Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2001-06-22
2003-05-06
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C428S413000, C428S422800, C428S901000, C428S138000, C528S106000, C528S116000, C528S118000, C528S119000
Reexamination Certificate
active
06558797
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a resin coated copper foil, copper-clad laminates using it, and printed wiring boards using such laminates.
BACKGROUND ART
Abreast with the trend toward miniaturization and higher performance of electronic devices, the printed wiring boards incorporated in such electronic devices are also making headway toward higher degree of density through various means such as multiplication of lamination layers, thinning of the laminated structure, reduction of through-hole diameter and decrease of hole intervals. Further, the printed wiring boards mounted in the information terminal devices such as cellular phones and mobile computers, especially the plastic packages having MPU mounted directly on the boards and the printed wiring boards adapted for various types of modules, are required to be capable of processing a large volume of information at high speed. This calls for speed-up of signal processing, reduction of transmission loss and further downsizing, for which even higher densification and finer wiring of the printed circuit boards are indispensable.
In order to meet the request for finer wiring, a so-called buildup printed wiring board—in which a resin coated copper foil without using glass cloth or the like is attached on the board, then the through-holes and interstitial via holes are formed by laser or other means and then circuits are formed on the board—has been devised and is gaining ground in the art.
On the other hand, for the printed circuit boards adapted with MPU (micro processing units) or the printed circuit boards for modules, a high Tg (glass transition temperature) material with excellent heat resistance is required to secure higher connection reliability than ever demanded. One method for realizing a high Tg material is to cure an epoxy resin with a polyfunctional phenol resin. With this resin system, it is possible to obtain a cured product which is low in water absorption and also has a Tg of 170° C. or higher. However, since the high Tg resin systems have the property of being hard and brittle, they have the problem that when used with a resin coated copper foil, their adhesion to such a copper foil proves to be unsatisfactory. When using a resin system with low adhesion to the copper foil, there tends to take place exfoliation or breaking of the lines in molding or mounting of the substrate. Adhesion to the copper foil will become an important factor as the densification of wiring advances in the future.
As a technique for improving adhesion between copper foil and resin, it has been practiced to treat the copper foil with a coupling agent, as for instance disclosed in JP-A-54-48879, but in the case of the hard and brittle resin system such as high Tg resin system, mere treatment of the copper foil with a commercially available coupling agent can not provide a stronger chemical adhesion to the resin than possible with the conventional FR-4 material. Also, when the copper foil is treated with a silane coupling agent, there remains a residue on the substrate surface after formation of circuits, which may exert adverse effect on prevention of staining in the ensuing plating step or adhesion to the solder resist.
DISCLOSURE OF THE INVENTION
The present invention has been made in view of these circumstances, and it is intended to provide a resin coated copper foil which has low water absorption, high heat resistance and good adhesion to the copper foil; copper-clad laminates using the said copper foil, and printed wiring boards using such laminates.
The present invention provides a resin coated copper foil obtained by applying on one side of a copper foil an adhesive composition comprising as essential components (a) an epoxy resin, (b) a polyfunctional phenol, (c) a curing accelerator as required, and (d) a compound having a triazine ring or an isocyanuric ring.
The present invention also provides the copper-clad laminates obtained by using the said resin coated copper foil, and the printed wiring boards obtained by forming circuits on said copper-clad laminates.
BEST MODE FOR CARRYING OUT THE INVENTION
A detailed description of the present invention follows.
The adhesive composition used for the resin coated copper foil of the present invention is a thermosetting resin composition containing an epoxy resin.
As the epoxy resin (a) constituting a component of the said adhesive composition, there can be used, for instance, bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, bisphenol epoxy resins, phenolic novolak epoxy resins, cresol novolak epoxy resins, bisphenol A novolak epoxy resins, bisphenol F novolak epoxy resins, phenolic salicylaldehyde novolak epoxy resins, alicyclic epoxy resins, aliphatic chain epoxy resins, glycidyl ester type epoxy resins, glycidyl-etherified products of bifunctional phenols, glycidyl-etherified products of bifunctional alcohols, glycidyl-etherified products of polyphenols, and their hydrogenation products and halides. These compounds may be used either singly or as a combination of two or more of them.
The polyfunctional phenol (b), which is another component of the said adhesive (or thermosetting resin) composition, can be used with or in place of a condensate of bisphenol A and formaldehyde. Examples of the polyfunctional phenols usable in this invention include bisphenol F, bisphenol A, bisphenol S, polyvinyl phenol, novolak resins obtainable by reacting phenols such as phenol, cresol, alkyl phenols (such as p-t-butylphenol and p-octylphenol), catechol, bisphenol F, bisphenol A, bisphenol S, etc., with aldehydes such as formaldehyde and acetaldehyde in the presence of an acidic catalyst, and their halides. These phenols can be used either singly or by combining two or more of them. Novolak resins, especially those obtainable by reacting bisphenol A with aldehydes are preferably used.
The amount of the polyfunctional phenol to be blended in the composition is selected such that the amount of the phenolic hydroxyl group will fall within the range of 0.5 to 1.5 equivalent to one equivalent of epoxy group.
In the said adhesive composition, a curing accelerator (c) may be contained as required. As such a curing accelerator, it is possible to use any compound having a catalytic function to accelerate the etherification reaction of epoxy resin and phenolic hydroxyl group. Such compounds include alkaline metal compounds, alkaline earth metal compounds, imidazole compounds, organic phosphorus compounds, secondary amines, tertiary amines, and quaternary ammonium salts. Use of imidazole having its imino group masked with acrylonitrile, isocyanate, melamine acrylate or the like is preferable as it can provide a prepreg having 2 or more times longer pot life than conventional prepregs.
It is possible to use two or more types of curing accelerator. This curing accelerator is used in an amount of preferably 0.01 to 5 parts by weight per 100 parts by weight of the epoxy resin. If the amount of the curing accelerator is less than 0.01 part by weight, its accelerating effect may prove to be unsatisfactory, and if its amount exceeds 5 parts by weight, the composition tends to deteriorate in pot life.
Examples of the said imidazole compounds include imidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 1-benzyl-2-methylimidazole, 2-heptadecylimidazole, 4,5-diphenylimidazole, 2-methylimidazole, 2-phenylimidazoline, 2-undecylimidazoline, 2-heptadecylimidazoline, 2-isopropylimidazole, 2,4-dimethylimidazole, 2-phenyl-4-methylimidazole, 2-ethylimidazoline, 2-isopropylimidazoline, 2,4-dimethylimidazoline, and 2-phenyl-4-methylimidazoline. As the masking agent, acrylonitrile, phenylene diisocyanate, toluidine isocyanate, naphthalene diisocyanate, methylenebisphenyl isocyanate, melamine acrylate and the like can be used.
The compound having a triazine or isocyanuric ring, used as yet another component (d) of the said adhesive composition, is not subject to any specific restrictions, but the compounds represented by the following formula (I)
Arata Michitoshi
Kobayashi Kazuhito
Takano Nozomu
Antonelli Terry Stout & Kraus LLP
Dawson Robert
Feely Michael
Hitachi Chemical Company Ltd.
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