| PATENT ASSIGNEE'S COUNTRY | Japan |
| UPDATE | 01.00 |
| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | 25.01.00 |
| PATENT TITLE |
Resin composition to be plated |
| PATENT ABSTRACT |
A resin composition for plating comprising a thermoplastic resin and aluminum borate or amorphous silica, or both as an inorganic filler. The resin compositionexhibits excellent plating characteristics and excellent electrical characteristics. |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | 05.05.97 |
| PATENT FOREIGN APPLICATION PRIORITY DATA | This data is not available for free |
| PATENT REFERENCES CITED | This data is not available for free |
| PATENT PARENT CASE TEXT | This data is not available for free |
| PATENT CLAIMS |
What is claimed is: 1. A surface-leached resin composition for plating, comprising 30-95 wt. % of a polymer alloy consisting of polyetherimide and polyphenylene ether and 5-70 wt. % ot amorphous silica having an aspect ratio of 10 or less, an average diameter of 0.01-100 .mu.m. and a SiO.sub.2 purity of 96% or more, wherein said resin composition is surface leached after being molded, providing a resulting molded article having an adhesion strength of greater than 1 kg/cm.sup.2, and a dielectric constant of 4.0 or less. 2. The surface-leached resin composition of claim 1, having a dielectric constant of 4.0 or less and a dielectric loss tangent of 0.01 or less in the high frequency region of 100 KHz to 300 GHz. 3. The surface-leached resin composition of claim 1, wherein the resin composition exhibits a plate film adhesion strength of greater than 1 kg/cm when molded by injection, etched in an alkaline solution with a concentration of 1-15 N, and plated by non-electrolytical copper plating. 4. The surface-leached resin composition of claim 1, wherein the amorphous silica has an aspect ratio of 5 or less. 5. The surface-leached resin composition of claim 1, wherein the amorphous silica has a SiO.sub.2 purity of 99% or more. 6. The surface-leached resin composition of claim 1, wherein said amorphous silica has an average diameter of 0.01-50 .mu.m. 7. The surface-leached resin composition of claim 1, which contains 10-60 wt % of said amorphous silica. 8. The surface-leached resin composition of claim 1, wherein said amorphous silica is an amorphous silica surface treated with a silane coupling agent, wherein said silane coupling agent is present in an amount of 0.0001-1 part by weight for 100 parts by weight of amorphous silica. 9. The surface-leached resin composition of claim 3, wherein said alkaline solution has a concentration of 3-12N. -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition which can be plated. The resin composition has superior plating characteristics and excellent electrical characteristics, and is particularly useful as a material for electric or electronic parts such as printed circuit boards, wiring circuit boards, connectors, housing, and insulators. More particularly, because the resin composition of the present invention is thermoplastic and has excellent plating and electrical characteristics, it is suitable as a material for manufacturing three dimensional circuit boards, molded interconnection devices (MID), and molded circuit boards (MCB) using injection molding techniques. 2. Discussion of the Background Because thermoplastic resin compositions having superior plating characteristics can be easily processed by injection molding or extrusion molding into three dimensional articles, such compositions are abundantly used for various electric or electronic parts, automobile parts, mechanical parts, and ornamental articles. Conventional resin compositions capable of being plated exhibit adequate plating characteristics due to improvements in the shape and size of fillers which are added to such compositions and development in the plating technology. In addition to the excellent plating characteristics thermoplastic resins used for electronic parts, such as printed circuit boards, wiring circuit boards, connectors, housing, and insulators, must have excellent electrical characteristics. Here, the plating characteristics indicate the capability of connecting the plated resin composition and the plating metal, that is, the adhesion between the resin composition and the metal plating film. Excellent resin-metal adhesion means excellent plating characteristics. Excellent electrical characteristics, on the other hand, are characteristics required for an insulating resin material, particularly a high frequency insulating resin material. Specifically, a material having excellent electrical characteristics must have a low dielectric constant (.epsilon.) and a low dielectric loss tangent (tan .delta.). However, conventional resins and resin compositions to be plated have a high dielectric constant and a high dielectric loss tangent. For example, resins to be plated disclosed in Japanese Patent Application Laid-open Nos. 136841/1981, 230276/1993, and 98637/1989 have excellent plating characteristics and possess an extremely high value industrially. However, because of their poor electrical characteristics, application of these resins must be limited. For example, it is difficult to use these resins for electronic parts used in the high frequency wave region due to a large signal loss. On the other hand, the adhesion strength between a molded resin and a metal plating film is largely affected by the physical characteristics of the resin surface, that is, roughness of the resin surface. In particular, the plating adhesion strength is remarkably improved by forming uniformly small anchoring pores (hereinafter called "micropores"). This is called the anchoring effect. In many cases, a chemical etching process using an acid, an alkali, or an organic solvent is used for forming micropores on the surface of molded resins. Such micropores can be easily formed by a chemical etching process which comprises, for example, manufacturing molded articles from a resin composition comprising a prescribed amount of inorganic filler which is soluble in an acid, an alkali, or an organic solvent and immersing the molded resin surface in a specific solvent (the acid, alkali, or organic solvent) to cause the inorganic filler to dissolve out and be removed. In this manner a resin composition comprising a thermoplastic resin and a specific inorganic filler which is soluble in an acid, an alkali, or an organic solvent has been conventionally used as the resin composition to be plated. Various fillers, such as calcium carbonate, glass, magnesium carbonate, magnesium oxide, calcium pyrophosphate, barium sulfate, barium carbonate, and zinc oxide, are used as the inorganic filler. These conventional inorganic fillers, however, impair the electrical characteristics of the resins, for example, by increasing the dielectric constant or the dielectric loss tangent. The increase in the dielectric constant or the dielectric loss tangent causes the signal loss to increase or delays the signal transmission speed, particularly when the product is used as an insulating material for electronic parts, inter alia, electronic parts for high frequency wave signals. Here, the high frequency signals are signals of a frequency in the range of 1 GHz or larger. Specific equipment using high frequency signals includes cellular phones, PHS, pocket bells, satellite terminals, navigation systems, wireless LANs, and the like. Conventionally, there has been no report disclosing resin compositions having both excellent plating characteristics and excellent electrical characteristics (low dielectric constant and low dielectric loss tangent). Because of miniaturization and high integration of electronic parts in recent years, great attention is given to the technologies for manufacturing electronic parts by injection molding which is suitable for molding small and integrated parts. An object of the present invention is therefore to provide a thermoplastic resin composition for plating, suitable for injection molding and having both excellent plating characteristics and excellent electrical characteristics. In view of this situation the present inventors have conducted extensive studies and found that the addition of a specific inorganic filler to a thermoplastic resin produces a resin composition exhibiting both excellent plating characteristics and excellent electrical characteristics. SUMMARY OF THE INVENTION Accordingly, a specific object of the present invention is to provide a resin composition exhibiting both excellent plating characteristics and excellent electrical characteristics comprising a thermoplastic resin and aluminum borate or amorphous silica, or both. Other objects, features and advantages of the invention will hereinafter become more readily apparent from the following description. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Aluminum borate and amorphous silica used in the present invention have aspect ratios of 10 or smaller, preferably 5 or smaller, and an average particle diameter of 0.01-100 .mu.m. The resin composition of the present invention preferably has a dielectric constant of 4.0 or smaller and a dielectric loss tangent of 0.01 or smaller in the high frequency region of 100 KHz to 300 GHz. Resins represented by commercially available thermoplastic resins are used as the thermoplastic resins of the present invention. Specific examples of such thermoplastic resins include general purpose resins, such as polyethylene (PE), polypropylene (PP), polystyrene (PS), polymethyl methacrylate (PMMA), ABS resin, and AS resins; engineering plastics, such as polyacetate (POM), polycarbonate (PC), polyphenylene ether (PPE), polyamide (PA: nylon), polyethylene terephthalate (PET), and polybutylene terephthalate (PBT); and other thermoplastic resins such as polyphenylene sulfide (PPS), polyether sulfone (PES), polyether imide (PEI), polyether ether ketone (PEEK), polyketone (PK), polyimide (PI), polycyclohexanedimethanol terephthalate (PCT), polyallylate (PAR), and various liquid crystal polymers (LCP). These resins may be used individually or may be used as a polymer alloy or a polymer blend which is a multicomponent polymer system consisting of two or more of these resins chemically or physically blended in prescribed proportions. A denatured product of these resins can also be used. The denatured product here means a synthetic resin or a mixture of synthetic resins, of which a part of the basic component is replaced by another component when the resins are reacted or compounded. Given as preferred combinations of resins in multicomponent polymer systems are, as binary systems, PPE/PS, PPE/PC, PPE/PA, PPE/PET, PPE/PBT, PPE/PEI, PPE/PPS, PPE/PES, PPE/PEEK, PPE/PCT, PPE/LCP, PEI/PC, PEI/PEEK, PEI/LCP, PEI/PET, PEI/PBT, LCP/PAR, LCP/PEEK, LCP/PET, LCP/PBT, LCP/PC, LCP/PCT, and LCP/PEEK, and as ternary systems, PPE/PC/PS, PPE/PEI/PC, PPE/PEI/PS, PEI/PPE/LCP, PEI/PC/LCP, PEI/PEEK/LCP, and the like. A compatibilizer or the like may be added to these polymer alloys or polymer blends to improve compatibility among the polymers. Given as examples of specific compatibilizers which can be used are copolymers of epoxy-modified-MMA and MMA; copolymers of epoxy-modified-St and St; copolymers of epoxy-modified-St and MMA; copolymers of epoxy-modified-MMA and St; copolymers of St and maleic anhydride; copolymers of St and MMA; and copolymers of maleic anhydride and vinyl compound. These copolymers may be random copolymers, block copolymers, alternating copolymers, or graft copolymers. The thermoplastic resin used in the present invention may contain various additives which may improve the basic characteristics of the resins, such as mechanical characteristics, electrical characteristics, heat resistance, molding processability, fluidity, flame retarding characteristics, UV resistance, chemical resistance, and outward appearance of the molded products, and to provide a color or glossiness to the products. Plasticizers, thermal stabilizers, oxidation stabilizers, cross-linking agents, flame retardants, UV absorbers, coloring agents, glossing agents, and the like are given as examples of specific additives. The inorganic fillers used in the present invention which are aluminum borate and amorphous silica are respectively shown by the following formulas: nAl.sub.2 O.sub.3.mB.sub.2 O.sub.3 (1) wherein n and m individually represent an integer of 1-100, and SiO.sub.2 (2) Aluminum borate is industrially manufactured from Al.sub.2 O.sub.3 and B.sub.2 O.sub.3 by a method called an external flux process. The amorphous silica is preferably that containing 96% or more, preferably 99% or more, of silicon oxide (SiO.sub.2). Such an amorphous silica is manufactured, for example, by melting quartz (crystalline silica) and cooling the molten silica. The dielectric constant and dielectric loss tangent are high if the amount of silicone oxide in the amorphous silica is less than 96%. The aluminum borate and amorphous silica used in the present invention are powdery or globular fillers having an aspect ratio, which is the ratio of the length along the long axis to the length along the short axis, of 10 or less, preferably 5 or less, and an average diameter of 0.01-100 .mu.m, preferably 0.1-50 .mu.m. The closer the aspect ratio to 1, that is, the closer the shape of the filler to a sphere, the greater the degree of improvement in the plating characteristics. If the aspect ratio is too large, specifically larger than 10, the shape of the micropores is fibrous, remarkably decreasing the plate adhesion strength. If the average particle diameter is less than 0.01 .mu.m, it is difficult for the catalysts for non-electrolytic plating to adhere to the surface of the molded product. This results not only in insufficient adhesion strength, but also uneven plating. If the average particle diameter is larger than 100 .mu.m, the micropores are too large to provide sufficient anchoring. As a result, only weak physical bonding is obtained between the plated film and the resin. The amount of the inorganic filler, that is, aluminum borate or amorphous silica, is 5-70 parts by weight, preferably 10-60 parts by weight, for 100 parts by weight of the total amount of the thermoplastic resin and the inorganic filler. If the amount of the inorganic filler is less than 5 parts by weight, sufficient plating adhesion strength cannot be obtained; if larger than 70 parts by weight, the fluidity of the resulting resin composition is remarkably lowered and molding processability is impaired. In order to improve dispersibility and affinity to the resin, thermal stability and oxidation stability, the inorganic fillers used in the present invention may be surface-treated by a conventional method. The addition of a coupling agent is given as an example of the method of surface treatment. Given as examples of coupling agents which can be preferably used are silane coupling agents, such as vinyltrichlorosilane, vinyltris(.beta.-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, .gamma.-methacryloxypropyltrimethoxysilane, .beta.-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, .gamma.-glycidoxypropyltrimethoxysilane, .gamma.-glycidoxypropyl-methyldiethoxysilane, N-.beta.-(aminoethyl)-.gamma.-aminopropyl-trimethoxysilane, N-.beta.-(aminoethyl)-.gamma.-aminopropylmethyl-dimethoxysilane, .gamma.-aminopropyltriethoxysilane, N-phenyl-.gamma.-aminopropyltrimethoxysilane, .gamma.-mercaptopropyltrimethoxysilane, .gamma.-chloropropyltrimethoxysilane, di(3-triethoxy-silylpropyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltrimethoxysilane, 3-aminopropyltriethoxy-silane, N-2(aminoethyl)-3-aminopropyltrimethoxysilane, vinyltri(2-methoxyethoxy)silane, 3-methacryloyloxypropyltrimethoxysilane, and 3-glycidyloxypropyltrimethoxysilane; and titanate coupling agents, such as triisostearoylisopropyl titanate, di(dioctylphosphate)diisopropyl titanate, didodecylbenzenesulfonyldiisopropyl titanate, and diisostearyldiisopropyl titanate. These coupling agents can be used in an amount which does not impair the electrical characteristics or plating characteristics, usually in an amount of 0.0001-1 part by weight for 100 parts by weight of the inorganic filler. Aluminum borate and amorphous silica which are incorporated in a thermoplastic resin as an inorganic filler in the resin composition of the present invention may be used either individually or in combination. Further, it is possible to use inorganic fillers other than aluminum borate and amorphous silica to an extent which does not impaire the electrical characteristics and plating characteristics. Given as examples of such other inorganic fillers which can be used together are glass, glass single fiber, glass fiber, glass balloons, shirasu balloons, chopped strands, carbon fiber, carbon, carbon black, alamide, potassium tatanate, magnesium borate, calcium carbonate, magnesium carbonate, magnesium sulfate, calcium sulfate, aluminum sulfate, pyrophosphate, silicon nitride, aluminum nitride, boron nitride, silicon carbide, alumina, alumina fiber, silica, mica, talc, diatomaceous earth, clay, volcanic ash, lime stone, bentonite, titanium oxide, magnesium oxide, calcium oxide, molybdenum disulfide, and the like. The resin composition of the present invention can be manufactured by a conventional process for manufacturing common composite materials. Industrially, a melt-kneading method is preferred in view of productivity and economy. Specific examples of such methods include a kneading method using a biaxial or uniaxial extruder, and a method using a batch-type heating melt-kneader which is typified by the laboplast mill. Because the resin composition of the present invention is thermoplastic, injection molding or extrusion molding can be used for manufacturing molded products from the resin composition. Films or membranes can also be manufactured by a solvent cast method using an organic solvent or the like. In the same way as in the case of conventional resin compositions for plating, the strength of adhesion between the molded products made from the resin composition of the present invention and the plating metal film (the plating adhesion strength) depends on the physical characteristics of the molded surface of the resin composition, specifically the roughness of the molded resin surface. It is possible to remarkably improve the plating adhesion strength from the anchoring effect obtained by forming uniform micropores of an appropriate size on the surface of the molded article before plating. In the same manner as in the case of molded products made from conventional resin compositions for plating, chemical etching is effective for producing the micropores. As mentioned above, the chemical etching can be carried out by immersing the molded resin surface in an acid, alkali, or organic solvent, or the like and dissolving and removing the inorganic filler from the surface of the molded article. Because aluminum borate and amorphous silica used in the present invention is soluble in alkaline aqueous solutions, it is possible to dissolve aluminum borate or amorphous silica and remove these from the surface of molded articles by chemically etching that surface with an alkaline aqueous solution, thereby producing micropores which are effective for plating. As the alkaline aqueous solution, aqueous solutions of sodium hydroxide, potassium hydroxide, lithium hydroxide, and the like are preferred in view of the solubility of aluminum borate and amorphous silica, and also in view of economy. These alkaline aqueous solution may be used either individually or mixed. The preferred concentration of the alkaline aqueous solution is in the range of 1 N to 15 N, and particularly in the range of 3 N to 12 N. If the alkali concentration is too small, it takes a long time for the aluminum borate or amorphous silica to dissolve out; if the concentration is too high, the resin may exhibit conspicuous deterioration, resulting in a decrease in the plating adhesion strength. In the case where inorganic fillers other than aluminum borate or amorphous silica are used, these other inorganic fillers may be chemically etched together with aluminum borate and amorphous silica. In this case, the etching solution is selected taking into consideration the characteristics (e.g., the solubility, corrosivity, etc.) of such other inorganic fillers. For instance, when calcium carbonate, pyrophosphate, or barium sulfate is used together with aluminum borate or amorphous silica, an acid, such as sulfuric acid, hydrochloric acid, chromic acid, phosphoric acid, acetic acid, or boric acid, a mixture of two or more of these acids, or aqueous solution of one or more of these acid can be used. When glass-type or alumina-type fillers are used together, an alkali, such as an aqeous solution of potassium hydroxide, sodium hydroxide, or lithium hydroxide, or mixture of these, at any optional concentration, can be used. In any of the above cases, the chemical etching is carried out at room temperature (20.degree. C.) to 120.degree. C., preferably at a temperature of 50.degree. C. to 100.degree. C. If the etching temperature is too low, it takes a long time for the inorganic fillers to dissolve out; if too high, deterioration of the resin is conspicuous. To improve the rate of dissolution of the organic fillers it is possible to agitate the mixture, irradiate the mixture with ultrasonic waves, or bubble air through the mixture, during the chemical etching. In addition, to carry out the chemical etching more effectively a procedure called pre-etching, which consists of exposing the inorganic fillers by dissolving the resin on the surface of molded article (a skin layer of resin), may be applied. Conventional methods of pre-etching can be used. Among organic solvents, alkaline solutions, and acids commonly used for pre-etching, organic solvents or acids are particularly preferred in the present invention. Preferred organic solvents used for pre-etching are, for example, chloroform, dichloromethane, benzene, toluene, xylene, pyridine, hexane, tetrahydrofuran, acetonitrile, ethyl acetate, N,N-dimethylformamide, N-methylpyrrolidone, and dimethylsulfoxide. Sulfuric acid, hydrochloric acid, chromic acid, nitric acid, or phosphoric acid, or mixtures of these are given as preferred examples of the acids. Except for the chemical etching step and the pre-etching step, the molded products produced from the resin composition of the present invention may be plated by non-electrolyte plating or electrolytic plating in the same manner as in conventional resin compositions for plating. As previously mentioned, the resin composition of the present invention preferably has a dielectric constant of 4.0 or less and a dielectric loss tangent of 0.01 or less in the high frequency region of 100 KHz to 300 GHz. Resin compositions having a dielectric constant greater than 4.0 or a dielectric loss tangent greater than 0.01 in the above frequency region may unduly increase signal loss when used as an insulating material for electronic parts, particularly the electronic parts or materials used in a high frequency region of 1 GHz or greater, making it difficult to reasonably design circuits and the like. Such parts or materials are unusable in some on applications. Other features of the invention will become apparent in the course of the following description of the exemplary embodiments which are given for illustration of the invention and are not intended to be limiting thereof. |
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