The NC (Numerical Control) Drill file defines hole locations, tool numbers and finished hole sizes (X&Y coordinates). For Prototype(Engineering Level = Limited Review on quote form) PCBs, all holes will be treated like plated through holes. The following two design features could create a difference between the design file and the received PCBs:
- Non-plated holes in the design file will finish with a larger diameter (+/- 0.005") than intended.
- Non-plated holes in the design file cannot be guaranteed to remain unplated (even a hole that has no external pad).
For Prototype boards (Engineering Level = Limited Review on the quote form) PCBs: Specified holes < 0.018" will be treated as vias, and drilled approximately the same size as specified. The smallest available bit is 0.0135". If your drill is smaller, it will be increased to this size.
Hole sizes > 0.250" will finish as non-plated for Prototype (Engineering Level = No Engineering Limited Review on quote form) PCBs. Holes > 0.250" are considered a cut-out as they require different processing.