Definition

A blind via connects an outer layer to one or more inner layers but does not go through the entire board thickness. Blind vias are created by controlled-depth drilling (mechanical or laser) or by drilling the sub-composite before lamination. They save routing space by allowing traces on inner layers beneath the via. Blind vias are more expensive than through-hole vias and require careful process control for depth accuracy. Common in HDI designs, they're designated by layer range (e.g., 1-2 for L1 to L2).