Polyamic acid composition, polyimide film utilizing the same, and metal laminate

Abstract

This invention provides a polyamic acid composition and a metal laminate comprising a polyimide film formed by imidizing the polyamic acid composition. The polyamic acid composition comprises at least one diamine, at least one acid dianhydride, and an organic solvent. The diamine further comprises a diamine whose main chain or branches contain alkyl groups having four or more carbon atoms. This invention includes a diamine monomer containing alkyl groups having a predetermined number of carbon atoms, thereby exhibiting excellent processability not only through low viscosity but also simultaneously ensuring low dielectric loss, high adhesion, and excellent dimensional stability.

Description

Technical Field

[0001] The present invention relates to a polyamic acid composition comprising a diamine monomer containing an alkyl group having a predetermined number of carbon atoms, and a polyimide film and metal laminate formed from said composition that can simultaneously ensure low dielectric loss, high adhesion and excellent dimensional stability. Background Technology

[0002] Flexible copper clad laminate (FCCL) is mainly used as the substrate for flexible printed circuit boards (FPCBs). In addition, it is also used in electromagnetic wave shielding materials for surface-mount heating elements, flat cables, and packaging materials. Recently, with the miniaturization, increasing density, and higher efficiency of electronic devices using printed circuit boards, the application of FCCL has further increased.

[0003] The aforementioned flexible copper-clad laminates typically consist of a polyimide insulating layer and a copper foil layer. Based on their manufacturing methods, such flexible copper-clad laminates can be broadly classified into those manufactured by laminating copper foil layers onto a polyimide film and those manufactured by laminating polyimide layers onto a copper foil layer. In other words, flexible copper-clad laminates can be manufactured by bonding or by casting.

[0004] Flexible copper-clad laminates manufactured by adhesive bonding involve attaching the copper foil layer to a polyimide film using a separate adhesive, such as an epoxy adhesive. The properties of the final flexible copper-clad laminate, including heat resistance, chemical resistance, flame retardancy, and electrical properties, are determined by the characteristics of the adhesive or adhesive film used. Therefore, the inherent excellent flexibility and heat resistance of polyimide resin cannot be fully utilized.

[0005] On the other hand, flexible copper-clad laminates manufactured by casting do not use adhesives. Instead, they are produced by coating a copper foil layer with polyimide varnish and then heat-treating it under appropriate conditions to form a polyimide resin layer on the copper foil layer. However, due to the poor adhesion between the polyimide layer and the copper foil in casting-based flexible copper-clad laminates, a separate thermoplastic polyimide must be used to ensure the adhesion between the insulating layer and the copper foil. This leads to increased production costs and decreased production efficiency. Furthermore, the introduction of a multi-layered insulating layer may cause structural deformation and interlayer delamination problems in both the flexible copper-clad laminate and the printed circuit board. Summary of the Invention

[0006] Technical issues

[0007] The present invention addresses the aforementioned problems. Its technical objective is to provide a novel polyamic acid composition that, even without containing a separate thermoplastic polyimide or adhesive, can simultaneously ensure high adhesion, low dielectric loss rate, excellent flexibility, and dimensional stability, as well as a polyimide film formed from said composition and a metal laminate having a polyimide insulating layer, by changing the composition and adjusting its content of the polyamic acid composition constituting the polyimide.

[0008] Other objects and advantages of the present invention will be more clearly illustrated by the following detailed description of the invention and the claims.

[0009] Technical solution

[0010] To achieve the above objectives, the present invention provides a polyamic acid composition comprising: at least one diamine, at least one acid dianhydride, and an organic solvent, wherein the diamine further comprises a diamine whose main chain or branches contain alkyl groups having four or more carbon atoms.

[0011] In one embodiment of the present invention, the alkyl group may be a linear aliphatic alkyl group having 4 to 40 carbon atoms.

[0012] In one embodiment of the present invention, based on 100 mol% of the diamine, the content of the diamine containing alkyl groups with 4 or more carbon atoms can be greater than 0 mol% and less than 30 mol%.

[0013] In one embodiment of the present invention, the diamine may further comprise a diamine whose main chain contains one or more ester groups and an aromatic ring.

[0014] In one embodiment of the present invention, based on 100 mol% of the diamine, the content of the diamine containing the ester group and the aromatic ring can be in the range of 5 to 30 mol%.

[0015] In one embodiment of the present invention, the mixing ratio of the diamine containing an alkyl group having 4 or more carbon atoms to the diamine containing an ester group and an aromatic ring is in the range of 1:1.1 to 1:5 mol%.

[0016] In one embodiment of the present invention, the at least one diamine may comprise one or more of the group consisting of fluorinated aromatic diamines, sulfone aromatic diamines, hydroxyl aromatic diamines, ether aromatic diamines, non-fluorinated aromatic diamines, and alicyclic diamines.

[0017] In one embodiment of the present invention, the at least one acid dianhydride may comprise one or more of the group consisting of fluorinated aromatic acid dianhydrides, non-fluorinated aromatic acid dianhydrides, sulfone aromatic acid dianhydrides, and alicyclic acid dianhydrides.

[0018] In one embodiment of the present invention, the polyamic acid composition may further contain inorganic fillers.

[0019] In one embodiment of the present invention, the viscosity of the polyamic acid composition at 25°C can be from 10,000 to 50,000 cps.

[0020] Furthermore, the present invention provides a polyimide film formed by imidizing the aforementioned polyamic acid composition.

[0021] Furthermore, the present invention provides a metal laminate comprising: at least one metal layer, and a polyimide film formed on one side of the metal layer or between the metal layers and formed by imidizing the polyamic acid composition.

[0022] In one embodiment of the invention, the metal laminate can be formed by coating a polyamic acid composition onto a metal layer and then drying and imidizing it, without containing thermoplastic polyimide or adhesive.

[0023] In one embodiment of the present invention, the metal layer may be selected from copper, aluminum, iron, silver, palladium, nickel, chromium, molybdenum, tungsten or alloys thereof.

[0024] In one embodiment of the present invention, the polyimide film may have a thickness of 1 to 50 μm.

[0025] Meanwhile, the present invention provides a printed circuit board comprising the aforementioned polyimide film, specifically a flexible printed circuit board.

[0026] The effects of the invention

[0027] In one embodiment of the present invention, a diamine containing an alkyl group having a predetermined number of carbon atoms is used as a component of a polyamic acid composition constituting a polyimide, thereby enabling the simultaneous achievement of high adhesion, low dielectric loss rate, excellent flexibility, and dimensional stability.

[0028] Furthermore, by eliminating the use of thermoplastic polyimide or adhesives alone, production costs can be reduced and production efficiency improved. Additionally, the low viscosity of the polyamic acid composition simplifies the manufacturing process and reduces process costs.

[0029] Meanwhile, in this invention, since the metal laminate can be manufactured by simply coating a polyamic acid composition onto the metal layer and then drying and imidizing it, the possibility of deformation and interlayer delamination problems that occur with flexible metal laminates (FCCLs) and flexible printed circuit boards (FPCBs) when using multilayer insulating layers is avoided, thereby ensuring high reliability.

[0030] Therefore, the polyamic acid composition of the present invention can be advantageously used as a material for low-dielectric flexible metal laminates (FCCLs) or flexible printed circuit boards (FPCBs) for 5G mobile devices, specifically as an insulating layer material, and can also be applied without limitation to a variety of other technical fields.

[0031] The effects of the present invention are not limited to the examples described above, and this specification contains many more effects. Attached Figure Description

[0032] Figure 1 This is a diagram illustrating a method for determining dimensional stability according to an embodiment of the present invention. Detailed Implementation

[0033] The present invention will now be described in detail. The embodiments of the present invention are provided to illustrate the invention more completely to those skilled in the art. The following embodiments can be modified into many other forms, and the scope of the present invention is not limited to the following embodiments. Throughout this specification, the same reference numerals refer to the same structures.

[0034] Unless otherwise defined, all terms used in this specification (including technical and scientific terms) may be used in the sense that would be commonly understood by one of ordinary skill in the art to which this invention pertains. Furthermore, unless explicitly defined otherwise, terms as defined in commonly used dictionaries should not be ideally or over-interpreted.

[0035] Furthermore, throughout the specification, when a part is described as "containing" a certain component, unless specifically stated otherwise, it means that other components may be further included, rather than excluding other components. Also, throughout the specification, "above" or "on" includes not only cases where it is located above or below the object part, but also cases where there is another part in between, and does not necessarily mean that it is located above based on the direction of gravity.

[0036] <Polyamic Acid Composition>

[0037] One example of the present invention is a polyamic acid composition for forming a polyimide precursor [poly(amic acid) (PAA)] polymer, specifically a polyimide precursor solution for forming an insulating layer of a conventional flexible metal laminate (FCCL) or flexible printed circuit board (FPCB) known in the art.

[0038] In one specific example, the polyamic acid composition comprises: at least one diamine, at least one acid dianhydride, and an organic solvent, wherein the diamine further comprises a diamine whose main chain or branches contain alkyl groups having four or more carbon atoms. If desired, it may also contain at least one or more additives commonly used in the art.

[0039] The alkyl group contained in the diamine monomer is an aliphatic alkyl group having at least four carbon atoms, specifically a linear aliphatic alkyl group. Such alkyl groups inhibit charge migration between polymer chains and induce porosity, thereby reducing the dielectric loss of the polyimide resin itself. Therefore, it can be used as a low-dielectric material that can accelerate signal transmission speed and reduce transmission loss.

[0040] Furthermore, compared to the conventionally robust and rigid aromatic or alicyclic moieties, the alkyl groups contained in the aforementioned diamine monomers are relatively soft and possess a higher degree of flexibility. Therefore, by creating pores between the polymer chains, the excellent flexibility and adhesiveness of the polyimide resin itself can be utilized. In particular, by including predetermined aliphatic functional groups, the adhesion properties to the substrate can be significantly improved compared to conventional diamines containing phenyl or ether groups. Thus, even without a separate adhesive or thermoplastic polyimide, a flexible metal laminate and printed circuit board with high adhesion, flexibility, and high reliability can be provided even with only a single polyimide insulating layer.

[0041] There are no particular limitations on the presence of alkyl groups in the reactants of the polyamic acid composition of the present invention, provided that the molecule contains a diamine functional group and the main chain or side chain of the molecule contains alkyl groups with a predetermined number of carbon atoms.

[0042] At this point, when the alkyl group has 3 or fewer carbon atoms, the reduction in dielectric loss is not significant; however, when the number of carbon atoms is too high, the viscosity increases, leading to reduced processability and handleability. Therefore, this invention requires adjusting the number of carbon atoms in the alkyl group contained in the diamine to a predetermined range. For this purpose, this invention uses an aliphatic alkyl group having at least 4 carbon atoms, for example, preferably a diamine with a linear aliphatic alkyl group having 4 to 40 carbon atoms, specifically 5 to 38 carbon atoms, and more specifically 6 to 36 carbon atoms.

[0043] In one specific example, the aforementioned diamine containing an alkyl group having four or more carbon atoms can be further specified as compounds represented by chemical formulas 1 to 3 below. However, it is not limited thereto.

[0044] [Chemical Formula 1]

[0045]

[0046] [Chemical Formula 2]

[0047]

[0048] [Chemical Formula 3]

[0049]

[0050] Of the above chemical formulas 1 to 3,

[0051] n and m may be the same or different from each other, and each is an independent integer from 4 to 40. Furthermore, compounds substituted with one or more substituents selected from the group consisting of halogens, CF3, –OH, and amines known in the art, although not individually represented in the above chemical formulas, are also within the scope of this invention.

[0052] Non-limiting examples of diamines containing alkyl groups having 4 or more carbon atoms include tetramethylenediamine, hexamethylenediamine, decamethylenediamine, dodecamethylenediamine, and primamine.

[0053] The content of the diamine containing alkyl groups with 4 or more carbon atoms in this invention is not particularly limited, and can be appropriately adjusted within a range known in the art to reduce dielectric loss. As an example, based on 100 mol% of the diamine, the content of the diamine containing alkyl groups with 4 or more carbon atoms can be greater than 0 mol% and less than 30 mol%, specifically within the range of 5 to 20 mol%. When the content of the alkyl-containing diamine corresponds to the aforementioned range, the desired dielectric loss reduction effect can be achieved while forming a polyamic acid resin with high flexibility, high adhesion, and high molecular weight; exceeding the aforementioned content range may lead to a decrease in dimensional stability.

[0054] The polyamic acid composition of the present invention comprises at least one diamine (a) known in the art, and at least one acid dianhydride (b).

[0055] The diamine(a) component is not limited to any compound having an intramolecular diamine structure. For example, aromatic, alicyclic, or aliphatic compounds, or combinations thereof, with a diamine structure can be used. As specific examples, the following diamines can be used alone or in mixtures of two or more: fluorinated aromatic diamines with introduced fluorine substituents, sulfone-based aromatic diamines, hydroxyl-based aromatic diamines, ether-based aromatic diamines, non-fluorinated aromatic diamines, and alicyclic diamines.

[0056] As a non-limiting example of a diamine monomer (a) that may be used, p-phenylenediamine (PDA), diaminodiphenyl ether (ODA), 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (2,2'-TFDB), 2,2'-bis(trifluoromethyl)-4,3'-diaminobiphenyl (2,2'-Bis(trifluoromethyl)-4,3'-Diaminobiphenyl), 2,2'-bis(trifluoromethyl)-5,5'-diaminobiphenyl (2,2'-Bis(trifluoromethyl)-5,5'-Diaminobiphenyl), and 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (2,2'-Bis(trifluoromethyl)-4,4'-diaminodiphenyl) may be employed. ether, 6-FODA), bis(aminophenyl)hexafluoropropane (DBOH), bis(aminophenyl)hexafluoropropane (4BDAF), bis(aminophenyl)propane (6HMDA), bis(aminophenyl)diphenyl sulfone (DBSDA), bis(4-aminophenyl) sulfone (4,4'-DDS), bis(3-aminophenyl) sulfone (3,3'-DDS), sulfonyl phthalic anhydride (SO2DPA), 4,4'-diaminodiphenyl ether (4,4'-ODA), or a mixture thereof, etc.

[0057] As an example, the fluorinated first diamine can be 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (2,2'-TFDB) or 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6-FAPB), which can induce linear polymerization. Furthermore, the sulfone-based second diamine can be bis(4-aminophenyl)sulfone (4,4'-DDS) or 3,3'-DDS. Furthermore, the hydroxyl-based third diamine can be 2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane (BIS-AP-AF). Furthermore, the ether-based fourth diamine can be 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether (6-FODA) or diaminodiphenyl ether (ODA). In addition, 2,2-bis(3-amino-4-methylphenyl)-hexafluoropropane (BIS-AT-AF), m-tolidine, or p-phenylenediamine (p-PDA) can be used as non-fluorinated 5-diamines. In addition, as non-limiting examples of alicyclic diamines that may be used, 2,2-bis(3-amino-4-hydroxycyclohexyl)hexafluoropropane, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane (MACM), 4,4'-methylenebicyclohexylamine (PACM), 1,3-bis(aminomethyl)cyclohexane (1,3-BAC), 1,4-bis(aminomethyl)cyclohexane (1,4-BAC), cis-1,2-cyclohexanedimethylamine, trans-1,2-cyclohexanedimethylamine, 1,4-cyclohexyldiamine (CHDA), bis(4-aminocyclohexyl) ether, or mixtures thereof may be used.

[0058] The content of at least one diamine monomer (a) selected from the above-mentioned fluorinated aromatic diamines, sulfone aromatic diamines, hydroxyl aromatic diamines, ether aromatic diamines, non-fluorinated aromatic diamines, and alicyclic diamines is not particularly limited, and can be 0 to 100 mol% based on 100 mol% of total diamines, specifically 10 to 90 mol%, and more specifically 20 to 80 mol%. However, the content of at least one of the aromatic to alicyclic diamines included should meet the requirement of 100 mol% of total diamines.

[0059] In the above-mentioned diamine monomer (a), based on 100 mol% of total diamine, the mixing ratio of non-fluorinated aromatic diamine and ether diamine can be 0~100:100~0:0 mol percentage, specifically 10~90:90~10 mol percentage, and can be appropriately adjusted within the usual range known in the art.

[0060] In one specific example, based on 100 mol% of total diamines, the mixing ratio of non-fluorinated aromatic diamines, ether diamines, and diamines containing alkyl groups with 4 or more carbon atoms can be 40-65:5-30: greater than 0 mol% and less than 30 mol%, more specifically, it can be 50-65:10-25:5-20 mol%. When the content ratio of non-fluorinated aromatic diamines, ether diamines, and diamines containing alkyl groups with 4 or more carbon atoms corresponds to the aforementioned range, a polyamic acid resin with desired high thermal properties and high adhesion can be formed.

[0061] On the other hand, in this invention, a diamine containing one or more ester groups and an aromatic ring on the main chain may also be included as a component of the diamine.

[0062] When such alkyl diamines / acid dianhydrides are mixed with diamines containing ester groups and aromatic rings, the dielectric loss reduction effect of the polyimide resin itself can be enhanced.

[0063] As non-limiting examples of diamines containing an ester group and an aromatic ring that may be used, there are 4-aminophenyl-4-aminobenzoate (APAB), 1,4-phenylene-di-4-aminobenzoate (ABHQ), or mixtures thereof.

[0064] The content of the diamine containing ester groups and aromatic rings in this invention is not particularly limited, and can be appropriately adjusted within a range known in the art to consider the effect of improving dimensional stability. As an example, based on 100 mol% of the diamine, the content of the diamine containing ester groups and aromatic rings can be in the range of 5 to 30 mol%, specifically in the range of 10 to 20 mol%.

[0065] Furthermore, considering the effect of reducing dielectric loss, it is preferable to adjust the mixing ratio of the diamine containing alkyl groups with 4 or more carbon atoms to the diamine containing ester groups and aromatic rings within a predetermined range. As an example, the mixing ratio of the diamine containing alkyl groups with 4 or more carbon atoms to the diamine containing ester groups and aromatic rings can be in the range of 1:1.1 to 1:5 mol%, specifically 1:1.2 to 1:4 mol%.

[0066] The dianhydride (b) monomer contained in the polyamic acid composition of the present invention is not limited to any compound having an intramolecular dianhydride structure. For example, aromatic, alicyclic, or aliphatic compounds or combinations thereof having an dianhydride structure can be used. As specific examples, the following dianhydrides can be used alone or in mixtures of two or more: fluorinated aromatic dianhydrides with introduced fluorine substituents, non-fluorinated aromatic dianhydrides, sulfone-based aromatic dianhydrides, and alicyclic dianhydrides.

[0067] The aforementioned fluorinated dianhydride monomers are not particularly limited to aromatic acid dianhydrides that have been introduced with fluorine substituents. Non-limiting examples of usable fluorinated dianhydrides include 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6-FDA), 4-(trifluoromethyl)pyromellitic dianhydride (4-TFPMDA), or mixtures thereof.

[0068] Furthermore, there are no particular limitations on the non-fluorinated dianhydride monomers, as long as they are non-fluorinated aromatic dianhydrides without fluorine substituents. Non-limiting examples of usable non-fluorinated triacid dianhydride monomers include pyromellitic dianhydride (PMDA), 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride (BPDA), benzophenone tetracarboxylic dianhydride (BTDA), oxydiphthalic dianhydride (ODPA), 4,4-(4,4-isopropylidenediphenoxy)bis(phthalic anhydride) (BPADA), bis(3,4-dicarboxyphenyl)dimethylsilanedianhydride (SiDA), or mixtures thereof.

[0069] Furthermore, there are no particular limitations on sulfone-based dianhydride monomers as long as they are dianhydrides with a sulfone group introduced, such as 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA).

[0070] Furthermore, there are no particular limitations on alicyclic dianhydrides as long as they are compounds containing a non-aromatic alicyclic ring within the compound and also possess an acid dianhydride structure. Non-limiting examples of usable alicyclic dianhydrides include cyclobutanetetracarboxylic dianhydride (CBDA), 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA), bicyclo[2,2,2]-7-octen-2,3,5,6-tetracarboxylic dianhydride (BCDA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA), 1,1'-bicyclohexane-3,3',4,4'-tetracarboxylic dianhydride (H-BPDA), 1,2,4,5-cyclohexanetetracarboxylic dianhydride (H-PMDA), and cyclopentanone bis-spirorbornene. Bis-spironorbornane (cpODA), bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic acid 2,3:5,6-dianhydride (7CI, 8CI) or a mixture thereof.

[0071] The content of at least one dianhydride monomer (b) selected from the above-mentioned fluorinated aromatic acid dianhydrides, non-fluorinated aromatic acid dianhydrides, sulfone aromatic acid dianhydrides, and alicyclic acid dianhydrides is not particularly limited. Based on 100 mol% of total dianhydrides, each monomer can be 0 to 100 mol%, specifically 10 to 90 mol%, and more specifically 20 to 80 mol%. However, the content of at least one of the above-mentioned aromatic acid dianhydrides to alicyclic acid dianhydrides should meet the requirement of 100 mol% of total dianhydrides.

[0072] In the polyamic acid composition of the present invention, the ratio (a / b) of the molar number of the diamine component (a) to the molar number of the acid dianhydride component (b) can be from 0.7 to 1.3, preferably from 0.8 to 1.2, and more preferably from 0.9 to 1.1.

[0073] Furthermore, the polyamic acid composition of the present invention can use organic solvents known in the art as solvents for the solution polymerization reaction of the aforementioned monomers without limitation. As an example of a usable solvent, one or more polar solvents selected from m-cresol, N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), acetone, diethyl acetate, and dimethyl phthalate (DMP) can be used. In addition, low-boiling-point solutions such as tetrahydrofuran (THF), chloroform, or solvents such as γ-butyrolactone can also be used. In this case, the content of the solvent (first solvent for polymerization) is not particularly limited, but in order to obtain appropriate molecular weight and viscosity of the polyamic acid composition (polyamic acid solution), the content is preferably 50 to 95% by weight, more preferably 70 to 90% by weight, based on the total weight of the polyamic acid composition.

[0074] As needed, the polyamic acid compositions of the present invention may further include, to take into account, dimensional stability, improved CTE, mechanical properties, low stress, and also include inorganic fillers known in the art.

[0075] Non-limiting examples of usable inorganic fillers include silica, calcium carbonate, magnesium carbonate, alumina, magnesium oxide, clay, magnesium silicate monohydrate (Talc), calcium silicate, titanium oxide, antimony oxide, glass fiber, aluminum borate, barium titanate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, titanium oxide, barium zirconate, calcium zirconate, boron nitride, silicon nitride, talc, and mica. Preferably, at least one of the group consisting of talc, mica, silica, and calcium carbonate is used. Furthermore, the amount of inorganic filler used is not particularly limited and can be appropriately adjusted considering the aforementioned warpage characteristics and mechanical properties.

[0076] Furthermore, the average particle size of the aforementioned inorganic filler can be appropriately adjusted within a range known in the art, for example, from 0.1 to 10 μm. When the average particle size of the aforementioned inorganic filler is less than 0.1 μm, the surface area of ​​the inorganic filler increases, and its dispersibility in the polyimide precursor solution may be poor; when the average particle size is greater than 10 μm, the uniformity of the appearance will be reduced due to the agglomeration of inorganic filler on the appearance of the polyimide layer.

[0077] In this invention, a polyamic acid composition can be manufactured by reacting the aforementioned diamine, acid dianhydride, and alkyl-containing diamine in a solvent. As an example, a polyamic acid composition can be formed by comprising at least one diamine component, at least one acid dianhydride, and an alkyl-containing diamine, wherein the equivalent ratio of diamine (a) to acid dianhydride (b) is about 1:1.

[0078] The viscosity (at 25°C) of the polyamic acid composition constructed as described above can be from about 10,000 to 50,000 cps, specifically from 15,000 to 38,000 cps. When the viscosity of the polyamic acid composition corresponds to the aforementioned range, the thickness can be easily adjusted when coating the polyamic acid composition, and a uniform coating surface can be achieved.

[0079] As needed, the polyamic acid composition of the present invention may further comprise one or more commonly known additives in the art, without impairing the above-described objectives and effects. Specific examples of additives that may be used include plasticizers, antioxidants, flame retardants, dispersants, viscosity modifiers, leveling agents, catalysts, dehydrating agents, thermal conductivity improvers, electrical property improvers, abrasion resistance improvers, tracking resistance improvers, reinforcing agents, acid resistance improvers, dyes, etc. They may be used alone or in combination of two or more.

[0080] <Polyimide film>

[0081] Another embodiment of the present invention is a polyimide film made from the aforementioned polyamic acid composition, specifically a polyimide film imidized by ring-closing dehydration of a polyamic acid resin solution formed by solution polymerization of a polyamic acid composition containing alkyl diamine at high temperature.

[0082] In one specific example, the polyimide film comprises polyimide with a weight-average molecular weight (Mw) of 20,000 g / mol to 100,000 g / mol. More specifically, the weight-average molecular weight (Mw) of the polyimide resin may be 40,000 to 60,000 g / mol.

[0083] The polyimide film of the present invention can be manufactured according to conventional methods known in the art, for example by coating a polyamic acid composition onto a substrate and then drying and imidizing it.

[0084] There is no particular limitation on the method of coating the above-described polyamic acid composition onto the substrate, and conventional coating methods known in the art can be used without restriction. As an example, various methods can be employed, such as casting, dip coating, die coating, roll coating, slot die coating, comma coating, or a combination thereof.

[0085] At this point, the substrate can be any commonly known substrate in the art, preferably a metal substrate or a heat-resistant polymer substrate capable of withstanding curing temperatures above 100°C. Furthermore, the drying and imidization processes can be appropriately carried out under conditions known in the art. For example, drying can be performed at 100 to 200°C, and the imidization process can be performed at 300 to 400°C for 5 to 60 minutes.

[0086] The thickness of the polyimide film manufactured as described above is not particularly limited and can be appropriately adjusted within a range known in the art. As an example, in order to ensure excellent low dielectric properties, mechanical properties and dimensional stability, the thickness can be 5 to 100 μm, preferably 7 to 80 μm, and more preferably 10 to 50 μm.

[0087] <Metal Laminates>

[0088] Another embodiment of the present invention is a metal laminate, specifically a flexible metal cladlaminate comprising a polyimide insulating layer or a polyimide film formed by imidizing the aforementioned polyamic acid composition.

[0089] Based on the insulating layer, the aforementioned metal laminate can be a single-sided or double-sided structure with metal layers disposed on one or both sides of the insulating layer. More specifically, the aforementioned metal laminate includes: at least one metal layer; and a polyimide insulating layer formed on one side of the metal layer or between the metal layers, and formed by imidizing a polyamic acid composition containing a predetermined alkyl diamine / acid dianhydride.

[0090] The aforementioned metal layer can be made of metals or alloys known in the art that are conductive and flexible, such as copper, aluminum, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, or alloys thereof. Copper foil is preferred. Examples of usable copper foil include CFL (TZA_B, HFZ_B), Mitsui (HSVSP, MLS-G), Nikko (RTCHP), Furukawa, and ILSIN. Furthermore, rolled copper foil or electrolytic copper foil can be used, and rust-resistant copper foil can be used to prevent surface oxidation / corrosion.

[0091] Furthermore, a surface roughness (Rz) can be formed on the surface of the metal layer that contacts the polyimide insulating layer. The range of the surface roughness (Rz) is not particularly limited, and for example, it can be from 0.6 to 3.0 μm. The thickness of such a metal layer is not particularly limited, but considering the thickness and mechanical properties of the metal laminate, it can be less than 5 μm, preferably 1 to 3 μm.

[0092] The thickness of the polyimide insulating layer is not particularly limited and can be appropriately adjusted within a range known in the art. For example, the thickness can be 1 to 50 μm, specifically 5 to 50 μm, and more specifically 7 to 50 μm. Apart from this, the composition of the polyimide insulating layer is the same as described above, and a separate description of it is omitted here.

[0093] On the other hand, the metal laminate of the present invention forms a polyimide insulating layer by coating a polyamic acid composition onto a metal layer and then drying and imidizing it, and does not contain thermoplastic polyimide or adhesives, which differs from conventional metal laminates. In particular, the metal laminate of the present invention can have a low dielectric loss rate (Df) due to the reduced dielectric loss of the polyimide itself, and can exhibit excellent flexibility and high adhesion even without thermoplastic polyimide and / or adhesives.

[0094] In one specific example, the dielectric loss (Df) of the aforementioned metal laminate, measured at frequencies above 10 GHz and below 28 GHz, can be less than 0.007; the adhesion strength between the polyimide insulating layer and the metal layer, according to IPC-TM-650 2.4.9, can be greater than 0.7 kgf / cm; and the dimensional change rate in the MD direction, according to IPC-TM-650 2.2.4, can be within ±0.2%, and the dimensional change rate in the TD direction can be within ±0.2%. More specifically, the dielectric loss (Df) measured at frequencies above 10 GHz and below 28 GHz can be between 0.0020 and 0.0069, or between 0.0022 and 0.0040. Furthermore, according to IPC-TM-6502.4.9, the adhesion strength between the polyimide insulation layer and the metal layer can be 0.7 to 1.5 kgf / cm, and according to IPC-TM-6502.2.4, the dimensional change rate in the MD direction can be within ±0.15%, and the dimensional change rate in the TD direction can be within ±0.15%.

[0095] Printed Circuit Boards

[0096] Another embodiment of the present invention is a printed circuit board, specifically a flexible printed circuit board (FPCB) comprising a polyimide insulating layer or a polyimide film formed by imidizing the aforementioned polyamic acid composition.

[0097] Such a printed circuit board can be a single-layer or multi-layer printed circuit board including at least one metal circuit pattern.

[0098] The printed circuit board of the present invention can be manufactured according to methods known in the art. Specifically, it can be manufactured by forming through holes on at least one of the above-mentioned metal laminates, such as copper-clad laminates, and then etching copper foil to form a circuit after through-hole plating.

[0099] Because the aforementioned polyamic acid composition, polyimide film utilizing it, metal laminate, and printed circuit board of the present invention are manufactured by comprising a diamine / anhydride having a predetermined number of carbon atoms, they exhibit low dielectric loss rate (Df) and, even without the presence of a separate thermoplastic polyimide and / or adhesive, high adhesion, excellent flexibility, and dimensional stability. Therefore, the metal laminate and printed circuit board of the present invention can be advantageously used as metal laminates and / or printed circuit boards for various electrical and electronic devices such as mobile communication devices or their base station devices that process high-frequency signals above 1 GHz, network-related electronic devices such as servers and routers, and mainframe computers, and are particularly preferred for use in low-dielectric metal laminates (FCCLs) for 5G mobile devices. Furthermore, they can be applied to various technical fields requiring low dielectric loss rate, high adhesion, excellent flexibility, and dimensional stability.

[0100] The present invention will now be described in detail through embodiments, the contents of which are as follows. However, the following embodiments are merely illustrative of the present invention, and the present invention is not limited to the following embodiments.

[0101] [Examples 1-5]

[0102] The polyamic acid composition is manufactured using the composition containing diamine and acid dianhydride as described in Table 1 below. Specifically, p-phenylenediamine (PDA), m-toluidine (m-TB), 4,4'-diaminodiphenyl ether (ODA), 4-aminobenzoic acid-4-aminophenyl ester (APAB), 1,4-Phenylene-di-4-aminobenzoate (ABHQ), trimethylenediamine (TrA, n=3), tetramethylenediamine (TeA, n=4), and PA (Priamine 1075, n=36) were used as diamine components, and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) was used as the acid dianhydride component.

[0103] After coating the above-described polyamic acid composition onto a substrate (copper foil: 12 μm thickness), it is dried at 100–200°C for 5–15 minutes. Then, for imidization, it is heat-treated at 300–400°C for at least 20 minutes. At this point, the molecular weight (Mw) of the polyimide precursor is 20,000 g / mol or higher. Thus, a polyimide film with a final film thickness of approximately 20 μm and a copper-clad laminate (FCCL) consisting of the polyimide film and the copper foil are manufactured.

[0104] [Table 1]

[0105]

[0106] [Comparative Examples 1-4]

[0107] Using the composition described in Table 1 above, except that, the polyimide films and copper-clad laminates of Comparative Examples 1 to 4 were manufactured in the same manner as those of Examples 1 to 5 above.

[0108] [Experimental Example: Physical Property Evaluation]

[0109] The physical properties of the polyimide films and copper-clad laminates manufactured in Examples 1-5 and Comparative Examples 1-4 were evaluated using the following methods, and the results are shown in Table 2 below.

[0110] At this point, the physical properties in Table 2 below are based on a polyimide film thickness of 12 μm.

[0111] <Methods for evaluating physical properties>

[0112] 1) Viscosity measurement

[0113] After preparing bubble-free polyimide precursor resin in a 100 mL sample vial, the viscosity at room temperature was measured using a viscometer (Brookfield).

[0114] 2) Dielectric loss (Df) measurement

[0115] After preparing a 9*10cm sample, etching was performed, followed by drying at 110℃ for 1 hour. Then, it was stored in a constant temperature and humidity chamber at 23℃ / 50% for 24 hours, and the 10GHz resonance cavity was measured using a Keysight NetworkAnalyzer under hygroscopic conditions.

[0116] 3) Adhesion strength test

[0117] The adhesive strength was determined according to IPC-TM-650 2.4.9 standard. Specifically, a 1 mm pattern was formed on the copper foil surface, and the adhesive strength between the copper foil and the polyimide film was measured by pulling the copper foil surface at a 90° angle using a Shimadzu Universal Testing Machine (UTM).

[0118] 4) Determination of dimensional stability after heating

[0119] The dimensional stability after heating was determined according to IPC-TM-650 2.2.4 standard. See below. Figure 1 As shown, after preparing a sample measuring 30cm (MD) * 27cm (TD), holes were formed within the sample at intervals of 25cm in the MD direction and 23cm in the TD direction. After etching the sample with the formed holes, the spacing between the holes (initial spacing) was measured. Next, the sample was heat-treated at 150°C for 30 minutes and then stored at room temperature for 24 hours. The spacing between the holes was measured again (later spacing), and the dimensional change rate was determined according to the following mathematical formula 1. In the measured dimensional change rate, positive values ​​represent elongation, and negative values ​​represent shrinkage.

[0120] [Mathematical Expression 1]

[0121]

[0122] [Mathematical Expression 2]

[0123]

[0124] In Equations 1 and 2 above,

[0125] MD = Rate of change of length (MD)

[0126] TD = Dimensional change rate in the lateral direction (TD)

[0127] (AB)i = the initial distance between points A and B.

[0128] (AB)f = the later interval between points A and B.

[0129] (AC)i = the initial distance between points A and C.

[0130] (AC)f = the later interval between points A and C.

[0131] (CD)i = the initial distance between points C and D.

[0132] (CD)f = the later interval between points C and D.

[0133] (BD)i = the initial distance between points B and D.

[0134] (BD)f = the later spacing between points B and D.

[0135] [Table 2]

[0136]

[0137] As shown in Table 2 above, in the cases of Examples 1 to 4, which contain diamines containing alkyl groups having a predetermined number of carbon atoms, it can be seen that not only is there excellent processability due to the appropriate viscosity, but also low dielectric loss, high adhesion and excellent dimensional stability are ensured at the same time.

[0138] Specifically, in Examples 1 to 5 using diamines with 4 or more carbon atoms, compared to Comparative Examples 1 to 4 which did not contain the aforementioned diamines or diamines containing alkyl groups and having 3 carbon atoms, lower dielectric loss characteristics and viscosity characteristics were observed. In particular, as the number of carbon atoms contained in the diamine increased, the dielectric loss characteristics of the polyimide film were improved. Furthermore, when diamines with 4 or more carbon atoms were mixed with ester-containing diamines, superior performance in terms of dimensional stability after heating was confirmed.

Claims

1. A polyamic acid composition comprising: At least one diamine, At least one acid dianhydride, and Organic solvents, The diamine further includes diamines whose main chain or branches contain alkyl groups with 4 or more carbon atoms.

2. The polyamic acid composition according to claim 1, wherein, The alkyl group is a linear aliphatic alkyl group with 4 to 40 carbon atoms.

3. The polyamic acid composition according to claim 1, wherein, The diamine containing an alkyl group having four or more carbon atoms is selected from compounds represented by the following chemical formulas 1 to 3: Chemical Formula 1 Chemical formula 2 Chemical formula 3 Of the above chemical formulas 1 to 3, n and m may be the same or different from each other, and each is an independent integer from 4 to 40.

4. The polyamic acid composition according to claim 1, wherein, Based on 100 mol% of the diamine, the content of the diamine containing alkyl groups with 4 or more carbon atoms is greater than 0 mol% and less than 20 mol%.

5. The polyamic acid composition according to claim 1, wherein, The diamine also includes diamines whose main chain contains one or more ester groups and an aromatic ring.

6. The polyamic acid composition according to claim 5, wherein, Based on 100 mol% of the diamine, the content of the diamine containing ester group and aromatic ring is in the range of 5 to 30 mol%.

7. The polyamic acid composition according to claim 5, wherein, The mixing ratio of the diamine containing an alkyl group with 4 or more carbon atoms to the diamine containing an ester group and an aromatic ring is in the range of 1:1.1 to 1:5 mol%.

8. The polyamic acid composition according to claim 1, wherein, The at least one diamine comprises one or more selected from the group consisting of fluorinated aromatic diamines, sulfone aromatic diamines, hydroxyl aromatic diamines, ether aromatic diamines, non-fluorinated aromatic diamines, and alicyclic diamines.

9. The polyamic acid composition according to claim 1, wherein, The at least one acid dianhydride comprises one or more selected from the group consisting of free-fluorinated aromatic acid dianhydrides, non-fluorinated aromatic acid dianhydrides, sulfone-based aromatic acid dianhydrides, and alicyclic acid dianhydrides.

10. The polyamic acid composition according to claim 1, It also contains inorganic fillers.

11. The polyamic acid composition according to claim 1, wherein, The viscosity at 25°C is 10,000 to 50,000 cps.

12. A polyimide film formed by imidizing the polyamic acid composition according to any one of claims 1 to 11.

13. The polyamic acid composition according to claim 12, wherein, The weight-average molecular weight (Mw) of the polyimide film is between 20,000 g / mol and 100,000 g / mol.

14. A metal laminate comprising: At least one metal layer; as well as A polyimide insulating layer formed on one side of the metal layer or between the metal layers and formed by imidizing the polyamic acid composition according to any one of claims 1 to 11.

15. The metal laminate according to claim 14, wherein, The metal laminate forms a polyimide insulating layer by coating a polyamic acid composition onto a metal layer and then drying and imidizing it, and does not contain thermoplastic polyimide or adhesive.

16. The metal laminate according to claim 14, wherein, The metal layer is selected from copper, aluminum, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, or alloys thereof.

17. The metal laminate according to claim 14, wherein, The polyimide insulating layer has a thickness of 1 to 50 μm.

18. The metal laminate according to claim 14, wherein, The dielectric loss Df of the metal laminate measured at frequencies above 10 GHz and below 28 GHz is below 0.

007. According to IPC-TM-650 2.4.9, the adhesion strength between the polyimide insulation layer and the metal layer is above 0.7 kgf / cm. According to IPC-TM-650 2.2.4, the dimensional change rate in the MD direction is within ±0.2%, and the dimensional change rate in the TD direction is within ±0.2%.

19. A printed circuit board comprising the polyimide film of claim 12.

Images