Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-07-29
2001-01-30
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S222000, C525S227000, C525S242000, C525S244000, C525S329700, C525S333300, C428S500000, C524S081000
Reexamination Certificate
active
06180725
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resin composition constituting the laminate for electric circuits boards and a laminate comprising such a resin composition. More particularly, it relates to a resin composition for reducing the dielectric constant and increasing the peeling strength of electric circuit boards and a laminate comprising such a resin composition.
2. Description of the Related Arts
Syndiotactic polystyrene (sPS) has the properties of high melting point, low dielectric constant, low specific gravity, and excellent chemical resistance, which make it very useful in many applications. However, it suffers a major deficiency, that is, poor adhesion to other materials. In particular, its poor adhesion to copper foils makes it unsatisfactory for making electric circuit substrates even though it has more ideal dielectric properties than the epoxy resins and the cyanate resins used nowadays. In order to solve the above-mentioned problem, attempts have been made by incorporating an aminosilane coupling agent to improve the adhesive strength to copper foils. See for example, Japanese Patent Application Laid-Open No. 9012746. The coupling agent, however, generally deteriorates the dielectric properties of the substrates.
Accordingly, the invention aims to improve the adhesive strength of the electric circuit substrates to copper foils without deteriorating the dielectric properties.
DETAILED DESCRIPTION OF THE INVENTION
An object of the invention is to provide a resin composition constituting the laminate for an electric circuit board, which improves the peeling strength of copper foils from the electric circuit substrate as well as improves the dielectric properties of the substrates.
Another object of the invention is to provide a laminate for an electric circuit board comprising such a resin composition.
To attain the above objects, the resin composition in accordance with the present invention is incorporated with a functionalized syndiotactic styrene-based copolymer which has microfoaming when being cured. The functional group of the functionalized copolymer contributes to the enhancement of the adhesivity to copper foils, while its microfoaming contributes to the decrease of the dielectric constant.
The resin composition according to the present invention comprises: (a) 20-100 parts by weight of a syndiotactic polystyrene, (b) 1-40 parts by weight of a functionalized syndiotactic styrene-based copolymer having microfoaming when being cured, (c) 1-40 parts by weight of an epoxy-styrene copolymer, and (d) 0-40 parts by weight of an additive.
In the resin composition according to the present invention, a syndiotactic polystyrene having a syndiotacticity of over 90% is preferably used as the component (a), which is typically prepared by using a metallocene catalyst. The molecular weight of the syndiotactic polystyrene to be used in the present invention is not specifically limited, but is preferably within the range of 1×10
5
to 5×10
5
in terms of weight-average molecular weight.
In the resin composition according to the present invention, a functionalized syndiotactic styrene-based copolymer having microfoaming when being cured is employed as the component (b). Especially preferred are functionalized syndiotactic styrene/para-alkylstyrene copolymers. Illustrative of such copolymers include oxidized styrene/para-methylstyrene copolymer, halogenated syndiotactic styrene/para-methylstyrene copolymer, carboxylated styrene/para-methylstyrene copolymer, metallized styrene/para-methylstyrene copolymer, aminated styrene/para-methylstyrene copolymer, and silylated styrene/para-methylstyrene copolymer. The molecular weight of the functionalized syndiotactic styrene-based copolymer to be used in the present invention is preferably within the range of 3×10
3
to 2×10
5
in terms of weight-average molecular weight.
The general process for preparing the functionalized syndiotactic styrene-based copolymer of the present invention will be described below.
Taking the reaction of styrene and para-methylstyrene monomers as an example, the two monomers are copolymerized by using a metallocene catalyst. The catalyst system may also include an activating cocatalyst such as methyl aluminoxane (MAO).
wherein x and y are the molar ratio of the respective monomer, and x+y=100.
Suitable metallocene catalysts have a delocalized &pgr;-bonded moiety with a constrained geometry. The catalysts may be further described as a metal coordination complex comprising a IVB-VIB Groups metal and a delocalized &pgr;-bonded moiety with a constrained geometry. In this regard, references are made to U.S. Pat. Nos. 4,542,199; 4,530,914; 4,665,047; 4,752,597; 5,026,798; and 5,272,236. Preferred catalyst complexes include zirconocene and titanocene coordination compounds with single or double cyclopentadienyl derivatives which form the constrained ligand geometry.
The activating cocatalyst can be methyl aluminoxane (MAO), a trialkyl aluminum, a dialkyl aluminum, a salt of an inert and non-coordinating anion, or a mixture thereof. Illustrative of trialkyl aluminum includes trimethyl aluminum, triethyl aluminum, tripropyl aluminum, trisopropyl aluminum, tributyl aluminum, and triisobutyl aluminum (TIBA). The salt of an inert and non-coordinating anion can be borates. Borates suitable for use in the present invention include N,N-dimethyl anilinium tetrakis(pentafluorophenyl)borate, triphenyl carbenium tetrakis(pentafluorophenyl)borate, trimethyl ammonium tetrakis(pentafluorophenyl)borate, ferrocenium tetrakis(pentafluorophenyl)borate, dimethyl ferrocenium tetrakis(pentafluorophenyl)borate, and silver tetrakis(pentafluorophenyl)borate. Preferably, the activating cocatalyst is methyl aluminoxane, or a mixture of a trialkyl aluminum and a borate. Suitable diluents for the polymerization reaction include aliphatic and aromatic hydrocarbons such as propane, butane, pentane, cyclopentane, hexane, toluene, heptane, isooctane, and the like, which can be used individually or collectively.
In general, the polymerization reaction is carried out by mixing styrene and p-methylstyrene in the presence of the catalyst in a copolymerization reactor, with thorough mixing at a temperature between 0° C. to 100° C. The polymerization is carried out under an inert gas atmosphere in absence of moisture.
In the styrene/p-methylstyrene copolymer, the benzylic protons in p-methylstyrene unit can be easily converted to various functional groups, such as —COOH, —OH, —NH
2
, —Cl, —Br, —M, COOM (M=metal, e.g. Li, Na, K and Ca), under mild reaction conditions. Most functionalization reactions of benzylic protons in organic compounds can be applied to those of benzylic protons in p-methylstyrene. With regard to the functionallization of benzylic protons, references are made to U.S. Pat. No. 5,543,484 (Chung, et al.); U.S. Pat. No. 5,548,029 (Powers et al.); and U.S. Pat. No. 5,162,445 (Powers, et al.)
In the resin composition according to the present invention, an epoxy/styrene copolymer is employed as the component (c). A particularly preferred epoxy/styrene copolymer is glycidyl methacrylate/styrene copolymer with a melt index ranging from 0.01 to 30. The molar content of glycidyl methacrylate (GMA) to styrene in the copolymer may ranges from 1/99 to 50/50.
The component (d), that is, the additives to be used herein are typically flame retardants, flame retardant aids, crystallizing agents, crystallizing aid agents, or combinations thereof.
According to another aspect of the invention, there is also provided a laminate for a printed circuit board, which comprises a sheet made from the resin composition as set forth above being laminated with a glass cloth and a copper foil. The glass cloth may preferably be impregnated with the functionalized syndiotactic styrene-based copolymer or the epoxy/styrene copolymer as set forth above. It is more preferable that the copper foil is coated with the functionalized syndiotactic styrene-based copolymer or the epox
Chen In-Mau
Kuo Wen-Faa
Tsai Hsien-Yin
Acquah Samuel A.
Darby & Darby
Industrial Technology Research Institute
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