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The role and advantages of PCB circuit board back drilling

2020/05/14 16:38
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What is the back drilling of the PCB circuit board, in fact, the back drilling is a special kind of deep-drilling control. In the production process of the PCB multilayer board, such as the production of 12-layer circuit board, we need to connect the first layer to the ninth layer , Usually we drill through holes (one time drilling) and then sink copper. In this way, the first layer is directly connected to the twelfth layer. In reality, we only need to connect the first layer to the ninth layer. The tenth to twelfth layers are not connected by wires, like a pillar. This column affects the signal path and causes signal integrity problems in communication signals. So the extra column (called STUB in the industry) was drilled from the reverse side (secondary drilling). So it is called back drill, but it is generally not so clean, because the subsequent process will electrolyze a little copper, and the drill tip itself is also sharp. Therefore, the circuit board manufacturer will leave a small point. The length of the left STUB is called the B value, which is generally in the range of 50-150UM.
What are the advantages of drilling PCB circuit board back
1. Reduce noise interference;
2. The local plate thickness becomes smaller;
3. Improve signal integrity;
4. Reduce the use of buried blind holes and reduce the difficulty of PCB circuit board production.
What is the role of drilling holes on the back of the PCB circuit board
In fact, the role of back-drilling is to drill out PCB through-hole sections that do not have any connection or transmission function, to avoid reflection, scattering, delay, etc., which cause high-speed signal transmission. In addition to factors such as design, PCB board materials, transmission lines, connectors, chip packaging and other factors, via holes have a greater impact on signal integrity.