CO2 Laser Drilling of Glass (TGV)
For optoelectronic packaging applications through glass vias (TGVs) are an important technology for thermal and electrical connections. Limitations of conventional mechanical or laser‑based vias processing techniques are the resulting large hole diameters (> 100 µm) and/or the long structuring times.
At Fraunhofer IZM CO2‑laser based drilling of glass, was developed, realising almost cylindrical holes (low conicity) with a diameter smaller than 100 µm. The processing time of such a hole is only 0.25 seconds (in 500 µm thin glass). The fast drilling speed, unrivalled compared to other lasers, and much lower equipment cost makes the CO2‑laser very suitable for economic industrial micro-machining of glass substrates. In addition the generated glass surface is very smooth and the diameter as well as the conicity of the hole can be adjusted by parameter variation.
Due to the thermal ablation process the development of thermally induced stresses cannot be avoided, but depending on the layout, in particular the pitch, the resulting stresses are non‑critical. If required different thermal pre‑ and post‑treatments for reducing mechanical stress and increasing reliability can be applied.