CONTRACT MANUFACTURING
Using precision motion to optimise PCB manufacturing
Point-to-point wiring of electronic circuits came to an end for all but the most specialised of devices, such as audiophile hi-fi systems, after the introduction of printed circuit boards (PCBs).
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ntricate copper traces, combined with predrilled mounting holes, enabled industrial-scale production of electronic hardware to drastically reduce the time taken to populate a board with components. Thanks to the later development of surface mount technology, thousands of components can now be assembled onto a single PCB, packing immense processing power into tiny envelopes. However, ever- shrinking board features are requiring higher levels of manufacturing precision, and the continued growth of the Internet of Things and advanced digital tools, like AI and machine learning, are putting manufacturers under pressure to ramp up production and remove productivity bottlenecks to keep pace with current and
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future market demand. This article looks at how the adoption of laser control and precision motion systems can address these challenges, giving fabricators the tools needed to optimise a range of PCB operations, including stencil manufacturing and laser direct imaging (LDI).
Laser operations
Before any components can be assembled onto a PCB, the copper traces that guide the flow of electricity through the circuit must be produced. Traditional methods rely on photo-tool films and UV light to project an inverted circuit image onto the photo- resist layer of the PCB, with subsequent chemical etching of the underlying copper leaving only the desired trace
FEBRUARY 2024 | ELECTRONICS FOR ENGINEERS
intact. However, this method is not only plagued with image distortion issues, but also struggles to resolve the tiny features being incorporated into many modern PCB designs. Consequently, laser direct imaging (LDI), a method which uses a CNC UV laser to expose areas of the photo-resist layer with great precision, has been adopted in most large-scale PCB manufacturing operations, allowing intricate features to be effortlessly etched into the board.
Precision laser techniques are also used in the production of stainless-steel PCB stencils, which house strategically placed openings that guide the solder paste deposition process. The geometry of these apertures will ultimately determine the position of the assembled components,
Umberto, Unsplash
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