Method for manufacturing metal-clad laminate

Abstract

To provide a metal clad laminate with reduced transmission loss in high frequency transmission and excellent dimensional stability.SOLUTION: A method for manufacturing a metal clad laminate including a first single-sided metal clad laminate having a first metal layer and a first insulating resin layer, a second single-sided metal clad laminate having a second metal layer and a second insulating resin layer, and adhesive layers arranged in contact with the first insulating resin layer and the second insulating resin layer, includes the steps of: preparing the first single-sided metal clad laminate and the second single-sided metal clad laminate; laminating a resin layer serving as an adhesive layer composed of a thermoplastic resin or a thermosetting resin on either one or both of the first insulating resin layer or the second insulating resin layer; and bonding the first single-sided metal clad laminate and the second single-sided metal clad laminate via the adhesive layer so that the respective insulating resin layers face each other for thermo-compression bonding. The adhesive layer is composed of the thermoplastic resin or the thermosetting resin, and satisfies the following conditions: (i) a storage elastic modulus at 50°C is 1,800 MPa or less, (ii) a maximum value of a storage elastic modulus in a temperature range from 180°C to 260°C is 800 MPa or less, and (iii) a glass transition temperature (Tg) is 180°C or less.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In recent years, with the progress in miniaturization, weight reduction, and space-saving of electronic devices, there has been an increasing demand for flexible printed circuits (FPCs), which are thin, lightweight, flexible, and have excellent durability even when repeatedly bent. Because FPCs allow for three-dimensional, high-density packaging even in limited spaces, their applications are expanding to include wiring for moving parts in electronic devices such as hard disk drives, DVDs, and smartphones, as well as components such as cables and connectors.

[0003] In addition to the aforementioned increase in density, the advancement of device performance has created a need to accommodate higher transmission signal frequencies. When transmitting high-frequency signals, if transmission loss along the transmission path is significant, problems such as electrical signal loss and longer signal delay times occur. Therefore, reducing transmission loss will become increasingly important in FPCs in the future. To accommodate high-frequency signal transmission, FPCs are increasingly using liquid crystal polymers, which have lower dielectric constants and lower dielectric loss tangents, as their dielectric layers, instead of the commonly used polyimide. However, while liquid crystal polymers have excellent dielectric properties, there is still room for improvement in their heat resistance and adhesion to metal layers.

[0004] Fluorine-based resins are also known as polymers that exhibit low dielectric constants and low dielectric loss tangents. For example, an insulating film has been proposed as an FPC material capable of handling high-frequency signal transmission and offering excellent adhesiveness, in which a polyimide adhesive film having a thermoplastic polyimide layer and a highly heat-resistant polyimide layer is bonded to both sides of a fluororesin layer (Patent Document 1). The insulating film of Patent Document 1 uses a fluororesin, and therefore has excellent dielectric properties. However, it has issues with dimensional stability. In particular, when applied to FPCs, there is concern that the dimensional change before and after circuit processing by etching will be significant. This makes it difficult to increase the thickness of the fluororesin and to increase the thickness ratio.

[0005] Meanwhile, as a technology related to adhesive layers used in electronic materials, the application of resin compositions containing epoxy resin and phenoxy resin, and resin compositions containing thermoplastic polyimide and maleimide compounds, etc. to adhesive sheets has been proposed (Patent Documents 2 and 3). The film-like adhesive sheets of Patent Documents 2 and 3 have the advantage of having a low glass transition temperature and exhibiting high adhesion to laminate materials. However, Patent Documents 2 and 3 do not consider the possibility of application to high-frequency signal transmission or application to adhesive layers in metal-clad laminates. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-24265 [Patent Document 2] Patent No. 6191800 [Patent Document 3] Patent No. 5553108 Summary of the Invention [Problem to be solved by the invention]

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

[0008] As a result of extensive research, the inventors have discovered that the above problems can be solved by using an adhesive layer with a low glass transition temperature and a low modulus of elasticity in a metal-clad laminate, and have thus completed the present invention.

[0009] The metal-clad laminate of the present invention comprises a first single-sided metal-clad laminate having a first metal layer and a first insulating resin layer laminated on at least one surface 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 surface of the second metal layer; The metal-clad laminate includes an adhesive layer that is arranged so as to abut the first insulating resin layer and the second insulating resin layer and is laminated between the first single-sided metal-clad laminate and the second single-sided metal-clad laminate. The metal-clad laminate of the present invention is characterized in that the adhesive layer is made of a thermoplastic resin or a thermosetting resin and satisfies the following conditions (i) to (iii): (i) The storage modulus at 50°C is 1800 MPa or less; (ii) the maximum storage modulus in the temperature range from 180°C to 260°C is 800 MPa or less; (iii) a glass transition temperature (Tg) of 180°C or less; Meet the following.

[0010] The metal-clad laminate of the present invention may have a total thickness T1 of the first insulating resin layer, the adhesive layer, and the second insulating resin layer in the range of 70 to 500 μm, and the ratio (T2 / T1) of the thickness T2 of the adhesive layer to the total thickness T1 may be in the range of 0.5 to 0.8.

[0011] In the metal-clad laminate of the present invention, the first insulating resin layer and the second insulating resin layer may both have a multilayer structure in which a thermoplastic polyimide layer, a non-thermoplastic polyimide layer, and a thermoplastic polyimide layer are laminated in this order, The adhesive layer may be provided in contact with the two thermoplastic polyimide layers.

[0012] In the metal-clad laminate of the present invention, the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer may contain a tetracarboxylic acid residue and a diamine residue, and the content of the diamine residue derived from the diamine compound represented by the following general formula (1) may be 80 molar parts or more per 100 molar parts of all the diamine residues:

[0013] [ka]

[0014] In formula (1), the linking group Z represents a single bond or -COO-; Y independently represents a monovalent hydrocarbon having 1 to 3 carbon atoms which may be substituted with a halogen atom or a phenyl group, an alkoxy group having 1 to 3 carbon atoms, 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.

[0015] In the metal-clad laminate of the present invention, the thermal expansion coefficient of the first insulating resin layer, the adhesive layer, and the second insulating resin layer may be in the range of 10 ppm / K or more and 30 ppm / K or less.

[0016] In the metal-clad laminate of the present invention, the first metal layer and the second metal layer may both be made of copper foil.

[0017] The circuit board of the present invention is obtained by processing the first metal layer and / or the second metal layer of any of the above metal-clad laminates into wiring. [Effects of the Invention]

[0018] The metal-clad laminate of the present invention has a structure in which two single-sided metal-clad laminates are bonded together via an adhesive layer having specific parameters, which allows for a thicker insulating resin layer and ensures dimensional stability. Furthermore, when applied to circuit boards that transmit high-frequency signals of 10 GHz or higher, it is possible to reduce transmission loss. Therefore, the reliability and yield of the circuit board can be improved. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic diagram showing a configuration of a metal-clad laminate according to one embodiment of the present invention. [Figure 2] 1 is a schematic cross-sectional view showing the configuration of a metal-clad laminate according to a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the accompanying drawings.

[0021] [Metal-clad laminate] FIG. 1 is a schematic diagram showing the configuration of a metal-clad laminate according to one 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 with an adhesive layer (B). Specifically, 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). The first single-sided metal-clad laminate (C1) includes 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) includes a second metal layer (M2) and a second insulating resin layer (P2) laminated on at least one side of the second metal layer (M2). The adhesive layer (B) is arranged so as to abut against the first insulating resin layer (P1) and the second insulating resin layer (P2). In other words, 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 laminated in this order. The first metal layer (M1) and the second metal layer (M2) are respectively located on the outermost sides, and the first insulating resin layer (P1) and the second insulating resin layer (P2) are arranged inside them, and the adhesive layer (B) is further interposed between the first insulating resin layer (P1) and the second insulating resin layer (P2).

[0022] <Single-sided metal-clad laminate> The configuration of the pair of single-sided metal-clad laminates (C1, C2) is not particularly limited, and common FPC materials can be used, including commercially available copper-clad laminates, etc. The first single-sided metal-clad laminate (C1) and the second single-sided metal-clad laminate (C2) may have the same configuration or different configurations.

[0023] (metal layer) The material of the first metal layer (M1) and the second metal layer (M2) is not particularly limited, but 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 these, copper or copper alloys are particularly preferred. The material of the wiring layer in the circuit board of this embodiment, which will be described later, is also the same as that of the first metal layer (M1) and the second metal layer (M2).

[0024] The thickness of the first metal layer (M1) and the second metal layer (M2) is not particularly limited, but 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 to 25 μm. From the viewpoint of production stability and handling, the lower limit of the thickness of the metal foil is preferably 5 μm. When copper foil is used, it may be rolled copper foil or electrolytic copper foil. Furthermore, commercially available copper foil may be used as the copper foil.

[0025] Furthermore, the metal foil may be subjected to a surface treatment using, for example, siding, aluminum alcoholate, aluminum chelate, or a silane coupling agent, for the purpose of, for example, rust prevention or improving adhesive strength.

[0026] (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, and examples thereof include polyimide, epoxy resin, phenolic resin, polyethylene, polypropylene, polytetrafluoroethylene, silicone, ETFE, etc., but are preferably made of polyimide. Furthermore, the first insulating resin layer (P1) and the second insulating resin layer (P2) are not limited to a single layer, and may be made of a laminate of multiple resin layers. In addition, when referring to polyimide in the present invention, in addition to polyimide, polyamideimide, polyetherimide, polyesterimide, This refers to a resin made of a polymer having an imide group in the molecular structure, such as polysiloxane imide or polybenzimidazole imide.

[0027] <Adhesive layer> The adhesive layer (B) is composed of a thermoplastic resin or a thermosetting resin, and satisfies the following: (i) a storage modulus at 50°C of 1800 MPa or less, (ii) a maximum storage modulus from 180°C to 260°C of 800 MPa or less, and (iii) a glass transition temperature (Tg) of 180°C or less. Examples of such resins include polyimide resins, polyamide resins, epoxy resins, phenoxy resins, acrylic resins, polyurethane resins, styrene resins, polyester resins, phenolic resins, polysulfone resins, polyethersulfone resins, polyphenylene sulfide resins, polyethylene resins, polypropylene resins, silicone resins, polyetherketone resins, polyvinyl alcohol resins, polyvinyl butyral resins, styrene-maleimide copolymers, maleimide-vinyl compound copolymers, or (meth)acrylic copolymers, benzoxazine resins, bismaleimide resins, and cyanate ester resins. From these, resins that satisfy the conditions (i) to (iii) can be selected or designed to satisfy the conditions (i) to (iii) and used in the adhesive layer (B).

[0028] When the adhesive layer (B) is a thermosetting resin, it may contain an organic peroxide, a curing agent, a curing accelerator, etc., and if necessary, a curing agent and a curing accelerator, or a catalyst and a co-catalyst may be used in combination. The amounts of the curing agent, curing accelerator, catalyst, co-catalyst, and organic peroxide to be added, and whether or not they are added, may be determined within a range that ensures the above conditions (i) to (iii).

[0029] <Layer thickness> When the total thickness T1 of the first insulating resin layer (P1), the adhesive layer (B), and the second insulating resin layer (P2) of the metal-clad laminate (C) is defined as 70 to 500 μm, and preferably 100 to 300 μm. If the total thickness T1 is less than 70 μm, the effect of reducing transmission loss when used in a circuit board becomes insufficient, and if it exceeds 500 μm, productivity may decrease.

[0030] The thickness T2 of the adhesive layer (B) is preferably, for example, in the range of 50 to 450 μm, and more preferably in the range of 50 to 250 μm. If the thickness T2 of the adhesive layer (B) is less than the above lower limit, the transmission loss as a high-frequency substrate may increase. On the other hand, if the thickness of the adhesive layer (B) exceeds the above upper limit, problems such as reduced dimensional stability may occur.

[0031] 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 0.5 to 0.7. If the ratio (T2 / T1) is less than 0.5, it becomes difficult to make T1 70 μm or more, and if it exceeds 0.8, problems such as reduced dimensional stability occur.

[0032] The thickness T3 of both the first insulating resin layer (P1) and the second insulating resin layer (P2) is preferably within a range of, for example, 12 to 100 μm, and more preferably within a range of 12 to 50 μm. If the thickness T3 of the first insulating resin layer (P1) and the second insulating resin layer (P2) is less than the above-mentioned 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 above-mentioned upper limit, problems such as reduced productivity may occur. Note that the first insulating resin layer (P1) and the second insulating resin layer (P2) do not necessarily have to have the same thickness.

[0033] <Thermal expansion coefficient> The first insulating resin layer (P1) and the second insulating resin layer (P2) should have a coefficient of thermal expansion (CTE) of 10 ppm / K or more, preferably in the range of 10 ppm / K to 30 ppm / K, and more preferably in the range of 15 ppm / K to 25 ppm / K. If the CTE is less than 10 ppm / K or more than 30 ppm / K, warping may occur or dimensional stability may decrease. A polyimide layer having the desired CTE can be obtained by appropriately changing the combination of raw materials used, the thickness, and the drying and curing conditions.

[0034] The adhesive layer (B) has high thermal expansion but low elasticity and a low glass transition temperature, so that even if the CTE exceeds 30 ppm / K, it can alleviate the internal stress generated during lamination. The overall coefficient of thermal expansion (CTE) of the first insulating resin layer (P1), adhesive layer (B), and second insulating resin layer (P2) is preferably 10 ppm / K or more, more preferably 10 ppm / K to 30 ppm / K, and even more preferably 15 ppm / K to 25 ppm / K. If the CTE of the entire resin layers is less than 10 ppm / K or exceeds 30 ppm / K, warping may occur or dimensional stability may decrease.

[0035] <Glass transition temperature (Tg)> The adhesive layer (B) has a glass transition temperature (Tg) of 180°C or lower, preferably 160°C or lower. By setting the glass transition temperature of the adhesive layer (B) to 180°C or lower, thermocompression bonding can be performed at low temperatures, which alleviates internal stress generated during lamination and suppresses dimensional changes after circuit processing. If the Tg of the adhesive layer (B) exceeds 180°C, the temperature required for bonding between the first insulating resin layer (P1) and the second insulating resin layer (P2) becomes high, which may impair dimensional stability after circuit processing.

[0036] <Storage modulus> The adhesive layer (B) has a storage modulus of 1800 MPa or less at 50°C, and a maximum storage modulus of 800 MPa or less in the temperature range of 180°C to 260°C. These properties of the adhesive layer (B) are thought to be the factors that alleviate internal stress during thermocompression bonding and maintain dimensional stability after circuit processing. Furthermore, the adhesive layer (B) preferably has a storage modulus of 800 MPa or less at the upper limit temperature (260°C) of the temperature range, and more preferably has a storage modulus of 500 MPa or less. By achieving such a storage modulus, warping is less likely to occur even after the solder reflow process after circuit processing.

[0037] <Dielectric loss tangent> When the first insulating resin layer (P1) and the second insulating resin layer (P2) are applied to, for example, a circuit board, the dielectric loss tangent (Tan δ) at 10 GHz is preferably 0.02 or less, more preferably 0.0005 to 0.01, and even more preferably 0.001 to 0.008, in order to suppress deterioration of dielectric loss. If the dielectric loss tangent at 10 GHz of the first insulating resin layer (P1) and the second insulating resin layer (P2) exceeds 0.02, problems such as electrical signal loss are likely to occur in the transmission path of high-frequency signals when applied to a circuit board. On the other hand, the lower limit of the dielectric loss tangent at 10 GHz of the first insulating resin layer (P1) and the second insulating resin layer (P2) is not particularly limited, but consideration is given to controlling the physical properties as insulating resin layers of a circuit board.

[0038] When the adhesive layer (B) is applied to, for example, a circuit board, in order to suppress deterioration of dielectric loss, the dielectric loss tangent (Tanδ) at 10 GHz is preferably 0.015 or less, more preferably 0.01 or less, and even more preferably 0.006 or less. If the dielectric loss tangent at 10 GHz of the adhesive layer (B) exceeds 0.015, when the adhesive layer (B) is applied to a circuit board, problems such as loss of electrical signals are likely to occur in the transmission path of high-frequency signals. On the other hand, there is no particular lower limit for the dielectric loss tangent at 10 GHz of the adhesive layer (B).

[0039] <Dielectric constant> When the first insulating resin layer (P1) and the second insulating resin layer (P2) are used as insulating resin layers for a circuit board, for example, the insulating resin layer as a whole preferably has a dielectric constant of 4.0 or less at 10 GHz in order to ensure impedance matching. If the dielectric constants of the first insulating resin layer (P1) and the second insulating resin layer (P2) at 10 GHz exceed 4.0, when used in a circuit board, this leads to an increase in the dielectric loss of the first insulating resin layer (P1) and the second insulating resin layer (P2), which is likely to cause problems such as loss of electrical signals on the transmission path of high-frequency signals.

[0040] When the adhesive layer (B) is applied to, for example, a circuit board, the dielectric constant at 10 GHz is preferably 4.0 or less to ensure impedance matching. If the dielectric constant at 10 GHz of the adhesive layer (B) exceeds 4.0, when the adhesive layer (B) is applied to a circuit board, this leads to an increase in the dielectric loss of the adhesive layer (B), which is likely to cause problems such as loss of electrical signals on the transmission path of high-frequency signals.

[0041] <effect> In the metal-clad laminate (C) of this embodiment, the thickness of the adhesive layer (B) itself is increased to reduce the dielectric loss tangent of the entire insulating resin layer and enable high-frequency transmission. However, materials with a low elastic modulus, such as the adhesive layer (B), generally exhibit a high thermal expansion coefficient, so increasing the layer thickness may result in a decrease in dimensional stability. Here, the dimensional change that occurs when the metal-clad laminate (C) is subjected to circuit processing is thought to occur mainly due to the following mechanisms a) to c), and the sum of b) and c) is thought to be manifested as the dimensional change after etching. a) During the production of the metal-clad laminate (C), internal stress accumulates in the resin layer. b) When the circuit is processed, the metal layer is etched, which releases the internal stress accumulated in a), causing the resin layer to expand or contract. c) When processing the circuit, the metal layer is etched, causing the exposed resin to absorb moisture and expand.

[0042] The causes of the internal stress in (a) above are (a) the difference in thermal expansion coefficients between the metal layer and the resin layer, and (b) internal strain in the resin caused by film formation. Here, the magnitude of the internal stress caused by (a) is affected not only by the difference in thermal expansion coefficients, but also by the temperature difference ΔT between the temperature at the time of bonding (heating temperature) and the temperature at which it cools and solidifies. In other words, since the internal stress increases in proportion to the temperature difference ΔT, even if the difference in thermal expansion coefficients between the metal layer and the resin layer is small, the higher the temperature required for bonding, the greater the internal stress. In the metal-clad laminate (C) of this embodiment, the adhesive layer (B) is used, which satisfies the above conditions (i) to (iii), thereby reducing the internal stress and ensuring dimensional stability.

[0043] Furthermore, 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 and suppresses warping and dimensional changes. Furthermore, even during heating processes such as solder reflow during semiconductor chip mounting, the first insulating resin layer (P1) or the second insulating resin layer (P2) blocks direct contact with heat and oxygen, making it less susceptible to oxidative degradation and less likely to cause dimensional changes. In this way, the layer structure of the first insulating resin layer (P1), adhesive layer (B), and second insulating resin layer (P2) has additional advantages.

[0044] [Manufacturing of metal-clad laminates] The metal-clad laminate (C) can be produced, for example, by the following method 1 or method 2. [Method 1] A method in which a resin composition that will become the adhesive layer (B) is formed into a sheet to form an adhesive sheet, and the adhesive sheet is placed between the first insulating resin layer (P1) of a first single-sided metal-clad laminate (C1) and the second insulating resin layer (P2) of a second single-sided metal-clad laminate (C2), and they are bonded together by thermocompression. [Method 2] A method in which a solution of a resin composition that will become the 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 dried, and then the coated film sides are bonded together and thermocompressed.

[0045] The adhesive sheet used in Method 1 can be produced, for example, by applying a solution of the resin composition that will become the adhesive layer (B) to any supporting substrate, drying it, and then peeling it off from the supporting substrate to obtain an adhesive sheet. Furthermore, in the above, the method for applying the solution of the resin composition that will form the adhesive layer (B) onto the supporting substrate or the insulating resin layer (P1, P2) is not particularly limited, and it is possible to apply it using a coater such as a comma, die, knife, or lip.

[0046] The metal-clad laminate (C) of this embodiment obtained as described above can be used to manufacture circuit boards such as single-sided FPCs or double-sided FPCs by processing the first metal layer (M1) and / or the second metal layer (M2) into wiring circuits, for example by etching the first metal layer (M1) and / or the second metal layer (M2).

[0047] [Preferable 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.

[0048] FIG. 2 is a schematic cross-sectional view showing the structure of a metal-clad laminate 100 according to 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, the metal layer 101 and the polyimide layer 110 form a single-sided metal-clad laminate 130 as a first single-sided metal-clad laminate (C1) or a second single-sided metal-clad laminate (C2). In this embodiment, the first single-sided metal-clad laminate (C1) and the second single-sided metal-clad laminate (C2) have the same configuration.

[0049] Each of the polyimide layers 110 may have a structure in which multiple polyimide layers are laminated. For example, in the embodiment shown in Fig. 2, a three-layer structure is formed including non-thermoplastic polyimide layers 111 made of non-thermoplastic polyimide as base layers, and thermoplastic polyimide layers 112 made of thermoplastic polyimide provided on both sides of the non-thermoplastic polyimide layers 111. However, each of the polyimide layers 110 is not limited to a three-layer structure.

[0050] 2, the outer thermoplastic polyimide layers 112, 112 of two single-sided metal-clad laminates 130, 130 are each bonded to an 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 together in the metal-clad laminate 100, and serves to thicken 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).

[0051] Next, the non-thermoplastic polyimide layer 111 and thermoplastic polyimide layer 112 constituting the polyimide layers 110, 110 will be described. Note that the term "non-thermoplastic polyimide" generally refers to a polyimide that does not soften or exhibit adhesiveness even when heated. In the present invention, however, a non-thermoplastic polyimide having a storage modulus of 1.0×10 at 30°C measured using a dynamic viscoelasticity measuring device (DMA) is used. 9 Pa or more, and the storage modulus at 350°C is 1.0 × 10 8 The term "thermoplastic polyimide" generally refers to a polyimide whose glass transition temperature (Tg) can be clearly confirmed. In the present invention, however, the term "thermoplastic polyimide" refers to a polyimide whose storage modulus at 30°C measured by DMA is 1.0 × 10 9 Pa or more, and the storage modulus at 350°C is 1.0 × 10 8 Polyimides with a modulus of less than 1 Pa are also referred to as polyimides.

[0052] Non-thermoplastic polyimide layer: The non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 contains a tetracarboxylic acid residue and a diamine residue. In the present invention, the tetracarboxylic acid residue refers to a tetravalent group derived from a tetracarboxylic dianhydride, and the diamine residue refers to a divalent group derived from a diamine compound. The polyimide preferably contains an aromatic tetracarboxylic acid residue derived from an aromatic tetracarboxylic dianhydride and an aromatic diamine residue derived from an aromatic diamine.

[0053] (tetracarboxylic acid residue) The non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 preferably contains, as tetracarboxylic acid residues, tetracarboxylic acid residues derived from at least one of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ), and tetracarboxylic acid residues derived from at least one of pyromellitic dianhydride (PMDA) and 2,3,6,7-naphthalenetetracarboxylic dianhydride (NTCDA).

[0054] 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") tend to form ordered polymer structures and reduce the dielectric loss tangent and moisture absorption by suppressing molecular motion. BPDA residues can impart self-supporting properties to gel films as polyamic acids in polyimide precursors, but they also tend to increase the CTE after imidization and lower the glass transition temperature, reducing heat resistance.

[0055] From this viewpoint, the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 is controlled so that the total content of BPDA residues and TAHQ residues is preferably within a range of 30 to 60 parts by mole, more preferably 40 to 50 parts by mole, relative to 100 parts by mole of all tetracarboxylic acid residues. If the total content of BPDA residues and TAHQ residues is less than 30 parts by mole, the formation of an ordered structure of the polymer may be insufficient, resulting in a decrease in moisture absorption resistance and an insufficient reduction in dielectric loss tangent. If the total content exceeds 60 parts by mole, there is a risk of an increase in CTE, an increase in the amount of change in in-plane retardation (RO), and a decrease in heat resistance.

[0056] Furthermore, 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") possess rigidity, which enhances in-plane alignment, lowers CTE, and also plays a role in controlling in-plane retardation (RO) and glass transition temperature. However, because PMDA residues have a low molecular weight, excessive amounts of them increase the imide group concentration in the polymer, increasing the polar groups and increasing hygroscopicity, which in turn increases the dielectric loss tangent due to the influence of moisture within the molecular chain. Furthermore, NTCDA residues tend to make films brittle due to their highly rigid naphthalene backbone, which increases the modulus of elasticity. Therefore, the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer preferably contains 40 to 70 parts by mole of PMDA residues and NTCDA residues in total, relative to 100 parts by mole of all tetracarboxylic acid residues, more preferably 50 to 60 parts by mole, and even more preferably 50 to 55 parts by mole. If the total of PMDA residues and NTCDA residues is less than 40 parts by mole, the CTE may increase and heat resistance may decrease. If it exceeds 70 parts by mole, the imide group concentration in the polymer may increase, the polar groups may increase, and low moisture absorption may be impaired, the dielectric loss tangent may increase, and the film may become brittle and the self-supporting ability of the film may decrease.

[0057] The total amount of at least one of BPDA residue and TAHQ residue and at least one of PMDA residue and NTCDA residue is preferably 80 molar parts or more, and more preferably 90 molar parts or more, per 100 molar parts of all tetracarboxylic acid residues.

[0058] Furthermore, it is advisable to set the molar ratio of at least one of BPDA residues and TAHQ residues to at least one of PMDA residues and NTCDA residues {(BPDA residues + TAHQ residues) / (PMDA residues + NTCDA residues)} within a range of 0.4 to 1.5, preferably within a range of 0.6 to 1.3, and more preferably within a range of 0.8 to 1.2, to control the formation of an ordered structure of the CTE and polymer.

[0059] Because PMDA and NTCDA have rigid backbones, they are able to control the in-plane molecular orientation in polyimides compared to other common acid anhydride components, thereby suppressing the coefficient of thermal expansion (CTE) and improving the glass transition temperature (Tg). Furthermore, because BPDA and TAHQ have larger molecular weights than PMDA, increasing their loading ratio reduces the imide group concentration, thereby reducing the dielectric loss tangent and moisture absorption rate. On the other hand, increasing the loading ratio of BPDA and TAHQ reduces the in-plane molecular orientation in polyimides, leading to an increase in CTE. Furthermore, the formation of an ordered intramolecular structure progresses, increasing the haze value. From these perspectives, the combined loading amount of PMDA and NTCDA is preferably within the range of 40 to 70 mol parts, preferably 50 to 60 mol parts, and more preferably 50 to 55 mol parts, per 100 mol parts of the total acid anhydride components as raw materials. If the total amount of PMDA and NTCDA charged is less than 40 parts by mole per 100 parts by mole of the total acid anhydride components of the raw materials, the in-plane orientation of the molecules will decrease, making it difficult to achieve a low CTE, and the heat resistance and dimensional stability of the film will decrease due to a decrease in Tg.On the other hand, if the total amount of PMDA and NTCDA charged exceeds 70 parts by mole, the moisture absorption rate will decrease and the elastic modulus will tend to increase due to an increase in the imide group concentration.

[0060] BPDA and TAHQ are effective in suppressing molecular motion and reducing the imide group concentration, thereby lowering the dielectric loss tangent and moisture absorption rate, but they also increase the CTE of the polyimide film after imidization. From this perspective, the combined amount of BPDA and TAHQ charged is preferably 30 to 60 parts by mole, more preferably 40 to 50 parts by mole, and even more preferably 40 to 45 parts by mole, per 100 parts by mole of the total acid anhydride components of the raw materials.

[0061] 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'-diphenylsulfonetetracarboxylic acid dianhydride, 4,4'-oxydiphthalic anhydride, 2,3',3,4'-biphenyltetracarboxylic acid dianhydride, 2,2',3,3'-, 2,3,3',4'-, or 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, 2,3',3,4'-diphenylethertetracarboxylic acid dianhydride, bis(2,3-dicarboxyphenyl)ether dianhydride, 3,3'',4,4''-, 2,3,3'',4''-, or 2,2'',3,3''-p-terphenyltetracarboxylic acid dianhydride, 2,2-bis(2,3- or 3,4-dicarboxyphenyl)-propane dianhydride, ...4-dicarboxyphenyl)methane dianhydride, bis(2,3- or 3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3- or 3,4-dicarboxyphenyl)ethane dianhydride, 1,2,7,8-, 1,2,6,7- or 1,2,9,10-phenanthrenetetracarboxylic 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 acid Dianhydrides, 2,6- or 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-(or 1,4,5,8-)tetrachloronaphthalene-1,4,5,8-(or 2,3,6,7-)tetracarboxylic dianhydride, 2,3,8,9-, 3,4,9,10-, 4,5,10,11- or 5,6,11,12-perylene-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride, ethylene glycol Examples include tetracarboxylic acid residues derived from aromatic tetracarboxylic dianhydrides such as bisanhydrotrimellitate.

[0062] (diamine residue) The diamine residue contained in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 is preferably a diamine residue derived from a diamine compound represented by general formula (1).

[0063] [ka]

[0064] In formula (1), the linking group Z represents a single bond or -COO-; Y independently represents a monovalent hydrocarbon having 1 to 3 carbon atoms, which may be substituted with a halogen atom or a phenyl group, or an alkoxy group having 1 to 3 carbon atoms, or a perfluoroalkyl group having 1 to 3 carbon atoms, or an alkenyl group; n represents an integer of 0 to 2; and p and q independently represent integers of 0 to 4. Here, "independently" means that in formula (1), the multiple substituents Y and the integers p and q may be the same or different. In formula (1), the hydrogen atoms in the two terminal amino groups may be substituted, for example, -NR2R3 (where R2 and R3 independently represent any substituent such as an alkyl group).

[0065] The diamine compound represented by general formula (1) (hereinafter sometimes referred to as "diamine (1)") is an aromatic diamine having one to three benzene rings. Diamine (1) has a rigid structure, which has the effect of imparting an ordered structure to the entire polymer. This results in a polyimide with low gas permeability and low moisture absorption, and the moisture content inside the molecular chain can be reduced, thereby lowering the dielectric loss tangent. Here, a single bond is preferred as the linking group Z.

[0066] Examples of diamine (1) include 1,4-diaminobenzene (p-PDA; paraphenylenediamine), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-n-propyl-4,4'-diaminobiphenyl (m-NPB), and 4-aminophenyl-4'-aminobenzoate (APAB).

[0067] The non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 preferably contains 80 molar parts or more, more preferably 85 molar parts or more, of diamine residues derived from diamine (1) per 100 molar parts of all diamine residues. By using diamine (1) in an amount within the above range, an ordered structure is easily formed throughout the polymer due to the rigid structure derived from the monomer, and a non-thermoplastic polyimide having low gas permeability, low moisture absorption, and low dielectric loss tangent is easily obtained.

[0068] Furthermore, when the diamine residues derived from diamine (1) are in the range of 80 to 85 parts by mole relative to 100 parts by mole of all diamine residues in the non-thermoplastic polyimide, it is preferable to use 1,4-diaminobenzene as diamine (1) from the viewpoint of a more rigid structure with excellent in-plane orientation.

[0069] Other diamine residues contained in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 include, for example, 2,2-bis-[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)biphenyl, bis[1-(3-aminophenoxy)]biphenyl, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)]benzyl, benzophenone, 9,9-bis[4-(3-aminophenoxy)phenyl]fluorene, 2,2-bis-[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis-[4-(3-aminophenoxy)phenyl]hexafluoropropane, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 3,3'-diaminodiphenylethane, 3,3'-diamino Biphenyl, 3,3'-dimethoxybenzidine, 3,3''-diamino-p-terphenyl, 4,4'-[1,4-phenylenebis(1-methylethylidene)]bisaniline, 4,4'-[1,3-phenylenebis(1-methylethylidene)]bisaniline, bis(p-aminocyclohexyl)methane, bis(p-β-amino-t-butylphenyl)ether, bis(p-β-methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-aminopentyl)benzene, p-bis(1,1-dimethyl-5-amino) (aminopentyl)benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis(β-amino-t-butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylenediamine, p-xylylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, 2'-methoxy-4,4'-diaminobenzanilide, 4,4'-diaminobenzanilide, 1,Examples of the diamine residue include those derived from aromatic diamine compounds such as 3-bis[2-(4-aminophenyl)-2-propyl]benzene and 6-amino-2-(4-aminophenoxy)benzoxazole, and those derived from aliphatic diamine compounds such as dimer acid diamines in which the two terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl groups or amino groups.

[0070] In the non-thermoplastic polyimide, the thermal expansion coefficient, storage modulus, tensile modulus, etc. can be controlled by selecting the types of the tetracarboxylic acid residue and diamine residue, or by selecting the molar ratio of each when two or more types of tetracarboxylic acid residues or diamine residues are used. Furthermore, in the case where the non-thermoplastic polyimide has a plurality of polyimide structural units, they may be present as blocks or randomly, but from the viewpoint of suppressing variations in in-plane retardation (RO), they are preferably present randomly.

[0071] In addition, it is preferable that the tetracarboxylic acid residue and the diamine residue contained in the non-thermoplastic polyimide are both aromatic groups, because this improves the dimensional accuracy of the polyimide film in a high-temperature environment and reduces the amount of change in in-plane retardation (RO).

[0072] 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 molecular weight of the imide group (-(CO)2-N-) in the polyimide divided by the molecular weight of the entire polyimide structure. If the imide group concentration exceeds 33%, the molecular weight of the resin itself decreases, and the low moisture absorption property also deteriorates due to the increase in polar groups. By selecting the above combination of acid anhydride and diamine compound, the molecular orientation in the non-thermoplastic polyimide is controlled, thereby suppressing the increase in CTE that accompanies a decrease in imide group concentration and ensuring low moisture absorption.

[0073] The weight-average molecular weight of the non-thermoplastic polyimide is, for example, 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 film tends to have reduced strength and 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.

[0074] The thickness of the non-thermoplastic polyimide layer 111 is preferably in the range of 6 μm to 100 μm, more preferably in the range of 9 μm to 50 μm, from the viewpoints of ensuring the function as a base layer and transportability during production and thermoplastic polyimide coating. If the thickness of the non-thermoplastic polyimide layer 111 is less than the above lower limit, electrical insulation and handleability become insufficient, and if the thickness exceeds the above upper limit, productivity decreases.

[0075] From the viewpoint of heat resistance, the non-thermoplastic polyimide layer 111 preferably has a glass transition temperature (Tg) of 280° C. or higher.

[0076] Furthermore, from the viewpoint of suppressing warpage, the thermal expansion coefficient of the non-thermoplastic polyimide layer 111 is preferably in the range of 1 ppm / K or more and 30 ppm / K or less, more preferably in the range of 1 ppm / K or more and 25 ppm / K or less, and even more preferably in the range of 15 ppm / K or more and 25 ppm / K or less.

[0077] Furthermore, the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 may contain optional components such as plasticizers, other curable resin components such as epoxy resins, curing agents, curing accelerators, coupling agents, fillers, solvents, and flame retardants. However, some plasticizers contain many polar groups, which may promote the diffusion of copper from the copper wiring, so it is preferable to avoid using plasticizers as much as possible.

[0078] Thermoplastic polyimide layer: The thermoplastic polyimide constituting the thermoplastic polyimide layer 112 contains a tetracarboxylic acid residue and a diamine residue, and preferably contains an aromatic tetracarboxylic acid residue derived from an aromatic tetracarboxylic acid dianhydride and an aromatic diamine residue derived from an aromatic diamine.

[0079] (tetracarboxylic acid residue) The tetracarboxylic acid residue used in the thermoplastic polyimide constituting the thermoplastic polyimide layer 112 may be the same as those exemplified as the tetracarboxylic acid residue in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer.

[0080] (diamine residue) The diamine residue contained in the thermoplastic polyimide constituting the thermoplastic polyimide layer 112 is preferably a diamine residue derived from a diamine compound represented by any of the general formulae (B1) to (B7).

[0081] [ka]

[0082] In formulas (B1) to (B7), R1 independently represents a monovalent hydrocarbon group or alkoxy group having 1 to 6 carbon atoms, linking groups A independently represent a divalent group selected from -O-, -S-, -CO-, -SO-, -SO2-, -COO-, -CH2-, -C(CH3)2-, -NH-, or -CONH-, and n1 independently represents an integer of 0 to 4. However, formula (B3) excluding those that overlap with formula (B2), and formula (B5) excluding those that overlap with formula (B4). Here, "independently" means that in one or more of formulas (B1) to (B7), multiple linking groups A, multiple R1s, or multiple n1s may be the same or different. In the above formulas (B1) to (B7), the hydrogen atoms in the two terminal amino groups may be substituted, for example, -NR2R3 (where R2 and R3 independently represent any substituent such as an alkyl group).

[0083] The diamine represented by formula (B1) (hereinafter sometimes referred to as "diamine (B1)") is an aromatic diamine having two benzene rings. In this diamine (B1), the amino group directly bonded to at least one benzene ring and the divalent linking group A are located at the meta position, which increases the degree of freedom of the polyimide molecular chain and provides high flexibility, which is thought to contribute to improving the flexibility of the polyimide molecular chain. Therefore, the use of diamine (B1) enhances the thermoplasticity of the polyimide. Here, the linking group A is preferably -O-, -CH2-, -C(CH3)2-, -CO-, -SO2-, or -S-.

[0084] Examples of the diamine (B1) include 3,3'-diaminodiphenylmethane, 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylpropane, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminobenzophenone, and (3,3'-bisamino)diphenylamine.

[0085] The diamine represented by formula (B2) (hereinafter sometimes referred to as "diamine (B2)") is an aromatic diamine having three benzene rings. In this diamine (B2), the amino group directly bonded to at least one benzene ring and the divalent linking group A are located at the meta position, which increases the degree of freedom of the polyimide molecular chain and provides high flexibility, which is thought to contribute to improving the flexibility of the polyimide molecular chain. Therefore, the use of diamine (B2) enhances the thermoplasticity of the polyimide. Here, -O- is preferred as the linking group A.

[0086] Examples of the diamine (B2) include 1,4-bis(3-aminophenoxy)benzene, 3-[4-(4-aminophenoxy)phenoxy]benzenamine, and 3-[3-(4-aminophenoxy)phenoxy]benzenamine.

[0087] The diamine represented by formula (B3) (hereinafter sometimes referred to as "diamine (B3)") is an aromatic diamine having three benzene rings. This diamine (B3) has two divalent linking groups A directly bonded to one benzene ring, which are mutually meta-positioned. This increases the degree of freedom of the polyimide molecular chain, resulting in high flexibility, which is thought to contribute to improving the flexibility of the polyimide molecular chain. Therefore, the use of diamine (B3) enhances the thermoplasticity of the polyimide. Here, -O- is preferred as the linking group A.

[0088] Examples of 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.

[0089] The diamine represented by formula (B4) (hereinafter sometimes referred to as "diamine (B4)") is an aromatic diamine having four benzene rings. This diamine (B4) has high flexibility due to the presence of an amino group directly bonded to at least one benzene ring and a divalent linking group A at the meta position, which is thought to contribute to improving the flexibility of the polyimide molecular chain. Therefore, the use of diamine (B4) enhances the thermoplasticity of the polyimide. Here, the linking group A is preferably -O-, -CH2-, -C(CH3)2-, -SO2-, -CO-, or -CONH-.

[0090] 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.

[0091] The diamine represented by formula (B5) (hereinafter sometimes referred to as "diamine (B5)") is an aromatic diamine having four benzene rings. In this diamine (B5), two divalent linking groups A directly bonded to at least one benzene ring are located at meta positions relative to each other, which increases the degree of freedom of the polyimide molecular chain and provides high flexibility, which is thought to contribute to improving the flexibility of the polyimide molecular chain. Therefore, the use of diamine (B5) enhances the thermoplasticity of the polyimide. Here, -O- is preferred as the linking group A.

[0092] Examples of the diamine (B5) include 4-[3-[4-(4-aminophenoxy)phenoxy]phenoxy]aniline, 4,4'-[oxybis(3,1-phenyleneoxy)]bisaniline, and the like.

[0093] The diamine represented by formula (B6) (hereinafter sometimes referred to as "diamine (B6)") is an aromatic diamine having four benzene rings. This diamine (B6) has high flexibility due to the presence of at least two ether bonds, which is thought to contribute to improving the flexibility of the polyimide molecular chain. Therefore, the use of diamine (B6) enhances the thermoplasticity of the polyimide. Here, the linking group A is preferably -C(CH3)2-, -O-, -SO2-, or -CO-.

[0094] Examples of 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).

[0095] The diamine represented by formula (B7) (hereinafter sometimes referred to as "diamine (B7)") is an aromatic diamine having four benzene rings. This diamine (B7) has a highly flexible divalent linking group A on both sides of the diphenyl skeleton, which is thought to contribute to improving the flexibility of the polyimide molecular chain. Therefore, the use of diamine (B7) enhances the thermoplasticity of the polyimide. Here, -O- is preferred as the linking group A.

[0096] Examples of the diamine (B7) include bis[4-(3-aminophenoxy)]biphenyl, bis[4-(4-aminophenoxy)]biphenyl, and the like.

[0097] The thermoplastic polyimide constituting the thermoplastic polyimide layer 112 preferably contains 60 or more molar parts, preferably 60 to 99 molar parts, more preferably 70 to 95 molar parts, of diamine residues derived from at least one diamine compound selected from diamines (B1) to (B7) per 100 molar parts of all diamine residues. Because diamines (B1) to (B7) have flexible molecular structures, using at least one diamine compound selected from these compounds in the above-mentioned ranges improves the flexibility of the polyimide molecular chain and imparts thermoplasticity. If the total amount of diamines (B1) to (B7) in the raw materials is less than 60 molar parts per 100 molar parts of all diamine components, the polyimide resin will lack flexibility and will not exhibit sufficient thermoplasticity.

[0098] Furthermore, the diamine residue contained in the thermoplastic polyimide constituting the thermoplastic polyimide layer 112 is preferably a diamine residue derived from a diamine compound represented by general formula (1). The diamine compound represented by formula (1) [diamine (1)] is as described in the description of non-thermoplastic polyimides. Diamine (1) has a rigid structure and acts to impart an ordered structure to the entire polymer, thereby suppressing molecular motion and reducing the dielectric loss tangent and moisture absorption. Furthermore, when used as a raw material for thermoplastic polyimide, polyimides with low gas permeability and excellent long-term heat-resistant adhesiveness can be obtained.

[0099] The thermoplastic polyimide constituting the thermoplastic polyimide layer 112 may contain diamine residues derived from diamine (1) in an amount preferably in the range of 1 to 40 parts by mole, more preferably in the range of 5 to 30 parts by mole. By using diamine (1) in an amount within the above range, an ordered structure is formed throughout the polymer due to the rigid structure derived from the monomer, resulting in a polyimide that is thermoplastic yet has low gas permeability and moisture absorption and excellent long-term heat-resistant adhesiveness.

[0100] The thermoplastic polyimide constituting the thermoplastic polyimide layer 112 may contain diamine residues derived from diamine compounds other than diamines (1) and (B1) to (B7) within the scope that does not impair the effects of the invention.

[0101] In the thermoplastic polyimide, the thermal expansion coefficient, tensile modulus, glass transition temperature, etc. can be controlled by selecting the types of the tetracarboxylic acid residue and diamine residue, or by selecting the molar ratio of two or more types of tetracarboxylic acid residues or diamine residues. When the thermoplastic polyimide has a plurality of polyimide structural units, they may be present as blocks or randomly, but are preferably present randomly.

[0102] In addition, by making both the tetracarboxylic acid residue and the diamine residue contained in the thermoplastic polyimide aromatic groups, the dimensional accuracy of the polyimide film in a high-temperature environment can be improved and the amount of change in the in-plane retardation (RO) can be suppressed.

[0103] 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 molecular weight of the imide group (-(CO)2-N-) in the polyimide divided by the molecular weight of the entire polyimide structure. If the imide group concentration exceeds 33%, the molecular weight of the resin itself decreases, and the low moisture absorption property also deteriorates due to the increase in polar groups. By selecting the above combination of diamine compounds, the molecular orientation in the thermoplastic polyimide is controlled, thereby suppressing the increase in CTE that accompanies a decrease in the imide group concentration and ensuring low moisture absorption.

[0104] The weight-average molecular weight of the thermoplastic polyimide is preferably in the range of 10,000 to 400,000, and more preferably in the range of 50,000 to 350,000. If the weight-average molecular weight is less than 10,000, the film tends to have reduced strength and 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.

[0105] The thermoplastic polyimide constituting the thermoplastic polyimide layer 112 serves as an adhesive layer for, for example, the insulating resin of a circuit board, and therefore a completely imidized structure is most preferable in order to suppress copper diffusion. However, a portion of the polyimide may be in the form of an amic acid. The imidization rate can be determined by measuring the infrared absorption spectrum of the polyimide thin film by the single-reflection ATR method using a Fourier transform infrared spectrophotometer (commercially available: FT / IR620 manufactured by JASCO Corporation) and determining the imidization rate at 1015 cm -1 Based on the benzene ring absorber near 1780cm -1 It is calculated from the absorbance of the C=O stretching derived from the imide group.

[0106] From the viewpoint of ensuring adhesive properties, the thickness of the thermoplastic polyimide layer 112 is preferably in the range of 1 μm to 10 μm, more preferably in the range of 1 μm to 5 μm. If the thickness of the thermoplastic polyimide layer 112 is less than the lower limit, adhesiveness becomes insufficient, and if the thickness exceeds the upper limit, dimensional stability tends to deteriorate.

[0107] In order to suppress warping, the thermoplastic polyimide layer 112 should have a thermal expansion coefficient of 30 ppm / K or more, preferably in the range of 30 ppm / K to 100 ppm / K, and more preferably in the range of 30 ppm / K to 80 ppm / K.

[0108] In addition to polyimide, the resin used for the thermoplastic polyimide layer 112 may contain optional components such as plasticizers, other curable resin components such as epoxy resins, curing agents, curing accelerators, inorganic fillers, coupling agents, bulking agents, solvents, and flame retardants. However, some plasticizers contain many polar groups, which may promote the diffusion of copper from the copper wiring, so it is preferable to avoid using plasticizers as much as possible.

[0109] In order to ensure dimensional stability after circuit processing in the metal-clad laminate 100, the overall thermal expansion coefficient of the two polyimide layers 110 and the adhesive polyimide layer 120 should 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. 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 described in Figure 1.

[0110] (Polyimide synthesis) The polyimide constituting the polyimide layer 110 can be produced by reacting the acid anhydride and diamine in a solvent to form a precursor resin, followed by heating and ring-closing. For example, polyamic acid, a polyimide precursor, can be obtained by dissolving approximately equimolar amounts of the acid anhydride and diamine components in an organic solvent and stirring the mixture at a temperature ranging from 0 to 100°C for 30 minutes to 24 hours to cause polymerization. The reaction components are dissolved in the organic solvent so that the resulting precursor is present in an organic solvent at a concentration of 5 to 30 wt %, preferably 10 to 20 wt %. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide, N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone, 2-butanone, dimethyl sulfoxide, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, and triglyme. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. The amount of such an organic solvent to be used is not particularly limited, but it is preferable to adjust the amount so that the concentration of the polyamic acid solution (polyimide precursor solution) obtained by the polymerization reaction is about 5 to 30% by weight.

[0111] In the synthesis of polyimide, the above-mentioned acid anhydrides and diamines can be used singly or in combination of two or more. By selecting the types of acid anhydrides and diamines, or by selecting the respective molar ratios when two or more types of acid anhydrides or diamines are used, it is possible to control the thermal expansion, adhesiveness, glass transition temperature, etc.

[0112] The synthesized precursor is usually advantageously used as a reaction solvent solution, but can be concentrated, diluted, or replaced with another organic solvent as needed. Furthermore, the precursor is generally advantageously used because of its excellent solvent solubility. The method for imidizing the precursor is not particularly limited, and a suitable method is, for example, heat treatment in the solvent at a temperature in the range of 80 to 400°C for 1 to 24 hours.

[0113] [Circuit board] The metal-clad laminate 100 is useful primarily as a circuit board material for FPCs, rigid-flex circuit boards, and the like. That is, a circuit board such as an FPC, which is one embodiment of the present invention, can be manufactured by forming a wiring layer by patterning one or both of the two metal layers 101 of the metal-clad laminate 100 using a conventional method. Although not shown, this circuit board includes a resin laminate in which a first insulating resin layer (P1), an adhesive layer (B), and a second insulating resin layer (P2) are laminated in this order, and a wiring layer provided on one or both surfaces of the resin laminate. [Example]

[0114] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following examples, various measurements and evaluations were carried out according to the following methods unless otherwise specified.

[0115] [Measurement of dielectric constant and dielectric loss tangent] The dielectric constant (Dk) and dielectric loss tangent (Df) of the polyimide film at 10 GHz were measured using a vector network analyzer (Agilent, product name E8363C) and an SPDR resonator. The material used for the measurement was left for 24 hours under the conditions of temperature: 24-26°C and humidity: 45%-55% RH.

[0116] [Measurement of storage modulus and glass transition temperature (Tg)] The storage modulus of the adhesive layer was measured by peeling the adhesive layer (50 μm thick) from the substrate film, cutting it into a 5 mm x 20 mm piece, and heating it in an oven at 120°C for 2 hours and then at 170°C for 3 hours. The resulting sample was heated in stages from 30°C to 400°C at a heating rate of 4°C / min using a dynamic viscoelasticity analyzer (DMA: manufactured by UBM, product name: E4000F) at a frequency of 11 Hz. The maximum temperature at which Tanδ was maximized during the measurement was defined as Tg.

[0117] [Measurement of dimensional change rate] The dimensional change rate was measured using the following procedure. First, a 150 mm square test piece was used, and a dry film resist was exposed and developed at 100 mm intervals to form a position measurement target. The dimensions before etching (normal state) were measured in an atmosphere of 23±2°C and 50±5% relative humidity, and then the copper on the test piece other than the target was removed by etching (liquid temperature 40°C or less, time 10 minutes or less). After leaving the test piece in an atmosphere of 23±2°C and 50±5% relative humidity for 24±4 hours, the dimensions after etching were measured. The dimensional change rate relative to the normal state was calculated at three locations in the MD (longitudinal direction) and TD (transverse direction), and the average of these values ​​was used as the dimensional change rate after etching. The dimensional change rate after etching was calculated using the following formula.

[0118] Dimensional change rate after etching (%) = (BA) / A x 100 A: Target distance before etching B: Target distance after etching

[0119] Next, the test piece was heat-treated in an oven at 250°C for 1 hour, and the distance between the target positions was measured after that. The dimensional change rate after etching was calculated at three locations in each of the MD (longitudinal direction) and TD (transverse direction), and the average of these values ​​was used as the dimensional change rate after heat treatment. The dimensional change rate after heating was calculated using the following formula.

[0120] Dimensional change rate after heating (%) = (C-B) / B x 100 B: Target distance after etching C: Target distance after heating

[0121] The abbreviations used in the examples 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: Croda Japan Co., Ltd. (product name: PRIAMINE1075) 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: approximately 340) VG3101L: (trade name, manufactured by Printec Co., Ltd., multifunctional epoxy resin, epoxy equivalent: 210, softening point: 39 to 46°C) SR35K: (product name, manufactured by Printec Co., Ltd., epoxy resin, epoxy equivalent: 930-940, softening point: 86-98°C) YDCN-700-10: (trade name, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., cresol novolac epoxy resin, epoxy equivalent 210, softening point 75-85°C) Mirex XLC-LL: (Product name, manufactured by Mitsui Chemicals, phenolic resin, hydroxyl equivalent: 175, softening point: 77°C, water absorption: 1% by mass, heating mass loss rate: 4% by mass) HE200C-10: (trade name, manufactured by Air Water Inc., phenolic resin, hydroxyl equivalent: 200, softening point: 65 to 76°C, water absorption: 1% by mass, heat mass loss: 4% by mass) HE910-10: (trade name, manufactured by Air Water Inc., phenolic resin, hydroxyl equivalent: 101, softening point: 83°C, water absorption rate: 1% by mass, heat mass loss rate: 3% by mass) SC1030-HJA: (product name, manufactured by Admatechs Co., Ltd., silica filler dispersion, average particle size: 0.25 μm) Aerosil R972: (trade name, manufactured by Nippon Aerosil Co., Ltd., silica, average particle size: 0.016 μm) Acrylic rubber HTR-860P-30B-CHN: (sample name, manufactured by Teikoku Chemical Industries Co., Ltd., weight average molecular weight: 230,000, glycidyl functional group monomer ratio: 8%, Tg: -7°C) Acrylic rubber HTR-860P-3CSP: (sample name, manufactured by Teikoku Chemical Industries Co., Ltd., weight average molecular weight: 800,000, glycidyl functional group monomer ratio: 3%, Tg: -7°C) A-1160: (trade name, manufactured by GE Toshiba Corporation, γ-ureidopropyltriethoxysilane) A-189: (trade name, manufactured by GE Toshiba Corporation, γ-mercaptopropyltrimethoxysilane) Curesol 2PZ-CN: (trade name, manufactured by Shikoku Chemicals Corporation, 1-cyanoethyl-2-phenylimidazole) RE-810NM: (trade name, manufactured by Nippon Kayaku Co., Ltd., diallyl bisphenol A diglycidyl ether, liquid form) Foret SCS: (trade name, manufactured by Soken Chemical & Engineering Co., Ltd., styryl group-containing acrylic polymer, Tg: 70°C, weight-average molecular weight: 15,000) 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: (Product name, manufactured by Mizushima Ferroalloy Co., Ltd., boron nitride filler) NMP: (N-methyl-2-pyrrolidone, manufactured by Kanto Chemical Co., Ltd.)

[0122] (Synthesis Example 1) <Preparation of Resin Solution A for Adhesive Layer> Cyclohexanone was added and stirred to a composition consisting of (a) epoxy resin and phenolic resin as thermosetting resins, and (c) inorganic filler, with the product names and composition ratios (unit: parts by mass) shown in Table 1. To this was added (b) acrylic rubber as a high molecular weight component shown in Table 1 and stirred, and then (e) coupling agent and (d) curing accelerator shown in Table 1 were added and stirred until the components were uniform, yielding resin solution A for the adhesive layer.

[0123] [Table 1]

[0124] (Synthesis Example 2) <Synthesis of polyimide resin (PI-1) and preparation of resin solution B for adhesive layer> A 300 mL flask equipped with a thermometer, stirrer, condenser, and nitrogen inlet tube was charged with 15.53 g of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (Shin-Etsu Chemical Co., Ltd., trade name: LP-7100), 28.13 g of polyoxypropylenediamine (BASF Ltd., trade name: D400, molecular weight: 450), and 100.0 g of NMP and stirred to prepare a reaction solution. After the diamine dissolved, the flask was cooled in an ice bath, and 32.30 g of 4,4'-oxydiphthalic dianhydride, previously purified by recrystallization from acetic anhydride, was added in small portions to the reaction solution. After 8 hours of reaction at room temperature (25°C), 67.0 g of xylene was added, and the mixture was heated to 180°C while blowing in nitrogen gas, thereby azeotropically removing the xylene and water. The reaction mixture was poured into a large amount of water, and the precipitated resin was collected by filtration and dried to obtain polyimide resin (PI-1). The molecular weight of the resulting polyimide resin (PI-1) was measured by GPC, and the number average molecular weight (Mn) was 22,400 and the weight average molecular weight (Mw) was 70,200, in terms of polystyrene. Using the polyimide resin (PI-1) obtained above, each component was blended in the composition ratio (unit: parts by mass) shown in Table 2 to obtain a resin solution B for adhesive layer.

[0125] [Table 2]

[0126] (Synthesis Example 3) <Preparation of polyamic acid solution for insulating resin layer> Under a nitrogen atmosphere, 64.20 g of m-TB (0.302 mol), 5.48 g of bisaniline-M (0.016 mol), and DMAc (to a solids concentration of 15 wt%) were added to the reaction vessel and stirred at room temperature. Next, 34.20 g of PMDA (0.157 mol) and 46.13 g of BPDA (0.157 mol) were added, and the mixture was stirred at room temperature for 3 hours to polymerize the mixture, yielding polyamic acid solution 1 (viscosity: 26,500 cps).

[0127] (Synthesis Example 4) <Preparation of polyamic acid solution for insulating resin layer> Polyamic acid solution 2 (viscosity: 2,650 cps) was prepared in the same manner as in Synthesis Example 3, except that the raw material composition was changed to 69.56 g of m-TB (0.328 mol), 542.75 g of TPE-R (1.857 mol), DMAc in an amount such that the solids concentration after polymerization would be 12 wt %, 194.39 g of PMDA (0.891 mol), and 393.31 g of BPDA (1.337 mol).

[0128] (Production Example 1) <Preparation of Resin Sheet A for Adhesive Layer> Resin solution A for the adhesive layer was applied to the silicone-treated surface of a release substrate (length x width x thickness = 320 mm x 240 mm x 25 μm) so that the thickness after drying was 50 μm, and then heated and dried at 80 ° C for 15 minutes, and then further dried at 120 ° C for 15 minutes, after which it was peeled off from the release substrate to prepare resin sheet A. In addition, to evaluate the physical properties after curing, resin sheet A was heated in an oven at 120 ° C for 2 hours and at 170 ° C for 3 hours. At this time, the cured resin sheet A had a Tg of 95 ° C, a storage modulus of 960 MPa at 50 ° C, and a maximum storage modulus of 7 MPa from 180 ° C to 260 ° C.

[0129] (Production Example 2) <Preparation of Resin Sheet B for Adhesive Layer> Resin solution B for the adhesive layer was applied to the silicone-treated surface of a release substrate (length x width x thickness = 320 mm x 240 mm x 25 μm) so that the thickness after drying was 50 μm, and then heated and dried at 80 ° C for 15 minutes, and then further dried at 120 ° C for 15 minutes, after which it was peeled off from the release substrate to prepare resin sheet B. Resin sheet B was also heated in an oven at 120 ° C for 2 hours and at 170 ° C for 3 hours to evaluate its physical properties after curing. At this time, the cured resin sheet B had a Tg of 100 ° C or less, a storage modulus of 1800 MPa or less at 50 ° C, and a maximum storage modulus of 70 MPa from 180 ° C to 260 ° C.

[0130] (Production Example 3) <Preparation of single-sided metal-clad laminate> Polyamic acid solution 2 was uniformly applied onto copper foil 1 (electrolytic copper foil, thickness: 12 μm, surface roughness Rz on the resin layer side: 0.6 μm) to a thickness of approximately 2 to 3 μm after curing, and then heated and dried at 120°C to remove the solvent. Next, polyamic acid solution 1 was uniformly applied onto the copper foil 1 to a thickness of approximately 21 μm after curing, and then heated and dried at 120°C to remove the solvent. Polyamic acid solution 2 was further uniformly applied onto the copper foil 1 to a thickness of approximately 2 to 3 μm after curing, and then heated and dried at 120°C to remove the solvent. Further, stepwise heat treatment was performed from 120°C to 360°C to complete the imidization, and single-sided metal-clad laminate 1 was prepared. The dimensional change rate of single-sided metal-clad laminate 1 was as follows. Dimensional change rate after etching in MD (longitudinal) direction: 0.01% Dimensional change rate after etching in the transverse direction (TD): -0.04% Dimensional change rate after heating in MD (longitudinal) direction: -0.03% Dimensional change rate after heating in TD direction (transverse direction): -0.01%

[0131] <Preparation of Polyimide Film> The copper foil 1 of the single-sided metal-clad laminate 1 was etched away using an aqueous ferric chloride solution to prepare a polyimide film 1 (thickness: 25 μm, CTE: 20 ppm / K, Dk: 3.40, Df: 0.0029).

[0132] [Example 1] Two single-sided metal-clad laminates 1 were prepared, and the insulating resin layer side of each was overlapped on both sides of resin sheet A, and the sheets were pressed together at 180°C for 2 hours under a pressure of 3.5 MPa to prepare metal-clad laminate 1. The evaluation results of metal-clad laminate 1 were as follows. Dimensional change rate after etching in MD direction: -0.02% Dimensional change rate after etching in the TD direction: -0.03% Dimensional change rate after heating in MD direction: -0.02% Dimensional change rate after heating in the TD direction: -0.02% There was no warpage and no problem with dimensional change in the metal-clad laminate 1. Furthermore, the CTE of the resin laminate 1 (thickness: 100 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 1 was 24.1 ppm / K.

[0133] [Example 2] Two single-sided metal-clad laminates 1 were prepared, and the insulating resin layer side of each was overlapped on both sides of resin sheet B, and the laminates were pressed together 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 the TD direction: -0.05% Dimensional change rate after heating in MD direction: -0.03% Dimensional change rate after heating in the TD direction: -0.04% There was no warpage and no problem with dimensional change in the metal-clad laminate 2. Furthermore, the CTE of the resin laminate 2 (thickness: 100 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 2 was 23.3 ppm / K.

[0134] (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., product name: adhesive perfluororesin EA-2000, thickness: 50 μm, Tm: 303°C, Tg: none) was used instead of resin sheet A and was pressed at 320°C for 5 minutes under a pressure of 3.5 MPa. The evaluation results of the metal-clad laminate 3 are as follows. Dimensional change rate after etching in MD direction: -0.11% Dimensional change rate after etching in the TD direction: -0.13% Dimensional change rate after heating in MD direction: -0.19% Dimensional change rate after heating in the TD direction: -0.20% There was no warpage and no problem with dimensional change in the metal-clad laminate 3. Furthermore, the CTE of the resin laminate 3 (thickness: 100 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 3 was 27.6 ppm / K.

[0135] (Reference example 1) Copper foil 1, resin sheet A, polyimide film 1, resin sheet A and copper foil 1 were stacked in this order and pressure-bonded at 180° C. for 2 hours under a pressure of 3.5 MPa to prepare 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 the TD direction: -0.05% Dimensional change rate after heating in MD direction: -0.12% Dimensional change rate after heating in the TD direction: -0.14% There was no warping and no problem with dimensional change in the metal-clad laminate 4. Furthermore, the CTE of the resin laminate 4 (thickness: 100 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 4 was 23.9 ppm / K.

[0136] It can be seen that Examples 1 and 2 have lower dimensional change rates after etching and heating than Comparative Example 1 and Reference Example 1, respectively. In Comparative Example 1, lamination by thermocompression bonding at 320°C was performed without any problems in adhesion, but sufficient adhesion could not be obtained by thermocompression bonding under the same conditions as Examples 1 and 2 (temperature: 180°C, time: 2 hours, pressure: 3.5 MPa). Reference Example 1 was also performed to verify the positional configuration of resin sheet A.

[0137] [Example 3] A single-sided metal-clad laminate 1 was prepared, and resin solution A for the adhesive layer was applied to the surface on the insulating resin layer side so that the thickness after drying would be 50 μm.Then, the laminate was heated and dried at 80°C for 15 minutes, and then further dried at 120°C for 15 minutes to prepare a single-sided metal-clad laminate 1 with an adhesive layer. Next, the adhesive layer side of the single-sided metal-clad laminate 1 with adhesive layer was overlapped with the insulating resin layer side of another single-sided metal-clad laminate 1, and then the laminate was pressed together 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 MD direction: -0.03% Dimensional change rate after etching in the TD direction: -0.03% Dimensional change rate after heating in MD direction: -0.02% Dimensional change rate after heating in the TD direction: -0.02% The metal-clad laminate 1' was free from warpage and had no problem with dimensional change. The CTE of the resin laminate 1' (thickness: 100 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 1' was 23.1 ppm / K.

[0138] [Example 4] Two single-sided metal-clad laminates 1 with adhesive layers were prepared, and after the adhesive layer faces were placed together, 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 MD direction: -0.03% Dimensional change rate after etching in the TD direction: -0.03% Dimensional change rate after heating in MD direction: -0.03% Dimensional change rate after heating in the TD direction: -0.03% There was no warping and no problem with dimensional change in the metal-clad laminate 5. Furthermore, the CTE of the resin laminate 5 (thickness: 150 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 5 was 23.8 ppm / K.

[0139] [Example 5] A single-sided metal-clad laminate 1 was prepared, and resin solution A for the adhesive layer was applied to the surface on the insulating resin layer side so that the thickness after drying would be 75 μm.Then, it was heated and dried at 80°C for 15 minutes, and then further dried 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 adhesive layers were prepared, and after the adhesive layer faces were placed together, 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 the TD direction: -0.01% Dimensional change rate after heating in MD direction: 0.01% Dimensional change rate after heating in the TD direction: 0.02% There was no warpage in the metal-clad laminate 6, and no problem with dimensional change. The CTE of the resin laminate 6 (thickness: 200 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 6 was 22.8 ppm / K.

[0140] (Synthesis Example 5) Under a nitrogen stream, 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 charged into a 500 ml separable flask and mixed thoroughly at 40°C for 30 minutes to prepare a polyamic acid solution. This polyamic acid solution was heated to 190°C and stirred for 4.5 hours, after which 112 g of xylene was added to complete the imidization, preparing polyimide adhesive solution 1. The solids content of the resulting polyimide adhesive solution 1 was 29.1 wt% and the viscosity was 7,800 cps. The weight-average molecular weight (Mw) of the polyimide was 87,700.

[0141] (Synthesis Example 6) 34.4 g (10 g as solid content) 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 the mixture was diluted with 1.297 g of NMP and 3.869 g of xylene to prepare resin solution C for the adhesive layer.

[0142] <Preparation of Resin Sheet C for Adhesive Layer> Resin solution C for the adhesive layer was applied to the silicone-treated surface of a release substrate (length x width x thickness = 320 mm x 240 mm x 25 μm) so that the thickness after drying was 50 μm, and then heated and dried at 80 ° C for 15 minutes, and then further dried at 120 ° C for 15 minutes, after which it was peeled off from the release substrate to prepare resin sheet C. In addition, 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 cured resin sheet D. The cured resin sheet D had a Tg of 95 ° C, a storage modulus of 1220 MPa at 50 ° C, and a maximum storage modulus of 26 MPa from 180 ° C to 260 ° C.

[0143] [Example 6] A single-sided metal-clad laminate 1 was prepared, and resin solution C for the adhesive layer was applied to the surface on the insulating resin layer side so that the thickness after drying would be 50 μm.Then, it was heated and dried at 80°C for 15 minutes, and then further dried at 120°C for 15 minutes to prepare a single-sided metal-clad laminate 3 with an adhesive layer. Next, the adhesive layer side of the adhesive layer-attached single-sided metal-clad laminate 3 was placed on the insulating resin layer side of the single-sided metal-clad laminate 1, and then the two were pressed together at 180°C for 2 hours under a pressure of 3.5 MPa to prepare the metal-clad laminate 7. The evaluation results of the metal-clad laminate 7 are as follows. Dimensional change rate after etching in MD direction: -0.02% Dimensional change rate after etching in the TD direction: -0.02% Dimensional change rate after heating in MD direction: -0.03% Dimensional change rate after heating in the TD direction: -0.03% There was no warpage and no problem with dimensional change in the metal-clad laminate 7. Furthermore, the CTE of the resin laminate 7 (thickness: 100 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 7 was 23.4 ppm / K.

[0144] Furthermore, any of the single-sided metal-clad laminates with adhesive layers described in the examples can be applied to the production of multilayer circuit boards, and in this case, it is considered preferable that the thickness of the adhesive layer is 100 μm or less and that the thickness ratio of the adhesive layer in the insulating resin layer is 80% or less.

[0145] Although the embodiments of the present invention have been described in detail above for the purpose of illustration, the present invention is not limited to the above-described embodiments and various modifications are possible. [Explanation of symbols]

[0146] 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

Claims

1. a first single-sided metal-clad laminate having a first metal layer and a first insulating resin layer laminated on at least one surface 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 surface of the second metal layer; an adhesive layer disposed so as to contact 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 first insulating resin layer and the second insulating resin layer each have a multilayer structure in which a thermoplastic polyimide layer, a non-thermoplastic polyimide layer, and a thermoplastic polyimide layer are laminated in this order; the adhesive layer is provided in contact with the two thermoplastic polyimide layers, Steps 1 to 3 below: Process 1: providing the first single-sided metal-clad laminate and the second single-sided metal-clad laminate; Step 2: a step of laminating a resin layer serving as an adhesive layer made of a thermoplastic resin or a thermosetting resin on either or both of the first insulating resin layer and the second insulating resin layer; Step 3: After step 2, a step of bonding the first single-sided metal-clad laminate and the second single-sided metal-clad laminate together via the adhesive layer so that their insulating resin layers face each other, and thermocompression bonding the first single-sided metal-clad laminate and the second single-sided metal-clad laminate; Equipped with The adhesive layer is made of a thermoplastic resin or a thermosetting resin, and meets the following conditions (i) to (iii): (i) a storage modulus at 50°C of 1220 MPa or less; (ii) the maximum storage modulus in the temperature range of 180°C to 260°C is 26 MPa or less; (iii) a glass transition temperature (Tg) of 95°C or less; A method for producing a metal-clad laminate, characterized in that

2. 2. The method for producing a metal-clad laminate according to claim 1, wherein the resin layer in step 2 is a coating film obtained by coating and drying a thermoplastic resin, a thermosetting resin, or a resin solution thereof.

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