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102 I-CONNECT007 MAGAZINE I APRIL 2026 and thin it down so the CO 2 can penetrate it (Figure 5). • Conformal mask: Copper is either pre-etched or the process is used on panels where no copper exists on the top layer (common in build-up processes) (Figure 6). When Should You Use Which Method? For prototyping and mid-size production: The Combi process is the gold standard for flexibility. It combines the high CO 2 productivity (which natu- rally stops at the target copper pad) with the preci- sion of UV or pico lasers (which can ablate copper and achieve smaller diameters). For mass production: Standard mass-market HDI often utilizes pure CO 2 configurations to maxi- mize throughput on pre-defined stack-ups. For ultra-small vias (<75 microns): CO 2 becomes physically limited at these sizes. One must switch to UV-nano, pico-green, or pico-UV. These sourc- es offer the precision needed for microvias but require careful energy management and process fine-tuning (Figure 8): • Risk of low energy: Not reaching the target copper pad (open circuit) • Risk of high energy: Penetrating through the target copper (damage to the inner layer) Cutting Applications Cutting performance is strictly material dependent. While any laser can cut, the best match ensures the cleanest edge and fastest speed: • Flex materials: UV nano is a classical solution or pico-green lasers for minimizing the HAZ/ carbonization and achieving the clean edge • PTFE: CO 2 or pico-green lasers have the best absorption threshold for PTFE • Ceramics: Pico is often the best match for brittle ceramic substrates Ablation (Depth Routing by Laser) Depth routing with a laser is used, for example, to reach contact pads on inner layers. • Constant thickness: If the layer to be re- moved is uniform and you need to protect the layer beneath, an ultra-short pulse laser is ideal for cold ablation. • Variable thickness: If the layer to be re- moved is dielectric and its thickness is incon- sistent, a CO 2 or IR laser is better, as these sources are reflective of copper, which acts as a natural safety stop. Figure 7: Blind vias drilled by Combi process. Figure 8: Good quality ultra-small blind vias drilled by ultra- short pulse lasers. Figure 9: Cutting of flex materials by ultra short pulse lasers. Figure 5: CO 2 copper direct pulsing process. Figure 6: CO 2 conformal mask process. D R I V I N G I N N OVAT I O N