Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2000-05-18
2001-10-09
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S032000, C528S045000, C528S059000, C528S272000, C526S335000, C568S606000, C568S027000, C568S028000, C568S038000, C568S308000, C568S579000, C558S254000, C560S330000, C564S017000, C564S032000, C564S047000
Reexamination Certificate
active
06300456
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to electron donor/acceptor compounds and to curable adhesive compositions comprising those electron donor/acceptor compounds.
BACKGROUND OF THE INVENTION
Adhesive compositions, particularly conductive adhesives, are used for a variety of purposes in the fabrication and assembly of semiconductor packages and microelectronic devices. The more prominent uses are the bonding of integrated circuit chips to lead frames or other substrates, and the bonding of circuit packages or assemblies to printed wire boards.
There exist electron acceptor/donor adhesives, using vinyl ethers as donors, for use in low modulus adhesives, particularly in fast-cure adhesives for die attach applications. However, the number of suitable vinyl ethers as donors is limited due to high volatility and difficulty in preparation. Thus, there is a need for the development of new electron donor/acceptor compounds for use in adhesives applications.
SUMMARY OF THE INVENTION
This invention relates to compounds containing both an electron donor group and an electron acceptor group (electron donor/acceptor compound). The electron donor group is a carbon to carbon double bond attached to an aromatic ring and conjugated with the unsaturation in the ring. The electron acceptor group is a maleate, fumurate, maleimide, or acrylate. This invention is also an adhesive composition comprising one or more of the inventive electron donor/acceptor compounds, a curing agent, and optionally, one or more fillers.
DETAILED DESCRIPTION OF THE INVENTION
The electron donor/acceptor compounds of this invention will have one of the structures depicted here:
in which
Ar is an aromatic or heteroaromatic ring or fused ring having 3 to 10 carbon atoms within the ring structure, in which the heteroatom is N, O or S;
R
1
, R
2
and R
3
are independently hydrogen, a branched, cyclic or linear alkyl group having 1 to 12 carbon atoms, or Ar as described above; preferably, R
1
R
2
and R
3
are hydrogen or a methyl or ethyl group;
G is —OR
4
, —SR
4
, —N(R
1
)(R
2
), Ar as described above, or an alkyl group having 1 to 12 carbon atoms, in which R
1
and R
2
are as described above, and R
4
is Ar as described above or an alkyl group having 1 to 12 carbon atoms, preferably 1 to 4 carbon atoms;
Q is an alkyl group having 1 to 12 carbon atoms;
X is:
Z is an alkyl group, a siloxane, a polysiloxane, a C
1
to C
4
alkoxy-terminated siloxane or polysiloxane, a polyether, a polyester, a polyurethane, a poly(butadiene) or an aromatic, polyaromatic, or heteroaromatic group; and
E is
in which Y is O or N(R
1
) and R
1
, R
2
, and R
3
and Q are as described above.
The electron donor group is a carbon-carbon double bond that is attached directly to an aromatic ring and conjugated with the unsaturation in the aromatic ring. The aromatic ring can be any molecular moiety that meets the classical definition of an aromatic compound, that is it contains cyclic clouds of delocalized &pgr; electrons above and below the plane of the molecule and the &pgr; clouds have a total of (4n+2) electrons.
The aromatic ring may also contain electron donating substituents, which will increase the electron density on the carbon to carbon double bond, leading to higher reactivity. The reactivity of the electron donor group will also be affected by steric interaction. An increase in the number of alkyl substituents on the carbon to carbon double bond will decrease the reactivity. Preferably, all substituents on the carbon to carbon double bond will be hydrogen, or will be hydrogen with a methyl group as the only other substituent.
Starting materials for Z group moieties are commercially available from a number of sources; for example, aromatic and polyaromatic materials may be obtained from BASF or Bayer; siloxanes and polysiloxanes from Gelest; polyethers from BASF; polyesters from Uniqema or Bayer; poly(butadiene)s from Elf-Atochem; polyurethanes from Bayer or BASF; and the branched or linear alkanes from Uniqema.
The Z groups may contain cyclic moieties or heteroatoms, and may contain pendant hydroxyl or thiol groups depending on the synthetic route for making the electron donor compound; for example, if one of the starting compounds contains a hydroxyl or thiol functionality that is reacted with an epoxy functionality, the Z group will contain a pendant hydroxyl or thiol group.
The exact composition or molecular weight of Z is not critical to the invention and can range widely depending on the requirements of the end use for the electron donor compound. For example, Z can be a methylene group or a high molecular weight polymeric entity. The composition of Z can be chosen to give specific material properties in a final formulation, such as, rheological properties, hydrophilic or hydrophobic properties, toughness, strength, or flexibility. For example, a low level of crosslinking and free rotation about polymeric bonds will impart flexibility to a compound, and the presence of siloxane moieties will impart hydrophobicity and flexibility. The molecular weight and chain length will affect viscosity, the higher the molecular weight and the longer the chain length, the higher the viscosity.
The electron acceptor starting compounds can be fumarates and maleates, acrylates and maleimides. Suitable acrylates are numerous and are commercially available, for example, from Sartomer. Suitable maleimides are easily prepared, for example, according to procedures described in U.S. Pat. Nos. 6,034,194 and 6,034,195 to Dershem. In general, the carboxyl group in the acrylate, maleate and fumarate compounds will be the reactive functionality for linking the electron acceptor to a co-reactive functionality on the Z group. The maleimides will contain a separate functionality, as shown in the examples, for reacting with a co-reactive functionality on the Z group.
Suitable reaction routes can be designed by determining on a specific addition or condensation reaction, then choosing functionalities for the starting electron-donor compound and the starting electron-acceptor compound to participate in that reaction. Although one skilled in the art can devise suitable variations in reactions by choice and location of functionality (whether on the starting electron-donor or starting electron-acceptor compound), it will be understood that the choices may be limited in practice by the commercial availability of starting materials or ease of synthesis routes.
Representative synthetic routes include:
1. the reaction of isocyanate functionality with (i) hydroxyl; or (ii) amine; or (iii) thiol functionality to create a carbamate linkage, urea or thiocarbamate respectively;
2. the substitution of a halogen with (i) hydroxyl; or (ii) amine; or (iii) thiol functionality to create an ether linkage, amine or thio-ether respectively;
3. the reaction of an epoxy functionality with (i) hydroxyl; or (ii) amine; or (iii) thiol functionality to create an ether linkage, amine or thio-ether respectively.
The electron donor/acceptor compounds can be formulated into an adhesive, coating, potting or encapsulant composition. In addition to the electron donor/acceptor compound, the formulations will contain one or more curing agents and may contain a conductive or nonconductive filler.
Exemplary curing agents are thermal initiators and photoinitiators and will be present in an amount of 0.1% to 10%, preferably 0.1% to 3.0%, by weight of the electron donor compound. Preferred thermal initiators include peroxides, such as butyl peroctoates and dicumyl peroxide, and azo compounds, such as 2,2′-azobis(2-methyl-propanenitrile) and 2,2′-azobis(2-methyl-butanenitrile). A preferred series of photoinitiators is one sold under the trademark Irgacure by Ciba Specialty Chemicals. In some formulations, both thermal initiation and photoinitiation may be desirable; for example, the curing process can be started by irradiation, and in a later processing step curing can be completed by the application of heat to accomplish the thermal cure.
In general, these compositions will cur
Dawson Robert
Gennaro Jane E.
National Starch and Chemical Investment Holding Corporation
Peng Kuo-Liang
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