Electric heating – Metal heating – By arc
Reexamination Certificate
2002-03-29
2003-09-16
Elve, M. Alexandra (Department: 1725)
Electric heating
Metal heating
By arc
C219S121670, C219S121850
Reexamination Certificate
active
06621046
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of cutting prepreg that is used for manufacturing a laminated plate.
2. Description of the Background Art
Prepreg is formed into an elongated shape through the following processes: an elongated base member such as glass cloth or paper is impregnated with a varnish of a thermosetting resin; and heated and dried so that the thermosetting resin is semi-set. The dried prepreg is cut along a length direction and in a width direction orthogonal to the length direction into a rectangular shape that has a constant dimension. The cut prepreg is next applied. For example, a plurality of sheets of prepreg cut as described above are superposed with both of the surfaces of each sheet covered with copper foil, etc. The superposed sheets are heated and pressed to form a molded product. Thus, a copper-clad laminate is manufactured.
When cutting prepreg in the manner described above, a cutting blade, such as a guillotine, a rotary cutter, a shirring blade or a saw blade, is used. However, since the prepreg is formed by a fragile semi-set resin adhering to a base member, the cutting process tends to generate cutting dust of the resin and the base member. The cutting dust is scattered around to cause degradation in the work environment. Furthermore, the cutting dust tends to adhere to the prepreg and to be mixed into the molded product or affixed thereon as foreign matter when molded in the next process with the copper foil. In recent years, there have been increasing demands for high-density circuit patterns that are very sensitive to foreign matter. Thus, there have been strong demands for the prevention of the generation of cutting dust that is introduced into the work environment.
In order to solve this problem, a method has been proposed in which a portion of prepreg to be cut is heated by an infrared heater and thereby softened. The prepreg is cut at the softened portion so that it is possible to prevent the generation and scattering of cutting dust. However, when the prepreg is heated by an infrared heater as mentioned above, portions other than the portion of the prepreg to be cut are also widely heated with the result that the prepreg resin in the heated portions may set, resulting in degradation in the quality.
Moreover, as disclosed in Japanese Laid-Open Patent Application No. 3-94988, another method in which a laser light beam is used to cut prepreg has been proposed. In this method, the prepreg is cut not by a shearing force, etc., but by a burning process of a laser light beam. Therefore, the prepreg can be cut without generating cutting dust. However, in this method, both the base member and the resin need to be simultaneously cut by using a laser light beam. Thus, when the base substrate is made of glass fibers, it is necessary to use a laser light beam with high output power. The resulting problem is that the resin is carbonized due to irradiation of the high-power laser light beam, resulting in degradation in the quality.
The present invention has been devised to solve the above-mentioned problems, and its objective is to provide a method of cutting prepreg which eliminates the necessity of applying a heating process, etc., to portions other than a portion of the prepreg to be cut, and which can also prevent the generation of cutting dust when cutting.
SUMMARY OF THE INVENTION
According to an aspect of the present invention, a method of cutting prepreg that has been formed by impregnating a base member with a resin and semi-cured into a predetermined dimension, is provided. The method includes directing a laser light beam onto a surface of the prepreg to soften the resin of the portion irradiated by the laser light beam, and cutting the softened portion of the resin with a cutting blade. With this arrangement, the cutting blade cuts the softened portion of the prepreg resin so that it becomes possible to prevent the resin from scattering as cutting dust when cutting with the cutting blade.
According to a further aspect of the present invention, the method of cutting prepreg has an arrangement wherein the laser beam is directed to the prepreg with an irradiation position being fixed while the prepreg is being fed (transferred) so that the prepreg resin of the portion irradiated with the laser beam is heated and softened. Furthermore, the softened portion of the prepreg is cut by a cutting blade that is placed forward of the irradiation position with respect to the feeding direction of the prepreg. With this arrangement, the prepreg resin is heated and softened at the portion irradiated with the laser light beam, and cut by a cutting blade that is placed forward of the irradiation position in the feeding direction. Therefore, it is not necessary to shift the position of the laser light beam and the cutting blade. Moreover, as the prepreg is transferred, the portion at which the resin is heated and softened by the irradiation of the laser light beam is cut so that the generation of cutting dust due to the cutting process is prevented.
According to a further aspect of the present invention, the method of cutting prepreg has an arrangement in which the irradiation position of the laser light beam is shifted when irradiating the surface of the prepreg. Thus, it is possible to freely shift the cutting position.
According to a further aspect of the present invention, the method of cutting prepreg has an arrangement in which the cut end portion of the prepreg is irradiated with a laser light beam after being cut by the cutting blade. With this arrangement, the laser light beam further softens and fuses the cut end portion of the prepreg so that the prepreg forms a smooth face. Thus, resin dust is prevented from coming off the cut end face of the prepreg.
According to a further aspect of the present invention, the method of cutting prepreg has an arrangement in which a laser light beam is fixed with respect to the portion of the prepreg cut by the cutting blade while the prepreg is being transferred. With this arrangement, the irradiation positions of the laser light beam and the cutting blade do not have to be shifted. Furthermore, as the prepreg is transferred, the cut portion of the prepreg can be heated so that resin dust is prevented from coming off the cut end face of the prepreg.
According to a further aspect of the present invention, the method of cutting prepreg has an arrangement in which a carbon oxide gas laser is used as the laser light beam. With this arrangement, by properly selecting the output of the carbon oxide gas laser, it is possible to heat and soften the prepreg resin without causing carbonization thereof.
According to a further aspect of the present invention, the method of cutting prepreg has an arrangement in which the cutting blade comprises upper and lower rotary blades with at least the lower rotary blade being driven to rotate. With this arrangement, the rotation of the rotary blades can be controlled depending on the state of the prepreg.
According to a further aspect of the present invention, the method of cutting prepreg has an arrangement in which a reflection mirror is placed on a light path of a laser light beam emitted from a laser oscillator so that a laser light beam is reflected by the reflection mirror to a predetermined irradiation position of the prepreg. With this arrangement, by changing the number, the positions and the angles of one or more reflection mirrors, the irradiation position of the laser beam is easily adjusted without requiring a change of the position of the laser oscillator.
According to a further aspect of the present invention, the method of cutting prepreg has an arrangement in which a light-converging lens is placed at an outlet that outputs the reflected laser light beam from the at least one reflection mirror so that the laser light beam that has passed through the light-converging lens is directed onto the prepreg. With this arrangement, even when the distances of the light paths from the laser oscillator to the irradiation p
Elve M. Alexandra
Matsushita Electric & Works Ltd.
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