Electronics > Beginners
Creating controller for LED display, help / review needed
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Lt_Flash:
Just have a look at connection width to ground plane now under ATMega chip and compare it to several small vias that were there before. Also, just to make sure, you can add more vias to bottom GND plane under the chip, just to be sure you're safe :)

In regards to capacitors - in the example picture I've shown there was a ground trace going to via under the chip and that's not good, of course. In your case - you've got a solid connection to ground, so it's good path for current to flow.

Now, after you've put the solid ground plane you can see there are still gaps in top ground like ones near IC3. You can either put vias to bottom ground plane in this case or rearrange your traces so they would be closer to each other to resolve this issue. The same with MAX3468 - rearrange traces so GND plane can fill the space, add vias to GND near bottom connector. And also, this is my personal preference, but I prefer to use solid joining of polygons to components, not the 3-point joint like you've done. Effectively you've created three thin traces to each ground from ground plane. You can usually change this in polygon settings. Nothing too bad about this as it's still a good solid connection, just my preference.
Lt_Flash:
By the way, you still need several vias from top ground to bottom one, that's important, as they must be well connected to each other! Usually you put some vias in corners of the board, but not too close to the sides, and also, of course, you put vias in the middle to fill all the gaps and usually under the chips too.
muktupavels:
Is there any recommendations or something like that about vias? How many do I need? Is one via under chip enough? Centered?
capt bullshot:
If you want to go this route (placing vias all over the board), I'd recommend to place them in a raster (maybe 5mm ... 10mm). IMO this isn't necessary for this kind of circuit, but won't harm anyway. Another good thing to look where to place the vias: If a plane (no matter which side of the board) is slotted by one or more traces, place vias left and right of these traces, to the plane on the other side will connect over the slot.

From my experience, this board looks good enough, though it may be a good excercise to go all the way. I'm more concerned about the other board, you should do the same style redesign there.

Anyway (another IMO), I wouldn't have redone the board, but in the first place just bodged some solid ground connections across the existing boards (most important would be to solidly ground and tie together the USB and RJ45 shields) to see if this strategy helps (has done quite often).
Lt_Flash:
Usually it depends on how much current is going from VCC to ground. In your case it's a low-power board, so you don't need too many vias and they not necessarily should be under the ICs. You put vias under ICs usually under QFN ICs that have a thermal pad under them, like LiPo chargers or DPAK MOSFETs. So, just put several vias about 1cm away from corners of the board and you should be fine. And, just to be sure, you can add some vias where ground planes are not looking too solid. And I'd add vias everywhere where traces have broken your GND plane just to refill it.
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