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October 2015 • The PCB Design Magazine 55 solderability preservative (OSP) finish is typical- ly thought of as a temporary finish and it does not have a significant impact on the insertion loss when compared to the same circuit using bare copper. Another plated finish which showed no significant difference in insertion loss for this study was immersion silver. When considering the conductivity of raw silver it is actually one of the few plated finish metals which has higher conductivity than copper. However, the immer- sion silver process will deposit a very thin layer of silver on the copper conductor and due to skin depth the benefit of silver will not be real- ized except at higher frequencies. Still, it will not negatively impact insertion loss at the low- er frequencies. The other plated finishes considered were ENIG, ENIPIG and immersion tin. As stated be- fore, these losses are dependent on the thick- ness of the circuit and the study evaluated mi- crostrip transmission line circuits on a 5mil low-loss substrate to exaggerate the conductor effects of the added plated finish. In this study the circuits with the ENIG plated finish had the highest losses, then circuits using ENIPIG had less loss and the immersion tin circuits were lower. If more details from this study are desired, contact me and I'll be glad to provide an over- view of the study. PCBDESIGN John Coonrod is a senior market development engineer for rogers Corporation. To read past columns, or to reach Coonrod, click here. A new generation of digital devices that will protect consumers from cyber-attacks could be a step closer thanks to a grant of over £1 million from the engineering and Physical Sciences re- search Council (ePSrC) awarded to the university of Bristol for a research project to protect con- sumers' sensitive data. Digital devices, such as smart banking cards or smart phones, are widely used to store private and sensitive data about peoples' digital lives. however, securing these devices is a major task for the computing industry. The research project by the university's Cryp - tography research group hopes to address the is- sue of leakage-related at- tacks. information leakage via side channels is a widely recognised threat to cyber security. in particular small devices are known to leak infor - mation through physical channels, i.e., power consumption, electromagnetic radiation, and timing behaviour. in other words, the power con- sumed by mobile phones can reveal information about the data stored on the phone and attackers can steal this data by managing to capture the leakage. Dr. elisabeth Oswald, reader in Applied Cryp- tography in the Cryptography research group and who is leading the project, said: "Our previ- ous research has shown that in the case of small embedded devices, the nature of the leakages can be appropriately modelled using statistical tools. "This project's research hypothesis is that one can make meaningful statements about the leak- age behaviour of new implementations on such small devices by utilising a priori derived models." As the world gets even more digital, and attack- ers become more sophis- ticated, this is another im- portant step on the arms race between the good guys and the bad guys. How Leaky is Your Device? lightning speed laminates IMPACT OF FINAL PLATED FINISH ON PCB LOSS

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