PCB News - The cost advantage of even-numbered PCB circuit boards

The cost advantage of even-numbered PCB circuit boards

The circuit board designer may design odd-numbered layers.

If the wiring does not require an additional layer, why use it? Wouldn't reducing layers make the circuit board thinner? If there is one less circuit board, wouldn't the cost be lower? However, in some cases, adding a layer will reduce the cost.

Odd-numbered circuit boards need to add a non-standard laminated core layer bonding process on the basis of the core structure process. Compared with the nuclear structure, the production efficiency of factories that add foil to the nuclear structure will decrease. Before lamination and bonding, the outer core requires additional processing, which increases the risk of scratches and etch errors on the outer layer.

Because of the lack of a layer of dielectric and foil, the cost of raw materials for odd-numbered circuit boards is slightly lower than that of even-numbered circuit boards. However, the processing cost of odd-numbered circuit boards is significantly higher than that of even-numbered circuit boards. The processing cost of the inner layer is the same; but the foil/core structure obviously increases the processing cost of the outer layer.

The best reason not to design a circuit board with odd-numbered layers is that the odd-numbered layer circuit boards are easy to bend. When the circuit board is cooled after the multilayer circuit bonding process, the different lamination tension of the core structure and the foil-clad structure will cause the circuit board to bend. As the thickness of the circuit board increases, the risk of bending of the composite circuit board with two different structures of the circuit board A OEM foundry material is greater. The key to eliminating circuit board bending is to adopt a balanced stack. Although a certain degree of bending of the circuit board meets the specification requirements, the subsequent processing efficiency will be reduced, resulting in an increase in cost. Because special equipment and craftsmanship are required during assembly, the accuracy of component placement is reduced, which will damage the quality.

When an odd-numbered circuit board appears in the design, the following methods can be used to achieve balanced stacking, reduce circuit board production costs, and avoid circuit board bending. The following methods are arranged in order of preference.

1. Add a blank signal layer near the center of the circuit board stack. This method minimizes stacking imbalance and improves the quality of the circuit board. Wire the odd-numbered layers first, then add a blank signal layer, and mark the remaining layers. Used in microwave circuits and mixed media (different dielectric constants) circuits.

2. A signal layer and use it. This method can be used if the power layer of the design circuit board is an even number and the signal layer is an odd number. The added layer does not increase the cost, but it can shorten the delivery time and improve the quality of the circuit board.

3. Add an additional power layer. This method can be used if the power layer of the design circuit board is odd and the signal layer is even. A simple method is to add a layer in the middle of the stack without changing other settings. First, follow the odd-numbered circuit board type wiring, then copy the ground layer in the middle, and mark the remaining layers. This is the same as the electrical characteristics of a thickened layer of foil.

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