Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
1999-06-07
2002-04-23
Moore, Margaret G. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C428S704000, C427S058000, C427S096400, C427S386000, C427S385500, C525S523000, C525S533000, C525S534000, C528S363000, C528S403000, C528S405000, C528S409000, C528S418000
Reexamination Certificate
active
06376080
ABSTRACT:
This invention relates to a method of preparing a polybenzoxazine and a method of coating a device using such a polybenzoxazine.
BACKGROUND OF THE INVENTION
Electronic devices such as circuit boards, semiconductors, transistors, and diodes are often coated with materials such as epoxy resins for protection. Such coating materials are often cured on the surface of an electronic device by heat. But electronic devices often are sensitive to heat, and too much heat may adversely affect the performance of a device. Further, if the coating material shrinks or expands significantly in response to heat, the device it coats may be warped. Thus, it is desirable to develop methods for curing coating materials at relatively low temperatures in short time periods and to develop coating materials that have a near-zero volume change upon heat treatment so as to minimize the possiblities of damaging the coated devices.
SUMMARY OF THE INVENTION
In general, the invention relates to methods of preparing a polybenzoxazine (PBO) composition at relatively low temperature in short time periods. The methods can be used, for example, to provide a coating on electronic devices such as circuit boards and semiconductors. The preferred PBO compositions have high glass transition temperature, good electrical properties (e.g., dielectric constant), low flammability, and a near-zero percent shrinkage and expansion upon demolding, postcuring, and cooling.
In one aspect, the invention features a method of preparing a PBO including heating a molding composition having a benzoxazine and a heterocyclic dicarboxylic acid to a temperature sufficient to cure the molding composition, thereby forming the PBO.
In another aspect, the invention features a method of preparing a PBO including heating a molding composition having a benzoxazine and a catalyst to a temperature in the range of about 150° C. to about 250° C. to cure the molding composition in about 1 minute to about 5 minutes, thereby forming the PBO. Preferably, the method can be carried out in the range of about 160° C. to about 210° C. in about 2 minutes to about 4 minutes.
In another aspect, the invention features a method of coating a device including heating a molding composition having a benzoxazine and a heterocyclic dicarboxylic acid to a temperature sufficient to cure the molding composition, thus forming a PBO which coats a surface of the device. The device can be an electronic device such as a semiconductor or a circuit board.
In another aspect, the invention features a method of coating a device including heating a molding composition including a benzoxazine to a temperature sufficient to cure the composition, thereby forming a polymer composition. The polymer composition forms on a surface of the device, and results in essentially no warpage of the device after post curing the molding composition. The device can be a semiconductor or a circuit board.
The invention also relates to a molding composition including a benzoxazine and a heterocyclic dicarboxylic acid; a polymer composition including a polybenzoxazine and a heterocyclic dicarboxylic acid; and a device coated with a polymer composition including a polybenzoxazine and a heterocyclic dicarboxylic acid.
The invention also relates to a benzoxazine-containing molding composition that has a post cure volume change of less than 0.15%, preferably less than 0.10%, and more preferably less than 0.05%. A post cure volume change includes shrinkage or expansion and is measured according to the procedure described subsequently in the application.
The invention also relates to a benzoxazine-containing molding composition. The composition, when applied on a FR-4 board, results in essentially no warpage of the device after post cure. Warpage is measured according to the procedure described subsequently in the application.
The invention still further relates to a device coated with a polymer composition including a polybenzoxazine, an epoxy resin, and a phenolic resin.
The heterocyclic dicarboxylic acid includes an X,Y-containing heterocyclic moiety and a dicarboxylic acid moiety which is bonded to the X,Y-containing cyclic moiety. The heterocyclic dicarboxylic acid is of formula (I):
X is N, O, or NR
a
, where R
a
is hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, aralkyl, or heteroaralkyl. Preferably, X is N or O. More preferably, X is N. Y is O, S, NR
b
, or C(R
c
) (R
d
), where R
b
is hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, aralkyl, or heteroaralkyl, and where each of R
c
and R
d
, independently, is hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, alkoxy, hydroxyl, hydroxylalkyl, carboxyl, halo, haloalkyl, amino, aminoalkyl, nitro, cyano, alkylcarbonyloxy, alkyloxycarbonyl, alkylcarbonyl, formyl, aminocarbonyl, alkylcarbonylamino, alkylsulfonylamino, aminosulfonyl, aminocarbonyloxy, or alkyloxycarbonylamino. Preferably, Y is O or S. More preferably, Y is S. Z is a bond, S, O, or NR
e
, where R
e
is hydrogen, alkyl, cycloalkyl, heterocyclo-alkyl, aryl, heteroaryl, aralkyl, or heteroaralkyl. Preferably, Z is a bond or S. More preferably, Z is a bond. Each of R
1
, R
2
, and R
3
, independently, is hydrogen, alkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, alkoxy, hydroxyl, hydroxylalkyl, carboxyl, halo, haloalkyl, amino, aminoalkyl, alkylcarbonyloxy, alkyloxycarbonyl, alkylcarbonyl, alkylcarbonylamino, aminocarbonyl, alkylsulfonylamino, aminosulfonyl, sulfonic acid, or alkylsulfonyl. R
1
and R
2
, optionally, can join together to form a cyclic moiety. Likewise, R
2
and R
3
, optionally, can join together to form a cyclic moiety. The cyclic moiety formed by joining R
1
and R
2
, or R
2
and R
3
is substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocycloalkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl. Preferably, R
1
and R
2
join together to form a cyclic moiety. More preferably, the cyclic moiety is aromatic. An example of such an aromatic cyclic moiety is a benzene ring. The cyclic moiety can be further substituted by groups such as alkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, alkoxy, hydroxyl, hydroxylalkyl, carboxyl, halo, haloalkyl, amino, aminoalkyl, alkylcarbonyloxy, alkyloxycarbonyl, alkylcarbonyl, alkylcarbonylamino, aminocarbonyl, alkylsulfonylamino, aminosulfonyl, sulfonic acid, or alkylsulfonyl. m is 0 or 1. Preferably, m is 0. When m is 0, R
3
and the carbon atom to which R
3
bonded are deleted, and Y is directly bonded to the carbon atom to which R
2
is bonded. n is 0, 1, 2, 3, 4, 5, or 6. Preferably, n is 1.
The X,Y-containing heterocyclic moiety can be saturated, unsaturated, or aromatic. In one embodiment, the X,Y-containing heterocyclic moiety can be a furan, a thiophene, a thiazole, an oxazole, an imidazole, a pyridine, a piperidine, or a pyrimidine. Preferably, the X,Y-containing heterocyclic moiety is a thiazole.
Examples of heterocyclic dicarboxylic acid of formula (I) include 2-(2-benzthiazolyl)-succinic acid and (2-benzthiazolylthio)-butanedioic acid, available from Ciba Geigy under the trade name IRGACOR 252LD and IRGACOR 252FC, respectively.
It should be noted that heterocyclic dicarboxylic acid can form an acid anhydride. Such an acid anhydride is also within the scope of this invention.
As used herein, alkyl is a straight or branched hydrocarbon chain containing 1 to 8 carbon atoms. Examples of alkyl include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, and 2-methylhexyl.
As used herein, cycloalkyl is a cyclic alkyl group containing 3 to 8 carbon atoms. Some examples of cycloalkyl are cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, adamantyl, and norbornyl. Heterocycloalkyl is a cycloalkyl group containing 1-3 heteroatoms such as nitrogen, oxygen, or sulfur. Examples of heterocycloalkyl include piperidinyl, piperazinyl, tetrahydropyranyl, tetrahydrofuryl, and morpholinyl.
As used herein, aryl i
Loctite Corporation
Moore Margaret G.
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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