Abstract: A method for removal of curling of a circuit printable flexible substrate comprising a metal foil and a film layer of an aromatic polyamideimide or an aromatic polyimide formed by coating on the said metal foil a solution of an aromatic polyamideimide, an aromatic polyimide precursor or an aromatic polyimide, and drying the coated solution layer to setting, whose curling is produced to direct the metal foil surface to face outside, which comprises sliding under tension the curled circuit printable flexible substrate on a curved surface of a bar having a curvature radius of 0.5-25 mm, at which the substrate is turned back at a turning angle of not less than 90.degree., placing the metal foil layer in contact with the bar, at a temperature of not higher than 80.degree. C. A method employing two such bars is also disclosed.

Abstract: An aromatic imide polymer laminate material usable as a flexible circuit board substrate is produced by the process comprising coating a surface of a metallic foil with a solution of an aromatic imide polymer comprising at least 90 molar % of recurring unit of the formula (I): ##STR1## wherein R is a symmetrical bivalent aromatic radical having no substituent, and dissolved in a solvent consisting essentially of at least one phenolic compound; and heat drying the resultant solution layer to form an aromatic imide polymer solid layer firmly bonded directly to the metallic foil.