Hi
So I have this layout at the moment and I am considering to grounding for these components, the image shows 8 pairs of grounds at the top and 8 and another 8 at the bottom, this pattern continues and there are 128 Gnd pads, 64 top & 64 bottom
The upper pairs are diodes, the lower are Resistor/Capacitor.
This is then replicated elsewhere on the board.
I was considering a via in pad for each but that lines up to a lot of holes in rows, then I thought about a ground pour on layer 1 with thermal restraints, or just tracks through all of them and Via’s scattered.
What are your thoughts on how best to achieve this and avoid tombstoning?
6 layer board Gnd on 2 & 5
Edit - the upper components are 0603 the lower are 0805
Thanks
If in the top row you put one via in the middle of two GND pads you will end up with 8 vias. I don’t think that is a lot. You can do the same for the bottom row. Personally I am not so fond of vias in a pad. So I would take a little bit more space and place vias in between two GND pads.
As for tombstoning, usually it gets more often happening with smaller components like 0402 or smaller.
With 0805 and 0603 I never experienced tombstoning using the default shapes.
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Thanks for the reply @LilyTronics .
I have quite a densely populated board which is ultimately why I needed to go via in pad, I have always avoided pads between components where they will overlap the via - don’t know why, just felt wrong.
I was worried about doing a via in every pair as I will end up with a wall of 64 via’s in a row for the 128 pads which will start to divide up the other flooded planes and may even make a weak line down almost the full length of the board.
The max current per four pads is 50mA which makes me think a single via per 8 pads may be sufficient with a balanced trace through the lot.
What tools does Kicad have to warn about this sort of thing? I am wondering if it will tell me the board will fail or if I can configure it to tell me…
I realised after posting this question yesterday it may not be apparent that it entirely related to kicad, I am trying to become more familiar with kicad and its tools so I do this via the issues I face, I appreciate it not being closed already.
Thanks
Yes I can imagine 64 vias is a lot. It also depends on the frequencies that are being used. The higher the frequencies, the more vias you need for proper grounding. Perhaps one via per 4 GND pads is a nice compromise. KiCad has a calculator for calculating the max current per via, and other characteristics of the via like resistance, capacitance etc.
Further there are no warnings or KiCad tells you if the board will fail.
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