| 摘要 |
PROBLEM TO BE SOLVED: To produce a void-free prepreg without lowering the productivity and generating warpage of the substrate by a simple modification of the apparatus. SOLUTION: A substrate 10 is successively immersed in a primary impregnation tank 23 containing a thermosetting resin varnish for primary impregnation and then a secondary impregnation tank 24 containing a thermosetting resin varnish for secondary impregnation having a viscosity higher than that of the primary impregnation varnish. The transfer time T from the start A of immersion of the substrate 10 in the primary impregnation tank 23 to the start B of immersion in the secondary impregnation tank 24 and the time (t) to move the substrate 10 through the atmosphere in the above transfer process satisfy the formula t=aT (a is a number of 0.8 to 0.98).
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