“ECN #442: Due to EMI issue on v3, inner2 ground plane has a cutout under U5. For v4, removed cutout. Ground and power planes now overlap in region D-17. Ensure sufficient dielectric. — L.C.”
“Show me the boardview again,” Maya said, leaning over Dev’s monitor. nb8511-pcb-mb-v4 boardview
Dev stared. “You can’t overlap power and ground planes. That’s a capacitor the size of the whole board. It would oscillate like crazy.” “ECN #442: Due to EMI issue on v3,
“Overlap,” Maya whispered.
The fix was insane but simple: drill a tiny hole through the overlapping region to break the capacitive coupling, then backfill with non-conductive epoxy. It took three hours of microsurgery under a stereo microscope. When they powered up the board again, C442 stayed cold. The 3.3V rail held steady. Ensure sufficient dielectric
“It’s like having a map of a city with no street names,” her lab partner, Dev, grumbled, rubbing his eyes. They’d been at it for fourteen hours. The boardview showed the physical location of every resistor, capacitor, and via on the four-layer PCB. But without the netlist—the logical connections—it was just a pretty picture of silkscreen and copper.