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98 I-CONNECT007 MAGAZINE I APRIL 2026 Mechanism: This is an almost purely thermal process. The pulse is long enough to vibrate the molecules of the dielectric (resin/glass) until they reach their boiling point and vaporize. Result: High volume removal. It is the fastest way to drill a via, but because the pulse is long, heat has time to spread. This creates a heat-affected zone (HAZ) and requires a copper "stop" layer be- cause the laser cannot easily ablate copper. 2. Nanosecond Lasers (10 -9 s): The Thermal Process Nanosecond pulses are the traditional solid-state workhorse of the industry. Mechanism: Photothermal. The laser heats the material until it reaches its boiling point, at which point it evaporates. Result: Because the pulse is relatively long in molecular terms, heat spreads into the surround- ing resin and glass. This creates a HAZ, which can lead to charring or carbonization on the sidewalls. 3. Picosecond Lasers (10 -12 s): The Cold Ablation Picosecond pulses are significantly faster; they are so fast that they change the physics of the cut. Mechanism: Mostly photolytic. The pulse dura- tion is shorter than the "thermalization time" of the material. The laser breaks molecular bonds before heat can travel to the next molecule. Result: Often called cold ablation. The edges are incredibly clean, there is almost no HAZ, and car- bonization is nearly eliminated. 4. Femtosecond Lasers (10 -15 s): The Ultrafast Frontier Femtosecond pulses represent the current peak of industrial laser technology. Mechanism: Non-linear absorption. Energy is delivered so instantaneously that even materials normally transparent to light are forced to absorb the energy and vaporize. Result: Perfection. Precision is at the molecular level, allowing for features so small and clean that they are difficult to see even under a high-pow- ered microscope. In current PCB manufacturing, CO 2 and UV-nano remain the industry standards for high-volume production. However, as designs push toward the miniaturization of features and the use of sensitive materials, picosecond (pico) technology is increas- ingly adopted to achieve cold ablation results. While femtosecond lasers represent the pinnacle of precision, they remain a rare case in the PCB industry, reserved for highly specialized R&D or ultra-high-end semiconductor packaging. Which Wavelength Should I Choose? While the terms microsecond, nanosecond, or picosecond describe the pulse duration, the color Figure 1: Comparison of long pulse and short pulse lasers. D R I V I N G I N N OVAT I O N