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68 The PCB Magazine • March 2014 by Julie Mouzon, Jérôme Petry and Laurence Vast circuit Foil luxemBourg Ultra-flat and almost No Profile eD-Copper Foils for High-speed Digital PCBs Ultra-flat and almost No Profile eD-Copper Foils for High-speed Digital PCBs F e a t u r e Abstract Copper surface roughness has become a sig- nificant factor that influences conductor loss in high-speed PCBs, particularly for signals above the 10 GHz range. Surface roughness is also an important consideration for etching very nar- row-pitch HDI applications. A new type of ED copper foil achieves a very smooth surface. Specific ultra-flat, zinc-free, ar- senic-free treatments with the highest density and uniformity are being applied on such to- pographies. This significant increase in active contact surface provides secure bond strength to a large number of proprietary low- and very low-loss resin systems. The reduction of the foil's treatment profile has essential advantag- es, since insertion loss is improved, therefore allowing new opportunities in the antenna and high-speed digital arena. Introduction As our planet becomes more interconnected, the infrastructure needed to capture and work with increasing amounts of data must respond and deliver faster results to more users than ever before. Studies foresee that global data center traffic will increase four-fold over the next years and six-fold for global cloud traffic [1] . In order to cope with an increased demand for improved resin systems with better electrical properties, many new dielectrics have already been introduced to the market, and many oth- ers are at their final development stage. BPA predicts for the period between 2012 and 2018 [2] (Table 1). Several publications have shown that with increasing frequencies, overall transmission losses will rise [3] . Microwave designers mini- mize conductor losses to achieve the required table 1: low-loss ccl surface in 1000 m 2 .