Metal-clad laminate and circuit board

Abstract

A metal-clad laminate includes a first single-sided metal-clad laminate having a first metal layer and a first insulating resin layer laminated on a surface of at least one side of the first metal layer, a second single-sided metal-clad laminate having a second metal layer and a second insulating resin layer laminated on a surface of at least one side of the second metal layer, and an adhesive layer disposed in abutment with the first and second insulating resin layers and laminated between the first and second single-sided metal-clad laminates. The adhesive layer is composed of a thermoplastic resin or a thermosetting resin, satisfies (i) a storage elastic modulus at 50°C is 1800 MPa or less, (ii) a maximum value of a storage elastic modulus in a temperature range of 180°C to 260°C is 800 MPa or less, and (iii) a glass transition temperature is 180°C or less. The first and second insulating resin layers 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, and the adhesive layer is disposed in contact with the two thermoplastic polyimide layers.

Description

[0001] This application is a divisional application of the patent application No. 201910885101.4 with the title of "Metal-clad laminate and circuit board" filed on September 19, 2019. TECHNICAL FIELD

[0002] The present application relates to a metal-clad laminate and a circuit board useful as an electronic component. BACKGROUND

[0003] In recent years, along with the progress of miniaturization, weight reduction, and space saving of electronic devices, the demand for flexible printed wiring boards (Flexible Printed Circuits (FPCs)) that are thin and light, have flexibility, and have excellent durability even when repeatedly bent has increased. With respect to FPCs, three-dimensional and high-density mounting can be achieved even in limited spaces, and thus its use has gradually expanded, for example, in wiring of movable parts of electronic devices such as Hard Disk Drives (HDDs), Digital Video Discs (DVDs), smartphones, or the like, or in parts such as cables, connectors, and the like.

[0004] In addition to the high densification described above, the high performance of devices is being promoted, and thus the handling of high frequency of transmitted signals is also required. When high frequency signals are transmitted, in the case where the transmission loss in the transmission path is large, adverse situations such as loss of electric signals or lengthening of the signal delay time occur. Therefore, in the future, the reduction of transmission loss also becomes important in FPCs. In order to cope with high frequency signal transmission, FPCs using liquid crystal polymers having lower dielectric constant and lower dielectric loss factor as dielectric layers are used instead of polyimides, which are generally used as FPC materials. However, although liquid crystal polymers have excellent dielectric properties, there is room for improvement in heat resistance or adhesion to metal layers.

[0005] In addition, fluorine-based resins are also known as polymers that exhibit low dielectric constant and low dielectric loss factor. For example, as an FPC material capable of coping with high frequency signal transmission and having excellent adhesion, an insulating film in which a thermoplastic polyimide layer and a high heat-resistant polyimide layer are respectively attached to both surfaces of a fluorine-based resin layer has been proposed (Patent Literature 1). The insulating film of Patent Literature 1 is excellent in dielectric properties because a fluorine-based resin is used, but there is a problem in dimensional stability, and in particular, when applied to FPCs, there is a concern that the dimensional change before and after circuit processing due to etching becomes large. Therefore, it is difficult to increase the thickness of the fluorine-based resin and to increase the thickness ratio.

[0006] Also, as a technology related to an adhesive layer used in electronic materials, a resin composition containing an epoxy resin and a phenoxy resin or a resin composition containing a thermoplastic polyimide and a maleimide compound or the like has been proposed for use in an adhesive sheet (Patent Literature 2, Patent Literature 3). The film-shaped adhesive sheet of Patent Literature 2 and Patent Literature 3 has the advantage of having a low glass transition temperature and exhibiting high adhesion to a laminated material. However, in Patent Literature 2 and Patent Literature 3, the possibility of application to high-frequency signal transmission or the application to an adhesive layer of a metal-clad laminate has not been studied.

[0007] [Related Art Documents]

[0008] [Patent Literature]

[0009] [Patent Literature 1] Japanese Patent Application Laid-Open (JP A) No. 2017-24265

[0010] [Patent Literature 2] Japanese Patent (JP B) No. 6191800

[0011] [Patent Literature 3] Japanese Patent (JP B) No. 5553108 SUMMARY

[0012] [Problems to be Solved by the Invention]

[0013] An object of the present application is to provide a metal-clad laminate and a circuit board which can reduce transmission loss even in high-frequency transmission and which are excellent in dimensional stability.

[0014] [Means of Solving the Problems]

[0015] The present inventors made diligent studies and as a result, found that the problems can be solved by using an adhesive layer having a low glass transition temperature and a low elastic modulus in a metal-clad laminate, thereby completing the present application.

[0016] The metal-clad laminate of the present application is a metal-clad laminate including:

[0017] a first single-sided metal-clad laminate having a first metal layer and a first insulating resin layer laminated on at least one side of the first metal layer;

[0018] a second single-sided metal-clad laminate having a second metal layer and a second insulating resin layer laminated on at least one side of the second metal layer; and

[0019] an adhesive layer disposed so as to abut the first insulating resin layer and the second insulating resin layer, laminated between the first single-sided metal-clad laminate and the second single-sided metal-clad laminate.

[0020] In the metal-clad laminate of the present application, the adhesive layer is composed of a thermoplastic resin or a thermosetting resin, and satisfies the following conditions (i) to (iii):

[0021] (i) the storage elastic modulus at 50°C is 1800 MPa or less;

[0022] (ii) the maximum value of the storage elastic modulus in the temperature range of 180°C to 260°C is 800 MPa or less;

[0023] (iii) the glass transition temperature (Tg) is 180°C or less.

[0024] In the metal-clad laminate of the present application, 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 sequentially stacked, and the adhesive layer is disposed in contact with both of the thermoplastic polyimide layers.

[0025] In the metal-clad laminate of the present application, the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer contains a tetracarboxylic acid residue and a diamine residue, and the content of the diamine residue derived from a diamine compound represented by the following general formula (1) with respect to 100 mol of the total diamine residue is 80 mol or more.

[0026] [Chem. 1]

[0027]

[0028] In formula (1), the linking group Z represents a single bond or -COO-, Y independently represents a halogen atom or a monovalent hydrocarbon having 1 to 3 carbons which can be substituted with a phenyl group, or an alkoxy group having 1 to 3 carbons, or a perfluoroalkyl group having 1 to 3 carbons, or an alkenyl group, n represents an integer of 0 to 2, and p and q independently represent an integer of 0 to 4.

[0029] In the metal-clad laminate of the present application, the thermal expansion coefficient of the entirety of the first insulating resin layer, the adhesive layer, and the second insulating resin layer can be in the range of 10 ppm / K or more and 30 ppm / K or less.

[0030] In the metal-clad laminate of the present application, the first metal layer and the second metal layer can each contain a copper foil.

[0031] The circuit substrate of the present application is formed by processing the first metal layer and / or the second metal layer of any of the metal-clad laminates into a wiring.

[0032] [Effects of the Invention]

[0033] The metal-clad laminate of the present application can increase the thickness of the insulating resin layer and ensure dimensional stability by having an adhesive layer with specific parameters interposed between two single-sided metal-clad laminates. In addition, when used in a circuit substrate or the like that transmits high-frequency signals of 10 GHz or more, transmission loss can be reduced. Thus, reliability and yield can be improved in the circuit substrate. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a schematic diagram showing the configuration of a metal-clad laminate according to an embodiment of the present application.

[0035] Figure 2 is a schematic cross-sectional view showing the configuration of a metal-clad laminate according to a preferred embodiment of the present application.

[0036] [Explanation of Symbols]

[0037] 100: Metal-clad laminate

[0038] 101: Metal layer

[0039] 110: Polyimide layer

[0040] 111: Non-thermoplastic polyimide layer

[0041] 112: Thermoplastic polyimide layer

[0042] 120: Adhesive polyimide layer

[0043] 130: Single-sided metal-clad laminate

[0044] B: Adhesive layer

[0045] C: Metal-clad laminate

[0046] C1: First single-sided metal-clad laminate

[0047] C2: Second single-sided metal-clad laminate

[0048] M1: First metal layer

[0049] M2: Second metal layer

[0050] P1: First insulating resin layer

[0051] P2: Second insulating resin layer

[0052] T1: Total thickness

[0053] T2, T3: Thickness DETAILED DESCRIPTION

[0054] An embodiment of the present application will be described with reference to the accompanying drawings.

[0055] [metal-clad laminate]

[0056] Figure 1 is a schematic view showing the constitution of a metal-clad laminate according to an embodiment of the present application. The metal-clad laminate (C) according to the present embodiment has a structure in which a pair of single-sided metal-clad laminates are attached by an adhesive layer (B). That is, the metal-clad laminate (C) includes a first single-sided metal-clad laminate (Cl), a second single-sided metal-clad laminate (C2), and an adhesive layer (B) laminated between the first single-sided metal-clad laminate (Cl) and the second single-sided metal-clad laminate (C2). Here, the first single-sided metal-clad laminate (Cl) has a first metal layer (Ml) and a first insulating resin layer (Pl) laminated on at least one side of the first metal layer (Ml). The second single-sided metal-clad laminate (C2) has a second metal layer (M2) and a second insulating resin layer (P2) laminated on at least one side of the second metal layer (M2). Further, the adhesive layer (B) is disposed so as to abut against the first insulating resin layer (Pl) and the second insulating resin layer (P2). That is, the metal-clad laminate (C) has a structure in which a first metal layer (Ml) / a first insulating resin layer (Pl) / an adhesive layer (B) / a second insulating resin layer (P2) / a second metal layer (M2) are laminated in this order. The first metal layer (Ml) and the second metal layer (M2) are located at the outermost sides, and the first insulating resin layer (Pl) and the second insulating resin layer (P2) are disposed inside them, and further, the adhesive layer (B) is disposed so as to be interposed between the first insulating resin layer (Pl) and the second insulating resin layer (P2).

[0057] [Single-sided metal-clad laminate]

[0058] The constitution of the pair of single-sided metal-clad laminates (Cl, C2) is not particularly limited, and as a material for an FPC, a general material can be used, and a commercially available copper-clad laminate or the like can also be used. Further, the constitution of the first single-sided metal-clad laminate (Cl) and the second single-sided metal-clad laminate (C2) can be the same or different.

[0059] [metal layer]

[0060] The material for the first metal layer (Ml) and the second metal layer (M2) is not particularly limited, and for example, copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof, or the like can be mentioned. Among them, copper or a copper alloy is particularly preferable. Further, the material for the wiring layer in the circuit substrate according to the present embodiment described later is also the same as the first metal layer (Ml) and the second metal layer (M2).

[0061] The thickness of the first metal layer (M1) and the second metal layer (M2) is not particularly limited, and for example, in the case of using a metal foil such as a copper foil, it is preferably 35 μm or less, and more preferably in the range of 5 μm to 25 μm. From the viewpoint of production stability and handling properties, the lower limit of the thickness of the metal foil is preferably set to 5 μm. Furthermore, in the case of using a copper foil, it can be a rolled copper foil or an electrolytic copper foil. In addition, as the copper foil, a commercially available copper foil can be used.

[0062] In addition, the metal foil can also be subjected to surface treatment with, for example, a plate wall, an aluminum alcoholate, an aluminum chelate, a silane coupling agent, or the like for the purpose of rust prevention treatment or improvement of adhesion.

[0063] (insulating resin layer)

[0064] As the first insulating resin layer (P1) and the second insulating resin layer (P2), any resin having electrical insulation can be used, and there is no particular limitation, and for example, polyimide, epoxy resin, phenol resin, polyethylene, polypropylene, polytetrafluoroethylene, silicone, ethyl tetrafluoroethylene (ETFE), or the like can be exemplified, but it is preferably composed of polyimide. In addition, the first insulating resin layer (P1) and the second insulating resin layer (P2) are not limited to a single layer, and can be a layer in which a plurality of resin layers are laminated. Furthermore, in the case where polyimide is mentioned in the present application, in addition to polyimide, it means a resin including polyamide-imide, polyether-imide, polyester-imide, polysiloxane-imide, polybenzimidazole-imide, and the like, which are polymers having an imide group in the molecular structure.

[0065] <adhesive layer>

[0066] The adhesive layer (B) is composed of a thermoplastic resin or a thermosetting resin, and satisfies (i) a storage elastic modulus at 50°C of 1800 MPa or less, (ii) a maximum value of the storage elastic modulus in the range of 180°C to 260°C of 800 MPa or less, and (iii) a glass transition temperature (Tg) of 180°C or less. As the resin, for example, polyimide resin, polyamide resin, epoxy resin, phenoxy resin, acrylic resin, polyurethane resin, styrene resin, polyester resin, phenol resin, polysulfone resin, polyether sulfone resin, polyphenylene sulfide resin, polyethylene resin, polypropylene resin, silicone resin, polyether ketone resin, polyvinyl alcohol resin, polyvinyl butyral resin, styrene-maleimide copolymer, maleimide-vinyl compound copolymer or (meth) acrylic copolymer, benzoxazine resin, bismaleimide resin, cyanate ester resin, and the like can be exemplified, and among these resins, a material satisfying conditions (i) to (iii) or designed in such a manner as to satisfy conditions (i) to (iii) can be selected and used in the adhesive layer (B).

[0067] In the case where the adhesive layer (B) is a thermally hardenable resin, an organic peroxide, a hardening agent, a hardening accelerator, or the like can be contained, and a hardening agent and a hardening accelerator, or a catalyst and a cocatalyst can be used in combination as needed. The amount of addition of the hardening agent, the hardening accelerator, the catalyst, the cocatalyst, and the organic peroxide, and the presence or absence of the addition can be determined within a range in which the conditions (i) to (iii) can be ensured.

[0068] <Layer thickness>

[0069] In the metal-clad laminate (C), when the total thickness of the first insulating resin layer (Pl) and the adhesive layer (B) and the second insulating resin layer (P2) is set as Tl, the total thickness Tl is preferably in a range of 70 μm to 500 μm, more preferably in a range of 100 μm to 300 μm. If the total thickness Tl is less than 70 μm, the effect of reducing the transmission loss when the circuit board is manufactured is insufficient, and if it exceeds 500 μm, the productivity can be decreased.

[0070] Further, the thickness T2 of the adhesive layer (B) is preferably in a range of 50 μm to 450 μm, more preferably in a range of 50 μm to 250 μm, for example. If the thickness T2 of the adhesive layer (B) does not satisfy the lower limit value, the transmission loss can be increased as a high-frequency substrate. On the other hand, if the thickness of the adhesive layer (B) exceeds the upper limit value, adverse conditions such as a decrease in dimensional stability can be caused.

[0071] Further, the ratio (T2 / Tl) of the thickness T2 of the adhesive layer (B) to the total thickness Tl is preferably in a range of 0.5 to 0.8, more preferably in a range of 0.5 to 0.7. If the ratio (T2 / Tl) is less than 0.5, it is difficult to set Tl to be 70 μm or more, and if it exceeds 0.8, adverse conditions such as a decrease in dimensional stability can be caused.

[0072] The thickness T3 of each of the first insulating resin layer (Pl) and the second insulating resin layer (P2) is preferably in a range of 12 μm to 100 μm, more preferably in a range of 12 μm to 50 μm, for example. If the thickness T3 of each of the first insulating resin layer (Pl) and the second insulating resin layer (P2) does not satisfy the lower limit value, problems such as warping of the metal-clad laminate (C) can be caused. If the thickness T3 of each of the first insulating resin layer (Pl) and the second insulating resin layer (P2) exceeds the upper limit value, adverse conditions such as a decrease in productivity can be caused. Further, the first insulating resin layer (Pl) and the second insulating resin layer (P2) can not necessarily have the same thickness.

[0073] <Thermal expansion coefficient>

[0074] The coefficient of thermal expansion (CTE) of the first insulating resin layer (P1) and the second insulating resin layer (P2) can be 10 ppm / K or more, preferably in the range of 10 ppm / K or more and 30 ppm / K or less, and more preferably in the range of 15 ppm / K or more and 25 ppm / K or less. If the CTE is less than 10 ppm / K or exceeds 30 ppm / K, warping or a decrease in dimensional stability can occur. By appropriately changing the combination, thickness, drying, and hardening conditions of the raw materials used, a polyimide layer having a desired CTE can be produced.

[0075] The adhesive layer (B) is high in thermal expansion, low in elasticity, and low in glass transition temperature, and thus can moderate internal stress generated at the time of lamination even if the CTE exceeds 30 ppm / K.

[0076] In addition, the coefficient of thermal expansion (CTE) of the entire first insulating resin layer (P1), adhesive layer (B), and second insulating resin layer (P2) can be 10 ppm / K or more, preferably in the range of 10 ppm / K or more and 30 ppm / K or less, and more preferably in the range of 15 ppm / K or more and 25 ppm / K or less. If the CTE of the entire resin layer is less than 10 ppm / K or exceeds 30 ppm / K, warping or a decrease in dimensional stability can occur.

[0077] < Glass Transition Temperature (Tg) >

[0078] The glass transition temperature (Tg) of the adhesive layer (B) is 180°C or lower, and can be preferably in the range of 160°C or lower. By setting the glass transition temperature of the adhesive layer (B) to 180°C or lower, thermal compression bonding at low temperatures can be performed, and thus internal stress generated at the time of lamination can be moderated, and dimensional changes after circuit processing can be suppressed. If the Tg of the adhesive layer (B) exceeds 180°C, the temperature at the time of adhesion with the first insulating resin layer (P1) and the second insulating resin layer (P2) interposed therebetween becomes high, and dimensional stability after circuit processing can be impaired.

[0079] < Storage Elastic Modulus >

[0080] The storage elastic modulus of the adhesive layer (B) at 50°C is 1800 MPa or less, and the maximum value of the storage elastic modulus in the temperature range of 180°C to 260°C is 800 MPa or less. It is considered that the characteristics of the adhesive layer (B) are the main reason for relaxing internal stress at the time of heat pressing and maintaining dimensional stability after circuit processing. In addition, the storage elastic modulus of the adhesive layer (B) at the upper limit temperature (260°C) of the temperature range is preferably 800 MPa or less, and more preferably in the range of 500 MPa or less. By setting the storage elastic modulus, warping is less likely to occur even after a reflow soldering step after circuit processing.

[0081] <Medium Loss Factor>

[0082] The first insulating resin layer (P1) and the second insulating resin layer (P2) can have a medium loss factor (Tan δ) at 10 GHz of preferably 0.02 or less, more preferably in the range of 0.0005 or more and 0.01 or less, and further preferably in the range of 0.001 or more and 0.008 or less, for example, in the case of being applied to a circuit substrate, in order to suppress deterioration of dielectric loss. If the medium loss factor at 10 GHz of the first insulating resin layer (P1) and the second insulating resin layer (P2) exceeds 0.02, an adverse situation such as loss of an electric signal on a transmission path of a high-frequency signal is likely to occur when applied to a circuit substrate. On the other hand, the lower limit value of the medium loss factor at 10 GHz of the first insulating resin layer (P1) and the second insulating resin layer (P2) is not particularly limited, but is considered in terms of control of the physical properties of the insulating resin layer as a circuit substrate.

[0083] The adhesive layer (B) can have a medium loss factor (Tan δ) at 10 GHz of preferably 0.015 or less, more preferably 0.01 or less, and further preferably 0.006 or less, for example, in the case of being applied to a circuit substrate, in order to suppress deterioration of dielectric loss. If the medium loss factor at 10 GHz of the adhesive layer (B) exceeds 0.015, an adverse situation such as loss of an electric signal on a transmission path of a high-frequency signal is likely to occur when applied to a circuit substrate. On the other hand, the lower limit value of the medium loss factor at 10 GHz of the adhesive layer (B) is not particularly limited.

[0084] <Dielectric Constant>

[0085] The first insulating resin layer (P1) and the second insulating resin layer (P2) are preferably, as a whole, 4.0 or less in dielectric constant at 10 GHz, for example, in the case of application as an insulating resin layer of a circuit board, in order to ensure impedance matching. If the dielectric constant at 10 GHz of the first insulating resin layer (P1) and the second insulating resin layer (P2) exceeds 4.0, then in the case of application to a circuit board, deterioration of dielectric loss of the first insulating resin layer (P1) and the second insulating resin layer (P2) occurs, and adverse conditions such as loss of electric signals on the transmission path of high frequency signals are easily generated.

[0086] The adhesive layer (B) is preferably 4.0 or less in dielectric constant at 10 GHz, for example, in the case of application as a circuit board, in order to ensure impedance matching. If the dielectric constant at 10 GHz of the adhesive layer (B) exceeds 4.0, then in the case of application to a circuit board, deterioration of dielectric loss of the adhesive layer (B) occurs, and adverse conditions such as loss of electric signals on the transmission path of high frequency signals are easily generated.

[0087] <Effects>

[0088] In the metal-clad laminate (C) of the present embodiment, in order to realize low dielectric loss factor of the whole insulating resin layer and to cope with high frequency transmission, the thickness of the adhesive layer (B) itself is increased. However, a material having a low modulus of elasticity such as the adhesive layer (B) generally exhibits a high coefficient of thermal expansion, and thus increasing the layer thickness can possibly result in a decrease in dimensional stability. Here, the dimensional change of the metal-clad laminate (C) generated at the time of circuit processing is considered to be mainly generated through the following mechanisms of a) to c), and the total amount of b) and c) is exhibited as a dimensional change after etching.

[0089] a) Internal stress is accumulated in the resin layer at the time of manufacturing of the metal-clad laminate (C).

[0090] b) At the time of circuit processing, the internal stress accumulated in a) is released by etching the metal layer, and the resin layer expands or shrinks.

[0091] c) At the time of circuit processing, the resin exposed by etching the metal layer absorbs moisture and expands.

[0092] The main cause of the internal stress of a) is 1) the difference in the coefficient of thermal expansion between the metal layer and the resin layer, and 2) the internal strain of the resin due to film formation. Here, the magnitude of the internal stress caused by 1) is not only affected by the difference in the coefficient of thermal expansion, but also by the temperature difference ΔT from the temperature at the time of adhesion (heating temperature) to the temperature at which cooling and solidification are completed. That is, since the internal stress becomes larger in proportion to the temperature difference ΔT, even if the difference in the coefficient of thermal expansion between the metal layer and the resin layer is small, the higher the temperature of the resin required for adhesion, the larger the internal stress becomes. In the metal-clad laminate (C) of the present embodiment, by using a layer satisfying the conditions (i) to (iii) as the adhesion layer (B), the internal stress is reduced to ensure dimensional stability.

[0093] In addition, since the adhesion 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 warping and dimensional changes are suppressed. Furthermore, in a heating step such as reflow during mounting of a semiconductor chip, since direct heat or contact with oxygen is blocked by the first insulating resin layer (P1) or the second insulating resin layer (P2), it is difficult to be affected by oxidative deterioration, and dimensional changes are less likely to occur. Thus, there are also advantages brought about by the characteristics of the layer configuration of the first insulating resin layer (P1), the adhesion layer (B), and the second insulating resin layer (P2).

[0094] [Manufacture of Metal-clad Laminate]

[0095] The metal-clad laminate (C) can be manufactured, for example, by the following Method 1 or Method 2.

[0096] [Method 1]

[0097] A method in which a resin composition to be the adhesion layer (B) is formed into a sheet shape to form an adhesion sheet, the adhesion sheet is arranged and attached between the first insulating resin layer (P1) of the first single-sided metal-clad laminate (C1) and the second insulating resin layer (P2) of the second single-sided metal-clad laminate (C2), and heat pressure bonding is performed.

[0098] [Method 2]

[0099] A method in which a solution of a resin composition to be the adhesion layer (B) is applied to either one 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) at a prescribed thickness and dried, and heat pressure bonding is performed on one side of the applied film.

[0100] The adhesion sheet used in Method 1 can be manufactured, for example, by a method in which a solution of a resin composition to be the adhesion layer (B) is applied to an arbitrary support substrate and dried, and the adhesion sheet is peeled off from the support substrate.

[0101] Further, in the present embodiment, the method of applying the solution of the resin composition to be the adhesive layer (B) on the support substrate or the insulating resin layer (P1, P2) is not particularly limited, and for example, a coater such as a comma coater, a die coater, a doctor blade, or a lip coater can be used.

[0102] The metal-clad laminate sheet (C) of the present embodiment obtained as described above can be manufactured into a circuit substrate such as a single-sided FPC or a double-sided FPC by performing a wiring circuit process on the first metal layer (M1) and / or the second metal layer (M2).

[0103] [Preferred configuration example of metal-clad laminate sheet]

[0104] 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 sheet (C) of the present embodiment are described in more detail.

[0105] Figure 2 is a schematic cross-sectional view showing the structure of the metal-clad laminate sheet 100 of the present embodiment. As shown in Figure 2 the metal-clad laminate sheet 100 includes metal layers 101, 101 as the first metal layer (M1) and the second metal layer (M2), polyimide layers 110, 110 as the first insulating resin layer (P1) and the second insulating resin layer (P2), and an adhesive polyimide layer 120 as the adhesive layer (B). Here, a single-sided metal-clad laminate sheet 130 as a first single-sided metal-clad laminate sheet (C1) or a second single-sided metal-clad laminate sheet (C2) is formed by the metal layers 101 and the polyimide layers 110. In the present embodiment, the first single-sided metal-clad laminate sheet (C1) and the second single-sided metal-clad laminate sheet (C2) have the same configuration.

[0106] Each of the polyimide layers 110, 110 can have a structure in which a plurality of polyimide layers are laminated. For example, in the configuration shown in Figure 2 each of the polyimide layers 110, 110 is not limited to a three-layer structure.

[0107] In Figure 2In the shown metal-clad laminate 100, the outer thermoplastic polyimide layers 112, 112 in the two single-sided metal-clad laminates 130, 130 are each bonded to the adhesive polyimide layer 120, forming the metal-clad laminate 100. The adhesive polyimide layer 120 is an adhesive layer for bonding the two single-sided metal-clad laminates 130, 130 in the metal-clad laminate 100, and is a layer for thickening the insulating resin layer of the metal-clad laminate 100 while ensuring dimensional stability. Regarding the adhesive polyimide layer 120, as explained for the adhesive layer (B).

[0108] Next, the non-thermoplastic polyimide layer 111 and the thermoplastic polyimide layer 112 constituting the polyimide layers 110, 110 are explained. Further, the so-called "non-thermoplastic polyimide" is generally a polyimide that does not show softening and adhesion even upon heating, but in the present application refers to a polyimide having a storage elastic modulus of 1.0 x 10 9 Pa or more at 30°C and a storage elastic modulus of less than 1.0 x 10 8 Pa at 350°C, as measured using a dynamic viscoelasticity measuring device (dynamic mechanical analyzer (DMA)). Further, the so-called "thermoplastic polyimide" is generally a polyimide in which a glass transition temperature (Tg) can be clearly confirmed, but in the present application refers to a polyimide having a storage elastic modulus of 1.0 x 10 9 Pa or more at 30°C and a storage elastic modulus of more than 1.0 x 10 8 Pa at 350°C, as measured using a DMA.

[0109] The non-thermoplastic polyimide layer:

[0110] The non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 is one containing a tetracarboxylic acid residue and a diamine residue. Further, in the present application, the so-called tetracarboxylic acid residue refers to a quadrivalent group derived from a tetracarboxylic dianhydride, and the so-called 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.

[0111] (Tetracarboxylic acid residue)

[0112] 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'-biphenyl tetracarboxylic dianhydride (BPDA) and 1,4-phenylene bis(trimellitic acid monoester) dianhydride (TAHQ), and tetracarboxylic acid residues derived from at least one of pyromellitic dianhydride (PMDA) and 2,3,6,7-naphthalenetetracarboxylic dianhydride (NTCDA).

[0113] The tetracarboxylic acid residues derived from BPDA (hereinafter, also referred to as "BPDA residues") and the tetracarboxylic acid residues derived from TAHQ (hereinafter, also referred to as "TAHQ residues") easily form an ordered structure of a polymer, and can reduce the dielectric loss tangent or the hygroscopicity by suppressing the movement of molecules. The BPDA residues can impart self-supportability to a gel film of a polyamic acid which is a precursor of the polyimide, but on the other hand, there is a tendency to increase the CTE after imidization and to reduce the glass transition temperature and the heat resistance.

[0114] From the viewpoint described above, the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 is controlled so that the BPDA residues and the TAHQ residues are contained in a range of preferably 30 mol% or more and 60 mol% or less, more preferably 40 mol% or more and 50 mol% or less, of 100 mol% of all the tetracarboxylic acid residues. If the total of the BPDA residues and the TAHQ residues is less than 30 mol%, the formation of the ordered structure of the polymer becomes insufficient, the hygroscopic resistance decreases, or the reduction of the dielectric loss tangent becomes insufficient, and if it exceeds 60 mol%, there is a concern that the heat resistance decreases in addition to the increase in the CTE or the increase in the amount of change in the in-plane retardation (RO).

[0115] In addition, tetracarboxylic acid residues derived from pyromellitic dianhydride (hereinafter, also referred to as "PMDA residues") and tetracarboxylic acid residues derived from 2,3,6,7-naphthalene tetracarboxylic dianhydride (hereinafter, also referred to as "NTCDA residues") have rigidity, and thus are residues that function to improve in-plane orientation, to lower CTE, and to control in-plane retardation (RO) or glass transition temperature. On the other hand, PMDA residues have a small molecular weight, and thus if the amount thereof becomes excessive, the imide group concentration of the polymer becomes high, the polar group increases, the moisture absorption becomes large, and the dielectric loss factor increases due to the influence of moisture in the molecular chain. In addition, NTCDA residues have a tendency to make the film brittle and to increase the elastic modulus due to the high rigidity of the naphthalene skeleton.

[0116] Therefore, the non-thermoplastic polyimide that constitutes the non-thermoplastic polyimide layer contains PMDA residues and NTCDA residues in a range of preferably 40 mol% or more and 70 mol% or less, more preferably 50 mol% or more and 60 mol% or less, and further preferably 50 mol% to 55 mol% in total, relative to 100 mol% of all tetracarboxylic acid residues. If the total of PMDA residues and NTCDA residues is less than 40 mol%, there is a concern that CTE increases or heat resistance decreases, and if it exceeds 70 mol%, there is a concern that the imide group concentration of the polymer becomes high, the polar group increases, and low moisture absorption is impaired, the dielectric loss factor increases, or the film becomes brittle and the self-supporting property of the film decreases.

[0117] In addition, the total of at least one of BPDA residues and TAHQ residues and at least one of PMDA residues and NTCDA residues can be 80 mol% or more, and preferably 90 mol% or more, relative to 100 mol% of all tetracarboxylic acid residues.

[0118] In addition, the molar ratio {(BPDA residues + TAHQ residues) / (PMDA residues + NTCDA residues)} of at least one of BPDA residues and TAHQ residues to at least one of PMDA residues and NTCDA residues can be in a range of 0.4 or more and 1.5 or less, preferably in a range of 0.6 or more and 1.3 or less, and more preferably in a range of 0.8 or more and 1.2 or less, and CTE and the formation of the ordered structure of the polymer can be controlled.

[0119] PMDA and NTCDA have a rigid skeleton, and thus, compared with other general anhydride components, the in-plane orientation of molecules in the polyimide can be controlled, and the coefficient of thermal expansion (CTE) is suppressed and the glass transition temperature (Tg) is increased. In addition, compared with PMDA, BPDA and TAHQ have a large molecular weight, and thus, as the imide group concentration decreases due to an increase in the incorporation ratio, the dielectric loss factor decreases or the moisture absorption rate decreases. On the other hand, if the incorporation ratio of BPDA and TAHQ increases, the in-plane orientation of molecules in the polyimide decreases, and the CTE increases. Furthermore, the formation of an ordered structure within the molecule is promoted, and the haze value increases. From this point of view, the total incorporation amount of PMDA and NTCDA with respect to 100 mol of all the anhydride components of the raw material can be in the range of 40 mol to 70 mol, preferably in the range of 50 mol to 60 mol, and more preferably in the range of 50 mol to 55 mol. If the total incorporation amount of PMDA and NTCDA with respect to 100 mol of all the anhydride components of the raw material is less than 40 mol, the in-plane orientation of molecules decreases, and it becomes difficult to lower the CTE, and in addition, the heat resistance or dimensional stability of the film at the time of heating due to a decrease in Tg decreases. On the other hand, if the total incorporation amount of PMDA and NTCDA exceeds 70 mol, there is a tendency for the moisture absorption rate to deteriorate due to an increase in the imide group concentration, or the elastic modulus to increase.

[0120] In addition, BPDA and TAHQ have an effect of suppressing the molecular motion or lowering the dielectric loss factor or the moisture absorption rate due to a decrease in the imide group concentration, but increase the CTE of the polyimide film after imidization. From this point of view, the total incorporation amount of BPDA and TAHQ with respect to 100 mol of all the anhydride components of the raw material can be in the range of 30 mol to 60 mol, preferably in the range of 40 mol to 50 mol, and more preferably in the range of 40 mol to 45 mol.

[0121] As the tetracarboxylic acid residue other than the BPDA residue, the TAHQ residue, the PMDA residue, and the NTCDA residue contained in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111, for example, a tetracarboxylic acid residue derived from an aromatic tetracarboxylic dianhydride such as 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 2,3',3,4'-diphenyl ether tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, or 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,3',3,4'-diphenyl ether tetracarboxylic dianhydride, bis(2,3-dicarboxyphenyl)ether dianhydride, 3,3",4,4"-p-terphenyl tetracarboxylic dianhydride, 2,3,3",4"-p-terphenyl tetracarboxylic dianhydride, or 2,2",3,3"-p-terphenyl tetracarboxylic dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-propane dianhydride, or 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, or bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)sulfone dianhydride, or bis(3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, or 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,2,7,8-phenanthrene-tetracarboxylic dianhydride, 1,2,6,7-phenanthrene-tetracarboxylic dianhydride, or 1,2,9,10-phenanthrene-tetracarboxylic dianhydride, 2,3,6,7-anthracene tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)tetrafluoropropane dianhydride, 2,3,5,6-cyclohexane dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, or 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-(or 1,4,5,8-)tetrachloronaphthalene-1,4,5,8-(or 2,3,6,7-)tetracarboxylic dianhydride, 2,3,8,9-perylene-tetracarboxylic dianhydride, 3,4,9,10-perylene-tetracarboxylic dianhydride, 4,5,10,11-perylene-tetracarboxylic dianhydride, or 5,6,11,12-perylene-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride, ethylene glycol bis-trimellitic anhydride, and the like can be exemplified.

[0122] (diamine residue)

[0123] As the diamine residue contained in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111, a diamine residue derived from a diamine compound represented by General Formula (1) is preferable.

[0124] [Chemical Formula 2]

[0125]

[0126] In Formula (1), the linking group Z represents a single bond or -COO-, Y independently represents a halogen atom or a monovalent hydrocarbon having a carbon number of 1 to 3 which can be substituted with a phenyl group, or an alkoxy group having a carbon number of 1 to 3, or a perfluoroalkyl group having a carbon number of 1 to 3, or an alkenyl group, n represents an integer of 0 to 2, and p and q independently represent an integer of 0 to 4. Here, the term "independently" means that the plurality of substituents Y in Formula (1), and further the integers p, q can be the same or different. Further, in Formula (1), the hydrogen atoms in the two terminal amino groups can be substituted, for example, can also be -NR2R3 (here, R2, R3 independently represent an arbitrary substituent such as an alkyl group).

[0127] The diamine compound represented by General Formula (1) (hereinafter, sometimes referred to as "diamine (1)") is an aromatic diamine having 1 to 3 benzene rings. Diamine (1) has a rigid structure, and thus has an effect of imparting an ordered structure to the entire polymer. Therefore, a polyimide having low gas permeability, low moisture absorption, and a low dielectric loss factor can be obtained, and the moisture in the inside of the molecular chain can be reduced. Here, as the linking group Z, a single bond is preferable.

[0128] As diamine (1), for example, 1,4-diaminobenzene (p-phenylenediamine (p-PDA)), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-n-propyl-4,4'-diaminobiphenyl (m-NPB), 4-aminophenyl-4'-amino benzoate (APAB), and the like can be exemplified.

[0129] The non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 can contain, relative to 100 mol of all diamine residues, preferably 80 mol or more, more preferably 85 mol or more of diamine residues derived from diamine (1). By using diamine (1) in the above range, an ordered structure is easily formed in the entire polymer by the rigid structure derived from the monomer, and a non-thermoplastic polyimide having low gas permeability, low moisture absorption, and a low dielectric loss factor is easily obtained.

[0130] In addition, in the case where the diaminophenyl group derived from the diamine (1) is in the range of 80 to 85 mol% with respect to 100 mol% of all diaminophenyl groups in the non-thermoplastic polyimide, it is preferable to use 1,4-diaminobenzene as the diamine (1) from the viewpoint of a structure that is more rigid and excellent in in-plane orientation.

[0131] As the other diaminophenyl groups contained in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111, for example, diaminophenyl groups derived from aromatic diamine compounds such as 2,2-bis-[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)]biphenyl, bis[l-(3-aminophenoxy)]biphenyl, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)]benzophenone, 9,9-bis[4-(3-aminophenoxy)phenyl]fluorene, 2,2-bis-[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis-[4-(3-aminophenoxy)phenyl]hexafluoropropane, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4,4'-methylenebis-o-toluidine, 4,4'-methylenebis-2,6-xylylenediamine, 4,4'-methylene-2,6-diethylaniline, 3,3'-diaminodiphenylethane, 3,3'-diaminobiphenyl, 3,3'-dimethoxybenzidine, 3,3"-diamino-p-terphenyl, 4,4'-[l,4-phenylenebis(l-methylethylidene)]bisaniline, 4,4'-[l,3-phenylenebis(l-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(l,l-dimethyl-5-aminopentyl)benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis(β-amino-t-butyl)toluene, 2,4-diaminotoluene, m-xylylene-2,5-diamine, p-xylylene-2,5-diamine, m-phenylenediamine, p-phenylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-l,3,4-oxadiazole, piperazine, 2'-methoxy-4,4'-diaminobenzanilide, 4,4'-diaminobenzanilide, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, 6-amino-2-(4-aminophenoxy)benzoxazole, and the like, diaminophenyl groups derived from dimer acid-type diamines in which both terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl groups or amino groups, and the like aliphatic diamine compounds.

[0132] In the non-thermoplastic polyimide, by selecting the types of the tetracarboxylic acid residue and the diamine residue, or the molar ratio of each when two or more kinds of tetracarboxylic acid residues or diamine residues are used, the coefficient of thermal expansion, the storage elastic modulus, the tensile elastic modulus, and the like can be controlled. In addition, in the non-thermoplastic polyimide, when a plurality of polyimide structural units are present, they can be present in a block form or randomly, but from the viewpoint of suppressing variation in in-plane retardation (RO), it is preferable that they be present randomly.

[0133] Further, by making both the tetracarboxylic acid residue and the diamine residue contained in the non-thermoplastic polyimide aromatic groups, the dimensional accuracy of the polyimide film in a high-temperature environment can be improved, and the amount of variation in in-plane retardation (RO) can be reduced, and thus this is preferable.

[0134] The imide group concentration of the non-thermoplastic polyimide is preferably 33% or less, and more preferably 32% or less. Here, the "imide group concentration" is the value obtained by dividing the molecular weight of the imide group portion (-(CO)2-N-) in the polyimide by the molecular weight of the entire structure of the polyimide. If the imide group concentration exceeds 33%, the molecular weight of the resin itself decreases, and the low moisture absorption property also deteriorates due to an increase in the number of polar groups. By selecting the combination of the acid anhydride and the diamine compound to control the orientation of the molecules in the non-thermoplastic polyimide, an increase in CTE accompanying a decrease in the imide group concentration is suppressed, and a low moisture absorption property is ensured.

[0135] The weight average molecular weight of the non-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, for example. If the weight average molecular weight is less than 10,000, there is a tendency for the strength of the film to decrease and for the film to become brittle. On the other hand, if the weight average molecular weight exceeds 400,000, there is a tendency for the viscosity to increase excessively and for film thickness unevenness, streaks, and the like to occur easily during the coating operation.

[0136] From the viewpoint of ensuring the function as a base layer and the handling properties during manufacture and during coating of the thermoplastic polyimide, the thickness of the non-thermoplastic polyimide layer 111 is preferably in the range of 6 μm or more and 100 μm or less, and more preferably in the range of 9 μm or more and 50 μm or less. If the thickness of the non-thermoplastic polyimide layer 111 is less than the lower limit value, the electrical insulation or the operability becomes insufficient, and if it exceeds the upper limit value, the productivity decreases.

[0137] From the viewpoint of heat resistance, the glass transition temperature (Tg) of the non-thermoplastic polyimide layer 111 is preferably 280°C or more.

[0138] In addition, from the viewpoint of suppressing warping, the coefficient of thermal expansion of the non-thermoplastic polyimide layer 111 can be in a range of 1 ppm / K or more and 30 ppm / K or less, preferably in a range of 1 ppm / K or more and 25 ppm / K or less, and more preferably in a range of 15 ppm / K or more and 25 ppm / K or less.

[0139] In addition, in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111, other hardening resin components such as plasticizers, epoxy resins, and the like, hardening agents, hardening accelerators, coupling agents, fillers, solvents, flame retardants, and the like can be appropriately blended as arbitrary components. However, among the plasticizers, there are substances containing a large number of polar groups, and there is a concern that the substances promote the diffusion of copper from the copper wiring, and thus it is preferable that plasticizers are not used as much as possible.

[0140] The thermoplastic polyimide layer 112:

[0141] The thermoplastic polyimide constituting the thermoplastic polyimide layer 112 is a thermoplastic polyimide containing a tetracarboxylic acid residue and a diamine residue, and preferably contains an aromatic tetracarboxylic acid residue derived from an aromatic tetracarboxylic dianhydride and an aromatic diamine residue derived from an aromatic diamine.

[0142] (Tetracarboxylic acid residue)

[0143] As the tetracarboxylic acid residue used in the thermoplastic polyimide constituting the thermoplastic polyimide layer 112, the same as exemplified as the tetracarboxylic acid residue in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer can be used.

[0144] (Diamine residue)

[0145] As the diamine residue contained in the thermoplastic polyimide constituting the thermoplastic polyimide layer 112, a diamine residue derived from a diamine compound represented by General Formula (B1) to General Formula (B7) is preferable.

[0146] [Chem. 3]

[0147]

[0148] In formulae (B1) to (B7), R1independently represents a monovalent hydrocarbon group or alkoxy group having 1 to 6 carbon atoms, the linking group A independently represents a divalent group selected from -0-, -S-, -CO-, -SO-, -S02-, -COO-, -CH2-, -C(CH3)2-, -NH-, or -CONH-, and n1independently represents an integer of 0 to 4. Among them, formula (B3) is removed from formula (B2), and formula (B5) is removed from formula (B4). Here, the term "independently" means that the plurality of linking groups A, the plurality of R1, or the plurality of n1in one formula or two or more of the formulae (B1) to (B7) can be the same or different. Further, in the formulae (B1) to (B7), the hydrogen atoms in the terminal two amino groups can be substituted, for example, can also be -NR2R3(where R2, R3independently represent an arbitrary substituent such as an alkyl group).

[0149] The diamine represented by formula (B1) (hereinafter, sometimes expressed as "diamine (B1)") is an aromatic diamine having two benzene rings. It is considered that the diamine (B1) has an increased degree of freedom of the polyimide molecular chain and has high flexibility by being in the meta position with respect to the divalent linking group A through the amino group directly bonded to at least one benzene ring, which contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using the diamine (B1), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -0-, -CH2-, -C(CH3)2-, -CO-, -S02-, -S- are preferable.

[0150] As the diamine (B1), for example, 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, (3,3'-diamino)diphenylamine, and the like can be exemplified.

[0151] The diamine represented by formula (B2) (hereinafter, sometimes expressed as "diamine (B2)") is an aromatic diamine having three benzene rings. It is considered that the diamine (B2) has an increased degree of freedom of the polyimide molecular chain and has high flexibility by being in the meta position with respect to the divalent linking group A through the amino group directly bonded to at least one benzene ring, which contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using the diamine (B2), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -0- is preferable.

[0152] As the diamine (B2), for example, 1,4-bis(3-aminophenoxy)benzene, 3-[4-(4- aminophenoxy)phenoxy]aniline, 3-[3-(4-aminophenoxy)phenoxy]aniline, and the like can be exemplified.

[0153] The diamine represented by the formula (B3) (hereinafter, sometimes expressed as "diamine (B3)") is an aromatic diamine having three benzene rings. It is considered that the diamine (B3) has high flexibility by being in the meta position to each other through the two divalent linking groups A directly bonded to one benzene ring, and contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using the diamine (B3), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -0- is preferred.

[0154] As the diamine (B3), for example, 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,3-bis(3- aminophenoxy)benzene (APB), 4,4'-[2-methyl-(1,3-phenylene)bis(oxy)]dianiline, 4,4'-[4- methyl-(1,3-phenylene)bis(oxy)]dianiline, 4,4'-[5-methyl-(1,3-phenylene)bis(oxy)]dianiline, and the like can be exemplified.

[0155] The diamine represented by the formula (B4) (hereinafter, sometimes expressed as "diamine (B4)") is an aromatic diamine having four benzene rings. It is considered that the diamine (B4) has high flexibility by being in the meta position to the divalent linking group A through the amino group directly bonded to at least one benzene ring, and contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using the diamine (B4), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -0-, -CH2-, -C(CH3)2-, -SO2-, -CO-, -CONH- are preferred.

[0156] As the diamine (B4), bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3- aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(3- aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)]benzophenone, bis[4,4'-(3- aminophenoxy)]benzanilide, and the like can be exemplified.

[0157] The diamine represented by formula (B5) (hereinafter, sometimes expressed as "diamine (B5)") is an aromatic diamine having four phenyl rings. It is considered that the diamine (B5) has an increased degree of freedom of the polyimide molecular chain by being in the meta position to each other through the two divalent linking groups A directly bonded to at least one of the phenyl rings, and has high flexibility, which contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using the diamine (B5), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -0- is preferable.

[0158] As the diamine (B5), 4-[3-[4-(4-aminophenoxy)phenoxy]phenoxy]aniline, 4,4'-[oxybis(3,1-phenyleneoxy)]dianiline, and the like can be exemplified.

[0159] The diamine represented by formula (B6) (hereinafter, sometimes expressed as "diamine (B6)") is an aromatic diamine having four phenyl rings. It is considered that the diamine (B6) has high flexibility by having at least two ether bonds, which contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using the diamine (B6), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -C(CH3)2-, -0-, -SO2-, -CO- are preferable.

[0160] As the diamine (B6), for example, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), bis[4-(4-aminophenoxy)phenyl]ether (BAPE), bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), bis[4-(4-aminophenoxy)phenyl]ketone (BAPK), and the like can be exemplified.

[0161] The diamine represented by formula (B7) (hereinafter, sometimes expressed as "diamine (B7)") is an aromatic diamine having four phenyl rings. The diamine (B7) has a divalent linking group A having high flexibility on both sides of the diphenyl skeleton, and it is therefore considered that it contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using the diamine (B7), the thermoplasticity of the polyimide is improved. Here, as the linking group A, -0- is preferable.

[0162] As the diamine (B7), for example, bis[4-(3-aminophenoxy)]biphenyl, bis[4-(4-aminophenoxy)]biphenyl, and the like can be exemplified.

[0163] The thermoplastic polyimide constituting the thermoplastic polyimide layer 112 can contain diamine residues derived from at least one diamine compound selected from diamine (B1) to diamine (B7) in a range of more than 60 mol %, preferably more than 60 mol % and less than 99 mol %, more preferably more than 70 mol % and less than 95 mol %, relative to 100 mol % of all diamine residues. Diamine (B1) to diamine (B7) contain a molecular structure having a bending property, and thus by using at least one diamine compound selected from these compounds in the above range, the softness of the polyimide molecular chain can be improved, and thermoplasticity can be imparted. If the total amount of diamine (B1) to diamine (B7) in the raw material is less than 60 mol % relative to 100 mol % of all diamine components, the softness of the polyimide resin is insufficient and sufficient thermoplasticity cannot be obtained.

[0164] Further, as the diamine residues contained in the thermoplastic polyimide constituting the thermoplastic polyimide layer 112, diamine residues derived from diamine compounds represented by General Formula (1) are also preferable. As to diamine compounds represented by Formula (1) [diamine (1)], as described in the description of the non-thermoplastic polyimide. Diamine (1) has a rigid structure, and has an effect of imparting an ordered structure to the entire polymer, and thus can reduce the dielectric loss tangent or the moisture absorption by suppressing the movement of the molecules. Furthermore, by being used as a raw material of the thermoplastic polyimide, a polyimide having low gas permeability, excellent long-term heat-adhesion resistance can be obtained.

[0165] The thermoplastic polyimide constituting the thermoplastic polyimide layer 112 can contain diamine residues derived from diamine (1) in a range of preferably more than 1 mol % and less than 40 mol %, more preferably more than 5 mol % and less than 30 mol %. By using diamine (1) in the above range, the entire polymer forms an ordered structure by the rigid structure derived from the monomer, and thus a polyimide that is thermoplastic and has low gas permeability and moisture absorption, excellent long-term heat-adhesion resistance can be obtained.

[0166] The thermoplastic polyimide constituting the thermoplastic polyimide layer 112 can contain diamine residues derived from diamine compounds other than diamine (1) and diamine (B1) to diamine (B7) within a range that does not impair the effects of the invention.

[0167] In the thermoplastic polyimide, by selecting the types of the tetracarboxylic acid residues and the diamine residues, or the molar ratio of each when two or more kinds of tetracarboxylic acid residues or diamine residues are used, the coefficient of thermal expansion, the tensile elastic modulus, the glass transition temperature, and the like can be controlled. Further, in the thermoplastic polyimide, in the case where a plurality of polyimide structural units are present, they can exist in a block form, or can exist randomly, but it is preferable that they exist randomly.

[0168] Further, by setting both the tetracarboxylic acid residue and the diamine residue contained in the thermoplastic polyimide to aromatic groups, the dimensional accuracy of the polyimide film under a high temperature environment can be improved, and the amount of change in in-plane retardation (RO) can be suppressed.

[0169] The imide group concentration of the thermoplastic polyimide is preferably 33% or less, and more preferably 32% or less. Here, the "imide group concentration" represents a value obtained by dividing the molecular weight of the imide group portion (-(CO)2-N-) in the polyimide by the molecular weight of the entire structure of the polyimide. If the imide group concentration exceeds 33%, the molecular weight of the resin itself decreases, and the low moisture absorption property also deteriorates due to an increase in the polar group. By controlling the orientation property of the molecules in the thermoplastic polyimide by selecting the combination of the diamine compounds, the increase in CTE accompanying a decrease in the imide group concentration is suppressed, and the low moisture absorption property is ensured.

[0170] 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, for example. If the weight average molecular weight is less than 10,000, there is a tendency for the strength of the film to decrease and for the film to easily become brittle. On the other hand, if the weight average molecular weight exceeds 400,000, there is a tendency for the viscosity to excessively increase, and for film thickness unevenness, streaks, and other adverse conditions to easily occur during the coating work.

[0171] The thermoplastic polyimide that constitutes the thermoplastic polyimide layer 112 becomes an adhesive layer in the insulating resin of the circuit substrate, for example, and thus it is most preferable to be a structure that is completely imidized in order to suppress the diffusion of copper. Of these, a part of the polyimide can also be an amic acid. The imidization rate is determined by measuring the infrared absorption spectrum of a polyimide film using a Fourier transform infrared spectrophotometer (commercially available product: FT / IR 620 manufactured by Japan Spectroscopic Co., Ltd.) and using the first reflection attenuated total reflection (ATR) method, and thus the absorbance of the benzene ring absorber near 1015 cm -1 is calculated based on the absorbance of the C=0 stretch originating from the imide group at 1780 cm -1 .

[0172] From the viewpoint of ensuring the adhesive property, the thickness of the thermoplastic polyimide layer 112 is preferably in the range of 1 μm or more and 10 μm or less, and more preferably in the range of 1 μm or more and 5 μm or less. In the case where the thickness of the thermoplastic polyimide layer 112 is less than the lower limit value, the adhesiveness is insufficient, and if it exceeds the upper limit value, there is a tendency for the dimensional stability to deteriorate.

[0173] The coefficient of thermal expansion of the thermoplastic polyimide layer 112 can be 30 ppm / K or more, preferably in a range of 30 ppm / K or more and 100 ppm / K or less, and more preferably in a range of 30 ppm / K or more and 80 ppm / K or less, from the viewpoint of suppressing warping.

[0174] In addition, in the resin used in the thermoplastic polyimide layer 112, other than the polyimide, other hardening resin components such as a plasticizer, an epoxy resin, a hardening agent, a hardening accelerator, an inorganic filler, a coupling agent, a filler, a solvent, a flame retardant, and the like can be appropriately blended as arbitrary components. However, among the plasticizers, there are substances containing a large amount of a polar group, and there is a concern that the substances promote the diffusion of copper from the copper wiring, and thus it is preferable that the plasticizer is not used as much as possible.

[0175] In the metal-clad laminate 100, in order to ensure dimensional stability after circuit processing, the coefficient of thermal expansion of the entire two polyimide layers 110 and the adhesive polyimide layer 120 can be 10 ppm / K or more, and can be preferably in a range of 10 ppm / K or more and 30 ppm / K or less, and more preferably in a range of 15 ppm / K or more and 25 ppm / K or less.

[0176] Further, in the metal-clad laminate 100, with respect to 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 of the thickness T2 of the adhesive polyimide layer 120 to the total thickness T1 (T2 / T1), as described in the Figure 1

[0177] (Synthesis of Polyimide)

[0178] ​The polyimide constituting the polyimide layer 110 can be produced by reacting the acid anhydride and the diamine in a solvent and performing heat ring closure after producing a precursor resin. For example, the acid anhydride component and the diamine component in approximately equal molar amounts are dissolved in an organic solvent, and the polymerization reaction is performed by stirring at a temperature in the range of 0°C to 100°C for 30 minutes to 24 hours, whereby a polyamic acid as a polyimide precursor is obtained. At the time of the reaction, the reaction components are dissolved in the range of 5% by weight to 30% by weight, preferably in the range of 10% by weight to 20% by weight, of the produced precursor in the organic solvent. As the organic solvent used in the polymerization reaction, for example, N,N-dimethylformamide, N,N-dimethyl acetamide (DMAc), N-methyl-2-pyrrolidone, 2-butanone, dimethyl sulfoxide, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, or the like can be exemplified. Two or more of these solvents can also be used in combination, and further, an aromatic hydrocarbon such as xylene or toluene can also be used in combination. The amount of the organic solvent used is not particularly limited, but it is preferably used in an amount adjusted so that the concentration of the polyamic acid solution (polyimide precursor solution) obtained by the polymerization reaction becomes approximately 5% by weight to 30% by weight.

[0179] In the synthesis of the polyimide, the acid anhydride and the diamine can each be used only one kind, or two or more kinds can be used in combination. By selecting the kinds of the acid anhydride and the diamine, or the respective molar ratios when two or more kinds of the acid anhydride or the diamine are used, the thermal expansion property, the adhesion property, the glass transition temperature, and the like can be controlled.

[0180] The synthesized precursor is generally advantageously used as a reaction solvent solution, but can be concentrated, diluted, or replaced with another organic solvent as needed. The precursor is generally excellent in solvent solubility, and thus can be advantageously used. The method of imidizing the precursor is not particularly limited, and for example, heat treatment at a temperature in the range of 80°C to 400°C in the solvent for 1 hour to 24 hours is preferably employed.

[0181] [Circuit Substrate]

[0182] The metal-clad laminate 100 is useful mainly as a circuit substrate material such as an FPC, a rigid and flexible circuit substrate, and the like. That is, by patterning one or both of the two metal layers 101 of the metal-clad laminate 100 using a conventional method to form a wiring layer, a circuit substrate such as an FPC of an embodiment of the present application can be produced. Although not shown, the circuit substrate includes a resin laminate in which the first insulating resin layer (P1), the adhesion layer (B), and the second insulating resin layer (P2) are sequentially laminated, and a wiring layer provided on one side or both sides of the resin laminate.

[0183] [Examples]

[0184] The present application is specifically described below by way of examples, but the present application is not limited by any of these examples. Furthermore, in the following examples, unless otherwise specified, various measurements and evaluations were performed as described below.

[0185] [Measurement of dielectric constant and dielectric loss factor]

[0186] The dielectric constant (Dk) and dielectric loss factor (Df) of the polyimide film at 10 GHz were measured using a vector network analyzer (manufactured by Agilent, trade name: E8363C) and a split post dielectric resonator (SPDR). Furthermore, the material used in the measurement was a material that had been left for 24 hours under conditions of a temperature of 24°C to 26°C and a humidity of 45% to 55% RH.

[0187] [Measurement of storage elastic modulus and glass transition temperature (Tg)]

[0188] Regarding the storage elastic modulus of the adhesive layer, after the adhesive layer (thickness: 50 m) was removed by peeling from the base material film, it was cut into 5 mm x 20 mm, heated in an oven at 120°C for 2 hours, and heated at 170°C for 3 hours. The resulting sample was measured using a dynamic viscoelasticity measuring device (DMA: manufactured by UBM, trade name: E4000F) by performing stepwise heating at a temperature increase rate of 4°C / minute from 30°C to 400°C, and the measurement was performed at a frequency of 1 Hz. In addition, the maximum temperature at which the Tan delta value was the largest in the measurement was defined as Tg.

[0189] [Measurement of dimensional change rate]

[0190] The measurement of the dimensional change rate was performed in the following order. First, a 150 mm square test piece was used to perform exposure and development of the dry film resist at 100 mm intervals, thereby forming a target for position measurement. After the size before etching (normal state) was measured in an atmosphere at a temperature of 23 ± 2°C and a relative humidity of 50 ± 5%, the copper of the test piece other than the target was removed by etching (liquid temperature: 40°C or lower, time: 10 minutes or less). After standing in an atmosphere at a temperature of 23 ± 2°C and a relative humidity of 50 ± 5% for 24 ± 4 hours, the size after etching was measured. The dimensional change rate with respect to the normal state was calculated for each of three places in the MD direction (long direction) and the TD direction (width direction), and the average value of each was taken as the dimensional change rate after etching. The dimensional change rate after etching was calculated by the following equation.

[0191] Dimensional change rate after etching (%) = (B - A) / A x 100

[0192] A: Distance between targets before etching

[0193] B: Distance between targets after etching

[0194] Next, the test piece was heat-treated in an oven at 250°C for 1 hour, and the distance between the targets after the heat treatment was measured. The dimensional change ratio after the heat treatment was calculated for each of the three positions in the MD direction (long direction) and the TD direction (width direction), and the average value of each was taken as the dimensional change ratio after the heat treatment. The dimensional change ratio after the heat treatment was calculated by the following equation.

[0195] Dimensional change ratio after heat treatment (%) = (C - B) / B x 100

[0196] B: Distance between targets after etching

[0197] C: Distance between targets after heat treatment

[0198] The abbreviations used in this example represent the following compounds.

[0199] BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride

[0200] PMDA: pyromellitic dianhydride

[0201] BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride

[0202] m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl

[0203] TPE-R: 1,3-bis(4-aminophenoxy)benzene

[0204] Bisaniline-M: 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene

[0205] DDA: manufactured by Croda Japan Co., Ltd. (trade name: PRIAMINE 1075)

[0206] N-12: dodecanedioic acid dihydrazide

[0207] DMAc: N,N-dimethylacetamide

[0208] R710: (trade name, manufactured by Printec (K.K.), bisphenol-type epoxy resin, epoxy equivalent weight: 170, liquid at room temperature, weight average molecular weight: about 340)

[0209] VG3101L: (trade name, manufactured by Printec (K.K.), multifunctional epoxy resin, epoxy equivalent weight: 210, softening point: 39°C to 46°C)

[0210] SR35K: (trade name, manufactured by Printec Co., Ltd., epoxy resin, epoxy equivalent: 930 to 940, softening point: 86°C to 98°C)

[0211] YDCN-700-10: (trade name, manufactured by New Japan Chemical Co., Ltd., cresol novolak type epoxy resin, epoxy equivalent 210, softening point 75°C to 85°C)

[0212] Milex XLC-LL: (trade name, manufactured by Mitsui Chemicals, Inc., phenol resin, hydroxyl equivalent: 175, softening point: 77°C, water absorption: 1 mass%, mass reduction rate by heating: 4 mass%)

[0213] HE200C-10: (trade name, manufactured by Air Water Inc., phenol resin, hydroxyl equivalent: 200, softening point: 65°C to 76°C, water absorption: 1 mass%, mass reduction rate by heating: 4 mass%)

[0214] HE910-10: (trade name, manufactured by Air Water Inc., phenol resin, hydroxyl equivalent: 101, softening point: 83°C, water absorption: 1 mass%, mass reduction rate by heating: 3 mass%)

[0215] SC1030-HJA: (trade name, manufactured by Admatechs Co., Ltd., silica filler dispersion liquid, average particle diameter: 0.25 μm)

[0216] Aerosil R972: (trade name, manufactured by Japan Aerosil Co., Ltd., silica, average particle diameter: 0.016 μm)

[0217] Acrylic rubber HTR-860P-30B-CHN: (sample name, manufactured by Teikoku Chemical Industries Co., Ltd., weight average molecular weight: 230,000, glycidyl functional monomer ratio: 8%, Tg: -7°C)

[0218] Acrylic rubber HTR-860P-3CSP: (sample name, manufactured by Teikoku Chemical Industries Co., Ltd., weight average molecular weight: 800,000, glycidyl functional monomer ratio: 3%, Tg: -7°C)

[0219] A-1160: (trade name, manufactured by GE Toshiba Silicones Co., Ltd., γ-ureidopropyl triethoxysilane)

[0220] A-189: (trade name, manufactured by GE Toshiba Silicones Co., Ltd., γ-mercaptopropyl trimethoxysilane)

[0221] Curezol 2PZ-CN: (trade name, manufactured by Shikoku Chemicals Corporation, 1-cyanoethyl-2-phenylimidazole)

[0222] RE-810NM: (trade name, manufactured by Nippon Kayaku Co., Ltd., diallyl bisphenol A diglycidyl ether, property: liquid)

[0223] PHORET SCS: (trade name, manufactured by Sanko Chemical Industry Co., Ltd., styrene group-containing acrylic polymer, Tg: 70°C, weight average molecular weight: 15000)

[0224] BMI-1: (trade name, manufactured by Tokyo Chemical Industry Co., Ltd., 4,4'-bismaleimidediphenylmethane)

[0225] TPPK: (trade name, manufactured by Tokyo Chemical Industry Co., Ltd., tetraphenylphosphonium tetraphenylborate)

[0226] HP-P1: (trade name, manufactured by Sumitomo Metal Industries, Ltd., boron nitride filler)

[0227] NMP: manufactured by Kanto Chemical Co., Inc., N-methyl-2-pyrrolidone)

[0228] (Synthetic Example 1)

[0229] Preparation of Resin Solution A for Adhesive Layer

[0230] Cyclohexanone was added to a composition containing the trade name and composition ratio (unit: mass parts) shown in Table 1 as (a) an epoxy resin and a phenol resin, (c) an inorganic filler, and the mixture was stirred. To this, the acrylic rubber shown in Table 1 as (b) a high molecular weight component was added and stirred, and further, the coupling agent and the hardening accelerator shown in Table 1 as (e) and (d) were added, and the mixture was stirred until the components were uniform, to obtain Resin Solution A for Adhesive Layer.

[0231] [Table 1]

[0232]

[0233] (Synthetic Example 2)

[0234] Synthesis of Polyimide Resin (PI-1) and Preparation of Resin Solution B for Adhesive Layer

[0235] In a 300 mL flask equipped with a thermometer, a stirrer, a cooling tube, and a nitrogen inlet tube, 15.53 g of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: LP-7100), 28.13 g of polyoxypropylenediamine (manufactured by BASF Co., Ltd., trade name: D400, molecular weight: 450), and 100.0 g of NMP were charged and stirred to prepare a reaction solution. After the diamine was dissolved, 32.30 g of 4,4'-oxydiphthalic anhydride, which was refined in advance by recrystallization from acetic anhydride, was added little by little to the reaction solution while the flask was cooled in an ice bath. After 8 hours of reaction at normal temperature (25°C), 67.0 g of xylene was added and distilled off together with water by heating at 180°C while blowing nitrogen. The reaction solution was poured into a large amount of water, and the precipitated resin was filtered off and dried to obtain a polyimide resin (PI-1). The molecular weight of the obtained polyimide resin (PI-1) was measured by gel permeation chromatography (GPC), and as a result, the number average molecular weight Mn = 22400 and the weight average molecular weight Mw = 70200 in terms of polystyrene.

[0236] Using the obtained polyimide resin (PI-1), each component was formulated in the composition ratio (unit: mass parts) shown in Table 2 to obtain a resin solution B for an adhesive layer.

[0237] [Table 2]

[0238] Discrimination Name Synthesis Example 2 Thermoplastic resin PI-1 100 Reactive plasticizer RE-810NM 40 Compound having a styryl group PHORET SCS 40 Compound having a maleimide group BMI-1 40 Hardening accelerator TPPK 0.2 Inorganic filler HP-P1 22 Solvent NMP 270

[0239] (Synthetic Example 3)

[0240] Preparation of polyamic acid solution for insulating resin layer

[0241] Under nitrogen flow, 64.20 g of m-TB (0.302 mol) and 5.48 g of bisaniline-M (0.016 mol) and DMAc in an amount such that the concentration of the solid component after polymerization was 15% by weight were charged into a reaction tank, and stirring was performed at room temperature to dissolve them. Next, after 34.20 g of PMDA (0.157 mol) and 46.13 g of BPDA (0.157 mol) were added, the polymerization reaction was continued by stirring at room temperature for 3 hours to prepare a polyamic acid solution 1 (viscosity: 26,500 cps).

[0242] (Synthetic Example 4)

[0243] Preparation of polyamic acid solution for insulating resin layer

[0244] A polyamic acid solution 2 (viscosity: 2,650 cps) was produced in the same manner as in Synthesis Example 3, except that 69.56 g of m-TB (0.328 mol), 542.75 g of TPE-R (1.857 mol), DMAc in an amount such that the concentration of the solid component after polymerization was 12% by weight, 194.39 g of PMDA (0.891 mol), and 393.31 g of BPDA (1.337 mol) were used as raw materials.

[0245] (Production Example 1)

[0246] Preparation of Resin Sheet A for Adhesive Layer

[0247] The resin solution A for adhesive layer was applied to the silicone-treated surface of a release base (length x width x thickness = 320 mm x 240 mm x 25 μm) at a dried thickness of 50 μm, and then heated and dried at 80°C for 15 minutes, and further heated and dried at 120°C for 15 minutes, and then peeled from the release base, thereby producing the resin sheet A. In addition, with respect to the resin sheet A, in order to evaluate the properties after hardening, it was heated in an oven at 120°C for 2 hours, and heated at 170°C for 3 hours. After that, the Tg of the resin sheet A after hardening was 95°C, the storage elastic modulus at 50°C was 960 MPa, and the maximum value of the storage elastic modulus in the range of 180°C to 260°C was 7 MPa.

[0248] (Production Example 2)

[0249] Preparation of Resin Sheet B for Adhesive Layer

[0250] The resin solution B for adhesive layer was applied to the silicone-treated surface of a release base (length x width x thickness = 320 mm x 240 mm x 25 μm) at a dried thickness of 50 μm, and then heated and dried at 80°C for 15 minutes, and further heated and dried at 120°C for 15 minutes, and then peeled from the release base, thereby producing the resin sheet B. In addition, with respect to the resin sheet B, in order to evaluate the properties after hardening, it was heated in an oven at 120°C for 2 hours, and heated at 170°C for 3 hours. After that, the Tg of the resin sheet B after hardening was 100°C or less, the storage elastic modulus at 50°C was 1800 MPa or less, and the maximum value of the storage elastic modulus in the range of 180°C to 260°C was 70 MPa.

[0251] (Production Example 3)

[0252] Preparation of Single-Sided Metal-Clad Laminate

[0253] On a copper foil 1 (electrolytic copper foil, thickness: 12 μm, surface roughness Rz on the resin layer side: 0.6 μm), polyamide acid solution 2 was uniformly applied in a manner that the hardened thickness became about 2 μm to 3 μm, and then heated and dried at 120°C to remove the solvent. Next, polyamide acid solution 1 was uniformly applied thereon in a manner that the hardened thickness became about 21 μm, and heated and dried at 120°C to remove the solvent. Further, polyamide acid solution 2 was uniformly applied thereon in a manner that the hardened thickness became about 2 μm to 3 μm, and heated and dried at 120°C to remove the solvent. Further, a stepwise heat treatment was performed from 120°C to 360°C to complete imidization, and a single-sided metal-clad laminate 1 was produced. The dimensional change rate of the single-sided metal-clad laminate 1 was as follows.

[0254] Dimensional change rate after etching in the MD direction (longitudinal direction) : 0.01%

[0255] Dimensional change rate after etching in the TD direction (width direction) : -0.04%

[0256] Dimensional change rate after heating in the MD direction (longitudinal direction) : -0.03%

[0257] Dimensional change rate after heating in the TD direction (width direction) : -0.01%

[0258] Preparation of polyimide film

[0259] The copper foil 1 of the single-sided metal-clad laminate 1 was etched and removed using an aqueous ferric chloride solution, and a polyimide film 1 (thickness: 25 μm, CTE: 20 ppm / K, Dk: 3.40, Df: 0.00029) was produced.

[0260] [Example 1]

[0261] Two single-sided metal-clad laminates 1 were prepared, and the faces of the respective insulating resin layers were overlapped with both faces of the resin sheet A, and pressure bonding was performed at 180°C under a pressure of 3.5 MPa for 2 hours, and a metal-clad laminate 1 was produced. The evaluation results of the metal-clad laminate 1 were as follows.

[0262] Dimensional change rate after etching in the MD direction: -0.02%

[0263] Dimensional change rate after etching in the TD direction: -0.03%

[0264] Dimensional change rate after heating in the MD direction: -0.02%

[0265] Dimensional change rate after heating in the TD direction: -0.02%

[0266] The metal-clad laminate 1 had no warpage and no dimensional change. In addition, the CTE of a resin laminate 1 (thickness: 100 μm) prepared by etching and removing the copper foil 1 in the metal-clad laminate 1 was 24.1 ppm / K.

[0267] [Example 2]

[0268] Two metal-clad laminates 1 were prepared by aligning the respective insulating resin layer sides with both sides of the resin sheet B, and pressure bonding at 180°C for 2 hours under a pressure of 3.5 MPa. The evaluation results of the metal-clad laminates 2 are described below.

[0269] MD direction after etching dimensional change rate: -0.05%

[0270] TD direction after etching dimensional change rate: -0.05%

[0271] MD direction after heating dimensional change rate: -0.03%

[0272] TD direction after heating dimensional change rate: -0.04%

[0273] The metal-clad laminate 2 had no warpage and no dimensional change. In addition, the CTE of a resin laminate 2 (thickness: 100 μm) prepared by etching and removing the copper foil 1 in the metal-clad laminate 2 was 23.3 ppm / K.

[0274] [Comparative Example 1]

[0275] A metal-clad laminate 3 was prepared in the same manner as in Example 1, except that a fluororesin sheet (manufactured by Asahi Glass Company, trade name: Sticking Perfluoro Resin EA-2000, thickness: 50 μm, Tm: 303°C, Tg: none) was used instead of the resin sheet A, and pressure bonding was performed at 320°C for 5 minutes under a pressure of 3.5 MPa.

[0276] The evaluation results of the metal-clad laminate 3 are described below.

[0277] MD direction after etching dimensional change rate: -0.11%

[0278] TD direction after etching dimensional change rate: -0.13%

[0279] MD direction after heating dimensional change rate: -0.19%

[0280] TD direction after heating dimensional change rate: -0.20%

[0281] The metal-clad laminate 3 had no warpage and no dimensional change. In addition, the CTE of a resin laminate 3 (thickness: 100 μm) prepared by etching and removing the copper foil 1 in the metal-clad laminate 3 was 27.6 ppm / K.

[0282] (Reference Example 1)

[0283] A metal-clad laminate 4 was prepared by lamination in the order of the copper foil 1, the resin sheet A, the polyimide film 1, the resin sheet A, and the copper foil 1, and pressure bonding was performed at 180°C for 2 hours under a pressure of 3.5 MPa.

[0284] The evaluation results of the metal-clad laminate 4 are described below.

[0285] MD direction: -0.04%

[0286] TD direction: -0.05%

[0287] MD direction: -0.12%

[0288] TD direction: -0.14%

[0289] The metal-clad laminate 4 had no warpage, and the dimensional change was also not problematic. In addition, the CTE of a resin laminate 4 (thickness: 100 μm) prepared by etching and removing the copper foil 1 in the metal-clad laminate 4 was 23.9 ppm / K.

[0290] It was found that the dimensional change after etching and the dimensional change after heating were low even in Example 1 and Example 2, compared with Comparative Example 1 and Reference Example 1, respectively. Further, in Comparative Example 1, the lamination by heat pressure bonding at 320°C was performed, and the adhesion was not problematic, but sufficient adhesion force could not be obtained by heat pressure bonding under the same heat pressure bonding conditions (temperature: 180°C, time: 2 hours, pressure: 3.5 MPa) as in Example 1 and Example 2. In addition, Reference Example 1 was performed for the purpose of verification of the position of the resin sheet A.

[0291] [Example 3]

[0292] A single-sided metal-clad laminate 1 was prepared, and the adhesive layer resin solution A was applied to the side of the insulating resin layer so as to have a dry thickness of 50 μm, and then heat-dried at 80°C for 15 minutes and further dried at 120°C for 15 minutes, to thereby prepare a single-sided metal-clad laminate 1 with an adhesive layer.

[0293] Next, the adhesive layer side of the single-sided metal-clad laminate 1 with an adhesive layer was overlapped with the side of the insulating resin layer of the other single-sided metal-clad laminate 1, and pressure bonding was performed at 180°C for 2 hours under a pressure of 3.5 MPa, to thereby prepare a metal-clad laminate 1'.

[0294] The evaluation results of the metal-clad laminate 1' are described below.

[0295] Etching after size change rate in MD direction: -0.03%

[0296] Etching after size change rate in TD direction: -0.03%

[0297] Heating after size change rate in MD direction: -0.02%

[0298] Heating after size change rate in TD direction: -0.02%

[0299] The metal-clad laminate 5 did not warp, and there was no problem with the dimensional change. In addition, the CTE of a 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.

[0300] [Example 4]

[0301] Two pieces of the single-sided metal-clad laminate 1 with an adhesive layer were prepared, the adhesive layer sides were overlapped with each other, and then pressure bonding was performed at 180°C for 2 hours under a pressure of 3.5 MPa to prepare a metal-clad laminate 5.

[0302] The evaluation results of the metal-clad laminate 5 are described below.

[0303] Etching after size change rate in MD direction: -0.03%

[0304] Etching after size change rate in TD direction: -0.03%

[0305] Heating after size change rate in MD direction: -0.03%

[0306] Heating after size change rate in TD direction: -0.03%

[0307] The metal-clad laminate 5 did not warp, and there was no problem with the dimensional change. In addition, the CTE of a 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.

[0308] [Example 5]

[0309] A single-sided metal-clad laminate 1 was prepared, and the adhesive layer was applied to the side of the insulating resin layer with the resin solution A in such a manner that the dried thickness would be 75 μm, and then heat drying was performed at 80°C for 15 minutes, and further drying was performed at 120°C for 25 minutes to prepare a single-sided metal-clad laminate 2 with an adhesive layer.

[0310] Two pieces of the single-sided metal-clad laminate 2 with an adhesive layer were prepared, the adhesive layer sides were overlapped with each other, and then pressure bonding was performed at 180°C for 2 hours under a pressure of 3.5 MPa to prepare a metal-clad laminate 6.

[0311] The results of evaluation of the metal-clad laminate 6 were as follows.

[0312] Etching after size change rate in the MD direction: -0.01%

[0313] Etching after size change rate in the TD direction: -0.01%

[0314] Heating after size change rate in the MD direction: 0.01%

[0315] Heating after size change rate in the TD direction: 0.02%

[0316] The metal-clad laminate 6 had no warpage and no problem in size change. In addition, the CTE of a resin laminate 6 (thickness: 200 μm) prepared by etching and removing the copper foil 1 in the metal-clad laminate 6 was 22.8 ppm / K.

[0317] (Synthetic Example 5)

[0318] A polyamic acid solution was prepared by charging 44.98 g of BTDA (0.139 mole), 75.02 g of DDA (0.140 mole), 168 g of NMP, and 112 g of xylene into a 500-ml separable flask, and mixing them sufficiently at 40°C for 30 minutes under a nitrogen stream. The polyamic acid solution was warmed to 190°C, and heated and stirred for 4.5 hours, and 112 g of xylene was added to prepare an imidized polyimide adhesive solution 1. The solid content of the obtained polyimide adhesive solution 1 was 29.1% by weight, and the viscosity was 7,800 cps. In addition, the weight average molecular weight (Mw) of the polyimide was 87,700.

[0319] (Synthetic Example 6)

[0320] The polyimide adhesive solution 1 obtained in Synthetic Example 5 was diluted by adding 1.297 g of NMP and 3.869 g of xylene to 34.4 g (solid content: 10 g) of the polyimide adhesive solution 1, 1.25 g of N-12, and 2.5 g of Exolit OP935 (manufactured by Clariant Japan, Ltd.), to prepare a resin solution C for an adhesive layer.

[0321] Preparation of Resin Sheet C for an Adhesive Layer

[0322] The adhesive layer was applied to the silicone-treated surface of the release substrate (length x width x thickness = 320 mm x 240 mm x 25 μm) with the resin solution C at a dried thickness of 50 μm, and then dried at 80°C for 15 minutes. Further drying was performed at 120°C for 15 minutes, and then the resin sheet C was prepared by peeling from the release substrate. In addition, with respect to the resin sheet C, in order to evaluate the properties after hardening, the resin sheet was heated in an oven at 120°C for 2 hours and at 170°C for 3 hours to prepare a hardened resin sheet D. The Tg of the hardened resin sheet D was 95°C, the storage elastic modulus at 50°C was 1220 MPa, and the maximum value of the storage elastic modulus in the range of 180°C to 260°C was 26 MPa.

[0323] [Example 6]

[0324] The single-clad metal laminate 1 was prepared, and the adhesive layer was applied to the surface on the side of the insulating resin layer with the resin solution C at a dried thickness of 50 μm, and then dried at 80°C for 15 minutes and further dried at 120°C for 15 minutes to prepare the single-clad metal laminate 3 with an adhesive layer.

[0325] Next, the single-clad metal laminate 3 with an adhesive layer was overlapped with the surface on the side of the insulating resin layer of the single-clad metal laminate 1, and then pressure-bonded at 180°C for 2 hours under a pressure of 3.5 MPa to prepare the metal-clad laminate 7.

[0326] The results of evaluation of the metal-clad laminate 7 are described below.

[0327] Etching after MD direction size change rate: -0.02%

[0328] Etching after TD direction size change rate: -0.02%

[0329] Heating after MD direction size change rate: -0.03%

[0330] Heating after TD direction size change rate: -0.03%

[0331] The metal-clad laminate 7 had no warpage, and the dimensional change was also not problematic. In addition, the CTE of the resin laminate 7 (thickness: 100 μm) prepared by etching and removing the copper foil 1 in the metal-clad laminate 7 was 23.4 ppm / K.

[0332] In addition, any of the single-clad metal laminates with an adhesive layer described in the examples can also be applied to the manufacture of a multilayer circuit substrate. In addition, it is considered that the thickness of the adhesive layer in the case is preferably 100 μm or less, and the thickness ratio of the adhesive layer in the insulating resin layer is preferably 80% or less.

[0333] The embodiments of the present application are described in detail above for the purpose of illustration, but the present application is not limited to the embodiments described above, and various modifications can be made thereto.

Claims

1. A metal-clad laminate comprising: a first single-sided metal-clad laminate having a first metal layer and a first insulating resin layer laminated on a surface of at least one side of the first metal layer; a second single-sided metal-clad laminate having a second metal layer and a second insulating resin layer laminated on a surface of at least one side of the second metal layer; and an adhesive layer disposed in abutment with the first insulating resin layer and the second insulating resin layer, laminated between the first single-sided metal-clad laminate and the second single-sided metal-clad laminate, and characterized in that: the adhesive layer is composed of a thermoplastic resin or a thermosetting resin, and satisfies the following conditions (i) to (iii): (i) a storage elastic modulus at 50°C is 1800 MPa or less; (ii) a maximum value of a storage elastic modulus in a temperature range of 180°C to 260°C is 800 MPa or less; and (iii) a glass transition temperature is 180°C or less, the adhesive layer is disposed in contact with both of the thermoplastic polyimide layers, and a non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer contains a tetracarboxylic acid residue and a diamine residue, and a content of a diamine residue derived from a diamine compound represented by the following general formula (1) with respect to 100 mol of the total diamine residue is 80 mol or more: General Formula (1) wherein the linking group Z represents a single bond or -COO-, Y independently represents a halogen atom or a monovalent hydrocarbon having a carbon number of 1 to 3 which can be substituted with a phenyl group, or an alkoxy group having a carbon number of 1 to 3, or a perfluoroalkyl group having a carbon number of 1 to 3, or an alkenyl group, n represents an integer of 0 to 2, and p and q independently represent an integer of 0 to 4.

2. The metal-clad laminate according to claim 1, wherein a thermal expansion coefficient of the entirety of the first insulating resin layer, the adhesive layer, and the second insulating resin layer is in a range of 10 ppm / K or more and 30 ppm / K or less.

3. The metal-clad laminate according to claim 1, wherein each of the first metal layer and the second metal layer contains a copper foil.

4. A circuit substrate obtained by processing the first metal layer and / or the second metal layer of the metal-clad laminate according to any one of claims 1 to 3 into a wiring. ​ ​ ​ ​ The first and second insulating resin layers each have a multilayer structure of a thermoplastic polyimide layer, a non-thermoplastic polyimide layer, and a thermoplastic polyimide layer, in this order, wherein the non-thermoplastic polyimide is a polyimide having a storage elastic modulus of 1.0 x 10 9 Pa or more at 30°C and less than 1.0 x 10 8 Pa at 350°C, and the thermoplastic polyimide is a polyimide having a storage elastic modulus of 1.0 x 10 9 Pa or more at 30°C and 1.0 x 10 8 Pa or more at 350°C. ​ ​ ​ ​ ​ ​

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