Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2000-12-28
2003-08-12
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C428S418000, C428S901000, C428S473500, C525S423000, C427S386000
Reexamination Certificate
active
06605353
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an epoxy-modified polyimide, and an innovative photosensitive composition and a printed wiring board using the epoxy-modified polyimide and more specifically relates to an epoxy-modified polyimide to be used especially in electronic material field, its production method, as well as a photosensitive composition containing the epoxy-modified polyimide and a photoreaction initiator and excellent in heat resistance, chemical resistance, an insulating property, and flexibility, a material for an electric wiring board using the polyimide, especially, a solder protection film (a solder resist), a coverlay film, and a printed wiring board.
2. Description of the Prior Art
Recently, electronic apparatuses have rapidly been made multifunctional and high-performance and miniaturized and following that, electronic parts are required to be miniaturized and made light weight. For that, as compared with a common rigid printed wiring board as a wiring board to mount electronic parts thereon, a flexible printed wiring board (hereafter referred to as FPC) excellent in flexibility has drawn more attention than ever and the demand has sharply been increased.
Meanwhile, a polymer film, so-called a coverlay film, is stuck to the surface of a FPC for the purpose of protecting the conductor face. A method employed as a method for laminating the coverlay film onto the surface of the conductor face is generally carried out by overlaying the coverlay film processed to have a prescribed shape and bearing an adhesive in one side to a FPC, properly positioning them, and then thermally laminating them each other by pressing or the like. However, the adhesive employed for that case is mainly an epoxy type or acrylic type adhesive or the like and in the case of using such an adhesive, there is a problem that the heat resistance for soldering or the heat resistance of the adhesion strength at a high temperature is low and that the flexibility is inferior and the function of the coverlay film as a base film has not sufficiently been utilized.
Further, in the case a coverlay film is stuck to a FPC using a conventional epoxy or acrylic adhesive before the laminating, it is required for the coverlay film to be processed to form holes and windows positioned at terminal parts of a circuit and junctions of constituent parts. However, not only it is difficult to form holes or the line in a thin coverlay film but also it is required to carry out the positioning conformation of the holes or the like of the coverlay film to the terminal parts of the circuit and junctions of the constituent parts of the FPC almost though a manual work and thus the workability and the positioning precision have been low and the cost has been high.
In order to improve the workability and the positioning precision, a method for forming a protection layer on a conductor face by applying a photosensitive composition and a photosensitive coverlay film (also called as a photosensitive dry film resist) have been developed and the workability and the positioning precision have been improved.
Nevertheless, for the foregoing coverlay film, acrylic type resins have been used and they are insufficient in the heat resistant temperature and brittleness as a film. From the view of improving the heat resistance and the mechanical strength as a film, a photosensitive polyimide has, therefore, been required to be used. Subsequently, there have been developed photosensitive polyimides into which methacryloyl group is introduced with the ester bond linkaged (Japanese examined Patent Publication No. 55-030207, Japanese examined Patent Publication No. 55-041422) and photosensitive polyimides into which amine compounds or diisocyanate compounds having methacryloyl group are introduced in the carboxy group part of the polyamide acid (Japanese unexamined Patent Publication No. 54-145794, Japanese unexamined Patent Publication No. 59-160140, Japanese unexamined Patent Publication No. 03-170547, Japanese unexamined Patent Publication No. 03-186847, Japanese unexamined Patent Publication No. 61-118424).
However, since those photosensitive polyimides are processed to be converted into polyimides by layering them in polyamide acid state on a FPC, exposing and developing the resultant layer, and then carrying out imidation for the layer, the FPC has to be heated to 250° C. or higher for the imidation reaction. Further, for some photosensitive polyimides, the acryloyl group has to be removed by heat and during the removal process, there occurs a problem that the film thickness is significantly lessened.
As a photosensitive polyimide which does not require the heat treatment at a high temperature after exposure and development, a method was proposed (Japanese unexamined Patent Publication Number 59-108031) which comprises steps of previously synthesizing a diamine having a carbon—carbon double bond, causing reaction of the diamine with an acid dianhydride to obtain a polyamide acid, and causing imidation of the resultant polyamide acid to use the obtained compound as a photosensitive resin. In this case, since the imidation is carried out before the exposure and development, it is no need to carry out heat treatment at a high after the exposure and development.
However, by the method proposed in the Japanese unexamined Patent Publication Number 59-108031, it is difficult to produce the diamine compound having a carbon—carbon double bond at high yield. The reason why is that when a dinitro compound having a carbon—carbon double bond, from which the diamine compound is generally produced by reduction, is reduced, the carbon—carbon double bond also tends to be reduced. Subsequently, the problem caused is that the yield is lowered and therefore the diamine compound having a carbon—carbon double bond inevitably becomes expensive.
In addition to that, the formation process of a solder protection film (e.g. a solder resist) is almost essential one in the printed wiring board manufacture. As a solder resist for a printed wiring board for industrial use, there conventionally used are thermosetting type solder resist compositions of alkyd/melamine resins, epoxy/melamine resin, two-part epoxy resins, and the likes, and these thermosetting solder resists are applied to the surface of a printed wiring board by printing or other methods and then hardened by heating to form a protection film.
However, those conventionally used solder resists require a relatively long time and high temperature for hardening by heating after application to be lower the productivity and cause a problem that substrate warping and shrinking easily occurs owing to the high heat hardening temperature. For the purpose of solving those problems, ultraviolet ray (UV)-curable solder resists used for printed wiring boards for consumer use have been studied and, in spite of that, found the properties are not satisfactory. Moreover, for printed wiring boards for industrial use, the conductor thickness of such as a copper foil has to be thicker, about 50 to 70 &mgr;m, as comparison consumer-use one having thickness of at most 60 &mgr;m, usually 40 &mgr;m, and a industrial-use solder resist has to be applied to be thick. On the contrary, a UV-curable solder resist for consumer use has a problem in the hardenability in case of a thick film and has to be thin. Nevertheless, if the thickness of the solder resist is made thin, there occurs a problem that the insulation property and the heat resistance for soldering which are required for printed wiring boards for industrial use become unsatisfactory and the reliability is deteriorated.
Furthermore, in the case of a flexible printed wiring board not only for industrial use but also for consumer use, additionally to the foregoing reliability, excellent film-formability and flexibility are required and hence conventional thermosetting and UV-curable solder resists are unsatisfactory. Subsequently, a photosensitive solder resist is desired o be developed for the use of a printed wiring board
Hara Shoji
Nojiri Hitoshi
Okada Koji
Dawson Robert
Fitch Even Tabin & Flannery
Kaneka Corporation
Keehan Christopher M.
LandOfFree
Epoxy-modified polyimide, photosensitive composition,... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Epoxy-modified polyimide, photosensitive composition,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Epoxy-modified polyimide, photosensitive composition,... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3076497