Gerber file - Via and PTH query

Hi.

I'm new to using PCB software (self taught via youtube videos). I'm using DesignSpark 7.1 and it's
fabulous!!! No more AutoCAD drawings for me.

I'm just not sure how to check it against my original board. My original had a top ground plane, bottom traces and about 100 odd jumpers. This new design is 3 layers - middle is ground plane, hence no jumpers.

After doing the schematic, creating the PCB view and locating the components, I ran the "Auto Route Nets". Eventually with some shuffling, I ended up with zero errors. I've done a design rule check and again no errors.

Short of having it manufactured, is there anything else I can check or look for. The via's it made on it's own and burying the ground plane I find difficult to follow / check. Any suggestions appreciated.

3 layer board? Usually it's 2 or 4. I think most of us have ground plane on top and/or bottom, but route traces through it when necessary so it's not an unbroken plane (usually this is fine).

Always run your gerbers through a gerber viewer tool (there are some nice online ones).

You may be able to make it easier to follow the routing by turning off the ground plane layer so it doesn't get in the way.

DrAzzy:
3 layer board? Usually it's 2 or 4

Yes sorry, it would be 4 layers, however since I only need 3, I've got tracedstop and bottom and ground plan in the centre. Nothing on the 4th (inside layer).

For the ground plane, is it easy to change it from the inner layer to the outer? I wasn't sure how to do that.

The gerber viewer tool - can you tell me how it helps (briefly)?

I'll try check by turning the ground plane off as you suggested.

2 more quick questions - for the "copper pour" I simply inserted 2 pads near the edge of the board, with a single trace (net called "pour top"), then used this to attach the pours. I did this top and bottom. Is this ok?

Also, should I be worried about an error such as: "Gap in Net "Pour bottom" between (4838,1583) and (4909,1483) Pour bottom". I had hundreds of these after the pours. Pour settings: 25mil spoke width, 10 isolation gap and 2500 sq mil min copper.

I've been doing more checking and reading, but can't find the answer about copper pours. I've now adjusted my board to 4 layers (top, gnd, power and bottom).

With the top "copper pour" for example, I need to select a net to attach it to. Is it ok to attach it to new net that I make called say "pour top"? PS. The board is essentially a number of shift registers. (this relates to a scoreboard project I've raised in this forum).

I would highly3 recommend you to only use two layers.
You can still have ground planes with two layers.
A four layer PCB would only be necessary for very specitific high frequency designs, not Arduino. . .
.

Do not make your traces too narrow.
I do not tent my vias others do.
Make sure your finished hole sizes are large enough and there is enough pad left.

Edit:
Ground plane pads should have thermal relief.

LarryD:
I would highly3 recommend you to only use two layers.
You can still have ground planes with two layers.
A four layer PCB would only be necessary for very specific high frequency designs, not Arduino. . .
.

Thanks Larry.
I did create 2 layers when I made the PCB by hand. This time I’d like to get it made professionally by a PCB manufacturer. With the 2 layers only, I had to add an odd 120 jumpers which was way too much work, too fiddly and looked messy - hence the 3 layers.

I’ve now just drawn it as 4 layers (as 3 is odd - excuse the pun). There is a power(5V) and ground plane inner, then trace planes top and bottom. No jumpers need. Costs a bit extra, but I don’t mind given the prototype I built works.

Traces - yes, I’ve set them at 30mil. Spaces 40mil. Pad sizes typically between 50 to 70mil (I’ve beefed them all up). Would this be ok? :slight_smile:

Also, copper fill - can it be on it’s own - i.e. not joined to a specific traces (just a fictitious one)?

50-70 is OK

Attach island copper pours to GND with VIAs

You are aware that plated through holes to the other side means you avoid jumpers on double sided boards.
i.e. to jump over a trace, go to the other side, go over the trace, come back to the first side :wink:
No jumpers needed.
.

Here is a viewer to check your trace and pad clearance.
http://www.viewplot.com/

.

What to look for in the gerber viewer? Everything! Does each layer look like you expect it to? Did the silk come out right? I usually do 2-3 iterations of this fixing mostly trivial problems, then more often than not, another couple when I upload it to my board house and see their preview.

I am also with larry - you really don't need to go 4 layers. It makes the boards considerably more expensive, and unless you're doing exotic stuff, it's fine to just run traces in the same layer of the ground plane. I'm not familiar with the design software you're using, but it will offer some way to do a copper pour that fills all area not taken up with other traces, provided there's a contiguous path.

I usually do 2 layer boards, and fill both top and bottom layer with ground pour. It makes routing easier to not have to worry about ground, and I can tell which pins are grounded when debugging without checking the schematic by looking for whether they're tied to the ground plane.

You want the copper pour to be in the same net as ground (or power, for a power plane)!

LarryD:
50-70 is OK
Attach island copper pours to GND with VIAs

You are aware that plated through holes to the other side means you avoid jumpers on double sided boards.
i.e. to jump over a trace, go to the other side, go over the trace, come back to the first side :wink:

Copper pours attached to gnd via vias - yes, that makes perfect sense. Done.
Plated through holes - yes, only after alot of reading I worked that out.
The software has also created a stack of vias. From what I've learnt, these also connect top and bottom but without holes. I assume vias can be covered with soldermask?

Viewer to check traces and pad clearances - ta.

PS. Does that mean its "ok" to go ahead with 4 planes? ::slight_smile:

cjcj:
Copper pours attached to gnd via vias - yes, that makes perfect sense. Done.
Plated through holes - yes, only after alot of reading I worked that out.
The software has also created a stack of vias. From what I've learnt, these also connect top and bottom but without holes. What? I assume vias can be covered with soldermask?
Called tenting, I like them to be left uncovered as you can solder fill easily if needed.

Viewer to check traces and pad clearances - ta.
Gives you a heads up on possible placement problems.

PS. Does that mean its "ok" to go ahead with 4 planes? ::slight_smile:
Did I mention you should go with 2 sided PCBS, yes I did! ! !
You'll be sorry.

:sleeping:

DrAzzy:
What to look for in the gerber viewer? Everything! Does each layer....

Thanks for the advice. Yes, I'll look more closely. I see now what you mean about using the ground plane also for other traces - I never thought of that. This should then allow me to get away with 2 layers only. I'll give it a go.

Larry, the "Viewplot" freeware is excellent. Ta.

Can someone please tell me if I create a board with only 2 planes, connecting the copper pour ground on the base and power on the top, when creating the copper pours, should I keep on the setting "thermal on pads"?

I found with the setting on, 2 pads didn't end up with "spokes". When I turned off the setting, all pads touched the copper pour completely. Any suggestions?

cjcj:
Can someone please tell me if I create a board with only 2 planes, connecting the copper pour ground on the base and power on the top, when creating the copper pours, should I keep on the setting "thermal on pads"?

I found with the setting on, 2 pads didn't end up with "spokes". When I turned off the setting, all pads touched the copper pour completely. Any suggestions?

The thermals are good, generally speaking - they make it much easier to solder those pads (the connected ground plane pulls heat away while soldering).

Were those two pads then not connected? One hopes the program flagged that up - sometimes the positions of the pads and nearby layout keep it from touching if thermals are enabled - you can manually run a trace from those pads, or adjust the layout so the problem doesn't occur. You may also be able to turn off thermals on a per-part basis.

Yes there should be a setting to turn on/off thermal reliefs.
I always use reliefs with my PCB program.

Make sure you add mounting holes and a few LEDs to your board :wink:

I do not usually use a power plane, just a ground plane, power traces are wider.
Power is never one long snaking trace, remember star.
Make sure decoupling capacitors are close to the I.C. power pins.

Thanks DrA. The pads are connected. I think it's the balance between the spoke width and isolation gap (see attached pdf and images below. An error does appear. Just not sure what is the best settings.

04_display.png

07_display.png

11_display.png

Larry, yes I would therefore prefer to add thermals too. Mounting holes - check. No power plane - too many jumpers - I have the top as 5V plane. On the plus - I've now only got 2 planes not 4. ::slight_smile: . Decoupling capacitors right next to each IC - check.

Please do check attachment for suggestion on best way forwards.

spoke thermal error.pdf (207 KB)

04_display.png

07_display.png

11_display.png

The board above I’ve finished as 2 sided and top and bottom copper pours attached to ground plane. Thanks all.

I’m now trying to draw up my led digit board as Gerber files but am stuck on a few points.

PCB details:
2 sided. 305mm x 480mm x 1.6mm board. Board for 365 leds, 52 resistors, 1 header. LEDs to be inserted on top face. All soldering on bottom face. 95% of traces on bottom face. Black soldermask top face. Green soldermask on bottom face. Silkscreen on bottom face.

So the issues I’m having are:

  • LED components come with a top and bottom pad including PHT. How do I turn off the pad on the top face? (see photo 1 and 2 below)
  • With the components, the silkscreen ends up on the top. How do I move it to the bottom?
  • When producing gerber files, do I need to mirror any
  • In creating gerber files, do I need to pick “mirror” in any plots?

If it helps, I’m using DesignSpark for the drawing.

01_top.png

02_bottom.png

03_bottom.png

Problem resolved.

  1. changed LED symbol - put pads only on bottom layer and silkscreen as well. Plotted gerber files, then opened in "viewplot" (thanks Larry), and I could see the copper pads were only on the bottom and holes still drilled. Text was also on the bottom plane and "reversed" automatically.