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Design007-Dec2018

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62 DESIGN007 MAGAZINE I DECEMBER 2018 Semiconductor Die Placement Embedded semiconductor elements can be mounted onto the core substrate with the active surface in the faceup orientation or facedown. Facedown mounting is typically selected for a direct interface (flip-chip) to the core surface. The faceup orientation will be preferred if the semiconductor requires a more direct path to the backside of the die for thermal dissipation. Part 7 of this series will examine alterna- tive techniques for embedded semiconductor die placement and termination methodologies. DESIGN007 Vern Solberg is an independent technical consultant specializing in surface mount technology, microelectronics design, and manufacturing technology. To read past columns or contact Solberg, click here. street-edge quality of saw and laser singula- tion. Following singulation, the die elements are subject to physical inspection and electri- cal testing. Test and Reliability Screening Although wafer-level testing will sort out most defective die elements, testing and screening are commonly performed while the singulated elements remain on the tape frame carrier using a flying probe tester or dedicated test platform. Testing will ensure the semicon- ductor meets the manufacturer's quality and reliability specifications. The phrase "known good die" (KGD) designates bare die elements that could be relied upon to exhibit the same quality and reliability as the equivalent single- chip packaged device. Meanwhile, "known quality die" (KQD) is based on general yield expectations and does not always reflect defect levels or early failure rates. Materials chemist Freddy Kleitz from the Faculty of Chemistry of the University of Vienna and international scientists have developed a new nanostructured anode material for lithium ion batteries, which extends the capacity and cycle life of the batteries. Based on a meso- porous mixed metal oxide in combination with graphene, the material could provide a new approach how to make better use of batteries in large devices such as electric or hybrid vehicles. Nanostructured lithium ion battery materials could provide a good solution," says Kleitz of the Department of Inorganic Chemistry—Functional Materials of the Univer- sity of Vienna, who together with Claudio Gerbaldi, leader of the Group for Applied Materials and Electrochemistry at the Politecnico di Torino, Italy, is the study's main author. As a first step, based on a newly designed cook- ing procedure, the researchers were able to mix copper and nickel homogenously and under controlled manner to achieve the mixed metal. Based on nanocasting—a method to produce mesoporous materials—they cre- ated structured nanoporous mixed metal oxide particles, which due to their extensive network of pores have a very high active reaction area for the exchange with lithium ion from the battery's electrolyte. The scientists then applied a spray drying procedure to wrap the mixed metal oxide particles tightly with thin gra- phene layers. "Compared to existing approaches, our innovative engineering strategy for the new high-performing and long-lasting anode material is simple and efficient. It is a water- based process and therefore environmen- tally friendly and ready to be applied to industrial level," the study authors conclude. (Source: University of Vienna) Pushing Lithium Ion Batteries to the Next Performance Level

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