Precise removal of thin films
Precise removal of conductive coatings
Application example from cutting-edge research
Defined ablation of thin films
Thanks to the concentration of the energy of the laser beam in ultra-short pulses, the material to be processed can be vaporized directly. The heat input into the material remains minimal. The ultrashort pulse laser is therefore ideally suited for the ablation of a thin layer from a heat-sensitive base material. One application example is the selective ablation of a conductive silver layer from a hemispherical piezo element.
Laser structuring of piezo actuators for planar ultrasonic motors
For a novel piezo drive developed at the Institute of Design and Production in Precision Engineering
at the University of Stuttgart
(https://www.ikff.uni-stuttgart.de), hemispherical structured piezo elements
are required. The elements are coated with a conductive material a few micrometers thick. This layer has to be selectively removed, so that four areas of equal size are created, which are electrically separated from each other. Further requirements are a sharp edge between the coated and the ablated area and the avoidance of thermal influence on the base material. While the good focusability of the laser beam ensures a sharp-edged transition between the coated and ablated areas, a clean separation of the coated areas without thermal damage to the base material requires a thorough adjustment of the process parameters.
In order to avoid heat accumulation effects, a high feed rate of the laser beam over the workpiece and thus a low pulse overlap must be used. If the pulse overlap is too high, thermal damage to the base material can occur. Furthermore, for optimum processing quality, the energy density of the laser beam in the focus must be correctly selected. Typically, energy densities in the range of 5 to 15 times the ablation threshold are selected. With such a parameter combination of high feed rate together with moderate pulse energies, the complete coating is not yet removed after only one processing step. Only after several processing steps is the coating reliably removed completely.
The hemispherical piezo elements were fixed in a block chuck. Thanks to the modern system technology available at LightPulse LASER PRECISION, the workpiece can be rotated. This ensured a consistent, homogeneous machining result over the entire hemisphere. Several of the hemispherical piezo elements were successfully structured. These were subsequently used to build a prototype of an ultrasonic motor at the IKFF of the University of Stuttgart. Thus, an innovative drive concept became reality using the ultrashort pulse laser .
In order to avoid heat accumulation effects, a high feed rate of the laser beam over the workpiece and thus a low pulse overlap must be used. If the pulse overlap is too high, thermal damage to the base material can occur. Furthermore, for optimum processing quality, the energy density of the laser beam in the focus must be correctly selected. Typically, energy densities in the range of 5 to 15 times the ablation threshold are selected. With such a parameter combination of high feed rate together with moderate pulse energies, the complete coating is not yet removed after only one processing step. Only after several processing steps is the coating reliably removed completely.
The hemispherical piezo elements were fixed in a block chuck. Thanks to the modern system technology available at LightPulse LASER PRECISION, the workpiece can be rotated. This ensured a consistent, homogeneous machining result over the entire hemisphere. Several of the hemispherical piezo elements were successfully structured. These were subsequently used to build a prototype of an ultrasonic motor at the IKFF of the University of Stuttgart. Thus, an innovative drive concept became reality using the ultrashort pulse laser .
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