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PCB Tech

PCB Tech

PCB Tech

PCB Tech

How to reduce the adverse effects caused by the parasitic effects of the vias in the via design of the PCB circuit board
2021-09-07
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Author:Jack

In the process of designing the PCB circuit board, seemingly simple vias, if you do not leave a sound, it is likely to bring great negative effects to the circuit board. Today, I will tell you how to reduce the adverse effects of the parasitic effects of the vias in the via design of the PCB circuit board:

PCB circuit board

1. The pins of the power supply and the ground should be drilled nearby, and the lead between the via and the pin should be as short as possible, because they will increase the inductance. At the same time, the power and ground leads should be as thick as possible to reduce impedance.

2. Try not to change the layers of the signal traces on the PCB circuit board, that is to say, try not to use unnecessary vias.

3. The use of a thinner PCB circuit board is beneficial to reduce the two parasitic parameters of the via.

4. Considering the cost and signal quality, choose a reasonable size of the via hole. For example, for the 6-10 layer memory module PCB circuit board design, it is better to use 10/20Mil (drilled/pad) vias. For some high-density small-size boards, you can also try to use 8/18Mil Of vias. Under current technical conditions, it is difficult to use smaller vias. For power or ground vias, you can consider using a larger size to reduce impedance.
5. Place some grounded vias near the vias of the signal layer to provide the nearest loop for the signal. It is even possible to place a large number of redundant ground vias on the PCB circuit board. Of course, the design needs to be flexible.

   The via model discussed earlier is the case where there are pads on each layer. Sometimes, we can reduce or even remove the pads of some layers. Especially when the density of vias is very high, it may lead to the formation of a broken groove in the copper layer to isolate the loop. To solve this problem, in addition to moving the position of the via, we can also consider placing the via on the copper layer. The pad size is reduced.