What is a backdrill?

Who cares about it and why should I care about it?

What decision should I take?

Backdrilling is a technique used by high speed PCB designers to remove the unused part of a plated-through-hole (vias) so the via acts less like an antenna. Stubs can cause reflections and impedance problems in high speed digital PCB design and backdrilling is one method to control them. 

General Characteristics

• Mostly performed on rigid PCBs with 8 or more layers

• Board thickness is over 2.5mm

• Minimum hold size is 0.3mm

• Backdrill is 0.2mm larger than the vias

• Tolerance of backdrill depth is +/-0.05MM

Advantages:

• Less signal attenuation with improved impedance matching

• Increased channel bandwidth

• Increased data rates

• Reduced EMI/EMC radiation

• Reduced excitation of resonance modes

• Reduced via-to-via crosstalk

• Reduced deterministic jitter

• Lower bit error rate (BER)