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  Circuit substrate material, circuits comprising the same, and method of manufacture thereofUSPTO Application #: 20060141132Title: Circuit substrate material, circuits comprising the same, and method of manufacture thereof Abstract: An electrical circuit material having a conductive layer disposed a substrate, wherein the substrate is formed from a thermosetting composition comprising a polybutadiene or polyisoprene resin; an optional, functionalized liquid polybutadiene or polyisoprene resin; an optional butadiene- or isoprene-containing copolymer; an optional low molecular weight polymer; an optional curing agent; a cross-linking agent; a particulate fluoropolymer; and about 20 to about 50 percent by weight, based on the total weight of the thermosetting composition, of a magnesium hydroxide having a low ionic content. Use of magnesium hydroxide allows the composition to attain a high level of flame retardancy without use of halogenated flame retardants, while maintaining good moisture absorption and other physical properties. (end of abstract) Agent: Cantor Colburn LLP - Bloomfield, CT, US Inventors: Murali Sethumadhavan, Vincent R. Landi, Bruce G. Kosa USPTO Applicaton #: 20060141132 - Class: 427058000 (USPTO) Related Patent Categories: Coating Processes, Electrical Product Produced The Patent Description & Claims data below is from USPTO Patent Application 20060141132. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefits of U.S. Provisional Patent Application Ser. No. 60/423,281 filed Nov. 1, 2002, which is fully incorporated herein by reference. BACKGROUND [0002] This disclosure relates generally to a method of making thermosetting compositions for use in electrical circuit materials and the resulting products, and in particular to thermosetting polybutadiene and polyisoprene circuit substrate materials. [0003] As used herein, a circuit material is an article used in the manufacture of circuits and multi-layer circuits, and includes circuit laminates, bond plies, resin coated conductive layers, and cover films. Circuit laminates, bond plies, resin coated conductive layers, and cover films in turn are formed from dielectric materials that can comprise a thermosetting or thermoplastic polymer. The dielectric material in a bond ply, resin covered conductive layer, or cover film may comprise a substantially non-flowable dielectric material, i.e., one that softens or flows during manufacture but not use of the circuit, whereas the dielectric material in a circuit laminate (e.g., a dielectric substrate) is designed to not soften or flow during manufacture or use of the circuit or multi-layer circuit. Dielectric substrate materials are further typically divided into two classes, flexible and rigid. Flexible dielectric substrate materials generally tend to be thinner and more bendable than the so-called rigid dielectric materials, which typically comprise a fibrous web or other forms of reinforcement, such as short or long fibers or fillers. [0004] A circuit laminate as used herein refers to one or two conductive layers fixedly attached to a dielectric substrate, which is formed from a dielectric material. Patterning a conductive layer of a laminate, e.g., by etching, provides a circuit. Multi-layer circuits comprise a plurality of conductive layers, at least one of which contains a conductive wiring pattern. Typically, multi-layer circuits are formed by laminating one or more circuits together using bond plies, and, in some cases, resin coated conductive layers, in proper alignment using heat and/or pressure. The bond plies are used to provide adhesion between circuits and/or between a circuit and a conductive layer, or between two conductive layers. In place of a conductive layer bonded to a circuit with a bond ply, the multi-layer circuit may include a resin coated conductive layer bonded directly to the outer layer of a circuit. In such multi-layer structures, after lamination, known hole forming and plating technologies may be used to produce useful electrical pathways between conductive layers. [0005] Polybutadiene and polyisoprene thermosetting materials have been successfully employed as rigid electrical circuit substrates. These materials have typically used halogenated, particularly brominated, flame retardant additives to achieve the necessary levels of flame retardancy. In recent years, brominated flame retardants have come under scrutiny, such that certain of them will be banned by January 2008. The remaining brominated flame retardants will require special incineration/disposal procedures. In light of the impending ban, manufacturers are placing additional pressures upon suppliers to produce flame retardant additives that are effective, yet that do not contain halogens. [0006] The most commonly used alternative flame retardant additives are phosphorous/nitrogen compounds. However, phosphorous/nitrogen compounds possess high dielectric constants, loss factors, and moisture absorption properties. These properties are adverse to intended uses in applications such as the electronic industries, automobile industries, and particularly in circuit boards and related applications. Accordingly, there remains a need for non-halogen containing flame retardant thermosetting compositions that provide the desired flame retardant properties without impairing physical properties such as electrical and moisture absorption properties. SUMMARY [0007] The above discussed and other problems and deficiencies of the prior art are overcome or alleviated by a substrate for an electrical circuit material, wherein the substrate is formed from a thermosetting composition comprising a polybutadiene or polyisoprene resin; an optional, functionalized liquid polybutadiene or polyisoprene resin; an optional butadiene- or isoprene-containing copolymer; an optional low molecular weight polymer; a cross-linking agent; a particulate fluoropolymer; and about 20 to about 50 percent by weight, based on the total weight of the thermosetting composition, of a magnesium hydroxide having less than about 1000 ppm of ionic contaminants, and further wherein the substrate has a UL-94 rating of at least V-1. [0008] In another embodiment, an electrical circuit material comprises a substrate and a layer of conductive metal disposed on the substrate, wherein the substrate is formed from a thermosetting composition comprising a polybutadiene or polyisoprene resin; an optional, functionalized liquid polybutadiene or polyisoprene resin; an optional butadiene- or isoprene-containing copolymer; an optional low molecular weight polymer; a cross-linking agent; a particulate fluoropolymer; and about 20 to about 50 percent by weight, based on the total weight of the thermosetting composition, of a magnesium hydroxide having a low ionic content, and further wherein the substrate has a UL-94 rating of at least V-1. [0009] Use of magnesium hydroxide in the thermosetting compositions allows the substrate materials to achieve a desired flame retardancy without use of brominated flame retardants, but does not adversely affect properties such as dielectric constant or moisture absorbance. The above-discussed and other features and advantages will be appreciated and understood by those of ordinary skill in the art from the following detailed description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0010] Referring now to the drawings, wherein like elements are numbered alike in the several FIGURES: [0011] FIG. 1 is a schematic representation of a diclad circuit material containing a woven web; and [0012] FIG. 2 is a schematic representation of a circuit material. DETAILED DESCRIPTION [0013] A thermosetting composition having particular utility as a substrate for an electrical circuit material comprises a thermosetting polybutadiene or polyisoprene resin system; about 20 to about 50 percent by weight, based on the total weight of the composition, of magnesium hydroxide having a low ionic content; a crosslinking agent; and a particulate fluoropolymer. [0014] Use of magnesium hydroxide as a flame retardant agent allows the circuit material to achieve the desired flame retardancy in the absence of halogenated flame retardants, particularly brominated flame retardants. Dielectric properties are also acceptable with use of magnesium hydroxide. This result is particularly surprising in view of the fact that magnesium hydroxide has a high dielectric constant and the presence of such large amounts of magnesium hydroxide would have been expected to greatly increase the dielectric constant of the composition. However, the inventors hereof have discovered that use of a particular polybutadiene or polyisoprene thermosetting composition, together with about 20 to about 50 percent by weight of a magnesium hydroxide having a low ionic content, produces a thermosetting composition exhibiting excellent flame retardancy, electrical and moisture resistance properties. [0015] A number of commercially available magnesium hydroxides are suitable for use in the present thermosetting compositions, for example those available under the trade name MAGNIFIN.RTM. from Albemarle Corp. According to the product literature, MAGNIFIN.RTM. H51V and MAGNIFIN.RTM. H10IV are magnesium hydroxides having a low ionic content, and are treated (coated) with an aminosilane. Low ionic content is herein defined as containing less than about 1,000 ppm, preferably less than about 500 ppm by weight of ionic contaminants such as chloride ion. In addition, it is preferred that the magnesium hydroxide has a low total metal content, herein defined as less than about 500 ppm, preferably less than about 400 ppm, more preferably less than about 300 ppm by weight of metal contaminants such as iron, aluminum, chromium, manganese, copper, and the like. It is especially preferred that the amount of iron oxide be limited to less than about 100 ppm, preferably less than about 50 ppm. Other suitable magnesium hydroxides are commercially available under the trade name MAGSHIELD from Martin Marietta Corp., ZEROGEN from J. M. Huber Engineering materials, and FR20 from Dead Sea Bromine Group. [0016] In addition, the particulate size of the magnesium hydroxide can impact the electrical and flame retardant properties of the substrate material. Preferably the magnesium hydroxide has an average surface area (BET) of about 3 to about 12 square meters per gram, preferably about 5 to about 10, and an average particle size of about 0.1 to about 2 micrometers. The magnesium hydroxide comprises about 20 to about 50 percent by weight of the total thermosetting composition (i.e., resin system as described below, curing agent, crosslinking agent, particulate fluoropolymer, and magnesium hydroxide, but exclusive of any reinforcing glass web or filler). [0017] The magnesium hydroxide is used in combination with a polybutadiene or polyisoprene thermosetting resin system comprising (1) a polybutadiene or polyisoprene resin; (2) an optional, functionalized liquid polybutadiene or polyisoprene resin; (3) an optional butadiene- or isoprene-containing copolymer; and (4) an optional low molecular weight polymer. [0018] As a first component, the resin system comprises a polybutadiene resin, a polyisoprene resin, or mixture thereof. The polybutadiene or polyisoprene resins may be liquid or solid at room temperature. Liquid resins may have a molecular weight greater than about 5,000, but preferably have a molecular weight of less than about 5,000 (most preferably between about 1,000 and about 3,000). The preferably liquid (at room temperature) resin portion maintains the viscosity of the composition at a manageable level during processing to facilitate handling, and it also crosslinks during cure. Polybutadiene and polyisoprene resins having at least 90% 1,2-addition by weight are preferred because they exhibit the greatest crosslink density upon cure owing to the large number of pendant vinyl groups available for crosslinking. High crosslink densities are desirable because the products exhibit superior performance in an electrochemical cell environment at elevated temperatures. A preferred resin is B3000 resin, a low molecular weight polybutadiene liquid resin having greater than 90 weight percent (wt. %) 1,2-addition. B3000 resin is commercially available from Nippon Soda Co., Ltd. [0019] The resin system further optionally comprises a functionalized liquid polybutadiene or polyisoprene resin. Examples of appropriate functionalities for butadiene liquid resins include but are not limited to epoxy, maleate, hydroxy, carboxyl and methacrylate. Examples of useful liquid butadiene copolymers are butadiene-co-styrene and butadiene-co-acrylonitrile. Possible functionalized liquid polybutadiene resins include Nisso G-1000, G-2000, G-3000; Nisso C-1000; Nisso BN-1010, BN-2010, BN-3010, CN-1010; Nisso TE-2000; and Nisso BF-1000 commercially available from Nippon Soda Co., Ltd. and Ricon 131/MA commercially available from Colorado Chemical Specialties, Inc. Continue reading... Full patent description for Circuit substrate material, circuits comprising the same, and method of manufacture thereof Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Circuit substrate material, circuits comprising the same, and method of manufacture thereof patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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