Definition

Aspect ratio is the ratio of hole depth (board thickness) to hole diameter. Higher aspect ratios make it more difficult to achieve uniform copper plating throughout the hole. Standard capability is 8:1 to 10:1 (e.g., 0.2mm hole in 1.6mm board = 8:1). Advanced processes can achieve 12:1 to 15:1. For micro-vias, aspect ratio is typically limited to 0.75:1 to 1:1 due to the laser drilling and plating limitations. Exceeding capability limits can cause barrel cracking and reliability failures.