MICROWAVE-TRANSPARENT THERMOSETTING RESIN COMPOSITIONS, ELECTRICAL LAMINATES OBTAINED THEREFROM, AND PROCESS OF PRODUCING THESE
Document Number
CA Patent 2362609
Publication Date
2000-08-17
Link
Inventors
ROLLEN DONALD C (US)
LANE SCOTT A (US)
AUSTILL TIMOTHY W (US)
Abstract
Abstract of
CA2362609
The present invention relates to a thermosetting resin composition with excellent electrical properties comprising (a) one or more terminally unsaturated urethane resins, (b) styrene, and (c) brominated styrene. The aforementioned composition finds great utility as a printed circuit board laminate suitable for use at microwave frequencies.
Microwave-transparent thermosetting resin compositions, electrical laminates obtained therefrom, and process of producing these
Inventor: LANE SCOTT A; ROLLEN DONALD C; (+1)
Applicant: GIL TECHNOLOGIES
EC:B32B5/26; C08F212/04; (+4)
IPC: C08J5/24; B32B5/26; B32B15/08(+22)
Publication info: AU2672299 A - 2000-08-29
2
MICROWAVE-TRANSPARENT THERMOSETTING RESIN COMPOSITIONS, ELECTRICAL LAMINATES OBTAINED THEREFROM, AND PROCESS OF PRODUCING THESE
Inventor: ROLLEN DONALD C (US); LANE SCOTT A (US); (+1)
Applicant: GIL TECHNOLOGIES (US)
EC:B32B5/26; C08F212/04; (+4)
IPC: C08J5/24; B32B5/26; B32B15/08(+22)
Publication info: CA2362609 A1 - 2000-08-17
3
MICROWAVE-TRANSPARENT THERMOSETTING RESIN COMPOSITIONS, ELECTRICAL LAMINATES OBTAINED THEREFROM, AND PROCESS OF PRODUCING THESE
Inventor: LANE SCOTT A (US); ROLLEN DONALD C (US); (+1)
Applicant: GIL TECHNOLOGIES (US)
EC:B32B5/26; C08F212/04; (+4)
IPC: C08J5/24; B32B5/26; B32B15/08(+22)
Publication info: EP1173501 A1 - 2002-01-23
4
MICROWAVE-TRANSPARENT THERMOSETTING RESIN COMPOSITIONS, ELECTRICAL LAMINATES OBTAINED THEREFROM, AND PROCESS OF PRODUCING THESE
Inventor:
Applicant:
EC:B32B5/26; C08F212/04; (+4)
IPC: C08J5/24; B32B5/26; B32B15/08(+23)
Publication info: JP2002536518T T - 2002-10-29
5
MICROWAVE-TRANSPARENT THERMOSETTING RESIN COMPOSITIONS, ELECTRICAL LAMINATES OBTAINED THEREFROM, AND PROCESS OF PRODUCING THESE.
Inventor: LANE SCOTT A (US)
Applicant: GIL TECHNOLOGIES (US)
EC:B32B5/26; C08F212/04; (+4)
IPC: C08J5/24; B32B5/26; B32B15/08(+22)
Publication info: MXPA01008222 A - 2002-10-23
6
MICROWAVE-TRANSPARENT THERMOSETTING RESIN COMPOSITIONS, ELECTRICAL LAMINATES OBTAINED THEREFROM, AND PROCESS OF PRODUCING THESE
Inventor: LANE SCOTT A (US); ROLLEN DONALD C (US); (+1)
Applicant: GIL TECHNOLOGIES (US); LANE SCOTT A (US); (+2)
EC:B32B5/26; C08F212/04; (+4)
IPC: C08J5/24; B32B5/26; B32B15/08(+22)
Publication info: WO0047655 A1 - 2000-08-17
List of citing documents
Claims
WHAT ISCLAIMED IS : 1. A thermosetting resin composition, comprising:
(a) One or more terminally unsaturated urethanes selected
from the group of:
1) one characterized by the formula:
EMI21.1
where R, is H orCH3, R2 is an organic residue from a
monohydricalcohol and R3 is an organic residue from
a diisocyanate; 2) and one characterized by the formula:
EMI21.2
where R, is H orCH3, R2 is an organic residue from a monohydricalcohol andR3 is an organic residue from a diisocyanate, andR4 is an isocyanurate compound of the followingstructure:
EMI22.1
and (b) Styrene monomer; and (c) Bromostyrene, characterized by the formula:
EMI22.2
wherein, the ratio of the sum of components (a) to the sum of components (b) and (c) is less than 0.2, and the ratio of (b) to (c) isless than 1.5.
2. The composition according to claim 1 further comprising a catalyst in about 0.1% to about 2% by weight of the total composition.
3. The composition according to claim 2 wherein the catalyst is selected from the group consisting of the t-butyl peroctoate, t-butyl peroxy benzoate,dicumyl peroxide,benzoyl peroxide, cumene hydrogen peroxide, t-butyl perbenzoate, t-butyl peroxide and combinations thereof.
4. The composition according to claim 3 wherein the catalyst comprisest-butyl peroctoate in about 0.2% by weight of the total composition.
5. The composition according to claim 3 wherein the catalyst comprises t-butyl peroxy benzoate in about 0.25% by weight of the total composition.
6. The composition according to claim 3 wherein the catalyst
comprisesdicumyl peroxide in about 0.25% by weight of the total
composition.
7. The composition according to claim 1 wherein said styrene
monomer is selected from the group consisting of styrene, halogenated
styrene, and an alpha alkyl styrene.
8. The composition of claim 7 wherein said styrene monomer is
an alpha alkyl styrene.
9. The composition of claim 7 wherein said styrene monomer isa-halogenated styrene.
10. The composition of claim 9 wherein said halogenated
styrene monomer is selected from the group consisting of dibromostyrene, tribromostyrene andpentabromobenzyl acrylate.
11. The composition of claim 1 further comprising divinyl
benzene in about 0.1% to about 10% by weight of the total composition.
12. The composition of claim 11 wherein the divinyl benzene is from about 0.5% to about 5% by weight of the total composition.
13. The composition of claim 12 wherein the divinyl benzene is from about1% to about 4% by weight of the total composition.
14. The composition of claim 1 further comprising additives
selected from the group consisting of moisture scavengers,molecular
3-ethyl-2-methyl-2- (3-methytbutyl)-1, 3-oxazolidine and combinations thereof.
15. The composition of claim 14 wherein the oxide comprises titanium dioxide.
16. The composition of claim 14 wherein the oxide comprises expanded polyethylene compounds.
17. The composition of claim 14 wherein the filler which modifiesrheology is calcine kaolin.
18. The composition of claim 14 wherein the monomer which modifies viscosity and performance comprises methyl methacrylate.
19. A method of producing an electrical laminate comprising the steps of:
(1) impregnating at least one substrate with a thermosetting resin composition comprising catalysts which induce free radical cure, polymerization, or UV initiation, in about 0.1 % to about 2% by weight of the total composition; and
(2) curing the resin impregnated substrate to produce an electrical laminate.
20. The method of claim 19 wherein the curing mechanism is selected from the group consisting of heating without pressure, heating with pressure, electron beam processing, and ultra-violet light processing in conjunction with U. V. initiators.
21. The method of claim 19 wherein the substrates are materials selected from the group consisting of organic or inorganic fillers, wovenfiberglass, glass paper, glass cloth, glass mat, polyimide paper, woven polymeric fibers and non-wovenpolymer fiber reinforcements.
22. The method of claim 19 further comprising cladding anelectrically conductive layer on at least one side of the impregnated substrate before curing.
23. The method of claim 19 further comprising cladding anelectrically conductive layer on at least one side of the impregnated substrate after curing.
24. The method of claim 22 wherein the electrically conductive layer is a metal selected from the group of aluminum, silver, gold, brass and copper.
25. The method of claim 23 wherein the electrically conductive layer is a metal selected from the group consisting of aluminum, silver, gold, brass and copper.
26. The method of claim 19 wherein the impregnating step involves more than one substrate and the method further comprises laminating the substrates before the curing step.
27. The method of claim 26 wherein the curing mechanism is selected from the group consisting of heating without pressure, heating with pressure, electron beam processing, and ultra-violet light processing in conjunction with U. V. initiators.
28. The method of claim 26 wherein the substrates are materials selected from the group consisting of organic or inorganic fillers, wovenfiberglass, glass paper, glass cloth, glass mat, polyimide paper, woven polymeric fibers and non-wovenpolymer fiber reinforcements.
29. The method of claim 26 further comprising cladding anelectrically conductive layer on at least one side of the impregnated substrate before curing.
30. The method of claim 19 further comprising cladding an electrically conductive layer on at least one side of the impregnated substrate after curing.
31. The method of claim 29 wherein theelectrically conductive layer is a metal selected from the group of aluminum, silver, gold, brass and copper. ~
32. The method of claim 30 wherein the electrically conductive layer is a metal selected from the group consisting of aluminum, silver, gold, brass and copper.
33. An electrical laminate obtained by
(1) impregnating at least one substrate with a thermosetting resin composition comprising:
One or more terminal unsaturated urethanes selected from
the group of:
1) one characterized by the formula:
EMI26.1
where R, is H orCH3, R2 is an organic residue from a monohydric
alcohol andR3 is an organic residue from a diisocyanate; (2) and one characterized by the formula:
EMI26.2
where R, is H orCH3, R2 is an organic residue from a monohydricalcohol and R3 is an organic residue from a diisocyanate, andR4 is an isocyanurate compound of the following structure:
EMI26.3
and
(b) Styrene monomer; and
(c) Bromostyrene, characterized by the formula:
EMI27.1
wherein, the ratio of the sum of components (a) to the sum of
components (b) and (c) isless than 0.2, and the ratio of (b) to (c) is
less than 1.5; and (d) catalysts which induce free radical cure,
polymerization, or UV initiation, in about 0.1% to about 2% by weight
of the total composition; and
(2) curing the resin impregnated substrate to produce
an electrical laminate.
34. The laminate of claim 33 wherein the composition resin further comprises ahalogenated vinyl functional monomer.
35. The laminate of claim 34 wherein the composition further comprises glacial methacrylic acid.
36. The laminate of claim 35 wherein the composition further comprises divinyl benzene.
37. The laminate of claim 36 wherein the composition further comprises additional components selected from the group consisting of moisture scavengers,molecular sieves, organic fillers, inorganic fillers, monomers to increase or decrease the dielectric constant, monomer to reduce the dissipation factor, polyethylene fillers, monomers to modify rheology, surface active agents, monomers to modify viscosity and performance, colorants, fluorescent dye, U. V.blockers, wetting agents, air release agents, defoaming agents, flame retardant synergists, adhesion promoters, epoxies, styrene, vinyl toluene,t-butyl styrene,paramethyl styrene, diallyl phthalate, and 2,4, ethyl-methylimidazole, 3-ethyl-2-methyl- 2-3(3-methylbutyl)-1,3-oxazolidine, methyl methacrylate and combinations thereof.
38. The laminate of claim 37 wherein the substrates are materials selected from the group consisting of organic or inorganic filles, woven fiberglass, glass paper,glass cloth, glass mat, polyimide paper, woven polymeric fibers and non-wovenpolymer fiber reinforcements.
39. The laminate of claim 38 further comprising anelectrically conductive layer clad on at least one side of the cured impregnated substrate.
40. The laminate of claim 39 wherein theelectrically conductive layer is a metal selected from the group of aluminum, silver, gold, brass and copper.
41. The laminate of claim 38 wherein more than one substrate is impregnated with the thermosetting resin and are laminated together before the curing step.
42. The laminate of claim 41 having an electrical conductive layer clad on at least one side of the laminated cured substrates.
43. The laminate of claim 42 wherein the electrical conductive layer is a metal selected from the group of aluminum, silver, gold, brass and copper.
44. An electrical laminate, comprising at least one reinforcement substrate and a crossed linked, thin wall thermosetting resin composition comprising: (a) One or more terminally unsaturated
urethanes selected from the group of:
1) one characterized by the formula:
EMI29.1
where R, is H orCH3, R2 is an organic residue from a monohydricalcohol and R3 is an organic residue from a diisocyanate;
2) and one characterized by the formula:
EMI29.2
where R, is H orCH3, R2 is an organic residue from a monohydricalcohol and R3 is an organic residue from a diisocyanate,and R4 is an isocyanurate compound of the following structure:
EMI30.1
and
(b) Styrene monomer; and
(c) Bromostyrene, characterized by the formula:
EMI30.2
wherein, the ratio of the sum of components (a) to the sum of components (b) and (c) isless than 0.2, and the ratio of (b) to (c) isless than 1.5; and (d) catalysts which induce free radical cure, polymerization, or UV initiation, in about 0.1 % to about 2% by weight of the total composition.
45. The laminate of claim 44 further comprising an electrically conductive cladding on at least one side.
46. Amultilayer electrical laminate comprising a combination of single sided and double sided laminates according to the laminate of claim 45.
47. The laminate of claim 44 wherein the thickness range is from about 0.003 to about 0.120 inches thick.
This is a regular application based on Provisional Application
No. 60/032,288 filed December 3,1996 and pursuant to 37 C. F. R. 1.53 (b) this application claims the benefit of thefiling date of same. The entire specification ofProvisional Application No.60/032,288 is herein incorporated by reference.
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.
BACKGROUND OF THE INVENTION
All publications and patent applications herein are incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference.
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(Dk), high dissipation factor(Df), high variability ofDk and D, with frequency, and consistency ofDk and D, from lot to lot of production material.
Thermoplastic polymers such as polytetrafluoroethylene (PTFE) which haveexceptional 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 hazardouschemicals are required to modify its surface during fabrication of the circuit.
A thermoset material would have much greatermechanical properties over a much broader temperature range. Additionally, since thermoset materials have bettermechanical 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. Suchcompositions would have greatutility as circuit board substrates and the laminates made from these thermosetting resins can be utilized in many applications such as in therapidly growingwireless 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 andrelated applications generally know to those skilled in this art.
Accordingly, the present invention provides a thermosetting resin composition comprising (a) a terminally unsaturated urethane resin selected from the group of 1):
EMI3.1
where R, is H or CH3, R2 is an organic residue from a monohydric alcohol and R3 is an organic residue from a diisocyanate;
and 2):
EMI3.2
where R, is H orCH3, R2 is an organic residue from a monohydric
alcohol, R3 is an organic residue from a diisocyanate, and R4 is an isocyanurate compound of the following structure ;
EMI3.3
and (b) an ethylenically unsaturated monomer from the group of 1) styrene and 2) bromostyrene with the following structures:
EMI4.1
<SEP> ICI
<tb> <SEP> I <SEP> I <SEP> =C.'H=
<tb> i
<tb> <SEP> rlm
<tb> <SEP> Styrcne <SEP> BromosLyrene
<tb>
where m = 1 to 3.
Additionally, to achieve the desired properties (i.e., microwave transparency, fire retardation, and good thermal performance) the ratio of (a) to the sum of (b) 1) and (b) 2) is less than 0.15, and the ratio of (b) 1) to(b) 2) is less than 1.2.
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; 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 beclad with an electrical conducting material on one or both sides.
The electrical laminates of the present invention are produced by (a) continuous lamination or (b) a batch process:
(a) The compositions of the present invention are uniquely suitable to the continuous lamination methods of Barrel et al. (U. S. Patent No.
4,587,161 and No. 4,803,022). The combination of materials in the outlined ratios provideslower viscosities then previous compositions, (U. S. Patent No.4,420,509 and No. 4,446,173). Lower viscosities provide more rapid impregnation of reinforcements to allow higher line-speeds and consequently higher machine output. In the continuous lamination process, the desired composition is formulated with a free-radical source, (i. e., peroxide, azo-compound, etc.) to initiate cure. Optionally, the material is postcured in a batch convection oven to furtherlower the dissipation factor of the laminate. Therefore, we have found the combination of continuous lamination with additional batch cure provides unexpected improvements in electrical performance. While the continuous lamination temperatures and times are known in the art, we have found the optimum secondary batch oven cure profile to be350 F for 1 hourdwell, (or range from150 F for 3 hours to450 F for 30 minutes).
(b) The method to manufacture the laminate with a batch
process involves
1) A layer of carrier film, such as polyethylene terephthalate of 1.42 mills thick, was placed on a 1/4th inch thick glass plate of 1.25 by 1.25 ft. The dimensions of the film were large enough to protrude around the edges of the glass plate.
2) A one foot square piece of 1 oz. per sq. foot weight of copper foil was placed treatment side up on the carrier film.
3) A film of a resin composition, prepared according to the present invention, was metered onto the copper foil by using a wire-wound rod designed to provide a coating of the target thickness of the laminate.
Wire-wound rods are well known throughout the coatings industry.
4) A layer of glass cloth, woven or nonwoven, was laid onto the resin film and allowed to saturate for approximately 2 minutes. If a plurality of layers were used, the layers were placed onto the resin film approximately 2 minutes apart to allow the resin mixture to saturate the glass.
5) An additional layer of copperfoil, of the same size and weight as 2), was placed treatment side down on the laminate so as to align the edges with the first sheet of copper foil.
6) Another layer of carrier film, of the same size and dimensions as 1), was placed on top of the copper foil.
7) Two 1/2 inch wide by 12 inches long shims of the target laminate thickness were placed on opposing sides of the laminate, on top ~ of the carrier film, but <RTI still on the glass plate.
8) A rod ouf 1/2 inch thick steel was placed on the shims at one edge of the laminate and gently pulled to the opposing edgewhile being forced by hand to ride on the shims. As the rod moved across the laminate, excess resin composition was allowed to drain out of the laminate.
9) Another plate of glass of equivalent dimensions as 1), was placed on top of the laminate.
10) The laminate was placed in a forced air convection oven at150-250 F for 15 minutes to 1 hour.
11) The laminate, stillbetween the glass plates, was removed from the oven andallowed to cool to room temperature. At this time, the two glass plates and two layers of carrier film were removed.
12) Post cure from350 F for 1 hour in a forced air convention oven.
The thermosetting resin composition may also further contain the
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 otherconventional curing methods in conjunction with the
appropriate initiators. The electrical laminates may further comprise an
electrical conductive cladding on at least one side.
One skilled in the art can easily make any necessary adjustments in
accordance with the necessities of the particular situation.
Further objects and advantages of the present invention will be clear
from the description thatfollows.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is anenlarged cross-sectional view of a part of an electrical
laminate which comprises anelectrically conductivemetal layer 1 and a
cross linkedthin-wall body of the invented composition 2.
Fig. 2 is anenlarged cross-sectional view of an electrical laminate which exemplifies a double-sided metal clad electrical laminate, further
provided with two metal conductive layers 1, and anelectrically insulating
thin-wall body of the invented composition 2.
Fig. 3 is anenlarged cross-sectional view of an electrical laminate
which exemplifies amultilayered electrical laminate, of the structure of a
combination of single-sided and double sided metal clad electrical
laminates asillustrated in Fig. 1 and Fig. 2.
Fig. 4 is anenlarged cross-sectional view of an electrical laminate
which comprises anelectrically conductive layer 1, a crosslinkedthin-wall
body of the invented composition 2, and an uniformly dispersed inorganic
or organic filler 3.
Fig. 5 is anenlarged cross-sectional view of an electrical laminate
which comprises anetectrically conductive metal layer 1, acrosslinked
thin-wall body of invented composition 2, and nonwoven glass fibers 4.
Fig. 6 is anenlarged cross-sectional view of an electrical laminate
which comprises an electrically conductive metal layer 1, acrosslinked thin-wall body of invented composition 2, and woven glass cloth 5.
Fig. 7 is an enlarged cross-section view of part of an example of a double-sided metal clad electrical laminate of Fig. 6 further provided with an electrically conductive metal layer 1 on the other surface.
Fig. 8 is anenlarged cross-sectional view of an electrical laminate which comprises an electrically conductive metal layer 1, a crosslinkedthin-wall body of the invented composition 2, and an aramid non-woven sheet6.
DETAILED DESCRIPTION OF THE INVENTION
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belons. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are described.
The present invention comprises resin compositions of moderate cost with excellent electrical properties up to at least 20 GHz which may be flame retardant and heat resistant. The present compositions haveutility as electricalinsulators, electrical laminates, electrically insulating encapsulants, electrically insulating adhesives and other electrical andrelated applications.
One component of these compositions is a terminally unsaturated urethane resin, known in the industry as a urethane vinyl ester:
EMI8.1
where R, is H orCH3, R2 is an organic residue from a monohydricalcohol andR3 is an organic residue from a diisocyanate. This resin is manufactured by reacting a diisocyanate with two molar equivalents of monohydric alcohol containing a vinylidene group in the presence of a polar solvent(typically styrene) which also acts as a reactive monomer for crosslinking. Examples of this art are well known throughout the industry.
The diisocyanate utilized may be aromatic or aliphatic, monomeric or polymeric, etc. Theonly requirements are that the diisocyanate contain isocyanate groups capable of reacting with the monohydricalcohol and not interfere with the subsequent crosslinking reactions. Examples of the diisocyanate are 2,4 toluene diisocyanate, 2,6 toluene diisocyanate, 2,4diphenylmethane diisocyanate, and 2,6'-diphenyl methane diisocynate.
Examples of the monohydric alcohol that contains avinylidene group are hydroxyethyl methacrylate, hydroxyethyl acrylate,hydroxypropyl methacrylate, andhydroxypropyl acrylate.
Another component of these compositions is aterminally unsaturated urethane resin, known in the industry as an isocyanurate vinyl ester:
EMI9.1
where R, is H orCH3, R2 is an organic residue from a monohydric alcool,R3 is an organic residue from a diisocyanate, andR4 is an isocyanurate compound of the following structure;
EMI10.1
This resin is manufactured by the methods of Kuehn et al. (U. S.
Patent No. 4,145,544 and No. 4,243,788). For examples of these resins refer to the aforementioned patents.
It has been found that a combination of one or more of these resins with styrene and dibromostyrene in certain ratios will yield a composition with excellent properties suitable as a matrix resin for high frequency electrical applications. The main embodiment thereof, is a printed circuit board laminate suitable for microwave antennas and the like. The preferred ratio forterminally unsaturated urethane resin toethylenically unsaturated monomer has been determined to beless than 0.15. Or in the case where 1 mole of 2, 4'-toluene diisocyanate is reacted with 2 moles of hydroxylpropylmethacrylate, less than 27% by weight of this resin (without monomer) is desired in ethylenically unsaturated monomer. In the case where an isocyanurate vinyl ester is manufactured from the same materials in different ratios, less than about 35% by weight of resin (without monomer) is desired inethylenically unsaturated monomer.
Oneskilled in the art canreadily obtain the aforementioned ratios frommolecular weight and weight percent information. Examples 2 & 3 of
TABLE 1 contain a urethane modified vinyl ester with a molecular weight of approximately 4200, styrene monomer ofmolecular weight 104.15, and dibromostryene of average molecular weight 263.95. Using this information, the ratios of urethane modified vinyl ester to total monomer
would be 0.01 and 0.02 for Examples 2 & 3 respectively. Additionally, the
ratio of styrene to dibromostyrene would be 0.50, and 1.16 for Exampies 2
& 3 respectively.
The second main component of these compositions is an
ethylenically unsaturated monomer from the group of 1) styrene and 2)
bromostyrene. Examples of bromostyrene include monobromostyrene,
dibromostyrene, and tribromostyrene. Additionally, theideal molar ratio of
styrene to bromostyrene has been found to beless than 1.2. Maintaining
the desired ratios provides a composition with excellent electrical
properties at microwave frequenciesalong with desirable thermal and
mechanical properties.
An optional component may be divinyl benzene (referred herein as
DVB), or any other ethylenically multiunsaturated monomer. DVB can be
about 0.1% to about 10% by weight; preferably about 0.5% to about 5%
by weight of the total composition; more preferably about1% to about 4% by weight of the total composition and most preferably about 2.5% by
weight of the total composition. Divinyl benzene increases the crosslink
density and therefore thermal performance of the composition. Other
polyfunctional crosslinking monomers may also be used such as divinyl
toluene and the like.
The third and fourth components contribute to the mechanical and
thermal properties of a composition but do not need to be present to
obtain the excellent electrical properties.
Catalysts and polymerization and U. V. initiators may also be
components of the compositions of the present invention. There are many
choices available;particularly, catalyst which induce free-radical cure. The
preferred catalyst ist-butyl peroctoate at about 0.1 to about 2% by weight
of the total composition (preferably about 0.2% by weight of the total
composition); benzoate at about 0.1 to about 2% by weight of the total
composition (preferably 0.25% by weight of the total composition).
Alternate catalysts include benzoyl peroxide, cumene hydrogen peroxide and others known to those skilled in this art. Combination of catalysts may also be used.Curing mechanisms may be utilized including electron beam processing and ultra-violet light processing in conjunction with UV initiators, radiation, heating with or without pressure, and other conventional curing methods in conjunction with the appropriate initiators.
Additional components, such as moisture scavengers may also be added. Free moisture in the composition will negatively affect the dissipation factor. Therefore a component, such as3-ethyl-2-methyl-2- (3- methylbutyl)-1, 3-oxazolidine (available from Angus Chemical Co.) can be added to minimize the free water in the composition. Theoxazolidine compound will chemically react with the water to eliminate it. Alternately, a molecular sieve could be utilized. Molecular sieves are well known as moisture reducers throughout the coatings industry.Molecular sieves function by physically trapping the free water.
Another additional component may be titanium dioxide which increases the dielectric constant, but reduces the dissipation factor. This combination of electrical properties is desirable for some specific high frequency applications. The titanium dioxide may be in a range of from about 1 to about 60% by weight of the total composition; preferably about 10 to about 40% by weight of the total composition; more preferably about 25% by weight of the total composition.
Another component which may be added is polyethylenefiller, (such as expanded polyethylene compound, available from AmericanFillers and
Abrasives). The polyethylenewill lower both the dielectric constant and dissipation factor. The polyethylene may be in a range of from about 1 to about 60% by weight of the total composition; preferably about 5 to about 40% by weight of the total composition; more preferably about 10% by weight of the total composition.
Otheroptional additives include organic and/or inorganic fillers, for example, calcine kaolin, to modify rheology; surface active agents, to aid processing; other monomers, such as methyl methacrylate to modify viscosity and possibly performance ; epoxies; colorants; fluorescent dyes;
U. V. blocking agents; wetting agents; air release agents; defoaming agents; flame retardant synergists (for example, antimony compounds); adhesion promoters (for example, epoxy resin"EPON828"Shell Chemical Co.) ;additional monomers including styrene, vinyltoluene, tbutyl styrene,para-methyl styrene, diallyl phthalate, 2,4-ethyl-methyl imidazole, and otherconventional additives.
The present invention further comprises electrical laminates utilizing the thermosetting resin compositions herein described which have excellent electrical properties and which may be flame retardant and heat resistant. The present thermosetting resin compositions can also be utilized in existing cost effective technologies to manufacture various types of electrical laminates. Examples of these technologies include, but are not limited to, continuous lamination, such as that described in U. S.
Patent No. 4,803, 022 toBarell et al. which is incorporated herein by reference; production of printed circuit boards, such as described in U. S.
Patents Nos. 4,671,984 and 4,751,146 to Masahiko Maeda et al. which are incorporated herein by reference; production of electrical laminates such as described in U. S. Patent No. 4,336,297 to Yasuo Fushiki et al. and U. S. Patent No. to Kazuyuki Tanaka et al. which are both incorporated herein by reference; continuous belt press lamination, such as the equipment offered by GreCon Corp.; and traditional press or vacuum press lamination.
An electrical laminate of the present invention is produced by infiltrating or impregnating at least one substrate, or multiple substrates, with a resin composition of the present invention to prepare resininfiltrated or resin-impregnated substrates which are laminated by passagebetween rollswhile removinginterlaminar gasbubbles.
Subsequently, the resulting laminate is heated, with or without pressure, to cure the resin composition whereby the electrical laminate is obtained.
Other cure mechanisms can also be utilized. The electrical laminate of this invention can be continuously produced.
For curing the resin composition, organic peroxides can be used as curing catalysts. The organic peroxides include, for example,t-butyl perbenzoate, t-butyl peroxide,benzoyl peroxide, t-butyl peroctoate,t-butyl peroxy benzoate, dicumyl peroxide, etc. If necessary, the curing can be controlled by use of curing accelerators or polymerization inhibitors.
Characteristics of the resin composition can be improved byincorporating therein toplasticizers, stabilizers, thickeners, fillers, coloring agents,lubricants, etc.
A copper-clad laminate can be obtained by subjecting substrates impregnated with an uncured resin composition and copper foil to laminatedmolding to unite them in a body, or by inserting an adhesive between substrates impregnated with an uncured resin and copper foil and then subjecting them to laminated molding to unite them in a body.A copper-clad laminate can be obtained by also preparing a laminate by laminate molding and then unite this laminate and a copperfoil laminate in a body through an adhesive. Adhesives such as epoxy resins, butyrylmodified epoxy resins, etc. can be used.
The present electrical laminates may be from about 0.001 to about 0.25 inches thick and may be metal clad on one or both sides or notclad in metal. A preferred embodiment is about 0.002 to about 0.20 inches thick. A more preferred embodiment is about 0.003 to about 0.120 inches thick.
Suitable cladding metals include aluminum, silver, gold, brass and most preferably copper. The metal cladding may be in various forms and weight. The weight may range from about 0.25 to about 5oz/ft2 The form can be anyconventional type, such as,foil, anelectrodeposited layer orrolled annealed metal, such as for example, rolled annealed copper.
A preferred embodiment comprises a copper clad electrical laminate suitable for subsequent processing as a circuit board,stripline, microstripline microwave components and other related applications. The preferred embodiment of this composition is an electrical laminate from 0.003 to 0.120 inches thick with metal foil clad on one or both sides.
Suitable reinforcement components include organic or inorganic fillers, wovenfiberglass, glass paper, glass mat, glass cloth, polyimide paper (suchas"THERMOUNT"from DuPont), woven polymeric fibers and non-wovenpolymer fiber reinforcements and the like. The reinforcement components of the laminates of the present invention may be in the range of about 25% to 75% by weight of the total laminate, preferably about 30% ta about 40%, and more preferably about 35%.
The performance of this composition differs from similar materials mainly in electrical performance. These properties,especially dissipation factor, are very important when considering high frequency applications.
Typical electrical properties of an 0.030" thick laminate of approximate 20% (by weight) of fiberglass reinforcement are:
Frequency (GHz): 2.5 10.0
Dielectric constant: 3.20 3.22
Dissipation factor: 0.0031 0.0048
The electrical properties of the same laminate at 1 MHZ are:
Dielectric constant: 3.20
Dissipation factor: 0.0029
The above data shows the consistency of the dielectric constant and dissipation factor of a laminate comprising the inventive compositions across a wide range of frequencies. This feature is highly desirable for compositions utilized as dielectric materials.
This embodiment of the present invention isclearly superior in electrical properties over presently available compositions.
The invention will be further clarifie by a consideration of the following examples which are to be considered as illustrative of the present invention. It should be understood that the invention is not limited to the specific details of the examples.
EXAMPLES
The unsaturated urethane resins are manufactured according to U. S.
Patent Nos. 4,587,161 and 4,803,022 of Kuehn etal., manufactured according to methods known in the art, or commercially available as
Palatal 48001 KR (BASF, Germany) or 580-05 (Reichold ChemicalsInc.,
USA) in the case of a urethanevinyl ester, and as ITP 1041 and ITP 1070(Reichold Chemicals Inc., USA), in the case of a isocyanurate vinyl ester.
Theethylenically unsaturated monomers styrene and dibromonostyrene arecommercially available.
The general method of preparing the resin compositions is as follows.
1) The ingredients, (listed in TABLE 1), are added to a mixing vessel.
2) The ingredients are mixed for 5 to 15 minutes with a Cowlesdissolver operating at high shear, about 100 to 500 rpm), at room temperature. Higher shear rates may be used, but could entrain air.
Optionally, the mixturecould be degassed in a vacuum (25-29 inches of Hg).
3) At this point, the composition is ready for use. The typical cure schedule for the thermoset resin is:
a. 20 minutes at 210 degrees F, optionally up to
225 degrees F. Temperatures greater than250 F produce
undesirable reactions during cure andyield poor quality
product. Lower temperatures than210 F may be used with
longer times.
b. Depending upon the desired product, a post
cure is often necessary to optimize the electrical properties.
One to three hours at350 F is preferred.
Examples 1 to 9
The general method of preparing electrical laminates from the resin compositions is asfollows. The specific electrical laminates embodied in
Examples 1 to 9 were made as indicated below and as further indicated in
TABLE 1 whichfollows below. All laminates are 30 mil dielectric thickness with 18-20% by weight E-glass reinforcement.
1) The ingredients, listed in TABLE1, are added to a mixing vessel.
2) The ingredients are mixed for 5 to 15 minutes with a Cowlesdissolver operating at high shear, (about 100 to 500 rpm), at room temperature. Higher shear rates may be used, butcouid entrain air.
Optionally, the mixturecould be degassed in a vacuum (25-29 inches of
Hg).
3) The mixture is heated to 85-100 degrees Fahrenheit, or any temperature below the point at which the catalyst undergoes considerable decomposition to form free radicals. The resin mixture is heated to facilitate impregnating the reinforcement.
4) The composition is utilized with one of the following processes:
a. The resin mixture is used to impregnate the
reinforcement (s) in the lab according to the method outlined in
application No. 08/483,086, incorporated herein by reference.
The residence times and temperatures can be found in
TABLE 1. It has been discovered, that when using this
lamination process, temperatures above250 F will produce
poor quality laminates, and thusshould be avoided.
b. the resin composition is used to impregnate the
reinforcement (s) in the lab according to the same method as
above (a), with the following exceptions. Rather than curing
the laminate in an oven, the appropriate catalysts and
promoters are chosen, and the laminate is left undisturbed
and allowed to cure at room temperature for 1 to 24 hours.
The catalyst half-life, quantity of catalyst, and type and
amount of promoters will dictate the amount of time needed to
cure at room temperature. These examples can be found in
TABLE 1 under"Room Temp."Cure Method.
c. Alternately, the composition can impregnate the
reinforcement by our patented continuous lamination process,
(Barrell et al. U. S. Patent No. 4,803,022). These examples
can be found in TABLE 1 under"Continuous"Cure Method.
5) The laminate is post-cured for 1 hour at350 F. Post-cure reduces the dissipation factor of the laminate. Therefore, a post-cure is desirable, but not required.
Table 1
Examples of New Invention
EMI19.1
Ingredient <SEP> Designation <SEP> Example <SEP> 1 <SEP> Example <SEP> 2 <SEP> Example <SEP> 3 <SEP> Example <SEP> 4 <SEP> Example <SEP> 5 <SEP> Example <SEP> 6 <SEP> Example <SEP> 7 <SEP> Example <SEP> 8 <SEP> Example <SEP> 9
Example <SEP> 1 <SEP> Example <SEP> 2 <SEP> Example <SEP> 3 <SEP> Example <SEP> 4 <SEP> Example <SEP> 5 <SEP> Example <SEP> 6 <SEP> Example <SEP> 7 <SEP> Example <SEP> 8 <SEP> Example <SEP> 9
<tb> NOTES: 1 MHZ Dielectric Constant and 1 Mhz Dissipation Factor are determined by Test Method IPC-TM-650 2.5.5.4
Db/inch is the insertion loss (S21 parameter) of a 50 ohm mivostrip transmission. This is an indication of the suitability of the material at microwave frequencies
CURE METHOD:"Continous"= Continous lamination method outlined in U. S. Patent of Barrell et al.
"Room Temp."= Room Temperature cure method outlined in specification "220 F 30 min."= lamination method outlined in specification "Post Cure"= time at temperature in a forced-air convection oven % Water absorption obtained by Test Method IPC-TM-650 2.6.2.1
Copper Adhesion Values are In pound per inch width as outlined in Test Method IPC-TM-650 2.4.9
Glass Transition Values are in degree Celsius and are obtained by Test Method IPC-TM-650 2.4.24B <RTI Although the invention has been described in conjunction with specific embodiments, it is evident that many alternatives and variations will be apparent to thoseskilled in the art in light of the foregoing description. Accordingly, the invention is intended to embrace all of the alternatives and variations that fall within the spirit and scope of the appended claims.
