JP7301495B2 - Metal-clad laminates and circuit boards - Google Patents

Description

TECHNICAL FIELD The present invention relates to a metal-clad laminate and a circuit board useful as electronic parts.

In recent years, with the progress of miniaturization, weight reduction, and space saving of electronic devices, flexible printed circuit boards (FPCs) that are thin, lightweight, flexible, and have excellent durability even after repeated bending have been developed. Circuits are in increasing demand. Since FPCs can be mounted three-dimensionally and at high density even in a limited space, their applications are expanding, for example, to the wiring of movable parts of electronic devices such as HDDs, DVDs, and smartphones, as well as components such as cables and connectors. I'm doing it.

In addition to the higher density described above, the performance of equipment has advanced, so it is also necessary to deal with higher frequency transmission signals. 2. Description of the Related Art When transmitting a high-frequency signal, if the transmission loss in the transmission path is large, problems such as the loss of the electrical signal and the increase in signal delay time occur. Therefore, reduction of transmission loss will be important for FPC in the future. In order to cope with high-frequency signal transmission, instead of polyimide, which is widely used as an FPC material, a liquid crystal polymer having a lower dielectric constant and a lower dielectric loss tangent is used as a dielectric layer. However, although liquid crystal polymers are excellent in dielectric properties, there is room for improvement in heat resistance and adhesiveness to metal layers.

Fluorine-based resins are also known as polymers exhibiting a low dielectric constant and a low dielectric loss tangent. For example, as an FPC material that can handle high-frequency signal transmission and has excellent adhesiveness, a polyimide adhesive film having a thermoplastic polyimide layer and a highly heat-resistant polyimide layer is laminated on both sides of a fluorine-based resin layer. An insulating film has been proposed (Patent Document 1). The insulating film of Patent Document 1, which uses a fluororesin, is excellent in terms of dielectric properties, but has a problem of dimensional stability. worried about it getting bigger. Therefore, it becomes difficult to increase the thickness of the fluororesin and to increase the thickness ratio.

By the way, as a technology related to an adhesive layer having polyimide as a main component, there are a polyimide made from a diamine compound derived from an aliphatic diamine such as dimer acid, and an amino compound having at least two primary amino groups as functional groups. is applied to an adhesive layer of a coverlay film (Patent Document 2). The crosslinked polyimide resin of Patent Document 2 does not generate a volatile component composed of a cyclic siloxane compound, has excellent solder heat resistance, and exhibits adhesive strength between the wiring layer and the coverlay film even in an environment where it is repeatedly exposed to high temperatures. It has the advantage of not lowering the However, Patent Literature 2 does not discuss applicability to high-frequency signal transmission or application to adhesive layers in metal-clad laminates.

JP 2017-24265 A Japanese Unexamined Patent Application Publication No. 2013-1730

SUMMARY OF THE INVENTION An object of the present invention is to provide a metal-clad laminate and a circuit board which are capable of reducing transmission loss even in high-frequency transmission and are excellent in dimensional stability.

As a result of intensive research, the present inventors have found that the above problems can be solved by providing a metal-clad laminate with an adhesive layer composed of a specific polyimide in a predetermined thickness ratio, and have completed the present invention. .

A metal-clad laminate of the present invention is a first single-sided metal-clad laminate having a first metal layer and a first insulating resin layer laminated on at least one surface of the first metal layer. ,
a second single-sided metal-clad laminate having a second metal layer and a second insulating resin layer laminated on at least one surface of the second metal layer;
arranged to abut on the first insulating resin layer and the second insulating resin layer and laminated between the first single-sided metal-clad laminate and the second single-sided metal-clad laminate an adhesive layer;
It has
In the metal-clad laminate of the present invention, the total thickness T1 of the first insulating resin layer, the adhesive layer, and the second insulating resin layer is within a range of 70 to 500 μm, and the total thickness T1 The ratio (T2/T1) of the thickness T2 of the adhesive layer to the thickness is within the range of 0.5 to 0.96.
Further, in the metal-clad laminate of the present invention, the adhesive layer has a polyimide containing a tetracarboxylic acid residue and a diamine residue,
The polyimide, with respect to 100 mole parts of the diamine residue,
It is characterized by containing 20 mol parts or more of a diamine residue derived from a dimer acid-type diamine in which two terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl groups or amino groups.

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

In the metal-clad laminate of the present invention, even if the overall thermal expansion coefficient of the first insulating resin layer, the adhesive layer, and the second insulating resin layer is in the range of 10 ppm/K or more and 30 ppm/K or less. good.

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

The circuit board of the present invention is obtained by processing the first metal layer and/or the second metal layer in any one of the above metal-clad laminates into wiring.

The metal-clad laminate of the present invention has a structure in which two single-sided metal-clad laminates are bonded together by an adhesive layer into which a specific diamine residue is introduced, thereby ensuring dimensional stability and achieving a low dielectric constant and a low dielectric loss tangent. made possible. By using the metal-clad laminate of the present invention, it can be applied to circuit boards and the like that transmit high-frequency signals of 10 GHz or more, for example. Therefore, it is possible to improve the reliability and yield of the circuit board.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the structure of the metal-clad laminated board of one embodiment of this invention. It is a graph which shows the dynamic viscoelastic behavior of adhesive polyimide and fluorine-type resin. 1 is a schematic cross-sectional view showing the configuration of a metal-clad laminate according to a preferred embodiment of the present invention; FIG.

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

[Metal clad laminate]
FIG. 1 is a schematic diagram showing the configuration of a metal-clad laminate according to one embodiment of the present invention. The metal-clad laminate (C) of the present embodiment has a structure in which a pair of single-sided metal-clad laminates are bonded together with an adhesive layer (B). That is, the metal-clad laminate (C) includes a first single-sided metal-clad laminate (C1), a second single-sided metal-clad laminate (C2), these first single-sided metal-clad laminates (C1) and It comprises an adhesive layer (B) laminated between second single-sided metal-clad laminates (C2). Here, the first single-sided metal-clad laminate (C1) comprises a first metal layer (M1) and a first insulating resin layer laminated on at least one surface of the first metal layer (M1). (P1) and The second single-sided metal-clad laminate (C2) comprises a second metal layer (M2) and a second insulating resin layer (P2) laminated on at least one surface of the second metal layer (M2). and have The adhesive layer (B) is arranged so as to contact the first insulating resin layer (P1) and the second insulating resin layer (P2). That is, the metal-clad laminate (C) consists of a first metal layer (M1)/first insulating resin layer (P1)/adhesive layer (B)/second insulating resin layer (P2)/second metal It has a structure in which layers (M2) are stacked in this order. The first metal layer (M1) and the second metal layer (M2) are positioned on the outermost side, respectively, and the first insulating resin layer (P1) and the second insulating resin layer (P2) are located inside them. Further, an adhesive layer (B) is interposed between the first insulating resin layer (P1) and the second insulating resin layer (P2).

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

(metal layer)
Materials for the first metal layer (M1) and the second metal layer (M2) are not particularly limited, but examples include copper, stainless steel, iron, nickel, beryllium, aluminum, zinc, indium, silver, gold, Tin, zirconium, tantalum, titanium, lead, magnesium, manganese, alloys thereof, and the like. Among these, copper or a copper alloy is particularly preferable. The material of the wiring layer in the circuit board of this embodiment, which will be described later, is also the same as that of the first metal layer (M1) and the second metal layer (M2).

The thicknesses of the first metal layer (M1) and the second metal layer (M2) are not particularly limited. A range of 5 to 25 μm is preferable. From the viewpoint of production stability and handling, the lower limit of the thickness of the metal foil is preferably 5 μm. When copper foil is used, it may be rolled copper foil or electrolytic copper foil. Moreover, as a copper foil, the copper foil marketed can be used.

Moreover, the metal foil may be subjected to a surface treatment with, for example, siding, aluminum alcoholate, aluminum chelate, silane coupling agent, or the like, for the purpose of antirust treatment and adhesion strength improvement.

(insulating resin layer)
The first insulating resin layer (P1) and the second insulating resin layer (P2) are not particularly limited as long as they are made of an electrically insulating resin, such as polyimide, epoxy resin, and phenol resin. , polyethylene, polypropylene, polytetrafluoroethylene, silicone, ETFE, and the like, preferably polyimide. Moreover, the first insulating resin layer (P1) and the second insulating resin layer (P2) are not limited to a single layer, and may be a laminate of a plurality of resin layers. In the present invention, the term "polyimide" means a resin composed of a polymer having an imide group in its molecular structure, such as polyamideimide, polyetherimide, polyesterimide, polysiloxaneimide, and polybenzimidazoleimide, in addition to polyimide.

<Adhesive layer>
The adhesive layer (B) is a thermoplastic polyimide containing a tetracarboxylic acid residue derived from a tetracarboxylic anhydride and a diamine residue derived from a diamine compound (hereinafter sometimes referred to as "adhesive polyimide" )including.
In the present invention, the term "tetracarboxylic acid residue" means a tetravalent group derived from a tetracarboxylic dianhydride, and the term "diamine residue" refers to a divalent group derived from a diamine compound. means the basis of Further, "thermoplastic polyimide" generally refers to a polyimide whose glass transition temperature (Tg) can be clearly confirmed. A polyimide having a storage modulus of 1.0×10 ⁸ Pa or more at 300° C. and less than 3.0×10 ⁷ Pa at 300° C. In addition, "non-thermoplastic polyimide" generally refers to polyimide that does not soften or exhibit adhesiveness when heated. A polyimide having a storage modulus of 1.0×10 ⁹ Pa or more at °C and a storage modulus of 3.0×10 ⁸ Pa or more at 300°C.

(tetracarboxylic acid residue)
The adhesive polyimide can contain, without particular limitation, a tetracarboxylic acid residue derived from a tetracarboxylic acid anhydride generally used in thermoplastic polyimides. A total of 90 mol parts of a tetracarboxylic acid residue derived from a tetracarboxylic anhydride represented by the following general formula (1) (hereinafter sometimes referred to as "tetracarboxylic acid residue (1)) By containing a total of 90 mol parts or more of the tetracarboxylic acid residue (1) with respect to 100 mol parts of the tetracarboxylic acid residue, the flexibility and heat resistance of the adhesive polyimide are improved. If the total amount of the tetracarboxylic acid residues (1) is less than 90 mol parts, the solvent solubility of the adhesive polyimide tends to decrease.

In general formula (1), X represents a single bond or a divalent group selected from the following formulae.

In the above formula, Z represents -C ₆ H ₄ -, -(CH ₂ )n- or -CH ₂ -CH(-O-C(=O)-CH ₃ )-CH ₂ -, where n is 1 Indicates an integer from ~20.

Tetracarboxylic dianhydrides for deriving the tetracarboxylic acid residue (1) include, for example, 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3′, 4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), 4,4'-oxydiphthalic anhydride (ODPA) , 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), p-phenylene Bis(trimellitic acid monoester acid anhydride) (TAHQ), ethylene glycol bisanhydrotrimellitate (TMEG), and the like can be mentioned.

The adhesive polyimide may contain a tetracarboxylic acid residue derived from an acid anhydride other than the tetracarboxylic acid anhydride represented by the general formula (1) as long as the effect of the invention is not impaired. Such tetracarboxylic acid residues are not particularly limited, but examples include pyromellitic dianhydride, 1,4-phenylenebis(trimellitic acid monoester) dianhydride, 4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'- or 2,3,3',4'-benzophenonetetracarboxylic dianhydride, 2,3',3,4'- diphenyl ether tetracarboxylic dianhydride, bis(2,3-dicarboxyphenyl) ether dianhydride, 3,3'',4,4''-, 2,3,3'',4''- or 2 ,2'',3,3''-p-terphenyltetracarboxylic dianhydride, 2,2-bis(2,3- or 3,4-dicarboxyphenyl)-propane dianhydride, bis(2 ,3- or 3,4-dicarboxyphenyl)methane dianhydride, bis(2,3- or 3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3- or 3, 4-dicarboxyphenyl)ethane dianhydride, 1,2,7,8-, 1,2,6,7- or 1,2,9,10-phenanthrene-tetracarboxylic dianhydride, 2,3, 6,7-anthracenetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)tetrafluoropropane dianhydride, 2,3,5,6-cyclohexane dianhydride, 1,2, 5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 4,8-dimethyl- 1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 2,6- or 2,7-dichloronaphthalene-1,4,5,8 -tetracarboxylic dianhydride, 2,3,6,7- (or 1,4,5,8-) tetrachloronaphthalene-1,4,5,8- (or 2,3,6,7-) Tetracarboxylic dianhydride, 2,3,8,9-, 3,4,9,10-, 4,5,10,11- or 5,6,11,12-perylene-tetracarboxylic dianhydride , cyclopentane-1,2,3,4-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride anhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'-bis(2,3-dicarboxyphenoxy)diphenylmethane dianhydride, ethylene glycol bis-anhydrotrimellitate, etc. Examples include tetracarboxylic acid residues derived from aromatic tetracarboxylic dianhydrides.

(diamine residue)
The adhesive polyimide contains 20 mol parts or more, preferably 40 mol parts or more, more preferably 60 mol parts or more of the dimer acid-type diamine residue derived from the dimer acid-type diamine with respect to 100 mol parts of the diamine residue. contains. By containing the dimer acid-type diamine residue in the above amount, the dielectric properties of the adhesive layer (B) are improved, and the thermocompression bonding properties are improved by lowering the glass transition temperature (lowering Tg) of the adhesive layer (B). The internal stress due to the improvement of the elastic modulus and the reduction of the elastic modulus can be alleviated. When the dimer acid-type diamine residue is less than 20 mol parts with respect to 100 mol parts of the diamine residue, it is interposed between the first insulating resin layer (P1) and the second insulating resin layer (P2). The adhesive layer (B) may not have sufficient adhesiveness, and the high elastic modulus of the adhesive layer (B), which has high thermal expansion, may cause the first and second metal layers (M1 , M2) after etching may deteriorate.

Here, the dimer acid-type diamine means that the two terminal carboxylic acid groups (-COOH) of the dimer acid are substituted with primary aminomethyl groups (-CH ₂ -NH ₂ ) or amino groups (-NH ₂ ). means a diamine consisting of Dimer acid is a known dibasic acid obtained by an intermolecular polymerization reaction of unsaturated fatty acids, and its industrial production process is almost standardized in the industry. It is obtained by dimerization with Etc. Industrially obtained dimer acid is mainly composed of dibasic acid with 36 carbon atoms obtained by dimerizing unsaturated fatty acids with 18 carbon atoms such as oleic acid and linoleic acid. , any amount of monomeric acids (18 carbon atoms), trimer acids (54 carbon atoms), and other polymerized fatty acids of 20 to 54 carbon atoms. In the present invention, it is preferable to use dimer acid whose content is increased to 90% by weight or more by molecular distillation. Moreover, although a double bond remains after the dimerization reaction, in the present invention, the dimer acid includes the one which is further hydrogenated to reduce the degree of unsaturation.

As a feature of the dimer acid-type diamine, it is possible to impart properties derived from the skeleton of the dimer acid to the polyimide. That is, the dimer acid-type diamine is a macromolecular aliphatic with a molecular weight of about 560 to 620, so that the molar volume of the molecule can be increased and the polar groups of the polyimide can be relatively reduced. Such features of the dimer acid-type diamine are considered to contribute to improving the dielectric properties by reducing the dielectric constant and the dielectric loss tangent while suppressing the deterioration of the heat resistance of the polyimide. In addition, since it has two freely moving hydrophobic chains having 7 to 9 carbon atoms and two chain aliphatic amino groups having a length close to 18 carbon atoms, it not only gives the polyimide flexibility, Since polyimide can have an asymmetrical chemical structure or a non-planar chemical structure, it is thought that a low dielectric constant and a low dielectric loss tangent of polyimide can be achieved.

Dimer acid-type diamines are commercially available, for example, PRIAMINE 1073 (trade name), PRIAMINE 1074 (trade name), and PRIAMINE 1075 (trade name) manufactured by Croda Japan, Versamin 551 (trade name) manufactured by BASF Japan. ), Versamin 552 (trade name), and the like.

Further, the adhesive polyimide contains a diamine residue derived from at least one diamine compound selected from diamine compounds represented by the following general formulas (B1) to (B7), based on 100 mol parts of all diamine components. The total content is preferably in the range of 20 to 80 mol parts, more preferably in the range of 20 to 60 mol parts. Since the diamine compounds represented by the general formulas (B1) to (B7) have a flexible molecular structure, by using at least one diamine compound selected from these in an amount within the above range, the polyimide molecule It can improve chain flexibility and impart thermoplasticity. If the total amount of the diamine compounds represented by the general formulas (B1) to (B7) exceeds 80 mol parts per 100 mol parts of all the diamine components, the flexibility of the polyimide becomes insufficient and Tg increases. , the residual stress due to thermocompression bonding increases, and the post-etching dimensional change rate tends to deteriorate.

In formulas (B1) to (B7), R ₁ independently represents a monovalent hydrocarbon group having 1 to 6 carbon atoms or an alkoxy group, and the linking group A independently represents -O-, -S-, -CO- , —SO—, —SO ₂ —, —COO—, —CH ₂ —, —C(CH ₃ ) ₂ —, —NH— or —CONH—, wherein n ₁ is independently Indicates an integer from 0 to 4. However, the formula (B3) that overlaps with the formula (B2) is excluded, and the formula (B5) that overlaps with the formula (B4) is excluded.
The term “independently” means that in one or more of the above formulas (B1) to (B7), multiple linking groups A, multiple R ₁ or multiple n ₁ may be the same. It means good and can be different. Further, in formulas (B1) to (B7), the hydrogen atoms in the two terminal amino groups may be substituted, for example —NR ₂ R ₃ (wherein R ₂ and R ₃ are independently alkyl (meaning any substituent such as a group).

The diamine represented by formula (B1) (hereinafter sometimes referred to as "diamine (B1)") is an aromatic diamine having two benzene rings. In this diamine (B1), the amino group directly attached to at least one benzene ring and the divalent linking group A are at the meta position, so that the degree of freedom of the polyimide molecular chain is increased and has high flexibility. It is thought that it contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, the use of the diamine (B1) enhances the thermoplasticity of the polyimide. Here, the linking group A is preferably -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -CO-, -SO ₂ -, -S-, or -COO-.

Diamines (B1) include, for example, 3,3'-diaminodiphenylmethane, 3,3'-diaminodiphenylpropane, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,3-diaminodiphenyl ether , 3,4'-diaminodiphenyl ether, 3,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylpropane, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminobenzophenone, (3,3'-bisamino ) diphenylamine and the like.

The diamine represented by formula (B2) (hereinafter sometimes referred to as "diamine (B2)") is an aromatic diamine having three benzene rings. This diamine (B2) has an amino group directly attached to at least one benzene ring and a divalent linking group A at the meta position, so that the degree of freedom of the polyimide molecular chain is increased and has high flexibility. It is thought that it contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, the use of the diamine (B2) enhances the thermoplasticity of the polyimide. Here, the connecting group A is preferably -O-.

Examples of the diamine (B2) include 1,4-bis(3-aminophenoxy)benzene, 3-[4-(4-aminophenoxy)phenoxy]benzenamine, 3-[3-(4-aminophenoxy)phenoxy] Benzenamine and the like can be mentioned.

The diamine represented by formula (B3) (hereinafter sometimes referred to as "diamine (B3)") is an aromatic diamine having three benzene rings. This diamine (B3) has two divalent linking groups A directly linked to one benzene ring at the meta-position to each other, so that the degree of freedom of the polyimide molecular chain is increased and has high flexibility. It is thought that this contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, the use of the diamine (B3) enhances the thermoplasticity of the polyimide. Here, the connecting group A is preferably -O-.

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

The diamine represented by formula (B4) (hereinafter sometimes referred to as "diamine (B4)") is an aromatic diamine having four benzene rings. This diamine (B4) has high flexibility due to the fact that the amino group directly connected to at least one benzene ring and the divalent linking group A are in the meta position, and improve the flexibility of the polyimide molecular chain. considered to contribute. Therefore, the use of the diamine (B4) enhances the thermoplasticity of the polyimide. Here, the linking group A is preferably -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -SO ₂ -, -CO-, or -CONH-.

Diamines (B4) include bis[4-(3-aminophenoxy)phenyl]methane, bis[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]ether, bis Examples include [4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)]benzophenone, bis[4,4'-(3-aminophenoxy)]benzanilide and the like.

The diamine represented by formula (B5) (hereinafter sometimes referred to as "diamine (B5)") is an aromatic diamine having four benzene rings. This diamine (B5) has two divalent linking groups A directly attached to at least one benzene ring at the meta position to each other, so that the degree of freedom of the polyimide molecular chain is increased and has high flexibility. It is thought that it contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, the use of the diamine (B5) enhances the thermoplasticity of the polyimide. Here, the connecting group A is preferably -O-.

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

The diamine represented by formula (B6) (hereinafter sometimes referred to as "diamine (B6)") is an aromatic diamine having four benzene rings. Since this diamine (B6) has at least two ether bonds, it has high flexibility, and is considered to contribute to the improvement of the flexibility of the polyimide molecular chain. Therefore, the use of the diamine (B6) enhances the thermoplasticity of the polyimide. Here, the linking group A is preferably -C(CH ₃ ) ₂ -, -O-, -SO ₂ -, or -CO-.

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

The diamine represented by formula (B7) (hereinafter sometimes referred to as "diamine (B7)") is an aromatic diamine having four benzene rings. Since this diamine (B7) has highly flexible divalent linking groups A on both sides of the diphenyl skeleton, it is believed that this contributes to the improvement of the flexibility of the polyimide molecular chain. Therefore, the use of the diamine (B7) enhances the thermoplasticity of the polyimide. Here, the connecting group A is preferably -O-.

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

The adhesive polyimide may contain a diamine residue derived from a diamine compound other than the dimer acid-type diamine and diamines (B1) to (B7) as long as the effects of the invention are not impaired. As the diamine residue derived from a diamine compound other than the dimer acid-type diamine and the diamines (B1) to (B7), those generally used as diamine compounds used in thermoplastic polyimides can be used without limitation. .

In the adhesive polyimide, by selecting the types of the tetracarboxylic acid residue and the diamine residue, and the respective molar ratios when applying two or more tetracarboxylic acid residues or diamine residues, the thermal expansion coefficient , tensile modulus, glass transition temperature, etc. can be controlled. Moreover, when the adhesive polyimide has a plurality of polyimide structural units, they may exist as blocks or may exist randomly, but preferably exist randomly.

The imide group concentration of the adhesive polyimide is preferably 20% by weight or less. Here, "imide group concentration" means a value obtained by dividing the molecular weight of the imide group (-(CO) ₂ -N-) in the polyimide by the molecular weight of the entire structure of the polyimide. When the imide group concentration exceeds 20% by weight, the molecular weight of the resin itself becomes small, and the low hygroscopicity deteriorates due to the increase in polar groups, resulting in an increase in Tg and elastic modulus.

The weight average molecular weight of the adhesive polyimide is, for example, preferably within the range of 10,000 to 400,000, more preferably within the range of 20,000 to 350,000. If the weight-average molecular weight is less than 10,000, the strength of the adhesive layer (B) is lowered and the adhesive layer (B) tends to become brittle. On the other hand, if the weight-average molecular weight exceeds 400,000, the viscosity increases excessively, and defects such as unevenness in the thickness of the adhesive layer (B) and streaks tend to occur during coating.

Adhesive polyimides are most preferably fully imidized structures. However, part of the polyimide may be amic acid. The imidization rate is around 1015 cm ⁻¹ by measuring the infrared absorption spectrum of the polyimide thin film by the single reflection ATR method using a Fourier transform infrared spectrophotometer (commercial product: FT/IR620 manufactured by JASCO Corporation). can be calculated from the absorbance of C═O stretching derived from the imide group at 1780 cm ⁻¹ based on the benzene ring absorber of .

(crosslink formation)
When the adhesive polyimide has a ketone group, the ketone group is reacted with the amino group of an amino compound having at least two primary amino groups as functional groups to form a C=N bond, thereby cross-linking. Structures can be formed. By forming a crosslinked structure, the heat resistance of the adhesive polyimide can be improved. Preferred tetracarboxylic anhydrides for forming an adhesive polyimide having a ketone group include, for example, 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), and preferred diamine compounds include , 4,4′-bis(3-aminophenoxy)benzophenone (BABP) and 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene (BABB).

Examples of amino compounds that can be used for crosslinking the adhesive polyimide include dihydrazide compounds, aromatic diamines, and aliphatic amines. Among these, dihydrazide compounds are preferred. Aliphatic amines other than dihydrazide compounds tend to form a crosslinked structure even at room temperature, and there is concern about the storage stability of varnishes. On the other hand, aromatic diamines require high temperatures to form a crosslinked structure. Thus, when a dihydrazide compound is used, both storage stability of the varnish and shortening of the curing time can be achieved. Examples of dihydrazide compounds include oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, and maleic acid. dihydrazide, fumaric acid dihydrazide, diglycolic acid dihydrazide, tartaric acid dihydrazide, malic acid dihydrazide, phthalic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, 2,6-naphthoedioic acid dihydrazide, 4,4-bisbenzene dihydrazide, 1,4 Dihydrazide compounds such as -naphthoic acid dihydrazide, 2,6-pyridinedioic acid dihydrazide, and itaconic acid dihydrazide are preferred. The above dihydrazide compounds may be used alone or in combination of two or more.

The adhesive polyimide can be produced by reacting the tetracarboxylic dianhydride and the diamine compound in a solvent to form a polyamic acid, followed by heat ring closure. For example, a tetracarboxylic dianhydride and a diamine compound are dissolved in an organic solvent in approximately equimolar amounts and stirred at a temperature within the range of 0 to 100° C. for 30 minutes to 24 hours for a polymerization reaction to form a polyimide precursor. A polyamic acid is obtained. In the reaction, the reaction components are dissolved in the organic solvent so that the resulting precursor is within the range of 5 to 50% by weight, preferably within the range of 10 to 40% by weight. Examples of organic solvents used in the polymerization reaction include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2 -butanone, dimethylsulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diglyme, triglyme, cresol and the like. Two or more of these solvents can be used in combination, and aromatic hydrocarbons such as xylene and toluene can also be used in combination. The amount of such an organic solvent to be used is not particularly limited, but the amount used is adjusted so that the concentration of the polyamic acid solution obtained by the polymerization reaction is about 5 to 50% by weight. is preferred.

It is usually advantageous to use the synthesized polyamic acid as a reaction solvent solution, but if necessary, it can be concentrated, diluted, or replaced with another organic solvent. Polyamic acid is also advantageously used because it is generally excellent in solvent solubility. The viscosity of the polyamic acid solution is preferably in the range of 500 cps to 100,000 cps. If the thickness is out of this range, for example, defects such as thickness unevenness and streaks are likely to occur in the film during the coating operation using a coater or the like.

The method of imidizing polyamic acid to form an adhesive polyimide is not particularly limited, for example, heat treatment such as heating in the above solvent at a temperature within the range of 80 to 400 ° C. for 1 to 24 hours is preferable. adopted by

When cross-linking the adhesive polyimide obtained as described above, the above amino compound is added to the resin solution containing the adhesive polyimide having a ketone group, and the ketone group in the adhesive polyimide and the amino compound are combined. Condensation reaction with primary amino groups. Due to this condensation reaction, the resin solution is cured into a cured product. In this case, the amount of the amino compound added is 0.004 mol to 1.5 mol, preferably 0.005 mol to 1.2 mol, more preferably 0.005 mol to 1.2 mol in total of the primary amino group per 1 mol of the ketone group. The amino compound can be added at 0.03 mol to 0.9 mol, most preferably 0.04 mol to 0.5 mol. If the amino compound is added in such an amount that the total amount of primary amino groups is less than 0.004 mol with respect to 1 mol of the ketone group, the cross-linking of the adhesive polyimide by the amino compound is not sufficient. The adhesive layer (B) tends to exhibit less heat resistance, and when the amount of the amino compound added exceeds 1.5 mol, the unreacted amino compound acts as a thermoplastic agent to improve the heat resistance of the adhesive layer (B). tends to decrease.

The condensation reaction conditions for cross-linking are not particularly limited as long as the ketone groups in the adhesive polyimide react with the primary amino groups of the amino compound to form imine bonds (C=N bonds). The temperature of the heat condensation is, for example, 120° C. for reasons such as releasing water generated by the condensation to the outside of the system, or simplifying the condensation step when the heat condensation reaction is subsequently performed after the synthesis of the adhesive polyimide. It is preferably within the range of -220°C, more preferably within the range of 140-200°C. The reaction time is preferably about 30 minutes to 24 hours, and the end point of the reaction is, for example, 1670 cm by measuring the infrared absorption spectrum using a Fourier transform infrared spectrophotometer (commercial product: FT/IR620 manufactured by JASCO Corporation). It can be confirmed by the reduction or disappearance of the absorption peak derived from the ketone group in the polyimide resin around ⁻¹ and the appearance of the absorption peak derived from the imine group around 1635 cm ⁻¹ .

The thermal condensation of the ketone group of the adhesive polyimide and the primary amino group of the amino compound can be performed, for example, by (a) a method of adding an amino compound and heating following synthesis (imidation) of the adhesive polyimide, ( b) A method in which an excessive amount of an amino compound is charged in advance as a diamine component, and following the synthesis (imidization) of the adhesive polyimide, the adhesive polyimide is heated together with the remaining amino compound that does not participate in imidization or amidation, or (c) a method of heating an adhesive polyimide composition to which an amino compound is added after processing it into a predetermined shape (for example, after applying it to an arbitrary substrate or after forming it into a film); can be done.

In order to impart heat resistance to the adhesive polyimide, the formation of the imine bond has been described as the formation of the crosslinked structure, but the method is not limited to this. can be mixed and cured.

By using the adhesive polyimide obtained as described above, the adhesive layer (B) has excellent flexibility and dielectric properties (low dielectric constant and low dielectric loss tangent). In addition, as will be described later, the adhesive polyimide has a sufficiently low storage elastic modulus in a temperature range of around 100 ° C., so the adhesion temperature is significantly lowered compared to other adhesive resins such as fluorine resins. be able to.

<Layer thickness>
The metal-clad laminate (C) has a total thickness T1 of 70 to 70, where T1 is the total thickness of the first insulating resin layer (P1), the adhesive layer (B) and the second insulating resin layer (P2). It is in the range of 500 μm, preferably in the range of 100-300 μm. If the total thickness T1 is less than 70 μm, the effect of reducing transmission loss when used as a circuit board is insufficient, and if it exceeds 500 μm, there is a risk of reduced productivity.

Also, the thickness T2 of the adhesive layer (B) is, for example, preferably in the range of 50 to 450 μm, more preferably in the range of 50 to 250 μm. If the thickness T2 of the adhesive layer (B) is less than the above lower limit, the dielectric loss tangent may not be sufficiently reduced, and problems such as insufficient dielectric properties may occur. On the other hand, if the thickness of the adhesive layer (B) exceeds the above upper limit, problems such as reduced dimensional stability may occur.

Further, 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 0.96, and preferably in the range of 0.5 to 0.75. preferable. If the ratio (T2/T1) is less than 0.5, the low dielectric loss tangent is insufficient and sufficient dielectric properties cannot be obtained. If it exceeds 0.96, problems such as deterioration of dimensional stability occur.

Both the thickness T3 of the first insulating resin layer (P1) and the second insulating resin layer (P2) are preferably, for example, within the range of 12 to 50 μm, more preferably within the range of 12 to 25 μm. If the thickness T3 of the first insulating resin layer (P1) and the second insulating resin layer (P2) is less than the above lower limit, problems such as warping of the metal-clad laminate (C) may occur. If the thickness T3 of the first insulating resin layer (P1) and the second insulating resin layer (P2) exceeds the above upper limit, problems such as deterioration of transmission characteristics when used as a circuit board occur. The first insulating resin layer (P1) and the second insulating resin layer (P2) do not necessarily have the same thickness.

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

The adhesive polyimide has high thermal expansion but low elasticity, so even if the CTE exceeds 30 ppm/K, the internal stress generated during lamination can be relaxed.
In addition, the overall thermal expansion coefficient (CTE) of the first insulating resin layer (P1), the adhesive layer (B) and the second insulating resin layer (P2) is preferably in the range of 10 ppm/K or more and 30 ppm/K or less. Among them, it is more preferably within the range of 15 ppm/K or more and 25 ppm/K or less. If the CTE is less than 10 ppm/K or more than 30 ppm/K, warping will occur and dimensional stability will decrease.

<Glass transition temperature (Tg)>
The adhesive polyimide preferably has a glass transition temperature (Tg) of 250° C. or lower, more preferably 40° C. or higher and 200° C. or lower. When the Tg of the adhesive polyimide is 250° C. or less, thermocompression bonding can be performed at a low temperature, so that internal stress generated during lamination can be relaxed and dimensional change after circuit processing can be suppressed. When the Tg of the adhesive polyimide exceeds 250° C., the temperature increases when interposing and bonding between the first insulating resin layer (P1) and the second insulating resin layer (P2), and after circuit processing. may impair the dimensional stability of the

<Storage modulus>
The adhesive polyimide is characterized by having a temperature range of 40 to 250° C. in which the storage elastic modulus sharply decreases with increasing temperature. Such properties of the adhesive polyimide are considered to be the factors that relax the internal stress during thermocompression bonding and maintain the dimensional stability after circuit processing. The adhesive polyimide preferably has a storage modulus of 5×10 ⁷ [Pa] or less at the upper limit temperature of the temperature range, and is within the range of 1×10 ⁵ to 5×10 ⁷ [Pa]. is more preferred. With such a storage elastic modulus, even if the upper limit of the above temperature range is taken as the upper limit, thermocompression bonding is possible at 250° C. or less, ensuring adhesion and suppressing dimensional change after circuit processing.

<Dielectric loss tangent>
For example, when the first insulating resin layer (P1) and the second insulating resin layer (P2) are applied to a circuit board, the dielectric loss tangent (Tan δ) at 10 GHz is preferably is 0.02 or less, more preferably in the range of 0.0005 to 0.01, and still more preferably in the range of 0.001 to 0.008. When the dielectric loss tangent at 10 GHz of the first insulating resin layer (P1) and the second insulating resin layer (P2) exceeds 0.02, when applied to a circuit board, the electric signal is not transmitted on the high-frequency signal transmission path. Inconvenience such as loss is likely to occur. On the other hand, the lower limit value of the dielectric loss tangent at 10 GHz of the first insulating resin layer (P1) and the second insulating resin layer (P2) is not particularly limited, but the physical property control as the insulating resin layer of the circuit board is considered. .

For example, when the adhesive layer (B) is applied to a circuit board, the dielectric loss tangent (Tan δ) at 10 GHz is preferably 0.004 or less, more preferably 0.0005 or more and 0 in order to suppress deterioration of dielectric loss. It is preferably in the range of 0.004 or less, more preferably in the range of 0.001 or more and 0.0035 or less. If the dielectric loss tangent of the adhesive layer (B) at 10 GHz exceeds 0.004, problems such as loss of electrical signals on the transmission path of high-frequency signals are likely to occur when applied to a circuit board. On the other hand, the lower limit of the dielectric loss tangent at 10 GHz of the adhesive layer (B) is not particularly limited.

<Dielectric constant>
For example, when the first insulating resin layer (P1) and the second insulating resin layer (P2) are applied as an insulating layer of a circuit board, the insulating layer as a whole has a dielectric constant at 10 GHz in order to ensure impedance matching. A ratio of 4.0 or less is preferred. When the dielectric constant at 10 GHz of the first insulating resin layer (P1) and the second insulating resin layer (P2) exceeds 4.0, when applied to a circuit board, the first insulating resin layer (P1) and This leads to deterioration of the dielectric loss of the second insulating resin layer (P2), and problems such as loss of electrical signals tend to occur on the transmission path of high-frequency signals.

The adhesive layer (B) preferably has a dielectric constant of 4.0 or less at 10 GHz in order to ensure impedance matching when applied to a circuit board, for example. If the dielectric constant of the adhesive layer (B) at 10 GHz exceeds 4.0, the dielectric loss of the adhesive layer (B) will deteriorate when applied to a circuit board, resulting in loss of electrical signals on the transmission path of high-frequency signals. Inconvenience such as

<Action>
In the metal-clad laminate (C) of the present embodiment, an adhesive polyimide having a low dielectric loss tangent is used as the adhesive layer (B) in order to reduce the dielectric loss tangent of the entire insulating layer and to enable high-frequency transmission. is used, and the thickness of the adhesive layer (B) itself is increased. However, increasing the layer thickness of adhesive polyimide, which is a thermoplastic resin, generally leads to a decrease in dimensional stability.
Here, the dimensional change that occurs when metal-clad laminates are subjected to circuit processing is mainly caused by the following mechanisms i) to iii), and the total amount of ii) and iii) is the dimensional change after etching. It is thought that it will be expressed as
i) Internal stress is accumulated in the resin layer during the production of the metal-clad laminate.
ii) By etching the metal layer during circuit processing, the internal stress accumulated in i) is released and the resin layer expands or contracts.
iii) When the metal layer is etched during circuit processing, exposed resin absorbs moisture and expands.

The internal stress i) is caused by a) the difference in coefficient of thermal expansion between the metal layer and the resin layer, and b) the internal strain of the resin caused by film formation. Here, the magnitude of the internal stress caused by a) is affected not only by the difference in coefficient of thermal expansion, but also by the temperature difference ΔT between the temperature at the time of bonding (heating temperature) and the temperature at the time of cooling and solidification. That is, since the internal stress increases in proportion to the temperature difference ΔT, even if the difference in thermal expansion coefficient between the metal layer and the resin layer is small, the internal stress increases as the resin requires a higher temperature for adhesion. .

FIG. 2 is a graph showing the dynamic viscoelastic behavior of the adhesive polyimide used for the adhesive layer (B) of this embodiment and the fluororesin (adhesive PFA resin). In FIG. 2, the vertical axis indicates storage modulus and the horizontal axis indicates temperature. In the same figure, the curve a plotted with black squares shows the change in the storage elastic modulus of the adhesive polyimide, and the curve b plotted with white squares shows the change in the fluorine resin to be compared. It shows the change in storage modulus. As can be seen from FIG. 2, in the curve a (adhesive polyimide), the storage elastic modulus decreases to 1×10 ⁷ [Pa] or less in the temperature range around 100°C. Therefore, in a temperature range higher than the temperature ta indicated by the dashed line, it has sufficient fluidity and exhibits adhesive performance. On the other hand, curve b (fluorine-based resin) shows that the temperature at which the storage modulus decreases to around 1×10 ⁷ [Pa] is around 300° C., and sufficient fluidity cannot be obtained unless the temperature is higher than the temperature tb indicated by the dashed line. properties and adhesion performance cannot be obtained. That is, it is understood that curve a (adhesive polyimide) shows adhesive performance at a heating temperature nearly 200° C. lower than curve b (fluororesin). For this reason, even if the adhesive polyimide used for the adhesive layer (B) of the present embodiment has a large coefficient of thermal expansion, it can be Since it can be adhered, it is presumed that dimensional changes that occur when circuits are processed can be greatly suppressed compared to the fluororesin to be compared.
As described above, in the present invention, the adhesive layer (B) is thickened to reduce the dielectric loss tangent of the entire insulating layer, thereby enabling high-frequency transmission and ensuring dimensional stability.

Further, since the adhesive layer (B) is laminated between the first insulating resin layer (P1) and the second insulating resin layer (P2), it functions as an intermediate layer and prevents warping and dimensional change. suppress Furthermore, direct contact with heat and oxygen is blocked by the first insulating resin layer (P1) or the second insulating resin layer (P2) even in a heating process such as solder reflow when mounting a semiconductor chip, for example. Therefore, it is less likely to be affected by oxidative deterioration and is less susceptible to dimensional change. In this way, there is also an advantage due to the characteristics of the layer structure of the first insulating resin layer (P1), the adhesive layer (B) and the second insulating resin layer (P2).

[Manufacturing of metal-clad laminate]
The metal-clad laminate (C) can be produced, for example, by Method 1 or Method 2 below. The adhesive polyimide that forms the adhesive layer (B) may be crosslinked as described above.
[Method 1]
The adhesive polyimide or its precursor to be the adhesive layer (B) is formed into a sheet to form an adhesive sheet, and the adhesive sheet is used as the first insulating resin layer of the first single-sided metal-clad laminate (C1). (P1) and the second insulating resin layer (P2) of the second single-sided metal-clad laminate (C2), and are bonded together by thermocompression bonding.
[Method 2]
The adhesive polyimide solution or the precursor solution thereof to be the adhesive layer (B) is applied to the first insulating resin layer (P1) of the first single-sided metal-clad laminate (C1) or the second single-sided metal-clad laminate. A method in which either one or both of the second insulating resin layers (P2) of the laminated plate (C2) are coated with a predetermined thickness and dried, and then the coating film side is bonded together and thermocompression bonded.

The adhesive sheet used in method 1 is, for example, (1) a method in which a polyamic acid solution is applied to an arbitrary supporting substrate, dried, imidized by heat treatment, and then peeled off from the supporting substrate to form an adhesive sheet; (2) A method of applying a polyamic acid solution to an arbitrary supporting substrate and drying it, then peeling off the polyamic acid gel film from the supporting substrate and imidizing it by heat treatment to form an adhesive sheet, (3) a supporting substrate. It can be manufactured by a method such as applying the solution of the adhesive polyimide to the material, drying it, and then peeling it off from the supporting substrate to form an adhesive sheet.
In the above, the method of applying the polyimide solution (or polyamic acid solution) onto the supporting substrate or the insulating resin layer is not particularly limited, and may be applied by a coater such as a comma, die, knife, or lip. is possible.

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

[Preferred configuration example of metal-clad laminate]
Next, the case where the first insulating resin layer (P1), the second insulating resin layer (P2), and the adhesive layer (B) are all polyimide will be described as an example. The plate (C) will be described more specifically.

FIG. 3 is a schematic cross-sectional view showing the structure of the metal-clad laminate 100 of this embodiment. As shown in FIG. 3, the metal-clad laminate 100 includes metal layers 101 and 101 as a first metal layer (M1) and a second metal layer (M2), a first insulating resin layer (P1) and It has polyimide layers 110, 110 as a second insulating resin layer (P2) and an adhesive polyimide layer 120 as an adhesive layer (B). Here, the metal layer 101 and the polyimide layer 110 form a single-sided metal-clad laminate 130 as a first single-sided metal-clad laminate (C1) or a second single-sided metal-clad laminate (C2). In this aspect, the first single-sided metal-clad laminate (C1) and the second single-sided metal-clad laminate (C2) have the same configuration.

Each of the polyimide layers 110 and 110 may have a structure in which a plurality of polyimide layers are laminated. For example, in the embodiment shown in FIG. 3, the non-thermoplastic polyimide layers 111 and 111 made of non-thermoplastic polyimide and the thermoplastic polyimide layers provided on both sides of the non-thermoplastic polyimide layers 111 and 111 are used as the base layers. It has a three-layer structure with thermoplastic polyimide layers 112 , 112 . Note that the polyimide layers 110, 110 are not limited to the three-layer structure.

In the metal-clad laminate 100 shown in FIG. 3, the outer thermoplastic polyimide layers 112, 112 of the two single-sided metal-clad laminates 130, 130 are laminated to the adhesive polyimide layer 120, respectively, to form the metal-clad laminate 100. are doing. The adhesive polyimide layer 120 is an adhesive layer for bonding the two single-sided metal-clad laminates 130, 130 together in the metal-clad laminate 100, and also ensures the dimensional stability of the metal-clad laminate 100. It has the function of improving dielectric properties. The adhesive polyimide constituting the adhesive polyimide layer 120 is as described for the adhesive layer (B) above.

Next, the non-thermoplastic polyimide layer 111 and the thermoplastic polyimide layer 112 constituting the polyimide layers 110, 110 will be briefly described.

Non-thermoplastic polyimide layer:
The polyimide used for the non-thermoplastic polyimide layer 111 is a non-thermoplastic polyimide layer 111 obtained by reacting an acid anhydride component containing an aromatic tetracarboxylic acid anhydride component with a diamine component containing an aliphatic diamine and/or an aromatic diamine. Thermoplastic polyimides are preferred. As acid anhydrides and diamines, monomers generally used for synthesizing non-thermoplastic polyimides can be used, and description thereof is omitted here. Thermal expansibility, adhesion, glass transition temperature, etc. can be controlled by selecting the types of acid anhydrides and diamines, and the respective molar ratios when two or more acid anhydrides or diamines are used. .

The polyimide constituting the non-thermoplastic polyimide layer 111 preferably has an imide group concentration of 33% or less, more preferably 32% or less. When the imide group concentration exceeds 33%, the flame retardancy of the polyimide is lowered, and the increase in polar groups also deteriorates the dielectric properties.

The thickness of the non-thermoplastic polyimide layer 111 is preferably in the range of 6 μm or more and 100 μm or less from the viewpoint of ensuring the function as a base layer and transportability during manufacturing and thermoplastic polyimide coating, and is 9 μm. More preferably, the thickness is in the range of 50 μm or more. If the thickness of the non-thermoplastic polyimide layer 111 is less than the above lower limit, the electrical insulation and handleability will be insufficient, and if it exceeds the upper limit, productivity will decrease.

From the viewpoint of heat resistance, the non-thermoplastic polyimide layer 111 preferably has a glass transition temperature (Tg) of 280° C. or higher, more preferably 300° C. or higher.

In addition, from the viewpoint of suppressing warpage, the thermal expansion coefficient of the non-thermoplastic polyimide layer 111 is within the range of 1 ppm/K or more and 30 ppm/K or less, preferably 1 ppm/K or more and 25 ppm/K or less, more preferably It is preferably in the range of 15 ppm/K or more and 25 ppm/K or less.

In addition, the non-thermoplastic polyimide used for the non-thermoplastic polyimide layer 111 may include optional components such as a plasticizer, other curing resin components such as epoxy resin, a curing agent, a curing accelerator, a coupling agent, a filler, and a solvent. , a flame retardant, etc. can be appropriately added. However, some plasticizers contain a large amount of polar groups, which may promote the diffusion of copper from the copper wiring. Therefore, it is preferable not to use plasticizers as much as possible.

Thermoplastic polyimide layer:
The polyimide used for the thermoplastic polyimide layer 112 is preferably a thermoplastic polyimide obtained by reacting an acid anhydride component including an aromatic tetracarboxylic acid anhydride component with an aliphatic diamine and/or an aromatic diamine. As acid anhydrides and diamines, monomers generally used for synthesizing thermoplastic polyimides can be used, and description thereof is omitted here. Thermal expansibility, adhesion, glass transition temperature, etc. can be controlled by selecting the types of acid anhydrides and diamines, and the respective molar ratios when two or more acid anhydrides or diamines are used. . From the viewpoint of improving dielectric properties, it is preferable to use an adhesive polyimide for forming the adhesive polyimide layer 120 as the adhesive layer (B) as the polyimide used for the thermoplastic polyimide layer 112 .

The polyimide constituting the thermoplastic polyimide layer 112 preferably has an imide group concentration of 33% or less, more preferably 32% or less. When the imide group concentration exceeds 33%, the flame retardancy of the polyimide is lowered, and the increase in polar groups also deteriorates the dielectric properties.

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, from the viewpoint of ensuring the adhesion function. When the thickness of the thermoplastic polyimide layer 112 is less than the above lower limit, the adhesiveness becomes insufficient, and when it exceeds the upper limit, the dimensional stability tends to deteriorate.

From the viewpoint of suppressing warpage, the thermoplastic polyimide layer 112 has a thermal expansion coefficient of 30 ppm/K or more, preferably 30 ppm/K or more and 100 ppm/K or less, more preferably 30 ppm/K or more and 80 ppm/K or less. should be within range.

In addition to polyimide, the resin used for the thermoplastic polyimide layer 112 includes optional components such as plasticizers, other curing resin components such as epoxy resins, curing agents, curing accelerators, inorganic fillers, coupling agents, Fillers, solvents, flame retardants, and the like can be blended as appropriate. However, some plasticizers contain a large amount of polar groups, which may promote the diffusion of copper from the copper wiring. Therefore, it is preferable not to use plasticizers as much as possible.

In the metal-clad laminate 100, in order to ensure dimensional stability after circuit processing, the total thermal expansion coefficient of the two polyimide layers 110 and the adhesive polyimide layer 120 is preferably 10 ppm/K or more, preferably 10 ppm/K. It is preferably in the range of 30 ppm/K or more, more preferably 15 ppm/K or more and 25 ppm/K.
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 of the thickness T2 of the adhesive polyimide layer 120 to the total thickness T1 (T2/T1) is as described with reference to FIG.

[Circuit board]
Metal-clad laminate 100 of the present embodiment is mainly useful as a circuit board material such as FPC and rigid-flex circuit board. That is, one embodiment of the present invention is formed by patterning one or both of the two metal layers 101 of the metal-clad laminate 100 of the present embodiment into a pattern to form a wiring layer. Circuit boards such as FPC can be manufactured.

EXAMPLES The present invention will be specifically described below by way of examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, various measurements and evaluations are as follows.

[Measurement of permittivity and dissipation factor]
A vector network analyzer (manufactured by Agilent, trade name E8363C) and an SPDR resonator were used to measure the permittivity and dielectric loss tangent of the resin sheet at 10 GHz. The materials used for the measurement were left for 24 hours under the conditions of temperature: 24-26°C and humidity: 45°C-55% RH.

[Measurement of glass transition temperature (Tg)]
For the glass transition temperature, a polyimide film having a size of 5 mm × 20 mm was measured using a dynamic viscoelasticity measuring device (DMA: manufactured by UBM, trade name: E4000F), and the temperature was increased from 30 ° C. to 400 ° C. Measurement was performed at 4° C./min and a frequency of 11 Hz, and the temperature at which the change in elastic modulus (tan δ) was maximum was taken as the glass transition temperature.

[Measurement of dimensional change rate]
The dimensional change rate was measured by the following procedure. First, using a test piece of 150 mm square, a target for position measurement is formed by exposing and developing a dry film resist at intervals of 100 mm. After measuring the dimensions before etching (normal state) in an atmosphere with a temperature of 23 ± 2 ° C and a relative humidity of 50 ± 5%, the copper other than the target of the test piece is etched (liquid temperature 40 ° C or less, time within 10 minutes) Remove by After standing for 24±4 hours in an atmosphere with a temperature of 23±2° C. and a relative humidity of 50±5%, the dimensions after etching are measured. The dimensional change rate with respect to the normal state at each of three points in the MD direction (longitudinal direction) and the TD direction (width direction) is calculated, and the average value of each is taken as the dimensional change rate after etching. The post-etching dimensional change rate was calculated by the following formula.

Post-etching dimensional change rate (%) = (B - A) / A x 100
A; Distance between targets before etching B; Distance between targets after etching

Next, this test piece is heat-treated in an oven at 250° C. for 1 hour, and the distance between the position targets after that is measured. The dimensional change rate after etching at each of three points in the MD direction (longitudinal direction) and the TD direction (width direction) is calculated, and the average value of each is taken as the dimensional change rate after heat treatment. The heating dimensional change rate was calculated by the following formula.

Heating dimensional change rate (%) = (C - B) / B x 100
B; Distance between targets after etching C; Distance between targets after heating

The abbreviations used in the examples represent the following compounds.
BPDA: 3,3′,4,4′-biphenyltetracarboxylic dianhydride BPADA: 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride PMDA: pyromellitic dianhydride Anhydride m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl TPE-R: 1,3-bis(4-aminophenoxy)benzenebisaniline-M: 1,3-bis[2-( 4-aminophenyl)-2-propyl]benzene NMP: N-methyl-2-pyrrolidone DMAc: N,N-dimethylacetamide BTDA: 3,3',4,4'-benzophenonetetracarboxylic dianhydride DDA: carbon Number 36 aliphatic diamine (manufactured by Croda Japan Co., Ltd., trade name: PRIAMINE 1074, amine value: 205 mgKOH/g, mixture of dimer diamine with cyclic structure and chain structure, content of dimer component: 95% by weight or more)
BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane N-12: Dodecanedioic acid dihydrazide OP935: Organic phosphinate aluminum salt (manufactured by Clariant Japan, trade name; Exolit OP935)

(Synthesis example 1)
<Preparation of resin solution for adhesive layer>
In a 500 mL 4-necked flask equipped with a nitrogen inlet tube, stirrer, thermocouple, Dean-Stark trap, and condenser, 44.92 g BTDA (0.139 mol), 75.08 g DDA (0.141 mol), 168 g of NMP and 112 g of xylene were charged and mixed at 40° C. for 30 minutes to prepare a polyamic acid solution. This polyamic acid solution was heated to 190° C., heated and stirred for 4 hours, and distilled water and xylene were removed from the system. Then, the polyimide solution 1 (solid content: 29.5% by weight, weight average molecular weight: 75,700) in which imidation was completed by cooling to 100 ° C., adding 112 g of xylene and stirring, and further cooling to 30 ° C. was prepared.

(Synthesis example 2)
<Preparation of resin solution for adhesive layer>
42.51 g of BPADA (0.082 mol), 17.15 g of DDA (0.033 mol), 20.08 g of BAPP (0.049 mol), 208 g of NMP and 112 g of xylene except that the raw material composition was A polyamic acid solution was prepared in the same manner as in Synthesis Example 1. This polyamic acid solution was treated in the same manner as in Synthesis Example 1 to prepare polyimide solution 2 (solid content: 20.1% by weight, weight average molecular weight: 69,900).

(Synthesis Example 3)
<Preparation of resin solution for adhesive layer>
45.61 g of BPADA (0.088 mol), 28.03 g of DDA (0.052 mol), 14.36 g of BAPP (0.035 mol), 203 g of NMP and 109 g of xylene except that the raw material composition was A polyamic acid solution was prepared in the same manner as in Synthesis Example 1. This polyamic acid solution was treated in the same manner as in Synthesis Example 1 to prepare polyimide solution 3 (solid content: 22.4% by weight, weight average molecular weight: 71,300).

(Synthesis Example 4)
<Preparation of polyamic acid solution for insulating resin layer>
Under a nitrogen stream, 64.20 g of m-TB (0.302 mol) and 5.48 g of bisaniline-M (0.016 mol) were added to the reactor, and an amount that would give a solid content concentration of 15% by weight after polymerization. of DMAc was added and dissolved by stirring at room temperature. 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 at room temperature with continuous stirring for 3 hours, and polyamic acid solution 4 (viscosity: 26,500 cps) were prepared.

(Synthesis Example 5)
<Preparation of polyamic acid solution for insulating resin layer>
69.56 g of m-TB (0.328 mol), 542.75 g of TPE-R (1.857 mol), DMAc in an amount to give a solids concentration of 12% by weight after polymerization, 194.39 g of PMDA ( Polyamic acid solution 5 (viscosity: 2,650 cps) was prepared in the same manner as in Synthesis Example 4, except that 0.891 mol) and 393.31 g of BPDA (1.337 mol) were used as the raw material composition.

(Production example 1)
<Preparation of resin sheet for adhesive layer>
169.49 g (50 g as solids) of polyimide solution 1 was blended with 1.8 g of N-12 (0.0036 mol) and 12.5 g of OP935, and 6.485 g of NMP and 19.345 g of xylene were added. to prepare polyimide varnish 1.

Polyimide varnish 1 was applied to the silicone-treated surface of the release substrate (length × width × thickness = 320 mm × 240 mm × 25 μm) so that the thickness after drying was 50 μm, and then dried by heating at 80 ° C. for 15 minutes. A resin sheet 1 was prepared by peeling from the release substrate. Resin sheet 1 had a Tg of 78° C. and a dielectric constant (Dk) and a dielectric loss tangent (Df) of 2.68 and 0.0028, respectively. The storage modulus characteristics of the resin sheet 1 are as follows.
Steep temperature range of storage modulus: 40 to 74°C
Storage modulus (40° C.); 5.0×10 ⁸ Pa
Storage modulus (74° C.); 1.1×10 ⁷ Pa
Storage modulus (250° C.); 3.0×10 ⁶ Pa

(Production example 2)
<Preparation of resin sheet for adhesive layer>
Polyimide solution 2 was applied to the silicone-treated surface of the release substrate (vertical × horizontal × thickness = 320 mm × 240 mm × 25 μm) so that the thickness after drying was 50 μm, and then dried by heating at 80 ° C. for 15 minutes. A resin sheet 2 was prepared by peeling from the release substrate. The Tg of the resin sheet 2 was 142° C., and the dielectric constant (Dk) and dielectric loss tangent (Df) were 2.80 and 0.0030, respectively. The storage modulus characteristics of the resin sheet 2 are as follows.
Steep gradient temperature range of storage modulus; 118 to 150°C
Storage modulus (118° C.); 1.4×10 ⁹ Pa
Storage modulus (150° C.); 9.0×10 ⁶ Pa

(Production example 3)
<Preparation of resin sheet for adhesive layer>
A resin sheet 3 was prepared in the same manner as in Preparation Example 2 using the polyimide solution 3. The Tg of the resin sheet 3 was 108° C., and the dielectric constant (Dk) and dielectric loss tangent (Df) were 2.80 and 0.0028, respectively. The storage modulus characteristics of the resin sheet 3 are as follows.
Steep temperature range of storage modulus: 88-116°C
Storage modulus (88° C.); 1.1×10 ⁹ Pa
Storage modulus (116° C.); 8.3×10 ⁶ Pa

(Production example 4)
<Preparation of single-sided metal-clad laminate>
On a copper foil 1 (electrolytic copper foil, thickness: 12 μm, surface roughness Rz on the resin layer side: 0.6 μm), polyamic acid solution 5 is uniformly applied so that the thickness after curing is about 2 to 3 μm. After coating, the solvent was removed by heating and drying at 120°C. Next, the polyamic acid solution 4 was uniformly applied thereon so that the thickness after curing was about 21 μm, and dried by heating at 120° C. to remove the solvent. Further, the polyamic acid solution 5 was evenly applied thereon so that the thickness after curing was about 2 to 3 μm, and then dried by heating at 120° C. to remove the solvent. Further, stepwise heat treatment was performed from 120° C. to 360° C. to complete imidization, and a single-sided metal-clad laminate 1 was prepared. The dimensional change rate of the single-sided metal-clad laminate 1 is as follows.
Dimensional change rate after etching in MD direction (longitudinal direction); 0.01%
Dimensional change rate after etching in the TD direction (width direction); -0.04%
Dimensional change after heating in MD direction (longitudinal direction); -0.03%
Dimensional change rate after heating in the TD direction (width direction); -0.01%

<Preparation of polyimide film>
A polyimide film 1 (thickness: 25 μm, CTE: 20 ppm/K, Dk: 3.40, Df: 0.0029) was removed by etching away the copper foil layer of the single-sided metal-clad laminate 1 using an aqueous ferric chloride solution. prepared.

[Example 1]
Two single-sided metal-clad laminates 1 are prepared, and the insulating resin layer side surfaces of the respective resin sheets 1 are superposed on both sides of the resin sheet 1 and crimped at 180° C. for 2 hours under a pressure of 3.5 MPa to bond the metal. A tension laminate 1 was prepared. The evaluation results of the metal-clad laminate 1 are as follows.
Dimensional change rate after etching in MD direction; -0.03%
Dimensional change rate after etching in TD direction; -0.04%
Dimensional change rate after heating in MD direction; 0.02%
Dimensional change rate after heating in TD direction; 0.00%
The metal-clad laminate 1 had no warp and no problem of dimensional change. Also, the resin laminate 1 (thickness: 100 μm) prepared by etching away the copper foil layer in the metal-clad laminate 1 had a CTE of 23.7 ppm/K, and Dk and Df of 2.97 and 0.97, respectively. 0029. These evaluation results are shown in Table 1.

(Comparative example 1)
Instead of resin sheet 1, a fluororesin sheet (manufactured by Asahi Glass Co., Ltd., trade name; adhesive perfluororesin EA-2000, thickness; 50 μm, Tg; none) was used, and a pressure of 3.5 MPa was applied at 320° C. for 5 minutes. A metal-clad laminate 2 was prepared in the same manner as in Example 1, except that the metal-clad laminate was crimped. Table 1 shows the evaluation results of the metal-clad laminate 2 and the resin laminate 2 after removing the copper foil. Table 1 shows the evaluation results.

(Reference example 1)
The copper foil 1, the resin sheet 1, the polyimide film 1, the resin sheet 1, and the copper foil 1 were laminated in this order, and pressed at 180° C. for 2 hours with a pressure of 3.5 MPa to prepare a metal-clad laminate 3. . Table 1 shows the evaluation results of the metal-clad laminate 3 and the resin laminate 3 after removing the copper foil.

(Reference example 2)
A metal-clad laminate 4 was prepared in the same manner as in Reference Example 1, except that the polyimide film 1 was not used. Table 1 shows the evaluation results of the metal-clad laminate 4 and the resin laminate 4 after removing the copper foil.

Table 1 summarizes the above results.

It can be seen that the dimensional change rate after etching and the dimensional change rate after heating in Example 1 are lower than those in Comparative Example 1, Reference Example 1, and Reference Example 2, respectively. In Comparative Example 1, lamination was performed by thermocompression bonding at 320°C, but sufficient adhesion could not be obtained by thermocompression bonding at 180°C. In addition, Reference Examples 1 and 2 were performed to verify the positional configuration of the resin sheet 1 .

[Example 2]
A metal-clad laminate 5 was prepared in the same manner as in Example 1, except that the resin sheet 2 was used. The metal-clad laminate 5 had no warp and had no problem of dimensional change.

[Example 3]
A metal-clad laminate 6 was prepared in the same manner as in Example 1, except that the resin sheet 3 was used. The metal-clad laminate 6 had no warp and no problem of dimensional change.

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

DESCRIPTION OF SYMBOLS 100... Metal-clad laminate, 101... Metal layer, 110... Polyimide layer, 111... Non-thermoplastic polyimide layer, 112... Thermoplastic polyimide layer, 120... Adhesive polyimide layer, 130... Single-sided metal-clad laminate

Claims (5)

a first single-sided metal-clad laminate having a first metal layer and a first insulating resin layer laminated on at least one surface of the first metal layer;
a second single-sided metal-clad laminate having a second metal layer and a second insulating resin layer laminated on at least one surface of the second metal layer;
arranged to contact the first insulating resin layer and the second insulating resin layer and laminated between the first single-sided metal-clad laminate and the second single-sided metal-clad laminate an adhesive layer having a dielectric loss tangent of 0.004 or less at a frequency of 10 GHz measured using an SPDR dielectric resonator ;
A metal-clad laminate comprising
The total thickness T1 of the first insulating resin layer, the adhesive layer and the second insulating resin layer is within the range of 70 to 500 μm, and the ratio of the thickness T2 of the adhesive layer to the total thickness T1 (T2 /T1) is in the range of 0.5 to 0.96,
The adhesive layer has a polyimide containing a tetracarboxylic acid residue and a diamine residue,
The polyimide, with respect to 100 mole parts of the diamine residue,
A metal-clad laminate containing 20 mole parts or more of a diamine residue derived from a dimer acid-type diamine in which two terminal carboxylic acid groups of a dimer acid are substituted with primary aminomethyl groups or amino groups. board. Both the first insulating resin layer and the second insulating resin layer have a multilayer structure in which a thermoplastic polyimide layer, a non-thermoplastic polyimide layer and a thermoplastic polyimide layer are laminated in this order,
2. The metal-clad laminate according to claim 1, wherein the adhesive layer is provided in contact with the two thermoplastic polyimide layers. 3. The metal-clad laminate according to claim 2, wherein the thermal expansion coefficient of said first insulating resin layer, said adhesive layer and said second insulating resin layer as a whole is in the range of 10 ppm/K or more and 30 ppm/K or less. 4. The metal-clad laminate according to any one of claims 1 to 3, wherein both the first metal layer and the second metal layer are made of copper foil. A circuit board formed by processing the first metal layer and/or the second metal layer of the metal-clad laminate according to any one of claims 1 to 4 into wiring.

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