Answers to via processing when drawing PCB boards

qwqwqw2088

Answers to via processing when drawing PCB boards [Copy link]

1. What is the function and principle of adding grounding via holes near the via holes of the routing? The via holes of the PCB board can be classified into the following types according to their functions: 1. Signal via holes (the via hole structure requires the minimum impact on the signal) 2. Power and ground via holes (the via hole structure requires the via hole to have the minimum distributed inductance) 3. Heat dissipation via holes (the via hole structure requires the via hole to have the minimum thermal resistance) The via holes mentioned above are grounding type via holes. The function of adding grounding via holes near the via holes of the routing is to provide the shortest return path for the signal. Note: The via hole where the signal changes layers is an impedance discontinuity point, and the return path of the signal will be disconnected from here. In order to reduce the area surrounded by the return path of the signal, some ground via holes must be drilled around the signal via hole to provide the shortest signal return path and reduce the EMI radiation of the signal. This radiation increases significantly with the increase of the signal frequency. 2. In what cases should more ground vias be drilled? There is a saying: drilling too many ground vias will destroy the continuity and integrity of the ground layer. The effect is counterproductive. First of all, if too many vias are drilled, the continuity and integrity of the power layer and the ground layer will be caused. This situation should be avoided resolutely. These vias will affect the integrity of the power supply, thereby causing signal integrity problems, which is very harmful. Drilling ground vias usually occurs in the following three situations: 1. Drilling ground vias is used for heat dissipation; 2. Drilling ground vias is used to connect the ground layer of a multi-layer board; 3. Drilling ground vias is used to change the layer of a high-speed signal; 3. But all of these situations should be carried out under the condition of ensuring the integrity of the power supply. That is to say, as long as the interval of the ground vias is controlled, is it allowed to drill more ground vias? Is it okay to drill ground vias at an interval of one-fifth of the wavelength? If I drill more ground vias to ensure the connection of the ground of the multi-layer board, although there is no partition, will it affect the integrity of the ground layer and the power layer? If the copper foil of the power layer and the ground layer is not partitioned, the impact is not great. In current electronic products, the maximum EMI test range is 1Ghz. Then the wavelength of a 1Ghz signal is 30cm, and the 1/4 wavelength of a 1Ghz signal is 7.5cm=2952mil. In other words, if the interval of the vias can be less than 2952mil, it can well meet the connection of the stratum and play a good shielding role. Generally, we recommend that it is sufficient to drill ground vias every 1000mil.

our单片机

Correct vias can achieve the shortest path for current to ground

yang_alex

The ground holes I saw were mainly for heat dissipation. I didn't expect there are so many details!