| ??? 07/20/09 22:16 Modified: 07/20/09 22:19 Read: times Msg Score: +1 +1 Good Answer/Helpful |
#167636 - Locating of vias... Responding to: ???'s previous message |
Lukas said:
One more little question... I saw few graphic cards where gnd islands were used on outer layers short while ago. Corresponding gnd vias were ramdomly and in random count placed on the PCB from my opinion. Are there any rules or is it a product of some kind of design SW? I dont know what places I should put them on because the islands are in various shapes and somewhere they are oblong and out of the way. Vias should be located at the edges of ground planes, every 10mm along the edge. Special HF-circuits have them every 1...2mm, or so. Within the ground planes locate them forming a grid of about 10mm times 10mm. Yes, there is a theory which says that a too uniform grid can show resonances at certain frequencies, but this is only valid for the most demanding HF-applications. Where components like decoupling caps must be connected to the ground plane, use at least 2...3 vias connecting the corresponding ground pin to the ground plane. Ground fills between signal traces can only act as a shield, if they are connected to the ground plane by the help of vias every 10mm, or so. Without these vias ground fills don't work as a shield, but can even increase the stray coupling! Kai |
| Topic | Author | Date |
| PCB design - ground plate... | 01/01/70 00:00 | |
| excuse... | 01/01/70 00:00 | |
| You can use a local ground plane, but... | 01/01/70 00:00 | |
| So, if I understand it well... | 01/01/70 00:00 | |
| Yes, of course, but... | 01/01/70 00:00 | |
| Yes, but... | 01/01/70 00:00 | |
| No overlap | 01/01/70 00:00 | |
| Version B, but without FB... | 01/01/70 00:00 | |
| so... | 01/01/70 00:00 | |
| PCB layout... | 01/01/70 00:00 | |
| Answers... | 01/01/70 00:00 | |
| EMC | 01/01/70 00:00 | |
| Hhm, I wouldn't do that... | 01/01/70 00:00 | |
| AC power supply | 01/01/70 00:00 | |
| ground vias | 01/01/70 00:00 | |
| Locating of vias... | 01/01/70 00:00 | |
| Thank you very much... | 01/01/70 00:00 | |
| Sideplating? Thermal vias? | 01/01/70 00:00 | |
| Stackup | 01/01/70 00:00 | |
| Not such a good idea | 01/01/70 00:00 | |
| interrupted/split planes | 01/01/70 00:00 | |
| Elaboration | 01/01/70 00:00 | |
| Thank you... | 01/01/70 00:00 | |
| Nice link, Rob! | 01/01/70 00:00 | |
| Elaboration | 01/01/70 00:00 | |
| Explanation | 01/01/70 00:00 | |
| Elaboration | 01/01/70 00:00 | |
| What you propose isn't well suited for 4 layer boards | 01/01/70 00:00 | |
Hi Kai | 01/01/70 00:00 |