PCB Laser Drilling Machines: The Core Technology for Micro-via Fabrication in High-Speed ​​AI Server PCBs

As the computing power of large-scale models continues to evolve, the adoption of GPU clusters, high-speed NVLink interconnects, and 800G/1.6T optical modules is driving a transition in AI server PCBs—moving from traditional multi-layer boards toward advanced High-Density Interconnect (HDI) and Any-Layer HDI (AL-HDI) architectures. PCB laser drilling machines have become indispensable core equipment in the manufacturing of PCBs for AI computing. They address critical industry challenges—such as high-density BGA escape routing, the creation of micro-vias (including blind and buried vias), and the processing of ultra-low-loss materials—thereby ensuring the stable transmission of ultra-high-speed signals, such as 112G PAM4 and PCIe 6.0.

Traditional server PCBs typically consist of 14–20 layers, utilize standard FR-4 laminates, and rely on mechanical drilling for through-hole fabrication. In contrast, AI server computing boards, UBB (Universal Baseboard) interconnect boards, and switch boards often reach 20–30 layers. High-end platforms may employ up to 8-stage HDI, utilizing advanced M7/M8/M9 series ultra-low-loss materials—characterized by extremely low dissipation factors (Df), high glass-fiber content, and high material hardness. With GPU and NVSwitch chips featuring thousands of BGA pins and pad pitches reduced to 0.65–0.8 mm, conventional mechanical drills cannot effectively create escape vias within such confined pad areas. Consequently, techniques like “via-in-pad,” blind/buried vias, and any-layer interconnects must be achieved through laser drilling.

Mechanical drilling is limited by the physical constraints of the drill bit; it struggles to consistently produce micro-vias smaller than 100 μm. Furthermore, mechanical bits suffer from rapid wear and high breakage rates. When processing high-speed M8/M9 materials, mechanical drilling often results in excessive hole-wall roughness and significant resin smearing. Because high-speed signals are extremely sensitive to the quality of the hole wall, any roughness can increase insertion loss, cause impedance discontinuities, and trigger signal reflections—ultimately leading to the closure of high-speed “eye diagrams.” This represents a primary bottleneck for production yields in AI server PCBs. Laser drilling is a non-contact machining process that utilizes a controllable laser spot to reliably produce micro-vias ranging from 50 to 150 μm. It supports various structures—such as blind vias, buried vias, stepped vias, and thermal vias—and serves as a foundational process for achieving high-density interconnects (HDI).

In current production lines for AI server PCBs, laser drilling primarily employs three technologies, each suited to specific process requirements:
CO₂ nanosecond lasers are a mature, high-efficiency solution, ideal for the rapid ablation of resin dielectric layers; they are the primary choice for mass-producing blind vias. However, as a thermal process, they can cause substrate carbonization, residual adhesive at the bottom of the via, and an extensive heat-affected zone (HAZ) when used on advanced, low-loss materials (such as M9-grade laminates), which can negatively impact high-speed electrical performance.
UV nanosecond lasers (355 nm) feature higher photon energy and superior “cold” ablation characteristics compared to CO₂ lasers. With a smaller laser spot and the ability to process copper foil and dielectric layers simultaneously, they offer an optimal balance between precision and mass-production efficiency—making them the most widely adopted solution for AI server HDI boards today.
Picosecond ultrafast lasers represent a next-generation technology. Their extremely short pulse duration enables true “cold” processing, where heat does not have time to diffuse into the surrounding material. This results in virtually no carbonization or recast layers, producing clean via walls with extremely low roughness. They are perfectly suited for M9+ grade materials and PCBs used in 1.6T optical modules, ensuring maximum signal integrity for data rates of 112G and beyond. While they represent the future upgrade path for high-end computing PCBs, they also entail higher equipment costs and more demanding process requirements.

In the actual manufacturing workflow for AI server PCBs, laser drilling is critical in several key areas:
First, micro-via escape routing in BGA (Ball Grid Array) regions and “Via-in-Pad” structures. Since a large number of pins beneath a GPU require interlayer connections within a confined space, laser-drilled blind vias can be placed directly within the pads. This eliminates the need for routing space outside the pads, significantly increasing routing density—a standard configuration for high-density computing boards.
Second, “Any-Layer” interconnect technology. Unlike the traditional 2+N+2 structure, Any-Layer HDI (High-Density Interconnect) technology utilizes laser-drilled blind vias to establish direct connections between any two layers. This minimizes signal via stubs, reduces high-speed signal loss, and supports long-distance interconnects for standards such as NVLink and PCIe 6.0.
Third, the fabrication of thermal via arrays for heat dissipation: Given the extremely high power consumption of AI chips, PCBs are densely populated with arrays of thermally conductive micro-vias. Laser drilling enables the high-density, uniform placement of these thermal vias, creating efficient heat-dissipation channels while simultaneously facilitating power plane connectivity—thereby balancing power integrity with thermal management.
Fourth, the processing of hybrid-laminated high-speed boards: AI-focused PCBs often employ a hybrid stack-up of high-speed materials with varying dielectric constants (Dk) and dissipation factors (Df). Because these materials possess distinct physical properties, laser drilling parameters can be fine-tuned to accommodate the composite structure—comprising resin, glass fiber, and copper foil—thereby mitigating the risks of delamination and cracking.

Naturally, laser drilling for AI-computing PCBs imposes more rigorous demands on equipment capabilities. First, alignment precision is critical; cumulative deviation following multi-layer lamination must be kept within ±25μm, necessitating high-precision CCD-based visual positioning to prevent blind via misalignment. Second, hole-shape consistency is essential—ensuring that tens of thousands of micro-vias across a single board maintain uniform diameters and depths, which keeps impedance fluctuations within a ±5% range. Third, mass-production stability is required, characterized by high repetition rates and high throughput to meet the large-volume orders for computing boards from major PCB manufacturers. Fourth, the process must integrate effectively with downstream operations—such as desmearing, electroplating, and back-drilling—to control via-wall roughness and ensure high yields during the subsequent electroplating phase.

As computing power continues to scale—driven by the adoption of 1.6T and 3.2T optical modules and next-generation high-speed interconnect standards—PCB micro-vias will become increasingly smaller, and requirements for lower material signal loss will grow more stringent. Consequently, the adoption of ultra-fast picosecond laser drilling is set to continue its upward trajectory. Meanwhile, domestic laser drilling equipment has seen rapid breakthroughs, gradually breaking the monopoly held by overseas manufacturers. Through continuous iteration in precision, stability, after-sales support, and process integration, this equipment enables domestic PCB manufacturers to deliver high-end boards for AI servers, thereby reducing costs within the computing hardware supply chain.

At the fundamental level, the competition in computing power is a competition in interconnect technology. Laser drilling machines for PCBs are no longer merely tools for creating holes; they have become critical equipment that determines the signal bandwidth, interconnect density, and maximum achievable yield of PCBs used in AI servers. From HDI (High-Density Interconnect) to Any-Layer, and from nanosecond to ultrafast picosecond processes, the ongoing evolution of laser drilling technology is fortifying the hardware interconnect foundation for increasingly large-scale, high-bandwidth AI computing clusters.