The 4-layer PCB (Printed Circuit Board) primarily consists of traces on the first and fourth layers, with the remaining layers serving other purposes such as ground and power. Issues arise in the design of 6 and 8-layer PCBs when additional auxiliary signal layers are introduced.
Each layer within a PCB serves a specific function: there are layers designated for power distribution, main signal transmission, auxiliary signal routing, and grounding. The general design principles for 6 and 8-layer PCBs are fundamentally similar.
The substrate of a PCB is typically composed of insulating materials that are both rigid and thermally conductive, ensuring minimal bending. The visible copper material seen on the surface is known as copper foil. Originally covering the entire board, portions of this foil are etched away during manufacturing, leaving behind a network of small circuits known as traces. These traces, also referred to as wires or wiring, establish connections between components on the PCB.
PCB boards are commonly colored green or brown, indicative of the solder mask which serves as an insulating protective layer. This layer shields the copper traces, preventing unintended soldering and ensuring electrical isolation.
Modern electronics, such as motherboards and graphics cards, extensively utilize multilayer PCBs, significantly expanding the available wiring area. Multilayer boards incorporate multiple single or double-sided PCBs, separated by insulating layers and fused together under pressure.
The term “layers” in PCBs refers to independent wiring layers, typically an even number that includes the outermost layers. A typical PCB structure ranges from 4 to 8 layers. While the number of layers can be visually discerned by examining a cross-section of the PCB, this is often impractical due to the required precision.
Instead, another method involves identifying the number of layers by observing via holes, which facilitate circuit connections within multilayer boards. Motherboards and display cards commonly utilize 4-layer PCBs, though variants with 6, 8, or even 10 layers also exist.
To determine the layer count of a PCB, observe the via holes: in 4-layer boards used for motherboards and display cards, via holes penetrate through the entire board from the first to the fourth layer, while in 6/8-layer boards, via holes may only appear on one side of the PCB.
A practical tip involves holding the PCB against a light source: if light shines through the via holes, indicating a 6/8-layer board; if not, it suggests a 4-layer board.
In conclusion, PCB stands for Printed Circuit Board, serving as a platform where conductive copper sheets are attached to an insulating substrate for creating circuit connections. PCBs can have circuits on one side (single-layer boards), both sides (double-sided boards), or multiple layers (multilayer boards), enabling complex electronic designs.
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This revision aims to clarify and organize the information while maintaining the original content’s technical details about PCBs.
