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74 PCB007 MAGAZINE I MARCH 2018 water for rinsing after developing is not as ef- fective as hard water. It was decided that to improve the efficiency of post-developer rins- ing, the engineers added 200 ppm of calcium carbonate to the rinsing solution. This made a marked difference in the quality of the rinsing and the subsequent plating quality. In Figure 2, one can see the remaining cop- per that was not etched away. This illustrates that resist residue remained in the areas that should no longer have resist. The remaining residues—most likely from incomplete devel- opment—acted to prevent complete removal of the copper during the develop, etch, and strip (DES) process. Summary Based on the changes discussed above, the fabricator solved the mouse bite and pitting issues. However, one can see from this case study that there were several factors that con- tributed to the defects. From this study it is quite clear that most defects are not caused by just one process issue. It is usually a combi- nation of factors that must be vetted proper- ly. From there, the experienced troubleshoot- er can make corrections to the processes and eliminate loss of yield. PCB007 References "Pits and Mouse Bite Issues, Part 2," PCB007 Magazine, January 2018, p.90. Michael Carano is VP of technology and business development for RBP Chemical Technology. To reach Carano, or read past columns, click here. Figure 2: Copper remaining after etching; resist residues prevented the complete etching of the copper. Researchers from Electronics and Computer Sci- ence (ECS) at the University of Southampton will use bio- inspired algorithms and machine learning to develop fault-tolerant robotic swarms in a new scheme funded by the Engineering and Physical Sciences Research Council (EPSRC). Assistant Professor Dr. Danesh Tarapore from ECS's Agents, Interaction and Complexity research group will lead the New Investigator Award project that will create groups that can rapidly detect faults and adapt to environmental changes, paving the way for real-world applications such as the monitoring of pollutants in large bodies of water. The research will lead to the next generation of robot swarms, ca- pable of sustained operation for extend- Scientists Pave the Way for Resilient Robot Swarms ed periods of time without human intervention. "Robots are increasingly becoming an important part of our day-to-day lives, automating tasks like keeping our homes clean and packing parcels at large warehous- es," Danesh explains. "Our aging population and the need to substitute human workers in dangerous and repeti- tive tasks mean that new tasks are emerging on the hori- zon, such as automation in agriculture and environmental monitoring. This will require robots to do more and work in large-numbers as part of a swarm, act- ing over vast areas and efficiently per- forming their mission. EPSRC's New Investigator Award is a new scheme that supports researchers who have recently entered their first ac- ademic lectureship position.

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