KR20220169914A - Adhesive agent, adhesive sheet and flexible copper clad laminate - Google Patents

Abstract

According to the present invention, developed is an adhesive for a flexible copper-clad laminate (FCCL), that provides the FCCL with excellent dimensional stability without copper foil breakage or wrinkles while achieving both properties comparable to those of the casting method 2-layer FCCL and productivity higher than that of the lamination method 2-layer FCCL and provided are an adhesive sheet manufactured by the same and a lamination method FCCL. The present invention provides: an adhesive, as an adhesive for an FCCL for bonding a polyimide film substrate and a copper foil that make up the FCCL, which includes a solvent-soluble polyimide, a phenoxy resin having a glass transition temperature (Tg) of 120℃ or less, an epoxy resin, and an epoxy resin hardener; an adhesive sheet using the same; an FCCL; and a manufacturing method thereof.

Description

Adhesive, adhesive sheet and flexible copper clad laminate {ADHESIVE AGENT, ADHESIVE SHEET AND FLEXIBLE COPPER CLAD LAMINATE}

The present invention relates to a flexible copper clad laminate (FCCL) used for a flexible printed wiring board and the like, an adhesive and an adhesive sheet for manufacturing the same.

BACKGROUND ART In recent years, demand for various types of printed wiring boards is increasing along with weight reduction, miniaturization, and high density of electronic products, but, among them, demand for flexible printed wiring boards is particularly increasing. Main flexible printed wiring board materials include flexible copper-clad laminates, coverlay films, and interlayer insulating materials (bonding sheets). Among them, a flexible copper-clad laminate for a flexible printed wiring board is generally formed of various insulating materials, using an insulating film having flexibility such as a polyimide film as a base material, and heating and pressing a metal foil on the surface of the base material through various adhesive materials. It is manufactured by a bonding method.

There is a flexible copper-clad laminate (hereinafter also referred to as "three-layer FCCL") using a thermosetting resin such as an epoxy resin or an acrylic resin as an adhesive between copper foil and a polyimide film. These thermosetting adhesives have the advantage of being able to bond at a relatively low temperature, but as the required properties such as heat resistance, chemical resistance, electrical reliability, dimensional stability, and thinning become stricter, it is difficult to cope with 3-layer FCCL. Therefore, flexible copper-clad laminates (hereinafter also referred to as "two-layer FCCL") in which a metal layer is directly formed on a polyimide film or a thermoplastic polyimide is used for an adhesive layer are increasing. This two-layer FCCL is superior in heat resistance, dimensional stability and electrical reliability in particular to that of the three-layer FCCL, and can also contribute to thinning.

There are three types of manufacturing methods for the two-layer FCCL: the lamination method, the casting method, and the sputtering method, and each has advantages and disadvantages.

Since the laminated two-layer FCCL uses a process of bonding an adhesive sheet in which a thermoplastic polyimide (TPI) adhesive layer is formed on one or both sides of a polyimide film and a conductive metal foil, productivity is high among the three methods (patent literature 1, 3-5). In general, high solder heat resistance corresponding to lead-free solder and dimensional stability corresponding to high-density mounting are required for two-layer FCCL. However, since the laminated two-layer FCCL uses high-melting-point thermoplastic polyimide (TPI) as an adhesive, the lamination process inevitably requires a high temperature of 300 ° C. or higher and a high pressure, which deteriorates the dimensional stability after etching and heating. . Various improvements have been made to increase dimensional stability, but dimensional stability is still insufficient. Moreover, from the viewpoint of copper foil breakage, wrinkle prevention, etc., the combined use of a heat-resistant protective film has become essential, and a problem remains from the viewpoint of cost.

The casting method 2-layer FCCL uses a process of imidizing by casting (coating) a polyimide precursor on a conductive metal foil and heating it (Patent Documents 6 and 7), but has an essential drawback that productivity is low and a long device is required. there is. In order to improve dimensional stability and reliability of copper foil adhesion, low thermal expansion polyimide and high adhesive polyimide with improved adhesion of copper foil are used, and three layers are coated on the copper foil at an arbitrary thickness ratio whose thermal expansion coefficient after curing matches that of copper. A method of curing has been developed, and a wide continuous coating and curing process of single-sided two-layer FCCL by a floating method and a high-speed and wide continuous lamination process of double-sided two-layer FCCL have also been developed. As a result of these improvements, currently, the casting method 2-layer FCCL has the most stable properties among the three methods, but it has not been able to overcome the essential drawback of low productivity and requiring a pole device.

The sputtering method 2-layer FCCL is a process of laminating a conductive metal on a polyimide film by sputtering, and is advantageous for fine pattern formation due to the characteristics that thinning of the conductor layer is easy and the interface between the metal and the film is smooth (Patent Document 2 ). However, since the sputtering method requires a vacuum deposition facility, the production cost is high and the productivity is low, the price of FCCL is also the most expensive among the three methods.

On the other hand, a method of using a film made of a thermosetting resin composition containing a solvent-soluble polyimide resin containing a phenylindan structure and an epoxy resin as an interlayer insulating material or adhesive of a multi-layer board has been reported (Patent Documents 8 and 9). In Patent Literature 8, a thermosetting resin composition is used as an interlayer insulating material for a build-up multilayer substrate using a rigid substrate such as FR-4 as a core material. In addition, in Patent Document 9, when manufacturing a build-up multilayer printed wiring board by overlapping copper foil on a flexible copper clad board as a core material, a thermosetting resin composition is used as an adhesive for bonding copper and copper foil on the surface of a flexible copper clad board, and the thermosetting resin composition A phenoxy resin having a glass transition temperature (Tg) of 130° C. or higher is used. However, the adhesive of Patent Document 9 is not a material for adhering the polyimide film substrate constituting the FCCL and the copper foil. In addition, Patent Document 10 discloses an adhesive containing a polyimide resin and a crosslinking agent as an adhesive for adhering a polyimide film and copper foil constituting FCCL. However, Patent Literature 10 discloses that the adhesive exhibits a high softening point (20 to 220° C.), a low dielectric constant, and a low dielectric loss tangent, but does not mention dimensional stability at all.

Japanese Unexamined Patent Publication No. 6-232553 Japanese Unexamined Patent Publication No. 2002-280684 Japanese Unexamined Patent Publication No. 2003-71982 Japanese Unexamined Patent Publication No. 2003-136631 Japanese Unexamined Patent Publication No. 2014-198385 Japanese Unexamined Patent Publication No. 2016-215651 Japanese Unexamined Patent Publication No. 2019-081379 Japanese Unexamined Patent Publication No. 2006-328214 Japanese Unexamined Patent Publication No. 2013-35881 Japanese Unexamined Patent Publication No. 2019-172989

In the two-layer FCCL, the laminated two-layer FCCL is the most excellent in terms of productivity, and the casting two-layer FCCL is the most excellent in terms of characteristics. For this reason, it has been desired to realize characteristics at the level of the two-layer FCCL of the casting method by using the process of the lamination method. Since the laminated two-layer FCCL has a high lamination temperature of 300° C. or more, a highly heat-resistant film such as a polyimide film is used in combination during lamination to eliminate defects such as copper foil breakage and wrinkles. In addition, dimensional stability was inevitably deteriorated due to high-temperature lamination. Therefore, there has been a demand for an adhesive capable of laminating the adhesive layer and the copper foil without causing such a defect and providing an FCCL having excellent dimensional stability.

The present invention has been made in view of the above circumstances, and its purpose is to achieve both the characteristics of the two-layer FCCL level of the casting method and the productivity of the two-layer FCCL or higher of the laminate method, as well as to have no defects such as copper foil breakage or wrinkles, and to have excellent dimensional stability. It is to develop an adhesive for flexible copper clad laminates that provides FCCL, and to provide adhesive sheets and laminated flexible copper clad laminates (hereinafter also referred to as "2. Two-layer FCCL") manufactured using the same.

As a result of repeated intensive studies, the inventors of the present invention have found that, in a laminated two-layer FCCL, thermoplastic polyimide (TPI) as an adhesive is selected from a specific solvent-soluble polyimide, a phenoxy resin having a glass transition temperature (Tg) of 120° C. or less, and an epoxy resin. By changing to a thermosetting adhesive of a polymer alloy containing a resin and an epoxy resin curing agent, it is possible to improve dimensional stability, which is an improvement in the properties of a laminated two-layer FCCL, and to achieve properties comparable to those of a casting two-layer FCCL. In addition, it was found that defects such as copper foil breakage and wrinkles were eliminated during lamination, and the present invention was completed.

That is, the present invention is an adhesive for a flexible copper-clad laminate for bonding a copper foil to a polyimide film substrate constituting a flexible copper-clad laminate, wherein a solvent-soluble polyimide having a repeating unit represented by the following general formula [I], a glass transition temperature ( An adhesive containing a phenoxy resin having a Tg) of 120°C or less, an epoxy resin, and an epoxy resin curing agent.

(Wherein, Z is an aromatic or alicyclic tetracarboxylic acid dianhydride residue, and Ar is an aromatic diamine residue having a phenylindan structure)

In addition, the present invention is an adhesive sheet for a flexible copper-clad laminate in which an adhesive layer for bonding copper foil is laminated on one or both sides of a polyimide film base material constituting the flexible copper-clad laminate, wherein the adhesive layer comprises the adhesive of the present invention An adhesive sheet containing

In addition, the present invention provides a flexible copper-clad laminate formed by sequentially laminating an adhesive layer and copper foil on one or both surfaces of a polyimide film substrate, wherein the adhesive layer contains the adhesive of the present invention.

In addition, the present invention is a method for manufacturing the flexible copper-clad laminate of the present invention, comprising laminating a copper foil on the adhesive sheet of the present invention at a temperature of 70 to 120 ° C., and then curing the adhesive layer at a temperature of 200 ° C. or less. A manufacturing method is provided.

Conventionally, when the adhesive layer of the adhesive sheet and the copper foil are laminated at a high temperature, defects such as copper foil breakage or wrinkles occur, and these defects are particularly noticeable when the copper foil thickness is as thin as 18 μm or less. By laminating an adhesive layer on the surface of a polyimide film substrate using the specific adhesive of the present invention to produce an adhesive sheet, the adhesive layer of the adhesive sheet and the copper foil can be laminated at a relatively low temperature even when the thickness of the copper foil is thin, It is possible to provide a flexible copper-clad laminate having no defects such as broken copper foil or wrinkles. Therefore, since there is no need to go through a lamination process at high temperature and high pressure, which is one of the main causes of deterioration in dimensional stability, and the thermal curing temperature is 200° C. or lower, the dimensional stability of the flexible copper-clad laminate can be greatly improved. As a result, it is possible to provide a flexible copper-clad laminate that achieves both the characteristics of a two-layer FCCL level by the casting method and productivity equal to or higher than that of a two-layer FCCL by the laminate method.

The adhesive for a flexible copper-clad laminate of the present invention is an adhesive for adhering a polyimide film base material and copper foil constituting a flexible copper-clad laminate, and is a solvent-soluble polyimide having a repeating unit represented by the following general formula [I], Tg is 120 ° C. The following phenoxy resins, epoxy resins, and epoxy resin curing agents are contained.

In the above general formula, Z is an aromatic or alicyclic tetracarboxylic acid dianhydride residue, and Ar is an aromatic diamine residue having a phenylindan structure.

(solvent soluble polyimide)

In the repeating unit represented by the general formula [I] of the solvent-soluble polyimide in the present invention, an aromatic tetracarboxylic acid di-anhydride residue represented by Z is introduced into the polyimide. The anhydride is not particularly limited, but benzophenonetetracarboxylic di-anhydride or biphenyltetracarboxylic di-anhydride is preferred.

As the alicyclic tetracarboxylic dianhydride for introducing the alicyclic tetracarboxylic dianhydride residue represented by Z into the polyimide, bicyclo[2.2.2]octo-7-ene-2,3,5,6 -Tetracarboxylic acid dianhydride, norbornane-2-spiro-α-cycloalkanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic Acid di-anhydride, 1,2,3,4-cyclobutanetetracarboxylic di-anhydride, 1,2,3,4-cyclopentanetetracarboxylic di-anhydride, 1,2,4,5-cyclohexanetetracar boxylic acid di-anhydride, 2,3,5-tricarboxycyclopentylacetic acid di-anhydride, 3,5,6-tricarboxynorbornane-2-acetic acid di-anhydride, 2,3,4,5-tetrahydrofurantetracar Boxylic di-anhydride, 1,3,3a,4,5,9b-hexahydro-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphth[1,2-c]-furan -1,3-dione, 1,3,3a,4,5,9b-hexahydro-5-methyl-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphth[1, 2-c] -furan-1,3-dione, 1,3,3a,4,5,9b-hexahydro-8-methyl-5- (tetrahydro-2,5-dioxo-3-furanyl) -Naphth[1,2-c]-furan-1,3-dione, 5-(2,5-dioxotetrahydrofural)-3-methyl-3-cyclohexene-1,2-dicarboxylic acid Di-anhydride, bicyclo[2,2,2]-octo-7-ene-2,3,5,6-tetracarboxylic acid di-anhydride, bicyclo[2,2,1]-heptane-2,3, 5,6-tetracarboxylic acid dianhydride and decahydrodimethanonaphthalene-2,3,6,7-tetracarboxylic acid dianhydride, etc. are mentioned.

The phenylindane structure in an aromatic diamine residue having a phenylindan structure represented by Ar is a structure in which the following indan skeleton is substituted with a phenyl group which may have a substituent, and the substituent is a halogen atom or 1 to 5 carbon atoms, preferably includes an alkyl group having 1 to 3 carbon atoms. As the aromatic diamine residue (Ar) having a phenylindan structure, a diamine residue containing a structure in which a phenyl group which may have a substituent at one or two positions of the following indan skeleton is substituted, and among these, the following general formula [II] It is preferably a diamine residue represented by

In formula [II], R ₁ , R ₂ and R ₃ each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, preferably an alkyl group having 1 to 3 carbon atoms. In addition, each of R ₄ and each of R ₅ independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and preferably represents an alkyl group having 1 to 3 carbon atoms.

As the aromatic diamine for introducing the aromatic diamine residue (Ar) having a phenylindan structure into the polyimide, 5-amino-1-(4'-aminophenyl)-1,3,3-trimethylindan, 6-amino-1 -(4'-aminophenyl)-1,3,3-trimethylindane, 5-amino-6-methyl-1-(3'-amino-4'-methylphenyl)-1,3,3-trimethylindane, 5 -Amino-1-(4'-amino-Ph', Ph'-dichloro-phenyl)-Ph, Ph-dichloro-1,3,3-trimethylindane, 6-amino-1-(4'-amino-Ph ', Ph'-dichloro-phenyl)-Ph, Ph-dichloro-1,3,3-trimethylindane, 4-amino-6-methyl-1-(3'-amino-4'-methyl-phenyl)-1 ,3,3-trimethylindane, Ph-amino-1-(Ph'-amino-2',4'-dimethylphenyl)-1,3,3,4,6-pentamethylindane, and the like. Ph and Ph' in the above exemplary compounds represent unspecified positions in the phenyl ring in the phenyl indane structure.

The content of the aromatic diamine component (Ar component) having a phenylindan structure constituting the solvent-soluble polyimide is 50 mol% or more, preferably 60 mol% of the total diamine components, from the viewpoint of enhancing compatibility between the solvent-soluble polyimide and the epoxy resin. or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, and particularly preferably 90 mol% or more.

The solvent-soluble polyimide may be a block copolymer having a repeating unit other than the repeating unit represented by the above general formula [I], and other aromatic diamine residues, aliphatic diamine residues or alicyclic diamine residues, or diaminopolysiloxane as a main chain You may have a repeating unit which has a diamine residue in the inside. As the diamine for introducing the diamine residue having the diaminopolysiloxane in the main chain into the polyimide, α,ω-bis(2-aminoethyl)polydimethylsiloxane, α,ω-bis(3-aminopropyl)polydimethylsiloxane, α ,ω-bis(4-aminophenyl)polydimethylsiloxane, α,ω-bis(4-amino-3-methylphenyl)polydimethylsiloxane, α,ω-bis(3-aminopropyl)polydiphenylsiloxane, α, (omega)-bis (4-aminobutyl) polydimethylsiloxane etc. are mentioned.

The solvent-soluble polyimide having a repeating unit represented by the general formula [I] is obtained by subjecting an aromatic or alicyclic tetracarboxylic dianhydride and an aromatic diamine having a phenylindan structure to a dehydration condensation reaction.

The method for synthesizing the solvent-soluble polyimide may be a known method, and is not particularly limited, but the above-mentioned tetracarboxylic dianhydride and aromatic diamine are used in approximately equal amounts, in an organic polar solvent, in the presence of a catalyst and a dehydrating agent. A solvent-soluble polyimide can be synthesized by reacting at 160 to 200°C for several hours. As the organic polar solvent, N-methylpyrrolidone (NMP), γ-butyrolactone, N,N'-dimethylacetamide, N,N'-dimethylformamide, dimethylsulfoxide, tetramethylurea, tetrahydrothiocyanate Ophen-1,1-oxide and the like are used.

The solvent-soluble polyimide is preferably a block copolymer, and the block copolymer can be synthesized by performing a block copolymerization reaction. For example, it can be produced by a two-step sequential addition reaction, in which a polyimide oligomer is synthesized from tetracarboxylic dianhydride and aromatic diamine in the first step, and then in the second step, tetracarboxylic dianhydride and It can be set as block copolymerization polyimide by polycondensing by adding/or aromatic diamine further.

As a catalyst for the block copolymerization reaction, the dehydration imidation reaction can be promoted by using a two-component acid-base catalyst using an equilibrium reaction of lactone. Specifically, a two-component catalyst of γ-valerolactone and pyridine or N-methylmorpholine is used. As shown in the following formula, water is generated as the imidation proceeds, and the generated water becomes an acid-base catalyst by being involved in the equilibrium of lactones and exhibits a catalytic action.

The water produced by the imidation reaction is removed out of the system by azeotropy with a dehydrating agent such as toluene or xylene coexisting in the polar solvent. When the reaction is completed, water in the solution is removed, and the acid-base catalyst becomes γ-valerolactone and pyridine or N-methylmorpholine and is removed out of the system. In this way, a high-purity polyimide solution can be obtained.

As another two-component catalyst, oxalic acid or malonic acid and pyridine or N-methylmorpholine can be used. In the reaction solution at 160 to 200°C, oxalate or malonate promotes the imidation reaction as an acid catalyst. A catalytic amount of oxalic acid or malonic acid remains in the resulting polyimide solvent. After applying this polyimide solution to a substrate, it is heated to 200° C. or higher, and solvent removal is performed to form a film. When forming a film, oxalic acid or malonic acid remaining in the polyimide is thermally decomposed as shown in the following formula and is removed from the system as a gas.

By the above method, a high-purity solvent-soluble polyimide can be obtained. The oxalic acid-pyridine-based catalyst is more active than the valerolactone-pyridine-based catalyst and can produce high molecular weight polyimide in a short time.

The molecular weight of the synthesized solvent-soluble polyimide is preferably from 10,000 to 400,000 as a weight average molecular weight (Mw) in terms of polystyrene. When the molecular weight of the solvent-soluble polyimide is within this range, it is preferable because good solvent solubility, film properties and insulating properties can be achieved.

The term "solvent solubility" in the present invention is a term used for the organic polar solvent used in the synthesis of polyimide and the solvent used for the adhesive composition described later, and polyimide is 20% by weight using these solvents. It means that a solution of % solid content can be produced. Examples of the solvent include NMP, γ-butyrolactone, DMF, and DMAC. The synthesized polyimide can be used in the form of a solution dissolved in the organic polar solvent or a solvent used for an adhesive composition described later, for example, in a solid content of 10 to 30% by weight.

In addition, since the solvent-soluble polyimide of the present invention is a fully imidized polyimide, it does not require heat treatment at high temperature for imidization after applying the adhesive to the polyimide film substrate. Therefore, it is possible to provide a flexible copper-clad laminate having higher dimensional stability compared to polyamic acid (polyimide precursor), which requires heat treatment at high temperature (300 ° C. or more) for imidization after applying the adhesive to the polyimide film substrate. There is an advantage.

(epoxy resin)

Although the epoxy resin in this invention is not specifically limited, Preferably, the epoxy resin of the rigid structure which has 2 or more glycidyl groups is suitable. The molecular weight (Mw) of the epoxy resin is usually 200 to 2,000, preferably 280 to 1,000. Particularly preferred are biphenyl-type epoxy resins, naphthalene-type epoxy resins, dicyclopentadiene-type epoxy resins, and bisphenol A-type epoxy resins, which may be used alone or in combination of two or more.

The epoxy resin in the present invention is an epoxy resin compatible with solvent-soluble polyimide, and is a resin capable of changing the characteristics of solvent-soluble polyimide. Since the epoxy resin and the solvent-soluble polyimide resin are compatible, a compatible polymer alloy is produced by mixing the epoxy resin and the solvent-soluble polyimide.

(epoxy resin curing agent)

The curing agent in the present invention is not particularly limited as long as it cures an epoxy resin, and examples thereof include a novolac phenol resin and a resin having a naphthalene structure and an aralkyl structure. As the novolak phenol resin, phenol novolac resin, cresol novolak resin, triazine-modified novolac resin, benzoguanamine-modified bisphenol A type novolac resin, benzoguanamine-modified cresol novolac-type phenol resin, benzoguanamine-modified phenol Novolac-type phenolic resins, melamine-modified bisphenol A-type novolac resins, melamine-modified cresol novolac-type phenolic resins, and melamine-modified phenol novolac-type phenolic resins. Examples of the resin having a naphthalene structure and an aralkyl structure include 1-naphthol aralkyl resin, 2-naphthol aralkyl resin, and 1,6-naphthalenediol aralkyl resin.

The amount of the curing agent used for the epoxy resin is preferably 0.5 equivalent or more and 1.2 equivalent or less in terms of hydroxyl equivalent. If the amount of the curing agent used is less than 0.5 equivalent, appropriate Tg may not be obtained, so 0.5 equivalent or more is preferable, but 0.6 equivalent or more is more preferable. In addition, when the amount of the curing agent used exceeds 1.2 equivalents, the water absorption properties of the resin may deteriorate. Therefore, 1.2 equivalents or less is preferable, but 1.0 equivalents or less is more preferable.

As a curing agent, an aromatic amine-based resin can also be suitably used. The aromatic amine resin is not particularly limited as long as it can cure the epoxy resin, but 4,4'-diaminodiphenylsulfone, 4,4'-bis(4-aminophenoxy)biphenyl, 2,2-bis [4-(4-aminophenoxy)phenyl]propane, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, trimethylenebis(4-aminobenzo 8), polytetramethylene oxide-di-p-aminobenzoate, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl , 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3aminophenoxy)phenyl] sulfone, 9,9'-bis(4-aminophenyl)fluorene, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, etc. can be exemplified, either alone or in combination of two. The above can be used in combination.

Although the amount of aromatic amine-based resin used is not limited, the amount of aromatic amine compound used when the number of moles of the epoxy resin is set to 1 is optimal at 0.3 to 1.5 moles. By setting the amount of aromatic amine-based resin (total number of moles) to be 0.3 or more, an adhesive layer having an appropriate thermal expansion coefficient can be easily obtained. From this point of view, the amount of aromatic amine-based resin used (total number of moles) is more preferably 0.4 or more. Moreover, the adhesive layer which has an appropriate thermal expansion coefficient can be obtained easily also by making the usage-amount (total number of moles) of aromatic amine-type resin into 1.5 or less. From this point of view, the amount of aromatic amine-based resin used is more preferably 1.2 or less.

(phenoxy resin)

The phenoxy resin in the present invention is a phenoxy resin having a glass transition temperature (Tg) of 120° C. or less, and specifically, those having a molecular weight (Mw) of 10,000 or more are suitable. BPF type, BPA/BPS type, BP/BPS type, etc. are suitable. As for commercial products, for example, JER1256 (weight average molecular weight (hereinafter referred to as Mw) 48,000, glass transition temperature (hereinafter referred to as Tg) 95 ° C., manufactured by Mitsubishi Chemical Corporation), PKHJ (Mw 57,000, Tg 98 ° C., GabrielPhenoxies manufactured), PKHH (Mw 52,000, Tg 92°C, manufactured by GabrielPhenoxies), PKFE (Mw 60,000, Tg 98°C, manufactured by GabrielPhenoxies), FX-310 (Mw 45,000, Tg 110°C, manufactured by Nippon-Tsu Epoxy Seisei), etc. can

By using a phenoxy resin having a glass transition temperature (Tg) of 120 ° C. or less in combination, flexibility and adhesiveness are imparted to the adhesive layer formed of the adhesive, as in the case of the solvent-soluble polyimide resin, and the adhesive layer and the copper foil are bonded at a relatively low temperature. can be combined The Tg of the phenoxy resin is preferably 80 to 115 ° C. to prevent defects such as copper foil breakage and wrinkles when laminating the adhesive layer and the copper foil, and to set the Tg of the adhesive layer made of the adhesive to the optimum range described later. , more preferably 85 to 113 ° C, most preferably 90 to 110 ° C. Tg of a phenoxy resin can be measured based on IPC-TM-650-2.4.24.3.

The weight ratio of the solvent-soluble polyimide resin (solid content) and the phenoxy resin in the adhesive composition is usually 1:1.2 to 12.0, preferably 1:1.3 to 10.0, more preferably 1:1.4 to 9.5, still more preferably 1: 1.5 to 9.0.

The total content (% by weight) of the solvent-soluble polyimide resin, the phenoxy resin, the epoxy resin and the epoxy resin curing agent in the adhesive composition is usually 10 to 50% by weight. If the total content of the solvent-soluble polyimide resin and the phenoxy resin is less than 10% by weight, the adhesive strength and flexibility of the adhesive layer formed from the adhesive composition may be low, so relative to the total weight including the epoxy resin and the epoxy resin curing agent 15% by weight or more is preferred, and 20% by weight or more is more preferred. In addition, since the breaking strength as a film may decrease when the total content of the solvent-soluble polyimide resin and the phenoxy resin exceeds 50% by weight, 45% by weight or less relative to the total weight including the epoxy resin and the epoxy resin curing agent It is preferred, and 40% by weight or less is more preferred.

The adhesive of the present invention may be an adhesive composition containing a curing accelerator, a flame retardant and the like in addition to the above solvent-soluble polyimide, epoxy resin, curing agent and phenoxy resin.

(curing accelerator)

A curing accelerator may be used in combination with the adhesive of the present invention, if necessary. As the curing accelerator, common ones such as various imidazoles can be used. You can choose mainly from the viewpoint of reaction speed or pot life.

(flame retardant)

A flame retardant may be added to the adhesive of the present invention to impart flame retardancy, if necessary. As the halogen-free flame retardant, condensed phosphoric acid esters, phosphazenes, polyphosphates, HCA (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) derivatives, etc. can be used. .

An adhesive ( composition) can be prepared.

The solvent that can be used in the adhesive composition of the present invention is not particularly limited, but a high boiling point solvent such as NMP, γ-butyrolactone, methyl benzoate, diethylene glycol monomethyl ether acetate or diethylene glycol monomethyl ether acetate and cyclohexanone or MEK (methyl ethyl ketone), etc. It is preferable to combine a low boiling point solvent.

(Tensile modulus and Tg of adhesive film)

The adhesive (composition) of the present invention heat-hardens a semi-cured film made of the adhesive at 180°C for 90 minutes, and the obtained film has a tensile modulus of 1 to 10.0 GPa and a Tg (glass transition temperature) of 120 to 190°C. It is an adhesive that becomes

The film for measuring the tensile modulus and Tg is produced as follows. That is, the resin varnish prepared as described above is applied to the shiny side of the 18 μm electrodeposited copper foil with a bar coater, dried at a temperature of 150 ° C. to manufacture The volatile content of the solvent is adjusted to 0.6 wt%. An 18 μm electrodeposited copper foil shiny surface is superimposed on the adhesive sheet surface of this copper foil with adhesive, and put into a vacuum press to heat and press at 1 MPa at 180° C. for 90 minutes (vacuum degree: 5 torr). Subsequently, the tensile modulus and Tg of the adhesive film of about 20 μm obtained by etching the entire surface of the copper foil are measured. Tensile modulus was measured based on IPC-TM-650-2.4.18.3, and Tg was measured based on IPC-TM-650-2.4.24.3.

Here, the tensile elastic modulus is mainly related to the dimensional stability of FCCL, but at the same time it is also related to warpage and bending of the printed wiring board. Warpage occurs due to a mismatch between the polyimide film used as the core material and the adhesive layer, particularly in tensile modulus or thermal expansion coefficient. Since such a mismatch occurs even in an adhesive sheet having a double-sided symmetrical structure, it is desirable to set the tensile modulus and thermal expansion coefficient to equal values between the polyimide film and the adhesive layer, but realizing this is a very difficult problem for solvent-soluble polyimide resins. was As a solution to this, it is effective to make the tensile modulus of elasticity of the adhesive layer less than the tensile modulus of elasticity of the core polyimide film substrate. When the tensile modulus of elasticity of the adhesive layer is greater than or equal to the tensile modulus of elasticity of the core polyimide film base material, the thermal strain of the core polyimide film base material increases and the rate of dimensional change after heating increases. Further, when the tensile modulus of elasticity of the adhesive layer is less than 1 GPa, bending of the FCCL is likely to occur. The tensile modulus of elasticity is preferably within the range of 1.1 to 5.0 GPa, more preferably 1.2 to 3.0 GPa, and particularly 1.2 to 2.5 GPa.

In addition, the Tg (glass transition temperature) of the film produced with the adhesive is preferably 125 to 185°C, more preferably 130 to 180°C.

(adhesive sheet)

Laminate method 2. A two-layer FCCL adhesive sheet can be obtained by B-staging the adhesive (composition) of the present invention to a semi-cured state (B state) on one or both surfaces of a polyimide film substrate. Specifically, as described above, a resin varnish prepared by diluting the adhesive (composition) of the present invention with a suitable mixed organic solvent such as NMP/MEK is applied to one or both sides of a polyimide film substrate as a core material for a gravure coater or thin film. Coating is performed using a die coater or the like. In the present invention, in order to make the dimensional stability equal to that of the casting method 2-layer FCCL, it is preferable to set the coating thickness, coating temperature and heat curing temperature of the adhesive layer to the following specific ranges.

The coating thickness of the adhesive layer is required to be equal to or greater than the minimum thickness to embed the roughened surface of the copper foil to be laminated. is preferable Since this coating thickness particularly affects dimensional stability, in addition to this condition, the thickness of the adhesive layer on one side is 20% or less, preferably 15% or less, more preferably 13% or less of the thickness of the core polyimide film. It is desirable to do The thickness of the adhesive layer of the adhesive sheet preferably satisfies both of the above two conditional ranges, but the absolute value of the thickness is also preferably 1.6 to 4.0 μm, more preferably 2.0 to 3.5 μm, particularly 2.5 to 2.9 μm. By setting the thickness of the adhesive layer within this range, the difference in physical properties (mainly tensile modulus and thermal expansion coefficient) between the adhesive layer and the core polyimide film does not surface in the physical properties of FCCL as a composite film, and adhesive properties can be maintained. Further, the thickness of the adhesive layer of the adhesive sheet is preferably 1.5 to 3.5 μm when the adhesive sheet is heated and cured in a dryer at 180° C. for 90 minutes.

The composite layer is obtained by setting the tensile modulus and Tg of the film made of the adhesive (composition) of the present invention within the above-specified range, and setting the thickness of the adhesive layer of the adhesive sheet to 1.6 to 4.0 μm, preferably 1.8 to 2.9 μm. The dimensional stability of FCCL as a film can be made almost equal to that of the core polyimide film. Accordingly, it has become possible to provide an adhesive sheet and a laminated 2.2-layer FCCL having excellent properties comparable to those of the casting-method 2-layer FCCL and productivity higher than that of the laminated 2-layer FCCL. In addition, by realizing the above conditions, it is possible to prevent the occurrence of warpage due to the mismatch of thermal expansion coefficients of the single-sided, two-layer FCCL, so that warpage can be suppressed even without resorting to the TPI bilateral symmetrical structure that is currently widely used.

Since the coating temperature of the adhesive layer (including the drying temperature after coating) also becomes a factor in giving the FCCL thermal deformation, the coating temperature is preferably 150°C or less.

(Flexible copper clad laminate (FCCL))

Laminate method 2. A two-layer flexible copper clad laminate (FCCL) can be produced by laminating (bonding) copper foil on the surface of the adhesive layer of the adhesive sheet produced as described above and then curing the adhesive layer. The adhesive layer of the adhesive sheet and the copper foil can be laminated using a laminator at 70 to 120°C, preferably 75 to 115°C, and more preferably 80 to 110°C. By laminating at such a relatively low temperature, a flexible copper-clad laminate without defects such as copper foil breakage and wrinkles can be produced. The thickness of the copper foil is usually 1.5 to 20 μm, preferably 5 to 18 μm. The curing temperature of the adhesive layer, which is the largest factor of thermal deformation, is preferably 200°C or less, more preferably 195°C or less, particularly 190°C or less, and preferably 150°C or more, more preferably 160°C or more.

By producing the adhesive sheet and the FCCL as described above, the rate of dimensional change after etching and heating can be equal to that of the two-layer FCCL by the casting method.

One of the main causes of deterioration in dimensional stability after etching and heating of a conventional laminated two-layer FCCL was that deformation occurred in the lamination process with copper foil under high temperature and high pressure of 300 ° C. or higher. In the present invention, by using a polymer alloy adhesive containing a specific solvent-soluble polyimide, which is a thermosetting resin, a phenoxy resin having a Tg of 120° C. or less, an epoxy resin, and an epoxy resin curing agent, at a relatively low temperature without copper foil breakage or wrinkles. The copper foil laminate of and thermal curing at 200° C. or lower is possible, and the dimensional shrinkage rate can be greatly improved by reducing the strain generated in each process.

(Example)

Hereinafter, the present invention will be described in detail based on examples, but the present invention can be modified into various other embodiments, and is not limited to the following examples.

1. Synthesis of solvent-soluble polyimide resin

(Synthesis Example 1)

A cooling pipe provided with a stirrer, a nitrogen inlet pipe, and a water container was attached to a glass separable three-necked flask. 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (hereinafter referred to as BPDA) 58.84 g (0.2 mol), 5-amino-1- (4'-aminophenyl) -1,3,3 -Trimethylindan 26.64 g (0.1 mol) (phenylindan structure-containing aromatic diamine), valerolactone 1.5 g (0.015 mol), pyridine 2.4 g (0.03 mol), NMP 200 g, and toluene 30 g were added, and the mixture was stirred at room temperature under a nitrogen atmosphere. After stirring at 200 rpm for 30 minutes, the temperature was raised to 180°C and the mixture was heated and stirred for 1 hour. During the reaction, the toluene-water azeotrope was removed.

After cooling to room temperature, 44.13 g (0.15 mol) of BPDA, 66,60 g (0.25 mol) of 6-amino-1-(4'-aminophenyl)-1,3,3-trimethylindane, 360 g of NMP, and 90 g of toluene were added. After stirring at room temperature for 30 minutes, the temperature was raised to 180°C, followed by heating and stirring for 1 hour. The reaction was terminated by heating and stirring at 180°C for 2 hours and 30 minutes while removing the azeotropic reflux product of water and toluene out of the system. [gamma]-butyrolactone was added and diluted to the obtained product, and the block-copolymerization polyimide solution of 20 weight% of solid content was obtained.

(Synthesis Example 2)

A cooling pipe provided with a stirrer, a nitrogen inlet pipe, and a water container was attached to a glass separable three-necked flask. 3,4,3',4'-benzophenonetetracarboxylic acid dianhydride (hereinafter referred to as BTDA) 64.45 g (0.2 mol), 5-amino-1- (4'-aminophenyl) -1,3,3 -Trimethylindan 26.64 g (0.1 mol) (a phenyl indan structure-containing aromatic diamine), valerolactone 1.5 g (0.015 mol), pyridine 2.4 g (0.03 mol), NMP 200 g, and toluene 30 g were added, and the mixture was stirred at room temperature under a nitrogen atmosphere. After stirring at 200 rpm for 30 minutes, the temperature was raised to 180°C and the mixture was heated and stirred for 1 hour. During the reaction, the toluene-water azeotrope was removed.

After cooling to room temperature, 48.33 g (0.15 mol) of BTDA, 66,60 g (0.25 mol) of 6-amino-1-(4'-aminophenyl)-1,3,3-trimethylindane, 360 g of NMP, and 90 g of toluene were added. After stirring at room temperature for 30 minutes, the temperature was raised to 180°C, followed by heating and stirring for 1 hour. The reaction was terminated by heating and stirring at 180°C for 2 hours and 30 minutes while removing the azeotropic reflux product of water and toluene out of the system. [gamma]-butyrolactone was added and diluted to the obtained product, and the block-copolymerization polyimide solution of 20 weight% of solid content was obtained.

(Synthesis Example 3)

A cooling pipe provided with a stirrer, a nitrogen inlet pipe, and a water container was attached to a glass separable three-necked flask. 3,4,3',4'-benzophenonetetracarboxylic acid dianhydride (hereinafter referred to as BTDA) 64.45 g (0.2 mol), 4,4'-diaminodiphenyl ether 20.02 g (0.1 mol), Valero 1.5 g (0.015 mol) of lactone, 2.4 g (0.03 mol) of pyridine, 200 g of NMP, and 30 g of toluene were charged, and after stirring at room temperature at 200 rpm for 30 minutes under a nitrogen atmosphere, the mixture was heated to 180°C and heated and stirred for 1 hour. During the reaction, the toluene-water azeotrope was removed.

After cooling to room temperature, 48.33 g (0.15 mol) of BTDA, 66.60 g (0.25 mol) of 5-amino-1-(4'-aminophenyl)-1,3,3-trimethylindane, 360 g of NMP, and 90 g of toluene were added. , After stirring at room temperature for 30 minutes, the temperature was raised to 180°C and heating and stirring were performed for 1 hour. The reaction was terminated by heating and stirring at 180°C for 2 hours and 30 minutes while removing the azeotropic reflux product of water and toluene out of the system. [gamma]-butyrolactone was added and diluted to the obtained product, and the block-copolymerization polyimide solution of 20 weight% of solid content was obtained.

(Synthesis Example 4)

A cooling pipe provided with a stirrer, a nitrogen inlet pipe, and a water container was attached to a glass separable three-necked flask. 3,4,3',4'-benzophenonetetracarboxylic acid dianhydride (hereinafter referred to as BTDA) 64.45 g (0.2 mol), 5-amino-1- (4'-aminophenyl) -1,3,3 -trimethylindane 15.98 g (0.06 mol), 1,3-bis (3-aminopropyl) tetramethyldisiloxane 9.94 g (0.04 mol), valerolactone 1.5 g (0.015 mol), pyridine 2.4 g (0.03 mol), 200 g of NMP and 30 g of toluene were introduced, and after stirring at room temperature for 30 minutes, the temperature was raised to 180°C and stirred for 1 hour. During the reaction, the toluene-water azeotrope was removed.

After cooling to room temperature, 48.33 g (0.15 mol) of BTDA, 66.60 g (0.25 mol) of 5-amino-1-(4'-aminophenyl)-1,3,3-trimethylindane, 360 g of NMP, and 90 g of toluene were added. , After stirring at room temperature for 30 minutes, the temperature was raised to 180°C and heating and stirring were performed for 1 hour. The reaction was terminated by heating and stirring at 180°C for 2 hours and 30 minutes while removing the azeotropic reflux product of water and toluene out of the system. [gamma]-butyrolactone was added and diluted to the obtained product, and the block-copolymerization polyimide solution of 20 weight% of solid content was obtained.

2. Preparation of adhesive composition, production of adhesive sheet and FCCL

(Example 1)

347 parts by weight of dicyclopentadiene type epoxy resin "HP-7200H" (manufactured by DIC, epoxy equivalent 283, resin solid content 80% by weight), 183 parts by weight of melamine-modified cresol novolac resin "EXB-9854" (manufactured by DIC, hydroxyl value) 151, resin solid content 80% by weight), 290 parts by weight of soluble polyimide resin (Synthesis Example 1, resin solid content 20% by weight), 91 parts by weight of phenoxy resin "jER1256" (manufactured by Mitsubishi Chemical Corporation, Mw ≈ 48,000, Tg 95 ° C. , Resin solid content 100% by weight), 57 parts by weight of a phosphazene derivative "FP-100" (manufactured by Fushimi Pharmaceutical Co., Ltd.), 0.7 parts by weight of a mixture consisting of 2-ethyl-4methylimidazole, γ-butyrolactone as a solvent /cyclohexanone mixed solvent was added to prepare a resin varnish having a resin solid content of 40% by weight.

(Example 2)

337 parts by weight of biphenyl type epoxy resin "NC-3000H" (manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent 275, resin solid content 80% by weight), 202 parts by weight of melamine-modified phenolic novolak resin "LA-7054" (manufactured by DIC Corporation, hydroxyl value) 125, resin solid content 60% by weight), 98 parts by weight soluble polyimide resin (Synthesis Example 2, resin solid content 20% by weight), 170 parts by weight phenoxy resin "jER1256" (manufactured by Mitsubishi Chemical Corporation, Mw ≒ 48,000, Tg 95 ° C. , Resin solid content 100% by weight), 57 parts by weight of a phosphazene derivative "FP-100" (manufactured by Fushimi Pharmaceutical Co., Ltd.), 0.7 parts by weight of a mixture consisting of 2-ethyl-4methylimidazole, γ-butyrolactone as a solvent /cyclohexanone mixed solvent was added to prepare a resin varnish having a resin solid content of 40% by weight.

(Example 3)

349 parts by weight of naphthol aralkyl type epoxy resin "ESN-165" (Nittetsu Epoxy Seizo, made by epoxy equivalent 265, resin solid content 80% by weight), 177 parts by weight of melamine-modified phenolic novolac resin "LA-7054" (manufactured by DIC, Hydroxyl value 125, resin solid content 60% by weight), 290 parts by weight of soluble polyimide resin (Synthesis Example 3, resin solid content 20% by weight), 91 parts by weight of phenoxy resin “jER1256” (manufactured by Mitsubishi Chemical Corporation, Mw ≒ 48,000, Tg 95 ° C., 100% by weight of resin solid content), 57 parts by weight of a phosphazene derivative “FP-100” (manufactured by Fushimi Pharmaceutical Co., Ltd.), and 0.7 parts by weight of 2-ethyl-4methylimidazole, γ-buty as a solvent A resin varnish having a resin solid content of 40% by weight was prepared by adding a mixed solvent of rolactone/cyclohexanone.

(Example 4)

337 parts by weight of biphenyl type epoxy resin "NC-3000H" (manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent 275, resin solid content 80% by weight), 202 parts by weight of melamine-modified phenolic novolac resin "LA-7054" (manufactured by DIC Corporation, hydroxyl value) 125, resin solid content 60% by weight), 98 parts by weight of soluble polyimide resin (Synthesis Example 1, resin solid content 20% by weight), 170 parts by weight of phenoxy resin "FX-310" (Nittetsu Epoxy Seizo, Mw ≒ 45,000, Tg 110 ° C., resin solid content 100% by weight), 57 parts by weight of a phosphazene derivative "FP-100" (manufactured by Fushimi Pharmaceutical Co., Ltd.), 0.7 parts by weight of 2-ethyl-4methylimidazole as a solvent. A mixed solvent of γ-butyrolactone/cyclohexanone was added to prepare a resin varnish having a resin solid content of 40% by weight.

(Example 5)

372 parts by weight of dicyclopentadiene type epoxy resin "HP-7200H" (manufactured by DIC Corporation, epoxy equivalent 283, resin solid content 80% by weight), 128 parts by weight of aromatic amine "Elasmer 250P" (manufactured by Kumiai Kagaku Kogyo Co., Ltd., MW= 488, resin solid content 100% by weight), 290 parts by weight of soluble polyimide resin (Synthesis Example 4, resin solid content 20% by weight), 91 parts by weight of phenoxy resin “jER1256” (manufactured by Mitsubishi Chemical Corporation, Mw ≒ 48,000, Tg 95 ° C. , Resin solid content 100% by weight), 57 parts by weight of a phosphazene derivative "FP-100" (manufactured by Fushimi Pharmaceutical Co., Ltd.), 0.7 parts by weight of a mixture consisting of 2-ethyl-4methylimidazole, γ-butyrolactone as a solvent /cyclohexanone mixed solvent was added to prepare a resin varnish having a resin solid content of 40% by weight.

(Example 6)

372 parts by weight of dicyclopentadiene type epoxy resin "HP-7200H" (manufactured by DIC Corporation, epoxy equivalent 283, resin solid content 80% by weight), 128 parts by weight of aromatic amine "Elasmer 250P" (manufactured by Kumiai Kagaku Kogyo Co., Ltd., MW= 488, resin solid content 100% by weight), 98 parts by weight of soluble polyimide resin (Synthesis Example 3, resin solid content 20% by weight), 170 parts by weight of phenoxy resin "FX-310" (Nittetsu Epoxy Seizo, Mw ≒ 45,000, Tg 110 ° C., resin solid content 100% by weight), 57 parts by weight of a phosphazene derivative "FP-100" (manufactured by Fushimi Pharmaceutical Co., Ltd.), 0.7 parts by weight of 2-ethyl-4methylimidazole as a solvent. A mixed solvent of γ-butyrolactone/cyclohexanone was added to prepare a resin varnish having a resin solid content of 40% by weight.

The resin varnish prepared in Examples 1 to 6 was diluted to a solid content of 20%, applied with a gravure coater on a 20 μm polyimide film (Kapton (registered trademark) EN), and dried at a temperature of 150 ° C. B of double-sided coating An adhesive sheet (film thickness on one side: 2.8 μm) was prepared. Volatile content was adjusted to 0.6 wt%. To this adhesive sheet, 12 μm Rz = 1.8 μm copper foil was bonded to both sides with a laminator at a lamination temperature of 110 ° C or 100 ° C, and then heated with a dryer at 180 ° C for 90 minutes to heat-harden the adhesive layer to form a double-sided copper foil FCCL. made Similarly, the resin varnish of each of the above examples was diluted to a solid content of 20%, applied on a 20 μm polyimide film (Kapton (registered trademark) EN) with a gravure coater, and dried at a temperature of 150 ° C. A sheet (film thickness on one side: 2.8 μm) was prepared. Volatile content was adjusted to 0.6 wt%. To this adhesive sheet, a 12 μm Rz = 1.8 μm copper foil was bonded to one side with a laminator at a lamination temperature of 110 ° C or 100 ° C, and then heated with a dryer at 180 ° C for 90 minutes to heat and cure the adhesive layer to obtain single-sided copper foil FCCL. made

(Comparative Example 1)

337 parts by weight of biphenyl type epoxy resin "NC-3000H" (manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent 275, resin solid content 80% by weight), 202 parts by weight of melamine-modified phenolic novolac resin "LA-7054" (manufactured by DIC Corporation, hydroxyl value) 125, resin solid content 60% by weight), 190 parts by weight of phenoxy resin "jER1256" (manufactured by Mitsubishi Chemical Corporation, Mw ≈ 48,000, Tg 95 ° C., resin solid content 100% by weight), 57 parts by weight phosphazene derivative "FP-100" (manufactured by Fushimi Seiyakusho Co., Ltd.), a mixed solvent of γ-butyrolactone/cyclohexanone as a solvent was added to a mixture consisting of 0.7 parts by weight of 2-ethyl-4methylimidazole to prepare a resin varnish having a resin solid content of 40% by weight. .

(Comparative Example 2)

347 parts by weight of dicyclopentadiene type epoxy resin "HP-7200H" (manufactured by DIC, epoxy equivalent 283, resin solid content 80% by weight), 183 parts by weight of melamine-modified cresol novolac resin "EXB-9854" (manufactured by DIC, hydroxyl value) 151, resin solid content 80% by weight), 290 parts by weight of soluble polyimide resin (Synthesis Example 1, resin solid content 20% by weight), 303 parts by weight of phenoxy resin ERF-001M30 (Nittetsu Epoxy Seizo, Tg 146 ° C., 30% by weight of resin solid content), 57 parts by weight of a phosphazene-based derivative "FP-100" (manufactured by Fushimi Seiyakusho Co., Ltd.), and 0.7 parts by weight of 2-ethyl-4methylimidazole, γ-butyrolactone/ A resin varnish having a resin solid content of 40% by weight was prepared by adding a mixed solvent of cyclohexanone.

Double-sided copper-clad FCCL and single-sided copper-clad FCCL were produced in the same manner as in Examples 1 to 6 using the resin varnishes of Comparative Examples 1 to 2.

(Comparative Examples 3 to 5)

As commercially available FCCLs, the following were used.

Comparative Example 3: Commercially available casting method 2-layer FCCL

Comparative Example 4: Commercially available lamination method 2-layer FCCL

Comparative Example 5: Commercial 3-layer FCCL

(Evaluation of various characteristics)

Peel strength, solder heat resistance, and dimensional stability were evaluated using the double-sided copper-clad FCCL produced as described above, and Tg and C.T.E were evaluated using a film obtained by etching the double-sided copper-clad FCCL on the entire surface by TMA method (thermo-mechanical analysis method). done by The test method was based on JIS C 6471.

In addition, evaluation of warpage was performed using the single-sided copper-clad FCCL produced as described above. Specifically, a sample cut into 100 mm × 100 mm was placed with the copper foil face up on a mirror board, and the lifting was measured. 5 mm or less was evaluated as no occurrence of warpage. In addition, the entire surface of the copper foil was etched, and lifting was measured in the same way.

(Tensile modulus and Tg of adhesive film)

The tensile modulus and Tg of the films produced from the resin varnish (adhesive composition) prepared in Examples 1 to 6 and Comparative Example 1 were measured by the following methods.

A resin varnish (adhesive composition) was applied to the shiny side of an 18 μm electrolytic copper foil with a bar coater, and dried at a temperature of 150 ° C. to produce a semi-cured state (B state) copper foil with adhesive (adhesive thickness: about 21 μm). . The volatile content of the solvent was adjusted to 0.6 wt%. An 18 μm electrodeposited copper foil shiny surface was superimposed on the adhesive sheet surface of this copper foil with adhesive, put into a vacuum press, and molded by heating and pressing at 1 MPa at 180 ° C. for 90 minutes (vacuum degree 5 torr). Next, the tensile modulus and Tg of the adhesive film of about 20 µm obtained by etching the entire surface of the copper foil were measured. The tensile modulus of elasticity is measured in accordance with IPC-TM-650-2.4.18.3, a strip-shaped sample with a width of 10 mm is set in a tensile/compression tester with a distance between chucks of 50 mm, and tensile strength is measured at a tensile speed of 50 mm/min. and obtained from the relationship between tensile stress and strain. Tg was measured based on IPC-TM-650-2.4.24.3. IPC-TM-650-2.4.18.3 and IPC-TM-650-2.4.24.3 followed the method described in "IPC-TM-650 TEST METHODS MANUAL".

Tables 1 to 4 show the composition and characteristic evaluation results of the FCCLs of Examples 1 to 6 and Comparative Examples 1 to 5.

From the results of Tables 1 to 4, the FCCLs (Examples 1 to 6) produced using the adhesive of the present invention were produced using an adhesive having a film Tg of less than 120 ° C using a phenoxy-modified epoxy resin. Compared to FCCL (Comparative Example 1), it can be seen that the dimensional stability is improved and warpage of the single-sided plate is not observed. In addition, in the case of an adhesive using a phenoxy resin having a Tg of more than 120 ° C., since the polyimide film and copper foil do not adhere at a lamination temperature of 100 ° C., lamination cannot be performed, and copper foil breaks at a lamination temperature of 125 ° C. ( Comparative Example 2). In addition, when the FCCLs of Examples 1 to 6 are compared with the commercially available 2-layer FCCL by casting method (Comparative Example 3), it can be seen that even though they are manufactured by the lamination process, the same characteristics as the 2-layer FCCL by casting method are realized. can

By using the adhesive and adhesive sheet of the present invention, it is possible to provide a flexible copper-clad laminate (2. 2-layer FCCL) that achieves both the properties of a casting-type two-layer FCCL level and productivity equal to or higher than that of a laminated two-layer FCCL.

Claims (14)

An adhesive for a flexible copper-clad laminate for bonding a copper foil to a polyimide film substrate constituting the flexible copper-clad laminate, comprising a solvent-soluble polyimide having a repeating unit represented by the following general formula [I], a glass transition temperature (Tg) of 120 ° C. An adhesive containing the following phenoxy resins, epoxy resins and epoxy resin curing agents.

(Wherein, Z is an aromatic or alicyclic tetracarboxylic acid dianhydride residue, and Ar is an aromatic diamine residue having a phenylindan structure) According to claim 1,
An adhesive having a tensile modulus of elasticity of 1 to 10.0 GPa and a Tg of 120 to 190 ° C. According to claim 1 or 2,
An adhesive having a glass transition temperature (Tg) of the phenoxy resin of 80 to 115 ° C. According to claim 3,
An adhesive having a glass transition temperature (Tg) of the phenoxy resin of 90 to 110 ° C. According to any one of claims 1 to 4,
An adhesive in which the weight ratio of the solvent-soluble polyimide resin (solid content) and the phenoxy resin contained in the adhesive is 1:1.2 to 12.0. According to any one of claims 1 to 5,
An adhesive in which the total content of the solvent-soluble polyimide resin and the phenoxy resin is 10 to 50% by weight relative to the total content of the solvent-soluble polyimide resin, the phenoxy resin, the epoxy resin and the epoxy resin curing agent contained in the adhesive. An adhesive sheet for a flexible copper-clad laminate formed by laminating an adhesive layer for adhering copper foil to one or both surfaces of a polyimide film substrate constituting the flexible copper-clad laminate, wherein the adhesive layer is any one of claims 1 to 6 An adhesive sheet containing the adhesive described above. According to claim 7,
An adhesive sheet having a tensile modulus of elasticity of a film obtained by heating and curing a semi-cured film made of the adhesive at 180° C. for 90 minutes is less than the tensile modulus of elasticity of a polyimide film substrate. According to claim 7 or 8,
An adhesive sheet having a thickness of the adhesive layer of 1.6 to 4.0 μm. According to any one of claims 7 to 9,
The adhesive sheet wherein the adhesive sheet is an adhesive sheet having an adhesive layer having a thickness of 1.5 to 3.5 μm when the adhesive sheet is heat-cured at 180° C. for 90 minutes. A flexible copper-clad laminate formed by sequentially laminating an adhesive layer and copper foil on one or both surfaces of a polyimide film substrate, wherein the adhesive layer contains the adhesive according to any one of claims 1 to 6. According to claim 11,
A flexible copper-clad laminate in which the thickness of the copper foil is 1.5 to 18 μm. According to claim 11 or 12,
A flexible copper-clad laminate in which the surface roughness Rz of the surface of the copper foil in contact with the adhesive layer is less than the thickness of the adhesive layer. A method for manufacturing the flexible copper-clad laminate according to any one of claims 11 to 13, after laminating copper foil on the adhesive sheet according to any one of claims 7 to 10 at a temperature of 70 to 120 ° C. A manufacturing method comprising curing the adhesive layer at a temperature of 200° C. or lower.