Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2000-05-23
2001-04-03
Trinh, Ba K. (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C549S541000, C549S555000, C549S556000, C549S558000, C549S559000, C549S560000
Reexamination Certificate
active
06211389
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to methods for reducing the chloride content of epoxy compound starting materials. Epoxy materials treated according to the invention are useful in a variety of applications, e.g., in the field of microelectronic devices. Thus, epoxy materials treated according to the invention are especially useful to formulate encapsulants and underfills for microelectronic devices.
BACKGROUND OF THE INVENTION
Microelectronic devices are useful in a variety of consumer and industrial applications. Microelectronic devices are prepared utilizing a variety of chemical formulations, e.g., encapsulants and/or underfills. A typical component of encapsulants and underfills is a compound having at least one epoxy reactive group. A common impurity of such epoxy-containing compounds is chloride. Unfortunately, chloride is known to corrode the wire bonds within microelectronic devices. Thus, a major problem associated with microelectronic devices is the tendency of certain residual impurities (e.g., chloride) within the microelectronic devices to decrease the reliability of the device by enhancing the corrosion of the wire bonds within the device, thereby increasing the risk of the device's failure.
There are only limited examples in the prior art of the use of chemical means to reduce the chloride content of epoxy-containing compounds. Thus, prior art methods of reducing the chloride content of epoxy-containing compounds utilize alkoxide/hydroxide bases in various organic solvents. However, these prior art methods suffer from a variety of deficiencies, e.g., high cost, high degree of complexity in setting up and running the reactions required to reduce the chloride content, insufficient chloride content reduction for chloride-sensitive end use applications, and the like.
Accordingly, there is a need in the art for new and better methods of reducing chloride content of epoxy compound starting materials. In addition, there is a need for epoxy compounds having reduced chloride content. Further, it would be highly desirable if such epoxy compound starting materials could be treated to reduce the chloride content thereof without suffering from increased viscosity.
BRIEF DESCRIPTION OF THE INVENTION
In accordance with the present invention, methods have been developed for the reduction of the chloride content of epoxy compound starting materials. Invention methods comprise subjecting specifically defined combinations comprising an epoxy resin starting material and other components to conditions sufficient to produce a treated epoxy compound (i.e., an epoxy compound having a chloride content which is reduced relative to that of the epoxy resin starting material), and separating the treated epoxy compound from the combination. Other components contemplated for use in the practice of the present invention comprise, alternatively, mixtures of crown ether, organic solvent and suitable base; mixtures of crown ether-like solvent and suitable base; mixtures of aprotic solvents and hydrides (other than tin hydride); mixtures of nonhalogenated organic solvent and reducing metal; and the like; as well as suitable combinations of any two or more thereof. Surprisingly, the treated epoxy compound separated from the combination contains substantially reduced chloride levels relative to the epoxy compound starting material.
In accordance with a further aspect of the present invention, products (i.e., treated epoxy compounds, encapsulants and fillers) are provided which have been produced by the invention methods. In addition, there are provided formulations made from treated epoxy compounds provided by invention methods. Surprisingly, the invention products contain substantially reduced chloride levels relative to products made without utilizing the invention methods.
The present invention provides many advantages over the art. For example, invention methods of reducing chloride content of epoxy compounds and compounds produced thereby are useful in preparing more reliable microelectronic devices. Invention methods provide purified epoxy compounds having reduced viscosity. Such formulations are useful in increasing the processibility of the formulation utilized in the preparation of microelectronic devices, thereby decreasing the cost of the prepared device and reducing the incidence of device failure. Other advantages of the present invention can be readily recognized by those of ordinary skill in the art.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the present invention, there are provided methods of reducing the chloride content of an epoxy compound starting material. In one aspect, invention methods accomplish this reduction utilizing organic solvent(s), crown ether(s) and suitable base(s). These invention methods comprise:
a) subjecting a combination comprising an epoxy compound starting material, an organic solvent, a crown ether, and a suitable base to conditions sufficient to produce a treated epoxy compound, wherein the chloride content of the treated epoxy compound is reduced by at least a predetermined value, relative to the chloride content of the epoxy compound starting material, and
b) separating the treated epoxy compound from the combination.
As utilized herein, “chloride” includes ionic chlorine, hydrolyzable chlorine (e.g., C—Cl containing compounds; 1,2 chlorohydrin; and the like), and non-hydrolyzable chlorine (e.g., methyl chloride and the like). Chloride content is the amount of chloride present in, or associated with, an epoxy-containing compound (e.g., an epoxy compound starting material, portions thereof, a treated epoxy compound, and the like). The chloride content can readily be determined in a variety of ways, as are well known to those of skill in the art. Exemplary methods which can be employed for this purpose include X-ray fluorescence spectroscopy (XRF), infrared spectroscopy (IR), gas chromatography (GC), gas chromatography-mass spectroscopy (GCMS), mass spectroscopy (MS), atomic absorption (AA), inductively coupled plasma (ICP), and the like. Methodologies useful for measurement of chloride content are well documented and known to those of skill in the art. See, for example, ASTM D-18470 (for measuring amount of total chloride) and ASTM D-1726 (for measuring amount of hydrolyzable chlorides).
Epoxy compound starting materials contemplated for treatment in accordance with the present invention include epoxy resins and epoxy diluents. Epoxy resins include resins in liquid or solid form which have at least two epoxy groups and which are capable of cross linking (i.e., homo- or hetero-polymerizing) in a formulation useful as an encapsulant or an underfill for microelectronic devices. Epoxy resins may have a range of molecular weights, and specifically include low molecular weight epoxy resins, which are epoxy resins having a molecular weight of no greater than 500. Epoxy resins can have a variety of epoxy equivalent weights (EEW), including EEWs in the range from about 45 to about 500, in a preferred range from about 90 to about 230, or in a presently preferred range from about 125 to about 200. Exemplary epoxy resins contemplated for use in the practice of the present invention include resins typically having in the range of about 2 to about 6 glycidyl groups, with a preferred range of about 2 to about 4 glycidyl groups. Exemplary epoxy resins include resins of the general formulae:
wherein
X=
or
wherein:
X is as defined above,
each of R
1
-R
6
is independently hydrogen, an alkyl, a substituted alkyl or a nonchloro-halogen, and
n=0 to 6; or
wherein:
X is as defined above, and
each of R
1
-R
6
is independently hydrogen, a lower alkyl, a substituted lower alkyl, or a nonchloro-halogen; or
wherein:
X is as defined above, and
each of R
1
-R
4
is independently hydrogen, an alkyl, a substituted alkyl, or a nonchloro-halogen; or
wherein:
X is as defined above, and
each of R
1
-R
3
is independently hydrogen, an alkyl, a substituted alkyl, or a nonchloro-halogen; or
wherein:
X is as defined
Dexter Corporation
Gray Cary Ware & Freidenrich
Reiter Stephen E.
Trinh Ba K.
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