Abstract: The present invention provides a substrate provided with a land to which the tip of a magnetic wire is to be soldered and a resin wall formed around and higher than the land. The resin wall has an inclined surface inclined at an angle greater than 90° with respect to the land.

Abstract: A method for forming an article, comprises providing a stannous alkoxide-containing pattern on a substrate. This stannous alkoxide-containing pattern is obtained from a non-aqueous stannous alkoxide composition that comprises component (a) comprising a water-insoluble stannous alkoxide complex comprising stannous ions, in an amount of at least 1 weight %, and a photocurable component (b), non-photocurable water-insoluble polymer component (c) having a molecular weight of at least 10,000, or both the photocurable component (b) and the non-photocurable water-insoluble polymer component (c). When photocurable component (b) is present, the water-insoluble stannous alkoxide composition further comprises photosensitizer component (d) that is different from all of components (a) through (c).

Abstract: A multilayer wiring substrate includes a number of insulating layers, each insulating layer including a glass ceramic. A number of internal conductor layers are formed between the insulating layers. Via conductors penetrate through the insulating layers and mutually connect the internal conductor layers in different layer locations. Surface conductor layers are formed on an outer surfaces in a lamination direction of the insulating layers. The insulating layers include outside insulating layers and inside insulating layers. A first aspect ratio representing an oblateness and sphericity of an external filler contained in the outside insulating layers is larger than a second aspect ratio representing an oblateness and sphericity of an internal filler contained in the inside insulating layers. A thermal expansion coefficient of the outside insulating layers is smaller than a thermal expansion coefficient of the inside insulating layers.

Abstract: Reaction products of guanidine compounds or salts thereof, polyepoxide compounds and polyhalogen compounds may be used as levelers in metal electroplating baths, such as copper electroplating baths, to provide good throwing power. Such reaction products may plate with good surface properties of the metal deposits and good physical reliability.

Abstract: An adhesion promotion process and composition for enhancing adhesion between a copper conducting layer and a dielectric material during manufacture of a printed circuit board. The composition contains a corrosion inhibitor, an inorganic acid, and an alcohol which is effective to increase copper-loading in the composition.

Abstract: There are provided a substrate for printed wiring excellent in light transmission property, heat resistance, mechanical strength and resistance to thermal coloration; a printed wiring laminate; and a resin composition used to produce the substrate and the laminate. The substrate for printed wiring comprises an aromatic polyether-typed polymer having a glass transition temperature, as measured by differential scanning calorimetry (DSC, heating rate: 20° C./minute), of from 230° C. to 350° C.

Abstract: A halogen-free resin composition includes (A) 100 parts by weight of epoxy resin; (B) 1 to 100 parts by weight of benzoxazine resin per 100 parts by weight of (A); (C) 1 to 100 parts by weight of styrene-maleic anhydride per 100 parts by weight of (A); (D) 0.5 to 30 parts by weight of amine curing agent per 100 parts by weight of (A); and (E) 5 to 150 parts by weight of halogen-free flame retardant per 100 parts by weight of (A). The composition obtains properties of low dielectric constant, low dissipation factor, high heat resistance and flame retardancy by specific composition and ratio. Thus, a prepreg or a resin film, which can be applied to a copper clad laminate and a printed circuit board, is formed.

Abstract: A metal-clad phenolic resin laminate obtained by heating and pressing a lamination which comprises: (i) a central layered portion comprising one paper base prepreg which is made of a paper base impregnated with a first phenolic resin composition containing a resol-based resin, or a predetermined number of the paper base prepregs laid on each other; (ii) outer layered portions laid on an upper and a lower sides of the central layered portion, in which each of the outer layered portions comprises one glass fiber substrate prepreg which is made of a glass fiber substrate impregnated with a second phenolic resin composition containing a resol-based resin, or a predetermined number of the glass fiber substrate prepregs laid on each other; and (iii) a metal foil laid at least on one of the outer layered portions laid on the upper and lower sides of the central layered portion.

Abstract: When a multilayer ceramic substrate with a cavity is reduced in thickness, a bottom wall portion defining the bottom of the cavity is reduced in thickness, thereby leading to the problem that the bottom wall portion is likely to be broken. A bottom wall portion defining a cavity of a multilayer ceramic substrate has a stack structure formed with a high thermal expansion coefficient layer sandwiched between first and second low thermal expansion coefficient layers. This configuration generates compression stress in the low thermal expansion coefficient layers during a cooling process after firing, thereby allowing the mechanical strength at the bottom wall portion to be improved.

Abstract: A production process for producing a glass fiber fabric that has good smoothness and is excellent in resin impregnation property is provided wherein glass fiber yarns are woven to obtain a glass fiber fabric.

Abstract: A polyamide-imide resin obtained by a process comprising the step of reacting an aromatic diisocyanate with a diimide dicarboxylic acid containing 40 mol % or more of a compound represented by the following general formula (1) and 20 mol % or more of a compound represented by the following general formula (2).

Abstract: The present invention provides a circuit creation technology that improves conductive line manufacture by adding active and elemental palladium onto the surface of a substrate. The palladium is disposed in minute amounts on the surface and does not form a conductive layer by itself, but facilitates subsequent deposition of a metal onto the surface, according to the pattern of the palladium, to form the conductive lines.

Abstract: A laminate of the present invention comprises a plating-target material including a layer-A, that is subjected to electroless copper plating and has a surface roughness such that an arithmetic mean roughness Ra measured at a cutoff value of 0.002 mm is less than 0.5 ?m. The 90° anti-peeling adhesive force of the layer-A is 1.0 N/25 mm or less. Furthermore, the layer-A includes a polyimide resin having a siloxane structure formed by polymerizing a diamine component having a structure represented by Formula (6) in a content of 5 to 95 mol % based on the entire diamine component. A sheet containing the layer-A has an elongation modulus of 1.8 GPa or less. The plating-target material of the present invention has a high adhesiveness to an electroless plating film formed on its surface, even if the surface is not so rough, and it is possible to favorably form electroless plating on the entire surface.

Abstract: The present invention is to provide an epoxy resin composition uniformly containing a large amount of inorganic fillers, excellent in heat resistance and flame resistance, and having good impregnation into a base material, and a prepreg using the epoxy resin composition, having good tackiness, and being easy in handling. Furthermore, it is to provide a printed wiring board using a metal-clad laminate formed using the prepreg and/or the prepreg or the epoxy resin composition, capable of easily conducting an ENEPIG process, and a semiconductor device using the printed wiring board, excellent in performances. An epoxy resin composition comprises a solid epoxy resin, a silica nanoparticle having an average particle diameter of 1 nm or more and 100 nm or less, and a silica particle having an average particle diameter larger than that of the silica nanoparticle, in the range of 0.1 ?m or more and 5.0 ?m or less.

Abstract: Disclosed herein are an epoxy resin composition for a printed circuit board, an insulating film, a prepreg, and a multilayer printed circuit board, the epoxy resin composition for a printed circuit board including a liquid crystal oligomer, an epoxy resin, an amino triazine novolac hardener, and an inorganic filler; the insulating film and the prepreg each being manufactured by using the resin composition; and the multilayer printed circuit board including the insulating film or the prepreg.

Abstract: Support materials for printing electrically conductive structures by means of inkjet printing with inks which contain conductive particles lead to low resistances for the printed structures without thermal post-treatment when they contain a microporous layer with a mean pore size of less than 100 nm as an outer layer.

Abstract: A resin composition includes (A) 100 parts by weight of epoxy resin; (B) 20 to 100 parts by weight of polybutadiene styrene divinylbenzene graft terpolymer resin; (C) 2 to 20 parts by weight of di-tert-butylhydroquinone (DTBHQ); (D) 5 to 50 parts by weight of polyphenyl ether modified cyanate ester resin; and at least one of (E) inorganic filler, (F) chain extending sealing agent, and (G) catalyst. The resin composition is characterized by specific ingredients and proportions thereof to attain high heat resistance, low dielectric constant Dk, and low dielectric dissipation factor Df, and being halogen-free, and therefore is applicable to protective film of printed circuit boards, insulating protective film of electronic components, and resin insulation film of leadframes.

Abstract: A composite material (1) comprising at least one prepreg (3), said prepreg comprising at least one polymeric resin and optionally at least one fibrous reinforcement; and a conducting ink (2) applied to at least one surface of said prepreg (3); where the conducting ink (2) has a surface tension lower than the surface energy of the at least one surface of said prepreg (3) to which the ink (2) is applied.

Abstract: A method of manufacturing a printed circuit board includes arranging a core layer in which a bending prevention portion of at least two layers that are metal layers having different thermal expansion coefficients is disposed between a plurality of insulating members; forming a circuit pattern so as to have a desired pattern on at least one of the inside of the core layer and an outer face of the core layer; and forming an insulating layer including an opening portion that exposes the circuit pattern on the core layer.

Abstract: Disclosed is a resin composition exhibiting a low thermal expansion coefficient, as well as higher heat resistance, flame resistance and insulation reliability than ever before when used in a multilayer printed wiring board that requires fine wiring work. Also disclosed are a prepreg, a resin sheet, a metal-clad laminate, a printed wiring board, a multilayer printed wiring board and a semiconductor device, all of which comprising the resin composition. The resin composition of the present invention comprises (A) an epoxy resin, (B) a cyanate resin and (C) an onium salt compound as essential components.

Abstract: The invention relates to a thermosetting resin composition which includes a metal filler component, a fluxing component and a thermosetting resin binder. The metal filler component includes at least one of bismuth (Bi) and indium (In), and tin (Sn). The fluxing component, which at least one of a compound of structural formula (1) below and a compound of structural formula (2) below, is used. In the above formulas, R1 to R6 are each a hydrogen or alkyl group, and X is an organic group which has a lone electron pair or double bond ? electrons and is capable of coordinating with a metal.

Abstract: A varnish composition includes composition (A): an epoxy resin, composition (B): a hardener, composition (C): an accelerator, composition (D): phosphor-containing flame retardant, and composition (E): fillers, wherein composition (A) includes composition (A-1): phosphor-containing epoxy resin, phosphor-containing and silicon-containing epoxy resin, or a mixture thereof; composition (A-2): dicyclopentadiene epoxy resin; and composition (A-3): oxazolidone epoxy resin.

Abstract: An objective of this invention is to provide an interlayer dielectric film with a carrier material used in a multilayer printed circuit board, which exhibits sufficient rigidity for a thin multilayer printed circuit board. According to the present invention, there is provided an interlayer dielectric film with a carrier material comprising a carrier material comprised of a metal foil or resin film and an interlayer dielectric film formed on one side of the carrier material, wherein the interlayer dielectric film is comprised of a base material impregnated with a resin; the base material has a thickness of 8 ?m to 20 ?m; and when the resin is cured at 170° C. for one hour under a pressure of 30 kgf/cm2, an elongation percentage of the interlayer dielectric film in a planar direction is 0.05% or less as determined by a TMA method.

Abstract: A circuit subassembly, comprising a dielectric layer formed from a dielectric composition comprising, based on the total volume of the composition: about 15 to about 65 volume percent of a dielectric filler; and about 35 to about 85 volume percent of a thermosetting composition comprising: a poly(arylene ether), and a carboxy-functionalized polybutadiene or polyisoprene polymer.

Abstract: Electrographic printing of one or more multi-channeled layers produces a specialty item. Such electrographic printing includes forming a desired print image, electrographically, on a receiver member utilizing predetermined sized marking particles; and, where desired, forming one or more final multi-channeled layers utilizing marking particles of a predetermined size or size distribution.

Abstract: A composite material, a high-frequency circuit substrate made from the composite material, and a method of making the high-frequency circuit substrate. The composite material includes: a thermosetting composition including a butadiene styrene copolymer resin with a molecular weight less than 11,000 containing more than 60 percent of vinyl, a polybutadiene resin with polarity groups containing more than 60 percent vinyl, and a maleic anhydride grafted polybutadiene styrene copolymer with a molecular weight of more than 50,000; a fiberglass cloth; a powder filler; and a cure initiator. The composite material permits easy manufacture of the prepreg and high bonding of the copper foil. The high-frequency circuit substrate made from the composite material has low dielectric constant, low dielectric loss tangent, and excellent heat resistance, and is convenient for the processing operation. The composite material is suitable for making the circuit substrate.

Abstract: There is provided a printed circuit board. The printed circuit board may be configured to include: a core layer in which a bending prevention portion of at least two layers is interposed between a plurality of insulating members and includes metal layers having different thermal expansion coefficients is disposed; a circuit pattern that is formed so as to have a desired pattern on at least one of the inside of the core layer and an outer face of the core layer; and an insulating layer that is formed on the core layer and includes an opening portion that exposes the circuit pattern, and a method of manufacturing the printed circuit board. According to the above-described printed circuit board and the method of manufacturing the printed circuit board, by disposing a bending prevention portion inside the printed circuit board, a printed circuit board capable of improving the progress rate and the productivity and a method of manufacturing the printed circuit board can be provided.

Abstract: An anisotropic conductive joint package in which an anisotropic conductive film is joined to at least one conductive material selected from among the group consisting of gold (Au), silver (Ag), copper (Cu), aluminum (Al), magnesium (Mg), nickel (Ni), a tin oxide doped with indium (ITO), molybdenum (Mo), iron (Fe), palladium (Pd), beryllium (Be), and rhenium (Re).

Abstract: Phosphorus-containing oligomer is represented by formula (1): (R1 represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a phenyl group; n is the number of repeating units and an integer of 1 or more; X is a structural unit represented by structural formula (x1) or (x2) below; Y is a hydrogen atom, a hydroxyl group, or a structural unit represented by the formula (x1) or (x2); and, in the formula (x1) or (x2), R2, R3, R4, and R5 each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group, or an aralkyl group), wherein the content of components whose n is 2 or more in the formula (1) is in the range of 5% to 90% in peak area in GPC measurement.

Abstract: A conductive paste comprising 88-94% by mass of Ag powder having an average particle size of 3 ?m or less and 0.1-3% by mass of Pd powder, the total amount of the Ag powder and the Pd powder being 88.1-95% by mass. A multilayer ceramic substrate obtained by laminating and sintering pluralities of ceramic green sheets, and having conductor patterns and via-conductors inside, the via-conductors being formed in via-holes having diameters of 150 ?m or less after sintering, containing Ag crystal particles having a particle size of 25 ?m or more, and having a porosity of 10% or less.

Abstract: This invention provides an embossed release paper that has high heat resistance and embossing properties. The embossed release paper comprises a paper base material, an ionizing radiation-cured resin layer, and a heat-cured silicone layer stacked in that order, the embossed release paper having embosses. The embossed release paper has high heat resistance and thus is suitable for use in synthetic leather production and melamine decorative sheet production that involve surface emboss pattern formation.

Abstract: Disclosed is an epoxy resin composition essentially containing (A) an epoxy resin having a structure represented by the general formula (1), (B) a curing agent, (C) an inorganic filler and (D) a cyanate resin and/or a prepolymer thereof, wherein Ar represents a fused aromatic hydrocarbon group; r is an integer of 1 or more; X is a hydrogen or an epoxy group (glycidyl ether group); R1 represents one selected from the group consisting of a hydrogen, a methyl group, an ethyl group, a propyl group, a butyl group, a phenyl group and a benzyl group; n is an integer of 1 or more; p and q are an integer of 1 or more; and p's and q's in respective repeating units may be the same as or different from one another.

Abstract: A circuitized substrate which includes at least one circuit layer and at least one substantially solid dielectric layer comprised of a dielectric composition which includes a cured resin material and a predetermined percentage by weight of particulate fillers, but not including continuous or semi-continuous fibers as part thereof.

Abstract: Disclosed herein is a crosslinkable thermoset monomer. The crosslinkable thermoset monomer has acetylene groups as crosslinking groups introduced at both ends of the backbone. Also disclosed herein is a composition for producing a printed circuit board which comprises the crosslinkable thermoset monomer. The composition exhibits excellent mechanical and thermal properties. Therefore, the composition can be used as a material for next-generation boards that are becoming lighter in weight and smaller in size and thickness. Also disclosed herein is a printed circuit board using the composition.

Abstract: It is an object of the invention to provide a composite with sufficiently reliable bonding and adequately minimized generation of fluff from flaking resin dust and fibers. This object is achieved by the composite (100) of the invention that comprises a fiber sheet (101) impregnated with a resin composition (102), wherein the 20° C. storage elastic modulus of the cured resin composition (102) is 100-2000 MPa. The composite (100) optionally contains perforations (103).

Abstract: Provided is a multi-layer article comprising an electrically conductive metal layer adheringly contacting the surface of a polymeric composite film less than 500 ?m in thickness, having a surface, the polymeric composite film comprising a polymer and a plurality of surface-modified hexagonal boron nitride particles dispersed therewithin. A process of film casting onto a conductive metal layer is provided.

Abstract: Disclosed is a halogen-free resin composition for printed wiring board production, which is remarkably reduced in quality deterioration due to moisture absorption of a semi-cured resin film (layer). Also disclosed is a copper film with resin or the like. The resin composition is characterized by containing a component A (one or more resins selected from the group consisting of bisphenol-A epoxy resins, bisphenol-F epoxy resins and bisphenol-AD epoxy resins, which have an epoxy equivalent of not more than 200, while being in a liquid state at 25 DEG C.), a component B (a linear polymer having a crosslinkable functional group), a component C (a crosslinking agent), a component D (an imidazole-based epoxy resin curing agent) and a component E (a phosphorus-containing epoxy resin). The resin composition is also characterized by containing 0.5-3.0% by weight of phosphorus atoms per 100% by weight of the resin composition. In the copper foil with resin, a resin layer is formed by using the resin composition.

Abstract: Disclosed is a printed wiring board which attains aims of printed wiring boards required for realizing high-speed, high-frequency semiconductor devices, namely a printed wiring board having low dielectric constant, low dielectric loss tangent and low linear expansion coefficient. Also disclosed is a composite woven fabric suitably used as a base material for such a printed wiring board. Specifically disclosed is a composite woven fabric containing quartz glass fibers and polyolefin fibers, in which the ratio of the quartz glass fibers to the composite woven fabric is set at 10 vol % or more and 90 vol % or less. It is preferred that the quartz glass fibers each have a filament diameter of 3 ?m or more and 16 ?m or less, and the composite woven fabric has a thickness of 200 ?m or less.

Abstract: A low-temperature sintering ceramic material showing little variation in composition after firing, realizing high bending strength in a sintered body, and capable of forming a reliable ceramic substrate showing high peel strength of a surface electrode includes a main constituent ceramic material containing about 48 weight % to about 75 weight % in terms of SiO2 of Si, about 20 weight % to about 40 weight % in terms of BaO of Ba, and about 5 weight % to about 20 weight % in terms of Al2O3 of Al, and an accessory constituent ceramic material containing, relative to 100 parts by weight of the main constituent ceramic material, about 2 parts to about 10 parts by weight in terms of MnO of Mn and about 0.1 parts to about 10 parts by weight respectively in terms of TiO2 and Fe2O3 of at least one selected from Ti and Fe, and substantially not includes both Cr oxide and B oxide.

Abstract: To provide a ceramic composition not only having little compositional variation after burning, but a high flexural strength of the sintered body, and a high Q value in a microwave band, a ceramic composition used for forming a ceramic layer of a multi-layer ceramic substrate contains 47.0 to 67.0 wt. % of SiO2, 21.0 to 41.0 wt. % of BaO, and 10.0 to 18.0 wt. % of Al2O3, and contains as a first additive, 1.0 to 5.0 parts by weight of CeO2, relative to a total of 100 parts of SiO2, BaO and Al2O3, and as a second additive, 2.5 to 5.5 parts by weight of MnO, relative to a total of 100 parts by weight of SiO2, BaO, Al2O3 and CeO2, and is substantially free of Cr. As a third additive, at least one of Zr, Ti, Zn, Nb, Mg and Fe, and as a fourth additive, a Co component and/or a V component, may be contained.

Abstract: An electrical structure and method of forming. The electrical structure includes a first substrate, a first dielectric layer, an underfill layer, a first solder structure, and a second substrate. The first dielectric layer is formed over a top surface of the first substrate. The first dielectric layer includes a first opening extending through a top surface and a bottom surface of said first dielectric layer. The first solder structure is formed within the first opening and over a portion of the top surface of said first dielectric layer. The second substrate is formed over and in contact with the underfill layer.

Abstract: Organosilicon composites are described, comprising 30 to 90 vol. % of a cured organosilicon copolymer derived by curing an organosilicon polymer having, in the same copolymer, silicon-containing repeating units comprising a silicon hydride and silicon-containing repeating units comprising a C1-10 ethylenically unsaturated group; and 10 to 70 vol. % of a dielectric filler. The composites are used in the manufacture of circuit subassemblies.

Abstract: Embodiments of the present invention provide methods of treating a surface of a substrate. In one particular aspect, embodiments of the present invention provide methods of treating a surface of a substrate that promote binding of one or more metal elements to the surface. According to some embodiments of the invention, films are formed on any conducting, semiconductive or non-conductive surface, by thermal reaction of molecules containing reactive groups in an organic solvent or in aqueous solution. The thermal reaction may be produced under a variety of conditions. In another aspect, the present invention provides a printed circuit board, comprising: at least one substrate; a layer of organic molecules attached to the at least one substrate; and a metal layer atop said layer of organic molecules.

Abstract: A metal nano particle can be supported and immobilized on a substrate uniformly. Thus, disclosed is a method for supporting a nano metal particle, which comprises applying a silane coupling agent having at least one functional group capable of capturing a metal (e.g., an imidazole group, an amino group, a diamino group, a mercapto group, and a vinyl group) in its molecule on a substrate, and then contacting the silane coupling agent with a nano particle of a metal (e.g., gold, platinum, silver, copper, palladium, nickel, cobalt), wherein the silane coupling agent may be produced by the reaction between an azole compound with an epoxysilane compound, and wherein the metal nano particle to be contacted with the silane coupling agent is preferably coated with an ionic fluid. Also disclosed is a substrate having a metal nano particle supported thereon, which is produced by the method.

Abstract: There are provided a flame-retardant resin composition for a multilayer wiring board and a multilayer wiring board having the same. The flame-retardant resin composition for a multilayer wiring board according to an exemplary embodiment of the present invention includes a composite epoxy resin including a naphthalene modified epoxy resin, a cresol novolac epoxy resin, a rubber modified epoxy resin and a phosphorous-based epoxy resin, as well as a flame retardant represented by a specific chemical formula. The flame-retardant resin composition for a multilayer wiring board and the multilayer wiring board having the same disclosed herein exhibits excellent flame retardancy, moisture resistance and peel strength.

Abstract: Provided are a resin composition whose storability is not reduced, a prepreg which uses the resin composition and which is uniformly colored, a laminated board, a multilayer printed wiring board having excellent results in reliability tests such as a thermal shock test and the like, and a semiconductor device. The resin composition is a resin composition for a multilayer printed wiring board, comprising (A) a novolac type epoxy resin, (B) a curing agent, (C) an inorganic filler, and (D) a colorant, wherein the exothermic peak temperature of the resin composition, as measured by DSC, is within ±5° C. of the exothermic peak temperature of a resin composition composed of (A) a novolac type epoxy resin, (B) a curing agent, and (C) an inorganic filler.

Abstract: Provided are a method for producing a phosphorus-containing phenolic compound in which reactivity is considerably excellent in the reaction between a phosphorus-containing compound and an aromatic nucleus of a phenol; in the case of using a polyhydric phenol or a phenolic resin as the phenol, a novel phosphorus-containing phenolic compound that serves as a curing agent for an epoxy resin and imparts excellent heat resistance to a cured product; a curable resin composition containing the novel phosphorus-containing phenolic compound; a cured product of the curable resin composition; a printed wiring board; and a semiconductor sealing material. An aromatic aldehyde (a1) having an alkoxy group as a substituent on an aromatic nucleus is allowed to react with an organic phosphorus compound (a2) intramolecularly having a P—H group or a P—OH group. The resultant reaction product is then allowed to react with a phenol (a3).

Abstract: A process is described for treating metal surfaces printed wiring boards and similar substrates to provide improved creep corrosion resistance on such surfaces. A modified organic solderability preservative composition is used in combination with an emulsion polymer to provide a modified polymer coating on the metal surface finish via a chemical reaction to provide enhanced corrosion protection of the surface.

Abstract: In order to produce a carrier foil for printed circuit boards, which is particularly suitable for high component densities, it is proposed that said carrier foil be produced from a polymer material comprising a thermoplastically processable, substantially fully fluorinated plastics material.

Abstract: A varnish includes an epoxy resin, a curing agent, an accelerator agent and fillers. The fillers include sericite powders. The sericite powders have composition of SiO2 in weight ratio of 55±3%. Furthermore, the Mohs' scale of hardness of the sericite powder is between 2 to 3. Glass fabric cloth is dipped into the varnish so as to form a prepreg with better machined-work capability.