Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1999-09-21
2001-05-08
Lam, Cathy (Department: 1775)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S320200, C428S413000, C174S258000
Reexamination Certificate
active
06228467
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a heat resistant insulating film, a base plate for a printed circuit board employing it, and a method for producing the printed circuit board. More particularly, it relates to a thermoplastic resin film which is excellent in soldering heat resistance, flexibility, chemical resistance, mechanical strength and electrical properties and which is excellent also in a thermoforming property at a low temperature (a heat-bonding property), a base plate wherein this film is used as an insulator for a printed circuit board, and a method for producing the board.
BACKGROUND ART
Heretofore, as the most common printed circuit board, a board has been used wherein a prepreg (hereinafter referred to as a glass epoxy resin) obtained by impregnating a thermosetting epoxy resin to a glass cloth (a non-woven fabric of glass fibers) is used as an insulator, and a conductive foil such as a copper foil is bonded thereto by hot press molding usually under such conditions as a pressure of from 10 to 40 kgf/cm
2
at a temperature of from 170 to 230° C. for from 30 to 120 minutes.
The glass epoxy resin is excellent in soldering heat resistance or chemical resistance and relatively inexpensive, but it has had problems that as it contains glass fibers, cracks are likely to be imparted when an impact of dropping, etc. is exerted, thus leading to conduction failure, and it takes a long time for curing the epoxy resin during the hot press molding and thus the productivity is poor.
Further, in recent years, in correspondence with miniaturization and reduction in weight of electronic appliances including notebook personal computers and portable telephones, high densification of wirings and miniaturization and reduction in weight of circuit boards have been required, and a study on a multi-layer board using a thermoplastic resin film as an insulating layer has been actively carried out for the purpose of satisfying the requirements.
When a thermoplastic resin film is used as an insulator for a printed circuit board, various merits can be expected. As compared with a conventional glass epoxy resin, miniaturization and reduction in weight of the circuit board can be realized, the impact resistance can be improved, and the molding time for the hot press molding can be shortened, which is advantageous from the viewpoint of the productivity. Inherently, the insulator for a printed circuit board is required to have soldering heat resistance from the process of its production, and if it is possible to use a heat resistant thermoplastic resin such as a polyether ketone resin or a polyimide resin, it can be expected to obtain a circuit which is excellent in the electrical properties at a high temperature and which is reliable in a high temperature atmosphere.
However, such a heat resistant thermoplastic resin has a high temperature for molding, and it will be necessary to use an adhesive such as an epoxy resin or to carry out hot press molding at a high temperature of at least 260° C., for bonding with a conductive material or for forming a multilayer structure for the substrate, and it takes time to raise or lower the temperature, whereby the superiority of the thermoplastic resin will be lost in the productivity. Further, in the case of a crystalline resin, the bonding property can not be obtained unless it is heated to a temperature close to the melting point, and if the temperature exceeds the melting point, the resin turns to start flowing and undergoes flow deformation. On the other hand, the polyimide resin is excellent in heat resistance, chemical resistance, mechanical strength, etc., but the hygroscopicity is large, and the dimensional stability is inadequate, and the price of the starting material is very high.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a thermoplastic resin film which is excellent in soldering heat resistance, flexibility, chemical resistance, mechanical strength and electrical properties and which is excellent also in the thermoforming property at a low temperature (a heat bonding property) and a base plate for a printed circuit board wherein the film is used as a film insulator, and to provide an industrially advantageous method for producing a board.
The present inventors have conducted extensive studies and as a result, they have found a base plate for a printed circuit board and a method for producing a board employing it, which are capable of solving the above problems, by using a film insulator which comprises a polyarylketone resin and a non-crystalline polyether imide resin having a specific composition and which has a certain specific thermal properties imparted, and further by controlling the thermal properties of the film at the time of assembling and processing a printed circuit board within a certain specific range, and have accomplished the present invention.
Namely, the gist of the present invention resides in a heat resistant insulating film which comprises from 65 to 35 wt % of a polyarylketone resin and from 35 to 65 wt % of a non-crystalline polyether imide resin and of which the glass transition temperature is from 150 to 230° C. and the peak temperature of crystal fusion is at least 260° C., as measured when the temperature is raised by the differential scanning calorimetry, and the heat of crystal fusion &Dgr;Hm and the heat of crystallization &Dgr;Hc generated by crystallization during the temperature rise, satisfy the following relation:
[(&Dgr;
Hm−&Dgr;Hc
)/&Dgr;
Hm]≦
0.35
Further, another gist of the present invention resides in a base plate for a printed circuit board, having a conductive foil heat-bonded to at least one side of a film insulator which comprises from 65 to 35 wt % of a polyarylketone resin and from 35 to 65 wt % of a non-crystalline polyether imide resin and of which the glass transition temperature is from 150 to 230° C. and the peak temperature of crystal fusion is at least 260° C., as measured when the temperature is raised in the differential scanning calorimetry, if necessary after forming a through-hole and filling a conductive paste therein, and of which, after the heat bonding, the heat of crystal fusion &Dgr;Hm and the heat of crystallization &Dgr;Hc generated by crystallization during the temperature rise, as measured when the temperature is raised by the differential scanning calorimetry, satisfy the following relation:
[(&Dgr;
Hm−&Dgr;Hc
)/&Dgr;
Hm]≦
0.5
Furthermore, another gist of the present invention resides in a method for producing a printed circuit board, which comprises subjecting the conductive foil of the above-mentioned base plate for a printed circuit board to etching treatment required for forming a circuit, followed by heat-bonding via a film insulator to form a multi-layer structure, wherein, after the heat bonding, the heat of crystal fusion &Dgr;Hm and the heat of crystallization &Dgr;Hc, satisfy the following relation:
[(&Dgr;
Hm−&Dgr;Hc
)/&Dgr;
Hm]≧
0.7
According to the present invention, it is possible to provide a thermoplastic resin film which is excellent in soldering heat resistance, flexibility, chemical resistance, mechanical strength and electrical properties and which is excellent also in a thermoforming property at a low temperature (a heat bonding property), a base plate for a printed circuit board wherein this film is used as a film insulator, and a method for producing the board.
REFERENCES:
patent: 4687615 (1987-08-01), Kondo et al.
patent: 5095078 (1992-03-01), Mizuno et al.
patent: 6060175 (2000-05-01), Swisher
Kondo Kouji
Nomoto Kaoru
Takagi Jun
Taniguchi Kouichirou
Yamada Shingetsu
Lam Cathy
Mitsubishi Plastics Inc.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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