INSULATION SUBSTRATE FOR PRINTED CIRCUIT AND INSULATION FILM OR SHEET

摘要

PROBLEM TO BE SOLVED: To suppress the heat shrinkage property of an insulation substrate for circuit and at the same time secure a desirable low dielectric constant and a low dielectric loss characteristic by laminating a poor hygroscopic insulation film for suppressing thermal shrinkage on a plastic film containing an extended cavity where the cavity is formed by extension. SOLUTION: A plastic film 1 containing an extension cavity where a fine cavity is formed by extension forms at least two types of incompatible resin mixtures (a mixture between polyester such as polyethylene telephtharate and polystyrene resin such as polystyrene) in film shape, for example, by T die extrusion and forms an independent cavity with a shear slide on a different resin interface by extending the non-extended film. A cavity content ranges from 30 to 50%. A hygroscopic insulation film 2 is a single-substance synthetic resin film such as polyetheleneterephtharate film and is as thick as 50-300μm. The film 2 suppresses heat shrinkage in one piece with the plastic film 1 containing extended cavity.