LASER PROCESSING METHOD, AND METHOD FOR MANUFACTURING METHOD MULTILAYER FLEXIBLE PRINTED WIRING BOARD USING THE LASER PROCESSING METHOD

摘要

PROBLEM TO BE SOLVED: To form a via hole with a smallest possible number of shots without having a resin residual in the via hole and generating deformation and penetration of an inner layer circuit pattern exposed in the via hole.SOLUTION: In the laser processing method, via holes 23, 24 are formed by removing a layer to be processed that includes: a flexible insulating base 1 having conformal masks 7, 8a provided on the surface; and an adhesive layer 12, which is provided below the insulating base, and which has a light absorption degree higher than that of the insulating base material 1, and a decomposition temperature lower than that of the insulating base material 1 in the wavelength region of a processing laser beam. After applying one shot of pulsed light having a first energy density, with which deformation and penetration of a conductive film 2A are not caused, and with which the insulating base material 1 can be removed by one shot, pulsed light having a second energy density smaller than the first energy density is applied, the second energy density being a density with which the remaining layer to be processed can be removed with a predetermined number of shots without causing deformation and penetration of the conductive film 2A.