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22 DESIGN007 MAGAZINE I MARCH 2020 steps need to be taken to protect the copper at assembly and prevent oxidation, but all of the nets should be defined and operational at this point. We have etched our way to a functional electrical part! Design Tips for a Better Etching Process As with the copper plating portion of manu- facturing, some design decisions can have an impact on the manufacturability of the PCB at the etch process. Etching is an exercise in getting fresh etchant chemistry in contact with the copper and sweeping away the byproducts as quickly as possible. Isolating critical traces on your de- sign without much copper around it can lead to over-etching (i.e., etching more than the traces that are surrounded by copper) of these traces. Critical traces embedded in copper pour with limited space can have the opposite prob- lem. Replenishing the etchant solution be- comes more challenging. These traces can ex- hibit mild under-etching. For every half-ounce of copper, a good de- sign has 8–10 mils of space between the trace and the embedded plane. Adding copper thiev- ing around isolated traces helps to maintain the intent of the trace and provides a bit more space, keeping all of the features etched close to their nominal values. DESIGN007 Bob Tise is an engineer at Sunstone Circuits, and Matt Stevenson is the VP of sales and marketing at Sunstone Circuits. To read past columns or contact Tise and Ste- venson, click here. Bob Tise Matt Stevenson Researchers are investigating how to make electronic components from eco-friendly, biodegradable materials to help address a growing public health and environmen- tal problem: around 50 million tonnes of electronic waste are produced every year. Less than 20% of the e-waste we produce is formally recycled. Much of the rest ends up in landfills, contaminat- ing soil and groundwater, or is informally recycled, expos- ing workers to hazardous substances like mercury, lead and cadmium. Improper e-waste management also leads to a significant loss of scarce and valuable raw materials, like gold, platinum and cobalt. For example, there is wide- spread interest in develop- ing organic field effect transis- tors (FET), which use an electric field to control the flow of elec- tric current and could be used in sensors and flexible flat-panel displays. Researchers are especially keen to find biocomposite mate- rials that work well in resistive random access memory (RRAM) devices. These devices have non-volatile memo- ry: they can continue to store data even after the pow- er switch is turned off. Biocomposite materials are used for the insulating layer sandwiched between two conduc- tive layers. Researchers have experimented with dispers- ing different types of nanoparticles and quantum dots within natural materials, such as silk, gelatin and chito- san, to improve electron transfer. An RRAM made with ce- tyltrimethylammonium-treated DNA embedded with silver nanoparticles has also shown excellent performance. "We believe that function- al devices made with these fas- cinating materials will become promising candidates for com- mercial applications in the near future with the development of materials science and advanc- es in device manufacturing and optimization technology," the re- searchers conclude. (Source: ACN Newswire) Bringing the Green Revolution to Electronics

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