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58 PCB007 MAGAZINE I JUNE 2020 The different finishes were deposited on a single end 50Ω transmission trace (250 mm in length and 0.52 mm in width). Insertion loss measuring equipment was VNA 2VA67 (Rhode and Schwartz). As shown in the graph and summarized in the table (Figure 2), the inser- tion loss of low nickel and nickel-free gold sur- face finishes show a significant improvement in insertion loss value as compared to thick (120–240 µin or 3–6 µm) nickel gold finishes. As the industry continues down the path of massive data transfer and miniaturization, the frequency of RF signal transmission will con- tinue to increase. As 10 and greater GHz RF frequencies are designed into PCBs, special al- lowance must be made to minimize transmis- sion loss due to copper roughness and type of surface finish used. PCB007 Reference 1. S. Hinaga, A. Rakov, M.Y. Koledintseva, & J.L. James, "Insertion Loss Reduction Through Non-Roughening In- ner Layer Surface Treatments," Proceedings of IPC APEX EXPO, March 2014. George Milad is the national accounts manager for technology at Uyemura. To read past columns or contact Milad, click here. tery are permanently altered by the ions passing from one terminal of the battery to the other. In a lithium-ion battery, one electrode is made of graph- ite, and the other of lithium compounds with transition metals, such as iron, cobalt, or nickel. At the lithium elec- trode, lithium atoms give up electrons, swim through the battery fluid (electrolyte), and wait at the other electrode. The electrons flow out the battery, through the circuit, and into the second electrode, where they rejoin the lithium ions. When charged, the ions and electrons retrace their steps, and the battery can be used again. Charging cycles leaves ions at the graphite elec- trode, and the battery loses capacity over time. When a battery is "fast-charged," lithium ions start layering (plating) over the carbon electrode instead of transporting (inter- calating) into the material. Prolonged lithium plating can cause uncontrolled growth of dendrites, causing short-cir- cuiting and even fires. Das and team have been able to under- stand the microscopic changes that de- grade a battery's electrodes and develop physics-based models to predict them. These models can aid battery manufac- turers to reduce battery health diagnos- tics costs and make batteries safer for consumers. (Source: MIT News) Growing up in Kolkata, India, Supratim Das saw that a ready supply of electric power was a luxury his fam- ily didn't have. "I wanted to do something about it," Das says. He's been investigating what causes the batteries that power the world's mobile phones and electric cars to deteriorate over time. Lithium-ion batteries power most rechargeable devices today. Lithium has properties that make lithium-ion bat- teries portable and powerful. In principle, rechargeable batteries shouldn't expire. In practice, however, they can only be recharged a finite number of times before they lose their ability to hold a charge. An ordinary battery eventually stops working when the terminals of the bat- Lighting the Way to Better Battery Technology

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