Annular Ring Tolerances a Volume Shop Actually Holds
Volume PCB shops hold a real-world minimum annular ring of 0.002 inches for Class 2 designs when artwork grants 0.005 inches of nominal land margin over tool size.
Finished Hole Size
Dimensional Boundary
Final internal diameter measurements of plated through-holes define physical clearance for component pin insertion and press-fit connections on completed circuit boards. The finished hole size specifies the final functional diameter remaining after mechanical drilling, copper electrodeposition, and solder mask processing steps. Manufacturing drawings designate nominal dimensions alongside specific upper and lower limits to guarantee mechanical fit during component assembly.
Standard PCB fabrication guidelines enforce specific drill bit oversizing calculations to account for total copper wall build-up during electroplating processes.
Plating Allowance
Mechanical drill selection requires adding combined copper and surface finish plating thicknesses onto target final internal dimensions. Drill size calculation subtracts target internal clearance from bit selection calculations, where electrolytic copper deposition typically adds between twenty-five and forty micrometers of copper plating wall thickness inside each hole. The finished hole size depends directly on copper plating distribution across panel surfaces, where higher current densities at panel edges increase wall plating thickness compared to board centers.
Solder mask entry into non-plugged holes or hot air solder leveling coatings can further alter final internal boundaries. Fabricators monitor bath chemistry, agitation rates, and current density settings to maintain precise plating deposition limits across entire manufacturing panels.
Quality Tolerance
Pin gauge testing verifies final hole dimensions against specified lower boundaries. Non-compliant hole dimensions cause mechanical insertion failure or insufficient solder capillary action during wave soldering.