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60 The PCB Design Magazine • February 2014 also part of insertion loss. This is loss that is associated with the copper conductors and fin- ish. There is no perfect conductor, but copper is very good for conductivity. If another metal is added to the copper, the overall conductivity will typically decrease which causes more loss. The different finishes used in the PCB industry are typically lower in conductivity than copper and more loss occurs when some plated metal finish is added to the copper conductor. Also, the surface roughness of the copper conduc- tor can cause more loss with a rougher (high- profile) copper surface. Conductor losses are frequency-dependent due to skin depth, and at some frequencies, the conductor losses are minimal while other frequencies can be signifi- cant. Thermal management issues can be a con- cern when insertion loss causes the circuit to heat up when RF power is applied. A circuit with lower insertion loss will heat less with applied power. In the case of high-speed digital applica- tions, insertion loss will cause the digital pulse to decrease in amplitude and cause possible distortion. Having a circuit with low insertion loss will allow the digital signal to maintain the good integrity needed. There are many potential interactions be- tween PCB fabrication, circuit design and material properties which need to be under- stood to ensure the finished circuit will meet the needs of the end user. It is always recom- mended to consult the circuit material's man- ufacturer for new designs and applications to ensure the optimum material is used for the application. PCBDESIGN FAQ: MICRoWAVE PCB MATERIALS continues John Coonrod is a market development engineer for Rogers Corporation's Advance Circuit Materials Division. To contact Coonrod, click here. CliCk To View Video Interview What happens when the task of simulating thousands of jobs has grown so tedious that determin- ing solutions one by one would take years? how about sampling a few hundred cases and creat- ing models that will simulate millions of cases in seconds! SiSoft is forging successful Doe responsiveness modeling and has published a white paper to prove it. Design of Experiments: What's That? by Real Time with... PCBDesign007 lightning speed laminates

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