| 摘要 |
PURPOSE:To improve the drilling performance of a laminated sheet and consequently make it possible to increase the number of piled-up sheets at drilling by a method wherein glass cloth, which is embrittled so as to make both the longitudinal and lateral bending strengths of the laminated sheet not larger than specified values, is employed as base material. CONSTITUTION:Glass cloth, which is embrittled so as to make both the longitudinal and lateral bending strengths of a laminated sheet not larger than 50kg/mm<2>, is employed as base material. The positional accuracy of the small diameter drilled hole clearly correlates with the bending strength of the laminated sheet. The decrease of the amount of curve of the drilled hole is proportionate to that of the bending strength of the laminated sheet. However, the bending strength of the base material having not small than 50kg/mm<2> does not effect the decrease of the amount of curve of the drilled hole. Further, if the bending strength of the base material is not larger than 20kg/mm<2>, the breakage or the like of the base material may develop during coating process and forming under heat and pressure, resulting in being apt to reduce productivity. Furthermore, in order to lower the bending strength of the laminated sheet, embrittled glass cloth is necessary. As normal embrittle treatment, comparatively longer heat cleaning at high temperature such as 400 deg.C or higher, immersion in acid or alkaline solution or mechanical opening or the like of glass cloth is employed. |
