Bring 3 A from the source header to the load with a one-way drop at or under 45 mV, and heatsink the exposed pad.
How PCBGrade measures this
Board 90 × 40 mm, two layers. J1 pin 1 and J2 pin 1 are 12 V. J1 pin 2, J2 pin 2, and U1’s exposed pad are GND. All three parts are locked. U1 is TF-HEAT1 and dissipates 1 W into that pad. This is not a temperature or airflow result. Copper is 35 µm and ρ = 1.724×10⁻⁸ Ω·m. One-way resistance is measured on the 12 V net only, from J1 pin 1 to J2 pin 1. The return path is not added. When a trace path exists, only those traces and the vias on that path count. A parallel pour is ignored, so a pour can only make the estimate higher than the copper you actually drew. With no trace, an axis-aligned GND or 12 V rectangle that contains both pad centres is used instead. R = ρ·L/(w·t). The limit is R ≤ 0.015 Ω (40). At 3 A that is Vdrop = I·R ≤ 0.045 V, printed from the same R. The straight run is 62 mm. Routing length on that same path is ≤ 70 mm (10). Extra width is not penalised. THERMAL is x 28–52 mm, y 22–39 mm. F.Cu GND pour inside that rectangle, overlapping the exposed pad, must be ≥ 250 mm² after the pad’s 3 × 3 mm box is removed (15). The box is the pad’s bounding square, 9 mm², not a circle. At least 6 GND vias inside THERMAL, each through from F.Cu to B.Cu, drill ≥ 0.30 mm, pad ≥ 0.60 mm, the whole pad inside the rectangle, centres ≥ 0.60 mm apart, and a B.Cu GND pour present (15). Vias in the exposed pad count. Two GND vias closer than the DRC clearance are still the same net, so that spacing is this rule and not a clearance error. A via that misses any of those checks is not counted. The editor’s via is 0.60 / 0.30 mm, which meets the size limits. DRC is clearance 0.20 mm, width 0.25 mm, copper-to-edge 0.50 mm, via pad 0.60 mm, and drill 0.30 mm (10), plus connectivity (10). A thermal miss caps the score at 69, so a board with no heatsink work cannot pass on the copper alone. An open or shorted net caps the score at 60. Overlapping F.Cu GND pours are merged before the pad box is removed, so drawing the same copper twice does not raise the area. A pour that is not a rectangle is clipped to THERMAL and measured by that polygon, not by its bounding box. The pad box is removed only where it overlaps the polygon. A via that misses the drill, the pad size, the spacing, or the rectangle is left out of the count and does not fail the vias that pass. A via is on GND only when a trace or a pad of that net touches it. The pour is not filled, so a via that only sits in the pour is not counted.
- resistance/drop · 40 pts
- thermal geometry · 30 pts
- connectivity/DRC · 20 pts
- routing/copper efficiency · 10 pts
- Cap 69: A missing pour or too few valid thermal vias caps the score at 69.
- Cap 60: An open or shorted net caps the score at 60.
- Cap 69: Copper outside the outline cannot pass, and neither can a short between nets.