CONTRACT MANUFACTURING
and any mistakes in solder placement can lead to costly rework, or even the scrappage of entire batches. As electronic devices have advanced and surface mount components have become smaller, the size of these apertures has decreased accordingly, requiring greater levels of laser cutting precision to manufacture them. Furthermore, in addition to requiring motion in the XY plane, the introduction of multi-level stencils necessitates Z-plane movement to create voids at varying depths.
Synchronised solutions To achieve the positional accuracy required for LDI and PCB stencil production, advanced mechanical systems offering tight synchronisation of axis motions are essential. Gantry systems can provide precise positioning in three translational degrees of freedom, as well as the long travels and rapid speeds needed to meet the demands of modern PCB manufacturing. The ability to adjust laser power and pulse characteristics is also vital, requiring closed-loop communication between the motion controller and the laser. Fortunately, cutting-edge systems
that combine precise motion platforms with intelligent control systems, like those engineered by Physik Instrumente, are now available to ensure dynamic laser power adjustment and rapid, accurate positioning across the entire work envelope. Unfortunately, the high speeds afforded by these precision motion systems can sometimes increase the possibility of positional errors, due to the mechanical acceleration limits of the hardware. This is especially prevalent when making rapid changes in direction, during the processing tight corners, for example. Until recently, the only way to account for this was to either slow the entire process down, negatively affecting operational efficiency, or rely on an operator to manually reduce the speed when required. The latter not only introduces the possibility of human error and variability between operators, but also prevents the process from being fully automated. The development of advanced motion controllers offering ‘look ahead’ intelligence, such as the ACS-based A-824 and G-900 with EtherCAT connectivity from Physik Instrumente (PI), has changed the game completely, anticipating challenging features ahead of time and automatically
reducing speeds where errors may exceed specifications. Another method to avoid sudden changes in direction during the processing of tight corners is a technique known as ‘sky writing’. This technique strategically turns off the laser while adding smooth loops of extra movement, avoiding the rapid accelerations associated with directly tracing out a right-angled corner. The laser is then turned back on once it re- joins the desired processing path.
Keeping up with demand Maximum operational efficiency in PCB production can only be realised through complete automation, combining specialised positioning hardware with intelligent control systems for maximum throughput without processing errors. The development of advanced motion controllers capable of simultaneously optimising laser power and the processing path, using techniques like look ahead intelligence and sky writing, gives manufacturers the ability to create the increasingly intricate features required for modern boards while ensuring that, as electronic devices continue to shrink, profits do not follow suit.
FEBRUARY 2024 | ELECTRONICS FOR ENGINEERS
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