In industry, it's common to cut steel using 50-200 W $\mathrm{CO}_2$ laser.
Meanwhile, for making holes in PCB (35 $\mu$m of Cu), DPSS 355 nm laser is usually used and secondary $\mathrm{CO}_2$ to drill through glass.
Why $CO_2$ cuts steel easily, but cannot be used to make holes in Copper?
UPDATE: Will it help to add thin layer of black paint + pre-heat to 200 °C to get through damn 0.035 mm of Cu?
can You read German? here http://de.wikipedia.org/wiki/Laserschneiden all Your questions are answered. The English pendant is much shorter and does not deal Your problems. In case You can't read that, some short excerpt: Main problem with copper and Aluminium are high reflectivity at 10 µm, the high thermal conductivity and and no "assistance" from oxidation possible. One special problem is "Einstechen" (initial penetration?). I don't know an English expression for that. It is the making of a hole when starting a cut. This is a time consuming step in laser cutting anyhow. Now, making holes in a PCB is more or less "Einstechen" all the time. Georg
CO2 lasers, typically operating at a wavelength of 10.6 micrometers, are highly effective for cutting steel but face challenges with copper due to copper's high reflectivity and thermal conductivity at this wavelength. The material properties of copper cause it to reflect a significant portion of the CO2 laser light, preventing efficient absorption of the energy needed to cut or drill through it. Additionally, copper's high thermal conductivity disperses the absorbed heat quickly, making it difficult to achieve the localized energy density required for material removal.
On the other hand, DPSS lasers, particularly those operating at 355 nm (ultraviolet range), can be more effective for materials like copper due to the higher absorption rates of UV light in these materials. The shorter wavelength allows for tighter focusing and higher energy density at the target spot, facilitating precise material ablation without significant heat spread.
Adding a thin layer of black paint and pre-heating copper to 200°C could potentially improve the absorption of CO2 laser energy by reducing reflectivity and initially raising the material's temperature. This approach aims to increase the efficiency of the laser-material interaction by:
Enhancing Absorption: The black paint can absorb laser energy more effectively than the shiny copper surface, converting it into heat that can assist in piercing the copper.
Pre-Heating: By elevating the temperature of the copper, you lower the energy requirement needed to reach the melting point, making it easier for the laser to initiate and sustain the cutting or drilling process.
While these strategies might improve the CO2 laser's ability to make holes in copper, the success of such approaches can vary. They may be practical for thin layers of copper, like the 35 μm thickness mentioned, but it's essential to consider the potential for changes in material properties, such as oxidation or paint-induced impurities. Experimentation with laser parameters and treatment processes would be necessary to optimize results.
