Issue link: https://iconnect007.uberflip.com/i/1520701
MAY 2024 I DESIGN007 MAGAZINE 39 in the class, and depending on which glass type you use, it may vary significantly. From the Isola datasheet, we get a varia- tion in Dk from 3.6 (for the 106) to 4.2 (for the 7628). Also, the Df varies from 0.02 (for the 7628) to 0.03 (for the 106) at 5GHz. e dielectric constant of resin is less than that of the fiber. Increasing the resin content in the laminate reduces the effective Dk of the PCB. So, you should take an average of each class to hone them down. Figures 3 and 4 compare these variables. From these graphs, we can see that 370HR has a rather high Df and an average Dk. A better selection may be the EM-285 or EM-828, which both exhibit lower Dk and Df by comparison. Also, because EMC is a Chi- nese manufacturer, it will undoubtedly be of low cost. If you are looking for a flex material, then the Isola P96 has reasonable properties. Also, to further reduce costs and improve power integrity, expensive high-speed mate- rial should not be used between the planes. A standard FR-4 material has a higher dielectric constant (Dk), which increases capacitance of the planes, and has a higher dissipation factor (Df ), which dampens electromagnetic energy through the relatively high loss of the material. e materials planner allows designers to strike a balance between performance and production costs. You can set up a list of mate- rials from your preferred suppliers and then compare them directly to get the best material for your product. Key Points • Materials used for the fabrication of the multilayer PCBs absorb high frequencies and reduce edge rates and that loss in the transmission line. • It is the dielectric material between the copper signal and plane layers in the PCB that affects signal velocity. Figure 3: Dissipation factor of comparable dielectric materials. (Source: iCD Materials Planner)