Composition and method for improving durability of electrically insulating and waterproofing gel coating systems

Abstract

This invention discloses a composition for forming a conformal adhesive coating to protect a substrate from various environmental influences, wherein the composition includes at least one film-forming agent, at least one additive, and, if desired, at least one solvent. The composition is deformable, flowable, electrically insulating, and fluorine-free when applied as a coating. The adhesive coating, a method of applying this coating to a substrate, and the coated substrate are also disclosed. Non-limiting examples of such substrates include a printed circuit board, an assembled electronic device, or an automotive part.

Description

[Technical Field]

[0001] This invention generally relates to a gel-like coating for forming a protective coating on a substrate, and a method for manufacturing the same. This invention also relates to compositions for manufacturing such coatings, and methods for applying such coatings to a substrate that may contain an electronic device (such as a printed circuit board). [Previous Technology]

[0002] Electronic devices include conductive and insulating components that can be adversely affected by exposure to harsh environments. Exposure to liquids such as water will typically lead to corrosion or a short circuit of these components, which will ultimately impair the function of the electronic device. In addition, as these devices become more complex with increasing functionality, they are used in more hazardous environments (such as moisture, corrosive gases, and atomized or bulk liquids) that can degrade the functionality of the device.

[0003] Electronic devices fail when exposed to such environments because the conductive medium provides a path for current from components under bias. Most of these failures manifest as corrosion of electronic components or malfunction of those components. In addition to failure of the components themselves, conformal coatings can also fail under these harsh conditions due to chemical degradation, which can ultimately lead to loss of insulating properties.

[0004] Therefore, durable electrical insulating coatings are becoming a more popular form of protection for such devices. Traditional coatings require masking specific areas to ensure that current flow through connectors, test points, or grounding contacts is not impeded. This process is expensive and time-consuming, which has an adverse effect on the entire electronic manufacturing process.

[0005] Conventional conformal coatings aim to improve durability by increasing their mechanical strength. Furthermore, conventional conformal coating chemicals rely on forming a highly cross-linked network that is not easily deformed. This necessitates a trade-off during electronic device manufacturing processes: a rigid and stiff coating (e.g., masking or selective coating of specific components).

[0006] Therefore, there is a need for a coating that exhibits improved functional durability, allowing it to perform its function throughout the entire lifespan of the device while maintaining its deformability and flowability. Due to the improved functional durability, the disclosed coating, when applied to various devices or substrates, can be used in a variety of applications (such as in automotive, household and industrial appliances, consumer electronics, aerospace, military, and chemical industries) to protect devices or substrates from various environmental influences. Non-limiting examples of potential uses include coatings and methods that allow protection of electronic devices from harsh environments and contaminants (such as particles containing dust and dirt, and liquids containing water and bodily fluids). Furthermore, there is a need for a coating that can be applied (e.g., on a printed circuit board) without the need for masking components prior to coating. There is also a need for a durable, deformable, and flowable coating that can cover the entire printed circuit board without impeding the functionality of the device. [Summary of the Invention]

[0007] In view of the foregoing, a composition for forming a durable gel-like coating to protect a device or substrate is disclosed, a method for manufacturing the coating and a method for using the coating, and a device and substrate protected by the coating are disclosed.

[0008] In one embodiment, a composition for forming a conformal coating to protect a substrate from various environmental influences is disclosed, the composition comprising: at least one film-forming agent; and at least one additive and, if desired, at least one solvent, wherein the composition is deformable, flowable, electrically insulating, and fluorine-free when applied as a coating.

[0009] also discloses a conformal coating for protecting an electronic component from various environmental influences, the coating comprising: at least one film-forming agent; and at least one additive and, if necessary, at least one solvent, wherein the coating is deformable, flowable, electrically insulating, and fluorine-free.

[0010] In another embodiment, a method of treating an electronic device with a conformal coating is disclosed, the method comprising: applying the conformal coating to the electronic device, the conformal coating comprising a film-forming agent and an additive, the coating composition further comprising, as needed, at least one solvent, dye, pigment or combination thereof.

[0011] In yet another embodiment, various devices or substrates on which a coating is applied are disclosed. These devices or substrates may comprise an automotive part or a printed circuit board having one of the gel-like coatings described herein. The gel-like coating described herein is made from a composition comprising: at least one film-forming agent; and at least one additive that improves at least one of the mentioned performance properties of the coating.

Implementation Method

[0020] Cross-reference to related applications This application claims priority to U.S. Provisional Application No. 63 / 121,747, filed December 4, 2020, and U.S. Provisional Application No. 63 / 240,533, filed September 3, 2021, the full text of which is incorporated herein by reference.

[0021] As used herein, "conformal coating" refers to a film that follows the contour of a substrate (such as a printed circuit board or an assembly thereof) to which it is applied in a continuous manner without breaks or openings. The conformal coatings described herein protect substrates (such as electronic circuits) from the effects of the environment and liquids or particles (including water, sweat or other moisture, dirt and dust, and chemicals).

[0022] As used herein, "film-forming agent" means a material capable of forming a viscous, continuous film when applied to a solid surface. Film-forming agents described herein are typically used in the form of organic or aqueous solutions or dispersions (including organic or aqueous solvents that allow the film-forming material to form a film upon solvent evaporation).

[0023] As used herein, "glue" or "gel-like" refers to a material or a material composite that forms an internal network due to chemical cross-linking and / or physical bonding between its constituent components. A glue coating exhibits non-Newtonian, viscoelastic, viscoplastic, and / or elasto-viscoplastic flow properties.

[0024] As used herein, “deformability” or “deformability” refers to the ability of an adhesive to undergo strain (e.g., stretching, bending, etc.) under compressive, tensile, or shear stresses typically induced during electronic device assembly or at temperature ranges common during electronic device handling.

[0025] As used herein, “flow” or “flowable” means the ability of a gel to behave like a fluid, which undergoes a steady rate of shear deformation under the application of shear stress.

[0026] As used herein, a "non-Newtonian fluid" or a version thereof means a fluid that does not obey Newton's law of viscosity (e.g., a fluid whose viscosity may vary based on applied stress or force). The resulting coating exhibits non-Newtonian behavior described by a nonlinear relationship between the coating's shear stress and shear rate, or the presence of a yield stress. A non-Newtonian fluid includes a single-phase or multiphase fluid exhibiting non-Newtonian behavior, which may also contain one or more components. Non-Newtonian fluids are sometimes referred to as complex fluids. In one embodiment, the non-Newtonian flow system is viscoelastic.

[0027] As used herein, "viscoelastic" means a material that exhibits both viscous and elastic properties when subjected to deformation (i.e., a material that both stores and dissipates energy during a periodic / cyclic oscillatory shear deformation). This is typically reported based on non-zero measurable values ​​of both a storage modulus G' and a loss modulus G'".

[0028] As used herein, "viscoplasticity" refers to an inelastic behavior of a material in which it undergoes irreversible deformation when a critical load level (known as the yield stress) is reached. The main difference between viscoplastic and viscoelastic materials lies in the presence of a yield stress. A viscoplastic material has a yield stress below which it will not flow, while a viscoelastic material will deform and flow under any finite shear stress.

[0029] As used herein, "elastoviscoplastic" refers to a broad class of materials that exhibit elastic, viscous, and plastic responses under applied shear stress or strain at different levels, such as the adhesive coatings described in this patent. Below a critical stress (often referred to as a yield stress), the material does not undergo steady flow but rather transient deformation, some of which elastically accumulates strain and some energy is dissipated through plastic (irreversible) deformation. When the critical load level is reached (i.e., above the yield stress), the material begins to flow like a liquid but still exhibits viscoelasticity (i.e., it has measurable values ​​for the elastic modulus G' and the loss modulus G") because some of the initial deformation is elastically stored and some of the external work applied to the material is viscously dissipated. When the applied load is removed, this elastoviscoplastic response can be distinguished in a rheometer by a portion (i.e., elastic) recoil or unloading, but some irreversible deformation is accumulated due to the plastic properties of the material.

[0030] As used herein, "durability" refers to the ability of a coating material to maintain its functional properties (e.g., electrical insulation, hydrophobicity, appearance, morphology, and physical and chemical properties) even after exposure to various environmental stresses. Changes in coating performance can be caused by various stresses, including (but not limited to): continuous exposure to heat, repeated and intermittent exposure to extreme temperatures, low-temperature exposure, high-temperature and / or moisture exposure, salt spray exposure, exposure to toxic or corrosive gases, UV exposure, and other chemical exposures. These stresses can cause damage to the coating material, including (but not limited to) cracking, oxidation, chain scission, free radical crosslinking, phase separation, phase change, coating flow, browning, delamination, blistering, and the like.

[0031] Industry-standard tests used to assess the durability of conformal coatings to meet lifecycle requirements are set by suppliers of electronic components, companies that assemble electronic components or PCBs into consumer or automotive devices, or third-party organizations that regulate how conformal coatings should be evaluated. Some of these industry-standard tests include Ford Motor Company's Enterprise Engineering Test Procedure, Volkswagen VW 80000 Motor Vehicle Electrical and Electronic Components Test Procedure, BMW Group Standard 95011-5 Conformal Coating Conformity Assessment for Motor Vehicles, IPC-CC-830C, and MIL-STD-810G.

[0032] As used herein, a “solventized coating” means a coating containing a solvent to help it spread when applied to a substrate (e.g., to a composition still containing a solvent). If “solventized” or any version thereof is not used in conjunction with “coating”, the coating is considered to be a dry coating on a substrate or device (e.g., without a solvent).

[0033] As used herein, "electrical insulation" means the property of a material to provide resistance to an electric current. For example, in a non-limiting embodiment, when a gel coating is applied to an active component under bias, the coating provides a resistance greater than 103 ohms or a dielectric breakdown voltage greater than 1.5 kV / mil.

[0034] In one embodiment, a gel-like coating comprises a composition exhibiting either viscous or elastic properties. Unlike a purely elastic material, a viscoelastic material will flow like a viscous liquid under load, but will maintain the elastic properties of a solid when not under load. Viscoelasticity has been well studied and the behavior of viscoelastic materials is known in this art.

[0035] In another embodiment, a gel-like coating comprises a composition exhibiting elastoviscoplastic properties. Unlike a viscoelastic material, an elastoviscoplastic material has a critical load level (i.e., yield stress) below which it will not flow. Elastoplasticity has been well studied and the behavior of elastoviscoplastic materials is known in this art. The elastic and plastic properties associated with the disclosed compounds allow the material to resist liquid contamination and material deformation attributable to body forces (e.g., gravity), and the viscous properties allow the material to redistribute itself under stress and over time, such as shifting or uniformly covering a surface when a force is applied.

[0036] Therefore, the properties of a gel-like coating make it advantageous for use as a coating on electronic devices. The film-forming agent includes materials that adhere to or adsorb onto the surface of the electronic device to maintain a thin film typically in the range of nanometers to hundreds of micrometers. Thicker films can be obtained when the fluid exhibits a yield stress.

[0037] Using a gel-like coating achieves benefits not present in conventional conformal or vacuum coatings. The viscous or plastic properties of a film-forming agent eliminate the need to mask specific components before coating an electronic device. Typically, masking specific components (e.g., connectors and ground traces) is used to allow current to flow through the masked area in the coating. Instead, a gel-like coating exhibits viscoplastic properties by flowing or deforming when a component is introduced into the electronic device. The flow or deformation of the gel coating allows the component to be connected to the electronic device without interference. The gel-like coating will exhibit non-Newtonian, viscoelastic, viscoplastic, or elastoviscoplastic properties. Since current will be transmitted to the component, it is not necessary to mask the component; however, masking can still be performed if required.

[0038] In alternative embodiments, the film-forming agent that achieves the various mechanical properties of the coating may be a combination of polyamide, polyacrylonitrile, polyacrylamide, polycarbonate, polyurethane, polyterephthalate, polysulfide, or the like. The film-forming agent may have a unique polymer topology, including linear polymers, cyclic polymers, branched polymers, hyperbranched polymers, grafted polymers, star polymers, bottle brush polymers, adhesives with various branching functionalities, or combinations thereof. Alternative embodiments may be made from homopolymers, copolymers of two or more monomers, polymer mixtures, or interpenetrating polymer networks of one or more polymer or copolymer types. The copolymer may be block, statistical, random, or alternating copolymers. Furthermore, alternative embodiments of the film-forming agent may be made from a loosely crosslinked polymer network containing covalent bonds, dynamic bonds (hydrogen bonding, metal-organic coordination, pi-pi stacking, etc.), polymer entanglement, or combinations thereof (i.e., wherein adhesive properties or elasto-plastic flow properties are maintained). All types of crosslinking can occur before or after the composition is applied to the substrate.

[0039] In one embodiment, a composition is described for forming a coating that has increased performance under extreme conditions such as high and low temperatures, exposure to UV light, high humidity environments, corrosive salt environments, environments with toxic or corrosive gas mixtures, and the sustained performance of long-lifecycle products such as automobiles.

[0040] For example, in one embodiment, a conventional coating system known to degrade upon exposure to a catalytically active metal can be enhanced by adding a metal passivator and an antioxidant. The concentrations of the passivator and antioxidant are selected based on the decomposition rate of the adhesive coating and the area of ​​exposure of the catalytically active metal. The passivator and antioxidant are also selected based on their relative affinity for the catalytically active metal and their solubility in the adhesive coating. Furthermore, the passivator and antioxidant can be selected such that they preferentially migrate from the overall coating to an interface. The catalytically active metal initiates the decomposition of the coating by generating free radicals. The passivator shields the catalytically active metal from the influence of other components of the coating. The primary antioxidant and co-antioxidant neutralize the free radicals. Additional additives (such as acid scavengers) may also be added to inhibit the generation of undesirable byproducts from free radical neutralization by the primary antioxidant and co-antioxidant.

[0041] Previous electrical insulating adhesive coatings did not contain stabilizers to increase the durability of the formulation. Therefore, the present invention addresses the problems and defects of previous compositions. In one embodiment, a passivating component is applied to a metal substrate in a first layer prior to applying an adhesive coating in a second layer. In another embodiment, a method is disclosed for applying an adhesive coating to a board in a first layer followed by applying an antioxidant-rich layer. Combinations of these embodiments may also be used.

[0042] The method of determining the properties and amount of additives and formulating additives into an adhesive coating system through various unit operations is a non-limiting approach of the present invention that differs from previous procedures.

[0043] The properties of the additives formulated into the coating have a direct impact on the coating's durability. Proprietary additive combinations are necessary to prevent chemical and mechanical degradation of the coating itself and to protect the underlying substrate. For example, a metal substrate in contact with the coating can catalyze the degradation of the coating, resulting in poor electrical insulation performance. In this case, a proprietary combination is needed, consisting of a metal passivator to shield the metal / coating interface and a primary antioxidant and a co-antioxidant to protect the coating.

[0044] Proprietary additive formulations can address various failure mechanisms of both coatings and active substrates based on the environment in which electronic components are exposed. As shown in Figure 5, a passivating agent formulated into the coating can migrate to the metal / coating interface to inhibit the catalytic degradation of other components in the coating. This invention relates to selecting appropriate additives that can migrate to an interface in a self-phase manner to strengthen the interface and maintain the integrity of the coating. A primary antioxidant formulated into the coating can suppress any free radicals attributable to exposure to an active metal or formed due to exposure to the environment. A co-antioxidant formulated into the coating will further deactivate any byproducts of the reaction between a primary antioxidant and free radicals. This invention relates to identifying appropriate proprietary additive mixtures based on the electronic device and the environment in which it operates, while maintaining the deformability of the coating.

[0045] Similar to proprietary additives engineered for environmental performance requirements, this application also addresses a method for engineered coating deformability. For example, for coating bonding, the coating must be engineered to have sufficient ductility and exhibit elasto-visco-plastic flow properties in the normal, tensile, and compressive directions. The coating can be engineered to exhibit a pencil hardness lower than 6B. When measured at frequencies between 1 rad / s and 100 rad / s, the storage and loss moduli of the coating in the shear and tensile directions are less than 10⁶ Pa at 25⁰C. The coating yields when deformed at 25⁰C with a yield stress of less than 10⁴ Pa in the shear and tensile directions between 1 rad / s and 100 rad / s.

[0046] In one embodiment, a custom additive formulation for improving the performance of an existing coating is disclosed. For example, if an adhesive coating degrades at higher temperatures, the present invention relates to a process of modifying the composition or incorporating an additive that will increase the durability of the coating by allowing it to resist degradation. Higher temperatures can cause oxidative degradation of the coating, which will alter its chemical structure and prevent it from performing its function. In this case, an antioxidant additive will inhibit the oxidation of the coating, making it more durable under those conditions.

[0047] The additive mixture described herein can be selected based on the defects identified in the coating's performance. The additive mixture is then formulated to address these defects. For example, if copper is identified as a catalyst for the free radical decomposition of the initiating coating, the additive mixture will consist of a passivating agent that migrates to the coating / copper interface to inhibit catalysis and an antioxidant to inhibit any free radicals generated.

[0048] The addition of such additives will also result in the maintenance of the adhesive properties of the coating, which will prevent problems such as flow, liquefaction, cracking, rupture and other macroscopic removal modes of the coating when exposed to extreme environments.

[0049] In one embodiment, the additive includes at least one corrosion inhibitor (such as a carboxylic acid). A non-limiting example of a carboxylic acid that can be used in this invention is Irgacor 843TM sold by BASF.

[0050] In one embodiment, the additive includes at least one passivating agent, such as acehydrazine, triazole, or a mixture thereof. Non-limiting embodiments of acehydrazine that can be used in this invention include dodecanoic acid, 1,12-bis[2-(2-hydroxybenzoyl)acehydrazine] (CAS No. 63245-38-5) or phenylpropionic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, 2-[3-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxopropyl]acehydrazine (CAS No. 32687-78-8).

[0051] Non-limiting embodiments of triazoles that can be used in this invention include benzoxamide, 2-hydroxy-N-1H-1,2,4-triazol-3-yl- (CAS No. 36411-52-6), 1H-benzotriazol-1-methylamine, N,N-bis(2-ethylhexyl)-aryl-methyl- (CAS No. 94270-86-7) or 1H-1,2,4-triazol-1-methylamine, N,N-bis(2-ethylhexyl)- (CAS No. 91273-04-0).

[0052] In one embodiment, the additive includes at least one primary antioxidant, such as an amine or phenol. Non-limiting embodiments of amine primary antioxidants that can be used in this invention include the reaction product of aniline, N-phenyl-,2,4,4-trimethylpentene (CAS No. 68411-46-1), alkylated amines, 1-naphthylamine, N-phenyl-aryl-(1,1,3,3-tetramethylbutyl) (CAS No. 68259-36-9), or 4,4'-dioctyldiphenylamine (CAS No. 101-67-7).

[0053] Non-limiting embodiments of the main antioxidants that can be used in this invention include phenylpropionic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, octadecyl ester (CAS No. 2082-79-3), phenylpropionic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, 2,2-bis[[3-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxopropoxy]methyl]-1,3-propanediester (CAS No. 6683-19-8), C7-C9 alkyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid The reactants of isomers of esters (CAS No. 125643-61-0), 1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris{[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl}- (CAS No. 27676-62-6), or phenylpropionic acid, 3-(1,1-dimethylethyl)-4-hydroxy-5-methyl-, 2,4,8,10-tetraoxazolo[5.5]undecane-3,9-dimethylbis(2,2-dimethyl-2,1-ethylenedimethyl) ester (CAS No. 90498-90-1).

[0054] In one embodiment, the additive includes at least one co-antioxidant, such as a phosphite or a thioether. Non-limiting examples of phosphite co-antioxidants that can be used in this invention include tris(2,4-di-tert-butylphenyl) phosphite (CAS No. 31570-04-4), butylidene bis[2-tert-butyl-5-methyl-p-phenylene]-P,P,P',P'-tetradecylbis(phosphine) (CAS No. 13003-12-8), and 12H-dibenzo[d,g][1,3,2]phosphine dioxane, 2,4,8,10-tetra(1,1-dimethylethyl)-6-[(2-ethylhexyl)oxy]- (CAS No. 126050-54-2).

[0055] Non-limiting embodiments of thioether co-antioxidants that can be used in this invention include propionic acid, 3-(dodecylthio)-, 1,1'-[2,2-bis[[3-(dodecylthio)-1-oxopropoxy]methyl]-1,3-propanediyl] ester (CAS No. 29598-76-3) and propionic acid, 3,3'-thiobis-, 1,1'-tetrazyl ester (CAS No. 10595-72-9).

[0056] In one embodiment, the composition disclosed herein comprises a tackifier. Non-limiting examples of tackifiers that may be used herein include low molecular weight hydrogenated hydrocarbon resins, partially hydrogenated water-white hydrocarbon resins, water-white alicyclic hydrocarbon resins, aromatic-modified alicyclic hydrocarbon resins, and combinations thereof.

[0057] In one embodiment, the composition disclosed herein comprises a plasticizer. Non-limiting examples of plasticizers that may be used herein include hydrogenated alicyclic hydrocarbon resins, trimellitic esters, esters, epoxidized vegetable oils, high molecular weight phthalates, cycloalkanes, and polysiloxane oils.

[0058] In one embodiment, the additive may comprise one or more acid scavengers. Non-limiting examples of acid scavengers that may be used herein include stearates, carbonates, hydroxides, and hydrotalcites. For example, acid scavengers comprise calcium stearate, zinc calcium stearate or octyl stearate epoxidized, zinc carbonate, magnesium carbonate, and aluminum hydroxide, magnesium hydroxide, and synthetic hydrotalcites comprising magnesium / aluminum hydrotalcites.

[0059] In one embodiment, the composition comprises a UV dye. One non-limiting example of a UV dye that may be used is 2,2'-(2,5-thiophenediyl)bis(5-tert-butylbenzoxazole), 2,2'-(1,2-ethylidene)bis(4,1-phenylene)bisbenzoxazole, Solvent Yellow 43, Carbon Black, Pigment Yellow 101, N,N'-bis(2,6-diisopropylphenyl)-3,4,9,10-perylenetetramethyldiimide, other perylene dyes, and anthracene dyes.

[0060] The compositions disclosed herein offer various benefits superior to existing, conventional compositions. Non-limiting examples of these benefits include: ● Increased inertness and durability of more environmentally friendly materials. ● Engineering a coating formulation to respond to a substrate, wherein one of the additives migrates from the overall coating to the substrate in question to strengthen the interface between the coating and the substrate. ● Engineering a coating formulation to respond to the environment, wherein one of the additives migrates to the coating / air interface to enhance its properties. ● Engineering a coating formulation to respond to a stimulus such as heat or magnetism, using the stimulus to manipulate one of the additives to initiate a reaction or migration within the coating (e.g., to the interface). ● Engineering a coating formulation to respond to the absorption of foreign components, wherein the additives respond to, calibrate, or deactivate any external material from harsh environments (such as moisture, toxic gases such as sulfur oxides, or undesirable particles such as metal particles / shavings). ● Engineering a coating to have discrete rheological properties across the entire cross-section.

[0061] The above-mentioned benefits can be used to protect an electronic device from conductive materials (such as water or bodily fluids, dust or other particles and the like) from the external environment. Compositions for manufacturing novel colloidal coatings, methods for treating substrates with colloidal coatings, and graphic representations of substrates including colloidal coatings are provided in Figures 2 to 7.

[0062] Referring to Figure 2, the schematic diagram shown herein illustrates one setup for measuring the insulation resistance on the printed circuit board described herein. Specifically, Figure 2 shows how to measure the insulation properties of various circuits on a coated industry-standard IPC-B-25A board when it is immersed in tap water at 20 V for 30 minutes.

[0063] The mechanism by which the additives disclosed herein improve properties is illustrated in Figures 5 and 6, which demonstrate an interface where the additive migrates from the coating to either the substrate surface (Figure 3) or the air surface (Figure 4). For example, Figure 3 shows (several) additives migrating from the coating to the coating / substrate interface. This embodiment can be used to apply a passivation layer to a substrate. Figure 4 shows a second schematic diagram demonstrating additive migration from the coating to the coating / air interface. This embodiment can be used to increase the mechanical properties of the coating itself.

[0064] The mechanism described above can be specifically selected by changing the manner in which the composition comprising various additives is applied to the substrate. For example, as shown in FIG5, the stepwise application of one of the various additives is demonstrated by coating the substrate with a passivating agent (in step 1) before applying the composition having one or more additives (in step 2). Finally, step 3 of FIG5 shows the application of an insulating layer (e.g., to resist molecular diffusion, increase resistance, etc.) on top of the composition.

[0065] Once the desired coating is applied to the substrate by any of the methods described herein (including the step-by-step method of FIG5), an adhesive coating is formed.

[0066] In some embodiments, the coatings described herein may be formulated to allow the additives to migrate out of the coating depending on the desired effect. For example, Figure 6 illustrates a schematic diagram of an example additive migrating to a specific material (such as rust or metal particles) from the external environment that can affect the coating's performance. In addition to metal particles, materials from the environment that can affect the coating's performance may include moisture, dust, welding flux residues, and any fluids (such as antifreeze, windshield washer fluid, brake fluid, etc.) that the coating may come into contact with after assembly into the device.

[0067] In another embodiment, the coating described herein may be formulated to allow the additive to migrate to the surface of the coating to provide an insulating layer on top of the coating. For example, Figure 7 shows a sixth schematic diagram demonstrating an additive migrating from the coating to the coating / air interface to enhance the properties at the air-coating interface.

[0068] Various mechanisms allow us to modify additives to achieve the desired properties that allow the disclosed durable coatings to be used in a variety of applications (such as automotive electronic coatings that can withstand high temperatures and harsh environments that would otherwise cause hydrolysis, thermal decomposition, or oxidative decomposition). Generally, the present invention provides colloidal coatings that exhibit improved durability properties, thereby providing uses that were previously not feasible for colloidal coatings.

[0069] In some embodiments, the coating may have electrically insulating properties. As used herein, a coating having electrically insulating properties is defined as a coating through which no or very little current flows under the influence of an electric field. Generally, an electrically insulating system is a material that has almost no conductivity, thereby allowing almost no current to flow through it.

[0070] In various embodiments, a portion or all of the internal components of an electronic device may be coated with an adhesive coating before any additional components are introduced into the device, without masking any part of the electronic device. Components may be introduced after the coating is applied, and the coating will not inhibit current flow between the components and the electronic device. Manufacturing costs and difficulty are typically increased due to masking. Because the need for masking has been greatly reduced or completely eliminated, the use of an adhesive coating as disclosed herein can result in reduced manufacturing costs and difficulty.

[0071] The viscoplastic properties of the film-forming agents described herein allow the gel-like coating to flow under certain conditions. This allows for easy reprocessing of coated printed circuit board assemblies. With conventional conformal and vacuum coatings that do not exhibit flow or deformation, it is difficult to reprocess coatings to solder or repair existing components.

[0072] In some embodiments, the solvated coating may be spread on a substrate as described by the spreading factor (S) shown in the following equation:

[0073] In the above equation, represents the surface energy between the substrate and air, represents the surface energy between the substrate and the coating, and represents the surface energy between the coating and air. Spreading can occur when the spreading coefficient is positive or greater than . When the spreading coefficient is positive, this means that wetting of the coating on the substrate will be completed. On the other hand, when the spreading coefficient is not positive, only partial or incomplete wetting is achieved. Alternatively, the spreading liquid can form droplets or floating lenses.

[0074] In one embodiment, when applied as a coating, the thickness of the dried or unsolvated gel coating can range from 1 µm to 500 µm (e.g., 5 µm to 100 µm, 10 µm to 50 µm). The coating thickness can be measured by non-destructive optical techniques (e.g., elliptic polarization), spectral reflectance techniques (e.g., interferometry), and confocal microscopy. Non-limiting examples of destructive methods for measuring coating thickness include SEM. Conventional coatings (e.g., conformal and vacuum coatings) are typically much thicker. For example, the thickness of conventional coatings is typically in the range of hundreds of micrometers, which can impede both radio frequency and Wi-Fi transmission of electronic devices and further act as a thermal insulator. A thinner range of gel coating adversely affects the functionality of an electronic device and does not act as a thermal insulator. A non-limiting example of a functional electronic device is a fully assembled printed circuit board. A fully assembled printed circuit board having a gel coating will exhibit normal radio frequency performance, normal thermal properties, and other normal functionality.

[0075] In one embodiment, at least one film-forming agent may comprise a hydrophobic material, such as one of polyolefins, polyacrylates, polyurethanes, epoxy resins, polyamides, polyimides, and polysiloxanes.

[0076] In one embodiment, the disclosed composition may further include additives that improve the manufacture of the composition (such as surfactants, dispersants, and the like). The composition may also include additives that modify and improve the rheological properties of a chemical formulation. Examples of surfactants may include ionic and nonionic industrial surfactants (such as Triton-X, Capstone, and the like), and molecules exhibiting surface-active properties (such as fatty acid alcohols, esters, acids, or amides). Examples of dispersants and rheology modifiers may include electrostatically stabilized molecules (such as long-chain polyacrylic acid), sterically stabilized highly branched polymer molecules, nanoparticles or submicron-sized metal oxide particles that increase overall viscosity. Other materials exhibiting elasto-visco-plastic properties may be used as a gel coating.

[0077] In some embodiments, the compositions described herein may also be suspended or dissolved in a suitable carrier solvent. Non-limiting examples of suitable carrier solvents may be low molecular weight mineral oils, paraffins or isoalkanes, alkanes or isoalkanes, low molecular weight linear or cyclic polysiloxanes, alkyl acetates, ketones, wholly or partially halogenated hydrocarbons (including but not limited to alkanes, alkenes, alkynes, aromatic compounds and the like) or aldehydes. In one embodiment, the carrier solvent includes methylcyclohexane.

[0078] One of the gel-like coatings described herein can be designed to protect against different types of liquids. A gel-like coating can exhibit hydrophobic, hydrophilic, oleophobic, or oleophilic properties, or any combination thereof. In one embodiment, the gel-like coating contains a hydrophobic material (such as a polysiloxane).

[0079] In some embodiments, the gel coating can be aesthetically modified. The refractive index of the coating can be engineered using techniques known in the art. In one embodiment, the gel coating can be engineered to match the refractive index of a transparent material. Matching the refractive index of a transparent material maintains the clarity and transparency of the final product. In other embodiments, the refractive index of the gel coating can be engineered to match the refractive index of other desired materials.

[0080] In one embodiment, a method for protecting an electronic device from liquid contamination is described. In this embodiment, the protection of the electronic device can be achieved by treating the electronic device with an adhesive coating as disclosed above.

[0081] Many different methods can be used to form the described coating. Non-limiting examples of methods that can be used to form the disclosed coating include physical procedures such as printing, spraying, dipping, rolling, brushing, jetting, scraping, or needle application. Other techniques can also be used to form a moisture-proof coating.

[0082] As previously disclosed, the properties of an adhesive coating allow for the processing of an electronic device without the need to mask the components prior to processing. Therefore, the disclosed method covers the processing of electronic devices having components, whether masked or unmasked. Components can be introduced after the coating without impeding the current flow between the electronic device and the components.

[0083] In one embodiment, part or all of an internal component of an electronic device may be coated with an adhesive coating in a single application. In another embodiment, the adhesive coating may be applied as a coating to only specific portions of the electronic device. Furthermore, in yet another embodiment, the adhesive coating may be applied to the electronic device in multiple applications.

[0084] Conventional conformal coatings and vacuum coatings have limited application methods. Certain coating methods are unavailable due to the need to mask numerous components on electronic devices. A wide variety of application methods can be used to apply the described coating. Certain application methods allow for the application of a relatively thin gel-like coating to an electronic device. Non-limiting examples of how a gel-like coating can be applied to an electronic device include atomized or non-atomized spraying, dip coating, film coating, jetting, or needle application. The gel-like coating can also be applied using other methods (e.g., through vapor deposition). Non-limiting examples of such vapor deposition techniques include chemical vapor deposition (CVD), plasma-based coating processes, atomic layer deposition (ALD), physical vapor deposition (PVD), vacuum deposition processes, sputtering, etc.

[0085] In one embodiment, using any of the disclosed methods for applying a gel-like coating to an electronic device will result in a gel-like coating on the electronic device having a thickness in the range of 1 µm to 100 µm. The coating thickness may not inhibit the functionality or thermal properties of the electronic device. Furthermore, the viscous properties of the gel-like coating may allow the coating to deform or flow when a component is introduced.

[0086] As indicated above, a non-limiting example of an electronic device to which an adhesive coating can be applied is a printed circuit board. The use of conventional conformal coatings and vacuum coatings on printed circuit boards is expensive due to the need to mask numerous components and the limited number of application methods available. For example, dip coating is difficult to use as a conformal coating application because the coating penetrates everywhere and therefore the masking must be perfect. In this example, the printed circuit board can be coated with an adhesive coating using a dip coating method because no masking is required. Any connector (such as a male connector connected to a base female connector on the printed circuit board) can be connected after coating without affecting current. The adhesive coating flows or deforms under an applied force to allow for connection. Exemplary deposition method

[0087] In one embodiment, the disclosed composition can be administered using a syringe and a needle. For example, a syringe may be fitted with a needle having a gauge size in the range of 10 to 32 (such as a needle having a gauge size of 16, 18 or 20), which will vary depending on the desired application.

[0088] In another embodiment, the disclosed composition can be applied using a manual spraying device. For example, a handheld spray gun can be used to atomize a coating (such as by using compressed air or nitrogen).

[0089] In another embodiment, the disclosed composition can be applied using an automated application mechanism suitable for applying a coating to an electronic device. For example, various nozzles, such as a Nordson Asymtek™ wide-beam spray valve, can be used to apply a coating as described herein. In other embodiments, the nozzle may include a spray valve, including a PVA coating valve, or a valve used in a PVA Delta 6 automated coating application machine. Measurement Technology

[0090] After a coating is applied to an electronic device, various properties can be measured in the following manner.

[0091] The hydrophobicity or hydrophilicity of a coating can be measured by observing the contact angle formed by a water droplet on the surface of the coating. The oleophobicity or oleophilicity of a coating can be measured by observing the contact angle formed by a droplet of hexadecane on the surface of the coating.

[0092] The electrical insulation of a coating can also be determined by measuring the dielectric withstand voltage on a coated circuit board. A continuously increasing voltage can be applied to the coated circuit board, and the voltage at which current arcs through air can be determined. This voltage is a measure of the effectiveness of the coating.

[0093] The electrical insulation of a coating can also be determined by measuring the electrical properties (such as loss tangent or dielectric constant) of a material in the coating using a mesh analyzer.

[0094] The non-Newtonian, viscoelastic, viscoplastic, and elastoviscoplastic properties of the coating can be measured by observing various properties. A rheometer can be used to measure the coating's response to an applied stress or strain to study the coating's deformation. The viscoelastic modulus can be measured using a small-angle oscillating stress scan, and the yield stress and high shear viscosity can be measured using a stress scan. The degree of deformation can also be measured by quantifying the hardness, modulus, viscosity, failure strain, creep, and ductility in the tensile, compressive, and shear directions.

[0095] The features and advantages of the present invention are further demonstrated by the following examples, which are provided for illustrative purposes only and should not be construed as limiting the present invention in any way. Examples

[0096] The following examples disclose a method for preparing a gel-like coating according to the present invention. Non-Newtonian, viscoelastic, viscoplastic, and / or elastoviscoplastic compositions are used as a coating applied to an electronic device. After preparation, the composition can be applied to an electronic device using known techniques to form a protective coating. Example 1

[0097] The following examples provide a method according to the present invention for preparing a polysiloxane-free colloidal coating having one of the improved performance properties.

[0098] Manufacturing a composition comprising one of the following components: an electrical insulator / film-forming agent / rheology modifier comprising 8.99 wt% of a styrene block copolymer and 8.99 wt% of a polyalphaolefin; a passivating agent comprising 0.18 wt% of dodecanoic acid and 1,12-bis[2-(2-hydroxybenzoyl)pyrazine]; a primary antioxidant comprising 0.05 wt% of phenylpropionic acid and 3,5-bis(1,1-dimethylethyl)-4-hydroxy-octadecyl ester; a co-antioxidant comprising 0.09 wt% of propionic acid, 3,3'-thiobis- and 1,1'-tetratrialkyl esters; and a UV dye comprising 0.02 wt% of 2,2'-(2,5-thiophenediol)bis(5-tert-butylbenzoxazole).

[0099] These components were added to a glass beaker and mixed in a carrier solvent comprising 81.74% by weight of methylcyclohexane. The mixture was stirred for 8 hours at room temperature using a magnetic stirrer. Example 2

[0100] To manufacture a composition substantially similar to Example 1 but without a UV dye. The composition comprises the following components: an electrical insulator / film-forming agent / rheology modifier comprising 8.99 wt% of a styrene block copolymer and 8.99 wt% of a polyalphaolefin; a passivating agent comprising 0.18 wt% of dodecanoic acid and 1,12-bis[2-(2-hydroxybenzoyl)pyrazine]; a primary antioxidant comprising 0.05 wt% of phenylpropionic acid and 3,5-bis(1,1-dimethylethyl)-4-hydroxy-octadecyl ester; and a co-antioxidant comprising 0.09 wt% of propionic acid and 3,3'-thiobis-,1,1'-tetratrialkyl ester.

[0101] These components were added to a glass beaker and mixed in a carrier solvent comprising 81.74% by weight of methylcyclohexane. The mixture was stirred for 8 hours at room temperature using a magnetic stirrer. Comparative Example 1

[0102] This comparative composition is similar to Examples 1 and 2, but does not contain additives including passivating agents, antioxidants and dyes. It comprises the following components: an electrical insulator / film-forming agent / rheology modifier comprising 8.99 wt% of a styrene block copolymer and 8.99 wt% of a polyalphaolefin, mixed in a carrier solvent comprising 82 wt% of methylcyclohexane.

[0103] Add all ingredients to a glass beaker and stir with a magnetic stirrer at room temperature for 8 hours. Example 3

[0104] This example is based on a formulation having a styrene-[ethylene-(ethylene-propylene)]-styrene (SEEPS) block copolymer and additives. The composition comprises: 4% by weight of SEEPS polymer; white mineral oil (8%); a passivating agent comprising 0.08% by weight of phenylpropionic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, 2-[3-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxopropyl] acehydrazine; 0.08% by weight of a major phenolic antioxidant comprising a reactant comprising an isomer of C7-9-alkyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; and 0.12% by weight of a thioether antioxidant comprising propionic acid, 3,3'-thiobis-, 1,1'-tetratrialkyl ester, etc., mixed in a carrier solvent comprising 87.7% by weight of methylcyclohexane.

[0105] Add all ingredients to a glass beaker and stir with a magnetic stirrer at room temperature for 8 hours. Comparative Example 2

[0106] This comparative composition is similar to Example 3, but does not contain additives including passivating agents, antioxidants and dyes, and comprises the following components: 4% by weight of styrene-[ethylene-(ethylene-propylene)]-styrene (SEEPS) and 8% by weight of white mineral oil, etc., mixed in a carrier solvent comprising 88% by weight of methylcyclohexane.

[0107] Add all ingredients to a glass beaker and stir with a magnetic stirrer at room temperature for 8 hours. Example 4

[0108] This example is based on a formulation having a styrene-[ethylene-(ethylene-propylene)]-styrene (SEEPS) block copolymer with an end block stabilizer and other additives.

[0109] The composition comprises: 4% by weight of a styrene block copolymer and 7% by weight of a polyalphaolefin; 1.1% by weight of a hydrocarbon resin end-block stabilizer, 0.11% by weight of a passivating agent benzoylamine, 2-hydroxy-N-1H-1,2,4-triazol-3-yl-, 0.11% by weight of a phenolic antioxidant phenylpropionic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, octadecyl ester, 0.06% by weight of a thioether antioxidant propionic acid, 3,3'-thiobis-, 1,1'-tetratrialkyl ester, etc., mixed in a carrier solvent comprising 87.62% by weight of methylcyclohexane.

[0110] The hydrocarbon resin terminal block stabilizer was added to a beaker of methylcyclohexane and stirred at 80⁰C until dissolved. All other components were then added and stirred at room temperature for 8 hours. Comparative Example 3

[0111] This comparative composition is similar to Example 4, but does not contain additives including passivating agents, antioxidants and dyes. It comprises the following components: the composition comprises 4% by weight of styrene block copolymer and 7% by weight of polyalphaolefin mixed in 89% by weight of methylcyclohexane.

[0112] Add all ingredients to a glass beaker and stir with a magnetic stirrer at room temperature for 8 hours. Example 5

[0113] This example is based on a formulation having one of the following: 3.55 wt% styrene-ethylene / butene-styrene (SEBS); 0.89 wt% styrene-ethylene / propylene-styrene (SEPS) block copolymer; 3.55 wt% polyalphaolefin; a passivating agent including 0.18 wt% dodecanoic acid and 1,12-bis[2-(2-hydroxybenzoyl)pyrazine]; a phenolic antioxidant including 0.045 wt% phenylpropionic acid and 0.045% 3,5-bis(1,1-dimethylethyl)-4-hydroxy-octadecyl ester; and a thioether antioxidant including 0.09% propionic acid and 3,3'-thiobis- and 1,1'-tetratrialkyl ester, all mixed in 81.74 wt% methylcyclohexane.

[0114] Add all ingredients to a glass beaker and stir with a magnetic stirrer at room temperature for 8 hours. Example 6

[0115] This example is based on a formulation having one of the following: 3.55% by weight of styrene-ethylene / butene-styrene (SEBS); 0.53% by weight of styrene-ethylene / propylene-styrene (SEPS); and maleic anhydride-treated SEBS block copolymers - SEBS (3.55%), SEPS (0.53%), and maleic anhydride-treated SEBS. (0.36%); 3.55% by weight of polyalphaolefin; passivating agent including 0.08% by weight of dodecanoic acid and 1,12-bis[2-(2-hydroxybenzoyl)pyrazine]; phenolic antioxidant including 0.02% by weight of phenylpropionic acid and 0.045% by weight of 3,5-bis(1,1-dimethylethyl)-4-hydroxy-octadecyl ester; thioether antioxidant including 0.04% by weight of propionic acid and 3,3'-thiobis- and 1,1'-tetratrialkyl ester, etc., are mixed in a solvent including 81.74% by weight of methylcyclohexane.

[0116] Add all ingredients to a glass beaker and stir with a magnetic stirrer at room temperature for 8 hours. Example 7

[0117] This example is based on a formulation containing polyisobutylene and SEEPS copolymer. Specifically, 10% by weight of polyisobutylene (10%), 10% by weight of SEEPS polymer; 0.1% by weight of a passivating agent including benzoylamine and 2-hydroxy-N-1H-1,2,4-triazol-3-yl-; 0.2% by weight of a phenolic antioxidant including an isomer of C7-9-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate alkyl ester; and 0.1% by weight of a thioether antioxidant including propionic acid, 3,3'-thiobis-, and 1,1'-tetraalkyl ester, are mixed in a solvent including 79.60% by weight of isoparaffin.

[0118] Add all ingredients to a glass beaker and stir with a magnetic stirrer at room temperature for 8 hours. Example 8

[0119] This example is based on a formulation having a polyethylene / polypropylene (PE / PP) copolymer and a polysiloxane oil. The composition comprises 3% by weight of the PE / PP copolymer; 10% by weight of methyl-terminated PDMS (30,000 cSt); 0.13% by weight of a passivating agent comprising dodecanoic acid and 1,12-bis[2-(2-hydroxybenzoyl)pyrazine]; 0.04% by weight of a phenolic antioxidant comprising phenylpropionic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy- and octadecyl ester; and 0.04% by weight of propionic acid, 3,3'-thiobis- and 1,1'-tetratrialkyl ester, etc., mixed in a solvent comprising 86.80% by weight of methylcyclohexane.

[0120] Add all ingredients to a glass beaker and stir with a magnetic stirrer at room temperature for 8 hours. Example 9

[0121] This example is based on a formulation containing lithium stearate and alumina. Specifically, the composition comprises: 2.8 wt% lithium stearate, 1.1 wt% organosilicon-treated hydrophobic alumina; 9.4 wt% polyalphaolefin; a passivating agent comprising 0.13% dodecanoic acid and 1,12-bis[2-(2-hydroxybenzoyl)pyrazine]; a phenolic antioxidant comprising 0.03% phenylpropionic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, octadecyl ester; a thioether antioxidant comprising 0.07% propionic acid, 3,3'-thiobis-, 1,1'-tetratrialkyl ester; and a UV dye comprising 0.01 wt% 2,2'-(2,5-thiophenediol)bis(5-tert-butylbenzoxazole), an azeotropic fluoroether solvent mixture (86.49%).

[0122] Add the mixture of lithium stearate, polyalphaolefin and azeotropic fluoroether solvent into a beaker and stir at 60°C until the lithium stearate is completely dissolved.

[0123] Cool the mixture to room temperature and add the organosilicon-treated hydrophobic alumina, mixing using a high-shear homogenizer. Add the remaining ingredients and mix until dissolved. Example 10

[0124] The following examples provide a method according to the present invention for preparing a polyacrylate coating having improved performance properties.

[0125] A 20 mL scintillation vial with a diaphragm cap was filled with a stir bar, 0.500 g butyl acrylate, 2.500 g methyl methacrylate, 0.060 g azobisisobutyronitrile (AIB), and 1.500 g n-butyl acetate. After sealing the vial, the solution was slowly flushed with nitrogen gas through the diaphragm cap using a hypodermic needle while stirring for 30 minutes. After flushing, the inlet and outlet needles were removed, and the vial was transferred to an aluminum heating block and heated at 85°C with stirring for 5 hours. To quench the reaction, the vial was removed from the heating block, aerated, and cooled in an ice bath. Example 11

[0126] The following examples provide a method according to the present invention for preparing a polyacrylate coating having improved performance properties.

[0127] A 20 mL scintillation vial with a diaphragm cap was filled with a stir bar, 2.000 g of ethylhexyl 2-acrylate, 1.700 g of isobornyl methacrylate, 0.074 g of azobisisobutyronitrile (AIBN), and 0.200 g of n-butyl acetate. After sealing the vial, the solution was slowly flushed with nitrogen gas through the diaphragm cap using a hypodermic needle while stirring for 30 minutes. After flushing, the inlet and outlet needles were removed, and the vial was transferred to an aluminum heating block and heated at 85°C with stirring for 5 hours. To quench the reaction, the vial was removed from the heating block, aerated, and cooled in an ice bath.

[0128] The reaction mixture was diluted to 10.7 wt% using n-butyl acetate and mixed at room temperature for 30 minutes using a magnetic stirrer. Industrial Applicability

[0129] The disclosed composition for forming a conformal coating, a conformal coating for a device or substrate, and a method for coating a device or substrate with a conformal coating can be used to protect a device or substrate from various environmental influences by virtue of its use as a protective layer.

[0130] In one embodiment, the surface may include a metal and the environment is not corrosive or water-based, such as condensate, tap water, sweat, sebum, salt water, carbonated beverages, coffee, liquid coolant, or antifreeze. In one embodiment, the surface includes a metal exhibiting galvanic corrosion and the environment is not causing galvanic corrosion. More generally, the surface may include any metal capable of oxidation and the environment is not causing oxidation selected from air, oxygen, or water vapor.

[0131] In another embodiment, the surface includes active electronic devices in a printed circuit board and the undesired environment includes corrosive gases selected from chlorine, water vapor, hydrogen sulfide, hydrogen chloride, or oxides of nitrogen and sulfur. In yet another embodiment, the surface includes active electronic devices in a printed circuit board and the undesired environment includes conductive liquids selected from water, sweat, and other corrosive fluids.

[0132] A conformal coating constructed according to the principles of the present invention generally exhibits improved functional durability while maintaining deformability due to the combination of at least one film-forming agent and at least one additive.

[0133] For example, at least one film-forming agent may include polyolefins, polyacrylates, polyurethanes, epoxy resins, polyamides, polyimides, polysiloxanes, or combinations thereof.

[0134] One or more additives may be selected from: antioxidants; passivators; UV absorbers or stabilizers; rheology modifiers; tackifiers; wetting agents; thickeners; plasticizers; dispersants; leveling agents; defoamers; processing aids; or combinations thereof.

[0135] Antioxidants may include phenolic antioxidants, amine antioxidants, thioether antioxidants, phosphite antioxidants, or combinations thereof.

[0136] Phenolic antioxidants can be selected from: phenylpropionic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, octadecyl ester (CAS# 2082-79-3), phenylpropionic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, 2,2-bis[[3-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxopropoxy]methyl]-1,3-propanediol (CAS# 6683-19-8), C7-C9 alkyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (CAS# Reactants of isomers of 125643-61-0), 1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris{[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl}- (CAS# 27676-62-6), or phenylpropionic acid, 3-(1,1-dimethylethyl)-4-hydroxy-5-methyl-, 2,4,8,10-tetraoxazolo[5.5]undecane-3,9-dimethylbis(2,2-dimethyl-2,1-ethylenedimethyl) ester (CAS# 90498-90-1), and combinations thereof.

[0137] Amine antioxidants can be selected from: the reaction products of aniline, N-phenyl-, 2,4,4-trimethylpentene (CAS# 68411-46-1), 1-naphthylamine, N-phenyl-aryl-(1,1,3,3-tetramethylbutyl) (CAS# 68259-36-9), 4,4'-dioctyldiphenylamine (CAS# 101-67-7), other alkylated amines, and combinations thereof.

[0138] The thioether antioxidant can be selected from: propionic acid, 3-(dodecylthio)-, 1,1'-[2,2-bis[[3-(dodecylthio)-1-oxopropoxy]methyl]-1,3-propanediyl] ester (CAS# 29598-76-3) or propionic acid, 3,3'-thiobis-, 1,1'-tetrazyl ester (CAS# 10595-72-9) and combinations thereof.

[0139] The antioxidant phosphite can be selected from: tris(2,4-di-tert-butylphenyl) phosphite (CAS# 31570-04-4), butylidene bis[2-tert-butyl-5-methyl-p-phenylene]-P,P,P',P'-tetradecylbis(phosphine) (CAS# 13003-12-8), 12H-dibenzo[d,g][1,3,2]phosphine dioxane, 2,4,8,10-tetratetra(1,1-dimethylethyl)-6-[(2-ethylhexyl)oxy]- (CAS# 126050-54-2) or tris(2,4-di-tert-butylphenyl) phosphite (CAS# 31570-04-4) and combinations thereof.

[0140] The passivating agent may include acehydrazine or triazole, selected from: dodecanoic acid, 1,12-bis[2-(2-hydroxybenzoyl)acehydrazine] (CAS# 63245-38-5), phenylpropionic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, 2-[3-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxopropyl]acehydrazine (CAS# 32687-78-8), 1,2,4-triazole (CAS# 288-88-0), 2-hydroxy-N-1H-1,2,4-triazol-3-ylbenzylamine (CAS# 36411-52-6), 1H-benzotriazole-1-methylamine, N,N-bis(2-ethylhexyl)-aryl-methyl- (CAS# 94270-86-7), 1H-1,2,4-triazol-1-methylamine, N,N-bis(2-ethylhexyl)-(CAS# 91273-04-0) and combinations thereof.

[0141] UV absorbers or stabilizers may include carbon black, rutile titanium dioxide, hindered amines, benzophenone and combinations thereof.

[0142] The rheology modifier may include sodium polyacrylate, polyamide wax, polyethylene wax, hydrogenated castor oil, attapulgite clay, calcined silica, precipitated silica, metal oxide particles, and combinations thereof.

[0143] The tackifier may include chlorinated polyolefins, cyanoacrylate primers, polyester alkyl ammonium salts, amino-functionalized polyethers, maleic anhydride, carboxylated polypropylene, glycidyl methacrylate-functionalized polyolefins, trimethoxyvinyl silane, silane, and combinations thereof.

[0144] The wetting agent or dispersant may include alkyl ammonium salts of polycarboxylic acids, alkyl ammonium salts of acidic polymers, salts of unsaturated polyamines and acidic polyesters, maleic anhydride-functionalized ethylene butyl acrylate copolymers, other ionic or nonionic surfactants, and combinations thereof.

[0145] The tackifier may include hydrogenated hydrocarbon resins or alicyclic hydrocarbon resins.

[0146] Plasticizers may include hydrogenated alicyclic hydrocarbon resins, trimellitic acid esters, high molecular weight phthalates, polysiloxane oils, octyl epoxy esters, or hydrogenated light cycloalkane petroleum distillates.

[0147] The leveling agent may include polysiloxane, liquid polyacrylate, ionic surfactant, nonionic surfactant or a mixture thereof.

[0148] The disclosed composition can be formulated in one or more solvents, such as aromatic solvents selected from toluene, xylene and naphtha, solvents selected from isoparaffins, hexane, methylcyclohexane, alkanes of alkenes, alcohols selected from butanol, alkyl acetates selected from tert-butyl acetate, alkyl ethers, ketones selected from methyl ethyl ketone, aldehydes and wholly or partially halogenated hydrocarbons.

[0149] The composition may also include at least one pigment or UV dye selected from the following: 2,2'-(2,5-thiophenediyl)bis(5-tert-butylbenzoxazole) (CAS# 7128-64-5), 2,2'-(1,2-ethylidene)bis(4,1-phenylene)bisbenzoxazole (CAS# 1533-45-5), Solvent Yellow 43 (CAS# 19125-99-6), Carbon Black (CAS# 1333-86-4), Pigment Yellow 101 (CAS# 2387-03-3), N,N'-bis(2,6-diisopropylphenyl)-3,4,9,10-perylenetetramethyldiimide (CAS# 82953-57-9), other perylene dyes and anthracene dyes.

[0150] When formulated in a solvent or once the solvent evaporates upon application, the composition may exhibit viscoelastic, viscoplastic, or elastoviscoplastic flow properties. It may also be non-polysiloxane, non-halogenated, or both.

[0151] The composition may have a volatile organic compound content of 650 g / L or less.

[0152] When applied to various surfaces, it can also have a thickness ranging from 25 nm to 500 µm.

[0153] In one embodiment, the composition exhibits electrical insulating properties such that when the composition is placed between two metal contacts, it prevents current leakage or arcing between the metal contacts. The electrical insulating properties also prevent current from flowing from an active electronic device on a printed circuit board to a conductive medium or the environment, or prevent electrostatic discharge from a charge carrier to an active electronic device on a printed circuit board.

[0154] As stated herein, the additives described herein provide enhanced durability against oxidative degradation compared to a composition without the additives. For example, the additives may provide enhanced mechanical stability to the composition without undergoing liquefaction, hardening, or other phase transitions compared to a composition without the additives. In one embodiment, one or more of the additives preferentially migrate to the coating / substrate interface to isolate the substrate from the remainder of the coating. For example, when the composition is formed into an adhesive coating as described herein, the additive may be a passivating agent that migrates to and adsorbs onto the coating / substrate interface to inhibit catalytic activity from the substrate. One or more of the additives preferentially migrate to uncoated areas of the substrate to protect the substrate from environmental impacts.

[0155] Considering the description and practice of the invention disclosed herein, those skilled in the art will understand other embodiments of the invention. The description and examples are intended to be illustrative only, wherein the true scope of the invention is indicated by the following claims. [Simplified Explanation of the Diagram]

[0012] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0013] Figure 1 is a flowchart illustrating one of the mechanisms of action of a representative antioxidant (AO) additive according to one of the disclosed embodiments.

[0014] Figure 2 is a schematic diagram showing one of the surface insulation resistance measurement settings.

[0015] Figure 3 shows a schematic diagram of an example additive migrating from the coating to the coating / substrate interface to prevent degradation of the coating or substrate.

[0016] Figure 4 shows a schematic diagram of an example additive migrating from the coating to the coating / air interface to prevent degradation of the coating or substrate.

[0017] Figure 5 shows a schematic diagram illustrating the step-by-step application of various additives.

[0018] Figure 6 shows a schematic diagram of the migration of an exemplary additive to one of the target-specific components from the external environment that may affect the coating performance.

[0019] Figure 7 shows a schematic diagram of one of the exemplary additives migrating from the coating to the coating / air interface to change the mechanical or diffusion properties at the interface.

Claims

1. A composition for forming a conformal coating to protect a substrate, the composition comprising: At least one film-forming agent comprising at least one of a polyolefin, polyacrylate, polyurethane, epoxy resin, polysiloxane, or a combination thereof; and at least one additive comprising at least one passivating agent comprising nitric acid hydrazine or triazole, selected from the group consisting of: dodecanoic acid bis[2-(2-hydroxybenzoyl)nitric acid hydrazine] (CAS# 63245-38-5), 1,2-bis(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (CAS# 32687-78-8), 1,2,4-triazole (CAS# 288-88-0), 2-hydroxy-N-1H-1,2,4-triazole-3-ylbenzoylamine (CAS# 288-88-0). Combinations of 36411-52-6), 1H-benzotriazole-1-methylamine, N,N-bis(2-ethylhexyl)-aryl-methyl- (CAS# 94270-86-7), 1H-1,2,4-triazole-1-methylamine, N,N-bis(2-ethylhexyl)- (CAS# 91273-04-0), and the like; wherein the composition is configured to form a deformable, flowable, and electrically insulating conformal coating.

2. The composition of claim 1, wherein the at least one additive further comprises at least one additive selected from the group consisting of: antioxidants, UV absorbers or stabilizers, rheology modifiers, tackifiers, wetting agents, thickeners, plasticizers, dispersants, leveling agents, defoamers, processing aids, and combinations thereof.

3. The composition of claim 2, wherein the antioxidant comprises phenolic antioxidants, amine antioxidants, thioether antioxidants, phosphite antioxidants, or combinations thereof.

4. The composition of claim 3, wherein the phenolic antioxidant is one or more compounds selected from the group consisting of: phenylpropionic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, octadecyl ester (CAS# 2082-79-3), phenylpropionic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-, 2,2-bis[[3-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxopropoxy]methyl]-1,3-propanediol (CAS# 6683-19-8), C7-C9 alkyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (CAS# 2082-79-3). One of the reaction products of 125643-61-0), 1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris{[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl}- (CAS# 27676-62-6), or phenylpropionic acid, 3-(1,1-dimethylethyl)-4-hydroxy-5-methyl-, 2,4,8,10-tetraoxazolo[5.5]undecane-3,9-dimethylbis(2,2-dimethyl-2,1-ethylenediyl) ester (CAS# 90498-90-1), and combinations thereof.

5. The composition of claim 3, wherein the amine antioxidant is one or more compounds selected from the group consisting of: aniline, the reaction product of N-phenyl-2,4,4-trimethylpentene (CAS# 68411-46-1), 1-naphthylamine, N-phenyl-aryl-(1,1,3,3-tetramethylbutyl) (CAS# 68259-36-9), 4,4'-dioctyldiphenylamine (CAS# 101-67-7), other alkylated amines, and combinations thereof.

6. The composition of claim 3, wherein the thioether antioxidant is one or more compounds selected from the group consisting of: pentaerythritol tetra[3-lauryl thiopropionate] (CAS# 29598-76-3), 3,3'-thiodipropionate ditetracetate (CAS# 10595-72-9), and combinations thereof.

7. The composition of claim 3, wherein the phosphite antioxidant is selected from one or more compounds of the group consisting of: tris(2,4-di-tert-butylphenyl) phosphite (CAS# 31570-04-4), butylidene bis[2-tert-butyl-5-methyl-p-phenylene]-P,P,P',P'-tetradecylbis(phosphine) (CAS# 13003-12-8), 12H-dibenzo[d,g][1,3,2]phosphine dioxane, 2,4,8,10-tetratetra(1,1-dimethylethyl)-6-[(2-ethylhexyl)oxy]- (CAS# 126050-54-2), tris(2,4-di-tert-butylphenyl) phosphite (CAS# 31570-04-4), and combinations thereof.

8. The composition of claim 2, wherein the UV absorber or the stabilizer comprises one or more compounds selected from the group consisting of: carbon black, rutile titanium dioxide, hindered amines, benzophenone, and combinations thereof.

9. The composition of claim 2, wherein the rheology modifier comprises one or more compounds selected from the group consisting of: sodium polyacrylate, polyamide wax, polyethylene wax, hydrogenated castor oil, attapulgite clay, calcined silica, precipitated silica, metal oxide particles, and combinations thereof.

10. The composition of claim 2, wherein the adhesive comprises one or more compounds selected from the group consisting of: chlorinated polyolefins, cyanoacrylate primers, polyester alkyl ammonium salts, amino-functionalized polyethers, maleic anhydride, carboxylated polypropylene, glycidyl methacrylate-functionalized polyolefins, trimethoxyvinyl silane, silane, and combinations thereof.

11. The composition of claim 2, wherein the wetting agent or the dispersant comprises one or more compounds selected from the group consisting of: alkyl ammonium salts of polycarboxylic acids, alkyl ammonium salts of acidic polymers, salts of unsaturated polyamines and acidic polyesters, maleic anhydride-functionalized ethylene butyl acrylate copolymers, other ionic or nonionic surfactants, and combinations thereof.

12. The composition of claim 2, wherein the tackifier comprises at least one of a hydrogenated hydrocarbon resin or an alicyclic hydrocarbon resin.

13. The composition of claim 2, wherein the plasticizer comprises at least one compound selected from the group consisting of: hydrogenated alicyclic hydrocarbon resins, trimellitic acid esters, high molecular weight phthalates, polysiloxane oils, octyl epoxy esters, and hydrogenated light cycloalkane petroleum distillates.

14. The composition of claim 2, wherein the leveling agent comprises at least one compound selected from the group consisting of: polysiloxane, liquid polyacrylate, ionic surfactant, nonionic surfactant, and combinations thereof.

15. The composition of claim 1, further comprising at least one pigment or UV dye selected from the group consisting of: 2,2'-(2,5-thiophenediyl)bis(5-tert-butylbenzoxazole) (CAS# 7128-64-5), 2,2'-(1,2-ethylidene)bis(4,1-phenylene)bisbenzoxazole (CAS# 1533-45-5), Solvent Yellow 43 (CAS# 19125-99-6), Carbon Black (CAS# 1333-86-4), Pigment Yellow 101 (CAS# 2387-03-3), N,N'-bis(2,6-diisopropylphenyl)-3,4,9,10-perylenetetramethyldiimide (CAS# 82953-57-9), other perylene dyes, and anthracene dyes.

16. The composition of claim 1, wherein the conformal coating exhibits viscoelastic, viscoplastic, or elastoviscoplastic flow properties.

17. The composition of claim 1, wherein the composition is free of polysiloxane.

18. The composition of claim 1, wherein the composition is non-halogenated.

19. The composition of claim 1, comprising a volatile organic compound content of 650 g / L or less.

20. The composition of claim 1, wherein the conformal coating has a thickness in the range of 25 nm to 500 µm on the substrate.

21. The composition of claim 1, wherein the conformal coating acts as a protective interface between the surface and the environment.

22. The composition of claim 21, wherein the surface comprises a metal and the environment is a corrosive or conductive environment selected from environments having high humidity, condensation, tap water, sweat, sebum, salt water, carbonated beverages, coffee, liquid coolant or antifreeze.

23. The composition of claim 22, wherein the surface comprises a metal exhibiting galvanic corrosion and the environment causes galvanic corrosion, or wherein the environment is an oxidizing environment containing at least one gas selected from air, oxygen, and water vapor.

24. The composition of claim 22, wherein the surface includes electronic devices in a printed circuit board, and the undesired environment includes at least one corrosive gas selected from the group consisting of chlorine, water vapor, hydrogen sulfide, hydrogen chloride, or oxides of nitrogen and sulfur, or at least one conductive liquid selected from the group consisting of water, sweat, and other corrosive fluids.

25. The composition of claim 1, which exhibits electrical insulating properties, thereby mitigating at least one of the following: current leakage or arcing between two metal contacts when the composition is placed between the two metal contacts; current flowing from active electronic devices on a printed circuit board to a conductive medium or the environment; electrostatic discharge from charge carriers to active electronic devices on a printed circuit board.

26. The composition of claim 1, wherein the additive provides the composition with at least one of the following properties: enhanced durability against oxidative degradation compared to a composition without the additive; and enhanced mechanical stability compared to a composition without the additive, and wherein the composition does not undergo liquefaction, hardening or other phase transitions.

27. The composition of claim 1, wherein one or more of the additives are present at the interface between the coating and the substrate or in areas of the substrate without the coating after application to the substrate.

28. The composition of claim 1, wherein the at least one passivating agent is present at the interface between the coating and the substrate and adsorbed thereon to inhibit the catalytic activity of the substrate.

29. The composition of claim 1, comprising at least one solvent.

30. A conformal coating for protecting electronic components, the conformal coating comprising: At least one film-forming agent comprising at least one of a polyolefin, polyacrylate, polyurethane, epoxy resin, polysiloxane, or a combination thereof; and at least one additive comprising at least one passivating agent comprising nitric acid hydrazine or triazole, selected from the group consisting of: dodecanoic acid bis[2-(2-hydroxybenzoyl)nitric acid hydrazine] (CAS# 63245-38-5), 1,2-bis(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (CAS# 32687-78-8), 1,2,4-triazole (CAS# 288-88-0), 2-hydroxy-N-1H-1,2,4-triazole-3-ylbenzoylamine (CAS# 288-88-0). Combinations of the following, including 36411-52-6), 1H-benzotriazole-1-methylamine, N,N-bis(2-ethylhexyl)-aryl-methyl- (CAS# 94270-86-7), 1H-1,2,4-triazole-1-methylamine, N,N-bis(2-ethylhexyl)- (CAS# 91273-04-0), and others, wherein the conformal coating is deformable, flowable, and electrically insulating.

31. The conformal coating of claim 30, comprising at least one solvent.

32. A method for treating an electronic device with a conformal adhesive coating, the method comprising: The conformal coating is applied to the electronic device, wherein the conformal coating comprises: at least one film-forming agent comprising at least one of a combination of polyolefin, polyacrylate, polyurethane, epoxy resin, polysiloxane, or the like; and at least one additive comprising at least one passivating agent comprising nitric acid hydrazine or triazole, selected from the group consisting of: dodecanoic acid bis[2-(2-hydroxybenzoyl)nitric acid hydrazine] (CAS# 63245-38-5), 1,2-bis(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (CAS# 32687-78-8), 1,2,4-triazole (CAS# 288-88-0), 2-hydroxy-N-1H-1,2,4-triazole-3-ylbenzoylamine (CAS# 10 ... Combinations of the following, including 36411-52-6), 1H-benzotriazole-1-methylamine, N,N-bis(2-ethylhexyl)-aryl-methyl- (CAS# 94270-86-7), 1H-1,2,4-triazole-1-methylamine, N,N-bis(2-ethylhexyl)- (CAS# 91273-04-0), and others, wherein the conformal coating is deformable, flowable, and electrically insulating.

33. The method of claim 32, wherein the conformal coating further comprises at least one solvent.

34. A substrate having a conformal adhesive coating thereon, the conformal adhesive coating comprising: At least one film-forming agent comprising at least one of a polyolefin, polyacrylate, polyurethane, epoxy resin, polysiloxane, or a combination thereof; and at least one additive comprising at least one passivating agent comprising nitric acid hydrazine or triazole, selected from the group consisting of: dodecanoic acid bis[2-(2-hydroxybenzoyl)nitric acid hydrazine] (CAS# 63245-38-5), 1,2-bis(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (CAS# 32687-78-8), 1,2,4-triazole (CAS# 288-88-0), 2-hydroxy-N-1H-1,2,4-triazole-3-ylbenzoylamine (CAS# 288-88-0). Combinations of the following, including 36411-52-6), 1H-benzotriazole-1-methylamine, N,N-bis(2-ethylhexyl)-aryl-methyl- (CAS# 94270-86-7), 1H-1,2,4-triazole-1-methylamine, N,N-bis(2-ethylhexyl)- (CAS# 91273-04-0), and others, wherein the conformal coating is deformable, flowable, and electrically insulating.

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