By EKSPLA
Forming high-aspect-ratio holes in glass substrates is becoming more important, especially in the semiconductor field. Femtosecond lasers can form low-taper, high-aspect-ratio TGVs in glass at high quality, with low chipping, no cracking, and a smooth inner hole wall. FemtoLux 30 operating in GHz burst mode produces high-aspect-ratio TGVs in glass substrates by percussion drilling. Splitting the single high-energy pulse into 50 pulses in a GHz burst achieves aspect ratios above 1:80 and controls the hole’s depth to a resolution of 0.1 µm by tuning the burst configuration. The technology was validated for AN100, BK7, BF33, D263, EXG, fused silica and soda-lime glass. Combining a long GHz burst with beam shaping narrows the vias further: a single 180 µJ burst forms 1 µm diameter TGVs through 0.5 mm glass, an aspect ratio of 1:500, in one laser shot. Because each via needs only one burst, thousands can be formed per second. TGVs can also be formed by combining MHz+GHz burst mode with bottom-up milling. Bottom-up milling gives zero-taper structures and the MHz+GHz burst raises throughput; together they produced a matrix of 200 µm diameter holes in BF33 and D263 glass.
