Curable Electrical Bonding Composition

Abstract

Provided herein are curable electrical bonding compositions for metallic conductors and methods of use thereof. The curable electrical bonding compositions include at least one conductive metal and at least one curable polymer.

Description

[Technical field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] All applications in which a foreign or domestic priority claim is identified in the PCT application filed with this application, including U.S. Provisional Application No. 63 / 296,781, filed January 5, 2022, are incorporated by reference herein under 37 CFR 1.57 and Rules 4.18 and 20.6.

[0002] The present invention relates generally to joining metallic electrical conductors, such as bus bars. [Background technology]

[0003] In the manufacture of products that carry large currents, it is desirable to reduce the electrical resistance between two large metal conductors, such as busbars, at a fastened joint. Typically, a preload from a steel bolt or stud is used to create a significant amount of force to bring the metal parts together. Aluminum busbars are preferred due to their low cost. However, naturally occurring oxides, including the very tough aluminum oxide, often reduce the electrical conductivity of the surface.

[0004] Traditional solutions include nickel, copper, silver, and tin plating, which is an expensive, wasteful, and environmentally challenging process. Other solutions include applying petroleum grease to the joints, but the grease-like compositions build up on surfaces and equipment, creating hazards and challenges for manufacturing operations. Additionally, the grease-like compositions cannot be reliably applied to the underside of the busbar substrate, limiting application or process sequence options. Summary of the Invention

[0005] For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention are described herein. Not all such objects or advantages may be achieved in any particular embodiment of the invention. Thus, for example, one skilled in the art will understand that the invention may be embodied or implemented to achieve or optimize one or more advantages as taught herein, without necessarily achieving other objects or advantages as may be taught or suggested herein.

[0006] The present disclosure includes curable electrical bonding compositions, methods of using the compositions, and metal conductors (eg, bus bars) comprising the compositions.

[0007] In one aspect, a curable electrical bonding composition is described that includes at least one conductive metal selected from the group consisting of zinc, tin, cadmium, nickel, platinum, gold, silver, copper, aluminum, palladium, rhodium, stainless steel, and alloys thereof, and at least one curable polymer.

[0008] In some embodiments, the composition includes a conductive metal at a concentration of about 40-60 wt. %. In some embodiments, the at least one conductive metal has a D of about 1-20 μm. 50 In some embodiments, the at least one conductive metal is a powder having a particle size distribution of about 5 to 15 μm D 50 In some embodiments, the composition has a particle size distribution. In some embodiments, the composition includes a low durometer elastomer. In some embodiments, the curable electrical bonding composition has a viscosity of about 10,000 to 250,000 cps. In some embodiments, the composition has a viscosity of about 100,000 to 200,000 cps.

[0009] In some embodiments, the curable electrical bonding composition further comprises a cure additive selected from the group consisting of a catalyst, a curing agent, a crosslinking agent, a drying agent, a curing metal, a curing peroxide, and combinations thereof. In some embodiments, the curable electrical bonding composition comprises platinum. In some embodiments, the curable electrical bonding composition has a cure temperature of about 20-30° C.

[0010] In another aspect, an electrical bond assembly is described. The assembly comprises two or more metallic conductors and a curable electrical bond composition disposed between the two or more metallic conductors. In some embodiments, the two or more metallic conductors comprise aluminum.

[0011] In another aspect, a cured electrical joint assembly is described that includes two or more metallic conductors and a cured electrical joint composition disposed between the two or more metallic conductors, the cured electrical joint composition including at least one conductive metal selected from the group consisting of zinc, tin, cadmium, nickel, platinum, gold, silver, copper, aluminum, palladium, rhodium, stainless steel, and alloys thereof, and at least one cured polymer.

[0012] In some embodiments, the cured electrical bonding composition has an electrical resistance of about 150-1,500 μOhms at a bolt clamp load of about 1-4 kN. In some embodiments, the curable electrical bonding composition has an electrical resistance of up to about 10 μOhms at a bolt clamp load of about 7-10 kN. In some embodiments, the device is selected from the group consisting of a vehicle powertrain, an energy storage device, a solar device, and a server electrical component device.

[0013] In another aspect, a method of fastening a first metallic conductor to a second metallic conductor is described, the method comprising applying a curable electrical bonding composition to the first metallic conductor and contacting the second metallic conductor with the curable electrical bonding composition and the first metallic conductor.

[0014] In some embodiments, the method further comprises compressing the curable electrical bonding composition between the first metal conductor and the second metal conductor. In some embodiments, the compressing comprises applying a force of about 7-10 kN. In some embodiments, the curable electrical bonding composition is applied by squeeze application, screen, stencil, dispense application, dip coating, spray coating, nozzle, aerosol, inkjet, gravure, flexography, manual, and combinations thereof. In some embodiments, the curable electrical bonding composition is applied in a dot array on a surface of at least one of the two or more metal conductors. Further, in some embodiments, the dot array ranges from 10 microns to 12 microns. In some embodiments, the curable electrical bonding composition is applied to the underside of at least one of the two or more metal conductors without spilling, bleeding, dripping, or settling.

[0015] In another aspect, a method of curing an electrical bond assembly is described. The method includes applying at least one of heat, light, pressure, and combinations thereof to the electrical bond assembly. In some embodiments, the curing occurs at a temperature of about 20-30° C. In some embodiments, the method further includes bolting the first metallic conductor to the second metallic conductor. [Brief description of the drawings]

[0016] [Figure 1] 1 is a graph showing the force vs. resistance relationship of the cured electrical bonding composition disclosed herein compared to other bonding compositions.

[0017] [Figure 2A] FIG. 2 is a schematic cross-sectional view of a dot array dispersion of a curable electrical bonding composition before a metallic conductor is bolted thereto, according to one embodiment.

[0018] [Figure 2B] FIG. 2 is a schematic cross-sectional view of the uniform spread of a curable electrical bonding composition after a metallic conductor is bolted, according to one embodiment.

[0019] [Diagram 3] 1 is a graph showing force versus resistance of a cured electrical bonding composition according to one embodiment compared to a commercially available composition.

[0020] [Figure 4A] 1 is a photographic image of a dot array dispersion of a curable electrical bonding composition prior to bolting a metal conductor, according to one embodiment.

[0021] [Figure 4B] 1 is a photographic image of a curable electrical bonding composition after bolting a metal conductor, according to one embodiment. Detailed Description of the Invention

[0022] The present disclosure relates to a curable electrical bonding composition for joining metal conductors, such as bus bars, with reduced electrical resistance between the two metal conductors, reducing the number of process steps and material waste. In some embodiments, the curable electrical bonding composition comprises one or more conductive metals and a curable polymer.

[0023] Conductive metal As used herein, "conductive metal" refers to any one of the elements of Groups 1-13 of the Periodic Table of the Elements, plus tin and lead of Group 14, antimony of Group 15, and the lanthanides and actinides, or a metal alloy of any two or more of such elements. In some embodiments, the element or metal alloy has a volume resistivity (ρ) of less than 0.0001 ohm-centimeters at 20° C. and a resistivity (ρ) of less than 1×10 at 20° C. 6It can have a conductivity (K) of more than Siemens per meter (S / m). Examples of such elements are silver, copper, gold, aluminum, calcium, molybdenum, zinc, lithium, tungsten, nickel, iron, palladium, platinum, tin, lead, titanium, mercury, and blends thereof. Examples of such metal alloys are brass (a metal alloy of copper and zinc), bronze (a metal alloy of copper and tin), 67Cu33Zn, carbon steel, grain-oriented electrical steel, MANGANIN (a trade name for a metal alloy of the formula Cu86Mn12Ni2 by Isabelenhutte Heusler GmbH&Co.KG, Dilenburg, Germany), Konstantin (a metal alloy of 55% copper and 45% nickel), Nichrome (a metal alloy of nickel, chromium, and optionally iron), and blends thereof.

[0024] In some embodiments, the conductive metal may be, but is not limited to, zinc, tin, cadmium, nickel, platinum, gold, silver, copper, aluminum, palladium, rhodium, stainless steel, and alloys thereof. In some embodiments, the conductive metal includes or is zinc. Only one type of conductive metal may be used, or multiple types may be used.

[0025] In some embodiments, the curable electrical bonding composition comprises 25%, 30%, 35%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90% by weight of a conductive metal at, or about, or at least about, or any range of values ​​therebetween. For example, in some embodiments, the amount of conductive metal in the curable electrical bonding composition is in, or is about, any one of the following ranges: 20-40 weight percent, 40-60 weight percent, 60-80 weight percent, 45-55 weight percent, 46-54 weight percent, 47-53 weight percent, 48-52 weight percent, or 49-51 weight percent (based on the total weight of the composition).

[0026] The conductive metals used in the present disclosure may be provided as finely divided particles having any one or more of the following morphologies: powder, flake, spherical, granular, nodular, crystalline, other irregular morphologies, or mixtures thereof. In some embodiments, the conductive metal may be a metal powder.

[0027] In some embodiments, the conductive metal has a D of 0.1 μm, 0.15 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 25 μm, 30 μm, 40 μm, 50 μm, 75 μm, 100 μm, 125 μm, 150 μm, or 200 μm, or about these values, or any range of values ​​therebetween. 50 In some embodiments, the conductive metal has an average particle size of, or about, 0.1 μm, 0.15 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 25 μm, 30 μm, 40 μm, 50 μm, 75 μm, 100 μm, 125 μm, 150 μm, or 200 μm, or about, or about any range of values ​​therebetween.

[0028] In some embodiments, the metal powder penetrates the native oxide layer of the busbar, hi further embodiments, the metal powder prevents galvanic corrosion of the metal conductor. Curable and Cured Polymers

[0029] The curable polymer may be or may include an elastomer, such as silicone, polybutene, styrene block polymers, and combinations thereof. In some embodiments, the curable polymer may be or may include a low durometer elastomer. In some embodiments, the curable polymer is configured to form a matrix in which elements (e.g., conductive metals) may be suspended. In some embodiments, the curable polymer includes or is a silicone matrix. In further embodiments, the curable polymer (e.g., elastomer) provides a durable seal that prevents further oxidation and contamination of the joint.

[0030] In some embodiments, the curable electrical bonding composition comprises 25%, 30%, 35%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90% by weight of a curable polymer, or about these values, or at least these values, or at least about these values, or any range of values ​​therebetween. For example, in some embodiments, the amount of curable polymer in the curable electrical bonding composition is in, or is about, any one of the following ranges: 20-40 weight percent, 40-60 weight percent, 60-80 weight percent, 45-55 weight percent, 46-54 weight percent, 47-53 weight percent, 48-52 weight percent, or 49-51 weight percent (based on the total weight of the composition).

[0031] After the curable polymer cures, a cured polymer is formed. The cured polymer of the present disclosure provides significant manufacturing process advantages over commercially available non-curable bonding compositions. The cured polymer provides a durable seal to prevent further oxidation and contamination of the joint. In addition, the cured polymer of the present disclosure provides high resistance until the joint is fully tightened.

[0032] Hardening additives In some embodiments, the curable electrical bonding composition includes a curing additive that aids in curing of the composition. In some embodiments, the curing additive may be selected from the group consisting of a catalyst, a curing agent, a crosslinking agent, a drying agent, and combinations thereof. In some embodiments, the catalyst is a thermal catalyst, a photochemical catalyst, and combinations thereof. In some embodiments, the curing additive includes a curing metal and / or a curing peroxide. In some embodiments, the curing metal includes platinum. In some embodiments, the crosslinking agent includes an epoxy resin. In some embodiments, the thermal catalyst includes a thermal stabilizer. In some embodiments, the photochemical catalyst includes a UV absorber. In some embodiments, the photochemical catalyst includes a light stabilizer.

[0033] Additional additives In some embodiments, the curable electrical bonding composition includes an additional additive, which in some embodiments is selected from the group consisting of pigments, dyes, surfactants, pigment dispersing aids, leveling agents, wetting agents, emulsifiers, anti-crush agents, defoamers, anti-sagging agents, antioxidants, fillers, and combinations thereof.

[0034] Curable electrical bonding composition The curable electrical bonding composition includes a conductive metal and a curable polymer. In some embodiments, the conductive metal (e.g., metal powder) is suspended in a polymer matrix (e.g., elastomeric matrix). In some embodiments, the conductive metal (e.g., metal powder) is in matrix form. In some embodiments, the curable electrical bonding composition is in a range of 1,000 cps, 2,000 cps, 3,000 cps, 4,000 cps, 5,000 cps, 6,000 cps, 7,000 cps, 8,000 cps, 9,000 cps, 10,000 cps, 11,000 cps, 12,000 cps, 13,000 cps, 14,000 cps, 15,000cps, 16,000cps, 17,000cps, 18,000cps, 19,000cps, 20,000cps, 21,000cps, 22,000cps s, 23,000cps, 24,000cps, 25,000cps, 26,000cps, 27,000cps, 28,000cps, 29,000cps, 30,000 cps, 40,000cps, 50,000cps, 60,000cps, 70,000cps, 80,000cps, 90,000cps, 100,000cps, 11 0,000cps, 120,000cps, 130,000cps, 140,000cps, 150,000cps, 160,000cps, 170,000cps, 180 The viscosity may be, for example, about 1,000 cps, 190,000 cps, 200,000 cps, 210,000 cps, 220,000 cps, 230,000 cps, 240,000 cps, or 250,000 cps, or at least about these values, or at least about these values, or any range of values ​​therebetween. For example, in some embodiments, the viscosity may be about 1,000 cps to about 10,000 cps, about 10,000 cps to about 25,000 cps, about 50,000 cps to about 150,000 cps, or about 100,000 cps to about 250,000 cps.

[0035] In some embodiments, the curable electrical bonding compositions are configured to provide metal (e.g., metal conductors, metal sheets) protection against corrosion and oxidation. In some embodiments, the curable electrical bonding compositions are configured to provide metal protection for conductors such as copper and aluminum. In further embodiments, the cured electrical compositions exhibit extremely high durability under harsh environmental conditions. In some embodiments, the cured electrical compositions are configured to provide superior adhesion to a range of metal substrate types compared to other bonding compositions. In some embodiments, the cured electrical compositions are configured to provide superior shear strength compared to other bonding compositions. Cured electrical bonding material and method for curing same

[0036] After curing of the electrical bonding composition, a cured electrical bonding material is formed. The cured electrical bonding material includes a conductive metal and a cured polymer. In some embodiments, the cured electrical bonding material includes additional compounds and / or elements (e.g., curing additives) that were included in the curable electrical bonding composition prior to curing. In some embodiments, the cured electrical bonding material has a compressibility of 0.5 N / mm 2 , 1N / mm 2 , 2N / mm 2 , 3N / mm 2 , 4N / mm 2 , 5N / mm 2 , 6N / mm 2 , 7N / mm 2 , 8N / mm 2 , 9N / mm 2 , 10N / mm 2 , 11N / mm 2 , 12N / mm 2 , 13N / mm 2 , 14N / mm 2 , 15N / mm 2 , 16N / mm 2 , 17N / mm 2 , 18N / mm 2 , 19N / mm 2 , 20N / mm 2 , 21N / mm 2 , 22N / mm 2 , 23N / mm 2 , 24N / mm2 , 25N / mm 2 , 26N / mm 2 , 27N / mm 2 , 28N / mm 2 , 29N / mm 2 , 30N / mm 2 , 35N / mm 2 , 40N / mm 2 , 45N / mm 2 , or 50N / mm 2 In some embodiments, the cured electrical bonding material has a tensile bond strength of 0.5 N / mm 2 , 1N / mm 2 , 2N / mm 2 , 3N / mm 2 , 4N / mm 2 , 5N / mm 2 , 6N / mm 2 , 7N / mm 2 , 8N / mm 2 , 9N / mm 2 , 10N / mm 2 , 11N / mm 2 , 12N / mm 2 , 13N / mm 2 , 14N / mm 2 , 15N / mm 2 , 16N / mm 2 , 17N / mm 2 , 18N / mm 2 , 19N / mm 2 , 20N / mm 2 , 21N / mm 2 , 22N / mm 2 , 23N / mm 2 , 24N / mm 2 , 25N / mm 2 , 26N / mm 2 , 27N / mm 2 , 28N / mm 2 , 29N / mm 2 , 30N / mm 2 , 35N / mm 2 , 40N / mm 2 , 45N / mm 2 , or 50N / mm 2 , or any range of values ​​therebetween.

[0037] Curing of the electrical bonding composition into a cured electrical bonding material can be accomplished by curing the curable polymer. In some embodiments, curing is accomplished by application of heat, light, pressure, etc. to increase the adhesive strength of the electrical bonding material. In some embodiments, curing is accomplished using a thermal catalyst or a photochemical catalyst. In some embodiments, the curable electrical bonding composition is cured at room temperature. In some embodiments, heat is applied to the electrical bonding composition to cure or assist the curing process. In some embodiments, curing is carried out at a temperature of, or at about, or at least about, or at any range of values ​​therebetween: 20° C., 21° C., 22° C., 23° C., 24° C., 25° C., 26° C., 27° C., 28° C., 29° C., 30° C., 31° C., 32° C., 33° C., 34° C., 35° C., 40° C., 45° C., 50° C., 55° C., 60° C., 65° C., 70° C., 75° C., 80° C., 85° C., 90° C., 95° C., 100° C., 110° C., 120° C., 130° C., 140° C., 150° C., 160° C., 170° C., 180° C., 190° C., or 200° C. In some embodiments, the curable electrical bonding composition is exposed to oxygen gas (e.g., air) to cure or aid in curing the composition. In some embodiments, the curable electrical bonding composition is exposed to light (e.g., ultraviolet (UV) light) to cure or aid in curing the composition. In some embodiments, curing occurs in the absence of heat, light, etc. In some embodiments, curing occurs at atmospheric pressure. In some embodiments, curing occurs under a pressure of 2 atm, 3 atm, 4 atm, 5 atm, 6 atm, 7 atm, 8 atm, 9 atm, 10 atm, 11 atm, 12 atm, 13 atm, 14 atm, 15 atm, 16 atm, 17 atm, 18 atm, 19 atm, 20 atm, 25 atm, 30 atm, 35 atm, 40 atm, 45 atm, 50 atm, or 55 atm, or any range of values ​​therebetween.

[0038] In some embodiments, the curable electrical bond composition includes a first portion including a conductive metal and a curable polymer and a second portion including a curing additive. In some embodiments, the first portion of the curable electrical bond composition and the second portion of the curable electrical bond composition are stored separately. In some embodiments, the curing process begins when the curable polymer comes into contact with the curing additive. In some embodiments, the curing process begins when the first portion of the curable electrical bond composition and the second portion of the curable electrical bond composition are mixed. In some embodiments, the curing process begins when the first portion of the curable electrical bond composition and the second portion of the curable electrical bond composition are mixed and exposed to light.

[0039] Electrical Joint Assembly In some embodiments, the electrical joint assembly comprises a curable electrical joint material disposed between two or more metallic conductors. In some embodiments, the curable electrical joint material is cured between the two or more metallic conductors. In some embodiments, the electrical joint assembly comprises a cured electrical joint material disposed between two or more metallic conductors. In some embodiments, the electrical joint material fastens the two or more metallic conductors together. In some embodiments, the curable electrical joint material is cured after being disposed and spread between the two or more metallic conductors. In other embodiments, the curable electrical joint material is cured after the two or more metallic conductors are bolted together. In some embodiments, the metallic conductor is a bus bar. In some embodiments, the metallic conductor is bare aluminum.

[0040] In some embodiments, the electrical joint assembly conducts high current. In some embodiments, the electrical joint material reduces electrical resistance between two metal conductors at a fastened joint. In some embodiments, a bolt clamp load of 1 kN, 2 kN, 3 kN, 4 kN, 5 kN, 6 kN, 7 kN, 8 kN, 9 kN, 10 kN, 11 kN, 12 kN, 13 kN, 14 kN, 15 kN, 16 kN, 17 kN, 18 kN, 19 kN, or 20 kN, or at least about these values, or at least about these values, or any range of values ​​therebetween, is applied to the electrical joint material. For example, in some embodiments, the bolt clamp load applied to the electrical joint material is in or approximately in any one of the following ranges: 1-16 kN, 2-15 kN, 3-14 kN, 4-13 kN, 5-12 kN, 6-11 kN, 7-10 kN, or 8-9 kN.

[0041] Application method Some embodiments of the present application relate to methods for applying the curable electrical bonding compositions disclosed herein. The curable electrical bonding compositions can be applied to the joint surface by a variety of deposition methods. Examples of suitable methods include screen or stencil printing, dispense application, dip coating, spray coating, or other methods such as nozzle, aerosol, inkjet, gravure, flexographic printing, or manual.

[0042] In some embodiments, the curable electrical bonding composition can be applied by squeeze application. In some embodiments, squeeze application of the curable electrical bonding composition has been observed to remove dust and other foreign matter on the joint by pushing debris captured during the bolting operation to the end of the joint. In some embodiments, squeeze application of the curable electrical bonding composition removes dust and other foreign matter from the joint. Some embodiments of the methods disclosed herein do not plate the electrical joint. In some embodiments of the methods disclosed herein, the method of applying the curable electrical bonding composition to one or more electrical joints does not plate the one or more electrical joints.

[0043] A low contact force of the plated material can provide a resistance low enough to pass rapid manufacturing tests. However, such low contact force of the plated material ultimately fails due to insufficient clamp load. As shown in FIG. 1, the cured electrical joint composition disclosed herein has been observed to provide a high resistance until the bolt is fully tightened, as compared to other joint compositions and methods. Furthermore, after the bolt clamp force is applied to the metal conductors, the electrical resistance between two or more metal conductors is significantly reduced, as compared to other joint compositions and joining methods. As shown in FIG. 1, in some embodiments, the cured electrical joint composition disclosed herein provides a high resistance before the bolt clamp force is applied to the two or more metal conductors. After the bolt clamp force is applied, the two or more metal conductors fastened by the cured electrical joint composition provide a similar or lower electrical resistance than other fastening methods, such as commercial electrical grease or plating. Such superior advantages of the cured electrical joint composition allow for detection of electrical joints with insufficient clamp loads during the manufacturing process, thus making the detection of manufacturing defects more effective.

[0044] In some embodiments, the curable electrical bonding composition can be dispensed in a dot array to achieve uniform spreading. In some embodiments, the dots can be applied with a high aspect ratio. In some embodiments, the curable electrical bonding composition is dispensed in a range of about 5 microns to about 500 microns. In some embodiments, the curable electrical bonding composition is dispensed in a range of about 10 microns to about 250 microns. In some embodiments, the curable electrical bonding composition is dispensed in a range of about 10 microns to about 12 microns. As shown in Figures 2A and 2B, application of high aspect ratio dots has been observed to improve the performance of the curable electrical bonding composition by inducing high shear forces during compression.

[0045] In some embodiments, the curable electrical bonding composition can be applied to the underside of a busbar without spilling, bleeding, dripping, or settling. In some embodiments, the curable electrical bonding composition allows for assembly of metal conductors or busbars at any angle. In some embodiments, the curable electrical bonding composition can be applied at any orientation of the joint or busbar. In further embodiments, the curable electrical bonding composition can be applied prior to final assembly and joint fastening.

[0046] In some embodiments, the curable electrical bonding composition is applied as a tape. For example, in some embodiments, the curable electrical bonding composition is applied as a film that includes a single-sided adhesive or a double-sided adhesive with embedded metal. In further embodiments, the tape includes a backing carrier film.

[0047] In some embodiments, the curable electrical bonding composition is applied to bare metal conductors. In some embodiments, the metal conductors are not plated. In some embodiments, the curable electrical bonding composition is applied to bare copper. In some embodiments, the curable electrical bonding composition is applied to bare aluminum.

[0048] Equipment and Applications The curable electrical bonding compositions and methods of use described herein can be utilized in a wide range of applications and devices. In some embodiments, the electrical bonding compositions are used in situations where low electrical resistance is required between busbars. In some embodiments, the electrical bonding compositions can be used to fasten vehicle powertrain components, energy storage (e.g., battery) components, solar components, and server electrical components. EXAMPLES

[0049] The curable electrical bonding compositions of the present disclosure can be prepared and utilized as disclosed herein. Additional embodiments are disclosed in more detail in the following examples, which are not intended to limit the scope of the claims in any way.

[0050] Example 1 - Electrical Resistance to Force of Curable Electrical Bonding Composition The curable electrical bonding compositions disclosed herein provide advantages over commercially available electrical greases. In this example, a 10 μm D 50 A curable electrical bonding composition sample was prepared comprising zinc powder having a particle size distribution, a curable low durometer silicone matrix, and a platinum hardening metal. The curable electrical bonding composition sample comprised a zinc powder concentration of about 50% by weight. The curable electrical bonding composition was applied and spread between two metal conductors. The metal conductors comprised bare aluminum bus bars. The curable electrical bonding composition was cured in the presence of oxygen gas (e.g., air) to form a cured electrical bonding assembly. The resistance of the cured electrical bonding composition was recorded over a range of forces applied to the cured electrical bonding assembly.

[0051] FIG. 3 provides a graph of force versus resistance for a cured electrical composition according to one embodiment compared to a commercially available product. For example, at a bolt clamp load of about 1 kN to about 4 kN, the cured electrical composition disclosed herein exhibits a resistance of about 150 μOhms to about 1,500 μOhms, while the grease-like composition exhibits a resistance of about 200 μOhms within the same clamp load. Such high resistance prior to full tightening provides an excellent opportunity to detect under-tightened joints. Furthermore, at a bolt clamp load of about 7 kN to about 10 kN, the cured electrical composition disclosed herein exhibits a resistance of about 2 μOhms to about 10 μOhms, similar to the resistance of the grease-like composition.

[0052] Example 2 - Dot application process of the curable electrical bonding composition The application process of the curable electrical bonding composition further improved the fastening performance of the curable electrical bonding composition, and the high aspect ratio dot or spot application of the curable electrical bonding composition provided improved fastening performance due to the high shear forces induced during compression. Figure 4A shows a photographic image of the dot array dispersion of the curable electrical bonding composition sample of Example 1 before bolting the metal conductor. After bolting the metal conductor, the curable electrical bonding composition was evenly spread on the surface of the metal conductor, as shown in Figure 4B.

Claims

1. 1. A curable electrical bonding composition comprising: at least one conductive metal selected from the group consisting of zinc, tin, cadmium, nickel, platinum, gold, silver, copper, aluminum, palladium, rhodium, stainless steel, and alloys thereof; at least one curable polymer.

2. The composition of claim 1, wherein the composition comprises the conductive metal at a concentration of about 40-60% by weight.

3. The at least one conductive metal has a D of about 1 to 20 μm. 50 3. The composition of claim 1 or 2, which is a powder having a particle size distribution.

4. The at least one conductive metal has a D of about 5 to 15 μm. 50 The composition of claim 3 having a particle size distribution.

5. The composition of any one of claims 1 to 4, wherein the composition comprises a low durometer elastomer.

6. The composition of any one of claims 1 to 5, wherein the curable electrical bonding composition has a viscosity of about 10,000 to 250,000 cps.

7. The composition of claim 6, wherein the composition has a viscosity of about 100,000 to 200,000 cps.

8. 8. The composition of any one of claims 1 to 7, wherein the curable electrical bonding composition further comprises a curing additive selected from the group consisting of a catalyst, a curing agent, a crosslinking agent, a drying agent, a curing metal, a curing peroxide, and combinations thereof.

9. The composition of claim 8 , wherein the curable electrical bonding composition comprises platinum.

10. The composition of any one of claims 1 to 9, wherein the curable electrical bonding composition has a cure temperature of about 20-30°C.

11. 1. An electrical interface assembly comprising: two or more metallic conductors; and a curable electrical bonding composition according to any one of claims 1 to 10 disposed between the two or more metallic conductors.

12. The electrical interface assembly of claim 11 , wherein the two or more metallic conductors comprise aluminum.

13. 1. A hardened electrical connection assembly comprising: two or more metallic conductors; A cured electrical bonding composition disposed between the two or more metallic conductors, the cured electrical bonding composition comprising: at least one conductive metal selected from the group consisting of zinc, tin, cadmium, nickel, platinum, gold, silver, copper, aluminum, palladium, rhodium, stainless steel, and alloys thereof; at least one cured polymer; and 1. A hardened electrical joint assembly comprising:

14. The cured electrical joint assembly of claim 13, wherein the cured electrical joint composition has an electrical resistance of about 150 to 1,500 μOhms at a bolt clamp load of about 1 to 4 kN.

15. The cured electrical joint assembly of claim 12, wherein the curable electrical joint composition has an electrical resistivity of up to about 10 μOhms at a bolt clamp load of about 7-10 kN.

16. 14. An apparatus comprising the hardened electrical interface assembly of claim 13, said apparatus being selected from the group consisting of a vehicle powertrain, an energy storage device, a solar device, and a server electrical component device.

17. 1. A method of fastening a first metallic conductor to a second metallic conductor, comprising the steps of: applying a curable electrical bonding composition according to any one of claims 1 to 10 to a first metallic electrical conductor; contacting a second metallic conductor with the curable electrical bonding composition and the first metallic conductor.

18. 20. The method of claim 17, further comprising compressing the curable electrical bonding composition between the first metallic conductor and the second metallic conductor.

19. The method of claim 18, wherein the compressing step comprises applying a force of about 7-10 kN.

20. 20. The method of claim 17, wherein the curable electrical bonding composition is applied by squeeze application, screen, stencil, dispense application, dip coating, spray coating, nozzle, aerosol, ink jet, gravure, flexography, manual, and combinations thereof.

21. 21. The method of claim 20, wherein the curable electrical bonding composition is applied in a dot array onto a surface of at least one of the two or more metallic conductors.

22. The method of claim 21 , wherein the array of dots ranges from 10 microns to 12 microns.

23. 23. The method of any one of claims 17-22, wherein the curable electrical bonding composition is applied to the underside of at least one of the two or more metallic conductors without spilling, bleeding, dripping, or settling.

24. 12. A method of curing an electrical bond assembly according to claim 11, comprising applying at least one of heat, light, pressure, and combinations thereof to the electrical bond assembly.

25. The method of claim 24, wherein the curing is carried out at a temperature of about 20 to 30°C.

26. The method of any one of claims 17 to 23, further comprising the step of bolting the first metallic conductor to the second metallic conductor.

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