Advantages of Even Layer PCBs

1. Low cost

Due to the lack of a layer of dielectric and foil, the raw material cost of odd-numbered PCBs is slightly lower than that of even-numbered PCBs. However, the processing cost of odd-layer PCBs is significantly higher than 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 a non-standard lamination bonding process based on the core structure process. Factories adding foil to the core structure will be less productive compared to the core structure. The outer core requires additional processing prior to lamination, which increases the risk of scratching and etching errors on the outer layer.

2. Balance the structure and avoid bending

The best reason to design a PCB without an odd number of layers is that it bends easily. When cooling the PCB after the multi-layer circuit bonding process, the different lamination tensions will cause the PCB to bend as the core structure and the foil coating structure cool. As the thickness of the board increases, so does the risk of bending a composite PCB with two different structures. The key to eliminating board bending is to use balanced layering. Although a certain degree of bent PCB meets specifications, subsequent PCBA processing will be less efficient, resulting in increased costs. Since assembly requires special equipment and processes, the placement accuracy of the parts is reduced, thus compromising the quality.

Changes are easier to understand: in the process of PCB technology, the four-layer board is better than the three-layer board control, mainly in terms of symmetry, the warpage of the four-layer board can be controlled below 0.7% (IPC600 standard), but the three-layer board The size and warpage will exceed the standard, which will affect the reliability of SMT and the whole product, so for general PCB designers, don't design odd-layer boards, even if the function of odd-numbered layers, design the counterfeit as an even-numbered layer, and put five layers The PCB design is divided into 6 layers, and the 7-layer PCB design is divided into eight layers.

Based on the above reasons, the design of PCB multilayer boards mostly uses even layers, and rarely uses odd layers.