Microvias are the core interconnection structure of HDI PCBs, and their machining accuracy, wall quality, and dimensional stability directly determine the wiring density and service reliability of high-density circuits. Laser drilling and mechanical drilling are two mainstream microvia machining technologies, with essential differences in processing principles, applicable aperture range, machining precision, and substrate adaptability. With the upgrading of HDI towards ultra-fine pitch and high layer count, the performance gap between the two processes in microvia manufacturing becomes increasingly prominent, forming distinct application boundaries in high-end and conventional PCB production.

Mechanical drilling adopts high-speed rotating carbide drill bits to physically cut PCB substrates, which is a traditional contact processing technology. Its applicable microvia aperture is generally limited to 150μm or above, and it is difficult to stably process ultra-fine holes below 100μm. Affected by bit vibration, mechanical extrusion, and tool wear, mechanical drilling has relatively low dimensional accuracy with a tolerance of ±10–15μm, and the hole wall is prone to burrs, resin cracks, and copper foil delamination. In terms of production cost, mechanical drilling has low unit tool cost and is suitable for large-aperture, low-density microvia batch processing. However, the drill bit has a short service life and needs frequent replacement, resulting in high maintenance costs for ultra-fine hole processing, and it is easy to cause mechanical stress damage to thin substrates and flexible boards.

Laser drilling is a non-contact ablation processing technology, mainly using UV laser and CO₂ laser for microvia manufacturing. UV laser is suitable for precision processing of copper and dielectric layers, capable of stably drilling ultra-fine microvias of 25–100μm with a machining tolerance of ±5μm, far exceeding mechanical drilling in precision. CO₂ laser is mainly used for rapid ablation of dielectric materials, featuring high processing efficiency. The non-contact processing mode completely eliminates mechanical vibration and extrusion stress, avoiding substrate delamination, crack damage, and hole wall burrs. The processed microvia has smooth and uniform hole walls, no residual resin dirt, and excellent electroplating adhesion, which significantly improves the reliability of via hole interconnection.

In terms of processing efficiency and scenario adaptability, laser drilling has absolute advantages in high-end HDI production. Modern high-speed laser drilling equipment can process up to 10,000 vias per second, supporting batch processing of dense microvias and stacked vias, and is fully compatible with thin dielectric substrates (25–100μm) and flexible PCB materials. Mechanical drilling is only applicable to low-density HDI boards with large-aperture microvias and thick substrates. For high-precision scenarios such as via-in-pad and stacked microvias required by high-end smartphones and automotive HDI PCBs, laser drilling is the only feasible process. In summary, mechanical drilling is cost-effective for conventional large-size microvia processing, while laser drilling is the core process for ultra-fine, high-precision, high-density PCB microvia manufacturing.