Definition

Panel bars (also called rails, borders, or tooling strips) are the frame around the perimeter of a PCB panel that holds individual boards together during fabrication and assembly. They provide structural support to keep the array rigid through solder paste printing, pick-and-place, and reflow, preventing warping that causes registration issues. This is particularly important for thin boards or designs with large internal cutouts. The bars include space for tooling holes (fixturing), fiducial marks (machine vision alignment), and sometimes test coupons or impedance structures. Conveyor systems grip these rails to transport panels between SMT stations, making adequate width essential for reliable handling. Panel bars also create a buffer zone between edge-mounted components and conveyor mechanisms, allowing components closer to the board edge than on unpanelized boards. For wave or selective soldering, the rails provide mounting points for pallets and fixtures. Individual boards connect via breakaway tabs with mouse bites or V-score lines. Typical width is 5-15mm depending on requirements. Wider bars provide more rigidity and tooling space but reduce panel utilization.