ULTRA-SHORT PULSE LASERS IN PCB SEPARATION

Laser cutting system for printed circuit boards using inline measurement technology

Until now, stamping, mechanical sawing or milling and (later) laser systems have been used in PCB separation (i.e. the singling out by machine of identical components on a printed circuit board). The more advanced laser systems enable separation in accordance with more complex cutting patterns, while sawing is limited to applications where rectangular structures have to be cut out quickly. Here laser separation systems have the advantage that they can minimise mechanical stress. However, even the most advanced UV laser systems can thermally stress a circuit board, although they can work with minimal cutting widths due to their small focal diameters. Traces of powder can often be seen at the cut edges and this is a typical sign of thermal stress.

Ultra-short pulse laser systems are the better alternative. Thanks to their ultra-short light flashes, these laser systems enable the “cold” processing of materials, such as drilling microfine spray holes in injection nozzles for engines or cutting biocompatible materials for medical implants. The ultra-short pulse laser-separator built by ic-automation GmbH in Mainz is extremely compact and with a footprint of only 2 square metres is only marginally larger than the ultra-short pulse laser itself which is also used here. An air-cushioned granite bed with direct drives on a granite base guarantees the highest degree of precision with an absolute positioning accuracy of less than 10 microns. The measuring systems built in to the machine cover all three dimensions; in addition to high-resolution XY measurement via a vision system with dome lighting, a measuring head from Precitec Optronik in Neu-Isenburg provides the height focusing system of the laser with the height information of the component, operating in accordance with the chromatic-confocal measuring principle. Variations in height and distortion of the components are measured and offset in 4 degrees of freedom. The requirements to be fulfilled for ic-automation were absolute system accuracy of less than 10 micrometres and a repeat accuracy that was more precise by a factor of 2. With the TruMicro 5000 from Trumpf in Ditzingen, ic-automation found a suitable ultra-fast laser system in the “green light” wavelength spectrum and in the pico-second range. With its telecentric scanner optics, the laser system also achieved an absolute degree of accuracy amounting to less than 30 micrometres.

In summary, it can be said that ic-automation acquired one of the most compact PCB separators with ultra-short laser pulses that is available on the market. The handling with vacuum suction, either manual or automated assembly and internal transport via shuttle boats with magnetic masks for clamping the cut components represent a high degree of automation, which is even on a par with inline measurement technology. Thanks not least to the compact utility design, production is at the highest possible level of quality – a requirement for electronic components in the automotive industry and for high-quality industrial products.