Over the past decade, ultrafast lasers (pulse durations of pico and femto seconds) have made it from the research lab into commercially available systems. Ultrafast lasers are increasingly useful for surface micro machining, micro and nano structuring, and 3D processing. They are capable of processing almost any material without causing extensive heating, also referred to as the heat affected zone (HAZ). In fact, in the laser process, the material is being removed by sublimation, which drastically reduces burring and debris formation. With pulse durations shorter than a few picoseconds, the physics of the interaction between the laser and the material is different than for nanosecond processing. It is really a vaporization method and, as such, it provides high dimensional accuracy compared to any other material process method. However, ultrafast lasers are still costly and should only be considered when no other method, including nanosecond lasers, works. Therefore, they are most cost effective in the production of very small features in materials such as ceramics, glass, metals, PCBS, and plastics.
Selecting the most optimum ultrafast laser requires matching the proper wavelength to the material. Picosecond and femtosecond lasers are available in green, Infrared (IR), and ultraviolet (UV) wavelengths. Each wavelength varies in focus spot size, and should be chosen based on the required size of the features being machined. A few examples of the best wavelength choices for material are picosecond IR for glass cutting and femtosecond green for plastic applications.
In general, the faster the laser, the lower the overall throughput. Therefore, ultrafast lasers such as femtosecond lasers are typically limited to material thicknesses below 250um.
To get an idea of the different processing rates for nanosecond versus picosecond and femtosecond, the table below compares general parameters.
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