Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-07-01
2001-05-01
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S455000, C528S094000, C528S118000, C544S196000, C544S197000, C544S198000
Reexamination Certificate
active
06225378
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a resin composition to be employed as a substrate of high frequency printed circuit boards. In particular, the invention relates to a novel triazine hardener (curing agent), a resin composition containing the triazine hardener, and a high frequency printed circuit board having low dielectric constant prepared therefrom.
DESCRIPTION OF THE RELATED ART
Epoxy resins, phenolic resins, polyester resins, polyimide resins, BT resins, cyanate ester, PTFE resins and PPE resins have been employed as the resin materials in the preparation of structural substrates of printed circuit boards. It has been disclosed in EPO patent No. 548,970 and U.S. Pat. No. 5,068,309 that the printed circuit boards prepared from dicyanate ester resins have relatively low dielectric constant. However, as the preparation of the dicyanate ester resins requires the use of toxic and high volatile cyanogen halide, epoxy resins are currently being employed in the preparation of structural substrates of printed circuit boards. In the preparation of printed circuit board laminate, epoxy resins are first reacted with a chain extender, and then mixed with hardeners (curing agents), curing promoters and solvents to obtain a mixture, called varnish. The varnish is used to impregnate a woven glass cloth to obtain prepregs. Then the prepregs are laminated with copper clads or foils to form a printed circuit board laminate.
The dielectric constant of epoxy resin-based substrate materials for printed circuit boards currently in use, for example FR-4, are still too high, and thus are not suitable for use in the high frequency applications. Moreover, using epoxy resins as the resin materials of a structural substrate necessitates particular hardeners, which are usually of high cost and have high moisture-absorbing characteristics.
SUMMARY OF THE INVENTION
An object of the invention is to provide a hardener for epoxy resins that is safe and not expensive.
Another object of the invention is to provide an epoxy resin composition for which the substrate material obtained therefrom has lower dielectric constant.
The above objects are achieved by providing a triazine hardener having the formula I or formula II as shown below and an epoxy resin composition containing the triazine hardener.
wherein n is integer from 1 to 5;
R
1
is hydrogen, halogen, C
1
-C
4
alkyl, or C
1
-C
4
alkoxyl; and
R
2
is aliphatic amine, aliphatic alcohol, alicyclic amine or alicyclic alcohol.
DETAILED DESCRIPTION OF THE INVENTION
The trazine hardener of formula I is ether type triazine and is prepared by reacting cyanuric chloride with phenol derivatives as shown in the reaction scheme below.
The triazine hardener of formula II is an amine type triazine and is prepared by reacting cyanuric chloride with amine derivatives as shown in reaction scheme below.
The reactant, cyanuric chloride, is nontoxic and nonvolatile, and thus the process of producing the triazine hardener of the invention is safe and environment friendly. Moreover, the triazine hardener of the invention has superior solubility and thus can facilitate the preparation of the resin substrate. In addition, the triazine of the invention has at least 3 active hydrogen in its structure. This can increase the functionality of the epoxy resin, and result in a larger crosslinking density with the epoxy resin, thereby increasing the thermal resistance and mechanical strength of the resultant substrate. The triazine of the invention also has lower dielectric constant (Dk), and thus the printed circuit boards prepared therefrom have relatively low dielectric constant.
The epoxy resin composition of the invention includes epoxy resins, the triazine mentioned above, suitable curing promoters and solvents. The amount of the epoxy resins is 45-95 percent by weight, preferably 60-90, based on the total amount of the composition. The amount of the triazine hardener is such that the ratio between the equivalent of the active hydrogen in the triazine and the equivalent of the epoxide groups of the epoxy resin is about 0.5-1.2, preferably 0.8-1.0.
According to the invention, suitable epoxy resins include but are not limited to bisphenol-A epoxy resin, brominated epoxy resin (bromine content: 10-60 wt %), novolac epoxy resin, multifunctional epoxy resin, aliphatic epoxy resin. Mixture of the above mentioned epoxy resins in a predetermined ratio is also suitable for use. Examples of the epoxy resins are bisphenol A epoxy resin, tetrabromo bisphenol A epoxy resin, tetrabromo bisphenol A polyphenol epoxy resin, ortho-cresol novolac epoxy resin, N,N,N′,N′-tetra(2,3-epoxypropyl)-P′,P′-methylaniline, N,N-bis(2,3-epoxypropyl)-4-amino-phenylepoxypropyl ether and 4-epoxypropylene-N,N-bisepxoypropylaniline and the like.
According to the invention, suitable curing promoters include but are not limited to tertiary amines, quaternary ammonium salts, imidazoles and boron trifluorideamine complexes. Examples of these curing promoters are triethyl amine HCl complex, triethyl amine HBr complex, triethyl amine, bismethyl aniline, trimethylphenyl ammonium chloride, trimethyl ammonium hydroxide, tetrabutyl ammonium hydroxide, triphenylethyl phosphonium chloride, triphenylethyl phosphonium acetate, tetrabutyl phosphonium iodide and 2-methyl imidazole.
Optionally, the epoxy resin composition of the invention can also include one or more solvents. Examples of the solvents suitable for use in the invention include acetone, methylethyl ketone, toluene, xylene and N,N′-dimethyl formamide. Mixtures of the above-mentioned solvents are also suitable for use.
When the epoxy resin composition is used to prepare the substrate of printed circuit boards, it is mixed with suitable solvents to form varnish. Woven glass fiber clothes are then impregnated with the varnish to give prepregs. The prepregs are then laminated and hot pressed to form epoxy resin substrate laminate. The process of fabricating the substrate laminate is familiar to those skilled in this art and thus the detailed description is omitted. The epoxy resin substrates fabricated by using the epoxy resin composition of the invention have a dielectric constant of about 4.0.
REFERENCES:
patent: 3755322 (1973-08-01), Winter et al.
patent: 3963714 (1976-06-01), Gerendas et al.
patent: 4514399 (1985-04-01), Regnier et al.
patent: 4670558 (1987-06-01), Ebel et al.
patent: 5068309 (1991-11-01), Shimp et al.
patent: 3611420 (1987-10-01), None
patent: 19528882 (1997-02-01), None
patent: 0 548 970A2 (1993-06-01), None
patent: 51-032887 (1976-03-01), None
Makromol. Chem. (1979) p. 2123-2131, 1979.
Cheng Kung-Lung
Hong Se-Tsun
Hsu Kuo-Yuan
Kang Hung-Chou
Ma Jie-Hwa
Aylward D.
Darby & Darby
Dawson Robert
Industrial Technology Research Institute
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