GND on bottom of PCB

Layout
1

Hi,
I want to have all of the bottom layer of the PCB as GND.
I will have 4x strip connectors through the PCB all around the PIC 18LF4520 (surface mount) to connect GND pins to bottom.
Is this possible? and how do I do it please?
Camerart.

2

Add a copper zone :wink:

1 Like
3

Hi R,
The answer of an expert to a dunce :slight_smile:
Can you point me to a list of instructions on how to do that please?
C

4

http://docs.kicad.org/stable/en/pcbnew.html#_creating_copper_zones

:wink:

1 Like
5

Hi J,
Thanks. It looks mighty complicated.

EDIT: I clicked on the ā€˜make zoneā€™ icon (there are two that look alike?) but the page didnā€™t change to the one in the instructions, puzzled.

C.

6

In kicad clicking the button to select a tool, only selects the tool. You always need to click somewhere on the canvas to get to the next step. (The dialog opens when you place the first corner of your zone)

1 Like
7

Hi R,
The paged opened :slight_smile:
I think the zones may be a bit too difficult for me at the moment. I think I can do what I am trying to do, by hand tracking.
Thanks to both.
C.

8

?!?

1 Like
9

Hi J,
Thatā€™s better for me (Iā€™m more visual)
Thanks.
C.

10

Hi J,
Watched the video, and now I have a bottom layer GND plane, marvellous:)

If Iā€™m allowed to be critical about the video:
I wish he had done some practice runs before filming, because he does tend to mumble when correcting minor errors also he should have a constant speed of delivery.

Sometimes itā€™s almost impossible to keep up with his mouse clicking. As learners we may not be up to his speed.

All in all though it helped me greatly.
Thanks.
C.

11

Hereā€™s a photo of the board:)
Thanks to all.
C.

1265Ɨ1217 196 KB

12

You need to add some vias from the ground track to the plane or it wonā€™t do much

1 Like
13

Do you not get any DRC errors? C4 pin 2 does not look like it has a connection to ground.
Also, I would increase the clearance around your 3V3 and +5V tracks and move them away from any pads. They pass quite close to several pads and could potentially cause shorts if there is any misalignment of the solder mask. Be sure to move any silkscreen off of pads, like the C1, C2, and C5 ref ids.

The 3V3 and GND tracks that run under U2 are probably not necessary.

If you donā€™t want the values rendered on the screen you can turn them off under the ā€œRenderā€ tab.

Although I too would probably add a few vias, especially near U1 and C3, but his board is not quite as bad as it first appears. There are connections between the ground plane and tracks on the top through many of the pin headers.

Edit: I see you are running the crystal signals out to a connector, is this necessary? Itā€™s not really a very good idea.

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14

Regarding your xtal stuff, have a look at this:

Your capacitors should be between the crystal and the uC.

It might also be a good idea to add some guarding area.
Example application note, XTAL layout guidelines start at page 32

Just to be clear: Your board will probably work without doing it that way. But it might not be as hardened against EMI as it otherwise could be.

15

More questions concerning your crystal oscillator:

32 MHz seems a bit high for a crystal value especially when the PIC has a 4x PLL, I would consider an 8 or 10 MHz crystal.

Is that crystal footprint an 0603? I would expect the body to be much wider, are you sure there is enough room there for the crystal? The values of C4 and C5 should be chosen according to the crystal datasheet, 22pF seems a bit high for 32 MHz, but then, as I said, I would suggest a lower freq. crystal.

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16

That was from 2014 - @ChrisGammell does make new ones every now and thenā€¦ just grabbed that one as it was just about filled zones and you had trouble applying the documentation. Here is a more recent one:

Check out his channel.

1 Like
17

Hi D,
I connect through the board via the connectors.
C

18

Hi J,
Iā€™ll check it plus others while Iā€™m at it. I have some bad habits, and should do a refresher, thanks.
C.

19

Hi 1,
I saw the missing connection on C4, Iā€™ll just add a wire later.
I added some clearance between 3.3v and GND.
Iā€™ll cut the crystal to connector tracks.
EDIT:I now realise that I should have omited the XTL CAP co0nnections to the connectors, then both CAPs would route to GND ok.
The XTL is only there in case I need it later, otherwise Iā€™ll use the internal OSC.
Thanks.
C.

20

Hi R,
I usually follow this:

If it stops working Iā€™ll look into your suggestion, thanks.
C