Textiles: weaving – Fabrics – Drier felts
Reexamination Certificate
1999-09-27
2001-09-04
Calvert, John J. (Department: 3765)
Textiles: weaving
Fabrics
Drier felts
C139S42000D, C139S4260TW, C442S233000
Reexamination Certificate
active
06283166
ABSTRACT:
TECHNICAL FIELD
This invention relates to a glass woven fabric which is used as a base material for a printed wiring board to be used in electronic equipment, computer, communication equipment and the like, and to a laminate for printed wiring board in which the above glass woven fabric is used as a base material.
BACKGROUND ART
Glass fibers are broadly used in the electronics field because of their excellent thermal resistance, dimensional stability, electrical characteristics and the like, and in particular, glass woven fabrics prepared by subjecting glass fibers to weaving are much in demand as a base material for a printed wiring board because of their excellent characteristics.
Such a packaging system is now increasing that IC or the like is automatically inserted into a printed wiring board. This automatic insertion is accompanied by drying of solder resist, heating such as fusing or the like, etc, and hence, the printed wiring board becomes exposed to severe conditions. Therefore, that the printed wiring board is changed in dimension by heat has become a problem. Particularly, when the dimensional change in the warp direction and that in the weft direction are different, it follows that anisotropy is caused in the warp and weft directions in the step of processing the printed wiring board.
Thus, the dimensional stability level in the conventional printed wiring boards has become unsatisfactory, and a printed wiring board free from anisotropy as to dimensional change has become necessary.
Moreover, in the case of conventional glass woven fabrics prepared by plain weave, fine irregularities resulting from the weave pattern of the woven fabric appear on the surface of the base board. As in recent years, the wiring of the printed wiring board has been made finer and the wiring density has been made higher, and therefore, it has been necessary that the irregularities be as small in number as possible.
In order to solve such problems, a printed wiring board has been proposed in which a unidirectionally arranged woven fabric of glass fibers (referred to herein-after as the UD material) is used as a base material. For example, JP-A-1-216,829, JP-A-1-216,830, JP-A-4-270,657, JP-B-7-90,606, JP-B-7-90,607, JP-A-8-39,686 and the like disclose a process and apparatus for producing a printed wiring board in which the UD material is used.
The production of a printed wiring board in which the UD material is used as a base material is characterized in that the printed wiring board can be produced without undergoing the conventional weaving step, varnish-impregnating step and pressing step, but there must be prepared its own peculiar production devices such as a yarn-arranging device and a continuously resin-coating device, and hence, a new investment in plant and equipment is required. Moreover, the above production has many undissolved technical problems and has not reached a practical use stage.
Furthermore, in recent years, a remarkable advance has been seen with respect to a technique of perforating the printed wiring board with a laser. However, when a printed wiring board in which a glass woven fabric is used as the base material is subjected to laser processing, such a problem is caused in some cases that holes having a uniform diameter cannot be perforated because in the conventional glass woven fabric of plain weave, present are portions in which fibers are woven with one another and portions of resin alone.
Accordingly, an object of this invention is to provide a glass woven fabric having characteristics equivalent to conventional unidirectionally arranged woven fabrics (the UD material), and to thereby make it possible to obtain a printed wiring board excellent in dimensional stability and surface smoothness by the conventional process, as it is, for producing a printed wiring board which is now generally used.
Another object is to provide a printed wiring board which enables the uniform perforation when the printed wiring board is subjected to perforation with a laser.
DISCLOSURE OF INVENTION
This invention has been made for achieving the above-mentioned objects and is a glass woven fabric composed of glass fiber warp threads and glass fiber weft threads, characterized in that the glass fiber warp threads are woven with the glass fiber weft threads at intervals of at least 10 mm in each of the warp and weft directions and characterized by comprising a glass fiber woven fabric portion having non-woven portions in each of which a warp layer in which only the above glass fiber warp threads are successively placed side by side and a weft layer in which only the above glass fiber weft threads are successively placed side by side are laminated.
That is to say, in the glass woven fabric of this invention, such crossing that the up-and-down relation between the glass fiber warp thread and the glass fiber weft thread is reversed, namely weaving, is not caused over at least 10 mm in the warp direction and over at least 10 mm in the weft direction. Accordingly, in the above-mentioned non-woven portions, each of which is a tetragonal region in which weaving of the above warp threads with the above weft threads is not caused, the warp layer in which only the warp threads are successively placed side by side (referred to hereinafter merely as “the warp layer” in some cases) and the weft layer in which only the weft threads are successively placed side by side (referred to herein-after merely as “the weft layer” in some cases) are present in the form of a laminate.
In this invention, the thread count in 25 mm of glass woven fabric (density of yarn) is not particularly limited; however, when the performance of a loom of thread is taken into consideration, the thread count is generally 10 to 100, preferably 30 to 80 and most preferably 30 to 60 in both warp and weft. Accordingly, when this is applied to the glass woven fabric of this invention, it follows that glass fiber warp threads and glass fiber weft threads are woven in a unit of about 8 to 40 threads or more.
Moreover, in the glass woven fabric of this invention as a base material for the printed wiring board, the above-mentioned glass fiber woven fabric portion may have, at its both ends, weave texture portions of glass fiber, the weave texture of which is selected from the group consisting of plain weave texture, twill weave texture and satin weave texture and, in addition, continuous weave texture portions having a width of at least 2 mm, the weave texture of which is selected from the group consisting of plain weave texture, twill weave texture and satin weave texture, may exist between the non-woven portions of the above-mentioned glass fiber woven fabric portion, at intervals of at least 10 mm in the warp direction and/or the weft direction.
Furthermore, the ratio between the glass fiber amounts per 25 mm in the warp and weft directions of the above-mentioned glass fiber woven fabric [(number of glass fiber warp threads×denier of glass fiber warp thread)/(number of glass fiber weft threads×denier of glass fiber weft thread)] is preferably 0.7 to 1.4.
Also, this invention includes a prepreg prepared by impregnating and coating the above-mentioned glass woven fabric with a synthetic resin and also a printed wiring board in which the above-mentioned glass woven fabric is used as a base material.
REFERENCES:
patent: 4550051 (1985-10-01), Spielau et al.
patent: 4707565 (1987-11-01), Kasai et al.
patent: 4943334 (1990-07-01), Medney et al.
patent: 5047279 (1991-09-01), Nasu et al.
patent: 5269863 (1993-12-01), Middelman
patent: 62-276053 (1987-11-01), None
patent: 1-216830 (1989-08-01), None
patent: 1-216829 (1989-08-01), None
patent: 4-270657 (1992-09-01), None
patent: 6-136632 (1994-05-01), None
patent: 7-66513 (1995-03-01), None
patent: 7-90606 (1995-10-01), None
patent: 7-90607 (1995-10-01), None
patent: 8-18180 (1996-01-01), None
patent: 8-39686 (1996-02-01), None
Miyasato Keita
Sato Eiji
Calvert John J.
Foley & Lardner
Muromoto Jr. Robert H.
Nitto Boseki Co. Ltd.
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