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78 DESIGN007 MAGAZINE I NOVEMBER 2021 als to avoid uninten- tionally, but mistak- enly, creating designs that were effectively unmanufacturable. It was also important to understand the con- sequences of speci- fying custom design features and selective finishes on cost-effective manufacture. Johnson enquired whether there was an easy way of avoiding misunderstanding, in response to which Bushie re-emphasised the importance of involving the fabricator as early as possible at the design stage, for expert guid- ance on materials, constructions and special features. He illustrated and discussed many examples of details to be considered, with an impressive air of calm professional experience and capability that instilled confidence in his wisdom without over-dramatising the poten- tial pitfalls. Johnson commented that copper surface roughness had become a much-discussed topic in the context of high-frequency performance and asked Bushie for a view. at was a more complex subject than could be explained in- depth within the timeframe of this interview but put simply, roughness caused small phase changes in signals travelling in or near the sur- face, resulting in increased losses. Bushie dis- cussed the attributes of some of the smoother- finish copper foils now available, and made the point that choice of foil was yet another element to be taken into consideration when specifying the material stack-up. Fortunately, RF designers had become increasingly aware of foil effects on edge-coupled and broadside- coupled features. Vardya reminded viewers of the amount of detail information available in the numerous webinars that ASC had published and were freely available on their website. He summed up by saying that if a designer took nothing else away from this discussion, it was the principle of approaching a PCB fabricator as early as possible in the design phase of a complex circuit board. Doing so could add a lot of value and potentially save significant time and expense when presenting the design for manufacture. ASC has accumulated an abundance of experi- ence over many years of assisting designers to understand the realities of PCB materials and processes and the benefits of effective design for manufacture. He gave his assurance that any discussion held with ASC would be in commercial confidence. is RealTime with... video was a valuable reminder of the multiplicity of factors to be taken into consideration when designing PCBs for RF and microwave applications, and the generosity of American Standard Circuits in sharing their knowledge and experience is to be commended. I was particularly impressed and reassured by John Bushie's relaxed and unpretentious presentation style. Twenty minutes well spent! DESIGN007 Visit I-007eBooks to download your copies of American Standard Circuits' micro eBooks today: The Printed Circuit Designer's Guide to… Fundamentals of RF/ Microwave PCBs The Printed Circuit Designer's Guide to... Flex and Rigid-Flex Fundamentals The Printed Circuit Designer's Guide to … Thermal Management: A Fabricator's Perspective Pete Starkey is an I-Connect007 technical editor. John Bushie Anaya Vardya

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