The Drill class is based on the smallest production drill size (TOOLSIZE) used to manufacture your board,.
This is not to be confused with the finished size hole size (ENDSIZE) that you have defined in your design/CAD system.
For more information on holes sizes and how to calculate the TOOLSIZE vs the ENDSIZE please refer to our PCB Design Guidelines – Drilled Holes page.
- The smallest of these values determines the pattern class.
- The Classification table shows the lower limit values of any given class.
- The Annular Ring values OAR and IAR in the Classification table are for plated holes (PTH).
- For connected non-plated (NPTH) holes we recommend a minimum annular ring of 0.30mm (300µm or 12mil).
- As NPTH holes have no plated barrel, a smaller annular ring may lift during soldering or break away even during normal operating conditions.
For more information please see our current Classification table on below.