Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2000-02-25
2001-10-23
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S125000, C528S128000, C528S171000, C528S172000, C528S173000, C528S174000, C528S179000, C528S183000, C528S185000, C528S188000, C528S220000, C528S229000, C528S350000, C526S935000, C525S422000
Reexamination Certificate
active
06307008
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a high-temperature adhesive of polyimide and also to a high-temperature adhesive tape of polyimide. More particularly, this invention relates to a polyimide adhesive which has excellent high-temperature stability and bonding strength and is thus capable of having high processability. It also relates to an insulating adhesive tape utilized as a material in electronic industries, the tape having high electrical insulation and heat-resistance properties and capable of being bonded through thermo-melting. Also, the present invention is concerned With lead frames and semiconductor devices employing the tape.
BACKGROUND ART
Polyimide obtained by reacting tetracarboxylic acid dianhydride with diamine is hereafter to be widely used in areas where high-temperature stability is required, by virtue of its various excellent properties and good thermal stability. In addition to the excellent high-temperature stability, polyimide also has good mechanical strength, dimensional stability, flame lame retardance and electrical insulation and is broadly applied in the materials of electric and electronic appliances, aeronautics and space instruments and transport machinery. It is also used as the high-temperature adhesive of various high performance materials in these fields.
Conventional polyimide, however, normally has an excellent thermal stability with a poor melt-feasibility due to its high softening point. On the other hand, the resin developed for improving the melt-feasibility is inferior in high-temperature stability. Thus the performance of polyimide has both merits and drawbacks.
Generally in the use of conventional polyimide, for example, in film manufacture, wire coating, cover sheet or adhesive, the linear chain structure causes high-packing density between chains and limits the chain mobility even in high temperatures. Therefore, conventional polyimide has an excellent thermal stability like a thermoset, but has a poor melt-feasibility and poor adhesive properties. On the other hand, the melt-feasible polyimide, especially in adhesive use, has a lower glass transition temperature and softening point than conventional polyimide. So, melt-feasible polyimide has as a poor thermal stability and a high C.T.E. (Coefficient of Thermal Expansion).
In the polyimide adhesive or adhesive tape in IC package tapes, a good melt-feasibility and a good spreadability onto a substrate like an IC chip, a protective layer on an IC chip or a leadframe are necessary in the bonding process. After bonding, the excellent adhesive property and thermal stability of the adhesive even in subsequent high-temperature processes, such as wire bonding and epoxy molding, are very important to guarantee the semiconductor package reliability.
SUMMARY OF THE INVENTION
The present invention was developed in order to obtain polyimide of good melt-feasibility and also good thermal stability. Another object of the present invention is to provide an insulating adhesive tape employing a polyimide adhesive which can maintain its excellent insulating property for a long period of time. The insulating adhesive tape also has an appropriate adhesive property which can be bonded at the high temperature (the temperature at which adhesion is carried out) of not more than 450° C., in a short adhesion time of not more than 10 seconds, and an adhesive strength sufficient: for use with various semiconductor materials. In. adhesion, the insulating adhesive tape also does not cause contamination damage to the wire bonding on the surfaces of lead frames and IC chips. The insulating adhesive tape has heat resistance large enough to withstand heating during a wire bonding step so that it does not allow a lead to make the slightest movement, thereby making the wire bonding strength high enough to obtain excellent electronic reliability.
To satisfy the above-mentioned properties, a small amount of triamine or tetraamine was used as a monomer instead of diamine to react the polyamic acid or polyimide. Triamine or tetraamine was useful to break the chain structure, to decrease the packing density between chains, and to increase the melt-feasibility and adhesive property of polyimide.
The crosslinking caused-by triamine or tetraamine acts to increase the thermal stability of polyimide especially at the temperature of the wire bonding and epoxy molding process.
DETAILED DESCRIPTION OF THE INVENTION
The object of this invention is to provide polyimide and its polyamic acid precursor because both are excellent in melt-feasibility in addition to being superior in high-temperature stability, which is inherent to polyimide, and have outstanding high-temperature adhesion so as to excellent be for use in multipurpose applications.
This invention provides a polyamic acid resin having recurring units represented by the following Formula I:
wherein,
R is a tetravalent organic group; R1 is a divalent organic group; R2 is a trivalent or tetravalent organic group; R3 is a divalent organic group represented by the following formula:
wherein,
R4 is an alkylene group containing 0-20 carbon atoms; and n′ is the number of a recurring unit; and l, m and n each are molar numbers of the corresponding recurring units under the condition that l/(m+n) ranges from 99.985/0.015 to 80/15 as expressed in terms of molar ratio and m/l+n) is from 1/2000 to 500/1 as expressed in terms of molar ratio.
This invention further provides a polyamic acid ester resin wherein the carboxyl group in the polyamic acid resin is esterified, and a polyimide resin obtained by subjecting said polyamic acid resin or its corresponding polyamic acid ester resin to a dehydrating or alcohol-eliminating ring-closure.
This invention further provides a polyamic acid resin of Formula I, which is prepared by reacting a diamino compound, including the novel triamino compound or tetraamino compound, with a dianhydride in an organic solvent.
The precursor polymer of this invention is polyamic acid which is obtained from:
(1) a dihydride having the following Formula II:
wherein R is a tetravalent radical selected from the group consisting of aliphatic radicals having 2 or more carbon atoms, cyclo-aliphatic radicals, monoaromatic radicals, condensed polyaromatic radicals, and non-condensed polyaromatic radicals wherein aromatic radicals are mutually connected with a bond or a crosslinking function. As examples of the tetravalent radical group R, the following ones can be referred to:
(2) a diamine having the following Formula III:
H
2
N—R1—NH
2
(III)
wherein R1 is a divalent radical selected from the group consisting of aliphatic radicals, cyclo-aliphatic radicals, monoaromatic -radicals, condensed polyaromatic radicals, and non-condensed polyaromatic radicals wherein aromatic radicals are mutually connected with a bond or a crosslinking function. As examples of the divalent radical group R1, the following ones can be referred to:
(3) a triamine or a tetraamine having the following Formula IV:
wherein,
R2 is a trivalent or tetravalent radical selected from the group consisting of aliphatic radicals, cyclo-aliphatic radicals, monoaromatic radicals, condensed polyaromatic radicals and non-condensed polyaromatic radicals wherein aromatic radicals are mutually connected with a bond or a crosslinking function. As examples of the trivalent or tetravalent radical group R2, the following ones can be referred to:
(4) a diamine containing the following siloxane Formula V:
wherein R4 is an alkylene group containing 0-20 carbon atoms n′ is the number of a recurring unit.
Preferable, concrete examples of said dianhydride include aromatic tetracarboxylic acid dianhydrides such as ethylenetetracarboxylic dianhydride, butanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, pyromellitic dianhydride, 3,3′,4,4′-benzophenonetetracarboxylic dianhydride 2,2′,3,3′-benzophenonetetracarboxylic dianhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 2,2′,3,3′-biphenyltetrac
Chang Kyeong Ho
Kim Soon Sik
Kweon Jeong Min
Lee Kyung Rok
Hampton-Hightower P.
Harrison & Egbert
Saehan Industries Corporation
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