Laser Micro-Machining & Precision Stent CAM Prepress Guide

1. The Physics of Ultrafast Laser Ablation

In standard nanosecond lasers, laser energy heats the metal past its melting point and ejects it with assist gas, leaving a distinct Heat-Affected Zone (HAZ) and dross recast. Ultrafast femtosecond (10^-15 s) and picosecond (10^-12 s) pulses deposit energy faster than the thermal lattice relaxation time of the electrons, transforming solid matter directly into vapor plasma with zero heat conduction into adjacent stent struts.

2. Optical Fluence & Rayleigh Depth of Focus

Ablation efficiency is governed by the peak optical fluence F (Joules per square centimeter):

To cut precision tubes or foils cleanly without kerf taper, the material thickness should remain within the Rayleigh range (depth of focus) of the focusing objective.

3. Micro-Bridge Tab Retention Rules

Due to the high frequency acoustic shockwaves generated by pulsed laser ablation, unconstrained micro-features will vibrate and distort if parted completely in a single cut. CAM engineers insert sub-micron micro-bridge tabs:

• Tab Width: Typically 0.8x to 1.2x foil thickness (40–80 µm).
• Tab Release: Cut on the final pass at attenuated laser power or snapped during automated post-machining ultrasonic bath cleaning.