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18 PCB007 MAGAZINE I JUNE 2025 Stefan, can you explain a bit about the dura- bility, productivity and application range of the pico combination machine, and why this laser is a superior development over its predecessors? Endurance and performance are there because the bottleneck in these UV nanosec- ond laser systems are typically the UV optics. UV light at 355 nanometers is quite aggres- sive, and this requires a high maintenance routine. Also, the lifetime of the laser sources is more limited because the laser beam is so aggressive. When switching to the green wavelength, we know that a lot of these crit- ical optical components in the beam path are less damaged by the wavelength itself. is enables more uptime for production. In addition, the application spectrum of the machine is enlarged. Laser processing of heat-sensitive materials can be improved for a lot of PCB-relevant applications like drill- ing, cutting, and ablation. What is the reason for using different wave- lengths, and what is the difference between the UV and the green wavelength? Within the visible laser light spectrum, the human eye can see from 400 to 750 nanome- ters—from violet to red. Within this visible range, there is a range of color distribution. A laser has only one wavelength, while a common light source has a broad range of wavelengths. So, a laser always appears in one certain color. A UV laser emits lights typically at 355 nanometers, which is not vis- ible to the eye. A green laser is 532 nanometers. Infra- red lasers have a one-micron wavelength. We have the CO 2 laser, more in the infrared range with 9.4 µm. Wavelength is critical because every material has different reflectivity and absorption behavior, but all common wavelengths are absorbed in the same way. With a red material, for example, red light is reflected, and all other parts of the visible light are absorbed. By understanding that the appearance of a color indicates the absorp- tion behavior of different wavelengths, we can estimate roughly which laser is suitable for the processing of a certain materials. Using the same explanation, copper appears red. So, we know red lasers are reflected, and other wavelengths are absorbed. But the goal is always the same. We want to put the energy from the laser into the material in the most effi- cient way, heat it up, and then vaporize it. is is the reason for the different wavelengths. Yet, because of the extreme short pulse duration of the picosecond laser, we can over- come the physics of linear absorption. ese short pulses allow us to use a wavelength that is typically not absorbed by the material now triggering absorption. If you put a green laser in the nanosecond regime into glass, it will go through it without significant absorption. We can see it in our daily lives, through windows or the glasses we wear. It's not absorbed. But if you make the pulses shorter, we can trigger a non-linear absorption, glass stops the light, and is absorbed by it. Now, we can use picosecond lasers to pro- cess materials that were typically unsuitable. is was a breakthrough in the past decade when it came to ultra-short pulse laser pro- cessing. Many materials are now of inter- est compared to the material limitations of nanosecond lasers.