PCB Tech - How to distinguish the number of layers of a multilayer PCB?

With the rapid development of integrated circuit technology, the number of layers of circuit boards has also evolved from the initial single-layer and double-layer boards to more than a dozen or even higher multi-layer boards. Therefore, this brings a lot of difficulties for many people to distinguish the number of PCB layers. When there are more layers, it is more difficult to distinguish the number of PCB layers. Therefore, it is necessary to master a method for quickly distinguishing the number of PCB layers.

The substrate of the circuit board itself is made of insulating and heat-insulating materials that are not easy to bend. The small circuit material that can be seen on the surface is copper foil. The copper foil was originally covered on the entire circuit board, but part of it was etched away during the manufacturing process, and the remaining part became a network of small circuits. NS. These lines are called wires or wiring, and are used to provide circuit connections to parts on the circuit board.

Usually the color of the circuit board is green or brown, which is the color of solder mask. It is an insulating protective layer, which can protect the copper wire and prevent the parts from being welded to the wrong place. Multilayer boards are now used on motherboards and graphics cards, greatly increasing the area that can be wired. Multilayer boards use more single or double-sided wiring boards, and put a layer of insulating layer between each layer of boards and press them together.

The number of layers of the PCB board means that there are several independent wiring layers. Usually the number of layers is even and contains the two outermost layers. Common multi-layer PCB boards generally have a structure of 4 to 8 layers. The number of layers of many PCB boards can be distinguished by looking at the cut surface of the multi-layer PCB board. But in fact, no one can have such good eyesight. So, let me teach you a way to distinguish the number of PCB layers.

The circuit connection of the multilayer board is through buried via and blind via technology. Most motherboards and display cards use 4-layer PCB boards, and some use 6, 8-layer, or even 10-layer PCB boards. If you want to distinguish the number of PCB layers, you can identify it by observing the via holes, because the 4-layer boards used on the motherboard and the display card are the first and fourth layers of wiring, and the other layers have other uses (ground and power) . Therefore, like the double-layer board, the via hole will penetrate the PCB board.

If some vias appear on the front of the PCB but cannot be found on the reverse, then it must be a 6/8-layer board. If the same via holes can be found on both sides of the PCB, it will naturally be a 4-layer board. Tips for distinguishing the number of PCB layers: point the motherboard or display card towards the light source, if the position of the guide hole can transmit light, it means that it is a 6/8-layer board; otherwise, it is a 4-layer board.