parts, and still more preferably 50 to 55 mole parts with respect to 100 mole parts of all the tetracarboxylic acid residues. If the total of the PMDA residue and the NTCDA residue is less than 40 mole parts, the CTE may increase or the heat resistance may decrease. If it exceeds 70 mole parts, the imide group concentration of the polymer increases, the polar groups increase, the low hygroscopicity is impaired, and the dielectric tangent may increase, or the film may become brittle and the self-supporting property of the film may decrease.

[0081] In addition, the total of at least one of the BPDA residue and the TAHQ residue and at least one of the PMDA residue and the NTCDA residue is preferably 80 mole parts or more, more preferably 90 mole parts or more with respect to 100 mole parts of all the tetracarboxylic acid residues.

[0082] In addition, the molar ratio {(BPDA residue + TAHQ residue) / (PMDA residue + NTCDA residue)} of at least one of the BPDA residue and the TAHQ residue to at least one of the PMDA residue and the NTCDA residue is in the range of 0.4 or more and 1.5 or less, preferably in the range of 0.6 or more and 1.3 or less, more preferably in the range of 0.8 or more and 1.2 or less, and it is good to control the formation of the ordered structure of the CTE and the polymer.

[0083] Since PMDA and NTCDA have a rigid backbone, compared with other general anhydride components, it is possible to control the in-plane orientation of molecules in the polyimide, and there are effects of suppressing the coefficient of thermal expansion (CTE) and improving the glass transition temperature (Tg). In addition, since BPDA and TAHQ have a larger molecular weight compared with PMDA, increasing the charging ratio reduces the imide group concentration, which is effective in reducing the dielectric tangent and the moisture absorption rate. On the other hand, when the charging ratio of BPDA and TAHQ increases, the in-plane orientation of molecules in the polyimide decreases, leading to an increase in CTE. Furthermore, the formation of the ordered structure within the molecule progresses, and the haze value increases. From such a viewpoint, the total charged amount of PMDA and NTCDA is preferably in the range of 40 to 70 mol parts, more preferably in the range of 50 to 60 mol parts, still more preferably in the range of 50 to 55 mol parts, with respect to 100 mol parts of the total anhydride component of the raw materials. When the total charged amount of PMDA and NTCDA is less than 40 mol parts with respect to 100 mol parts of the total anhydride component of the raw materials, the in-plane orientation of the molecules decreases, making it difficult to reduce the CTE, and the heat resistance and dimensional stability of the film during heating due to the decrease in Tg also decrease. On the other hand, when the total charged amount of PMDA and NTCDA exceeds 70 mol parts, the moisture absorption rate deteriorates due to the increase in the imide group concentration, and the elastic modulus tends to increase.

[0084] In addition, BPDA and TAHQ are effective in reducing the dielectric tangent and the moisture absorption rate due to the suppression of molecular motion and the decrease in the imide group concentration, but increase the CTE of the polyimide film after imidization. From such a viewpoint, the total charged amount of BPDA and TAHQ is preferably in the range of 30 to 60 mol parts, more preferably in the range of 40 to 50 mol parts, with respect to 100 mol parts of the total anhydride component of the raw materials.

[0085] Examples of tetracarboxylic acid residues other than the above BPDA residues, TAHQ residues, PMDA residues, and NTCDA residues contained in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 31 include, for example, 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 2,3',3,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-, 2,3,3',4'- or 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,3',3,4'-diphenylether 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.Tetracarboxylic acid residues derived from aromatic tetracarboxylic dianhydrides such as 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-anthracene tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)tetrafluoropropane dianhydride, 2,3,5,6-cyclohexane dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 2,6- or 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-(or 1,4,5,8-)tetrachloronaphthalene-1,4,5,8-(or 2,3,6,7-)tetracarboxylic dianhydride, 2,3,8,9-, 3,4,9,10-, 4,5,10,11- or 5,6,11,12-perylene-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride, ethylene glycol bisanhydrotrimellitate, etc. are mentioned.

[0086] (Diamine residue) As the diamine residue contained in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 31, a diamine residue derived from a diamine compound represented by the general formula (A1) is preferable.

[0087] [Chemical formula]

[0088] In formula (A1), the linking group Z represents a single bond or -COO-, and Y independently represents a monovalent hydrocarbon having 1 to 3 carbon atoms which may be substituted with a halogen atom or a phenyl group, or an alkoxy group having 1 to 3 carbon atoms, or a perfluoroalkyl group having 1 to 3 carbon atoms, or an alkenyl group. n represents an integer from 0 to 2, and p and q independently represent integers from 0 to 4. Here, "independently" means that in the above formula (A1), a plurality of substituents Y, and further the integers p and q may be the same or different. In the above formula (A1), the hydrogen atoms in the two terminal amino groups may be substituted, for example, it may be -NR2R3 (where R2 and R3 independently mean any substituent such as an alkyl group).

[0089] The diamine compound represented by the general formula (A1) (hereinafter sometimes referred to as "diamine (A1)") is an aromatic diamine having 1 to 3 benzene rings. Since diamine (A1) has a rigid structure, it has an effect of imparting an ordered structure to the entire polymer. Therefore, a polyimide with low gas permeability and low hygroscopicity can be obtained, and since the moisture inside the molecular chain can be reduced, the dielectric loss tangent can be lowered. Here, as the linking group Z, a single bond is preferred.

[0090] Examples of the diamine (A1) include 1,4-diaminobenzene (p-PDA; paraphenylenediamine), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-n-propyl-4,4'-diaminobiphenyl (m-NPB), 4-aminophenyl-4'-aminobenzoate (APAB), and the like.

[0091] The non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 31 preferably contains a diamine residue derived from diamine (A1) in an amount of preferably 80 mol parts or more, more preferably 85 mol parts or more, per 100 mol parts of all diamine residues. By using diamine (A1) in an amount within the above range, due to the rigid structure derived from the monomer, an ordered structure is likely to be formed in the whole polymer, and it is easy to obtain a non-thermoplastic polyimide having low gas permeability, low hygroscopicity, and low dielectric tangent.

[0092] Further, when the diamine residue derived from diamine (A1) is in the range of 80 mol parts or more and 85 mol parts or less per 100 mol parts of all diamine residues in the non-thermoplastic polyimide, from the viewpoint of a more rigid and excellent in-plane orientation structure, it is preferable to use 1,4-diaminobenzene as diamine (A1).

[0093] Other diamine residues contained in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 31 include, for example, 2,2-bis-[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)biphenyl, bis[1-(3-aminophenoxy)]biphenyl, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)]benzophenone, 9,9-bis[4-(3-aminophenoxy)phenyl]fluorene, 2,2-bis-[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis-[4-(3-aminophenoxy)phenyl]hexafluoropropane, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 3,3'-diaminodiphenylethane, 3,3'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 3,3''-diamino-p-terphenyl, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisaniline, 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisaniline, bis(p-aminocyclohexyl)methane, bis(p-β-amino-t-butylphenyl)ether, bis(p-β-methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-aminopentyl)benzene, p-bis(1,1-dimethyl-5-aminopentyl)benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis(β-amino-t-butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, 2'-methoxy-4,4'-diaminobenzanilide, 4,4'-diaminobenzanilide, 1,Diamine residues derived from aromatic diamine compounds such as 3-bis[2-(4-aminophenyl)-2-propyl]benzene and 6-amino-2-(4-aminophenoxy)benzoxazole, and diamine residues derived from aliphatic diamine compounds such as dimer acid type diamines in which two terminal carboxylic acid groups of dimer acid are substituted with primary aminomethyl groups or amino groups.

[0094] In non-thermoplastic polyimide, by selecting the types of the above tetracarboxylic acid residues and diamine residues, and the molar ratios of each when applying two or more types of tetracarboxylic acid residues or diamine residues, the coefficient of thermal expansion, storage modulus, tensile modulus, etc. can be controlled. Also, in non-thermoplastic polyimide, when it has a plurality of structural units of polyimide, it may be present as a block or randomly, but from the viewpoint of suppressing the variation in in-plane retardation (RO), it is preferably present randomly.

[0095] Note that by making both the tetracarboxylic acid residue and the diamine residue contained in the non-thermoplastic polyimide aromatic groups, it is preferable because the dimensional accuracy of the polyimide film under a high-temperature environment can be improved and the change amount of in-plane retardation (RO) can be reduced.

[0096] The imide group concentration of the non-thermoplastic polyimide is preferably 33% or less, and more preferably 32% or less. Here, the "imide group concentration" means the value obtained by dividing the molecular weight of the imide group (- (CO) 2 -N-) in the polyimide by the molecular weight of the entire structure of the polyimide. When the imide group concentration exceeds 33%, the molecular weight of the resin itself decreases, and the low moisture absorption property deteriorates due to the increase in polar groups. By selecting the combination of the above acid anhydride and diamine compound, by controlling the molecular orientation in the non-thermoplastic polyimide, the increase in CTE accompanying the decrease in imide group concentration is suppressed, and low moisture absorption is ensured.

[0097] The weight average molecular weight of the non-thermoplastic polyimide is preferably in the range of, for example, 10,000 to 400,000, more preferably in the range of 50,000 to 350,000. If the weight average molecular weight is less than 10,000, the strength of the film tends to decrease and it 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 film thickness unevenness and streaks tend to occur during the coating operation.

[0098] The thickness of the non-thermoplastic polyimide layer 31 is preferably in the range of 6 μm or more and 100 μm or less, more preferably in the range of 9 μm or more and 50 μm or less, from the viewpoint of ensuring the function as a base layer and the transportability during production and when coating the thermoplastic polyimide. If the thickness of the non-thermoplastic polyimide layer 31 is less than the above lower limit value, the electrical insulation and handling properties become insufficient, and if it exceeds the upper limit value, the productivity decreases.

[0099] From the viewpoint of heat resistance, the non-thermoplastic polyimide layer 31 preferably has a glass transition temperature (Tg) of 280 °C or higher.

[0100] Also, from the viewpoint of suppressing warping, the coefficient of thermal expansion of the non-thermoplastic polyimide layer 31 is preferably in the range of 1 ppm / K or more and 30 ppm / K or less, more preferably in the range of 1 ppm / K or more and 25 ppm / K or less, and even more preferably in the range of 15 ppm / K or more and 25 ppm / K or less.

[0101] In addition, for the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 31, as optional components, for example, plasticizers, other cured resin components such as epoxy resins, curing agents, curing accelerators, coupling agents, fillers, solvents, flame retardants, etc. can be appropriately blended. However, some plasticizers contain many polar groups, and there is a concern that they may promote the diffusion of copper from the copper wiring. Therefore, it is preferably not to use plasticizers as much as possible.

[0102] Thermoplastic polyimide layer: The thermoplastic polyimide constituting the thermoplastic polyimide layer 33 contains a tetracarboxylic acid residue and a diamine residue, and preferably contains an aromatic tetracarboxylic acid residue derived from an aromatic tetracarboxylic dianhydride and an aromatic diamine residue derived from an aromatic diamine.

[0103] (Tetracarboxylic acid residue) As the tetracarboxylic acid residue used for the thermoplastic polyimide constituting the thermoplastic polyimide layer 33, the same ones as those exemplified as the tetracarboxylic acid residue in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer can be used.

[0104] (Diamine residue) As the diamine residue contained in the thermoplastic polyimide constituting the thermoplastic polyimide layer 33, a diamine residue derived from a diamine compound represented by general formulas (B1) to (B7) is preferable.

[0105] [Chemical formula]

[0106] In formulas (B1) to (B7), R1 independently represents a monovalent hydrocarbon group or an alkoxy group having 1 to 6 carbon atoms, the linking group A independently represents a divalent group selected from -O-, -S-, -CO-, -SO-, -SO2-, -COO-, -CH2-, -C(CH3)2-, -NH- or -CONH-, and n1 independently represents an integer of 0 to 4. However, those overlapping with formula (B2) are excluded from formula (B3), and those overlapping with formula (B4) are excluded from formula (B5). Here, "independently" means that in one or more of the above formulas (B1) to (B7), a plurality of linking groups A, a plurality of R1 or a plurality of n1 may be the same or different. In the above formulas (B1) to (B7), the hydrogen atoms in the two terminal amino groups may be substituted, for example, -NR2R3 (where R2 and R3 independently represent any substituent such as an alkyl group).

[0107] The diamine represented by formula (B1) (hereinafter sometimes referred to as "diamine (B1)") is an aromatic diamine having two benzene rings. In this diamine (B1), since the amino group directly bonded to at least one benzene ring and the divalent linking group A are in the meta position, the degree of freedom of the polyimide molecular chain increases and it has high flexibility, which is considered to contribute to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B1), the thermoplasticity of the polyimide is enhanced. Here, as the linking group A, -O-, -CH2-, -C(CH3)2-, -CO-, -SO2-, -S- are preferable.

[0108] Examples of the diamine (B1) include 3,3'-diaminodiphenylmethane, 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfone, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylpropane, 3,4'-diaminodiphenylsulfide, 3,3'-diaminobenzophenone, (3,3'-bisamino)diphenylamine, and the like.

[0109] The diamine represented by formula (B2) (hereinafter sometimes referred to as "diamine (B2)") is an aromatic diamine having three benzene rings. In this diamine (B2), since the amino group directly bonded to at least one benzene ring and the divalent linking group A are in the meta position, the degree of freedom of the polyimide molecular chain increases and it has high flexibility, which is considered to contribute to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B2), the thermoplasticity of the polyimide is enhanced. Here, as the linking group A, -O- is preferable.

[0110] Examples of the diamine (B2) include 1,4-bis(3-aminophenoxy)benzene, 3-[4-(4-aminophenoxy)phenoxy]benzeneamine, 3-[3-(4-aminophenoxy)phenoxy]benzeneamine, and the like.

[0111] The diamine represented by formula (B3) (hereinafter sometimes referred to as "diamine (B3)") is an aromatic diamine having three benzene rings. In this diamine (B3), two divalent linking groups A directly bonded to one benzene ring are in the meta position to each other, so that the degree of freedom of the polyimide molecular chain increases and it has high flexibility, which is considered to contribute to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B3), the thermoplasticity of the polyimide is enhanced. Here, as the linking group A, -O- is preferable.

[0112] Examples of the diamine (B3) include 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,3-bis(3-aminophenoxy)benzene (APB), 4,4'-[2-methyl-(1,3-phenylene)bisoxy]bisaniline, 4,4'-[4-methyl-(1,3-phenylene)bisoxy]bisaniline, 4,4'-[5-methyl-(1,3-phenylene)bisoxy]bisaniline and the like.

[0113] The diamine represented by formula (B4) (hereinafter sometimes referred to as "diamine (B4)") is an aromatic diamine having four benzene rings. In this diamine (B4), an amino group directly bonded to at least one benzene ring and a divalent linking group A are in the meta position, so that it has high flexibility, which is considered to contribute to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B4), the thermoplasticity of the polyimide is enhanced. Here, as the linking group A, -O-, -CH2-, -C(CH3)2-, -SO2-, -CO-, -CONH- are preferable.

[0114] Examples of the diamine (B4) include 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)]benzamide and the like.

[0115] The diamine represented by formula (B5) (hereinafter sometimes referred to as "diamine (B5)") is an aromatic diamine having four benzene rings. In this diamine (B5), two divalent linking groups A directly bonded to at least one benzene ring are in the meta position to each other, so that the degree of freedom of the polyimide molecular chain increases and it has high flexibility, and it is considered to contribute to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B5), the thermoplasticity of the polyimide is enhanced. Here, as the linking group A, -O- is preferable.

[0116] Examples of diamine (B5) include 4-[3-[4-(4-aminophenoxy)phenoxy]phenoxy]aniline, 4,4'-[oxybis(3,1-phenyleneoxy)]bisaniline, and the like.

[0117] The diamine represented by formula (B6) (hereinafter sometimes referred to as "diamine (B6)") is an aromatic diamine having four benzene rings. This diamine (B6) has high flexibility due to having at least two ether bonds, and is considered to contribute to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B6), the thermoplasticity of the polyimide is enhanced. Here, as the linking group A, -C(CH3)2-, -O-, -SO2-, -CO- are preferable.

[0118] Examples of diamine (B6) include, for example, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), bis[4-(4-aminophenoxy)phenyl]ether (BAPE), bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), bis[4-(4-aminophenoxy)phenyl]ketone (BAPK), and the like.

[0119] The diamine represented by formula (B7) (hereinafter sometimes referred to as "diamine (B7)") is an aromatic diamine having four benzene rings. Since this diamine (B7) has highly flexible divalent linking groups A on both sides of the diphenyl skeleton, it is considered to contribute to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B7), the thermoplasticity of the polyimide is enhanced. Here, as the linking group A, -O- is preferred.

[0120] Examples of the diamine (B7) include bis[4-(3-aminophenoxy)]biphenyl, bis[4-(4-aminophenoxy)]biphenyl, and the like.

[0121] The thermoplastic polyimide constituting the thermoplastic polyimide layer 33 contains, based on 100 mol parts of all diamine residues, 60 mol parts or more, preferably in the range of 60 mol parts or more and 99 mol parts or less, more preferably in the range of 70 mol parts or more and 95 mol parts or less, of diamine residues derived from at least one diamine compound selected from diamines (B1) to diamines (B7). Since diamines (B1) to diamines (B7) have a molecular structure with flexibility, by using at least one diamine compound selected from these in an amount within the above range, the flexibility of the polyimide molecular chain can be improved and thermoplasticity can be imparted. If the total amount of diamines (B1) to diamines (B7) in the raw materials is less than 60 mol parts with respect to 100 mol parts of all diamine components, the flexibility of the polyimide resin is insufficient and sufficient thermoplasticity cannot be obtained.

[0122] In addition, as the diamine residue contained in the thermoplastic polyimide constituting the thermoplastic polyimide layer 33, a diamine residue derived from a diamine compound represented by the general formula (A1) is also preferable. The diamine compound [diamine (A1)] represented by the formula (A1) is as described in the explanation of non-thermoplastic polyimide. Since diamine (A1) has a rigid structure and has the effect of imparting an ordered structure to the entire polymer, the dielectric tangent and hygroscopicity can be reduced by suppressing the movement of molecules. Furthermore, by using it as a raw material for thermoplastic polyimide, a polyimide with low gas permeability and excellent long-term heat-resistant adhesiveness can be obtained.

[0123] The thermoplastic polyimide constituting the thermoplastic polyimide layer 33 may contain a diamine residue derived from diamine (A1) preferably in the range of 1 to 40 mol parts, more preferably in the range of 5 to 30 mol parts. By using diamine (A1) in an amount within the above range, an ordered structure is formed in the entire polymer due to the rigid structure derived from the monomer. Therefore, a polyimide with low gas permeability and hygroscopicity and excellent long-term heat-resistant adhesiveness can be obtained while being thermoplastic.

[0124] The thermoplastic polyimide constituting the thermoplastic polyimide layer 33 can contain a diamine residue derived from a diamine compound other than diamines (A1), (B1) to (B7) as long as the effects of the invention are not impaired.

[0125] In thermoplastic polyimide, by selecting the types of the above-mentioned tetracarboxylic acid residue and diamine residue, and the molar ratio of each when applying two or more kinds of tetracarboxylic acid residues or diamine residues, the coefficient of thermal expansion, tensile elastic modulus, glass transition temperature, etc. can be controlled. Also, in thermoplastic polyimide, when there are a plurality of structural units of polyimide, they may exist as blocks or randomly, but it is preferable that they exist randomly.

[0126] In addition, by making both the tetracarboxylic acid residue and the diamine residue contained in the thermoplastic polyimide aromatic groups, it is possible to improve the dimensional accuracy of the polyimide film in a high-temperature environment and suppress the change amount of the in-plane retardation (RO).

[0127] The imide group concentration of the thermoplastic polyimide is preferably 33% or less, more preferably 32% or less. Here, the "imide group concentration" means a value obtained by dividing the molecular weight of the imide group (- (CO) 2 - N -) in the polyimide by the molecular weight of the entire structure of the polyimide. When the imide group concentration exceeds 33%, the molecular weight of the resin itself decreases, and the low moisture absorption property deteriorates due to the increase in polar groups. By selecting the combination of the above diamine compounds and controlling the molecular orientation in the thermoplastic polyimide, an increase in CTE accompanying a decrease in the imide group concentration is suppressed, and low moisture absorption is ensured.

[0128] The weight average molecular weight of the thermoplastic polyimide is preferably in the range of, for example, 10,000 to 400,000, more preferably in the range of 50,000 to 350,000. When the weight average molecular weight is less than 10,000, the strength of the film tends to decrease and it tends to become brittle. On the other hand, when the weight average molecular weight exceeds 400,000, the viscosity excessively increases and defects such as film thickness unevenness and streaks tend to occur during the coating operation.

[0129] Since the thermoplastic polyimide constituting the thermoplastic polyimide layer 33 becomes, for example, an adhesive layer in the insulating resin of the circuit board, a structure that is completely imidized is most preferable in order to suppress the diffusion of copper. However, a part of the polyimide may be an amic acid. The imidization rate is measured by using a Fourier transform infrared spectrophotometer (commercially available product: FT / IR620 manufactured by JASCO Corporation) and measuring the infrared absorption spectrum of the polyimide thin film by the single reflection ATR method, and is calculated from the absorbance of the C=O stretching derived from the imide group at 1780 cm -1 near the benzene ring absorber as a reference. -1 It is calculated from the absorbance of the C=O stretching derived from the imide group at.

[0130] From the viewpoint of ensuring the adhesion function, the thickness of the thermoplastic polyimide layer 33 is preferably in the range of 1 μm or more and 10 μm or less, and more preferably in the range of 1 μm or more and 5 μm or less. When the thickness of the thermoplastic polyimide layer 33 is less than the above lower limit value, the adhesiveness becomes insufficient, and when it exceeds the upper limit value, the dimensional stability tends to deteriorate.

[0131] From the viewpoint of suppressing warping, the coefficient of thermal expansion of the thermoplastic polyimide layer 33 is preferably in the range of 30 ppm / K or more, preferably in the range of 30 ppm / K or more and 100 ppm / K or less, and more preferably in the range of 30 ppm / K or more and 80 ppm / K or less.

[0132] In addition to polyimide, the resin used for the thermoplastic polyimide layer 33 may be appropriately blended with other curable resin components such as plasticizers, epoxy resins, curing agents, curing accelerators, inorganic fillers, coupling agents, fillers, solvents, flame retardants, etc. as optional components.

[0133] The non-thermoplastic polyimide and thermoplastic polyimide for forming the non-thermoplastic polyimide layer 31 and the thermoplastic polyimide layer 33 can be produced in the same manner as the above DDA-based polyimide by reacting an acid anhydride component and a diamine component in a solvent to generate a polyamic acid and then heating and ring-closing it. In the synthesis of the non-thermoplastic polyimide and the thermoplastic polyimide, only one kind of the above acid anhydride and diamine may be used, or two or more kinds may be used in combination. By selecting the types of the acid anhydride and diamine and the respective molar ratios in the case of using two or more kinds of acid anhydrides or diamines, the thermal expansibility, adhesiveness, glass transition temperature, etc. can be controlled.

[0134] <Coefficient of Thermal Expansion> In the metal-clad laminate 10, the coefficient of thermal expansion (CTE) of the entire resin laminate 20 is preferably 10 ppm / K or more, preferably in the range of 10 ppm / K or more and 30 ppm / K or less, and more preferably in the range of 15 ppm / K or more and 25 ppm / K or less. If the CTE is less than 10 ppm / K or exceeds 30 ppm / K, warping may occur or dimensional stability may decrease. By appropriately changing the combination of raw materials used, the thickness, and the drying and curing conditions, a polyimide layer having a desired CTE can be obtained.

[0135] <Dielectric tangent> In the metal-clad laminate 10, the dielectric tangent (Tanδ) of the entire resin laminate 20 at 10 GHz is preferably 0.02 or less, more preferably in the range of 0.0005 or more and 0.01 or less, and even more preferably in the range of 0.001 or more and 0.008 or less. When the dielectric tangent of the entire resin laminate 20 at 10 GHz exceeds 0.02, when applied to a circuit board, problems such as electrical signal loss on the transmission path of high-frequency signals are likely to occur. On the other hand, the lower limit of the dielectric tangent of the entire resin laminate 20 at 10 GHz is not particularly limited, but physical property control as an insulating resin layer of the circuit board is considered.

[0136] <Dielectric constant> In the metal-clad laminate 10, when the resin laminate 20 is applied as, for example, an insulating resin layer of a circuit board, in order to ensure impedance matching, the dielectric constant of the entire resin laminate 20 at 10 GHz is preferably 4.0 or less. When the dielectric constant of the entire resin laminate 20 at 10 GHz exceeds 4.0, when applied to a circuit board, it leads to an increase in dielectric loss, and problems such as electrical signal loss on the transmission path of high-frequency signals are likely to occur.

[0137] [Manufacture of metal-clad laminate] The metal-clad laminate 10 can be manufactured, for example, by preparing resin sheets corresponding to a first transmission loss suppression layer BS1, a second transmission loss suppression layer BS2, a plurality of dimensional accuracy maintenance layers PL, and one or more intermediate transmission loss suppression layers BS3, and disposing and laminating these resin sheets between a first metal layer M1 and a second metal layer M2 and then thermocompression bonding them.

[0138] The metal-clad laminate 10 of the present embodiment obtained as described above can be used to manufacture a circuit board such as a single-sided FPC or a double-sided FPC by performing wiring circuit processing such as etching the first metal layer M1 and / or the second metal layer M2.

[0139] [Circuit board] The above metal-clad laminate 10 is mainly useful as a circuit board material such as an FPC or a rigid-flex circuit board. By processing one or both of the first metal layer M1 and the second metal layer M2 of the metal-clad laminate 10 into a pattern by a conventional method to form a wiring layer, a circuit board such as an FPC according to an embodiment of the present invention can be manufactured. Although not shown in the drawings, this circuit board includes a resin laminate 20 and a wiring layer provided on one or both surfaces of the resin laminate 20, and can reduce transmission loss even in high-frequency transmission and has excellent dimensional stability.

Example

[0140] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, various measurements and evaluations are as follows.

[0141] [Measurement of viscosity] For the measurement of viscosity, an E-type viscometer (manufactured by Brookfield Engineering Laboratories, Inc., product name: DV-II+Pro) was used to measure the viscosity at 25°C. The rotation speed was set so that the torque was 10% to 90%, and after 2 minutes had elapsed since the start of the measurement, the value when the viscosity became stable was read.

[0142] [Measurement of storage modulus] A resin sheet with a size of 5 mm × 20 mm was measured using a dynamic viscoelasticity measuring device (DMA: manufactured by UBM, product name; E4000F) at a heating rate of 4 °C / min from 30 °C to 400 °C and a frequency of 11 Hz.

[0143] [Measurement of Coefficient of Thermal Expansion (CTE)] A polyimide film with a size of 3 mm × 20 mm was heated from 30 °C to 265 °C at a constant heating rate while applying a load of 5.0 g using a thermomechanical analyzer (manufactured by Bruker, product name; 4000SA), held at that temperature for 10 minutes, then cooled at a rate of 5 °C / min, and the average coefficient of thermal expansion (coefficient of thermal expansion) from 250 °C to 100 °C was determined.

[0144] [Measurement of Dielectric Constant and Dissipation Factor] The dielectric constant (Dk) and dissipation factor (Df) of the resin sheet at 10 GHz were measured using a vector network analyzer (manufactured by Agilent, product name; E8363C) and an SPDR resonator. The materials used for the measurement were left standing for 24 hours under the conditions of temperature; 24 - 26 °C, humidity; 45 °C - 55% RH.

[0145] [Measurement of Dimensional Change Rate] The measurement of the dimensional change rate was carried out according to the following procedure. First, using a 150 mm square sample, a target for position measurement was formed by exposing and developing a dry film resist at 100 mm intervals. After measuring the dimensions before etching (normal state) in an atmosphere of temperature 23 ± 2 °C and relative humidity 50 ± 5%, the copper other than the target on the test piece was removed by etching (liquid temperature 40 °C or lower, time within 10 minutes). After standing for 24 ± 4 hours in an atmosphere of temperature 23 ± 2 °C and relative humidity 50 ± 5%, the dimensions after etching were measured. The dimensional change rates in the vertical and horizontal directions at three locations with respect to the normal state were calculated, and the average value of each was taken as the dimensional change rate after etching. The dimensional change rate after etching was calculated by the following formula.

[0146] Dimensional change rate after etching (%) = (B - A) / A × 100 A; Target distance before etching B; Target distance after etching

[0147] Next, the test piece is heat-treated in an oven at 250°C for 1 hour, and then the distance between the position targets is measured. The dimensional change rates after etching at three locations in the vertical and horizontal directions are calculated, and the average value of each is taken as the dimensional change rate after heat treatment. The heat dimensional change rate is calculated by the following formula.

[0148] Heat dimensional change rate (%) = (C - B) / B × 100 B; Target distance after etching C; Target distance after heating

[0149] [Measurement of surface roughness (Rz; ten-point mean roughness) of copper foil] Using a stylus-type surface roughness meter (manufactured by Kosaka Laboratory Ltd., product name: Surfcoader ET-3000), it was determined under the measurement conditions of Force; 100 μN, Speed; 20 μm, Range; 800 μm. The surface roughness was calculated by a method conforming to JIS-B0601:1994.

[0150] The abbreviations used in the synthesis examples represent the following compounds. BTDA: 3,3',4,4'-Benzophenone tetracarboxylic dianhydride PMDA: Pyromellitic dianhydride BPDA: 3,3',4,4'-Biphenyltetracarboxylic dianhydride BPADA: 2,2-Bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride DAPE: 4,4’-Diaminodiphenyl ether p-PDA: p-Phenylenediamine BAPP: 2,2-Bis[4-(4-aminophenoxy)phenyl]propane m-TB: 2,2'-Dimethyl-4,4'-diaminobiphenyl TPE-R: 1,3-Bis(4-aminophenoxy)benzene DDA: An aliphatic diamine with 36 carbon atoms (manufactured by Clariant Japan Co., Ltd., trade name: PRIAMINE 1074, amine value: 205 mg KOH / g, a mixture of cyclic and chain dimeric diamines, content of dimer component: 95% by weight or more) OP935: Aluminum organic phosphonate (manufactured by Clariant Japan, trade name: Exolit OP935) N-12: Dodecanedioic acid dihydrazide DMAc: N,N-dimethylacetamide NMP: N-methyl-2-pyrrolidone

[0151] (Synthesis Example 1) 312 g of DMAc was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 14.67 g of DAPE (0.073 mol) was dissolved in this reaction vessel while stirring. Next, 23.13 g of BTDA (0.072 mol) was added. Thereafter, stirring was continued for 3 hours to prepare a polyamic acid resin solution a with a solution viscosity of 2,960 mPa·s.

[0152] (Synthesis Example 2) 200 g of DMAc was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 1.335 g of m-TB (0.0063 mol) and 10.414 g of TPE-R (0.0356 mol) were dissolved in this reaction vessel while stirring. Next, 0.932 g of PMDA (0.0043 mol) and 11.319 g of BPDA (0.0385 mol) were added. Thereafter, stirring was continued for 2 hours to prepare a polyamic acid resin solution b with a solution viscosity of 1,420 mPa·s.

[0153] (Synthesis Example 3) 250 g of DMAc was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 2.561 g of p-PDA (0.0237 mol) and 16.813 g of DAPE (0.0840 mol) were dissolved in this reaction vessel while stirring. Next, 18.501 g of PMDA (0.0848 mol) and 6.239 g of BPDA (0.0212 mol) were added. Thereafter, stirring was continued for 3 hours to prepare a polyamic acid resin solution c with a solution viscosity of 29,500 mPa·s.

[0154] (Synthesis Example 4) 250 g of DMAc was placed in a reaction vessel equipped with a thermocouple and a stirrer and capable of introducing nitrogen. 12.323 g of m-TB (0.0580 mol) and 1.886 g of TPE-R (0.0064 mol) were dissolved in this reaction vessel while stirring. Next, 8.314 g of PMDA (0.0381 mol) and 7.477 g of BPDA (0.0254 mol) were added. Thereafter, stirring was continued for 3 hours to prepare a polyamic acid resin solution d with a solution viscosity of 31,500 mPa·s.

[0155] (Synthesis Example 5) (Preparation of Resin Solution e for Adhesive Layer) 44.92 g of BTDA (0.139 mol), 75.08 g of DDA (0.141 mol), 168 g of NMP and 112 g of xylene were charged into a 500 mL four-necked flask equipped with a nitrogen inlet tube, a stirrer, a thermocouple, a Dean-Stark trap and a condenser tube, and mixed at 40 °C for 30 minutes to prepare a polyamic acid solution. This polyamic acid solution was heated to 190 °C and heated and stirred for 4 hours to remove the water and xylene distilled out of the system. Thereafter, it was cooled to 100 °C, 112 g of xylene was added and stirred, and further cooled to 30 °C to complete imidization, and a resin solution e for adhesive layer (solid content; 29.5% by weight) was obtained.

[0156] (Synthesis Example 6) (Preparation of Resin Solution f for Adhesive Layer) A polyamic acid solution was prepared in the same manner as in Synthesis Example 5, except that 42.51 g of BPADA (0.082 mol), 34.30 g of DDA (0.066 mol), 6.56 g of BAPP (0.016 mol), 208 g of NMP, and 112 g of xylene were used as the raw material composition. This polyamic acid solution was treated in the same manner as in Synthesis Example 5 to obtain a resin solution f for the adhesive layer (solid content: 30.0% by weight).

[0157] (Production Example 1) <Preparation of Polyimide Film> On the surface of one side of an electrolytic copper foil 1 (thickness 12 μm, Rz; 2.1 μm), the resin solution c of polyamic acid was uniformly coated so that the thickness after curing would be about 25 μm, and then dried by heating at 120°C to remove the solvent. Further, a stepwise heat treatment from 120°C to 360°C was performed within 30 minutes to complete imidization. The copper foil was etched and removed using an aqueous solution of ferric chloride to obtain a polyimide film 1 (thickness; 25 μm, Dk; 3.4, Df; 0.0085, CTE; 16 ppm / K, minimum value of storage modulus (100 - 250°C) 2.9 GPa ) was prepared.

[0158] (Production Example 2) <Preparation of Polyimide Film> A polyimide film 2 (thickness; 25 μm, Dk; 3.3, Df; 0.0034, CTE; 17 ppm / K, minimum value of storage modulus (100 - 250°C) 3.0 GPa ) was prepared in the same manner as in Production Example 1, except that resin solution d was used.

[0159] (Production Example 3) <Preparation of Polyimide Film> On the surface of one side of the electrolytic copper foil 1 (thickness 12 μm, Rz; 2.1 μm), the resin solution a was uniformly applied so that the thickness after curing would be about 2 - 3 μm, and then it was dried by heating at 120°C to remove the solvent. Next, the resin solution d was uniformly applied thereon so that the thickness after curing would be about 21 μm, and then it was dried by heating at 120°C to remove the solvent. Further, the resin solution a was uniformly applied thereon so that the thickness after curing would be about 2 - 3 μm, and then it was dried by heating at 120°C to remove the solvent. In this way, after forming a three-layer polyamic acid layer, a stepwise heat treatment was performed from 120°C to 360°C to complete imidization. The copper foil layer was etched away using an aqueous ferric chloride solution to prepare a polyimide film 3 (thickness; 25 μm, Dk; 3.4, Df; 0.0052, CTE; 21 ppm / K, minimum value of storage modulus (100 - 250°C) 2.8 GPa ) was prepared.

[0160] (Production Example 4) <Preparation of Polyimide Film> On the surface of one side of the electrolytic copper foil 1 (thickness 12 μm, Rz; 2.1 μm), the resin solution b was uniformly applied so that the thickness after curing would be about 2 - 3 μm, and then it was dried by heating at 120°C to remove the solvent. Next, the resin solution d was uniformly applied thereon so that the thickness after curing would be about 21 μm, and then it was dried by heating at 120°C to remove the solvent. Further, the resin solution b was uniformly applied thereon so that the thickness after curing would be about 2 - 3 μm, and then it was dried by heating at 120°C to remove the solvent. In this way, after forming a three-layer polyamic acid layer, a stepwise heat treatment was performed from 120°C to 360°C to complete imidization. The copper foil layer was etched away using an aqueous ferric chloride solution to prepare a polyimide film 4 (thickness; 25 μm, Dk; 3.3, Df; 0.0032, CTE; 23 ppm / K, minimum value of storage modulus (100 - 250°C) 2.7 GPa ) was prepared.

[0161] (Production Example 5) <Preparation of Resin Sheet> 169.49 g of resin solution e (50 g as solid content) was blended with 1.8 g of N-12 (0.0036 mol) and 12.5 g of OP935, and diluted by adding 6.485 g of NMP and 19.345 g of xylene to prepare polyimide varnish 1.

[0162] After polyimide varnish 1 was applied to the silicone-treated surface of the release substrate so that the thickness after drying would be 25 μm, it was dried by heating at 80°C, and resin sheet 1 was prepared by peeling it off from the release substrate. The dielectric constant (Dk) and dielectric loss tangent (Df) of resin sheet 1 were 2.7 and 0.0023, respectively.

[0163] (Production Example 6) <Preparation of Resin Sheet> Resin sheet 2 was prepared in the same manner as Production Example 6, except that the thickness after drying was made to be 50 μm. The dielectric constant (Dk) and dielectric loss tangent (Df) of resin sheet 2 were 2.7 and 0.0023, respectively.

[0164] (Production Example 7) <Preparation of Resin Sheet> Resin sheet 3 was prepared in the same manner as Production Example 6, except that the thickness after drying was made to be 75 μm. The dielectric constant (Dk) and dielectric loss tangent (Df) of resin sheet 3 were 2.7 and 0.0023, respectively.

[0165] (Production Example 8) <Preparation of Resin Sheet> Resin sheet 4 was prepared in the same manner as Production Example 6, except that the thickness after drying was made to be 5 μm. The dielectric constant (Dk) and dielectric loss tangent (Df) of resin sheet 4 were 2.7 and 0.0023, respectively.

[0166] (Production Example 9) <Preparation of Resin Sheet> After applying the resin solution f for the subsequent layer onto the silicone-treated surface of the release substrate so that the thickness after drying becomes 25 μm, it was heat-dried at 80 °C and peeled off from the release substrate to prepare the resin sheet 5. The dielectric constant (Dk) and the dissipation factor (Df) of the resin sheet 5 were 2.8 and 0.0028, respectively.

[0167] (Production Example 10) <Preparation of Resin Sheet> The resin sheet 6 was prepared in the same manner as in Production Example 10, except that the thickness after drying was made to be 50 μm. The dielectric constant (Dk) and the dissipation factor (Df) of the resin sheet 6 were 2.8 and 0.0028, respectively.

[0168] [Example 1] Two electrolytic copper foils 1, two resin sheets 1, one resin sheet 2, and two polyimide films 4 were prepared, and after laminating them in the order of electrolytic copper foil 1 / resin sheet 1 / polyimide film 4 / resin sheet 2 / polyimide film 4 / resin sheet 1 / electrolytic copper foil 1, they were thermocompression bonded at 160 °C and 4 MPa for 60 minutes to prepare the double-sided metal-clad laminate 1. The evaluation results for the double-sided metal-clad laminate 1 were as follows. Dimensional change rate after etching in the MD direction; -0.05% Dimensional change rate after etching in the TD direction; -0.04% Dimensional change rate after heating in the MD direction; -0.03% Dimensional change rate after heating in the TD direction; 0.03% Also, the dielectric constant (Dk) and the dissipation factor (Df) of the resin laminate 1 (thickness: 150 μm) prepared by etching and removing the electrolytic copper foil 1 in the double-sided metal-clad laminate 1 were 2.9 and 0.0026, respectively. The total thickness of the dimensional accuracy maintenance layer was 33% of the total thickness of the resin laminate 1.

[0169] [Example 2] Two electrolytic copper foils 1, two resin sheets 1, one resin sheet 3, and two polyimide films 4 were prepared. After laminating them in the order of electrolytic copper foil 1 / resin sheet 1 / polyimide film 4 / resin sheet 3 / polyimide film 4 / resin sheet 1 / electrolytic copper foil 1, they were thermocompression bonded at 160 °C and 4 MPa for 60 minutes to prepare a double-sided metal-clad laminate 2. The evaluation results of the double-sided metal-clad laminate 2 are as follows. Dimensional change rate after etching in MD direction; -0.06% Dimensional change rate after etching in TD direction; -0.04% Dimensional change rate after heating in MD direction; -0.04% Dimensional change rate after heating in TD direction; 0.04% Also, the dielectric constant (Dk) and dielectric tangent (Df) of the resin laminate 2 (thickness: 175 μm) prepared by etching and removing the electrolytic copper foil 1 in the double-sided metal-clad laminate 2 were 2.92 and 0.0026, respectively. The total thickness of the dimensional accuracy maintaining layer was 29% of the total thickness of the resin laminate 2.

[0170] [Example 3] Two electrolytic copper foils 1, one resin sheet 1, two resin sheets 2, and two polyimide films 4 were prepared. After laminating them in the order of electrolytic copper foil 1 / resin sheet 2 / polyimide film 4 / resin sheet 1 / polyimide film 4 / resin sheet 2 / electrolytic copper foil 1, they were thermocompression bonded at 160 °C and 4 MPa for 60 minutes to prepare a double-sided metal-clad laminate 3. The evaluation results of the double-sided metal-clad laminate 3 are as follows. Dimensional change rate after etching in MD direction; -0.02% Dimensional change rate after etching in TD direction; 0.03% Dimensional change rate after heating in MD direction; -0.06% Dimensional change rate after heating in TD direction; -0.02% Also, the dielectric constant (Dk) and dielectric tangent (Df) of the resin laminate 3 (thickness: 175 μm) prepared by etching and removing the electrolytic copper foil 1 in the double-sided metal-clad laminate 3 were 2.9 and 0.0026, respectively. The total thickness of the dimensional accuracy maintaining layer was 29% of the total thickness of the resin laminate 3.

[0171] [Example 4] A double-sided metal-clad laminate 4 was prepared in the same manner as in Example 1, except that polyimide film 1 was used instead of polyimide film 4. When the double-sided metal-clad laminate 4 was evaluated, there was no problem with dimensional change. Also, the dielectric constant (Dk) and dielectric tangent (Df) of the resin laminate 4 (thickness: 150 μm) prepared by etching and removing the electrolytic copper foil 1 in the double-sided metal-clad laminate 4 were 2.9 and 0.0044, respectively. The total thickness of the dimensional accuracy maintaining layer was 33% of the total thickness of the resin laminate 4.

[0172] [Example 5] A double-sided metal-clad laminate 5 was prepared in the same manner as in Example 1, except that polyimide film 2 was used instead of polyimide film 4. When the double-sided metal-clad laminate 5 was evaluated, there was no problem with dimensional change. Also, the dielectric constant (Dk) and dielectric tangent (Df) of the resin laminate 5 (thickness: 150 μm) prepared by etching and removing the electrolytic copper foil 1 in the double-sided metal-clad laminate 5 were 2.9 and 0.0027, respectively. The total thickness of the dimensional accuracy maintaining layer was 33% of the total thickness of the resin laminate 5.

[0173] [Example 6] A double-sided metal-clad laminate 6 was prepared in the same manner as in Example 1, except that polyimide film 3 was used instead of polyimide film 4. When the double-sided metal-clad laminate 6 was evaluated, there was no problem with dimensional change. Also, the dielectric constant (Dk) and dielectric tangent (Df) of the resin laminate 6 (thickness: 150 μm) prepared by etching and removing the electrolytic copper foil 1 in the double-sided metal-clad laminate 6 were 2.9 and 0.0033, respectively. The total thickness of the dimensional accuracy maintaining layer was 33% of the total thickness of the resin laminate 6.

[0174] [Example 7] A double-sided metal-clad laminate 7 was prepared in the same manner as in Example 1, except that a resin sheet 5 was used instead of the resin sheet 1 and a resin sheet 6 was used instead of the resin sheet 2. When the double-sided metal-clad laminate 7 was evaluated, there were no problems with dimensional changes. Also, for the resin laminate 7 (thickness: 150 μm) prepared by etching and removing the electrolytic copper foil 1 in the double-sided metal-clad laminate 7, the dielectric constant (Dk) and the dissipation factor (Df) were 3.0 and 0.0029, respectively. The total thickness of the dimensional accuracy maintaining layer was 33% of the total thickness of the resin laminate 7.

[0175] [Example 8] A double-sided metal-clad laminate 8 was prepared in the same manner as in Example 1, except that a resin sheet 4 was used instead of the resin sheet 1. When the double-sided metal-clad laminate 8 was evaluated, there were no problems with dimensional changes. Also, for the resin laminate 8 (thickness: 110 μm) prepared by etching and removing the electrolytic copper foil 1 in the double-sided metal-clad laminate 8, the dielectric constant (Dk) and the dissipation factor (Df) were 3.0 and 0.0027, respectively. The total thickness of the dimensional accuracy maintaining layer was 45% of the total thickness of the resin laminate 8.

[0176] [Comparative Example 1] Two electrolytic copper foils 1, two resin sheets 2, and one polyimide film 1 were prepared, laminated in the order of electrolytic copper foil 1 / resin sheet 2 / polyimide film 1 / resin sheet 2 / electrolytic copper foil 1, and then thermocompression bonded at 160 °C and 4 MPa for 60 minutes to prepare a double-sided metal-clad laminate 9. The evaluation results for the double-sided metal-clad laminate 9 are as follows. Dimensional change rate after etching in the MD direction; 0.02% Dimensional change rate after etching in the TD direction; 0.08% Dimensional change rate after heating in the MD direction; -0.10% Dimensional change rate after heating in the TD direction; -0.05% Also, for the resin laminate 9 (thickness: 125 μm) prepared by etching and removing the electrolytic copper foil 1 in the double-sided metal-clad laminate 9, the dielectric constant (Dk) and the dissipation factor (Df) were 2.8 and 0.0035, respectively. The total thickness of the dimensional accuracy maintaining layer was 20% of the total thickness of the resin laminate 9.

[0177] The above has described the embodiments of the present invention in detail for illustrative purposes. However, the present invention is not limited to the above embodiments, and various modifications are possible.

Description of Reference Numerals

[0178] 10... metal-clad laminate, 20... resin laminate, M1... first metal layer, M2... second metal layer, BS1... first transmission loss suppression layer, BS2... second transmission loss suppression layer, BS3... intermediate transmission loss suppression layer, PL... dimensional accuracy maintenance layer, 31... non-thermoplastic polyimide layer, 33... thermoplastic polyimide layer

Claims

1. a first metal layer; a first transmission loss suppression layer provided in contact with one side of the first metal layer; a second metal layer; a second transmission loss suppression layer provided in contact with one side of the second metal layer; a plurality of resin layers interposed between the first transmission loss suppression layer and the second transmission loss suppression layer; comprising a resin laminate is formed by the first transmission loss suppression layer, the second transmission loss suppression layer, and the plurality of resin layers, the resin laminate at least two or more dimensional accuracy maintenance layers; an intermediate transmission loss suppression layer laminated between the dimensional accuracy maintenance layers; having the following conditions i and ii; i) The dielectric tangent at 10 GHz measured by a split post dielectric resonator (SPDR) after humidity conditioning for 24 hours under the constant temperature and humidity conditions of 23°C and 50% RH (normal state), where the dielectric tangents of the first transmission loss suppression layer and the second transmission loss suppression layer are Df １ , and the dielectric tangent of the dimensional accuracy maintaining layer is Df ２ When this is the case, Df １ < Df ２ are in the relationship of; ii) the total thickness of the dimensional accuracy maintenance layers is in the range of 29 to 45% of the total thickness of the resin laminate; satisfying a metal-clad laminate in which the dielectric tangent (Tanδ) of the entire resin laminate at 10 GHz is in the range of 0.0005 or more and 0.0033 or less.

2. The metal-clad laminate according to claim 1, wherein the dimensional accuracy maintenance layer is a low thermal expansion polyimide layer having a minimum value of storage modulus in the temperature range of 100°C to 250°C in the range of 1.0 to 8.0 GPa and a thermal expansion coefficient in the range of 15 to 25 ppm / K.

3. The resin constituting the first transmission loss suppression layer and the second transmission loss suppression layer is a polyimide formed by reacting an acid anhydride component and a diamine component, and contains 50 mol parts or more of a dimer diamine in which two terminal carboxylic acid groups of dimer acid are substituted with primary aminomethyl groups or amino groups, based on 100 mol parts of the total amount of the diamine component. The metal-clad laminate according to claim 1 or 2.

4. a first wiring layer; a first transmission loss suppression layer provided in contact with one side of the first wiring layer; a second wiring layer; a second transmission loss suppression layer provided in contact with one side of the second wiring layer; a plurality of resin layers interposed between the first transmission loss suppression layer and the second transmission loss suppression layer; comprising a resin laminate is formed by the first transmission loss suppression layer, the second transmission loss suppression layer, and the plurality of resin layers, the resin laminate at least two or more dimensional accuracy maintenance layers; an intermediate transmission loss suppression layer laminated between the dimensional accuracy maintenance layers; having the following conditions i and ii; i) The dielectric tangent at 10 GHz measured by a split post dielectric resonator (SPDR) after humidity conditioning for 24 hours under constant temperature and humidity conditions of 23°C and 50% RH (normal state), where the dielectric tangents of the first transmission loss suppression layer and the second transmission loss suppression layer are Df １ , and the dielectric tangent of the dimensional accuracy maintaining layer is Df ２ . When this is the case, Df １ < Df ２ is in the relationship; ii) the total thickness of the dimensional accuracy maintenance layers is in the range of 29 to 45% of the total thickness of the resin laminate; satisfying A circuit board in which the dielectric tangent (Tanδ) of the entire resin laminate at 10 GHz is in the range of 0.0005 or more and 0.0033 or less.

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