Laser processing method and production method of multilayer flexible printed wiring board using laser processing method

Abstract

There is provided a laser processing method of forming via holesandby removing processed layers including a flexible insulating base member, in which conformal masksandare provided on the surface, and an adhesive layerhaving a higher absorbance in a wavelength area of processing laser and a lower decomposition temperature than the insulating base member, the method including radiating one shot of pulse light having a first energy density that can remove the insulating base memberby one shot without causing the deformation and penetration of a conducting filmA, and subsequently radiating pulse light having a second energy density that is lower than the first energy density and can remove the rest of the processed layers by a predetermined number of shots without causing the deformation and penetration of the conducting filmA.