Stock material or miscellaneous articles – Composite – Of metal
Reexamination Certificate
1998-07-14
2001-08-21
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of metal
C428S473500, C528S171000, C528S172000, C528S173000, C528S175000, C528S183000, C528S188000, C528S220000, C528S229000, C528S350000, C528S353000, C528S50200C
Reexamination Certificate
active
06277495
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a polyimide film which has high elasticity, low thermal expansion properties equal to those of metals and low water absorption properties, a method for its manufacture and a metal laminated plate of improved curl containing the polyimide film as the base material.
BACKGROUND OF THE INVENTION
Polyimides that are obtained by condensation polymerization of pyromellitic dianhydride and 4,4′-diaminodiphenyl ether have superior heat resistance and electrical insulating capacity and are used primarily for flexible printed circuit boards. Most recently, their uses have been expanded to semiconductor packages. High processability and capacity for high precision are required, a high modulus of elasticity, low thermal expansion characteristics like that of metals and low water absorbing capacity are sought as the characteristics of polyimides and various studies have been conducted. For example, in Japanese Patent Application Public Disclosure No. 60-210629 [1985], Japanese Patent Application Public Disclosure No. 64-16832 [1989], Japanese Patent Application Public Disclosure No. 64-16833 [1989], Japanese Patent Application Public Disclosure No. 64-16834 [1989], Japanese Patent Application Public Disclosure No. 1-131241 [1989] and Japanese Patent Application Public Disclosure No. 1- 131242 [1989], an example of a three component polyimide comprised of pyromellitic dianhydride, 4,4′-diaminodiphenyl ether and p-phenylenediamine is described in which p-phenylenediamine is used in combination as the diamine component for the purpose of increasing the modulus of elasticity. Expansion to a four component polyimide can also be effected by adding 3,3′-4,4′-biphenyltetra-carboxylic acid dianhydride to the aforementioned three-component system for the purpose increasing the modulus of elasticity. Examples of four component polyimides are described in Japanese Patent Application Public Disclosure No. 59-164328 [1984] and Japanese Patent Application Public Disclosure No. 61-111359 [1986]. In addition, an attempt to improve the physical properties of four component polyimides by controlling the procedure of addition of the monomers during polymerization is presented, for example, in Japanese Patent Application Public Disclosure No. 5-25273 [1993]. Further, an attempt to improve physical properties by drawing during film making is described, for example, in Japanese Patent Application Public Disclosure No. 1-20238 [1989].
A high modulus of elasticity, low thermal expansion capacity equivalent to that of metals and low water absorbing capacity are necessary as characteristics for use in semiconductor packages as described above. Although the three-component polyimides that are obtained in Japanese Patent Application Public Disclosure No. 60-210629 [1985], Japanese Patent Application Public Disclosure No. 64-16832 [1989], Japanese Patent Application Public Disclosure No. 64-16833 [1989], Japanese Patent Application Public Disclosure No. 64-16834 [1989], Japanese Patent Application Public Disclosure No. 1-131241 [1989] and Japanese Patent Application Public Disclosure No. 1-131242 [1989] have a higher modulus of elasticity than the polyimides that are obtained from pyromellitic dianhydride and 4,4′-diaminodiphenyl ether, a modulus of elasticity sufficient for use as semiconductor packages cannot be obtained. Further, with the four-component polyimides that are obtained in Japanese Patent Application Public Disclosure No. 59-164328 [1984] and Japanese Patent Application Public Disclosure No. 61-111359 [1986], it is necessary to use a large quantity of p-phenylenediamine for the purpose of obtaining a sufficient modulus of elasticity. As a result, there is the problem that the coefficient of thermal expansion becomes excessively lower than that of the metal. With the four component polyimide described in Japanese Patent Application Public Disclosure No. 5-25273 [1993], the modulus of elasticity and thermal expansion capacity are sufficient for this use. However, there is the problem that there is a high coefficient of water absorption. Further, with the three-component polyimide that is obtained in Japanese Patent Application Public Disclosure No. 1-20238 [1989], there are the problems in that the modulus of elasticity is markedly increased and that flexibility is lost as a result of drawing, that the coefficient of thermal expansion is considerably decreased and that there are great differences in thermal behavior from the metal when the film is affixed.
Consequently, this invention has the objective of providing a polyimide film of high elasticity, low thermal expansion characteristics equal to those of metal and low water absorbing capacity, a method for its manufacture and metal laminated plates of improved curl in which it is the base material.
SUMMARY OF THE INVENTION
This invention, which solves the aforementioned problems, is a polyimide film having a birefringence less than 0.01 and a coefficient of thermal expansion of 10 to 22 ppm/° C. comprising a block component and a random component which are molecularly bonded, wherein the block component of the polyimide comprises a segment derived from an aromatic diamine compound of a rigid structure and an aromatic tetracarboxylic acid compound, and the random component of the copolymerized polyimide comprises a segment derived from an aromatic diamine compound of a flexible structure and at least two types of aromatic tetracarboxylic acid compounds.
In a separate embodiment of the invention is described a method for the manufacture of polyimide film characterized in that an aromatic diamine compound having a rigid structure and an aromatic tetracarboxylic acid compound are mixed for the time required for reaction in an organic solvent that is nonreactive with the reaction components at a ratio of aromatic tetracarboxylic acid compound of 95 to 105 mole % relative to the aromatic diamine compound having a rigid structure, after which the aromatic diamine compound having a flexible structure is added, the aromatic tetracarboxylic acid compound (A) is then added and a different aromatic tetracarboxylic acid compound (B; A≈B) is added so that the total aromatic tetracarboxylic acid compound, i.e., (A)+(B), and total aromatic diamine component are in an essentially equimolar quantity, these substances then being mixed for the time required for reaction and the copolymerized polyamic acid solution that is obtained is cyclized, after which drawing is performed, the solvent is eliminated and formation is effected and a metal laminated plate characterized in that the polyimide film described that is obtained in this way is used as the base material and is laminated with metal.
DETAILED DESCRIPTION OF THE INVENTION
The block component of the polyimide that forms the copolymerized polyimide of this invention consists of repeated polyimide molecular chains that are obtained from one aromatic diamine compound having a rigid structure and one aromatic tetracarboxylic acid compound and is obtained by formation in the first stage of polymerization. The random component of the copolymerized polyimide is formed by reacting the aromatic diamine compound having a flexible structure and at least two or more aromatic tetracarboxylic acid compound in the second stage of polymerization. The polyimide film that has been formed by drawing a copolymerized polyimide that is formed by molecular bonding of the block component of the polyimide and the random component of the copolymerized polyimide that are obtained in this way can have the superior physical properties of high elasticity, low thermal expansion characteristics equivalent to those of metal and low water absorbing characteristics.
It is essential that the birefringence of the polyimide film that is obtained by drawing be controlled to l
Kubo Michihiro
Sawasaki Koichi
Uhara Kenji
E. I. Du Pont de Nemours and Company
Nakarani D. S.
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