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32 PCB007 MAGAZINE I JUNE 2019 are important. The traditional fabrication pro- cess is subtractive where you etch in, resulting in an interconnect with a trapezoidal geometry. However, it is difficult and inaccurate to create a microtrace that is less than roughly 88 µm (0.0035 inches) with a trapezoidal geometry. The definition becomes imperative and should have well-defined, squared edges. This is ac- complished using some additive or semi-addi- tive methods. Some of the dry-film photoresist materials are used for that, and we're going to see that become more and more prevalent as people must use microtraces and microfea- tures. Ormet's sintering paste is one of the best innovations for any-layer HDI vias along with innovations with DuPont's conductive inks, which will help define the printed electronics needs that are now happening. Johnson: That's very comprehensive, Mike. Is there anything else you'd like to mention? Creeden: There's always something else to con- sider. The inquisitive mind of a design engi- neer is always trying to look and consider ev- erything, and that's where diligence pays off. It's a relentless profession where the pursuit of excellence is what makes us move forward. And ensuring your materials are appropriate for your circuit is no longer a thing of the fu- ture. It's our present challenge, and we should make it our success story. Johnson: Thank you, Mike. Creeden: Thank you, Nolan. I appreciate this opportunity to serve. PCB007 Compared with lithium-ion batteries, lithium-sulphur batteries offer several advantages, including a theoreti- cal energy density of approximately 1,000–1,500 Wh/kg compared to lithium-ion batteries' 350 Wh/kg. The problem with lithium-sulphur batteries so far has been their instability, and consequently, their low cycle life. But the new prototype from Chalmers researchers demonstrated an 85% capacity retention after 350 cy- cles. The new design avoids the two main problems with the degradation of lithium-sulphur batteries—one, that the sulphur dissolves into the electrolyte and is lost, and two, a "shuttling effect" where sulphur molecules migrate from the cathode to the anode. In this de- sign, these undesirable issues can be dras- tically reduced. The researchers note that there is still a long journey to go before the technology can achieve full market potential. New man- ufacturing processes will need to be devel- oped to make them commercially viable. The research was published in the Jour- nal of Power Sources. (Source: Chalmers University of Technology) Researchers at Chalmers University of Technology in Sweden recently unveiled a promising breakthrough for lithium-sulphur batteries, using a catholyte with the help of a graphene sponge. The researchers' novel idea is a porous, sponge-like aerogel made of reduced graphene oxide that acts as a free-standing electrode in the battery cell and allows for better and higher utilisation of sulphur. They previously experimented with combining the cathode and electrolyte into one liquid—a "catholyte." The concept can help save weight in the battery as well as offer faster charging and better power capabilities. Graphene Sponge Helps Lithium-sulphur Batteries Reach New Potential

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