Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-01-12
2001-01-09
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...
C528S120000
Reexamination Certificate
active
06172143
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a resin composition for use in a liquid sealant and a liquid sealant using the resin composition. More particularly, the present invention relates to a resin composition for use in a liquid sealant, which is liquid and has moisture resistance and soldering heat resistance, as well as to a liquid sealant using the resin composition.
2. Description of Related Art
To electronic parts such as those obtained by mounting a semiconductor chip on a metal plate (which is a lead frame) and connecting them electrically using a bonding wire or the like, sealing has been conducted in order to improve, in particular, their reliability. As the sealant for such sealing, ceramics or thermosetting resins are used. Of these sealants, epoxy resin compositions are in wide use for the good balance between economy and properties.
In the fields of semiconductors and electronic parts, higher density, higher integration and smaller size have been strong requirements in recent years. To respond to such requirements, the lead frames or metal wires used in semiconductors or electronic parts are being made increasingly thinner and the circuit patterns used as well in semiconductors and electronic parts are being made increasingly finer.
In the fields of semiconductors and electronic parts, change is being seen also in the method for mounting a sealed electronic part on an electronic circuit, in keeping pace with the above-mentioned higher density and higher integration. As an example, in bonding an electronic part to a substrate with solder, a reflow soldering method (wherein the whole portion of an electronic part is heated) has come to be adopted.
When a substrate such as semiconductor chip of higher density, higher integration or smaller size is sealed according to a conventional transfer molding method, the substrate receives a high pressure during molding; as a result, the substrate easily gives rise to circuit disconnection or poor contact due to displacement of electrode and there has arisen a new problem of reduced yield due to the generation of defects.
In order to solve the above problem of the transfer molding method caused by the high pressure during molding, it is easily conceived of, for example, a new molding method of using a liquid resin (e.g. a liquid epoxy resin) so that substantially no pressure is applied to a substrate during molding. No liquid resin usable in such a molding method, however, has been provided.
Epoxy resin compositions for sealing, used in the conventional transfer molding method, generally have a high viscosity and are substantially unsuitable for use in the above-mentioned new molding method wherein a substrate receives substantially no molding pressure. Moreover, with these epoxy resin compositions, there have been cases that when they are used in mounting by reflow soldering method, the absorbed moisture present in epoxy resin receives thermal shock during mounting and generates peeling or cracking in cured resin; therefore, the epoxy resin compositions have a problem in reliability.
In the conventional transfer molding method, it was proposed as a measure for the above-mentioned reliability problem to (1) increase the amount of inorganic material used in epoxy resin composition for sealing, to reduce the proportion of epoxy resin (this resin is a moisture-absorbing source) or (2) use an epoxy resin of biphenyl type or dicyclopentadiene type skeleton which has a low moisture absorption and which is solid at ordinary temperature.
The epoxy resin compositions for sealing wherein the above measure is used, however, inevitably have a high viscosity. It is therefore apparent that they are unusable in the above-mentioned molding method wherein a substrate receives substantially no molding pressure.
SUMMARY OF THE INVENTION
The object of the present invention is to alleviate the above-mentioned problems of the prior art and provide (1) a resin composition for use in a liquid sealant, which is liquid and has moisture resistance and soldering heat resistance and (2) a liquid sealant using the resin composition.
The present invention provides a resin composition for use in a liquid sealant, which is composed mainly of an epoxy compound and a polycarbodiimide resin, the proportion of the polycarbodiimide resin being 0.1 to 10 parts by weight relative to 100 parts by weight of the epoxy compound, and which is liquid or fluid at ordinary temperature.
The present invention also provides a liquid sealant comprising:
a resin composition which is composed mainly of an epoxy compound and a polycarbodiimide resin, the proportion of the polycarbodiimide resin being 0.1 to 10 parts by weight relative to 100 parts by weight of the epoxy compound,
an epoxy resin curing agent,
an epoxy resin curing accelerator, and
an inorganic powder,
which liquid sealant is liquid or fluid at ordinary temperature.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is hereinafter described in detail.
The epoxy compound used in the present invention is not a monofunctional compound but a compound having at least two epoxy groups in the molecule, and is preferably liquid at ordinary temperature. Specific examples thereof are bisphenol aromatic epoxy resins such as bisphenol A type, bisphenol F type and the like; and alicyclic epoxy resins such as 2,2-bis(3,4-epoxycyclohexyl)propane, 3,4-epoxycyclohexylmethyl-epoxycyclohex anecarboxylate and the like. At least one of these resins is used as a main material of the resin composition for a liquid sealant, of the present invention.
A solid epoxy compound can be used in combination with the liquid epoxy compound as long as the present liquid sealant described later is at least fluid at ordinary temperature. Such a solid epoxy compound can be exemplified by a high-molecular bisphenol A type epoxy resin, a cresol novolac type epoxy resin and a naphthalene type epoxy resin.
As the polycarbodiimide resin used in the present invention, there can be mentioned a compound having a carbodiimide group-containing repeating unit represented by the following formula (1):
wherein R is an isocyanate residue, and n is such an integer that the molecular weight of the polycarbodiimide resin becomes 100 to 50,000.
There is no particular restriction as to the process for producing the polycarbodiimide. The polycarbodiimide resin can be produced by, for example, a process which comprises subjecting an organic polyisocyanate to the decarboxylation and condensation of isocyanate group. The organic polyisocyanate to be subjected to the decarboxylation and condensation is preferably an organic diisocyanate. The organic diisocyanate can be exemplified by phenylene-1,3-diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane-4,4′-diisocyanate, 3,3′-dimethylbiphenylene-4,4′-diisocyanate, 1,3-xylylene diisocyanate, tetramethylxylylene diisocyanate, dicyclohexylmethane-2,4′-diisocyanate, dicyclohexylmethane-4,4-diisocyanate, ethylene diisocyanate and hexamethylene-1,6-diisocyanate. These diisocyanates can be used singly or in admixture.
As the carbodiimidization catalyst used in the carbodiimidization reaction of the organic polyisocyanate, there can be mentioned, for example, phosphorene compounds such as 1-phenyl-2-phosphorene-1-oxide, 1-phenyl-3-methyl-2-phosphorene-1-oxide, 1-ethyl-3-methyl-2-phosphorene-1-oxide, 1-ethyl-2-phospho rene-1-sulfide, 1,3-dimethyl-2-phosphorene-1-sulfide and the like; metal carbonyl complexes such as pentacarbonyliron, nonacarbonyliron, hexacarbonyltungsten and the like; acetylacetonate complexes of iron, aluminum, chromium, zirconium, etc.; and phosphoric acid esters such as trimethyl phosphate, triethyl phosphate, triphenyl phosphate and the like.
The above carbodiimidization catalysts can be used singly or in admixture. The amount of the carbodiimization catalyst used is 30 parts by weight or less, preferably 0.01 to 10 parts by weight relative to 100 parts by weight of the organic diisocyanate.
The carbodiimi
Amano Satoshi
Tomita Hideshi
Aylward D.
Dawson Robert
Kubovcik & Kubovcik
Nisshinbo Industries Inc.
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