Due to the lack of one layer of dielectric and foil, the cost of raw materials for odd numbered PCBs is slightly lower than that for even numbered PCBs. However, the processing cost of odd layer PCBs is significantly higher than that of even layer PCBs. The processing cost of the inner layer is the same; But the foil/core structure significantly increases the processing cost of the outer layer.

　　Odd layer PCBs require the addition of non-standard stacked core bonding processes on the basis of core structure technology. Compared to the nuclear structure, the production efficiency of factories that add foil outside the nuclear structure will decrease. Before laminating and bonding, the outer core requires additional processing, which increases the risk of scratches and etching errors on the outer layer.

　　The best reason for not designing PCBs with odd layers is that odd layer circuit boards are prone to bending. When the PCB is cooled after the multi-layer circuit bonding process, the different lamination tensions between the core structure and the foil structure during cooling can cause the PCB to bend. As the thickness of the circuit board increases, the risk of bending composite PCBs with two different structures increases. The key to eliminating circuit board bending is to use balanced stacking. Although the PCB with a certain degree of bending meets the specification requirements, the subsequent processing efficiency will decrease, resulting in increased costs. Due to the need for special equipment and processes during assembly, the accuracy of component placement is reduced, which will damage the quality.

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