TWI867682B - Manufacturing method of metal-clad laminate - Google Patents

Abstract

A method for manufacturing a metal-clad laminate comprises: step 1 of preparing the first single-sided metal-clad laminate and the second single-sided metal-clad laminate; step 2 of laminating a resin layer made of a thermoplastic resin or a thermosetting resin as the adhesive layer on either or both of the first insulating resin layer or the second insulating resin layer; and step 3 of hot-pressing the first single-sided metal-clad laminate and the second single-sided metal-clad laminate after step 2 so that the respective insulating resin layers are opposed to each other via the adhesive layer. The adhesive layer is composed of a thermoplastic resin or a thermosetting resin and satisfies the following requirements: (i) the storage elastic modulus at 50°C is less than 1800 MPa; (ii) the maximum value of the storage elastic modulus in the temperature range of 180°C to 260°C is less than 800 MPa; and (iii) the glass transition temperature (Tg) is less than 180°C.

Description

Manufacturing method of metal-clad laminate

The present invention relates to a metal-clad laminate and a circuit substrate useful as electronic components.

In recent years, with the progress of miniaturization, lightness, and space saving of electronic equipment, there is an increasing demand for flexible printed wiring boards (Flexible Printed Circuits, FPCs) that are thin, lightweight, flexible, and have excellent durability even when bent repeatedly. FPCs can be installed three-dimensionally and at high density even in limited spaces, so their use is gradually expanding in wiring of movable parts of electronic equipment such as hard disk drives (HDDs), digital video discs (DVDs), and smart phones, as well as parts such as cables and connectors.

In addition to the above-mentioned high density, the performance of equipment is being promoted, so it is also necessary to cope with the high frequency of the transmission signal. When transmitting high-frequency signals, if the transmission loss in the transmission path is large, it will cause undesirable conditions such as loss of electrical signals or prolonged signal delay time. Therefore, in the future, it will also be important to reduce transmission loss in FPC. In order to cope with high-frequency signal transmission, FPCs using liquid crystal polymers with lower dielectric constants and low dielectric loss factors as dielectric layers are used instead of polyimide commonly used as FPC materials. However, although liquid crystal polymers have excellent dielectric properties, there is room for improvement in heat resistance or adhesion to metal layers.

In addition, fluorine-based resins are also widely known as polymers that exhibit low dielectric constants and low dielectric loss factors. For example, as an FPC material that can cope with high-frequency signal transmission and has excellent adhesion, an insulating film has been proposed in which a polyimide adhesive film having a thermoplastic polyimide layer and a high heat-resistant polyimide layer is bonded to both sides of a fluorine-based resin layer (Patent Document 1). Since the insulating film of Patent Document 1 uses a fluorine-based resin, it has excellent dielectric properties, but there are problems with dimensional stability. In particular, when applied to FPC, there is a concern that the dimensional change before and after circuit processing due to etching will increase. Therefore, it is difficult to increase the thickness of the fluorine-based resin and improve the thickness ratio.

As a technology related to adhesive layers used in electronic materials, the application of resin compositions containing epoxy resins and phenoxy resins or resin compositions containing thermoplastic polyimide and maleimide compounds in adhesive sheets has been proposed (Patent Documents 2 and 3). The film-like adhesive sheets of Patent Documents 2 and 3 have the advantages of low glass transition temperatures and high adhesion to laminated materials. However, Patent Documents 2 and 3 do not study the possibility of application to high-frequency signal transmission or the application to adhesive layers of metal-clad laminates. [Prior Art Documents] [Patent Documents]

[Patent Document 1] Japanese Patent Publication No. 2017-24265 [Patent Document 2] Japanese Patent Publication No. 6191800 [Patent Document 3] Japanese Patent Publication No. 5553108

[Problem to be solved by the invention] The purpose of the present invention is to provide a metal-clad laminate and a circuit substrate that can reduce transmission loss even in high-frequency transmission and have excellent dimensional stability.

[Technical means for solving the problem] The inventors of the present invention have conducted diligent research and found that the problem can be solved by using an adhesive layer with a low glass transition temperature and a low elastic modulus in a metal-clad laminate, thereby completing the present invention.

The metal-clad laminate of the present invention is a metal-clad laminate as follows, comprising: A first single-sided metal-clad laminate having a first metal layer and a first insulating resin layer laminated on at least one side of the first metal layer; A second single-sided metal-clad laminate having a second metal layer and a second insulating resin layer laminated on at least one side of the second metal layer; and An adhesive layer is arranged in a manner abutting against the first insulating resin layer and the second insulating resin layer, and laminated between the first single-sided metal-clad laminate and the second single-sided metal-clad laminate. The manufacturing method of a metal-clad laminate of the present invention includes step 1 of preparing the first single-sided metal-clad laminate and the second single-sided metal-clad laminate; step 2 of laminating a resin layer composed of a thermoplastic resin or a thermosetting resin as the adhesive layer on either or both of the first insulating resin layer or the second insulating resin layer; and step 3 of hot-pressing the first single-sided metal-clad laminate and the second single-sided metal-clad laminate after step 2, so that the respective insulating resin layers are opposite to each other through the adhesive layer. The adhesive layer is composed of a thermoplastic resin or a thermosetting resin and meets the following conditions (i) to (iii): (i) the storage elastic modulus at 50°C is less than 1800 MPa; (ii) the maximum value of the storage elastic modulus in the temperature range of 180°C to 260°C is less than 800 MPa; (iii) the glass transition temperature (Tg) is less than 180°C.

In the method for manufacturing a metal-clad laminate of the present invention, the resin layer in step 2 is a coating film obtained by coating a thermoplastic resin, a thermosetting resin or a resin solution thereof and drying it.

In the manufacturing method of the metal-clad laminate of the present invention, the first insulating resin layer and the second insulating resin layer may both have a multi-layer structure in which a thermoplastic polyimide layer, a non-thermoplastic polyimide layer and a thermoplastic polyimide layer are sequentially laminated, and the adhesive layer may be arranged in contact with the two thermoplastic polyimide layers.

[Effect of the invention] The metal-clad laminate of the present invention has a structure in which two single-sided metal-clad laminates are bonded together with an adhesive layer having specific parameters interposed therebetween, thereby increasing the thickness of the insulating resin layer and ensuring dimensional stability. In addition, when applied to a circuit substrate that transmits high-frequency signals above 10 GHz, transmission loss can be reduced. Therefore, reliability and yield can be improved in the circuit substrate.

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

[Metal-clad laminate] FIG. 1 is a schematic diagram showing the structure of a metal-clad laminate of an embodiment of the present invention. The metal-clad laminate (C) of this embodiment has a structure in which a pair of single-sided metal-clad laminates are bonded together using an adhesive layer (B). That is, the metal-clad laminate (C) includes a first single-sided metal-clad laminate (C1), a second single-sided metal-clad laminate (C2), and an adhesive layer (B) laminated between the first single-sided metal-clad laminate (C1) and the second single-sided metal-clad laminate (C2). Here, the first single-sided metal-clad laminate (C1) has a first metal layer (M1) and a first insulating resin layer (P1) laminated on at least one side of the first metal layer (M1). The second single-sided metal-clad laminate (C2) has a second metal layer (M2) and a second insulating resin layer (P2) laminated on at least one side of the second metal layer (M2). Furthermore, the adhesive layer (B) is arranged in contact with the first insulating resin layer (P1) and the second insulating resin layer (P2). That is, the metal-clad laminate (C) has a structure in which the first metal layer (M1)/first insulating resin layer (P1)/adhesive layer (B)/second insulating resin layer (P2)/second metal layer (M2) are stacked in sequence. The first metal layer (M1) and the second metal layer (M2) are located at the outermost sides, respectively, and the first insulating resin layer (P1) and the second insulating resin layer (P2) are arranged inside them, and the adhesive layer (B) is arranged between the first insulating resin layer (P1) and the second insulating resin layer (P2).

<Single-sided metal-clad laminate> The structure of a pair of single-sided metal-clad laminates (C1, C2) is not particularly limited. As FPC materials, general materials can be used, and commercially available copper-clad laminates can also be used. Furthermore, the structures of the first single-sided metal-clad laminate (C1) and the second single-sided metal-clad laminate (C2) can be the same or different.

(Metal layer) The materials of the first metal layer (M1) and the second metal layer (M2) are not particularly limited, and examples thereof include: copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof. Among them, copper or copper alloys are particularly preferred. Furthermore, the material of the wiring layer in the circuit substrate of the present embodiment described later is also the same as that of the first metal layer (M1) and the second metal layer (M2).

The thickness of the first metal layer (M1) and the second metal layer (M2) is not particularly limited. For example, when a metal foil such as copper foil is used, it is preferably 35 μm or less, and more preferably in the range of 5 μm to 25 μm. From the perspective of production stability and handling, the lower limit of the thickness of the metal foil is preferably 5 μm. Furthermore, when a copper foil is used, it can be a rolled copper foil or an electrolytic copper foil. In addition, as the copper foil, a commercially available copper foil can be used.

The metal foil may be subjected to surface treatment using, for example, a sheet metal, an aluminum alkoxide, an aluminum chelate, a silane coupling agent, etc., for the purpose of rust prevention or improvement of adhesion.

(Insulating resin layer) The first insulating resin layer (P1) and the second insulating resin layer (P2) are not particularly limited as long as they are made of a resin having electrical insulation properties. Examples thereof include polyimide, epoxy resin, phenolic resin, polyethylene, polypropylene, polytetrafluoroethylene, silicone, tetrafluoroethylene (ETFE), etc., but preferably they are made of polyimide. In addition, the first insulating resin layer (P1) and the second insulating resin layer (P2) are not limited to a single layer, but may be a layer having multiple resin layers laminated. Furthermore, when polyimide is mentioned in the present invention, in addition to polyimide, it refers to a resin containing a polymer having an imide group in the molecular structure such as polyamide imide, polyether imide, polyester imide, polysiloxane imide, polybenzimidazole imide, etc.

<Adhesive layer> The adhesive layer (B) is composed of a thermoplastic resin or a thermosetting resin and satisfies (i) a storage modulus of elasticity at 50°C of 1800 MPa or less, (ii) a maximum value of a storage modulus of elasticity at 180°C to 260°C of 800 MPa or less, and (iii) a glass transition temperature (Tg) of 180°C or less. Examples of the resin include polyimide resins, polyamide resins, epoxy resins, phenoxy resins, acrylic resins, polyurethane resins, styrene resins, polyester resins, phenol resins, polysulfone resins, polyethersulfone resins, polyphenylene sulfide resins, polyethylene resins, polypropylene resins, silicone resins, polyetherketone resins, polyvinyl alcohol resins, and polyvinyl butyral resins. , styrene-maleimide copolymer, maleimide-vinyl compound copolymer or (meth) acrylic acid copolymer, benzoxazine resin, dimaleimide resin and cyanate resin, etc. Among these resins, materials satisfying conditions (i) to (iii) can be selected or designed in a manner satisfying conditions (i) to (iii) and used in the adhesive layer (B).

When the adhesive layer (B) is a thermosetting resin, it may contain an organic peroxide, a hardener, a hardening accelerator, etc., and may also contain a hardener and a hardening accelerator, or a catalyst and a co-catalyst as needed. Within the range that the above conditions (i) to (iii) can be ensured, it is sufficient to determine the amount of hardener, hardening accelerator, catalyst, co-catalyst and organic peroxide to be added, and whether to add them.

<Layer thickness> In the metal-clad laminate (C), when the total thickness of the first insulating resin layer (P1), the adhesive layer (B), and the second insulating resin layer (P2) is set to T1, the total thickness T1 is in the range of 70 μm to 500 μm, preferably in the range of 100 μm to 300 μm. If the total thickness T1 is less than 70 μm, the effect of reducing the transmission loss when manufacturing the circuit board is insufficient, and if it exceeds 500 μm, the productivity may be reduced.

In addition, the thickness T2 of the adhesive layer (B) is preferably within the range of 50 μm to 450 μm, and more preferably within the range of 50 μm to 250 μm. If the thickness T2 of the adhesive layer (B) does not meet the lower limit, the transmission loss may increase as a high-frequency substrate. On the other hand, if the thickness of the adhesive layer (B) exceeds the upper limit, it may cause undesirable conditions such as decreased dimensional stability.

In addition, the ratio (T2/T1) of the thickness T2 of the adhesive layer (B) to the total thickness T1 is in the range of 0.5 to 0.8, preferably in the range of 0.5 to 0.7. If the ratio (T2/T1) is less than 0.5, it is difficult to set T1 to 70 μm or more, and if it exceeds 0.8, it will cause problems such as reduced dimensional stability.

The thickness T3 of the first insulating resin layer (P1) and the second insulating resin layer (P2) is preferably within a range of, for example, 12 μm to 100 μm, and more preferably within a range of 12 μm to 50 μm. If the thickness T3 of the first insulating resin layer (P1) and the second insulating resin layer (P2) does not satisfy the lower limit, problems such as warping of the metal-clad laminate (C) may occur. If the thickness T3 of the first insulating resin layer (P1) and the second insulating resin layer (P2) exceeds the upper limit, undesirable conditions such as decreased productivity may occur. Furthermore, the first insulating resin layer (P1) and the second insulating resin layer (P2) may not necessarily have the same thickness.

<Coefficient of Thermal Expansion> The coefficient of thermal expansion (CTE) of the first insulating resin layer (P1) and the second insulating resin layer (P2) may be 10 ppm/K or more, preferably 10 ppm/K or more and 30 ppm/K or less, and more preferably 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 or reduced dimensional stability may occur. By appropriately changing the combination of raw materials used, thickness, drying and curing conditions, a polyimide layer having a desired CTE can be produced.

The adhesive layer (B) has high thermal expansion but low elasticity and low glass transition temperature, so it can relieve the internal stress generated during lamination even if the CTE exceeds 30 ppm/K. In addition, the overall thermal expansion coefficient (CTE) of the first insulating resin layer (P1), the adhesive layer (B), and the second insulating resin layer (P2) can be 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 overall CTE of these resin layers is less than 10 ppm/K or exceeds 30 ppm/K, warping will occur or dimensional stability will decrease.

<Glass transition temperature (Tg)> The glass transition temperature (Tg) of the adhesive layer (B) is 180°C or less, preferably 160°C or less. By setting the glass transition temperature of the adhesive layer (B) to 180°C or less, low-temperature heat pressing can be performed, thereby relieving the internal stress generated during lamination and suppressing dimensional changes after circuit processing. If the Tg of the adhesive layer (B) exceeds 180°C, an interlayer exists between the first insulating resin layer (P1) and the second insulating resin layer (P2), and the temperature during bonding becomes high, which may impair the dimensional stability after circuit processing.

<Storage elastic coefficient> The storage elastic coefficient of the adhesive layer (B) at 50°C is 1800 MPa or less, and the maximum value of the storage elastic coefficient in the temperature range of 180°C to 260°C is 800 MPa or less. It is believed that the characteristics of the adhesive layer (B) are the main reasons for relieving the internal stress during hot pressing and maintaining the dimensional stability after circuit processing. In addition, the storage elastic coefficient of the adhesive layer (B) at the upper limit temperature (260°C) of the temperature range is preferably 800 MPa or less, and more preferably 500 MPa or less. By setting the storage elastic coefficient to the above, warping is not easy to occur even after the reflow step after circuit processing.

<Dielectric loss factor> When the first insulating resin layer (P1) and the second insulating resin layer (P2) are applied to a circuit board, for example, in order to suppress the deterioration of dielectric loss, the dielectric loss factor (Tanδ) 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 further preferably in the range of 0.001 or more and 0.008 or less. If the dielectric loss factor of the first insulating resin layer (P1) and the second insulating resin layer (P2) at 10 GHz exceeds 0.02, when applied to a circuit board, it is easy to cause problems such as loss of electrical signals on the transmission path of high-frequency signals. On the other hand, there is no particular lower limit on the dielectric loss factor of the first insulating resin layer (P1) and the second insulating resin layer (P2) at 10 GHz, but the physical property control of the insulating resin layer as a circuit board is considered.

When the adhesive layer (B) is applied to a circuit board, for example, the dielectric loss factor (Tanδ) at 10 GHz is preferably 0.015 or less, more preferably 0.01 or less, and further preferably 0.006 or less in order to suppress the deterioration of dielectric loss. If the dielectric loss factor of the adhesive layer (B) at 10 GHz exceeds 0.015, when applied to a circuit board, it is easy to cause disadvantages such as loss of electrical signals on the transmission path of high-frequency signals. On the other hand, there is no particular limit to the lower limit of the dielectric loss factor of the adhesive layer (B) at 10 GHz.

<Dielectric constant> When the first insulating resin layer (P1) and the second insulating resin layer (P2) are used as insulating resin layers of a circuit board, for example, in order to ensure impedance matching, the dielectric constant of the insulating resin layer as a whole is preferably 4.0 or less at 10 GHz. If the dielectric constant of the first insulating resin layer (P1) and the second insulating resin layer (P2) at 10 GHz exceeds 4.0, when applied to a circuit board, the dielectric loss of the first insulating resin layer (P1) and the second insulating resin layer (P2) deteriorates, which may easily cause the loss of electrical signals on the transmission path of high-frequency signals.

When the adhesive layer (B) is used in a circuit board, for example, the dielectric constant at 10 GHz is preferably 4.0 or less in order to ensure impedance matching. If the dielectric constant of the adhesive layer (B) at 10 GHz exceeds 4.0, the dielectric loss of the adhesive layer (B) deteriorates when used in the circuit board, which easily causes the loss of electrical signals in the transmission path of high-frequency signals.

<Function> In the metal-clad laminate (C) of this embodiment, the thickness of the adhesive layer (B) itself is increased in order to achieve a low dielectric loss factor for the entire insulating resin layer and to cope with high-frequency transmission. However, generally, materials with a low modulus of elasticity, such as the adhesive layer (B), show a high thermal expansion coefficient, so increasing the layer thickness may lead to a decrease in dimensional stability. Here, the dimensional change caused by circuit processing of the metal-clad laminate (C) is considered to be mainly caused by the following mechanisms a) to c), and the total amount of b) and c) becomes the dimensional change after etching. a) When the metal-clad laminate (C) is manufactured, internal stress is accumulated in the resin layer. b) During circuit processing, the metal layer is etched to release the internal stress accumulated in a), and the resin layer expands or contracts. c) During circuit processing, the metal layer is etched, and the exposed resin absorbs moisture and expands.

The main causes of the internal stress in a) are 1) the difference in thermal expansion coefficient between the metal layer and the resin layer, and 2) the internal strain of the resin caused by film formation. Here, the magnitude of the internal stress caused by 1) affects not only the difference in thermal expansion coefficient, but also the temperature difference ΔT from the temperature at the time of adhesion (heating temperature) to the temperature of cooling and solidification. That is, since the internal stress increases in proportion to the temperature difference ΔT, even if the difference in thermal expansion coefficient between the metal layer and the resin layer is small, the higher the temperature of the resin required for adhesion, the greater the internal stress. In the metal-clad laminate (C) of this embodiment, by using a layer satisfying the above conditions (i) to (iii) as the adhesive layer (B), internal stress is reduced and dimensional stability is ensured.

In addition, since the adhesive layer (B) is laminated between the first insulating resin layer (P1) and the second insulating resin layer (P2), it functions as an intermediate layer to suppress warping and dimensional change. Furthermore, in a heating step such as reflow soldering when mounting a semiconductor chip, direct heat or contact with oxygen is blocked by the first insulating resin layer (P1) or the second insulating resin layer (P2), so it is difficult to be affected by oxidative degradation and dimensional change is unlikely to occur. In this way, the advantages brought by the characteristics of the layer structure of the first insulating resin layer (P1), the adhesive layer (B) and the second insulating resin layer (P2) are also possessed.

[Manufacturing of Metal-Clad Laminated Board] The metal-clad laminate (C) can be manufactured, for example, by the following method 1 or method 2. [Method 1] A method in which a resin composition to be an adhesive layer (B) is formed into a sheet to form an adhesive sheet, and the adhesive sheet is arranged and bonded between a first insulating resin layer (P1) of a first single-sided metal-clad laminate (C1) and a second insulating resin layer (P2) of a second single-sided metal-clad laminate (C2), and then heat-pressed. [Method 2] A method in which a solution of a resin composition to be an adhesive layer (B) is applied to a predetermined thickness on either or both of the first insulating resin layer (P1) of the first single-sided metal-clad laminate (C1) or the second insulating resin layer (P2) of the second single-sided metal-clad laminate (C2), and after drying, one side of the coated film is bonded by heat pressing.

The adhesive sheet used in method 1 can be produced, for example, by applying a solution of a resin composition to be an adhesive layer (B) on an arbitrary support substrate, drying it, and then peeling it off from the support substrate to make an adhesive sheet. In addition, in the above, there is no particular limitation on the method of applying the solution of the resin composition to be the adhesive layer (B) on the support substrate or the insulating resin layer (P1, P2), and for example, the application can be performed using an applicator such as a notch wheel, a mold, a scraper, or a die lip.

The metal-clad laminate (C) of the present embodiment obtained as described above can be processed into a circuit board such as a single-sided FPC or a double-sided FPC by etching the first metal layer (M1) and/or the second metal layer (M2) to form a wiring circuit.

[Preferred Configuration Example of Metal-Clad Laminate] Next, the first insulating resin layer (P1), the second insulating resin layer (P2), the adhesive layer (B), the first metal layer (M1), and the second metal layer (M2) in the metal-clad laminate (C) of this embodiment will be described in more detail.

Fig. 2 is a schematic cross-sectional view showing the structure of the metal-clad laminate 100 of the present embodiment. As shown in Fig. 2, the metal-clad laminate 100 includes: metal layers 101, 101 as a first metal layer (M1) and a second metal layer (M2); polyimide layers 110, 110 as a first insulating resin layer (P1) and a second insulating resin layer (P2); and an adhesive polyimide layer 120 as an adhesive layer (B). Here, a single-sided metal-clad laminate 130 is formed as a first single-sided metal-clad laminate (C1) or a second single-sided metal-clad laminate (C2) by a metal layer 101 and a polyimide layer 110. In this form, the first single-sided metal-clad laminate (C1) and the second single-sided metal-clad laminate (C2) have the same structure.

The polyimide layers 110, 110 may be a structure in which a plurality of polyimide layers are stacked. For example, in the form shown in FIG. 2, a three-layer structure is formed including non-thermoplastic polyimide layers 111, 111 made of non-thermoplastic polyimide as a base layer, and thermoplastic polyimide layers 112, 112 made of thermoplastic polyimide disposed on both sides of the non-thermoplastic polyimide layers 111, 111. Furthermore, the polyimide layers 110, 110 are not limited to a three-layer structure.

In the metal clad laminate 100 shown in FIG2 , the outer thermoplastic polyimide layers 112, 112 of two single-sided metal clad laminates 130, 130 are respectively bonded to the adhesive polyimide layer 120 to form the metal clad laminate 100. The adhesive polyimide layer 120 is an adhesive layer for bonding the two single-sided metal clad laminates 130, 130 in the metal clad laminate 100, and is a layer for thickening the insulating resin layer of the metal clad laminate 100 while ensuring dimensional stability. The adhesive polyimide layer 120 is as described above for the adhesive layer (B).

Next, the non-thermoplastic polyimide layer 111 and the thermoplastic polyimide layer 112 constituting the polyimide layers 110, 110 are described. The so-called "non-thermoplastic polyimide" is generally a polyimide that does not soften or show adhesiveness even when heated, but in the present invention, it refers to a polyimide having a storage modulus of 1.0×10 ⁹ Pa or more at 30°C and a storage modulus of 1.0×10 ⁸ Pa or more at 350°C as measured using a dynamic viscoelasticity measuring device (dynamic mechanical analyzer (DMA)). The so-called "thermoplastic polyimide" is generally a polyimide with a clearly identifiable glass transition temperature (Tg), but in the present invention, it refers to a polyimide having a storage modulus of 1.0×10 ⁹ Pa or more at 30°C and a storage modulus of less than 1.0×10 ⁸ Pa at 350°C as measured using DMA.

Non-thermoplastic polyimide layer: The non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 is a material containing tetracarboxylic acid residues and diamine residues. Furthermore, in the present invention, the so-called tetracarboxylic acid residues represent tetravalent groups derived from tetracarboxylic dianhydride, and the so-called diamine residues represent divalent groups derived from diamine compounds. Polyimide preferably contains aromatic tetracarboxylic acid residues derived from aromatic tetracarboxylic dianhydride and aromatic diamine residues derived from aromatic diamine.

(Tetracarboxylic acid residues) The non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 preferably contains tetracarboxylic acid residues derived from at least one of 3,3',4,4'-biphenyl tetracarboxylic dianhydride (BPDA) and 1,4-phenylene bis(trimellitic acid monoester) dianhydride (TAHQ) and tetracarboxylic acid residues derived from at least one of pyromellitic dianhydride (PMDA) and 2,3,6,7-naphthalene tetracarboxylic dianhydride (NTCDA) as tetracarboxylic acid residues.

Tetracarboxylic acid residues derived from BPDA (hereinafter, also referred to as "BPDA residues") and tetracarboxylic acid residues derived from TAHQ (hereinafter, also referred to as "TAHQ residues") easily form an ordered structure of the polymer, and can reduce the dielectric loss factor and hygroscopicity by inhibiting the movement of molecules. BPDA residues can give self-supporting properties to the gel film of polyamide, which is a precursor of polyimide, but on the other hand, they tend to increase the CTE after imidization, lower the glass transition temperature, and reduce heat resistance.

From the above viewpoint, the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 is controlled to contain BPDA residues and TAHQ residues in a total amount preferably in a range of 30 mol parts or more and 60 mol parts or less, and more preferably in a range of 40 mol parts or more and 50 mol parts or less, relative to 100 mol parts of all tetracarboxylic acid residues. If the total amount of BPDA residues and TAHQ residues is less than 30 mol parts, the formation of the ordered structure of the polymer becomes insufficient, the moisture absorption resistance decreases, or the reduction of the dielectric loss factor becomes insufficient. If it exceeds 60 mol parts, in addition to the increase in CTE or the increase in the variation of the in-plane retardation (RO), there is a concern that the heat resistance decreases.

In addition, tetracarboxylic acid residues derived from pyromellitic dianhydride (hereinafter also referred to as "PMDA residues") and tetracarboxylic acid residues derived from 2,3,6,7-naphthalenetetracarboxylic dianhydride (hereinafter also referred to as "NTCDA residues") have rigidity, and therefore are residues that play a role in improving in-plane orientation, suppressing CTE to a low level, and controlling in-plane retardation (RO) or glass transition temperature. On the other hand, PMDA residues have a small molecular weight, so if the amount becomes too large, the imide group concentration of the polymer becomes high, the polar group increases, the hygroscopicity becomes greater, and the dielectric loss factor increases due to the influence of moisture inside the molecular chain. In addition, NTCDA residues tend to make the film brittle and increase the modulus of elasticity due to the highly rigid naphthalene skeleton. Therefore, the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer preferably contains PMDA residues and NTCDA residues in a total amount of preferably 40 mol parts or more and 70 mol parts or less, more preferably 50 mol parts or more and 60 mol parts or less, and further preferably 50 mol parts to 55 mol parts relative to 100 mol parts of all tetracarboxylic acid residues. If the total of PMDA residues and NTCDA residues is less than 40 mol parts, there is a concern that CTE may increase or heat resistance may decrease. If it exceeds 70 mol parts, there is a concern that the concentration of amide groups in the polymer may increase, polar groups may increase and low hygroscopicity may be impaired, the dielectric loss factor may increase, or the film may become brittle and the self-supporting property of the film may decrease.

The total amount of at least one of BPDA residues and TAHQ residues and at least one of PMDA residues and NTCDA residues may be 80 mol parts or more, preferably 90 mol parts or more, based on 100 mol parts of all tetracarboxylic acid residues.

In addition, the molar ratio of at least one of the BPDA residue and the TAHQ residue to at least one of the PMDA residue and the NTCDA residue {(BPDA residue + TAHQ residue) / (PMDA residue + NTCDA residue)} can be set to a range of greater than 0.4 and less than 1.5, preferably within a range of greater than 0.6 and less than 1.3, and more preferably within a range of greater than 0.8 and less than 1.2, to control the CTE and the formation of an ordered structure of the polymer.

PMDA and NTCDA have a rigid skeleton, so compared with other general anhydride components, they can control the in-plane orientation of molecules in polyimide, and have the effect of suppressing the coefficient of thermal expansion (CTE) and improving the glass transition temperature (Tg). In addition, compared with PMDA, BPDA and TAHQ have a larger molecular weight, so the concentration of imide groups decreases as the loading ratio increases, which has an effect on reducing the dielectric loss factor or reducing the moisture absorption rate. On the other hand, if the loading ratio of BPDA and TAHQ increases, the in-plane orientation of molecules in polyimide decreases, resulting in an increase in CTE. Furthermore, the formation of an ordered structure within the molecule is promoted, and the haze value increases. From the above viewpoint, the total amount of PMDA and NTCDA charged can be in the range of 40 to 70 mol parts, preferably in the range of 50 to 60 mol parts, and more preferably in the range of 50 to 55 mol parts, relative to 100 mol parts of all the acid anhydride components of the raw material. If the total amount of PMDA and NTCDA charged is less than 40 mol parts relative to 100 mol parts of all the acid anhydride components of the raw material, the in-plane orientation of the molecules decreases, and it becomes difficult to lower the CTE. In addition, the heat resistance or dimensional stability of the film during heating due to the decrease in Tg decreases. On the other hand, if the total amount of PMDA and NTCDA charged exceeds 70 mol parts, there is a tendency that the moisture absorption rate deteriorates due to the increase in the imide group concentration, or the elastic modulus increases.

In addition, BPDA and TAHQ have the effect of lowering the dielectric loss factor and moisture absorption rate due to the suppression of molecular motion or the reduction of the imide group concentration, but the CTE of the polyimide film after imidization increases. From this viewpoint, the total amount of BPDA and TAHQ charged can be in the range of 30 mol parts to 60 mol parts, preferably in the range of 40 mol parts to 50 mol parts, and more preferably in the range of 40 mol parts to 45 mol parts, relative to 100 mol parts of all the acid anhydride components of the raw materials.

Examples of tetracarboxylic acid residues other than the BPDA residue, TAHQ residue, PMDA residue, and NTCDA residue contained in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 include 3,3',4,4'-diphenylsulfonate tetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 2,3',3,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 2,3,3',4'-benzophenonetetracarboxylic dianhydride or 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,3',3,4'-diphenylethertetracarboxylic dianhydride, bis(2,3-dicarboxyphenyl)ether dianhydride, 3,3'',4,4''-terphenyltetracarboxylic dianhydride, 2,3,3'',4''-terphenyltetracarboxylic dianhydride or 2,2'',3,3''-terphenyltetracarboxylic dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-propane dianhydride or 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride or bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)sulfonate dianhydride or bis(3,4-dicarboxyphenyl)sulfonate dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride or 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,2,7, 8-phenanthrene-tetracarboxylic dianhydride, 1,2,6,7-phenanthrene-tetracarboxylic dianhydride or 1,2,9,10-phenanthrene-tetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)tetrafluoropropane dianhydride, 2,3,5,6-cyclohexane dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride or 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-(or 1,4,5,8 tetracarboxylic acid residues derived from aromatic tetracarboxylic acid dianhydrides such as tetrachloronaphthalene-1,4,5,8-(or 2,3,6,7-)tetracarboxylic dianhydride, 2,3,8,9-perylene-tetracarboxylic dianhydride, 3,4,9,10-perylene-tetracarboxylic dianhydride, 4,5,10,11-perylene-tetracarboxylic dianhydride or 5,6,11,12-perylene-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride, and ethylene glycol bis(trimellitic)anhydride.

(Diamine residue) As the diamine residue contained in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111, a diamine residue derived from a diamine compound represented by the general formula (1) is preferred.

[Chemistry 2]

In formula (1), the linking group Z represents a single bond or -COO-, Y independently represents a halogen atom or a monovalent hydrocarbon having 1 to 3 carbon atoms which may be substituted with 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 of 0 to 2, and p and q independently represent integers of 0 to 4. Here, the term "independently" means that there are a plurality of substituents Y in the formula (1), and further, the integers p and q may be the same or different. Furthermore, in the formula (1), the hydrogen atoms in the two amino groups at the terminals may be substituted, for example, -NR ₂ R ₃ (here, R ₂ and R ₃ independently represent any substituent such as an alkyl group).

The diamine compound represented by the general formula (1) (hereinafter, sometimes referred to as "diamine (1)") is an aromatic diamine having 1 to 3 benzene rings. Diamine (1) has a rigid structure and thus has the effect of imparting an ordered structure to the polymer as a whole. Therefore, a polyimide having low air permeability and low hygroscopicity can be obtained, and the water content inside the molecular chain can be reduced, thereby reducing the dielectric loss factor. Here, the linking group Z is preferably a single bond.

Examples of the diamine (1) include 1,4-diaminobenzene (p-phenylenediamine (p-PDA)), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-n-propyl-4,4'-diaminobiphenyl (m-NPB), and 4-aminophenyl-4'-aminobenzoate (APAB).

The non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 may contain diamine residues derived from diamine (1) in an amount of preferably 80 mol parts or more, more preferably 85 mol parts or more, relative to 100 mol parts of all diamine residues. When the diamine (1) is used in an amount within the above range, it is easy to form an ordered structure for the entire polymer by utilizing the rigid structure derived from the monomer, and it is easy to obtain a non-thermoplastic polyimide with low air permeability, low moisture absorption and low dielectric loss factor.

When the diamine residues derived from the diamine (1) are 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, 1,4-diaminobenzene is preferably used as the diamine (1) from the viewpoint of obtaining a more rigid structure with excellent in-plane orientation.

Examples of other diamine residues contained in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 include 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'-methylenebis-o-toluidine, 4,4'-methylenebis-2,6-dimethylaniline, 4,4'-methylenebis-2,6-diethylaniline, 3,3'-diaminodiphenylethane, 3,3'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 3,3''-diamino-p-terphenyl, 4,4'-[1,4-phenylenebis(1-methylethyl)benzidine] )]bisaniline, 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisaniline, bis(p-aminocyclohexyl)methane, bis(p-β-amino-tert-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-tert-butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylene diamine diamine residues derived from aromatic diamine compounds such as p-xylylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, 2'-methoxy-4,4'-diaminobenzanilide, 4,4'-diaminobenzanilide, 1,3-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 both terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl groups or amino groups.

In the non-thermoplastic polyimide, by selecting the types of the tetracarboxylic acid residues and diamine residues, or by using two or more tetracarboxylic acid residues or diamine residues, their respective molar ratios can be controlled to control the thermal expansion coefficient, storage elastic coefficient, tensile elastic coefficient, etc. In addition, in the non-thermoplastic polyimide, when having a plurality of structural units of polyimide, they may exist in the form of blocks or randomly, but from the viewpoint of suppressing the deviation of the in-plane retardation (RO), it is preferably present randomly.

Furthermore, it is preferred that both the tetracarboxylic acid residue and the diamine residue contained in the non-thermoplastic polyimide are aromatic groups because the dimensional accuracy of the polyimide film in a high temperature environment can be improved and the variation of the in-plane retardation (RO) can be reduced.

The imide group concentration of the non-thermoplastic polyimide is preferably 33% or less, and more preferably 32% or less. Here, "imide group concentration" refers to 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. If the imide group concentration exceeds 33%, the molecular weight of the resin itself decreases, and the low hygroscopicity also deteriorates due to the increase in polar groups. By selecting the combination of the acid anhydride and the diamine compound, the orientation of the molecules in the non-thermoplastic polyimide is controlled, thereby suppressing the increase in CTE accompanying the decrease in the imide group concentration and ensuring low hygroscopicity.

The weight average molecular weight of the non-thermoplastic polyimide is preferably in the range of 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 decreases and the film tends to become brittle. On the other hand, if the weight average molecular weight exceeds 400,000, the viscosity increases excessively and the film thickness is uneven, streaks, and other undesirable conditions tend to occur during the coating operation.

From the viewpoint of ensuring the function as a base layer and the handling properties during manufacturing and coating of thermoplastic polyimide, the thickness of the non-thermoplastic polyimide layer 111 is preferably in the range of 6 μm to 100 μm, and more preferably in the range of 9 μm to 50 μm. If the thickness of the non-thermoplastic polyimide layer 111 is less than the lower limit, the electrical insulation or handling properties become insufficient, and if it exceeds the upper limit, the productivity decreases.

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

In addition, from the viewpoint of suppressing warp, the thermal expansion coefficient of the non-thermoplastic polyimide layer 111 can be in the range of 1 ppm/K to 30 ppm/K, preferably in the range of 1 ppm/K to 25 ppm/K, and more preferably in the range of 15 ppm/K to 25 ppm/K.

In addition, for example, a plasticizer, other curing resin components such as epoxy resin, a curing agent, a curing accelerator, a coupling agent, a filler, a solvent, a flame retardant, etc. may be appropriately formulated as an arbitrary component in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111. However, there are substances containing a large amount of polar groups in the plasticizer, and there is a concern that the substance promotes the diffusion of copper from the copper wiring, so it is preferable not to use the plasticizer as much as possible.

Thermoplastic polyimide layer: Thermoplastic polyimide constituting the thermoplastic polyimide layer 112 contains tetracarboxylic acid residues and diamine residues, preferably contains aromatic tetracarboxylic acid residues derived from aromatic tetracarboxylic dianhydride and aromatic diamine residues derived from aromatic diamine.

(Tetracarboxylic acid residue) As the tetracarboxylic acid residue used in the thermoplastic polyimide constituting the thermoplastic polyimide layer 112, 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.

(Diamine residue) As the diamine residue contained in the thermoplastic polyimide constituting the thermoplastic polyimide layer 112, a diamine residue derived from a diamine compound represented by general formula (B1) to general formula (B7) is preferred.

[Chemistry 3]

In formula (B1) to formula (B7), _R1 independently represents a monovalent alkyl group or alkoxy group having 1 to 6 carbon atoms, linking group A independently represents a divalent group selected from -O-, -S-, -CO-, -SO-, -SO ₂ -, -COO-, -CH ₂ -, -C(CH ₃ ) ₂ -, -NH- or -CONH-, and _n1 independently represents an integer from 0 to 4. In formula (B3), the repeating group in formula (B2) is excluded, and the repeating group in formula (B4) is excluded from formula (B5). Here, "independently" means that the multiple linking groups A, multiple _R1 or multiple _n1 in one or more formulas of formula (B1) to formula (B7) may be the same or different. In the above formulae (B1) to (B7), the hydrogen atoms in the two terminal amino groups may be substituted, and may be, for example, -NR ₂ R ₃ (wherein R ₂ and R ₃ independently represent any substituent such as an alkyl group).

The diamine represented by formula (B1) (hereinafter, sometimes referred to as "diamine (B1)") is an aromatic diamine having two benzene rings. The diamine (B1) is directly bonded to at least one benzene ring, and the amino group and the divalent linking group A are located at the meta position, so that the degree of freedom of the polyimide molecular chain increases and the polyimide molecular chain has high flexibility, which contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B1), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -O-, _-CH2- , -C( _CH3 ) _2- , -CO-, _-SO2- , -S- are preferred.

Examples of the diamine (B1) include 3,3'-diaminodiphenylmethane, 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenylsulfone, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylpropane, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminobenzophenone, and (3,3'-bisamino)diphenylamine.

The diamine represented by formula (B2) (hereinafter, sometimes referred to as "diamine (B2)") is an aromatic diamine having three benzene rings. The diamine (B2) is directly bonded to the amino group on at least one benzene ring and the divalent linking group A is in the meta position, so that the degree of freedom of the polyimide molecular chain is increased and the polyimide molecular chain has high flexibility, which contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B2), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -O- is preferably used.

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

The diamine represented by formula (B3) (hereinafter, sometimes referred to as "diamine (B3)") is an aromatic diamine having three benzene rings. The diamine (B3) is believed to increase the degree of freedom of the polyimide molecular chain and have high flexibility due to the two divalent linking groups A directly bonded to one benzene ring, thereby contributing to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B3), the thermoplasticity of the polyimide is improved. Here, the linking group A is preferably -O-.

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

The diamine represented by formula (B4) (hereinafter, sometimes referred to as "diamine (B4)") is an aromatic diamine having four benzene rings. The diamine (B4) is considered to have high flexibility due to the amino group directly bonded to at least one benzene ring and the divalent linking group A being at the meta position, and thus contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using the diamine (B4), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -O-, _-CH2- , -C( _CH3 ) _2- , _-SO2- , -CO-, and -CONH- are preferred.

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, and bis[4,4'-(3-aminophenoxy)]benzanilide.

The diamine represented by formula (B5) (hereinafter, sometimes referred to as "diamine (B5)") is an aromatic diamine having four benzene rings. The diamine (B5) is considered to increase the degree of freedom of the polyimide molecular chain and have high flexibility due to the two divalent linking groups A directly bonded to at least one benzene ring, which contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B5), the thermoplasticity of the polyimide is improved. Here, the linking group A is preferably -O-.

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

The diamine represented by formula (B6) (hereinafter, sometimes referred to as "diamine (B6)") is an aromatic diamine having four benzene rings. The diamine (B6) is considered to have high flexibility due to having at least two ether bonds, and contributes to improving the flexibility of the polyimide molecular chain. Therefore, by using diamine (B6), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -C( _CH3 ) _2- , -O-, _-SO2- , and -CO- are preferred.

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

The diamine represented by formula (B7) (hereinafter, sometimes referred to as "diamine (B7)") is an aromatic diamine having four benzene rings. The diamine (B7) has a highly flexible divalent linking group A on both sides of the diphenyl skeleton, and is therefore considered to contribute to improving the flexibility of the polyimide molecular chain. Therefore, by using the diamine (B7), the thermoplasticity of the polyimide is improved. Here, the linking group A is preferably -O-.

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

The thermoplastic polyimide constituting the thermoplastic polyimide layer 112 may contain diamine residues derived from at least one diamine compound selected from diamine (B1) to diamine (B7) in an amount of 60 mol parts or more, preferably in a range of 60 mol parts or more and 99 mol parts or less, and more preferably in a range of 70 mol parts or more and 95 mol parts or less, relative to 100 mol parts of all diamine residues. Diamine (B1) to diamine (B7) have a molecular structure having flexibility, and therefore, by using at least one diamine compound selected from these compounds 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 diamine (B1) to diamine (B7) in the raw materials is less than 60 mol parts relative to 100 mol parts of all diamine components, the polyimide resin will be insufficiently flexible and sufficient thermoplasticity will not be obtained.

In addition, as the diamine residue contained in the thermoplastic polyimide constituting the thermoplastic polyimide layer 112, it is also preferred to be a diamine residue derived from a diamine compound represented by the general formula (1). The diamine compound represented by the general formula (1) [diamine (1)] is as described in the description of the non-thermoplastic polyimide. Diamine (1) has a rigid structure and has the function of imparting an ordered structure to the polymer as a whole, thereby suppressing the movement of molecules and reducing the dielectric loss factor or moisture absorption. Furthermore, by using it as a raw material for thermoplastic polyimide, a polyimide with low air permeability and excellent long-term heat resistance and adhesion can be obtained.

The thermoplastic polyimide constituting the thermoplastic polyimide layer 112 may contain diamine residues derived from the diamine (1) in an amount preferably in the range of 1 mol to 40 mol, more preferably in the range of 5 mol to 30 mol. By using the diamine (1) in an amount in the above range, the polymer as a whole forms an ordered structure by utilizing the rigid structure derived from the monomer, thereby obtaining a thermoplastic polyimide having low air permeability and moisture absorption and excellent long-term heat-resistant adhesion.

The thermoplastic polyimide constituting the thermoplastic polyimide layer 112 may contain a diamine residue derived from a diamine compound other than diamine (1) and diamine (B1) to diamine (B7) within a range not impairing the effects of the present invention.

In thermoplastic polyimide, by selecting the types of tetracarboxylic acid residues and diamine residues, or by using two or more tetracarboxylic acid residues or diamine residues, their respective molar ratios can be controlled to control the thermal expansion coefficient, tensile elastic coefficient, glass transition temperature, etc. In addition, in the case of having a plurality of structural units of polyimide in thermoplastic polyimide, they may exist in the form of blocks or randomly, but preferably exist randomly.

Furthermore, by making both the tetracarboxylic acid residue and the diamine residue contained in the thermoplastic polyimide into aromatic groups, the dimensional accuracy of the polyimide film in a high temperature environment can be improved and the variation of the in-plane retardation (RO) can be suppressed.

The imide group concentration of the thermoplastic polyimide is preferably 33% or less, and more preferably 32% or less. Here, "imide group concentration" refers to 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. If the imide group concentration exceeds 33%, the molecular weight of the resin itself decreases, and the low hygroscopicity also deteriorates due to the increase in polar groups. By selecting the combination of the diamine compounds, the orientation of the molecules in the thermoplastic polyimide is controlled, thereby suppressing the increase in CTE accompanying the decrease in the imide group concentration and ensuring low hygroscopicity.

The weight average molecular weight of the thermoplastic polyimide is preferably in the range of 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 decreases and the film tends to become brittle. On the other hand, if the weight average molecular weight exceeds 400,000, the viscosity increases excessively and defects such as uneven film thickness and streaks tend to occur during coating.

The thermoplastic polyimide constituting the thermoplastic polyimide layer 112 serves as an adhesive layer in the insulating resin of the circuit board, for example. Therefore, in order to suppress the diffusion of copper, a completely imidized structure is most preferably used. Part of the polyimide may also be an amide. The imidization rate is measured by using a Fourier transform infrared spectrometer (commercial product: FT/IR620 manufactured by JASCO Corporation) and using the attenuated total reflectance (ATR) method to measure the infrared absorption spectrum of the polyimide film. The benzene ring absorber near 1015 cm ^-1 is used as a reference, and the absorbance of the C=O stretching of the imide group at 1780 cm ^-1 is calculated.

From the viewpoint of ensuring adhesion performance, the thickness of the thermoplastic polyimide layer 112 is preferably within a range of 1 μm to 10 μm, and more preferably within a range of 1 μm to 5 μm. If the thickness of the thermoplastic polyimide layer 112 is less than the lower limit, adhesion is insufficient, and if it exceeds the upper limit, dimensional stability tends to deteriorate.

From the viewpoint of suppressing warp, the thermal expansion coefficient of the thermoplastic polyimide layer 112 may be 30 ppm/K or more, preferably 30 ppm/K or more and 100 ppm/K or less, and more preferably 30 ppm/K or more and 80 ppm/K or less.

In addition, in addition to polyimide, the resin used in the thermoplastic polyimide layer 112 may contain, as an arbitrary component, a plasticizer, other curing resin components such as epoxy resin, a curing agent, a curing accelerator, an inorganic filler, a coupling agent, a filler, a solvent, a flame retardant, etc. However, there are substances containing a large amount of polar groups among plasticizers, and there is a concern that such substances promote the diffusion of copper from copper wiring, so it is preferred not to use plasticizers as much as possible.

In the metal-clad laminate 100, in order to ensure dimensional stability after circuit processing, the overall thermal expansion coefficient of the two polyimide layers 110 and the adhesive polyimide layer 120 may be greater than 10 ppm/K, preferably within the range of greater than 10 ppm/K and less than 30 ppm/K, and more preferably within the range of greater than 15 ppm/K and less than 25 ppm/K. Furthermore, in the metal-clad laminate 100, the total thickness T1 of the two polyimide layers 110 and the adhesive polyimide layer 120, the thickness T2 of the adhesive polyimide layer 120, and the ratio (T2/T1) of the thickness T2 of the adhesive polyimide layer 120 to the total thickness T1 are as shown in FIG. 1.

(Synthesis of polyimide) The polyimide constituting the polyimide layer 110 can be produced by reacting the acid anhydride and the diamine in a solvent and heating and ring-closing the resulting precursor resin. For example, approximately equal molar amounts of the acid anhydride component and the diamine component are dissolved in an organic solvent, and the polymerization reaction is carried out at a temperature in the range of 0°C to 100°C for 30 minutes to 24 hours while stirring, thereby obtaining a polyamide acid as a polyimide precursor. During the reaction, the reaction components are dissolved in such a manner that the generated precursor is in the range of 5% by weight to 30% by weight, preferably in the range of 10% by weight to 20% by weight in the organic solvent. As organic solvents used in the polymerization reaction, for example, N,N-dimethylformamide, N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone, 2-butanone, dimethyl sulfoxide, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, etc. Two or more of these solvents may be used in combination, and aromatic hydrocarbons such as xylene and toluene may also be used in combination. In addition, the amount of the organic solvent used is not particularly limited, but it is preferably used in an amount adjusted to a concentration of about 5% to 30% by weight of the polyimide solution (polyimide precursor solution) obtained by the polymerization reaction.

In the synthesis of polyimide, the acid anhydride and diamine may be used alone or in combination of two or more. By selecting the types of the acid anhydride and diamine, or the molar ratio of the two or more acid anhydrides or diamines, thermal expansion, adhesion, glass transition temperature, etc. can be controlled.

The synthesized precursor is usually advantageously used as a reaction solvent solution, but may be concentrated, diluted or replaced with other organic solvents as needed. In addition, the precursor is generally excellent in solvent solubility and can be advantageously used. The method of imidizing the precursor is not particularly limited, and for example, the following heat treatment can be preferably adopted: heating in the solvent at a temperature condition in the range of 80°C to 400°C for 1 hour to 24 hours.

[Circuit board] The metal-clad laminate 100 is mainly useful as a circuit board material such as an FPC, a rigid and a flexible circuit board. That is, by processing one or both of the two metal layers 101 of the metal-clad laminate 100 into a pattern to form a wiring layer using a conventional method, a circuit board such as an FPC which is an embodiment of the present invention can be manufactured. Although the illustration is omitted, the circuit board includes a resin laminate body in which a first insulating resin layer (P1), an adhesive layer (B) and a second insulating resin layer (P2) are sequentially laminated, and a wiring layer is provided on one side or both sides of the resin laminate body. [Example]

The present invention is specifically described below 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.

[Measurement of dielectric constant and dielectric loss factor] The dielectric constant (Dk) and dielectric loss factor (Df) of the polyimide film at 10 GHz were measured using a vector network analyzer (manufactured by Agilent, trade name E8363C) and a split post dielectric resonator (SPDR). The material used in the measurement was left at a temperature of 24°C to 26°C and a humidity of 45% to 55%RH for 24 hours.

[Measurement of storage elastic coefficient and glass transition temperature (Tg)] Regarding the storage elastic coefficient of the adhesive layer, the adhesive layer (thickness 50 μm) was peeled off from the base film, cut into 5 mm × 20 mm, and heated in an oven at 120°C for 2 hours and at 170°C for 3 hours. The obtained sample was heated stepwise from 30°C to 400°C at a heating rate of 4°C/min using a dynamic viscoelasticity measuring device (DMA: manufactured by UBM, trade name: E4000F), and measured at a frequency of 1 Hz. In addition, the maximum temperature at which the Tanδ value in the measurement is the largest is defined as Tg.

[Measurement of dimensional change rate] The dimensional change rate was measured in the following order. First, a 150 mm square test piece was used, and the dry film resist was exposed and developed at intervals of 100 mm to form a target for position measurement. After measuring the size before etching (normal state) in an atmosphere of temperature 23±2°C and relative humidity 50±5%, the copper other than the target of the test piece was removed by etching (liquid temperature below 40°C, time within 10 minutes). After standing for 24±4 hours in an atmosphere of temperature 23±2°C and relative humidity 50±5%, the size after etching was measured. The dimensional change rate relative to the normal state was calculated at 3 locations each in the MD direction (long side direction) and the TD direction (width direction), and the average value of each was taken as the dimensional change rate after etching. The dimensional change rate after etching is calculated using the following formula.

Dimension change rate after etching (%) = (B-A)/A×100 A: Target distance before etching B: Target distance after etching

Next, heat the test piece in an oven at 250°C for 1 hour, and measure the distance between the position targets afterwards. Calculate the dimensional change rate after etching at three locations in the MD direction (longitudinal direction) and TD direction (width direction), and take the average value of each as the dimensional change rate after heat treatment. The dimensional change rate after heating is calculated using the following formula.

Dimension change rate after heating (%) = (C-B)/B×100 B: Target distance after etching C: Target distance after heating

The abbreviations used in this embodiment represent the following compounds: BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride PMDA: pyromellitic dianhydride BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl TPE-R: 1,3-bis(4-aminophenoxy)benzene Bisaniline-M: 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene DDA: manufactured by Croda Japan Co., Ltd. (trade name: PRIAMINE 1075) N-12: dodecanedioic acid dihydrazide DMAc: N,N-dimethylacetamide R710: (Trade name, manufactured by Printec Co., Ltd., bisphenol-type epoxy resin, epoxy equivalent: 170, liquid at room temperature, weight average molecular weight: about 340) VG3101L: (Trade name, manufactured by Printec Co., Ltd., multifunctional epoxy resin, epoxy equivalent: 210, softening point: 39°C to 46°C) SR35K: (Trade name, manufactured by Printec Co., Ltd., epoxy resin, epoxy equivalent: 930 to 940, softening point: 86°C to 98°C) YDCN-700-10: (trade name, manufactured by Nippon Steel & Sumitomo Chemical Co., Ltd., cresol novolac type epoxy resin, epoxy equivalent 210, softening point 75℃～85℃) Milex XLC-LL: (trade name, manufactured by Mitsui Chemicals Co., Ltd., phenolic resin, hydroxyl equivalent: 175, softening point: 77℃, water absorption: 1% by mass, heating mass reduction rate: 4% by mass) HE200C-10: (trade name, manufactured by Air Water Co., Ltd., phenolic resin, hydroxyl equivalent: 200, softening point: 65℃～76℃, water absorption: 1% by mass, heating mass reduction rate: 4% by mass) HE910-10: (trade name, manufactured by Air Water Co., Ltd., phenol resin, hydroxyl equivalent: 101, softening point: 83°C, water absorption: 1% by mass, mass loss rate on heating: 3% by mass) SC1030-HJA: (trade name, manufactured by Admatechs Co., Ltd., silica filler dispersion, average particle size: 0.25 μm) Aerosil R972: (trade name, manufactured by Japan Aerosil Co., Ltd., silica, average particle size: 0.016 μm) Acrylic rubber HTR-860P-30B-CHN: (Sample name, manufactured by Teikoku Chemical Industry Co., Ltd., weight average molecular weight: 230,000, glycidyl functional monomer ratio: 8%, Tg: -7°C) Acrylic rubber HTR-860P-3CSP: (Sample name, manufactured by Teikoku Chemical Industry Co., Ltd., weight average molecular weight: 800,000, glycidyl functional monomer ratio: 3%, Tg: -7°C) A-1160: (Trade name, manufactured by GE Toshiba Co., Ltd., γ-ureidopropyl triethoxysilane) A-189: (Trade name, manufactured by GE Toshiba Co., Ltd., γ-butylenepropyl trimethoxysilane) Curezol 2PZ-CN: (trade name, manufactured by Shikoku Chemical Industry Co., Ltd., 1-cyanoethyl-2-phenylimidazole) RE-810NM: (trade name, manufactured by Nippon Kayaku Co., Ltd., diallylbisphenol A diglycidyl ether, properties: liquid) PHORET SCS: (trade name, manufactured by Soken Chemical Co., Ltd., styrene-containing acrylic polymer, Tg: 70°C, weight average molecular weight: 15000) BMI-1: (trade name, manufactured by Tokyo Chemical Industry Co., Ltd., 4,4'-bismaleimide diphenylmethane) TPPK: (trade name, manufactured by Tokyo Chemical Industry Co., Ltd., tetraphenylphosphonium tetraphenylborate) HP-P1: (trade name, manufactured by Mizushima Alloy Steel Co., Ltd., boron nitride filler) NMP: (N-methyl-2-pyrrolidone, manufactured by Kanto Chemical Co., Ltd.).

(Synthesis Example 1) <Preparation of Resin Solution A for Adhesive Layer> Cyclohexanone is added to a composition containing epoxy resin and phenol resin as (a) thermosetting resin and (c) inorganic filler as shown in Table 1 with the product names and composition ratios (unit: parts by mass), and the mixture is stirred and mixed. Acrylic rubber as (b) high molecular weight component shown in Table 1 is added thereto and stirred, and (e) coupling agent and (d) curing accelerator shown in Table 1 are further added and stirred until the components are uniform, thereby obtaining Resin Solution A for Adhesive Layer.

[Table 1] Differentiation Name Synthesis Example 1 Epoxy R710 twenty four VG3101L twenty one SR35K 20 YDCN-700-10 1.4 Phenolic resin XLC-LL 1.2 HE910-10 17 HE200C-10 15 Inorganic filler R972 0.82 SC1030-HJA 61 Coupling agent A-189 0.29 A-1160 0.59 Hardening accelerator 2PZ-CN 0.025 Acrylic rubber HTR-860P-30B-CHN 27 HTR-860P-3CSP 12

(Synthesis Example 2) <Synthesis of polyimide resin (PI-1) and preparation of resin solution B for adhesive layer> In a 300 mL flask equipped with a thermometer, a stirrer, a cooling tube, and a nitrogen inflow tube, 15.53 g of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: LP-7100), 28.13 g of polyoxypropylenediamine (manufactured by BASF, trade name: D400, molecular weight: 450) and 100.0 g of NMP were placed and stirred to prepare a reaction solution. After the diamine was dissolved, 32.30 g of 4,4'-oxydiphthalic anhydride, which had been purified by recrystallization from acetic anhydride, was added little by little to the reaction solution while the flask was cooled in an ice bath. After reacting at room temperature (25°C) for 8 hours, 67.0 g of xylene was added, and the mixture was heated at 180°C while nitrogen was blown in, thereby removing xylene by azeotropy with water. The reaction solution was poured into a large amount of water, and the precipitated resin was filtered out and dried to obtain a polyimide resin (PI-1). The molecular weight of the obtained polyimide resin (PI-1) was measured by gel permeation chromatography (GPC), and the result was that the number average molecular weight Mn = 22400 and the weight average molecular weight Mw = 70200 in terms of polystyrene conversion. Using the obtained polyimide resin (PI-1), each component was prepared in the composition ratio (unit: mass parts) shown in Table 2 to obtain a resin solution B for an adhesive layer.

[Table 2] Differentiation Name Synthesis Example 2 Thermoplastic resin PI-1 100 Reactive plasticizer RE-810NM 40 Compounds having a styryl group PHORET SCS 40 Compounds having a maleimide group BMI-1 40 Hardening accelerator TPPK 0.2 Inorganic filler HP-P1 twenty two Solvent NMP 270

(Synthesis Example 3) <Preparation of polyamide solution for insulating resin layer> Under nitrogen flow, 64.20 g of m-TB (0.302 mol) and 5.48 g of bisaniline-M (0.016 mol) and DMAc in an amount of 15 wt% solid content concentration after polymerization were added to a reaction tank and stirred at room temperature to dissolve. Next, 34.20 g of PMDA (0.157 mol) and 46.13 g of BPDA (0.157 mol) were added, and the polymerization reaction was continued at room temperature for 3 hours with continuous stirring to prepare polyamide solution 1 (viscosity: 26,500 cps).

(Synthesis Example 4) <Preparation of polyamide solution for insulating resin layer> Polyamide solution 2 (viscosity: 2,650 cps) was prepared in the same manner as in Synthesis Example 3 except that 69.56 g of m-TB (0.328 mol), 542.75 g of TPE-R (1.857 mol), DMAc in an amount of 12 wt% solid content after polymerization, 194.39 g of PMDA (0.891 mol) and 393.31 g of BPDA (1.337 mol) were used as raw material compositions.

(Production Example 1) <Preparation of adhesive layer resin sheet A> The adhesive layer resin solution A was applied to the silicone treated surface of a release substrate (length × width × thickness = 320 mm × 240 mm × 25 μm) in a manner to a thickness of 50 μm after drying, and then dried at 80°C for 15 minutes, and then dried at 120°C for 15 minutes, and then peeled from the release substrate to prepare a resin sheet A. In addition, in order to evaluate the physical properties after curing, the resin sheet A was heated in an oven at 120°C for 2 hours and at 170°C for 3 hours. After that, the Tg of the hardened resin sheet A is 95°C, the storage elastic modulus at 50°C is 960 MPa, and the maximum value of the storage elastic modulus at 180°C to 260°C is 7 MPa.

(Production Example 2) <Preparation of adhesive layer resin sheet B> The adhesive layer resin solution B was applied to the silicone treated surface of a release substrate (length × width × thickness = 320 mm × 240 mm × 25 μm) in a manner to a thickness of 50 μm after drying, and then dried at 80°C for 15 minutes, and then dried at 120°C for 15 minutes, and then peeled from the release substrate to prepare a resin sheet B. In addition, in order to evaluate the physical properties after curing, the resin sheet B was heated in an oven at 120°C for 2 hours and at 170°C for 3 hours. After that, the Tg of the cured resin sheet B is below 100°C, the storage modulus of elasticity at 50°C is below 1800 MPa, and the maximum value of the storage modulus of elasticity at 180°C to 260°C is 70 MPa.

(Production Example 3) <Preparation of a single-sided metal-clad laminate> Polyamide solution 2 is uniformly applied to copper foil 1 (electrolytic copper foil, thickness: 12 μm, surface roughness Rz of the resin layer side: 0.6 μm) in a manner that the thickness after curing becomes approximately 2 μm to 3 μm, and then heat-dried at 120°C to remove the solvent. Next, polyamide solution 1 is uniformly applied thereon in a manner that the thickness after curing becomes approximately 21 μm, and heat-dried at 120°C to remove the solvent. Furthermore, polyamide solution 2 is uniformly applied thereon in a manner that the thickness after curing becomes approximately 2 μm to 3 μm, and then heat-dried at 120°C to remove the solvent. Then, a stepwise heat treatment is performed from 120°C to 360°C to complete imidization and produce a single-sided metal-clad laminate 1. The dimensional change rate of the single-sided metal-clad laminate 1 is as follows. Dimensional change rate after etching in the MD direction (long side direction): 0.01% Dimensional change rate after etching in the TD direction (width direction): -0.04% Dimensional change rate after heating in the MD direction (long side direction): -0.03% Dimensional change rate after heating in the TD direction (width direction): -0.01%

<Preparation of polyimide film> The copper foil 1 of the single-sided metal laminate 1 was etched away using an aqueous solution of ferric chloride to prepare a polyimide film 1 (thickness: 25 μm, CTE: 20 ppm/K, Dk: 3.40, Df: 00029).

[Example 1] Prepare two single-sided metal-clad laminates 1, overlap the surfaces of the insulating resin layers of each sheet with both surfaces of the resin sheet A, and press-bond them at 180°C for 2 hours under a pressure of 3.5 MPa to prepare the metal-clad laminate 1. The evaluation results of the metal-clad laminate 1 are as follows. Dimensional change rate after etching in the MD direction: -0.02% Dimensional change rate after etching in the TD direction: -0.03% Dimensional change rate after heating in the MD direction: -0.02% Dimensional change rate after heating in the TD direction: -0.02% The metal-clad laminate 1 has no warping and no problem with dimensional change. In addition, the CTE of the resin laminate 1 (thickness: 100 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 1 is 24.1 ppm/K.

[Example 2] Prepare two single-sided metal-clad laminates 1, overlap the surfaces of the insulating resin layers of each sheet with the two surfaces of the resin sheet B, and press-bond them at 180°C for 2 hours under a pressure of 3.5 MPa to prepare metal-clad laminate 2. The evaluation results of metal-clad laminate 2 are as follows. Dimensional change rate after etching in MD direction: -0.05% Dimensional change rate after etching in TD direction: -0.05% Dimensional change rate after heating in MD direction: -0.03% Dimensional change rate after heating in TD direction: -0.04% Metal-clad laminate 2 has no warping and no problem with dimensional change. In addition, the CTE of the resin laminate 2 (thickness: 100 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 2 is 23.3 ppm/K.

(Comparative Example 1) Metal-clad laminate 3 was prepared in the same manner as in Example 1 except that a fluororesin sheet (manufactured by Asahi Glass Co., Ltd., trade name: Adhesive Perfluororesin EA-2000, thickness: 50 μm, Tm: 303°C, Tg: None) was used instead of resin sheet A and a pressure of 3.5 MPa was applied at 320°C for 5 minutes for compression bonding. The evaluation results of metal-clad laminate 3 are as follows. Dimensional change rate after etching in MD direction: -0.11% Dimensional change rate after etching in TD direction: -0.13% Dimensional change rate after heating in MD direction: -0.19% Dimensional change rate after heating in TD direction: -0.20% The metal-clad laminate 3 has no warping and no problem with dimensional change. In addition, the CTE of the resin laminate 3 (thickness: 100 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 3 is 27.6 ppm/K.

(Reference Example 1) Copper foil 1, resin sheet A, polyimide film 1, resin sheet A, and copper foil 1 were overlapped in this order and pressed together at 180°C for 2 hours under a pressure of 3.5 MPa to prepare a metal-clad laminate 4. The evaluation results of the metal-clad laminate 4 are as follows. Dimensional change rate after etching in MD direction: -0.04% Dimensional change rate after etching in TD direction: -0.05% Dimensional change rate after heating in MD direction: -0.12% Dimensional change rate after heating in TD direction: -0.14% The metal-clad laminate 4 had no warping and no problem with dimensional change. In addition, the CTE of the resin laminate 4 (thickness: 100 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 4 is 23.9 ppm/K.

It can be seen that Example 1 and Example 2 have lower dimensional change rates after etching and after heating than Comparative Example 1 and Reference Example 1, respectively. In Comparative Example 1, lamination by heat pressing at 320°C was performed, and there was no problem with adhesion, but sufficient adhesion could not be obtained by heat pressing under the same heat pressing conditions as Example 1 and Example 2 (temperature: 180°C, time: 2 hours, pressure: 3.5 MPa). In addition, Reference Example 1 was performed to verify the positional configuration of the resin sheet A.

[Example 3] Prepare a single-sided metal-clad laminate 1, apply an adhesive layer resin solution A to the surface of the insulating resin layer side in a manner to a thickness of 50 μm after drying, heat dry at 80°C for 15 minutes, and further dry at 120°C for 15 minutes to prepare a single-sided metal-clad laminate 1 with an adhesive layer. Secondly, overlap the adhesive layer surface of the single-sided metal-clad laminate 1 with the surface of the insulating resin layer side of another single-sided metal-clad laminate 1, and apply a pressure of 3.5 MPa at 180°C for 2 hours for compression bonding to prepare a metal-clad laminate 1'. The evaluation results of the metal-clad laminate 1' are as follows. Dimensional change rate after etching in the MD direction: -0.03% Dimensional change rate after etching in the TD direction: -0.03% Dimensional change rate after heating in the MD direction: -0.02% Dimensional change rate after heating in the TD direction: -0.02% The metal-clad laminate 1' has no warping and no problem with dimensional change. In addition, the CTE of the resin laminate 1' (thickness: 100 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 1' is 23.1 ppm/K.

[Example 4] Two single-sided metal-clad laminates 1 with adhesive layers were prepared, and after the adhesive layers were overlapped, they were pressed together at 180°C for 2 hours under a pressure of 3.5 MPa to prepare a metal-clad laminate 5. The evaluation results of the metal-clad laminate 5 are as follows. Dimensional change rate after etching in the MD direction: -0.03% Dimensional change rate after etching in the TD direction: -0.03% Dimensional change rate after heating in the MD direction: -0.03% Dimensional change rate after heating in the TD direction: -0.03% The metal-clad laminate 5 had no warping and no problem with dimensional change. In addition, the CTE of the resin laminate 5 (thickness: 150 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 5 is 23.8 ppm/K.

[Example 5] A single-sided metal-clad laminate 1 was prepared, and an adhesive layer resin solution A was applied to the surface of the insulating resin layer in a manner to a thickness of 75 μm after drying, followed by heat drying at 80°C for 15 minutes and further drying at 120°C for 25 minutes to prepare a single-sided metal-clad laminate 2 with an adhesive layer. Two single-sided metal-clad laminates 2 with an adhesive layer were prepared, and after the adhesive layers were overlapped, they were pressed together at 180°C for 2 hours under a pressure of 3.5 MPa to prepare a metal-clad laminate 6. The evaluation results of the metal-clad laminate 6 are as follows. Dimensional change rate after etching in MD direction: -0.01% Dimensional change rate after etching in TD direction: -0.01% Dimensional change rate after heating in MD direction: 0.01% Dimensional change rate after heating in TD direction: 0.02% The metal-clad laminate 6 has no warping and no problem with dimensional change. In addition, the CTE of the resin laminate 6 (thickness: 200 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 6 is 22.8 ppm/K.

(Synthesis Example 5) Under a nitrogen flow, 44.98 g of BTDA (0.139 mol), 75.02 g of DDA (0.140 mol), 168 g of NMP and 112 g of xylene were placed in a 500 ml separable flask and mixed thoroughly at 40°C for 30 minutes to prepare a polyamide solution. The polyamide solution was heated to 190°C, heated and stirred for 4.5 hours, and 112 g of xylene was added to prepare a polyimide adhesive solution 1 after imidization. The solid content of the obtained polyimide adhesive solution 1 was 29.1% by weight and the viscosity was 7,800 cps. In addition, the weight average molecular weight (Mw) of the polyimide was 87,700.

(Synthesis Example 6) 34.4 g (solid content: 10 g) of the polyimide adhesive solution 1 obtained in Synthesis Example 5 was mixed with 1.25 g of N-12 and 2.5 g of Exolit OP935 (manufactured by Clariant Japan Co., Ltd.), and 1.297 g of NMP and 3.869 g of xylene were added for dilution to prepare a resin solution C for an adhesive layer.

<Preparation of adhesive layer resin sheet C> The adhesive layer resin solution C was applied to the silicone treated surface of a release substrate (length × width × thickness = 320 mm × 240 mm × 25 μm) to a thickness of 50 μm after drying, and then dried at 80°C for 15 minutes, and then dried at 120°C for 15 minutes, and then peeled from the release substrate to prepare resin sheet C. In addition, in order to evaluate the physical properties after curing, resin sheet C was heated in an oven at 120°C for 2 hours and at 170°C for 3 hours to prepare a cured resin sheet D. The Tg of the hardened resin sheet D is 95°C, the storage elastic modulus at 50°C is 1220 MPa, and the maximum storage elastic modulus at 180°C to 260°C is 26 MPa.

[Example 6] Prepare a single-sided metal-clad laminate 1, apply an adhesive layer resin solution C to the surface of the insulating resin layer side in a manner to a thickness of 50 μm after drying, heat dry at 80°C for 15 minutes, and further dry at 120°C for 15 minutes to prepare a single-sided metal-clad laminate 3 with an adhesive layer. Next, overlap the adhesive layer surface of the single-sided metal-clad laminate 3 with the surface of the insulating resin layer side of the single-sided metal-clad laminate 1, and press-bond them at 180°C for 2 hours under a pressure of 3.5 MPa to prepare a metal-clad laminate 7. The evaluation results of the metal-clad laminate 7 are as follows. Dimensional change rate after etching in the MD direction: -0.02% Dimensional change rate after etching in the TD direction: -0.02% Dimensional change rate after heating in the MD direction: -0.03% Dimensional change rate after heating in the TD direction: -0.03% The metal-clad laminate 7 has no warping and no problem with dimensional change. In addition, the CTE of the resin laminate 7 (thickness: 100 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 7 is 23.4 ppm/K.

In addition, any single-sided metal-clad laminate with an adhesive layer described in the embodiments can also be applied to the manufacture of a multi-layer circuit board. In addition, it is considered that the thickness of the adhesive layer in the above case is preferably 100 μm or less, and the thickness ratio of the adhesive layer in the insulating resin layer is preferably 80% or less.

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

100: Metal-clad laminate 101: Metal layer 110: Polyimide layer 111: Non-thermoplastic polyimide layer 112: Thermoplastic polyimide layer 120: Adhesive polyimide layer 130: Single-sided metal-clad laminate B: Adhesive layer C: Metal-clad laminate C1: First single-sided metal-clad laminate (single-sided metal-clad laminate) C2: Second single-sided metal-clad laminate (single-sided metal-clad laminate) M1: First metal layer M2: Second metal layer P1: First insulating resin layer P2: Second insulating resin layer T1: Total thickness T2, T3: Thickness

FIG1 is a schematic diagram showing the structure of a metal-clad laminate according to an embodiment of the present invention. FIG2 is a schematic cross-sectional diagram showing the structure of a metal-clad laminate according to a preferred embodiment of the present invention.

B: Adhesive layer

C: Metal-clad laminate

C1: The first single-sided metal-clad laminate (single-sided metal-clad laminate)

C2: Second single-sided metal-clad laminate (single-sided metal-clad laminate)

M1: First metal layer

M2: Second metal layer

P1: First insulating resin layer

P2: Second insulating resin layer

T1: Total thickness

T2, T3: thickness

Claims (3)

A method for manufacturing a metal-clad laminate, the metal-clad laminate comprising: a first single-sided metal-clad laminate having a first metal layer and a first insulating resin layer laminated on at least one side of the first metal layer; a second single-sided metal-clad laminate having a second metal layer and a second insulating resin layer laminated on at least one side of the second metal layer; and an adhesive layer for resisting The method comprises the steps of: first, forming a first metal-clad laminated board and a second metal-clad laminated board in a manner of being connected to the first insulating resin layer and the second insulating resin layer, and being laminated between the first metal-clad laminated board and the second metal-clad laminated board, and the manufacturing method comprises the steps of: step 1: preparing the first metal-clad laminated board and the second metal-clad laminated board; step 2: The first step is to laminate a resin layer made of thermoplastic resin or thermosetting resin as the adhesive layer on either or both of the first insulating resin layer or the second insulating resin layer; the second step is to heat-press the first single-sided metal-clad laminate and the second single-sided metal-clad laminate after the first step is to make the insulating resin layers face each other through the adhesive layer. The adhesive layer is composed of a thermoplastic resin or a thermosetting resin and meets the following conditions (i) to (iii): (i) the storage elastic coefficient at 50°C is less than 1800MPa; (ii) the maximum value of the storage elastic coefficient in the temperature range of 180°C to 260°C is less than 800MPa; (iii) the glass transition temperature (Tg) is less than 180°C. As described in the first item of the patent application, the manufacturing method of the metal-clad laminate, wherein the resin layer of the adhesive layer in step 2 is a coating film obtained by coating a thermoplastic resin, a thermosetting resin or a resin solution thereof and drying it. As described in item 1 of the patent application, the manufacturing method of the metal-clad laminate, wherein the first insulating resin layer and the second insulating resin layer both have a multi-layer structure formed by sequentially stacking a thermoplastic polyimide layer, a non-thermoplastic polyimide layer and a thermoplastic polyimide layer, and the adhesive layer is arranged in contact with the two thermoplastic polyimide layers.