Metal-clad laminates, circuit boards, electronic devices and electronic equipment

Abstract

The present invention provides a metal-clad laminate that ensures adhesion between the metal layer and the insulating resin layer, suppresses rupture of the insulating resin layer, and maintains sufficient elongation. [Solution] A metal-clad laminate comprising an insulating resin layer and a metal layer laminated on one or both sides of the insulating resin layer, wherein the insulating resin layer has a polyimide layer (A) in contact with the metal layer and a polyimide layer (B) laminated adjacent to the polyimide layer (A). The storage modulus E' of the polyimide layer (A) at 300°C is 1.5 × 10⁻⁶ 9 Below [Pa], the storage modulus E' of the polyimide layer (B) at 300°C is 1.8 × 10⁻⁶. 9 The pressure is greater than or equal to [Pa], and when the metal layer is removed, the maximum valley depth of the insulating resin layer measured on the exposed surface of the polyimide layer (A) is Sv [μm], and the thickness of the polyimide layer (A) is d [μm], satisfying the relationship 2d ≥ Sv > 0.5d.

Description

[Technical Field]

[0001] The present invention relates to a metal-clad laminate useful as a circuit board material, a circuit board using the same, an electronic device, and an electronic device. [Background technology]

[0002] With the miniaturization, weight reduction, and space-saving advancements in electronic devices, the demand for flexible printed circuit boards (FPCs) is increasing. FPCs are thin, lightweight, flexible, and possess excellent durability even after repeated bending. Because FPCs enable three-dimensional and high-density mounting even in limited spaces, their applications are expanding to various electronic components.

[0003] With the increasing sophistication of electronic devices such as portable electronic devices in recent years, there is a growing demand for further miniaturization (fine pitch) of wiring patterns in FPCs (Flexible Printed Circuits). To meet this demand, metal-clad laminates such as CCL (Copper Clad Laminate), which are the materials used for FPCs, require thinner copper foil and insulating resin layers than before. However, as the insulating resin layer becomes thinner, it becomes more prone to breakage when tensile force is applied during the circuit processing process, which may result in a decrease in the reliability and yield of the FPC.

[0004] Regarding prior art concerning the mechanical strength of insulating resin layers in metal-clad laminates, Patent Document 1 proposes a polyimide film having high Young's modulus, high elongation, low water absorption, controlled coefficient of thermal expansion, and high glass transition temperature by containing specific chemical structural units.

[0005] Furthermore, Patent Document 2 proposes using a polyimide layer having a specific storage modulus as the polyimide layer in contact with the metal layer. However, Patent Document 2 aims to ensure adhesion at the interface with adjacent polyimide layers and does not consider the suppression of fracture of the insulating resin layer or its effect on elongation. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent No. 4962046 [Patent Document 2] Japanese Patent No. 7212515 [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] As the thinning of the insulating resin layer progresses, it is considered that one of the causes for the easy occurrence of breakage is related to the surface roughness of the metal layer. The surface of the metal foil used for the metal-clad laminate is usually roughened to ensure adhesion to the insulating resin layer, and the surface roughness is controlled within a predetermined range.

[0008] However, there may be a portion on the metal foil having an abnormal protrusion height (abnormal roughening portion). According to the findings obtained by the present inventors, when laminating with the insulating resin layer using a metal foil having such an abnormal roughening portion, the protruding portion of the abnormal roughening portion bites deeply into the insulating resin layer, and it is presumed that this serves as a starting point for breakage or causes a decrease in elongation. The breakage of the insulating resin layer due to such an abnormal roughening portion of the metal foil increases as the thinning of the insulating resin layer progresses, and there is a concern that it will become a major problem in the future. On the other hand, since the surface roughness of the metal foil plays an important role in the adhesion to the insulating resin layer, there is a limit to suppressing breakage and elongation reduction by improving the metal foil side.

[0009] Therefore, an object of the present invention is to provide a metal-clad laminate that can suppress breakage of the insulating resin layer and maintain sufficient elongation while ensuring adhesion between the metal layer and the insulating resin layer. [Means for Solving the Problems]

[0010] As a result of intensive studies, the inventors of the present invention have found that the above problems can be solved by considering the relationship between the surface roughness of the insulating resin layer and the thickness of the polyimide layer in contact with the metal layer in a metal-clad laminate, and controlling the storage elastic modulus of adjacent polyimide layers within a specific range, thereby completing the present invention.

[0011] That is, the metal-clad laminate of the present invention is a metal-clad laminate including an insulating resin layer and a metal layer laminated on one or both sides of the insulating resin layer, where the insulating resin layer has a polyimide layer (A) in contact with the metal layer and a polyimide layer (B) laminated adjacent to the polyimide layer (A), the storage elastic modulus E' at 300 °C measured using a dynamic viscoelasticity measuring device (DMA) of the polyimide layer (A) is 1.5 × 10 9 [Pa] or less, the storage elastic modulus E' at 300 °C measured using a dynamic viscoelasticity measuring device (DMA) of the polyimide layer (B) is 1.8 × 10 9 [Pa] or more, when the maximum valley depth Sv [μm] of the insulating resin layer measured on the exposed surface of the polyimide layer (A) when the metal layer is removed and the thickness d [μm] of the polyimide layer (A) are defined, the following formula (1); 2d ≧ Sv > 0.5d ··· (1) is satisfied.

[0012] In the metal-clad laminate of the present invention, the relationship between the thickness d of the polyimide layer (A) and the maximum peak height Sp of the metal layer may be the following formula (2); d < Sp ··· (2) is satisfied.

[0013] In the metal-clad laminate of the present invention, the adhesion strength of the interface between the metal layer and the polyimide layer (A) may be higher than 1.0 kN / m, and the elongation at break of the insulating resin layer may be higher than 30%.

[0014] The metal-clad laminate of the present invention may have an insulating resin layer comprising a polyimide layer (A), a polyimide layer (B), and a polyimide layer (A') laminated adjacent to the polyimide layer (B). In this case, the polyimide layer (A) and the polyimide layer (A') are thermoplastic polyimide layers containing thermoplastic polyimide as the main component of the resin, and the thermoplastic polyimide contains diamine residues derived from a diamine component and acid dianhydride residues derived from a tetracarboxylic dianhydride component, and may also contain a total of 30 mol% or more of acid dianhydride residues derived from pyromellitic dianhydride (PMDA) and / or acid anhydride residues derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) relative to the total acid dianhydride residues. The polyimide layer (B) is a non-thermoplastic polyimide layer containing non-thermoplastic polyimide as the main component of the resin, wherein the non-thermoplastic polyimide contains diamine residues derived from a diamine component and acid dianhydride residues derived from a tetracarboxylic dianhydride component, and may also contain in the range of 5 mol% to 100 mol% of diamine residues derived from a diamine compound represented by the following general formula (A1) in the total diamine residues, and may also contain in the range of 5 mol% to 90 mol% of acid dianhydride residues derived from pyromellitic dianhydride (PMDA) in the total acid dianhydride residues.

[0015] [ka]

[0016] In general formula (A1), the linking group X1 independently represents a single bond or -CONH-, Y independently represents a monovalent hydrocarbon group or alkoxy group having 1 to 3 carbon atoms, n1 represents an integer from 0 to 2, and p and q independently represent integers from 0 to 4.

[0017] The circuit board of the present invention comprises an insulating resin layer and a circuit wiring layer laminated on one or both sides of the insulating resin layer, The insulating resin layer comprises a polyimide layer (A) in contact with the circuit wiring layer and a polyimide layer (B) laminated adjacent to the polyimide layer (A). The storage modulus E' of the polyimide layer (A), measured using a dynamic viscoelasticity analyzer (DMA), is 1.5 × 10⁻⁶. 9 [Pa] or less, The storage modulus E' of the polyimide layer (B) at 300°C, measured using a dynamic viscoelasticity analyzer (DMA), is 1.8 × 10⁻⁶. 9 [Pa] or higher, When the circuit wiring layer is removed, the maximum valley depth of the insulating resin layer measured on the exposed surface of the polyimide layer (A) is Sv [μm], and the thickness of the polyimide layer (A) is d [μm], then the following equation (1): 2d≧Sv>0.5d ··· (1) It is characterized by satisfying the relationship.

[0018] The electronic device or electronic equipment of the present invention is characterized by comprising the circuit board of the present invention. [Effects of the Invention]

[0019] The metal-clad laminate of the present invention ensures adhesion between the metal layer and the insulating resin layer while suppressing fracture of the insulating resin layer, and maintaining sufficient elongation. Therefore, in circuit boards manufactured by processing the metal-clad laminate of the present invention, yield can be improved and reliability can be ensured. Accordingly, the metal-clad laminate of the present invention is particularly suitable for use as a circuit board material such as FPC in electronic devices and electronic equipment. [Brief explanation of the drawing]

[0020] [Figure 1] This is a schematic diagram showing the cross-sectional structure in the thickness direction of a metal-clad laminate according to a preferred embodiment of the present invention. [Modes for carrying out the invention]

[0021] Embodiments of the present invention will be described with reference to the drawings as appropriate.

[0022] [Metal-clad laminate] Figure 1 shows a cross-sectional configuration of a metal-clad laminate 100 according to a preferred embodiment of the present invention. The metal-clad laminate 100 comprises a metal layer 10 and an insulating resin layer 20 laminated on one side of the metal layer 10. The metal-clad laminate 100 is a single-sided metal-clad laminate in which the metal layer 10 is laminated on one side of the insulating resin layer 20. The metal-clad laminate of the present invention may also be a double-sided metal-clad laminate in which a metal layer (not shown) is laminated on the other side of the insulating resin layer 20.

[0023] Furthermore, Figure 1 shows a preferred example in which the insulating resin layer 20 has a three-layer laminated structure consisting of a thermoplastic polyimide layer 21 as polyimide layer (A), a non-thermoplastic polyimide layer 22 as polyimide layer (B) laminated adjacent to polyimide layer (A), and a thermoplastic polyimide layer 23 as polyimide layer (A') laminated adjacent to the non-thermoplastic polyimide layer 22. The thermoplastic polyimide layers 21 and 23 are adhesive resin layers that mainly ensure adhesion to the metal layer 10, and the non-thermoplastic polyimide layer 22 is a base resin layer that mainly ensures mechanical properties. The materials of the thermoplastic polyimide layer 21 and the thermoplastic polyimide layer 23 may be the same or different, but it is preferable that they have the same resin composition. The thicknesses of the thermoplastic polyimide layer 21 and the thermoplastic polyimide layer 23 may be the same or different.

[0024] Since Figure 1 is merely an example, the insulating resin layer 20 does not need to have a three-layer structure; it may have two layers or four or more layers. Furthermore, the metal-clad laminate of the present invention may include any resin layer other than those mentioned above, as long as it does not impair the effects of the invention. Such any resin layer may be composed of a material other than polyimide. In this invention, "polyimide" refers to resins made of polymers having imide groups in their molecular structure, including polyimide, polyamideimide, polyetherimide, polyesterimide, polysiloxaneimide, and polybenzimidazoleimide.

[0025] In the present invention, the laminated structure of the thermoplastic polyimide layer 21 and the metal layer 10 may be formed by a casting method in which a precursor solution of thermoplastic polyimide is applied onto a metal foil that becomes the metal layer 10, or may be formed by thermocompression bonding the thermoplastic polyimide layer 21 and the metal foil.

[0026] In the metal-clad laminate 100, the storage modulus E' at 300°C measured using a dynamic viscoelasticity measuring device (DMA) of the thermoplastic polyimide layer 21 is 1.5×10 9 [Pa] or less. The thermoplastic polyimide layer 21 has good filling properties to the metal foil during pressing due to its low storage modulus at high temperatures, and high adhesion can be ensured. In particular, as the thickness of the thermoplastic polyimide layer 21 is reduced, the adhesion to the metal layer 10 decreases. Therefore, it is preferable to lower the storage modulus at high temperatures so that good adhesion can be ensured even for a thin film. From this perspective, the storage modulus E' of the thermoplastic polyimide layer 21 at 300°C is preferably in the range of 1.0×10 7 ~1.5×10 9 , and more preferably in the range of 3.0×10 7 ~1.2×10 9 .

[0027] In the metal-clad laminate 100, the storage modulus E' at 300°C measured using a dynamic viscoelasticity measuring device (DMA) of the non-thermoplastic polyimide layer 22 as the polyimide layer (B) is 1.8×10 9The storage modulus E' of the non-thermoplastic polyimide layer (B) is 1.8 × 10⁻¹⁰. 9 ~1.0×10 10 It is preferably within the range of 2.0 × 10 9 ~5.0×10 9 A range within this scope is preferable.

[0028] Furthermore, when the metal-clad laminate 100 is removed, and the maximum valley depth of the insulating resin layer 20 measured on the exposed surface S of the thermoplastic polyimide layer 21 is Sv [μm], and the thickness of the thermoplastic polyimide layer 21 is d [μm], then the following equation (1) applies: 2d≧Sv>0.5d ··· (1) satisfies the relationship. Since the polyimide layer (B) has a high storage modulus at high temperatures, it has excellent heat resistance and can prevent wrinkles and deformation during pressing. However, increasing the elastic modulus reduces the toughness. However, when the relationship between the surface roughness of the insulating resin layer 20 and the thickness of the polyimide layer (A) satisfies Equation (1), even when the protrusions of the roughened abnormal sites on the metal surface reach the non-thermoplastic polyimide layer 22 as the polyimide layer (B) during pressing, the polyimide layer (A) with relatively high toughness functions to prevent stress concentration on the cracks of the polyimide layer (B) by preventing crack propagation, and the elongation at break of the insulating resin layer 20 can be increased. When Equation (1) is not satisfied and 2d < Sv, the insulating resin layer 20 is likely to break when a tensile force is applied during circuit processing or the like. On the other hand, when Sv ≤ 0.5d, the thickness d of the thermoplastic polyimide layer 21 is too large with respect to the maximum valley depth Sv, so it cannot be thinned and it becomes difficult to cope with miniaturization. Also, the adhesion between the thermoplastic polyimide layer 21 and the metal layer 10 may decrease. Therefore, the upper limit of the thickness d of the thermoplastic polyimide layer 21 is preferably, for example, 5 μm or less, more preferably 4 μm or less, and even more preferably 3 μm or less.

[0029] In addition, the effect of the present invention is more significantly exhibited in the case where the insulating resin layer 20 is thinned. Therefore, the metal-clad laminate 100 satisfies the following Equation (1a); 2d ≥ Sv > 0.7d ··· (1a) and may satisfy the relationship of the following Equation (1b) 2d ≥ Sv > 0.9d ··· (1b) and may satisfy the relationship of the following Equation (1c), and furthermore, may satisfy the relationship of the following Equation (1c) 2d ≥ Sv ≥ d ··· (1c) as well. In other words, even when the bottom of grooves or depressions where the convex shape of the roughened abnormal area of ​​the metal layer 10 is transferred is close to the thickness of the thermoplastic polyimide layer 21 or exceeds the thickness and reaches the non-thermoplastic polyimide layer 22, the relationship of equation (1a), equation (1b), and further equation (1c) above are satisfied, so that the polyimide layer (A) acts to hinder crack propagation, thereby preventing stress concentration in the polyimide layer (B) and increasing the elongation at break of the insulating resin layer 20.

[0030] The maximum valley depth Sv of the insulating resin layer 20 is a transfer of the convex shape of the roughened abnormal areas of the metal layer 10. Therefore, there is a certain degree of correlation between the absolute value of the maximum valley depth Sv of the insulating resin layer 20 and the absolute value of the maximum peak height Sp of the metal layer 10. Thus, by measuring the surface roughness of the metal foil that will become the metal layer 10 in advance, it is possible to estimate what the maximum valley depth Sv of the insulating resin layer 20 will be. Furthermore, the reason for specifying "the maximum valley depth of the insulating resin layer 20 measured on the exposed surface S of the thermoplastic polyimide layer 21" is that, although the surface roughness is measured on the exposed surface S of the thermoplastic polyimide layer 21, it is assumed that recesses (valleys) may be formed that exceed the thickness of the thermoplastic polyimide layer 21.

[0031] Furthermore, the relationship between the thickness d of the thermoplastic polyimide layer 21 and the maximum peak height Sp of the metal layer 10 in the metal-clad laminate 100 is given by the following equation (2); d <Sp ··· (2) The relationship may be as shown in equation (2). When the thermoplastic polyimide layer 21 is thinned, the roughened shape of the metal foil surface (especially the convex shape of the roughened abnormal areas) may penetrate the thermoplastic polyimide layer 21 and be transferred to the non-thermoplastic polyimide layer 22 as traces such as grooves or depressions, which tend to become the starting point of fracture. However, in the present invention, by making the storage modulus E' of the non-thermoplastic polyimide layer 22 sufficiently high and satisfying the above equation (1), it is possible to prevent the above traces from reaching a depth that would become the starting point of fracture, and the thermoplastic polyimide layer 21 as the polyimide layer (A) acts to hinder crack propagation, thereby increasing the elongation at break of the insulating resin layer 20. Therefore, in the present invention, even if the thickness d of the thermoplastic polyimide layer 21 is thinned to a thickness that could not be achieved conventionally, the occurrence of fracture can be suppressed and the reliability of the FPC can be ensured.

[0032] When measuring the maximum valley depth Sv of the insulating resin layer 20, the exposed surface S of the thermoplastic polyimide layer 21 is revealed by removing the metal layer 10 from the metal-clad laminate 100. The method for removing the metal layer 10 is not particularly limited, and known methods can be used, such as wet etching or dry etching. For example, when removing the copper foil from a flexible copper-clad laminate where the metal layer is copper foil, it is preferable to remove the copper foil by immersing it in an etching solution of ferric chloride at a liquid temperature of 30°C for 3 minutes, then immersing it in pure water to wash off the etching solution and then drying it.

[0033] As described above, in the present invention, the storage modulus E' of the thermoplastic polyimide layer 21 at 300°C, as measured using a dynamic viscoelasticity measuring device (DMA), is 1.5 × 10⁻⁶. 9By keeping the pressure below [Pa], sufficient adhesion strength at the interface between the metal layer 10 and the thermoplastic polyimide layer 21 is ensured. Specifically, the adhesion strength at the interface between the metal layer 10 and the thermoplastic polyimide layer 21 is preferably greater than 1.0 kN / m, more preferably 1.2 kN / m or more, and even more preferably in the range of 1.5 to 3.0 kN / m. Therefore, it is possible to suppress peeling of the metal layer and circuit wiring layer during and after the circuit processing process, thereby improving yield and the reliability of the FPC. The adhesion strength can be measured by the method described in the examples below.

[0034] Furthermore, in this invention, the storage modulus E' of the non-thermoplastic polyimide layer 22, measured using a dynamic viscoelasticity measuring device (DMA), is 1.8 × 10⁻⁶. 9 The tensile strength is greater than [Pa] and satisfies the relationship in equation (1), making it difficult for the insulating resin layer 20 to break even when tensile force is applied during the circuit processing process. Specifically, the elongation at break of the insulating resin layer 20 is preferably greater than 30%, more preferably 40% or more, and even more preferably in the range of 50 to 100%. Therefore, it is possible to suppress the occurrence of breakage of the insulating resin layer 20 during and after the circuit processing process, thereby improving yield and the reliability of the FPC. The elongation at break can be measured by the method described in the examples below.

[0035] Next, we will describe in more detail each layer that makes up the metal-clad laminate 100.

[0036] <Metal layer> There are no particular restrictions on the material of the metal layer 10, and examples include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and alloys thereof. Among these, copper or copper alloys are particularly preferred. The copper foil may be rolled copper foil or electrolytic copper foil, and commercially available copper foil can be used. The material of the circuit wiring layer in the circuit board of the present invention, which will be described later, is the same as that of the metal layer 10. Furthermore, the metal foil may be subjected to surface treatments such as siding, aluminum alkoxide, aluminum chelate, or silane coupling agents for purposes such as rust prevention or improved adhesion.

[0037] The surface roughness of the metal foil, which is the raw material for the metal layer 10, for example, Sz (maximum height), is preferably 0.5 μm or more, more preferably in the range of 0.7 to 6.0 μm, and even more preferably in the range of 1.0 to 5.5 μm, from the viewpoint of ensuring adhesion with the thermoplastic polyimide layer 21. If the surface roughness Sz is less than 0.5 μm, the adhesion with the insulating resin layer 20 will be insufficient, and if it exceeds 6.0 μm, it will cause deterioration of the circuit's transmission characteristics and a decrease in the mechanical strength of the resin. Furthermore, if the surface roughness Sz becomes too large, it may affect the elongation at break of the insulating resin layer 20. However, in this invention, we focus on the existence of roughening abnormalities that cannot be fully identified by surface roughness Sz alone.

[0038] <Insulating resin layer> The thermoplastic polyimide layer 21 as polyimide layer (A) and the thermoplastic polyimide layer 23 as polyimide layer (A') contain thermoplastic polyimide as the main component of the resin, and the non-thermoplastic polyimide layer 22 as polyimide layer (B) contains non-thermoplastic polyimide as the main component of the resin. Here, "main component of the resin" means a component that makes up more than 50% by weight of the resin component, preferably 70% by weight or more, more preferably 80% by weight or more, and most preferably 90-100% by weight of the resin component. In addition, in the present invention, "non-thermoplastic polyimide" generally refers to polyimide that does not soften or exhibit adhesive properties even when heated, but in the present invention, the storage modulus at 30°C measured using a dynamic viscoelasticity measuring device (DMA) is 5.0 × 10⁻⁶. 9 The pressure is greater than [Pa], and the storage modulus at 300°C is 1.8 × 10⁻⁶. 9This refers to polyimides with a storage modulus of [Pa] or higher. Furthermore, "thermoplastic polyimides" generally refer to polyimides whose glass transition temperature (Tg) can be clearly determined, but in this invention, the storage modulus at 30°C measured using a dynamic viscoelasticity analyzer (DMA) is 1.0 × 10⁻⁶. 8 The pressure is greater than [Pa] and the storage modulus at 300°C is 1.5 × 10⁻⁶. 9 This refers to polyimides with a pressure of [Pa] or less.

[0039] Non-thermoplastic polyimide layer: The non-thermoplastic polyimide used in the non-thermoplastic polyimide layer 22 is a non-thermoplastic polyimide obtained by reacting a tetracarboxylic anhydride component with a diamine component. Preferably, the non-thermoplastic polyimide contains an acid dianhydride residue derived from a tetracarboxylic dianhydride and a diamine residue derived from a diamine compound. In this invention, a diamine residue refers to a divalent group derived from a diamine component, and an acid dianhydride residue refers to a tetravalent group derived from a tetracarboxylic dianhydride.

[0040] While monomers commonly used in the synthesis of non-thermoplastic polyimides can be used as the acid anhydride components and diamines that serve as raw materials for non-thermoplastic polyimides, it is preferable that the non-thermoplastic polyimide contains the residues exemplified below in order to control the storage modulus of the non-thermoplastic polyimide layer 22 within an appropriate range.

[0041] (Acid dianhydride residue) The non-thermoplastic polyimide preferably contains an acid dianhydride residue derived from at least one of the following acid dianhydride residues: a BPDA residue derived from 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA), a TAHQ residue derived from 1,4-phenylenebis(trimellitic acid monoester) dianhydride (TAHQ), a PMDA residue derived from pyromellitic acid dianhydride (PMDA), and an NTCDA residue derived from 2,3,6,7-naphthalenetetracarboxylic acid dianhydride (NTCDA).

[0042] To control the storage modulus of the non-thermoplastic polyimide layer 22 within an appropriate range, it is preferable that the non-thermoplastic polyimide contains a total of 5 mol% to 90 mol% of PMDA residues per 100 mol% of the total acid dianhydride residues. In this case, the lower limit of the PMDA residue content is preferably 30 mol% or more, more preferably 50 mol% or more. From a similar viewpoint, it is preferable that the non-thermoplastic polyimide contains a total of 5 mol% to 90 mol% of BPDA residues per 100 mol% of the total acid dianhydride residues. In this case, the lower limit of the BPDA residue content is preferably 10 mol% or more, more preferably 20 mol% or more. Furthermore, it is preferable that the sum of BPDA residues and PMDA residues be 80 mol% or more, preferably 90 mol% or more, per 100 mol% of the total acid dianhydride residues.

[0043] The non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 22 may include known acid dianhydride residues contained in non-thermoplastic polyimides as acid dianhydride residues other than those mentioned above.

[0044] (Diamine residue) The diamine residues included in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 22 are preferably diamine residues derived from a diamine compound represented by general formula (A1).

[0045] [ka]

[0046] In general formula (A1), the linking group X1 independently represents a single bond or -CONH-, Y independently represents a monovalent hydrocarbon group or alkoxy group having 1 to 3 carbon atoms, n1 represents an integer from 0 to 2, and p and q independently represent integers from 0 to 4. Here, "independently" means that in formula (A1), the linking group X1, the multiple substituents Y, and the integers p and q may be the same or different. In formula (A1), the hydrogen atoms in the two terminal amino groups may be substituted, for example, -NR2R3 (where R2 and R3 independently represent any substituent such as an alkyl group). A single bond is preferred for the linking group X1.

[0047] Examples of diamines (A1) include 1,4-diaminobenzene (p-PDA; paraphenylenediamine), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-n-propyl-4,4'-diaminobiphenyl (m-NPB), 2'-methoxy-4,4'-diaminobenzanilide, and 4,4'-diaminobenzanilide.

[0048] In order to control the storage modulus of the non-thermoplastic polyimide layer 22 to an appropriate range, the non-thermoplastic polyimide preferably contains diamine residues derived from diamine (A1) in a total amount of 5 mol% to 100 mol%, more preferably 60 mol% to 100 mol%, and even more preferably 70 mol% to 100 mol%, relative to 100 mol% of the total diamine residues.

[0049] The non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 22 may include known diamine residues as diamine residues other than those mentioned above. It is preferable to use only aromatic compound residues for both the acid dianhydride residues and diamine residues contained in the non-thermoplastic polyimide, as this can improve dimensional accuracy in high-temperature environments.

[0050] 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.

[0051] From the viewpoint of heat resistance, the non-thermoplastic polyimide layer 22 preferably has a glass transition temperature (Tg) of 280°C or higher, and more preferably 300°C or higher.

[0052] Furthermore, the average in-plane thermal expansion coefficient of the non-thermoplastic polyimide layer 22 is preferably in the range of 1 ppm / K to 30 ppm / K, more preferably in the range of 1 ppm / K to 25 ppm / K, and more preferably in the range of 15 ppm / K to 25 ppm / K.

[0053] Furthermore, the non-thermoplastic polyimide layer 22 may be appropriately blended with optional components, such as fillers and flame retardants, as long as they do not impair the effects of the invention.

[0054] Thermoplastic polyimide layer: In the example configuration shown in Figure 1, the thermoplastic polyimide layers 21 and 23 may each be composed of the same or different types of thermoplastic polyimide. The thermoplastic polyimide used in the thermoplastic polyimide layers 21 and 23 is a thermoplastic polyimide obtained by reacting a tetracarboxylic anhydride component with a diamine component. Preferably, the thermoplastic polyimide contains an acid dianhydride residue derived from a tetracarboxylic dianhydride and a diamine residue derived from a diamine compound.

[0055] While monomers commonly used in the synthesis of thermoplastic polyimides can be used as the acid anhydride components and diamines that serve as raw materials for thermoplastic polyimides, it is preferable that the thermoplastic polyimide contains the residues exemplified below in order to control the storage modulus of the thermoplastic polyimide layers 21 and 23 within an appropriate range.

[0056] (Acid dianhydride residue) The thermoplastic polyimide preferably contains acid dianhydride residues similar to those exemplified as acid dianhydride residues in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 22. In this case, in order to control the storage modulus of the thermoplastic polyimide layers 21 and 23 to an appropriate range, it is preferable to include PMDA residues and / or BPDA residues in a total of preferably 30 mol% or more, more preferably 50 mol% or more, and even more preferably 50 mol% to 100 mol% or less, per 100 mol% of the total acid dianhydride residues.

[0057] (Diamine residue) The diamine residues contained in the thermoplastic polyimide constituting the thermoplastic polyimide layers 21 and 23 are preferably diamine residues derived from diamine compounds represented by general formulas (B1) to (B7).

[0058] [ka]

[0059] In formulas (B1) to (B7), R1 independently represents a monovalent hydrocarbon group or alkoxy group having 1 to 6 carbon atoms, linking group A independently represents a divalent group selected from -O-, -S-, -CO-, -SO-, -SO2-, -COO-, -CH2-, -C(CH3)2-, -NH-, or -CONH-, and n1 independently represents an integer from 0 to 4. However, any overlap between formula (B2) and formula (B5) is excluded. Here, "independently" means that in one or more of the above formulas (B1) to (B7), multiple linking groups A, multiple R1, or multiple n1 may be the same or different. In addition, in the above formulas (B1) to (B7), the hydrogen atoms in the two terminal amino groups may be substituted, for example, -NR2R3 (where R2 and R3 independently represent any substituent such as an alkyl group).

[0060] Examples of diamines represented by formula (B1) include 3,3'-diaminodiphenylmethane, 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylpropane, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminobenzophenone, and (3,3'-bisamino)diphenylamine. Examples of diamines represented by formula (B2) include 1,4-bis(3-aminophenoxy)benzene, 3-[4-(4-aminophenoxy)phenoxy]benzeneamine, and 3-[3-(4-aminophenoxy)phenoxy]benzeneamine. Examples of diamines represented by formula (B3) include 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,3-bis(3-aminophenoxy)benzene (APB), 4,4'-[2-methyl-(1,3-phenylene)bisoxy]bisaniline, 4,4'-[4-methyl-(1,3-phenylene)bisoxy]bisaniline, and 4,4'-[5-methyl-(1,3-phenylene)bisoxy]bisaniline. Examples of diamines represented by formula (B4) include bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)]benzophenone, and bis[4,4'-(3-aminophenoxy)]benzanilide. Examples of diamines represented by formula (B5) include 4-[3-[4-(4-aminophenoxy)phenoxy]phenoxy]aniline and 4,4'-[oxybis(3,1-phenyleneoxy)]bisaniline. Examples of diamines represented by formula (B6) include 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), bis[4-(4-aminophenoxy)phenyl]ether (BAPE), bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), and bis[4-(4-aminophenoxy)phenyl]ketone (BAPK). Examples of diamines represented by formula (B7) include bis[4-(3-aminophenoxy)]biphenyl and bis[4-(4-aminophenoxy)]biphenyl.

[0061] To control the storage modulus of the thermoplastic polyimide layers 21 and 23 within an appropriate range, the thermoplastic polyimide preferably contains a total of 60 mol% or more, more preferably 70 mol% or more, and even more preferably 70 mol% to 100 mol%, of diamine residues derived from one or more diamine compounds selected from diamine (B1) to diamine (B7) relative to 100 mol% of the total diamine residues. Since diamine (B1) to diamine (B7) have flexible molecular structures, using at least one diamine compound selected from these in the above range can improve the flexibility of the polyimide molecular chain and impart thermoplasticity. If the total amount of diamine residues derived from one or more diamine compounds selected from diamine (B1) to diamine (B7) is less than 60 mol% of 100 mol% of the total diamine components, the polyimide resin will lack flexibility and sufficient thermoplasticity cannot be obtained.

[0062] Furthermore, the thermoplastic polyimide constituting the thermoplastic polyimide layers 21 and 23 may also preferably contain a diamine residue derived from the diamine compound represented by the general formula (A1) described above. In this case, the thermoplastic polyimide may contain the diamine residue derived from diamine (A1) in an amount preferably between 1 mol% and 40 mol%, more preferably between 5 mol% and 30 mol%, based on 100 mol% of the total diamine components. The diamine compound represented by formula (A1) [diamine (A1)] is as described in the explanation of non-thermoplastic polyimide.

[0063] The thermoplastic polyimide constituting the thermoplastic polyimide layers 21 and 23 may include known diamine residues as diamine residues other than those mentioned above. Furthermore, by making the acid dianhydride residues and diamine residues contained in the thermoplastic polyimide solely aromatic compound residues, dimensional accuracy in high-temperature environments can be improved.

[0064] 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.

[0065] From the viewpoint of adhesion to metal foils and other insulating layers, the thermoplastic polyimide layers 21 and 23 preferably have a glass transition temperature (Tg) in the range of 150°C to less than 300°C, more preferably 200 to 290°C, and most preferably 200 to 280°C.

[0066] Furthermore, the thermoplastic polyimide layers 21 and 23 have an average coefficient of thermal expansion in the in-plane direction greater than 30 ppm / K, preferably in the range of greater than 30 ppm / K and 100 ppm / K or less, and more preferably in the range of greater than 30 ppm / K and 80 ppm / K or less.

[0067] Furthermore, the thermoplastic polyimide layers 21 and 23 may be appropriately blended with optional components, such as fillers and flame retardants, as long as they do not impair the effects of the invention.

[0068] Polyimide synthesis: The nonplastic polyimide constituting the non-thermoplastic polyimide layer 22 and the thermoplastic polyimide constituting the thermoplastic polyimide layers 21 and 23 can be produced by reacting a tetracarboxylic dianhydride and a diamine compound in a solvent to produce polyamic acid, followed by heating and ring closure. For example, polyamic acid, a precursor of polyimide, can be obtained by dissolving a tetracarboxylic dianhydride and a diamine compound in an organic solvent in approximately equimolar amounts and allowing a polymerization reaction to occur by stirring at a temperature in the range of 0 to 100°C for 30 minutes to 24 hours. In the reaction, the reactants are dissolved in the organic solvent in a range of 5 to 50% by weight, preferably 10 to 40% by weight, to produce the precursor. Examples of organic solvents used in polymerization reactions include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethyl sulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, and cresol. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. There are no particular restrictions on the amount of such organic solvents used, but it is preferable to adjust the amount used so that the concentration of the polyamic acid solution obtained by the polymerization reaction is about 5 to 50% by weight.

[0069] The synthesized polyamic acid is usually advantageous to use as a reaction solvent solution, but it can be concentrated, diluted, or replaced with other organic solvents as needed. Furthermore, polyamic acid is advantageous to use because it generally has excellent solvent solubility. The viscosity of the polyamic acid solution is preferably in the range of 500 mPa·s to 100,000 mPa·s. If it falls outside this range, defects such as uneven thickness and streaks are more likely to occur in the film during coating operations, for example, with a coater.

[0070] The method for imidizing polyamic acid is not particularly limited, and heat treatment such as heating at a temperature in the range of 80 to 400°C for 1 to 24 hours is preferably employed. For non-thermoplastic and thermoplastic polyimides, a completely imidized structure is most preferred. However, a portion of the polyimide may be amide acid. The imidization rate is determined by measuring the infrared absorption spectrum of the polyimide thin film using a Fourier transform infrared spectrophotometer (commercially available: JASCO FT / IR620) by the single-reflection ATR method, where the imidization rate is 10¹⁵ cm⁻¹. -1 Using a nearby benzene ring absorber as a reference, 1780 cm -1 It can be calculated from the absorbance of the C=O stretching originating from the imide group.

[0071] In non-thermoplastic and thermoplastic polyimides, the coefficient of thermal expansion, tensile modulus, glass transition temperature, etc., can be controlled by selecting the types of acid dianhydride residues and diamine residues, and the molar ratios of each when two or more acid dianhydride residues or diamine residues are applied. Furthermore, in non-thermoplastic and thermoplastic polyimides, if there are multiple polyimide structural units, they may exist as blocks or randomly, but random arrangement is preferable.

[0072] <Layer thickness> In the metal-clad laminate 100, the thickness of the metal layer 10 is not particularly limited, but for example, when using copper foil, in order to accommodate miniaturization, the upper limit of the thickness is preferably 25 μm or less, more preferably 12 μm or less, and even more preferably 9 μm or less. From the viewpoint of production stability and handling, the lower limit of the thickness of the copper foil is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more.

[0073] In the metal-clad laminate 100, the thickness of the insulating resin layer 20 is not particularly limited, but in order to accommodate miniaturization, the upper limit of the thickness is preferably 20 μm or less, more preferably 12 μm or less, and even more preferably 9 μm or less. The lower limit of the thickness of the insulating resin layer 20 is preferably 5 μm or more, more preferably 4 μm or more, and even more preferably 3 μm or more. If the thickness of the insulating resin layer 20 exceeds 20 μm, it becomes difficult to accommodate miniaturization. If the thickness of the insulating resin layer 20 is less than 3 μm, it becomes difficult to ensure sufficient insulation in the circuit board.

[0074] The thickness of the non-thermoplastic polyimide layer 22 is not particularly limited, but from the viewpoint of ensuring the function as a base resin layer while accommodating miniaturization, and further ensuring transportability during manufacturing and thermoplastic polyimide coating, the upper limit of the thickness is preferably 18 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less. The lower limit of the thickness is preferably 1 μm or more, more preferably 1.5 μm or more, and even more preferably 2 μm or more. If the thickness of the non-thermoplastic polyimide layer 22 exceeds the upper limit, it becomes difficult to accommodate miniaturization, and if it is below the lower limit, the electrical insulation and handling properties become insufficient, and the elongation at break of the insulating resin layer 20 tends to decrease.

[0075] The thickness of the thermoplastic polyimide layers 21 and 23 is not particularly limited, but the upper limit of the thickness is preferably 5 μm or less, more preferably 4 μm or less, and even more preferably 3 μm or less, and the lower limit of the thickness is preferably 0.3 μm or more, more preferably 0.4 μm or more, and even more preferably 0.5 μm or more. If the thickness of the thermoplastic polyimide layers 21 and 23 exceeds the upper limit, dimensional stability tends to deteriorate, and if it is below the lower limit, adhesion becomes insufficient, and the elongation at break of the insulating resin layer 20 tends to decrease.

[0076] [Manufacturing of metal-clad laminates] The metal-clad laminate 100 can be manufactured by, for example, repeatedly applying and drying a polyamic acid solution onto a metal foil a predetermined number of times, followed by imidization, or by heat-pressing a metal foil onto a resin film containing a thermoplastic polyimide layer 21, although these methods are not shown in the figures. The method of applying the polyamic acid solution onto the metal foil is not particularly limited and can be applied using, for example, a coater such as a comma, die, knife, or lip. Furthermore, a double-sided metal-clad laminate can be manufactured by further heat-pressing a metal foil onto the thermoplastic polyimide layer 23 of the metal-clad laminate 100.

[0077] The metal-clad laminate 100 obtained in this embodiment can be used to manufacture circuit boards such as single-sided FPCs by processing the metal layer 10 with wiring circuits, for example.

[0078] [Circuit board] A circuit board according to one embodiment of the present invention can be manufactured by processing the metal layer 10 of a metal-clad laminate 100 into a pattern by a conventional method to form a wiring layer. Although not shown in the figures, the circuit board of this embodiment comprises an insulating resin layer 20 and a circuit wiring layer laminated on at least one or both sides of the insulating resin layer 20. The configuration of the insulating resin layer 20 is the same as that of the metal-clad laminate 100 shown in Figure 1. In other words, the circuit board of the present invention has an insulating resin layer 20 which includes a thermoplastic polyimide layer 21 as a polyimide layer (A) in contact with the circuit wiring layer, and a non-thermoplastic polyimide layer 22 as a polyimide layer (B) laminated adjacent to polyimide layer (A). Furthermore, the storage modulus E' of the thermoplastic polyimide layer 21 at 300°C, as measured using a dynamic viscoelasticity measuring device (DMA), is 1.5 × 10⁻⁶. 9 [Pa] or less, The storage modulus E' of the non-thermoplastic polyimide layer 22 at 300°C, measured using a dynamic viscoelasticity analyzer (DMA), is 1.8 × 10⁻⁶. 9 [Pa] or higher, When the circuit wiring layer is removed, the maximum valley depth of the insulating resin layer 20 measured on the exposed surface S of the thermoplastic polyimide layer 21 is Sv [μm], and the thickness of the thermoplastic polyimide layer 21 is d [μm]. Then, the following equation (1) applies: 2d≧Sv>0.5d ··· (1) It satisfies the relationship.

[0079] In the circuit board of the present invention, when measuring the maximum valley depth Sv of the insulating resin layer 20, the exposed surface S of the thermoplastic polyimide layer 21 is revealed by removing the circuit wiring layer from the circuit board. The method for removing the circuit wiring layer is not particularly limited, and known methods can be used, and either wet etching or dry etching may be used. For example, when removing a copper wiring layer made of copper, the copper wiring layer can be etched by immersing it in a ferric chloride etching solution at a liquid temperature of 30°C for 3 minutes to remove the copper foil, similar to the procedure described for flexible copper-clad laminates, and then immersing it in pure water to wash off the etching solution and then drying it. If the circuit board is incorporated into an electronic device such as a smartphone, it is preferable to disassemble it, for example, and peel off the bonding sheet, coverlay, etc. of the circuit board before etching the circuit wiring layer.

[0080] The circuit board of this embodiment can preferably be applied as, for example, an FPC, a rigid-flex circuit board, or the like.

[0081] [Electronic Devices / Electronic Equipment] The electronic devices and electronic equipment according to embodiments of the present invention include the circuit board described above. Examples of electronic devices of the present invention include display devices such as liquid crystal displays, organic EL displays, and electronic paper, organic EL lighting, solar cells, touch panels, camera modules, inverters, converters, and their components. Examples of electronic equipment include HDDs, DVDs, mobile phones, smartphones, tablet terminals, electronic control units (ECUs) and power control units (PCUs) of automobiles. The circuit board is preferably used in these electronic devices and electronic equipment as components such as wiring for movable parts, cables, and connectors. [Examples]

[0082] The present invention will be described in detail below with reference to examples, but the present invention is not limited in any way by these examples. In the following examples, unless otherwise specified, various measurements and evaluations are performed as described below.

[0083] [Measurement of the thickness of the polyimide layer] Flexible copper-clad laminates were processed in the thickness direction using a JEOL CROSSECTION POLISHER (IB-09010CP) under an acceleration voltage of 5.5kV. After pretreatment of the resulting specimen cross-sections, the thickness of five arbitrary points in each polyimide layer was measured using a Hitachi High-Tech electron microscope (Scanning Electron Microscope / SU-3800), and the average of these measurements was defined as the film thickness.

[0084] [Measurement of Storage Modulus] A 5mm x 20mm polyimide film was measured using a dynamic viscoelasticity analyzer (DMA: TA Instruments, product; RSA3) under the conditions of heating from 30°C to 400°C at a rate of 5°C / min and a frequency of 1 Hz. The storage modulus at 30°C was 5.0 × 10⁻⁶. 9 The pressure is greater than [Pa], and the storage modulus at 300°C is 1.8 × 10⁻⁶. 9Polyimides with a storage modulus of [Pa] or higher were classified as "non-thermoplastic." The storage modulus at 30°C was 1.0 × 10⁻⁶. 8 The pressure is greater than [Pa] and the storage modulus at 300°C is 1.5 × 10⁻⁶. 9 Polyimides with a Pa of [Pa] or less were classified as "thermoplastic."

[0085] [Maximum valley depth (Sv), maximum mountain height (Sp), maximum height (Sz)] A flexible copper-clad laminate was etched by immersing it in a ferric chloride etching solution at 30°C for 3 minutes to remove the copper foil, then immersing it in pure water to wash off the etching solution, and finally drying it. This process exposed the surface of the polyimide layer (A) of the insulating resin layer. The surface roughness of the polyimide layer (A) of the sample was measured using a Keyence laser microscope (VK-X3000) in laser microscope mode (50x objective lens), and the entire measurement area was measured. The maximum valley depth (Sv), maximum peak height (Sp), and maximum height (Sz) were calculated for the entire measurement field according to the ISO 25178 standard. (Filter type: Gaussian, S-filter: 0.8 μm, F-operation: waviness removal strength 5, L-filter: 0.01 mm)

[0086] [Viscosity measurement] Viscosity was measured at 25°C using an E-type viscometer (Brookfield, product name: DV-II+Pro). The rotation speed was set so that the torque was between 10% and 90%, and the value was read after 2 minutes had elapsed since the start of measurement, when the viscosity had stabilized.

[0087] [Measurement of weight-average molecular weight (Mw) of polyimides] The measurements were performed using gel permeation chromatography (Tosoh Corporation, product name: HLC-8420GPC). Polystyrene was used as the standard substance, and N,N-dimethylacetamide was used as the eluent.

[0088] [Measurement of adhesion strength] Samples were prepared by etching the copper foil on the coated side of a single-sided copper-clad laminate and processing it into a circuit with a width of 1.0 mm. The surface of the polyimide layer was fixed to an aluminum plate with double-sided tape, and measurements were taken using a Strograph VE-1D manufactured by Toyo Seiki Seisakusho Co., Ltd. The copper foil was pulled in a 180-degree direction at a speed of 50 mm / min, and the median strength when 10 mm was peeled off was determined and defined as the adhesion strength. Adhesion strengths exceeding 1.0 kN / m were evaluated as "○", and those below 1.0 kN / m were evaluated as "×".

[0089] [Elongation at break] Samples were prepared by etching copper foil from a flexible copper-clad laminate to form a film. These samples were cut to a width of 12.7 mm and a length of 200 mm and measured using a Strograph VG1F manufactured by Toyo Seiki Seisakusho Co., Ltd. The samples were pulled at a speed of 50 mm / min with a chuck distance of 101.6 mm, and the elongation at break was determined from the amount of elongation at the time of fracture. Samples with an elongation at break exceeding 30% were evaluated as "○", and those below 30% were evaluated as "×".

[0090] <Material> The abbreviations used in the examples and comparative examples refer to the following compounds. PMDA: Pyromelit acid dianhydride BTDA:3,3',4,4'-benzophenonetetracarboxylic dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic acid dianhydride m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl TPE-R: 1,3-bis(4-aminophenoxy)benzene BAPP: 2,2-Bis[4-(4-aminophenoxy)phenyl]propane DMAc: N,N-dimethylacetamide Copper foil 1: Rolled copper foil, thickness: 9μm, Sz=2.3μm, Sp=1.1μm Copper foil 2: Electrolytic copper foil, thickness: 9μm, Sz=5.2μm, Sp=3.2μm

[0091] (Synthesis Example 1) 255.0 parts by weight of DMAc was mixed with 21.43 parts by weight of m-TB (100.92 moles) and stirred at room temperature for at least 30 minutes until completely dissolved. Next, 16.26 parts by weight of PMDA (74.56 moles) and 7.31 parts by weight of BPDA (24.85 moles) were added and stirred at room temperature for 4 hours to obtain polyamic acid solution 1 with a viscosity of 27,400 mPa·s and a weight-average molecular weight of 117,000.

[0092] Polyamic acid solution 1 was uniformly applied to the substrate so that the cured thickness was approximately 25 μm, and then heated and dried at a temperature of 140°C or lower to remove the solvent. Furthermore, heat treatment was performed by gradually increasing the temperature from 140°C to 360°C to complete the imidation and prepare the obtained polyimide film 1. The storage modulus of the obtained polyimide film 1 was 2.2 × 10⁻⁶. 9 It had a temperature of Pa (300°C) and was non-thermoplastic.

[0093] (Synthesis Example 2) 264.0 parts by weight of DMAc was mixed with 23.20 parts by weight of BAPP (56.53 moles) and stirred at room temperature for at least 30 minutes until completely dissolved. Next, 11.95 parts by weight of PMDA (54.77 moles) and 0.85 parts by weight of BPDA (2.88 moles) were added and stirred at room temperature for 4 hours to obtain polyamic acid solution 2 with a viscosity of 1,700 mPa·s and a weight-average molecular weight of 200,000. The storage modulus of polyimide film 2, prepared in the same manner as in synthesis example 1, is 1.2 × 10⁻⁶. 9 It had a temperature of Pa (300°C) and was thermoplastic.

[0094] (Synthesis Example 3) 264.0 parts by weight of DMAc was mixed with 10.55 parts by weight of TPE-R (36.10 mol parts) and 7.66 parts by weight of m-TB (33.10 mol parts), and the mixture was stirred at room temperature for at least 30 minutes to completely dissolve the compounds. Next, 10.89 parts by weight of PMDA (49.93 mol parts) and 6.90 parts by weight of BTDA (21.40 mol parts) were added, and the mixture was stirred at room temperature for 4 hours to obtain polyamic acid solution 3 with a viscosity of 3,800 mPa·s and a weight-average molecular weight of 219,000. The storage modulus of polyimide film 3, prepared in the same manner as in synthesis example 1, is 5.6 × 10⁻⁶. 8 The temperature was Pa (300°C), and it was thermoplastic.

[0095] (Synthesis Example 4) 263.0 parts by weight of DMAc was mixed with 20.22 parts by weight of m-TB (69.20 moles) and stirred at room temperature for at least 30 minutes until completely dissolved. Next, 10.89 parts by weight of PMDA (49.93 moles) and 6.90 parts by weight of BTDA (21.40 moles) were added and stirred at room temperature for 4 hours to obtain polyamic acid solution 4 with a viscosity of 3,800 mPa·s and a weight-average molecular weight of 180,000. The storage modulus of polyimide film 4, prepared in the same manner as in Synthesis Example 1, is 2.1 × 10⁻⁶. 9 It had a temperature of Pa (3000°C) and was non-thermoplastic.

[0096] [Example 1] Polyamic acid solution 2 was applied to copper foil 1, aiming for a cured thickness of 2.0 μm, then heated and dried at 140°C or below to remove the solvent. Polyamic acid solution 1 was then applied again, aiming for a cured thickness of 5.0 μm, and heated and dried at 140°C or below to remove the solvent. Furthermore, polyamic acid solution 2 was applied again, aiming for a cured thickness of 2.0 μm, and heated and dried at 140°C or below to remove the solvent. Subsequently, the temperature was gradually increased from 140°C to 360°C to perform imidization, and a single-sided copper-clad laminate 1 was prepared. Copper foil 1 was placed on the polyimide layer side of the obtained single-sided copper-clad laminate 1, and lamination was performed using a hot roll laminating machine at a lamination pressure of 1 kN / cm². 2A flexible copper-clad laminate 1 having copper foil on both sides was obtained by continuously heat laminating at a lamination temperature of 350°C. The thickness of each polyimide layer was measured by electron microscopy from the cross-section of the obtained flexible copper-clad laminate 1, and the thicknesses were found to be 2.4 μm for the first layer, 5.1 μm for the second layer, and 2.2 μm for the third layer, in the order in which they were applied. The evaluation results of the flexible copper-clad laminate 1 are shown in Table 1. In Table 1, the storage modulus at 300°C for the layer corresponding to polyimide layer (A) is "E'(A)", the storage modulus at 300°C for the layer corresponding to polyimide layer (B) is "E'(B)", the thickness of the layer corresponding to polyimide layer (A) is "d", and the maximum valley depth of the insulating resin layer measured on the exposed surface of the layer corresponding to polyimide layer (A) when the copper foil is removed is "Sv".

[0097] [Example 2] Polyamic acid solution 2 was applied to copper foil 1 to a thickness of approximately 0.5 μm after curing, then heated and dried at a temperature of 140°C or lower to remove the solvent. Next, polyamic acid solution 1 was applied to the copper foil 1 to a thickness of approximately 8.0 μm after curing, then heated and dried at a temperature of 140°C or lower to remove the solvent. Finally, polyamic acid solution 2 was applied to the copper foil 1 to a thickness of approximately 0.5 μm after curing, then heated and dried at a temperature of 140°C or lower to remove the solvent. Afterward, the temperature was gradually increased from 140°C to 360°C to perform imidization, and a single-sided copper-clad laminate 2 was prepared. Copper foil 1 was placed on the polyimide layer side of the obtained single-sided copper-clad laminate 2, and lamination was performed using a hot roll laminating machine at a lamination pressure of 1 kN / cm². 2 A flexible copper-clad laminate 2 was obtained by continuously thermal laminating at a lamination temperature of 350°C, with copper foil on both sides. The thickness of each polyimide layer was measured by electron microscopy from the cross-section of the obtained flexible copper-clad laminate 2, and the thicknesses were found to be 0.6 μm for the first layer, 8.2 μm for the second layer, and 0.7 μm for the third layer, in the order of application. The evaluation results of the flexible copper-clad laminate 2 are shown in Table 1.

[0098] [Example 3] Polyamic acid solution 2 was applied to copper foil 1, aiming for a cured thickness of 1.0 μm, then heated and dried at 140°C or below to remove the solvent. Next, polyamic acid solution 1 was applied again, aiming for a cured thickness of 7.0 μm, then heated and dried at 140°C or below to remove the solvent. Finally, polyamic acid solution 2 was applied again, aiming for a cured thickness of 1.0 μm, then heated and dried at 140°C or below to remove the solvent. Afterward, the temperature was gradually increased from 140°C to 360°C to perform imidization, preparing a single-sided copper-clad laminate 3. Copper foil 1 was placed on the polyimide layer side of the obtained single-sided copper-clad laminate 3, and lamination was performed using a hot roll laminating machine at a lamination pressure of 1 kN / cm². 2 A flexible copper-clad laminate 3 was obtained by continuously thermal laminating at a lamination temperature of 350°C, with copper foil on both sides. The thickness of each polyimide layer was measured by electron microscopy from the cross-section of the obtained flexible copper-clad laminate 3, and the thicknesses were found to be 1.2 μm for the first layer, 6.8 μm for the second layer, and 0.9 μm for the third layer, in the order of application. The evaluation results of the flexible copper-clad laminate 3 are shown in Table 1.

[0099] [Example 4] Polyamic acid solution 2 was applied to copper foil 2, aiming for a cured thickness of 1.5 μm, and then heated and dried at 140°C or below to remove the solvent. Next, polyamic acid solution 1 was applied to the copper foil 2, aiming for a cured thickness of 6.0 μm, and then heated and dried at 140°C or below to remove the solvent. Furthermore, polyamic acid solution 2 was applied to the copper foil 2, aiming for a cured thickness of 1.5 μm, and then heated and dried at 140°C or below to remove the solvent. Afterward, the temperature was gradually increased from 140°C to 360°C to perform imidization, and a single-sided copper-clad laminate 4 was prepared. Copper foil 2 was placed on the polyimide layer side of the obtained single-sided copper-clad laminate 4, and lamination was performed using a hot roll laminating machine at a lamination pressure of 1 kN / cm². 2 A flexible copper-clad laminate 4 having copper foil on both sides was obtained by continuous thermal lamination at a lamination temperature of 350°C. The thickness of each polyimide layer was measured by electron microscopy from the cross-section of the obtained flexible copper-clad laminate 4, and the thicknesses were found to be 1.5 μm for the first layer, 6.2 μm for the second layer, and 1.7 μm for the third layer, in the order in which they were applied. The evaluation results of the flexible copper-clad laminate 4 are shown in Table 1.

[0100] [Example 5] Polyamic acid solution 2 was applied to copper foil 2, aiming for a cured thickness of 3.0 μm, and then heated and dried at 140°C or below to remove the solvent. Next, polyamic acid solution 1 was applied to the copper foil 2, aiming for a cured thickness of 3.0 μm, and then heated and dried at 140°C or below to remove the solvent. Furthermore, polyamic acid solution 2 was applied to the copper foil 2, aiming for a cured thickness of 3.0 μm, and then heated and dried at 140°C or below to remove the solvent. Afterward, the temperature was gradually increased from 140°C to 360°C to perform imidization, and a single-sided copper-clad laminate 5 was prepared. Copper foil 2 was placed on the polyimide layer side of the obtained single-sided copper-clad laminate 5, and lamination was performed using a hot roll laminating machine at a lamination pressure of 1 kN / cm². 2 A flexible copper-clad laminate 5 was obtained by continuously thermal laminating at a lamination temperature of 350°C, with copper foil on both sides. The thickness of each polyimide layer was measured by electron microscopy from the cross-section of the obtained flexible copper-clad laminate 5, and the thicknesses were found to be 2.9 μm for the first layer, 2.8 μm for the second layer, and 3.2 μm for the third layer, in the order of application. The evaluation results of the flexible copper-clad laminate 5 are shown in Table 1.

[0101] [Example 6] Polyamic acid solution 2 was applied to copper foil 1 with a target thickness of 2.0 μm after curing, and then heated and dried at a temperature of 140°C or lower to remove the solvent. Polyamic acid solution 1 was then applied again with a target thickness of 3.0 μm after curing, and then heated and dried at a temperature of 140°C or lower to remove the solvent. Subsequently, the temperature was gradually increased from 140°C to 360°C to perform imidization, and a flexible single-sided copper-clad laminate 6 was prepared. The thickness of each polyimide layer was measured by electron microscopy from the cross-section of the obtained flexible single-sided copper-clad laminate 6. The thicknesses were found to be 2.2 μm for the first layer and 5.3 μm for the second layer, in the order of application. The evaluation results of the flexible single-sided copper-clad laminate 6 are shown in Table 1.

[0102] [Example 7] Polyamic acid solution 2 was applied to copper foil 1, aiming for a cured thickness of 1.0 μm, then heated and dried at 140°C or below to remove the solvent. Next, polyamic acid solution 1 was applied again, aiming for a cured thickness of 2.0 μm, then heated and dried at 140°C or below to remove the solvent. Finally, polyamic acid solution 2 was applied again, aiming for a cured thickness of 1.0 μm, then heated and dried at 140°C or below to remove the solvent. Afterward, the temperature was gradually increased from 140°C to 360°C to perform imidization, preparing a single-sided copper-clad laminate 7. Copper foil 1 was placed on the polyimide layer side of the obtained single-sided copper-clad laminate 7, and lamination was performed using a hot roll laminating machine at a lamination pressure of 1 kN / cm². 2 A flexible copper-clad laminate 7 having copper foil on both sides was obtained by continuous thermal lamination at a lamination temperature of 350°C. The thickness of each polyimide layer was measured by electron microscopy from the cross-section of the obtained flexible copper-clad laminate 7, and the thicknesses were found to be 1.2 μm for the first layer, 2.3 μm for the second layer, and 0.9 μm for the third layer, in the order in which they were applied. The evaluation results of the flexible copper-clad laminate 7 are shown in Table 1.

[0103] [Example 8] Polyamic acid solution 2 was applied to copper foil 2, aiming for a cured thickness of 3.0 μm, and then heated and dried at 140°C or below to remove the solvent. Next, polyamic acid solution 1 was applied to the copper foil 2, aiming for a cured thickness of 18.0 μm, and then heated and dried at 140°C or below to remove the solvent. Furthermore, polyamic acid solution 2 was applied to the copper foil 2, aiming for a cured thickness of 3.0 μm, and then heated and dried at 140°C or below to remove the solvent. Afterward, the temperature was gradually increased from 140°C to 360°C to perform imidization, and a single-sided copper-clad laminate 8 was prepared. Copper foil 2 was placed on the polyimide layer side of the obtained single-sided copper-clad laminate 8, and lamination was performed using a hot roll laminating machine at a lamination pressure of 1 kN / cm². 2 A flexible copper-clad laminate 8 was obtained by continuously thermal laminating at a lamination temperature of 350°C, with copper foil on both sides. The thickness of each polyimide layer was measured by electron microscopy from the cross-section of the obtained flexible copper-clad laminate 8, and the thicknesses were found to be 3.1 μm for the first layer, 18.4 μm for the second layer, and 3.2 μm for the third layer, in the order of application. The evaluation results of the flexible copper-clad laminate 8 are shown in Table 1.

[0104] [Comparative Example 1] Polyamic acid solution 2 was applied to copper foil 1, aiming for a cured thickness of 1.0 μm, and then heated and dried at 140°C or below to remove the solvent. Next, polyamic acid solution 3 was applied to the copper foil 1, aiming for a cured thickness of 7.0 μm, and then heated and dried at 140°C or below to remove the solvent. Furthermore, polyamic acid solution 2 was applied again, aiming for a cured thickness of 1.0 μm, and then heated and dried at 140°C or below to remove the solvent. Afterward, the temperature was gradually increased from 140°C to 360°C to perform imidization, and a single-sided copper-clad laminate 9 was prepared. Copper foil 1 was placed on the polyimide layer side of the obtained single-sided copper-clad laminate 9, and lamination was performed using a hot roll laminating machine at a lamination pressure of 1 kN / cm². 2 A flexible copper-clad laminate 9 was obtained by continuously thermal laminating at a lamination temperature of 350°C, with copper foil on both sides. The thickness of each polyimide layer was measured by electron microscopy from the cross-section of the obtained flexible copper-clad laminate 9, and the thicknesses were found to be 1.1 μm for the first layer, 7.2 μm for the second layer, and 0.8 μm for the third layer, in the order of application. The evaluation results of the flexible copper-clad laminate 9 are shown in Table 1.

[0105] [Comparative Example 2] Polyamic acid solution 4 was applied to copper foil 1 with a target thickness of 1.0 μm after curing, then heated and dried at 140°C or below to remove the solvent. Next, polyamic acid solution 1 was applied again with a target thickness of 7.0 μm after curing, then heated and dried at 140°C or below to remove the solvent. Finally, polyamic acid solution 4 was applied again with a target thickness of 1.0 μm after curing, then heated and dried at 140°C or below to remove the solvent. Afterward, the temperature was gradually increased from 140°C to 360°C to perform imidization, and a single-sided copper-clad laminate 10 was prepared. Copper foil 1 was placed on the polyimide layer side of the obtained single-sided copper-clad laminate 10, and lamination was performed using a hot roll laminating machine at a lamination pressure of 1 kN / cm². 2A flexible copper-clad laminate 10 having copper foil on both sides was obtained by continuous thermal lamination at a lamination temperature of 350°C. The thickness of each polyimide layer was measured by electron microscopy from the cross-section of the obtained flexible copper-clad laminate 10, and the thicknesses were found to be 1.2 μm for the first layer, 7.4 μm for the second layer, and 0.9 μm for the third layer, in the order in which they were applied. The evaluation results of the flexible copper-clad laminate 10 are shown in Table 1.

[0106] [Comparative Example 3] Polyamic acid solution 2 was applied to copper foil 1 with a target thickness of 0.5 μm after curing, then heated and dried at 140°C or below to remove the solvent. Next, polyamic acid solution 1 was applied again with a target thickness of 9.0 μm after curing, then heated and dried at 140°C or below to remove the solvent. Finally, polyamic acid solution 2 was applied again with a target thickness of 0.5 μm after curing, then heated and dried at 140°C or below to remove the solvent. Afterward, the temperature was gradually increased from 140°C to 360°C to perform imidization, and a single-sided copper-clad laminate 11 was prepared. Copper foil 1 was placed on the polyimide layer side of the obtained single-sided copper-clad laminate 11, and lamination was performed using a hot roll laminating machine at a lamination pressure of 1 kN / cm². 2 A flexible copper-clad laminate 11 having copper foil on both sides was obtained by continuous thermal lamination at a lamination temperature of 350°C. The thickness of each polyimide layer was measured by electron microscopy from the cross-section of the obtained flexible copper-clad laminate 11, and the thicknesses were found to be 0.4 μm for the first layer, 8.8 μm for the second layer, and 0.6 μm for the third layer, in the order in which they were applied. The evaluation results of the flexible copper-clad laminate 11 are shown in Table 1.

[0107] [Comparative Example 4] Polyamic acid solution 2 was applied to copper foil 2 with a target thickness of 1.0 μm after curing, then heated and dried at 140°C or below to remove the solvent. Next, polyamic acid solution 1 was applied with a target thickness of 7.0 μm after curing, then heated and dried at 140°C or below to remove the solvent. Furthermore, polyamic acid solution 2 was applied again with a target thickness of 1.0 μm after curing, then heated and dried at 140°C or below to remove the solvent. Afterward, the temperature was gradually increased from 140°C to 360°C to perform imidization, and a single-sided copper-clad laminate 12 was prepared. Copper foil 2 was placed on the polyimide layer side of the obtained single-sided copper-clad laminate 12, and lamination was performed using a hot roll laminating machine at a lamination pressure of 1 kN / cm². 2 A flexible copper-clad laminate 12 having copper foil on both sides was obtained by continuous thermal lamination at a lamination temperature of 350°C. The thickness of each polyimide layer was measured by electron microscopy from the cross-section of the obtained flexible copper-clad laminate 12, and the thicknesses were found to be 1.0 μm for the first layer, 7.2 μm for the second layer, and 0.9 μm for the third layer, in the order in which they were applied. The evaluation results of the flexible copper-clad laminate 12 are shown in Table 1.

[0108] [Comparative Example 5] Polyamic acid solution 2 was applied to copper foil 1, aiming for a cured thickness of 2.5 μm, then heated and dried at 140°C or below to remove the solvent. Next, polyamic acid solution 1 was applied again, aiming for a cured thickness of 4.0 μm, then heated and dried at 140°C or below to remove the solvent. Finally, polyamic acid solution 2 was applied again, aiming for a cured thickness of 2.5 μm, then heated and dried at 140°C or below to remove the solvent. Afterward, the temperature was gradually increased from 140°C to 360°C to perform imidization, preparing a single-sided copper-clad laminate 13. Copper foil 1 was placed on the polyimide layer side of the obtained single-sided copper-clad laminate 13, and laminated using a hot roll laminating machine at a lamination pressure of 1 kN / cm². 2 A flexible copper-clad laminate 13 having copper foil on both sides was obtained by continuous thermal lamination at a lamination temperature of 350°C. The thickness of each polyimide layer was measured by electron microscopy from the cross-section of the obtained flexible copper-clad laminate 13, and the thicknesses were found to be 2.7 μm for the first layer, 3.8 μm for the second layer, and 2.8 μm for the third layer, in the order in which they were applied. The evaluation results of the flexible copper-clad laminate 13 are shown in Table 1.

[0109] [Table 1]

[0110] From Table 1, the storage modulus E' at 300°C for the polyimide layer (A) is 1.5 × 10⁻⁶. 9 [Pa] or less, and the storage modulus E' at 300°C for the polyimide layer (B) is 1.8 × 10⁻⁶ 9 The flexible copper-clad laminates of Examples 1 to 8, which have a pressure of [Pa] or higher and satisfy the relationship of formula (1), were confirmed to have sufficient adhesion between the copper layer and the insulating resin layer for practical use, as well as sufficient elongation for practical use. On the other hand, in Comparative Example 1, the storage modulus E' of the polyimide layer (B) at 300°C was 1.8 × 10⁻⁶. 9 Because the pressure was less than [Pa], it was suspected that the resulting deterioration in mechanical properties caused appearance defects, making it unsuitable for use as a flexible copper-clad laminate. Furthermore, in Comparative Example 2, the storage modulus E' at 300°C for the layer corresponding to the polyimide layer (A) was 1.5 × 10⁻⁶. 9 Because it exceeded [Pa], sufficient adhesion for practical use could not be obtained. Furthermore, Comparative Examples 3 to 5 did not satisfy formula (1), resulting in insufficient elongation at break (Comparative Examples 3 and 4) or insufficient adhesion (Comparative Example 5), thus failing to meet the required characteristics as flexible copper-clad laminates. The reason for this is thought to be that in Comparative Examples 3 and 4, Sv exceeded 2d, resulting in sufficient adhesion, but the roughening abnormalities reached deep into the second layer of the polyimide layer, preventing sufficient elongation at break. In Comparative Example 5, Sv was less than 0.5, resulting in insufficient adhesion.

[0111] Although embodiments of the present invention have been described in detail above for illustrative purposes, the present invention is not limited to the above embodiments and various modifications are possible. [Explanation of Symbols]

[0112] 10…Metal layer, 20…Insulating resin layer, 21,23…Thermoplastic polyimide layer, 22…Non-thermoplastic polyimide layer, 100…Metal-clad laminate, S…Exposed surface

Claims

1. A metal-clad laminate comprising an insulating resin layer and a metal layer laminated on one or both sides of the insulating resin layer, The insulating resin layer comprises a polyimide layer (A) in contact with the metal layer and a polyimide layer (B) laminated adjacent to the polyimide layer (A). The storage modulus E' of the polyimide layer (A), measured using a dynamic viscoelasticity analyzer (DMA), is 1.5 × 10⁻⁶. ９ [Pa] or less, The storage modulus E' of the polyimide layer (B), measured using a dynamic viscoelasticity analyzer (DMA), is 1.8 × 10⁻⁶. ９ [Pa] or greater, When the metal layer is removed, the maximum valley depth of the insulating resin layer measured on the exposed surface of the polyimide layer (A) is Sv [μm], and the thickness of the polyimide layer (A) is d [μm], then the following equation (1): 2d≧Sv>0.5d... (1) A metal-clad laminate characterized by satisfying the following relationship.

2. The relationship between the thickness d of the polyimide layer (A) and the maximum peak height Sp of the metal layer is given by the following equation (2): d<Sp... (2) A metal-clad laminate according to claim 1, relating to the above.

3. The metal-clad laminate according to claim 2, wherein the adhesion strength of the interface between the metal layer and the polyimide layer (A) is higher than 1.0 kN / m.

4. The metal-clad laminate according to claim 2, wherein the elongation at break of the insulating resin layer is higher than 30%.

5. The insulating resin layer comprises the polyimide layer (A), the polyimide layer (B), and a polyimide layer (A') laminated adjacent to the polyimide layer (B). The polyimide layer (A) and the polyimide layer (A') are thermoplastic polyimide layers containing thermoplastic polyimide as the main component of the resin component. The thermoplastic polyimide contains diamine residues derived from a diamine component and acid dianhydride residues derived from a tetracarboxylic dianhydride component, and further contains, in total, 30 mol% or more of acid dianhydride residues derived from pyromellitic dianhydride (PMDA) and / or acid anhydride residues derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) relative to the total acid dianhydride residues. The polyimide layer (B) is a non-thermoplastic polyimide layer containing non-thermoplastic polyimide as the main component of the resin component, The non-thermoplastic polyimide contains diamine residues derived from a diamine component and acidic dianhydride residues derived from a tetracarboxylic dianhydride component, and further contains, in the total diamine residues, diamine residues derived from a diamine compound represented by the following general formula (A1) in an amount of 5 mol% to 100 mol%, and The metal-clad laminate according to claim 1, wherein the total acid dianhydride residues contain acid dianhydride residues (PMDA residues) derived from pyromellitic acid dianhydride (PMDA) in an amount of 5 mol% to 90 mol%. 【Chemistry 1】 [In general formula (A1), the linking group X1 independently represents a single bond or -CONH-, Y independently represents a monovalent hydrocarbon group or alkoxy group having 1 to 3 carbon atoms, n1 represents an integer from 0 to 2, and p and q independently represent integers from 0 to 4.]

6. A circuit board comprising an insulating resin layer and a circuit wiring layer laminated on one or both sides of the insulating resin layer, The insulating resin layer comprises a polyimide layer (A) in contact with the circuit wiring layer and a polyimide layer (B) laminated adjacent to the polyimide layer (A). The storage modulus E' of the polyimide layer (A), measured using a dynamic viscoelasticity analyzer (DMA), is 1.5 × 10⁻⁶. ９ [Pa] or less, The storage modulus E' of the polyimide layer (B), measured using a dynamic viscoelasticity analyzer (DMA), is 1.8 × 10⁻⁶. ９ [Pa] or greater, When the circuit wiring layer is removed, the maximum valley depth of the insulating resin layer measured on the exposed surface of the polyimide layer (A) is Sv [μm], and the thickness of the polyimide layer (A) is d [μm], then the following equation (1): 2d≧Sv>0.5d... (1) A circuit board characterized by satisfying the following relationship.

7. An electronic device characterized by comprising the circuit board described in claim 6.

8. An electronic device characterized by comprising the circuit board described in claim 6.

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