1. **Visual inspection**
Considering that various layers in a PCB circuit board are closely integrated, it is generally not easy to determine the actual number of layers. However, with careful observation of the board’s faults, distinctions can still be made. On close inspection, one may notice one or more layers of white insulating material between the layers of the PCB circuit board. This serves as the insulating layer designed to prevent short circuit issues between the different layers of the PCB. Currently, multi-layer PCB circuit boards predominantly employ single or double-sided wiring boards, with an insulating layer placed between each layer, which are then pressed together. The term “number of layers” in the context of a PCB circuit board refers specifically to the presence of multiple independent wiring layers, and the visibility of the insulating layer between these layers becomes the most straightforward method for us to ascertain the number of layers in the PCB circuit board.
2. **Guide hole and blind hole alignment method**
The light guide hole method employs the “guide hole” present on the PCB circuit board to identify the number of layers contained within the board. The underlying principle is based on the fact that the circuit connections in multi-layer PCB circuit boards utilize via technology. To determine the number of layers in the PCB circuit board, we can make observations of the via holes to derive our conclusion.
1. On the most basic PCB circuit board (single-sided motherboard), the components are concentrated on one side, while the wiring is on the other. For a multi-layer board, holes must be drilled so component pins can pass through and connect layers via vias. This allows soldering of the component pins on the opposite side.
2. For example, in a 4-layer board, routing is done on the 1st and 4th layers (signal layers). The remaining layers serve as the ground and power layers. The purpose of placing the signal layers between the power and ground layers is to reduce interference and facilitate signal correction. If board guide holes are visible on the front but not on the back of the PCB, it indicates a 6/8-layer board. If guide holes are visible on both sides, it is likely a 4-layer board.
3. Currently, many manufacturers use an alternative routing method, incorporating buried and blind vias. Blind vias connect internal layers to the surface without going through the entire board, while buried vias connect only internal layers and are invisible from the surface. Since blind vias do not penetrate the entire board, they can be detected by holding the board against a light source; if light does not pass through, it indicates six layers or more. This method of detecting vias can be helpful, though not always precise.
4. Accumulation method: This is more of a practical approach than a formal method. By examining traces and component placements on various public PCBs, one can estimate the number of layers. Given the rapid advancements in IT hardware and the limited number of PCB manufacturers with redesign expertise, this approach remains useful for determining board layers.
Considering that various layers in a PCB circuit board are closely integrated, it is generally not easy to determine the actual number of layers. However, with careful observation of the board’s faults, distinctions can still be made. On close inspection, one may notice one or more layers of white insulating material between the layers of the PCB circuit board. This serves as the insulating layer designed to prevent short circuit issues between the different layers of the PCB. Currently, multi-layer PCB circuit boards predominantly employ single or double-sided wiring boards, with an insulating layer placed between each layer, which are then pressed together. The term “number of layers” in the context of a PCB circuit board refers specifically to the presence of multiple independent wiring layers, and the visibility of the insulating layer between these layers becomes the most straightforward method for us to ascertain the number of layers in the PCB circuit board.
2. **Guide hole and blind hole alignment method**
The light guide hole method employs the “guide hole” present on the PCB circuit board to identify the number of layers contained within the board. The underlying principle is based on the fact that the circuit connections in multi-layer PCB circuit boards utilize via technology. To determine the number of layers in the PCB circuit board, we can make observations of the via holes to derive our conclusion.
1. On the most basic PCB circuit board (single-sided motherboard), the components are concentrated on one side, while the wiring is on the other. For a multi-layer board, holes must be drilled so component pins can pass through and connect layers via vias. This allows soldering of the component pins on the opposite side.
2. For example, in a 4-layer board, routing is done on the 1st and 4th layers (signal layers). The remaining layers serve as the ground and power layers. The purpose of placing the signal layers between the power and ground layers is to reduce interference and facilitate signal correction. If board guide holes are visible on the front but not on the back of the PCB, it indicates a 6/8-layer board. If guide holes are visible on both sides, it is likely a 4-layer board.
3. Currently, many manufacturers use an alternative routing method, incorporating buried and blind vias. Blind vias connect internal layers to the surface without going through the entire board, while buried vias connect only internal layers and are invisible from the surface. Since blind vias do not penetrate the entire board, they can be detected by holding the board against a light source; if light does not pass through, it indicates six layers or more. This method of detecting vias can be helpful, though not always precise.
4. Accumulation method: This is more of a practical approach than a formal method. By examining traces and component placements on various public PCBs, one can estimate the number of layers. Given the rapid advancements in IT hardware and the limited number of PCB manufacturers with redesign expertise, this approach remains useful for determining board layers.
