Printed circuit board

High-speed PCB design considerations in the design of the stack

In high-speed PCB design, the number of layers of the PCB depends on the complexity of the board, from the PCB processing, multilayer PCB is a number of “double-sided PCB” through the stacking, pressing process manufacturing out, but the number of layers of multilayer PCB, the stacking sequence between the layers and the choice of plate is by the board designer decision, which is called the “PCB stack design.

A PCB design of the number of layers and lamination scheme depends on the following factors.

(1) hardware cost: the number of PCB layers and the final hardware cost is directly related to the more layers the higher the cost of hardware to consumer products as the representative of the hardware PCB generally has the highest limit for the number of layers, such as laptop products, the motherboard PCB layers are usually 4 to 6 layers, rarely more than 8 layers.

(2) high-density components out of line: BGA package devices represented by high-density components, the number of layers of such components out of line basically determines the number of layers of PCB wiring.

(3) signal quality control: for high-speed signals are more concentrated PCB design, if the focus on signal quality, then it is required to reduce the adjacent layer wiring to reduce crosstalk between signals, which is when the ratio of the number of wiring layers and the number of reference layers (Ground layer or Power layer) is best 1:1, which will cause the increase in the number of layers of PCB design; conversely, if the signal quality control is not mandatory requirements, you can use the adjacent wiring layer scheme, thereby reducing the number of PCB layers.

(4) schematic signal definition: schematic signal definition will determine whether the PCB wiring “smooth”, a bad schematic signal definition will lead to PCB wiring is not smooth, wiring layer increase; (5) PCB manufacturers processing capability base.

(5) PCB manufacturers processing capability baseline: PCB designers to give the design of the layer stack (stacking method, stacking thickness, etc.), must be fully considered PCB manufacturers processing capability baseline, such as: processing processes, processing equipment capabilities, common PCB board models, etc..

In short, high-speed PCB design, PCB lamination design needs to seek priority and balance among all the above design influencing factors.


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