Coatings for waterproofing electronic components

Abstract

Provided is a waterproof circuit board coating composition comprising at least one passivating agent, preferably comprising a molecule comprising a thio-functional group, preferably a thiol group, an azolic moiety or an azole, and combinations thereof; at least one binder component comprising an organic or inorganic film-forming polymer and / or one or more polymer precursors polymerizable on a substrate surface; and optionally one or more additives. Methods for making and using the coating composition and coated circuit boards are also provided.

Description

[Technical field]

[0001] The present disclosure generally relates to so-called "waterproof" coating compositions, which enhance the water resistance of the coated substrate by depositing thin and ultra-thin coating layers, and the coating compositions are useful for coating electronic components, particularly circuit boards. The coating compositions include at least one passivating agent for passivating metal components of the circuit board and one or more film-forming polymers and / or polymer precursors, and deposit a water-resistant layer forming a passivated polymer coating. The present disclosure also relates to a method for making such coating compositions, a method for depositing a passivated polymer coating on a substrate, and electronic components, particularly circuit boards, coated with a passivated polymer coating, preferably an ultra-thin water-resistant layer. [Background technology]

[0002] This section provides background information that is not necessarily prior art to the inventive concepts related to the present disclosure.

[0003] Many substrate surfaces benefit from various types of coatings, including functional layers, e.g., layers that improve corrosion resistance and / or form water-resistant coatings. Water-resistant conformal coatings find particular application on electronic components such as printed circuit boards (PCBs), which are key components of electronic systems such as tablets and mobile phones.

[0004] Printed circuit boards use conductive traces glued or otherwise attached to a non-conductive substrate to mechanically support and electrically connect the electronic components on the substrate. The conductive traces are generally metal traces of copper, aluminum, and other conductive metal elements. It is becoming increasingly important to achieve moisture-resistant printed circuit boards (PCBs) and maintain functionality in a variety of service environments, especially in the handheld electronics market. In an attempt to protect electronic devices, some form of conformal coating is often used over the entire printed circuit board. Conformal coating materials are typically polymeric films that conform to the contours of the printed circuit board to provide barrier protection to the components of the board. To provide barrier protection, conformal coatings typically have a dry thickness of about 50 to 250 μm (micrometers), which is about 1 mil to 10 mils dry coating thickness. The mass of the coating add-on adds weight to the device, which manufacturers try to minimize, especially in handheld devices. The thickness of such polymeric coatings also tends to impede heat dissipation, which is also undesirable. Some conformal coating compositions also have the disadvantage of containing volatile solvents, which evaporate to form the final coating. As used herein, volatile organic compounds (VOCs) are compounds that participate in photochemical reactions in the atmosphere, except for those designated by the EPA as having negligible photochemical reactivity (see EPA.gov), such as CO, CO 2 By carbon is meant any compound of carbon except carbonic acid, metal carbides or carbonates, and ammonium carbonate.

[0005] Protective thin coatings are provided by vacuum processes such as chemical vapor deposition (CVD), in which a chemical reaction forms both solid and volatile products from volatile precursors, and the solid products are deposited on the substrate. However, the coating builds up in thickness slowly in vacuum processing, which is a disadvantage for fast-moving electronics manufacturing. Vacuum processes also have economic disadvantages in the need for specialized chambers, and environmental disadvantages in the use of volatile precursors.

[0006] Therefore, there is a need for a coating composition that allows for rapid, water-resistant coating deposition and a deposition method that passivates corrosion-prone metal traces, provides lightweight, cost-effective protection for electronic components, and does not require a vacuum during application. Such coating compositions are preferably applicable to electronic devices, particularly printed circuit boards. Summary of the Invention [Means for solving the problem]

[0007] Applicant has developed coating compositions and processes for applying them that provide better waterproofing performance at low thicknesses compared to conformal coatings, and avoid the slow application processes and complex equipment associated with CVD and other vacuum deposition processes, in addition to other advantages that will become apparent from the following description. Coating compositions, coating methods, and coated substrates that overcome one or more of the above disadvantages are provided.

[0008] In one aspect (aspect 1) of the present disclosure, A) at least one dissolved and / or dispersed passivating agent; B) at least one dissolved and / or dispersed binder component comprising an organic or inorganic film-forming polymer and / or one or more polymer precursors polymerizable on the substrate surface, the film-forming polymer and / or one or more polymer precursors being either 1) reactive with (A) or 2) non-reactive with (A). and optionally C) one or more dissolving and / or dispersing additives selected from waxes, adhesion promoters, flow modifiers, wetting agents, rheology modifiers, stabilizers, catalysts, photoinitiators, biocides and biostats; D) A circuit board waterproof coating composition is provided that comprises, consists essentially of, or consists of at least one solvent or solvent system that includes an organic solvent.

[0009] In a similar embodiment (embodiment 2), A) at least one soluble and / or dispersible passivator, preferably comprising a molecule containing a thio functional group, preferably a thiol group, an azolic moiety or an azole, and combinations thereof; B) Binders of the following types: 1) an organic or inorganic film-forming polymer which does not react with (A); 2) an organic or inorganic film-forming polymer capable of reacting with (A); 3) one or more polymer precursors, e.g., monomers, oligomers, and / or prepolymers, that are polymerizable on the substrate surface and do not react with (A); 4) one or more polymer precursors, e.g., monomers, oligomers and / or prepolymers, capable of polymerizing on the substrate surface and reacting with (A); A soluble and / or dispersible binder component comprising one or more of and C) optionally one or more dissolving and / or dispersing additives selected from waxes, adhesion promoters, levelling agents, flow modifiers, wetting agents, rheology modifiers, stabilizers, catalysts, pigments, photoinitiators, biocides and biostats; D) Optionally, a circuit board waterproof coating composition is provided that comprises, consists essentially of, or consists of at least one organic solvent.

[0010] Embodiment 3: The circuit board waterproof coating composition of embodiment 1 or 2, wherein the passivating agent (A) is different from the binder component (B), and wherein (A) is present in an amount of about 0.5 to about 60 weight percent, (B) is present in an amount of about 1 weight percent to about 97 weight percent, (C) is present in an amount of about 1 to 80 weight percent, and the remainder to 100 weight percent is (D) at least one organic solvent, all based on the total weight of the coating composition.

[0011] Aspect 4: The waterproof circuit board coating composition according to any one of Aspects 1 to 3, wherein at least a portion of the passivating agent (A) comprises a thiol group, an azolic moiety, or an azole, and further comprises a second functional group.

[0012] Embodiment 5: The waterproof circuit board coating composition according to any one of embodiments 1 to 4, wherein at least a portion of the binder component (B) is grafted to at least some molecules of the passivator (A).

[0013] Embodiment 6: The waterproof circuit board coating composition of any of the embodiments 1-5, wherein the organic or inorganic film-forming polymer of (B) comprises a polymer or copolymer of an olefin monomer and a vinyl ester, preferably a block copolymer, and most preferably an ethylene vinyl acetate copolymer.

[0014] Embodiment 7: The waterproof circuit board coating composition of any of Embodiments 1-6, wherein the one or more polymer precursors comprise a UV curable monomer, oligomer, and / or prepolymer.

[0015] Embodiment 8: The waterproof circuit board coating composition of any of embodiments 1-7, wherein (A) comprises a molecule having both a thiol functional group and an azolic moiety.

[0016] Embodiment 9: The waterproof circuit board coating composition of any one of Embodiments 1-8, wherein (A) comprises a mercaptosilane oligomer.

[0017] Embodiment 10: The waterproof coating composition for circuit boards according to any one of embodiments 1 to 9, wherein (C) comprises a wax having a melting point of about 50 to 100° C.

[0018] Embodiment 11: The circuit board waterproof coating composition of any of embodiments 1-10, wherein the one or more polymer precursors comprise an olefinic monomer comprising at least one of a (meth)acrylate monomer, a vinyl monomer, styrene, acrylonitrile, and mixtures thereof.

[0019] Another aspect of the present disclosure (Aspect 12) is provided, which comprises: a) applying a coating composition according to any one of the preceding embodiments to a surface of a substrate, optionally including one or more conductive traces attached thereto, preferably the substrate is an electronic component, more preferably a circuit board, most preferably a printed circuit board; b) drying the coating composition on the substrate surface; c) optionally UV curing the coating composition on the substrate surface; d) during any of steps a)-c), reacting available reactive functional groups of the binder component (B) and the passivating agent (A) with the coating composition components and optionally the conductive traces, preferably the metal traces, thereby depositing a water insoluble passivating polymer film on the substrate surface.

[0020] A related embodiment (embodiment 13) provides a passivating polymer film deposited on a circuit board according to the method of embodiment 12, the film being removable from the circuit board by peeling.

[0021] Another related embodiment (embodiment 14) provides an electronic component, preferably a circuit board, coated according to embodiment 12, wherein the electronic component exhibits no current leakage while immersed in distilled water for 30 minutes under an applied power of 3, preferably 10, more preferably 20, and most preferably 30 volts.

[0022] Another aspect (aspect 15) of the present disclosure is the following: (a)(A) a passivator; (B1) an organic or inorganic film-forming polymer and / or (B2) one or more polymer precursors capable of polymerization on the substrate surface and optionally (C) at least one additive A liquid coating composition comprising: (b) applying a coating composition to the exposed surface of the circuit board, thereby allowing reaction and adsorption of (A) to the metal portions of the surface, thereby maintaining the composition in a liquid state; (c) solidifying the composition, e.g., removing solvent from the layer and optionally curing, to form an ultra-thin film having a thickness sufficient to waterproof the surface; The method includes a method of waterproofing a circuit board comprising, consisting essentially of, or consisting of the steps of: The final coating may have a thickness of about 0.2-1.6 μm, 0.6-15 microns, or a similar range, depending on thickness, cost, and weight constraints required to meet the waterproofing test, i.e., minimizing these parameters, as can be readily implemented by one of ordinary skill in the art.

[0023] Another embodiment (Embodiment 16) of the present disclosure is a printed circuit board comprising an adherent passivating polymeric coating applied to a surface of the printed circuit board and a conductive trace attached thereto, the polymeric coating comprising: a cured binder matrix comprising one or more organic or inorganic film-forming polymers, optionally crosslinked, a reaction product of one or more polymer precursors, or a reaction product of a film-forming polymer and one or more polymer precursors; a passivator comprising a thio functional group, preferably a thiol group, an azolic moiety, an azole, and combinations thereof, and / or a reaction product of the passivator with at least a portion of the conductive trace and / or component a; and Optionally, the printed circuit board comprises, consists essentially of, or consists of particles of wax that are insoluble in the cured binder matrix and dispersed therein.

[0024] A related embodiment (embodiment 17) is the substrate of embodiment 16, wherein the adherent polymeric coating comprises a polymer-forming olefin monomer comprising at least one of a (meth)acrylate monomer, a vinyl monomer, styrene, acrylonitrile, and mixtures thereof.

[0025] Another aspect (Aspect 18) of the present disclosure is essentially or consists of an passivating polymer film deposited on a substrate surface, wherein the substrate surface is a tape, backing, or other support, whereby it is applied as a tape or via lamination to a final-use article for later transfer to the final-use article, for example, as a pre-formed film to be transferred.

[0026] Another aspect (Aspect 19) of the present disclosure that essentially or consists of a polymer water-resistant coating of any of the foregoing aspects can be prepared using an olefinic monomer and / or a reactive diluent that can be completely solubilized or at least partially solubilized in a solvent. In one embodiment, the present disclosure provides a coated substrate comprising at least one conductive metal trace on a non-conductive substrate, wherein the metal trace and the non-conductive substrate are deposited thereon with an adherent waterproof polymer coating that is a reaction product of the above coating composition, and the metal trace is passivated by the coating.

[0027] In one embodiment of the present invention, the coating is applied to a conductive trace on a printed circuit board. In one embodiment, the passivating agent may include molecules containing thiol functional groups, azolic moieties or azoles, and combinations thereof. In one embodiment, the binder component is Based on the total weight of the composition, about 0.5 to 45% by weight of a binder component selected from a polyester or a copolymer of an olefin and a vinyl ester, preferably a block copolymer, most preferably an ethylene vinyl acetate copolymer, or Based on the total weight of the composition, the binder component containing an ethylenically unsaturated, optionally UV-curable organic molecule may contain about 20 to 98% by weight.

[0028] In one embodiment, optional additives (C) can be present and can comprise about 2 to 80 wt %, based on the total weight of the composition, of one or more additives selected from waxes, adhesion promoters, flow modifiers, wetting agents, rheology modifiers, stabilizers, catalysts, photoinitiators, biocides, biostats and passivators or other additives useful in polymeric coatings.

[0029] The following terms used in the specification and claims have the meanings defined herein. The term "ultrathin" as used herein is based on the definition in IPC-CC-830, where ultrathin (UT) conformal coatings are characterized by having a thickness of 12.5 microns (0.49 mils) or less and are organic, inorganic, or a combination of organic and inorganic components. "Bath" is understood in the coating art to mean a composition in a vessel in which an article to be treated is immersed or partially immersed to allow the article or a portion thereof to contact the composition in the vessel. For example, a coating bath will be understood to mean a coating composition in a vessel commonly used in a process for applying a coating composition. "Stage" as used herein refers to the duration of a time or step of a process, and refers to a cleaning stage, a rinsing stage, a coating stage, which may also refer to a bath used to perform the step, for example, a rinsing stage may refer to a rinsing bath used in a rinsing step of a process.

[0030] The term "solvent" means a liquid that serves as a medium for at least partially dissolving a solute, e.g., a component of a coating composition or concentrate according to the present disclosure, and may include water, organic molecules, inorganic molecules, and mixtures thereof, unless otherwise specified in the description. A "solvent system" or "solvent mixture" is understood to include two or more solvents. The term "soluble" with respect to any component means that the component dissolves in the solvent or solvent system or reaction mixture or coating composition, thereby forming a solution, and acts as a "solute" that does not form a separate phase, whether liquid or solid, e.g., a precipitate visible to the human eye.

[0031] The term "olefin monomer" as used herein means a monomer having at least one carbon-carbon double bond (C=C) in its structure, also known as ethylenic unsaturation. Olefinic monomers may include (meth)acrylate monomers, vinyl monomers, and other polymerizable monomers having a C=C structure. The term "(meth)acrylate monomer" as used herein includes acrylic acid, methacrylic acid, and esters thereof, which may be substituted or unsubstituted. Vinyl monomers as used herein include those having a vinyl functionality, -CH=CH, in their structure. 2 As used herein, "attached to a substrate" means adhered, deposited, laminated, printed, etched, pressed, embossed, or otherwise attached to a substrate.

[0032] "Passivation" and grammatical variations thereof will be understood by those skilled in the art to mean a reduction in the chemical reactivity of a surface. For example, a metal surface forms a more passive surface that is less prone to corrosion by chemical reaction, coordination complexation, or separation of the metal surface by contacting the metal surface with one or more compositions. In this disclosure, a "water-resistant coating" is defined as a coating layer that adheres to a surface and forms a barrier that resists corrosion damage to the substrate associated with immersion in water or other aqueous electrolytes while power is applied. The water-resistant coating layer can desirably resist and / or prevent the penetration of oxygen and / or water-containing fluids into the coated surface. Certain water-resistant coatings disclosed herein also passivate some or all of the metal surfaces on printed circuit boards, particularly traces. One gauge of water-resistant coating performance is the prevention or reduction of damage to assembled printed circuit boards due to exposure to water or aqueous liquids as a result of immersion, condensation, or moisture when powered up, i.e., when voltage is applied to the printed circuit board. Damage associated with such exposure of improperly protected circuit boards includes electrochemical migration phenomena such as dendritic growth and conductive anodic filament formation, as well as corrosive degradation of conductive traces and conductive connections to electronic components.

[0033] For a variety of reasons, the coating compositions and concentrates disclosed herein are preferably substantially free of many ingredients used in compositions for similar purposes in the prior art. Specifically, at least some embodiments of the coating compositions or concentrates according to the present invention preferably minimize the presence of the following components, each independently copper, gold, silver, oxidizers such as peroxides and peroxyacids, permanganates, perchlorates, chlorates, chlorites, hypochlorites, permanganates, hexavalent chromium, sulfuric acid and sulfates, nitric acid and nitrate ions, as well as fluorine, formaldehyde, formamide, hydroxylamine, cyanide, cyanates, rare earth metals, boron, e.g., borax, borates, strontium, and / or free halide ions, e.g., fluoride, chloride, bromide, or iodide, in grams per liter, more preferably in ppm, less than 1.0, 0.5, 0.35, 0.10, 0.08, 0.04, 0.02, 0.01, 0.001, or 0.0002 percent, more preferably inclusive of the values ​​given in the order of increasing preference.

[0034] Also, at least some embodiments as deposited coatings according to the present invention preferably minimize the components listed below, each independently comprising less than 1.0, 0.5, 0.35, 0.10, 0.08, 0.04, 0.02, 0.01, 0.001, or 0.0002 percent of each of the components listed above and further unreacted monomer or solvent, more preferably comprising the above values ​​in parts per thousand (ppt), with the given order being increasingly more preferred.

[0035] The simple terms "metal" or "metallic" will be understood by those skilled in the art to mean a material, whether an article or a surface, that is composed of atoms of a metallic element. For example, aluminum is a metallic element that is present in an amount of at least 55, 65, 75, 85, or 95 atomic percent, in the order of increasing priority, e.g., the simple term "aluminum" includes pure aluminum and aluminum in its alloys that contain at least 55, 65, 75, 85, or 95 atomic percent of aluminum atoms, in the order of increasing priority, as specified. A bare metal surface will be understood to mean a metal surface in the absence of a coating layer other than an oxide of the metal that derives from the metal surface by aging in air and / or water.

[0036] Unless otherwise stated in the examples, or otherwise specifically stated, all numbers used herein expressing amounts of ingredients, reaction conditions, or defining ingredient parameters should be understood to be modified in all instances by the term "about." Throughout the specification, unless expressly stated otherwise: percent, "parts," and ratio values ​​are by weight or mass; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the present invention includes the meaning that mixtures of any two or more members of that group or class are equally suitable or preferred; the description of components in chemical terms includes the amount of the component upon addition to any combination defined in the specification, or the amount of the component that is present in the composition by chemical reaction between one or more newly added components and one or more components already present in the composition when other components are added. refers to a component when formed in situ; the definition of a component in ionic form further implies the presence of sufficient counterions to provide electrical neutrality to the composition as a whole and to any substances added to the composition; and thus, any implicitly defined counterions are preferably selected from among other components that are explicitly defined in ionic form, whenever possible, but otherwise such counterions may be freely selected other than to avoid counterions that act detrimentally to the purposes of this invention; molecular weight (MW) is weight average molecular weight; molecular weight (Mn) is number average molecular weight; the term "mole" means "gram moles," and the term itself and all of its grammatical variations can be used for any chemical species defined by all of the types and numbers of atoms present therein, regardless of whether the species is ionic, neutral, unstable, hypothetical, or is in fact a stable neutral substance with well-defined molecules.

[0037] This section provides a general summary of the disclosure and is not an exhaustive disclosure of its entire scope or all features, aspects, or objectives. These and other features and advantages of the present disclosure will become more apparent to those skilled in the art from the detailed description of the preferred embodiments. The drawings accompanying the detailed description are described below. [Brief description of the drawings]

[0038] [Figure 1] FIG. 1 is a graph showing the results of current leakage tests performed on printed circuit boards coated in accordance with the present invention and on printed circuit boards coated with comparative commercial coatings. [Figure 1] FIG. 2 is a confocal image at 10× magnification using polarized light of a printed circuit board coated according to Example 11F at a thickness of 12 microns. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present disclosure relates to A) at least one soluble and / or dispersible passivator, preferably comprising a molecule containing a thio functional group, preferably a thiol group, an azolic moiety or an azole, and combinations thereof; B) Binders of the following types: 1) an organic or inorganic film-forming material, e.g., a polymer, which does not react with (A); 2) an organic or inorganic film-forming material capable of reacting with (A), e.g., a polymer; 3) one or more polymer precursors, e.g., monomers, oligomers, and / or prepolymers, that are polymerizable on the substrate surface and do not react with (A); 4) one or more polymer precursors, e.g., monomers, oligomers and / or prepolymers, capable of polymerizing on the substrate surface and reacting with (A); A soluble and / or dispersible binder component comprising one or more of and C) optionally, one or more additives such as waxes, adhesion promoters, flow modifiers, rheology modifiers, stabilizers, catalysts, photoinitiators, biocides and biostats; A circuit board coating composition, preferably liquid, is provided comprising:

[0040] The at least one passivating agent (A) comprises one or more compositions capable of reacting with, coordinating with, or otherwise modifying at least one metal present in the electrical component, thereby producing a less reactive surface for the metal components of the printed circuit board. The surface of the metal components is less corroded, especially when contacted with water, saline, or the like. Desirably, the at least one passivating agent (A) comprises a molecule comprising at least one of a thio-functional group, preferably a thiol, an azolic moiety or an azole, and combinations thereof. Preferred passivating agents include thiol-functional compounds and azolic moiety-containing compounds.

[0041] The thio functional groups may be thioesters, thioethers, thiols, and derivatives thereof, such as thiolates and disulfides, e.g., thiolsulfinates, thiolsulfonates, and sulfonic acids, as well as other organic molecules containing mercapto groups that can react with, coordinate to, or otherwise modify metals used as traces or electrical components on at least one printed circuit board and suitable for incorporation into polymeric coatings according to the present disclosure.

[0042] In one embodiment, the thiofunctional material is a thioether. The thioether can be monofunctional or polyfunctional. Desirably, the number of thioether functional groups per molecule is at least 1 and can be up to 10, and optionally, more than 10 thioether functional groups per molecule can be used, provided that the additional functional groups do not interfere with the objectives of the present invention. The thioether can also contain other functional groups. Non-limiting examples include dimethylsulfide, methionine, 2,2-thiodiacetic acid, 3,3-thiodipropionic acid, thioanisole, and S-acetylmercaptosuccinic anhydride. The thioether can also be part of a ring or aromatic system. Non-limiting examples include thiophene, 2-thiophenecarboxylic acid, tetrathiafulvalene, 2-thiophenecarboxaldehyde, 3-thiophenecarboxaldehyde, thiazolidine, 4-thiazolidinecarboxylic acid, xylazine, and phenothiazine.

[0043] Thiol-functional compounds suitable for use as at least one passivating agent (A) may have a single thiol functional group or multiple thiol functional groups. Desirably, the number of thiol functional groups per molecule is at least 1 and may be up to 10, and optionally, more than 10 thiol functional groups per molecule can be used, provided that the additional functional groups do not interfere with the objectives of the present invention. Non-limiting examples of useful types of thiol-functional compounds include alkylene glycol mercaptans, alkyl mercaptans, and esters of mercaptocarboxylic acids.

[0044] The alkylene glycol dimercaptan may desirably correspond to the general formula I: [ka] In the formula, “a” and “c” are independently 2 to 4, and “b” is 1 to 6.

[0045] Desirably, the alkylene glycol dimercaptan can be ethylene glycol dimercaptan, propylene glycol dimercaptan, ethylene / propylene glycol dimercaptan, and mixtures thereof.

[0046] In general, the esters of mercaptocarboxylic acids can be based on mercaptocarboxylic acids of Cl-C22, preferably Cl-C18, more preferably C2-C12. Preferred esters of mercaptocarboxylic acids include esters of mercaptopropionic acid and polyfunctional alcohols, esters of mercaptoacetic acid and polyfunctional alcohols, and combinations thereof. Desirably, the polyfunctional alcohols can include alkyl and aryl alcohols having two or more OH functional groups. Suitable alcohols include alkylene glycols and polyalkylene glycols, such as diethylene glycol, dipropylene glycol, glycerol, trimethylolpropane, pentaerythritol, and dipentaerythritol.

[0047] Non-limiting examples of thiol functional compounds useful in the present invention include 2,2'-oxydi-1-ethanethiol, 1,8-dimercapto-3,6-dioxaoctane, tetra(ethylene glycol digthiol, ethylene glycol dimercaptoacetate (GDMA), ethylene glycol dimercaptopropionate (GDMP), trimethylolpropane mercaptopropionate (TMPMP), pentaerythritol tetrakis 3-mercaptopropionate (PPTMP), tetra(ethylene glycol digthiol), ethylene glycol dimercaptoacetate (GDMA), ethylene glycol dimercaptopropionate (GDMP), trimethylolpropane mercaptopropionate (TMPMP), pentaerythritol tetrakis 3-mercaptopropionate (PPTMP), tetra(ethylene glycol digthiol), tetra(ethylene glycol digthiol), tetra(ethylene glycol digthiol), tri ... pentaerythritol tetrakis 2-mercaptopropionate (PETMP), pentaerythritol tetrakis 2-mercaptoacetate (PETMA), dipentaerythritol tetrakis 3-mercaptopropionate (DiPETMP), dipentaerythritol tetrakis 2-mercaptoacetate (DiPETMA), dipentaerythritol hexakis 3-mercaptopropionate, dipentaerythritol hexakis 3-mercaptoacetate, and ethoxylated trimethyl ether. Examples of thiol-functional compounds include trimercapto-functional compounds based on ethoxylated trimethylolpropane, such as trimethylolpropane tri-3-mercaptopropionate, desirably with a degree of ethoxylation ranging from 5 to 12 moles of ethoxylation per thiol group, one such product being commercially available as Thiocure® ETTMP1300. Other examples of thiol-functional compounds include thiol-functionalized silane oligomers, including alkoxysilane oligomers having one or more thiol functional groups, such as mercaptoethoxysilane oligomers, such as Coatosil® T-Cure, thiol-functionalized polycaprolactones, such as polycaprolactone tetra(3-mercaptopropionate), such as Thiocure® PCL4MP1350, and thioesters of tris-hydroxyethyl isocyanurate, such as Thiocure® Tempic.

[0048] In other embodiments, the thiol-functional compound can have a second functional group, including, but not limited to, ethylenic unsaturation, an azolic group, a silanol group, or a hydroxyl group.

[0049] Suitable thiol-functional compounds that also contain one or more silicon atoms include mercaptoalkoxysilanes of the general formula II: [ka] During the ceremony, the substituents R are identical or different and are C1-C8 alkyl (preferably CH), alkenyl (preferably C2-C12 alkenyl), aryl (preferably C6-C10 aryl), aralkyl (preferably C7-C16 aralkyl) or a group OR', the substituents R' are identical or different and are a C1-C24 (preferably C1-C4 or C12-C18) branched or unbranched monovalent alkyl or alkenyl group, an aryl group (preferably a C6-C10 aryl group), or an aralkyl group (preferably a C7-C16 aralkyl group); -R” is NH 2 or NHR′, -x is 1 to 3.

[0050] When x=1, R″ is preferably —CH 2 -,-CH 2 CH 2 -,-CH 2 CH 2 CH 2 -,-CH 2 CH 2 CH 2 CH 2 -,-CH(CH 3 )-,-CH 2 CH(CH 3 )-,-CH(CH 3 )CH 2 -,-C(CH 3 ) 2 -,-CH(C 2 H 5 )-,-CH 2 CH 2 CH(CH 3 )-,-CH 2 CH(CH 3 )CH2 -or, [ka] It is.

[0051] When x=2, R″ is preferably CH, —CH—CH 2 ,-CH 2 -CH,C-CH 3 ,-CH-CH 2 -CH 2 ,-CH-CH-CH 3 or -CH 2 -CH-CH 2 It is.

[0052] Preferred (mercapto)alkoxysilanes of formula II include: 3-mercaptopropyl(trimethoxysilane), 3-mercaptopropyl(triethoxysilane), 3-mercaptopropyl(diethoxymethoxysilane), 3-mercaptopropyl(tripropoxysilane), 3-mercaptopropyl(dipropoxymethoxysilane), 3-mercaptopropyl(tridodecanoxysilane), 3-mercaptopropyl(tritetradecanooxysilane), 3-mercaptopropyl(trihexadecanoxysilane), 3-mercaptopropyl(trioctadecanoxysilane), 3-mercaptopropyl(didodecanooxy)tetradecanooxysilane, 3-mercaptopropyl(dodecanoxy)tetradecanooxy(hexadecanoxy)silane, (dimethoxymethylsilane), 3-mercaptopropyl(methoxydimethylsilane), 3- Mercaptopropyl(diethoxymethylsilane), 3-mercaptopropyl(ethoxydimethylsilane), 3-mercaptopropyl(dipropoxymethylsilane), 3-mercaptopropyl(propoxydimethylsilane), 3-mercaptopropyl(diisopropoxymethylsilane), 3-mercaptopropyl(isopropoxydimethylsilane), 3-mercaptopropyl(dibutoxymethylsilane), 3-mercaptopropyl(butoxydimethylsilane), 3-mercaptopropyl(diisobutoxymethylsilane), 3-mercaptopropyl(isobutoxydimethylsilane), 3-mercaptopropyl(didodecanooxymethylsilane), 3-mercaptopropyl(dodecanoxydimethylsilane), 3-mercaptopropyl(ditetradecanooxymethylsilane), -mercaptopropyl(tetradecanoxydimethylsilane), 2-mercaptoethyl(trimethoxysilane), 2-mercaptoethyl(triethoxysilane), 2-mercaptoethyl(diethoxymethoxysilane), 2-mercaptoethyl(tripropoxysilane), 2-mercaptoethyl(dipropoxymethoxysilane), 2-mercaptoethyl(tridodecanoxysilane), 2-mercaptoethyl(tritetradecanooxysilane), 2-mercaptoethyl(trihexadecanoxysilane), 2-mercaptoethyl(trioctadecanooxysilane), 2-mercaptoethyl(didodecanooxy)tetradecanooxysilane,2-Mercaptoethyl(dodecanoxy)tetradecanoxy(hexadecanoxy)silane, 2-Mercaptoethyl(dimethoxymethylsilane), 2-Mercaptoethyl(methoxydimethylsilane), 2-Mercaptoethyl(diethoxymethylsilane), 1-Mercaptoethyl(ethoxydimethylsilane), 1-Mercaptomethyl(trimethoxysilane), 1-Mercaptomethyl(triethoxysilane), 1-Mercaptomethyl(diethoxymethoxysilane), 1-Mercaptomethyl(dipropoxymethoxysilane), 1-Mercaptomethyl(trippropoxy) Silane), 1-mercaptomethyl(trimethoxysilane), 1-mercaptomethyl(dimethoxymethylsilane), 1-mercaptomethyl(methoxydimethylsilane), 1-mercaptomethyl(diethoxymethylsilane), 1-mercaptomethyl(ethoxydimethylsilane), 1,3-dimercaptopropyl(trimethoxysilane), 1,3-dimercaptopropyl(triethoxysilane), 1,3-dimercaptopropyl(tripropoxysilane), 1,3-dimercaptopropyl(tridodecanoxysilane), 1,3-dimercaptopropyl(tritetradecylsilane), 1,3-Dimercaptopropyl (trihexadecanoxysilane), 2,3-Dimercaptopropyl (trimethoxysilane), 2,3-Dimercaptopropyl (triethoxysilane), 2,3-Dimercaptopropyl (tripropoxysilane), 2,3-Dimercaptopropyl (tridodecanoxysilane), 2,3-Dimercaptopropyl (tritetradecanoxysilane), 2,3-Dimercaptopropyl (trihexadecanoxysilane), 3-Mercaptobutyl (trimethoxysilane), 3-Mercaptobutyl (triethoxysilane) mercaptobutyl(diethoxymethoxysilane), 3-mercaptobutyl(tripropoxysilane), 3-mercaptobutyl(dipropoxymethoxysilane), 3-mercaptobutyl(dimethoxymethylsilane), 3-mercaptobutyl(diethoxymethylsilane), 3-mercaptobutyl(dimethylmethoxysilane), 3-mercaptobutyl(dimethylethoxysilane), 3-mercaptobutyl(tridodecanoxysilane), 3-mercaptobutyl(tritetradecanooxysilane), 3-mercaptobutyl(trihexadecanoxysilane),3-mercaptobutyl(didodecanoxy)tetradecanoxysilane or 3-mercaptobutyl(dodecanoxy)tetradecanoxy(hexadecanoxy)silane. These compounds and the other compounds of formula I can be used individually or mixtures of compounds can be used.

[0053] Representative non-limiting examples that are preferred for use in the coating compositions include passivating agents that have a second functional group in / on the molecule. Thiol-functionalized polyacrylate oligomers and prepolymers with reactive unsaturation (thiol-functionalized urethane acrylates, polyester acrylates, amino acrylates, epoxy acrylates, etc.). Preferred examples include EBECRYL ultraviolet (UV) and electron beam (EB) energy curable prepolymers, e.g., mercapto-modified polyester acrylate resins. -Mercaptobenzotriazole, which has a thiol functional group on the triazole ring, fused to benzene thiol-functional silanes as described above, particularly 3-mercaptopropyltrimethoxysilane, and silanol-containing thiol precursors which upon hydrolysis produce thiol-functional silanes, such as, but not limited to, Dow Coming Z-6062, Momentive A-189, Evonik MTMO, HENGDA-M2133, SHinEtsu KBM-803, Wacker GF70, and Coatosil Tcure, silane oligomers of about 600-700 g / mol; Thiofunctional silanes, such as 2-(3-trimethoxysilylpropylthio)thiophene Thiols with polar functional groups in the molecule, such as ether moieties, hydroxyl functional groups, acid functional groups, etc., non-limiting examples include dithiothreitol, poly(ethylene glycol) methyl ether thiol, poly(ethylene glycol) 2-mercaptoethyl ether acetate, and · Azolic moieties containing silanes such as N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole.

[0054] Other preferred materials for use as at least one passivating agent (A) are compounds having an azolic moiety or azole compounds. Azolic functional compounds suitable for use as at least one passivating agent (A) may have a single azole moiety or multiple azole moieties, i.e., a single azole ring or multiple azole rings. Desirably, the number of azolic moieties per molecule is at least 1 and may be up to 10, and optionally, more than 10 azolic moieties per molecule may be used, provided that the additional functional groups do not interfere with the objectives of the present invention. Non-limiting examples of useful types of azole ring functional compounds include triazoles, imidazoles, triazines, tetrazoles and oxazoles, alone or thiol modified.

[0055] Non-limiting examples include substituted and unsubstituted benzotriazoles, mercaptobenzotriazoles including alkyl substituted benzothiazoles such as tolyltriazole, methylbenzotriazole, and the like.

[0056] Triazole chemicals such as tolyltriazole (TTA), benzotriazole (BZT), and mercaptobenzotriazole (MBT) are preferred as at least one passivator (A) for copper-containing traces. Triazole compounds form protective cuprous oxide (CuO) on the surface of the metal. 2 It is believed that the copper is passivated by forming an O) film.

[0057] Suitable thiol modified azoles include 2-mercaptobenzoxazole, benzothiazole, mercaptobenzotriazole, mercaptobenzothiazole, 2,5-dimercapto-1,3,4-thiadiazole, 2-amino-5-ethylthio-1,3,4-thiadiazole (AETD), 2-amino-5-ethyl-1,3,4-thiadiazole, 5-(phenyl)-4H-1,2,4-triazole-3-thiol, 5-mercapto-1-methyl-tetrazole, 5-mercapto(Na salt) ... Examples of 5-mercapto-1-acetic acid (Na salt)-tetrazole, 5-mercapto-1-phenyl-tetrazole (5Mc-1Ph-T), 5-phenyl-tetrazole (5Ph-T), 5-phenyl-tetrazole, 5-mercapto-1-phenyl-tetrazole (5Mc-1Ph-T), 5-aminotetrazole (5NH2-T), 5-(4'-dimethylaminobenzylidene)-2,4-dioxotetrahydro-1,3-thiazole, 2-mercaptobenzothiazole, 2-(octadecylthio)benzothiazole and combinations thereof.

[0058] Other suitable azoles include: 1,2,4-Triazoles and derivatives: 3-amino-1,2,4-triazole, 4-amino-1,2,4-triazole, 4-amino-4H-1,2,4-triazole-3thiol, 4-amino-5-methyl-4H-1,2,4-triazole-3thiol, 4-amino-5-ethyl-4H-1,2,4-triazole-3thiol, 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole, bis-(4-amino-5-mercapto-1,2,4-triazol-3-yl)-butane Imidazole and derivatives: 2-mercapto-1-methylimidazole, 4-methyl-1-(p-tolyl)-imidazole, 4-methyl-1-phenylimidazole, 4-methyl-1-(o-tolyl)-imidazole, benzimidazole, 2-mercaptobenzimidazole, 2-thiobenzylbenzimidazole, 2-thiomethylbenzimidazole, 5-methoxy-2-(octadecylthio)benzimidazole · Thiadiazoles and derivatives: 2,5-dimercapto-1,3,4-thiadiazole, 5-phenyl-1,3,4-thiadiazole-2-thiol, 2-(5-mercapto-1,3,4-thiadiazole-2-yl)-phenol, potassium 5-mercapto-3-phenyl-1,3,4-thiadiazole-2-thione, 5-phenyl-2-amino-1,3,4-thiadiazole, 5-(4-methoxyphenyl)-2-amino-1,3,4 -thiadiazole, 5-(4-nitrophenyl)-2-amino-1,3,4-thiadiazole, 5-methyl-[1,3,4]thiadiazol-2-ylsulfanyl)-acetic acid, (4-dimethylamino-benzylidene)-hydrazide, 2-amino-5-(4-pyridinyl)-1,3,4-thiadiazole, 1,2-dihydro-3-(octadecylthio)benzotriazine, 2,4,6-trimercapto-1,3,5-triazine (TMTA) Benzotriazole derivatives are also suitable, such as N-[benzotriazol-1-yl-(phenyl)-methylene]-biphenyl-hydrazine, N-[benzotriazol-1-yl-(4-methoxy-phenyl)-methylene]-N-phenyl-hydrazine, N-(2-thiazolyl)-1H-benzotriazole-1-carbothioamide, N-(furan-2-ylmethyl)-1H-benzotriazole-1-carbothioamide, N-benzyl-1H-benzotriazole-1-carbothioamide, 1-(2-thienylcarbonyl)-benzotriazole and 1-(2-pyrrolecarbonyl)-benzotriazole. Derivatives of benzotriazole, namely 5-pentyl-BTA, 5-chloro-BTA, N-[benzotriazol-1-yl-(phenyl)-methylene]-N-phenyl-hydrazine, N-[benzotriazol-1-yl-(4-methoxy-phenyl)-methylene]-N-phenyl-hydrazine, N-(2-thiazolyl)-1H-benzotriazole-1-carbothioamide, N-(furan-2-ylmethyl)-1H-benzotriazole-1-carbothioamide, N-benzyl-1H-benzotriazole-1-carbothioamide, 1-(2-thienylcarbonyl)-benzotriazole, 1-(2-pyrrolecarbonyl)-benzotriazole, are also desirable for use as the at least one passivation agent (A).

[0059] In a preferred embodiment, the coating provides a waterproof function to the coated circuit board of an electronic device such as a mobile phone, meaning it enhances water resistance. The passivator may be a solid or a liquid. In some embodiments, the passivator is preferably a liquid at ambient temperature, generally about 2°C to 100°C, preferably 10°C to 32°C. In some embodiments, the passivator may be chemically reactive with the film-forming polymer of the coating composition. Alternatively, in other embodiments, the passivator is non-reactive with the film-forming polymer of the coating composition, such that the passivator is dispersed in the polymer matrix of the coating and may advantageously migrate within the applied and dried coating. The mobility of the passivator allows it to interact with damaged traces, for example, after initiation of corrosion or physical damage due to the creation of new component connections, providing, for example, self-healing repassivation of metals.

[0060] The binder component (B) is a binder of the following types: B1) an organic or inorganic film-forming polymer that does not react with (A); B2) an organic or inorganic film-forming polymer capable of reacting with (A); B3) one or more polymer precursors, e.g., monomers, oligomers, and / or prepolymers, that are polymerizable on the substrate surface and are non-reactive with (A); B4) one or more polymer precursors, e.g., monomers, oligomers and / or prepolymers, capable of polymerizing on the substrate surface and reacting with (A). may include one or more of the following.

[0061] In some embodiments, the coating composition is deposited on the end-use article, e.g., an electronic component to be coated, or the coating composition forms a removable film, a removable backing, or a foam, etc. on a tape, which is later transferred to the end-use article, e.g., as a preform film.

[0062] (First binder type) The binder component (B) of the coating composition may comprise an organic or inorganic film-forming polymer that is non-reactive with the passivating agent. The film-forming polymer produces a physical, continuous and flexible film upon drying down and may be thermoplastic or thermosetting. In some embodiments, these film-forming polymers may have elongation values ​​of greater than 100%.

[0063] Suitable examples of film-forming polymers include polyesters, polyurethanes, polyolefins, olefin copolymers, (meth)acrylate copolymers, and combinations thereof that are non-reactive with the passivating agent in the coating composition.

[0064] In a preferred embodiment, a suitable type of olefin copolymer, i.e., made from olefin monomers, may be an ethylene-vinyl acetate copolymer (so-called EVA resin). Desirably, the weight ratio of ethylene to vinyl acetate monomer comprising the EVA copolymer may range from 95:5 to 50:50, with a preferred ethylene to vinyl acetate monomer ratio ranging from 60:40 to 80:20. This ratio may desirably be selected to compatibilize the EVA copolymer with the other components of the coating composition, thereby controlling the solubility of the EVA copolymer within the formulated coating. The ethylene to vinyl acetate monomer ratio may also be selected such that upon drying and / or curing of the coating composition, the composite coating is present with the passivating agent as a dispersed second phase within the polymer matrix of the dried coating.

[0065] Suitable types of (meth)acrylate copolymers for use as the film-forming polymer that is non-reactive with the passivating agent can be the reaction product of (meth)acrylate monomers and any other ethylenically unsaturated comonomers. Ethylenically unsaturated monomers and comonomers can be copolymerized to form (meth)acrylate copolymers by polymerization processes that are well known in the art. The resulting copolymers can include reaction products of various monomers, such as methacrylic acid monomers, methacrylate ester monomers, acrylic acid monomers, acrylate ester monomers, styrene monomers, α-methylstyrene monomers, acrylonitrile monomers, methacrylonitrile monomers, hydroxyl-functional methacrylate ester monomers such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and isobomyl (meth)acrylate. Particularly preferred (meth)acrylate esters include C1-C22 linear and branched alkyl esters. Preferred (meth)acrylate copolymers can be prepared from the monomers listed above and polymerized via free radical reactions involving alkyl esters of acrylic and methacrylic acid in the presence of a radical generator. Generally speaking, (meth)acrylate monomers having alkyl chain lengths of 2 to 18 carbons are preferred, with alkyl chain lengths of 4 to 8 carbons being particularly preferred.

[0066] Other film-forming polymers that are non-reactive with the passivating agent include polyesters, which are usually the reaction product of carboxylic acids and alcohol precursors, and polyurethanes, which are usually prepared from polyisocyanates and alcohol precursors. Non-limiting representative examples of polyesters include homopolymers and copolymers of epsilon-caprolactone. Non-limiting representative examples of polyurethanes include the reaction products of aliphatic polyisocyanates with hydroxide-functional reactants such as polyether alcohols and aliphatic alcohols, preferably having 2 or more moles of hydroxyl per molecule. Particularly preferred polyisocyanates include those based on hexamethylene diisocyanate. In general, when a hydrophobic, flexible polymer is desired, aliphatic precursors without ring structures are preferred.

[0067] (Second binder type) The binder component (B) of the coating composition may include organic or inorganic film-forming polymers that can react with the passivating agent. In some embodiments, it may be advantageous for the binder (thermosetting or thermoplastic) utilized to have functional groups that are reactive with the passivating agent. One preferred type of functional group is one that reacts with thiols. Non-limiting examples of thiol-reactive functional groups include epoxy, isocyanate, carboxylic acid, and -ene (C=C) bonds.

[0068] Similar to the first binder type, the backbone of the film-forming polymer can be polyester, polyurethane, polyolefin, olefin copolymer, (meth)acrylate copolymer, and combinations thereof, but with different functional groups than the first binder type, the second binder type can react with the passivating agent in the coating composition. Non-limiting examples of binders having one or more of these groups reactive with the passivating agent include isocyanate-terminated polyurethanes, polyester and (meth)acrylate copolymers containing ester linkages, carboxyl-terminated polyesters, ethylene acrylic acid copolymers, polyolefins containing unsaturation, e.g., polybutadiene, and copolymers of polybutadiene, such as copolymers of acrylonitrile and butadiene.

[0069] (The third binder type) Polymer precursors that form blocks to produce polymers, thereby forming a coating on a substrate, are useful as binders in the present invention. Thus, the binder component (B) of the coating composition may include one or more polymer precursors, e.g., monomers, oligomers, and / or prepolymers, that are polymerizable on the substrate surface and are not reactive to the passivating agent. In some embodiments, it is preferred to apply the coating composition to the substrate, i.e., PCB, followed by substantial polymerization to form a cured coating. Some polymerization after application of the coating composition to the substrate may occur prior to a curing step, e.g., exposure to UV or thermal energy. UV curing of one or more polymer precursors, e.g., monomers, oligomers, and / or prepolymers, is preferred. Any curing mechanism that is compatible with the components of the coating composition and produces a solid, adherent coating after curing may be used.

[0070] UV curable coatings are widely known in the art and may include (meth)acrylate monomers, i.e., acrylate and methacrylate monomers, and similar oligomers with functionality ranging from 1 to 10 or more ethylenic unsaturations per molecule. UV curable materials offer many advantages that are widely known in the art, such as the ability to cure and apply rapidly in the absence of solvents.

[0071] The UV-curable film-forming polymer precursor may comprise a mixture of monomers, oligomers, and / or polymer precursors with ethylenic unsaturation and photoinitiators. The binder polymer precursor may have one or more ethylenically unsaturated groups. Examples of suitable (meth)acrylate monomers, i.e., acrylate and methacrylate monomers with polymerizable double bonds that can be used to form both UV-curable and thermosetting polymer binders, include, but are not limited to, alkyl acrylates, alkyl methacrylates, hydroxyalkyl acrylates, hydroxyalkyl methacrylates, substituted alkyl acrylates or alkyl methacrylates such as 2-ethylhexyl acrylate or 2-ethylhexyl methacrylate, and other acrylates and methacrylates such as isobomyl acrylate and mixtures thereof.

[0072] Other suitable examples of (meth)acrylate monomers, i.e., acrylate and methacrylate monomers having multiple double bonds, include ethylene glycol diacrylate, propylene glycol diacrylate, diethylene glycol diacrylate, dipropylene glycol diacrylate, triethylene glycol diacrylate, tripropylene glycol diacrylate, tetraethylene glycol diacrylate, tetrapropylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, ethoxylated bisphenol A diacrylate, bisphenol diglycidyl ether diacrylate, resorcinol diglycidyl ether diacrylate, 1,3-propanediol diacrylate, 1,4-butanediol diacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, cyclohexanedimethanol diacrylate, ethoxylated neopentyl glycol diacrylate, propoxy and polymethacrylate functional monomers such as, but not limited to, ethylated neopentyl glycol diacrylate, ethoxylated cyclohexane dimethanol diacrylate, propoxylated cyclohexane dimethanol diacrylate, epoxy polyacrylates, aryl urethane polyacrylates, aliphatic urethane polyacrylates, polyester polyacrylates, trimethylolpropane tri(meth)acrylate, glycerol tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate triacrylate, ethoxylated glycerol tri(meth)acrylate, propoxylated glycerol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, melamine triacrylate, epoxy novolac triacrylate, aliphatic epoxy triacrylates, and mixtures thereof.

[0073] Preferred tetraacrylates that are suitable alone or in combination with the above monomers include, but are not limited to, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, propoxylated pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, ethoxylated dipentaerythritol tetra(meth)acrylate, propoxylated dipentaerythritol tetra(meth)acrylate, divinylbenzene, divinyl succinate, diallyl phthalate, triallyl phosphate, triallyl isocyanurate, tris(2-acryloylethyl)isocyanurate, aryl urethane tetra(meth)acrylate, aliphatic urethane tetra(meth)acrylate, polyester tetra(meth)acrylate, melamine tetra(meth)acrylate, epoxy novolac tetra(meth)acrylate, and mixtures thereof.

[0074] Other suitable multifunctional acrylates include, but are not limited to, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol octa(meth)acrylate, and mixtures thereof. These monomers can be used to form both UV-curable and thermosetting polymeric binders.

[0075] The coating composition can be a one-pot material or, if desired, can be applied in two or more parts that react together on the substrate to form the coating. Preferred embodiments include UV-curable coating compositions in which the passivating agent (A) utilized is substantially non-reactive with other components of the UV-curable coating composition before, during, or after application and curing.

[0076] (The fourth binder type) Another type of binder useful in the binder component (B) can be a binder comprising one or more polymer precursors that are polymerizable at the substrate surface and can react with the passivating agent, such as monomers, oligomers, and / or prepolymers. In some embodiments, it is preferred to effect substantial polymerization of the coating composition and, after applying the coating composition to a substrate, e.g., a PCB, to react the passivating agent with functional groups in the coating composition. For example, the monomers, oligomers and / or prepolymers can also contain functional groups reactive with the passivating agent. Non-limiting examples include binders polymerizable by UV energy having a functional group reactive with at least one of a thio functional group, preferably a thiol functional group, an azolic moiety or an azole. Typically, the UV curable polymer precursor has ethylenic unsaturation that can react directly with the thiol functional groups in the passivating agent. In a preferred embodiment, the passivating agent comprises a polythiol in which the ethylenic unsaturation present in one or more polymer precursors, e.g., monomers, oligomers and / or prepolymers of the binder (B), is reactive. During curing of a UV curable coating containing a polythiol, the attached thiol functional groups can be formed within the cured coating by reaction with the polymerizable monomers, oligomers and / or prepolymers. Non-limiting examples of thiol-reactive functional groups that can be present on the polymer precursor include epoxy, isocyanate, ene (C=C) bonds, and carboxylic acids.

[0077] In another embodiment, the passivator comprises a second functional group, different from and in addition to a thio functional group, an azolic moiety, or an azole. In this embodiment, one or more polymer precursors, e.g., monomers, oligomers, and / or prepolymers, capable of polymerization at the substrate surface are reactive with the second functional group. This occurs most frequently when utilizing UV-curable polymer precursors, as disclosed herein, that have ethylenic unsaturation reactive to the various second functional groups of the passivator. A non-limiting example of a passivator with a second functional group is vinyl imidazole, which has an azole moiety and a second functional group in the form of a vinyl group. The UV-curable polymer precursor comprises an ethylenic unsaturation that reacts with the vinyl functional group of the passivator upon exposure to UV curing conditions.

[0078] Other non-limiting examples of second functional groups with which the ethylenic unsaturation of the UV-curable polymer precursor of the binder can react include silane, hydroxyl and carboxyl functional groups. Non-limiting examples of materials having both thiol or thiol functional groups or azolic moieties and a different second functional group include thio and thiol functional groups, azolic moieties with silanes, hydroxyl-containing thiol compounds, and carboxyl-containing thiols. Non-limiting examples include 2-(3-trimethoxysilylpropylthio)thiophene, 3-mercaptopropyltrimethoxysilane, N-(3-triethoxysilylpropyl)-4,5-dihydroimidazole, 6-mercapto-hexanol and mercaptopropionic acid, respectively. UV-curable coating compositions that are widely known in the art are described elsewhere herein.

[0079] As disclosed herein, several types of binders may be used alone or in combination. The combination of passivator and binder provides metal passivation chemistry that supports performance at thinner coating layers. One aspect of the invention provides flexible coatings, typically based on a first and optionally a second binder type. These polymeric binders provide coating compositions that are free of all fluoro-based chemistry suitable for thermal drying / curing and provide low viscosity to allow the use of spray application processes. Primary polymer binders with elongation at break exceeding 1000% (ASTM D1708 (19 mm dogbone 1.3 mm thick) can be used. Coatings containing the first and second binder types can also be applied as peelable films. The resulting flexible coatings after drying / curing reduce leakage currents and visible corrosion compared to commercial benchmarks. Another aspect of the invention provides stiffer, less flexible coatings, typically based on the third and fourth binder types. These polymer binders provide coating compositions free of all fluoro-based chemicals and can provide solvent-free formulations. The resulting coating compositions are low viscosity such that a spray application process can be used and can be dual cured (e.g., ambient and UV or thermal). The resulting stiffer UV-cured coatings provide very low current leakage and visible corrosion, even after 30 minutes of submersion in saline electrolyte powered at 20V bias.

[0080] Desirably, the passivator and film-forming binder are compatible with and soluble in the solvent carrier and / or reactive diluent of the coating composition. In some embodiments, the passivator and film-forming binder may be selected such that upon drying, phase separation occurs, thereby forming a second phase within the composite coating in which the passivator is obtained. This second phase may be present as isolated globules or zones within the composite coating, or may exhibit stratified layers in the coating, including at least a first layer having a higher concentration of passivator and a second layer having a lower concentration of passivator. Surprisingly, it has been found that selecting a weight ratio of film-forming binder to passivator of about 100:1 to 1:100, and the solubility of the passivator in the binder or binder reaction product or matrix of the deposited coating to meet the above-specified criteria, allows for the selection of a coating morphology that remains two-phase adherent upon drying.

[0081] In some embodiments, it may be desirable to select the concentration of the passivator to be greater than the solubility limit of the passivator in the binder, such that a second phase of the reservoir of passivator is provided to the dried coating upon drying. Without wishing to be bound by theory, it is believed that such a second phase can act as a reservoir of the passivator within the coating, such that the passivator is available to contact corrosive or physical damage (e.g., corresponding to the initiation of corrosion) on the printed circuit board. This function may enable the coating to prevent or mitigate undesirable consequences of changes in the service environment. Examples of changes in the service environment include electronic devices, such as mobile phones, that contain coated PCBs that are in contact with or immersed in water or aqueous solutions, especially in a powered-on state. Without the coating features described in this embodiment, degradation pathways such as dendritic growth between traces and corrosive damage to the traces would cause catastrophic damage to the device.

[0082] In some embodiments, the water-resistant coating is applied to all conductive surfaces of the printed circuit board, including one or more connection surfaces. An electrical connection is established when the coated surfaces of the printed circuit board and the connector come into contact with sufficient force to deform or penetrate the coating. This process of intrusively establishing an electrical connection can be considered a change in the service environment, and the uniform presence of the passivator stored not only within the continuous phase of the coating matrix, but also within reservoirs or stratified layers within the coating, allows the coating to respond by migration of the passivator to areas of the coating that have been disturbed or damaged, where the passivator repassivates the disturbed or damaged coating / conductor interface. The present invention provides a coating composition and dried coating that allows PCB subunits to be repeatedly connected, disconnected, and reconnected while maintaining water-resistant performance.

[0083] The present invention is useful for coating selected surfaces of electronic components, such as circuit boards, particularly printed circuit boards (PCBs). A printed circuit board is a non-conductive material with conductive traces, also called "lines," "tracks," or "conductors," on the board. Electronic components, such as integrated circuits (ICs), resistors, capacitors, inductors and connectors, switches and relays, are attached to the board, with the traces connecting the components to form a working circuit or assembly. Depending on the number of components and the interconnection density, the board may be either single-sided (one signal layer on the top of the board), double-sided (two signal layers on the top and bottom of the board), or multi-layered (two or more layers). The components are interconnected by traces on the PCB surface, often embedded between layers of the board. If inadequately protected, corrosion or breakage of the traces can reduce the electrical conductivity along the trace paths and cause damage associated with electrochemical migration phenomena such as dendritic growth and conductive anodic filament formation.

[0084] Metals suitable for use as the metal surface of the trace include copper, iron, zinc, nickel, tin, lead, cobalt, titanium, molybdenum, ruthenium, palladium, rhodium and rhenium, mixtures thereof, alloys thereof, and mixtures of alloys thereof. A preferred metal article for coating includes a conductive metal trace attached to a substrate in accordance with the present disclosure, which may desirably include copper, zinc, iron, tin, lead, and mixtures thereof, alloys thereof, and mixtures of alloys thereof. Preferably, the metal is copper or a copper alloy. The metal trace may include, consist essentially of, or consist of copper, zinc, iron, mixtures thereof, alloys thereof, and mixtures of alloys thereof.

[0085] Carbon may be present as a layer on the metal surface of the PCB to augment or replace some or all of the metal components. In one embodiment, conductive carbon, such as graphene, graphite, etc., comprises at least a portion of the trace. In some embodiments, a conductive carbon-containing ink is used as a second layer on the metal trace to replace the gold plating of the trace. Conductive carbon-containing inks known in the art are typically carbon pigments, such as carbon black and / or other carbons as described above, dispersed in a thermosetting polymer medium. Examples of carbon uses are crossover connectors that allow for less complicated board manufacturing processes, connections where wear resistance is required (slide connections), and as a low-cost alternative to gold plating (often used in combination with copper).

[0086] The coating compositions and processes according to the present disclosure can also be applied to carbon-containing portions of PCBs, providing similar benefits as for metal traces.

[0087] In one embodiment, the substrate is a circuit board having metal traces attached thereto, preferably a printed circuit board useful in electronic devices. Typically, the circuits on a printed circuit board are printed using copper traces, aluminum traces, or other suitable conductive metals.

[0088] Suitable solvents useful in the present disclosure are organic solvents, which may optionally contain water, provided it does not interfere with the objectives of the present invention. Desirably, the solvent provides a single-phase solution or a readily dispersible mixture of the passivator and binder. Preferred types of solvents include ketones, aromatic hydrocarbons, aliphatic hydrocarbons, ethers, glycol ethers, glycol ether esters, esters, and alcohols. Non-limiting representative examples of useful solvents include methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl amyl ketone, toluene, xylene, pentane, hexane, heptane, monoalkyl ethers of propylene glycol, dialkyl ethers of propylene glycol, ethers of monoalkyl ethylene glycol, dialkyl ethers of ethylene glycol, monoalkyl ether acetates of propylene glycol, monoalkyl ethylene glycol, butanol, isopropanol, isobutanol, propyl acetate, butyl acetate, amyl acetate, isobutyl isobutyrate, butyl propionate, pentyl propionate, and other acetate ethers.

[0089] The coating composition may be solvent-free if desired. Therefore, the range of solvent amounts is generally quite broad and tends to vary depending on the application method and other components of the coating composition. As a general matter, organic solvents may be absent or present in amounts of only ppm for applications where one wishes to minimize the use of organic solvents, or may comprise up to 95% by weight of the coating composition, for example for immersion applications.

[0090] In a preferred embodiment, the coating composition is applied to an electronic component or tape, support, or backing by spraying and is later applied to a substrate for the end use. The preferred concentration of the solvent in the coating composition varies depending on the binder and passivating agent used, but generally varies between 40% and 90% by weight of the formulation. In another embodiment, the coating is applied by dipping. The preferred range in this case can vary between 75% and 95% by weight. In another embodiment, the coating composition is applied to a removable backing substrate and applied to circuit components as a laminated film or tape.

[0091] The amount of the non-solvent component is provided herein as the concentration of the relevant components in the formulation excluding the solvent, and this can be added by methods known to those skilled in the art. - The passivating agent can be present in the coating composition of the present invention in an amount of about 0.5% to about 55% by weight of the formulation, excluding the solvent. Within this range, desirably, the amount is at least, in order of decreasing priority, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16% by weight, and at least economically, in order of decreasing priority, 50, 47, 45, 43, 40, 38, 36, 34, 32, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17% by weight or less.

[0092] - The binder (film-forming polymer, polymer precursor, and combinations thereof) can be present in the coating composition of the present invention in an amount of about 25% to about 99% by weight of the formulation, excluding the solvent. Within this range, desirably, the amount is at least, in order of decreasing priority, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 61, 62, 63, 64, 65, 66% by weight, and at least economically, in order of decreasing priority, 97, 95, 92, 90, 88, 85, 83, 80, 78, 76, 74, 72, 70, 68% by weight or less.

[0093] -Optional additives may not be included in the coating composition. Alternatively, optional additives may be present in the coating composition of the present invention in an amount of about 0.01% to about 15% by weight of the formulation, excluding solvent. Within this range, the amount is desirably at least in order of preference 0.02, 0.04, 0.05, 0.07, 0.09, 0.1, 0.2, 0.4, 0.5, 0.7, 0.9, 1.0, 1.2, 1.5, 1.7, 2.0, 2.2, 2.5, 2.7, 3.0, 3.2, 3.5, 3.7, 4.0, 4.2, 4.5, 4.7, The solvent may be 5.0, 5.2, 5.5, 5.7, 6.0, 6.2, 6.4, 6.5, 6.7, 6.9, 7.0% by weight, and, at least economically, may be 14, 13, 12, 11, 10, 9.75, 9.50, 9.25, 9.0, 8.7, 8.5, 8.3, 8.0, 7.7, 7.5, 7.2% by weight or less, in order of decreasing priority. As mentioned above, the solvent may be absent from the coating composition. Alternatively, the solvent may be present in the coating composition of the present invention in a total amount of about 0.01% by weight to about 95% by weight. Within this range, desirably the amount may be, at least in order of increasing priority, 0.1, 0.5, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50 weight percent and, at least for economic reasons, up to 92, 90, 85, 80, 75, 70, 68, 65, 63, 60, 58, 55, 53 weight percent.

[0094] For each of the above identified components, amounts greater than the preferred amounts can be used within the scope of the present invention, provided that they do not interfere with the objectives of the present invention, such as by causing instability in the coating composition, etc.

[0095] Suitable olefinic monomers useful in the present disclosure are desirably soluble in the coating composition and / or the solvent present in the coating composition. The process according to the present disclosure can be carried out with a single olefinic monomer or a mixture of olefinic monomers.

[0096] The total monomer concentration in a coating composition according to the present disclosure may be, at least in order of preference, about 0.05, 0.1, 0.25, 0.5, 0.75, 1.0, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0% by weight, and may be, at least economically, about 7.0, 8.0, 9.0, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 75% by weight or less. Higher percentages of monomers may be used, provided that the increased amount does not prevent the benefits of the present invention from being obtained. In some embodiments, the total monomer concentration in a coating composition according to the present disclosure may desirably be 0.1 to 50% by weight, preferably 5 to 15% by weight, based on the total weight of the coating composition.

[0097] Optional components of the compositions and concentrates can be one or more additives such as waxes, adhesion promoters, flow modifiers, rheology modifiers, stabilizers, catalysts, photoinitiators, biocides, and biostats.

[0098] Optional additives may desirably be selected based on preferred electrical or dielectric properties specified in the conformal coating design of the end-use device, such as tablets, cell phones, etc. For example, where an additive may be selected for the end-use device for dielectric strength, a preferred wax additive may have a dielectric constant greater than 1, more preferably >2, and most preferably >4. Such additives may contain functional groups such as C=O, or -O- or -NH- or aromatic rings to provide specific dielectric properties to the conformal coating. Wetting agents and flow modifiers find utility within the present invention to promote thickness uniformity of the coating composition applied onto a substrate, such as a printed circuit board. Preferred examples include polydimethylsiloxane, polyether modified polydimethylsiloxane, and polydimethylsiloxane with functional groups including amine, carboxyl, or phosphorus-based acid moieties.

[0099] A suitably selected photoinitiator or combination of photoinitiators in the coating formulation absorbs in the peak wavelength band of a radiation source such as a mercury arc UV lamp and initiates polymerization to effect curing in the surface and bulk of the coating. Those skilled in the art of energy curable compositions, primarily for UV light, LED and visible light curable compositions, also know that the appropriate type of photoinitiator or photoinitiators can be combined with co-initiators, synergists or catalysts to significantly improve cure efficiency and performance. Preferably, the photoinitiator is present in the coating composition in an amount of from 1 to 6 weight percent, preferably at least 1, 1.5, 2, 2.5, or 3 and 6, 5.5, 5.0, 4.5, 4, 3.5 or 3 or less, based on the total weight of the UV curable material in the formulation.

[0100] Conventional free radical photoinitiators useful in the present invention are classified according to their chemical group and include, but are not limited to, (1) hydroxyacetophenones, (2) alkylaminoacetophenones, (3) benzil ketals and dialkoxyacetophenones, (4) benzoin ethers, (5) phosphine oxides, (6) acyloximino esters, (7) photoacid generators, (8) photobase generators, (9) 2,2-bis(2-chlorophenyl)-4,4,5,5-tetraphenyl-1,2-biimidazole (BCIM) and HABI, (10) benzophenones, (11) organosulfur compounds such as thiols, (12) substituted benzophenones, (13) benzoylformate esters, (14) anthraquinones, (15) camphorquinones, (16) oxime esters, (17) anthracene proxy radicals, and mixtures thereof. Specific examples of such photoinitiators include benzyldimethylamino-(4-morpholinophenyl)butanone-1, benzil dimethyl ketal, dimethoxyphenylacetophenone, a-hydroxybenzyl phenyl ketone, 1-hydroxy-1-methylethyl phenyl ketone, oligo-2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone, benzophenone, methyl orthobenzoyl benzoate, methyl benzoyl formate, 2,2-diethoxyacetophenone, 2,2-disecbutoxyacetophenone, p-phenylbenzophenone, non, 2-isopropylthioxanthene, 2-methylanthraquinone, 2-ethylanthraquinone, 2-chloroanthraquinone, benzyl, benzoin, benzoin methyl ether, benzoin isopropyl ether, a-phenylbenzoin, thioxanthone, diethylthioxanthone, 1,5-acetonaphthalene, 1-hydroxycyclohexyl phenyl ketone, ethyl p-dimethylaminobenzoate, titanocene, dibenzylidene ketone, 1,2-diketone, ketocoumarin, and mixtures thereof.

[0101] Exemplary free radical photoinitiators useful in the present invention are commercially available under trade names including: Irgacure® 184, Irgacure® 1173, Omnirad 102, Esacure KIP 150, Esacure KIP EM, Irgacure® 2959, Omnirad 669, Irgacure® 127, Irgacure® Micro-PICS, Esacure ONE, Irgacure® 907, Quadracure MMMP-3, Irgacure® 369, Omnipol 910, Quadracure BDMD-3, Irgacure® 379, Benzyl Dimethyl Ketal (BDK), Irgacure® 651 (DMPA), Diethoxyacetophenone (DEAP), Vicure® 10, Lucirin® TPO, Lucirin® TPO-L, Irgacure® 819, BAPO, Speedcure® PDO, Irgacure® PAG (103, 203, 108, 121), Irgacure® oxe01, Irgacure® oxe02, Esacure 1001M, Trigonal PI, Sandoray® 1000, Phenyl Tribromomethyl Sulfone (BMPS), Trichloromethyl-S-Triazine, O-Nitrobenzyl Carbamate, Ciba PLA-1, Irgacure® 907, Darocure® 1173, Ciba PLA-2, Speedcure® MBP, Esacure TZT, Genocure® MBB, Uvecryl® P36, Omnipol BP, Genopol BP-1, Speedcure® 7005, Goldcure 2700, Trigonal 12 (PBZ) (4-Phenylbenzophenone), Goldcure 2300, Speedcure® BMS, Esacure 1001M (sulphonylketone), Irgacure® MBF and Genocure® MBF, TX-A, Irgacure® 754 and 2-Ethylanthraquinone.

[0102] One skilled in the art of energy curable formulations can substitute cationic photopolymerizable monomers or oligomers for the free radical photopolymerizable components of this example. Conventional cationic photoinitiators potentially useful in such inventions are classified according to chemical group and include, but are not limited to, (1) sulfonium salts, (2) iodonium salts, (3) ferrocenium salts, and mixtures thereof.

[0103] Typical commercial examples of cationic photoinitiators useful in such inventions are Irgacure® 250, Irgacure® 270, Irgacure® PAG290, Irgacure® GSID26-1, QL cure 211, QL cure 212, SP150, Sp170, Omnicat 550, Imnicat 555, Omnicat 650, Esacure 1187, Irgacure MacroCat, Hycure 810, Uvacure® 1600, Sarcat CD 1012, Omnicat 440, Omnicat 445, Irgacure® 250, UV 9310, Rhodorsil 2047, Rhodorsil® 2076, Irgacure® 261, Omnicat 320, Omnicat 430, Omnicat 432, Speedcure® 937, Speedcure® 938, Speedcure® 976 and 992.

[0104] Molecular or polymeric coinitiators, synergists and catalysts useful in the present invention are classified based on chemical group and include, but are not limited to, (1) primary, secondary and tertiary amines, (2) amides, (3) alpha amino acids, (4) thioxanthones, (5) thiols and mixtures thereof. Specific examples useful in the present invention include, but are not limited to, 2-ethylhexyl-p-dimethylaminobenzoate, ethyl 4-(dimethylamino)benzoate, trimethylolpropane tris(3-mercaptopropionate), methyldimethanolamine, poly(ethylene glycol)bis(p-dimethylaminobenzoate), polyethylene glycol-di(B-(4(pacctylphcnyl)piperazine))propionate, and mixtures thereof.

[0105] Commercially available examples of coinitiators, synergists and catalysts useful in the present invention include, but are not limited to, Genocure® EHA, Genocure® EPD, Genocure® MEDA, Speedcure® DMB, Speedcure® EDB, Omnirad IADB, Omnipol ASA and Omnipol SZ, ITX (isopropylthioxanthene), Kayacure DETX (diethylthioxanthone), Speedcure® CTX (chlorothioxanthone), Kayacure RTX (dimethylthioxanthone), Kayacure DITX (diisopropylthioxanthone), Speedcure® CPTX (1-chloro-4-propoxythioxanthone), Omnipol TX, Genopol TX-1.

[0106] Adhesion promoters find utility within the present invention to improve adhesion of an applied coating to a substrate such as a printed circuit board. Preferred examples often have functional groups such as amines, thiols, carboxyls, and phosphorus-based acids to provide adhesion of the coating to the metal traces or backing substrate.

[0107] In one embodiment, the coating composition is provided as a concentrate comprising a passivator, at least one binder component, and, optionally, sufficient solvent to homogeneously dissolve and / or disperse the passivator and binder components to achieve a stable concentrate that does not tend to separate into separate liquid phases or form solid precipitates visible to the human eye, and the separated liquid phases are not readily reincorporable after storage at 25° C. for at least one month. The concentrate can be formulated to be diluted with a solvent to form a working concentration, or alternatively, as a bath replenisher known in the art to supplement a previously formed bath. Alternatively, the coating composition can be provided as a ready-to-use solution.

[0108] The process of making the coating compositions of the present disclosure includes dissolving and / or dispersing the passivator and binder components in at least one of a solvent or reactive diluent. The coating composition components are stirred together in a container to form a bath, for example from a single component, a separate combination of two or more of the components, or a coating composition concentrate.

[0109] This disclosure demonstrates a method for water-resistant coating of a substrate, particularly a printed circuit board. The process is fast, efficient, and adaptable to a variety of substrates and metal traces. In one embodiment, for example, a method for forming a polymer film on a substrate to waterproof a circuit board according to the present disclosure includes: a) applying a coating composition as described herein to a surface of a substrate, optionally including one or more conductive traces attached thereto, preferably the substrate is an electronic component, more preferably a circuit board, most preferably a printed circuit board; b) drying the coating composition on the substrate surface; c) optionally UV curing the coating composition on the substrate surface; d) during any of steps a)-c), reacting available reactive functional groups of the binder component (B) and the passivator (A) with the coating composition components and optionally the conductive traces, preferably the metal traces, thereby depositing a water insoluble passivated polymer film on the substrate surface.

[0110] A coated substrate according to the present disclosure includes at least one metal trace attached to a substrate and a passivating polymer coating on at least one surface of the metal trace. In one embodiment, the substrate is a non-conductive material and the metal trace is a conductive material, preferably a printed circuit board.

[0111] The thickness of the passivating polymer coating layer may range from about 0.2 to about 40 microns, depending on the binder selected and the environment of use, from about 0.6 to 3.8 microns, such as ultra-thin coating applications, less than 0.6 to 12 microns, 8 to 15 microns or 11 to 25 microns, or even 40 microns or more for certain applications such as strippable coatings, provided that the thickness does not interfere with the performance of the coating layer. Within this range, desirably the coating thickness may be, at least in increasing order of preference, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.9, 1.0, 1.2, 1.5, 1.7, 2.0, 2.2, 2.4, 2.5, 2.7, 3.0, 3.2, 3.5, 3.7, 3.8, 4.0, 4.2, 4.5, 4.7, 5.0, 5.2, 5.5, 5.7, 6.0, 6.2, 6.4, 6.5, 6.7, 6.9, 7.0 microns, and, at least economically, in increasing order of preference, 40, 35, 30, 25, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9.75, 9.50, It can be 9.25, 9.0, 8.7, 8.5, 8.3, 8.0, 7.7, 7.5, 7.2 microns or less. In one embodiment, for ultra-thin coatings, the thickness ranges from about 700 nm to about 1600 nm.

[0112] The coatings formed according to the present disclosure are water resistant, meaning that they are resistant to immersion for at least 30 minutes under water or an aqueous electrolyte, such as saline or artificial sweat, while power is applied. The coatings also significantly reduce the formation of dendrites between adjacent metal traces on the substrate. Dendrite formation is a problem in existing systems, and can lead to circuit failure due to the formation of a short circuit between two traces through a dendrite. Using the process of the present disclosure, a coating is obtained that reduces the formation of dendrites between traces on a test circuit board. When tested as described in the examples below, preferably no dendrites are formed. This is far below the large number of dendrites formed during this testing using conventional coating processes.

[0113] Prior to the coating step utilizing the coating composition according to the invention, at least a portion of the substrate to be coated, e.g., the metal surface of the metal traces, can be cleaned using any method known in the art for removing contaminants from metal surfaces, such as solvent cleaning, cleaning with fluoro-based fluids, or plasma methods. The substrate surface can also be rinsed prior to coating, either with water alone or with a pre-rinse solution containing one or more substances that can further improve the performance, e.g., adhesion, water resistance, etc., of the polymer coating subsequently formed on the substrate surface, including the metal traces. A so-called pre-conditioning treatment can be employed, although coating processes without a pre-conditioning step are also suitable.

[0114] Within this specification, the embodiments have been described in a manner that makes it possible to write a clear and concise specification, but it is intended and will be understood that the embodiments may be variously combined or separated without departing from the invention, For example, it will be understood that all preferred features described herein are applicable to all aspects of the invention described herein.

[0115] In some embodiments, the invention described herein can be construed to exclude any element or process step that does not materially affect the basic and novel characteristics of the composition, article, or process. Further, in some embodiments, the invention can be construed to exclude any element or process step not specified herein.

[0116] Although the present invention has been illustrated and described herein with reference to specific embodiments, the present invention is not intended to be limited to the details shown. In the experiments disclosed herein, a selected passivation agent was used in an exemplary manner to deposit a passivating polymer coating on a printed circuit board, thereby passivating the metal traces on the board. This is only one example of an article that can benefit from the coating of the present invention. Rather, various modifications in the details can be made within the scope and range of equivalents of the claims without departing from the present invention. The exemplary embodiments are provided so that this disclosure will be thorough and fully convey the scope to those skilled in the art. Numerous specific details are shown, such as examples of specific components, devices, and methods, to provide a thorough understanding of the embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be used, that the exemplary embodiments can be embodied in many different forms, and neither should be construed as limiting the scope of the present disclosure. In some exemplary embodiments, well-known processes, well-known device structures, and well-known technologies have not been described in detail. EXAMPLES

[0117] (Test board) Unless otherwise noted herein, the test boards were commercially available, IPC-Association Connecting Electronics Industries (formerly Institute for Printed Circuits, also known as IPC) approved PCB-B-25A test printed circuit boards (PCBs). These test printed circuit boards were IPC / Surface Mount Technology Association (SMTA) compliant and met the guidelines for use in solder mask (IPC-SM-804C) and conformal coating (IPC-CC-830A) testing. Each test printed circuit board was a 1.6 mm (0.062 in) thick FR-4 grade glass-reinforced epoxy laminate and was a simple print-and-etch with bare copper traces that did not form a complete circuit, i.e., no current would flow through the PCB-B-25A without a corrosion-induced conductive electrical path, i.e., no short circuit. The grid of the PCB-B-25A used in testing was Grid F.

[0118] (UV curing parameters) Unless otherwise stated herein, test substrates coated with a UV curable coating composition, whether by a single or multi-step coating application process, were UV cured using a conveyor equipped with an H+ bulb. The UV energy source provided sufficient curing energy to the substrate surface to cure the coating. Depending on the initiator used, at least one of the following energy levels was provided, as a minimum, as known in the UV coating art:

[0119] [Table 1]

[0120] (Water resistance test) The effectiveness of the coating in providing water resistance to example printed circuit boards was tested as follows: The coated test circuit board was connected to a voltage supply in the OFF position, immersed in water or an electrolyte solution ("artificial sweat"), and then a voltage was applied for 30 minutes. Unless otherwise stated herein, saline electrolyte refers to artificial sweat. The composition of the artificial sweat is as follows: 100ml DI 5g NaCl 5g Na 2 HPO 4 -12H 2 O 2ml 99% acetic acid

[0121] Formation of a Short Circuit: A voltage is selected for testing between 3 and 30V and is kept constant for the duration of the test. If no complete circuit exists, no current will flow. As degradation based on corrosion of the conductive traces begins, the current reading will increase from zero, creating a short circuit and allowing current to flow. During the 30 minute immersion, an in-line ammeter is used to detect current leakage from the charged printed circuit board by measuring the current passing through the circuit during the test period, less current observed is good. Readings were taken every second for 30 minutes. The average current reported (mA) is the average of the current measured over the entire 30 minute experiment. The maximum current reported (mA) is the single maximum current value observed during the 30 minute experiment.

[0122] Dendrite and Oxide Formation: Coating performance was also judged by the number of dendrites or bulk oxide formation visible at 12x magnification between and on the traces after testing. Fewer dendrites and less oxide indicate better performance, while dendrite and visually observable oxide formation are indicators of corrosion. Separate rating scales are employed for each of dendrite and oxide formation. For dendrites, the scale is represented by letters A-D, where A indicates no dendrites formed and increasing to D indicates widespread dendrites between all traces in the test area. Oxide formation is represented by numbers 0-4, where 0 indicates no oxide formation in the test area and increasing to 4 indicates widespread oxide formation on more than 100% of the traces in the test area.

[0123] (Example 1) In this example, five different coating compositions were made using the ingredients shown in Table 1-1 below. [Table 2]

[0124] A coating composition containing the components and amounts specified in Table 1-1 was prepared by the following procedure: 40% VA EVA polymer was dissolved in the first solvent listed with stirring at a temperature of 70° C. The second solvent was then added, followed by the addition of the specified thiol. Stirring was continued until the coating composition was clear with no visible solids.

[0125] The coating composition was then sprayed onto the printed circuit board using an air-pressurized paint spray gun. The gun pressure and number of spray passes were adjusted to achieve a coating thickness of 8-15 microns. The board was then heat cured at 90°C for 15 minutes, followed by 120°C for 10 minutes.

[0126] These coated printed circuit boards were then subjected to the water resistance tests described above at biases of 3, 12, and 30 V in distilled water and at a bias of 20 V under the artificial sweat solution described in the Water Resistance Test, with the results reported in Table 1-2 below.

[0127] For the coating compositions in Table 1-1, the effect of solvent and EVA to thiol ratio on corrosion was measured and is shown in Table 1-2. [Table 3]

[0128] The toluene / xylene solvent system performed worse than the MIBK / PMA system, with a 50:50 ratio of EVA to thiol providing the greatest effect.

[0129] (Example 2) A coating composition containing the ingredients in Table 2-1 in the amounts specified was prepared by the following procedure: The specified EVA polymer was dissolved in the first solvent listed with stirring at a temperature of 70° C. The second solvent was then added, followed by the addition of the specified thiol. Stirring was continued until the coating composition was clear with no visible solids.

[0130] The study also included a commercially available UV-cured urethane acrylate product as a comparative example that was deposited at a typical coating thickness of 50 microns and a lower than recommended usage thickness of 12 microns. [Table 4]

[0131] The coating compositions, other than the comparative commercial products, were then sprayed onto the printed circuit boards using an air pressurized paint spray gun. The gun pressure and the number of spray passes produced were adjusted to produce coating thicknesses between 8 and 15 microns. The boards were then heat cured at 90°C for 15 minutes, followed by 120°C for 10 minutes. The commercial products were applied and cured to thicknesses of 12 microns and 50 microns.

[0132] These coated printed circuit boards were then subjected to the above water resistance tests at biases of 3, 12, and 30 V in distilled water and at a bias of 20 V under the artificial sweat solution described in the water resistance test, with the results shown in Table 2-2 below. [Table 5]

[0133] The effect of solvent and EVA to thiol ratio on corrosion was measured for the coating compositions in Table 2-1 and is shown in Table 2-2. The results show that multiple variations of the present invention perform better at lower coating thicknesses of 8-15 microns than commercial products that require higher coating thicknesses for good corrosion performance.

[0134] FIG. 1 shows a graph of leakage current test results from test PCB boards coated according to Example 1: Formulation 2D and Comparative Example 1: Formulation PC40 12u for a 30 minute water resistance test in 30V water. The amount of leakage current is measured in 1 second increments over the period, with less being better. Graph line markers are provided at 50 second intervals. The test PCB of Comparative Example 1 had a measured current leakage that rose rapidly over the 30 minute test period. In contrast, Example 1 had a current leakage of less than 1 / 10,000 of 1 mA. FIG. 1 shows this negligible level of leakage as a flat line close to zero.

[0135] Within the scope of the invention variations, the 40% vinyl acetate EVA polymer performed best under the conditions found in the previous example with a 50:50 EVA to thiol ratio using MIBK / PMA solvent, however the 25% vinyl acetate EVA polymer performed best with other solvents at the highest EVA thiol ratio, indicating that these conditions must be tailored to the polymer of choice.

[0136] (Example 3) Coating compositions containing the ingredients and amounts specified in Table 3-1 were prepared by the following procedure: 40% VA EVA polymer was dissolved in the first solvent listed with stirring at a temperature of 70° C. The second solvent was then added, followed by the addition of the specified thiol, triazole, or other additive. Stirring was continued until the coating composition was clear with no visible solids. [Table 6] The coating composition was then sprayed onto the printed circuit board using an air-pressurized paint spray gun. The gun pressure and the number of spray passes produced were adjusted to produce a coating thickness of 8-15 microns. The board was then heat cured at 90°C for 15 minutes, followed by 120°C for 10 minutes.

[0137] These coated printed circuit boards were then subjected to the above water resistance tests in distilled water at a bias of 30 V and under the artificial sweat solution described in the water resistance test at a bias of 20 V, with the results shown in Table 3-2 below. [Table 7]

[0138] The effect of changing the thiol to other small molecules for the coating compositions in Table 3-1 was measured and is shown in Table 3-2. The Vitamin E system performed very poorly, indicating that the (thiol / triazole) may not be the only reducing agent. The thiol and triazole were effective.

[0139] (Example 4) A coating composition containing the ingredients and amounts specified in Table 4-1 was prepared by the following procedure: 40% VA EVA polymer was dissolved in the first solvent listed with stirring at a temperature of 70° C. The second solvent was then added, followed by the addition of the specified thiol. Stirring was continued until the coating composition was clear with no visible solids. This study also includes a comparative example of a commercial product, as shown in Example 2, with a typical coating thickness of 50 microns. [Table 8]

[0140] The test circuit boards had polyamide masking tape applied over a portion of the test area as a mask. The coating composition was then sprayed onto the printed circuit board using an air-pressurized paint spray gun. The gun pressure and the number of spray passes produced were adjusted to result in a coating thickness of 8-15 microns. The boards were then heat cured at 90°C for 15 minutes, followed by 120°C for 10 minutes. Commercial products were applied and cured according to the recommended directions for use.

[0141] After curing, the mask was removed to expose uncoated test areas on the circuit board to simulate repair. Formulation IB from Example 1 was then applied to these exposed areas via a spray gun as described above, and was applied to the exposed areas of all boards regardless of the original formulation used to coat the board, and dried at 90°C for 15 minutes, followed by 120°C for 10 minutes.

[0142] These printed circuit boards with repaired coatings were then subjected to the water resistance tests described above, specifically, the repaired areas were tested at 30V bias under distilled water and at 20V bias under an artificial sweat solution also described in the water resistance tests. The tests and results are shown below in Table 4-2. [Table 9]

[0143] For repaired coated substrates, the effectiveness of the repair is determined and is displayed in Table 4-2. The repaired areas performed better in the 30V distilled water test. Both offered protection in the 20V artificial sweat test, but not to the same standard as the 30V distilled water.

[0144] (Example 5) A coating composition containing the ingredients in Table 5-1 in the amounts specified was prepared by the following procedure: 40% VA EVA polymer was dissolved in the first solvent listed with stirring at a temperature of 70° C. The second solvent was then added, followed by the addition of the specified thiol. Stirring was continued until the coating composition was clear with no visible solids. [Table 10]

[0145] The printed circuit board was then immersed in the coating composition while held vertically. The board was allowed to dry at room temperature for 1 hour and then thermally cured at 90° C. for 15 minutes, followed by 120° C. for 10 minutes. The thickness of the coating was determined to be 3.8 microns.

[0146] These coated printed circuit boards were then subjected to the water resistance tests described above at 30 V bias in distilled water and 20 V bias in an artificial sweat solution also described in the water resistance tests. For the coating compositions of Table 5-1, the effect of dip application was determined and is shown in Table 5-2. [Table 11]

[0147] Paint application was shown to be protective, but not as protective as spray application.

[0148] (Example 6) A coating composition containing the ingredients in Table 6-1 in the amounts specified was prepared by the following procedure: 40% VA EVA polymer was dissolved in the first solvent listed with stirring at a temperature of 70° C. The second solvent was then added, followed by the addition of the specified thio compound. Stirring was continued until the coating composition was clear with no visible solids. [Table 12]

[0149] The coating composition was then sprayed onto the printed circuit board using an air-pressurized paint spray gun. The gun pressure and the number of spray passes produced were adjusted to produce a coating thickness of 8-15 microns. The board was then heat cured at 90°C for 15 minutes, followed by 120°C for 10 minutes.

[0150] These coated printed circuit boards were then subjected to the water resistance test described above in distilled water at a bias of 30 V and in an artificial sweat solution described in the water resistance test at a bias of 20 V.

[0151] The effect of changing the thiols to other small molecules for the coating compositions in Table 6-1 was measured and is shown in Table 6-2. Thiophenes were found to be effective. [Table 13]

[0152] (Example 7: UV-curable coating composition) Coating compositions containing the materials and amounts specified in Tables 7-1 and 7-2 were prepared as follows: Component 7A was prepared by combining the materials listed in Table 7-1 and mixing until a clear solution was obtained. [Table 14]

[0153] Component 7B was prepared by combining the materials set forth in Table 7B by simple mixing. [Table 15]

[0154] Component 7A was used as a precoat layer over which Component 7B, a UV curable coating mixture, was applied. Component 7A was sprayed onto a test printed circuit board using an air pressurized paint spray gun, followed by drying for 5 minutes at ambient temperature (approximately 25°C) to form an amine precoat layer, which measured 0.6 g / m2 after drying.

[0155] Component 7B was then applied onto the precoat layer and allowed to dry for 10 minutes at ambient temperature, after which the Component 7A / B coating was UV cured using a conveyor equipped with an H+ bulb as described in the UV cure parameters above. The total cured coating thickness of the combined layers was 25 microns.

[0156] A set of coated printed circuit boards were then subjected to the water resistance test described above, the first set at 30V in distilled water and the second set at 20V under saline electrolyte, with the results shown in Table 7-3 below. [Table 16]

[0157] (Example 8: UV-curable coating composition for forming an ultra-thin coating layer) Coating Composition 8, containing the materials and amounts specified in Table 8-1, was prepared by combining the materials with mixing to achieve a uniform mixture. [Table 17]

[0158] The coating composition of Example 8 was sprayed onto a printed circuit board using an air pressurized paint spray gun, followed by drying at 70° C. for 10 minutes, and then UV cured under UV curing parameters on a conveyor equipped with an H+ bulb according to the UV curing procedure described herein. After drying and curing, the thickness of the applied coating was measured to be 900 nm.

[0159] The coated printed circuit boards were then subjected to the above water resistance test in distilled water at 3V, with the results shown in Table 8-2 below. [Table 18]

[0160] (Example 9) UV-curable coating composition for forming an ultra-thin coating layer Coating Compositions 9A and 9B containing the materials and amounts specified in Table 9-1 were prepared by mixing and combining the materials to achieve a uniform mixture. [Table 19]

[0161] Coatings 9A and 9B were sprayed onto printed circuit boards with an air pressurized paint spray gun, then dried at ambient temperature (approximately 25° C.) for 5 minutes and heat dried at 70° C. for 10 minutes, after which the dried coatings were UV cured on a conveyor equipped with an H+ bulb according to the UV curing procedure described in UV Curing Parameters. After drying and curing, the thicknesses of the applied coatings were measured to be 704 nm and 1570 nm, respectively.

[0162] The coated printed circuit board was then subjected to a water resistance test in water with an applied bias of 3V as described in Table 9-2 below. [Table 20]

[0163] (Example 10 - Effect of additives) Formulations using mercaptoalkoxysilane oligomers provide a thiol functional group and a silane second functional group on the same molecule. Upon hydrolysis, the thiol-containing silanol precursor produces a thiol-functional silane, thereby advantageously providing a film-forming polymer useful as both a passivator and binder component. Concentrates were prepared as shown in the table below. [Table 21]

[0164] The concentrated formulations above were diluted with butyl acetate to achieve a sprayable concentration of coating composition for use with an air pressurized paint spray gun. Each coating composition was sprayed onto a printed circuit board, followed by drying at ambient temperature (approximately 25° C.) for 5 minutes, and then heat drying at 126° C. for 5 minutes.

[0165] The coated printed circuit board was then subjected to a water resistance test in water with an applied bias of 3V as described in Table 10-2 below. [Table 22]

[0166] (Example 11 Plug and Play Example)

[0167] The following examples provide conformal coating compositions and coated PCBs with coating films of selected hardness. Coating solutions containing the ingredients and amounts specified in Table 11-1 were prepared as follows: The materials were dissolved in solvents in the order listed. Formulations with low and high passivation levels were used to prepare examples of tunable adhesion. Formulations were applied using a conventional air pressurized spray gun.

[0168] Adhesion Test Adhesive Peel: Adhesion was tested by first placing an adhesive masking layer on top of the coating for the 20V sweat test (see next section for details). After the sweat test, the adhesive masking was removed. If the waterproof coating was completely removed by the action of pulling on the adhesive masking layer, the coating is considered peelable. Note whether the coating has good adhesion or not. Good adhesion: the coating was not removed with the masking agent. Partial peeling: Part of the coating was removed with a masking agent. Peelable: The entire coating could be peeled off from the PCB.

[0169] Crosshatch: A 1mm crosshatch is made on the copper and on the PCB. 100% of the coating remains on the PCB. No: 0% of the coating remains on the PCB.

[0170] This removability is useful for reworking the PCB. As the results in Table 11-2 show below, the coatings show either good adhesion at low thiol levels (Examples 11D, 11F, 11H) or partial strippability at very high thiol levels (Examples 11A, 11B, 11C, 11E, 11G). The comparison does not have tunable adhesion.

[0171] The coating film has viscoelastic properties and passivation activity, both of which contribute to providing a water-resistant connection to the conductive surface of the PCB in the presence of a coating layer at the interface between the separate connector and the PCB conductive surface. In some embodiments, the conductor penetrates the conformal coating, thereby establishing an electrical connection with the PCB that is a water-resistant electrical connection. In other embodiments, it is not necessary to drill holes in the conformal coating to achieve an electrical connection with the PCB that is a water-resistant electrical connection.

[0172] Due to the modified coating hardness and passivation agent, the coatings of the present disclosure are suitable for use as plug-and-play waterproof electrical connections. Plugging in the electrical conductivity of the coating allows for easy addition of electronic components, e.g., microchips or other components, to a PCB by drilling and / or simply inserting with low force into empty connection points on the PCB, while maintaining the electrical conductivity and water resistance of the dried conformal coating.

[0173] [Table 23]

[0174] Plug and play refers to a coating that allows electrical components to be easily and with low force pressed into a device for assembly, aiding in rapid repair processes in manufacturing, rework, and service environments. This allows for faster and less expensive manufacturing of circuit boards and consumer electronics. Examples of microchips with I / O (input / output) pins that act as piercing connections through conformal coatings are known in the art, typically using pin-type metal connectors for assembly on a PCB.

[0175] [Table 24]

[0176] The test results are shown in Table 11-2. The tests measured characteristics of the cured conformal coatings such as voltage withstand limits, adhesion and force required to penetrate the cured layer sufficiently to establish an electrical connection to evaluate their suitability for use as plug-and-play type coatings, as well as corrosion resistance and average and maximum current carry tests.

[0177] A 12 micron thick coating of Example 11F containing polycaprolactone (PCL), used to enhance the dielectric breakdown strength of the coating, was examined using a Zeiss LSM800 confocal microscope using polarized light. Figure 2 is a confocal image at 10x magnification using polarized light of a printed circuit board coated according to Example 11F at a thickness of 12 microns. The polycaprolactone appears as bright spots in the coating that can be seen using polarized light from the confocal microscope. The polycaprolactone is distributed across the entire surface of the printed circuit board. Example 11F at a thickness of 12 microns exhibited 100% adhesion, a voltage withstand limit of 3000 volts, and excellent corrosion resistance and current carrying capability. Dielectric strength is an essential property of plastic insulators, providing excellent protection of devices against components under high voltage.

[0178] (Example 12) This study examines the effects of three flow modifier additives and some of their combinations with each other. Coating solutions containing the ingredients in Table 12-1 and in the amounts specified were prepared by the following procedure: The specified polyester polymer was dissolved in the solvent with stirring at a temperature of 70°C. The thiol was then added, followed by the remaining ingredients. Stirring was continued until the coating solution was clear with no visible solids.

[0179] [Table 25]

[0180] The coating solution was sprayed onto the printed circuit boards with an air-pressurized paint spray gun. The gun pressure and number of spray passes were adjusted to achieve a coating thickness of 8-15 microns. The boards were then heat cured at 90°C for 15 minutes, followed by 120°C for 10 minutes.

[0181] These coated printed circuit boards were then subjected to the water resistance tests described above at 18 and 30 V bias in distilled water and at 20 V bias under an artificial sweat solution as described in the Water Resistance Test.

[0182] The effect of flow modifiers and their combinations for the coating solutions in Table 12-1 are shown in Table 12-2. Both formulations 12B and 12D have similar excellent performance, both with flow modifiers.

[0183] [Table 26]

[0184] The foregoing disclosure is written in accordance with relevant legal standards, and the description of the embodiments is provided for illustrative purposes, and therefore the description is exemplary rather than limiting in nature. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but may be interchangeable, where applicable, and may be used in selected embodiments even if not specifically shown or described. The same can also be varied in many ways. Such variations should not be considered as departures from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

[0185] The terms used herein are for the purpose of describing particular exemplary embodiments only and are not intended to be limiting. As used herein, the singular forms "a," "an," and "the" may be intended to include the plural unless the context clearly indicates otherwise. The terms "comprises," "comprising," "including," and "having" are inclusive and thus specify the presence of a stated feature, integer, step, operation, element, and / or component, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The steps, processes, and operations of the methods described herein should not be construed as necessarily requiring performance in the particular order described or illustrated, unless specifically identified as an order of performance. It should also be understood that additional or alternative steps may be employed.

[0186] Variations and modifications to the disclosed embodiments will be apparent to those of ordinary skill in the art and are within the scope of this disclosure. Thus, the scope of legal protection given to this disclosure can only be determined by studying the following claims.

Claims

1. A) at least one dissolving and / or dispersing passivating agent comprising a molecule containing a thio functional group and an azole functional group; B) at least one dissolved and / or dispersed binder component comprising an organic or inorganic film-forming polymer comprising a copolymer of an olefin monomer and a vinyl ester monomer and / or one or more polymer precursors polymerizable on the substrate surface comprising an olefinic monomer, the film-forming polymer and / or the one or more polymer precursors being either 1) reactive with (A) or 2) non-reactive with (A); At least one of the dissolved and / or dispersed binder components does not contain a fluorine atom-containing polymer. and C) optionally one or more dissolution and / or dispersion additives selected from waxes, adhesion promoters, flow modifiers, wetting agents, rheology modifiers, stabilizers, catalysts, photoinitiators, biocides and biostats; D) a circuit board waterproof coating composition comprising at least one solvent or solvent system comprising an organic solvent, A composition in which the passivator (A) is present in an amount of 0.5 to 60 wt % and the binder component (B) is present in an amount of 1 wt % to 97 wt %, based on the total weight of the coating composition.

2. A) at least one dissolving and / or dispersing passivating agent comprising molecules containing at least one of a thio functional group, an azole functional group, and combinations thereof; B) Binders of the following types: 1) an organic or inorganic film-forming polymer comprising a copolymer of olefin monomers and vinyl ester monomers which do not react with (A); 2) organic or inorganic film-forming polymers, including copolymers of olefin and vinyl ester monomers capable of reacting with (A); 3) one or more polymer precursors capable of polymerizing on the substrate surface comprising olefinic monomers and which do not react with (A); 4) one or more polymer precursors capable of polymerizing on the substrate surface and reacting with (A), comprising olefinic monomers; A dissolving and / or dispersing binder component comprising one or more of: The dissolved and / or dispersed binder component does not contain a fluorine atom-containing polymer. and C) one or more dissolved and / or dispersed wax additives; and D) optionally a circuit board waterproof coating composition comprising at least one organic solvent, A composition wherein the passivating agent (A) is present in an amount of from 2 to 17 percent by weight of the composition, excluding solvent.

3. The circuit board waterproof coating composition of claim 1, wherein (C) is present in an amount of 1 to 80 weight percent, and the remainder to 100 weight percent is (D) at least one organic solvent, based on the total weight of the coating composition.

4. 3. The waterproof circuit board coating composition of claim 1 or 2, wherein at least a portion of the passivating agent (A) further comprises a second functional group different from the thio functional group and the azole functional group.

5. 3. The waterproof circuit board coating composition of claim 1 or 2, wherein at least a portion of the binder component (B) is grafted to at least some molecules of the passivator (A).

6. 3. The waterproof circuit board coating composition of claim 1 or 2, wherein the organic or inorganic film forming polymer of (B) comprises an ethylene vinyl acetate copolymer.

7. 3. The waterproof circuit board coating composition of claim 1 or 2, wherein the one or more polymer precursors comprise UV curable monomers, oligomers, and / or prepolymers.

8. 3. The waterproof circuit board coating composition of claim 2, wherein (A) comprises a molecule having both thiol and azole functional groups.

9. 3. The waterproof circuit board coating composition of claim 2, wherein (A) comprises a mercaptosilane oligomer.

10. 3. The waterproof coating composition for circuit boards according to claim 1, wherein (C) comprises a wax having a melting point of 50 to 100°C.

11. 3. The waterproof circuit board coating composition of claim 1 or 2, wherein the one or more polymer precursors comprise olefinic monomers including at least one of (meth)acrylate monomers, vinyl monomers, styrene, acrylonitrile, and mixtures thereof.

12. a) applying the coating composition of claim 1 or 2 to a substrate surface, optionally including one or more conductive traces attached thereto; b) drying the coating composition on the substrate surface; c) optionally UV curing the coating composition on the substrate surface; d) during any of steps a)-c), reacting available reactive functional groups of the binder component (B) and the passivating agent (A) with the coating composition components and optionally the conductive traces, thereby depositing a water insoluble passivating polymer film on the substrate surface.

13. 13. A passivating polymer film deposited on a circuit board according to the method of claim 12, wherein the film is removable from the circuit board by peeling it off.

14. 13. An electronic component coated according to the method of claim 12, wherein the electronic component exhibits no current leakage while immersed in distilled water for 30 minutes under an applied power of 3 volts.

15. 1. A method for waterproofing a circuit board, comprising: The method is (a) providing a circuit board waterproof coating composition according to claim 1 or 2; (b) applying a coating composition to the exposed surface of the circuit board, thereby allowing reaction and adsorption of (A) to the metal portions of the surface, thereby maintaining the composition in a liquid state; (c) solidifying and optionally curing the composition to form an ultra-thin film having a thickness sufficient to waterproof the surface.

16. 13. A printed circuit board comprising an adherent, passivating polymeric coating applied to a surface of the printed circuit board according to the method of claim 12 and a conductive trace attached thereto, the polymeric coating comprising: a) one or more organic or inorganic film-forming polymers comprising copolymers of olefin monomers and vinyl ester monomers, optionally crosslinked; a reaction product of one or more polymer precursors comprising olefinic monomers; a cured binder matrix comprising a reaction product of the film-forming polymer and the one or more polymer precursors, wherein the cured binder matrix does not comprise a fluorine atom-containing polymer; b) a passivation agent and / or a reaction product of the passivation agent with at least a portion of the conductive trace and / or component a, the passivation agent comprising at least one of a thio functional group, an azole functional group, and combinations thereof; and c) Optionally, a printed circuit board containing particles of wax that are insoluble in and dispersed within the cured binder matrix.

17. 17. The substrate of claim 16, wherein the adherent polymeric coating comprises a polymer-forming olefin monomer comprising at least one of (meth)acrylate monomers, vinyl monomers, styrene, acrylonitrile, and mixtures thereof.

18. 13. A passivated polymer film deposited on a substrate surface according to the method of claim 12, wherein the substrate surface is a tape, backing or other support, thereby forming a removable film for subsequent transfer to an end-use article.

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