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66 DESIGN007 MAGAZINE I APRIL 2024 copper and non-copper areas. e difference in depth oen deems the silkscreen illegible. Designers should avoid silkscreen altogether. When that is not an option, be sure to relegate silkscreen to the top of copper features. While this does not affect board functionality it may be an issue for customers meticulous about aesthetics, which we have seen rise exponen- tially since the release of Steve Jobs' biography. Final Finish Since heavy copper PCBs are already more costly than their skinnier counterparts, a com- mon cost-saving habit is to specify SnPb or Pb- free HASL final finish. We encourage custom- ers to use either OSP or an immersion finish as these are applied chemically to the PCB sur- face. Conversely, HASL finishes involve coat- ing the PCBs with flux and then dipping them into a pot of molten solder. On the way out, we clear the holes of solder and create a flat sur- face by blowing at the panel with high pressure air knives. While this works well for standard designs, heavy copper PCBs oen heat sink the solderpot resulting in an uneven surface finish. HASL operators habitually re-dip these pan- els and create yet another thermal excursion. Multiple thermal shocks like this are harm- ful to thicker copper designs and can result in delamination or, at a minimum, a weakening of the overall package. Conclusion Heavy copper designs are a neat segment of the PCB market. A close working relation- ship between the designer and fabricator is an essential formula for success. Conversely, designing in a vacuum and ignoring the man- ufacturing pitfalls can lead to a path of failure and frustration. ere are numerous other technologies that could be considered heavy copper, particularly in the thermal management PCB realm. ese include E-coins, U-coins, via farms, and filled plated-shut vias that could serve as alternate solutions for high power needs. Regrettably, this article is not a fully comprehensive compi- lation of every possible design consideration. is is merely an opening salvo intended to launch you down the right path to producing these high-calorie PCBs. DESIGN007 Yash Sutariya is president of Saturn Electronics Corporation. New phased-array transmitter design overcomes common problems of CMOS technology in the 300 GHz band, as reported by scientists from Tokyo Tech. Today, most frequencies above the 250 GHz mark remain unallocated. However, high-frequency elec- tromagnetic waves become weaker at a fast pace when travelling through free space. Now, a research team led by Professor Kenichi Okada from Tokyo Institute of Technology (Tokyo Tech) and NTT Corporation have recently developed a 300 GHz-band transmitter that solves these issues through several key innovations. Their work will be presented in the 2024 IEEE International Solid-State Circuits Conference. The researchers tested their design through both simulations and experiments, obtaining very prom- ising results. Remarkably, the proposed transmitter achieved a data rate of 108 Gb/s in on-PCB probe measurements, which is substantially higher than other state-of-the-art 300 GHz-band transmitters. Moreover, the transmitter also displayed remark- able area efficiency compared to other CMOS-based designs alongside low power consumption, high- lighting its potential for miniaturized and power-con- strained applications. Some notable use cases are sixth-generation (6G) wireless communications, high- resolution terahertz sensors, and human body and cell monitoring. (Source: Tokyo Institute of Technology) Tapping Into the 300 GHz Band with an Innovative CMOS Transmitter