PCB design rule check keeps failing — annular ring and acid trap errors I don't understand

Both of these are really common first-board errors, and neither is hard to fix once you know what's actually being measured.

Annular ring is the copper ring left around the drilled hole after drilling — basically pad diameter minus drill diameter, divided by two. If you bumped up the via size but the drill size went up by the same amount, the annular ring didn't actually change, which is probably why it just moved to different vias instead of clearing. Fix it by increasing pad diameter relative to drill size, not just scaling both together. Most EDA tools have a via "style" or preset you can edit directly instead of dragging pad and drill separately and hoping they land right.

Acid trap (also called an "acute angle" or "etch trap") is a sharp, narrow-angle trace corner — typically under 90°, often where two traces meet a pad at an awkward angle. During etching, the acid used to remove unwanted copper can pool in that narrow angle longer than the surrounding area and over-etch it, which can thin or break the trace. Fix is just geometric: round the corner, or redraw the junction so traces meet at 90°+ instead of an acute angle. Most tools have a "no acid traps" or similar DRC rule that'll highlight exactly where to fix it — worth turning that on permanently, not just running it once.

Once you've fixed both, re-run DRC against your actual fab house's minimum annular ring and trace/space numbers, not just the tool's defaults — see our breakdown of what PCB design rules and DRC actually check for why the fab house's real numbers matter more than generic defaults.