Veneers featuring polymer films and metallic layers

Abstract

In one aspect, a plating comprises a polymer film and a first metallic layer bonded to the polymer film. The polymer film has an electrically conductive charge and a surface resistivity of 1 megaohm / square or less. The first metallic layer has a thickness of 100 µm or less. The plating contains less than 15 ppm of Pd. The metallic layer is formed on the polymer film by direct electrochemical deposition of the first metallic layer onto the polymer film.

Description

Title of the invention: VENEERS HAVING POLYMER FILMS AND METAL LAYERS Technical field

[0001] The scope of this disclosure relates to veneers having polymer films and metallic layers. PREVIOUS ART

[0002] Flexible copper clads (FCCs) are required for a wide variety of applications, including circuits in consumer electronics, electromagnetic shielding film, battery current collectors, and heaters for wind turbines. Typically, polyimide films used for FCCs are metallized by lamination, a copper casting process, or the deposition of a seed layer, followed by electrolytic metallization. As these applications evolve, they require thinner dielectrics and copper, either to achieve thinner circuit lines and gaps, to reduce overall device dimensions, or to reduce device weight.Using a conductive seed layer followed by electroplating is an efficient way to deposit copper in thin films, as the technique allows copper to be deposited in any thickness. However, seed layer deposition can be expensive or alter the electronic properties of the plating.

[0003] Metal-clad laminates, such as copper-clad laminates, are used in electronic devices for a number of electronic components intended for flexible circuits, as well as for circuit packaging. Copper-clad laminates based on polyimide films are usually prepared either by rolling for metal thicknesses greater than 5 μm or by spraying for metal thicknesses less than 5 μm. Plating (e.g., electrochemical plating or electroless plating) is another laminate production method that has received some attention, but it is not widely used for the production of laminates having a copper thickness less than 5 μm. In addition, it is generally accepted that the reliability of copper-clad polyimide laminates is below consumer standards for electronic devices.

[0004] Metal clad laminates produced by plating traditionally have poor thermal reliability compared to metal clad produced by spraying or rolling copper foil. The most reliable clad laminates use electroless nickel seed layers. The adhesion between the Copper and polyimide clad films are complex due to the presence of volatile compounds in the film, degradation of the film surface by plating chemicals, and the use of film materials that lack the functionality for strong chemical bonding to copper, among other factors.

[0005] In addition, during the operation of electronic devices, electric and magnetic fields are generated by the electronic components in the device, which may interfere with the operation of other electronic components in the same device or in other nearby devices. This phenomenon is called electromagnetic interference (EMI). Metals are commonly used for EMI shielding due to their high electrical conductivity, which allows them to absorb EMI waves. The degree of shielding effectiveness is not a constant for each shielding material, but is influenced by the frequency of the incoming signal. The shielding effectiveness is determined by: a) the electrical conductivity of the shield; b) the thickness, uniformity, and smoothness of the shield; c) the physical properties of the shield; d) the frequency and impedance of the incident field; and e) the magnetic permeability of the material.There is also a need for thin shielding films that include a thin metal layer for EMI shielding of electronic components. DETAILED DESCRIPTION

[0006] In a first aspect, a plating comprises a polymer film and a first metal layer bonded to the polymer film. The polymer film comprises an electrically conductive filler and has a surface resistivity of 1 megaohm / square or less. The first metal layer has a thickness of 100 pm or less. The plating has less than 15 ppm Pd. The metal layer is formed on the polymer film by direct electrochemical deposition of the first metal layer onto the polymer film.

[0007] Polymer films bonded to metal layers can be used to form veneers. In one embodiment, polymer compositions useful for polymer films may include polyimides (PI), poly(amide-imides) (PAI), poly(ester-imides), poly(amide-ester-imides), polycarbonates (PC), poly(ethylene naphthalates) (PEN), polystyrenes (PS), poly(methyl methacrylates) (PMMA), poly(ethylene terephthalates) (PET), poly(ethylene terephthalates) glycols (PETG), poly(cyclohexylene-dimethylene terephthalates) glycols (PCTG), polyetherimides (PEI), polysulfones, polyethersulfones, polyarylsulfones, polyaryletherketones (PAEK) such as polyetheretherketones (PEEK) and polyetherketoneketones (PEKK), and cyclic olefin copolymers. In one embodiment, Polymer compositions having an imide group are particularly useful. Polymer compositions having an imide group and containing aromatic monomers are usually very stable from a thermal, chemical and electrochemical point of view at the low (anodic) and high (cathodic) potentials used in lithium-ion batteries.

[0008] Depending on the context, the term "diamine" as used herein is intended to refer to: (i) the unreacted form (i.e., a diamine monomer); (ii) a partially reacted form (i.e., the portion or portions of an oligomer or other polymer precursor derived from or otherwise attributable to the diamine monomer); or (iii) a fully reacted form (the portion or portions of the polymer derived from or otherwise attributable to the diamine monomer). The diamine may be functionalized with one or more moieties, depending on the particular embodiment chosen in practicing the present invention.

[0009] Indeed, the term "diamine" is not intended to be limiting (or interpreted literally) as to the number of amine moieties in the diamine component. For example, (ii) and (iii) above include polymeric materials that may have two, one, or zero amine moieties. Alternatively, the diamine may be functionalized with additional amine moieties (in addition to the amine moieties at the ends of the monomer that react with the dianhydride to propagate a polymer chain). Such additional amine moieties could be used to crosslink the polymer or to impart other functionality to the polymer.

[0010] Similarly, the term "dianhydride", as used herein, is intended to refer to the component that reacts with (is complementary to) the diamine and in combination is capable of reacting to form an intermediate (which can then be cured into a polymer). Depending on the context, the term "anhydride", as used herein, may refer not only to an anhydride moiety per se, but also to a precursor to an anhydride moiety, such as: (i) a pair of carboxylic acid groups (which can be converted to an anhydride by a dehydration reaction or a reaction of a similar type); or (ii) an acid halide (e.g., chloride) ester functionality (or any other functionality presently known or developed in the future which is) capable of conversion to an anhydride functionality.

[0011] Depending on the context, the term "dianhydride" may refer to: (i) the unreacted form (i.e., a dianhydride monomer, whether the anhydride functionality is in true anhydride form or in anhydride precursor form, as discussed in the preceding paragraph); (ii) a partially reacted form (i.e., the portion(s) of an oligomeric composition or other precursor or partially reacted polymer composition reacted from a monomer of dianhydride or otherwise attributable thereto); or (iii) a fully reacted form (the portion(s) of the polymer derived from or otherwise attributable to a dianhydride monomer).

[0012] The dianhydride may be functionalized with one or more moieties, depending on the particular embodiment chosen in practicing the present invention. Indeed, the term "dianhydride" is not intended to be limiting (or interpreted literally) as to the number of anhydride moieties in the dianhydride component. For example, (i), (ii), and (iii) (in the paragraph above) include organic substances that may have two, one, or zero anhydride moieties, depending on whether the anhydride is in the precursor state or in the reacted state. Alternatively, the dianhydride component may be functionalized with additional anhydride moieties (in addition to the anhydride moieties that react with the diamine to yield a polymer). Such additional anhydride moieties could be used to crosslink the polymer or to impart other functionality to the polymer.

[0013] A number of polymer production methods can be used to prepare polymer films. It would be impossible to discuss or describe all possible production methods useful in practicing the present invention. It should be noted that the monomer systems of the present invention are capable of providing the advantageous properties described above in a number of production methods. The compositions of the present invention can be produced in the manner described herein and can be readily produced in any of the many (perhaps countless) ways within the skill of the art, using any conventional or unconventional production technology.

[0014] Although methods and materials similar or equivalent to those described herein may be used in practicing or testing the present invention, suitable methods and materials are described herein.

[0015] Where a quantity, concentration or other value or parameter is given as a range, preferred range or list of upper and lower preferred values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper limit or preferred value and any lower limit or preferred value, whether or not the ranges are separately disclosed. Where a range of numerical values ​​is cited herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values ​​cited when defining a range.

[0016] In describing certain polymers, it should be understood that sometimes applicants refer to the polymers by the monomers used to produce them or the amounts of the monomers used to produce them. Although such a description may not include the specific nomenclature used to describe the final polymer or contain product-by-process terminology, any reference to monomers and amounts should be interpreted to mean that the polymer is produced from those monomers or that amount of the monomers, and the corresponding polymers and their compositions.

[0017] The materials, methods and examples herein are provided for illustrative purposes only and, unless otherwise indicated, are not intended to be limiting.

[0018] As used herein, the terms "comprises," "comprising," "includes," "including," "presents," "presenting," or any other variation thereof are intended to cover non-exclusive inclusion. For example, a method, process, article, or apparatus that includes a list of elements is not necessarily limited to only those elements, but may include other elements not expressly listed or inherent in that method, process, article, or apparatus. Furthermore, unless expressly stated otherwise, "or" means an inclusive 'or' and not an exclusive 'or'. For example, a condition A or B is satisfied by any of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

[0019] Similarly, the terms "a" or "an" are used to describe elements and components of the invention. This is done solely for convenience and to give a general meaning of the invention. This description should be interpreted as including one or at least one, and the singular also includes the plural, unless it is obvious otherwise.

[0020] It is understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and / or sections, such elements, components, regions, layers and / or sections should not be limited by these terms. These terms are used only to distinguish one element, component, region, layer and / or section from another element, component, region, layer and / or section. Thus, a first element, a first component, a first region, a first layer and / or a first section could be referred to as a second element, component, region, layer and / or section without departing from the teachings of the present invention. Similarly, the terms "top" and "bottom" are relative only to each other. It will be recognized that when a element, component, layer or the like is inverted, what was "bottom" before the inversion will be "top" after the inversion and vice versa. When an element is referred to as being "on" or "arranged upon" another element, this expression means positioning on or under the object part, but does not essentially mean positioning on the upper face of the object part based on a direction of gravity and it may be positioning directly on the other element or there may be intermediate elements between them. On the other hand, when an element is referred to as being "directly on" or "arranged directly upon" another element, there are no intermediate elements present.

[0021] Furthermore, it will also be understood that when an element, component, region, layer and / or section is referred to as being "between" two elements, components, regions, layers and / or sections, it may be the only element, component, region, layer and / or section between the two elements, components, regions, layers and / or sections, or one or more intermediate elements, components, regions, layers and / or sections may also be present. Organic solvents

[0022] Organic solvents useful for the synthesis of polymers of the present invention are preferably capable of dissolving the polymer precursor materials. Such a solvent should also have a relatively low boiling point, for example, less than 225°C, so that the polymer can be dried at moderate (i.e., more convenient and less expensive) temperatures. A boiling point less than 210, 205, 200, 195, 190, or 180°C is preferred.

[0023] Useful organic solvents include: N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), methyl ethyl ketone (MEK), N,N'-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetramethylurea (TMU), glycol ethyl ether, diethylene glycol diethyl ether, 1,2-dimethoxyethane (monoglyme), diethylene glycol dimethyl ether (diglyme), 1,2-bis-(2-methoxyethoxy)ethane (triglyme), gamma-butyrolactone and bis-(2-methoxyethyl) ether, tetrahydrofuran (THF), ethyl acetate, hydroxyethyl acetate-glycol monoacetate, acetone, and mixtures thereof. In one embodiment, preferred solvents include N-methylpyrrolidone (NMP) and dimethylacetamide (DMAc). Diamines

[0024] In one embodiment, an aromatic diamine may be used to form a polymer having an imide group. Aromatic diamines may include fluorinated aromatic diamines, such as 2,2'-bis(trifluoromethyl)benzidine (TFMB), 2,2'-bis-(4-aminophenyl)hexafluoropropane, 4,4'-diamino-2,2'-trifluoromethyldiphenyloxide, 3,3'-diamino-5,5'-trifluoromethyldiphenyloxide, 9,9'-bis(4-aminophenyl)fluorene, 4,4'-trifluoromethyl-2,2'-diaminobiphenyl, 4,4'-oxy-bis[2-trifluoromethyl)benzeneamine] (1,2,4-OBABTF), 4,4'-oxy-bis[3-trifluoromethyl)benzeneamine], 4,4'-thiobis[(2-trifluoromethyl)b enzeneamine], 4,4'-thiobis[(3-trifluoromethyl)benzeneamine], 4,4'-sulfoxyl-bis[(2-trifluoromethyl)benzeneamine, 4,4'-sulfoxyl-bis[(3-trifluoromethyl)b enzeneamine], 4,4'-keto-bis[(2-trifluoromethyl)benzeneamine], 1,l-bis[4'-(4”-amino-2”-trifluoromethylphenoxy)phenyl]cyclopentane, 1,l-bis[4'-(4”-amino-2”-trifluoromethylphenoxy)phenyl]cyclohexane, 2-trifluoromethyl-4,4'-diaminodiphenyl ether;l,4-(2'-trifluoromethyl-4',4”-diaminodiphenoxy)benzene, l,4-bis(4'-aminophenoxy)-2-[(3',5'-ditrifluoromethyl)phenyl]benzene (6F-amine), l,4-bis[2'-cyano-3'(“4-aminophenoxy)phenoxy]-2-[(3',5'-ditrifluoro-methyl)phenyl]benzene (6FC-diamine), 3,5-diamino-4-methyl-2',3',5',6'-tetrafluoro-4'-tri-fluoromethyldiphenyloxide, 2,2-bis[4(4-aminophenoxy)phenyl]phthalein-3',5'-bis(trifluoromethyl)anilide (6FADAP) and 3,3',5,5'-tetrafluoro-4,4'-diamino-diphenylmethane (TFDAM). ;

[0025] Other useful diamines may include 4,4'-diaminobiphenyl, 4,4'-diaminoterphenyl, 4,4'-diaminobenzanilide (DABA), 4,4'-diaminophenyl benzoate, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenylmethane (MDA), 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), 4,4'-bis(4-aminophenoxy)biphenyl (BAPB), 4,4'-diaminodiphenyl ether (ODA), 3,4'-diaminodiphenyl ether, 4,4'-isopropylidenedianiline, 2,2'-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4-aminophenyl 3-aminobenzoate, bis(p-beta-amino-t-butylphenyl)ether, p-bis-2-(2-methyl-4-aminopentyl)benzene. In one embodiment, the diamine is a triamine, such as N,N-bis(4-aminophenyl)-n-butylamine, N,N-bis(4-aminophenyl)methylamine or N,N-bis(4-aminophenyl)aniline.

[0026] Other useful diamines may include 1,2-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene (RODA), 1,2-bis(3-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1 -(4-aminophenoxy)-3-(3-aminophenoxy)benzene, 1,4-bis-(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 1-(4-aminophenoxy)-4-(3-aminophenoxy)benzene, 2,2-bis(4-[4-aminophenoxy]phen yl)propane (BAPP), 2,2'-bis(4-phenoxyaniline)isopropylidene.

[0027] Other useful diamines may include p-phenylenediamine (PPD), m-phenylenediamine (MPD), 2,5-dimethyl-1,4-diaminobenzene, 2,5-dimethyl-1,4- phenylenediamine (DPX), l,4-naphthalenediamine, 1,5-naphthalenediamine, 1,5-diaminonaphthalene, m-xylylenediamine and p-xylylenediamine.

[0028] Other diamines useful for forming polymers having an imide group may include an aliphatic diamine, such as 1,2-diaminoethane, 1,6-diaminohexane (HMD), 1,4-diaminobutane, 1,5-diaminopentane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane (DMD), 1,11-diaminoundecane, 1,12-diaminododecane (DDD), 1,16-hexadecamethylenediamine, 1,3-bis(3-aminopropyl)-tetramethyldisiloxane, tran5-1,4-diaminocyclohexane (CHDA), isophoronediamine (IPDA), bicyclo[2.2.2]octane-1,4-diamine and combinations thereof. Other aliphatic diamines suitable for practicing the invention include those having six to twelve carbon atoms or a combination of longer and shorter chain diamines as long as both the developability and flexibility of the polymer are maintained. Long chain aliphatic diamines can increase flexibility.

[0029] Other diamines useful for forming a polymer having an imide group may include an alicyclic diamine (which may be fully or partially saturated), such as a cyclobutanediamine (e.g., cis-1,3-diaminocyclobutane and trans-1,3-diaminocyclobutane, 6-amino-3-azaspiro[3.3]heptane and 3,6-diaminospiro[3.3]heptane), bicyclo[2.2.1]heptane-1,4-diamine, isophoronediamine, and bicyclo[2.2.2]octane-1,4-diamine. Other alicyclic diamines may include cA-1,4-cyclohexanediamine, trans-1,4-cyclohexanediamine, l,4-bis(aminomethyl)cyclohexane, 4,4'-methylenebis(cyclohexylamine), 4,4'-methylenebis(2-methylcyclohexylamine), bis(aminomethyl)norbornane. Dianhydrides

[0030] In one embodiment, aromatic dianhydrides may be used to form a polymer having an imide group. The dianhydrides may be used in their tetraacid form (or monoesters, diesters, triesters, or tetraesters of the tetraacid) or their diester acid halides (chlorides). However, in some embodiments, the dianhydride form may be preferred because it is generally more reactive than the acid or ester.

[0031] Examples of suitable aromatic dianhydrides include 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2-(3',4'-dicarboxyphenyl)-5,6-dicarboxybenzimidazole dianhydride, 2-(3',4'-dicarboxyphenyl)-5,6-dicarboxybenzoxazole dianhydride, 2-(3',4'-dicarboxyphenyl)-5,6-dicarboxybenzothiazole dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 2,3,3',4'-benzophenonetetra carboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride (BTDA), 2,2',3,3'-biphenyltetracarboxylic acid dianhydride, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride, 4,4'-thiodiphthalic acid anhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, bis(3,4-dicarboxyphenyl)sulfoxide dianhydride (DSDA), bis(3,4-dicarboxyphenyloxadiazole-1,3,4)-p-phenylene dianhydride, bis(3,4-dicarboxyphenyl)-2,5-oxadiazole-1,3,4-dianhydride, bis(3',4'-dicarboxydiphenyl ether)-2,5-oxadiazole-1,3,4-dianhydride, anhydride 4,4'-oxydiphthalic acid (ODPA), bis(3,4-dicarboxyphenyl)thioether dianhydride, bisphenol A dianhydride (BPADA), bisphenol S dianhydride, bis-1,3-isobenzofuranedione, l,4-bis(4,4'-oxyphthalic anhydride)benzene, bis(3,4-dicarboxyphenyl)methane dianhydride, perylene-3,4,9,10-tetracarboxylic acid dianhydride, l,3-bis-(4,4'-oxydiphthalic anhydride)benzene, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, anhydride 4,4'-(hexafluoroisopropylidene)diphthalic acid (6FDA) and 9,9-bis(trifluoromethyl)-2,3,6,7-xanthenetetracarboxylic dianhydride. ,

[0032] Other useful dianhydrides may include 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,3,5,6-bicyclo-[2,2,2]-octene-(7)-2,3,5,6-tetracarboxylic dianhydride, cyclopentadienyl tetracarboxylic dianhydride, ethylenetetracarboxylic dianhydride, pyromellitic dianhydride (PMDA), tetrahydrofurantetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, phenanthrene-1,8,9,10-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, benzene-1,2,3,4-tetracarboxylic dianhydride and thiophene-2,3,4,5-tetracarboxylic dianhydride.

[0033] In one embodiment, dianhydrides for forming a polymer having an imide group may include alicyclic dianhydrides, such as cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA), hexahydro-4,8-ethanol-1H,3H-benzo[1,2-c:4,5-c']difuran-1,3,5,7-tetrone (BODA), 1,4:2,3-dianhydride 3-(carboxymethyl)-l,2,4-cyclopentanetricarboxylic acid (TCA) and mesobutane-1,2,3,4-tetracarboxylic dianhydride.

[0034] In one embodiment, wherein the polymer further comprises aromatic amide constituents, an additional dicarbonyl chloride suitable for forming the polymer may comprise terephthaloyl chloride (TPCI) , isophthaloyl chloride (IPCI), biphenyldicarbonyl chloride (BPCI), naphthalenedicarbonyl chloride, terphenyldicarbonyl chloride, 2-fluoroterephthaloyl chloride and trimellitic anhydride.

[0035] In one embodiment, the poly(amide-ester-imides) can be produced from polyols which can react with carboxylic acid or ester acid halides to generate ester linkages.

[0036] The dihydric alcohol component may be virtually any alcoholic diol containing two esterifiable hydroxyl groups. Mixtures of suitable diols may also be included. Suitable diols for use herein include, for example, ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, etc.

[0037] The polyhydric alcohol component may be virtually any polyhydric alcohol containing at least 3 esterifiable hydroxyl groups in order to achieve the above-described synthetic process advantages of the present invention. Mixtures of such polyhydric alcohols may be suitably used. Suitable polyhydric alcohols include, for example, tris(2-hydroxyethyl)isocyanurate, glycerol, 1,1,1-trimethylolethane, 1,1,1-trimethylolpropane, and mixtures thereof.

[0038] In some instances, useful diamine and dianhydride monomers contain ester groups. Examples of such monomers include diamines, such as 4-aminophenyl 4-aminobenzoate and 4-amino-3-methylphenyl 4-aminobenzoate, and dianhydrides, such as p-phenylene-bis(trimellitate) dianhydride.

[0039] In some instances, useful diamine and dianhydride monomers contain amide groups. Examples of such monomers include diamines, such as 4,4'-diaminobenzamide (DABAN), and dianhydrides, such as N,N'-(2,2'-bis(trifluoromethyl)-[1,1'-biphenyl]-4,4'-diyl)bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxamide) and N,N'-(9H-fluoren-9-ylidenedi-4,1-phenylene)bis[1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxamide].

[0040] Higher order copolymers having an imide group may comprise any of the monomers described above. Imidization catalysts

[0041] In one embodiment, an imidization catalyst (sometimes referred to as an "imidization accelerator") may be used as a conversion chemical compound that may help lower the imidization temperature for the formation of a polymer having an imide group and shorten the imidization time. The polyamic acid casting solutions of the present invention comprise both a polyamic acid solution combined with an amount of Conversion chemicals. Conversion chemicals that have been found useful in the present invention include, but are not limited to, (i) one or more dehydrating agents and / or cocatalysts, such as aliphatic acid anhydrides (acetic anhydride, trifluoroacetic anhydride, propionic anhydride, monochloroacetic anhydride, bromoadipic anhydride, etc.) and aromatic acid anhydrides; and (ii) one or more imidization catalysts, such as aliphatic tertiary amines (triethylamine, etc.), aromatic tertiary amines (dimethylaniline, N,N-dimethylbenzylamine, etc.) and heterocyclic tertiary amines (pyridine, alpha, beta and gamma picoline, 3,5-lutidine, 3,4-lutidine, isoquinoline, etc.) and guanidines (e.g., tetramethylguanidine). In one embodiment, an imidization catalyst does not comprise a diazole.Other useful dehydrating agents may include diacetyl ether, butyryl ether, benzoyl ether, 1,3-dichlorohexylcarbodiimide, N,N-dicyclohexylcarbodiimide, benzenesulfonyl chloride, thionyl chloride, and phosphorus pentachloride. In some embodiments, the dehydrating agent may also act as a catalyst to improve the reaction kinetics for imidization. The anhydride dehydrating material is typically used in a slight molar excess relative to the amount of amide acid groups present in the polyamic acid solution. In one embodiment, the amount of dehydrating agent used is typically about 2.0 to 4.0 moles per equivalent of the polyamic acid formula unit. Generally, a comparable amount of tertiary amine catalyst is used.The ratio of these catalysts and their concentration in the polyamic acid solution will influence the imidization kinetics and film properties. Polymer films may have imidization catalysts present in the polymer film in an amount ranging from 1 part per million (ppm) to 1% by weight, 10 ppm to 0.1% by weight, or 100 ppm to 0.01% by weight. Electroconductive charges

[0042] In one embodiment, the electrically conductive fillers may include metals (such as gold, silver, copper, etc.), conductive mixed metal oxides (such as cuprates, superconducting oxides, indium tin oxide, antimony tin oxide, titanium / tin / zirconium mixed oxides, etc.), organic compounds, such as polyaniline, polythiophene, polypyrrole, poly(phenylene-vinylene), polydialkylfluorenes, carbon black, graphite, graphene, multi-walled and single-walled carbon nanotubes and other nanotube structures and carbon nanofibers. In one embodiment, an electrically conductive filler may be an inorganic filler, an organic filler, or a mixture thereof.

[0043] In one embodiment, an electrically conductive filler is carbon black. In one embodiment, the electrically conductive filler is selected from the group consisting of acetylene blacks, superabrasive furnace blacks, conductive furnace blacks, channel-type conductive blacks, carbon nanotubes, carbon fibers, fine thermal blacks, and mixtures thereof. For carbon black, oxygen complexes on the surface of the carbon particles act as an electrically insulating layer. Therefore, a low volatile content is generally desired for high conductivity. However, the difficulty of dispersing carbon black must also be considered. Surface oxidation increases the deagglomeration and dispersion of carbon black.In some embodiments, when the electrically conductive filler is carbon black, the carbon black has a volatile compound content of less than or equal to 1%. Other charges

[0044] In one embodiment, other fillers for a polymer film may include other inorganic and organic fillers not described above for electrically conductive fillers. The inorganic fillers may include thermally conductive fillers, such as metal oxides, inorganic nitrides, and metal carbides. In one embodiment, the inorganic fillers may include diamond, clay, talc, sepiolite, mica, dicalcium phosphate, metal oxides, including magnetic metal oxides, transparent conductive oxides, and powdered metal oxides.In one embodiment, the inorganic fillers may include inorganic oxides, such as silicon, aluminum, zinc, and titanium oxides, hollow (porous) silicon oxide, antimony oxide, zirconium oxide, indium tin oxide, antimony tin oxide, mixed titanium / tin / zirconium oxides, and binary, tertiary, quaternary, and higher order oxides of one or more cations selected from silicon, titanium, aluminum, antimony, zirconium, indium, tin, zinc, niobium, and tantalum. In one embodiment, particulate composites (e.g., single or multiple core / shell structures) may be used, wherein one oxide encapsulates another oxide within a particle.

[0045] In one embodiment, the inorganic fillers may include other ceramic compounds, such as boron nitride, aluminum nitride, ternary or higher order compounds containing boron, aluminum and nitrogen, gallium nitride, silicon nitride, aluminum nitride, zinc selenide, zinc sulfide, zinc telluride, silicon carbide and combinations thereof or higher order compounds, containing multiple cations and multiple anions and may include oxycarbons and oxynitrides.

[0046] In one embodiment, the fillers for a polymer film may have a median particle size, d50, in a range of 0.1 to 10 µm, 0.1 to 5 µm, 0.2 to 5 µm, or 0.2 to 3 µm. The filler size may be determined using a laser particle size analyzer, with the filler dispersed in an organic solvent (optionally using a dispersant, adhesion promoter, and / or coupling agent). The median particle size, d50, is the equivalent spherical diameter based on a median volume distribution of the particles. If the median particle size is less than 0.1 µm, the filler particles may exhibit a tendency to agglomerate, or become unstable, in the organic solvents used in the production of the polymers.If the median particle size of the agglomerated particles is greater than 10 μm, the dispersion of the filler component in the polymer film may be too inhomogeneous (or it may be inappropriately too large for the film thickness). A relatively inhomogeneous dispersion of the filler component in the film may result in low mechanical elongation of the film, low flexural life of the film, and low dielectric strength. In one embodiment, the fillers may require intense grinding and filtration to disintegrate unwanted agglomeration of the particles, as is common when attempting to disperse certain fillers in a polymer matrix. Such grinding and filtration may be expensive and may not be able to remove all unwanted agglomerates. In one embodiment, the average aspect ratio of the filler may be 1 or greater.In some embodiments, the filler is selected from the group consisting of needle-like (acicular) fillers, fibrous fillers, platelet fillers, polymeric fibers, and mixtures thereof. In one embodiment, the fillers may have an aspect ratio of at least 1, at least 2, at least 4, at least 6, at least 8, at least 10, at least 12, at least 15, at least 25, at least 50, at least 100, at least 200, or at least 300 to 1.

[0047] In one embodiment, the filler comprises a mixture of fillers having any number of particle types, particle sizes, and particle shapes, wherein a mixture may be a mixture of the same type of fillers or different types of fillers.

[0048] In one embodiment, the fillers may be coated with a coupling agent. For example, a filler particle may be coated with aminosilane, phenylsilane, acrylic or methacrylic coupling agents derived from the corresponding alkoxysilanes. The trimethylsilyl-functional surface blocking agents may be introduced onto the surface of the particle by reaction of the fillers with hexamethyldisilazane. In one embodiment, the fillers may be coated with a dispersant. In one embodiment, the fillers may be coated with a combination of a coupling agent and a dispersant. Alternatively, the coupling agent, dispersant, or combination thereof may be incorporated directly into the polymer film and not necessarily coated onto the fillers. Polymer films

[0049] In one embodiment, a polymer film that is a polyimide film may be produced by combining a diamine and a dianhydride (monomer or other form of polyimide precursor) together with a solvent to form a polyamic acid (also referred to as polyamide acid) solution. The dianhydride and diamine may be combined in a molar ratio of about 0.90 to 1.10. The molecular weight of the polyamic acid formed therefrom may be adjusted by adjusting the molar ratio of the dianhydride and diamine.

[0050] In one embodiment, a polyamic acid casting solution is derived from the polyamic acid solution. The polyamic acid casting solution and / or the polyamic acid solution are combined with conversion chemicals such as: (i) one or more dehydrating agents, such as aliphatic acid anhydrides (acetic anhydride, etc.) and / or aromatic acid anhydrides; and (ii) one or more catalysts, such as aliphatic tertiary amines (triethylamine, etc.), aromatic tertiary amines (dimethylaniline, etc.), and heterocyclic tertiary amines (pyridine, picoline, isoquinoline, etc.). The anhydride dehydrating material is often used in molar excess relative to the amount of amide acid groups in the polyamic acid. The amount of acetic anhydride used is usually about 2.0 to 4.0 moles per equivalent (repeating unit) of polyamic acid.Typically, a comparable amount of tertiary amine catalyst is used. Dispersed or solvent-suspended fillers are then added to the polyamic acid solution as described above.

[0051] In one embodiment, the polyamic acid solution is dissolved in an organic solvent at a concentration of about 5.0 or 10% to 15, 20, 25, 30, 35, or 40% by weight. In one embodiment, a suspension comprising an electrically conductive filler is prepared, wherein the suspension has an electrically conductive filler content in a range of 0.1 to 70, 0.5 to 60, 1 to 55, 2 to 50, or 5 to 45% by weight. The suspensions may or may not be ball milled to achieve the desired particle size. The suspensions may or may not be filtered to remove any residual large particles. A polyamic acid solution may be prepared by methods well known in the art. The polyamic acid solution may or may not be filtered. In some embodiments, the solution is mixed in a high shear mixer with the filler suspension. When a polyamic acid solution is prepared with a slight excess of diamine, an additional dianhydride solution may or may not be added to increase the viscosity of the mixture to the desired level for film casting. The amount of the polyamic acid solution and filler suspension may be adjusted to achieve the desired filler levels in the cured film. In some embodiments, the mixture is cooled to a temperature below 10°C and mixed with conversion chemicals prior to casting.

[0052] The solvated mixture (polyamic acid casting solution) may then be cast or coated onto a support, such as an endless belt or rotating drum, to yield a partially imidized gel film. Alternatively, it may be cast onto a polymeric support such as PET, other forms of Kapton® polyimide film (e.g., Kapton® HN or Kapton® E films), or other polymeric supports. The gel film may be peeled from the drum or belt, placed on a stretching frame, and cured in an oven, using convective and radiant heat to remove the solvent and complete imidization to a solids level greater than 98%. The film may then be separated from the support, oriented as in stretching under continued heating (drying and curing) to yield a polyimide film.

[0053] Useful methods for producing polyimide films can be found in U.S. Patent Nos. 5,166,308 and 5,298,331, which are incorporated by reference in this specification for all the teachings contained therein. Many variations are also possible, such as,

[0054] (a) a process in which the diamine and dianhydride constituents are previously mixed together, then the mixture is added in portions to a solvent while stirring.

[0055] (b) a process in which a solvent is added to a stirred mixture of constituents diamine and dianhydride (unlike (a) above).

[0056] (c) a process in which the diamines are exclusively dissolved in a solvent, then dianhydrides are added in a ratio that regulates the reaction rate.

[0057] (d) a process in which the dianhydride constituents are exclusively dissolved in a solvent, then amine constituents are added in a ratio to regulate the reaction rate.

[0058] (e) a process wherein the diamine constituents and the dianhydride constituents are dissolved separately in solvents, then these solutions are mixed in a reactor.

[0059] (f) a process wherein the polyamic acid having an excess of constituent amine and another polyamic acid having an excess of dianhydride constituent are formed beforehand, then reacted with each other in a reactor, in particular so as to create a non-statistical or block copolymer.

[0060] (g) a process wherein a specific portion of the amine constituents and the dianhydride constituents are reacted first, then the residual diamine constituents are reacted or vice versa.

[0061] (h) a process in which the conversion chemical compounds (catalysts) are mixed with polyamic acid to form a polyamic acid casting solution, and then cast to form a gel film.

[0062] (i) a process in which the constituents are added in part or in whole in any order to some or all of the solvent, also in which some or all of any constituent may be added as a solution in some or all of the solvent.

[0063] (j) a process in which one of the dianhydride constituents is first reacted with one of the diamine constituents yielding a first polyamic acid. Then another dianhydride constituent is reacted with another amine constituent to yield a second polyamic acid. Then the amic acids are combined in any of several ways before the film is formed.

[0064] In one embodiment, the solvated mixture (the polyamic acid casting solution) may be mixed with a crosslinking precursor and then cast to form a polymer film. In one embodiment, a polymer film contains crosslinked polymer in a range of 80 to 99% by weight. In some embodiments, the polymer film contains between any two of the following values, including extremes: 80, 85, 90, 95, and 99% by weight of crosslinked polymer. In yet another embodiment, the polymer film contains 91 to 98% by weight of crosslinked polymer.

[0065] In one embodiment, a crosslinking reaction includes chemical compounds, such as reactive amines, that can participate in a chemical reaction that crosslinks the polymer chains in the film. In one embodiment, heat can be used to crosslink the polymer. In one embodiment, irradiation from a light source can be used to crosslink the polymer via a photoinitiated process. In one embodiment, an additional reactive chemical species can be used to crosslink the polymer. In one embodiment, a combination of these methods can be used to crosslink the polymer.

[0066] Crosslinking of the polymer may be determined by a number of methods. In one embodiment, the gel fraction of the polymer may be determined using an equilibrium swelling method, by comparing the weight of a dried film before and after crosslinking. In one embodiment, a polymer The crosslinked polymer solution may have a gel fraction in the range of 20-100%, 40-100%, 50-100%, 70-100%, or 85-100%. In one embodiment, the crosslinked network may be identified using rheological methods. A time sweep measurement of oscillation at a specific stress, frequency, and temperature may be used to confirm the formation of the crosslinked network. Initially, the loss modulus (G”) value is greater than the storage modulus (G') value, indicating that the polymer solution behaves as a viscous liquid. Over time, the formation of a crosslinked polymer network is evidenced by the crossing of the G' and G” curves. The crossing, referred to as the “gel point,” represents the point at which the elastic component predominates over the viscous component.

[0067] In one embodiment, the electrically conductive filler is first dispersed in a solvent to form a suspension. The suspension is then dispersed in the polyamic acid solution. In one embodiment, the concentration of electrically conductive filler relative to the polyimide (in the final film) is in the range of 5 to 65 wt%, 5 to 50 wt%, 10 to 40 wt% or 15 to 35 wt%, based on the total weight of the polymer film. In one embodiment, the concentration of electrically conductive filler relative to the polyimide (in the final film) is at least 5, at least 10, at least 15, at least 20 or at least 25 wt% based on the total weight of the polymer film.The composition of the cured film can be calculated from the composition of the constituents in the mixtures, excluding the DMAc solvent (which is removed during curing) and taking into account the removal of water during the conversion of the polyamic acid to polyimide. When using electrically conductive fillers, as the filler concentration increases, the conductivity of the polyimide film also increases. In one embodiment, an electrically conductive polymer film may have a surface resistivity of 1 megaohm / square or less, 0.5 megaohm / square or less, 0.1 megaohm / square or less, or 50,000 ohms / square or less. Those skilled in the art will recognize that in addition to filler levels, the characteristics of the electrically conductive filler, such as particle size, morphology, aspect ratio, surface oxidation, etc. will have an influence on the surface resistivity of the polymer film containing them.

[0068] In one embodiment, mixing the filler slurry with a polyamic acid solution to form the polyamic acid casting filled solution is performed using high shear mixing. In this embodiment, if the filler is present at more than 65% by weight in the final film, the film may be too brittle and may not be sufficiently flexible to form a self-supporting, mechanically strong, flexible sheet. In addition, if the filler is present at a level of less than 5% by weight, films formed therefrom may not be sufficiently conductive.

[0069] In one embodiment, the casting solution may also include any of a number of additives, such as processing aids (e.g., oligomers), antioxidants, light stabilizers, flame retardant additives, antistatic agents, heat stabilizers, ultraviolet absorbers, or miscellaneous reinforcing agents.

[0070] In one embodiment, a coextrusion process may be used to form a multilayer polymer film having two or more layers, for example, a three-layer polymer film having an inner core layer sandwiched between two outer layers. In this process, for a three-layer polyimide film, a finished solution of polyamic acid is filtered and pumped through a slot die, the stream being split to form the first outer layer and the second outer layer of a three-layer coextruded film. In some embodiments, a second polymer stream is filtered and then pumped to the casting die to form the central core polymer layer of a three-layer coextruded film. The flow rates of the solutions may be adjusted to achieve the desired layer thickness.In one embodiment, the polymer composition and filler content of the first and second outer layers are the same, while in another embodiment, the polymer composition and / or filler content of the first and second outer layers are different. In some embodiments, the polymer composition and filler content of the core layer may be the same as or different from one or both of the outer layers.

[0071] In one embodiment, the multilayer film is prepared by simultaneous extrusion of the first outer layer, the core layer, and the second outer layer. In some embodiments, the layers are extruded through a single-cavity or multi-cavity extrusion die. In another embodiment, the multilayer film is produced using a single-cavity die. If a single-cavity die is used, the laminar flow of the streams must be of a viscosity high enough to prevent mixing of the streams and to provide uniform lamination. In some embodiments, the multilayer film is prepared by casting from the slot die onto a moving stainless steel belt. In one embodiment, for a polymer having an imide group, the belt is then passed through a convection oven to evaporate the solvent and imidize the polymer to produce a "green" film.The raw film can be peeled off the casting belt and rolled up. The raw film can then be passed through a stretching furnace to produce a polymer film. fully cured. In some embodiments, during stretching, shrinkage may be minimized by constraining the film along the edges (i.e., using clamps or pins).

[0072] In one embodiment, the outer layers of the present invention may also be applied to the core layer during an intermediate production stage of manufacturing the polymer film, for example on a gel film or a green film.

[0073] In forming the imide-containing polymer, the term "gel film" refers to a sheet of polyamic acid that is loaded with volatile compounds, primarily solvent, to such an extent that the polyamic acid is in a gel-swollen or rubbery state and can be formed in a chemical conversion process. The volatile content is usually in the range of 70 to 90% by weight and the polymer content is usually in the range of 10 to 30% by weight of the gel film. The final film becomes "self-supporting" at the gel film stage. It can be removed by peeling from the support onto which it was cast and heated to a final curing temperature. The gel film generally has an amic acid to imide ratio of between 10:90 and 50:50, most commonly 30:70.

[0074] The gel film structure may be prepared by the method described in U.S. Patent No. 3,410,826. This patent discloses mixing a chemical conversion agent and a catalyst, such as a lower fatty acid anhydride and a tertiary amine, into the polyamic acid solution at a low temperature. This mixing is followed by casting the polyamic acid solution as a film onto a casting drum. The film is slightly heated after casting, for example to 100°C, to activate the conversion agent and catalyst to transform the cast film into a polyamic acid / polyimide gel film.

[0075] Another type of polymer film is a "green film" which, for a polyimide film, is partly polyamic acid and partly polyimide and which can be formed in a thermal conversion process. A green film generally contains about 50 to 75% by weight of polymer and 25 to 50% by weight of solvent. In general, it should be strong enough to be substantially self-supporting. The green film can be prepared by casting the polyamic acid solution as a film onto a suitable support such as a drum or casting belt and removing the solvent by gentle heating to a temperature of up to 150°C. A small proportion of amic acid units in the polymer, for example up to 25%, can be converted to imide units.

[0076] The application of the polymer films of the present invention can be carried out in numerous ways. Such methods include the use of a slot die, dip coating or transfer roll coating of a film, followed by metering using a doctor blade, doctor roller, pressure rollers, or an air knife. The coating can also be applied by brushing or spraying. These techniques allow the preparation of laminates coated on both sides and on both sides. When preparing double-coated structures, coatings can be applied to both sides of a polymer either simultaneously or consecutively before proceeding to the polymer curing and drying step.

[0077] The thickness of the polymer film may be adjusted depending on the intended purpose of the film or the specifications of the end application. In one embodiment, the polymer film has a total thickness in the range of 1 to 300 μm, 2 to 200 μm, 5 to 150 μm, 10 to 100 μm, or 20 to 80 μm.

[0078] In one embodiment, for a two- or three-layer polymer film, the core layer has a thickness in the range of 0.75 to 225 µm, 1.5 to 150 µm, 3.75 to 112.5 µm, or 7.5 to 75 µm, and the outer layer(s) each has a thickness in the range of 0.25 to 75 µm, 0.5 to 50 µm, 1.25 to 37.5 µm, or 2.5 to 25 µm. In one embodiment, for a three-layer film, the thicknesses of the outer layers may be the same or different. Veneers

[0079] In one embodiment, a veneer may comprise a polymer film and a metal layer bonded to the polymer film. In one embodiment, a veneer may comprise a polymer film, with metal layers bonded to both sides of the polymer film.

[0080] The platings may be formed as single-sided or double-sided platings by a number of well-known methods. In one embodiment, a metal plating process may be used to form a plating, such as a polyimide film. In one embodiment, a polyimide film comprises a thermoplastic polyimide layer. A metal layer may be formed on the thermoplastic polyimide layer of the polymer film by plating a metal layer. In one embodiment, a metal layer may be 100 μm or less, 50 μm or less, 25 μm or less, 10 μm or less, 5 μm or less, 3 μm or less, or 1 μm or less. Using a plating process to form metal layers on polymer films allows for smoother interfaces to be formed.Traditional lamination of metal foils onto polymer films relies on the surface roughness of the foils to provide good adhesion to the polymer film, but may also require roughnesses that are greater than the thickness of a thin metal film.

[0081] In one embodiment, a polymer film may be bonded to a first metal layer in a plating process to form a single-sided plating. In a embodiment, the surface of the polymer film to be plated may be plasma treated prior to formation of the metal layer. Thus, a formed plating comprises the polymer film and a thin conductive layer. In one embodiment, for a multi-layer polymer film, the use of a thermoplastic polymer layer as an outer layer to be bonded to the metal layer allows for strong adhesion between the polymer film and the metal layer despite the smooth appearance of the interface between the layers and without the use of additional primer or intermediate adhesive layers.

[0082] In one embodiment, a polymer film may be bonded to a first metal layer by direct electrochemical deposition of a metal layer onto a polymer film (direct metallization). The term "direct electrochemical deposition of a metal layer" or "direct plating" onto a polymer film means that an electrolytic plating process is used to form and build up a metal layer on a polymer film, without initially using an electroless plating process or physical vapor deposition or chemical vapor deposition to form an initial metal layer on the polymer film. Eliminating this seed layer from the process makes direct metallization faster and less expensive than traditional methods of making copper platings. In one embodiment, the plating is substantially free of Pd.The term “substantially free of Pd” is intended to mean that no significant amount of Pd is detectable in the plating when analyzed by inductively coupled plasma mass spectrometry (ICP-MS), as described below. Substantially free of Pd means that less than 15 ppm, less than 10 ppm, or less than 5 ppm of Pd is detected. In some cases, trace amounts of Pd may be detected in the digested plating when using ICP-MS, even when no Pd catalyst was used in the plating process. In the case of a process using a Pd catalyst, however, Pd levels greater than 5 ppm, 10 ppm, or 15 ppm may be detected. For example, in a process using a Pd-based catalyst, 200 ppm of metallic Pd might have been used and can be detected in the plating when using ICP-MS at levels of about 20 ppm.

[0083] In one embodiment, a polymer film may be bonded to a first and second metal layer to form a double-sided plating. One or both of the metal layers may be formed using a plating process. In one embodiment, the surface of the polymer film to be plated may be plasma treated prior to formation of the metal layers. In one embodiment, the thicknesses of the first and second metal layers may individually be 100 μm or less, 50 μm or less, 25 μm or less, 10 μm or less, 5 μm or less, 3 μm or less, or 1 μm or less. In one embodiment, the thicknesses of the metal layers may be the same or different. In one embodiment, a double-sided plating may include a thin metal layer on one side and a metal foil on the other side, the thin metal layer being formed using a plating process and the metal foil then being laminated to the plating on a side opposite the thin metal layer. In one embodiment, a metal foil may have a thickness in the range of 5 to 200 μm, 5 to 100 μm, 10 to 75 μm, or 10 to 50 μm.In one embodiment, for a multi-layer polymer film, the use of a thermoplastic polymer layer as an outer layer to be bonded to the metal layer(s) allows for strong adhesion between the polymer film and the metal layer(s) despite the smooth appearance of the interface between the layers and without the use of additional primer or intermediate adhesive layers. Applications

[0084] In one embodiment, the platings of the present invention are useful for bonding pads of flexible printed circuit board chips or semiconductor devices or packaging materials for CSP (chip scale package), chip on flex (COF), COL (chip on lead), LOC (lead on chip), multi-chip module (“MCM”), micro-ball grid array (“BGA”) and / or tape automated bonding (“TAB”).

[0085] In another embodiment, the platings of the present invention may be used for wafer-level integrated circuit packaging, wherein a composite is made using a polymer film according to the present invention interposed between a conductive layer (usually a metal) having a thickness of less than 100 µm and a wafer comprising a plurality of integrated circuit chips. In one embodiment (wafer-level integrated circuit packaging), the conductive via is connected to the chips by a conductive via, such as a wire bond, a conductive metal, a solder bump, or the like.

[0086] In another embodiment, the platings of the present invention are used as a material for constructing a planar transformer component. These planar transformer components are commonly used in power supply devices.

[0087] In another embodiment, the veneers of the present invention are used as a material for constructing high density integrated circuits (HDICs) comprising ultrafine features, such as very narrow center distances and very tight lines and spacing, which support good signal integrity of high speed signal transmission at a high frequency. These circuits are used for constructing a display module, a touch panel, sensors and camera modules in mobile electronic devices.

[0088] In one embodiment, a shielding film, which provides EMI shielding for electronic devices and components, such as flexible printed circuit board, antennas and chips on flex, comprises a plating. To provide EMI shielding, the shielding film comprises a uniform metal layer, which is highly conductive, adheres strongly to the base material and exhibits long-term retention of high electrical conductivity.

[0089] In yet another embodiment, the platings of the present invention may be used with thick metal foils to form heating resistors, such as those described in U.S. Patent Application No. 2011 / 0229680 A1. These resistors are typically used in automotive and aeronautical applications.

[0090] In one embodiment, platings having a polymer film and first and second metal layers bonded to the polymer film may be used as current collectors in electrochemical devices, such as lithium-ion batteries, capacitors, supercapacitors, fuel cells, and redox flow batteries. Any electrochemical device in which the conductivity of a current collector may be useful in completing a circuit and providing power to an external device could benefit from the use of the current collectors having a polymer film and metal layers bonded to the polymer film. For example, a lithium-ion cell includes a positive electrode (cathode), a negative electrode (anode), and a separator, at least one of which, preferably all of which, are in ionically conductive contact with an electrolyte solvent.

[0091] The advantageous properties of this invention may be observed by reference to the following examples which illustrate, but are not limited to, the invention. All parts and percentages are by weight unless otherwise indicated. Examples Test Methods Particle size

[0092] The size of the filler particles in the suspensions is measured by laser diffraction using a particle size analyzer (Mastersizer 3000, Malvem Instruments, Inc., Westborough, MA). DMAc is used as the carrier fluid. Surface resistivity

[0093] According to ASTM D257, to measure surface resistivity, a Loresta AX MCP-T370 equipped with a 4-point linear PSP probe (Mitsubiushi Chemical Analytech Co., LTD, Kanagawa, Japan) to measure the surface resistivity at 15 locations evenly distributed over a ~12"x2" piece of polymer film. The 15 measurements are averaged to determine the surface resistivity of the film. Surface resistivity can be measured on either side of the polymer film containing electrically conductive fillers. Metal detection

[0094] Approximately 300 mg of veneer is digested in aqua regia in closed microwave digestion vessels at 900 W for 15 minutes. Internal vessel temperatures reach -250 °C. Samples are cooled to room temperature after digestion and checked for complete dissolution of solids. Samples are then placed on a hot plate to drive off aqua regia. Once dry, each sample is reconstituted in a 2% HNO3 V / V solution. Diluted samples are analyzed for 105-Pd in ​​triplicate with a He and H2 gas collision cell on an inductively coupled plasma mass spectrometer (7700 ICP-MS 6, Agilent Technologies, Santa Clara, CA). Carbon black suspension

[0095] For some embodiments, a carbon black slurry for providing an electrically conductive filler is prepared, consisting of 9.5 wt% carbon black powder (Conductex® 7055U, Aditya Birla Group, Marietta, GA), 17.25 wt% polyamic acid (13.06 wt% PMDA / ODA and 4.19 wt% PMDA / BPDA / / ODA / PPD), and 73.25 wt% DMAc. High shear grinding and mixing are used to achieve complete uniform dispersion of the slurry particles. The median particle size, d5o (the equivalent spherical diameter based on a median particle volume distribution) of the filler particles is less than 1 μm. Multi-layer polymer film

[0096] Polyamic acid solutions for producing the core layer and outer layers are prepared separately by a chemical reaction between the appropriate molar equivalents of the monomers in a dimethylacetamide (DMAc) solvent. Typically, the diamine dissolved in DMAc is stirred under nitrogen and the dianhydride is added as a solid over a period of several minutes. Stirring is continued to achieve maximum viscosity of the polyamic acid. Carbon black slurry (at the appropriate loading to impart the desired surface resistivity) is added to the polyamic acid solutions and mixed using a high shear mixer. The viscosity is adjusted by regulating the amount of dianhydride in the polyamic acid composition. Examples 1 to 3

[0097] For Examples 1-3 (E1-E3), a two-layer polyimide film having an electrically conductive layer on one side and a dielectric insulator on the other side (DuPont™ Kapton® 200RS100, available from DuPont de Nemours, Inc., Wilmington, DE) is used as the multilayer polymer layer. Both layers contain a polyimide derived from a molar ratio of about 1:1 dianhydride to diamine, the dianhydride being PMDA and the diamine being ODA. For these films, the surface resistivity is measured on the surface having the electrically conductive layer. Example 4

[0098] For Example 4 (E4), the core layer polymer composition contains a polyimide derived from a molar ratio of about 1:1 of dianhydride to diamine. The dianhydride composition contains the BPDA / PMDA monomers in a molar ratio of 88:12 and the diamine composition contains the PPD / ODA monomers in a molar ratio of 95:5. The thermoplastic outer layers also contain a polyimide derived from a molar ratio of about 1:1 of dianhydride to diamine. The dianhydride composition contains the PMDA and ODPA monomers in a molar ratio of 20:80 and the diamine composition is 100 mol% RODA monomer.

[0099] Multilayer films are cast by coextrusion. Three separate streams of polyamic polymer are extruded simultaneously through a multi-cavity extrusion die onto a moving heated belt to form a coextruded three-layer polyimide film. The flow rates of the polyamic acid solutions are adjusted to obtain a three-layer film in which the core layer has a thickness of about 38 μm and the thermoplastic outer layers each have a thickness of about 6 μm. The E4 film includes a carbon black suspension sufficient to provide a surface resistivity of about 100 Ω / square.

[0100] The extruded multilayer film is dried at an oven temperature in the range of about 95 to about 150°C. The self-supporting film is peeled off the belt and heated using radiant heaters in a stretching oven at a temperature of about 110 to about 805°C (surface temperature of the radiant heaters) to completely dry and imidize the polymers.

[0101] The films of E1-E4 are metallized with copper to form a metallic layer on a polymer film. Prior to metallization, film samples are cut to approximately 5 in2 or 25 in2 and attached in a stainless steel frame. All film surfaces are cleaned using a 2-step plasma treatment process. Cleaning is performed at 300 mTorr plasma exposure with a N2 / CF4 / O2 mixture for 5 minutes for the first step, followed by 30 seconds of exposure to an O2 plasma for the second step. After the plasma treatment, the films are immersed in a 1 M aqueous NaOH solution at 45 °C for 90 seconds with gentle agitation, then rinsed under a stream of tap water for 2 minutes. Finally, the films are electroplated in a plating cell as described below.

[0102] Electroplating is performed using a DuPont MICROFILL™ EVF-II process. Copper electroplating baths are prepared by combining 200 g / l copper as copper sulfate pentahydrate, 100 g / l sulfuric acid, 50 ppm chloride ion, 1.25 ml / l MICROFILL™ EVF-IIXB, 33 ml / l MICROFILL™ EVF-II XL and 10 ml / l MICROFILL™ EVF-II XC. The films are electroplated in a 5.5 L or 1.5 L plating cell with air agitation set at 2 L / min and the temperature is set at 24°C (75°F) via a heated water bath. Films are mounted between two 5” x 7” or 2” x 6” stainless steel frames with a 4.5” x 5.5” or 1.5” x 3.25” window and processed as follows:

[0103] 1. The films are plated at the current density shown in Table 1 for 10 minutes 24 seconds in a bright acid copper bath to a target thickness of 1 pm.

[0104] 2. after electrolytic copper plating, the films are rinsed with water deionized for 120 seconds, removed from the frame, immersed in ANTITARNISH™ 7130 (DuPont) for 15 seconds, rinsed with deionized water for 30 seconds and air dried. Comparative example 1

[0105] For Comparative Example 1 (CEI), the polymer composition contains the same polyimide as described for E4. The film is cleaned using the 2-step plasma process described above followed by the post-plasma base rinse.

[0106] After plasma treatment, electroless plating is performed for the IEC film, prior to electroplating, by processing the film sequentially using a CIRCUPOSIT™ 6500 electroless copper deposition process without using a stripping step, and then processed as follows:

[0107] 1. the film is immersed in CIRCUPOSIT™ 6520A Pre-Dip (DuPont de Nemours, Inc., Wilmington, DE) at pH 2 at room temperature for 30 seconds with gentle agitation.

[0108] 2. the film is then immersed in CIRCUPOSIT™ 6530 catalyst (DuPont) set at a Pd2+ ion concentration of 200 ppm at 50°C for 60 seconds with gentle stirring.

[0109] 3. the film is then rinsed under a jet of tap water for 60 seconds.

[0110] 4. the film is then immersed in a solution of CIRCUPOSIT™ 6540 reducer (DuPont) at 32°C for 60 seconds with gentle agitation.

[0111] 5. the film is then rinsed under a jet of tap water for 60 seconds.

[0112] 6. the film is then immersed in an autocatalytic copper plating bath CIRCUPOSIT™ 6550 (DuPont) at approximately 34°C for 2.5 minutes.

[0113] 7. the film is then rinsed under a jet of tap water for 60 seconds.

[0114] After electroless plating, the IEC film is dried and stored in a desiccator before being used for electroplating.

[0115] The electroless plating process forms a layer of about 80-120 nm of copper on the polyimide film. The electroless plating process is then followed by an electrolytic plating process, which is carried out by processing the film sequentially using the MICROFILL™ EVF-II process described above. Before placing the film in the MICROFILL™ EVF-II bath, it is pre-cleaned as follows:

[0116] 1. the film is pretreated with RONACLEAN™ LP-200 cleaner (DuPont) for 120 seconds at 40°C.

[0117] 2. the film is then rinsed in deionized (DE) water for 120 seconds.

[0118] 3. the film is then treated in 40 g / l sulfuric acid for 30 seconds before its transfer to the electroplating bath. [Tables 1] Example Core layer polyimide Outer layer polyimide Current density (A SD) Surface resistivity (Q / sq) Coverage nPd content (ppm) El PMDA / ODA PMDA / ODA 0.54 96 full 0.1 E2 PMDA / ODA PMDA / ODA 1.08 96 edge 0.0 E3 PMDA / ODA PMDA / ODA 0.27 96 full 0.0 E4 PMDA / ODA PMDA / ODPA / / R ODA 0.54 97 full 0.0 IEC PMDA / ODA PMDA / ODPA / / R ODA 0.54 97 full 11.7

[0119] Table 1 summarizes the film properties. The coverage of the metal layer is characterized by "full" (complete coverage of the polymer film by the metal layer), "edge" (some coverage of the polymer film from the edges of the film toward the center but with polymer visible toward the center of the film), and "none" (substantially no metal coverage of the polymer film). El- E4 show that a direct electroplating process, which directly electrochemically deposits a metal layer onto a polymer film, can be used to form a plating with excellent coverage of the metal layer on the polymer film without an initial electroless step using a seed layer. By adjusting the deposition parameters, such as current density, complete coverage can be achieved.

Claims

Claims

1. A plating comprising a polymer film and a first metal layer bonded to the polymer film: the polymer film comprising an electroconductive filler and having a surface resistivity of 1 megaohm / square or less; the first metal layer having a thickness of 100 pm or less; the plating having less than 15 ppm of Pd; and the metal layer being formed on the polymer film by direct electrochemical deposition of the first metal layer onto the polymer film.

2. The plating of claim 1, the polymer film comprising a polymer comprising an imide group.

3. The veneer of claim 1, the polymer film comprising a multilayer film comprising: a first outer layer comprising a first polymer; a second outer layer comprising a second polymer; and a core layer comprising a third polymer, the core layer being located between the first and second outer layers and the electrically conductive filler being present in one or more of the layers.

4. The plating of claim 3, wherein one or more of the first, second, and third polymers comprises a polymer comprising an imide group.

5. The plating of claim 1, wherein the electrically conductive filler is present in the polymer film at a concentration in a range of 5 to 65% by weight, based on the total weight of the polymer film.

6. An electronic device comprising the plating of claim i

7. 1. An energy storage device comprising the plating of claim 1, wherein the energy storage device is selected from the group consisting of lithium ion batteries, capacitors, supercapacitors, fuel cells, and redox flow batteries.

8. A shielding film for an electronic circuit, comprising the plating of claim 1.

9. A heating resistor comprising the plating of claim 1.