A PFC copper busbar is not simply a wider trace. The spacing between switching nodes, magnetics, DC-link capacitors and the heat spreader changes loss, EMI and solder-joint stress at the same time, especially in 800V automotive power supplies.
Map the actual switching loop before sizing copper
Separate rectifier input, PFC inductor, switching bridge and DC-link output paths. High-frequency paths need a small loop and controlled parasitic inductance; lower-frequency paths need cross-section, terminal temperature rise and insulation margin. Put both requirements on the same layout review drawing.
Coordinate pads, cooling and EMI in the DFM review
SMT busbar pads should be designed with copper mass, paste venting, stencil zoning and underside support in mind. The gap to a heat sink must also allow for reflow distortion, thermal expansion and service-tool access.
- Record switching frequency, continuous and peak current and target rise
- Compare loop impedance, end voltage drop and thermal images
- Repeat checks after reflow, temperature cycling and vibration
RFQ inputs for a PFC busbar
Include the PCB land pattern, busbar thickness, plating, nozzle direction, insulation keep-outs, ambient range and packaging orientation. EMI and thermal limits must name the fixture and installation boundary so a lab result is not treated as a vehicle-wide rating.