Machining of through-glass vias (TGVs) with femtosecond laser GHz burst modes

Through-Glass Vias (TGVs) are crucial in semiconductor and electronics industries, enabling high-density interconnections in devices from automotive sensors to Micro-Electro-Mechanical Systems. They support device miniaturization and improve electronic package performance by enabling vertical electrical connections through glass substrates. Femtosecond laser pulses can drill transparent materials like glass with minimal thermal effects, though throughput and aspect ratios can be limiting factors. Our research investigates femtosecond laser burst modes in the GHz regime for percussion drilling of materials such as fused silica, diamond, silicon carbide, and sapphire. We found that long, well-formed channels can be produced, in some cases reaching into tens of millimeters with an aspect ratio of 1:100, outperforming conventional single-pulse techniques. These results indicate increased micromachining efficiency for TGVs and potential applications in advanced optics, biomedical devices, and beyond, demonstrating the enhanced performance of GHz burst mode femtosecond laser machining.