A curable composition is formulated from an epoxy resin; a flame-retardant additive essentially free of phenolic groups and of epoxy groups; and a thermoplastic resin. The preferred epoxy resin is a mixture of an epoxy resin with less than 2 glycidyl ether groups per molecule and an epoxy resin that has greater than 2 glycidyl ether groups per molecule. The preferred flame-retardant additive is a brominated heterocyclic compound that preferable is triazine. The preferred thermoplastic resin is a poly(phenylene ether). The inventive curable compositions advantageously can be combined with reinforcement in the manufacture of circuit boards having excellent electrical properties, good solvent resistance, and good thermal expansion characteristics.

None
Not applicable.
The present invention relates to curable flame retardant compositions and more particularly to curable epoxy compositions containing a brominated triazine flame retardant additive which compositions are ideally suited for fabricating circuit boards.
Metal-clad boards, particularly such boards for use in fabricating printed circuits, are well-known in the art. The simplest of such boards generally comprises a resinous plastic (polymeric) substrate to which is bonded at least one thin sheet of an electrically conductive material, preferably copper. The resinous plastic substrate can be clad with the metal foil on one or both sides, depending upon the desired use, and can be rigid or flexible depending upon the composition of the resinous plastic substrate, the choice of reinforcement (if any), and the intended use of the board.
A number of polyphenylene ether compositions having favorable dielectric properties and utility in circuit board manufacture are known. However, there is a growing need in the industry for laminates with good thermal performance, solvent resistance, and improved dielectric properties such as dissipation factor and dielectric constant. Due to deficiencies in one or more properties, many such compositions have not attained wide commercial use. Specifically, while polyphenylene ethers are excellent dielectrics, deficiencies often are found in areas such as solvent resistance, flammability, and resistance to high temperatures. Polyphenylene ethers often are combined with polyepoxides in an attempt to improve upon the aforementioned properties, but such combinations have not been found to be wholly satisfactory either.
In addition to excellent dielectric properties, resinous compositions useful in printed circuit board manufacture also should be highly flame-retardant. A V-1 rating, as determined by Underwriters Laboratories test procedure UL-94, is universally required, with V-0 usually being necessary. The V-0 rating requires a flame-out time (FOT) of not more than 10 seconds in any trial and a cumulative FOT of not more than 50 seconds for five samples. As a practical matter, purchasers often mandate a maximum cumulative FOT of 35 seconds.
The fabricated board should not lose substantial weight and its surface should not be appreciably marred by contact with methylene chloride, a solvent commonly used for cleaning. Since connections with the printed circuit typically are made by soldering, the board must be solder-resistant as evidenced by the lowest possible percent increase in thickness (Z-axis expansion) when exposed to liquid solder at 288xc2x0 C. In addition to all these properties of the cured material, a relatively short curing time is highly desirable.
In preparing rigid metal-clad boards, it is common to form individual lamina, commonly called prepregs, by formulating a resinous binder composition made from epoxy, modified styrene, or the like. A solvent solution of the resin is placed in an apparatus known as a xe2x80x9cdip tank.xe2x80x9d Continuous webs of reinforcement can be pre-impregnated in the tank and then dried in a vertical or horizontal treating tower or oven. Normally, the resin is partially cured or B-staged after exiting the treater tower or oven. The copper foil, optionally coated with an adhesive, is placed on one side of the prepreg and subjected to heating under pressure to effect a bond between the metal foil and the substrate. Multiple prepregs can be used in forming a single composite board. Additionally, multilayer printed wiring boards will have a number of interposed laminae and copper sheets.
Pressing of the boards can be effected in a press by placing the foil/substrate structure between the platens and closing the press, or a continuous belt can be used. The curing cycle in the press will depend upon the nature and thickness of the laminate, the time and temperature of the cycle being those required to cure the substrate, and the bonding adhesive layer, if present. Sufficient pressure is required to effect adequate flow of the adhesive and/or substrate resins in order to wet-out and bond adequately. The pressure must be sufficient to prevent blistering which is due to the release of gases resulting either from retained volatiles in the substrate or adhesive layers, or resulting from by-products of the curing process.
Japanese patent 64[1988]-3223 describes blends of bisphenol-A diglycidyl ether, TBBPA diglycidyl ether, epoxy phenol novolac and curing agents such as amines. However, the resulting material produces laminates with inferior solvent resistance and is, thus, not suitable from printed circuit board laminates.
Japanese patents Hei 2[1990]-55721 and Hei 2[1990]-55722 describe laminates with improved chemical resistance, comprising (1) a bisphenol poly(glycidyl ether), epoxy novolac, and brominated bisphenol reaction product; (2) a poly(phenylene ether); (3) a novolac resin; (4) a lead salt; and (5) Sb2O3. However, the resulting trichloroethylene resistance still is not adequate in the cured product, and surface roughening is observed.
Walles et al. (U.S. Pat. No. 4,975,319) describe compositions comprising (1) a bisphenol poly(glycidyl ether), epoxy novolac, and brominated bisphenol reaction product; (2) a poly(phenylene ether); (3) a novolac resin, curing agents, and hardeners that produce laminates with dissipation factors in the range of 0.011-0.016.
Hallgren et al. (U.S. Pat. No. 5,043,367) describes (1) poly(phenylene ether); (2) halogenated bisphenol diglycidyl ether non-halogenated diglycidyl ether, and various curing agents which produce solvent resistant laminates having dissipation factors in the range of 0.011-0.013.
Katayose et al. (U.S. Pat. No. 5,218,030) describes the use of (i) a poly(phenylene ether) containing pendant allyl or propargyl groups; (ii) triallylcyanurate or triallylisocyanurate; and optionally (iii) a flame retardant; or (iv) an antimony-containing auxiliary flame retardant.
Katayose et al. (U.S. Pat. No. 5,352,745) disclose compositions with improved solvent resistance comprising a high molecular weight functionalized poly(phenylene ether) resin (xcex7=0.30-0.56 IV PPO) produced through reactive extrusion of poly(phenylene ether) with maleic anhydride. Formulation of (i) the reaction product of poly(phenylene ether) (PPE) with an unsaturated acid or acid anhydride with, (ii) triallylcyanurate or triallylisocyanurate, (iii) a brominated epoxy resin, (iv) novolac resins, and (v) a cure catalyst, produces flame retardant and solvent resistant resins useful in the production of printed circuit boards. This patent shows that a portion of the amino functionalized end groups contain capping residues. The skilled artisan would recognize that such end groups would comprise less than 10% of the hydroxyl end groups and would not be sufficient to significantly accelerate the cure rate of an allylic thermoset.
Chao et al. (U.S. Pat. No. 5,213,886) describe blends of low molecular weight poly(phenylene ether) compounds and epoxy resins. Tracy et al. (U.S. Pat. No. 5,834,565) describe blends of low molecular weight poly(phenylene ether) compounds in thermosetting matrices such as epoxy resins and unsaturated polyesters. These thermosetting compositions exhibit improved processability over analogous compositions containing high molecular weight poly(phenylene ether) compounds.
None of the foregoing art discloses the present flame-retardant blends that display excellent electrical properties, good solvent resistance, and good thermal expansion characteristics.
A curable composition is formulated from an epoxy resin; a flame retardant additive essentially free of phenolic groups and epoxy groups preferably having toluene solubility of greater than 15 g/100 ml toluene at 50xc2x0 C.; and a thermoplastic resin. The preferred epoxy resin component comprises an epoxy resin or mixture of epoxy resins with have on average greater than 2 glycidyl ether groups per molecule. The preferred flame-retardant additive is a brominated triazine compound. The preferred thermoplastic resin is a resin having a Tg greater than 130xc2x0 C. and most preferably a poly(phenylene ether).
The inventive curable compositions advantageously can be combined with reinforcement in the manufacture of circuit boards having excellent electrical properties, good solvent resistance, and thermal properties.
The present invention includes flame retardant and solvent resistant laminates with excellent thermal and dielectric properties ideally suited for electrical laminates. Such compositions comprise (a) an epoxy resin and curing agent therefor; (b) a flame-retardant additive essentially devoid of epoxy groups and of phenolic groups; and (c) a thermoplastic resin.
The epoxy resin component comprehends molecules containing one or more oxirane ring groups. Useful epoxy resins include, for example, glycidyl ethers, partial reaction products of glycidyl ethers with phenols (either monomeric or polymeric), or cycloaliphatic epoxies. Epoxy resins useful in the present invention include those described in Chemistry and Technology of the Epoxy Resins; Ellis, B. Ed.; Blackie Academic and Professional imprint of Chapman and Hall: London (1993). Preferred epoxies include, for example, multifunctional glycidyl ethers exemplified by epoxidized phenol-formaldehyde novolacs, epoxidized cresol-formaldehyde novolacs and other epoxidized alkylphenol-formaldehyde novolacs, epoxidized 1,1,1-tris(4-hydroxyphenyl)ethane, epoxidized 1,1,2,2-tetra(4-hydroxyphenyl) ethane, epoxidized phenol-dicyclopentadiene novolacs, and epoxidized phenol-benzaldehyde novolacs. Preferably, the epoxy resin component is essentially free of bromine atoms. This means that the epoxy resin component has less than a 1% bromine atom content.
Useful catalysts/curing agents for the epoxy resin component include those described by B. Ellis in Chemistry and Technology of The Epoxy Resins, Chapman and Hall, New York, N.Y. (1993) and also in U.S. Pat. Nos. 5,141,791, 4,923,912, and 4849,486, the disclosures of which are expressly incorporated herein by reference. Catalysts effective as curing agents for epoxy resins, such as, for example, imidazoles, may be utilized in the practice of the invention. Particularly useful imidazoles include, for example, imidazole, 1-methylimidazole, 1,2-dimethylimidazole, 2-methylimidazole, 2-heptadecylimidazole, 2-ethyl4-methylimidazole, 2-undecylimidazole, and 1-(2-cyanoethyl)-2-phenylimidazole. Preferred imidazoles include, for example, 1,2-dimethylimidazole and 2-heptadecylimidazole. Particularly preferred in the practice of the present invention, however, is a catalyst package formed from a dicyanadiamide, benzyldimethylamine, and 2-methylimidazole. For present purposes, catalysts for cure of the epoxy resin are included within the term xe2x80x9ccuring agentxe2x80x9d. That is, a catalyst can be a curing agent.
Brominated heterocyclic compounds useful in the present invention include any compound containing both bromine groups and a heterocyclic moiety, such as, for example, triazine, pyrrole, or oxidized derivatives thereof. Preferred brominated heterocyclic compounds are brominated triazines. Such compounds often are prepared by the condensation of a brominated phenol or mixture of brominated phenols with a cyanuric halide, such as cyanuric chloride, most often in the presence of a basic catalyst. The most preferred brominated triazines are those represented by structures 1 and 2, below, where structure 1 corresponds to 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine (Chemical Abstracts Registry No. 25713-60-4), and structure 2 corresponds to 2,2xe2x80x2-[(1-methylethylidene)bis[(2,6-dibromo-4,1-phenylene)oxy]]bis[4,6-bis[(2,4,6-tribromophenyl)oxy]-1,3,5-triazine (Chemical Abstracts Registry No. 329736-04-1).
The flame retardant additive is essentially free of phenolic groups and of epoxy (oxirane) groups. This means that the flame retardant additive contains less than 1 wt-% phenolic group or epoxy group content.
Thermoplastic compounds useful in the inventive curable composition include those having Tg""s greater than 120xc2x0 C. because thermoplastics with lower Tg""s have deleterious effect on the thermal performance of the cured composition. Representative of such preferred thermoplastic compounds include, for example, poly(phenylene ether) compounds, polyimides, and poly(styrene-co-maleic anhydride). Poly(phenylene ether) resins are commercially available as blends with homopolystyrene (Tg=100xc2x0 C.) and as such are not suitable for the present invention because of the deleterious effects of the low Tg resin on thermal properties of the laminate. Thus, the present curable compositions are essentially free of styrene homopolymers, i.e., contain less than 1 wt-% styrene homopolymer content.
Poly(phenylene ether) compounds are the most preferred thermoplastic compounds for use in the novel curable composition and include all known poly(phenylene ether) compounds, poly(phenylene ether) copolymers, and derivatized poly(phenylene ether) resins synthesized therefrom. Poly(phenylene ether) compounds are described in the art in numerous patents and references, and generally contain recurring units of the following structure, 3.
wherein R1-4 independently are hydrogen; alkyl, alkenyl; alkynyl; aryl; mixed alkyl-, alkenyl-, or alkynyl-aryl hydrocarbons, and such groups optionally containing a substituent selected from one or more of a carboxylic acid, an aldehyde, an alcohol, and an amino substituent.
Useful copolymers include oxidative polymerization products of 2,6-dimethylphenol and 2,3,6-trimethylphenol. Derivatized resins include, for example, poly(phenylene ether) compounds containing pendant allylic, propargylic radicals, or end-group derivatized resins formed through, for example, reaction of the terminal hydroxyl groups of the poly(phenylene ether) with an acid chloride, ester, or anhydride. Typical of end-group derivatized resins are the reaction products of a poly(phenylene ether) with trimellitic anhydride acid chloride, methacrylic anhydride, or acrylic anhydride. Derivatized resins also include the reaction products of produced by reaction of a poly(phenylene ether) with an unsaturated acid, anhydride, or a hydroxylated acid or anhydride which are most optimally prepared in the polymer melt by process such as by extrusion at temperatures of between about 200xc2x0-350xc2x0 C. Exemplary reactants for such melt extrusion process include unsaturated acid, anhydride, or a hydroxylated acid or anhydride including maleic anhydride, maleic acid, citric acid, malic acid, and the like.
Preferred poly(phenylene ether) compounds for use in the present invention include low molecular weight poly(phenylene ether) compounds having number average molecular weights from about 1,000 to 10,000 g/mol, or weight average molecular weight of from about 3,000 to 35,000 g/mol. Such materials may be prepared using by oxidative polymerization of alkylated phenols by known procedures. Alternatively, these materials may be prepared by the reaction of a high molecular poly(phenylene ether) with a peroxide and a phenol, or with a peroxide alone. In a preferred embodiment, a high molecular weight poly(phenylene ether) with a number average molecular weight of about 45,000 g/mol is reacted in a toluene solution at about 50xc2x0-90xc2x0 C. with benzoyl peroxide and bisphenol-A. Such low molecular weight polymers may be isolated by precipitation in an non-solvent, such as methanol, or more preferably by volatilization of the solvent and melt extrusion of the resulting polymer at temperatures from about 2000xc2x0-300xc2x0 C.
When using the preferred thermoplastic resin, poly(phenylene ether), it is advantageous to use a flame retardant additive that is mutually soluble in an aromatic hydrocarbon solvent which preferably is toluene. The minimum amount of flame retardant required to achieve UL-94 V-0 flammability rating often is less than 30 parts by weight of the total composition. The preferred brominated flame retardants should have good solubility in aromatic hydrocarbon solvent of choice, say toluene, at temperatures below about 50xc2x0 C. Generally, a solubility of 15 g/100 ml toluene at 50xc2x0 C. is sufficient. Because of such toluene solubility, the preferred flame retardant resin compositions can be prepared as homogeneous solutions, which allows for uniform impregnation of a fibrous reinforcement. Thus, it is highly advantageous in the practice of the present invention to use toluene soluble brominated flame retardant additives with a poly(phenylene ether) thermoplastic compound, the epoxy resin and curing agents and catalysts therefor, in a toluene solvent or a mixture of solvents which contain greater than 50% by weight toluene, advantageously 80% by weight toluene, and preferably 100% toluene.
Other thermosetting resins optionally may be blended with the epoxy resin component in forming the curable composition disclosed herein including, for example, cyanate esters, bismaleimides, and unsaturated polyesters. Such thermosetting resins are known to the art and are disclosed in, for example, U.S. Pat. Nos. 4,604,452, 4,785,075, 4,902,752, 4,983,683, 5,068,309, and 5,149,863.
Cyanate esters useful in the present invention include, for example, those that could be formed by replacement of glycidyl groups(-CH2CHOCH2) of epoxy resins with xe2x80x94CN groups. Useful cyanate ester compounds include, but are not limited to the following: 1,3- and 1,4-dicyanatobenzene; 2-tert-butyl-1,4-dicyanatobenzene; 2,4-dimethyl-1,3-dicyanatobenzene; 2,5-di-tert-butyl-1,4-dicyanatobenzene; tetramethyl-1,4-dicyanatobenzene; 4-chloro-1,3-dicyanatobenzene; 1,3,5-tricyanatobenzene; 2,2xe2x80x2- and 4,4xe2x80x2-dicyanatobiphenyl; 3,3xe2x80x25,5xe2x80x2-tetramethyl-4,4xe2x80x2-dicyanatobiphenyl; 1,3-, 1,4-, 1,5-, 1,6-, 1,8-, 2,6-, and 2,7-dicyanatonaphthalene; 1,3,6-tricyanatonaphthalene; bis(4cyanatophenyl)methane; bis(3-chloro-4-cyanatophenyl)methane; bis(3,5-dimethyl4-cyanatophenyl)methane; 1,1-bis(4-cyanatophenyl)ethane; 2,2-bis(4-cyanatophenyl)propane; 2,2-bis(3,3-dibromo-4-cyanatophenyl)propane; 2,2-bis(4-cyanatophenyl)-1,1,1,3,3,3-hexafluoropropane; bis(4-cyanatophenyl)ester; bis(4-cyanatophenoxy)benzene; bis(4-cyanatophenyl)ketone; bis(4-cyanatophenyl)thioether; bis(4-cyanatophenyl)sulfone; tris(4-cyanatophenyl)phosphate, and tris(4-cyanatophenyl)phosphate.
Also useful are cyanic acid esters derived from phenolic resins, e.g., as disclosed in U.S. Pat. No. 3,962,184; cyanated novolac resins derived from novolac, e.g., as disclosed in U.S. Pat. No. 4,022,755; cyanated bis-phenol-type polycarbonate oligomers derived from bisphenol-type polycarbonate oligomers, e.g., as disclosed in U.S. Pat. No. 4,026,913; cyano-terminated polyarylene ethers, e.g., as disclosed in U.S. Pat. No. 3,595,900; dicyanate esters free of ortho hydrogen atoms, e.g., as disclosed in U.S. Pat. No. 4,740,584; mixtures of di- and tricyanates, e.g., as disclosed in U.S. Pat. No. 4,709,008; polyaromatic cyanates containing polycyclic aliphatic groups, e.g., as disclosed in U.S. Pat. No. 4,528,366, e.g., QUARTEXTM(trademark) 7187, available from Dow Chemical Company (Midland, Mich.); fluorocarbon cyanates, e.g., as disclosed in U.S. Pat. No. 3,733,349; and cyanates, e.g., as disclosed in U.S. Pats. Nos. 4,195,132 and 4,116,946, all of the foregoing patents being expressly incorporated herein by reference.
Polycyanate compounds obtained by reacting a phenol-formaldehyde precondensate with a halogenated cyanide also may be useful for present purposes. Examples of preferred cyanate ester resin compositions include low molecular weight (Mn) oligomers, e.g., from about 250 to about 5000, e.g., bisphenol-A dicyanates such as AroCyTM(trademark); xe2x80x9cB-30 Cyanate Ester Semisolid Resinxe2x80x9d; low molecular weight oligomers of tetra o-methyl bis-phenol F dicyanates, such as xe2x80x9cAroCyTM(trademark); M-30 Cyanate Ester Semisolid Resinxe2x80x9d; low molecular weight oligomers of thiodiphenol dicyanates, such as AroCyTM(trademark); xe2x80x9cT-30xe2x80x9d, all of the foregoing being commercially available from Ciba-Geigy Corp., Hawthorne, N.Y.
Bismaleimide resins include, for example, resins derived from aromatic diamines, such as those described in U.S. Pat. No. 4,389,516. Generally, bismaleimides are synthesized, for example, by reacting a diluted ether solution of a diamine to a similar diluted ether solution of maleic anhydride to form a maleamic acid, which can be disposed in acetic anhydride and converted to the corresponding bismaleimide in the presence of potassium acetate (see U.S. Pat. No. 2,444,536).
Reinforcements known to one skilled in the art can be used, including but not limited to, inorganic and organic materials, such as woven or non-woven glass fabrics of the E-, NE-, S-, T- and D-type glasses and quartz, and the like. They may be in the form of glass roving cloth, glass cloth, chopped glass, hollow glass fibers, glass mat, glass surfacing mat, and non-woven glass fabric, ceramic fiber fabrics, and metallic fiber fabrics. In addition, synthetic organic reinforcing fillers may also be used in the present invention including, for example, organic polymers capable of forming fibers. Illustrative examples of such reinforcing organic fibers include, for example, poly(ether ketone), polyimide benzoxazole, poly(phenylene sulfide), polyesters, aromatic polyamides, aromatic polyimides or polyetherimides, acrylic resins, and poly(vinyl alcohol). Fluoropolymers such as polytetrafluoroethylene, can be used in the present invention. Also included as reinforcement are natural organic fibers known to those skilled in the art, including cotton cloth, hemp cloth, felt, carbon fiber fabrics, and natural cellulosic fabrics such as Kraft paper, cotton paper; and glass fiber containing paper. Such reinforcing fillers may be provided in the form of monofilament or multifilament fibers and could be used either alone or in combination with another type of fiber, through, for example, co-weaving or core/sheath, side-by-side, orange-type or matrix and fibril constructions, or by other methods known to one skilled in the art of fiber manufacture. Such fillers could be supplied in the form of, for example, woven fibrous reinforcements, non-woven fibrous reinforcements, or papers.
Coupling agents, incorporated into the reinforcing material, are known in the art to improve adhesion of the fibrous reinforcement to the cured resin composition. For the purposes of the present invention, representative coupling agents include, for example, silane-, titanate-, zirconate-, aluminum-, and zircoaluminum-based coupling agents, as well as other agents known to those skilled in the art.
Among the other materials that may be present are inert, particulate fillers such as talc, clay, mica, silica, alumina, and calcium carbonate. Fabric wettability enhancers (e.g. wetting agents and coupling agents) and polar liquids such as n-butyl alcohol, methyl ethyl ketone, polysiloxanes, and tetrahydrofuran, may be advantageous under certain conditions. Such materials as antioxidants, thermal and ultraviolet stabilizers, lubricants, antistatic agents, dyes, and pigments also may be present.
The curable compositions of the invention are dissolved in an effective amount of an inert organic solvent, typically to a solute content of about 30%-60% by weight. The identity of the solvent is not critical, provided it may be removed by suitable means such as evaporation. Examples of suitable solvents include aromatic hydrocarbons, such as toluene or xylene, cycloaliphatic ethers such as tetrahydrofuran, chlorinated hydrocarbons such as chloroform, amides such as dimethylformamides, or mixtures of the above solvents with an aromatic or chlorinated hydrocarbon, ketone, ether, amide other solvent known to the art. Aromatic hydrocarbons, especially toluene, are useful in the preferred embodiment where the thermoplastic resin is a poly(phenylene ether). The order of blending and dissolution also is not critical; however, in order to avoid premature curing, catalyst and curing agent (hardener) components generally should not be brought initially into contact with polyphenylene ether and polyepoxides at a temperature below about 50xc2x0 C. Proportions of components and bromine herein do not include solvent.
In this application all amounts and proportions are by weight and units are in the metric system, unless otherwise indicated. Also, all citations referred to herein are expressly incorporated herein by reference.

Curable epoxy resin compositions with brominated triazine flame retardants


Hydrogen is stored by adsorbing the hydrogen to a carbon nanomaterial that includes carbon nanospheres. The carbon nanospheres are multi-walled, hollow carbon nanostructures with a maximum diameter in a range from about 10 nm to about 200 nm. The nanospheres have an irregular outer surface with graphitic defects and an aspect ratio of less than 3:1. The carbon nanospheres can store hydrogen in quantities of at least 1.0% by weight.

1. The Field of the Invention
The present invention relates generally to the storage of molecular hydrogen. More particularly, the present invention relates to the storage of hydrogen using carbon nanospheres.
2. The Related Technology
The limited supplies of fossil fuels and the increasing number of densely populated metropolitan cities with poor local air quality have spurred interest in developing new energy sources. Hydrogen has emerged as a promising candidate for replacing various aspects of the world's current energy production system. Hydrogen is attractive as a fuel source because it can be produced from renewable sources and burns pollution-free or can be used in pollution-free fuel cells, as the combustion or reaction product is water.
The single greatest impediment to the use of hydrogen as an energy source is the lack of a convenient, cost-effective storage system for vehicles. Traditional methods for storing hydrogen employ large, heavy high-pressure tanks that are not practical or cost effective for widespread use in the transportation industry.
Extensive research is being performed to develop a hydrogen storage system suitable for the transportation industry and other industries that require a light-weight and safe storage mechanism. Possible current approaches include (i) physical storage via compression or liquefaction, (ii) chemical storage in irreversible hydrogen carriers (e.g., methanol or ammonia), (iii) reversible metal and chemical hydrides, and (iv) gas-on-solid adsorption.
Carbon based adsorbents have been studied for their potential to store hydrogen. Initial efforts to store hydrogen in carbon involved "activated" carbons. However, activated carbons are ineffective in storing hydrogen because only a small fraction of the pores in the typically wide pore-size distribution are small enough to interact strongly with hydrogen molecules at room temperature and moderate pressures. Recently, single-walled and multi-walled nanotubes have been studied for their potential to store hydrogen. Recent work relating to carbon nanotubes has shown that various differences in carbon nanotubes can have significant impact on the ability of carbon nanotubes to store hydrogen. However, despite extensive efforts to optimize carbon nanotubes for hydrogen storage, storage capacity in carbon nanotubes is not currently feasible for most applications.

Hydrogen storage apparatus using porous carbon nanospheres


This invention provides a method for removing flux residue and similar other residues formed on the surfaces of micro electronic components during soldering operations using solder paste and fluxing agents in electronic module assembly component fabrication by a semi-aqueous solvent cleaning process using propylene glycol alkyl ether solvents, preferably the mono alkyl ethers, as replacements for xylene. The electronic components may contain plastic components, for example, a plastic grid array (PBGA) in addition to silicon device chip(s), C4 decaps and SMTs on a ceramic chip carrier with solder columns. Preferred solvents are dipropylene glycol mono methyl ether and tripropylene glycol mono methyl ether, which are both water soluble.

1. Field of the Invention
The present invention relates generally to a method for removing flux residue and other surface contaminants formed on the surfaces of microelectronic components during soldering operations using solder paste in electronic module assembly, and, more particularly, to a semi-aqueous solvent cleaning process for removing flux residues that are formed on a chip, substrate, card or other electronic component containing plastic components.
2. Description of Related Art
Semiconductor devices are becoming smaller and more dense with the evolution of new technology. However, increases in circuit density produce a corresponding increase in overall device enhancements and semiconductor manufacturers are therefore constantly challenged to improve the quality, design and other aspects of their products. Some electronic modules carry silicon device chip, surface mount components (SMT) as well as plastic components like plastic ball grid array module (PBGA) on a ceramic chip carrier. For those type components special consideration is required for the assembly fabrication procedures and cleaning methods to remove flux residues formed during solder connections to assure cleaning solvent and process compatibility with all the module materials including plastic components.
Assembly fabrication processes for electronic circuit devices typically use solder connections for electrically joining an electronic device to a support substrate, solder ball and solder column attachment to chip carrier, for ceramic ball grid array (CBGA) and ceramic column grid array (CCGA) connections to organic board or a printed circuit board (PCB), and to attach other SMT components to a PCB.
C4 technology (controlled collapse chip connection), also called flip-chip bonding, is used for example to attach a semiconductor chip to a ceramic substrate. This bonding method involves connecting an array of solder bumps on the chip circuit structure side to C4 bonding pads on the substrate by high temperature solder reflow in a furnace under N2 or forming gas (5% H2 with 95% N2), typically requiring reflow temperature of 350-365xc2x0 C. for the 97/3 Pb/Sn alloy in the presence of a rosinbased Alpha 102 solder flux to form a solder bond. The flux residue formed in the C4 joining process is removed in a solvent cleaning process using xylene or chlorinated solvents. Low temperature soldering processes in electronic module assembly operations generally employ low melting alloys or solder paste of which Pb37/Sn63 eutectic paste is widely used. For example, eutectic solder paste is used to attach 90/10 Pb/Sn solder balls and solder columns to a ceramic chip carrier in a ceramic ball grid array (CBGA) and ceramic column grid array (CCGA), to attach solder balls to a plastic chip carrier in a plastic ball grid array (PBGA), to attach PBGA and other plastic components to a ceramic chip carrier, to join surface mount components as capacitors/resistors to a chip carrier, and for mounting of electronic components onto PCBs.
Solder pastes typically comprise a solder powder, for example, eutectic Sn-Pb alloy (Pb37%-Sn63%), melting temperature about 183xc2x0 C., eutectic Bi-Sn alloy, melting temperature about 135xc2x0 C., ternary alloy Bi-Sn-Pb and Sn-In along with other additives for wettability, flow properties, and compatibility with screen printing or dispensing methods. Various types of pastes that are used in soldering processes in electronics assembly include: water soluble solder paste flux formulations, no-clean (NC) flux pastes, and non-water soluble paste compositions. The fluxing agents generally used in solder pastes are, organic acids or salts, fatty acids or esters, polycarboxylic acids and derivatives, hydroxy carboxylic acids, organic acid esters, rosin acid and ester compositions, typically abietic acid and its derivatives, and in some cases amines including alkanolamines, aliphatic amines, and aromatic amines.
The presence of flux in solder pastes used for solder connections, for example, in the fabrication of BGA, CBGA, CCGA, SMT discretes, and solder ball and column attachment to a chip carrier for package-to-organic board connections, provides surface wettability of the contacting surfaces during joining which is essential for solder bond integrity.
In the cooling cycle of the thermal profile for joining, the solder hardens and at the same time, vaporized residual flux and its decomposition products deposit on the various exposed surfaces. In a subsequent step, the electronic assembly is then subjected to a solvent cleaning operation to remove flux residue prior to further processing.
The flux residue must be removed from all critical surfaces prior to further operation since it can cause function failure during long term use due to, for example, stress corrosion during exposure to temperature and humidity environment. It is therefore necessary after chip joining and other soldering processes during fabrication of electronic circuit assemblies, that the flux residue be cleaned off (removed) before subsequent operations.
Rosin fluxes are natural products comprising a complex mixture of cyclic hydrocarbon acid fractions which form almost 90% of the rosin flux chemical composition and about 10% neutral fraction constituting their corresponding methyl esters, alcohols, acetate and decarboxylated products. Among the rosin acids which are the major components of the mixture, abietic acid is present up to between about 50 to about 60 percent, dihydroabietic acid about 14%, and tetrahydroabietic acid and dehydroabietic acid being the minor constituents of the rosin acid mixture. These rosin fluxes and other fluxes are known to promote wetting of metal surfaces by their chemically reacting with an oxide layer on the surface of tin and/or lead providing an oxide-free metal exposed surface of high surface energy which thermodynamically should readily wet clean contacting metal surfaces on the substrate and provide reliable solder interconnection.
In the case of water soluble solder paste flux, residue after a soldering operation is generally removed by aqueous cleaning with water alone or water in conjunction with a suitable surfactant. With solder pastes which contain flux and other organic constituents which are not water soluble, flux residue cleaning processes traditionally have employed halogenated hydrocarbons, such as, perchloroethylene, and aromatic hydrocarbons as xylene similar to the rosin flux residue cleaning with xylene in the C4 chip join process. The halogenated hydrocarbon solvents, however, are undesirable due to their harmful effects on the environment and on human health as stated above.
With xylene there are also safety concerns as it is a highly flammable and volatile solvent having a flash point of 85xc2x0 F. which requires special high cost equipment for chemical safety in manufacturing environment as well as for compliance with rules for air emissions of hazardous air pollutants. In addition to these problems in the use of xylene, perchloroethylene and related solvents, there is a concern as to their viability as flux residue cleaning solvents in instances where the electronic module or ceramic chip carrier may contain plastic components mounted thereon prior to another soldering operation using solder paste, for example, eutectic solder paste for low temperature reflow process (220xc2x0 C. peak temperature). For example, fabrication of an electronic module with a 42.5 mmxc3x9742.5 mm ceramic chip carrier with solder columns involves (1) C4 chip and C4 decaps attachment using alpha 102 rosin flux with high temperature solder reflow at 360xc2x0 C. peak temp; (2) flux residue cleaning with xylene; (3) solder joining SMTs and a plastic component (PBGA) with water soluble paste with low temperature solder reflow at 220xc2x0 C. peak temperature; (4) flux residue cleaning with deionized water; (5) solder column attachment using solder paste with non-water soluble flux component at 220xc2x0 C. peak temperature solder reflow; and (6) flux residue cleaning. A problem associated with such a module assembly process and other fabrication processes employing plastic components such as a PBGA is that although xylene is an effective cleaning solvent for flux residues from various types of flux compositions used in solder pastes, it may not be a suitable solvent for removing flux residue from the type electronic module described above because of a concern for its effect on the integrity of the plastic component. Deionized H2O with or without added surfactant compositions are not entirely effective in removing the flux residue from non-water soluble solder pastes. In view of the problems with the use of xylene and related solvents, there is a need for an alternative method of cleaning flux residue to provide an environmentally acceptable cleaning solution to remove flux residues in soldering processes involving the use of solder pastes. Furthermore, the new alternate cleaning method should also be effective in removing flux residue post SMT (surface mount technology) from low temperature reflow operations at 220xc2x0 C. peak temperature.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide an environmentally safe method for effective removal of flux residue from electronic components following soldering processes using solder paste based on rosin derivatives and other fluxing materials, and particularly to provide a non-hazardous method of removing flux residues formed during solder reflow in electronic component assembly fabrication processes.
It is another object of the present invention to provide an environmentally safe semi-aqueous cleaning method for flux residue cleaning which method can be used to remove flux residues from electronic assemblies including those containing plastic components.
A further object of the invention is to provide a method for cleaning flux residues from electronic assemblies including those containing plastic components using non-hazardous solvents which are free of environmental regulations for chlorinated solvents and for xylene type solvents.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The above and other objects and advantages, which will be apparent to one of skill in the art, are achieved in the present invention which is directed to, in a first aspect, a method for removing flux residues from electronic modules following soldering operations using solder paste comprising the steps of:
supplying an electronic component which may include a plastic component and having contact pads with screened-on solder paste such as an eutectic solder paste (63%Sn/37%Pb);
placing the component with paste screened side into contact with and aligning with a second component joining regions such as pads;
subjecting the resulting assembly to solder reflow in a furnace at typically a 210xc2x0 C. peak temperature to melt and thereby relfow the solder regions, and allowing the joined module assembly to cool, e.g., to room temperature;
subjecting the joined module assembly having a flux residue deposit on the module surface to a flux residue cleaning process comprising the steps of, providing a solvent cleaning composition comprising a propylene glycol mono alkylether, preferably a dipropylene glycol alkyl etherxe2x80x94or a tri-propylene glycol alkyl ether, or mixture thereof, wherein the alkyl group is hydrocarbon radical represented by the formula CnH2n+1, where n=1 to 8, preferably 1 to 4;
contacting the module with the cleaning composition at an elevated temperature of for example about 50xc2x0-80xc2x0 C. to about 100xc2x0-120xc2x0 C. or higher for an effective time, usually about 5 min. to 60 min., to soften, swell, dissolve, remove or strip-off the flux residue deposit from the various surfaces of the module assembly; and contacting the cleaned substrate having cleaning solvent carry-over, with water, preferably hot deionized water, e.g., 40 to 80xc2x0 C. to remove the solvent from the substrate surfaces and preferably followed by a water rinse using pressure spray or immersion with agitation, and drying, for example, by blowing N2 or air and heating at elevated temperature to remove any absorbed water.
In another aspect of the invention, a cleaning composition is provided for removing flux residues, such as residue formed during component joining operations using solder paste, and flux residue deposits such as those formed from the use of rosin and other types of fluxing agents in forming solder connections, from electronic modules which may contain plastic components consisting essentially of, in weight %:
a mono, di- and/or tri-propylene glycol mono alkyl ether wherein the alkyl group is a hydrocarbon radical represented by the formula CnH2n+1 where n=1 to 8, preferably 1 to 4, in an amount of about 30% to about 100%, preferably 50% to 70%; and
the balance essentially water.
In another aspect of the invention, the propylene glycol ether may be a di alkyl ether, with the proviso that the propylene glycol composition be water soluble. Preferably the mono ethers are employed but mixtures of mono ethers and di ethers may also be used if the composition is water soluble. The following description will be directed to mono ethers for convenience.
The immersion time for softening/swelling, dissolving, removing or stripping off the flux residue deposit using the method of the invention is typically dependent on the temperature of the cleaning composition whereas at higher temperatures, a lower contact time is generally needed for removal of the flux residue.
This invention generally relates to bond and assembly processes in microelectronics as component attachment involving solder connections using solder paste with organic flux components or using rosin and other type of fluxes, for example in attachment of a semiconductor device to insulative substrate or chip carriers, substrate-to-board interconnections in the fabrication of multi-chip-module (MCM) and single-chip-module (SCM) electronic components, and for devicesubstrate package interconnection to an organic board or a printed circuit board (PCB), and to attach other electronic components onto a PCB.
This invention particularly relates to the removal of flux residues that are formed in soldering processses using solder paste with solder fluxes, such as rosin-based and other types of fluxing agents, under solder reflow conditions. The invention is also concerned with removal of flux residues formed in other types of solder interconnections, such as, for example, electronic package-to-board connections, SMT discretes as resistors/capacitor attachment to substrate, solder joining solder balls and solder columns to substrate in the fabrication of ceramic ball garid array (CBGA) and ceramic column grid array (CCGA), to name a few, which may carry plastic components such as plastic ball grid array (PBGA) in addition to the silicon device chips soldered to a substrate. More particularly, this invention is concerned with a semi-aqueous cleaning method for flux residues formed in soldering operations, with environmentally safe organic solvents having compatibility with plastic components, which solvents are to replace halogenated solvents and aromatic hydrocarbons particularly, perchloroethylene, xylene, and related solvents which have been identified as hazardous air pollutants (HAPs) and which are hazardous to human health and to the environment besides being unsuitable for use to remove flux residue from electronic modules containing plastic components due to concern for possible detriment to plastic components.
In the fabrication of micro electronic devices, soldering processes for interconnections are an integral part of the assembly for electrically joining semiconductor devices to a substrate, and for attachment of solder balls and solder columns to the substrate BSM (back side metal). In the controlled collapse chip connection (C4) or flip-chip technology that employs solder bumps or solder columns on silicon chip circuit side for connecting to ceramic chip carrier, a flux, typically rosin-based Alpha-102 flux, is applied on C4s and solder columns and/or solder wettable metal pads on the substrate prior to assembling/aligning and then the assembly is subjected to solder reflow process in a programmed furnace in oxygen-free ambient of N2 or forming gas (5% H2+95% N2). The peak temperature used in solder reflow profile depends on the Pb/Sn alloy composition used for chip attachment. With 90% Pb/10% Sn, and 97% Pb/3% Sn alloy, peak temperature in the reflow process generally can reach 360xc2x0 C. With eutectic solder 37Pb/63Sn paste compositions, such as used for BGA join, wire column join, SMT discrete attachment, and seal band attachment, the peak temperature during interconnections typically are between about 210xc2x0 C. to about 220xc2x0 C.
Under these solder reflow conditions, the flux promotes wetting of the metal surface necessary to assure metal-metal contact and bonding, and itself undergoes thermally induced chemical changes that lead to formation of volatile species most of which are readily removed during the process. However, some of these reactive species undergo secondary crosslinking reactions resulting in deposition of carbonaceous flux residues on critical surfaces. It is necessary that the flux residue be cleaned prior to subsequent operations as its presence can be detrimental to the electronic device operation due to metal corrosion concerns under temperature-humidity environment causing product reliability problems.
As stated earlier, xylene and chlorinated solvents such as perchloroethylene are commonly used for cleaning flux residues on critical surfaces in the high temperature chip joining process using rosin based flux and in other soldering processes, for example, in eutectic solder reflow at 210xc2x0 C. peak temperature, using non-water soluble solder paste with various types of fluxing agents.
The inventors have found that flux residues formed in solder connection processes using solder paste and other low temperature solder connections using various types of organic fluxing agents, can be effectively cleaned with propylene glycol mono alkylether or aryl ether and acyl ether solvents, such as propylene glycol mono alkylether, dipropylene glycol- and tripropylene glycol mono alkylethers when used alone or in combination with each other or in combination with water at an elevated temperature and with a later water rinse step.
In particular, it has been found according to this invention, that soldering flux residues can be readily removed from electronic components which may contain plastic component, for example, plastic grid array (PBGA) in addition to silicon device chip(s) and SMTs by exposing the assembly preferably at an elevated temperature, to a propylene glycol alkyl ether or a di- and/or tri-propylene glycol alkyl ether, or a combination thereof, followed by a water rinse step. In an alternate process, the propylene glycol alkyl ether solvents can also be used in an aqueous solution containing about 30% to about 100%, preferably from about 50% to about 70% of one or more of these solvents, the balance being water, preferably deionized water, followed by a water rinse step.
The preferred organic solvents of the invention are the propylene glycol mono alkylether, dipropylene glycol mono alkyl ether and tri-propylene glycol mono alkyl ethers. These solvents may be represented by the formula R1O(AO)xR2 wherein R1 and R2 are independently selected from the group consisting of hydrogen atoms, aryl and acyl groups and preferably alkyl groups of the formula CnH+2n+1 where n=1-8 atoms, preferably 1-4 atoms, A is a straight or branched chain, preferably branched chain C3 alkylene group as xe2x80x94[CH2CH(CH3)]xe2x80x94, and X is 1 to 3 with the proviso that one of R1 or R2 is hydrogen and the other is an aryl, alkyl or acyl group, preferably an alkyl group of C1-C8, and most preferably C1-C4, e.g., methyl, ethyl, propyl or isopropyl, butyl or isobutyl groups. The aryl group may be phenyl and the acyl group acetyl for example.
As discussed above, di alkyl ethers may be employed if the cleaning composition is water soluble. Preferably the mono alkyl ethers are employed.
Various exemplary solvents that are suitable for use in the stripping compositions to remove residual flux deposits according to this invention include: di(propylene glycol) methyl ether (fp. 75xc2x0 C.), di(propylene glycol) butyl ether (fp 96xc2x0 C.), tri(propylene glycol) mono methyl ether (fp. greater than 109xc2x0 C.), tri(propylene glycol) monobutyl ether (fp greater than 109xc2x0 C.), and tri(propylene glycol) n-propyl ether. The alkyl group is about C1-C8, preferably C1-C4.
The solvent cleaning composition is used to contact the electronic component and flux residue and cause softening and/or swelling or dissolution of the flux residue resulting in its essentially complete removal from the various surfaces of the substrate. The contacted parts are then preferably subjected to immersion in water, preferably hot deionized water, to wash off the solvent carry-over from the cleaning bath, and then thoroughly rinsed with deionized water by pressurized spray or other means of agitation to remove any residual cleaning solvent off the surface of the substrate followed by drying. Alternately, the contacted parts can be rinsed with a low boiling solvent such as acetone or 2-propanol (IPA) which allows for rapid drying but water rinsing is preferred according to this invention due to the hazards associated with the use of these low boilng volatile solvents of which IPA is classified as a VOC i.e., a volatile organic compound.
In a representative process for flux residue cleaning after solder column attachment to a ceramic chip carrier using solder paste, a ceramic chip carrier or substrate having silicon device chip(s), also referred to as C4 chip, and C4 decaps, and SMTs and in addition carrying a plastic grid array (PBGA) was accomplished by the semi-aqueous cleaning method according to this invention. Typically, the chip carrier assembly after soldering operation is immersed in the solvent cleaning composition of the invention at between about 60xc2x0 C.-80xc2x0 C. with mechanical agitation or immersion spray for between about 5 minutes to about 20 minutes under constant agitation. The parts are then immersed in a second tank containing hot deionized water at about 50xc2x0 C., again with constant agitation so as to remove cleaning solvent carry-over and any residual organics, followed by a thorough rinse with deionized water and dried. Alternatively, after the first solvent cleaning step, the parts are subjected to a second solvent cleaning in a second bath, then first water rinse to remove organic solvent followed by a second thorough water rinse and finally the drying the parts. As stated earlier, instead of water rinse, a low boiling solvent such as IPA (2-propanol) can also be used instead of water to remove or wash off the higher boiling cleaning solvent adhering to the substrate surface to accelerate drying by blowing nitrogen. However, a water rinse is preferred according to this invention because of the safety and environmental issues associated with the use of volatile organic solvents. Removal of the residue can be accelerated by continuous solvent flow or spray under pressure or ultrasonic spray. After solvent cleaning and rinsing, the parts were dried at between about 90 to about 100xc2x0 C. under N2 and allowed to cool in an inert atmosphere. Surface analysis of cleaned surfaces by x-ray photoelectron spectroscopy (XPS) provided surface elemental composition on various surfaces which was compared with the corresponding surfaces prior to solvent cleaning and thus the degree of cleaning achieved by the semi-aqueous cleaning method described above. Based on the XPS analysis results, efficient and effective removal of flux residue from ceramic and solder surfaces is obtained.
The semi-aqueous solvent cleaning method of this invention uses high boiling essentially water soluble solvents which have no environmental regulatory or health hazard issues, and which do not require any high cost cleaning equipment. When using these solvents without adding water, the solvent can be easily recovered by distillation and reused providing the benefit of waste minimization. The intermediate water rinse used to remove the organic solvent from the module surface is preferably containerized for recovery or disposal after multiple rinses due to build-up of washed-off solvent, while the final rinse water can be drain discharged as it contains insignificant level of organic contaminants.

Cleaning method to remove flux residue in electronic assembly

International Business Machines Corporation


A reinforced undergarment at least including underpants and, in certain embodiments, a pair of hose or stockings permanently or removably secured to the underpants so as to define a pair of pantyhose, wherein the undergarment, and particularly the underpants are formed from a flexible material including a plurality of interconnected portions disposed and configured to overly predetermined areas of the wearer""s body so as to exert a supporting and/or retaining force thereon and thereby shape the wearer""s body, or at least certain portions thereof, into a desired configuration. The interconnected portions of the undergarment are at least partially formed from an elastic material of varying densities such that different support and/or retaining force are exerted on predetermined portions of the wearer""s body. The underpants include at least a first support portion and a second support portion, wherein the first support portion is disposed beneath the buttocks of the wearer and has a sufficient density to exert an uplifting force thereon. The second support portion includes a reinforced panel of predetermined density disposed in overlying, retaining relation to the wearer""s abdomen so as to exert an inwardly directed, retaining force thereon. The various embodiments of the undergarment may include additional support portions disposed in overlying, retaining relation to other predetermined portions of the wearer""s body.

1. Field of the Invention
The present invention is directed towards a reinforced undergarment designed to support and shape predetermined portions of the wearer""s body. In one embodiment, the invention may comprise at least a pair of underpants, but in preferred embodiments, the invention is in the nature of a pair of underpants in combination with a pair either integrally formed or attached stockings, such that the undergarment comprises a pair of reinforced pantyhose. In either embodiment, the undergarment is formed of an at least partially elastic material of varying densities and includes a plurality of support portions which are specifically structured and disposed to exert retaining and/or supportive forces on various parts of a wearer""s body, including the buttocks, abdomen, waist, and upper thigh regions.
2. Description of the Related Art
The wearing of undergarments, whether simple underpants or more elaborate girdles designed to aid a person in the support and retention of certain body parts, is a well known and accepted practice. This practice is supported in great part due to the fact that the fashion trends in modern day society, which include the last several decades as well, have placed heavy pressure on women, almost exclusively, to have a slim and trim figure that can be likened to an hour-glass. However, there are a number of reasons, some of which people cannot control, for the failure of many women to achieve the slender and perfect figure which modern day society exhaults. Some of the reasons for the variance in the shape of people""s bodies include aging, child birth, over eating, lack of exercise, as well as certain distinct body characteristics and/or physical tendencies, any or all of which can serve to limit people""s potential for obtaining the current trend and preference for a slender body. In addition, even those people who are fortunate enough to have a body type which meets the current fashions, meaning a body which is generally tall, slender, etc., have relatively few years in their life span during which the aforementioned preferred body shape or configuration xe2x80x9cnaturallyxe2x80x9d occurs. This is the period of a person""s life, particularly women, when a slim attractive figure is less difficult to maintain, in terms of diet, exercise, etc. and is normally considered to exist during the late teens and the early twenties and/or those years of the person""s life that may generally be referred to as young adulthood.
Accordingly, many people, if not a majority of people in today""s society, require some sort of help in terms of trying to obtain an improved figure or body shape. Even some persons who are diligent in performing exercise and/or in following a healthy, low fat, reduced calorie diet may require some sort of help in achieving this goal. For example, as the body ages or upon the occurrence of events such as child birth, exercise and dietary restrictions are frequently not adequate, in and of themselves, to maintain a person""s slender, well shaped figure.
In years past, foundation garments such as girdles were used by women, and occasionally men, in the effort to project a slimmer, more acceptable figure, particularly in the area of the waist, abdomen, buttocks, etc. However, the conventional structure and design of such foundation garments involve the use of extremely dense elastic or other wearable material to surround and tightly retain the waist, abdomen and/or buttocks area of a wearer. The extended use of such girdles and similar foundation garments often result in the wearer becoming uncomfortable, at best, and in some instances, can be potentially harmful due to a reduction in circulation or blood flow to some of the areas of the body surrounded by such girdles. In addition, such conventional foundation garments also frequently included semi-rigid stays or similar reinforcing components, strategically located so as to further retain and/or constrict predetermined parts of the body, which may have more of a tendency to protrude or which were abnormally enlarged, such as is prevalent in people who are overweight. Discomfort associated with wearing such components is well known.
Because of these problems and other disadvantages associated with known foundation garments designed to aid in the shaping or support of certain portions of a wearer""s body, there remains a long felt need in the garment industry for an improved, reinforced undergarment. If any such improved undergarment were developed, it would preferably be reinforced or otherwise structured and designed to support and shape at least some parts of a wearer""s body which are commonly identified as xe2x80x9cproblemxe2x80x9d areas, such as but not limited to a xe2x80x9cpot-bellyxe2x80x9d or the xe2x80x9csaddle-bagsxe2x80x9d that many women have on their thighs just below the buttocks. In addition, any such improved undergarment would preferably also be reinforced or otherwise structured and designed to aid a person with at least temporarily improving her or his figure in a manner which is comfortable and which allows one to wear such reinforced undergarments for an extended amount of time. If any such improved undergarment were developed, it would preferably include at least an undergarment portion in the nature of a pair of underpants, although ideally, it would also comprise a pair of stockings or hose as well, which could either be permanently or removably secured to the underpants, so as to substantially define the undergarment as a pair of pantyhose. Although any such improved undergarment could have a variety of embodiments, it would preferably be at least partially formed from an elastic, flexible material, wherein at least the underpant portion is structured to include a plurality of interconnected support portions of varying densities which are configured to overly predetermined parts of a wearer""s body so as to support and otherwise retain and/or uplift the various, predetermined portions of the wearer""s body, and thereby, to collectively aid the body in assuming a preferred shape or configuration, without being uncomfortable or otherwise derogatorily affecting the wearer.
The present invention is intended to address these and other needs which remain in the art and relates to an improved undergarment. The undergarment of the present invention comprises in one embodiment, at least a pair of underpants, and in more preferred embodiments, a combination of underpants and fixedly attached or integrally formed stockings or hose, such that the undergarment assumes the form of a pair of xe2x80x9cpantyhosexe2x80x9d. Regardless of the embodiment, the undergarment of the present invention is specifically designed and structured to support and shape predetermined parts of the wearer""s body so as to provide an overall improved xe2x80x9cfigurexe2x80x9d through the exertion of retaining and supporting forces on the wearer""s body.
More specifically, the undergarment of the present invention is structurally reinforced such that at least the underpants are formed from an elastic, flexible material including a plurality of interconnected support portions which may vary relative to one another in density. For purposes of clarity, the term xe2x80x9cdensityxe2x80x9d, as used herein when referring to the various support portions of the undergarment structure, refers to the density of the weave of threads utilized in the formation of the undergarment. Specifically, the term xe2x80x9cDernierxe2x80x9d is used in this art as being representative of the xe2x80x9cweave countxe2x80x9d, wherein the higher the weave count number, the denser the material. Accordingly greater reinforcement or support forces may be exerted on the parts of the body which are contacted by support portions of the undergarment, which are more dense and thereby have a higher Dernier or weave count. By way of example, the material from which undergarment of the present invention is formed preferably includes a combination of Lycra(trademark) and Poliamide(trademark). One preferred percentage of such a combined composition would be Lycra comprising substantially 34% and Poliamide comprising substantially 66%. Naturally, other percentages of the combination of materials, as set forth above, could be utilized, as well as a variety of different materials other than those indicated. Further, with regard to the density of the material from which the various portions of the undergarment are formed, a representative range of the Dernier or weave count would be from substantially 40, representing the least dense components of the undergarment, to a Dernier of substantially 70, representing the more dense portions of the undergarment of the present invention.
More specifically, the structural features of the present invention include the underpants having an open upper end defining a waist portion and in certain embodiments including a waist band disposed in surrounding relation to the open upper end. When utilized, the waist band has a somewhat enlarged width and is formed from an elastic material of sufficient density to exert a retaining, supportive force about the waist, thereby providing the waist of the wearer with a slimmer appearance. The opposite end of the underpants terminate into conventionally disposed leg openings, which encircle opposite legs of the wearer about the respective thigh area. As set forth above, the undergarment of the present invention may be in the form of a pantyhose wherein, the underpants are permanently secured to the upper end of a pair of stockings or hose. Also, in the various embodiments of the present invention, the stockings may extend along the full length of the leg of the wearer and include feet and ankle enclosing portions, integrally secured to the lower end of the hose. Alternatively, the stockings may include open lower ends and may extend along only a portion of the length of the legs, such as above the knee or to a mid-calf location. The stockings are also formed from an elastic material preferably having a Dernier of 40, wherein the material from which the stockings are formed have sufficient density to at least exert a graduated support on the legs extending along their entire length, from the ankle towards the thigh of the wearer. The support of the legs in this manner thereby adds to the total leg comfort and facilitates extended wear of the undergarment of the present invention.
The underpants are dimensioned and configured to extend over at least a majority of those portions of the lower torso of the wearer wherein shaping and support are typically most needed and preferred. Accordingly, the plurality of interconnected support portions include at least a first support portion extending at least partially beneath the buttocks of the wearer. Further, the first support portion includes at least two elongated segments, wherein each segment includes a somewhat curvilinear configuration extending generally from the crotch outwardly and upwardly, such that each buttock is separately supported by a different one of the segments. The first support portion is formed from a material that has a first density, which is sufficient to exert a supportive, uplifting force on the buttocks. Each of the segments, extend outwardly from a respective or corresponding buttock, towards the waist portion of the underpants and in overlying relation to a separate hip area on different sides of the wearer. Due to the intended uplifting, supportive force exerted by the first support portion, it is formed of a material preferably having a Dernier or weave count of substantially 70, which is greater than the densities of at least the majority of remainder of the support portions incorporated in the underpants.
The underpants further includes a second support portion in the form of a panel disposed in overlying relation to the abdominal area of the wearer. This second support portion has a sufficient density to exert an inwardly directed force against the abdomen so as to prevent or significantly reduce any protrusion or outwardly extending bulge of the abdomen. The disposition and structure of the abdominal panel of the second support portion thereby projects a slimmer configuration, particularly in the area of the abdomen or lower stomach of the wearer. Further, the density of the second support portion may of course vary but, in at least one embodiment has a substantially equal density as that of the first support portion.
A third and fourth support portions are adjacently positioned in overlying, surrounding relation to different parts of the wearer""s thigh. More specifically, the third support portion includes a material formed of somewhat lesser density than that of the first and second support portions and is disposed adjacent to and somewhat below the elongated segments of the first support portion which are disposed in supporting, uplifting relation to the buttocks of the wearer. This third support portion could be more generally defined as a xe2x80x9cmodelingxe2x80x9d band disposed, dimensioned and configured to slim the hip and thighs of the wearer and depending upon the embodiment, may extend above the thigh area, upwardly to a position somewhat adjacent to a mid or upper portion of the elongated segments, defining the first support portion.
The aforementioned fourth support portion includes two substantially annular bands disposed in encircling relation to different thighs of the wearer and are more specifically disposed substantially at the junction between the upper ends of the stockings or hose and the lower, leg openings of the underpants. The density of the fourth support portion is somewhat greater than that of the third support portion and, in certain embodiments, may have a density substantially equal to that of the first and second support portions. The encircling bands defining the fourth support portion are disposed, configured, and structured to exert a medium, supportive and retaining force or pressure on the wearer""s body, so as to eliminate bulges commonly occurring about the upper thighs of the wearer.
One or more additional support portions may be formed on the underpants and disposed and configured to contact or specifically overly predetermined areas of the lower torso of the wearer""s body so as to exert a retaining force thereon and thereby further add to the shaping characteristics of the reinforced undergarment of the present invention.
These and other objects, features and advantages of the present invention will become more clear when the drawings as well as the detailed description are taken into consideration.


An electrical safety outlet for accepting a plug to provide power to electrical appliances including a power supply and an intelligent circuitry for controlling the power supply to the electrical outlet; the intelligent circuitry includes circuits for determining temperature condition in the outlet, mechanical plug insertion into the outlet, load presence on the outlet, and current capacity conditions.

1. Field of the Invention
The present invention relates to a logic control device that can be integrated into any double or single household or commercial electrical outlet. It controls the outlet and transforms it into a safe and xe2x80x9csmartxe2x80x9d outlet. The device can also be integrated into an extension cord, adapter or placed over an outlet as a cover plate. The logic circuit in the smart outlet instantly senses the state and condition of itself and the physical and electrical changes that occur.
2. Description of the Related Art
Every year thousands of people are killed or injured by accidents and fires caused by faulty electrical devices or appliances causing electrical shock. Many protective devices are being implemented to protect young children from accidentally accessing an electrical outlet, causing injuries due to electrical shock. Modern appliances that are more prone to cause accidents are equipped with ground fault protection. Such ground fault circuitry interrupters either interrupt the power until the electric circuit is restored to normal, for example, by manually resetting an electro-mechanical breaker. Some circuits automatically power-up when normal power resumes. Conveniently, such ground fault circuit interrupters are wired, for example directly into the tool, device or appliance, or it is molded into the cord designated for the tool or device line. Ground fault interrupters are developed to sense minute imbalances in a circuit by current leakage to ground.
Standard electrical built-in outlets either in the home or in an industrial setting, may be also equipped with a ground fault circuit interrupter, a GFCI. Such GFCI devices provide a test and reset function which both work together so that a tripped GFCI cannot be reset if the GFCI circuit no longer provides ground fault protection. The test button can still be operated in the event of an open neutral condition even though the GFCI circuit is no longer powered. A built-in line load reversal feature also prevents the GFCI from resetting if the load and the conditions are mistakenly reversed. The GFCI receptacle face will be live, but there will be no power delivered to devices downstream, indicating a load reversal.
An intelligent circuit interrupt system is disclosed, for example, in U.S. Pat. No. 6,111,733 in which an intelligent circuit is electrically connected between an AC source and a load for interrupting a flow of AC from the source to the load upon detection of an interrupt condition. A circuit interrupter electrically connected to phase and neutral terminals of the AC source defines the interrupt condition. A relay switch with a relay coil and phase and neutral contacts is included such that line and load ends of the phase contact are electrically connected, respectively, between the interrupt means load side phase port and a phase terminal of the load. Line and load ends of the neutral contact are electrically connected, respectively, between the interrupt neutral port and a neutral terminal of the load. The relay coil is electrically coupled between load sides of said phase and neutral contacts for controlling the contacts in response to the interrupt signal. An open-contact miswiring detector (OCMD) is electrically connected to one of the phase and neutral contacts for detecting a miswiring condition when the contacts are in an open state, and a closed-contact miswiring detector (CCMD) is electrically connected to the OCMD and to one of the neutral and phase contacts for detecting a miswiring condition when the contacts are in a closed state. A timing signal generator generates system timing signals. A test circuit electrically coupled to the interrupt means and the timing signal generator tests the interrupt means operability. An alarm circuit is electrically responsive to the test circuit, the timing signal generator, the OCMD and the CCMD for communicating an open-contact miswiring condition, a closed-contact miswiring condition, an operational failure condition, and a need for external testing condition. A power supply is electrically connected between the load ends of the phase and neutral contacts, and to the timing signal generator.
Thus, there is continuous need for an electrical outlet having additional safety features to protect against hazards inherent with standard outlets, such as fire hazards due to overheating, insertion of improper objects into the outlet and current overload. In addition, there is a need to provide an outlet which is capable of detecting whether a load is present.
It is an object of the present invention to provide an outlet connected to an intelligent circuit, making the outlet a logically controlled device. The intelligent circuit is mounted inside or alongside a standard electrical code-approved outlet box, such that the outlet itself can be installed in the same or similar manner as any outlet is installed. The outlet with the intelligent circuit is preferably a wall mount single or double outlet box and creates thereby a xe2x80x9csmart outlet.xe2x80x9d Thus, existing industry standard outlet-related functions are maintained. The smart outlet does not alter normal operation of any appliance or device, and does not change or modify the normal flow of electricity or any of its characteristic. It operates at the rated voltage, amperage and frequency, for example, at 120Vac and 10Amp for residential use, or at 240Vac, 15 Amp for commercial use, either at 50 or 60 Hz. The smart outlet of the present invention allows normal operation of any device or appliance plugged to the outlet directly or through an extension cord. It can be used with any standard on/off, a remote control unit or any other switching device.
Generally, power supplies from household or industrial outlets deliver power as soon as the device or appliance is plugged in or, power is always present and uninterrupted at the outlet, power or extension cord and appliance or device, except for an interruption within or at this device, yet in general all devices and appliances remain fully or partially powered, in particular power and extension cords. When a smart outlet is used and the electrical plug of an electrical device or appliance is properly inserted, the device is initially always turned off. The logic circuit will sense this condition and the power will remain off, i.e., the smart outlet will not provide any power to the device or appliance. Only when the power switch of the device or appliance is turned on and the circuit is electrically completed, can the device or the appliance draw power and operate. Thus, if a bulb in a lamp is unscrewed while the lamp switch is on, one may touch the contacts inside the socket and not experience an electrical shock. The smart outlet is designed such that it will shut off the power, when the circuit is interrupted (for example, the bulb is unscrewed or has burned out). The power will remain off until the electrical circuit is re-established, and the electrical device or appliance is turned on again.
Thus, only a properly operating electrical device or appliance may be powered up with the device of the present invention. If the electrical circuit is interrupted or overloaded, a fault is detected and the logic circuit of the smart outlet shuts the power to the connected device or appliance off.
The smart outlet is designed to continually monitors any or all of the designed functions, such as it monitors proper and full plug insertion, load presence, current load on the outlet and it senses the outlet temperature.
Accordingly, it is an important object of this invention to monitor whether the blades of the plug are fully and correctly inserted into the slotted openings of the socket, before the outlet provides power. This aspect is of particular importance to promote child safety, because children are known to be attracted to inserting a variety of foreign objects such as bobby pins, metal nails or needles, which may cause disastrous injuries to children. Thus, the smart outlet monitors the acceptance of a properly and fully (completely) inserted plug with standard, acceptable prongs, in good mechanical conditions.
In one embodiment, it is contemplated to utilize a radiation source, such as a light source, for example, an LED, which is positioned inside the socket assembly and within a light conducting means. For example, the light conducting means channel may extend through the outlet perpendicularly to the slotted plug openings for the outlet contacts. At each end of the light conducting channel, a photo sensor is positioned. The photo sensors may be cadmium-sulphide photo cells, photo diodes or photo transistors. When the blades of the plug are fully inserted into the slotted openings of the socket, the blades interrupt the radiation stream in the radiation conducting channels and the illumination of the photo sensors is interrupted. The photo sensors are connected to a logic circuit that controls power to the outlet. While radiation, or specifically, light is emitted from the radiation source, specifically, the diodes, impinges on the photo sensors, no power is provided to the outlet contacts. Preferably, the circuitry includes logic means, such as an xe2x80x9cANDxe2x80x9d gate and/or appropriate software in a micro controller to sense that both photosensor are simultaneously substantially light blocked or un-illuminated which indicates a correct insertion. This insures that both blades are fully inserted into the outlet contacts. When both photo sensors are simultaneously blocked, the software will permit a relay in the circuit to close. Power can only reach the outlet contacts when the relay is closed. Thus, a broken plug, or a single wire, clip or other invalid object will not cause electric power to be applied to the outlet.
It can easily be appreciated that the invention also contemplates to utilize as a radiation source a non-visible light LED i.e., ultra-violet radiation.
It is yet another object of the present invention to provide a current overload sensor. This feature addresses the problems of overloading outlets with too many appliances or devices, which causes overheating and potential fire. The load current is measured by the voltage drop across a resistor positioned in the current path. This voltage drop is then amplified by a gain block, typically an op amp, integrated by a network, and then tested for magnitude by a comparator. If a current overload occurs, the output of the comparator will go high, thus signaling that event to the micro controller. This will engage a software routine to turn off a relay, and thus removing the line voltage from the socket. An indicator light will be turned on at this point, such as a red LED, showing that an overload has occurred.
Another aspect of the invention is to provide sensing the load presence and current load on the outlet. The monitoring of the load presence makes it possible to only allow power to be present when a load is drawing a specified minimum amount of current. That is, a device or appliance which is turned off, will not draw current and thus, no voltage will be applied. This will also eliminate a major cause for electric shocks. The invention makes it possible to detect even a very small load, such as the load of an electric clock which draws only a few milliamperes. This feature is also particularly important as a child safety feature, because, as discussed above in conjunction with the monitoring of proper plug insertion, a child might insert a proper plug, having cut, open or raw wires extending from the plug, that is, the plug is not attached to any device. In such instance, the circuitry will not allow power to go to the outlet and, thus, the plug will not be under power.
Further, the invention provides for monitoring the temperature in the outlet. Changes in the temperature are observed. If the temperature deviates or exceeds a safe operating temperature, no power is provided to the outlet. This feature alone eliminates one of the major causes of electrical fires, since overheating of electrical outlets is one of a major fire hazards. Overheating is often caused by a defective plug, that is, a plug which is either physically damaged, rusty, or corroded. Rust, corrosion or dirt on the plug blades causes a high electrical resistance to exist between the blades of the plug and the outlet contacts. This high resistance causes a power loss and will raise the temperature of the outlet structure. Ultimately, the combustion temperature of the wall material or the insulation on the wiring may be reached, and a fire will occur. In order to prevent such overheating, the present invention provides a temperature sensing means which interrupts the power supply to the device or appliance if the sensed temperature raises above a set temperature. Good electrical practice dictates that the outlet temperature should not rise higher than about 70xc2x0 C. to 80xc2x0 C., depending on the local code. However, this threshold can be set for any code mandated, or safe operating temperature.
One embodiment for monitoring the outlet temperature utilizes a thermistor, but any other device for sensing temperature may be used. The thermistor is preferably placed in close physical contact with the plastic body of the outlet structure, so that the thermistor temperature is approximately equal to the outlet temperature. The electrical resistance of a thermistor varies inversely as a function of its temperature. By means of well known electronic circuitry, preferably a comparator or a Schmitt trigger, the electrical resistance of the thermistor and hence its temperature, can be compared with an accurate internal reference.
Only when each or all monitoring results are satisfactory, the outlet provides power to the appliances or devices connected to the outlet, either directly of via an extension cord. All monitoring is continuous, regardless of the appliance""s state, and can work with almost any electrical appliance, device, machine or electrical motor.
It is also an object of the invention to provide an outlet connected to an intelligent circuit as discussed above, in which the outlet also provides all functions of a ground fault interrupter.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are intended solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims.

Safety electrical outlet with logic control circuit