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Figure 6: Safelight imaging area.
The develop-etch-strip lines were equipped with digital pressure sensors and flow meters, enabling the ultimate in accurate setting and monitoring of process parameters for consistency and reproducibility. Etching technology had been developed to the highest level, with copper thickness, copper line profile and surface roughness measured continuously over the whole width of the panel. These parameters were particularly relevant in automotive medium- and long-range radar applications. At the upper end of the thickness scale, it was possible to etch 400-micron copper at a line speed of 1.6 metres per minute. At the lower end, for applications such as modified semi-additive technology, it was more cost-effective to produce 5-micron copper by differential etching down from 12 microns than to buy it in as ultra-thin copper-clad. A cupric chloride etchant was used, on a closed loop recycling system with copper recovery, and all the process chemistry was managed on lean principles with the minimisation of waste and a high level of environmental responsibility.
Figure 7: Develop-etch-strip lines.
Figure 8: Differential etching line.
Figure 9: Robot AGV takes etched panels for inspection.
After automated optical inspection, verification and, where necessary, automated optical repair, the etched innerlayer panels proceeded through surface preparation and bonding treatment to the lay-up area, where there was the option of pinned or pin-less tooling. The pin-less optical registration system had been refined and optimised in cooperation with the equipment supplier to achieve a layer-to-layer registration accuracy of ± 5 microns, and a proprietary self-learning software solution enabled the accuracy to be continuously measured and refined for any particular design.
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