Multi-layer PCBA processing involves manufacturing printed circuit boards with 4 or more conductive layers (separated by insulating substrates) and assembling components on these boards. This technology addresses the demand for compact, high-density PCBs in modern electronics—allowing more components, traces, and vias to be packed into a smaller space while improving signal integrity, reducing crosstalk, and enhancing thermal management.

　　The core of multi-layer PCBA processing lies in layer fabrication and lamination—a precise, multi-step process. First, individual core layers (typically double-sided PCBs with copper traces) are fabricated using standard etching techniques. Each layer is coated with a prepreg (a resin-impregnated fiberglass sheet) that acts as an adhesive and insulator. The layers are then stacked in a predetermined order (e.g., signal layers, power layers, ground layers) and pressed together under high temperature (170–190°C) and pressure (200–300 psi) in a vacuum laminator. This bonds the layers into a single, rigid multi-layer PCB.

　　After lamination, drilling and plating create electrical connections between layers. Through-holes (connecting all layers) or blind/buried vias (connecting specific layers only) are drilled using laser or mechanical drills, then plated with copper to form conductive paths. For high-density PCBs (e.g., 12-layer boards for smartphones), microvias (diameter <0.15mm) are used to save space.

　　Component assembly for multi-layer PCBs follows SMT or mixed SMT/DIP processes, but with additional considerations:

　　Thermal management: Multi-layer boards often include dedicated ground or power planes that act as heat sinks, requiring careful component placement to avoid overheating.

　　Signal integrity: Traces on inner layers are shielded from external interference, but layer stacking must be optimized (e.g., placing signal layers between power and ground planes) to minimize crosstalk.

　　Testing: Automated optical inspection (AOI) and X-ray inspection are essential to detect defects in inner layers or hidden vias, while in-circuit testing (ICT) verifies electrical connections across all layers.

　　Multi-layer PCBA processing is widely used in electronics requiring high density and performance: smartphones (6–8 layer PCBs), laptops (8–12 layer PCBs), medical imaging equipment (12–16 layer PCBs), and aerospace electronics (16–24 layer PCBs). While it is more expensive than single or double-layer PCBs (costs increase by 50–100% for each additional 4 layers), multi-layer technology enables the miniaturization and functionality of modern electronic devices.