PCB circuit boards can be divided into single-sided, double-sided, and multi-layer. Multilayer boards refer to circuit boards with more than 4 layers, and currently there are over 100 layers of PCBs. Why are PCB multilayer boards even numbered?

　　1. Relatively speaking, even layer PCBs do have more advantages than odd layer PCBs. Due to the lack of a layer of medium and foil, the raw material cost of odd layer PCBs is slightly lower than that of even layer PCBs, but its processing cost is significantly higher than that of even layer PCBs. Odd layer PCBs require the addition of non-standard laminated core bonding processes on top of the core structure process. Before lamination bonding, the outer core requires additional processing, which increases the risk of scratches and etching errors on the outer layer.

　　2. Odd layer circuit boards are prone to bending. When the PCB cools down after the multi-layer circuit bonding process, different lamination tensions can cause the PCB to bend. The key to eliminating circuit board bending is to use balanced stacked, odd layer PCBs

　　Special equipment and processes are required during assembly, resulting in reduced processing efficiency and increased costs, which will also damage quality. Simply put, in PCB

　　In the process technology, four layer boards are easier to control than three layer boards, mainly in terms of symmetry. The degree of warpage of four layer boards can be controlled below 0.7% (according to the standard of IPC600); And the warpage of the three-layer board will exceed this standard, which will affect

　　Due to the reliability of SMT patches and the entire product, most designers do not design odd layer boards. Even if odd layers are used to achieve functionality, they will design them as pseudo even layers. Based on the above reasons, most PCB multilayer boards are designed as even numbered layers, with fewer odd numbered layers.