PCB designing for 6 layer

Layout
1

Dear Kicad

I have few questions related PCD designing this is a 6 layer board and i am pretty new to PCB designing

Questions:

  • now if i understand correctly all the ground points in the circuit are connected to the ground plane am i correct i was wondering can i route normal data through the ground plane?
  • And all the VCC from source to device are connected using power plane am i correct i was wondering can i use this layer as well to route data using the power plane?

Regards

2

IMHO, you shouldn’t for both situation. Excluding vias.

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3

Thanks keryseykaryu

then what is the purpose of Ground/power layers internet says they are reference points but i am bit confused.

  1. Are all ground point in the circuit connected to the ground plane am i correct?
  2. now how does devices get power is it from the power plane if yes then basically there are multiple devices requiring different voltages. in that case how is the power plane used?

Regards
Nick

4

Those planes make it easy to get power/GND to your devices as one just has to put a via besides the pin that needs it and it will ‘dive’ to get the appropriate connection. That’s way easier and less error prone than routing signals/power/etc. by hand all over the place.

For I-can-‘tap’-into-Vcc-or-GND-anywhere-I-want to work, those planes have to be undisturbed planes, without other tracks routing through on that layer. Even other layers (signal) can be affected, unless you use buried vias.

Not so simple… let’s say you got analog ground and digital ground.
Means, you have two ground planes on that ground layer… you naturally will align/orient/place components that need either so, that the respective planes get “as clean and big as possible”… or whatever your design rule tells you.

The same is true for different voltages. You then have a couple of power planes on the power layer and hopefully align/orient/place components so, that you just have to ‘dive’ with a via, instead of laying a track.

example:

https://www.maximintegrated.com/en/app-notes/index.mvp/id/4359

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SUPERB thanks for the explaination Joan_Sparky

basically i can see that the power plane is a single layer seperated/cut into different voltage levels correct?

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…while still obeying design rules for EMI, safety spacing, etc… I had seen a nice pic of a layout a couple of days ago with even 230VAC in there, but I couldn’t find it, otherwise I would have linked it.

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I am looking for footprints you can help me as much as possible main components footprint required are

  • TPS65217C
  • AM3358BZCZ100
  • MT41K256M16HA-125:E
  • MTFC4GLDEA 0M WT
  • LAN8710AI

Regards

8

Well, the topic is more about PCB design in general rather than KiCad in particular.
KiCad allows using any layers the way you see fit, including routing signals on ground/power planes. As long as you know what you’re doing it’s not a problem to do that.

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Easy to find in the standard KiCad libraries. Two of them easy to create.

TPS65217C - VQFN-48 - UQFN-48-1EP_6x6mm_Pitch0.4mm from Housings_DFN_QFN.pretty
AM3358BZCZ100 - NBGA-324 - Easy to create using Footprint Wizzard (BGA) build-in Footprint Editor.
MT41K256M16HA-125:E - TFBGA-96 - BGA-96_pitch0.8mm_dia0.4mm from SMD_Packages.pretty
MTFC4GLDEA 0M WT - WFBGA-153 - Easy to create using Footprint Wizzard (BGA) build-in Footprint Editor with a few pad deletions.
LAN8710AI - QFN-32 - QFN-32-1EP_5x5mm_Pitch0.5mm from Housings_DFN_QFN.pretty

876×725 51.1 KB

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12

THANKS A LOT ANDY now i am getting more confidence on Kicad

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Thanks a ton keruseykaryu

can you tell me how did you calculate the

  1. outline x margin
  2. outline y margin

is it 15.10 -13.60 = 1.50 mils divide by 2 = .75 mils

rest other things i understood

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Exactly with a bit margin (To do not fully cover silkscreen). When you have a pad grid, the other things like: solder mask openning (Very important in BGA!), silk outline, orientation marks, etc. are easy to adjust in footpirnt editor.

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thanks keruseykaryu

please can you verify this footprint dimensions pad pitch, pad size , x , y margin is it correct or not
also how do i remove the middle 3 columns of the pad as the datasheet says 3 colums are 1.8 CTR non-conductive over mould

1768×1672 297 KB

footprint

2906×1838 303 KB

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Pass the footprint to the editor and…

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Just a quick update keruseykaryu I am able to delete the pads using delete key in the footprint editor

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thanks keryseykaryu do you think the calculations are correct

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No. The manufacturer recommend 0.35mm ball pad.
The pad must be smaller than ball diameter if pitch are higher than 0.65mm.

PS. There is a lot of manufacturer’s application notes about the BGA design considerations.

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Please note that for smallest bga with 0.25 mm pad dia, it’s often recommended by Datasheets to have paste bigger than pad.

And that don’t seems to be supported by kicad.

Arbitrary mask, pad, paste shapes non related to each other’s would be a bliss.

I have real life examples when mask also cannot be same shape as pad.

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file a wishlist entry here (https://bugs.launchpad.net/kicad) with good examples for the Devs to understand and support your case, report back with a link so others can chime in and vote on it to get some backing for it to be implemented some day?

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22

I did file a bunch of stuff on both launchpad and bugs.

I guess I should contribute also with some c++.

Maybe I have a look at the code.
Problem is have other tasks, so I may just end up contributing with cash donation.

Makes sense I think.

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