RF Board Layout: Partitioning to Reduce Signal Coupling Radio boards are usually described as difficult, and most of the difficulty comes from signal coupling rather than from the active circuitry. A receiver that works on the bench can lose sensitivity once the transmitter beside it starts switching, not because any…

Special Processes in PCB Prototyping: Impedance, HDI and Hard Gold Most prototype boards are built with a standard process: drilled, plated, etched and finished. Some designs need more. Impedance-controlled nets, laser-drilled microvias, heavy copper layers and selective finishes all sit outside the basic flow, and each one changes what the…

PCBA Soldering Requirements for the PCB Design Soldering does not begin at the assembly house; it begins with the board design. Heat resistance, board shape, edge clearance, fiducial marks and panelization all have to be correct before the first board reaches the paste printer. When they are not, the line…

Transmission Line Types in High-Speed PCB Layout High-speed design is often described as if it starts at some magic clock frequency, but frequency is not what matters. What matters is whether the edge of the signal is fast enough and the trace long enough that the conductor behaves like a…

Component Tolerance and Reliability: Designing Away Overdrive Every board that leaves a design review carries some probability of being unreliable. The question is how large that probability is and whether it was measured or assumed. Engineers often design at the edge of a component rating and then rely on the…

Plasma Treatment in PCB Fabrication: Desmear and Surface Activation Plasma treatment has moved from a specialty step to a routine one in PCB fabrication, because the surfaces that modern boards rely on, including polyimide, PTFE, filled resins and laser-drilled via walls, are chemically inert and do not wet reliably without…

12 PCB Layout Tips for Spacing, Decoupling and Teardrops Most layout problems that reach the assembly line were decided long before the file was released, and a handful of them account for the majority of rework. The PCB layout tips below cover the spacing, placement and pad decisions that affect…

Reading an Eye Diagram: Jitter, Noise, and Signal Quality Serial links are verified in the frequency domain with insertion loss, and in the time domain with an eye diagram. The second view is often more informative for layout work, because it shows the combined effect of every impairment in the…

Signal Routing Order: Prioritizing Nets on Dense Boards On a dense board, the order in which nets are routed matters as much as the routing itself. A clock line routed after the data bus has to detour around obstacles that the bus already occupied, and the resulting length, layer changes,…

PCB Design Release Checklist: DRC, DFM, Gerber, and CAM Review Routing the last net is not the end of a layout. The work that follows, often called post-processing, is what decides whether the design can be manufactured, tested, and assembled without intervention from the fabricator. Designs that skip this stage…