Manufacturing method of metal-clad laminate

Abstract

A method for manufacturing a metal-clad laminate. The metal-clad laminate includes: a first single-sided metal-clad laminate having a first metal layer and a first insulating resin layer laminated on at least one side of the first metal layer; a second single-sided metal-clad laminate having a second metal layer and a second insulating resin layer laminated on at least one side of the second metal layer; and an adhesive layer disposed abutting against the first and second insulating resin layers, laminated between the first and second single-sided metal-clad laminates. The manufacturing method includes: a step 1 of preparing the first and second single-sided metal-clad laminates; a step 2 of depositing a resin layer as an adhesive layer, composed of thermoplastic resin or thermosetting resin, onto either or both of the first or second insulating resin layers; and a step 3 of hot-pressing the first and second single-sided metal-clad laminates together, such that the respective insulating resin layers are opposite each other with the adhesive layer in between.

Description

[0001] This invention is a divisional application of the invention patent application filed on September 19, 2019, with application number 201910885101.4 and title "Metal-Clad Laminates and Circuit Boards". Technical Field

[0002] The present invention relates to a method for manufacturing a metal-clad laminate useful as an electronic component. Background Technology

[0003] In recent years, with the advancements in miniaturization, weight reduction, and space-saving of electronic devices, the demand for thin, lightweight, flexible, and highly durable flexible printed circuit boards (FPCs) that withstand repeated bending has increased. FPCs allow for three-dimensional and high-density installation even in limited spaces, thus their applications are expanding in wiring, cables, connectors, and other components of moving parts in electronic devices such as hard disk drives (HDDs), digital video discs (DVDs), and smartphones.

[0004] In addition to the aforementioned increase in density, the advancement of device performance necessitates addressing the need for higher frequency transmission signals. When transmitting high-frequency signals, significant transmission losses along the transmission path can lead to adverse effects such as signal loss or increased signal delay. Therefore, reducing transmission losses is becoming increasingly important in future FPCs. To address high-frequency signal transmission, FPCs using liquid crystal polymers with lower dielectric constants and lower dielectric loss factors as the dielectric layer are being used instead of polyimide, which is commonly used as FPC materials. However, while liquid crystal polymers offer excellent dielectric properties, there is room for improvement in their heat resistance and adhesion to metal layers.

[0005] Furthermore, fluorinated resins are widely known as polymers exhibiting low dielectric constants and low dielectric loss factors. For example, as an FPC material capable of handling high-frequency signal transmission and possessing excellent adhesion, an insulating film has been proposed (Patent Document 1) formed by bonding a polyimide adhesive film having a thermoplastic polyimide layer and a high-heat-resistant polyimide layer to both sides of a fluorinated resin layer. While the insulating film in Patent Document 1 exhibits excellent dielectric properties due to the use of fluorinated resins, dimensional stability remains a concern, particularly in FPC applications, where there are concerns about significant dimensional changes before and after circuit processing due to etching. Therefore, increasing the thickness of the fluorinated resin and improving the thickness ratio are challenging.

[0006] Furthermore, regarding technologies related to adhesive layers used in electronic materials, the application of resin compositions containing epoxy resin and phenoxy resin, or resin compositions containing thermoplastic polyimide and maleimide compounds, in adhesive sheets has been proposed (Patent Document 2, Patent Document 3). The film-like adhesive sheets of Patent Document 2 and Patent Document 3 have the advantages of low glass transition temperature and high adhesion to laminated materials. However, Patent Document 2 and Patent Document 3 do not investigate the possibility of applications for high-frequency signal transmission or their application as adhesive layers for metal-clad laminates.

[0007] [Existing Technical Documents]

[0008] [Patent Literature]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 2017-24265

[0010] [Patent Document 2] Japanese Patent No. 6191800

[0011] [Patent Document 3] Japanese Patent No. 5553108 Summary of the Invention

[0012] [The problem the invention aims to solve]

[0013] The purpose of this invention is to provide a method for manufacturing a metal-clad laminate that can reduce transmission loss and has excellent dimensional stability even in high-frequency transmission.

[0014] [Technical means to solve the problem]

[0015] Through diligent research, the inventors discovered that the aforementioned problem could be solved by using an adhesive layer with a low glass transition temperature and low elastic modulus in the metal-clad laminate, thus completing the present invention.

[0016] The metal-clad laminate of the present invention is a metal-clad laminate comprising:

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

[0018] The second single-sided metal-clad laminate has 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 is configured to abut against the first insulating resin layer and the second insulating resin layer, and is laminated between the first single-sided metal-clad laminate and the second single-sided metal-clad laminate.

[0020] The manufacturing method of the metal-clad laminate of the present invention includes a step 1 of preparing a first single-sided metal-clad laminate and a second single-sided metal-clad laminate; a step 2 of laminating a resin layer, which is composed of thermoplastic resin or thermosetting resin as the adhesive layer, onto either or both of the first insulating resin layer or the second insulating resin layer; and a step 3 of hot-pressing the first single-sided metal-clad laminate and the second single-sided metal-clad laminate after step 2, so that the respective insulating resin layers are opposite each other through the adhesive layer.

[0021] The adhesive layer is composed of thermoplastic resin or thermosetting resin and satisfies the following conditions (i) to (iii):

[0022] (i) The storage elastic modulus at 50°C is below 1800 MPa;

[0023] (ii) The maximum value of the storage elastic modulus in the temperature range of 180℃~260℃ is below 800MPa;

[0024] (iii) The glass transition temperature (Tg) is below 180℃.

[0025] In the manufacturing method of the present invention, the resin layer in step 2 is a coating film after coating with thermoplastic resin, thermosetting resin or resin solution thereof and drying.

[0026] In the manufacturing method of the present invention, both the first insulating resin layer and the second insulating resin layer may have a multilayer structure formed by sequentially stacking a thermoplastic polyimide layer, a non-thermoplastic polyimide layer, and a thermoplastic polyimide layer.

[0027] The adhesive layer may be disposed in contact with the two thermoplastic polyimide layers.

[0028] [The effects of the invention]

[0029] The metal-clad laminate of the present invention, by bonding two single-sided metal-clad laminates together with an adhesive layer having specific parameters as a separator, can increase the thickness of the insulating resin layer and ensure dimensional stability. Furthermore, when applied to circuit boards transmitting high-frequency signals above 10 GHz, transmission losses can be reduced. Therefore, improved reliability and yield can be achieved in circuit boards. Attached Figure Description

[0030] Figure 1 This is a schematic diagram illustrating the structure of a metal-clad laminate according to an embodiment of the present invention.

[0031] Figure 2 This is a schematic cross-sectional view illustrating the structure of a metal-clad laminate according to a preferred embodiment of the present invention.

[0032] [Explanation of Symbols]

[0033] 100: Metal-clad laminate;

[0034] 101: Metal layer;

[0035] 110: Polyimide layer;

[0036] 111: Non-thermoplastic polyimide layer;

[0037] 112: Thermoplastic polyimide layer;

[0038] 120: Adhesive polyimide layer;

[0039] 130: Single-sided metal-clad laminate;

[0040] B: Adhesive layer;

[0041] C: Metal-clad laminate;

[0042] C1: First single-sided metal-clad laminate;

[0043] C2: Second single-sided metal-clad laminate;

[0044] M1: First metal layer;

[0045] M2: Second metal layer;

[0046] P1: First insulating resin layer;

[0047] P2: Second insulating resin layer;

[0048] T1: Total thickness;

[0049] T2, T3: Thickness. Detailed Implementation

[0050] The embodiments of the present invention will be described with reference to the accompanying drawings.

[0051] [Metal-clad laminate]

[0052] Figure 1This is a schematic diagram illustrating the structure of a metal-clad laminate according to an embodiment of the present invention. The metal-clad laminate (C) of this embodiment has a structure in which a pair of single-sided metal-clad laminates are bonded together using an adhesive layer (B). Specifically, the metal-clad laminate (C) includes a first single-sided metal-clad laminate (C1), a second single-sided metal-clad laminate (C2), and an adhesive layer (B) stacked between these first single-sided metal-clad laminates (C1) and the second single-sided metal-clad laminate (C2). Here, the first single-sided metal-clad laminate (C1) has a first metal layer (M1) and a first insulating resin layer (P1) stacked on at least one side of the first metal layer (M1). The second single-sided metal-clad laminate (C2) has a second metal layer (M2) and a second insulating resin layer (P2) stacked on at least one side of the second metal layer (M2). Furthermore, the adhesive layer (B) is disposed in contact with the first insulating resin layer (P1) and the second insulating resin layer (P2). That is, the metal-clad laminate (C) has a structure formed by sequentially stacking a first metal layer (M1), a first insulating resin layer (P1), an adhesive layer (B), a second insulating resin layer (P2), and a second metal layer (M2). The first metal layer (M1) and the second metal layer (M2) are located on the outermost sides, and the first insulating resin layer (P1) and the second insulating resin layer (P2) are disposed on their inner sides. Furthermore, an adhesive layer (B) is disposed between the first insulating resin layer (P1) and the second insulating resin layer (P2).

[0053] Single-sided metal-clad laminate

[0054] The composition of the pair of single-sided metal-clad laminates (C1, C2) is not particularly limited. As an FPC material, general materials can be used, or commercially available copper-clad laminates, etc. Furthermore, the composition of the first single-sided metal-clad laminate (C1) and the second single-sided metal-clad laminate (C2) can be the same or different.

[0055] (Metal layer)

[0056] There are no particular limitations on the materials used for the first metal layer (M1) and the second metal layer (M2). Examples include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, tin, zirconium, tantalum, titanium, lead, magnesium, manganese, and their alloys. Among these, copper or copper alloys are particularly preferred. Furthermore, the material of the wiring layer in the circuit board of this embodiment, described later, is the same as that of the first metal layer (M1) and the second metal layer (M2).

[0057] The thickness of the first metal layer (M1) and the second metal layer (M2) is not particularly limited. For example, when using metal foil such as copper foil, it is preferably 35 μm or less, and more preferably within the range of 5 μm to 25 μm. From the viewpoint of production stability and processability, the lower limit of the metal foil thickness is preferably set to 5 μm. Furthermore, when using copper foil, rolled copper foil or electrolytic copper foil can be used. In addition, commercially available copper foil can be used as the copper foil.

[0058] In addition, metal foils can also be treated with surface treatments such as plate walls, aluminum alkoxides, aluminum chelates, and silane coupling agents for the purpose of rust prevention or improved adhesion.

[0059] (Insulating resin layer)

[0060] The first insulating resin layer (P1) and the second insulating resin layer (P2) can be made of any electrically insulating resin and are not particularly limited. Examples include polyimide, epoxy resin, phenolic resin, polyethylene, polypropylene, polytetrafluoroethylene, silicone, and ethylene tetrafluoroethylene (ETFE), but polyimide is preferred. Furthermore, the first insulating resin layer (P1) and the second insulating resin layer (P2) are not limited to single layers and can also be layers consisting of multiple resin layers. Moreover, when polyimide is mentioned in this invention, it refers to resins containing polymers such as polyamide-imide, polyether-imide, polyester-imide, polysiloxane-imide, and polybenzimidazole-imide that have imide groups in their molecular structure, in addition to polyimide itself.

[0061] <Adhesive layer>

[0062] The adhesive layer (B) is composed of thermoplastic resin or thermosetting resin and satisfies the following conditions: (i) the storage elastic modulus at 50°C is 1800 MPa or less; (ii) the maximum storage elastic modulus at 180°C to 260°C is 800 MPa or less; and (iii) the glass transition temperature (Tg) is 180°C or less. Examples of resins include: polyimide resin, polyamide resin, epoxy resin, phenoxy resin, acrylic resin, polyurethane resin, styrene resin, polyester resin, phenolic resin, polysulfone resin, polyethersulfone resin, polyphenylene sulfide resin, polyethylene resin, polypropylene resin, silicone resin, polyetherketone resin, polyvinyl alcohol resin, polyvinyl butyral resin, styrene-maleimide copolymer, maleimide-vinyl compound copolymer or (meth)acrylic acid copolymer, benzoxazine resin, bismaleimide resin and cyanate ester resin, etc. Among these resins, materials that satisfy conditions (i) to (iii) or designed in a manner that satisfies conditions (i) to (iii) may be selected for use in the adhesive layer (B).

[0063] When the adhesive layer (B) is a thermosetting resin, it may contain organic peroxides, hardeners, hardening accelerators, etc., and may also contain a combination of hardeners and hardening accelerators, or catalysts and co-catalysts, as needed. Within the range that can ensure the conditions (i) to (iii), it is sufficient to determine the amount of hardener, hardening accelerator, catalyst, co-catalyst, and organic peroxide added, as well as whether they are added at all.

[0064] <Layer Thickness>

[0065] In the metal-clad laminate (C), when the total thickness of the first insulating resin layer (P1), the adhesive layer (B), and the second insulating resin layer (P2) is set as T1, the total thickness T1 is in the range of 70 μm to 500 μm, preferably in the range of 100 μm to 300 μm. If the total thickness T1 is less than 70 μm, the effect of reducing transmission loss during circuit board fabrication is insufficient; if it exceeds 500 μm, productivity may decrease.

[0066] Furthermore, the thickness T2 of the adhesive layer (B) is preferably in the range of 50 μm to 450 μm, and more preferably in the range of 50 μm to 250 μm. If the thickness T2 of the adhesive layer (B) does not meet the lower limit value, transmission loss may increase as a high-frequency substrate. On the other hand, if the thickness of the adhesive layer (B) exceeds the upper limit value, adverse conditions such as decreased dimensional stability may occur.

[0067] Furthermore, the ratio (T2 / T1) of the thickness T2 of the adhesive layer (B) to the total thickness T1 is in the range of 0.5 to 0.8, preferably in the range of 0.5 to 0.7. If the ratio (T2 / T1) is less than 0.5, it is difficult to set T1 to 70 μm or more; if it exceeds 0.8, adverse conditions such as decreased dimensional stability will occur.

[0068] The thickness T3 of both the first insulating resin layer (P1) and the second insulating resin layer (P2) is preferably in the range of, for example, 12 μm to 100 μm, and more preferably in the range of 12 μm to 50 μm. If the thickness T3 of the first insulating resin layer (P1) and the second insulating resin layer (P2) does not meet the lower limit value, problems such as warping of the metal-clad laminate (C) may occur. If the thickness T3 of the first insulating resin layer (P1) and the second insulating resin layer (P2) exceeds the upper limit value, adverse conditions such as decreased productivity may occur. Furthermore, the first insulating resin layer (P1) and the second insulating resin layer (P2) may not necessarily be of the same thickness.

[0069] <Coefficient of thermal expansion>

[0070] 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 higher, preferably in the range of 10 ppm / K or higher and 30 ppm / K or lower, more preferably in the range of 15 ppm / K or higher and 25 ppm / K or lower. If the CTE is less than 10 ppm / K or exceeds 30 ppm / K, warping or a decrease in dimensional stability will occur. By appropriately changing the combination of raw materials used, the thickness, and the drying and curing conditions, a polyimide layer with the desired CTE can be produced.

[0071] Although the adhesive layer (B) has high thermal expansion, it has low elasticity and low glass transition temperature. Therefore, even if the CTE exceeds 30 ppm / K, it can mitigate the internal stress generated during lamination.

[0072] Furthermore, the overall coefficient of thermal expansion (CTE) of the first insulating resin layer (P1), the adhesive layer (B), and the second insulating resin layer (P2) can be 10 ppm / K or more, preferably in the range of 10 ppm / K or more and 30 ppm / K or less, and more preferably in the range of 15 ppm / K or more and 25 ppm / K or less. If the overall CTE of these resin layers is less than 10 ppm / K or exceeds 30 ppm / K, warping or a decrease in dimensional stability will occur.

[0073] <Glass transition temperature (Tg)>

[0074] The glass transition temperature (Tg) of the adhesive layer (B) is below 180°C, preferably below 160°C. By setting the glass transition temperature of the adhesive layer (B) to below 180°C, low-temperature hot pressing can be performed, thus mitigating internal stress generated during lamination and suppressing dimensional changes after circuit fabrication. If the Tg of the adhesive layer (B) exceeds 180°C, the temperature during adhesion becomes higher due to the presence of a dielectric between the first insulating resin layer (P1) and the second insulating resin layer (P2), potentially impairing the dimensional stability of the circuit after fabrication.

[0075] <Storage elastic modulus>

[0076] The adhesive layer (B) has a storage elastic modulus of 1800 MPa or less at 50°C, and a maximum storage elastic modulus of 800 MPa or less in the temperature range of 180°C to 260°C. These properties of the adhesive layer (B) are considered the main reason for mitigating internal stress during hot bonding and maintaining dimensional stability after circuit fabrication. Furthermore, the storage elastic modulus of the adhesive layer (B) at the upper limit temperature (260°C) of the aforementioned temperature range is preferably 800 MPa or less, more preferably 500 MPa or less. By setting this storage elastic modulus, warping is less likely to occur even after the reflow soldering step following circuit fabrication.

[0077] <Dielectric Loss Factor>

[0078] When the first insulating resin layer (P1) and the second insulating resin layer (P2) are applied to a circuit board, in order to suppress the deterioration of dielectric loss, the dielectric loss factor (Tanδ) at 10 GHz is preferably 0.02 or less, more preferably in the range of 0.0005 or more and 0.01 or less, and even more preferably in the range of 0.001 or more and 0.008 or less. If the dielectric loss factor of the first insulating resin layer (P1) and the second insulating resin layer (P2) at 10 GHz exceeds 0.02, then when applied to a circuit board, adverse conditions such as loss of electrical signals in the transmission path of high-frequency signals are likely to occur. On the other hand, there is no particular limitation on the lower limit value of the dielectric loss factor of the first insulating resin layer (P1) and the second insulating resin layer (P2) at 10 GHz, but the physical property control of the insulating resin layer as a circuit board is taken into consideration.

[0079] When the adhesive layer (B) is applied to a circuit board, for example, in order to suppress the deterioration of dielectric loss, the dielectric loss factor (Tanδ) at 10 GHz is preferably 0.015 or less, more preferably 0.01 or less, and even more preferably 0.006 or less. If the dielectric loss factor of the adhesive layer (B) at 10 GHz exceeds 0.015, then when applied to a circuit board, adverse conditions such as loss of electrical signals in the transmission path of high-frequency signals are likely to occur. On the other hand, there is no particular limitation on the lower limit of the dielectric loss factor of the adhesive layer (B) at 10 GHz.

[0080] <Dielectric constant>

[0081] When the first insulating resin layer (P1) and the second insulating resin layer (P2) are used as insulating resin layers in a circuit board, in order to ensure impedance matching, the dielectric constant of the insulating resin layer as a whole is preferably 4.0 or less at 10 GHz. If the dielectric constant of the first insulating resin layer (P1) and the second insulating resin layer (P2) at 10 GHz exceeds 4.0, when applied to a circuit board, it will lead to the deterioration of the dielectric loss of the first insulating resin layer (P1) and the second insulating resin layer (P2), which can easily cause adverse conditions such as loss of electrical signals on the transmission path of high-frequency signals.

[0082] When the adhesive layer (B) is applied to a circuit board, for example, to ensure impedance matching, the dielectric constant at 10 GHz is preferably 4.0 or less. If the dielectric constant of the adhesive layer (B) at 10 GHz exceeds 4.0, when applied to a circuit board, it will lead to a deterioration of the dielectric loss of the adhesive layer (B), which may easily cause adverse conditions such as loss of electrical signals on the transmission path of high-frequency signals.

[0083] <Function>

[0084] In the metal-clad laminate (C) of this embodiment, the thickness of the adhesive layer (B) is increased to achieve a low dielectric loss factor for the entire insulating resin layer and to cope with high-frequency transmission. However, materials with low elastic modulus, such as the adhesive layer (B), generally exhibit a high coefficient of thermal expansion, so increasing the layer thickness may lead to a decrease in dimensional stability. Here, the dimensional changes that occur during circuit fabrication of the metal-clad laminate (C) are considered to be mainly generated through mechanisms a) to c) below, and the sum of b) and c) is manifested as the dimensional change after etching.

[0085] a) During the manufacture of the metal-clad laminate (C), internal stress is accumulated in the resin layer.

[0086] b) During circuit fabrication, the internal stress accumulated in a) is released by etching the metal layer, causing the resin layer to expand or contract.

[0087] c) During circuit fabrication, the exposed resin absorbs moisture and expands as the metal layer is etched.

[0088] The main causes of the internal stress in a) are 1) the difference in thermal expansion coefficients between the metal layer and the resin layer, and 2) the internal strain of the resin caused by film formation. Here, the magnitude of the internal stress caused by 1) affects not only the difference in thermal expansion coefficients, but also the temperature difference ΔT from the temperature at the time of adhesion (heating temperature) to the temperature at which it is cooled and cured. That is, since the internal stress increases proportionally to the temperature difference ΔT, even if the difference in thermal expansion coefficients between the metal layer and the resin layer is small, the internal stress increases the higher the temperature required for adhesion of the resin. In the metal-coated laminate (C) of this embodiment, dimensional stability is ensured by using a layer that satisfies the conditions (i) to (iii) as the adhesive layer (B) to reduce internal stress.

[0089] Furthermore, since the adhesive layer (B) is stacked between the first insulating resin layer (P1) and the second insulating resin layer (P2), it functions as an intermediate layer, suppressing warpage and dimensional changes. Moreover, during heating steps such as reflow soldering in semiconductor chip assembly, direct heat or contact with oxygen is shielded by the first insulating resin layer (P1) or the second insulating resin layer (P2), making it less susceptible to oxidative degradation and dimensional changes. Thus, it also possesses the advantages of the layered structure of the first insulating resin layer (P1), the adhesive layer (B), and the second insulating resin layer (P2).

[0090] [Manufacturing of metal-clad laminates]

[0091] Metal-clad laminates (C) can be manufactured, for example, using method 1 or method 2.

[0092] [Method 1]

[0093] A resin composition that will become the adhesive layer (B) is formed into a sheet to form an adhesive sheet, and the adhesive sheet is disposed and bonded 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) by heat pressing.

[0094] [Method 2]

[0095] A method of heat-pressing one side of the coated film after applying a solution of the resin composition that will become the adhesive layer (B) to either 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) to a specified thickness and drying it.

[0096] The adhesive sheet used in Method 1 can be manufactured, for example, by coating a solution of a resin composition that forms an adhesive layer (B) onto any support substrate and then peeling it off from the support substrate after drying.

[0097] Furthermore, the method of applying the solution of the resin composition that will become the adhesive layer (B) to the supporting substrate or the insulating resin layer (P1, P2) is not particularly limited, and the coating can be performed using a coating machine such as a notched wheel, a mold, a scraper, or a die lip.

[0098] The metal-clad laminate (C) of this embodiment obtained as described above can be used to process wiring circuits by etching the first metal layer (M1) and / or the second metal layer (M2), and can be used to manufacture circuit boards such as single-sided FPCs or double-sided FPCs.

[0099] [Preferred configuration example of metal-clad laminate]

[0100] Next, the first insulating resin layer (P1), the second insulating resin layer (P2), the adhesive layer (B), the first metal layer (M1), and the second metal layer (M2) in the metal-clad laminate (C) of this embodiment will be described in more detail.

[0101] Figure 2 This is a schematic cross-sectional view showing the structure of the metal-clad laminate 100 of this embodiment. (As shown...) Figure 2 As shown, the metal-clad laminate 100 includes: metal layers 101, 101 serving as a first metal layer (M1) and a second metal layer (M2); polyimide layers 110, 110 serving as a first insulating resin layer (P1) and a second insulating resin layer (P2); and an adhesive polyimide layer 120 serving as an adhesive layer (B). Here, a single-sided metal-clad laminate 130 serving as a first single-sided metal-clad laminate (C1) or a second single-sided metal-clad laminate (C2) is formed by the metal layer 101 and the polyimide layer 110. In this embodiment, the first single-sided metal-clad laminate (C1) and the second single-sided metal-clad laminate (C2) have the same configuration.

[0102] Both polyimide layers 110 and 110 can be structures consisting of multiple stacked polyimide layers. For example, in... Figure 2 In the illustrated configuration, a three-layer structure is formed, comprising a non-thermoplastic polyimide layer 111, 111 made of non-thermoplastic polyimide as a base layer, and thermoplastic polyimide layers 112, 112 made of thermoplastic polyimide respectively disposed on both sides of the non-thermoplastic polyimide layer 111, 111. Furthermore, the polyimide layers 110, 110 are not limited to a three-layer structure.

[0103] exist Figure 2In the illustrated metal-clad laminate 100, the outer thermoplastic polyimide layers 112, 112 of the two single-sided metal-clad laminates 130, 130 are respectively bonded to an adhesive polyimide layer 120 to form the metal-clad laminate 100. The adhesive polyimide layer 120 is an adhesive layer used to bond the two single-sided metal-clad laminates 130, 130 in the metal-clad laminate 100, and is also a layer used to thicken the insulating resin layer of the metal-clad laminate 100 while ensuring dimensional stability. The adhesive polyimide layer 120 is as described in the explanation of adhesive layer (B).

[0104] Next, the non-thermoplastic polyimide layer 111 and the thermoplastic polyimide layer 112 constituting the polyimide layers 110 and 110 will be described. Furthermore, the term "non-thermoplastic polyimide" generally refers to polyimide that does not soften or become sticky even when heated, but in this invention, it refers to a stored elastic modulus of 1.0 × 10⁻⁶ at 30°C, as measured using a dynamic viscoelasticity measuring device (Dynamic Mechanical Analysis, DMA). 9 The storage elastic modulus above Pa and at 350℃ is 1.0 × 10⁻⁶. 8 Polyimides with a glass transition temperature (Tg) of 1.0 × 10⁻⁶ Pa or higher. Furthermore, the term "thermoplastic polyimide" generally refers to a polyimide with a clearly identifiable glass transition temperature (Tg), but in this invention, it refers to a polyimide with a storage modulus of elasticity of 1.0 × 10⁻⁶ at 30°C as measured using DMA. 9 The storage elastic modulus above Pa and at 350℃ is less than 1.0×10⁻⁶. 8 Pa's polyimide.

[0105] Non-thermoplastic polyimide layer:

[0106] The non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 is a non-thermoplastic polyimide containing tetracarboxylic acid residues and diamine residues. Furthermore, in this invention, a tetracarboxylic acid residue refers to a tetravalent group derived from tetracarboxylic dianhydride, and a diamine residue refers to a divalent group derived from a diamine compound. The polyimide preferably contains aromatic tetracarboxylic acid residues derived from aromatic tetracarboxylic dianhydride and aromatic diamine residues derived from aromatic diamines.

[0107] (Tetracarboxylic acid residues)

[0108] The non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 preferably contains tetracarboxylic acid residues derived from at least one of 3,3',4,4'-biphenyl tetracarboxylic dianhydride (BPDA) and 1,4-phenylene bis(trimellitic acid monoester) dianhydride (TAHQ), as well as tetracarboxylic acid residues derived from at least one of pyromellitic dianhydride (PMDA) and 2,3,6,7-naphthalenetetracarboxylic dianhydride (NTCDA).

[0109] Tetracarboxylic acid residues derived from BPDA (hereinafter also referred to as "BPDA residues") and tetracarboxylic acid residues derived from TAHQ (hereinafter also referred to as "TAHQ residues") readily form ordered structures in polymers, which can reduce the dielectric loss factor or hygroscopicity by inhibiting molecular motion. BPDA residues can impart self-supporting properties to the gel film of polyamic acid as a polyimide precursor, but on the other hand, they tend to increase the CTE after imidization, decrease the glass transition temperature, and reduce heat resistance.

[0110] From the aforementioned perspective, the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 is controlled to contain BPDA residues and TAHQ residues in a total range preferably between 30 and 60 moles, more preferably between 40 and 50 moles, relative to 100 moles of all tetracarboxylic acid residues. If the total amount of BPDA and TAHQ residues is less than 30 moles, the formation of the ordered structure of the polymer becomes insufficient, the moisture resistance decreases, or the reduction of the dielectric loss factor becomes insufficient. If it exceeds 60 moles, there is a concern that the heat resistance will decrease, in addition to the increase in CTE or the increase in the change in in-plane retardation (RO).

[0111] Furthermore, tetracarboxylic acid residues derived from pyromellitic dianhydride (hereinafter also referred to as "PMDA residues") and tetracarboxylic acid residues derived from 2,3,6,7-naphthalenetetracarboxylic acid dianhydride (hereinafter also referred to as "NTCDA residues") possess rigidity, thus playing a role in improving in-plane orientation, lowering CTE, and controlling in-plane delay (RO) or glass transition temperature. On the other hand, due to their small molecular weight, excessive amounts of PMDA residues lead to a higher concentration of imide groups in the polymer, an increase in polar groups, and greater hygroscopicity, resulting in an increased dielectric loss factor due to the influence of moisture within the molecular chain. Additionally, NTCDA residues tend to cause the film to become brittle due to the highly rigid naphthalene backbone and increase the elastic modulus.

[0112] Therefore, the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer contains PMDA residues and NTCDA residues in a total range preferably of 40 to 70 moles or more, more preferably 50 to 60 moles or more, and even more preferably 50 to 55 moles or more, relative to 100 moles of all tetracarboxylic acid residues. If the total amount of PMDA and NTCDA residues is less than 40 moles, there is a concern that the CTE may increase or the heat resistance may decrease. If it exceeds 70 moles, there is a concern that the concentration of imide groups in the polymer may increase, the polar groups may increase, the low hygroscopicity may be impaired, the dielectric loss factor may increase, or the film may become brittle and the self-support of the film may decrease.

[0113] In addition, the total of at least one of BPDA residues and TAHQ residues and at least one of PMDA residues and NTCDA residues may be 80 moles or more relative to 100 moles of all tetracarboxylic acid residues, preferably 90 moles or more.

[0114] In addition, the molar ratio of at least one of BPDA residues and TAHQ residues to at least one of PMDA residues and NTCDA residues {(BPDA residues + TAHQ residues) / (PMDA residues + NTCDA residues)} can be set to a range of 0.4 or more and 1.5 or less, preferably a range of 0.6 or more and 1.3 or less, and more preferably a range of 0.8 or more and 1.2 or less, to control the formation of the ordered structure of CTE and polymer.

[0115] PMDA and NTCDA have rigid frameworks, thus, compared to other common anhydride components, they can control the in-plane orientation of molecules in polyimide, resulting in suppression of the coefficient of thermal expansion (CTE) and improvement of the glass transition temperature (Tg). Furthermore, compared to PMDA, BPDA and TAHQ have larger molecular weights; therefore, as the loading ratio increases, the concentration of imide groups decreases, thereby effectively reducing the dielectric loss factor or moisture absorption rate. On the other hand, if the loading ratio of BPDA and TAHQ increases, the in-plane orientation of molecules in polyimide decreases, leading to an increase in CTE. Furthermore, the formation of an ordered intramolecular structure is promoted, and the haze value increases. From this perspective, the total loading amount of PMDA and NTCDA relative to 100 molar parts of all anhydride components in the raw material can be in the range of 40 to 70 molar parts, preferably in the range of 50 to 60 molar parts, and more preferably in the range of 50 to 55 molar parts. If the total amount of PMDA and NTCDA is less than 40 moles relative to 100 moles of all anhydride components in the raw material, the in-plane orientation of the molecules decreases, and low CTE becomes difficult. In addition, the decrease in Tg leads to a decrease in the heat resistance or dimensional stability of the film during heating. On the other hand, if the total amount of PMDA and NTCDA exceeds 70 moles, there is a tendency for the moisture absorption to decrease due to the increase in imide group concentration, or for the elastic modulus to increase.

[0116] Furthermore, while BPDA and TAHQ are effective in reducing the dielectric loss factor and moisture absorption rate due to the inhibition of molecular motion or the decrease in imide group concentration, they can increase the CTE of the imidized polyimide film. From this perspective, the total amount of BPDA and TAHQ relative to 100 molar parts of all anhydride components of the raw material can be in the range of 30 to 60 molar parts, preferably in the range of 40 to 50 molar parts, and more preferably in the range of 40 to 45 molar parts.

[0117] Other than the BPDA, TAHQ, PMDA, and NTCDA residues contained in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111, tetracarboxylic acid residues may include, for example, 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, 4,4'-oxyphthalic anhydride, 2,3',3,4'-biphenyltetracarboxylic 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, and bis(2,3-dicarboxyphenyl) ether dianhydride. 3,3”,4,4”-p-terphenyltetracarboxylic acid dianhydride, 2,3,3”,4”-p-terphenyltetracarboxylic acid dianhydride or 2,2”,3,3”-p-terphenyltetracarboxylic acid 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-) Tetracarboxylic acid residues derived from aromatic tetracarboxylic acid dianhydrides such as tetrachloronaphthalene-1,4,5,8-(or 2,3,6,7-)tetracarboxylic acid dianhydride, 2,3,8,9-perylene-tetracarboxylic acid dianhydride, 3,4,9,10-perylene-tetracarboxylic acid dianhydride, 4,5,10,11-perylene-tetracarboxylic acid dianhydride or 5,6,11,12-perylene-tetracarboxylic acid dianhydride, cyclopentane-1,2,3,4-tetracarboxylic acid dianhydride, pyrazine-2,3,5,6-tetracarboxylic acid dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic acid dianhydride, thiophene-2,3,4,5-tetracarboxylic acid dianhydride, 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride, and ethylene glycol bis(triphenyl) anhydride.

[0118] (diamine residues)

[0119] The diamine residues contained in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 are preferably diamine residues derived from a diamine compound represented by general formula (1).

[0120] [Chemistry 2]

[0121]

[0122] In formula (1), the linker Z represents a single bond or -COO-, Y independently represents a halogen atom or a monovalent hydrocarbon with 1 to 3 carbon atoms that can be substituted by a phenyl group, or an alkoxy group with 1 to 3 carbon atoms, or a perfluoroalkyl group with 1 to 3 carbon atoms, or an alkenyl group, n represents an integer from 0 to 2, and p and q independently represent integers from 0 to 4. Here, "independently" means that the multiple substituents Y in formula (1), and consequently the integers p and q, can be the same or different. Furthermore, in formula (1), the hydrogen atoms in the two terminal amino groups can be substituted, for example, they can also be -NR2R3 (here, R2 and R3 independently represent any substituents such as alkyl groups).

[0123] The diamine compound represented by general formula (1) (hereinafter sometimes referred to as "diamine (1)") is an aromatic diamine having one to three benzene rings. Diamine (1) has a rigid structure and therefore has the effect of imparting an ordered structure to the polymer as a whole. Therefore, polyimides with low air permeability and low moisture absorption can be obtained, reducing the moisture inside the molecular chain and thus reducing the dielectric loss factor. Here, the linker Z is preferably a single bond.

[0124] Examples of diamines (1) include: 1,4-diaminobenzene (p-phenylenediamine, p-PDA), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-n-propyl-4,4'-diaminobiphenyl (m-NPB), 4-aminophenyl-4'-aminobenzoate (APAB), etc.

[0125] The non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 may contain preferably 80 moles or more, more preferably 85 moles or more, of diamine residues derived from diamine (1) relative to 100 moles of all diamine residues. By using diamine (1) in amounts within the aforementioned range, it is easy to form an ordered structure of the polymer as a whole by utilizing the rigid structure derived from the monomer, and a non-thermoplastic polyimide with low air permeability, low moisture absorption, and low dielectric loss factor can be easily obtained.

[0126] Furthermore, from the viewpoint of a more rigid structure with excellent in-plane orientation, 1,4-diaminobenzene is preferred as diamine (1) when the diamine residues derived from diamine (1) are in the range of 80 to 85 moles relative to 100 moles of all diamine residues in the non-thermoplastic polyimide.

[0127] Other diamine residues contained in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 may include, for example, 2,2-bis-[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)]biphenyl, bis[1-(3-aminophenoxy)]biphenyl, bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)]benzophenone, 9,9-bis[4-(3-aminophenoxy)phenyl]fluorene, 2 2,2-bis-[4-(4-aminophenoxy)phenyl]hexafluoropropane, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-ditoluidine, 4,4'-methylene-2,6-diethylaniline, 3,3'-diaminodiphenylethane, 3,3'-diaminobiphenyl, 3,3'-dimethoxybiphenylamine, 3,3”-diamino-p-terphenyl, 4,4'-[1,4-phenylenebis(1-methylethylene)] Bisaniline, 4,4'-[1,3-phenylenebis(1-methylethylene)]bisaniline, bis(p-aminocyclohexyl)methane, bis(p-β-amino-tert-butylphenyl) ether, bis(p-β-methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-aminopentyl)benzene, p-bis(1,1-dimethyl-5-aminopentyl)benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis(β-amino-tert-butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylenediamine Diamine residues derived from aromatic diamine compounds such as p-xylyldiamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, 2'-methoxy-4,4'-diaminobenzoylaniline, 4,4'-diaminobenzoylaniline, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, and 6-amino-2-(4-aminophenoxy)benzoxazole; and diamine residues derived from aliphatic diamine compounds such as dimer acid type diamines whose two terminal carboxylic acid groups are substituted with primary aminomethyl or amino groups.

[0128] In non-thermoplastic polyimides, the coefficient of thermal expansion, storage modulus of elasticity, and tensile modulus of elasticity can be controlled by selecting the types of tetracarboxylic acid residues and diamine residues, or by using the molar ratio of two or more tetracarboxylic acid residues or diamine residues. Furthermore, in non-thermoplastic polyimides having multiple polyimide structural units, they can exist in a block form or randomly, but from the viewpoint of suppressing in-plane retardation (RO) deviation, a random form is preferred.

[0129] Furthermore, by setting both the tetracarboxylic acid residues and diamine residues contained in the non-thermoplastic polyimide as aromatic groups, the dimensional accuracy of the polyimide film under high temperature conditions can be improved, and the change in in-plane retardation (RO) can be reduced, which is therefore preferred.

[0130] The imide group concentration of the non-thermoplastic polyimide is preferably 33% or less, more preferably 32% or less. Here, "imide group concentration" refers to the value obtained by dividing the molecular weight of the imide group (-(CO)2-N-) in the polyimide by the molecular weight of the overall structure of the polyimide. If the imide group concentration exceeds 33%, the molecular weight of the resin itself decreases, and the low hygroscopicity also deteriorates due to the increase in polar groups. By selecting the combination of the acid anhydride and diamine compound, the orientation of the molecules in the non-thermoplastic polyimide is controlled, thereby suppressing the increase in CTE that accompanies the decrease in imide group concentration and ensuring low hygroscopicity.

[0131] 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. If the weight-average molecular weight is less than 10,000, the film tends to become brittle due to decreased strength. On the other hand, if the weight-average molecular weight exceeds 400,000, the viscosity tends to increase excessively, and defects such as uneven film thickness and streaks are prone to occur during coating operations.

[0132] From the viewpoint of ensuring the function of the base layer and the portability during manufacturing and thermoplastic polyimide coating, the thickness of the non-thermoplastic polyimide layer 111 is preferably in the range of 6 μm or more and 100 μm or less, more preferably in the range of 9 μm or more and 50 μm or less. If the thickness of the non-thermoplastic polyimide layer 111 is less than the lower limit, the electrical insulation or operability becomes insufficient; if it exceeds the upper limit, the productivity decreases.

[0133] From the viewpoint of heat resistance, the glass transition temperature (Tg) of the non-thermoplastic polyimide layer 111 is preferably 280°C or higher.

[0134] Furthermore, from the viewpoint of suppressing warping, the coefficient of thermal expansion of the non-thermoplastic polyimide layer 111 can be in the range of 1 ppm / K or more and 30 ppm / K or less, preferably in the range of 1 ppm / K or more and 25 ppm / K or less, and more preferably in the range of 15 ppm / K or more and 25 ppm / K or less.

[0135] Furthermore, the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer 111 can be suitably formulated with, for example, plasticizers, other curing resin components such as epoxy resin, curing agents, curing accelerators, coupling agents, fillers, solvents, flame retardants, etc., as arbitrary components. However, plasticizers contain substances with a large number of polar groups, which may promote the diffusion of copper from copper wiring; therefore, it is preferable to avoid using plasticizers as much as possible.

[0136] Thermoplastic polyimide layer:

[0137] The thermoplastic polyimide constituting the thermoplastic polyimide layer 112 is a thermoplastic polyimide containing tetracarboxylic acid residues and diamine residues, preferably containing aromatic tetracarboxylic acid residues derived from aromatic tetracarboxylic acid dianhydrides and aromatic diamine residues derived from aromatic diamines.

[0138] (Tetracarboxylic acid residues)

[0139] The tetracarboxylic acid residues used in the thermoplastic polyimide constituting the thermoplastic polyimide layer 112 may be the same as those exemplified in the non-thermoplastic polyimide constituting the non-thermoplastic polyimide layer.

[0140] (diamine residues)

[0141] The diamine residues contained in the thermoplastic polyimide constituting the thermoplastic polyimide layer 112 are preferably diamine residues derived from diamine compounds represented by general formulas (B1) to (B7).

[0142] [Chemistry 3]

[0143]

[0144] In formulas (B1) to (B7), R1 independently 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 -O-, -S-, -CO-, -SO-, -SO2-, -COO-, -CH2-, -C(CH3)2-, -NH-, or -CONH-, and n1 independently represents an integer from 0 to 4. Wherein, those that are repeated in formula (B2) are removed from formula (B3), and those that are repeated in formula (B4) are removed from formula (B5). Here, "independently" means that in one or more formulas (B1) to (B7), multiple linking groups A, multiple R1s, or multiple n1s may be the same or different. Furthermore, in formulas (B1) to (B7), the hydrogen atoms in the two terminal amino groups may be substituted, for example, they may also be -NR2R3 (here, R2 and R3 independently represent any substituent such as alkyl groups).

[0145] The diamine represented by formula (B1) (hereinafter sometimes referred to as "diamine (B1)") is an aromatic diamine having two benzene rings. It is believed that the diamine (B1) increases the degree of freedom and high flexibility of the polyimide molecular chain by having an amino group directly bonded to at least one benzene ring in the meta position with a divalent linker A, thus contributing to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B1), the thermoplasticity of polyimide is improved. Here, the linker A is preferably -O-, -CH2-, -C(CH3)2-, -CO-, -SO2-, or -S-.

[0146] Examples of diamines (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'-diaminodibenzophenone, (3,3'-diamino)diphenylamine, etc.

[0147] The diamine represented by formula (B2) (hereinafter sometimes referred to as "diamine (B2)") is an aromatic diamine having three benzene rings. It is believed that the diamine (B2) increases the degree of freedom and high flexibility of the polyimide molecular chain by having an amino group directly bonded to at least one benzene ring in the meta position with a divalent linker A, thus contributing to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B2), the thermoplasticity of polyimide is improved. Here, the linker A is preferably -O-.

[0148] Examples of diamines (B2) include 1,4-bis(3-aminophenoxy)benzene, 3-[4-(4-aminophenoxy)phenoxy]aniline, and 3-[3-(4-aminophenoxy)phenoxy]aniline.

[0149] The diamine represented by formula (B3) (hereinafter, sometimes referred to as "diamine (B3)") is an aromatic diamine having three benzene rings. It is believed that the diamine (B3) increases the degrees of freedom and high flexibility of the polyimide molecular chain by having two divalent linker A groups directly bonded to one benzene ring in the meta position, thus contributing to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B3), the thermoplasticity of polyimide is improved. Here, -O- is preferably used as the linker A.

[0150] Examples of diamines (B3) include: 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,3-bis(3-aminophenoxy)benzene (APB), 4,4'-[2-methyl-(1,3-phenylene)dioxy]bisaniline, 4,4'-[4-methyl-(1,3-phenylene)dioxy]bisaniline, 4,4'-[5-methyl-(1,3-phenylene)dioxy]bisaniline, etc.

[0151] The diamine represented by formula (B4) (hereinafter sometimes referred to as "diamine (B4)") is an aromatic diamine having four benzene rings. It is believed that the diamine (B4) possesses high flexibility due to the amino group directly bonded to at least one benzene ring and the divalent linker A being in the meta position, thus contributing to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B4), the thermoplasticity of polyimide is improved. Here, the linker A is preferably -O-, -CH2-, -C(CH3)2-, -SO2-, -CO-, or -CONH-.

[0152] Examples of diamines (B4) include: bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)]benzophenone, bis[4,4'-(3-aminophenoxy)]benzoylaniline, etc.

[0153] The diamine represented by formula (B5) (hereinafter, sometimes referred to as "diamine (B5)") is an aromatic diamine having four benzene rings. It is believed that the diamine (B5) increases the degree of freedom and flexibility of the polyimide molecular chain by having two divalent linker A groups directly bonded to at least one benzene ring in the meta position, thus contributing to the improvement of the flexibility of the polyimide molecular chain. Therefore, by using diamine (B5), the thermoplasticity of polyimide is improved. Here, -O- is preferably used as the linker A.

[0154] Examples of diamines (B5) include 4-[3-[4-(4-aminophenoxy)phenoxy]phenoxy]aniline and 4,4'-[oxybis(3,1-phenoxy)]bisaniline.

[0155] The diamine represented by formula (B6) (hereinafter, sometimes referred to as "diamine (B6)") is an aromatic diamine having four benzene rings. It is believed that said diamine (B6) possesses high flexibility due to having at least two ether bonds, which contributes to improving the flexibility of the polyimide molecular chain. Therefore, by using diamine (B6), the thermoplasticity of polyimide is improved. Here, the linking group A is preferably -C(CH3)2-, -O-, -SO2-, or -CO-.

[0156] Examples of diamines (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).

[0157] The diamine represented by formula (B7) (hereinafter sometimes referred to as "diamine (B7)") is an aromatic diamine having four benzene rings. The diamine (B7) has highly flexible divalent linker groups A on both sides of the diphenyl backbone, which is considered to contribute to improving the flexibility of the polyimide molecular chain. Therefore, by using diamine (B7), the thermoplasticity of polyimide is improved. Here, -O- is preferred as the linker group A.

[0158] Examples of diamines (B7) include bis[4-(3-aminophenoxy)]biphenyl and bis[4-(4-aminophenoxy)]biphenyl.

[0159] The thermoplastic polyimide constituting the thermoplastic polyimide layer 112 may contain diamine residues derived from at least one diamine compound selected from diamines (B1) to (B7) in an amount ranging from 60 moles to 99 moles, more preferably from 70 moles to 95 moles, relative to 100 moles of all diamine residues. Diamines (B1) to (B7) contain flexible molecular structures; therefore, by using at least one diamine compound selected from these compounds in amounts within the aforementioned range, the flexibility of the polyimide molecular chain can be improved, and thermoplasticity can be imparted. If the total amount of diamines (B1) to (B7) in the raw material is less than 60 moles relative to 100 moles of all diamine components, the polyimide resin lacks sufficient flexibility and cannot achieve adequate thermoplasticity.

[0160] Furthermore, the diamine residues contained in the thermoplastic polyimide constituting the thermoplastic polyimide layer 112 are preferably diamine residues derived from a diamine compound represented by general formula (1). Regarding the diamine compound represented by formula (1) [diamine (1)], as described in the description of non-thermoplastic polyimides, diamine (1) has a rigid structure and imparts an ordered structure to the polymer as a whole, thus reducing the dielectric loss factor or hygroscopicity by inhibiting molecular movement. Furthermore, by using it as a raw material for thermoplastic polyimides, polyimides with low air permeability and excellent long-term heat resistance and adhesion can be obtained.

[0161] The thermoplastic polyimide constituting the thermoplastic polyimide layer 112 may contain diamine residues derived from diamine (1) in a range preferably of 1 mole or more and 40 mole or less, more preferably of 5 mole or more and 30 mole or less. By using diamine (1) in amounts within the range described above, the polymer as a whole forms an ordered structure by utilizing the rigid structure derived from the monomer, thus obtaining a thermoplastic polyimide with low air permeability and moisture absorption, and excellent long-term heat resistance and adhesion.

[0162] The thermoplastic polyimide constituting the thermoplastic polyimide layer 112 may contain diamine residues derived from diamine compounds other than diamine (1) and diamine (B1) to diamine (B7) to a extent that does not impair the effects of the invention.

[0163] In thermoplastic polyimides, the coefficient of thermal expansion, tensile modulus of elasticity, glass transition temperature, etc., can be controlled by selecting the types of tetracarboxylic acid residues and diamine residues, or by using the molar ratio of two or more tetracarboxylic acid residues or diamine residues. Furthermore, in thermoplastic polyimides having multiple polyimide structural units, they can exist in a block form or randomly, but randomly is preferred.

[0164] Furthermore, by setting both the tetracarboxylic acid residues and diamine residues contained in the thermoplastic polyimide as aromatic groups, the dimensional accuracy of the polyimide film under high temperature conditions can be improved, and the change in in-plane delay (RO) can be suppressed.

[0165] The imide concentration of the thermoplastic polyimide is preferably 33% or less, more preferably 32% or less. Here, "imide concentration" refers to the value obtained by dividing the molecular weight of the imide group (-(CO)2-N-) in the polyimide by the molecular weight of the polyimide structure as a whole. If the imide concentration exceeds 33%, the molecular weight of the resin itself decreases, and the low hygroscopicity also deteriorates due to the increase in polar groups. By selecting the combination of the diamine compounds, the orientation of the molecules in the thermoplastic polyimide is controlled, thereby suppressing the increase in CTE that accompanies the decrease in imide concentration and ensuring low hygroscopicity.

[0166] The weight-average molecular weight of the thermoplastic polyimide is preferably in the range of 10,000 to 400,000, and more preferably in the range of 50,000 to 350,000. If the weight-average molecular weight is less than 10,000, the film tends to become brittle due to decreased strength. On the other hand, if the weight-average molecular weight exceeds 400,000, the viscosity tends to increase excessively, and defects such as uneven film thickness and streaks are prone to occur during coating operations.

[0167] The thermoplastic polyimide constituting the thermoplastic polyimide layer 112 serves, for example, as an adhesive layer in the insulating resin of a circuit board. Therefore, to suppress copper diffusion, a fully imidized structure is most preferred. A portion of the polyimide may also be an amyl acid. The imidization rate was measured using a Fourier transform infrared spectrophotometer (commercially available: FT / IR620 manufactured by Nippon Spectrophotometer) and the attenuated total reflection (ATR) method, thereby obtaining the infrared absorption spectrum of the polyimide film at 10¹⁵ cm⁻¹. -1 Based on the nearby benzene ring absorber, according to the source at 1780cm -1 The absorbance is calculated from the C=O stretching of the imide group.

[0168] From the viewpoint of ensuring adhesive performance, the thickness of the thermoplastic polyimide layer 112 is preferably in the range of 1 μm or more and 10 μm or less, more preferably in the range of 1 μm or more and 5 μm or less. If the thickness of the thermoplastic polyimide layer 112 is less than the lower limit value, the adhesive performance is insufficient; if it exceeds the upper limit value, there is a tendency for dimensional stability to deteriorate.

[0169] From the viewpoint of suppressing warping, the coefficient of thermal expansion of the thermoplastic polyimide layer 112 can be 30 ppm / K or more, preferably in the range of 30 ppm / K or more and 100 ppm / K or less, and more preferably in the range of 30 ppm / K or more and 80 ppm / K or less.

[0170] Furthermore, in addition to polyimide, the resin used in the thermoplastic polyimide layer 112 may contain, for example, plasticizers, other curing resin components such as epoxy resin, curing agents, curing accelerators, inorganic fillers, coupling agents, fillers, solvents, flame retardants, etc., as any component. However, plasticizers contain substances with a large number of polar groups, which may promote the diffusion of copper from copper wiring; therefore, it is preferable to avoid using plasticizers as much as possible.

[0171] In the metal-clad laminate 100, in order to ensure the dimensional stability of the circuit after processing, the overall coefficient of thermal expansion of the two polyimide layers 110 and the adhesive polyimide layer 120 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.

[0172] Furthermore, in the metal-clad laminate 100, the total thickness T1 of the two polyimide layers 110 and the adhesive polyimide layer 120, the thickness T2 of the adhesive polyimide layer 120, and the ratio (T2 / T1) of the thickness T2 of the adhesive polyimide layer 120 to the total thickness T1 are as follows: Figure 1 As explained in the text.

[0173] (Synthesis of polyimide)

[0174] The polyimide constituting the polyimide layer 110 can be manufactured by reacting the acid anhydride and diamine in a solvent and then heating to close the ring after forming the precursor resin. For example, a polymerization reaction is carried out by dissolving approximately equimolar amounts of the acid anhydride and diamine components in an organic solvent and stirring at a temperature in the range of 0°C to 100°C for 30 minutes to 24 hours, thereby obtaining polyamic acid as a polyimide precursor. During the reaction, the reaction components are dissolved in an organic solvent at a concentration in the range of 5% to 30% by weight, preferably 10% to 20% by weight. Examples of organic solvents used in polymerization reactions include: N,N-dimethylformamide, N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone, 2-butanone, dimethyl sulfoxide, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diethylene glycol dimethyl ether, and triethylene glycol dimethyl ether. Two or more of these solvents may be used in combination, and aromatic hydrocarbons such as xylene and toluene may also be used in combination. Furthermore, there are no particular limitations on the amount of the organic solvent used, but it is preferable to adjust the concentration of the polyamic acid solution (polyimide precursor solution) obtained through the polymerization reaction to approximately 5% to 30% by weight.

[0175] In the synthesis of polyimide, the acid anhydride and diamine may be used individually or in combination with two or more. By selecting the types of acid anhydride and diamine, or the molar ratio of two or more acid anhydrides or diamines, the thermal expansion, adhesion, glass transition temperature, etc., can be controlled.

[0176] Synthesized precursors are generally advantageous for use as reaction solvent solutions, but can be concentrated, diluted, or replaced with other organic solvents as needed. Furthermore, the precursors typically have excellent solvent solubility, which is advantageous for their use. There are no particular limitations on the method of imidizing the precursor; for example, heat treatment in the solvent at a temperature ranging from 80°C to 400°C for 1 hour to 24 hours is preferred.

[0177] [Circuit board]

[0178] The metal-clad laminate 100 is primarily used as a circuit board material for FPCs, rigid and flexible circuit boards, etc. Specifically, by using conventional methods to pattern one or both of the two metal layers 101 of the metal-clad laminate 100 to form a wiring layer, a circuit board such as an FPC, as described in one embodiment of the present invention, can be manufactured. Although not shown in the figures, the circuit board includes a resin laminate consisting of a first insulating resin layer (P1), an adhesive layer (B), and a second insulating resin layer (P2) stacked sequentially, and a wiring layer disposed on one or both sides of the resin laminate.

[0179] [Example]

[0180] The present invention will be specifically described below through examples, but the present invention is not limited to these examples in any way. Furthermore, in the following examples, unless otherwise specified, various measurements and evaluations are described below.

[0181] [Determination of dielectric constant and dielectric loss factor]

[0182] The dielectric constant (Dk) and dielectric loss factor (Df) of a polyimide film at 10 GHz were determined using a vector network analyzer (Agilent Technologies, trade name E8363C) and a split post dielectric resonator (SPDR). Furthermore, the material used in the measurements was subjected to conditions of 24°C–26°C and 45%–55% RH for 24 hours.

[0183] [Determination of storage elastic modulus and glass transition temperature (Tg)]

[0184] Regarding the storage elastic modulus of the adhesive layer, the adhesive layer (50 μm thick) was peeled off from the substrate film, cut into 5 mm × 20 mm pieces, and heated in an oven at 120°C for 2 hours, followed by heating at 170°C for 3 hours. The resulting samples were then measured using a dynamic viscoelasticity measuring device (DMA: UBM, trade name: E4000F), with phased heating from 30°C to 400°C at a heating rate of 4°C / min, at a frequency of 1 Hz. Furthermore, the maximum temperature at which the measured Tanδ value is highest was defined as Tg.

[0185] [Determination of Dimensional Change Rate]

[0186] The dimensional change rate was determined in the following order. First, a 150mm square test piece was exposed and developed with dry film resist at 100mm intervals to form a target for position determination. After measuring the dimensions before etching (normal state) in an atmosphere of 23±2℃ and 50±5% relative humidity, the copper outside the target on the test piece was removed by etching (liquid temperature below 40℃, time within 10 minutes). After standing for 24±4 hours in an atmosphere of 23±2℃ and 50±5% relative humidity, the dimensions after etching were measured. The dimensional change rate relative to the normal state was calculated at three locations each in the MD direction (long side direction) and 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 using the following formula.

[0187] Dimensional change rate after etching (%) = (BA) / A × 100

[0188] A: Distance between targets before etching

[0189] B: Distance between targets after etching

[0190] Next, the test piece was heated in an oven at 250°C for 1 hour, and the distance between the targets was measured afterward. The dimensional change rate relative to the etched dimensions was calculated at three locations each in the MD direction (long side direction) and TD direction (width direction), and the average value of each was taken as the dimensional change rate after heat treatment. The dimensional change rate after heat treatment was calculated using the following formula.

[0191] Dimensional change rate after heating (%) = (CB) / B × 100

[0192] B: Distance between targets after etching

[0193] C: Distance between targets after heating

[0194] The abbreviations used in this embodiment represent the following compounds.

[0195] BPDA: 3,3',4,4'-Biphenyltetracarboxylic acid dianhydride

[0196] PMDA: Pyromellitic dianhydride

[0197] BTDA: 3,3',4,4'-benzophenone tetracarboxylic dianhydride

[0198] m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl

[0199] TPE-R: 1,3-Bis(4-aminophenoxy)benzene

[0200] Bisaniline-M: 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene

[0201] DDA: Manufactured by Croda Japan Co., Ltd. (trade name: PRIAMINE 1075)

[0202] N-12: Dodecanedioic acid dihydrazide

[0203] DMAc: N,N-dimethylacetamide

[0204] R710: (Trade name, manufactured by Printec (stock), bisphenol-type epoxy resin, epoxy equivalent: 170, liquid at room temperature, weight average molecular weight: approximately 340)

[0205] VG3101L: (Trade name, manufactured by Printec (stock), multifunctional epoxy resin, epoxy equivalent: 210, softening point: 39℃~46℃)

[0206] SR35K: (Trade name, manufactured by Printec Corporation, epoxy resin, epoxy equivalent: 930-940, softening point: 86℃-98℃)

[0207] YDCN-700-10: (Trade name, manufactured by Nippon Steel & Sumitomo Chemical Co., Ltd., cresol varnish type epoxy resin, epoxy equivalent 210, softening point 75℃~85℃)

[0208] Milex XLC-LL: (Trade name, manufactured by Mitsui Chemicals, Inc., phenolic resin, hydroxyl equivalent: 175, softening point: 77°C, water absorption: 1% by mass, weight loss upon heating: 4% by mass)

[0209] HE200C-10: (Trade name, Air-water (strain), Phenolic resin, Hydroxyl equivalent: 200, Softening point: 65℃~76℃, Water absorption: 1% by mass, Weight loss upon heating: 4% by mass)

[0210] HE910-10: (Trade name, Air-water (strain) manufacturing, Phenolic resin, Hydroxyl equivalent: 101, Softening point: 83℃, Water absorption: 1% by mass, Weight loss upon heating: 3% by mass)

[0211] SC1030-HJA: (Trade name, manufactured by Admatechs, silica filler dispersion, average particle size: 0.25μm)

[0212] Aerosil R972: (Trade name, manufactured by Aerosil Japan Co., Ltd., silica, average particle size: 0.016μm)

[0213] Acrylic rubber HTR-860P-30B-CHN: (Sample name, manufactured by Teikoku Chemical Industries, Ltd., weight average molecular weight: 230,000, glycidyl functional group monomer ratio: 8%, Tg: -7℃)

[0214] Acrylic rubber HTR-860P-3CSP: (Sample name, manufactured by Teikoku Chemical Industries, Ltd., weight average molecular weight: 800,000, glycidyl functional group monomer ratio: 3%, Tg: -7℃)

[0215] A-1160: (Trade name, manufactured by GE Toshiba, γ-ureopropyltriethoxysilane)

[0216] A-189: (Trade name, manufactured by GE Toshiba, γ-mercaptopropyltrimethoxysilane)

[0217] Curezol 2PZ-CN: (Trade name, manufactured by Shikoku Chemical Industry Co., Ltd., 1-Cyanoethyl-2-phenylimidazole)

[0218] RE-810NM: (Trade name, manufactured by Nippon Kayaku Co., Ltd., diallyl bisphenol A diglycidyl ether, appearance: liquid)

[0219] PHORET SCS: (Trade name, manufactured by Zongyan Chemical Co., Ltd., styrene-containing acrylic polymer, Tg: 70℃, weight average molecular weight: 15000)

[0220] BMI-1: (Trade name, manufactured by Tokyo Kasei Corporation, 4,4'-bismaleimide diphenylmethane)

[0221] TPPK: (Trade name, manufactured by Tokyo Chemical Industry Co., Ltd., tetraphenylphosphonium tetraphenylborate)

[0222] HP-P1: (Trade name, manufactured by Mizushima Alloy Iron Co., Ltd., boron nitride filler)

[0223] NMP: (Manufactured by Kanto Chemical Co., Ltd., N-methyl-2-pyrrolidone)

[0224] (Synthesis example 1)

[0225] <Preparation of Resin Solution A for Adhesive Layer>

[0226] Cyclohexanone was added to a composition containing (a) a thermosetting resin and phenolic resin, and (c) an inorganic filler, as shown in Table 1, and the mixture was stirred. Acrylic rubber, as shown in Table 1, as a high molecular weight component (b), was then added and stirred. Coupling agent (e) and curing accelerator (d) as shown in Table 1 were further added and stirred until all components were homogeneous, yielding resin solution A for the adhesive layer.

[0227] [Table 1]

[0228]

[0229]

[0230] (Synthesis example 2)

[0231] <Synthesis of polyimide resin (PI-1) and preparation of resin solution B for adhesive layer>

[0232] A reaction solution was prepared by adding 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 polyoxypropylene diamine (manufactured by BASF Corporation, trade name: D400, molecular weight: 450), and 100.0 g of NMP to a 300 mL flask equipped with a thermometer, stirrer, cooling tube, and nitrogen inlet tube, and stirring. After the diamine dissolved, 32.30 g of 4,4'-oxyphthalic anhydride, which had been purified by recrystallization from acetic anhydride, was added little by little to the reaction solution while the flask was cooled in an ice bath. After reacting at room temperature (25°C) for 8 hours, 67.0 g of xylene was added, and the mixture was heated at 180°C while blowing nitrogen gas, thereby azeotropically removing the xylene with water. The reaction solution was injected into a large amount of water, the precipitated resin was filtered out, and dried to obtain polyimide resin (PI-1). The molecular weight of the obtained polyimide resin (PI-1) was determined by gel permeation chromatography (GPC). The results, converted to polystyrene, showed that the number average molecular weight Mn = 22400 and the weight average molecular weight Mw = 70200.

[0233] Using the obtained polyimide resin (PI-1), each component was formulated according to the composition ratio (unit: parts by mass) shown in Table 2 to obtain resin solution B for adhesive layer.

[0234] [Table 2]

[0235] distinguish name Synthesis example 2 thermoplastic resin PI-1 100 Reactive plasticizers RE-810NM 40 Compounds containing styrene groups PHORET SCS 40 Compounds with maleimide groups BMI-1 40 hardening accelerator TPPK 0.2 Inorganic packing HP-P1 22 solvent NMP 270

[0236] (Synthesis example 3)

[0237] <Preparation of polyamic acid solution for insulating resin layer>

[0238] Under a nitrogen atmosphere, 64.20 g of m-TB (0.302 mol), 5.48 g of bisphenylamine-M (0.016 mol), and DMAc with a solid content of 15% by weight after polymerization were added to the reaction vessel and stirred at room temperature to dissolve them. Next, after adding 34.20 g of PMDA (0.157 mol) and 46.13 g of BPDA (0.157 mol), the polymerization reaction was carried out by continuous stirring at room temperature for 3 hours to prepare polyamic acid solution 1 (viscosity: 26,500 cps).

[0239] (Synthesis Example 4)

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

[0241] Except for the use of 69.56 g of m-TB (0.328 mol), 542.75 g of TPE-R (1.857 mol), DMAc with a solid content of 12% by weight after polymerization, 194.39 g of PMDA (0.891 mol), and 393.31 g of BPDA (1.337 mol) as raw materials, polyamic acid solution 2 (viscosity: 2,650 cps) was prepared in the same manner as in synthesis example 3.

[0242] (Production example 1)

[0243] <Preparation of Resin Sheet A for Adhesive Layer>

[0244] The adhesive layer, made of resin solution A, was applied to the silicone-treated surface of a release substrate (320mm x 240mm x 25μm) with a dried thickness of 50μm. After drying at 80°C for 15 minutes, it was further dried at 120°C for 15 minutes and then peeled off from the release substrate, thus preparing resin sheet A. Furthermore, to evaluate the properties of the cured resin sheet A, it was heated in an oven at 120°C for 2 hours and then at 170°C for 3 hours. After curing, the resin sheet A had a Tg of 95℃, a storage modulus of elasticity of 960MPa at 50℃, and a maximum storage modulus of elasticity of 7MPa between 180℃ and 260℃.

[0245] (Production example 2)

[0246] <Preparation of Resin Sheet B for Adhesive Layer>

[0247] The adhesive layer, made of resin solution B, was applied to the silicone-treated surface of a release substrate (320mm x 240mm x 25μm) with a dried thickness of 50μm. After drying at 80°C for 15 minutes, it was further dried at 120°C for 15 minutes and then peeled off from the release substrate, thus preparing resin sheet B. Furthermore, to evaluate the properties of the cured resin sheet B, it was heated in an oven at 120°C for 2 hours and then at 170°C for 3 hours. After curing, the Tg of resin sheet B was below 100°C, the storage modulus of elasticity at 50°C was below 1800MPa, and the maximum storage modulus of elasticity between 180°C and 260°C was 70MPa.

[0248] (Production example 3)

[0249] <Preparation of single-sided metal-clad laminates>

[0250] Polyamic acid solution 2 is uniformly coated onto copper foil 1 (electrolytic copper foil, thickness: 12 μm, surface roughness Rz on the resin layer side: 0.6 μm) to a hardened thickness of approximately 2 μm to 3 μm, and then dried at 120°C to remove the solvent. Next, polyamic acid solution 1 is uniformly coated onto it to a hardened thickness of approximately 21 μm, and dried at 120°C to remove the solvent. Then, polyamic acid solution 2 is uniformly coated onto it to a hardened thickness of approximately 2 μm to 3 μm, and dried at 120°C to remove the solvent. Finally, a staged heat treatment is performed from 120°C to 360°C to complete imidization, producing a single-sided metal-coated laminate 1. The dimensional change rate of the single-sided metal-coated laminate 1 is as described below.

[0251] Dimensional change rate after etching in the MD direction (long side direction): 0.01%

[0252] Dimensional change rate after etching in the TD direction (width direction): -0.04%

[0253] Dimensional change rate after heating in the MD direction (long side direction): -0.03%

[0254] Dimensional change rate after heating in the TD direction (width direction): -0.01%

[0255] <Preparation of Polyimide Films>

[0256] The copper foil 1 of the single-sided metal-coated laminate 1 was removed by etching with ferric chloride aqueous solution to prepare a polyimide film 1 (thickness: 25 μm, CTE: 20 ppm / K, Dk: 3.40, Df: 00029).

[0257] [Example 1]

[0258] Two single-sided metal-clad laminates 1 were prepared, and their insulating resin layer sides were aligned with the two sides of resin sheet A. They were then pressed together at 180°C for 2 hours under a pressure of 3.5 MPa to prepare the metal-clad laminate 1. The evaluation results of the metal-clad laminate 1 are as follows.

[0259] Dimensional change rate after etching in the MD direction: -0.02%

[0260] Dimensional change rate after etching in the TD direction: -0.03%

[0261] Dimensional change rate in the MD direction after heating: -0.02%

[0262] Dimensional change rate after heating in the TD direction: -0.02%

[0263] The metal-clad laminate 1 exhibits no warping and no dimensional variations. Furthermore, the CTE of the resin laminate 1 (thickness: 100 μm) prepared by etching away the copper foil 1 from the metal-clad laminate 1 is 24.1 ppm / K.

[0264] [Example 2]

[0265] Two single-sided metal-clad laminates 1 were prepared, and their insulating resin layer sides were aligned with the two sides of resin sheet B. They were then pressed together at 180°C for 2 hours under a pressure of 3.5 MPa to prepare the metal-clad laminate 2. The evaluation results of the metal-clad laminate 2 are as follows.

[0266] Dimensional change rate after etching in the MD direction: -0.05%

[0267] Dimensional change rate after etching in the TD direction: -0.05%

[0268] Dimensional change rate in the MD direction after heating: -0.03%

[0269] Dimensional change rate after heating in the TD direction: -0.04%

[0270] The metal-clad laminate 2 exhibits no warping and no dimensional variations. Furthermore, the CTE of the resin laminate 2 (thickness: 100 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 2 is 23.3 ppm / K.

[0271] (Comparative Example 1)

[0272] Except that a fluoropolymer sheet (manufactured by Asahi Glass Co., Ltd., trade name: adhesive perfluoropolymer EA-2000, thickness: 50 μm, Tm: 303 °C, Tg: none) was used instead of resin sheet A, and the metal-coated laminate 3 was prepared in the same manner as in Example 1, except that a pressure of 3.5 MPa was applied at 320 °C for 5 minutes to perform the pressing.

[0273] The evaluation results of the metal-clad laminate 3 are as follows.

[0274] Dimensional change rate after etching in the MD direction: -0.11%

[0275] Dimensional change rate after etching in the TD direction: -0.13%

[0276] Dimensional change rate in the MD direction after heating: -0.19%

[0277] Dimensional change rate after heating in the TD direction: -0.20%

[0278] The metal-clad laminate 3 exhibits no warping and no dimensional variations. Furthermore, the CTE of the resin laminate 3 (thickness: 100 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 3 is 27.6 ppm / K.

[0279] (Refer to Example 1)

[0280] The copper foil 1, resin sheet A, polyimide film 1, resin sheet A and copper foil 1 are overlapped in sequence and pressed together at 180°C for 2 hours at a pressure of 3.5 MPa to prepare the metal-coated laminate 4.

[0281] The evaluation results of the metal-clad laminate 4 are as follows.

[0282] Dimensional change rate after etching in the MD direction: -0.04%

[0283] Dimensional change rate after etching in the TD direction: -0.05%

[0284] Dimensional change rate in the MD direction after heating: -0.12%

[0285] Dimensional change rate after heating in the TD direction: -0.14%

[0286] The metal-clad laminate 4 exhibits no warping and no dimensional variations. Furthermore, the CTE of the resin laminate 4 (thickness: 100 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 4 is 23.9 ppm / K.

[0287] It can be seen that, even when compared with Comparative Example 1 and Reference Example 1, Examples 1 and 2 show lower dimensional change rates after etching and heating. Furthermore, in Comparative Example 1, lamination using hot pressing at 320°C showed no problem with adhesion, but hot pressing under the same conditions as Examples 1 and 2 (temperature: 180°C, time: 2 hours, pressure: 3.5 MPa) could not achieve sufficient adhesion. Additionally, Reference Example 1 was conducted to verify the positional configuration of resin sheet A.

[0288] [Example 3]

[0289] Prepare a single-sided metal-coated laminate 1. Apply the adhesive layer with resin solution A to the side of the insulating resin layer with a thickness of 50 μm after drying. Then heat and dry at 80°C for 15 minutes, and further dry at 120°C for 15 minutes to prepare the single-sided metal-coated laminate 1 with adhesive layer.

[0290] Next, after the adhesive layer of the single-sided metal-clad laminate 1 with the adhesive layer is overlapped with the insulating resin layer side of the other single-sided metal-clad laminate 1, it is pressed together by applying a pressure of 3.5 MPa at 180°C for 2 hours to prepare the metal-clad laminate 1'.

[0291] The evaluation results of the metal-clad laminate 1' are as follows.

[0292] Dimensional change rate after etching in the MD direction: -0.03%

[0293] Dimensional change rate after etching in the TD direction: -0.03%

[0294] Dimensional change rate in the MD direction after heating: -0.02%

[0295] Dimensional change rate after heating in the TD direction: -0.02%

[0296] The metal-clad laminate 1' exhibits no warping and no dimensional variations. Furthermore, the CTE of the resin laminate 1' (thickness: 100 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 1' is 23.1 ppm / K.

[0297] [Example 4]

[0298] Prepare two single-sided metal-coated laminates 1 with adhesive layers. After overlapping the adhesive layers, press them together at 180°C for 2 hours at a pressure of 3.5 MPa to prepare the metal-coated laminate 5.

[0299] The evaluation results of the metal-clad laminate 5 are as follows.

[0300] Dimensional change rate after etching in the MD direction: -0.03%

[0301] Dimensional change rate after etching in the TD direction: -0.03%

[0302] Dimensional change rate in the MD direction after heating: -0.03%

[0303] Dimensional change rate after heating in the TD direction: -0.03%

[0304] The metal-clad laminate 5 exhibits no warping and no dimensional variations. Furthermore, the CTE of the resin laminate 5 (thickness: 150 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 5 is 23.8 ppm / K.

[0305] [Example 5]

[0306] Prepare a single-sided metal-coated laminate 1. Apply the adhesive layer with resin solution A to the side of the insulating resin layer with a thickness of 75 μm after drying. Then heat and dry at 80°C for 15 minutes, and further dry at 120°C for 25 minutes to prepare a single-sided metal-coated laminate 2 with an adhesive layer.

[0307] Prepare two single-sided metal-coated laminates 2 with adhesive layers. After overlapping the adhesive layers, press them together at 180°C for 2 hours at a pressure of 3.5 MPa to prepare the metal-coated laminate 6.

[0308] The evaluation results of the metal-clad laminate 6 are as follows.

[0309] Dimensional change rate after etching in the MD direction: -0.01%

[0310] Dimensional change rate after etching in the TD direction: -0.01%

[0311] Dimensional change rate in the MD direction after heating: 0.01%

[0312] Dimensional change rate after heating in the TD direction: 0.02%

[0313] The metal-clad laminate 6 exhibits no warping and no dimensional variations. Furthermore, the CTE of the resin laminate 6 (thickness: 200 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 6 is 22.8 ppm / K.

[0314] (Synthesis Example 5)

[0315] Under a nitrogen stream, 44.98 g of BTDA (0.139 mol), 75.02 g of DDA (0.140 mol), 168 g of NMP, and 112 g of xylene were added to a 500 ml separable flask and mixed thoroughly at 40 °C for 30 minutes to prepare a polyamic acid solution. The polyamic acid solution was then heated to 190 °C and stirred for 4.5 hours. 112 g of xylene was added to prepare imidized polyimide adhesive solution 1. The resulting polyimide adhesive solution 1 had a solid content of 29.1% by weight and a viscosity of 7,800 cps. Furthermore, the weight average molecular weight (Mw) of the polyimide was 87,700.

[0316] (Synthesis Example 6)

[0317] 34.4 g (10 g solids) of the polyimide adhesive solution 1 obtained in Synthesis Example 5 was mixed with 1.25 g of N-12 and 2.5 g of Exolit OP935 (manufactured by Clariant Japan Co., Ltd.), and then diluted with 1.297 g of NMP and 3.869 g of xylene to prepare resin solution C for adhesive layer.

[0318] <Preparation of Resin Sheet C for Adhesive Layer>

[0319] The adhesive layer, made of resin solution C, was applied to the silicone-treated surface of a release substrate (320mm x 240mm x 25μm) with a dried thickness of 50μm. After drying at 80°C for 15 minutes, it was further dried at 120°C for 15 minutes and then peeled off from the release substrate, thus preparing resin sheet C. Furthermore, to evaluate the properties of the cured resin sheet C, it was heated in an oven at 120°C for 2 hours and then at 170°C for 3 hours to prepare a cured resin sheet D. The cured resin sheet D has a Tg of 95℃, a storage modulus of elasticity of 1220MPa at 50℃, and a maximum storage modulus of elasticity of 26MPa between 180℃ and 260℃.

[0320] [Example 6]

[0321] Prepare a single-sided metal-coated laminate 1. Apply the adhesive layer with resin solution C to the side of the insulating resin layer with a thickness of 50 μm after drying. Then heat and dry at 80°C for 15 minutes, and further dry at 120°C for 15 minutes to prepare a single-sided metal-coated laminate 3 with an adhesive layer.

[0322] Next, the adhesive layer of the single-sided metal-clad laminate 3 with adhesive layer is overlapped with the insulating resin layer side of the single-sided metal-clad laminate 1, and then pressed together with a pressure of 3.5 MPa at 180°C for 2 hours to prepare the metal-clad laminate 7.

[0323] The evaluation results of the metal-clad laminate 7 are as follows.

[0324] Dimensional change rate after etching in the MD direction: -0.02%

[0325] Dimensional change rate after etching in the TD direction: -0.02%

[0326] Dimensional change rate in the MD direction after heating: -0.03%

[0327] Dimensional change rate after heating in the TD direction: -0.03%

[0328] The metal-clad laminate 7 exhibits no warping and no dimensional variations. Furthermore, the CTE of the resin laminate 7 (thickness: 100 μm) prepared by etching away the copper foil 1 in the metal-clad laminate 7 is 23.4 ppm / K.

[0329] Furthermore, any single-sided metal-clad laminate with an adhesive layer described in the embodiments can also be used in the manufacture of multilayer circuit boards. Additionally, it is considered that the thickness of the adhesive layer in this 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.

[0330] The embodiments of the present invention have been described in detail above for illustrative purposes, but the present invention is not limited to the described embodiments and various modifications can be made.

Claims

1. A method for manufacturing a metal-clad laminate, the metal-clad laminate comprising: The first single-sided metal-clad laminate has a first metal layer and a first insulating resin layer laminated on at least one side of the first metal layer; The second single-sided metal-clad laminate has a second metal layer and a second insulating resin layer laminated on at least one side of the second metal layer; and An adhesive layer, disposed in contact with the first insulating resin layer and the second insulating resin layer, is laminated between the first single-sided metal-clad laminate and the second single-sided metal-clad laminate. The thickness of the adhesive layer is in the range of 50 μm to 450 μm, the thickness of the first insulating resin layer and the second insulating resin layer is in the range of 12 μm to 100 μm, and the ratio of the thickness of the adhesive layer to the total thickness of the first insulating resin layer and the adhesive layer and the second insulating resin layer is in the range of 0.5 to 0.

8. Both the first and second insulating resin layers have a multilayer structure consisting of a thermoplastic polyimide layer, a non-thermoplastic polyimide layer, and a thermoplastic polyimide layer stacked sequentially. The non-thermoplastic polyimide has a storage elastic modulus of 1.0 × 10⁻⁶ at 30°C, as measured using a dynamic mechanical analyzer. 9 The storage elastic modulus above Pa and at 350℃ is 1.0 × 10⁻⁶. 8 Polyimides with a strength above Pa, and thermoplastic polyimides with a storage elastic modulus of 1.0 × 10⁻⁶ at 30°C as determined using a dynamic mechanical analyzer. 9 The storage elastic modulus above Pa and at 350℃ is less than 1.0×10⁻⁶. 8 The manufacturing method of Pa is characterized by comprising the following steps 1 to 3: Step 1: Preparation steps for the first single-sided metal-clad laminate and the second single-sided metal-clad laminate; Step 2: The step of laminating a resin layer, which is composed of a thermoplastic resin or a thermosetting resin, as the adhesive layer onto either or both of the first insulating resin layer or the second insulating resin layer. Step 3: Following step 2, the step of hot-pressing the first single-sided metal-coated laminate and the second single-sided metal-coated laminate together causes the first insulating resin layer and the second insulating resin layer to face each other through the adhesive layer. The adhesive layer is composed of thermoplastic resin or thermosetting resin, and satisfies the following conditions (i) to (iii): (i) The storage elastic modulus at 50°C is below 1800 MPa; (ii) The maximum value of the storage elastic modulus in the temperature range of 180℃ to 260℃ is below 800 MPa; (iii) The glass transition temperature is below 180°C.

2. The method for manufacturing the metal-clad laminate according to claim 1, characterized in that, The resin layer in step 2 is a coating film made by applying a thermoplastic resin or its resin solution, or a thermosetting resin or its resin solution and drying it.

3. The method for manufacturing the metal-clad laminate according to claim 1, wherein... The adhesive layer is disposed in contact with the two thermoplastic polyimide layers.

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