Blind hole production in circuit board

摘要

A method of producing blind holes in a circuit board (1), to allow contacting of two copper layers (2, 3) through an interposed glass-reinforced dielectric layer (4), involves (a) drilling a hole (6) through a first copper layer (2) using a laser at a wavelength (preferably 266-1064 nm) suitable for copper removal; (b) extending the hole (6) down to the second copper layer (3) using a second laser at a wavelength (preferably 1064-10600 nm) at which copper reflects the laser radiation; and (c) chemically removing dielectric residues (9) from the second copper layer (3), preferably using a permanganate solution optionally assisted by mechanical brushing. Preferably, the blind hole is subsequently etched with a sodium persulphate solution.