LPKF laser welding for microfluidics.
At K 2013 LPKF will be presenting its new PrecisionWeld laser system designed for microfluidic applications. The system can reportedly create weld seams with a thickness of 100 µm and has positioning repeatability of 10 µm. This is accomplished by separating the housing from the processing compartment.
This design has been used in practice, as it was based on the company’s ProtoLaser systems which have been used in the PCB prototyping sector for many years.
It uses a scanner system to guide the laser beam and a positioning table. This expands the effective working area to 320 x 320mm. In addition, an integrated camera system allows for the detection of specially applied fiducial marks, or it can use the geometric elements of the device itself. This allows compensation for tolerances in the device or its fixture.
With the LPKF PrecisionWeld, parts can be joined using classic transmission laser welding as well as the new clear-joining technology.
In transmission laser welding, the two parts to be joined have different absorption properties, e.g. a laser-absorbing basal unit has a clear cover plate. The laser beam passes through the upper laser-transparent layer but is absorbed when it hits the lower part, so that the energy in the light is converted to heat and melts the plastic. A moderate joining pressure is applied which promotes thermal conduction into the upper part, producing a reliable and precise weld seam.
Because it has a laser wavelength of 1,940 nm, the LPKF PrecisionWeld is also capable of joining two transparent components. This the clear-joining technology: at this wavelength, most technical polymers absorb enough of the light to melt at high energy densities. The laser beam is focused precisely on the welding horizon to apply the energy where it is required to create a weld – without needing any special additives.
Other features of the PrecisionWeld include a setting which identifies the surface of the component and automatically adjusts the focus to the optimal position. The system is remarkably compact and needs only to be connected to a power supply and a compressed air line for operation. It is small enough to be equipped with rollers and fits through every laboratory door.