HDI (High-Density Interconnect) boards and ordinary multilayer boards are two mainstream types of PCBs, differing significantly in manufacturing processes, precision, and performance, which determine their applicability in different electronic products. Ordinary multilayer boards are mature in technology and low in cost, suitable for general electronic equipment, while HDI boards are designed for high-density, high-frequency scenarios, with more complex processes and higher precision requirements.

The most obvious process difference lies in wiring density and drilling technology. Ordinary multilayer boards adopt traditional mechanical drilling, with a minimum line width/line spacing (L/S) of 75/75μm (IPC-2221 standard) and a minimum hole diameter of 0.3mm due to drill strength limitations. They use a one-time lamination process, with through vias as the main interlayer connection method, which forms "via stubs" that occupy 30% or more of the wiring space. In contrast, HDI boards use laser direct imaging (LDI) technology with ultra-thin dry film (5μm thickness), achieving an L/S of 30/30μm or even 20/20μm (IPC-2226 Class 6 standard). Laser drilling is used to process microvias—CO₂ laser for 0.075mm blind vias and UV laser for 0.05mm microblind vias—avoiding via stubs and significantly improving wiring density.

Another key difference is the lamination and interlayer connection process. Ordinary multilayer boards are laminated all at once, with limited flexibility in interlayer connection. HDI boards adopt a build-up process (layer-by-layer lamination + laser drilling), enabling direct interconnection between any layers and forming a "via-stub-free" structure. This process reduces interlayer connection space by 70% and improves signal integrity, making it suitable for 0.4mm Pitch BGA packaging. In terms of material and precision control, ordinary multilayer boards mainly use FR-4 substrates with relatively precision (exposure alignment tolerance ±50μm), while HDI boards use low-loss substrates (such as PTFE and LCP) for high-frequency scenarios and achieve high-precision control through digital management—laser drilling positioning accuracy is ±1.5μm, and copper thickness uniformity deviation is less than 3%.

Reliability and cost also differ between the two. HDI boards use electroplating hole-filling technology, reducing the aspect ratio of vias to ≤0.5, which lowers shear stress on the hole wall copper layer during thermal cycling and reduces solder joint failure rate to less than 0.1%. However, HDI boards have more complex processes, higher material costs, and longer production cycles, while ordinary multilayer boards have lower costs and higher production efficiency, making them the first choice for non-high-density, non-high-frequency applications.