Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
1997-12-04
2001-02-13
Sellers, Robert E. L. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C427S386000, C523S427000, C523S466000, C525S438000, C525S454000, C525S524000, C525S528000, C525S531000, C525S111000, C525S120000
Reexamination Certificate
active
06187442
ABSTRACT:
BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
The present invention relates to thermosetting resin compositions with excellent electrical properties; electrical laminates made therefrom; and methods of producing these.
2. Technology Review
Electrical laminates such as circuit boards are produced by laminating sheets of electrical conducting material onto a base substrate of insulation material. The performance of the finished circuit board is effected by the electrical characteristics of the base substrate material.
Commercially available thermoset resin systems with acceptable electrical performance at high frequencies (>350 MHZ) are restricted in their applications due to high cost. The lower cost alternatives that are available do not perform satisfactorily at high frequencies due to unacceptable electrical properties, such as high dielectric constant (D
k
), high dissipation factor (D
f
), high variability of D
k
and D
f
with frequency, and consistency of D
k
and D
f
from lot to lot of production material.
Thermoplastic polymers such as polytetrafluoroethylene (PTFE) which have exceptional electrical performance at high frequencies are commercially available. The primary drawbacks associated with these materials are very high raw material costs and special processing considerations that add substantial cost to the final product. Because of the physical properties, very high laminating temperatures and pressures are also required to fabricate an electrical laminate from PTFE. Furthermore, due to the inability to “wet” PTFE, costly and hazardous chemicals are required to modify its surface during fabrication of the circuit.
A thermoset material would have much greater mechanical properties over a much broader temperature range. Additionally, since thermoset materials have better mechanical properties, this would allow the circuit board fabricator to use conventional cost effective processes.
A need exists for thermosetting resin compositions, and electrical laminates made therefrom, of low to moderate cost with acceptable electrical properties at frequencies up to at least 20 GHz. Such compositions would have great utility as circuit board substrates and the laminates made from these thermosetting resins can be utilized in many applications such as in the rapidly growing wireless communication market, in high speed computers, in high definition televisions, and in various other electrical and related applications.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a thermosetting resin composition which can be made flame retardant and which can be utilized in existing cost effective technologies to manufacture electrical laminates therefrom. Additionally, the present invention resin compositions can have utility as, for example, electrical insulators, encapsulants, insulating adhesives and in various other electrical and related applications generally know to those skilled in this art.
Accordingly, the present invention provides a thermosetting resin composition comprising (a) a first vinyl ester resin synthesized from diglycidyl ether of bisphenol A, bisphenol A, and glacial methacrylic acid, in about 1% to about 95% by weight of the total composition; and (b) a resin selected from the group consisting of (1) a second different vinyl ester synthesized from diglycidyl ether of bisphenol A with glacial methacrylic acid, and (2) an unsaturated polyester, in about 1% to about 69% by weight of the total composition.
The composition resins may also further contain monomers which would, for example, aid in the adhesion of a metal foil to the laminate; increase crosslink density and thermal performance; provide fire retardation, etc. Catalysts which, for example, induce free-radical cure may also be added. Other components may include moisture scavengers, compounds which increase or reduce the dielectric constant, and/or reduce the dissipation factor, polyethylene fillers, other fillers, organic or inorganic, which modify rheology, surface agents, viscosity and performance modifiers, wetting agents, air release agents, defoaming agents, flame retardant synergists, adhesion promoters, and other additional monomers and conventional additives known in the art.
Other objects of the present invention are to provide electrical laminates, and methods for producing these laminates containing the composition resins of the present invention, which have excellent electrical properties and which may be flame retardant or heat resistant. Accordingly, the present invention further provides electrical laminates from about 0.003 inches to about 0.120 inches thick which may or may not be clad with an electrical conducting material on one or both sides.
The electrical laminates of the present invention are produced by impregnating at least one reinforcement substrate with a thermosetting resin composition comprising a mixture of (a) a first vinyl ester resin, synthesized from diglycidyl ether of bisphenol A, bisphenol A, and glacial methacrylic acid, in about 1% to about 95% by weight of the total composition; (b) a resin selected from the group consisting of (1) a second different vinyl ester synthesized from diglycidyl ether of bisphenol A with glacial methacrylic acid, and (2) an unsaturated polyester, in about 1% to about 69% by weight of the total composition; and (c) catalysts which induce free radical cure, polymerization, or U.V. initiation in about 0.1% to about 2.0% by weight of the total composition; and curing the resin impregnated substrate to produce an electrical laminate.
The thermosetting resin composition may also further contain the above mentioned added components and may be cured by electron beam processing, radiation, heat with or without pressure, ultra violet light processing, and other conventional curing methods in conjunction with the appropriate initiators. The electrical laminates may further comprise an electrical conductive cladding on at least one side.
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Austill Timothy Wayne
Even Thomas Edward
Johnson Philip Andrew
Lane Scott Alan
Schneller Marina V.
Sellers Robert E. L.
Spencer George H.
The Alpha Corporation of Tennessee
Venable
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